Porous structure and gas permeability of carbon-carbon base composite Gravimol in production process high-temperature st
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Vol. 53, No. 3, September, 2012
POROUS STRUCTURE AND GAS PERMEABILITY OF CARBON-CARBON BASE COMPOSITE GRAVIMOL IN PRODUCTION PROCESS HIGH-TEMPERATURE STAGES G. M. Butyrin1 and V. V. Konokotin1 Translated from Novye Ogneupory, No. 5, pp. 46 – 52, May, 2012.
Original article submitted April 12, 2011. Results are provided for study of the porous structure and gas permeability of carbon-carbon base composite Gravimol for wing cowling of space shuttle Buran in the production process high-temperature stage. The nature of porosity redistribution is shown for the three main groups of material pores in the production process and their role in the final stage, i.e., borosiliciding. Keywords: Gravimol composite, carbon-carbon base (C–C-base), porous structure (PS), pore size distribution, carbonization (Cb) stabilizing heat treatment (HT-1), compaction with pyrolytic carbon (CPC), borosiliciding.
scribed level of properties, a component was subjected to secondary cycles of CPC (SCPC) and HT-2 (SHT-2). The apparent density ra, pycnometric density rp, and open (permissible) porosity P0 were determined for a collection of specimens. Measurements were made in accordance with GOST 2409, using standard isooctane (2,2,4-trimethylpentane, C8H18) as substitution medium with low surface tension (18.77 ´ 103 N/m at 20°C) for which the temperature dependence for density is known with an error of ±0.00005 g/cm3 [1, 2]. Isooctane is not a strongly acting poisonous substance (in contrast to methanol and ethanol); its MPC in a workspace atmosphere is 300 mg/m3, i.e., the fourth class of danger (GOST 12433). The porous structure (PS), including specific pore volume V and nature of its distribution with respect to size of pores of equivalent radius (Requ), and also the volume of pore traps V* and pore capillaries DV for a porous C–C-carcass, were studied by means of a mercury porosimetry method [3, 4] on specimens after determining ra, rp and P0, and drying (scales L420S with IR-drying YTC 01 L, Sartorius, FRG). For this an AutoPore 9200 (Micromeritics, USA) was used, connected to a PC for information storage and processing. According to Micromeritics the capacity method for determining volume of mercury entering provides a resolving capacity of the estimate of not less than 1 mliter, and with respect to pressure ±1% of the total manometer scale (0 – 0.24, 0 – 3.45, 0 – 34.5, and 0 – 414 MPa). This was confirmed in work by the authors in studying the structure of graph-
INTRODUCTION Choice and treatment technology for manufacturing and testing heat protection systems for the nose cone and wing edges for reusable reentry space shuttle Buran is one of the most critical tasks during its creation. Some aspects are presented in the article for forming a porous carbon-carbon base (C–C-base) for creating a carbon-ceramic composite. Gravimol with a protective self-healing glass-silicide coating, is intended for heat protection of space equipment. EXPERIMENTAL PART A study of the nature of a porous C–C-base (carcass) structure of the future composi
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