阅读说明：本技术 一种制备Cu2Se热电材料的方法 (Preparation of Cu2Method for Se thermoelectric material ) 是由 赵德刚 王永鹏 王文莹 李福金 王磊 于 2020-04-03 设计创作，主要内容包括：本发明公开了一种制备Cu<Sub>2</Sub>Se热电材料的方法,该方法利用湿法球磨—微波合成—湿法球磨—急速热压的工艺流程,快速制得Cu<Sub>2</Sub>Se块体材料,该方法原料混合均匀、升温速率快、合成时间短、工艺操作简单、耗能低、生产成低、生产周期短、设备要求简单,可得到高纯无杂相的Cu<Sub>2</Sub>Se块体材料,极大的提高了该热电材料的制备效率,适用于大规模生产制备。(The invention discloses a method for preparing Cu 2 The method for preparing the Se thermoelectric material utilizes the technological processes of wet ball milling, microwave synthesis, wet ball milling and rapid hot pressing to quickly prepare the Cu 2 The Se block material has the advantages of uniform mixing of raw materials, high heating rate, short synthesis time, simple process operation, low energy consumption, low production cost, short production period and simple equipment requirement, and can obtain high-purity Cu without impurity phase 2 The Se block material greatly improves the preparation efficiency of the thermoelectric material and is suitable for large-scale production and preparation.)

1. Preparation of Cu₂A method of Se thermoelectric material, characterized by comprising the steps of:

(1) uniformly mixing copper powder and selenium powder through wet ball milling, and then carrying out cold pressing to obtain a block body;

(2) putting the block obtained by cold pressing into a quartz tube, vacuumizing and sealing, and embedding the sealed quartz tube into a wave-absorbing material for microwave synthesis, wherein the microwave material is a mixture of graphite powder and quartz sand;

(3) crushing the blocks synthesized by the microwave and performing wet ball milling;

(4) carrying out rapid hot-pressing sintering on the powder obtained by ball milling to obtain Cu₂A Se thermoelectric material.

2. The method of claim 1, further comprising: in the step (1), the molar ratio of the copper powder to the selenium powder is 2: 1.

3. The method of claim 1, further comprising: in the step (1), ball milling is carried out in the presence of absolute ethyl alcohol, the ball milling rotating speed is 100-300 revolutions per minute, the ball milling time is 20-30 minutes, and the ball-material ratio is 40-60: 1.

4. A method according to claim 1 or 2, characterized by: in the step (1), the uniformly mixed raw materials are subjected to constant pressure for 5-10 minutes at room temperature under the condition of 40-50MPa, and a block is obtained.

5. The method of claim 1, further comprising: in the step (2), the mass of the quartz sand is 20-35wt% of the total mass of the wave-absorbing material.

6. The method of claim 1 or 4, wherein: in the step (2), the granularity of the graphite powder is below 100 meshes; the granularity of the quartz sand is 20-40 meshes.

7. The method of claim 1 or 4, wherein: in the step (2), the microwave power is 700-900W, and the microwave synthesis time is 5-10 minutes.

8. The method of claim 1, further comprising: in the step (3), ball milling is carried out in the presence of absolute ethyl alcohol, the ball milling rotating speed is 150-200 revolutions per minute, the ball milling time is 1-2 hours, and the ball-material ratio is 40-60: 1.

9. The method of claim 1, further comprising: and (4) putting the ball-milled powder into a rapid hot-pressing furnace for vacuum hot-pressing.

10. The method of claim 1 or 8, wherein: in the step (4), the pressure of the rapid hot-pressing sintering is 50-60MPa, and the temperature is 400-^oC, the heating rate is 90-110^oC/min, and the time is 30-40 min.

Technical Field

The invention relates to Cu₂A method for preparing a Se thermoelectric material, in particular to Cu with simple process and less time consumption₂A preparation method of a Se thermoelectric semiconductor material belongs to the technical field of new energy materials.

Background

The thermoelectric material is energy capable of realizing mutual conversion of heat energy and electric energyThe thermoelectric conversion efficiency of the source material depends on the ZT value of the material and the temperature difference between the cold end and the hot end, wherein ZT is a thermoelectric figure of merit which is the most important dimensionless parameter for measuring the thermoelectric material, and ZT = sigma S²T/κ, where σ is the electrical conductivity, S is the Seebeck coefficient, T is the absolute temperature, and κ is the total thermal conductivity. The thermoelectric material has the advantages of no mechanical movement, high reliability and long service life, and is an important material in the fields of waste heat recovery, space batteries and space refrigeration. Currently, the thermoelectric materials widely studied in the world are mainly: bi₂Te₃SnSe, PbTe, skutterudite, SiGe, Cu-based diamond thermoelectric material, Cu₂Se-based liquid thermoelectric materials, Half-Heusler alloy thermoelectric materials, and the like.

Cu and Se can form CuSe and Cu₂Se、Cu₃Se₂And CuSe₂The compound with good thermoelectric property is CuSe or Cu₂Se。

Cu₂Se has attracted extensive attention as a thermoelectric material featuring "phonon liquid-electronic crystal" due to its good electrical properties and extremely low thermal conductivity, and data indicate that Cu is₂Se has a remarkable transformation point of about 400K, which is represented by α -Cu₂Se conversion to β -Cu₂Se and very high Seebeck coefficient at phase transition point, β -Cu at high temperature₂Se is an anti-fluorite structure phase, has a good electric transport channel, and Cu ions can freely migrate at lattice gap positions, so that phonons are strongly scattered, and the mean free path of the phonons is reduced; after the process optimization and the energy band engineering optimization, Cu₂The ZT value of Se can reach 1.5-2.1 at the temperature of 1000K. Plum rain adopts microwave melting and hot-pressing sintering in CN109439939A to prepare a CuSe bulk compound, and the thermoelectric property of the CuSe bulk compound is characterized by reaching 0.35 at 700K. And Cu₂Compared with Se, the melting point of the CuSe compound is only 387 ℃, the CuSe compound cannot be used in a temperature region above 400 ℃, the stability of the thermoelectric material is lower at high temperature, and the ZT value is only Cu at 700K₂50% of Se. The single microwave melting method can successfully prepare the CuSe compound, but the preparation of Cu is difficult₂Se compounds, the reason being: 1. uneven mixing can cause other Cu and Se compounds to be generated in the synthesis process; 2. the traditional wave-absorbing material is difficult to enable the microwave temperature to rapidly reach the melting point, and the microwave smelting cannot be realized.

Cu₂The difficulty in the preparation of Se is: the melting point temperature is 1113 ℃, the melting point is high, the melting point difference of Cu and Se elements is large, and the Se element is easy to volatilize in the preparation process. The preparation method mainly comprises a hydrothermal synthesis method, a self-propagating high-temperature synthesis method, a high-temperature melting method and an SPS one-step high-temperature synthesis method. Among these methods, hydrothermal synthesis, self-propagating high-temperature synthesis and high-temperature fusion require longer preparation time, while the one-step high-temperature synthesis of SPS has the advantages of fast reaction and short preparation period, but the equipment cost is high.

Therefore, Cu which is more convenient for industrial popularization is still lacked at present₂A method for preparing Se thermoelectric material.

Disclosure of Invention

For the existing Cu₂The preparation method of the Se thermoelectric material has the defects of high production cost, long production period and the like, and the invention provides a method for preparing Cu₂The method for Se thermoelectric material comprises the technological processes of wet ball milling, microwave synthesis, wet ball milling and rapid hot pressing, and has the advantages of uniform mixing, high heating rate, short production period, simple process, low production cost and energy consumption, convenient operation, high product density and batch production.

The specific technical scheme of the invention is as follows:

preparation of Cu₂A method of Se thermoelectric material, the method comprising the steps of:

(1) ball-milling and uniformly mixing copper powder and selenium powder, and then cold-pressing to obtain a block body;

(2) putting the block obtained by cold pressing into a quartz tube, vacuumizing and sealing, and embedding the sealed quartz tube into a wave-absorbing material for microwave synthesis, wherein the microwave material is a mixture of graphite powder and quartz sand;

(3) crushing and ball-milling the blocks synthesized by the microwave;

(4) ball milling is carried outThe obtained powder is rapidly hot-pressed and sintered to obtain Cu₂A Se thermoelectric material.

Further, in the step (1), Cu powder and Se powder are used as raw materials, the purity of the Cu powder and the Se powder is 99.99% or more, and the granularity of the raw materials is generally below 200 meshes. The molar ratio of the Cu powder to the Se powder is 2: 1.

Further, in the step (1), the copper powder and the selenium powder are uniformly mixed by adopting a wet ball milling mode. The ball milling is carried out in the presence of absolute ethyl alcohol, the ball milling rotating speed is 100-300 r/m, the ball milling time is 20-30 minutes, and the ball-material ratio is 40-60: 1. The milling media for ball milling may be milling media commonly used in the art that do not affect the feedstock, such as absolute ethanol. The key point of the invention is ball milling mixing and ball milling with ethanol, and the ball milling can realize uniform mixing of the raw materials; the ethanol can prevent high temperature generation during ball milling, oxidation of raw materials, and generation of other impurity phase (such as Cu)₃Se₂) Thereby preventing the molar ratio of the raw materials from changing.

Further, in the step (1), the cold pressing is cold pressing at room temperature, and the uniformly mixed raw materials are subjected to constant pressure for 5-10 minutes under the pressure of 40-50MPa, so that a pressing block can be obtained. The shape of the briquettes obtained by cold pressing can be controlled at will, in one embodiment of the invention, the briquettes are cylindrical, all raw materials are pressed into one cylindrical briquette, and the radius of the bottom surface of the briquette is 10-15 mm.

Further, in the step (2), the block obtained by cold pressing is filled into a quartz tube, and the quartz tube is vacuumized and sealed, wherein the quartz tube is preferably a quartz tube with the carbon-plated inner wall. Vacuum sealing may be performed by methods conventional in the art. For example, the block obtained by cold pressing is put into a quartz tube, the inside of the quartz tube is vacuumized by a vacuum packaging machine and a vacuum pump, and the quartz tube is vacuumized to 10 DEG^-2And (4) sealing by flame to form a vacuum sealed environment below Pa.

Further, in the step (2), the sealed quartz tube is placed into a corundum crucible, a layer of refractory cotton is uniformly laid on the periphery and the bottom of the inner wall of the corundum crucible, and a wave-absorbing material is added into the corundum crucible, so that the quartz tube is embedded into the wave-absorbing material, and the microwave synthesis temperature can reach the temperature for forming Cu₂Temperature of Se. The wave-absorbing material is the key for realizing the invention, is obtained by screening a large number of experiments by the inventor, and is a mixture of graphite powder and quartz sand. Only by adopting the wave-absorbing material can the copper powder and the selenium powder be ensured to be capable of synthesizing pure Cu in a microwave mode₂Se。

Further, in the step (2), in the wave-absorbing material, the purity of graphite powder is 99.9% or more, and the granularity is less than or equal to 100 meshes. And adding a small amount of quartz sand, wherein the dosage of the quartz sand is 20-35% of the total mass of the wave-absorbing material, and the granularity is 20-40 meshes.

Further, in the step (2), the microwave synthesis can be performed by using a microwave experimental device commonly used in laboratories. The microwave power is 700-900W, and the microwave synthesis time is 5-10 minutes. Microwave synthesis of Cu₂The Se process only needs 5-10min, greatly shortens the synthesis preparation time and greatly shortens the preparation period.

Further, in the step (3), the microwave-synthesized block is crushed and then ball-milled. In order to make the ball milling more effective, the crushed blocks may be ground by hand to about 200 μm and then ball milled. The ball milling is carried out in the presence of absolute ethyl alcohol, the ball milling rotating speed is 150-. Wet ball milling can further reduce the production of impurity phases.

Further, in the step (4), the rapid hot pressing sintering is carried out in a rapid hot pressing furnace, and the hot pressing is carried out under vacuum. In one embodiment of the invention, a rapid hot-pressing sintering method is provided, wherein the sintering pressure is 50-60MPa, the vacuum degree is 1-10Pa, and the temperature is 400-^oC, the heating rate is 90-110^oC/min, and the heat preservation time is 30-40 min.

The invention provides a method for rapidly preparing Cu₂The method for preparing the Se thermoelectric material utilizes the technological processes of wet ball milling, microwave synthesis, wet ball milling and rapid hot pressing to quickly prepare the Cu₂The Se block material has the advantages of uniform mixing of raw materials, high heating rate, short synthesis time, simple process operation, low energy consumption, low production cost, short production period and equipment requirementSimple and can obtain high-purity Cu without impurity phase₂The Se block material greatly improves the preparation efficiency of the thermoelectric material and is suitable for large-scale production and preparation.

Drawings

FIG. 1 Cu prepared in example 1₂XRD pattern of Se thermoelectric material.

FIG. 2 Cu prepared in example 1₂Element area distribution diagram and EDS energy spectrum of Se thermoelectric material.

FIG. 3 Cu prepared in example 1₂Cross-sectional electron scan of the Se thermoelectric material.

FIG. 4 Cu prepared in example 1₂Graph of electrical conductivity of Se thermoelectric material as a function of temperature.

FIG. 5 Cu prepared in example 1₂Seebeck coefficient of Se thermoelectric material is plotted against temperature.

FIG. 6 Cu prepared in example 1₂Graph of power factor versus temperature for Se thermoelectric materials.

FIG. 7 Cu prepared in example 1₂Graph of thermal conductivity of Se thermoelectric material as a function of temperature.

FIG. 8 Cu prepared in example 1₂Graph of ZT values of Se thermoelectric materials as a function of temperature.

Fig. 9 XRD pattern of the thermoelectric material prepared in comparative example 1.

Detailed Description

The invention is explained in more detail below with reference to the figures and the specific embodiments. It is to be understood that the following description is illustrative only and is not limiting in its content.

In the following examples, the thermoelectric property test method of the product of each example is as follows:

the electrical conductivity is measured using the van der Waals method, and the Seebeck coefficient is derived from the slope of the thermal electromotive force over a range of 0-5k versus temperature difference all measurements are collected with a temperature step of 25 k.

Power factor according to PF = σ S²Calculating, PF is the power factor; σ is the conductivity; s is the seebeck coefficient.

ZT value according to ZT = σ S²T/κ calculation, where T is absolute temperature.

In the following embodiments, the density detection method of each product is as follows: the density test was performed using the archimedes drainage method. With Cu₂And calculating the relative density of each product by taking the theoretical density of Se as a reference, namely the density.