TUBULAR BODY CONTAINING SiC FIBERS

Abstract

Provided is a tubular body containing SiC fibers having high thermal conductivity. The tubular body containing SiC fibers includes a SiC fiber layer wound in a tubular form, an inner SiC coating layer covering an inner surface of the SiC fiber layer, and an outer SiC coating layer covering an outer surface of the SiC fiber layer. The inner and outer SiC coating layers are bound to each other in gaps provided in the SiC fiber layer.

Claims

1. A tubular body containing SiC fibers, the tubular body comprising: a SiC fiber layer wound in a tubular form; an inner SiC coating layer covering an inner surface of the SiC fiber layer; and an outer SiC coating layer covering an outer surface of the SiC fiber layer, wherein the inner SiC coating layer and the outer SiC coating layer are bound to each other in gaps provided in the SiC fiber layer.

2. The tubular body containing SiC fibers according to claim 1, wherein the inner SiC coating layer is composed of sintered SiC.

3. The tubular body containing SiC fibers according to claim 1, wherein the tubular body has a cross-sectional shape of a polygon, circle, ellipse, or round shape having irregularities on an outer circumference thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a perspective view showing a tubular body containing SiC fibers of the present invention.

[0018] FIG. 2 shows partial cross-sections of the tubular body containing SiC fibers of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0019] An embodiment of a tubular body containing SiC fibers of the present invention will be described in detail below with reference to the accompanying drawings.

[0020] FIG. 1 is a perspective view showing the tubular body containing SiC fibers. FIG. 2 shows partial cross-sections of the tubular body containing SiC fibers of the present invention.

[0021] A tubular body 10 containing SiC fibers of the present invention comprises a SiC fiber layer 20 wound in a tubular form, an inner SiC coating layer 30 covering the inner surface of the SiC fiber layer 20, and an outer SiC coating layer 40 covering the outer surface of the SiC fiber layer 20.

[0022] The SiC fiber layer 20 has a structure in which the SiC fibers are bundled into strands, braided, and helically wound to enhance combined effect. The SiC fiber layer 20 is provided with patterned gaps (voids) between the intersecting fibers (see FIG. 1).

[0023] The inner SiC coating layer 30 is formed, for example, in a CVD furnace at 1000° C. to 1400° C. by supplying SiCl.sub.4 and CH.sub.4 together with H.sub.2 that acts as a diluent gas. The formed CVD-SiC film has a thickness of, for example, about 300 μm. The inner SiC coating layer 30 is not required to have as much corrosion resistance as the outer SiC coating layer; it is thus possible to use a sintered SiC material, for example.

[0024] Similarly to the inner SiC coating layer 30, the outer SiC coating layer 40 is formed, for example, in a CVD furnace at 1000° C. to 1400° C. by supplying SiCl.sub.4 and CH.sub.4 together with H.sub.2 that acts as a diluent gas. The formed CVD-SiC film has a thickness of, for example, about 500 μm.

[0025] The inner and outer SiC coating layers 30, 40 are tightly and closely bound to each other in the gaps provided in the SiC fiber layer 20 (see FIG. 2). Specifically, the outer SiC coating layer 40 is made thicker than the inner SiC coating layer 30, which configuration allows film formation in the gaps as well as on the surface of the SiC fiber layer 20. Such coating layers are bound to each other while interposing the SiC fiber layer 20 in between due to binding of the materials of the SiC layers that are identical in terms of, for example, thermal expansion rates. Accordingly, layer separation is less likely to occur. In the structure of the inner and outer SiC coating layers (with the SiC fiber layer in between), these layers may be stacked multiple times in repetition.

[0026] The cross-sectional shape of the tubular body may be a circle, ellipse, polygon, such as triangle and quadrangle, or round shape having irregularities on the outer circumference thereof. Accordingly, the tubular body containing SiC fibers can be more widely used.

[0027] The following describes a method for producing the tubular body 10 containing SiC fibers of the present invention, which is configured as described above. Examples of the method for producing the tubular body containing SiC fibers of the present invention include a method that involves use of a graphite base material or sintered SiC, which will be described below.

[0028] [Graphite Base Material]

[0029] Step 1: Preparing Graphite Base Material

[0030] A graphite base material is prepared that does not react in a later process such as in CVD treatment. The graphite base material is shaped into a round bar having a specified diameter and length.

[0031] Step 2: Coating Inner SiC

[0032] A SiC film is formed on the entire surface (the outer peripheral surface) of the graphite base material by CVD method (Chemical Vapor Deposition method). The SiC film has a thickness of about 300 μm.

[0033] Step 3: Winding First SiC Fiber Layer

[0034] SiC fibers are wound into strands and braided to be helically wound by a commercially available automatic loom around the surface of the graphite base material coated with the inner SiC film.

[0035] Step 4: Forming Outer SiC Coating Layer

[0036] Similarly to the inner SiC coating layer, a SiC film is formed on the entire surface (on the outer peripheral surface) of the graphite base material with the SiC fibers wound therearound by the CVD method. The SiC film has a thickness of about 500 μm.

[0037] Step 5: Outer Shape Processing

[0038] The outer shape of the outer SiC coating layer is adjusted by, for example, cutting.

[0039] Step 6: Winding Second SiC Fiber Layer

[0040] Similarly to the first SiC fiber layer, the SiC fibers are wound into strands and braided to be helically wound by a commercially available automatic loom around the surface of the graphite base material coated with the outer SiC film.

[0041] Step 7: Forming Outer SiC Coating Layer

[0042] A SiC film is formed on the entire outer peripheral surface of the graphite base material with the SiC fibers wound therearound by the CVD method. The SiC film has a thickness of, for example, about 500 μm.

[0043] Step 8: Cutting/Severing of Outer Shape/Length

[0044] The outer shape (diameter, length, and so on) of the tubular body obtained in Step 7 is adjusted by machining (cutting, severing, or other machining technique).

[0045] Step 9: Removing Graphite Base Material

[0046] The graphite base material is removed in a high-temperature and oxidizing environment.

[0047] Step 10: Shaping

[0048] The tubular body is ground or polished, and then chamfered and cleaned.

[0049] [Sintered SiC]

[0050] Step 20: Preparing Sintered SiC Base Material

[0051] A pipe-shaped sintered SiC base material is prepared. The sintered SiC base material can be produced by, for example, extrusion molding to make a green body and then sintering of the green body at 2200 ° C. in an inert gas.

[0052] Step 21: Coating Inner SiC

[0053] A SiC film is formed on the entire surface (outer peripheral surface) of the sintered SiC base material by CVD method (Chemical Vapor Deposition method). The SiC film has a thickness of about 300 μm. Use of the tubular sintered SiC base material allows omission of forming the CVD-SiC layer in Step 21.

[0054] Step 22: Winding First SiC Fiber Layer

[0055] The SiC fibers are wound into strands and braided to be helically wound by a commercially available automatic loom around the surface of the sintered SiC base material coated with the inner SiC film.

[0056] Step 23: Forming Outer SiC Coating Layer

[0057] Similarly to the inner SiC coating layer, a SiC film is formed on the entire surface (on the outer peripheral surface) of the sintered SiC base material with the SiC fibers wound therearound by the CVD method. The SiC film has a thickness of about 500 μm.

[0058] Step 24: Outer Shape Processing

[0059] If necessary, the outer shape of the outer SiC coating layer is adjusted by, for example, cutting.

[0060] Step 25: Winding Second SiC Fiber Layer

[0061] Similarly to the first SiC fiber layer, the SiC fibers are bundled into strands and braided by a commercially available automatic loom to be wound around the surface of the sintered SiC base material coated with the outer SiC film.

[0062] Step 26: Forming Outer SiC coating Layer

[0063] A SiC film is formed on the entire outer peripheral surface of the sintered SiC base material with the SiC fibers wound therearound by the CVD method. The SiC film has a thickness of about 500 μm.

[0064] Step 27: Cutting/Severing of Outer Shape/Length

[0065] The outer shape (diameter, length, and so on) of the tubular body obtained in Step 26 is adjusted by machining (cutting, severing, or machining technique).

[0066] Step 28: Shaping

[0067] The tubular body is ground or polished, and then chamfered and cleaned.

[0068] The above has described a method for producing a tubular body having two SiC fiber layers; it is also possible to produce a tubular body having only one SiC fiber layer or three or more SiC fiber layers.

[0069] According to the above-described present invention, the inner and outer SiC coating layers are bound to each other in the gaps provided in the SiC fiber layer. This configuration provides a tubular body having high thermal conductivity and mechanical strength.

[0070] A preferred embodiment of the present invention has been described above. The present invention, however, should not be limited to the above-described embodiment; various modifications can be made without departing from the gist of the present invention.

[0071] Further, the present invention should not be limited to combinations described in the embodiment; the present invention can be implemented by various combinations.

INDUSTRIAL APPLICABILITY

[0072] The present invention can be widely applied to, for example, cladding tubes for storing nuclear fuel.

EXPLANATION OF REFERENCE NUMERALS

[0073] 10 tubular body containing SiC fibers

[0074] 20 SiC fiber layer

[0075] 30 inner SiC coating layer

[0076] 40 outer SiC coating layer