XRD Measurements (xrd + measurement)

Distribution by Scientific Domains


Selected Abstracts


Kinetics of liquid phase synthesis of ethyl tert -butyl ether from tert -butyl alcohol and ethanol catalyzed by ,-zeolite supported on monolith

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2002
S. Assabumrungrat
This paper compared the performance of ,-zeolite and Amberlyst-15 catalysts on a liquid phase synthesis of ethyl tert -butyl ether (ETBE) from ethanol (EtOH) and tert -butyl alcohol (TBA) ,-Zeolite was synthesized and deposited on monolith support. Its structure was confirmed by an XRD measurement and its composition was analyzed by an XRF measurement. It was found that even though the catalytic activity of ,-zeolite was lower than that of Amberlyst-15, the selectivity of ETBE was much higher than that of Amberlyst-15, resulting in almost the same level of ETBE yield. The dehydration of TBA to isobutene (IB) was the major side reaction. The kinetic study of the reaction catalyzed by ,-zeolite supported on monolith was carried out by using a semibatch reactor. The effect of external mass transfer was investigated by varying stirring speeds. The activity-based rate expressions were developed taking into account of water inhibition. Three temperature levels of 323, 333, and 343 K were performed in the study to obtain the parameters in the Arrhenius's equation and the Van't Hoff's equation. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 292,299, 2002 [source]


Study on the phase evolution of (Pb,Cu)Sr2(Y,Ca)Cu2Oz (z , 7)

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006
T. Maeda
Abstract The formation process of (Pb(1+x )/2Cu(1,x )/2)Sr2(Y1,xCax)Cu2Oz is investigated by means of X-ray diffractometory (XRD), thermal analysis and scanning electron microscopy for nominal compositions of x = 0,0.5. It is shown by XRD measurement that nearly single-phase samples are obtained at x = 0,0.4 by firing at 1000 °C in air for only 1 h. In the heating step, the existence of partial melting state slightly below the firing temperature is clearly observed in the results of differential thermal analysis. It is concluded that this causes the extremely rapid formation of this compound. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Control of orientation for carbazole group in comb copolymers arranged by method of organized molecular films

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2007
Hiroko Hoshizawa
Abstract We investigated the molecular orientation of organized molecular films with regard to solid-state structures for newly synthesized comb copolymers with N -vinylcarbazole (NVCz) by in-plane and out-of plane X-ray diffraction (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). In the bulk state, hydrogenated and fluorinated comb copolymers form side-chain crystals for a two-dimensional lattice spacing of 4.2 and 5.0,Å, respectively. The findings suggest that the carbazole rings in the main-chain are arranged in opposition to each other. From the results of the DSC measurement, sharp-shaped melting peaks appear on the relatively lower temperature side of the thermograms. This result supports the formation of side-chain crystals in the synthesized comb copolymers. These monolayers of the copolymers on the water surface were extremely condensed, except for the fluorocarbon:NVCz,=,1:1 copolymer. From the in-plane XRD measurement of multilayers on solids, the changes in the two-dimensional lattice structure of fluorinated comb copolymer films containing NVCz units, as opposed to their bulk state, were confirmed. It seems that these structural changes are caused by the stronger ,,, interaction between the carbazole rings rather than the van der Waals interaction between fluorocarbons. Copyright © 2007 John Wiley & Sons, Ltd. [source]


High Velocity Oxy Fuel Spraying of Cold Work Tool Steels- A Novel Approach to Thick Coatings for Wear Protection Applications,

ADVANCED ENGINEERING MATERIALS, Issue 12 2009
Arne Röttger
Abstract Within this work, HVOF sprayed coatings based on X220CrVMo13-4 cold work steel were applied to a S235JR construction steel substrate. The investigations focus on the influence of particle size and spray parameters on the coating microstructure, analyzed by means of optical microscope (OM) and scanning electron microscopy (SEM). Additional XRD measurements and micro hardness plots across the interface between substrate material and coating were carried out. Furthermore, the influence of particle size on the detected phases and coating porosity was studied. The results were compared with an X220CrMoV13-4 reference sample produced by HIP. [source]


Low-Temperature Fabrication of Oxide Composites for Solid-Oxide Fuel Cells

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2004
Hongpeng He
Composites of yttria-stabilized zirconia (YSZ) with Sr-doped LaCrO3 (LSC) and Sr-doped LaMnO3 (LSM) were prepared by impregnation of a porous YSZ matrix with aqueous solutions of the appropriate metal salts, followed by sintering to various temperatures. XRD measurements showed that perovskite phases formed after sintering at 1073 K, a temperature well below that at which solid-state reactions with YSZ occur. The conductivities of the LSC,YSZ and LSM,YSZ composites prepared in this way were maximized at a sintering temperature of 1373 K for LSC,YSZ and 1523 K for LSM,YSZ, although reasonable conductivities were achieved at much lower temperatures. The conductivities of the two composites increased much more rapidly with the content of the conductive oxide than has been found with conventional composites formed by mixing and sintering the oxide powders. The implications for using this approach to develop novel electrodes for SOFC applications are discussed. [source]


Formation Mechanism of Hydrous Zirconia Particles Produced by the Hydrolysis of ZrOCl2 Solutions: III, Kinetics Study for the Nucleation and Crystal-Growth Processes of Primary Particles

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001
Koji Matsui
The formation rate and primary particle size of monoclinic, hydrous zirconia particles produced by the hydrolysis of various ZrOCl2 solutions (with and without the addition of HCl, NH4OH, NaCl, CaCl2, or AlCl3) were measured to clarify the effects of the H+ and Cl, ion concentrations on the nucleation and crystal-growth processes of primary particles of hydrous zirconia. Chemical-kinetic analyses, to which Avrami,Erofeev's equation was applied, and XRD measurements revealed that both the rate constant and the primary particle size of the hydrous zirconia decreased as the concentrations of H+ and/or Cl, ions produced by hydrolysis increased. The nucleation rate per unit of ZrOCl2 concentration and the crystal-growth rate of the primary particles of the hydrous zirconia were determined by analyzing the relationships between the rate constant and primary particle size. The nucleation rate per unit of ZrOCl2 concentration revealed almost no change and remained constant as the H+ and/or Cl, ion concentrations increased, except in the case of a slight increase for ZrOCl2 solutions with added HCl. The crystal-growth rate decreased as the H+ and/or Cl, ion concentration increased. The present kinetic analyses revealed that the decrease in rate constant with increasing H+ and/or Cl, ion concentrations resulted from the decrease in the crystal-growth rate. The decreasing tendency of the crystal-growth rate was attributed to interference with crystal growth by the Cl, ions attracted onto the particle surface through the formation of an electric double layer. The formation mechanisms for the primary particles of hydrous zirconia were determined based on the present experimental results. [source]


Synthesis of Fluorinated Chitin Derivatives via Enzymatic Polymerization

MACROMOLECULAR BIOSCIENCE, Issue 10 2006
Akira Makino
Abstract Summary: Synthesis of fluorinated chitin derivatives has been achieved using chitinase from Bacillus sp. as a catalyst. 6,-Fluoro- (1a), 6-fluoro- (1b) and 6,6,-difluoro- (1c) chitobiose oxazoline derivatives were newly prepared as TSAS monomers for chitinase. Ring-opening polyaddition of these monomers proceeded effectively at pH 8.0,9.0 and 30,40,°C, giving rise to alternatingly 6-fluorinated chitin derivatives (2a and 2b) from 1a and 1b, and fully 6-fluorinated chitin derivative (2c) from 1c under total control of regioselectivity and stereochemistry. XRD measurements revealed that polysaccharides 2a and 2b had crystalline structures similar to that of , -chitin. [source]


In situ micro-Raman and X-ray diffraction study of diamonds and petrology of the new ureilite UAE 001 from the United Arab Emirates

METEORITICS & PLANETARY SCIENCE, Issue 7 2008
Dominik C. HEZEL
This is the first report of a meteorite in this country. The sample is heavily altered, of medium shock level, and has a total weight of 155 g. Bulk rock, olivine (Fo79.8,81.8) and pyroxene (En73.9,75.2, Fs15.5,16.9, Wo8.8,9.5) compositions are typical of ureilites. Olivine rims are reduced with Fo increasing up to Fo96.1,96.8. Metal in these rims is completely altered to Fehydroxide during terrestrial weathering. We studied diamond and graphite using micro-Raman and in situ synchrotron X-ray diffraction. The main diamond Raman band (LO = TO mode at ,1332 cm,1) is broadened when compared to well-ordered diamond single crystals. Full widths at half maximum (FWHM) values scatter around 7 cm,1. These values resemble FWHM values obtained from chemical vapor deposition (CVD) diamond. In situ XRD measurements show that diamonds have large grain sizes, up to >5 ,m. Some of the graphite measured is compressed graphite. We explore the possibilities of CVD versus impact shock origin of diamonds and conclude that a shock origin is much more plausible. The broadening of the Raman bands might be explained by prolonged shock pressure resulting in a transitional Raman signal between experimentally shock-produced and natural diamonds. [source]


MOVPE of InN films on GaN templates grown on sapphire and silicon(111) substrates

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008
Muhammad Jamil
Abstract This paper reports the study of MOVPE of InN on GaN templates grown on sapphire and silicon(111) substrates. Thermodynamic analysis of MOVPE of InN performed using NH3 as nitrogen source and the experimental findings support the droplet-free epitaxial growth of InN under high V/III ratios of input precursors. At a growth pressure of 500 Torr, the optimum growth temperature and V/III ratio of the InN film are 575,650 °C and >3 × 105, respectively. The surface RMS roughness of InN film grown GaN/sapphire template is ,0.3 nm on 2 ,m × 2 ,m area, while the RMS roughness of the InN film grown on GaN/Si (111) templates is found as ,0.7 nm. The X-ray diffraction (XRD) measurement reveals the (0002) texture of the InN film on GaN/sapphire template with a FWHM of 281 arcsec of the InN (0002) , rocking curve. For the film grown on GaN/Si template under identical growth conditions, the XRD measurements show the presence of metallic In, in addition to the (0002) orientation of InN layer. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


The effect of the film H content on the crystallization of laser processed and thermally annealed HWCVD a-Si:H

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3-4 2010
A. H. Mahan
Abstract We demonstrate the use of laser processing to affect the nucleation of crystallites in thermally annealed HWCVD a-Si:H thin films. The influence of film H content is investigated by XRD measurements during in situ 600 °C thermal anneal on both as grown films and on films that have been laser irradiated. All laser irradiated films show a reduced incubation time (,o) for crystallization compared to as-grown films, with the largest differences exhibited for samples with higher film H. We show that a recently developed model for a nucleation center in a-Si:H can be used to explain how the film H content affects this change in ,o and also predict the magnitude of this change with laser processing (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Growth of high-quality hexagonal InN on 3C-SiC (001) by molecular beam epitaxy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005
Hiroyuki Yaguchi
Abstract We have grown hexagonal InN (h-InN) films on 3C-SiC (001) substrates by RF-N2 plasma molecular beam epitaxy taking account of small lattice mismatch between h-InN (10-10) and 3C-SiC (110). It was found from X-ray diffraction (XRD) measurements that h-InN grows with h-InN (0001) || 3C-SiC (001) and h-InN (1-100) || 3C-SiC (110). XRD measurements also revealed that the h-InN epitaxial layers grown on 3C-SiC (001) are composed of single domain. Strong and sharp photoluminescence from the h-InN was clearly observed at around 0.69 eV. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Low and Wide Phase Transition Temperature Dimesogenic Compounds Consisting of a Cholesteryl and 4-(trans -4- n -Alkylcyclohexyl)phenoxy Mesogens

CHINESE JOURNAL OF CHEMISTRY, Issue 3 2006
Chun-Bo Zhang
Abstract Unsymmetrical dimesogenic compounds with cholesteryl and 4-(trans -4- n -alkylcyclohexyl)phenoxy parts were synthesized by condensation of cholester-3-yl 6-bromohexanoate with appropriate 4-(trans -4- n -alkylcyclohexyl)- phenols. Structures and thermal phase behaviour of these dimesogenic compounds have been confirmed by IR, 1H NMR, elemental analysis, DSC, polarity microscopy and XRD measurements. Their thermal phase behaviour was significantly different with that of other cholesterol-based dimesogens while they exhibited low and wide phase transition temperature. [source]