Method of making workpieces of ceramic products

FIELD: chemistry.

SUBSTANCE: invention relates to production of materials based on zirconium dioxide stabilised with yttrium oxide, and can be used in making composite ceramic articles used in electrical engineering, mechanical engineering, chemical industry, metallurgical industry and other industries. The method of making workpieces of ceramic articles involves producing zirconium dioxide stabilised with yttrium oxide by coprecipitation after mixing with constant stirring of zirconyl nitrate and yttrium acetate solutions and subsequent hydrothermal synthesis of oxides in a supercritical fluid reactor. Heat treatment is carried out by drying at temperature of 80°C for two hours and calcining in air at temperature of 500°C for 1.5 hours. The obtained nanopowder is granulated and workpieces are moulded, which are pre-sintered in air at temperature of 800-1000°C for 1 hour at heating rate of 5°C/min. After cooling in switched off furnace conditions, the workpieces undergo mechanical treatment and final sintering in air at temperature of 1200-1300°C for 5 hours.

EFFECT: method enables to make workpieces of ceramic articles with improved physical and mechanical properties: microhardness of at least 10000 MPa from weakly agglomerated high-purity nanopowder of zirconium dioxide stabilised with yttrium oxide.

1 ex, 4 dwg

 

The invention relates to the field of molding ceramic materials based on zirconium dioxide stabilized with yttrium oxide, and can be used for casting composite ceramic products used in electrical engineering, mechanical engineering, chemical, metallurgical and other industries.

The main raw material for the production of structural oxide nanoceramic currently are synthesized in various ways nanoporosity zirconium oxide. The zirconium oxide has a very high strength (from 900 to 1200 MPa) and almost two times higher viscosity at break compared to aluminum oxide. These properties allow the use of zirconium oxide in the areas that require high stability under high stress for a long time.

The study of the processes of nanostructured ceramic and composite materials on the basis dioxide ZrO2that include the original synthesis of nanopowders, molding, compacting and sintering, is an actual problem of modern physical science, because it can be expected that new results have been obtained for fundamental studies of the properties of nanoceramic and developed methods for their manufacture will create the basis for introducing the elaborately the x nanoceramic in high-tech industrial production (cutting tool, bearing bone implants and so on).

There are many patents and articles dedicated to the creation of ceramic materials based on nano-Zirconia.

A method of obtaining nanopowder Zirconia deposition from colloidal solutions, which consists in the synthesis of nanoparticles from the source reagent solution and interrupting the reaction at a certain point in time (Herron N., Calabrese J.., Forneth W.E., Wang Y. // Science - 1993. V.259. No. 5100. P.1426), then disperse system is transferred from a liquid colloidal state in the dispersed solid (RF Patent No. 2042630, CL C01G 25/02, publ. 09.08.1995; RF Patent №2058939, CL C01G 25/02, publ. 27.04.1996). Among all methods of obtaining isolated nanoparticles and nanopowders method of deposition of colloidal solutions has the highest selectivity and allows you to get stable nanoclusters with a very narrow size distribution, which is very important. The main problem of the method of deposition of colloidal solutions related to how to avoid coalescence of the nanoparticles.

A method of obtaining a high-strength ceramic material of tetragonal Zirconia (A.S. NO. 1349199, SW 35/48, publ. 27.09.2000). The disadvantage of this invention is the marginal density of sintered samples and, consequently, low Flexural strength and low the hardness.

A method of obtaining Zirconia ceramics consisting in that the powder material is partially stabilized Zirconia is heated in the first heat treatment furnaces up to 1200°C, and then to 1580°C in an atmosphere of oxygen, resulting in sintering of a powder material (A.S. NO. 655954, SW 35/48, publ. 05.04.1979).

Obtained in this way ceramics has the following mechanical properties: density of 5.5 g/cm3and the strength of the PA curve up to 450 MPa, which is insufficient for structural ceramics and instrumental purposes.

In addition, the need for two-stage firing increases the consumption of the process and reduces performance.

A method of obtaining Zirconia ceramics consisting in that the powder material is zirconium dioxide with the addition of 5.5 wt.% the yttrium oxide is sintered in Selidovo oven at 1500-1510°C followed by cooling in liquid nitrogen (A.S. USSR №1512957, CL SW 35/48, publ. 07.10.1989). Obtained in this way ceramics has a mechanical characteristic bending strength up to 1280 MPa. However, the described method is characterized by a high energy intensity and low adaptability.

The closest analogue adopted for the prototype, is a method of manufacturing ceramics based on zirconium dioxide (RF patent No. 2194028, SW 35/486, 26.02.2001 g)comprising a mixture dioxide C is rcone with yttrium oxide by co-deposition from solutions of salts, in the moment of deposition in solutions of chlorides of zirconium and yttrium add fluorides of sodium and potassium in an amount of 0.5-1.0 wt.%, carry out the heat treatment of the mixture at 1250-1300°C, molding preform and sintering at a temperature of 1600-1700°C followed by rapid cooling to a temperature 1270-1300°C with a speed of 480-600°C/h the Disadvantage of this method of manufacturing ceramics based on zirconium dioxide is the need to use toxic fluorides, high temperature heat treatment and sintering.

Therefore one of the objectives of the present invention is to develop technology without the use of toxic fluoride and less energy intensive method of casting ceramic articles of nanopowder Zirconia with high physical-mechanical properties.

The technical result of the invention:

- high quality chemically pure preparations of ceramic products of complex shapes of various functional purposes with high physical-mechanical properties of hardness equal to not less than 10000 MPa and stored nanostructure obtained by the proposed method nanopowder tetragonal Zirconia stabilized with yttrium oxide Zr0,92Y0,08O2with crystallite size of 10-20 nm, forming a weakly bound agglomerates of a size not more than 100 nm, the area specific surface nanoease 70-100 m2/g;

- the content of the tetragonal Zirconia stabilized with yttrium oxide is not less than 95% in the blanks of ceramic after sintering;

- reducing the intensity of way through the use of lower temperatures during the preliminary and final sintering blanks.

In the method of manufacturing ceramics based on zirconium dioxide, comprising mixing a source of salts by co-deposition from solution heat treatment, forming blanks and sintering, made the following distinctive features:

1) mix solutions zirconyl nitrate and yttrium acetate served in a supercritical fluid reactor, where the hydrothermal synthesis of oxides at a temperature of 375°C and the pressure in the reactor 217,75 ATM for 20 minutes.

2) centrifuged obtained suspension;

3) heat treatment of the obtained powder of zirconium oxide stabilized with yttrium, carried out by drying at a temperature of 80°C for two hours and calcination in air at 500°C for 1.5 hours;

4) spend compound powder with isopropyl alcohol in a ratio of 20:1, then it granularit and molded workpiece;

5) after molding blanks its compact and carry out the preliminary sintering in air at a temperature of 800-100°C for 1 hour, moreover, heating is carried out at a speed of 5°C/min;

6) after cooling of the workpieces in the off mode the oven, carry out their machining;

7) the final sintering is conducted in air at a temperature of 1200-1300°C for 5 hours.

Novelty and inventive step are confirmed by the fact that in the studied literature distinguishing features of the claimed invention is not detected.

The invention is characterized by the images presented on the figures:

Figure 1. The diffraction pattern of the sample powder Zr0.92Y0.08O2after calcinations at 500°C.

Figure 2. TEM image of the powder particles Zr0.92Y0.08O2after calcinations at 500°C.

Figure 3. The temperature dependence of deformation (line 1) and the coefficient of thermal expansion α (line 2) compacted sample during sintering.

Figure 4. Pattern compacted material: 1 - before sintering and 2 after sintering at 1200°C.

The invention is carried out as follows.

For the synthesis of nano-sized powder of zirconium dioxide stabilized with yttrium (Zr0.92Y0.08O2) use the method of chemical deposition 1M solution zirconyl nitrate and 1M solution of yttrium acetate in distilled water. It is known that yttrium oxide stabilizes at room temperature tetragonally structures is zirconium dioxide, while the unstabilized zirconium dioxide crystallizes at room temperature in the monoclinic modification.

Salt solution serves high-pressure pump in a supercritical fluid reactor, where the hydrothermal synthesis for 20 min at achieving operating parameters: temperature 375°C and the pressure in the reactor 217,75 ATM. Made while the transition to the supercritical state, the rapid recovery of the oxides and their joint crystallization. The resulting milky white suspension is cooled in the heat exchanger, followed by centrifugation to produce a separation of the solid phase taps.

The solid is dried in a drying Cabinet at a temperature of 80°C for two hours, then calcined in a muffle furnace at 500°C in air for 1.5 hours. The temperature of calcination was determined on the basis of the data of thermal analysis, performed using the methods of differential thermal analysis and differential scanning calorimetry using thermoanalyzer SDT Q600.

Phase composition and structure of the synthesized powder of zirconium dioxide stabilized with yttrium, after annealing was determined by the method of x-ray phase analysis (diffractometer Rigaku Ultima IV (CuKα radiation, Ni - filter). According to the filing ICDD resulting material is Ognian the m solid solution of Zr 1-xYxO2and has a tetragonal lattice with a spatial group R42 cable line/nmc. From the analysis of the diffraction pattern (Figure 1) were calculated lattice parameters, a=3.5821 Å, C=5.2340 Å and determined the degree of tetragonality C/a=1,46.

To determine the exact elemental composition of the material was performed by x-ray analysis using raster ion-electron microscope Quanta 200 3D. It is established that the composition of the synthesized material corresponds to the composition Zr0.92Y0.08O2.

The study of powder Zr0.92Y0.08O2using transmission electron microscopy (TEM, electron microscope JEM-2100) showed that the powder consists of particles of ellipsoidal shape with an average size of ~ 10 nm (Figure 2).

To determine the topographic and structural features powder Zr0.92Y0.08O2also used the method of atomic force microscopy (AFM), which allows to obtain three-dimensional image of the dielectric materials. The experiments were conducted using scanning probe laboratory NTegra Aura in tapping mode, phase contrast. As a result of experiments it was determined that the powder Zr0.92Y0.08O2consists of elongated particles of irregular shape with an average size of ~10 nm in length, forming a weakly bound agglomerates with an average size is m ~100 nm, that is consistent with the data transmission electron microscopy.

Nanosized powder Zr0.92Y0.08O2later used as source material upon receipt of Zirconia.

Using analytical screening machines produce the connection of the source of nanosized powder with an organic additive izopropilovym alcohol in the ratio of 20:1 and granularit order to obtain homogeneous particles press powder with an average size of 1-3 microns. Use press powder ensures a uniform filling of the mold, i.e. the homogeneous material for subsequent pressing.

Formed into the workpiece, which received press powder poured into the elastic mold when using volumetric or gravimetric dosing and, if necessary, pre-compacted manually or with the help of oscillations.

Molded blank compact by cold isostatic pressing, and then placed in an electric muffle furnace to a substrate of refractory and chemically inert material of corundum. The preliminary sintering is carried out at a temperature of 800-1000°C for 1 hour in air atmosphere. The heating is carried out at a rate of ~5°C/min, cooling - off oven.

Behavior skorrektirovannogo powder during sintering was investigated by the method of d is latimeria (dilatometer NETZSCH DIL 402 C). The results of thermomechanical analysis in the temperature range from 20 to 1500°C is shown in Figure 3.

It is established that the seal skorrektirovannogo material begins at a temperature of ~650°C and continues up to 1500°C (Fig. 3, line 1). The maximum speed of the sintering process occurs at a temperature of 1040°C (Fig. 3, line 2). Therefore, it is reasonable preliminary sintering skorrektirovannogo of the material should be in the temperature range 800-1000°C, carrying out heating at a rate of ~5°C/min Pre-sintering skorrektirovannogo material provides the necessary mechanical strength sufficient for subsequent mechanical processing.

With the aim of obtaining blanks with the required size and shape with high surface after pre-sintering the exercise of their machining. Mechanical treatment is carried out using a universal grinding machine and automatic high-precision table saws. Precision machining is determined by technical conditions. After processing on universal grinding machine perform visual inspection of the surface of the workpieces. Cracks and chips are not allowed.

Conduct final sintering blanks of ceramic materials at a temperature of 1200-1300°C for 5 hours. During the final sintering is going on is it the rapid development of recrystallization "heal" holes and the formation of a homogeneous fine-grained recrystallized microstructure in the whole volume of sintered material. Increasing the sintering temperature leads to the appearance in the sintered material, in addition to the original tetragonal phase (Fig. 4 indicated by ■), monoclinic phase (Fig. 4 indicated with •) with a spatial group R/C1, and with increasing sintering temperature, the proportion of monoclinic phase increases. The influence of sintering temperature on the phase composition of the material was established according to x-ray phase analysis (Figure 4). The appearance of the monoclinic phase may be due to recrystallization skorrektirovannogo material during sintering, resulting in the increase of the initial grain size in the material. The monoclinic phase is characterized by a larger crystallite size than getregvalue. The increase in grain size of the investigated Zirconia ceramics was actually installed at the microstructural analysis using scanning electron ion microscope Quanta 200 3D. The detected change of the phase composition and grain structure (size and shape of the grains) Zirconia ceramic correlate with the change of microhardness Hv.

Controlling the geometrical dimensions of the resulting ceramic samples after the final sintering is performed on the calibration scales using calipers and feeler gauges.

The invention is further illustrated by a concrete example of its implementation.

To prepare 1 kg nanoease zirconium dioxide stabilized with yttrium oxide is prepared 1M solution zirconyl nitrate and 1M solution of yttrium acetate in distilled water for what take 1829,6436 g ZrO(NO3)2*H2O, molecular weight of zirconyl nitrate monohydrate 249,24848 g/mol, and 299,4848 g Y(CH3-COO)3*4H2O, molecular weight of yttrium acetate tetrahydrate 338 g/mol.

A solution of salts of the high-pressure pump P-401 is served in a supercritical fluid reactor R-401,5L, where the hydrothermal synthesis. The transition to the supercritical state is carried out by increasing the temperature of the reactor and, at the same time, the internal pressure. In the reactor a rapid recovery of the oxides and their joint crystallization. The reaction time is 20 min at achieving operating parameters. The operating parameters of the reactor a temperature of 375°C, pressure - 217,75 ATM. The resulting milky white suspension is cooled in heat exchanger E-402. then centrifugation to produce a separation of the solid phase from the water.

The solid is dried in a drying Cabinet at a temperature of 80°C for two hours, then calcined in a muffle furnace at 500°C in air for 1.5 hours. The final material was nanoporosem dioxide circus is tion, yttrium-stabilized Zr0.92Y0.08O2with a crystallite size of not more than 20 nm, forming a weakly bound agglomerates of a size not more than 100 nm, the impurity content of not more than 0.2 wt/ % and a specific surface area of 73 m2/g, specific adsorption BET method using gas adsorption analyzer TriStar II 3020 (Figure 1).

The obtained nanopowder zirconium dioxide stabilized with yttrium oxide Zr0.92Y0.08O2connect with isopropyl alcohol in a ratio of 20:1 using analytical screening machines and granularit order to obtain press powder. Formed into the workpiece, which received press powder poured into a plastic mold using volumetric or gravimetric dosing and pre-compacted by hand or with the help of oscillations.

Molded blank compact by cold isostatic pressing, and then placed in an electric muffle furnace to a substrate of refractory and chemically inert material of corundum.

Conduct a preliminary sintering at a temperature of 900°C for 1 hour in air atmosphere. Heating is carried out at a rate of ~5°C/min, cooling - off oven. Carry out machining of workpieces.

Spend the final sintering of the ceramic blanks mater what Alov for 5 hours at a temperature of 1200°C in air.

In the result, the final sintering the proportion of monoclinic phase in the blanks is 5%. The average grain size is ~150 nm. The results of microhardness Vickers, measured by microhardness tester 402 MVD) Instron showed that the microhardness of the samples during sintering temperature of 1200°C was Hv=10100 MPa.

Thus, the task of developing technology, without the use of toxic fluorides and with less intensity, method of casting ceramic articles from nanoease Zirconia with high physical-mechanical properties solved. The obtained preform of ceramic products with a hardness of not less than 10000 MPa from synthesized by the proposed method slaboaglomerirovannye nanoscale high-purity powder of zirconium dioxide stabilized with yttrium oxide Zr0.92Y0.08O2with predetermined physical-chemical parameters: with an average crystallite size of the powder is not more than 20 nm, forming a weakly bound agglomerates of a size not more than 100 nm, a specific surface area of 70-100 m2/g phase structure tetragonally zirconium dioxide stabilized with yttrium oxide.

The method of casting ceramic articles, including the production of zirconium dioxide stabilized with yttrium oxide by the n conjunction precipitation after mixing under stirring solutions of the starting salts, heat treatment, forming blanks and sintering, characterized in that the mixture of solutions zirconyl nitrate and yttrium acetate served in a supercritical fluid reactor, where the hydrothermal synthesis of oxides at a temperature of 375°C and the pressure in the reactor 217,75 ATM for 20 min, centrifuged, the resulting suspension, the heat treatment of the obtained powder of zirconium oxide stabilized with yttrium oxide, is carried out by drying at a temperature of 80°C for two hours and calcination in air at 500°C for 1.5 h, and then spend the compound powder with isopropyl alcohol in a ratio of 20:1, granularit it and is formed into the workpiece, which is compact and subjected to preliminary sintering in air at a temperature of 800-1000°C for 1 h, and heating is carried out at a speed of 5°C/min, after cooling in the off mode the oven carry out machining of the workpieces, and then spend the final sintering in air at a temperature of 1200-1300°C for 5 hours



 

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FIELD: construction.

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3 cl, 13 ex, 2 tbl

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1 tbl, 4 ex

FIELD: chemical industry.

SUBSTANCE: invention refers to powdered zirconium oxide, way of its production and its application in fuel cells, notably for production of electrolyte substances for ceramic fuel cells. The powdered zirconium oxide containing up to 10 mole % of at least one metal oxide from the scandium, yttrium groups, the group of rare-earth elements and/or their mixtures is characterized by the extension density from 1.2 to 2.5 g/cm³ measured according to ASTM B 417.

EFFECT: powdered zirconium oxide characterized by a high electrical conductance and a high mechanical strength after agglomerating up to gas-impermeable bodies, and an efficient way of its production.

37 cl, 3 dwg, 1 tbl, 8 ex

FIELD: chemistry.

SUBSTANCE: present invention relates to highly pure zirconium oxide powder for applying coatings on substrates meant for use in conditions with cyclic thermal loads, such as blades, guide devices and on the sealing surface of gas-turbine engines. The highly pure zirconium oxide powder, which is stabilised with yttrium or ytterbium, contains from approximately 0 to approximately 2 wt % hafnium oxide, from approximately 6 to approximately 25 wt % yttrium oxide or from approximately 10 to approximately 36 wt % ytterbium oxide, from approximately 0 to approximately 0.15 wt % impurity oxides. The impurity oxides include the following in wt %: 0-0.02 SiO2, 0-0.005 Al2O3, 0-0.01 CaO, 0-0.01 Fe2O3, 0-0.005 MgO, 0-0.01 TiO2. The coatings which form a thermal barrier have multiple vertical microcracks which are uniformly distributed on the entire coating, which increases resistance of the coatings to thermal fatigue. The coatings are applied via thermal spraying with possible subsequent thermal treatment.

EFFECT: longer service life of coated substrates.

15 cl, 7 ex, 9 tbl, 11 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing a micro- and nanoporous ceramic and can be used in machine-building, chemical industry and power engineering to produce filter materials, catalyst supports and components of porous systems with special properties. The method of producing micro- and nanoporous ceramic based on zirconium dioxide involves preparation of a suspension of fine powder with a binding component, pouring the suspension into a mould, gelling and dehydrating the gel substance, drying and sintering the material. The gel substance is dehydrated by evacuation through a microporous substrate made from cordierite ceramic with micro- and nano-sized pore distribution. The microporous substrate determines the size and distribution of pores formed in the material.

EFFECT: obtaining a porous ceramic based on zirconium dioxide with given pore size.

2 ex, 4 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing wear resistant ceramic based on zirconium dioxide which is partially stabilised with yttrium oxide, and can be used in making components for tribological application as a draw plate, draw ring, bearings etc. The method employs chemical deposition of zirconium and yttrium hydroxides from a mixture of salts with specific surface area of not less than 200 m2/g, with further thermal treatment of powder at temperature 900-1000°C. Sintering of the workpieces formed from said powder is carried out in the region of existence of a tetragonal phase: sintering to temperature 1300-1350°C is carried out while heating at a rate of 750-1000°C per hour, holding for 2-3 hours and subsequent cooling at a rate of 1000-1100°C per hour. Fast raising and sharp cooling enable to obtain a ceramic with size of structural elements of up to 200 nm and with 100% content of tetragonal crystalline phase.

EFFECT: high wear resistance of the ceramic in conditions of dry friction in a pair with steel.

2 cl, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to making refractory and ceramic articles based on zircon and can be used mechanical engineering, aviation and electrical engineering industries. The mixture contains the following in wt %: 84-86 zircon concentrate with particle size of 1-2 mcm with aluminium oxide in amount of not more than 0.2% and 14-16 zirconium dioxide stabilised with 5% yttrium oxide, having particle size of 15-20 nm.

EFFECT: invention enables to obtain a dense, fine-grained zircon based ceramic which does not contain a glass phase.

1 tbl, 1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a composite target in form of a rod, made from ceramic powder and meant for evaporation under the effect of an electron beam, containing zirconium dioxide and at least one zirconium dioxide stabiliser. The stabiliser used is at least one element from a group of oxides of rare-earth elements, titanium oxide and niobium oxide. The target is distinguished by that, the said zirconium dioxide stabiliser is contained in molar concentration of 2-30%, and the said zirconium dioxide is 90% more than the formed monoclinic phase. The target has density of 3.9 g/cm3, average diametre pores d50 less than 2mcm and porosity ranging from 30 to 50%. The target is used when making a heat barrier with low heat conduction and high thermal resistance and mechanical strength from ceramics, formed through evaporation under the effect of an electron beam.

EFFECT: obtaining a target with optimum mechanical properties and heat resistance.

16 cl, 3 ex

The invention relates to a method of manufacturing ceramics based on zirconium dioxide stabilized with yttrium oxide, with small additions of fluorides of sodium and potassium, obtained by chemical deposition from solutions of salts

FIELD: nanotechnology.

SUBSTANCE: invention relates to the field of nanomaterials. A method is proposed for production of fluorescent labels based on biocompatible and biodegradable nanoparticles of silicon for application in vivo by the reaction of disproportionation of silicon monoxide at a temperature of 950°C in air atmosphere followed by interaction of the resulting nanoparticles of silicon with dimethylsulfoxide. The proposed method enables to produce two outfits of nanoparticles with the size of 2.0-2.5 nm with photoluminescence peaks at 676 nm and 774 nm.

EFFECT: production of hydrophilic biocompatible and biodegradable fluorescent labels of nanocrystalline silicon, having sustained bright luminescence and narrow function of size distribution, resistant to high temperatures (up to 220°C) without the use of toxic substances in the process of their synthesis; resulting nanoparticles are applicable as labels in vivo in imaging of deep-seated tissues and organs.

1 cl, 3 dwg

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