Search results for "Surfaces"
showing 10 items of 2837 documents
Effect of a filler on the dielectric properties of an epoxy resin
1983
The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
Structural and in depth characterization of newly designed conducting/insulating TiN O /TiO2 multilayers obtained by one step LP-MOCVD growth
2001
Abstract TiNxOy/TiO2 multilayers have been grown by LP-MOCVD using titanium isopropoxide (TIP) precursor during the whole growth, but with an ammonia flow interrupted for the TiO2 layers. The one step growth process used to grow these structures allowed to stack the conducting and insulating layers without any growth breakdown. SIMS and TEM analyses showed the presence of an alternated insulating/conducting layers structure. Moreover, electrical measurements allowed to measure the dielectric part of insulating TiO2 stacked in these structures, whose permittivity was found to be about 80 for a MOS structure. Thus, such multilayers may lead to very promising applications in the microelectroni…
Complex permittivity of FeCl3/AOT/CCl4 microemulsions probed by AC impedance spectroscopy
2009
Abstract The complex permittivity of FeCl 3 /AOT/CCl 4 microemulsions in the 1–10 5 Hz frequency range has been measured by the conventional AC complex impedance technique. Measurements as a function of the volume fraction of the dispersed phase (FeCl 3 + AOT) and temperature at fixed salt-to-AOT molar ratio ( R , R = 0.5) show that the entrapment of FeCl 3 clusters significantly enhances the local permittivity of the AOT reverse micelles and the number density of charge carriers resulting from the peculiar state of the confined inorganic salt. An estimate of the apparent static permittivity of the FeCl 3 ionic clusters entrapped in the core of AOT reverse micelles gives the very high an…
Noninvasive monitoring of polymer curing reactions by dielectrometry
2011
A microwave sensor system for the noninvasive monitoring of the curing process of a thermoset material placed inside a metallic mold is described. The microwave sensor is designed as an open-ended coaxial resonator with a curved surface adapted to the mold inner shape. The analysis of the microwave resonator comprises a recently developed method for deembedding the effect of coupling network in overcoupled resonators, so the range of permitted measurements encompass both low and high dielectric losses of polymeric materials. Results show that noninvasive, continuous monitoring of the microwave dielectric properties of the thermoset material can be performed in real time, allowing one to che…
The multimodal detection as a tool for molecular material-based gas sensing
2013
Abstract The adsorption of a target gas on a material induces a change in several physical characteristics, such as the dielectric constant, the work function or the conductivity. The use of different transducers sensitive to the variation of these parameters appears to be a relevant methodology worthy of investigation. In the field of sensors, molecular materials present interesting and potentially valuable features as sensing elements for real gas sensor applications. In this article, we review the different types of conductimetric transducers and also show how a molecular material-based microwave transducer can be used for gas sensing. Among conductimetric transducers, resistors have bee…
Chiral polyisocyanates, a special class of helical polymers
2001
Abstract Polyisocyanates (nylon 1) offer a lot of fascinating properties due to their dynamic helical conformation, which gives rise to orientational phenomena (large persistence length) or chiral amplification. This paper summarizes new results on polyisocyanates that appeared after the review by Bur and Fetters [Chem Rev 76 (1976) 727]. It starts with an overview of new synthetic methods, and then describes chiral polyisocyanates, their properties and the theoretical concepts developed to understand the experimental findings. Thereafter concentrated solutions (gels and LC phases) as well as photochromic polyisocyanates are discussed in detail. Finally, solid phase composite materials from…
Identification of high-affinity phage-displayed VH fragments by use of a quartz crystal microbalance with dissipation monitoring
2021
10 Pág. Departamento de Tecnología de Alimentos
Compositional dependence of element-specific magnetic moments in Ni2MnGa films
2009
Element-specific magnetic moments were investigated for epitaxial Ni2Mn1+xGa1−x and (Ni2MnGa)1−x(Co2FeSi)x Heusler films using x-ray absorption spectroscopy and x-ray circular magnetic dichroism in transmission. The epitaxial films of the Ni2MnGa-derived compositions were prepared by dc-sputtering on Al2O3 substrates at 773 K. X-ray diffraction confirms a (1 1 0) oriented growth. An increase in the Mn concentration reduces the magnetic spin moment of both Mn and Ni. An increase in the content of Co2FeSi in the Ni2MnGa compound leads to an increase in the Mn and Ni spin moments and to a decrease in Tm for 5% Co2FeSi and finally to a suppression of the phase transition for 20% Co2FeSi. The or…
Dielectric barrier discharge at the triglycine sulfate crystal surface: the role of the electric field of the domain structure
2014
Dielectric barrier discharges (DBD) at the triglycine sulfate crystal surface, generated in air under controlled gas pressure, have been investigated. Electrical characterization of these DBD discharges, produced at temperatures below as well as above the ferroelectric phase transition, are presented. The influence of the electric field of the domain structure on these DBD discharges are discussed in the frame of a model which takes into account the dynamics of the domain structure of the ferroelectric barrier under the action of an external voltage.
Pbca-Type In2O3: The High-Pressure Post-Corundum phase at Room Temperature.
2014
High-pressure powder X-ray diffraction and Raman scattering measurements in cubic bixbyite-type indium oxide (c-In2O3) have been performed at room temperature. On increasing pressure c-In2O3 undergoes a transition to the Rh2O3-II structure but on decreasing pressure Rh2O3-II-type In2O3 undergoes a transition to a previously unknown phase with Pbca space group which is isostructural to Rh2O3-III. On further decrease of pressure, we observed a phase transition to the metastable corundum-type In2O3 near room conditions. Recompression of the metastable corundum-type In2O3 at room temperature leads to a transition to the Rh2O3-III phase, thus showing that the Rh2O3-III phase is the post-corundum…