【摘要】：熱電材料是一種利用固體中載流子(電子和空穴)運動實現(xiàn)熱能和電能直接相互轉(zhuǎn)換的功能材料,主要應用于溫差發(fā)電和熱電制冷。熱電材料的能量轉(zhuǎn)化效率高低采用一個無量綱的熱電優(yōu)值ZT進行衡量,ZT值越大,材料熱電性能越優(yōu)異。含銅的硫化物系列熱電材料具有較高的ZT值,其中黝銅礦晶體結(jié)構(gòu)復雜且高度對稱,本身具有較低的晶格熱導率及穩(wěn)定性。因此本課題選取黝銅礦系熱電材料作為主要研究對象,從材料制備和連接兩方面進行研究,提升材料的熱電性能并實現(xiàn)與電極間的高可靠性連接。采用熔煉+退火+熱壓燒結(jié)制備黝銅礦系熱電材料,對制備過程中各階段得到的材料進行晶體結(jié)構(gòu)測試及微觀組織分析,發(fā)現(xiàn)Cu12Sb4S13熱電材料中存在第二相,影響材料整體的熱電性能。通過摻雜Ni元素等電位取代Cu12Sb4S13中的Cu,抑制第二相的析出,最終獲得單一相組成的Cu10.4Ni1.6Sb4S13熱電材料。對摻雜元素前后的材料進行熱電性能測試及各項參數(shù)對比,發(fā)現(xiàn)摻雜后的材料熱電性能有所提升。在溫度為427℃時,Cu12Sb4S13熱電材料ZT值為0.54,Cu10.4Ni1.6Sb4S13熱電材料ZT值為0.85。Cu10.4Ni1.6Sb4S13熱電材料熔點為604℃,使用溫度為420℃,為保證熱電材料服役溫度和穩(wěn)定性,選擇熔點在420℃-604℃之間的釬料體系。本課題首先采用Al-Si-Cu釬料和Zn-Al釬料對Cu10.4Ni1.6Sb4S13熱電材料與Cu電極進行釬焊連接,得到的接頭界面出現(xiàn)貫穿裂紋和溶蝕等缺陷,通過調(diào)節(jié)工藝參數(shù)仍無法消除,需更換釬料種類;采用Ag-Cu-Sn釬料對Cu10.4Ni1.6Sb4S13熱電材料與Cu電極進行釬焊連接,在釬焊溫度為500℃,保溫時間為5min時,所得接頭的界面結(jié)構(gòu)為:Cu10.4Ni1.6Sb4S13/Cu2S3Sn/Sn S+Ag3Sn/Cu3Sn/Cu。在釬焊連接過程中,熱電材料中的S元素發(fā)生較為嚴重的擴散且擴散距離較遠,導致釬縫中生成大量硫化物。隨著釬焊溫度升高,S元素擴散程度加大,擴散到電極側(cè)的S元素與Cu結(jié)合生成Cu2S化合物層而使母材產(chǎn)生溶蝕現(xiàn)象,溶蝕程度逐漸變大,溶蝕寬度呈指數(shù)性增長,最高接頭強度只有3.1MPa。為了減緩接頭擴散反應,采用Ag-Cu-Sn釬料并添加Ni擴散阻隔層對Cu10.4Ni1.6Sb4S13熱電材料與Cu電極進行釬焊連接,釬焊溫度為480℃,保溫時間為2.5min,所得接頭的界面結(jié)構(gòu)為:Cu10.4Ni1.6Sb4S13/Ni Sb+Ni Sb S+Cu2S3Sn/Sn S+Ag3Sn/Ni3Sn2/Ni/(Cu,Ni)3Sn2/Ag3Sn+Cu3Sn/Cu3Sn,發(fā)現(xiàn)Ni擴散阻隔層能夠有效地阻礙熱電材料中S元素的擴散。釬焊工藝參數(shù)對接頭界面組織和力學性能具有重要影響,在釬焊溫度為480℃,保溫時間為5min時,熱電材料側(cè)反應層清晰明顯且厚度適中,界面各區(qū)域形成了良好的冶金結(jié)合,接頭平整且無明顯缺陷,界面結(jié)構(gòu)最優(yōu),此時接頭抗剪強度可達9.3MPa,相較無擴散阻隔層提升200%。對接頭斷口進行分析,得到Cu10.4Ni1.6Sb4S13/Cu接頭斷裂機制為沿晶脆性斷裂,斷裂位置出現(xiàn)在熱電材料側(cè)反應層及熱電材料上。
[Abstract]:Thermoelectric material is a kind of functional material which uses the motion of carrier (electron and hole) in solid to realize the direct conversion between heat energy and electric energy. It is mainly used in thermoelectric power generation and thermoelectric refrigeration. The energy conversion efficiency of thermoelectric materials is measured by a dimensionless thermoelectric excellence value (ZT). The larger the ZT value is, the better the thermoelectric properties of the materials are. The copper sulfide series of thermoelectric materials have a high ZT value, among which tetrahedrite has a complex crystal structure and a high symmetry, and has low lattice thermal conductivity and stability. Therefore, this paper selects tetrahedrite series thermoelectric material as the main research object, from the material preparation and the connection two aspects carries on the research, enhances the material thermoelectric performance and realizes the high reliability connection with the electrode. Tetrahedrite series thermoelectric materials were prepared by melting annealing and hot pressing sintering. The second phase was found in Cu12Sb4S13 thermoelectric materials by crystal structure test and microstructure analysis. The thermoelectric properties of the whole material are affected. The second phase precipitation was inhibited by doping Ni element instead of Cu, in Cu12Sb4S13, and the mono-phase Cu10.4Ni1.6Sb4S13 thermoelectric material was obtained. The thermoelectric properties of the materials before and after doping were tested and compared with each other, and it was found that the thermoelectric properties of the doped materials were improved. When the temperature is 427 鈩，

本文編號：2420133