Raman Scattering and X-ray Diffraction Studies on Zinc(II)Bromide Solutions in Methanol and N,N-Dimethylformamide in the Temperature Range 77-333 K

1994 ◽  
Vol 49 (12) ◽  
pp. 1119-1130
Author(s):  
Toshiyuki Takamuku ◽  
Keisuke Nakamura ◽  
Mikito Ihara ◽  
Toshio Yamaguchi
Keyword(s):  
Raman Scattering ◽  
Methanol Solution ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Temperature Range ◽  
Methanol Solutions ◽  
Species Being ◽  
Bromide Solutions

Abstract The structure of zinc(II) bromo complexes in methanol and N,N-dimethylformamide (DMF) (molar ratio [solvent]/[ZnBr2] = 10, temperature range 77 -333 K) has been investigated by Raman scattering and X-ray diffraction. In the methanol solution symmetric Zn - Br vibrations (γ1) of the dibromo- and tribromozinc(II) complexes were observed at 209 and 184 cm-1, respectively. With decreasing temperature the intensity of the γ1 band decreased for the dibromo and increased for the tribromo complex. In addition, the γ1 band for the tetrabromo complex appeared in the supercooled and glassy methanol solutions. In the DMF solution only one band, assigned to both the dibromo-and tribromozinc(II) complexes, was observed. Its intensity did not change with temper­ature. The X-ray diffraction data revealed that the average number of Zn -Br interactions within the zinc (II) bromo complexes does not change with temperature while the number of nonbonding Br ··· Br interactions within the complexes increases from 1.5 at 298 K to 1.9 at 243 K for the methanol solution and from 1.3 at 298 K to 1.8 at 243 K for the DMF solution. These Raman and X-ray results have confirmed that in both methanol and DMF solutions at high temperatures the dibromo species is predominantly formed, whereas at low temperatures the tribromo complex is favored, the tetrabromo species being formed only in the supercooled and glassy methanol solutions. The temperature dependent equilibrium shifts of the zinc(II) bromo complexes in the methanol and DMF solutions are discussed together with previously reported results for the aqueous phase.

X-ray diffraction study revealing phase coexistence in barium titanate stannate

2004 ◽  
Vol 19 (10) ◽  
pp. 2834-2840 ◽  
Author(s):  
Volkmar Mueller ◽  
Horst Beige ◽  
Hans-Peter Abicht ◽  
Christian Eisenschmidt
Keyword(s):  
Phase Transition ◽  
Ferroelectric Phase ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Temperature Range ◽  
Xrd Study ◽  
Xrd Patterns ◽  
Tetragonal Phase Transition

In this paper, the results of a temperature dependent x-ray diffraction (XRD) study on BaTi0.95Sn0.05O3 (BTS-5) ceramics are compared with dielectric measurements. The orthorhombic-tetragonal phase transition at T2 = 306 K is found to proceed in a considerably wider temperature range than expected from the dielectric anomaly. Although the macroscopic properties of BTS-5 indicate a rather sharp ferroelectric phase transition at Tc = 358K, we observe anomalous XRD-patterns in a 25 K wide temperature range. This is interpreted in terms of mechanically clamped tetragonal and cubic phase, coexisting in the vicinity of Tc in grains with inhomogeneous Sn-distribution.

scholarly journals Structural and optical characterization of the crystalline phase transformation of electrospinning TiO2 nanofibres by high-temperatures annealing

2019 ◽  
Vol 65 (5 Sept-Oct) ◽  
pp. 459
Author(s):  
O. Secundino-Sánchez ◽  
J. Diaz-Reyes ◽  
J. F. Sánchez-Ramírez ◽  
And J.L. Jiménez-Pérez
Keyword(s):  
Phase Transformation ◽  
Raman Scattering ◽  
High Temperatures ◽  
Crystalline Phase ◽  
Annealing Temperature ◽  
Crystal Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Range ◽  
Wide Range

The electrospinning technique has been used to synthesize TiO2 nanofibres, which by annealing at high temperatures in a wide range achieves the crystal phase transformation of anatase to rutile passing through the anatase+rutile mixed. The investigated temperature range was 0-1000°C. The TiO2 nanofibres chemical stoichiometry and surface morphology were obtained by Scanning Electron Microscopy and Energy Dispersive Spectrometry. The nanofibres diameter was ranged from 137.0 to 115.3 nm in the annealing temperature interval of 0-1000°C. The influence of the annealing temperature on the structure and crystal phase quality of the TiO2crystal has been investigated by X-ray diffraction and Raman scattering. Clear evidence of nanofibres structural transformation from pure anatase to pure rutile structures, including the quasi-amorphous and anatase+rutile mixed phases has been confirmed by Raman scattering. By X-ray diffraction was found that the nanofibres crystalline phases present as preferential growth direction (101) for anatase and (110) for rutile. The Raman spectroscopy exhibits the anomalous behaviour for band broadening and shifting of Raman bands with increasing crystallite size that form the nanofibres. The room-temperature photoluminescence presents radiative bands whose main band redshifts, from 2.56 to 1.32 eV, as the crystalline phase transforms in the investigated annealing temperature range.

Reaction Synthesis of Cr2AlC Ceramics Powders

2012 ◽  
Vol 624 ◽  
pp. 13-16
Author(s):  
Chun Long Guan ◽  
Zi Ping Zhang ◽  
Ying Chun Shan ◽  
Chun Hua Wang
Keyword(s):  
Effect Of Temperature ◽  
Molar Ratio ◽  
Reaction Synthesis ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Solid Reaction ◽  
X Ray ◽  
Temperature Range

Polycrystalline Cr2AlC was fabricated by a solid reaction synthesis of a mixture of Cr, Al and graphite powders in a flowing or the atmosphere in the temperature range of 700 to 1450 °C. The products for identification and analysis were characterized by X-ray diffraction (XRD). The effects of the composition of the initial elemental powders and temperature of purity and formation of Cr2AlC were examined. It is found that the co-existence of Cr7C3 with Cr2AlC is attributed to the surplus of carbon in the starting powders at 1350 °C, selecting the starting materials with a Cr: Al: C molar ratio of 2: (1.1-1.6): 1. For sample obtained from the starting elemental powders with the Cr: Al: C molar ratio of 2: 1.2: 0.94, no other phases but Cr2AlC were detected. In addition, the effect of temperature on the formation of Cr2AlC ceramic powders was carried out.

Effect of Hydrated Metal Salts on the Coordination Product of Cobalt(II) halide and PNP Type Ligand, 2,6-bis(di-tertbutylphosphinomethyl) pyridine

2018 ◽  
Author(s):  
Tasneem Siddiquee ◽  
Abdul Goni
Keyword(s):  
Metal Salts ◽  
Molar Ratio ◽  
Pincer Complexes ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Pincer Ligand ◽  
Tetrahedral Geometry ◽  
X Ray ◽  
Distorted Tetrahedral Geometry ◽  
Cobalt Center

Chemical treatment of CoX<sub>2</sub><b><sup>. </sup></b>6H<sub>2</sub>O (X = Cl, Br, I) with the potentially tridentate PNP pincer ligand 2,6-bis(di-<i>tert</i>-butylphosphinomethyl)pyridine in 1:1 molar ratio results in cobalt(II) halide-PNP pincer complexes. The effect of the hydrated metal source on molecular structure and geometry of the complexes was studied by single crystal X-ray diffraction analysis. The complexes are neutral and the cobalt center adopts a penta-coordinate system with potential atropisomerization. Within the unit cell there are two distinct molecules per asymmetric unit. One of the two phosphorus atoms in the PNP ligand was observed to be partially oxidized to phosphinoxide. Disorder in the structure reflects a mixture of square pyramidal and distorted tetrahedral geometry.

scholarly journals Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 346
Author(s):  
Sonam Goyal ◽  
Maizatul Shima Shaharun ◽  
Ganaga Suriya Jayabal ◽  
Chong Fai Kait ◽  
Bawadi Abdullah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Support ◽  
Oxidation Potential ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Optimum Parameters ◽  
Reduction Of Co2 ◽  
Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

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