阅读说明：本技术 一种石墨复合的SnSe2热电材料的制备方法 (Graphite composite SnSe2Method for preparing thermoelectric material ) 是由 宋吉明 梁小龙 周宁宁 何文涛 李周 于 2021-08-24 设计创作，主要内容包括：本发明公开了一种SnSe-(2)纳米片复合膨胀石墨(G)热电材料的制备方法,属于能源转换技术领域。首先采用油相合成方法制备出SnSe-(2)纳米粒子,随后按一定质量比称取适量的SnSe-(2)纳米粒子和膨胀石墨,研磨充分且混合均匀,得到SnSe-(2)-X wt%G(X为复合G的质量比)前驱体粉末,然后将前驱体粉末在合适的压力和温度下进行退火、热压烧结得到SnSe-(2)-X wt%G块体热电材料。本发明制备的SnSe-(2)-X wt%G热电材料的电导率为390～2450 S/m,热导率为0.34～0.55 Wm～(-)～(1)K～(-1)。本发明制备热电材料具有烧结温度低,制备周期短,操作简便,对设备要求低等优点,实现了SnSe-(2)基热电材料热电最优值显著提高的制备方法。(The invention discloses SnSe 2 A preparation method of a nano-sheet composite expanded graphite (G) thermoelectric material belongs to the technical field of energy conversion. Firstly, preparing SnSe by adopting an oil phase synthesis method 2 Nano particles, then weighing appropriate SnSe according to a certain mass ratio 2 Grinding the nano particles and the expanded graphite fully and mixing uniformly to obtain SnSe 2 X wt% G (X is the mass ratio of composite G) precursor powder, and then annealing and hot-pressing sintering are carried out on the precursor powder at proper pressure and temperature to obtain SnSe 2 -X wt% G bulk thermoelectric material. SnSe prepared by the invention 2 The electrical conductivity of the-X wt% G thermoelectric material is 390 to 2450S/m, and the thermal conductivity is 0.34 to 0.55 Wm ‑ 1 K ‑1 . The thermoelectric material prepared by the invention has the advantages of low sintering temperature, short preparation period, simple and convenient operation, low requirement on equipment and the like, and realizes the SnSe 2 The preparation method has the advantage that the thermoelectric optimum value of the base thermoelectric material is obviously improved.)

1. Graphite composite SnSe₂The preparation method of the thermoelectric material comprises the following concrete implementation steps:

（1）SnSe₂preparing a nano sheet: preparation of an anion precursor: adding 0.1-0.3 g of selenium powder into a 50 ml three-neck flask, adding 1-3 ml of oleylamine and 1-3 ml of n-dodecyl mercaptan, continuously stirring by using a magnetic rotor, and heating to 30-50 ℃; preparing a cation solution: 0.2-0.4 g SnCl is added into a 100 ml three-neck flask in turn₂·2H₂O, 1-5 ml of oleylamine, 1-5 ml of oleic acid and 10-30 ml of octadecene are stirred by a magnetic rotor, vacuumizing and nitrogen circulation is performed for 2-5 times, stirring is performed for 20-30 min at room temperature in a nitrogen atmosphere, then the temperature is increased to 120-140 ℃, heat preservation is performed for 20-30 min, and after the heat preservation is finished, the temperature is continuously increased to 160-200 ℃ and kept for 5-10 min; mixing the anion and cation solutions: quickly injecting the anion precursor into a cation solution, keeping the mixed solution at 180 ℃ for 40-60 min, adding a sample which is completely reacted into a certain proportion of methylbenzene and isopropanol, washing for 2-3 times at a high rotating speed, and washing for 2-3 times at a slightly low rotating speed to obtain a sample, and storing the sample in a vacuum drying oven;

（2）SnSe₂compounding nanosheets and G: weighing G with different masses and SnSe synthesized in the step (1)₂Mixing the nano sheets, and fully grinding the nano sheets in a glove box to obtain uniformly mixed SnSe₂-X wt% G composite powder;

(3) the pellet is prepared by solid-phase reaction, high-frequency furnace heating and hot-pressing sintering, namely the composite powder is heated at the speed of 5-15 ℃/min, the solid-phase reaction is carried out for 1-5 h in the weak reducing atmosphere at the temperature of 400-500 ℃, and the SnSe after the reaction is obtained₂Filling the-X wt% G powder into a graphite grinding tool, sealing the graphite grinding tool with a carbon rod from top to bottom, wrapping the graphite grinding tool with carbon paper, and carrying out hot pressing for 10-30 min under the axial pressure of 35-65 MPa and the temperature of 450-550 ℃ to obtain SnSe with high density and high purity₂-X wt% G bulk thermoelectric material;

(4) detecting the SnSe obtained by the preparation method₂The @ X wt% G composite thermoelectric material has the electric conductivity and the thermal conductivity of 390-2450S/m and the thermal conductivity of 0.34-0.55 Wm^-1K^-1。

Technical Field

The invention relates to a novel thermoelectric material, namely graphite compounded SnSe₂A preparation method of thermoelectric material belongs to the technical field of energy conversion.

Background

The thermoelectric material is a material capable of realizing interconversion of heat energy and electric energy, and can be used for thermoelectric refrigeration and thermoelectric power generation. At present, thermoelectric devices assembled by utilizing P-type and N-type semiconductor thermoelectric materials have the advantages of high stability, small volume, long service life, environmental protection and the like, so that the thermoelectric devices have wide application prospects in the fields of sensors, refrigeration, waste heat recycling, aerospace and the like. However, the performance of thermoelectric materials is usually measured by the thermoelectric figure of merit, ZT = S²Sigma T/k, wherein S is Seebeck coefficient, sigma is electric conductivity, T is absolute temperature, and k is thermal conductivity. The power factor of the material is PF = S²And sigma. Therefore, excellent thermoelectric materials require a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity at the same time. Harmonizing the relationship between the parameters is important for improving the ZT value of the material and realizing the conversion efficiency of the thermoelectric material.

SnSe₂The material is a semiconductor material with cheap and nontoxic raw materials, has good photoelectric property, energy storage property and thermoelectric conversion property, has certain flexibility, and has wide application prospect in the fields of photoelectric detectors, flexible all-solid-state supercapacitors and thermoelectric conversion. Patent (patent CN109607495A, a solution method for preparing polycrystalline SnSe₂Method of material) preparation of SnSe by solution method₂The process is complex and the period is long. Wu et al doped SnSe with Cl element₂In the method, selenium atoms are replaced to play a role of a donor center, so that the carrier concentration is increased by 2 orders of magnitude to improve the conductivity, but the raw materials are expensive and have certain toxicity (ACS Appl. Energy Mater.2019, 2, 12, 8481-8490). Currently, SnSe is prepared by an oil phase process₂The nano material is not reported, and the method is simple, quick, environment-friendly and low in cost. Layered SnSe₂Base materials are receiving a great deal of attention in the thermoelectric field due to their inherently low thermal conductivity and high seebeck,the low conductivity is the bottleneck of excellent thermoelectric material, and the low-cost expanded graphite can extract SnSe₂Of SnSe in the present application₂The nano-sheet is taken as a substrate, and the composite technology is utilized to prepare the nano-film on SnSe₂The medium composite expanded Graphite (Graphite is abbreviated as G) improves the thermoelectric performance of the sample. Firstly, preparing precursor SnSe of thermoelectric material by adopting an oil phase method₂Nanosheet, G is added, and the high-density block thermoelectric material SnSe is prepared by combining high-frequency furnace heating and hot-pressing sintering processes₂G, samples of different G composition ratios are prepared, the samples being abbreviated to SnSe according to the content of G₂X wt% G, X wt% representing the mass fraction.

The invention obtains SnSe by an oil phase synthesis method₂Nanosheet and G mixed to prepare SnSe₂A composite material. By characterizing and testing various aspects of hot-pressed tablets, applicants discovered that SnSe₂The sample performance of 3 wt% is best, and in order to clearly understand the structural characteristics of the composite material, the sample after hot pressing is subjected to SEM, XRD, TEM and other characterization. The preparation method is simple, the method is easy to operate, and N-type SnSe can be quickly obtained by the method₂The thermoelectric property of the composite material is about 0.26 at 723K, and the composite material is SnSe₂The sample is 2 times of the pure sample, and the thermoelectric property of the material is obviously improved by the graphite with low price.

Disclosure of Invention

The invention relates to graphite compounded SnSe₂A method for preparing thermoelectric material. The method has the advantages of simple preparation process, low raw material price, good repeatability and easy mass synthesis. The nano composite material prepared by the invention has higher electrical conductivity, higher Seebeck coefficient and lower thermal conductivity, shows good thermoelectric property, and is a potential thermoelectric conversion material. Meanwhile, the method improves the thermoelectric property of the matrix material by compounding the expanded graphite into the original matrix, and provides a good example for the preparation of the composite thermoelectric material.

The invention is realized by the following technical scheme:

graphite composite SnSe₂The preparation method of the thermoelectric material is characterized in that SnSe is used as a raw material₂Nanosheets and G as starting materials. According to the general formula SnSe₂SnSe synthesized by an oil phase method and weighed according to the mass ratio of-X wt% G₂Mixing the nanosheets and the G in an agate mortar, and fully grinding the nanosheets and the G in a glove box to obtain a uniformly mixed sample; then putting the mixture into an alumina crucible, putting the alumina crucible into a tubular furnace, vacuumizing the tubular furnace, treating the mixture for 1 to 5 hours at 400 to 500 ℃ in weak reduction mixed gas, and cooling the mixture to room temperature to obtain SnSe₂Nano sheets and G are used as raw material composite powder; then the obtained product is put into a graphite grinding tool, and the SnSe with good crystallinity and high purity is prepared by heating in a high-frequency furnace and hot-pressing sintering₂-X wt% G bulk thermoelectric material.

Further, the synthesis method comprises the following specific steps:

（1）SnSe₂preparing a nano sheet: SnSe₂The nanosheets are prepared by an oil phase method. Preparation of an anion precursor: adding 0.1-0.3 g of selenium powder into a 50 ml three-neck flask, adding 1-3 ml of oleylamine and 1-3 ml of n-dodecyl mercaptan, continuously stirring by using a magnetic rotor, and heating to 30-50 ℃. Preparing a cation solution: 0.2-0.4 g SnCl is added into a 100 ml three-neck flask in turn₂·2H₂O, 1-5 ml of oleylamine, 1-5 ml of oleic acid and 10-30 ml of octadecene, and stirring by using a magnetic rotor. And (3) performing vacuum pumping-nitrogen circulation for 2-5 times, stirring at room temperature for 20-30 min under the nitrogen atmosphere, then heating to 120-140 ℃, preserving heat for 20-30 min, and continuing to heat to 160-200 ℃ after heat preservation is finished and keeping for 5-10 min. Mixing the anion and cation solutions: and (3) quickly injecting the anion precursor into a cation solution, and keeping the mixed solution at 180 ℃ for 40-60 min. And adding toluene and isopropanol in a certain proportion into the sample which is completely reacted in a centrifugal tube, wherein the toluene is used as a dispersing agent, the isopropanol is used as a precipitating agent, washing is carried out for 2-3 times at a high rotating speed, and washing is carried out for 2-3 times at a slightly low rotating speed to obtain a sample, and the sample is stored in a vacuum drying oven.

（2）SnSe₂Compounding nanosheets and G: weighing G and synthesized SnSe with different masses₂Mixing the nano sheets, and fully grinding the nano sheets in a glove box to obtain uniformly mixed SnSe₂-X wt% G composite powder.

(3) Preparing the pellets by solid-phase reaction, high-frequency furnace heating and hot-pressing sintering, namely heating the mixed powder at the speed of 5-15 ℃/min, carrying out solid-phase reaction for 1-5 h in a weak reducing atmosphere at the temperature of 400-500 ℃, and carrying out the SnSe after the reaction₂Filling the-X wt% G powder into a graphite grinding tool, sealing the graphite grinding tool with a carbon rod from top to bottom, wrapping the graphite grinding tool with carbon paper, and carrying out hot pressing for 10-30 min under the axial pressure of 35-65 MPa and the temperature of 450-550 ℃ to obtain SnSe with high density and high purity₂-X wt% G bulk thermoelectric material.

(4) Detecting the SnSe obtained by the preparation method₂The @ X wt% G composite thermoelectric material has the electric conductivity and the thermal conductivity of 390-2450S/m and the thermal conductivity of 0.34-0.55 Wm^-1K^-1。

FIG. 1 shows SnSe synthesized by oil phase method₂Nanosheet Scanning Electron Microscope (SEM)

FIG. 2 shows the resulting SnSe₂Nanosheet and SnSe₂-3 wt% G powder, SnSe₂X-ray diffraction Pattern (XRD) of 5 wt% G powder sample

FIG. 3 is SnSe of the resulting hot pressed sample₂-3 wt% G high power transmission electron microscopy (HRTEM)

FIG. 4 is a graph of conductance data of the obtained thermoelectric material at different temperatures

FIG. 5 shows thermoelectric figure of merit (ZT) of the obtained thermoelectric material at different temperatures

The specific implementation mode is as follows:

the invention is illustrated in detail below with reference to the examples:

example 1:

SnSe₂the preparation of the nano-sheet comprises the following specific preparation process

(1) Preparation of an anion precursor: a50 ml three-necked flask was charged with 0.2 g selenium powder and then 2 ml oleylamine and 2 ml n-dodecyl mercaptan were added and heated to 40 ℃ with constant stirring using a magnetic rotor and injected into the cationic solution under nitrogen.

(2) Preparing a cation solution: 0.25 g of SnCl was added to a 100 ml three-necked flask₂·2H₂O, 3 ml oleylamine, 3 ml oleic acid and 20 ml octadecene and stirring with a magnetic rotorAnd (4) stirring. And (3) performing vacuum pumping-nitrogen gas circulation for 3 times, stirring at room temperature for 23 min under the nitrogen atmosphere, then heating to 130 ℃, preserving heat for 30 min, and continuing to heat to 180 ℃ after heat preservation is finished and keeping for 5 min.

(3) And (3) quickly injecting the anion precursor in the step (1) into the step (2), and keeping the mixed solution at 180 ℃ for 45 min. Adding a sample which is completely reacted into a centrifugal tube, adding a certain proportion of methylbenzene and isopropanol, using the methylbenzene as a dispersing agent, using the isopropanol as a precipitating agent, washing for 3 times at a high rotating speed, washing for 3 times at a slightly low rotating speed, and drying the sample in vacuum for facilitating subsequent characterization and test to obtain the SnSe₂Nanosheets.

Example 2: x = 3 wt% G composite SnSe₂The preparation of the thermoelectric material comprises the following specific preparation process

(1) Solid-phase reaction: x = 3 wt%, according to SnSe₂Weighing 6G of SnSe according to the mass ratio of the nanosheets to the G₂And mixing the nanosheets and 0.18 g G in an agate mortar, and fully grinding in a glove box to obtain a uniformly mixed sample. Then it was charged into an alumina crucible at 95% Ar +5% H₂In the mixed gas, the mixture is subjected to solid phase reaction for 2 hours at 450 ℃ to obtain G composite SnSe₂Powder, i.e. SnSe₂-3 wt% G thermoelectric material feedstock.

(2) The high-frequency furnace heating and hot-pressing sintering process comprises the following steps: SnSe₂Charging-3 wt% G thermoelectric material raw material into a graphite grinding tool with inner diameter of 13 mm, sealing with carbon rod from top to bottom and wrapping with carbon paper, hot-pressing at 500 deg.C under axial pressure of 45 MPa for 20 min, cooling, releasing pressure, closing hot-pressing instrument, and naturally cooling to obtain SnSe₂-3 wt% G thermoelectric material.

Example 3: x = 5 wt% graphite compounded SnSe₂The preparation of the thermoelectric material comprises the following specific preparation process

(1) Solid-phase reaction: x = 5%, according to SnSe₂Weighing 6G of SnSe according to the mass ratio of the nanosheets to the G₂And mixing the nanosheets and 0.30 g G in an agate mortar, and fully grinding in a glove box to obtain a uniformly mixed sample. Then the mixture is put into an alumina crucible, and the content of the mixture is 95 percent Ar+5% H₂In the mixed gas, the mixture is subjected to solid phase reaction for 2 hours at 450 ℃ to obtain G composite SnSe₂Powder, i.e. SnSe₂-5 wt% G thermoelectric material feedstock.

(2) The high-frequency furnace heating and hot-pressing sintering process comprises the following steps: SnSe obtained in the step (1)₂Filling 5 wt% of G powder into a graphite grinding tool with the inner diameter of 13 mm, sealing the upper part and the lower part by using a carbon rod, wrapping the upper part and the lower part by using carbon paper, carrying out hot pressing for 20 min in an environment with axial pressure of 45 MPa and the temperature of 500 ℃, then starting to cool, relieve pressure and close a hot pressing instrument to naturally cool a sample to obtain G composite SnSe₂Precursor powder, i.e. SnSe₂-5 wt% G thermoelectric material.

Example 4: graphite composite SnSe₂Thermoelectric performance test of thermoelectric material

The samples of example 3 were tested for thermal and electrical conductivity, and thermal conductivity was measured by a Netzsch LFA-467 laser thermal conductivity meter (Germany speed-resistant Co.); and the conductivity is obtained by measuring related parameters on a German LSR-3 Seebeck coefficient/resistance tester and calculating.

FIG. 1 is an SEM image of the resulting sample of example 1, and it can be seen that the sample is in the form of nanoplatelets; FIG. 2 shows SnSe₂Nanosheet and SnSe₂-3 wt% G powder, SnSe₂XRD pattern of 5 wt% G powder sample, from which it is clear that the phase predominantly present in the sample is SnSe₂(PDF # 89-2939), and a characteristic peak of G is also present in the sample in which 3 wt% G and 5 wt% G are combined, and the intensity of the peak is significantly enhanced with an increase in the amount of G combined. FIG. 3 is SnSe₂HRTEM image of-3 wt% G bulk thermoelectric material, from which it is evident that SnSe₂The black region is G. FIG. 4 is a graph of conductance data of the obtained thermoelectric material at different temperatures, wherein the conductance gradually increases with the increase of the temperature, and the conductance of a sample with 3 wt% G composite is 2450S/m at a temperature of 723K. FIG. 5 shows thermoelectric figure of merit (ZT) of the obtained thermoelectric material at different temperatures, and a sample SnSe at 723K₂Thermoelectric figure of merit of 0.26, specific undoped SnSe, for 3 wt% G₂The sample was increased by a factor of 2.