Symposium CB
Non Conventional and Emerging Routes to Advanced Ceramics

Session CB-1 - Solution-based Processing

CB-1:IL01  From Inorganic Molecules to Functional Oxide Materials: A Liasson towards Electronic Device Applications
S. SANCTIS, J. KRAUSMANN, R.C. HOFFMANN, J.J. SCHNEIDER, Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universitaet Darmstadt, Darmstadt, Germany

Inorganic coordination compounds have the impact to be processed into inorganic oxide materials at relatively low temperatures and under benign conditions. They have the advantage compared to other precursor routes, that their molecular structure and elemental composition can be tailored with respect to their metal constitution and surrounding ligand environment to fit the needs of a specific application. According to their chemical composition and their molecular structure an understanding of oxide materials derived from such a molecular precursor route can be deduced. To achieve this the molecular conversion into the oxide phase has to be unravelled. Once this is obtained the conversion pathway of the precursor compound allows to understand oxide formation and based on that the electronic material performance of the functional oxides. The whole process offers the chance to a most complete understanding how a certain ligand environment can be employed to fine tune the electronic properties of functional metal oxides. One of our interests in this area is especially devoted to the intriguing electronic properties of transparent conducting oxides and their apllication in field effect transistor devices.


CB-1:IL02  Solution Based Processing of Nanotitania Allotropes and their Applications in Energy and Environment
S. CASSAIGNON, Sorbonne University (UPMC), Chimie de la Matière Condensée de Paris, CNRS UMR7574, Paris, France

Emergence of nanotechnology increasingly shows examples of the material potentiality possessing at least one dimension less than 100 nm. The preparation of nano-objects by soft chemistry in aqueous media with crystal structure, size and morphology perfectly controlled is based on the
 use of molecular precursors and adjustment of physico-chemical parameters (acidity, ionic strength, temperature) during the precipitation of the solid. The growth of nano-crystals can be 
limited or favored in some crystallographic 
directions. It is also possible to involve redox
 processes in addition to the acido-basic reactions.
This can significantly enhance the potentiality of this chemistry in the design of particles. Furthermore, the synthesis of hierarchical materials with multiple scales of organization and often formed from the assembly of nanoparticles, raises a growing interest, mainly thanks to their ability to combine the functions of the various elementary units. This allows to consider interesting applications of these systems in various fields and especially in the field of Energy, either for conversion or storage and Photocatalysis.


CB-1:L03  Gallium-based Oxynitride Nanoparticles and their Photocatalytic Activity
YUSUKE ASAKURA, SHU YIN, Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, Japan

Nitride/oxynitride possess very unique properties because of incorporation of nitrogen 2p orbital into valence band. Especially, they have been applied as a visible-light responsive photocatalyst. For catalytic application, morphological control is one of the ways for improvement of activities. Morphological control of nitrides/oxynitrides cannot be easily accomplished, although it can improve the photocatalytic activities. In this study, nanoparticles of gallium-based oxynitrides was synthesized. Gallium-based oxynitrides including gallium oxynitride and solid solution of gallium nitrides and zinc oxides were known as visible-light responsive photocatalysts. Firstly, the precursor oxides (beta-Ga2O3 and ZnGa2O4) with nanoparticle were synthesized through hydrothermal reactions, and the obtained oxides were treated under NH3 flow. The XRD patterns of the nitrided samples shows only peaks attributed to wurtzite GaN phase, although the peaks were broad. The nitrided samples possessed small nanoparticle size, judging from the TEM images. The photocatalytic activities of the nitrided samples were evaluated by photocatalytic decomposition of NOx reaction. The higher surface and the longer absorption edge of nanoparticle lead to effective enhancement for photocatalytic reaction.


CB-1:L05  Photocatalytic Activities of Carbon-doped TiO2 Based Composites
CHIAKI NODA, YUSUKE ASAKURA, SHU YIN, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan

Carbon-doped TiO2 (C-TiO2) prepared by solvothermal process exhibit high visible-light responsive photocatalytic activity for deNOx. Meanwhile, there have been reported that composites containing two-dimensional compounds, such as graphitic carbon nitride (g-C3N4) and graphene, show higher photocatalytic activities. Therefore, the combinations of C-TiO2 with g-C3N4 and/or reduced graphene (rGO) were carried out in order to further improve their photocatalytic ativities. Composites of C-TiO2 and g-C3N4 (C-TiO2+C3N4), C-TiO2 and rGO (C-TiO2+rGO), and C-TiO2, g-C3N4 and rGO (C-TiO2+C3N4+rGO) were synthesized by solvothermal method. C-TiO2 were mixed with g-C3N4 and/or GO in solvent containing water and ethanol, and heated at 120 °C for 3 h. Their photocatalytic activities were evaluated by the conversion ratio of NO gas under LED lights with wavelengths 627, 530, 445, and 390 nm. The as-synthesized C-TiO2 possessed anatase single phase.The X-ray diffraction (XRD) patterns of C-TiO2+C3N4, C-TiO2+rGO, and C-TiO2+C3N4+rGO showed peaks attributed to each component. As for the photocatalytic activity, C-TiO2+C3N4 and C-TiO2 and rGO showed lower activity compared to that of C-TiO2. However, C-TiO2+C3N4+rGO showed higher photocatalytic activity for wavelengths 445 and 390 nm.

 
Session CB-2 - Polymer Derived Ceramics

CB-2:IL01  Polymer-derived High-pressure Phases via Intermediate Amorphous Materials
YOSHIYUKI SUGAHARA, Department of Applied Chemistry, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan; Kagami Memorial Research Institute for Materials Science and Technology, Waseda University, Tokyo, Japan

High-pressure phases are attracting increasing attention. High pressure and high temperature are generally required for their preparation, and milder conditions are advantageous for their production. In general, crystalline ambient-pressure phases are converted into high-pressure phases, but the use of amorphous materials could lower the conditions required for their crystallization. Polymer-derived ceramics (PDCs) have been developed as novel ceramic processing, and amorphous PDCs can be prepared by pyrolyses at relatively low temperatures. The use of amorphous PDCs as intermediates for high-pressure phase synthesis was thus investigated. One example is preparation of cubic silicon nitride from amorphous materials prepared by the pyrolysis of perhydropolysilazane using a shock-compression apparatus. It was clearly observed that the use of amorphous materials was advantageous for cubic silicon nitride crystallization. The other example is the preparation of cubic boron nitride from amorphous materials obtained via pyrolysis of a reaction product between boric acid and urea under ammonia using a belt-type apparatus. The formation of cubic boron nitride was promoted by the use of amorphous materials containing controlled amounts of water.


CB-2:IL02  Polymer-derived Ceramic Nanocomposites for Applications at High Temperatures and in Harsh Environments
E. IONESCU, Darmstadt University of Technology, Institute for Materials Science, Darmstadt, Germany

Polymer-derived ceramic nanocomposites (PDC-NCs) can be synthesized via thermal conversion of suitable single-source precursors, leading in a first step to amorphous single-phase ceramics, which subsequently undergo phase separation processes to furnish bi- or multiphase ceramic nanocomposites. PDC-NCs have been shown to be excellent candidate materials suitable for applications at ultrahigh-temperatures and under harsh environments. In the present work, amorphous SiMC-, SiMCN- and SiMBCN-based materials (M = Hf, Ta) were synthesized via cross-linking and ceramization of tailor-made polymeric single-source precursors. High-temperature annealing of the obtained amorphous ceramics led to ceramic nanocomposites with promising compositions, such as SiC/MC, MN/Si3N4/SiBCN or MC/MB2/SiC. The presented results emphasize a convenient preparative approach to nano-structured ultrahigh-temperature stable materials starting from greatly compliant single-source precursors. Recent results concerning the stability of the prepared ceramic nanocomposites in ultraharsh environments (i.e., oxidative atmosphere, combustion atmosphere, hydrothermal environment) will be highlighted and discussed.


CB-2:L03  Multiple Stages of Structure Formation in Silicon Oxycarbide Ceramics
P. KROLL, The University of Texas at Arlington, Arlington, TX, USA

Combining structure modeling, ab-initio molecular dynamic simulations, million-atom-simulations, experimental as well as computational NMR studies we explore the structure of SiCO ceramics. We observe distinct stages of structure formation of the “free” carbon phase, which is embedded in and surrounded by the glass network. Isolated carbon units of a molecular precursor are initially well dispersed throughout the material. Upon annealing they combine to larger but finite segregations of single-layered carbon sheets. These carbon segregations separate the surrounding SiCO glass matrix, essentially confining it in small domains. Continuity and sizes of these domains are related to the amount of free carbon and to the composition of the material. Further annealing yields formation of tubular carbon structures, depending on composition and viscosity of the surrounding SiCO glass phase. Ultimately, tubular structures convert into large graphitic segregations.


CB-2:L04  Molecular Route Syntheses of Inorganic C-N Compounds in Ultra-high Pressure and Temperature 
MASASHI HASEGAWA, KEN NIWA, TOSHIFUMI FUKAI, YUKI JIN, Department of Materials Physics, Nagoya University, Nagoya, Japan

The synthesis technique in high pressure and high temperature conditions is useful to synthesize C-N inorganic compounds.  The most familiar target materials by using this synthetic technique is C3N4 because cubic C3N4 has been theoretically expected to be harder than diamond.  In addition to researches on hard materials, recent studies also focus on the capability of the C-N compounds for hydrogen storage materials. Accordingly, various kinds of molecular materials have been tried as a precursor so as to synthesize the C-N compounds including cubic C3N4 in high pressure and temperature.  We have tried to synthesize C-N inorganic compounds from heterocyclic compounds in high pressure using the laser-heated diamond-anvil-cell. LH-DAC gives easily high pressure and high temperature conditions. We have used some organic compounds having a five or six-membered ring of carbon and nitrogen atoms as starting materials. By the SEM-EDX and TEM-EELS analyses and X-ray diffraction measurements, it is found that the starting organic material is converted to characteristic compound. For example, 1,2,4-triazole which has a five-membered ring, is converted to an C-N graphitic phase in 10 GPa. The detailed results will be also reported in the presentation at the conference.


CB-2:L06  Synthesis of Fluorinated Polysilazanes and their Application as Protective Hydrophobic Coatings
P. FURTAT, G. MOTZ, Department of Ceramic Materials Engineering, Bayreuth University, Bayreuth, Germany; R. MACHADO, Department of Chemical Engineering, Federal University of Santa Catarina, Florianopolis, Brazil

A new approach to synthesize fluorine-modified polysilazanes for the application as protective coatings with decreased surface energy was developed by the reaction of the liquid oligosilazane Durazane® 1800 and 2,2,2-trifluoroethanol using tetra-n-butylammoniumfluoride as selective catalyst to activate Si-H groups for simultaneous reactions with both N-H and O-H groups. Calcium borohydride was used as reaction inhibitor to terminate the reaction resulting in a solid, soluble fluorinated polysilazane. The proposed reaction mechanisms and the resulting polymer structures were investigated with NMR, FTIR, XPS spectroscopy and elemental analysis. Whereas the remaining silazane Si-H and N-H bonds provide an excellent adhesion of the coatings to the substrate, the CF3 groups decrease the surface energy leading to an increased contact angle of up to 15 % to water and 40 % to hexadecane in comparison to unmodified polysilazanes. When tested as mold release coatings, the fluorinated silazanes reduced the adhesive strength of a phenolic resin in aluminum substrate from 12.7 to 2.8 MPa. Moreover, the chemical resistance of the fluorinated polysilazanes coatings in contact with acids and bases (HCl and KOH) is remarkably improved, offering a great potential to protect metals from corrosion.


CB-2:L07  Novel Glass-ceramics from Glass Powders and Reactive Preceramic Polymer Binders
H. ELSAYED^{1, 2}, E. BERNARDO¹, ¹Department of Industrial Engineering, University of Padova, Italy; ²Ceramics Department, National Research Centre, El-Bohous Street, Cairo, Egypt

The processing of sintered glass-ceramics is often conditioned by the debinding step. Typical carbonaceous polymeric binders, namely subjected to complete decomposition upon firing, may determine some defects in the final glass-ceramic directly, by causing some gas evolution continuing even at an advanced state of densification, or indirectly, by offering poor adhesion between particles. The present investigation is aimed at exploring a novel concept, based on the adoption of silicone polymers, providing an abundant ceramic residue after firing. Some glasses (belonging to the CaO-MgO-Al2O3-SiO2 and CaO-B2O3-SiO2 systems), normally yielding useful glass-ceramics by heat treatment, were reproduced in form of ‘silica-defective’ variants, featuring a SiO2 content, in the overall formulation, reduced up to 15 wt%. The overall silica content was recovered by mixing powders of the new glasses with silicone binders: upon firing in air, the interaction between glass powders and polymer-derived silica led to glass-ceramics with the same assemblage than those formed by the reference glasses. The new approach has been successfully applied to the manufacturing of glass-ceramic joints for SOFCs as well as of 3D-printed glass-ceramic scaffolds for tissue engineering.


CB-2:L08  Generation and Control of Microporosity in Polymer-derived SiCN Ceramics
C. DRECHSEL, T. KONEGGER, Institute of Chemical Technologies and Analytics, TU Wien, Vienna, Austria

(Ultra-)microporous ceramics open new potential fields of application for ceramic materials, e.g. in environment-related fields such as membrane-based separation. Microporous non-oxide ceramics are of special interest due to their improved high temperature properties, facilitating applications under harsh conditions. Furthermore, a tailorable and well-defined pore size as well as pore stability under anticipated operating conditions are crucial factors for a prospective applicability. In this work, micropore evolution and stability in polymer-derived SiCN ceramics was investigated. In order to identify critical parameters affecting micropore evolution, the structure of the starting precursor polymer as well as processing conditions were varied systematically. Mechanisms affecting pore formation and pore stability are identified through in-depth characterization techniques including physisorption with various gases, small-angle X-ray scattering, thermogravimetry, and NMR, thereby elucidating relevant factors for the successful generation of suitable materials with well-tailorable microporosity.


CB-2:L09  Molecular Design of Novel 0D, 1D and 2D Nanocarbon-based Ceramic Composites
G. MERA, R. RIEDEL, TU Darmstadt, Institute for Materials Science, Darmstadt, Germany

The possibility to incorporate an extremely high content of carbon into the microstructure is a particular characteristic of polymer-derived ceramics (PDCs). The concentration, organization as well as the interface bonding of the segregated carbon phase with the surrounding matrix has been shown to play an important role on the nanostructure of materials as well as on their functional properties. Applications such as energy storage, photoluminescence, temperature and pressure sensors, are directly related to free-C phase in PDCs. In order to study the effect of the free-C phase (i.e., content, organization, interfaces etc.), novel SiO2- and Si3N4-nanocarbon ceramic composites were produced upon the pyrolysis of preceramic precursors consisting of a highly crosslinked polysiloxanes and polysilazanes covalently functionalized with 0D, 1D and 2D-nanocarbons. As the polymers deliver C-free SiO2 and Si3N4 upon pyrolysis, the nanocarbons were the exclusive carbon source in the obtained ceramics. The nanocomposites were structurally characterized and their thermal stability against crystallization and decomposition was carefully analyzed. Furthermore, selected functional properties thereof will be highlighted and discussed within the context of prospective energy-related applications.

 
Session CB-3 - Microwave Processing

CB-3:IL02  Microwave Versus Conventional Sintering of Pure and TiO2 doped MgAl2O4 Ceramics: Sintering Trajectory and Mechanisms
S. MARINEL¹, R. MACAIGNE¹, D. GOEURIOT², S. SAUNIER², ¹CRISMAT Laboratory, University of Caen Normandy, France; ²Ecole des Mines de Saint-Etienne, Dép. Science des Matériaux et des Structures, Saint-Etienne, France

The MgAl2O4 oxide is a structural ceramic that can lead to transparent ceramic when full density is achieved. Therefore MgAl2O4 oxide attracts much interest in multiple market segments such as the military, aerospace, jewelry and lasers. To control the processing route to get full transparent ceramics, understanding the MgAlO4 sintering mechanisms and trajectory is of primary importance. Considering our latest development in microwave sintering of materials, including the contactless dilatometry apparatus and the specific temperature calibration method, a fundamental study of the microwave sintering is now possible. In this communication, the microwave and conventional sintering of pure and TiO2 doped MgAl2O4 ceramics is presented. For each material and process, the dominant diffusion mechanism leading to densification was determined through isothermal shrinkage curves kinetics exploitation. Otherwise the sintering trajectories were determined as well as the pore size and distribution vs density. From those data, a systematic comparison of the microwave sintering over conventional process is discussed. In particular; it is shown that TiO2 doping, through the creation of point defects, can change the main diffusion mechanism during microwave sintering of MgAl2O4 based material.


CB-3:IL04  In Situ and Ex Situ Characterization of Microwave-assisted Synthesis of Functional Oxide Nanoparticles
L. TINAT, E. CAZYUS-CLAVERIE, D. PORTEHAULT, C. CHANEAC, O. DURUPTHY, Laboratoire de Chimie de la Matière Condensée de Paris, UPMC Sorbonne Universités, Paris, France 

In the domain of oxide nanoparticles syntheses in aqueous solution, microwave oven is an interesting alternative to conventional oven for it allows a direct heating of the reacting medium and consequently higher temperature ramp. Consequences can be observed directly on the final product that generally presents smaller particles size and, in some cases, a structure modification.[1] Here, we have studied the possibility to control structure and composition of multicationic spinel nanoparticles from Co, Ni and Fe divalent salts in alkaline conditions. We have demonstrate that mixed spinels are obtained with microwave heating rather than segregated hydroxides. To get more insight on the impact of fast microwave heating we have performed in situ EXAFS and SAXS experiments on the microwave assisted aqueous synthesis of SnO2 nanoparticles in a specifically designed apparatus. We have determined the nucleation and growth conditions of tin precursors for different temperature ramp conditions up to 1 °C/s in microwave while conventional heating could only reach 2 °C/min. Microwave assisted flow syntheses were also developed.
[1] F. Dufour, S. Cassaignon, O. Durupthy, C. Colbeau-Justin, C. Chanéac, Eur. J. Inorg. Chem. 2707 (2012)


CB-3:IL05  Electromagnetic Field Effects in High-temperature Microwave Processing of Materials
K.I. RYBAKOV, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia, and Advanced School of General and Applied Physics, Lobachevsky State University of Nizhny Novgorod, Russia

Studies of high-temperature processing of materials have demonstrated enhancement of sintering, changes in the activation energies of diffusion-based mass transport processes, reduction in the temperature of solid-state phase transformations, etc. There is a growing body of experimental evidence that suggests that a direct action of the electromagnetic field is responsible for many of these "microwave effects". An analysis suggests that nonlinear interactions of charged vacancies and other defects with the high-frequency electric field can result in rectification of the alternating particle flows and produce net driving forces for mass transport. It has been shown that during microwave sintering of ceramics these effects can drive mass flows from the bulk of the grains into the grain boundaries resulting in an enhanced densification. Recently it has been demonstrated experimentally that microwave heating can be used to achieve ultra-rapid, the so-called flash sintering of ceramics. The implementation of this process is contingent upon fast and efficient control over the overheating instability (thermal runaway) that results from volumetric heating. Rapid sintering of powder metals can be accomplished by purposely using the resonant nature of microwave heating.


Session CB-4 - Electrical Field and Pressure Assisted Synthesis and Sintering

CB-4:IL01  Spark Plasma Sintering Mechanisms of Zirconium Oxycarbides and Alumina
A. MAITRE, G. ANTOU, N. PRADEILLES, Lab. SPCTS, CEC, Limoges, France

The identification of densification mechanism during HP and SPS is developed using an approach based on classical creep investigation. This latter is generalised using continuum mechanics based sintering models. Its benefit is to directly determine the densification parameters from the analysis of shrinkage rates of the porous material, rather than to transpose the creep mechanisms identified for dense material at given thermomechanical conditions to the densification progress. This approach is applied to compare the densification mechanisms involved at the initial stage of HP and SPS for a sub-micrometric α-alumina powder. From the stress exponent and activation energy values, it is shown that the main mechanism involves grain boundary sliding accommodated by dislocation motion and particle fracture in both cases. Therefore, the high heating rate in SPS could reduce the existence of surface diffusion phenomena at the beginning of the consolidation process. The kinetics of SPSed zirconium oxycarbides have been also investigated. A change of densification mechanism appears during the intermediate and final sintering stages. During this last stage, the deformation mechanism is similar to the one involved during creep of dense ZrCxOy ceramics.


CB-4:IL02  Ultra-high Pressure Synthesis of New Nitrides
KEN NIWA, MASASHI HASEGAWA, Nagoya University, Nagoya, Japan

Nitrides have been attracting much attention in the field of fundamental science and industrial application such as semiconductor (GaN), hard-material (BN) and magnetic material (Fe4N). In addition, the transition metal oxynitrides have been intensively developed for photocatalyst in the visible light region. In the synthesis of nitrides, direct nitridation by using molecular nitrogen or ammonia gas in the furnace at high temperature is a more simple and conventional method. However, there still remains technical and fundamental difficulties to synthesize new nitrides, although many challenges have been made so far. On the other hand, in the last two-decade, new nitrides have been successfully synthesized by high-pressure experiments. For example, the direct nitridation under gigapascal pressure range succeeded in the formation of novel nitrides such as cubic Si3N4 (Zerr et al. 1999) and PtN2 (Crowhurst et al. 2006) etc. Direct nitridation under high pressure enables us to synthesize nitrogen-rich nitrides and avoid the decomposition in the case of unexpected high temperature. Our recent topics of new nitrides for platinum group, 3d transition metal and gropu-14 elements, will be presented in the talk.


CB-4:L03  Low Temperature Development of Calcium Sialons along the Alpha/(alpha+beta) Phase Boundary using Nano-size Oxi-nitride Precursors and Spark Plasma Sintering Technique
B.A. AHMED, A.S. HAKEEM, T. LAOUI, King Fahd University of Petroleum and Minerals (KFUPM) Dhahran, Saudi Arabia

Calcium stabilized alpha-sialon ceramics (along the alpha/alpha + beta phase boundary) were synthesized using spark plasma sintering (SPS) technique and nano-sized starting powder precursors at relatively low temperatures of 1500 °C and 1600 °C. Development of sialon ceramic materials has been worked upon for the chemical compositions represented by Ca0.5Si12-(1+n)Al1+nOnN16-n, where n value was varied from 0.6 to 1.6 along the alpha/(alpha+beta) phase boundary. Effect of both the oxide content (‘n’ value) and sintering temperature on the formation of final phases, densification and mechanical properties was investigated. All samples resulted in densified ceramics. The density values were found to be in the range of 3.13-3.19g/cm3 and were comparable to the values reported in literature for similar compositions synthesized via conventional sintering techniques at temperatures greater than 1700 °C. For the samples synthesized at 1500 °C and 1600 °C remarkable Vickers hardness (HV10) of 20 GPa and 19 GPa was measured, respectively. With the increase in ‘n’ value and for higher sintering temperature, a slight decrease in hardness was observed due to grain growth phenomenon.


CB-4:IL05  Flash Sintering of Alumina and other Oxide Ceramics
V.M. SGLAVO, M. BIESUZ, Department of Industrial Engineering, University of Trento & INSTM, Florence, Italy

Flash sintering is an innovative, energy efficient consolidation technique which allows very rapid densification of particulate ceramic materials at temperatures much lower than conventional ones. In flash sintering the electric current is forced to flow into the green body until the “flash event” occurs. This is characterized by extremely rapid densification (in the order of seconds or minutes), electrical resistivity drop and bright light emission. Several mechanisms have been proposed to explain the flash event: including generalized Joule heating causing a sort of “ultra-fast firing” process, localized overheating at the particle/particle contact point leading to particle surface softening/melting, field-induced lattice disorder nucleation, current-induced modification of the defects chemistry. Flash sintering has been applied on several high temperature ionic conductor (YSZ, GDC), protonic conductors (BaCe0.8Gd0.2O3−δ), semi-conductors (SiC), composites (ZrO2-Al2O3, glass-Al2O3) and electrically conductive (MnCo2O4, LSCF) ceramics. Instead, only few attempts have been reported on flash sintering of insulating ceramics like alumina. In the present work, 99.8% pure alumina was used in flash-sintering experiments in order to understand possible conduction mechanisms and densification phenomena. The influence of some operating conditions, such as electrical field intensity, current density and electrode materials was also studied. The results obtained also on other oxide ceramics (namely zirconia) allow to point out that the flash event is triggered by the activation of a “controlled” dielectric breakdown and in the modification of the defect chemistry. The current flow remarkably enhances mass transport phenomena (even considering the internal Joule effect), causing an unexpected densification and grain growth.


CB-4:IL06  Spark Plasma Sintering of ceramics: From Controlling the Microstructures to the Development of Complex Shapes
C. MANIERE¹, G. CHEVALLIER¹, L. DURAND², F. AHMAD¹, G. CHEVALLIER¹, A. WEIBEL¹, F. MAUVY³, R. EPHERRE¹, C. ELISSALDE³, M. MAGLIONE³, C. ESTOURNES¹, ¹CIRIMAT, Université de Toulouse, CNRS, UT3, INPT, Toulouse Cedex, France; ²CEMES, Univ. Toulouse, CNRS, Toulouse Cedex, France; ³ICMCB, CNRS UPR 9048, Université Bordeaux, Pessac, France

Pulsed Electric Current Sintering (PECS) techniques have known a huge development over the last two decades. In particular, Spark Plasma Sintering (SPS) is an extremely powerful technique to sinter all classes of powders (metallic, ceramic) as well as composites. It consists in applying simultaneously a load and a high intensity pulsed direct current on tools containing powder to sinter. The very fast temperature increase is driven by the Joule’s effect and the grain growth is almost suppressed. We will illustrate via several examples the potentialities of this technology: i) In terms of control of microstructures. 3Y-ZrO2 ceramics with grain size around 300 nm exhibit high mechanical properties (fracture strength and toughness). ii) In tailoring the properties of composites materials. Elaboration of multimaterials mixing at different scale a ferroelectric phase and low losses dielectric material leads to composites with adjustable permittivity values and tenability iii) In developing complex shapes. The modeling of the process by finite element method coupling three main physics, Electric Thermal and Mechanic (ETM) allows now to predict the evolutions of temperature, grain size and porosity during the process and to develop tools to elaborate complex shapes.


CB-4:IL08  High Pressure Synthesis and Crystal Growth of BN and Related Materials
TAKASHI TANIGUCHI, National Institute for Materials Science, Tsukuba, Japan

Hexagonal boron nitride BN (hBN) and cubic BN (cBN) are known as the representative crystal structures of BN. The former is chemically and thermally stable, and has been widely used as an electrical insulator and heat-resistant materials. The latter, which is a high-density phase, is an ultra-hard material second only to diamond. In addition to those, wruztite BN (wBN) is also known as other polymorphic phase. As crystal growth technique is not, however, applicable for wBN due to its thermodynamically metastable nature, fundamental properties of wBN with bulk crystalline form is not well studied so far. The key issue to obtain high purity BN crystals is to reduce oxygen and carbon contamination in the growth circumstances. Then an attractive potential of hBN as a deep ultraviolet (DUV) light emitter and also superior properties as substrate of graphene devices were realized. By using high purity hBN crystal as a starting materials, high purity cBN sintered body and also highly oriented wBN crystalline form were obtained. In this paper, our recent studies on hBN, cBN and wBN synthesis under high pressure will be reported.


CB-4:L09  Effect of DC Current on Creep behavior of 8Y-ZrO2
KOJI MORITA, BYUNG-NAM KIM, HIDEHIRO YOSHIDA, KEIJIRO HIRAGA, YOSHIO SAKKA, National Institute for Materials Science, Tsukuba, Japan

The effect of DC current on high temperature phenomena of ceramics has attracted considerable attention as a new factor in the material manufacture processing. In particular, the flash sintering reported firstly by Raj et al. has widely been studied in the field of powder sintering. Although it is important to understand the mechanism of the flash event, flash sintering is a very steep event (< 5 s) and is not easy to discuss the mechanism. In order to discuss the mechanism of the current effects under more mild conditions, therefore, the present study examined the tensile behavior with and without electric current conditions using 8Y-ZrO2 as a reference material. By imposing DC current higher than a critical power Pc, flash event similar to that of powder sintering occurs even in the 8Y-ZrO2 bulk. The Pc value is about 100-200 mW/mm3 at around 1000 °C. For currents lower than Pc, the imposed current increases sample temperature depending on the imposed value, but does not enhance the rate of deformation. For currents higher than Pc, the field can enhance the deformation rate up to 10 times compared with that of no field conditions. The enhanced deformation cannot be explained only by the increment of sample temperature and it is likely to occur by the flash event.


Session CB-5 - Functionally Graded Materials

CB-5:IL01  Metal-ceramics Functionally Graded Materials
YOSHIMI WATANABE, Nagoya Institute of Technology, Nagoya, Japan

Functionally graded materials (FGMs) are well known as a relatively new class of inhomogeneous composite materials having gradient property. The gradient property in the FGMs is caused by a position-dependent chemical composition, microstructure, or atomic order. Ones on the typical FGMs are metal-ceramics FGMs. These FGMs are generally fabricated by powder metallurgy, melt-processing technique, chemical vapor deposition, physical vapor deposition and so on. Among them, the melt-processing technique is an effective way to fabricate continuous graded structure. In this lecture, fabrication of metal-ceramic FGMs with continuous graded structure under centrifugal force will be presented. Fabrication methods of FGMs under the centrifugal force are classified into three categories, namely centrifugal method (application of centrifugal casting), centrifugal slurry method (centrifugal sedimentation) and centrifugal pressurization method (simple pressurization by the centrifugal force). Some results from the centrifugal method, centrifugal slurry method and centrifugal mixed-powder method, as one of centrifugal pressurization method, will be described.


CB-5:IL02  MAX Phase Reinforced SiC/SiC Composites
XIAOWEI YIN, LAIFEI CHENG, LITONG ZHANG, Northwestern Polytechnical University, Xi'an, China

Owing to the unique nanolaminate crystal structure, the MAX phases with A = Al and Si offer not only unique mechanical properties, but also tailorable functional properties, which make them attractive functional phase for ceramic matrix materials. Formation of MAX phase in fiber reinforced ceramic matrix composites is extending the application fields of advanced ceramic composite materials. This work focuses on the process, microstructure and properties of SiC fibers reinforced SiC matrix composites with the in-situ formation of Ti3Si(Al)C2. The SiCf/SiC-Ti3Si(Al)C2 composites exhibit unique multi-functional properties.


CB-5:L03  Analysis of FGM Beam Model for Thermal Stability Behavior with Heat Conduction Effect
YOUNG-HOON LEE, TAE-KYUNG LIM, JI-HWAN KIM, Department Mechanical and Aerospace Engineering, College of Engineering, Seoul National University, Seoul, South Korea

Functionally Graded Materials (FGMs) beam models are based on the neutral surface concept as well as the homogenized properties. Also, First-order Shear Deformation Theory of Beam (FSDTB) is used in thermal environments. In the analysis, the neutral surface shift depends on the temperatures and volume fractions of the material. An important thing is that the surface shift results in the uncoupled set of stress resultants within the temperature fields. Furthermore, the improved temperature-dependent shear correction factor is to evaluate more reasonable shear correction for the FGMs model. Validity of this work is presented as compared with the experimental results for the thermo-elastic vibration of step-formed FGM model. Moreover, the natural frequencies of the homogenized model decrease as the increase of temperature up to the thermal buckling at the critical temperature. Also, the neutral surface shift results in the lower thermal buckling state than the previous work neglecting the shift. Moreover, homogenization method considers the interactions of particles, then the natural frequencies are increased than the data using the rule of mixture model. Further, the homogenization method yields higher thermal stresses than without using the method.

 
Session CB-6 - Other Non Traditional or Novel Routes

CB-6:IL01  Novel Colloidal Syntheses in Molten Salts Toward Complex Nanoparticles
D. PORTEHAULT, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, Paris, France

Nanoparticles impact various fields of materials science. The range of solids reported as nanoparticles is however narrow compared to the portfolio of solid state chemistry for bulk materials. Many of such solids unreported at the nanoscale show properties without equivalent among more common phases often studied as nanoparticles. Because nanoscaling can modify, if not enhance, properties of eg. ultrahardness, catalysis, magnetism or energy conversion, efforts to reach such unreported nanoparticles are of high importance. Yet, they face a synthetic challenge: how to produce nanoparticles of solids typical of solid state chemistry and its protocols at high temperature? We will show some efforts that our team is putting since few years to reach such challenging nano-objects, by focusing on liquid-phase syntheses using high temperature inorganic molten salts as solvents. We will discuss the case of nanomaterials with properties different than those of bulk phases: metal borides for catalysis and thermoelectricity, and perovskite oxides for spintronic and fuel cells.


CB-6:IL02  High Temperature Adhesives Derived from SiBCN Precursors
SUN CHANG, JIANQIANG WANG, XINGANG LUAN, LAIFEI CHENG, Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an, China

Use of high temperature adhesives in air is extremely important for ceramic components. A novel adhesive for joining Al2O3 ceramic was made using polyborosilazanes (usually denoted as PSNB). The ceramic joints were heat-treated at temperatures ranging from 1300 to 1500 °C in air surroundings. The bonding strength was tested at room temperature and high temperatures respectively. The best performance of bonding strength at room temperature was 15.73 MPa. The formation of Al2O3·B2O3 means the reaction of adhesive and adhesion, and results in improving the bonding strength apparently. Compared to the bonding strength at room temperature, the bonding strength at 800 °C was 12.91 MPa, i.e. only decreased by 18%. To obtain an adhesive with high temperature bonding strength and low preparation temperature, polysilazane (PSNB) was modified by PBSZ, PSO, nano-Al2O3 as additives. Effects of the SiO2 to B2O3 ratio and stick pressure on microstructure and high temperature strength of the modified adhesives has been investigated. The bond strength of the modified adhesive reaches up to 12.08 MPa at room temperature, what is more, the strength still has 6.65 MPa at 1000 oC which is 2 times higher than the unmodified one. Other additives also were employed for the bonding of SiC ceramic.


CB-6:L03  Hybrid Simulations of Formation of Nanocomposite Materials with a Scaffold of Carbon Nanotubes and Boron Carbide Matrix by Means of Chemical Vapor Infiltration Technique
A.N. VOLKOV, Department of Mechanical Engineering, University of Alabama, Tuscaloosa, AL, USA

Nanocomposites with a scaffold of carbon nanotubes (CNTs) and a ceramic matrix is a promising class of light-weight high-temperature materials with large strength and toughness. The goal of the present paper is to develop a hybrid computational model for simulations of gas-assisted fabrication of such materials based of the chemical infiltration technique. The model includes a mesoscopic model of CNT materials, where every nanotube is represented by a chain of cylindrical segments, a kinetic model of gas flow through a microporous CNT network material, and a model of chemical decomposition of gas mixture on the nanotube surfaces and deposition of boron carbide. Gas flow through the CNT network is simulated by the Direct Simulation Monte Carlo method. The structure of CNTs in the film is obtained in preliminary dynamic mesoscopic simulations, leading to self-assembly of nanotubes into a continuous network of bundles. Then the infiltration of a reactive gas mixture through a mesoporous carbon nanotube film and deposition of amorphous boron carbide is studied based on the developed hybrid model. The effectiveness of the material deposition and uniformity of distribution of the deposited boron carbide are discussed as functions of the film porosity and CNT scaffold temperature.


CB-6:L04  Effect of Gold Nanoparticles on Corrosion Behavior of Melting Gel Coatings on Stainless Steel
L.C. KLEIN¹, S. KALLONTZI¹, L. FABRIS¹, A. ARPINO¹, A. JITIANU^{2, 3}, J. MOSA⁴, M. APARICIO⁴, ¹Rutgers University, Department of Materials Science and Engineering, Piscataway, NJ, USA; ²Department of Chemistry, Davis Hall, Lehman College-CUNY, Bronx, NY, USA; ³Chemistry Program, The Graduate Center, The City University of New York, New York, NY, USA; ⁴Instituto de Cerámica y Vidrio-CSIC, Campus de Cantoblanco, Madrid, Spain

Melting gels prepared by the hydrolysis of substituted alkoxysilanes have been applied to stainless steel and magnesium for protection against corrosion. Both thin and thick coatings have shown resistance to salt solutions, with capacitive behavior, a significantly higher impedance modulus, and little change over weeks of exposure. This indicates that the melting gel coating has good adherence to the metal and that it is hermetic. Composition 65 mol% methyltriethoxysilane (MTES)-35 mol% dimethyldiethoxysilane (DMDES) was prepared with citrate-stabilized Au nanoparticles. The electrochemical impedance behavior was recorded, along with studies of anodic polarization. The presence of the Au nanoparticles did not change the response significantly from what had been recorded on thick coatings without Au nanoparticles. However, the Au nanoparticles changed the flow behavior of the melting gels, such that the coatings were easier to apply.


CB-6:IL06  Electrospinning of Mesoporous Ceramic Nanofibers
O. ELISHAV¹, V. BEILIN², G.E. SHTER², G.S. GRADER², ¹The Nancy and Stephen Grand Technion Energy Program, Technion I.I.T, Haifa, Israel, ²The Wolfson Department of Chemical Engineering, Technion I.I.T, Haifa, Israel

Mesoporous nanofibers provide advantageous chemical and physical properties especially for applications in energy, absorbents and other functional materials. Electrospinning is a simple approach to produce polymer, ceramic and composite fibers of various diameters and morphologies. Moreover, core-shell electrospun nanofibers were fabricated previously using coaxial nozzles or emulsion method. Recently we synthesized ceramic nanofibers with unique lamellar-like mesoporous structure using a single nozzle electrospinning process, followed by thermal treatment. The fibers morphology consist of inner Fe-Al-O core with elongated mesopores and an outer thin accordion-like Fe-rich shell, obtained by restructuring of initially uniform fibers. A general mechanism for the formation of this morphology is suggested, where the final structure depends greatly on the heating rate stage and chemical composition of the precursors. The proposed mechanism suggests that this structure is possible in the presence of a metal-organic component with low melting point and high volatility below the polymer main decomposition temperature. The presented nanofibers are highly promising in material research, especially in applications requiring an accessible porous core surface.


CB-6:L07  Synthesis of Nano-carbons and Nano-Ilmenites using Super-High-Energy Ball Milling
SATOSHI OHARA, Joining and Welding Research Institute, Osaka University, Ibaraki, Japan

The ball milling process is common in grinding machines as well as in reactors where various functional materials can be created by mechanochemical synthesis. A simple milling process reduces both CO2 generation and energy consumption during materials production. Herein a unique ball milling approach to produce sophisticated nanocarbons is reported. It is demonstrated that unique carbon nanostructures, including carbon nanotubes, carbon onions, and new carbon nanorings are synthesized by super-high-energy ball milling of steel balls [1,2]. This paper also shows the synthesis of ilmenite nanoparticles [3] and quenching ilmenite with a high-temperature and high-pressure phase using super-high-energy ball milling [4].
[1] S. Ohara, Z. Tan, J. Noma, T. Hanaichi, K. Sato, and H. Abe, Solid State Comm., 150, p.198-200, (2010). [2] Z. Tan, H. Chihara, C. Koike, H. Abe, K. Kaneko, K. Sato, and S. Ohara, Astronomical Journal, 140, p.1456-1461, (2010). [3] S. Ohara, K. Sato, Z. Tan, H. Shimoda, M. Ueda, and T. Fukui, J. Alloys and Compounds, 504, p.L17-L19 (2010). [4] T. Hashishin, Z. Tan, K. Yamamoto, Q. Nan, J. Kim, C. Numako, T. Naka, J.-C. Valmalette, and S. Ohara, Scientific Reports, 4, p.4700-1-6, (2014).


CB-6:L08  The Film Boiling Chemical Vapor Infiltration for the Elaboration of Oxide/Oxide Composites
C. BESNARD, L. MAILLE, Université de Bordeaux, LCTS, Lab. des Composites ThermoStructuraux, CNRS, CEA, SAFRAN, Pessac, France; P. DAVID, CEA Le Ripault, Commissariat à l’Energie Atomique, Monts, France; A. ALLEMAND, CEA Le Ripault, Commissariat à l’Energie Atomique, Monts, France and Université de Bordeaux, LCTS, Lab. des Composites ThermoStructuraux, CNRS, CEA, SAFRAN, Pessac, France

Nowadays, oxide/oxide composites are most of the time elaborated by sintering or chemical vapor infiltration. This work focuses on an original and fast process developed by French Atomic Energy Commission: the film boiling chemical vapor infiltration [1]. This technology, already used to elaborate C/C or SiC/C composites [2] [3], is composed of a porous preform fixed to a carbon resistor or susceptor. This sample is immersed into a liquid precursor and heated above the precursor decomposition temperature. A film of vapor is created locally around the sample. The vapor decomposes inside the preform and leads to the densification. In this work, aluminium tri-sec butoxide and tetraethyle orthosilicate were used to infiltrate alumina and silica in oxide preforms. Two experimental parameters have been studied: generator intensity and time. A patent “Elaboration of oxide/oxide composites by film boiling chemical vapor infiltration” has been filed [4].
[1] HOUDAYER M., SPITZ et al. Commissariat à l'Energie Atomique. US Patent n° 4472454 [2] DELHAES P. Carbon, 40, 2002, pp641–657. [3] DAVID P., KLEIN J., et al.16th International conference on composite materials, 2007. [4] ALLEMAND A., BROISSON P., et al. 23/02/2017, N°1751427.


CB-6:IL09  Environmental Friendly Process for Inorganic Functional Ceramics
SHU YIN, Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan

Environmental friendly process for the synthesis of inorganic functional ceramics plays important roles in practical manufacture and applications. In the present talk, various kinds of optical responsive functional ceramic nanomaterials successfully synthesized by environmental friendly green processes, such as hydrothermal/solvothermal process, mechanochemical doping process, oxygen plasma treatment process and a water molecular controlled-release solvothermal process (WCRSP) will be introduced. The composites combined the high-sensitive anion doped photocatalysts with up-conversion or long afterglow phosphors showed excellent deNOx photocatalytic activity under UV/ visible / NIR light irradiation, or even after turning off light irradiation. The mixed valence state tungsten based homogeneous nanomaterials possessed excellent IR light responsive properties, implied their potential applications as smart window materials and photothermal ablation cancer therapy materials. Significant contributions are expected for the development of optical responsive functional materials by green processes.


CB-6:IL10  Alternative Methods of Synthesis of Calcium Silicates
N. BETANCUR, J.C. RESTREPO, O.J. RESTREPO, Cement and Buiilding Materilas Group of Research. School of Mines, Universidad Nacional de Colombia, Medellin, Colombia

The synthesis methods alternative to the solid state reaction method are gaining more and more interest, due to the possibility of reducing the energy consumption of the processes and the production of nanoparticles with physical properties superior to those obtained by the traditional method. These methods can be classified according to the state of aggregation of their raw materials or to the type of energy resource used to generate the reaction, be it mechanical, chemical or thermal. Among the alternative methods, the flame aerosol pyrolysis method (FSP) is of great interest at present, because its scaling to pilot plants has been successful and the products obtained have excellent morphological and structural characteristics One example of this is the company Lurederra de España, which together with several European universities developed the FSP-advanced project for the construction of a pilot plant.