CO - 8th International Conference
Advanced Inorganic Fibre Composites for Structural and Thermal Management Applications


Session CO-1 - Production and Properties of Reinforcements, Preforms, and Matrix Materials

CO-1:IL01  Oxide Ceramic Fibers - State of the Art and New Developments
B. CLAUSS, S. PFEIFER, German Institutes of Textile and Fiber Research (DITF Denkendorf), Denkendorf, Germany; M.R. BUCHMEISER, DITF Denkendorf and University of Stuttgart, Institute of Polymer Chemistry, Stuttgart, Germany

Ceramic fibers are the key components of ceramic matrix composites (CMCs). The temperature limit of the composite materials is mainly determined by the long-term stability of the fibers. The use of oxide based ceramic fibers is limited by grain growth and creep at high temperatures. Therefore, research in the field of oxide ceramic fibers is focused on the optimization of the fiber structure and stoichiometry in order to push the temperature limit of the fibers further while preserving ore even improving their mechanical properties. At DITF Denkendorf research activities in this field are ongoing and different fiber types are under development. A new pure mullite fiber has already been developed to a high technical level and the potential of zirconia toughened alumina fibers is currently examined. Also first steps for the development of YAG fibers have been done. The interest of industry in oxide CMCs has been continuously growing during the last years. The potential of oxidic CMC materials for different applications in the fields of power engineering and aerospace has been realized, which will also lead to an increasing demand for high end oxide ceramic fibers.

CO-1:IL02  High-performance SiC-polycrystalline Fiber
TOSHIHIRO ISHIKAWA, Tokyo University of Science, Yamaguchi, Sanyo-Onoda, Yamaguchi, Japan

SiC polycrystalline fibers show very high heat-resistance and excellent mechanical properties up to very high temperatures (~2000oC). Presently, these fibers are actively evaluated for the aerospace applications. The structural performances of the composite materials are strongly dominated by the fiber’s strength, and then an increase in the fiber’s strength would become much more important. Up to now, we have clarified the relationship between the strength and the fine structure of the SiC polycrystalline fiber. The strength of the SiC polycrystalline fiber was decreased inverse proportion to one-half power of the size of the contained defect. And, it was clarified that the smaller the defect size became, the higher the strength became. These defects are formed during the conversion process from the raw material (amorphous Si-Al-C-O fiber) into SiC polycrystalline fiber. In this conversion process, the decomposition of the amorphous Si-Al-C-O fiber and the subsequent sintering of the decomposed fiber proceed as well. Since these changes proceed in the inside of each filament, strict control should be needed to minimize residual defects. By a decrease in the defects, much higher strengths will be expected.

CO-1:IL03  A Novel PAN/Silazane Hybrid Material for Processing of Carbon Fibers with Extraordinary Oxidation Resistance
G. MOTZ, University of Bayreuth, Ceramic Materials Engineering, Bayreuth, Germany; L. RIBEIRO, R.A.F. MACHADO, Federal University of Santa Catarina Materials Engineering, Florianopolis, Brazil

Carbon fibers (CFs) are currently the most important reinforcement component used for high performance composites like Carbon Fiber reinforced Plastics (CFRPs), Carbon Fiber reinforced Carbon (CFCs) and Ceramic Matrix Composites (CMCs), which are key materials for the modern economy. CFs possess very interesting properties like low density, high tensile strength, high Young’s modulus and excellent chemical and thermal stability under non-oxidizing conditions. Their biggest drawback is the insufficient oxidation stability at temperatures >400°C. The most efficient protection methods used nowadays are based on very expensive and complicated multilayered coating systems. But micro-crack formation in the coating systems after a long-term oxidation in combination with thermal stress lead to the complete oxidation of CFs. Therefore, a novel hybrid polymer on the basis of acrylonitrile (AN) and a commercial available oligosilazane (ML33) were developed as a precursor for processing of carbon fibers (CFs) via the dry-spinning process. Whereas PAN is used as the typical precursor for CFs the ceramic SiCN phase, derived from the polysilazane after pyrolysis, improves the intrinsic oxidation stability up to 800 °C. Also crystallization of the ceramic phase is avoided up to 1500 °C.

CO-1:IL04  Structure and Properties of Carbon Fibers
H. PETERLIK, University of Vienna, Faculty of Physics, Vienna, Austria

Carbon fibers consist of graphene planes set up in a turbostratic configuration with a high preferred orientation with respect to the fiber axis. This structural feature is essential for the extremely high Young’s modulus of the fibers. In-situ X-ray diffraction allows to determine the structural parameters governing the elastic properties of carbon fibers and furthermore to follow the evolution of these parameters with load and temperature. This allows realizing a measurement with environmental conditions identical to the one in use in aerospace applications, which is a particular advantage in comparison to other nanostructure measurement techniques such as electron microscopy. In-situ experiments up to nearly 2000 oC show the effectivity of a thermal treatment without load to obtain a stable structure. A comparison of measurements of fiber bundles and single fibers is presented, for structural as well as for mechanical test methods, and the advantages and disadvantages of each test method are discussed.

CO-1:L05  High Temperature Potential of Oxide Ceramic Fibers Investigated by Mini-composites Approach
K. TUSHTEV, R.S.M. ALMEIDA, K. REZWAN, Advanced Ceramics, University of Bremen, Bremen, Germany

The high temperature performance of all-oxide ceramic matrix composites based on the weak matrix concept strongly depends on the properties of the fiber reinforcement. Despite showing high strength at room temperature, commercial oxide fibers are susceptible to strength loss mainly due to grain growth at temperatures exceeding 1000°C. In this work, the microstructure evolution and the mechanical properties of Nextel 610 and Nextel 720 after heat treatment at temperatures ranging from 1000 °C to 1400 °C were investigated. In addition, the properties of the fibers embedded in porous alumina and mullite-alumina matrix was evaluated using mini-composites sintered at different temperatures. Tensile tests on mini-composites revealed the effect of matrix composition on the mechanical performance of the fibers. The investigations showed higher sensitivity of Nextel 610 to the matrix composition, probably due to chemical species diffusion. The limit of the load-bearing capacity of the mini-composites was investigated by comparing the results with mechanical tests on fiber bundles. Composite design in terms of fiber, matrix composition and sintering parameters is discussed.

CO-1:L06  In-situ Formed h-BN Platelet Reinforced Boron Carbide Composites Sintered via SPS
FAN ZHANG, ZHENGYI FU, WEIMIN WANG, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China

Boron carbide (B4C) ceramics with a small amount of cubic boron nitride (c-BN) as additive were fabricated by spark plasma sintering (SPS). During the sintering, The c-BN phases start transform into hexagonal phase at 1400℃ and 50MPa, and in-situ formed h-BN entirely at 1800℃ and 50MPa. The in-situ synthesized h-BN platelets were dispersed in B4C matrix homogenously, and limited the growth of B4C grains. Meanwhile, the phase transformation caused the driving force of B4C increasing, and promoted the densification of B4C. By comparing the density of B4C-5vol%c-BN and pure B4C ceramics fabricated at the same conditions, it was amusive to find that the phase transformation of cBN can ameliorate the sinterability of B4C. The sample with 5 vol%cBN as sintering additive was found to have excellent integrated mechanical properties with a hardness of 30.5 GPa, bending strength of 470 MPa and a fracture toughness of 3.84 MPa•m1/2. Higher cBN content resulted in unconspicuous improvement of bending strength and fracture toughness but obvious decreasing of hardness. The main toughening mechanisms, leading to the increased fracture toughness such as crack deflection, crack branching, crack bridging and pulling-out were characterized and discussed.

CO-1:L07  An Original Way to Produce Carbon Reinforcements: Polyoxometalate - Reduced Graphene Oxide Nanocomposite
C. DEBIEMME-CHOUVY1, B. THOMAS2, I. LUCAS1, M.M.T. TRAN1, A. VEILLERE2, J.-M. HEINTZ2, J.-F. SILVAIN2, 1Laboratoire Interfaces et Systèmes Electrochimiques, LISE - UMR 8235, Sorbonne Universités, UPMC Univ Paris 06, CNRS, Paris, France; 2Institut de Chimie de la Matière Condensée de Bordeaux, ICMCB-CNRS, Pessac Cedex, France

Nowadays metal (copper, aluminum and silver) matrix composite materials with specific thermal and/or electrical properties imply the use the graphene sheets which can notably be fabricated by chemical reduction of graphene oxide (GO). This method has the advantage of bulk quantity production but the chemical species used as reducing agent, such as hydrazine, are toxic and do not prevent the aggregation of the reduced GO (rGO) sheets in suspension in the absence of any stabilizer. An alternative green method for producing stable rGO has been developed using polyoxometalates (POMs) anions. We have employed a method based on the use of reduced POMs. This method is rapid, nontoxic and a high amount of POM@rGO can be prepared. These POM@rGO nanocomposites have been characterized by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS)1 and correlated with the process parameters.
1- C. Debiemme-Chouvy, B. Thomas, I. T. Lucas, T. T. M. Tran, J.-M. Heintz, A. Veillère, J.-F. Silvain, ChemPlusChem 82 (2017) 186-189.

CO-1:IL08  Development of Non-oxide Ceramic Fibers
A. NOETH, A. RÜDINGER, Fraunhofer Center for High Temperature Materials and Design HTL, Bayreuth, Germany; M. ROTHMANN, Werner Humbs, BJS Ceramics GmbH, Germany

Non-oxide ceramic fibers, mainly SiC fibers, are used as reinforcements in ceramic matrix composites (CMC). In contrast to monolithic ceramics, these composites show a damage-tolerant fracture behavior. CMCs are currently intensively developed for the application in gas turbines enabling higher operating temperatures in comparison to metals, which significantly improves energy efficiency. This paper starts with the presentation of the state of the art of non-oxide ceramic fibers including the different types of fibers and their properties. Then, the principles of the fabrication of ceramic fibers including the different process steps from the synthesis of the precursors and spinning dopes to pyrolysis and sintering of the fibers will be illustrated. Various factors controlling the fiber properties will be described and possibilities to enhance the fiber properties and quality will be discussed. While commercial SiC fibers are fabricated by a melt-spinning route, at Fraunhofer Center HTL the dry-spinning route is favored. The process flow of this route will be illustrated and the challenges in upscaling the fabrication process will be discussed.

CO-1:L10  Manufacturing Condition using the MI-PIP Hybrid Technique to Make a High Thermal Conductive SiC Fiber-Reinforced SiC Matrix Composite
KOHEI EJIRI, Tokyo University of Science, Noda-shi, Chiba, Japan; M. KOTANI, Japan Aerospace Exploration Agency, Mitaka-shi, Tokyo, Japan; S. OGIHARA, Tokyo University of Science, Noda-shi, Chiba, Japan

CO-1:L11  Development of a Colloidal SiC-C-slurry for the Manufacturing of SiC/SiC Composites
A. HELD, S. KNOHL, W. KRENKEL, Department of Ceramic Materials Engineering, University of Bayreuth, Bavaria, Germany

SiC-based Ceramic Matrix Composites (CMC) are increasingly used for applications in aeronautics, space and gas turbines because of their superior thermo-mechanical performance and low densities compared to conventional Ni-based superalloys. A colloidal-based SiC/SiC manufacture route is described based on SiC-C slurries avoiding the costly and time-consuming pyrolysis step of conventional SiC/SiC routes. The development of an aqueous SiC-C slurry is explained and the challenges of this route, such as slurry homogeneity, viscosity, green body density and residual silicon, are addressed. These properties are related to microstructure and properties of the raw materials. The three-step manufacturing process, starting with a multilayer coating on the SiC-fibers by Atomic Layer Deposition (ALD), the slurry impregnation of the fiber preform as well as the infiltration with molten silicon to obtain a dense and homogeneous SiC/SiC composite is discussed in details.

CO-1:L12  Preceramic Prepreg Production and use to produce low cost CMCs

Mass production of Ceramic Matrix Composites is still far from being achieved, mainly because of high production costs. In order to get a good performance-to-cost ratio, basalt and carbon fibers are still the main possible solutions, since ceramic fibers, although being now mass produced for aerospace applications, are not expected to lower their price soon, due to the choice of end users to produce the SiC fibers they need, without really increasing commercial availability. However, the potentialities of Carbon and Basalt fibers still appear to be underevaluated. Basalt reinforced CMC are tolerant to temperature up to 1200°C, although most themomechanical resistance is lost above 600°C, due to fiber re-crystallisation. With C fibers pseudoplastic rupture behaviour is possible up to 1000°C, although fibers oxidation may vanish this potential advantage. Both can be prepared from hand lay-up lamination of Preceramic Prepregs, which termoset at T below 250°C to produce panels or components. Thermoset Preceramic Polimer Matrix Composite can be then pyrolysed to a CMC, taking care of avoiding deformation. During the talk, mass production of Polysiloxane Preceramic Prepregs, their possible use to produce low cost CMC, their possible applications and end-of-life recycle are discussed.

CO-1:L13  Thermal Condensation Reaction of Polydimethylsilane in a CO2 Atmosphere for Synthesis of Polycarbosilane

Polycarbosilane (PCS) is known to be derived from polydimethylsilane (PDMS) by thermal condensation reaction in an inert atmosphere at temperatures of 400-450 ºC. In this process. Si-Si bonds in PDMS main chains are converted to Si-C bonds by methyl group insertion. This chemical reaction is called “Kumada rearrangement". Recently, we began to introduce high pressures of CO2 (2-5 bar) on the condensation reaction of PDMS in order to reduce hydrogen activity in the system, which may quench radicals formed during the chain scission. Consequently, we can obtain viscose liquid “PCS” at temperatures of 340-380 ºC with weight yields beyond 90%. CO2 is found to be an effective promoter for “Kumada rearrangement”. The properties and molecular structure of thus obtained “PCS” highly depends on synthesis conditions, such as CO2 pressure, heat treatment temperature, holding time and CO2/PDMS ratio. In cases of high CO2/PDMS ratios, the condensates tend to form swelled gels after immersing in toluene. These gels usually contain a less amount of Si-H groups and a more amount of Si-O-Si bridges than liquid “PCS”. In the presentation, we will describe about many kinds of “PCS”, which are various in molecular structures and viscoelastic natures, obtained under the CO2 environments.
Session CO-2 - Interfaces / Interphases

CO-2:IL01  Active Metal Brazing of Composites for Thermal Management Applications
R. ASTHANA1, M. SINGH2, N. SOBCZAK3, J.J. SOBCZAK3, 1University of Wisconsin-Stout, Menomonie, Wisconsin, USA; 2Ohio Aerospace Institute, Cleveland, OH, USA; 3Foundry Research Institute, Krakow, Poland

Robust integration technologies are central to manufacturing complex shape parts from ceramics and composites, laminates, and cellular materials. While industrial braze alloys containing active elements that promote wetting and bonding have mitigated some of the challenges in joining many ceramics, empirical evaluation of the effectiveness of braze alloys to wet and bond some less researched materials such as diborides and porous carbon is critical for their emerging potential in thermal management applications. This requires investigations of the classical wetting behavior as well as extensive brazing trials to screen promising combinations based on detailed microstructural observations of the bonded region and exploration of the engineering properties and performance of the joints. In this presentation, a survey of key results from our last decade’s empirical research to demonstrate wetting and brazing of diborides, carbon/carbon, and porous carbon to high-temperature metals and alloys will be presented. Brazing approaches for different ceramic and metal combinations together with the observations on interface microstructure using OM, SEM, EDS, and TEM, and selected engineering properties will be highlighted to reveal the systems that are promising for further exploration.

CO-2:IL02  Interfaces and Interface Design in CMCs
J. LAMON, CNRS/Ecole Normale Supérieure Paris - Saclay, Laboratoire de Mécanique et Technologie, Cachan, France

The interfacial domain is a physical entity that influences significantly composite mechanical behavior. It consists of a fiber/matrix interface or an interphase bonded to the fiber and the matrix. This paper discusses the main features of the interfacial domain in CMCs, with respect to composite mechanical behaviour, not only from a qualitative but also from a quantitative point of view. Various functions are assigned to the interfacial domain. Depending on circumstances, the interfacial domain or the matrix is the weakest element, so that it initiates cracks or it causes crack deflection. Crack deflection was a topical issue in the literature. But an additional contribution of debonded interfaces to composite mechanical behaviour has been sought through the concept of tailored interfacial domain in SiC/SiC composites. Data on interfacial characteristics are provided. The techniques of measurement of these characteristics are outlined. Finally guidelines to the selection of interfacial domain are discussed.

CO-2:IL03  Fiber-matrix Interfaces Optimized for Nuclear and Thermomechanical Applications
C. FELLAH, J. BRAUN, C. SAUDER, Den-Service de Recherche de Métallurgie Appliquée (SRMA), CEA, Université Paris-Saclay, Gif-sur-Yvette, France;
M.-H. BERGER, MINES ParisTech, PSL Research University, MAT - Centre des matériaux, CNRS UMR 7633, Evry, France

SiC/SiC composites are currently considered for cladding application, either in fast or in thermal neutron nuclear reactors. The fiber-matrix coupling in those composites has aroused interest because of its influence on the thermomechanical properties of the material. For the considered applications, a thin (< 100 nm) pyrocarbon interphase is deposited on the fiber by CVI (Chemical Vapor Infiltration), before matrix densification. However, even though the reinforcements employed have similar thermomechanical properties, the mechanical properties of resulting composites can strongly vary from one fiber to another. An understanding of the mechanisms governing the fiber/matrix bonding was conducted. The local structure at the different interfaces was analyzed by TEM. On the other hand, the extreme surface was characterized by X-ray Photoelectron Spectrometry and Inverse Gas Chromatography. These analyses have led to a better understanding of the fiber-matrix coupling, leading to several optimization paths in order to improve the mechanical behavior of SiC/SiC composites.

CO-2:IL05  Pyrocarbon Interphases in Carbon/Carbon and Ceramic-Matrix Composites: Modelling Activities
G.L. VIGNOLES, University of Bordeaux, CNRS, Safran, CEA : Lab. for ThermoStructural Composites (LCTS) - UMR5801, Pessac, France

Toughness and damage-tolerance of Ceramic Matrix Composites (CMC) and Carbon/Carbon (C/C) composites are obtained by engineering the fiber/matrix or bundle/matrix interface in such a way that matrix cracks do not propagate in a catastrophic manner through the reinforcing fibers. Pyrocarbon (PyC) interphase may be considered as a reference solution. Its performance highly depends on its nanotexture that has to be accurately tailored through its fabrication process: chemical vapor deposition or infiltration (CVD/CVI). Control of pyrocarbon microstructure by CVI is a key issue in the processing of PyC interphases in CMC as well as of matrices in high-performance carbon/carbon composites. The gas-phase chemistry plays a key role in the various nanotextural transitions. In this presentation, we will review several modeling projects concerning pyrocarbon. First, we will present a multiscale modeling approach of pyrocarbon CVD/CVI, giving clues on the process/nanotexture relationship; second, an image-based atomistic approach elucidating the impact of nanotexture on some mechanical properties; finally, we will describe a study of the effect of interfaces on the non-linear mechanical behaviour of a 3D carbon/carbon composite.

CO-2:L06  RE2Si2O7 Disilicates: Promising Oxidation and Corrosion Resistant Weak Interface in SiCf/SiC CMC
JINGYANG WANG, High-Performance Ceramics Division, Shenyang National Laboratory for Materials Science, Institute of Metal Research, CAS, Shenyang, China

Weak interfacial phase between fiber and matrix enhances the toughness of ceramic matrix composite (CMC) through interface debonding and fiber pullout. Beyond typical BN and graphite interfaces, oxidation and corrosion resistant interface is crucial important for the optimal long-term stability of CMC in harsh environments. This presentation shows that rare earth disilicates RE2Si2O7 are promising interfacial phase in SiCf/SiC CMC due to their damage tolerance, moderate elastic stiffness and strength, plastic deformation capability, good high temperature oxidation and corrosion resistances, and compatible thermal expansion coefficient with SiC. Our work provides a fundamental understanding of the requested properties of RE2Si2O7 and will guide the design of novel weak interface in SiC/SiC CMCs.

Session CO-3 - Processing and Fabrication of MMCS, CMCS, and C/C Composites

CO-3:IL01  Design, Structure and Properties of Organomorphic Composites as New Materials
E.A. BOGACHEV, Joint Stock Company "Kompozit", Korolev, Moscow region, Russia

Properties of any composite to a great extent depend on its reinforcement. Techniques of composites preforms production are characterized by a wide variety. Preforms of biomorphic composites made from wood rank a specific place among them. Similar to biomorphic preforms a reinforcement of new materials - organomorphic composites - can be formed with an organic feedstock: a stack of staple (around 50-60 mm in length) filaments of carbon fiber precursor (f.e. polyacrylonitrile) or silicon carbide fiber precursor (polycarbosilane). Non-oxidizing annealing (carbonization) of the stacks with simultaneous pressing of them allows to create uniform, high dense (0.4-0.5 ρfiber) preforms having equivalent pore diameter from several microns to 30-40 µm. The preforms can be one, two or three-dimensionally oriented. As it was experimentally established by testing organomorphic C/C & SiC/SiC composites have properties which conventional composites do not have, especially for the applications where small thickness, low surface roughness and low permeability are very important.

CO-3:IL02  Fast and Ultra-fast Sintering of Ceramics by Plastic Deformation as Dominating Mechanism
ZHENGYI FU, Wuhan University of Technology, Wuhan, China

In traditionally sintering, the atomic diffusion may cause also grain growth, besides contributes to densification. Undesirable grain growth results in degradation. Attempts have been made to gain full density, while keep the grains with limited growth. A new process was proposed to sinter ceramic powders at a lower temperature close to the onset point of grain growth, at the same time apply a higher pressure to the compact. Fully dense micro-sized ceramics with limited grain growth were made by the new route. The samples show excellent mechanical properties. The plastic deformation under high pressure and at relatively high temperature is suggested to be the dominating mechanism for the densification process. The second method is based on combustion reaction heating plus quick pressing (CR/QP) for producing dense nano-grain ceramics. The heat generated by combustion reaction is applied to act as a heating source, which supplies a fast heating rate of 1300-1600℃/min to the sample. Dense nano-grain ceramics were obtained in several minutes. The process has higher heating rate and shorter densification time than traditional sintering processes, which leads to no or limited grains coarsening. It is suggested that the plastic flow mechanism plays an important role in the densification.

CO-3:L03  Multi-functionally Graded Electroconductive Alumina
I. HUSSAINOVA, Tallinn University of Technology, Tallinn, Estonia

Multifunctionality has emerged as a strategic priority for development of novel materials. As nature provides a rich source of inspiration, a large number of approaches is related to mimicking the features of biological species. Here we report development of multifunctionally graded ceramics demonstrating gradient of both mechanical and electrical properties, which is achieved by controlled incorporation of graphene encapsulated ceramic nanofibers into a host structure. Alumina was chosen as an important structural ceramic. The composites with alternation of grain sizes in layers were produced by adding thin inter-layers of graphenated alumina nanofibers. The samples were consolidated by Spark Plasma Sintering technique at 1350 °C in nitrogen atmosphere under 50 MPa pressure. The effect of inter-layers on microstructure, mechanical and electrical properties of alumina as well as anisotropy of these properties were studied. Vickers hardness, fracture toughness and nanoindentation tests have been performed to show graduation of the mechanical properties. Materials with gradient grain size and, therefore, hardness throughout the bulk combined with highly anisotropic electroconductivity are reported.

CO-3:IL04  Additive Manufacturing of Ceramics and Composites
TATSUKI OHJI, NAOKI KONDO, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan

For realizing complex-shaped products with reduced lead-time, additive manufacturing (AM) technologies for ceramics products have been developed in “High-Value Added Ceramic Products Manufacturing Technologies” project (sponsored by the Japanese government) since 2014. The project deals with two technologies for producing ceramic green bodies; powder layer manufacturing (powder bed fusion, or indirect selective laser sintering) and slurry layer manufacturing (stereolithography) due to adjustability of green density, relatively good precision, complex-shaping capability, etc., in addition to ceramic laser sintering (direct selective laser sintering). The paper will describe the up-to-date research achievements in this project, including the unique-structured 3D bodies never attainable in conventional methods. Particularly the paper addresses a number the technical items which should be carefully considered and properly selected, for optimizing the AM procedures. It will show what sorts of technical items we have, how those are connected and correlated each other and what should be considered and selected in each item in order to obtain sound products through AM approach, taking an example of powder layer manufacturing.
This work was conducted as a part of ”High-value added ceramic products manufacturing technologies project” supported by CSTI, SIP, “Innovative design/manufacturing technologies (managed by NEDO)”.

CO-3:IL05  New Approaches for the Manufacture of C/C-SiC Composite Materials
W. KRENKEL, N. LANGHOF, Ceramic Materials Engineering, University of Bayreuth, Bayreuth, Germany 

Carbon and silicon carbide represent the most common matrices of ceramic matrix composites (CMCs), mainly used for friction products, engine components, thermal shields, and ballistic protection. C/C-SiC composites, manufactured via the reactive melt infiltration (RMI) process, in particular made by Liquid Melt Infiltration (LSI), are well-established structural materials whose matrix comprise mainly of carbon as well as of silicon carbide. The LSI-process offers some unique possibilities for a comparatively fast and simple fabrication of CMC composites with different microstructures and properties, conventionally based on thermosets (like phenolics) as precursors and traditional forming techniques like warm pressing and resin transfer molding (RTM). Newly developed continuous fiber reinforced C/C-SiC materials based on thermoplastic precursors like Polyetherimid (PEI) or Polyetheretherketon (PEEK) as well as short fiber reinforced C/C-SiC composites manufactured by a layer-by-layer manufacture of net shaped non-woven preforms (as a first approach of an additive manufacture of C/C-SiC materials) offer new opportunities for a cost-efficient fabrication of CMC components. The correlations between the manufacture parameters and the material's properties are discussed.

CO-3:IL06  Rapid Densification of CMCs by Controlling the Multi-scale Pores in CVI Process
LAIFEI CHENG, Science and Techonology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi'an, China

Ceramic matrix composites (CMCs) have received much attention in the aircraft, aerospace, et al. due to their low density, high specific strength, excellent mechanical properties and good electromagnetic (EM) wave absorbing properties. To fabricate fiber reinforced CMCs, chemical vapor infiltration (CVI), which aids the production of irregular-shaped components and avoids fiber damage at high temperature, has been effectively used to fabricate CMCs. As the application of CVI CMCs rapidly grows, for CMCs with enclosed structure or thick-section, the classical CVI process is difficult to satisfy the requirement of high density, due to the bottleneck problem that the depositing channels were easily to be plugged. In present work, machining-aided CVI (MACVI) are used to facilitate the matrix deposition, in which the machining hole performed as infiltration-assisting holes for reactant gas. Firstly, the enhancement on mechanical performances of C/SiC composites via MACVI were demonstrated due to the more matrix deposited and higher load carried. Secondly, the minimum reflection loss (RL) of MACVI-C/SiC composites also improved (up to307%) against that of CVI-C/SiC composites due to the multiple reflection of EM wave in periodic micro-holes. Finally, the multi-scale pores can be backfilled using carbon nanotubes or other materials, which led to some unique properties such as thermal, electrically conductivity and mechanical strength.

CO-3:IL07  An Overview on the Recent Researches on Metal Matrix Composites
Y. LE PETITCORPS, LCTS UMR 5801, University of Bordeaux, Pessac, France

The conference will recap the main results and applications in the field of reinforcement of Al, Mg, Cu and Ti matrices with particles (SiC, TiC, diamond), short or continuous fibers (carbon, silicon carbide, alumina) or continuous filaments. The talk will then be focused on the reinforcement of titanium matrix composites TMCs. Several processes have already been investigated in order to fabricate the TMCs such as the Foil/Fiber/Foil or the Electron beam PVD coating of the matrix on individual fibers. Concerning the first one, the spacing between the fibers is not well controlled, for the second process, the spacing is perfect but the sputtering speed is too low (few microns per hours). Recently two new processes have been studied. For the first one, the SiC fiber is drawn at a high speed (few meter/second) through the melted titanium allowing the coating of the filament with the required thickness in order to reach a volume fraction of fiber around 30%. For the second one, titanium wires are strand around a SiC fibre, the diameter of the titanium wire as well as the number of wires control the volume fraction. For the first process it is important to control the wettability and the reaction between the fiber and the matrix, for the second one, it is important to avoid the mechanical damage of the fiber during the strand. For these two processes, the wrapped fibers are hot pressed in order to densify the composite. The advantages and drawbacks and applications of these two processes will be discussed.

CO-3:IL08  Additive Manufacturing of Light Weight and High Power Density Propulsion Systems
M.C. HALBIG, NASA Glenn Research Center, Cleveland, OH, USA; M. SINGH, Ohio Aerospace Institute, Cleveland, OH, USA

Advanced manufacturing methods are needed for enabling innovative propulsion component designs for applications in turbine engines and hybrid electric systems. Compared to conventional manufacturing, components can be more geometrically complex, compact, multi-material, innovatively cooled, integrated, and multifunctional. Advanced materials offer lighter weight and better performance than conventional materials. For turbine engine applications, silicon carbide (SiC) based composites are being pursued using binder jetting and laminated object manufacturing (LOM). For electric motors, additive processes are being applied toward optimized component designs to include the housing, rotor, and stators with 3-D printing and wire imbedded coils and with direct printed 3-phase coils. The electrical conductivity of silver conductor coils is being optimized by evaluating alternate sintering methods and additions of graphene and carbon nanostructures. The new components offer increases in temperature capability, efficiency, and power density for reductions in energy consumption and emissions.

CO-3:IL09  High Temperature Molybdenum Matrix Composites
S. MILEIKO, Institute of Solid State Physics of Russian Academy of Sciences, Chernogolovka, Russia 

Molybdenum-matrix composites reinforced with oxide and silicide fibres have been successfully produced by the internal crystallisation method. The composites are characterised by high damage tolerance: the value of notch sensitivity can be as high as 1. The composites are sufficiently strong and creep resistant at temperatures up to 1400oC. The oxidation rate of the composites at high temperatures is some orders of the magnitudes lower than that of pure molybdenum. An optimization of the composition of the fibres and fabrication parameters will generate a new family of heat resistant materials characterised with a necessary balance of three main characteristics of such materials those being creep resistance – damage tolerance – oxidation resistance.

CO-3:L10  Ceramic Matrix Composites (CMCs) for High Temperature Industrial Applications
L. CAVALLI, F. GIACOMETTI, F. BERNARDINELLO, Petroceramics spa, Stezzano, Italy

CMCs feature attractive properties for several engineering applications, especially where lightweight, high mechanical and high temperature stability are required. In particular CCMs favorably combine the lightweight and the toughness of polymeric matrix composites with the high temperature resistance and the hardness of ceramics. Here a new class of continuous carbon fibers CMCs obtained by an original approach and withstanding much higher operating temperature and resistance are presented. Preforms of phenolic and silicone resins are obtained using innovative carbon fiber based pre-pregs using straightforward compression molding and vacuum bagging techniques. Perform densification is performed in two different ways: polymer impregnation and pyrolysis (PIP) and liquid silicon infiltration (LSI) which can strongly increase the temperature resistance. The versatility of this approach enable the processing of a wide range of preforms of different raw materials, and by wisely varying and combining densification methods CCMs with customized features are obtained in a cost-effective way. Examples of physical, mechanical and thermal properties are given and appraised for some industrial relevant applications like automotive, aeronautic and aerospace.

CO-3:L11  Impact of Matrix Composition on the Properties of SiC/ SiC Ceramic Matrix Composites
K. SCHOENFELD, H. KLEMM, Fraunhofer IKTS, Dresden, Germany

Advanced ceramic matric composites (CMCs), in particular non-oxide CMC based on silicon carbide fibers and SiC matrices (SiC/SiC), are increasingly used for components in the hot gas path of advanced gas turbines in the aerospace and aircraft industry due to their excellent properties compared to traditional super alloys. Besides a superior property level at ambient and elevated temperatures of the composites, the damage tolerance crack behavior is the most important requirement for these applications in aero engines preventing a catastrophic failure of the ceramic component during service. In the present study SiC/SiC composites were fabricated by a precursor infiltration and pyrolysis process (PIP). Several matrix systems with and without fiber coating were used in order to achieve a flaw tolerant behavior. The composites were analyzed regarding their mechanical properties. Special emphasis was placed on the crack formation and propagation behavior in correlation to the microstructural features of the composites. Finally some idea about the design of flaw tolerant CMC will be provided.

CO-3:L12  New Large-scale Production Method for C/C-SiC Ceramics
D.J. NESTLER, J. STILLER, L. KROLL, University of Technology Chemnitz, Chemnitz, SN, Germany

At Chemnitz University of Technology, the chairs of Lightweight Structures and Polymer Technology, Composite Materials and Polymer Chemistry develop a fully automated, large-scale production process for fibre reinforced ceramics. In comparison to the state of the art, the first production step “shaping” is realised through thermoset injection moulding. Using this method, the complete process can be automated. Simultaneously, the injection moulding technology allows complex geometries with near net shape in short cycle times of about five minutes. Thereby, the large-scale production offers with a wide range of shot weights (few mg up to 100 kg) also in multi-component technology. In addition, several manufacturing steps can be omitted, which improves the reproducibility and working in closed environments is better for the employees’ health. Further process steps, like pyrolysis and silicon infiltration follow the state of the art. Although, this promising approach significantly shortens the fibres, the defined plastic processing is highly reproducible and generates similar mechanical properties like manual processes, due to the better fibre-matrix interaction in the plastic composite. In addition, continuous fibre preforms can be inserted to fulfil higher requirements.

Session CO-4 - Ultrahigh Temperature Ceramic Composites (UHTCCs) and Laminated Composite Structures

CO-4:IL01  Joining of Ceramics and CMC for Extreme Applications
M. FERRARIS, Politecnico di Torino, Torino, Italy

Innovation in manufacturing and testing of joined components for extreme applications developed at GLANCE-Glasses, Ceramics and Composites research group at Politecnico di Torino, Italy ( will be presented and briefly discussed. The combination of advanced design of interfaces and joining materials/technologies, selective matrix removal from the composite surface, laser structuring and mechanical machining of the composite/metal surfaces will be discussed and compared to existing solutions. Several mechanical tests have been developed at Politecnico di Torino and used to measure the shear strength of joined materials, but few standard tests are available and universally accepted. Commonly adopted lap test methods do not properly measure shear strength and a comparison of data obtained by different lap test methods is not possible, nor a comparison between different joining materials. J-TECH@POLITO, a recently funded Advanced Joining Technology research center at Politecnico di Torino, will be introduced. Finally, opportunities for common research activity within cooperative research projects (such as KMM-VIN and the Italy Chapter of the American Ceramic Society) will be briefly reviewed.

CO-4:IL02  Mechanical Properties and Microstructure of Unidirectional UHTCCs

The impelling demand for materials able to operate at temperature above 2000 °C pushes the scientific research towards continuous search of materials possessing a combination of properties more and more challenging. C/SiC composites are currently the most used materials for aerospace applications, such as nose cones, leading edges and rocket nozzles, owing to excellent mechanical properties and thermal shock resistance but their operational limit is ~1600 °C. ISTEC activities have been recently focused on fabrication of continuous carbon fiber reinforced ZrB2- and ZrC- based ceramic matrix composites (UHTCCs) which have the potential to operate above 2000 °C. This lecture illustrates processing techniques and characterization of unidirectional (1D) UHTCMCs focusing on the aspects of matrix densification, fiber/matrix interface, fracture behavior, thermal shock and oxidation behavior.

CO-4:IL03  Design, Fabrication and Properties of Cf/(ZrB2)-ZrC-SiC Ultra-high Temperature Ceramic Matrix Composites
DE WEI NI, J. WANG, X. CHEN, S. DONG, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China

Transition-metal carbides and diborides (ZrC, ZrB2, HfC, and HfB2, etc.), which are known as ultra-high temperature ceramics(UHTCs), show high melting points (>3000 °C) and good oxidation resistance at elevated temperatures. Continuous carbon fiber reinforced UHTCs composites (Cf/UHTCs), combining the toughening effect of carbon fibers with the unique properties of UHTCs, have been considered as the most potential candidates for thermal protection components in hypersonic flight vehicles. Compared with polymer infiltration and pyrolysis (PIP), and slurry infiltration (SI), reactive melt infiltration (RMI) is a fast and low-cost fabrication process for dense Cf/UHTCs composites. In the present work, a novel method combining sol-gel and RMI techniques was proposed to prepare Cf/(ZrB2)-ZrC-SiC composites. Firstly, Cf/B4C-C and Cf/ZrC-C preforms with various pore structures were prepared by sol-gel process. Then molten ZrSi2/Si alloys were infiltrated into the porous preforms, resulting in the in-situ formation of (ZrB2)-ZrC-SiC matrix through the reaction between ZrSi2/Si and B4C-C/C. Microstructure formation mechanism of the porous preforms and (ZrB2)-ZrC-SiC matrix, as well as the mechanical properties, oxidation and ablation resistance of the Cf/(ZrB2)-ZrC-SiC were investigated.

CO-4:L04  Novel UD UHTCMCs Produced by EPD and Sintering
S. FAILLA1, 2, L. ZOLI1, P. GALIZIA1, D. SCITI1, 1CNR-ISTEC, Faenza, Italy; 2University of Parma, Italy

In this work we present novel ultra-high-temperature ceramics matrix composites (UHTCMCs) for aerospace featuring optimized fiber/matrix interfaces and fibers distribution. The microstructures were produced by electrophoretic deposition of ZrB2 on unidirectional carbon fibers followed by slurry infiltration and consolidation by hot pressing. Different matrix and coating compositions were tested. The microstructure and properties are discussed. Typical values of flexural strength and fracture toughness are 330 MPa and 14 MPa m1/2, respectively.

CO-4:L05  Low Temperature Spark Plasma Sintering of TiB2 Ceramics with High-entropy Alloy as Sintering Aid
WEI JI, ZHENGYI FU, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, China

TiB2-based ceramics is a promising but difficult to prepare material. In this work, high-entropy alloy (HEA) was synthesized by mechanical alloying, and phase evolutions, microstructure, thermal properties and annealing behaviors were investigated. Then the HEA was used as sintering aid for the densification of TiB2 by spark plasma sintering. The wettability between the two components and the microstructure and mechanical properties of the composites were investigated. Excellent wettability was confirmed via sessile drop method by a high-temperature microscopy. No brittle phase can be found in the cermet. TEM observation reveals a tight interface between TiB2 and the HEA and also shows a structure of nanoparticles embedded in the amorphous matrix in the liquid phase. An optimized sintering temperature as low as 1600 °C was obtained for the TiB2-5 wt. % HEA composite with the unique combination of mechanical properties.

Session CO-5 - Property, Modeling and Characterization

CO-5:IL01  Multi-scale Modelling of CMCs
E. BARANGER, LMT, ENS Paris-Saclay, CNRS Cachan, France

In order to achieve robust designs of ceramic matrix composite parts, the modelling of the mechanical behaviour under long-term multi-axial multi-physic loadings is a great challenge to avoid too expansive experimental campaigns. Such models should account for the available information at different scales. In this paper, two approaches of multi-scale modelling are presented. The first approach relies on a macroscopic mechanical description adapted to multi-axial non-proportional loadings. This description allows the separation between different crack network contributions. A multi-physic micro enrichment is used to predict the lifetime under oxidizing environment. The paper presents a strategy to efficiently use this kind of model in a numerical context through model reduction techniques and in an experimental context through the definition of accelerated ageing tests. The second approach relies on the fine description of the microstructure. While generally this kind of micro description leads to a very large amount of data, the paper focuses on a parsimonious versatile representation of the microstructure and crack patterns. For that, the generalized finite element method is used.

Session CO-6 - Composites for Thermal Management

CO-6:IL01  Unsteady Modelling of CVI for Production of SiC-matrix Composites
A.V. KULIK, M.S. RAMM, M.V. BOGDANOV, STR Group, Inc. - Soft-Impact, Ltd., Saint Petersburg, Russia; V.I. KULIK, Baltic State Technical University, Saint Petersburg, Russia

Chemical Vapour Infiltration (CVI) is one of the most efficient technologies for production of Ceramic Matrix Composites (CMCs), particularly composites with SiC matrices. The advantage of CVI is ability to provide premium quality of the produced CMCs. The challenge is that fabrication of high-quality material requires long process duration which significantly increases the production cost. This makes it an important problem to find optimal reactor design and process conditions providing high densification degree and short process duration. In the recent years, numerical modelling has proved to be a helpful tool for CVI research facilitating the technology development and optimization. To simulate CVI process, a number of physical phenomena must be described self-consistently: conjugate heat transfer, flow of multicomponent gas mixture in gas and in the porous medium, and chemical deposition of the matrix material inside the pore space of the preform. One of the most significant features of CVI to be modelled is its essentially unsteady nature. This is mostly due to the preform densification which is a gradual long-term process of filling the pores by the matrix deposited from the gas phase. This work focuses on macroscopic modelling of CVI accounting for the unsteady effects.

CO-6:L03  Interphase Creation in Cu/C Composites using an Innovative Solid-liquid Co-existent Process
C. AZINA1, 2, I. CORNU1, B. MORTAIGNE3, Y.F. LU2, J.-F. SILVAIN1, 2, 1Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), CNRS, Pessac, France; 2Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA; 3DGA/DS/Mission pour la Recherche et l'Innovation Scientifique, Paris, France

High thermal conductivities and low thermal expansion coefficients (CTE) are required for heat-sink materials as they promote rapid heat dissipation and allow thermo-mechanical strains upon thermal cycling. Currently Cu or Al heat sinks are being used. However, they are not suitable due to the large CTE mismatch with the ceramic and silicon parts of components. To overcome this issue, we propose to replace the Cu and Al heat sinks by metal matrix composites (MMCs), more particularly Cu matrix composites reinforced with carbon. The synthesis of composite materials by alloying the matrix with carbide forming elements has been investigated using a well-known process used for Al-based composites. The solid-liquid coexistent process allows the formation of a liquid phase which enhances the reactivity between the carbide forming element and the carbon reinforcement. Ti-alloyed Cu or Zr- alloyed Cu powders were introduced in the Cu/C mixture and sintered under mechanical load. Fully dense materials were obtained. For the addition of Ti-alloyed Cu powders, the creation of regular and homogeneous TiC interphases was observed whereas for the Zr-alloyed Cu the creation of a non-regular ZrC interphases was analyzed. Chemical analyses have shown that all Ti and Zr has reacted with carbon.

Session CO-7 - Applications

CO-7:IL01  Ceramic Composites for Space Structures
M. KROEDEL, ECM Engineered Ceramic Materials GmbH, Moosinning, Germany

This paper will present and highlight the benefits and advantages using ceramic composite materials for extremely mechanically and thermally stable structures and mirrors mainly for space born as well as for ground based opto-mechanical applications. Starting with a comparison between different ceramic, ceramic composites and metal materials suitable in general for such application this paper will present the excellent performance of ceramic composites structures with verification and test results of carbon fiber reinforced silicon carbide composite structures. This will be demonstrated based on developments and test results of very complex monolithic structures. In addition, a short introduction to the manufacturing capabilities of HB-Cesic with regards to making such monolithic structures will follow at the end of the paper.

CO-7:IL03  Ceramic Composites for Industrial High Temperature Applications
R. WEISS, Schunk Kohlenstofftechnik GmbH, Heuchelheim, Germany

All industrial high temperature applications of CMC components are cost driven. Therefore, a continuous progress in manufacturing technologies is necessary. The CMC materials as well as the manufacturing process have to be cost efficient and tailored in order to fulfill mechanical, thermal and corrosion requirements. Improved cost efficiency of carbon/carbon carriers can be archieved by cheaper raw materials or optimized design. However, machinability of such low-cost materials has to be adapted due the lower mechanical properties of these grades. Solutions of these problems will be shown. Cost reductions for high temperatures can be realized by an improvement of energy efficiency. The contribution of CMC´s to such cost saving will be demonstrated by new furnace and relining concepts. CMC trays for heat treatment of metals require contact corrosion resistance. Existing concepts to overcome these problems will be presented in more detail. Contact corrosion can be avoided by the application of oxide/oxide composites, hybrids of C/C and Oxide/Oxide or surface coated C/C.

CO-7:IL04  SiC/SiC for Fuel Cladding and Other Nuclear Applications
C. SAUDER, J. BRAUN, C. LORRETTE, CEA Saclay, DEN/DMN, Gif sur Yvette, France

Ceramic Matrix Composites (CMCs) are largely studied for the improvement of safety of nuclear fission reactors. There are also studied for a long time in fusion materials research programs. Silicon carbide-reinforced silicon carbide (SiC/SiC) composites are the most suitable for these applications related to the high stability of SiC phase under neutron irradiation. Nevertheless, final characteristics that are required represent a high challenge for scientific community. The object of present lecture is to provide an overview of planned nuclear applications using SiC/SiC including constraints related to each application followed by a discussion of the advances made in the development of these materials, in addition to related concepts. A particular focus on fuel cladding application will be proposed.

Cimtec 2018

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