Abstract: The high temperature coating for the protection of ceramic materials, in particular porous ones, from erosion and chemical and/or mechanical failure according to the invention comprises a barrier (primer) layer and an emissivity glaze (topcoat) layer, with the following weight compositions:barrier layer:silicon tetraboride (with over 96 weight % of SiB.sub.4): 0.1 to 10%;quartz glass: 90 to 99.9%;emissivity glaze layer:silicon tetraboride (with over 96 weight % of SiB.sub.4): 1.5 to 5.0%;high silica glass: 95 to 98.5%.

Abstract: Aluminum nitride whiskers are produced by reducing alumina with carbon in a nitrogen atmosphere, at a temperature of 1800.degree. to 2000.degree. C., in the presence of a growth activator containing a solvent element, according to a process that essentially comprises the step of periodically feeding, through the working area of a horizontal furnace equipped with a graphite heating device, counter to a flow of nitrogen, a graphite container charged with a mixture of alumina, carbon and carbonyl iron, as a growth activator, which is present in an amount capable of implementing the VLS mechanism, the time taken by the container to pass through the working zone being in the range of 20 to 120 minutes.

Abstract: The production of SiC whiskers and of mats thereof on a substrate by treatment, at 1250.degree. to 1500.degree. C., of a gaseous mixture including hydrogen and sources of Si and C atoms which are in the form of at least one oxygen-free compound, in the presence of a metal type catalyst, by a semi-continuous or periodic process, is characterized in that, during the growth period, an Al-Fe catalyst is introduced into the gas phase in the reaction zone, by means of carbon reduction of aluminosilicate ceramics, which comprise at least 73 weight % of Al.sub.2 O.sub.3 and 0.3 to 3.0 weight % of iron oxides and the substrate is a carbonized rayon fiber based carbon fabric which has been pre-treated, prior to carbonization, with a solution of borax and a solution of diammonium phosphate until the quantities of boron and phosphorus in the fabric do not amount to more than 4 and 2 weight %, respectively.

Abstract: A process for making light, fibrous heat insulating materials wherein the silica fibers used in the process are quartz fibers formed by spraying quartz. The fibers are predispersed in water until there is formed a homogeneous flowing slurry from which is molded a green fibrous block, with simultaneous partial removal of water. This green fibrous block is dispersed in water and mixed with an aqueous emulsion containing an organosilicon binder, a boron-containing sintering adjuvant and a surface-active agent. A green billet is molded from the suspension thus obtained, a portion of the water being simultaneously removed by suction. The green billet is compressed until the desired height is obtained and then it is dried, in the compressed state, at a temperature of up to 300.degree. C. The billet is released from pressure and fired at high temperature.

Abstract: A process for producing a low porosity, high temperature coating on a porous substrate based on ceramic fibers of refractory compounds. The coating comprises from 30.8 to 41.9 weight % of silica (SiO.sub.2) from a silica sol, from 30.2 to 49.4 weight % of alumina (Al.sub.2 O.sub.3), from 4.0 to 16.3 weight % of silicon carbide (SiC), and from 11.6 to 16.6 weight % of molybdenum disilicide (MoSi.sub.2). The coating has an emissivity of not less than 0.8 and an operating temperature of up to 1500.degree. C. The process is carried out without a firing step and includes the steps of preparing a slurry comprising from 65 to 75 weight % of a silica sol having a content of 20 to 50 weight % of SiO.sub.2 and from 25 to 35 weight % of a mixture of particles of the refractory compounds Al.sub.2 O.sub.3, SiC, and MoSi.sub.

Abstract: A process for manufacturing a heat insulating material including alumina based fibers and aluminosilicate binder. The process includes the steps of: (a) milling alumina based fibers, having a mean diameter less than or equal to 2 .mu.m, in water until a mean aspect ratio (l/d) of 30 to 130 is obtained; (b) vacuum molding a billet from the resulting aqueous, fibrous, flowing slurry; (c) fixing the billet in a frame, while compressing it slightly; (d) drying the slightly compressed billet in the frame to form a dried billet; (e) preparing an aluminosilicate binder having low durability; (f) impregnating the dried billet, fixed in the frame, with the binder; (g) gelling the binder to produce a semi-finished product; (h) removing the semi-finished product from the frame; (i) drying the semi-finished product; and (j) firing the semi-finished product.

Abstract: The high temperature coating for the protection of ceramic materials, in particular porous ones, from erosion and chemical and/or mechanical failure according to the invention comprises a barrier (primer) layer and an emissivity glaze (topcoat) layer, with the following weight compositions:barrier layer:silicon tetraboride (with over 96 weight % of SiB.sub.4): 0.1 to 10%;quartz glass: 90 to 99.9%; emissivity glaze layer:silicon tetraboride (with over 96 weight % of SiB.sub.4): 1.5 to 5.0%;high silica glass: 95 to 98.5%.