Abstract: A load comprising one or more porous substrates (10) for densification is heated in an oven into which a reaction gas containing at least one carbon-precursor hydrocarbon is admitted, the effluent gas being extracted from the oven via an extraction pipe (26) connected to an outlet from the oven. The content in the effluent gas of at least one compound selected from allene, propine, and benzene is measured, and as a function of the measured content, the process is controlled by adjusting at least one parameter selected from the rate at which the reaction gas is admitted into the oven, the rate at least one component of the reaction gas is admitted into the oven, the transit time of the gas through the oven, the temperature to which the substrate(s) is/are heated, and the pressure that exists inside the oven. The at least one parameter is adjusted in such a manner as to maintain the measured content at a value which is substantially constant.

Abstract: A pipe for feeding a gas into an oven, a furnaces, or the like (such as a CVI/CVD oven), and in particular into a reaction chamber structure inside the oven, is provided with a gastight tubular sealing device extending radially outward of the pipe and defining a path that is practically gastight, through which there extends the feed pipe. The tubular sealing device is preferably at least partially flexible in the transverse direction and/or the axial direction so as to accommodate positioning defects between a location situated in the reaction chamber and a location where the gas feed pipe penetrates the oven (which defects may be due, for example, to asymmetrical thermal expansion/contraction).

Abstract: Carbon nanotubes are incorporated in the fiber structure by growing them on the refractory fibers of the substrate so as to obtain a three-dimensional substrate made of refractory fibers and enriched in carbon nanotubes. The substrate is densified with a matrix to form a part of composite material such as a friction part of C/C composite material.

Abstract: A pipe for feeding a gas into an oven, a furnaces, or the like (such as a CVI/CVD oven), and in particular into a reaction chamber structure inside the oven, is provided with a gastight tubular sealing device extending radially outside the pipe and defining a path that is practically gastight, along which there extends the as feed pipe. The tubular sealing device is preferably at least partially flexible in the transverse direction and/or the axial direction so as to accommodate positioning defects between a location situated in the reaction chamber and a location where the gas feed pipe penetrates into the oven (which defects may be due, for example, to asymmetrical thermal expansion/contraction).

Abstract: A load comprising one or more porous substrates (10) for densification is heated in an oven into which a reaction gas containing at least one carbon-precursor hydrocarbon is admitted, the effluent gas being extracted from the oven via an extraction pipe (26) connected to an outlet from the oven. The content in the effluent gas of at least one compound selected from allene, propine, and benzene is measured, and as a function of the measured content, the process is controlled by adjusting at least one parameter selected from the rate at which the reaction gas is admitted into the oven, the rate at least one component of the reaction gas is admitted into the oven, the transit time of the gas through the oven, the temperature to which the substrate(s) is/are heated, and the pressure that exists inside the oven. The at least one parameter is adjusted in such a manner as to maintain the measured content at a value which is substantially constant.

Abstract: Heat treatment is performed on preforms placed in an enclosure accompanied by sweeping with an inert gas under reduced pressure, and with a gaseous effluent being exhausted continuously via a first effluent outlet connected to an effluent exhaust circuit. At the end of the heat treatment, the first gaseous effluent outlet is closed so as to isolate the effluent exhaust circuit from the enclosure, sweeping of the enclosure with the inert gas is interrupted, and the heat-treated preforms are left in the enclosure and are subjected to densification by admitting a reagent gas into the enclosure via at least one reagent gas admission duct opening out into the enclosure, with gaseous effluent being exhausted via a second effluent outlet separate from the first, said second outlet being closed during the heat treatment step. Advantageously, metal, in particular sodium, contained in the gaseous effluent exhausted from the enclosure during the heat treatment step is neutralized.

Abstract: A method for densification of porous by CVI in which substrates are loaded into a loading zone of an oven and heated to a temperature at which a desired matrix material is formed from a precursor gas(es). A reative gas containing the precursor gas(es) is admitted into the end of the oven and heated upstream from the loading zone of the substrates. The reactive gas is also preheated prior to entering the oven so that, upon entering the oven, it is brought to an intermediate temperature between ambient temperature and the temperature to which the substrates are heated. In this manner, a very small temperature gradient is obtained throughout the loading zone.

Abstract: Carbon nanotubes are incorporated in the fiber structure by growing them on the refractory fibers of the substrate so as to obtain a three-dimensional substrate made of refractory fibers and enriched in carbon nanotubes. The substrate is densified with a matrix to form a part of composite material such as a friction part of C/C composite material.

Abstract: Heat treatment is performed on preforms placed in an enclosure accompanied by sweeping with an inert gas under reduced pressure, and with a gaseous effluent being exhausted continuously via a first effluent outlet connected to an effluent exhaust circuit. At the end of the heat treatment, the first gaseous effluent outlet is closed so as to isolate the effluent exhaust circuit from the enclosure, sweeping of the enclosure with the inert gas is interrupted, and the heat-treated preforms are left in the enclosure and are subjected to densification by admitting a reagent gas into the enclosure via at least one reagent gas admission duct opening out into the enclosure, with gaseous effluent being exhausted via a second effluent outlet separate from the first, said second outlet being closed during the heat treatment step. Advantageously, metal, in particular sodium, contained in the gaseous effluent exhausted from the enclosure during the heat treatment step is neutralized.

Abstract: An installation for densification of porous substrates by CVI comprises an oven, a zone for loading substrates in the oven, means for heating substrates loaded in the loading zone, at least one inlet for admitting reactive gas in the oven, and at least one gas heating zone situated in the oven between the reactive gas inlet and the loading zone. At least one gas preheating device is located outside the oven and is connected to the gas inlet so as to preheat the reactive gas before it enters the oven.

Abstract: An installation for densification of porous substrates by CVI comprises an oven, a zone for loading substrates in the oven, means for heating substrates loaded in the loading zone, at least one inlet for admitting reactive gas in the oven, and at least one gas heating zone situated in the oven between the reactive gas inlet and the loading zone. At least one gas preheating device is located outside the oven and is connected to the gas inlet so as to preheat the reactive gas before it enters the oven.

Abstract: A gas preheater for a CVI furnace designed for the densification of annular porous substrates arranged in a plurality of vertical annular stacks of substrates, comprising: a sleeve made of heat conductive material resting upon the bottom wall of a susceptor and delimiting a gas preheating chamber, with a gas inlet opening in the gas preheating chamber; a heat exchange assembly located in the gas preheating chamber; a gas distribution plate resting upon the sleeve, covering the gas preheating chamber and provided with a plurality of passages for preheated gas; a load supporting plate for supporting stacks of annular substrates and provided with a plurality of passages in communication with respective passages of the gas distribution plate and registration with internal volumes of respective stacks of annular substrates; and nozzles inserted in passages communicating the gas preheating zone with the internal volumes of respective stacks of annular substrates for adjusting the flows of preheated gas respectively