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11.
Kolyaganova O. V. Duridivko M. O. Klimov V. V. Le M. D. Kharlamov V. O. Bryuzgin E. V. Navrotsky A. V. Novakov I. A. 《Colloid Journal》2022,84(4):416-426
Colloid Journal - The paper discusses the formation of hydrophobic coatings based on linseed oil and copolymers of glycidyl methacrylate and (fluoro)alkyl methacrylates on the surface of pinewood... 相似文献
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E.M. Larson A.J.G. Ellison F.W. Lytle A. Navrotsky R.B. Greegor J. Wong 《Journal of Non》1991,130(3):260-272
The La L1 and L3 XANES and L3 EXAFS have been investigated for the series of glasses 10K2O---50SiO2---x La2O3 (x = 1, 5, 10) and (10 − x)K2O---40SiO2−(x/3)La2O3 (x = 7.5, 5, 2.5) and model compounds La2O3, LaAlO3, LaPO4, La2NiO4, La2CuO4 and La(OH)3. An edge resonance at 25 eV above the L1 edge in the glass spectra is concentration-dependent, decreasing in intensity with increasing lanthanum concentration. The 2s → nd forbidden transition increases with La2O3 concentration, indicating a reduction in the ‘average’ site symmetry of the first coordination shell of La. Mapping X(k) space, which is a new and promising technique, was employed to extract bond distance, coordination number and thermal parameters from the EXAFS. By this method, one calculates the complete X(k) space a function of all physically reasonable values of the adjusted parameters in all possible combinations. The advantage in this method is the assurance of a global minimum. Bond lengths were comparable to those obtained by Fourier transforming the phase corrected EXAFS. The values are 2.42 Å (± 0.03 Å) for La---O. The coordination numbers (N ≤ 7 ± 1.5) were derived by mapping and comparison to the published structures for other La compounds. X(k) mapping is compared with least-squares fitting the data, and the correlation between the Debye-Waller factor and coordination number is also discussed. 相似文献
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Thermochemical and crystallographic properties of MgTi2O5, MgTiO3, and Mg2TiO4 have been studied to characterize stability relations, structural variations, and order-disorder phenomena. Enthalpies of formation, decomposition, and order-disorder transitions were determined by high-temperature solution calorimetry and transposed-temperature-drop calorimetry on synthetic powders. X-Ray lattice parameter measurements and Rietveld refinements of neutron diffraction data were used to evaluate intracrystalline cation distributions and their variation with quenching temperature. MgTiO3 is the most stable phase and apparently retains a fully ordered MgTi distribution to at least 1673 K. Both MgTi2O5 and Mg2TiO4 are stable only at high temperature because of the configurational entropy arising from cation disorder. The disorder in MgTi2O5 appears to vary continuously throughout the range 773–1373 K and is accompanied by changes in lattice parameters. Mg2TiO4 undergoes a cubictetragonal transition at 933 ± 20 K involving the appearance of long-range order on octahedral sites. However, thermochemical evidence suggests that MgTi octahedral short-range order changes gradually, perhaps over an interval of several hundred degrees. Models for describing the order-disorder and accompanying enthalpy changes are discussed. 相似文献
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The high temperature heat content of crystalline PbF2 increases rapidly between 625 and 750 K, with an antropy incre ase of 16.5 JK-1 mol-1. The region of rapid heat content increase correlates with a large increase in ionic conductivity and is associated with fluoride ion disorder. 相似文献
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Wei Zhou Quan Shi Brian F. Woodfield Alexandra Navrotsky 《The Journal of chemical thermodynamics》2011,43(6):970-973
The low temperature (2 to 300) K heat capacity of monoclinic hafnia (HfO2) was measured using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). The thermodynamic functions in this temperature range were derived by curve fitting. The standard entropy and enthalpy of hafnia at T = 298.15 K was calculated to be 56.15 ± 0.57 J · mol?1 · K?1 and 9.34 ± 0.09 kJ · mol?1, respectively. The results are in fairly good agreement with old data, which only covered temperatures from (50 to 298) K. Hafnia has a higher heat capacity than zirconia at all temperatures from (2 to 300) K. 相似文献
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Yasmine Guefrachi Geetu Sharma Dandan Xu Gaurav Kumar Katherine P. Vinter Omar A. Abdelrahman Xinyu Li Saeed Alhassan Paul J. Dauenhauer Alexandra Navrotsky Wei Zhang Michael Tsapatsis 《Angewandte Chemie (International ed. in English)》2020,59(24):9579-9585
Commonly used methods to assess crystallinity, micro‐/mesoporosity, Brønsted acid site density and distribution (in micro‐ vs. mesopores), and catalytic activity suggest nearly invariant structure and function for aluminosilicate zeolite MFI two‐dimensional nanosheets before and after superheated steam treatment. Yet, pronounced reaction rate decrease for benzyl alcohol alkylation with mesitylene, a reaction that cannot take place in the zeolite micropores, is observed. Transmission electron microscopy images reveal pronounced changes in nanosheet thickness, aspect ratio and roughness indicating that nanosheet coarsening and the associated changes in the external (mesoporous) surface structure are responsible for the changes in the external surface catalytic activity. Superheated steam treatment of hierarchical zeolites can be used to alter nanosheet morphology and regulate external surface catalytic activity while preserving micro‐ and mesoporosity, and micropore reaction rates. 相似文献
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High-temperature calorimetric measurements of the enthalpies of solution in molten 2PbO · B2O3 of (NixMg1?x)O and (NixZn1?x)O permit the calculation of the enthalpy of the zincite to rocksalt transformation in ZnO, and the enthalpies of mixing, relative to rocksalt standard states, in the two solid solution series. The enthalpy of the zincite to rocksalt transformation is 24,488 ± 3,592 J mole?1 with a corresponding positive entropy change of 0.48 ± 3.3 J K?1 mole?1. The small positive entropy change for the transformation necessitates a very flat and perhaps negative slope for the phase boundary. Both solid solutions, when referred to rocksalt standard states, show negative enthalpies of mixing. For (NixMg1?x)O the negative enthalpies of mixing are fitted by a subregular model, where ΔHmix = XAXB(BXA + AXB), with A = ?21,971 ± 4,953 J mole?1 and B = ?5103 ± 1151 J mole?1. The associated negative excess entropies of mixing, calculated from the heats of mixing and previously measured activity-composition relations, are similarly modeled with A = ?10.7 J K?1 mole?1 and B = + 1.1 J K?1 mole?1. Negative enthalpies of mixing in (NixZn1?x)O conform to a regular solution model with W = ?13520 ± 5581 J mole?1. The negative enthalpies of mixing are interpreted in terms of a tendency toward ordering in the solid solutions, the proposed ordering scheme finding support in spectroscopic, structural, and magnetic data. These tendencies toward order are used to explain observed phase relations and thermodynamic properties in some other systems containing a transition metal cation and another ion of similar size, namely carbonates, hydrated sulfates and the systems CuOMO (M = Mg, Co, Ni). 相似文献
20.
Claine L. Snow Stacey J. Smith Brian E. Lang Quan Shi Juliana Boerio-Goates Brian F. Woodfield Alexandra Navrotsky 《The Journal of chemical thermodynamics》2011,43(2):190-199
The iron oxides and iron oxyhydroxides exist as several different polymorphs, and a thermodynamic understanding of these polymorphs can provide us with an understanding of their relative stability and chemical reactivity. This study provides heat capacity measurements for lepidocrocite (γ-FeOOH) over the temperature range (0.8 to 38) K and akaganéite (β-FeOOH) over the range (0.7 to 302) K. Fits of the heat capacity of the two samples below T = 15 K showed similar behavior to previously published fits of goethite (α-FeOOH), which required a linear term and an anisotropic gap parameter to model accurately the antiferromagnetic spin–wave contributions. The akaganéite measurements were compared to previously reported measurements all of which showed significant disagreement. It is believed that the measurements reported here are the most reliable. Also, the presence of adsorbed water contributes significantly to the heat capacity of akaganéite, and the standard molar entropy at T = 298.15 K of the hydrated form was calculated to be (81.8 ± 2) J · mol?1 · K?1. 相似文献