RESUMO
A simple and accurate method was developed for determining silicon in gasoline using inductively coupled plasma optical emission spectroscopy (ICP-OES). For sample inroduction a Burgener nubulizer and a Cyclonic spray chamber were used. A gasoline sample was diluted with isooctane and then introduced into the cooled spray chamber of the ICP-OES. Good linearity was achieved in the silicon concentration range 0.1 - 10.0 mg x kg(-1), and the correlation coefficient was 0.999 96. The detection limit for silicon was 0.012 mg x kg(-1) and the silicon recoveries from gasoline samples were 95.8% - 98.4%, with relative standard deviations of less than 3.0% The method was proved to be simple, reliable and highly sensitive, and suitable for determining silicon in samples of motor gasoline, ethanol-gasoline and methanol-gasoline fuel mixtures those containing not more than 15% (V/V) oxygenates.
RESUMO
A facile polycrystalline Pb/Sn-codoped In4Pb0.01SnySe3 material is obtained, its thermoelectric performance is evaluated, and the intrinsic reasons have been studied. This material shows an excellent ZT value of 1.4 at 733 Kelvin, among the best values of the relative materials, thus making it a promising candidate for the mid-temperature thermoelectric application.
RESUMO
The overall hexa-gonal framework of the title compound, penta-sodium ammonium trimanganese(II) borophosphate sesquihydrate, consists of tube-like borophosphate anions, (∞) (1){[B(3)P(2)O(11)(OH)](4-)}, made up of corner-sharing PO(4) and BO(4) tetra-hedra and BO(2)(OH) triangles, forming ten-membered ring windows. The tubes are inter-connected via distorted MnO(6) octa-hedra, establishing a three-dimensional open-framework structure with two different types of ring-channels (12- and six-membered) that run along [001]. The 12-membered ring channels are occupied by NH(4) (+) ions and water mol-ecules. The ten-membered ring windows in the walls of the tubes are occupied by Na(+) ions. The remaining Na(+) ions and the water mol-ecules, one of which is half-occupied, reside within the six-membered ring channels. The structural setup is consolidated by an O-Hâ¯O hydrogen bond between the OH group and an opposite O atom of the framework. Donor-acceptor distances ranging from 2.80 to 3.35â Å between the ammonium N atom, water O atoms and framework O atoms indicate further hydrogen-bonding inter-actions.
