用于吖内酯合成的二氧化钛纳米晶体材料(英文)

Titanium dioxide nanoparticles were prepared by a electrochemical reduction method using para-meters such as current density, solvent polarity, distance between electrodes, and concentration of stabilizers to control the size of the nanoparticles. The nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microsco-py, and their catalytic performance was tested for the synthesis of a series of 4-aryldiene-2-phenyl-5(4)-oxazolones from the cyclodehydration and condensation of the respec-tive aldehyde, hippuric acid and acetic anhydride. Easy availability, reusability and eco-friendliness were some prominent features of the nanocrystalline titanium dioxide catalyst.     

Drastic increase of selectivity for H2O2 formation in direct oxidation of H2 to H2O2 over supported Pd catalysts due to their bromination

Incorporation of bromide anions (1.0 wt%) in supported Pd catalysts (viz. Pd supported on Al2O3, ZrO2, SiO2, H-beta or Ga2O3) leads to a drastic increase in their selectivity for H2O2 formation in the direct oxidation of H2 to H2O2 by O2(at room temperature) in an aqueous acidic (0.03 M H3PO4) reaction medium; the selectivity increase is accompanied by a large decrease in the H2O2 decomposition activity of the catalysts.     

Effects of gamma irradiation on some chemicals using an NaI (Tl) detector

The present work was carried out to find out the gamma ray shielding properties and to study the effects using an NaI (Tl) detector using radioactive sources ⁵⁷Co, ¹³³Ba, ¹³⁷Cs, ⁵⁴Mn, ⁶⁰Co and ²²Na at energies 122, 356, 511, 662, 840, 1170, 1275 and 1330?keV, for some chemicals, namely, sodium thiosulfate (Na₂S₂O₃), benzoic acid (C₇H₆O₂), sodium hydroxide (NaOH), poly vinyl alcohol (PVA) (C₂H₄O), potassium nitrate (KNO3), naphthalene (C₁₀H₈). Mass attenuation coefficient (µ_m) values obtained from the experiment were used to determine the effective atomic numbers (Z_eff) and effective electron densities (N_eff), atomic cross-sections (σ_t) and electronic cross-sections (σ_e); it will be observed from the present work that the variation in the obtained values is only due to the increase or decrease in the gamma ray energy and the chemical composition of the sample. It was seen that the calculated and obtained values showed good agreement. The investigated data are useful in the electronic industry, plastic industry, building materials and agriculture fields. From the present work it was found that the PVA could be used as a better gamma shielding material.     

Matter of age: growing anisotropic gold nanocrystals in organic media

We investigated the influence of the reduction state of gold ions on the growth of gold nanocrystals in N,N-dimethyl formamide (DMF). While freshly prepared solutions of AuCl3 produce spherical nanocrystals, aged precursor solutions containing mainly Au+ ions and Au(0) atoms lead to various branched nanoparticles. Furthermore, we show that also the amount of the reducing and stabilisation agent tetra-n-octylammonium formate (TOAF) plays a decisive role on the shape of the nanocrystals, allowing us to grow triangular and cubic nanoparticles.     

Cr(VI) Oxidation of Cholesterol—A Kinetic Study Using N-Cetylpicolinium Dichromates,A Class of Novel Phase Transfer Oxidants

Kinetics and Catalysis - Kinetic study of cholesterol oxidation has been studied using a series of N-cetylpicolinium dichromates (CPDC), a class of phase transfer oxidants, in acetic acid medium...     

Linear and Non-linear Double Diffusive Convection in a Fluid-Saturated Anisotropic Porous Layer with Cross-Diffusion Effects

The double diffusive convection in a horizontal anisotropic porous layer saturated with a Boussinesq binary fluid, which is heated and salted from below in the presence of Soret and DuFour effects is studied analytically using both linear and non-linear stability analyses. The linear analysis is based on the usual normal mode technique, while the non-linear analysis is based on a minimal representation of double Fourier series. The generalized Darcy model including the time derivative term is employed for the momentum equation. The critical Rayleigh number, wavenumbers for stationary and oscillatory modes, and frequency of oscillations are obtained analytically using linear theory. The effects of anisotropy parameter, solute Rayleigh number, and Soret and DuFour parameters on the stationary, oscillatory convection, and heat and mass transfer are shown graphically. Some known results are recovered as special cases of the present problem.