JPH0350161A - Silicon nitride-based ceramic molded body - Google Patents

Abstract

PURPOSE:To improve heat, oxidation and wear resistances and insulating property by using an aggregate or mixture of amorphous fine particles consisting essentially of Si, N and B or the amorphous fine particles and crystalline fine particles of Si3N4 and specifying an X-ray small angle scattering intensity to air. CONSTITUTION:A silicon nitride-based ceramic molded body is made of an aggregate or mixture of amorphous fine particles consisting essentially of Si, N and B and crystalline fine particles of alpha-Si3N4 and Eb-Si3N4 having <=500Angstrom particle size. The amorphous fine particles consist of Si, N and B as essential components, C, O and H as optional components in atomic ratios of N/Si=0.05-2.5, B/Si=0.01-3, C/Si<=1.5 and H/Si<=0.1. The ratios of the X-ray small angle scattering intensity of the molded body to air at 1 deg. and 0.5 deg. are regulated to 1-20 each. The molded body maintains a superior mechanical strength at such a high temp. as >=1,500 deg.C as well as at room temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a silicon nitride ceramic molded body having excellent heat resistance, oxidation resistance, and wear resistance, and particularly excellent mechanical strength at high temperatures.

[Prior art 1 Ceramic molded bodies mainly made of silicon nitride have excellent high-temperature strength, thermal shock resistance, and oxidation resistance, so they are used as high-temperature structural materials for gas turbines, diesel engines, etc., or as cutting tools, etc. It is attracting attention as a high-performance material that can make a significant contribution to energy and resource conservation.

Conventionally, as such ceramic molded bodies, there have been two types of molded bodies: 6
9717, JP 49-20206, JP 62-202863, U.S. Patent No. 448266
9), ■ 5i-N-0 obtained by firing perhydropolysilazane or metallopolysilazane
Yarn molded product or 51-N-0-M thread molded product (patent application 1986-
46966, US Pat. No. 4,397,828),
■ 5i-C-containing ceramic molded bodies obtained by firing polycarbosilane (JP-A-53-93314, JP-A-54-3815, JP-A-54-16521), ■ polytitanocarbosilane, or 5t-Ti-C molded body or 5i-Z obtained by firing polyzirconocarbosilane
r-C based molded product (JP-A-56-88877, JP-A-5
No. 6-134567), etc. are known.

However, since the above-mentioned material (1) has a high carbon atom content in the raw material, a high content of silicon carbide or free carbon remains in the molded product obtained by thermally decomposing it. Therefore, this material has the disadvantage that phase separation and reactions occur at high temperatures, causing a decline in properties, and that the high insulation properties, high strength, thermal shock resistance, etc. inherent to silicon nitride and silicon oxynitride are significantly reduced. be.

Although the molded product (①) has excellent mechanical strength at room temperature, it has the disadvantage that its mechanical strength at high temperatures decreases significantly. Since silane and polyzirconocarbosilane melt when heated, an infusibility step is essential for producing ceramic molded bodies. This complicates the manufacturing process, and oxygen is mixed in during the infusibility process, resulting in deterioration of the mechanical strength and heat resistance of the molded product.

[Problem to be solved by the invention]

An object of the present invention is to provide a ceramic molded body which, unlike the conventional ceramic molded bodies, has excellent heat resistance, oxidation resistance, abrasion resistance, and insulation properties, and has particularly excellent mechanical strength at high temperatures. .

[Means to solve the problem]

According to the present invention, the above-mentioned whistle has silicon, nitrogen and boron as essential components, carbon, oxygen and hydrogen as optional components, and the ratio of each element is expressed as an atomic ratio, N/Si: 0°05-2 .5
．． N/Si-0,01-3, C/Si=1.5 or less,
H7si=o, 1 or less and substantially silicon,
Amorphous consisting of nitrogen and boron or amorphous consisting of silicon, nitrogen and boron and α-Si3 with a crystal grain size of 500 Å or less
A silicon nitride ceramic made of an aggregate or mixed system of crystalline fine particles of N, β-5i, and N, and whose small-angle X-ray scattering intensity is 1 to 20 times that of air at 11 and 0.5 degrees, respectively. The problem is solved by molded bodies.

The first feature of the silicon nitride ceramic molded body of the present invention is that silicon, nitrogen, and boron are essential components, carbon, oxygen, and hydrogen are optional components, and the ratio of each element is expressed as an atomic ratio.
/Si:0.05-2.5, N/Si;0.01-3,
C/Si=1.5 or less and N/Si.0.1 or less.

Unlike other metal components or non-metal components such as Ti, Zr, and kQ, boron used in the present invention is an extremely effective component that does not reduce the mechanical strength of silicon nitride ceramic molded bodies at high temperatures. .

The reason why boron exhibits such effects is not clear at present, but it is thought to be due to the following reasons.

■Since the ionic radius of boron is smaller than that of silicon, boron penetrates between silicon and nitrogen during high-temperature heat treatment, inhibiting the hexagonal crystallization of silicon nitride, resulting in an amorphous state that is metastable. is maintained up to high temperatures.

(2) Furthermore, even if crystal nuclei are formed, boron exists between silicon and nitrogen atoms, so crystal growth is suppressed, and as a result, the amorphous state is maintained up to high temperatures.

The effective content of these components is expressed as the atomic ratio of each element: N/Si=0.05-2.5 B/Si=0.01-3 C/Si1.5 or less N/Si=0. The preferable atomic ratio is N/Si=O, 1 to 2.3 B/SilI0.05-2 C/Si=1.2 or less and N/Si=0.05 or less. More preferable atomic ratios are N/Si=0.5-2.0 B/Si=O0l-I C/5l=0.5 or less If/Si! There are IO, OIl and below.

If the atomic ratio is not within the above range, the ceramic molded body will not be able to fully demonstrate its mechanical strength, heat resistance, and wear resistance, and will not be able to fully demonstrate its mechanical strength, especially at high temperatures. unable to perform as well as possible.

A second feature of the silicon nitride ceramic molded body of the present invention is that its structure is amorphous consisting essentially of silicon, nitrogen and boron, or amorphous consisting of silicon, nitrogen and boron and having a crystal grain size of 500 Å or less. It consists of an aggregate or mixed system of crystalline fine particles of α-Si3N, β-8i, and N4.

The structure of the silicon nitride ceramic molded body according to the present invention is as follows:
α-5 that is amorphous even at high temperatures of 1500 to 1750°C, or that is amorphous and has a crystal grain size of 500 Å or less
It is an aggregate or mixed system of crystalline fine particles of i, N4 and β-5i, N4.

The silicon nitride ceramic molded body of the present invention having such a structure maintains excellent mechanical strength not only at room temperature but also at high temperatures of 1,500°C or higher, and therefore has extremely excellent mechanical strength at high temperatures. It is.

The reason why the ceramic molded body of the present invention exhibits such excellent effects is not necessarily clear, but since it maintains the above-mentioned unique structure even at high temperatures, it is likely to be resistant to fracture.
This is probably because factors that cause jl, such as grain boundaries, coarse particles, or pores, do not occur.

A third feature of the silicon nitride ceramic molded body of the present invention is that the small-angle X-ray scattering intensity ratio is in the range of 1 to 20 times the scattering intensity of air at lo and 0.5 degrees, respectively.

A preferable small-angle scattering intensity is 1-10 times, and a more preferable intensity is in a range of 1-5 times.

The small-angle scattering intensity is determined by the micropores inside the molded body, that is, the voids (
This detects the presence of voids or pores, and if micropores exist in the molded object, small-angle scattering will be observed due to the uneven distribution of electron density within the system.

In Guyet's theory of small-angle scattering, the scattering intensity can be expressed by the following formula.

1 (h)-(Δp)"V"exp(-h"Rg
'/3) 1(h); Scattering intensity Δρ in vector measurement in reciprocal space; Electron density difference Rg between scattering void and surroundings, radius of inertia V; Volume of scatterer 4πsinθ h; λ λ; Wavelength of X-ray θ ; By the scattering angle, the scattering angle at a certain scattering angle θ! (h) is proportional to the volume of voids with radius of inertia Rg, and if density correction is performed, it can be used as a measure of the amount of voids in the molded body.

The measurement of small-angle scattering intensity is generally performed by the method described in Experimental Chemistry Course 4 Solid State Physics J (1956) edited by the Chemical Society of Japan, but in the measurement of the molded object according to the present invention,
The method shown below is adopted.

[Measurement method of small-angle X-ray scattering intensity ratio] PSPC: (Position detection proportional counter)-5 was connected to Rigaku Denki Co., Ltd. RJ-200B model, and the tube voltage was 45 KV and the tube current was 95 + 11A1 first and second slits respectively. 0.2
Use mmφ, 0.15+nmφ, 0.02°
The scattering intensity was measured by integrating each time for 1000 seconds. As a material, cut out 18 mg of a molded body with a length of 15 mm, and lo+n
The intensity ratio [(
silicon nitride molded body)/Bi(air)] was calculated.

Another feature of the silicon nitride ceramic molded body according to the present invention is that it maintains the above-mentioned amorphous state even when heated in an inert gas atmosphere, such as nitrogen gas, for about one hour.

Therefore, the silicon nitride ceramic molded body of the present invention has almost no change in its mechanical strength even at high temperatures, so it can be said to be a unique heat-resistant material not found in conventional silicon nitride ceramic molded bodies.

The silicon nitride ceramic molded body according to the present invention has a repeating unit represented by the general formula, and has a number average molecular weight of lO
A polyborosilazane obtained by reacting a boron compound with a polysilazane having a molecular weight ranging from It can be obtained by firing in a gas atmosphere or a mixed gas atmosphere in a temperature range of 600 to 1750°C.

The method for manufacturing this ceramic molded body will be specifically explained below.

[Manufacturing raw material J As described above, the raw material has a repeating unit represented by the above general formula and has a number average molecular weight of 100 to 500.
A polyborosilazane obtained by reacting a boron compound with a polysilazane in the range of 0.000 is used.

(Polysilazane) As the polysilazane, one having a repeating unit represented by the above general formula is used.

In the general formula, R', R'' and Ro are substituents or skeletons consisting of a hydrogen atom, a hydrocarbon group, a nitrogen atom, an oxygen atom, a carbon atom and a silicon atom, and R', R'' and Ro are all the same or At least one type may be different.

Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and an aryl group.

In this case, alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decyl, etc., and alkenyl groups include vinyl, allyl, butenyl, pentenyl, hexenyl, hebutynyl, octyl, decenyl, etc. Examples of the aryl group include phenyl, tolyl, xylyl, naphthyl, and the like.

Specific examples of the polysilazane preferably used include those having a repeating unit of the general formula and a number average molecular weight of 100 to 50;
000 cyclic inorganic polysilazane, chain inorganic polysilazane, or a mixture thereof.

If such polyberhydrosilazane is used as a starting material, it is possible to produce a silicon nitride ceramic molded body containing the above-mentioned silicon and nitrogen as essential components and hydrogen as an optional component.

Such polysilazane can be obtained, for example, by reacting a halosilane such as dichlorosilane with a base such as pyridine, and then reacting an adduct of dichlorosilane and a base with ammonia. (Tokugan Sho 6
0-145903).

In addition, in order to exhibit even higher performance as a ceramic molded body, the silazane high polymer proposed by the present inventors,
That is, the above polysilazane or A, 5t as a raw material
ack, Ber, 54. p740 (1921), W, M
, 5cantlin, Inorganic Chem
istry, II (1972), A.5eyFert
h, the silazane polymer disclosed in U.S. Pat. No. 4,397,328, etc., is combined with tertiary amines such as trialkylamine, secondary amines having a sterically hindered group, phosphine, etc. Using a basic compound as a solvent or adding it to a non-basic solvent, such as hydrocarbons,
Number average molecular weight 200 to 500.000 obtained by heating at -78℃ to 300℃ to perform a dehydration condensation reaction
, preferably from 500 to 10,000.

Furthermore, crosslinking → N11i (
n・1 or 2), the atomic ratio of nitrogen bonded to the silicon atom and silicon (N/Si) is 0.8 or more, and the number average molecular weight is 200-500.000, preferably 500-1
A value of 0°000 is preferred. This modified polysilazane can be produced by carrying out a dehydrogenation condensation reaction of polysilazane using ammonia or hydrazine (Japanese Patent Application No. 62-202767).

In addition, the repeating unit is →SiH, NIL)- and -+5
iH30+- and a degree of polymerization of 5 to 300, preferably 5 to +00 (Japanese Unexamined Patent Publication No. 62-195
024) can also be preferably used.

In addition, the composition formula (R3iHNH) x [(R3iH),
, , N), -x (wherein R is an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, or a group other than these groups in which the atom directly connected to Si is carbon, an alkylsilyl group, represents an alkylamino group or an alkoxy group, and 0, 4 < x < 1).
Polyorganohydrosilazane represented by
-293472) can also be used.

(Boron Compound) As the boron compound, either organic or inorganic boron compounds can be used. Examples of organic boron compounds include alkoxides, alkylborons, alkenylborons, and alkylaminoborons, and examples of inorganic boron compounds include borane, boron halides, aminoborons, and the like.

Boron compounds preferably used in the present invention are compounds represented by the following general formulas (I) to (IV).

B(R'), (1) (B'BO), (n)R
″R゛B(R'),・L
(rV) (In these formulas, R4 may be the same or different, and represents a hydrogen atom, a halogen atom, a carbon atom number of 1 to
It is an alkyl group, alkenyl group, cycloalkyl group, aryl group, alkoxy group, alkylamino group, hydroxyl group, or amino group having 20 groups, and L is a compound that forms a complex with B(R'). ) Specific compounds thereof are illustrated below.

Among B(R') and ([), those having a halogen atom as R4 include fluoroborane, tribromoborane, trifluoroborane, trichloroborane, difluoroborane, cyodoborane, iodoborane, dibromomethylborane, dichloromethylborane, Difluoromethylborane, difluoromethoxyborane, cyodomethylborane, ethynyldifluoroborane, difluorovinylborane, dibromoethylborane, dichloroethylborane, dichloroethoxyborane, ethyldifluoroborane, ethylcyodoborane, bromodimethylborane, dibromo(
dimethylamino)borane, chlorodimethylborane, chlorodimethoxyborane, fluorodimethylborane, fluorodimethoxyborane, digloloisobrobylborane, dichloroethylborane, difluoropropoxyborane, bromo(dimethylamino)methylborane, chlorodivinylborane, dibromobutylborane, butyldigloloborane, butyldifluoroborane, butoxydifluoroborane, butoxydifluoroborane, bromodiethylborane,
Dibromo(diethylamino)borane, chlorodiethylborane, chlorodiethoxyborane, dichloro(pentafluorophenyl)borane, dichloro(diethylamino)borane, (diethylamino)difluoroborane, bromobis(dimethylamino)borane, chlorobis(dimethylamino)borane, bis (dimethylamino)fluoroborane, dibromophenylborane, dichlorophenylborane,
Difluorophenylborane, difluorophenoxyborane, cyodophenylborane, dibromo(1,3-dimethyl-1-butenyl)borane, dibromo(3,3-dimethyl-I-butenyl)borane, dibromo(I-ethyl-
1-butenyl)borane, dibromo-1-hexenylborane, dibromo(2-methylcyclopentyl)borane, 2
-Methylcyclopentyl-dichloroborane, dibromohexylborane, dibromo(2-methylpentyl)borane, dichloroexiborane, dibromo(dipropylamino)borane, chlorodibrobylborane, chloro(1,1,
2-trimethylpropyl)borane, dichloro(diisopropylamino)borane, butyl(dimethylamino)fluoroborane, dichloro(4-methylphenyl)borane,
Dichloro(methylphenylamino)borane, bromo(dimethylamino)phenylborane, chloro(dimethylamino)phenylborane, 9-bromo-9-borabicyclo[
3,3,13 nonane, 9-chloro-9-borabicyclo[
3,3,11 nonane, diethylaminogulor (!-butenyloxy) borane, dichlorooctylborane, bromobis(l-methylpropyl)borane, bromodibutylborane, dibromo(dibutylamino)borane, chlorobis(2-methylpropyl)borane, difluoroborane,
Dichloro(dibutylamino)borane, dibutylfluoroborane, bromobis(diethylamino)borane, chlorobis(diethylamino)borane, dichloro(2°4.6
-trimethylphenyl)borane, 3-bromo-7-methyl-3-borabicyclo[3,3,1]nonane, (diethylamino)chloro(cyclopentenyloxy)borane,
dichloro(+,2,3,4.5-pentamethyl-2,4
-cyclopentadien-1-yl)borane, dibromo(
+, 2,3,4.5-pentamethyl-2,4-cyclopentadien-1-yl)borane, cyodo(+,2,3
, 4.5-pentamethyl-2,4-cyclopentadien-1-yl)borane, chlorodisyglopentylborane,
Chloro(diethylamino)phenylborane, bromodicyclopentylborane, (l-butyl-!-hexenyl)
Dichloroborane, bromodipentylborane, chlorodiphenylborane, bromodiphenylborane, dichloro(diphenylamino)borane, chloro(diisopropylamino)phenylborane, chloro(dipropylamino)phenylborane, bromobis(2-bromo-1-hexenyl)borane , chlorobis(2-chloro-1-hexenyl)
Borane, Chlorodicyclohexylborane, Chlorology I
-hexenylborane, chloro(1-ethyl-■-butenyl)(+,1,2-trimethylpropyl)borane, chloro-1-hexenyl(+,1,2-trimethylpropyl)borane, [methyl(4-bromophenyl) )amino]chloro(phenyl)borane, chloro(2-phenylethynyl)(1+1,2-)'dimethylpropyl)borane, chloro(dibutylamino)phenylborane, chlorooctyl(+,1,2-trimethylpropyl)borane, Chlorobis(dibutylamino)borane, fluorobis(2,4
, 6-trimethylphenyl)borane, (l-bromo-!
-hexenyl)bis(2-methylpentyl)borane, (
l-bromo-1-hexenyl)diphenylborane, bis(l-butyl-1-hexenyl)chloroborane, (5-
Examples include chloro-1-pentenyl)bis(1,2-dimethylpropyl)borane.

Examples of R4 having an alkoxy group include dihydroxymethoxyborane, dimethoxyborane, methoxydimethylborane, methyldimethoxyborane, trimethoxyborane, ethyldimethoxyborane, dimethylaminomethoxymethylborane, (dimethylamino)dimethoxyborane, diethyl Methoxyborane, dimethoxypropylborane, bis(dimethylamino)methoxyborane, ethoxydiethylborane, butyldimethoxyborane, jetoxyethylborane, triethoxyborane, cyclopentyldimethoxyborane, methoxydipropylborane, dimethoxyphenylborane, (2-methylcyclopentyl) ) dimethoxyborane, butoxydiethylborane, ethoxydiethylborane, hexyldimethoxyborane, 3-methoxy-3-borabicyclo-[3,3,1]nonane, 9
-methoxy-9-borabicyclo(3,3,11 nonane,
Dibutylmethoxyborane, methoxybis(1-methylpropyl)borane, methoxybis(2-methylpropyl)
Borane, propoxydipropylborane, triisopropoxyborane, triproxyborane, butoxydipropylborane, dibutylethoxyborane, diethyl(hexyloxy)borane, dibutoxyethylborane, dite
rt-butoxyethylborane, dicyclopentylmethoxyborane, dibutylpropoxyborane, ethoxydipentylborane, (hexyloxy)dipropylborane, tributoxyborane, tri-tert-butoxyborane,
Tris(2-butoxy)borane, tris(2-methylpropoxy)borane, methoxydiphenylborane, dicyclohexyl(methoxy)borane, dibutyl(2-penten-3-yloxy)borane, dibutoxypentylborane, ethoxydiphenylborane, (2 -aminoethoxy)diphenoxyborane, dibutyl(l-cyclohexenyloxy)borane, bromodipentylborane, dibutyl(hexyloxy)borane, dibutoxyhexylborane, dihexyloxyprobylborane, tripentyloxyborane, butoxydiphenylborane, ( 2-Methylpropoxy) diphenylborane, diphenoxyphenylborane, triphenoxyborane, tricyclohexyloxyborane, methoxybis(2,4,6-trimethylphenyl)borane, tribenzyloxyborane, tris(3
-methylphenoxy)borane, trioctyloxyborane, trinonyloxyborane, triotadecyloxyborane, etc.

Those having an alkenyl group as Ro include ethynylborane, vinylborane, dihydroxyvinylborane, 2-propenylborane, ethynyldimethoxyborane,
Methyldivinylborane, trivinylborane, 1-hexenyldihydroxyborane, dimethoxy(3-methyl-
1,2-butadienyl)borane, diethyl-2-propenylborane, dihydroxy(2-phenylethynyl)borane, (diethylamino)jethynylborane, diethylaminodi-1-propynylborane, 2-butenyldiethylborane, diethyl(2-methyl- 2-propenyl)borane, bis(dimethylamino)(1-methyl-2-
propenyl)borane, 2-butenylbis(dimethylamino)borane, tri-2-propenylborane, tri(2-
propenyloxy)borane, diethyl(3-methyl-2
-butenyl)borane, 2-furobenyldipropylborane, (diethylamino)di-1-propynylborane, butyl-di-2-propenylborane, 2-butenyldipropylborane, diethyl(1-ethyl-2-butenyl)borane, (2-Methyl-2-propenyl)dipropylborane, diethyl(1゜1-dimethyl-3-buten-I-yloxy)borane, diethyl(1-hexen-4-yloxy)borane, 9-(2propenyl)- 9-borabicyclo[3,3,1]nonane, dibutyl-2-propenylborane, (3-methyl-2-butenyl)dipropylborane, 9-(2-butenyl)-9-borabicyclo(3,3,
I) Nonane, tri-2-butenylborane, tris(2-
methyl-2-propenyl)borane, hexyldi-2-propenylborane, 2-butenyldibutylborane, bis(
l,2-dimethylpropyl)(2-phenylethynyl)
Examples include borane, bis(l,2-dimethylpropyl)-1-octenylborane, and the like.

Those having an alkylamino group or an amino group as Ro include aminoborane, diaminoborane, aminodimethylborane, (dimethylamino)borane, dimethyl(methylamino)borane, methylbis(methylamino)borane, tris(methylamino)borane, (dimethylamino)
Dimethylborane, bis(dimethylamino)borane, bis(dimethylamino)methylborane, aminodipropylborane, (diethylamino)dimethylborane, (dimethylamino)diethylborane, tris(dimethylamino)borane, inpropylbis(dimethylamino)borane , dimethyl(phenylamino)borane, bis(methylamino)phenylborane, bis(dimethylamino)-1-pyrrolylborane, aminodibutylborane, diethylborane,
Dimethylaminodipropylborane, bis(dimethylamino)phenylborane, dibutyl(dimethylamino)borane, di-tert-butyl(dimethylamino)borane,
Examples include dibutyl(diethylamino)borane, tris(diethylamino)borane, dimethylaminodiphenylborane, aminobis(2,4,6-trimethylphenyl)borane, and the like.

Those having a hydroxyl group as R4 include boric acid, hydroxyborane, dihydroxy(methyl)borane, hydroxydimethylborane, ethyldihydroxyborane, dihydroxybrobylborane, 2-phenylhydroxyborane, diethyl Hydroxyborane, butyldihydroxyborane, cyclopentyldihydroxyborane, pentyldihydroxyborane, (3-aminophenyl)dihydroxyborane, phenylhydroxyborane, heptyldihydroxyborane, dihydroxy(2 ~ phenylethyl) borane, dihydroxy(l-naphthalenyl) borane, hydroxybis(2,4,6-trimethylphenyl)borane, hydroxydiphenylborane, and the like.

Those having an alkyl group as Ro include methylborane, dimethylborane, ethylborane, trimethylborane, diethylborane, ethyldimethylborane, diethylmethylborane, 3-methyl-2-butylborane, triethylborane, (+, 1,2-trimethyl propyl)borane, dibutylborane, triisopropylborane, tripropylborane, bis(3-methyl-2-butyl)borane, bis(+, 1,2-trimethylpropyl)borane,
tri-tert-butylborane, tributylborane, tris(l-methylpropyl)borane, tris(2-methylpropyl)borane, tris(2-methylpropyl)borane, tripentylborane, tris(l,2-dimethylpropyl)borane, Examples include trihexylborane and trioctylborane.

Those having a cycloalkyl group as R4 include cyclopentylborane, cyclohexylborane, dicyclohexylborane, cyclohexyl(1゜1.2-trimethylpropyl)borane, tricyclopentylborane, tricyclohexylborane; those having an aryl group as R4 include , tri-l-naphthylborane, tris(
Examples include 2,4,6-trimethylphenyl)borane, tribenzylborane, tris(4-methylphenyl)borane, triphenylborane, phenylborane, and ethyldiphenylborane.

Examples of Ro having a hydrogen atom include borane.

(R'BO), (II) includes boroxine, trifluoroboroxine, trimethylboroxine, trimethoxyboroxine, triethylboroxine, triethoxyboroxine, triphenylboroxine, triphenoxyboroxine, tris(4 -ethynylphenyl)boroxine, tris(dimethylamino)boroxine, tributylboroxine, tributoxyboroxine, tricyclohexylboroxine, and the like.

dichloroborazine, 2,4,6-tribromoborazine,
2.4.6-drifluoroborazine, horazine, 1-methylborazine, 2,4.6-trichloro-1,3,5
-trimethylborazine, 2,4,6-dribromo 1,
3.5-trimethylborazine, 2,4. Lotrifluoro-1,3,5-trimethylborazine, 1,3.5-trimethylborazine, 2,4゜6-trimethylborazine,
2,4.6-trimethoxyborazine, 2,4-dichloro-1,3,5,6-titramethylborazine, 2-chloro-1,3,4,5,6-pentamethylborazine, 2,4
．． 6-dolichloro-1,3,5-triethylborazine,
Hexamethylborazine, 1,3.5-triethylborazine, 2,4.6-triethylborazine, 1,3.5-tripropylborazine, 2,4.6-driethylborazine 1.3
．． 5-trimethylborazine, 1,3.5-tributyl-
2,4,6-tri,chloroborazine, hexaethylborazine, 2,4゜6-dolichloro1,3.5-triphenylborazine, 2,4゜6-triphenylborazine, 2
, 4.6-tri(diethylamino)borazine, 2,4.
6- ) Su(bis(trimethylsilyl)amino)borazine, 2,4.6-tris(dimethylamino)1,3.5
-trimethylborazine, 1,3.5-trimethyl-2,
Examples include 4,6-triphenylborazine.

B(R'), :L(IV) is borane-phosphine, borane-hydrazine, trifluoroborane-methanol, cyanoborane-ammonia, difluoroborane-
Methylamine, borane-methylamine, tribromoborane-dimethyl salsaide, trichloroborane-dimethyl salsaide, trifluoroborane-dimethyl ether, trifluoroborane-ethanol, borane-isocyanomethane, dibromoborane-dimethylsulfide,
Dichloroborane-dimethylsulfide, tochloroborane-dimethylamine, trifluoroborane-ethylamine, dianoborane-methylamine, bromoborane-dimethylsulfide, chloroborane-dimethylsulfide, difluoroborane-dimethylamine, iodoborane-dimethylsulfide, chloroborane-dimethyl Amine, borane-dimethylamine, borane-dimethylphosphine, tribromoborane-trimethylphosphine,
Tribromoborane-trimethylamine, trichloroborane-trimethylamine, trichloroborane-trimethylphosphine, trifluoroborane-trimethylamine, trifluoroborane-trimethylphosphine, triiodoborane-trimethylphosphine, dianoborane-dimethylamine, difluoroborane-trimethylamine, Bromoborane-trimethylphosphine, chloroborane-trimethylphosphine, fluoroborane-trimethylamine, iodoborane-trimethylamine, iodoborane-trimethylphosphine, borane-trimethylamine, trimethylborane-ammonia, trimethoxyborane-ammonia, borane-trimethyl Phosphite, borane-trimethylphosphine, trifluoroborane-2-methylimidazole, trifluoroborane-tetrahydrofuran, chloroborane-tetrahydrofuran, trichloroborane-diethyl ether, trifluoroborane-diethyl ether, dibromoborane-diethyl ether, diglo Roborane-diethyl ether, dianoborane-trimethylamine, bromoborane-diethyl ether, dibromoborane-trimethylamine, dibromomethylborane-trimethylphosphine, chloroborane-diethyl ether, borane-tert-butylamine, borane-diethylamine, tribromoborane-pyridine, Trichloroborane-pyridine, trifluoroborane-pyridine, borane-pyridine, borane-4-aminopyridine, bromodimethylborane-trimethylphosphine, diglocyanoborane-pyridine, trifluoroborane-phenol, cyanoborane-pyridine, dibromomethylborane -Pyridine, borane-4-methylpyridine, trifluoroborane-1-hexanol, tribromoborane-triethylamine, trichloroborane-triethylamine, chloroborane-triethylamine, borane-triethylamine, trimethylborane-trimethylamine, borane-tris(dimethylamino)phosphine , trifluoroborane-methoxybenzene, trifluoroborane-4-methylaniline, borane-2,6-
dimethylpyridine, trifluborane dibutyl ether,
Phenyldichloroborane-triethylamine, tribromoborane-triphenylphosphine, trichloroborane-triphenylphosphine, trifluoroborane-
Triphenylphosphine, borane-triphenylamine, borane-triphenylphosphine, trimethylborane-triphenylamine, triphenylborane-trimethylamine, triphenylborane-pyridine, triphenylborane-triethylamine, and the like can be mentioned. In addition to the above substances, tetraborane (10), pentaborane (9), pentaborane (11), hexaborane (lO), hexaborane (12), octaborane (12
), octaborane (18), isononaborane (15),
nonaborane (+5), decaborane (14), 1, J,'
-bipentaborane (9), ■, 2'-biventaborane (
9), 2,2'-bipentaborane (9), I-carbahexaborane (7), 2-carbahexaborane (9), ■
, 2-dicarbahexaborane (6), 1.2-dicarbapentaborane (7), 2,4-dicarbaheptaneborane (7), 2.3-dicarbahexaborane (8), 1.
7-dicarbaoctaborane (8), 1,2-dicarbadodecaborane (12), 1,7-dicarbadodecaborane (
12), 1,12-Dicarbadodecaborane (12) also gives good results.

Most of these boron compounds are commercially available, but even those that are not commercially available can be produced in the same manner as those that are commercially available.

The mixing ratio of polysilazane and boron compound is preferably from 0.05 to 0.05 so that the B/Si atomic ratio is 0.01-3.
2, more preferably 0.1 to 1. If the amount of the boron compound added is greater than this, the boron compound will simply be recovered unreacted without increasing the reactivity with polysilazane, and if it is less than this, no significant increase in molecular weight will occur.

The reaction can be carried out without a solvent, but it is more difficult to control the reaction than when using an organic solvent, and a gel-like substance may be produced, so it is generally better to use an organic solvent.

As for the reaction solvent, one that does not show reactivity with polysilazane and boron compounds is used. Such non-reactive solvents include hydrocarbons, halogenated hydrocarbons, ethers,
Sulfur compounds etc. are used.

There are no particular restrictions on the reaction temperature and pressure, but the reaction temperature is preferably below the boiling point of the reaction solvent and the boron compound.

The structure of the resulting polyborosilazane varies depending on the type of polysilazane and boron compound used, but in the case of a monofunctional polymer, it has the following structure in which a pendant group is introduced into St and/or N of the main chain of polysilazane. .

l 11OR''
0 1 B(R'), B(R')
.

In di- or tri-functional polymers, a cyclic, crosslinked structure is formed in the polysilazane skeleton via B atoms. The cyclic structure includes a structure in which two functional groups in one molecule of the boron compound are condensed with adjacent silicon atoms and nitrogen atoms of polysilazane. A crosslinked structure occurs when two or more F functional groups of a boron compound are condensed with two or more molecules of polysilazane.

Moreover, some trifunctional polymers have the above-mentioned cyclic structure and crosslinked structure at the same time.

This product has a number average molecular weight of 200,000 to 500,000 and is soluble in organic solvents.

[Solidification process]

If necessary, a hardening agent for promoting solidification and a ceramic powder for preventing the occurrence of cracks after firing the compact and increasing the strength can be added to the polyborosilazane described above. These polyborosilazane are filled into a mold having a desired shape and solidified.

Conditions such as temperature, pressure, atmospheric gas, and holding time in this solidification step are appropriately selected depending on the type of raw material, whether or not a hardening agent or ceramic powder is used, or the amount used.

For example, when solid polyborosilazane is used, it is dissolved in an organic solvent such as a hydrocarbon, a halogenated hydrocarbon, or an ether, and then filled into a mold having a desired shape. Next, it can be solidified by heating at normal pressure to a temperature higher than the boiling point of the organic solvent used, or by heating under reduced pressure to remove the organic solvent.

In addition, when using liquid polyborosilazane,
After filling this into a mold of the desired shape, the temperature is raised to any temperature from room temperature to 400°C under vacuum or in various gas atmospheres described later at normal pressure to 100°C, and maintained at that temperature. solidified. The purpose of the solidification process can be achieved by heating and maintaining the material for a period of about 0.5 hours to about 72 hours.

Furthermore, a method of filling a mold having a desired shape with solid polyborosilazane and maintaining the mold at room temperature of -400° C. under the above-mentioned atmospheric gas at a pressure in the range of normal pressure to 100 atm.

Inert gas such as nitrogen, argon, etc. as atmospheric gas:
Reducing gases such as ammonia, methylamine, and hydrazine; oxidizing gases such as air, oxygen, and ozone; or mixed gases thereof can be used.

As curing agents, organic amines such as alkylamines and alkylene diamines, carboxylic anhydrides such as oxalic anhydride and malonic anhydride, alkyl isocyanates such as isocyanates such as methyl isocyanate and dimethylsilyl diisocyanate, and butane dithiol. , thiols such as benzenedithiol, carboximides such as malonic acid imide and succinimide, periodic table of elements
Metal alkoxides containing metals selected from groups A and M to V, iron, cobalt, nickel, copper, silver, gold, mercury, zinc, ruthenium, mu, palladium, indium, titanium, hafnium , zirconium, titanium, hafnium, zirconium, aluminum, boron, phosphorus, and other halides are used.

In addition, for the purpose of preventing cracks and increasing strength,
Examples of the ceramic powder that may be added as necessary include nitrides, carbides, and oxides of various metals.

Any conventionally known mold can be used as the mold, but
In order to improve the removability of the molded product and protect the surface of the molded product, the inner surface of the mold is coated with a mold release agent, such as a silicone-based mold release agent, or a thin layer of grease is applied, or an organic solvent is used. It is desirable to apply the grease dispersed in the liquid by spraying or brushing.

[Firing Step] The molded body obtained in the solidification step is then heated and fired, preferably in the presence of the above-described inert gas, reducing gas, oxidizing gas, or a mixed gas thereof. This firing is carried out at 600°C to 20°C/min, preferably at 5°C for 1 minute or less.
This is carried out by heating the temperature to 1750° C. and maintaining it at this temperature for an additional 48 hours.

In some cases, good results can be obtained by pressure firing such as hot pressing.

If the firing temperature is less than 600°C, the formation of ceramic will be insufficient and sufficient hardness cannot be imparted.

Furthermore, if the firing temperature exceeds 1750°C, undesirable decomposition reactions will begin, resulting in a noticeable decrease in strength.

The ceramic molded body of the present invention is manufactured by the method described above, but if the ceramic molded body after firing is impregnated with the polyborosilazane, and the solidification and firing are repeated, a good surface with further densification can be obtained. A ceramic molded body can also be obtained.

[Effects of the Invention] The structure of the silicon nitride ceramic molded body according to the present invention is such that the formation of crystalline material is substantially suppressed not only at room temperature but also at high temperatures, and is amorphous or α- with a crystal grain size of 500 Å or less. It is an aggregate or mixed system of crystalline fine particles of 5i, N4 and β-5i, N4, and the X-ray small angle scattering intensity ratio to air is 1 to 20 at 1'' and 0.56, respectively.
Since the molded product has a high mechanical strength, particularly high-temperature strength, it maintains high mechanical strength compared to conventional silicon nitride ceramic molded products even if it is crystallized at a higher temperature. In addition, since this silicon nitride ceramic molded body is based on silicon nitride, it has excellent high-temperature strength (especially thermal shock resistance) and electrical insulation, and also has excellent oxidation resistance and wear resistance with little free carbon. be.

Therefore, the ceramic molded body of the present invention is an aircraft material,
Suitable for use in the fields of space development materials, ship materials, marine construction materials, land transportation equipment materials, construction and civil engineering materials, mechanical work materials, precision machinery materials, automatic 11 (materials), etc.

〔Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Reference example 1 Blow gas into a four-loaf flask with an internal volumetric capacity! .

Equipped with mechanical stirrer and dewar condenser. After purging the inside of the reactor with deoxygenated dry nitrogen, 490% of degassed dry pyridine was placed in a four-bottle flask.
This was chilled on ice. Next, when 51.6 g of dichlorosilane was added, a white solid adduct (SiH, CQ, 2C, H
, N) was generated. The reaction mixture was ice-cooled, and while stirring, 51.0 g of purified ammonia was blown into the reaction mixture through a sodium hydroxide tube and an activated carbon tube.

After the reaction was completed, the reaction mixture was centrifuged, washed with dry pyridine, and then filtered under a nitrogen atmosphere to obtain filtrate 850-. When the solvent was distilled off from the filtrate 5-1 under reduced pressure, 0.102 g of solid resin perhydropolysilazane was obtained.

The number average molecular weight of the obtained polymer was 980 as measured by GPC. Also, the IR of this polymer
Examining the (infrared absorption) spectrum (solvent: dry 0-xylene; concentration of perhydropolysilazane: 10.2 g/Q), the wave number (cm-') is 3350 (apparent extinction coefficient ε・0.557Qg-' mark). −°) and +175 N
Absorption based on l(; 5it of 2170 (ε=3.14)
(Absorption based on; 5it of 1020-820 (and 5
It was confirmed that absorption based on iNSi was exhibited.

In addition, when inspecting this polymer's °IINMR (proton nuclear magnetic resonance) spectrum (60 MHz, solvent CDCl group (harmful substance TMS), it was confirmed that both showed a wide absorption range. That is, 64.8 and 4.4(br,
5iH); 1.5 (br, NH) absorption was confirmed.

Reference example 2 The reaction was carried out using the same apparatus as in Reference Example 1.

That is, 450 kg of degassed dry tetrahydrofuran was placed in the fourth flask shown in Reference Example 1, and cooled in a dry ice-methanol bath. Next, dichlorosilane 46
．． Added 2g. This solution was cooled, and 44.2 g of anhydrous methylamine was blown into the solution as a mixed gas with nitrogen while stirring.

After the reaction was completed, the reaction mixture was centrifuged, washed with dry tetrahydrofuran, and then filtered under a nitrogen atmosphere to obtain filtrate 820-. When the solvent was distilled off under reduced pressure, 8.4 g of viscous oily N-methylsilazane was obtained. The number average molecular weight of the obtained polymer was +100 when measured by GPC.

Reference Example 3 A four-loop flask with an internal volume of 1Q was equipped with a gas blowing tube, a mechanical stirrer, and a dewar condenser. After purging the inside of the reactor with deoxidized dry nitrogen, 300 d of dry digloromethane and 24.3 g (0,211 m) of methyldichlorosilane were placed in a four-bottle flask.

Q) was added and cooled on ice. Ammonia purified through a sodium hydroxide tube and an activated carbon tube with stirring 18.
Ig (1,06 moQ) was injected.

After the reaction was completed, the reaction mixture was centrifuged, washed with dry dichloromethane, and filtered under a nitrogen atmosphere. When the solvent is distilled off from the filtrate under reduced pressure, a colorless transparent methyl (hydro) is produced.
8.81g of silazane was obtained. The number average molecular weight of this product was 380 as measured by GPC.

Reference example 4 A four-loaf flask with an internal volume of IQ equipped with a dropping funnel, condenser, mechanical stirrer, and gas blowing pipe.
After replacing the inside of the reactor with deoxygenated dry nitrogen, 200 g of dry chlorobenzene and 50 g of boron trichloride were placed in a four-bottle flask and cooled on ice. Next, 17 g of dry acetonitrile was added dropwise to form a white solid adduct (CHYOC).
N-BCQ, ) was generated. After the dropwise addition was completed, 22 g of ammonium chloride dried at 110° C. was added. The reaction mixture was heated under reflux for 5 hours to obtain a colorless and transparent solution. After cooling to room temperature, 45-diethylamine was added dropwise. After the reaction was completed, the filtrate was filtered under a nitrogen atmosphere to remove the solvent, yielding 21 g of B-1 lis(diethylamino)borazine as a non-transparent liquid.

Example 1 Pyridine solution of perhydropolysilazane obtained in Reference Example 1 (concentration of perhydropolysilazane: 5.20% by weight)
) 600d and trimethylborate 30d (0,254
mol) into an autoclave with an internal volume of LQ, and
The reaction was carried out with stirring at .degree. C. for 3 hours. After cooling to room temperature, add 500 d of dry 0-xylene and apply at a pressure of 3 to 5 mmH.
g.

When the solvent was removed at a temperature of 50 to 70°C, 38 g of polyborosilazane having a number average molecular weight of 2100 in the form of a white solid was obtained.

After dissolving the obtained polysilazane in toluene and adjusting the concentration, it was poured into a Teflon mold and heated for 7 days under a nitrogen stream.
By removing the solvent at 0°C, a transparent molded body (75+u
+φX 8mm) was obtained. Next, the temperature was raised to 1000°C at a heating rate of 0.1''C/min under an ammonia gas atmosphere, and then 1000°C at a heating rate of 10°C/min under a nitrogen atmosphere.
By raising the temperature to 750°C and firing at 1750°C for 1 hour, a black disc-shaped ceramic molded body was obtained.
The elemental analysis results show that Si: 50. F1%N:3
8.7%, Coo, 60%, 0:2.40%, B:6.
When the structure was analyzed by powder X-ray diffraction measurement, it was found that it was amorphous. Moreover, the X-ray scattering intensity ratio of the obtained molded article was 20 or less in both cases of 1'' and 0.5''.

Example 2 Reference example! Pyridine solution of perhydropolysilazane obtained in (Concentration of perhydropolysilazane: 4.90% by weight)
) 500- and tris(butylamine)borane 45aQ (
0,165 mol) was placed in an autoclave having an internal volume of 1Q, and the reaction was carried out at 120° C. with stirring for 3 hours.

When the solvent was removed in the same manner as in Example 1, 36 g of polyborosilazane with a number average molecular weight of 2350 in the form of a white solid was obtained.
Obtained.

The obtained polyborosilazane was dissolved in ○-xylene, the concentration was adjusted, and then poured into a Teflon mold and the solvent was removed at 100°C under a nitrogen stream to obtain a transparent molded product (
20+nmφX 10mm) was obtained. Next, the temperature was raised to 1750°C at a rate of 3°C/min at 2000 atm in a nitrogen atmosphere, and then at 1750°C for 1 hour in a nitrogen atmosphere.
By performing the IP treatment, a black disc-shaped ceramic molded body was obtained. The elemental analysis results show that Si: 50.
6%, N: 39.3%, Co0.70%, O: 2.15
%, B: 6.75%. When its structure was analyzed by powder X-ray diffraction measurement, it was found to be amorphous. Moreover, the X-ray scattering intensity ratio of the obtained molded body was 20 or less in both cases of 16 and 0.5'.

Example 3 γ-picoline solution of N-methylsilazane obtained in Reference Example 2 (concentration of N-methylsilazane, 8.60% by weight
) 600- and tributylborate 130 mol (0,
482 mol) into an autoclave with an internal volume of IQ,
The reaction was carried out at 160° C. for 5 hours with stirring. When the solvent was distilled off under reduced pressure in the same manner as in Example 1, 48 g of polyborosilazane having a number average molecular weight of 1880 in the form of a pale yellow solid was obtained.

The obtained polyborosilazane was crushed under a nitrogen atmosphere, then filled into a tungsten mold for hot pressing, and then under an ammonia atmosphere at 5°C/min, 300kg/cn! 15 under the condition of
The temperature was raised to 00°C, then raised to 1750°C at 10°C/min under a nitrogen atmosphere, and fired at 1750°C for 3 hours to produce a black disc-shaped ceramic molded body (70 mmφ
8 mm) was obtained. The elemental analysis results are based on weight, Si:
48.9χ, N: 38.2%, C: 0.40%, O: 2
．． When the structure was analyzed by powder X-ray diffraction measurement, it was found that it was amorphous. Moreover, the X-ray scattering intensity ratio of the obtained molded body was 20 or less at both angles of 1° and 0.5°.

Example 4 O-xylene solution of methyl(hydro)silazane obtained in Reference Example 3 (concentration of methyl(vitro)silazane = 6°4
0 wt %) 300 d was placed in a four IQ flask, cooled on ice, and 50 g (0,427 mol) of boron trichloride was added over 2 hours, followed by stirring at 25° C. for 3 hours under a nitrogen stream to carry out the reaction. In this solution, 200d of l, l, l-
Add 3,3,3 hexamethyldisilazane and incubate at 80°C.
Stir for an hour to form a precipitate. This precipitate was filtered and the solvent of the filtrate was distilled off under reduced pressure to obtain 58 g of polyborosilazane having a number average molecular weight of 4,800 in the form of a pale yellow solid.

The obtained polyborosilazane (b;
0IIl+Ilφx8mm) was obtained. Next, the temperature was raised to 1750°C at a heating rate of 0.1°C/min under a nitrogen atmosphere.
By firing at 1750° C. for 1 hour, a black disc-shaped ceramic molded body was obtained. The elemental analysis results for grass clippings are: Si: 50.6%, N: 25.5X, C: 15.4%,
O: 1.68%, B: 6.78%. When its structure was analyzed by powder X-ray diffraction measurement, it was found to be amorphous. Moreover, the X-ray scattering intensity ratio of the obtained molded product was 20 or less in both cases of 1'' and 0.5'.

Example 5 Reference example! Pyridine solution of perhydropolysilazane obtained in (Concentration of perhydropolysilazane: 4.70% by weight)
) 600+*l and 55 g (0,187 mol) of B-tris(diethylamino)borazine obtained in Reference Example 4 were placed in an autoclave having an internal volume of 1Q, and the reaction was carried out with stirring at 80°C for 2 hours. After cooling to room temperature, the solvent was distilled off under reduced pressure in the same manner as in Example 1 to obtain 64 g of polyborosilazane having a number average molecular weight of 2,800 in the form of a white solid.

After dissolving the obtained polyborosilazane in 0-xylene and adjusting the concentration, it was poured into a Teflon mold and the solvent was removed at 80°C under a nitrogen stream to obtain a transparent molded body (
40mmφX 8mm) was obtained. Next, the temperature was raised to 600°C at a heating rate of 0.1°C/min under an ammonia gas atmosphere, and then at a heating rate of 10°C/min under a nitrogen atmosphere.
By raising the temperature to 750°C and firing at 1750°C for 1 hour, a black disc-shaped ceramic molded body was obtained. The elemental analysis results are: Si: 50.6%, N: 35% by weight
, 8%, C: 2,50%, 0: 1.28%, B: 5.
Powder X-ray diffraction measurement revealed that 2e=20.5a, 3pi, 34.5", 35
There is a broad peak that seems to be related to α-Si3N near 2θ-35, 5°, and 36″ near 2θ-3
A peak thought to be related to 3N was observed, and the obtained ceramic molded body contained ultrafine particles of α-5i,
It was found that the structure was one in which N and β-Si3N were dispersed.

In addition, the X-ray scattering intensity ratio of the obtained molded body was I” and 0.5
In all cases of 0, it was 20 or less.

Claims (1)

[Claims] (1) Silicon, nitrogen, and boron are essential components, carbon, oxygen, and hydrogen are optional components, and the ratio of each element is expressed as an atomic ratio, N/Si=0.05 to 2.5, B/Si= 0.01
~3, C/Si = 1.5 or less, H/Si = 0.1 or less, an amorphous substance consisting essentially of silicon, nitrogen and boron, or an amorphous and crystalline substance consisting of silicon, nitrogen and boron Particle size is 5
α-Si_3N_4 and β-Si_3N_ of 00 Å or less
A molded silicon nitride ceramic formed of an aggregate or mixed system of crystalline fine particles according to No. 4, characterized in that the small-angle X-ray scattering intensity ratio with respect to air is 1 to 20 times at 1° and 0.5°, respectively. body.