The problem of low-temperature synthesis of 13-SIC in heat treatment of gels of hydrolyzed ethyl silicate is considered. Data obtained in DTA, IR, Raman spectroscopy, and EPR physicochemical investigations of the process of gel transformation in heat treatment in air are presented. A mechanism of the organization of the carbon system in a gel and possible ways of synthesizing SiC at low temperatures are suggested. Synthesis of SiC in heat treatment of gels of ethyl silicate at a rate exceeding 10 K/min is established by the x-ray method beginning with 773 K.The sol-gel process is acquiring wide application in the creation of new composite materials. Special attention is paid to self-reinforcement and dispersion strengthening of refractory matrices based on corundum or other re~actory fillers. The kind of binder used for shaping the articles and the method of their production play a large role in the technology of ceramics and refractories. The problem of using binders for synthesizing new phases with specified properties is very important for materials science. Metal alkoxides are used for creating two-phase materials, and silicon compounds are used for synthesizing SiC [ 1, 2]. 2 For this reason, organization of the carbon system from polyorganosiloxanes in the silica of binders based on silicon alkoxide is of obvious practical and theoretical value.We prepared gels using I~TS-32 ethyl silicate (TU 6-02-895 -86) as the initial material. The ethyl silicate was hydrolyzed by the method developed in [3] in an aqueous acid medium without o~anic binders bymeans of an AOL 012-4 propeller mixer (GOST 8212-56). The catalyst in the hydrolysis was HC1 or HNO 3. The gel was heat-treated in a drying cabinet of the SNOL-3.5,3.5,3.5/3,5-IL type (TU 16-681.032-84) and a high-temperature furnace of the SVK type (GOST 15150 -69). The gel was calcined at a rate of 5 to 30°C/rain to the requisite temperature with subsequent cooling with the furnace. The gels were heattreated at a controlled rate of temperature growth at a step of 100°C from 200 to 1300°C in the high-temperature furnace of an OD-103 derivatograph in an air atmosphere. i Kharkov State Polytechnic University, Kharkov, Ukraine. 2 U.S. Patent No. 457133; Application 62-25605, Japan.
306Differential thermal analysis of the gels in different media was conducted using an OD-103M derivatograph. Infrared spectra before and after the heat treatment were obtained on a UR-20 spectrophotometer in the range of 400 -4000 cm-1. Tablets of a mixture of the analyzed material and a standard (single-crystal potassium bromide) were prepared for the experiments. The process of the organization of the carbon system in a gel cluster in the course of heat treatment was studied by the method of electron paramagnetic resonance (EPR) • using a JES-ME-3XP spectrophotometer and by the method of Raman spectroscopy using a MOLE microprobe. The macroscopic structure of the gels and the phase composition of the heat-treated specimens were determined using a MIN-8 microscope, and the x-ray investiga...
