METHOD AND DEVICE FOR DEPOSITING A COATING ON AN ENDLESS FIBER

Abstract

A device for implementing a method for depositing a coating on a continuous fiber from a precursor of the coating in the liquid phase, includes a tubular reactor having a U-shaped section to contain the fiber and the precursor of the coating in the liquid phase, a laser source to generate a laser beam in the reactor intended to heat the surface of a segment of the fiber in the presence of the precursor of the coating in the liquid phase, and a device for making the fiber travel inside the reactor.

Claims

1. A device for implementing a method for depositing a coating on a continuous fiber from a precursor of the coating in the liquid phase, the device comprising a tubular reactor having a U-shaped section to contain the fiber and the precursor of the coating in the liquid phase, a laser source to generate a laser beam in the reactor intended to heat the surface of a segment of the fiber in the presence of the precursor of the coating in the liquid phase, and a device for making the fiber travel inside the reactor.

2. The device according to claim 1, wherein the travel device comprises a first mandrel from which the fiber is intended to be unwound, and a second mandrel on which the coated fiber is intended to be wound.

3. The device according to claim 1, comprising at least two laser sources configured to generate respectively at least two laser beams at two distinct locations in the reactor.

4. The device according to claim 1, wherein the laser source is configured to generate at least two laser beams at two distinct locations in the reactor.

5. The device according to claim 1, comprising several laser sources angularly distributed around the reactor to generate laser beams crossing each other inside the reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate exemplary embodiments thereof without any limitation. In the figures:

[0023] FIGS. 1 to 5 schematically illustrate variants of devices for implementing a method for depositing a coating on a continuous fiber from a precursor of the coating in the liquid phase, and

[0024] FIG. 6 schematically illustrates a device for implementing a method for depositing a coating on a continuous fiber from a precursor of the coating in the supercritical phase.

DETAILED DESCRIPTION

[0025] FIG. 1 shows a device 100 for the implementing a method according to a first embodiment of the invention. The device 100 allows implementing a method for depositing a coating by calefaction, that is to say in which the formation of the coating is carried out in the presence of a liquid phase of a precursor of the coating. The device 100 comprises a tubular reactor 110, a laser source 120, and a travel device 130. A continuous fiber 140 made of ceramic or carbon as well as a precursor 150 of the coating in the liquid state, are present in the reactor 110.

[0026] The tubular reactor 110 has a U-shaped section capable of containing a coating precursor in the liquid state 150 while allowing the formation of the coating by a method according to the invention. More specifically, the reactor 110 comprises a low (here straight and horizontal) portion 112 and two vertical (here also straight) portions 113 and 114 which extend from the low portion 112. In the example illustrated, the coating precursor 150 is present in the low portion 112 of the reactor. The reactor 110 here comprises a first opening 115 and a second opening 116 respectively at the ends of the vertical portions 113 and 114. The fiber 140 runs through the entire reactor 110 between the openings 115 and 116, and is immersed in the coating precursor 150 at the low portion 112 of the reactor. The reactor 110 can comprise means (not represented) for filling and/or purging the coating precursor 150. The reactor 110 may have a tube section which is circular or which has other shapes.

[0027] The laser source 120 allows generating a laser beam 121 inside the reactor 110. In this example, the laser source 120 is located above the low portion 112 of the reactor 110, outside the latter. The laser beam 120 is directed towards the fiber 140 present in the reactor 110. Of course, other configurations of the reactor 110 and of the laser source 120 can be envisaged, as long as the laser beam 121 allows heating the fiber 140 in the presence of the coating precursor 150. The laser beam 121 can have various shapes and for example form a point or “spot”, or a more extended shape so as to cover a larger fiber segment.

[0028] Those skilled in the art know how to determine the characteristics of the laser beam 121 necessary to ensure the formation of the coating on the fiber 140, in particular by modifying the focusing, the power of the laser source 120 or the wavelength of the laser beam 121. Particularly, those skilled in the art will adapt the characteristics of the laser beam 121 as a function of the material constituting the fiber 140 and of the coating precursor 150 used.

[0029] The reactor 110 can be advantageously made of a material transparent to the laser beam 121 generated by the laser source 120 such that the laser beam 121 can reach a location inside the reactor 110 and meet the fiber 140 with a view to heating it. The laser source 120 may, in an exemplary embodiment not illustrated, be inside the reactor 110.

[0030] The travel device 130 here includes a first mandrel 131 from which the fiber 140 can be unwound, the first mandrel 131 can be a mandrel for storing the fiber 150 before it is coated, and a second mandrel 132 on which the fiber 150 can be wound once coated. The fiber 150 can thus circulate in the reactor 110 from the first mandrel 131 up to the second mandrel 132. The centering elements 133, 134 of the fiber 150 in the reactor 120 here ensure that the fiber 150 does not touch the wall of the reactor 120 and that it is sufficiently tensioned. The travel device 130 can be controlled by control means not represented, so as to make the fiber 150 travel in the device 100 continuously or semi-continuously (that is to say step by step). The travel device 130 can for example make the fiber 150 travel in the device 100 in both directions.

[0031] A device 200 according to a second embodiment of the invention is represented in FIG. 2. Unless otherwise indicated, the corresponding reference signs between FIGS. 1 and 2 (100 becomes 200) designate identical characteristics.

[0032] The device 200 still comprises a first laser source 220a for generating a beam 221a. Compared to the device 100, the device 200 further comprises a second laser source 220b for generating a second laser beam 221b at another location in the reactor 210. More specifically, the second laser beam 221b allows heating a segment of the fiber 240 distinct from the fiber segment heated by the first laser beam 221a coming from the first laser source 220a. Such a device 200 is advantageous in that it allows increasing the kinetics of deposition of the coating because the two laser sources 220a and 220b can operate simultaneously. It also allows using two laser beams 221a and 221b having different characteristics.

[0033] A device 300 according to a third embodiment of the invention is represented in FIG. 3. Unless otherwise indicated, the corresponding reference signs between FIGS. 1 and 3 (100 becomes 300) refer to identical characteristics.

[0034] The device 300 still comprises a laser source 320, placed in the same way as the laser sources 120 and 220a with respect to the reactor 310. With respect to the device 100, the laser source 320 is configured to generate several laser beams 321a, 321b, 321c in the direction of the fiber 340. More specifically, the laser beams 321a-321c allow here heating several distinct segments of the fiber 340 simultaneously. The laser beams 321a-321c follow here different paths converging at the laser source 320. Such a device 300 is advantageous in that it also allows increasing the kinetics of deposition of the coating.

[0035] A device 400 according to a fourth embodiment of the invention is represented in FIG. 4. Unless otherwise indicated, the corresponding reference signs between FIGS. 1 and 4 (100 becomes 400) designate identical characteristics.

[0036] The device 400 here comprises a first laser source 420a, placed in the same way as the laser sources 120, 220a and 320 with respect to the reactor 410, and a second laser source 420b located opposite the first laser source 420a with respect to the reactor 410. The laser beams 421a and 421b generated by each of the laser sources 420a and 420b cross each other at the fiber 440 and the directions that carry their paths are coincident. In this example, the laser sources 420a and 420b (as well as the beams 421a and 421b) are angularly distributed around the reactor 410, and are thus angularly separated by 180°. This disposition allows heating the fiber uniformly and thus obtaining a homogeneous deposition, while increasing the kinetics of the deposition.

[0037] A device 500 according to a fifth embodiment of the invention is represented in section in FIG. 5. Unless otherwise indicated, the corresponding reference signs between FIGS. 1 and 5 (100 becomes 500) designate identical characteristics.

[0038] FIG. 5 only shows a cross section of the low portion 512 of the reactor 510, on which three laser sources 520a-520c can be seen to generate respectively three laser beams 521a-521c which cross each other at the fiber 540 immersed in the coating precursor 550. The three laser sources 520a-520c are angularly distributed around the low portion 512 of the reactor 510, and are thus angularly separated by 120°. As for the device 400, this disposition allows heating the fiber more uniformly and thus obtaining a homogeneous deposition, while increasing the kinetics of the deposition.

[0039] The devices 100, 200, 300, 400 and 500 described above allow implementing a method for depositing a coating on a continuous carbon or ceramic fiber from a precursor of the coating, in which at least one segment of the fiber is heated in the presence of a precursor of the coating in the liquid state (calefaction). The aforementioned devices are equipped with travel devices that allow carrying out the method continuously that is to say by repeating successively the heating step on consecutive segments of the fiber.

[0040] FIG. 6 shows a device 600 for implementing a similar deposition method, but in which the precursor of the coating is in the supercritical state.

[0041] The device 600 comprises an enclosure 601 provided with an inlet port 602 and with an outlet port 603. A neutral gas (for example argon) can be introduced into the enclosure 601 through the inlet port. 602. The outlet port 603 allows recovering the gas mixture which has circulated in the enclosure 601 so as not to let it escape into the external environment.

[0042] A reactor 610 is present inside the enclosure 601. The reactor 610 here takes the general shape of a rectilinear tube open at its ends. More specifically, the reactor 610 comprises an inlet opening 611 and an outlet opening 612 through which the continuous fiber 640 can respectively enter and exit the reactor 610. A precursor of the coating consisting of a gas or gas mixture is also introduced into the reactor 610 through the inlet opening 611 (arrow 611a) and discharged from the reactor through the outlet opening 612 (arrow 612a). A laser source 620 is also present to generate a laser beam 621 in the reactor at a location thereof where the fiber 640 is present, similarly to the devices described above. A travel device 630 may be present in the enclosure to ensure the displacement of the fiber 640 in the reactor 610 and ensure a deposition continuously or semi-continuously. The travel device may comprise a first mandrel 631 from which the fiber 640 is unwound, and a second mandrel 632 on which the coated fiber 640 is wound.

[0043] In the device 600, the characteristics of the laser beam 621 (for example its power or its wavelength) can be advantageously chosen to switch the coating precursor to the supercritical state only in the vicinity of the fiber segment 640 which is heated by the laser beam 621, and thereby ensure the formation of the coating on the heated fiber segment 640. The enclosure 601 can be controlled in temperature and in pressure to ensure the passage of the precursor to the supercritical state. Such a method and such a device 600 allow reducing the energy required to perform the deposition, while increasing the kinetics, the reproducibility and the homogeneity of the deposition. It will be noted that the different dispositions of the laser source presented for the devices in which a precursor is used in the liquid state can be applied similarly to the device 600.

Example 1

[0044] A pyrocarbon interphase (PyC) is deposited on a strand of silicon carbide (SiC) fibers by calefaction by using a device similar to the device 100 described above. The coating precursor in the liquid state is ethanol. The laser source is a 1,000 Watt Nd:YAG laser generating a laser beam with a wavelength on the order of 1,064 nm. The laser beam is focused at a point of the strand of fibers that travel continuously at a speed of 120 mm/min in the reactor.

[0045] A homogeneous interphase coating was thus obtained on the strand of fibers having a thickness of 0.3 μm.

Example 2

[0046] A pyrocarbon (PyC) interphase is deposited on a strand of silicon carbide (SiC) fibers by a supercritical method by using a device similar to the device 600 described above. The coating precursor to be used in the supercritical state which is introduced into the reactor is methane. The laser source is a 100 watt laser diode generating a laser beam with a wavelength on the order of 808 nm. The laser beam is focused at a point of the strand of fibers that travel continuously at a speed of 120 mm/min in the reactor.

[0047] A homogeneous interphase coating was thus obtained on the strand of fibers having a thickness of 0.3 μm.