Carbides overview

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. 

An Overview of Reported Claims of Bulk Cobalt Carbide Being Observed after/when Performing Fischer-Tropsch Synthesis over Supported Cobalt-Based Catalysts... 

This volume, which is unique in its coverage, provides a general introduction to the properties and nature of transition metal carbides and nitrides, and covers their latest applications in a wide variety of fields. It is directed at both experts and nonexperts in the fields of materials science, solid-state chemistry, physics, ceramics engineering and catalysis. The first chapter provides an overview, with other chapters covering theory of bonding, structure and composition, catalytic properties, physical properties, new methods of preparation, and spectroscopy and microscopy. 

This section presents a brief overview of a few other compounds that have not been described in previous sections. Because it can function as a nonmetal, silicon forms sihcides with several metals. These materials are often considered as alloys in which the metal and silicon atoms surround each other in a pattern that may lead to unusual stoichiometry. Examples of this type are Mo3Si and TiSi2. In some sihcides, the Si-Si distance is about 235 pm, a distance that is quite close to the value of 234 pm found in the diamond-type structure of elemental silicon. This indicates that the structure contains Si22-, and CaSi2 is a compound of this type. This compound is analogous to calcium carbide, CaC2 (actually an acetylide that contains C22- ions (see Chapter 10)). 

In Chapters 20 and 21 we shall look at individual elements of the c -block in detail. However, a few general points are given here as an overview. In general, the metals are moderately reactive and combine to give binary compounds when heated with dioxygen, sulfur or the halogens (e.g. reactions 19.1-19.3), product stoichiometry depending, in part, on the available oxidation states (see below). Combination with H2, B, C or N2 may lead to interstitial hydrides Section 9.7), borides Section 12.10), carbides Section 13.7) or nitrides Section 14.6). 

Different types of thermodynamic data were measured for the boron carbide phase. An overview is given in Table 12 [91, 154-166]. 

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