Direct and Simultaneous Determination of Several Impurity Elements in Manganese Tetroxide using ICP-AES

A rapid method for the determination of impurity elements, such as Zn, Ni, Co, Cr, Cu, Cd and Pb in manganese tetroxide was developed, using inductively coupled plasma atomic emission spectrometry （ICP-AES）. The critical instrumental parameters such as sample flow rate and radio frequency incident were thoroughly optimized. The effect of matrix was also examined. The sensitivity was investigated using calibration curves obtained in presence of the matrix. The obtained recoveries for Ni, Co, Cr, Cu, and Cd at the μg· g^ -1 level were satisfactory and practically independent of the matrix used for the calibration standards. The recoveries of Pb and Zn were less suffwient. The method can be applied for routine analysis and quality control purposes at μg· g^-1 level of concentration.

First-principles Investigation on Solution Hardening of Interstitial Impurity Elements (O,N) inγ-TiAl

We have calculated the electronic Structures of O-doped and N-doped r-TiAl using the firstprinciples discrete variational method (DVM) with the aim to understand the solution hardening effects of oxygen and nitrogen in r-TiAl. Our combination analysis on the electronic density, density of states (DOS) and the local environment total bond orders (LTBO) will show that, X atom (X is O or N) can strongly bind with its six surrounding atoms via electronic hybridizations of Ti-3d/X-2p and Al-3p/X-2p. As a sequence, there forms a 'hard' cohesive region around the impurity atom. A pinning model based on the calculations is proposed to explain the hardening effects. The consistent results are obtained between the present calculation and formal test experiments.

Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

The model of dislocations was used to construct the model of grain boundary (GB) with pure rare earths, and rare earth elements and impurities. The influence of the interaction between rare earth elements and impurities on the cohesive properties of 5.3° low angle GB of Fe was investigated by the recursion method. The calculated results of environment sensitive embeding energy( E ESE ) show that the preferential segregation of rare earth elements towards GBs exists. Calculations of bond order integrals (BOI) show that rare earth elements increase the cohesive strength of low angle GB, and impurities such as S, P weaken the intergranular cohesion of the GB. So rare earth element of proper quantity added in steel not only cleanses other harmful impurities off the GBs, but also enhances the intergranular cohesion. This elucidates the action mechanism of rare earth elements in steel from electronic level and offers theoretical evidence for applications of rare earth elements in steels.

Selective lithium recovery from black powder of spent lithiumion batteries via sulfation reaction:phase conversion and impurities influence

The aim of this study is to present a new understanding for the selective lithium recovery from spent lithium-ion batteries(LIBs)via sulfation roasting.The composition of roasting products and reaction behavior of impurity elements were analyzed through thermodynamic calculations.Then,the effects of sulfuric acid dosage,roasting temperature,roasting time,and impurity elements were assessed on the leaching efficiency of valuable metals.Characterization methods such as X-ray diffraction(XRD),scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),and X-ray photoelectron spectroscopy(XPS)were employed to analyze the phase transformation mechanism during roasting process.The results indicate that after sulfation roasting(n(H_(2)SO_(4)):n(Li)=0.5,550℃,2 h),94%lithium can be selectively recovered by water leaching and more than 95%Ni,Co,and Mn can be leached through acid leaching without the addition of reduction agent.During the sulfation roasting process,the lithium in LiNi_(x)Mn_(y)Co_zO_(2)is mainly converted to Li_(2)SO_(4),while the Ni,Co and Mn are first transformed to sulfate and then converted into oxide form.In addition,impurity elements such as Al and F will combine with lithium to form LiF and LiAlO_(2),which will reduce the leaching rate of lithium.These results provide a new understanding on the mechanisms of phase conversion during sulfation roasting and reveal the influence of impurity elements for the lithium recovery from spent LIBs.

Impurity formation mechanism of silicon carbide crystals smelted by Acheson process

In order to further promote the application of SiC refractories in modern steel metallurgy,the occurrence forms and formation mechanism of impurities in SiC crystals smelted by Acheson process were investigated.The techniques of inductively coupled plasma-atomic emission spectrometry,X-ray diffraction,and scanning electron microscopy were combined to examine the types and occurrence forms of impurities in smelted SiC crystals.The results showed that the main impurities in the SiC are free Si,free C,oxides(CaO·Al_(2)O_(3)·2SiO_(2),3Al_(2)O_(3)·2SiO_(2),CaO·SiO_(2) and SiO_(2))and alloy phases(Fe_(x)Si_(y),Fe_(x)Si_(y)Ti_(z) and Fe_(x)Al_(y)Si_(z)).The formation process of impurities during the smelting of SiC can be described as follows:At high temperature,the SiO_(2) and Fe,Ti related oxide impurities present in the raw materials are reduced to Si,Fe,and Ti metal melts.After the reduction process,the free Si,Fe_(x)Si_(y) and Fe_(x)Si_(y)Ti_(z) are precipitated from the melt during cooling.Free Si primarily exists in aggregated form within the SiC crystal,while the alloy phase is predominantly found at the interface between SiC and free Si,with Fe_(x)Si_(y)Ti_(z) embedded within FexSiy.Towards the end of the cooling process,other impurity oxides such as Al_(2)O_(3),CaO,and some unreduced SiO_(2) solidify to form calcium-aluminum-silicate glass phases,predominantly located between SiC grains.The remaining C from the reaction is mainly dispersed as free C within the SiC crystal and at the interface between SiC and free Si.