本文選題：MgH2　切入點：FAPAS　出處：《太原理工大學》2015年碩士論文

【摘要】：熱電材料是一種能夠利用材料內(nèi)部載流子運動將電能和熱能直接轉換的新型功能材料，具有質量輕、壽命長、體積小、清潔環(huán)保等許多優(yōu)點，在汽車尾氣回收和工業(yè)余熱、廢熱的再利用方面得到了初步的推廣。熱電材料的種類多種多樣，其中鎂硅基熱電材料以其原料豐富、無毒、安全可靠的特點得到了人們的廣泛關注。 本文主要針對傳統(tǒng)制備方法制備鎂硅基熱電材料過程中容易造成Mg的揮發(fā)和氧化等問題，設計了以MgH2代替Mg，并結合電場激活壓力輔助合成（Field-Activated and Pressure-Assisted Synthesis，簡稱FAPAS）技術實現(xiàn)了Bi摻雜的Mg2Si和Mg2Si1-xSnx（0.3≤x≤0.5）鎂硅基熱電材料的快速燒結成型（一步合成法），并對其熱電性能和熱穩(wěn)定性進行了表征。該方法工藝簡便，制備時間短，樣品具有納米片層結構，且純凈致密。主要研究結果總結如下： 以MgH2粉、Si粉和Bi粉為原料，運用一步合成法制備出不同配比且不同Bi含量的Mg2Si塊體材料，實驗結果表明，改變MgH2與Si配比和Bi含量對材料的熱導率和電導率均有一定的影響。當MgH2與Si配比為1.95:1且摻入1at.%-Bi時，所得Mg2Si樣品在775K獲得最佳ZT值，ZTmax=0.77。 以MgH2粉、Si粉、Sn粉和Bi粉為原料，運用一步合成法制備出不同Bi含量的Mg2Si1-xSnx基熱電材料，實驗結果表明，當x=0.4時，，Mg2Si1-xSnx熱電材料的性能達到最佳，同時在此基礎上通過摻入不同含量的Bi進一步提高材料的熱電性能。當溫度為770K時，Mg2Si0.6Sn0.4Bi0.01的樣品獲得了最大ZT值，為1.29。將制備的樣品進行自然時效處理和退火處理。自然時效處理后的Mg2Si0.6Sn0.4Bi0.02的樣品在整個測溫區(qū)間的性能為最佳，當溫度在775K時ZTmax=1.29。退火處理的樣品ZT值在700K之后上升趨勢都趨于平緩，且三者ZT值較為接近，說明熱電性能趨于穩(wěn)定。當溫度在775K時，Mg2Si0.6Sn0.4Bi0.01樣品退火后ZTmax=0.9。
[Abstract]:Thermoelectric material is a kind of carrier material will be able to use within the new functional material electrical and thermal energy conversion, has the advantages of light weight, long life, small size, clean and environmental protection and many other advantages, in the automobile exhaust gas recycling and industrial waste heat, waste heat recycling has been popularized. Various types of thermoelectric materials among them, magnesium and silicon based thermoelectric materials with its rich raw materials, non-toxic, safe and reliable characteristics has been widespread concern.
In this paper, the volatilization of Mg and oxidation problems caused by traditional preparation method of magnesium silicon based thermoelectric materials in the process of design, using MgH2 instead of Mg, and combined with the field activated pressure assisted synthesis (Field-Activated and Pressure-Assisted Synthesis, referred to as FAPAS) technology to achieve the Bi doped Mg2Si and Mg2Si1-xSnx (x = 0.3 ~ 0.5 rapid sintering of silicon) magnesium based thermoelectric materials (one-step synthesis method), and the thermoelectric properties and thermal stability were investigated. The method has the advantages of simple process, short preparation time, samples with nano lamellar structure, dense and pure. The main results are as follows:
Using MgH2 powder, Si powder and Bi powder as raw material, using one step synthesis of different ratio and different Bi content Mg2Si bulk materials, the experimental results show that the change of the MgH2 and Si ratio and Bi content on the thermal conductivity and electrical conductivity have a certain impact. When the ratio of MgH2 and Si for 1.95:1 and doped in 1at.%-Bi, the Mg2Si ZT 775K in the sample to obtain the best value, ZTmax=0.77.
Using MgH2 powder, Si powder, Sn powder and Bi powder as raw material, using one step synthesis of Mg2Si1-xSnx based thermoelectric materials with different Bi content, the experimental results show that when x=0.4, the performance of Mg2Si1-xSnx thermoelectric materials to achieve the best, and on this basis through adding different content of Bi to further improve the thermoelectric properties of materials when the temperature is 770K, Mg2Si0.6Sn0.4Bi0.01 sample obtained the maximum ZT value, natural aging treatment and annealing treatment for 1.29. prepared samples. After natural aging treatment of Mg2Si0.6Sn0.4Bi0.02 samples in the whole range of ZTmax=1.29. is the best, when the temperature in the 775K annealed sample ZT value increased in 700K after the trend is flat, and the three ZT values are close to that of thermoelectric performance tends to be stable. When the temperature at 775K, Mg2Si0.6Sn0.4Bi0.01 after annealing ZTmax=0.9.

【學位授予單位】：太原理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TB34

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