Isothermal thermo-analytical study and decomposition kinetics of non-activated and mechanically activated indium tin oxide(ITO) scrap powders treated by alkaline solution

Isothermal decomposition process of chemically transforming indium tin oxide（ITO） powders into indium（III） hydroxide powders was investigated. Two types of powders were analyzed, i.e., non-activated and mechanically activated. It has been found that in the case of activated sample, shorter induction periods appear, which permits growth of smaller crystals, while in the case of non-activated sample, long induction periods appear, characterized by the growth of larger crystals. DAEM approach has shown that decomposition processes of non-activated and mechanically activated samples can be described by contracting volume model with a linear combination of two different density distribution functions of apparent activation energies（Ea）, and with first-order model, with a single symmetrical density distribution function of Ea, respectively. It was established that specific characteristics of particles not only affect the mechanism of decomposition processes, but also have the significant impact on thermodynamic properties.

A New Method of Preparing Alkanethiol-Protected Gold Nanoparticals

In a new two-phase system (tetrahydrofuran/saturated NaCl aqueous solution) monolayer protected clusters (MPCs) were prepared.The AuCl- 4 anion in saturated electrolyte aqueous solution was transferred into the organic phase of tetrahydrofuran by tetra-n-butylammonium bromide ((C 4H 9) 4NBr) and was reduced quickly by sodium borohydride in the presence of alkanethiol.The functionalized MPCs were characterized by solubility,transmission electron microscopy (TEM),Fourier transform infrared spectroscopy (FTIR),energy-dispersive X-ray (EDX) analysis and UV-vis spectroscopy.Electrochemical measurements of MPCs in CH 2Cl 2 exhibited 7 pairs of reversible voltammetric waves within the potential range of -1.0 to 1.0V (vs Ag/AgCl),which was ascribed to the quantized capacitance charging of nanoparticle double layers.All the results show that the new preparing method is feasible.

Reaction kinetics of isopropyl palmitate synthesis

In this study, the kinetics of isopropyl palmitate synthesis including the reaction mechanism was studied based on the two-step noncatalytic method. The liquid-phase diffusion effect on the reaction process was eliminated by adjusting the stirring rate. The results showed that the two-step reaction followed a tetrahedral mechanism and conformed to second-order reaction kinetics. Nucleophilic attack on the carbonyl carbon afforded an intermediate, containing a tetrahedral carbon center. The intermediate ultimately decomposed by elimination of the leaving group, affording isopropyl palmitate. The experimental data were analyzed at different temperatures by the integral method. The kinetic equations of the each step were deduced, and the activation energy and frequency factor were obtained. Experiments were performed to verify the feasibility of kinetic equations, and the result showed that the kinetic equations were reliable. This study could be very signi ficant to both industrial application and determining the continuous production of isopropyl palmitate.

Mullite whiskers prepared by molten salt method using Si powders

Mullite whiskers were prepared from Si powders in molten Al2(SO4)3-Na2SO4 mixture salts with different Al/Si molar ratio(R)of raw materials.The resulting mullite whiskers,had been investigated using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectrometer(EDS)and infrared spectroscopy analysis(FT-IR).Mullite phase was obtained in molten salts when the temperature reached at 850℃.SEM and EDS results revealed that two kinds of microstructures were formed in the final product,Al-rich mullite pellets and clusters of tiny mullite crystals,and the content of Al-rich mullite pellets increased with the higher Al/Si molar ratio(R)adopted in raw materials.A new oxidation-dissolution mechanism was proposed to explain mullite whiskers growth.According to thermodynamic analysis,mullite phase might be spontaneously formed as the temperature reached the decomposition temperature of aluminum sulfate(1023 K).