Aphichart Rodchanarowan

Evaluation of the effects of additives, pulsing, and temperature on morphologies of copper electrodeposited from chloride media

Conventional copper recovery from chalcopyrite involves size reduction, flotation, smelting, and electrochemical purification. An alternative metal extraction process using chloride media would eliminate smelting. The use of chlorides has the additional advantage of reducing cell voltage and current requirements relative to sulfate based systems that are used to extract copper from oxide, silicate, hydroxide, and some sulfide minerals. However, chloride based systems are more likely to produce irregular electrodeposits that cannot be removed by traditional methods. Chloride solutions also present additional challenges related to the corrosive nature of the solutions. The effects are reported of additives, pulsing, and temperature on the topography, as characterized by root-mean-squared roughness, of copper electrodeposits made from chloride media.

Improving the morphology of copper electrodeposits from halide media using additives and mass transport control

Most of world’s copper reserves are in the form of the mineral chalcopyrite (CuFeS2). Traditional copper recovery from chalcopyrite is made by size reduction, flotation, smelting, and electrochemical purification. Alternative metal extraction technology using halide media allows for the elimination of the smelting process. The use of halides has the additional advantage of reducing cell voltage and current requirements relative to sulfate based systems that are used in connection with copper extraction from other minerals. The elimination of smelting and the reduction in energy utilization make this an environmentally attractive alternative for copper recovery. However, the halide based systems are more difficult to control in the electrochemical reduction process due to irregular electrodeposits and they have additional challenges related to the corrosive nature of the solutions. This study identifies relevant parameters associated with reducing irregular electrodeposits while simultaneously reducing power consumption relative to traditional processing technologies.

Synthesis of Ternary Semiconductor Silver Bismuth Telluride by Chemical Bath Deposition

In this study, the synthesis of the ternary semiconductor sensitized silver bismuth telluride (AgBiTe2: SBT) particles was produced in the solution of AgNO3, Bi (NO3)3×5H2O and Na2O3Te by using a chemical bath deposition (CBD) method and annealing at 200°C for 1 h. According to scanning electron microscopy (SEM), the particle size of SBT after annealing was bigger than before annealing. Based on X-ray diffraction, the SBT after annealing for 1h became more crystalline. In addition, the XRF data also demonstrated that the SBT powder consists of Ag, Bi, and Te as dominant elements. The XRD result confirms a successful growth of the SBT particles with rhombohedral crystal structure. Based on the obtaining results, the SBT particles were successfully synthesized and potentially applied for solar cell application.

The Influence of Aluminium Dross on Cement Paste's Porosity

In this study aluminium dross, an industrial waste product from the aluminum casting industry which contains mostly aluminum, aluminium oxide, and volatile gases such as ammonia (NH3), methane (CH4) and hydrogen (H2). In this study it is used as an admixture in cement paste to observe its effects on the porosity and bulk density of the material. The parameters used in the study include; the effects when different quantities of aluminium dross are added to portland cement (portland cement:aluminium dross by weight; 1: 0.05, 1: 0.10, and 1: 0.20) and the effect of different sized particles of aluminium dross (average diameter of aluminium dross particles; <45, 60, and 90 μm) on porosity and bulk density of cement paste. According to the study, as the amount of aluminium dross content in cement paste increases, the area fraction of porosity in the cement paste increases; yet the bulk density of cement paste decreases. In addition, when the particle size of aluminium dross decreases both of the pores size in the cement paste and bulk density of cement paste decrease.

Synthesis, characterization, and magnetic properties of tetracyanonitridochromates

The reaction of S=1/2 [PPh4]2[CrV(N)(CN)4] with [M(NCMe)x][BF4]2 (M=V, Fe, Co, Ni, x=6; M=Mn, x=4) and [CrII(NCMe)6](BARF)2 [BARF=tetrakis(3,5-trifluoromethylphenyl)borate] led to materials of nominal MII[CrV(N)(CN)4]·MeCN composition, albeit contaminated with cationic and/or anionic impurities. VII[CrV(N)(CN)4] exhibits strong antiferromagnetic coupling (θ=−352 K) and orders as an antiferromagnet (Tc=10.0 K) while MII[CrV(N)(CN)4] (M=Cr, Mn, Fe, Co, Ni) are weak ferromagnets (canted antiferromagnets) that order between 4.5 (Co) and 10.5 (Fe) K.

Uncertainty Quantification for Flow and Transport in Highly Heterogeneous Porous Media Based on Simultaneous Stochastic Model Dimensionality Reduction

Groundwater flow models are usually subject to uncertainty as a consequence of the random representation of the conductivity field. In this paper, we use a Gaussian process model based on the simultaneous dimension reduction in the conductivity input and flow field output spaces in order quantify the uncertainty in a model describing the flow of an incompressible liquid in a random heterogeneous porous medium. We show how to significantly reduce the dimensionality of the high-dimensional input and output spaces while retaining the qualitative features of the original model, and secondly how to build a surrogate model for solving the reduced-order stochastic model. A Monte Carlo uncertainty analysis on the full-order model is used for validation of the surrogate model.

Rechargeable organic–air redox flow batteries

A rechargeable organic–air flow battery based on aqueous electrolytes is proposed and tests are conducted in a divided cell with a three-electrode configuration. Quinoxaline is used as the negative redox couple due to its low electrode potential of c.a. −0.9 V vs. Hg|HgO in aqueous electrolytes. High-surface-area nickel mesh and manganese-dioxide electrodes were employed for oxygen evolution and reduction, respectively, together with a low-cost hydroxide doped polybenzimidazole (m-PBI) separator (c.a. 20 μm). In typical alkaline electrolytes (2 M NaOH), the open-circuit voltage of the flow battery was c.a. 0.95 V, which is comparable to existing organic-based batteries. The average charge and discharge cell voltage ranges at 5–10 mA cm−2 were 1.7–1.95 V and 0.4–0.7 V, respectively. Despite using low-cost materials, average coulombic and energy efficiencies of the batteries were c.a. 81 and 25%, respectively, at 7.5 mA cm−2 over 20 cycles.

Effect of Dealloying Conditions on Nanoporous Surface of Cu-Zn Alloy

This research aims to develop a porous layer surface using two steps: the radio frequency (R.F.) sputtering and dealloying. The glass substrate was firstly coated with Cu-Zn using the R.F. sputtering method. Then nano-porous layer surface is produced by dealloying-corrosion to dissolve unwanted element (Zn) from the base metal (Cu). The characterization techniques are scanning electron microscope (FE-SEM) for topographical analysis, X-ray fluorescent (XRF) for chemical analysis, and potentiostat for electrochemical measurement. It was found that the coated specimens obtained by R.F. sputtering are uniformly distributed by Cu-Zn alloys on the substrate’s surface. In addition, after dealloying, it was found that the diameter of the ligament size and pore size are in the nano-scale over the substrate’s surface.

Development of Pitting Corrosion Monitoring Device under Sodium Chloride Droplet by Means of Wet-Dry Cyclic Method

Pitting corrosion caused by wet-dry cycles under corrosive media droplet is one of the key concerns for passive film of metallic materials, particularly stainless steels and aluminum alloys, exposed to atmosphere during service. In this context, the formation of corrosion can lead to high investment cost dealing with corrosion mitigation strategy, e.g. materials selection, electrochemical corrosion control, etc. Based on materials selection perspectives, it is very necessary to have proper understanding of localized corrosion behaviors of metallic materials under solution droplet. Therefore, the present study aims to develop a methodology for pitting corrosion monitoring that can be suitably used for extending better understanding on corrosion phenomena occurring under wet-dry cycles of droplet. A special liquid handling apparatus controlled by Arduino software was constructed and used for generating NaCl solution droplet at given dimension on the surface of stainless steel specimens based on Pendant drop principle. This was recognized as wet cycle. During dry cycle, such NaCl solution droplet was naturally dried off in various conditions of relative humidity. Pitting initiation was observed through a high-resolution CCD camera. Droplet morphology and evaporation time were evaluated at the temperature of 27°C and relative humidity of 10% and 60%. The research results revealed that pitting corrosion started at 1st cycle without rust formation. Afterwards, the rust formation was clearly noticed when testing cycles of 15 were exceeded.

Photocatalytic Comparative Study of TiO 2 , ZnO, Ag-G-ZnO and Ag-G-TiO 2 Nanocomposite Films

In this study, the photocatalytic properties and morphology of TiO2, ZnO, Ag-graphene-zinc oxide (Ag-G-ZnO) and Ag-graphene-titanium dioxide (Ag-G-TiO2) nanocomposite were compared. The Ag-G-ZnO and Ag-G-TiO2 nanocomposite were successfully prepared by thermal decomposition of colloidal solution. These prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy and photocatalytic activities. The results from XRD patterns show that Ag-G-TiO2 composites and the Ag-G-ZnO nanocomposites were in the form of fcc and hcp crystal structure, respectively. The SEM images show that at calcination of 500 °C for 3 h, the composite thin film of Ag-G-ZnO and Ag-G-TiO2 were homogenous. In the case of the photocatalytic experiments using methylene blue dye (MB) under UV irradiation, the order of the photocatalytic activities from high to low performances are Ag-G-ZnO, Ag-G-TiO2, ZnO and TiO2, respectively.