Computer simulations of the growth of binary alloy thin films in two and three dimensions were performed using an extension of the Solid on Solid model. Snapshots for a range of interactions and diffusion rates are presented and critically compared to experiment. A wide variety of distinct phases is identified and their growth conditions analyzed. These findings are summarized in a phase diagram. In addition, a fractal analysis of the domains is performed. It is found that for negative interactions the islands are two-dimensional, while for positive interactions, regardless of diffusion rate, a fractal dimension of 1.78 is obtained. / by Mark R. Bouwens. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

This thesis describes Monte-Carlo computer simulations of binary alloys, with comparisons between small angle neutron scattering (SANS) data, and numerically integrated solutions to the Cahn-Hilliard-Cook (CHC) equation. Elementary theories for droplet growth are also compared with computer simulated data. Monte-Carlo dynamical algorithms are investigated in detail, with special regard for universal dynamical times. The computer simulated systems are Fourier transformed to yield partial structure functions which are compared with SANS data for the binary Iron-Chromium system. A relation between real time and simulation time is found. Cluster statistics are measured in the simulated systems, and compared to droplet formation in the Copper-Cobalt system. Some scattering data for the complex steel PE16 is also discussed. The characterisation of domain size and its growth with time are investigated, and scaling laws fitted to real and simulated data. The simple scaling law of Lifshitz and Slyozov is found to be inadequate, and corrections such as those suggested by Huse, are necessary. Scaling behaviour is studied for the low-concentration nucleation regime and the high-concentration spinodal-decomposition regime. The need for multi-scaling is also considered. The effect of noise and fluctuations in the simulations is considered in the MonteCarlo model, a cellular-automaton (CA) model and in the Cahn-Billiard-Cook equation. The Cook noise term in the CHC equation is found to be important for correct growth scaling properties.

Thesis (Ph. D.)--State University of New York at Binghamton, Mechanical Engineering Department, 2005. / Includes bibliographical references (leaves 149-155).

Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 238-246.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, March 1999. / Includes bibliographical references. Also available on the Internet.

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Massive binary evolution is crucial for our understanding of many pheno- mena in the Universe, such as high-mass X-ray binaries or the formation of compact systems emitting gravitational waves. In this work, we study the loss of angular momentum from binary systems caused by radiation driven stellar winds, which are characteristic for hot, massive stars. Calculating numerically ballistic trajectories of particles ejected from the binary surface, we establish the average specific angular momentum loss as a function of the system's mass ratio for binaries in semidetached and contact stages. We initiate the outflow on the Roche lobes or even on further equipotentials of the Roche potential in case of over-contact systems. Moreover, we implement two models of the radiation driven wind. Firstly, we eject particles from the surface of the binary with a non-zero initial velocity, but we then let them evolve only under the influence of the system's gravity. In the second model, we develop a simple method for computing the radiative acceleration due to the radiation pressure from the bi- nary surface. Our results can be used in further calculations of the evolution of massive binary systems.

A series of compositions across the niobium-rhodium- silicon ternary diagram from Nb₃Rh to 75 atomic percent niobium-25 percent silicon, were prepared by arc-melting compacts of high-purity powders. Both x-ray diffractometer and camera techniques were used to analyze the resulting structures. No measurable amount of silicon was found to substitute for rhodium in the Nb₃Rh structure. The 75 percent niobium-25 atomic percent silicon composition contains niobium plus an unidentified phase assumed to be Nb₅Si₃. The Nb-Rh sigma phase extends into the ternary system to at least 10 atomic percent silicon. All ternary alloys investigated contained three phases. These phases were one or more unidentified phases combined with either A₃B or sigma or both. / M.S.

In this thesis I present the search for ultracool dwarf companions to main sequence stars, subgiants and white dwarfs. The ultracool dwarfs identified here are benchmark objects, with known ages and distances. The online data archives, the two micron all sky survey (2MASS) and SuperCOSMOS were searched for ultracool companions to white dwarfs, where one M9 1 companion to a DA white dwarf is spectroscopically confirmed as the widest separated system of its kind known to date. The age of the M9 1 is constrained to a minium age of 1.94Gyrs, based on the estimated age of the white dwarf from a spectroscopically derived Teff and log g and an initial-final mass relation. This search was extended using the next generation surveys, the sloan digital sky survey (SDSS) and the UK infrared deep sky survey (UKIDSS), where potential white dwarf + ultracool dwarf binary systems from this search are presented. A handful of these candidate systems were followed-up with second epoch near infrared (NIR) imaging. A new white dwarf with a spectroscopic M4 companion and a possible wide tertiary ultracool component is here confirmed. Also undertaken was a pilot imaging survey in the NIR, to search for ultracool companions to subgiants in the southern hemisphere using the Anglo-Australian telescope. The candidates from that search, as well as the subsequent follow-up of systems through second epoch NIR/optical imaging and methane imaging are presented. No systems are confirmed from the current data but a number of good candidates remain to be followed-up and look encouraging. A search for widely separated ultracool objects selected from 2MASS as companions to Hipparcos main-sequence stars was also undertaken. 16 candidate systems were revealed, five of which had been previously identified and two new L0 2 companions are here confirmed, as companions to the F5V spectroscopic system HD120005 and the M dwarf GD 605. The properties of HD120005C were calculated using the DUSTY and COND models from the Lyon group, and the age of the systems were inferred from the primary members. For GD 605B no age constraint could be placed due to the lack of information available about the primary, but HD120005C has an estimated age of 2-4Gyr. In the final part of this thesis I investigate correlations with NIR broadband colours (J - H, H - K and J - K) with respect to properties, Teff , log g and [Fe/H] for the benchmark ultracool dwarfs, both confirmed from the searches undertaken in this work and those available from the literature. This resulted in an observed correlation with NIR colour and Teff, which is presented here. I find no correlation however with NIR colours and log g or [Fe/H], due in part to a lack of suitable benchmarks. I show that despite the current lack of good benchmark objects, this work has the potential to allow UCD properties to be measured from observable characteristics, and suggest that expanding this study should reveal many more benchmarks where true correlation between properties and observables can be better investigated.

A physico-chemical approach (theory of dissociation and reaction) is developed, which can be used in binary diffusion couple to determine diffusion parameters of the product phases with wide homogeneity range, as well as phases with narrow homogeneity range. It is demonstrated that this approach is basically equivalent to the diffusion based treatment. However, physico-chemical approach pedagogically sheds light on the chemical reactions occurring during interdiffusion at the interphase interfaces and morphology develops in the interdiffusion zone. This theory can be used in any binary systems for any end-member condition to explain single phase or multiphase diffusion controlled growth. Ni-Al and Ag-Zn systems are considered here to calculate diffusion parameters following physico-chemical approach. It is evident from our theoretical analysis and experimental evidence that in the presence of a stable Kirkendall marker plane one should expect duplex grain morphology in a particular phase layer. On the other hand, there is another model which is used rather frequently, is the theory of partitioning of flux. Although, the theory of partitioning of flux is used several times, we found that this theory does not count the mobility of both the species and therefore is not suitable to use in most of the interdiffusion systems. We have first modified this theory to take into account the mobility of both the species and then further extended to develop the relations for the integrated diffusion coefficient and the ratio of diffusivities of the species. The versatility of these two different models (that is the theory dissociation and reaction and the partitioning of flux) is examined in the Co-Si system with respect to different end-member compositions. From our analysis, we found that the applicability of the theory of partitioning of flux is rather limited but the theory of dissociation and reaction can be used in any binary systems. The theory of dissociation and reaction is then used to elucidate this behaviour in a single phase of β-NiAl and to calculate the diffusion parameter at the Kirkendall marker planes in the interdiffusion zone. To apply the physico-chemical approach, Ni-and Al-rich part of the phase is treated as two different phases and the plane corresponding to eqiatomic composition is considered as virtual interface between them. Possible dissociation and reaction equations are considered to combine with the flux equations to derive the relation for diffusion coefficient. Further experiments are conducted in the Cu-Sn, Au-Sn and Ni-Sn systems, which are important for flip chip bonding related to micro electronics industry. Different diffusion parameters, such as integrated diffusion coefficient, tracer diffusion coefficient of elements and the ratio of diffusivities are determined, which shed lights on the atomic mechanism of diffusion. Subsequently, the theory of dissociation and reaction is used when possible to explain the growth of the phases in the interdiffusion zone.