Fluorination-assisted electrothermal vaporization (ETV)-inductively coupled plasma-atomic emission spectrometry (ICPAES) for the direct determination of trace amounts of refractory impurity elements in silicon carbide ceramic powders using slurry sampling has been developed. Investigation indicated that a polytetrafluoroethylene (PTFE) emulsion is a useful fluorinating reagent for the destruction of silicon carbide and simultaneous vaporization of the refractory impurities like B, Mo, Ti, and Zr. The vaporization behaviors of the analytes in slurry and solution were comparatively investigated in the presence of PTFE. The fluorinating vaporization processes and the influence factors for this method have been also studied in detail. The experimental results indicated that 80mg silicon carbide (10ml of 0.8% (m/v) slurry) could be destroyed and vaporized completely with 600mg of PTFE under the selected conditions. Calibrationwas performed using the standard addition method with aqueous standard solutions. The accuracy was checked by comparison of the results with those obtained by solution fluorination-assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES involving a wet-chemical decomposition of the sample. Detection limits between 0.5mg g−1 (B) and 0.2mg g−1 (Mo) were achieved. In most cases, the precision expressed as relative standard deviation (R.S.D.) was better than 8%. © 2001 Elsevier Science B.V. All rights reserved.

hermal vaporization inductively coupled plasma atomic emission spectrometry (ETV-ICP-AES) was employed for the direct determination of trace impurities in silicon carbide ceramic powders. The vaporization behaviors of silicon and five trace elements (Al, Cr, Cu, Fe and V) were studied in the presence and absence of polytetrafluoroethylene (PTFE) as fluorinating reagent. It was found that, during a 60 s ashing step at 800℃, about 97% of 100 mg of SiC can be decomposed and evaporated without considerable losses of the trace elements investigated. Calibration was performed using the standard addition method and the calibration curve method, applying spiked slurries and aqueous standard solutions, respectively. The accuracy was checked by comparison of the results with those obtained by solution fluorination assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES involving wet chemical decomposition of the sample. Detection limits between 0.3μg g-1 (Al) and 0.08μg g-1 (Cu) were achieved. The precision, expressed as the relative standard deviation (RSD), was between 6.0% (for 18.2μg g-1 of Cr) and 2.8% (for 177μg g-1 of Fe).

Nickel oxide (NiO) nanotubules were fabricated by a dodecylsulfate-mediated templating method in a homogeneous precipitation process. The nanotubules obtained have diameters of 20-160nm and wall thickness of 8-50 nm with lengths up to several micrometers. The crystallinity, morphology and structure features of the NiO nanotubules were investigated by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), infrared (IR) spectrum, etc.

Novel nano-structured clays were synthesized from cation exchange reaction by the intercalation of rhodium complexes with ligand spacers into clay. Expansion of interlayer space of the modified clays depends on the spacers. A unique conformation of pillar complexes was detected by cross polarization magic angle spinning (CP MAS) NMR.

Titania was synthesized from laurylamine hydrochloride (LAHC) and Ti(SO4)2 under different acidic conditions. The effect of acidity on the structural and textural evolution of titania has been investigated by X-ray diffraction (XRD), nitrogen adsorption-desorption, transmission electron micrographs (TEM), FTIR spectroscopy and thermogravimetric analysis (TGA). With increasing the pH value in the initial mixture, the obtained samples transformed from nanoparticles with intra-particle mesostructures (pH 0.6 and 2.0) to nanoparticles with nonporous structure (pH 3.7), and finally to worm-like porous materials with inter-particle mesostructures (pH 4.2)resulted from the aggregates of nanoparticles. The obtained mesoporous nanoparticles (pH 0.6 and 2.0) have mean diameter of ca. 25 nm, and the pore size distributions are bimodal with fine intra-particle pores and larger inter-particle pores. The intra-particle mesostructure not only retard the growth of nanocrystallites, but also prevent phase transition of anatase to rutile at high temperature. The BET surface area of the TiO2 calcined at 300 C decreased from 212 to 74 m2/g with pH increasing from 0.6 to 4.2.