A preparation method of a phase separation temperature-sensitive molybdenum-nickel nano-alloy

Abstract

The application relates to a preparation method of a phase separation temperature-sensitive molybdenum-nickel nano-alloy, and belongs to the technical field of nanometer materials. The preparation comprises the following steps: 1) dissolving nickel chloride hexahydrate, then adding sodium hydroxide, heating and stirring, washing and drying; 2) grinding the nickel hydroxide precursor obtained in the step 1), and then heat-treating under a reducing atmosphere; 3) adding the nickel nanoparticles obtained in the step 2) and ammonium molybdate into water, stirring, then carrying out hydrothermal reaction, washing and drying; 4) heat-treating the molybdenum-doped molybdenum-nickel nanoparticle intermediate obtained in the step 3) under a reducing atmosphere to obtain phase separation MoNi x nano-alloy particles. The whole process is simple, pollution-free, low in material cost, capable of obtaining nano-alloys with polycrystal faces and high crystal boundary resistance values, the high crystal boundary resistance caused by the polycrystal faces can be rapidly reduced under thermal activation, and the alloy can be combined with a flexible substrate to manufacture a temperature sensor, so the alloy has certain commercial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly to a preparation method of a phase separation temperature-sensitive molybdenum-nickel nanometer alloy. BACKGROUND

[0002] Flexible and stretchable devices have attracted great interest and have a wide range of applications due to their compressibility, bendability and compatibility with irregular and curved surfaces. Compared with traditional rigid sensors, they have the advantages of mechanical strength, biocompatibility, multifunctionality and comfort. Temperature is one of the most important detection means in the sensing field, which can deliver information through contact and non-contact methods, making temperature particularly prominent in human-computer interaction sensing applications. However, traditional rigid temperature probes cannot achieve conformal contact with uneven surfaces. This problem plays a crucial role in the development of flexible and wearable temperature sensors. Therefore, it is necessary to develop soft, flexible, biocompatible, lightweight, durable and non-irritating temperature sensors to meet the requirements of wearable devices.

[0003] Negative temperature coefficient (NTC) thermistors have obvious advantages compared with integrated circuit (IC) temperature sensors, because they have a simpler structure while having equally high temperature sensitivity. However, NTC thermistors also face major challenges when actually used as flexible temperature sensors, because typical NTC thermistor materials (ceramics) usually require high annealing temperatures of 600 °C or higher to form or activate. Since most flexible substrates are not compatible with such high temperatures. So far, further progress in the research of flexible temperature sensors based on thermistors has been greatly limited. SUMMARY

[0004] The present application aims to solve the above-mentioned problems in the prior art, and provides a preparation method of a phase separation temperature-sensitive molybdenum-nickel nanometer alloy, which obtains a material with a high crystal face, a high crystal boundary resistance and a very high thermosensitive constant value. The preparation process of the present application is simple, pollution-free, and the material cost is low; the high crystal boundary resistance caused by the crystal face of the material will rapidly decrease under thermal activation, which can be combined with a flexible substrate to make a temperature sensor, and has certain commercial application prospect.

[0005] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0006] A preparation method of a phase separation temperature-sensitive molybdenum-nickel nanometer alloy, comprising the following steps:

[0007] 1) Dissolve nickel chloride hexahydrate, then add sodium hydroxide, heat and stir, wash and dry to obtain a nickel hydroxide precursor;

[0008] 2) grinding the nickel hydroxide precursor obtained in step 1), and then heat treating under a reducing atmosphere to obtain nickel nanoparticles;

[0009] 3) adding the nickel nanoparticles obtained in step 2) and ammonium molybdate into water, stirring, and then hydrothermally reacting, washing, and drying to obtain a molybdenum-doped molybdenum-nickel nanoparticle intermediate;

[0010] 4) heat treating the molybdenum-doped molybdenum-nickel nanoparticle intermediate obtained in step 3) under a reducing atmosphere to obtain phase-separated MoNi x nanoparticle alloy.

[0011] In step 1), the concentration ratio of the nickel chloride hexahydrate to the sodium hydroxide is 10-20:1; the temperature for heating and stirring is 80-120 DEG C, and the time is 30-60 min.

[0012] In step 2), the temperature for heat treatment is 400-600 DEG C, and the time is 1-4 h.

[0013] In step 3), the mass ratio of the nickel nanoparticles to the ammonium molybdate is 1:4-8.

[0014] In step 3), the temperature for hydrothermal reaction is 100-160 DEG C, and the time is 12-24 h.

[0015] In step 4), the temperature for heat treatment is 400-600 DEG C, and the time is 1-4 h.

[0016] The phase-separated temperature-sensitive molybdenum-nickel nanoparticle alloy based on phase separation has a polycrystal face structure and a high crystal boundary resistance, and the thermal sensitivity constant B value is as high as 17058 K in the range of 20-23 DEG C and 16800 K in the range of 20-25 DEG C.

[0017] The phase-separated temperature-sensitive molybdenum-nickel nanoparticle alloy based on phase separation is used for making a temperature sensor, in particular, a temperature sensor combined with a flexible substrate.

[0018] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0019] 1. The present application provides a preparation method of a phase-separated molybdenum-nickel nanoparticle alloy, which has a simple and pollution-free preparation process, low material cost, and can obtain a nanoparticle alloy with a polycrystal face and a high crystal boundary resistance value.

[0020] 2、The application uses the phase-separated MoNi nano-alloy as a thermistor material, and the phase-separated nano-alloy has a plurality of crystal faces and a very high grain boundary resistance, the high grain boundary resistance is derived from the plurality of crystal face structures, and shows a fast response time and a super-high thermistor constant value under thermal activation, which is the first report of the phase-separated MoNi nano-alloy in the temperature sensing field.

[0021] 3、In addition, the phase-separated MoNi x nano-alloy particles prepared by the application show excellent repeatability and stability. The phase-separated MoNi nano-alloy prepared by the application promotes the development of temperature sensors and wearable electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM images of the nickel nano-particles obtained in Example 1; wherein, (a) heat treatment temperature 600 ℃, (b) heat treatment temperature 400 ℃;

[0023] Figure 2 SEM images of the samples obtained in Example 1 and Comparative Example 1; wherein, (a) and (b) are Example 1; (c) and (d) are Comparative Example 1;

[0024] Figure 3 TEM images of the sample of Example 1; wherein, (a) alloy image, (b) diffraction image, (c) high-resolution image;

[0025] Figure 4 EDS and element distribution images of the sample of Example 1; wherein, (a) element distribution image, (b) element content image;

[0026] Figure 5 Variation trends of the resistance and the thermistor constant B value of the sample of Example 1; wherein, (a) variation trend of the resistance with temperature, (b) variation trend of the thermistor constant B value;

[0027] Figure 6 Variation trends of the resistance and the thermistor constant B value of the sample of Comparative Example 1; wherein, (a) variation trend of the resistance with temperature, (b) variation trend of the thermistor constant B value;

[0028] Figure 7 Continuous dynamic response graph of the sample of Example 1 at a heating voltage of 20-100℃; wherein, (a), (b), (c) and (d) are device 1, device 2, device 3 and device 4, respectively.

[0029] Figure 8 Continuous dynamic response graph of the sample of Example 1 at a heating voltage of 20-200℃; wherein, (a) is device 1, and (b) is device 2. DETAILED DESCRIPTION

[0030] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear, specific and understandable, the present application will be further described in detail below in combination with the drawings and examples.

[0031] Example 1

[0032] 1) Using nickel chloride hexahydrate as the nickel source, 2.38 g of the nickel source was dissolved in 100 ml of water at 50 ℃ and stirred until uniform, 0.02 g of sodium hydroxide was dissolved in 50 ml of water and stirred until uniform, then slowly added to the nickel-containing solution, and the solution changed from green to dark green, then stopped adding;

[0033] 2) The above uniform solution was heated to 100 ℃ and stirred for a certain time, then washed to neutral after cooling to room temperature, and dried to obtain a nickel hydroxide precursor;

[0034] 3) The nickel hydroxide precursor was ground into fine powder, then heated to 600 ℃ or 400 ℃ at a heating rate of 5 ℃ / min under a hydrogen argon atmosphere for 120 min, to obtain nickel nanoparticles;

[0035] 4) The obtained nickel nanoparticles were dispersed in water, stirred uniformly, then a certain amount of ammonium molybdate was added and stirred, and the mass ratio of nickel nanoparticles to ammonium molybdate was 1:4;

[0036] 5) The above mixture was transferred to a 50 mL polytetrafluoroethylene hydrothermal kettle, and heated at 120 ℃ for 20 h, then washed after cooling to room temperature, and dried to obtain a molybdenum-doped molybdenum nickel nanoparticle intermediate;

[0037] 6) The product of step 5) was heated to 600 ℃ at a heating rate of 5 ℃ / min under a hydrogen argon atmosphere for 2 h, to obtain phase-separated MoNi x nanoparticle alloy.

[0038] 7) The MoNi x nanoparticle alloy of step 6) was mixed with terpineol, stirred and ground to a viscous state, then brushed on an Al2O3 ceramic tube, welded to a test base and aged for 24 h to reach a stable state for performance testing, and all devices used in the present application were made by this method.

[0039] Comparative Example 1

[0040] The difference between Comparative Example 1 and Example 1 is that the nickel source used is nickel nitrate hexahydrate, with a mass of 2.98 g.

[0041] From Figure 1As can be seen from the above, the nickel nanoparticles in Example 1 are composed of overlapping and aggregated small nanoparticles. The nanoparticle sizes obtained at different temperatures are different because high temperatures cause lattice contraction, resulting in smaller particle sizes. Smaller grains are considered to be beneficial for heat conduction, and the samples used in subsequent tests were all obtained after treatment at 600 °C.

[0042] See Figure 2 Example 1 shows the phase-separated MoNi obtained when nickel chloride hexahydrate was used as the nickel source. x Nanoalloys, which consist of interconnected nanoparticles.

[0043] The sample obtained in Comparative Example 1 using nickel nitrate hexahydrate as the nickel source was a nanorod composed of nanoparticles.

[0044] from Figure 3 As can be seen from Example 1, the phase-separated MoNi x Nano-alloy particles, which have polycrystalline faces and polycrystalline phases.

[0045] Figure 4 The phase-separated MoNi obtained in Example 1 x The elemental distribution diagram of the nano-alloy particles shows that Mo is mainly distributed on the surface.

[0046] The multiphase separated MoNi of the present invention x The nano-alloy has polycrystalline facets and extremely high grain boundary resistance (approximately 700 MΩ, 33% humidity), and exhibits fast response time and ultra-high thermistor constant B value (17058 K at 20~23 ℃, 16800 K at 20~25 ℃), which is the highest sensitivity of nickel-based alloy thermistors to date.

[0047] The thermistor constant (B value) is defined as follows:

[0048]

[0049] Among them, R T R g T1 and T2 are the resistance of the sensor at the standard temperature (20 ℃), the resistance of the sensor at the test temperature, the standard temperature (20 ℃), and the test temperature, respectively.

[0050] from Figure 5 As can be seen from Example 1, the phase-separated MoNi x The nano-alloy particles exhibit good temperature sensitivity, with a B value as high as 17058 K in the range of 20~23 ℃ and as high as 16800 K in the range of 20~25 ℃.

[0051] from Figure 6It can be seen from the temperature sensitivity of the sample obtained in Comparative Example 1, with a B value of 6500 K in the range of 20~70 ℃.

[0052] Therefore, compared with Comparative Example 1, the phase-separated MoNi prepared in Example 1 is superior. x Nano-alloy particles exhibit superior thermodynamic constants. Furthermore, Figure 5 and Figure 6 The B values ​​of the two samples exhibit different trends, which may be related to their different crystal structures. According to the electron insertion / extraction trap model, Figure 6 The medium sample has more defects, which is reflected in its higher resistance value, and the electrons are in deeper traps, so more energy is required to escape the traps. As the temperature rises, more and more electrons escape, reaching a peak at 70 °C.

[0053] Figure 5 and Figure 6 MoNi obtained from two formulations x The different sensitivity B values ​​of the alloys may be due to the different pH values ​​resulting from different raw materials, which is reflected in the different morphologies in their SEM images. Therefore, the different nucleation and growth methods lead to differences in performance.

[0054] The present invention further tests sensors coated with this sensitive material, as shown in Figure 7 and... Figure 8 The continuous dynamic response diagrams of the sample based on Example 1 in the heating voltage range of 20~100℃ and 20~200℃ are shown respectively. Each device was prepared according to the method of Example 1. Multiple devices were prepared and their performance was tested to verify the repeatability of the preparation process and the properties of the sensitive materials involved.

[0055] from Figure 7 As can be seen from Example 1, the phase-separated MoNi x The nano-alloy particles still exhibit good continuity, repeatability, and stability at different humidity levels from 20 to 100 °C (test conditions were 75% relative humidity).

[0056] from Figure 8 As can be seen from Example 1, the phase-separated MoNi x The nano-alloy particles still exhibit good continuity, repeatability, and stability at different humidity levels from 20 to 200 °C (test conditions were 75% relative humidity).

[0057] In this invention, the humidity in the test conditions is controlled by a saturated salt solution.

[0058] In summary, the phase-separated MoNi prepared in Example 1 of this invention... xThe nano-alloy particles show excellent repeatability and stability, and the high resistance value is derived from the high grain boundary resistance caused by the polycrystal face. The application provides a promising nano-alloy design strategy, and particularly promotes the development of wearable temperature sensors.

Claims

1. A method for preparing molybdenum-nickel nanoalloys based on phase separation temperature sensitivity, characterized in that, Includes the following steps: 1) Dissolve nickel chloride hexahydrate, then add sodium hydroxide, heat and stir at 80~120℃ for 30~60 min, wash and dry to obtain nickel hydroxide precursor; wherein the molar concentration ratio of nickel chloride hexahydrate to sodium hydroxide is 10:

1. 2) Grind the nickel hydroxide precursor obtained in step 1), and then heat-treat it at 400~600℃ for 1~4 h in a reducing atmosphere to obtain nickel nanoparticles; 3) Add the nickel nanoparticles obtained in step 2) and ammonium molybdate to water at a mass ratio of 1:4~8 and stir. Then, perform a hydrothermal reaction at 100~160℃ for 12~24 h, wash and dry to obtain molybdenum-doped nickel-molybdenum nanoparticle intermediates. 4) The molybdenum-doped molybdenum-nickel nanoparticle intermediate obtained in step 3) is heat-treated at 400-600℃ for 1-4 hours in a reducing atmosphere to obtain phase-separated MoNi. x The nano-alloy particles have a polycrystalline structure and high grain boundary resistance. The thermistor constant B value is as high as 17058 K in the range of 20~23℃ and as high as 16800 K in the range of 20~25℃.

2. A molybdenum-nickel nanoalloy based on phase separation temperature, characterized in that: It was prepared by the method of claim 1.

3. The application of the phase separation temperature-sensitive molybdenum-nickel nanoalloy as described in claim 2, characterized in that: Used to make temperature sensors.

4. The application as described in claim 3, characterized in that: Used to create temperature sensors when combined with flexible substrates.

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