KR20120102961A - Method for preparing thermoelectric device - Google Patents

Abstract

PURPOSE: A method for manufacturing a thermoelectric element is provided to improve thermoelectric performance by forming a nano-material layer for maximizing phonon scattering on the porous area. CONSTITUTION: A porous thermoelectric element is manufactured. A nano-material layer is formed on the internal or external surface of the porous thermoelectric element. The porous thermoelectric element is formed by mixing base material of the porous thermoelectric element, a doping agent, and foaming mixture. The nano-material layer is nano-coated on the external surface of the porous thermoelectric element. The nano coating is micro arc discharge coating. The micro arc discharge coating is performed under the condition of pH9-11.

Description

Thermoelectric device manufacturing method {Method for preparing thermoelectric device}

The present invention relates to a method of manufacturing a thermoelectric element.

The proliferation of fossil energy use causes global warming and energy depletion. In response to such problems, recently, renewable energy development and thermoelectric element development programs have been actively conducted in various countries around the world including Korea. In particular, since all equipment and electronics do not thermodynamically overcome the limitations of the Carnot cycle, the waste heat accounts for most of the energy input. Therefore, if the waste heat energy can be reused and applied to new areas, it will be a good methodology to overcome the energy crisis.

Meanwhile, thermoelectric devices and modules are largely divided into a power generation field using the seebeck effect and a cooling field using the peltier effect. In the cooling field, heat generation increases with the development of the IT industry, along with the miniaturization, high power consumption, high integration, and slimness of electronic components, and the generated heat acts as an important factor to reduce the malfunction and efficiency of electronic devices.

In order to solve this problem, the thermoelectric device is used. Also, considering the noiselessness, fast cooling speed, local cooling, and eco-friendliness of the thermoelectric device, the applicability in the future is inevitably increased.

In the field of power generation, many efforts are being studied worldwide to reproduce electric energy by using a large amount of waste heat discarded from automobiles, waste incinerators, steel mills, power plants, geothermal energy, electronic devices, and body temperature. In particular, thermoelectric power generation is a volumetric power generation, and can be combined with other power generations, so the applicability to the future is very large. In addition, since it does not emit global pollutants during the production of electrical energy, it is also compatible with environmentally friendly performance, which will accelerate the propagation speed of thermoelectric power.

However, the commercialization of thermoelectric cooling and power generation has not been universalized worldwide, and the research is also being carried out on the scale of labs of national application institutes and academia. Recently, many thermoelectric devices and modules have been studied as solutions for rising energy prices and environmental problems. Considering their applicability, the future market is large.

Conventional thermoelectric elements are mainly manufactured by mechanical alloying by mixing metal raw materials in a certain component ratio. That is, the bulk type thermoelectric element uses a basic process of initial melting, crushing, and sintering, and a dopant is added thereto to manufacture p-type and n-type semiconductors. In addition, the prepared semiconductor powder is melted and grown in the form of an ingot, thereby making a thermoelectric device through a pulverization and cooling, pressurization, and baking process.

When the thermoelectric device is manufactured using the above process, the production time is long and the production yield itself is low as 30 to 40%, which causes a large problem in mass productivity. In addition, the module is manufactured by using the manufactured thermoelectric element, and in the fabrication of the module, additional processes such as forming a substrate pattern of a metallization element, and heterojunction with the element are performed, thereby improving reliability and mass-producing the module. It will cause a decrease in yield.

As a result, the existing processes have a disadvantage that the process process is complicated and difficult to control the process conditions, which includes expensive process costs and makes it difficult to manufacture reproducible devices and modules.

In the present invention, to solve the problems of the prior art as described above, an object of the present invention is to provide a method of manufacturing a thermoelectric element and a module having a simple manufacturing process, easy control of process conditions, and excellent reproducibility. There is.

Method for manufacturing a thermoelectric device according to an embodiment of the present invention for solving the above problems is to prepare a porous thermoelectric device; And forming a nanomaterial layer on the inner or outer surface of the porous thermoelectric device.

The porous thermoelectric device may be formed by mixing and extruding a base material, a doping material, and a foamed mixture of the thermoelectric device.

The nanomaterial layer may be formed of one or more materials selected from the group consisting of metal and nonmetal materials.

The metal forming the nanomaterial layer may be at least one selected from the group consisting of Sb, Se, Ni, Ag, Cu, Zn, Mn, Y, Fe, and Nb.

In addition, the base metal forming the nanomaterial layer may be one or more selected from the group consisting of SiO, TiO ₂ , BaTiO ₃ , and Fe ₂ O ₃ .

The nanomaterial layer may be formed by nanocoating a porous outer surface of the thermoelectric device.

The nano coating may be a micro arc discharge coating.

The micro arc discharge coating may be carried out at the pH 9-11 conditions.

The micro arc discharge coating may be carried out at low temperature conditions of 25 ~ 50 ℃.

The nano-coating may be performed by gas phase spraying.

The nanomaterial layer may be formed by directly injecting into the internal pores of the thermoelectric device.

Ultrasonic vibration may be used when the nanomaterial is directly injected into the internal pores of the thermoelectric device.

According to an embodiment of the present invention, the method may further include forming an antioxidant film.

The anti-oxidation film may be formed by thermally pressing through aluminum and copper foil after forming an epoxy silicone resin.

According to an embodiment of the present invention, the nanomaterial layer may be formed of two or more layers.

According to the exemplary embodiment of the present invention, after the porous thermoelectric device is manufactured, a nanomaterial layer capable of maximizing phonon scattering may be formed on the porous surface or the inside thereof, thereby improving thermoelectric performance according to thermal conductivity reduction. In addition, by keeping the surface area wide, the device can be made thin and small to cope with high-integration applications, and the thermoelectric device can be easily designed by freely forming metal and nonmetal materials in the nanomaterial layer. The process time is shortened and high reliability such as chemical resistance and durability can be secured, and the problem of oxidation of materials generated during module manufacturing can be solved, and the bonding strength of each layer is excellent, and the doping material is included. Controllable and easy to manufacture multi-component thermoelectric element layer.

1 is a scanning electron micrograph of a porous thermoelectric plate according to an embodiment of the present invention,
Figure 2 is a scanning electron micrograph of the surface after the nanomaterial layer is coated on the surface of the porous thermoelectric device according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

The present invention relates to a method of manufacturing a thermoelectric device capable of reducing thermal conductivity through maximizing phonon scattering, specifically, manufacturing a porous thermoelectric device; And forming a nanomaterial layer on the inner or outer surface of the porous thermoelectric device.

The porous thermoelectric device may be manufactured by mixing and extruding a base material, a doping material, and a foamed mixture of the thermoelectric device.

The thermoelectric element base material is one or more selected from the group consisting of BiTe, Znsb, InSe, CoSb, PbTe, GeTe, and FeSi, but is not particularly limited thereto.

In addition, at least one selected from the group consisting of Sb, Se, Ni, Ag, Cu, Zn, Mn, Y, Fe, and Nb is used as the doping material mixed in the base material. In some cases, when the particle size is too large, the particle size is made small by crushing or pulverizing.

A solvent such as alcohol, acetone, toluene is added to at least one foaming solution selected from the group consisting of TiH ₂ , ZrH ₂ , PVC, PVA, PMEA, methylcellulose, monoglycerides, albumin, gelatin, alkyl sulfates, and starch. To make a foamed mixture, which is then extruded into a desired mold.

Extrusion molding is preferably carried out at a constant temperature and pressure to ensure a predetermined porosity, for example, it can be carried out at a temperature of 400 ~ 600 ℃ and a pressure of 20 ~ 100 Mpa.

In addition, in order to control the desired pore size and shape, the composition ratio of the base material, the doping material, and the foamed mixture of the thermoelectric device may be controlled. Each device can be manufactured by adjusting within the range of.

The next step is to form a nanomaterial layer on the inner or outer surface of the porous thermoelectric element.

According to an embodiment of the present invention, the nanomaterial layer may be formed by nanocoating a porous outer surface of the thermoelectric element to maximize phonon scattering.

The nanomaterial layer may be at least one selected from metals and nonmetals to form a large number of phonon scattering layers on a porous pore surface. For example, Sb, Se, and Ni, which are doping materials used in manufacturing the porous thermoelectric device, may be used. At least one metal selected from the group consisting of Ag, Cu, Zn, Mn, Y, Fe, and Nb, or 1 selected from the group consisting of SiO, TiO ₂ , BaTiO ₃ , and Fe ₂ O ₃ It may include more than one type of nonmetal, but is not limited thereto.

In addition, the nano-coating for forming a nanomaterial layer on the surface of the porous thermoelectric device may be coated using a dry, bulk, wet method using the metal and non-metallic materials, the coating method is not particularly limited.

The coating method does not use a strong acid to coat the nanomaterial layer by generating a difference between pulse, current density, and voltage in a weakly alkaline aqueous solution having a pH of 9-11. This is called a micro-arc discharge coating method, and by using such a process, it is possible to prepare a fast process time in an environment-friendly condition using a weak alkali solution at a low temperature such as 25 ~ 50 ℃.

The weak alkaline aqueous solution may use one or more alkaline aqueous solutions selected from the group consisting of KNO ₃ , KCl, K ₂ HPO ₄ , KOH, K ₂ SO ₄ , and K ₃ PO ₄ , but is not limited thereto.

This not only solves the problems of poor acid resistance due to the use of a strong acid, but also has an advantageous effect in terms of cost since it does not coat at a high temperature of 50 ° C. or more using a relatively strong acid.

According to another embodiment of the present invention, the metal and non-metallic materials may be made into a sol state and the nanomaterial layer may be coated by a gas phase spraying method such as an aerosol or cold spray.

In addition, by forming a plurality of mixed coating materials to form a hybrid (hybrid) coating material can be maximized by the process simplification of the thermal conductivity reduction effect according to the multi-layer forming interface.

In some cases, the nanomaterial layer may be formed in a multilayer of two or more layers such as Sb-> Ag-> Ni, and the type and order of the materials may be variously selected.

In addition, according to another preferred embodiment of the present invention, the nanomaterial layer may be formed by direct injection into the internal pores of the thermoelectric element.

That is, after mixing the base material, the binder and the foam mixture of the thermoelectric element, and cast it in a given mold to proceed with the binder and sintering to produce a porous thermoelectric element. After the casting film is removed, metal and non-metallic materials are spread on the upper portion, and then injected into the internal pores of the porous thermoelectric element using ultrasonic vibration. After sintering through a process such as HIP, SPS.

The nanomaterial layer according to the present invention may have a thickness of 0.01 to 1 μm, preferably 0.1 to 0.1 μm.

In addition, in order to prevent oxidation, an epoxy resin may be slightly applied to the surface, and then aluminum or copper foil may be attached and then compressed to form an antioxidant film.

Hereinafter, preferred embodiments of the present invention will be described. The embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art, and the following examples can be modified in various other forms, and the scope of the present invention is It is not limited to an Example. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the inventive concept to those skilled in the art.

Example  One

BiTe and ZnSb were used as a base material of the thermoelectric element, Ag was mixed as a doping material, and toluene was added to the methyl cellulose foam solution to make a foamed mixture, which was put in a fixed mold and extruded to prepare a porous thermoelectric element. . Extrusion was carried out at a temperature of 450 ° C. and a pressure of 50 MPa.

Then, Ni was coated on the surface of the porous thermoelectric element by a wet coating method. Coating conditions were carried out at 30 ℃ using a micro arc discharge coating in a KOH aqueous solution of pH 10, to form a nanomaterial layer of 0.1 ㎛ thickness.

Experimental Example  One

In Example 1, the plate of the porous thermoelectric element before the nanomaterial layer was formed (FIG. 1) and the surface form after the nanomaterial layer was formed (FIG. 2) were measured by a scanning electron microscope. 2 is shown.

Next, FIG. 1 is a surface photograph of a porous thermoelectric device, and it can be seen that a thermoelectric material layer having a large pore size, various particle shapes, and a large particle distribution is formed.

On the other hand, after coating the Ag nanomaterial layer on the surface of the porous thermoelectric device in Figure 2, it can be seen that the particle pores are uniform and the plate-shaped nanomaterial layer is formed in the crystalline phase. Accordingly, it can be seen that a more homogeneous and various doping material can be manufactured with a coating capable of coating a small size.

Claims (15)

Manufacturing a porous thermoelectric element; And
The method of manufacturing a thermoelectric device comprising the step of forming a nanomaterial layer on the inner or outer surface of the porous thermoelectric device.
The method of claim 1, wherein the porous thermoelectric device is formed by mixing and extruding a base material, a doping material, and a foamed mixture of the thermoelectric device.
The method of claim 1, wherein the nanomaterial layer is formed by nanocoating a porous outer surface of the thermoelectric device.
The method of claim 3, wherein the nano coating is a micro arc discharge coating.
The method of claim 4, wherein the micro arc discharge coating is performed at a condition of pH 9-11.
The method of claim 5, wherein the micro arc discharge coating is performed at a temperature of 25 ° C. to 50 ° C. 7.
The method of claim 3, wherein the nano-coating is a gas phase spraying method.
The method of claim 1, wherein the nanomaterial layer is formed of at least one material selected from metals and nonmetals.
The method of claim 8, wherein the metal forming the nanomaterial layer is one or more selected from the group consisting of Sb, Se, Ni, Ag, Cu, Zn, Mn, Y, Fe, and Nb. Way.
The method of claim 8, wherein the base metal forming the nanomaterial layer is at least one selected from the group consisting of SiO, TiO ₂ , BaTiO ₃ , and Fe ₂ O ₃ .
The method of claim 1, wherein the nanomaterial layer is formed by direct injection into internal pores of the thermoelectric device.
The method of claim 11, wherein ultrasonic vibration is used when a doping material is directly injected into the internal pores of the thermoelectric element.
12. The method of claim 11, further comprising forming an antioxidant film.
The method of claim 13, wherein the anti-oxidation film is formed by thermally pressing Al and Cu foils after forming an epoxy silicone resin.
The method of claim 1, wherein the nanomaterial layer is formed of two or more layers.

Images