18 resultados para chemical method
Resumo:
Short-range-order (SRO) has been quantitatively evaluated in an Fe-18Al (at%) alloy using atom probe tomography (APT) data and by calculation of the generalised multicomponent short-range order (GM-SRO) parameters, which have been determined by shell-based analysis of the three-dimensional atomic positions. The accuracy of this method with respect to limited detector efficiency and spatial resolution is tested against simulated D03 ordered data. Whilst there is minimal adverse effect from limited atom probe instrument detector efficiency, the combination of this with imperfect spatial resolution has the effect of making the data appear more randomised. The value of lattice rectification of the experimental APT data prior to GM-SRO analysis is demonstrated through improved information sensitivity.
Resumo:
The nanowire and whisker heterostructures of tin dioxide were fabricated by the chemical vapor deposition technique. It was demonstrated that various structures of tin oxide can be obtained by controlling the thickness of gold layer and the partial pressure of source vapor at growing sites. 12.5 and 25 nm thicknesses are preferable for the epitaxial growth of nanowires and heterostructure through vapor-liquid-solid mechanism, respectively. The tin dioxide whiskers with core-shell structure were fabricated by vapor-solid mechanism. Meanwhile, the influences of various factors on the tin dioxide growth are also discussed.
Resumo:
Nitrogen-14 solid-state NMR (SSNMR) is utilized to differentiate three polymorphic forms and a hydrochloride (HCl) salt of the amino acid glycine. Frequency-swept Wideband, Uniform Rate, Smooth Truncated (WURST) pulses were used in conjunction with Carr-Purcell Meiboom-Gill refocusing, in the form of the WURST-CPMG pulse sequence, for all spectral acquisitions. The 14N quadrupolar interaction is shown to be very sensitive to variations in the local electric field gradients (EFGs) about the 14N nucleus; hence, differentiation of the samples is accomplished through determination of the quadrupolar parameters C