Mesoporous titanium dioxide nanosized powder with high specific surface area and anatase wall was synthesized via hydrothermal process by using cetyltrimethylammonium bromide (CTAB) as surfactant-directing agent and pore-forming agent. The resulting materials were characterized by XRD, nitrogen adsorption, FESEM, TEM, and FT-IR spectroscopy. The as-synthesized mesoporous TiO2 nanoparticles have mean diameter of 17.6nm with mean pore size of 2.1nm. The specific surface area of the as-synthesized mesoporous nanosized TiO2 exceeded 430m2/g and that of the samples after calcination at 600℃ still have 221.9m2/g. The mesoporous TiO2 nanoparticles show significant activities on the oxidation of Rhodamine B (RB). The large surface area, small crystalline size, and well-crystallized anatase mesostructure can explain the high photocatalytic activity of mesoporous TiO2 nanoparticles calcined at 400℃.

Researchers have been playing with advanced synthetic materials known as polymers and composites for several de-cades now. In the 1980s, a buzz word for materials scientists was "intelligent" or "smart" materials. In the mid-1990s the new buzzing became the creation nanostructured materials.[1] Nanometer is one billionth part of a meter. Literally "nano" represents 0.000000001 or 10 9. Defined broadly, the term "nanostructured" is used to describe materials characterized by structural features of less than 100nm in average size. The average size of an atom is of the order of 1 to 2 A in radius. 1 nanometer comprises 10 A, and hence in one nanometer, there may be 3-5 atoms, depending on the atomic radii. Man-ufactured products are made from atoms and the properties of such products depend on their atomic structure. If the car-bon atoms in coal are rearranged, diamonds can be made. Seashells, as we all know, are extraordinary tough and this crack and shatter resistant property are attributed by an ex-quisite nanostructure.[2] Nanotech is the most significant emerging materials technology for the next century. Research in nanostructured materials is motivated by the belief that ability to control the nanostructure of these materials can re-sult in enhanced properties at the macroscale viz. increased hardness, ductility, catalytic enhancement, selective absorp-tion, higher efficiency optical or electrical behavior. Experi-ments in the field of nanostructured materials have produced very significant and interesting results. The science of ceramic nanoparticles is no exception with much success in areas in-cluding synthesis, surface science, texturology, catalysis etc.[3] Chemistry of Nanoparticles Within the intermediate region of 2-10nm, neither quan-tum chemistry nor classical laws of physics hold. For example--in spherical nanoparticles with a size of 3nm, 50% of the atoms or ions are on the surface, allowing the possibility of manipulation of bulk properties by surface effects.[3] As the particles become smaller in size they may take on different morphologies that may alter surface chemistry and adsorp-tion properties in addition to increasing the surface area. These nanoparticles also possess a much greater number of defect sites per unit surface area, which are believed to be responsible for the observed chemistry. As the size of a parti-cle decreases, the percentage of atoms residing on the surface increases and of course these surface atoms are expected to be more reactive than their bulk counterparts as a result of coordinative unsaturation. Because of this and because of the fact that surface-to-volume ratio is large, it is not unusual to see unique chemical, physical or adsorptive properties and characteristics for nanoparticles.

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.

A method has been developed for the determination of trace impurities in silicon nitride (Si3N4) powders by fluorination assisted electrothermal vaporization (ETV)/ICP-AES using the slurry sampling technique. Polytetrafluoroethylene (PTFE) emulsion as a fluorinating reagent not only effectively destroys the skeleton of Si3N4, but also carries out selective volatilization between the impurity elements (Cu, Cr) and the matrix (Si). The experimental parameters influencing fluorination reactions were optimized. The detection limits for Cu and Cr are 1.05ng/mL (Cu) and 1.58ng/mL (Cr), the RSDs are in the range of 1.9-4.2%. The proposed method has been applied to the determination of Cu and Cr in Si3N4 ceramic powders. The analytical results were compared with those obtained by independent methods.

Semiconductor CdS nanotube arrays were synthesized within the pores of the PAO membranes by using molecular anchor templating synthesis method. The CdS nanotube arrays obtained were characterized using scanning electron microscopy (SEM), X-ray diffractomemter (XRD) and transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopic analyzer (EDS), respectively. The formation mechanism of CdS nanotube was also discussed. This is the first report on the highly ordered CdS nanotube arrays with 60lm in length and 100nm in outer diameter. The present method shows the advantages of simplicity, high efficiency and low cost.