CN118660610A - Preparation method of copper sulfide-based plastic thermoelectric composite material - Google Patents
Preparation method of copper sulfide-based plastic thermoelectric composite material Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 38
- OMZSGWSJDCOLKM-UHFFFAOYSA-N copper(II) sulfide Chemical compound [S-2].[Cu+2] OMZSGWSJDCOLKM-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000000463 material Substances 0.000 claims abstract description 73
- 239000000843 powder Substances 0.000 claims abstract description 52
- 239000010949 copper Substances 0.000 claims abstract description 49
- 238000000498 ball milling Methods 0.000 claims abstract description 36
- 238000005245 sintering Methods 0.000 claims abstract description 21
- 239000000126 substance Substances 0.000 claims abstract description 19
- 238000000034 method Methods 0.000 claims abstract description 14
- 230000001681 protective effect Effects 0.000 claims abstract description 12
- 239000004065 semiconductor Substances 0.000 claims abstract description 10
- 238000002490 spark plasma sintering Methods 0.000 claims abstract description 6
- 239000011159 matrix material Substances 0.000 claims description 16
- 239000002244 precipitate Substances 0.000 claims description 4
- 238000011160 research Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 34
- 230000009286 beneficial effect Effects 0.000 description 9
- 238000002441 X-ray diffraction Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 5
- 229910052709 silver Inorganic materials 0.000 description 5
- 229910052802 copper Inorganic materials 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000000969 carrier Substances 0.000 description 3
- 238000012512 characterization method Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 241000282414 Homo sapiens Species 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 230000036760 body temperature Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000005057 refrigeration Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000002918 waste heat Substances 0.000 description 2
- WHBHBVVOGNECLV-OBQKJFGGSA-N 11-deoxycortisol Chemical compound O=C1CC[C@]2(C)[C@H]3CC[C@](C)([C@@](CC4)(O)C(=O)CO)[C@@H]4[C@@H]3CCC2=C1 WHBHBVVOGNECLV-OBQKJFGGSA-N 0.000 description 1
- 229910002899 Bi2Te3 Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 108091006149 Electron carriers Proteins 0.000 description 1
- 229910000927 Ge alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000000875 high-speed ball milling Methods 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000005551 mechanical alloying Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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- 239000011343 solid material Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 239000002226 superionic conductor Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/80—Constructional details
- H10N10/85—Thermoelectric active materials
- H10N10/851—Thermoelectric active materials comprising inorganic compositions
- H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
- C30B28/02—Production of homogeneous polycrystalline material with defined structure directly from the solid state
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/46—Sulfur-, selenium- or tellurium-containing compounds
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
- H10N10/01—Manufacture or treatment
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Abstract
The invention relates to the technical field of thermoelectric materials, and particularly discloses a preparation method of a copper sulfide-based plastic thermoelectric composite material, which comprises the following steps: step 1, powder preparation: putting the Cu simple substance powder and the S simple substance powder into a ball mill, and performing ball milling for the first time in a protective atmosphere to obtain Cu 1.8 S powder; then putting Cu 1.8 S powder and plastic semiconductor material Ag 2 S into a high-energy ball mill according to the proportion of 20% -40% of x, and performing ball milling for the second time in protective atmosphere to obtain Cu 1.8S-xAg2 S powder; step 2 sintering: and (2) sintering the powder prepared in the step (1) by adopting a spark plasma sintering method to form a block Cu1.8S-xAg 2 S plastic thermoelectric composite material, wherein the sintering temperature is 300-500 ℃, the sintering time is 5-30 min, and the sintering pressure is 10-50 Mpa. The invention solves the problem of poor thermoelectric performance of the existing copper sulfide thermoelectric material, obtains the copper sulfide base block thermoelectric composite material with plasticity, and enriches the research of the material system in the thermoelectric application field.
Description
The application relates to a copper sulfide-based plastic thermoelectric composite material and a preparation method thereof, which are respectively applied for the patent application number 2020112819194 and the case name of the patent application number 2020112819194 of 11-16 of 2020.
Technical Field
The invention relates to the technical field of thermoelectric materials, in particular to a preparation method of a copper sulfide-based plastic thermoelectric composite material.
Background
The thermoelectric material is a novel functional material capable of realizing direct conversion of heat energy and electric energy by utilizing the transport effect of carriers and phonons in the solid material. At present, the utilization rate of human beings to energy sources is low, more than 60% of energy sources are released into the atmosphere in the form of waste heat, and a thermoelectric device formed by high-performance thermoelectric materials is expected to improve the comprehensive utilization rate of the existing energy sources and relieve the energy crisis, so that the thermoelectric materials are also gaining more and more attention. The thermoelectric device formed by serially connecting p-type thermoelectric materials and n-type thermoelectric materials is widely applied, can be applied to deep space exploration power supply, automobile exhaust waste heat recovery and the like in the field of pyroelectric, and is mainly applied to electronic element refrigeration, small-volume refrigeration refrigerators and the like in the aspect of electric temperature difference.
The nondimensional performance figure of merit ZT of a thermoelectric material is an important index for characterizing the conversion efficiency of the thermoelectric material, and the ZT value can be expressed as: zt=σs 2T/(κL+κe), where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, κ L is the lattice thermal conductivity, and κ e is the carrier thermal conductivity. Since the three important parameters S, sigma and kappa e for determining the thermoelectric performance of the material are interrelated, how to realize independent regulation (or cooperative regulation) of the parameters is the core for improving the thermoelectric performance. The existing high-performance thermoelectric materials comprise Bi2Te3, pbTe, pbS, si-Ge alloy and the like, but the materials relate to rare noble metal elements or toxic and harmful elements, and the development concept of the green high-performance thermoelectric materials is violated. Therefore, searching and researching a compound formed by elements which are nontoxic, harmless, low-cost and abundant and can be applied to an industrial production method as a proper thermoelectric material is also an important basic work.
Cu1.8S materials are an intrinsic class of p-type semiconductors, with a suitable forbidden band width (1.2 eV) and are known as thin film solar cells and optoelectronic devices at the earliest. The Cu1.8S material has a hexagonal phase structure (R3-mh) at room temperature, and can be converted into a cubic phase structure (Fm 3-m) when the temperature is increased to more than 364K. The material has the property of a super-ionic conductor after forming a high temperature phase structure because its crystal structure consists of S ions constituting a face-centered cubic sub-lattice to ensure rigidity of the material, while Cu ions have ultra-high mobility as in a molten state or in a solution. In addition, the Cu1.8S material has high-concentration copper vacancies, a large number of conductive vacancies formed in the energy band enable the Cu1.8S to show excellent conductivity, and the Cu1.8S material is a potential thermoelectric material with commercial application value due to the fact that Cu and S elements are rich, low in cost and environment-friendly.
However, the Cu1.8S material still has the problems of high heat conductivity and low Seebeck coefficient at present, so that the thermoelectric performance is poor. Therefore, how to improve the thermoelectric performance of the Cu1.8S material is still the focus of research in the technical field.
Disclosure of Invention
The invention provides a copper sulfide-based plastic thermoelectric composite material and a preparation method thereof, which are used for solving the problems that a Cu1.8S material still has high heat conductivity and low Seebeck coefficient in the prior art, so that the thermoelectric performance is poor.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
The chemical general formula of the copper sulfide-based plastic thermoelectric composite material is Cu 1.8S-xAg2 S, wherein x is 20% -40%, the material comprises a matrix phase Cu1.8S and a plastic second phase Ag 2 S, and the second phase Ag 2 S is dispersed and distributed in the matrix phase Cu1.8S in the form of nano precipitates.
The technical principle and effect of the technical scheme are as follows:
1. In this scheme, as described above, since a plurality of thermoelectric parameters of the thermoelectric material have mutual coupling effects, it is difficult to cooperatively optimize, and since lattice thermal conductivity of the material is relatively independent, the inventors found that thermoelectric performance of the thermoelectric material can be optimized by softening lattice and introducing different scale defects to enhance phonon scattering, and thus the inventors obtained a copper sulfide-based plastic thermoelectric composite material by introducing Ag 2 S having plasticity into Cu 1.8 S material.
2. According to the technical scheme, the plastic second phase Ag 2 S is dispersed and distributed in the matrix phase Cu 1.8 S in the form of nano precipitates, and verification by the inventor shows that the interaction of the plastic second phase Ag 2 S and the matrix phase Cu 1.8 S greatly improves the thermoelectric figure of merit of the copper sulfide-based thermoelectric composite material. The reasons for this are mainly three: (1) The use of the plastic material Ag 2 S as a second phase dispersed in the matrix material helps to reduce the mechanical strength of the material, thereby significantly reducing the lattice thermal conductivity of the matrix material Cu 1.8 S; (2) The large amount of introduced second phase can promote the generation of doping reaction, and the small amount of metal ions replace Cu ions in Cu 1.8 S, so that electron carriers are introduced due to the difference of ionic electronegativity, and the Seebeck coefficient is optimized; (3) A large amount of Ag 2 S second phase is dispersed in the matrix material to help to enhance the scattering effect of phonons and prevent the transportation of carriers, so that the method is helpful to reduce the heat conductivity of the Cu 1.8 S material and optimize the Seebeck coefficient of the Cu 1.8 S, and finally is beneficial to improving the thermoelectric figure of merit of the Cu 1.8 S material.
3. The plastic thermoelectric composite material provided by the technical scheme is prepared from Cu 1.8 S and a plastic material Ag 2 S, and because the thermoelectric performance and the strength of the finally prepared plastic thermoelectric composite material depend on the effect of Ag 2 S with different concentrations on the Cu 1.8 S material, excessive (the mass fraction exceeds 40%) second phase can obviously deteriorate the electrical property of the Cu 1.8 S material, further the thermoelectric performance of the material is deteriorated, if the adding amount is too small (less than 20%), the brittle Cu 1.8 S material is difficult to have flexibility, and the use of the thermoelectric material is influenced by too much brittleness, so the technical scheme adopts Ag 2 S with a certain concentration to prepare the plastic composite material.
4. The composite thermoelectric material with plasticity prepared by the scheme can be used for preparing wearable flexible thermoelectric devices, and heat transfer loss can be further reduced by forming closer interface contact with a human body heat source, so that the power generation efficiency is improved, such as a thermoelectric watch, a miniature body temperature detector and the like, and on the other hand, the plasticity of the material is improved, so that the shape requirements of different thermoelectric device preparations can be met, and the application range of the composite thermoelectric material is wider.
Further, the second phase Ag 2 S has a monoclinic structure.
The beneficial effects are that: such a structure enables to obtain a plastic copper sulfide-based thermoelectric composite material and to improve its thermoelectric performance.
The invention also discloses a preparation method of the copper sulfide-based plastic thermoelectric material, which comprises the following steps:
Step 1, powder preparation: putting the Cu simple substance powder and the S simple substance powder into a ball mill, and performing ball milling for the first time in a protective atmosphere to obtain Cu 1.8 S powder; then putting Cu 1.8 S powder and plastic semiconductor material Ag 2 S into a high-energy ball mill according to the proportion of 20% -40% of x, and performing ball milling for the second time in protective atmosphere to obtain Cu 1.8S-xAg2 S powder;
Step 2 sintering: and (2) sintering the powder prepared in the step (1) by adopting a spark plasma sintering method to form a block Cu1.8S-xAg 2 S plastic thermoelectric composite material, wherein the sintering temperature is 300-500 ℃, the sintering time is 5-30 min, and the sintering pressure is 10-50 Mpa.
The beneficial effects are that:
1. Through X-ray diffraction analysis on the prepared copper sulfide-based plastic thermoelectric composite material, the copper sulfide-based plastic thermoelectric composite material is found to have a Cu1.8S matrix phase and a second phase Ag 2 S, so that the thermoelectric performance of the copper sulfide-based plastic thermoelectric composite material can be greatly improved, and the strength of the Cu 1.8 S matrix material is reduced.
2. During ball milling, the plastic semiconductor material Ag 2 S and Cu 1.8 S powder can be uniformly mixed by proportioning the ball material ratio, the ball milling speed and the ball milling time.
3. The SPS is adopted to sinter the Cu 1.8S-xAg2 S powder, so that a compact block Cu 1.8S-xAg2 S plastic thermoelectric composite material with small grain size can be formed, the density of the thermoelectric composite material can be improved, and the practical use is satisfied. The sintering temperature has a large influence on the block, the activation degree of the powder is insufficient due to the fact that the temperature is too low, the powder is difficult to sinter into a compact block, the grain size is too large due to the fact that the sintering temperature is too high, the heat conductivity of the material is increased, and the thermoelectric performance of the material is deteriorated.
Further, the protective atmosphere in the step 1 is H 2 with a mass fraction of 5% and N 2 with a mass fraction of 95%.
The beneficial effects are that: the protective atmosphere can enable the powder to react in an anaerobic environment, oxidation is avoided, and meanwhile, a small amount of hydrogen forms a reducing atmosphere, so that the powder can react rapidly.
Further, the rotational speed in the first ball milling in the step 1 is 300-450 rpm, and the ball milling time is 1-6 h.
The beneficial effects are that: the ball milling rotating speed and time can ensure that the copper simple substance and the sulfur simple substance powder are fully reacted to form Cu 1.8 S powder.
Further, the rotation speed in the second ball milling in the step 1 is 800-1000 rpm, and the ball milling time is 0.5-2 h.
The beneficial effects are that: under the high-speed ball milling condition, the added plastic semiconductor material Ag 2 S can be compounded with Cu 1.8 S powder rapidly.
Further, the weight ratio of the ball body to the material in the first ball milling and the second ball milling in the step 1 is 20-50:1.
The beneficial effects are that: the weight ratio can ensure the full mixing of materials.
Further, the balls for the first ball milling and the second ball milling in the step 1 comprise balls with diameters of 3mm, 6mm and 10mm, and the total weights of the balls with different diameters are equal.
The beneficial effects are that: the ball milling device has the advantages that the balls with different diameters are used, so that the phenomenon that the balls are co-rotated due to the fact that the diameters of the balls are consistent can be avoided, the ball milling effect is poor, and the reaction between the powder bodies is insufficient.
Further, the purity of the Cu simple substance powder and the S simple substance powder in the step1 is more than 99.95%, and the purity of the plastic semiconductor powder Ag 2 S is more than 99.9%.
The beneficial effects are that: the high-purity Cu simple substance powder, the S simple substance powder and the plastic semiconductor powder Ag 2 S are adopted, so that the generation amount of impurity phases can be reduced, and the situation that the thermoelectric performance of the prepared thermoelectric composite material is poor is avoided.
Drawings
FIG. 1 is a scanning electron microscope image of embodiment 1 of the present invention;
FIG. 2 is a scanning electron microscope image of embodiment 2 of the present invention;
FIG. 3 is an XRD contrast pattern of inventive example 1 and comparative example 1;
FIG. 4 is an XRD contrast pattern of inventive example 2 and comparative example 1;
FIG. 5 is an XRD contrast pattern for inventive example 3 and comparative example 1;
FIG. 6 is a graph of thermal conductivity as a function of temperature for inventive example 1 and comparative example 1;
FIG. 7 is a graph of thermal conductivity as a function of temperature for inventive example 2 and comparative example 1;
FIG. 8 is a graph of thermal conductivity as a function of temperature for inventive example 3 and comparative example 1;
FIG. 9 is a graph showing the thermoelectric figure of merit as a function of temperature for example 1 and comparative example 1 of the present invention;
FIG. 10 is a graph showing the thermoelectric figure of merit as a function of temperature for example 2 and comparative example 1 of the present invention;
FIG. 11 is a graph showing the thermoelectric figure of merit as a function of temperature for example 3 and comparative example 1 of the present invention;
FIG. 12 is a pit chart of a sample after hardness test of comparative example 1 of the present invention;
FIG. 13 is a pit chart of a sample after hardness test in example 1 of the present invention.
Detailed Description
The following is a further detailed description of the embodiments:
Example 1:
the chemical formula of the copper sulfide-based plastic thermoelectric composite material is Cu 1.8S-xAg2 S, in the embodiment, x is 20%, and the material comprises a matrix phase Cu1.8S and a plastic second phase Ag 2 S, wherein the second phase Ag 2 S is dispersed and distributed in the matrix phase Cu1.8S in the form of nano precipitates.
The preparation method of the copper sulfide-based plastic thermoelectric composite material comprises the following steps:
step 1, powder preparation:
3.12g of simple substance Cu powder with the purity of more than 99.95% (mass fraction) and 0.88g of simple substance S powder are weighed, the two simple substance powder are put into a vacuum ball milling tank, the rotating speed of the vacuum ball milling tank is regulated to 430rpm, and the Cu1.8S powder is obtained after ball milling for 3 hours in a protective atmosphere.
And then 0.80g of Ag 2 S powder with the purity of more than 99.9% (mass fraction) is weighed, the prepared Cu 1.8 S powder and Ag 2 S powder are put into a high-energy ball mill, the rotating speed of a vacuum ball milling tank is regulated to 800rpm, and ball milling is carried out for 0.5h under protective atmosphere, so that Cu1.8S-20wt% Ag 2 S powder is obtained.
In the embodiment, the protective atmosphere is H2 with the mass fraction of 5% and N2 with the mass fraction of 95%, the spheres in the ball milling tank are stainless steel spheres, the diameters of the spheres are 3mm, 6mm and 10mm, the weights of the spheres with the three diameters are equal, the weight ratio of the total weight of the powder to the spheres is 1:20-50, and the ratio in the embodiment is 1:20.
Step 2 sintering:
And (3) sintering the Cu1.8S-20wt% Ag 2 S powder prepared in the step (1) by adopting a spark plasma sintering method, firstly pouring the Cu1.8S-20wt% Ag 2 S powder into a graphite die with the diameter of 15mm, and sintering for 5min at the temperature of 400 ℃ and the pressure of 50Mpa to form the bulk Cu1.8S-20wt% Ag 2 S plastic thermoelectric composite material. The second phase of the Cu1.8S-20wt% Ag 2 S plastic thermoelectric composite material is Ag 2 S and has a monoclinic structure.
Examples 2 to 3:
The difference from example 1 is that the amount of Ag 2 S added in example 2 was 1.2g, i.e., x was 30%, and that the amount of Ag 2 S added in example 3 was 1.6g, i.e., x was 40%.
Comparative example 1:
The difference from example 1 is that no plastic second phase Ag 2 S was added, i.e. comparative example 1 gave a pure phase of cu1.8s.
Comparative examples 2 to 3:
The difference from example 1 is that the mass fraction of the second phase Ag 2 S added in comparative example 2 was 5% and the mass fraction of the second phase Ag 2 S added in comparative example 3 was 50%.
Comparative example 4:
The difference from example 1 is that the balls of 10mm were used in the ball milling in step1 of comparative example 4.
Samples prepared in examples 1 to 3 and comparative examples 1 to 4 were taken for experimental detection:
1. SEM characterization
The thermoelectric material samples prepared in examples 1 to 3 and comparative examples 1 to 4 were detected by using a scanning electron microscope, and the obtained electron microscope images are shown in fig. 1 and 2, and it can be observed that the grain size of the bulk sample gradually decreases and nano pores appear as the second phase doping amount of Ag 2 S increases, and the presence of the nano pores can cause a certain blocking effect on the transmission of carriers, slightly reduce the electrical conductivity and the power factor of the material, but also can have a strong scattering effect on phonons, thereby remarkably reducing the lattice thermal conductivity of the copper sulfide material and improving the ZT value of the matrix material.
2. XRD (X-ray diffraction) characterization:
the thermoelectric material samples prepared in examples 1 to 3 and comparative examples 1 to 4 were examined by an X-ray diffractometer, and the examination results are shown in fig. 3, 4 and 5, respectively, taking example 1, example 2, example 3 and comparative example 1 as examples.
XRD detection results show that after a large amount of plastic semiconductor second phase Ag 2 S is added, a polycrystalline block material taking Cu 1.8 S as a main phase can be synthesized by combining a mechanical alloying (ball milling) method and an SPS sintering method, the existence of the second phase AgCuS and Ag 2 S is detected, and the fact that part of Ag in Ag 2 S is doped into a crystal lattice of Cu 1.8 S is proved, the rest of Ag 2 S is still dispersed and distributed in a Cu 1.8 S matrix material in a second phase form, and the left shift of a part of diffraction peak represents the expansion of the crystal lattice and also indicates the occurrence of a small amount of doping reaction.
3. Characterization of thermoelectric performance
3.1 Thermal conductivity
The performance of thermoelectric materials is characterized by a dimensionless thermoelectric figure of merit ZT, with the formula ZT = σs 2 T/κ, where σs 2 represents the power factor, T is absolute temperature, and κ is the thermal conductivity.
Samples of thermoelectric materials prepared in examples 1 to 3 and comparative examples 1 to 4 were cut into piecesThe wafers of (2) were used to measure thermal conductivity and tested using a laser thermal conductivity meter to give thermal conductivity at 773K, as shown in table 2. Taking example 1, example 2, example 3 and comparative example 1 as examples, graphs of thermal conductivity measured with temperature change are shown in fig. 6, 7 and 8, respectively, and it can be observed from fig. 6 to 7 that the thermal conductivity of the samples obtained by using the present application is much lower than that of comparative example 1.
3.2ZT value
ZT values can be obtained from the above formula zt=σs 2 T/κ calculations, with ZT values obtained at 773K, as shown in table 2. Further, taking example 1, example 2, example 3 and comparative example 1 as examples, the change in ZT value with temperature is shown in fig. 9, 10 and 11, respectively; from fig. 9 to 11, it can be observed that the ZT values of the samples prepared in examples 1 to 3 and comparative example 1 increased with the increase in temperature, whereas the ZT values of the samples prepared in examples 1 to 3 increased more than that of comparative example 1.
4. Hardness of
The samples of thermoelectric materials prepared in examples 1 to 3 and comparative examples 1 to 4 were subjected to microhardness test, the experimental results are shown in table 2, and the pit patterns of the samples detected in example 1 and comparative example 1 are shown in fig. 12 and 13, wherein fig. 12 is a pit pattern of the sample detected in comparative example 1, and fig. 13 is a pit pattern of the sample detected in example 1, and the lower the hardness, the larger the pit area, the hardness of the thermoelectric material sample obtained in example 1 was proved to be much smaller than that of comparative example 1.
Table 2 shows the results of the tests of examples 1 to 3 and comparative examples 1 to 4
From table 2 above, it can be seen that:
1. Compared with comparative example 1 without the second phase, the maximum thermoelectric figure of merit in this scheme is increased by a factor of approximately 3, indicating that the interaction of the plastic second phase Ag 2 S with the matrix phase Cu 1.8 S results in a greater increase in thermoelectric figure of merit for copper sulfide-based thermoelectric composites.
2. As is clear from comparative examples 2 and 3, an excessive amount (50% by mass) of the second phase significantly deteriorates the electrical properties of the Cu 1.8 S material, thereby causing deterioration of the thermoelectric properties thereof, and if the amount of addition is too small (5% by mass), it is difficult to make the brittle Cu 1.8 S material flexible, and too large brittleness also affects the use of the thermoelectric material.
In conclusion, experiments prove that the copper sulfide-based thermoelectric composite material provided by the invention has good thermoelectric performance and high compactness, and can be used in the fields of thermoelectric watches, miniature body temperature detectors and the like.
The foregoing is merely exemplary of the present application, and specific materials and characteristics common general knowledge known in the art will not be described in any detail herein. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the scope of the application, which is also to be considered as the scope of the application, and which does not affect the effect of the application and the utility of the patent. The protection scope of the present application is subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.
Claims (7)
1. A preparation method of a copper sulfide-based plastic thermoelectric composite material is characterized by comprising the following steps: the chemical general formula of the material is Cu 1.8S-xAg2 S, wherein x is 20% -40%, the material comprises a matrix phase Cu1.8S and a plastic second phase Ag 2 S, the second phase Ag 2 S is dispersed and distributed in the matrix phase Cu1.8S in the form of nano precipitates, and the second phase Ag 2 S is in a monoclinic structure;
The preparation method comprises the following steps:
Step 1, powder preparation: putting the Cu simple substance powder and the S simple substance powder into a ball mill, and performing ball milling for the first time in a protective atmosphere to obtain Cu 1.8 S powder; then putting Cu 1.8 S powder and plastic semiconductor material Ag 2 S into a high-energy ball mill according to the proportion of 20% -40% of x, and performing ball milling for the second time in protective atmosphere to obtain Cu 1.8S-xAg2 S powder;
Step 2 sintering: and (2) sintering the powder prepared in the step (1) by adopting a spark plasma sintering method to form a block Cu1.8S-xAg 2 S plastic thermoelectric composite material, wherein the sintering temperature is 300-500 ℃, the sintering time is 5-30 min, and the sintering pressure is 10-50 Mpa.
2. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the protective atmosphere in the step 1 is H 2 with a mass fraction of 5% and N 2 with a mass fraction of 95%.
3. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the rotating speed of the first ball milling in the step 1 is 300-450 rpm, and the ball milling time is 1-6 h.
4. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the rotating speed of the second ball milling in the step 1 is 800-1000 rpm, and the ball milling time is 0.5-2 h.
5. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the weight ratio of the ball body to the material in the first ball milling and the second ball milling in the step 1 is 20-50:1.
6. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the spheres used for the first ball milling and the second ball milling in the step 1 comprise spheres with diameters of 3mm, 6mm and 10mm, and the total weights of the spheres with different diameters are equal.
7. The method for preparing the copper sulfide-based plastic thermoelectric composite material according to claim 1, wherein: the purity of the Cu simple substance powder and the S simple substance powder in the step 1 is more than 99.95%, and the purity of the plastic semiconductor powder Ag 2 S is more than 99.9%.
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