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.

Measurement of flow stress in hot axisymmetric compression tests

Abstract: This paper describes good practice for the measurement of hot flow stress in metallic materials. It is applicable to hot (isothermal) uniaxial axisymmetric compression tests at medium to high rates of strain (10−4–102 s−1) at deformation temperatures below the solidus.Guidance is provided on appropriate testpiece geometries and methods of verifying the temperature distribution along the length of the testpiece. Flow diagrams are given showing all the steps that are necessary, including the correction factors that need to be applied for deformational heating and for the determination of true stress. Details are given of the calibration procedures that should be followed to provide traceability to the National Measurement System.Technical input to the document has been provided by a steering group containing academic researchers and representatives of industrial users and producers of a wide range of engineering materials. An experimental and modelling programme on an aluminium alloy, AA5052; on 316...

Photodegradation of dye pollutant under UV light by nano-catalyst doped titania thin films

Abstract: Undoped and manganese ion-doped TiO 2 powders and thin films have been prepared by sol–gel route. The concentration of the manganese in TiO 2 powders and films varied from 2 to 10 mol%. These powders were annealed at different temperatures from 300 to 1000 °C while films were annealed at 450 °C for 1 h. Prepared samples were characterized by XRD, SEM, XPS, spectroscopic and contact angle measurement techniques. Photocatalytic activity, in terms of rate constant measured by degradation of methylene blue dye, under UV exposure was found to increase from 0.27 to 0.36 for 5 mol% doping while very small photo activity has been observed under visible light exposure. Hydrophillicity also shows the same behavior. Optical studies revealed the generation of allowed energy band in the forbidden gap at ∼0.63 eV below the conduction band. It has been concluded that Mn doping increases photocatalytic activity by scavenging the photogenerated electrons, thereby increasing the life time of charge carriers and increasing the exposed surface area by reducing the crystallite size.

Disordered Fermi Liquid in Epitaxial Graphene from Quantum Transport Measurements

Abstract: We have performed magnetotransport measurements on monolayer epitaxial graphene and analyzed them in the framework of the disordered Fermi liquid theory. We have separated the electron-electron and weak-localization contributions to resistivity and demonstrated the phase coherence over a micrometer length scale, setting the limit of at least 50 ps on the spin relaxation time in this material.