Chemical and Biomolecular Engineering - Research Publications
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ItemThe mechanism for hydrothermal growth of zinc oxide(ROYAL SOC CHEMISTRY, 2012)
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ItemInfluence of air bubble size on float-sink of spheres in a gas-solid fluidized bed(ELSEVIER SCIENCE BV, 2012-01)
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ItemDifferential Etching of ZnO Native Planes under Basic Conditions(AMER CHEMICAL SOC, 2012-04-03)The in situ dissolution of polished (0001), (101(-)0), and (0001(-)) surfaces of ZnO was studied using Atomic Force Microscopy under alkaline conditions. In aqueous NaOH solution the (0001) plane forms a stepped surface whereas the (0001(-)) plane converts into more stable {101(-)1(-)} planes. Dissolution of the (101(-)0) plane leaves a combination of (0001) and (101(-)1(-)) planes. Dissolution in solutions containing both NaOH and Na(3)citrate causes the (0001) plane steps to increase in number and reduce in height, and cause an overall increase in the rate of dissolution in the [101(-)0] directions. These observations are explained using a mechanism based on edgewise dissolution where the etching rate depends on the number of surface oxygen atoms per zinc atom. Large areas of single index faces (over 50 μm(2)) of (0001) and (0001(-)), suitable for surface chemistry studies, were also generated by chemical dissolution.
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ItemTemperature-Responsive Solid-Liquid Separations with Charged Block-Copolymers of Poly(N-isopropyl acryamide)(AMER CHEMICAL SOC, 2012-01-10)Temperature responsive charged block-copolymers of poly(N-isopropylacrylamide) (PNIPAM) have been used in the solid-liquid separation of alumina mineral particles from aqueous solution. The effects of temperature, polymer charge-sign and fraction of charged segment have been investigated. Batch settling and adsorption studies showed that rapid sedimentation results for suspensions with polymers of opposite charge-sign to the particle surface-charge (counterionic) at 50 °C. Cooling the suspensions after flocculation at 50 °C was found to increase the final solids volume fraction of the sediment beds formed through a mechanism related to partial desorption of polymer and the reduction of the hydrophobic attraction. Suspension stability results after dosing with polymers of similar charge-sign to the particle surface-charge (co-ionic) at both 25 and 50 °C. Increasing the amount of polymer charge increased the influence of polymer charge-sign on the adsorption and solid-liquid separation behavior. The performance of the charged block copolymers are compared to that of the random charged copolymer and neutral homopolymer PNIPAM structures.
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ItemCompressive strength and capillary pressure: competing properties of compressible sediments that determine breakthrough pressure(Filtech Exhibitions Germany, 2012)