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51.
Y.X. Han 《Applied Surface Science》2008,254(7):2054-2058
Diamond nucleation on copper (Cu) substrates was investigated by graphite seeding and CO2 laser irradiation at initial stages of the combustion-flame deposition. A graphite aerosol spray was used to generate a thin layer of graphite powders (less than 1 μm) on Cu substrates. The graphite-seeded Cu substrates were then heated by a continuous CO2 laser to about 750 °C within 1 min. It was found that diamond nucleation density after this treatment was more than three times as much as that on the virgin Cu substrates. As a consequence, diamond films up to 4 μm were obtained in 5 min. The enhancement of diamond nucleation on the graphite-seeded Cu substrates was attributed to the formation of defects and edges during the etching of the seeding graphite layers by the OH radicals in the flame. The defects and edges served as nucleation sites for diamond formation. The function of the CO2 laser was to rapidly heat the deposition areas to create a favorable temperature for diamond nucleation and growth. 相似文献
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C.J. Mena-Duran T. Lopez D.H. Aguilar J.A. Odriozola 《Applied Surface Science》2007,253(13):5762-5766
Groundwater pollution by nitrates is a widespread problem in many locations in the world. The underground aquatic mantle of the Peninsula of Yucatan is highly vulnerable due to its karstic nature. Adsorption methods are a good choice for nitrate elimination. In this work, a natural calcium bentonite was modified by acid thermoactivation with HCl and H2SO4, and tested as a media for nitrate removal in an aqueous solution. The nitrate concentration in the solution was measured by FT-IR, using the Lambert-Beer law. Clay characterization was carried out by X-ray diffraction and FT-IR spectroscopy; surface area was measured by the BET method. 相似文献
53.
S.M. Al-Marzoug 《Optics Communications》2006,268(1):84-89
The design of hard X-ray optics for astrophysical technology is one of the key technologies for investigating active galaxies and clusters of galaxies. In the present paper, we have optimized multilayer mirrors of platinum-carbon layer pairs for the hard X-ray region at different grazing angles. The Luus-Jaakola optimization procedure has been implemented for the global optimization of multialyer mirrors. With this algorithm it is not necessary to specify initially the number of layers present in a design. 相似文献
54.
Zhongxin Liu Hongwei Song Ruifei Qin Guohui Pan Xue Bai 《Solid State Communications》2006,137(4):199-202
Ag enwrapped Y2O3:Eu3+ nanoparticles were prepared by a wet chemistry method, which was dispersed in liquid (glycol) or dried to powders. Their luminescence properties were studied in comparison to those in the un-enwrapped ones. The results demonstrated that in glycol the 5D0-7F2 transitions for Ag enwrapped Y2O3:Eu3+ nanoparticles became stronger than that for un-enwrapped ones, while the excitation charge transfer band shifted blue. On the contrary, the 5D0-7F2 transitions in Ag enwrapped Y2O3:Eu3+ powders became weaker than those in the un-enwrapped ones. It was suggested that in liquid the Ag shells thinly deposited in the surface of Y2O3:Eu3+ and insulated the Y2O3:Eu3+ from the liquid, which contained large organic vibration modes. As a result, the surface nonradiative energy transfer from Eu3+ to the organic modes decreased, and emission intensity of 5D0-7F2 increased. In the Y2O3:Eu3+ powders, the Ag shells absorbed the excitation light, leading to the decrease in excitation density and the intensity of 5D0-7F2. 相似文献
55.
Preparation of Eu2+ ions activated strontium hexa-aluminate phosphor using the combustion method is described. An efficient phosphor can be prepared by this method at reaction temperatures as low as 500 °C in a few minutes. Powder X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscope analysis were used to characterize the as prepared product and the optical properties were studied by photoluminescence (PL) spectra. Thermally stimulated luminescence studies also have been carried out on SrAl12O19:Eu2+ phosphor. The TSL glow curve is broad and indicates two dominant peaks at 206 and 345 °C. Defect centres formed in irradiated phosphor have been studied using the technique of electron spin resonance. One of the centres is characterized by an isotropic g-value of 2.0055 and is assigned to a F+ centre. The two annealing stages of F+ centre in the region 125-230 and 340-390 °C appear to correlate with the release of carriers resulting in TSL peaks at 206 and 345 °C, respectively. 相似文献
56.
An organo-metallic complex, [(CH3)4N][Ni(dmit)2] (dmit2− = (1,3-dithiole-2-thione-4,5-dithiolate), abbreviated as MeNi, is synthesized. The nonlinear optical absorption properties of MeNi dissolved in acetone have been studied using the open-aperture Z-scan technique with 40 ps pulse width at 1064 nm and 1 ns, 15 ns pulse width at 1053 nm, respectively. Strong saturable absorption has been found when the sample solution is irradiated by 40 ps and 1 ns laser pulses. While irradiated with 15 ns laser pulse, a stronger reverse saturable absorption has been found. The nonlinear optical absorption coefficients are −1.03 × 10−11 m/W, −1.85 × 10−11 m/W and 3.84 × 10−10 m/W, respectively. The mechanism responsible for the difference between the results is analyzed. All the results suggest that this material may be a promising candidate for the application to laser pulse compression in the near-infrared waveband. 相似文献
57.
Cubic boron nitride is synthesized by the reaction of Li3N and B203 under high pressure and high temperature (4.0-5.0 GPa, 1350-1500℃). The minimum pressure of cBN formation is 4.0 GPa. The present condition of cBN formation is clearly lower than the eutectic temperature of Li3BN2 and BN in the Li3N-hBN system (5.5 GPa, 1610℃). The content of cBN in the sample increases, while the content of hBN decreases with the temperature and pressure. The maximum conversion rate (5.0 GPa, 1500℃) is about 34%, which is higher than that in the hBN-Li3N system. The cBN crystals are octahedral or tetrahedral in shape and approximately 20 μm in diameter. 相似文献
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A new route to obtain metal oxide nanotubes is presented: an inorganic coordination complex precursor containing the metal ions and impregnated into alumina membrane templates yield hollow tubular nanostructures of LaNiO3 by calcination at 600 °C as characterized by powder X-ray diffraction (XRD). Scanning electron microscopy (SEM) shows that the resulting nanotubes have 200 nm in diameter in good agreement with the template pore. Transmission electron microscopy (TEM) and dark field transmission electron microscopy (DF-TEM) show that the nanotubes with 10-20 nm walls and internal separations are composed of 3-5 nm crystals. 相似文献
60.
Chen Y.W. Gan D.J. Kreiling S. Song C.S. Lu S.Q. Wang Z.J. 《Applied Physics A: Materials Science & Processing》2003,76(1):129-132
Applied Physics A - The research work in this letter is on the microtribological properties of poly(ether ketone ketone) (PEKK) and sulfonated PEKK (S-PEKK) thin films. Polystyrene (PS) was used as... 相似文献