A novel geometry for powder X-ray diffraction (XRD), termed ‘focal construct geometry’ (FCG) is introduced and developed with both non-ideal samples and non-ideal sample conditions. FCG utilises an annular beam that has the unique feature of ‘focusing’ scattering maxima at single loci along a primary axis, hence offering diffraction data of enhanced intensity. This main advantage of FCG can be used within fields in need of rapid material identification, such as security screening in airports. A theoretical comparison between FCG and conventional transmission mode XRD showed that even though FCG suffers from broader diffraction peaks, an alternative approach to FCG data interpretation has the potential to provide narrower scattering maxima than conventional XRD. However, in order to employ this approach, discrimination between converging and diverging FCG scattering maxima is essential. Peak broadening was investigated by altering various aspects of FCG instrumentation components by either pencil beam XRD or FCG, indicating broad diffraction peaks independent of the beam geometry employed. Development of FCG resulted in the successful analysis of non-ideal samples, such as non-crystalline liquid samples, samples exhibiting preferred orientation and samples with large grain size, demonstrating advantages over conventional XRD. Furthermore, ideal samples (in terms of crystallinity, preferred orientation and grain size) were analysed by FCG under non-ideal conditions. This involved randomly orientating a single planar sample with respect to the primary axis, contrary to previous research that present FCG with a single planar sample normal to the primary axis. Sample rotation resulted in FCG scattering maxima with different xyz coordinates depending on the degree, axis and direction of rotation. Moreover, FCG analysis of multiple samples (normal to the primary axis) showed that as with all XRD arrangements, a priori knowledge of the samples’ position along the primary axis is required for effective data analysis. Investigation into the ability of FCG’s annular beam to act as a pre-sample coded aperture demonstrated an alternative method to interpret FCG images by recovering conventional XRD data. Additionally, two novel post-sample encoders (linear wire and Archimedean spiral) were considered. This enabled spatial discrimination of unknown samples along a primary axis and material identification for conventional XRD techniques. Combination of FCG with an absorbing edge post-sample encoder indicated discrimination between converging and diverging FCG scattering maxima. This ability can enable interpretation of single FCG images, as well as depth information of unknown samples within an inspection volume (e.g. airport luggage), hence enabling material identification. / © Cranfield University 2014

This thesis present photoluminescence spectroscopy and X-ray diffraction analyses of four different cadmium zinc telluride samples with different quality and features and similar zinc molar concentration of 10%. Photoluminescence spectroscopy of the samples let us obtain several physical parameters of the samples which are indicators of quality, composition, structure, and impurity levels of the samples. The band gap energy of the samples obtained from the photoluminescence spectra at low temperatures helped us to estimate zinc molar concentration of the samples. Temperature dependence of band gap energy in these samples has been analyzed and exciton-LO phonon interactions in the samples has been analyzed. From temperature dependence of full width at half maximum of the photoluminescence peak several parameters including concentration of impurity centers and inhomogeneity of the samples are determined and compared in order to check the quality of the samples. Thermal quenching of the photoluminescence peak has been analyzed and the processes which are associated with each parameter are determined and discussed. X-ray diffraction analyses of the sample for the location and width of the peaks have been analyzed and several characteristics of the samples including quality, lattice constant and zinc molar concentration of the samples are determined and compared. The parameters that are obtained from these analyses are compared with the ones from the photoluminescence spectra and showed a good agreement between the results of these two non-destructive characterization techniques. / Graduate / 0605 / 0544 / 0794

This thesis present photoluminescence spectroscopy and X-ray diffraction analyses of four different cadmium zinc telluride samples with different quality and features and similar zinc molar concentration of 10%. Photoluminescence spectroscopy of the samples let us obtain several physical parameters of the samples which are indicators of quality, composition, structure, and impurity levels of the samples. The band gap energy of the samples obtained from the photoluminescence spectra at low temperatures helped us to estimate zinc molar concentration of the samples. Temperature dependence of band gap energy in these samples has been analyzed and exciton-LO phonon interactions in the samples has been analyzed. From temperature dependence of full width at half maximum of the photoluminescence peak several parameters including concentration of impurity centers and inhomogeneity of the samples are determined and compared in order to check the quality of the samples. Thermal quenching of the photoluminescence peak has been analyzed and the processes which are associated with each parameter are determined and discussed. X-ray diffraction analyses of the sample for the location and width of the peaks have been analyzed and several characteristics of the samples including quality, lattice constant and zinc molar concentration of the samples are determined and compared. The parameters that are obtained from these analyses are compared with the ones from the photoluminescence spectra and showed a good agreement between the results of these two non-destructive characterization techniques. / Graduate / 0605 / 0544 / 0794

No description available.

This thesis covers three topics related to the field of crystal engineering. Three different approaches to improving the understanding of hydrogen bonding are covered; analysis of a family of related molecules, investigations of specific functional groups and a systematic, data-driven study of intramolecular hydrogen bonding patterns. Chapters 2 to 4 and chapter 11 cover the background theory to the different methods used to obtain the data discussed in the remainder of the thesis. X-ray and neutron diffraction techniques are discussed, along with sections describing the Cambridge Structural Database, which was used as a data source throughout this work, and a brief section on intermolecular forces. Crystal structure analyses of seventeen gem-alkynol molecules are given in chapters 5 to 10. The gem-alkynol functionality is particularly interesting for a study of intermolecular interactions as it is a combination of both a strong and weak hydrogen bonding group. The group of molecules was investigated with the aim of locating robust supramolecular motifs. The group is subdivided into sections containing molecules with similar structures and their packing patterns are discussed. The second experimental section, chapters 12 and 13, comprises statistical studies into the function of the azido and cyano functional groups as hydrogen bond acceptors. The technique used was to use the Cambridge Structural Database as a data source for the main analysis, then complement the results with simple theoretical calculations. The remaining chapter, 14, describes a systematic analysis of intermolecular hydrogen bonded motifs. A data-driven approach was designed which allows direct comparison of motifs by means of a probability ordered list.

About a hundred samples of y-manganese dioxide covering three materials coded SBP- A, Faradiser M and R2 have been reduced chemically by insertion of H through controlled additions of hydrazine hydrate solutions at about 1 °C. The H-inserted samples and the starting materials were subjected to chemical analysis for oxidation state, X-ray diffraction (XRD) for structure study and Fourier Transform Infrared (FTIR) spectroscopy to gain information on OH bonding. Additional techniques including FTIR spectroscopy at low temperature (~ -180 °C), electrode potential measurement and scanning electron microscopy (SEM) have also been applied. The intergrowth structure of the starting materials consisted of ramsdellite intercepted with pyrolusite layers, known as de Wolff faults, and quantified by the fraction of pyrolusite layers Pr. An additional structural parameter for these materials was the amount of micro twinning (Tw) across the 021/061 ramsdellite planes. This parameter, introduced by Pannetier, is given in percent. Values of (Pr , Tw) have been given as (0.41 , 17) for SBP-A, (0.70,10) for Faradiser M and (0.41, ~100) for R2. Upon H-insertion, the structure of the starting materials expanded homogeneously in a direction and to an extent which depended on the Pr and Tw parameters. Faradiser M, with high Pr and very low Tw, expanded homogeneously in the direction of the b lattice dimension up to an insertion level of 0.69 of s in MnOn/Hs. Above this level, the initial structure changed suddenly into the structure of the final product: the insertion then proceeded homogeneously in the new phase. The main changes were an expansion of the octahedra and a rotation leading to hinged tunnels. This is the first time that the existence of two solid solutions in the MnO2/H system has been noted. With SBP-A, the amount of microtwinning restricted the homogeneous expansion of SBP-A to s = 0.28, which occurred predominantly in the a direction. Further insertion broke the twinning boundary and formed a demicrotwinned phase of composition MnOn Ho.68 in which the tunnels were also hinged. Thereafter H-insertion proceeded heterogeneously from 0.28 to 0.68 in s. Above s = 0.68, the structure developed homogeneously towards that of the fully H-inserted product. The extensive microtwinning in R2 allowed for a homogeneous expansion, thought to be isotropic to maintain the microtwinned structure, up to s = 0.39. Higher insertion levels led to the expansion to proceed heterogeneously to a composition of MnOn Ho.63. Above s = 0.63, a new phase, the final product, was formed with fully demicrotwinned structure and fully hinged tunnels. R-insertion into y-manganese dioxide has never been reported to occur in three stages previously. The FTIR study at room temperature has shown absence of OH bond vibrations at insertion levels prior to the hinging of the tunnels, in contrast to their presence after the structure has rotated and the tunnels had hinged. This is seen as a strong indication of H mobility in the initial structure. The hinging is necessary for OH bonding as it brings the 02 and 01 oxygens closer allowing the proton to bond both covalently and by H-bonding. At low temperature, initially mobile hydrogen could be trapped and OR bonds formed only in H-inserted R2. This was linked to 061-microtwinning. The absence of OH bonds at low temperature in SBP-A and Faradiser M led to the conclusion that these materials have no 061 micro twinning faults. The absence of OH bonds at low temperature in the starting materials, particularly in R2, strongly questions the postulated OH groups in the structure of y-MnO2, according to the cation vacancy model. Electrode potential data supported the above conclusions in terms of the stages of the H-insertion. The battery activity of the materials seemed to be related to the extent at which the materials kept the initial structure with non-hinged tunnels. Comparison with previous works on the same materials suggested that the differences could be accounted for by the kinetics of the H-insertion. While protons in this work were released spontaneously on the surface of the MnO x , their diffusion into the bulk was slow due to the low temperature. In the compared literature, the reverse applies.

<p>In this study we report on the effect of the deposition parameters on the morphology and structural properties of CNTs, synthesized by means of the hot-wire chemical vapour deposition technique. SEM, Raman and XRD results show that the optimum deposition conditions for the HWCVD synthesis of aligned MWCNTs, with diameters between 50 and 150 nm and lengths in the micrometer range are: Furnace temperature of 500 &ordm / C, deposition pressure between 150 and 200 Torr, methane/hydrogen dilution of 0.67 and a substrateto- filament distance of 10 cm.</p>

Thesis (Ph.D)--University of Adelaide, 1955. / Typewritten copy.

Doctor of Philosophy / Department of Grain Science and Industry / Yong Cheng Shi / Wheat bran is a by-product of the wheat flour milling industry. The number of food products containing wheat bran is on the rise because it is a well-recognized good source of dietary fiber. Currently, bran is a low-value commodity used mostly in animal feed, but it has the potential for more extensive applications. To understand the functional and nutritional properties of wheat bran and better use wheat bran in food, it is critical to understand the physical structure of wheat bran. For the first time, solid-state ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance (¹³C CP/MAS NMR), X-ray diffraction (XRD), and small angle X-ray scattering (SAXS) were used to study the physical structure of wheat bran and its dissected layers. The XRD and Solid-State ¹³C CP/MAS NMR both confirmed the presence of crystalline cellulose in untreated bran, enzymatically treated bran, and dissected bran layers. Destarched and deproteinized wheat bran (DSDPB) was treated with a mixture of either 7 or 9% sodium hydroxide and 12% urea solvent and structure of the extracted polymers was investigated. Three and 6 cycle dissolution schemes, were examined involving the repeated cooling of the solvent bran mixture to -12.6 °C and then agitating it at 25 °C. When 7% NaOH/12% urea (6 cycle) was applied to DSDPB, 84.1% of the material was solubilized including 89.8% of the arabinoxylans (AX). This procedure recovered more wheat bran AX for characterization than any previous study using alkaline dissolution. Wheat bran was enzymatically and hydrothermally treated to maximize the soluble fraction. Unlike previous research, the starch and protein were kept and not removed before endoxylanase treatment. The retained protein and glucose polymers (starch, β-glucan, cellulose) could provide functional benefits in addition to the arabinoxylan and could make the process more economical. Wheat bran hydrolyzed with thermostable α-amylase, protease, and xylanase was the recommended treatment. The combined solubles had a viscosity of 23 cP (10% w/w solids) and ranged in estimated molecular weight from ~600 to 20,000. The percentage of untreated wheat bran AX that was solubilized was 50% and the percentage of AX in the solubles was 23%.

No description available.