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Number of results: 10
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Abstract

An ecoefficient, economical and sustainable valorization process for the synthesis of Co3O4 from waste lithium-ion battery (LIB) by leaching-solvent extract-scrubbing-precipitation stripping route has been developed. Through an optimization, the waste LIB cathode was leached using 2000 mole/m3 of H2SO4 and 5 Vol. % of the H2O2 at a pulp density of 100 kg/m3 under leaching time 60 minutes and temperature 75 °C. From the separated leach liquor, cobalt was purified by saponified Cyanex 272. From cobalt, loaded Cyanex 272 impurities were scrubbed and the CoC2O4·2H2O was recovered through precipitation stripping. Finally, the precipitate was calcined to synthesize Co3O4, which is a precursor for LIB cathode materials manufacturing. From TGA-DTA, followed by XRD analysis it was confirmed that at 200 °C the CoC2O4·2H2O can be converted to anhydrous CoC2O4 and at 350 °C the anhydrous can be converted to Co3O4 and at 1100 °C the Co3O4 can be converted to CoO. Through reported route waste LIB can back to LIB manufacturing process through a versatile and flexible industrial approach.
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Abstract

At present, industrial development is increasing pollution of soils, air and natural waters. These pollutants have a negative effect on the health and life of living organisms. Metals which interfere with the natural biological balance and inhibit self-cleaning processes in water bodies have particularly toxic effects. Cobalt, which gets into the environment from industrial sewage from electrochemical plants and the metallurgical industry, also belong to this group. This is also relatively rare and precious element, so it is important to look for additional sources of its recovery. Chemical and physicochemical methods such as: precipitation, extraction, membrane processes – nanofiltration, reverse osmosis, sorption and ion exchange are used to recover cobalt. The choice of method depends on: the kind and composition of wastewaters as well as on form and concentration of the pollutants. Ion exchange resins produced by Purolite which were used to remove cobalt ions from solutions with concentrations corresponding to its contents in galvanic wastewater was the subject of the study. It has been shown that the C 160 ion exchange resin has the best the sorption properties for Co2+ ions (54.7 mg/g). In case of this ion exchange resin, after sorption process carried out in one 50 minute cycle, cobalt concentration decreased from about 30 g/L to about 9 g/L. The values of the sorption capacity do not depend on the method of introducing the solution into an ion exchange column (pouring or dropping). E ach of the tested ion exchange resins is characterized by a high degree of cobalt concentration after regeneration using mineral acids, which can be advantageous in selecting the recovery method for this metal.
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Abstract

This work presents the studies on the electrochemical process of thin palladium layers formation onto electrodeposited cobalt coatings. The suggested methodology consists of the preparation of thick and smooth cobalt substrate via galvanostatic electrodeposition. Cobalt coatings were prepared under different cathodic current density conditions from acidic bath containing cobalt sulphate and addition of boric acid. Obtained cobalt layers were analyzed by x-ray diffraction to determine their phase composition. Freshly prepared cobalt coatings were modificated by the galvanic displacement method in PdCl2 solution, to obtain smooth and compact Pd layer. The comparison of electrocatalytic properties of Co coatings with Co/Pd ones enabled to determine the influence of Palladium presence in cathodic deposits on the hydrogen evolution process.
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Abstract

The paper presents the effect of ZrO2 layer deposition by the ALD process on the physicochemical properties of cobalt-based alloys (Realloy C and EOS CoCr SP2) intended for application in prosthetic dentistry. The paper shows the results of the surface roughness measurements made by the AFM method as well as the wettability and free surface energy measurements. Additionally,potentiodynamic tests of pitting corrosion resistance and electrochemical impedance spectroscopy in a solution of artificial saliva were carried out. Tests were carried out on the samples in the initial state and after surface modification with the ZrO2 layer. Based on these results, the usefulness (e.g. enhancement of corrosion resistance and biocompatibility) of the proposed ZrO2 layer on the cobalt alloys was assessed.
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Abstract

The work presents the results of the studies of Co-Cr-Mo casting alloys used in the production of frame casts of removable dentures, crowns and bridges in dental prosthetics. The studies were performed on four Co-Cr-Mo alloys of different contents of Mo, W and other additives. Electrochemical tests were performed, which aimed at examining the corrosion resistance of the alloys and observing the alloy structure after chronoamperometric tests with the potential in the area of the occurrence of the passive layer breakpoint. The alloy microstructure images after chronoamperometric tests show the presence of non-uniformly distributed general corrosion. Moreover, a project of cobalt alloy casting was elaborated using a ceramic mold casting. Additionally, analysis of the obtained microstructure was performed. The microstructure of the examined alloys was of the dendrite type. This microstructure was chemically inhomogeneous and consisted of an austenitic matrix formed by a solid cobalt solution and chromium in the core dendritic structure.
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Abstract

The paper presents results of research on cobalt and nickel ions removal from monocomponent solutions using Purolite ion exchange resins. It has been shown that C 160 ion exchange resin has the best sorption properties for both ions (Qe – 72.5 mg Co/g and 88.2 mg Ni/g). Regeneration process of this ion exchanger has high efficiency, achieving about 93% for cobalt ions and about 84% in case of nickel ions. It has been shown that the use of ion exchange method with suitable ion exchange resins guarantees effective removal of cobalt and nickel ions from solutions with very high concentrations corresponding to contents of these metals in industrial wastewaters (e.g. galvanic). In case of C 160 ion exchange resin, after the sorption process is carried out in one 50 minute cycle, the cobalt concentration decreased from about 30 000 mg/L to about 9 500 mg/L (approx. 68%), whereas nickel concentration reached about 6 300 mg/L (approx. 79%). Studied chelating resins don’t have such high sorption capacities. In their case, it is required to convert cobalt and nickel ions into complex forms. The kinetics of studied processes were described by pseudo-second order equations.
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Abstract

The aim of our research was to investigate the genotoxic effects of cobalt chloride and copper chloride in mouse bone marrow cells using the micronucleus (MN) assay. The three different concentrations of cobalt chloride (11.2, 22.5 and 45 mg kg-1) and copper chloride (1.17, 2.35 and 4.70 mg kg-1) were injected intraperitoneally to mice for 24 and 48 hours. It was observed that both of these heavy metals induced a significant increase in frequency of micronucleated polychromatic erythrocytes (MNPCE) at different concentrations in mice for 24 and 48 hours when compared with the control. Furthermore, the significant reduction for the polychromatic erythrocyte/normochromatic erythrocyte (PCE/NCE) ratio which is indicative of bone marrow cytotoxicity was observed in bone marrow cells which were treated with copper chloride at all concentrations for 24 and 48 hours. No reduction of the PCE/NCE ratio was observed both 24 and 48 hours after all the doses of cobalt chloride tested as compared to the negative control. These results lead us to the conclusion that copper chloride may have genotoxic and cytotoxic properties due to induction in the frequency of MN and a reduction in PCE/NCE ratio in bone marrow cells of mice, whereas cobalt chloride induced only genotoxic effect in mice bone marrow
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Abstract

The paper presents the results of research on the determination of the effect of pouring temperature on the macrostructure of the castings subjected to complex (surface and volume) modification and double filtration. Tested castings were made of post-production scrap (gating system parts) of IN-713C superalloy. Tests included the evaluation of the number of grains per 1 mm2 , mean grain surface area, shape factor and tensile strength. Casting temperature below 1470 °C positively influenced the modification effect. The grains were finer and the mechanical properties increased, especially for castings with thicker walls. On the other hand, manufacture of thin walled castings of high quality require pouring temperature above 1480 °C.
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Abstract

In current casting technology of cored, thin walled castings, the modifying coating is applied on the surface of wax pattern and, after the removal of the wax, is transferred to inner mould surface. This way the modification leading to grain refinement occur on the surface of the casting. In thin walled castings the modification effect can also be seen on the other (external) side of the casting. Proper reproduction of details in thin walled castings require high pouring temperature which intensify the chemical reactions on the mould – molten metal interface. This may lead to degradation of the surface of the castings. The core modification process is thought to circumvent this problem. The modifying coating is applied to the surface of the core. The degradation of internal surface of the casting is less relevant. The most important factor in this technology is “trough” modification – obtaining fine grained structure on the surface opposite to the surface reproduced by the core.
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Abstract

The paper presents the results concerning impact of modification (volume and surface techniques), pouring temperature and mould temperature on stereological parameters of macrostructure in IN713C castings made using post-production scrap. The ability to adjust the grain size is one of the main issues in the manufacturing of different nickel superalloy castings used in aircraft engines. By increasing the grain size one can increase the mechanical properties, like diffusion creep resistance, in higher temperatures. The fine grained castings. on the other hand, have higher mechanical properties in lower temperatures and higher resistance to thermal fatigue. The test moulds used in this study, supplied by Pratt and Whitney Rzeszow, are ordinarily used to cast the samples for tensile stress testing. Volume modification was carried out using the patented filter containing cobalt aluminate. The macrostructure was described using the number of grains per mm2 , mean grain surface area and shape index. Obtained results show strong relationship between the modification technique, pouring temperature and grain size. There was no significant impact of mould temperature on macrostructure.
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