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.

Fluorination assisted electrothermal vaporization (ETV) was employed as sample introduction technique for the direct determination of trace amounts of impurities in titanium dioxide solid powder by inductively coupled plasma atomic emission spectrometry (ICP-AES). A polytetrafluoroethylene (PTFE) emulsion is used as a fluorination reagent to promote the vaporization of impurity elements in TiO2 powder from the graphite tube; the vaporization behavior of matrix element (Ti) and analyte (Cr, Cu, Fe and V) were studied. Under the selected conditions, about 100mg solid sample (10ml of 1%m/v TiO2 slurry) was pipetted into furnace, a pre-volatilization of the matrix could be performed by an ashing time of 70 s at 800℃ to eliminate the matrix effect, and then the analytes were vaporized into plasma at the vaporizing temperature of 2600℃. Calibration was performed using the standard addition method. The accuracy was checked by comparison of the results with solution fluorination assisted ETV-ICP-AES and pneumatic nebulization (PN)-ICP-AES based on the wet-chemical decomposition. Limits of detection between 0.07μg g−1 (Cr) and 0.2μg g−1 (V) were achieved. © 2000 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).

Eu2 +,Dy3 + co-doped strontium aluminate (SrAl2O4) phosphor nanoparticles with high brightness and long afterglow were prepared by glycine-nitrate solution combustion synthesis at 500℃, followed by heating the resultant combustion ash at 1100℃ in a weak reductive atmosphere of active carbon. The average particle size of the SrAl2O4:Eu,Dy phosphor nanoparticles ranges from 15 to 45nm as indicated by transmission electron microscopy (TEM). The broad-band UV-excited luminescence of the SrAl2O4:Eu,Dy phosphor nanoparticles was observed at kmax=513nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ion. The results indicated that the main peaks in the emission and excitation spectrum of phosphor nanoparticles shifted to the short wavelength compared with the phosphor obtained by the solid-state reaction synthesis method. The decay speed of the afterglow for phosphor nanoparticles was faster than that obtained by the solid-state reaction method.

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.