Papers by Keyword: Crystallinity

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Authors: Tabet A. Tamer, Fauziah Abdul Aziz, Radiman Shahidan
Abstract: The purpose of this study was to develop practical and reliable small-angle x-ray scattering and x-ray diffraction methods to study the nanostructure of the wood cell wall and to use these methods to systematically study the nanostructure of Acacia mangium wood grown in Sabah, Malaysia. Methods to determine the microfibril angle (MFA) distribution, the crystallinity of wood, and the average size of cellulose crystallites were developed and these parameters were determined as a function of the tree age and the distance from pith towards the bark. The mean MFA in Acacia mangium increases rapidly as a function of the number of the year and after the 7th year-old it varies between 6° and 10°. The thickness of cellulose crystallites for Acacia mangium appears to be constant as a function of the tree age after 10-year-old. The obtained mean value is 3.20 nm. The size of the cellulose crystallites was also quite constant after 11 year-old. The maximum value of the width of the crystallites for Acacia mangium was 2.34 nm at the pith region, while the minimum value was 0.290 nm at the bark region. The mass fraction of crystalline cellulose in wood is the crystallinity of wood and the intrinsic crystallinity of cellulose. The crystallinity of wood increases from the 3nd year-old to the 10th year-old from the pith and is constant after the 10th year.
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Authors: Jie Zhang, Hua Zhang, Jian Chun Zhang
Abstract: As to demonstrate the effect of treatment temperature on hemp fibre, this article recorded and compared the change of supramolecular structure and properties of hemp fibre under different processing temperature (150°C and -30°C). The result shows: the change of processing temperature can affect the crystallinity of hemp fibre, with the rise of treatment time, the crystallinity of fiber increases at high temperature and is contrary at low temperature. Meantime, the degree of thermodynamic change is higher at low processing temperature than that of high temperature. Furthermore, with the rise of treatment time, the moisture regain of fibre fluctuates under high temperature and rises under low temperature.
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Authors: Xiang Ju Meng, Tatsuo Kimura, Tatsuki Ohji, Kazumi Kato
Abstract: Semi-crystalline mesoporous titania films were prepared by the reactions of titanium isopropoxide (TTIP) in acidic aqueous solutions containing EO106PO70EO106 triblock copolymer (F127) and 1,3,5-triisopropylbenzene (TIPBz). Adsorption experiments of dye molecules over the mesoporous films calcined at different temperatures and prepared with different TTIP/F127 molar ratios showed that adsorption property of the dye molecules would be related to the crystallinity of the frameworks and the macroporosity at the surfaces.
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Authors: Zhao Qun Du, Yun Xu, Wei Dong Yu
Abstract: Polylactic fiber is a new environment-friendly fiber and has wide application, while there are few studies on its characters and structures. The main content in present paper is to analyze element content and functional group as well as thermal properties. The elementary analysis method shows that the contents of C, H and O elements are 49.83%, 5.63% and 44.54%, respectively; it has good accordance with the theoretical results. Gas chromatography mass spectrum method proves that the functional groups of PLA fiber are lactide and acetaldehyde as well as 2,3-pentanedione, and whose total content is larger than 70%. IR spectroscopy depicts that there exist significant absorbing peaks by -C=O-, -C-O-, -OH- within 1000cm-1-1300cm-1, and -C=O- within 1000cm-1-1300cm-1. The absorbing peak of ultraviolet spectrum is 260 nm avelength. Crystallinity is 61.72% and orientation degree is 93.36% and 84.30% in Full Wave at Half Maximum and in Area calculations based on X-ray. These results will be greatly helpful in the qualitative analysis and indectification of Polylactic fiber.
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Authors: Yan Qi Liu, Xin Xin Xiao, Hong Li, Xue Hong Li, Liu Zhi Yang
Abstract: By means of non-aqueous solvent, V-type amylose-hexanol complex which B-type microcrystalline starch made a combination with hexanol was prepared. Study the influence of the reaction temperature, dropping time and cooling temperature on the V-type complexes’ crystallinity. The optimal synthetic conditions were found through the single factor experiment as follows:reaction temperature at 70°C, dropping time of 6min, cooling to room temperature. V-type complex was prepared under optimum conditions, the highest crystallinity reached 73.7%.
1827
Authors: Masahiro Toyoda, Beata Tryba, Fumi Koujin, Tomoki Tsumura, Michio Inagaki
Abstract: Carbon-coated TiO2 photocatalysts were prepared by a simple heat treatment of the powder mixtures of anatase-type TiO2 with PVA at a temperature of 700 and 900 oC in a N2 atomosphere. Diffuse optical reflectance spectra for carbon-coated TiO2 showed the absorption edge for anatase structure clearly, overlapping with absorption due to coated carbon over whole range of wavelegth. These carbon-coated TiO2 photocatalysts had relatively high apparent BET surface area, from 50 to 170 m2/g, which suggested the formation of porous carbon layers, and showed relatively high adsorption of various pollutants, methylene blue (MB), reactive black (RB-5), phenol (Ph) and iminoctadine triacetate (IT), in water. Photocatalytic activity of carbon-coated TiO2 thus prepared was evaluated through the determination of the rate constant for the decomposition of different pollutants in water. Rate constant values were strongly depend on the pollutants, but their dependence on the crystallinity of TiO2 phase. The relations between adsorptivity and rate constant for four pollutants looked similar with each other, and the pollutants adsorbed in the larger amount was decomposed with the higher rate. Adsorptivity of carbon-coated TiO2 photocatlysts was determined and discussed on the relations to BET surface area, amount of carbon coated and also rate constant k for the decomposition of MB, RB5, Ph and IT. Adsorptivity of carbon-coated catalysts depends strongly on the adsorbate (pollutant) but also on the surface nature of carbon layer on TiO2 particles. The relations between adsorptivity and rate constant k for four pollutants looked similar, suggesting that the pollutant adsorbed in the larger amount being decomposed with the higher rate.
180
Authors: Zhen Hong, Alexandre Mello, L. Luan, Marcos Farina, L.R. Andrade, C.L. Ferreira, S. Paik, B. Deng, J.G. Eon, J. Terra, Antonella M. Rossi, Donald E. Ellis, J.B. Ketterson
Abstract: Crystalline hydroxyapatite thin coatings have been prepared using a novel opposing RF magnetron sputtering approach at room temperature. X-ray diffraction (XRD) analysis shows that all the principal peaks are attributable to HA, and the as-deposited HA coatings are made up of crystallites in the size range of 50-100nm. Fourier transform infrared spectroscopy (FTIR) studies reveal the existence of phosphate, carbonate and hydroxyl groups, suggesting that HA coatings are carbonated. Finally, in vitro cell culture experiments have demonstrated that murine osteoblast cells attach and grow well on the as-sputtered coatings. These results encourage further studies of hydroxyapatite thin coatings prepared by the opposing RF magnetron sputtering approach as a promising candidate for next-generation bioimplant materials.
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Authors: Vita Zalite, Janis Locs
Abstract: In current research three different prepared calcium deficient hydroxyapatite samples were evaluated for dental application. Lyophilized (lyoCDHAp), spray dried (spCDHAp) powders and wet precipitates (pCDHAp) were characterized by XRD, FTIR, SEM and BET analysis. Results showed, that various drying processes did not affect initial crystallinity, phase and chemical composition of samples. Small agglomerates (up to 2 μm) beside separated particles for lyoCDHAp and spCDHAp were observed in SEM analysis. LyoCDHAp and spCDHAp powders could be used as desensitizing component in the dentifrice, while pCDHAp could be more resorbable due to smaller particle size and induce remineralization of caries sites in the enamel.
139
Authors: Xu Dong Luo, Dian Li Qu, Guo Dong Zhang, Hai Xiao Liu
Abstract: Mg-Al spinel has been synthesized by using alkali corrosion slag from aluminum profile factory, decomposed magnesite and used MgO-C brick as the main raw materials. The influence of decomposed magnesite and used MgO-C brick powder after calcinations process on crystalline constitution and micro-morphology of synthesized Mg-Al spinel specimens are discussed. The synthesized specimens are characterized by XRD and SEM, and the crystallinity of crystalline phase is calculated by X' Pert plus software. The experimental result shows that the crystalline phase periclase increases with the increasing of magnesia generated by used MgO-C brick powder. The crystallinity of crystalline phase is maximum when the addition of used MgO-C brick powder after calcined at 800°C is 30wt%. Magnesia generated by sintering decomposed magnesite powder at 700°C showed more effective than magnesia generated by used MgO-C brick powder to react with impurity in alkaline corrosion slag.
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