Coating apparatus – Gas or vapor deposition
Patent
1997-06-04
2000-04-18
Silbaugh, Jan H.
Coating apparatus
Gas or vapor deposition
96323, 96325, 96328, 261 76, 261 781, 261118, 261DIG54, C23C 1600
Patent
active
060510714
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to industrial installations for fabricating composite material parts, which installations include ovens for chemical vapor deposition or infiltration. More particularly, the invention relates to a gas extraction device for such installations.
BACKGROUND OF THE INVENTION
A known technique for fabricating composite material parts, in particular parts made of thermostructural composite materials such as carbon-carbon composites or ceramic matrix composites, consists in making preforms of the parts and in densifying the preforms in a chemical vapor deposition or infiltration oven. Preforms for parts are generally constituted by fibrous textures or fabrics. The preforms, optionally held in shape by tooling, are inserted into an oven into which there is admitted a gas whose composition is selected as a function of the nature of the matrix of the composite material. Under predetermined conditions of temperature and pressure, the gas diffuses throughout the pores in the preforms and, by decomposition of one of its components or by reaction between a plurality of its components, it leaves behind a solid deposit that progressively densifies the preforms by filling up their pores and thus forming the matrix.
Since chemical vapor deposition or infiltration takes place under low pressure, it is necessary to provide pumping means connected to the oven. An industrial installation for chemical vapor infiltration and operating with a water ring pump is described in document WO 87/04733.
The gaseous reaction products and/or the residues of the gas as extracted from the oven by pumping may give rise to difficulties because they are toxic or corrosive, or because they tend to form unwanted deposits.
This applies in particular when fabricating parts made of composite materials in which the matrices are at least mainly constituted by a ceramic such as a silicon carbide (e.g. SiC), or, more particularly, when the matrix includes at least one ceramic such as boron carbide (B.sub.4 C) or a silicon-boron-carbon (Si--B--C) ternary system as described in document EP-A-0 483 009.
The precursors used in the gas then generally include gaseous halides, in particular gaseous chlorides, which, in addition to being corrosive and toxic, can also form considerable solid deposits on leaving the oven. This applies in particular to boron trichloride BCl.sub.3, a precursor for the element boron.
In the above-mentioned installation that uses a water ring pump, it has thus been observed by the Applicant that the presence of moisture at the inlet to the pump gives rise to solid deposits because of reaction with the gaseous chlorides, thereby progressively and inescapably clogging the pumping pipework. It is then necessary to perform frequent maintenance, or indeed replacement, of the components in the pumping device, which operations require great precautions to be taken because of the unwanted solid deposits are frequently of an unstable nature.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide a gas extraction device which avoids the abovementioned drawbacks, in particular which avoids unwanted deposited forming that could give rise to clogging. Another object of the present invention is to provide an extraction device including means for treating corrosive and toxic gases coming from the oven prior to discharging them to the atmosphere.
This object is achieved by a gas extraction device comprising a dry pump having an inlet connected to the oven to enable the desired low pressure conditions to be established inside the oven and to enable residual gases to be extracted therefrom; and a hydrolysis reactor connected to an outlet of the dry pump and designed to receive the residual gases coming from the oven, the hydrolysis reactor having a first outlet for solid deposits or acid solutions coming from hydrolysis of the gases it receives, and a second outlet for gas that is connected to the atmosphere.
Advantageously, means are provided for injecting a gas, prefe
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Charvet Jean-Luc
Goujard Stephane
Lee Dae Young
Silbaugh Jan H.
Societe Nationale d'Etude et de Construction de Moteurs d'Aviati
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