Structural features of a carbon plastic material infiltrated with molten silicon

Abstract

The structure of a SiC-C composite prepared from carbon plastic plates infiltrated with molten silicon and hot-pressed organic bond composed of a ten-layer package of LU-24P unidirectional carbon tape is studied. A technology for giving a fibrous structure to Si-impregnated carbon plastic plates in the SiC-C composite is proposed.Components manufactured from SiC structural wear-resistant materials by a technology developed at the ARIAG (All-Russia Research Institute for Abrasives and Grinding, St. Petersburg, Russia) [1] using recrystallization and reaction sintering techniques have found widespread applications in paper-making, textile, chemical and refractory sectors of industry in Russia and republics of the former Soviet Union. However, wider industrial use of such SiC components is limited by their rather high brittleness which makes them less suitable over a wide temperature range not only for SiC ceramics, but also for all kinds of ceramic parts manufactured from high-melting compounds [2].A method for removing this shortcoming has been proposed in [3,4], the so-called "structural design" aimed at improving the resistance to brittle fracture of these materials. For example, an effective means of enhancing the resistance of ceramic matrix composites [5] is to reinforce them with carbon fibers based on polyacrylonitrile (PAN) [6]. We have conducted tests on siliconized carbon fibers (Kulon, LU-24P ribbon, UKN-5000P grade, VMN-4 (carbon filament) + PVS (copper wire)) under a microscope (at´100 magnification). In siliconized specimens, silicon carbide pseudomorphosis was observed to form on carbon fiber, where the carbon fiber was partially converted to silicon carbide, with a clear tendency to retain the shape and geometric dimensions. Based on the data obtained, carbon fiber materials (carbon plastics) infiltrated with molten silicon were studied with a view towards preparing SiC materials and components reinforced with carbon fibers.The precursor specimens for silicon infiltration study were carbon plastic plated with dimensions of 30´17´2 mm prepared by hot pressing of a package assembled from 10 layers (LU-24P carbon ribbon and epoxyphenol-novolacbutyral (EPNB) binder) with a single-layer thickness of 0.2 mm. The volumetric ratio of components in the slopreg (reinforcement:matrix) was about 60 : 40. The slopreg stacking pattern was -45°(1 layer)/0°(2 layers)/ ± 45°(1 layer); the setting time at 180°C was 6 h.The carbon plastic lamellar specimens were subjected to infiltration with molten silicon (Kr1 grade) using an induc- Fig. 1. Photomicrograph of the cross section on intact carbon plastic specimens prepared from hot-pressed LU-24P carbon tape and EPNB binder: carbon fibers (shown as filament-like and granular areas); EPNB binder (shown dark), and pores (shown black);´90.