5 research outputs found
Reactivity of HTcO4 with methanol in sulfuric acid: Tc-sulfate complexes revealed by XAFS spectroscopy and first principles calculations
The reaction between HTcO4 and MeOH in 13 M H2SO4 was investigated by 99Tc NMR, UV-visible and X-ray absorption fine structure (XAFS) spectroscopy. Experimental results and first principles calculations show the formation of Tc(+5) sulfate complexes. The results expand the fundamental understanding of Tc in high acid solutions
On the nature of heptavalent technetium in concentrated nitric and perchloric acid
The speciation of Tc(+7) was performed in HClO4 and HNO3 by 99-Tc NMR, UV-Vis and XAFS spectroscopy. The speciation of Tc(+7) depends on the concentration and strength of the acid. Pertechnetic acid, HTcO4, forms above 8 M HClO4 while in concentrated HNO3, [TcO4]− is still the predominant species. EXAFS spectroscopy shows that the structure of HTcO4 in HClO4 is similar to the one in H2SO4. The reactivity of Tc(+7) was analyzed in the frame of the partial charge model. The partial charge calculated on the Tc atoms (ΔTc) indicates that HTcO4 (ΔTc = +057) is more electrophilic than [TcO4]− (ΔTc = +0.52). The difference in the oxidizing properties between [TcO4]− and HTcO4 is given from the reaction of these species with 12 M HCl(aq). In 13 M sulfuric acid HTcO4 is reduced to Tc(+5) while [TcO4]− is not reduced in 6 M H2SO4
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Low temperature OMCVD of thin rhodium films
Thin, highly reflective rhodium films with metal compositions greater than 98% (elemental weight percentage) have been deposited by chemical vapor deposition using Rh(allyl){sub 3} (allyl = {eta}{sup 3}-C{sub 3}H{sub 5}) in the presence of a hydrogen plasma. Uniform, crystalline films that adhere well to several types of substrates result from depositions at temperatures as low as 150{degrees}C. Depositions using H{sub 2} (no plasma), or an argon plasma yields material that is amorphous, contains a significant amount (>14%) of residual carbon, and has a dramatically slower growth rate. The composition of these materials does not vary significantly from that of the materials obtained from the in vacuo thermal deposition with Rh(allyl){sub 3}. 23 refs