Development of precursor ceramics using organic silicon polymer

Abstract

This paper relates to the Bridge Building Award, which was presented to the author (Toshihiro Ishikawa) by the American Ceramic Society on 27 January 2020. We have developed many types of functional ceramics using polycarbosilane as a raw material. Since 1983, several grades of SiC‐based fibers have been produced from polycarbosilane by Ube Industries, Ltd. Of these grades, we developed the highest heat‐resistant SiC‐polycrystalline fiber (Tyranno SA), which can withstand up to 2000°C, using an organic silicon polymer (poly‐aluminocarbosilane) containing a small amount of aluminum as a precursor material. By employing curing (in air) and firing (in nitrogen atmosphere at 1300°C) processes using the precursor fiber, an amorphous fiber (Si‐Al‐C‐O fiber) containing a small amount of aluminum was obtained; subsequent heat treatment at higher temperatures (~2000°C) in argon atmosphere led to carbothermal reduction (SiO2 + 3C SiC + 2CO(g)) and a sintering process, producing the abovementioned SiC‐polycrystalline fiber (Tyranno SA). In the same year, using the same raw precursor fiber (Si‐Al‐C‐O fiber), we also developed a new type of tough, thermally conductive SiC composite (SA‐Tyrannohex) with high strength up to 1600°C in air. This ceramic consists of a highly ordered, close‐packed structure of very fine hexagonal columnar SiC‐polycrystalline fibers with a thin interfacial carbon layer between them. Further, by using the polycarbosilane as a starting material, we successfully developed a strong photocatalytic fiber (TiO2/SiO2 fiber) with a gradient surface layer composed of TiO2‐nanocrystals, making the best use of controlled phase separation (bleed‐out) of additives (titanium (IV) tert‐butoxide) contained in polycarbosilane. In this paper, the story of the development of these materials and the subsequent progress will be described along with the historical background.

Porous Noble Metal‐Based Nanomaterials in Biomedical Applications

“…The noble metal composition enables these nanomaterials to excite surface charge carriers, promoting electron transfer between species and facilitating chemical transformations under external electrical potentials. [ 91 ] Furthermore, the unique porous structures enhance the plasmon effect, resulting in a larger surface area for electrochemical reactions and increased reaction rates [30a] . Based on these mechanisms, electrochemical applications of porous noble metal‐based nanomaterials can be categorized into three parts: 1) electrode‐involved biosensing; 2) nanoenzyme‐based biosensing; and 3) nanoenzyme‐based therapy.…”

The effects of adding nano‐alumina filler on the properties of polymer‐derived SiC coating

“…Polymer‐derived ceramics is a developed method for the preparation of fibers, bulk, and thin films 14,15 . This method can be used for the coating of large surfaces, complex geometries, and fibers 16 .…”

“…Polymer-derived ceramics is a developed method for the preparation of fibers, bulk, and thin films. 14,15 This method can be used for the coating of large surfaces, complex geometries, and fibers. 16 In this technique, a suitable polymer is dissolved in a solvent and coated on the substrate by applying different methods such as dip coating, 17 spin coating, 18 and sol-gel.…”