Installation for silicification

Abstract

Installation for silicification The invention relates to an installation for the silicification of a fibrous preform comprising: - an upper chamber (10) including a holding support (12) for holding said preform (13); - a lower chamber (20) including a bath support (23) adapted to support a container (21) adapted to contain a bath of an infiltration composition (25) comprising molten silicon; - heating means (22); and - a displacement member (26) for putting the holding support (12) and the bath support (23) into relative motion;the installation further comprising a closing device (40) disposed between the lower chamber (20) and the upper chamber (10) and allowing the installation to be moved from an open position, where the upper chamber and the lower chamber are in fluidic communication, to a separation position, where the lower and upper chambers are hermetically separated from each other. Figure for the abbreviation: Fig. 1.;

Description

Title of the invention: Installation for silicification technical field

[0001] The present description relates to an installation for the silicification of fibrous reinforcements and a process that this installation makes possible. Prior art

[0002] Ceramic matrix composite (CMC) materials can withstand temperatures ranging from 600°C to 1400°C.

[0003] Due to their superior resistance to high temperatures, CMCs require less cooling. Since this cooling is traditionally obtained from a source in the compressor, which impacts the turbomachine's efficiency, CMC materials therefore improve engine efficiency, thereby reducing fuel consumption.

[0004] Furthermore, their use helps to optimize the performance of turbomachines, in particular by reducing the overall mass of the turbomachine, which further contributes to a decrease in fuel consumption and therefore to a significant reduction in pollutant emissions.

[0005] Among CMC materials, we find in particular materials comprising a silicon carbide fiber reinforcement and a silicon carbide matrix.

[0006] Such materials are called SiC / SiC and are generally obtained by infiltrating molten silicon into a fibrous reinforcement formed by silicon carbide fibers.

[0007] During such an infiltration, a silicon bath is generally used which also includes boron in known proportions, the boron protecting the fibers from the corrosion that molten silicon could cause in the absence of boron.

[0008] However, it is generally observed that after the infiltration of the preform carried out, the remaining silicification bath no longer presents the same proportions between boron and silicon.

[0009] The remaining bath cannot be reused for a subsequent infiltration process and the remainder of the bath is then entirely replaced by a new silicification bath.

[0010] However, the loss of the unused infiltration bath represents a significant cost, which could be avoided if the infiltration bath could be recycled.

[0011] Such recycling is neither possible nor envisaged in existing installations and that is why there remains a need for an installation which would allow the recycling of the silicon bath, without compromising on the performance of said installation for the silicification step of the fibrous preforms. Description of the invention

[0012] The present presentation aims precisely to propose an installation that meets the needs stated above.

[0013] The invention relates to an installation for the silicification of at least one fibrous preform comprising: - an upper chamber comprising a support for holding said preform; - a lower chamber comprising a bath support suitable for supporting a container suitable for containing a bath of an infiltration composition comprising molten silicon; - heating means for at least the said lower room; and - a displacement device allowing the support and the bath support to move in relative motion; the installation further includes a closing device disposed between the lower chamber and the upper chamber and allowing the installation to be moved from an open position, where the upper chamber and the lower chamber are in fluidic communication, to a separation position, where the lower and upper chambers are hermetically separated from each other.

[0014] The installation according to the invention advantageously allows a recycling step of the infiltration composition to be carried out in the same installation as that which was used for silicification.

[0015] Recycling ensures a reduction in raw material losses and therefore a significant economic gain for the process as a whole.

[0016] Furthermore, in an installation described above, recycling can be carried out directly after silicification thanks to the closing device which allows the lower chamber in which the support suitable for containing the infiltration composition is located to be isolated.

[0017] Since recycling the infiltration composition generally requires a temperature increase, the proposed installation configuration makes it possible to take advantage of the temperature already present in the lower chamber after silicification, without needing to convey the used infiltration composition bath out of the installation, thus minimizing heat losses and reducing heating requirements.

[0018] An infiltration bath will be said to be "used" when it has participated in the carrying out of a silicification step of one or more fibrous preforms.

[0019] The displacement member allows the fibrous preform(s) held by the support to be brought into contact with the bath of the infiltration composition.

[0020] A relative movement of the support and the bath support is described, because it It is sufficient that one of the two supports be mobile relative to the other.

[0021] In one embodiment, the displacement member allows the bath support to be moved from the lower chamber to the upper chamber.

[0022] This embodiment can be carried out with an elevating bath support which allows the infiltration composition bath to be moved from the lower chamber to the upper chamber, and thus to bring at least part of the fibrous preform(s) into contact with the infiltration composition bath.

[0023] In an alternative embodiment, the displacement member allows the retaining support to be moved from the upper chamber to the lower chamber.

[0024] In an alternative embodiment, the installation includes two movement members, one allowing the support to be lowered and the other allowing the bath support to be raised.

[0025] In one embodiment, the installation further includes a gas source connected to the lower chamber. Optionally, a humidifier may also be connected to the lower chamber.

[0026] The gas source and, where applicable, the humidifier advantageously enable a recycling process for the used infiltration composition.

[0027] Indeed, the inventors have found that bringing the used infiltration composition bath into contact with a treatment atmosphere makes it possible to recycle the infiltration composition.

[0028] More specifically, the infiltration composition preferably comprises silicon and boron in known proportions, with all other species present in the infiltration composition being present at a concentration of 100 ppm or less. Preferably, the sum of the mass concentrations for species other than silicon or boron is 100 ppm or less.

[0029] Such infiltration compositions ensure on the one hand infiltration into the porosity of the fibrous preforms of molten silicon, and on the other hand boron makes it possible to protect the preforms against the corrosion that the molten silicon would cause in its absence.

[0030] However, after the infiltration of the preforms by the infiltration composition, it was found that the proportions of boron and silicon of the remainder of the bath are no longer the same as those of the initial composition, which makes the used infiltration composition unsuitable for reuse as is.

[0031] In order to allow the reuse of the infiltration composition, it is proposed by the inventors to remove the boron from the used infiltration composition to obtain a treated used infiltration composition comprising only silicon and possibly other elements including boron in a content less than or equal to 500 ppm.

[0032] It will then suffice to determine the quantity of used infiltration composition thus obtained and then add boron in a known quantity to produce a new infiltration composition.

[0033] The gas sources of the proposed installation make it possible to impose on the lower chamber of the installation a treatment atmosphere capable of removing boron from the used infiltration composition.

[0034] For example, the gas sources can be an argon source and / or a dihydrogen source.

[0035] Without wishing to be bound by the theory, the inventors consider that such an atmosphere can react with the used infiltration composition to form a volatile species of boron monohydride HBO, which then escapes from the bath of used infiltration composition which is thus depleted in boron.

[0036] The proposed installation makes it possible, on the one hand, to carry out the recycling step of the used infiltration composition and, on the other hand, to limit the quantity of reagents used for this purpose. Indeed, since the lower chamber can be hermetically sealed from the upper chamber, this greatly reduces the volume of the chamber in which such a step can be carried out.

[0037] In one embodiment, the support further includes a weighing element.

[0038] This embodiment allows for excellent monitoring of the silicification step of the fibrous preforms.

[0039] Indeed, when the preforms are brought into contact with the infiltration composition bath, they become loaded by capillary action with the infiltration composition.

[0040] Monitoring the mass of the preforms makes it easy to control the progress of the silicification of the preforms.

[0041] In one embodiment, the heating means are induction heating means.

[0042] In one embodiment, the heating means are resistive means.

[0043] In one embodiment, the heating means for the upper chamber and The heating methods for the lower room are separate.

[0044] In such an embodiment, it is possible to heat one, the other or both chambers, which in particular ensures excellent thermal homogeneity of the chamber in an open position.

[0045] However, this embodiment advantageously allows only the lower chamber to be heated in a separation position, which ensures substantial energy savings, given the volumes considered.

[0046] According to another aspect, the invention also relates to a silicification process for a fibrous preform, carried out in an installation just described, the process comprising at least: - a silicification stage during which the installation is in a position of opening and in which the fibrous preform is in contact with the infiltration composition bath; and - a recycling step of the infiltration composition, carried out in the lower chamber and during which the installation is in a separation position.

[0047] Such a process makes it possible to take advantage of the advantages already described for the installation and thus have a silicification process in which the used infiltration composition can be reprocessed.

[0048] The process ensures that the silicification step, carried out by infiltration of the infiltration composition into the fibrous preforms, can be carried out under conditions similar to those of the prior art.

[0049] The recycling step can be carried out in the lower chamber alone, which is smaller than the entire enclosure. This step ensures, on the one hand, better use of the raw material by recycling the treated used infiltration composition, and on the other hand, requires no handling of said treated used infiltration composition since it is already in the installation.

[0050] Moreover, the installation is already at a high temperature, necessary for the silicification stage, which allows for energy savings since the recycling stage does not require heating from ambient temperature.

[0051] In one embodiment, the recycling step is carried out by introducing a treatment atmosphere into the lower chamber.

[0052] Such an embodiment of the recycling step has been described above, in connection with the gas sources possibly connected to the lower chamber.

[0053] In one embodiment, the recycling step can be carried out by a treatment atmosphere comprising, or even consisting of, a partial pressure of argon between 1.0 bar and 5.0 bar, a partial pressure of dihydrogen between 0.0 bar and 1.0 bar and a partial pressure of water vapor between 0.0 bar and 1.0 bar.

[0054] In an alternative embodiment, the treatment atmosphere may include, or even consist of, a partial pressure of dihydrogen of between 1.0 bar and 5.0 bar, and a partial pressure of water vapor of between 0.0 bar and 1.0 bar.

[0055] In the present application the partial pressure of a gas takes its usual meaning in the field of ideal gas thermodynamics, and is intended to represent the pressure which would be exerted by the molecules of that gas if it alone occupied the volume offered to the mixture, at the temperature of said mixture.

[0056] In one embodiment, the treatment atmosphere can be brought to the lower chamber by bubbling in the used infiltration composition.

[0057] In one embodiment, the temperature of the upper chamber during the silicification step is between 1400°C and 1500°C, and the temperature of the lower chamber during the recycling stage is between 1400°C and 1600°C.

[0058] As described above, the installation described makes it possible to reuse for the recycling stage a large part of the heat already used for the silicification stage, which reduces the energy requirement of the whole process.

[0059] In one embodiment, the recycling step can be carried out for a duration of between 1 hour and 10 hours. Brief description of the drawings

[0060] [Fig-1] Fig. 1 represents an installation in one embodiment of the invention in an open position.

[0061] [Fig.2] The [Fig.2] represents an installation in an embodiment of the invention in a separation position. Description of the implementation methods

[0062] The invention is now described by means of figures, which are provided for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0063] Fig. 1 illustrates an embodiment of the invention in which the installation is in an open position.

[0064] Such an installation comprises an upper chamber 10 and a lower chamber 20.

[0065] The upper chamber here includes a support 12 from which are suspended fibrous preforms 13, here numbering 4.

[0066] The number of fibrous preforms 13 is in no way limiting to the installation. In particular, a single fibrous preform 13 could be suspended from the support 12.

[0067] In the embodiment shown, the installation further includes heating means 11 and 22.

[0068] Here the heating means 11 of the upper chamber 10 are distinct from the heating means 22 of the lower chamber 20.

[0069] This is not at all necessary, although it is preferable that the heating means 11 of the upper chamber 10 be separate from the heating means 22 of the lower chamber 20 in order to be able to selectively heat one or the other of the chamber 10 or 20, according to the needs of the processes of the invention.

[0070] Each of the two heaters 11 and 22 can be inductive or resistive depending on the particular choices for the design of the installation.

[0071] In [Fig.1], the installation is shown in a position where the two chambers 10 and 20 are in fluidic communication.

[0072] Indeed, the closing member 40, which will be described in more detail with the embodiment illustrated by [Fig.2], is open.

[0073] In addition, the installation includes a bath support 23, supporting a container 21, which contains a bath of the infiltration composition 25.

[0074] In [Fig. 1], the bath of the infiltration composition 25 is in contact with the lower end of the fibrous preforms 13, in order to allow the infiltration of the infiltration composition 25 into the latter by capillarity.

[0075] In one embodiment, the preforms comprise or are made of silicon carbide.

[0076] In addition to what has been described above, the installation includes a displacement member 26 which allows the bath support 23 to be raised, and thus brought closer to the fibrous preforms 13.

[0077] The installation finally includes a balance 24 which allows the quantity of infiltration composition present in the container 21 to be quantified.

[0078] In one embodiment, not illustrated here, the support 12 can also include a weighing element which then makes it possible to determine precisely the mass gain of the fibrous preforms 13, and thus to quantify the progress of the silicification step.

[0079] Elements 31, 32, 33 and 34 will be described in more detail with [Fig.2] and are for [Fig.1] identical to what will be described below.

[0080] Figure 2 illustrates an installation of the invention in a separation position, also called the closed position.

[0081] Fig. 2 illustrates common elements with those already described for Fig. 1, which common elements then bear the same numerical legends.

[0082] In the shown closed position, the lower chamber 20 is hermetically sealed from the upper chamber 10.

[0083] This closed position is achieved here by interposition between the two chambers of the closing member 40, here a sliding door.

[0084] It is understood that a closure is “hermetic” when it ensures that gases cannot pass through said closure either to enter the lower chamber 20, or to leave it.

[0085] In addition, in the closed position, the lower chamber accommodates the bath support 23, the container 21 comprising the infiltration composition 25, as well as the scale 24.

[0086] The presence of these elements in the lower chamber 20 is ensured by the rest position of the displacement member 26.

[0087] In a similar but not shown embodiment, the moving member can allow the movement of the retaining support 12, and thus allows in a opening position of the installation, to lower the fibrous preforms 13 towards the bath 25, rather than raising the bath 25 towards the preforms 13 as shown in [Fig.l].

[0088] In the closing configuration it is understood that the closing member 40 makes it possible to hermetically isolate the lower chamber 20 from the upper chamber 10, in other words, the gases from the chamber 10 cannot go into the chamber 20 and vice versa a.

[0089] The installation further comprises, in the embodiment shown, two gas sources 31 and 32, as well as a humidifier 33 and a gas injection lance 34.

[0090] Sources 31 and 32 can, for example, be respectively an argon source and a dihydrogen source.

[0091] These sources 31, 32 and the humidifier 33, in coordination with the injection lance 34, allow the delivery of a treatment atmosphere in the lower chamber 20 and in a closed position of the installation.

[0092] Figure 2 illustrates that the recycling of the used infiltration composition can take place without requiring its transport. Furthermore, the closed position of the installation ensures a smaller volume in the lower chamber than in the absence of the closing device 40, thus reducing the reactive gas requirements.

[0093] Finally, the described installation allows recycling to be carried out directly in the same installation as the silicification takes place.

[0094] This, as indicated above, makes it possible to limit heat losses between the silicification stage and the recycling stage, which reduces the costs of the process by lowering its heating requirements.

[0095] In addition, if it is necessary to supply heat for the recycling stage, only the heating means 22 of the lower chamber 20 can then be used, and the gain achieved through the independence of the heating means 22 and 11 will then be noted.

[0096] Moreover, in an embodiment not shown, the installation may only include the heating means 22, which are then sufficient to heat the entire installation, i.e. the lower chambers 20 and upper chambers 10, in the open position.

[0097] Throughout this application, the expression "between ... and ..." shall be understood inclusive.

Claims

Demands

1. Installation for the silicification of at least one fibrous preform comprising: - an upper chamber (10) including a holding support (12) for holding said preform (13); - a lower chamber (20) including a bath support (23) adapted to support a container (21) adapted to contain a bath of an infiltration composition (25) comprising molten silicon; - heating means (22) for at least said lower chamber; and - a displacement member (26) for putting the holding support (12) and the bath support (23) into relative motion;the installation further comprising a closing device (40) disposed between the lower chamber (20) and the upper chamber (10) and allowing the installation to be moved from an open position, where the upper chamber and the lower chamber are in fluidic communication, to a separation position, where the lower and upper chambers are hermetically separated from each other.;

2. Installation according to claim 1, wherein the displacement member (26) allows the bath support (23) to be moved from the lower chamber (20) to the upper chamber (10).

3. Installation according to claim 1 or 2, wherein the installation further comprises a gas source (31, 32) and optionally a humidifier (33) connected to the lower chamber (20).

4. Installation according to any one of claims 1 to 3, wherein the support (12) further comprises a weighing element.

5. Installation according to any one of claims 1 to 4, wherein the heating means (11, 22) are induction heating means.

6. A silicification process for a fibrous preform, carried out in an installation according to any one of claims 1 to 5, the process comprising at least: - a silicification step during which the installation is in an open position and in which the fibrous preform (13) is in contact with the infiltration composition bath (25); and - a recycling step of the infiltration composition, carried out in the lower chamber (20) and during which the installation is in an closing position.

7. Silicification process according to claim 6, wherein the recycling step is carried out by introducing a treatment atmosphere into the lower chamber (20).

8. A silicification process according to claim 6 or 7 wherein the temperature of the upper chamber during the silicification step is between 1400°C and 1500°C, and the temperature of the lower chamber during the recycling step is between 1400°C and 1600°C.

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