Abstract: The invention concerns (1) thermochemically treating by pack-cementation a carbon-containing material, which may have an open porosity, to generate a refractory carbide coating on its surface and, if the material is porous, within the material; and (2) the use of specific alloys as a pack for thermochemically treating carbon-containing materials, optionally with an open porosity, in a halogenated atmosphere. Pack-cementation is carried out under reduced pressure using an element E (to be transported and to be reacted with the carbon in the material to generate the expected carbide) alloyed to an element M, and using a halide (chloride or fluoride, preferably a fluoride) of the same element M, of low volatility, present in the solid form.

Abstract: A method of manufacturing a metal part coated with a layer of polycrystalline diamond includes fabricating a metal substrate having a surface to be coated, the metal substrate containing titanium, vanadium or alloys thereof; depositing a layer of at least 10% graphitic plus amorphous carbon and designed to diffuse fully through the titanium; and depositing a diamond coating on the carbon layer.

Abstract: An optical fiber comprising an optical core enclosed in optical cladding, both made of a silica-based material, and a protective layer constituted by amorphous boron. The amorphous boron layer is deposited on a non-crystalline carbon which is itself deposited directly on the optical cladding. Also, a method is provided for depositing an amorphous boron layer on an optical fiber and includes a deposition step of depositing a layer of carbon on the fiber, followed by a subsequent step of depositing the amorphous boron protective layer chemically from the vapor phase on the layer of carbon.

Abstract: A method of applying an amorphous boron-based protective coating to an optical fiber comprising an optical core enclosed in optical cladding, both made of a silica-based material, wherein the boron is applied to the surface of said optical fiber chemically from the vapor phase at a temperature lying in the range 1050.degree. C. to 1250.degree. C., by reducing boron chloride BCl.sub.3 by means of hydrogen H.sub.2. The amorphous boron protective coating imparts mechanical protection to the fiber, and enhanced abrasion resistance, enabling the fiber to be used in optical cables of high capacity and that are highly compact. The thickness of the resin coating can be about half that required when a carbon protective coating is used, and can even be eliminated. The coating further provides sealing properties comparable to those provided by a carbon coating.

Abstract: The surface treatment of carbonaceous material (1) is characterised in that a layer of SiC (2) is formed on the carbonaceous material (1) by thermochemical conversion of the carbonaceous material (1) by a precursor of Si (4) at a temperature which is higher than the temperature for the formation, from said precursor, of a gaseous reactive intermediate (generally SiO), so as to obtain a surface layer (3) permitting an adherent diamond deposit (3).Pieces which are at least locally coated with `SiC/diamond`.

Abstract: Apparatus for depositing diamond on a substrate assisted by microwave plasma, comprising two zones, a plasma formation zone located in a waveguide and a diamond deposition zone located outside the waveguide. The apparatus includes means making it possible to form a stable plasma in the deposition zone, so as to considerably increase the substrate surface which can be treated.

Abstract: The manufacture of a refractory composite material protected against corrosion and comprising fibrous reinforcement densified by a matrix, comprises a step of forming, either within the matrix or at its surface, at least one continuous layer constituted by a ternary silicon-boron-carbon system obtained by chemical vapor deposition or infiltration. The elements silicon and boron are thereby distributed uniformly, with the boron content in the Si-B-C system being not less than 5% in atom percentage.

Abstract: A porous substrate is placed inside an enclosure and a gas flow is injected into the enclosure under predetermined conditions of temperature and pressure to form a solid deposit within the accessible pores inside the substrate. A wall that is permeable to the gas flow is interposed on the path of the flow between its inlet into the enclosure and the substrate, the wall not being in contact with the substrate, thereby forming around the substrate a region which is free from strong turbulence so that infiltration is performed essentially under diffusion conditions, thereby minimizing the deposition gradient within the volume of the substrate.

Abstract: A composite material containing carbon is protected against oxidation by forming, on the composite material, an inner layer, an intermediate layer containing boron or a boron compound, and an outer layer of silicon carbide. The inner layer formed on the composite material before the intermediate layer is formed, is made of a refractory carbide that does not contain boron and that is at least 60 microns thick, said inner layer insulating the intermediate layer from the carbon contained in the composite material.