Yu. P. Toporov

On the role of electrostatic forces in the adhesion of polymer particles to solid surfaces

Abstract Simultaneous measurements have been made of the adhesive force and double electric charge of particles after their removal from a metal surface. For the systems investigated, the adhesive force and charge on the particles increase with particle diameter according to a power law with an exponent close to 2. Such dependence can be explained on the basis of the electrostatic nature of the adhesive forces. A double electric layer exists at the interface between the particles and the metal surface. A calculation was made of the surface density of charge for the polyvinyl chloride particle-steel system.

Influence of adhesion on the sliding and rolling friction

Abstract Yet in 1934, one of the authors had developed the molecular friction theory explaining the external friction by dissipation of energy on the molecular unevenness of the bodies in friction. This theory distinctly determines the role of adhesion in the processes of the external sliding friction. the adhesion forces are used in this theory only for explaining deviation from the Amontons law expressing the proportionality of the friction force to the normal load. The rolling friction process (in the absence of deformations) represents a process of formation and breakage of adhesion bonds. Using the electron theory as the basis, the mechanism of influence of the electrostatic component of adhesion on the rolling friction is considered, the electrostatic component being attributable to the formation of a double electric layer when solids are in friction, and when its plates are separated as the contact is broken.

On the initiation of DD reactions in the zirconium-deuterium system

Abstract The possibility of initiating DD reactions on vibro-milling of zirconium together with heavy water and deuterated polypropylene has been investigated. Weak emission of neutrons has been detected both during the vibro-milling process and some time after its completion.

The effect of mechanical activation on the heat capacity of powdered tungsten

We have studied the heat capacity (Cp) of a mechanically activated tungsten powder. It is established that the mechanical processing leads to an increase in Cp of the metal powder at low temperatures and modifies the character of the temperature dependence of this parameter. The dependences of Cp and its heating-induced variation on the treatment duration have been determined. It is concluded that the observed effects are related to the accumulation of defects in the metal grain volume during mechanical activation and their annealing in the course of heating.

Thermal activation currents of biocompatible nanocrystalline calcium hydroxyapatite Ca10(PO4)6(OH)2

Nanocrystalline stoiochiometric calcium hydroxyapatite, Ca10(PO4)6(OH)2 (NCHA), a counterpart of the inorganic osseous tissue component, is synthesized under biomimetic conditions. Methods of physico-chemical analysis (XRD, IRS, derivatography, DSC, ESCA, SEM, TEM) are used to identify the products of synthesis. The temperature dependence of thermally stimulated currents (TSCs) of NCHA is studied in the temperature range of 300–600 K and the effect of the dispersion degree on TSCs is analyzed.

Effect of mechanical activation on the thermal stability of polytetrafluoroethylene powder

It was found that processing in a planetary activator leading to amorphization of the structure of polytetrafluoroethylene powder was not accompanied by a noticeable decrease in its thermal stability. It was established that the temperature at the onset of melting drops slightly, the melting rate increases, and the enthalpy of the endoeffect declines noticeably heating.

Exoemission Analysis of Energy Levels in the Surface Layer of Biocompatible Ca10(PO4)6(OH)2

Thermostimulated exoelectron emission from sintered hydroxyapatite (HAP), Ca10(PO4)6(OH)2 , prepared by the alkoxy method was studied in the temperature range 300–800 K. The results were used to determine trap depths, the frequency factor in the Boltzmann probability of thermal release, lifetime of conduction-band electrons, and charge density at active centers in the surface layer of the material. The exoelectron emission data are correlated with earlier thermostimulated current measurements and structural studies of phase transitions in HAP. Possible lines of further research are discussed.

On Diagnostics of Double Electric Layer in the Zone of Metal–Polymer Adhesion Contact Using the Positron-Annihilation-Probe Method

Application of the positron-annihilation-probe technique for nondestructive diagnostics of the double electric layer (DEL) at the polymer–metal interface and, hence, of the electric component of polymer adhesion to the metal is described. Separated curves of angular correlation of positron-annihilation radiation (ACPAR) for metal, polymer, and metal with a polymer layer allow detecting the presence of a strong electric field of a DEL at the nickel–epoxy-resin interface. The value of the DEL potential is determined to be 15 keV. The method of a positron-annihilation probe allows identifying the presence of a DEL on the internal interfaces of materials and estimating its energy parameters so as to correctly reflect the value of the contribution of the electrostatic component to the interphase interaction.

The influence of mechanical activation on the adsorption properties of powdered tungsten

Mechanical activation in a planetary ball mill activator changes the adsorption properties of powdered tungsten. The activation leads to changes in both the adsorption energy and the concentration of active adsorption sites on the surface, thus resulting in a change in the adsorption capacity. The character and degree of the change in the adsorption properties depends nonlinearly on the duration of the mechanical effect.

Effect of the mechanical activation of fillers on the parameters of thermostimulated current in polymer composites

The influence of the mechanical activation of powdered fillers on the character of thermoactivation processes in polymer composites involving these fillers has been studied. It is demonstrated that thermostimulated current spectroscopy is a promising method for investigating the interaction of fillers with polymer matrices in electret compositions.