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Showing 1 to 20 of 38 for “"surface segregation"”.
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The effects of evaporation rate, solvent, and substrate on the surface segregation of block copolymers
The surface chemistry of two systems of block copolymers was studied using angular dependent X-ray Photoelectron Spectroscopy poly(dimethyl (XPS). Surface concentration siloxane-b-sulfone)/polysulfone profiles of [PDMS/PSF] blends cast at several rates of solvent evaporation, and cast on several …
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Silicon Carbon(001) Gas-Source Molecular Beam Epitaxy From Methyl Silane and Silicon Hydride: The Effects of Carbon Incorporation and Surface Segregation on Growth Kinetics
… is due to a complex interaction among competing surface reactions. During growth of the initial Si-rich sublayer, C strongly segregates to the second layer resulting in charge transfer from surface Si atom dangling bonds of to C backbonds. This, in turn, decreases the Si2H6 sticking probability …
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A theoretical study of surface kinetic processes in the Mbe growth of compound semiconductors
The surface kinetics processes in the molecular beam epitaxy (MBE) growth of GaAs (100) and the MBE doping kinetics are studied theoretically, using a stochastic model which is based on the master equation approach and random distribution approximation. The kinetic processes included in the model …
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Smart Surfaces in Biobased Materials
… rule of mixing. This indicated the absence of surface segregation of the F-endgroup and it is explained with the fact that the micellar structure is retained in the solid state, suppressing surface segregation. The solid state micelles were visualized as dome-like protrusions by height image …
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Ion bombardment induced compositional changes in compound semiconductor surfaces studied by XPS combined with LEISS
Surface compositional change of GaP, GaAs, GaSb, InP, InAs, InSb, GeSi and CdSe single crystals due to low keV noble gas ion beam bombardment has been investigated by combining X-ray Photoelectron Spectroscopy (XPS) and Low Energy Ion Scattering Spectroscopy (LEISS). The purpose of using this …
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Silicon (011) and Silicon Germanium (011) Gas-Source Molecular Beam Epitaxy: Surface Reconstructions, Growth Kinetics, and Germanium Segregation
Ge surface segregation occurs during Si1--xGex(011) GS-MBE. Ge surface coverages thetaGe increase with x, ranging from 0.27 to 0.74 ML for x = 0.04--0.20. At a given film composition, theta Ge decreases with decreasing Ts due to the corresponding increase in the fraction of H-bonded Si surface …
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Segregation and embrittlement in metallic interfaces : bounds, models, and trends
… limits on grain size stabilization via segregation in metals and provide specific thermodynamic models for grain size stabilization of polycrystals via alloying for use in future alloy design. While grain boundary segregation is desirable to inhibit grain growth, such segregation is …
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High-throughput synthesis and screening of binary alloys for hydrogen evolution and oxidation reactions
… were used for the analysis of bulk composition, surface composition and structure respectively. The compositional analysis reveals that alloy formation and synthesis of nearly the whole compositional range of the alloy systems were achieved. Surface segregation of Au in the Pd-Au alloy system and …
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Interfacial Segregation in Perovskites and Applications to Boundary Layer Devices
Interfacial segregation is a term used to describe the compositional heterogeneity that exists between the bulk and interface in materials due to interfacial effects which are distinct from bulk effects. Segregation in solids is of great theoretical importance, and also plays an active role in …
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Carbon Incorporation Pathways and Lattice Site Distributions in Silicon Carbide/silicon(001) and Germanium Carbide/germanium(001) Alloys Grown by Molecular Beam Epitaxy
… ordered Si4C layers which form as a result of C surface segregation. (2) In contrast to Si1-yC y/Si(001), I find that irrespective of y and Ts values, complete substitutional C incorporation in Ge1-yCy/Ge(001) is not possible. A fraction of the total C concentration is always incorporated in …
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Surface modification of polymer membranes by self-organization
… hydrophilic materials, as well as hydrophilic surface modification of hydrophobic membranes using coating and surface graft polymerization techniques. In many applications, the first approach results in unacceptable compromises in mechanical, thermal, and chemical stability. Coating and …
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Effects of size and surface on optical properties of NaYF4:Yb,Er Nanoparticles
… This thesis focused on the effects of size and surface on optical properties of hcp NaYF4:Yb,Er particles, which is one of the most efficient near infrared-to-visible UC materials. Room temperature emission spectra showed that for hcp NaYF4:Yb,Er nanoparticles with sizes from ~ 11 to 110 nm, the …
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Thermal and low-energy ion doping of silicon(001) during molecular beam epitaxy: Dopant incorporation kinetics and mechanisms
… R$\sb{\rm Si}$ (0.18-4.7 $\mu$m h$\sp{-1}).$ Surface segregation during thermal doping led to severe profile broadening and low temperature-dependent incorporation probabilities $\sigma\sb{\rm d,th}.$ On the other hand, $\sigma\sb{\rm d}$+ for In-ions at energies E$\sb{\rm In}$+ $\ge$ 200 eV …
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Molecular order at polymer surfaces via X-ray photoelectron spectroscopy
Molecular order in surfaces is probed for several different repeat unit Spectroscopy (XPS) is chemistries. X-ray Photoelectron used, particularly with angular dependence, to obtain the compositional gradient information from the top 6 run of the surface. It is found that all materials investigated …
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The Effects of Molecular Architecture on the Rheological and Mechanical Properties of Polymeric Systems
… architecture and end-group functionality on the surface segregation characteristics of branched polymers in blends with commercially available linear polymers were also investigated. In the blends of branched PEIs with polystyrene (PS), the surface migration of PEIs correlates with the changes in …
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Synthesis of Well-Defined Multi-End Functionalized Polymers via Living Anionic Polymerization
… require specific properties at polymer surfaces that differ from the bulk, while retaining the advantageous properties of the bulk polymer. In this thesis, we describe work aimed at producing a series of multi-end functionalized polystyrene and polyisoprene additives with a wide range of …
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Computational and Data-Driven Design of Perturbed Metal Sites for Catalytic Transformations
… In addition, novel physics effect controlling surface reactivity beyond conventional understanding is uncovered. Secondly, we develop a computational and data-driven framework to model high entropy alloy (HEA) catalysis, incorporating thermodynamic descriptor-based phase stability evaluation, …
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Low Energy Ion Bombardment Effects in Supersaturated Copper-Indium Alloys
… increasingly compensated by radiation-assisted surface segregation. Even at room temperature, however, the steady state In concentration in the altered layer during irradiation, while reduced, remained supersaturated and enhanced diffusion to ion bombardment-created point defect sinks resulted …
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The low-temperature sintering behavior of (La,Ca)CrO₃
… a solid solution, (La,Ca)CrO<sub>3</sub>. The surface segregation of Ca and phase separation of CaCrO<sub>4</sub> are discussed.</p> <p>The second paper addresses the sintering behavior of (La<sub>.6</sub>Ca<sub>.4</sub>)<sub>x</sub>CrO<sub>3</sub> where x is varied between 0.95 to 1.05. …
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Siloxane modified polyurea and polyurethane urea segmented copolymers
… between the segments. In addition, the surface structure of segmented polyether urea and polyurethane urea copolymers were modified in two ways: siloxane urea segmented copolymers were synthesized and physically blended into the system, and siloxane oligomers of controlled molecular …
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