Abstract: An installation for chemical vapor infiltration of porous preforms of three-dimensional shape extending mainly in a longitudinal direction, the installation comprising a reaction chamber of parallelepiped shape, the side walls of the reaction chamber including heater means and a plurality of stacks of loader devices arranged in the reaction chamber. Each loader device being in the form of an enclosure of parallelepiped shape provided with support elements for receiving porous preforms for infiltrating.

Abstract: A loader device is arranged for densifying porous preforms of stackable shape by means of directed stream chemical vapor infiltration in a reaction chamber of an infiltration oven. The device comprises a support tray, a first stack having a plurality of bottom rings arranged on the support tray and a plurality of injection orifices, a second stack comprising a plurality of top rings and a plurality of discharge orifices extending between the outer periphery and inner periphery of each ring. The device includes a first non-porous wall corresponding to the porous preforms and arranged on the support tray inside the bottom rings of the first stack, and a second non-porous wall corresponding to the porous preforms extending between the bottom ring situated at the top of the first stack and the top ring situated at the top of the second stack.

Abstract: An installation for chemical vapor infiltration of porous preforms of three-dimensional shape extending mainly in a longitudinal direction, the installation comprising a reaction chamber of parallelepiped shape, the side walls of the reaction chamber including heater means and a plurality of stacks of loader devices arranged in the reaction chamber. Each loader device being in the form of an enclosure of parallelepiped shape provided with support elements for receiving porous preforms for infiltrating.

Abstract: A loader device is arranged for densifying porous preforms of stackable shape by means of directed stream chemical vapor infiltration in a reaction chamber of an infiltration oven. The device comprises a support tray, a first stack having a plurality of bottom rings arranged on the support tray and a plurality of injection orifices, a second stack comprising a plurality of top rings and a plurality of discharge orifices extending between the outer periphery and inner periphery of each ring. The device includes a first non-porous wall corresponding to the porous preforms and arranged on the support tray inside the bottom rings of the first stack, and a second non-porous wall corresponding to the porous preforms extending between the bottom ring situated at the top of the first stack and the top ring situated at the top of the second stack.

Abstract: A loader device for loading porous substrates of three-dimensional shapes extending mainly in a longitudinal direction into a reaction chamber of an infiltration oven for densification of the preforms by directed flow chemical vapor infiltration. The device comprising at least one annular loader stage formed by first and second annular vertical walls arranged coaxially relative to each other and defining between them an annular loader space for the porous substrates to be densified. First and second plates respectively cover the bottom portion and the top portion of the annular loader space. The first and second annular vertical walls include support elements arranged in the annular loader space so as to define between them unit loader cells, each for receiving a respective substrate to be densified. The device also comprises gas feed orifices and gas exhaust orifices in the vicinity of each unit loader cell.

Abstract: A composite material part is made by forming a fiber preform (20), forming holes (22) extending within the preform from at least one face thereof, and densifying the preform with a matrix formed at least in part by a chemical vapor infiltration (CVI) type process. The holes (22) are formed by removing material from the preform with fibers being ruptured, for example by machining using a jet of water under pressure, the arrangement of the fibers in the preform with the holes being substantially unchanged compared with the initial arrangement before the holes were formed. This enables the densification gradient to be greatly reduced, and it is possible in a single densification cycle to obtain a density that, in the prior art, required a plurality of cycles separated by intermediate scalping.

Abstract: To densify thin porous substrates (1) by chemical vapor infiltration, the invention proposes using loading tooling (10) comprising a tubular duct (10) disposed between first and second plates (12, 13) and around which the thin substrates for densification are disposed radially. The tooling as loaded in this way is then placed inside a reaction chamber (20) in an infiltration oven having a reactive gas admission inlet (21) connected to the tubular duct (11) to enable a reactive gas to be admitted into the duct which distributes the gas along the main faces on the substrates (1) in a flow direction that is essentially radial. The reactive gas can also flow in the opposite direction, i.e. it can be admitted into the tooling (10) from its outer envelope (16) and can be removed via the duct (11).

Abstract: A method of densifying porous substrates by chemical vapor infiltration comprises loading porous substrates for densification in a loading zone of an enclosure (10), heating the internal volume of the enclosure, and introducing a reagent gas into the enclosure though an inlet situated at one end of the enclosure. Before coming into contact with substrates (20) situated in the loading zone, the reagent gas admitted into the enclosure is preheated, at least in part, by passing along a duct (30) connected to the gas inlet and extending through the loading zone, the duct being raised to the temperature inside the enclosure, and the preheated reagent gas is distributed in the loading zone through one or more openings (33) formed in the side wall (32) of the duct, along the duct.

Abstract: Annular substrates (20) are stacked in an enclosure where they define an inside volume (24) and an outer volume (26) outside the stack. A gas containing at least one precursor of a matrix material to be deposited within the pores of the substrates is channeled inside the enclosure to a first one (24) of the two volumes, and a residual gas is extracted from the enclosure from the other one (26) of the volumes. One or more leakage passages (22) allow the volumes to communicate with each other, other than through the substrates. The total section of the leakage passages has a value lying between a minimum value for ensuring that a maximum gas pressure in the first volume is not exceeded until the end of densification, and a maximum value such that a pressure difference is indeed established between the two volumes from the beginning of densification.

Abstract: A dry pump (32) has an inlet connected to the oven (10) for the purpose of establishing the desired low pressure conditions inside the oven and for extracting residual gas therefrom, a hydrolysis reactor (50) is connected to an outlet of the dry pump in order to receive residual gases coming from the oven, the hydrolysis reactor includes a first outlet (52) for solid deposits or for acid solutions coming from hydrolysis of the gases it receives, and it has a second outlet (54) for gas which is connected to the atmosphere. Gas injection means (46, 48) are located between the inlet of the dry pump (32) and the hydrolysis reactor (50) to prevent any backflow from the hydrolysis reactor towards the pump. Water feed means (74, 76) are connected to the hydrolysis reactor (50), at least via the second outlet (54) thereof, in order to put into solution the acid vapors that come from the hydrolysis reactor, thereby avoiding discharging them in the atmosphere.

Abstract: A composite material protected by oxidation at intermediate temperatures exceeding 850.degree. C. comprises fiber reinforcement densified by a matrix which includes at least one self-healing phase including a glass-precursor component such as B.sub.4 C or an Si--B--C system, together with excess free carbon (C) at a mass percentage lying in the range 10% to 35%. The, or each, self-healing phase can be interposed between two ceramic matrix phases, e.g. of SiC. While the material is exposed to an oxidizing medium, oxidation of the free carbon promotes oxidation of the precursor and transformation thereof into a glass capable of plugging the cracks in the matrix by self-healing.

Abstract: The interphase is formed by nanometric scale sequencing of a plurality of different constituents including at least a first constituent that intrinsically presents a lamellar microtexture, and at least a second constituent that is suitable for protecting the first against oxidation. A plurality of elementary layers of a first constituent of lamellar microtexture, e.g. selected from pryolytic carbon, boron nitride, and BC.sub.3 are formed in alternation with one or more elementary layers of a second constituent having a function of providing protection against oxidation and selected, for example, from SiC, Si.sub.3 N.sub.4, SiB.sub.4, SiB.sub.6, and a codeposit of the elements Si, B, and C. The elementary layers of the interphase are preferably less than 10 nanometers thick and they are formed by chemical vapor infiltration or deposition in pulsed form.

Abstract: The pyrolytic carbon lamellar interphase is formed on the reinforcing fibers inside a chamber in which a plurality of successive cycles is performed, each cycle comprising: injecting a reaction gas in which the pyrolytic carbon precursor is selected from alkanes, excluding methane taken as a sole component, alkenes, alkynes, and aromatic hydrocarbons, and mixtures thereof; the gas is maintained inside the chamber for a first predetermined time period to form an interphase layer of controlled thickness of nanometer size; the gaseous reaction products are then evacuated during a second time period; the cycles being performed consecutively in the chamber until the thickness desired for the interphase has been obtained, thereby achieving a lamellar interphase that is highly anisotropic, whose lattice fringe texture has distorted fringes of total length (L.sub.2) not less than 4 nanometers on average with maximum values exceeding 10 nanometers.

Abstract: The pyrolytic carbon lamellar interphase is formed on the reinforcing fibers inside a chamber in which a plurality of successive cycles is performed, each cycle comprising: injecting a reaction gas in which the pyrolytic carbon precursor is selected from alkanes, excluding methane taken as a sole component, alkenes, alkynes, and aromatic hydrocarbons, and mixtures thereof; the gas is maintained inside the chamber for a first predetermined time period to form an interphase layer of controlled thickness of nanometer size; the gaseous reaction products are then evacuated during a second time period; the cycles being performed consecutively in the chamber until the thickness desired for the interphase has been obtained, thereby achieving a lamellar interphase that is highly anisotropic, whose lattice fringe texture has distorted fringes of total length (L.sub.2) not less than 4 nanometers on average with maximum values exceeding 10 nanometers.

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.