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21.
利用碳黑(Vulcan XC-72R)中加入硫酸钴和吡啶(Py)作为催化剂前驱体,经溶剂分散热处理构建了一类新型的高效氧还原CoPy/C复合催化剂.并运用循环伏安法(CV)和旋转圆盘电极(RDE)技术研究了不同Co含量的CoPy/C催化剂在碱性介质中对氧还原的电催化活性.结果表明:Co的存在对氧的催化剂活性位的形成有重要影响,800℃下所制备的10%Co30%Py/C(质量分数)复合催化剂表现出最佳的氧还原催化活性.以其制备的气体扩散电极在3.0 mol·L-1KOH电解质溶液(O2气氛)中0.014 V(相对于标准氧电极(RHE))即可产生明显的氧还原电流.同40%Py/C相比,10%Co30%Py/C催化氧还原的起峰电位正移了71 mV,同时表现出明显的极限扩散电流.在-0.16 V时电流密度达到最大值,电流密度为1.0 mA·cm-2,半波电位在-0.07 V.透射电镜分析表明所制备的碳黑载吡啶钴(10%Co30%Py/C)催化剂平均粒径为20 nm. 相似文献
22.
A semi-analytical solution is obtained for a rotating stress-free edge disk of constant thickness and density. In the plastic
range, the Hill’s quadratic orthotropic yield criterion is adopted. In the elastic range, the Hooke’s law holds with thermal
effects included. The analysis of singularities performed may be used for correct implementation of numerical codes and preliminary
engineering design. 相似文献
23.
H. A. Attia 《Journal of Applied Mechanics and Technical Physics》2005,46(1):68-76
An unsteady flow and heat transfer to an infinite porous disk rotating in a Reiner—Rivlin non-Newtonian fluid are considered. The effect of the non-Newtonian fluid characteristics and injection (suction) through the disk surface on velocity and temperature distributions and heat transfer is considered. Numerical solutions are obtained over the entire range of the governing parameters.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 1, pp. 85–95, January–February, 2005. 相似文献
24.
Zonghua Wang Qiang Han Jianfei Xia Linhua Xia Mingyu Ding Jie Tang 《Journal of separation science》2013,36(11):1834-1842
Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene‐based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π–π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC‐MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84–13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene‐based SPE disk in environmental analytical. 相似文献
25.
26.
本文以HNO3、NaOH、Fe(NO3)3和SiO2浆料为原料,采用沉淀法制备了1种SiO2/Fe2O3复合磨粒,通过X射线衍射仪(XRD)、飞行时间二次离子质谱仪(TOF-SIMS)和扫描电子显微镜(SEM)对其结构进行表征,结果表明Fe2O3包覆到SiO2的表面,复合粒子具有很好的分散性.用UNIPOL-1502抛光机研究了所制备复合磨粒在镍磷敷镀的硬盘基片中的抛光性能,抛光后硬盘基片的表面粗糙度Ra由抛光前的8.87nm降至3.73nm;抛光后表面形貌的显微镜观测结果表明新制备的复合磨粒表现出较好的抛光性能. 相似文献
27.
Using an integral transform, the mixed boundary value problem of a conducting, elliptical disk on a dielectric half-space in an electric field is reduced to the solution of an integral equation. An analytical expression of the electric system capacitance is derived, which is a function of the eccentricity of the elliptical disk. The electric charge and electric stress distribute non-uniformly over the surface of the elliptical disk and display local singularities at the edge of the elliptical disk. The square root singularity of the electric field at the edge of the elliptical disk leads to the divergent of the resultant force on the elliptical disk, which is physically unrealistic. There likely exist geometrical constraint and/or field constraint to limit the presence of the square root singularity of the electric field. For any symmetric conductor in an infinite space that consists of air (vacuum) and a semi-infinite dielectric material with symmetric plane being in the interface between the air and the dielectric material, the electric potential in the space is independent of the dielectric constant of the dielectric material. 相似文献
28.
Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror(SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit. 相似文献
29.
Interaction of forced and self-sustained vibrations of one disk rotor is described by nonlinear finite-degree-of-freedom dynamical system. The shaft of the rotor is supported by two journal bearings. The combination of the shooting technique and the continuation algorithm is used to study the rotor periodic vibrations. The Floquet multipliers are calculated to analyze periodic vibrations stability. The results of periodic motions analysis are shown on the frequency response. The quasi-periodic motions are investigated. These nonlinear vibrations coexist with the periodic forced vibrations. 相似文献
30.
Free vibration of polar orthotropic circular plates with elastic growth stresses and drying stresses
This study was performed to analyze effect of transverse growth stresses and drying stresses on natural frequencies of transverse free vibration of thin tree disk with free boundary condition. Using Rayleigh-Ritz method and finite element method, explicit closed form expression was derived for homogeneous orthotropic circular plates with internal stresses, which enables to predict both the effects of growth stresses, drying stresses, and combined growth and drying stresses on the natural frequency changes. This model can be used for predicting growth stresses from known natural frequencies. The same approach can also be undertaken to validate models visco-elastic drying stresses. 相似文献