Electrostatic Contribution to the Enthalpy of Charging at Hematite/Electrolyte Interface

A calorimetry study of hematite surface reactions is reported, with special emphasis on the estimation of the electrostatic contribution to the enthalpy of charging. The calorimetry titrations were performed outside the point of zero charge region where the electrostatic contribution is significant. The results were interpreted by the surface complexation model. The interpretation enabled the evaluation of standard protonation and deprotonation enthalpies as well as the electrostatic contribution to these quantities. Copyright 1999 Academic Press.     

A Remark on the Norm of Integer Order Favard Spaces

For a generator $A$ of a $C_0$-semigroup $T(\cdot)$ on a Banach space $X$ we consider the semi-norm $M^{k}_x:=\limsup_{t\to 0+}\|t^{-1}(T(t)-I)A^{k-1}x\|$ on the Favard space ${\cal F}_{k}$ of order $k$ associated with $A$. The use of this semi-norm is motivated by the functional analytic treatment of time-discretization methods of linear evolution equations. We show that sharp inequalities for bounded linear operators on ${\cal D}(A^k)$ can be extended to the larger space ${\cal F}_{k}$ by using the semi-norm $M^{k}_{(\cdot)}$. We also show that $M^{k}_{(\cdot)}$ is a norm equivalent to the norms that are usually considered in the literature if A has a bounded inverse.     

Preparation and characterization by infrared emission spectroscopy and applications of new mineral-based composite materials of biomedical interest

New composite materials based on clay minerals had been prepared by reductive calcination. These materials exhibit very strong infrared (IR) emission at quite low temperatures. The structural properties and emission capabilities of the new materials have been studied by various theoretical and experimental methods. In addition, a brief overview of the medical and other practical applications of IR-emitting materials is presented. The basic principles of IR emission spectroscopy are discussed with special respect to low temperatures (close to human-body temperature). Furthermore, DFT calculations on a kaolinite structure of chemical composition of [Al₄Si₄ O₈(OH)₁₆]^4? have been performed. The calculated bond distances and IR spectrum are in good agreement with experimental observations. Structural and compositional characterization of the new composite materials have been performed by various structural analytical methods. An interesting effect on the IR phosphorescence of composite samples has been established. After 2 hours of IR light exposure at room temperature from the FT-IR spectrometer, the composite materials exhibited enhanced emission of IR radiation with relaxation time about 40 min. Finally, two practical applications of the composites have been investigated, namely polyamide-based fabrics and rubber preservatives.     

Subdivision algorithms and the kernel of a polyhedron

The kernelK of a convex polyhedronP ₀, as defined by L. Fejes Tóth, is the limit of the sequence (P _n), whereP _n is the convex hull of the midpoints of the edges ofP _n−1. The boundary ∂K of the convex bodyK is investigated. It is shown that ∂K contains no two-dimensional faces and that ∂K need not belong toC ². The connection with similar algorithms from CAD (computer aided design) is explained and utilized. R. J. Gardner was supported in part by a von Humboldt fellowship.     

Conductivity of water-in-oil microemulsions: Comparison of the Boltzmann statistics and the charge fluctuation model

The electrical conductivity of water-in-oil microemulsions is interpreted on the basis of the distribution of ionic charges among the droplets. The charging energy is approximated by the Born energy. In the interpretation, the hydrodynamic radius is distinguished from the water core radius. The Boltzmann statistics are compared with the fluctuation theory. The former approach is more realistic due to its consideration of the discrete nature of charge, while the latter better fits the data obtained with the AOT-water-isooctane system.     

Reversible charging of the ice-water interface. II. Estimation of equilibrium parameters

Equilibrium parameters characterizing the ice-water interface were obtained from electrokinetic and potentiometric data. The dependency of surface potential on pH was measured by the ice electrode. Electrokinetic zeta potentials were measured by electrophoresis. In the interpretation, the 1-pK and 2-pK concepts of the surface complexation model, developed for metal oxides, were used. The equilibrium parameters (constants of surface reactions) were determined. The results were confirmed by numerical simulations. Both 1-pK and 2-pK models fit the experimental data well.