We report a sonochemical process for a single-pot synthesis of high molecular weight poly(methylsilane) (PMS) of composition [(CH3SiH) x (CH3Si) y (CH3SiH2) z ] n , where x + y + z = 1 and 0.65 ≥ (x + z) ≥ 0.23 by the sodium polycondensation reaction of CH3SiHCl2 in a solvent mixture of hexane or toluene and tetrahydrofuran (THF) using ultrasonic activation (47 kHz, 130 W). This polycondensation reaction takes place in two stages:  (1) 10−25 h of reaction in which an oligo(methylsilane) (OMS) oil (0.91 ≥ (x + z) ≥ 0.83) is obtained that gives low ceramic residue yields of silicon-rich SiC on pyrolysis in argon and (2) 25−40 h of reaction during which is obtained a PMS solid that gives high ceramic residue yields of near stoichiometric SiC on pyrolysis. PMS also may be prepared by branching of the oligo(methylsilane) with sodium and ultrasonication for ∼5 h in a toluene and THF solvent mixture. PMS is soluble in hexane and toluene and its pyrolysis in argon gives a ceramic residue yield up to 90%. In addition to the main product of the condensation reaction, a high molecular weight PMS may be extracted from large NaCl crystals (the other product of the CH3SiHCl2/Na reaction). A comparison of sonochemical and conventional (reflux) activation also is provided. Ceramic fibers, films, and solid monoliths were prepared from PMS without requiring a curing step.

[(Trimethylsilyl)amino]titanium trichloride, (CH3)3‐SiNHTiClj, was isolated as a red‐orange crystalline solid in 58% yield from the reaction of TiCl4 with [(CH3)3Si]2NH in 1:1 molar ratio in dichloromethane at —78°C. Pyrolysis of (CH3)3SiNHTiCl3 at 600°C furnished titanium nitride. This precursor is suitable for the preparation of composites and was employed to prepare Si3N4‐TiN and Ti‐TiN powders by adding Si3N4 particles or titanium powders to a solution of (CH3), SiNHTiCl3 in dichloromethane, drying and pyrolyzing the resulting solid. This precursor also has been used as a binder to prepare Si3N4‐TiN and Ti‐TiN bodies. High‐resolution transmission electron microscopic studies of the Si3N4‐TiN composite showed that titanium nitride is concentrated on the surface of the Si3N4 particles.

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The dynamic vacuum wasca. torr during film formation and the molecular precursors were heated to a temperature defined as (80"-120 "C) so that sublimation/distillation into the heated chamber occurred at a rate of ca. 0.1 g/ h. The temperature gradient within the heated furnace was determined to be less than 50 "C and the furnace temperature, T,, was maintained at 25 "C above the highest temperature at which avisible amount ofthe M(N(SiMe,),),compound passed through the hot wall reactor without decomposition. The volatile products of the deposition reaction were passed through a U-tube filled with glass beads immersed in I-N, and those that were condensed in this manner were analyzed by 'H and "C{'H} NMR and GC/MS. The glass reactor tube was cleaned with 20% HNO, overnight (ca. 12 h), 10% HCI for 2 h followed by extensive washing with deionized water, then acetone, and finally dried in an oven at 175°C for 16 h prior to use. Silicon(100) wafers (from Virginia Semiconductor, Inc.), quartz and glass plates were cut into 1 cm x 2 cm plates, washed with 10% aq. HF for 30 s, followed by immersion in deionized water (10 s) and acetone (10 s), prior to drying. The tube furnace was loaded with the substrates, glass, silicon and quartz alternating randomly throughout its length (ca. 30 cm). The source chamber was loaded (ca. 0.5 to 0.8 g) in a drybox, sealed, and attached to the tube furnace. The system was then evacuated and heated to the predetermined decomposition temperature, Td, for 1 h before the source chamber was opened, evacuated for 10 min, and heated to T,.The films were analyzed by XRD (employing a Scintag XDS-2000 diffractometer, Cu Ka, and SEMiEDAX employing a JEOL LSM 820 microscope with a Kevex detection system (Quantum Detector Kevex Delta 4). The EDAX data were analyzed using Quantex 6.2 software. This technique allows the detection of elements with atomic number 25 to within at best I at-%. The topography of the films was studied by SEM (JEOL 800) with a resolution of less than 1 pm. The quality of adhesion of the film to the substrate was evaluated by the qualitative "Scotch Tape test", wherein two strips of 3M Scotchtape, crossed in an "X" on the surface of the film, are pulled off and examined for particles. For a film to pass the "Scotch Tape test" no particles of the film are visually transferred from the substrate to the tape.