NTC thermistor material based on silicon carbide and preparation method thereof

Abstract

The invention relates to the technical field of thermistor materials, in particular to a silicon carbide-based NTC thermistor material and a preparation method thereof. The NTC thermistor material based on silicon carbide is prepared from the following raw materials in percentage by mass: 0.1-0.5 wt% of a fluxing agent, namely nano zinc oxide, 0.05-0.2 wt% of a fluxing agent, namely nano yttrium oxide, 0.4-2.0 wt% of a toughening agent, namely nano zirconium oxide, 0.1-0.5 wt% of a toughening agent, namely nano titanium nitride, 0.4-2.0 wt% of a tempering agent, namely nano strontium titanate, and the balance of silicon carbide. 0.5-4.0% of nano rare earth metal carbide and the balance of silicon carbide. The NTC thermistor material has excellent high temperature resistance and high and low temperature impact resistance, the resistance deviation is lower than 0.5% after 1500 times of cyclic high and low temperature impact, and the NTC thermistor material can meet the use requirements of highly integrated circuits, IGBTs and other modules.

Description

Technical Field

[0001] The present invention relates to the technical field of thermistor materials, and in particular to a silicon carbide-based NTC thermistor material and a preparation method thereof. Background Art

[0002] NTC thermistor material has the opposite performance to PTC thermistor material. It is a negative temperature coefficient thermistor, that is, it shows different resistance values ​​at different temperatures. The higher the temperature, the lower the resistivity of the NTC thermistor material. NTC thermistor material is usually a solid solution material composed of transition metal oxides. It plays an important role in temperature measurement, temperature control, temperature compensation, surge suppression, etc. and has the advantages of high sensitivity, fast response speed, small size, and easy remote control. The thermal constant of commonly used NTC thermistor materials, that is, the B value, is generally B 25 / 85 , B 25 / 85 Generally, it is 2000~6000K, and the resistivity is generally 5~8*10 5 Ω·cm, which is suitable for low temperature, high frequency, high power and large temperature attenuation compensation, is widely used in daily life and industrial production, such as refrigerators, air conditioners, electric water heaters, microwave ovens, rice cookers, mobile phone batteries, induction cookers, temperature control instruments, medical instruments, fire alarms, integrated circuits, IGBT modules and other fields.

[0003] Existing NTC thermistor ceramic components are primarily composed of metal oxides containing manganese (Mn) and nickel (Ni). After 1,000-1,500 cycles of high and low temperature shock, their resistance value deviation is approximately 2-3%. While this can meet the needs of household appliances, the development of third-generation semiconductor technology, such as highly integrated circuits and IGBT modules, has placed higher demands on NTC thermistor materials, requiring them to have better high-temperature resistance and high-temperature shock resistance. To this end, the present invention provides a silicon carbide-based NTC thermistor material and a preparation method thereof. Summary of the Invention

[0004] In order to meet the requirements of NTC thermistor materials for better high temperature resistance and high and low temperature impact resistance in the fields of highly integrated circuit modules, IGBT modules, etc., the present invention provides a silicon carbide-based NTC thermistor material and a preparation method thereof.

[0005] The present invention provides an NTC thermistor material based on silicon carbide, which is realized by the following technical solutions:

[0006] A silicon carbide-based NTC thermistor material is made of the following raw materials in percentage by mass: 0.1-0.5wt% of a fluxing agent—nano zinc oxide, 0.05-0.2wt% of a fluxing agent—nano yttrium trioxide, 0.4-2.0wt% of a toughening agent—nano zirconium oxide, 0.1-0.5wt% of a toughening agent—nano titanium nitride, 0.4-2.0% of a tempering agent—nano strontium titanate, 0.5-4.0% of a nano rare earth metal carbide, and the balance is silicon carbide; the nano rare earth metal carbide is at least one of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, MAX phase niobium aluminum carbide, and MAX phase tantalum aluminum carbide.

[0007] The NTC thermistor material of the present invention has excellent high temperature resistance and high and low temperature impact resistance. After 1500 cycles of high and low temperature impact, the resistance deviation is less than 0.5%, which can meet the use requirements of modules such as highly integrated circuits and IGBTs.

[0008] Preferably, the silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.3-0.4wt% of flux - nano zinc oxide, 0.05-0.10wt% of flux - nano yttrium trioxide, 0.8-1.0wt% of toughening agent - nano zirconium oxide, 0.2-0.4wt% of toughening agent - nano titanium nitride, 0.6-1.0% of tempering agent - nano strontium titanate, 2.4-3.2% of nano rare earth metal carbide, and the balance is silicon carbide.

[0009] By adopting the above technical solution, the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor material can be improved.

[0010] Preferably, the nano rare earth metal carbide is composed of at least one of MXene multilayer nanosheet niobium carbide and MXene multilayer nanosheet tantalum carbide combined with at least one of MAX phase niobium aluminum carbide and MAX phase tantalum aluminum carbide.

[0011] Preferably, the nano rare earth metal carbide is composed of MXene multilayer nanosheet tantalum carbide and MAX phase niobium aluminum carbide in a mass ratio of 3:2.

[0012] Preferably, the nano rare earth metal carbide is composed of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, and MAX phase tantalum aluminum carbide in a mass ratio of 4:3:3.

[0013] By optimizing the design of the ratio of nano rare earth metal carbide components, not only the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor material can be effectively improved, but also the impact toughness of the NTC thermistor material can be effectively improved without affecting the overall temperature compensation and surge suppression performance.

[0014] Preferably, the silicon carbide is composed of 5-20wt% of surface single-atom modified silicon carbide 6H-SiC, 5-40wt% of surface doped graphene-modified silicon carbide 6H-SiC, 5-20wt% of cubic silicon carbide 3C-SiC, and the balance is hexagonal silicon carbide 6H-SiC; the surface single-atom modified silicon carbide 6H-SiC includes a silicon carbide 6H-SiC carrier and an active metal fixed on the surface of the silicon carbide 6H-SiC carrier in the form of a single atom, The active metal is at least one of Mn, Co, Ni, Cu, Zn, and Bi; the content of the single-atom active metal doped on the surface of the surface single-atom modified silicon carbide 6H-SiC is 0.5-5wt%; the surface-doped graphene-modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC carrier and graphene sintered on the surface of the silicon carbide 6H-SiC carrier by nanosilver; the graphene content in the surface-doped graphene-modified silicon carbide 6H-SiC is 0.2-2wt%.

[0015] Preferably, the silicon carbide is composed of 10-12wt% of surface single-atom modified silicon carbide 6H-SiC, 20-24wt% of surface doped graphene modified silicon carbide 6H-SiC, 5-10wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0016] By adopting the above technical solution, the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor material can be improved.

[0017] Preferably, the active metals in the surface single-atom modified silicon carbide 6H-SiC are Mn, Co, and Bi, and the mass ratio of Mn, Co, and Bi is 3:1:1; the content of doped single-atom active metals in the surface of the surface single-atom modified silicon carbide 6H-SiC is 2-3wt%; the content of graphene in the surface doped graphene modified silicon carbide 6H-SiC is 0.8-1.2wt%.

[0018] By adopting the above technical solution, the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor can be further improved.

[0019] The method for preparing the silicon carbide-based NTC thermistor material provided by the present invention is achieved by the following scheme:

[0020] A method for preparing an NTC thermistor material based on silicon carbide comprises the following steps:

[0021] Step 1: Place accurately measured flux-nano zinc oxide, flux-nano yttrium trioxide, toughener-nano zirconium oxide, toughener-nano titanium nitride, tempering agent-nano strontium titanate, and nano rare earth metal carbide in a planetary ball mill, use tungsten carbide grinding beads for wet ball milling, the solid-liquid ratio is 1: (1.0-2.0), and the ball milling speed is 120-200 rpm for 15-30 minutes. After the obtained ball-milled mixture is dried, it is added to another planetary ball mill, and accurately measured silicon carbide is added to the planetary ball mill. Use tungsten carbide grinding beads for dry ball milling, and ball milling is carried out at a ball milling speed of 60-80 rpm for 240-300 seconds to obtain a uniformly mixed NTC ceramic mixture;

[0022] Step 2: Place the NTC ceramic mixture in step 1 into a forming mold for cold isostatic pressing. The molding temperature is 20-50° C. The molding pressure is: first pressurized to 200 MPa at 10-20 MPa / s, held for 30-60 seconds, then pressurized to 300-400 MPa at 5-10 MPa / s, held for 120-180 seconds, then reduced to 200 MPa at 5-10 MPa / s, held for 30-40 seconds, and then reduced to 0 MPa at 20-25 MPa / s. The molding speed is 0.5-2 mm / s. After completing the cold isostatic pressing process, the NTC ceramic preform can be obtained.

[0023] Step 3, the NTC ceramic preform in step 2 is subjected to rapid sintering treatment, heating to 800-850°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 1650-1680°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 2180-2250°C at 100-200°C / min and holding for 2-4h, cooling to 600-650°C at a cooling rate of 40-80°C / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material;

[0024] Step 4: Stress relief treatment is performed on the semi-finished NTC thermistor material obtained in step 3. The temperature is raised to 200-240°C at 20-60°C / min in an inert atmosphere and kept at this temperature for 1-2 hours. The temperature is then raised to 400-420°C at 40-80°C / min and kept at this temperature for 4-8 hours. The finished NTC thermistor material is obtained after the furnace is naturally cooled to room temperature.

[0025] The preparation method provided in the present invention is simple to operate and easy to implement industrial production, which is beneficial to reducing the production cost of NTC thermistor materials, thereby lowering the market threshold for them to enter the market of highly integrated circuits, IGBTs and other modules, and facilitating the rapid entry of the above-mentioned NTC thermistor materials into the supply chain market of highly integrated circuits, IGBTs and other modules.

[0026] Preferably, in step three, the NTC ceramic preform in step two is subjected to a rapid sintering treatment, heating to 820°C at 100°C / min and holding for 0.5h, then heating to 1660°C at 150°C / min and holding for 1.0h, then heating to 2240°C at 200°C / min and holding for 3h, cooling to 640°C at a cooling rate of 50-60°C / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material.

[0027] By optimizing the rapid sintering parameters, the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor can be further improved, and the overall impact toughness of the NTC thermistor can also be improved.

[0028] In summary, the present invention has the following advantages:

[0029] 1. The NTC thermistor material of the present invention has excellent high temperature resistance and high and low temperature impact resistance. After 1500 cycles of high and low temperature impact, the resistance deviation is less than 0.5%, which can meet the use requirements of highly integrated circuits, IGBTs and other modules.

[0030] 2. The silicon carbide composition obtained by surface modification of silicon carbide in the present invention can further improve the high temperature resistance and high and low temperature impact resistance of the NTC thermistor as a whole, and can also improve the impact toughness of the NTC thermistor as a whole.

[0031] 3. The preparation method provided in the present invention is simple to operate and easy to implement industrial production, which is conducive to reducing the production cost of NTC thermistor materials, thereby lowering the market threshold for them to enter the market of highly integrated circuits, IGBTs and other modules, and facilitating the rapid entry of the above-mentioned NTC thermistor materials into the supply chain market of highly integrated circuits, IGBTs and other modules.

[0032] 4. The optimization of the rapid sintering parameters in the preparation method provided in the present invention can further improve the overall high temperature resistance and high and low temperature impact resistance of the NTC thermistor, and can also improve the overall impact toughness of the NTC thermistor. DETAILED DESCRIPTION

[0033] In order to further understand the present invention, preferred embodiments of the present invention are described below with reference to examples and comparative examples.

[0034] Example

[0035] The invention discloses an NTC thermistor material based on silicon carbide, which is made of the following raw materials in percentage by mass: 0.1-0.5 wt% of a fluxing agent, nano zinc oxide; 0.05-0.2 wt% of a fluxing agent, nano yttrium trioxide; 0.4-2.0 wt% of a toughening agent, nano zirconium oxide; 0.1-0.5 wt% of a toughening agent, nano titanium nitride; 0.4-2.0% of a tempering agent, nano strontium titanate; 0.5-4.0% of a nano rare earth metal carbide; and the balance being silicon carbide.

[0036] The preferred formula for silicon carbide-based NTC thermistor material is as follows: 0.3-0.4wt% fluxing agent - nano zinc oxide, 0.05-0.10wt% fluxing agent - nano yttrium trioxide, 0.8-1.0wt% toughening agent - nano zirconium oxide, 0.2-0.4wt% toughening agent - nano titanium nitride, 0.6-1.0% tempering agent - nano strontium titanate, 2.4-3.2% nano rare earth metal carbide, and the balance is silicon carbide.

[0037] The nano rare earth metal carbide is at least one of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, MAX phase niobium aluminum carbide, and MAX phase tantalum aluminum carbide.

[0038] Preferably, the nano rare earth metal carbide is composed of at least one of MXene multilayer nanosheet niobium carbide and MXene multilayer nanosheet tantalum carbide, combined with at least one of MAX phase niobium aluminum carbide and MAX phase tantalum aluminum carbide.

[0039] Further preferably, the nano rare earth metal carbide is composed of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, and MAX phase tantalum aluminum carbide in a mass ratio of 4:3:3.

[0040] Further preferably, the nano rare earth metal carbide is composed of MXene multilayer nanosheets of tantalum carbide and MAX phase of niobium aluminum carbide in a mass ratio of 3:2.

[0041] Further preferably, the silicon carbide consists of 5-20wt% of surface single-atom modified silicon carbide 6H-SiC, 5-40wt% of surface doped graphene modified silicon carbide 6H-SiC, 5-20wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0042] The surface-modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC support and an active metal fixed to the surface of the silicon carbide 6H-SiC support in the form of single atoms. The active metal is at least one of Mn, Co, Ni, Cu, Zn, and Bi. The content of the single-atom active metal doped on the surface of the surface-modified silicon carbide 6H-SiC is 0.5-5 wt%.

[0043] The surface-doped graphene-modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC carrier and graphene sintered on the surface of the silicon carbide 6H-SiC carrier through nano-silver, and the content of the graphene is 0.2-2wt%.

[0044] Further preferably, the silicon carbide is composed of 10-12wt% surface single-atom modified silicon carbide 6H-SiC, 20-24wt% surface doped graphene modified silicon carbide 6H-SiC, 5-10wt% cubic silicon carbide 3C-SiC, and the balance hexagonal silicon carbide 6H-SiC. The active metals in the surface single-atom modified silicon carbide 6H-SiC are Mn, Co, and Bi, and the mass ratio of Mn, Co, and Bi is 3:1:1. The content of the doped single-atom active metal in the surface of the surface single-atom modified silicon carbide 6H-SiC is 2-3wt%. The graphene content in the surface doped graphene modified silicon carbide 6H-SiC is 0.8-1.2wt%.

[0045] A method for preparing an NTC thermistor material based on silicon carbide comprises the following steps:

[0046] Step 1: Place accurately measured flux-nano zinc oxide, flux-nano yttrium trioxide, toughener-nano zirconium oxide, toughener-nano titanium nitride, tempering agent-nano strontium titanate, and nano rare earth metal carbide in a planetary ball mill, use tungsten carbide grinding beads for wet ball milling, the solid-liquid ratio is 1: (1.0-2.0), and the ball milling speed is 120-200 rpm for 15-30 minutes. After the obtained ball-milled mixture is dried, it is added to another planetary ball mill, and accurately measured silicon carbide is added to the planetary ball mill. Use tungsten carbide grinding beads for dry ball milling, and ball milling is carried out at a ball milling speed of 60-80 rpm for 240-300 seconds to obtain a uniformly mixed NTC ceramic mixture;

[0047] Step 2: Place the NTC ceramic mixture in step 1 into a forming mold for cold isostatic pressing. The molding temperature is 20-50° C. The molding pressure is: first pressurized to 200 MPa at 10-20 MPa / s, held for 30-60 seconds, then pressurized to 300-400 MPa at 5-10 MPa / s, held for 120-180 seconds, then reduced to 200 MPa at 5-10 MPa / s, held for 30-40 seconds, and then reduced to 0 MPa at 20-25 MPa / s. The molding speed is 0.5-2 mm / s. After completing the cold isostatic pressing process, the NTC ceramic preform can be obtained.

[0048] Step 3, the NTC ceramic preform in step 2 is subjected to rapid sintering treatment, heating to 800-850°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 1650-1680°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 2180-2250°C at 100-200°C / min and holding for 2-4h, cooling to 600-650°C at a cooling rate of 40-80°C / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material;

[0049] Preferably, in step three, the NTC ceramic preform in step two is subjected to a rapid sintering treatment, heating to 820° C. at 100° C. / min and holding for 0.5 h, then heating to 1660° C. at 150° C. / min and holding for 1.0 h, then heating to 2240° C. at 200° C. / min and holding for 3 h, then cooling to 640° C. at a cooling rate of 50-60° C. / min, and then naturally cooling to room temperature to obtain a semi-finished NTC thermistor material;

[0050] Step 4: Stress relief treatment is performed on the semi-finished NTC thermistor material obtained in step 3. The temperature is raised to 200-240°C at 20-60°C / min in an inert atmosphere and kept at this temperature for 1-2 hours. The temperature is then raised to 400-420°C at 40-80°C / min and kept at this temperature for 4-8 hours. The finished NTC thermistor material is obtained after the furnace is naturally cooled to room temperature.

[0051] Example 1: A silicon carbide-based NTC thermistor material is made of the following raw materials in percentage by mass: 0.4 wt% of nano zinc oxide (model CW-ZnO-002, particle size 200 nm, Shanghai Chaowei Nanotechnology), 0.06 wt% of nano yttrium trioxide (model HN-Y03, particle size 150-200 nm, monoclinic form, Hangzhou Hengna New Materials Co., Ltd.), 0.94 wt% of nano zirconium dioxide (model CW-ZrO2-002, particle size 50 nm, 3Y tetragonal phase, Shanghai Chaowei Nanotechnology), and 0.4 wt% of nano titanium nitride (model CW-TiN-002, particle size 700 nm, cubic form, Shanghai Chaowei Nanotechnology). , 0.8% of nano-strontium titanate (CAS No. 12060-59-2, Ningbo Luofei Nanotechnology Co., Ltd., LF-SrTi03-N100, average particle size 100nm), 1.8% of MXene multilayer nanosheets of tantalum carbide (niobium carbide (Nb2CTx) MXene multilayer nanosheets, sheet diameter: 1-10μm thickness: 100-300nm, Zhongke Leiming (Beijing) Technology), 1.2% of MAX phase niobium aluminum carbide (MAX phase niobium aluminum carbide Nba4AlC3, average particle size 3μm, Zhongke Leiming (Beijing) Technology), and the remainder is hexagonal silicon carbide 6H-SiC (customized by Xi'an Qiyue Biotechnology Co., Ltd., average particle size 0.5-1μm).

[0052] A method for preparing an NTC thermistor material based on silicon carbide comprises the following steps:

[0053] Step 1: Place accurately measured nano-zinc oxide, nano-yttrium oxide, nano-zirconium oxide, nano-titanium nitride, nano-strontium titanate, MXene multilayer nanosheet tantalum carbide, and MAX phase niobium aluminum carbide in a planetary ball mill and perform wet ball milling with tungsten carbide beads at a solid-liquid ratio of 1:1.5 at a ball milling speed of 120 rpm for 20 minutes. After drying the resulting ball-milled mixture, add it to another planetary ball mill, add accurately measured hexagonal silicon carbide 6H-SiC to the planetary ball mill, and perform dry ball milling with tungsten carbide beads at a ball milling speed of 60 rpm for 300 seconds to obtain a uniformly mixed NTC ceramic mixture.

[0054] Step 2: Place the NTC ceramic mixture in step 1 into a molding mold for cold isostatic pressing. The molding temperature is 20°C, and the molding pressure is: first pressurize to 200 MPa at 20 MPa / s, hold the pressure for 60 seconds, then pressurize to 320 MPa at 10 MPa / s, hold the pressure for 150 seconds, then reduce the pressure to 200 MPa at 5 MPa / s, hold the pressure for 40 seconds, and then reduce the pressure to 0 MPa at 20 MPa / s. The molding speed is 0.5 mm / s. After completing the cold isostatic pressing process, the NTC ceramic preform can be obtained.

[0055] Step 3: The NTC ceramic preform in step 2 is subjected to a rapid sintering treatment, heating to 820°C at 100°C / min and holding for 0.5h, then heating to 1660°C at 150°C / min and holding for 1.0h, then heating to 2240°C at 200°C / min and holding for 3h, then cooling to 640°C at 60°C / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material;

[0056] Step 4: The semi-finished NTC thermistor material obtained in step 3 is subjected to stress relief treatment. The temperature is raised to 220° C. at 25° C. / min in an inert atmosphere and kept at this temperature for 2 hours. The temperature is then raised to 420° C. at 50° C. / min and kept at this temperature for 6 hours. The finished NTC thermistor material is obtained after the furnace is naturally cooled to room temperature.

[0057] The difference between Example 2 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.1wt% of nano zinc oxide, 0.05wt% of nano yttrium trioxide, 0.4wt% of nano zirconium dioxide, 0.1wt% of nano titanium nitride, 0.4% of nano strontium titanate, 0.3% of MXene multilayer nanosheet tantalum carbide, 0.2% of MAX phase niobium aluminum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0058] The difference between Example 3 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.5wt% of nano zinc oxide, 0.2wt% of nano yttrium trioxide, 2wt% of nano zirconium dioxide, 0.5wt% of nano titanium nitride, 2% of nano strontium titanate, 2.4% of MXene multilayer nanosheet tantalum carbide, 1.6% of MAX phase niobium aluminum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0059] The difference between Example 4 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.4wt% of nano zinc oxide, 0.06wt% of nano yttrium trioxide, 0.94wt% of nano zirconium dioxide, 0.4wt% of nano titanium nitride, 0.8% of nano strontium titanate, 3% of MXene multilayer nanosheet tantalum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0060] The difference between Example 5 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.4wt% nano zinc oxide, 0.06wt% nano yttrium trioxide, 0.94wt% nano zirconium dioxide, 0.4wt% nano titanium nitride, 0.8% nano strontium titanate, 3% MAX phase niobium aluminum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0061] The difference between Example 6 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in the following mass percentages: 0.4wt% of nano zinc oxide, 0.06wt% of nano yttrium trioxide, 0.94wt% of nano zirconium dioxide, 0.4wt% of nano titanium nitride, 0.8% of nano strontium titanate, 1.2% of MXene multilayer nanosheet niobium carbide, 0.9% of MXene multilayer nanosheet tantalum carbide, 0.9% of MAX phase tantalum aluminum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0062] The difference between Example 7 and Example 1 is that the hexagonal silicon carbide 6H-SiC is replaced by a silicon carbide composition, and the silicon carbide composition consists of 5wt% of surface single-atom modified silicon carbide 6H-SiC, 20wt% of surface-doped graphene-modified silicon carbide 6H-SiC, 10wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0063] The surface single-atom modified silicon carbide 6H-SiC includes a silicon carbide 6H-SiC carrier and an active metal fixed on the surface of the silicon carbide 6H-SiC carrier in the form of a single atom. The active metals are Mn and Ni, and the mass ratio of Mn to Ni is 3:2.

[0064] The preparation method of surface single-atom modified silicon carbide 6H-SiC is as follows: first, 1 L of a 20 wt% citric acid aqueous solution is prepared, 100 g of silicon carbide 6H-SiC is weighed and immersed in the 20 wt% citric acid aqueous solution for 6 h, and then taken out and dried for use; then, 0.032 mol of manganese dichloride tetrahydrate and 0.02 mol of nickel dichloride hexahydrate are dissolved in 500 mL of deionized water to obtain a metal impregnation solution, 100 g of the silicon carbide 6H-SiC carrier treated with citric acid is immersed in the metal impregnation solution, and ultrasonic dispersion is performed at an ultrasonic frequency of 44 kHz and an ultrasonic power of 1200 W. The mixture was treated for 8 hours, mechanically stirred at 320 rpm for 24 hours, and then the supernatant was removed. The solid material obtained by centrifugation was placed in a 120°C blast drying oven and dried for 12 hours. After the drying was completed, the obtained solid material was placed in a planetary ball mill and ball-milled at 120 rpm for 30 minutes to obtain a solid powder. The obtained solid powder was heated to 540°C at 5°C / min under an argon atmosphere and calcined for 4 hours. The obtained solid material was placed in a planetary ball mill and ball-milled at 80 rpm for 60 minutes to obtain surface single-atom modified silicon carbide 6H-SiC with a particle size of 0.5-1 μm and a doping rate of 2.65 wt%.

[0065] The surface-doped graphene-modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC carrier and graphene sintered on the surface of the silicon carbide 6H-SiC carrier through nano-silver.

[0066] The preparation method of surface-doped graphene-modified silicon carbide 6H-SiC is as follows: 4.4 g of 2-ethyl-4-methylimidazole 2E4MI and 3.35 g of silver acetate AgAc were added to 1 kg of dichloromethane at room temperature, and magnetic stirring was carried out at 200 rpm for 2 h to obtain a clear and transparent Ag(2E4MI)2Ac complex solution. 5 g of graphene (CAS No. 1034343-98-0, thickness 0.55-1.2 nm, diameter 0.5-3 μm, specific surface area 554.36 m 2 / g, brand Zhongke Leiming) and 5g of polyvinyl pyrrolidone were ultrasonically dispersed at an ultrasonic frequency of 44 kHz and an ultrasonic power of 1200 W for 4 hours, and then 50g of silicon carbide 6H-SiC was added, and ultrasonic dispersion was continued for 60 minutes to obtain a dispersion liquid; the dispersion liquid was then subjected to reduced pressure distillation to remove dichloromethane in the Ag(2E4MI)2Ac complex solution to obtain a solid, and the obtained solid was sintered at 215°C for 5 hours to obtain a block solid, and the block solid was subjected to air flow milling to obtain surface-doped graphene-modified silicon carbide 6H-SiC with an average particle size of 1-3 μm and a graphene loading rate of 0.84%.

[0067] The difference between Example 8 and Example 1 is that the hexagonal silicon carbide 6H-SiC is replaced by a silicon carbide composition, and the silicon carbide composition consists of 10wt% of surface single-atom modified silicon carbide 6H-SiC, 20wt% of surface-doped graphene-modified silicon carbide 6H-SiC, 10wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0068] The difference between Example 9 and Example 1 is that the hexagonal silicon carbide 6H-SiC is replaced by a silicon carbide composition, and the silicon carbide composition consists of 20wt% of surface single-atom modified silicon carbide 6H-SiC, 40wt% of surface-doped graphene-modified silicon carbide 6H-SiC, 20wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0069] The difference between Example 10 and Example 1 is that the hexagonal silicon carbide 6H-SiC is replaced by a silicon carbide composition, and the silicon carbide composition consists of 20wt% of surface-doped graphene-modified silicon carbide 6H-SiC, 10wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0070] The difference between Example 11 and Example 1 is that the hexagonal silicon carbide 6H-SiC is replaced by a silicon carbide composition, and the silicon carbide composition consists of 10wt% of surface single-atom modified silicon carbide 6H-SiC, 10wt% of cubic silicon carbide 3C-SiC, and the remainder is hexagonal silicon carbide 6H-SiC.

[0071] The difference between Example 12 and Example 7 is that the surface single-atom modified silicon carbide 6H-SiC includes a silicon carbide 6H-SiC carrier and an active metal fixed on the surface of the silicon carbide 6H-SiC carrier in the form of a single atom, the active metals are Mn, Co, and Bi, and the mass ratio of Mn, Co, and Bi is 3:1:1.

[0072] The preparation method of surface single-atom modified silicon carbide 6H-SiC is as follows: first, prepare 1L of 20wt% citric acid aqueous solution, weigh 200g of silicon carbide 6H-SiC, soak it in the 20wt% citric acid aqueous solution for 6h, take it out and dry it for use; then prepare 0.05mol of manganese dichloride tetrahydrate, 0.0156mol of cobalt dichloride hexahydrate, and 0.0044mol of bismuth nitrate pentahydrate and dissolve them in 500mL of deionized water to obtain a metal impregnation solution, soak 200g of the silicon carbide 6H-SiC carrier treated with citric acid in the metal impregnation solution, and ultrasonically treat it at a frequency of 44kHz and an ultrasonic power of 1. The mixture was ultrasonically dispersed at 200W for 12 hours and mechanically stirred at 320 rpm for 24 hours. The supernatant was then removed and the solid material obtained by centrifugation was placed in a 120°C blast drying oven and dried for 12 hours. After drying, the obtained solid material was placed in a planetary ball mill and ball-milled at 120 rpm for 30 minutes to obtain a solid powder. The obtained solid powder was heated to 540°C at 5°C / min under an argon atmosphere and calcined for 4 hours. The obtained solid material was placed in a planetary ball mill and ball-milled at 80 rpm for 60 minutes to obtain surface single-atom modified silicon carbide 6H-SiC with a particle size of 0.5-1 μm and a doping rate of 2.21 wt%.

[0073] The difference between Comparative Example 1 and Example 7 is that: in step 1, accurately measured nano-zinc oxide, nano-yttrium oxide, nano-zirconium oxide, nano-titanium nitride, nano-strontium titanate, MXene multilayer nanosheet tantalum carbide, MAX phase niobium aluminum carbide, and hexagonal silicon carbide 6H-SiC are placed in a planetary ball mill and wet-milled using tungsten carbide beads. The solid-liquid ratio is 1:15, and the ball milling is carried out at a ball milling speed of 120 rpm for 20 minutes. The uniformly mixed NTC ceramic mixture is then dried.

[0074] The difference between Comparative Example 2 and Example 7 is that: in step 2, the NTC ceramic mixture in step 1 is placed in a molding mold for cold isostatic pressing treatment, the molding temperature is 20°C, the molding pressure is: first pressurized to 320 MPa at 20 MPa / s, maintained at pressure for 240 seconds, and then reduced to 0 MPa at 20 MPa / s, and the molding speed is 0.5 mm / s. After completing the cold isostatic pressing treatment, the NTC ceramic preform can be obtained.

[0075] The difference between Comparative Example 3 and Example 7 is that: in step 3, the NTC ceramic preform in step 2 is subjected to rapid sintering treatment, heating to 2240°C at 200°C / min and holding for 3h, cooling to 640°C at 60°C / min, and then naturally cooling to room temperature to obtain a semi-finished NTC thermistor material.

[0076] The difference between Comparative Example 4 and Example 7 is that the preparation method of the NTC thermistor material based on silicon carbide is as follows:

[0077] Step 1: Place accurately measured nano-zinc oxide, nano-yttrium oxide, nano-zirconium oxide, nano-titanium nitride, nano-strontium titanate, MXene multilayer nanosheet tantalum carbide, and MAX phase niobium aluminum carbide in a planetary ball mill and perform wet ball milling with tungsten carbide grinding beads at a solid-liquid ratio of 1:15 at a ball milling speed of 120 rpm for 20 minutes. After drying the resulting ball-milled mixture, add it to another planetary ball mill, add accurately measured hexagonal silicon carbide 6H-SiC to the planetary ball mill, and perform dry ball milling with tungsten carbide grinding beads at a ball milling speed of 60 rpm for 300 seconds to obtain a uniformly mixed NTC ceramic mixture.

[0078] Step 2: Place the NTC ceramic mixture in step 1 into a molding mold for cold isostatic pressing. The molding temperature is 20°C, and the molding pressure is: first pressurize to 200 MPa at 20 MPa / s, hold the pressure for 60 seconds, then pressurize to 320 MPa at 10 MPa / s, hold the pressure for 150 seconds, then reduce the pressure to 200 MPa at 5 MPa / s, hold the pressure for 40 seconds, and then reduce the pressure to 0 MPa at 20 MPa / s. The molding speed is 0.5 mm / s. After completing the cold isostatic pressing process, the NTC ceramic preform can be obtained.

[0079] Step 3: The NTC ceramic preform in step 2 is subjected to rapid sintering treatment, heating to 820°C at 100°C / min and holding for 0.5h, then heating to 1660°C at 150°C / min and holding for 1.0h, then heating to 2240°C at 200°C / min and holding for 3h, then cooling to 640°C at 60°C / min, and naturally cooling to room temperature to obtain the finished NTC thermistor material.

[0080] The difference between Comparative Example 5 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in mass percentage: 0.4wt% of nano zinc oxide, 0.06wt% of nano yttrium trioxide, 0.94wt% of nano zirconium dioxide, 0.4wt% of nano titanium nitride, 0.8% of nano strontium titanate, and the remainder is hexagonal silicon carbide 6H-SiC.

[0081] The difference between Comparative Example 6 and Example 1 is that a silicon carbide-based NTC thermistor material is made of the following raw materials in percentage by mass: 0.4wt% of nano zinc oxide, 0.06wt% of nano yttrium trioxide, 0.94wt% of nano zirconium dioxide, 0.4wt% of nano titanium nitride, 1.8% of MXene multilayer nanosheet tantalum carbide, 1.2% of MAX phase niobium aluminum carbide, and the remainder is hexagonal silicon carbide 6H-SiC.

[0082] Performance test: NTC thermistor discs with a diameter of 10 mm and a thickness of 2 mm were prepared using the formula and process in Examples 1-12 and Comparative Examples 1-6. After coating silver paste electrodes at both ends, the discs were placed in a muffle furnace at 750°C for 30 minutes to obtain the NTC thermistors to be tested. The prepared NTC thermistors to be tested were heated in a muffle furnace at 85°C, 250°C, and 400°C. The electrical properties were tested using a Keithley 2600B multi-channel test system in the United States, and the B 25 / 85 、B 85 / 250 、B 250 / 400 . B value (thermal constant) calculation formula: B T1 / T2 =[(T1*T2) / (T2-T1)]*ln(R T1 / R T2 ), where T1 and T2 are both Kelvin temperatures, T1 is the starting test temperature, T2 is the terminal test temperature, R T1 is the resistance at the starting test temperature, R T2 is the resistance of the terminal at the test temperature.

[0083] High and low temperature impact resistance test: The NTC thermistor to be tested is heated from 25℃ to 400℃ for 1500 cycles. 0次 / 25℃ 、R 0次 / 400℃ 、R 1500次 / 25℃ 、R 1500次 / 400℃ , R 0次 / 25℃ The initial resistance tested at 25°C, R 0次 / 400℃ is the test resistance at the initial temperature rise of 400°C, R 1500次 / 25℃ is the resistance tested at 25°C after 1500 cycles, R 1500次 / 400℃ Calculate ΔR for the resistance measured at 400°C after 1500 cycles 25℃ (absolute value) = |(R 0次 / 25℃ -R 1500次 / 25℃ ) / R 0次 / 25℃| , ΔR 25℃ is the resistance change rate at 25°C after 1500 cycles; ΔR 400℃ (absolute value) = |(R 0次 / 400℃ -R 1500次 / 400℃ ) / R 0次 / 25℃|,ΔR 400℃ It is the resistance change rate at 400°C after 1500 cycles.

[0084] Table 1: Test parameters of NTC thermistor materials in Examples 1-12 and Comparative Examples 1-6

[0085]

[0086]

[0087] In combination with Example 7 and Comparative Example 1 and Table 1, it can be seen that in step 1, the accurately measured flux-nano zinc oxide, flux-nano yttrium trioxide, toughener-nano zirconium oxide, toughener-nano titanium nitride, tempering agent-nano strontium titanate, and nano rare earth metal carbide are placed in a planetary ball mill, and wet ball milling is performed using tungsten carbide grinding beads. The solid-liquid ratio is 1: (1.0-2.0), and the ball milling speed is 120-200 rpm for 15-30 min. The resulting ball-milled mixture is dried and added to another planetary ball mill. Accurately measured silicon carbide is added to the planetary ball mill, and dry ball milling is performed using tungsten carbide grinding beads. The ball milling speed is 60-80 rpm for 240-300 s to obtain a uniformly mixed NTC ceramic mixture, which can maintain the morphological characteristics of the silicon carbide combination to a large extent, thereby effectively improving the comprehensive performance of the NTC thermistor material.

[0088] Combining Example 7 and Comparative Example 2 with Table 1, it can be seen that the cold isostatic pressing method provided in step 2 can improve the comprehensive performance of the NTC thermistor material compared with the conventional cold isostatic pressing method.

[0089] It can be seen from Example 7 and Comparative Example 3 and Table 1 that the rapid sintering method provided by the present invention can improve the comprehensive performance of the NTC thermistor material compared with the conventional sintering molding method.

[0090] It can be seen from Example 7 and Comparative Example 4 and Table 1 that the stress relief treatment method in step 4 can effectively eliminate stress, thereby improving the comprehensive performance of the NTC thermistor material.

[0091] Combining Example 1 and Comparative Examples 5-6 with Table 1, it can be seen that the addition of nano-strontium titanate and nano-rare earth metal carbide can improve the mechanical strength, thermal conductivity and high and low temperature impact resistance of the NTC thermistor material.

[0092] Combining Examples 1-12 and Comparative Examples 1-6 with Table 1, it can be seen that the NTC thermistor material of the present invention has excellent high temperature resistance and high and low temperature impact resistance. After 1500 cycles of high and low temperature impact, the resistance deviation is less than 0.5%, which can meet the use requirements of modules such as highly integrated circuits and IGBTs.

[0093] It can be seen from Examples 1-12 and Comparative Examples 1-4 in conjunction with Table 1 that the preparation method provided in the present invention is simple to operate and is easy to implement in industrial production, thereby helping to reduce the production cost of NTC thermistor materials, thereby lowering the market threshold for them to enter the market for highly integrated circuits, IGBTs and other modules, and facilitating the rapid entry of the above-mentioned NTC thermistor materials into the supply chain market for highly integrated circuits, IGBTs and other modules.

[0094] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. An NTC thermistor material based on silicon carbide, characterized by: The silicon carbide-based NTC thermistor material is made of the following raw materials in percentage by mass: 0.1-0.5wt% of fluxing agent - nano zinc oxide, 0.05-0.2wt% of fluxing agent - nano yttrium trioxide, 0.4-2.0wt% of toughening agent - nano zirconium oxide, 0.1-0.5wt% of toughening agent - nano titanium nitride, 0.4-2.0% of tempering agent - nano strontium titanate, 0.5-4.0% of nano rare earth metal carbide, and the balance is silicon carbide; the nano rare earth metal carbide is at least one of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, MAX phase niobium aluminum carbide, and MAX phase tantalum aluminum carbide.

2. The silicon carbide-based NTC thermistor material according to claim 1, characterized in that: The silicon carbide-based NTC thermistor material is made of the following raw materials in percentage by mass: 0.3-0.4wt% of a fluxing agent - nano zinc oxide, 0.05-0.10wt% of a fluxing agent - nano yttrium trioxide, 0.8-1.0wt% of a toughening agent - nano zirconium oxide, 0.2-0.4wt% of a toughening agent - nano titanium nitride, 0.6-1.0% of a tempering agent - nano strontium titanate, 2.4-3.2% of nano rare earth metal carbide, and the balance is silicon carbide.

3. The silicon carbide-based NTC thermistor material according to claim 1 or 2, characterized in that: The nano rare earth metal carbide is composed of at least one of MXene multilayer nanosheet niobium carbide and MXene multilayer nanosheet tantalum carbide, and at least one of MAX phase niobium aluminum carbide and MAX phase tantalum aluminum carbide.

4. The silicon carbide-based NTC thermistor material according to claim 3, characterized in that: The nano rare earth metal carbide is composed of MXene multilayer nanosheet tantalum carbide and MAX phase niobium aluminum carbide in a mass ratio of 3:

2.

5. The silicon carbide-based NTC thermistor material according to claim 3, characterized in that: The nano rare earth metal carbide is composed of MXene multilayer nanosheet niobium carbide, MXene multilayer nanosheet tantalum carbide, and MAX phase tantalum aluminum carbide in a mass ratio of 4:3:

3.

6. The silicon carbide-based NTC thermistor material according to claim 1, characterized in that: The silicon carbide is composed of 5-20 wt% of surface single-atom modified silicon carbide 6H-SiC, 5-40 wt% of surface doped graphene modified silicon carbide 6H-SiC, 5-20 wt% of cubic silicon carbide 3C-SiC, and the balance of hexagonal silicon carbide 6H-SiC; the surface single-atom modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC carrier and an active metal fixed on the surface of the silicon carbide 6H-SiC carrier in the form of a single atom, wherein the active metal The metal element is at least one of Mn, Co, Ni, Cu, Zn, and Bi; the content of the single-atom active metal doped on the surface of the surface single-atom modified silicon carbide 6H-SiC is 0.5-5wt%; the surface doped graphene-modified silicon carbide 6H-SiC comprises a silicon carbide 6H-SiC carrier and graphene sintered on the surface of the silicon carbide 6H-SiC carrier by nanosilver, and the graphene content in the surface doped graphene-modified silicon carbide 6H-SiC is 0.2-2wt%.

7. The silicon carbide-based NTC thermistor material according to claim 6, characterized in that: The silicon carbide consists of 10-12 wt% of surface single-atom modified silicon carbide 6H-SiC, 20-24 wt% of surface doped graphene modified silicon carbide 6H-SiC, 5-10 wt% of cubic silicon carbide 3C-SiC, and the remainder of hexagonal silicon carbide 6H-SiC.

8. The silicon carbide-based NTC thermistor material according to claim 6 or 7, characterized in that: The active metals in the surface single-atom modified silicon carbide 6H-SiC are Mn, Co, and Bi, and the mass ratio of Mn, Co, and Bi is 3:1:1; the content of the single-atom active metal doped on the surface of the surface single-atom modified silicon carbide 6H-SiC is 2-3wt%; the content of graphene in the surface doped graphene modified silicon carbide 6H-SiC is 0.8-1.2wt%.

9. A method for preparing a silicon carbide-based NTC thermistor material according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Place accurately measured flux-nano zinc oxide, flux-nano yttrium trioxide, toughener-nano zirconium oxide, toughener-nano titanium nitride, tempering agent-nano strontium titanate, and nano rare earth metal carbide in a planetary ball mill, use tungsten carbide grinding beads for wet ball milling, the solid-liquid ratio is 1: (1.0-2.0), and the ball milling speed is 120-200 rpm for 15-30 minutes. After the obtained ball-milled mixture is dried, it is added to another planetary ball mill, and accurately measured silicon carbide is added to the planetary ball mill. Use tungsten carbide grinding beads for dry ball milling, and ball milling is carried out at a ball milling speed of 60-80 rpm for 240-300 seconds to obtain a uniformly mixed NTC ceramic mixture; Step 2: Place the NTC ceramic mixture in step 1 into a forming mold for cold isostatic pressing. The molding temperature is 20-50° C. The molding pressure is: first pressurized to 200 MPa at 10-20 MPa / s, held for 30-60 seconds, then pressurized to 300-400 MPa at 5-10 MPa / s, held for 120-180 seconds, then reduced to 200 MPa at 5-10 MPa / s, held for 30-40 seconds, and then reduced to 0 MPa at 20-25 MPa / s. The molding speed is 0.5-2 mm / s. After completing the cold isostatic pressing process, the NTC ceramic preform can be obtained. Step 3, the NTC ceramic preform in step 2 is subjected to rapid sintering treatment, heating to 800-850°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 1650-1680°C at 100-200°C / min and holding for 0.5-1.0h, then heating to 2180-2250°C at 100-200°C / min and holding for 2-4h, cooling to 600-650°C at a cooling rate of 40-80°C / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material; Step 4: Stress relief treatment is performed on the semi-finished NTC thermistor material obtained in step 3. The temperature is raised to 200-240°C at 20-60°C / min in an inert atmosphere and kept at this temperature for 1-2 hours. The temperature is then raised to 400-420°C at 40-80°C / min and kept at this temperature for 4-8 hours. The finished NTC thermistor material is obtained after the furnace is naturally cooled to room temperature.

10. The method for preparing a silicon carbide-based NTC thermistor material according to claim 9, characterized in that: In the step three, the NTC ceramic preform in the step two is subjected to a rapid sintering treatment, heating to 820° C. at 100° C. / min and holding for 0.5 h, then heating to 1660° C. at 150° C. / min and holding for 1.0 h, then heating to 2240° C. at 200° C. / min and holding for 3 h, cooling to 640° C. at a cooling rate of 50-60° C. / min, and naturally cooling to room temperature to obtain a semi-finished NTC thermistor material.

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