JPS63225508A - Production of sialon powder - Google Patents

Abstract

PURPOSE:To easily obtain the title fine Sialon powder, by decomposing decomposable Si compd. Al compd., and carbon compd. in a hot gas contg. steam to form and collect a mixedaerosol dispersoid. and baking the dispersoid in the atmosphere contg. nitrogen cpds. CONSTITUTION:Air is introduced into a furnace 1 from a duct 2, and fuel is introduced from a burner 3 and burned to generate a hot gas. A decomposable silicon silicon compd. (e.g., SiCl4) and a decomposable carbon compd. (e.g., A heavy oil) are introduced into the furnace 1 from a nozzle 4, a decomposable aluminum compd. (e.g., AlCl3) is introduced from a nozzle 5, and the material are decomposed. As a result, the mixed dispersoid contg. the respective aerosols of silicon oxide, aluminum, oxide and elementary carbon is formed. The dispersoid is then collected by solid-gas separation the obtained carbon-contg. composition is baked in the gas atmosphere contg. nitrogen compds., and Sialon powder is obtained.

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a novel method for producing sialon powder suitable as a raw material for producing sialon sintered bodies.

[Prior art and its problems]

Sialon is 5in-, ^j! ,0. It is a compound represented by N@-, and the ceramic sintered body obtained by molding and sintering its powder has significantly higher mechanical strength and corrosion resistance at high temperatures than conventional metal materials. Because of its excellent properties, it is expected to be used in engines, gas turbines, etc. However, the use of sialon powder produced by conventional manufacturing methods has the disadvantage that the mechanical strength of the resulting ceramic sintered bodies varies too much. The finer the Sialon powder, the easier it is to sinter.
This is because the higher the purity, the smaller the variation in the strength of the obtained sintered body, but this fineness and high purity cannot be ensured with conventional sialon powder. That is, the method for producing sialon powder according to the prior art is A.
j! A common method is to mix clay, which is a relatively uniform mixture of tos- and SiO'l, with carbon powder using a ball mill or the like, and then heat the mixture in a nitrogen or gas atmosphere to reduce and nitride it. However, this method is a batch method, which not only has problems such as the complexity of the work process when mixing and charging the raw materials and the contamination of impurities, but also the generated sialon powder is coarse grained, so it is not necessary as a raw material for sintered bodies. In order to obtain fine powder, it is necessary to grind for a long time using a grinder such as a ball mill or a vibration mill, which increases costs, complicates the work process, and introduces impurities during the work process. There is a problem. Furthermore, it is fundamentally and essentially impossible to obtain ultrafine powder of 1 micron or less using such mechanical grinding methods. [Basic idea] The present inventors et al. After carrying out various meter readings in order to solve these problems in the conventional technology, we first developed a composition consisting of silicon oxide, aluminum oxide, and elemental carbon, which has sufficiently high uniformity and has fine constituent particles. High purity and fine sialon powder can be easily produced by heating the fine carbon-containing composition referred to in the present invention, which is produced in one step by gas phase reaction, in a nitrogen-containing compound gas atmosphere. (Disclosure of the Invention) In other words, the present invention is directed to the production of a decomposable silicon compound, a decomposable aluminum compound, and a decomposable aluminum compound in a hot gas containing water vapor. A mixed aerosol dispersoid containing aerosols of silicon oxide, aluminum oxide and elemental carbon is produced by charging and decomposing a carbon compound, and the produced dispersoid is collected by a solid-gas separation operation. The present invention is described in detail below.The present invention is described in detail below. The mixed aerosol 2 referred to above means a dispersoid in which silicon oxide, aluminum oxide, and elemental carbon are mixed as fine solid particles in a gas.Among such aerosols, an aerosol of elemental carbon is Aerosols of silicon oxide or aluminum oxide can be obtained by charging and decomposing decomposable carbon compounds in hot gas, and aerosols of silicon oxide or aluminum oxide can be obtained by decomposing decomposable carbon compounds such as silicon tetrachloride or aluminum trichloride. It can be obtained by pyrolysis, oxidative decomposition, or hydrolysis by charging the aluminum compound into hot gas containing water vapor. In the present invention, first, by simultaneously charging and decomposing the decomposable carbon compound, decomposable silicon compound, and decomposable aluminum compound into hot gas containing water vapor,
A mixed aerosol containing aerosols of silicon oxide, aluminum oxide, and elemental carbon is immediately generated. The decomposable silicon compound that can be used in the present invention has the general formula (1) % formula % (1) (where n is an integer from 1 to 4, and X is a hydrogen atom, a halogen atom, an alkyl group, an aryl group) or an alkoxyl group, and when n≧2, X may be the same or different,
To illustrate this as a specific compound, for example, 5i
Cj! n, HSiCj! Ri, HJiCI! m
, i, 5icz, 5ilia, 5iJa
, Sieg C1b, SigFa s (CHt)4s
i, (CH25iCj! t,,CH25iCj!
a, SiF4, Si (OCJs) a, etc. The decomposable aluminum compound used in the present invention is a compound represented by the general formula (2) % formula % (2) (where X has the same meaning as defined in formula (1) above). For example, Azcj! is a specific compound. s, It^lICl1*, H! Aj
ICIt. ＾＾! Brs, ^l H*, (CHs) sA j
! , (CJs) J j! , (CJs)s^j! ,
Al4(OCRs)s -＾j! (OCtlls
)s1^j! (OCsHy) s, A l (OCJ
J s, A ffi C0CIH□)8, ＾j! (O
CJaCHs)s, etc. Furthermore, the decomposable carbon compound used in the implementation of the present invention is one that can easily decompose and produce elemental carbon (soot) when charged into hot gas, as described later, and can be left as it is to generate carbon. Phase or liquid phase state, or those that can easily become liquid phase state by increasing temperature can be suitably used. Examples of this include LPG, naphtha, gasoline, fuel oil,
Petroleum products such as kerosene, light oil, heavy oil, lubricating oil, liquid paraffin, etc.: methane, ethane, propane, butane, pentane, methanol, ethanol, propatool, ethylene, acetylene, n-paraffin, butadiene, isoprene, isobutylene, benzene , toluene, xylene, cyclohexane, cyclohexene, dicyclopentadiene, ethylbenzene, styrene, cumene, pseudocumene, mesitylene, alkylbenzene, α-methylstyrene, dicyclododecatriene, diisobutylene, vinyl chloride, chlorobenzene% C1 fraction mixture, Petrochemical products such as ethylene bottoms; tar, pitch, creosote oil, naphthalene, anthracene, carbazole,
Tar products such as tar acid, phenol, cresol, xylenol, pyridine, picoline, and quinoline; soybean oil, coconut oil, linseed oil, cottonseed oil, rapeseed oil, tung oil, castor oil, whale oil, beef tallow, squalane, oleic acid, stearin Preferred examples include oils and fats such as acids, but of course they are not limited to these. In the present invention, since the purpose of the decomposable carbon compound is to supply carbon, the type of decomposable carbon compound can be selected from a wide range other than those mentioned above, but from the viewpoint of ease of handling and carbon yield, toluene, Preferred are xylene, benzene, kerosene, light oil, heavy oil, C9 fraction mixture, ethylene bottoms, and the like. A furnace is used to obtain the carbon-containing composition of the present invention. The furnace heating device usually uses a combustion burner, an electric heating element, etc., and also includes a nozzle for charging decomposable silicon compounds, decomposable aluminum compounds, and decomposable carbon compounds, a hot gas charging duct, and a mixed aerosol discharge duct. A device having a furnace surrounded by a refractory material is preferably used. The present invention requires that a spatial region at least 700° C. or higher, preferably 1400° C. or higher, exist as a decomposition reaction zone in the furnace. At temperatures above this temperature, elemental carbon is obtained from decomposable carbon compounds, silicon oxide is obtained from decomposable silicon compounds in an atmosphere containing water vapor, and aluminum oxide is obtained from decomposable aluminum compounds as fine particles. This produces a mixed aerosol state, which is a mixture of gas and these fine solid particles. The proportions of silicon, aluminum and carbon in the mixed aerosol can be easily adjusted simply by controlling the flow rate of each component introduced into the hot gas through the nozzle. Therefore, when charging these, it is best to keep the decomposable silicon compounds, decomposable aluminum compounds, and decomposable carbon compounds in the gas phase or liquid phase to make it easier to adjust the charging flow rate and to easily generate fine aerosols. desirable in terms of
A method in which a solid phase, for example, a decomposable silicon compound is dissolved in a liquid phase, for example, a hydrocarbon, can also be easily adopted. In addition to the aerosol of silicon oxide or aluminum oxide in the mixed aerosol, even if elemental silicon or elemental aluminum has some silicon halide or aluminum halide interposed therein, this will not be a particular hindrance to the implementation of the present invention. Furthermore, the aluminum oxide referred to in the present invention may of course contain aluminum hydroxide. In the present invention, as a method for obtaining hot gas containing water vapor, water vapor may be injected into hot gas obtained by an electric heating method, a high frequency heating method, or a discharge method, but hydrogen, methane, ethane, propane, butane, etc. Alternatively, a method of burning with air a combustible material that inevitably produces water vapor as a combustion component, such as a hydrocarbon used as a raw material, is convenient in terms of equipment and desirable from the standpoint of thermal efficiency. The decomposable silicon compounds and decomposable aluminum compounds used in the practice of the present invention have the property of being changed into solid substances of elemental silicon and elemental aluminum by thermal decomposition reaction in a hot kite containing water vapor, and also by hydrolysis with water vapor. It has the property of changing into silicon oxide and aluminum oxide by reaction, and these reactions are extremely fast (0.1 seconds to 0.1 seconds).
Since it is completed in about 5 seconds, the residence time in the reaction system is 1
If the reaction time is about seconds to 10 seconds, in an atmosphere where heat and water vapor coexist, the decomposable silicon compound and the decomposable aluminum compound will hardly volatilize out of the reaction system in an unreacted gas state. The mixed aerosol obtained as described above is discharged outside the furnace, and then the solid dispersoids contained in the aerosol are removed into solid gas by a collection device such as a bag filter, cyclone, or electrostatic precipitator. By performing a separation operation and collecting it,
A carbon-containing composition according to the present invention is obtained. In order to reduce the heat load on the collection device, it is desirable to cool the discharged hot gas in advance.The cooling method may be arbitrary, but for example, cooling the zone after the reaction or injecting water can be used. Measures can be taken to do so. The carbon-containing composition thus collected has extremely excellent physical properties as a raw material for producing sialon powder, since the fine powders of silicon oxide, aluminum oxide, and elemental carbon are mixed very uniformly. That is, this carbon-containing composition is heated at 1,350 to 1,650°C in a nitrogen-containing compound gas atmosphere such as nitrogen or ammonia using a high-frequency heating furnace, a current-carrying resistance furnace, or the like.
The extremely fine sialon powder of the present invention can be easily obtained by sintering for about 20 hours, preferably 5 to 12 hours. In addition, in the step of firing the carbon-containing composition in a nitrogen-containing compound gas atmosphere, the carbon-containing composition is once tightened, for example, pressurized and compressed to increase the bulk specific gravity, and then heated.
This is particularly preferred for obtaining finer sialon powder. This is because when a carbon-containing composition is heated in a state where the bulk specific gravity is small, a rod-shaped composite carbide with particles growing in one direction tends to grow, but once it is tightened and the bulk specific gravity becomes thick (after heating, This is based on the experimental findings of the present inventors that particles having a spherical shape with uniform particle sizes can be obtained, and it is more preferable to tighten the bulk specific gravity to at least 0.151/cc or more. , %W reduction can be easily carried out by pressurization, compression, stirring granulation, etc. Although the sialon powder obtained as a result of carrying out the present invention may contain elemental carbon, such To remove the elemental carbon contained, the SiAlON powder was heated to 500% in the presence of oxygen.
By heating to ~1000°C, iS carbon can be easily removed by combustion. Such combustion removal can be easily carried out by heating in air or in a hot gas atmosphere containing oxygen by burning the fuel with excess air. In this process, a carbon-containing composition, which is a raw material for producing Sialon powder, is prepared by charging a decomposable silicon compound, a decomposable aluminum compound, and a decomposable carbon compound into hot gas containing water vapor, where a chemical reaction occurs, that is, thermal decomposition. , oxidative decomposition, hydrolysis, etc. to produce fine particles of silicon oxide, aluminum oxide, and elemental carbon, and these fine particles are simultaneously obtained by mixing in the gas phase, so there is no need for conventional mechanical methods. A carbon-containing composition in which extremely fine particles are uniformly mixed can be obtained without the need for extensive pulverization and mixing.Moreover, unlike the conventional batch method, the carbon-containing composition can be produced continuously and in one step. Since the powder can be obtained, the complexity of the conventional work process is significantly reduced.Furthermore, since the sialon powder of the present invention obtained from this carbon-containing composition is already a fine powder, and (no need to mechanically crush coarse particles,
This has the remarkable effect of eliminating all problems such as increased costs, complexity of work processes, and contamination of impurities during work processes. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 Using the furnace shown in Fig. 1 (diameter 300 mm, length 3 s), air was supplied from duct 2, and propane as a hot air fuel was supplied from combustion burner 3 at 100 N rrf 8.3.
5iCj! as a decomposable silicon compound. i was mixed in advance with heavy oil A as a decomposable carbon compound at a weight ratio of 1:0.7 at 14 kg/h.
From nozzle 4 at a flow rate of ^ficj! as a decomposable aluminum compound! 3 was charged into the furnace through nozzle 5 at a flow rate of 4 kg/h. The inside of the furnace is approximately 1 at position A in Figure 1.
The temperature was maintained at 350°C. The aerosol generated in the furnace is extracted from the duct 6 and collected with a bag filter after cooling, and the carbon-containing composition according to the present invention is collected at a rate of 6.6 kg/h.
(dry weight) was obtained. The carbon-containing composition contains 24.8% by weight of silicon, 11.9% by weight of aluminum, and 23.9% by weight of carbon.
(The remainder is 38% by weight of bonding oxygen, 0.4% by weight of hydrogen attached to carbon, and 0.1% by weight or less of others),
As a result of ESCA spectrum analysis, the bonding forms between silicon or aluminum and other elements include 5i-0 bond, Aj
! Only -0 binding was observed. Also, the bulk specific gravity is 0.088
g/cc. 30 g of this carbon-containing composition was placed in a cylindrical container, compressed on the l-axis to give a bulk specific gravity of 0.32 g/cc, and then fired at 1500° C. for 9 hours in a N gas atmosphere using a horizontal annular resistance furnace. Once cooled, it was heated to 700° C. in air to burn off the remaining elemental carbon to obtain 17.9 g of powder. As a result of X-ray analysis, this powder obtained was confirmed to be β-Sialon, and as a result of chemical analysis, it was confirmed that it was 5iixA.
j! The value of 2 in z(hNs-x) was 2.0. Furthermore, the average particle diameter of this powder was 0.12 μ- by electron microscopic image analysis, and the particle shape was found to be uniformly spherical. Examples 2 to 5 In addition to propane, methane and hydrogen were used as fuel for hot air, and the decomposable silicon compounds, decomposable aluminum compounds, and decomposable carbon compounds shown in Table 1 were used, respectively. A carbon-containing composition according to the present invention having the composition shown in Table 1 was obtained in the same manner as in Example 1. As a result of ESCA spectrum analysis of the carbon-containing composition, it was found that bonds between silicon or aluminum and other elements were observed. The form is S
To0 combination, ^j! Only -0 bond was observed. This means that a mixture of CJ! The sialons were then fired at the temperatures and times shown in Table 2 to obtain sialon in the amounts shown in Table 2. As a result of X-ray analysis, the obtained sialon was confirmed to be β-sialon, and as a result of chemical analysis, it was confirmed that it was 5it-zA.
j! The Z values for tQJs-z were the values shown in Table 2, respectively. Furthermore, the average particle diameters of the powders as determined by electron microscopy analysis were shown in Table 2, and the particle shapes were observed to be uniformly spherical. Table 2

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one example of a furnace used in carrying out the present invention. In the drawings, 1; furnace material 2: duct 3: combustion burner 4: nozzle 5: nozzle 6: duct is shown.

Claims (1)

[Claims] (1) Charge decomposable silicon compounds, decomposable aluminum compounds, and decomposable carbon compounds into hot gas containing water vapor.
A carbon-containing composition obtained by decomposing a mixed aerosol dispersoid containing aerosols of silicon oxide, aluminum oxide, and elemental carbon, and collecting the generated dispersoid by a solid-gas separation operation. A method for producing sialon powder, which comprises firing the powder in a nitrogen-containing compound gas atmosphere.