Papers by Keyword: Sulfurization

Abstract: This paper reports on the effect of a sulfurization thermal process of the silicon carbide surface on the properties of Ni/4H-SiC Schottky barrier. In particular, the incorporation of sulfur (S) in the 4H-SiC near-surface region was observed at the process performed at 800 °C, without any significant effect on the surface morphology. On the other hand, Ni/4H-SiC Schottky contacts fabricated on the sulfurized 4H-SiC surface showed a 0.3 eV reduction of the average barrier height with a narrower distribution, with respect to the untreated sample. These results were explained by an increase of the 4H-SiC electron affinity after sulfurization, and a Fermi level pinning effect.

Abstract: This paper reports on the synthesis of thin films of tungsten disulfide (WS₂) by сhemical vapour deposition (CVD) using powders of sulfur and tungsten oxide obtained from tungsten metal powder. It is shown that the synthesized ultra-thin 2-dimensional (2D) films of WS₂ have appropriate structural and optical properties suitable for their application in the manufacturing of electronic and optoelectronic devices. Proposed method for the synthesis of 2D few-layered WS₂ can significantly accelerate the synthesis rate and will make it possible to control the stoichiometry and shapes of nanocrystals by controlling the amount of sulfur by magnetic mechanism. Moreover, obtained few-layered crystals demonstrate long-term stability to external factors, since the synthesis and the research carried out during the year. During this time, no signs of degradation of the TMDs structure were detected.

Abstract: Single-phase ytterbium sulfides (Yb₂S₃ and YbS) were synthesized by sulfurization of Yb₂O₃ with CS₂ gas and heat treatments. Four kinds of Yb₂O₃ powders with different particle sizes and specific surface areas were employed as starting materials. When specific surface area of Yb₂O₃ powder is about 50 m²/g, a new polymorphic form Yb₂S₃ with an orthorhombic structure could be obtained by the sulfurization at 600°C for 8 hr. Single-phase hexagonal Yb₂S₃ was also synthesized form former three kinds of Yb₂O₃ powders by sulfurization above 1000 °C for 8 hr. Subsequently, the synthesized Yb₂S₃ powders were heat-treated under different conditions. Upon heat treatment at 1000 °C for 3 hr in Ar/CS₂ atmosphere, orthorhombic Yb₂S₃ phase underwent phase transition to hexagonal Yb₂S₃ phase. Moreover, XRD results showed that orthorhombic Yb₃S₄ was main phase after heat treatment at 1050°C for 8 hr under Ar atmosphere and Yb₂S₃ disappeared upon prolonged (12 hr) heat treatment. Single Yb₃S₄ phase could be obtained after treatment at 1000 °C for 3 hr, or at 1200 °C for 1 hr, under vacuum (~1.2×10^-3 Pa). YbS was formed upon treatment at 1200 °C for 5 hr. Single-phase YbS with a homogeneity range of YbS_1.11-1.15 could be synthesized by treatment at 1500 °C for 3 hr. PartialYb₂S₃ transformed to Yb₃S₄ at 1300 °C for 1 hr by spark plasma sintering.

Abstract: This paper mainly introduces a novel route for copper recovery from waste printed circuit boards (WPCBs) via mechanochemistry. Copper in the crust is most commonly present as copper-iron-sulfide and copper-sulfide minerals (about 80%) and there exist many methods to extract copper from cooper ores in mineral engineering. It seems an alternative to transform the metallic components in obsolete materials to their corresponding compounds common in nature. By means of mechanochemistry, copper and sulfur were verified to form into copper sulfide in the model experiment, where, meanwhile, the optimal ball milling time was determined (20 minutes). In the real experiment, WPCB fragments and sulfur were mixed and ground for 20 minutes, no copper was detected by XRD analysis but copper sulfide was left. After leaching in sulfuric acid (3M) and hydrogen peroxide (30 wt%), the yield of copper reached nearly 95% and, also, resin was conserved for further utilization. This paper, for the first time, reports the green recovery route combining mechanical activation and sulfurization and may provide an alternative in other studies of metal recovery.

Abstract: Cu₂ZnSnS₄ and Cu₂ZnGeS₄ thin films made from the earth abundant and non-toxic materials are quaternary semiconducting compounds which have received increasing interest for solar cells applications. Cu₂ZnSnS₄ and Cu₂ZnGeS₄ thin films have been synthesized by sulfurization of radio frequency magnetron sputtered precursors. The structural and optical properties of the thin films have been investigated and discussed. The result of X-ray diffraction demonstrates that the Cu₂ZnSnS₄ and Cu₂ZnGeS₄ thin films have kesterite (KS; space group I) crystal structure. An obvious blue shift is observed in the Raman spectra as smaller Ge replaces Sn. It is due to the fact that the radius of Ge cation is smaller than that of Sn cation , which results in the shrink of the lattice. Further transmission spectra demonstrate that the values of band gap for CZTS and CZGS thin films are 1.54 eV and 1.98 eV, respectively.

Abstract: Cu₂ZnSnS₄ thin films have been synthesized through sulfurization of co-electrodeposited Cu-Zn-Sn metallic precursor. The obtained metallic precursor shows homogeneous surface. Combination of X-ray diffraction, energy dispersive X-Ray spectroscopy and Raman spectroscopy results shows that kesterite structure of Cu₂ZnSnS₄ is formed, demonstrating that co-electrodeposition-sulfurization is a viable process for the synthesis of Cu₂ZnSnS₄ film.

Abstract: Polycrystalline CuIn(Se,S)2 (CISS) thin films with chalcopyrite structure were synthesized by sol-gel spin-coating method. Sequential reduction, selenization and sulfurization treatments were performed with hydrogen, Se and H2S vapor, respectively. The effects of different sulfurization times on the films were also studyed. X-ray diffraction (XRD), and SEM analysis have been employed to examine the structural properties and surface morphology of polycrystalline CISS thin films. The experimental results demonstrated that the obtained CISS had good crystallinity and uniformity.

Abstract: Cu2ZnSnS4(CZTS) thin films was potentiostatically deposited on molybdenum coated glass substrates using the electrochemical deposition method As-deposited and annealed in furnace, The polycrystalline CZTS thin films with tetragonal crystal structure have been studied from structural analysis results , XRD and Raman spectroscopy results show these thin films exhibit a strong preferential orientation along the (112), The energy gap of Cu2ZnSnS4 was estimated to be 1.8 eV via ultravioletvisible (UVvis) absorption spectrum of Cu2ZnSnS4 which suggests that CZTS films Can be useful as an absorber layer in thin film solar cells.

Abstract: In this study, the regeneration behavior of modified semi-coke supported (Fe, Zn, Ce) sorbents were investigated using a fixed bed reactor. The effects of the regeneration temperature, space velocity and oxygen concentration have been considered in order to obtain suitable regeneration conditions. The most suitable regeneration conditions were obtained including 650°C regeneration temperature, 4vol.% of oxygen content and 4000h-1 of space velocity. Typical properties of the sorbents before and after regeneration were characterized using XRD and BET methods. Then the sorbents were tested 3 cycle experiments of desulfurization and regeneration for the purpose of duration test. The breakthrough curves changed slightly and the sulfur capacity only decreased 14.2%, it proved that the sorbents had good regenerability, which implied that the sorbents could be used for hot gas desulfurization.

Abstract: In this study, vertically aligned CuInS₂ nanorod arrays were successfully fabricated by sulfurization method with porous alumina template, which was used to prepare CuInS₂ thin film in the reported paper. The nanorod arrays showed the diameters of about 200nm and the length of about 1μm, and highly vertically aligned on the CuInS₂ thin film, were characterized by scanning electron microscope. The sample was identified as the single chalcopyrite phase and the crystal structure with (112), (200)/(004), (202)/(204) and (116)/(312) atomic planes orientation by Raman scattering and X-ray diffraction, respectively. The Cu: In: S atomic ratio of 1:0.84:1.94 was exhibited in the sample by energy dispersive X-ray spectroscopy.