Papers by Keyword: Nanocrystalline

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Authors: H. Rojas-Chávez, Fidel Reyes-Carmona, Gabriel Plascencia, D. Jaramillo-Vigueras
Abstract: Synthesis of intermetallic PbSe induced by high-energy ball milling has been studied. Systematic analysis of transformation in the resulting phases of milling from 0 to 10 h has been traced by characterizing the microstructures in terms of morphology, crystallite size, and percentages of phases formed as a function of milling time. Results reveal the formation of two phases. Where the system of PbO-Se transforms gradually to PbSe. Complete transformation is achieved after 10 h of milling time. Study of particle structure by the Rietveld Method further corroborates the value of the nano-order crystallite diameters as evaluated from the microscopic studies.
Authors: Irina V. Belova, Graeme E. Murch
Authors: Ennio Bonetti, Luca Pasquini, E. Sampaolesi
Authors: Z.H. Cao, X.K. Meng
Abstract: The strain rate sensitivity of rolled nanocrystalline (NC) Ni was studied by nanoindentation. The grain continuously grows from 20 nm to 92 nm after rolling deformation. The stress driven grain boundary migration accompanied by dislocation emission leads to the grain growth. The strain sensitivity first increase and then decrease with the increased rolling strain, which has a similar variation of dislocation density in rolled NC Ni. The remarkable shift of rate sensitivity is attributed to the dislocation supported grain boundary mediated process.
Authors: J. Lorimier, Frédéric Bernard, Olivier Isnard, J.C. Niepce, J.F. Bérar
Authors: Andrzej Calka, Stephen Wilkins, Hidehisa Hashizume, D.J. Cookson, J.I. Nikolov
Authors: Alain Portavoce, Khalid Hoummada, Lee Chow
Abstract: Ge and B diffusion was studied in nanocrystalline Si, and Pd and Si self-diffusion was studied in nanocrystalline Pd2Si during and after Pd/Si reactive diffusion. These experiments showed that grain boundary (GB) diffusion kinetic is the same in micro-and nanoGBs, whereas triple junction (TJ) diffusion is several orders of magnitude faster than GB diffusion. In addition, GB segregation and GB migration can significantly modify atomic diffusion profiles in nanocrystalline materials, and atomic transport kinetics can be largely increased in nanograins compared to micro-grains, as well as during reactive diffusion, probably due to an increase of point defect concentration. These observations show that atomic transport in nanometric layers during reactive diffusion is complex, since GBs and TJs are moving and the proportion of GBs and TJs is changing during the layer growth.
Authors: Xi Xin Wang, Jian Ling Zhao, Zhao Hui Meng, Jia Wei Yan
Abstract: Titania nanoparticles were successfully synthesized through an easily controlled and simple autothermal gelation process. Effects of H2O2 concentrations, solvent quantity and dissolving temperature were investigated in detail. DSC–TGA and XRD analysis showed that the synthesized TiO2 nanoparticles were in anatase phase at 400°C and in rutile phase at 650°C. TEM image indicated that the titania nanoparticles were uniform and approximately spherical, the average grain size of the product was about 20 nm.
Authors: Z. Balogh, Lajos Daróczi, Z. Erdélyi, S. Szabó, R. Juhász, Dezső L. Beke
Abstract: Barkhausen noise properties of amorphous and nanocrystallized FINEMET type soft magnetic materials are investigated. It is obtained that the amorphous-nanocrystalline tranformation has a well observable effect on both the root main square, RMS, values and the critical exponents of the probability distributions of peak heights and durations.
Authors: Marta Santos, A.F. Azevedo, F.A. Souza, M.R. Baldan, N.G. Ferreira
Abstract: In this work, the achievement and characterization of boron-doped nanocrystalline diamond films is presented. A series of experiments varying boron doping levels from 2,000 to 30,000 ppm and film growth times during 6, 10 and 16 h were performed. These films were analyzed by Scanning Electron Microscoy (SEM), Atomic Force Microscopy (AFM), Raman spectroscopy and Cyclic Voltammetry (CV) measurements. The results showed that the films presented two morphologies: ultra and nanocrystalline diamond. From Raman spectroscopy, the doping level increase for all the films, independent of growth time, increased the boron acceptor number and it was confirmed by Mott-Schottky plot (MSP). Electrochemical response showed the influence of boron content in the work potential window, mainly for films grown during 6 h. However, the reversibility was almost independent on the boron content for samples grown during 16 h.
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