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Method for preparing porous nano magnesium silicon based block body thermoelectric material by hot press method in electric field reaction

A technology of electric field reaction hot pressing and thermoelectric materials, applied in the direction of metal silicide, etc., can solve the problems of reducing the thermoelectric transmission performance of Mg2Si thermoelectric materials, complex preparation process, lowering reaction temperature, etc., to reduce the thermal conductivity of the product and achieve high purity. , the effect of simple process

Inactive Publication Date: 2014-06-11
TAIYUAN UNIV OF TECH
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Problems solved by technology

The main problems are: due to the large difference between the melting points of the two, the preparation process is complicated and time-consuming, and the grain growth is serious in the later stage of sintering.
Using MgH 2 After replacing pure Mg powder with pure Mg powder, it can effectively reduce the content of MgO in the product, lower the reaction temperature to 350°C, and obtain nano-scale Mg after 15-20 hours of replacement reaction. 2 Si powder, but impurities are inevitably reintroduced in the later densification sintering process, and the sintering temperature is 650-700 ° C, resulting in serious grain growth and a serious reduction in Mg 2 Thermoelectric Transport Properties of Si Thermoelectric Materials

Method used

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  • Method for preparing porous nano magnesium silicon based block body thermoelectric material by hot press method in electric field reaction
  • Method for preparing porous nano magnesium silicon based block body thermoelectric material by hot press method in electric field reaction

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Experimental program
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Embodiment approach 1

[0014] The reactant MgH 2 Powder (particle size≤45μm, purity≥99.5%), nano Si powder (particle size≤50nm, purity≥99.90%), rare earth metal Y powder (particle size≤45μm, purity≥99.5%) and heavy metal Bi powder (particle size ≤45μm, purity ≥99.5%), the molar mixing ratio is 1.995:0.995:0.005:0.005 (x=0.005, y=0.005), ball milling for 1-3 hours to ensure uniform mixing to form a mixed powder 9, and then the mixed powder 9 Place between the upper indenter 6 and the lower indenter 7 in the graphite mold 4, place the assembled graphite mold in the reaction chamber 3, contact the upper electrode 2 and the lower electrode 5, vacuumize to below 10Pa, and then Pass the Ar protective gas 11 into the cavity from the gas cylinder 12 until the pressure in the cavity reaches 10 5 Pa and keep. Turn on the commercial frequency AC power supply 10 and pressurize 1 in one direction to realize synchronous reaction and sintering densification. Set the heating rate of the powder to 35°C / min. When ...

Embodiment approach 2

[0016] The reactant MgH 2 Powder (particle size≤45μm, purity≥99.5%), nano Si powder (particle size≤50nm, purity≥99.90%), rare earth metal Y powder (particle size≤45μm, purity≥99.5%) and heavy metal Bi powder (particle size ≤45μm, purity ≥99.5%), the molar mixing ratio is 1.995:0.099:0.005:0.01 (x=0.005, y=0.01), ball milling for 1-3 hours to ensure uniform mixing to form a mixed powder 9, and then the mixed powder 9 Place between the upper indenter 6 and the lower indenter 7 in the graphite mold 4, place the assembled graphite mold in the reaction chamber 3, contact the upper electrode 2 and the lower electrode 5, vacuumize to below 10Pa, and then Pass He protective gas 11 into the cavity from the gas cylinder 12 until the pressure in the cavity reaches 10 5 Pa and keep. Turn on the commercial frequency AC power supply 10 and pressurize 1 in one direction to realize synchronous reaction and sintering densification. Set the heating rate of the powder to 40°C / min. When the te...

Embodiment approach 3

[0018] The reactant MgH 2 Powder (particle size≤45μm, purity≥99.5%), nano Si powder (particle size≤50nm, purity≥99.90%), rare earth metal Y powder (particle size≤45μm, purity≥99.5%) and heavy metal Bi powder (particle size ≤45μm, purity ≥99.5%), the molar mixing ratio is 1.99:0.99:0.01:0.01 (x=0.01, y=0.01), ball milling for 1-3 hours to ensure uniform mixing, forming mixed powder 9, and then mixing powder 9 Place between the upper indenter 6 and the lower indenter 7 in the graphite mold 4, place the assembled graphite mold in the reaction chamber 3, contact the upper electrode 2 and the lower electrode 5, vacuumize to below 10Pa, and then Pass the 50%Ar+50%He protective gas 11 into the cavity from the gas cylinder 12 until the pressure in the cavity reaches 10 5Pa and keep. Turn on the commercial frequency AC power supply 10 and pressurize 1 in one direction to realize synchronous reaction and sintering densification. Set the heating rate of the powder to 40°C / min. When th...

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Abstract

The invention relates to a method for preparing a porous nano magnesium silicon based block body thermoelectric material by a hot press method in an electric field reaction, and belongs to the technical field of thermoelectric materials and preparation methods. The method is characterized in that the method for preparing the porous nano Mg2Si-based block body thermoelectric material by the hot press method in the electric field reaction realizes reactive synthesis and compact sintering of Mg2Si in one step, so that the method is simple in step, low in cost, and high in purity of products. Various doping substances are convenient to add, and the products have porous nano-structures. Sustained pollution to the products in a multi-step preparation method can be effectively avoided. Meanwhile, reaction and compact sintering are performed at the same time, so that the temperature and time required by the preparation of products are reduced, and grain coarsening is effectively inhibited. Under the effect of protective gases, reaction byproducts are gathered in grain boundary in the form of nanoholes, so that grain growth is further inhibited and phonon scattering is enhanced. The generated products are completely reacted, the grain size is less than 70nm, the sectional hole ratio is about 5-15%, and holes and the nanocrystals coexist to the benefit of reducing the heat conductivity of the products.

Description

technical field [0001] The method for preparing porous nano-magnesium-silicon-based block thermoelectric materials by an electric field reaction hot pressing method of the present invention belongs to the technical field of thermoelectric materials and preparation methods, and specifically relates to a method for preparing porous nano Mg in one step by using an electric field reaction hot pressing method 2 A method for Si-based bulk thermoelectric materials by which Mg 2 Reactive synthesis and densification sintering of Si, the product is Mg with a particle size of less than 70nm and contains certain nanopores 2 Si-based thermoelectric materials. Mg prepared by this method 2 Si-based bulk thermoelectric materials have porous and nanometer features, which help to obtain high thermoelectric conversion performance. Background technique [0002] Currently Mg 2 The traditional preparation method of Si is to use simple Mg powder and Si powder to react directly, or use other me...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B30/00C01B33/06
Inventor 陈少平樊文浩孟庆森李育德张机源李洋
Owner TAIYUAN UNIV OF TECH
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