Preceramic polymers were proposed over 30 years ago as precursors for the fabrication of mainly Si-based advanced ceramics, generally denoted as polymer-derived ceramics (PDCs). The polymer to ceramic transformation process enabled significant technological breakthroughs in ceramic science and technology, such as the development of ceramic fibers, coatings, or ceramics stable at ultrahigh temperatures (up to 2000°C) with respect to decomposition, crystallization, phase separation, and creep. In recent years, several important advances have been achieved such as the discovery of a variety of functional properties associated with PDCs. Moreover, novel insights into their structure at the nanoscale level have contributed to the fundamental understanding of the various useful and unique features of PDCs related to their high chemical durability or high creep resistance or semiconducting behavior. From the processing point of view, preceramic polymers have been used as reactive binders to produce technical ceramics, they have been manipulated to allow for the formation of ordered pores in the meso-range, they have been tested for joining advanced ceramic components, and have been processed into bulk or macroporous components. Consequently, possible fields of applications of PDCs have been extended significantly by the recent research and development activities. Several key engineering fields suitable for application of PDCs include high-temperature-resistant materials (energy materials, automotive, aerospace, etc.), hard materials, chemical engineering (catalyst support, food- and biotechnology, etc.), or functional materials in electrical engineering as well as in micro/nanoelectronics. The science and technological development of PDCs are highly interdisciplinary, at the forefront of micro- and nanoscience and technology, with expertise provided by chemists, physicists, mineralogists, and materials scientists, and engineers. Moreover, several specialized industries have already commercialized components based on PDCs, and the production and availability of the precursors used has dramatically increased over the past few years. In this feature article, we highlight the following scientific issues related to advanced PDCs research: (1) General synthesis procedures to produce silicon-based preceramic polymers.
(2) Special microstructural features of PDCs.
(3) Unusual materials properties of PDCs, that are related to their unique nanosized microstructure that makes preceramic polymers of great and topical interest to researchers across a wide spectrum of disciplines.
(4) Processing strategies to fabricate ceramic components from preceramic polymers.
(5) Discussion and presentation of several examples of possible real-life applications that take advantage of the special characteristics of preceramic polymers. Note: In the past, a wide range of specialized international symposia have been devoted to PDCs, in particular organized by the American Ceramic Society, the European Materials Society, and the Materials Research Society. Most of the reviews available on PDCs are either not up to date or deal with only a subset of preceramic polymers and ceramics (e.g., silazanes to produce SiCN-based ceramics). Thus, this review is focused on a large number of novel data and developments, and contains materials from the literature but also from sources that are not widely available.

Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics

Carbon nitride powder prepared by solid-state reaction between cyanuric chloride or its fluoro analogue and lithium nitride. The determined, by elemental analysis, atomic N/C ratio (1.33) in the synthesized material is consistent with C 3 N 4 stoichiometry. Combined material characterization data, obtained by FTIR, Raman, UV-Vis, (13C) MAS NMR, XPS, TGA/DTA and pyrolysis-EIMS methods, provide substantial evidence for graphite-like sp 2 -bonded structure composed of building blocks of s-triazine rings bridged by the three-fold coordinated nitrogen atoms in the bulk carbon nitride.

Powder synthesis and characterization of amorphous carbon nitride, a-C3N4

The first detailed structural characterisation of a functionalised tri-s-triazine derivative, trichloro-tri-s-triazine, is reported, which is a promising starting material for numerous compounds including graphitic C3N4 phases. DFT calculations show that a C3N4 structure based on tri-s-triazine should exist and that it is ∼30 kJ mol−1 more stable than the previously reported C3N4 phase of lowest energy.

Tri-s-triazine derivatives. Part I. From trichloro-tri-s-triazine to graphitic C3N4 structures

This review highlights the synthesis, processing and properties of non-oxide silicon-based ceramic materials derived from silazanes and polysilazanes. A comprehensive summary of the preparation of precursor compounds containing Si–N–Si units, including commercially available materials, is followed by the discussion of various processing techniques. The fabrication of dense bulk ceramics in the Si/E/C/N systems is reported which involves cross-linking of the polymeric ceramic precursor followed by a polymer-to-ceramic transformation step. The cross-linked precursor can be milled, compacted and pyrolysed to form dense, additive-free, amorphous silicon carbonitride monoliths or polycrystalline composites which withstand oxidation in air at 1600°C. Furthermore, an overview is given on the fabrication of silazane derived powders and coatings involving chemical vapour deposition (CVD) methods utilising volatile precursors. Fibre spinning and fibre properties, as well as other processing techniques like infiltration of preforms, the preparation of porous ceramics and joining are briefly discussed. A state of the art of the mechanical properties of polymer derived amorphous Si/C/N and Si/B/C/N ceramics with respect to hardness as well as high-temperature creep and oxidation resistance is summarised. Finally, some important aspects of industrial applications will be considered. The review is in part based on our own work related to the polysilazane derived ceramics, but will also cover a comprehensive state of the art including the published literature in this field.

Silazane derived ceramics and related materials

A review of the preparation of carbon nitride films

Organosilicon carbodiimides have been successfully applied as single-source precursor compounds for the synthesis of novel ternary Si-, C-, and N-containing solid phases. Their thermally induced decomposition gives either amorphous silicon carbonitrides or polycrystalline silicon nitride and silicon carbide mixtures, materials that are presently of technological interest for their exceptional hardness, strength, toughness, and high temperature resistance even in corrosive environments. This review is concerned with the synthesis, characterization, and thermal stability of element carbodiimides. The main part of this paper is focused on polymeric silicon-based carbodiimides obtained by the reaction of chloro(organo)silanes with bis(trimethylsilyl)carbodiimide. In the case of RSiCl3, novel poly(silylcarbodiimide) gels are formed. Starting from silicon tetrachloride, new crystalline SiCN phases (namely, SiC2N4 and Si2CN4), have been isolated. Their crystal structures as well as their thermal behavior in the ...

Inorganic solid-state chemistry with main group element carbodiimides

In this article we present the synthesis of three-dimensionally ordered ternary BC 2 N crystals produced under high-temperature and high-pressure conditions. Unit cell dimensions are a = 2.4820 ± 0.0007 A and c = 6.620 ± 0.003 A. The composition BC 2 N is derived from Vegard's law and quantitative electron energy loss spectroscopy. The ordered arrangement of atoms in the unit cell is discussed.

Jeffrey P. Nicolich

Papers

Inorganic solid-state chemistry with main group element carbodiimides

Synthesis and Structure of Three‐Dimensionally Ordered Graphitelike BC2N Ternary Crystals

Synthesis and Structure of Three-Dimensionally Ordered Graphitelike BC2N Ternary Crystals.