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Structural and thermal characterisation of nanostructured alumina templates
I.W.M. Brown,M.E. Bowden,T. Kemmitt,K.J.D. MacKenzie 한국물리학회 2006 Current Applied Physics Vol.6 No.3
Nanostructured anodic aluminium oxide materials containing a two dimensional array of high aspect ratio aligned pores of 200 nm.C. Thermal analysis shows two discrete irreversible exothermic eventsat 850.C and 1020 .C. XRD and27Al MAS NMR show the progressive development of local and long range order in the heated struc-tures and indicate a reaction sequence of amorphous Al2O3 ! h-Al2O3 ! a-Al2O3 (corundum). NMR shows the co-existence of alumin-ium in 4, 5 and 6-coordinated sites through most of the heating sequence until the stable (6-coordinated) corundum phase is established.Phosphorus impurities incorporated during the membrane fabrication process crystallise as an AlPO4 phase above 850 .C and play animportant role in directing the chemical, physical and structural outcomes of the heat treatment.
A. Kirchner,I.W.M. Brown,M.E. Bowden,T. Kemmitt,G. Smith 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4
Porous anodic alumina discs supporting palladium lms as elements of hydrogen-purifying membranes have been examined for theirhigh-temperature behaviour. The method employed to fabricate the porous alumina support is the so-called ‘hard anodising’ technique,which oers substantially higher growth rates while producing mechanically robust lms. These alumina membranes were found to pos-sess a thermal stability better than commercial Anopore. membranes. Upon long-term exposure at 800.C they transform intoc-aluminawithout major deformation. Ultra-thin palladium lms deposited across the alumina pores by physical vapour deposition are continuousand stable in reducing atmospheres to at least 700.C but are oxidised and destroyed by heating in air.
Rapid transition from continental breakup to igneous oceanic crust in the South China Sea
Larsen, H. C.,Mohn, G.,Nirrengarten, M.,Sun, Z.,Stock, J.,Jian, Z.,Klaus, A.,Alvarez-Zarikian, C. A.,Boaga, J.,Bowden, S. A.,Briais, A.,Chen, Y.,Cukur, D.,Dadd, K.,Ding, W.,Dorais, M.,Ferré,, E. Nature Publishing Group 2018 Nature geoscience Vol.11 No.10
Effects of hydrated lime on radionuclides stabilization of Hanford tank residual waste
Wang, Guohui,Um, Wooyong,Cantrell, Kirk J.,Snyder, Michelle M.V.,Bowden, Mark E.,Triplett, Mark B.,Buck, Edgar C. Elsevier 2017 CHEMOSPHERE - Vol.185 No.-
<P><B>Abstract</B></P> <P>Chemical stabilization of tank residual waste is part of a Hanford Site tank closure strategy to reduce overall risk levels to human health and the environment. In this study, a set of column leaching experiments using tank C-104 residual waste were conducted to evaluate the leachability of uranium (U) and technetium (Tc) where grout and hydrated lime were applied as chemical stabilizing agents. The experiments were designed to simulate future scenarios where meteoric water infiltrates through the vadose zones into the interior of the tank filled with layers of grout or hydrated lime, and then contacts the residual waste. Effluent concentrations of U and Tc were monitored and compared among three different packing columns (waste only, waste + grout, and waste + grout + hydrated lime). Geochemical modeling of the effluent compositions was conducted to determine saturation indices of uranium solid phases that could control the solubility of uranium. The results indicate that addition of hydrated lime strongly stabilized the uranium through transforming uranium to a highly insoluble calcium uranate (CaUO<SUB>4</SUB>) or similar phase, whereas no significant stabilization effect of grout or hydrated lime was observed on Tc leachability. The result implies that hydrated lime could be a great candidate for stabilizing Hanford tank residual wastes where uranium is one of the main concerns.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hanford tank residual waste could be stabilized by grout. </LI> <LI> Addition of hydrated lime stabilized uranium from leaching through CaUO<SUB>4</SUB>. </LI> <LI> XRD, SEM/EDS and thermodynamic model revealed uranium mineral transformation. </LI> </UL> </P>