JPH0471040B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method and apparatus for producing SiC whiskers, and in particular to high-performance materials used in composite materials such as fiber-reinforced plastics (FRP), fiber-reinforced metals (FRM), and fiber-reinforced ceramics (FRC). This paper proposes a method and equipment for continuously and efficiently producing high-quality SiC whiskers on an industrial scale using a vapor phase method. (Prior art) Currently known methods for producing SiC whiskers include a solid phase method using solid raw materials of carbon and silicon, a gaseous method of carbon and silicon, or a gaseous reaction of carbon and silicon with a solid, or a gaseous mixture thereof. There is a law. The solid phase method is a method of leading to the following reaction from solid SiO ₂ and C: SiO ₂ +CSiO+CO SiO+3COSiC+2CO ₂ CO ₂ +C2CO, and is a technology in which so-called gaseous SiO and CO are reacted to precipitate and grow SiC whiskers. be. For example, the technology disclosed in Japanese Patent Publication No. 59-9516, which belongs to the solid-phase method, uses rice husk ash as the Si source and carbon black as the C source, and the This method involves heating to 1700℃. Furthermore, the technology disclosed in JP-A-61-227993 proposes a method of heating at a temperature of 1400 to 1700°C in a non-oxidizing atmosphere using silicic anhydride as a Si source and activated carbon as a C source. are doing. As a manufacturing apparatus used to carry out the above-mentioned solid phase method, for example, Japanese Utility Model Publication No. 59-38447 discloses a reaction vessel for producing SiC whiskers made of graphite material, and Publication No. 227999 discloses a furnace body having a passage with a temperature gradient along the longitudinal direction, a raw material filling area provided along the passage, and a plurality of sample storage units having a whisker generation area and an exhaust pipe. We are proposing an SiC whisker manufacturing device consisting of a container and a container. On the other hand, gas phase methods include a method in which a gaseous silicon halide such as silicon tetrachloride is reacted with a gaseous carbon compound such as carbon tetrachloride as a Si source at high temperature in a hydrogen stream, methyltrichlorosilane, etc. A method using thermal decomposition of organic silane is known. For example, the technology disclosed in Japanese Patent Publication No. 59-45635 introduces a silicon halide gas and a carbon halide gas into a heated reaction tube via a carrier gas (H ₂ ), and Alternatively, β-
This is a method for growing SiC whiskers, and in Japanese Patent Publication No. 59-45636, a porcelain tube or a graphite tube filled with carbon powder is inserted into a jacket tube.
We are proposing a method for producing silicon carbide whiskers by generating a mixed gas of silicon tetrachloride and hydrogen while heating to 1300℃. (Problems to be Solved by the Invention) The above two conventional techniques shown as solid-phase methods have the following problems: (1) In addition to producing a large amount of granular SiC as a by-product, unreacted particulates of the raw material remain; These generated
Since it is mixed in SiC whiskers, it is not possible to obtain high-purity whiskers suitable as reinforcing materials for metals and ceramics. Therefore, additional complicated steps are required to separate and purify these particulates, and the yield of whiskers is also low. (2) Due to the slow reaction rate, it is difficult to continuously produce large amounts of high aspect ratio whiskers. (3) Reaction temperature is high. There were other problems. In addition, regarding the equipment used for such solid phase method,
All of them are batch-type production devices, which not only cannot perform continuous production, but also require a large number of reaction vessels in order to perform large-scale, efficient production, resulting in a large-scale device. Next, the above two conventional techniques described as gas phase methods both have a problem in that the silicon halide used as the raw material is expensive. Furthermore, these conventional methods do not include any specific disclosure regarding continuous production means on an industrial scale. Furthermore, in these methods, the generated whiskers grow and precipitate on a fixed cylindrical substrate or the inner wall of a porcelain tube that serves as the substrate. Therefore, since the precipitate is grown on the substrate, the length, diameter, and other shapes may vary due to subtle temperature variations on the substrate surface, the density of the precipitated whiskers, and differences in reactant gas concentration depending on the location of the substrate. It becomes uniform. An object of the present invention is to develop a technique that can overcome the problems of the conventional solid phase method and gas phase method described above. (Means for Solving the Problems) In order to achieve the above-mentioned purpose, the present invention provides a method having the following features, namely, a method for producing SiC by vapor phase synthesis of silicon sulfide and a carbon compound.
To obtain whiskers, metal silicon particles are sequentially charged into a preliminary reaction vessel having a production gas outlet and a reaction gas inlet, and the metal silicon particles in the preliminary reaction vessel are
It is maintained in a temperature atmosphere of 1000 to 1400°C, and hydrogen sulfide gas and carrier gas are blown into it from the bottom to generate silicon sulfide gas, which is discharged from the top.Then, the silicon sulfide gas is continuously generated. is introduced via a carrier gas into the main reaction vessel maintained at 1130 to 1500°C, and brought into contact with carbon compounds in the presence of generated nuclei to precipitate whiskers and continue to grow them. The present invention provides a method for producing SiC whiskers, which is characterized in that the whiskers are discharged intermittently or intermittently, and as a device used to carry out the method, a gas dispersion plate is disposed near the bottom of a main body equipped with heating equipment. , a raw material charging port is provided on the upper wall of the gas distribution plate, a produced gas discharge port is provided at the top, and a reactant gas inlet and a carrier gas inlet are provided in the bottom of the vessel below the distribution plate. A fluidized bed for generating whiskers, which comprises a pre-reaction vessel for fluidized bed for silicon generation, a main body equipped with heating equipment, a pipe for supplying a generation nucleus material and a pipe for supplying a carbon compound, and a whisker outlet at the bottom. In order to solve the above-mentioned problems, we proposed an SiC whisker manufacturing apparatus in which a main reaction vessel, and the pre-reactor and main reactor are connected by a conveying pipe equipped with heating equipment. (Operation) The basic principle of the present invention is to bring silicon sulfide into contact with a mixed gas of hydrogen sulfide and hydrogen to produce silicon sulfide gas, and to react with propylene gas (C ₃ H ₆ ) to form SiC. The point is to generate whiskers, and the research of "Egashira et al." which was confirmed in the laboratory as a whisker vapor phase synthesis method; [References: Makoto Egashira, Hiroaki Katsuki, Katsumi Mori, Hiroaki Kaneko, Watari Kurahashi, Masahachi Kawazumi , "Ceramic Industry Association Magazine" 93.535
~540 (1985)] is known. According to this study, the above method is thought to be based on the following reaction. Overall reaction formula: Si+1/3C ₃ H ₆ →SiC+H ₂ (1) When SiS is used as an intermediate; Si+H ₂ S→SiS+H ₂ SiS+1/3C ₃ H ₆ →SiC+H ₂ S (2) When SiS ₂ is used as an intermediate Case; Si+2H ₂ S→SiS ₂ +2H ₂ SiS+1/3C ₃ H ₆ +H ₂ →SiC+2H ₂ S This known method based on desk experiments yields whiskers with a larger aspect ratio than the conventional technique described above, and the starting materials are inexpensive. It has excellent characteristics such as fast whisker growth, high purity whiskers, and no particulate matter. However, according to the explanation in the above-mentioned "References", this method is a batch method research using a small tube furnace, and the technology is not developed for specific measures to enable continuous and mass production, which is essential for industrialization. It was considered unsuitable for continuous and mass production due to the lack of disclosure and various constraints. As a result of extensive research based on the basic principle shown in the above reference, the present inventors have developed a two-step process that uses a fluidized bed reaction in each of the silicon sulfide gas generation process and the SiC whisker precipitation growth process. It has been found that by employing a fluidized bed method, various problems faced by the above-mentioned conventional techniques can be solved, and high-quality whiskers can be produced continuously and efficiently on an industrial scale. The present invention will be explained in detail below. The method of the invention consists of a first step in which silicon sulfide gas is generated and a second step in which SiC whiskers are precipitated from the gas. The first step is to continuously or intermittently supply metal silicon 2, which is one of the raw materials, to the lower part of the fluidized bed preliminary reaction vessel 1 for silicon sulfide generation. This silicon sulfide generating fluidized bed pre-reaction vessel 1 has a generated gas outlet 3 above, a reaction gas inlet 5 and a carrier gas inlet 6 at the bottom, and above each gas inlet 5, 6. A gas dispersion plate 4 having a large number of gas outlets is provided, and the metal silicon 2 is charged and held on this gas dispersion plate 4. In addition, on the side wall of this fluidized bed pre-reaction vessel 1,
A raw material charging port 13 is provided for charging metallic silicon, and the metallic silicon supplied from this port has a particle size of 2 mm or less. If the size is larger than that, the reaction efficiency will be poor. In addition, if the particle size is less than 0.04 mm, there is a possibility that it will be scattered along with the gas from the generated gas outlet 3, so it is recommended to use metal silicon particles with a particle size of 0.04 to 2 mm. is desirable. As for the material of the reaction vessel, it is desirable to use a heat-resistant material such as alumina, mullite, or silicon carbide, since the inside of the vessel reaches a high temperature of 1000° C. or more. After charging the metal silicon as a raw material,
Next, hydrogen sulfide gas and carrier gas (H ₂ ) are introduced in a mixed state from the gas inlets 5 and 6 of the preliminary reaction vessel, and are brought into contact with the metal silicon 2 to generate silicon sulfide gas. The produced gas is discharged via a carrier gas from a produced gas outlet 3 provided at the neck of the reaction vessel 1, and transferred to the next fluidized bed main reaction vessel 8 in a heat-retained state. Note that in order to generate silicon sulfide gas in the preliminary reaction vessel 1 of the first stage, the inside of the vessel must be heated at 1000 °C.
It is necessary to maintain the temperature at or above 1130°C, which is the boiling point of silicon disulfide. However, the melting point of metallic silicon is 1414
℃, the metal silicon will melt at a temperature higher than this temperature, so it is desirable to maintain the temperature inside the container within the range of 1000 to 1400℃. Therefore, the preliminary reaction vessel 1 and the transfer pipe 9 for transferring silicon sulfide gas have an internal temperature of 1000 to 1400°C.
It is necessary to provide heating equipment 7a, 7b such as an electric furnace so that the temperature is maintained within this range. Further, as the carrier gas, argon,
An inert gas such as helium or a reducing gas such as hydrogen or a mixture thereof can be used. When these gases are blown into the container together with hydrogen sulfide gas, it is most desirable to operate the metal silicon charged in the container so that it gradually becomes a fluidized bed from an initial fixed layer. This is because a fluidized bed is preferable in terms of reaction efficiency. However, it is undesirable for the metal silicon particles to scatter from the gas outlet together with the blown gas. In this sense, in order to efficiently generate silicon sulfide gas, it is desirable to further adjust the gas velocity under the porous gas distribution plate 4 on which metal silicon is deposited. The degree of this adjustment varies depending on the particle size of the metal silicon, but it is preferably 10 times or less the speed at which the metal silicon layer starts to fluidize. If this value is exceeded, there is a high possibility that metal silicon particles will be scattered from the gas outlet. In the second step of the present invention, the silicon sulfide gas produced in the first step is heated together with the carrier gas so that the internal temperature reaches 1130 to 1500.
The carbon compound and the produced material are similarly supplied through the carbon compound supply pipe 10 and the produced material supply pipe 11, respectively, and whisker production is carried out in the reaction vessel 8. This is the process of precipitating and growing. Examples of the carbon compounds include paraffin hydrocarbons such as methane, ethane, propane, butane, and pentane; olefin hydrocarbons such as ethylene, propylene, butylene, and amylene; acetylene hydrocarbons such as acetylene, arylene, and butyne;
Aromatic hydrocarbons such as benzene, naphthalene and anthracene, alicyclic hydrocarbons such as cycloparaffin and cycloolefin, or mixtures thereof can be used. In addition, these carbon compounds may be supplied in any of the gas, liquid, or solid states, but those that are liquid or solid at room temperature are made into fine particles and slurried using water or an organic solvent. From the viewpoint of handling, it is preferable to use a solid state, a state dispersed in the carrier gas, a solution dissolved in an organic solvent or the like, or a state modified into a gas state by heating. In addition, the carbon compound used in the present invention is
As mentioned above, it is possible to select from a wide range of types and forms, but in terms of reaction efficiency, whisker yield, ease of handling, etc., methane, ethane, propane, ethylene, propylene,
It is desirable to use acetylene, arylene, etc. On the other hand, the nucleating materials include metals such as iron, nickel, titanium, manganese, cobalt, copper, vanadium, chromium, aluminum, and silicon, as well as oxides, carbides, nitrides, sulfides, halides, and sulfates of these metals. , inorganic substances such as nitrates or metal alcoholates such as ethyl silicate, ethyl titanate, general formula M(C ₅ H ₅ ) ₂ [M: Fe, Ni,
Organometallic compounds such as metallocenes represented by Ti, Mn, Co, Cu, V, Cr] or mixtures thereof can be used. These nucleating materials may be in any state such as gas, liquid, or solid when supplied, but those in a liquid or solid state at room temperature are made into fine particles and made into a slurry with water or an organic solvent. In terms of handling, it is preferable to use a dispersion in the above-mentioned carrier gas, a solution of water in an organic solvent, or a gas by heating. As explained above, the production nuclei used in the present invention can be selected from a wide range of types and forms, but the reaction efficiency, whisker yield, ease of handling, and even after whisker production are Organic metal compounds containing iron, nickel, manganese, etc. are desirable from the viewpoint of ease of removing generated nuclei. Now, at the stage of using this main reaction vessel 8, due to the reaction between silicon sulfide gas and carbon compound,
In order to generate SiC whiskers, it is necessary to cause the two to react in a gas phase. From this,
The temperature inside the main reaction vessel 8 for whisker production is
It is necessary to raise the temperature to 1130℃ or higher, which is the boiling point of silicon sulfide. On the other hand, if the temperature is too high, the SiC whisker production reaction becomes difficult to occur, so the upper limit is set at 1500°C. The temperature inside the so-called container 8 is 1130~
Set the temperature to 1500℃. This fluidized bed main reaction vessel 8 for whisker production is provided with heating equipment such as an electric furnace to heat and maintain the interior within the above temperature range. In addition, the material of the container itself has an internal temperature of 1130℃ or higher, so
Heat-resistant materials such as alumina, mullite, and silicon carbide are preferred. The carrier gas plays a role in controlling the concentration of the hydrogen sulfide gas blown in from the bottom and the silicon sulfide gas generated, as well as the gas flow rate in the main reaction vessel for whisker production. In addition, the carbon compound fed into the main reaction vessel for whisker generation reacts with silicon sulfide gas.
It acts to generate SiC, and the generated nucleating material is suspended in the form of fine particles in the main reaction vessel for whisker generation, and acts as a nucleus or substrate for the precipitation and growth of whiskers. Therefore, the generated whiskers grow using the generated nuclei as seeds and are fluidized along the flow of the carrier gas, granulated silicon gas, etc., and the reaction is completed. (Example) FIG. 1 shows a preferred specific example of the SiC whisker manufacturing apparatus according to the present invention. The fluidized bed preliminary reaction vessel 1 for producing silicon sulfide gas is made of silicon carbide and has a cylindrical shape with an inner diameter of 150 mm and a flow rate of 1000 mm, and the fluidized bed main reaction vessel 8 for producing SiC whiskers is made of silicon carbide and has an inner diameter of 300 mm and a flow rate of 1000 mm. It is 3000mm cylindrical. Each of these containers 1 and 8 was installed in electric furnaces 7a to 7c, respectively. Metallic silicon with an average particle size of 0.3 mm was charged into a preliminary reaction vessel 1 for producing silicon sulfide whose interior was maintained at 1200°C, and hydrogen sulfide gas and hydrogen gas were blown from the bottom through the respective inlets 5 and 6. It was crowded. The total flow rate of hydrogen sulfide gas and hydrogen gas was 204 ml/s, and the ratio was 5:95. The generated silicon sulfide gas is transferred to the main reaction vessel 8 for whisker production whose interior is maintained at 1300°C.
At the same time, propylene gas 4 is released from the top of the container 8.
ml/s and ferrosen gas at 2×10 ^-3 ml/s were introduced, respectively. These various gases were continuously supplied in the above fixed amounts. The precipitated and grown whiskers are removed from the whisker outlet 12 provided at the bottom of the main reaction vessel 8.
The gas was then discharged and recovered using a rotary valve 14 while being sealed. The whiskers thus obtained were analyzed using X-rays, and their length, diameter, etc. were measured using a microscope. In addition, the whisker yield was calculated from the weight of whiskers obtained per unit time and the weight of propylene gas charged. These results are shown in Table 1 below. Examples 1 to 4 shown in the table show the amounts of hydrogen sulfide gas, hydrogen gas, propylene gas, and ferrocene gas used and the temperatures in the preliminary reaction vessel 1 for silicon sulfide gas generation and the main reaction vessel 8 for whisker generation. This is an example of manufacturing by changing.

【table】

[Table] (Effects of the Invention) As can be seen from the above explanation and the results of the examples, high quality SiC whiskers can be produced continuously and efficiently when manufactured according to the method described above using the apparatus according to the present invention. can be manufactured. In particular, since a fluidized bed using a carrier gas is used, it is possible to control the concentration and amount of silicon sulfide gas generated.Furthermore, by changing the raw materials, the amount of the carrier gas, and the temperature inside each container, the amount and length of whiskers can be adjusted.
It can be manufactured continuously on an industrial scale while controlling the diameter etc. Furthermore, the whiskers generated in the present invention are
Because the whisker grows using fine particles of the nucleating material that exist in suspension in the main reaction vessel for whisker generation,
The generation conditions are made more uniform, and compared to the whiskers found in the above-mentioned conventional technologies, in which whiskers grow using the surface of a fixed substrate as a nucleus, whiskers with high uniformity in length and diameter can be obtained continuously. . The Si source material of the present invention is metallic silicon,
Since it is cheaper than the silicon halide gas used in conventional technology, it is possible to ultimately supply inexpensive whiskers, which can be used for FRP, FRM, FRC.
It is suitable as a composite reinforcing material such as.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a preferred example of the SiC whisker manufacturing apparatus according to the present invention. 1...Preliminary reaction container, 2...Metal silicon, 3
...Produced gas outlet, 4...Gas distribution plate, 5...
Reaction gas inlet, 6...Carrier gas inlet, 7
a-7c... Heating equipment, 8... Main reaction vessel, 9...
...Transport pipe, 10...Carbon compound supply pipe, 11
... Nucleus supply pipe, 12... Whisker outlet, 13... Raw material charging port, 14... Rotary valve.

Claims (1)

[Claims] 1. By vapor phase synthesis of silicon sulfide and a carbon compound.
To obtain SiC whiskers, metal silicon particles are sequentially charged into a preliminary reaction vessel having a generated gas outlet and a reaction gas inlet, and the metal silicon particles in the preliminary reaction vessel are
It is maintained in a temperature atmosphere of 1000 to 1400°C, and hydrogen sulfide gas and carrier gas are blown into it from the bottom to generate silicon sulfide gas, which is discharged from the top.Then, the silicon sulfide gas is continuously generated. is introduced via a carrier gas into the main reaction vessel maintained at 1130 to 1500°C, and brought into contact with carbon compounds in the presence of generated nuclei to precipitate whiskers and continue to grow them. A method for producing SiC whiskers, characterized by selectively or intermittently discharging them. 2. A gas distribution plate is provided near the bottom of the main body equipped with heating equipment, a raw material charging port is provided on the upper wall of the gas distribution plate, and a produced gas discharge port is provided on the top, while a gas distribution plate is provided below the distribution plate. A fluidized bed pre-reaction vessel for silicon sulfide generation is provided with a reaction gas inlet and a carrier gas inlet at the bottom of the vessel, and a production nucleating material supply pipe and a carbon compound supply pipe are arranged in the main body equipped with heating equipment. A fluidized bed main reaction vessel for producing whiskers is provided with a whisker discharge port at the bottom thereof, and the preliminary reactor and the main reactor are connected by a conveying pipe equipped with heating equipment. Manufacturing equipment.