Electron probe microanalysis for revealing occurrence mode of scandium in Bayer red mud

Red mud is a bauxite residue generated during the process of alumina production. In this research, the occur- rence mode of scandium in the Bayer red mud was investi- gated mainly by electron probe microanalysis （EPMA）. The Bayer red mud used in this work is composed of 21.47 wt% hematite, 12.13 wt% goethite, 8.86 wt% gibbsite, 5.02 wt% perovskite, 9.70 wt% quartz, 3.23 wt% anhydrite, 29.92 wt% Na_2Al_2Si_5O_14 and 9.67 wt% Al_3Fe_5O_12. Besides, the scandium content in the Bayer red mud is 84.32 × 10-6, indicating that this Bayer red mud is an important scandium resource deserving exploitation. The EPMA results show that the scandium within the Bayer red mud is mainly occurring in the iron minerals of hematite and goethite with the isomorphism form, but its distribution is not homogeneous in these iron minerals with the Sc_2O_3 content between 330 × 10-6 and 2040 × 10-6. This study provides a theoretical base for the further experimental work on the scandium extraction from this Bayer red mud.

Detection of distribution of copper inside and outside of lysosomes in cultured hepatolenticular degeneration fibroblasts by electron probe X-ray microanalysis

OBJECTIVE: To observe the distribution of copper in the subcellular structure for the understanding of primary pathogenesis of hepatolenticular degeneration (HLD). METHODS: Skin fibroblasts taken from HLD patients were cultured as an in vitro model of HLD, and the control cells taken from healthy volunteers were clutured in the same way. The distribution of copper inside and outside of lysosomes in fibroblasts was detected by quantitative electron probe X-ray microanalysis. The relationship between the subcellular location of copper and the genotype of the patients, and relationship between the distribution of copper and the course of the disease were analyzed. RESULTS: The content of Cu^(2+) inside lysosomes of HLD cells (14.6±2.1 mmol/kg) and of heterozygote cells (11.6±0.6 mmol/kg) was higher than that of normal cells (4.5±1.2 mmol/kg) (P<0.01). The content of Cu^(2+) outside lysosomes of HLD cells (17.5±4.2 mmol/kg) and of heterozygote cells (12.0±0.9 mmol/kg) was higher than that of normal cells (4.7±1.2 mmol/kg) (P<0.01). The distribution of copper in the subcellular structure was correlated with disease courses of HLD patients. With the progression of the disease, more copper was deposited in lysosomes (r=0.85, P<0.01). The content of copper in the diffused cytoplasmic compartment in HLD cells was correlated with that of sulfur (r=0.86, P<0.05), but not in heterozygote and normal cells. CONCLUSIONS: In the early stage of HLD, copper is accumulated outside lysosome, which is paralleled with increase of metallothionein-like proteins (copper and sulfur-binding proteins). With the development of the disease, more copper is deposited inside lysosome than outside lysosome. We conclude that the up-regulation expression of copper and sulfur-binding proteins and copper accumulation in lysosomes may play an important role in lowering the ATP7B gene mutation-induced toxic effects of free copper on the cell.

Interdiffusion in the Fe_2O_3-TiO_2 system

Interdiffusion in the Fe203-TiO2 system was investigated by the diffusion couple method in the temperature range of 1323 to 1473 K. The diffusion concentration curves of Ti4＋ cations were obtained by electron probe microanalysis, according to which the Boltzmann-Matano method optimized by Broeder was used to calculate the interdiffusion coeffi- cients. The interdiffusion coefficients almost increased linearly with the mole fraction of Ti4＋ cations increasing, and they were in the range of 10-12-10-11cm2-s-1. The increase of temperature could also lead to the increase of the interdiffusion coefficients at a constant concentration of Ti4＋ cations. It was also found that the thickness growth of the diffusion layer obeyed the parabolic rate law.

Determination of phase diagrams using the diffusion couple technique

It has been demonstrated that the diffusion couple technique is a powerful and efficient approach in establishing phase relationships of ternary systems. Accurate data on the phase equilibria can be obtained if the appropriate alloys are employed as end members of the diffusion couple. It is desirable to combine the diffusion couple technique with an investigation of the afterwards selected equilibrated alloys so that the precision and reliability of the obtained information about a ternary isotherm could be guaranteed.

Effects of the precipitation of stabilizers on the mechanism of grain fracturing in a zirconia metering nozzle

The mechanism of grain fracturing in a zirconia metering nozzle used in the continuous casting process was studied. The phase composition, microstructure, and chemical composition of the residual samples were studied using an X-ray fluorescence analyzer, scanning electron microscope, and electron probe. Results revealed that the composition, structure, and mineral phase of the original layer, transition layer, and affected layer of the metering nozzle differed because of stabilizer precipitation and steel slag permeation. The stabilizer MgO formed low-melting phases with steel slag and impure SiO2 on the boundaries（pores） of zirconia grains; consequently, grain fracturing occurred and accelerated damage to the metering nozzle was observed.

Phase Equilibria in Zn-Al-Cu-Si System at 285℃

As a part of the systematic investigation on phase relationships of Zn-Al based alloys containing Cu and/or Si, the equilibrium phase transformations of the quaternary Zn-Al-Cu-Si system at 285℃ were investigated by using X-ray diffracti on, scanning electron microscopy and electron probe microanalysis techniques. A five-phase of (α+β+εT'+σ) and a four- phase of (β+ε+η+σ) were detected separately coexisting in the Zn-Al-Cu-Si system at 285℃. Then the 285℃ isothermal section of Zn-Al-Cu-Si system (with 0.1% -Si content) was established, and an equilibrium reaction was determined at 286℃ as the following pattern, β+T'=α+ε

Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner

Phase equilibria of the Mg-Sn-Ag system in Mg-rich corner at 320 and 400℃ were experimentally investigated with nine ternary alloys subjected to electron probe microanalysis and X-ray diffraction techniques.No ternary compounds were observed at both isothermal sections.Two three-phase triangles,i.e.hcp(Mg)+Mg_(2)Sn+Mg_(3)Ag and Mg_(2)Sn+Mg_(3)Ag+MgAg(bcc_B2),were both observed at 320 and 400℃.A new three-phase region of Ag3Sn+Mg2Sn+MgAg(bcc_B2)was additionally observed at 320℃,which implied that the binary phase Ag3Sn has a considerable solubility of Mg in the ternary system at the temperature.And the maximal solubility of Mg in Ag3Sn was measured to be 27.2 at.%.This result is not consistent with the thermodynamic calculated isothermal section at 350℃ from Wang et al.[11]and put forward a new requirement or refinement for the optimization of the Mg-Sn-Ag ternary system.At 400℃,the maximal solubility of Sn in the Mg3Ag phase was determined to be about 3.0 at.%Sn,and the solubility of Ag in Mg2Sn was negligible.The temperature of ternary eutectic reaction at Mg-rich corner(L↔hcp(Mg)+Mg_(54)Ag_(17)+Mg_(2)Sn)was measured by differential scanning calorimetry.The partial isothermal sections in Mg-rich corner of the ternary system at 320 and 400℃ were then constructed based on the above experimental data.

Depositional Environments of the Upper Permian Quartzose Sandstone(Shandong Province, North China): Insight from Trace Element Geochemistry

The depositional environment of the Upper Permian quartzose sandstone （Kuishan sandstone in Shihezi Formation of Upper Permian） in the North China epicontinental basin is controversial. In order to test the previous hypotheses, we analyzed sedimentological characteristics of the Kuishan sandstones in outcrops and boreholes, and carried out trace element geochemical analysis by electron probe microanalyzer. Three lithofacies were recognized, including normal-graded conglomerate （Cng）, trough and planar cross-bedded coarse sandstone （CStpc）, and planar cross-bedded medium sandstone （MSpc）. Normal-graded conglomerate （Cng） formed in the meandering river or deltaic distributary channels. Trough and planar cross-bedded coarse sandstone （CStpc） formed in meandering river or distributary channels of near-source deltaic plain. Planar cross-bedded medium sandstone （MSpc） formed in the siliciclastic beach with highto moderate-energy conditions. By the petrology and trace elements analysis, three relatively large-scale transgressions were revealed. Each transgression was reflected by the lower content of Ba and ratios of Fe/Mn, and the high content of B and ratios of B/Ga. The ratios of Ni/Co of all samples are all lower than 2, suggesting oxygen-enriched shallower water en- vironment during deposition of the Kuishan sandstones.

Effect of Ce on solute redistribution in liquid ahead of solid–liquid interface during solidification of Fe–4 wt.%Si alloy

The high efficiency of Ce addition in grain refinement ofδ-ferrite in a cast Fe–4 wt.%Si alloy was verified.In order to further understand the solute effect of Ce on the grain refinement of δ-ferrite,the conventional directional solidification technique,which enabled to freeze the solid–liquid interface to room temperature,was used to investigate the interfacial morphology and solute redistribution in the liquid at the front of the interface,together with thermodynamic calculation of the equilibrium partition coefficients of Ce and Si in Fe–4 wt.%Si–Ce system using the Equilib module and the FsStel database in FactSage software system.Metallographic examination using a laser scanning confocal microscope showed a transition of the solid–liquid interface from planar to cellular in the Fe–4 wt.%Si alloy after adding 0.0260 wt.%Ce during the directional solidification experiment.Further,electron probe microanalysis revealed an enhanced segregation of Si solute in the liquid at the front of the solid–liquid interface due to the Ce addition.This solute segregation is considered as the cause of planar to cellular interface transition,which resulted from the creation of constitutional supercooling zone.Thermodynamic calculation indicated that Ce also segregated at the solid–liquid interface and the Ce addition had negligible effect on the equilibrium partition coefficient of Si.It is reasonable to consider that the contribution of Ce to the grain refinement ofδ-ferrite in the cast Fe–4 wt.%Si alloy as a solute was marginal.