Chandigarh, India
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Bharuth-Ram K.,Durban University of Technology | Bharuth-Ram K.,University of KwaZulu - Natal | Doyle T.B.,University of KwaZulu - Natal | Doyle T.B.,Materials Research Division | And 4 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2017

Conversion electron Mössbauer spectroscopy (CEMS) measurements have been performed on single crystal Al2O3 implanted with 56Fe and 57Fe ions to a total fluence of 1.2×1016/cm2, corresponding to a concentration of approx. 4at.%. The CEM spectrum in the 'as-implanted' state is in good agreement with earlier studies. Annealing at temperatures above 600°C resulted in significant changes, with the spectra after the annealing at TA ≥800°C displaying paramagnetic doublets characteristic of superparamagnetic nanoclusters. Magnetization curves of the annealed sample show hysteresis loops with zero coercive field while the analysis of low temperature magnetic isotherms in terms of the Langevin function for superparamagnetic particles yields an average radius of 2-3nm for the Fe clusters. © 2017.

Hameed M.Z.,Materials Research Division | Hameed M.Z.,Princess Sumaya University for Technology
European Journal of Scientific Research | Year: 2012

The properties of ceramic bodies made by slip casting of kaolin clay with grog content between 10% - 60% were investigated. Casting slip of proper consistency and of high solid content (66%) was prepared by mixing fine powder of kaolin with grog in dry form. Sodium silicate (water glass) is used in proper proportion as defluculent. Solid rectangular bars and crucible shape parts are casted, dried and then sintered at temperatures 1200-1400 DC. The shrinkage, density, porosity, water absorption, and the modulus of rupture (M.O.R) were measured on the solid samples. The uniformity of the shape of the casted hollow parts was also investigated. It is found that increasing grog content to 60% helps to decrease the drying shrinkage to less than 2% from 6% but increase porosity and water absorption by a factor of 6, and consequently decreases the bulk density from 2400 to 2000 kg/m3. All the physical properties are improved with increasing the sintering temperature. The fracture strength is highly fluctuated at sintering temperature of 1200DC. At 1300 °C, a sharp deterioration in the MOR occurs for grog content above 40%, while at 1400°C a modulus of rupture (M.O.R) of steady vale of 1.3 GPa is achieved in all samples regardless the proportion of grog content. © EuroJournals Publishing, Inc. 2012.

Bharuth-Ram K.,Durban University of Technology | Doyle T.B.,Materials Research Division | Doyle T.B.,University of KwaZulu - Natal | Zhang K.,University of Gottingen | And 2 more authors.
Physics Procedia | Year: 2015

A 460 nm thick amorphous SiO2 layer, formed on a Si (100) surface by air-annealing the Si substrate at 1100°C for 24 h, was implanted with 57Fe to a fluence of 1 x 1016/cm2 at room temperature and annealed at temperatures up to 1000°C. The implanted and annealed samples were studied by conversion electron Mössbauer spectroscopy (CEMS) and magnetization measurements. The CEMS spectra up to an annealing temperature of 600°C showed the presence of a singlet due to dispersed Fe ions and paramagnetic doublets with hyperfine parameters characteristic of Fe2+ and Fe3+. The spectrum after the 1000°C annealing was dominated (> 80%) by ferromagnetic sextets, the main components of which were sextets with a hyperfine field of 320(20) kOe and 264(20) kOe, showing the formation of Fe0 clusters, in agreement with previous observations. Magnetization measurements (m(H)) on the sample after the 1000°C annealing showed a small hysteresis at 4 K and saturation magnetization with zero hysteresis at room temperature, reached with application of small external field. The CEMS measurement on this sample was repeated after storing the sample under ambient conditions for a period of 6 months. The spectrum showed complete disappearance of the ferromagnetic sextets and the presence only of paramagnetic doublets due to Fe2+. Evidently progressive oxidation of the Fe clusters had occurred. Magnetization results confirm the paramagnetic transformation of the Fe clusters. © 2015 The Authors. Published by Elsevier B.V.

News Article | March 9, 2016

The institutions will serve as "platforms" to develop new bulk and thin film crystalline hard materials through state-of-the-art instrumentation. They will foster an environment that combines multidisciplinary expertise with the best tools available, providing access to the instrumentation, data and new materials created. The Cornell University award is a multi-institution effort in collaboration with Johns Hopkins University, Clark Atlanta University and Princeton University. The National Science Foundation (NSF) will provide up to $25 million over the next five years to support the platforms, with each eligible for a one-time, five-year renewal. The platforms, which add to NSF's portfolio of mid-scale infrastructure and instrumentation, will advance a focused research area of national importance and expand access beyond traditional user facilities. "We see the platforms as pushing the frontiers in materials research," said Fleming Crim, NSF assistant director for mathematical and physical sciences (MPS). "In its first call for proposals, NSF is focusing on crystal growth because the U.S. has fallen behind in this area of science after having been a global leader in material synthesis, which is essential for advancing basic materials research and will add to the important investment the foundation is making in mid-scale instrumentation." The MPS mid-scale research infrastructure program, begun over the last few years to meet critical research needs, has received strong support from the community. "MIPs will serve as focal points that promote cross-fertilization of ideas between internal and external researchers, thanks to their unique convergence of expertise," said Linda Sapochak, acting director for NSF's Materials Research Division. "To accelerate research outcomes, the platforms will focus on a targeted materials grand challenge and/or technological outcome that addresses a national priority. Along with the discovery of new materials, research conducted at a MIP will lead to the understanding of new materials phenomena." The platforms program was inspired by the paradigm the administration set forth in its Materials Genome Initiative. Launched in 2011, the initiative seeks to "discover, manufacture and deploy advanced materials in half the time and at a fraction of the cost." The MIPs program will enable researchers using the platforms to develop new materials, new techniques and the next generation of instrumentation that will lead to understanding and discovering all kinds of new phenomena. Additionally, the processes used by these platforms will move between theory, measurement and actual fabrication with the aim of accelerating discovery of new materials in half the time. The science will accelerate the development of technologies in a wide range of areas, such as microelectronics, fuel and solar cells and new biomaterials, generating economic gains for the nation. The effort is data-intensive and researchers not directly involved with the platform will also have access to, and benefit from, the generated data. The awardees will act as "nexus of activity" for a focused research theme, where platforms are equipped with user facilities. Researchers from across the nation who also engage in this area of research will be able to use these resources to accelerate their own work. Access to the platform is free to academic users and includes not just instrumentation, but also expertise in synthesis, characterization, and theory/modeling/simulation. Additionally, the platforms will enable researchers to work in new ways, fostering new approaches to multidisciplinary education and training. "Without question, one of the most exciting aspects to these awards will be to see just how quickly these platforms can accelerate the pace of materials development," said Sean L. Jones, NSF materials research program director. "The awards are fairly complementary to one another and accelerate research in two distinct material systems likely to have a significant impact on technology as they transform the field at the most fundamental level." Cornell's Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM) will focus primarily on oxide and oxide-based two-dimensional films on new substrates—physical materials meant for next generation electronics. Researchers using the platform will search for "new materials" where the combination of 2-D materials coupled with novel substrates will yield new phenomena, such as smaller, faster, smarter computer chips. More information about this platform is available here. Using Penn State University's platform, researchers will study metal chalcogenide materials, which include sulfides, selenides and tellurides. Metal chalcogenides have become quite popular for a range of technical applications, including digital circuits and flexible electronics. Called the Two-Dimensional Crystal Consortium (2DCC), the new facility at Penn State will foster the growth of a national community of users who develop new materials for next-generation electronics that are faster, use less energy, and can be built on flexible substrates, as well as other applications. More information about this platform is available here. Explore further: Discovery of the specific properties of graphite-based carbon materials

McKenzie J.F.,King's College | McKenzie J.F.,University of KwaZulu - Natal | Doyle T.B.,Materials Research Division
Astronomy and Astrophysics | Year: 2010

This letter reports on the important features of an analysis of the combined theory of gravity - inertial - Rossby waves on a β-plane in the Boussinesq approximation. In particular, it is shown that the coupling between higher frequency gravity - inertial waves and lower frequency Rossby waves, arising from the accumulated influences of the β effect, stratification characterized by the Väisäla - Brunt frequency N, the Coriolis frequency f , and the component of vertical propagation wave number kz, may lead to an unstable coupling between buoyancy - inertial modes with westward propagating Rossby waves. "Supersonic" fast rotators (such as Jupiter) are predicted to be unstable in a fairly narrow band of latitudes around their equators. The Earth is moderately supersonic and exhibits instability within about 34° of its equator. Slow "subsonic" rotators (e.g. Mercury, Venus, and the Sun's corona) are unstable at all latitudes except those very close to the poles where the β effect vanishes. © ESO 2010.

McKenzie J.F.,Durban University of Technology | McKenzie J.F.,University of KwaZulu - Natal | Doyle T.B.,Materials Research Division | Doyle T.B.,University of KwaZulu - Natal | Rajah S.S.,Durban University of Technology
Physics of Plasmas | Year: 2012

The theory of fully nonlinear stationary electrostatic ion cyclotron waves is further developed. The existence of two fundamental constants of motion; namely, momentum flux density parallel to the background magnetic field and energy density, facilitates the reduction of the wave structure equation to a first order differential equation. For subsonic waves propagating sufficiently obliquely to the magnetic field, soliton solutions can be constructed. Importantly, analytic expressions for the amplitude of the soliton show that it increases with decreasing wave Mach number and with increasing obliquity to the magnetic field. In the subsonic, quasi-parallel case, periodic waves exist whose compressive and rarefactive amplitudes are asymmetric about the "initial" point. A critical "driver" field exists that gives rise to a soliton-like structure which corresponds to infinite wavelength. If the wave speed is supersonic, periodic waves may also be constructed. The aforementioned asymmetry in the waveform arises from the flow being driven towards the local sonic point in the compressive phase and away from it in the rarefactive phase. As the initial driver field approaches the critical value, the end point of the compressive phase becomes sonic and the waveform develops a wedge shape. This feature and the amplitudes of the compressive and rarefactive portions of the periodic waves are illustrated through new analytic expressions that follow from the equilibrium points of a wave structure equation which includes a driver field. These expressions are illustrated with figures that illuminate the nature of the solitons. The presently described wedge-shaped waveforms also occur in water waves, for similar "transonic" reasons, when a Coriolis force is included. © 2012 American Institute of Physics.

Kumar S.,Thapar University | Verma N.K.,Thapar University | Singla M.L.,Materials Research Division
Pigment and Resin Technology | Year: 2012

Purpose - The purpose of this paper is to investigate the reflective properties of titania (TiO2) nanoparticle-based coating. Design/methodology/ approach - TiO2 nanoparticles, synthesised by sol-gel method, were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and ultraviolet-visible absorption spectroscopy (UV-vis). The coating material has been prepared by dispersing titania nanoparticles in an acrylic binder with different pigment to binder weight ratio. The reflectors were prepared by applying this coating material to different coating thicknesses to aluminium sheets. Findings - In the study reported here, the coating material could produce reflectors with diffuse reflectance, ~99 per cent, using coating material, having binder by weight ratio between 14 and 20 per cent, and thickness, 0.15?mm. On exposing the developed reflectors to different levels of illumination (upto 20,000 lux), they were still found to have diffuse reflectance of more than 96 per cent almost throughout the visible spectrum. Practical implications - The fabricated reflectors find applications in commercial optical products, such as: reflective panels, luminaries, etc. Originality/value - As of today, the reflective coatings used are of conventional type, which employ bulk TiO2 particles. In this study, we are reporting TiO2 nanoparticle-based highly reflective coating. This is an original work, and, to the best of our knowledge, no one has ever reported on "TiO2 nanoparticle-based reflective coatings". Copyright © 2012 Emerald Group Publishing Limited. All rights reserved.

Zangenberg J.,Materials Research Division | Poulsen S.H.,ISC Innovative Engineering | Bagger A.,Anne Bagger ApS | Bagger A.,Technical University of Denmark | And 2 more authors.
International Journal of Adhesion and Adhesives | Year: 2012

The structural behavior of a new connection design, the embedded adhesive connection, used for laminated glass plates is investigated. The connection consists of an aluminum plate encapsulated in-between two adjacent triple layered laminated glass plates. Fastening between glass and aluminum is ensured using a structural adhesive. At first, the elastic and viscoelastic material properties of the adhesive are identified where the influence of load-rate and failure properties are also examined. Through an inverse analysis using the finite element method, the experimental observations are replicated to identify a material model of the adhesive. The material model consists of an elastic and linear viscoelastic formulation suitable for a numerical implementation of the material. Based on two relevant load cases, out-of-plane bending and in-plane shear, the connection performance is investigated both for short and long-term durations. Using the finite element method, the connection experiments are replicated, which enables a parametric variation of the connection geometry. The numerical tool developed can be used to evaluate the connection behavior for different configurations and further usage in a design situation. The embedded connection shows promising potential as a future fastening system for load-carrying laminated glass plates. © 2012 Elsevier Ltd.

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