Role Of Sb Research Articles

Growth of Epitaxial Co Layers on Sb-Passivated GaAs(110) Substrates

The role of Sb in the formation of the Co/GaAs(110) interfaces has been investigated by angular photoelectron diffraction (PD), synchrotron-radiation (SR) core-level photoemission and low-energy electron diffraction. We find that Co forms a metastable bcc phase on GaAs(110), with its principal crystallographic axes parallel to the substrate. From polar-angle-scanned PD, we determine an outward expansion of up to 14% of the lattice constant perpendicular to the surface, for epitaxial Co films grown on nontreated substrates. By Sb passivation of the GaAs(110) surface prior to the Co deposition, the epitaxial quality of the metallic overlayer is improved. The resulting Co phase is found to grow in a perfect bcc (110) orientation with a minor disruption of the substrate underneath and a reduced intralayer spacing outward expansion of less than 1%.

Ammoxidation of propane to acrylonitrile on FeSbO 4

The properties of FeSbO 4 (Fe:Sb = 1:1 and 1:2) for propane (amm)oxidation have been investigated. Both catalysts showed little selective oxidation activity, however, both were active and selective for propane ammoxidation to acrylonitrile. The 1:2 catalyst showed increased selectivity, relative to the 1:1 catalyst, for acrylonitrile but at the expense of propane conversion. XRD and FT-IR showed the major phases present were rutile FeSbO 4 and Sb 2O 4. XPS studies showed the surface of both catalysts to be antimony rich and TPD studies showed the major pathway to acrylonitrile was a two-stage process via propene and an allylic intermediate, although there is a direct contribution from a one-stage mechanism via an alkyl intermediate. It is postulated that the degree of surface oxidation is critical in determining the dominant surface intermediate. The rate limiting step in the ammoxidation reaction is considered to be dissociative adsorption of propane on the surface, the adsorption rate of propane being orders of magnitude lower than for propene, as manifested by TPD experiments. The role of Sb and Fe are discussed, together with the principal surface mechanisms.

The intergranular corrosion and stress corrosion cracking of mild steel in clarke's solution

Measurements have been made of the corrosion rates and stress corrosion crack velocities for mild steel exposed to hydrochloric acid containing antimony additions at open circuit and various applied potentials. Cracking occurs within a sharply defined range of potentials, within which markedly slower intergranular corrosion occurs, while general corrosion occurs at potentials above or below those that promote cracking. It is suggested that the role of Sb in the cracking mechanism is essentially the same as the role of oxide films in other environments, of restricting lateral dissolution at the crack sides.

Differential scanning calorimetry of semiconducting As-Se glasses containing Sb

The compositional dependence of the glass transition temperature (T g), and the temperature of the maximum rate of crystallization (T p) of As-Se glasses containing Sb has been measured using non-isothermal DSC. The variation of these characteristic temperatures is found useful in interpreting the structural changes in As-Sb-Se glasses. The role of Sb in these glasses and its effect on the crystallization characteristics is analyzed.

The influence of matching for SB on MLC typing is significant but marginal.

To investigate the role of SB in MLC typing responses, reactions of lymphocytes from 23 DW3-positive, HLA-D-heterozygous individuals against 9 Dw3 homozygous typing cells (HTCs) were evaluated. Significantly more clear typing reactions were observed in those combinations that were matched for SB as compared with those that were mismatched. Nevertheless, MLC responses towards HTCs that were HLA-D/DR- and SB-compatible could be very strong. An additional analysis of the influence of HLA-B and the newly defined determinants LB-Q1 and LB-Q2 demonstrated that in combinations that were matched for these markers as well, stabilized relative responses could still be over 100%.