Science and Technology of Nanomaterials

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Authors: Chuan Bao Cao, Ruitao Lv, He Sun Zhu
Abstract: Nanorods of a compound semiconductor, BiOCl, have been prepared from BiCl3 solutions containing a nonionic surfactant, t-octyl-(OCH2CH2)xOH, x=9, 10 (Triton X-100). Powder X-ray diffraction (XRD) pattern indicated that the product was pure tetragonal phase bismoclite (BiOCl). The product was also characterized by the techniques of scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) and transmission electron microscope (TEM). The as-obtained BiOCl nanorods possess mean diameters less than 40nm and lengths ranging in 160-400nm. Selected area electron diffraction (SAED) pattern showed the single-crystal nature of as-prepared BiOCl nanorods. The growth mechanism of BiOCl nanorods has also been proposed.
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Authors: Bin Chen, Jing Hong Fan, J. Wang, X. Peng, Xiao Lin Wu
Abstract: Molluscan shells is a natural ceramic composite with excellent fracture strength and fracture toughness, which are attributed to their unique microstructures. Sanning electron microscope (SEM) observation on Bivalva shell showed that the shell consists of laminated aragonite and organic layers. These aragonite and organic layers are provided with the scale and characteristics of nanometer. The effect and function of these nanometer structures were analyzed based on Griffith criterion and energy-dissipation idea. The higher fracture strength and fracture roughness of bionanocomposite-molluscan shell were well explained with nanometer viewpoint.
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Authors: K.H. Ang, I. Alexandrou, N.D. Mathur, R. Lacerda, I.Y.Y. Bu, G. Amaratunga, S. Haq
Abstract: An electric arc discharge in de-ionised water between a solid graphite cathode and an anode made by compressing Ni and C containing powders in a mass ratio of Ni:C = 7:3 was used here to prepare carbon encapsulated Ni nanoparticles in the form of powder suspended in water. The morphology of the produced material was analysed using high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The magnetic properties of the samples were determined using a Princeton vibrating sample magnetometer (VSM). Collection of the powder produced from different depths in the water container has proved to be an effective method for obtaining samples with narrow particle size distribution. Further material purification by dry NH4 plasma etching was used to remove the amorphous carbon content of the samples. XRD and HRTEM analysis showed that the material synthesized is fcc Ni particles with mean particle size ranging from 14 to 30 nm encapsulated in 2 to 5 graphitic cages. The data suggests that the process reported has the ability to mass-produce carbon encapsulated ferromagnetic nanoparticles with desired particle size distribution, and hence with controlled size-dependent magnetic properties.
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Authors: Leszek Adam Dobrzański, Ryszard Nowosielski, J.J. Wysłocki, A. Przybył, J. Konieczny
Abstract: Structure, magnetic and mechanical properties of the nanocrystalline composite material of the SILAME® type were tested. The composite material was obtained by solidification of the nanocrystalline powder obtained in the high energy grinding of the initially crystallized Co68Fe4Mo1Si13,5B13,5 amorphous strip with the silicon polymer. The metallic powder was mixed with the silicon polymer in a different weight ratio and next the effect of Co68Fe4Mo1Si13,5B13,5 powder weight ratio on the magnetic and physical properties of the composite was investigated.
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Authors: S. Kawi, Y.P. Tang, K. Hidajat, L.E. Yu
Abstract: Hydrothermal and precipitation methods have been applied to synthesize nanoscale CeO2 catalysts for selective catalytic reduction of NO with hydrocarbon under oxygen-rich condition. The former procedure has the advantage of enhancing the hydrothermal stability of nanomaterial. BET results show that their surface areas are about 30-80 m2/g. Based on TEM results, hydrothermally prepared CeO2 shows very uniform grain shaped particles with size around 10-20 nanometers. Its thermal stability up to 1200°C has been confirmed by in-situ XRD. Furthermore, deNOx reaction with propene as reducing agent in the presence of 5% oxygen has been carried out to compare catalysts prepared by the above two methods. Results show that hydrothermally prepared catalyst is more active than the one prepared by precipitation method. The latter one lost half of its activity in the presence of 5% water vapor, while the former one could stand up to 10% water vapor in the gas mixture without losing much activity.
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Authors: R.P. Marathe, K. Mantri
Abstract: ETS-4 with a Si:Ti ratio of 10:1 has been successfully synthesized in our laboratory and its characterization was done using X-ray diffraction (XRD) and scanning electron microscope (SEM). The thermal behavior was studied by thermogravimetric analysis (TGA). The synthesized crystals were pelletized under high pressure without any binder. Thus the pellets have a bidispersed pore structure – intracrystalline macropores and crystal micropores of the order of 0.4 nanometers. Equilibrium isotherms of oxygen, nitrogen and methane on the ETS-4 sample were measured volumetrically. The capacity compares favorably with that of a commercially available adsorbent of similar pore size. Langmuir isotherm fits well to the experimental equilibrium data.
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Authors: Jian Min Zhu, G.B. Ma, F. Li, S.S. Huang, Q. Li, X.Q. Xin, Nai Ben Ming
Abstract: By means of solid-state reactions method, ZnSnO3 nanoparticles were prepared in the reactions of ZnCl2 and SnCl4·5H2O with KOH in the presence of added KCl crystal, and were assembled into 3-D aggregates with tetragonal-like shape in the size range of 20-200 nm. The products were characterized by powder X-ray diffraction (XRD), and the microstructures of the samples were investigated by transmission electron microscope (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) in detail. Probable mechanisms for the formation of such tetragonal-like shape of ZnSnO3 3-D aggregates are proposed.
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Authors: Wei Wei, Guang Chen
Abstract: The purpose of this study is to obtain an upper bound solution of ECAP at 0 = ψ and φ=90 deg, which aims at analysis of the relations between ECAP upper bound pressure and the die angles of φ and ψ. The results show that the value of pressing load and the equivalent strain, e ε , decreases as the angle ψ increases at φ=90 deg, but the equivalent strain, e ε , decreases rapidly and no less than 0.90. The measured maximum load required for ECAP is in good agreement with the values obtained from the upper bound solution.
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Authors: S. Soltanian, M. Delfany, X.L. Wang, M.J. Qin, H.K. Liu, S.X. Dou
Abstract: MgB2 polycrystalline bulk samples with additions of 0, 5, 10 and 20% wt.% nano-sized BN powders were prepared using the reaction in-situ method. All the samples were sintered at 850°C for 1h in Ar. All the samples were characterized by X-ray diffraction, scanning electron microscopy (SEM) and magnetic measurements. The X-ray diffraction patterns show that the BN does not react with Mg and B during the heat treatment and remains as a separate phase. The synthesized materials thus contain two separate BN and MgB2 phases. In addition, the samples contain a small, almost constant amount of MgO. SEM shows that the samples contain MgB2 grains with average grain sizes of about 250 nm. Magnetic measurement results show that the critical current density and irreversibility fields decrease slightly as the BN level increases. The Tc drops slightly from 38.9 to 38.2 K and has a sharp transition with a transition width of less than 1 K. The field dependence of Jc for all the samples is also presented.
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Authors: S.C. Shen, K. Hidajat, L.E. Yu, S. Kawi
Abstract: This paper reported that nanorods of Zn-Al-O composites could be synthesized through hydrothermal process and followed by solid reaction during calcination. The nanorods composites showed high thermal stability up to 900 °C without observed sintering between individual nanoparticles.
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