WO2014158052A1

WO2014158052A1 - Method for producing ceramic gradient material

Info

Publication number: WO2014158052A1
Application number: PCT/RU2013/000264
Authority: WO
Inventors: Сергей Николаевич КУЛЬКОВ; Светлана Петровна БУЯКОВА; Сергей Григорьевич ПСАХЬЕ
Priority date: 2013-03-29
Filing date: 2013-03-29
Publication date: 2014-10-02
Also published as: RU2592652C2; RU2014151346A

Abstract

The invention relates to powder metallurgy, and specifically to the production of ceramic gradient materials on the basis of metal oxide powders. The method for producing a ceramic gradient material includes first obtaining a polydisperse ceramic powder of a metal oxide or of a mixture of metal oxides using a plasma-chemical method by means of spraying aqueous solutions of salts of a metal or of a mixture of salts of metals into a high-frequency discharge plasma through a slot nozzle having a variable cross-section of 0.1-100 microns. An organic binder is added to the powder and the molding mixture is mixed and is poured into a mold. The molding mixture is cured for stratification by particle size and the resulting product is sintered isothermally.

Description

METHOD FOR PRODUCING CERAMIC GRADIENT

MATERIAL

FIELD OF TECHNOLOGY

The invention relates to powder metallurgy, in particular to the manufacture of gradient ceramic materials based on powders of metal oxides or mixtures thereof and can be used to obtain products with variable porosity, for example, bone implants, filters, drug carriers, etc. with increased resistance to thermal impacts.

Known methods for producing gradient materials are:

- in the sequential deposition of layers of various powders and their selective sintering (Wang, Chunchau, Ni, Yiadong. Cu / Fe Powder

Gradient Material Sintering by Laser Processing // Proceedings SPIE. Vol. 3550. Pp. 60-64. 1998) [1];

- in pressing and sintering a frame made of titanium carbide powder followed by impregnation with titanium nickelide and alloying with iron to create a gradient structure (Sivokha V.P., Rudai V.V., Mironov Yu.P., Kulkov S.N. Composite materials TiC -NiTi with a gradient structurally unstable matrix / Physical Mesomechanics, 2004, 7th Special Issue 4.1, pp. 241-244) [2];

The disadvantages of these methods include the following: The main disadvantage for all known is a sharp change in the properties in macro-volumes of the material.

In addition to the indicated drawback, the known method [1] does not allow to obtain sintered regions from various powders lying in the same plane, which leads to the presence of a vertical interface between the product areas, and the disadvantage of the method [2] is the multistage process of obtaining a gradient material. A known method of producing composite materials with a gradient structure (RU2164260, C22C1 / 04, C22C29 / 00, B22F3 / 12, publ. 20.03.2001) [3], including the preparation of the mixture, pressing and sintering in the backfill, while the mixture is prepared from compounds selected from the group consisting of carbides, oxycarbides, carbonitrides, nitrides with the addition of steels or alloys containing elements that can evaporate during sintering, and sintering is carried out in vacuum at 1200-1500 ° C with a holding time of 10-300 min, while one of pressing surfaces free of backfill.

The disadvantages of this method [3] is the multi-stage process and the limited method for using only metal impregnation materials with a melting point in the range from 1200 ° C to 1500 ° C.

The closest in technical essence is a method of obtaining a ceramic gradient material (RU2454297, B22F3 / 12,

С04В35 / 64, С22С1 / 10, publ. June 27, 2012) [4] based on zirconium dioxide. A finely dispersed powder in the form of supersaturated solid solutions on the basis of 2GO with components dissolved in it selected from the group of stabilizing oxides of the tetragonal phase is pressed at a pressure of 550-800 Pa and sintered at 500-1700 ° C for 1-5 hours.

The disadvantage of the gradient material obtained by the known method [4] is that it has insufficiently high resistance to thermal effects during cyclic exposure and is at temperatures of 1400-600 ° C less than 50 cycles.

SUMMARY OF THE INVENTION An object of the invention is to develop a method for producing a ceramic gradient material, in which the structure provides a uniform change in the mechanical properties of product cross section and, as a result, high resistance to thermal influences.

The specified technical result is achieved by the fact that in the method for producing a ceramic gradient material, which consists in molding a preform and sintering it, a polydisperse ceramic metal oxide powder or a mixture of metal oxide powders is first obtained by the plasma-chemical method by spraying aqueous solutions of metal salts or mixtures of metal salts into a high-frequency discharge plasma through a slot nozzle of variable cross-section from 0.1 to 100 μm, then an organic binder is added to the obtained powder, mix the molding mixture, pour it into the mold, hold the molding mixture to separate it into fractions and sinter the obtained preform with isothermal exposure.

A polydisperse ceramic metal oxide powder or a mixture of metal oxide powders is obtained with a particle morphology - from individual nanocrystallites 20-50 nm in size to spherical hollow particles up to 250 microns in size.

The molding mixture has the following ratio of components, wt.%: Metal oxide powder or a mixture of metal oxide powders 80-85; organic bunch the rest.

Polydisperse ceramic metal oxide powder or a mixture of metal oxide powders is an oxide powder: A1 ₂ 0 ₃ , Zr0 ₂ , CaO, Y ₂ 0 ₃ , MgO.

Paraffin, or wax, or a mixture of paraffin and wax in a ratio of 9: 1 is used as an organic ligament.

The molding mixture is stirred at a temperature of 85-90 ° C.

The molding mixture is kept in a form to separate it into fractions for 1-10 hours at a temperature of 75-90 ° C.

The resulting preform is sintered at a temperature of 1300 - 1700 ° C with an isothermal exposure of 1-5 hours.

The essence of the invention lies in the fact that a ceramic material with a gradient structure is obtained from a polydispersed ceramic metal oxide powder or a mixture of metal oxide powders obtained by the plasma-chemical method by spraying aqueous solutions of metal salts or mixtures of metal salts into a high-frequency discharge plasma through a slot nozzle of variable cross section from 0.1 to 100 μm. As a result of the high temperature of the plasma, rapid evaporation-decomposition of the salt occurs with the formation of particles of a powder of a polydispersed metal oxide or a mixture of metal oxides. In this case, a polydisperse ceramic metal oxide powder or a mixture of metal oxide powders with particle morphology is obtained — from individual nanocrystallites 20-50 nm in size to spherical hollow particles up to 250 microns in size. The presence of polydisperse particles will provide the necessary different density of the casting when it is aged after casting.

In the obtained polydisperse ceramic metal oxide powder or a mixture of metal oxide powders to obtain a molding mixture, an organic binder is added, which is: paraffin, or wax, or a mixture of paraffin and wax in a ratio of 9: 1. The ratio of the components of the molding mixture is as follows, wt.%: Metal oxide powder or a mixture of powders of metal oxides 80-85; organic bunch the rest.

At a temperature of 85-90 ° C, the molding mixture is thoroughly mixed for 25-50 hours, then it is poured into the mold and kept at the melting temperature of the organic binder 75-90 ° C for 1-10 hours. As a result, the formation mixture is stratified into fractions due to the gradient deposition of fractions of the obtained powder particles. Varying the exposure time (1-10 hours) and the temperature at which the organic binder is located (75-90 ° С), i.e. the process of stratification of the molding mixture into fractions in the form, you can get a ceramic material with a given gradient structure and, therefore, resistance to thermal influences. After the specified time, the resulting preform is sintered at a temperature of 1300 - 1700 ° C with isothermal exposure for 1-5 hours. Ceramic material obtained by the proposed method has gradually changing porosity and a uniform (smooth) change in properties over the entire volume of the material obtained as it moves away from the surface into the volume. The obtained ceramic gradient material has a variable porosity structure in the volume - from 20 to 75 vol.%.

The stability of the obtained ceramic gradient material during cyclic exposure at a temperature of 1600 ° C for at least 200 cycles.

EXAMPLES OF SPECIFIC IMPLEMENTATION

Example 1

To obtain a polydisperse ceramic powder of zirconium oxide, an aqueous solution of zirconium nitrate is taken and sprayed through a slot nozzle of variable cross-section - from 0.1 to 100 μm into a high-frequency discharge plasma.

An organic binder is added to the obtained polydisperse ceramic powder of zirconium oxide taken in an amount of 80 wt.% - a mixture of paraffin and wax (9: 1) in an amount of 20 wt.%, Then stirred for 50 hours at a temperature of 85-90 ° C. The resulting moldable mixture is poured / injected into the mold and kept in this state, i.e. at a temperature of 90 ° C for 2 hours. The resulting preform is sintered at a temperature of 1550 ° C with an isothermal exposure of 1 hour.

The stability of the obtained ceramic gradient material during cyclic exposure at a temperature of 1600 ° C for 200 cycles.

Example 2

To obtain a polydisperse ceramic powder of aluminum oxide, an aqueous solution of aluminum nitrate salt is taken and sprayed through a slot nozzle of variable cross section - from 0.1 to 100 μm into a high-frequency discharge plasma. In the obtained polydisperse ceramic powder of alumina, taken in an amount of 85 wt.% Add an organic binder - paraffin in an amount of 15 wt.%, Then stirred for 35 hours at a temperature of 85-90 ° C. The resulting moldable mixture is poured / injected into the mold and kept in this state, i.e. at a temperature of 75 ° C for 10 hours. The resulting preform is sintered at a temperature of 1300 ° C with an isothermal exposure of 5 hours.

The stability of the obtained ceramic gradient material during cyclic exposure at a temperature of 1600 ° C 220 cycles.

Example 3

To obtain a polydisperse ceramic powder of zirconium, magnesium, and yttrium oxides, take an aqueous solution of the nitric acid salt of zirconium, magnesium, and yttrium, spray it through a slot nozzle of variable cross section, from 0.1 to 100 μm, into a high-frequency discharge plasma.

The resulting polydisperse ceramic powder of zirconium, magnesium and yttrium oxides taken in an amount of 82 wt.%. add an organic binder - wax in an amount of 18 wt.%, then mix for 40 hours at a temperature of 85-90 ° C. The resulting moldable mixture is poured / injected into the mold and kept in this state, i.e. at a temperature of 85 ° C for 2 hours. The resulting preform is sintered at a temperature of 1700 ° C with an isothermal exposure of 1 hour.

The stability of the obtained ceramic gradient material during cyclic exposure at a temperature of 1600 ° C 210 cycles.

Example 4

To obtain a polydisperse ceramic powder of zirconium and calcium oxides, an aqueous solution of zirconium and calcium nitrate is taken, sprayed through a slot nozzle of variable cross section - from 0.1 to 100 μm into a high-frequency discharge plasma.

An organic binder is added to the obtained polydisperse ceramic powder of zirconium and calcium oxides taken in an amount of 84 wt.% - a mixture of paraffin and wax (9: 1) in an amount of 16 wt.%, then stirred for 25 hours at a temperature of 85-90 ° C. The resulting moldable mixture is poured / injected into the mold and kept in this state, i.e. at a melting point of an organic binder of 80 ° C for 6 hours. The resulting preform is sintered at a temperature of 1600 ° C with an isothermal exposure of 3 hours.

SUBSTITUTE SHEET (RULE 26)

Claims

CLAIM

1. A method of obtaining a ceramic gradient material, which consists in forming a preform and sintering it, characterized in that the polydisperse ceramic metal oxide powder or a mixture of metal oxide powders is first obtained by the plasma-chemical method by spraying aqueous solutions of metal salts or mixtures of metal salts into a high-frequency discharge plasma through a gap a nozzle of variable cross section from 0.1 to 100 μm, then an organic binder is added to the obtained powder, the molding mixture is mixed, d Lee pour it into a mold, molding the mixture incubated for its separation into fractions and the resulting preform is sintered with isothermal exposure.

2. The method according to claim 1, characterized in that the polydisperse ceramic metal oxide powder or a mixture of metal oxide powders is obtained with a particle morphology - from individual nanocrystallites with a size of 20-50 nm to spherical hollow particles up to 250 microns in size.

3. The method according to claim 1, characterized in that the molding mixture has the following ratio of components, wt.%:

metal oxide powder or a mixture of powders of metal oxides 80-

85,

organic bunch the rest.

4. The method according to any one of claim 1 or claim 2 or claim 3, characterized in that the polydispersed ceramic metal oxide powder or a mixture of metal oxide powders is an oxide powder: Al ₂ O ₃ , ZrO ₂ , CaO, Y ₂ O ₃ , MgO.

5. The method according to any one of claim 1 or claim 3, characterized in that paraffin, or wax, or a mixture of paraffin and wax in a ratio of 9: 1 is used as an organic bond.

6. The method according to claim 1, characterized in that the molding sand is mixed at a temperature of 85-90 ° C for 25-50 hours.

SUBSTITUTE SHEET (RULE 26)

7. The method according to claim 1, characterized in that the moldable mixture is kept in a mold for stratification into fractions for 1-10 hours at a temperature of 75-90 ° C.

8. The method according to claim 1, characterized in that the obtained preform is sintered at a temperature of 1300 - 1700 ° C with an isothermal exposure of 1-5 hours.

SUBSTITUTE SHEET (RULE 26)