原位反应合成AgCuO复合材料中立方氧化铜的形成机制及性质研究
发布时间：2019-05-16 12:50
【摘要】：银氧化铜(AgCuO)电触头材料是一种新型环保的颗粒增强体金属基复合材料。它拥有银的高导电导热性、易加工性,以及氧化物(CuO)的高稳定性、与银基体界面结合好、抗熔焊性好等,因而备受关注。在前期原位反应合成法制备AgCuO中,发现所得到的AgCuO电触头材料组织中有立方、单斜两种晶体结构的CuO颗粒存在；并且立方晶体结构CuO颗粒在随后的大塑性变形中,易产生变形,形成纤维状的CuO增强相,有益于AgCuO电触头材料性能的提高。但立方CuO的形成机制尚不清楚,这对制备纤维状CuO增强相及数量调控至关重要。因此,本论文采用了第一性原理模拟计算,及热力学计算分析,并与实验验证相结合的手段,对原位反应合成AgCuO复合材料中立方CuO的形成热力学条件、机制及性质进行了研究,最终得到了如下结论：根据第一性原理,对两种晶体结构CuO的热力学性质进行了计算,通过声子谱分析发现两种CuO结构的热力学不稳定性主要是由O原子造成的,其中单斜CuO的热力学性质无论是低温时还是高温时都由Cu原子和O原子共同主导,而立方CuO的热力学性质在低温时由Cu原子主导,高温时由O原子主导。同时还获得了两种结构CuO的热力学性质(包括熵(S)、焓(H)、自由能(G)、热容(Cp))以及与温度的变化关系；并根据吉布斯自由能差,计算得出了两种晶体结构CuO之间的相转变热力学温度为1013.28K(即740.13℃)。通过对原位反应合成法制备AgCuO中,有关CuO反应的热力学计算与分析后,发现采用原位反应合成法制备AgCuO过程中,形成立方氧化铜的方式有以下三种：a)Cu与O2直接反应合成立方CuO,合成温度应低于883K(即609.85℃)；b)烧结反应过程中生成部分的Cu2O与O2反应合成立方CuO,该方式的反应温度应低于742.99K(即469.84℃)；c)Cu与O2反应合成单斜的CuO后,在后期烧结时发生相转变得到立方CuO,该方式的转变温度应低于1048.49K(即775.3℃)。通过相关实验论证结果表明：Cu与O2直接反应合成立方CuO(即第一种合成方式)与烧结反应过程中生成部分的Cu2O与O2反应合成立方CuO(即第二种合成方式)这两种方式发生的可能性小,或者不发生；而以Cu与O2反应合成单斜的CuO后,在后期烧结时发生相转变生成立方CuO(第三中方式)是原位反应合成法制备AgCuO中立方CuO的主要形成方式。实验还证实了1048K(即775℃)左右的温度即是单斜CuO与立方CuO之间相转变温度,这一温度与模拟和理论计算温度十分接近。实验结果还发现,Ag的存在对形成立方CuO的相变以及形成量有一定的影响。最后,研究了这两种晶体结构CuO的力学和微观性质。得出立方CuO的延性好于单斜CuO的延性；立方CuO为间接带隙半导体,单斜CuO为直接带隙半导体,立方CuO中的Cu原子与O原子之间无明显相互作用,而单斜CuO中的Cu原子与O原子之间有相互作用；立方CuO的导电性优于单斜CuO导电性,其导电性主要来自于Cu原子的3d10轨道贡献。
[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，
本文编号：2478290
[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，
本文编号：2478290
本文链接：https://www.wllwen.com/kejilunwen/cailiaohuaxuelunwen/2478290.html
