Stability of Structure, Phase and Elemental Composition of ChemicallyDeposited and Electrodeposited Gold Layers in Multilayer SystemsAuchemically reduced; electrodeposited /Co-W/Cusputtered / Glass-Ceramics
The changes in the structure and elemental composition of Au and Co-W thin layers after thermal treatment of 200 h at 200-300 oC and 50 h at 450 oC were systematically studied using the X-ray microanalysis of scanning electron microscope XL-30 ESEN Philips. The phase stability was evaluated by X-ray diffraction (XRD). The electrodeposited Co-W layer (W 46.0-53.0 wt. % depending on the electrodeposition regime) is amorphous and maintains its amorphous state after heating at 200 oC for 200 h and subsequent heating (+) at 300 oC for 150 h. Co-W amorphous layers prevent interdiffusion of Au and Cu atoms and formation of intermetallics AuCu in the systems of layers Au chemically reduced; Au electrodeposited /Co-W/Cu sputtered / glass-ceramics. The chemically reduced 0.4 � m Au layers maintain their structure and phase in the systems of layers upon heating at 200 oC for 200 h and subsequent heating (+) at 300 oC for 50 h. The Au layer maintains its Au content 85-86 wt. % upon heating at 450 oC for 50 h, the cobalt content of the layer up to 8.6 wt. % and content of oxygen bonded to Au of 8.6 wt. %. The electrodeposited Au layers (0.8 - 1.0 � m) maintain their structure at heating at 200 oC and 300 oC for 200 h. After additional heating at 450 oC for 30-50 h gold content in the layer decreases from 98.4 wt. % to 85.0 wt. %, cobalt content increases to 7.6 wt. % and oxygen to 7.2 wt. %. Functional properties of the above multilayer systems deteriorate by mutual diffusion of metal atoms and formation of brittle intermetallics. The latter may give rise to the formation of monolithic films, cause the deterioration of mutual adhesion of the layers and complete reactions of the upper conducting Sn, Au layers with the base metal Ni, Cu, Ti, Sn (15, 16). This diffusion can worsen the properties of very thin (0.5-1.0 � m) metal layers electrodeposited on a Cu layer (1-2 � m) sputtered on glass-ceramics (15).
Kinetics and mechanism of reaction at room temperature in thin Au/metal couples
Abstract The reaction kinetics of compound formation at room temperature in thin film Au/Me (Me = Al, Cd, Ga, In, Pb, Sb, Sn, Zn) couples have been investigated by X-ray diffraction. The decrease in the (111) diffraction peak of gold or of the metal, or the increase in the diffraction peak of the corresponding compound, has been followed as a function of time. These reactions were found to be diffusion controlled. The interdiffusion coefficients have been calculated for the investigated couples and the relation D = 3.66 × 10-11 exp(-0.015Tt) has been found to exist between the diffusion coefficient D(cm2s-1) and the melting temperature Tt(K) of the metal.
Thermodynamics on the Carbochlorination of Titanium-bearing Ores
The equilibrium compositions of the multi-component, multi-phase and multi-reaction system of carbochlorination of titanium-bearing ores are calculated with HSC, a computational chemistry software. The thermodynamic equilibrium calculation of the reaction system shows that a complete conversion of titanium-bearing ores is feasible at a temperature near 200oC. At temperatures ranging from 800 to 1600oC, the products of the reaction system are all in gaseous phase. Thermodynamic analysis accords with the industrial practice. The simulated results provide reasonable scientific basis for improving suitable technological conditions of the carbochlorination reduction.