Papers by Keyword: Crystallite Size

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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.
Authors: Ali Shokuhfar, M.R. Dashtbayazi, M.R. Alinejad, Tolou Shokuhfar
Abstract: In this research work, a high-energy ball mill has been applied to prepare an Al/SiC nanocomposite. The formation mechanism of the nanocomposite was investigated. This nanocomposite contained the nanocrystalline characteristics. Crystallite size, lattice strain and particle size of the nanocomposite as a function of milling time were determined. SEM micrographs showed that the nanocomposite powders agglomerated after milling. The particle size analysis confirmed the agglomeration of the nanocomposite particles. TEM observations showed that the SiC particles were in the nanometer size and these particles embedded in the Al matrix, and the nanocomposite produced in the final stage of mechanical alloying. In addition, a simple model checked for the refinement of the crystallite and the particle size of nanocomposite.
Authors: V. Psycharis, N. Kalamakis, N. Boukos, C. Trapalis, A. Bourlinos, M. Karakasides
Authors: Rahmat Doni Widodo, A. Manaf, P. Sardjono
Abstract: Barium hexaferrite and strontium titanate are respectively well established permanent magnet and piezoelectric materials which are technologically and scientifically attractive due to their potential for various applications in the field of magnetic electronics functional materials. However, the material properties for both require a careful control of grain structure as well as microstructure design to meet specific applications. In this work, we report some results of materials characterization especially particles and crystallites in a BaFe12O19/SrTiO3 composite which were promoted during mechanical milling. The composite was synthesized using a planetary ball mill with a ball to powder ratio 10:1. Changing in the particle and crystallite-sizes at various milling time up to 60 hours are studied with the aid of particle-size analyzer and X-ray diffraction. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ~8 μm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean crystallite size of the particles was found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100 °C the millled powder transformed into particles of nanograin. The crystallite growth kinetics at isothermal temperatures follow the relaxation equation with the activation energy value for BHF (QBHF) and STO (QSTO) are respectively 73.63 kJ/mol and 122.69 kJ/mol.
Authors: S.C. Silva, José Hélio Duvaizem, Rubens Nunes de Faria, Hidetoshi Takiishi
Abstract: The first goal of this work involved the study of HDDR powders obtained from annealed alloys with the general formula: PrxFe77.9-xCo16B6Nb0.1 (x = 12; 12.5; 13; 13.5 and 14). The alloys were processed at desorption / recombination temperature of 840°C. The highest magnetic properties were obtained with 13.5 at. % Pr (Br= 1000mT and µ0iHc= 890mT). The alloy with a minimum praseodymium content (12 at. %) exhibited the lowest magnetic properties (Br= 350mT e iHc= 120mT). The second aim of the work involved the characterization of HDDR powders using X-ray diffraction for phase quantification and mean crystallite sizes determination of the hard magnetic phase. The processed powders were characterized by scanning electron microscopy (SEM).
Authors: Johar Banjuraizah, Zainal Arifin Ahmad
Abstract: CaCu2.8Co0.2Ti4O12 ceramics were prepared by microwave-assisted sol gel method. The properties of materials can be highly dependent on crystallite size therefore measuring the crystallite size is among the important part in materials research work. In the present study, the crystallite size of the CaCu2.8Co0.2Ti4O12 ceramics sintered at temperature ranged from 975-1125°C were investigated. Different methods, approach and strategy of crystallite size measurement were demonstrated in this papers.Keywords: Crystallite size, CCTO
Authors: Evon Y. Lin Foo, Sabar Derita Hutagalung
Abstract: The effect of chitosan as a capping agent on the synthesis of ZnS nanoparticles via wet chemical route was studied. The used of chitosan as a capping agent for ZnS nanoparticles had allow the synthesis to be carried out in water which is a more simple and environmental friendly. In dilute acetic acid, the amines in the chitosan will protonated to become NH3+ ions. The positive charges around the ZnS nanoparticles are then used to disperse the nanoparticles via electrostatic repulsion. Chitosan also has an effect on the size of produced nanoparticles. From the X-ray analysis found that the crystallite size of nanoparticles decreases with the increasing of the chitosan concentration. The increase in chitosan concentration will promote the growth of the nanoparticles and subsequently produced smaller nanoparticles.
Authors: J. Cornejo, Verónica Martínez, S. Ordoñez
Authors: Soheila Rahavi, Ahmad Monshi, Rahmatollah Emadi, Ali Doostmohammadi, Hamed Akbarian
Abstract: The study reported here focuses on the crystallite size of synthetic hydroxyapatite (HAp) obtained using sol-gel method and natural HAp obtained by processing the natural bone. Human and camel bones were used for obtaining natural HAp. HAp particles were produced, characterized and compared for their crystallite size. The average crystallite size of the samples was derived from the X-ray Diffraction (XRD) data using the Scherrer formula and a new method called modified scherrer equation that was came by developing the Scherrer formula. The results showed the crystallite size of HAp gained from different sources were different. The crystallite size of synthetic, human and camel bone-derived HAp, were approximately 18, 23 and 29 nanometer, respectively. These values were less than those obtained from TEM images. It seems that calculated crystallite size using XRD data and Scherrer equations is less than the real size. This important finding must be taken into consideration in applying Scherrer equations.
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