Nanohybrid materials have been prepared and examined for their electrocatalytic activity. The nanocomposites have been prepared from carbon nanomaterials (multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets), cadmium selenide quantum dots and metallophthalocyanines (MPcs). The MPcs used in this work are cobalt tetraamino-phthalocyanine (CoTAPc) and tetra (4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt (II)) (CoPyPc). Their activity has also been explored in different forms; polymeric MPcs, iodine doped MPcs and covalently linked MPcs. The premixed drop-dry, sequential drop-dry and electropolymerisation electrode modification techniques were used to prepare nanocomposite catalysts on the glassy carbon electrode (GCE) surface. The sequential drop dry technique for MPc and MWCNTs gave better catalytic responses in terms of limit of detection, catalytic and electron transfer rate constants relative to the premixed. MWCNTs and CdSe-QDs have been used as intercalating agents to reduce restacking of graphene nanosheets during nanocomposite preparation. Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for electrochemical characterization modified GCE. X-ray photoelectron spectroscopy, X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, infra-red spectroscopy, Raman spectroscopy were used to explore surface functionalities, morphology and topography of the nanocomposites. Electrocatalytic activity and possible applications of the modified electrodes were tested using oxygen reduction reaction, l-cysteine oxidation and paraquat reduction. Activity of nanocomposites was found superior over individual nanomaterials in these applications.

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In 1844 Charles Goodyear obtained U.S. Patent #3,633 for his “Gum Elastic Composition”. In a published circular, which describes his patent for the sulfur vulcanization of gum elastic composition, he stated: “No degree of heat, without blaze, can melt it (rubber)… It resists the most powerful chemical reagents. Aquafortis (nitric acid), sulphuric acid, essential and common oils, turpentine and other solvents… …” Goodyear's sulfur vulcanization of rubber fueled much of the industrial revolution and made transportation possible, as it exists today. In doing so, Goodyear created one of the most difficult materials to recycle. Rubber will not melt, dissolve, or lend itself to the usual methods of chemical decomposition. Ironically, Goodyear recognized this problem and in 1853 he patented the process of adding ground rubber to virgin material, now currently known as regrind blending. Today, scrap tires represent one of the most serious sources of pollution in the world. Studies estimate that there are roughly 2 billion scrap tires in U.S. landfills and more are being added at a rate of over 273 million tires per year. Current methods of recycling waste tires are crude, ineffective, and use rubber powder as a low cost filler instead of a new rubber. The groundwork for a very simple and effective method of producing high-quality rubber goods using 100% scrap rubber was discovered in 1944 by A. V. Tobolsky et al. This application, however, was not recognized until recently in our laboratory. The process as studied to date represents a method of creating quality, high-value added rubber goods with nothing other than heat and pressure. High pressure is required to obtain a void-free compaction of the rubber particles by forcing all of the free surfaces into intimate contact. High temperature then activates the chemical rearrangement, scission, and reformation of the chemical bonds thus providing new bridges between the once fractured interfaces. This occurs both within and between particles. The technique of high-pressure high-temperature sintering has worked on all types of thermoset materials. Typical mechanical properties for sintered SBR powder rubber are as follows: 1.3 MPa 100% Modulus, 12.0 MPa Tensile Strength and 300% Elongation at Break. The goal of this research is two-fold. First, to gain an understanding of the variables that control the process of high-pressure high-temperature sintering. Second, to study the factors governing the mechanism of fusion with the hope of controlling and exploiting this process so that tires can be recycled to produce high quality and high-value added products.

BaBibliography: pages 88-92. / A variety of ceramic and ultrahard materials have been subjected to both solid particle and cavitation erosion. The materials tested include three grain sizes of alumina, stabilised zirconias, sialon, cubic boron nitride and polycrystalline diamond, and these have a range of microstructural, physical and mechanical properties. The damage modes are described for the two types of erosion and the results are critically discussed. It has been shown that different properties and microstructural features control the respective types of erosion. Hardness is the critical property which controls material loss during solid particle erosion. Cavitation erosion in contrast is less sensitive to hardness, but is extremely defect sensitive and preferentially attacks weak or damaged regions on the target. Grain size and shape, and th.e properties of the grain boundary or intergranular phase exert a strong influence on both types of erosion. It has in addition been concluded, that a propensity for a stress induced phase transformation, such as that exhibited by stabilised zirconia, will benefit the resistance of a ceramic to erosion. Ultrahard materials generally outperform the structural ceramics that were tested. While it was not possible to ascertain the effects of grain size conclusively, a large extent of intergrowth between the crystallites during manufacture appears to be beneficial to erosion resistance.

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Thesis (Ph. D.)--Georgia State University, 1997. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 79-83).

Thesis (Ph. D.)--School of Pharmacy and School of Dentistry. University of Missouri--Kansas City, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.