A ceramic valve plate material for new energy vehicles and a preparation method thereof

Abstract

The application relates to the field of ceramic materials, in particular to a ceramic valve plate material for new energy vehicles and a preparation method thereof, which is prepared from boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder with a mass ratio of 100:(3-5):(2-4):(1-2):(3-6). The prepared ceramic valve plate material has excellent mechanical properties and can meet the performance requirements of ceramic valve plates of new energy vehicles.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, specifically to a ceramic valve plate material for new energy vehicles and its preparation method. Background Technology

[0002] The thermal management system of new energy vehicles presents unprecedented performance challenges to valve plate materials. As a core component controlling the flow of coolant, refrigerant, and battery thermal management media, valve plates need to operate stably for extended periods under alternating pressure, friction, thermal cycles, and corrosive environments containing ethylene glycol, weak acids / alkalines, and other media. While traditional metal valve plates have good machinability, they suffer from inherent defects such as poor corrosion resistance, rapid wear rate, and short fatigue life, making it difficult to meet performance requirements. Although ceramic valve plates improve corrosion resistance, their hardness and wear resistance are insufficient, making them prone to erosion failure in coolants containing solid particles.

[0003] Boron carbide, with its extremely high hardness, excellent chemical stability, and low density, is an ideal candidate material for preparing long-life valve plates. However, the industrial application of boron carbide has long been constrained by two major technical bottlenecks: first, its strong covalent bond characteristics result in extremely poor intrinsic sintering properties, requiring temperatures exceeding 2200℃ under pressureless conditions to achieve densification, at which temperature abnormal grain growth leads to insufficient material strength; second, its low fracture toughness and poor impact resistance make it prone to brittle fracture under high-pressure alternating loads. These defects limit the industrial application of boron carbide. Summary of the Invention

[0004] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a ceramic valve plate material for new energy vehicles and its preparation method.

[0005] The technical solution adopted is as follows: A ceramic valve plate material for new energy vehicles is prepared from boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder.

[0006] Furthermore, the mass ratio of boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder is 100:(3~5):(2~4):(1~2):(3~6).

[0007] Furthermore, the aluminum powder has a particle size ≤100nm. Nano-sized aluminum powder has higher surface activity, allowing for more complete contact and thus enabling the aluminothermic reaction with chromium oxide, zirconium oxide, and boron oxide.

[0008] Furthermore, the aluminum powder undergoes surface modification treatment with a silane coupling agent. Nano-sized aluminum powder is prone to agglomeration; after surface modification with a silane coupling agent, it can be more fully mixed with the remaining components, thereby promoting the uniform occurrence of the aluminothermic reaction and ensuring the uniform distribution of subsequent products.

[0009] Furthermore, the silane coupling agent is any one of KH-550, KH-560, or KH-570.

[0010] Furthermore, the surfaces of the chromium oxide and zirconium oxide are coated with aluminum oxide.

[0011] When the sintering temperature exceeds 1250℃, the aluminothermic reaction occurs, releasing a large amount of heat through combustion. Alumina, acting as an inert protective layer, effectively delays the aluminothermic reaction without reducing its final reactivity. This ensures the aluminothermic reaction temperature matches the sintering temperature, avoiding the intense exothermic reaction in the low-temperature region that can lead to internal porosity and cracking, and reducing the possibility of premature aluminothermic reaction during ball milling. Boron oxide's reactivity with aluminum is much lower than that of chromium oxide and zirconium oxide, and because the amount of boron oxide is small and readily soluble in water, it was not coated.

[0012] This invention also provides a method for preparing ceramic valve plate material for new energy vehicles, as detailed below: Boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder are mixed, ball-milled and then added to a mold for spark plasma sintering.

[0013] Furthermore, the temperature for spark plasma sintering is 1800~2000℃. Sintering at this temperature promotes densification while avoiding abnormal grain growth caused by excessively high sintering temperatures. During spark plasma sintering, the sintering temperature is monitored in real time using thermocouples built into the SPS equipment. If the temperature exceeds 2000℃, it can be adjusted by increasing the cooling rate (purging with cold argon gas).

[0014] Furthermore, the discharge plasma sintering time is 10~20 min.

[0015] Furthermore, the spark plasma sintering is carried out in two stages: the sintering pressure in the first stage is 10~20MPa, and the sintering pressure in the second stage is 50~60MPa.

[0016] The beneficial effects of this invention are: This invention provides a ceramic valve plate material for new energy vehicles, prepared from boron carbide, chromium oxide, zirconium oxide, boron oxide, and aluminum powder. During spark plasma sintering, the aluminum powder can simultaneously undergo an aluminothermic reaction with chromium oxide, zirconium oxide, and boron oxide to generate alumina and elemental chromium, zirconium, and boron. The elemental chromium, zirconium, and boron then generate chromium boride and zirconium boride as reinforcing phases at high temperatures, achieving dispersion strengthening. Simultaneously, the generated liquid alumina or the low-melting-point boron-aluminum oxide liquid phase generated by the reaction fills the gaps between boron carbide particles, promoting particle rearrangement through capillary force and viscous flow, accelerating material transport, reducing sintering temperature, decreasing porosity during sintering, and increasing density. The ceramic valve plate material prepared by this invention has excellent mechanical properties and can meet the performance requirements of ceramic valve plates for new energy vehicles. Attached Figure Description

[0017] Figure 1 This is a SEM image of the cross-section of the ceramic valve plate material prepared in Example 1 of the present invention.

[0018] Figure 2 This is a SEM image of the cross-section of the ceramic valve plate material prepared in Example 5 of the present invention.

[0019] Figure 3 This is a SEM image of the cross-section of the ceramic valve plate material prepared in Example 6 of the present invention. Detailed Implementation

[0020] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters. Example 1:

[0021] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder and silane coupling agent modified aluminum powder in a mass ratio of 100:4:3:1.5:4.5.

[0022] The preparation method of silane coupling agent modified aluminum powder is as follows: Add 10g of nano-aluminum powder (average particle size 50nm) to a flask, add 100ml of anhydrous ethanol, and sonicate for 15min. Then place the flask in a 40℃ constant temperature water bath. When the temperature stabilizes, add 10g of silane coupling agent KH-570 and 5ml of deionized water. Stir for 5h under nitrogen protection. After the reaction is complete, centrifuge, collect the product, wash with anhydrous ethanol, and then vacuum dry.

[0023] The preparation method of chromium oxide@aluminum oxide is as follows: Add 100 ml of 1 mol / L ammonia solution to a flask, then place it in a water bath at 80-90°C. Slowly add 30 ml of 1 mol / L aluminum nitrate solution while stirring. After reacting for 2 hours, add 300 ml of 1 mol / L nitric acid to the flask to allow the precipitate to slowly hydrolyze. Continue stirring and aging for 15 hours to obtain a clear sol. Add 0.3 mol of chromium oxide powder to the sol, and continue stirring and heating to evaporate and dry it to obtain the precursor. Heat-treat the precursor at 600°C in air for 2 hours.

[0024] The preparation method of zirconium oxide@alumina is as follows: Add 100 ml of 1 mol / L ammonia solution to a flask, then place it in a water bath at 80-90°C. Slowly add 30 ml of 1 mol / L aluminum nitrate solution while stirring. After reacting for 2 hours, add 300 ml of 1 mol / L nitric acid to the flask to allow the precipitate to slowly hydrolyze. Continue stirring and aging for 15 hours to obtain a clear sol. Add 0.3 mol of zirconium oxide powder to the sol, and continue stirring and heating to evaporate and dry it to obtain the precursor. Heat-treat the precursor at 600°C in air for 2 hours.

[0025] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder, and silane coupling agent-modified aluminum powder were added to a ball mill jar and ball-milled for 10 hours in a planetary ball mill. The mixture was then poured into a mold and subjected to spark plasma sintering using an SPS-1050T spark plasma sintering system from Sumitomo Coal Industries, Ltd. The spark plasma sintering temperature was 1900℃, the sintering time was 15 min, and the heating rate was 100℃ / min. The sintering pressure was 15 MPa when the temperature was below 1000℃ and 55 MPa when the temperature was above 1000℃. Figure 1 The image shows a cross-section of the ceramic valve plate material prepared in this embodiment. It can be seen that the cross-section is flat and the internal structure is dense. Example 2:

[0026] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide@aluminum oxide, zirconium oxide@aluminum oxide, boron oxide powder and silane coupling agent modified aluminum powder in a mass ratio of 100:5:4:2:6.

[0027] The preparation methods for silane coupling agent modified aluminum powder, chromium oxide@aluminum oxide, and zirconium oxide@aluminum oxide are the same as in Example 1.

[0028] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder, and silane coupling agent modified aluminum powder were added to a ball mill jar and mixed and milled on a planetary ball mill for 10 hours. The mixture was then added to a mold and subjected to discharge plasma sintering using an SPS-1050T discharge plasma sintering system from Sumitomo Coal Industries, Ltd. of Japan. The discharge plasma sintering temperature was 2000℃, the discharge plasma sintering time was 20 min, and the heating rate was 100℃ / min. The sintering pressure was 20 MPa when the temperature was below 1000℃ and 60 MPa when the temperature was above 1000℃. Example 3:

[0029] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide@aluminum oxide, zirconium oxide@aluminum oxide, boron oxide powder and silane coupling agent modified aluminum powder in a mass ratio of 100:3:2:1:3.

[0030] The preparation methods for silane coupling agent modified aluminum powder, chromium oxide@aluminum oxide, and zirconium oxide@aluminum oxide are the same as in Example 1.

[0031] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder, and silane coupling agent modified aluminum powder were added to a ball mill jar and mixed and milled on a planetary ball mill for 10 hours. The mixture was then added to a mold and subjected to discharge plasma sintering using an SPS-1050T discharge plasma sintering system from Sumitomo Coal Industries, Ltd. of Japan. The discharge plasma sintering temperature was 1800℃, the discharge plasma sintering time was 10 min, and the heating rate was 100℃ / min. The sintering pressure was 10 MPa when the temperature was below 1000℃ and 50 MPa when the temperature was above 1000℃. Example 4:

[0032] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide@aluminum oxide, zirconium oxide@aluminum oxide, boron oxide powder and silane coupling agent modified aluminum powder in a mass ratio of 100:3:4:1:6.

[0033] The preparation methods for silane coupling agent modified aluminum powder, chromium oxide@aluminum oxide, and zirconium oxide@aluminum oxide are the same as in Example 1.

[0034] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder, and silane coupling agent modified aluminum powder were added to a ball mill jar and mixed and milled on a planetary ball mill for 10 hours. The mixture was then added to a mold and subjected to discharge plasma sintering using an SPS-1050T discharge plasma sintering system from Sumitomo Coal Industries, Ltd. of Japan. The discharge plasma sintering temperature was 2000℃, the discharge plasma sintering time was 15 min, and the heating rate was 100℃ / min. The sintering pressure was 20 MPa when the temperature was below 1000℃ and 60 MPa when the temperature was above 1000℃. Example 5:

[0035] This is essentially the same as Example 1, except that chromium oxide powder and zirconium oxide powder are used instead of chromium oxide@aluminum oxide and zirconium oxide@aluminum oxide.

[0036] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide powder, zirconium oxide powder, boron oxide powder and silane coupling agent modified aluminum powder in a mass ratio of 100:4:3:1.5:4.5.

[0037] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide powder, zirconium oxide powder, and silane coupling agent-modified aluminum powder were added to a ball mill jar and ball-milled for 10 hours in a planetary ball mill. The mixture was then poured into a mold and subjected to spark plasma sintering using an SPS-1050T spark plasma sintering system from Sumitomo Coal Industries, Ltd. The spark plasma sintering temperature was 1900℃, the sintering time was 15 minutes, and the heating rate was 100℃ / min. The sintering pressure was 15 MPa when the temperature was below 1000℃ and 55 MPa when the temperature was above 1000℃. Figure 2 The image shows a SEM image of the cross-section of the ceramic valve plate material prepared in this embodiment. It can be seen that the cross-section is relatively rough and there are localized areas where the sintering is not very dense. Example 6:

[0038] It is basically the same as Example 1, except that aluminum powder is used instead of silane coupling agent to modify aluminum powder.

[0039] A ceramic valve plate material for new energy vehicles is prepared from boron carbide powder, chromium oxide@aluminum oxide, zirconium oxide@aluminum oxide, boron oxide powder and aluminum powder (average particle size 50 nm) in a mass ratio of 100:4:3:1.5:4.5.

[0040] The preparation methods for chromium oxide@aluminum oxide and zirconium oxide@aluminum oxide are the same as in Example 1.

[0041] The preparation method of the above-mentioned ceramic valve plate material for new energy vehicles is as follows: Boron carbide powder, chromium oxide@alumina, zirconium oxide@alumina, boron oxide powder, and aluminum powder were added to a ball mill jar and ball-milled for 10 hours in a planetary ball mill. The mixture was then poured into a mold and subjected to spark plasma sintering using an SPS-1050T spark plasma sintering system from Sumitomo Coal Industries, Ltd. The spark plasma sintering temperature was 1900℃, the sintering time was 15 minutes, and the heating rate was 100℃ / min. The sintering pressure was 15 MPa when the temperature was below 1000℃ and 55 MPa when the temperature was above 1000℃. Figure 3 The image shows a cross-section of the ceramic valve plate material prepared in this embodiment. It can be seen that the cross-section is relatively flat and the internal structure is relatively dense.

[0042] Comparative Example 1: It is basically the same as Example 1, except that chromium oxide@aluminum oxide is not added.

[0043] Comparative Example 2: It is basically the same as Example 1, except that zirconium oxide@aluminum oxide is not added.

[0044] Comparative Example 3: It is basically the same as Example 1, except that silane coupling agent is not added to modify aluminum powder.

[0045] Performance testing: The performance of the samples prepared in Examples 1-6 and Comparative Examples 1-3 was tested; The flexural strength of the specimens was measured using an Instron 3345 universal testing machine. The three-point bending method was adopted, based on standard GB / T 4741-1999, with specimen dimensions of 3mm × 4mm × 26mm. The indenter movement speed was set to 0.5mm / min, and the span was 20mm.

[0046] The fracture toughness of the specimens was measured using an Instron 3345 universal testing machine. The single-sided notched beam method was used, and the standard adopted was GB / T 23806-2009. The standard size of the specimen was 2mm × 4mm × 20mm, the notch depth was 2mm, the test span was 16mm, and the indenter movement speed was set to 0.05mm / min.

[0047] The test results are shown in Table 1 below: Table 1: As shown in Table 1 above, the ceramic valve plate material prepared by the present invention has excellent mechanical properties.

[0048] A comparison between Example 1 and Example 5 shows that alumina coating greatly improves the mechanical properties of ceramic valve plate materials.

[0049] A comparison between Example 1 and Example 6 shows that silane coupling agent-modified aluminum powder can greatly improve the mechanical properties of ceramic valve plate materials.

[0050] The comparison between Example 1 and Comparative Example 1 shows that the addition of chromium oxide@aluminum oxide plays a positive role in improving the mechanical properties of ceramic valve plate materials.

[0051] The comparison between Example 1 and Comparative Example 2 shows that the addition of zirconium oxide@alumina plays a positive role in improving the mechanical properties of ceramic valve plate materials.

[0052] The comparison between Example 1 and Comparative Example 3 shows that the addition of silane coupling agent modified aluminum powder plays a positive role in improving the mechanical properties of ceramic valve plate materials.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ceramic valve plate material for new energy vehicles, characterized in that, It is prepared from boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder.

2. The ceramic valve plate material for new energy vehicles as described in claim 1, characterized in that, The mass ratio of boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder is 100:(3~5):(2~4):(1~2):(3~6).

3. The ceramic valve plate material for new energy vehicles as described in claim 1, characterized in that, The particle size of the aluminum powder is ≤100nm.

4. The ceramic valve plate material for new energy vehicles as described in claim 1, characterized in that, The aluminum powder is surface modified with a silane coupling agent.

5. The ceramic valve plate material for new energy vehicles as described in claim 4, characterized in that, The silane coupling agent is any one of KH-550, KH-560 or KH-570.

6. The ceramic valve plate material for new energy vehicles as described in claim 1, characterized in that, The chromium oxide and zirconium oxide are coated with aluminum oxide.

7. A method for preparing a ceramic valve plate material for new energy vehicles as described in any one of claims 1 to 6, characterized in that, Specifically as follows: Boron carbide, chromium oxide, zirconium oxide, boron oxide and aluminum powder are mixed, ball-milled and vacuum-dried, and then added to a mold for spark plasma sintering.

8. The method for preparing ceramic valve plate material for new energy vehicles as described in claim 7, characterized in that, The temperature for spark plasma sintering is 1800~2000℃.

9. The method for preparing ceramic valve plate material for new energy vehicles as described in claim 7, characterized in that, The time for spark plasma sintering is 10~20 min.

10. The method for preparing ceramic valve plate material for new energy vehicles as described in claim 7, characterized in that, The spark plasma sintering process is carried out in two stages. The sintering pressure in the first stage is 10~20MPa, and the sintering pressure in the second stage is 50~60MPa.

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