Solid-Solid Phase Transition in Trimethylolpropane (TRMP)

2002 ◽  
Vol 216 (12) ◽  
Author(s):  
D. Chandra ◽  
H. Mandalia ◽  
W.-M. Chien ◽  
D. W. Lindle ◽  
R. Rudman
Keyword(s):  
Room Temperature ◽  
Solid Phase ◽  
X Ray Diffraction ◽  
Storage Material ◽  
X Ray ◽  
Α Phase ◽  
Energy Storage Material ◽  
Plastic Phase ◽  
Solid Phase Transition ◽  
Thermal Energy Storage Material

An orientationally disordered crystalline (ODIC) plastic phase (γ) was observed in Trimethylolpropane (TRMP) during heating by high resolution thermal and X-ray diffraction analyses. TRMP is a potential thermal energy storage material. The enthalpies of solid-solid (α → γ at 327.8 K) and fusion (γ → liquid at 332.7 K) transitions are 16.36 kJ/mol and 0.9 kJ/mol, respectively. Supercooling was observed during solidification of melts, and this supercooled γ phase began to transform to a metastable crystalline phase, designated as α′, after 20 minutes at room temperature. The lattice parameters of the monoclinic α phase, obtained from this study, are:

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

scholarly journals Получение, структура, диэлектрические и магнитные свойства керамики SrFe-=SUB=-2/3-=/SUB=-W-=SUB=-1/3-=/SUB=-O-=SUB=-3-=/SUB=-

2018 ◽  
Vol 60 (3) ◽  
pp. 510
Author(s):  
А.В. Павленко ◽  
А.В. Турик ◽  
Л.А. Шилкина ◽  
С.П. Кубрин ◽  
Ю.B. Русалев ◽  
...  
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Solid Phase ◽  
Ceramic Technology ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solid Phase Reactions ◽  
Perovskite Type ◽  
Perovskite Type Structure

AbstractPolycrystalline samples of SrFe_2/3W_1/3O_3 (SFWO) ceramic were obtained by solid-phase reactions with subsequent sintering using conventional ceramic technology. X-ray diffraction analysis showed that at room temperature, the SFWO ceramic is single-phase and has a perovskite-type structure with tetragonal symmetry and parameters a = 3.941(9) Å, c = 3.955(6) Å, and c/a = 1.0035. In studying the magnetic properties and the Mössbauer effect in SFWO ceramics, it is found that the material is a ferrimagnet, and the iron ions are only in the valence state of Fe^3+. It is suggested that in the temperature range of T = 150–210°C, a smeared phase transition from a cubic (paraelectric) phase to a tetragonal (ferroelectric) phase takes place in SFWO with decreasing temperature.

scholarly journals Polar and non-polar structures of NH4TiOF3

2019 ◽  
Vol 52 (1) ◽  
pp. 23-26
Author(s):  
O. Boytsova ◽  
I. Dovgaliuk ◽  
D. Chernyshov ◽  
A. Eliseev ◽  
P. O'Brien ◽  
...  
Keyword(s):  
Room Temperature ◽  
Phase 1 ◽  
Structural Features ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Starting Compound ◽  
Different Temperatures ◽  
Fourfold Axis

Ammonium oxofluorotitanate, NH4TiOF3, is probably the best known precursor for the synthesis of anatase mesocrystals. Transformation of NH4TiOF3 into TiO2 through thermal decomposition, accompanied by hydrolysis, preserves some structural features of the precursor. Currently, any discussion of the mechanism of this transformation is difficult, as the exact crystal structure of the starting compound is not available and no intermediate structures are known. This article describes the outcome of single-crystal and powder X-ray diffraction studies, revealing the existence of two polymorphs of the parent NH4TiOF3 at different temperatures. A second-order phase transition from the polar Pca21 α phase (1), stable at room temperature, to the Pma2 β phase (2) above ∼433 K has been demonstrated. The direction of the pseudo-fourfold axis in NH4TiOF3 coincides with the orientation of the fourfold axis of anatase mesocrystals, consistent with a topotactical transformation.

Study of Electrical and Aging Properties on the La-Doped Aurivillius Phase Ferroelectrics BaBi4Ti4O15

2013 ◽  
Vol 319 ◽  
pp. 9-13
Author(s):  
Bai Wei Yu ◽  
Qian Qian Zheng ◽  
Li Jing Pan ◽  
Dong Hua Zhang ◽  
Yan Xue Tang ◽  
...  
Keyword(s):  
Relative Permittivity ◽  
Marked Improvement ◽  
Room Temperature ◽  
Solid Phase ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Aging Properties ◽  
T Phase ◽  
La Doped

Aurivillius phase ferroelectrics Ba(Bi1−xLax)4Ti4O15(x=0-0.05) (BBiLxT) was synthesized by a modified high-temperature solid-phase route.The structure, the dielectric, the ferroelectric and the aging properties were investigated systematically. With the La3+doping, the room temperature relative permittivity of the samples is increased, and dielectric loss is decreased. For the BBiLxT phase, only a weak variation with respect to the F2mm space group can be suggested from single crystal X-ray diffraction. The microstructure confirms the samples have a well-proportioned grain size and a higher density. The substitution also results in a marked improvement in the remnant polarization. The doping of La3+in BBiLxT ceramics increased the room temperature relative permittivity aging properties.

Untersuchungen zur Polymorphie der Cäsium-Dodekahalogeno-closo-Dodekaborate Cs2[B12X12] (X = Cl–I)

2020 ◽  
Vol 75 (8) ◽  
pp. 777-790
Author(s):  
Ioannis Tiritiris ◽  
Kevin U. Bareiß ◽  
Thomas Schleid
Keyword(s):  
Phase Transitions ◽  
Defect Structure ◽  
Room Temperature ◽  
Solid Phase ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Space Group ◽  
X Ray ◽  
Cubic System ◽  
Cesium Salts

AbstractThermoanalytic DSC and temperature-dependent X-ray diffraction investigations on the cesium dodecahalogeno-closo-dodecaborates Cs2[B12X12] (X = Cl–I) have revealed solid-solid phase transitions from their trigonal room-temperature α-forms (e.g. α-Cs2[B12Cl12]: a = 959.67(3) pm, c = 4564.2(2) pm, Z = 6, space group R$\overline{3}$) into cubic high-temperature modifications. The isotypic title compounds crystallize in the space group Pm$\overline{3}$n (e.g. β-Cs2[B12Cl12]: a = 1051.98(6) pm, Z = 2) with a W3O-type defect structure. The statistic occupation of six possible positions with only four Cs+ cations results in a cation-deficient A2B arrangement for Cs2[B12X12]. Upon cooling the β-phase, a third polymorph was observed, which also crystallizes in the cubic system, but now in the space group Ia$\overline{3}$d (e.g. γ-Cs2[B12Cl12]: a = 2102.2(3) pm, Z = 16), and has to be regarded as a phase with only a partially disordered cation substructure. In this crystal structure the [B12X12]2− anions exhibit a NaTl-type arrangement, in which the Cs+ cations occupy suitable interstices. The phase transitions of the differently halogenated cesium salts follow no specific trend as the transition from the trigonal α- to the cubic β-form occurs at 178 °C for the chlorinated, at 270 °C for the iodinated and at 325 °C for the brominated examples. On further heating however, β-Cs2[B12I12] starts to decompose at 945 °C first, followed by β-Cs2[B12Br12] and β-Cs2[B12Cl12] at 959 °C and 983 °C, respectively.

scholarly journals Molecular Dynamics Simulations of Two-Step Process Enable Room-Temperature Synthesis of α-FAPbI3

2020 ◽  
Author(s):  
Paramvir Ahlawat ◽  
Haizhou Lu ◽  
Amita Ummadisingu ◽  
Haiyang Niu ◽  
Michele Invernizzi ◽  
...  
Keyword(s):  
Room Temperature ◽  
Solid Phase ◽  
Perovskite Solar Cells ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
Sequential Deposition ◽  
Solid Phase Transition ◽  
Dynamics Simulations ◽  
Methylammonium Lead Iodide ◽  
Temperature Crystallization

It is well established that the lack of understanding the crystallization process in two-step sequential deposition has a direct impact on efficiency, stability and reproducibility of perovskite solar cells. Here, we try to understand the solid-solid phase transition occuring during two-step sequential deposition of methylammonium lead iodide and formamidinium lead iodide. Using metadynamics, X-ray diffraction and Raman spectroscopy, we reveal the microscopic details of this process. We find that the formation of perovskite proceeds through intermediate structures and report polymorphs found for methylammonium lead iodide and formamidinium lead iodide. From simulations, we discover a possible crystallization pathway for the highly efficient metastable α-phase of formamidinium lead iodide. Guided by these simulations, we perform experiments that results in the room temperature crystallization of α-formamidinium lead iodide.

Cryogenic mechanical milling of high density polyethylene

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Ana Paula Cysne Barbosa ◽  
Michael Stranz ◽  
Frank Katzenberg ◽  
Uwe Köster
Keyword(s):  
Mechanical Milling ◽  
Solid Phase ◽  
Polarized Light ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Monoclinic Modification ◽  
X Ray ◽  
Responsible Mechanism ◽  
Solid Phase Transition ◽  
Melting And Crystallization

AbstractHDPE was analyzed after being submitted to cryogenic mechanical milling (CMM) by X-ray diffraction (WAXS), polarized light microscopy and differential scanning calorimetry (DSC). After CMM, besides the known phase transformation of the orthorhombic PE crystals into the monoclinic modification, slight changes in the melting and crystallization behavior as well as an unexpected increase in crystallinity were observed. The observed results can be explained by assuming a solid/solid phase transition as the responsible mechanism.

Prepartion of Organophilic Bentonite / Paraffin Composite Phase Change Energy Storage Material with Melting Intercalation Method

2011 ◽  
Vol 284-286 ◽  
pp. 126-131 ◽  
Author(s):  
Yi Zhang ◽  
Xiao Peng Wang ◽  
Dong Xu Li
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Energy Storage Materials ◽  
Mass Ratio ◽  
X Ray Diffraction ◽  
Storage Material ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Energy Storage Material ◽  
Scanning Electron

Organophilic Bentonite / Paraffin composite phase change energy storage materials (OB/P PCM composite) were prepared by melting intercalation method. Under high temperature, no melt paraffin seep out from the PCM of organophilic bentonite/paraffin (OB/P) mass ratio is 2:1, which paraffin content is largest. Samples were tested by X ray diffraction (XRD), Scanning Electron Microscope (SEM), Differential scanning calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Paraffin was well intercalated into layerd bentonite. Melting point and fussion heat of composite PCM with mass ratio2:1 are 45.7 °C and 68.7 kJ/kg, it can be added to solar energy.

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