JPS6259599A - Production of fibrous aggregate consisting of silicon nitride and silicon nitride oxide - Google Patents

Abstract

PURPOSE:To readily produce a nitride based fibrous aggregate having good performance, by mixing powder forming an alloy, e.g. Mg, Cu, etc., on an Si surface layer with SiO2 and silicon nitride, molding the resultant mixture and heating the molded material in a specific gas stream. CONSTITUTION:One or more of Mg, Cu, Fe, Mn, Ni or a salt thereof and, as necessary, Al and carbon are added to Si powder and the resultant mixture is heated to <=1,450 deg.C in an inert or reducing atmosphere to form an alloy on the Si surface. SiO2 and silicon nitride are added to the power, 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 or a reducing gas stream to grow fibrous crystals. The resultant fibrous aggregate consisting of the silicon nitride and 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 a method for producing a fibrous crystal (including whiskers) aggregate made of silicon nitride and silicon oxynitride, and more specifically, a method for producing a fibrous crystal (including whiskers) aggregate made of silicon nitride and silicon oxynitride. By combining specific metals such as, pre-forming an alloy on the surface layer of silicon, and mixing this with silicon dioxide by adding silicon dioxide to moderate crystals of silicon nitride, or forming ('b) Conventional technology and problems Silicon oxynitride and silicon nitride Because of its good properties such as heat resistance and mechanical strength, its fibers are also important as heat-resistant, heat-insulating materials or composite reinforcing materials, and various methods have been proposed. That is, conventional methods for producing silicon nitride fibers generally involve reacting silicon or silicon monoxide vapor obtained by heating silicon, reducing silicon compounds or oxides such as silicon dioxide, or reacting silicon and silicon dioxide with nitrogen. However, the yield is low in all of these methods, and there is also a method of manufacturing from rice husks, but the fibers are fine. In addition, regardless of the method, the crystals that are formed are not deposited in the raw material but on a distant substrate or the inner wall of the furnace, so it is difficult to separate and recover them as silicon nitride, so they are used as insulation materials or aggregates for composite materials such as glass and metal. 'j5 1 6827, but in that case, a monofilament-like m-woven fabric of silicon nitride could not be obtained, and the aggregate was fragile and difficult to handle.

(C) Problems to be Solved The present inventors have discovered that silicon nitride and silicon oxynitride are similar to 491
．． As a result of extensive research in order to obtain a pyramidal aggregate, we first formed an alloy of silicon and magnesium with additive metals on the surface layer of Carbo:111 as needed, and then nitrided the molded product mixed with silicon dioxide. As a result, silicon nitride and silicon oxynitride fibrous structures with excellent crystallinity and fineness were produced from the surface layer to the interior of the molded body (first method). Furthermore, by granulating the silicon alloy and silicon dioxide in the first method described above, an aggregate having a thin and long fibrous structure with good shape retention was produced (second method).

Carbon can be added and heated to form an alloy on the surface layer of silicon, leading to a reaction between the active silicon-containing alloy and silicon dioxide.

In other words, the true nature is the temperature at which silicon oxynitride begins to form (105
By suppressing the incorporation of catalytic metals such as magnesium, aluminum or copper into silicon dioxide up to 0°C), silicon oxynitride fibrous crystals with well-evened crystallinity and fineness can be produced by the reactions shown in 1) and 2) and 7. This manufacturing method makes it possible to generate silicon nitride whiskers using formulas 3), 4), and 5) from silicon-containing alloys or silicon monoxide vapor with good reproducibility.

S 1 (9) + S 102 (S) - 1 → 2sio (
g) I) 2sio(g) + 28+ +2N2-28t
2ON2(s) 2)3 S 1(S)+2 N2
-1--→ S13N4(S)3)3sio(g)+
ae −+a 38i(s)+ 3004)
3Si(■+2N2□→ Si3N, (S)5) (e)
Effects of the invention (1) An alloy phase is formed with silicon, magnesium, aluminum, copper as a catalyst, manganese, iron, and nickel. According to these preparation methods, the compound is combined with silicon at 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, and sometimes Mg (OR) 2
produces 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 to form a magnesium-silica melt.・This provides alloy particles that undergo little change and cause less contamination of the main di-metal surface.

(3) Furthermore, in the process of forming alloy particles, the corners of the silicon particles, which make up the majority of them, become rounded and uniform, so that the reaction with silicon dioxide proceeds uniformly in the next step.

Furthermore, the advantage of forming an alloy is not only that the metal composition is made uniform, but also that it is possible to easily prevent contamination by dust generated during mixing and molding of metal particles, or its escape into equipment.

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

In the binder and 17, carboxymethi/I/Rainbow 7 no 1 Norose, Mel 4x Roussel Doguchi・-zu, Polyvinyl
Neal alcohol is used as an a-t 0% by weight solution. These binders are added in a proportion of 2 to 10% by weight of the total amount of the powder mixture. In the present invention, the mixed powder is granulated; - Nosum, multicomponent alloy particles, and silicon dioxide gradually react to form a liquid phase made of silicon dioxide and countless silicon spherules inside the molded body, and the above-mentioned , l) As a result of the reaction in 5.2) progressing slowly and uniformly, silicon oxynitride crystals with less unreacted substances and less silicon nitride melt than those in the previous application are present inside the molded body. generate.

In addition, when carbon is melted into the alloy, 2), 3),
4.) Since the solubility of nitrogen increases in the alloy liquid phase in the reaction, the production of silicon oxynitride and silicon nitride with good crystallinity is promoted.

6) Adding silicon nitride seed crystals causes nitridation of the metal droplets that combine with nitrogen, which contributes to the formation of crystal nuclei by generating ions with a structure similar to that of nitrogen, which plays the role of controlling the direction of crystal growth. The growth of silicon fibrous crystals was promoted.Silicon nitride crystals are thin and have a karami effect, so the shape of the obtained fibrous aggregates is large, and the formation of an alloy phase in the silicon surface layer and the granulation of reactants are effective. It proves the gender.

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

g) Examples of the invention Example 1 Silicon 2.81. g (mole ratio 10) and magnesium 0.
07g (molar ratio (L, S), copper 0.02g (molar ratio (L, S)
molar ratio 0.03), aluminum 0.02g (molar ratio 0.03), aluminum 0.02g (molar ratio 0.03),
．． 1) 0.05g of carbon (molar ratio 0)
After mixing 12), the mixture is formed into a cylindrical shape of 15 mmφ x 10 nm. The molded body is placed in a silicon nitride port, covered with a lid, and loaded into the center of a high anolyte/mina combustion tube.

It was heated in a resistance heating furnace while flowing 30 rnl/force of argon and 5 ml/min of hydrogen, and the temperature was increased at a rate of 10°C per minute and held at 1420°C for 30 minutes. Through this process, the surface layer of silicon contains aluminum and 0.3% of magnetic silicon.
After adding 5g and mixing thoroughly, form it into a cylinder of 1oflφx7m, place it in a silicon nitride container, and fill it with nitrogen gas for 30m17.
hydrogen gas was introduced at a rate of 3'/min, and the temperature was raised to 1470°C at a rate of 8°C/'min. The molded body begins to swell after 5 minutes have elapsed, gradually rises, and swells continuously until about 2 hours have elapsed, and the fibrous crystals grow. The operation holding temperature is 1470°C for 4 hours.

Through this process, the molded body becomes 10 to 12 times bulkier, and an aggregate of silicon nitride and silicon oxynitride, which is mainly cocoon-like σ-shaped, is obtained. The bulk specific gravity of this material is O and B. As a result of measuring a part of the aggregate with a microscope, the silicon oxynitride has a thickness of 1 to 3 l1m, a length of 50 to 300 μm, and an average length of 1
．． It is a relatively uniform fibrous crystal with a diameter of 00 μm. Silicon nitride hardens with a diameter of 0.5 to 1 μm and is uniformly distributed from the surface to the inside of the aggregate. Growth of fibrous crystals starts at 1400℃ and continues to be α-type until kept at 1470℃ for 30 minutes. It is thought that silicon nitride crystals grow inside the compact as the silicon alloy in the liquid phase becomes gaseous. Incidentally, the remaining amorphous silica phase is formed as the molded product expands rapidly, and most of it is in the form of fibers, and some of it serves as a link between the fibers. In this way, most of the aggregate obtained by heat-treating the green compact in which silicon dioxide and α-type silicon nitride are added to the alloy-forming particles of silicon, copper, magnesium, and aluminum with carbon added thereto. It can be converted into a fibrous structure of silicon nitride and silicon oxynitride with good crystallinity.

Example 2 0.02 g of manganese (mole ratio 0.031 was used instead of copper in Example 1, 2.24 g of silicon (7 g)
0.60064 ml of silicon dioxide was added to the alloy-forming particles obtained by
Formation of a fibrous aggregate obtained by adding H (-e ratio 1), 10% by weight of its total amount, α-type indoor gael element o, ag, and performing the -C treatment under the same conditions as in Example 1. The phase is S + 2 ON 2
19'15, α-8i3N483%, β-8i3N4
It was 18%.

Example 3 0.011 g of manganese (molar ratio 0) was used instead of copper in Example 1.
．． 02) Nickel/l/0°Ollg (molar ratio 0.02
), 2.24 g of silicon (molar ratio 0.8), 7 g of magnesium o, o (molar ratio 0.3), and 0 aluminum
．． 02g (molar ratio 0.1), carbon o, o5g (
The fine powders having a molar ratio of 0.2) are mixed and molded. Next, this molded body was heat-treated in the same manner as in Example 1 to obtain alloy-forming particles containing 0.6006 g of silicon dioxide (molar ratio 1), 10% by weight of the total amount, and 0.3 g of α-type silicon nitride. A male-like aggregate of tl1 and silicon oxynitride with good entanglement properties was obtained. The generated phase is 5i2ON221%, α-8
The i3N content was 425%, and the β-8i3N4 content was 25%. In this example, it is possible to use different combinations and types of the heavy metal fine powders as the catalyst.

Example 4 An alloy was formed by using 0.03 g of cuprous chloride and 0.02 g (molar ratio O, Oa) of copper as the copper substitute υ in Example 1, but sufficiently removing crystal water. In addition, Table 1 shows the results of the fibrous aggregate obtained by processing under the same conditions as in Example 1 except that the blending ratio of silicon and silicon dioxide was changed.

Example 5 In place of copper in Example 1, more than one salt, that is,
Copper carbonate 0.03g (0.01g as metal, molar ratio 0.
015), manganese nitrate o, otg (0.0 as metal
08g, molar ratio 0.015), the results of the formed phases of crystals and monolithic aggregates are shown in the table.

Example 6 2.24 g of silicon (molar ratio 8), 0.02 g of copper (molar ratio 0.08), and 0.07 g of magnesium (molar ratio 0.3)
, 0.02 g of aluminum (molar ratio 0.1), and 0.05 g of carbon (molar ratio 0.1) are mixed together.

This mixture was applied to the surface layer of silicon in the same manner as in Example 1.
An alloy phase such as Cu2, A]Mg, MgSi2 is formed and molded. The molded body was dried at 80°C for 20 hours and then ground in a mortar to give a mass of 7 Qmesh (0,2 at) to 20
Adjust the particle size to Qmesh (0.07ff>. 2.5g of granulated soybean and p200Kg/i to 103ff
It is formed into a cylindrical shape of φ×7 mm, placed in a silicon nitride container, and nitrogen gas is introduced at a rate of 30-7 minutes to obtain an aggregate of silicon nitride and silicon oxynitride at a rate of 7° C./minute.

The silicon oxynitride crystals were the same as in Example 1, but the yield of silicon nitride crystals was increased. The results of the generated phases are shown in Tables 1 and 2.

Example 7 Silicon was increased to 8.87 g (molar ratio 12) and manganese was increased to 0.87 g.
04g (molar ratio 0.5), magnesium 0.07g
(molar ratio 0.3>, aluminum 0.02g (molar ratio 0
．． After mixing each of the fine powders of 1), an alloy phase is formed on the surface layer of silicon under the same conditions as in Example 1.

This alloy particle 2. Add 0.28 g of β-type silicon nitride crystal (10% by weight of the total amount) to 36 g (molar ratio 1) of silicon dioxide O (mole ratio 12) and mix, and then form into a cylinder of 7 flφ. . Put this into the combustion tube again, add nitrogen for 30 to 1 minute, and add hydrogen for 5 liters! JA, iSaze 3 to 1470°C at a heating rate of 8°C per minute while supplying tl/min.
Hold for 0 minutes at 1510°C for 3 hours Silicon oxynitride has a thickness of 1 to 3 μm, a length of 20 to 100 μm, and an average length of 70
μm, silicon nitride has a thickness of 0.5 to 11J, m, and a length of 10
The crystal structure became shorter from 0 to 200 μm. As in Examples 1 to 6, copper, iron, manganese, nickel/L/
Silicon oxynitride with good crystallinity and β
A fibrous aggregate consisting of silicon nitride with many types was obtained.

The results of the generated phase at that time are shown in Table 2 and Example 22. Furthermore, increase the silicon/silicon dioxide ratio (Mo/I/) to 15.1
When it was set to 8, the bulk of the molded product was 6 times and 4 times, respectively, and the fibrous structure showed a tendency to shorten and harden.

When the silicon/silicon dioxide ratio (mo)v) was decreased to 8 or less, the production of silicon nitride was sharply reduced.

Therefore, the upper limit of the molar ratio of silicon and silicon dioxide to obtain a fibrous aggregate of silicon oxynitride and α- and β-type silicon nitride υ with good crystallinity is preferably 12.1. ．． 1, -2-1' (b) Effects of the Invention As described above, the method of the present invention makes it possible to produce a nitride-based fibrous aggregate with good 41' performance relatively easily.

The fibrous aggregate made of silicon nitride and silicon oxynitride obtained by the present invention is in space. Materials for Kaiyo and environmental chemicals,
Heat-resistant and heat-insulating materials used in light alloys, ceramics, high-temperature electricity, etc., nuclear power, petrochemical plants, etc., as well as metals, plastics, and gas! The figure is a scanning electron microscope photograph of silicon nitride and silicon oxynitride crystals. (X200
) Designated agent 11'-・Island 1

Claims (1)

[Claims] 1. Silicon powder containing magnesium, copper, iron, manganese,
Aluminum and carbon are added as necessary to a mixture of at least one metal selected from nickel or its salt, and 145% is added in an inert or reducing atmosphere.
Heat to below 0°C to form an alloy-forming powder, add and mix silicon dioxide and silicon nitride to this alloy powder, or granulate and shape as required, and heat this compact to above 1380°C in a nitrogen or reducing gas flow. A method for producing a fibrous aggregate made of silicon nitride and silicon oxynitride, characterized by heating. 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 containing silicon alloy-forming powder and silicon nitride is granulated to a particle size of 0.07 to 2 mm.