Papers by Keyword: Zinc

Abstract: The anatase phase of titanium dioxide ceramic material plays important rule in heterogeneous photocatalysis, beside the global phase amount and powder morphology. Some of structural parameters are useful to predict several properties, including the crystallization process and mechanism of the irreversible anatase-to-rutile phase transition. The photocatalytic process is based on charge transference from electron-hole pair to material surface, starting some redox reactions in aqueous media. The stable positive defects harm the recombination event and improve the final properties of that material. Modifiers with lower oxidation state than titanium (IV) is applicable for this purpose, what idea becomes the objective of this work. The Sol-Gel method was used to prepare bare and zinc doped-titanium dioxide powder samples reaching good compositional homogeneity for both samples calcined at 500 oC for 4 hours. Rietveld refinement carried out from raw x-ray diffraction patterns was used to demonstrate the formation of solid solution between zinc and titanium oxides. Besides that result, the determination of bandgap energy and SEM images corroborated the structural changes caused by zinc insertion in anatase phase and important difference in powder morphology was observed for zinc doped powder samples in order to reduce the agglomeration degree for better performance for heterogeneous photocatalysis applications.

Abstract: This research examines the influences of minor addition of Zn on the thermal and mechanical properties in Sn-0.7Cu solder alloy. The addition of 0.5, 1.0 and 1.5 wt.% of Zn were added into Sn-0.7Cu by using conventional casting method. It show that minor Zn addition has refined and promoted the nucleation of β-Sn phase. The vickers hardness show a increases the hardness of Sn-0.7Cu solder alloy with increasing amount of Zn. For thermal properties, with a small addition of Zn, it did not change the melting but has a slight decrease the undercooling of Sn-0.7Cu solder alloy.

Abstract: In this study, the effect of Zinc (Zn) addition on microstructure, interfacial IMC and wettability properties of Sn-0.7Cu lead free solder alloy was investigated. The addition of 0.5, 1.0 and 1.5 wt.% Zn into Sn-0.7Cu was developed by using conventional casting method. The result revealed that the addition of Zn has refined the β-Sn phase. The thickness of interfacial IMC decreased with 0.5 wt.% and 1.0 wt.% Zn addition but increased after 1.5 wt.% of Zn was added. The wettability of Sn-0.7Cu also improved by the Zn addition. It can be concluded that a small amount of Zn addition up to 1.0 wt.% decreased the thickness of IMC and improved the wettability. However, when 1.5 wt.% Zn was added, the interfacial IMC and wettability become worse.

Abstract: The zinc (Zn) substituted hydroxyapatite were synthesized using a chemical precipitation method. The chemical precursors were prepared from di-ammonium hydrogen orthophosphate, calcium oxide (CaO) derived from chicken eggshell and zinc nitrate (Zn(NO₃)₂). The Zn(NO₃)₂ contents in the prepared samples were varied from 1 to 25 %wt of CaO. The Zn substituted hydroxyapatite were heated at the various temperatures from 200 to 1300 °C in the furnace with an incremental temperature of 100 °C. The crystal structure, function group and morphology of sample were analyzed by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM), respectively. The results show that the hydroxyapatite doped Zn was a hydroxyapatite phase as well as pure hydroxyapatite. The crystalline size of sample decreased with increasing the Zn content. And, the crystallinity of hydroxyapatite phase was increased following by increasing heat treatment temperature. However, the amount of Zn has the effect on phase transformation of hydroxyapatite phase after heat treatment. Zn concentration accelerates hydroxyapatite transforms to β-tricalcium phosphate phase.

Abstract: Concrete is still the most commonly used building material. The main component of concrete is Portland cement. Due to increasing use of secondary products containing zinc, the amount of zinc in the clinker or in the secondary raw materials is increasing in recent years. Portland clinker can gain zinc from solid waste or tires which are widely used as a fuel for a burning in rotary kiln. In the case of secondary raw materials, zinc may be present in the primary material, where the manufacturing process leads to its removal and concentrating to "waste" which is used in the cement industry. The biggest problem with cement doped with zinc is the retardation of hydration and decreasing of mechanical properties. The main aim of this work is describing and evaluation of zinc effect on the course of Portland cement hydration.

Abstract: In this work, microstructure and corrosion properties of zinc electroplated steel before and after black chromating was investigated. The test samples were prepared by electrodeposition process, using a commercially-available alkaline electrolyte. Subsequently, the galvanized samples were applied with a black chromate-based passivation layer and a clear top-coat layer. Their microstructures were examined using X-ray diffractometry and scanning electron microscopy. The corrosion resistance of the samples was assessed with the salt spray test, following the ASTM B117, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization in 5 wt.% NaCl solutions. The study showed that zinc electroplated steels exhibit (110) crystallographic orientation. The passivation and top-coat layers did not affect the microstructure of the zinc layer, and covered uniformly on the zinc layer for all sets of samples. The corrosion resistant results obtained from salt spray testing and electrochemical testing revealed that the microstructure of zinc coatings prepared by using different applied current did not influence on their corrosion resistance markedly. While black passivation followed by top coating provided a significant improvement on corrosion resistance of the coatings.

Abstract: The FAME (Flexible and Mobile Economic Processing Technologies) project targets the development of flexible and economic processing technologies for small and low-grade European ore deposits with complex mineralogy, targeting greisen, skarn and pegmatite ores. Amongst the valuable elements to be recovered are W, Sn, Li and minor constituents like In, Ge, Ga, Nb or Ta. To improve the processing of by-product sulfides to recover critical elements like In or Ga and to develop innovative processing strategies for raw materials, biohydrometallurgical technologies are investigated. There are different approaches in FAME for the biohydrometallurgical recovery of valuable metals from low grade ores: 1) the extraction of Li from zinnwaldite and lepidolite, 2) the heap leaching of low grade sulfide ore unsuitable for conventional processing to recover Zn and In, and 3) the bioleaching of sulfide concentrates in a two-stage tank process for recovery of Zn and Cu. So far the most promising results were achieved for heap-leaching of low-grade Zn-In ores achieving 7.4 ppm In in the leaching solution and for Li extraction (28%) from zinnwaldite.

Abstract: Heap biooxidation is the most economic option of treating processing plants tailings and refractory ores containing non-ferrous and precious metals and sulphides.Pyrite tailings of copper ore processing (Sample 1), tailings of sulphide copper-nickel ore processing (Sample 2) and double refractory gold-bearing ore (Sample 3) were studied.Autotrophic microorganisms Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans were used for the tests. The duration of heap biooxidation tests for Samples 1, 2 and 3 was 6, 10 and 16 months, respectively. The rates of copper and zinc recovery into solution during heap biooxidation of Sample 1 were 68% and 71%, respectively; the rates of copper and nickel recovery from Sample 2 were 50% and 75%, respectively. Base metals were extracted from solution to selective high-grade concentrates after biooxidation.Biooxidation tailings of Samples 1 and 3 were leached using an alkaline sodium cyanide solution. The recovery of gold from Sample 1 and Sample 2 was 65% and 85%, respectively.

Abstract: With the increase of environmental restrictions, chromium and cadmium-based coatings have been replaced by zinc layers. These coatings can be obtained through electrodeposition, whose industrially established pH range is from 5.0 to 5.8, and stirring speed is uncontrolled, which has led to part rejections. In addition, the corrosion resistance of zinc coatings is inferior to cadmium and chromium coatings, which has boosted the research of zinc composite coatings. The proposed work presents the performance of zinc-bentonite composite coatings in regards to corrosion relating to pH variation and stirring speed. The samples were degreased for 5 minutes in a commercial degreasing solution at a temperature of 55 °C, with magnetic stirring and, posteriorly, submitted to a pickling process with a duration of 1 to 2 minutes in a commercial bath, followed by a washing process with deionized water. The electrolyte used for electrodeposition was a zinc bath with a chemical composition of 85 g/l ZnCl₂, 210 g/l KCl and 25 g/l H₃BO₃. For the zinc-bentonite electrodepositions 20 g/l of bentonite nanoparticles was added to the bath. Zinc and zinc-bentonite coatings were characterized by scanning electron microscopy, open circuit potential and potentiodynamic polarization. This work shows that a 5.2 pH is the most recommended for the zinc electrodeposition process. Potentiodynamic polarization tests indicated that pure zinc coatings developed in the stirring speed of 380 rpm and zinc-bentonite produced in the stirring speed of 710 rpm showed the best results.

Abstract: Zinc oxide nanoparticles (ZnO NPs) has been reported on toxicity effects on environmental organisms. However, Zn is a plant essential microelement which is involved in various physiological functions. In this study, MS medium, adding 0, 10 and 20 mgL^-1 ZnO NPs were used for culturing wild type (WT) and transgenic expressing PAP1 under tissue culture condition. Effects of ZnO NPs concentrations on the accumulations of total soluble sugar (TSS) and flavonoid biomaterials in WT and transgenic plants were analysis. Membrane stability of each plant was assayed by lipid peroxidation measurement. Malondialdehyde, a byproduct of the membrane lipid peroxidation, was presented. The result showed that both WT and transgenic grown in medium, adding ZnO NPs enhanced the accumulations of TSS and flavonoids. All of PAP1 transgenic lines had a better response under ZnO NPs concentration and elevated higher biomaterials than WT did. Medium adding 20 mgL^-1 ZnO NPs affected the highest accumulation of both biomaterials especially in transgenic plant. Higher accumulation of biomaterials is presented in treatment adding ZnO NPs and plant membrane stability of this treatment is better than that of medium without ZnO NPs. However, medium with 10 mgL^-1 ZnO NPs showed the proper result of plant membrane stability.