Atomic mobilities and vacancy wind effects for diffusion in ternary silver-zinc-cadmium solid solutions

Diffusion in the silver-zinc-cadmium system was investigated at 600°C with semiinfinite, vapor-solid couples in order to determine the atomic mobilities and contribution of the vacancy wind effect to the intrinsic diffusion fluxes of silver, zinc and cadmium in the alpha phase region. Atomic mobilities and vacancy wind parameters were computed at selected compositions in the alpha phase along isoconcentration lines of 11 at. pct Zn, 18 at. pct Zn, 5 at. pct Cd and 9 at. pct Cd. The existence of significant interactions between the diffusing species was indicated by the results of an earlier investigation; consequently, the vacancy wind effect was taken into consideration in the calculation of the mobilities. The mobilities of zinc and cadmium, determined by the method of Dayananda, were found to increase with increasing zinc and cadmium concentrations with the mobility of zinc being greater than that of cadmium. The results of the investigation show that the vacancy wind effect significantly affects the total intrinsic flux of each of the three species for diffusion in ternary silver-zinc-cadmium alloys. This investigation reports the experimental observation of the vacancy wind effect in a ternary system.     

Simulation model for electron irradiated IGZO thin film transistors

An efficient drain current simulation model for the electron irradiation effect on the electrical parameters of amorphous In-Ga-Zn-O (IGZO) thin-film transistors is developed.The model is developed based on the specifications such as gate capacitance,channel length,channel width,flat band voltage etc.Electrical parameters of un-irradiated IGZO samples were simulated and compared with the experimental parameters and 1 kGy electron irradiated parameters.The effect of electron irradiation on the IGZO sample was analysed by developing a mathematical model.     

Hydrothermal preparation of ZnO:CNT and TiO<Subscript>2</Subscript>:CNT composites and their photocatalytic applications

ZnO:CNT and TiO₂:CNT composites were fabricated under mild hydrothermal conditions (T = 150–240 °C) with an autogenous pressure. The as prepared composites were characterized using X-ray diffraction, Scanning electron microscopy and FTIR spectroscopy. Photocatalytic applications of the composites were investigated using indigo caramine dye. The effect of the catalyst content, pH of the medium, source and intensity of illumination on the photodegradation of the indigo caramine dye was studied and the efficiency of the composites were investigated based on different parameters like percent transmittance (%T), percent decomposition, and chemical oxygen demand of the dye solution to obtain optimum treatment conditions. The results obtained exhibit higher photocatalytic activity when compared to the reagent grade ZnO, TiO₂ and hydrothermally prepared ZnO:AC and TiO₂:AC composites.     

The influence of the die and floating plug geometry on the drawing process of tubing

Nowadays, the development of tube drawing process with a floating plug technique has moved our limit up to the production of thick-walled tubes; production of which still belongs to marginal techniques which are different from drawing of standard tubes. The submitted paper is basically a survey of research in fundamental characteristics of tube drawing with a floating plug with the aim to summarize some important results from the theory, which have not yet been published in any English publication. The purpose of this survey is to fill the gap in English literature to promote transfer and exploitation of knowledge. Research in fundamental characteristics was further developed and conditions under which it is possible to draw thick-walled tubes are defined. Confirmed possibility of thick-walled tubes drawing with support provided by a floating plug having negative overlap is the result of theoretical study and practical verification, which enables further moving of drawing process limit.     

Diffusional analysis of a multiphase oxide scale formed on a Mo-Mo3Si-Mo5-SiB2 alloy

Diffusional analyses were performed to understand the oxidation at 1300 °C of a multiphase Mo-13.2Si-13.2B (at.%) alloy. During oxidation, a protective glass scale formed with an intermediate layer of (Mo+glass) between the base alloy and external glass scale. Compositional profiles across the (Mo+glass) layer and the external glass scale were determined, and interdiffusion fluxes and effective interdiffusion coefficients for the various components were determined by using “MultiDiFlux” software. The motion of the (alloy/Mo+glass) and (Mo+glass/glass) interphase boundaries after passivation was examined. Additionally, vapor-solid diffusion experiments at 1300 °C were carried out with single-phase Mo₃Si and T2 specimens in addition to a multiphase Mo-10Si-10B (at.%) alloy. These specimens were exposed to vacuum to induce silicon loss resulting in the formation of a Mo layer. An average effective interdiffusion coefficient of Si in Mo at 1300 °C was estimated from the Mo₃Si-vapor couple to be in the order of 8×10⁻¹⁷ m²/s. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.     

A transfer-matrix method for analysis of multicomponent diffusion with any number of components

A transfer-matrix method (TMM) is presented for the development of concentration and flux profiles in multicomponent diffusion involving any numbern of components. From interdiffusion fluxes or concentration gradients available at an initial positionx _s, the authors derive expressions for the transfer matrix and its integral so that the concentrations or interdiffusion fluxes of the components can be obtained at any coordinatex. The TMM requires data for interdiffusion coefficients, which are obtained as average values over selected regions by the method of moments developed by Dayananda. Expressions for the concentrations are also obtained from initial conditions on the fluxes or the concentration gradients. The method is also applicable to the case when all the concentrations are known at two ends of a region over which the diffusion coefficients are considered constant. The integration of the fluxes over time, or over the coordinatex, can be evaluated using the transfer-matrix approach, provided the value of the interdiffusion flux is given at a given coordinate. The TMM is applicable to any number of components and can be regarded as a compact generalization of the solutions available for ternary diffusion couples with constant interdiffusion coefficients. An application of the method is illustrated with the experimental data for a ternary Cu-Ni-Zn diffusion couple, and the results are compared with those based on the Fujita-Gosting solution. This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University.     

Growth of silicides and interdiffusion in the Mo-Si system

Solid-solid diffusion couples assembled with disks of Mo and Si were annealed at selected temperatures, over the temperature range from 900 °C to 1350 °C, for the development of diffusion structure and determination of interdiffusion coefficients for the silicides of Mo. Layers of MoSi₂ and Mo₅Si₃ were observed to form in the diffusion zone; the MoSi₂ layer was one to two orders of magnitude larger in thickness than the Mo₅Si₃ layer. The MoSo₂ layer developed a columnar microstructure with evidence of texture and preferential growth of grains in the direction of diffusion. The Si-to-Mo ratio, determined by microprobe analysis across the thickness of the MoSi₂ layer, varied within the approximate range from 1.9 to 2.0. From the concentration profiles, integrated interdiffusion coefficients as well as energies of activation for interdiffusion were determined for the silicide layers. On the basis of the observed stoichiometric range for the MoSi₂ phase, average values of the interdiffusion coefficients were also estimated. Relations are derived between the growth-rate constant and the integrated interdiffusion coefficient for the MoSi₂ phase. The evaluated activation energies for interdiffusion in the MoSi₂ and Mo₅Si₃ phases are 130±20 and 210±10 kJ/mol, respectively.     

Multiphase Diffusion in Fe−Ni−Al System at 1000°C: I. Diffusion structures and diffusion paths

Multiphase diffusion was investigated in the Fe−Ni−Al system at 1000°C with several series of solid-solid diffusion couples assembled with selected β(bcc) and γ(fcc) alloys for the development of diffusion structures. The series of couples were characterized by a common β or γ terminal alloy joined to selected alloys of the other phase. The diffusion structures developed for the various couples exhibited interfaces of either planar, wavy, acicular, or flowery morphologies. Diffusion paths for the couples were determined by electron microprobe analysis. On the basis of isoconcentration contours in the vicinity of interfaces, the path-crossings of the (β+γ) two-phase region were found to be parallel to tie-lines for planar β/γ interfaces but were spread out into a band inclined to tie-lines for nonplanar interfaces. The band spread of path crossings for nonplanar β/γ interfaces showed compositional variations mainly on the γ-side of interfaces. G. H. CHENG formerly a Graduate Student at Purdue University     

Diffusion structures in multiphase Cu-Ni-Zn couples

Isothermal, multiphase diffusion was investigated with infinite diffusion couples in the Cu-Ni-Zn system at 775°C. The couples were assembled with disks of a β (bcc) ternary alloy sandwiched between disks of selected binary, Cu-Ni α (fcc)alloys and were annealed for 2 hr to 2 days. The diffusion structures were investigated metallographically and by electron probe analysis. The couples developed multiphase structures that showed transitions from planar interfaces to nonplanar morphologies with changes in composition of the α -terminal alloys. The various structures are described by the aid of composition paths. The velocity of planar interfaces is discussed in terms of intrinsic fluxes in the adjacent phases. This paper is based upon a thesis submitted by R. D. SISSON, JR. to Purdue University in partial fulfillment of the requirements of the M.S. Metallurgical Engineering degree.     

Multiphase diffusion in Ag-Zn alloys

Multiphase diffusion was studied in Ag-Zn alloys at 600°C with vapor-solid diffusion couples. The experiments were performed with a β(bcc) alloy as vapor-source material and with diffusion disks (fcc) of either pure silver or an α alloy. The diffused couples were studied metallo-graphically and by electron microprobe analysis. Interdiffusion coefficients for each of the phases were calculated from data on the expansion of the couple and the motion of the α/β interface on the basis of new relations developed from an analysis of two-phase vapor-solid couples. Also, the compositions at the α/β interface differed little from those determined from an equilibrated two-phase alloy.