Search results for "Tact"
showing 10 items of 1313 documents
Influence of the tip effect of a carbon nanostructure on low current electrical arc initiation
2009
During their setting off, circuit breakers and vacuum switch devices are accompanied by an electric arc whose physical and chemical properties are governed by emissive current sites at the cathode surface called cathode spots. Assuming the continuity of the current on the cathode surfaces, the cathode spots contribute to supply the electrical arc by electron emission and material ejection. Thus they cause erosion on the contact electrodes inducing a dysfunction of contactors. The apparition of these cathode spots is due essentially to dust particles and surface irregularities at different scales. This experimental work represents a contribution to the understanding of the electrical arc beh…
Extra tension at electrode-nanowire adhesive contacts in nano-electromechanical devices
2017
Abstract We report a strong tangential component of the reaction force at electrode to nanowire adhesive contact which was previously established using electrostatic attraction. The reaction force tangential component absolute value was found to be comparable to or even bigger than the corresponding normal component. This effect is important for understanding of the mechanics of nano-electromechanical devices. Both the experiment and the corresponding theory are presented. Fitting of the obtained analytical solutions to experimental data was used to measure the reaction force acting at the contact for several nanowire-electrode configurations.
The effect of substrate roughness on the static friction of CuO nanowires
2012
Abstract The dependence of static friction on surface roughness was measured for copper oxide nanowires on silicon wafers coated with amorphous silicon. The surface roughness of the substrate was varied to different extent by the chemical etching of the substrates. For friction measurements, the nanowires (NWs) were pushed by an atomic-force microscope (AFM) tip at one end of the NW until complete displacement of the NW was achieved. The elastic bending profile of a NW during this manipulation process was used to calculate the ultimate static friction force. A strong dependence of static friction on surface roughness was demonstrated. The real contact area and interfacial shear strength wer…
Nanosecond thermo-optical dynamics of polymer loaded plasmonic waveguides
2013
The thermo-optical dynamics of polymer loaded surface plasmon waveguide (PLSPPW) based devices photo-thermally excited in the nanosecond regime is investigated. We demonstrate thermo-absorption of PLSPPW modes mediated by the temperature-dependent ohmic losses of the metal and the thermally controlled field distribution of the plasmon mode within the metal. For a PLSPPW excited by sub-nanosecond long pulses, we find that the thermo-absorption process leads to modulation depths up to 50% and features an activation time around 2ns whereas the relaxation time is around 800ns, four-fold smaller than the cooling time of the metal film itself. Next, we observe the photo-thermal activation of PLSP…
Pickering Emulsions of Fluorinated TiO2: A New Route for Intensification of Photocatalytic Degradation of Nitrobenzene
2020
International audience; Fluorination of the TiO2 surface has been often reported as a tool to increase the photocatalytic efficiency due to the beneficial effects in terms of production of oxidizing radicals. Moreover, it is shown that the unique amphiphilic properties of the fluorinated TiO2 (TiO2-F) surface allow one to use this material as a stabilizer for the formulation of Pickering emulsions of poorly soluble pollutants such as nitrobenzene (NB) in water. The emulsions have been characterized in terms of size of the droplets, type of emulsion, possibility of phase inversion, contact angle measurements, and optical microscopy. The emulsified system presents micrometer-sized droplets of…
Plano-concave microlenses with epsilon-near-zero surface-relief coatings for efficient shaping of nonparaxial optical beams
2017
Abstract Epsilon-near-zero (ENZ) materials, including artificial metamaterials, have been advanced to mold laser beams and antenna-mediated radiated waves. Here we propose an efficient method to control Ohmic losses inherent to natural ENZ materials by the assembly of subwavelength structures in a nonperiodic matrix constituting an ENZ metacoating. Implemented over plano-concave transparent substrates whose radius can be of only a few wavelengths, ENZ surface-relief elements demonstrate to adequately shape a plane wave into highly localized fields. Furthermore, our proposal provides an energy efficiency even higher than an ideally-lossless all-ENZ plano-concave lens. Our procedure is satisf…
Surface characterization of functional poly(diacetylene) and poly(butadiene) mono- and multilayers
1982
The surface properties of Langmuir-Blodgett mono- and multilayers of a variety of amphiphilic poly(diacetylene)s and poly(butadiene)s were investigated by contact angle, streaming potentialζ, ellipsometry, and X-ray photoelectron spectroscopic (XPS) measurements. Captive air and octane angles varied between approximately 60° and 105° for hydrophobicx-layers and 31° to 46° for hydrophilic surfaces depending on the particular head group, whereas advancing angles determined via the vertical plate method are considerably higher. Negative streaming potentials were obtained for all surfaces. Positively charged monolayers yielded less negativeζ- potential values (−28 mV) than negatively charged (−…
Relating morphology to nanoscale mechanical properties: from crystalline to mesomorphic iPP
2005
Abstract A nanoindentation technique using an atomic force microscope (AFM) was applied to characterize the mechanical behaviour of several isotactic polypropylene (iPP) samples. The samples were solidified from the melt with a CCT (continuous cooling transformation) procedure spanning a wide range of cooling rates thanks to a fast quenching apparatus developed by the authors. The influence of instrumental parameters on the nanoscale mechanical properties (indentation depth, Young's modulus) shows that for modulus determination one has to rely on simpler methods of force curve analysis based on trace curve alone. Structure homogeneity up to the scale of macroscopic samples used to evaluate …
Formation and Characterization of Self-Assembled Films of Thiol-Derivatized Poly(Dimethylsiloxane) on Gold
1997
Poly(dimethylsiloxane) (PDMS) copolymers containing propanethiol side chain “stickers” for forming self-assembled films on gold surfaces have been studied by various experimental techniques including ellipsometry, contact angle measurements, FT-IR, angle-dependent XPS, and ToF−SIMS. The results show that the thiol-containing side chains do not all chemisorb to the gold surfaces. In addition, the concentration of these sticker units was found to have a dominant effect on the polymer film thickness, the surface wetting properties, and the orientation of the PDMS backbone. Ab initio calculations reveal that the IR-active PDMS Si−O stretching bands can be used as indications of chain orientatio…
SAXS/WAXS study of the annealing process in quenched samples of isotactic poly(propylene)
1999
The structural rearrangement in samples of quenched isotactic poly(propylene) (iPP) submitted to different annealing treatments has been studied using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) at the synchrotron radiation source of DESY, Hamburg. From a quantitative analysis of the WAXS profiles the values of the α-monoclinic, mesomorphic, and amorphous mass fractions coexisting in the material were determined. It is demonstrated that the SAXS patterns were characterized by two different long-period values that are attributed to α- and mesomorphic periodicity, respectively. The related α- and mesomorphic volume phase fractions, calculated from the analysis of the SAXS …