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排序方式: 共有159条查询结果,搜索用时 31 毫秒
21.
Qinglin Sai Changtai Xia Han Rao Xiaodong Xu Peng Xu 《Journal of luminescence》2011,131(11):2359-2364
The Mn-, Cr-doped and Mn, Cr-co-doped MgAl2O4 powders have been synthesized via a gel-solid reaction method. Energy transfer from Mn2+ to Cr3+ has been observed for the first time in the co-doped MgAl2O4 phosphors. When excited with blue light with a wavelength of 450 nm at room temperature, both green emission from Mn2+ around 520 nm and red emission from Cr3+ around 675and 693 nm were generated. Moreover, the color of the emission can be modified by controlling the doping concentrations of Mn2+ and Cr3+. Therefore, MgAl2O4: Mn2+, Cr3+ could be used as a single-phased phosphor for white LED with a blue LED chip. The energy transfer in terms of Mn2+ to Cr3+ is determined by means of radiation and reabsorption. 相似文献
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NIR FT-Raman研究铝酸钠溶液的碳酸化过程 总被引:2,自引:0,他引:2
本文用NIRFT-Raman光谱仪原位跟踪了铅酸钠溶液的碳酸化过程,观察到此过程的Raman光谱呈现振荡现象和非重线性,认为在碳酸化过程中,可能产生Al2(OH)离子和进一步缩聚形成的离子。 相似文献
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Undoped and aluminum-doped zinc oxide (ZnO) thin films have been grown on polycrystalline α-alumina substrates by ultrasonic spray pyrolysis (USP) technique using zinc acetate dihydrate and aluminum chloride hexahydrate (Al source) dissolved in methanol, ethanol and deionized water. A number of techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and photoluminescence (PL) were used to characterize the obtained ZnO thin films. It was seen that the orientation changed with increase in substrate temperature. During the ZnO deposition Zn source reacted with polycrystalline α-Al2O3 substrate to form an intermediate ZnAl2O4 spinel layer. It has been interestingly found that the intensity of green emission at 2.48 eV remarkably increased when the obtained ZnO:Al films were deposited at 380 °C. The FTIR absorbance intensity of spectroscopic band at 447±6 cm−1 is very sensitive to oxygen sublattice disorder resulting from non-stoichiometry, which is consistent with the result of PL characterization. 相似文献
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A review on developments of liquid membranes (LMs) in the field of gas and vapor separation of the last 16 years is presented. Liquid membrane configurations employing supports, i.e. immobilized, supported and contained liquid membranes are focussed and detailed information on the respective materials, i.e. supports (supplier, type, thickness, pore width, porosity, tortuosity), liquids and carriers, are presented together with their specific separation tasks. Performance of different LMs in terms of permeability and selectivity as well as stability (duration of testing, applied differential pressures) are compared and discussed. Finally, different preparation methods of LMs are illustrated. 相似文献
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Pt-Sn/MgAl2O4催化剂的TPR和H2-TPD研究 总被引:3,自引:0,他引:3
Pt Sn/MgAl 2O 4 catalysts prepared by co impregnation with nominal 0 35% platinum and varying content of tin (0~2 5%) were characterized by temperature programmed reduction (TPR) and temperature programmed desorption of hydrogen (H 2 TPD). TPR results showed that platinum catalyzed the reduction of tin. However, the average oxidation state of tin after reduction depended upon the concentration of tin on the catalysts. H 2 TPD data indicated that tin addition inhibited the inactivated adsorption of hydrogen but promoted the activated adsorption, implying that tin modified both the ensembles of platinum and metal support interface, thus increasing hydrogen mobility and promoting hydrogen spillover. 相似文献
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Tuong Lan Nguyen Masayuki Dokiya Shaorong Wang Hiroaki Tagawa Takuya Hashimoto 《Solid State Ionics》2000,130(3-4):229-241
The electrical property of (La1−xSrx)1−z(Al1−yMgy)O3−δ (LSAM; x≤0.3, y≤0.15 and z≤0.1) was measured using the DC four-probe method as a function of temperature (500–1000°C) and oxygen partial pressure (1–10−22 atm). Among LSAMs, (La0.9Sr0.1)AlO3−δ showed the highest ionic conductivity, σi=1.3×10−2 S cm−1 at 900°C. A simultaneous substitution at A and B sites or A site deficiency is expected to create larger oxygen vacancy and higher ionic conductivity. However, it showed a negative effect. The effect of the vacancy increase did not effect monotonously the ionic conductivity. It was found that the concentration of oxygen vacancy, [VO], influences not only the oxide ion conductivity, σi, but also the mobility, μv, of [VO]. These properties exhibit a maximum at around [VO]=0.05. With the increase in [VO], the activation energy, Ea, of the ionic conduction dropped from 1.8 to ca. 1.0 eV at [VO]=0.05 and became almost constant at [VO]>0.05. The dependency of the pre-exponential term, μ0v, and Ea on [VO] was analyzed and their effect on μv and σi was discussed with respect to crystal structure and defect association. It was estimated that the crystal structure mainly governs these properties. The effect of defect association could not be ignored but is considered to be a complicated correlation. 相似文献
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Mesoporous nanocrystalline NiO-Al2O3 powders with high surface area were synthesized via ultrasound assisted co-precipitation method and the potential of the selected samples as catalyst was investigated in dry reforming reaction for preparation of synthesis gas. The prepared samples were characterized by N2 adsorption (BET), X-ray diffraction (XRD), Temperature programmed reduction and oxidation (TPR, TPO) and scanning electron microscopy (SEM) techniques. The effects of pH, power of ultrasound irradiation, aging time and calcination temperature on the textural properties of the catalysts were studied. The sample prepared under specified conditions (pH10, 70 W, without aging time and calcined at 600 °C) exhibited the highest surface area (249.7 m2 g−1). This catalyst was calcined at different temperature and employed in dry reforming of methane and the catalytic results were compared with those obtained over the catalysts prepared by impregnation and co-precipitation methods. The results showed that the catalyst prepared by ultrasound assisted co-precipitation method exhibited higher activity and stability with lower degree of carbon formation compared to catalysts prepared by co-precipitation and impregnation methods. 相似文献