SU1002273A1 - Batch for making products of aluminium nitride - Google Patents

Description

 CHARGE TO GET PRODUCTS FROM NITRIDE The invention relates to the composition of the charge for the production of aluminum nitride products, which can be used as a refractory, electrical insulating material that is chemically resistant to corrosive media. A number of compositions based on aluminum nitride containing a significant amount of additives up to 50 May are known. - including metals tl} 2, 3j. These formulations refer to composite materials that increase the ceramics. However, such a significant amount of additives in mothers reduces its refractoriness, resistance to aggressive media, impairs its electrical insulating properties, and increases the deformation under load at high temperatures. Known mixture on the basis of aluminum nitride, containing 5.0-10.0 wt. additives of 1tri oxide and silicon oxide C Products are calcined at 1700 and 1800®С with an exposure of 1 h in nitrogen ALUMINUM. This mixture is used to absorb the composite material in the L-IN-SiO system in order to create a fibrous structure. However, this composition of the charge does not allow for high density aluminum nitride products despite the relatively high firing temperatures and specific pressing pressures. Products with an addition of 5.0 wt.% And 5.0 wt.% SiO have a minimum porosity of 4.5. The pressing pressure is 500 NPA. The calcining temperature is ISOO C. The known charge for obtaining high-density aluminum nitride products is 90, 00-99, 85 wt. A1N powder and 10.00-0.15 May; yttria or lanthanum oxides, or yttrium aluminum garnet 53- Such a composition allows to obtain high-density ceramics with a smaller amount of additives and at lower specific pressing pressures (.J 50-200 MPa), but at significant calcining temperatures (T750-1850C). at low temperatures, the open porosity of the samples reaches 10-251. The disadvantage of this composition is the relatively high firing temperatures for obtaining dense products, which leads to the contamination of ceramics by the material of furnace parts (carbon, refractory metals, etc.), as well as to the dissociation of A IN into its constituent elements. In addition, the additives used are refractory soybeans (molasses with a melting point:, Y., about 1950 / T, and the sintering of aluminum nitride is due to the liquid phase resulting from the interaction of refractory additives with impurities, AION, are present in aluminum nitride. Therefore, using such a composition, it is impossible to obtain high-density products at calcining temperatures of 1750-1900s using powders of high purity with an A1N content of more than 99.0 wt. (content, AlON, less than O, 5 Such powders are obtained by low-temperature m methods of synthesis from salts and oxides, plasma-chemical method of synthesis, gas-phase deposition, etc. These powders have a high dispersion (Syii - 5-30) and therefore do not require subsequent grinding in the manufacture of products, which is accompanied by the grinding of grinding bodies (iron, alumina , tungsten carbide, as well as A1 hydrolysis to form A (OH) ", from which ALOi A10N impurities are formed during roasting of products. The closest proposed mixture is based on aluminum nitride powder and yttrium-aguminium garnet additive, which makes it possible to obtain dense ceramics at a lower calcination temperature. This mixture contains 0.1-10.0 wt.% UzA150; 2. From such a charge with a relative density of 92.5, products are obtained at a firing temperature of 1700-1800 C. They are pressed at a specific value of 500 Mnats. The latter composition’s drawbacks are high firing temperature, which complicates the technology) of obtaining the products, as well as the need to use high pressing pressure ( 500 MPa) to obtain dense products. Such high pressing pressures make it difficult to produce high-quality compacts without splitting and repressions from aluminum nitride powders, which are characterized by high dispersion and, consequently, a choice for a large reject rate in the manufacture of products. Such high pressing pressures also limit the production of large-sized aluminum nitride products, since it is very difficult to manufacture molds that can withstand such pressures, and more complex press presses are required. In addition, this mixture is sufficiently effective, since the resulting material has a porosity of 7.5, which reduces its strength, increases gas permeability, reduces its chemical resistance in aggressive media, and consequently, limits its scope in engineering. The object of the invention is to reduce the firing temperature of the products, the specific pressure of the pressing while reducing the porosity of the products. The goal is achieved by the fact that the charge, including A1N and the additive contains as an additive CaO and SiO and / or CaO and in the following ratio of components, wt.%: CaO0.1-9.0, 4-13.6 AIMAll other and weight ratio CaO: Sif, is from 1:10 to 1.6; 1 0.1–12.0 or CaO 0.2–13.6 B.2. C The rest is A1N with a ratio by weight of CaO: P-0 from 1:10 to 8: 1. These additives of calcium oxide and silicon oxide or calcium oxide and boron oxide can be taken together or separately, since they give a similar result. The essence of the invention is as follows. During firing (the firing temperature is 1500-1900 0, these additives form a liquid phase, apparently dissolving aluminum nitride, which activates the process of sintering aluminum nitride, which is likely to flow through the liquid phase sintering process with partial dissolution of the solid phase. Et9 leads to a decrease in temperature firing; reducing the porosity of the material and reducing the specific pressing pressure required to obtain dense products. This composition allows to obtain products of aluminum nitride with a density close to theoretical from powder They are of high purity with an A1N content of more than 99.0 wt% due to the fact that the formation of a liquid phase from the proposed composition of the charge does not require interaction with impurities, A ION, A12.0 C. The liquid phase is formed due to melting or formed during roasting or injected low-melting glass, borates or calcium silicates. The liquid phase occurs in the temperature range of 11001500 C. The lower limit of the ratio of the components of the mixture (1.0 wt.) is due to the low efficiency of a small amount of the additive, the upper (15.0 wt.% | by defining specimens during firing and baking to backfill or container. In ceramics containing an additive in an amount greater than 15.0 wt.%, The refractoriness decreases, the deformation under load increases, the chemical resistance deteriorates. The ratios by weight of -CaCI from 1:10 to 1, 6: 1 or CaO: Q., from 1:10 to 8: 1 are associated with the pg amount of the additive and probably affect the solubility of aluminum nitride in the liquid phase. and, consequently, on the process of liquid-phase sintering of aluminum nitride. The lower limits of the mass ratio of calcium oxide to silicon oxide CaO: S102, (1:10) or calcium oxide to boric oxide CaO: HAO-a, (1:10) relate to the maximum amount of additive, upper - CaO::, 0 (1.6: 1) or CaO: P.O. 8: 1 to the minimum amount of additive. The additive can be introduced in the form of powders of oxides, various silicium or organo-boron compounds and substances containing the indicated oxides: synthesized glass or crystalline compounds (calcium borates, calcium silicates). Of the proposed composition, the charge of the product can be made by any known method: not only semi-dry pressing, but also slip casting from suspensions in organic solvents, hot casting, drawing, hot pressing, and these compositions are prepared by mixing the components. An example of execution. Industrial spray of aluminum nitride with an A1N content of more than 99.0 wt.% Is mixed with the addition of the composition specified in the tabica. The charge is formed into billets, which are burned in a high-temperature furnace in an oxygen-free atmosphere in the temperature range of 1500-1900 C. Table 1 shows examples of experimental formulations and the results achieved on the properties of products made from the proposed mixture. The proposed composition of the charge is more efficient than the known one, since it allows one to obtain dense products at 1500–1650 ° C, which significantly reduces the energy consumption for the manufacture of products, reduces the pollution of ceramics by the material of furnace parts, as well as the dissociation of aluminum nitride into its constituent elements. This composition of the charge makes it possible to use highly productive, less energy-intensive industrial furnaces with corundum lining, operating at a temperature of up to. Products from the proposed 1x1 can be molded at pressures of 100-150 MPa. These pressures are lower than the pressures of forming articles from a mixture of known composition, which makes it possible to obtain products without repressions and delaminations from gonodisperse powders of aluminum nitride. Such a composition allows the production of large-sized articles from AIN without the use of complex molds and press equipment. The proposed composition of the charge makes it possible to obtain products with a relative density of 95.0–99, with a total porosity of 1.0–5, in the entire range of roasting temperatures of 1500–1900 ° C (porosity of 0.0–0, is open). The proposed additives are cheaper and more abundant in nature, while yttrium and lanthanum compounds are less common in the earth's crust. Yttrium and lanthanum oxides are scarce and expensive, and yttrium, an aluminum grant, is also difficult to manufacture. The economic effect from the replacement of the additive. The suggested 10 tons of products will be about 25,000 rubles. Properties of the material obtained are given in table 2. The resulting material can be used in electronic, radio 710022738

nical, aeronautical and other branches of heat-resistant electrical insulators, industrial containers as fire-rated materials for the operation of aggressive media,

resistant structural material such as liquid aluminum, gallium.

Examples to the charge

Table 1 Interval Examples, Material in Material

3 Fire resistance

72000 C in non-oxidizing compounds 6 and 1 contain the additive in the amount above the expected and examples 17 and 15 contain it below this interval. In this case, it is much inferior in properties to the claimed. Table 2

T

Specific volume

electrical resistance, ohm cm, 20 С

Linear coefficient of thermal expansion Zp-eOO C

1 / hail

The temperature of the onset of deformation under load 2 kg / cm

Claims (6)

1. Japanese Patent ff 9-203b9, cl. 20/3 / С239, published, 197. 2. Japanese Patent No. 50-1569, cl. 20/3 / SPZ, published 1975. 3. USSR Author's Certificate No. 410001, cl. C 8 35/58, 197. l. Fakhretdinov, FA, Kalinin, V. B., et al. Ceramics of enhanced heat resistance from aluminum nitride. M., Refractories, 1980, N- 3, 50-53. 5.R b. KI, Kuznetsova I.G. et al. The effect of some additives on the sintering and microstructure of ceramics made of aluminum nitride, the proceedings of the Moscow Institute of Chemical Technology. D. And. Mendeleev, c. 108, M., 1979, 6. Japanese patent number iB-18925, cl. 20/3 / С229, published 1973 (prototype).