Papers by Keyword: Nanocrystalline

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Authors: Jiong Li Li, Sha Sha Li, Yan Cai Xiong
Abstract: The operation with a combination of three processing routes: cryomilling, hot isostatic pressing (HIPping) and hot extrusion was adopted in the present study for preparation of the bulk nanocrystalline Al 7050. The microstructure and fractography of the bulk material were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Furthermore, the chemical composition, density and tensile properties of the material were also measured. Microstructural investigation showed that the grain size of the bulk nanocrystalline Al 7050 ranged from 100nm to 200nm. Numerous dispersoids with a diameter/length of ~50nm were observed on grain boundaries and inside the grains. Besides, one phase of these dispersoids existed in the bulk nanocrystalline Al 7050 was identified as Al6(FeMn). These dispersoids dispersed within the bulk nanocrystalline Al 7050, to some extent, increased the mechanical properties and thermal stability of the material. The resulted sample exhibited ultimate strength of 412MPa with an elongation of 5.2% when tested under tensile load, which was a bit lower than that of the traditionally wrought Al 7050-T6. The present results suggested that improper selected starting powder and milling parameters resulted in the flake-like morphology of the cryomilled powder. The flake-like morphology made it difficult for the cryomilled powder to fill the can entirely and achieve a high density material, which led to the weak interface within the bulk material and in turn degraded the mechanical properties of the bulk nanocrystalline Al 7050 prepared in the present work.
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Authors: R. Rahouadj, O. El Kedim, Ph. Lesage, M. Abdellaoui, Eric Gaffet
351
Authors: Ke Tang, Xin Hong, Jin Gang Qi
Abstract: FAU-type(NaY) zeolites nanocrystals have been synthesized through crystallization of gel in mesoporous system of carbon nanotubes(CNTS) with a internal diameter of 20~30 nm. Investigation by using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscope (TEM) shows that the nanocrystals possess the typical nanosized zeolites structural characteristics which is different from those of microsized zeolites.
594
Authors: S. Van Petegem, Jan Kuriplach, Helena Van Swygenhoven, R. Meyer, Charles Dauwe, Danny Segers
204
Authors: Yun Shan Bai, Lu De Lu, Jian Chun Bao
Abstract: Nanocrystalline Fe3+-doped La2Zr2O7 series solid solutions were prepared by a convenient salt-assisted combustion process using glycine as fuel. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The results showed the La ion can be partially replaced by Fe ion. The partial substituted products were still single-phase solid solutions and the crystal form remained unchanged. TEM images reveal that the products are composed of well-dispersed square-shaped nanocrystals. The method provides a convenient and low-cost route for the synthesis of nanostructures of oxide materials. The fluorescence of La1.8Fe0.2Zr2O7 nanocrystals was evaluated by the UV-visible absorption spectra and the fluorescence spectra. The results indicate that (LaxFe1-x)2Zr2O7 nanocrystals prepared by this method are a kind of potential fluorescent-emitted material.
1257
Authors: S. Inthong, Gobwute Rujijanagul, Sukum Eitssayeam, Tawee Tunkasiri, Kamonpan Pengpat
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Authors: Nezar Gassem Elfadill, M. Roslan Hashim, Khaled M. Chahrour, Chun Sheng Wang
Abstract: Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}Nanocrystalline cupric oxide (CuO) film was prepared by sputtering of pure copper metal on n-type single crystalline Si substrate under argon-oxygen ambient. Structural and morphological analyses of the as-deposited CuO films were performed by X-ray diffraction (XRD) diffractometer and Field Emission Scanning Electron Microscopy (FESEM). The results show Single crystalline granular nanocrystalline (002) CuO films, with 18 nm crystallite size. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed for p-CuO/n-Si hetrojunction. Diode parameters such as saturation current (Is=9.5E-6 A) and ideality factor (n=1.86) were extracted from the dark I-V characteristics. Potential barrier height of the junction (ϕi=1.1V) was revealed from (1/C2- V) plot. Normal 0 false false false EN-US X-NONE AR-SA /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";}
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Authors: Lan Anh Luu Thi, Duc Hieu Nguyen, Mateus Manuel Neto, Ngoc Trung Nguyen, Thach Son Vo
Abstract: Nanocrystalline titania (TiO2) thin films prepared by spray pyrolysis deposition on to the heated glass in a temperature range of TS = 350 ÷ 450oC. Analysis of optical transmission spectral of films reveals an optical band gap of about 3.2÷3.4 eV and the transmittance above 80% for TiO2 films with thickness of 0.8÷1.6 µm. X-ray diffraction (XRD) analysis demonstrates that the films are found of anatase phase in crystal structure. The AFM photographs show the nano-size of the constituents. The crystallize size and crystalline of the samples is discussed with respect to the film thickness and deposition temperature.
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Authors: Wolfgang Lechner, Werner Puff, Gerhard Wilde, R. Würschum
Abstract: A positron annihilation study of free volumes was performed on Cu-Zr and Al-Sm alloys in the course of repeated cold rolling (RCR) in order to contribute to the microscopic understanding of the complex processes of solid-state amorphization and nanocrystallization. In addition to positron lifetime spectroscopy, which yields information on the size of free volumes, twodimensional Doppler broadening technique was applied in order to study the local chemical environment of free volumes on an atomistic scale. Both in Cu60Zr40 and Al92Sm8 a characteristic variation of the chemical environment of free volumes with the number of folding and rolling (F&R) cycles could be observed. In the first (Al-Sm) and intermediate state (Cu-Zr) of F&R, free volumes with an enhanced amount of Sm or Zr content in the local environment occur, indicating interfacial segregation or the formation of solute-vacancy complexes. Upon further F&R cycling, a complete (Cu-Zr) or partially amorphous structure (Al-Sm) is obtained with the free volumes exhibiting a chemical environment characteristic of the average chemical composition. In contrast to melt-spun or ball-milled amorphous alloys, free volumes of the size of a few missing atoms are found in amorphous alloys prepared by RCR presumably due to strong athermal conditions of F&R cycling.
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