氢辅助镁热还原二氧化钛制备氢化钛研究

【作者】 王卓；

【导师】 魏永刚； 徐浩元； 舒波；

【作者基本信息】 昆明理工大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 钛金属虽然在地壳中的储量非常丰富,但由于目前工业化生产钛金属的Kroll法的生产周期长、成本高,导致其价格昂贵。因此,开发一种低成本、短流程的钛冶炼方法具有重要意义。氢辅助镁热还原法是一种直接还原二氧化钛制备金属钛的方法。和常规的镁热还原二氧化钛的方法相比,它不仅突破了镁热还原二氧化钛的热力学极限,同时生产的产品纯度更高,所需的温度更低,时间更短,生产能耗能够有效降低,并且有望实现工业化生产。目前,科研人员已经对氢辅助镁热还原法进行了大量研究,但是氢化钛中氧的存在形式和分布规律,Ti-O-H固溶体的形成机理及氢对镁热还原Ti O₂和氢化钛抗氧化的增强机制还有待进一步研究。本文首先通过热力学理论计算对氢协同作用下镁热还原Ti O₂过程反应机制进行了研究。结果表明,在700℃时,氧含量为1.5wt%是金属镁还原二氧化钛的热力学极限。但是在镁热还原Ti O₂体系中引入氢气可以使Ti-O固溶体转变为Ti-O-H固溶体,而Ti-O-H固溶体的氧势高于Ti-O固溶体的氧势,稳定性较差,能使二氧化钛被还原至更低氧含量。其次,通过实验研究了影响还原效果的因素。结果表明,在氢辅助镁热还原过程中,当原料、还原剂和助熔剂按Ti O₂:Mg:Mg Cl₂的质量比为1:1.2:1,温度为650℃,时间为2h时可获得氧含量最低的还原产物氢化钛。通过XPS检测和AES检测对还原产物氢化钛中氧的存在形式和分布规律进行了研究。结果表明,还原产物中氧的来源有两处,一是在还原过程中未被完全还原从而残留在还原产物中的固溶氧,二是还原产物在空气中被氧化产生的表面氧。并且还原产物中表面氧含量远大于其内部的固溶氧含量。通过第一性原理计算研究了还原产物氢化钛的抗氧化机理。结果表明,还原产物氢化钛具备更强的抗氧化性是因其表面氧原子的结合能比金属钛低。本研究通过使用不同粒度的二氧化钛作为原料进行还原和脱氧。结果表明,在原料粒度为0.05mm的情况下可获得最低表面氧和固溶氧含量的氢化钛产物。其中,原料粒度过小会加剧其表面二次氧化程度,粒度过大时原料内部的固溶氧脱除困难,都不利于获得低氧产物。本研究最终可获得氧含量为0.23wt%的低氧氢化钛粉末。更多还原

【Abstract】 Although titanium is very abundant in the earth’s crust,it is expensive due to the long production cycle and high cost of the Kroll method for industrial production of titanium.Therefore,it has important meaning to develop new titanium smelting technologies with continuous production,short process and low cost.Hydrogen-assisted magnesiothermic reduction method is a direct reduction of Ti O₂ to prepare titanium metal.Compared with conventional magnesiothermic reduction of Ti O₂,it not only breaks through the thermodynamic limit of magnesiothermic reduction of Ti O₂,but also high purity products,lower reduction temperature and energy consumption can be effectively reduced,and is expected to achieve industrial production.At present,researchers have conducted a large number of studies on the hydrogen-assisted magnesiothermic reduction method,but the existence form and distribution law of oxygen in titanium hydride,the formation mechanism of Ti-O-H solid solution,and the enhancement mechanism of hydrogen on metallothermic reduction of Ti O₂ and titanium hydride anti-oxidation need to be further studied.In this thesis,the magnesiothermic reduction of Ti O₂ process under hydrogen coordination was studied by thermodynamic calculation.The results show that 1.5wt%oxygen content is the thermodynamic limit of Ti O₂ reduction by magnesium metal at 700℃.However,the introduction of hydrogen into the magnesiothermic reduction Ti O₂ system can transform the Ti-O solid solution into Ti-O-H solid solution,and the oxygen potential of the Ti-O-H solid solution is higher than that of the Ti-O solid solution,and the stability is poor,so that the titanium dioxide is reduced to a lower oxygen content.Secondly,the factors affecting the reduction effect are studied through experiments.The results show that titanium hydride with the lowest oxygen content can be obtained when the mass ratio of raw material,reducing agent and flux of Ti O₂:Mg:Mg Cl₂ is1:1.2:1,temperature is 650℃and time is 2h in the process of hydrogen-assisted magnesiothermic reduction.The form and distribution of oxygen in titanium hydride were studied by XPS and AES.The results show that there are two sources of oxygen in the reduction products,one is the solid dissolved oxygen that is not completely reduced in the reduction process,and the other is the surface oxygen produced by the oxidation of the reduction products in the air.And the surface oxygen content of the reduction products is much larger than the solid dissolved oxygen content of the reduction products.The antioxidation mechanism of reduced product titanium hydride was studied by first principles calculation.The results show that titanium hydride has stronger oxidation resistance because the binding energy of oxygen atoms on its surface is lower than titanium.In this study,titanium dioxide with different particle size was used as raw material for reduction and deoxidation.The results showed that titanium hydride products with the lowest surface oxygen and solid solution oxygen content could be obtained when the raw material particle size was 0.05mm.Among them,the small particle size of the raw material will aggravate the secondary oxidation degree of its surface,but when the particle size is too large,the removal of solid dissolved oxygen inside the raw material is difficult,which is not conducive to obtaining low oxygen products.In this study,low-oxygen titanium hydride powder with oxygen content of0.23wt%was obtained.更多还原