Showing papers by "Anvar A. Zakhidov published in 2000"
TL;DR: Negative Poisson's ratios are predicted for body-centered-cubic phases that likely exist in white dwarf cores and neutron star outer crusts, as well as those found for vacuumlike ion crystals, plasma dust crystals, and colloidal crystals
Abstract: Negative Poisson's ratios are predicted for body-centered-cubic phases that likely exist in white dwarf cores and neutron star outer crusts, as well as those found for vacuumlike ion crystals, plasma dust crystals, and colloidal crystals (including certain virus crystals). The existence of this counterintuitive property, which means that a material laterally expands when stretched, is experimentally demonstrated for very low density crystals of trapped ions. At very high densities, the large predicted negative and positive Poisson's ratios might be important for understanding the asteroseismology of neutron stars and white dwarfs and the effect of stellar stresses on nuclear reaction rates. Giant Poisson's ratios are both predicted and observed for highly strained coulombic photonic crystals, suggesting possible applications of large, tunable Poisson's ratios for photonic crystal devices.
88 citations
TL;DR: Nickel and gold meshes having three-dimensional periodicity at different wavelengths and nanoscale structural fidelity have been prepared byelectrodeposition within close-packed silica sphere arrays.
80 citations
TL;DR: Using a high temperature solution infiltration process, ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer is infiltrated into 3D periodic opal lattices with the silica opal diameters of 180, 225, and 300 nm to form periodic composite structures as discussed by the authors.
Abstract: Using a high temperature solution infiltration process, ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer is infiltrated into three-dimensional (3D) periodic opal lattices with the silica opal diameters of 180, 225, and 300 nm to form periodic composite structures. By etching out the silica opal, inverse copolymer opals can be fabricated, which retains the 3D periodic structure of the original silica opal lattice. In addition to the optical observation, x-ray diffraction and dielectric study were carried out to characterize the change in the ferroelectric behavior of the composites and inverse opals. Although the copolymer in the composites and inverse opals remains ferroelectric, the ferroelectric transition in the composites and inverse opal becomes diffused and moves to a lower temperature, which is due to the random stress introduced by the irregular voids and interfaces and may be made use of to facilitate the transformation of the copolymer into a relaxor. These results suggest the...
27 citations
TL;DR: In this paper, the optical reflection, electrical conductivity, and magnetoconductance of porous opal carbon replicas which have a periodic nanoscale structure have been studied, and the results indicate that the electrical and optical properties can be controlled by pyrolysis technique and porous graphite can be obtained.
Abstract: The optical reflection, electrical conductivity, and magnetoconductance of porous opal carbon replicas which have a periodic nanoscale structure have been studied. The temperature dependence of resistivity in green opal carbon replica is different from that in red opal carbon replica. The electrical properties of replica heat treated up to 3000 °C are consistent with those of pyrolitic graphite. The periodicity is found to decrease with this heat treatment by scanning electron microscopy and reflection measurements. Due to alkali metal doping, optical reflection spectra of replica with a heat treatment temperature of 2800 °C have changed drastically. The occurrence of positive magnetoconductance indicates the existence of quantum effect at low temperature. These results indicate that the electrical and optical properties can be controlled by pyrolysis technique and porous graphite can be obtained.
18 citations
01 Jan 2000
TL;DR: In this article, a method for making a nano-engineered thermoelectric (NETE) coating on silica particles is described. But the process consists of coating the particles with gold and then coating them with a thermodynamic material, e.g., Skutterudite.
Abstract: A nano-engineering approach has been developed for the synthesis of the thermoelectric composite materials. A possible way for enhancing ZT is to incorporate thermoelectric materials, e.g. Skutterudite, into the nano-sized pores of three-dimensional periodic arrays. The present study reports the development of a method for making a Nano-Engineered Thermoelectric (NETE) coating on silica particles. The coated particles are assembled into three-dimension array of opals to form NETE composite. The process consists of coating silica particles with gold and then with thermoelectric material. Gold coating has the advantage that post-coating assembly provides a continuous network of Skutterudite-filled gaps between gold interconnects. The second coating was carried out by chemical co-precipitation of Co and Sb precursors from a solid solution onto the surfaces of the gold-coated particles under controlled conditions. Through further heat-treatments (calcination, reduction and alloying), a Skutterudite layer has been formed in high purity. Both the gold-and gold/Skutterudite-coated particles retain the morphology of the original silica particles. In this paper, the processing conditions and materials characterizations are reported and discussed
3 citations
TL;DR: In this article, the opals themselves consist of close-packed silica spheres, which serve as a template for the growth of the nickel arrays within the void space between SiO2 spheres.
Abstract: Electrochemical methods have been used to produce three-dimensionally periodic metal meshes and spheres. Nickel is initially deposited into porous opal sheets. The opals themselves consist of close-packed silica spheres, which serve as a template for the growth of the nickel arrays within the void space between SiO2 spheres. Dissolution of the SiO2 spheres results in open, three-dimensionally periodic nickel mesh structures. The metal meshes can then be oxidized in air to produce nonconducting NiO meshes. This results in an inverse template that can be used for the growth of three-dimensionally periodic metal sphere arrays. Details on the preparation and characterization of these materials are presented.