阅读说明：本技术 一种原位生成的核壳结构热电材料及其制备方法 (In-situ generated core-shell structure thermoelectric material and preparation method thereof ) 是由 林建平 谢可 胡亚辉 张颖 郑中华 于 2020-07-27 设计创作，主要内容包括：本发明涉及一种原位生成的核壳结构热电材料及其制备方法,涉及能量转换材料技术领域。该原位生成的核壳结构热电材料是基体材料经热处理后由许多核壳结构小颗粒构成的块体材料,核壳结构小颗粒包括内核和依附在内核表面的原位生成的外壳,所述外壳可为单质元素,也可是多种单质元素共存。本发明还涉及上述原位生成的核壳结构热电材料的制备方法,必选步骤包括粉碎、热处理、合成块体,可选步骤包括置换反应,后续热处理。相对于非核壳结构热电材料,本发明的一种原位生成的核壳结构热电材料可显著增强热电材料的声子散射,降低热电材料的导热系数,提高热电性能,从而提高热电材料能量转换效率。(The invention relates to an in-situ generated core-shell structure thermoelectric material and a preparation method thereof, relating to the technical field of energy conversion materials. The in-situ generated core-shell structure thermoelectric material is a block material formed by a plurality of core-shell structure small particles after a base material is subjected to heat treatment, the core-shell structure small particles comprise an inner core and an in-situ generated shell attached to the surface of the inner core, and the shell can be a simple substance element or a plurality of simple substance elements. The invention also relates to a preparation method of the in-situ generated core-shell structure thermoelectric material, which comprises the following optional steps of crushing, heat treatment and block synthesis, and the optional steps comprise replacement reaction and subsequent heat treatment. Compared with a thermoelectric material with a non-core-shell structure, the thermoelectric material with the core-shell structure generated in situ can obviously enhance phonon scattering of the thermoelectric material, reduce the heat conductivity coefficient of the thermoelectric material and improve the thermoelectric performance, thereby improving the energy conversion efficiency of the thermoelectric material.)

1. The in-situ generated core-shell structure thermoelectric material is characterized in that the in-situ generated core-shell structure thermoelectric material is a block material formed by a plurality of core-shell structure small particles after a base material is subjected to heat treatment, and the core-shell structure small particles comprise an inner core and an in-situ generated shell attached to the surface of the inner core.

2. The in-situ generated core-shell thermoelectric material as claimed in claim 1, wherein the matrix material is Zn₄Sb₃、Cu₂One of Se.

3. The in-situ generated core-shell structure thermoelectric material as claimed in claim 1, wherein the particle size of the matrix material powder is 1nm-1 mm.

4. The in-situ generated core-shell thermoelectric material as claimed in claim 1, wherein the core material is a base material with off-stoichiometric ratio in Zn₄Sb₃In the thermoelectric material as the base material, the core material is Zn deviating from the stoichiometric ratio after the precipitation of Zn_4-xSb₃(0<x<0.07) or Zn_4-xSb₃And a mixture of ZnSb; in Cu₂In the thermoelectric material with Se as a matrix material, the core material is Cu which deviates from the stoichiometric ratio after Cu is precipitated_2-ySe(0<y<0.4) or Cu_{2- y}Se、Cu₃Se₂And a mixture of CuSe.

5. The in-situ generated core-shell thermoelectric material as claimed in claim 1, wherein the shell material is a simple substance phase precipitated from the matrix material after heat treatment, and is in Zn₄Sb₃In the thermoelectric material as the matrix material, the shell material is Zn₄Sb₃After heat treatment of the base material, from Zn₄Sb₃Zn simple substance separated out from the matrix material; in Cu₂In the Se medium base material, the shell material is Cu₂Se base material is heat treated from Cu₂Cu simple substance precipitated from Se matrix material.

6. The in-situ generated core-shell structure thermoelectric material as claimed in claim 5, wherein the shell layer thickness of the outer shell is 5nm to 1 mm.

7. The in-situ generated core-shell structure thermoelectric material as claimed in claim 5, wherein the shell can be replaced by metal with abundant content on earth or being environment-friendly or capable of effectively improving thermoelectric performance by using replacement reaction to obtain a replaced shell; in Zn/Zn_4-xSb₃In the thermoelectric material with the core-shell structure, the shell Zn is replaced into one of elementary substances Fe, Sn, Cu, Hg and Ag which are actively arranged behind Zn; in Cu/Cu_2-yIn the Se core-shell structure thermoelectric material, the shell Cu is replaced into one of simple substances Hg and Ag which are actively arranged behind Cu.

8. The in-situ generated core-shell thermoelectric material according to claim 7, wherein the displacement shell is one of pure phase after displacement or coexisting phase of in-situ generated shell and displacement shell in Zn/Zn_4-xSb₃In the thermoelectric material with the core-shell structure, the replacement amount of a Cu simple substance is regulated and controlled to form Cu/Zn_4-xSb₃Thermoelectric material with core-shell structure or Cu/Zn formation_4-xSb₃One of core-shell structure thermoelectric materials; in Cu/Cu_2-yIn the Se nuclear shell structure thermoelectric material, the replacement amount of the Ag simple substance is regulated and controlled to form Ag/Cu_2-ySe core-shell structure thermoelectric material or Ag/Cu_2-ySe core-shell structure thermoelectric material.

9. The preparation method of the in-situ generated core-shell structure thermoelectric material according to any one of claims 1 to 8, characterized by comprising the following steps:

s1, grinding the base material into powder in a grinding mode;

s2, carrying out heat treatment on the powder in the step S1, and precipitating a shell metal simple substance;

s3, synthesizing the powder subjected to the heat treatment in the step S2 into a block material to obtain the thermoelectric material with the core-shell structure.

10. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S1, the grinding manner is one of agate grinding bowl grinding, ball milling, high energy ball milling and turbo type grinding.

11. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S1, the grinding is performed under an inert atmosphere of nitrogen or argon or in air.

12. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S1, the ground powder is sieved by a screen, the particle size of the powder is 100-800 meshes, and the powder is preferably spherical, or ball milling or high energy ball milling is adopted to obtain micron-sized and nano-sized particles.

13. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S2, the atmosphere condition of the powder heat treatment is vacuum, inert gas nitrogen or argon.

14. The method of claim 9, wherein in step S2, Zn is added to the thermoelectric material with core-shell structure₄Sb₃The heat treatment temperature of the matrix powder is selected within the range of 100-300 ℃, the preferred temperature range is 180-230 ℃, and Zn is in the temperature range₄Sb₃The speed of Zn precipitation of the matrix is fastest; for Cu₂The heat treatment temperature of the Se matrix powder is selected to be within the range of 100-400 ℃, the preferred temperature is within the range of 100-230 ℃, and in the temperature range, Cu is added₂The Se matrix precipitates Cu at the highest speed.

15. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S2, the heat treatment time of the powder is 0.5H to 72H.

16. The method for preparing an in-situ generated core-shell thermoelectric material according to claim 9, wherein in step S2, an optional step is added, in which the powder after heat treatment is subjected to a displacement reaction, so that the shell thereof becomes a simple substance phase of other elements or a coexisting phase of the shell and the displaced shell generated in situ; preference is given to Zn/Zn after heat treatment_4-xSb₃Core shell powder immersed in CuSO₄In the solution, the replacement of Zn by Cu is realized to form Cu/Zn_4-xSb₃Thermoelectric material with core-shell structure or Cu/Zn formation_4-xSb₃A core-shell structure thermoelectric material; preferably Cu/Cu after heat treatment_2-ySe core-shell powder immersed in Ag₂SO₄In the solution, the replacement of Ag for Cu is realized to form Ag/Cu_2-ySe core-shell structure thermoelectric material or Ag/Cu_2-ySe core-shell structure thermoelectric material.

17. The method of claim 9, wherein in step S3, the powder synthesis method is one of hot pressing sintering, plasma activated sintering, spark plasma sintering or low temperature cold pressing sintering.

18. The method for preparing an in-situ generated core-shell thermoelectric material as claimed in claim 9, wherein in step S3, the sintering temperature of the powder synthesized block is 100 ℃ to 760 ℃; for Zn/Zn_4-xSb₃The sintering temperature of the core-shell powder is 100-760 ℃, and the preferred sintering temperature is 180-230 ℃; for Cu/Cu_2-yThe Se nuclear shell powder is sintered at 100-600 deg.c, preferably 100-230 deg.c.

19. The method of claim 9, further comprising an optional step of repeating the step S3 of preparing the core-shell thermoelectric material in which the block is finally obtainedCarrying out heat treatment, and further obtaining a nano precipitated phase different from the matrix material in the inner core; preference is given to bulk Zn/Zn after sintering_4-xSb₃In the thermoelectric material with the core-shell structure, bulk Zn/Zn is added_4-xSb₃After the thermoelectric material with the core-shell structure is subjected to heat treatment again at 180-230 ℃, part of ZnSb nano-phase is separated out from the core; preferably bulk Cu/Cu after sintering_2-yIn the thermoelectric material with Se nuclear shell structure, bulk Cu/Cu is added_2-yAfter the Se nuclear shell structure thermoelectric material is subjected to heat treatment again at the temperature of between 100 and 230 ℃, part of Cu is separated out from the core₃Se₂Nanophase or CuSe nanophase or Cu₃Se₂And a CuSe nanophase.

Technical Field

The invention relates to the technical field of energy conversion materials, in particular to an in-situ generated core-shell structure thermoelectric material and a preparation method thereof.

Background

In conventional energy consumption processes, up to 60% of the energy is converted to heat, a large amount of which is wasted in the form of waste heat. This waste not only causes greenhouse effect but also causes serious environmental pollution problems. The thermoelectric material can realize the direct interconversion of heat energy and electric energy, and realize the effective utilization of waste heat. The thermoelectric device does not need moving parts, has reliable performance, long service life, easy precise control and no pollution, and is widely applied to the aspects of aerospace, military, life, industry and the like.

Currently, thermoelectric performance of thermoelectric materials is not high enough, which results in low energy conversion efficiency of thermoelectric materials. The core-shell structure reduces the thermal conductivity by increasing the interface, and is one of effective methods for improving the thermoelectric performance of the material. The invention provides an in-situ generated core-shell structure thermoelectric material and a preparation method thereof, which effectively scatter phonons through a core-shell structure, reduce thermal conductivity and improve thermoelectric performance.

Disclosure of Invention

The invention aims to provide an in-situ generated core-shell structure thermoelectric material and a preparation method thereof, which can effectively reduce the heat conductivity coefficient, optimize the thermoelectric performance and improve the energy conversion efficiency.

The technical problem to be solved by the invention is realized by adopting the following technical scheme.

The invention provides an in-situ generated core-shell structure thermoelectric material and a preparation method thereof, wherein the in-situ generated core-shell structure thermoelectric material is a block material formed by a plurality of core-shell structure small particles after a base material is subjected to heat treatment, and the core-shell structure small particles comprise an inner core and an in-situ generated shell attached to the surface of the inner core; wherein the matrix material is Zn₄Sb₃Or Cu₂One of Se; the core material is a base material deviating from the stoichiometric ratio. In Zn₄Sb₃In the matrix material, the core material is separated from the stoichiometric ratio after Zn is separated outZn_4-xSb₃(ii) a In Cu₂In the Se matrix, the core material is Cu which deviates from the stoichiometric ratio after Cu is precipitated_2-ySe; the shell material is a simple substance phase precipitated from a base material after heat treatment. For example, in Zn₄Sb₃In the matrix material, the shell material is Zn₄Sb₃After the base material is subjected to heat treatment, a Zn elementary substance is separated out from the base material; in Cu₂In the Se matrix material, the shell material is Cu₂After the Se base material is subjected to heat treatment, the base material is separated out of a Cu simple substance.

Further, the particle size of the matrix material powder is 1nm-1 mm.

Further, the shell layer thickness of the shell is 5nm-1 mm.

Further, the shell can be replaced by metal which is abundant in the earth or is environment-friendly or can effectively improve thermoelectric performance by utilizing a replacement reaction. In Zn/Zn_4-xSb₃In the thermoelectric material with the core-shell structure, shell Zn can be replaced by elementary substances with activity such as Fe, Sn, Cu, Hg, Ag and the like arranged behind Zn; in Cu/Cu_2-yIn the Se core-shell structure thermoelectric material, shell Cu can be replaced by elementary substances with Hg, Ag and other activities arranged behind Cu;

further, the displacement shell may be a pure phase after displacement, or may be a coexisting phase of the shell and the displacement shell generated in situ. In Zn/Zn_4-xSb₃In the thermoelectric material with the core-shell structure, Cu/Zn can be formed by regulating and controlling the replacement amount of a Cu simple substance_4-xSb₃Thermoelectric materials of core-shell structure, Cu/Zn can also be formed_4-xSb₃A core-shell structure thermoelectric material; in Cu/Cu_2-yIn the Se nuclear shell structure thermoelectric material, Ag/Cu can be formed by regulating and controlling the replacement amount of Ag simple substance_2-ySe core-shell structure thermoelectric material can also form Ag/Cu_2-yA Se core-shell structure thermoelectric material;

the invention provides a preparation method of the in-situ generated core-shell structure thermoelectric material, which is characterized by comprising the following steps of:

s1, grinding the base material into powder in a grinding mode;

s2, carrying out heat treatment on the powder in the step S1, and precipitating a shell metal simple substance;

s3, synthesizing the powder subjected to the heat treatment in the step S2 into a block material to obtain the thermoelectric material with the core-shell structure;

further, in step S1, the grinding method is one of grinding using an agate bowl, ball milling, high energy ball milling, and turbo type milling.

Further, in step S1, the milling is performed under an inert atmosphere of nitrogen or argon or in air.

Further, in step S1, the powder after grinding is sieved by a screen, the particle size of the powder is 100-800 mesh, and the shape of the powder is preferably spherical, or a ball milling or high energy ball milling method is adopted to obtain micron and nanometer level particles.

Further, in step S2, the atmosphere conditions for the powder heat treatment are vacuum, inert gas nitrogen or argon.

Further, in step S2, Zn is treated₄Sb₃The heat treatment temperature of the matrix powder is selected within the range of 100-300 ℃, the preferred temperature range is 180-230 ℃, and Zn is in the temperature range₄Sb₃The speed of Zn precipitation of the matrix is fastest; for Cu₂The heat treatment temperature of the Se matrix powder is selected to be within the range of 100-400 ℃, the preferred temperature is within the range of 100-230 ℃, and in the temperature range, Cu is added₂The Se matrix precipitates Cu at the highest speed.

Further, in step S2, the powder heat treatment time is 0.5H to 72H.

Further, in step S2, an optional step is added, in which the powder after heat treatment is subjected to a displacement reaction, so that the shell of the powder becomes a simple substance phase of another element or a coexisting phase of the shell generated in situ and the displaced shell; preference is given to Zn/Zn after heat treatment_4-xSb₃Core shell powder immersed in CuSO₄In the solution, the replacement of Zn by Cu is realized to form Cu/Zn_4-xSb₃Thermoelectric material with core-shell structure or Cu/Zn formation_4-xSb₃A core-shell structure thermoelectric material;preferably Cu/Cu after heat treatment_2-ySe core-shell powder immersed in Ag₂SO₄In the solution, the replacement of Cu by Ag is realized. Formation of Ag/Cu_2-ySe core-shell structure thermoelectric material or Ag/Cu_2-ySe core-shell structure thermoelectric material.

Further, in step S3, the powder synthesis block method is one of hot-press sintering, plasma activated sintering, spark plasma sintering or low-temperature cold-press sintering.

Further, in step S3, the sintering temperature of the powder synthesis block is 100-760 ℃; for Zn/Zn_4-xSb₃The sintering temperature of the core-shell powder is 100-760 ℃, and the preferred sintering temperature is 180-230 ℃; for Cu/Cu_2-yThe Se nuclear shell powder is sintered at 100-600 deg.c, preferably 100-230 deg.c.

Further, in step S3, an optional step is added, in which the finally obtained bulk thermoelectric material with a core-shell structure is subjected to heat treatment again, and a nano precipitated phase different from the matrix material is further obtained in the core; preference is given to bulk Zn/Zn after sintering_4-xSb₃In the thermoelectric material with the core-shell structure, bulk Zn/Zn is added_4-xSb₃After the thermoelectric material with the core-shell structure is subjected to heat treatment again at 180-230 ℃, part of ZnSb nano-phase is separated out from the core; preferably bulk Cu/Cu after sintering_2-yIn the thermoelectric material with Se nuclear shell structure, bulk Cu/Cu is added_2-yAfter the Se nuclear shell structure thermoelectric material is subjected to heat treatment again at the temperature of between 100 and 230 ℃, part of Cu is separated out from the core₃Se₂Nanophase or CuSe nanophase, or Cu₃Se₂And a CuSe nanophase.

The invention has the following advantages: the phonon scattering of the thermoelectric material can be obviously enhanced, the heat conductivity coefficient of the thermoelectric material is reduced, and the thermoelectric performance is improved, so that the energy conversion efficiency of the thermoelectric material is improved by 10-15%.

Drawings

FIG. 1 shows examples 1, 2 and 3 of the present invention, three-layered core-shell structure Zn/Zn_4-xSb₃a/ZnSb thermoelectric material and a preparation method thereof.

In the figure: the thermoelectric material comprises 1, Zn4Sb3 materials, 2, Zn4Sb3 powder materials, 3, Zn shells, 4, Zn4-xSb3 cores, 5, powder Zn/Zn4-xSb3 core-shell structure thermoelectric materials, 6, block Zn/Zn4-xSb3 core-shell structure thermoelectric materials, 7, ZnSb nano-phase and 8, Zn/Zn4-xSb3/ZnSb three-core-shell structure thermoelectric materials.

FIG. 2 shows three-layered core-shell structure Cu/Zn of examples 4, 5 and 6 according to the present invention_4-xSb₃a/ZnSb thermoelectric material and a preparation method thereof.

In the figure: 1, Zn4Sb3 material, 2, Zn4Sb3 powder material and 3, Zn shell; 4, a Zn4-xSb3 inner core, 5, powder Zn/Zn4-xSb3 core-shell structure thermoelectric material, 7, ZnSb nanophase, 9, Cu shell and 10, powder Cu/Zn4-xSb3 core-shell structure thermoelectric material; 11, a block Cu/Zn4-xSb3 core-shell structure thermoelectric material, and 12, a Cu/Zn4-xSb3/ZnSb three-level core-shell structure thermoelectric material.

FIG. 3 is TEM contrast electron microscope images of a Zn4Sb3 non-core-shell structure thermoelectric material and a Zn/Zn4-xSb3 core-shell structure thermoelectric material.

In the figure: (a) a Zn4Sb3 non-core-shell structure thermoelectric material, and (b) a Zn/Zn4-xSb3 core-shell structure thermoelectric material.

FIG. 4 is a thermoelectric property diagram of a Zn/Zn4-xSb3 core-shell structure thermoelectric material and a non-core-shell structure Zn4Sb3 thermoelectric material.

Detailed Description

For a better understanding of the present invention, reference is made to the following examples, which are included to illustrate, but are not to be construed as the limit of the present invention.