JPH0365527A - Silicon oxicarbide glass and its article - Google Patents

Abstract

PURPOSE: To obtain a glass compsn. which is stable up to 1,650°C and does not decompose in an oxidizing or reducing atmosphere by compounding tetraoxysilicon, monocarbosiloxane, dicarbosiloxane, tetracarbosilicon and specific silicon, oxygen and carbon.

CONSTITUTION: This glass compsn. consists of about 34 to 48 wt.% tetraoxysilicon, about 11 to 29 wt.% monocarbosiloxane, about; 11 to 27 wt.% dicarbosiloxane, up to about 22 wt.% tetracarbosilicon and the silicon, oxygen and carbon distributed in the multiple atom units consisting of about 3 to 9 wt.% elementary carbon dispersed in a glass matrix. This glass has resistance to devitrification and is structurally stable up to at least 1,650°C. The term 'structurally stable' refers to a bulk material which holds the same microstructure at the high temp. of 1650°C described above from room temp.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to glass compositions, particularly glass compositions comprising silicon, oxygen and carbon.

Amorphous (non-running) silica is fire-resistant glass, but it has a rating of 1100
It is easily lost at temperatures higher than ℃! S (crystallize). Devitrification is where the disordered structure that makes up the glass becomes ordered or crystallized. Crystallization allows one of the key attributes of glassy silimeno, namely its low coefficient of thermal expansion, to be combined with other desirable properties.
．． It declines sharply along with many of the special goods. For this reason, much research has been conducted in search of ways to increase the resistance to devitrification in silica glass compositions.

The reaction between silicon, carbon and oxygen has been widely studied. Among the known reactions that occur in silicon, carbon and oxygen systems is the reaction in which oxygen ε silicon combines to form silica SiO2. The silica then begins to crystallize and form cristobalite at temperatures above 1100°C. Cristobalite is one of the commonly found mineral forms of silica.

The carbon can react with the silica present and any remaining elemental carbon readily oxidizes when exposed to air at temperatures above 600°C.

The thermodynamics of the reaction of silicon, carbon and oxygen was described in 1972 by Gulbransen, E.A. and Jansson, S.A.
``High Temperature Oxidation, Reduction and Volatilization Reactions of Silicon and Carbon Silicon (The tllg
h-Temperature Oxidat1on,
Rcduction, and Volat! l1za
tlon Reactions ol' 5t11co
n and 5 ilicon carbide) J.

Based on the thermodynamic solution of Gulbransen et al., it was shown that silica and carbon form gaseous silicon monoxide and carbon monoxide or solid silicon carbide SiC at 1200°C. However, the formation of materials containing silicon, oxygen and carbon was not expected. Gulbranscn et al. conclude that the use of silica in reducing atmospheres above 1125° C. is not recommended due to the formation of oppressive silicon monoxide gas. Similarly, the use of silicon carbide in an oxygen-containing environment was also discouraged as severe oxidation could occur due to oxidation of the silicon carbide.

There is a material in which 1 to 3% of carbon is added to silica and is called functional carbon-modified glassy silica (herein referred to as "black glass"). A method for making black glass is disclosed in Smith et al., US Pat. No. 3,378,431. That is, a carbonaceous organic material such as carbowax is added to silica and the mixture is
Hot press at 200°C to form black glass. In addition, Smithni L! ! (Sa+ith, C, F6.
Jr.) was admitted to Alfred University (Alfred, New York, USA) in May 1973.
The Vibrational Spectrum of Highly Purified and Chemically Substituted Glassy Silica
.

rHlgh Purity and Che+*1ca
lly 5ubstituted Vltreous
The properties of black glass were determined by infrared spectroscopy in 5ilicas) J. Smith discloses that the carbon in the black glass is combined with oxygen in carbonato-type groups in addition to the elemental carbon dispersed in the glass. The carbonato group represents a specific bonding mode in which one carbon atom is bonded to three oxygen atoms, and has the structure of the following formula.

The mechanical strength of part \ -O / part black glass is similar to that of carbon-free silica glass, but the resistance to devitrification of black glass is lower than that of ordinary silica glass, which begins to devitrify at about 1100°C. devitrification of black glass begins at about 1250°C. Because of its great thermal stability, black glass can be used at higher temperatures than glassy silica can withstand.

In industrially produced silicon carbide ceramic long fibers sold under the trademark Nicalon J, approximately 10% oxygen is introduced into the m-rag to cross-link the m-fibers. The fibers are pyrolyzed, during which oxygen becomes part of the fibers as an amorphous impurity, probably in the form of silica.The degradation that such fibers exhibit after heat treatment in various environments The behavior is mer (
Mah, T. et al., 1984, Journal of Materials Science.
nce) J Vol. 19, pp. 1191-1201.
5tability of' SICFibres (
N1calon-registered trademark)''.

According to the findings of Mah, T. et al., “Ncalon
) The strength of the J fiber deteriorated when the fiber was exposed to temperatures above 1200°C. As the fiber deteriorated, carbon oxide was lost from the fiber, and β-silicon carbide particles grew within the fiber.

Ceramic materials are generally characterized by their high strength and low fracture toughness and their resistance to crack propagation in the material. There is one case.

7. ◆'i 'a&'
;) method and 12. The development of τ-width/Lamic combination has been completed. "Nicalon-1 is an excellent lamic fiber, but it can withstand temperatures higher than 1200'C (7)
J deterioration zuro. Desired 1. Nicalon (N[
ealon), J fibers may be one way to obtain improved ceramic cold fillers. j
, 1.2. As is clear from the theory in Section L, the characteristics of known ceramic or glass compositions, especially compositions containing silicon, oxygen and carbon, are as follows:
At a temperature of 250° C./l, deterioration occurs due to decomposition or devitrification of the glass or ceramic.

Therefore, the object of the present invention is to provide a glass matrix consisting of silicon, oxygen and carbon, with a significant portion of the carbon atoms bonded to the silicon atoms (5,5) and the remaining carbon dispersed in the glass matrix as elemental carbon. 1. Make a glass that looks like
:fii"ru 111-. Ninoyo...) na Ganos X
11 composition at temperatures up to at least 1650°C;:! When 5 H = , 3 is held, there is no oxidizing or reducing effect on J (in the surrounding atmosphere).

The present invention also...) Hi! Ni:)'s ``1st example is methyl silicate glass made of silicon, oxygen, and carbon.
- Manufactured by thermal decomposition of resin:! The decision is to do so.

Yet another object of the invention is a method of making articles from such glasses consisting of ion, oxygen, S and carbon.

BRIEF DESCRIPTION OF THE INVENTION The present inventor has prepared a glass composition of Δ1 in silicone resin by thermal decomposition in a non-oxidizing atmosphere. I discovered that there is a (“erut”)
Surprisingly, thermal decomposition of such silicone resins in a non-oxidizing atmosphere does not produce mixtures of silica, cristobala, silicon carbide, carbon oxide or phosphoric acid with carbon. tl+light (7ta.

To prepare the glass of the present invention, silicon, oxygen and 9:
θ) Forms a glass in which a significant portion of carbon atoms are chemically bonded to silicon atoms. In one method of the present invention, methyl silicone resin is heated in a non-oxidizing atmosphere to pyrolyze the resin. 4 As used herein, "non-oxidizing atmosphere" refers to an atmosphere that removes reaction products from the pyrolyzed resin without affecting the reactions that occur during pyrolysis. Examples of such non-oxidizing atmospheres are active atmospheres such as helium, argon or nitrogen, and reducing atmospheres such as hydrogen and the like.

If the C resin is cross-linked prior to thermal decomposition, thermal decomposition can occur under reduced pressure of about 10-4 atmospheres or higher or even in a true confinement. A suitable methyl silicone resin is disclosed in U.S. Pat. No. 4,026,868.
It can be produced by the method described in Section 1 (herein incorporated by reference).

Methyl silicone is composed of siloxane chains with methyl groups bonded to silicon atoms.

The siloxane chain has the following structure 17 formed by the intersection of the silicon atom -f and the oxygen atom, and the bond f'T I/C.

On this siloxane chain, there are some combinations of methyl amounts that form polymethylpolysiloxane.

Basic single samurai structure in polymethylborish Dgisa〉・
;z is I.limePrusiloxy, dimethylsiloxy, and heptanomethylsiloxane. The monofunctional trimethylsiloxylli position at the end of the siloxane chain is as follows:
I have an i-structure.

Dimethylsiloxy has 2% C-ability Qi that constitutes a chain or ring.
and has the following horizontal positions:

Monomethylsiloxane is a trifunctional unit that not only extends the siloxane chain but also crosslinks a large amount, and has the following structure.

The methyl silicone resin may also contain unsubstituted tetrafunctional units having the structure:

-0-3i-0- Polymer structures can be assembled from these unit structures to form polymethylpolysiloxanes having the desired number of methyl groups per silicon atom.

By varying the ratio of methyl groups to silicon atoms, different methyl silicone resins are produced having more or less methyl groups as organic substituents.

Methyl silicone resins typically have a ratio of methyl groups to silicon atoms of about 2:1 or less. The methylsilicone resin used in the present invention consists of about 5% by weight dimethylsiloxy and about 95% by weight monomethylsiloxy, and is referred to herein as methylsilicone precursor resin, sometimes referred to as precursor resin or resin. Sometimes.

During pyrolysis, gas is evolved causing weight loss of the resin and the resin densifies. The pyrolysis reaction is completed when the weight of the pyrolyzed resin becomes approximately constant. Weight loss during pyrolysis was determined to be approximately 11-35%. It has been found that the methyl silicone precursor resin can be thermally decomposed at temperatures in the range of about 900-1600<0>C.

The glasses produced by the method of the invention have unique properties and properties. These glasses are at least 165
It does not crystallize at temperatures up to 0°C and does not decompose in oxidizing or reducing atmospheres. Furthermore, a significant portion of the carbon present within the glasses of the present invention is bonded to silicon, with the remainder existing as elemental carbon dispersed within the glass matrix, with no detectable carbonate groups present. 'There is no EL. The carbon-silicon bonds found in the glasses of the present invention are unknown in conventional silica glasses. Carbon in silica glasses, especially black glasses, is only known to exist as an unbonded element in the silica matrix or as carbon bonded to oxygen in carbonato groups.

Glasses formed by the method of the invention and characterized by unique properties as described above are referred to herein as silicon oxycarbide glasses.

When methyl silicone precursor resin is thermally decomposed, silicon,
A silicon oxycarbide glass is produced which is characterized by having electrons "continuously" between oxygen and carbon atoms.

In silicon oxycarbide glasses, silicon atoms are present in four types of polyatomic units.

One i1i, herein referred to as tetraoxysilicon
At this position, a silicon atom is bonded to four oxygen atoms.

In the second unit, referred to herein as monocarbosiloxane, the silicon atom is bonded to three oxygen atoms and one carbon atom. In the third unit, herein referred to as dicarbosiloxane, the silicon atom is bonded to two oxygen atoms and two carbon atoms. In the fourth unit (referred to herein as tetracarbosilicon), a silicon atom is bonded to four carbon atoms. The pyrolyzed precursor resin contains these polyatomic units: about 34-44% by weight tetraoxysilicon, about 19-29% by weight monocarbosiloxane, about 17-27% by weight dicarbosiloxane, about Up to 6% by weight of tetracarbosilicon is distributed in the matrix, forming a glass containing about 3 to 9% by weight of elemental carbon dispersed as atoms or small clusters within the glass matrix. These units are connected primarily by silicon-oxygen bonds, with only a small number of bonds between carbon atoms and oxygen atoms.

The glass also has about 56% to 66% of the silicon atoms bonded to at least one carbon atom, and about 3% to 9% by weight of carbon with elemental carbon dispersed within the glass matrix in the form of atoms or small clusters. Oxysilicon carbide glass with carbon present 4, ':l, τil1, 1. When silicon, oxygen, and carbon nx'+ are called oxides, 1-ε is formed.

Making an article of '1' oxycarbide glass (,
Pulverize the pyrolyzed resin 1. -4 and powdered with
l? ;! , i, then consolidated with the gay oxycarbide powder 1. 'C form the article. One method of bodb1nos is about 1550-...165
This means applying a small off-axis (unidirectional) pressure of 5 ksi to the powder at 0°C.
i; i iΩ; densification I, which is sufficient for 0 to form an object.

Molded articles can also be formed directly from the methyl silicone precursor resin. First, a resin is dissolved in a solvent such as toluene, and then γ-aminopropyltriethoxysilane is added to crosslink the resin. The solution is cast into a desired shape and allowed to dry and harden up to the chamber 21.

This crosslinked resin is slowly pyrolyzed in a non-oxidizing atmosphere as described herein. Thermal decomposition is carried out at a low rate to avoid the formation of voids and bubbles in the gas and heavy loss of resin.
It costs 4. Thermal decomposition is complete when the weight of the pyrolyzed resin stabilizes.In this way, the crosslinked resin becomes densified 1.
, about 3 to 9 L1% tetraoxysilicon, about 11
...211 heavy parts of monocarposi + 1 giraffe, about 11 =
21 weight 73% dicarbosyl, 1'~zan, about 12-2
The polyatomic il 1 position consisting of 2% by weight of tetracarbosilicon is distributed in the 1st and 2nd positions, and about 3 to 9% L1% of elemental carbon is present in the matrix λ with an elementary -r-:1: or small Clusters and I7 form a dispersed silicon oxycarbide glass. The crosslinked silicon oxycarbide glasses formed from the precursor resins are referred to herein as crosslinked silicon oxycarbide glasses.

Crosslinked resin oxysilicon carbide glasses also include about 52-62% of the silicon atoms bonded to at least one carbon atom, and about 3-9ffij1% of the carbon dispersed within the glass matrix in atoms or small clusters. However, the composition of silicon, oxygen and carbon assembled together with silicon oxycarbide glass present in elemental carbon 2215 is also 100%.
b I can.

The methyl silicone precursor resin can be crosslinked to any degree but not completely.

Such partially crosslinked resins, when pyrolyzed according to the method of the present invention, can form silicon oxycarbide glass compositions that are intermediates in the aforementioned compositions. 1
, thus about 34-48% by weight tetraoxysilicon, about 11-29% by weight monocarbosiloxane, about 11% by weight
= 27% by weight or more of dicarbosiloxane, up to about 22% by weight of polyatomic units consisting of tetroactive L-bodies are distributed, and about 3-9% by weight of elemental carbon is atomically distributed within the glass matrix. Or silicon oxycarbide glasses can be formed that are dispersed as small clusters.

Kiranimata, Shi. Silicon oxycarbide glasses, such as those described above, have approximately 52% to 66% of the silicon atoms bonded to carbon forces on at least one side, and approximately 3% to 9% by weight of carbon atoms within the glass matrix. Alternatively, it can also be referred to as a composition of silicon, oxygen and carbon aggregated as a silicon oxycarbide glass dispersed in small clusters.

The crosslinked precursor resin solution can also be drawn into fibers. That is, a solid object is immersed in the resin solution.
Crosslinking of the precursor resin solution is allowed to proceed until the viscosity is such that it can then be pulled out of the solution to form a strand of resin.

Such a dipping step then allows the resin solution to be stretched to form fibers. Alternatively, the resin solution can be strained in a Teflon cove under somewhat reduced pressure. When the resin hardens and the toluene evaporates, the m-fibers shrink and do not protrude from the tube.

The fibers can be fully crosslinked by heating to about 50'C to facilitate J[12 handling.

The fibers are then pyrolyzed in a non-oxidizing atmosphere or under reduced pressure as described above.

A ceramic composite material can be formed that includes ceramic fibers in a matrix of oxycarbide glass and ceramic filler. That is, a precursor resin is dissolved in a solvent, and ceramic particles are dispersed in the solution to form an infiltrant slurry. The particulate ceramic filler controls the shrinkage of the composite matrix during pyrolysis and can be selected to be compatible with the fiber reinforcement used and the matrix. Some examples of ceramic fillers include powdered silicon carbide, diatomaceous earth, and aluminosilicate 2S called mullite.
There is i0 3A1203.

A ceramic fiber or bundle or cloth of fibers is drawn through the agitated infiltrant slurry. Some examples of ceramic fibers are carbon fibers, silicon carbide fibers, and aluminoborosilicate fibers. The impregnated fibers are then shaped and dried to evaporate the solvent. One molding method involves spirally wrapping impregnated Fipal around a drum to form a panel. By applying heat and pressure, the layers of fibers can be consolidated to form a continuous resin matrix surrounding the ceramic fibers. The composite is then pyrolyzed in a non-oxidizing atmosphere or under reduced pressure as described above.

The resin is densified into a substantially amorphous silicon oxycarbide glass that bonds the ceramic fibers to form a continuous matrix around the fibers. Ceramic fillers can be dispersed in the glass, partially sintered, or completely sintered, depending on the pyrolysis temperature used.

In some cases, to reduce porosity in composites,
The ceramic composite material can be re-infiltrated with a solution of the precursor resin dissolved in a solvent. That is, the composite is placed in a re-infiltrant solution under reduced pressure.

Pressure is applied to the solution to pack it into the pores of the composite. After re-infiltration, the toluene is evaporated and the re-infiltrated composite is pyrolyzed in a non-oxidizing atmosphere or under reduced pressure as described above. Re-infiltration and pyrolysis can be repeated as many times as necessary until the desired degree of density is achieved in the matrix.

A matrix of amorphous silicon oxycarbide glass bonding the ceramic filler surrounds the ceramic fibers and protects them from decomposition in oxidizing and reducing atmospheres at temperatures up to at least 1650°C. The inert nature of silicon oxycarbide glasses has been shown to readily accommodate ceramic fibers without reacting with them or degrading their properties. The viscous, silicon oxycarbide glass containing a suitable ceramic filler can be used as a matrix material for any known ceramic fibers.

The following description of the invention will be better understood with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION Glass can be defined by two basic characteristics. One is that glass is formed from extremely viscous liquids, and the other is that the glass-forming liquid forms a polymerized network with short-range order. Although the glasses of the present invention are not formed from supercooled liquids, they do have short-range ordered network channels. The glasses of the present invention are formed by pyrolyzing a methyl silicone precursor resin in a non-oxidizing atmosphere instead of subcooling the liquid. However, the glass of the present invention has the same short-range ordering properties as conventional glasses.

Preferred methylsilicone resins for use in the present invention consist primarily of monomethylsiloxane units, many of whose iB positions have a hydrogen atom on one oxygen atom, ie, contain a hydroxyl group. When crosslinking occurs in the resin, hydroxyl groups react to form bonds between silicon and oxygen atoms and water is produced. Other silicone resins made according to the method of the aforementioned U.S. Pat. No. 4,026,868 also consist of silicon, oxygen and carbon, with the carbon bonded to the silicon (but with some elemental carbon), by pyrolysis. may be present in the glass matrix), it has been shown that unique carbonate-free glasses can be formed.

Silicone resin has a three-dimensional structure with short-range order. In addition, silicone resin is described as 't7 (according to Chemistry 17i theoretical composition). Siri:
1 ゛ / Chemistry in resin 1; i-theoretical unit j, oxygen 1 to 1,000,
1) and the right "machine 1 group 1." the bonded silicon atom to h1
7. I'm here. These σ) groups are formed from a --valent hydrocarbon amount and a 111117-genated J--valent hydrocarbon group. For example, 1.1 to 8 carbon atoms are 1
'f Argyl group, 5-10 0) carbon atoms Q-
cyclyl group, alkyl;, a group (vinyl, alkyl, etc.);
, t'' and FJ are nyl groups.

In this specification I+, four inserts of dubon L in silicotone resin are used.
li (standing, 1 silicon base 2r 0) zymogen-F- and 3
Individual tノ) 12 M residues are bonded to Arisobu, the gay atoms are bonded to 2 oxygen atoms and 2 a-type JJ+, ■) Residues, silicon atoms are bonded to 3 An oxygen atom and a single white machine,
group (, T residue which also has two bonds, and silicon atom r is 4
It is called an Ω residue bonded to 17 oxygen atoms. Mineral resins that can be thermally decomposed to form glass have a ratio of organic groups to silicon atoms between about 0.5:1 and about 1.7:1σ). , , M residue, 'r residue 2. (,D
remainder, group and Ω remainder], (combining Cg; i-+' t
-r il.

The glass of the present invention has a resistance to failure of C7 and an ε of less than 1650.
The temperature in °C is "C structural 1.': stable;!:!.

``The term ``stable horizontally'' means that from room temperature to the above S≦l
Essentially keeping the same Miku n structure up to R! It refers to a bulk material that has a certain amount of structure, which means that the microstructure has small cracks. Small and small curvatures, such as the formation of small viscocrystalline regions of about 100 to 1 mm in a matrix that is otherwise amorphous, are due to the nature of the balloon material. The horizontally stable glass is woody and amorphous, but in the western part of the glass, t5
・”For example, Graffito, Cristobalai I-1:7-
is the small crystallized region of silicon carbide a -1, and l:
- Or the glass surface” - “Chris from 8th grade”
・6W of Palite 1. , may be used.

stomach.

Okiji carbonized glass articles are made according to some methods of the present invention. I can do it. Hitotto tD 5
In the method, the decomposed resin is crushed) 1. τ, 0. 1-・
Powder icy to produce a particle size in the range of -2 microns, t: "iJ-l. To obtain a silicon oxycarbide particle size in the range of 0.1 to 2 microns, °A"l・Richon Mill or Yu J? A powder 1i'/Ig, such as a mill, is used. For grinding with an atricine mill, approximately 5206 liquid (for example, water), about 35% grinding medium (such as a grinding medium (such as a ball with a diameter of 1.2 mm that is harder than the material),
A solution consisting of pulverized silicon carbide glass particles occupying the remaining portion is stirred with an impeller. When the solution is heated with an impeller of 1°00 rpm, the glass powder becomes finely pulverized and becomes powder. A weekly J□11 mil grind is performed using a similar solution, but with grinding media and
To stir the solution, use a 5- to 8-meter ball to stir the grinding vessel at a relatively slow speed.

Thereafter, the crushed powder is densified by applying dry C1 and 1F to form a molded product. Lr
For densification, apply a pressure of at least about 5 k, si, at about 1550-=1650°C, - and C2,
4. Ri+, at about 1200-1650°C at least about 8
k S 1σ) Reduce the isotropic pressure i! : b”τ
I can do it. Heat ε pressure 1:] to the desired degree of the article! Apply until it is densified or completely densified.

Casting or molding 1. Another method for forming oxidized silicon carbide glass articles from precursor resins involves dissolving the methyl silicone precursor resin in a solvent and curing it with a curing agent. Can be bridged. Representative examples of solvents known to be suitable for dissolving the precursor resin are l.
toluene and toluene and isopropyl alcohol-/+,
It is a mixture of divination. The resin can be dissolved in the solvent in a ratio of up to about 8 parts resin to 17 parts solvent. Representative examples of curing agents that have been found to be suitable for crosslinking precursor resins include ammonium oxide <-,-''
-Salt such as rim etc. 1. (commercially available silicones containing amines such as γ-amino, nopropyltriethoxysilane, and σ) acids such as hydrochloric acid. This curing agent is a crosslinking agent that is added to the resin in an amount of about 0.1-4%.
Dry the iW main body resin at room temperature1. The precursor resin is preferably dried at such a rate that the solvent evaporates from the resin without forming voids in the resin. is molded or cast into the desired form before or during crosslinking.

Next, the cured precursor resin is thermally decomposed in a non-oxidizing atmosphere in the same manner as described above. Because the precursor resin is crosslinked in this aspect of the invention, pyrolysis can also be carried out in a vacuum. The heating rate during pyrolysis must be controlled so that gas evolution occurs without forming voids or bubbles in the resin. Preferably, a heating rate of less than 1.0° C./min is used to allow sufficient gas generation without forming bubbles, voids or defects in the glass.

Thermal decomposition is complete when weight loss from the precursor resin due to water, methyl groups, and other decomposition products has substantially ceased. During pyrolysis, the precursor resin densifies and forms a crosslinked resin oxysilicon carbide glass.

EXAMPLES The following examples are provided to illustrate the silicon oxycarbide glasses of the present invention and methods of making the glasses and glass articles. In the following examples, the above-mentioned U.S. Pat. No. 4.02
A silicone resin manufactured by the method described in No. 6.868, having methyl groups, and composed of about 5 weight percent D residues and 95 weight percent T residues was used.

90% methyl silicone precursor resin in a non-oxidizing atmosphere
Thermal decomposition was carried out by heating to a temperature in the range of 0 to 1600°C. During pyrolysis, a weight Iu loss of the precursor resin occurred as water, methyl groups, and other decomposition products were produced. Thermal decomposition is almost complete when the weight of the resin to be thermally decomposed becomes stable. The weight loss measured during pyrolysis ranged from about 11-35%. This change in weight loss is believed to be due to differences in the amount of solvent retained and changes in the degree of crosslinking that had occurred prior to the onset of pyrolysis. As already explained, these precursor resins generate water during crosslinking. These resins crosslink at room temperature or when curing coagents are added to promote crosslinking. Therefore, the amount of water generated from the resin before pyrolysis begins varies depending on the degree of crosslinking that has occurred before pyrolysis. The more crosslinking that has occurred prior to pyrolysis, the more water is lost and the less weight will be lost from the resin during pyrolysis.

Examples 1-3 Three pyrolysis experiments were conducted according to the method of the invention. One uncured precursor resin and two cured or crosslinked precursor resins were pyrolyzed, during which weight loss was determined by thermogravimetric analysis. Thermoheavy analysis is a method of measuring the weight loss of a sample during heating. Two experiments were heated in a hydrogen atmosphere and one in a helium atmosphere at a rate of 10° C./min until weight loss stopped. The measured weight loss and final composition of the silicon oxycarbide glasses formed after pyrolysis are shown in Table 1.

Table I - Thermogravimetric analysis of pyrolyzed resins Conventional carbon and silicon values were determined by conventional wet chemistry techniques for dissolved carbon and silicon. Oxygen content was measured by neutron activation.

The weight loss data measured by thermogravimetric analysis in Examples 1 to 3 is shown in the graph of FIG. In the graph of FIG. 1, the % weight loss of each sample is plotted on the vertical axis and the increase in heating temperature is plotted on the horizontal axis. As shown in the graph of FIG. 1, significant weight loss occurred for each sample even at temperatures such as 900°C, but at 1200°C the weight loss was nearly complete.

Example 4 A sample of consolidated silicon oxycarbide glass was produced by pyrolyzing a precursor resin at 1400°C with flowing hydrogen. That is, the precursor resin was placed in a molybdenum boat and pyrolyzed as described herein. The pyrolyzed precursor resin was milled in six 25 gram batches in a planetary mill using an agate mortar and 1/4 inch diameter agate media. This yielded 150 grams of silicon oxycarbide powder with a surface area of 2.2 rrr/g (which corresponds to an equivalent spherical diameter of approximately 1.16 μm).

Approximately 120 g of the resulting silicon oxycarbide powder was hot pressed in a 2 inch diameter die butted with a graphite sheet separating agent. This graphite sheet prevents the powder from sticking to the die during hot pressing. The sample was heated to 1650'C at a rate of 10°C/min.
It was held at 0° C. for 30 minutes, during which time a uniaxial pressure of 6 ks i was applied. A nearly completely dense sample was produced with the properties shown in Table H below.

Table ■ - Properties of consolidated silicon oxycarbide glass When this hot-boiled material was subjected to high-resolution transmission electron microscopy, particle sizes ranging from 20 to 1
00 angstrom beta silicon carbide particles were shown to be present. Almost no signs of crystallization were observed in the X-ray diffraction analysis of this treated material.

Example 5 By slowly pyrolyzing the crosslinked precursor resin,
A sample of crosslinked resin oxysilicon carbide glass was prepared. Equal amounts of toluene and precursor resin were mixed with a crosslinker in an amount of about 4% by weight relative to the precursor resin. The mixture was poured into a glass dish and kept at room temperature for 24 hours to slowly evaporate the toluene. The precursor resin was crosslinked as the toluene evaporated. This cross-linked sample is
Heating from room temperature to 500℃ in 0 hours, then heating from 500℃ to 800℃ in 16 hours, and heating to 80℃ in 4 hours.
After heating from 0°C to 1100°C, the temperature was maintained at 1100°C for 1 hour. This indicates that the overall heating rate was approximately 0.6°C/min.

The sample was then cooled in the oven. A fully dense sheet of crosslinked resin oxysilicon carbide glass having a thickness of about 2 a+m was obtained.

Example 6 A hot-pressed sample of silicon oxycarbide glass was heated in air at 1420° C. and 1520° C. for 240 hours to examine the oxidation resistance and structural stability or devitrification resistance of the glass. No weight loss due to decomposition of silicon or carbon in the glass was measured. Cross-sectional X-ray diffraction revealed no signs of crystallization in the bulk material of any of the specimens. Exposed surface X-ray diffraction showed signs of surface crystallization to cristobalite within about 0.002 inches of the surface on both specimens.

Examples 7-9 The composition of two different glasses is not always well defined by simply stating the amount of each element in the glass. Rather, it is the short-range order in the glass that gives it different properties. Therefore, by characterizing the short-range ordered structure in a glass, various glass compositions can be defined, and the glasses of the present invention are defined by their short-range ordered structure.

Silicon oxycarbide glass samples were prepared by pyrolyzing samples of the precursor resin at 1100° C. with flowing hydrogen. A sample of resin-cured silicon oxycarbide glass was prepared by adding a sample of cross-linked precursor resin to 1100
It was prepared by pyrolysis under flowing hydrogen at °C. The 29 silicon solid state nuclear magnetic resonance spectra recorded for these samples are shown in FIGS. 2 and 4. Figure 3 is a 29 silicon nuclear magnetic resonance spectrum obtained for a sample of Nlcalon J silicon carbide fiber. On the vertical axis, the intensity of the radiation measured in the excited sample is plotted; The horizontal axis shows the chemical shift in ppm from the tetramethylsilicon standard fixed at the zero point of the horizontal axis.
Plotted in (parts per million). The chemical shift characteristics t'tppm are known for many polyatomic units; for example, the characteristic ppm of tetraoxysilicon, dicarbonoxane, and monocarbosiloxane is 1981
Springer Verlag Berlin Heidelberg (Springer Verlag Berli)
n Iledelbcrg), Deal (P, D
lehl) and Kosfelt (1?, Kosrel)
d), Basic Principles and Progress of rNMR, 29 Silicon-NM
R spectroscopic measurement results (NMRBa5ic Pr1nclpl
esand Progress 2931-NMR5p
cctroscop+c Re5ults)” No. 18
6, 184 and 178. Therefore, each of the peaks in FIGS. 1, 2, and 3 defines a specific silicon polyatomic width short-range chichicho structure.

In FIG. 2, a spectrum of silicon oxycarbide glass is shown containing peaks numbered 1-3. The broadest peak 1 represents small amounts of tetracarbosiloxane and Otake's dicarbosiloxane, peak 2 defines monocarbosiloxane, and peak 3 defines tetraoxysilicon. By integrating the area under each peak, each fraction of these polyatomic 11 positions can be determined.

The integrated area under each peak in FIG. The composition of the silicon oxycarbide glass is revealed, including siloxane and 39% tetraoxysilicon.

The spectrum shown in Figure 2 is expressed as “Nicalon”.
It can be compared with the silicon carbide spectrum in FIG. 3 measured on the J silicon carbide fiber sample. In Figure 3, “
The composition of Nlcalon J is about 75% silicon carbide, about 7% dicarbosiloxane, about 13% monocarbosiloxane, and about 5% tetraoxysilicon. As can be seen from the spectrum in Figure 3,
Nicalon J m fiber consists primarily of silicon carbide with small amounts of dicarbosiloxane, monocarbosiloxane and tetraoxysilicon.

In contrast, the spectrum in Figure 2 shows that silicon oxycarbide consists primarily of dicarbosiloxane, monocarbosiloxane, and tetraoxysilicon.

This latter combination of polyatomic units binds carbon and silicon in a manner previously unknown in glasses, resulting in a resistance to devitrification and decomposition of This is a characteristic of glass.

The spectrum of the crosslinked resin oxysilicon carbide glass shown in FIG.
% tetracarbosilicon, about 16% dicarbosiloxane, about 1694 monocarbosiloxane and about 43%
(tetraoxysilicon). Peak 1 is tetracarbosilicon, peak 2 is dicarbosiloxane, peak 3 is monocarbosiloxane, and peak 4 is tetraoxysilicon. As can be seen by comparing Figures 2 to 4, resin-cured oxysilicon carbide glass differs from Nicalon J fiber in terms of composition, and resin-cured oxysilicon glass also differs from Nicalon J fiber. It differs from silicon oxycarbide glass in terms of composition.

Tip Example 10 Silicon oxycarbide glass fibers were produced by the following method. That is, the solution of precursor resin and toluene was 1:1.
γ-aminopropyltriethoxysilane corresponding to 2% of the resin was added as a curing agent. The solution was crosslinked until it could be stretched to form strands. The fibers of the precursor resin were drawn out of the solution by dipping the ends of a 9.5II+11 diameter fiber blank into the resin solution and pulling. After repeating this procedure several times, the mMe was added to 50° C. to dry and crosslink sufficiently to facilitate removal. The fiber nails were then thermally decomposed according to the method described in Suimon 111 to form silicon oxycarbide glass fibers f1t having a diameter of about 013III11.

Example 11 A ceramic composite having an amorphous silicon oxycarbide ceramic matrix was produced. First, precursor resin 3
An infiltrant slurry was prepared consisting of 1 part by weight, 3 parts by weight of 0.2 micron silicon carbide powder, and 4 parts by weight of toluene. The slurry was infiltrated into the agitated continuous carbon fiber tow by drawing it through the tow.

A tow is a strand created by weaving individual fibers together. The infiltrated tow was wrapped around a hexagonal drum to form a unidirectional resin-impregnated panel. After the toluene had evaporated, the dried panels were removed from the drum. The panels were cut into tapes and several tapes were stacked in a rectangular die that maintained the unidirectional alignment of the fibers. While applying a pressure of 300 MPa to the heavy tape, the die was slowly heated to 200° C. and maintained for 15 minutes. The resin flowed to fill the t81 gap between the fiber tow and the tape layer, forming a bar with a continuous matrix of crosslinked resin and silicon carbide powder surrounding the mHE tow. This bar was taken out from the Gui and placed in an argon atmosphere for 2 hours.
Heat to 1200'C at °C/min, 1200'C for 30 minutes
Pyrolyzed by keeping at A carbon fiber reinforced ceramic composite was formed having a matrix of amorphous silicon oxycarbide glass bonding the ceramic filler. This ceramic composite material has a density of 1.73g/
cc, and the open porosity was 19% by volume. Small bars were machined from this composite panel and the mechanical properties were measured using a three point bending test. The ultimate bending strength is 200MPa and the breaking energy is 2.3Kj
It was larger than /rrr. The composite exhibited non-brittle ebb and flow characterized by fiber debonding and pull-out upon fracture.

Example 12 A second ceramic composite was formed using the procedure described in Example 11. However, the infiltrant slurry contained 2 parts by weight of precursor resin and 3 parts by weight of 3.5 micron silicon carbide powder.
parts by weight, and 5 parts by weight of toluene.

The ceramic fibers were Nlcalon J silicon carbide fibers coated with boron nitride. The impregnated and consolidated fiber panels were pyrolyzed to a density of 2.0
8g/cc, open porosity 18%, ultimate bending strength 31
2MPa1 fracture energy is 2.4Kj/rr? A ceramic composite was formed.

Example 13 A third ceramic composite was formed using the procedure of Example 11. However, the infiltrant slurry has a precursor resin of 2
parts by weight, 3 parts by weight of 2 micron mullite powder, and 5 parts by weight toluene. The ceramic fibers were aluminoborosilicate fibers. Mullite is an aluminosilicate refractory ceramic with the chemical formula 2SiO.3A1203. The impregnated and consolidated fiber panels were pyrolyzed to form a composite ceramic with a density of 2.39 g/cc, an open porosity of 13.5%, and an ultimate bending strength of 200 MPa.

[Brief explanation of drawings]

FIG. 1 is a graph showing weight loss data measured during pyrolysis of a methyl silicone precursor resin. Figure 2 is a graph showing the 29 silicon nuclear magnetic spectrum of silicon oxycarbide glass. Figure 3 is a graph showing the 29 silicon nuclear magnetic spectrum of silicon oxycarbide glass.
It is a graph showing the 29 silicon nuclear magnetic resonance spectrum of J. FIG. 4 is a graph showing the 29 silicon nuclear magnetic resonance spectrum of resin-cured silicon oxycarbide glass.

Claims (33)

[Claims] (1) about 34-48% by weight of tetraoxysilicon, about 1
1-29% by weight monocarbosiloxane, about 11-27
silicon, oxygen and carbon distributed in polyatomic units consisting of weight percent dicarbosiloxane, up to about 22 weight percent tetracarbosilicon, and about 3 to 9 weight percent elemental carbon dispersed in a glass matrix. It consists of
A glass composition that is structurally stable at temperatures up to at least 1650°C. (2) Silicon, oxygen and carbon approximately 38-48% by weight
of tetraoxysilicon, about 11-21% by weight monocarbosiloxane, about 11-21% by weight dicarbosiloxane, about 12-22% by weight tetracarbosilicon, and about 3-9% by weight dispersed in a glass matrix. % of elemental carbon distributed in polyatomic units consisting of % of elemental carbon.
Glass as described. (3) Silicon, oxygen and carbon are about 34-44% by weight
of tetraoxysilicon, about 19-29% by weight monocarbosiloxane, about 17-27% by weight dicarbosiloxane, up to about 6% tetracarbosilicon, and about 3-9% by weight dispersed in a glass matrix. 2. The glass of claim 1, wherein the glass is distributed in polyatomic units consisting of elemental carbon. (4) A glass composition consisting of silicon, oxygen and carbon as a silicon oxycarbide glass mass and structurally stable at temperatures up to at least 1650°C, wherein about 52-66% of the silicon atoms contain at least one A glass composition in which about 3 to 9 weight percent carbon is bonded to carbon atoms and is present as elemental carbon dispersed within a glass matrix. (5) A glass composition consisting of silicon, oxygen and carbon as a resin-cured silicon oxycarbide glass mass and structurally stable at temperatures up to at least 1650°C, wherein about 56-66% of the silicon atoms are at least A glass composition in which about 3-9% by weight of carbon is present as elemental carbon dispersed in a glass matrix. (6) A glass composition consisting of silicon, oxygen and carbon as a resin-cured silicon oxycarbide glass mass and structurally stable at temperatures up to at least 1650°C, wherein about 52-62% of the silicon atoms are at least A glass composition in which about 3-9% by weight of carbon is present as elemental carbon dispersed in a glass matrix. (7) A method for producing glass comprising heating a methyl silicone precursor resin in a non-oxidizing atmosphere to a temperature at which the resin thermally decomposes, wherein said heating results in substantial weight loss from the thermally decomposing resin. Implemented for a period of time until the end of
A method of forming a silicon oxycarbide glass in which the pyrolyzed resin is structurally stable at temperatures up to at least 1650°C. (8) The method according to claim 7, wherein the heating is performed at a temperature of 900 to 1650°C. (9) Before the heating step, it also includes the step of crosslinking the methyl silicone precursor resin by dissolving it in a solvent and adding a curing agent, so that the crosslinked resin oxysilicon carbide glass forms after pyrolysis. It is formed,
The method according to claim 7. (10) When the heating is performed, the weight loss from the resin is about 11 to 3
8. The method of claim 7, wherein the method is carried out for a period of time such that 5%. (11) The method according to claim 7, wherein the heating is performed in a hydrogen gas atmosphere. (12) carrying out the heating in a helium gas atmosphere;
The method according to claim 7. (13) Heating the methyl silicone precursor resin in a non-oxidizing atmosphere to a temperature at which the resin thermally decomposes,
carried out for a period of time until the weight loss from the pyrolytic resin has substantially ceased, and the resulting deposit is ground into a powder of about 0.1 to 2 microns in size, and the powder is densified to produce an article. A method of making a silicon oxycarbide glass article comprising consolidating said powder particles by applying heat and pressure to produce a silicon oxycarbide glass article. (14) The method according to claim 13, wherein the heating step is performed at a temperature of 900 to 1650°C. (15) The method according to claim 13, wherein the heating step is performed in a hydrogen gas atmosphere. 16. The method of claim 13, wherein the heating step is conducted for a period of time such that the weight loss from the resin is about 11-35%. (17) the compacting step comprises at least about 5 ksi
Uniaxial pressure is applied to the powder and the powder is
Claim 1 comprising heating to 550-1650°C.
The method described in 3. (18) the compacting step comprises at least about 8 ksi
An isotropic pressure of approximately 1 is applied to the powder, and the powder is
Claim 1 comprising heating to 200 to 1600°C.
The method described in 3. (19) Dissolving the methyl silicone precursor resin in a solvent and adding a curing agent to crosslink the resin, molding the resin to form an article, evaporating the solvent from the crosslinked resin, and dissolving the resin in a non-oxidizing atmosphere. a crosslinked resin oxysilicon carbide glass article comprising heating said resin to a temperature at which said resin pyrolyzes and carrying out said heating for a period of time until the weight loss from the pyrolysing resin substantially ceases. Production method. (20) The method according to claim 19, wherein the curing agent is ammonium hydroxide. (21) The method of claim 19, wherein the curing agent is a silicon-containing amine. (22) The method according to claim 19, wherein the heating step is performed at a temperature of 900 to 1650°C. (23) The method according to claim 19, wherein the heating step is performed in a hydrogen gas atmosphere. (24) The method according to claim 19, wherein the heating step is performed in a vacuum. 25. The method of claim 19, wherein the heating step is performed at a heating rate that minimizes void formation in the glass. 26. The method of claim 19, wherein the heating step is conducted for a period of time such that the weight loss from the resin is about 11-35%. 27. The method of claim 19, wherein the heating step is performed at a heating rate of less than about 1° C./min. 28. The method of claim 19, wherein the evaporation step is performed at an evaporation rate that prevents the formation of voids in the resin. (29) about 38-48% by weight tetraoxysilicon, about 11-21% by weight monocarbosiloxane, about 11-2
Silicon, oxygen distributed in polyatomic units consisting of 1% by weight dicarbosiloxane, about 12-22% by weight tetracarbosilicon, and about 3-9% by weight elemental carbon dispersed in a glass matrix. and glass fibers made of carbon. (30) Dissolving a methyl silicone precursor resin in a solvent, adding a curing agent to the dissolved resin, crosslinking this resin until it has a viscosity that can be formed into fibers, and stretching this resin to form fibers, evaporating the solvent from the resin, heating the resin in a non-oxidizing atmosphere to a temperature at which the resin decomposes, and continuing the heating for a period of time until weight loss from the pyrolytic resin substantially ceases. A method for producing silicon oxycarbide glass fibers, comprising carrying out the steps. (31) A composite ceramic comprising at least one ceramic fiber within a matrix of silicon oxycarbide glass bonding a ceramic filler, wherein the glass comprises about 34-48% by weight of tetraoxysilicon, about 11-29% by weight % monocarbosiloxane, about 11-2
A composite ceramic consisting of silicon, oxygen and carbon distributed in polyatomic units consisting of 7% by weight dicarbosiloxane and about 3-9% by weight elemental carbon dispersed in a glass matrix. (32) Dissolving the precursor resin in a solvent and adding particulate ceramic filler to this resin to form a composite resin, impregnating at least one type of ceramic fiber with the composite resin, and molding the impregnated fiber to form a composite resin. a material, evaporate the solvent from the impregnated fibers, and heat the shaped fibers in a non-oxidizing atmosphere to a temperature at which the resin pyrolyzes; A method of manufacturing a ceramic composite comprising forming a matrix of silicon oxycarbide glass and ceramic filler surrounding ceramic fibers by carrying out the process for a period of time up to the end of the process. 33. The method of claim 32, further comprising the step of consolidating the layer of impregnated fibers to form a continuous composite resin matrix around the fibers by applying heat and pressure prior to the heating step. .