Alloying effects of V on stability,elastic and electronic properties of TiFe2 via first-principles calculations

The alloying effects of V on structural,elastic and electronic properties of TiFe_2 phase were investigated by the first-principles calculations based on the density functional theory.The calculated energy properties including cohesive energy and formation enthalpy indicate V atom would preferentially substitute on 6h sites of Fe atoms in the lattice of TiFe_2 to form the intermetallic Ti_4Fe_7(V).The calculated results of polycrystalline elastic parameters confirm that the plasticity of TiFe_2 would be improved with the addition of V.By discussing the percentage of elastic anisotropy,anisotropy in linear bulk modulus and directional dependence of elastic modulus,it is revealed that the anisotropy of TiFe_2 and Ti_4Fe_7(V) is small.Finally,the density of states,charge density distribution and Mulliken population for TiFe_2 and Ti_4Fe_7(V) were calculated,suggesting there is a mixed bonding with metallic,covalent and ionic nature in TiFe_2 and Ti_4Fe_7(V) compounds.These results also clarify that the reason for the improvement of plasticity with the addition of V in TiFe_2 is the weakened bonding of covalent feature between Ti and V atoms.

Ca3TiFe2O8对铁矿石烧结过程中液相生成温度的影响

通过扫描量热法(DSC)和粉末X射线衍射(XRD),研究了几种不同纯矿物与Ca3TiFe2O8混合的烧结过程,检测液相生成及吸放热反应前后的物相组成。结果表明,在烧结过程中,与Ca3TiFe2O8混合试样液相出现温度都比纯相的熔点低。其中,等质量混匀烧结过程中,Ca3TiFe2O8+CaFe2O4和Ca3TiFe2O8+Fe2O3分别在1213℃和1215℃开始出现液相,Ca3TiFe2O8+CFA和Ca3TiFe2O8+SFC则更低,分别在1204℃、1205℃开始出现液相。试验发现,Ca3TiFe2O8和CaFe2O4可以稳定共存,但与Fe2O3、CFA和SFC混合出现液相后会发生分解,它仅是一个中间产物。尽管如此,可以认为适当控制含钛铁矿石的烧结条件,有Ca3TiFe2O8生成,可以降低液相生成温度,有助于改善烧结过程中的扩散条件。

Porous TiFe_(2) intermetallic compound fabricated via elemental powder reactive synthesis

Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis.Herein,porous Ti Fe2intermetallics were fabricated by the reactive synthesis of elemental powders.The phase transformation and pore formation of porous TiFe2intermetallics were investigated,and its corrosion behavior and hydrogen evolution reaction(HER)performance in alkali solution were studied.Porous TiFe2intermetallics with porosity in the range of 34.4%-56.4%were synthesized by the diffusion reaction of Ti and Fe elements,and the pore formation of porous TiFe2intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect.The porous TiFe2samples exhibit better corrosion resistance compared with porous 316L stainless steel,which is related to the formation of uniform nanosheets on the surface that hinder further corrosion,and porous TiFe2electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm-2,suggesting a good catalytic performance.The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance,showing its potential in the field of filtration and separation.

CaCl_2熔盐电解钛精矿制备TiFe合金

在CaCl2熔盐中,以通Ar气保护条件下经过熔融后再凝固的钛精矿作为阴极,进行电解制备钛铁合金,探讨电解过程中TiFe合金的形成机制。在电解电压为3.1V,电解温度900℃时,研究了电解时间对电解产物的影响。研究结果表明,实验室条件下,可以通过熔盐电解钛精矿的方法制备成分均匀的TiFe合金。钛精矿在电解过程中经历了优先生成Fe,然后逐步形成TiFe的合金化历程,中间产物包括CaTiO3、TiO2、Ti2O3、TiO、Fe、TiFe2,Ti的还原是分多步完成的。

温度对钛精矿熔盐电解制备钛铁合金的影响

在CaCl2熔盐中,以钛精矿为阴极,电解制备了钛铁合金,并对产物进行了XRD和SEM检测。对比不同温度下电解产物的结果表明,温度对扩散合金化过程影响显著,不同温度下电解产物的物相和结构有明显不同。850℃下电解的最终产物是颗粒大小为1μm的TiFe2和Ti离散球型结构,而900℃下电解的最终产物是颗粒大小为3μm的TiFe空间网状结构。

Ti-Fe系金属间化合物价电子结构与性能分析

在钛与钢的连接界面处,由于母材组元的相互扩散和反应,形成了TiFe和TiFe2金属间化合物,对接头性能影响很大。运用固体与分子经验电子理论,计算TiFe和TiFe2的价电子结构和共价键键能,并从价电子结构层次分析TiFe和TiFe2热稳定性和脆性。结果表明:TiFe2比TiFe具有更牢固的共价键络,因此其热稳定性更好;TiFe和TiFe2的脆性因子均小于0.08,表现为本征脆性。

CaO-TiO_2-Fe_2O_3三元系中Ca_3TiFe_2O_8的生成机理

钒钛磁铁矿是烧结矿重要的原料之一,Ca_3TiFe_2O_8作为钒钛烧结矿中矿物被发现之后,其生成机理尚不明确.本文采用X射线衍射分析、元素能谱分析和TG-DSC分析相结合的方法,研究了Ca_3TiFe_2O_8的生成机理以及不同温度、CaO与TiO_2含量下Ca_3TiFe_2O_8的生成规律.实验结果表明,Ca_3TiFe_2O_8由Ca2Fe2O5和Ca Ti O3反应生成,即CaO和Fe2O3反应生成Ca2Fe2O5;其后,与Ca Ti O3反应生成Ca_3TiFe_2O_8.反应时间越长,Ca_3TiFe_2O_8的生成量越大,但反应温度对Ca_3TiFe_2O_8生成的影响并不明显.另外,还发现CaO含量越高,Ca_3TiFe_2O_8越易于生成,而且等摩尔Fe2O3和CaO下只要存在TiO_2,就会有Ca_3TiFe_2O_8生成.