Preparation method of powdery nano composite thermoelectric material

Abstract

The invention discloses a preparation method of a powdery nano-composite thermoelectric material, which comprises the following steps: (1) putting graphene oxide into deionized water according to a ratio, and carrying out ultrasonic treatment until liquid is in a uniform and transparent state; (2) sequentially adding sodium tartrate, TeO2, KOH and Bi (NO3) 3.5 H2O into the uniform and transparent liquid; (3) adding KBH4 into the solution obtained in the step (2), and then carrying out stirring reaction; (4) transferring the stirred solution obtained in the step (3) into a hydrothermal reaction kettle; (5) after the hydrothermal reaction kettle is naturally cooled to room temperature, taking out a product in the hydrothermal reaction kettle, and washing the product with deionized water until supernate is neutral; then washing the product with absolute ethyl alcohol at least twice; (6) a mixture of the product obtained in the step (5) and absolute ethyl alcohol is put into a centrifugal tube, then the centrifugal tube is put into a high-speed centrifugal machine to be centrifuged, and (7) the centrifuged product is subjected to vacuum drying, and the powdery nano-composite thermoelectric material is obtained after drying is completed. The invention provides a preparation method of a powdery nano composite thermoelectric material, which has the advantages of simple steps, convenience in operation and low cost, and can obtain a thermoelectric material with stable performance and high efficiency.

Description

Technical Field

[0001] The invention relates to a method for preparing a powdered nano composite thermoelectric material, and belongs to the field of thermoelectric materials. Background Art

[0002] At present, the problem of energy shortage is becoming more and more serious, and the discovery of thermoelectric materials has given people hope for solving the problem. As a new type of energy material, thermoelectric materials can realize the direct conversion between thermal energy and electrical energy, so they have received widespread attention. The performance indicators of thermoelectric materials are generally measured by dimensionless merit ZT, which is expressed as follows:

[0003] ZT=S 2 σT / k

[0004] Among them: S is the Seebeck coefficient; σ is the electrical conductivity; k is the thermal conductivity; T is the thermodynamic temperature. It can be seen from the above formula that only materials with high electrical conductivity, high Seebeck coefficient and low thermal conductivity have high ZT values. The Seebeck coefficient, electrical conductivity and thermal conductivity restrict each other and are difficult to regulate independently, so it is difficult to improve the ZT value of the material. The low ZT value of thermoelectric materials is still the main reason restricting its application and promotion. Although the ZT value of Bi2Te3-based alloy thermoelectric materials can reach about 1 near room temperature, there is still room for improvement in its ZT value. After continuous exploration, researchers have found that the ZT value of Bi2Te3-based alloy thermoelectric materials can be improved by reducing the material dimension and preparing composite materials. In recent years, graphene has become a hot research topic due to its excellent electrical conductivity, high carrier mobility and excellent mechanical properties. Therefore, if appropriate methods can be used to prepare graphene / Bi2Te3-based alloy composites, the high electrical conductivity of graphene and the high Seebeck coefficient of Bi2Te3-based alloys can be fully utilized, which will further improve the thermoelectric performance of Bi2Te3. However, the current preparation methods of graphene / Bi2Te3 nanocomposite thermoelectric materials are mainly solution mixing and mechanical mixing. The graphene / Bi2Te3 nanocomposite thermoelectric materials prepared by the above two methods are prone to oxidation of the Bi2Te3 nanostructure in the composite material, thereby affecting the improvement of the thermoelectric performance of the composite material. Summary of the invention

[0005] The present invention successfully prepares a powdered graphene / Bi2Te3 composite thermoelectric material in one step by a hydrothermal in-situ synthesis method. The method can prevent the oxidation of Bi2Te3 nanostructures during the preparation of the composite material, and provides a new method for improving the thermoelectric performance of Bi2Te3.

[0006] Compared with the existing preparation method of powdered thermoelectric materials, the present invention has high preparation efficiency, low cost and simple operation. The preparation method of the powdered nanocomposite thermoelectric material is to solve the technical problem of poor thermoelectric performance of Bi2Te3-based alloys in the prior art.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a powdered nanocomposite thermoelectric material comprises the following steps:

[0009] (1) placing graphene oxide in deionized water at a mass volume ratio of 0.5-5 mg:100 mL, and performing ultrasonic treatment until the liquid is uniform and transparent;

[0010] (2) sodium tartrate, TeO2, KOH and Bi(NO3)3·5H2O are added to the above-mentioned uniform and transparent liquid in sequence, wherein the material ratio of graphene oxide, TeO2 and Bi(NO3)3·5H2O is 0.5-10 mg: 0.1-1 g: 0.2-2 g; at the same time, the concentration of sodium tartrate in the solution is ensured to be 0.1-0.15 mol / L, and the concentration of KOH is ensured to be 0.5-1.5 mol / L;

[0011] (3) adding KBH4 to the solution obtained in step (2) to make the concentration of KBH4 in the solution be 0.25-0.35 mol / L, and then stirring the reaction for 0.3-1 h;

[0012] (4) transferring the stirred solution obtained in step (3) to a hydrothermal reaction kettle and heating at a temperature of 100-200° C. for 5-50 h;

[0013] (5) After the hydrothermal reactor is naturally cooled to room temperature, the product is taken out and washed with deionized water until the supernatant is neutral; then, the product is washed with anhydrous ethanol at least twice;

[0014] (6) placing a mixture of the product obtained in step (5) and anhydrous ethanol into a centrifuge tube, wherein the mass volume ratio of the product to the anhydrous ethanol is 1 g: 5 mL to 30 mL, and then placing the mixture into a high-speed centrifuge for centrifugation at a speed of 1000 to 8000 rpm for 1 to 10 minutes;

[0015] (7) The centrifuged product is vacuum dried at a temperature of 50-150° C. for a drying time of 2-10 h, and a powdered nanocomposite thermoelectric material is obtained after drying.

[0016] Preferably, the mass volume ratio of the above-mentioned graphene oxide to deionized water is preferably 1 mg:100 mL.

[0017] Preferably, the concentration of the sodium tartrate is preferably 0.12 mol / L, and the concentration of KOH is preferably 1 mol / L.

[0018] Preferably, the concentration of the KBH4 is preferably 0.3 mol / L, and the stirring reaction time is preferably 0.5 h.

[0019] Preferably, the temperature of the hydrothermal reaction is preferably 150° C., and the heating time is preferably 24 h.

[0020] Preferably, the centrifugal speed is 5000 rpm and the centrifugal time is 5 minutes.

[0021] Preferably, the vacuum drying temperature is preferably 100° C., and the drying time is preferably 5 h.

[0022] The beneficial effects of the present invention are:

[0023] (1) The preparation steps are simple, the operation is convenient, and the cost is low;

[0024] (2) The prepared powdered nanocomposite thermoelectric material has excellent thermoelectric properties; the thermoelectric figure of merit ZT of the obtained powdered nanocomposite thermoelectric material reaches 1.83 within the measured temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The graphene oxide powder obtained by this method is

[0026] Figure 2 It is the ZT value of the thermoelectric performance of r GO / Bi2Te3 composite materials prepared by hydrothermal method by adding different contents of graphene oxide. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0028] A method for preparing a powdered nanocomposite thermoelectric material comprises the following steps:

[0029] (1) Weigh 1 mg of graphene oxide and put it into 100 mL of deionized water, and perform ultrasonic treatment until the liquid becomes uniform and transparent;

[0030] (2) 0.1 mol / L sodium tartrate, 0.5 g TeO2, 1 mol / L KOH and 0.5 g Bi(NO3)3·5H2O were added to the above homogeneous transparent liquid in sequence;

[0031] (3) adding 0.3 mol / L KBH4 to the solution obtained in step (2), and then stirring the reaction for 0.5 h;

[0032] (4) transferring the stirred solution obtained in step (3) to a hydrothermal reactor and heating at 150° C. for 24 h;

[0033] (5) After the hydrothermal reactor is naturally cooled to room temperature, the product is taken out and washed with deionized water until the supernatant is neutral; then, the product is washed twice with anhydrous ethanol;

[0034] (6) placing a mixture of the product obtained in step (5) and anhydrous ethanol into a centrifuge tube, wherein the mass volume ratio of the product to anhydrous ethanol is 1 g:10 mL, and then placing the mixture into a high-speed centrifuge for centrifugation at a speed of 5000 rpm for 5 minutes;

[0035] (7) The centrifuged product is vacuum dried at a drying temperature of 100° C. for 5 h, and a powdered nanocomposite thermoelectric material is obtained after drying.

[0036] Table 1 Comparison of ZT values ​​of rGO / Bi2Te3 composites prepared by different methods in recent years

[0037]

[0038] The following are the corresponding references for different methods:

[0039] [1]H.Ju,M.Kim,J.Kim.A facile fabrication of n-type Bi2Te 3nanowire / graphene layer-by layer hybrid structures and their improved thermoelectric performance,Chemical Engineering Journal.2015,275:102-112.

[0040] [2]BB Liang, ZJSong, MHWang, LJWang, W.Jiang, Fabrication and thermoelectric properties of graphene / Bi2Te 3composite materials. Journal of Nanomaterials. 2013, (2013): 1-5.

[0041] [3]K.Agarwal,V.Kaushik,D.Varandani,A.Dhar,B.R.Mehta.Nanoscalethermoelectric properties ofBi2Te 3-graphene nanocomposites:conducting atomicforce,scanning thermal and kelvin probe microscopy studies.Journal ofAlloysand Compounds.2016,(681):394-401.

[0042] [4]S.Kumar,S.Singh,P.K.Dhawan,R.R.Yadav,N.Khare.Effect ofgraphenenanofillers on the enhanced thermoelectric properties of Bi2Te 3nanosheets:Elucidating the role of interface in de-coupling the electrical and thermalcharacteristics.Nanotechnology.2018,29(13):135703.

[0043] [5]Y.W.Zhang,H.G.Ma,B.Sun,B.W.Liu,H.Q.Liu,L.J.Kong,B.M.Liu,X.P.Jia,X.Chen.Thermoelectric performance ofgraphene composited BiSbTe bulks by highpressure synthesis.Journal ofAlloys and Compounds.2017,(715):344-348.

[0044] [6]Du Y,Li J,Xu J,et al.Thermoelectric Properties of Reduced GrapheneOxide / Bi2Te3 Nanocomposites[J].Energies,2019,12(12):1-10

[0045] [7]H.Ju,J.Kim.Preparation and structure dependent thermoelectricproperties of nanostructured bulk bismuth telluride with graphene,Journal ofAlloys&Compounds.2016,664:639-647.

[0046] According to Table 1 and Figure 2 As shown, the thermoelectric figure of merit ZT of the powdered nanocomposite thermoelectric material obtained by the present invention reaches 1.83 within the measured temperature range, which is far higher than the ZT value of the rGO / Bi2Te3 composite material obtained by the prior art.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a powdered nanocomposite thermoelectric material, characterized in that: The following steps are involved: (1) placing graphene oxide in deionized water at a mass volume ratio of 0.5-5 mg:100 mL, and performing ultrasonic treatment until the liquid is uniform and transparent; (2) sodium tartrate, TeO2, KOH and Bi(NO3)3·5H2O are added to the above-mentioned uniform and transparent liquid in sequence, wherein the material ratio of graphene oxide, TeO2 and Bi(NO3)3·5H2O is 0.5-10 mg: 0.1-1 g: 0.2-2 g; at the same time, the concentration of sodium tartrate in the solution is ensured to be 0.1-0.15 mol / L, and the concentration of KOH is ensured to be 0.5-1.5 mol / L; (3) adding KBH4 to the solution obtained in step (2) to make the concentration of KBH4 in the solution be 0.25-0.35 mol / L, and then stirring the reaction for 0.3-1 h; (4) transferring the stirred solution obtained in step (3) to a hydrothermal reaction kettle and heating at a temperature of 100-200° C. for 5-50 h; (5) After the hydrothermal reactor is naturally cooled to room temperature, the product is taken out and washed with deionized water until the supernatant is neutral; then, the product is washed with anhydrous ethanol at least twice; (6) placing a mixture of the product obtained in step (5) and anhydrous ethanol into a centrifuge tube, wherein the mass volume ratio of the product to the anhydrous ethanol is 1 g: 5 mL to 30 mL, and then placing the mixture into a high-speed centrifuge for centrifugation at a speed of 1000 to 8000 rpm for 1 to 10 minutes; (7) The centrifuged product is vacuum dried at a temperature of 50-150° C. for a drying time of 2-10 h, and a powdered nanocomposite thermoelectric material is obtained after drying.

2. The method for preparing a powdered nanocomposite thermoelectric material according to claim 1, wherein the mass volume ratio of graphene oxide to deionized water is preferably 1 mg:100 mL.

3. The method for preparing a powdered nanocomposite thermoelectric material according to claim 1 or 2, wherein the concentration of sodium tartrate is preferably 0.12 mol / L, and the concentration of KOH is preferably 1 mol / L.

4. A method for preparing a powdered nanocomposite thermoelectric material according to any of the above claims, wherein the concentration of KBH4 is preferably 0.3 mol / L, and the stirring reaction time is preferably 0.5 h.

5. A method for preparing a powdered nanocomposite thermoelectric material according to any of the above claims, wherein the temperature of the hydrothermal reaction is preferably 150°C and the heating time is preferably 24 hours.

6. A method for preparing a powdered nanocomposite thermoelectric material according to any of the above claims, wherein the centrifugal speed is preferably 5000 rpm and the centrifugal time is preferably 5 minutes.

7. A method for preparing a powdered nanocomposite thermoelectric material according to any of the above claims, wherein the vacuum drying temperature is preferably 100°C and the drying time is preferably 5 hours.

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