Experimental study of the contribution of interfacial friction to the deformation resistance of particle-reinforced polymers

A study has been made of the dissipative properties of heavily filled elastomers as influenced by friction of the elastic matrix on the surface of the solid filler particles. In order to model the frictional surface, specimens were predamaged by cyclic deformation, with strain amplitudes sufficient to cause separation of the matrix from the filler. The predeformation operation was performed by means of a mechanical system having individual particle-matrix bonds, so that it was possible to evaluate the contribution of interfacial friction to the resistance of the polymer. When external pressure was applied to the specimens, the width of the hysteresis loop increased with increasing pressure, obviously reflecting an increase of the surface friction in the matrix. It was established that for a given volumetric fill, the dissipation of mechanical energy increased with decreasing particle size (with increasing frictional surface area). The significant influence of interfacial friction on the level and rate of strain relaxation was demonstrated experimentally.Paper presented at the 9th International Conference on the Mechanics of Composite Materials (Riga, October 1995).Translated from Mekhanika Kompositnykh Materialov, Vol. 31, No. 5, pp. 579–583, September–October, 1995.     

Effect of the cationic composition of cryolite-alumina melts on the anodic overvoltage

Steady-state polarization of anodes prepared from platinum or glassy carbon is studied in a laboratory cell in a cryolite-alumina melt containing small amounts of potassium and lithium fluorides and various alumina amounts. The surface area of the anodes reaches a few centimeters squared. An insignificant depolarization of the anodic process is discovered following the replacement of a fraction of sodium ions in the electrolyte by potassium ions in an amount of ～3.9 mol % KF (～4.1 wt %) and a noticeable depolarization, following the substitution of K⁺ in an amount of ～7.1 mol % KF (～7.6 wt %). Substituting lithium ions in an amount of ～3.7 mol % LiF (～1.8 wt %) for a fraction of sodium ions leads to an insignificant polarization. A significant effect of a general cryolite ratio on polarization is discovered. A noticeable increase in the anodic polarization is fixed at an alumina concentration equal to 5–5.5 wt %.     

Research on the Interfacial Friction in Filled Polymers

A procedure is developed for studying the interfacial friction in filled polymers. The paper presents results of experiments on physical models which represent an elastic matrix contacting with the friction surface. The friction law established experimentally was used to develop computational algorithms describing the processes of cyclic loading and relaxation in filled polymers in the case of permanent contact between the matrix and a hard inclusion and on detachment of the matrix from the inclusion.     

A Photonic Nanojet as Tunable and Polarization‐Sensitive Optical Tweezers

The ability to manipulate small objects with focused laser beams has opened a venue for investigating dynamical phenomena relevant to both fundamental and applied sciences. However, manipulating nano‐sized objects requires subwavelength field localization, provided by auxiliary nano‐ and microstructures. Particularly, dielectric microparticles can be used to confine light to an intense beam with a subwavelength waist, called a photonic nanojet (PNJ), which can provide sufficient field gradients for trapping nano‐objects. Herein, the scheme for wavelength‐tunable and nanoscale‐precise optical trapping is elaborated, and the possibility of lateral nanoparticle movement using the PNJ's side lobes is shown for the first time. In addition, the possibility of subwavelength positioning using polarization switching is shown. The estimated stability with respect to Brownian motion is higher compared to conventional optical trapping schemes.     

Experimental studies on the adhesion strength of a polymer-metal bond depending on the contact zone geometry

Theoretical investigation of the stress-strain state at special points of constructions, e.g., in adhesion joints, has demonstrated that the stress state in the contact zone strongly depends on the configuration of the zone. In order to verify these results, some experiments were carried out. Cylindrical polymer specimens having a circular groove at one of its ends were cemented to steel mushrooms and tested for abruption in tension and cantilever bending. The experiments showed that the adhesive strength depended on the profile of the joint and had a maximum at the optimum value of the angle of the joint and a minimum when the groove was absent. The ratio between the maximum and minimum strength values was 1.5 in tension and 2.5 in bending. The greater effect in the latter case can be explained by the high gradient of the stresses in bending. The experimental results confirmed the possibility of controlling the adhesive strength by changing the contact geometry in accord with the stress-strain calculations.Institute of the Mechanics of Continuous Media, Russian Academy of Sciences, Perm', Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 493–498, July–August, 1999.     

Regioselective synthesis of 1-alkyl-5-(indol-3-yl- and -2-yl)pyrrolidin-2-ones from available reagents

The reaction under mild conditions of 1-alkyl-5-hydroxypyrrolidin-2-ones with different indoles having a free 3 position leads exclusively to 1-alkyl-5-(indol-3-yl)pyrrolidin-2-ones but if position 3 is occupied to 1-alkyl-5-(indol-2-yl)pyrrolidin-2-ones.     

Metal anodes oxidation rate forecasted by results of electrolysis

This work represented the results from electrolysis tests of low-melting cryolite-alumina melts at temperatures of 790 and 850°C using metal anodes based on Cu-Fe-Ni and Cu-Al. The duration of experiment was at least 72 h. With these results, oxide layer dissolution/erosion rate and anodic material oxidation depth was calculated in arbitrary units (alloy cm/year) with examples of extrapolated (forecasted) experimental data of oxidation depth and oxide layer thickness for a long period. The oxide layer formed on the anode surface by electrolysis of the studied materials was found to decelerate further oxidation all over the period of tests.     

Rate of metallic anode oxidation in the course of electrolysis of cryolite-alumina melts. Derivation of basic equations

The well known oxidation law is offered as a basis for the new method that allowed predicting the service life of metallic anodes by extrapolation of the experimental results (time dependences of the substrate oxidation depth, oxide layer mass and its chemical composition) to a long-term period (a year). The suggested calculation technique allows predicting the steady state characterized by constant equal rates of metallic anode oxidation and erosion of its oxide layer and also the constant oxide layer thickness in the case when it features an ability to hinder further oxidation.     

Diffusion in the aged aluminium film on iron

Metallic coatings of many types can be applied to steel to provide outstanding, long-term corrosion protection. A thin Al film is studied at an Fe substrate by the molecular dynamics method at temperatures ranging from 300 K to 1173 K. Al atoms are found to penetrate the Fe matrix at a temperature of 873 K. The potential energy of the system changes step-like at a temperature of 1173 K. At such temperature mean square atomic displacement significantly changes. The behaviors of the Al and Fe diffusion coefficients are mainly determined by the temperature dependence of the diffusion activation energy.