Excess Gibbs potential model for multicomponent hydrogen clathrates

A new thermodynamic calculation procedure is introduced to predict the equilibrium conditions of multicomponent gas hydrates containing hydrogen. This new approach utilizes an excess Gibbs potential term to account for second- or higher-order water-cavity distortions due to the presence of multiple guest species. The excess Gibbs potential describes changes in reference chemical potentials according to different compositions of guest mixtures in the hydrate phase. To determine the equilibrium conditions of multicomponent gas hydrates, the excess Gibbs potential term is incorporated to the Lee-Holder model along with the Zele-Lee-Holder cell distortion model. For binary gas hydrates between hydrogen and the other gas molecule, the predicted equilibrium pressure deviates within 10-20% from the experimental value. For the ternary and quaternary mixture hydrates, the model prediction is reasonably good but its error increases with increasing pressure and temperature under the presence of THF.     

Evolution of the Si-condensed species in a multicomponent polymeric system

Alcoholic sol-gel systems were prepared using a pre-hydrolyzed tetraethyl orthosilicate (TEOS) sol as the main component. Ti and Zr alkoxides were also introduced in order to provide properties of technological interesttowards producing the final ceramics. The molar ratios Si:Ti:Zr were 82:7:11, respectively. Six potential chelating molecules were used as modifying agents in order to control the reactivity of Ti and Zr, avoiding precipitation. The products were characterized by spectroscopic techniques including Small Angle X-ray Scattering (SAXS), ²⁹Si NMR, UV-Vis and Fourier Transform Infrared (FTIR) spectroscopies. The radial distribution functions (RDF) of the gels and calcined solids were obtained; in addition, the porosimetry study of the solids calcined at 873 K in air was performed. The results are mainly discussed in terms of the condensation of the Si species; however, the influence of Ti, Zr and the modifying agent structures is also considered.     

Thermal decomposition of ammonium nitrate dispersed in a multicomponent nitrate system

To obtain the kinetic curves of thermal decomposition of ammonium nitrate occurring together with decomposition of metal nitrates contained in a mixture, the ammonia contents evolved from samples heated under thermoanalytical conditions were determined by the Kjeldahl method.

---

Zusammenfassung Der aus unter thermoanalytischen -Bedingungen erhitzten Proben freigesetzte Ammoniakgehalt wird durch das Kjeldahlverfahren bestimmt, um die kinetischen Kurven der thermischen Zersetzung von Ammoniumnitrat zusammen mit der Zersetzung von Metallnitraten in Gemischen zu erhalten.

---

, , , .

     

Partial miscibility in multicomponent polymer system

It has been shown, using the significant structure theory of liquids, that a lower critical solution temperature behavior as well as a upper critical solution temperature behavior can be expected for polymer–polymer systems and that a phase diagram of closed-loop-type in a polymer–polymer–solvent system can be possible. In this article the sublimation energy of a mixture was expressed as a quadratic form of segment surface fractions on pure components rather than that of mole fractions, and the effect of the segment surface fractions on critical compositions was explained. The calculated partial miscibilities were in good agreement with the experiment.     

Theoretical model for the phase transition of a membrane as a multicomponent system

A theoretical model is given that describes the nature of a membrane that is made up of several species of lipids. The model will partially simulate the biomembrane through numerical analysis.     

A case study on biological activity in a surface-bound multicomponent system: the biotin-streptavidin-peroxidase system

The adsorption of multiple protein layers on biotinylated organic surfaces has been characterized using surface plasmon resonance (SPR) and atomic force microscopy (AFM). Diffusion-limited loading of the biotinylated self-assembled monolayers (SAMs) ensures a precise control of the streptavidin surface density. For the subsequent interaction with biotinylated peroxidase, SPR data hint at a streptavidin density dependent orientation during peroxidase adsorption. Microcontact printed well-defined two-dimensional patterned surfaces of biotinylated organothiols and protein-resistant OEG-thiols allow an in-situ differentiation of specific and nonspecific adsorption (e.g., mono- vs multilayer adsorption). Additionally, the very important issue of biological activity of surface-bound enzymes is addressed by comparing the enzyme activities in solution with that for surface-bound species.     

Controlling hydrogel properties by tuning non-covalent interactions in a charge complementary multicomponent system

Mixing small molecule gelators is a promising route to prepare useful and exciting materials that cannot be accessed from any of the individual components. Here, we describe pH-triggered hydrogelation by mixing of two non-gelling amphiphiles. The intermolecular interactions among the molecules can be tuned either by controlling the degree of ionization of the components or by a preparative pathway, which enables us to control material properties such as gel strength, gel stiffness, thermal stability, and an unusual shrinking/swelling behaviour.

The properties of a charge complementary multicomponent gel can be tuned either by pH change or by varying the preparative pathway.     

Destabilisation of magnesium hydride by germanium as a new potential multicomponent hydrogen storage system

MgH(2) has too high an operating temperature for many hydrogen storage applications. However, MgH(2) ball-milled with Ge leads to a thermodynamic destabilisation of >50 kJ mol(-1)(H(2)). This has dramatically reduced the temperature of dehydrogenation to 130 °C, opening up the potential for Mg-based multicomponent systems as hydrogen stores for a range of applications.     

Formation and characterization of a multicomponent equilibrium system derived from cis- and trans-1-aminomethylcyclohexane-1,2-diol

Both cis and trans isomers of amino diols 3-6 were prepared stereoselectively. In the reactions between 3-6 and phenyl isothiocyanate, the ring closure proceeded regioselectively and resulted only in spiro derivatives of 2-phenyliminooxazolidines 9, 10, 13, and 14. The reaction of cis- (or trans-)1-aminomethylcyclohexane-1,2-diol 4 (or 6) with 1 equiv of an aromatic aldehyde 15a-g in EtOH at room temperature resulted in a complex, multicomponent equilibrium mixture of 16a-g and 18a-g (or 17a-g and 19a-g), in each case consisting of a five-component, ring-chain tautomeric system 16A-E (or 17A-E), involving the Schiff base, two epimeric spirooxazolidines, two epimeric condensed 1,3-oxazines, and some of the four tricyclic compounds 18A-D (or 19A-D). The five-component, ring-chain equilibria were found to be adequately described by the Hammett-Brown linear free energy equation.     

Adsorption of gases on binary and multicomponent semiconductors of the ZnSe-CdTe system

Adsorption of carbon monoxide(II) and oxygen on powders and nanofilms of solid solutions and binary compounds of the ZnSe-CdTe system was studied volumetrically, and by piezoquartz microweighing and IR spectroscopy of multiple disturbed complete internal reflections. The mechanisms and principles of adsorption were established in dependence on the conditions of the habitus of an experimental sample and the composition of the system’s semiconductors, based on an analysis of IR spectra; the thermodynamic and kinetic characteristics of adsorption; experimental dependences αp = f(T), αT = f(P), and αT = f(t); and the acid-base and other physicochemical characteristics of adsorbents and the electron nature of adsorbate molecules. Conclusions drawn earlier as to the retention of local active centers on the surface of a diamond-like semiconductor (which are responsible for adsorption and catalytic processes) upon a change in the habitus of a sample were confirmed. Certain features in the behavior of solid solutions (ZnSe) _x (CdTe)_{1 − x} were revealed alongside commonalities with binary compounds (ZnSe, CdTe), testifying to the presence of critical points on “adsorption characteristics-composition” diagrams. The most active adsorbents (with respect to CO and O₂) were discovered on the basis of these diagrams, which were used in creating highly sensitive and selective sensors.     

Instantaneous low temperature gelation by a multicomponent organogelator liquid system based on ammonium salts

A new synergistic multicomponent organogelator liquid system (MOGLS) was discovered during the standard protocol of tartaric acid-mediated racemic resolution of (+/-)- trans-1,2-diaminocyclohexane. The MOGLS is formed by a 0.126 M methanolic solution of (1 R,2 R)-(+)-1,2-diaminocyclohexane L-tartrate and 1 equiv of concentrated hydrochloric acid. Nonreversible gelation of oxygenated and nitrogenated solvents occurs efficiently at low temperature. Several features make this system unique: (1) it is a multicomponent solution where each of the five components is required for the organogelation property; (2) the multicomponent organogelator liquid system (MOGLS) is formed by simple, small, and commercially available chiral building blocks dissolved in a well-defined solvent system (MeOH/HCl/H2O); (3) the chiral building blocks are easily amenable for further modifications in structure-property relationship studies; (4) the gelation phenomenon takes place efficiently at low temperature upon warming up the isotropic solution, conversely to the typical gel preparation protocol (gel formation upon cooling down the isotropic solution); (5) the formed organic gels are not thermoreversible in spite of the noncovalent interactions that hold the 3D-fibrillar network together.     

Synergistic effects in multicomponent electrocatalysts: the Pb-Ir-O system

The ionic interactions were studied in aqueous solutions of Na(3)IrCl(6) + Pb(NO(3))(2) in order to develop a facilitated electrosynthesis of iridium-based catalytic surfaces. Spectroscopic studies indicated that ion pair charge-transfer complexes [IrCl(6)(3-)]-Pb(II) (K = 6 x 10(3)) and [Ir(H(2)O)Cl(5)(2-)]-Pb(II) (K = 2 x 10(3)) were formed in fresh and aged solutions, respectively. Electrochemical studies showed that interactions between the Ir(H(2)O)Cl(5)(2-) and Pb(II) species lead to synergistic lowering of the overpotential that was necessary for nucleation and growth of mixed metal oxide PbIrOx on the surface of glassy carbon electrodes. The Ir:Pb stoichiometry of the PbIrOx surface films was the same (1:1) as that of the high-temperature phase of Pb-Ir-O pyrochlore. Compared to IrOx, the PbIrOx films displayed enhanced catalytic activity toward the electrooxidation of carbohydrates. This was ascribed to synergism that involved retention of carbohydrate molecules at the Pb(II) sites of a PbIrOx film and oxidation at the adjacent Ir(IV) sites. The synergistic electroplating utilizing interactions between the partially aquated transition metal complex and posttransition metal ion represents a new synthetic route to highly homogeneous and reactive films of mixed metal oxides.     

L-Proline promoted fluorescent sensor for Mg2+ detection in a multicomponent sensory system

Mg(2+) can lead to the fluorescence enhancement of a dye molecule as high as 47.3-fold while L-proline acts as a promoter in this multicomponent sensory system. The fluorescence color could be easily detected by the naked eye under a UV-lamp.     

Analysis of Gibbs adsorption equation and thermodynamic relation between Gibbs standard energies of adsorption and micellization through a surface equation of state

The calculation of surface molecular areas through Gibbs adsorption equation has been questioned in some early works on the belief that these areas have been obtained from the apparently constant slope of the surface tension vs. logarithm of concentration curve along the entire region at which surface tension declines rapidly as the concentration increases. This premise leads to consider that Gibbs equation predicts that surface saturation is reached at the beginning of this region. However, through an analysis of the forementioned curve in accordance to Gibbs equation, it can be easily shown that surface saturation is attained at the end of the region. On the other hand, based on a thermodynamic model, it is also shown that the adsorption process, and thus, surface saturation, proceeds before micellization.     

A general method of calculating phase equilibria in a multicomponent system by means of a hill-climbing minimization procedure

A generalization of the method of calculating the state of equilibrium of a multicomponent system, using a hill-climbing minimization procedure, is proposed. Moreover, an original method of calculating values for partial free energies from the state of equilibrium has been made an essential part of the general schedule.     

Expansion of a multicomponent laser plasma cloud

It is shown that the mechanism of the electrodynamic expansion of a plasma cloud satisfactorily describes ion acceleration for two-component plasmas (ions of a fixed mass and electrons) but cannot be applied to the expansion of multicomponent plasmas. The main drawback of the known models is the assumption of the collision-free expansion of laser plasma clouds. It cannot be used to simulate the expansion of a multicomponent plasma cloud. An algorithm was proposed that takes into account collisions of ions with different masses in the electrodynamic model for the expansion of plasma clouds containing both matrix and trace contaminant ions. The algorithm and software on its basis allow one to calculate the energies of ions of different masses acquired in the process of ion acceleration in the laser plasma containing both matrix and contaminant ions. The results of numerical calculations are compared both with similar results obtained for the collision-free model of the expansion of the plasma cloud and with the experimental data. Taking into account collision processes in the electrodynamic model of plasma cloud expansion allows one to calculate the acceleration of trace contaminant ions in multicomponent laser plasma and reach a good qualitative agreement with the experimental data.