Search Results (6)

The origin of chemical ordering in liquid and supercooled liquid Ge₂Sb₂Te₅ (GST) was investigated using ab initio molecular dynamics (AIMD) simulations. Bond dynamics were analyzed via continuous (${\mathrm{\tau }}_{\mathrm{con}}$) and intermittent (${\tau }_{int}$) lifetimes. The intermittent lifetime (${\tau }_{int}$) reveals that chemically ordered Ge-Te and Sb-Te bonds are the most stable, although ${\mathrm{\tau }}_{\mathrm{con}}$ exhibits a stability anomaly. The faster increase of ${\tau }_{int}$ for these bonds upon cooling explains the overall chemical ordering. A novel ordering mechanism was identified through the analysis of bond separation dynamics. Te-Te ‘wrong’ bonds exhibit a unique dynamic instability, breaking and separating much faster than any other bond type, which actively drives the system towards chemical order. A correlation between lifetime and bond strength, as calculated by the Integrated Crystal Orbital Hamilton Population (ICOHP), supports these dynamic findings. Chemical ordering shows a positive correlation with medium-range structural order, evidenced by the instability of 4-fold rings containing wrong bonds. This study provides a detailed dynamic origin for ordering in liquid GST, highlighting the role of Te-Te bond relaxation. Full article

The results of studies on the distribution of rare elements among the products of distillation processing of polymetallic mattes are present in this article. Schemes of the developed technological equipment for the implementation of the extraction processes of rare elements via the vacuum distillation of mattes are presented. Technological tests were performed with a matte of lead, copper, and antimony plants at 1100–1250 °C and a pressure of up to 700 Pa. It was established that As, Cd, Bi, In, and Ge, by more than 90% in total, are extracted into condensate and dust in the distillation process of volatile components from mattes of lead production. At the same time, antimony is distributed between the distillate residue and condensate. Antimony by 90.47%, arsenic by 78.83% and cadmium by 98.72% are distributed into sulfide condensate and dust in the distillation of copper production matte. From the matte of the antimony plant, Sb and Bi (90.76% and 89.78%, respectively) are transferred into the condensate and cyclone dust. Arsenic is distributed between the liquid and vapor phases. Based on calculations, Se and Te will be mainly concentrated in the distillation residue. High-grade copper mattes obtained in processing mattes from lead and copper plants can be further used to obtain metallic copper by converting. The condensate and dust can be processed separately or with the dust of the mainline production for rare metal extraction. Antimony matte processing condensate containing more than 70% Sb can be directed to the process of crude antimony refining. Full article

Controlling material thickness and element interdiffusion at the interface is crucial for many applications of core-shell nanowires. Herein, we report the thickness-controlled and conformal growth of a Sb₂Te₃ shell over GeTe and Ge-rich Ge-Sb-Te core nanowires synthesized via metal-organic chemical vapor deposition (MOCVD), catalyzed by the Vapor–Liquid–Solid (VLS) mechanism. The thickness of the Sb₂Te₃ shell could be adjusted by controlling the growth time without altering the nanowire morphology. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to examine the surface morphology and the structure of the nanowires. The study aims to investigate the interdiffusion, intactness, as well as the oxidation state of the core-shell nanowires. Angle-resolved X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface chemistry of the nanowires. No elemental interdiffusion between the GeTe, Ge-rich Ge-Sb-Te cores, and Sb₂Te₃ shell of the nanowires was revealed. Chemical bonding between the core and the shell was observed. Full article

Ge-rich Ge–Sb–Te compounds are attractive materials for future phase change memories due to their greater crystallization temperature as it provides a wide range of applications. Herein, we report the self-assembled Ge-rich Ge–Sb–Te/Sb₂Te₃ core-shell nanowires grown by metal-organic chemical vapor deposition. The core Ge-rich Ge–Sb–Te nanowires were self-assembled through the vapor–liquid–solid mechanism, catalyzed by Au nanoparticles on Si (100) and SiO₂/Si substrates; conformal overgrowth of the Sb₂Te₃ shell was subsequently performed at room temperature to realize the core-shell heterostructures. Both Ge-rich Ge–Sb–Te core and Ge-rich Ge–Sb–Te/Sb₂Te₃ core-shell nanowires were extensively characterized by means of scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman microspectroscopy, and electron energy loss spectroscopy to analyze the surface morphology, crystalline structure, vibrational properties, and elemental composition. Full article

We report the self-assembly of core–shell GeTe/Sb₂Te₃ nanowires (NWs) on Si (100), and SiO₂/Si substrates by metalorganic chemical vapour deposition, coupled to the vapour–liquid–solid mechanism, catalyzed by Au nanoparticles. Scanning electron microscopy, X-ray diffraction, micro-Raman mapping, high-resolution transmission electron microscopy, and electron energy loss spectroscopy were employed to investigate the morphology, structure, and composition of the obtained core and core–shell NWs. A single crystalline GeTe core and a polycrystalline Sb₂Te₃ shell formed the NWs, having core and core–shell diameters in the range of 50–130 nm and an average length up to 7 µm. Full article

A selective separation and recycling system for metal ions was developed by homogeneous liquid-liquid extraction (HoLLE) using a fluorosurfactant. Sixty-two different elemental ions (e.g., Ag, Al, As, Au, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, In, Ir, La, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Re, Rh, Ru, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Te, Ti, Tl, Tm, V, W, Y, Yb, Zn, and Zr) were examined. By changing pH from a neutral or alkaline solution (pH ≥ 6.5) to that of an acidic solution (pH < 4.0), gallium, zirconium, palladium, silver, platinum, and rare earth elements were extracted at >90% efficiency into a sedimented Zonyl FSA^® (CF₃(CF₂)_n(CH₂)₂S(CH₂)₂COOH, n = 6–8) liquid phase. Moreover, all rare earth elements were obtained with superior extraction and stripping percentages. In the recycling of rare earth elements, the sedimented phase was maintained using a filter along with a mixed solution of THF and 1 M sodium hydroxide aqueous solution. The Zonyl FSA^® was filtrated and the rare earth elements were recovered on the filter as a hydroxide. Furthermore, the filtrated Zonyl FSA was reusable by conditioning the subject pH. Full article