Selective Flotation of Elemental Sulfur from Pressure Acid Leaching Residue of Zinc Sulfide

An efficient flotation process was developed to selectively recover elemental sulfur from a high-sulfur pressure acid leaching residue of zinc sulfide concentrate. The process mineralogy analysis showed that the sulfur content reached 46.21%, and 81.97% of the sulfur existed as elemental sulfur which was the major mineral in the residue and primarily existed as pellet aggregate and biconical euhedral crystal. An elemental sulfur concentrate product with 99.9% of recovery and 83.46% of purity was obtained using the flotation process of one-time blank rougher, two-time agent-added roughers, and two-time cleaners with Z-200 as collector and Na2S + ZnSO4 + Na2SO3 as depressant. The flotation experiment using return water indicated that the cycle use of return water had no adverse effect on the flotation performance of elemental sulfur. The process mineralogy analysis manifested that main minerals in the residue directionally went into the flotation products. Most of elemental sulfur entered the concentrate while other minerals almost completely went into the tailing. Main valuable elements lead, zinc, and silver entered the tailing with sulfides and could be recovered by lead smelting. The proposed process can realize the comprehensive recovery of valuable components in the high-sulfur residue and thus it has wide industrial application prospect.

Modulation of sulfur partial pressure in sulfurization to significantly improve the photoelectrochemical performance over the Cu2ZnSnS4 photocathode

We designed a facile method for modulating sulfur pressure in a semi-closed system to enhance the PEC performance of the CZTS photocathode.

Recrystallization of Cu–In–S thin films studiedin situby energy-dispersive X-ray diffraction

The recrystallization of Cu–In–S thin films has been monitored in real time by means of synchrotron-based energy-dispersive X-ray diffraction. To trigger recrystallization, nanocrystalline Cu–In–S layers with [Cu]/[In] < 1 were covered with layers of CuS or pure Cu, so that the overall ratio [Cu]/[In] > 1. The bilayer films were heated to 773 K and the evolution of the microstructure was monitoredin situ viadiffraction spectra. In the first step of the analysis, the diffraction data were used to identify solid-state phase transitions as a function of temperature. In a further step, single-line profile analysis of the 112 CuInS2reflection was used to study grain growth in this material system. The recrystallization was investigated under two sulfur pressure conditions and for different [Cu]/[In] ratios. The recrystallization is composed of three steps: consumption of the CuIn5S8phase, grain growth, and a transition from the Cu–Au-type to the chalcopyrite-type structure of CuInS2. Increasing the sulfur pressure during heating systematically reduces the temperature at which grain growth sets in. Various paths to control the recrystallization of Cu–In–S thin films are proposed.

Cobalt Base Clad Layer Resistance on the Corrosion under Low Sulfur Pressure

The paper considers the sulphidation of the clad layers made of the cobalt base powder and prepared by the multi-overlapped tracks and sublayers fabricated using laser cladding process applied at 800°C under sulphur partial pressure ps2= 10e-8 atm and ps2= 10e-10 atm for 24 hours. The phase compositions of the scale were different. In both cases changes in the layer under the scale exhibited similar tendency – decomposition of the carbides from the interdendritic regions and severe internal corrosion along the dendrite boundaries.

Copper Sulfide Assisted Recrystallization of Cu-poor CuInS2 Observed in-situ by Polychromatic X-ray Diffraction

The microstructural changes during heating of bi-layers of Cu-poor CuInS2 and CuS under different sulfur excess conditions were studied. This was done by means of energy dispersive X-ray diffraction of polychromatic synchrotron radiation in a vacuum setup where the sulfur pressure conditions can be controlled. Understood as the formation of a new microstructure, the recrystallization of the Cu-poor CuInS2 phase was characterized by a change in the reflection profile (from Cauchy-type to Gauss-type), the reduction of the breadth and a subsequent normalized-intensity increase of the 112 reflection. The Cauchy component of the breadth was used to monitor the recrystallization under different sulfur and heating rate conditions. The main results are: a) Cu availability for the consumption of the CuIn5S8 phase is a pre-requisite for recrystallization, b) in presence of the Cu2-xS phase, increased sulfur pressure enhances recrystallization.

Fabrication of Ni Sulfides by Thermal Sulfidation

The microstructure of Ni sulfides prepared by thermal sulfidation of pure Ni and their dependence of fabrication parameters were investigated by means of scanning electron microscopy and X-ray diffractions. Sulfidation was made by isothermally annealing Ni with the sulfur in vacuum sealed glass ampoules at 673 K for 120 – 600s under the sulfur pressure of 100 and 220 kPa. The sulfide layers formed in the early stage were found to consist of spherical particles smaller than 0.5um, which were grown and agglomerated with increasing annealing temperature. Thickness of sulfides developed on Ni substrate was found to increase with increasing annealing time and sulfur pressure. It was also found that compositions of dominant Ni sulfides changed with varying annealing time. At the initial stage, only Ni3S2 sulfide was formed on pure Ni, which was tightly bonded to Ni substrate. On increasing annealing time, NiS sulfide was formed. On further increasing annealing time, NiS1.97 sulfide was formed, which always coexisted with NiS sulfide. A mechanism for sulfidation of Ni is proposed as follows: 3Ni + 2S Ni3S2, Ni3S2 +S NiS, NiS + S NiS1.97

Thermal Sulfidation Behavior of Ti-Ni Alloys

Ti and Ni sulfides were formed on the surface of Ti-Ni alloys by isothermal annealing at various sulfur pressures, and then microstructures of the surface sulfide layers were investigated by means of scanning electron microscopy and X-ray diffractions. Morphology of sulfurized surface changed from granular shape to porous shape at the sulfur pressure of 80 kPa, which is related to the change in sulfide from NiS1.97 to NiS. Two-layered sulfide was observed in which the inner layer was mainly Ti8.2S11 , and the outer layer was a mixture of NiS1.97 and NiS. The discharge curve of the Ti and Ni sulfides cathode formed on the Ti-Ni current collector at the first cycle showed a plateau voltage of 1.6 V, and the discharge capacity was found to be about 530 mAh/g-NiS1.97.

Transformation Behavior and Mechanical Properties of an Equiatomic Ti-Ni Alloy with Surface Sulfide Layers

Surface sulfide layers were formed on the surface of Ti-50.0(at%)Ni alloys by isothermal annealing at 873 K for 3.6 ks under the sulfur pressure of 80 kPa, and then transformation behavior and mechanical properties were investigated by means of differential scanning calorimetery(DSC), thermal cycling tests under constant load, and tensile tests. The DSC peaks were broadened and martensitic transformation start temperature(Ms) increased from 281 K to 289 K by sulfurization. An equiatomic Ti-Ni alloy with surface sulfide layers showed good shape memory characteristics and partial superelasticity.