Preparation Method of Negative Temperature Coefficient Thermistor Material for Measuring Temperature of New Energy Vehicle Engine

Abstract

The invention discloses a preparation method of a negative temperature coefficient thermistor material for measuring the temperature of a new energy vehicle engine. The method uses raw materials such as calcium carbonate, cerium oxide, niobium pentoxide, and manganese dioxide as raw materials through processes of mixing and grinding, calcination, re-grinding, cold isostatic pressing, high-temperature sintering, and electrode coating processes to obtain a CaCeNbMnO7 composite thermistor material with a special structure, which has Ca2Nb2O7 as the main phase and a network conductive channel formed by the connection of structures such as cerium oxide and manganese oxide. The composite thermistor of the invention has the advantages of strong thermal cycle stability, high linearity, and large B value. The prepared CaCeNbMnO7 ceramic disc-shaped high-density ceramic material has good density, and the aging drift rate after aging at 500 °C for 400 h is less than 2%. It has excellent negative temperature coefficient characteristics and is suitable for use as a temperature sensing element for monitoring the temperature of a new energy vehicle engine.

Description

Technical Field

[0001] The present invention relates to a preparation method of a negative temperature coefficient thermistor material for measuring the temperature of a new energy vehicle engine. Technical Background

[0002] With the transformation of the global energy structure and the improvement of environmental awareness, the development of new energy vehicles has attracted increasing attention. New energy vehicles have advantages such as energy conservation, emission reduction, and environmental protection, and their development is of great significance for promoting the sustainable development of the global automotive industry. However, in the actual use process, the overheating problem of the new energy vehicle engine is a key issue restricting its performance and lifespan. The overheating problem of the new energy vehicle engine mainly stems from two aspects: on the one hand, it is the internal thermodynamic process of the engine, including combustion, work, and heat dissipation, etc.; on the other hand, it is external factors, including the design of the cooling system, ventilation conditions, and the usage environment, etc. The overheating problem will lead to problems such as a decline in engine performance, accelerated wear, and reduced reliability, and may even cause safety accidents in severe cases.

[0003] A temperature sensor is a detection device that can convert temperature information into an electrical signal or a digital signal for further processing and control. In new energy vehicles, temperature sensors are mainly used to monitor the temperatures of key components such as batteries, motors, electronic controls, and engine casings to ensure their normal operation and prevent overheating. In recent years, with the intelligence, electronization, miniaturization, and lightening of automobiles, the requirements for temperature sensors in new energy vehicles have become increasingly strict. In addition to size requirements such as miniaturization and integration, temperature sensors are also required to have characteristics such as strong anti-interference ability, resistance to harsh environments, strong adaptability, high stability, and high reliability.

[0004] To solve the above problems, researchers mainly use negative temperature coefficient thermosensitive materials as the sensitive body in temperature sensors to ensure the rapid and accurate identification of potential safety hazards of new energy vehicle engines. For the CaCeNbMnO7 composite thermistor material, its structure is mainly composed of Ca2Nb2O7, and cerium oxide and manganese oxide and other structures are interconnected to form a network conductive channel. The CaCeNbMnO7 composite thermistor material with a special structure has a higher density, a smaller aging drift rate, and a relatively higher B value than general single-phase NTC thermistor ceramic resistors. It not only ensures the accuracy, durability, and stability of temperature monitoring in complex and harsh environments but also well solves the timely and rapid monitoring of the temperature of the new energy vehicle engine casing, and can reduce many property losses and safety problems caused by the overheating of the new energy vehicle engine casing. This CaCeNbMnO7 composite thermistor material is expected to be applied to the temperature monitoring of new energy vehicle engines. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method of a negative temperature coefficient thermistor material for measuring the temperature of a new energy vehicle engine, aiming at the problems of accuracy, durability and stability of temperature monitoring of the new energy vehicle engine in a complex environment. The method uses raw materials calcium carbonate, cerium oxide, niobium pentoxide and manganese dioxide as raw materials, and through processes such as mixing and grinding, calcination, re-grinding, cold isostatic pressing, high-temperature sintering process, and electrode process, a CaCeNbMnO7 composite thermistor material with a special structure is obtained, which has Ca2Nb2O7 as the main phase and a network conductive channel formed by the connection of structures such as cerium oxide and manganese oxide. The composite thermistor of the present invention has the advantages of strong thermal cycle stability, high linearity and large B value. The prepared CaCeNbMnO7 disc-shaped high-density ceramic material has good density, and the aging drift rate after aging at 500 °C for 400 h is less than 2%, and it has excellent negative temperature coefficient characteristics, and is suitable as a temperature sensing element for monitoring the temperature of a new energy vehicle engine.

[0006] A preparation method of a negative temperature coefficient thermistor material for measuring the temperature of a new energy vehicle engine according to the present invention, the method uses raw materials calcium carbonate, cerium oxide, niobium pentoxide and manganese dioxide as raw materials, and through processes such as mixing and grinding, calcination, re-grinding, cold isostatic pressing, high-temperature sintering process, etc., a relatively dense CaCeNbMnO7 ceramic blank is prepared. The specific operation is carried out according to the following steps:

[0007] a. According to the molar ratio of CaCeNbMnO7, respectively weigh the raw materials calcium carbonate, cerium oxide, niobium pentoxide and manganese dioxide. Place the raw materials in a beaker containing absolute ethanol according to the ratio of raw materials:absolute ethanol = 1 g:3 mL and stir for 30 min. Keep warm at 80 °C and 120 °C for 12 h successively, then place in a ball mill for mixing and grinding for 6-8 h, then calcine at 1200 °C for 2-4 h, and grind again for 6 h to obtain dispersed CaCeNbMnO7 powder;

[0008] b. Mold the powder obtained in step a with a mold with a diameter of 10 mm, apply a pressure of 20 MPa, and keep the pressure for 15 s to obtain a CaCeNbMnO7 ceramic green body material;

[0009] c. Vacuum package the ceramic green body obtained in step b and perform cold isostatic pressing at 200-300 MPa for 1-3 min, then keep warm at a temperature of 1100-1300 °C for 4-8 h, and cool to room temperature to obtain a disc-shaped high-density CaCeNbMnO7 composite ceramic material.

[0010] d. Place the disc-shaped high-density ceramic obtained in step c in a high-temperature box furnace for sensitization treatment for 50 h, and age it at 500 °C for 400 h. Then, polish both sides of the sheet with 1500-mesh fine sandpaper for 1 min each, ultrasonically clean it with alcohol for 30 min, coat platinum paste electrodes on both the front and back sides, and then anneal it continuously at 900 °C for 1 h to obtain a CaCeNbMnO7 composite thermistor material applicable to measuring the temperature of the engine housing of new energy vehicles with a temperature range of 25 - 525 °C and a material constant B 25℃ / 525℃ = 3652 K - 4865 K.

[0011] The CaCeNbMnO7 composite thermistor material obtained by the method of the present invention has a layered perovskite structure as the main phase, and cerium oxide and manganese oxide and other structures are interconnected to form a network conductive channel. It has relatively good high-temperature stability and good NTC performance at the same time, and can be used as a temperature sensing element for monitoring the temperature of the engine housing of new energy vehicles. Compared with the prior art: The process of preparing the CaCeNbMnO7 composite thermistor material in the present invention has unique features:

[0012] The present invention realizes for the first time a high-density high-temperature NTC thermistor that can be applied in the medium-high temperature wide temperature range of 25 - 525 °C and used for a long time;

[0013] The preparation method of the present invention solves the problems of low sensitivity, low temperature resistance, and narrow measurement temperature range of the temperature sensing element of new energy vehicles in high-temperature environments such as complex ambient temperature monitoring, and provides technical support for the stable application of medium-high temperature thermistors in complex and special environments;

[0014] The CaCeNbMnO7 composite thermistor material prepared by the method of the present invention has a good linear relationship between Ln(ρ) and 1000 / T at a temperature of 25 - 525 °C, and the Pearson coefficient can reach 0.999; the aging drift rate after aging at 500 °C for 400 h is less than 2%. Description of the Drawings

[0015] Figure 1 XRD spectrum of the CaCeNbMnO7 composite thermistor material prepared by the present invention;

[0016] Figure 2 Resistance-temperature characteristic curve of the CaCeNbMnO7 composite thermistor material prepared by the present invention; Detailed Description of the Invention

[0017] Example 1

[0018] a. Weigh 2.043 g of calcium carbonate, 3.478 g of cerium oxide, 2.686 g of niobium pentoxide, and 1.793 g of manganese dioxide respectively as raw materials according to the molar ratio of CaCeNbMnO7. Place the raw materials in a beaker containing alcohol according to the ratio of raw materials: absolute ethanol = 1 g: 3 mL and stir for 30 min. Keep warm at 80 °C and 120 °C for 12 hours successively, then place them in a ball mill for mixing and grinding for 6 h, then calcine at 1200 °C for 4 h, and grind again for 6 h to obtain 10 g of dispersed CaCeNbMnO7 powder;

[0019] b. Mold the powder obtained in step a with a mold of 10 mm in diameter, apply a pressure of 20 MPa, and keep the pressure for 15 s to obtain a CaCeNbMnO7 ceramic green body material;

[0020] c. Vacuum package the ceramic green body material obtained in step b and perform cold isostatic pressing at 200 MPa for 1 min, then keep warm at 1100 °C for 4 h, and cool to room temperature to obtain a disc-shaped CaCeNbMnO7 composite ceramic block material;

[0021] d. Place the disc-shaped high-density ceramic obtained in step c in a high-temperature box furnace for sensitization treatment for 50 h, and perform aging treatment at 500 °C for 400 h. Then polish both sides of the sheet with 1500-mesh fine sandpaper for 1 min respectively, then ultrasonically clean with alcohol for 30 min, coat platinum paste electrodes on both the front and back sides, and then continuously anneal at 900 °C for 1 hour, that is, obtain a CaCeNbMnO7 composite thermistor material applicable to measuring the temperature of the engine housing of new energy vehicles with a temperature range of 25 - 525 °C and a material constant B 25℃ / 525℃ = 3652 K.

[0022] After aging at 500 °C for 400 h, the absolute value of the resistance deviation is greater than 1.93%.

[0023] Example 2

[0024] a. Weigh 2.043 g of calcium carbonate, 3.478 g of cerium oxide, 2.686 g of niobium pentoxide, and 1.793 g of manganese dioxide respectively as raw materials according to the molar ratio of CaCeNbMnO7. Place the raw materials in a beaker containing alcohol according to the ratio of raw materials: absolute ethanol = 1 g: 3 mL and stir for 30 min. Keep warm at 80 °C and 120 °C for 12 hours successively, then place them in a ball mill for mixing and grinding for 6 h, then calcine at 1200 °C for 2 h, and grind again for 8 h to obtain 10 g of dispersed CaCeNbMnO7 powder;

[0025] b. Mold the powder obtained in step a with a mold of 10 mm in diameter, apply a pressure of 20 MPa, and keep the pressure for 15 s to obtain a CaCeNbMnO7 ceramic green body material;

[0026] c. Vacuum package the green ceramic material obtained in step b, then perform cold isostatic pressing at a pressure of 300 MPa for 3 min, and then keep it at a temperature of 1200 °C for 8 h. After cooling to room temperature, a disk-shaped CaCeNbMnO7 composite ceramic bulk material is obtained;

[0027] d. Place the disk-shaped high-density ceramic obtained in step c in a high-temperature box furnace for sensitization treatment for 50 h, and age it at a temperature of 500 °C for 400 h. Then, polish both sides of the sheet with 1500-mesh fine sandpaper for 1 min respectively, and then ultrasonically clean it with alcohol for 30 min. Coat platinum paste electrodes on both the front and back sides, and then continuously anneal it at a temperature of 900 °C for 1 h, thus obtaining a CaCeNbMnO7 composite thermistor material applicable to measuring the temperature of the engine housing of new energy vehicles with a temperature range of 25 - 525 °C and a material constant B 25℃ / 525℃ = 4865 K.

[0028] After aging at 500 °C for 400 h, the absolute value of the resistance deviation is less than 1.82%.

[0029] Example 3

[0030] a. Weigh 2.043 g of calcium carbonate, 3.478 g of cerium oxide, 2.686 g of niobium pentoxide, and 1.793 g of manganese dioxide respectively as raw materials according to the molar ratio of CaCeNbMnO7. Place the raw materials in a beaker containing alcohol according to the ratio of raw materials: absolute ethanol = 1 g: 3 mL and stir for 30 min. Keep it at 80 °C and 120 °C for 12 h successively, then place it in a ball mill for mixing and grinding for 6 h, and then calcine it at 1200 °C for 3 h and grind it again for 8 h to obtain 10 g of dispersed CaCeNbMnO7 powder;

[0031] b. Mold the powder obtained in step a with a mold of 10 mm in diameter, apply a pressure of 20 MPa, and keep the pressure for 15 s to obtain a CaCeNbMnO7 green ceramic body material;

[0032] c. Vacuum package the green ceramic material obtained in step b, then perform cold isostatic pressing at a pressure of 300 MPa for 2 min, and then keep it at a temperature of 1300 °C for 4 h. After cooling to room temperature, a disk-shaped CaCeNbMnO7 composite ceramic bulk material is obtained;

[0033] d. Place the circular high-density ceramic obtained in step c in a high-temperature box furnace for sensitization treatment for 50 h, and then age it at a temperature of 500 °C for 400 h. Then, polish both sides of the sheet with 1500-mesh fine sandpaper for 1 min each, and then ultrasonically clean it with alcohol for 30 min. Coat platinum paste electrodes on both the front and back sides, and then continuously anneal it at a temperature of 900 °C for 1 hour, thus obtaining a CaCeNbMnO7 composite thermistor material applicable to measuring the temperature of the engine housing of new energy vehicles with a temperature range of 25 - 525 °C and a material constant of B 25℃ / 525℃ = 4023 K.

[0034] After aging at a temperature of 500 °C for 400 h, the absolute value of the resistance deviation is less than 1.85%.

[0035] The above is only the specific implementation manner of the present invention, but the design concept of the present invention is not limited thereto.

Claims

1. A preparation method of a negative temperature coefficient thermistor material for measuring the temperature of a new energy vehicle engine, characterized in that: Using calcium carbonate, cerium oxide, niobium pentoxide and manganese dioxide as raw materials, with the layered perovskite structure Ca2Nb2O7 as the main phase, and the cerium oxide and manganese oxide structures connected to each other to form a network conductive channel, the specific operation is carried out according to the following steps: a. Weigh the raw materials calcium carbonate, cerium oxide, niobium pentoxide and manganese dioxide respectively according to the molar ratio of CaCeNbMnO7. Place each raw material in a beaker containing absolute ethanol and stir for 30 min. Keep warm at 80 °C and 120 °C for 12 h successively, place it in a ball mill for mixing and grinding for 6 - 8 h, then calcine at 1200 °C for 2 - 4 h, and grind again for 6 h to obtain dispersed CaCeNbMnO7 powder, where the raw material: absolute ethanol = 1 g: 3 mL; b. Mold the powder obtained in step a with a mold of 10 mm in diameter, apply a pressure of 20 MPa, and keep the pressure for 15 s to obtain a CaCeNbMnO7 ceramic green body material; c. Vacuum package the ceramic green body obtained in step b and perform cold isostatic pressing at 200 - 300 MPa for 1 - 3 min, then keep warm at a temperature of 1100 - 1300 °C for 4 - 8 h, and cool to room temperature to obtain a disc-shaped high-density CaCeNbMnO7 composite ceramic material; d. Place the disc-shaped high-density composite ceramic material obtained in step c in a high-temperature box furnace for sensitization treatment for 50 h, and carry out aging treatment at a temperature of 500 °C for 400 h. Then, polish both sides of the disc body with fine sandpaper of 1500 mesh for 1 min respectively, ultrasonically clean with alcohol for 30 min, coat platinum paste electrodes on both the front and back sides, and continuously anneal at a temperature of 900 °C for 1 h, thus obtaining a CaCeNbMnO7 composite thermistor material applicable to measuring the temperature of the engine housing of new energy vehicles with a temperature range of 25 - 525 °C and a material constant of B 25℃ / 525℃ = 3652 K - 4865 K.

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