Microcrystalline Ceramic Composites by Active Filler Controlled Reaction Pyrolysis of Polymers

1992 ◽  
Vol 274 ◽  
Author(s):  
Peter Greil ◽  
Michael Seibold ◽  
Tobias Erny
Keyword(s):  
Composite Materials ◽  
Dimensional Change ◽  
Ceramic Composites ◽  
Silicon Oxycarbide ◽  
Preceramic Polymers ◽  
Active Filler ◽  
Polymer Derived Ceramic ◽  
Property Changes ◽  
Low Dimensional ◽  
Carbide Inclusions

ABSTRACTPyrolytic conversion of preceramic polymers such as polysilanes, -silazanes, or -siloxanes to ceramics may be significantly influenced by the resence of active filler dispersoids. Based on thermodynamic and microstructural considerations a variety of suitable polymer-filler systems can be found which allow the fabrication of microcrystalline composite materials with low dimensional change upon polymer- ceramic conversion. As an example the active filler controlled reaction pyrolysis of polysiloxane with addition of titanium powder was investigated. A composite material with microcrystalline titanium carbide inclusions embedded in an amorphous (< 1000 °C) or nanocrystalline (>1000 °C) silicon oxycarbide matrix was formed. Property changes with increasing pyrolysis temperature can be attributed to various microstructural transformations. Thus, a variety of potential fillers may be used to tailor the microstructure of polymer-derived ceramic composite materials in order to fabricate bulk materials and components with a broad range of compositions and properties.

scholarly journals Insights into the Microstructural Evolution Occurring during Pyrolysis of Metal-Modified Ceramers Studied through Selective SiO2 Removal

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3276
Author(s):  
Aitana Tamayo ◽  
Juan Rubio ◽  
Fausto Rubio ◽  
Mᵃ Angeles Rodriguez
Keyword(s):  
Structural Characteristics ◽  
Domain Size ◽  
Ceramic Composites ◽  
Silicon Oxycarbide ◽  
Crosslinking Degree ◽  
Molecular Precursors ◽  
Textural Characterization ◽  
Polymer Derived Ceramic ◽  
Ultimate Properties ◽  
Lower Carbon

Silicon oxycarbide ceramers containing 5% aluminum, zirconium, and cobalt with respect to the total Si amount are prepared from a commercial polysiloxane and molecular precursors and pyrolyzed at temperatures ranging from 500 to 1000 °C. HF etching is carried out to partially digest the silica phase, thus revealing structural characteristics of the materials, which depend upon the incorporated heteroatom. From the structural and textural characterization, it was deduced that when Al enters into the ceramer structure, the crosslinking degree is increased, leading to lower carbon domain size and carbon incorporation as well. On the contrary, the substitution by Zr induced a phase-separated SiO2-ZrO2 network with some degree of mesoporosity even at high pyrolysis temperatures. Co, however, forms small carbidic crystallites, which strongly modifies the carbonaceous phase in such a way that even when it is added in a small amount and in combination with other heteroatoms, this transient metal dominates the structural characteristics of the ceramer material. This systematic study of the ceramer compounds allows the identification of the ultimate properties of the polymer-derived ceramic composites.

scholarly journals Structure and Thermodynamics of Silicon Oxycarbide Polymer-Derived Ceramics with and without Mixed-Bonding

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4075
Author(s):  
Casey Sugie ◽  
Alexandra Navrotsky ◽  
Stefan Lauterbach ◽  
Hans-Joachim Kleebe ◽  
Gabriela Mera
Keyword(s):  
Phenyl Group ◽  
Silicon Oxycarbide ◽  
Enthalpies Of Formation ◽  
Hydroxyl Groups ◽  
Preceramic Polymers ◽  
Calorimetric Measurements ◽  
Polymer Derived Ceramic ◽  
Carbon Nanoscrolls ◽  
Carbon Substitution ◽  
Heat Of Dissolution

Silicon oxycarbides synthesized through a conventional polymeric route show characteristic nanodomains that consist of sp2 hybridized carbon, tetrahedrally coordinated SiO4, and tetrahedrally coordinated silicon with carbon substitution for oxygen, called “mixed bonds.” Here we synthesize two preceramic polymers possessing both phenyl substituents as unique organic groups. In one precursor, the phenyl group is directly bonded to silicon, resulting in a SiOC polymer-derived ceramic (PDC) with mixed bonding. In the other precursor, the phenyl group is bonded to the silicon through Si-O-C bridges, which results in a SiOC PDC without mixed bonding. Radial breathing-like mode bands in the Raman spectra reveal that SiOC PDCs contain carbon nanoscrolls with spiral-like rolled-up geometry and open edges at the ends of their structure. Calorimetric measurements of the heat of dissolution in a molten salt solvent show that the SiOC PDCs with mixed bonding have negative enthalpies of formation with respect to crystalline components (silicon carbide, cristobalite, and graphite) and are more thermodynamically stable than those without. The heats of formation from crystalline SiO2, SiC, and C of SiOC PDCs without mixed bonding are close to zero and depend on the pyrolysis temperature. Solid state MAS NMR confirms the presence or absence of mixed bonding and further shows that, without mixed bonding, terminal hydroxyls are bound to some of the Si-O tetrahedra. This study indicates that mixed bonding, along with additional factors, such as the presence of terminal hydroxyl groups, contributes to the thermodynamic stability of SiOC PDCs.

Composites Obtained from Alumina and Polymer Derived Ceramic

2018 ◽  
Vol 912 ◽  
pp. 141-146 ◽  
Author(s):  
Glauson Aparecido Ferreira Machado ◽  
Rosa Maria Rocha ◽  
Ana Helena Almeida Bressiani
Keyword(s):  
Heat Treatment ◽  
Silicon Carbide ◽  
Linear Shrinkage ◽  
Density Variation ◽  
Silicon Oxycarbide ◽  
Alternative Route ◽  
Preceramic Polymer ◽  
Pure Alumina ◽  
Polymer Derived Ceramic ◽  
Alumina Composites

Alumina-mullite composites with low shrinkage can be made by reaction bond using mixtures of alumina, aluminum and silicon carbide. In this work, an alternative route is used to produce alumina composites with low shrinkage. Here alumina samples containing additions of 10 and 20 wt% of a preceramic polymer were warm-pressed and treated in the range of 900 -1500°C to produce alumina based composites. The obtained composites were analyzed by linear shrinkage and compared to pure alumina samples sintered at the same temperature range. It were also evaluated the density variation and crystalline phases formed during heat treatment of alumina composites. Results showed that alumina-silicon oxycarbide and alumina-mullite composites were obtained with lower shrinkage than pure alumina samples.

Silicon carbide fibers and whiskers for ceramic matrix composites (review)

2021 ◽  
Vol 87 (8) ◽  
pp. 51-63
Author(s):  
A. M. Shestakov
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
High Temperature ◽  
Composite Materials ◽  
Ceramic Matrix Composites ◽  
Ceramic Materials ◽  
Ceramic Composites ◽  
Silicon Compounds ◽  
Reinforcing Fillers ◽  
Operating Temperatures

An increase the operating temperature range of structural elements and aircraft assemblies is one of the main goals in developing advanced and new models of aerospace equipment to improve their technical characteristics. The most heat-loaded aircraft structures, such as a combustion chamber, high-pressure turbine segments, nozzle flaps with a controlled thrust vector, must have a long service life under conditions of high temperatures, an oxidizing environment, fuel combustion products, and variable mechanical and thermal loads. At the same time, modern Ti and Ni-based superalloys have reached the limits of their operating temperatures. The leading world aircraft manufacturers — General Electric (USA), Rolls-Royce High Temperature Composite Inc. (USA), Snecma Propulsion Solide (France) — actively conduct fundamental research in developing ceramic materials with high (1300 – 1600°C) and ultrahigh (2000 – 2500°C) operating temperatures. However, ceramic materials have a number of shortcomings attributed to the high brittleness and low crack resistance of monolithic ceramics. Moreover, manufacturing of complex configuration and large-sized ceramic parts faces serious difficulties. Nowadays, ceramic composite materials with a high-temperature matrix (e.g., based on ZrC-SiC) and reinforcing filler, an inorganic fiber, (e.g., silicon carbide) appeared most promising for operating temperatures above 1200°C and exhibited enhanced energy efficiency. Ceramic fibers based on silicon compounds possess excellent mechanical properties: the tensile strength more than 2 GPa, modulus of elasticity more than 200 GPa, and thermal resistance at a temperature above 800°C, thus making them an essential reinforcing component in metal and ceramic composites. This review is devoted to silicon carbide core fibers obtained by chemical vapor deposition of silicon carbide onto a tungsten or carbon core, which makes it possible to obtain fibers a 100 – 150 μm in diameter to be used in composites with a metal matrix. The coreless SiC-fibers with a diameter of 10 – 20 μm obtained by molding a polymer precursor from a melt and used mainly in ceramic composites are also considered. A comparative analysis of the phase composition, physical and mechanical properties and thermal-oxidative resistance of fibers obtained by different methods is presented. Whiskers (filamentary crystals) are also considered as reinforcing fillers for composite materials along with their properties and methods of production. The prospects of using different fibers and whiskers as reinforcing fillers for composites are discussed.

Surfactant-based selective assembly approach for Si-embedded silicon oxycarbide composite materials in lithium-ion batteries

2020 ◽  
Vol 401 ◽  
pp. 126091 ◽  
Author(s):  
Jihye Jang ◽  
Hyeongwoo Kim ◽  
Hyojun Lim ◽  
Ki jae Kim ◽  
Hun-Gi Jung ◽  
...  
Keyword(s):  
Composite Materials ◽  
Lithium Ion Batteries ◽  
Lithium Ion ◽  
Silicon Oxycarbide ◽  
Selective Assembly

Polymer Derived Ceramic Seals for Application in SOFC

2007 ◽  
Vol 534-536 ◽  
pp. 1061-1064 ◽  
Author(s):  
Sung Jin Hong ◽  
Deug Joong Kim
Keyword(s):  
Thermal Expansion ◽  
Thermal Properties ◽  
Glass Matrix ◽  
Ceramic Composite ◽  
Ceramic Composites ◽  
Filler Materials ◽  
N2 Atmosphere ◽  
Polymer Derived Ceramic ◽  
Oxycarbide Glass

Polymer derived ceramic composites have been developed for SOFC seals. The formation and properties of the ceramic composite derived from a mixture with polysiloxane and filler were investigated. In the presence of filler materials such as ZrO2 and AlCo, the thermal properties of the ceramic composite could be controlled. The mixtures with polymethylsiloxane and fillers were prepared and their conversions to ceramic composites by annealing in N2 atmosphere were studied. The microcrystalline composites with filler embedded in a silicon-boron-oxycarbide glass matrix were formed. The thermal expansion behaviors were measured and discussed.

Carbon-Nanotube-Reinforced Polymer-Derived Ceramic Composites

2004 ◽  
Vol 16 (22) ◽  
pp. 2036-2040 ◽  
Author(s):  
L. An ◽  
W. Xu ◽  
S. Rajagopalan ◽  
C. Wang ◽  
H. Wang ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Ceramic Composites ◽  
Reinforced Polymer ◽  
Polymer Derived Ceramic

Development of Functionally Graded Anti-Oxidation Coatings for Carbon/Carbon Composites

2007 ◽  
Vol 280-283 ◽  
pp. 1851-1856 ◽  
Author(s):  
Jae Ho Jeon ◽  
Hai Tao Fang ◽  
Zhong Hong Lai ◽  
Zhong Da Yin
Keyword(s):  
Composite Materials ◽  
Cutting Tools ◽  
Functional Materials ◽  
Ceramic Composites ◽  
Research Area ◽  
Research Field ◽  
Functionally Graded ◽  
Carbon Composites ◽  
Metal Composite ◽  
Dielectric Ceramic

The concept of functionally graded materials (FGMs) was originated in the research field of thermal barrier coatings. Continuous changes in the composition, grain size, porosity, etc., of these materials result in gradients in such properties as mechanical strength and thermal conductivity. In recent years, functionally graded structural composite materials have received increased attention as promising candidate materials to exhibit better mechanical and functional properties than homogeneous materials or simple composite materials. Therefore the research area of FGMs has been expending in the development of various structural and functional materials, such as cutting tools, photonic crystals, dielectric and piezoelectric ceramics, thermoelectric semiconductors, and biomaterials. We have developed functionally graded structural ceramic/metal composite materials for relaxation of thermal stress, functionally graded anti-oxidation coatings for carbon/carbon composites, and functionally graded dielectric ceramic composites to develop advanced dielectric ceramics with flat characteristics of dielectric constant in a wide temperature range. This paper introduces functionally graded coatings for C/C composites with superior oxidation resistance at high temperatures.

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