Surface Chemistry

Potential applications of diamond-like carbon (DLC) coatings range from precision tools and biomedical implants to micro mechanical devices and engine components. Where uniform coatings are required on substrates with complex geometries, plasma enhanced chemical vapour deposition (PECVD) is often a preferred deposition method. As a non-line of sight process, the geometry of the substrate is often considered negligible. For this reason analysis of PECVD coatings, such as amorphous carbon, has mostly been concerned with reactor deposition variables, such as bias voltage, pressure and gas ratios. Samples are therefore usually prepared and positioned to minimise the influence of other variables. By depositing nominally similar DLC films on silicon samples positioned horizontally and vertically on the reactor cathode plate it was possible to examine the variations in the coating characteristics and mechanical properties that occur due to the geometry of the substrate being coated. Topographic measurements and analysis of bonding structures revealed significant heterogeneity in the coatings. Electron microscopy showed variation in surface structure as well as thickness disparities of up to 50% in the vertical sample. Atomic force microscopy showed roughness, Ra, varied from 0.37 nm to 15.4 nm between samples. Raman spectroscopy highlighted variations in the sp2/sp3 bonding ratios whilst micro wear tests demonstrated how these variations reduce the critical load performance. These effects are explained in terms of the deposition mechanisms involved and are related to variation in deposition species and geometrical field enhancements within the deposition chamber. Improved understanding of these local variations will aid in the optimization of coatings for complex substrate geometries.

An experimental study of nanofluids intended for enhanced oil recovery is presented in this work. An aqueous solution of anionic surface-active agents with addition of light non-ferrous metal nanoparticles was used as the focus of the study. It is shown that the use of the nanofluid permitted a 70–90% reduction of surfacetension on an oil boundary in comparison with surface-active agent aqueous solution and is characterized by ashift in dilution. Use the developed nano-suspension results in a considerably increase EOR

Bulk characteristics and deposition of gold nanoparticles on mica modified by (PAH) was studied byUV–visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM),dynamic light scattering (DLS) and atomic force microscopy (AFM). The size of gold nanoparticles (AuNPs)was 15 nm as determined by TEM and AFM. The electrophoretic mobilities and electrokinetic chargeof particles were quantitatively evaluated for a broad range of pH and ionic strength. Using Henry’smodel, it was calculated that the zeta potential of particles varied between − 50 mV and − 80 mV forpH 2 and pH 11, respectively (at 10−2M of NaCl). Measurements of nanoparticle deposition kineticswere performed under diffusion-controlled transport conditions using AFM and SEM imaging of particlemonolayers. The influence of the bulk suspension concentration was systematically studied. Additionally,the maximum coverage of particle monolayers, which monotonically increased with ionic strength, wasdetermined by SEM. The obtained data were in agreement with theoretical predictions derived from therandom sequential adsorption (RSA) model. It was also confirmed that by varying the bulk suspensionconcentration and ionic strength one can prepare homogeneous gold particle monolayers of controlledcoverage.

The experiment’s οbjective is tο determine the activated carbοn/charcοal (AC)’s adsοrptiοn capacity in methylene blue (MB), and determine the relatiοnship οf AC dοsage οr the cοncentratiοn οn remοving MB as cοrrelated by the amοunt οf adsοrptiοn. The experiment fοund that an increase in the mass οf AC decreases the absοrbance ratiο. The amοunt οf MB adsοrbed decreased with the increase in AC’s mass. The percentage οf adsοrptiοn increased frοm 20.50% tο 99.10%, increasing AC’s mass frοm 1 mg tο 100 mg. Likewise, the experiment fοund that the οptimum AC cοncentratiοn fοr 95.90% remοval οf MB was 25 mg/100 mL. Furthermοre, the experiment shοwed the varying AC cοncentratiοn as the amοunt οf MB remοved with the AC cοncentratiοn’s functiοn. Therefοre, mοre AC cοncentratiοn meant that a larger effluent, e.g., MB’s vοlume at a fixed dοsage οr cοncentratiοn, cοuld be purified.

The effects of weathering on the surface properties of wood-plastic composites (WPC) were examined. High-density polyethylene (HDPE) based WPCs made from modified wood flour (untreated, extractives free, and holocellulose (delignified) fibers) were subjected to accelerated (xenon-arc) weathering. Colorimetery and Fourier-transform infrared spectroscopy were employed to monitor the color change and surface chemistries of the weathered WPC surface. The com­ positional

Includes vita. Advisory Committee: Adriaan Van Heiningen, Ober Chair and Prof. of Chemical Engineering, Co-Adviser; Douglas W. Bousfield, Prof. of Chemical Engineering, Co-Advisor; Yang Xiang, Research Engineer in Chemical Engineering. Thesis (M.S.) in Chemical Engineering--University of Maine, 2001. Bibliography: leaves 122-131.