ABSTRACT
Rigid metamaterials were prepared by embedding TiO2 microspheres into polyethylene. These structures exhibit a series of Mie resonances where the lowest-frequency one is associated with a strong dispersion in the effective magnetic permeability. Using time-domain terahertz spectroscopy, we experimentally demonstrated the magnetic nature of the observed resonance. The presented approach shows a way for low-cost massive fabrication of mechanically stable terahertz metamaterials based on dielectric microresonators.
ABSTRACT
Accurate control of residual defect density is required for reliable investigation and use of ferroelectric materials. After reviewing the long term endeavor to decrease defect contributions in bulk materials, which reached mass production decades ago, recent challenges are underlined. These mostly result from the continuous trend towards integration which has reached the nanometre range. The contribution of solid state chemistry is of key relevance for improving the present processing routes and suggesting alternative ones, for example by controlling a large density of charged defects to reach unprecedented functionalities. Some of these breakthroughs are reviewed.
ABSTRACT
In this study we show that pure and well crystallized nanoparticles of Ba(x)Sr(1-x)TiO(3) (BST) can be synthesized over the entire range of composition through the hydrolysis and further crystallization of alkoxide precursors under supercritical conditions. To our knowledge, this is the first time that the whole ferroelectric solid solution has been produced in a continuous way, using the same experimental conditions. The composition of the powder can be easily controlled by adjusting the feed solution composition. The powders consist of soft-aggregated monocrystalline nanoparticles with an average particle size ranging from approximately 20 to 40 nm. Ferroelectric ceramics with accurately adjustable Curie temperature (100-390 K) can thus be obtained by sintering.
ABSTRACT
Pure and well-crystallized Barium Strontium Titanate (BST) nanoparticles with controlled Ba/Sr ratio have been successfully synthesized under supercritical conditions using a continuous-flow reactor in the temperature range of 150-380 degrees C at 26 MPa. To synthesize the Ba0.6Sr0.4TiO3 composition, alkoxides, ethanol and water were used. The resulting nanopowder consists of fine particles with an average particle size of 23 nm. The results show that the Ba/Sr ratio of this powder can be accurately controlled from the composition of precursor. The characterization of the as-synthesized Ba0.6Sr0.4TiO3 solid-solution and the dielectric properties of the sintered ceramics are here reported.
Subject(s)
Barium Compounds/chemistry , Chromatography, Supercritical Fluid/methods , Crystallization/methods , Magnetics , Nanotubes/chemistry , Nanotubes/ultrastructure , Nitrates/chemistry , Strontium/chemistry , Barium Compounds/analysis , Electric Conductivity , Electrochemistry/methods , Materials Testing , Nanotechnology/methods , Nanotubes/analysis , Nitrates/analysis , Particle Size , Strontium/analysis , Surface PropertiesABSTRACT
Se describre la experiencia de un equipo multidisciplinario de tratamiento para NF Labiopalatinos en la IX Región, entre 1980 y 1986, en 250 NF de ambos sexos, portadores de diversos tipos de fisuras en las que predominan las formas más complejas de lesión. Se expone un algo-ritmo de trabajo organizado integral el que es necesario para dar al NF la mejor atención. Se comenta el apoyo de gran valor de entidades comunitarias benéficas (local: COANIFIS e internacional: INTERPLAST) en el tratamiento completo, complejo y de alto costo en estas patologías
