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131.
用微型催化反应装置评价,并结合X射线粉末衍射(XRD)、表面积和孔结构测试、程序升温还原(TPR)、氢化学吸附和热重分析等方法研究了负载型PtSn/γ-Al2O3,PtSn/MCM-41和PtSn/Al2O3/MCM-41催化剂的丙烷脱氢反应催化性能.发现PtSn/Al2O3/MCM-41催化剂具有较PtSn/MCM-41催化剂高的丙烷脱氢反应活性和较PtSn/γ-Al2O3催化剂高的反应稳定性.实验结果表明,纯硅MCM-41载体表面的锡物种因与载体相互作用较弱故易被还原,导致铂金属分散度和催化剂的丙烷脱氢活性较低.用Al2O3修饰MCM-41可以增强Sn物种与Al2O3/MCM-41载体之间的相互作用,提高PtSn/Al2O3/MCM-41催化剂铂金属分散度和丙烷脱氢催化活性.并且,积炭后的PtSn/Al2O3/MCM-41催化剂具有较高的铂金属表面裸露度,故具有较高的丙烷脱氢反应稳定性.PtSn/Al2O3/MCM-41催化剂优良的丙烷脱氢催化性能町能不仅与Sn-载体Al2O3/MCM-41较强的相互作用有关,而且与Al2O3/MCM-41载体的介孔结构有关. 相似文献
132.
采用非晶态络合物法制备了La0.9Cu0.1MnO3和LaCoO3钙钛矿催化剂, 并利用固定化溶胶工艺合成了Pt纳米粒子负载的Pt/La0.9Cu0.1MnO3和Pt/LaCoO3复合催化剂. 通过透射电镜(TEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等手段对催化剂的微观结构、形貌及Pt的价态进行了研究; 考察了催化剂的CO催化氧化发光性能. 结果表明, 若La0.9Cu0.1MnO3催化剂表面上负载的Pt纳米颗粒形成团聚, 则在其CO催化氧化发光谱中出现发光峰分裂的现象, 而在Pt纳米颗粒分散较好的Pt/LaCoO3体系中却没有出现这一情况. 因此可以利用CO催化发光谱来初步判断贵金属纳米颗粒在载体表面的分散状态. 相似文献
133.
134.
高灵敏度化学光谱法测定金、铂和钯 总被引:6,自引:1,他引:6
三正辛胺负载泡塑对贵金属有极强的吸附能力。本文通过对三正辛胺负载泡塑对金、铂、钯吸附性能的研究,以及NO3^-和Fe^3 离子干扰的消除,拟定了金、铂、钯的快速、简便、富集系数高的三正辛胺负载泡塑分离法,一次摄谱的测定范围(10g样品)为:Au0.1-5000ng/g;Pt0.2-5000ng/g;Pd0.1-1000ng/g。 相似文献
135.
136.
Recent advances in terahertz imaging 总被引:10,自引:0,他引:10
D.M. Mittleman M. Gupta R. Neelamani R.G. Baraniuk J.V. Rudd M. Koch 《Applied physics. B, Lasers and optics》1999,68(6):1085-1094
We review recent progress in the field of terahertz “T-ray” imaging. This relatively new imaging technique, based on terahertz
time-domain spectroscopy, has the potential to be the first portable far-infrared imaging spectrometer. We give several examples
which illustrate the possible applications of this technology, using both the amplitude and phase information contained in
the THz waveforms. We describe the latest results in tomographic imaging, in which waveforms reflected from an object can
be used to form a three-dimensional representation. Advanced signal processing tools are exploited for the purposes of extracting
tomographic results, including spectroscopic information about each reflecting layer of a sample. We also describe the application
of optical near-field techniques to the THz imaging system. Substantial improvements in the spatial resolution are demonstrated.
Received: 29 January 1999 / Published online: 7 April 1999 相似文献
137.
应用小角X射线散射(SAXS)技术,对乙二醇合成法、浸渍还原法和微波加热法制备的Pt/C催化剂粉体内纳米Pt颗粒的团聚效应进行了研究,得到了不同方法制备的Pt颗粒及其团聚体的特征尺寸、体积分布、表面积变化、团聚程度等信息,并利用透射电镜(TEM)对3种样品进行了测试。实验结果表明:微波加热法制备的催化剂中,Pt颗粒较好地分散于C载体上,且Pt颗粒具有尺度小、分布范围窄、总表面积大和团聚体较少等特征;常规浸渍和乙二醇还原两种方法制备的催化剂中Pt颗粒大小分布相似,但乙二醇还原法制备的催化剂总表面积和团聚体尺度更大,数量也更多。 相似文献
138.
We derive Debye series expansion (DSE) for infinitely long multilayered cylinders normally incident by shaped beam. Typically the interaction between multilayered cylinders and Gaussian beam is derived in detail, and localized approximation is introduced to calculate the beam shaped coefficients. Finally DSE is employed to the study of rainbow scattering by graded-index polymer optical fiber (GI-POF). 相似文献
139.
Nobuaki Kitazawa Dhebbajaji Yaemponga Masami Aono Yoshihisa Watanabe 《Journal of luminescence》2009,129(9):1036-1041
Thin films of microcrystalline (C8H17NH3)2PbBr4 have been prepared by the two-step growth process as follows: (1) precipitation of nanometer-sized PbBr2 particles on substrates by vapor deposition and then (2) growth of (C8H17NH3)2PbBr4 films by exposing PbBr2 particles to C8H17NH3Br vapor. Atomic force microscope observations reveal that the substrate is fully covered with nanometer-sized rodlike precipitates. X-ray diffraction studies suggest that (C8H17NH3)2PbBr4 films are found to be microcrystalline form, single phase and highly oriented with the c-axis perpendicular to the substrate surface. (C8H17NH3)2PbBr4 films show a clear exciton absorption and free-exciton emission even at room temperature. At low temperatures below 40 K, the emission band separates into three bands at 3.07 (A-band), 3.14 (B-band) and 3.20 (C-band) eV, respectively. Both A- and C-bands correspond to the free-exciton emission with large binding energies. On the contrary, time-resolved PL spectra indicate that the B-band is attributed to phosphorescence formed by the intersystem crossing. 相似文献
140.
Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography 总被引:1,自引:0,他引:1
XiaoYang Zhu Gang Cheng ShuJie Wang ShuXi Dai ShaoMing Wan XingTang Zhang ZuLiang Du 《中国科学G辑(英文版)》2008,51(10):1448-1454
Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work,
we used this method to construct nanostructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence
of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was
investigated. The Pt-Cu-Cu
x
O-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties
of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The I–V curves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography
is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices.
Supported by the National Natural Science Foundation of China (Grant No. 90306010), the Program for New Century Excellent
Talents in University of China (Grant No. NCET-04-0653), the National Basic Research Program of China (Grant No. 2007CB616911),
and the Science and Technology Department of Henan Province (Grant No. 072300420100) 相似文献