JPS6259600A - Production of fibrous aggregate of silicon nitride oxide - Google Patents

Abstract

PURPOSE:To readily produce a fibrous aggregate of a silicon nitride oxide having improved shape holding property, by mixing powder forming an alloy, e.g. Mg, Cu, etc., on an Si surface layer with SiO2 and silicon nitride oxide, molding the resultant mixture and heating the molded material in a specific gas stream. CONSTITUTION:One or more of Mg, Cu, Fe, Mn, Ni, Co, Cr or a salt thereof and, as necessary, Al are added to Si powder and the resultant mixture is heated to <=1,450 deg.C in an inert or a reducing resultant mixture is heated to <=1,450 deg.C in an inert or a reducing atmosphere to form an alloy on the Si surface. SiO2 and silicon nitride oxide are added to the powder, mixed therewith and, as necessary, granulated and molded into a given shape. The resultant molded material is heated to >=1,380 deg.C in nitrogen gas stream to grow fibrous crystals. The resultant fibrous aggregate crystals of the silicon nitride oxide obtained by this method has improved performance as heat-resistant and heat insulating materials, composite reinforcing materials, etc.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to silicon oxynitride fibrous crystals (including whiskers)
More specifically, the method for manufacturing the aggregate is to combine silicon with specific metals such as magnesium and copper, and if necessary, add aluminum to create an alloy on the surface of the silicon.
By adding silicon dioxide to silicon oxynitride seed crystals and reacting them by mixing or granulating them, it is possible to improve crystallinity and waxiness.According to the method of the inventors' earlier application, silicon and silicon dioxide can be combined. A molded body made by adding specific metals such as magnesium, aluminum, and copper or their salts and silicon oxynitride seed crystals is heated and nitrided.
Silicon dioxide, magnesium, aluminum and metal cavities such as copper or iron, magnesium and aluminum H
It diffuses from around 600℃ and continues to melt to form silicon,
Although it easily forms alloys with metals such as copper or iron, it also dissolves and associates with silicon dioxide, making it difficult to form a silica melt, resulting in a reduction in the reaction of silicon dioxide. Therefore, (C) Problems to be Solved The present inventors have conducted intensive research to solve the above problems, and have found that a silicon oxynitride fibrous structure with excellent crystallinity and fineness extends from the surface layer to the inside of the molded product. (first method). Furthermore, by granulating the silicon alloy and silicon dioxide in the first method, an aggregate with good shape retention and a fine fibrous structure was formed (second method).

(d) Means for Solving the Problems of the Invention In the present invention, in order to improve the drawbacks of the previous application, a lam which forms an alloy in advance on the surface layer of silicon with various metals and adds or granulates silicon dioxide to the alloy, By suppressing the incorporation of catalytic metals such as aluminum or copper, silicon oxynitride aggregates with good crystallinity and fineness can be produced (1).
, 2) is a manufacturing method that enables the production with good reproducibility using the reaction formula shown in 2).

5i (S) + 8 i 02 (S) ---1 →
2SiO@) l) 2SiO(g)+2Si(S)+2
N2-2Si2ON2(S) 2) In connection with the above reaction, the effect of granulation with silicon alloy particles and silicon dioxide will be explained in more detail.

(e) Effect of the invention (1) Forms magnesium and aluminum, copper or manganese as a catalyst, iron, nickel, and co-alloy phase in silicon. According to these preparation methods, a silicon alloy is formed in a relatively low temperature range, but it is advantageous to carry out the process so as to reach the melting point of silicon, 1420°C.

(2) Magnesium easily combines with oxygen and moisture in the air to form an oxide film, sometimes producing Mg(OH)2 fibers. When an oxide film is formed on the surface of magnesium, it becomes difficult to form an alloy with a catalyst such as silicon or copper, but it tends to react with silicon dioxide and form a magnesium-silicate melt.

Therefore, in order to obtain an active magnesium component, in the present invention, magnesium is heated with silicon and various metals in advance to form alloy particles.

This provides alloy particles that are less likely to change over time due to oxidation of magnesium or aluminum components and are less likely to cause contamination on the main silicon metal surface.

(3) Furthermore, in the process of forming alloy particles, the corners of the silicon particles, which make up the majority of the particles, become rounded and uniform, so that the reaction with silicon dioxide in the next step can be prevented from scattering.

(4) To granulate alloy particles and silicon dioxide, binder and water are added, mixed, dried, crushed, and granulated into particles of 0.07 to 2 ff using a sieve.

As a binder, carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol are used in the range of 3 to 10%.
Use as a wt% solution. These binders are added in a proportion of 2 to 101% by weight of the total amount of the powder mixture. In the present invention, it is believed that by granulating the mixed powder, contact between the reactants becomes better, so that the reaction proceeds more evenly.

(5) When the above granular material is molded and heated in a nitrogen atmosphere, the multi-component alloy particles and silicon dioxide particles gradually react with each other, resulting in less liquid leakage melt consisting of silicon dioxide inside the molded material and oxynitriding with good crystallinity. Silicon is produced.

The above action is reliable and complete, and the effect is very large, proving the effectiveness of forming an alloy phase in the silicon surface layer and granulating the reactant.

The invention will be explained in further detail by the following examples.

(n Examples of the invention Example 1 0.007 g of copper to 2.556.y of silicon (molar ratio 5)
(molar ratio 0.006), aluminum 0.007 g (
(molar ratio 0.02) and magnesium 0.138g (molar ratio 0.3) are mixed. After thoroughly mixing this mixture, it is formed into a cylindrical shape of iomφ.

After placing the compact into a silicon nitride container, it was covered with a lid and rapidly raised in a resistance heating furnace at a heating rate of 20'4 while introducing argon and hydrogen at 80'/5'4/min. After holding at 650°C for 30 minutes, the temperature was raised to 1420°C at a temperature increase rate of 7°C/min and held for 80 minutes. By this process, after silicon surface LOflφX7fl
Formed into a cylindrical shape and placed in a silicon nitride boat and heated with nitrogen gas for 30 minutes.
1470°C at a rate of 7'c/min.
and held at this temperature for 5 hours.

Through this step, the molded body becomes more than ten times as bulky, and a fluffy silicon oxynitride aggregate that is difficult to crumble is obtained.

A part of this bulky aggregate was measured using a microscope, and as shown in the figure, the thickness was 0.5 to 3μ and the length was 50 to 300μ.
It is a relatively uniform crystal with an average length of 100μ, and the surface is thinner and longer, and clean ones can reach 2%. The electrification was determined by powder X-ray diffraction using an internal standard at -°C, but 1430 to 1470°C is suitable.

If 0.5 mol or more of magnesium is added, alloy nodules remain in the center of the aggregate, making it impossible to obtain a uniform fibrous aggregate. If the amount of magnesium added is reduced to 0.1 mol or less, the formation of needle-like crystals with good crystallinity will be reduced. Magnesium is commercially available with a purity of 99% or higher.
A powder having a fineness of 0 μm or less, preferably 50 μm or less is suitable. Of silicon and silicon dioxide, silicon is suitable for growing crystals with uniform fineness when a commercially available powder with a purity of 99% and io~50 μm is used, and the mixing ratio is 3.5% silicon. It has been found that silicon oxynitride crystals can be obtained even if the ratio is varied within the range of ~5 to 1 (molar ratio) of silicon dioxide.

The appropriate particle size for silicon dioxide is 10 to 60 microns, and if the particle size is fine or coarser than that, it will remain unsuitable. voice metal,
Molar ratio of aluminum and magnesium: 5:1:0.
006: 0.02: 2.556 g (mole ratio) of mostly fibrous silicon aggregates of 01 and 0.014 cupric chloride
8g (Mo/V ratio 0.006 as copper), magnesium,
0.188 g (molar ratio 0.3) of each fine powder is mixed.

This mixture was applied to one part of the molded body by the same process as in Example 1.
An aggregate that has reached several times the size is generated. Fibrous crystals have a thickness of 1 to 5 μm, a length of 30 to 200 μm, and an average of 80 μm.
It can be seen that the long ones reach 2n, and the generated phases are 5i2ON268%, α-8i3N412%, β-81
3N44%.

The temperature range for fibrous crystal formation is 1880-1500℃
However, 1430 to 1470°C is suitable.

When adding heavy metals, salts which are converted to metals under the reaction conditions, such as chlorides, nitrates, sulfates, carbonates, can be used.

Example 3 As in Example 1, Mg M n 2,
AlMg and Mg28i are formed. Next, 0.6006 g of silicon dioxide (7 ratio 1) and 10% by weight of the total amount of silicon oxynitride crystals were added to the alloy particles, and 0.8 m/! of 3% methyl cellulose solution was added. Add and shape. The molded body was dried at 80°C for 20 hours and then ground in a mortar to form a 7Qmesh.
(0,2g++++)~200mesh (0,07m
). 2.5g of granulated material and D200
It was formed into a cylindrical shape of 10flφX7se++ at Kg/i, placed in a silicon nitride container, introduced nitrogen gas at a rate of 80'/min, heated to 1470°C at a rate of 7°C/min, and held at this temperature for 5 hours. .

Through this process, the molded body becomes more than ten times as bulky, and a fluffy silicon oxynitride aggregate that is hard to crumble is obtained.

The fibrous crystals are as thin as 0.2 to 2 μm and have a length of 70 to 300 mm.
μm, and the average length was 120 μm, which led to uniform crystal nucleation. As a result, we were able to generate an aggregate consisting of thin fibrous crystals.

Examples 4 to 20 Copper, iron, manganese, nickel, cobalt, and chromium metal are treated with their salts in the same manner as in Example 1 or 3 to obtain silicon oxynitride fibrous crystals with good crystallinity. was able to obtain.

The production conditions and yield of the produced phase are shown in the following table.

@) Effects of the Invention As described above, the present invention makes it possible to easily produce a silicon oxynitride fibrous aggregate having good shape retention and consisting of thin, entangled crystals.

The silicon oxynitride fibrous crystal aggregate obtained by the present invention can be used as a heat-resistant and heat-insulating material used in space, ocean, and environmental chemical materials, light alloys, ceramics, high-temperature electricity, etc., or nuclear power, petrochemical, and other plants. It can be used as a composite reinforcing material for plastics, glass, etc. to improve the performance of bottles, and it can also be used in filters.

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Claims (1)

[Claims] 1. Silicon powder containing magnesium, copper, iron, manganese,
If necessary, aluminum is added to a mixture of at least one metal selected from nickel, cobalt, and chromium or its salt, and heated to 1450°C or less in an inert or reducing atmosphere to form an alloy-forming powder, A silicon oxynitride fibrous aggregate characterized by adding silicon dioxide and silicon oxynitride to this alloy powder, mixing it, or granulating it as necessary, molding it, and heating this molded product to 1380°C or higher in a nitrogen stream. manufacturing method. 2. The method according to claim 1, wherein a metal or a salt thereof is added to silicon and heated to alloy the silicon. 3. The method according to claim 1, wherein a mixture of silicon dioxide in which silicon oxynitride crystals are added to silicon alloy-forming powder is granulated to a particle size of 0.07 to 2 mm.