Showing papers in "Chemistry of Materials in 1990"

Raman Spectroscopy of Carbon Materials: Structural Basis of Observed Spectra

Abstract: calculations of the phonon density of states, Al-Jishi and Dresselha~s~~~~~ have attributed the second-order bands

Conductive polymer/oxide bronze nanocomposites. Intercalated polythiophene in V2O5 xerogels

Abstract: \"C) in 46% yield.5 The analogous gallium compound [Me2Ga(p-Sb-t-Bu2)I3 (2) has been prepared in 74% yield by a virtually identical p r~cedure .~ X-ray analysise revealed that 1 and 2 are both trimeric in the solid state. The six-membered rings of both compounds adopt a distorted twist-boat conformation that is devoid of symmetry. The structure of 1 is illustrated in Figure 1. Atoms In(l), Sb(2), Sb(3), and In(3) of 1 are approximately planar, and In(2) and Sb(1) lie 0.494 and 1.243 A out of the idealized plane respectively. As expected, there is a significant variation in the endocyclic bond angles, particularly a t antimony. The average endocyclic bond angles at In and Sb are 106.94 (5)\" and 121.64 (6)\", respectively, in 1. The In-Sb bond lengths in 1 vary from 2.822 (1) to 2.889 (1) A. The average In-Sb bond length of 2.855 (2) A compares with that of 2.844 (1) A in [(t-B~~Sb)(Cl)In(p-Sb-t-Bu~)]~, the only other structurally authenticated organometallic indium stibinide.* Both values are close to the sum of covalent radii for In and Sb (2.84 A) and somewhat larger than the bond distance in InSb (2.805 A). Films of InSb have been grown on Si(100) wafers from precursor 1 in a horizontal hot-wall r e a ~ t o r . ~ The temperatures of the saturator and deposition zones were 125 and 450 O C respectively, and H2 (10 Torr) was employed as the carrier gas. Growth rates were -1.0 pm/h. The films were characterized by X-ray photoelectron spectroscopy after etching with ionized argon. The corrected In(4d) and Sb(4d) signals a t 18.5 and 33.5 eV, respectively, compare well with the literature values of 19.0 and 34-35 eV.8 Moreover, the X P S experiments established an In:Sb stoichiometry of 1:l and indicated that the carbon impurity level was barely above the limit of detectability by this technique ( 1000 ppm). Examination of the films by X-ray diffraction indicated that they are polycrystalline. Preliminary experiments indicate that 2 is a useful precursor for the formation of GaSb.

Amorphous metallic powders prepared by chemical reduction of metal ions with potassium borohydride in aqueous solution

Abstract: Amorphous metal-metalloid powders have been prepared by chemical reduction of Fe2+, Co2+, and Ni2+ ions with potassium borohydride in aqueous solution. The chemical composition of the samples, TM-B-O, varies with the metal and with the preparation steps. The as-prepared Co-B-O and Ni-B-O samples are definitely amorphous, while the Fe-B-O sample mainly consists of bcc I±-Fe. Crystallization of the samples through thermal treatment has been investigated by X-ray diffraction. The Co-B-O sample evolves toward fee metallic cobalt accompanied first by metastable o-Co3B and, at high temperature, by t-Co2B. The Ni-B-O sample gives rise to fee metallic Ni and o-Ni3B, which decomposes at higher temperatures. Iron borides are not detected in the thermal treatment of the Fe-B-O sample. No evidence of metal oxides is present in all the samples, thus suggesting the prevalent bonding of oxygen to boron.