發(fā)布時間：2018-06-17 13:20

  本文選題：Pb + Te基熱電材料　； 參考：《清華大學(xué)》2015年博士論文

【摘要】：PbTe基熱電器件能直接將熱能轉(zhuǎn)化為電能而發(fā)電,主要應(yīng)用于太空探測器電源、汽車廢熱回收和工業(yè)廢熱利用。目前,PbTe基熱電電極接頭主要采用機械方法連接,導(dǎo)致器件重量增加、結(jié)構(gòu)復(fù)雜和使用不便,接頭接觸電阻和熱阻也較大,降低了器件熱電轉(zhuǎn)化效率;另外,PbTe基熱電電極接頭高溫端要求在550oC及一定應(yīng)力條件下長期穩(wěn)定工作,因此接頭制備難度較大。本論文以開發(fā)高性能PbTe基熱電電極接頭為目標(biāo),期望獲得綜合性能良好的冶金結(jié)合接頭。本論文首先采用一步熱壓燒結(jié)法進行Ni/PbTe、Nb/PbTe、Fe/PbTe和Mo/PbTe四種熱電電極接頭的連接試驗,研究了接頭的界面結(jié)構(gòu),分析了接頭界面擴散與反應(yīng)行為,討論了接頭界面結(jié)構(gòu)形成機制。對Ni/PbTe接頭而言,Ni與PbTe可能形成共晶液相,界面既可能發(fā)生液固或固固等置換反應(yīng)生成Ni3±xTe2相和液態(tài)Pb,還可能發(fā)生反應(yīng)析出三元相和共晶相;形成的液相和生成的液態(tài)Pb會大量滲透入Ni箔晶界。對Nb/PbTe接頭而言,Nb與PbTe不會形成共晶液相,Nb與PbTe發(fā)生固相置換反應(yīng)生成Nb3Te4相和液態(tài)Pb,生成的液態(tài)Pb也不會滲透入Nb晶界。Nb3Te4反應(yīng)層的生長是由Nb原子通過Nb3Te4擴散至PbTe界面的擴散速率控制的生長過程。對Fe/PbTe和Mo/PbTe接頭而言,Fe和Mo與PbTe在連接溫度范圍內(nèi)既不會形成共晶液相也不會發(fā)生置換反應(yīng)。本論文選用NiFeMo合金和Fe/Ni雙層金屬兩種電極材料與PbTe進行連接,分析了界面結(jié)構(gòu)及其形成機理。相比Ni/PbTe接頭,NiFeMo與PbTe的共晶溫度提高,NiFeMo與PbTe沒有發(fā)生明顯的界面反應(yīng),Fe原子和Mo原子的存在抑制了Ni與PbTe的界面反應(yīng)。對Fe/Ni/PbTe接頭而言,可能形成五種界面結(jié)構(gòu),分別為:(1)Fe(Ni)/非連續(xù)顆粒狀(Fe,Ni)1.12Te/PbTe(Ni);(2)Fe/Fe(Ni)/Ni(Fe)/PbTe(Ni);(3)Fe/Fe0.88Ni0.12/Ni(Fe)/Ni3±xTe2/PbTe(Ni);(4)Fe/Fe0.88Ni0.12/(Fe,Ni)1.26Te+Pb/PbTe;(5)Fe/孔洞Fe0.88Ni0.12/(Fe,Ni)1.26Te+Pb/PbTe。通過對各接頭界面結(jié)構(gòu)、力學(xué)性能、熱電性能和電學(xué)性能的分析,結(jié)果表明Fe/6μmNi/PbTe接頭在連接工藝650℃/150min時制備的界面結(jié)構(gòu)Fe/Fe0.88Ni0.12/Ni(Fe)/Ni3±xTe2/PbTe較優(yōu),接頭既能實現(xiàn)良好連接又能抑制晶界滲透,是較理想的PbTe基熱電電極接頭。
[Abstract]:PbTe based thermoelectric devices can directly convert heat energy into electric energy and generate electricity. It is mainly used in space detector power source, automobile waste heat recovery and industrial waste heat utilization. At present, the PbTe based thermoelectric electrode joint is mainly connected by mechanical method, which leads to the increase of device weight, the complexity of structure and the inconvenience of application. The contact resistance and thermal resistance of the joint are also large, which reduces the thermoelectric conversion efficiency of the device. In addition, the high temperature end of PbTe based thermoelectric electrode joint is required to work stably for a long time under 550 OC and certain stress conditions, so it is difficult to prepare the joint. The aim of this thesis is to develop high performance PbTe based thermoelectric electrode joints and to obtain metallurgical bonding joints with good comprehensive properties. In this paper, the bonding tests of four kinds of thermoelectric electrode joints (Ni / PbTeN, Fe / PbTe and Mo / PbTe) were carried out by means of one step hot pressing sintering method. The interface structure of the joint was studied, the diffusion and reaction behavior of the interface was analyzed, and the formation mechanism of the interface structure of the joint was discussed. For Ni / PbTe joints, the eutectic liquid phase may be formed between Ni / PbTe and Ni / PbTe. The interface may produce Ni3 鹵xTe2 phase and liquid Pb2 phase, and precipitate ternary and eutectic phases at the interface. The formed liquid phase and the resulting liquid Pb permeate into the grain boundary of Ni foil in large quantities. For NB / PbTe joints, NB and PbTe do not form eutectic liquid phase substitution reaction between NB and PbTe to form Nb3Te4 phase and liquid PbTe, and the resulting liquid Pb will not permeate into NB grain boundary. Nb3Te4 reaction layer grows by NB atom diffusing through Nb3Te4 to PbTe. The diffusion rate of the interface controls the growth process. For Fe / PbTe and Mo / PbTe joints, there is neither eutectic liquid phase nor substitution reaction between Fe, Mo and PbTe in the range of bonding temperature. In this paper, two kinds of electrode materials, NiFeMo alloy and Fe / Ni bilayer metal, were used to connect with PbTe, and the interface structure and formation mechanism were analyzed. Compared with the eutectic temperature of NiFeMo and PbTe, there is no obvious interfacial reaction between NiFeMo and PbTe. The existence of Fe atom and Mo atom inhibits the interfacial reaction between Ni and PbTe. 瀵笷e/Ni/PbTe鎺ュご鑰岃█,鍙�鑳藉舰鎴愪簲绉嶇晫闈⒕l撴瀯,鍒嗗埆涓，

本文編號：2031193