The thermal decomposition of ettringite, Ca6[Al(OH)6]2(SO4)3·∼26H2O, was studied with pulsed neutron time-of-flight diffraction combined with Rietveld structure refinement. Like prior investigations, transition from a crystalline to amorphous state occurred following the loss of ∼20 water molecules. In contrast to earlier investigations, which relied upon indirect measurements of water and hydroxyl occupancies, the present study inferred the occupancies directly from Rietveld crystal structure refinement of the diffraction data. The decomposition pathway was shown to be more complex than previously envisioned, involving the simultaneous loss of hydroxyl and water molecules. Nuclear magnetic resonance (NMR) spectroscopy studies of the rigid lattice lineshapes of fully and partially hydrated ettringite were performed and confirmed our decomposition model. 相似文献
The research work carried out on cement exhausts centers mostly around vegetation and crop productivity (1-3) with little
or no work on root nodulation. Soil plus foliar application of exhaust dusts did not affect soil/nodule rhizobial population,
nodule initiation, and possible N2-fixing capacity inCajanus cajan, Vigna radiata, Vigna mungo,Vigna catjung, andGlycine max. The nodular biochemistry was investigated in detail. The heme protein leghemoglobin was higher compared to the control.
The levels of intermediary N compounds like total ureides of the nodules, which may serve as indirect evidence of symbiotic
N2 fixation, were higher in the treated plants. There were also increments in free proline, free amino acids, soluble proteins,
soluble starch, soluble sugars, total nitrogen, and phenols in the treated plants. The levels of total nitrates, soluble sucrose,
and soluble SH compounds of the nodule of the control and treated plants did not show a significant difference. The activities
of ascorbate peroxidase, catalase, glutathione reductase, and Superoxide dismutase were significantly higher, possibly indicating
their role in alleviation of H2O2 and O
2-
damage by the exhausts. Enzymes like nitrate reductase, nitrite reductase, and glutamine synthetase, and also the activities
of acid and alkaline phosphatases were not affected. The presence of beneficial soil microbes likeAzotobacter, Azospirillum, and mycorrhizae was not affected at all. 相似文献
A new approach is provided for preparing radiopaque and angiogenic poly(propylene fumarate) (PPF) bone cements by integrating Sr‐doped n‐TiO2 nanowires and ginsenoside Rg1 suitable for treating osteonecrosis. High aspect ratio radiopaque TiO2‐nanowires are synthesized by strontium doping in supercritical CO2 for the first time, showing a new phase, SrTiO3. PPF is synthesized using a transesterification method by reacting diethyl fumarate and propylene glycol, then functionalized using maleic anhydride to produce terminal carboxyl groups, which are subsequently linked to the nanowires. The strong interfacial adhesion between functionalized PPF and nanowires is examined by scanning electron microscopy, Fourier transform infrared, X‐ray photoelectron spectroscopy, thermal analysis, and mechanical testing. An angiogenic modulator, ginsenoside Rg1, is integrated into the bone cement formulation with the mechanical properties, radiopacity, drug release, and angiogenesis behavior of the formed composites explored. The results show superior radiopacity and excellent release of ginsenoside Rg1 in vitro, as well as a dose‐dependent increase in the branching point numbers. The present study suggests this new methodology provides sufficient mechanical properties, radiopacity, and angiogenic activity to be suitable for cementation of necrotic bone.
