Crystallization of silica promoted by residual hydrogen bonding interactions at high temperature

2018 ◽  
Vol 20 (18) ◽  
pp. 12827-12834
Author(s):  
Xiaojiao Zhang ◽  
Yang Liu ◽  
Wenchuan Lai ◽  
Zaoming Wang ◽  
Wang Xu ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
High Temperature ◽  
Low Temperature ◽  
Crystalline Silica ◽  
Hydrogen Bonding Interactions ◽  
Novel Approach ◽  
Residual Hydrogen ◽  
Fluorinated Graphene

A novel approach to prepare crystalline silica through calcination of the composite of silica and highly fluorinated graphene at a relatively low temperature is demonstrated.

Viscoelastic Behavior of Segmented Elastomers

1967 ◽  
Vol 40 (4) ◽  
pp. 1105-1110 ◽  
Author(s):  
Stuart L. Cooper ◽  
Arthur V. Tobolsky
Keyword(s):  
Hydrogen Bonding ◽  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Viscoelastic Behavior ◽  
Temperature Transition ◽  
Hydrogen Bonding Interactions ◽  
Structural Nature ◽  
Hard Segments

Abstract Viscoelastic behavior of linear segmented elastomers was examined. The unusual properties found in spandex systems are also observable in hydrocarbon block co-polymers, indicating that hydrogen bonding interactions are perhaps not essential. Low temperature properties of segmented systems are governed by the structural nature of the associated flexible segments, which determines the value of the major glass transition temperature (Tg). It appears that an association of the hard segments provides a broad temperature range of enhanced rubbery modulus. This occurs between the major Tg and a secondary high temperature transition.

scholarly journals The phase transition of rubidium hydrogen carbonate, RbHCO3

2017 ◽  
Vol 73 (7) ◽  
pp. 975-979 ◽  
Author(s):  
Carla Larvor ◽  
Berthold Stöger
Keyword(s):  
Phase Transition ◽  
Hydrogen Bonding ◽  
High Temperature ◽  
Hydrogen Atom ◽  
Low Temperature ◽  
Three Dimensional ◽  
Disorder Phase Transition ◽  
Dimensional Network ◽  
Hydrogen Carbonate ◽  
Index 2

Rubidium hydrogen carbonate, RbHCO3, features an order/disorder phase transition atTC= 245 K from the high-temperature (HT) disorderedC2/mmodification to the low-temperature (LT)C-1 modification. The crystal structures are characterized by [HCO3]22−pairs of hydrogen carbonate groups connected by strong hydrogen bonding. The [HCO3]22−pairs are connected by Rb+cations into a three-dimensional network. In HT-RbHCO3, the hydrogen atom is disordered. In LT-RbHCO3, ordering of the hydrogen atom leads to atranslationengleichesymmetry reduction of index 2. The lost reflections and rotations are retained as twin operations.

scholarly journals Hydrogen-bonding in mono-, di- and tetramethylammonium dihydrogenphosphites

2021 ◽  
Vol 236 (1-2) ◽  
pp. 33-41
Author(s):  
Matthias Kogler ◽  
Berthold Stöger
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
High Temperature ◽  
Low Temperature ◽  
Crystal Structures ◽  
Point Symmetry ◽  
Temperature Dependent ◽  
Threefold Axis ◽  
Quotient Graphs ◽  
Hydrogen Bonding Networks

Abstract The crystal structures of methylammonium and dimethylammonium dihydrogenphosphite (MA⋅H2PO3, I2/a and DMA⋅H2PO3, P 2 1 / c $P{2}_{1}/c$ ) are built of infinite chains of hydrogen bonded H 2 P O 3 − ${\mathrm{H}}_{\mathrm{2}}\mathrm{P}{\mathrm{O}}_{\mathrm{3}}^{-}$ anions. The chains are connected by the ammonium cations via hydrogen bonding to di- (DMA⋅H2PO3) and triperiodic (MA⋅H2PO3) networks. Tetramethylammonium dihydrogenphosphite monohydrate (TMA⋅H2PO3⋅H2O) features temperature dependent dimorphism. The crystal structure of the high-temperature (HT, cubic P213) and low-temperature (LT, orthorhombic P212121) phases were determined at 150 and 100 K, respectively. The hydrogen bonding network in the HT phase is disordered, with H 2 P O 3 − ${\mathrm{H}}_{\mathrm{2}}\mathrm{P}{\mathrm{O}}_{\mathrm{3}}^{-}$ and H2O being located on a threefold axis and is ordered in the LT phase. On cooling, the point symmetry is reduced by an index of 3. The lost symmetry is retained as twin operations, leading to threefold twinning by pseudo-merohedry. The hydrogen-bonding networks of the HT and LT phases can be represented by undirected and directed quotient graphs, respectively.

18-Krone-6 und kleine Carbonsäuren. Bildung und Struktur binärer Addukte mit Ameisen-und Essigsäure sowie ternärer mit Essigsäure und Wasser/18-Crown-6 and Small Carboxylic Acids. Formation and Structure of Binary Adducts with Formic and Acetic Acid, as well as Ternary Ones with Acetic Acid and Water

1998 ◽  
Vol 53 (2) ◽  
pp. 242-248 ◽  
Author(s):  
Antje Albert ◽  
Dietrich Mootz
Keyword(s):  
Hydrogen Bonding ◽  
Acetic Acid ◽  
High Temperature ◽  
Low Temperature ◽  
Binary Systems ◽  
Intermolecular Hydrogen Bonding ◽  
Temperature Form ◽  
Set Up ◽  
High Temperature Form ◽  
Ether Molecule

Abstract The melting diagrams of the binary systems 18-crown-6/formic acid and 18-crown-6/acetic acid have been set up and the crystal structures of the adducts 18C6 · 2 HCOOH (1, space group P 21/c with Z = 2 formula units per unit cell) and 18C6 · 2 CH3COOH (2, C2/m, Z = 2) determined. Furthermore three ternary phases, 18C6 · CH3COOH · H2O (3, P21/c, Z = 4) and dimorphic 18C6 · 2 CH3COOH · 4 H2O (high temperature form 4, P21/n, Z = 2; low temperature form 5, P21/n, Z = 2) have been characterized in the same way. In each structure the crown ether molecule has the (pseudo) D3d conformation common for many of its complexes. Various aspects of the intermolecular hydrogen bonding are described.

scholarly journals The order/disorder phase transition of hypophosphorous acid H3PO2

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Martin Nastran ◽  
Berthold Stöger
Keyword(s):  
Phase Transition ◽  
Hydrogen Bonding ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Rotation Axis ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Hypophosphorous Acid ◽  
Disorder Phase Transition

Abstract Hypophosphorous acid, H3PO2 is dimorphic with a phase transition in the 200–225 K range. The H3PO2 molecules are connected by hydrogen bonding to infinite chains extending in the [100] direction. In the high-temperature phase (P21212, Z ′ = 1 2 ${Z}^{\prime }=\frac{1}{2}$ ), the hydrogen bonds are disordered about a two-fold rotation axis. On cooling below the phase transition temperature, the hydrogen bonds become ordered, resulting in a symmetry reduction of the klassengleiche type of index 2. In the low-temperature phase (P212121, Z ′ = 1 ${Z}^{\prime }=1$ ), the c parameter is doubled with respect to the high-temperature phase. The hydrogen-bonding topology of the high- and low-temperature phases are double-infinite directed and undirected linear graphs, respectively.

Exsolution and inversion in pigeonite from the Whin Sill, Northern England

1978 ◽  
Vol 36 (1) ◽  
pp. 474-475
Author(s):  
P.P.K. Smith
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Homogeneous Nucleation ◽  
Silicate Mineral ◽  
Antiphase Boundaries ◽  
Two Phase ◽  
Primitive Form ◽  
The Core ◽  
Nucleation Mechanisms ◽  
And Inversion

Grains of pigeonite, a calcium-poor silicate mineral of the pyroxene group, from the Whin Sill dolerite have been ion-thinned and examined by TEM. The pigeonite is strongly zoned chemically from the composition Wo8En64FS28 in the core to Wo13En34FS53 at the rim. Two phase transformations have occurred during the cooling of this pigeonite:- exsolution of augite, a more calcic pyroxene, and inversion of the pigeonite from the high- temperature C face-centred form to the low-temperature primitive form, with the formation of antiphase boundaries (APB's). Different sequences of these exsolution and inversion reactions, together with different nucleation mechanisms of the augite, have created three distinct microstructures depending on the position in the grain.In the core of the grains small platelets of augite about 0.02μm thick have farmed parallel to the (001) plane (Fig. 1). These are thought to have exsolved by homogeneous nucleation. Subsequently the inversion of the pigeonite has led to the creation of APB's.

Superconducting Wind Generators with Capacities of 10 MW and Larger

2020 ◽  
Vol 10 (10) ◽  
pp. 59-67
Author(s):  
Victor N. ANTIPOV ◽  
◽  
Andrey D. GROZOV ◽  
Anna V. IVANOVA ◽  
◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Wind Power ◽  
State Of The Art ◽  
Superconducting Materials ◽  
Commercial Application ◽  
Synchronous Generators ◽  
High Temperature Superconducting ◽  
Wind Generators ◽  
Main Factor

The overall dimensions and mass of wind power units with capacities larger than 10 MW can be improved and their cost can be decreased by developing and constructing superconducting synchronous generators. The article analyzes foreign conceptual designs of superconducting synchronous generators based on different principles: with the use of high- and low-temperature superconductivity, fully superconducting or only with a superconducting excitation system, and with the use of different materials (MgB2, Bi2223, YBCO). A high cost of superconducting materials is the main factor impeding commercial application of superconducting generators. In view of the state of the art in the technology for manufacturing superconductors and their cost, a conclusion is drawn, according to which a synchronous gearless superconducting wind generator with a capacity of 10 MW with the field winding made of a high-temperature superconducting material (MgB2, Bi-2223 or YBCO) with the «ferromagnetic stator — ferromagnetic rotor» topology, with the stator diameter equal to 7—9 m, and with the number of poles equal to 32—40 has prospects for its practical use in the nearest future.

SOMERS LTA COPPER

Alloy Digest ◽  
1980 ◽  
Vol 29 (12) ◽  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Physical Properties ◽  
Copper Foil ◽  
Heat Treating ◽  
Dielectric Substrates ◽  
Printed Circuits

Abstract SOMERS LTA Copper is a wrought copper foil that can be annealed at 350 F in 15 minutes to the full-soft condition; its use simplifies the manufacture of printed circuits (LTA = Low-Temperature Annealable). LTA Copper is especially useful for foil weights up to and including one ounce per square foot (0.0014-inch thick) for laminating to high-temperature dielectric substrates. This datasheet provides information on composition, physical properties, and elasticity as well as fatigue. It also includes information on forming, heat treating, and machining. Filing Code: Cu-407. Producer or source: Olin Corporation.

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