69 publications from this institution
High-purity Fe was manufactured using anion-exchange separation (AES), oxidation refining, and hydrogen-argon plasma arc melting. As a result, the purity o
The thermodynamic properties of aluminium make its oxidation by various reactant gases an important side-reaction of melting.Magnesium, as a major alloying component plays a further important role in determining the properties of the heterogeneous dross formed during the melting of aluminium alloys.The formed dross may entrap significant amounts of the metal, whose specific amount can be determined by a method including a thermo-mechanical treatment in an induction furnace with no special provisions, allowing most of the entrapped metal to be cast into blocks.Further significant portion of the contained metal is obtained by grinding and physical classification.These steps also a modelling of the industrial dross treatment.The remaining metal content in the fine residue was determined by a special chemical method.The metal content of the dross obtained from the melting of Al alloys of various Mg concentrations were typically in the 70 -85 % range.Magnesium was found to play an important role in determining the mass and the metal content of the dross.The useful effect of applying simple NaCl as melting additive was pointed out.1.
Most of the 3d-type transition metals have long been staple materials in industry. The advent of modern electronics has brought about a dynamically increasing need for a number of transition metals at an extremely high level of purity. Fields of application include materials for conductors, IC bonding, high-fidelity signal transmission (like Cu), new compound-type semiconductors, opto-electronic devices (like Fe and Zn) and thin films with special magnetic or magneto-optic properties (like Cr, Co and Fe).
Soldering scrap, generated in large quantities by modern electronic industry, is basically lead-free but contains significant concentrations of copper and silver. This is a valuable raw material, and high purity tin can be obtained by electrolytic refining. There are a number of advantages in applying pure hydrochloric acid–tin chloride media, if the difficulties of solution stability, electrolytic efficiency and deposit morphology can be overcome. An aqueous procedure was developed on the basis of potentiodynamic studies and long-term electrorefining experiments. It can be used for an efficient purification of the valuable waste material in a single operational step. The formation of chloro-complex ionic species may offer a beneficial level of natural inhibition, therefore the inefficient and in some respects harmful organic additives should be omitted. The tendency of Sn(II) oxidation and precipitation can be overcome by properly controlling the concentration of the main components in the electrolyte solution. The virtual cathodic current efficiency can be increased close to the theoretical value by optimizing the composition of the electrolyte solution, the applied apparent current density and the technological parameters of the PCR (periodical current reversal) electric supply. The loose structure of a deposited metal may satisfy the technical requirements but it requires special cell arrangement and care during operation. Electrolyte circulation should only be applied for the control of composition. The attainable purity – of close to 99.99% – surpasses the standard technical requirements.
No abstract is provided for this article.
White LED bulbs – dominant in lighting technology – can become a significant secondary source for the recovery of valuable rare metals, if a proper extractive metallurgical technology is developed. We have found an efficient way to separate the “phosphors” (phosphor coated LED chips) from the metallic base shells in dilute sodium carbonate and calcium hydroxide solutions. The leaching reactions of the separated phosphors was studied thermodynamically and the process was examined experimentally. The contained base metals and rare earth elements could be efficiently leached in 1 M HCl acid in 1 h, only Ga and In showed inert behavior toward acid solubilization. The separation of the valuable components has been devised by standard hydrometallurgical techniques.
The main characteristics of electrolytic reduction applied to indium recovery from aqueous chloride solutions were considered theoretically and examined experimentally. Also other media were considered for comparison. Potentiodynamic examinations pointed out that chloride electrolytes are superior to sulphuric and nitric acid-based ones for efficient indium deposition. The optimum conditions, allowing higher than 90% cathodic current efficiencies, were determined by galvanostatic experiments. In contrast, similar sulphate electrolytes could only yield lower than 50% efficiencies because of a stronger hydrogen evolution. The galvanostatic results confirmed the findings of the potentiodynamic study. The cathodic polarisation curves revealed the major characteristics of the deposition process, implying a reduction of the electroactive In 3+ ions. Coupled processes are the dynamic transformations of complex species and various rates of simultaneous hydrogen evolution. The structure and the elemental composition of the—relatively dense—cathodic deposits were examined by scanning electron microscopy and energy-dispersive X-ray analysis. Various levelling agents were also tested, and gelatine (up to a concentration of 1 g/dm 3 in the chloride electrolyte) was found efficient in grain refining. Graphical abstract
