Browsing by Subject "X-ray diffraction"
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- ItemRestrictedHigh temperature study on thin aluminium coatings deposited onto thick platinum substrates(Elsevier, 2009) Topić, M; Pineda-Vargas, C A; Bucher, R; du Plessis, H E; Breedt, B; Pischedda, V; Nxumalo, S; Lang, C IIntermetallics formation in the Pt–Al binary system at temperatures in the range of 20–600 °C have been investigated by the study of thin aluminium coatings deposited on thick platinum substrates. In order to characterise the changes caused by elevated temperature several techniques such asmicroscopy, X-ray diffraction, nuclear microprobe techniques and microhardness testing were used. In addition to changes in morphology, the high temperature X-ray diffraction (XRD) analysis showed that the initial phase formed when Pt and Al reacted was Pt2Al3. The formation of Pt2Al3 phase started at 250 °C and it is followed by the PtAl and Pt3Al phases. Furthermore, the Pt–Al intermetallics increased the surface hardness; the process of surface hardening by formation of intermetallics without compromising the purity of pure platinum is of great importance for jewellery and other applications where the properties such as hardness and scratch resistance are crucial.
- ItemOpen AccessInclusion complexes of 2-methoxyestradiol with dimethylated and permethylated β-cyclodextrins: models for cyclodextrin-steroid interaction(2014) Caira, Mino R; Bourne, Susan A; Samsodien, Halima; Smith, Vincent JThe interaction between the potent anticancer agent 2-methoxyestradiol (2ME) and a series of cyclodextrins (CDs) was investigated in the solid state using thermal analysis and X-ray diffraction, while the possibility of enhancing its poor aqueous solubility with CDs was probed by means of equilibrium solubility and dissolution rate measurements. Single crystal X-ray diffraction studies of the inclusion complexes between 2ME and the derivatised cyclodextrins heptakis(2,6-di-O-methyl)-β-CD (DIMEB) and heptakis(2,3,6-tri-O-methyl)-β-CD (TRIMEB) revealed for the first time the nature of the encapsulation of a bioactive steroid by representative CD host molecules. Inclusion complexation invariably involves insertion of the D-ring of 2ME from the secondary side of each CD molecule, with the 17-OH group generally hydrogen bonding to a host glycosidic oxygen atom within the CD cavity, while the A-ring and part of the B-ring of 2ME protrude from the secondary side. In the case of the TRIMEB·2ME complex, there is evidence that complexation proceeds with mutual conformational adaptation of host and guest molecules. The aqueous solubility of 2ME was significantly enhanced by CDs, with DIMEB, TRIMEB, randomly methylated β-CD and hydroxypropyl-β-CD being the most effective hosts. The 2:1 host-guest β-CD inclusion complex, prepared by two methods, yielded very rapid dissolution in water at 37 °C relative to untreated 2ME, attaining complete dissolution within 15 minutes (co-precipitated complex) and 45 minutes (complex from kneading).
- ItemMetadata onlyThe plasticisation of polyhydroxybutyrate in vivo(Elsevier, 1992) Harrison, Susan T L; Chase, Howard A; Amor, Stuart R; Bonthrone, Karen M; Sanders, Jeremy K MThe influence of a variety of treatments on the mobility and crystallinity of poly(hydroxybutyrate) (PHB) in whole cells and native granules has been proved using 13C-n.m.r. spectroscopy and X-ray powder diffraction, and correlated with the known biological effects of these treatments. It was concluded that at least water is responsible for PHB plasticization in vivo, and that only native mobile PHB is susceptible to depolymerases. Another, probably hydrophobic, component appears to be involved either as plasticizer or nucleation inhibitor. Three states of the granule are identified in addition to the native, biologically-competent state: freeze-drying of whole cells leads to a partially-immobilized amorphous state which can be restored virtually to native mobility by rehydration; extended centrifugation of native granules in aqueous suspension, or treatment with hydrophobic detergents under certain conditions, leads to a crystalline state that is less susceptible to exogenous depolymerase; and heating to 95 degrees C or refrigeration has no detectable effect on mobility but leads to inactivation of the granule, presumably via damage to superficial membrane or protein.