摘要
由于在高温下缺乏实验检测方法,反应的中间产物寿命短、浓度低,很难通过实验手段获得准确的分析数据,本文采用从头算分子动力学模拟方法对氟磷酸钙真空碳热还原的反应机理进行研究。结果表明:在1723K下,Ca_5(PO_4)_3F与C摩尔比为1∶12时,Ca_5(PO_4)_3F中的P原子态密度(PDOS)比较接近单个P原子态密度,C原子与O原子具有明显的共价键特征,还原效果最好;PDOS结果显示在费米能级附近,Ca原子与P原子、C原子没有形成共价键,故没有出现中间产物Ca_3P_2和CaC_2;由此推测氟磷酸钙碳热还原反应机理,首先C与Ca5(PO4)3F中PO3-4反应,不断脱去PO3-4中的O原子,PO3-4→PO_3^(2-)→PO_2^-→PO→P,然后C与O^(2-)结合生成CO,Ca^(2+)分别与O^(2-)、F^-结合生成CaO、CaF_2。
The carbon thermal reduction of Ca_5（PO_4）_3Fin vacuum wasmodeled and simulated by ab initio molecular dynamics simulation with software Material Studio,to understand the reduction mechanisms. The influence of the reduction temperature and molar ratio of Ca_5（PO_4）_3F/C on the P-extraction was investigated. The simulatedresults show that the optimized reduction occurs at 1723 K and a molar ratio of 1∶ 12,because the atomic P＇s partial density of state（PDOS） is fairly close to that of P-atom in Ca_5（PO_4）_3F,favorable for C-P co-valence bond formation; no Ca_3P_2 and CaC_2 intermediates emerge because Ca,P,and C atoms fail to form co-valence bonds near Fermi level. We suggest that the mechanisms may be：C atom forms CO by continuously depriving PO3-4in Ca_5（PO_4）_3Fof O^2- in the reaction path of PO4^3-→PO_3^2-→PO_2^-→PO→P; while the Ca^2＋ form Ca O and CaF_2 compounds with O^2- and F-1ions,respectively.
作者
刘予成
陈秀敏
李秋霞
杜远超
Liu Yucheng Chen Xiumin Li Qiuxia Du Yuanchao(Wenshan University, College of Chemistry and Engineering, Wenshan 663009, China Kunming University of Science and Technology, National Engineering Laboratory for Vacuum Metallurgy, Kunming 650093, China College of Chemistry and Chemical Engineering, Yunnan Normal University,Kunming 650092, China)
出处
《真空科学与技术学报》
EI
CAS
CSCD
北大核心
2017年第1期89-93,共5页
Chinese Journal of Vacuum Science and Technology
关键词
氟磷酸钙
真空
碳热还原
分子动力学模拟
机理
Fluorapatite
Vacuum
Carbothermal reduction
Molecular dynamics
Mechanism
