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61.
Influence of Substrate on the Transportation Properties of Co/Alq3 Granular Films on a Si Wafer 下载免费PDF全文
A series of Co0.48 (Alq3)0.52 granular films were deposited on silicon substrates using the co-evaporating technique. A crossover of magnetoresistance (MR) from negative to positive was observed in the samples, due to conducting channel switching. The transport properties of samples are greatly influenced by hydrofluoric acid pretreatment, as a result, positive MR decreases drastically and the temperature dependence of resistance changes a lot near room temperature. The result indicates that the native oxide layer plays an important role in the transport mechanism. Moreover, different resistivities of Si substrates influence the current distribution of conducting channels, leading to different transport behaviors accordingly. 相似文献
62.
Dispersion and alignment of carbon nanotubes in polycarbonate 总被引:2,自引:0,他引:2
M. Sennett E. Welsh J.B. Wright W.Z. Li J.G. Wen Z.F. Ren 《Applied Physics A: Materials Science & Processing》2003,76(1):111-113
Dispersion and alignment of carbon nanotubes in thermoplastic polymers such as polycarbonate have been studied. Dispersion
was accomplished by mixing in a conical twin-screw extruder and alignment was carried out using a fiber-spinning apparatus.
The effects of mixing time and fiber draw rates on dispersion and alignment were investigated. Uniform dispersions were produced
with relatively short residence times in the extruder. Excellent alignment of carbon nanotubes in nanocomposite filaments
was obtained when the fiber draw rate was greater than 70 m/min. The ability to closely control the dispersion and alignment
of carbon nanotubes in polymers is expected to lead to the development of nanocomposites with desirable electronic and structural
properties.
Received: 7 January 2002 / Accepted: 11 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-508/233-5521, E-mail: Michael.Sennett@natick.army.mil 相似文献
63.
Hui Tian 《Applied Surface Science》2009,255(7):4289-4292
Preparation of superhydrophobic silica-based thin film by adjusting different concentration of reverse (W/O) emulsion of resorcinol formaldehyde resin (re-RF) which was hybridised with silica sol has been developed. The hybrid films were coated by the mixing solution which included precursor solution (sol-gel process) and re-RF (sol-gel process). Rough surfaces were obtained by removing the organic polymer at high temperature and then the hydrophobic groups bonded onto the films were obtained by the reaction with trimethylchlorosilane (TMCS). Characteristic properties of the as-prepared cross-section and surface of the films were analyzed by scanning electron microscopy (SEM) and atom force microscopy (AFM). The experimental parameters are mainly varied the weight ratio of re-RF to silica sol from 0.2 to 4.0. The result showed that the contact angle of the modified silica film was greater than 160° when the weight ratio of re-RF to silica sol was 2.0. 相似文献
64.
65.
报道了一种可用于2μm商用激光器有效激发的中红外宽带发光玻璃. 采用真空熔融淬冷法制备了Pr3+掺杂硒基玻璃的系列样品, 测试了样品的吸收光谱以及2μm激光泵浦下的3~5μm中红外荧光光谱, 观察到了由激发态吸收造成的近红外荧光. 通过Judd-Ofelt理论计算了不同浓度Pr3+离子掺杂玻璃样品的强度参数Ωt (t=2, 4, 6)、辐射寿命和受激发射截面等光谱参数, 讨论Pr3+离子局域配位环境对发光特性的影响. 结果表明, 4.6μm和4.8μm对应的跃迁能级具有较好的发光特性, 相比其他体系玻璃具有更大的受激发射截面, 是一种理想的中红外激光基质材料. 相似文献
66.
GUO Pengjiang JIAO Baojuan CHEN Sanping HU Rongzu GAO Shengli & SHI Qizhen Department of Chemistry Northwest University Shaanxi Key Laboratory of Physico-lnorganic Chemistry Xi''''an China Department of Mathematics Northwest University Xi''''an China Xi''''an Modern Chemistry Research Institute Xi''''an China 《中国科学B辑(英文版)》2005,48(Z1)
The thermal behavior of the complex Pr[(C5H8NS2)3(C12H8N2)] in a dry nitrogen flow was examined by TG-DTG analysis. The TG-DTG investigations indicated that Pr[(C5H8NS2)3-(C12H8N2)] was decomposed into Pr2S3 and deposited carbon in one step where Pr2S3 predominated in the final products. The results of non-isothermal kinetic calculations showed that the decomposition stage was the random nucleation and subsequent growth mechanism (n = 2/3), the corresponding apparent activation energy ?was 115.89 kJ·mol-1 and the pre-expo-nential constant ln[A/s] was 7.8697. The empirical kinetics model equation was proposed as/(α) =3/2(1-α)[-ln(1-α)]1/3.The X-ray powder diffraction patterns of the thermal decomposition products at 800℃under N2 atmosphere show that the product can be indexed to the cubic Pr2S3 phase. The transmission electron microscopy (TEM) of the final product reveals the particle appearance of a diameter within 40 nm. The experimental results show that the praseodymium sulfide nanocrystal can be prepared from thermal decomposition of Pr[(C5H8NS2)3(C12H8N2)]. 相似文献
67.
以钛酸丁酯为原料,用溶胶-凝胶(Sol-gel)法制备了Pr2O3/TiO2纳米粒子.采用X光衍射仪对粉体的物相进行了表征.样品经500 ℃焙烧2 h后,0.5%(摩尔分数)Pr3 TiO2纳米粉末为单一的锐钛型结构.研究了US(超声波)/UV(紫外光)协同催化氧化水中苯酚的降解效果,考察了超声波声强、溶液pH值、反应温度和催化剂投加量对苯酚降解速率的影响.研究结果表明:US/UV协同催化氧化要比单独超声波或光化学处理效果显著,证实了声光联合技术具有明显的协同效应. 相似文献
68.
69.
A polyvinyl chloride (PVC) membrane based Pr(III) selective electrode was constructed using 1,6,7,12‐tetramine‐2,5,8,11‐tetraoxo‐1(12),6(7)‐di(biphenyl)dodecane (TATODBDD) as a neutral carrier. The sensor exhibits a Nernstian response for Pr(III) ions, a wide concentration range of 3.9×10?7?1.0×10?1 mol/L with a detection limit of 5.0×10?8 mol/L and slope of 19.5 mV/decade. The developed sensor revealed relatively good selectivity and high sensitivity for Pr(III) ions over the other lanthanide ions. The potentiometric response of the sensor is independent in the pH range 2.9–9.5. The advantages of sensor are low resistance, very fast response time (<10 s) with good selectivity. This sensor can be used up to 6 weeks without any divergences in potential response. 相似文献
70.
M3NS3, the First Nitride Sulfides of the Lanthanides (M = La? Nd, Sm) . The oxidation of the “light” lanthanides (M = La? Nd, Sm) with equimolar amounts of sulfur in the presence of NaN3 as nitrogen source results in the formation of the first lanthanide nitride sulfides: M3NS3 (evacuated silica vessels, some NaCl as flux, 850°C, 7 d). NaCl is afterwards removed from the not moisture sensitive crude product (faint- or orange-yellow to amber-co- loured transparent needles, oftenly intergrown to feltlike bunches) upon rinsing with water. The crystal structure was determined from X-ray single crystal data for the example of Sm3NS3 (orthorhombic, Pnma (no. 62), a = 1 201.18(7), b = 394.32(3), c = 1 285.27(6) pm, Z = 4, R = 0.027, Rw = 0.024), and M3NS3 (M = La? Nd) proved to be isostructural from Guinier powder data. There are three crystallographically different M3+ cations in six- (1 X) and sevenfold (2 X) coordination of the N3? and S2? anions. [(N3?)(M3+)4] tetrahedra connected via two corners forming linear chains [N(M1)1/1(M2)1/1(M3)2/2] 6+ build up the main structural feature. Arranged in the manner of a closest packing of rods, they are held together by three crystallographically different S2? which take care for charge neutrality and three-dimensional interconnection. 相似文献