Thermodynamic assessments were made to optimize thermodynamic models and parameter fits to selected experimental and first principles hypothetical predicted phase data within the Na–Al–Ti–H system. This enabled thermodynamic modeling of Ti solubility within the sodium alanates: NaAlH4 and Na3AlH6, and the relative stability of Ti-bearing phases. The modeling provides insights into the role of Ti originating from Ti-based activating agents commonly referred to as ‘catalysts’ in promoting reversibility of the Na–Al–H dehydrogenation and rehydrogenation reactions under moderate temperature and pressure conditions relevant to H storage applications. Preliminary assessments were made to evaluate H solubility in bcc-Ti and hcp-Ti, and stability of the hydride δ-TiH2. To model possible Ti dissolution in NaAlH4 and α-Na3AlH6, sub-lattice models were applied. A repulsive interaction is predicted by first principles calculations when Ti is dissolved in NaAlH4 or α-Na3AlH6, which becomes stronger with increasing temperature. Although Ti is virtually insoluble in NaAlH4 or α-Na3AlH6, a small addition of TiCl3 will induce a thermodynamic driving force for formation of TiH2 and/or TiAl3. The addition of pure Ti shows a weaker effect than TiCl3 and leads to formation of TiH2 only. Based on a combined interpretation of present thermodynamic modeling and prior experimental observations, the TiAl3 and TiH2 phases are ascribed to have a catalytic effect, not a thermodynamic destabilization effect, on the reversibility of the dehydrogenation/rehydrogenation reactions in the Na–Al–H system. 相似文献
Liquid–liquid phase diagrams of surfactant-based aqueous two-phase systems (ATPS) composed of TritonX-100, as a non-ionic surfactant, and two different salts have been studied at 298.15 K. The salts used were an inorganic salt, magnesium sulfate (MgSO4), and an organic salt, sodium citrate (Na3C6H5O7). The results show that the salt MgSO4 is more capable of inducing ATPS formation than the salt Na3C6H5O7. The experimental liquid–liquid equilibrium data were correlated using a modified virial model. Good agreement was obtained with the experimental data. 相似文献
A strategy for dual sensing of Na+ and K+ ions using Prussian blue nanotubes via selective inter/deintercalation of K+ ion and competitive inhibition by Na+ ion, is reported. The analytical signal is derived from the cyclic voltammetry cathodic peak position Epc of Prussian blue nanotubes. Na+ and K+ levels in a sample solution can be determined conveniently using one Prussian blue nanotubes sensor. In addition, this versatile method can be applied for the analysis of single type of either Na+ or K+ ions. The dual-ion sensor response towards Na+ and K+ can be described using a model based on the competitive inhibition effects of Na+ on K+ inter/deintercalation in Prussian blue nanotubes. Successful application of the Prussian blue nanotubes sensor for Na+ and K+ determination is demonstrated in artificial saliva. 相似文献
A series (SPUN) of segmented polyurethanes reinforced with the in situ-generated sodium silica-polyphosphate nano-phase (SSP) was characterized by thermogravimetry, differential calorimetry, wide-angle and small-angle X-ray diffraction and stress–strain relationships.
Cross-over from the rubber-like to the solid-like mechanical behavior of the SPUN above the apparent percolation threshold w ≈ 40% was considered as evidence for the onset of the “infinite clusters” of SSP nano-domains spanning the entire volumes of initial (i.e., undeformed) samples. The infinite clusters of SSP nano-domains crossed over from the mass fractal-like to the surface fractal-like behavior at the composition-dependent, characteristic X-ray scattering vectors q*. A continuous nano-phase of the polyurethane coexisting with a continuous nano-phase (infinite cluster) of the SSP is likely to be expanded due to the “negative pressure” effect. 相似文献
In this paper, we review the current technology for the storage of hydrogen on board a fuel cell-propelled vehicle. Having outlined the technical specifications necessary to match the performance of hydrocarbon. fue1, we first outline the inherent difficulties with gas pressure and liquid hydrogen storage. We then outline the history of transition metal hydride storage, leading to the development of metal hydride batteries. A viable system, however, must involve lighter elements and be vacuum-tight. The first new system to get serious consideration is titanium-activated sodium alanate, followed by the lithium amide and borohydride systems that potentially overcome several of the disadvantages of alanates. Borohydrides can alternatively produce hydrogen by reaction with water in the presence of a catalyst but the product would have to be recycled via a chemical plant. Finally various possible ways of making magnesium hydride decompose and reform more readily are discussed. The alternative to lighter hydrides is the development of physisorption of molecular hydrogen on high surface area materials such as carbons, metal oxide frameworks, zeolites. Here the problem is that the surface binding energy is too low to work at anything above liquid nitrogen temperature. Recent investigations of the interaction mechanism are discussed which show that systems with stronger interactions will inevitably require a surface interaction that increases the molecular hydrogen-hydrogen distance. 相似文献