Particular silicon nitride

The development of nanopores within silicon supports, particularly silicon nitride and silicon oxide, makes use of knowledge derived from electronics and semiconductor fabrication processes. Silicon wafers with thin oxide/nitride films can be readily attained and provide a useful platform for experimentation. Though these materials are not fundamentally nanoporous, techniques have been developed to incorporate nanopores. 

The market for silicon nitride is fast growing, particularly in structural and chemical resistance applications and as a thin film in semiconductor devices.P 1... 

CVD plays an increasingly important part in the design and processing of advanced electronic conductors and insulators as well as related structures, such as diffusion barriers and high thermal-conductivity substrates (heat-sinks). In these areas, materials such as titanium nitride, silicon nitride, silicon oxide, diamond, and aluminum nitride are of particular importance. These compounds are all produced by CVD. 1 1 PI... 

In this particular example as in many others, a proper analysis of cost is a crucial factor. An example is the production of balls for ball bearings. Coated ball bearings (or monolithic silicon nitride) greatly outperform steel balls but their cost is considerably higher. Steel balls in passenger-automobile applications are satisfactory and normally last the life of the car and the far-longer life of the ceramic balls is not needed. 

Organometallic polymer precursors offer the potential to manufacture shaped forms of advanced ceramic materials using low temperature processing. Polysilazanes, compounds containing Si-N bonds in the polymer backbone, can be used as precursors to silicon nitride containing ceramic materials. This chapter provides an overview of the general synthetic approaches to polysilazanes with particular emphasis on the synthesis of preceramic polysilazanes. 

In the area of preceramic polysilazanes, sufficient progress has been made to produce precursors for silicon nitride fibers, coatings and as binders for silicon nitride powder. However, particular problems still remain to be solved particularly with regard to reducing impurity levels and improving densification during pyrolysis. 

All silicon nitride ceramics are derived from synthetic materials, exclusively. The first report on the synthesis of Si3N4 was in 1859 by Sainte-Claire Deville and Wohler [3]. Among the problems of greatest concern to chemists in those days was the utilisation of atmospheric nitrogen for agricultural and industrial purposes. In particular, there was a need for a highly effective... 

Within the past decade, research on the development of new Si3N4 compositions has greatly intensified. These efforts have resulted in a proliferation of new synthetic procedures. Preparative routes have been developed with increasing emphasis on the control of purity and physical properties. Silicon nitride powders, fibers, coatings, and composites each have their own characteristic requirements, which can dictate the choice of a particular route (i). 

Metallurgical grade silicon is marketed in a coarsely crushed form or as a finely ground powder in different particle sizes. Powders with increased purity due to acid washing, particularly for the removal of metallic impurities, are specialty products. They are utilized, for example, in the manufacture of silicon nitride powder or reaction-bonded silicon nitride ceramic components and are therefore the starting materials for engineering ceramic specialties. 

Multicrystalline silicon wafers, with crystal sizes in the range 1-100 mm, ° are currently the main workhorse for the photovoltaics industry. Hydrogen passivation steps used in cell manufacture in recent years, particularly those involved in the deposition of silicon nitride layers on front surfaces, have reduced the impact of electrically active impurities and defects in MC-Si cells and reduced the performance deficit relative to monocrystalline cells. 

Compilations are frequently cited as the sources of PZCs/IEPs data. Parks [1] compiled the PZCs/IEPs of (hydr)oxides published up to 1965. PZCs/IEPs of (hydr)oxides and other materials published over the period 1966-1999 were compiled by the present author [2], and the updates [3065-3067] cover the period 2000-2005. The above five publications report a vast majority of reliable PZC/ IEP values published up to 2005. Several other reviews of PZCs/IEPs have been published. The reviews of PZCs limited to particular materials (e.g., iron oxides and silicon nitride) are cited in this book in the sections devoted to those materials. Many reviews report only one value (range) of PZC for a given material. These recommended values are close to the median of the values cited for those materials in this book, with a few exceptions. Typically, the PZC values are referenced (original literature or secondary sources). 

Properties. Properties of structural silicon nitride ceramics are given in Table 2. These values represent available, well-tested materials. However, test methodology and the quality of the specimens, particularly their surface finish, can affect the measured values. Another important material property is... 

In discussing bonds formed between the group 14 elements and nitrogen, two compounds of particular importance emerge cyanogen, C2N2, and silicon nitride. Tin(IV) nitride has recently been prepared. 

Many metal nitrides exhibit interesting properties such as extreme hardness, high melting points and resistance towards organic solvents and inorganic acids (Table 7-1). Several non-metallic nitrides also are of great interest. Among them, boron nitride and silicon nitride are of particular interest. The properties and preparation of these two compounds by CVD are described elsewhere (see Chapter 6). Most nitrides can be prepared by solid state reactions [142]. However, for the preparation of thin films, CVD is the method of choice. This section focuses on nitrides which have not been described in previous chapters. 

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