Polymer-derived ceramics

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. 

Greil P (1997) Near Net Shape Manufacturing of Polymer Derived Ceramics In Baxter J, Cot L, Fordham R Gabis V, Hellot Y (eds) Euro Ceramics 5 Part 3- Key Eng Mat 132-136 Trans Tech Publications, Switzerland, p 1981... 

The remaining discussion will focus on four key issues that must be addressed and understood to advance the technology of polymer-derived ceramic fibers. 

Summary Precursor-derived quaternary Si-B-C-N ceramics frequently possess an enhanced thermal stability compared to SiC, SisN4 or Si-C-N ceramics. The stability of the materials towards crystallization and/or decomposition is directly coimected to the molecular structure and the elemental composition of the polymeric precursors. This paper highlights recent investigations on the synthesis of boron-modified polysilazanes and polysilylcarbodiimides. Hydroboration of polyvinylsilazanes and dehydrocoupling reactions of boron-modified silanes with ammonia or amines as well as cyanamide are described. It is shown that simple organosilicon chemistry provides a means to efficiently optimize ceramic yields and tune elemental composition as well as thermal properties of the polymer-derived ceramics. 

Table 1. Survey of the temperature dependence of the main physico-chemical events on the thermal evolution of some polymer derived ceramic materials (after [147])...

SchubOO] Schubert R, Kastner F (2000) Influence of organic components and the parameters of plastic forming on essential properties of polymer-derived ceramic composites. J cfi/Berichte der DKG (German Ceramic Society Report) vol 77 No 5 pp 32-40... 

Table 4-1 summarizes the processes used to prepare commercially available polymer-derived ceramic fibers, as well as fibers being actively developed. Although the fiber compositions vary widely, they are all prepared by a process route similar to the one shown in Figure 4-1. Advantages inherent to the polymer approach include (Lipowitz, 1997a) ... 

TABLE 4-1 Processes for Commercial and Developmental Polymer-Derived Ceramic Fibers ... 

Freeman, H.A., N.R. Langley, C.T. Li, J. Lipowitz, and J.A. Rabe. 1993. Polymer derived ceramic fibers having improved thermal stability. U.S. PATENT 5,238,742, 1993 August 24. 

Lipowitz, J. 1991. Polymer-derived ceramic fibers. American Ceramic Society Bulletin 70(12) 1888-1894. 

Lipowitz, J., J.A. Rabe, L.K. Frevel, R.L. Miller. 1990. Characterization of nanoporosity in polymer-derived ceramic fibers by x-ray scattering techniques. Journal of Materials Science 25(4) 2118-2124. ... 

Narisawa, H.P., K. Nakoshiba, and K. Okamara. 1995. Effect of rapid heat treatments on electrical properties of polymer derived ceramic fibers. Pp. 287 292 in High-Temperature Ceramic-Matrix Composites II Manufacturing and Materials Development Vol. 58 in Ceramic Transactions, A.G. Evans and R. Naslain (eds.). Westerville, Ohio American Ceramic Society. 

The open porosity of the PAlCs-derived ceramic samples shows a weak dependence from the amount of aluminum and falls in the range f 8-13%. It increases up to w20% for the PCS-derived component. Such low values of open porosity have been already reported in the literature for similar polymer-derived ceramics [56] and indicate that this processing route is suitable for the fabrication of dense (up to 92% of theoretical density) covalent ceramics at low temperature. The porosity values measured for the ceramic products are comparable with the starting pre-ceramic samples. Indeed, results of the mercury infiltration experiments indicate that the pyrolysis process leads to the removal of the finer pore fraction (below lOnm) leaving almost unchanged the amount and the size of the coarser pores. 

Paolo Colombo would like to thank Prof. C. G. Pantano for the constant support and encouragement in pursuing research in the field of polymer-derived ceramics. He also gratefully acknowledges the fundamental contribution of Dr. J. C. Pivin, who performed the ion irradiation experiments as well as many characterizations on the specimens. 

M. Monthioux and O. Delverdier, Thermal behavior of (organosilicon) polymer-derived ceramics. V main facts and trends, J. Eur. Ceram. Soc. 1996, 16, 721—737. 

G. Passing, R. Riedel, H. Schonfelder, and R. J. Brook, Polymer-Derived Ceramic Components, in Euro-Ceramics II, Vol. 2, G. Ziegler and H. Hausner (Eds), Deutsche Keramische Gesellschaft, Koln, 1992, pp. 601-606... 

Fiber reinforced ceramic matrix composites (CMCs) are under active consideration for large, complex high temperature structural components in aerospace and automotive applications. The Blackglas resin system (a low cost polymer-derived ceramic [PDC] technology) was combined with the Nextel 312 ceramic fiber (with a boron nitride interface layer) to produce a sihcon oxycarbide CMC system that was extensively characterized for mechanical, thermal, and electronic properties and oxidation, creep mpture, and fatigue. A gas turbine tailcone was fabricated and showed excellent performance in a 1500-hour engine test. 

But CMCs will be commercially successful only when they are produced cost-effectively. Polymer-derived ceramic (PDC) technology is one of the most promising low cost fabrication methods for ceramic matrix composites, particularly for large, complex shapes. In PDC technology, a silicon-based polymer (siloxane, carbosilane, silazane, etc) with fiber or particle reinforcement is shaped and cured in the polymer condition and then pyrolyzed in a controlled atmosphere to form a stable silicon-based ceramic, such as silicon carbide, sihcon nitride, silicon oxycarbide, or silicon oxynitride. 

D. R. Petrak, Polymer-Derived Ceramics, Engineered Materials Handbook, Vol. 4 Ceramics and Glasses (Metals Park, OH ASM International, 1991), pp. 223-226. 

The purpose of this chapter is to provide an overview of the chemistry, processing and application of boron-containing preceramic polymers in the BN system. The nonoxide precursor route, also called the Polymer Derived Ceramics (PDCs) route, represents a chemical approach based on the use of air- and/or moisture-sensitive (molecular or polymeric) precursors by means of standard Schlenk techniques and vacuum/argon lines. This precursor route allows the chemistry (e.g., elemental composition, compositional homogeneity and atomic architecture) of molecular precursors to be controlled and tailored in order to provide the ensuing preceramic polymers... 

Delverdier, M. Monthioux, D. Mocaer and R. Pailler, Thermal behavior of polymer-derived ceramics. I. Si-C and SI-C-0 systems from both commercial and new polycarbosilane (PCS) precursors, J. Europ. Ceram. Soc., 12,2741 (1993). 

Riedel R, Mera G, Hauser R, Klonczynski A (2006) Silicon-based polymer-derived ceramics synthesis properties and applications a review. J Ceram Soc Jpn 114 425 44... 

Our previous results [1] showed that polymer stmcture and latent reactivity are the driving forces behind ceramic yields, while the chemical content is primarily responsible for the evolution of the ceramic composition. The studies determined that polymer-derived ceramic compositions are controlled mainly by the polymer monomeric units. 

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