Preparation method of novel ultrahigh-density ceramic material

Abstract

The invention provides a preparation method of a novel ultrahigh-density ceramic material, and relates to the technical field of ceramic material preparation. According to the invention, the ceramic raw material is subjected to high-temperature and high-pressure gradient sintering by using the large-cavity cubic press and the improved synthetic block to obtain the ultrahigh-density ceramic material, so that the physical properties such as hardness, density and bending resistance of the ceramic material are remarkably improved; compared with a ceramic material obtained through hot isostatic pressing sintering, the hardness of various ultrahigh-density ceramic materials obtained through the method is improved by about 7%-22%, the density is improved by about 0.6%-2.1%, and the bending strength is improved by about 12%-28%. The improvement of the performance can significantly expand the application of the ceramic material in the fields of aerospace, military industry, precise instruments, biomimetic materials and the like.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic material preparation, and in particular to a method for preparing a novel ultra-high density ceramic material. Background Art

[0002] Ceramics is a material composed of inorganic non-metallic solids with a variety of components, various elements (such as O, B, C and N), or in the form of oxides, carbides, borides and silicates of metal and non-metal elements. Its properties depend on the relationship between these elements. Industry insiders describe ceramics as "the art and science of making and using solid materials." The main difference between ceramics and other materials is that ceramic materials have lower density, high temperature resistance, corrosion resistance, wear resistance and other properties. Relying on the above properties, ceramic materials have been widely used in industry, machinery, aerospace, defense, precision instruments and other fields, including cutting tools, automobile engine parts, crucibles for melting metals and glass, turbochargers, brake discs, aerospace window materials and many other aspects. At the same time, it is also used in biomedical applications, such as orthopedic prostheses and dental implants. Ceramics produced specifically for medical and dental applications were later called "bioceramic dynamics."

[0003] At present, the industrial production of ceramic materials mostly uses hot isostatic pressing furnaces to sinter the formed embryos, but there are problems such as low ceramic hardness, sintered density of only 96-99%, low transparency, and small blocks, which seriously limit its application development. In addition, the internal pressure of existing ceramic sintering equipment during the manufacturing process of ceramic materials is only below 200 MPa, so its density, hardness and toughness are quite different from the theoretical values ​​of the material. If the density, hardness and toughness of ceramic materials need to be improved, the internal pressure of the ceramic sintering equipment during the manufacturing process of ceramic materials needs to be increased.

[0004] Publication No. CN101186510A discloses a method for preparing a block-shaped non-crack transparent nano-ceramic. Although the method successfully prepares a block ceramic by sintering the raw material powder under high pressure and high temperature using a hexahedral press, the block is still small and cannot be industrialized, and there is no clear description of the improvement of the hardness, density, bending resistance and other properties of the ceramic material. The present invention aims to provide a new method for preparing a large block of zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride, silicon boride and a composite ceramic material thereof that can significantly improve the hardness, density, bending resistance and transparency. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the shortcomings of the prior art, the present invention provides a new method for preparing ultra-high density ceramic materials using an improved large-cavity hexahedral press and an ultra-large synthetic block. The method achieves significant improvements in the block volume, hardness, density, bending resistance and other aspects of zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride, zirconium boride and their composite ceramic materials.

[0007] (II) Technical solution

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0009] The present invention provides a novel method for preparing ultra-high density ceramic materials, the preparation method comprising the following preparation steps:

[0010] (1) Powder vacuum treatment: Ceramic raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, heat to 1200-1300°C at 20°C / min, keep warm for more than 10 hours, and then cool to room temperature for use;

[0011] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form an embryo;

[0012] (3) High temperature and high pressure sintering: The embryo is placed in a modified synthetic block and kept warm for 1-2 hours at a pressure of 1-2 GPa and a temperature of 1200°C-2200°C using a large cavity six-sided top press. After sintering, the temperature is reduced and the pressure is released to obtain an ultra-high density ceramic material.

[0013] Furthermore, in step (1), the ceramic raw material powder is one or more of zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride, and silicon boride.

[0014] Furthermore, in step (2), the embryo body is a cylinder with a diameter of 150 mm and a height of 132 mm.

[0015] Furthermore, in step (3), the synthetic block comprises two talc bushings symmetrically distributed up and down, a circular hole is opened in the middle of the talc bushing, the inner side of the talc bushing is inlaid with a dolomite lining, the inner side of the dolomite lining is provided with a heat-insulating component which can be moved up and down, a heating component is provided in the heat-insulating component, ceramics are provided in the heating component, magnesium oxide sheets are provided at the upper and lower ends of the ceramics, pressure transmission components are provided at the outer ends of the magnesium oxide sheets, and a conductive component is provided in the pressure transmission component.

[0016] Wherein, the heat-insulating component is a samarium oxide tube, and the samarium oxide tube is a cylindrical structure.

[0017] Wherein, the heating component comprises a carbon heating tube, an inner side of the carbon heating tube is provided with a sample protection component which can move up and down, and an outer side of the carbon heating tube is in contact with an inner side of the heat preservation component.

[0018] The sample protection component is a magnesium oxide tube, the outer side of the magnesium oxide tube is bonded to the inner side of the carbon heating tube, the inner side of the magnesium oxide tube is bonded to the outer side of the ceramic, and the upper and lower ends of the ceramic are flush with the outer end surface of the magnesium oxide tube.

[0019] Wherein, magnesium oxide sheets are respectively arranged at the upper and lower ends of the ceramic, the outer end surface of the magnesium oxide sheet is flush with the outer end surface of the carbon heating tube, and the outer side surface of the magnesium oxide sheet is in contact with the inner side surface of the carbon heating tube.

[0020] Wherein, the conductive component includes a second molybdenum sheet, and the inner end surface of the second molybdenum sheet is bonded to the outer end surface of the magnesium oxide sheet.

[0021] A molybdenum column is arranged in the middle of the outer end face of the second molybdenum sheet, a molybdenum sheet is arranged on the upper end face of the molybdenum column, a metal plug is arranged on the outer end face of the first molybdenum sheet, and dolomite is inlaid in the middle of the outer end face of the metal plug.

[0022] Among them, the pressure transmission component includes a barium zirconate sheet, a magnesium oxide ring is arranged on the outer end face of the barium zirconate sheet, a pyrophyllite ring is arranged on the outer end face of the magnesium oxide ring, and the outer side faces of the pyrophyllite ring, the magnesium oxide ring, the barium zirconate sheet, and the samarium oxide tube are fitted with the inner side face of the pyrophyllite bushing.

[0023] Among them, the two outer end faces of the molybdenum sheet are provided with barium zirconate sheets, a through hole is opened in the middle of the barium zirconate sheet, a molybdenum column is arranged in the through hole, the molybdenum column can be moved up and down in the through hole, and the outer side of the molybdenum column is in contact with the through hole.

[0024] The outer side surface of the metal plug is in contact with the inner side surfaces of the pyrophyllite ring and the magnesium oxide ring, and the outer end surface of the metal plug is flush with the outer end surface of the pyrophyllite ring and the outer end surface of the pyrophyllite bushing.

[0025] When the synthetic block is in use, ceramic is filled in the magnesium oxide tube, and the upper and lower end surfaces of the ceramic are flush with the upper and lower end surfaces of the magnesium oxide tube. A carbon heating tube is set on the outer side of the magnesium oxide tube, and the carbon heating tube is bonded to the magnesium oxide tube. A samarium oxide tube is set on the outer side of the carbon heating tube, and the magnesium oxide tube is bonded to the samarium oxide tube. Magnesium oxide sheets are placed on the upper and lower end surfaces of the ceramic, and the outer side surface of the magnesium oxide sheet is bonded to the inner side surface of the carbon heating tube. After the magnesium oxide sheet is placed, the outer end surface of the magnesium oxide sheet is flush with the outer end surface of the carbon heating tube; then a second molybdenum sheet is placed on the outer end surfaces of the upper and lower magnesium oxide sheets respectively, and after the second molybdenum sheet is placed, the outer end surface of the second molybdenum sheet is flush with the outer end surface of the samarium oxide tube; barium zirconate sheets are symmetrically placed on the upper and lower ends of the samarium oxide tube, and the middle hole of the barium zirconate sheet A molybdenum column is placed inside, a magnesium oxide ring is placed on the outer end face of the barium zirconate sheet, a molybdenum sheet one is placed inside the magnesium oxide ring, the molybdenum sheet one is fitted with the outer end face of the barium zirconate sheet, a pyrophyllite ring is placed on the outer end face of the magnesium oxide ring, the inner hole size of the pyrophyllite ring is equal to the inner hole size of the magnesium oxide ring, a metal plug is placed inside the pyrophyllite ring and the magnesium oxide ring, the inner end face of the metal plug is fitted with the molybdenum sheet one, and the outer end face of the metal plug is inlaid with dolomite; pyrophyllite bushings are symmetrically arranged on the outer side of the samarium oxide tube, the outer side face of the samarium oxide tube is fitted with the inner side face of the pyrophyllite bushing, and the inner side face of the pyrophyllite bushing is inlaid with dolomite lining, at this time, the outer side faces of the metal plug, the magnesium oxide ring, and the barium zirconate sheet are fitted with the inner side face of the pyrophyllite bushing, and the outer end face of the pyrophyllite ring and the outer end face of the pyrophyllite bushing are located in the same plane.

[0026] Through the six top hammers of the six-sided top press, the six-sided top press is a prior art and no technical description is made. It can realize the extrusion force on the six sides of the device; the six side surfaces formed by the combination of the two talc bushings are pressurized at the same time to increase the pressure on the internal ceramic material, and the extrusion pressure is much greater than the pressure exerted on the ceramic material by the traditional hot pressing sintering or hot isostatic pressing sintering method; at the same time, the upper and lower top hammers are energized, and the way of energizing the upper and lower top hammers is not technically restricted, and the functions required by this application can be achieved; it is in contact with the upper and lower metal plugs (the metal plugs can be energized, and the specific material is not technically restricted), the plugs transmit the current to molybdenum sheet one, the molybdenum sheet one contacts the molybdenum column in the middle of the barium zirconate sheet, the molybdenum column contacts the molybdenum sheet two, and the molybdenum sheet two transmits the current evenly to the carbon heating tube, forming a loop up and down to heat the ceramic material in the magnesium oxide tube.

[0027] Furthermore, in step (3), the cylinder diameter of the six-sided top press is 1200 mm.

[0028] Furthermore, in step (3), sintering is carried out under gradient conditions, specifically, the synthetic block containing the embryo is placed on a six-sided top press, the pressure is increased to the initial pressure, and the temperature is raised to the initial temperature at a rate of 250-280°C / min; after the pressure and temperature reach the initial set values, the temperature and pressure are maintained for 10-20 minutes, and then the temperature and pressure setting values ​​are reached at a rate of 2kPa-4kPa / min, 350-400°C / min, and then maintained under these conditions for 1-2 hours.

[0029] (III) Beneficial effects

[0030] The present invention uses a large cavity six-sided top press and an improved synthesis block to perform high-temperature and high-pressure gradient sintering on ceramic raw materials to obtain ultra-high density ceramic materials, achieving a significant improvement in physical properties such as hardness, density and bending resistance of ceramic materials. The various ultra-high density ceramic materials obtained by the method of the present invention are about 7 to 22% higher in hardness, about 0.6 to 2.1% higher in density, and about 12 to 28% higher in bending strength than ceramic materials obtained by hot isostatic pressing. The above performance improvement can significantly expand the application of ceramic materials in aerospace, military industry, precision instruments, biomimetic materials and other fields.

[0031] The synthetic block provided by the present invention adopts a six-sided pressurization method, which can improve the uniformity of force around the ceramic material and ensure that the outer surface of the ceramic material is under uniform pressure as much as possible; and the ceramic material is heated on all sides at the same time through the carbon heating tube to ensure the uniformity of heating on the side of the ceramic material, and the dolomite, barium zirconate sheets, samarium oxide tubes, and magnesium oxide sheets are provided to have a thermal insulation effect to avoid the heat generated by the carbon heating tube from dissipating; at the same time, a talc ring is provided to cooperate with the talc bushing to seal its internal structure; the internal pressure and temperature are avoided again, and the present application avoids direct contact between the ceramic material and the top hammer when preparing the ceramic material, and avoids the wear of the top hammer surface by the interaction force of the ceramic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of the synthesis block.

[0033] Figure 2 Schematic diagram of the internal structure of the synthesis block.

[0034] Figure 3 It is a partial cross-sectional view of the upper part of the synthetic block.

[0035] Figure 4 A partial cross-sectional view of a samarium oxide tube of a synthetic block.

[0036] Figure 5 A partial cross-sectional view of the magnesium oxide sheet of the synthetic block.

[0037] Figure 6 Schematic diagram of the dolomite lining and wax stone bushing structure of the synthetic block.

[0038] Description of reference numerals:

[0039] 1. Pyrophyllite bushing, 2. Pyrophyllite ring, 3. Metal plug, 4. Dolomite, 5. Magnesium oxide ring, 6. Barium zirconate sheet, 7. Samarium oxide tube, 8. Molybdenum sheet 2, 9. Molybdenum sheet 1, 10. Molybdenum column, 11. Magnesium oxide sheet, 12. Carbon heating tube, 13. Magnesium oxide tube, 14. Ceramics, 15. Dolomite lining. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] A new type of ultra-high density zirconia ceramic material is prepared according to the following steps:

[0043] (1) Powder vacuum treatment: Zirconia raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, the temperature was raised to 1200°C at 20°C / min, kept at this temperature for more than 10 hours, and then cooled to room temperature for use;

[0044] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form a cylindrical embryo with a diameter of 150 mm and a height of 132 mm. (3) High-temperature and high-pressure sintering: The embryo is placed in an improved synthetic block and pressurized to 8 kPa using a large-cavity six-sided top press. The temperature is then raised to 1200°C at a rate of 260 / min, and the temperature is maintained at this temperature and pressure for 20 min. The temperature is then raised to 1600°C and 2 GPa at a rate of 2.5 kPa / min and 400°C / min. The temperature is then maintained at this condition for 2 h. After sintering, the temperature is lowered and the pressure is released to obtain an ultra-high density zirconia ceramic material.

[0045] The synthetic block comprises two pyrophyllite bushings 1 symmetrically distributed up and down, a circular hole is opened in the middle of the pyrophyllite bushing 1, the inner side of the pyrophyllite bushing 1 is inlaid with a dolomite lining 15, the inner side of the dolomite lining 15 is provided with a heat-insulating component which can be moved up and down, a heating component is provided in the heat-insulating component, a ceramic 14 (or ceramic material) is provided in the heating component, magnesium oxide sheets 11 are respectively provided at the upper and lower ends of the ceramic 14, pressure transmission components are respectively provided at the outer ends of the magnesium oxide sheets 11, and a conductive component is provided in the pressure transmission component.

[0046] The heat-insulating component is a samarium oxide tube 7, which is a cylindrical structure.

[0047] The heating component includes a carbon heating tube 12, which is a cylindrical structure. The inner side of the carbon heating tube 12 is provided with a sample protection component which can move up and down, and the outer side of the carbon heating tube 12 is in contact with the inner side of the heat preservation component.

[0048] The sample protection component is a magnesium oxide tube 13, which is a cylindrical structure. The outer side of the magnesium oxide tube 13 is in contact with the inner side of the carbon heating tube 12, and the inner side of the magnesium oxide tube 13 is in contact with the outer side of the ceramic 14. The upper and lower ends of the ceramic 14 are flush with the outer end surface of the magnesium oxide tube 13.

[0049] The upper and lower ends of the ceramic 14 are respectively provided with magnesium oxide sheets 11 , the outer end surface of the magnesium oxide sheet 11 is flush with the outer end surface of the carbon heating tube 12 , and the outer side surface of the magnesium oxide sheet 11 is in contact with the inner side surface of the carbon heating tube 12 .

[0050] The conductive component includes a molybdenum sheet 2 8, the inner end face of the molybdenum sheet 2 8 is bonded to the outer end face of the magnesium oxide sheet 11. A molybdenum column 10 is arranged in the middle of the outer end face of the molybdenum sheet 2 8, a molybdenum sheet 1 9 is arranged on the upper end face of the molybdenum column 10, a metal plug 3 is arranged on the outer end face of the molybdenum sheet 1 9, and dolomite 4 is inlaid in the middle of the outer end face of the metal plug 3.

[0051] The pressure transmission component includes a barium zirconate sheet 6, a magnesium oxide ring 5 is provided on the outer end face of the barium zirconate sheet 6, a pyrophyllite ring 2 is provided on the outer end face of the magnesium oxide ring 5, and the outer side faces of the pyrophyllite ring 2, the magnesium oxide ring 5, the barium zirconate sheet 6, and the samarium oxide tube 7 are fitted with the inner side face of the pyrophyllite bushing 1.

[0052] The outer end surface of the molybdenum sheet 2 8 is provided with a barium zirconate sheet 6, a through hole is provided in the middle of the barium zirconate sheet 6, a molybdenum column 10 is provided in the through hole, the molybdenum column 10 is located in the through hole and can move up and down, and the outer side surface of the molybdenum column 10 is fitted with the through hole. The outer side surface of the metal plug 3 is fitted with the inner side surface of the pyrophyllite ring 2 and the magnesium oxide ring 5, and the outer end surface of the metal plug 3 is flush with the outer end surface of the pyrophyllite ring 2 and the outer end surface of the pyrophyllite bushing 1.

[0053] Pyrophyllite bushing 1: utilizing its lubricity, after the six top hammers of the six-sided top press are squeezed, a sealing edge is formed at the connection between the adjacent top hammers to maintain the high pressure state of the cavity.

[0054] According to its material and structural characteristics:

[0055] Pyrophyllite ring 2: plays a role in sealing its internal structure;

[0056] The metal plug 3, the second molybdenum sheet 8, the first molybdenum sheet 9 and the molybdenum column 10 have a conductive function so as to conduct electricity to the carbon heating tube 12 to generate heat.

[0057] Dolomite 4: It has the function of transmitting pressure and heat insulation, transferring the top hammer pressure to the metal plug 3 to protect the internal heat from dissipating.

[0058] The magnesium oxide ring 5 has the function of transmitting pressure, and transmits the pressure of the top hammer to the barium zirconate sheet 6.

[0059] Barium zirconate sheet 6: It has the function of transmitting pressure and keeping warm, transferring the top hammer pressure to the molybdenum sheet 2 8, and also has the function of keeping warm to prevent the internal heat from diffusing.

[0060] The samarium oxide tube 7 has the functions of transmitting pressure and heat preservation, and transmits the top hammer pressure to the carbon heating tube 12; at the same time, it prevents the heat generated by the carbon heating tube 12 from dissipating.

[0061] The magnesium oxide sheet 11 cooperates with the magnesium oxide tube 13 to form a seal for the ceramic 14 material, and also has the function of heat preservation and pressure transmission, transmitting the pressure of the top hammer to the ceramic 14 material.

[0062] Dolomite lining 15 has a pressure transmission function, which transmits the pressure of the top hammer on the side to the samarium oxide tube 7.

[0063] When the present invention is used, the magnesium oxide tube 13 is filled with ceramic 14, and the upper and lower end surfaces of the ceramic 14 are flush with the upper and lower end surfaces of the magnesium oxide tube 13. The outer side surface of the magnesium oxide tube 13 is provided with a carbon heating tube 12, and the carbon heating tube 12 is fitted with the magnesium oxide tube 13. The outer side surface of the carbon heating tube 12 is provided with a samarium oxide tube 7, and the magnesium oxide tube 13 is fitted with the samarium oxide tube 7. Magnesium oxide sheets 11 are placed on the upper and lower end surfaces of the ceramic 14, and the outer side surface of the magnesium oxide sheet 11 is fitted with the inner side surface of the carbon heating tube 12. After the magnesium oxide sheet 11 is placed, the outer end surface of the magnesium oxide sheet 11 is flush with the outer end surface of the carbon heating tube 12; then molybdenum sheets 8 are placed on the outer end surfaces of the upper and lower magnesium oxide sheets 11 respectively, and after the molybdenum sheets 8 are placed, the outer end surface of the molybdenum sheets 8 is flush with the outer end surface of the samarium oxide tube 7; barium zirconate sheets 6 are symmetrically placed at the upper and lower ends of the samarium oxide tube 7, and the barium zirconate A molybdenum column 10 is placed in the middle hole of the sheet 6, a magnesium oxide ring 5 is placed on the outer end surface of the barium zirconate sheet 6, a molybdenum sheet 9 is placed inside the magnesium oxide ring 5, and the molybdenum sheet 9 is fitted with the outer end surface of the barium zirconate sheet 6, a pyrophyllite ring 2 is placed on the outer end surface of the magnesium oxide ring 5, and the inner hole size of the pyrophyllite ring 2 is equal to the inner hole size of the magnesium oxide ring 5, a metal plug 3 is placed inside the pyrophyllite ring 2 and the magnesium oxide ring 5, and the inner end surface of the metal plug 3 is fitted with the molybdenum sheet 9, The outer end face of the metal plug 3 is inlaid with dolomite 4; the outer side surface of the samarium oxide tube 7 is symmetrically provided with a pyrophyllite bushing 1, the outer side surface of the samarium oxide tube 7 is fitted with the inner side surface of the pyrophyllite bushing 1, and the inner side surface of the pyrophyllite bushing 1 is inlaid with a dolomite lining 15. At this time, the outer sides of the metal plug 3, the magnesium oxide ring 5, and the barium zirconate sheet 6 are fitted with the inner side surface of the pyrophyllite bushing 1, and the outer end face of the pyrophyllite ring 2 and the outer end face of the pyrophyllite bushing 1 are located in the same plane.

[0064] Through the six top hammers of the six-sided top press, the six-sided top press is a prior art and no technical description is made. It can realize the extrusion force on the six sides of the device; the six side surfaces formed by the combination of the two talc bushings 1 are pressurized at the same time to increase the pressure on the ceramic 14 material inside, and the extrusion pressure is much greater than the pressure exerted on the ceramic 14 material by the traditional hot pressing sintering or hot isostatic pressing sintering method; at the same time, the upper and lower top hammers are energized, and the way of energizing the upper and lower top hammers is not technically restricted, and the functions required by this application can be achieved; it contacts the upper and lower metal plugs 3 (the metal plugs 3 can be energized, and the specific material is not technically restricted), the plugs transmit current to the molybdenum sheet 9, the molybdenum sheet 9 contacts the molybdenum column 10 in the middle of the barium zirconate sheet 6, the molybdenum column 10 contacts the molybdenum sheet 2 8, and the molybdenum sheet 2 8 transmits the current evenly to the carbon heating tube 12, forming a loop up and down to heat the ceramic 14 material in the magnesium oxide tube 13.

[0065] In the description of the composite block, it needs to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the composite blocks shown and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the composite block.

[0066] Example 2

[0067] A new type of ultra-high density alumina ceramic material is prepared according to the following steps:

[0068] (1) Powder vacuum treatment: Alumina raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, the temperature was raised to 1300°C at 20°C / min, kept at this temperature for more than 10 hours, and then cooled to room temperature for use;

[0069] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form a cylindrical embryo with a diameter of 150 mm and a height of 132 mm;

[0070] (3) High temperature and high pressure sintering: The embryo is placed in a modified synthetic block and pressurized to 4 kPa using a large cavity six-sided top press. The temperature is then raised to 1000°C at a rate of 240 / min and the temperature is maintained at this temperature and pressure for 15 min. The temperature is then raised to 1800°C and 1.6 GPa at a rate of 3 kPa / min and 350°C / min. The condition is then maintained for 1.5 h. After sintering, the temperature is lowered and the pressure is released to obtain an ultra-high density alumina ceramic material.

[0071] Example 3

[0072] A new type of ultra-high density silicon nitride ceramic material is prepared according to the following steps:

[0073] (1) Powder vacuum treatment: Silicon nitride raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, the temperature was raised to 1300°C at 20°C / min, kept at this temperature for more than 10 hours, and then cooled to room temperature for use;

[0074] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form a cylindrical embryo with a diameter of 150 mm and a height of 132 mm;

[0075] (3) High temperature and high pressure sintering: The embryo is placed in the improved synthesis block and pressurized to 6 kPa using a large cavity six-sided top press. At the same time, the temperature is raised to 800 °C at a rate of 250 / min, and the temperature and pressure are maintained for 10 min. Then, the temperature reaches 2000 °C and 2 GPa at a rate of 4 kPa / min and 350 °C / min. The condition is then maintained for 1.2 h. After sintering, the temperature is reduced and the pressure is released to obtain an ultra-high density silicon nitride ceramic material.

[0076] Example 4

[0077] A new type of ultra-high density aluminum nitride ceramic material is prepared according to the following steps:

[0078] (1) Powder vacuum treatment: Aluminum nitride raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, the temperature was raised to 1200°C at 20°C / min, kept at this temperature for more than 10 hours, and then cooled to room temperature for use;

[0079] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form a cylindrical embryo with a diameter of 150 mm and a height of 132 mm;

[0080] (3) High temperature and high pressure sintering: The embryo is placed in the improved synthesis block and pressurized to 8 kPa using a large cavity six-sided top press. At the same time, the temperature is raised to 800 °C at a rate of 260 / min, and the temperature and pressure are maintained for 10 min. Then, the temperature is increased to 1800 °C and 1.8 GPa at a rate of 4 kPa / min and 360 °C / min. The condition is then maintained for 2 h. After sintering, the temperature is lowered and the pressure is released to obtain an ultra-high density aluminum nitride ceramic material.

[0081] Example 5

[0082] A new type of ultra-high density zirconium boride ceramic material is prepared according to the following steps:

[0083] (1) Powder vacuum treatment: Zirconium boride raw material powder with a particle size of micron or below is vacuum treated at 10 -2 Under vacuum conditions, the temperature was raised to 1300°C at 20°C / min, kept at this temperature for more than 10 hours, and then cooled to room temperature for use;

[0084] (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form a cylindrical embryo with a diameter of 150 mm and a height of 132 mm;

[0085] (3) High temperature and high pressure sintering: The embryo is placed in the improved synthetic block and pressurized to 6 kPa using a large cavity six-sided top press. At the same time, the temperature is raised to 700 °C at a rate of 280 / min and the temperature is maintained at this temperature and pressure for 10 min. The temperature is then raised to 1600 °C and 2 GPa at a rate of 2.8 kPa / min and 400 °C / min. The condition is then maintained for 1.8 h. After sintering, the temperature is lowered and the pressure is released to obtain an ultra-high density zirconium boride ceramic material.

[0086] Comparative Example

[0087] The ceramic raw material powder with a particle size of micron is ground by a ball mill, and then centrifugally cast into a cylindrical embryo with a diameter of 150 mm and a height of 132 mm. The embryo is sintered in a hot isostatic pressing furnace to obtain a ceramic material. The sintering conditions of the embryo in the hot isostatic pressing furnace are: 800-1200°C, 1 kPa, and the sintering time is 720-960 min. The grinding solvent is acetone.

[0088] The above method is used to prepare zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride and zirconium boride ceramic materials respectively.

[0089] Test example

[0090] Performance Testing

[0091] Test items:

[0092] 1. Hardness: GB / T 4340.1-2009 "Vickers hardness test for metallic materials Part 1: Test method" is used for testing.

[0093] 2. Density: Use the QB_T 1010-2015 method for determining the true density of ceramic materials and pigments.

[0094] 3. Bending resistance: GB / T 4741-1999 ceramic material bending strength test method is adopted.

[0095] Test samples: ceramic materials prepared in Examples 1-5 and zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride, and zirconium boride ceramic materials prepared in comparative examples.

[0096] The results are shown in Tables 1-3. The present invention uses a large cavity six-sided top press and an improved synthesis block to perform high-temperature and high-pressure gradient sintering on ceramic raw materials to obtain ultra-high density ceramic materials, achieving a significant improvement in physical properties such as hardness, density and bending resistance of ceramic materials. The various ultra-high density ceramic materials obtained by the method of the present invention are about 7-22% higher in hardness, about 0.6-2.1% higher in density, and about 12-28% higher in bending strength than ceramic materials obtained by hot isostatic pressing. The above performance improvements can significantly expand the application of ceramic materials in aerospace, military industry, precision instruments, biomimetic materials and other fields.

[0097] Table 1 Vickers hardness of ceramic materials

[0098]

[0099] Table 2 Density of ceramic materials

[0100]

[0101] Table 3 Bending strength of ceramic materials

[0102]

[0103]

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A novel method for preparing ultra-high density ceramic material, characterized in that: The preparation method comprises the following preparation steps: (1) Powder vacuum treatment: Ceramic raw material powder with a particle size of micron or below is vacuumed for 10 -2 Under vacuum conditions, heat to 1200-1300°C at 20°C / min, keep warm for more than 10 hours, and then cool to room temperature for use; (2) Powder molding: The vacuum-treated powder is dry-pressed at room temperature and 20 MPa to form an embryo; (3) High temperature and high pressure sintering: The embryo is placed in a modified synthetic block and kept warm for 1-2 hours at a pressure of 1-2 GPa and a temperature of 1200°C-2200°C using a large cavity six-sided top press. After sintering, the temperature is reduced and the pressure is released to obtain an ultra-high density ceramic material.

2. The method for preparing a novel ultra-high density ceramic material according to claim 1, characterized in that: The ceramic raw material powder in step (1) is one or more of zirconium oxide, aluminum oxide, silicon nitride, aluminum nitride and silicon boride.

3. The method for preparing the novel ultra-high density ceramic material according to claim 1, characterized in that: The embryo in step (2) is a cylinder with a diameter of 150 mm and a height of 132 mm.

4. The method for preparing a novel ultra-high density ceramic material according to claim 1, characterized in that: The synthetic block in step (3) comprises two pyrophyllite bushings symmetrically distributed up and down, a circular hole is opened in the middle of the pyrophyllite bushing, the inner side of the pyrophyllite bushing is inlaid with a dolomite lining, the inner side of the dolomite lining is provided with a heat-insulating component that can move up and down, a heating component is provided in the heat-insulating component, ceramics are provided in the heating component, magnesium oxide sheets are provided at the upper and lower ends of the ceramics, pressure transmission components are provided at the outer ends of the magnesium oxide sheets, and conductive components are provided in the pressure transmission components.

5. The method for preparing a novel ultra-high density ceramic material according to claim 1, characterized in that: In step (3), the cylinder diameter of the six-sided top press is 1200 mm.

6. The method for preparing a novel ultra-high density ceramic material according to claim 1, characterized in that: In step (3), sintering is carried out under gradient conditions, specifically, the synthetic block containing the embryo is placed on a large-cavity six-sided top press, the pressure is increased to the initial pressure, and the temperature is raised to the initial temperature at a rate of 250-280°C / min; after the pressure and temperature reach the initial set values, the temperature and pressure are maintained for 10-20 minutes, and then the temperature and pressure setting values ​​are reached at a rate of 2kPa-4kPa / min, 350-400°C / min, and then maintained under this condition for 1-2 hours.

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