Papers by Keyword: Zinc

Abstract: This Paper investigated the corrosion resistance and microstructural performance of zinc-magnesium oxide-tungsten boride (Zn-MgO-WB) composite coating on mild steel. Tungsten boride as an additive was co-deposited with zinc-magnesium oxide on mild steel via electrolytic deposition. The zinc-magnesium oxide and zinc-magnesium oxide-tungsten boride composite coatings were fabricated at the voltage of 0.6 and 0.8 V for 15 minutes and 45 °C. The effects of the deposits on the corrosion properties were examined. The corrosion behaviour was studied using linear polarization and weight loss method in 3.5% NaCl simulated environment. From the results obtained, it is evident that a decrease in applied potential influences the deposition of the coatings. The alloys with tungsten boride in their bath mixture performed better than those without. The zinc-magnesium oxide-tungsten boride (0.8 V) composite coated sample exhibits the least corrosion rate (Cr) of 0.0010482 mm/year and the microstructural examination of the sample via scanning electron microscope (SEM) unveiled homogeneous dispersion of particles and smooth morphology. The smooth morphology, defect-free surface, coupled with the uniform dispersion of the zinc-magnesium oxide-tungsten boride nanoparticles on the steel surface could have been responsible for high corrosion resistance performance of the coating in the simulated 3.5% NaCl medium. More so, the energy dispersive spectroscopy (EDS) revealed the presence of zinc, magnesium oxide, tungsten boride particles.

Abstract: The fibrillation mechanism of insulin in acid solution has been studied by small angle X-ray scattering (SAXS). It was observed that insulin monomer unfolded in both conditions. Furthermore, in zinc free solution, insulin tend to aggregate on heating start in the first 5 min. The fibrillation through aggregation process continues until 30 min on heating. The similar phenomenon occurs in the presence of zinc ions. The SAXS data suggest that the presence of zinc ions prevent the long cylindrical fibril at the beginning of heating. However, after 20 min heating, the large cylindrical fibril of insulin formed in both conditions.

Abstract: Constrained groove pressing (CGP), which is a severe plastic deformation technique, has been implemented on AISI 304 and commercially pure zinc samples in the present work. Four CGP passes were successfully applied to both materials providing a remarkable improvement in both strength and hardness values, despite reduced ductility. Average grain size values were diminished by around 45% for 304 stainless steel and 47% for commercially pure zinc. The highest levels of strengthening due to severe deformation were displayed after the initial passes for both materials. CGP was shown to be a viable method for strengthening based on deformation processing, whereby similar trends in microstructure and mechanical behavior were observed for both crystal structures.

Abstract: Waelz-oxide is a raw material for the production of metallic zinc. Waelz-oxide contains impurities of zinc and lead chlorides and fluorides. Halides have a negative effect on the process of zinc electrolysis. Halides have a relatively low boiling point; therefore, they are removed into the gas phase by calcining Waelz-oxide at 800–850 °С. To intensify the process, calcination is sometimes carried out at elevated temperatures of 1100–1250 °С. However, an increase in temperature leads to partial melting and granulation of the calcined product. In the present work, the chemical and phase composition of the initial and calcined Waelz-oxide was studied. Thermodynamic modeling of phase and chemical transformations of Waelz-oxide components during heating has been performed. Experiments on calcination of Waelz-oxide in laboratory conditions at temperatures of 600–1250 °C were carried out. It was found that partial melting and granulation of Waelz-oxide is the result of the formation of fusible eutectics containing lead oxide. Lead oxide is formed as a result of decomposition of lead sulfate when heated above 1100 °C. A similar effect is not observed at a standard calcination temperature of 850 °C.

Abstract: The aim of this paper is to establish a regulatory change of zinc powders key physicochemical properties with varying electroextraction conditions. It was studied influence zinc concentration, alkali concentration and current density. Quantitative dependencies of zinc powders particle size and specific surface area from mentioned electroextraction parameters are shown. At increasing of zinc concentration, decreasing of NaOH concentration and decreasing of current density of powders particle size growth, correspondingly specific surface area is declined. It is indicated, that electrolytic zinc powders bulk density varies from 0.61 g/cm³ to 0.75 g/cm³ with a decrease of average particle size from 121 μm to 68 μm. In comparison, spherical powders bulk density used in various industries is currently 2.45-2.6 g/cm³. In all experiments, metal zinc content varied in the range of 91.1-92.5%, the rest - ZnO. To a greater extent, this indicator depends on powder washing quality from alkali and storage conditions.

Abstract: In this study three-layered materials composed of one zinc layer between two magnesium layers were prepared. Diffusion at the Mg-Zn boundary leads to the formation of thermodynamically more stable, yet mechanically very brittle intermetallic phase. Homogenous distribution of the fine-grained MgZn₂ intermetallic phase in magnesium or zinc alloys has a positive effect on strength of these alloys. In a form of continuous thick layer stretching throughout the whole material, the phase may leads to deterioration of mechanical properties. However, the mechanism of fracture has not yet been sufficiently described. The Mg based materials with one layer of Zn were investigated in terms of chemical composition and mechanical properties and fractographic evaluation. The materials with 0.25 mm, 0.5 mm, 1 mm and 2 mm thick layer of Zn were processed via bidirectional hot pressing method at 300 °C and 500 MPa. The phase and chemical composition of prepared materials was characterized by XRD and SEM-EDS methods. The mechanical properties were evaluated based on the results of three-point bend test and fractographic analysis of fracture surface. The results showed formation of MgZn₂ intermetallic phase on the interface of Mg and Zn layers and solid solution of Zn in Mg. The results showed that the presence of Zn layer leads to improvement of mechanical properties when compared to pure Mg prepared at the same condition. The strengthening effect of solid solution and intermetallic phase may be the reason of the increase of flexural strength.

Abstract: Sn-0.7Cu lead free solder has become an alternative material to replace Sn-Pb solder. However, it has the weakness of high melting point and poor corrosion behavior. Through the study, Sn-0.7-xZn microstructure and phase changes were studied through scanning electron microscope (SEM) and X-ray diffraction (XRD). SEM result shows microstructure Cu₆Sn₅ is precipitated with rod like shape while CuZn is shown in bump oval shape whereas compounds that presented are Cu₆Sn₅ and Cu₅Zn₈ as shown in the XRD analysis result.

Abstract: Zink (Zn) in galvanized steel has a positive effect on improving the properties of the dissimilar metals weld between aluminum alloy and galvanized steel. Its distribution is important to be evaluated. The aim of this work is to investigate the effect of rotation speed and dwell time on the Zn distribution of the friction-stir-spot-welded (FSSW) dissimilar metals between aluminum alloy and galvanized steel. FSSW was subjected to 3 mm thick of Aluminum and 1 mm thick of galvanized steel with a plunge depth of 2.7 mm and a penetration rate of 0.9 mm/s. High strength steel (HSS) with a hardness of 70 HRC and a diameter of 12 mm was used as FSSW tool. Tool rotation was varied at 1000 rpm, 1200 rpm, 1600 rpm, and 2000 rpm while dwell time was varied of 3 s, 5 s, and 7 s. A Scanning Electron Microscope (SEM) was performed to reveal the Zn distribution after cross-sectioning, polishing, and etching. During the FSSW process, the heat was generated, Zn softened, and carried away by the materials flow due to tool rotation. Both the rotation speed and the dwell time played a role in increasing the distance and the amount of Zn flow in the welded zone. FSSW process in dissimilar metals between aluminum and galvanized steel formed the unique pattern of Zn distribution.

Abstract: Zinc is one of the important material in human blood because of its effect in defensive system work for properly and it plays an important role in growth, wound healing Medically zinc concentration effect directly in skin health so it's important to make a sensor for discover zinc and its concentration change in human blood for each of male and female. Optical fibers are used as a sensor for detecting zinc and its concentration by transmitted laser signal through the optical fiber by using different types (single mode fiber SMF, photonic crystal fiber PCF) by studying the results of output laser the detection can be seen for zinc concentration change, the design of small PCF which the same LMA_10 but smaller in its radius of core and cladding even the distance between cores. The smallest PCF size has the best detection for all zinc concentration change in blood all that was done by comsol Multiphysics 5.4 simulation program

Abstract: Error reasons of gold analytical determination in the chemical plant sludge are studied. The studied sludge is waste of BaCl₂ production. According to preliminary estimates it contains gold in sufficient quantity for industrial extraction. Comparison of direct sludge fire assay analysis and sludge dissolution in aqua regia, followed by gold atomic absorption determination in solution is made. The negative effect of Na⁺, Ca²⁺, Ba²⁺, Zn²⁺ ions presence in studied solutions was shown. Error quantitative estimate at alkali metals introducing into standard solutions is given. It is shown that Ca²⁺ and Ba²⁺ ions contribute the most error. Error increases linearly at addition of Ca²⁺ and Ba²⁺ ions. Growth error gradually slow down at increasing Na⁺, Zn²⁺ ion content.