Preparation Of Metal Phosphide By Vacuum Thermal Decomposition Of Phosphorus Iron And Phosphorus And Iron

This thesis intends to summarize the structure characterization, fabrication and utilization of metal phosphides, meawhile, to study the reaction of ferrophosphorus and nickel in the vacuum heating process. The reaction of ferrophosphorus with nickel and ferrophosphorus decomposition were theoretically calculated in thermodynamics, which help us obtained the critical temperature of the reaction. Then,the pyrolysis mechanism of Fe2 P, Fe2 NiP, NiP2 and NiP3 in vacuum were studied by the molecular dynamics simulation method. Finally, the experiment of ferrophosphorus and nickel in the vacuum was conducted. And the impact of the reaction conditions, including the nickel addition amount and the temperature, on the products was investigated.Thermodynamic calculations indicate that: Firstly, the thermodynamic analysis of ferrophosphorus(FeP, Fe2 P, Fe3P) shows that there are different degrees of decomposition about ferrophosphorus in 10 Pa ~ 100 Pa, 900 K ~ 1700 K range,accompanied generating phosphorus. Next, the thermodynamic analysis of the reaction of ferrophosphorus and nickel shows that: in 900K~1700K range, the Gibbs free energy values of generating Ni2 P,NiP2,Ni3 P,NiP3,Ni5P2,Ni6P5 are negative,indicating that it is theoretically feasible to obtain the nickel phosphide by the reaction of ferrophosphorus and nickel directly. And in 900 K ~ 1700 K range, the nickel phosphide are mainly Ni3 P and Ni5P2, while the ferrophosphorus are Fe2 P and Fe3 P.The ab initio molecular dynamics results show that:(1) at 1673 K,10Pa, 2 ps dynamic simulations of Fe2 P showed that Fe-P bonds are broken, while Fe-Fe bonds were stable.(2) 10 ps dynamic simulations are used to study the process of thermal decomposition of Fe2 NiP in vacuum under 1473K~1673K, 10 Pa. The results show that Fe-P bonds and Ni-P bonds are weakened, indicating that Fe-P bonds and Ni-P bonds are broken, but Ni-Fe bonds and Fe-Fe bonds are shorter, indicating that Ni-Fe bonds and Fe-Fe bonds are stable, when the temperature increases from 1473 K to1673K.(3) 5 ps dynamic simulations are used to study the process of thermal decomposition of NiP2 and NiP3 in vacuum at 1673 K. The results show that Ni-P bonds are weakened, indicating that Ni-P bonds intends to be broken.The experimental results show that:(1) there are two layers after the reaction of SiO2 in ferrophosphorus and CaO which molar ratio is 1:1 in vacuum at 10~40Pa,1573 K. the up of the layers is mainly composed of Ca2SiO4 and Ca3SiO5, the next is Fe2 P and the amount of silica is Si%﹤0.07%, which coincides well with the results of thermodynamic calculation.(2) In the experiments of ferrophosphorus and nickel reaction which molar ratio is desilicification ferrophosphorus:nickel=4~1:2~1, the results show that: under 10Pa~80Pa, in 1373K~1573K range, FeNi2 P is generated by all reaction of ferrophosphorus and nickel. And there are little Fe0.64Ni0.36 with the addition amount of nickel increasing. At 1573 K, the Ni3 P and Ni5P2 can not be detected in the products by the reaction of ferrophosphorus and nickel, indicating that the nickel phosphide(Ni3P and Ni5P2) is not stable at 1573 K.