JPH03113018A - Production of acid nitride ceramic fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing oxynitride ceramic fibers, and in particular to fiber reinforced plastics (FR).
P), strength useful for fiber reinforced concrete (FRC),
The present invention relates to a method for producing reinforcing fibers with excellent elastic modulus and corrosion resistance, or ceramic fibers with excellent heat resistance and corrosion resistance, which can be used as chemical filters, heat-resistant heat insulating materials, etc.

[Conventional technology]

Fiber materials are important for reinforcing plastics and concrete, and various other fiber materials are also used in the field of high-temperature materials such as heat-insulating curtains, heat-insulating cushioning materials, catalyst carriers, and high-temperature filters.

Glass fibers, carbon fibers, alumina fibers, silicon carbide fibers, organic polymer fibers, etc. have traditionally been used as fiber materials, but the properties required of materials are diversifying, and fibers with new functions are being developed. is long-awaited.

Oxynitride ceramic fiber is one of them, and when the oxynitride ceramic is glass, that is, oxynitride glass, compared to oxide glass,
Improves hardness, strength, elastic modulus, heat resistance, and corrosion resistance. or,
When the oxynitride ceramic is a polycrystalline ceramic, such as Sialon, the high temperature strength, strength, thermal shock resistance, etc. are improved compared to oxide ceramics.

As a method for obtaining these oxynitride ceramics or hybrid ceramics of oxide and nitride in the form of fibers, two types of methods have been studied.

1. Spinning method from flylide and nitride through melt It requires high temperature to melt oxide and nitride, and undesirable crystal phase and metal phase are generated due to decomposition of nitride or reduction of oxide. generate. A special spinning device is required to stably produce oxynitride glass (Japanese Patent Application Laid-open No. 1983
-310747).

(1) A method of obtaining precursor fibers using metal alkoxides and inorganic polymers as starting materials and nitriding and firing them (1) A method of spinning polycarbosilane and nitriding it is Che-mistry L.
etters 2059-2060 (1984), however, there are problems such as complicated synthesis of polycarbosilane and limitations on the composition of the oxynitride glass obtained.

(2) TiOt gel fiber or Ti-containing gel fiber is nitrided to form TiN or T
A method for producing TiN-coated Ti, fiber, or infrared-transparent oxynitride glass containing Ti is described in Journal of Materials 5ci.
ence 22.937-941 (1987), JP-A-62-263322, JP-A-63-40742, etc., the composition of the ceramics obtained is limited to a system containing Ti, which is extremely reactive with nitrogen. There is a drawback.

(3) Journal of Non-Cr
ystallineSoljdSfii, 208-22
2 (1986), JP-A-63-112437, JP-A-63
-242943 etc. However, in these cases, gel fibers manufactured solely from tetrafunctional alkoxides such as tetraethoxysilane contain almost no nitrogen even when nitrided under a stream of ammonia, so if monoalkyltrialkoxysilanes such as methyltriethoxysilane are used, In order to improve the efficiency of introducing nitrogen, a technique is disclosed in which nitrogen is used alone or in combination.

However, methyltriethoxysilane is expensive and has the problem of being limited to Si-based oxynitride compositions.

[Problem to be solved by the invention]

The present invention overcomes the drawbacks of the conventional methods mentioned above, namely, high temperature process is required, synthesis of precursors such as polycarbosilane is complicated, and only those containing special elements such as Tj can be used. Eliminates disadvantages such as the need to use expensive starting materials such as methyltriethoxysilane, the need for complex and expensive equipment, the complicated manufacturing process, and the limited ceramic composition. The object of the present invention is to provide a method for obtaining oxynitride ceramic fibers by a simple method with no restrictions on composition.

[Means to solve the problem]

In the production of oxynitride ceramic fibers using silicon alkoxide and aluminum alkoxide as the main raw materials, the present invention uses a sol obtained by hydrolyzing silicon alkoxide and aluminum alkoxide and sintering the sol in a non-oxidizing atmosphere so that carbon remains. A method for producing oxynitride ceramic fibers, which comprises firing gel fibers obtained by spinning a mixture of organic polymers at a viscosity of 10 poise or higher in a nitrogen and/or ammonia stream. Accordingly, the above problem can be solved.

The silicon alkoxide used in the present invention has the general formula (
RO)4si (R: alkyl group), specifically R is methyl, ethyl, n-propyl, n-
butyl, 1so-butyl, see-butyl, ter
Examples include t-butyl.

Further, as the silicon alkoxide, an oligomer which has undergone a polycondensation reaction in advance may be used.

The aluminum alkoxide used in the present invention is represented by the general formula (RO)380 (R: alkyl group), and specifically R is methyl, ethyl, n-propyl, 1so-propyl, n- Butyl, 1so-butyl, 5
Examples include ec-butyl and tert-butyl.

A spinnable sol can be obtained by hydrolyzing these silicon alkoxides and aluminum alkoxides, but this hydrolysis is best carried out in the presence of an organic solvent from the standpoint of miscibility between the two and uniformity of the reaction. preferable. The organic solvent used here is preferably one that dissolves silicon alkoxide and aluminum alkoxide, specifically methanol, ethanol, n-propanol,
rs.

Examples include alcohols such as -7' lovanol and sec-butanol, aromatic hydrocarbons such as toluene, benzene, and xylene, tetrahydrofuran, dimethylformamide, and carbon tetrachloride, but from the viewpoint of solubility. Alcohols are preferred.

In addition, in order to stably and reproducibly produce a sol with excellent spinnability, in the presence of a strong acid catalyst such as hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, or a sulfonic acid compound, per mol of silicon alkoxide, Partially hydrolyzed with 4 moles or less of water, the product is reacted with aluminum alkoxide, and the reaction mixture is converted into total alkoxide (aluminum alkoxide,
The amount of water is 2 moles or less, more preferably 1.5 moles or less, per 1 mole of the starting material (silicon alkoxide, oligomers of silicon alkoxide derivatives, other metal alkoxides described below, etc.). It is preferable to additionally add and perform hydrolysis.

The composition of the present invention may further include Si,
Aj! Other metal elements may also be used. For example, in order to facilitate vitrification and obtain oxynitride glass, Lj
%Na, alkali metals such as Cs, Be, Mg, Ca
5Sr, alkaline earth metals such as Ba, others, Ti%Z
Examples include the use of r, Ge, Y, B, Sb, etc.

Si, Aj! as a metal element! In the case of a composition containing only Si, Si is likely to scatter as SiO during the reductive nitriding process, and to prevent this, it is preferable to add other metal elements, such as alkaline earth metals such as Ca and Mg. The addition of is particularly preferred.

When adding these metal element components, there is no particular restriction on the type of compound, and examples include metal alkoxides, acetates, chlorides, nitrates, and the like.

Further, alkoxides of metals such as alkali metals and alkaline earth metals whose alkoxides are easily synthesized can also be added as metals to a reaction system using alcohol as a medium.

The sol obtained by the above hydrolysis has a certain degree of viscosity and threadability, but the concentration is low and insufficient for spinning, so it can be spun by performing an appropriate concentration operation. A viscous sol is obtained. This concentration operation may be either normal pressure distillation or reduced pressure distillation.

An organic polymer capable of retaining carbon when fired in an oxygen-free atmosphere, that is, a non-oxidizing atmosphere, is added to the viscous sol before spinning. The organic polymer is preferably one that is soluble in the solvent or alkoxide used, and is also resistant to addition reactions, such as phenol resins and epoxy resins.
It may also be a prepolymer whose molecular weight is increased by a condensation reaction or the like. Examples of these organic polymers include butylcellulose, nitrocellulose, polyvinyl butyral, polyacrylic acid, phenolic resin, and epoxy resin, but phenolic resin is preferred because it has a high residual carbon content and does not adversely affect stringiness. preferable.

These organic polymers can be added at any stage before spinning, or at an appropriate time such as before hydrolysis or concentration, but the amount of organic polymers added varies depending on the type of carbon remaining. Therefore, although it cannot be determined unconditionally, it is generally in the range of 10 to 100 parts by weight based on 100 parts by weight of the metal alkoxide or metal salt used in terms of oxide. 10
If it is less than 100 parts by weight, the carbon generated from the organic polymer in the reductive nitriding temperature range is encapsulated in the oxide ceramic and cannot contribute to the reductive nitriding reaction, which is undesirable.
If the amount is more than 1 part by weight, a large amount of unreacted carbon remains even after reductive nitridation, which is not preferable.

The viscous sol obtained by adding the organic polymer as described above is spun at a viscosity of 10 poise or more to obtain gel fibers.

When the sol is less than 10 poise, it is possible to form the sol into fibers, but it takes time to maintain the shape through gelation, making it extremely difficult to obtain gel fibers.

Further, known methods can be applied to the spinning, and gel fibers can be easily obtained by extrusion from a nozzle or the like.

The obtained gel fiber is fired under a nitrogen and/or ammonia stream to obtain an oxynitride ceramic fiber. Firing conditions vary depending on the composition of Kelfiber and whether nitrogen or ammonia is used as the gas, but -m is 600' in the case of ammonia.
For example, the temperature range is 800° C. or higher in the case of nitrogen gas.

[Effect]

Nitrogen atoms are introduced into gel fibers through a reductive nitriding reaction in which oxide ceramics are reduced with carbon and nitrogen in the atmosphere is introduced in the process. In the case of the present invention, silicon alkoxide and aluminum alkoxide It is possible to synthesize a precursor with excellent spinnability from a starting material whose main component is First, in the temperature range where the reductive nitriding reaction occurs, a state in which carbon derived from organic polymers is uniformly dispersed in the fiber is achieved, and conditions are established that facilitates the progress of reductive nitriding, making it easy to obtain oxynitride ceramic fibers. it is conceivable that.

In addition, it was effective to synthesize a precursor with particularly excellent spinnability by reacting partially hydrolyzed silicon alkoxide with aluminum alkoxide; This is thought to be due to the change to something relatively stable. Furthermore, in the composition containing an alkaline earth metal, there was little scattering of the Si source and the reduction nitridation progressed uniformly, but it is thought that the formation of a liquid phase during the nitriding process contributed.

[Example] Example 1 1 mole of tetraethoxysilane was dissolved in 4 moles of ethanol. To this was added a mixed solution of 1 mole of water and 2 moles of ethanol acidified with 1N hydrochloric acid, and the mixture was allowed to react at room temperature for 30 minutes. This reaction mixture was mixed with aluminum trisec
A solution of 1 mole of -butoxide dissolved in 4 moles of see-butanol was added, reacted and mixed.

A mixed solution of 1 mole of water and 1 mole of ethanol was added to this reaction mixture to carry out hydrolysis and polycondensation. To this solution, 54 g of phenol resin (novolac) and 6 g of hexamethylenetetramine as a crosslinking agent were added to make a homogeneous solution, and the solvent was distilled off under reduced pressure to obtain a viscous solution with a viscosity of 530 poise. Continuous gel fibers were obtained by extruding and spinning this viscous solution.

This gel fiber has a nitrogen flow rate of 0.5J! /mjn temperature and nitriding firing for 3 hours at 1400°C. Although 39% of the added Si source was scattered, the nitrogen content in the obtained fiber was 8.7%, and the crystal phase determined by X-rays was SiAl?
O! N? , AI! NsSiC% mullite, microcrystals of β-sialon.

Example 2 The gel fiber obtained in Example 1 was heated at a nitrogen flow rate of 0.5Q.
/l1in, and nitriding was performed at a temperature of 1500°C for 3 hours.

Although 55% of the added Si source was scattered, the nitrogen content in the obtained fiber was 22.7%, and the crystal phases determined by X-rays were SiAl, ogNtAiAN,
It was a microcrystal of SiC.

Comparative Example 1 Using the same method as Example 1, without adding phenolic resin,
A viscous solution with a viscosity of 650 poise was obtained, and this was extruded and spun to obtain continuous gel fibers.

This gel fiber was nitrided and fired under the same conditions as in Example 1. The nitrogen content in the obtained fiber was 0.01%
Below, little nitrogen was introduced and the crystalline phase was mullite.

Example 3 The amount of phenolic resin added in Example 1 was changed to 13.5
g and 1.5 g of hexamethylenetetramine, and the same procedure was performed except for the same procedure to obtain a viscous solution with a viscosity of 410 poise, from which gel fibers were obtained.

This gel fiber was heated with an ammonia flow of 1O, 5j2/ra
'rn, and nitriding was performed at a temperature of 1200'C for 3 hours. The nitrogen content in the obtained fiber was 1.9%, x*H
Mullite and microcrystals of an unknown phase were observed.

Comparative Example 2 The gel fiber obtained in Comparative Example 1 (corresponding to the system without the addition of phenolic resin in Example 3) was nitrided and fired under the same conditions as in Example 3. The nitrogen content in the obtained fiber was 0.01% or less, almost no nitrogen was introduced, and the crystal phase was mullite.

Example 4 1 mole of tetraethoxysilane was dissolved in 41 m+ of ethanol. Add a mixed solution of 1 mole of water and 2 moles of ethanol acidified with 1N hydrochloric acid to this, and
It was allowed to react for a minute. This reaction mixture was mixed with aluminum tri5
A solution of 1 mole of ec-butoxide dissolved in 4 moles of 5ec-butanol was added, reacted, and mixed. 0.167 mol of magnesium acetate tetrahydrate was added to this and completely dissolved.

A mixed solution of 0.33 mol of water and 1 mol of ethanol was added to this reaction mixture to carry out hydrolysis and polycondensation. To this solution, 57.7 g of phenol resin (novolak) and 6.4 g of hexamethylenetetramine as a crosslinking agent were added to make a homogeneous solution, and the solvent was distilled off under reduced pressure.
A viscous solution of 80 poise was obtained.

Continuous gel fibers were obtained by extruding and spinning this viscous solution.

This gel fiber is heated with nitrogen flow it O,51/win
Nitriding firing was performed at a temperature of 1400°C for 3 hours. Added Si
The source scattering was only 3.3%, the nitrogen content in the obtained fiber was 7.5%, the crystalline phase was mullite, β-sialon, )IgA ll go4.

Example 5 The gel fiber obtained in Example 4 was heated at a nitrogen flow rate of 0.5f.
/sin, and nitriding was performed at a temperature of 1500°C for 3 hours.

The scattering of the added Si source was only 3.3%, the nitrogen content in the obtained fiber was 16.4%, and the crystal phase determined by X-rays was β-sialon, MgA f , 0. It was microcrystalline.

Comparative Example 3 Using the same method as Example 4, without adding phenolic resin,
A viscous solution with a viscosity of 280 poise was obtained, and this was extruded and spun to obtain continuous gel fibers.

This gel fiber was nitrided and fired under the same conditions as in Example 4. The nitrogen content in the obtained fiber was 0.01%
Below, nitrogen was hardly introduced, and the crystal phases were α-cordierite and mullite.

Example 6 The amount of phenolic resin added in Example 4 was changed to 14.4
g, hexamethylenetetramine 1.6 g, and the other procedures were the same to obtain a viscous solution with a viscosity of 750 poise,
From this, gel fiber was obtained.

This gel fiber is heated with ammonia flow rate of 0.5N/win.
, Nitriding firing was carried out at a temperature of 1200'C for 3 hours. The nitrogen content in the obtained fiber was 2.8%, and mullite and microcrystals of an unknown phase were observed by X-ray analysis.

Comparative Example 4 The gel fiber obtained in Comparative Example 3 (corresponding to the system without the addition of phenolic resin in Example 6) was nitrided and fired under the same conditions as in Example 6. The nitrogen content in the obtained fiber was 1.2%, and the crystal phase was mullite, MgA 1 zoa
Met.

(Effect of the invention)

Claims (1)

[Claims] (1) In a method for producing oxynitride ceramic fibers using silicon alkoxide and aluminum alkoxide as the main raw materials, a sol obtained by hydrolyzing silicon alkoxide and aluminum alkoxide and an organic material that can retain carbon by firing in a non-oxidizing atmosphere are used. A method for producing oxynitride ceramic fibers, which comprises firing a gel fiber obtained by spinning a mixture of polymers at a viscosity of 10 poise or higher in a nitrogen and/or ammonia stream.