Thermal fatigue resistant ceramic and production process thereof

Abstract

The invention relates to thermal fatigue resistant ceramic and a production process thereof, and belongs to the technical field of ceramic material preparation, the thermal fatigue resistant ceramic comprises the following raw materials by mass: 90-100 parts of a base material, 5-10 parts of a flexibilizer, 1-3 parts of a sintering aid and 1-3 parts of an additive; wherein the base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and a nano zirconium oxide precursor according to the mass ratio of (0.75-1.25): (2-3): (80-85): (3-4): (3-4). The base material in the thermal fatigue-resistant ceramic selects the aluminum oxide as a main component, and the aluminum oxide has extremely high melting point and hardness and excellent chemical stability, so that the ceramic can keep stable physical and chemical properties in a high-temperature environment, and the thermal fatigue resistance of the ceramic is remarkably enhanced.

Description

Technical Field

[0001] The present application belongs to the technical field of ceramic material preparation, and more specifically, it relates to a thermal fatigue resistant ceramic and a production process thereof. Background Art

[0002] Ceramic materials are widely used in a variety of fields, including aerospace, automotive manufacturing, and electronic packaging, due to their excellent properties such as high temperature resistance, corrosion resistance, and wear resistance. However, during use, ceramic materials, especially when experiencing rapid temperature changes, can exhibit significant thermal fatigue. Thermal fatigue refers to the phenomenon in which the thermal stress resistance of ceramic materials gradually decreases over time under a certain load. It is divided into static fatigue and dynamic fatigue. Static fatigue is similar to delayed fracture in metals, while dynamic fatigue is closely related to the relationship between loading rate and material failure fracture.

[0003] Traditional ceramic material preparation often focuses on improving hardness and wear resistance, but lacks significant strength in thermal fatigue resistance. Due to the uneven distribution of thermal stress within the material, microcracks are prone to form and gradually expand, ultimately leading to material failure. Furthermore, the high coefficient of thermal expansion of traditional ceramic materials easily generates significant thermal stress during temperature fluctuations, further exacerbating thermal fatigue.

[0004] Therefore, a new thermal fatigue resistant ceramic and its production process are needed. Summary of the Invention

[0005] In order to solve the problems raised in the background technology, the present application provides a thermal fatigue resistant ceramic and a production process thereof.

[0006] This application provides a thermal fatigue resistant ceramic and a production process thereof, which adopts the following technical solutions: A thermal fatigue resistant ceramic comprising the following raw materials in parts by weight: 90-100 parts of base material, 5-10 parts of toughening agent, 1-3 parts of sintering aid and 1-3 parts of additive; The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and nano zirconium oxide precursor in a mass ratio of (0.75-1.25):(2-3):(80-85):(3-4):(3-4).

[0007] Furthermore, the nano zirconium oxide precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate and deionized water are mixed to obtain a template solution; a ZrOCl2·8H2O solution is then added to the template solution to adjust the pH value of the system to 9-11; the system is then allowed to stand at room temperature, filtered and washed to obtain a nano-zirconium oxide precursor.

[0008] Furthermore, the nano zirconium oxide precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate and deionized water are mixed at 40-50°C to obtain a template solution. Subsequently, a 0.5-1.5 mol / L ZrOCl2·8H2O solution is added to an equal volume of the template solution at 40-50°C, and a 6-7 wt% NH3·H2O solution is used to adjust the pH value of the system to 9-11. The system is then allowed to stand at room temperature for 12-24 hours, filtered, and washed alternately with pure ethanol and deionized water three times to obtain a nano-zirconium oxide precursor.

[0009] Furthermore, the mass ratio of the nonionic surfactant, sodium lauryl sulfate and deionized water is (2-3):20:(70-80).

[0010] Furthermore, the toughening agent is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol and nitric acid are mixed to obtain silica sol; carbon fibers are washed and dried, then immersed in the silica sol for 2-4 hours, then taken out and dried at 130-180° C. for 2-4 hours to obtain a toughening agent.

[0011] Furthermore, the toughening agent is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol, and nitric acid are mixed at a mass ratio of (150-250):(70-75):(40-50):0.0063 at 45-55°C for 1-3 hours to obtain a silica sol; the carbon fiber is washed with acetone, naturally aired to dry, and then immersed in the silica sol for 2-4 hours, then taken out and dried at 130-180°C for 2-4 hours to obtain a toughening agent.

[0012] Furthermore, the sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of (1-3): (0.1-0.2).

[0013] Furthermore, the additive is at least one of B4C, BN, and SiC.

[0014] Furthermore, a production process for thermal fatigue resistant ceramics includes the following preparation steps: S1, mixing the base material, toughening agent, sintering aid and additives in the formula parts by weight for 1-3 hours, then dry-pressing the mixture into a shape, and then drying to obtain a green body; S2. Then, the green body obtained in step S1 is heated to 400-500° C., kept at this temperature for 30-60 minutes, then raised to 1300-1500° C., kept at this temperature for 1-2 hours, then continued to be heated to 1600-1700° C., then kept at this temperature for 20-60 minutes, and then naturally cooled to room temperature to obtain a heat fatigue resistant ceramic.

[0015] Furthermore, a production process of thermal fatigue resistant ceramics includes the following preparation steps: S1. Mix the base material, toughening agent, sintering aid and additives in the formula parts by weight at a speed of 300-500 rpm for 1-3 hours at room temperature, then dry-press the mixture into a shape, and then dry it at 50-80° C. for 30-60 minutes to obtain a green body; S2. The green body obtained in step S1 is then heated to 400-500°C at a heating rate of 5-10°C / min under an inert atmosphere, kept at this temperature for 30-60 minutes, and then the temperature is further increased to 1300-1500°C at a heating rate of 10-20°C / min. After keeping the temperature for 1-2 hours, the temperature is further increased to 1600-1700°C at a heating rate of 5-10°C / min, and then kept at this temperature for 20-60 minutes. The green body is then naturally cooled to room temperature to obtain a heat-resistant fatigue-resistant ceramic.

[0016] Furthermore, in step S1, during the dry pressing process, the pressure is controlled to be 20-50 MPa, and the holding time is 5-20 minutes.

[0017] In summary, this application has the following beneficial effects: In the technical solution of this invention, the ratio of raw materials such as calcium carbonate, talc, and kaolin used in the base material helps control the sintering process and final performance of the ceramic. The introduction of these raw materials can adjust the sintering shrinkage, density, and microstructure of the ceramic, thereby improving the overall performance of the ceramic. The base material of this heat-resistant fatigue-resistant ceramic uses alumina as the main component. Alumina has an extremely high melting point, hardness, and excellent chemical stability. This enables the ceramic to maintain stable physical and chemical properties in high-temperature environments, thereby significantly enhancing its heat fatigue resistance.

[0018] By matching the thermal expansion of CaCO3 and zirconia, the thermal fatigue resistance of the resulting ceramic material is improved. Due to the significant difference in thermal expansion coefficients between CaCO3 and zirconia, the cooling contraction of the ceramic matrix when heated is different, creating microcracks between the particles and the matrix. These absorb the energy generated during the heating of the matrix, improving the thermal fatigue resistance of the material. During the sintering process, the nano-zirconia precursor component generates a nano-zirconia component. Due to its extremely small particle size and the resulting denser ceramic structure, it inhibits the transformation of the zirconia component from a tetragonal to a monoclinic structure. During the subsequent cooling process to room temperature, the zirconia crystal phase transition is no longer restricted. After the phase transition, stress relaxation occurs at the microcrack tips, hindering crack propagation and further improving the thermal fatigue resistance of the ceramic material.

[0019] The carbon fiber is surface modified, and after the surface of the carbon fiber is impregnated with silica sol, it is combined with the heat treatment process of this application. Its bonding strength with the ceramic matrix is enhanced, thereby improving the density of the composite material. In addition, the modified carbon fiber and the metal oxides in the sintering aid have a synergistic effect in promoting the densification of ceramics during the sintering process. During the first stage of heat treatment at 400-500°C, the silica sol on the surface of the carbon fiber has good fluidity and adhesion, which can fill the gaps between ceramic particles during the sintering process, thereby improving the density and strength of the material. The interface bonding formed between the silicate glass and other components helps to resist the interface separation and destruction caused by thermal stress, thereby improving the thermal fatigue resistance. Magnesium oxide can form a solid solution in ceramics, increase the toughness of the material, and help resist crack expansion and fracture caused by thermal stress. A small amount of lithium carbonate helps magnesium oxide lower the sintering temperature of the ceramic material, reduce pores, and improve its thermal fatigue resistance by promoting densification during the sintering process. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0021] The specific implementation methods of this application involve: The particle size of calcium carbonate, talc, alumina and kaolin is 25-50 μm and the purity is industrial pure; The components of the kaolin used are shown in Table 1 below: Table 1 Kaolin components

[0022] The carbon fiber is provided by Texas Carbon Fanbo Composite Materials Co., Ltd., with a length of 1-50mm and a carbon content greater than 95%.

[0023] Example 1 This application provides a thermal fatigue resistant ceramic and a production process thereof, which adopts the following technical solutions: A thermal fatigue resistant ceramic comprising the following raw materials in parts by weight: 90 parts of base material, 5 parts of toughening agent, 1 part of sintering aid and 1 part of additive; The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and nano zirconium oxide precursor in a mass ratio of 0.75:2:80:3:3.

[0024] The nano zirconium oxide precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate, and deionized water were mixed at a mass ratio of 2:20:70 at 40°C to obtain a template solution. A 0.5 mol / L ZrOCl2·8H2O solution was then added to an equal volume of the template solution at 40°C, and the pH value of the system was adjusted to 9 using a 6 wt% NH3·H2O solution. The system was then allowed to stand at room temperature for 12 hours, filtered, and washed three times alternately with pure ethanol and deionized water to obtain a nano-zirconia precursor. Wherein, the toughening agent is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol, and nitric acid were mixed at a mass ratio of 150:70:40:0.0063 at 45° C. for 1 hour to obtain a silica sol; the carbon fiber was washed with acetone, naturally aired to dry, and then immersed in the silica sol for 2 hours, then taken out and dried at 130° C. for 2 hours to obtain a toughening agent; The sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of 1:0.1; and the additive is B4C.

[0025] A production process for thermal fatigue resistant ceramics, comprising the following preparation steps: S1. Mix the base material, toughening agent, sintering aid and additives in the formula parts by weight at a speed of 300 rpm at room temperature for 1 hour, then dry-press the mixture at a pressure of 20 MPa and a holding time of 5 minutes, and then dry at 50° C. for 30 minutes to obtain a green body; S2. The green body obtained in step S1 is then heated to 400°C at a heating rate of 5°C / min under a nitrogen atmosphere, kept at this temperature for 30 minutes, and then the temperature is further increased to 1300°C at a heating rate of 10°C / min. After keeping this temperature for 1 hour, the temperature is further increased to 1600°C at a heating rate of 5°C / min, and then kept at this temperature for 20 minutes. Then, the green body is naturally cooled to room temperature to obtain a heat-resistant fatigue-resistant ceramic.

[0026] Example 2 A thermal fatigue resistant ceramic comprising the following raw materials in parts by weight: 95 parts of base material, 8 parts of toughening agent, 2 parts of sintering aid and 2 parts of additive; The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and nano zirconium oxide precursor in a mass ratio of 1:2.5:83:3.5:3.5.

[0027] The nano zirconium oxide precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate, and deionized water were mixed at a mass ratio of 2.5:20:75 at 45°C to obtain a template solution. A 1.0 mol / L ZrOCl2·8H2O solution was then added to an equal volume of the template solution at 45°C, and the pH value of the system was adjusted to 10 using a 6.5 wt% NH3·H2O solution. The system was then allowed to stand at room temperature for 18 hours, filtered, and washed three times alternately with pure ethanol and deionized water to obtain a nano-zirconia precursor. Wherein, the toughening agent is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol, and nitric acid were mixed at a mass ratio of 200:73:45:0.0063 at 50° C. for 2 hours to obtain a silica sol; the carbon fiber was washed with acetone, naturally aired to dry, and then immersed in the silica sol for 3 hours, then taken out and dried at 150° C. for 3 hours to obtain a toughening agent; The sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of 2:0.15; and the additive is B4C.

[0028] A production process for thermal fatigue resistant ceramics, comprising the following preparation steps: S1. Mix the base material, toughening agent, sintering aid and additives in the formula parts by weight at a speed of 400 rpm at room temperature for 2 hours, then dry-press the mixture at a pressure of 30 MPa and a holding time of 10 minutes, and then dry at 70° C. for 45 minutes to obtain a green body; S2. The green body obtained in step S1 is then heated to 450°C at a heating rate of 8°C / min under a nitrogen atmosphere, kept at this temperature for 45 minutes, and then further heated to 1400°C at a heating rate of 15°C / min. After keeping this temperature for 1.5 hours, the green body is further heated to 1650°C at a heating rate of 8°C / min, and then kept at this temperature for 40 minutes. The green body is then naturally cooled to room temperature to obtain a heat-resistant fatigue-resistant ceramic.

[0029] Example 3 A thermal fatigue resistant ceramic comprising the following raw materials in parts by weight: 100 parts of base material, 10 parts of toughening agent, 3 parts of sintering aid and 3 parts of additive; The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and nano zirconium oxide precursor in a mass ratio of 1.25:3:85:4:4.

[0030] The nano zirconium oxide precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate, and deionized water were mixed at a mass ratio of 3:20:80 at 50°C to obtain a template solution. A 1.5 mol / L ZrOCl2·8H2O solution was then added to an equal volume of the template solution at 50°C, and the pH of the system was adjusted to 11 using a 7 wt% NH3·H2O solution. The system was then allowed to stand at room temperature for 24 hours, filtered, and washed three times alternately with pure ethanol and deionized water to obtain a nano-zirconia precursor. Wherein, toughening agent is prepared by following steps: Tetraethyl orthosilicate, water, ethanol, and nitric acid were mixed at a mass ratio of 250:75:50:0.0063 at 55° C. for 3 hours to obtain a silica sol; the carbon fiber was washed with acetone, naturally aired to dry, and then immersed in the silica sol for 4 hours, then taken out and dried at 180° C. for 4 hours to obtain a toughening agent; The sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of 3:0.2; and the additive is SiC.

[0031] A production process for thermal fatigue resistant ceramics, comprising the following preparation steps: S1. Mix the base material, toughening agent, sintering aid and additives in the formula parts by weight at a speed of 500 rpm for 3 hours at room temperature, then dry-press the mixture at a pressure of 50 MPa and a holding time of 20 minutes, and then dry at 80° C. for 60 minutes to obtain a green body; S2. The green body obtained in step S1 is then heated to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere, kept warm for 60 minutes, and then further heated to 1500°C at a heating rate of 20°C / min. After keeping warm for 2 hours, the green body is further heated to 1700°C at a heating rate of 10°C / min, and then kept warm for 60 minutes. Then, the green body is naturally cooled to room temperature to obtain a heat-resistant fatigue-resistant ceramic.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is that the sintering aid in this comparative example is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of 1:0.5.

[0033] Comparative Example 2 The difference between this comparative example and Example 1 is that the sintering aid in this comparative example is magnesium oxide.

[0034] Comparative Example 3 The difference between this comparative example and Example 1 is that the toughening agent in this comparative example is obtained by mixing carbon fiber and silica sol in a mass ratio of 1:0.2; wherein the silica sol is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol, and nitric acid were mixed at a mass ratio of 150:70:40:0.0063 at 45° C. for 1 hour to obtain a silica sol.

[0035] Comparative Example 4 The difference between this comparative example and Example 1 is that the base material in this comparative example is obtained by mixing calcium carbonate, talc, aluminum oxide, and kaolin in a mass ratio of 0.75:2:83:3.

[0036] Comparative Example 5 The difference between this comparative example and Example 1 is that in step S2 of this comparative example, the temperature of the green body obtained in step S1 is further increased to 1300°C at a heating rate of 10°C / min under a nitrogen atmosphere, and after being kept warm for 1.5 hours, the temperature is further increased to 1600°C at a heating rate of 5°C / min, and then kept warm for 20 minutes, and then naturally cooled to room temperature, thereby obtaining a heat-resistant fatigue-resistant ceramic.

[0037] Comparative Example 6 The difference between this comparative example and Example 1 is that the base material in this comparative example is obtained by mixing calcium carbonate with a particle size of 25-50 μm, talc, aluminum oxide, kaolin, and zirconium oxide in a mass ratio of 0.75:2:80:3:3.

[0038] Performance Testing The thermal fatigue resistant ceramics prepared in Examples 1-3 and Comparative Examples 1-6 of the present application were subjected to performance tests.

[0039] Bending strength: Ceramic samples from different groups were prepared into samples with a size of 40 mm × 4 mm × 4 mm. The ceramics were then tested for strength using the three-point bending method with a loading frequency of 10 Hz and a stress ratio of 0.3. Each sample was tested five times, and the average value was recorded.

[0040] Thermal Expansion Coefficient: The thermal expansion coefficient of the sample was tested using an expansion coefficient meter according to the method described in DIN EN 821-1. The temperature was raised from 20°C to 1000°C at a controlled heating rate of 5°C / min. Each sample was tested 5 times, and the average value was recorded.

[0041] Fatigue strength: Referring to the method described in DIN EN 820-1, ceramic samples from different groups were heated to 1000°C at a heating rate of 10°C / min in a nitrogen atmosphere. The ceramics were tested for strength using the three-point bending method with a loading frequency of 10 Hz and a stress ratio of 0.3. Each sample was tested five times, and the average value was recorded.

[0042] Fatigue life: Ceramic samples from different groups were subjected to cyclic loading at 1000°C in a nitrogen atmosphere with a stress amplitude of 250 MPa. The number of fatigue cycles was recorded. Each sample was tested 5 times and the average value was recorded.

[0043] Fracture toughness: Ceramic samples from different groups were subjected to compact tensile tests at a test temperature of 1000°C and a loading rate of 0.5 mm / min. The fracture toughness was recorded. Each sample was tested 5 times and the average value was recorded.

[0044] The specific performance test results are shown in Table 2: Table 2 Thermal fatigue resistance performance test of ceramics prepared in Examples 1-3 and Comparative Examples 1-6

[0045] From the results shown in Table 2 above, it can be seen that the comprehensive performance of the heat-resistant fatigue-resistant ceramics prepared in Examples 1-3 of the present application is significantly better than that of the materials prepared in Comparative Examples 1-6, that is, within the technical solution defined in the present application, the comprehensive performance of the heat-resistant fatigue-resistant ceramics prepared is excellent. From the results in Comparative Examples 1 and 2, it can be seen that the use of a small amount of lithium carbonate is beneficial to improving the mechanical properties of the ceramics, and a larger amount will cause it to volatilize under high temperature conditions, which will reduce the mechanical properties. From the results in Comparative Example 3, it can be seen that the carbon fiber material coated with silica sol has a better reinforcing effect on the ceramics. From the results in Comparative Examples 4-6, it can be seen that the nano-zirconia precursor in the ceramic component, combined with the sintering process, can utilize the two processes of generating nano-zirconia from the zirconia precursor under high temperature conditions and the transformation of the zirconia crystal form, giving the ceramics better resistance to thermal stress.

[0046] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0047] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A thermal fatigue resistant ceramic, characterized in that: Including the following raw materials by weight: 90-100 parts of base material, 5-10 parts of toughening agent, 1-3 parts of sintering aid and 1-3 parts of additive; The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin and nano zirconium oxide precursor in a mass ratio of (0.75-1.25):(2-3):(80-85):(3-4):(3-4).

2. The thermal fatigue resistant ceramic according to claim 1, characterized in that: The nano-zirconia precursor is prepared by the following steps: A nonionic surfactant, sodium lauryl sulfate and deionized water are mixed to obtain a template solution; a ZrOCl2·8H2O solution is then added to the template solution to adjust the pH value of the system to 9-11; the system is then allowed to stand at room temperature, filtered and washed to obtain a nano-zirconium oxide precursor.

3. The thermal fatigue resistant ceramic according to claim 2, characterized in that: The mass ratio of nonionic surfactant, sodium lauryl sulfate and deionized water is (2-3):20:(70-80).

4. The thermal fatigue resistant ceramic according to claim 1, characterized in that: The toughening agent is prepared by the following steps: Tetraethyl orthosilicate, water, ethanol and nitric acid are mixed to obtain silica sol; carbon fibers are washed and dried, then immersed in the silica sol for 2-4 hours, then taken out and dried at 130-180° C. for 2-4 hours to obtain a toughening agent.

5. The thermal fatigue resistant ceramic according to claim 1, characterized in that: The sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of (1-3): (0.1-0.2).

6. The thermal fatigue resistant ceramic according to claim 1, characterized in that: The additive is at least one of B4C, BN and SiC.

7. A production process for the thermal fatigue resistant ceramic according to any one of claims 1 to 6, characterized in that: The method comprises the following preparation steps: S1, mixing the base material, toughening agent, sintering aid and additives in the formula parts by weight for 1-3 hours, then dry-pressing the mixture into a shape, and then drying to obtain a green body; S2. Then, the green body obtained in step S1 is heated to 400-500° C., kept at this temperature for 30-60 minutes, then heated to 1300-1500° C., kept at this temperature for 1-2 hours, then heated to 1600-1700° C., then kept at this temperature for 20-60 minutes, and then naturally cooled to room temperature to obtain a heat-resistant fatigue-resistant ceramic.

8. The production process of thermal fatigue resistant ceramics according to claim 7, characterized in that: In step S1, during the dry pressing process, the pressure is controlled at 20-50 MPa and the holding time is 5-20 minutes.

Images