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Differential Thermal Analysis (differential + thermal_analysis)
Selected AbstractsDependence of magnetoimpedance effect on nanocrystalline structure of Fe-based amorphous ribbonsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004I. Z. Rahman Abstract This study investigates the magnetoimpedance (MI) behaviour and its dependence on the nanocrystalline structure due to annealing of nominal composition Fe73.5Cu1Nb3Si13.5B9 metallic glass ribbons. Differential Thermal Analyses have shown two distinct stages of primary and secondary crystallisations at ,532 °C and ,703 °C, respectively. XRD, SEM and AFM have shown the evidence of nanocrystallization and surface roughness initiated by changes from glassy to primary crystalline state. Coercivity has decreased near the primary crystallisation temperature and a monotonous increase between the two stages of crystallisation. Beyond the secondary crystallization temperature, the coercivity value remained practically unchanged. Magnetoimpedance ratio (MIR) is found to be sensitive to the annealing temperature. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Nucleation and Crystallization of a Lead Halide Phosphate Glass by Differential Thermal AnalysisJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2002Hongsheng Zhao The nucleation and crystallization mechanisms of a lead halide phosphate glass [40P2O5·30PbBr2·30PbF2 (mol%)] were investigated by differential thermal analysis (DTA) and X-ray diffraction analysis. There were two crystalline phases in the crystallized samples: the major phase was PbP2O4, and the minor phase was PbP2O6. The average activation energy for crystallization, E, for two different particle sizes of this glass was determined to be 119 ± 4 kJ/mol by the Kissinger method and 124 ± 4 kJ/mol by the Augis,Bennett method. The Avrami constants were determined to be 1.6 and 2.5 for particle sizes of 203 and 1040 ,m, respectively, by the Ozawa equation, and 1.7 and 2.4 for particle sizes of 203 and 1040 ,m, respectively, by the Augis,Bennett equation. The decrease in the crystallization peak height in the DTA curve with increasing particle size suggested that the particles crystallize primarily by surface crystallization. A nucleation-rate type curve was determined by plotting either the reciprocal of the temperature corresponding to the crystallization peak maximum, 1/Tp, or the height of the crystallization peak, (,T)p, as a function of nucleation temperature, Tn. The temperature where nucleation can occur for this glass ranges from 360°,450°C and the maximum nucleation rate is at 420°± 10°C. [source] Improvement of the interfacial compatibility between sugar cane bagasse fibers and polystyrene for compositesPOLYMER COMPOSITES, Issue 2 2004Edgar García-Hernández Sugar cane bagasse fibers were modified by surface treatments using either physical or chemical methods in order to improve their adhesion to polystyrene matrices. The surface treatment methods used were alkaline treatment, treatment with silane coupling agents, physical coating with polystyrene and grafting of polystyrene with and without crosslinker. Fiber modifications were monitored by Fourier Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis coupled with Thermogravimetric Analysis (DTA-TGA) and Scanning Electron Microscopy (SEM). On the other hand, the improvement of the adhesion between sugar cane modified fibers and polystyrene was assessed by micromechanical pull-out and by macromechanical Iosipescu tests. It was found, from Interfacial Shear Strength values (IFSS), that substantial improvements in fiber-matrix compatibility were achieved. According to micro- and macromechanical test results, the IFSS increased for all treated fibers as compared to non-treated fibers. Particularly, both the coating the fibers or grafting with polystyrene using crosslinker resulted in substantial adhesion improvement to the polystyrene matrix in comparison with the non-treated fibers and fibers treated by alkaline and silane methods only. Polym. Compos. 25:134,145, 2004. © 2004 Society of Plastics Engineers. [source] Supporting mechanism of non-toxic chromium (III) acetate on silica for preparation of Phillips ethylene polymerization catalystsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Pengyuan Qiu Abstract Phillips catalyst is an important kind of industrial polyethylene catalyst. As early as in the late 1970s, CrO3 was substituted by chromium (III) acetate for the preparation of Phillips catalyst on the industrial scale owing to health and environmental considerations. There is still considerable research focusing on the relations between the preparation process and catalyst properties in academics. In this work, the supporting mechanism of chromium (III) acetate on silica has been studied by Thermogravimetry,Differential Thermal Analysis (TG-DTA), and Electron Spin Resonance (ESR), in comparison with that of supporting CrO3 on SiO2. The basic chromium (III) acetate supported on high surface area silica gel decomposed differently from that for bulk basic chromium acetate when decomposition temperature was decreased by 15 °C. The decomposition temperature was 299 °C for Cr3(OH)2(Ac)7/SiO2 catalyst precursor, which would be firstly transferred into CrO3 followed by supporting on silica surface as chromate species. The further weight loss came from thermal inductive reduction of chromate species into Cr2O3, which was also supported by the results of colors of catalysts. Moreover, with the increase of chromium loading of Cr3(OH)2(Ac)7/SiO2, such thermal inductive reduction became more severe. ESR spectra of Cr3(OH)2(Ac)7/SiO2 and CrO3/SiO2 catalyst precursors showed that a small amount of supported Cr5+ can exist stably on silica gel surface at temperatures higher than 200 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Synthesis, characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 familyCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2008M. F. Mostafa Abstract The crystal structure of bis-(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C19H18P)2 CoBr4] is determined: Mr = 933.203, monoclinic, P21, a = 9. 6977 (3) Å, b = 12.5547 (4)Å, c = 16.4503 (6)Å, , = 105.603 (2)°, V = 1929.04 (11)Å3, Z = 2, Dx = 1.607 Mg m -3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T1= 313±2 K, T2 = 320±4 K and T3= 360±1 K. The structural instability detected via the temperature dependence of permittivity at T1 is ascribed to order-disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K-375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and Crystal Structure of Mercury-Substituted Type-I Clathrates A8Hg4Sn42 (A = K, Rb, Cs)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2008Andreas Kaltzoglou Abstract The mercury-substituted type-I clathrates A8Hg4Sn42,with A = K, Rb or Cs, were obtained by fusion of the pure elements at high temperatures. The crystal structures of the compounds were refined from single-crystal X-ray diffraction data. They crystallize in the space group Pmn (No. 223), Z = 1 with a = 12.1255(4) Å for K8Hg4Sn42 (1), a = 12.1838(4) Å for Rb8Hg4Sn42 (2) and a = 12.2130(4) Å for Cs8Hg4Sn42 (3). The 3D framework of four-bonded atoms defines two types of polyhedral cages of different size that are fully occupied by the alkali-metal atoms. All three compounds are considered as formally charge-balanced Zintl phases without any homogeneity range. Differential thermal analysis (DTA) indicates that the stability of the clathrates significantly depends on the size of the encaged cations. The thermal stability of the title compounds and the binary phases A8Sn44 (A = K, Rb, Cs) is discussed. Temperature-dependent magnetic measurements for compound 3 show also the expected diamagnetic behaviour. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Order-Disorder Phase Transition in Type-I Clathrate Cs8Sn44,2,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2007Andreas Kaltzoglou Abstract The clathrate compound ,-Cs8Sn44,2 has been synthesized from its elements under inert gas conditions and has been characterized by single-crystal and powder X-ray diffraction. At room temperature, it crystallizes with cubic symmetry [a = 24.256(3) Å, space group Iad, Z = 8] and adopts a 2,×,2,×,2 superstructure of the type-I clathrate and a high ordering of the vacancies (,) in the Sn framework. Single crystals of ,-Cs8Sn44,2 reversibly transform at 90 °C to the high-temperature , form with primitive symmetry [a = 12.135(1) Å, space group Pmn, Z = 1] and a lower ordering of the defects. Differential thermal analysis corroborates the reversible character of the phase transition, which occurs with an enthalpy change of approximately 0.38 J,g,1. An atom-migration mechanism describing the order-disorder transition involving spiro-connected six-membered rings only (scsr mechanism) is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Human skin permeation of ,8 -tetrahydrocannabinol, cannabidiol and cannabinolJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2004Audra L. Stinchcomb ABSTRACT The purpose of this study was to quantify the in-vitro human skin transdermal flux of ,8 -tetrahydrocannabinol (,8 -THC), cannabidiol (CBD) and cannabinol (CBN). These cannabinoids are of interest because they are likely candidates for transdermal combination therapy. Differential thermal analysis and in-vitro diffusion studies with human tissue were completed for the compounds. Heats of fusion, melting points and relative thermodynamic activities were determined for the crystalline compounds, CBD and CBN. Flux, permeability, tissue concentration and lag times were measured in the diffusion experiments. CBN had a lower heat of fusion and corresponding higher calculated relative thermodynamic activity than CBD. Ethanol concentrations of 30 to 33% significantly increased the transdermal flux of ,8 -THC and CBD. Tissue concentrations of ,8 -THC were significantly higher than for CBN. Lag times for CBD were significantly smaller than for CBN. The permeabilities of CBD and CBN were 10-fold higher than for ,8 -THC. Combinations of these cannabinoids with ethanol will be further studied in transdermal patch formulations in vitro and in vivo, as significant flux levels of all the drugs were obtained. CBD, the most polar of the three drugs, and other more polar cannabinoids will also be the focus of future drug design studies for improved transdermal delivery rates. [source] Tricalcium Silicate T1 and T2 Polymorphic Investigations: Rietveld Refinement at Various Temperatures Using Synchrotron Powder DiffractionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2004Vanessa K. Peterson The lattice parameters, cell volume, and structure of a sample of phase pure triclinic tricalcium silicate were determined using in situ, high-temperature synchrotron powder diffraction and full-profile Rietveld refinement. The temperature range covered was from ambient to 740°C. Evidence of superstructure was found. The T2 type structure with disordered SiO4 tetrahedra was observed, and an average structure for the subcell (P, a= 11.7416(2) Å, b= 14.2785(2) Å, c= 13.7732(2) Å, ,= 105.129(1)°, ,= 94.415(1)°, and ,= 89.889(1)°) is presented. Differential thermal analysis and X-ray fluorescence was also performed. [source] Synthesis and characterization of Cu3TaIn3Se7 and CuTa2InTe4PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2008P. Grima-Gallardo Abstract Polycrystalline samples of Cu3TaIn3Se7 and CuTa2InTe4 were synthesized by the usual melt and anneal technique. X-ray powder diffraction showed a single phase behavior for both samples with tetragonal symmetry and unit cell parameter values a = 5.794 ± 0.002 Å, c = 11.66 ± 0.01 Å, c /a = 2.01, V = 391 ± 1 Å3 and a = 6.193 ± 0.001 Å, c = 12.400 ± 0.002 Å, c /a = 2.00, V = 475 ± 1 Å3, respectively. Differential thermal analysis (DTA) measurements suggested a complicated behavior near the melting point with several thermal transitions observed in the heating and cooling runs. From the shape of the DTA peaks it was deduced that the melting is incongruent for both materials. Magnetic susceptibility measurements (zero-field cooling and field cooling) indicated an antiferromagnetic character with transition temperatures of T = 70 K (Cu3TaIn3Se7) and 42 K (CuTa2InTe4). A spin,glass transition was observed in Cu3TaIn3Se7 with Tf , 50 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Study of the mechanical and thermal properties of Sn,5 wt% Sb solder alloy at two annealing temperaturesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003M. M. EL-Bahay Abstract Sn,5 wt% Sb alloy is one of the materials considered for replacing lead-containing alloys for soldering in electronic packaging. Differential thermal analysis (DTA) and specific heat of the sample were studied. Wetting contact angle measurements of the alloy on different substrates were carried out at high temperature. Microhardness tests as a function of temperature were performed to calculate the effective activation energy of the solder alloy Sn,Sb and compared with the pure elements Sn and Sb. Isothermal creep curves for alloy samples were obtained under different constant applied stresses at different working temperatures ranging from 463 K to 503 K, followed by annealing the samples at two different temperatures before and above the threshold value (Tm/2). The transient creep parameters and the values of the stress exponent n were calculated for the two annealing temperatures. Microstructure examinations of the as-cast alloy at room temperature and after the two annealing treatments with the effect of the cold work deformation and creep test on the structure change and properties of Sn,Sb alloys were reported. The stress rupture test was also measured. [source] Synthesis and Characterization of Two Novel, Mono-Lacunary Dawson Polyoxometalate-Based, Water-Soluble Organometallic Ruthenium(II) Complexes: Molecular Structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2006Yoshitaka Sakai Abstract The synthesis and structural characterization of a novel class of mono-lacunary Dawson polyoxometalate-(POM-)based, water-soluble organometallic complexes, which are expected to be effective homogeneous oxidation catalyst precursors in water, is described. The organometallic complexes K8[{(C6H6)Ru(H2O)}(,2 -P2W17O61)]·12H2O (1) and K8[{(p -cymene)Ru(H2O)}(,2 -P2W17O61)]·16H2O (2) were successfully prepared by direct reactions of the mono-lacunary Dawson POM K10[,2 -P2W17O61]·19H2O with the organometallic precursors [(C6H6)RuCl2]2 and [(p -cymene)RuCl2]2, respectively, in aqueous media and characterized by complete elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), and FT-IR and solution (1H, 13C, 31P, and 183W) NMR spectroscopy. The molecular structure of [{(C6H6)Ru(H2O)}(,2 -P2W17O61)]8, (1a), in which the binding of the cationic organometallic group {(C6H6)Ru(H2O)}2+ occurs through two oxygen atoms of the four available oxygen atoms in the mono-lacunary site of the POM, resulting in overall C1 symmetry, was successfully determined by single-crystal X-ray analysis. Interestingly, the hydrophilicity of the organometallic precursors is greatly enhanced by binding to a mono-lacunary Dawson POM with higher hydrophilicity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Powder second harmonic generation measurement and thermal decomposition mechanisms of a new organometallic compound [(18C6)Li][Cd(SCN)3]CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2009J. J. Zhang Abstract Single crystals of a novel nonlinear optical organometallic compound CLTC, ([(18C6)Li][Cd(SCN)3]), were grown from aqueous solutions via evaporation technique and characterized by IR spectroscopy, thermal gravimetric analysis and X-ray single-crystal diffraction. By X-ray single-crystal structural analysis it is revealed that the compound crystallized in a noncentrosymmetric space group Cmc21 of orthorhombic system with cell parameter a = 14.767(3) Å, b = 15.454(3) Å, c = 10.644(2) Å, V = 2429.0(8) Å3 and Z = 4. The thermal stability and thermal decomposition of CLTC crystal were investigated by means of thermogravimetry and differential thermal analysis. The second harmonic generation (SHG) efficiency was measured using the Kurtz and Perry powder technique. It was shown that the value of the SHG efficiency of CLCT powder was about 2 times higher than that of potassium dihydrogen phosphate (KDP). (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of NaCl filler on ferroelectric phase and polaron configurations of PVDF filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2007I. S. ElashmawiArticle first published online: 8 MAR 200 Abstract Polyvinyldene fluoride (PVDF) films filled with NaCl of mass fraction range 1 , W , 6 % were prepared by casting technique. Their crystalline structure, thermal, optical properties and Electron spin resonance (ESR) were examined. X-ray diffraction (XRD) and differential thermal analysis (DTA) measurements indicated a maximum ferroelectric ,-phase increment at 4%. DTA was used to identify the phase transition temperatures, the order of reaction and the activation energy of melting. The UV-Visible optical absorption implied a minimum value of the estimated optical energy gap at W = 4%. ESR spectra contained a Lorentizian signal exhibiting a minimum value of the symmetry factor at W = 4%. The energy levels of the optical gap boundaries were though to contribute to ESR transitions. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Growth and properties of an organometallic nonlinear optical crystal: bis(isothiocyanato)-bis(4-methylpyridine)zinc(II) (Zn(SCN)2(C6H7N)2)CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006L. Y. Zhu Abstract Bis(isothiocyanato)-bis(4-methylpyridine)zinc(II)(Zn(SCN)2(C6H7N)2), (abbreviated as ZBNC) single crystals of optical quality have been grown from acetone solution by the slow temperature-lowering method. Its solubilities at different temperatures in acetone were measured. The X-ray powder diffraction (XRPD) spectroscopy of ZBNC crystal was performed at room temperature. The second harmonic generation (SHG) efficiency was determined by powder technique of Kurtz and Perry using Nd:YAG laser, which is equivalent to KDP crystal. The thermal decomposition process was characterized by thermal gravity and differential thermal analysis (TG\DTA). The specific heat of the crystal is 1440.67 J/mol·K at 325 K. The IR spectrum was recorded in the 500,3500 cm,1 region, using KBr pellets on a Nicolet 170sx FT-IR spectrometer. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and characterization of potassium magnesium sulphate hexahydrate crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006M. Dhandapani Abstract Potassium magnesium sulphate hexahydrate (picromerite) was synthesized and single crystals were obtained from saturated aqueous solution by slow evaporation method at room temperature. The crystals were bright, colourless and transparent having well defined external faces. The grown crystals were characterized through Fourier Transform Infrared (FTIR) spectral studies and thermal analysis. The FTIR data were used to assign the characteristic vibrational frequencies of the various chemical bonds in the compound. The compound crystallizes in monoclinic lattice with the space group P21/c. The thermogravimetry (TG) indicates the removal of only two water molecules around 100 °C. A suitable decomposition pattern was formulated based on the percentage weight losses observed in TG of the compound. The results of differential thermal analysis (DTA) conform to the results of TGA. Differential scanning calorimetry (DSC) analysis carried out at high temperature suggests that the occurrence of two phase transitions in the crystal between 140 and 180 °C. When the crystal was cooled below the room temperature up to ,170 °C, no thermal anomaly was observed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Microstructural, thermal, and electrical properties of Bi1.7V0.3Sr2Ca2Cu3Ox glass-ceramic superconductorCRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2004T. S. Kayed Abstract A glass-ceramic Bi1.7V0.3Sr2Ca2Cu3Ox superconductor was prepared by the melt-quenching method. The compound was characterized by scanning electron microscopy, x-ray diffraction, differential thermal analysis, current-voltage characteristics, transport resistance measurements, and Hall effect measurements. Two main phases (BSCCO 2212 and 2223) were observed in the x-ray data and the values of the lattice parameters quite agree with the known values for 2212 and 2223 phases. The glass transition temperature was found to be 426 °C while the activation energy for crystallization of glass has been found to be Ea = 370.5 kJ / mol. This result indicates that the substitution of vanadium increased the activation energy for the BSCCO system. An offset Tc of 80 K was measured and the onset Tc was 100 K. The Hall resistivity ,H was found to be almost field-independent at the normal state. A negative Hall coefficient was observed and no sign reversal of ,H or RH could be noticed. The mobility and carrier density at different temperatures in the range 140-300 K under different applied magnetic fields up to 1.4 T were also measured and the results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Modeling the Porosity Formation in Austenitic SGI Castings by Using a Physics-Based Material Model,ADVANCED ENGINEERING MATERIALS, Issue 3 2010B. Pustal Abstract On solidification, microsegregations build up in solid phases due to changes in solid concentrations with temperature. Diffusion, which is a kinetic process, usually reduces the occurrence of microsegregations. This work is aimed at modeling such kinetic effects on the solidification of austenitic cast iron, using a holistic approach. For this purpose, a microsegregation model is developed and validated. Moreover, this model is directly coupled to a commercial process-simulation tool and thermodynamic software. A series of GJSA-XNiCr 20-2 clamp-rings is cast by varying the inoculation state and the number of feeders. The composition of this cast alloy is analyzed and the microstructure characterized to provide input data for the microsegregation model. In order to validate the software, cooling curves are recorded; differential thermal analysis, electron dispersive X-ray analysis and electron probe micro analysis are carried out. Furthermore, the porosity within the casting is analyzed by X-ray. By performing coupled simulations, the different cooling characteristics within the casting lead to pronounced differences in phase fractions and solidification temperatures which are due to dendrite arm coarsening. The hot spot effect below the feeders is assisted by a shift towards lower solidification temperatures over the solidification time. This shift is a result of the local cooling characteristics, which can only be predicted when process simulation is directly coupled with material simulation. The porosity predictions and the porosity analysis exhibit good agreement. A comparison between experimental and virtual cooling curves closes, implying that the novel coupling concept and its implementation are valid. [source] Graft copolymerization modification of silk fabric with an organophosphorus flame retardantFIRE AND MATERIALS, Issue 5 2010Guan Jinping Abstract This paper mainly deals with flame retardance of a silk fabric treated with a vinyl phosphate dimethyl 2-(methacryloyloxyethyl) phosphate (DMMEP) onto silk fabric by a graft copolymerization technique. This paper also explores the relationship between limiting oxygen index (LOI) and weight gain of DMMEP treated silk fabric. The paper also investigates the whiteness, handle, tensile strength and laundering durability of treated silk fabric. Microscale combustion calorimetry (MCC) is applied to test the heat release rate of silk fabric. Thermal gravimetric analysis (TG) and differential thermal analysis (DTA) are carried out to investigate the thermal decomposition behavior of DMMEP treated silk fabric. The kinetic parameters, activation energy and pre-exponential factor are determined using the Kissenger method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Zinc hydroxystannate-coated metal hydroxides as flame retardant and smoke suppression for flexible poly vinyl chlorideFIRE AND MATERIALS, Issue 4 2009Hongqiang Qu Abstract Zinc hydroxystannate (ZHS)-coated metal hydroxides were prepared. The effects of ZHS-coated metal hydroxides on flame retardancy and smoke suppression of flexible poly vinyl chloride were studied by means of the limiting oxygen index, smoke density rating and the char yield test. The mechanism was investigated by thermogravimerty (TG), differential thermal analysis, and differential TG analysis and scanning electron microscopy. The results showed that ZHS-coated metal hydroxides are more effective flame retardant and smoke suppressant than metal hydroxides, and it appears that tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-Temperature Contact Formation on n-Type Silicon: Basic Reactions and Contact Model for Seed-Layer ContactsADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Matthias Hörteis Abstract Contact formation on n-type silicon, especially using a high-temperature process, has been the subject of research for more than 40 years. After its application in microelectronics, n-type silicon is widely used in silicon solar cells as the emitter layer. The formation of a low ohmic contact grid using an industrially feasible process step is one of the key features required to improve the solar-cell efficiency. The contact materials, typically deposited in a printing step, have to fulfil several functions: opening the dielectric antireflection layer and forming an intimate metal-semiconductor contact with good mechanical adhesion and low specific contact resistance. As the used contact inks typically contain several functional materials, such as silver and a glass frit, the detailed contact formation is still not entirely understood. Therefore, the chemical reactions during the contact firing process have been studied in detail by thermogravimetric differential thermal analysis in combination with mass spectroscopy. Based on these studies, a contact ink has been developed, optimized and tested on silicon solar cells. In this paper, the mechanism of the etching process, the opening of a dielectric layer, the influence of different atmospheres and the impact of the glass-frit content are investigated. The observed microscopic contact structure, the resulting electrical solar-cell parameters and the studied reactions are combined to clarify the physics behind the high-temperature contact formation. [source] Effect of Ce, Sb, and Sn on Solarization and Crystallization of an X-Ray-Irradiated Photosensitive GlassINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Mohamad Hassan Imanieh The effect of Ce, Sb, and Sn photosensitive elements, individually and in combination with each other, on solarization and crystallization of an X-ray irradiated and a nonirradiated lithium silicate-based glass were investigated. According to the results, considering the crystallization behavior of the nonirradiated glasses, they were divided into Ce-bearing and Ce-free groups, in which the former group showed a clearer solarization tendency that manifested as an appearance of an absorbance peak at 318 nm in the spectrophotometry experiment. However, the results showed that in the irradiated glasses, the presence of Sb was more important in terms of improvement in crystallization view. Antimony decreased the differential thermal analysis (DTA) crystallization peak temperature from 655°C to 594°C and, in combination with the two other elements, changed the surface crystallization mechanism to a bulk one. The reactions that seemed to be responsible for the above-mentioned observations were discussed by spectrophotometry, DTA, X-ray diffraction, and scanning electron microscopic methods. [source] Preparation of Nano Carbonate-Substituted Hydroxyapatite from an Amorphous PrecursorINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008Yanbao Li Carbonated amorphous calcium phosphate (CACP) precursors were precipitated by the wet chemical method at 5°C in the presence of poly(ethylene glycol) and carbonates. The nano carbonate-substituted hydroxyapatite (HAp) was obtained after heat treat CACP precursors at a low temperature (800°C) for 3 h. The calcium phosphates were investigated by X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma, thermal gravimetric and differential thermal analysis, transmission electron microscopy, and scanning electron microscopy. The results show that calcium phosphate particles with a Ca/P molar ratio of 1.73 are AB-type carbonate-substituted HAp with about 50 nm in diameter. [source] Sol,Gel Synthesis of PZT,Glass Nanocomposites Using a Simple System and CharacterizationINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2006V. Kumar A simple inorganic system has been developed for the sol,gel synthesis of piezoelectric PZT,glass nanocomposites. Nanocrystalline PZT are nucleated from the amorphous xerogel through controlled heat treatment at 600°C. The formation of the crystalline phase, particle size, morphology, kinetics, and mechanism of crystallization of PZT in the glass matrix have been studied using X-ray diffraction, scanning electron microscopy, and differential thermal analysis. The piezoelectric characteristics of the PZT,glass compositions have been determined, and are correlated with the microstructure and the crystalline phase of PZT. [source] Diffraction thermometry and differential thermal analysisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2002E. H. Kisi A unit-cell parameter anomaly observed during the precipitation and growth of Ti3SiC2 from a Si-substituted TiC phase is interpreted as the release of latent heat. The observations are used to propose a powder diffraction method for conducting differential thermal analysis as part of in situ phase transition studies. [source] Induction of chemical and moisture resistance in Saccharum spontaneum L fiber through graft copolymerization with methyl methacrylate and study of morphological changesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Balbir Singh Kaith Abstract In this article, morphological modification of Saccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate,potassium per sulfate redox initiator has been reported. Different reaction parameters such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X-ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Synthesis, characterization, and acoustic properties of new soluble polyurethanes based on 2,2,-[1,4-phenylenebis(nitrilomethylylidene)diphenol and 2,2,-[4,4,-methylene-di-2-methylphenylene-1,1,-bis(nitrilomethylylidene)]diphenol,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007A. V. Raghu Abstract Eight novel polyurethanes based on 2,2,-[1,4-phenylenebis(nitrilomethylylidene)]diphenol and 2,2,-[4,4,-methylene-di-2-methylphenylene-1,1,-bis(nitrilomethylylidene)]diphenol acting as hard segments with two aromatic and two aliphatic diisocyanates (4,4,-diphenylmethane diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate) were prepared and characterized with Fourier transform infrared, UV spectrophotometry, fluorescence spectroscopy, 1H-NMR and 13C-NMR spectroscopy, thermogravimetric analysis, and differential thermal analysis. All the polyurethanes contained domains of semicrystalline and amorphous structures, as indicated by X-ray diffraction. The acoustic properties and solubility parameters were calculated with the group contribution method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Fire-resistant effect of nanoclay on intumescent nanocomposite coatingsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Zhen-yu Wang Abstract The aim of the study is the development of an intumescent nanocomposite coating to provide fire protection for the metallic substrate. Acrylic nanocomposites containing nanoclay and relative intumescent nanocoatings are prepared. The effect of nanoclay on the thermal degradation of an intumescent nanocomposite coating is analyzed by using differential thermal analysis, thermogravimetry, and X-ray diffraction. The influence of the added content of nanoclay on fire performance is studied by a fire protection test and measurements of the limiting oxygen index and effective thermal conductivity. The distribution of nanoparticles in the acrylic nanocomposite is characterized by transmission electron microscopy. The flame-retardant efficiency of the intumescent nanocomposite coating is improved by 1.5% well-distributed nanoclay particles. However, 3% nanoclay produces a negative effect on the fire performance of the coating. Fire protection tests and scanning electron microscopy observations reveal that the fire-retardant property of a conventional intumescent coating is destroyed by aging, whereas the nanocomposite coating modified with 1.5% nanoclay demonstrates good aging and fire resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1681,1689, 2007 [source] Catalytic performance of Brønsted acid sites during esterification of acetic acid with ethyl alcohol over phosphotungestic acid supported on silicaJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2007Abd El-Aziz A Said Abstract Different ratios of phosphotungestic acid supported on silica gel were prepared by an impregnation method with PWA loadings ranging from 1 to 30% w/w and calcined at 350 and 500 °C for 4 h in a static air atmosphere. The catalysts were characterized by thermogravimety (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N2 adsorption measurements. The surface acidity and basicity of the catalyst were investigated by the dehydration,dehydrogenation of isopropanol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas-phase estrification of acetic acid with ethanol was carried out at 185 °C in a conventional fixed-bed reactor at 1 atm using air as carrier gas. The results clearly revealed that the catalyst containing 10% w/w PWA/SiO2 is the most active and delivers reaction selectively to ester with 85% yield. The Brønsted acid site resulting from hydroxylation of tungsten oxide plays the main role in the formation of ester. Copyright © 2007 Society of Chemical Industry [source] Synthesis of ZSM-5 from diatomite: a case of zeolite synthesis from a natural materialJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2004Vilma Sanhueza Abstract A highly crystalline ZSM-5 product was obtained from diatomite, a natural raw material, both with and without the presence of diethanolamine. The synthesis process took 40 h, and was carried out under hydrothermal conditions, at autogenic pressure, and at a temperature of 180 °C. The resulting crystals were identified as ZSM-5 by X-ray diffraction and characterized by scanning electron microscopy, infrared spectroscopy, thermal gravimetry and differential thermal analysis. Copyright © 2004 Society of Chemical Industry [source] | |||||||||||||||||||||||||||||||||||||