THE HEATS OF CRYSTALLIZATION OF VACUUM DEHYDRATED MAGNESIUM SULPHATE HEPTAHYDRATE AND COBALTOUS CHLORIDE HEXAHYDRATE

1956 ◽  
Vol 34 (5) ◽  
pp. 583-590 ◽  
Author(s):  
J. W. S. Jamieson ◽  
G. B. Frost
Keyword(s):  
Magnesium Sulphate ◽  
X Ray Diffraction ◽  
Cobaltous Chloride ◽  
X Ray ◽  
Surface Areas ◽  
Chloride Hexahydrate ◽  
Heat Of Transition ◽  
Vacuum Dehydration ◽  
Chloride Monohydrate ◽  
Amorphous Character

Magnesium sulphate monohydrate prepared by vacuum dehydration of the heptahydrate does not yield a pattern of X-ray diffraction lines, and in this sense may be said to have an amorphous character. By measurement of the heats of solution of the “X-ray amorphous” and crystalline monohydrates, the heat of transition has been found to be 6550 cal. mole−1. Cobaltous chloride monohydrate prepared by vacuum dehydration appears to be microcrystalline. The heat of transition to the normal crystalline form is 1390 cal. mole−1. These values are related to the surface areas of the vacuum dehydrated products.

scholarly journals Microporous Materials Based on Norbornadiene-Based Cross-Linked Polymers

Polymers ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1382 ◽  
Author(s):  
Dmitry Alentiev ◽  
Dariya Dzhaparidze ◽  
Natalia Gavrilova ◽  
Victor Shantarovich ◽  
Elena Kiseleva ◽  
...  
Keyword(s):  
Pore Volume ◽  
Total Pore Volume ◽  
Amorphous Polymers ◽  
Co2 Uptake ◽  
Wide Angle ◽  
X Ray Diffraction ◽  
Pd Catalysts ◽  
X Ray ◽  
Positron Annihilation Lifetime ◽  
Surface Areas

New microporous homopolymers were readily prepared from norbornadiene-2,5, its dimer and trimer by addition (vinyl) polymerization of the corresponding monomers with 60–98% yields. As a catalyst Pd-N-heterocyclic carbene complex or Ni(II) 2-ethylhexanoate activated with Na+[B(3,5-(CF3)2C6H3)4]− or methylaluminoxane was used. The synthesized polynorbornenes are cross-linked and insoluble. They are glassy and amorphous polymers. Depending on the nature of the catalyst applied, BET surface areas were in the range of 420–970 m2/g. The polymers with the highest surface area were obtained in the presence of Pd-catalysts from the trimer of norbornadiene-2,5. The total pore volume of the polymers varies from 0.39 to 0.79 cm3/g, while the true volume of micropores was 0.14–0.16 cm3/g according to t-plot. These polymers gave CO2 uptake from 1.2 to 1.9 mmol/g at 273 K and 1 atm. The porous structure of new polymers was also studied by means of wide-angle X-ray diffraction and positron annihilation lifetime spectroscopy.

Structural and surface aspects of thermally treated copper aluminium mixed hydroxides

1991 ◽  
Vol 69 (10) ◽  
pp. 1511-1515 ◽  
Author(s):  
Awad I. Ahmed ◽  
S. E. Samra ◽  
S. A. El-Hakam
Keyword(s):  
Pore Structure ◽  
Copper Content ◽  
Textural Properties ◽  
Nitrogen Adsorption ◽  
Phase Changes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Structure Surface ◽  
Adsorption Desorption

CuO–Al2O3 catalysts containing various amounts of copper oxide have been prepared by precipitation. The phase changes were studied by X-ray diffraction. The results obtained revealed that the thermal treatment of solid CuO–Al2O3 at 700 °C produced only crystalline CuO. Heating to 900 °C led to the formation of copper alumina spinel together with unreacted CuO and γ-Al2O3. The spinel content was found to increase with increasing copper content. Nitrogen adsorption–desorption isotherms on the calcined samples have been measured. Surface areas have been calculated and the pore structure analysed. The textural properties of the system were found to depend on both the copper content and the calcination temperature. Key words: CuO, Al2O3 catalysts, structure, surface area, pore structure.

Drop Solution Calorimetric Studies of Interface Enthalpy of Cubic Silver (I) Oxide (Ag2O) Nanocrystals

2021 ◽  
Vol 878 ◽  
pp. 73-80
Author(s):  
Khansaa Al-Essa ◽  
A V Radha ◽  
Alexandra Navrotsky
Keyword(s):  
Thermodynamic Cycle ◽  
Solution Calorimetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Chemical Technique ◽  
Crystallite Sizes ◽  
Wet Chemical ◽  
Wet Chemical Technique ◽  
Calorimetric Studies

The nanoscale, cubic silver (I) oxide (Ag2O.nH2O) with different particles sizes and surface areas were synthesized by a wet chemical technique. The prepared crystallite size ranges were from (33.3±0.3 to 39.4±0.4 nm). Interface areas were estimated by comparing the surface areas measured by N2 adsorption to the crystallite sizes refined from X-ray diffraction data. The interface enthalpy of Ag2O.nH2O nanocrystal was measured using isothermal acid solution calorimetry in 25%HNO3 at 26°C. The interface enthalpy was verified by utilizing thermodynamic cycle. The enthalpies of drop solution (ΔHds) for Ag2O.nH2O are exothermic and range from (-62.228±0.197) to (-64.025±0.434 kJ/mol), while its interface enthalpy is (0.842±0.508 J/m2). This work provides the first calorimetric measurement of the interface enthalpy of nanocrystalline silver (I) oxide (Ag2O.nH2O).

scholarly journals Low-Cost Synthesis of Cu-Modified Immobilized Nanoporous TiO2 for Photocatalytic Degradation of 1H-Benzotriazole

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 19 ◽  
Author(s):  
Tihana Čižmar ◽  
Ivana Panžić ◽  
Krešimir Salamon ◽  
Ivana Grčić ◽  
Lucija Radetić ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Spin Coating ◽  
Low Cost ◽  
Electrochemical Anodization ◽  
Synthesis Methods ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas ◽  
Titanium Foils ◽  
The Given

Cu-modified immobilized nanoporous TiO2 photocatalysts, prepared by electrochemical anodization of titanium foils, were obtained via four different synthesis methods: hydrothermal synthesis, anodization with Cu source, electrodeposition, and spin-coating, using two different copper sources, Cu(NO3)2 and Cu(acac)2. The objective of this research was to investigate how copper modifications can improve the photocatalytic activity of immobilized nanoporous TiO2 under the UV/solar light irradiation. The best photocatalytic performances were obtained for Cu-modifications using spin-coating. Therefore, the effect of irradiated catalyst surface areas on the adsorption of model pollutants, methylene blue (MB) and 1H-benzotriazole (BT), was examined for samples with Cu-modification by the spin-coating technique. The mechanisms responsible for increased degradation of MB and BT at high Cu concentrations (0.25 M and 0.5 M) and decreased degradation at low Cu loadings (0.0625 M and 0.125 M) were explained. 1H-benzotriazole was used to study the photocatalytic activity of the given samples because it is highly toxic and present in most water systems. The characterization of the synthesized Cu-modified photocatalysts in terms of phase composition, crystal structure, and morphology were investigated using X-ray Diffraction, Raman Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-ray spectroscopy.

THE ADSORPTION OF ARGON ON SOME VACUUM DEHYDRATED SALTS

1955 ◽  
Vol 33 (2) ◽  
pp. 286-297 ◽  
Author(s):  
H. W. Quinn ◽  
R. W. Missen ◽  
G. B. Frost
Keyword(s):  
Water Vapor ◽  
Crystalline State ◽  
Capillary Structure ◽  
X Ray ◽  
Effect Of Water ◽  
Probable Distribution ◽  
Vacuum Dehydration ◽  
Low Pressures ◽  
Amorphous Character

Isotherms for the adsorption of argon on amorphous products formed by the vacuum dehydration of several hydrated salts have been determined. These have shown that the adsorption is physical and that dehydration results in the formation of products of large capillary volume. The probable distribution of capillary diameters has been estimated and correlated with the effect of water vapor at low pressures in catalyzing the crystallization of the amorphous intermediates. Consideration of these findings, in the light of data for the heats of transition from the amorphous to the crystalline state, suggests that the X-ray amorphous character is not entirely due to the capillary structure but that other changes occur. The possible nature of these is discussed.

Preparation and Characterization of Cellulose Nanowhiskers in N, N-Dimethylacetamide

2012 ◽  
Vol 528 ◽  
pp. 35-38 ◽  
Author(s):  
Ping Qu ◽  
Xuan Wang ◽  
Li Ping Zhang
Keyword(s):  
High Specific Surface Area ◽  
Degree Of Crystallinity ◽  
Gravimetric Analysis ◽  
Cellulose Nanowhiskers ◽  
X Ray Diffraction ◽  
Physical Treatment ◽  
X Ray ◽  
Microscopy Techniques ◽  
Amorphous Character

Reinforcement of polymer with plant whiskers is a way of improving mechanical properties. Cellulose nanowhiskers (CNW) were separated from commercially available wood pulpboard. Different microscopy techniques, thermal gravimetric analysis, X-ray diffraction were used to study the structure and properties of the microcrystalline cellulose (MCC) and CNW. Because of the high specific surface area of CNW, the increases in total amorphous character of the cellulose decrease the relative degree of crystallinity. After chemical and physical treatment, the CNW in the length of several μm and diameters ranging from 20 - 50 nm was obtained. Both the initial decomposing temperature and temperature of maximum decomposing rate of CNW is higher than MCC, but lower than wood pulpboard.

Sulphate resistance of silica fume blended mortars exposed to various sulphate solutions

2003 ◽  
Vol 30 (4) ◽  
pp. 625-636 ◽  
Author(s):  
Han-Young Moon ◽  
Seung-Tae Lee ◽  
Seong-Soo Kim
Keyword(s):  
Silica Fume ◽  
Magnesium Sulphate ◽  
Mercury Intrusion Porosimetry ◽  
Length Change ◽  
Sodium Sulphate ◽  
X Ray Diffraction ◽  
Replacement Ratio ◽  
Mortar Specimen ◽  
X Ray ◽  
Strength Deterioration

The different performances of silica fume blended mortars placed in various sulphate-bearing exposure conditions were investigated. Experimental study was carried out on mortars immersed in 5% sodium sulphate, 5% magnesium sulphate, and mixed 5% sodium sulphate and 5% magnesium sulphate solutions for 270 d of sulphate exposure. Another variable was the replacement ratio of cement with silica fume (0, 5, 10, and 15% of the cement by weight). The results showed conclusively that silica fume should be given serious consideration for use in sulphate environments. In other words, in a sodium sulphate solution, silica fume showed a beneficial effect on mitigating compressive strength reduction and length change of mortars. However, the strength deterioration factor of the mortar specimen with some silica fume content (especially 15% of the cement by weight) was greater than that of the mortar specimen without silica fume under Mg2+ ion oriented attack. These different sulphate deterioration mechanisms are presented in the study. Microstructural investigations such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDXA), and mercury intrusion porosimetry (MIP) were also used to support the explanation for these mechanisms.Key words: sodium sulphate, magnesium sulphate, silica fume, strength deterioration factor, length change.

scholarly journals Evaluation of Weld Filler Alloying Concepts for Residual Stress Engineering by Means of Neutron and X-Ray Diffraction

2014 ◽  
Vol 996 ◽  
pp. 469-474 ◽  
Author(s):  
Arne Kromm
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Reduction ◽  
Maximum Stress ◽  
Lattice Parameter ◽  
Filler Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stress Control ◽  
Surface Areas

Novel Low Transformation Temperature (LTT-) filler materials are specially designed for controlling residual stresses by means of adjusted martensite formation already during welding. Different alloying concepts compete for maximum stress reduction. Two newly developed LTT-alloys were evaluated concerning their potential for residual stress control. For this purpose residual stresses were determined in the surface and also in sub-surface areas of welded joints using X-ray diffraction and Neutron diffraction taking into account local variations of the unstrained lattice parameter.

scholarly journals Cu(II) and Cd(II) coordination polymers derived from pyrazine-2,3-dicarboxylato and 1-vinylimidazole ligands: Synthesis, characterization and hydrogen storage capacities

2019 ◽  
Vol 38 (1) ◽  
pp. 19 ◽  
Author(s):  
Semih Gorduk ◽  
Hakan Yilmaz ◽  
Omer Andac
Keyword(s):  
Thermal Analysis ◽  
Magnetic Susceptibility ◽  
Coordination Polymer ◽  
Hydrogen Storage ◽  
Coordination Polymers ◽  
Crystalline Form ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
Surface Areas

In this study, two new coordination polymers of Cu(II) and Cd(II) ions with pyrazine-2,3-dicarboxylic acid and 1-vinylimidazole were synthesized. The structures of these coordination polymers were characterized with elemental analysis, infrared spectroscopy, thermal analysis, powder X-ray diffraction, and magnetic susceptibility techniques. According to the results of the thermal analysis, the coordination polymers that contained water molecules decomposed below 100 °C, and the final products for both coordination polymers were the related metal oxides in an oxygen atmosphere. Powder X-ray diffraction analysis revealed that the coordination polymers were in the crystalline form. The hydrogen storage capacities and surface areas of the coordination polymers were also determined. The highest hydrogen storage capacities were measured as 296 ml/g for the Cu(II) coordination polymer and 330 ml/g for the Cd(II) coordination polymer at approximately 75 bar and 75 K.

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