|
|
Posters |
|
EXPLORING THE PARTIAL DISSOLUTION OF CELLULOSE FIBERS IN IONIC LIQUID
Alexa Scheer, Institute of Bioproducts and Paper Technology (BPTI)
Abstract: A key focus in biopolymer research and across a broad spectrum of industries is the dissolution of cellulose, which is considered essential for unlocking its full utilization potential. Ionic liquids, a class of salts that exhibit liquid properties at ambient temperatures, possess the ability to dissolve cellulose fibers. The formation of regenerated cellulose can be achieved by subsequently rinsing the dissolved fibers with anti-solvents. [1] However, the partial dissolution of fibers and precipitation of the solubilized components to form a network of regenerated cellulose and residual fibers, e.g. to densify paper, represents a field with limited existing research. Here we demonstrate the interaction between the ionic liquid 1-Ethyl-3-methylimidazoliumacrylate (EMIM-ACR) and paper fibers. Through microscopic imaging of individual fibers immersed in varying concentrations of EMIM-ACR, the influence of water content on the dissolution power of the ionic liquid was demonstrated. Distinct structures of regenerated cellulose were obtained by rinsing fiber bundles with either ethanol or water after immersion in ionic liquid at 80°C. Additionally, paper samples were immersed in EMIM-ACR for varying durations at 80°C, rinsed with water, and pressure dried. The formation of regenerated cellulose was confirmed by infinite focus microscopy. A significant compaction was determined with the measurement of air permeability using the Bendtsen and Gurley method. Our findings demonstrate the potential of using EMIM-ACR to create networks of regenerated cellulose and residual fibers by partial dissolution. The densification achieved by closing the fiber interstices via the presence of precipitated cellulose could be a promising approach for enhancing the density of paper. |
|
|
Attosecond Electron Control
Alexander Sagar Grossek, Hana Kristin Hampel, Daniel Hipp, Marcus Ossiander, Martin Schultze, Institute of Experimental Physics TU Graz
Abstract: We induce ultrafast electron dynamics in Xenon with short pulsed lasers and we measure the excitation/response of the electrons in a pump/probe scheme. We use an EUV pulse as the pump to excite coherent Rydberg states of Xenon and an IR pulse as the probe to analyze the dynamics of the Rydberg states. |
|
Physics informed neural networks reveal valid models for reactive diffusion of volatiles through paper
Alexandra Serebrennikova (1), Raimund Teubler (2), (1) Institute of Solid State Physics, (2) Institute of Analytical Chemistry and Food Chemistry
Abstract: We show how state-of-the art physics-informed neural networks (PINNs) serve us to identify mathematical transport models that correctly predict the transport of organic volatile molecules through a porous sorptive medium. Transporting molecules involves a complex interplay of diffusion, adsorption, desorption, and chemical reactions, with the relative importance of each process being determined by the polarity of the molecule. Here, physics-informed neural networks (PINNs) assess which of five different models, each presented as a set of partial differential equations, correctly predicts the transport of a highly polar and an apolar model compound through paper sheets, i.e., a particularly complex porous medium.
A model is suitable when two aspects are fulfilled: (i) The PINN can reproduce the experimentally determined time-dependent concentration profile within the paper cross-section and predict associated material constants such as sorption constants and effective diffusion coefficients (inverse problem). (ii) The PINN correctly predicts the concentration profile for transportation periods being much longer than the experimental observation time (forward problem). |
|
|
(Extreme) Ultraviolet Metaoptics
Anna Karner, David Grafinger, Marcus Ossiander, Insitute of Experimentalphysics, TU Graz
Abstract: Ultraviolet (UV) light carved out an essential role in countless applications such as high-resolution imaging/lithography, quantum optics and attosecond metrology, just to name a few. In spite of this, conventional optical elements for UV light are relatively scarce and expensive, as materials suited for the short wavelengths are hard to come by. Dielectric metasurfaces, whose function is based on the microscopic modulation of the electromagnetic (EM) wave instead of the macroscopic refraction/diffraction of light, could offer a formidable alternative to this
inherent problem. While these nanoscale optics have already established a prominent role in applications from infrared (IR) to the visible spectrum, the UV range still poses many challenges. Recent advances mainly involve high index dielectrics like HfO2 for the deep ultraviolet (DUV) range (Zhang et al., 2020), however, concepts down to the EUV region were already proposed, too (Ossiander et al., 2023). |
|
|
Organic Photovoltaics - with a research focus on stability and semi-transparency
Bernadette Ortner, Julia Hönigsberger, Institute for Chemistry and Technology of Materials, TU Graz
Abstract: Bernadette Ortner, Julia Hönigsberger, Virginia Lafranconi, Thomas Rath, Gregor Trimmel
Institute for Chemistry and Technology of Materials (ICTM), Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria
Organic solar cells (OSCs) have many advantages over other cell technologies. For example, it is possible to produce semi-transparent devices, which can also be manufactured from comparatively low amounts of materials in simple and fast processes.
In particular, semi-transparency of solar cells is of great interest in building integrated photovoltaics (BIPV) as well as for tandem devices. In the search for suitable materials for organic solar cells with high semitransparency in the visible wavelength region of the solar spectrum, the focus fell on efficient conjugated polymers such as D18, PTQ10 or PM6 and non-fullerene acceptors (NFA) such as M3, L8-BO and IEICO-4F, which absorb light in the near infrared range. Different strategies like reducing the layer thickness or donor:acceptor ratios were tested to increase the semitransparency. The creation of a semitransparent solar cell is part of the Peroptam project. The main aim of this project is the development of a bifacial tandem solar cell consisting of a semi-transparent organic and a perovskite solar cell.
Another important area of current research is the improvement of the stability of OSCs. Since single-junction devices have achieved efficiencies above 19% in recent years, it becomes increasingly important to focus more on longevity. Common active layer materials in organic solar cells are fluorinated or chlorinated to adjust their optical, electronic, and morphological properties. The photovoltaics research group at ICTM in collaboration with FELMI found an accumulation of fluoride at the MoO3/Al interface of a non-fullerene organic tandem solar cell containing a fluorinated donor polymer and an aluminum-containing recombination layer. A possible explanation for this phenomenon is the defluorination of the polymer and diffusion of fluorine species to the interface. Within the HalOMat project, we will investigate the origin, mechanism, and possible consequences of the halogen accumulation in detail. |
|
|
An analysis framework for spatiotemporal CDD tensor calculation and its application to similar material modelling fields
Bernhard Heininger, Institute of Strength of Materials
Abstract: Crystal plasticity is caused by the movement of line-like defects, the dislocations. Since their discovery in the early 20th century, several physical and mathematical approaches on different size scales have been developed to relate their movement to the observed macroscopic plastic deformation properties of crystalline materials, such as the flow stress and work hardening. Among these methods, the so-called Continuum Dislocation Dynamics (CDD) theory pursues the concept of representing the complex dislocation network in a continuum manner, introducing alignment- curvature- and velocity tensors of specific orders. The spatiotemporal evolution of the dislocation network is finally captured in a set of evolution equations expressed by these tensor-valued variables.
In CDD, on the one hand, the alignment- and curvature tensors exclusively
represent the geometrical information of the curved dislocation lines and can
be easily obtained from Discrete Dislocation Dynamics (DDD) data. On the
other hand, the velocity tensors, extracted from temporal snapshots of DDD
data, serve as a valuable tool to analyse the kinetics of the dislocation network due to external loadings. These principal concepts give reason for an analogous application in other fields of material modelling dealing with curved, line-like entities. Two possible applications may comprise the microstructural modelling of strongly oriented fibre materials and amorphous plastics, which are well known to consist of cross-linked polymer chains.
In the current poster, we demonstrate a continuously developed and improved
analysis framework for determining the above-mentioned tensor-valued vari-
ables from DDD data. We show the geometrical aspects incorporated in the
alignment- and curvature tensors and discuss their possibility for general usage
to line-like entities beyond dislocations. Furthermore, we show its current ability to reproduce results from DDD simulations based on the temporal evolution of the plastic strain rate. |
|
|
Synthesis and Characterization of a Bio-Based Transesterification Catalyst for Green Photopolymers
Bernhard Sölle, Polymer Competence Center Leoben (PCCl)/TU Graz
Abstract: In DLP (digital light processing) 3D printing, photosensitive resins are usually characterized by low viscosity, fast curing rates, high resolutions and adjustable mechanical properties. After curing, they usually behave like classic thermosets and therefore cannot be reprocessed or recycled. Since plastic pollution is one of the biggest challenges facing our society, ways to obtain sustainable materials are important. Therefore, not only bio-based monomers can be used, but also dynamic covalent bonds can be introduced into the photopolymer. A well-known example is the transesterification reaction between carboxylic acid ester bonds and free hydroxyl groups. The commonly used transesterification catalysts for such covalent adaptive networks have some drawbacks, such as their poor solubility and compromised curing speed, as well as reduced pot life. To overcome these problems, phosphate esters have been used as catalysts.[1] However, all organic phosphate esters mentioned in the literature are petroleum-based. To further improve the environmental footprint, we synthesized a new eugenol-based phosphate ester (EUGP) as a new transesterification catalyst. The catalyst is liquid and mixes well with the resin. Owing to the vinyl group, it can be covalently attached to the network and no migration takes place. Furthermore, we synthesized two different bio-based acrylates, bearing free OH- and ester moieties, based on lineseed oil and eugenol. The acrylated lineseed oil (AELO) is characterized by a high viscosity, therefore we synthesized acrylated eugenol (AEUG) which acts as a reactive diluent in our system.
To the best of our knowledge, we have successfully developed the first fully bio-based vitrimeric acrylate system for 3D printing applications. The photocurable network containing AELO and AEUG in a 1:1 ratio and 5 wt% of EUGP, exhibited high thermal stability (> 250 °C) and was able to relax 63% of the original stress within 50 minutes at 200 °C. This enables advanced applications, such as self-healing and re-shaping after 3D-printing.
References
[1] a) E. Rossegger, R. Höller, D. Reisinger, J. Strasser, M. Fleisch, T. Griesser, S. Schlögl, “Digital light processing 3D printing with thiol-Acrylate vitrimers.” Polym. Chem., 2021, 12, 639. b) E. Rossegger, R. Höller, D. Reisinger, M. Fleisch, J. Strasser, V. Wieser, T. Griesser, S. Schlögl, “High resolution additive manufacturing with acrylate based vitrimers using organic phosphates as transesterification catalyst.” Polymer, 2021, 221, 123631 |
|
|
Development of CuO/Cu$_2$O based MOx sensors for gas detection
Christian Maier
Abstract: Christian Maier$^1$, Larissa Egger$^1$, Anton Köck$^1$, Soeren Becker$^2$, Jan Steffen Niehaus$^2$, Klaus Reichmann$^3$
1. Materials Center Leoben Forschungs GmbH, Roseggerstraße 12, 8700 Leoben, Austria
2. Fraunhofer Center for Applied Nanotechnology CAN, Grindelallee 117, 20146 Hamburg, Germany
3. Institute for Chemistry and Technology of Materials, Graz University of Technology
Stremayrgasse 9, 8010 Graz, Austria
Nowadays indoor air quality is a widely discussed topic, because a variety of potentially harmful or even toxic gases such as carbon monoxide (CO) or volatile organic compounds (VOCs) can be present indoors. In particular high concentrations (> 1000 ppm) of CO$_2$ due to insufficient ventilation are a frequent burden that can lead to reduced concentration, headache and even more severe health issues, like respiratory and circulatory problems. Such potential health burdens are increasingly triggering the public awareness for the necessity to monitor air quality indoors, which can be performed by gas sensor devices. Metal oxide (MOx) based gas sensors are highly promising candidates due to their integrability in microelectronic systems [1-3], and high sensitivity to many AQ relevant gases. The sensing mechanism is based on a change of the conductivity of the MOx caused by various chemical reactions with gas molecules on their surface.
In this work, we develop and investigate various types of CuO and Cu$_2$O thin films as gas sensing materials. The sensors are tested against different target gases, including CO$_2$ and CO, to evaluate cross-sensitivity and humidity. Furthermore, the sensor devices are functionalized with different metallic nanoparticles (NPs) such as Au, Pt or Pd [4,5]. We will show that the metallic NPs increase the response to CO$_2$ and decrease cross-sensitivity to other gases and humidity.
References
[1] Barsan N, Koziej D and Weimar U 2007 Sens. Actuators B Chem. 121 18-35
[2] Gardner J W, Guha P K, Udrea F and Covington J A 2010 IEEE Sensors J. 2010, 10, 1833
[3] E. Lackner, J. Krainer, R. Wimmer-Teubenbacher, F. Sosada, C. Gspan, K. Rohracher, E. Wachmann, A. Koeck, 30th Eurosensors Conference, EUROSENSORS 2016, https://doi.org/10.1016/j.proeng.2016.11.200, Procedia Engineering 168 (2016) 297-300
[4] C. Wang, L. Yin, L. Zhang, D. Xiang and R. Gao, in Sensors, 10, 2010, 2088-2106
[5] F. Sosada-Ludwikowska, L. Reiner, L. Egger, E. Lackner, J. Krainer, R. Wimmer-Teubenbacher, V. Singh, S. Steinhauer, P. Grammatikopoulos, Anton Koeck, Nanoscale Adv., 2024, Accepted Manuscript, https://doi.org/10.1039/D3NA00552F
|
|
|
Synthesis and characterization of magnetic photopolymers for nanoimprint lithography
Christoph Schmidleitner, Polymer Competence Center Leoben GmbH
Abstract: Reversible switchable surfaces are desirable, as they enable the adjustment of various properties, e.g. wettability and adhesion. Different external stimuli can be used to introduce a property switch, such as temperature, light, pH-value, force or a combination of stimuli, for example, temperature and force, used in typical shape memory polymers. To circumvent mechanical defects, magnetism can be applied as external trigger. Therefore, iron oxide nanoparticles were incorporated into thiol-acrylate based photocurable resins, which could be structured by nanoimprint lithography. Firstly, iron oxide nanoparticles were synthesized via coprecipitation-method. Subsequently, the particles were functionalized using vinyl- and thiol-bearing siloxanes to enable covalent attachment of the particles. The synthesized nanoparticles were implemented into a thiol-acrylate resin, consisting of phenyl-bis-(2,4,6-trimethylbenzoyl)-phosphinoxide (BAPO) as photoinitiator, 2-hydroxy-3-phenoxypropyl acrylate (HPPA) as monomer, trimethylolpropane tris(3-mercaptopropionate) (TMPMP) as thiol crosslinker and trimethylolpropane triacrylate (TMPTA) as acrylic crosslinker. In a final step, nanoimprints were prepared with varying aspect ratios (1:3 and 1:6) and optical and digital 3D-microscopy were used to quantify the replication quality. Via laser scanning digital microscopy, the tilting of the micropillars under an external magnetic field was detected.
|
|
|
Exploiting retro oxa-Michael chemistry in polymers
David Edinger
Abstract: One way to obtain recyclable polymeric materials is to include reversible bonds in polymers. Herein, we study the reversibility of the oxa-Michael reaction and explore its scope and limitations in simple model systems and further in linear polymers as well as in polymer networks. The results show that the retro
oxa-Michael reaction of sulfone, acrylate or acrylonitrile based adducts is considerably fast at elevated temperatures (>100 °C) if Brønsted bases (e.g. KOH) are used as catalysts. Under these conditions, alcohols can easily be exchanged in oxa-Michael adducts within minutes. Furthermore, poly(ether)s derived
from oxa-Michael reactions can be depolymerized into small fragments in the presence of alcohols and show self-healing characteristics in networks. |
|
Graz micro computed Tomography Consortium
Eduardo Machado
Abstract: Graz µCT is a consortium of 13 Institutes from three Universities (TUG, KFU, MUG). In our laboratory, we have two state-of-the-art µCT machines from TESCAN. The UniTOM HR is the first dynamic micro-CT system to offer a sub-micron spatial resolution without compromising temporal resolution and in-situ capabilities. At the same time The UniTOM XL is a multi-resolution micro-CT optimized for high throughput, diverse sample types, and flexibility for your research. Since January 2022, we have performed experiments for colleagues within and outside the consortium |
|
|
Colorimetric assays on foil-based disposable microfluidic chips for monitoring the enzyme activity in industrial bioprocesses
Elisabeth Hengge
|
|
|
Hybrid metal-wood components for the mobility sector
Eva Graf, Institute of Materials Science, Joining and Forming (IMAT) - Research Group of Lightweight and Forming Technologies
Abstract: Hybrid components of wood-based materials offer a high potential for automotive lightweight applications.
The project. WoodC.A.R. demonstrated that it is possible to replace conventional heavy weight structural components such as a side impact beam in car doors with lightweight wood-based hybrid components without losses in mechanical performance.
The follow-up project CARpenTiER focuses on the implementation of wood-based hybrid components into the industrial sector. With the high variability of mechanical properties due to woods natural growth a lack of data regarding forming and joining arose. The goal is to overcome these obstacles by a function oriented process control and suitable finite element simulations that are possible to predict the components behavior.
For example, to investigate the bending behavior of hybrid aluminum-wood plates, commercial 1-mm-thick sheets of EN AW-6016-T4 aluminum alloy were adhesive-bonded with 4.2-mm-thick plates of birch wood. Orientations of the wood fibers parallel (longitudinal) as well as perpendicular (transverse) to the rolling direction of the aluminum alloy sheet and three different moisture contents (MC) of the wood plate were considered. The hybrid aluminum-wood plates were subjected to three-point bending at room temperature (RT). Simple wood plates without aluminum alloy sheets were also tested. The bending force-bending angle curves monitored during bending, the bending angles at maximum bending force and the surface strains were evaluated. Moreover, a finite element (FE) model of the testing setup was created using the LS-Dyna software. The different moisture contents did not significantly influence the bending angle; however, moisture decreased the maximum bending force. Debonding was identified as critical failure mechanism. The FE model that considered the experimentally determined material properties was able to predict the bending behavior for different moisture conditions.
Eva Graf(1), Philipp Matz(2), Peter Auer(1), Christian Kurzböck(2), Thomas Krenke(3), Johannes Painer(3), Lukas Gruber(3), Michael Frieß(4), Christoph Bauer(4), Christof Sommitsch(1), Josef Domitner(1)
(1) Graz University of Technology (TUG), Institute of Materials Science, Joining and Forming, Research Group of Lightweight and Forming Technologies, Inffeldgasse 11/I, 8010 Graz, Austria
(2) Virtual Vehicle Research GmbH (ViF), Inffeldgasse 21A, 8010 Graz, Austria
(3) Innovation Centre W.E.I.Z., W.E.I.Z. Forschungs & Entwicklungs gGmbH, Franz-Pichler-Straße 30, 8160 Weiz, Austria
(4) Weitzer Woodsolutions GmbH, Klammstraße 24, 8160 Weiz, Austria |
|
|
Shining light on the mechanical properties of anisotropic porous crystalline and cellulosic materials.
Florian P. Lindner, Institute of Solid State / Experimental Physics
Abstract: With over 90.000 synthesized structures and many versatile applications, ranging from catalysis, gas storage or drug delivery [1] to the seemingly impossible task of harvesting water from air in one of the harshest environments on the planet [2], so called metal organic frameworks (MOFs) are believed to be of key importance for tackling many of the problems that are imposed to humanity by climate change and population growth, as the 21st century unfolds.
However, many of the envisioned applications for MOFs rely crucially on their heat transport, as well as their mechanical properties. The later are of crucial importance when one thinks about the application of MOFs in industrial applications. Despite its importance, there is up to this date an insufficient understanding of the concrete structure-to-property relationships governing thermal transport in MOFs [3] and its connection to a MOFs mechanical properties.
Based on the inelastic scattering of light from acoustic phonons within a material, so called Brillouin light scattering (BLS) spectroscopy was recently found to be a promising non-contact, optical technique to measure mechanical properties of materials, like for example, their stiffness tensor or their complex longitudinal modulus [4].
In a first step acoustic phonon frequencies and elastic constants of a MOF-like structure with interesting water absorption properties, were measured using BLS and compared to results from state of the art DFT calculations. The measured values agree astonishingly well with our theoretical predictions. And are to be understood as a first important step towards a better understanding of mechanical properties of porous crystalline materials.
Furthermore, in collaboration with the Institute of Bioproducts and Paper Technology, we strive towards the implementation of the first functioning Brillouin Spectrometer in Graz at the Institute of Experimental Physics. With that step we want to intensify our research on the elastic properties of MOFs, but also extend the investigated class of materials towards cellulosic based materials. With cellulose being the most abundant biopolymer and its products such as paper, tissue, and paper board being necessities for our daily life, as well as a very promising, first study of the applicability of BLS for cellulosic fibers [5], we are keen to intensify the application of BLS in material science at the TU Graz.
[1] Wang et al., Adv. Funct. Matter (2023), 2308589
[2] Song et al., Nature Water (2023), 626-634
[3] Wieser et al.; Nanomaterials (2022), 12, 2142
[4] Merklein et al., Appl. Phys. Rev. 9, (2022) 041306
[5] Elsayad et al., Cellulose (2020), 27:4209-4220
|
|
|
Ultrasonic joining of additively manufactured reinforced carbon-fiber polyamide with reforested wood
Gean Henrique Marcatto de Oliveira, Institute of Materials Science, Joining and Forming (IMAT)
Abstract: Ultrasonic joining of additively manufactured reinforced carbon-fiber polyamide with reforested wood
Awan A., Oliveira G.H.M., Amancio-filho S.T.
Institute of Materials Science, Joining and Forming, BMK Endowed Professorship for Aviation, Graz University of Technology (TU Graz), Graz, Austria
The escalating carbon emissions contribute to a growing need for lightweight structures in air and road transportation. However, combining different materials requires non-conventional joining techniques. Ultrasonic Joining (U-Joining) is a cutting-edge friction-based joining technique developed in recent years to produce high-strength hybrid joints. This technique utilizes high-frequency ultrasonic vibrations and pressure to provide heat input at the joint interface. The U-joining has already been investigated for producing metal-polymer hybrid joints. However, a gap exists in the joining regarding environmentally sustainable materials, such as wood, which are derived from renewable sources. Therefore, the current study is focused on the feasibility of producing wood/polymer hybrid structures via the U-joining technique. The surface of the reforestation Oak was modified with laser texture for better mechanical interlocking at the joint interface. After that, additively manufactured carbon fiber-reinforced polyamide (PA6-15CF) was joined to as-received and laser-textured Oak using ultrasonic energy. In the U-Joining technique, frictional heat is generated at the joint interface by ultrasonic vibrations to melt the PA6-15CF component. The polymer component is then joined with the wood substrate under constant pressure at the end of ultrasonic vibrations. In this work, the U-joints with as-received and laser-textured Oak and Oak/PA6-15CF adhesive joints were produced, and their mechanical strength was compared. The as-received, laser-textured and adhesive joints showed shear strength of 3.9 ± 0.6 MPa, 9.3 ± 0.5 MPa and 10 ± 1.5 MPa, respectively. Fracture analysis showed a change in the failure mode from adhesive in the as-received wood joint to cohesive fracture for the laser-textured and adhesive wood joints. The polymer melted during ultrasound vibration completely filled the cavities formed on the surface of the wood by laser texturing. This filling of the cavities contributes to increasing the polymer mechanical interlocking on the wood surface, increasing its mechanical strength. Furthermore, the joint with textured wood has comparable lap-shear strength to the joint with adhesive wood. This outcome facilitates the manufacturing of hybrid structures using environmentally friendly, renewable materials, eliminating the need for potentially harmful adhesives and reducing the lengthy curing time typically required in the manufacturing process.
|
|
|
Shape memory polymer blends
Gregor Trimmel, Reinhold Pommer, Anna Hafner, Robert Saf, ICTM-Institute for Chemistry and Technology of Materials
Abstract:
Shape-memory polymers (SMPs) are stimuli-responsive materials which have the ability to recover from one or more temporary shape deformations into a predetermined, permanent configuration upon exposure to external triggers. This phenomenon is referred to as shape-memory effect (SME). Triggers can include temperature, electricity, magnetism, light or solvents. Development of SMPs has recently been driven by potential applications in numerous fields, such as construction, aerospace industry, soft robotics or biomedical devices.[1, 2] Polymer blending not only allows for the combination of favorable features of different raw materials, but also enables the cost-effective and convenient fabrication of material systems exhibiting shape-memory behavior.[3]
The present work deals with the investigation of thermo-responsive SMPs based on immiscible blends of ethylene-propylene-diene monomer rubber (EPDM) with a range of different thermoplastic materials (HDPE, PP, PP-c-PE and ULDPE).
|
|
|
Translation invariant dynamic mode decomposition for discrete dislocation dynamics
Gurudas Kar, Bernhard Heininger, and Thomas Hochrainer, Institute of Strength of Materials, Graz University of Technology, Kopernikusgasse 24/I, 8010 Graz, Austria
Abstract: Predicting the inelastic response of crystalline materials based on an evolving microstructure is one of the most challenging problems in applied physics. Especially the complexity involved in the evolution of the dislocation microstructure has so-far defied all attempts to build plasticity models directly on averaged descriptions of dislocations. Modern data driven methods offer new perspectives for developing physics-based models that can capture the inelastic response. In the current contribution, we focus on variants of the so-called dynamic mode decomposition (DMD)[1], which emerged in the fluid dynamics community. Recently introduced physically informed versions of DMD [2] promise to reduce computational costs and improve physical predictions.
We apply several DMD variants to data extracted from massive discrete dislocation dynamics simulations. Because these simulations are performed with periodic boundary conditions, we recently transferred the physical property of translation invariance to the non-linear so called extended DMD [3]. In this poster, we compare several DMD-based algorithms in their prediction of the spatio-temporal evolution of dislocation density variables during plastic deformation. The recently developed translation-invariant version shows superior properties in reconstructing and predicting dislocation density variables.
REFERENCES
1. Schmid, Peter J. "Dynamic mode decomposition of numerical and experimental data." Journal of fluid mechanics 656 (2010): 5-28.
2. Baddoo, Peter J., Benjamin Herrmann, Beverley J. McKeon, J. Nathan Kutz, and Steven L. Brunton. "Physics-informed dynamic mode decomposition." Proceedings of the Royal Society A 479, no. 2271 (2023): 20220576.
3. Hochrainer, Thomas, and Kar, Gurudas. “Translation invariant approximation of the Koopman operator for coupled non-linear systems”, submitted for publication |
|
|
Fabrication of continuous fiber composites utilizing a 3D printing test bench for controlled in-situ consolidation
Hannes Oberlercher, M. Laux, S. T. Amancio-Filho, Institute of Material Science, Joining and Forming, BMK Endowed Professorship for Aviation
Abstract: Continuous fiber reinforced composites (CFC) additive manufacturing (AM) is becoming increasingly important in the field of lightweight construction. The primary benefit is found in the automated manufacturing process and the production of complex geometries. Recent research on AM CFCs printed using traditional fusion filament fabrication (FFF) has revealed an increase in consolidation-related volumetric flaws, i.e. deconsolidation defects that reduce mechanical performance. Deconsolidation defects typically indicate either poor process parameter selection or insufficient in situ consolidation. This work is an inherent feature of traditional FFF, where no additional in situ consolidation pressure is applied. Several efforts have recently been made to modify the FFF of CFCs in order to minimize deconsolidation defects via in situ thermo-mechanical pressing. However, fundamental knowledge on the in situ thermo-mechanical consolidation of FFF-CFCs is limited. This paper investigates the stated issue and suggests solutions to reduce deconsolidation in FFF CF-PA6 laminates. We used a self-developed FFF 3D Printer in conjunction with a thermo-mechanical pressing unit for this purpose. The effect of extrusion-, consolidation-, and in situ consolidation pressure on laminate microstructure and flexural strength was investigated. A comparison with FFF laminates printed on a standard 3D printer was performed.
|
|
|
Effect on Paper Properties by Adding and Removing Xylan from Chemical Pulps
Jana Schaubeder, Graz University of Technology, Institute of Bioproducts and Paper Technology (BPTI)
Abstract: Xylan, one of the most abundant renewable polymers, is found primarily in the secondary cell wall, which gives plants their support and strength. To take advantage of the reinforcing effect of xylan in papermaking, it is essential to understand the role of xylan in pulp fibers, as it undergoes substantial changes during pulping. Removal and addition of xylan from pulps have been extensively investigated, but few studies have explored the combined effect of xylan adsorption and degradation at the same time, leaving the role of xylan on pulp and paper properties unclear. To address this knowledge gap, we investigated the role of xylan in pulp and paper sheets by (i) partially degrading xylan from refined elemental chlorine free bleached softwood kraft pulp (BSKP) using an endo-$\beta$-xylanase and by (ii) adsorbing beechwood xylan onto refined BSKP. Adsorption of 3% xylan resulted in improved fiber-fiber bonding concomitant with an increase in sheet density and a slight increase in mechanical performance. Enzymatic degradation of about 1% xylan from BSKP resulted in lower bond areas and decreased sheet densities. The enzymatic degradation led to a significant weakening of the fiber network in the hand sheets, which cannot be regained by adding xylan to the pulp fibers. These results show that the xylan location in pulps is critical for the resulting properties of paper hand sheets. |
|
Electrochemical investigation of symmetric aminoquinones
Janine Maier, Institute of Bioproducts and Paper Technology, TU Graz
Abstract: Quinones have a wide range of valuable properties and potential applications in medicinal chemistry, materials science, optoelectronic devices, and batteries. Molecular redesign using different functional groups like amines can optimize their properties and prevent undesired side reactions. However, particularly the synthesis of aminoquinones can be challenging at times, and there is a need for simple and efficient routes to access these compounds without metal catalysts or halogenated starting materials. Here, we demonstrate the synthesis and electrochemical characterization of a series of aminoquinones derived from renewable sources, namely vanillin or 2-methoxyhydroquinone. The aminoquinones were explored towards their stability at different pH values. At extreme pH values, the deeply colored aminoquinones decompose accompanied with a decolorization of the solutions within a few minutes (pH 14) or hours (pH 1). At intermediate pH values (3-8) the aminoquinones are stable upon storage in solution, where they feature a quasi-reversible redox chemistry and fast, diffusion limited kinetics. |
|
|
Copolymerization of epoxyeugenol and bisphenol A diglycidyl ether
Johanna Lang, Institute for Chemistry and Technology of Materials
Abstract: Johanna Lang(a), Johanna M. Uher(a), Susanne, M. Fischer(a), Assoc.Prof. Christian Slugovc(a)
(a) Christian Doppler Laboratory for Organocatalysis in Polymerization, Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse. 9, 8010 Graz, Austria;
Eugenol is a liquid phenolic compound accessible from renewable resources such as clove or cinnamon, by lignin degradation or by chemical synthesis[1]. Many monomers and their corresponding polymers have been prepared from eugenol[2]. Here, we perform the epoxidation of the double bond to obtain the corresponding liquid epoxide, namely 2-methoxy-4-(oxiran-2-ylmethyl)phenol
(epoxyeugenol, EE) in a single step, and test this monomer in the copolymerization with bisphenol A diglycidyl ether (DGEBA). In particular, we studied the polymerization reaction with 1-methylimidazol (1- MI) and Tris-2,4,6-dimethylaminomethyl phenol (K54) as initiators using isothermal and dynamic differential scanning calorimetry (DSC) to determine activation energies based on the Kissinger method[3] for different formulations.
[1] Zhang C., Xue J., Yang X., Ke Y., Ou R., Wang Y., Madbouly S. A., Wang Q. Prog. Polym. Sci. 2022, 125, 101473.
[2] Morales-Cerrada R. Molina-Gutierrez S., Lacroix-Desmazes P., Caillol S. Biomacromolecules 2021, 22, 3625–3648.
[3] Lascano D., Quiles-Carrillo L., Balart R., Boronat T., Montanes N. Polymers 2009, 11, 391. |
|
|
Chemo-mechanical coupling of vacancy condensation to voids at finite strains using phase-field modeling
Kevin Pendl, Institute of Strength of Materials (IFL), Graz University of Technology
Abstract: High vacancy concentrations in crystals may lead to the formation and growth of voids. Elevated concentrations may result from irradiation or large plastic deformation. In radiation materials science, void formation due to vacancy supersaturation has recently been modeled using spatially resolved approaches like the phase-field method, where mathematically sharp moving interfaces are substituted with diffuse inter-phase layers. The developed models for irradiated materials usually target microstructure evolution without incorporating the mechanical stress field. However, vacancies interact with the stress field via their eigenstrain field, which emerges from the relaxation of the surrounding crystal lattice if a single atom is removed. Therefore, understanding void formation and growth requires a proper coupling of vacancy diffusion to the stress field.
In our recent work [1], we proposed a model for coupling elastically driven vacancy diffusion at small strains with a phase-field model of void surfaces. The proposed model overcomes the shortcomings of former models in the literature, such as stress artifacts in the vicinity of voids. This is achieved by making the vacancy eigenstrain a function of the non-conserved order parameter that distinguishes the void and crystal phases. We present the extension of our model to finite strains. Using a multiplicative split of the deformation gradient, the kinematics of vacancy–void interactions and their impact on volumetric distortions are appropriately incorporated via the order parameter dependent vacancy eigenstrain. The thermodynamically consistent model was derived using the Coleman–Noll procedure and implemented in the multi-physics software tool DAMASK [2]. Results of the influence of chemo-mechanical coupling on void condensation are shown.
[1] K. A. Pendl and T. Hochrainer. Coupling stress fields and vacancy diffusion in phase-field models of voids as pure vacancy phase. Comput. Mater. Sci., 224:112157, May 2023.
[2] F. Roters et al. DAMASK – The Düsseldorf Advanced Material Simulation Kit for modeling multi-physics crystal plasticity, thermal, and damage phenomena from the single crystal up to the component scale. Comput. Mater. Sci., 158:420–478, February 2019. |
|
|
Designing innovative bulkheterojunction organic photocapacitors to facilitate wireless stimulation of neurons.
Konrad Binter
Abstract: Konrad Binter,a Mathias Polz,b Daniel Ziesel,b Thomas Rath,a Gregor Trimmel,a Theresa Rienmüller b,c
a Institute for Chemistry and Technology of Materials, NAWI Graz,
Graz University of Technology, Graz, Austria
b Institute of Health Care Engineering with European Testing Center of Medical Devices, Graz University of Technology, Graz, Austria
c BioTechMed Graz, Graz, Austria
Enhancing recovery processes in the aftermath of neurological disorders, such as stroke or brain trauma, is facilitated by the positive effects of neuronal stimulation. There is a current push to create lightweight and wireless devices for electrical stimulation with the aim of improving the overall quality of life for patients. Organic photocapacitors, known as photocaps, exhibit swift charging upon exposure to light, leading to the generation of an electric field that can be harnessed to stimulate cells in their proximity.
The contribution of our working group for this project is focused on the fabrication of bulk heterojunction photocapacitors that will meet the requirements that are necessary for this type of application. This involves creating innovative structures through the use of various interlayers and adjusting the properties of our device by modifying process parameters and incorporating suitable additives.
To determine if our photocap meets the requirment for clinical application there is a need to test the biocompatibility, electric field distribution, and influence on cellular growth. Biocompatibility assessments involve Chick Chorioallantoic Membrane (CAM) assays and colorimetric LDH cytotoxicity assays on cortical neurons. The investigation extends to the generated electric field's spatial distribution and long-term stability, utilizing a custom measurement system.
1 A. Savva, A. Hama, G. Herrera-Lopez, T. Schmidt, L. Migliaccio, N. Steiner, M. Kawan, H. Fiumelli, P. J. Magistretti, I. McCulloch, D. Baran, N. Gasparini, R. Schindl, E. D. Glowacki, S. Inal, Photo-Chemical Stimulation of Neurons with Organic Semiconductors. Adv. Sci. 2023, 10, 2300473. |
|
|
Smart photoswitchable Hydrogels from Azobenzene-crosslinked Carbohydrates
Konstantin Knaipp, Institute of Physical and Theoretical Chemistry, TU Graz
Abstract: Knaipp K. [a], Kargl R. [b], Stana Kleinschek K. [b], Gescheidt G. [a]
[a] Institute of Physical and Theoretical Chemistry, Graz Technical University, Austria
[b] Institute of Chemistry and Technology of Biobased Systems, Graz Technical University, Austria
Functional materials that can take up and release guest molecules upon stimulation with light can find applications in the area of targeted drug release. [1] Such systems are often based on azobenzene, a molecular photoswitch that can be photoisomerized between its cis and trans isomers. [2] The bacterial polysaccharide dextran and its modifications have been used in a wide variety of drug delivery systems. [3]
|
|
|
Surface functionalization of nanoporous gold for biosensing applications
Lara Marie Novak, Institute of Materials Physics, NAWI Graz
Abstract: Lara Marie Novak$^a$, Elisabeth Hengge$^b$, Eva-Maria Steyskal$^a$, Bernd Nidetzky$^b$, Roland Würschum$^a$
$^a$Institute of Materials Physics, NAWI Graz, TU Graz
$^b$Institute of Biotechnology and Biochemical Engineering, NAWI Graz, TU Graz
Nanoporous gold (npAu) electrodes are perfectly suited platforms for sensing applications due to their self-standing, well-conducting structure and high surface-to-volume ratio. They can be prepared particularly well by electrochemical dealloying, a process that removes the less noble component from an alloy. The material’s pore size can then be adjusted for the intended application through thermal annealing. By surface modification with covalently bound self-assembled monolayers (SAMs) that hold specific functional groups (FG), it is possible to bind active enzymes on the biocompatible carrier material for biosensing and catalysis.
The aim of our current research is to gain a fundamental understanding of the immobilization behaviour of enzymes on the nanoporous metal. To achieve this, the well-studied enzyme L-lactate oxidase (LOx) from Aerococcus viridans was chosen for a case study. LOx is highly selective in catalysing the oxidation of L-lactate while reducing an electron mediating species, which can further be detected electrochemically at the npAu electrode’s surface making the system useful for bio-applications. Immobilization of this enzyme on several SAMs provides insights into the effects of the different FGs (such as sulfonic acid, carboxylic acid, or amine groups) and the nanoporous metal as a carrier. Our study evaluates parameters such as catalytic effectiveness, immobilization yield, and stability of the immobilized biomolecule. These findings provide a promising basis for developing a future fast-responding L-lactate sensing platform.
This work is supported by the Lead Project Porous Materials @ Work for Sustainability at TU Graz, as well as NAWI Graz.
|
|
|
Structural evolution of nanoporous copper during dealloying studied via kinetic Monte Carlo simulation
Laura Kainz
|
|
Concrete corrosion analysis using optical chemical sensors and imaging
Leonard Sterz(1), Bernhard Müller(1), Isabel Galan(3), Cyrill Grengg(3), Marlene Sakoparnig(2), Florian Mittermayr(2), Joachim Juhart(2) and Torsten Mayr(1), (1) Institute of Analytical Chemistry and Food Chemistry, (2) Institute of Technology and Testing of Building Materials, (3) Institute of Applied Geosciences
Abstract: Introduction
Corrosion-related damages on concrete infrastructure account globally for several billion US dollars annually. Roughly 38% of these costs could be saved by the application of optimized materials and/or more efficient monitoring technologies. Currently, the most commonly used methods to assess the state of a concrete structure in terms of carbonation and chloride penetration, are phenolphthalein coloration and silver nitrate titration, respectively. However, the accuracy of the methods and the correlation of the obtained results with the actual state of the considered structure in terms of potential damage are constantly being questioned.
Methods
Optical chemical sensors are applied based on luminescent pH and chloride sensitive dyes, to quantitatively access the pH evolution and chloride concentration of cement-based construction materials. Dual lifetime referencing was applied for chemical imaging and sensor probes. For this method a fluorescent pH or chloride indicator dye (short lifetime) is combined with a phosphorescent reference dye (long lifetime) with similar spectral properties.
Results
We present high resolution pH imaging, demonstrated on various real concrete samples with different levels of carbonation and a comparison with the standard method (phenolphthalein coloration). We show that the imaging method provides high alkalinity pH-profiles of carbonation with a higher level of information than the standard method. Using this technique, we critically discuss crucial aspects of pH measurement, which have to be reconsidered when determining the pH of concrete structures. We also show an optical chloride sensor suitable for the measurement of released chloride from concrete powder samples and point out the challenges of sample preparation.
The promising results show that the application of this novel methodology will allow for a better assessment of the concrete structures’ state and for a better understanding of the processes taking place in cementitious matrices during hydration and exposure to the environment. The methodology has the potential to enable field measurements with a faster detection and on-sight decision making on the status of buildings.
|
|
|
Phonon bands and thermal conductivities of crystalline organic semiconductors using machine-learned Moment Tensor Potentials.
Lukas Legenstein, Institute of Solid State Physics
Abstract: Phonons affect transport properties in crystalline organic semiconductors either by scattering with charge carriers or as the main carriers of thermal energy. Modelling these phonons and their transport gives a distinct advantage compared to experiments by providing direct insight into the relevant processes at an atomistic level. With the advent of machine-learned potentials, which often achieve accuracies comparable to the ab initio methods they are trained on, the computational cost of these simulations is greatly reduced. In this work we first determine the vibrational properties of a prototypical hydrogen-bonded organic semiconductor with dispersion-corrected density functional theory and analyse the relations between its structure and vibrations. Then, we use machine-learned Moment Tensor Potentials (MTP) to reproduce the ab-initio phonons and find that excellent agreement can be achieved. Further, we go beyond the harmonic approximation by using MTPs to determine the lattice thermal conductivity by solving the Wigner transport equation. With this approach the “wave-like” conduction mechanisms arising from inter-band tunnelling are accounted, which turns out to increase the predicted thermal conductivity significantly in these systems. The relevance of the wave-like conduction is highlighted by comparing thermal conductivities of two polymorphs with only marginally different stacking motifs. Importantly, the presented approach provides direct insight into the (anisotropic) contributions of individual modes to the thermal conductivities. |
|
|
Modelling the Thermal Conductivity of Crystalline Polymers
Lukas Reicht, Institute of Solid State Physics
Abstract: Disordered polymers are typically characterized by a very low thermal conductivity on the order of 0.1 W/mK. In contrast, recent experiments showed that, when polymers are highly aligned (crystalline), polyethylene (PE) can reach a thermal conductivity of ~104 W/mK, which would be interesting for applications. Newly developed machine-learned potentials (MLP) promise to be an efficient and accurate tool for calculating these thermal conductivities. Applying a new methodology, however, requires a thorough benchmarking. We performed such a benchmarking for moment tensor potentials (MTPs), which are a flavour of machine-learned potential, by calculating various phonon related properties of polyethylene (PE), polythiophene (PT), and poly(3-hexyl-thiophene) (P3HT). Based on the calculated phonon band-structures, elastic constants, thermal expansion coefficients, and thermal conductivities, we conclude that the accuracy of MTPs can be substantially increased by a deliberate choice of training data adapted to the intended use case. Having established the accuracy of the trained MTPs, they are used to calculate thermal conductivities of PE and PT using the Boltzmann transport equation (BTE), non-equilibrium molecular dynamics (NEMD), and the approach-to-equilibrium molecular dynamics (AEMD). This provides complementary atomistic insights into the factors determining heat transport. |
|
|
3D Nanoprinting of advanced AFM Nanoprobes
Lukas Seewald, CD Laboratory DEFINE, Graz University of Technology
https://cloud.tugraz.at/index.php/s/rmx68gAncsycXAG
Abstract: 3D Nanoprinting of advanced AFM nanoprobes
L. M. Seewald (1), R. Winkler (1), M. Brugger-Hatzl (2) and H. Plank (1,2,3)
1 Christian Doppler Laboratory - DEFINE, Graz University of Technology, 8010 Graz, Austria
2 Graz Centre for Electron Microscopy, 8010 Graz, Austria
3 Institute of Electron Microscopy, Graz University of Technology, 8010 Graz, Austria
E-Mail: lukas.seewald@felmi-zfe.at
Scanning probe techniques have evolved into an indispensable technology pool for surface characterization in diverse research areas from materials science over biotechnology towards life sciences. In view of this, atomic force microscopy (AFM) plays a central role due to its low demands on surfaces and the compatibility with various environ-ments. At the same time, lateral resolution in the lowest nanometer range can be achieved for conventional setups, while advanced operation modes provide access to functional surface properties, including electrical, magnetic, thermal, optical or mechanical properties. The latter possibilities, however, require functional nanoprobes, which are mostly achieved by either coating of conventional nanoprobes or by fabrication of a solid functional nanoprobe tip, which not only increases the achievable resolution due to sharper apices but also eliminates the risk of delamination, which renders such probes useless. Related fabrication approaches include the mounting of specifically grown crystals on pre-structured cantilevers or the application of particle beam induced deposition techniques for direct growth of functional nanoprobes. Within this frame, focused electron beam induced deposition (FEBID) has evolved into a reliable, additive direct-write manufacturing technique at the nanoscale. Aside controlled fabrication of 3D (nano-)designs, material properties are naturally the decisive element when advanced operation modes are targeted. Aside of specifically designed precursor compounds, post-growth treatments, such as the exposure to temperatures / gases / electron beams in different environments, have considerably expanded the functional tunability towards the intended properties.[1]
In this contribution, FEBID-based 3D nanoprinting will be revisited in the context of the here relevant fabrication of advanced AFM nanoprobes. Process aspects to achieve high-fidelity geometrical replication and post-treatment processes to specifically tune materials properties are also included for further discussions of 3D nanoprobe concepts, which are developed in our workgroup in collaboration with industry. We will focus on thermal[2], electrical[3] and magnetic[4] nanoprobes, where we not only highlight the advantages but also demonstrate the superior performance in comparison to commercially available alternatives. We conclude the contribution with a view on ongoing activities but also discuss remaining challenges, to provide a comprehensive picture of the current status of FEBID-based, 3D nano-printing of advanced AFM nanoprobes.
1. Plank, H. et al. Focused Electron Beam-Based 3D Nanoprinting for Scanning Probe Microscopy: A Review. Micromachines 11, 48 (2019).
2. Sattelkow, J. et al. Three-Dimensional Nanothermistors for Thermal Probing. ACS Appl. Mater. Interfaces 11, 22655–22667 (2019).
3. Seewald, L. M. et al. 3D Nanoprinting of All-Metal Nanoprobes for Electric AFM Modes. Nanomaterials 12, 4477 (2022).
4. Winkler, R. et al. Additive Manufacturing of Co 3 Fe Nano-Probes for Magnetic Force Microscopy. Nanomater. 2023, Vol. 13, Page 1217 13, 1217 (2023).
|
|
|
Monosilane as a Cheap Feedstock for Branched Oligohydridosilanes
Madeleine Heurix, Institute of Inorganic Chemistry
Abstract: Recently, liquid phase deposition (LPD) attracted attention, due to its reduced production costs as compared to standard vacuum-based approaches. In this context, oligohydridosilanes like compound 1 are ideal precursors and decompose to elemental silicon upon heating to T > 300 °C.[1]
However, the high production cost of compound 1, prevented its implementation as industrial precursor so far. Therefore, this study was aimed to investigate possible synthetic routes, starting with a cheaper feedstock, to obtain higher silicon hydrides SinH2n+2. The method of Sundermeyer et al. and Fehér at al. was revisited, using monosilane to generate potassiumsilanide 2 and further potassiumisotetrasilanide 3[2].
The generation of compound 3 enabled the selective generation of compounds 4 and 5 which are oligohydridosilanes (Figure 1).
[1] S. Wieber, M. Patz, M. Trocha, H. Rauleder, E. Müh, H. Stueger, C. Walkner, WO2011061088A1.
[2] a) T. Lobreyer, W. Sundermeyer, H. Oberhammer, Chem. Ber. 1994, 127, 2111; b) F. Fehr, M. Krancher, M. Fehr, Z. Anorg. Allg. Chem. 1991, 606, 7
|
|
|
Introducing multiscale porosity to the ternary metal chalcogenide ZnIn2S4 for photocatalysis
Marco Sigl, ICTM, Institute for Chemistry and Technology of Materials
Abstract: Marco Sigl(a), Melissa Egger(a), Fernando Warchomicka(b), Heinz Amenitsch(c), Gregor Trimmel(a), Thomas Rath(a)
a) Institute for Chemistry and Technology of Materials, NAWI Graz, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.
b) Institute of Materials Science, Joining and Forming, Graz University of Technology, Kopernikusgasse 24, 8010 Graz, Austria.
c) Institute of Inorganic Chemistry, NAWI Graz, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.
Optimizing the catalytic activity of photocatalysts is of great interest for the realization of the energy revolution. Unlike photovoltaics, transferring sunlight into electrical energy, photocatalysts provide the possibility to employ sunlight for the synthesis of so called solar fuels, reactants for chemical reactions, or can be utilized for waste water treatment. However, for heterocatalysts a common problem is their usually low surface-area. Here, we apply a single source precursor method using metal xanthates for the synthesis of the established photocatalyst zinc indium sulfide. In combination with microsphere colloidal lithography, we successfully prepared hierarchically porous zinc indium sulfide thin films with macropores in the 300 nm regime with microspores around 1.6 nm. Furthermore, we performed photocatalytic dye degradation tests with Rhodamine B to confirm a 3.3-fold increase in specific catalytic activity compared to a bulk film. These results suggest promise to optimize photocatalytic activity via multiscale porosity.
References
1 H. Qian, Z. Liu, Z. Guo, M. Ruan and J. Ma, J. Alloys Compd., 2020, 830, 154639.
2 T. Yan, Q. Yang, R. Feng, X. Ren, Y. Zhao, M. Sun, L. Yan and Q. Wei, Front. Environ. Sci. Eng., 2022, 16, 131.
3 E. Vakalopoulou, T. Rath, F. G. Warchomicka, F. Carraro, P. Falcaro, H. Amenitsch and G. Trimmel, Mater. Adv., 2022, 3, 2884–2895.
4 J. Yu, Q. Yan and D. Shen, ACS Appl. Mater. Interfaces, 2010, 2, 1922–1926.
5 E. Vakalopoulo, T. Rath, M. Kräuter, A. Torvisco, R. C. Fischer, B. Kunert, R. Resel, H. Schröttner, A. M. Coclite, H. Amenitsch and Trimmel Gregor, ACS Appl. Nano Mater., 2022, 5, 1508–1520.
|
|
|
Synthesis of luminescent organic radicals for OLEDs
Marco Zechner
Abstract:
|
|
|
Effect of printing parameters to obtain porous Ni via LPBF
Marlene Eichlseder, Institute of Materials Science, Joining and Forming
Abstract: Laser Powder Bed Fusion (LPBF) is a method of additive manufacturing which offers the possibility to create highly complex structures. Nickel is a material used in many catalytic processes, which require a large surface area. This area can be increased by printing a structure with a large surface, such as a gyroid, or by printing the bulk material itself as porous material. For the latter approach, a printing parameter study was conducted to reveal the influence of various parameters on the density obtained. To achieve a low density, which is mainly based on lack-of-fusion defects, a reduced layer height is favourable as well as low surface energy input. |
|
Presentation of the paper: Ionizing Radiation Influence on 28-nm MOS Transistor’s Low-Frequency Noise Characteristics
Martin Apro, Institute of Electronics, TU Graz
Abstract: In this work, we report distinct scenarios concerning the minimum-sized (100x30 and 100x40 nm) transitions of low-frequency noise characteristics in high-k metal-gate bulk CMOS transistors induced by Total Ionizing Dose (TID). Due to strong bias dependence of the noise characteristics, differentiating between noise shifts caused by the effective biasing change and the contribution of the newly generated traps becomes extremely challenging. In order to better understand the effects of irradiation, transistor noise had to be characterized at several biasing points, both in linear and saturation regions, before and after exposure to 1 Grad (SiO2) of TID. We present examples of irradiation-generated Random Telegraph Noise (RTN) defects as well as various TID effects on noise Power Spectral Density (PSD) curves with pre-existing RTN sources.
|
|
|
Trapping the key intermediate in nucleophile-initiated Michael reactions
Matthias Steiner, Institute for Chemistry and Technology of Materials
Abstract: Matthias Steiner(a), Assoc.Prof. Christian Slugovc(a)
a Christian Doppler Laboratory for Organocatalysis in Polymerization, Institute for Chemistry and Technology of Materials, Graz University of Technology, Stremayrgasse. 9, 8010 Graz, Austria; matthias.steiner@tugraz.at
Phosphines are strong, versatile nucleophiles that are able to catalyze numerous reactions giving access to a wide variety of organic products. One reaction prominently catalyzed by phosphines is the oxa-Michael reaction, where alcohols react with Michael acceptors to form ethers. In our recent studies, we focused on oxa-Michael polymerization as a green alternative to aza- and thia-Michael reactions that employ toxic and environmentally unfriendly amines and thioles, respectively[1]. The first step in catalysis is the formation of a zwitterion, generated from a nucleophile and the Michael-acceptor.
In our research, ortho hydroxy substituted phosphines are reacted with Michael acceptors generating zwitterions that are highly stabilized through the interaction of the alkoxide and the phosphonium ions. The reaction of 2,4-di-tert-butyl-6-diphenylphosphino-phenol (1) with Michael acceptors proceeds in good to near quantitative yields and the obtained zwitterions are air and moisture stable. The crystal structures of some of the zwitterions were obtained as well.
Investigations into the kinetics of zwitterion formation are carried out in order to generate further understanding of the governing factors of phosphine-based Michael reaction catalysis. Thereby, we seek to improve catalysis in polymerization and additional investigations will also be focused on zwitterionic polymers from these stabilized charged compounds [2].
References
1 Fischer, S. M.; Renner, S.; Boese, A. D.; Slugovc, C. “Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions.” Beilstein J. Org. Chem. 2021, 17, 1689–1697.
2 Steiner, M. R.; Schmallegger, M.; Donner, L.; Hlina, J. A.; Marschner, C.; Baumgartner, J.; Slugovc, C. Beilstein J. Org. Chem. 2024, 20, 41–51.
|
|
|
Noble-metal free photocatalysis – nickel sulfide modified titania for solar hydrogen generation
Melissa Egger, ICTM
Abstract: The endeavor to meet the ever-growing energy demand employing renewable sources makes the development of technologies for their efficient utilization crucial. An important field of research is the solar-powered generation of chemical fuels such as hydrogen. The nontoxic, cheap, and abundant photocatalyst TiO2 is promising for this application, but suffers from low utilization of visible light and fast charge carrier recombination. Therefore, the use of cocatalysts is necessary, which enhance visible light utilization by lowering the band gap and improve charge carrier separation. Currently mostly noble-metals are used, but replacing them with metal sulfides can significantly lower the cost. We modified mesoporous titania films with a thin layer of nickel sulfide using nickel xanthates as single-source precursors. Xanthates provide a simple method to prepare homogeneous metal sulfide films with tunable stoichiometry, phase, and morphology, depending on the xanthate’s ligand. We prepared and characterized a range of different nickel xanthates, and evaluated the photocatalytic performance of our modified catalysts using hydrogen evolution experiments with methanol as sacrificial electron donor. The first hydrogen evolution experiments demonstrated a significant increase of 90 times the efficiency for the NiS modified films, compared to the pristine titania. |
|
|
3D printable metamaterial for orbital angular momentum generation
Michael Töfferl, Institute of Electrical Measurement and Sensor Systems
Abstract: Orbital angular momentum (OAM) in the millimetre wave regime is a key technology for future wireless communication. With an additional degree of freedom OAM can raise the maximum bandwidth and the capacity of data transfer. Besides telecommunication OAM beams can also be used for sensing applications e.g. by exploiting the rotational doppler effect. Metamaterials are one method for OAM generation. There are several ways of constructing these metamaterials including metallic resonant structures. One of the simplest ways are phase plates which do not need metallic structures and can even be 3d printed.
For this purpose, we present a 3D printable metamaterial for millimetre waves to generate OAM with a first order mode. We introduce a simple analytical approach to describe the phase shift for a square unit cell with a cylindrical hole. The concept of the metamaterial works by creating local phase shift per unit cell via modification of the geometry. This changes the effective permittivity and allows to construct an artificial pattern of unit cells to design a phase plate for OAM. Furthermore, a lens pattern is integrated to counteract the highly divergent behaviour of the generated OAM beam. The design also considers the possibility of manufacturing the metamaterial with a standard fused deposit modeling (FDM) 3D printer.
|
|
|
3D-Nanoprinting of advanced high-resolution Magnetic Force Microscopy Tips
Michele Brugger-Hatzl, Graz Centre for Electron Microscopy
Abstract: M. Brugger-Hatzl1 , R. Winkler2 , L. Seewald2 , M. Huth3 , S. Barth3 , and H. Plank1,2,4,*
1 Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria
2 Christian Doppler Laboratory - DEFINE, Graz University of Technology, 8010 Graz, Austria
3 Institute of Physics, Goethe University, 60438 Frankfurt am Main, Germany
4 Institute of Electron Microscopy and Nanoanalysis, Graz University of Technology, 8010 Graz, Austria
* email: harald.plank@felmi-zfe.at
Scanning electron microscopy (SEM) has truly unique advantages, as it provides information about surface morphology, granular composition or chemical composition. Nevertheless, when aiming on quantitative 3D nano-topography details and / or functional surface properties it runs into its conceptual limitations. These details, however, can be provided by atomic force microscopy (AFM), which therefore, is an ideal complementary technology. In particular, advanced AFM modes reveal functional surface properties such as electric conductivity, magnetic properties, surface potentials, mechanical peculiarities, or even optical and thermal properties. These advanced modes require functional AFM tips, which mostly rely on additional thin film coatings. This, in turn, entails two main disadvantages: (1) reduced lateral resolution due to increased apex radii, which is in conflict with the still decreasing feature sizes of nanoscale systems, and (2) delamination risks during AFM operation, which affects resolution, and lateral correlation to morphology. To exploit the full potential of advanced AFM modes, it is therefore of great interest to develop new approaches for the fabrication of functional high-resolution nano-probes.
Based on that motivation, focused electron beam induced deposition (FEBID) is used, which is an emerging additive direct-write manufacturing technology for novel 3D nano-probe concepts with industrial relevance.[1] In this contribution, the focus lies on the fabrication of magnetic tips for magnetic force microscopy (MFM) with the aim of fully magnetic high-resolution tips, which reveal an all-metal, coating free character. For that, we use a HCo3Fe(CO)12 precursor,[2] and studied the impact of FEBID process parameters, including electron energies, beam currents and precursor temperature by using a multitude of characterization techniques. In a second step, the focus lies on the optimization of tip geometries to provide sharpest apexes and most rigid overall designs to fulfil the high demands during AFM operation. By that, fabrication protocols were derived, which provides metal contents above 90 at.% with apex radii in the sub-10 nm regime on a regular basis. In the final step, the performance of such FEBID-based MFM tips is demonstrated with focus on lateral resolution, magnetic sensitivity, signal quality, and wear resistance. As will be shown, the here introduced MFM tips are superior in all aspects compared to commercially available MFM tips. By that, we demonstrate another FEBID-based 3D nano-probe concept for MFM aside of electric [3] and thermal nano-probes [4] with excellent properties, based on the unique possibilities of this emerging technology.
References
[1] H. Plank et al., “Focused electron beam-based 3D nanoprinting for scanning probe microscopy: A review”, Micromachines, vol. 11, no. 1. MDPI AG, Jan. 01, 2020. doi: 10.3390/mi11010048.
[2] F. Porrati et al., “Direct writing of CoFe alloy nanostructures by focused electron beam induced deposition from a heteronuclear precursor”, Nanotechnology, vol. 26, no. 47, p. 475701, Nov. 2015, doi: 10.1088/0957-4484/26/47/475701.
[3] L.M. Seewald et al., “3D Nanoprinting of All-Metal Nanoprobes for Electric AFM Modes”, Nanomaterials 2022, 12, 4477. https://doi.org/10.3390/ nano12244477
[4] J. Sattelkow et al., “Three-Dimensional Nanothermistors for Thermal Probing”, ACS Applied Materials & Interfaces 2019 11 (25), 22655-22667, doi: 10.1021/acsami.9b04497 |
|
|
Development of enzyme-modified metal electrodes for sucrose biosensing
Mislav Sušac, Institute of Biotechnology and Biochemical Engineering
Abstract:
Mislav Sušac 1), Elisabeth Hengge 1), Chao Zhong 1), Eva-Maria Steyskal 2), Roland Würschum 2) and Bernd Nidetzky 1)
1)Institute of Biotechnology and Biochemical Engineering, Graz University of Technology
2)Institute of Materials Physics, Graz University of Technology
Enzyme electrodes are miniature devices capable of transducing enzymatically catalyzed reaction into an electrochemical signal, which makes them an essential component for biosensors and bioelectrocatalysis. They consist of a redox active enzyme immobilized on an electrode material. Enzyme immobilization highly relies on the type of the electrode that is being employed and its intrinsic surface characteristics. Gold electrodes, with its high conductivity, makes it a perfect candidate. Since metals can sometimes cause protein denaturation, surface should be modified to minimize metal-protein contact. Self-assembled monolayers (SAMs), which are organic molecules that can bind spontaneously to the metal surface and can have a wide range of functional groups on their ends, can be employed to tailor the chemical and physical properties of surfaces [1]. For the first time, we employ a new flavin-adenine dinucleotide (FAD) dependent oxidoreductase, which can utilize a broad range of substrates and its low activity with molecular oxygen makes the system well suited for efficient electron transfer to the electrode [2]. The electrode system is designed as a plain gold electrode, whose surface is modified with SAMs and additionally immobilized enzymes. In this study, we use strongly charged surface groups to immobilize enzymes on metal electrodes by means of electrostatic interactions. Several SAMs were tested, having differently charged functional groups (e.g., sulfonic, amino, or carboxylic group). From the results obtained by cyclic voltammetry and chronoamperometry, 2-mercaptoethanesulfonic acid (MESA) proved to be the best candidate. The system was constructed by using extrinsic redox-active compounds (e.g., benzoquinone, ferricyanide ions, etc.) which act as mediators in the electron transfer cascade (mediated electron transfer, MET). The system was characterized by electrochemical and biochemical methods to gain complementary insights. The results not only show highly promising results for low concentration sucrose detection but also contribute to the fundamental understanding of the complex metal-SAM-enzyme interaction. In future studies, these findings will be used to construct novel enzyme electrodes based on nanoporous metals.
Reference:
[1] E. Hengge, et al., Phys. Chem. Chem. Phys., 23 (2021) 14457
[2] J. Bitter, et al., Nature Communications, 14 (2023) 7123
|
|
|
How accurate can machine-learned force fields describe spin-polarization dependent vibrations of HKUST-1 compared to density functional theory?
Nina Strasser, Institute of Solid State Physics
Abstract: Vibrations crucially impact the thermodynamic and transport properties of all materials, including metal-organic frameworks (MOFs). Accurately modelling vibrational properties of highly complex materials like MOFs can, however, become a sizable challenge. In many MOFs the situation is further complicated by the fact that they contain metal ions with unpaired spins, whose relative alignment in the solid can impact its (vibrational) properties.
In this study spin-dependent vibrational properties of the MOF HKUST-1 are explored using density functional theory and reproduced using machine-learned interatomic potentials [1]. Phonon bands were reproduced with an accuracy ranging from 3 to 7 cm^-1. Notably, the force-field parametrization process involves the explicit consideration of spins only during the generation of reference data, which were generated using active learning approaches [2] that combine ab initio and force-field-based molecular dynamics runs.
[1] I. S. Novikov, K. Gubaev, E. V. Podryabinkin, A. V. Shapeev, Mach. Learn.: Sci. Technol. 2021, 2, 025002.
[2] R. Jinnouchi, K. Miwa, F. Karsai, G. Kresse, R. Asahi, J. Phys. Chem. Lett. 2020, 11, 6946-6955. |
|
|
In operando monitoring electrodeposition of Mesoporous PtNi films by Grazing Incidence X-ray Scattering
Philipp Aldo Wieser, Institute of Inorganic Chemistry, TU Graz
Abstract: Micelle-assisted electrodeposition of mesoporous alloys has attracted a lot of interest recently, as these mesoporous films show promising properties for Fuel Cells, sensors, etc. However, previous studies have shown differences in the performance of these films depending on a variety of synthetic parameters, e.g., deposition rates and loading, suggesting changes in the morphology of the deposited films that hinder their successful application.
To understand and mitigate these morphological changes, we have characterized mesoporous PtNi films during electrochemical deposition by in operando Grazing Incidence Small and Wide Angle X-ray Scattering. The electrochemical deposition of PtNi was performed at potentials ranging from -0.6 to -1.0 V vs AgCl, from an aqueous electrolyte containing a triblock copolymer surfactant, Pluronic P123, as micellar templating agent.
Our custom developed miniaturized electrochemical cell with Kapton entrance windows and an X-ray beam path of 3 mm through the electrolyte in combination with the brilliant Synchrotron Source at the SAXS beamline at Elettra allowed us to monitor the growth of the mesoporous films with a temporal resolution of 1 s. The combination of the structural data from GISAXS, the chemical information from GIWAXS analysis and the chronoamperometry give novel insights into the kinetics of the micelle-assisted electrodeposition process. |
|
|
Investigation of 2D Material Surfaces with Helium Atom Scattering
Philipp Maier, Institute of Experimental Physics
https://www.tugraz.at/surfaces
|
|
|
Structural Characterisation of Nanoporous Copper
Prabhu Prasad Biswal, Institute of Solid State Physics
Abstract: Nanoporous metals are metals with features in the pore structure in the range of 100 nm or less. Nanoporous copper (np-Cu) has recently attracted attention as an alternative to nanoporous gold or platinum. Our np-Cu is prepared by in-situ alloying of aluminium and copper using a 3D laser printer, followed by annealing at 530° C, and a subsequent de-alloying process to remove aluminium. The structural properties of the prepared Al-Cu alloy and np-Cu, including morphology, crystal structures, and chemical composition were systematically compared using X-ray diffraction and X-ray fluorescence spectroscopy; scanning electron microscopy provides surface topography and composition. In addition, the pore size distribution and internal surface area of np-Cu are quantified using micro-computed tomography and mercury intrusion porosimetry. After de-alloying, domains retain their spatial position and extension while their composition changes. |
|
|
True minimum energy configurations of 2D stacked MOFs and COFs
Robbin Steentjes, Institute of Solid State Physics
Abstract: Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are renowned for their simplistic and modular crystal structure. They are often said to behave 'like LEGO®', combining organic linkers and metal-oxo nodes into predictable patterns. Many systems, however, are not as ideal as often assumed. For example, layered MOFs and COFs, where 2-dimensional nets are stacked in the third dimension to form 3D crystals can, and will, assume a wide variety of stacking modes.
In this contribution, we use Density Functional Theory (DFT) to generate data on the stacking energy as a function of the slip between neighboring layers. We use Gaussian Process Regression to interpolate the data, and map the stacking energy landscape. From this, we can identify local minima, which indicate stacking modes. |
|
Squaraines are strong(ly coupled) stuff: Modeling higher excitations with Davydov splitting
Robert Schwarzl, Maximilian Jeindl, Manuela Schiek, Davide Giavazzi, Anna Painelli, Frank C. Spano, Andreas Windischbacher, Peter Puschnig, Markus Koch, Institute of Experimental Physics, TU Graz; LIOS and ZONA, JKU Linz, PTB Braunschweig; University of Parma; Temple University, Philadelphia; University of Graz
Abstract: Squaraines are a versatile class of chromophores acting as organic semiconductors in the solid state. Numerous demonstrated applications ranging from dye-sensitized solar cells to various sensors utilize their pronounced structure-function relationship. In particular, the different crystal morphology has a major impact on the light-matter interaction, as was shown in recent experiments [1,2], and as such good models are required to gain insight into the nature of the resulting changes. As can be seen in references [3,4], the essential states model for donor-acceptor-donor chromophores is particularly useful for squaraines.
We report the results of applying this model to the orthorhombic polymorph of an anilino squaraine with iso-butyl side chains. This model system is especially interesting due to the oblique arrangement of four monomers in the unit cell, resulting in multiple splitting of the first excited state. Using transient absorption microscopy (TAM), which provides femtosecond temporal and (sub-)micrometer spatial resolution [5], first results of the Koch group at TU Graz indicate the existence of collective, polarization-dependent higher excitations. These results are consistent with multi-excitonic states resulting from the strong intermolecular coupling in the essential states model, a result I am particularly interested in discussing with other participants.
The abstract image shows the simplified geometry used to model intermolecular interactions in the essential states model.
[1]: Cryst. Growth Des. 2017, 17, 12, 6455–6466
[2]: J. Phys. Chem. Lett. 2021, 12, 12, 3053–3058
[3]: J. Phys. Chem. C 2015, 119, 33, 18964–18974
[4]: J. Phys. Chem. C 2020, 124, 7, 4032–4043
[5]: Opt. Express 30, 34385-34395 (2022)
|
|
|
Tris(trimethylsilyl)germane (Me3Si)3GeH: A Molecular Model for Sulfur Passivation of Ge(111) Surfaces
Roland Fischer, Institute of Inorganic Chemistry
Abstract: Treatment of hydrogen terminated germanium surfaces with various sulfur sources constitutes the method of choice for wet chemical surface passivation. [1] Such wet chemical protocols include the processing with e.g. ammonium sulfide as sulfur source. [2] Despite intensive investigations, details about the mechanism, the actual chemically active species, reaction kinetics and activation energies remain largely undisclosed.
As surface reactions are difficult to assess directly, we set out to investigate the reaction of tris(trimethylsilyl)germane, (Me3Si)3GeH, towards sulfur reagents by means of heteronuclear NMR spectroscopy and use it as a molecular model substance for a hydrogen terminated Ge(111) surface. Temperature dependent NMR spectroscopic investigations provided kinetic data for the reaction of (Me3Si)3GeH with sulfur and allowed for the determination of the activation parameters.
References:
[1] C. Claeys, E. Simonen, Eds., Germanium Based Technologies: From Materials to Devices (Elsevier, Oxford, 2007).
[2] J. Buriak, Chem. Rev., 2002, 102, 1271
[3] G. Okorn, R. Fischer, B. Steller, P. Engesser, H. Okorn-Schmidt, Solid State Phenomena, 2016, 255, 36.
|
|
|
Understanding steel behavior under high-temperature deformation
Saham Sharifi, Saeid Bakhtiari, Christof Sommitsch, Maria Cecilia Poletti, Institute of Materials Science, Joining, and Forming (IMAT)
Abstract: Continuous casting is the most common method for producing steel into semi-finished shapes like billets or slabs. Throughout this process, steel experiences mechanical and thermal stresses, which influence its mechanical properties. Decreased deformability in steel components during continuous casting heightens the risk of crack formation and eventual failure. Failure arises from several factors, including the nucleation of a soft phase, ferrite, within specific temperature ranges, the presence of stress-concentrating precipitates, and microstructural modifications due to elevated temperatures and applied stresses. In the present research, we investigated the microstructural changes in microalloyed steels during hot deformation, aiming to understand the decreased deformability during continuous casting. Employing the Gleeble 3800® thermomechanical simulator, we studied the deformation behavior of microalloyed steel over temperatures ranging from 650°C to 1100°C and strain rates of 0.1 s-1 to 0.001 s-1. Additionally, we examined microstructural changes at various deformation levels, using Optical Microscopy (OM) and Electron Backscatter Diffraction (EBSD) for characterization. Furthermore, we implemented a physically-based model capturing the thermomechanical behavior of steels, describing work hardening, dynamic restoration, phase transformations during deformation, and load distribution between phases. We aim to connect the microstructural changes during deformation to the reduced deformability in continuous casting processes using the findings of this study.
|
|
|
Investigation of the formation of nanoporous copper during electrochemical dealloying vai 4-point resistometry
Samuel Graf, Institute of Materials Physics
|
|
|
Isolation of Chiral Phase in 1,1’- Binaphthyl Thin Films.
Sanjay John, Institute of Solid State Physics, TU Graz
Abstract: The chiral phase isolation in Binaphthyl thin films is achieved through both kinetically driven and thermodynamically driven processes. Binaphthyl, an axially chiral molecule, exhibits distinct crystal structures, one for the racemic phase and another for the chiral phase. In this study, we demonstrate the kinetic isolation of the chiral phase in spin-coated thin films, while the thermodynamic isolation is accomplished through drop-casted thin films. The degree of isolation is highly influenced by the choice of solvent, concentration of the solution and the parameters of the spin coating. These results reveal that the isolation of the chiral phase by a kinetically driven process can be established under ambient conditions. We have also investigated the crystallization mechanism of both racemic and chiral phases in thin films. The crystallization of the chiral phase initiates from a metastable phase and slowly evolves towards the known chiral phase whereas the crystallization process in the racemic phase exhibits a rapid and immediate behavior.
|
|
|
Optimizing wrought AA2024, AA7075 and laser powder bed fusion printed AlSi10Mg similar and dissimilar refill friction stir spot welded joints
Sebastian Fritsche, Graz University of Technology, Institute of Materials Science, Joining and Forming
Abstract: Refill friction stir spot welding (RFSSW) is a solid-state spot joining method that has been successfully used for welding wrought aluminium alloys. In the aviation industry, wrought aluminium alloys of 2000 and 7000 series are widely used. Additionally, additive-manufactured aluminium parts are on the rise to reduce the weight of brackets and fixtures. In this research project, we investigate the RFSSW of AA2024-T3 and AA7075-T6 wrought aluminium joints and Laser Powder Bed Fusion printed AlSi10Mg similar and dissimilar joints. Finite Element simulations are established to better understand the welding process and to help find optimum process parameters. Furthermore, the process simulation helps to find the best tool geometries to reduce the process welding time. Design of experiments approaches are used to find suitable process parameters with high static lap-shear strength. Temperature measurements, hardness measurements, and microstructural analysis, as well as measuring geometrical features, like the hook, lead to a better understanding of how process parameters affect the welding process. The results of our study can be used to improve the quality of RFSSW joints and to develop new applications for the RFSSW technology. |
|
Observations of Random Telegraph Noise In Nanoscale CMOS Using Ring Oscillator Arrays
Semih Ramazanoglu, Alicja Michalowska-Forsyth, Institute of Electronics, Graz University of Technology
Abstract: This study provides observations of Random Telegraph Noise (RTN) in MOSFET transistors, focusing on the temporal and spectral properties of RTN in both time and frequency domains. To understand the RTN mechanism under switching transistor, various types of CMOS Ring Oscillators (ROSCs) were fabricated using 40 nm CMOS technology. The conducted experiments demonstrated the significant influence of RTN on $\Delta$f/fmean variations of up to 7.18 $\%$. Further research revealed the strong bias dependence of the RTN at different power supply levels ranging from 0.5 to 1 V. |
|
|
Ratiometric temperature sensing with thermally-activated delayed fluorescence emitters
Sergey M. Borisov, Andreas Russegger, Georg Schwendt, Institute of Analytical Chemistry and Food Chemistry
Abstract: Temperature sensing via luminescence is attractive in several applications such as mapping of temperature distribution and monitoring in small objects like microfluidic ships or live cells. Ratiometric approach enables referenced measurements with a simple instrumentation such as a set of two emission filters or even an RGB camera in case of spectrally compatible probes. Unfortunately, among a wide variety of reported luminescent temperature probes only a few show ratiometric capabilities.
Here we report two new groups of emitters that at ambient temperatures show simultaneous thermally-activated delayed fluorescence (TADF) and phosphorescence. In contrast to other complexes of platinum group metals that typically show only phosphorescence, the new emitters have comparably small singlet-triplet energy gap and thus show the dual emission. With temperature, phosphorescence gets gradually converted to TADF which enables ratiometric temperature read-out. Immobilization into polymers with low oxygen permeability eliminates oxygen cross-talk of the sensors. The unique feature of the new emitters is their suitability for simultaneous sensing/imaging of oxygen and temperature realized with a single indicator molecule. These dual sensors are obtained upon immobilization into oxygen-permeable polymers (such as polystyrene). Whereas oxygen concentration is obtained from the luminescence decay time, the temperature information is gained from the intensity ratio which does not depend on oxygen. Alternatively, addition of a second emitter makes it possible to read-out oxygen and temperature in the ratiometric mode.
|
|
|
Extending the scope of protein encapsulation into ZIFs
Simon Renner, Michael Hafner, Francesco Carraro, Paolo Falcaro, Institute of Physical and Theoretical Chemistry
Abstract: Among different metal-organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs) are of interest for the encapsulation of enzymes since the synthesis can be carried out in biocompatible conditions (i.e. water, room temperature).[1] This biocompatible process is called biomimetic mineralization: the metal ions accumulate on the enzyme surface and facilitate the MOF growth.[1] This means that the process can proceed only for enzymes that are negatively charged in the reaction environment.[2] This limitation can be overcome via the use of time-consuming and cumbersome enzyme surface functionalization protocols.[2] Here, we report the successful encapsulation of positively charged enzymes into ZIFs. This new, fast, and easy protocol broadens the field of application of ZIFs.
[1] K. Liang, R. Ricco, C. M. Doherty et al., Nat. Commun. 6 (2015), 7240.
[2] N. K. Maddigan, A. Tarzia, D. M. Huang et al., Chem. Sci. 9 (2018), 4217.
|
|
|
High precision fabrication of structured materials for optical sensing applications
Stefan Cesnik, Institute of Electrical Measurement and Sensor Systems
Abstract: Controlled structuring of materials offers new possibilities, ranging from fundamental research to material science or industrial applications. With two-photon polymerization (2PP) printing, we use a cutting edge technology to fabricate various structures in the mm to nm range. Additionally, we combine 2PP with initiated chemical vapor deposition (iCVD), resulting in the fabrication of ultra-thin sensing layers for different optical applications.
|
|
|
Lead-free tin halide perovskite solar cells - optimization of perovskite film crystallization
Stefan Moscher, TU Graz, ICTM
Abstract: Stefan Moscher, Konrad Binter, Lukas Troi, Gregor Trimmel, Thomas Rath
Institute for Chemistry and Technology of Materials, Stremayrgasse 9, 8010 Graz, Austria
Significant progress has been made in perovskite solar cells (PSCs) in recent years and remarkable efficiencies of over 25% are now being achieved in the laboratory. However, these systems contain lead, which has been shown to harm humans and the environment. That is why researchers worldwide are trying to replace the toxic lead and establish lead-free perovskite systems. Tin is a very good candidate for this, and efficiencies in these sustainable lead-free PSCs have also already been increased to nearly 15%. Tin is cheap, non-toxic, and also the electronic properties of tin are very similar to those of lead. Due to drawbacks such as the easy oxidation of the Sn2+ to Sn4+ in the tin perovskite layers and the limited robustness of tin halide perovskites to environmental influences such as temperature, oxygen and humidity, more research is needed to improve the efficiencies and long-term stability. The antisolvent process in the perovskite film crystallization is a critical factor in this regard. Initial results with the green antisolvent diethyl carbonate show that conventional antisolvents, such as chlorobenzene and toluene, could possibly be replaced to make the manufacturing process of PSCs more sustainable with the additional benefit of obtaining perovskite films with improved surface morphology. |
|
|
Synthesis and application of a brominated M3 based non-fullerene acceptor for organic solar cells
Suman Mallick, TU Graz
Abstract: Molecular structure engineering has proved to be an efficient strategy to modify the properties of photoactive materials for organic solar cells. Several studies focused on the halogenation of donor and acceptor molecules, in order to tune the energy levels, the absorption properties or the molecular packing of the materials. In particular, bromination of small-molecule acceptors increases the film crystallinity of the bulk heterojunction, leading to higher charge carrier mobilities, and therefore, to a more efficient charge transport. In this study, we synthesized a mono-brominated non-fullerene acceptor (figure 1, C1) derived from end-group modification of the M3 acceptor.1 |
|
|
Photo-Induced Structural Dynamics in Oriented Metal-Organic Framework Crystallites
Sumea Klokic
Abstract: Designing switchable metal-organic frameworks (MOFs) to respond to an external trigger with a controllable structural response, offers an immense potential to develop kinetically tunable structures for advanced applications (e.g., energy storage).[1] The switching process can often be triggered by an external stimulus, where light is particularly desirable owed to its clean, simple and remote usage.[2] However, the fundamental challenge of how to control the magnitude and duration of the induced structural response in photo-switchable MOF systems is in its infancy.[3] Here, especially the geometric crystal size and morphology is expected to affect the dynamic behavior of the MOF structure as it was shown for switchable MOFs during gas-uptake.[4] Yet, regulating the structural dynamics within photo-switchable MOFs offers an immense potential to develop kinetically tuneable MOF systems.[3a]
In this work, for the first time, we demonstrate on an epitaxially oriented DMOF-1-on-MOF film system[5] comprising azobenzene in the DMOF-1 pores (DMOF-1/AB)[6] that the photo-switching kinetics can be deliberately tuned by changing the crystallite size of the DMOF-1 structure. In a systematic study considering the length to width ratio of the DMOF-1 crystallite (aspect ratio), the photo-switching time constants as a function of the power density of the two light sources (forward switch at 343 nm, backward switch at 450 nm) were found to follow a power law behavior. Hence, with increasing aspect ratios the photo-switch can be precisely controlled and accelerated by over two orders of magnitude simply when altering the power density of the light sources.
|
|
Single-Source Precursors: A Versatile Tool for Liquid Phase Deposition
Thomas Lainer, Institute of Inorganic Chemistry
Abstract: Recently, solution processing of silicon based electronic devices has attracted considerable attention owing to the possibility of low-cost fabrication by printing processes.[1] Large area deposition and patterning materials can be achieved with this processing technique. As shown in recent studies silicon films of satisfactory quality can be obtained with the liquid phase deposition (LPD).[2] Best to our knowledge no examples of silicon-heteroelement thin layer structures processed by single source precursors are reported. A variety of different synthetic pathways was applied to isolate functionalized silicon hydrides. In this lecture we will present their synthesis and their deposition for silicon-heteroelement films.
References
1)Shimoda, T.; Matsuki, Y.; Furusawa, M.; Aoki, T.; Yudasaka, I.; Tanaka, H.; Iwasawa, H.; Wang, D.; Miyasaka, M.; Takeuchi, Y. Nature 2006, 440, 783
2)Haas M., Christopoulos V., Radebner J., Holthausen M., Lainer T., Schuh L., Fitzek H., Kothleitner G., Torvisco A., Fischer R., Wunnicke O., Stueger H. Angew. Chem. Int. Ed. 2017, 56, 14071–14074
|
|
Chitosan Thin-Film Modification with Small Fluorescent Molecules for the Investigation of Biological Solid-Liquid Interfaces
Tobias Dorn
Abstract: Dorn T. (1), Finsgar M. (2), Kleinschek K. S. (1), Wrodnigg T. M. (1), Kargl R. (1)
(1) Institute of Chemistry and Technology of Biobased Systems, Graz University of Technology, Austria
(2) Faculty of Chemistry and Chemical Engineering, University of Maribor, Slovenia
C-Glycosides, where the glycosidic linkage consists of a carbon-carbon bond, are stable against most chemical reactions as well as hydrolysis in biological systems compared to the naturally occurring O- and N-glycosides. [1] This stability makes C-glycosides interesting candidates for therapeutics against various diseases and for technological applications. With the introduction of ligation handles, such stable compounds can be covalently linked to polysaccharides via orthogonal conjugation methods. [2] Thus, specific biological properties of the polysaccharide backbone can be introduced by target specific choice of the sugar based small molecule entity.
For example, chitosan (poly-beta-1,4-D-glucosamine) can be used as a support to bind different molecules, like amino acids, peptides or different sugar derivatives, by chemical modification of the free amino moieties. [3] Due to the water solubility of chitosan, we already prepared thin-film coatings on various substrates and modified them with simple amino acids. [4] As a further proof-of-concept study, we synthesized a fluorescently marked C-glycosidic monosaccharide as well as iminosugar derivatives and modified chitosan thin-films with this compounds and other fluorescent molecules as spacers. The surfaces were analyzed by fluorescence spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and QCM-D. Synthetic details and the results of the surface analysis will be presented.
[1] J. Ati, P. Lafite, R. Daniellou, Beilstein journal of organic chemistry, 13, 1857, 2017
[2] A. Koschella, C.-Y. Chien, T. Iwata, M. S. Thonhofer, T. M. Wrodnigg, T. Heinze, Macromol. Chem. Phys., 221, 1900343, 2020.
[3] W. Neugebauer, R.E. Williams, J-R Barbier, R. Brzezinski, G. Willick, Int. J. Peptide & Protein Res., 47, 269-275, 1995.
[4] T. Katan, R. Kargl, T. Mohan, T. Steindorfer, M. Mozetic, J. Kovac, K. Stana Kleinschek, Biomacromolecules, 23, 731-742, 2022. |
|
|
Additive manufacturing of (Na1/2Bi1/2)TiO3 based piezoceramics via vat photopolymerization
Tobias Pötzelsberger
Abstract: Tobias Pötzelsberger (1), Anastasia Kucheryavaya (1), Max Schmallegger (2), Yue Liu (3), Lovro Fulanovic (3), Jurij Koruza (1)
(1) Institute for Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria
(2) Institute of Physical and Theoretical Chemistry, Graz University of Technology, Graz, Austria
(3) Department of Materials and Earth Sciences, Technical University of Darmstadt, Darmstadt, Germany
Piezoceramics enable the interconversion of electrical and mechanical signals and are therefore indispensable in robotics, energy conversion, medical technology, consumer electronics, and autonomous vehicles. While piezoceramics are traditionally being produced in continuous mass production lines, there is an increasingly large number of applications that require complex-shaped objects with minimum waste and a targeted property combination. This triggered the development of additive manufacturing technologies, whereby one of the promising techniques is vat photopolymerization. However, printing inks of piezoceramics are not readily available and their behaviour during photopolymerization is not well understood. The goal of this work was therefore to design stable photoactive suspensions using the piezoceramic material 0.94(Na1/2Bi1/2)TiO3 0.06BaTiO3, which is being considered as a lead-free alternative for Pb(Zr,Ti)O3 in high-power resonance applications.
The ceramic powders have been prepared by solid-state synthesis and the powder size and morphology were characterized. Various acrylate-based suspensions with different ceramic solid loads were prepared and stabilized. After investigating their rheological properties to ensure a suitable viscosity, the suspensions were polymerized using UV light of different intensities. In particular, the dependence of curing depth on different parameters, such as illumination wavelength, exposure energy, solid load and particle size was investigated. The photopolymerized samples have been benchmarked against samples prepared by conventional forming methods and their microstructures and electrical properties were compared. Despite minor differences in porosities, both samples exhibited similar piezoelectric coefficients and depolarization temperatures, demonstrating the suitability of vat photopolymerization for piezoceramic processing.
|
|
|
ZIF-8 biocomposites for environmental monitoring applications
Verena Lipic, Institute of Physical and Theoretical Chemistry
Abstract: Verena Lipic (a), Mercedes Linares-Moreau (a), Eva Maria Steyskal (b), Roland Würschum (b), Paolo Falcaro (a)
(a) Institute of Physical and Theoretical Chemistry, Graz University of Technology, Austria
(b) Institute of Materials Physics, Graz University of Technology, Austria
Metal-organic frameworks (MOFs) are extended materials synthesized by a modular approach involving inorganic centers (metal ions) bridged by organic constituents (linkers).[1] Due to their biocompatibility, MOFs have been combined with biomacromolecules for applications in biomedicine and biotechnology.[1] Encapsulating biomacromolecules within MOFs provides benefits like enhanced stability, protection, improved activity, selectivity, and controlled release. A well-known MOF in this field is Zeolitic Imidazolate Framework-8 (ZIF-8), composed of Zn$^{2+}$ cations and 2-methylimidazole (2-HmIm) ligands, which is known to create a protective barrier that prevents enzyme unfolding, preserving the native enzymatic activity.[1] Encapsulation of Burkholderia Cepacia lipase (BCL) on MOFs (BCL@ZIF-8) has been suggested as a strategy to improve the sensitivity and robustness of MOF-biocomposite-based sensors for the detection of environmental pollutants.[2] However, current efforts are needed to understand the influence of the synthetic conditions on the resulting BCL@ZIF-8 biocomposites’ properties, and to improve their encapsulation efficiency (EE%) and activity. In this study, we will present the synthesis of BCL@ZIF-8 biocomposites using different metal sources (Zn(NO$_{3}$)$_{2}$ and Zn(OAc)$_{2}$) as precursors for the ZIF-8 matrix, exploring their impact on crystallinity, enzymatic activity and EE% of the final biocomposite. Establishing this fundamental understanding of the BCL@ZIF-8 system's behavior will help develop MOF biocomposites with enhanced properties for sensing applications. This work was supported by the TU Graz Lead Project LP-03 “Porous Materials@Work for Sustainability” and NAWI Graz.
[1] Velásquez-Hernández, M. et al., Coord. Chem. Rev. (2021), 429.
[2] Ma, B. et al., Electrochim. Acta (2018), 283.
|
