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Laser surface modification involves rapid melting and solidification is an elegant technique used for locally tailoring the surface morphology of alumina in order to enhance its abrasive characteristics. COMSOL Multiphysics® based heat transfer modeling and experimental approaches were designed and used in this study for single and multiple laser tracks to achieve densely-packed multi-facet grains via temperature history, cooling rate, solidification, scanning electron micrographs, and wear rate. Multi-facet grains were produced at the center of laser track with primary dendrites extending toward the edge of single laser track. The multiple laser tracks study indicates the grain/dendrite size increases as the laser energy density increases resulting in multiplying the abrasive edges which in turn enhance the abrasive qualities.

Recent progress in layered transition metal dichalcogenides (TMDs) has led to various promising electronic and optoelectronic applications. However, the structure of materials plays a critical role in electronic and optoelectronic devices, and determines performance. Electronic and optoelectronic devices typically consist of multiple layers that form electrical homojunctions or heterojunctions. Therefore, in a device it can be expected that a WS2 layer may serve as the substrate for a subsequent layer in a multilayer device stack and determine how the layer grows. In transistor structures, roughness at the channel/gate dielectric interface introduces field variations and charge scattering. Therefore, understanding the relations between processing, surface morphology and properties is important. In this project, the effects of pulsed laser deposition (PLD) processing conditions on the surface morphology of few layered WS2 films were studied. WS2 films were synthesized under processing conditions that represent the extremes of surface supersaturation and kinetic energy transfer from the flux to the growing films, and evolution of the surface morphology was studied. The specific conditions were 1Hz/50mJ, 10Hz/50mJ, 1Hz/300mJ, and 10Hz/300mJ respectively. Combining AFM, XRD and Raman analyses, it was determined that deposition at 10Hz/300mJ, provided the best structural properties and surface morphology. Growth appeared to be 3D-cluster, and was governed by supersaturation rather than by surface diffusion processes. No clear correlation between mobility and surface roughness was found. Hall measurements and XPS data show the highest mobility was obtained with the highest S/W ratio, indicating that point defect scattering rather than scattering from surface roughness was dominant.

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The purpose of this study is to investigate the effects on DC sputtered thin films after different surface treatments on aluminum targets. Abrasive papers and nonwovens were used to polish the aluminum targets before sputtering. Surface morphology of the aluminum targets before and during sputtering were characterized using surface profiler. In addition, the erosion rate of the aluminum targets was obtained by measuring the changes of the erosion depth with sputtering time at a fixed processing condition. On the other hand, the surface morphology and electrical characteristics of the deposited thin films with respect to different aluminum targets were investigated. We found that surface roughness of the treated aluminum targets is of great importance to the stability of the film quality.

A range of geochemical reactions are controlled by the interfacial characteristics of rocks and minerals. Many engineered and natural systems are affected by geochemical reactions that occur at interfaces. Asphalt-aggregate adhesion in road construction is influenced by the interfacial characteristics of the aggregate. Likewise, the remediation of nonaqueous-phase liquid contaminants, such as trichloroethylene or methyl tert-butyl ether, is controlled by the interactions between mineral surfaces and the organic liquid. Many natural systems are also influenced by reactions at interfaces. The migration of petroleum in sedimentary basins is influenced by the wettability of the surfaces of the basin pore space. Adhesion of organisms, such as bacteria or lichens, to rock surfaces is controlled by the interactions of proteins and mineral surfaces. Rock and mineral surfaces are described by surface energy. Surface energy is a thermodynamic construct defined as the amount of work required to form more of a surface. Surface energy can be divided into van der Waals, Lewis acid, and Lewis base components. The ability to predict the magnitude of surface energy components is valuable in understanding species behavior. Surface energy is controlled by three master variables: surface chemistry, surface morphology, and surface coatings. While the surface energy of a number of minerals and aggregates has been characterized, there has not yet been a comprehensive study of the surface energies of a variety of the most common minerals and aggregates using consistent methodology. In addition there has not yet been a study of the effect of these three master variables on surface energies of natural minerals and rocks. This study measured the surface energy of 22 common minerals and 7 aggregates. The samples’ bulk and surface chemistries were characterized with wavelength and energy dispersive spectra analyses on an electron microprobe and x-ray photoelectron spectroscopy. The XPS was also used to quantify the organic and inorganic coatings on the surfaces. Results showed that van der Waals surface energy is typically between 40 and 60 ergs/cm2. Polar surface energy varies by 1 to 3 orders of magnitude, and thus is likely the most important component in accounting for changes between natural minerals.

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Kenaf fiber is increasingly getting the attention of the industries due to its excellent mechanical properties, feasibility, growth rate, and ease of cultivation. On the other hand, cellulose nanofibril is one of the important building blocks of all the bast fibers which significantly contributes to their mechanical properties. However, most of the studies in the literature have estimated the value of axial elastic modulus for fiber-bundles which has some unavoidable issues resulting in incorrect modulus. Moreover, the transverse elastic modulus is another important parameter that also needs to be studied. Hence, to compensate for the gap in the literature, a single unit of both kenaf microfiber and cellulose nanofibril have been subjected to nanomechanical characterization to analyze their surface morphology and determine their elastic modulus in the axial and transverse direction. The experiments also pave to a protocol to characterize micro and nanofibrils nanomechanically and determine their elastic moduli.

Reverse osmosis (RO) and nanofiltration (NF) membranes are pressure driven, diffusion controlled process. The influence of surface characteristics on membrane process performance is considered significant and is not well understood. Current mass transport models generally assume constant mass transfer coefficients (MTCs) based on a homogeneous surface. This work evaluated mass transfer processes by incorporating surface morphology into a diffusion-based model assuming MTCs are dependent on the thickness variation of the membrane’s active layer. To mathematically create such a surface layer, Gaussian random vectors embedded in a software system (MATLAB) were used to generate a three-dimensional ridge and valley active layer morphologies. A “SMOOTH” script was incorporated to reduce the influence of outlying data and make the hypothetical surfaces visually comparable to the AFM images. A nonhomogeneous solution diffusion model (NHDM) was then developed to account for surface variations in the active layer. Concentration polarization (CP) is also affected by this nonhomogeneous surface property; therefore, the NHDM was modified by incorporating the CP factor. In addition, recent studies have shown that the membrane surface morphology influences colloidal fouling behavior of RO and NF membranes. With consideration of the spatial variation of the cake thickness along the membranes, a fouling model was established by assuming cake growth is proportional to the localized permeate flow. Flux decline was assumed to be controlled by the resistance of cake growth and accumulated particle back diffusion at the membrane surface. A series of simulations were performed using operating parameters and water qualities data collected from a full-scale brackish water reverse osmosis membrane water treatment plant. The membrane channel was divided into a thousand uniform slices and the water qualities were iii determined locally through a finite difference approach. Prediction of the total dissolved solid (TDS) permeate concentration using the model was found to be accurate within 5% to 15% as an average percentage of difference (APD) using the NHDM developed in this research work. A comparison of the NHDM and the modified NHDM for concentration polarization (CP) with the commonly accepted homogeneous solution diffusion model (HSDM) using pilot-scale brackish water RO operating data indicated that the NHDM is more accurate when the solute concentration in the feed stream is low, while the NHDMCP appears to be more predictive of permeate concentration when considering high solute feed concentration. Simulation results indicated that surface morphology affects the water qualities in the permeate stream. Higher salt passage was expected to occur at the valley areas when diffusion mass transfer would be greater than at the peaks where the thin-film membrane is thicker. A rough surface tends to increase the TDS accumulation on the valley areas, causing an enhanced osmotic pressure at the valleys of membrane. To evaluate the impact of surface morphology on RO and NF performance, fouling experiments were conducted using flat-sheet membrane and three different nanoparticles, which included SiO2, TiO2 and CeO2. In this study, the rate and extent of fouling was markedly influenced by membrane surface morphology. The atomic force microscopy (AFM) analysis revealed that the higher fouling rate of RO membranes compared to that of NF membranes is due to the inherent ridge-and-valley morphology of the RO membranes. This unique morphology increases the surface roughness, leading to particle accumulation in the valleys, causing a higher flux decline than in smoother membranes. Extended fouling experiments were conducted using one of the RO membranes to compare the effect of different particles on actual water. It was determined that membrane flux decline was not affected by particle type when the feed water iv was laboratory grade water. On the other hand, membrane flux decline was affected by particle type when diluted seawater served as the feed water. It was found that CeO2 addition resulted in the least observable flux decline and fouling rate, followed by SiO2 and TiO2. Fouling simulation was conducted by fitting the monitored flux data into a cake growth rate model. The model was discretized by a finite difference method to incorporate the surface thickness variation. The ratio of cake growth term (�1) and particle back diffusion term (�2) was compared in between different RO and NF membranes. Results indicate that �2 was less significant for surfaces that exhibited a higher roughness. It was concluded that the valley areas of thin-film membrane surfaces have the ability to capture particles, limiting particle back diffusion.