Boron silicon carbonitride

Boron-containing nonoxide amorphous or crystalline advanced ceramics, including boron nitride (BN), boron carbide (B4C), boron carbonitride (B/C/N), and boron silicon carbonitride Si/B/C/N, can be prepared via the preceramic polymers route called the polymer-derived ceramics (PDCs) route, using convenient thermal and chemical processes. Because the preparation of BN has been the most in demand and widespread boron-based material during the past two decades, this chapter provides an overview of the conversion of boron- and nitrogen-containing polymers into advanced BN materials. 

Non-oxide preceramic polymers which are expected to yield, under convenient thermal and chemical conditions, boron-containing amorphous or crystallized ceramics including boron nitride (BN), boron carbide (B C), boron carbonitride (B-C-N), and boron silicon carbonitride Si-B-C-N. 

Initial explanations of the extraordinary high-temperature stability of precursor-derived Si-B-C-N ceramics were presented previously by Jalowiecki et al. 13 The authors investigated the microstructure of boron-doped silicon carbonitride composites by HR-TEM and found... 

R. Kumar, F. Phillipp, and F. Aldinger, Oxidation Induced Effects on the Creep Properties of Nano-Crystalline Boron Doped Silicon Carbonitrides, Mater. Sci. and Eng. A, 445 - 446, 251 - 258 (2007). 

Polymer derived ceramics have been known for the last four decades and are prepared via solid-state thermolysis of preceramic polymers. They exhibit a unique combination of remarkable properties due to their covalent bonding and amorphous nature. Thus, silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) based ternary PDCs have been shown to possess outstanding high-temperature properties such as stability with respect to crystallization and decomposition, oxidation and corrosion resistance as well as excellent thermomechanical properties (e.g., near zero steady state creep resistance up to temperatures far beyond 1000 °C). Their properties are directly influenced by the chemistry and the architecture of the preceramic precursors, thus there is an enormous potential in tuning the microstructure and properties of the PDCs by using tailored polymers. Furthermore, suitable chemical modification of the preceramic precursors leads to quaternary and multinary ceramics, as it has been shown for instance for silicon boron carbonitride ceramics in the last 25 years, which in some cases exhibit improved properties as compared to those of the ternary materials. 

The synthesis of a range of silicon boron carbonitride ceramics can conveniently be carried out by thermal treatment of suitable amorphous precursor molecules in which the desired atomic linkages are already in place. A series of new amorphous precursor molecules has been investigated by "B MAS NMR and double resonance techniques such as Si- B) Rotational Echo Adiabatic Passage DOuble Resonance (REAP-DOR) and B-j Si) Rotational Echo DOuble Resonance (REDOR) (van Wiillen and Jansen 2001). The results indicate the presence of hexagonal BN and (3-Si3N4 in some... 

As precise as possible a knowledge of the chemical composition is a crucial pre-requisite to any serious attempt to determine the geometric and topological structure of a multi-component random network. However, chemical analyses of refractive materials like the silicon boron carbonitrides discussed here is a difficult task. In general, there exist two different classes of procedures, destructive ones, such as wet chemical digestion, and non-destructive (physical) ones. 

Volume 1 starts with an introduction into novel ultra hard ceramics including diamond and diamond-like carbon, carbon nitrides and silicon nitrides as well as boron containing carbides, nitrides and carbonitrides. Here we wish to recognize the great fundamental and technological challenge of developing new superhard... 

The powder of silicon nitride of the SHS-Az type can contain in the structure from 40% up to 95% (a-nitride phase as anisotropic whiskers by a diameter 1 pm forming wave structure (Figure 8.2)). The particles of the boron nitride powder of the SHS-Az type are ultra fine and have the disc form, and the diameter of disks at 10-15 of time exceeds their thickness having the linear size about 20 nm. The crystal lattice BN has deformations of turbostrate kind with a degree of three-dimensional order 0.40-0.50. The powder of titanium carbonitride with composition TiCggNog of the SHS-Az type differs from similar powders of traditional technologies of synthesis of more branched structure, typical for formation of... 

Mohun s experiments included chlorine treatment of silicon carbide, aluminum carbide, boron carbide, titanium carbide, zirconium carbide, and zirconium carbonitride, generally at temperatures... 

Carbonitriding Ferritic nitrocarburizing Diffusion (pyk cementation) chromizing Diffusion (pack cementation) aluminizing Diffusion (pack cementation) siliconizing Boronizing (bonding)... 

Note TiN, titanium nitride TiC, titanium carbide B C, boron carbide Ti(CN), titanium carbonitride SiC, silicon carbide T1B2, titanium diboride AljOj, alumina WC, tungsten carbide... 

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