Effect of oxygen impurity on long-term thermal stability of Zr-based metallic glasses below glass transition temperature

Long-term thermal stability of a series of Zr-based metallic glasses with different oxygen contents below their glass transition temperatures was compared based on their deductive continuous-heating-transformation diagrams created by using the corollary of Kissinger analysis method. It is found that the influence of oxygen on the long-term thermal stability of Zr-based metallic glasses exhibits at lower temperature is different from that on their short-term thermal stability presented at higher temperature. For each kind of the Zr-based metallic glasses, there is a critical heating rate, φ , which corresponds to a critical c temperature, Tc. As heating rate is smaller than φ c and onset devitrification temperature is below Tc, the glass with higher oxygen content will have longer incubation period for onset devitrification. The values of φ c and Tc are related with the glasses’ reduced glass transition temperature Trg. The improving effect of oxygen impurity on the long-term thermal stability of Zr-based metallic glasses was discovered.

THE SEPARATION CRITERION OF IMPURITIES IN CRUDE METALS BY VACUUM DISTILLATION

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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.

Impurity distribution in distillate of terbium metal during vacuum distillation purification

The distribution rules of impurities in distilled terbium metal were investigated by vacuum distillation purificationexperiment and theoretical analysis.It is found that Ti impurity in distilled terbium is220mg/kg in the initial stage of the distillationpurification,increases slowly in the middle stage,and increases rapidly in the last stage,reaching2260mg/kg,and the modifiedseparation coefficient of Ti is1/19.02.The diffusion of the impurity Ti in liquid metal can reach a quasi-equilibrium state in theinitial stage of distillation purification and the calculated results agree well with experimental results;the distribution profile ofimpurity Cu is opposite to Ti,being380mg/kg in the initial stage,decreasing linearly to290mg/kg in the last stage,and themodified separation coefficient is17.99,and the theoretical calculated results are inconsistent with the experimental result.

Effects of grinding environment and lattice impurities on spodumene flotation

The effect of grinding on the spodumene flotation was investigated. The flotation response of spodumene ground by different mills was different, due to the variation of metal ions on spodumene surfaces caused by grinding environments and/or impurities. The samples were subjected to acid pickling treatment to remove most of the metal ions from the surfaces, and then all samples showed the same poor flotation response, which confirmed the significance of surface metal ions. Metal ion impurities may come from both grinding environments and lattice substitutions in spodumene. Density functional theory (DFT) calculation revealed that Fe and Ca could exist as lattice substitutions on the spodumene surface while Mg substitution is unlikely to occur. Furthermore, Fe is considered to be active site for the absorption of sodium oleate on the spodumene surface. Morphology analysis showed differences in particle size and shape for samples ground by different mills, resulting in different amounts of exposed surfaces. The particle size, cleavage characteristics caused by grinding environments, and metal ion impurities originated from grinding and isomorphous substitutions, play significant roles in the chemisorption of collector on the spodumene surface.

Hydrogenic donor impurity states and intersubband optical absorption spectra of monolayer transition metal dichalcogenides in dielectric environments

The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides(ML TMDs) under dielectric environments are theoretically investigated based on a two-dimensional(2D)nonorthogonal associated Laguerre basis set. The 2D quantum confinement effect together with the strongly reduced dielectric screening results in the strong attractive Coulomb potential between electron and donor ion, with exceptionally large impurity binding energy and huge intersubband oscillator strength. These lead to the strong interaction of the electron with light in a 2D regime. The intersubband optical absorption spectra exhibit strong absorption lines of the non-hydrogenic Rydberg series in the mid-infrared range of light. The strength of the Coulomb potential can be controlled by changing the dielectric environment. The electron affinity difference leads to charge transfer between ML TMD and the dielectric environment, generating the polarization-electric field in ML TMD accompanied by weakening the Coulomb interaction strength. The larger the dielectric constant of the dielectric environment, the more the charge transfer is, accompanied by the larger polarization-electric field and the stronger dielectric screening. The dielectric environment is shown to provide an efficient tool to tune the wavelength and output of the mid-infrared intersubband devices based on ML TMDs.

Hydrometallurgical purification of metallurgical grade silicon

The effects of the particle size of ground metallurgical grade silicon （MG-Si）, the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size less than 0.1 mm was most effective for acid leaching; the extraction yield of impurities was increased by 9% with HF leaching compared with HCl leaching and HNO3 leaching, and increased by 7% with ultrasonic stirring compared with mechanical stirring. The principle of hydrometallurgical purification of metallurgical grade silicon under ultrasonic fields was also discussed.

A DFT and TD-DFT study on electronic structures and UV-spectra properties of octaethyl-porphyrin with different central metals(Ni, V, Cu, Co)

In this work,the octaethyl-porphyrins with different central metals(M-OEP,M=Ni,VO,Cu,Co)were used to investigate the ground-state molecular structure,electron distribution and UV-spectra properties on molecular level by density functional theory(DFT).The results showed that the calculation structure parameters of metalloporphyrins agreed well with the experimental value.According to the Natural Bond Orbital(NBO)analysis,the charge distribution of different metalloporphyrins was found that the charge values of the central metal M decreased with the order of VO<Ni<Co<Cu,while the bonding strength between M and the coordinating atom N was VO>Ni>Co>Cu.At the same time,the frontier molecular orbital calculations showed that the SOMO energy of VO(OEP)molecules in the open-shell system was higher than that of Co(OEP)and Cu(OEP),which means that its UV absorption characteristic peak would be red-shifted.In addition,the IEFPCM model of Time-dependent Density functional theory(TD-DFT)was further utilized to simulate the four substance in toluene solution:Co(OEP),Ni(OEP),Cu(OEP)and VO(OEP),and the Soret band peaks were calculated respectively as:382 nm,383 nm,391 nm and 401 nm.Furthermore,the quantitative simulation analysis of metalloporphyrins was combined with experimental data.It could be found that the location rules of the four kinds of metalloporphyrins calculated absorption characteristic peaks were consistent with the experimental ones,and the relative errors of each peak were within 3%.These methods used above provide a theoretical path for analyzing and identifying unknown porphyrin compounds in petroleum.

Kernel polynomial representation for imaginary-time Green's functions in continuous-time quantum Monte Carlo impurity solver

Inspired by the recently proposed Legendre orthogonal polynomial representation for imaginary-time Green s functions G（τ）,we develop an alternate and superior representation for G（τ） and implement it in the hybridization expansion continuous-time quantum Monte Carlo impurity solver.This representation is based on the kernel polynomial method,which introduces some integral kernel functions to filter the numerical fluctuations caused by the explicit truncations of polynomial expansion series and can improve the computational precision significantly.As an illustration of the new representation,we re-examine the imaginary-time Green＇s functions of the single-band Hubbard model in the framework of dynamical mean-field theory.The calculated results suggest that with carefully chosen integral kernel functions,whether the system is metallic or insulating,the Gibbs oscillations found in the previous Legendre orthogonal polynomial representation have been vastly suppressed and remarkable corrections to the measured Green＇s functions have been obtained.

ULTRASONIC SEPARATION OF MICRO-SIZED INCLUSIONS IN MOLTEN METAL

The coagulation time and position of micro-sized non-metallic inclusions in molten metal during ultrasonic separation process were investigated, and the motion course of micro-sized non-metallic inclusions in an ultrasonic standing wave field was numerically simulated. The results of theoretical analysis and numerical simulation show that the movement of inclusions depends on the balance between the acoustic radiation force, effective buoyancy force and viscous drag force. It is presented that micro-sized inclusions, agglomerated at antinode-planes may be removed further with horizon tal ultrasound.``

Metal derivative(MD)/g-C_(3)N_(4) association in hydrogen production:A study on the fascinating chemistry behind,current trend and future direction

Metal derivative/graphitic carbon nitride(g-C_(3)N_(4))association is found promising in providing sustainable hydrogen production by photocatalytic water splitting process.Number of works reported on the synthesis and application of various metal based g-C_(3)N_(4)composites are increasing day by day.Mechanism of charge separation varies according to the metal candidate that gets couple with g-C_(3)N_(4).The present article thus explores the interesting chemistry behind various metal based heterojunction and demonstrates the charge separation route.A thorough investigation has been done on the current research trend in the area.As many metal free g-C_(3)N_(4)composites are reported nowadays as an alternative to metal derivatives,here compares metallic and metal free derivatives of g-C_(3)N_(4)based on four critical requirements of an industrial catalyst,ie,activity,stability,cost and toxicity.Challenges and future direction in the area are also discussed with significance.The systematic discussion and schematic illustration of charge transfer process in different heterojunctions with reference to the reported systems,given in the article can definitely contribute to the design and development of more efficient g-C_(3)N_(4)based heterojunctions in future for hydrogen production application.

Relationship between the Concentration of Impurity and Albedo in Snow Surface

Recent decline of cryosphere typified by retreat of glaciers is often explained by temperature rise due to global warming. However, the existence of glaciers shrinking since before 1950s warming accelerated suggested that decline of cryosphere may be due to not only temperature rise, but also another possibility. As a possible cause of snow and ice melting, it has been pointed out that the surface albedo reduction due to increase of snow impurity, aeolian dust and anthropogenic pollutant, for example. To clarify the quantitative relationship between albedo and impurity in snow surface, we investigated the correlativity of turbidity and metal concentration in snow to the snow surface albedo from the simultaneous observations on the snow-covered area in Yamagata, Japan. The observed albedo shows a tendency of decrease with the turbidity increase in snow surface, we could find strong correlation between the albedo and the turbidity in 76% of contribution factor using logarithmic regression analysis. The relationship of albedo to total concentration of Fe and Al in snow surface shows the similar tendency to turbidity, we could model the relationship using logarithmic equation with high value of contribution ratio, 74% and 66%, respectively. The concentration ratio of Fe/Al is nearly constant with about 0.75, which is close to mean crustal ratio of both elements, therefore, it can be said there is a strong correlation between the albedo and the concentration of mineral particle in snow surface. We cannot find a significant correlation between the albedo and total concentration of Na in snow surface. It can be considered that Na existed as dissolved ion has not significant effect to the albedo in snow surface. These results indicate that the snow albedo correlates strongly with the particulate matter in snow surface, which is typified by mineral particle.

低品位脉石英热压浸出工艺动力学研究

为解决低品位脉石英中杂质元素含量高的问题,采用湖北蕲春灵虬山脉石英为原料,研究了液固比、反应时间和反应温度对杂质去除效果的影响。结果表明,经过热压浸出工艺提纯后,石英砂SiO_(2)含量(质量分数,下同)由97.766%增至99.974%,主要金属元素杂质的去除率显著提高。阿弗拉米动力模型表明,杂质去除过程受内扩散和化学反应共同控制。研究结果为优化脉石英的提纯工艺提供了理论依据和实践指导。

钝化液中金属杂质对镀锌层三价铬钝化的影响

[目的]研究金属杂质离子对镀锌三价铬钝化效果的影响,为钝化液中金属杂质离子含量的控制提供参考。[方法]采用添加不同质量浓度的Fe^(2+)、Cu^(2+)和Zn^(2+)的三价铬钝化液对镀锌层进行钝化处理。通过三维视频显微镜、动电位极化曲线测试等研究了上述3种金属杂质离子对钝化膜外观及耐蚀性的影响。[结果]钝化液中Fe^(2+)的质量浓度超过0.1 g/L或Cu^(2+)的质量浓度超过0.03 g/L时即可导致钝化膜不均匀、颜色变暗甚至起粉,以及耐蚀性显著变差。钝化液中Zn^(2+)质量浓度小于2 g/L时对钝化膜外观和耐蚀性影响不大,但不小于4.0 g/L时会导致钝化膜耐蚀性严重下降,因此钝化液中Zn^(2+)的质量浓度应控制在4.0 g/L以内。[结论]3种金属杂质均会导致钝化膜性能下降,必须严格控制三者在钝化液中的含量。

常见点缺陷对硅光电池响应特性的影响

研究了硅光电池中常见点缺陷对器件在激光辐照下的响应特性的影响。根据第一性原理建立了晶胞模型,比较了空位缺陷以及含Fe,Cu杂质状态下硅材料的态密度图,在此基础上分析了常见点缺陷对硅光电池响应特性的影响。由于半导体材料对温度敏感,当光电池受激光辐照而出现温度变化时,其光电响应输出特性会发生变化。从光伏器件的光生电动势原理出发,根据响应输出模型以及一维热传导方程,计算了1064nm激光辐照下,空位和金属杂质两种本征点缺陷对光电池响应特性的影响规律。结果表明:空位和金属杂质两种缺陷都能够改变硅材料的能带结构和响应特性。当激光辐照波长为1064nm,功率密度为4×10^(5) W/cm 2时,其中间隙原子为Fe时对材料的电子结构和光学性质的影响最大。此时材料吸收系数高达23952cm^(-1),且量子效率值最大,导致光电池响应最为强烈,输出电压最小。

水平区熔法制备高纯铜的研究

选用纯度为99.996%的纯铜试样,采用水平区熔法在透明石英精炼室中的高纯石墨舟中对其精炼15次。结果表明:纯铜试样中间位置处金属杂质Zn、Ti、As、Cr、Ca的含量均小于0.2 g/t。非金属杂质Cl、N分别仅有不到0.1 g/t和1 g/t。

Impurities especially titanium in the rare earth metal gadolinium— before and after solid state electrotransport

Gadolinium was prepared by conventional procedures of fluorination, reduction, distillation and solid state electrotransport（SSE）. The electronegativities of the metals were found to have an important influence on the electrotransport process and result of the impurity element. Meanwhile, titanium particles in the distilled gadolinium as major metallic impurities were studied by high resolution transmission electron microscopy（HRTEM） before and after solid state electrotransport. The results showed that impurities especially titanium transported from anode to cathode during SSE. In the metal before SSE, there were impurities of titanium in strip shape or embedded round shape. After SSE processing, titanium particles in the metal smaller than 50 nm in the cathode, but existed 6 to 10 times bigger in the anode.

废旧金属旋转偏析纯化再生机理与方法

针对传统废旧金属回收方法流程长、效率低、传质慢的问题,借助水模型试验开展旋转偏析过程杂质强化去除的机理研究,为旋转偏析技术回收废旧金属提供动力学基础。试验分别通过流场可视化处理和流速的测定对溶质在废旧金属熔体中的传输进行分析,发现旋转偏析技术可以有效提高杂质原子在熔体中的传质效率,降低生长界面处杂质的传质阻力。水模型试验结果表明,旋转偏析炉内流场的循环运动模式有利于杂质向远离生长界面处运动,但在低转速条件下循环流动较弱,杂质的排除能力随着转速的增加而增加,但当转速增加到800r/min时,杂质无法有效向远结晶器端输送,不利于杂质去除;平均流速随着结晶器转速的增加而增加,结晶器转速从200r/min增加到800r/min时,各点流速平均增大2倍;流场平均流速随着结晶器浸入深度的增加而增加,结晶器转速为200r/min时,随着结晶器浸入水深的1/2增加到4/5,近结晶器液面端流速从0.02m/s增加到0.04m/s,其他各测速位点流速均有明显提高,平均流速增大1倍;流场平均流速随着结晶器直径与坩埚直径比例增大而增大,直径比从1/7增大到1/2,流场内平均流速增大了4倍左右。试验证明,适当增大转速、结晶器浸入深度以及结晶器与坩埚的直径比都能提高旋转驱动力,从而提高溶质在熔体中的传输速率,获得高效、均匀的浓度场。本研究中,在结晶器与坩埚直径比为1/3、结晶器浸入深度为4/5时,杂质的传输效果和浓度场的均匀度均较好,有利于旋转偏析过程杂质的有效脱除。在水模型基础上开展的铝熔体旋转偏析除杂研究结果表明,在结晶器转速为400r/min时,铅的去除效率最高可以达到66%,旋转偏析回收废旧金属资源可以改善传统回收方法流程长、效率低的问题,实现金属杂质的深度高效去除,满足金属资源的高值化回收利用需求。

CCUS海上管线设施的腐蚀与选材研究进展

海上碳捕集、利用与封存(CCUS)腐蚀环境相对陆上更为恶劣,管道与设施外部处于海洋环境中,内部为超临界CO_(2)及腐蚀性杂质。综述了CCUS中海上设施的腐蚀风险与选材情况。金属的腐蚀风险包括CO_(2)-H_(2)O相诱发的腐蚀风险、气相杂质诱发的腐蚀风险、Cl^(-)诱发的腐蚀风险。金属的选材主要包括碳钢、低合金钢、耐蚀合金等,应依据不同的CCUS工况选择合适的金属材料。此外,非金属材料在超临界CO_(2)介质环境中受到化学腐蚀及物理降解,在超临界CO_(2)测试后,非金属材料的渗透率、膨胀率增大,力学性能下降。长周期服役后,非金属管道存在老化风险。目前,超临界CO_(2)体系下材料的腐蚀失效机理研究有待进一步完善,CCUS海上设施选材还不成熟,尤其是在含有多种杂质气体的复杂工况下,仍需要更多地研究完善CCUS海上设施材料的选择体系,以支撑海上CCUS技术规模化应用。

微波消解-分光光度法测定金属钽中铁含量

本研究采用微波消解-分光光度法实现了金属钽中铁含量的测定。试验对试样处理方法、微波消解溶剂及消解温度进行了探究,结果表明,在200℃条件下,以氢氟酸、硝酸、水为溶剂消解金属钽效果最佳;为防止氟及其他杂质元素的干扰,对氢氟酸和酒石酸-硼酸溶液用量进行了优化,其最佳用量分别为2 mL和30 mL;进一步对微波消解的加标回收率进行计算,加标回收率为97.80%~98.43%,表明样品损失率较低,微波消解更适合作为金属钽前处理的方法。此外,对金属钽中铁含量进行重复性测试,结果表明该方法具有良好的重复性,相对标准偏差(RSD)为3.89%。