High-strength cordierite mass of low expansion and high porosity and method of production of such mass

FIELD: ceramic masses for manufacture of cordierite articles used as catalytic carriers.

SUBSTANCE: burnt ceramic article has average linear coefficient of thermal expansion below 5.0x10-7°C-1 at total porosity from 20% to 30%; amount of pores having size lesser than 2 mcm is about 86%. Pores are interconnected; they are longitudinal in shape and are oriented over oval axis in plane of sheets. Method of production of burnt cordierite ceramic article includes mixing plate talc, source of Al2O3 and one or more components from the following group: kaolin, burnt kaolin, silicon dioxide or corundum; each of them has particles lesser than 5 mcm. Mass thus obtained is extruded to cellular article after which burning is performed.

EFFECT: high resistance to thermal impacts; enhanced covering with suspension.

15 cl, 3 dwg, 2 tbl, 3 ex

 

This application is based on provisional applications U.S. 60/138930 from 11.06.99 and 60/174010 from 30.12.99, entitled "high Strength cordierite weight with low expansion and high porosity and method of reception" in the name Beall et al.

The invention relates to cordierite ceramic masses for use as catalytic carriers, in particular to the cordierite masses having a high resistance to thermal shock due to the low coefficient of thermal expansion (CTE), a good potriveste suspension of activated aluminum oxide with a large surface area due to the high level of fine porosity and a narrow distribution of pore size from very small, usually elongated pores.

The exhaust gases emitted by internal combustion engines that use hydrocarbon fuels, such as hydrocarbon gases, gasoline or diesel fuel, can cause serious pollution. Among the many pollutants in these exhaust gases are hydrocarbons and oxygenated compounds, the latter include oxides of nitrogen (NOx) and carbon monoxide (CO). The automotive industry for many years attempted to reduce the amount of pollutants from systems of motor vehicles, and the first cars equipped with catalytic converters were introduced in the mid 70-ies.

The cordierite substrate, usually in the form of a cellular mass (like a honeycomb), have long been preferred for use as substrates for the deposition of the catalytically active components for catalytic converters in cars, partly due to its high resistance cordierite ceramic materials to thermal shock. Porous ceramic materials having a combination of low coefficient of thermal expansion, high porosity and high strength, are particularly attractive for those with thin sheets of substrates automotive catalytic converters with good characteristics. In response to legislation requiring more efficient catalytic converters for the automotive market, has increased the need for cordierite monoliths with very thin sheets. More thin sheets reduce the weight of the substrate, which leads to a shorter time of extinction. In addition, it is possible to achieve high geometric surface area without increasing the weight of the substrate. Another advantage of thin sheets is that you can achieve a lower back pressure.

Despite the advantages of thin-walled cordierite honeycomb reducing the thickness of the cell reduces the strength of the ceramic material. This causes complications when packaging ka is eliticism Converter. If strength is sufficiently decreased, the packaging process can cause damage to the substrate material. So you need high strength material in order to compensate the reduction of the geometrical strength faced, when the thickness of the sheets is very small. In order to have a high level of Kazatomprom precoat coating of aluminum oxide with high surface area, which is applied on the sintered substrate, requires a high porosity. In addition, the high porosity reduces thermal mass of the substrate and allows you to have a shorter time of extinction of the catalytic Converter. Low coefficient of thermal expansion is important in order to prevent the destruction of the substrate material due to thermal shock. Unfortunately, it is known that high levels of porosity and low thermal expansion reduces the strength of the cordierite honeycomb. Low thermal expansion normally provide cracks inside the cordierite matrix, which expand during cooling due to the anisotropy of thermal expansion. The presence of microcracks inside the cordierite matrix helps to limit the strength of the masses. A high level of porosity of the matrix limits the strength of the material, because the pores reduce the space transverse to the about section on the attached load.

In U.S. patent 4.849.275 (Hamaguchi et al.) described cordierite ceramic honeycomb structure having a porosity between 30%and 42%, at least 70%, preferably at least 80% of the total volume of all pores in the mass consists of pores having a diameter between 0.5 and 5.0 microns.

In U.S. patent 4.877.670 (Hamanaka et al.) described cordierite mass having a low CTE, below 10×10-7/°C, and low total pore volume larger than 5 μm, preferably greater than 2 μm. Although the source described a narrow distribution of small pores, it is not described, the combination of a narrow distribution of pores of small size and not disclosed to the need for relatively elongated oriented pores, ensuring the formation of cordierite masses, having the property combination of high strength and low CTE below 5×10-7/°C.

In U.S. patent 4.869.944 (Harada et al.), which is the closest prototype to the claimed invention, described cordierite mass, with the crown-rump length not exceeding 3×10-7/°C in the axial direction and having a porosity of between 32 and 42%, where ≥40% of all of the pores are between 0.5 and 5.0 microns and ≤30% of the pores have a diameter of ≥10 μm. Although the source described a narrow distribution of small pores and a relatively low CTE with a total porosity greater than 30%, they are not disclosed and are not shown in any examples of narrow R is Opredelenie quite shallow, elongated and oriented long necessary to obtain the cordierite mass having a low CTE, below 5×10-7/°C., and a sufficiently high strength.

Therefore, the main task of the present invention is the provision of improved cordierite ceramic materials that have low thermal expansion, high total porosity and a narrow distribution of small elongated oriented pores.

The present invention relates to the annealed ceramic substrate and method for producing a ceramic substrate having a main crystal phase comprising cordierite, having a low thermal expansion and high total porosity. Porosity formed only small pores with a narrow size distribution and predominantly elongated form, which is reputed to be largely provides unexpectedly high strength of these substrates with a low CTE.

Sintered ceramic product according to the invention has an average linear coefficient of thermal expansion (25-800°C.) below about 5,0×10-7/°C, the total porosity in the range from 20% to about 30%. In addition, the annealed ceramic has such a distribution of pore sizes, wherein at least about 86% of the pores are pores with a size less than about 2 microns. In addition, the ceramic product has the structure of vzaimosvaz is the R long having, in the main, elongated shape, and the pores are predominantly oriented along the longitudinal axis in the plane of the sheets.

This invention relates also to a method for producing a sintered cordierite ceramic articles, comprising first compounding and plastical boot forming the inorganic cordierite powder comprising talc having an average particle size less than 2 microns, preferably lamellar talc with morphological index is greater than about 0.75. In addition, the download includes about 4% by weight of the boot of a mixture of inorganic powder dispersible source of education Al2About3having a specific surface area exceeding 50 m2/g, and one or more components of kaolin, calcined kaolin, silica and alumina, each of which has an average particle size below 5 microns.

Thus obtained plastician the powder loading, then turn in crude cell product by extrusion through a honeycomb extrusion head, then crude cell product is calcined at a temperature and for a time sufficient to convert crude cell product crystallized cordierite ceramic article having the aforementioned properties.

Figure 1 shows a micrograph of scanning electron microscope is, taken at magnification 500× with sample cordierite ceramic body according to the invention.

Figure 2 shows the micrograph of scanning electron microscope, photographed at magnification 500× with a comparative sample of cordierite ceramic body composition 2.

Figure 3 shows a graph showing the ratio of the cumulative intrusion on the diameter of the pores of example 1 according to the invention and two comparative examples 2 and 3.

Cordierite product according to the invention includes the distinguishing characteristics of the thin-walled cordierite honeycomb ceramic material with good resistance to thermal shock due to the low coefficient of thermal expansion (CTE)lower than approximately 5,0×10-7/°C, with good pokryvailo upstream coating of oxide of aluminum due to the high level of total porosity (>20%but less than 30%) and the structure of interconnected pores, and with good strength as a consequence of the distribution has a very small size, in particular the distribution where at least about 86% of the pores have an average size less than about 2 μm simultaneously with such orientation of the pores, which pores are preferably so that their long axes lie in the plane of the sheets. According to the invention KTR mean thermal expansion from 25 to 800°C, measured by dilatometry; in relation to satam what it means extending in the direction parallel to the length of the open channels.

The shape and orientation of the pores have an impact on the strength of the cordierite honeycomb. Cordierite ceramic body having elongated pores that are oriented perpendicular to the applied load, have increased strength compared to cordierite masses, which are spherical randomly oriented pores, thus reducing the concentration of the load.

In order to obtain the cordierite ceramic mass having the above-described unique combination of properties, you must use the boot mixes the particular combination of source materials with a very small average particle size and high surface area. The size of the particles, as it is used here, means the average particle diameter, determined by the sedimentation method.

According to the present invention in the preparation of the above-described ceramic products used plastilina mixture comprising (a) very fine talc having an average particle size of less than about 2 microns; (b) dispersible source of formation of Al2About3selected from the group of transition alumina, aluminum hydroxide or hydroxide oxide of aluminum, where Al2O3has a specific surface area exceeding 50 m2/g and comprising at least 4%by weight plasticiens inorganic compounds; (C) at least one component of kaolin, calcined kaolin, silica and alumina, each of which preferably has an average particle size less than 5 microns.

In a preferred embodiment, talc is a lamellar talc, which has a lamellar morphology of the particles, i.e. particles having two long dimension and a short dimension, or length and width of the plate, which is much more than its height. Preferably, the talc had morphological index higher than about 0.75. Morphological index (see U.S. patent 5.141.686) is a measure of the degree of plastinated talc. Conventional methods of measuring morphological index is placed in the holder so that the orientation of lamellar talc was maximized in the plane of the sample holder. Then for such oriented talc determine the diffraction pattern of x-rays. Morphological index semiquantitative plate connects the character of the talc with the intensities of the peaks of x-ray diffraction according to the following equation:

where Ixrepresents the intensity of the peak (004), and Iyis the intensity of reflection (020).

Under the source of formation of Al2O3involve himself Al2O3or D. the natives substance, having low solubility, which results in an Al2O3during the firing process. Some typical forming Al2O3components include alumina, Al(Oh)3(also known as the trihydrate of aluminum or mineral gibbsite), or a hydroxide of aluminum oxide (also known as the monohydrate, aluminum, or the mineral boehmite, or pseudoboehmite).

Dispersible component or source, forming Al2O3with high surface area, can be represented in the form of powder or in the form of Zola. Under dispersible component refers to the component in which the agglomerates of very small particles can be broken and dispersed into its constituent particles having the average particle diameter is less than approximately 0.3 microns. Under high surface area is meant a surface area greater than 50 m2/g, more preferably greater than about 100 m2/, Such powders may include boehmite, pseudoboehmite, gamma phase alumina, Delta phase alumina or other so-called transitional alumina. In a preferred embodiment, dispersible component or source, forming Al2O3with high surface area, includes boehmite having a surface area greater than 150 m2/year

Dispersible source of formation of the l 2About3for the present invention is a compound which when heated forms an Al2About3.

The average particle diameter of kaolin, if present, must be in the range between 0.2 and 2.0 microns, and the kaolin should be less than about 35% by weight of the total substrate. The balance required for the formation of cordierite Al2O3provided calcined kaolin or a source of formation of Al2O3and the balance on SiO2provided calcined kaolin or powder of silicon dioxide. Preferably, the silicon dioxide is present in the form of particles of silicon dioxide with a very high surface area (>50 m2/g). If you use soda clay, it should be very small, preferably with an average particle size less than 2 μm and, more preferably, less than 1 μm with a surface area of >10 m2/year

The above raw materials that make up plastilina mixture, combine at the stage of mixing, sufficient to ensure thorough mixing of the phases of the source material to make possible a complete reaction during thermal processing. At this point, add a binder system to facilitate the formation of an extrudable, i.e. being formed and subjected to molding the mixture. The preferred binder system is for use in the present invention includes as a binder a simple cellulose ether, selected from the group consisting of methylcellulose, methylcellulose derivatives, and combinations thereof, as a surfactant component, preferably stearic acid or sodium stearate, and a solvent comprising water. Excellent results were obtained using a binder system, which includes the following amounts per 100 mass parts of the inorganic raw material mixture of the sources of formation of aluminum oxide and silicon dioxide and talc: from about 0.2 to 2 mass parts of sodium stearate, about from 2.5 to 6.0 mass parts of methylcellulose or hydroxypropylmethylcellulose binder and about 20 to 50 mass parts of water.

In a separate embodiment, the preferred binder system for use in the present invention includes as a binder a simple cellulose ether selected from the group consisting of methylcellulose, methylcellulose derivatives, and combinations thereof, as a component, non-solvent comprising a poly alpha olefin, a surface-active component selected from the group consisting of stearic acid, lauryl ammonium, laurinovoj acid, oleic acid, palmitic acid and combinations thereof, and a solvent comprising water. Excellent results were obtained when using the years of the linking system, which includes the following amounts per 100 mass parts of the inorganic raw material mixture of: from about 2 to 10 mass parts of poly alpha olefin, from about 0.2 to 2 mass parts of the surface-active component, from about 2.5 to 5 mass parts hydroxypropylmethylcellulose binder and from about 8 to 25 mass parts of water.

Individual components of the binder system are mixed with the mass of the inorganic powder material suitable known manner to produce a homogeneous mixture of a ceramic material and a binder system that can be molded into the ceramic mass, for example, by extrusion. The obtained dense and homogeneous extrudable boot the mixture is then formed into crude product by any known method of forming ceramic articles, such as, for example, extrusion, injection molding, slip casting, pressure casting, centrifugal casting, dry pressing, etc. For the manufacture of thin-walled honeycomb substrate suitable for use as a catalyst carrier, preferably applied by extrusion through the die plate. Manufactured ceramic raw product is then dried and fired at a sufficient temperature and for a sufficient time to obtain annealed ceramic article containing cardieri is as its main phase. The conditions of drying and annealing may vary depending on the process conditions, such as the specific composition, the amount of raw products and equipment type.

The product can be dried by any conventional means, such as drying with hot air or dielectric drying, and dielectric drying is the preferred method.

The firing interval for forming cordierite mass must be 1340-1440°C at a holding time sufficient for almost complete conversion into the cordierite phase; can be used time 6-12 hours. The obtained sintered mass, preferably at least about 95% of the mass. consists of cordierite.

For further clarification of the principles of the present invention included an example of cordierite ceramics according to the invention together with two comparative examples. However, it should be understood that the examples are for illustrative purposes only, and the invention is unlimited by them, but in the invention can be made of various modifications and changes without disrupting its essence.

EXAMPLES

Boot a mixture of inorganic powder, suitable for formation of a ceramic material having as its main crystal phase of cordierite, are listed in table I, as indicated in mass percent. Boot mix, HDMI is tion of the invention 1 and comparative composition 2 were obtained by the Association and the dry components are mixed inorganic compounds, listed in table I. it Should be noted that the composition 1 includes boehmite having a surface area of 180 m2/g and lamellar talc having a morphological index of 0.91, whereas in the comparative composition 2 no fine Al2O3and included talc having a morphological index between 0.7 and 0.75. To these mixtures was added amount of organic binder system, specified in table I, and then such intermediate mixture was additionally mixed with deionized water to obtain plastilinovaya ceramic boot mix. The components of the binder system, listed in table I, are given in mass parts per 100 parts of the total inorganic material. Table I shows also the average particle size (in microns)used in the boot materials, commercially available starting materials. It should be noted that all dimensions of the particles in the composition 1 are sub-micron average particle size, whereas the comparative composition 2 includes a talc having an average particle size of about 6 microns.

Plastician mixture was extrudible through the extruder under conditions suitable for formation of a porous substrate with 816 cells/square inch, a length of about 5 inches, having a diameter of about 3 inches and cell wall thickness 2,72 mil (69 μm). Obtained from the compositions of raw when you have dried enough to remove any water or liquid phases that might be present, and then subjected to a cycle of heating and annealing, sufficient to remove the organic binder system and to carry out sintering the extruded rods and cells. Specifically, the crude mass was annealed at temperatures between about 1380-1420°C and kept for a time of about 8 hours, i.e. when the firing conditions suitable for the formation of ceramic masses, having as main phase of cordierite.

TABLE I

Boot COMPOSITION IN MASS PERCENT of

(in parentheses are the average particle size in microns, determined by the sedimentation method)
The original substanceComposition 1 according to the inventionComparative composition 2
Inorganic substances  
Talc39,95 (1,5)40,86 (6,6)
Kaolin16,55 (0,8)12,04 (0,8)
Annealed kaolin24,73 (0,8)29,68 (0,8)
Al2O35,73 (0,6)15,43 (0,4)
lO-x H2O (180 m2/g)11,05 (0,1)-
Docycycline 2,0 (3,8)2,0 (3,8)
Organic matter -
Metozel5,03,5
Lubricant1,00,5
Oil8,06,0

Table II summarizes selected properties of ceramic products obtained from the download of composition 1 and comparative composition 2 in table I. In comparative example 3 shows typical properties of a number of comparative cordierite ceramics having properties porosity indicated in the aforementioned patent Hamaguchi, in particular, the porosity between 30%and 42%, when the total volume of all pores in the mass, consisting of not less than 70%, specifically 71-73%, pores having a diameter between 0.5 and 5.0 microns. Properties included some ceramic masses, are the modulus of tensile strength (MNR) rods, in psi, the average coefficient of thermal expansion (CTE) of the rods in the temperature range from about 25 to 800°C (×10-7/° (C), the total porosity of ceramics, expressed in volume%, and the percentage of pores having an average size below 2 microns, where both porosity has been determined using the Nd-Parametrii. In addition, table II includes hydrostatic isostatic strength and crushing strength axis A, and C, each of which is expressed in psi.

Table II
Properties of annealed cordierite ceramicsComposition No. 1Comparative composition No. 2Comparative example No. 3
The density of cells816900811
Wall thickness2,722,702,72
KTR3,75,03,2
% porosity26,8to 25.331,9
% porosity (<2 μm)924120-22
MNR (psi)361288270
Hydrostatic isostatic strength FN (psi)20014575
The crushing strength axis (psi)364021201190
The crushing strength axis In (psi)31322486
The crushing strength axis (psi)253111

From table II it is seen that the sample according to the invention has declared porosity, s is I the total porosity in the range between 20 and about 30%, specifically 26,8%, and the distribution of pore size that is at least about 86% of the pores have a pore size less than about 2 microns, specifically 92%. In addition, the sample according to the invention has a low CTE of about 3.1×10-7/°C together with a sufficiently high strength in 361 psi. On the other hand, comparative samples have a much lower percentage distribution of <2 μm than the sample according to the invention, 41%and 19%, respectively, simultaneously with a lower strength 270 and 288 psi.

Figure 1 shows micrograms SAM obtained at 500×polished cross-section of the ceramic material, are molded from the above composition 1; cordierite honeycomb structure with 900 psi and a thickness of the sheet 0,0027 inch. Figure 1 shows the porous structure of the small uzkonapravlennyh and mostly elongated pores that are oriented along the plane of the sheet of the ceramic material. In particular, figure 1 shows that the average pore diameter of below 1 μm, as measured LP parametria, and that this mass can be detected very few large pores.

Figure 2 shows micrograms SAM obtained at 500×polished cross-section of the ceramic material of comparative example 3; cordierite honeycomb structure with 900 psi and a thickness of the sheet 0,0027 inch, molded in order to achieve the above-mentioned porosity, described in the patent Hamaguchi. Figure 2 shows Paris the th structure of roughly spherical pore with no preferred length or orientation. In particular, figure 2 shows that the average pore diameter of greater than 3 μm, as measured Nd-parametria, and that you can see a number of pores with a diameter of up to 30 microns in diameter. Probably, the presence of such pores affects the reduced strength of this particular ceramic material.

Figure 3 shows a plot of the cumulative intrusion from pore size (distribution of porosity cordierite mass made from the composition according to the invention of example 1 (curve a) and two comparative cordierite ceramics (curves b and C for comparative examples 2 and 3, respectively). Dimensions shown on these graphs were done using Nd-Parametrii. The points on the curves correspond to the cumulative intrusion at 40, 20, 10, 5, 2 and 0.5 μm. From the curves we can see that the mass according to the invention (curve A) has a much more narrow distribution of pore size than any of the comparative ceramic masses. Indeed, almost all detected pores have a size below 2 microns, whereas the comparative masses show a broad distribution with a significant volume of pores greater than 2 microns.

It should be understood that although the present invention is described with respect to some preferred and specific variants of its implementation, it should not be considered as limiting, since many possible modify the promotion, without departure from the essence and scope of the present invention, as defined in the claims.

1. Extruded sintered cordierite ceramic article having an average linear coefficient of thermal expansion 25-800°C below approximately 5,0·10-7/°C, the total porosity in the range from 20% to approximately 30% and having such a distribution of pore sizes that are at least about 86% of the pores are pores with a size less than about 2 microns.

2. Sintered cordierite ceramic article according to claim 1, which has a structure of interconnected pores with the pores having mostly elongated and preferably oriented along the longitudinal axis in the plane of the sheets.

3. Sintered cordierite ceramic article according to claim 1, which has the strength of MNR more than 300 psi.

4. Sintered cordierite ceramic article according to claim 1, which has a crushing strength along the axis And more 3640 psi.

5. Sintered cordierite ceramic article according to claim 1, which has a total porosity in the range of 23-30%.

6. Sintered cordierite ceramic article according to claim 1, which has the distribution of pore sizes that at least about 90% of the pores are pores with a size less than about 2 microns.

7. The method of obtaining extruded sintered porous cordierite ceramic articles, comprising the following stages:

(a) compounding and p is astical boot forming the inorganic cordierite powder, comprising talc having an average particle size less than about 2 μm, at least 4% by weight of a mixture of boot inorganic powder consisting of dispersible source of education Al2O3having a specific surface area exceeding 50 m2/g, and one or more components selected from the group of kaolin, calcined kaolin, silica and alumina, each of which has an average particle size below 5 μm,

(b) transformation by plasticized load of powder in a crude cell product by extrusion through a honeycomb extrusion head, and

(c) calcining the crude cell product at a temperature and for a time sufficient to convert crude cell product crystallized cordierite ceramic article having an average linear coefficient of thermal expansion 25-800°C below approximately 5,0·10-7/°C, total porosity in the range from 20% to approximately 30% and having such a distribution of pore sizes that are at least about 86% of the pores are pores with a size less than about 2 microns.

8. The method according to claim 7, in which the talc comprises lamellar talc having a morphological index above about 0.75.

9. The method according to claim 7, in which dispersible source of formation of Al2O3has a specific surface area greater than 100 m2/is.

10. The method according to claim 7, in which dispersible source of formation of Al2O3is a boehmite having a specific surface area of more than about 150 m2/year

11. The method according to claim 7, in which crystallized cordierite ceramic product has a structure of interconnected pores with the pores having mostly elongated and preferably oriented along the longitudinal axis in the plane of the sheet, the strength of the MNR over 300 psi, and the crushing strength along the axis And more 3640 psi.

12. Extrudable mixture for use in preparation of a substrate having cordierite as its primary phase having a chemical composition of a mixture of inorganic raw materials: from 11 to 17 wt.% Mao, from 33 to 41 wt.% Al2O3from 46 to 53 wt.% SiO2where the mixture of the inorganic materials include talc having an average particle size less than about 2 μm, at least 4% by weight of the boot of a mixture of inorganic powder consisting of dispersible source of education Al2O3having a specific surface area exceeding 50 m2/g, and one or more of the components selected from the group of kaolin, calcined kaolin, silica and alumina, each of which has an average particle size below 5 microns.

13. Extrudable mixture according to item 12, in which talc is the Wallpaper lamellar talc, having morphological index above about 0.75.

14. Extrudable mixture according to item 12, in which dispersible source of formation of Al2O3has a specific surface area greater than 100 m2/year

15. Extrudable mixture according to item 12, in which dispersible source of formation of Al2O3is a boehmite having a specific surface area of more than about 150 m2/year



 

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FIELD: ceramic masses for manufacture of cordierite articles used as catalytic carriers.

SUBSTANCE: burnt ceramic article has average linear coefficient of thermal expansion below 5.0x10-7°C-1 at total porosity from 20% to 30%; amount of pores having size lesser than 2 mcm is about 86%. Pores are interconnected; they are longitudinal in shape and are oriented over oval axis in plane of sheets. Method of production of burnt cordierite ceramic article includes mixing plate talc, source of Al2O3 and one or more components from the following group: kaolin, burnt kaolin, silicon dioxide or corundum; each of them has particles lesser than 5 mcm. Mass thus obtained is extruded to cellular article after which burning is performed.

EFFECT: high resistance to thermal impacts; enhanced covering with suspension.

15 cl, 3 dwg, 2 tbl, 3 ex

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1 ex, 2 tbl, 1 dwg

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1 tbl

FIELD: technological processes.

SUBSTANCE: invention relates to production of glass-ceramic material for radio engineering purposes and can be used in ceramic and aviation industry. Method of producing glass-ceramic material of cordierite composition includes grinding amorphous glass of magnesium aluminosilicate composition by wet method to produce an aqueous slurry with density 2.00-2.02 g/cm3, pH=2-4, fineness with sieve residue 0.063 mm 7-9%, with content of particles up to 5 mcm - 30-38%, forming blanks in porous moulds and their heat treatment. First stage of heat treatment is carried out at 850°C with holding for 3 hours, and the second - at 1350-1360°C with holding for 2-3 hours. Speed of lifting and lowering temperature not more than 500°C/h.

EFFECT: higher density of sintered material up to 96% of theoretical value and lower power consumption during its production.

1 cl, 3 ex, 1 tbl

FIELD: metallurgy; technological processes.

SUBSTANCE: invention relates to synthesis of heat-resistant coatings for protection of fecral alloys. Coating contains following components, wt%: monosubstituted aluminium phosphate Al(H2PO4)3 - 33.5, cordierite powder Mg2Al4Si5O18 - 37.5, powder of solid-electrolyte zirconium ceramic ZrO2 - 4, distilled water H2O - 25.

EFFECT: high strength and heat resistance of cordierite ceramic for electric heating elements.

1 cl

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