Synthesis of LiNi1/3Co1/3Mn1/3O2 cathode materials by using a supercritical water method in a batch reactor

LiNi_1/3Co_1/3Mn_1/3O₂ and LiCoO₂ cathode materials were synthesized by using a supercritical water (SCW) method with a metal salt solution in a batch reactor. Stoichiometric LiNi_1/3Co_1/3Mn_1/3O₂ was successfully synthesized in a 10-min reaction without calcination, while overlithiated LiCoO₂ (Li_1.15CoO₂) was synthesized using the batch SCW method. The physical properties and electrochemical performances of LiNi_1/3Co_1/3Mn_1/3O₂ were compared to those of Li_1.15CoO₂ by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and charge/discharge cycling tests. The XRD pattern of LiNi_1/3Co_1/3Mn_1/3O₂ was found to be similar to that of Li_1.15CoO₂, showing clear splitting of the (0 0 6)/(1 0 2) and (1 0 8)/(1 1 0) peak pairs as particular characteristics of the layered structure. In addition, both cathode powders showed good crystallinity and phase purity, even though a short reaction time without calcination was applied to the SCW method. The initial specific discharge capacities of the Li_1.15CoO₂ and LiNi_1/3Co_1/3Mn_1/3O₂ powders at a current density of 0.24 mA/cm² in 2.5-4.5 V were 149 and 180 mAh/g, and their irreversible capacity loss was 20 and 17 mAh/g, respectively. The discharge capacities of the Li_1.15CoO₂ and LiNi_1/3Co_1/3Mn_1/3O₂ powders decreased with cycling and remained at 108 and 154 mAh/g after 30 cycles, which are 79% and 89% of the initial capacities. Compared to the overlithiated LiCoO₂ cathode powders, the LiNi_1/3Co_1/3Mn_1/3O₂ cathode powders synthesized by SCW method had better electrochemical performances.     

Ultrasonic-assisted leaching kinetics in aqueous FeCl<Subscript>3</Subscript>-HCl solution for the recovery of copper by hydrometallurgy from poorly soluble chalcopyrite

We studied the ultrasonic effect on the leaching of copper from poorly soluble chalcopyrite (CuFeS₂) mineral in aqueous FeCl₃ solution. The leaching experiment employed two methods, basic leaching and ultrasonic-assisted leaching, and was conducted under the optimized experimental conditions: a slurry density of 20 g/L in 0.1M FeCl₃ reactant in a solution of 0.1M HCl, with an agitation speed of 500 rpm and in the temperature range of 50 to 99 °C. The maximum yield obtained from the optimized basic leaching was 77%, and ultrasonic-assisted leaching increased the maximum copper recovery to 87% under the same conditions of basic leaching. In terms of the leaching mechanism, the overall reaction rate of basic leaching is determined by the diffusion of both the product and ash layers based on a shrinking core model with a constant spherical particle; however, in the case of ultrasonic-assisted leaching, the leaching rate is determined by diffusion of the ash layer only by the removal of sulfur adsorbed on the surface of chalcopyrite mineral.     

Characteristics of an electrochemical reduction of Ta2O5 for the preparation of metallic tantalum in a LiCl–Li2O molten salt

The electrochemical reduction of Ta₂O₅ in a LiCl–Li₂O molten salt system has been carried out in an electrolytic cell with an integrated cathode assembly. During the electrochemical run, Ta₂O₅ reacts chemically with Li₂O to form LiTaO₃. The chronopotentiometry method was used to prepare the metallic tantalum from Ta₂O₅. The electrolysis of Li₂O and the reduction of Ta₂O₅ and/or LiTaO₃ take place simultaneously at the cathode part of an electrolysis cell. The recycle of Li₂O by an O²⁻ diffusion occurs in the cell. The results suggest that the metallic tantalum is prepared successfully by an electrochemical reduction in the LiCl–Li₂O molten salt.     

Development of spatial water resources vulnerability index considering climate change impacts

This study developed a new framework to quantify spatial vulnerability for sustainable water resources management. Four hydrologic vulnerability indices - potential flood damage (PFDC), potential drought damage (PDDC), potential water quality deterioration (PWQDC), and watershed evaluation index (WEIC) - were modified to quantify flood damage, drought damage, water quality deterioration, and overall watershed risk considering the impact of climate change, respectively. The concept of sustainability in the Driver-Pressure-State-Impact-Response (DPSIR) framework was applied in selecting all appropriate indicators (criteria) of climate change impacts. In the examination of climate change, future meteorological data was obtained using CGCM3 (Canadian Global Coupled Model) and SDSM (Statistical Downscaling Model), and future stream run-off and water quality were simulated using HSPF (Hydrological Simulation Program — Fortran). The four modified indices were then calculated using TOPSIS, a multi-attribute method of decision analysis. As a result, the ranking obtained can be changed in consideration of climate change impacts. This study represents a new attempt to quantify hydrologic vulnerability in a manner that takes into account both climate change impacts and the concept of sustainability.     

Secure communication in IPTV broadcasting

In internet protocol television (IPTV) broadcasting, service providers charge subscribing fee by scrambling the program with conditional access system (CAS) using control words (CWs). A smart card is used to decrypt the CWs and transfer them back to set-top box (STB) to descramble the scrambled program. Secure communication between STB and the smart card is closely related with the benefit of service providers and the legal rights of users. In addition, secure key exchange with mutual authentication in the communication between STB and the smart card is an essential part of secure communication that will significantly improve the security of the system. To provide secure communication with mutual authentication in IPTV broadcasting, there are several schemes. The schemes proposed a secure and efficient method for the communication between STB and the smart card. Unfortunately, the schemes still have some security flaws. In this paper, we review that the previous schemes are vulnerable to several attacks. Further, we recommend some modifications to the schemes to correct these security flaws and present a formal analysis about our improved protocol using a logic based formal method.     

A tensile crack in creeping solids with large damage near the crack tip

An asymptotic analysis of stationary mode I crack in creeping solids with large damage near crack tip is conducted. To consider the damage effect, Kachanov damage evolution law is utilized and incorporated into the power-law creep constitutive equation. With the compatibility equation, a nonlinear eigenvalue problem which can be solved by numerical approaches is established. From this result, the distribution of stress and strain rate are obtained with the coupling effect of damage and creep under plane stress condition. Also the influence of material parameters on the stress is examined. According to the result, it is shown that the creep exponent n and damage parameter (=/(1+k)) have a significant effect on determining the eigenvalue s and angular distribution of stress and strain rate near the crack tip. The creep exponent n plays the role to soften and damage parameter plays the role to harden the material near the crack tip. The stress and strain rate show quite different behavior from those of HRR problem.     

Influence of potassium pyrophosphate in electrolyte on coated layer of AZ91 Mg alloy formed by plasma electrolytic oxidation

The effect of potassium pyrophosphate in the electrolyte on plasma electrolytic oxidation (PEO) process for AZ91 Mg alloy was investigated. The morphologies and chemical compositions of the coating layer on the AZ91 Mg alloy were evaluated and corrosion resistance was also estimated by potentiodynamic polarization analysis. The coating layer on AZ91 Mg alloy coated from the Bath 2 containing 0.03 mol/L of potassium pyrophosphate for 360 s exhibited considerably dense structure and contained 11%–18% (mass fraction) of phosphorous. The higher content of phosphorous of coating layer coated from Bath 2 could be detected at the bottom of oxide layer, which strongly implied that the phosphorous ion might be concentrated at the barrier layer. Corrosion potential of coating layer of AZ91 Mg alloy increased and corrosion current density decreased with increasing the concentration of potassium pyrophosphate. The polarization resistance (R_p) of coating layer of AZ91 Mg alloy coated from Bath 2 was 4.65×10⁷ Ω/cm², which was higher than that (R_p=3.56×10⁴ Ω/cm²) of the sample coated from electrolyte without potassium pyrophosphate. The coating layer coated from Bath 2 containing 0.03 mol/L potassium pyrophosphate exhibited the best corrosion resistance.     

Extraction and separation of Pt(IV)/Rh(III) from acidic chloride solutions using Aliquat 336

Extraction and separation of Pt(IV)/Rh(III) from chloride solutions using Aliquat 336 (Quaternary ammonium salt made by the methylation of mixed tri octyl/decyl amine) diluted in kerosene as an extractant/synergist alone and mixed with organophosphorous extractants as synergists/extractants were carried out from an aqueous feed containing 0.0005 mol L⁻¹ Pt(IV)/Rh(III).Variation of hydrochloric acid concentration of aqueous phase from 0.005 to 10.0 mol L⁻¹ increased the percentage extraction of platinum up to 5.0 mol L⁻¹ there after it decreases. Whereas in the case of rhodium, from 0.005 to 1.0 mol L⁻¹ acid range the percentage extraction was decreased from 1.0 to 10.0 mol L⁻¹ acid range is favorable for extraction. Platinum(IV)/rhodium(III) separation factor of 279.2 was obtained at 1.0 mol L⁻¹ HCl concentration with 0.005 mol L⁻¹ Aliquat 336 and separation factor of 612.3 was obtained at 3.0 mol L⁻¹ HCl concentration with 0.01 mol L⁻¹ Aliquat 336. The present study optimized the various experimental parameters like phase contact time, effect of extractant, salts, temperature, loading capacity of extractant, stripping studies with various mineral acids/bases, recycling and reusing capacity of extractant up to ten cycles.