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Symposium CA
Advances in Processing Science and Manufacturing of High Performance Ceramics and Composites

ABSTRACTS

CA-1:IL01  Full Densification in Sintering, how can we achieve it?
SUK-JOONG L. KANG, KAIST, Daejeon, South Korea

Full densification is a primary goal of sintering for most ceramic materials and components, in particular transparent ceramics. If isolated pores do not contain any insoluble gases and are not entrapped within grains during sintering, full densification must always be possible. Therefore, selection of sintering atmosphere and suppression/control of grain growth are critical. This presentation will discuss general directions that we can consider to achieve this goal. We will first describe the classical theory of microstructural evolution during sintering and its limitations. Available sintering techniques that can enhance densification and suppress grain growth will then be reviewed briefly. Pore entrapment within grains is prone to occur extensively when abnormal grain growth (AGG) takes place. Particular emphasis will be placed on possible strategies that can suppress AGG and control grain growth in general according to the mixed mechanism principle of microstructural evolution, which we established a decade ago.


CA-1:IL02  Transparency in Polycrystalline Ceramics: Trivial Process or Nightmare?
A. LERICHE, Y. Lorgouilloux, LMCPA - UPHF, Valenciennes, France; J. BoehLmler, S. Lemonnier, ISL, St Louis, France

Since the last few years, transparent ceramics have been of great interest because of their many applications in fields such as ballistic protection or laser amplifying media. The achievement of high transparent polycrystalline ceramics requires the absence of residual porosity and impurities responsible for the light scattering. This implies a high quality of the starting powder and a perfect control of the manufacturing processes by using more sophisticated densification techniques like isostatic pressure, spark plasma or vacuum assisted sintering technologies. However, the quality of the starting powder is sometimes insufficient in terms of stoichiometry, impurities or particle morphology. In this case, a pre-treatment of the powder and the use of sintering aids are necessary to obtain transparency. Some examples of powder pretreatments and processing parameters adaptation allowing transparency and good mechanical properties will be developed for two types of ceramics: Erbium doped YAG for laser applications and MgAl2O4 for ballistic protection. These results were obtained in the frame of PhD works of A.Katz and M.Lagny on YAG ceramics processed by SPS and C.Gajdowski and R.Stocky on spinel ceramics processed by pressureless vacuum sintering and post-HIP.


CA-1:IL05  Towards High-performance all Solid State Batteries: Where Processing Comes into Play
O. GUILLON, Forschungszentrum Jülich GmbH, IEK-1, Jülich, Germany

Among possible future electrochemical storage technologies, all-solid-state batteries raise high expectations in terms of safety and energy density, especially by enabling high-capacity metallic anodes. The combination of solid electrolyte and compatible active cathode materials into thick composites cathodes with percolating pathways for ion and electron transport is one requirement of vital importance. Several approaches, such as tape casting and co-sintering, high-pressure Field Assisted Sintering Technique / Spark Plasma Sintering (FAST/SPS) or in-situ chemical synthesis for both Li and Na-based ceramic materials will be presented.


CA-1:L06  A Comprehensive Approach to Ceramic Forming Processes
W.M. CARTY, Alfred University, Alfred, NY, USA

Ceramic forming processes are dictated by rheology. The rheology dictates behavior and that behavior is controlled by the amount of excess liquid available for particle rearrangement and flow. It is proposed that ceramic forming processes can be connected through the use of specific volume diagrams, when plotted on a volume basis (rather than using the linear approach afforded by a mass basis). From this approach ceramic processing windows can be identified for forming processes such as vibratory casting, extrusion and plastic forming processes, and tape casting. The liquid content necessary for a given forming process is similar once the body is saturated, meaning that the packing efficiency of the system ultimately dictates the liquid content necessary for a given forming process. This approach eliminates the contribution of powder density, meaning that ceramic powders, whether oxides, carbides, or nitrides, can all be treated similarly and that the liquid content is a response rather than a variable.


CA-1:L07  Efficient Optimization of Debinding Processes
H. FRIEDRICH, H. ZIEBOLD, F. RAETHER, Fraunhofer ISC, Zentrum für Hochtemperatur-Leichtbau HTL, Bayreuth, Germany

Debinding is a critical step in powder metallurgical and ceramic processing with respect to time, cost and quality. Hence, significant improvements can be achieved by optimized heating cycles. In order to minimize the experimental and simulative effort a modular and well structured approach called AMI Analyze Measure Improve has been developed to define the required steps for the optimization of a specific debinding process. For example, constant debinding rates, based on TGA-measurements and the kinetic field approach are sufficient for small components with low binder content. Yet, material properties on heat transfer, reaction enthalpy and gas composition as well as gas permeability and strength have to be considered as a function of temperature, atmosphere and the state of debinding for large components or high binder contents. The AMI approach presented has been developed to achieve an efficient optimization process based on the specific debinding task. This also includes the development of user-apps allowing a simple on-site adaptation of debinding cycle for varying component geometries.


CA-1:L10  Improved Sintered Density at reduced Sintering Temperature: New Ceramic Body for 99,8%-Al2O3 Engineering Ceramics from Nabaltec AG
A. BIEGERL, Nabaltec AG, Schwandorf, Germany

Alumina is still the most important material for applications in the field of engineering ceramics. Therefore, material characteristics have to be engineered to the absolute possible maximum to make these parts to be resistant against friction, corrosion, fracture and pressure. This is only achievable by a careful coordination of the whole process chain starting from the raw materials and going through the production process. One approach is to use a very pure (> 99,99 %) alumina, but going this way leads to enormous raw material costs. A second route is to use standard 99,7 % alumina but often the necessary high-end ceramic properties cannot be reached. Therefore, we at Nabaltec AG have developed a new 99,8 %-Al2O3-ready-to-press powder for enabling our customers getting high-performance properties while using their conventional production routes. In addition, the raw material formulation makes it possible to reduce the necessary sintering temperature for 50 to 100 °C. Furthermore, customers can save time and energy in the debindering stage due to the reduced amount of organics by about 1 % compared to conventional RTP-granulates.


CA-1:L12  Study of Matrix Growth Mechanisms during the Injection and Filtration Process of Ceramic Suspensions into a Ceramic Matrix Composite Preform (CMC)
N. EBERLING-FUX, Safran Ceramics, Merignac, France

SiC/SiC-Si CMCs are currently manufactured using slurry cast process (SC) followed by silicon melt infiltration densification. One of the SC process developed in Safran Ceramics consists in injecting a SiC ceramic suspension and then in filtrating ceramic particles in order to build the granular matrix. Understand the build of the matrix during the SC process is necessary in order to optimize later the parts manufacturing. An interrupted experiment approach on CMC preform combined with microtomography scans of the matrix front line is proposed. The use of pressure and DEA sensors inside the mold during the process associated with the injection patterns expertise allow a good description of the matrix growth inside and outside the preform. The results are compared with the filtration model of Ruth.


CA-1:L13  The Influence of Carbon on the Microstructure and Wear Resistance of Alumina
R. MARDER1, Li-Or Cohen1, P. Ghosh1, I. Reimanis2, W.D. Kaplan1, 1Department of Materials Science and Engineering, Technion – Israel Institute of Technology, Haifa, Israel; 2Colorado Center for Advanced Ceramics, Metallurgical and Materials Engineering Department, Colorado School of Mines, USA

The influence of carbon as a dopant on grain growth and wear resistance of polycrystalline alumina was evaluated. Carbon was introduced into alumina by sintering in a carbon-rich environment (graphite furnace under flowing He), and/or by residual carbon from organic binders used during the green body consolidation process. Samples were sintered at 1600°C for 2 hours, and doping alumina with carbon resulted in a reduced grain size after sintering, correlated to solute-drag, or graphite particle-drag for higher concentrations of carbon (~3 wt.%). The material response to abrasive wear was estimated by measuring the time to section samples of a defined area using a diamond wafering saw. Sintering alumina with carbon resulted in a significant increase in wear resistance, thus the combination of reducing atmosphere and high carbon content has a positive effect on the microstructure and mechanical properties of alumina.


CA-1:L14  Three Sustainable Polypropylene Surface Treatments for the Compatibility Optimization of PP Fibers and Cement Matrix in Fiber Reinforced Concretes
b. malchiodi, P. Pozzi, C. Siligardi, University of Modena and Reggio Emilia, Department of Engineering Enzo Ferrari, Modena, Italy

Fiber reinforcement is a well-established solution to enhance toughness, prevent the formation and propagation of cracks, thus prevent the early degradation of cement-based products for structural applications. Polypropylene (PP) appears as a valuable fiber reinforcement due to high corrosion resistance, thermal stability, low density and cost. However, its apolar surface strongly affects the compatibility to inorganic matrix; therefore, several surface treatments have been studied, mainly chemical ones, and validated through mechanical testing. In this study, non-chemical surface treatments that might be more sustainable, fast and easy to perform at an industrial scale are investigated: sandblasting, UV-LED and UV-laser. Focusing on the physical-chemical properties, treatments are performed on PP plane supports and validated in terms of roughness and wettability modifications. Sandblasting and UV-laser mainly involve roughness improvements; so, they principally improve the mechanical phases compatibility. UV-LED exposures from 40min to 36h increase the PP photooxidation as detected by FTIR, colorimeter and roughness measurements. Moreover, significant contact angle reductions are observed suggesting an improved chemical affinity between UV-LED treated PP and inorganic matrix.


CA-2:IL01  Powder-Less Processing of Nano-structured Ceramics: Possible Fabrication of Various Advanced Ceramics from Solutions and/or Melts
MASAHIRO YOSHIMURA, Visiting Distinguished Chair Professor: National Cheng Kung University, Tainan,Taiwan; Professor Emeritus, Tokyo Institute of Technology,Tokyo, Japan

Nano-structured bulk ceramics have generally been fabricated by sophisticated sintering processes using carefully prepared fine powders or nano-particles.  These powder/shaping/sintering processes take multi-steps thus consume long times and a lot of energies even though they consume much less than so-called "high-tech." processes where highly energetic species like vapors, gases, molecules, atoms and/or ions are used as reactants in sophisticated equipments like sputtering, vaporization, PVD, CVD, etc., using microwave, beam, plasma, etc., in vacuum chambers or even in clean rooms.  In order to eliminate economical and environmental costs, we have challenged to fabricate polycrystalline ceramics by powder-less, fire-less and vacuum-less processing. First we proposed “Soft Processing”, which target the direct fabrication of ceramics in a solution by a single step process via the interfacial reaction between a solid substrate and reactant(s), and solute specie(s) in a solution.  These processes might prepare various ceramics films like BaTiO3, SrTiO2, CaWO4, LiCoO2, etc., at low temperatures, RT-150℃, without any post firing. Those process has developed to a new concept and technology “Glowing Integration Layer[GIL]” method(2008), where compositionally, structurally and/or functionally graded ceramics layers could be grown from the bottom substrate, i.e.  bio-active titanate film on Ti alloys, carbon film on carbides,etc. The patterned ceramics films can also be fabricated directly in solutions when those interfacial reactions are locally activated and/or scanned.  Other direct fabrication methods, ink-jet reaction method and spray deposition method have been developed for direct patterning of ceramics.  We have succeeded to fabricate CaWO4, BaWO4, TiO2 and CeO2 films and patterns.  The novel melt processing have been re-investigated for the direct fabrication of bulk ceramics particularly for binary and ternary eutectic systems.  Melt casting and annealing of the eutectic amorphous phase could produce nano-structured ceramics in HfO2-Al2O3-GdAlO3 and C12A7-CaYAlO4 systems, etc. Their unique nano-/micro-structures and properties have been studied.  Those nano-structured bulk ceramics may be useful for many structural applications as well as functional applications The importance of those powder-less processing, direct fabrications, of ceramics from solutions and/or melts has been demonstrated for the future sustainable society. I may add “Why I have proposed new concepts, methods and terms”.
Reference:
(1)    Yoshimura, M., J. Mater. Sci.,41 [5],1299-1306 (2006), 43[7]2085-2103(2008)
(2)    Yoshimura, M., J. Ceram Soc. Japan, 114 [11] pp. 888-895(2006)
(3)    Gallage, R., Yoshimura, M., et al., J.Electroceramics, 19(1),33-38(2009),Thin Solid Films,517(16),4515-4519(2009),
(4)    Yoshimura, M. et al., Mater. Sci. Eng. B,148, 2-6(2008)
(5)    Sugiyama,N and Yoshimura,M., Mater. Sci. Eng. B,161(1-3),31-35(2009)
(6)    S. Araki and M. Yoshimura, Int. J. Appl. Ceram. Technol., 1 [2] 155 (2004)
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(8)    N. Sakamoto,S. Araki and M.Yoshimura,J. Am.Ceram Soc.,92[1],S157-S161(2009)



CA-3:IL01  Characteristics of Si-B-C-N-based Ceramics
R. RIEDEL, Materials Science, TU Darmstadt, Germany

Si-B-C-N-ceramics have been under investigation for more than 30 years. The main scientific and engineering interest of this type of polymer-derived ceramics (PDCs) is related to their high-temperature resistance with regard to decomposition, crystallization and oxidation. This presentation will first highlight the historical development of the synthesis and high-temperature properties of Si-B-C-N-based ceramics in general. Then, in particular novel molecular concepts to modify the Si-B-C-N system with further elements from the transition metals will be discussed. Advanced multicomponent Si-M-B-C-N ceramics (M = metal) are synthesized, which show even enhanced high-temperature properties with respect to corrosion resistance as compared to the pristine Si-B-C-N-system. Therefore, Si-M-B-C-N-ceramics with M = Hf or Zr are considered to be promising candidate materials for future energy conversion devices such as combustion engines like stationary or nonstationary turbines. In this context, recent developments in the field of Si-B-C-N-based ceramics and ceramic nanocomposites will be highlighted and discussed.
Ref.: Antoine Viard, Diane Fonblanc, David Lopez-Ferber, Marion Schmidt, Abhijeet Lale, Charlotte Durif, Maxime Balestrat, Fabrice Rossignol, Markus Weinmann, Ralf Riedel


CA-3:IL02  Chemistry and Processability of Preceramic Polymers Towards Advanced Functional Ceramics
M. Balestrat, A. Lale, S. Bernard, Institute of Research on Ceramics-CNRS/University of Limoges, Limoges, France

A very convenient precursor route to produce high-tech ceramics including silicon carbide (SiC) and silicon nitride (Si3N4) is the polymer derived ceramics (PDCs) route. The implementation of the PDCs route is motivated by the possibility to generate ceramics without undesirable elements, tailored micro-/nanostructures and to process materials in particular shapes as well as with specific textures (dense or porous). The shaping potential of polymers is closely related to their chemistry and in particular to their degree of crosslinking, the type of bonds that link monomeric units as well as the nature of the functional groups attached to the elements composing the polymer backbone. Crosslinking chemistry offers precise control over the crosslinking reactions of liquid preceramic polymers. In this presentation, we describe an effective and a simple approach that consists of tailoring the crosslinking degree of liquid polysilazanes and polycarbosilanes with low molecular weight metal and metalloid-based species. This strategy allows synthesizing preceramic polymers which are shown to develop and extend the processability of neat polysilazanes/polycarbosilanes while forming ceramics with tailored functionalities according to their composition, shape, structure and texture.


CA-3:IL03  Evolution of Transient Microporosity in Polymer-derived Ceramics: in-situ Monitoring and Tailoring
T. KONEGGER, C. DRECHSEL, TU Wien, Institute of Chemical Technologies and Analytics, Wien, Austria; H. PETERLIK, University of Vienna, Vienna, Austria

Transient microporosity emerging during the pyrolytic conversion of preceramic polymers has been of growing scientific interest due to prospective application of microporous PDCs in fields such as membrane-based gas separation. The key to a successful implementation of these materials is the knowledge on how to affect and control size and stability of microporosity. Conventional ex-situ characterization of the micropore structure carried out after pyrolytic conversion is, however, limited to describing the final material structure, and does not yield information on actual structural conversion processes taking place during pyrolysis, an essential requirement for targeted tailoring of microporosity. By introducing in-situ small-angle X-ray scattering (SAXS) as a new characterization strategy, we are able to monitor actual processes taking place during the pyrolytic conversion process and to identify the effect of various processing parameters such as preceramic polymer chemistry, temperature, and pyrolysis atmosphere without requiring time-consuming systematic pyrolysis studies. This not only allows for a better understanding of the precursor systems evaluated in this work, but demonstrates the general suitability of in-situ SAXS for better understanding precursor-based conversion


CA-3:L06  In-Silico Simulations of Polymer Pyrolysis
P. KROLL, The University of Texas at Arlington, Arlington, TX, USA

Chemical reactions during thermal processing of hybrid organic-inorganic polymers transform the precursor into a ceramic. Here we present details – atom trajectories, principal mechanisms and their outcomes – of fundamental reactions in pyrolysis of polysiloxanes and polysilazanes obtained from quantum-chemical (ab-initio) Molecular Dynamic Simulations. We observe intra-chain and inter-chain coupling, cross-linking and elimination reactions, as well as Kumada-type reactions that incorporate carbon into the polymer backbone.


CA-3:L07  Development of a New Binder System for Polymer Derived Mullite Ceramics Made by Fused Deposition Modeling (FDM) Technique
F. SARRAF1, 2, F. CLEMENS1, S.V. CHURAKOV2, 1Empa – Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzlerland; 2University of Bern, Bern, Switzerland

Fabrication of Silicate ceramics from preceramic polymers by FDM has become popular during recent years due to their low processing temperature and thermoplastic behavior. Cross-linking and pyrolysis of bulk polymer derived ceramics are challenging and can cause large closed pores due to the accumulation of gas byproducts released during the cross-linking step. In this study, a thermoplastic polysiloxane powder was used as a raw material for extrusion-based additive manufacturing. To obtain pure mullite at 1600°C, filaments including alumina powder, MgO sintering additive and a thermoplastic binder system based on Ethylene vinyl alcohol (EVA) and polysiloxane was pre-pared. To avoid closed pore structure from the polysiloxane cross-linking process, Polyvinyl alcohol (PVA) as an additional binder additive was investigated. The effect of different EVA grades and PVA content on printability and debinding behavior was studied. EVA with a lower melt flow index (MFI) showed better compatibility with PVA additive in terms of mixing and printing process steps. Extracting 90% of PVA created inter-connected porous structure for efficient removal of gaseous products druing cross-linking and therefore closed spherical pore structure could be avoided in the dense sintered mullite structure.


CA-3:L08  Metal-modified Polymer-derived Ceramics for Stereolitho-graphy-based Fabrication of Catalyst Carrier Structures
J. Eßmeister, L. Schachtner, K. Föttinger, G. Pacholik, T. Konegger, TU Wien, Vienna, Austria

Polymer-derived ceramics exhibit outstanding thermal properties and allow for a direct introduction of metal centres into the ceramic matrix through chemical modification, rendering them ideal candidate material for catalysis applications. In order to overcome processing-related limitations of conventional shaping techniques, additive manufacturing techniques are highly suitable to obtain macroporous structures tailored toward high product flow. In this study, we report on the chemical modification of organosilicon polymers suitable for stereolithography-based structuring. The introduction of catalytically active centers is achieved either by modifying the photoactive base polymer with metalorganic moieties or by direct introduction of metal compounds. The shaped preceramic polymer structures are subsequently converted into metal-ceramic hybrids. Processing limits are discussed with respect to metal content, processability, and pyrolytic conversion behavior. Furthermore, phase development and microstructural evolution at different conversion temperatures are elucidated, and first results on the catalytic activity of the materials are presented.


CA-4:IL01  Process Control during Microwave Sintering: From Magnetron to Solid-State Radio Frequency Source
T. Garnault1,2, S. Marinel2, D. Bouvard1, J.-M. Chaix1, C. Harnois2, C. Manière2, G.l Kerbart2, 1Univ. Grenoble Alpes, CNRS, Grenoble INP, SIMaP, Grenoble, France; 2Laboratoire de Cristallographie et Sciences des Matériaux, Normandie Univ, ENSICAEN, UNICAEN, CNRS, CRISMAT, Caen, France

These last years, significant improvements in microwave processing technology (>1200°C) have been developed such as auto-adaptive PID microwave power, automatic impedance matching and automatized short-circuit plunger; if required. Those developments with the knowledge and skills acquired in terms of susceptors and thermal insulation materials, have allowed to produce efficiently by microwave sintering dense ceramics such as alumina, zirconia, etc. with a good reproducibility. These last years, the Solid State Radio Frequency (SSRF) technology as a source of microwave power has appeared in the market, delivering monochromatic microwave power up to several hundred watts at common frequencies (2.45 GHz, 915 MHz). One of the main advantages of SSRF source is its ability to tune frequency within the ISM (industrial, scientific and medical band) for load matching. Another advantage is the stability and the precision of the microwave power, which allows to easily measure and track the energy being applied to the load. Microwave processing of materials can undoubtedly take advantage of this technology. This communication will describe the use of a SSRF source for microwave sintering. A SSRF 2.40-2.5 GHz ISM band generator delivering a microwave power up to 900 W, with an auto-tuning load system, will be described and used to heat up various ceramic materials for sintering applications (alumina, zirconia, PZT based piezoelectric, etc.). The main advantages of this new MW generation source will be discussed in the frame of microwave sintering technology (process control, microstructures, etc.).


CA-4:IL02  Microwave Ultra-rapid Sintering of Ceramics
K.I. RYBAKOV, Yu.V. Bykov, S.V. Egorov, A.G. Eremeev, V.V. Kholoptsev, I.V. Plotnikov, A.A. Sorokin, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia

We have demonstrated that volumetric microwave power deposition on the order of 10–100 W/cm3 results in ultra-rapid densification of oxide ceramic materials, similar to flash sintering processes under an applied dc voltage. The experiments were carried out using 24 GHz 6 kW gyrotron systems for microwave processing of materials with fast and precise control over the microwave power. Based on the analysis of the power and shrinkage data, a mechanism responsible for the flash sintering effect has been suggested, equally applicable to both microwave and electric power deposition methods. The causal relationship between the development of thermal instability and the mass transport enhancement has been established. The results of the studies indicate that the enhanced mass transport is due to a change in the phase state of the grain boundaries caused by the intense volumetric energy deposition. Experiments on ultra-rapid localized densification have been accomplished using a focused beam of millimeter-wave radiation from a 263 GHz 1 kW gyrotron. By scanning the beam over the surface of a powder layer, extended consolidated structures have been obtained. These results suggest that ultra-rapid microwave sintering can be a promising method for additive manufacturing applications.


CA-4:IL03  Materials Processing under Non-equilibrium Reaction Field Induced by Microwave Irradiation
JUN FUKUSHIMA, H. Takizawa, Dept. of Appl. Chem., Tohoku University, Sendai, Miyagi, Japan

Microwave processing exhibits thermal effects such as rapid heating, internal heating, volumetric heating, and selective heating. Utilizing these features of microwave process leads to synthesis materials through difference route to conventional process. As a results, material synthesis in microwave non-equilibrium field has the potential to give us a novel crystal structure, composition, and structure that is different from these obtained by thermal equilibrium process. On the other hand, detailed mechanisms of microwave materials process have not been understood enough because chemical reactions under selective heating is far from the thermal equilibrium reaction. In order to verify the above-described non-equilibrium effects in solid-phase microwave processing, it is necessary to in-situ observation of a material processing during microwave irradiation, including temperature distribution measurement on a powder scale (micron scale) during microwave irradiation. In this presentation, the authors would like to show examples of in-situ observation of materials processing under microwave non-equilibrium field and present unique chemical reaction processes and synthesized materials.


CA-4:IL04  Breaking the Stability Threshold of Microwave Sintering: From the Multiphysics Simulation to Advanced Sintering Approaches
C. MANIERE1, G. LEE2,3, S. CHAN2, E. TORRESANI2, E.A. OLEVSKY2,3, S. MARINEL1, 1CRISMAT, CNRS, ENSICAEN, UNICAEN, Normandie Univ, France; 2Powder Technology Laboratory, Department of Mechanical Engineering, San Diego State University, San Diego, CA, USA; 3Department of NanoEngineering, University of California, San Diego, La Jolla, CA, USA

Microwave sintering is an advanced sintering approach allowing to transfer the heating energy directly to the specimen to sinter and the surrounding tooling. This process is very efficient for dielectrics and semi-conductors and allows: faster sintering cycles, lower the sintering temperatures, reducing the grain growth phenomenon, etc. Despite these advantages, the microwave sintering process suffers from high heterogeneity and instability explained by the high multiphysics nature of this process which gathers phenomena like: resonance, thermal runaway, hot spots, etc. The stabilization of this process is then an important challenge towards its industrialization. The Multiphysics simulation has a great role for the understanding and the optimization of this process and will be first presented. Then, the important role of susceptor for the stabilization of the thermal field will be presented with an application to the complex shapes and 3D printing.

 
CA-5:IL02  From Flash Sintering to Ultrafast Sintering without Electric Fields and Electrochemically Controlled Microstructural Evolution
JIAN LUO, University of California, San Diego, la Jolla, CA, USA

This talk will first discuss a series of studies of flash sintering [Viewpoint: Scripta 146: 260 (2018)]. First, we originally showed that flash sintering generally starts as a thermal runaway and developed a quantitative model [Acta 94:87 (2015)]. A recent study further showed that a bulk phase transition or a grain boundary complexion transition can trigger flash via a “forced” thermal runway [Acta 181:544 (2019)]. Second, we originally showed that ultrahigh heating rates of ~200 K/s enable the ultrafast sintering with and without an applied electric field [Acta 125:465 (2017)]. Subsequently, a general ultrafast high-temperature sintering was developed [Science 368:521 (2020)]. Other new technological innovations include (i) two-step flash sintering (TSFS) to densify ceramics with suppressed grain growth [Scripta 141:6 (2017)] and (ii) water-assisted flash sintering (WAFS) to flash ZnO at room temperature [Scripta 142:79 (2018)]. Recently, we combined advanced microscopy, DFT modeling, and ab initio molecular dynamics simulations to discover an electrochemically induced grain boundary transition that alters grain growth [Nature Communications 12:2374 (2021)]. Subsequently, we can tailor the microstructural evolution with applied electric fields in various systems and schemes.


CA-5:IL03  Flash Electrical Resistance Sintering of Tungsten Carbide
V.M. SGLAVO, I. MAZO, University of Trento, Department of Industrial Engineering, Trento, Italy

The electrical resistance sintering process has been explored in the present work for the densification of tungsten carbide (WC). The processing variable suitable to achieve “flash sintering” conditions in the conductive material have been studied to consolidate it in very short time. A specific setup has been realized to analyse the effect of currents and voltages applied directly to the powder compact under limited uniaxial pressure. Tungsten carbide was consolidated up to 95% relative density in less than 10 s under a current of 1500 A and a maximum voltage of 4 V. The possibility to activate the thermal runaway in a conductive material like WC, characterized by a positive temperature coefficient, was found in the abrupt electrical resistivity reduction of the green compact in the first instants; such evolution accounts for a transient regime characterized by a huge power dissipation and an intense temperature increase, similarly to what is observed in flash sintering of insulating ceramics. The densification behaviour was shown to depend inversely on the volume of the green body and directly on the applied pressure. The obtained results reveal new fascinating possibilities in the processing of conductive ceramics under the effect of electrical fields and currents.


CA-5:IL06  Impact of Electric Fields on Microstructure Evolution in Functional Oxides
W. RHEINHEIMER, FZ Jülich, Germany; RWTH Aachen University, Germany; Karlsruhe Institute of Technology, Germany; TU Darmstadt, Germany ; Purdue University, Germany

The present study investigates the impact of point defects and their redistribution on flash sintering and grain growth in electric field. Strontium titanate was chosen as a model system. A gradient in the microstructure was found after flash sintering and field assisted grain growth with larger grain sizes at the negative electrode. TEM-EDS measurements indicated Ti enrichment at the positive electrode for undoped strontium titanate and strong acceptor segregation for doped strontium titanate. At the negative electrode the boundaries showed less segregation. We infer that a gradient of the oxygen vacancy concentration is induced by the electric field with higher concentrations at the positive electrode. For strontium titanate it is well known that a high oxygen vacancy concentration reduces the space charge and acceptor segregation, yielding faster grain growth. Overall, the present study highlights the importance of point defect gradients and space charge for flash sintering.


CA-5:L07  Flash Spark Plasma Sintering on 3YSZ: Modification of Sintering Trajectories and Influence on the Formation of Grain Boundaries
T. HERISSON DE BEAUVOIR1, A. FLAUREAU1, G. CHEVALLIER1, A. WEIBEL1, C. ELISSALDE2, F. MAUVY2, R. CHAIM3, C. ESTOURNES1, 1CIRIMAT, CNRS-INP-UPS, Université Toulouse 3 - Paul Sabatier, Toulouse, France; 2CNRS, Université de Bordeaux, ICMCB, UMR 5026, Pessac, France; 3Department of Materials Science and Engineering, Technion - Israel Institute of Technology, Haifa. Israel

Flash Spark Plasma Sintering (Flash-SPS) corresponds to the use of SPS sintering under of very high electric current conditions, allowing reaching extremely high temperature ramps, exceeding 10000°C/min (>200°C/s). Under these conditions, densification takes place in just a few seconds with limited grain growth. This makes it possible in particular to limit the reduction of oxides such as BaTiO3 or to densify refractory materials. The use of Flash-SPS on a 3 mol% Yttria Stabilized Zirconia powder allowed its densification in just a few seconds, between 1500 and 1700 ° C. The resulting specimen have densities ranging from 85 to 95% and grain sizes <350 nm. The use of sintering maps shows a change in trajectories for samples prepared in Flash-SPS compared to samples prepared by conventional SPS. Vickers hardnesses are similar to those measured on fully dense samples, despite porosities of up to 15%. Microstructural observations (SEM, TEM) as well as electrical impedance measurements show grain boundary sizes up to 3 times finer than those observed on samples prepared by SPS, explaining the good mechanical performance measured. Flash-SPS thus makes it possible, by altering the densification mechanisms, to obtain original microstructures allowing the final properties to be modulated.


CA-5:L11  Sintering of Lead-free Functional Perovskites by Cool-SPS
L. FAURE,  U-C. Chung, F. Molinari, M. Suchomel, M. Maglione, M. Josse, ICMCB-UB-CNRS, UMR5026, Pessac, France

Many new sintering methods are being developed to sinter ceramics at low temperature. It has been proven previously that Cool-SPS[1] can be used to obtain highly densified ceramics of thermodynamically fragile materials at low temperature and high pressure, with an adapted sintering strategy. In the present work, we explore the Cool-SPS processing of lead-free functional perovskites. Several ceramics from this large family were rapidly and successfully densified by Cool-SPS, with final relative densities ranging from 90% to 99%. Experimental parameters were studied in order to investigate and optimize the sintering path. The evolution of these parameters illustrates steps like chemical reaction and densification and are likely linked to the relative density of the final ceramic. Moreover, the effect of the process conditions on the microstructures and dielectric properties of the final materials was investigated. In the end, we will demonstrate that Cool-SPS allows for the elaboration of dense ceramics of lead-free functional perovskites, paving the way towards more sustainable materials and processes. [1] https://doi.org/10.1016/j.jeurceramsoc.2018.04.005


CA-5:L13  Developing in situ Characterization of Cold Sintering Process Mechanisms by Impedance Spectroscopy Measurements
T. HERISSON DE BEAUVOIR,  P-L. Taberna, P. Simon, C. Estournès, CIRIMAT, Université de Toulouse, CNRS, Université Toulouse 3 - Paul Sabatier, Toulouse, France

The recent development of low-temperature sintering processes has allowed the elaboration of broad types of materials, such as thermodynamically fragile ceramics and molecular ceramics. Cold Sintering Process (CSP) in particular has emerged as a powerful technique for the preparation ceramic-polymer and ceramic-metal composites. So far, CSP densification mechanisms are assumed to rely on dissolution-precipitation mechanisms. However, recent work tend to show that these mechanisms are insufficient for accurate description of sintering behaviors of materials. The nature of chemical species at intergranular or grain boundary regions remain unclear, and experimental analyses need to be developed to obtain information on these regions and there reactivity. We propose here a novel approach based on in situ electrical diagnostic to follow the evolution of electrical properties during the Cold Sintering Process. Using impedance spectroscopy during the sintering process shows a multi-step evolution of electrical properties of grain boundary regions. It also allows to determine experimental conditions for the complete elimination of liquid phase. One of the greatest interest of impedance spectroscopy relies on its ability to isolate contributions from bulk, grain boundaries and interfaces.


CA-6:KL  Multi Materials Additive Manufacturing
A. MICHAELIS, Fraunhofer Institute of Ceramic Technologies and Systems, IKTS, Dresden, Germany

Additive manufacturing (AM) of ceramic materials is a powerful shaping technology offering completely new design possibilities. However, AM of ceramics is particularly challenging because the shaping process is embedded in a complex manufacturing scheme. In the case of multi-materials printing the thermal expansion behavior of the materials must be carefully adjusted for the co-sintering process. Know How from established 2D and 2,5 D multi-layer ceramic technologies such as LTCC (low temperature co-fired ceramics) or multi-component injection molding can be employed to address these issues. Examples of new additive manufacturing methods such as ceramic fused filament and ceramic 3D-thermoplastic printing. For a further functionalization of the AM parts, 2D printing technologies are applied. We present first results on this combination of 3D and 2D printing that we call 5 D printing. Furthermore, the hybridization, i.e. the combination of AM and conventional shaping technologies such as injection molding is covered.


CA-6:IL01  3D Printing of Composite Ceramics: Advances and Issues Compared to Traditional Manufacturing
B. INSERRA, B. Coppola, L. Montanaro, P. Palmero, J.M. Tulliani, Politecnico di Torino, Department of Applied Science and Technology (DISAT), INSTM R.U. PoliTO, Torino, Italy

Stereolithography (SL) is a process in which a light source of a certain wavelength selectively cures in a vat a resin with photopolymerizable monomers, a photoinitiator and the ceramic powder. In this work, alumina toughened zirconia samples were made by SL from inks based on commercial alumina and zirconia powders. The inks formulation was first set-up in terms of ceramic particle size distribution, solid loading, dispersant amount and viscosity. After optimization of the printing parameters, dilatometry was then used to determine the optimum debinding and sintering temperature of the printed parts. The microstructure of the sintered samples was investigated by means of X-ray diffraction and scanning electron microscopy. Vickers indentation was also used to determine either the hardness and the toughness parallel or perpendicular to the printing direction of the specimens, as well as three-point bending tests to calculate the modulus of rupture. A comparison of the features of the printed zirconia-alumina samples was also done with samples having the same composition and made by traditional processing.


CA-6:IL03  Sinter-cracking and Distortion Behaviors of Sintering 3D Printed Ceramics
Z. CORDERO, Department of Aeronautics and Astronautics, MIT, Cambridge, MA, USA

Binder jet 3D printing is a 3D printing technique in which powder particles are selectively bound together, layer-by-layer, with an organic binder to create a net-shaped green body. This component can then be sintered to create a strong dense component. Ideally, the 3D printed green body will shrink uniformly as it densifies; however, during sintering, various factors (e.g., differential shrinkage, external constraints, microstructural nonuniformity) can give rise to problems with distortion and cracking. In this talk I will describe how we use 3D printed specimens with precisely controlled geometries to probe the roles of design features and material properties on the slumping and cracking behaviors of sintering materials. By coupling these experiments with discrete element method simulations, we gain mechanistic insights into the factors that control these phenomena and identify processing and design strategies for creating net-shaped high-performance ceramic components.


CA-6:L04  A Colloidal Approach for the Fused Filament Fabrication: Multimaterial 3D Printing
B. FERRARI, A. Eguiluz, P. Ortega, O. Urra, J. Yus, A. Ferrandez-Montero, A.J. Sanchez-Herencia, Instituto de Ceramcia y Vidrio, CSIC, Madrid, Spain

Complex pieces can be fashioned through Fused Filament Fabrication (FFF) using bioresources and biodegradable polymers such as PolyLacti acid (PLA). FFF is a simple and cheap technique useful for multimaterial fabrication. Composite granules with inorganic charges up to 50 vol.%, and an extremely uniform dispersion of powders within the thermoplastic matrix, are key in the indirect printing of 100% ceramic materials. The dispersion and stabilization of inorganic particles (different in morphology and size) in a colloidal suspension allows the homogeneous mixing of phases, leading to the uniform distribution of the thermoplastic structurer among ceramic particles in granules, filaments and 3D printed parts. Moreover, this colloidal approach improves anchorage of inorganic particles to the polymeric matrix, and consequently printing conditions, comparing with the traditional fusion route used for mixing composites. The use of the Colloidal Feedstock provides a continuous printing at lower temperatures of customized products with added value. Its characterization in terms of thermal rheology provides the accurate conditions for the printing of high inorganic charged composites and hence for indirect printing of ceramic pieces with micro/nanostructures for different applications.


CA-6:L05  Comparison of Thermoplastic Material Extrusion-based Additive Manufacturing Methods for the Shaping Ceramic Materials
f. clemens, A. HADIAN, Empa, Dübendorf, Switzerland

 
For the shaping of thermoplastic ceramic feedstocks, e.g. a feedstock consists of thermoplastic additives and ceramic powders, warm pressing, extrusion, injection molding and even dip-coating has been explored in the past. In comparison to dry pressing, the green density can be set more precisely and reproducibly, therefore geometrical size deviation after sintering is significantly lower. Compared to water-soluble binder extrusion, there is less contamination due to lower abrasion. Another advantage is the higher green strength of thermoplastic shaping ceramic parts. Besides, thermoplastic-based ceramic feedstocks can be easily recycled and reused. The main disadvantage is the relatively long debinding times, compared to aqueous ceramic binder systems, and limited wall thicknesses due to diffusion limitation during the debinding processes. In the last years, the shaping of thermoplastic ceramic feedstocks was extended to material extrusion-based additive manufacturing (MEX-AM) method, successfully. In this talk, I will present an overview on different printer and extruder types, namely Bauden, direct-drive and screw-extruders for the shaping of ceramics. Material requirements as well as examples of 3D printed structures for commercial applications are discussed during this talk.

CA-6:L06  The Curing Performance of an Acrylate Resin Highly Loaded with an Ultraviolet (UV) Absorbing Ferrite Powder
A. HARMON, M. Roumanie, U. Soupremanien, Univ Grenoble Alpes CEA LITEN DTNM, Grenoble, France; D. Autissier, CEA Le Ripault, Monts, France

Stereolithography (SLA) is an additive manufacturing (AM) technique that can be used for printing small and complex ceramic parts. The printing consists of a layered manufacturing based on UV photosensitive resin (SR) highly loaded (>40%vol) with ceramic powder. The process depends on the curing control of the formulated resin that relies on: UV-absorption of photoinitiators (PI), its photochemical properties and on the optical properties of the load such as particle’s size, UV-light scattering (UVS) and absorption. In recent years, studies have showed that it is possible to shape ceramics, such alumina and zirconia that are UVS and non-absorbing materials, by SLA. In this study, a UVS and absorbing ferrite powder (0.26 µm; n=2.4515 + i1.171 at 365 nm) was used. Its absorbance was A=2.62 at 365 nm which quench the PI absorption. We pre-sinter the powder to increase the particle size and form the magnetic phase (50 µm; n=2.4405 + i0.11 at 365 nm) to reduce the absorbance (A=0.28). The treated powder was incorporated in a formulation that was mixed to control the particle size. We successfully printed ring-shapes cores with layers’ thicknesses of 50 µm and powder concentration of 45%vol by SLA. Further investigations should be performed to improve the final part’s properties.


CA-6:IL07  Selection of Surfactants for Lithography Based Shaping of Zirconia and Zirconia/Alumina Nanocomposites
T. GRAULE1, P. Zubrzycka1, P. Ozog2, L. Conti1, M. Borlaf1, D. Kata2, M. Radecka2, 1Empa, Swiss Laboratories for Materials Science and Technology, Laboratory for High Performance Ceramics, Dübendorf, Switzerland; 2AGH Krakow, Krakow, Poland

Electrostatic and/or steric stabilisation of highly loaded, ceramics based nanopowders is a prerequisite to receive highly reliable ceramic materials. Development of three-dimensional printing technologies, recently known as Additive Manufacturing of Ceramics. is based on the availability of these concepts for slurry preparation Agglomeration or re-agglomeration due to Van der Waals forces can be avoided using different concepts to increase the separation barrier by electrostatic or steric means. We recently performed studies to stabilize alumina and zirconia submicron and nanoparticles and transferred the concept to apply anion type and cation type comb copolymers as a promising alternative in case of the stabilization of titania [1-2] and other oxides. These slurries are used to shape ceramics by stereolithography using digital mirror devices [3, 4, 6-8] or by a defined spray granulation process and finally consolidation of ceramic granular materials by selective laser sintering SLS [5]. Here we present recent results of Stereolithography based Additive Manufacturing techniques applying zirconium oxide, aluminium oxide and aluminium nitride, demonstrating the necessity of a sophisticated powder treatment and powder handling procedure.


CA-6:L11  Comparing the Strength of Zirconia Disks Produced using Material Extrusion Additive Manufacturing and Cold Pressing 
A. HADIAN, F. Clemens, Empa, Dübendorf, Switzerland; M. Fricke, A. Liersch, Hochschule Koblenz, Höhr-Grenzhausen, Germany

A growing interest in material extrusion (MEX) additive manufacturing (AM) of ceramic parts can be noticed in the past few years. To be able to produce defect-free MEX zirconia disks, printing pa-rameters were adjusted until defect-free green microstructure of the printed disks could be ob-served using microscopy analysis. Using a new dynamic infill approach (i.e. actively changing the multiplier parameter for each layer) void-free printed disks with a smooth top surface were success-fully achieved. For debinding process, a two-step approach (i.e. solvent and thermal debinding) was used. The thermal debinding step was optimized using model-free kinetic analysis. To facilitate the commercialization of thermoplastic based MEX-AM process, mechanical properties of 3D printed and cold isostatic pressed ceramics disks has been investigated. A Ring-on-Ring (ROR) setup was used to investigate the biaxial flexural strength of sintered 3D printed and pressed (CIP) ceramic disks. For CIP zirconia disks, a mean strength of 656 MPa and a Weibull modulus of 3.8 were calcu-lated. It is assumed that inhomogeneous load distribution in ROR setup is the main reason for the low Weibull value for sintered pressed disks. Fractography of the disks having the lowest and high-est strength supports this idea. In comparison, a mean ROR strength of 530 MPa was calculated for the 3D printed zirconia disks with a Weibull modulus (i.e. m=4) close to the value obtained for the pressed disks.  While a difference in the mean strength of 3D printed and pressed disks can be ob-served, due to the overlapping of confidence intervals, it can be concluded that this difference is not statistically significant.

CA-6:L12  Large Scale Additive Manufacturing of Artificial Stone 
F. GOBBIN1, 2, H. Elsayed1, 3, J. Adrien4, G. Franchin1, A. Italiano2, E. Maire4, P. Colombo1, 5, 1University of Padova, Industrial Engineering Department, Padova, Italy; 2Desamanera Srl, Rovigo, Italy; 3Ceramics Department, National Research Centre, Cairo, Egypt; 4Université de Lyon, INSA de Lyon, MATEIS CNRS UMR5510, Villeurbanne Cedex, France; 5Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA, USA

In the current research, large scale (meter-sized), non-structural artificial stone components were fabricated by reactive powder bed Binder Jetting. The printer and materials were developed in a collaboration between Desamanera Srl and the Industrial Engineering Department of the University of Padova, (within project ADMIN4D). The printing bed was comprised of an inert granular mineral and a reactive inorganic binder powder, which was activated by the selective deposition of water. The printing parameters were controlled to achieve a good reaction quality in this specific condition. A fast setting system was developed to enable rapid printing with a suitable resolution, and the building up of a structure at the macro-scale. The main chemical, physical and mechanical characteristics of the printed parts were investigated. Furthermore, to study the printing steps and the final piece characteristics obtained with this specific technology a complete CT analysis was conducted in collaboration with INSA, Lyon (within project AMITIE). The production of large-scale pieces was possible with the described indirect powder bed technology. The synergy of printing process and starting materials allowed to consolidate, in a reduced time process, complex shape objects with a suitable resolution.


CA-7:IL02  Ceramics with Eutectic Microstructure by Viscous Flow Sintering and Controlled Crystallization of Al2O3-Y2O3 and Al2O3-Y2O3-ZrO2 Glass
D. GALUSEK, Centre for Functional and Surface Functionalized Glass, Alexander Dubček University of Trenčín, Trenčín, Slovakia

Ceramics with eutectic microstructure attracted attention due to their strength/toughness, high melting temperatures, resistance to oxidation, thermal stability and creep resistance. These properties result from the strong interface between phases in the microstructure, making them promising candidates for high temperature applications. Most of the time they are fabricated by the top-down approach, by controlled solidification of eutectic melts. Preparation of these materials by Bridgman and laser floating zone method, edge-defined film-fed growth, micro-pulling down, laser zone remelting, and selective laser melting was reported. All these methods require high temperatures, often > 2000 ºC. In this work, we adopted down-top approach to preparation of these materials, utilizing controlled crystallization of glasses with eutectic compositions. The glasses in the systems Al2O3-Y2O3 and Al2O3-Y2O3-ZrO2 were simultaneously densified under uniaxial pressure at temperatures up to 1600 ºC. The influence of processing parameters on densification, mechanical properties (Vickers hardness (HV), indentation fracture resistance) and microstructure development is discussed. Materials with a maximum HV of 18.1 ± 0.7 GPa and indentation fracture resistance of 4.9 ± 0.3 MPa·m1/2 were prepared.


CA-7:L04  Optical in-Line 3D-Quality Inspection Using White-Light Interferometry for CMC Aerospace Applications
J. MACKEN, R. Goller, Augsburg University of Applied Sciences, Department of Mechanical and Process Engineering, Augsburg, Germany

Ceramic Matrix Composites (CMCs) are becoming more attractive for aerospace applications like turbine blades or center bodies due to their high-temperature stability, mechanical strength, damage tolerance and weight saving potential. Due to the high-quality standards, a 100 % optical inspection is needed after final machining, which is typically done as a separate final step. The use of an in-line white-light interferometer can inspect the machined part during and after machining. This would eliminate a time-consuming separate inspection step, thus reducing the overall production cost. Furthermore, the use of big data could drive additional innovations, such as the detection of worn tools. The present work investigates the integration of the white-light interferometer sensor into the milling-machine. CMC-specific measurement parameters are found to enable efficient and low noise 3D-data collection. Critical quality defects such as roughness values and edge chipping of CMC-parts are assessed and validated using a 3D-microscope.


CA-7:IL05  A Practical Overview of Colloidal Strategies to Manufacture ad-hoc Designs of Advanced 2D and 3D Structures
Z. GONZALEZ1, 2 J. Yus1, E. USALA2, P. Ortega-Columbrans1, E. Espinosa2, A. Rodríguez2, A.J. Sanchez-Herencia1, B. Ferrari1, 1Instituto de Ceramica y Vidrio (ICV), CSIC, Madrid, Spain; 2BioPren Group. Chemical Engineering Department, Faculty of Science, Campus de Rabanales, Universidad de Cordoba, Cordoba, Spain

The stable nature of colloidal systems has tremendous potential to satisfy the manufacturing requirements of composite structures. It allows understanding the physics underlying, the stability and rheology of the feedstocks/pastes/inks. This enables materials delivery and assembly across the multiple scales required to achieve optimized properties. This talk includes a practical overview in which some colloidal strategies have allowed manufacturing highly homogeneous structures of nanocomposites and/or ceramic materials, unobtainable using traditional methods. The emphasis has been specially placed on fusing some of these colloidal strategies with specific additive manufacturing techniques. Both the mixtures handling in liquid media and the functionalization of materials surfaces have been key aspects in the applied examples. The work describes the preparation of inorganic-organic structures by heterocoagulation. Formulations of Cellulose nanofibers (CNFs), obtained from biomass valorization, and semiconductor-based nanoparticles such as TiO2 will be presented. These heterostructures have been also shaped in aerogel format and incorporated as filler of filaments for FFF. The role of CNFs has been additionally evaluated as biotemplate in the production of porous microstructures.


CA-7:L07  Novel Entropy-stabilized Ni-free Rock Salt Ceramics
M. Biesuz, V.M. Sglavo, University of Trento, Department of Industrial Engineering, Trento, Italy

Entropy-stabilized rock salt ceramics with composition (Mg, Co, Ni, Cu, Zn)O are of great scientific and technical interest due to their excellent Li storage capacity and conductivity which make them good candidates for solid battery applications. Nevertheless, the presence of nickel oxide is of a certain concern from health and environmental point of view. In the present work, a novel Ni-free high entropy rock salt ceramic was developed by replacing NiO with MnO. The starting powder was produced by co-precipitation from an equimolar cations solution and using NaOH as precipitating agent. Mineralogical, compositional and microstructural evolution upon annealing in air was studied by combining XRD, SEM, EDXS, TGA/DTA and dilatometric analysis. It is shown that both annealing temperature and Li2O addition to (Mg, Co, Mn, Cu, Zn)O play a key role in the high entropy phase stabilization, especially in the control of the secondary spinel-like phase content. Specifically, the charge compensation between Li_M^' and Mn_M^∙ in the rock salt structure is proposed to enhance the stability of the high entropy phase. Preliminary EIS analysis also points out interesting electrochemical properties.


CA-7:L08  Improving Mechanical Properties of Laminated Transparent Ceramics by Engineering Residual Stress Profiles
A. TALIMIAN, D. Galusek, Centre for Functional and Surface Functionalised Glass, A. Dubcek, University of Trencin, Trencin, Slovakia; A. Najafzadeh, Joint Glass Centre of the IIC SAS, TnUAD and FChPT STU, Trencin, Slovakia; V. Pouchly, K. Maca, CEITEC BUT, Brno University of Technology, Brno, Czech Republic

Although transparent ceramics exhibit greater strength than most glasses and glass ceramics, their application is limited due to the catastrophic nature of their fracture without warning. One approach to prevent such behaviour is to produce and engineer residual stress near the surface of the sample. In this study, multi-layer bodies were produced by thermo-compressing layers fabricated by aqueous tape casting of 8Y-FSZ, 10Y-FSZ and MgAl2O4. The fabricated bodies were densified by spark plasma sintering. The produced samples were characterised in terms of the chemical concentration profiles of the dopant (Y), optical transparency, mechanical strength and distribution of residual stress. The generation of compressive stress during sintering and its influence on optical transparency and mechanical properties of produced bodies were critically discussed.

 

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