Structure and magnetic properties of Cu-Fe fiber composites obtained using packet hydrostatic extrusion

The structure and magnetic properties of Cu-Fe fiber composites prepared by packet hydrostatic extrusion are studied. The number of armco-iron fibers in the copper matrix attained n ∼ 8 × 10¹⁰, and rated diameter d of fibers varied from 2 mm to 3 nm. A correlation is observed between the magnetization hysteresis curves and low-frequency magnetic susceptibility obtained on samples with various values of d. It is shown that the magnetic properties of composites in the submicrometer range of d values are satisfactorily described in the magnetization reversal theory for small ferromagnetic particles.     

Shape-Memory Effect in Polymer Composites with a Compactible Filler

The shape-memory effect has been investigated in formed porous polymers and composites under heating. An epoxy polymer, ultrahigh-molecular polyethylene, and polypropylene were used as the polymeric matrix and carbon materials of different bulk density were taken for the filler. An unconventional shape-memory effect, which is accompanied by an increase in volume, was created. Processing schemes by which this effect can be achieved are proposed. They make it possible to obtain products of varying configuration.     

Temperature-induced changes in the EPR spectrum of the magnetic center in kaolin

Studies of kaolin have revealed an effect characterized by an unusual temperature-induced change of the EPR spectrum of the Fe3+ ion, which is the magnetic probe in kaolin-clay. At low temperature (T=4.2 K) a resonance line with an effective g-value g1=4.13 +/- 0.16 is observed. At high temperature (T=288 K) one observes a resonance line with the effective g-value g2=2.15 +/- 0.1. The transition from the low- to high-temperature spectrum is gradual and it is accompanied by a redistribution of the absorption intensity. The observed properties of the temperature dependence of the EPR spectrum are characteristic of systems with a multiminimum potential.     

Shape restoration after combined deformation of a composite consisting of an epoxy polymer and thermoexpanded graphite

Size restoration is studied for samples of an epoxy polymer filled with thermoexpanded graphite upon their heating after deformation including extrusion with subsequent compression in a mold. The proposed scheme of combined deformation is shown to be applicable for implementing the shape memory effect, where the sample behaves as a material with a negative Poisson ratio.     

Mechanisms for flow and forced high elasticity of cross-linked polymers

A quantitative model is proposed for flow and forced high elasticity of cross-linked polymers based on the cluster model of amorphous state structure. The flow process is seen as the loss of displacement stability by the clusters, while forced high elasticity is related to the mechanical devitrification of the softpack matrix. Fractal analysis was used to show a turbulent regime for the forced high elasticity of cross-linked polymers.Kabardino-Balkariya State University, Nal'chik. Russia. Donetsk Physics and Mechanical Sciences University. Ukraine. Branch of the Institute of Ecology. Kashkhatau, Kabardino-Balkariya. Russia. Center for Composite Materials, Moscow State Open University, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 2, pp. 270–278, March–April, 1996.     

Structural and kinetic aspects of hydrostatic pressure effect on polymer network formation

Abstract

Effect of hydrostatic pressure up to 250 MPa on structurization kinetics and morphology of network polymers based on epoxy oligomers has been studied using the methods of measurements of resistivity and optical microscopy.     

Influence of equal-channel multi-angle pressing on mechanical and transport properties of a multi-fibrous NbTi superconductor

The effect of equal-channel multi-angle pressing combined with hydroextrusion and drawing followed by thermal treatment on critical current density, superconducting transition temperature and mechanical properties of a multi-fibre (210 fibres) superconducting wire made of a Nb + 50 wt% Ti alloy has been investigated.     

Structural and kinetic aspects of hydrostatic pressure effect on polymer network formation

Abstract

Effect of hydrostatic pressure up to 250 MPa on structurization kinetics and morphology of network polymers based on epoxy oligomers has been studied using the methods of measurements of volume resistivity and optical microscopy.