JPH05507263A - Coated fire-resistant composition and method for producing the 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 provides refractory metal carbides, refractory metal nitrides, refractory metal borides, or High quality material selected from diamond and containing refractory material with a coating layer of hydrated alumina coated refractory compositions for making quality preforms, in particular such to increase the dispersibility of compositions and to improve their oxidation resistance and chemical inertness. Regarding the method.

Another aspect of the present invention is a first coating layer of calcium component and a second coating layer of alumina component. and, in particular, a composition comprising a refractory substrate having a first base of calcium pyrophosphate. A coating layer and a second coating layer of hydrated alumina are deposited on an alpha alumina substrate. The present invention relates to a method for improving the strength of ceramic composites by comprising:

Upon firing of the composition, the second coating converts to the form of anhydrous crystalline alumina. .

Ceramic composites are typically silicon carbide, silicon nitride, aluminum silicates, Based on ceramic preforms based on aluminum oxide or mixtures thereof. fee. These preforms are embedded in a ceramic matrix and Form a complex.

Although ceramic composites are known to lose their strength at higher temperatures, This problem is still unresolved. All useful properties are acquired at the beginning of ceramic processing Occurs in stages.

The structural integrity of each material is subject to various thermal and mechanical stresses. must be maintained throughout.

Thus, a need exists for high temperature, high strength materials.

The unique properties of the present invention are that the ceramic matrix has unpredictable strength and toughness. makes it possible to use this composition as a preform for complexes Ru. Unpredictable results can result from delamination between the preform and the matrix. This is due to the coating, and this peeling action suppresses crack propagation in the composite. bring about limitations.

U.S. Pat. No. 4,249,913 discloses bonding metal matrices during high temperature processing. silicon carbide abrasive particles coated with alumina to prevent dissolution in the solution. Disclosed.

Alumina coatings are described as dense, anhydrous amorphous coatings; This coating is applied by a sputtering or vapor deposition process.

U.S. Pat. No. 4,801,510 discloses that 5-30% by weight of silicon carbide whiskers and , 70-95% by weight of alumina; It has a thin coating of Silicon carbide and alumina in the composite are processed by ball milling. The mixture is hot-pressed into a dense composite, and then alumina is deposited using vapor deposition technology. Cover with a thin film.

Summary of the invention The present invention provides refractory metal carbides, refractory metal nitrides, refractory metal borides, or High quality material selected from diamond and containing refractory material with a coating layer of hydrated alumina Coated refractory compositions for making quality preforms, thereby The coating layer improves the dispersibility of the composition. Furthermore, the present invention provides anhydrous crystalline alkali A fired composition comprising said refractory material having a coating layer of The coating further increases the oxidation resistance and chemical inertness of such compositions. Improve to.

Another aspect of the invention is directed to a method for manufacturing said composition comprising the steps of: shall be.

(a) The process of coating an aqueous suspension of finely ground refractory material with hydrated alumina. Cheng, (b) separating, washing and drying the coated refractory; and (c) Optionally baked for at least 1 hour at a temperature in the range 400-1100°C. The process of forming.

Yet another aspect of the present invention provides a first coating layer of calcium component and a second coating layer of alumina component. The present invention relates to a composition comprising a refractory substrate having a coating layer deposited thereon. The present invention further The first and second coatings form a new material, a portion of which is composed of anhydrous crystalline alumina. The target is a fired composition.

Another aspect of the invention provides a method for improving the strength and toughness of ceramic composites. , the method includes the following steps:

(a) Prepare an aqueous mixture of a refractory substrate, a calcium component precursor, and an aluminum salt a step of (b) collecting, washing and drying the coated refractory composition;

A further firing process forms a refractory composition coated with anhydrous crystalline alumina. be done.

This is a transmission electron micrograph of an object.

FIG. 2 shows a transmission pattern of the fired coated refractory composition produced by the method of the present invention. This is an electron micrograph.

FIG. 3 is a graphical diagram illustrating the higher isoelectric point of the coated refractory composition of the present invention.

4A and 4B illustrate the improved oxidation resistance of the coated refractory compositions of the present invention. Thermogravimetric analysis plot.

Detailed description of the invention The present invention provides coatings that exhibit enhanced dispersibility and improved oxidation resistance and chemical inertness. The composition includes a refractory metal carbide, a refractory metal carbide, and a refractory metal carbide. Hydrated alumina, selected from nitrides, refractory metal borides, and diamonds; In other words, the mixture of fine crystals of boehmatite and hydrated crystalline amorphous alumina Contains a fire-resistant material with a composite coating layer.

The coating raises the isoelectric point of the composition to that of alumina. The isoelectric point is It is defined as the pH at which the potential is zero. The increased isocenter and surface area is Related to increased dispersibility of compositions in water or solvent systems, e.g. during refractory production. In the slip casting process, it produces a useful and stable aqueous dispersion.

Refractory material, i.e. the substrate is finely powdered, with an average particle size of 1-2500 μm It is a crushed solid. Generally, the refractory substrate has a It has a surface area.

For best results, the refractory substrate has a surface area of 0.2 to 10 m2/g . In carrying out the invention, useful refractory materials include refractory metal carbides, refractory metals, etc. metal nitrides, refractory metal borides, or diamonds. For example, silicon carbide A refractory carbide such as is a suitable substrate. Other refractory carbides, these are Although stable in aqueous media, titanium carbide, tantalum carbide, niobium carbide, Zirconium carbide, tungsten carbide, molybdenum carbide, vanadium carbide, carbide Hafnium, thorium carbide, uranium carbide, and the like are suitable substrates. Sara In addition, diamond, titanium, zirconium, and silicon react with water. non-refractory nitrides, and non-water-reactive materials such as titanium and zirconium. Refractory borides can be coated with hydrated alumina by the method of the present invention .

The shape of the refractory particles can vary such as equiaxed, acicular and plate-like. appropriate The substrate has equiaxed particles in the size range of 1 to 2500 μm, an aspect ratio of 2 to 200 μm. acicular particles with an average diameter of 0.1 to 12 μm and an asymmetry of 5 to 200 They are plate-like particles having a spectral ratio and an average diameter of 5 to 2500 μm. Furthermore, the resistance Flammable substrates must not be soluble in water or dilute acids or bases.

The coating on the refractory substrate is composed of hydrated alumina, i.e. bomatite alumina and hydrated alumina. Contains a layer of mixture with amorphous alumina. The coating amount is 0.2 to 12% by weight. Typically, the amount is 3 to 6% by weight of the total acid group. Hydrated Alumina Coating Boma It is a mixture of tight, fine crystals and hydrated amorphous alumina, and therefore The surface area is larger than the specific surface area of the refractory particles, and is within the range of 0.5 to 40 m2/g. Typically, it is 2 to 15 m2/g.

The invention further provides that the coating is eta, theta, gamma, or Anhydrous crystalline alumina, such as alpha phase, or transition mixtures thereof, calcined The target composition is Unfired or fired compositions also have high strength, high toughness. Useful for the preparation of metallic matrix and ceramic matrix composites It is. The coating increases the surface area and isocenter of the alumina composition and increases It provides dispersibility, which allows uniform preforms to be obtained.

The enhanced dispersibility is due to the raised isoelectric point of alumina and the coated resistance. Based on the surface area of the fire. High-quality preforms are used in the production of high-performance composites. can be done. The coating also has a protective effect, for example refractory carbide protected from surface oxidation during high temperature processing under conditions of The fired coating composition is Shows improved oxidation resistance.

Another aspect of the invention is to increase the dispersibility of the composition in water or in a solvent system. and methods for improving the oxidation resistance and chemical inertness of said compositions. do. According to this method, the following steps are included in order to implement the present invention.

(a) forming an aqueous suspension of the refractory material and heating it to a temperature within the range of 40 to 95°C; , adjusting the pH within the range of 5 to 9; (b) While stirring and maintaining temperature and pH for 5 to 60 minutes, substantially Alkali metal aluminate, ammonium aluminate, aluminum chloride, aluminium nitrate of an aluminum salt selected from the group consisting of aluminum, and aluminum acetate. adding an aqueous solution, thereby depositing a hydrated aqueous solution on the surface of the refractory material as a coating layer. (c) separating and washing the coated refractories; a step of drying at 300°C, and (d) Optionally baked for at least 1 hour at a temperature ranging from 400 to 1100°C. The process of forming.

In the practice of the invention, an aqueous suspension of finely ground refractory material is prepared. . The solid concentration in an aqueous suspension is not particularly critical; It can be in the range of 1000g. All hydrated aluminum oxides produced of hydrated aluminum oxide to form a coating on the particles rather than a separate precipitate. is produced in the presence of suspended particles at a carefully controlled rate. acidic or basic Any of the water-soluble aluminum salts may be used as an aluminum oxide source For example, alkali metal aluminates, ammonium aluminate, ammonium chloride These include aluminum, aluminum nitrate, and aluminum acetate. aluminum salt An aqueous solution of aluminum is prepared and contains aluminum equivalent to 5-40% by weight Al2O3. sample and added to the aqueous suspension. If acidic aluminum salt is used, add alkali Add simultaneously and maintain the pH again in the range 5-9 during the coating process. Aluminic acid In the case of salts, the acid is added simultaneously while maintaining the pH in the range of 5-9 during the process. Added. Preferred aluminum oxide sources are sodium aluminate or aluminum mineral acids, typically hydrochloric acid, are added to these.

The aqueous suspension of refractory material is heated to a temperature in the range of 50-95°C and a pH of 5. It is adjusted to a range of ~9. Typically the pH will be within this range, if less than 5. If it exceeds 9, add a few drops of diluted base, and if it exceeds 9, add a few drops of diluted acid. to within the desired range. Add alkali metal aluminate to the stirred suspension. The salt solution is treated with a mineral acid, e.g. 5-20% H Add dropwise with CI. The thickness of the hydrated alumina coating layer is It is a function of the amount of alkali aluminate added. a temperature of 60-90°C, and 7 ．． At a mixture pH of 5 to 9, hydrated alumina typically has a rate of between 2 and 3% by weight. degree, the suspended refractory particles will be deposited on the surface. When the addition is complete, The suspension is stirred for 5-60 minutes while maintaining a similar temperature and pH range. This work The step stabilizes the hydrated alumina coating on the slurry particles.

The coated particles are then isolated, i.e. separated by filtration or centrifugation. , washed with water until free of soluble ions, especially sodium ions or chloride ions. and dry by heating to 100-300°C.

The final calcination step is optional; upon calcination, the composition is further exhibits improved oxidation resistance.

The refractory composition covered with the hydrated alumina coating is exposed to air for at least one hour or Calcinate by heating to 400-1100℃ in an inert atmosphere such as nitrogen. Ru. Calcining densifies the coating layer and causes a decrease in the specific surface area. decrease in surface area The extent depends on the time and temperature of the heating cycle. The coating was heated when the composition was heated. Anhydrous in gamma, eta, theta, or alpha alumina phase depending on temperature Transforms into crystalline transition alumina or transition mixtures thereof. fired composition may be further subjected to a coating process, and the entire process is completed to further improve oxidation resistance. May be repeated.

The isoelectric point of the compositions of the invention is a useful measure of surface charge.

A stable aqueous dispersion of particles in water or a solvent system has an isoelectric point in the range of about 6 to 9. It is obtained with particles that The isoelectric point determines the zeta potential of suspended particles over a range of pH. Determined by measuring the pH at which the zeta potential is zero. It will be done.

The coated refractory particles of the present invention exhibit an isoelectric point in the range of about 6-9. In contrast to this Therefore, the isoelectric point of uncoated refractory particles is usually less than 3. For example, SiC table The surface is between 2.0 and 2.5, reflecting the presence of silicon dioxide on its surface.

Referring to the drawings as an example, FIG. ); similar silicon carbide with hydrated alumina coating (plot B); and fired Similar with hydrated alumina coating where the coating is changed to crystalline anhydrous gamma alumina FIG. 2 is a graphical representation of zeta potential measurements of an aqueous dispersion of silicon carbide (Plot C).

The isoelectric point is 2.3 in plot A, 8.6 in plot B, and 8.6 in plot C. appears at 8.6, which means that the coated product has a lower isoelectric point than that of the original silicon carbide. This shows that it has a fairly high isoelectric point. The isoelectric point of 8.6 is the characteristic of alumina coating. It is a sign.

The improved oxidation resistance of the refractory carbide particles is demonstrated by thermogravimetric analysis (TGA) plots. It is clear from Figures 4A and 4B that they are 500 grit silicon carbide powder. The plot obtained for powder (Fig. 4A) and similar powder coated with hydrated alumina (Figure 4B). The temperature increase rate is up to 1000℃. and then kept at 1000°C for 1 hour with an air flow of 100cc/min. It was a minute. Figure 4A shows a mass increase of 0.36%, which is due to the silicon carbide particles This is thought to be due to surface oxidation. Hydrated alumina-coated silicon carbide is Approximately 2% mass, reflecting the dehydration of the lumina coating and its transformation to crystalline anhydrous transitional alumina. Shows a decrease.

The second composition includes a first coating layer of a calcium component and an alumina component deposited thereon. It is a fire-resistant substrate having a second coating layer of. Refractory substrates such as alpha alumina It may also be a high temperature crystal form of alumina. Aluminum, titanium, zirconium silicon oxides, carbides, borides, and nitrate surfaces covered with alumina coating. If so, it is a suitable substrate. The substrate has a wide range, depending on the shape of the particle. That is, the average particle size can vary from 0.1 to 2500 μm. It is a finely ground powder with a Particle shape can also be varied, That is, the particle shape can be equiaxed, needle-like, or plate-like. α alumina In the case of particles, calcium or sodium or beta alumina is present in the refractory substrate. You may. Additionally, the refractory substrate must not be soluble in water, dilute acids or bases. No. The surface area of the particles ranges from 0.02 to 20 m2/g. best results has 0 particles. This is achieved when the area is 1 to 20 m2/g.

The first coating contains a calcium component, e.g. calcium birophosphate, calcium phosphate. Amorphous refractories such as aluminum, calcium silicate, and calcium aluminate Contains natural calcium components. The second outermost coating is an alumina component, e.g. hydrated alumina, which may be alumina, boumatite, or mixtures thereof. No. The first and second coatings can be in amounts from 0.5 to 25% by weight, typically It is 8 to 12% by weight of the total acid group. The ratio of the first coating to the second coating is 0 by weight. ．． The range is 0.01 to 0.95.

Referring now to the drawings, FIG. 1 shows the refractory composition obtained by the method of the present invention. This is a transmission electron micrograph of an object. This micrograph reveals the coating layer on the substrate. That's it.

Figure 2 shows a refractory composition with a fired coating produced by the method of the invention. This is a transmission electron micrograph. The coating layer is dense and has a hydrated alumina part. has been converted to an anhydrous crystalline alumina coating.

Another aspect of the invention is a method of making the above.

The first step in carrying out the invention is to prepare a refractory substrate, a calcium component, and a soluble The method is to prepare an aqueous mixture of aluminum salts. In practicing the invention, An aqueous suspension of a flammable substrate is prepared. Commercially available plate-shaped α-alumina is used as the substrate. This is possible and preferred from the standpoint of cost, convenience, and operability. water-based suspension The concentration of particles in the suspension is not particularly critical, and is 100 to 10 per liter of water. 00 grams. The aqueous base suspension is heated to a temperature ranging from 40 to 90°C. and adjust the pH to a range of 5 to 9. Typically, the pH is in this range However, if the pH is less than 5 or more than 9, diluted acid or The pH is brought within the desired range by adding a few drops of dilute base.

Next, add the calcium salt and the desired alkali metal pyrophosphate, phosphate, or silicic acid. Prepare aqueous solutions with salts, aluminates, or mixtures thereof. sodium salt Preferably, the concentration can range from 50 to 200 g/u. For example, Piro Sodium phosphate crystals are suitable as a source of phosphoric acid. Soluble sodium silicate When selected as a metal silicate, the molar ratio of SiO/Na2O is 3.2471. A clear aqueous solution of can be used. In the case of sodium aluminate, 5 to A solution containing an amount corresponding to 40% by weight A 1203 may be used. Also, chloride Soluble calcium, such as calcium, calcium nitrate, or mixtures thereof Prepare an aqueous solution of the desired concentration of mu salt. While stirring, remove the desired alkali metal. The phosphate, silicate, or aluminate solution and the calcium salt solution are heated at the same temperature. to the aqueous suspension at the same rate, maintaining a similar range. pH is HCI ( 10-20%) kept between 5-9. This process is , carried out slowly over 1 to 3 hours. After the addition is complete, continue stirring and Maintain the same temperature range and pH for 60 minutes. Under these conditions, the substrate Depending on the alkali metal selected, e.g. amorphous calcium spirophosphate , calcium phosphate, calcium silicate, or calcium aluminate, or coated with a layer of these mixtures.

Thereafter, an aqueous solution of aluminum salt is prepared. Acidic or basic water-soluble aluminum Any of the nium salts can be used as the aluminum oxide source. example For example, alkali metal aluminate, ammonium aluminate, aluminum chloride, These include aluminum nitrate, aluminum acetate, and mixtures thereof. The solution used The liquid contains 5-40% by weight aluminum corresponding to A1203. acidic aluminum When using nium salts, add alkali at the same time to bring the pH to 5 during the coating process. Maintain in the range of ~9. In the case of aluminates, the pH is maintained at 5-9 throughout the process. Add acid at the same time while maintaining Preferred AI 203 sources are sodium or is an aluminate of potassium and a mineral acid, typically HCI, is added.

Hydrated aluminum oxide is a product in which all of the formed hydrated aluminum oxide is precipitated. The first coating is carefully controlled so that it covers the substrate rather than forming a occurs in the presence of the suspended first coated substrate. desired calcium The suspension of particles coated with the coating composition is heated to a temperature in the range of 50 to 95°C and a temperature in the range of 5 to 9°C. The pH is maintained at ambient temperature. Add aluminum salt solution drop by drop to the stirred suspension and maintain the pH between 5 and 9. The thickness of the hydrated alumina coating layer is It is a function of liquid concentration, temperature, mixture pH 1 and time. With a temperature of 60-90°C At a mixture pH in the range of 7°5 to 9, the hydrated alumina is typically 2 to 3 wt. % will deposit on the surface of the suspended refractory particles. Addition complete and stir the suspension for an additional 5 to 60 minutes while keeping the temperature and pH in the same range. do. This curing step stabilizes the hydrated alumina coating layer and this coating It is a mixture of amorphous alumina and bomatite alumina on solidified particles. Ru.

The coated particles are then isolated by filtration or centrifugation to remove soluble ions, Wash with water until especially sodium and chloride ions are removed, and heat to 100-300℃. Dry by heating.

The particulate composition has a composite coating of amorphous calcium and hydrated alumina. The coating is heated to 400-1100°C for at least 1 hour. Can be fired by heating. The coating is densified and the alumina is As a result, anhydrous crystalline alumina is formed.

The following procedure was used to characterize the products of the invention. The specific surface area is B Measured by ET nitrogen adsorption method.

Isoelectric point measurement is known as the PenKen System, Inc., Bedford Hills.

using an automatic electrokinetics analyzer manufactured by N.Y. It was carried out. This device measures the electrophoretic mobility of particles in dilute suspensions. Ta. Measurements should be made at different pH and the results plotted on a graph. The isoelectric point, that is, the pH at which the zeta potential became zero, was confirmed. thermal weight Analysis (TGA) was performed by DuPont M.

The analysis was carried out using a de1951 thermogravimetric analyzer. EDAX method is used for elemental analysis. Using. X-ray diffraction was used to identify the crystalline phase present.

The composition and manufacturing method of the present invention are explained in detail by the following examples. It is not intended to limit the scope of the disclosure. Each raw material of Examples 5 to 9 The composition is then calcined at a temperature in the range of 400-1100°C for at least 1 hour. It was.

Example 1 This example describes the production of a SiC refractory material coated with hydrated alumina.

500-grid SiC powder (Norton) with a specific surface area of 0.56 m2/g Company grade 1100GI) 475 while stirring well. 1 beaker to 3g of water. A stirred aqueous suspension of SiC was heated to 65°C. Heat and adjust pH to 8.5. Sodium aluminate [NaA 1 (OH) , 0.385 g A I 203 / c c equivalent, Vinings Co rp) suspension was added to the SiC suspension, and 20% MCI was added at the same time. Therefore, the pH was kept at 8.5. N a A I (OH) for about 1 hour After adding 50ml of the 4 solution, at pH 8.5 and temperature 65℃, for another 30 minutes. The suspension was stirred for a while. All AI 203 precipitates on StC, which is , corresponding to 3.89% by weight Al2O3 on product basis. To remove solids, filter the suspension. Collect by filtration until sodium ions and chloride ions are removed. Washed with deionized water. SiC coated with hydrated alumina was exposed to heat at 120°C in air. It was dried in an oven overnight.

Compared to 0.56 m2/g for the starting SiC, the product is It was found to have a surface area of 10.6 m2/g as measured by the method.

The isoelectric point (IEP) was determined using an automatic electrokinetics analyzer (PenK). en System 3000. Pen Ken Inc., Bedford Hills, N.

Y,) were measured on aqueous dispersions of particles. Starting SiC is 2.3 I EP and the IEP of the coated product was 8.6.

Thermogravimetric analysis (TGA) was performed using a DuPont Model 1951 thermogravimetric analyzer. This was done using The heating rate was 10°C/min up to 1000°C, then 10°C/min. The temperature was kept at 00° C. for 1 hour, and the air flow was 100 cc/min. uncoated Si C showed a weight increase of 0.36% due to surface oxidation. Alumina coated S iC showed a mass loss of approximately 2% due to dehydration of the hydrated alumina coating.

Example 2 This example demonstrates the manufacture of fine-grained SiC refractory material coated with hydrated alumina. Describe the structure.

Using the procedure of Example 1, Exalon ES with a surface area of 2.3 m2/H 500g of K #1200 SiC was used. Add sodium aluminate solution The time required was 2 hours.

The product has a surface area of 17°4 m2/g compared to 2.3 m2/g of the starting SiC. was found to have the following.

Example 3 This example describes the production of TIB 2 refractory material coated with hydrated alumina. Bell.

Using the procedure of Example 1, TIB 2 powder with a surface area of 0.53 m2/g Use 500g of powder (Union Carbide Grade HCT-30) did. The time for adding the sodium aluminate solution was 2 hours.

Ta.

Example 4 This example describes the production of a diamond refractory material coated with hydrated alumina. Ru.

25 g of diamond powder (Beta Diamond Products, In c, Grade 5JK-5) in a 1g beaker on a hot plate. 00 cc of deionized water. The beaker is equipped with a stirring blade and a pH probe. It was something like that.

The slurry was heated to 65°C.

The pH of the slurry was adjusted to 8.2 by adding 5 drops of 20% NaOH solution.

Sodium aluminate containing 0.385gA1203/mt over 2 hours 0.9 ml of the solution (Vinings, Corp.) was added dropwise to the stirred bath. . The pH was maintained at 8.2 using MCI (0.1M).

After the aluminum coating was applied, the system was stirred for 30 minutes at pH 8,2/65°C. The coating was cured.

The coated diamond powder is collected by filtration until free of chloride residues. and dried at 120° C. for 2 hours. The coated diamond powder is 4. It had a surface area of 2 m2/g.

Example 5 This example shows a plate with a composite coating of calcium pyrophosphate and hydrated alumina. The production of powder containing α-alumina is described.

150g of sodium birophosphate crystal (Na　P　Oψ10H20) in 1Ω of water Dissolved to obtain a 0.336M solution.

Dissolve 150g of anhydrous calcium chloride (CaC12) in 1g of water to make 1.35M A solution of was obtained.

Alumina powder with a surface area of 1.4 m2/g (Microgrit Corp , grade WCA #3) in a 41 beaker while stirring well. was added to 3 g of water.

A stirred aqueous suspension of alumina powder was heated to 75°C and 6N NaOH was added to 3 drops were added to adjust the pH to 8.0.

297ml of 00336M solution of NaP0・10H20 and CaC1 2 and 148 ml of a 1.35M solution of 2 were simultaneously added over 2 hours, and The addition kept the pH at 8.0. At pH 8.0 and temperature 75°C, further 3 The suspension was allowed to harden by stirring for 0 minutes. Sodium aluminate [N aA1 (OH), 0.385gA1203/cc equivalent, Vinings V Add drop by drop an aqueous solution from SA #33 Vinings Corp. to the suspension. and the pH was kept at 8.5 by controlled addition of 20% MCI. NaA 1 (OH)4 solution? &130ml over 2 hours, pH 8.5 and The suspension was allowed to harden by stirring for an additional 30 minutes at 75°C. Ta. ca2P2゜7 and AI203 are all precipitated on the core alumina, which is 71.59% by weight of Ca2P2O and 34.69% by weight of A12o on a product basis It was equivalent. c a 2 P 207 / A 120 E ratio is 0.339. It was.

The solids are recovered by filtering the suspension and sodium ions and chloride ions are removed. Washed with deionized water until free of on. The solid material is heated to 120°C in air. I dried it in a bun overnight.

When the product was analyzed for elements other than oxygen by EDAX analysis, on a weight basis, A1 was 96.383%, Cal was 684%, and Pl was 933%.

The surface area was 23.6rn2/g.

The product is then calcined at a temperature ranging from 400 to 1100°C for at least 1 hour. Ta.

Example The example is a plate-shaped α-aluminum with a composite coating of calcium silicate and hydrated alumina. 1 shows the production of a powder containing mina.

Alumina powder with a surface area of 0.4 m2/g (plate-shaped α aluminum manufactured by DuPont) n) 1.000 g was added to 2 fl of water in a 41 beaker while stirring well.

A stirred aqueous suspension of Al2O3 was heated to 80°C and 2,000 ml of 6N NaOH was added. 3 drops were added to adjust the pH to 9.0. The pH was adjusted to 9.0 by adding 20% MCI. Potassium silicate solution (per 1 g of solution, S i020.25 48 g of 2Si03) including g, and 148 ml of 1.35M Ca C12 solution. were added simultaneously over a period of 2 hours. At pH 9.0 and temperature 80°C, further The suspension was allowed to harden by stirring for 30 minutes.

Suspension of sodium aluminate [0,385 g At203/c c equivalent N aA1 (OH), Vinings VSA#38 Vinings Cor p., manufactured by P., was added dropwise to the suspension by controlled addition of 20% MCI. H was maintained at 8.0 d. N a A 1 (OH) 4 melt? &130m1, 2 o'clock After addition, stir for an additional 30 minutes at pH 8.0 and temperature 80°C. The suspension was cured by this.

All Ca5iO and AI203 precipitate on top of the core alumina, which is generated On a substance basis, Ca S 1030, 726% by weight, AI 2034, 6 This corresponded to 9% by weight. The CaSiO3/Al2O3 ratio was 0.155.

The solids are recovered by filtering the suspension and potassium and chloride ions are removed. Washed with deionized water until free of ions. Solids are placed in an oven at 120°C in air. It was dried by heating in a vacuum oven for 12 hours.

The surface area of the dried product was 17.3 m2/g.

The dried product was calcined at 1000°C for 1 hour and had a surface area of 8.4 m2/g. A powder was obtained.

The product was then calcined for at least 1 hour at a temperature ranging from 400 to 1100 °C. .

Example 7 This example shows a plate aluminum having three times the amount of composite coating as described in Example 5. The production of powder containing Na is shown. Calcium pyrophosphate and alumina are in the same proportion. Ru.

Dissolve 100g of calcium pyrophosphate crystals in 11 parts of water to obtain a 0.224M solution. Ta. 150 g of anhydrous calcium chloride was dissolved in 1 g of water to obtain a 1.35M solution.

200g of alumina powder (plate-like α-alumina similar to Example 5) was added while stirring well. and 1 g of water in a beaker.

The stirred plate-shaped alumina suspension was heated to 75°C, and a few drops of 6N NaOH were added. The pH was adjusted to 8.0. 0.224M Na4P2O7・10H20 solution 267 ml and 88.8 ml of 1°35M Ca C12 solution over 1 hour. and the pH was maintained at 8.0 by addition of 20% MCI. pH8, The suspension was hardened by stirring for an additional 30 minutes at O and a temperature of 75°C. did. Sodium aluminate [0,385g Al2O3/cc equivalent of NaA1 (OH), Vinings VSA #38, made by Vinings Corp. Add dropwise an aqueous solution of The pH was maintained at 8.5. N a A 1 (OH) 4 solution 78 ml in 2 hours After addition, stir for an additional 30 minutes at pH 8.5 and a temperature of 75°C. The suspension was cured by this. All Ca 2P207 and AI 203 is precipitated on the core alumina, which is the product base and Ca2P2O74,7 7% by weight, corresponding to A 120314.07% by weight. Ca2P2O7/A12 The o3 ratio was 0.339.

The solids are recovered by filtering the suspension and sodium and chloride ions are removed. The solution was washed with deionized water until it was free of water. The solid material is heated to 120°C in air. Dry in a bun overnight. The weight of dry solids recovered was 239.5 g, yield This corresponded to 97.2% of the total.

The surface area of the product was 57.2 m2/g.

The product is then calcined at a temperature ranging from 400 to 1100°C for at least 1 hour. Ta.

Example 8 This example uses four times the amount of alumina and one-fourth the amount of carbon pyrophosphate as Example 5. 1 shows the production of a powder containing platelet alumina with a composite coating with lucium.

The solution and procedure used were similar to those shown in Example 7, with sodium pyrophosphate 22.0 ml of calcium chloride, 7.4 ml of sodium aluminate, and 10 ml of sodium aluminate. The volume was changed to 4.0 ml.

All Ca2P2O7 and AI203 are precipitated on the core alumina, which is 70,398% by weight of Ca2P2O and 18.76% by weight of A1203 on product basis It was equivalent to The Ca2P207/AI203 ratio was 0.0212. Ta.

The amount of solids recovered as in Example 5 was 234.0 g, with 94.6% It corresponded to the yield.

The surface area of the product was 43.0 m2/g.

The product is then calcined at a temperature ranging from 400 to 1100°C for at least 1 hour. Ta.

Example 9 This example shows a carbonized carbon fiber with a composite coating of calcium pyrophosphate and hydrated alumina. 1 illustrates the production of a powder containing crystalline alumina coated with ion.

The solution used was similar to that described in Example 7.

500-grid SiC powder (Norton) with a surface area of 0.56 m2/g Company Grade 100G, 1. ) 1000g without stirring well. and added to 2500 ml of water in a 41 beaker. Stirred aqueous suspension at 75°C and the pH was adjusted to 8.5. Sodium aluminate (Vinin gs VSA #38) was added to the SiC suspension, and 20% HCI was added at the same time. The pH was kept at 8.5 by adding to N a A 1 (OH) 4 After adding 100 ml of solution over 2 hours, at pH 8.5 and temperature 75°C. The suspension was stirred for an additional 30 minutes. All Al2O3 is precipitated on SiC, This corresponded to 3.71% by weight Al 203 on a composition basis. Filter the suspension By doing this, the solids are recovered and sodium ions and chloride ions are eliminated. Washed with deionized water until clean. SiC coated with alumina was placed in air at 120°C. The coating was dried in an oven overnight and baked at 1000°C for 1 hour to form an anhydrous crystalline Converted to Mina.

Add the calcined product to 2500 ml of water in a 41 beaker with good stirring. Ta. Heat the stirred aqueous suspension to 75°C and add a few drops of 6N NaOH. , the pH was adjusted to 8.5. 0.224M Na4P2O7.10H20 solution 4 45 ml and 148 ml of 1.35M CaC12 solution were mixed over 2 hours. The pH was maintained at 8.5 by addition of 20% MCI. pH8,5 and 7 The suspension was cured by stirring for a further 30 minutes at a temperature of 5°C. aqueous Add sodium aluminate CVinings VSA #38) one drop at a time, pH was kept at 8.5 by controlled addition of 0% 1 (CI). Sodium aluminate After adding 130 ml of thorium solution over 2 hours, the pH was 8.5 and the temperature was 75°C. The suspension was cured by stirring for an additional 30 minutes at 30°C. All Ca P O and Al2O3 precipitate on silicon carbide particles coated with alumina, On a product basis, it was equivalent to C. The Ca2P2O7/Al2O3 ratio is 0.339. It was.

The solids are recovered by filtering the suspension and sodium and chloride ions are removed. The solution was washed with deionized water until it was free of water. The solid material is heated to 120°C in air. Dry in a bun overnight.

The surface area was 25.2rn2/g.

The product was calcined at 1000°C for 2 hours, and this calcined the alumina part of the coating. formed an anhydrous crystalline alumina coating.

The product is then calcined for at least 1 hour at a temperature ranging from 400 to 1100 °C. did.

Shi- Q Hi FIG.3 H abstract Refractory metal carbide, refractory metal nitride, refractory metal boride, or diamond Contains a refractory material selected from hydrated alumina coating layer or anhydrous crystalline alumina a coated refractory composition having a coating layer and for making high quality preforms, and A method for increasing the dispersibility and improving oxidation resistance of such compositions.

Furthermore, it has a first coating layer of calcium pyrophosphate and a second coating layer of hydrated alumina. a first coating layer of calcium pyrophosphate; and a second coating layer of anhydrous crystalline alumina. and a method for producing the composition.

International Shoulder Referee Loss O-↑/II Den@l/I’l Flow 11,,,, =, =N, P CT/US 91102814

Claims (34)

[Claims] 1. Diamond, refractory metal carbide, refractory metal nitride, refractory metal boride , or a mixture thereof, with a hydrated alumina coating, finely ground Coated refractory compositions to create high quality preforms containing recycled refractory materials thing. 2. Refractory materials include silicon carbide, titanium carbide, tantalum carbide, charcoal, etc. Niobium carbide, zirconium carbide, tungsten carbide, molybdenum carbide, vanadium carbide hafnium carbide, tellurium carbide, uranium carbide, titanium nitride, dinitride Consists of ruconium, silicon nitride, titanium borate, and zirconium borate A composition according to claim 1, selected from the group. 3. A composition according to claim 1, wherein the refractory material is silicon carbide. 4. the coating is a mixture of bomatite crystals and hydrated amorphous alumina; A composition according to any one of claims 1 to 3. 5. Diamond, refractory gold with enhanced dispersibility and improved oxidation resistance selected from metal carbides, refractory metal nitrides, refractory metal borides, or mixtures thereof. selected from eta, theta, gamma, alpha phase, or transition mixtures thereof. A coated refractory assembly comprising a refractory material having a selected anhydrous crystalline alumina coating. A product. 6. 6. The method of claim 1, wherein the coating increases the isoelectric point of the refractory material. The composition according to item 1. 7. 7. The set of claim 6, wherein the coating reduces chemical activity on the surface of the refractory material. A product. 8. (a) coating an aqueous suspension of refractory material with hydrated alumina; and (b) separating, cleaning and drying the coated refractories; A method for improving the dispersibility of a refractory material. 9. a step of baking at a temperature in the range of 400 to 1100°C for at least 1 hour; 9. The method of claim 8, further comprising. 10. (a) coating an aqueous suspension of refractory material with hydrated alumina; (b) separating, cleaning and drying the coated refractory; and (c) baking at a temperature in the range of 400 to 1100°C for at least 1 hour; improves the dispersibility of refractory materials and improves oxidation resistance during high-temperature processing under atmospheric conditions. How to improve. 11. The refractory material is diamond, refractory metal carbide, refractory metal nitride, Any one of claims 8 to 10, comprising a flammable metal boride or a mixture thereof. The method described in section. 12. The refractory material is substantially silicon carbide, titanium carbide, tantalum carbide, Niobium carbide, zirconium carbide, tungsten carbide, molybdenum carbide, vana carbide Dium, hafnium carbide, tellurium carbide, uranium carbide, titanium nitride, nitride Made of zirconium, silicon nitride, titanium borate, and zirconium borate. 12. The method according to claim 11, wherein the method is selected from the group consisting of: 13. The coating is a mixture of bomatite crystals and hydrated amorphous alumina 13. The method of claim 12. 14. (a) preparing an aqueous suspension of refractory material at a temperature ranging from 40 to 95°C; and adjusting the pH to a range of 5 to 9; (b) substantially alkali metal aluminate, ammonium aluminate, ammonium chloride; selected from the group consisting of aluminum, aluminum nitrate, and aluminum acetate. Add an aqueous solution of the ammonium salt with stirring and increase the temperature for 5 to 60 minutes. pH is maintained, thereby providing water as a coating layer on the surface of the refractory material. a step of precipitating Japanese alumina, and (c) Separating the coated refractories, washing them, and drying them at 100 to 300°C. degree A method for producing a refractory material coated with hydrated alumina, comprising: 15. Aluminum salt is an alkali metal aluminate and mineral acid is added at the same time 15. The method of claim 14, further comprising the step of: 16. Baking at a temperature ranging from 400 to 1100°C for at least 1 hour. 16. The method according to claim 14 or 15, further comprising the step of: 17. Fireproofing having a first coating of calcium component and a second coating of alumina component a composition comprising a ceramic substrate, wherein the first and second coatings have a total composition of from about 0.5 to 25% by weight of the product, and the ratio of the first coating to the second coating is about 0. ．． 01 to 0.095. 18. 18. The composition of claim 17, wherein the refractory substrate is alpha alumina. 19. The refractory substrate is aluminum, titanium, zirconium, silicon and a group selected from the group consisting of oxides, carbides, borides, and nitrides of mixtures thereof; the surface of the refractory substrate is coated with crystalline material made of alumina. 18. The composition of claim 17. 20. The first coating is calcium pyrophosphate, calcium phosphate, calcium silicate. selected from the group consisting of calcium aluminate, calcium aluminate, and mixtures thereof; A composition according to claim 17. 21. 18. The composition of claim 17, wherein the second coating is hydrated alumina. 22. 22. The hydrated alumina is primarily bomatite alumina. the method of. 23. Average particle size in the range 0.1 to 2500 μm and 0.1 to 50 m2/ A composition comprising platy alpha alumina having a surface area in the range of g. The alpha alumina has a first coating of calcium pyrophosphate deposited on it and a boma a second coating of tight alumina. 24. Fireproofing having a first coating of calcium component and a second coating of alumina component the first and second coatings are integrated to form a preform. A composition that provides a release action between the ceramic matrix and the ceramic matrix. 25. A first coating of calcium pyrophosphate and a second coating of dense anhydrous, crystalline alumina. A fired composition comprising an alpha alumina substrate having a coating of 2. 26. (a) Aqueous mixture of refractory substrate, calcium component precursor, and alumina salt and (b) recovering, washing and drying the coated refractory composition. process A method for improving the strength and toughness of a ceramic composition, comprising: 27. Prepare an aqueous mixture and then (a) Heating at a temperature ranging from 40 to 95°C and adjusting the pH to a range from 5 to 9. forming an aqueous suspension of the refractory substrate, (b) an aqueous suspension of a calcium component precursor containing a calcium salt and a pyrophosphate; , phosphates, silicates, and aluminates. and the aqueous suspension of the genus salt at the same time with stirring, and then for 5 to 60 minutes. The process of maintaining temperature and pH, and (c) After adding the aqueous solution of aluminum salt, the temperature and pH are adjusted for 5 to 60 minutes. The process of maintaining 27. The method of claim 26, comprising: 28. The coated refractory composition is heated at 400 to 1100°C for at least 1 hour. Claim 26 or 27, further comprising the step of firing at a temperature in the range of the method of. 29. According to claim 26 or 27, the refractory substrate is a high temperature crystalline material made of alumina. Method described. 30. The refractory substrate is titanium, zirconium, silicon, and mixtures thereof. a method selected from the group consisting of oxides, carbides, borides, and nitrides of Claim 26 or 27, wherein the refractory base is coated with a crystalline material made of alumina. The method described in. 31. The calcium salt is calcium chloride, calcium nitrate, or a mixture thereof. 30. The method of claim 29, wherein the method is selected from: 32. Aluminum salt, alkali metal aluminate, ammonium aluminate , aluminum chloride, aluminum nitrate, aluminum acetate, and mixtures thereof 32. The method of claim 31, wherein the method is selected from the group consisting of: 33. 33. The method of claim 32, wherein the aluminum salt is sodium aluminate. . 34. (a) heating to a temperature in the range of 40 to 95°C and a pH in the range of 5 to 9; preparing an aqueous suspension of a plate-like Al2O3 substrate while adjusting the (b) Simultaneously add calcium salt solution and alkali metal pyrophosphate solution, After that, a step of forming a first coating on the plate-shaped α-alumina while maintaining the temperature and pH; (c) After adding the alkali metal aluminate solution with stirring, the temperature and pH forming a second coating on the first coating while maintaining the (d) recovering, washing, and drying the coated refractory composition; and (e) heating the coated refractory composition at 400 to 1100°C for at least 1 hour; A process of firing at any temperature within a range a first coating of calcium pyrophosphate deposited thereon, and a first coating of boumatite. and a second coating of alumina.