JPH03183637A - Translucent silicon oxycarbonate glass and product using same - Google Patents

Abstract

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

Description

[Detailed description of the invention] Background of the invention The present invention relates to glass compositions.

More particularly, it relates to a translucent glass composition comprising silicon, oxygen and carbon.

Amorphous silica is a fire-resistant glass, but it is
It easily devitrifies at temperatures exceeding ℃.

Devitrification refers to the ordering or crystallization of the random structure that forms the bottom of the glass. Crystallization dramatically reduces the main attributes of vitreous silica (i.e., low coefficient of thermal expansion and many other desirable properties). Therefore, to develop methods to improve the devitrification resistance of silica glass compositions. A lot of research has been carried out.

The reaction between silicon, carbon and oxygen has been extensively studied. Among the known reactions involving the silicon-carbon-oxygen system, oxygen combines with silicon to form silica (SiO
Then, when the temperature exceeds 1100° C., silica crystallizes to form cristobalite. Cristobalite is one of the common mineral forms of silica. The carbon may react with the silica to form crystalline silicon carbide or escape as -carbon oxide gas.

Carbon that remains as elemental carbon is easily oxidized when exposed to air at temperatures above 600°C.

The thermodynamics of the reaction between silicon, carbon and oxygen is
Oxidation of Metals (Ox-1dati)
E. A. Gulbranscn and Nis A. Gulbranscn (on or Metals) Volume 4, No. 3 (1972)
& S.A.

Janssoo)'s paper "High-temperature oxidation, reduction and volatilization reactions of silicon and silicon carbide".According to the thermodynamic analysis of Gulbrandsen et al., 120
At 0°C, silica and carbon can be combined with gaseous silicon monoxide and carbon monoxide or solid silicon carbide (Si
C) has been shown to produce. However, it is not expected that materials containing silicon, oxygen and carbon will be produced.

Based on the conclusions of Gulbrandsen et al., the use of silica in reducing atmospheres above 1125° C. was not recommended due to the production of volatile silicon monoxide gas. Also, the use of silicon carbide in oxygen-containing environments where active oxidation is likely to occur has also been discouraged because it leads to oxidation of the silicon carbide.

There is an opaque black material that is functionally described as a carbon-modified vitreous silica. This glass is produced by adding 1 to 3% carbon to silica, and is referred to herein as "black glass."

A method for making black glass is disclosed in US Pat. No. 3,378,431 to With et al.

According to that method, a carbonaceous organic material such as carbowax is added to the silica and the resulting mixture
A black glass is produced by hot pressing at 0°C. C.F. Smith Jr. (C, F, Sm1
In his dissertation "Vibrational Spectra of Highly Purified Glassy Silica and Chemically Substituted Glassy Silica" (Alfred University, Alfred, NY, May 1973), The properties of the black glass were determined by infrared spectroscopy. Smith found that not only is elemental carbon dispersed in the black glass, but some of the carbon also combines with oxygen to form carbonate groups. The carbonato group is a name representing a specific form in which one carbon atom is bonded to three oxygen atoms, and it has the structure shown below.

The mechanical strength of black glass is equivalent to that of silica glass that does not contain carbon, but black glass shows improved devitrification resistance compared to ordinary silica glass. It begins to devitrify, whereas black glass begins to devitrify at about 1-250°C. By exhibiting this increased thermal stability, black glasses can be used at higher temperatures than silica glasses can withstand.

In continuous ceramic fibers of silicon carbide, sold under the trade name "Nicalon", crosslinking is effected by introducing about 10% oxygen into the fibers. Pyrolysis of the fibers occurs after racking, and oxygen is believed to be present in some fibers as amorphous contaminants (possibly silica). The degradation behavior that occurs is reported in the Journal of Materials Science.
of Material Science) Volume 19 (1
984), pages 11.91-1201, in the article by Mah et al. Mah et al. found that the strength of Nicalon fibers decreased with exposure to temperatures above 1000° C., regardless of the environmental conditions during heat treatment. Such fiber degradation was associated with the loss of carbon monoxide from the fibers and the growth of β-silicon carbide grains within the fibers.

In co-pending U.S. Patent Application No. 359,619,
Glass compositions are disclosed in which silicon atoms are combined with oxygen and carbon atoms and do not exhibit devitrification or decomposition at temperatures up to at least 1650°C. The glass composition of U.S. Patent Application No. 359,619 has about 3 to
It contains an additional 9% (by weight) of elemental carbon, and this free carbon imparts an opaque, black appearance to the glass composition.

Generally, ceramic materials exhibit brittle behavior characterized by high strength and low fracture toughness.

Fracture toughness is the resistance to crack growth in a material. The development of ceramic compositions has been investigated as a means of mitigating the brittle behavior of ceramics. "
"Nicalon" is an excellent ceramic fiber, but it has 1
Degrades at temperatures exceeding 200°C. Embedding "Nicalon" fibers in a protective ceramic matrix that has desirable mechanical properties and can withstand temperatures substantially higher than 1200° C. would result in an improved ceramic composite material. However, as is clear from the above discussion, the properties of known glass or ceramic compositions (particularly those containing silicon, oxygen and carbon) are
Deterioration occurs due to decomposition or devitrification of the glass or ceramic at temperatures exceeding 0 to 1250°C.

One of the objects of the present invention is to provide a silicone resin containing silicon, oxygen and carbon in a chemically bonded state such that a substantial portion of the carbon atoms are bonded to silicon atoms, and made from certain methyl silicone resins. An object of the present invention is to provide a glass composition.

In addition, silicon, oxygen, and carbon in a chemically bonded state in which a substantial portion of carbon atoms are bonded to silicon atoms;
It is also an object of the present invention to provide a translucent glass composition comprising up to trace amounts of elemental carbon dispersed in a glass matrix. At temperatures up to at least 1600° C., such glass compositions are structurally stable and do not decompose even in oxidizing or reducing atmospheres.

Furthermore, it is an object of the present invention to provide a process for producing such glass compositions consisting of silicon, oxygen and carbon by pyrolysis of certain methyl silicone resins.

Furthermore, it is an object of the present invention to provide a method for manufacturing articles using a glass composition as described above consisting of silicon, oxygen and carbon.

SUMMARY OF THE INVENTION The inventors have discovered that unique glass compositions can be obtained by thermally decomposing certain silicone resins in a non-oxidizing atmosphere. Surprisingly, it has been found that when such silicone resins are pyrolyzed in a non-oxidizing atmosphere, no silica, cristobalite, silicon carbide, carbon oxide, or mixtures of silica and carbon are produced. The inventors have also found that by pyrolyzing certain silicone resins, they can be made translucent, which does not exhibit an opaque or black appearance as a result of containing up to trace amounts of free carbon, allowing at least partial light transmission. It has also been found that glass compositions can be obtained.

In the present invention, a glass composition consisting of silicon, oxygen, and carbon in which a substantial portion of carbon atoms are chemically bonded to silicon atoms is produced by thermally decomposing a methyl silicone resin.

According to one method of the invention, methyl silicone resin is pyrolyzed by heating the resin in a non-oxidizing atmosphere. "Non-oxidizing atmosphere J" as used herein means an atmosphere that removes reaction products from the resin during pyrolysis without affecting the reactions that occur during pyrolysis. Examples of such non-oxidizing atmospheres These include inert atmospheres such as helium, argon and nitrogen, as well as reducing atmospheres such as hydrogen. Vacuum having a pressure less than about 10@-4 atmospheres can also be used.

Methyl silicone resins suitable for use in the method of the present invention can be prepared by the method described in US Pat. No. 2,676,182. In particular, Examples 2 and 4 described in U.S. Pat. The use of toluene to facilitate hydrogen separation will result in a methyl silicone resin particularly suitable for use in the process of the invention.

Methyl silicone resins are composed of siloxane chains with methyl groups bonded to silicon atoms. The siloxane chain is made up of alternately bonded silicon atoms and oxygen atoms. Polymethylpolysiloxanes are produced by bonding various combinations of methyl groups onto siloxane steels.

The basic structural units present in polymethylpolysiloxane are trimethylsiloxy units, dimethylsiloxy units and monomethylsiloxane units. The monofunctional trimethylsiloxy unit present at the end of the siloxane chain has the following structure.

CH.

CH3-3i-0- CH3 dimethylsiloxy unit is a bifunctional unit that forms a chain or cyclic siloxane, and has the following structure.

The HI-O-9i-0-CH5 monomethylsiloxane unit is a trifunctional unit that not only extends the siloxane chain but also causes crosslinking of the steel mass, and has the following structure.

CH.

-0-3i-0- Methyl silicone resins may also contain tetrafunctional unsubstituted units having the structure shown below, which are referred to herein as Q units.

-0-3i-0- By forming a polymer structure from these structural units, polymethylpolysiloxane having a desired number of methyl groups per silicon atom can be produced. That is, by changing the ratio of methyl groups to silicon atoms, various methyl silicone resins having different contents of organic substituents (ie, methyl groups) are produced. in general,
The ratio of methyl groups to silicon atoms present in the methyl silicone resin is about 2:1 or less. The methyl silicone resin used in the present invention is about 3=1 (i.e.
It consists of trimethylsiloxy units and tetrafunctional unsubstituted Q units present in a ratio up to the maximum polymerizable ratio of trimethylsiloxy units and Q units. Note that the trimethylsiloxy unit and Q unit are approximately O17:1
Preferably present in a ratio of ˜about 3:1, and about 1
Most preferably, they are present in a ratio of from :1 to about 3:1.

Hereinafter, such methyl silicone resin will be referred to as "methyl silicone precursor resin," but in some cases, it may simply be referred to as "precursor resin" or "resin J." The ratio of trimethylsiloxy units to Q units in the resin after polymerization is determined according to the theoretical initial composition of the resin when prepared by the method described above. It should be understood that this may also be lower.

Upon pyrolysis, the precursor resin densifies, releasing gas and exhibiting a weight loss. This reduction in weight is accompanied by a reduction in the volume of the precursor resin, resulting in an increase in the density of the resin. The pyrolysis reaction is substantially complete when the weight of the precursor resin undergoing pyrolysis reaches a substantially constant value.

However, if heating continues after weight loss has ended, the precursor resin may undergo further densification. Therefore, it may be desirable to stop the heating and pyrolysis after the precursor resin is fully densified, in other words after the volume has stopped decreasing.

Furthermore, when we measured the weight loss during thermal decomposition, we found that
It was found to be within the range of approximately 17-54%. Also,
It has been found that the methyl silicone precursor resin can be thermally decomposed at temperatures within the range of about 900-1600<0>C.

Glass produced by the method of the invention has unique properties and properties. At temperatures up to at least 61,600'C, these glasses are resistant to crystallization and do not decompose even in oxidizing or reducing atmospheres.6 Furthermore, a substantial portion of the carbon present in the glasses of the present invention is composed of silicon. As well as being bonded, the remaining carbon is present as elemental carbon dispersed within the glass matrix, so there are no detectable carbonate groups. The carbon-silicon bond discovered in the glass of the present invention was not known in conventional silica glasses.

In silica glass, especially black glass, carbon exists as an element in a non-bonded state in the silica matrix, or
Alternatively, it was only known to exist as a carbonato group formed by bonding carbon and oxygen. Glasses produced by the method of the present invention and having the above-mentioned unique properties are referred to herein as "oxy-silicon carbide glasses."

When the methyl silicone precursor resin as described above is thermally decomposed, an oxycarbon silicon glass characterized in that electrons are continuously shared between silicon, oxygen, and carbon atoms is obtained.

In oxycarbon silicon glass, silicon atoms are 4
It exists as a polyatomic unit of species. In the first unit, called tetraoxysilicon, ■ silicon atoms are bonded to four oxygen atoms. In the second unit, called monocarbosiloxane, one silicon atom is bonded to three oxygen atoms and one carbon atom. In the third unit, called dicarbosiloxane, one silicon atom is bonded to two oxygen atoms and two carbon atoms. In the fourth unit, called tetracarbosilicon, one silicon atom is bonded to four carbon atoms.

Although silicon oxycarbide glass is produced by thermal decomposition of a precursor resin containing polymerized trimethylsiloxy units and Q units in an arbitrary ratio, the ratio of trimethylsiloxy units to Q units in the precursor resin is not determined. It has been found that the composition and properties of silicon oxycarbide are affected. Precursor resins containing trimethylsiloxy units and Q units in a lower ratio than for the preferred precursor resins as described above, i.e., precursors containing trimethylsiloxy units and Q units in a ratio lower than about 0.7:1. If a body resin is used, an opaque silicon oxycarbide glass with a black appearance will be obtained.

When a suitable precursor resin containing trimethylsiloxy units and Q units in a ratio of 0.7:1 or greater is pyrolyzed, about 18 to 28% (by weight) of Te1-Laoxysilicon,
Polyatomic units comprising about 2% to 31% (by weight) monocarbosiloxane, about 12% to 22% dicarbosiloxane, and about 28% to 38% (by weight) tetracarbotylene. A translucent silicon oxycarbide glass is produced consisting of at least distributed silicon, oxygen and carbon and containing up to trace amounts of elemental carbon dispersed in the glass matrix in atomic states or in small rasters. Ru. Trace elemental carbon means an amount of elemental carbon that is insufficient to render the glass opaque, ie, to allow at least partial transmission of light through the glass.

Generally, such trace amounts are about 0. ] (by weight) The polyatomic units mentioned above are mainly bonded by silicon-oxygen bonds, and there are only a few bonds between carbon atoms and oxygen atoms.

Translucent glass like the one above is also about 73~83mm. A semi-semi-containing glass matrix in which each of the silicon atoms of the tongue is bonded to at least one carbon atom and up to trace amounts of elemental carbon are dispersed in the atomic state or in small rasters in the glass matrix. It can also be described as a composition of silicon, oxygen and carbon forming a transparent silicon oxycarbide glass mass.

To produce silicon oxycarbide glass products, the pyrolyzed precursor resin is pulverized. A desired product can be manufactured by combining the silicon oxycarbide glass powder thus obtained by hot compression. One example of a method for applying hot compaction is to apply a uniaxial pressure of at least about 5 ksi to the powder at a temperature of about 550-1600°C. The unit "rksi" represents the number of kilobonds per square inch, and 1k
si equals 1000 pounds per square inch. Such pressure-temperature conditions are sufficient to produce a densified product.

It is also possible to manufacture the molded part directly from the methyl silicone precursor resin. First, the precursor resin is dissolved in a solvent such as toluene and cast into the desired shape. The cast precursor resin is dried at room temperature and then slowly pyrolyzed in a non-oxidizing atmosphere as described herein. During such pyrolysis, low heating rates are used to prevent the formation of voids and air bubbles since gas evolution results in weight loss of the precursor resin. If the weight of the precursor resin is stabilized, the thermal decomposition will be complete.If a suitable precursor resin as described above is cast and thermally decomposed, Silicon distributed in polyatomic units such as
A translucent silicon oxycarbide glass consisting of at least oxygen and carbon is produced. However, when a precursor resin with a ratio of trimethylsiloxy units to Q units of less than 0.7:1 is cast and thermally decomposed, the resin exhibits a black appearance as a result of densification. An opaque silicon oxycarbide glass is produced.

Additionally, fibers can be formed from toluene solutions of precursor resins. If the precursor resin solution is treated with a base or acid to increase its viscosity, the strands of precursor resin can be drawn from the solution by dipping a solid object into the solution and then withdrawing it. Such a dipping method allows fibers to be formed from a precursor resin solution.

Alternatively, a mild vacuum can be used to draw the precursor resin solution into the Teflon tube. The fiber shrinks as the viscosity increases and the toluene evaporates, so it can be extruded from the Teflon tube. Approximately 50 such fibers
It can be strengthened by heating to ℃ to make it easier to handle. The fibers are then pyrolyzed in a non-oxidizing atmosphere as described above or in a vacuum.

Furthermore, it is also possible to produce ceramic composites containing ceramic fibers in a matrix of silicon oxycarbide glass and ceramic filler. That is, the infiltrating slurry is prepared by dissolving the precursor resin in a solvent and then dispersing particles of the ceramic filler in such solution.6 The particulate ceramic filler absorbs shrinkage of the matrix during pyrolysis. It is for adjusting,
The matrix may be selected so that it is compatible with the reinforcing fibers to be used. Examples of ceramic fillers include silicon carbide powder, diatomaceous earth, and an aluminosilicate called mullite (2Si02.3A1□○,).

Ceramic fibers (or fabrics made of such fibers) are then passed through the agitation slurry for infiltration. Examples of ceramic fibers include carbon fibers, silicon carbide fibers, and aluminoborosilicate fibers.6 After the impregnated fibers are shaped, the solvent is evaporated by drying. One example of a forming method is to spirally wrap the impregnated fibers onto a drum to form a panel. If the layers of fibers are combined by heating and pressure,
A continuous resin matrix can be formed that surrounds the ceramic fibers. The loose composite material is then pyrolyzed in a non-oxidizing atmosphere as described above or in vacuum. The precursor resin densifies to form a substantially amorphous silicon oxycarbide glass that binds the ceramic fibers, resulting in the formation of a continuous matrix around the fibers. Depending on the pyrolysis temperature used, the ceramic filler exhibits a dispersed, partially sintered or completely sintered state in the glass matrix.

If desired, by re-infiltrating the ceramic composite with a solution of the precursor resin in a solvent.
It can reduce its porosity. That is, the composite material is immersed in a re-penetration solution under vacuum conditions.

At that time, the solution is forced into the pores of the composite material by applying pressure.

After evaporation of the solvent, the re-infiltrated composite material is pyrolyzed in a non-oxidizing atmosphere as described above or in vacuum. By repeating such re-penetration and thermal decomposition as many times as necessary, the density of the matrix can be increased to a desired level.

The matrix of amorphous silicon oxycarbide glass and ceramic filler surrounds and protects the ceramic fibers, so that they decompose even in oxidized W surroundings and reducing atmospheres with temperatures up to at least 61,600'C. There's nothing left to do.

Silicon oxycarbide glass is chemically inert, so
It has been found that it is possible to embed ceramic fibers without reacting with them and degrading their properties. the result,
Silicon oxycarbide glasses containing suitable ceramic fillers can be used as a matrix for many known ceramic fibers.

After reading the detailed description below with reference to the attached drawings:
The invention will be more easily understood.

DETAILED DESCRIPTION OF THE INVENTION Glass can be defined by two basic characteristics. The first characteristic is that the glass is produced from an extremely viscous supercooled liquid. The second feature is that the glass-forming liquid has a network polymer structure that exhibits short-range order. Although the glass of the present invention is not produced from a supercooled liquid, it has a network polymer structure exhibiting short-range order9. It is produced by thermally decomposing a methyl silicone precursor resin in the silicone.

However, the glasses of the present invention exhibit short-range ordering properties found in common glasses.

Silicone resins have three-dimensional structures that exhibit short-range order, and they can be described using stoichiometric compositions. Stoichiometric units in silicone resins contain oxygen atoms and silicon atoms bonded to organic groups.

In silicone resins that can be thermally decomposed to produce glass, organic groups are limited to li hydrocarbon groups and monovalent halogenated hydrocarbon groups. Examples thereof include alkyl groups (f, such as methyl, ethyl, propyl, isopropyl, butyl, octyl, dodecyl, etc.), cycloalkyl groups (such as cyclopentyl, cyclohexyl, cyclohebutyl group), aryl group (e.g. phenyl group, naphthyl group, tolyl group, xylyl group, etc.), aralkyl group
For example, benzyl group, phenylethyl group, phenylpropyl group, etc.>, halogenated derivatives of the aforementioned groups (e.g. chloromethyl group, trifluoromethyl group, chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluoro Phenyl group, etc.
and alkenyl groups (for example, vinyl groups, allyl groups,
metallyl group, butenyl group, pentenyl group, etc.).

The four types of basic units present in silicone resins are an M unit in which one silicon atom is bonded to one oxygen atom and three organic groups, an M unit in which one silicon atom is bonded to two oxygen atoms, and A D unit formed by bonding to two organic groups, a T unit formed by one silicon atom bonded to three oxygen atoms and one organic group, and a T unit formed by one silicon atom bonded to four oxygen atoms. It is a Q unit formed by combining . Silicone resins capable of producing glass by thermal decomposition are composed of M units, T units, It is a combination of D units and Q units.

The glasses of the present invention are structurally stable at temperatures up to at least 16 JIIO°C and are therefore less susceptible to devitrification. "Structurally stable" here means that the bulk material maintains essentially the same microscopic structure within the range from room temperature to the specified high temperature. This means that minute changes in the microscopic structure For example, minute changes such as small crystallized regions of up to about 100 angstroms formed in an amorphous matrix,
has little effect on the properties of the bulk material, therefore
The structurally stable glasses of the present invention are essentially amorphous, but may contain small crystallized regions (e.g., consisting of graphite, cristobalite or silicon carbide) in the glass matrix. Alternatively, it may contain small amounts of cristobalite present on the glass surface.

In the present invention, silicon oxycarbide glass products can be manufactured according to several methods.

According to one method, a powder with a particle size of 0.1 to 2 microns is prepared by milling the precursor resin after pyrolysis. To achieve particle sizes of 0.1 to 2 microns, a grinder such as an attrition mill or a planetary mill can be used.

In an attrition mill, about 52% liquid (e.g. water), about 35% grinding media (e.g. 1.2 n+m diameter spheres harder than the material to be ground), and the balance crushed silicon oxycarbide. A mixture of glass particles is stirred by an impeller.

Stirring the mixture at a speed of 1000 rpm will pulverize the glass particles into a powder. In a planetary mill, a similar mixture is prepared, except that spheres with a diameter of 5 to 8 mm are used as the grinding medium, and the agitation is carried out by rotating the grinding vessel at a slow speed in a planetary manner.

The powder thus obtained is dried and combined by heating and pressure to obtain a molded article.

To do so, apply a uniaxial pressure of at least about 5 ksi at a temperature of about 1550-1600'C, or alternatively a temperature of about 1200-1600'C and at least about 8 ksi.
The heating and pressurization may be carried out under isobaric compression under a pressure of ksi until the product is densified to the desired degree.
Alternatively, it is continued until the product is completely densified.

According to another method for producing silicon oxycarbide glass products from cast or shaped precursor resins, a methyl silicone precursor resin is dissolved in a solvent and cast into the desired shape. . Examples of solvents that have been found suitable for dissolving the precursor resin include toluene and a mixture of toluene and isopropyl alcohol. The precursor resin can be dissolved in up to about 8 parts to 5 parts of solvent. The precursor resin after casting is dried at room temperature. Note that it is preferable that the over-drying be performed at a rate that allows the solvent to evaporate without forming voids in the precursor resin. In order to evaporate the solvent without forming voids in the precursor resin during drying, it is possible, for example, to place the precursor resin solution in a cylindrical dish with one end open and cover the open end with a piece of paper. It turned out to be good. Alternatively, the precursor resin, which is usually in powder form, can be formed by hot pressing.

The cast precursor resin is then pyrolyzed in a non-oxidizing atmosphere as described herein.

The heating rate during pyrolysis needs to be adjusted to allow gas to be released without forming voids or bubbles in the precursor resin. Preferably, a heating rate of less than 1.0° C. per minute is used to allow sufficient gas evolution without creating bubbles, voids or defects in the glass. Pyrolysis is substantially complete when weight loss due to release of water, methyl groups, and other decomposition products from the precursor resin has substantially ceased. Such pyrolysis may be continued until the glass is completely densified, ie until the volume ceases to decrease.

The precursor resin becomes densified upon pyrolysis and forms silicon oxycarbide glass.

EXAMPLE To explain in more detail the silicon oxycarbide glass and the process for producing glass and glass products of the present invention,
Examples are shown below. In these examples, four precursor resins were used which were prepared by the method described in U.S. Pat. To explain in detail, the first
The precursor resin consists of M units and Q units present in a ratio of about 0.5+1, the second precursor resin consists of M units and Q units present in a 1:1 ratio, and the third precursor resin The resin consists of M units and Q units present in a ratio of 2:1, and the fourth precursor resin consists of M units present in a ratio of 34.
unit and Q unit.

The methyl silicone precursor resin was pyrolyzed by heating to a temperature of 1100-1250°C in a non-oxidizing atmosphere. During pyrolysis, weight loss occurs due to the release of water, methyl groups and other decomposition products from the precursor resin. Pyrolysis is substantially complete when the weight of the precursor resin stabilizes. However, even after weight loss has ended, silicon oxycarbide glasses may undergo some densification. Therefore, heating and pyrolysis may be continued until the silicon oxycarbide glass is completely densified.The weight loss upon pyrolysis was measured and found to be in the range of approximately 17-54%. Ta. Note that part of the weight loss may be due to changes in the amount of solvent remaining from the time of preparation of the precursor resin.

Examples 1-4 The first, second, third and fourth precursor resins as described above were pyrolyzed according to the method of the present invention, with weight loss determined by thermogravimetric analysis. Thermogravimetric analysis is a method for measuring the weight loss of a sample during heating. The samples were heated to 1250'C in a hydrogen atmosphere at a rate of 10°C per minute. The measurement results of weight loss for each silicon oxycarbide glass obtained after pyrolysis are shown in Table 1 below.

Surprisingly, the second, third and fourth precursor resins consisting of M and Q units, respectively, present in a ratio of 1:1.2:] and 3:1 produce a translucent glass after pyrolysis. It has been found. The first precursor resin with an M/Q ratio of about 0.5:1 exhibited a black and opaque appearance after pyrolysis. Therefore, a precursor resin with an M/Q ratio of less than about 0.7+1 will produce a translucent silicon oxycarbide glass, whereas a precursor resin with an M/Q ratio of less than about 0.7:1 will produce a translucent silicon oxycarbide glass. is believed to produce an opaque silicon oxycarbide glass.

Mo5Q Hz MQ Hz M2Q Hz MsQ Hz 45 Black 17.5 Translucent 54 Translucent Not measured Translucent Example 1 The weight loss data obtained by thermogravimetric analysis in 2 and 3 are shown in the graph of FIG. In the graph of FIG. 1, the percentage weight loss of each sample is plotted on the vertical axis, while the increase in heating temperature is plotted on the horizontal axis.

Looking at the graph in FIG. 1, it can be seen that most of the weight loss for each sample occurred at temperatures up to 900°C, and that weight loss was nearly complete at 1200°C. According to X-ray diffraction analysis of the sample after pyrolysis, almost no crystallization was observed, and according to infrared spectroscopy analysis of the same sample, almost no bonding between carbon atoms and oxygen atoms was observed. . Note that the weight reduction in Example 4 showed the same pattern as in Examples 1.2 and 3.

The refractive index of the silicon oxycarbide glass sample of Example 2 was 1.58 when measured using sodium light having a wavelength of 5893 angstroms. Generally, glass is known to have a refractive index of about 1.5 to 1.9 at the sodium light wavelength of 5893 angstroms. The refractive index is the value obtained by dividing the phase velocity of an electromagnetic wave in free space by the phase velocity of the same electromagnetic wave in a particular medium.

Examples 5 and 6 The composition of various glasses can be roughly defined using the amount of each element present in the glass.

However, it is its short-range ordering properties that give glass its various properties. Therefore, by determining the short-range order characteristics in glasses, it is possible to define various types of glasses in terms of their properties. In Example 5, by measuring the proportion of polyatomic units (i.e., tetracarbosilicon, monocarbosiloxane, dicarbosiloxane and tetraoxysilicon) present in the translucent silicon oxycarbide glass according to the invention, , its short-range order properties are determined.

FIG. 2 shows the 29Si-solid state nuclear magnetic resonance spectrum recorded using the translucent silicon oxycarbide glass sample obtained in Example 2. FIG. 3 also shows a 29Si-nuclear magnetic resonance spectrum recorded using a sample of "Nicalon" silicon carbide fiber. On the vertical axis of FIGS. 2 and 3, the intensity of the electromagnetic waves measured for the excited sample is plotted. On the horizontal axis, the chemical shift from the tetramethylsilicon standard corresponding to its zero point is plotted in ppm. Chemical shift values of ppa+ units are known for many polyatomic units. For example, the chemical shift values for tetraoxysilicon, dicarbosiloxane and monocarbosiloxane are:
P. Deal and R. Kosfeldt (P, D
iehl & R, Kosfeld) m rNMR・
Basic Principles and Progress: 2
9Si-NMR Spectroscopic Results (
NMRBa5ic Pr1nciples and P
logress:29Si-NMR5pectrosc
(opic Re5ults) J (Schbringer-Verlag, Berlin-Heidelberg, 198
1 year> pages 186, 184 and 178. Therefore, each peak in Figures 2 and 3 represents a short-range ordering characteristic for a particular polyatomic unit.

The spectrum shown in FIG. 2 relates to the silicon oxycarbide glass obtained in Example 2 and includes peaks 1 to 4. Peak 1 is tetracarbosilicon, peak 2 is dicarbosiloxane, peak 3 is monocarbosiloxane, and peak 4 is tetraoxysilicon. By integrating the area under each peak, the proportion of each polyatomic unit present in the glass can be determined. Note that for the spectra in FIGS. 2 and 3, correction for background interference was performed prior to determining the area under each peak.

Integrating the area under each peak in the spectrum of FIG. 2, the composition of the silicon oxycarbide glass of Example 2 is approximately 33% tetracarbohydrate (expressed as a weight percentage with an error within approximately ±5%). It can be seen that silicon, about 17% dicarbosiloxane, about 26% monocarbosiloxane, and about 23% tetraoxysilicon.

Further, analysis of the nuclear magnetic resonance spectrum of such a glass shows that a large amount of elemental carbon is dispersed throughout the glass fB.

Let us examine the spectrum in Figure 3 recorded using a sample of "Nicalon" silicon carbide fibers in comparison with the spectrum in Figure 2. The composition of the "Nicalon" fiber shown in Figure 3 is (expressed as weight percentages) about 68% silicon carbide, about 8% dicarbosiloxane, about 17% monocarbosiloxane, and about 7% silicon carbide. It is made of tetraoxysilicon. As can be seen from the spectra 1 to 1 of FIG. 3, "Nicalon J fibers are mainly composed of silicon carbide, with low contents of dicarbosiloxane, monocarbosiloxane, and tetraoxysilicon.

In contrast, as shown by the spectra in Figure 2, silicon oxycarbide glasses contain, in addition to tetracarbosilicon, substantial amounts of dicarbosiloxanes, monocarbosiloxanes, and tetraoxysilicon. . Thus, silicon oxycarbide glasses exhibit unique short-range ordering properties that bond carbon and silicon in a manner not known in conventional glasses. This results in increased resistance to devitrification and decomposition, and is what characterizes the glasses of the invention.

The composition of the translucent silicon oxycarbide glass and "Nicalon" fibers obtained in Example 2 can also be described using the mole percentage of each polyatomic unit. Table 2 below shows the results of converting the compositions of these substances from weight percentages to mole percentages. In addition,
The compositions shown in Table 2 are ±5 (
weight)? It is believed that the error is within ±5 (mol)%.

Rai-i-inu monocarbosiloxane 26 26 17
1.3 Dicarposiloxane 17 17 8
Since the 7 molar units are based on molecular weight, mole percentages express the proportion of each polyatomic unit present in the sample on a molecular basis. Therefore, the proportion of gay atoms bonded to oxygen or carbon atoms can be determined using mole percentages. Oxycarbon of Example 5 (originally obtained in Example 2)
83? This means that the silicon atom of S is bonded to at least one carbon atom. However, in Nicalon J silicon carbide fiber, about 90 to 100% of silicon atoms are bonded to carbon atoms.

Example 7 Silicon oxycarbide glass was produced by pyrolyzing a methyl silicone resin containing 5% (by weight) D units and 95% (by weight) T units according to the method of the present invention. The silicon oxycarbide glass produced by densification of such resins contains (in weight percentages) about 39% tetraoxysilicon, about 24% monocarbosiloxane, about 22% dicarbosiloxane, and about 6% silicon oxycarbide. It consisted of tetracarbosilicon and about 3-9% elemental carbon dispersed in a glass matrix. It should be noted that silicon oxycarbide glass made from DT type methyl silicone resin is the subject of co-pending U.S. Patent Application No. 359,619.

In order to analyze the oxidation resistance and structural stability (or devitrification resistance) of silicon oxycarbide glass manufactured from the above-mentioned DT type methyl silicone resin, a hot-pressed sample of the glass was heated at 1400°C in air. and 1520℃
The mixture was heated for 240 hours. No weight loss due to decomposition of silicon or carbon present in the glass was observed. According to X-ray diffraction analysis of the cut surfaces, no internal crystallization was observed in any of the samples. Furthermore, X-ray diffraction analysis of the exposed surfaces revealed no crystallization (ie, formation of cristobalite) in the surface region to a depth of approximately 0.002 inches in any of the samples.

Although the silicon oxycarbide glass of Example 7 has a black appearance and has a different composition from the translucent silicon oxycarbide glass, it is due to the chemical bond between silicon atoms and carbon atoms. It contains no chemical bonds between carbon atoms and oxygen atoms. These points characterize the glass of the present invention.

Therefore, the silicon oxycarbide glass of Example 1 and the translucent silicon oxycarbide glasses of Examples 2.3 and 4 are
It is expected to have substantially the same devitrification resistance and decomposition resistance as the silicon oxycarbide glass obtained in Example 7.

[Brief explanation of drawings]

Figure 1 is a graph showing the weight loss during thermal decomposition of methyl silicone precursor resin, Figure 2 is a graph showing the 29Si nuclear magnetic resonance spectrum of translucent silicon oxycarbide glass, and Figure 3 is a graph showing the 29Si nuclear magnetic resonance spectrum of translucent silicon oxycarbide glass. ” is a graph showing a 29Si-nuclear magnetic resonance spectrum of silicon carbide fiber.

Claims (22)

[Claims] 1. Polyatomic units comprising about 12-31% (by weight) monocarbosiloxanes and dicarbosiloxanes, about 28-38% (by weight) tetracarbosilicon, and about 18-28% (by weight) tetraoxysilicon. at temperatures above about 1250°C, characterized by comprising silicon, oxygen and carbon distributed in a glass matrix and up to trace amounts of elemental carbon dispersed in the glass matrix and allowing at least partial transmission of light. and organizationally stable translucent glass. 2. about 18-28% (by weight) tetraoxysilicon, about 21-31% (by weight) monocarbosiloxane, about 12
~22% (by weight) dicarbosiloxane, and about 28%
A translucent glass as claimed in claim 1, comprising -38% (by weight) of tetracarbosilicon. 3. About 73-83% of the silicon atoms each contain at least 1
a structurally stable semi-container at temperatures above about 1250°C, characterized by consisting of silicon, oxygen and carbon forming agglomerates of silicon oxycarbide glass bonded with 1,250 carbon atoms. transparent glass. 4. M units and Q present in a ratio of about 0.7:1 or more
providing a methyl silicone precursor resin consisting of units, heating the precursor resin in a non-oxidizing atmosphere using a temperature that results in thermal decomposition of the precursor resin, and reducing the weight due to the thermal decomposition of the precursor resin. A translucent silicon oxycarbide glass that is structurally stable at temperatures of about 1250° C. or higher by continuing said heating for a period of time until the reduction is substantially stabilized. Glass manufacturing method. 5. 5. A method according to claim 4, wherein said heating is carried out at a temperature of 900-1600<0>C. 6. 5. The method of claim 4, wherein said heating is continued for a period of time until said precursor resin exhibits a weight loss of about 17-54%. 7. 5. The method of claim 4, wherein said heating is continued for a period of time until said precursor resin is fully densified. 8. 5. The method of claim 4, wherein said heating is performed in a hydrogen gas atmosphere. 9. 5. The method of claim 4, wherein said precursor resin consists of M units and Q units present in a ratio of about 0.7:1 to about 3:1. 10. (a) dissolving a methyl silicone precursor resin comprising M units and Q units present in a ratio of about 0.7:1 or greater in a solvent; (b) molding the precursor resin into a desired shape; c) evaporating the solvent from the precursor resin after molding, and then (d) heating the precursor resin in a non-oxidizing atmosphere using a temperature that results in thermal decomposition of the precursor resin, and A method for producing a translucent silicon oxycarbide glass product, comprising the steps of continuing the heating for a period of time until weight loss due to thermal decomposition of the precursor resin substantially ends. 11. 11. The method according to claim 10, wherein the heating step is carried out at a temperature of 900 to 1600<0>C. 12. 11. The method according to claim 10, wherein the heating step is performed in a hydrogen gas atmosphere. 13. Claim 1 wherein said heating step is carried out at a heating rate that minimizes the formation of voids in said glass.
The method described in 0. 14. 11. The method of claim 10, wherein the heating step is continued for a period of time until the precursor resin exhibits a weight loss of about 17-54%. 15. 11. The method of claim 10, wherein the heating step continues for a period of time until the precursor resin produces a fully densified glass. 16. 11. The method of claim 10, wherein the heating step is performed at a heating rate of less than about 1<0>C per minute. 17. 11. The method of claim 10, wherein the precursor resin consists of M units and Q units present in a ratio of about 0.7:1 to about 3:1. 18. about 18-28% (by weight) of tetraoxysilicon,
about 21-31% (by weight) monocarbosiloxane, about 1
2-22% (by weight) dicarbosiloxane, and about 2
A glass fiber characterized in that it consists of silicon, oxygen and carbon distributed in polyatomic units containing 8-38% (by weight) of tetracarbosilicon. 19. about 18-28% (by weight) of tetraoxysilicon,
about 21-31% (by weight) monocarbosiloxane, about 1
2-22% (by weight) dicarbosiloxane, and about 2
At least one ceramic fiber in a matrix consisting of oxycarbide glass consisting of silicon, oxygen and carbon distributed in polyatomic units containing 8 to 38% (by weight) of tetracarbosilicon and a ceramic filler A ceramic composite material characterized by: 20. providing a methyl silicone precursor resin consisting of M units and Q units present in a ratio of about 0.7:1 or more;
heating the precursor resin in a non-oxidizing atmosphere using a temperature that results in pyrolysis of the precursor resin and for a period of time until the pyrolytic weight loss of the precursor resin substantially stabilizes; produced by the method comprising continued heating, characterized in that it is made of silicon, oxygen and carbon chemically bonded in a state where there is substantially no chemical bond between oxygen atoms and carbon atoms; A translucent glass composition that is structurally stable at temperatures of about 1250°C or higher. 21. providing a methyl silicone precursor resin consisting of M units and Q units present in a ratio of up to about 0.7:1;
heating the precursor resin in a non-oxidizing atmosphere using a temperature that results in pyrolysis of the precursor resin and for a period of time until the pyrolytic weight loss of the precursor resin substantially stabilizes; produced by the method comprising continued heating, characterized in that it is made of silicon, oxygen and carbon chemically bonded in a state where there is substantially no chemical bond between oxygen atoms and carbon atoms; A glass composition that is structurally stable at temperatures of about 1250°C or higher. 22. providing a methyl silicone precursor resin consisting of M units and Q units present in a ratio of up to about 0.7:1;
heating the precursor resin in a non-oxidizing atmosphere using a temperature that results in pyrolysis of the precursor resin and for a period of time until the pyrolytic weight loss of the precursor resin substantially stabilizes; A method for producing glass, characterized in that by continuing the heating, a structurally stable silicon oxycarbide glass is produced at a temperature of about 1250° C. or higher.