The Vickers microhardness (VMH) of amorphous and crystalline chemical vapour-deposited silicon nitride (Pyrolytic-Si3N4) prepared under various deposition conditions using SiCl4, NH3 and H2 has been measured at room temperature The apparent VMH of Py-Si3N4 increases with decreasing indenter load, following the Meyer equation For the amorphous Py-Si3N4, the VMH value at a load of 100 g ranges from 2200 to 3200 kg mm−2 depending upon deposition temperature (Tdep) and total gas pressure (Ptot) On the other hand, the VMH of the crystalline Py-Si3N4 does not depend uponTdep andPtot but is affected by the preferred orientation The hardness of the deposition surfaces with the (110), (210) and (222) orientations is 3800 kg mm−2, while that of the cross-section with the (001) orientation is 3100 kg mm−2 The hardness of the crystalline Py-Si3N4 is also affected by the grain size For the fine grained Py-Si3N4 (about 1μm), the VMH varies from 4600 to 5000 kg mm−2 The hardnesses of three types of Py-Si3N4 are discussed in comparison with those of other ceramics

Chemical vapour-deposited silicon nitride

Ultra-rich combustion in parallel channels to produce hydrogen-rich syngas from propane

Syngas production from heptane in a non-catalytic counter-flow reactor

Siliconated pyrolytic graphite PG(Si) has been prepared by pyrolysis of a mixture of propane and silicon tetrachloride vapour at 1440 to 2025° C, a total gas pressure of 10 or 50 torr, and a partial pressure of silicon tetrachloride vapour of up to 13 torr. The amounts of silicon in PG(Si) are 0.02 to 4 wt %. The effects of the addition of silicon tetrachloride on the surface characteristics, the microstructure and the density of PG(Si) are examined.

Siliconated pyrolytic graphite. part 1. preparation and some properties.

Wide variety of carbon materials is classified into four families, diamond, graphite, fullerene and carbyne, on the basis of carbon-carbon bonds, sp3-sp3, flat sp2-sp2, curved sp2-sp2 and sp-sp. Crystalline structures of the compounds of other atoms neighboring to carbon in The Periodic Table, i.e., B4C, C3N4, SiC, BN, are discussed in the relation with the structural modifications in carbon.

Fundamental Science of Carbon Materials

Abstract Effects of different conditions during pyrolytic graphite preparation on the microstructure and density of the pyrolytic graphite have been examined. Pyrolytic graphite is obtained by pyrolysis of commercial propane gas in the deposition temperature range of 1346–2215° C at pressures of 5–200 torr and flow rates of 280–1050 cm 3 /min. The microstructure can be divided into fine regenerative, string, coarse and pebble structures which depend on the temperature and pressure, but are independent of the flow rate. These structures are closely related to the density. The density depends sensitively on the temperature and pressure and shows a minimum value in a certain condition. Three different heteromorphic phases are observed in the microstructure.

Yajima Seishi

Papers

Microstructure and Density of Pyrolytic Graphite

Mechanism of the Pyrolytic Graphite Formation