CN113173788A

CN113173788A - Rapid sintering preparation method of infrared transparent ceramic

Info

Publication number: CN113173788A
Application number: CN202110480745.2A
Authority: CN
Inventors: 范金太; 沈宗云; 钱凯臣; 张龙; 谢俊喜; 冯涛; 姜本学; 冯明辉; 陈柏键; 张露露; 范翔龙
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2021-04-30
Filing date: 2021-04-30
Publication date: 2021-07-27

Abstract

A rapid sintering preparation method of infrared transparent ceramics comprises the steps of firstly, pressing and forming nano powder into ceramic biscuit, putting the biscuit into a low-temperature region of a double-temperature-region muffle furnace, heating to a preset temperature, preserving heat, eliminating internal stress of a sample in the forming process, reducing water absorbed by the sample in the preparation process, then pushing the sample to a high-temperature region, carrying out heat preservation sintering, and cooling along with the furnace after sintering is finished to prepare the high-density nano-crystalline grain ceramics. The relative compactness of the obtained ceramic sample is 95-100%, the grain size is less than 250nm, and the ceramic sample has good optical performance and mechanical performance.

Description

Rapid sintering preparation method of infrared transparent ceramic

Technical Field

The invention relates to a rapid sintering preparation method of infrared transparent ceramic, and belongs to the field of preparation of transparent ceramic materials.

Background

Mature ceramic forming and sintering technologies have been in history for thousands of years, and pottery and porcelain prepared by different sintering process technologies meet different requirements of people in production and life. In recent years, the high-performance ceramic with densified fine grains prepared by adopting different sintering process technologies obtains better optical, mechanical, thermal, electrical, magnetic and other properties, meets more practical application requirements such as environmental protection, security protection, military industry, national defense and the like, and is pursued by related scientific researchers all the time. According to the Hall-Petch relationship, the smaller the grain size of the ceramic, the higher the hardness and strength. In the nanocrystalline ceramics, the smaller the crystal grain size and the higher the relative density, the smaller the loss such as optical scattering and absorption, and the closer the transmittance is to the theoretical transmittance, the wider the transmission band is.

By Y₂O₃Preparing Y from-MgO composite nano powder₂O₃The volume ratio of two phases of MgO is close to 1:1, the two phases are uniformly distributed, the mid-infrared transmittance can reach 84%, the theoretical transmittance is close, the room-temperature bending strength is over 400MPa, and the high-temperature (600 ℃) bending strength is over 350 MPa. 300 ℃ high temperature mid-infrared emissivityLess than 0.02, and better than the existing infrared transparent ceramics, such as sapphire, spinel and the like. The material can realize high near-infrared transmittance and visible translucency under the conditions of extremely fine grain size and high density, and becomes a hope and an important candidate for future hypersonic aircraft infrared window materials.

At present, many sintering techniques for preparing densified fine-grained ceramics, such as hot-pressing sintering (HP), Spark Plasma Sintering (SPS), and conventional sintering followed by assisted Hot Isostatic Pressing (HIP), have been used to prepare densified ceramics. But Y prepared by these sintering processes₂O₃MgO nano complex phase ceramic products have some problems, such as that spark plasma sintering is not suitable for preparing products with large size; the large-size sample prepared by hot-pressing sintering has uneven density and poor overall performance; the grain size of the samples sintered by conventional post-sintering assisted hot isostatic pressing is relatively large (>300nm), the average transmittance is low, the bending strength is greatly reduced, and the optimization is difficult; the sample prepared by adopting the hot-pressing sintering and spark plasma sintering processes is difficult to completely remove residual carbon-containing groups in the sample caused by carbon diffusion pollution of the graphite mold at high temperature, so that the thermal, optical, mechanical and other properties of the product can be influenced, the high-temperature properties such as thermal shock resistance and the like of the sample are not favorable, and the Y is finally influenced₂O₃-comprehensive properties of the MgO nano complex phase ceramic product.

In 2012, d.hotza et al, d.e.garcia, a.n.klein, and d.hotza.advanced ceramics with dense and fine-grained microstructure fastening, of the federal university of saint catalina, brazil [ j.n.klein].Rev.Adv.Mater.Sci.30(2012)273-281.]Report the preparation of dense fine-grained Al by rapid sintering₂O₃The method of the ceramic material is that the sample is directly put into a high temperature furnace from room temperature to be sintered and compacted quickly, and the alumina ceramic sample with compacted fine grains is obtained. However, this study also has the disadvantage that the sample is placed in a high temperature furnace from room temperature and the temperature difference changes sharply: (>The sample is easy to crack at 1000 ℃ and is not easy to prepare high-quality large-size samples. Therefore, the exploration of sintering preparation technology of high-quality large-size compact nanocrystalline ceramic products is industrialized and low-cost productionThe problems to be solved are solved urgently, the double-temperature-zone rapid sintering technology provided by the method of the invention just effectively solves the problems, large-size high-performance ceramic products can be prepared by rapid sintering, and the method has great significance for low-cost large-scale production and industrialization.

Disclosure of Invention

The invention aims to provide a rapid sintering preparation method of infrared transparent ceramics, which overcomes the defects of the existing ceramic sintering preparation process in the aspects of simultaneously realizing densification, grain refinement and high-quality large-size preparation. According to the method, a ceramic biscuit which is formed by pressing nanometer powder is placed in a low-temperature zone of a double-temperature zone muffle furnace to be heated to a preset temperature for heat preservation, internal stress of a sample in the forming process is eliminated, water absorbed by the sample in the preparation process is reduced, then the sample is pushed to a high-temperature zone for heat preservation and sintering, and after sintering is finished, the temperature is reduced along with the furnace, so that the nanometer grain ceramic with the grain size of 50-250nm and the relative density of 95% -100% is obtained. The method is easy to realize the preparation of large-size ceramic products, and the prepared ceramic products have better optical performance and mechanical performance. The method is characterized in that a sample is directly pushed from a low-temperature area to a high-temperature area for sintering, so that the sample reaches the sintering temperature at a very fast heating rate, the heating time is shortened, the sintering activity of powder is maintained, and the problems of abnormal growth of grain size, formation of large-size aggregates and large aggregated pores in the slow heating stage of conventional sintering are solved; the problem of reduced sintering activity of the powder in a longer temperature rise process is solved, the high-activity powder is quickly compact in a high-temperature sintering stage, and simultaneously can be compact in a short time and maintain fine grains. The low-temperature region heating and heat preservation stage is beneficial to eliminating the internal stress of the sample in the forming process and reducing the water absorbed by the sample from the environment in the preparation process; the sample is directly pushed from the low-temperature area to the high-temperature area, so that the temperature difference from the room temperature to the high-temperature area is reduced, and the sample is not easy to crack after being pushed to the high-temperature area. The technical method does not need auxiliary sintering such as pressure, microwave, magnetic field, current and the like; the sintering process has the advantages of no pollution of carbon-containing groups, simple sintering process, simple required sintering equipment, low production cost, suitability for preparing samples with large sizes and any shapes and convenience for industrial production.

The preparation method of the technical scheme comprises the following specific steps:

step 1.1) carrying out dry pressing on the nano powder to form a blank, and carrying out cold isostatic pressing treatment to obtain a ceramic biscuit;

step 1.2) placing the ceramic biscuit in the step 1.1) on a low-temperature sample table in a double-temperature-zone muffle furnace, heating the sample table along with the furnace to a preset temperature, and then preserving the heat; simultaneously, pre-heating a high-temperature area of the double-temperature-area muffle furnace to a preset temperature, and keeping the temperature for later use;

step 1.3) lifting heat insulation plates of a low-temperature region and a high-temperature region of a muffle furnace of a double-temperature region, pushing the sample in the step 1.2) to a sample table by using a push rod, conveying the sample to the high-temperature region, inserting the heat insulation plates back, carrying out heat insulation sintering on the sample, and cooling the sample along with the furnace after sintering is finished to obtain a high-density nanocrystalline grain ceramic sample;

and step 1.4) carrying out double-sided mirror polishing on the ceramic sample obtained in the step 1.3) to obtain a ceramic product.

The method for preparing infrared transparent ceramics by rapid sintering according to claim, wherein the method comprises the following steps:

the nano powder in the step 1.1) is Y₂O₃Nano powder and Al₂O₃Nano powder, ZrO₂Nanopowder or Y₂O₃-MgO composite nanopowder with a powder grain size of 5-100 nm.

The pressure in the dry pressing of the step 1.1) is 3-30 MPa.

The pressure of the cold isostatic pressing in the step 1.1) is 180-280MPa, and the pressure maintaining time is 3-20 min.

The rapid sintering preparation method of the infrared transparent ceramics according to claim 1 or 2, characterized in that the dual-temperature-zone muffle furnace of step 1.2) is a muffle furnace designed and manufactured independently, the temperature rise and control of the dual-temperature zone are independent, a heat insulation plate is arranged in the middle, and a sample is pushed by a push rod to push a sample platform.

The temperature rise rate of the low-temperature region along with the furnace in the step 1.2) is 1-10 ℃/min, the preset temperature is 800-.

The preset temperature of the high-temperature zone in the step 1.2) is 1200-1600 ℃.

The heat preservation sintering time in the step 1.3) is 10-200 min.

The relative compactness of the dense ceramic sample in the step 1.3) is between 95% and 100%.

The nano-crystalline grain ceramic in the step 1.3) has a grain size of less than 250 nm.

Compared with the prior art, the invention has the technical effects that:

1) the large-size compact fine-grain ceramic sample obtained by the method has high relative density (> 95%) and fine grain size (<250nm), and is superior to a sample prepared by auxiliary hot isostatic pressing sintering after conventional sintering.

2) The sample is placed in a low-temperature area to be heated and insulated, so that the internal stress of the sample in the forming process is eliminated, the water absorbed by the sample in the preparation process is reduced, and the sample is not easy to crack after being pushed to the high-temperature area.

3) The sample is directly pushed from the low-temperature area to the high-temperature area for sintering, so that the sample reaches the sintering temperature at a very fast heating rate, the sintering activity of the powder is maintained, and the problems of abnormal growth of grain size, formation of large-size aggregates and aggregative large pores in the heating stage of conventional sintering are solved. Solves the problem of reduced sintering activity of the powder in a longer temperature rise process, and can simultaneously realize compact sintering and grain refinement of large-size samples.

The technical method does not need auxiliary sintering such as pressure, microwave, magnetic field, current and the like; the sintering process has the advantages of no pollution of carbon-containing groups, simple sintering process, simple required sintering equipment, low production cost, suitability for preparing samples with large sizes and any shapes and convenience for industrial production. The rapid sintering technology of the dual-temperature zone provided by the method effectively solves a plurality of problems in the process of preparing high-quality large-size compact nanocrystalline transparent ceramic products with high efficiency, and has great significance for low-cost large-scale production and industrialization.

Drawings

FIG. 1 is a cross-sectional view of an autonomously designed dual temperature zone muffle.

FIG. 2 shows the densified fine grain Y obtained in example 1₂O₃SEM topography of the MgO complex phase ceramic.

FIG. 3 shows the densified fine grain Y obtained in example 1₂O₃-infrared transmittance curve of the MgO complex phase ceramic, wherein (a) is near infrared transmittance curve and (b) is middle infrared transmittance curve.

FIG. 4 is a graph of the densified fine-grained ZrO obtained in example 2₂SEM topography of the ceramic.

FIG. 5 is a graph of the densified fine grained ZrO produced in example 2₂The infrared transmittance curve of the ceramic, wherein (a) is a near-infrared transmittance curve and (b) is a mid-infrared transmittance curve.

Detailed Description

Following by adopting Y₂O₃-MgO composite nanopowder and ZrO₂Sintering of nano powder large size crack-free Y₂O₃-MgO complex phase ceramics and ZrO₂The present invention will be further described with reference to the following examples and drawings, which are only for the purpose of illustrating the present invention and should not be construed as limiting the scope of the present invention.

Example 1

By Y₂O₃-MgO composite nano powder, weighing 20g of powder

Pressurizing the die to 3MPa, dry-pressing the die to obtain a ceramic blank, and carrying out cold isostatic pressing treatment on the blank under the pressure of 280MPa for 3min for later use; heating a muffle furnace high-temperature area to 1600 ℃ for standby, placing a ceramic biscuit on a muffle furnace low-temperature area sample platform, heating to 1200 ℃ at a heating rate of 1 ℃/min, and keeping the temperature for 200 min; lifting the heat insulation plates of the high-temperature area and the low-temperature area, quickly pushing the sample table and the sample to the high-temperature area, carrying out heat preservation sintering for 10min, and cooling along with the furnace after sintering to obtain a high-density nanocrystalline ceramic sample; then carrying out double-sided high-precision mirror polishing to obtain the product with the thickness of 3.0mmY₂O₃-MgO nano complex phase ceramic product.

FIG. 2 shows Y obtained in example 1₂O₃-SEM topography of MgO nanocomposite ceramic; as can be seen, the average grain size is within 250 nm.

FIG. 3 shows Y obtained in example 1₂O₃-a transmittance curve of the MgO nano-composite ceramic, wherein (a) is a near infrared transmittance curve and (b) is a mid infrared transmittance curve.

Example 2

Using commercial ZrO₂Nano powder, weighing 80g powder

The mould is pressed to 30MPa and dry-pressed into a ceramic blank, and the blank is subjected to cold isostatic pressing treatment with the pressure of 180MPa and the pressure maintaining time of 20min for later use; heating a high-temperature area of a muffle furnace to 1200 ℃ for standby, placing a ceramic biscuit on a sample table of a low-temperature area of the muffle furnace, heating to 800 ℃ at a heating rate of 5 ℃/min, and keeping the temperature for 10 min; lifting the heat insulation plates of the high-temperature area and the low-temperature area, quickly pushing the sample table and the sample to the high-temperature area, carrying out heat preservation sintering for 200min, and cooling along with the furnace after sintering to obtain a high-density nanocrystalline ceramic sample; then carrying out double-sided high-precision mirror polishing to obtain ZrO with thickness of 3.0mm₂A ceramic product.

FIG. 4 shows ZrO produced in example 2₂SEM topography of the ceramic; as can be seen, the average grain size is within 250 nm.

FIG. 5 shows ZrO produced in example 2₂The transmittance curve of the ceramic, wherein (a) is a near-infrared transmittance curve and (b) is a mid-infrared transmittance curve.

In conclusion, the densified nanocrystalline ceramic sample obtained by the method has higher relative density (> 95%) and fine grain size (<250nm), and is superior to the sample prepared by the conventional auxiliary hot isostatic pressing sintering after sintering. Directly pushing a sample from a low-temperature area to a high-temperature area for sintering, so that the sample reaches the sintering temperature at a very fast heating rate, the sintering activity of powder is maintained, and the problems of abnormal growth of grain size, formation of large-size aggregates and aggregative large pores in the heating stage of conventional sintering are solved; solves the problem of reduced sintering activity of the powder in a longer temperature rise process, and can simultaneously realize compact sintering and grain refinement of large-size samples. The low-temperature region heating and heat preservation stage is beneficial to eliminating the internal stress of the sample in the cold isostatic pressing process and reducing the water absorbed by the sample from the environment in the preparation process; the sample is directly pushed from the low-temperature area to the high-temperature area, so that the temperature difference from the room temperature to the high-temperature area is reduced, and the sample is not easy to crack after being pushed to the high-temperature area. The technical method does not need auxiliary sintering such as pressure, microwave, magnetic field, current and the like; the sintering process has the advantages of no pollution of carbon-containing groups, simple sintering process, simple required sintering equipment, low production cost, suitability for preparing samples with large sizes and any shapes and convenience for industrial production. And the method with lower cost can be easily used for preparing other oxides or oxide composite ceramic materials.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the present invention in any way, so that any person skilled in the art can make modifications or changes in the technical content disclosed above. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. a kind of rapid sintering preparation method of infrared transparent ceramics, it is characterized in that, the low temperature zone that adopts the ceramic china of nano-powder to be pressed into shape is put into the low temperature zone in the double-temperature zone muffle furnace and is heated to preset temperature insulation, eliminates the sample in the low temperature zone. The internal stress caused by the molding process, and reduce the moisture absorbed by the sample during the preparation process, and then push the sample to a high temperature area for thermal sintering. It is 95% to 100% nanocrystalline ceramics.

2. the rapid sintering preparation method of infrared transparent ceramics according to claim 1, is characterized in that: the concrete steps of this preparation method are as follows:

Step 1.1) dry-pressing the nano-powder into a green body, and performing cold isostatic pressing to obtain a ceramic green body;

Step 1.2) The ceramic china body described in step 1.1) is placed on the low temperature zone sample stage in the dual temperature zone muffle furnace, and the temperature is raised to the preset temperature with the furnace heating; at the same time, the high temperature of the dual temperature zone muffle furnace is heated. The zone is pre-heated to the preset temperature and then kept at a constant temperature for use;

Step 1.3) Lift the heat insulation plates of the low temperature zone and the high temperature zone of the dual-temperature zone muffle furnace, push the sample described in step 1.2) to the high temperature zone by pushing the sample stage with a push rod, insert it back into the heat insulation plate, and carry out heat preservation and sintering of the sample, After sintering, the temperature is lowered in the furnace to obtain high-density nanocrystalline ceramic samples;

In step 1.4), double-sided mirror polishing is performed on the ceramic sample obtained in step 1.3) to obtain a ceramic product.

3. The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2, characterized in that, the nano-powder described in step 1.1) is Y ₂ O ₃ nano-powder, Al ₂ O ₃ nano-powder, Any one of ZrO ₂ nano-powder or Y ₂ O ₃ -MgO composite nano-powder, and the grain size of the powder is 5-100 nm.

4. The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2, wherein the pressure in the dry pressing of step 1.1) is 3-30 MPa.

5. The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2, characterized in that, the pressure of the cold isostatic pressing in step 1.1) is 180-280MPa, and the holding time is 3-20min.

6. the rapid sintering preparation method of infrared transparent ceramics according to claim 1 and 2, is characterized in that, the muffle furnace of double temperature zone described in step 1.2) is the muffle furnace of independent design and manufacture, and the temperature of double temperature zone heats up respectively Independent of temperature control, there is a heat insulation board in the middle, and the sample is pushed by the push rod to push the sample.

7. The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2, wherein the heating rate with the furnace described in step 1.2) is 1-10°C/min, and the preset temperature in the low temperature zone is 800-100°C/min. 1200℃, set the temperature in the low temperature zone lower than the temperature in the high temperature zone, and the holding time is 10-200min to eliminate the internal stress caused by the sample during the molding process and reduce the moisture absorbed by the sample during the preparation process.

8 . The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2 , wherein the preset temperature of the high temperature zone in step 1.2) is 1200-1600° C. 9 .

9. The rapid sintering preparation method of infrared transparent ceramics according to claim 1 or 2, characterized in that, the heat preservation sintering time described in step 1.3) is 10-200 min.