1,720,999 research outputs found
All optical switching at Gallium/semiconductor interfaces
No full textWe have observed for the first time that the interface between elemental gallium and semiconductors such as ZnSe or Si manifests optically induced reflectivity switching. This functionality is possible through controlling the coexistence of structural phases of Gallium with different optical properties in the nanoscale thick layer at the metal-semiconductor interface. A particular interest in Ga-semiconductor interfaces is driven by their technological importance for integrated photonic devices and the possibility to achieve high-contrast switching at certain wavelength ranges where the dielectric properties of the semiconductor match that of the interfacing gallium layer. Our results indicate that Ga films deposited directly on semiconductor elements could be useful in all-optical switching devices, optical limiters and as q-switching elements in low power fiber and semiconductors lasers
Optical nonlinearity and light-induced structural transformations in gallium nanoparticles
No full textWe report that gallium nanoparticles, prepared by light-assisted self-assembly, show a nonlinear response to low-power optical excitation. Reversible reflectivity changes of several percent are induced as the result of light-induced structural transformations in the meta
Electrical and Mechanical Properties of new Recyclable Power Cable Insulation Materials based upon Polyethylene Blends
No full textChemically crosslinked polyethylene (XLPE) has been used as electrical insulation for power cables since the 1970s due to its favourable combination of electrical and mechanical properties. However, as the electrical engineering community has become increasingly aware of the life cycle environmental impacts, XLPE has come under scrutiny for its lack of recyclability and the high process energies used in its manufacture. Although technologies are being developed to facilitate the re-use of XLPE at the end of its initial service life, the use of this material is inferior to fully recyclable and low process energy alternatives. In this investigation, we concentrated on the use of binary blends of linear and branched polyethylene (LPE / BPE) as potential replacement materials for XLPE, since such systems have the potential to combine comparable mechanical properties and enhanced breakdown strength with good recyclability. We compare the thin film AC ramp breakdown behaviour of blends as a function of temperature up to 97 oC. These consist of the same BPE in virgin and crosslinked states and in a blend with 20wt% LPE. These data are augmented with dynamic mechanical analysis. In concert, these data indicate that with appropriate morphological control the blended thermoplastic material exhibits superior properties to XLPE under conventional operating conditions and may even be suitable for higher temperature operation than XLPE. The paper will discuss the importance of polymer blending and blend physical properties in the context of the process requirements and the implications for cable manufacture and on cable electrical and environmental performance in comparison with XLPE
Light controls self-assembly of gallium nanoparticles
No full textLight dramatically influences and regulates the self-assembly of gallium nanoparticles grown by atomic beam deposition
Nonlinear optical response of gallium nanoparticles at the verge of a phase transition
No full textFor the first time we report on the substantial optical nonlinearity of elemental gallium nanoparticles. Their response is enhanced by bringing the nanoparticles to the verge of a structural phase transitio
Thermoplastic cable insulation comprising a blend of isotactic polypropylene and a propylene-ethylene copolymer
Get PDFThere is much interest in the development of replacement materials for crosslinked polyethylene (XLPE) that are both recyclable (i.e. thermoplastic) and capable of high temperature operation. Thermally, polypropylene is the ideal choice, although its stiffness and low electrical breakdown strength make for a challenging materials design problem. We report here on the compositional optimization of a propylene homopolymer/propylene-ethylene copolymer blend in terms of its dynamic mechanical properties and thin film electrical breakdown strength. The extrusion of a trial mini-cable using the optimized blend is also discussed, which is shown to exhibit a significantly improved electrical performance, as gauged by its DC breakdown strength, than an XLPE-insulated reference
First observation of light-controlled self-assembly of gallium nanoparticles with narrow size dispersion
No full textSummary form only given. We report growth processes that control the shape and size of particles as they form, through non-thermal processes, using a low-power (~ few mW) infrared diode laser. We study nanoparticle formation on the ends of optical fibers exposed to a gallium atomic-beam source under high vacuum. The results of the experiments and numerical modeling indicate that the growth of gallium nanoparticles in a laser-illuminated area is controlled through non-thermal laser-induced processes. We expect that by changing the deposition conditions (atomic beam flux, substrate temperature, etc.) and laser parameters (wavelength, power, etc.), the size, shape and spatial distribution of nanoparticles could be varied
Optical switching with self-assembled gallium nanoparticles on the tip of an optical fiber
No full textGallium nanoparticles self-assembled on the tip of an optical fiber show substantial intensity dependent reflectivity at only few millwatts of laser power in the fiber
Recyclable power cable comprising a blend of slow-crystallized polyethylenes
No full textCrosslinked polyethylene (XLPE) has a successful history as a cable insulation material. Nevertheless, in recent years, as environmental awareness has grown, concerns about the ease with which it can be recycled have emerged. Although technologies have been developed for XLPE recycling, this report concentrates instead on the development of a thermoplastic alternative. Specifically, a 20 : 80 blend of high density and low density polyethylene (HDPE : LDPE) was selected and subjected to a non-isothermal crystallization procedure. It was found that, provided the cooling rate falls between 0.5 and 10 K min-1, the blend exhibits superior breakdown strengths and high temperature mechanical stiffness compared to XLPE. A trial cable was then extruded from this blend using such a cooling rate. The breakdown behavior of the morphologically-designed cable was finally compared with that of LDPE and XLPE reference systems
- …
