XRD Patterns (xrd + pattern)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science


Selected Abstracts


Low temperature hydrothermal growth and optical properties of ZnO nanorods

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2009
J. H. Yang
Abstract Well-faceted hexagonal ZnO nanorods have been synthesized by a simple hydrothermal method at relative low temperature (90C) without any catalysts or templates. Zinc oxide (ZnO) nanorods were grown in an aqueous solution that contained Zinc chloride (ZnCl2, Aldrich, purity 98%) and ammonia (25%). Most of the ZnO nanorods show the perfect hexagonal cross section and well-faceted top and side surfaces. The diameter of ZnO nanorods decreased with the reaction time prolonging. The samples have been characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurement. XRD pattern confirmed that the as-prepared ZnO was the single-phase wurtzite structure formation. SEM results showed that the samples were rod textures. The surface-related optical properties have been investigated by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements showed each spectrum consists of a weak band ultraviolet (UV) band and a relatively broad visible light emission peak for the samples grown at different time. It has been found that the green emission in Raman measurement may be related to surface states. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Effect of Calcination Conditions and Excess Alkali Carbonate on the Phase Formation and Particle Morphology of Na0.5K0.5NbO3 Powders

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2007
Pornsuda Bomlai
Sodium-potassium niobate [Na0.5K0.5NbO3] powders were prepared following the conventional mixed oxide method. An orthorhombic XRD pattern, consistent with single-phase Na0.5K0.5NbO3, was obtained after calcination at 900C for 6 h. Introducing 5 mol% excess Na2CO3 and K2CO3 into the starting mixture allowed milder calcination conditions to be used, for example 800C for 2 h. Primary particles in 5 mol% excess samples were cuboid, with maximum sizes of ,2.5 ,m. Equiaxed 0.3,0.4-,m particles were formed for non-excess powders, and also for powders prepared with 1 and 3 mol% excess alkali carbonates. The results suggest liquid formation during calcination of the excess 5-mol% starting powders. [source]


Polystyrene/Montmorillonite Nanocomposites Prepared by In Situ Intercalative Polymerization: Influence of the Surfactant Type

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2004
Hisham A. Essawy
Abstract Summary: Na-montmorillonite (MMT) with a cation exchange capacity (CEC) of 90 meq/100 g was converted to MMT-CTAB and MMT-CPC by the intercalation of cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC), respectively. The intercalation of CPC onto the basal space of the montmorillonite expanded the basal space from 12.19 to 21.47 , whereas in the case of CTAB, the spacing was only expanded to 19.35 . The MMT-CPC and MMT-CTAB forms were subsequently used as hosts for the preparation of polystyrene nanocomposites via intercalative free-radical polymerization of styrene. Different structures were obtained by varying the preparation conditions; the exfoliated and intercalated nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and differential scanning calorimeter (DSC). The produced nanocomposites exhibited improved thermal stability in comparison with that of pure polystyrene above 400,C especially in the case of the nanocomposites based on the MMT-CPC, in which intercalation exists. A glass transition temperature (Tg) could not be detected for the prepared nanocomposites using DSC; this was assumed to result from the restricted molecular motion of the polymer chains. XRD pattern of PS nanocomposites prepared by intercalative polymerization. [source]


Bulk GaN single crystal growth for substrate by solvent-thermal method

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2004
T. I. Shin
Abstract We grew bulk GaN single crystals by solvent-thermal method. GaN single crystals were synthesized at 600,800 C and 6,8 MPa of N2 gas for 200 h. We used 99% pure Na as a flux. The mole fraction of Na / (Na+Ga) were 0.30,0.67. A pyramid GaN single crystal having a size of 1,3 mm grew on the bottom and wall of a sintered BN crucible. We confirmed wurtzite structure GaN which was grown single crystal through XRD pattern. The chemical composition was investigated by EPMA. Raman spectroscopy yielded narrow peaks representing only the modes allowed for the wurtzite structure. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Role of structural modification on the electrical properties of poly(ethylene terephthalate) irradiated with 90-MeV carbon ion beam

POLYMER ENGINEERING & SCIENCE, Issue 6 2008
A. Srivastava
Thin films of poly(ethylene terephthalate) (PET) having a thickness of 100 ,m were exposed to different ion fluence of swift heavy ions of carbon in the range of 5 1011 , 5 1013 ions/cm2. The effect of ion beam on structural and electrical modification has been studied by UV/vis, FTIR, X-ray diffraction (XRD), Differential Scanning Calorimetery (DSC), and AC electrical measurement techniques. On irradiation, a shift in absorption wavelength toward the red end of spectrum with increase of ion fluence was observed. The intensity of crystalline IR bands and main diffraction peak in XRD pattern were found to decrease with increase in ion fluence. It indicates the loss of crystallinity induced by ion-beam irradiation. The crystallite size was found to increase on irradiation. The melting temperature (Tm) of PET films increased at a low ion dose (5.0 1012 ions/cm2), while it decreased at higher ion fluence (50.0 1012 ions/cm2). The dielectric constant (,,) of PET films was increased with increase of ion fluence. The modifications brought about in the dielectric constant are correlated with chemical and molecular structural changes occurring on irradiation. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers. [source]


Intercalation and exfoliation of talc by solid-state shear compounding (S3C) using pan-mill equipment

POLYMER ENGINEERING & SCIENCE, Issue 4 2005
Weiguo Shao
The intercalation and exfoliation of talc have been realized by solid-state shear compounding (S3C) using pan-mill equipment that can exert fairly strong shear forces and has multifunctions such as pulverizing, mixing, and activation on materials. The structural features of pan-mill also show prospective in delaminating layered minerals. The morphology and structure of talc were investigated by using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characteristic peaks of talc interlayer spacing disappeared in the XRD pattern of PP/talc composite prepared by S3C, however, still remained in the XRD pattern of PP/talc prepared by the conventional mixing method. TEM confirms the intercalated and exfoliated structure of talc, and the well dispersion of talc in the PP matrix after talc and PP were co-milled. S3C is a new approach to prepare polymer/layered inorganic filler nanocomposite and has characteristics such as a simple process that needs neither organic ligands nor solvent. POLYM. ENG. SCI. 45:451,457, 2005. 2005 Society of Plastics Engineers. [source]


Synthesis and properties of magnetite/poly (aniline-co-8-amino-2-naphthalenesulfonic acid) (SPAN) nanocomposites

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2007
Kakarla Raghava Reddy
Abstract Composites were prepared by incorporating magnetite (Fe3O4) nanoparticles into the matrix of a sulfonated polyaniline (SPAN) [poly(aniline-co-8-amino-2-naphthalenesulfonic acid) PANSA] through chemical oxidative polymerization of a mixture of aniline and 8-amino-2-naphthalenesulfonic acid in the presence of magnetite nanoparticles. The composite, magnetite/SPAN(PANSA) was characterized by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), elemental analysis (EA), Fourier transform infrared (FT-IR) spectra, UV-vis spectroscopy, thermogravimetric analysis (TGA), conductivity and magnetic properties measurements. TEM image shows that magnetite nanoparticles were finely distributed into the SPAN matrix. XRD pattern of the nanocomposite reveals the presence of additional crystalline order through the appearance of a sharp peak at ,43 and 71. Conductivity of the nanocomposite (0.23,S/cm) is much higher than pristine copolymer (1.97,,10,2,S/cm). The results of FT-IR and UV-visible spectroscopy reveal the presence of molecular level interactions between SO groups in SPAN and magnetite nanoparticles in the composite. Copyright 2006 John Wiley & Sons, Ltd. [source]


Flux growth of La-doped lead zirconate stannate titanate antiferroelectric crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2008
Lin Wang
Abstract Relaxor antiferroelectric single crystals lead lanthanum zirconate stannate titanate (PLZST) with the composition around the morphotropic phase boundary (MPB) have been grown by flux method using 50 wt% PbO-PbF2 -B2O3 as a flux. The obtained crystals are light yellow in color. The XRD patterns revealed that the habitual faces of the obtained crystal are (001). The crystal morphology was studied and related to a layer growth mechanism controlled by two-dimensional growth. The chemical composition of as-grown crystal was analyzed by inductively coupled plasma atomic emission spectrometry (ICP), indicating a slight decrease of the amount of Ti compared to the starting materials. The result was verified by the XRD patterns with the phase transformation from the co-existence of tetragonal and rhombohedra phases to the single tetragonal phase. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Growth of ZnO single crystals by an induced nucleation from a high temperature solution of the ZnO-PbF2 system

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2007
Xinhua Li
Abstract To grow ZnO single crystals from a high temperature solution of the ZnO-PbF2 system, a gas cooling system was assembled at the bottom of the crucible to induce nucleation in the initial growth stage. The growth experiments were carried out in a homemade vertical Bridgman furnace and Pt crucible of 28 mm in diameter was used. The furnace temperature was set to 1100C and the flow rate of the oxygen gas was optimized as 3.0 l/min. ZnO crystal up to 5,8mm in the thickness was obtained with the lowering rate of 0.3 mm/h. XRD patterns showed that the as-grown crystal was pure ZnO Wurtzite phase. The impurity ions were analyzed by the glow discharge mass spectroscopy (GDMS) as 390.0 ppm and 40.0 ppm for Pb2+ and F - , respectively. ( 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Towards Understanding of the Selective Precipitation of Alkali Metal Cations in Presence of Dipicrylamine Anion

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2005
Suresh Eringathodi
Abstract Dipicrylamine anion (DPA,) precipitates out [K(DPA)] with high selectivity from salt bitterns containing Na+, K+, and Mg2+, whereas the same ligand shows poor selectivity towards K+ , and much higher selectivity towards Cs+ , in studies conducted with a mixture of K+, Rb+, and Cs+. Their single-crystal structures reveal that the K+ and Rb+ salts have similar layered structures, with 8 oxygen atoms from seven DPA, anions encapsulating the metal cation, whereas the Cs+ salt possesses a channel-like structure with the metal ion encapsulated by ten oxygen atoms from six DPA,. The conformation of DPA, in the [Cs(DPA)] single crystal matches closely that of DPA in crystalline state. MO and intermolecular C,HO interactions together stabilize the structures. The 133Cs NMR spectrum of the poorly soluble [Cs(DPA)] shows an upfield shift of the peak with respect to CsCl as a result of the interaction with the oxygen atoms of DPA,, whereas 23Na NMR spectrum of the highly soluble [Na(DPA)] shows no such upfield shift compared to NaCl. Powder XRD patterns of bulk [M(DPA)] (M = K+, Rb+, and Cs+) precipitates show that these are similar to the patterns obtained by simulation of the single-crystal X-ray data. The selectivity of precipitation correlates qualitatively with the size and hydration enthalpies of the ions. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]


Preparation and Tribological Properties of Inorganic Fullerene-like MoS2,

ADVANCED ENGINEERING MATERIALS, Issue 4 2006
Z. Zou
The decomposition temperature had little effect on the particle size with the addition of surface agent. It was just the crystallization that different from each other. With increasing the temperature, the peak width of XRD patterns sharpened, indicating that the crystallization of MoS2 particles went better. [source]


Combined First-Principle Calculations and Experimental Study on Multi-Component Olivine Cathode for Lithium Rechargeable Batteries

ADVANCED FUNCTIONAL MATERIALS, Issue 20 2009
Hyeokjo Gwon
Abstract The electrochemical properties and phase stability of the multi-component olivine compound LiMn1/3Fe1/3Co1/3PO4 are studied experimentally and with first-principles calculation. The formation of a solid solution between LiMnPO4, LiFePO4, and LiCoPO4 at this composition is confirmed by XRD patterns and the calculated energy. The experimental and first-principle results indicate that there are three distinct regions in the electrochemical profile at quasi-open-circuit potentials of ,3.5,V, ,4.1,V, and ,4.7,V, which are attributed to Fe3+/Fe2+, Mn3+/Mn2+, and Co3+/Co2+ redox couples, respectively. However, exceptionally large polarization is observed only for the region near 4.1,V of Mn3+/Mn2+ redox couples, implying an intrinsic charge transfer problem. An ex situ XRD study reveals that the reversible one-phase reaction of Li extraction/insertion mechanism prevails, unexpectedly, for all lithium compositions of LixMn1/3Fe1/3Co1/3PO4 (0,,,x,,,1) at room temperature. This is the first demonstration that the well-ordered, non-nanocrystalline (less than 1% Li,M disorder and a few hundred nanometer size particle) olivine electrode can be operated solely in a one-phase mode. [source]


Microarchitectural and Physical Changes During Fetal Growth in Human Vertebral Bone,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 4 2003
S Nuzzo
Abstract The ossification process in human vertebra during the early stage of its formation was studied by X-ray diffraction (XRD) and X-ray microtomography (,CT) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. Twenty-two samples taken from vertebral ossification centers of human fetal bone (gestational age ranging between 16 and 26 weeks) were investigated. The analysis of three-dimensional images at high spatial resolution (,10 and ,2 ,m) allows a detailed quantitative description of bone microarchitecture. A denser trabecular network was found in fetal bone compared with that of adult bone. The images evidenced a global isotropic structure clearly composed of two regions: a central region (trabecular bone) and a peripheral region (immature bone). XRD experiments evidenced hydroxyapatite-like crystalline structure in the mineral phase at any fetal age after 16 weeks. Interestingly, the analysis of XRD patterns highlighted the evolution of crystalline structure of mineralized bone as a function of age involving the growth of the hydroxyapatite crystallites. [source]


Preparation of LiMn2O4 powders via spray pyrolysis and fluidized bed hybrid system

AICHE JOURNAL, Issue 7 2006
Izumi Taniguchi
Abstract A novel technique has been developed to directly produce fine ceramic powders from liquid solution using a spray pyrolysis and fluidized bed hybrid system. Using this technique, the preparation of lithium manganese oxides LiMn2O4, which are the most promising cathode materials for lithium-ion batteries, has been carried out for various superficial gas velocities U0 = 0.30-0.91 m/s, static bed heights Ls = 50-150 mm, and medium particle sizes dpm,g = 294-498 ,m. The resulting powders had spherical nanostructured particles that comprised primary particles with a few tens of nanometer in size, and they exhibited a pure cubic spinel structure without any impurities in the XRD patterns. Moreover, the as-prepared powders showed better crystallinity and smaller specific surface area than those by conventional spray pyrolysis. The effects of process parameters on powder properties, such as specific surface area and crystallinity, were investigated for a wide range of superficial gas velocities and static bed heights. An as-prepared sample was used as cathode active materials for lithium-ion batteries and the cell performance has been investigated. Test experiments in the electrochemical cell Li/1M LiClO4 in PC/LiMn2O4 demonstrated that the sample prepared by the present technique was superior to that by the conventional spray pyrolysis and solid-state reaction method. 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]


Fabrication of poly(aniline- co -pyrrole) hollow nanospheres with Triton X-100 micelles as templates

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2008
Chuanqiang Zhou
Abstract A one-step route has been reported for the fabrication of poly(aniline- co -pyrrole) (PACP) copolymer hollow nanospheres via the oxidation polymerization of a mixture of aniline and pyrrole in the presence of Triton X-100. It was found that the variations in polymerization conditions, such as the concentrations of Triton X-100 and comonomers, and [pyrrole]/[aniline] molar ratios, could change the size and uniformity of copolymer hollow nanospheres. The result of DLS has attested the presence of the spherical Triton X-100 micelles swelled by the comonomers in reaction system, and such micelles might play template for the formation of hollow nanospheres, followed by developing a possible formation mechanism. The chemical structures and crystallinity of products were characterized by FTIR, UV,visible, 1H NMR spectra, and XRD patterns, respectively, to prove the copolymer chemical structures of hollow nanospheres. The thermal-stability and solubility of PACP were improved compared with homopolymers (polyaniline and pyrrole). 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3563,3572, 2008 [source]


UV Raman spectroscopic study on the phase transformation of ZrO2, Y2O3,ZrO2 and SO42,/ZrO2

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2002
Can Li
The phase evolution of zirconia (ZrO2), sulfated zirconia (SO42,/ZrO2) and yttrium oxide incorporated zirconia (Y2O3,ZrO2) from the tetrahedral phase to the monoclinic phase was studied using UV Raman spectroscopy, visible Raman spectroscopy and x-ray diffraction (XRD). It is clearly observed that there are discrepancies between the results from the UV Raman spectra, visible Raman spectra and XRD patterns. The phase change from tetragonal to monoclinic is always earlier or at lower calcination temperatures as observed by UV Raman spectroscopy than by visible Raman spectroscopy and XRD. UV Raman spectroscopy is found to be more sensitive at the surface region while visible Raman spectroscopy and XRD supply the information mainly from the bulk. The inconsistency in the results from the three techniques suggests that the phase transformation of zirconia starts from its surface region and then gradually develops into its bulk. For SO42,/ZrO2 and Y2O3,ZrO2, the transformation from the tetragonal to the monoclinic phase is significantly retarded owing to the presence of the sulfated groups and the yttrium oxide. Particularly, the tetragonal phase of Y2O3,ZrO2 can be maintained up to 800 C although its phase at the surface region changed into monoclinic at 500 C. Copyright 2002 John Wiley & Sons, Ltd. [source]


High-Temperature Crystalline Phases in Nylon 6/Clay Nanocomposites

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2005
Xiaohui Liu
Abstract Summary: Nylon 6/clay nanocomposites (N6CN) with different cooling histories were investigated by differential scanning calorimetry (DSC) and variable-temperature X-ray diffraction (XRD). Above the melting temperature, new endothermic peaks appeared in the DSC trace for N6CN. All the neat nylon 6 samples presented amorphous XRD patterns when heated up to the melting range. However, for N6CN samples, undefined crystalline structures remained in the substantially molten polymer matrix up to 300,C. XRD patterns of a quenched nylon 6 sample annealed at 210,C and N6CN samples annealed at 210, 230, and 300,C, respectively. [source]


Rietveld analysis of X-ray powder diffraction patterns as a potential tool for the identification of impact-deformed carbonate rocks

METEORITICS & PLANETARY SCIENCE, Issue 11 2009
Sarah A. Huson
Entire XRD patterns, single peak profiles and Rietveld refined parameters of carbonate samples from the Sierra Madera impact crater, west Texas, unshocked equivalent samples from 95 miles north of the crater and the Mission Canyon Formation of southwest Montana and western Wyoming were used to evaluate the use of X-ray powder diffraction as a potential tool for distinguishing impact deformed rocks from unshocked and tectonically deformed rocks. At Sierra Madera dolostone and limestone samples were collected from the crater rim (lower shock intensity) and the central uplift (higher shock intensity). Unshocked equivalent dolostone samples were collected from well cores drilled outside of the impact crater. Carbonate rocks of the Mission Canyon Formation were sampled along a transect across the tectonic front of the Sevier and Laramide orogenic belts. Whereas calcite subjected to significant shock intensities at the Sierra Madera impact crater can be differentiated from tectonically deformed calcite from the Mission Canyon Formation using Rietveld refined peak profiles, weakly shocked calcite from the crater rim appears to be indistinguishable from the tectonically deformed calcite. In contrast, Rietveld analysis readily distinguishes shocked Sierra Madera dolomite from unshocked equivalent dolostone samples from outside the crater and tectonically deformed Mission Canyon Formation dolomite. [source]


A detailed comparison of CVD grown and precursor based DWCNTs

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2008
R. Pfeiffer
Abstract Double-wall carbon nanotubes (DWCNTs) grown directly via a CVD method and DWCNTs produced by annealing C60 and ferrocene filled single-wall carbon nanotubes were studied with X-ray diffraction (XRD) and Raman spectroscopy. The samples showed the typical XRD patterns of hexagonally bundled tubes. The frequencies and linewidths of the inner tube radial breathing modes (RBMs) were (with in experimental precision) equal in all three samples only the intensities differed. Finally, all samples showed the typical clustering of the inner tube RBMs due to the distribution of inner-outer tube pairs. The only difference was the population of specific inner-outer tube pairs where the CVD and ferrocene based DWCNTs were rather similar and both differed from the C60 based DWCNTs. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Impact modified polyamide-6/organoclay nanocomposites: Processing and characterization

POLYMER COMPOSITES, Issue 2 2008
Isil Isik
The effects of melt state compounding of ethylene-butyl acrylate-maleic anhydride (E-BA-MAH) terpolymer and/or three types of organoclays (Cloisite 15A, 25A, and 30B) on thermal and mechanical properties and morphology of polyamide-6 are investigated. E-BA-MAH formed spherical domains in the materials to which it is added, and increased the impact strength, whereas the organoclays decreased the impact strength. In general, the organoclays increased the tensile strength (except for Cloisite 15A), Young's modulus and elongation at break, but the addition of E-BA-MAH had the opposite effect. XRD patterns showed that the interlayer spacing for the organoclays Cloisite 25A and Cloisite 30B increased in both polyamide-6/organoclay binary nanocomposites and in polyamide-6/organoclay/impact modifier ternary systems. TEM analysis showed that exfoliated-intercalated nanocomposites were formed. The crystallinities of polyamide-6/organoclay nanocomposites were in general lower than that of polyamide-6 (except for Cloisite 15A). In ternary nanocomposites, crystallinities generally were lower than those of polyamide-6/organoclay nanocomposites. Cloisite 15A containing ternary nanocomposites had higher tensile and impact strengths and Young's modulus than the ternary nanocomposites prepared with Cloisite 25A and Cloisite 30B, owing to its surface hydrophobicity and compatibility with the impact modifier. POLYM. COMPOS., 2008. 2007 Society of Plastics Engineers [source]


Effects of interactions among polyaniline, camphorsulfonic acid and silica on the structure and properties of their conductive hybrids

POLYMER ENGINEERING & SCIENCE, Issue 3 2008
Hsun-Tsing Lee
In this work, the effects of interactions among polyaniline (PAn), camphorsulfonic acid (CSA), and silica on the structure and properties of their sol-gel hybrids are investigated. These interactions were revealed by FTIR, UV,vis spectra, and XRD patterns. The interaction between PAn and CSA raises conductivities of the CSA-doped PAn/SiO2 (c-PAn/SiO2) hybrids. Moreover, the hydrogen bonding interaction between c-PAn and silicic acid (precursor of SiO2) leads to a less degree of three-dimensional network structure of the SiO2 component in a hybrid with higher PAn content. In addition, because of the interactions among CSA, Pan, and SiO2, the conductive c-PAn-rich phase distributes uniformly in the hybrid and thermal resistance of the hybrid is enhanced consequently. Besides, the c-PAn/SiO2 hybrid with higher SiO2 content exhibits more significant blue-shift of its polaron band, lower conductivity, and higher thermal resistance. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers [source]


Structural Characterization of Cobalt Thin Films Grown by Metal-Organic CVD,

CHEMICAL VAPOR DEPOSITION, Issue 5 2005
F. Chioncel
Abstract Cobalt thin films were produced by metal-organic CVD from C5H5Co(CO)2, at various temperatures and for various deposition times. The films have been grown onto glass substrates with no buffer. The crystalline structure, morphology, and composition of the films were analyzed by X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and Auger electron spectroscopy (AES). Routine XRD patterns were collected in symmetric geometry for phase identification and the sin2, diffraction technique was employed to calculate the average in-plane stress. Structural studies indicate that the films tend to grow in island mode, as predicted by theory, and have a structure between that of face-centered cubic (fcc) and hexagonal close-packed (hcp) cobalt. There is significant in-plane tensile stress at the interface with the substrate, which relaxes to a compressive stress an order of magnitude lower at the surface. The films have a relatively low impurity content, as determined by AES, except near the surface. [source]


Li4Ti5O12 Nanoparticles Prepared with Gel-hydrothermal Process as a High Performance Anode Material for Li-ion Batteries

CHINESE JOURNAL OF CHEMISTRY, Issue 6 2010
Zheng Qiu
Abstract Li4Ti5O12 (LTO) nanoparticles were prepared by gel-hydrothermal process and subsequent calcination treatment. Calcination treatment led to structural water removal, decomposition of organics and primary formation of LTO. The formation temperature of spinel LTO nanoparticles was lower than that of bulk materials counterpart prepared by solid-state reaction or by sol-gel processing. Based on the thermal gravimetric analysis (TG) and differential thermal gravimetric (DTG), samples calcined at different temperatures (350, 500 and 700C) were characterized by X-ray diffraction (XRD), field emitting scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammogram and charge-discharge cycling tests. A phase transition during the calcination process was observed from the XRD patterns. And the sample calcined at 500C had a distribution of diameters around 20 nm and exhibited large capacity and good high rate capability. The well reversible cyclic voltammetric results of both electrodes indicated enhanced electrochemical kinetics for lithium insertion. It was found that the Li4Ti5O12 anode material prepared through gel-hydrothermal process, when being cycled at 8 C, could preserve 76.6% of the capacity at 0.3 C. Meanwhile, the discharge capacity can reach up to 160.3 mAhg,1 even after 100 cycles at 1 C, close to the theoretical capacity of 175 mAhg,1. The gel-hydrothermal method seemed to be a promising method to synthesize LTO nanoparticles with good application in lithium ion batteries and electrochemical cells. [source]


Preparation, Characterization and Magnetic Properties of PANI/La-substituted LiNi Ferrite Nanocomposites

CHINESE JOURNAL OF CHEMISTRY, Issue 12 2006
Jing Jiang
Abstract Magnetic nanocomposites containing polyaniline (PANI)-coated La-substituted LiNi ferrite (LiNi0.5La0.02Fe1.98O4) were synthesized by in situ polymerization in aqueous solution of hydrochloric acid. The nanocomposites exhibited the magnetic hysteresis nature under applied magnetic field. The saturation magnetization (MS) and coercivity (HC) varied with the ferrite content. The obtained nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), UV-Visible spectroscopy and vibrating sample magnetometer (VSM). TEM and SEM studies showed that the nanocomposites present the core-shell structure. The results of XRD patterns, FT-IR and UV-Visible spectra indicated the formation of PANI-LiNi0.5La0.02Fe1.98O4 nanocomposites and showed that the interaction existed between PANI backbone and ferrite particles in the nanocomposites. The bonding mechanism in the nanocomposites has been proposed. [source]