Conversion kinetics of cerium oxide into sodium cerium sulfate in Na₂SO₄-H₂SO₄-H₂O solutions

The conversion of cerium oxide (CeO₂) into sodium cerium sulfate (NaCe(SO₄)₂·H₂O) in Na₂SO₄–H₂SO₄–H₂O solutions was studied at elevated temperatures using a batch-type glass reactor under atmospheric pressure. Sodium sulfate (Na₂SO₄) concentration, sulfuric acid (H₂SO₄) concentration and reaction temperature were chosen as dependent variables, and the effects of these three variables on the conversion of cerium oxide into sodium cerium sulfate in Na₂SO₄–H₂SO₄–H₂O solutions were investigated. The conversion includes two chemical reactions: cerium oxide dissolution and sodium cerium sulfate synthesis. The experimental data showed that increases of sodium sulfate concentration and sulfuric acid concentration decreased the conversion rate, whereas the conversion rate increased with increasing reaction temperature. The conversion kinetics of cerium oxide into sodium cerium sulfate for these three variables was analyzed and the fitted equation to the experimental data was determined. The variations of rate constant in dissolution and synthesis with temperature obeyed the Arrhenius equation with activation energies of 120 and 200 kJ/mol, respectively. In addition, the rate constant of cerium oxide dissolution was a function of the sodium sulfate concentration and sulfuric acid concentration at N−⁰.³ and C⁶.⁵, respectively, and for sodium cerium oxide synthesis at N−⁰.² and C−⁴.³

One-Step Coating of Full-Coverage CsPbBr₃ Thin Films via Mist Deposition for All-Inorganic Perovskite Solar Cells

In this work, one-step coating of CsPbBr₃ thin films using the mist deposition method is demonstrated. The CsPbBr₃ layer is composed of large grains with an average size of approximately 1.4 μm, and it fully covers the substrate surface, unlike the layers prepared by conventional one-step spin-coating methods, so that efficient carrier transport is realized. Carbon-based CsPbBr₃ perovskite solar cells (PSCs) fabricated using the mist deposition method exhibit a stabilized power conversion efficiency of 7.7%, which is a record value for carbon-based CsPbBr₃ PSCs prepared via a one-step solution process

Fabrication of CsPbBr₃ Thick Films by Using a Mist Deposition Method for Highly Sensitive X-ray Detection

X-ray imaging is a valuable technique used for medical imaging and non-destructive inspection of industrial products. However, the radiation may put humans at risk of developing cancer. Consequently, highly sensitive X-ray detectors, which enable X-ray imaging at a low dose rate, are required. Metal halide perovskite materials have demonstrated excellent X-ray detection performance including a high sensitivity owing to their high absorption coefficient, high carrier mobility, and long carrier lifetime. However, perovskite thick films with a large area, which is essential to realize the application of such materials to X-ray imaging devices have not been extensively investigated. To this end, in this study, a polymer is employed as a buffer layer to avoid film exfoliation, which makes it difficult to fabricate perovskite thick films, and a 110-μm-thick CsPbBr₃ film is successfully obtained using a scalable solution method. In addition, an X-ray detector based on the CsPbBr₃ thick film is fabricated, which demonstrates a sensitivity of 11, 840 μC Gyair⁻¹ cm⁻². This sensitivity is approximately 600 times higher than that of the existing commercial a-Se X-ray detectors

Electrodeposition and anodization of Al-TiO2 composite coatings for enhanced photocatalytic activity

In this study, we investigated the feasibility of a new process for the fabrication of Al-based composite coatings containing TiO₂ particles with high photocatalytic activity. In the first step of this process, Al-TiO₂ composite coatings were electrodeposited in a dimethyl sulfone-aluminum chloride bath with suspended TiO₂ particles yielding Al-matrix composite coatings with uniformly dispersed TiO₂ particles. Subsequently, the electrodeposited Al-TiO₂ composite coatings were anodized in oxalic aqueous solution. Through this anodization step, the Al matrix was converted into an alumina layer with many nanopores extending from the surface of the coating toward the substrate. As a consequence, a porous alumina layer supporting TiO₂ particles was formed. The photocatalytic activity of the anodized composite coatings was confirmed to be higher than that of the as-deposited coatings

黄銅鉱の酸化浸出反応に関する研究

京都大学0048新制・課程博士工学博士甲第3806号工博第974号新制||工||696(附属図書館)UT51-62-M21京都大学大学院工学研究科冶金学専攻(主査)教授 真嶋 宏, 教授 一瀬 英爾, 教授 小野 勝敏学位規則第5条第1項該当Kyoto UniversityDFA

Hull cell tests for evaluating the effects of polyethylene amines as brighteners in the electrodeposition of aluminum from dimethylsulfone-AlCl3 baths

Hull cell tests were carried out to examine a series of polyethylene amines to evaluate their abilities as brighteners in the electrodeposition of aluminum from a dimethylsulfone (DMSO2)-AlCl3 bath. The tests demonstrated the current density ranges that yielded bright, semi-bright, dull, burnt, and streaked Al deposits from the baths containing each polyethylene amine at a variety of concentrations. Among the amines examined in this study, triethylenetetramine (TETA) was found to be the most effective brightener, providing a bright Al deposit with the highest specular reflectance over a wide range of current densities. No correlation was found between the preferential crystal orientation of the Al and the brightness of the deposit, which along with the acquired scanning electron microscopy images, indicated that surface morphology was primarily responsible for the differences in brightness

Fabrication of TiAl3 coating on TiAl-based alloy by Al electrodeposition from dimethylsulfone bath and subsequent annealing

TiAl3 coating was formed on TiAl alloy by Al electrodeposition from a dimethylsulfone (DMSO2) bath and subsequent annealing. Before the Al electrodeposition, anodic dissolution of TiAl substrate in the DMSO2 bath was conducted to remove the surface oxide layer of the TiAl substrate. By performing the Al electrodeposition immediately after the anodic dissolution, uniform Al films adherent to the TiAl substrate could be obtained. Annealing at 650–1000 °C yielded a single TiAl3 layer or two layers of TiAl3 and TiAl2 on the TiAl substrate. The resulted TiAl3 layer was confirmed to show oxidation-resistance at high temperatures

Precipitation of cerium sulfate converted from cerium oxide in sulfuric acid solutions and the conversion kinetics

The conversion of cerium (IV) oxide into cerium (IV) sulfate in sulfuric acid solutions was studied in a batch-type glass reactor under atmospheric pressure. The effects of agitation speed, acid concentration, reaction temperature, initial amount of cerium (IV) oxide per sulfuric acid solutions (C/S), and particle size on the conversion process were investigated. All experiments were carried out in the range of 8–14 mol/dm³ for sulfuric acid concentration, 105–135°C for reaction temperature, 0.04–0.28 mol/dm³ for C/S, and 2.5–112.5 µm for average particle size. The conversion process involves the dissolution of cerium (IV) oxide and the precipitation of cerium (IV) sulfate. Cerium (IV) oxide reacted with sulfuric acid very slowly and then dissolved cerium (IV) in a saturated condition directly formed cerium (IV) sulfate indicating that the conversion rate was controlled by the dissolution rate of cerium (IV) oxide. Increases in sulfuric acid concentration and reaction temperature increased the dissolution rate, whereas increase in particle size decreased it. However, the C/S had no effect on the dissolution rate. In terms of the yield of precipitated cerium (IV) sulfate after reaction equilibrium, increases in sulfuric acid concentration and C/S increased the yield. However, the particle size and the reaction temperature had no effect on the yield of precipitated cerium (IV) sulfate. The kinetics of cerium (IV) oxide dissolution, under various conditions of sulfuric acid concentration, reaction temperature, C/S, and particle size, was interpreted by a shrinking core model with chemical reaction. The variation of rate constant upon dissolution with temperature obeyed the Arrhenius equation with an activation energy of 123 kJ/mol

Dissolution behavior of La₂O₃, Pr₂O₃, Nd₂O₃, CaO and Al₂O₃ in sulfuric acid solutions and study of cerium recovery from rare earth polishing powder waste via two-stage sulfuric acid leaching

This study describes a hydrometallurgical process to investigate the cerium recovery from rare earth polishing powder waste (REPPW) containing main elements such as cerium, lanthanum, praseodymium, neodymium, calcium and aluminum. First, dissolution experiments on La₂O₃, Pr₂O₃, Nd₂O₃, CaO and Al₂O₃ with 5 µm particle size in sulfuric acid solutions were carried out using a batch reactor with various acid concentrations (1–15 mol/dm³) at different temperatures (30–180°C). The effects of these two parameters on the dissolution reaction were studied. The obtained results showed that two sequential leaching steps were needed to separate cerium from the mixture of CeO₂, La₂O₃, Pr₂O₃, Nd₂O₃, CaO and Al₂O₃. The total process for cerium recovery from REPPW via two-stage acid leaching was then developed through the collection of experimental results. Moreover, the dissolution rate of Al₂O₃ was expressed by a shrinking core kinetics model. The variation of the dissolution rate constant with temperature obeyed the Arrhenius equation with activation energy of 130 kJ·mol⁻¹ and reaction rate constant as a function of the acid concentration of C⁰.⁴¹. On the basis of the above data, a k-T (reaction rate constant-reaction temperature) diagram for a CeO₂–Al₂O₃–H₂SO4–H₂O system that permits rational extraction of CeO₂ and Al₂O₃ was devised