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State Reaction (state + reaction)
Kinds of State Reaction Terms modified by State Reaction Selected AbstractsTheoretical Investigation of the Solid State Reaction of Silicon Nitride and Silicon Dioxide Forming Silicon Oxynitride (Si2N2O) under PressureCHEMINFORM, Issue 49 2003Peter Kroll Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis and characterization of compounds LixMn1+xFe2,2xO4 with spinel structure in the quasiternary system "LiO0,5 , MnOx , FeOx"CRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2006C. Wende Abstract The thermal decomposition of freeze-dried Li-Mn(II)-Fe(III)-formate precursors was investigated by means of DTA, TG and mass spectroscopy. By the thermal treatment of the prefired precursors between 400 and 1000°C, single phase solid solutions LixMn1+xFe2,2xO4 (0 , x , 1) with cubic spinel structure were obtained. To get single phase spinels, special conditions concerning the temperature T and the oxygen partial pressure p(O2) during the synthesis are required. Because of the high reactivity of the freeze-dried precursors, in comparison with the conventional solid state reaction, the reaction temperature can be lowered by 200°C. The cation distribution and the properties of the Li-Mn-ferrites were studied by chemical analysis, X-ray powder diffraction and magnetization measurements. It was found that for high substitution rates, almost all lithium occupies the tetrahedral coordinated A-sites of the spinel lattice AB2O4, while at small x-values, lithium ions are distributed over the tetrahedral and octahedral sites. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Crystal growth and structural refinement of NaMn7O12CRYSTAL RESEARCH AND TECHNOLOGY, Issue 10-11 2005E. Gilioli Abstract We report the crystal growth and the structural refinement of NaMn7O12, a manganite having a double perovskite structure. As in many similar compounds, there is coexistence of Mn3+ and Mn4+ but in this material they orderly occupy different sites for crystallographic reasons. Therefore, this peculiar structure can be considered as a model system for studying complex mechanisms such as charge, orbital and spin ordering. High purity bulk samples and "large" single crystals are needed to study tiny modifications in the crystallographic and magnetic structures associated to the ordering phenomena. Almost single phase (more than 96% pure) and single crystals (up to about 150 µm) of NaMn7O12 were synthesized by solid state reaction under pressure in a multi-anvil apparatus. Single crystal x-ray diffraction and SEM analysis have been used to characterize the crystals. The structure refinement indicates that NaMn7O12 crystallizes in the cubic Im3 space group, with a = 7.312 Å and Z = 2. Further studies are in progress to optimize the synthesis conditions, in order to grow larger crystals. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temperature-Dependent Solid-State Reactions With and Without Kirkendall Effect in Al2O3/ZnO, Fe2O3/ZnO, and CoXOY/ZnO Oxide Thin Film Systems,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Andriy Zolotaryov Temperature-dependent solid-state reactions and the occurrence of the Kirkendall effect are studied in thin film oxide systems applying optical reflection microscopy, X-ray reflectivity, (scanning) transmission electron microscopy, grazing-incidence X-ray diffraction measurements, and SQUID magnetometry. The efficiency of the simultaneous application of different analytical methods for the precise selection and investigation of the most interesting samples is demonstrated first on the example of the Al2O3/ZnO system, for which the spinel formation after a solid-state reaction and the formation of Kirkendall voids were already reported. The demonstrated methodology is then applied to study Fe2O3/ZnO and CoXOY/ZnO film pairs. The investigations clearly demonstrate the temperature-driven formation of a ferromagnetic spinel by a solid state reaction involving the Kirkendall effect in the Fe2O3/ZnO system, already after an annealing at 600,°C for 1,h. We also report on the solid state reaction in the CoXOY/ZnO system after annealing at 700,°C for 1,h, however without the Kirkendall effect and without any evidence of ferromagnetism of the final state. [source] Oxygen permeability and structural stability of a novel tantalum-doped perovskite BaCo0.7Fe0.2Ta0.1O3,,AICHE JOURNAL, Issue 3 2010Huixia Luo Abstract Dense BaCo0.7Fe0.2Ta0.1O3,, (BCFT) perovskite membranes were successfully synthesized by a simple solid state reaction. In situ high-temperature X-ray diffraction indicated the good structure stability and phase reversibility of BCFT at high temperatures. The thermal expansion coefficient (TEC) of BCFT was determined to amount 1.02 × 10,5 K,1, which is smaller than those of Ba0.5Sr0.5Co0.8Fe0.2O3,, (BSCF) (1.15 × 10,5 K,1), SrCo0.8Fe0.2O3,, (SCF) (1.79 × 10,5 K,1), and BaCo0.4Fe0.4Zr0.2O3,, (BCFZ) (1.03 × 10,5 K,1). It can be seen that the introduction of Ta ions into the perovskite framework could effectively lower the TEC. Thickness dependence studies of oxygen permeation through the BCFT membrane indicated that the oxygen permeation process was controlled by bulk diffusion. A membrane reactor made from BCFT was successfully operated for the partial oxidation of methane to syngas at 900°C for 400 h without failure and with the relatively high, stable oxygen permeation flux of about 16.8 ml/min cm2. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Fluorescence Detection of the Ornamental Fish Cardinal Tetra (Paracheirodon axelrodi)PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009Richard P. Brinn The fluorescence spectra of the tropical fish, Cardinal Tetra (Paracheirodon axelrodi), originating in the Amazon region of Brazil, were determined. These spectra were then treated using factor analysis, generating two contributing spectra and separating out the noise. Time-resolved fluorescence results indicated that the fluorescent system in the epidermis undergoes excited state reaction. Excited state proton transfer is suggested as being present. Both intentionally stressed and nonstressed individuals were used and some small differences were noted in the contributions of the two calculated contributing spectra to the experimental spectra, presumably as a function of stress. The results are compared with those obtained by the standard determination of cortisol level using the whole body extraction method and it is suggested that the method could be tested as an improved, nondestructive way to determine stress in this species, which is a necessary step in the development of "best management practices" of methods for storage and transport of the fish. [source] Dynamic Study of Excited State Hydrogen-bonded Complexes of Harmane in Cyclohexane,Toluene Mixtures,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2002Carmen Carmona ABSTRACT Photoinduced proton transfer reactions of harmane or 1-methyl-9H -pyrido[3,4- b]indole (HN) in the presence of the proton donor hexafluoroisopropanol (HFIP) in cyclohexane,toluene mixtures (CY,TL; 10% vol/vol of TL) have been studied. Three excited state species have been identified: a 1:2 hydrogen-bonded proton transfer complex (PTC), between the pyridinic nitrogen of the substrate and the proton donor, a hydrogen-bonded cationlike exciplex (CL*) with a stoichiometry of at least 1:3 and a zwitterionic exciplex (Z*). Time-resolved fluorescence measurements evidence that upon excitation of ground state PTC, an excited state equilibrium is established between PTC* and the cationlike exciplex, CL*, ,em, 390 nm. This excited state reaction is assisted by another proton donor molecule. Further reaction of CL* with an additional HFIP molecule produces the zwitterionic species, Z*, ,em, 500 nm. From the analysis of the multiexponential decays, measured at different emission wavelengths and as a function of HFIP concentration, the mechanism of these excited state reactions has been established. Thus, three rate constants and three reciprocal lifetimes have been determined. The simultaneous study of 1,9-dimethyl-9H -pyrido[3,4- b]indole (MHN) under the same experimental conditions has helped to understand the excited state kinetics of these processes. [source] Mössbauer studies of Fe-Zn sulphur spinelsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2007Sung Hwan Bae Abstract The polycrystalline sample of Zn doped Fe1,xZnxCr2S4(x = 0.1, 0.3) were prepared by solid state reaction. The crystal structure was determined to be the normal cubic spinel of space group Fd 3m and the lattice constants(x = 0.1, 0.3) were a0 = 9.9967(3) Å and a0 = 9.9926(3) Å, respectively. The magnetic moment values of Fe1,xZnxCr2S4 for the x = 0.3 were observed higher than that of the x = 0.1. The Néel temperatures were decreased to 153 K (x = 0.1), 135 K (x = 0.3) with Zn substitution concentration. This result is due to the decrease of A-B superexchange interaction by the replacement of Zn ions for A site. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Deficiency effects upon the physical properties of Pr0.8Sr0.2MnO3 manganite oxidePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006W. Cheikh-Rouhou Koubaa Abstract The effects of deficiency in praseodymium and in strontium upon the magnetic and magneto-transport properties of lacunar Pr0.8,x,xSr0.2MnO3 and Pr0.8Sr0.2,x,x MnO3 oxides have been investigated. Our synthesized samples have been elaborated using the conventional solid state reaction at high temperature. Crystallographic studies show that all our samples are single phase and crystallize in the orthorhombic system with Pnma space group. The praseodymium deficient samples Pr0.8,x,xSr0.2MnO3 exhibit three different regimes in the resistivity variation as a function of praseodymium deficiency amount: (i) at low concentration (0 , x , 0.1), a semiconductor behaviour is observed in the whole temperature range, (ii) at an intermediate amount (x = 0.15), a semiconductor-metallic transition is followed by a metallic-semiconductor one with decreasing temperature, and finally (iii) at x = 0.2 and 0.25, a metallic behaviour is observed below TC, whereas all the strontium deficient samples exhibit a semiconductor behaviour in the whole temperature range. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] BGO glasses: structural and optical characterizationPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005S. Polosan Abstract Mixtures of 30% Bi2O3 and 70% GeO2 (in molar percents) were prepared followed by the solid state reaction at 700 °C for 30 min. or 24 h using an Al2O3 crucible. After melting at 1050 °C for 10 min. the melt was poured into a preheated graphite plate and then naturally cooled to room temperature (RT). X-ray diffraction measurements (XRD) on the resulting BGO glasses have been performed, and optical absorption spectra recorded at room temperature on the samples obtained using various preparation conditions. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ag-rich Tetrahedrite in the El Zancudo Deposit, Colombia: Occurrence, Chemical Compositions and Genetic TemperaturesRESOURCE GEOLOGY, Issue 3 2010Alba Nury Gallego Hernández Abstract Chemical compositions of tetrahedrite,Ag-rich tetrahedrite,freibergite solid solutions (Ag-rich tetrahedritess) and homogenization temperatures of fluid inclusions in quartz and carbonates of seventeen samples from nine veins in the El Zancudo deposit, Antioquia, Colombia, were investigated to reveal the origin of silver in Ag-rich tetrahedritess, to derive their crystallization temperatures and to examine the relationship between chemical compositions of Ag-rich tetrahedritess and their crystallization temperatures. The ores consist of arsenopyrite, pyrite, sphalerite, Ag-rich tetrahedritess, galena, boulangerite, andorite, owyheeite, diaphorite, jamesonite, miargyrite, bournonite, chalcopyrite, and electrum. Ag-rich tetrahedritess forms about 10 volume % of the total ores and is one of the most common and widely distributed sulfosalts in this deposit. Ag-rich tetrahedritess is rich in Ag (1.13 to 31.02 wt%) and Sb (22.93 to 29.82 wt%), and poor in As (0.06 to 2.43 wt%), consistent with the reported incompatibilities of Ag and As in Ag-rich tetrahedritess. The Zn/(Zn + Fe)-, Ag/(Ag + Cu)- and Sb/(Sb + As + Bi)-atomic ratios exhibit some variations among the veins. Ag-rich tetrahedritess with higher Ag/(Ag + Cu) ratios coexist with diaphorite, whereas those with lower ratios are not associated with this sulfosalt. Ag-rich tetrahedritess in the assemblages of Ag-rich tetrahedritess+ sphalerite and of Ag-rich tetrahedritess+ bournonite + galena shows no Zn , Fe and Cu , Ag variations between core and rim, respectively, negating the possibility of solid state reaction during cooling. Ag-rich tetrahedritess is thus regarded as primary phase. Homogenization temperatures of primary fluid inclusions in quartz and carbonates co-existing with Ag-rich tetrahedritess define the mineralization temperatures of 134 to 263°C. Independent crystallization temperatures of Ag-rich tetrahedrite estimated based on Zn/(Zn + Fe) and Ag/(Ag + Cu) ratios of the Ag-rich tetrahedritess associated with silver minerals such as miargyrite, andorite and diaphorite using Sack's thermochemical database lie in a range between 170 and ,250°C. Both results are thus in good agreement. [source] ChemInform Abstract: New Noncentrosymmetric Tellurite Phosphate Material: Synthesis, Characterization, and Calculations of Te2O(PO4)2.CHEMINFORM, Issue 39 2010Min Kyung Kim Abstract The title compound is prepared by solid state reaction of TeO2 and P4O10 (evacuated silica tube, 550 °C, 24 h). [source] ChemInform Abstract: SrNp(PO4)2: An Original Ordered Modification of Cheralite.CHEMINFORM, Issue 39 2010Karin Popa Abstract The new title compound is prepared by solid state reaction of 237NpO2, Sr(NO3)2, and excess (NH4)2HPO4 (argon; 1. [source] ChemInform Abstract: Synthesis, Characterization, and Crystallographic Study of the PbO,Bi2O3,V2O5 System: Pb3-xBi2x/3V2O8 (0.20 , x , 0.50).CHEMINFORM, Issue 35 2010Prangya Parimita Sahoo Abstract The new title solid solution is synthesized by solid state reaction of stoichiometric mixtures of PbO, Bi2O3, and V2O5 (650 °C, 2 d). [source] ChemInform Abstract: Lithium Storage Capability of Lithium Ion Conductor Li1.5Al0.5Ge1.5 (PO4)3.CHEMINFORM, Issue 34 2010J. K. Feng Abstract The title compound with a NASICON structure is prepared by solid state reaction of stoichiometric amounts of Li2CO3, Al2O3, Ge, and NH4H2PO4 (Pt crucible, 700 and 950 °C, 2 h each) and characterized by XRD, cyclic voltammetry, AC impedance, DC conductivity measurements, and battery tests. [source] ChemInform Abstract: Magnetic and Crystal Structures of BiCrO3.CHEMINFORM, Issue 34 2010C. Darie Abstract Polycrystalline samples of the title compound are prepared by solid state reaction of Bi2O3 and Cr2O3 (Au capsule, 2 GPa, 805 °C) and characterized by powder neutron diffraction and magnetic susceptibility measurements. [source] ChemInform Abstract: Cooperative Jahn,Teller Distortion Leading to the Spin-1/2 Uniform Antiferromagnetic Chains in Triclinic Perovskites AgCuF3 and NaCuF3.CHEMINFORM, Issue 34 2010J. Tong Abstract AgCuF3 is synthesized by solid state reaction of AgF and CuF2 (773 K, 3 d). [source] Thermochemical Properties and Decomposition Kinetics of Ammonium Magnesium Phosphate MonohydrateCHINESE JOURNAL OF CHEMISTRY, Issue 1 2007Jian Wu Abstract Ammonium magnesium phosphate monohydrate NH4MgPO4·H2O was prepared via solid state reaction at room temperature and characterized by XRD, FT-IR and SEM. Thermochemical study was performed by an isoperibol solution calorimeter, non-isothermal measurement was used in a multivariate non-linear regression analysis to determine the kinetic reaction parameters. The results show that the molar enthalpy of reaction above is (28.795±0.182) kJ/mol (298.15 K), and the standard molar enthalpy of formation of the title complex is (,2185.43±13.80) kJ/mol (298.15 K). Kinetics analysis shows that the second decomposition of NH4MgPO4·H2O acts as a double-step reaction:an nth-order reaction (Fn) with n=4.28, E1=147.35 kJ/mol, A1=3.63×1013 s,1 is followed by a second-order reaction (F2) with E2=212.71 kJ/mol, A2=1.82×1018 s,1. [source] Preparation of Li4.4Al0.4Si0.6O4-xLi3BO3 Solid Electrolytes by Sol-Gel Method and Their Ionic ConductivityCHINESE JOURNAL OF CHEMISTRY, Issue 12 2002Hua-Ting Liu Abstract The Li4.4Al0.4Si0.6O4 -xLi3BO3 (x = 0 to 0.5) km conductors were prepared by the sol-gel method. The powder and sintered samples were characterized by DTA-TG, XBD, SEM and ac impedance techniques. The temperature of the preparation of powder patterns decreased by this method as compared to that of the preparation in solid state reaction. The conductivity and storability increased with Li3BO3, increasing from x = 0 to 0.2 in the Li4.4Al0.4S0.4O4-xLi3BO3, solid electrolytes. The particle size of the sintered pellets is about 0.12 ,m. The maximum conductivity at 20 °C is 3.165 × 10,5 S.cm,1 for Li4.4Al0.4Si0.6Q4 -0.2Li3BO3. [source] Determination of outer layer and bulk dehydration kinetics of trehalose dihydrate using atomic force microscopy, gravimetric vapour sorption and near infrared spectroscopyJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008Matthew D. Jones Abstract Knowledge of the kinetics of solid state reactions is important when considering the stability of many medicines. Potentially, such reactions could follow different kinetics on the surface of particles when compared with their interior, yet solid state processes are routinely followed using only bulk characterisation techniques. Atomic force microscopy (AFM) has previously been shown to be a suitable technique for the investigation of surface processes, but has not been combined with bulk techniques in order to analyse surface and bulk kinetics separately. This report therefore describes the investigation of the outer layer and bulk kinetics of the dehydration of trehalose dihydrate at ambient temperature and low humidity, using AFM, dynamic vapour sorption (DVS) and near infrared spectroscopy (NIR). The use of AFM enabled the dehydration kinetics of the outer layers to be determined both directly and from bulk data. There were no significant differences between the outer layer dehydration kinetics determined using these methods. AFM also enabled the bulk-only kinetics to be analysed from the DVS and NIR data. These results suggest that the combination of AFM and bulk characterisation techniques should enable a more complete understanding of the kinetics of certain solid state reactions to be achieved. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4404,4415, 2008 [source] Local structure of vanadium in doped LiFePO4JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010Ting Zhao LiFePO4 composites with 5,at.% vanadium doping are prepared by solid state reactions. X-ray absorption fine-structure spectroscopy is used as a novel technique to identify vanadium sites. Both experimental analyses and theoretical simulations show that vanadium does not enter into the LiFePO4 crystal lattice. When the vanadium concentration is lower then 1,at.%, the dopant remains insoluble. Thus, a single-phase vanadium-doped LiFePO4 cannot be formed and the improved electrochemical properties of vanadium-doped LiFePO4 previously reported cannot be associated with crystal structure changes of the LiFePO4via vanadium doping. [source] Dynamic Study of Excited State Hydrogen-bonded Complexes of Harmane in Cyclohexane,Toluene Mixtures,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2002Carmen Carmona ABSTRACT Photoinduced proton transfer reactions of harmane or 1-methyl-9H -pyrido[3,4- b]indole (HN) in the presence of the proton donor hexafluoroisopropanol (HFIP) in cyclohexane,toluene mixtures (CY,TL; 10% vol/vol of TL) have been studied. Three excited state species have been identified: a 1:2 hydrogen-bonded proton transfer complex (PTC), between the pyridinic nitrogen of the substrate and the proton donor, a hydrogen-bonded cationlike exciplex (CL*) with a stoichiometry of at least 1:3 and a zwitterionic exciplex (Z*). Time-resolved fluorescence measurements evidence that upon excitation of ground state PTC, an excited state equilibrium is established between PTC* and the cationlike exciplex, CL*, ,em, 390 nm. This excited state reaction is assisted by another proton donor molecule. Further reaction of CL* with an additional HFIP molecule produces the zwitterionic species, Z*, ,em, 500 nm. From the analysis of the multiexponential decays, measured at different emission wavelengths and as a function of HFIP concentration, the mechanism of these excited state reactions has been established. Thus, three rate constants and three reciprocal lifetimes have been determined. The simultaneous study of 1,9-dimethyl-9H -pyrido[3,4- b]indole (MHN) under the same experimental conditions has helped to understand the excited state kinetics of these processes. [source] ChemInform Abstract: Synthesis and Structural Chemistry of La18Li8Rh4MO39 (M = Ti, Mn, Ru).CHEMINFORM, Issue 42 2010Peter D. Battle Abstract The title compounds are synthesized by solid state reactions of stoichiometric mixtures of La2O3, Rh2O3, MO2 (M: Ti, Mn, Ru), and a 50% excess of Li2CO3 (800 °C, 12 h). [source] ChemInform Abstract: Structural Chemistry and Magnetic Properties of Ln18Li8Rh5-xFexO39 (Ln: La, Nd).CHEMINFORM, Issue 36 2010Peter D. Battle Abstract The title compounds (0.5 , x , 5) are synthesized by solid state reactions of stoichiometric mixtures of the metal(III) oxides and a 50% excess of Li2CO3 (air, 800 °C, 12 h; 1000 °C, 1 h). [source] ChemInform Abstract: Structure and Physical Properties of the Layered Pnictide-Oxides: (SrF)2Ti2Pn2O (Pn: As, Sb) and (SmO)2Ti2Sb2O.CHEMINFORM, Issue 32 2010R. H. Liu Abstract The title compounds are prepared by solid state reactions using SrPn (Pn: As, Sb), SrF2, Sm2O3, TiO2, and Ti as starting materials (1000,1150 °C, 50 h) and characterized by powder XRD, resistivity, susceptibility, Hall coefficient, thermoelectric power, and heat capacity measurements. [source] Photoinduced Electron Transfer Reactions by SmI2 in THF: Luminescence Quenching Studies and Mechanistic InvestigationsCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2005Edamana Prasad Dr. Abstract Photoluminescence quenching studies of SmI2 in dry THF were carried out in the presence of five different classes of compounds: ketone, alkyl chloride, nitrile, alkene and imine. The free energy change (,G,0) of the photoinduced electron transfer (PET) reactions was calculated from the redox potentials of the donor (SmI2) and acceptors. The bimolecular quenching constants (kq) derived from the Stern,Volmer experiments parallel the free energy changes of the PET processes. The observed quenching constants were compared with the theoretically derived electron transfer rate constants (ket) from Marcus theory and found to be in good agreement when a value of ,=167 kJ,mol,1 (40 kcal,mol,1) was used for the reorganization energy of the system. A careful comparison of the excited state dynamics of SmII in the solid state to the results obtained in solution (THF) provides new insight in to the excited states of SmII in THF. The activation parameters determined for the PET reactions in SmI2/1-chlorobutane system are consistent with a less ordered transition state and high degree of bond reorganization in the activated complex compared to similar ground state reactions. Irradiation studies clearly show that SmI2 acts as a better reductant in the excited state and provides an alternative pathway for rate enhancement in known and novel functional group reductions. [source] | |||||||||||||