Surfaces that exhibit a gradual change in their chemical and/or physical properties are termed as surface gradients. Based on the changes in properties they are classified either as physical or chemical gradients. Chemical gradients show variations in properties like polarity, charge, functionality concentration and have found potential applications in fields of biology, physics, biosensing, catalysis and separation science. In this dissertation, surface gradients have been prepared using controlled rate infusion (CRI). CRI is a simple method in which a surface gradient is formed by carrying out the infusion of organoalkoxysilane in a time-dependent fashion using a set infusion rate. Depending on concentration of silane, rate of infusion and time of infusion, the gradient profiles on surfaces can be varied and the surface chemistry of the substrate can be altered. Initial work in the dissertation focuses on demonstrating different gradient profiles and selectivity obtained using amine and/ or phenyl functionalized gradient stationary phases on thin layer chromatography (TLC) plates prepared by CRI. The presence of amine and phenyl on the surfaces were confirmed by X-ray Photoelectron Spectroscopy (XPS) and diffuse reflectance spectroscopy, respectively. The change in surface chemistry was demonstrated by changes in the selectivities of water and fat soluble vitamins. After successful preparation and characterization of single and multi-component stationary phase gradients for planar chromatography, single-component gradients were prepared for column chromatography (Silica monolithic columns). Similar to that observed for planar chromatography, the selectivity was evaluated from retention factors and was found to be different for a weak acid/weak base mixture. The results obtained showed the promising approach of using gradient stationary phases in column chromatography. This work was further extended to prepare amine and phenyl multi-component gradients on silica monolithic columns to investigate mixed-mode and synergistic effects. Finally, amine, phenyl and thiol gradients were also prepared on cellulose substrates, particularly water color paper, The goal was to study the formation of functionality gradients on cellulose substrates particularly the interaction between hydroxyl groups on cellulose and silanols and to study the stability of the silanes on the cellulose surface.

The development of alternative binder systems for tungsten carbide (WC) based cemented carbides has again become of relevance due to possible changes in EU regulations regarding the use of Cobalt (Co). A framework for the ICME (Integrated Computational Materials Engineering) based Materials Design is presented to accelerate the development of alternative binder systems. Part one of this work deals with the design of the cemented carbide composite hardness. It has been shown that the intrinsic binder hardness is comparable to a bulk metal alloy and that based on the binder solubilities a solid solution strengthening model developed in this work can be employed. Using a method presented in this work the non-equilibrium, frozen-in binder solubilities can be obtained. Both the design of the binder phase and composite hardness is presented based on a general Materials Design approach. Part two deals with a multiscale approach to model the surface gradient formation. The experimentally missing data on liquid binder diffusion has been calculated using AIMD (Ab initio Molecular Dynamics). The diffusion through the liquid cemented carbide binder has to be reduced to an effective diffusion value due to the solid carbides acting as obstacles that increase the diffusion path. The geometrical reduction of the diffusion has been investigated experimentally using the SIMS (secondary ion mass spectroscopy) technique in WC-Nickel-58Nickel diffusion couples. The geometrical contribution of the so-called labyrinth factor has been proven by the combination of the experiments and in conjunction with DICTRA simulations using the precise liquid AIMD diffusivities. Unfortunately, despite the improved kinetic database and the geometrical diffusion reduction, the surface gradient formation cannot be explained satisfactory in complex cemented carbide grades. Additional, but so far unidentified, contributions have to be considered to predict the surface gradient thickness. / <p>QC 20170919</p>