Thermistor with nanoparticle film and preparation method thereof

Abstract

The invention provides a thermistor with a nanoparticle film and a preparation method thereof, the thermistor comprises a matrix, conductive fillers and a composite heat-sensitive material, the conductive fillers are dispersed in the matrix, and the conductive fillers are mutually lapped to form a conductive network; the composite heat-sensitive material is dispersed in the matrix, the composite heat-sensitive material comprises a heat-sensitive ceramic material with a positive temperature coefficient and a nano-particle film arranged on the surface of the heat-sensitive ceramic material, and the nano-particle film comprises a shape memory material with thermal response. The thermistor provided by the invention has relatively small volume amplification, so that the occurrence probability that a conductive network formed by the conductive filler is disassembled is reduced, and the resistance value of the thermistor can be close to an original value before overprotection after overprotection, so that the stability of the thermistor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermistors, and particularly relates to a thermistor with a nanoparticle film and a preparation method thereof. Background Art

[0002] Thermistors are divided into positive temperature coefficient thermistors (PTC thermistors, i.e., Positive Temperature Coefficient thermistors) and negative temperature coefficient thermistors (NTC thermistors, i.e., Negative Temperature Coefficient thermistors) according to different temperature coefficients. Their resistance values can change with the change of temperature, so that they can be used as an overprotection electronic component, and thus can be widely used in overcurrent and overheat protection in industrial automation control systems, electronic devices, medical devices, automotive electronic control systems, aerospace, military and other fields.

[0003] However, in the related art, after the positive temperature coefficient thermistor undergoes overprotection, its resistance value at room temperature differs greatly from the original value before overprotection, resulting in insufficient stability. Summary of the Invention

[0004] The present invention provides a barium titanate-based thermistor with a nanoparticle film and a preparation method thereof. The thermistor can make its resistance value close to the original value before overprotection after overprotection, so as to improve its stability.

[0005] The first aspect of the present invention provides a thermistor, comprising:

[0006] A substrate;

[0007] A conductive filler, dispersed in the substrate, and the conductive fillers overlap with each other to form a conductive network;

[0008] A composite thermosensitive material, dispersed in the substrate, the composite thermosensitive material includes a thermosensitive ceramic material with a positive temperature coefficient and a nanoparticle film disposed on the surface of the thermosensitive ceramic material, and the nanoparticle film includes a shape memory material with a thermal response.

[0009] According to any of the foregoing embodiments of the present invention, the nanoparticle film further includes a conductive nanomaterial, and the mass ratio of the conductive nanomaterial to the shape memory material is 1:(10 - 20).

[0010] According to any of the foregoing embodiments of the present invention, the shape memory material includes a shape memory ceramic and / or a shape memory polymer.

[0011] According to any of the foregoing embodiments of the present invention, the shape memory material includes shape memory ceramics, and the shape memory ceramics include at least one of zirconia nanoparticles, cerium oxide nanoparticles, and titanium oxide nanoparticles.

[0012] According to any of the foregoing embodiments of the present invention, the shape memory material includes shape memory polymers, and the shape memory polymers include at least one of polyurethane, polylactone, polystyrene, and epoxy resin.

[0013] According to any of the foregoing embodiments of the present invention, the conductive nanomaterial includes one or more of nickel nanoparticles, single-walled carbon nanotubes, multi-walled carbon nanotubes, and iron nanoparticles.

[0014] According to any of the foregoing embodiments of the present invention, the thickness of the nanoparticle film is 10 nm - 100 nm.

[0015] According to any of the foregoing embodiments of the present invention, the mass percentage content of the composite thermosensitive material in the thermistor is 10% - 25%.

[0016] According to any of the foregoing embodiments of the present invention, the mass percentage content of the conductive filler in the thermistor is 5% - 10%.

[0017] The second aspect of the present invention provides a method for preparing a thermistor as described in any of the embodiments of the first aspect of the present invention, including:

[0018] Disperse the raw materials of the nanoparticle film in a solvent to form a slurry, wherein the raw materials of the nanoparticle film include a shape memory material with thermal response;

[0019] Immerse the positive temperature coefficient thermosensitive ceramic material in the slurry, and after drying, form a nanoparticle film on the surface of the thermosensitive ceramic material to obtain a composite thermosensitive material;

[0020] Mix the raw materials of the substrate, the conductor filler, and the composite thermosensitive material, and after pressing and sintering treatments, obtain the thermistor.

[0021] The third aspect of the present invention provides a temperature sensor, including a barium titanate-based thermistor as described in any of the embodiments of the first aspect of the present invention provided by the second aspect of the present invention or a barium titanate-based thermistor prepared by the preparation method described in any of the embodiments of the second aspect of the present invention.

[0022] The thermistor with a nanoparticle film provided by the present invention and its preparation method. The thermistor includes a substrate, a conductive filler, and a composite thermosensitive material. The conductive filler is dispersed in the substrate, and the conductive fillers are overlapped with each other to form a conductive network. The composite thermosensitive material is dispersed in the substrate. The composite thermosensitive material includes a thermosensitive ceramic material with a positive temperature coefficient and a nanoparticle film disposed on the surface of the thermosensitive ceramic material. The nanoparticle film includes a shape memory material with a thermal response. The above technical solution sets a nanoparticle film on the surface of the thermosensitive ceramic material, and the nanoparticle film includes a shape memory material with a thermal response, so that the nanoparticle film has a shape memory function. When the thermistor undergoes overprotection, it helps to reduce the volume increase of the thermosensitive ceramic material, and further reduces the probability of the conductive network formed by the conductive filler being disassembled, thereby helping the resistance value of the thermistor to approach the original value before overprotection after overprotection, so as to improve its stability.

[0023] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description. And in order to make the above and other objects, features and advantages of the present invention more obvious and understandable, the following specifically illustrates the specific embodiments of the present invention. Specific Embodiments

[0024] Unless otherwise specified, the terms used in the present invention have the well-known meanings commonly understood by those skilled in the art.

[0025] Unless otherwise specified, the numerical values of the various parameters mentioned in the present invention can be measured by various commonly used test methods in the art. For example, they can be measured according to the test methods given in the embodiments of the present invention.

[0026] The temperature of a positive temperature coefficient thermistor will increase rapidly with the increase of an abnormally high current. When the temperature reaches the Curie point, the thermosensitive ceramic material of the positive temperature coefficient thermistor will expand to disassemble the conductive network formed by the internal conductive filler, so that its resistance value increases rapidly to reduce its current to achieve the function of overprotection. After the abnormally high current is eliminated, ideally, it is expected that the thermal expansion of the thermosensitive ceramic material disappears and returns to its original shape, and the conductive network disassembled due to the thermal expansion will be restored again, so that the resistance value of the thermistor returns to the original value before overprotection. However, in actual situations, after the thermosensitive ceramic material in the thermistor undergoes high-temperature expansion, its structure will change, resulting in its volume being much larger than that before overprotection. In this way, part of the conductive network is still in a disassembled state, so the resistance value at room temperature is quite different from the original value before overprotection, resulting in insufficient stability.

[0027] In view of this, the present invention provides a barium titanate-based thermistor with a nanoparticle film and a preparation method thereof. The thermistor can make its resistance value approach the original value before overprotection after overprotection, so as to improve its stability.

[0028] In a first aspect, the present invention provides a thermistor, which includes a matrix, a conductive filler, and a composite thermosensitive material. The conductive filler is dispersed in the matrix, and the conductive fillers are overlapped with each other to form a conductive network; the composite thermosensitive material is dispersed in the matrix, and the composite thermosensitive material includes a thermosensitive ceramic material with a positive temperature coefficient and a nanoparticle film disposed on the surface of the thermosensitive ceramic material. The nanoparticle film includes a shape memory material with a thermal response.

[0029] The thermistor with a nanoparticle film provided by the present invention has a nanoparticle film disposed on the surface of the thermosensitive ceramic material, and the nanoparticle film includes a shape memory material with a thermal response. In this way, the above nanoparticle film can have a shape memory function. When the thermistor undergoes overprotection, it helps to reduce the volume increment of the thermosensitive ceramic material, and further reduces the probability of the conductive network formed by the conductive filler being disassembled. Therefore, it can help the resistance value of the thermistor to approach the original value before overprotection after overprotection, so as to improve its stability.

[0030] In some embodiments of the present invention, the matrix includes a crystalline polymer, such as polyethylene, polypropylene, polyvinyl fluoride, etc.

[0031] In an embodiment of the present invention, the nanoparticle film includes a shape memory material with a thermal response, which can help the shape of the thermosensitive ceramic material to change less after overprotection, that is, the volume increment is smaller. In addition, the nanoparticle film can also include other suitable materials to reduce the resistance value of the thermistor at room temperature to reduce its energy consumption.

[0032] In some embodiments of the present invention, the nanoparticle film further includes a conductive nanomaterial, and the mass ratio of the conductive nanomaterial to the shape memory material is 1:(10 - 20). When the mass ratio of the conductive nanomaterial to the shape memory material is within the above suitable range, it can not only make the thermistor have a lower resistance value at room temperature to reduce its energy consumption, but also further reduce the volume increment of the thermosensitive ceramic material after overprotection, thereby effectively reducing the resistance value change rate of the thermistor.

[0033] Exemplarily, the mass ratio of the conductive nanomaterial to the shape memory material can be but is not limited to 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, etc.

[0034] In some embodiments of the present invention, the conductive nanomaterial includes one or more of nickel nanoparticles, single-walled carbon nanotubes, multi-walled carbon nanotubes, and iron nanoparticles.

[0035] In the above embodiments, selecting a suitable shape memory material can help the thermosensitive ceramic material to have a lower volume increase after overprotection, so that the recovery rate of the conductive network formed by the conductive filler will also increase, which can further help the resistance value of the thermistor to approach the original value before overprotection after overprotection, thereby further improving the stability of the thermistor.

[0036] In some embodiments of the present invention, the shape memory material includes shape memory ceramics and / or shape memory polymers. The shape memory material includes the above-mentioned suitable materials, which can improve the structural strength of the composite thermosensitive material and reduce the volume increase of the thermosensitive ceramic material, and at the same time, can also help to increase the resistance value of the composite thermosensitive material during overprotection to enhance the overprotection effect.

[0037] Exemplarily, the shape memory material includes shape memory ceramics, and the shape memory ceramics include at least one of zirconia nanoparticles, ceria nanoparticles, and titanium oxide nanoparticles. The above nanoparticles can further enhance the stability of the thermistor while further improving its overprotection effect.

[0038] In some other examples, the shape memory material includes shape memory polymers, and the shape memory polymers include at least one of polyurethane, polycaprolactone, polystyrene, and epoxy resin.

[0039] The nanoparticle film formed by the above materials can improve its structural stability within a suitable thickness range, thereby further helping to reduce the volume increase of the thermistor.

[0040] In some embodiments of the present invention, the thickness of the nanoparticle film is 10nm - 100nm.

[0041] The thickness of the nanoparticle film refers to the distance between the side of the nanoparticle film close to the surface of the thermosensitive ceramic material and the side of the nanoparticle film far from the surface of the thermosensitive ceramic material along the radial direction of the thermosensitive ceramic material. This thickness can be obtained through tests such as SEM, EDS, TEM, and XPS.

[0042] In some examples, the thickness of the nanoparticle film can be, but is not limited to, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, 50nm, 51nm, 52nm, 53nm, 54nm, 55nm, 56nm, 57nm, 58nm, 59nm, 60nm, 61nm, 62nm, 63nm, 64nm, 65nm, 66nm, 67nm, 68nm, 69nm, 70nm, 71nm, 72nm, 73nm, 74nm, 75nm, 76nm, 77nm, 78nm, 79nm, 80nm, 81nm, 82nm, 83nm, 84nm, 85nm, 86nm, 87nm, 88nm, 89nm, 90nm, 91nm, 92nm, 93nm, 94nm, 95nm, 96nm, 97nm, 98nm, 99nm, 100nm or a range of values composed of any two values within the range of 100nm - 100nm.

[0043] In an embodiment of the present invention, the proportions of the components in the thermistor are within a suitable range, which can help to further improve its over - protection effect and stability, and reduce its energy consumption.

[0044] In some embodiments of the present invention, the mass percentage content of the composite thermosensitive material in the thermistor is 10% - 25%. When the mass percentage content of the thermosensitive ceramic material in the thermistor is within the above - mentioned suitable range, it can further help to improve its over - protection effect.

[0045] Exemplarily, the mass percentage content of the composite thermosensitive material in the thermistor can be, but is not limited to, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25% or a range of values composed of any two values within the range of 10% - 25%.

[0046] In some embodiments of the present invention, the mass percentage content of the conductive filler in the thermistor is 5% - 10%. When the mass percentage content of the conductive filler in the thermistor is within the above - mentioned suitable range, the thermistor can have a lower resistance value at room temperature to reduce its energy consumption.

[0047] Exemplarily, the mass percentage of the conductive filler in the thermistor can be, but is not limited to, 5%, 6%, 7%, 8%, 9%, 10%, or any range formed by any two values within the range of 5%-10%.

[0048] In some embodiments of the present invention, the conductive filler may include at least one of carbon nanotubes, graphene, and carbon nanofibers.

[0049] In an embodiment of the present invention, the thermosensitive ceramic material can be any positive temperature coefficient ceramic material well-known in the art, such as barium titanate particles, strontium titanate particles, and the like.

[0050] In some of the above embodiments, the particle size of the barium titanate particles is within a suitable range, which can help improve the sensitivity of the composite thermosensitive ceramic. In some embodiments, the particle size r of the barium titanate particles is 10 μm - 60 μm.

[0051] Exemplarily, the particle size r of the barium titanate particles can be, but is not limited to, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, or any range formed by any two values within the range of 10 μm - 60 μm.

[0052] The second aspect of the present invention provides a method for preparing a thermistor as described in any embodiment of the first aspect of the present invention, including:

[0053] Disperse the raw materials of the nanoparticle film in a solvent to form a slurry, wherein the raw materials of the nanoparticle film include a shape memory material with thermal response;

[0054] Immerse the thermosensitive ceramic material with a positive temperature coefficient in the slurry, and after drying, form a nanoparticle film on the surface of the thermosensitive ceramic material to obtain a composite thermosensitive material;

[0055] Mix the raw materials of the substrate, the conductor filler, and the composite thermosensitive material, and after pressing and sintering treatments, obtain the thermistor.

[0056] A third aspect of the present invention provides a temperature sensor, which includes a thermistor provided in the second aspect of the present invention or a thermistor prepared by the preparation method of any embodiment of the first aspect of the present invention.

[0057] The following embodiments more specifically describe the content disclosed in the present application. These embodiments are only for illustrative purposes, because various modifications and variations within the scope of the present application disclosure are obvious to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized according to conventional methods, and can be used directly without further treatment, and the instruments used in the embodiments are all commercially available.

[0058] Example 1

[0059] This example provides a preparation method of a thermistor, and the preparation method includes the following steps:

[0060] Disperse 100 mg of zirconia nanoparticles and 1 mg of polyethylene in 20 mL of ethanol to form a slurry;

[0061] Immerse 50 g of barium titanate thermosensitive ceramic material with an average particle size of 15 μm in the above slurry for 2 min, then dry at 60 °C for 20 min, and repeat 3 times (forming a thickness of about 5 nm each time) to form a nanoparticle film with a thickness of about 15 nm on the surface of the barium titanate thermosensitive ceramic material to obtain a composite thermosensitive material;

[0062] Mix and granulate 425 g of polyethylene, 25 g of conductive filler single-walled carbon nanotubes and the above composite thermosensitive material, and press it into a formed embryo with a diameter of about 1 cm and a thickness of about 0.6 cm under a pressure of 40 MPa;

[0063] Subject the above formed embryo to degassing at 600 °C for 5 h, and then sinter at 1400 °C for 5 h to obtain a thermistor. Among them, the mass percentage content of the composite thermosensitive material in the thermistor is about 10%, and the mass percentage content of the conductive filler single-walled carbon nanotubes in the thermistor is about 5%.

[0064] Example 2

[0065] Similar to the preparation method of Example 1, the difference is that: the zirconia nanoparticles are replaced with ceria nanoparticles.

[0066] Example 3

[0067] Similar to the preparation method of Example 1, the difference is that: the zirconia nanoparticles are replaced with titania nanoparticles.

[0068] Example 4

[0069] Similar to the preparation method of Example 1, except that: the zirconia nanoparticles are replaced by polyurethane and single-walled carbon nanotubes, and the mass ratio of polyurethane to single-walled carbon nanotubes is 10:1.

[0070] Example 5

[0071] Similar to the preparation method of Example 1, except that:

[0072] (1) 2000 mg of zirconia nanoparticles and 50 mg of polyethylene are dispersed in 30 mL of ethanol to form a slurry;

[0073] (2) 110 g of barium titanate thermosensitive ceramic material with an average particle size of 15 μm is impregnated in the above slurry;

[0074] (3) The mass percentage of the composite thermosensitive material in the thermistor is about 20%.

[0075] Example 6

[0076] Similar to the preparation method of Example 1, except that:

[0077] (1) 1000 mg of zirconia nanoparticles and 10 mg of polyethylene are dispersed in 25 mL of ethanol to form a slurry;

[0078] (2) 78 g of barium titanate thermosensitive ceramic material with an average particle size of 15 μm is impregnated in the above slurry;

[0079] (3) The mass percentage of the composite thermosensitive material in the thermistor is about 15%.

[0080] Example 7

[0081] Similar to the preparation method of Example 1, except that: it is repeated 4 times, the thickness of the nanoparticle film is about 20 nm, and the mass percentage of the composite thermosensitive material in the thermistor is about 10.1%.

[0082] Example 8

[0083] Similar to the preparation method of Example 1, except that: it is repeated 10 times, the thickness of the nanoparticle film is about 50 nm, and the mass percentage of the composite thermosensitive material in the thermistor is about 10.5%.

[0084] Example 9

[0085] Similar to the preparation method of Example 1, except that: it is repeated 10 times, the thickness of the nanoparticle film is about 90 nm, and the mass percentage of the composite thermosensitive material in the thermistor is about 11%.

[0086] Comparative Example 1

[0087] The preparation method of the thermistor provided in this comparative example includes the following steps:

[0088] Mix 425 g of polyethylene, 25 g of conductive filler single-walled carbon nanotubes, and 50 g of barium titanate thermosensitive ceramic material with an average particle size of 15 μm, granulate them, and press them into a formed embryo with a diameter of about 1 cm and a thickness of about 0.6 cm under a pressure of 40 MPa;

[0089] After degassing the above-mentioned formed embryo at 600 °C for 5 h, sinter it at 1400 °C for 5 h to obtain a thermistor. Among them, the mass percentage content of the composite thermosensitive material in the thermistor is about 10%, and the mass percentage content of the conductive filler single-walled carbon nanotubes in the thermistor is about 5%.

[0090] Comparative Example 2

[0091] Similar to the preparation method of Example 1, the difference is that: zirconia nanoparticles are replaced with silica.

[0092] Comparative Example 3

[0093] This comparative example provides a preparation method of a thermistor, including:

[0094] Disperse 100 mg of zirconia nanoparticles and 1 mg of polyethylene in 20 mL of ethanol to form a slurry;

[0095] Mix 50 g of barium titanate thermosensitive ceramic material with an average particle size of 15 μm, 425 g of polyethylene, and 25 g of conductive filler single-walled carbon nanotubes, granulate them, and press them into a formed embryo with a diameter of about 1 cm and a thickness of about 0.6 cm under a pressure of 40 MPa;

[0096] After degassing the above-mentioned formed embryo at 600 °C for 5 h, sinter it at 1400 °C for 5 h to obtain a semi-finished thermistor. Among them, the mass percentage content of the barium titanate thermosensitive ceramic material in the semi-finished thermistor is about 10%, and the mass percentage content of the conductive filler single-walled carbon nanotubes in the semi-finished thermistor is about 5%;

[0097] Immerse the above-mentioned semi-finished thermistor in the above-mentioned slurry for 2 min, dry it at 60 °C for 20 min, and repeat 3 times (forming a thickness of about 5 nm each time) to form a nanoparticle film with a thickness of about 15 nm on the surface of the above-mentioned semi-finished thermistor to obtain a finished thermistor.

[0098] Test Part

[0099] (1) Particle Size Test of Composite Thermosensitive Material

[0100] The particle size r of the composite thermosensitive materials prepared in the above examples and comparative examples after returning to room temperature through the Curie point was measured by the laser diffraction scattering method. 1 The test results are shown in Table 1.

[0101] (2) Thickness test of the nanoparticle film

[0102] The thickness test of the nanoparticle film was obtained through testing with a Raman spectrometer (Raman) in SEM. The composite thermosensitive material was fractured brittlely in liquid nitrogen to obtain the cross-sectional situation, and then the thickness of the nanoparticle film was obtained through Raman microscopic imaging (Raman Mapping) of the cross-section. The test results are shown in Table 1.

[0103] (3) Resistance value test

[0104] The samples to be tested prepared in the above examples and comparative examples were placed at room temperature (i.e., 25 °C), a voltage was applied to the above samples to be tested, and then a multimeter (manufacturer: HIOKI, model: RM3545) was used to measure the current value, and the resistance value R was calculated. 0 Then the above samples were placed at 80 °C for 5 min, and then the above samples were cooled from 80 °C to room temperature. After applying the same voltage to this sample, a multimeter was used to measure the current value, and this was repeated 3 times, and the resistance value R was calculated. 3 . Therefore, the increase rate α of the resistance value is equal to (R 3 -R 0 ) / R 0 ×100%, and the test results are shown in Table 1.

[0105] Table 1 Test results of examples and comparative examples

[0106]

[0107]

[0108] Note: A represents the mass percentage of the thermosensitive material in the thermistor.

[0109] According to Table 1, by comparing the test results of Examples 1-9 and Comparative Examples 1-2, it can be seen that in the present invention, by providing a nanoparticle film on the surface of the thermosensitive ceramic material, and this nanoparticle film includes a shape memory material with thermal response, so that the above nanoparticle film has a shape memory function. When the thermistor undergoes overprotection, it helps to reduce the increase rate of the particle size of the thermosensitive ceramic material, which can also be understood as the volume increase rate, and further reduce the probability of the conductive network formed by the conductive filler being disassembled, thereby being able to help the resistance value of the thermistor approach the original value before overprotection after overprotection, so as to improve its stability.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered within the scope of the claims and the specification of the present invention. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A thermistor having a nanoparticle film, characterized in that: include: matrix; Conductive fillers are dispersed in the matrix and overlap each other to form a conductive network; A composite thermosensitive material is dispersed in the matrix, wherein the composite thermosensitive material comprises a thermosensitive ceramic material having a positive temperature coefficient and a nanoparticle film arranged on the surface of the thermosensitive ceramic material, wherein the nanoparticle film comprises a shape memory material having a thermal response.

2. The thermistor according to claim 1, characterized in that: The nanoparticle film also includes a conductive nanomaterial, and the mass ratio of the conductive nanomaterial to the shape memory material is 1:(10-20).

3. The thermistor according to claim 1 or 2, characterized in that: The shape memory material includes shape memory ceramics and / or shape memory polymers.

4. The thermistor according to claim 3, characterized in that: The shape memory material includes shape memory ceramics, and the shape memory ceramics include at least one of zirconium oxide nanoparticles, cerium oxide nanoparticles, and titanium oxide nanoparticles.

5. The thermistor according to claim 3, characterized in that: The shape memory material includes a shape memory polymer, and the shape memory polymer includes at least one of polyurethane, polylactone, polystyrene, and epoxy resin.

6. The thermistor according to claim 2, characterized in that: The conductive nanomaterial includes one or more of nickel nanoparticles, single-walled carbon nanotubes, multi-walled carbon nanotubes and iron nanoparticles.

7. The thermistor according to claim 1, characterized in that: The thickness of the nanoparticle film is 10nm-100nm.

8. The thermistor according to claim 1, characterized in that: The mass percentage of the composite thermal-sensitive material in the thermistor is 10%-25%.

9. The thermistor according to claim 1, characterized in that: The mass percentage of the conductive filler in the thermistor is 5%-10%.

10. A method for preparing a thermistor according to any one of claims 1 to 9, characterized in that: include: Dispersing a raw material of a nanoparticle film in a solvent to form a slurry, wherein the raw material of the nanoparticle film includes a shape memory material having a thermal response; Thermosensitive ceramic material with a positive temperature coefficient is immersed in the slurry, and after drying, a nanoparticle film is formed on the surface of the thermosensitive ceramic material to obtain a composite thermosensitive material; The raw material of the matrix, the conductor filler and the composite thermal-sensitive material are mixed, and subjected to pressing and sintering treatment to obtain the thermistor.

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