Ceramically bonded silicon carbides

The main sources of infrared radiation used in spectrophotometers are (1) a nichrome wire wound on a ceramic support, (2) the Nernst glower, which is a filament containing zirconium, thorium and cerium oxides held together by a binder, (3) the Globar, a bonded silicon carbide rod. These are heated electrically to temperatures within the range 1200- 2000 °C when they will glow and produce the infrared radiation approximating to that of a black body. 

Pall Process Filtration Ceramic Candle Filter 1000°C (max.) 99.99% Supported both sides clay bonded silicon carbide filter... 

Shrink-resist science/technology development of, 26 391 Shrink-resist treatments, 26 391-393 additive, 26 393 chlorine-based, 26 392 chlorine-free, 26 392-393 Shuiskite, 6 471t Shutdown period, 29 494 Shutdown systems, 20 671-672 Shuttle vectors, 26 482-483 Sialon-bonded silicon carbide, 22 541 Siberian red lead, 6 468 S-iB-S block copolymers, 24 707 SiC-ceramic, 22 525. See also Silicon carbide... 

Slip-casting of technical ceramics has been steadily introduced over the past 60 years or so, and now it is standard practice to cast alumina crucibles and large tubes. The process has been successfully extended to include silica, beryllia, magnesia, zirconia, silicon (to make the preforms for reaction-bonded silicon nitride articles) and mixtures of silicon carbide and carbon (to make the preforms for a variety of self-bonded silicon carbide articles). Many metallics and intermetallics, including tungsten, molybdenum, chromium, WC, ZrC and MoSi2, have also been successfully slip-cast. 

Forrest, C.W., Kennedy, P. and Shennan, J.V. (1972) The fabrication and properties of self-bonded silicon carbide bodies, in Special Ceramics 5, The British Ceramic Research Association, Stoke-on Trent, UK. 

Infiltration combines a melt with a porous free-standing solid (the preform ). In the main and defining step of the process, the melt flows into open pores of the preform after solidification a new material results. Composites of all classes (polymer, ceramic and metal) are produced by this process, as are compounds such as reaction bonded silicon carbide. The process can also be adapted to make open-pored foams of carbon, ceramic, polymer or metal. 

The present study aims at investigating the Reaction Bonded Silicon Carbide (RBSC) process to produce porous mullite-bonded SiC ceramics. Wu and Claussen (1991) reported a technique to produce mullite ceramics starting from Al, SiC and AI2O3 powder mixtures. However for the purpose of this study it was decided to use only SiC and Al 03 as the precursor powders with SiC as the major component so that after completion of the reaction the microstructure would be SiC bonded with mullite phase, with no residual alumina. This material was then tested for its mechanical properties like Young s modulus. Modulus of Rupture. Properties of Silicate-based SiC refractories have been reported to a certain extent by Reddy and others. Its potential use as a refractory material has been evaluated by measuring its thermal shock resistance. A sample refractory that has been designed in the... 

The slopes of the lines in Figure 13.13, at > 0.75, are also typical for reaction-bonded silicon carbide [24, 28]. These data also indicate that over 75% of the measured axial tensile strain results from cavitation. The volumes generated by cavities are transferred primarily into axial tensile strain [25], which suggests that cavitation is the main creep mechanism of deformation in these ceramics. As the contribution of cavities to strain in SN 281 is dose to zero, creep in this material is fundamentally different from that of other grades of silicon nitride [15, 40, 41, 44]. The suppression of cavitation in SN281 is most likely the reason for its increased creep resistance. 

REFEL. Registered tradename (Reactor Fuel Element Laboratory) of the UKAEA Springfields laboratory, for reaction bonded silicon carbide developed there on the basis of P. Popper s original work at British Ceramic R.A. (Power Jets (R D) Ltd, Br. Pat. 866,813, 3/5/61). 

Hardness testing of the refractories is not an everyday procedure, yet it is very useful to remember that the hardness of self-bonded silicon carbide ceramics is in the range of 20-25 GPa, the hardness of nitride-bonded silicon carbide refractories is 16-20 GPa, and the hardness of alumina ceramics is 12-16 GPa, which is three to four times higher than with dense alumina silica dense refractories. 

For different classes of materials, the values of Weibull modulus fluctuate For structural ceramics, the material is considered to be homogeneous if the Weibull modulus is above 15-20 for itride-bonded silicon carbide, it is 15 for alumina brick, it is 6 for porcelain tableware, it is in the range 4-11 baked carbon anodes are considered to be homogeneous if the Weibull modulus is 6-9. We haven t found the values of the Weibull modulus for cathode carbon blocks. 

Tables 1.8 and 1.9 and Fig. 1.21 give some reference data on the values of the thermal coefficient of linear expansion for oxides, refractory, and ceramic materials [100-102]. Crystals with a cubic lattice (CaO, MgO) have equal values of linear coefficients of expansion along aU axes. The typical linear coefficients of thermal expansion for such materials are 6-8 x 10 and increase with the temperature up to 10-15 X 10 K . Anisotropic crystals with low symmetry have different values of linear coefficients of thermal expansion along different axes, but with a temperature increase, this difference becomes smaller. Materials with strong chemical bonds (silicon carbide, titanium diboride, diamond) have low values of linear coefficients of thermal expansion. However, these materials have high values of Debye characteristic temperature (values of the linear coefficients of thermal expansion grow below the Debye temperature and are almost constant above it).

Etzion R, Metson JB. Factors affecting corrosion resistance of silicon nitride bonded silicon carbide refractory blocks. J Am Ceram Soc. 2012 95 410-5. 

John D, Maurage R. Sialon bonded silicon carbide sidewall pieces for the aluminium reduction cell. Ceram Ind Int. 1992 182 42. 

Composites of silicon carbide (SiC) and silicon (Si) are fabricated by the reactive infiltration of molten Si into preforms of SiC particles and carbon. This product is often referred to as reaction bonded silicon carbide (RBSC). SiC materials are used in many applications due to their favorable properties including high hardness, high thermal conductivity, low thermal expansion and high stiffness. This paper demonstrates the manipulation of thermal and mechanical properties through the additions of third phase metals (e.g. A1 and/or Ti) to the infiltration alloy and through the additions of ceramic-forming, reactive materials to the preform. The effects of these additions on microstructural, physical, mechanical, and thermal properties are presented and discussed. 

Chakrabarti, S. Ghosh, and J. Mukerji, Influence of Grain Size, Free Silicon Content and Temperature on the Strength and Toughness of Reaction-Bonded Silicon Carbide, Ceramics International, 20,283-286, (1994). 

D. Deleeuw, Effects of Joining Pressure and Deformation on the Strength and Microstructure of Diffusion-Bonded Silicon Carbide, J. Am. Ceram. Soc., 75, 72S-27 (1992)... 

Properties of Dense Silicon Carbide. Properties of the SiC stmctural ceramics are shown in Table 1. These properties are for representative materials. Variations can exist within a given form depending on the manufacturer. Figure 2 shows the flexure strength of the SiC as a function of temperature. Sintered or sinter/HIP SiC is the preferred material for appHcations at temperatures over 1400°C and the Hquid-phase densified materials show best performance at low temperatures. The reaction-bonded form is utilized primarily for its ease of manufacture and not for superior mechanical properties. 

The history and development of polysilane chemistry is described. The polysilanes (polysilylenes) are linear polymers based on chains of silicon atoms, which show unique properties resulting from easy delocalization of sigma electrons in the silicon-silicon bonds. Polysilanes may be useful as precursors to silicon carbide ceramics, as photoresists in microelectronics, as photoinitiators for radical reactions, and as photoconductors. 

The term ceramics comes from the Greek keramikos, which means potter s clay or burnt stuff. While traditional ceramics were often based on natural clays, today s ceramics are largely synthetic materials. Depending on which ceramic and which definition is to be applied, ceramics have been described as inorganic ionic materials and as inorganic covalent (polymeric) materials. In fact, many ceramics contain both covalent and ionic bonds and can thus be considered to be or not to be (shades of Shakespeare) polymeric materials. Many of the new ceramics, such as the boron nitriles and the silicon carbides, are polymeric without containing any ionic bonds. 

What advantages do ceramics such as Silicon Carbide (eChapter 21.7) have relative to metals What are the disadvantages of ceramics Rotate the 3D model, and see if you can find a special orientation where planes of atoms are separated by largely empty space, devoid of bonds. What does the result of this investigation say about the physical properties of ceramics ... 

Benzene, ethylene and acetylene were the predominate observed volatiles at 550 °C whilst methane was evolved from 650 °C to 875 °C. An amorphous SiCO material was obtained at 1200 °C and bond redistribution and carbothermic reduction occurred up to 1800 °C to give a ceramic material composed of substantial amounts of crystalline fi-silicon carbide. The preparation of bulk ceramic components from materials in the system... 

For some uses it is important to form bonds that link different polysilane chains, to transform soluble, meltable polysilanes into insoluble resins. This process is vital if the polysilanes are to be used as precursors to silicon carbide ceramics, since, if cross-linking is not carried out, most of the polymer is volatilized before thermolysis to silicon carbide can take place. Several methods have therefore been developed to bring about cross-linking of polysilanes.109 110... 

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