【摘要】：銀氧化銅(AgCuO)電觸頭材料是一種新型環(huán)保的顆粒增強(qiáng)體金屬基復(fù)合材料。它擁有銀的高導(dǎo)電導(dǎo)熱性、易加工性,以及氧化物(CuO)的高穩(wěn)定性、與銀基體界面結(jié)合好、抗熔焊性好等,因而備受關(guān)注。在前期原位反應(yīng)合成法制備AgCuO中,發(fā)現(xiàn)所得到的AgCuO電觸頭材料組織中有立方、單斜兩種晶體結(jié)構(gòu)的CuO顆粒存在；并且立方晶體結(jié)構(gòu)CuO顆粒在隨后的大塑性變形中,易產(chǎn)生變形,形成纖維狀的CuO增強(qiáng)相,有益于AgCuO電觸頭材料性能的提高。但立方CuO的形成機(jī)制尚不清楚,這對(duì)制備纖維狀CuO增強(qiáng)相及數(shù)量調(diào)控至關(guān)重要。因此,本論文采用了第一性原理模擬計(jì)算,及熱力學(xué)計(jì)算分析,并與實(shí)驗(yàn)驗(yàn)證相結(jié)合的手段,對(duì)原位反應(yīng)合成AgCuO復(fù)合材料中立方CuO的形成熱力學(xué)條件、機(jī)制及性質(zhì)進(jìn)行了研究,最終得到了如下結(jié)論：根據(jù)第一性原理,對(duì)兩種晶體結(jié)構(gòu)CuO的熱力學(xué)性質(zhì)進(jìn)行了計(jì)算,通過(guò)聲子譜分析發(fā)現(xiàn)兩種CuO結(jié)構(gòu)的熱力學(xué)不穩(wěn)定性主要是由O原子造成的,其中單斜CuO的熱力學(xué)性質(zhì)無(wú)論是低溫時(shí)還是高溫時(shí)都由Cu原子和O原子共同主導(dǎo),而立方CuO的熱力學(xué)性質(zhì)在低溫時(shí)由Cu原子主導(dǎo),高溫時(shí)由O原子主導(dǎo)。同時(shí)還獲得了兩種結(jié)構(gòu)CuO的熱力學(xué)性質(zhì)(包括熵(S)、焓(H)、自由能(G)、熱容(Cp))以及與溫度的變化關(guān)系；并根據(jù)吉布斯自由能差,計(jì)算得出了兩種晶體結(jié)構(gòu)CuO之間的相轉(zhuǎn)變熱力學(xué)溫度為1013.28K(即740.13℃)。通過(guò)對(duì)原位反應(yīng)合成法制備AgCuO中,有關(guān)CuO反應(yīng)的熱力學(xué)計(jì)算與分析后,發(fā)現(xiàn)采用原位反應(yīng)合成法制備AgCuO過(guò)程中,形成立方氧化銅的方式有以下三種：a)Cu與O2直接反應(yīng)合成立方CuO,合成溫度應(yīng)低于883K(即609.85℃)；b)燒結(jié)反應(yīng)過(guò)程中生成部分的Cu2O與O2反應(yīng)合成立方CuO,該方式的反應(yīng)溫度應(yīng)低于742.99K(即469.84℃)；c)Cu與O2反應(yīng)合成單斜的CuO后,在后期燒結(jié)時(shí)發(fā)生相轉(zhuǎn)變得到立方CuO,該方式的轉(zhuǎn)變溫度應(yīng)低于1048.49K(即775.3℃)。通過(guò)相關(guān)實(shí)驗(yàn)論證結(jié)果表明：Cu與O2直接反應(yīng)合成立方CuO(即第一種合成方式)與燒結(jié)反應(yīng)過(guò)程中生成部分的Cu2O與O2反應(yīng)合成立方CuO(即第二種合成方式)這兩種方式發(fā)生的可能性小,或者不發(fā)生；而以Cu與O2反應(yīng)合成單斜的CuO后,在后期燒結(jié)時(shí)發(fā)生相轉(zhuǎn)變生成立方CuO(第三中方式)是原位反應(yīng)合成法制備AgCuO中立方CuO的主要形成方式。實(shí)驗(yàn)還證實(shí)了1048K(即775℃)左右的溫度即是單斜CuO與立方CuO之間相轉(zhuǎn)變溫度,這一溫度與模擬和理論計(jì)算溫度十分接近。實(shí)驗(yàn)結(jié)果還發(fā)現(xiàn),Ag的存在對(duì)形成立方CuO的相變以及形成量有一定的影響。最后,研究了這兩種晶體結(jié)構(gòu)CuO的力學(xué)和微觀性質(zhì)。得出立方CuO的延性好于單斜CuO的延性；立方CuO為間接帶隙半導(dǎo)體,單斜CuO為直接帶隙半導(dǎo)體,立方CuO中的Cu原子與O原子之間無(wú)明顯相互作用,而單斜CuO中的Cu原子與O原子之間有相互作用；立方CuO的導(dǎo)電性?xún)?yōu)于單斜CuO導(dǎo)電性,其導(dǎo)電性主要來(lái)自于Cu原子的3d10軌道貢獻(xiàn)。
[Abstract]:Silver copper oxide (AgCuO) electric contact material is a new type of environmentally friendly particle reinforced metal matrix composite. It has high conductivity, easy processing, high stability of oxide (CuO), good interface with silver matrix, good welding resistance and so on, so it has attracted much attention. In the preparation of AgCuO by in situ reaction synthesis, it was found that there were cubic and monoclinic CuO particles in the microstructure of AgCuO electrical contact materials. Moreover, the cubic crystal structure CuO particles are easy to deform and form a fiber-like CuO reinforced phase in the subsequent large plastic deformation, which is beneficial to the improvement of the properties of AgCuO electrical contact materials. However, the formation mechanism of cubic CuO is not clear, which is very important for the preparation of fiber-like CuO enhanced phase and quantitative regulation. Therefore, in this paper, the thermodynamic conditions, mechanism and properties of cubic CuO in-situ reaction synthesis of AgCuO composites were studied by means of first-principle simulation and thermodynamic calculation and analysis, and combined with experimental verification. Finally, the following conclusions are obtained: according to the first principle, the thermodynamic properties of CuO with two crystal structures are calculated. Through phonon spectrum analysis, it is found that the thermodynamic instability of the two CuO structures is mainly caused by O atoms. The thermodynamic properties of monoclinic CuO are dominated by Cu atom and O atom at low temperature and high temperature, while the thermodynamic properties of cubic CuO are dominated by Cu atom at low temperature and O atom at high temperature. At the same time, the thermodynamic properties of CuO with two structures, including entropy (S), enthalpy (H), free energy (G), heat capacity (Cp) and its relationship with temperature, were also obtained. According to the Gibbs free energy difference, the thermodynamic temperature of phase transition between the two crystal structures CuO is calculated to be 1013.28K (that is, 740.13 鈩，

本文編號(hào)：2478290