A heat-resistant fatigue-resistant ceramic and a production process thereof

Abstract

The application relates to a heat fatigue resistant ceramic and a production process thereof, and belongs to the technical field of ceramic material preparation, and comprises the following mass parts of raw materials: 90-100 parts of a base material, 5-10 parts of a toughening agent, 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, alumina, kaolin and a nano zirconium oxide precursor according to a mass ratio of (0.75-1.25):(2-3):(80-85):(3-4):(3-4). In the heat fatigue resistant ceramic, alumina is selected as a main component, the alumina has a very high melting point, hardness and excellent chemical stability, which enables the ceramic to maintain stable physical and chemical properties in a high-temperature environment, thereby significantly enhancing the heat fatigue resistance of the ceramic.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic material preparation, and more particularly, it relates to a kind of anti-thermal fatigue ceramic and its production process. BACKGROUND

[0002] Ceramic materials are widely used in aerospace, automobile manufacturing, electronic packaging and other fields due to their excellent high-temperature resistance, corrosion resistance, wear resistance and other characteristics. However, ceramic materials will exhibit significant thermal fatigue during use, especially when subjected to rapid temperature changes. Thermal fatigue refers to the gradual decrease in thermal stress of ceramic materials under certain loads over time, which 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 materials often focus on improving the hardness and wear resistance of the material during preparation, but there are obvious deficiencies in improving the thermal fatigue resistance. Due to uneven distribution of thermal stress within the material, micro-cracks are easily formed and gradually expanded, eventually leading to material failure. In addition, traditional ceramic materials have a large coefficient of thermal expansion, which can generate a large thermal stress when the temperature changes, further exacerbating the thermal fatigue of the material.

[0004] Therefore, a new anti-thermal fatigue ceramic and its production process are needed. SUMMARY

[0005] To solve the problems raised in the background art, the application provides an anti-thermal fatigue ceramic and its production process.

[0006] The application provides an anti-thermal fatigue ceramic and its production process, which adopts the following technical solutions:

[0007] An anti-thermal fatigue ceramic, comprising the following mass parts of raw materials:

[0008] 90-100 parts of base material, 5-10 parts of toughening agent, 1-3 parts of sintering aid and 1-3 parts of additive;

[0009] The base material is obtained by mixing calcium carbonate, talc, alumina, kaolin and nano zirconium oxide precursor in a mass ratio of (0.75-1.25):(2-3):(80-85):(3-4):(3-4).

[0010] Further, the nano zirconium oxide precursor is prepared by the following steps:

[0011] Mixing non-ionic surfactant, sodium dodecyl sulfate and deionized water to obtain a template solution; then adding ZrOCl2·8H2O solution into the template solution, adjusting the pH value of the system to 9-11; then placing the system at room temperature, filtering and washing to obtain the nano zirconia precursor.

[0012] Further, the nano zirconia precursor is prepared by the following steps:

[0013] Mixing non-ionic surfactant, sodium dodecyl sulfate and deionized water at 40-50℃ to obtain a template solution; then adding 0.5-1.5mol / L ZrOCl2·8H2O solution into the template solution at 40-50℃, adjusting the pH value of the system to 9-11 using 6-7wt% NH3·H2O solution; then placing the system at room temperature for 12-24 hours, filtering and washing alternately with pure ethanol and deionized water for 3 times to obtain the nano zirconia precursor.

[0014] Further, the mass ratio of non-ionic surfactant, sodium dodecyl sulfate and deionized water is (2-3):20:(70-80).

[0015] Further, the toughening agent is prepared by the following steps:

[0016] Mixing tetraethyl orthosilicate, water, ethanol and nitric acid to obtain a silica sol; washing the carbon fiber, drying, then immersing in the silica sol for 2-4 hours, then taking out and drying at 130-180℃ for 2-4 hours to obtain the toughening agent.

[0017] Further, the toughening agent is prepared by the following steps:

[0018] Mixing tetraethyl orthosilicate, water, ethanol and nitric acid at a mass ratio of (150-250):(70-75):(40-50):0.0063 at 45-55℃ for 1-3 hours to obtain a silica sol; washing the carbon fiber with acetone, then naturally airing to dry, then immersing in the silica sol for 2-4 hours, then taking out and drying at 130-180℃ for 2-4 hours to obtain the toughening agent.

[0019] Further, the sintering aid is obtained by mixing magnesium oxide and lithium carbonate at a mass ratio of (1-3):(0.1-0.2).

[0020] Further, the additive is at least one of B4C, BN and SiC.

[0021] Further, a production process of a heat fatigue resistant ceramic comprises the following preparation steps:

[0022] S1, the formula part quality of base material, toughening agent, sintering aid and additive are mixed for 1-3 hours, then the mixture is dry-pressed into shape, and then dried to obtain a green body;

[0023] S2, then the green body obtained in S1 is heated to 400-500 DEG C, and after holding for 30-60 minutes, the temperature is increased to 1300-1500 DEG C, and after holding for 1-2 hours, the temperature is continuously increased to 1600-1700 DEG C, and then held for 20-60 minutes, and then naturally cooled to room temperature, to obtain a heat fatigue resistant ceramic.

[0024] Further, a production process of a heat fatigue resistant ceramic comprises the following preparation steps:

[0025] S1, the formula part quality of base material, toughening agent, sintering aid and additive are mixed at a speed of 300-500 rpm under room temperature conditions for 1-3 hours, then the mixture is dry-pressed into shape, and then dried at 50-80 DEG C for 30-60 minutes to obtain a green body;

[0026] S2, then the green body obtained in S1 is heated to 400-500 DEG C at a heating rate of 5-10 DEG C / min under an inert atmosphere, and after holding for 30-60 minutes, the temperature is continuously increased to 1300-1500 DEG C at a heating rate of 10-20 DEG C / min, and after holding for 1-2 hours, the temperature is continuously increased to 1600-1700 DEG C at a heating rate of 5-10 DEG C / min, and then held for 20-60 minutes, and then naturally cooled to room temperature, to obtain a heat fatigue resistant ceramic.

[0027] Further, in S1, during the dry-pressing process, the pressure is controlled to be 20-50 Mpa, and the holding time is 5-20 minutes.

[0028] In summary, the present application has the following beneficial effects:

[0029] In the technical scheme of the present application, the ratio of the calcium carbonate, talc, kaolin and other raw materials in the base material helps to control the sintering process and the final performance of the ceramic. The introduction of these raw materials can adjust the sintering shrinkage, density and microstructure of the ceramic, and thus improve the overall performance of the ceramic. In the heat fatigue resistant ceramic, alumina is selected as the main component of the base material. Alumina has a very high melting point, hardness and excellent chemical stability, which enables the ceramic to maintain stable physical and chemical properties in a high temperature environment, thereby significantly enhancing its heat fatigue resistance.

[0030] The thermal fatigue resistance of the prepared ceramic material is improved by thermal expansion adaptation between CaCO3 and zirconia. The cooling shrinkage of the ceramic matrix is different when heated due to the large difference in the thermal expansion coefficient between CaCO3 and zirconia, micro-cracks are generated between the particles and the matrix, which can absorb the energy generated during the heating process of the matrix, and the thermal fatigue resistance of the material is improved. During the sintering process, the nano-zirconia precursor component generates nano-zirconia component. Due to the extremely small particle size, the ceramic structure becomes more dense, and the transformation of zirconia component from tetragonal structure to monoclinic structure is inhibited. During the subsequent process of reducing to room temperature environment, the zirconia crystal type transformation is no longer limited, and stress relaxation occurs at the tip of the micro-crack after phase change, which hinders crack propagation, further improving the thermal fatigue resistance of the ceramic material.

[0031] The carbon fibers are surface modified, and after the carbon fibers are impregnated with silica sol, the heat treatment process in the present application is used. The bonding force between the carbon fibers and the ceramic matrix is enhanced, thereby improving the density of the composite material. And the modified carbon fibers and metal oxides in the sintering aid have a synergistic effect in promoting the densification of the ceramic during the sintering process. During the first stage of heat treatment at 400-500℃, the silica sol on the surface of the carbon fibers has good fluidity and adhesion, and can fill the gaps between the ceramic particles during the sintering process, thereby improving the density and strength of the material. The interface bonding between the silicate glass and other components helps to resist interface separation and damage caused by thermal stress, thereby improving the thermal fatigue resistance. Magnesium oxide can form a solid solution in the ceramic, increase the toughness of the material, and help to resist crack propagation and fracture caused by thermal stress. A small amount of lithium carbonate helps magnesium oxide to reduce the sintering temperature of the ceramic material, reduce pores, and improve the thermal fatigue resistance by promoting densification during the sintering process. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0033] The specific embodiments in the present application involve:

[0034] The particle size of calcium carbonate, talc, alumina, and kaolin is 25-50μm, and the purity is industrial pure;

[0035] The components of the kaolin used are shown in Table 1 below:

[0036] Table 1 Components of Kaolin

[0037]

[0038] Carbon fiber was provided by Carbon Fiber Composites, Inc., with a length of 1-50 mm and a carbon content of greater than 95%.

[0039] Example 1

[0040] The application provides an anti-thermal fatigue ceramic and a production process thereof, and adopts the following technical scheme:

[0041] An anti-thermal fatigue ceramic comprises the following raw materials in parts by mass:

[0042] 90 parts of a base material, 5 parts of a toughening agent, 1 part of a sintering aid, and 1 part of an additive;

[0043] The base material is obtained by mixing calcium carbonate, talc, aluminum oxide, kaolin, and a nano-zirconium oxide precursor in a mass ratio of 0.75:2:80:3:3.

[0044] The nano-zirconium oxide precursor is prepared by the following steps:

[0045] A non-ionic surfactant, sodium dodecyl sulfate, and deionized water are mixed in a mass ratio of 2:20:70 at 40 DEG C to obtain a template solution; then, 0.5 mol / L ZrOCl2.8H2O solution is added to an equal volume of the template solution at 40 DEG C, and a 6wt% NH3.H2O solution is used to adjust the pH value of the system to 9; then, the system is left to stand at room temperature for 12 hours, filtered, and washed with pure ethanol and deionized water alternately for 3 times to obtain the nano-zirconium oxide precursor.

[0046] The toughening agent is prepared by the following steps:

[0047] Tetraethyl orthosilicate, water, ethanol, and nitric acid are mixed in a mass ratio of 150:70:40:0.0063 at 45 DEG C for 1 hour to obtain a silica sol; carbon fiber is washed with acetone, naturally air-dried until dry, then immersed in the silica sol for 2 hours, and then taken out and dried at 130 DEG C for 2 hours to obtain the toughening agent.

[0048] 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.

[0049] A production process of an anti-thermal fatigue ceramic comprises the following preparation steps:

[0050] S1, the base material, the toughening agent, the sintering aid, and the additive in the formula part by mass are mixed at a speed of 300 rpm for 1 hour at room temperature, then the mixture is dry-pressed to form a green body, the pressure is controlled to be 20 MPa, the pressure holding time is controlled to be 5 minutes, then the green body is dried at 50 DEG C for 30 minutes;

[0051] S2, then the blank obtained in S1 is heated to 400℃ at a heating rate of 5℃ / min under nitrogen atmosphere, and then the temperature is continuously increased to 1300℃ at a heating rate of 10℃ / min, and then the temperature is continuously increased to 1600℃ at a heating rate of 5℃ / min, and then the temperature is kept for 20 minutes, and then the temperature is naturally cooled to room temperature, thereby obtaining a heat fatigue resistant ceramic.

[0052] Example 2

[0053] A heat fatigue resistant ceramic comprises the following raw materials by mass fraction:

[0054] 95 parts of base material, 8 parts of toughening agent, 2 parts of sintering aid and 2 parts of additive.

[0055] The base material is obtained by mixing calcium carbonate, talc, alumina, kaolin and nano zirconium oxide precursor in a mass ratio of 1:2.5:83:3.5:3.5.

[0056] The nano zirconium oxide precursor is prepared by the following steps:

[0057] The non-ionic surfactant, sodium dodecyl sulfate and deionized water are mixed in a mass ratio of 2.5:20:75 at 45℃ to obtain a template solution; then 1.0mol / L ZrOCl2·8H2O solution is added to an equal volume of template solution at 45℃, and 6.5wt% NH3·H2O solution is used to adjust the pH value of the system to 10; then the system is left to stand at room temperature for 18 hours, filtered and washed with pure ethanol and deionized water alternately for 3 times to obtain the nano zirconium oxide precursor;

[0058] The toughening agent is prepared by the following steps:

[0059] The tetraethyl orthosilicate, water, ethanol and nitric acid are mixed in a mass ratio of 200:73:45:0.0063 at 50℃ for 2 hours to obtain a silica sol; the carbon fiber is washed with acetone, naturally air-dried to dryness, then immersed in the silica sol for 3 hours, and then taken out and dried at 150℃ for 3 hours to obtain the toughening agent;

[0060] 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.

[0061] A production process of a heat fatigue resistant ceramic comprises the following preparation steps:

[0062] S1, the base material, the toughening agent, the sintering aid and the additive in the formula mass are mixed at room temperature at a speed of 400rpm for 2 hours, and then the mixture is dry-pressed to form a blank, the pressure is controlled to be 30Mpa, the pressure holding time is 10 minutes, and then the blank is dried at 70℃ for 45 minutes.

[0063] S2, then the blank obtained in S1 is heated to 450℃ at a heating rate of 8℃ / min under nitrogen atmosphere, and then the temperature is continuously increased to 1400℃ at a heating rate of 15℃ / min after being kept for 45min, and then the temperature is continuously increased to 1650℃ at a heating rate of 8℃ / min after being kept for 1.5h, and then kept for 40min, and then naturally cooled to room temperature, thereby obtaining a heat fatigue resistant ceramic.

[0064] Example 3

[0065] A heat fatigue resistant ceramic comprises the following raw materials in mass parts:

[0066] 100 parts of base material, 10 parts of toughening agent, 3 parts of sintering aid and 3 parts of additive.

[0067] The base material is obtained by mixing calcium carbonate, talc, alumina, kaolin and nano zirconium oxide precursor in a mass ratio of 1.25:3:85:4:4.

[0068] The nano zirconium oxide precursor is prepared by the following steps:

[0069] The non-ionic surfactant, sodium dodecyl sulfate and deionized water are mixed in a mass ratio of 3:20:80 at 50℃ to obtain a template solution; then 1.5mol / L ZrOCl2·8H2O solution is added to an equal volume of template solution at 50℃, and 7wt% NH3·H2O solution is used to adjust the pH value of the system to 11; then the system is placed at room temperature for 24h, filtered and washed with pure ethanol and deionized water alternately for 3 times to obtain the nano zirconium oxide precursor.

[0070] The toughening agent is prepared by the following steps:

[0071] The tetraethyl orthosilicate, water, ethanol and nitric acid are mixed in a mass ratio of 250:75:50:0.0063 at 55℃ for 3h to obtain a silica sol; the carbon fiber is washed with acetone, naturally air-dried to dryness, then immersed in the silica sol for 4h, and then taken out and dried at 180℃ for 4h to obtain the toughening agent.

[0072] 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.

[0073] A production process of a heat fatigue resistant ceramic comprises the following preparation steps:

[0074] S1. Mix the base material, toughening agent, sintering aid and additives according to the formula at room temperature at a rate of 500 rpm for 3 hours. Then, dry press the mixture into a mold, control the pressure at 50 MPa, and hold the pressure for 20 minutes. Then, dry it at 80°C for 60 minutes to obtain the green body.

[0075] S2. Subsequently, the green body obtained in step S1 is heated to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere, held for 60 minutes, and then the temperature is further increased to 1500°C at a heating rate of 20°C / min. After holding for 2 hours, the temperature is further increased to 1700°C at a heating rate of 10°C / min, and then held for 60 minutes. Afterward, it is naturally cooled to room temperature to obtain a heat fatigue resistant ceramic.

[0076] Comparative Example 1

[0077] 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.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the sintering aid in this comparative example is magnesium oxide.

[0080] Comparative Example 3

[0081] 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 at a mass ratio of 1:0.2; wherein the silica sol is prepared in the following steps:

[0082] Tetraethyl orthosilicate, water, ethanol, and nitric acid were mixed at 45°C for 1 hour in a mass ratio of 150:70:40:0.0063 to obtain silica sol.

[0083] Comparative Example 4

[0084] 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, alumina and kaolin in a mass ratio of 0.75:2:83:3.

[0085] Comparative Example 5

[0086] The difference between this comparative example and Example 1 is that in step S2 of this comparative example, the green body obtained in step S1 is heated to 1300°C at a heating rate of 10°C / min under a nitrogen atmosphere, held at that temperature for 1.5 hours, and then heated to 1600°C at a heating rate of 5°C / min. After holding at that temperature for 20 minutes, it is then naturally cooled to room temperature to obtain a heat fatigue resistant ceramic.

[0087] Comparative Example 6

[0088] 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, alumina, kaolin, and zirconium oxide with a particle size of 25-50 μm in a mass ratio of 0.75:2:80:3:3.

[0089] Performance testing

[0090] The heat fatigue resistant ceramics prepared in Examples 1-3 and Comparative Examples 1-6 of this application were subjected to performance tests.

[0091] Bending strength: Ceramic samples from different groups were prepared into samples with dimensions of 40mm×4mm×4mm. The strength of the ceramics was then tested using the three-point bending method. The loading frequency was 10Hz and the stress ratio was 0.3. Each sample was tested 5 times, and the average value was recorded.

[0092] Coefficient of thermal expansion: The coefficient of thermal expansion of the sample was tested using an expansion coefficient measuring instrument, referring to the method described in DIN EN 821-1. The heating rate was controlled at 5℃ / min, and the temperature was increased from 20℃ to 1000℃. Different samples were tested. Each sample was tested 5 times, and the average value was recorded.

[0093] Fatigue strength: Following the method described in DIN EN 820-1, ceramic samples from different groups were heated to 1000°C in a nitrogen atmosphere at a heating rate of 10°C / min. The strength of the ceramics was tested using the three-point bending method, with a loading frequency of 10Hz and a stress ratio of 0.3. Each sample was tested 5 times, and the average value was recorded.

[0094] Fatigue life: Ceramic samples from different groups were subjected to cyclic loading at 1000℃ and 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.

[0095] Fracture toughness: Ceramic samples from different groups were subjected to a compact tensile test at a temperature of 1000℃ 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.

[0096] The specific performance test results are shown in Table 2 below:

[0097] Table 2. Test results of the thermal fatigue resistance ceramics prepared in Examples 1-3 and Comparative Examples 1-6

[0098]

[0099] As shown in Table 2 above, the comprehensive performance of the heat-resistant fatigue-resistant ceramics prepared in Examples 1-3 of this application is significantly better than that of the materials prepared in Comparative Examples 1-6. That is, within the technical scope defined in this application, the heat-resistant fatigue-resistant ceramics exhibit excellent comprehensive performance. The results from Comparative Examples 1 and 2 show that a small amount of lithium carbonate is beneficial for improving the mechanical properties of the ceramics, while a larger amount leads to its volatilization under high-temperature conditions, which in turn reduces the mechanical properties. The results from Comparative Example 3 show that the carbon fiber material coated with silica sol has a better reinforcing effect on the ceramics. The results from Comparative Examples 4-6 show that the nano-zirconia precursor in the ceramic composition, combined with the sintering process, can utilize the two processes of generating nano-zirconia from the zirconia precursor under high-temperature conditions and the zirconia crystal transformation, thus endowing the ceramics with better resistance to thermal stress.

[0100] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above 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 one or more embodiments or examples.

[0101] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A ceramic resistant to heat fatigue, characterized in that, Includes the following quantities of raw materials: 90-100 parts base material, 5-10 parts toughening agent, 1-3 parts sintering aid and 1-3 parts additive; The base material is obtained by mixing calcium carbonate, talc, alumina, kaolin, and nano-zirconia precursor in a mass ratio of (0.75-1.25):(2-3):(80-85):(3-4):(3-4); 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, dried, and then immersed in silica sol for 2-4 hours, then removed and dried at 130-180℃ for 2-4 hours to obtain toughening agent; The sintering aid is obtained by mixing magnesium oxide and lithium carbonate in a mass ratio of (1-3):(0.1-0.2).

2. The heat-fatigue resistant ceramic according to claim 1, characterized in that, The nano-zirconia precursor was prepared by the following steps: A template solution was prepared by mixing a nonionic surfactant, sodium dodecyl sulfate, and deionized water. Then, a ZrOCl2·8H2O solution was added to the template solution to adjust the pH of the system to 9-11. The system was then allowed to stand at room temperature, filtered, and washed to obtain nano-zirconia precursors.

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

4. The heat-fatigue resistant ceramic according to claim 1, characterized in that, The additive is at least one of B4C, BN, and SiC.

5. A production process for heat-resistant fatigue-resistant ceramics as described in any one of claims 1-4, characterized in that, The preparation steps include the following: S1. Mix the base material, toughening agent, sintering aid and additives according to the formula proportions for 1-3 hours, then dry press the mixture into shape, and then dry it to obtain a green body; S2. Then, the green body obtained in step S1 is heated to 400-500℃ and held for 30-60 minutes. The temperature is then increased to 1300-1500℃ and held for 1-2 hours. The temperature is then increased to 1600-1700℃ and held for 20-60 minutes. The green body is then allowed to cool naturally to room temperature to obtain a heat-resistant and fatigue-resistant ceramic.

6. The production process of a heat-resistant fatigue-resistant ceramic according to claim 5, 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