Conditions for the Occurrence of Spontaneous Oscillating Magnetic Relaxation in Synthetic Pt/Co/Ir/Co/Pt Ferrimagnets

Physics of the Solid State - It has been established that nonmonotonic magnetization relaxation in Pt/Co/Ir/Co/Pt synthetic ferrimagnets (SF) with perpendicular magnetic anisotropy is caused by the...     

An Insight into the Diffusion of Unsaturated Polyester (UP) Resin into Expanded Graphite (EG) to Improve the Mechanical Properties of the UP/EG Composites

Abstract

Polymer/expanded graphite (EG) nanocomposites have great importance in many industrial applications mainly due to their high electrical/thermal conductivity or flame retardancy. However, to fully employ the benefits of polymer/EG nanocomposites one must consider the high degree of porosity of EG. The high degree of porosity of EG can deteriorate the composites’ mechanical properties if the polymer chains cannot diffuse completely into the EG pores. In this article, an insight is given into the diffusion of unsaturated isophthalic polyester (UP) resin, consisting of a combination of maleic anhydride and isophthalic anhydride in the resin backbone, with two viscosities, into the pores of the EG particles of various degrees of porosity. The diffusion experiments were carried out on compressed EG tablets with the same density but different porosity due to the different porosity of the EG particles. The results showed that the diffusion rate of the UP resin with higher viscosity slightly decreased when the EG porosity decreased but, in the opposite way, it strongly increased for the low viscosity UP resin. The EG nanocomposites samples were molded at varying pressures. The micrographs of the fractured surfaces of the EG nanocomposites showed that the EG pores were not filled with resin, thus the EG nanocomposites had residual pores. It was found that composites containing EGs with higher expansion ratio and larger particles and pores showed larger residual pores. Furthermore, the composites prepared with the more viscous UP resin showed more residual pores. By applying a pressure of 10?bar instead of 1?bar, a reduction of 7–20% in the residual pores of the nanocomposites was observed which led to improved mechanical properties by up to 20% in flexural strength for the EG with the highest expansion ratio.     

Population Gratings Created by a Pair of Unipolar Attosecond Pulses in a Three-Level Atomic Medium

Optics and Spectroscopy - The possibility of inducing population gratings in a three-level resonant medium using a pair of unipolar attosecond pulses that do not overlap in the medium has been...     

Weak Coupling between Light and Matter in Photonic Crystals Based on Porous Silicon Responsible for the Enhancement of Fluorescence of Quantum Dots under Two-Photon Excitation

JETP Letters - The development of optical and, in particular, photoluminescent sensors is currently becoming more and more significant because of their universality, selectivity, and high...     

Precision Interferometry as a New Method for Studying the Conformational State of Protein and Its Interaction with a Solvent

Optics and Spectroscopy - A new method for studying the conformational state of a protein and its interaction with a solvent has been developed. The method is based on measuring the refractive...     

Study of the Spectrumof Low-Frequency Current Fluctuations in Filaments of Electric Lamps

Radiophysics and Quantum Electronics - We study experimentally the spectral characteristics of low-frequency current fluctuations in tungsten filaments of lighting lamps in the ranges of...     

Structurally and Surface-Modified Alumina Particles as a Reinforcement in Polyester-Based Composites with an Improved Toughness

Mechanics of Composite Materials - Commercial γ ? Al2O3 particles, Al2O3 n, and synthesized Al2O3 doped with iron oxide (Al2O3 Fe) were used as reinforcements to enhance the toughness of...     

Embedded solitons in the $$(2+1)$$(2+1)-dimensional sine-Gordon equation

Nonlinear Dynamics - An effective and simple method to solve nonlinear evolution partial differential equations is the self-similarity transformation, in which one utilizes solutions of the known...     

Catalytic Systems Based on the Metal Complexes of 1-Alkyl-4-Aza-1-Azoniabicyclo[2.2.2]Octane Bromides

Kinetics and Catalysis - The catalytic activity of supramolecular systems based on the complexes of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide (Alk = CnH2n+ 1, n = 16, 18) with lanthanum...