Nanometer material piezoresistor and preparation method thereof

Abstract

The invention discloses a nano-material piezoresistor and a preparation method thereof, and belongs to the technical field of piezoresistors, the preparation method of the nano-material piezoresistor comprises the following steps: S1, preparing raw materials for preparing the piezoresistor by mole percent: 94 to 96 percent of ZnO, 1.0 to 1.5 percent of Bi2O3, 0.5 to 1.5 percent of Co3O4, 0.3 to 0.8 percent of Mn2O3, 1.0 to 3.0 percent of Sb2O3 and 0.3 to 0.8 percent of NiO; s2, additives except ZnO are mixed, deionized water and a dispersing agent are added to prepare additive slurry, the additive slurry is dried and smashed after being sanded, and additive powder is obtained; s3, mixing ZnO with the additive powder, adding deionized water, a dispersing agent and a binder, and performing ball milling and refining in a ball mill to obtain total slurry; and S4, carrying out spray granulation, water-containing aging and dry-pressing molding on the total slurry, carrying out glue removal treatment on a green body subjected to dry-pressing molding, then carrying out high-temperature sintering, grinding and flattening, then carrying out heat treatment, coating silver electrodes on the upper and lower end surfaces, and coating insulating glaze on the side surfaces to obtain the piezoresistor. Wherein the dispersing agent improves the dispersity of the nano-powder, and the nano-powder has application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of varistors, and specifically to a nano-material varistor and a preparation method thereof. Background Art

[0002] Metal oxide surge arresters are important electrical appliances for overvoltage protection of power transmission and transformation equipment. Metal oxide surge arresters based on ZnO varistors have the advantages of fast response speed, flat volt-ampere characteristics, large current-carrying capacity, and low residual voltage, and are widely used in transient overvoltage protection, contact arc extinguishing, and voltage stabilization of AC / DC power systems at various voltage levels to achieve the protection of power transmission and transformation equipment against lightning and switching overvoltages. The ZnO varistors mainly used in metal oxide surge arresters are functional ceramic materials mainly composed of ZnO powder doped with various metal oxides, sintered to have advantages such as a high non-linear coefficient and strong transient energy absorption capacity. Under the action of a low electric field, the conductivity of the ZnO varistor is very low and can be considered in an insulating state; while under the action of a high electric field, the conductivity will increase sharply, and the ZnO varistor is in a conducting state, and through parallel connection, the protected equipment can be avoided from being impacted by high voltage division, realizing the effective modulation of the uneven distribution of the space electric field. For high-voltage power systems, their insulation level directly depends on the protection level of the surge arrester, and the performance of the ZnO varistor is the key factor affecting the protection level of the surge arrester. However, at present, the methods such as changing the doping formula and adjusting the sintering process commonly used in conventional preparation have very limited effects on the performance optimization of ZnO varistors, and it is difficult to achieve a substantial improvement and effective regulation of the comprehensive performance. There is an urgent need to achieve a breakthrough in the performance optimization of ZnO varistors through new technical means. Nano-additive oxide powders can increase the powder activity and improve the electrical properties of the finished product. However, due to its excessive surface activity, it is extremely easy to agglomerate, thus affecting the performance of the finished product. In the preparation process of ZnO, the performance of the total slurry will affect the performance of the ZnO varistor. The varistor prepared from the total slurry with good dispersibility has fewer defects, a uniform microstructure, and good electrical properties. Appropriate dosages of dispersants and pH values can enable the dispersants to be saturatedly adsorbed and evenly distributed on the surface of the powder, thereby improving the surface properties of the powder. The commonly used ammonium polyacrylate dispersant is an anionic dispersant. Studies have shown that the ammonium polyacrylate dispersant has the best electrostatic repulsion and dispersion effects at a pH value of 9-10. When the pH is 6, the viscosity of the total slurry is very large and loses fluidity, and it cannot be used to prepare non-linear resistors. When the pH value > 10, the possibility of agglomeration between ammonium polyacrylates increases, and at this time, only a small amount of dispersant is adsorbed on the particle surface, which will also affect the dispersion effect. The pH value of conventional zinc oxide slurries is generally about 8.6, and sometimes it is necessary to manually correct the pH value, which increases the uncontrollable factors in industrial production and brings inconvenience to industrial production. Summary of the Invention

[0003] In order to overcome the deficiencies of the above-mentioned existing technologies, the present invention provides a nanomaterial varistor and a preparation method thereof. By adding a dispersant obtained by copolymerizing an anionic monomer and a non-ionic monomer, the dispersion effect of metal oxides is improved without additionally adjusting the pH value, thereby obtaining a varistor with better electrical properties.

[0004] The technical solution for achieving the purpose of the present invention is as follows:

[0005] A preparation method of a nanomaterial varistor includes the following steps:

[0006] S1. Prepare the raw materials for the varistor in terms of molar percentage: 94-96% ZnO, Bi 2 O 3 1.0-1.5%, Co 3 O 4 0.5-1.5%, Mn 2 O 3 0.3-0.8%, Sb 2 O 3 1.0-3.0%, NiO 0.3-0.8%;

[0007] S2. Mix the additives except ZnO, add deionized water and a dispersant to form an additive slurry, grind it with sand and then dry and crush it to obtain an additive powder;

[0008] S3. Mix ZnO and the additive powder, add deionized water, a dispersant and a binder, and grind and refine them in a ball mill to obtain a total slurry;

[0009] The dispersant is copolymerized from monomer 1, monomer 2, monomer 3 and monomer 4, and the structural general formula is shown in formula 1:

[0010]

[0011] S4. Perform spray granulation, water-containing aging and dry pressing on the total slurry. Bake the dry-pressed green body at 400-500 °C for 1-4 h for debinding treatment, then perform high-temperature sintering, grind and level it and then perform heat treatment, keep it at 400-600 °C for 120-240 min, coat insulating glaze on the side and cure it to obtain a varistor.

[0012] Preferably, the high-temperature sintering temperature is 1000-1200 °C.

[0013] Preferably, in step S1, the solid content of the additive slurry is 20-50%, the addition amount of the dispersant is 0.1-1 wt% of the additive, more preferably 0.2-0.8 wt%, and grind the mixed slurry to a particle size of 400-600 nm.

[0014] Preferably, in step S2, the dosage of the dispersant is 0.1-1 wt% of the total mass of the powder material, more preferably 0.2-0.8 wt%, the dosage of the binder is 0.5-1% of the total mass of the powder material, and the ball milling time is 20-24 hours.

[0015] Preferably, in formula 1, R 1 , R 2 , R 3 , R 4 are each independently selected from one of H and CH 3 , R 5 is a carbon chain with a carbon atom length of 4-18, and the molar ratio a:b:c:d of monomer 1, monomer 2, monomer 3 and monomer 4 is (30-60):(20-30):(10-25):(10-15), and m is a natural number between 4 and 10.

[0016] Preferably, monomer 1 of the dispersant is one of acrylic acid or methacrylic acid, and monomer 3 is one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate or hydroxypropyl methacrylate; monomer 4 is N-vinylpyrrolidone; the preparation method of monomer 2 includes the following steps: heating the fatty alcohol and the catalyst to 85-90 °C, adding ethylene oxide or propylene oxide for chain extension reaction, after holding the reaction for 4-8 hours, adding allyl bromide as a chain terminator, adding acetic acid to adjust the pH value to 7, distilling off the unreacted substances under reduced pressure, collecting the fractions after rectification, and obtaining monomer 2.

[0017] Preferably, the catalyst is potassium hydroxide or sodium hydroxide; the addition amount of the catalyst is 2-5 mol% of the addition amount of the fatty alcohol; the molar ratio of the fatty alcohol to ethylene oxide or propylene oxide is 1:(4-10), and the molar ratio of the fatty alcohol to allyl bromide is 1:(1-1.5).

[0018] Preferably, the preparation method of the dispersant is as follows: under a nitrogen atmosphere, dissolve monomer 2 in distilled water, heat to 30-50 °C, slowly dropwise add the aqueous solutions of monomer 1, monomer 3 and monomer 4, and at the same time dropwise add the aqueous solution of the initiator. After the dropping is completed, keep the temperature at 30-50 °C for constant temperature reaction for 5-10 hours, then cool down, add ammonia water to adjust the pH to 7, and obtain the aqueous solution of the dispersant, which is freeze-dried to obtain the dispersant powder.

[0019] Preferably, the initiator is ammonium persulfate, and the molar dosage of the initiator is 0.5-5% of the sum of the molar amounts of monomers 1-4.

[0020] A nanomaterial varistor is prepared by the preparation method of the above-mentioned nanomaterial varistor.

[0021] Beneficial effects

[0022] The present invention provides a preparation method of a nanomaterial varistor. By adding a self-made dispersant to the additive slurry and the total ZnO slurry, the dispersant is copolymerized from acrylic acid monomers, acrylic acid hydroxy ester monomers, allyl alkyl polyoxy ether monomers and pyrrolidone monomers. The carboxylic acid groups of the acrylic acid monomers and the hydroxyl groups of the acrylic acid hydroxy ester monomers can be anchored on the surfaces of metal oxide particles such as zinc oxide through electrostatic adsorption or hydrogen bonding to enhance the anchoring strength. The allyl alkyl polyoxy ether monomers and the pyrrolidone monomers can respectively form long-chain and three-dimensional non-ionized steric hindrance layers on the surfaces of the metal oxide particles to further prevent particle aggregation. The dispersant of the present invention has a wide pH adaptation range, and there is no need to adjust the pH value of the total slurry in the process. The dispersion effect of metal oxides such as ZnO is good, the viscosity of the total slurry can be reduced, the leveling property can be improved, the ZnO grain size distribution after sintering is narrower, and there are no residues during the debinding and sintering processes, improving the electrical properties of the varistor. Description of the Drawings

[0023] Figure 1 is the structural general formula of the dispersant;

[0024] Figure 2 is the infrared spectrogram of monomer 2-A;

[0025] Figure 3 is the infrared spectrogram of dispersant 1. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] In the embodiments, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0028] Now, the raw materials used in the examples and comparative examples are described as follows:

[0029] ZnO: varistor grade, Nantong Jinqi Chemical Co., Ltd.;

[0030] Bi 2 O 3 : electronic grade, Shanghai Jiujia Powder Materials Co., Ltd.;

[0031] Sb 2 O 3 : electronic grade, Chengdu Dayu Functional Materials Co., Ltd.;

[0032] Mn 2 O 3 : Electronic grade, Chengdu Dayu Functional Materials Co., Ltd.;

[0033] Co 3 O 4 : Electronic grade, Shanghai Jiujia Powder Materials Co., Ltd.;

[0034] NiO, electronic grade, Shanghai Jiujia Powder Materials Co., Ltd.;

[0035] Polyvinyl alcohol: PVA-1788, industrial grade, Shanghai Petrochemical Co., Ltd.;

[0036] Ammonium polyacrylate: P856899, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0037] Release agent: HDA-80 type ceramic lubricant, Xi'an Xinzheng Electronic Materials Co., Ltd.;

[0038] Monomer 1: Methacrylic acid, 99%, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0039] Monomer 2-A: In a nitrogen atmosphere, 0.1 mol of lauryl alcohol and 3 mmol of potassium hydroxide were added to a dry reaction kettle, heated to 120 °C to melt, evacuated and dehydrated for 30 minutes to ensure an anhydrous environment, cooled to 85 °C, 0.4 mol of ethylene oxide was slowly added, after holding the reaction for 4 hours, 0.12 mol of allyl bromide was added as a chain terminator, acetic acid was added to adjust the pH to about 7, potassium acetate solid was removed by filtration, the filtrate was distilled under reduced pressure to remove unreacted propylene oxide and low boilers, washed several times with deionized water, the aqueous phase was separated, the organic phase was dried with anhydrous sodium sulfate, the desiccant was recovered by filtration, and further distilled under reduced pressure to obtain Monomer 2-A. The infrared spectrum of Monomer 2-A was measured by the potassium bromide tablet method using a Vertex-70 type infrared spectrometer from German Elemeraor Company, as Figure 2 shown.

[0040] Monomer 2-B: The preparation method is different from that of Monomer 2-A in that lauryl alcohol is replaced by 1-butanol;

[0041] Monomer 3: 2-Hydroxyethyl methacrylate, 96%, purchased from Shanghai Macklin Biochemical Co., Ltd.;

[0042] Monomer 4: N-Vinylpyrrolidone, 99%, Sigma-Aldrich;

[0043] Dispersant 1: Self-made, and the preparation method is as follows:

[0044] Under a nitrogen atmosphere, 0.3 mol of monomer 2-A was dissolved in distilled water and heated to 45 °C in a four-necked flask until dissolved. 0.4 mol of monomer 1, 0.15 mol of monomer 3, 0.15 mol of monomer 4, and ammonium persulfate were separately dissolved in deionized water and added to the dropping funnel of the four-necked flask. Under mechanical stirring, the aqueous solutions of monomer 1, monomer 3, monomer 4, and ammonium persulfate were slowly added dropwise, and the dropping time was controlled within 2 h. After the reaction temperature was kept at 45 °C for 4 h, the temperature was decreased. Ammonia water was added to adjust the pH to 7. The reaction solution was slowly poured into 3 to 5 times the volume of cold acetone, and mechanical stirring was carried out to precipitate the polymer. The precipitate was collected by filtration, washed repeatedly with fresh acetone 2 to 3 times, and finally vacuum dried in an oven at 40 °C for 12 h to obtain dispersant 1. Using a Vertex-70 type infrared spectrometer from German Elemeraor Company, the infrared spectrum of dispersant 1 was measured by the potassium bromide tablet method. As Figure 3 shown, the characteristic peak of -OH of monomer 3 was detected at 3402 cm -1 . The stretching vibration peaks of saturated -CH -1 were detected at 2931 cm -1 and 2858 cm 2 . The C=O stretching vibration peak of the carboxylic acid of monomer 1 was detected at 1727 cm -1 . The C=O stretching vibration absorption peak of pyrrolidone of monomer 4 was detected at 1640 cm -1 . The C-O-C contraction vibration peak of monomer 2 was detected at 1099 cm -1 , proving the successful synthesis of the dispersant.

[0045] Dispersant 2: Self-made. Compared with the preparation method of dispersant 1, the difference lies in that the addition amount of monomer 1 is 0.6 mol, the addition amount of monomer 2-A is 0.2 mol, the addition amount of monomer 3 is 0.1 mol, and the addition amount of monomer 4 is 0.1 mol;

[0046] Dispersant 3: Self-made. Compared with the preparation method of dispersant 1, the difference lies in that monomer 2-A is not added, and the addition amount of monomer 1 becomes 0.7 mol;

[0047] Dispersant 4: Self-made. Compared with the preparation method of dispersant 1, the difference lies in that monomer 3 is not added, and the addition amount of monomer 1 becomes 0.55 mol;

[0048] Dispersant 5: Self-made. Compared with the preparation method of dispersant 1, the difference lies in that monomer 4 is not added, and the addition amount of monomer 1 becomes 0.55 mol;

[0049] Unless otherwise specified, the component raw materials used in each example and comparative example of the present invention are all commercially available raw materials, and the component raw materials used in each parallel experiment are all of the same kind.

[0050] Example 1

[0051] S1. Prepare the raw materials for the varistor in terms of molar percentage: ZnO 95.1%, Bi 2 O 3 1.28%, Co 3 O 4 0.52%, Mn 2 O 3 0.5%, Sb 2 O 3 2.1%, NiO 0.5%;

[0052] S2. Mix the additives except ZnO, add deionized water and a dispersant to form an additive slurry with a solids content of 20%. The addition amount of the dispersant is 0.4 wt% of the total mass of the powder. Use a NETZSCH horizontal sand mill to grind at a main machine speed of 1000 rpm, a feed pump speed of 30 rpm, and circulate once until the particle size of the mixed slurry is 450 nm. After grinding, dry and pulverize to obtain the mixed additive powder;

[0053] S3. Mix ZnO and the additive powder, add deionized water, a dispersant and a binder into a polyurethane ball mill tank. The dosage of the dispersant is 0.4 wt% of the total mass of the powder, and the dosage of the binder is 0.9% of the total mass of the powder. Use agate balls as the grinding medium (powder: deionized water: agate balls = 1:0.66:2.5), and use a ball mill (GMJ-8-5, Wuxi Hengguang Powder Equipment Co., Ltd.) to carry out ball milling and refinement treatment at a speed of 400 r / min for 24 h to obtain the total slurry;

[0054] The dispersant is dispersant 1;

[0055] S4. Use an industrial high-speed centrifugal spray dryer to spray granulate the total slurry. The inlet air temperature of the equipment is 220 °C, the outlet air temperature is 110 °C, and the atomizer speed is 40 Hz; Moisture aging: Use a halogen moisture analyzer (HB43-SHalogen, Mettler-Toledo Instruments Co., Ltd.) to measure the actual moisture content of the powder after spray granulation. Taking the powder moisture content of 1.5% as the target, add a certain amount of deionized water to increase the moisture content, and at the same time add a demolding agent of 0.7% of the powder mass to assist the dry pressing forming of the powder. Mix the two and evenly spray them on the powder, then seal and stand for 20 h; Dry pressing forming: Use a two-way powder hydraulic press (Y79-25, Shanghai Huchi Electric Appliance Development Co., Ltd.) for dry pressing forming. The density of the obtained circular green body is 3.25 g / cm 3About, the size is about Φ48mm×4.5mm; The dry-pressed green body is subjected to debinding treatment: using a high-temperature electric furnace to keep it at 500°C for 2h to remove the remaining organic matter; Then high-temperature sintering: using a muffle furnace to carry out high-temperature sintering at 1150°C for 1h; After grinding and leveling, heat treatment (keep it at 540°C for 180min), apply silver electrodes on the upper and lower end faces, and apply insulating glaze on the side to obtain a varistor.

[0056] Example 2

[0057] Compared with Example 1, the difference is that the dispersant is Dispersant 2;

[0058] Example 3

[0059] Compared with Example 1, the difference is that the addition amounts of the dispersant in Step S2 and Step S4 are 0.2wt% of the powder mass respectively;

[0060] Example 4

[0061] Compared with Example 1, the difference is that the addition amounts of the dispersant in Step S2 and Step S4 are 0.6wt% of the powder mass respectively;

[0062] Example 5

[0063] Compared with Example 1, the difference is that the addition amounts of the dispersant in Step S2 and Step S4 are 0.8wt% of the powder mass respectively;

[0064] Comparative Example 1

[0065] Compared with Example 1, the difference is that the dispersant is Dispersant 3;

[0066] Comparative Example 2

[0067] Compared with Example 1, the difference is that the dispersant is Dispersant 4;

[0068] Comparative Example 3

[0069] Compared with Example 1, the difference is that the dispersant is Dispersant 5;

[0070] Comparative Example 4

[0071] Compared with Example 1, the difference is that the dispersant is ammonium polyacrylate;

[0072] Performance Test

[0073] 1. Total slurry viscosity: Measured using a Shanghai Changji NDJ-8S type rotational viscometer;

[0074] 2. Pinhole ratio: After polishing the varistor, it is tested with an OLYMPUS microscope (BX53M, OLYMPUS, Japan), and the pinhole ratio is calculated using the Olympus analysis software;

[0075] 3. Potential gradient of ZnO varistor: E 1mA = U 1mA / h, where: E 1mA is the potential gradient, V / mm; U 1mA is the voltage value of the varistor under a DC current of 1.0 mA, kV; h is the height of the varistor chip, mm.

[0076] 4. Nonlinear coefficient of ZnO varistor: α = 1 / log10(U 1mA / U 0.1mA ), where: α is the nonlinear coefficient; U 0.1mA is the voltage value of the varistor under a DC current of 0.1 mA, kV.

[0077] 5. Residual voltage ratio: The impulse current testing machine conducts an 8 / 20 μs lightning impulse current simulation test on the resistor chip, measures the residual voltage value U5kA of the resistor chip after passing through a 5 kA impulse current, and thus calculates the residual voltage ratio; calculates the residual voltage ratio of the varistor: K 5kA = U 5kA / U 1mA , where: K5kA is the residual voltage ratio under a 5 kA lightning current; U 5kA is the residual voltage of the varistor passing through 8 / 20 μs.

[0078] Table 1 Total slurry viscosity and electrical properties of varistors

[0079] Total slurry viscosity (mpa·s) Pinhole rate (%) Potential gradient (V / mm) Nonlinear coefficient Residual pressure ratio Example 1 17.6 4.10 336.1 55.6 1.645 Example 2 15.3 3.99 337.6 54.5 1.624 Example 3 36.8 4.74 332.5 44.2 1.701 Example 4 16.5 4.62 328.4 51.8 1.680 Example 5 46.8 5.77 321.9 48.3 1.695 Comparative Example 1 24.3 7.33 318.7 40.7 1.818 Comparative Example 2 22.3 6.78 324.7 43.9 1.724 Comparative Example 3 17.6 8.14 309.3 38.1 1.861 Comparative Example 4 13.6 6.68 322.5 46.7 1.671

[0080] It can be seen from the performance tests of the examples and comparative examples that appropriate dispersants and appropriate dosages can make the total slurry mix more evenly, further improve the uniformity of the microstructure of the varistor chip, and enhance the comprehensive electrical properties. This is because when the total slurry is unstable, the additives are prone to stratification, resulting in uneven distribution of additive oxides and a decline in electrical properties.

[0081] It can be seen from Examples 1, 3 to 5 that when the dosage of the dispersant is small, the viscosity of the total slurry is high, and the slurry is prone to instability. When the dosage of the dispersant is too large, there is too much organic polymer dispersant in the total slurry, resulting in too many pores on the resistor chip after the debinding process, an increase in the pinhole ratio, and a decline in electrical properties.

[0082] It can be seen from Example 1 and Comparative Examples 1-3 that when monomers 2-4 are respectively lacking in the dispersant, the dispersion effect will decline. This is because the dispersant provided by the present invention has a comb-shaped polymer structure, wherein monomer 1 and monomer 3 are anchored on the surface of metal oxide particles through electrostatic adsorption or hydrogen bonding, and monomer 2 and monomer 3 ensure the dispersion effect through long chains and steric non-ionizing steric hindrance. When any one monomer is lacking, the dispersion effect will decline to some extent, and when the steric hindrance structures of monomers 2 and 4 are lacking, the dispersion effect declines more significantly.

[0083] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a nanomaterial varistor, characterized in that: The following steps are involved: S1. Raw materials for preparing varistor are configured in molar percentage: ZnO 94-96%, Bi2O3 1.0-1.5%, Co3O4 0.5-1.5%, Mn2O3 0.3-0.8%, Sb2O3 1.0-3.0%, NiO 0.3-0.8%; S2. The additives other than ZnO are mixed, deionized water and a dispersant are added to form an additive slurry, which is sand-milled and dried to obtain an additive powder; S3. The ZnO and additive powders are mixed, deionized water, a dispersant and a binder are added, and the mixture is ball-milled in a ball mill to obtain a total slurry; The dispersant is copolymerized by monomer 1, monomer 2, monomer 3 and monomer 4, and the general structural formula is shown in Formula 1: S4. The total slurry is subjected to spray granulation, water-containing aging and dry pressing, the dry-pressed green body is subjected to binder removal treatment, and then sintered at high temperature, ground and flattened, and heat treated. Silver electrodes are coated on the upper and lower end faces, and insulating glaze is coated on the side to obtain a varistor.

2. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: In step S2, the solid content of the additive slurry is 20-50%, the added amount of the dispersant is 0.1-1wt% of the additive, and the mixed slurry is sand-milled to a particle size of 400-600nm.

3. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: In step S3, the amount of dispersant used is 0.1-1wt% of the total mass of the powder, the amount of binder used is 0.5-1% of the total mass of the powder, the ball milling time is 20-24 hours, and the binder is polyvinyl alcohol.

4. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: In formula 1, R1, R2, R3, and R4 are respectively selected from one of H and CH3, R5 is a carbon chain with a carbon atom length of 4 to 18, the molar ratio of monomer 1, monomer 2, monomer 3 and monomer 4 is a:b:c:d=(30 to 60):(20 to 30):(10 to 25):(10 to 15), and m is a natural number between 4 and 10.

5. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: The monomer 1 of the dispersant is one of acrylic acid or methacrylic acid, the monomer 3 is one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate or hydroxypropyl methacrylate; and the monomer 4 is N-vinyl pyrrolidone.

6. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: The preparation method of the monomer 2 comprises the following steps: heating the fatty alcohol and the catalyst to 85-90° C., adding ethylene oxide or propylene oxide to carry out a chain extension reaction, keeping the temperature for 4-8 hours, adding allyl bromide as a chain terminator, adding acetic acid to adjust the pH value to 6-7, and collecting the product after purification to obtain the monomer 2.

7. The method for preparing a nanomaterial varistor according to claim 6, characterized in that: The catalyst is potassium hydroxide or sodium hydroxide; the amount of the catalyst added is 0.1-3 mol% of the amount of the fatty alcohol added; the molar ratio of the fatty alcohol to ethylene oxide or propylene oxide is 1:(4-10), and the molar ratio of the fatty alcohol to allyl bromide is 1:(1-1.5).

8. The method for preparing a nanomaterial varistor according to claim 1, characterized in that: The preparation method of the dispersant is as follows: in a nitrogen atmosphere, monomer 2 is dissolved in distilled water, heated to 30-50° C., aqueous solutions of monomer 1, monomer 3 and monomer 4 are slowly added dropwise, and an aqueous solution of an initiator is added dropwise at the same time, after the addition is completed, a constant temperature of 30-50° C. is maintained for reaction for 5-10 hours, and then the temperature is lowered, ammonia water is added to adjust the pH to 7, and the aqueous solution of the dispersant is obtained, and the dispersant powder is obtained by freeze-drying.

9. The method for preparing a nanomaterial varistor according to claim 8, characterized in that: The initiator is ammonium persulfate, and the molar amount of the initiator is 0.5-5% of the total molar amount of 1-4 monomers.

10. A nanomaterial varistor, characterized in that: The nanomaterial varistor is prepared by the preparation method of any one of claims 1 to 9.

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