Macroporous SiCMoSi₂ceramics from templated hybrid MoCl₅–polymethylsilane

Abstract

A molybdenum-containing preceramic polymer, MoPMS, was synthesized for the first time by HCl elimination of polymethylsilane (PMS) and MoCl 5 at room temperature in tetrahydrofuran. The insoluble MoPMS prepared was embedded into the void spaces of a silica colloidal crystal template within the pot life of the polymer and successfully transformed to a three-dimensionally long-rangeordered macroporous SiC-MoSi 2 ceramic after pyrolysis at 1400 • C in an argon atmosphere followed by template removal in HF. The bead-inverse macroporous SiC-MoSi 2 ceramic, with a ceramic yield of about 88%, exhibits high temperature stability, high BET surface area, and semiconducting behavior. In addition, the macroporous SiC-MoSi 2 ceramic was used as a catalyst carrier for platinum-ruthenium coated on the surface of the pores. The preceramic polymer and the ceramic were characterized by IR, thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy, and BET surface area.

Synthesis and Electronical Property of Antimony-Substituted Polysilanes and Iron-Substituted Polysilanes

“…While for APS, it is the most likely that HCl was eliminated as a condensation of Si-H and Sb-Cl bonds, leading to the crosslinking of PMS through Si-Sb or Si-CH 2 -Sb bonds, as shown in Schemes (1) and (2). The similar Si-H consuming by reacting with other metallic halides has been reported [22][23][24]. Similarly for the PCMS-derived IPS, as shown in Scheme (3) and (4), a stable structure of SiFe(CO) 4 -Si might be formed with a consumption of Si-Cl bonds.…”

A modified polymethylsilane as the precursor for ceramic matrix composites

“…1), one can see that the peak of Si-H at 2106 cm À1 shrinks while the other peaks remain unchanged. The similar Si-H consuming which reacted with other metallic halides was reported by Wang [7] and Tsirlin [14]. Considering the releasing of HCl, the main reaction should be described as the following scheme:…”

“…In the previous work [6,7], active reactants like MoCl 5 and PBN were introduced to promote the crosslinking of PMS, resulting fully crosslinked product. But in this work, A-PMS is still a liquid instead of a solid.…”

“…Cao [6] heated PMS with polyborazine (PBN) at 70°C. The other organic and inorganic compounds such as MoCl 5 [7], TiCl 4 [8], TVS (Si(CH@CH 2 ) 4 ) [9] and Co 2 (CO) 8 [10] were also tried. Some of the above methods increased ceramic yield of PMS significantly, but it seems difficult to control the high reactivity of the additives that cause PMS turn to an insoluble and infusible solid.…”

Synthesis and Ceramization of Polymethylsilane Precursors Modified with Metal Chlorides

“…As an example, the microstructure of the pyrolysis product of PMS-20ಚMoCl 5 precursor prepared with a large amount of THF tetrahydrofuran 21,29 is shown in Fig. 11.…”