Optical properties of rough electrodes

The aim of the present review is to discuss in a unified and accessible manner the latest achievements in the optics of rough metal—electrolyte interfaces and to point out vital problems. Optical properties of slightly and highly rough surfaces are considered. The effect of the interactions of local electromagnetic modes with delocalized surface plasmons and with one another on the spectrum of electromagnetic excitation of the system and on the behaviour of the electric field near the interface is examined. It is shown how information about the geometrical structure of interfaces and the effect of adsorption on this structure, in particular, can be extracted from optical data.     

High-temperature gasification of carbon-containing raw materials with the use of electric-arc energy and calorific capacity of the gas fuel

Disposal of carbon-containing wastes in a plasma furnace is studied. The influence of the plasma generator power on gasifier efficiency is found for different waste humidities; dependences of specific energy consumption on the waste humidity and air flow rate are obtained. Experimental results are in good agreement with calculations. Sawdust gasification is performed in an electric-arc furnace with an additional heater. The composition of the resultant synthesis gas is analyzed, and the heater performance is determined. It is demonstrated that burning some part of the resultant gas in the heater allows energy consumption to be reduced by 20–25%, as compared with purely plasma gasification.     

Effect of diffusion layer structure on the electroreflectance of metals

The component of electroreflectance (ER) of metals due to the modulation of the diffusion layer characteristics has been investigated. It has been shown that the contribution of this effect to the total ER signal is greatest at large incidence angles. The diffusion contribution to ER is particularly great near the desorption peak of the organic substance. Analytical expressions for the diffusion component of ER as a function of the incidence angle and potential drop modulation frequency have been obtained. The theoretical conclusions have been verified experimentally.     

Erosion of plasma generator electrodes for various power supplies

The increase in the erosion of plasma generator electrodes with controlled rectifiers that is caused by the appearance of a pulsed current component when the power supply voltage and power decrease is experimentally studied. The recommendation of using plasma generators under nominal operating conditions of power supplies with short periods of low-current operation is substantiated.     

Chemical Control of Friction: Mixed Lubricant Monolayers

Controlling frictional behavior in nanoscale sheared systems can be made possible when the relationship between the macroscopic frictional response and the microscopic properties of the sheared systems is established. Here, a new approach is proposed for tuning the frictional response and obtaining desirable frictional properties. This tuning is achieved through shear-induced phase transitions in a mixed lubricant monolayer consisting of a base solvent and an additive. The interaction between the solvent and additive molecules and their relative concentrations are shown to be the major parameters in determining the magnitude of the friction force and the nature of the response (stick–slip or sliding).     

Temperature Dependence of Friction at the Nanoscale: When the Unexpected Turns Normal

The dynamics of frictional motion have been studied for hundreds of years, yet many key aspects of these important processes are not understood. The main challenge in predicting frictional response is the complexity of highly non-equilibrium processes going on in any tribological contact. This includes the continuous detachment and reattachment of multiple microscopic junctions at the sliding interface, the kinetics of which are controlled by the interface temperature. Our experiments reveal a non-monotonic enhancement of dry nanoscale friction at cryogenic temperatures for different material classes. We propose a model that reproduces the experimental observations and shows that the peak in temperature dependence of friction emerges from two competing processes acting at the interface: the thermally activated formation as well as the rupturing of an ensemble of atomic contacts. Our experiments and simulations provide a direct link between the temperature and velocity dependencies of friction, thus offering a new conceptual framework to describe the dynamics of dry nanoscale friction.     

Following Single Molecules by Force Spectroscopy

Dynamic force spectroscopy of single molecules, in which an adhesion bond is driven away from equilibrium by a spring pulled with velocity V, is described by a model that predicts the distribution of rupture forces (mean and variance), all amenable to experimental tests. The distribution has a pronounced asymmetry, which has recently been observed experimentally. The mean rupture force follows a (lnV)^2/3 dependence on the pulling velocity and differs from earlier predictions. Interestingly, at low pulling velocities a rebinding process is observed whose signature is an intermittent behavior of the spring force that delays the rupture. Based on the rupture mechanism, we propose a new “pick-up-and-put-down” method to manipulate individual molecules with scanning probes. We demonstrate that the number of molecules picked up by the tip and deposited at a different location can be controlled by adjusting the pulling velocity of the tip and the distance of closest approach of the tip to the surface.     

Friction on a Microstructured Elastomer Surface

The friction of microstructured polydimethylsiloxane samples against a glass surface is studied through force measurements and simultaneous optical microscopy. Both average friction forces and the amplitude of stick-slip oscillations are greatly reduced by the structuring. Optical microscopy reveals waves propagating through the contact in connection which stick-slip events. The experimental observations are interpreted with the help of simulations of a spring-block model for which parameters are directly derived from the experiment. Stress gradients across the contact area are found to play an important role for the frictional behavior.