RU2129999C1 - Method of manufacturing ceramic material - Google Patents

Abstract

FIELD: ceramics. SUBSTANCE: method of manufacturing alumina-based ceramic material, suitable as refractory material for military-destination armory constructions, including heat pretreatment of talc followed by mixing it with alumina, adding titanium oxide, joint wet milling of charge components, drying, calcination, pressing, and sintering is distinguished by that charge components, prior to be mixed, are separately dispersed until magnitude of specific surface not higher than 10000 sq.cm/g is attained, after which components are sieved and demagnetized, and, after charge is dried, it is additionally sieved. EFFECT: increased apparent density and mechanical strength. 6 cl, 1 tbl

Description

 The invention relates to the field of military equipment and can be used in the manufacture of high-strength material for armor-resistant construction.

 A known method of hardening of ceramics, according to which a metal film is applied to the surface of a ceramic material and subjected to heat treatment (see application EPO N 0152951, publ. 28.08.85, MKI C 04 B 41/88).

 The disadvantage of this method is the high complexity and lack of mechanical strength of the obtained material.

 A well-known manufacturing process for the production of corundum ceramic material, including preliminary firing of technical alumina, grinding alumina and electrofused corundum, casting from aqueous suspensions, sintering and firing of corundum (see the book by V. L. Balkevich "Technical Ceramics", Publishing House of Construction Literature, M. , 1968, p. 89).

 Corundum ceramic material obtained by a known method, often does not provide the necessary strength characteristics required, in particular, for the manufacture of armored structures.

 Closest to the proposed is a method for producing corundum ceramic material with a reduced sintering temperature (see the article by VB Lozhnikov et al. "Corundum ceramic material with a reduced sintering temperature", in the journal Glass and Ceramics, Moscow, Stroyizdat, N 8 for August 1992, pp. 21-22).

 According to this method, alumina in the form of technical alumina was mixed in a ball mill with boric acid, followed by heat treatment, and heat treatment of talc was simultaneously carried out. The heat-treated alumina and talc were subjected to joint grinding with modifying additives by a wet method in a ball mill, then dried, a thermoplastic slip was prepared, and sintered in an electric slot furnace.

 According to this method, a ceramic material was obtained using aluminum oxide in the form of heat-treated technical alumina of the GOO brand, as a result of which the strength characteristics of the final product were low. The grinding time is quite long, more than 50 hours. Combined grinding of aluminum oxide and modifying additives does not allow to obtain a material with optimal physical characteristics. The combination of these disadvantages significantly affected the quality of the obtained ceramic material and did not provide a uniform and equally dense with high strength characteristics of the workpiece.

 The proposed method is aimed at obtaining a ceramic material with a high apparent density and mechanical strength, which allows it to be used, in particular, in the manufacture of armored structures.

This goal is achieved by a method of producing a ceramic material based on aluminum oxide, including preliminary heat treatment of talc and its subsequent mixing with alumina and titanium oxide, joint wet grinding of the charge components, followed by drying and calcination, pressing and sintering, while before mixing the charge components they are separately dispersed to a specific surface area of not more than 10,000 cm ² / g, followed by their screening and magnetization, i.e. magnetic separation, and after drying the mixture spend its additional sieving.

Heat treatment of talc is carried out at a temperature of 1170 ^o C ± 10 ^o C.

 Talc dispersion is carried out for 1.5 hours.

 The components are mixed and co-milled wet for 3 hours.

Calcination of the charge is carried out at a temperature of 900 ^o C ± 30 ^o C.

 Cylinders made of ceramic material with an alumina content of at least 73% high (13 ± 1) mm and a diameter of (12 ± 1) mm are used as grinding bodies.

 According to the proposed method, the ceramic material was obtained as follows.

 The initial components were: a) aluminum oxide in the form of technical alumina GOST 6912.1-93 grade GK, with an α-form content of at least 85%; b) talc of the lump of the Onotsk deposit, TU21-25-207-86, which contains magnesium oxide (II), silicon oxide (IV) and impurities of calcium oxide (II), iron oxide (III), sodium and potassium oxides; c) titanium (IV) oxide, TU6-10-727-87.

 In the beginning, the components were prepared.

 To obtain the ceramic material, aluminum oxide was used in the form of technical alumina of the GK brand, since it is more stable in its physical and chemical characteristics, it has a higher α-content, less clogging impurities, in particular alkaline, which adversely affect mechanical strength, it allows to exclude preliminary heat treatment.

Talc was crushed on a jaw crusher, manually sorted, selecting ferruginous inclusions, subjected to heat treatment in a gas furnace at (117 ± 10) ^o C and dispersed. Alumina was also dispersed separately from talc for 4 hours. Titanium oxide, like other components, was also dispersed to
S _beats ≤ 10000 cm ² / g.

After this, all the starting components were mixed and wet co-milled in a ball mill of the MSh-60 type for 3 hours. After grinding, they were dried, washed on a 0355 grid, magnetization was carried out and calcined at a temperature of 900 ^o C, then they were again sieved and fresh powders were prepared, and then blanks were formed by double-sided pressing on hydraulic presses and subjected to sintering in gas furnaces at (1430 ± 10) ^o C.

Compared with the prototype of the proposed method, the dispersion of the starting components is carried out separately and up to S _beats. ≤ 10000 cm ² / g. This allows you to more evenly distribute the particles of the components among themselves and thereby create favorable conditions for effective sintering and obtaining a fine-grained structure, which determines the high mechanical strength of the obtained ceramic material. In addition, pre-dispersion reduces the wet grinding time.

In contrast to the prototype, talc was subjected to preliminary calcination at (117 ± 10) ^o C for 2 hours (at maximum temperature). This is significantly lower than the heat treatment temperature of the prototype. Lowering the firing temperature causes changes in the structural structure of the components of talc in comparison with the prototype, namely it increases the reactivity, increases the mutual penetration of the particles of the substance into each other and ultimately leads to more favorable conditions for the creation of a fine-crystalline structure. The use of 0355 mesh during sieving also made it possible to evenly distribute and increase the reactivity of the components.

 The combination of these operations ultimately led to a technical result - a ceramic material with high mechanical strength and apparent density.

 An example of a specific implementation.

Billets were made of ceramic material, including, kg:
Aluminum oxide in the form of technical alumina brand GK - 18.8
Talot of Onot - 0.7
Titanium Oxide - 0.5
As grinding media, cylinders made of ceramic material with an alumina content of at least 73% and a height of (13 ± 1) mm were used; diameter (12 ± 1) mm.

 Distilled water was used for wet mixing and co-milling.

The ratio of material: grinding media: water = 1: 3 - 4.5: 1
Talc was crushed, calcined at T ^o = 1170 ^o C ± 20 ^o C.

All components were dispersed to S _beats. ≤ 10000 cm ² / g. Preparation of the material (mixing the components and co-grinding by wet method) was carried out in the mill МШ-60 for 3 hours. Next, drying was performed, sieved through a 0355 sieve, magnetization was carried out, the charge was calcined at (900 ± 30) ^o C, again sieved through a 0355 mesh , prepared a pre-powder, formed blanks on a hydraulic press with double-sided pressing, by filling the pre-powder into a metal mold, compressing and shaping it and the necessary strength under pressure, sintered the preforms in a gas furnace with holding at maximum second temperature 1430 ^o C ± 10 ^o C for 2 - 2.5 hours.

 Technical characteristics of the obtained material are shown in the table.

 As can be seen from the table, the apparent density and hardness of the proposed ceramic material is higher than that of the prototype.

 The ceramic material obtained by the proposed method has high mechanical strength, which allowed it to be used for the manufacture of elements for armored structures, in particular bulletproof vests.

 The test results of the armor blocks obtained by the proposed method are positive, provide protection against bullets B-32 and LPS OB / SST cartridge 7.62 • 54P for the SVD rifle. Vitality of armor plates of 6-8 rounds.

Claims (6)

1. A method of manufacturing a ceramic material based on aluminum oxide, including preliminary heat treatment of talc and its subsequent mixing with aluminum oxide and the addition of titanium oxide, joint wet grinding of the charge components, followed by drying and calcination, pressing and sintering, characterized in that before mixing the components the charges carry out their separate dispersion to a specific surface area of not more than 10,000 cm ² / g, followed by their sifting and magnetization, and after drying, the charge is carried out for additional sifting. 2. The method according to claim 1, characterized in that the heat treatment of talc is carried out at (1170 ± 10) ^o C.  3. The method according to claim 1, characterized in that the dispersion of talc is produced within 1.5 hours  4. The method according to claim 1, characterized in that the mixing of the components and joint grinding by the wet method is carried out for 3 hours 5. The method according to claim 1, characterized in that the calcination of the charge is carried out at (900 ± 30) ^o C.  6. The method according to claim 1, characterized in that as the grinding media use cylinders of high alumina material.

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