Kinetic Investigation of Reaction Between Mineral Ulexite and Citric Acid

In this study, the dissolution kinetics of ulexite, a sodium-calcium-borate hydrate (Na₂O·2CaO·5B₂O₃·16H₂O) in citric acid solutions was investigated in a batch reactor. The rate of dissolution can be expressed according to surface chemical reaction controlling with changing fluid reactant concentration. The activation energy of the process was found to be 39.4 kJ/mol.     

Latent heat energy storage characteristics of building composites of bentonite clay and pumice sand with different organic PCMs

In the present work, six new kinds of building composite PCMs (BCPCMs), PS/octadecane, BC/octadecane, PS/CA–MA, BC/CA–MA, PS/PEG1000, and BC/PEG1000 composites, were prepared by using vacuum impregnation method. The maximum percent of PCM in the composites was assigned to be 12, 13, 18, 23, 30, and 42 wt%, respectively. The form‐stable BCPCMs were characterized using SEM, FT‐IR, DSC, and TG analysis techniques. The characterization results showed the existence of homogenous dispersion of the PCM into the PBM matrixes. The DSC measurements indicated that the melting temperatures of the form‐stable BCPCMs are in the range of 20–33°C while they have latent heats of melting in the range of about 28–55 J/g. These results make them promising BCPCMs for low temperature‐passive TES applications in buildings. Thermal cycling test indicated that the prepared BCPCMs have good thermal reliability and chemical stability. TG analysis proved that the prepared BCPCMs have good thermal durability. In addition, the thermal conductivity of BCPCMs was enhanced considerably by addition of expanded graphite (EG). The improvement in thermal conductivity of the BCPCMs caused appreciably reduction in their melting times. Copyright © 2014 John Wiley & Sons, Ltd.     

The Water-Soluble Peripheral Substituted Phthalocyanines as Corrosion Inhibitors for Copper in 0.1 N HCl: Gravimetric,Electrochemical, SEM-EDS,and Quantum Chemical Calculations

Protection of Metals and Physical Chemistry of Surfaces - Corrosion inhibition effects of water-soluble peripheral substituted cobalt, copper and zinc metallophthalocyanines (CoPc (1), CuPc (2) and...     

Effects of Mn and Gd Co-substituted into ZnO on Structural and Magnetic Properties

We have worked on the structural and magnetic properties of Zn_0.99?xMn_0.01Gd _x O _δ (for x = 0.02, 0.03, and 0.04) compounds prepared by using a sol–gel method. The x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy were used to understand the structural properties of the samples. We observed that co-substitution of Mn (1 %) and Gd (2–4 %) into the ZnO does not change the hexagonal structure. Scanning electron microscope (SEM) images show us that the grain size decreases with the increasing amount of the Gd into the ZnO matrix. The magnetic properties of the samples have been investigated by using magnetic hysteresis and DC susceptibility measurements. The ZMG1 sample shows a weak ferromagnetic behavior at room temperature, whereas the ZMG2 and ZMG3 samples exhibit a paramagnetic nature. Furthermore, it is also found that the magnetizations of the samples decrease with increasing Gd content in the ZnMnO system due to the enhancing interaction between Gd ³⁺ ions. We summarize that the co-substitution of Mn and Gd into the ZnO generates a room-temperature ferromagnetism, but it still needs more work to obtain strong and high coercivity magnetic loops for applications.     

Simulation of exhaust gas reforming of propane in a heat exchange integrated microchannel reactor

Exhaust gas reforming of propane to a hydrogen-rich mixture in a single, heat-exchange integrated, adiabatic, catalytic microchannel is modeled and simulated at different exhaust gas compositions from conventional gasoline and diesel fueled engines. Propane is considered as the model hydrocarbon for the complex fuels such as gasoline and diesel. The single microchannel is considered to be the characteristic unit of the catalytic exhaust gas reformer involving identical channels located parallel to each other. Steady-state simulations, carried out by the finite volume method, involve parametric variations of the total feed flow rate, and the amounts of propane and steam injected externally into the exhaust gas (reformer feed) stream. The results show that effective heat transfer and uniform temperature distribution, which are critical for the successful operation of the exhaust gas reformer, can be obtained in the microchannel configuration even at low gas hourly space velocities (GHSVs) at which the conventional packed-bed reformers usually lead to remarkable hot-spot formation. Production of H₂ and CO is favored by the addition of higher amounts of propane and steam into the reformer feed. Increasing the total feed flow rate, hence the GHSV is found to improve heat distribution along the microchannel at the expense of reduced product yields due to insufficient contact time.     

Optimization of dielectric heating parameters in the production of high‐voltage LiNiPO4‐core and carbon‐shell ceramics

Excellent core‐shell morphology and nanoscale high‐voltage LiNiPO₄@C cathode materials have been synthesized by a low‐level and long‐time microwave and solvothermal synthesis methodology. The effects of the changing physicochemical parameters on the crystal‐quality and electrochemical properties of the products have been evaluated in relation to the cycling stability. X‐ray diffraction analysis shows that it is possible to synthesize phase‐pure LiNiPO₄ material when the reaction parameters are carefully elaborated. High‐resolution transmission electron microscopy analysis reveals a core‐shell morphology with a coating thickness of 6‐8 nm for 30 minutes at 180°C solvothermal temperature and time‐spread microwave energy. This mentioned cathode material exhibits the best electrochemical properties, achieving a discharge capacity of 157 mAh·g^?1 at a 0.l C current rate, and shows a remarkable 81% capacity retention at the end of the 80th cycle.