THE INFRARED SPECTRA AND PHASE TRANSITIONS OF SOLID PIPERIDINIUM HALIDES

1962 ◽  
Vol 40 (4) ◽  
pp. 615-621 ◽  
Author(s):  
A. Cabana ◽  
C. Sandorfy
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Solid Films

The infrared spectra of solid films of piperidinium halides were measured at both room temperature and low temperatures. The spectra of the chloride and the bromide are not appreciably affected by cooling, but the spectrum of the iodide exhibits spectacular changes. These changes are explained by assuming the occurrence of a phase transition at about −15 °C. The possibility of a "chair" → "boat" interconversion is also discussed.

Room-temperature NaI/H2O compression icing: solute–solute interactions

2017 ◽  
Vol 19 (39) ◽  
pp. 26645-26650 ◽  
Author(s):  
Qingxin Zeng ◽  
Chuang Yao ◽  
Kai Wang ◽  
Chang Q. Sun ◽  
Bo Zou
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Bond Energy ◽  
Room Temperature ◽  
Solute Concentration ◽  
Solute Interaction ◽  
Solute Interactions

H–O bond energy governs the PCx for Na/H2O liquid–VI–VII phase transition. Solute concentration affects the path of phase transitions differently with the solute type. Solute–solute interaction lessens the PC2 sensitivity to compression. The PC1 goes along the liquid–VI boundary till the triple phase joint.

scholarly journals Temperature Dependence of the Bragg Peak-Intensity Close to the α-Incommensurate-β Transition in Quartz

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Hamit Yurtseven ◽  
Koray Kaymazlar
Keyword(s):  
Phase Transition ◽  
Temperature Dependence ◽  
Atmospheric Pressure ◽  
Low Temperatures ◽  
Order Parameter ◽  
Room Temperature ◽  
Bragg Peak ◽  
Threefold Axis ◽  
First Order ◽  
Peak Intensity

Quartz as a mineral has a stable crystalline phase at room temperature and atmospheric pressure; at low temperatures it is in the α phase and when it is heated up, it transforms into the β phase through the intermediate (incommensurate) phase within the temperature interval of nearly 1.3 K at around 847 K. The order parameter Q occurs due to a tilting of SiO4 tetrahedra around the threefold axis, which can be related to variation of the peak-intensity with the temperature in quartz. In this study, we analyze the temperature dependence of the Bragg peak-intensity measured through the α-β transition in quartz, as obtained from the literature according to a power-law formula. From our analysis, we deduce the values of the critical exponent β for the order parameter (Bragg peak-intensity) for the α-incommensurate (IC-)β transition. Our β values indicate that the β-IC phase transition is of a second order and that the IC-α phase transition is of a weak first order, as also reported in the literature.

scholarly journals Combinatorial discovery of small-molecule 1,2,3-triazolium ionic liquids exhibiting lower critical solution temperature phase transition

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Yen-Ho Chu ◽  
Mou-Fu Cheng ◽  
Yung-Hsin Chiang
Keyword(s):  
Phase Transition ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Phase Transitions ◽  
Small Molecule ◽  
Room Temperature ◽  
Solution Temperature ◽  
Temperature Phase ◽  
Critical Solution Temperature ◽  
True Value

Abstract Both lower and upper critical solution temperature (LCST and UCST) systems are two typical phase behaviors of thermoresponsive materials with solvents, in which LCST is far less common than UCST. Recent studies on ionic liquids carrying LCST phase transitions have predominantly focused on quaternary ammonium- and phosphonium-based ionic salts. Based on the 1,2,3-triazole core structure assemblable by azide-alkyne cycloaddition click reaction, this work reports the combinatorial synthesis of 1,3,4-trialkylated 1,2,3-triazolium ionic liquids in three libraries with a total of 160 ionic liquids and demonstrates, for the first time, their values in temperature-switchable phase transition with water. In this work, the successful discovery of a new thermoresponsive ionic liquid b26, based on the structure-and-phase separation study of b8 and b9, perfectly exemplified the true value of the tunability of ionic liquid fine structures. For all 160 ionic liquids synthesized, 155 are liquid at room temperature and 22 room-temperature ionic liquids were found to exhibit thermoresponsive phase transitions having low Tc values in water. To the best of our knowledge, this comprehensive study is the first report of small-molecule 1,2,3-triazolium ionic liquids that exhibit LCST property in water.

Notizen: Austausch von Nitrit- gegen Bromidanionen in Na3NO3 / Replacement of Nitrite by Bromide Anions in Na3NO3

1989 ◽  
Vol 44 (8) ◽  
pp. 996-998 ◽  
Author(s):  
M. Jansen ◽  
W. Müller
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Solid Solutions ◽  
Room Temperature ◽  
Mixed Crystals ◽  
Miscibility Gap ◽  
Temperature Range ◽  
Collective Interactions

Na3O(NO2) and Na3OBr are isostructural and form solid solutions with a miscibility gap χ = 0.28 to 0.62 as referred to Na3OBrx(NO2)1-x, at room temperature. Above 593 Κ formation of mixed crystals was observed for all compositions. In contrast to pure Na3O(NO2), the solid solutions do not undergo any phase transition in the investigated temperature range from 293 Κ to 130 K. These findings reveal that collective interactions between the dynamically disordered NO2--groups are involved in the phase transitions of Na3NO3.

Tunability of τf in perovskites and related compounds

2002 ◽  
Vol 17 (8) ◽  
pp. 2033-2040 ◽  
Author(s):  
P. L. Wise ◽  
I. M. Reaney ◽  
W. E. Lee ◽  
D. M. Iddles ◽  
D. S. Cannell ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Resonant Frequency ◽  
Room Temperature ◽  
Structural Phase ◽  
Structural Phase Transitions ◽  
Ionic Polarizability ◽  
Microwave Dielectrics ◽  
Related Compounds ◽  
Range Of Values

Tuning the temperature coefficient of resonant frequency (τf) in microwave dielectrics has been attributed to two main mechanisms: (i) dilution of the average ionic polarizability; (ii) the onset of an octahedral tilt transition above room temperature. The contributions of each mechanism have been isolated using ceramics in the Srn+1TinO3n+1, SrxCa1−x)3Ti2O7, and (SrxCa1−x)TiO3 series. In the Srn+1TinO3n+1 series, relative permittivity (εr) and τf are linearly proportional over a broad range of values, 100–37 and 800–140 ppm/°C, n = 4 and 1, respectively. No structural phase transitions occur on cooling from the prototype symmetry, and the mechanism of tuning is attributed solely to dilution of the average ionic polarizability as the SrO:SrTiO3 ratio increases. Exchanging Ca for Sr in the (SrxCa1−x)3Ti2O7 series resulted in an 80% reduction in the magnitude of τf from +320 to +50 ppm/°C but only 21% in permittivity (58 to 46). The effect was nonlinear and attributed primarily to the onset of a phase transition involving rotations of the octahedra on cooling. Superlattice reflections associated with the octahedral tilt transition have been identified.

scholarly journals Single-crystal-to-single-crystal phase transitions of commensurately modulated sodium saccharinate 1.875-hydrate

IUCrJ ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 139-147
Author(s):  
Toms Rekis ◽  
Achim M. Schaller ◽  
Surya Rohith Kotla ◽  
Andreas Schönleber ◽  
Leila Noohinejad ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Single Crystal ◽  
Room Temperature ◽  
Crystal Phase ◽  
Component Ratio ◽  
Sudden Increase ◽  
Sodium Cations ◽  
Triclinic Phase ◽  
General Organization

This work reports reversible, single-crystal-to-single-crystal phase transitions of commensurately modulated sodium saccharinate 1.875-hydrate [Na(sac)(15/8)H2O]. The phases were studied in the temperature range 298 to 20 K. They exhibit complex disordered states. An unusual reentrant disorder has been discovered upon cooling through a phase transition at 120 K. The disordered region involves three sodium cations, four water molecules and one saccharinate anion. At room temperature, the structure is an eightfold superstructure that can be described by the superspace group C2/c(0σ20)s0 with q = (0, 3/4, 0). It demonstrates maximum disorder with the disordered chemical entities having slightly different but close to 0.50:0.50 disorder component ratios. Upon cooling, the crystal tends to an ordered state, smoothly reaching a unified disorder component ratio of around 0.90:0.10 for each of the entities. Between 130 and 120 K a phase transition occurs involving a sudden increase of the disorder towards the disorder component ratio 0.65:0.35. Meanwhile, the space group and general organization of the structure are retained. Between 60 and 40 K there is another phase transition leading to a twinned triclinic phase. After heating the crystal back to room temperature its structure is the same as before cooling, indicating a complete reversibility of the phase transitions.

scholarly journals Room-temperature photo-induced martensitic transformation in a protein crystal

IUCrJ ◽  
2019 ◽  
Vol 6 (4) ◽  
pp. 619-629 ◽  
Author(s):  
Steven Dajnowicz ◽  
Patricia S. Langan ◽  
Kevin L. Weiss ◽  
Ilia N. Ivanov ◽  
Andrey Kovalevsky
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Martensitic Transformation ◽  
Room Temperature ◽  
Fluorescent Protein ◽  
Martensitic Phase ◽  
Protein Crystal ◽  
High Tech ◽  
X Ray ◽  
Martensitic Phase Transition

Martensitic transformations are the first-order crystal-to-crystal phase transitions that occur mostly in materials such as steel, alloys and ceramics, thus having many technological applications. These phase transitions are rarely observed in molecular crystals and have not been detected in protein crystals. Reversibly switchable fluorescent proteins are widely used in biotechnology, including super-resolution molecular imaging, and hold promise as candidate biomaterials for future high-tech applications. Here, we report on a reversibly switchable fluorescent protein, Tetdron, whose crystals undergo a photo-induced martensitic transformation at room temperature. Room-temperature X-ray crystallography demonstrates that at equilibrium Tetdron chromophores are all in the trans configuration, with an ∼1:1 mixture of their protonated and deprotonated forms. Irradiation of a Tetdron crystal with 400 nm light induces a martensitic transformation, which results in Tetdron tetramerization at room temperature revealed by X-ray photocrystallography. Crystal and solution spectroscopic measurements provide evidence that the photo-induced martensitic phase transition is coupled with the chromophore deprotonation, but no trans–cis isomerization is detected in the structure of an irradiated crystal. It is hypothesized that protein dynamics assists in the light-induced proton transfer from the chromophore to the bulk solvent and in the ensuing martensitic phase transition. The unique properties of Tetdron may be useful in developing novel biomaterials for optogenetics, data storage and nanotechnology.

Infrared Spectra of Water in Crystalline Hydrates: KSnCl3•H2O, an Untypical Monohydrate

1974 ◽  
Vol 52 (16) ◽  
pp. 2928-2931 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Water Molecules ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline KSnCl3•H2O were recorded between 4000 and 300 cm−1 at different degrees of deuteration and at temperatures between 30 and −160 °C. At low temperatures the spectra show a complexity indicative of the presence of several crystallographically distinct water molecules. These molecules occupy sites with nearly identical environments and at room temperature are spectroscopically indistinguishable. The environment of each of these molecules is asymmetric. Hydrogen bonds are very weak and probably highly bent. The water molecules are less separated from one another than in K2SnCl4•H2O and may share their potassium neighbors.

X-Ray Diffraction Study of the Phase Transition of the ${\rm Si}(111)(\sqrt{3} \times \sqrt{3})\mbox{-Ag}$ Surface

2003 ◽  
Vol 10 (02n03) ◽  
pp. 519-524 ◽  
Author(s):  
Toshio Takahashi ◽  
Hiroo Tajiri ◽  
Kazushi Sumitani ◽  
Koichi Akimoto ◽  
Hiroshi Sugiyama ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Low Temperatures ◽  
Diffuse Scattering ◽  
Room Temperature ◽  
Bragg Reflection ◽  
Grazing Incidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Displacive Phase Transition

The structure of the [Formula: see text] surface was studied at both room temperature and a low temperature of 50 K using grazing incidence X-ray diffraction. At low temperatures diffuse scattering was observed in addition to Bragg reflection. Least squares analyses for Bragg reflections using anisotropic Debye–Waller factors show that the structure at 50 K is consistent with an inequivalent triangle (IET) model, while the structure at room temperature is explained by a honeycomb-chained triangle (HCT) model with strong anisotropic Debye–Waller factors. From the temperature dependence of diffuse scattering, the phase transition temperature Tc and critical exponent β were determined to be about 150 K and 0.27. Some Bragg intensities showed discontinuous changes in their first derivatives at Tc. The results favor a displacive phase transition rather than an order–disorder one.

TEM of Phase Transitions in Tridymite and Cristobalite Based Materials.

2000 ◽  
Vol 6 (S2) ◽  
pp. 358-359
Author(s):  
Gustaaf Van Tendeloo
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
High Temperature ◽  
Solid State ◽  
Wide Temperature Range ◽  
Room Temperature ◽  
Paraelectric Phase ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Extended Defects

We have determined the structure of the paraelectric phase of BaAl2O4, which is a stuffed tridymite, by different TEM techniques and we will describe the phase transition between the ferroelectric room temperature phase and the paraelectric high temperature phase. We have also obtained HREM images of the higly radiation sensitive acristobalite phase of (Si0,9 Ge0,1)O2 and analysed the extended defects in this material.The stuffed tridymite BaAl2O4 is ferroelectric at room temperature and undergoes a paraelectric-ferroelectric (PEFE) phase transition. The transition is reversible, takes place over a wide temperature range (400K-670K) and has a dynamical character. BaAl2O4 is easily obtained by solid state reaction of BaCO3, and A12O4,. The stoichiometric amounts of the initial reagents were mixed, grinded in an agate mortar under acetone and pressed into a pellet. The pellet was annealed in alumina crucibles at 1000 °C and 1300 °C for 40 h in air and furnace cooled.

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