National Physical Laboratory

About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.

Grain boundary cavitation under various states of applied stress

Abstract: Submicrometre grain boundary cavities are produced in Nimonic 80A when plastic deformation in any of three different stress states is followed by a short anneal. Tension, torsion and compression specimens were plastically strained in a systematic manner and then annealed for 2 h at 750 °C. Detailed quantitative observations with a 1 MV microscope showed that the number of cavities per unit volume was a function of the shear strain and independent of the stress state. Furthermore the measurements revealed the surprising result that most cavities were on those grain boundaries which were parallel to the maximum principal stress axis. However, Preferential cavity growth occurred during subsequent tensile creep and cavities on these parallel boundaries either remained constant in size or diminished while those on boundaries which were orthogonal to the applied stress axis grew relatively quickly, thus producing the usual appearance of cavitated tensile samples. Plastic strain was more detrimental to torsional creep ductility when the direction of torque between plastic deformation and creep was reversed which is in accordance with the anisotropic cavitated boundary distribution. The results are compatible with the hypothesis that cavities are produced by grain interior slip and stabilized by plastic deformation induced internal tensile stresses.

Polymer electrolytes: characteristics and peculiarities

Abstract: Polymer electrolytes are an important component of many electrochemical devices This paper reviews state-of-the-art of the electrochemical and physical properties of polymer electrolytes This review mainly encompasses the properties of different salts, solvents, and polymer hosts, which are encaged in liquid electrolytes The additions of filler in polymer electrolytes result in composite polymer electrolytes, having high mechanical integrity and ionic conductivity, that are ideal electrolyte for these applications The next generation state-of-the-art room-temperature ionic liquids based electrolytes, which are far superior to corresponding nonionic solvent-based electrolytes, are also discussed

Determination of the relative signs of proton spin coupling constants by double irradiation

Abstract: The method of Evans [1] for determining relative signs of nuclear spin coupling constants by double irradiation experiments has been extended to the case where the three coupled nuclei are all protons. It is thus possible to demonstrate from the high resolution proton magnetic resonance spectrum of the ring protons of 2-Furoic acid that the three spin coupling constants are all of like sign.

Zinc oxide hierarchical nanostructures as potential NO2 sensors

Abstract: A superficial thermal evaporation method has been employed for the fabrication of hierarchical zinc oxide (ZnO) nanostructured films, composed of nanorods (NR's) and bunch of nanowires (BNW's), on glass substrate and the diverse atmospheric annealing effect on their structural, morphological, compositional, and gas sensing properties has been systematically studied and reported. Structural investigation corroborates the formation of crystalline hexagonal wurtzite ZnO. The arrays of vertically aligned nanorods and bunch of nanowires of ZnO were observed on the substrate surface. As-prepared ZnO NR's and BNW's are utilized as a sensing material for detection of toxic nitrogen dioxide (NO 2 ). The ZnO sensors exhibit high response to NO 2 along with rapid response and recovery time values @200 °C. In addition, ZnO sensors respond to a very small exposure of NO 2 gas i.e. 1 ppm. Furthermore, the developed sensors attain excellent stability and reproducibility in response. Finally, the interaction of NO 2 gas molecules with hierarchical nanostructured ZnO sensors has successfully been studied and discussed by employing an electrochemical impedance spectroscopy measurement.