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排序方式: 共有6207条查询结果,搜索用时 31 毫秒
991.
992.
Y.C. ZouM. Nie Y.M. Huang J.Q. WangH.L. Liu 《International Journal of Hydrogen Energy》2011,36(19):12343-12351
In this work, different shapes (powder and spherical) of ruthenium-active carbon catalysts (Ru/C) were prepared by impregnation reduction method for hydrogen generation (HG) from the hydrolysis reaction of the alkaline NaBH4 solution. The effects of temperature, amount of catalysts, and concentration of NaOH and NaBH4 on the hydrolysis of NaBH4 solution were investigated with different shapes of Ru/C catalysts. The results show that the HG kinetics of NaBH4 solution with the powder Ru/C catalysts is completely different from that with the spherical Ru/C catalysts. The main reason is that both mass and heat transfer play important roles during the reaction with Ru/C catalysts. The HG overall kinetic rate equations for NaBH4 hydrolysis using the powder Ru/C catalysts and the spherical catalysts are described as r = A exp (−50740/RT) [catalyst]1.05 [NaOH]−0.13 [NaBH4]−0.25 and r = A exp (−52,120/RT) [catalyst]1.00 [NaOH]−0.21 [NaBH4]0.27 respectively. 相似文献
993.
Evolution of unsteady flow near rotor tip during stall inception 总被引:1,自引:0,他引:1
Previously the features of circumferential propagation of self-induced tip leakage flow unsteadiness for a low speed isolated axial compressor rotor in the authors’ laboratory were discovered and investigated via numerical simulation,which only occurs below a critical stable flow point that is close to but not yet at the stall limit.Further in this paper,the detailed investigation on evolution of tip leakage flow during the throttling process into spike rotating stall was conducted by adopting the valve-throttling model.During this process,the development of the circumferential propagation of tip leakage flow unsteadiness was especially focused on.According to the unsteady characteristics of pressure signals,the evolvement of compressor flow field can be classified into four stages.As compressor throttled,the oscillation frequency of self-induced unsteady tip leakage flow decreased gradually,and thus resulted in the decrease of its circumferential propagation speed.The circumferential propagation of self-induced tip leakage flow unsteadiness is closely related with rotating instability.When the forward spillage of tip leakage flow at the leading edge occurred,the spike type rotating stall was initiated.Its flow struc-tures were given in the paper. 相似文献
994.
Anqiang Pan Daiwon ChoiJi-Guang Zhang Shuquan Liang Guozhong CaoZimin Nie Bruce W. AreyJun Liu 《Journal of power sources》2011,196(7):3646-3649
In this work, we have synthesized monoclinic Li3V2(PO4)3 nanobelts via a single-step, solid-state reaction process in a molten hydrocarbon. The as-prepared Li3V2(PO4)3 nanoparticles have a unique nanobelt shape and are ∼50-nm thick. When cycled in a voltage range between 3.0 V and 4.3 V at a 1C rate, these unique Li3V2(PO4)3 nanobelts demonstrate a specific discharge capacity of 131 mAh g−1 (which is close to the theoretical capacity of 132 mAh g−1) and stable cycling characteristics. 相似文献
995.
Reaction mechanisms for the limited reversibility of Li-O2 chemistry in organic carbonate electrolytes 总被引:1,自引:0,他引:1
Wu Xu Kang XuVilayanur V. Viswanathan Silas A. TowneJohn S. Hardy Jie XiaoZimin Nie Dehong HuDeyu Wang Ji-Guang Zhang 《Journal of power sources》2011,196(22):9631-9639
The Li-O2 chemistry in nonaqueous liquid carbonate electrolytes and the underlying reason for its limited reversibility was systematically investigated. X-ray diffraction data showed that regardless of discharge depth lithium alkylcarbonates (lithium propylenedicarbonate (LPDC), or lithium ethylenedicarbonate (LEDC), with other related derivatives) and lithium carbonate (Li2CO3) are constantly the main discharge products, while lithium peroxide (Li2O2) or lithium oxide (Li2O) is hardly detected. These lithium alkylcarbonates are generated from the reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. More significantly, in situ gas chromatography/mass spectroscopy analysis revealed that Li2CO3 and Li2O cannot be oxidized even when charged to 4.6 V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily oxidized, with CO2 and CO released from LPDC and LEDC and O2 evolved from Li2O2. Therefore, the apparent reversibility of Li-O2 chemistry in an organic carbonate-based electrolyte is actually an unsustainable process that consists of (1) the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharging and (2) the subsequent oxidation of these same alkylcarbonates during charging. Therefore, a stable electrolyte that does not lead to an irreversible by-product formation during discharging and charging is necessary for truly rechargeable Li-O2 batteries. 相似文献
996.
997.
998.
数值模拟的应用已成为铸造工艺的前沿课题,它能大幅度缩短产品试制周期,减少劳动力,提高劳动效率,有着巨大的经济效益和实用价值。对数值模拟技术在铸造过程中的应用状况作了较全面的论述,并提出铸造数值模拟技术的前沿性发展方向。 相似文献
999.
采用化学气相沉积法制备了Ni/Al2O3催化剂, 对其进行了加氢活性评价和表征. 结果表明, 在合适的条件下下, 可以得到具有高分散度和高活性的Ni/Al2O3催化剂. 在Al2O3载体中引入助剂可以减弱活性组分Ni与Al2O3载体之间的相互作用, 有利于NiO还原成Ni活性中心。化学气相沉积法制备的Ni/Al2O3催化剂比传统浸渍法制备Ni/Al2O3催化剂具有更高的加氢活性。透射电镜结果表明,Al2O3载体表面上活性相呈纳米分布,具有较高的分散度,该催化剂中Ni质量分数可降低32.5%,而其加氢催化活性不降低.化学气相沉积法制备的Ni/Al2O3催化剂可用于白油加氢精制. 相似文献
1000.
Dean W. Matson Gordon L. Graff Jonathan L. Male Bradley R. Johnson Zimin Nie Alan G. Joly Larry C. Olsen 《Thin solid films》2010,518(12):3194-5078
Thin film samples of CeCl3, CeBr3, and combinatorial compositions along the CeCl3-CeBr3 join were produced using thermal evaporation, which is being evaluated as a method for rapid screening of scintillator materials. The combinatorial thin films were shown to be compositionally reproducible from run-to-run within reasonable limitations. Analytical results suggest a continuous variation in the combinatorial samples in terms of their compositions, crystal structures, and luminescence characteristics. 相似文献