DEVICE FOR DIFFUSING A PRECURSOR WITH A CONTAINER HAVING AT LEAST ONE POROUS ELEMENT ALLOWING THE GENERATION OF AN AEROSOL TOWARDS A GROWTH SURFACE

Abstract

A precursor diffusion device configured to diffuse a growth precursor towards an external growth surface included on an external growth member, the diffusion device including a container including at least one porous element having a porosity configured to allow or prevent the passage of a precursor fluid through a thickness of the porous element, the porous element being configured so that the precursor fluid which passes through the thickness of the porous element generates an aerosol by fragmentation of the precursor fluid, the aerosol being formed of droplets of the precursor fluid. Also, a method for depositing a layer on a growth surface by such a diffusion device.

Claims

1. A diffusion device of a precursor configured to diffuse a growth precursor towards an external growth surface comprised on an external growth member, the diffusion device comprising a container internally delimiting at least one receiving enclosure, the container being at least partially constituted by at least one porous element, the porous element internally delimiting an inner surface, the inner surface at least partially delimiting the at least one receiving enclosure, the porous element externally delimiting a diffusion surface intended to face towards the external growth surface, the at least one receiving enclosure being configured to contain a precursor fluid comprising the growth precursor, the diffusion device comprising the precursor fluid contained in the receiving enclosure, the porous element having a porosity configured on the one hand to allow the precursor fluid to pass through a thickness of the porous element counted between the inner surface and the diffusion surface as long as a pressure of the precursor fluid contained in the receiving enclosure is strictly higher than a threshold pressure, on the other hand to prevent the precursor fluid from passing through the thickness of the porous element when the pressure of the precursor fluid contained in the receiving enclosure is lower than the threshold pressure, the threshold pressure being strictly higher than an external pressure prevailing outside the container; the porous element being configured so that the precursor fluid which passes through the thickness of the porous element generates, from the diffusion surface, an aerosol by fragmentation of the precursor fluid, the aerosol being formed of droplets of the precursor fluid and contained between the diffusion surface and the external growth surface.

2. The diffusion device according to claim 1, wherein the container is entirely formed by the porous element.

3. The diffusion device according to claim 1, comprising at least one pressurizing member configured to vary the pressure of the precursor fluid inside the receiving enclosure, so as to place the precursor fluid at a pressure higher than the threshold pressure, to allow the precursor fluid to pass through the porous element from the inner surface towards the diffusion surface.

4. The diffusion device according to claim 1, wherein the container extends generally along a longitudinal axis and comprises a sealed end and a fluid inlet end spaced apart from each other along the longitudinal axis, the porous element being located between these two ends and the receiving enclosure being configured to receive the precursor fluid at the fluid inlet end and to be closed at the sealed end.

5. The diffusion device according to claim 4, wherein the diffusion surface of the porous element has a first prismatic shape characterized by a first basic profile, the first prismatic shape being generated by the rectilinear translation of the first basic profile along the longitudinal axis, and wherein the inner surface of the porous element has a second prismatic shape characterized by a second basic profile, the second prismatic shape being generated by the rectilinear translation of the second basic profile along the longitudinal axis.

6. The diffusion device according to claim 5, wherein the first basic profile is a circle having a first radius, and wherein the second basic profile is a circle having a second radius strictly lower than the first radius, the thickness of the porous element being equal to a difference between the first radius and the second radius.

7. The diffusion device according to claim 4, wherein the porous element has a length, counted longitudinally along the longitudinal axis, the length being strictly greater than 80 cm.

8. The diffusion device according to claim 1, comprising: a first receiving enclosure delimited by a first inner surface, and configured to receive a first precursor fluid; and a second receiving enclosure delimited by a second inner surface and configured to receive a second precursor fluid.

9. The diffusion device according to claim 1, comprising an assembly member disposed at an assembly end of the diffusion device, the assembly member being configured to allow the fastening, at the assembly end, of an external element selected from: another diffusion device and the growth member.

10. The diffusion device according to claim 1, wherein the porous element is obtained by three-dimensional printing.

11. The diffusion device according to claim 1, wherein the container is shaped so that it can be inserted into a tubular clad.

12. A deposition method for depositing a layer on a growth surface, the deposition method comprising: a providing step in which a diffusion device according to claim 1 is provided, the at least one receiving enclosure being at least partially filled with a precursor fluid; a step of delivering a growth member comprising a growth surface; a positioning step, in which the growth surface is disposed opposite the diffusion surface of the diffusion device; a step of pressurizing the receiving enclosure of the diffusion device, in which the precursor fluid is placed at a pressure higher than the threshold pressure, so as to allow the precursor fluid to pass through the thickness of the porous element, so as to generate an aerosol by fragmentation of the precursor fluid when the precursor fluid passes through the thickness of the porous element, the aerosol then being formed of droplets of the precursor fluid, and directed towards the growth surface; a growth step in which the aerosol undergoes a chemical reaction at the growth surface to form the layer.

13. The deposition method according to claim 12, wherein the positioning step is implemented before the pressurizing step.

14. The deposition method according to claim 12, wherein at least one step selected from the positioning step, the pressurizing step and the growth step, is implemented in a growth chamber of a chemical growth furnace.

15. The deposition method according to claim 14, wherein the growth step is implemented in the chemical growth furnace, so that the chemical growth furnace places the growth chamber at a growth temperature to heat the growth member and the diffusion device at the growth temperature to promote the chemical reaction of the aerosol at the growth surface.

16. The deposition method according to claim 12, wherein the step of providing a diffusion device comprises a step of manufacturing the porous element by three-dimensional printing.

17. The deposition method according to claim 12, comprising a filling step in which the precursor fluid is introduced into the at least one receiving enclosure of the diffusion device.

18. The deposition method according to claim 12, wherein the providing step comprises providing a diffusion device according to claim 6, device wherein the first basic profile is a circle having a first radius, and wherein the second basic profile is a circle having a second radius strictly lower than the first radius, the thickness of the porous element being equal to a difference between the first radius and the second radius; and wherein the step of delivering a growth member comprises the delivery of a generally tubular growth member along a main axis, the growth member internally delimiting an outwardly open cavity at an insertion opening disposed at one end of the growth member considered along the main axis, the cavity delimiting at least the growth surface and being in the form of a third prismatic shape characterized by a third basic profile, the third prismatic shape being generated by the rectilinear translation of the third basic profile along of the main axis, the third basic profile being a circle having a radius strictly greater than the first radius, the positioning step comprising a step of inserting the diffusion device inside the cavity of the growth member through the insertion opening along the main axis.

19. The deposition method according to claim 18, wherein a length of the porous element counted along the longitudinal axis axis of the container is strictly greater than a length of the growth member counted along the main axis, so that after the step of inserting the diffusion device inside the growth member, the entire growth surface faces at least one portion of the external surface of the porous element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0096] Other aspects, aims, advantages and features of the invention will better appear on reading the following detailed description of preferred embodiments thereof, given as a non-limiting example, and made with reference to the appended drawings in which:

[0097] FIG. 1 is a schematic sectional view of a precursor diffusion device according to a first embodiment of the invention.

[0098] FIG. 2 is a schematic sectional view of a precursor diffusion device according to a second embodiment of the invention.

[0099] FIG. 3 is a schematic perspective view of two precursor diffusion devices according to one embodiment of the invention.

[0100] FIG. 4 is a schematic sectional view of a precursor diffusion device according to the embodiment of FIG. 1 and of a growth member.

[0101] FIG. 5 is a schematic view of some steps of the deposition method according to a particular embodiment of the invention.

[0102] FIG. 6 is a schematic view of some steps of the deposition method according to a particular embodiment of the invention.

DETAILED DESCRIPTION

[0103] In the figures and in the following description, the same reference numerals represent identical or similar elements. In addition, the different elements are not represented to scale in order to promote clarity of the figures. Furthermore, the different embodiments and variants do not exclude each other and can be combined together.

[0104] As illustrated in FIGS. 1 to 6, the invention concerns a precursor diffusion device 1, configured to diffuse a growth precursor towards a growth surface s101. Said growth surface is included on an external growth member 100, which may for example comprise a tubular clad 101. Such a growth member 100 can advantageously be used to accommodate a fuel pellet. The invention also concerns a method for depositing a layer 103 on said growth surface s101. Advantageously, it can therefore be provided that such a deposition method is used to deposit a protective layer 103 on a clad accommodating a fuel pellet, in order to limit or even eliminate the effects of the PCI.

[0105] As will be described in more detail below with reference to the deposition method, the diffusion device 1 is suitable for use in a chemical vapor deposition process. Consequently, the diffusion device 1 is adapted to remain intact at temperatures comprised between 1000° C. and 1500° C., and/or at low pressures, typically less than 10-6 Pa.

[0106] With reference to FIGS. 1 and 2, the diffusion device 1 comprises a container 10 internally delimiting at least one receiving enclosure 11. The container 10 is at least partially constituted by at least one porous element 30 which internally delimits an inner surface s31, and which externally delimits a diffusion surface s33 intended to face towards the external growth surface s101. The inner surface s31 then at least partially delimits the at least one receiving enclosure 11.

[0107] Advantageously, the porous element 30 consists essentially of or comprises a metallic material. The metallic material of the porous element 30 comprises at least one of the following materials in pure, alloy or oxide form: aluminum, stainless steel, nickel, or tungsten.

[0108] According to the non-limiting variants represented in FIGS. 1 and 2, the container 10 extends generally along a longitudinal axis X and comprises a sealed end 19 and a fluid inlet end 21 spaced apart from each other along the longitudinal axis X. The porous element 30 is located between these two ends and the receiving enclosure 11 can be closed at the sealed end 19. According to these variants, the container 10 is entirely formed by the porous element 30. The porous element 30 may for example have a length L1, counted longitudinally along the longitudinal axis X, which is strictly greater than 80 cm, and in particular strictly greater than 2 m. Furthermore, the diffusion surface s33 of the porous element 30 can have a first prismatic shape characterized by a first basic profile, said first prismatic shape being generated by the rectilinear translation of said first basic profile along the longitudinal axis X. The inner surface s31 of the porous element 30 has a second prismatic shape characterized by a second basic profile, said second prismatic shape being generated by the rectilinear translation of said second basic profile along the longitudinal axis X. More particularly, at least one surface selected from the diffusion surface s33 and the inner surface s31 of the porous element 30 is in the form of all or part of a cylindrical surface. FIG. 1 shows in particular a variant where the diffusion surface s33 and the inner surface s31 have the shape of a cylindrical surface. By “cylindrical surface” it should be mathematically understood a three-dimensional surface generated by a generating line which moves in a given direction based on a closed curved line called the directrix. In the present case, the directrix corresponds to the profile of the cross-section of the container 10 at the porous element 30 while the generating line is oriented parallel to the longitudinal axis X. According to the embodiments, the cross-section of the container 10 is circular, in order that the container 10 is shaped so that it can be inserted into a tubular clad 101. It is therefore clearly understood that according to the variant illustrated in FIG. 1, the diffusion surface s33 is tubular, and the inner surface s31 is tubular. In other words, the first basic profile is a circle having a first radius r1, the second basic profile is a circle having a second radius r2 strictly smaller than the first radius r1.

[0109] Said at least one receiving enclosure 11 of the diffusion device 1 is configured to contain a precursor fluid 15 comprising the growth precursor. In general, the receiving enclosure 11 is configured to receive the precursor fluid 15 at the fluid inlet end 21. The diffusion device 1 therefore comprises the precursor fluid 15 contained in the receiving enclosure 11. According to a first embodiment, the precursor fluid 15 is liquid, for example, the precursor fluid 15 may comprise a solid precursor agent dissolved in a solvent. Alternatively, the precursor fluid 15 may comprise a mixture of a solvent and a liquid precursor agent. According to one embodiment, the precursor agent comprises chromium oxide Cr.sub.2O.sub.3. In the non-limiting variant represented in FIG. 2, the diffusion device 1 comprises a first receiving enclosure 11a delimited by a first inner surface s31a, and configured to receive a first precursor fluid 15a, and a second receiving enclosure 11b delimited by a second inner surface s31b and configured to receive a second precursor fluid 15b. It is clearly understood that the use of the terms “first” and “second” is not restrictive and that according to the embodiment, there may be at least one additional receiving enclosure 11 of the same nature as the first and second receiving enclosures 11a, 11b and for which the same principles apply. In other words, the container 10 can delimit at least three separate receiving enclosures 11, that may possibly contain respectively precursor fluids 15 that are identical or different from one enclosure to another. Thus, the first precursor fluid 15a may be different from the second precursor fluid 15b. In this way, it is possible to generate two different types of aerosols via a single diffusion device 1. For example, this allows locally alternately or simultaneously diffusing, two different types of precursors, at the growth surface s101. For example, the second precursor fluid 15b may comprise a coolant configured to cool the porous element 30. Alternatively, it can be provided that the first precursor fluid 15a and the second precursor fluid 15b are identical.

[0110] The porous element 30 has a porosity configured on the one hand to allow said precursor fluid 15 to pass through a thickness e31 of the porous element 30 counted between said inner surface s31 and said diffusion surface s33 as long as a pressure of the precursor fluid 15 contained in the receiving enclosure 11 is strictly higher than a threshold pressure, and on the other hand to prevent the precursor fluid 15 from passing through said thickness e31 of the porous element 30 when the pressure of the precursor fluid 15 contained in the receiving enclosure 11 is lower than said threshold pressure. For example, the porous element 30 can comprise pores having an average diameter comprised between 2 μm and 100 μm. The threshold pressure is strictly higher than an external pressure prevailing outside the container 10. For example, the threshold pressure is between 2.105 Pa and 20.105 Pa. The porous element 30 is further configured so that the precursor fluid 15 which passes through the thickness e31 of the porous element 30 generates, from the diffusion surface s33, an aerosol 17 by fragmentation of the precursor fluid 15. Said aerosol 17 is formed of droplets of the precursor fluid 15 and is contained between the diffusion surface s33 and the external growth surface s101. According to the variant illustrated in FIG. 1, the thickness e31 of the porous element 30 is equal to a difference between the first radius r1 and the second radius r2. According to the variant illustrated in FIG. 2, a first thickness e31a is counted between the first inner surface s31a and the diffusion surface s33 of the porous element 30, and a second thickness e31b is counted between the second inner surface s31b and the diffusion surface s33 of the porous element 30. The first thickness e31a is strictly greater than the second thickness e31b. In this way, it is possible to adapt the thickness e31 through which the precursor fluid 15 passes according to the receiving enclosure 11a, 11b which contains it and/or the nature of this precursor fluid 15. Thus, the generated aerosol 17 or the diameter of the droplets constituting it may be different.

[0111] In general, the diffusion device 1 is configured to supply an aerosol 17 comprising at least one precursor agent at the growth surface s101 in a manner allowing the growth of a layer 103 on the growth surface s101. For example, said layer 103 may be a protective layer 103. Advantageously, the diffusion device 1 allows controlling the thickness of the protective layer 103 deposited on the growth surface s101.

[0112] FIG. 3 illustrates the formation of said aerosol 17 by two distinct diffusion devices 1. As illustrated in FIG. 3, the diffusion device 1 may comprise at least one pressurizing member 50 configured to vary the pressure of the precursor fluid 15 inside the receiving enclosure 11, so as to place the precursor fluid 15 at a pressure higher than the threshold pressure, to allow the precursor fluid 15 to pass through the porous element 30, from the inner surface s31 towards the diffusion surface s33. For example, the pressurizing member 50 comprises a pneumatic pump. The at least one pressurizing member 50 can be disposed at the fluid inlet end 21 of the porous element 30. In the non-limiting case where the diffusion device 1 comprises two receiving enclosures 11a, 11b, it can be provided that the diffusion device 1 comprises a pressurizing member 50 associated with each receiving enclosure 11a, 11b. Thus, it is possible to adapt the pressure at which the first precursor fluid 15a is placed and the pressure at which the second precursor fluid 15b is placed according to the nature of the precursor fluid 15a, 15b used.

[0113] Finally, and with particular reference to FIG. 4, the diffusion device 1 may comprise an assembly member 53 disposed at an assembly end 55 of the diffusion device 1. For example, the assembly end 55 is disposed at the fluid inlet end 21 of the container 10, seen along the longitudinal axis X. The assembly member 53 is configured to allow the fastening, at said assembly end 55, of an external element selected from: another diffusion device and the growth member 100. The previously described arrangements allow assembling several diffusion devices to each other, in order to match the shape of the growth surface s101. However, and as illustrated in FIG. 4, said assembly member 53 is configured to allow the fastening of the growth member 100. According to this variant, the diffusion device comprises two assembly members 53 made in one piece with the porous element. These assembly members 53 are in the form of annular shoulders disposed around the longitudinal axis X. In this case, it can be provided that the growth member 100 comprises at least one flange 105 configured to cooperate with the diffusion device 1, for example at the assembly end 55 of the diffusion device 1. FIG. 4 therefore illustrates a non-limiting variant in which two flanges 105 cooperate with the assembly members 53 of the diffusion device 1.

[0114] Advantageously, it can be provided that the porous element 30 is obtained by three-dimensional printing. Indeed, the manufacture of the porous element 30 by 3D printing allows both simply defining the shape of the porous element 30 even if this shape is complex, and also reducing the manufacturing costs. Furthermore, it is possible to obtain a specific shape of the porous element 30, for example a shape integrating a plurality of receiving enclosures 11a, 11b allowing storing different precursor fluids 15a, 15b before the implementation of a pressurizing step. In addition, 3D printing simply allows providing at least one assembly member 53 at the assembly end 55 of the diffusion device 1.

[0115] Alternatively, the porous element 30 can be obtained by a powder melting method.

[0116] The previously described arrangements allow proposing a diffusion device 1 adapted to generate an aerosol 17 comprising droplets of a precursor fluid 15 at a growth surface s101. Advantageously, the previously described diffusion device 1 allows controlling both the type of precursor fluid 15 comprised in the diffused aerosol 17, and the quantity of diffused aerosol 17. Furthermore, it is possible to locally diffuse said aerosol 17 close to the growth surface s101. Thus, any losses of precursor fluid 15 are limited. Finally, the diffusion device 1 allows homogeneously diffusing the precursor fluid 15 in the form of an ultra-divided or gaseous liquid over the entire growth surface s101, avoiding inhomogeneities. The fragmentation of the precursor fluid 15 allows improving its evaporation and its reactivity, in particular when used in a chemical vapor deposition method in a chemical growth furnace.

[0117] As indicated above, the invention also concerns a deposition method for depositing a layer 103 on a growth surface s101 of a growth member 100.

[0118] The deposition method illustrated for example in FIGS. 5 and 6 firstly comprises a providing step E10 in which a diffusion device 1 as previously described is provided. The step E10 of providing a diffusion device 1 may comprise a step E01 of manufacturing the porous element 30 by three-dimensional printing. Alternatively, the porous element 30 can be obtained by a powder melting method. Advantageously, the manufacture of the porous element 30 by 3D printing allows both simply defining the shape of the porous element 30 even in a complex shape, and also reducing the manufacturing costs. Furthermore, 3D printing simply allows providing at least one assembly member 53 at the assembly end 55 of the diffusion device 1 allowing the easier implementation of a positioning step E30 which will be described below. Finally, 3D printing allows obtaining a specific shape of the porous element 30, for example a shape integrating a plurality of receiving enclosures 11a, 11b allowing storing different precursor fluids 15a, 15b before the implementation of a pressurizing step E50 which will be described later.

[0119] Then, it can be provided that the deposition method comprises a filling step E03 in which the precursor fluid 15 is introduced into the at least one receiving enclosure 11 of the diffusion device 1. This filling step E03 is implemented before the pressurizing step E50. In this way, the at least one receiving enclosure 11 is at least partially filled with a precursor fluid 15 during the providing step E10.

[0120] The deposition method also comprises a step E20 of delivering a growth member 100 comprising a growth surface s101. According to the non-limiting variant illustrated in FIG. 5, the growth member 100 is generally tubular along a main axis X2, and internally delimits an outwardly open cavity 107 at an insertion opening 109 disposed at one end of the growth member 100 considered along the main axis X2. This cavity 107 at least partially delimits said growth surface s101.

[0121] Then, the deposition method comprises a positioning step E30, in which the growth surface s101 is disposed opposite the diffusion surface s33 of the diffusion device 1. As illustrated in FIG. 5, the providing step E10 may comprise providing a diffusion device 1 wherein the first basic profile is a circle having a first radius r1, and wherein the second basic profile is a circle having a second radius r2 strictly smaller than the first radius r1, the thickness e31 of the porous element 30 being equal to a difference between the first radius r1 and the second radius r2. The step E20 of delivering a growth member 100 may comprise the delivery of a growth member 100 in which the growth surface s101 having the form of a third prismatic shape characterized by a third basic profile, said third prismatic shape being generated by the rectilinear translation of said third basic profile along the main axis X2, said third basic profile being a circle having a radius r3 strictly greater than the first radius r1. Thus, the positioning step E30 may comprise a step E31 of inserting the diffusion device 1 inside the cavity 107 of the growth member 100 through the insertion opening 109 along the axis main X2. The main axis X2 is then parallel or coincident with the longitudinal axis X. Advantageously, it can be provided that a length L1 of the porous element 30 counted along the longitudinal axis X of the container 10 is strictly greater than a length L2 of the growth member 100 counted along the main axis X2, so that after the step E31 of inserting the diffusion device 1 inside the growth member 100, the entire growth surface s101 faces at least one portion of the external surface of the porous element 30. In this way, the aerosol 17 generation is uniform over the entire length L1 of the growth member 100 and over the entire surface of the growth surface s101.

[0122] The deposition method further comprises a step E50 of pressurizing the receiving enclosure 11 of the diffusion device 1 generally implemented after the positioning step E30. In this way, it is possible to position the external surface of the porous element 30 opposite the growth surface s101 to ensure a localized aerosol 17 generation close to the growth surface s101, homogeneously over the entire growth surface s101. During this pressurizing step E50, the precursor fluid 15 is placed at a pressure higher than the threshold pressure, so as to allow said precursor fluid 15 to pass through the thickness e31 of the porous element 30, in order to generate the aerosol 17 by fragmentation of the precursor fluid 15 when the precursor fluid 15 passes through the thickness e31 of the porous element 30, said aerosol 17 then being formed of droplets of the precursor fluid 15, and directed towards the growth surface s101. According to the embodiment represented in FIG. 6, the diffusion device 1 is provided with at least one pressurizing member 50 configured to implement the pressurizing step E50. For example, the pressurizing member 50 is configured to inject a pressurizing gas into the receiving enclosure 11.

[0123] Finally, the deposition method comprises a growth step E60 in which the aerosol 17 undergoes a chemical reaction at the growth surface s101 to form said layer 103. Therefore, the growth step E60 can be implemented in the chemical growth furnace, so that the chemical growth furnace places the growth chamber at a growth temperature to heat the growth member 100 and the diffusion device 1 at said growth temperature to promote the chemical reaction of the aerosol 17 at the growth surface s101. For example, the growth temperature is comprised between 1000° C. and 1500° C. Furthermore, during this growth step E60, the chemical growth furnace can place the growth chamber at a growth pressure so as to generate a growth vacuum allowing the growth of the layer 103 on the growth surface s101. For example, the growth pressure is lower than 10-6 Pa. Finally, the growth chamber can be placed in an inert atmosphere during the growth step E60, said inert atmosphere being obtained by the injection of an inert gas, for example argon or nitrogen. Advantageously, the pressurizing gas used during the pressurizing step E50 is identical to the inert gas used to place the growth chamber in an inert atmosphere.

[0124] In general, at least one step selected from the positioning step E30, the pressurizing step E50 and the growth step E60, is implemented in the growth chamber of the chemical growth furnace, preferably a chemical vapor deposition furnace. In this way, the pressurizing step E50 allows locally supplying a precursor agent contained in the precursor fluid 15 at the growth surface s101 to allow the growth of a layer 103 in the chemical vapor deposition furnace during the growth step E60.

[0125] In the case where the porous element 30 comprises a first receiving enclosure 11a and a second receiving enclosure 11b, the second receiving enclosure 11b can be configured to receive a coolant configured to cool the porous element 30 during the growth step E60. Thus, it is possible to cool the porous element 30 to avoid an undesirable deposition of the precursor fluid 15 in pores of the porous element 30, which could lead to clogging of said pores of the porous element 30 and/or to disruption of a homogeneous growth on the growth surface s101.

[0126] The previously described arrangements allow proposing a deposition method in which an aerosol 17 comprising droplets of a precursor fluid 15 is locally injected at Zo a growth surface s101. In this way, it is possible to control both the type of diffused aerosol 17, and the quantity of diffused aerosol 17. Thus, any losses of precursor fluid 15 are limited.