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101.
We prepared a one-stage microfluidic-based method for continuous synthesis of cobalt (Co) nanoparticles over reduced graphene oxide (rGO) to produce Co/rGO composites. These were generated by the coreduction of Co2+ ions and GO with NaBH4 which was confined within discrete aqueous plugs segmented by octane as continuous phase. Owing to the excellent transfer properties from recirculation in these plugs, ultrasmall Co nanoparticles were distributed homogeneously on the GO sheets without using any surfactants. As compared to batch methods, the average size of Co nanoparticles and the relative standard deviation decreased from 4.0 ± 1.42 nm and 35.9% to 2.0 ± 0.45 nm and 22.6%, respectively. The as-prepared Co/rGO composites exhibited superior activity towards the catalytic reduction of p-nitrophenol to p-aminophenol with NaBH4 compared with Co nanoparticles and rGO; this enhanced activity could be attributed to the synergistic effect between Co nanoparticles and rGO. 相似文献
102.
103.
阐述了熔模铸造铸件出现砂眼缺陷的特征与出现的部位,分析了砂眼缺陷产生的内、外部原因并提出了相应的对策。结果表明,砂眼是由于型壳内、外部的型砂和/或耐火材料进入型腔形成的,尽量减少影响型壳质量的人为因素,提高型壳质量是防止铸件砂眼最有效的措施。 相似文献
104.
105.
Manas M. Mandalahalli Evert C. Wagner Luis M. Portela Robert F. Mudde 《American Institute of Chemical Engineers》2020,66(1):e16696
In this work, the effect of an electrolyte (up to 2 M of NaCl dissolved in water) on a homogeneous dense bubbly flow, in an airlift bubble column, is studied using nonintrusive techniques. X-ray and high-speed imaging are used to investigate the bubble size distribution, the local and the global gas-fraction profiles. The major effect of the electrolyte is the bubble size distribution at the fine-pore sparger, which is a consequence of the bubble coalescence inhibition promoted by the electrolyte. The bubble plume widening, the increase in overall gas fraction, and the onset of bubble recirculation in the column can all be explained by the bubble size reduction at the fine-pore spargers. As a result of the bubble size reduction, the overall role of the electrolyte is in a reduction of the driving force for the liquid recirculation. Furthermore, an accumulation of the small bubbles causes a layer of foam at the free surface, which is dynamic in nature and induces additional bubble recirculation. 相似文献
106.
Zhenyu Wu Jinjin Cai Zhonghui Liu Lihang Wu Xiaojiang Liang Qinglong Xie Meizhen Lu Fengwen Yu Yong Nie Jianbing Ji 《American Institute of Chemical Engineers》2020,66(5):e16914
The hydrodynamic cavitation multiphase reactor (HCMR) is emerging as a promising alternative for the intensification of liquid–liquid heterogeneous reactions, but research on HCMR modeling is lacking. In this article, an HCMR model was developed using Prileschajew epoxidation as the model system. First, based on experimental measurements of oil/water two-phase flow downstream of hydrodynamic cavitation devices, semiempirical correlations were proposed to describe the droplet size and droplet size distribution (DSD) as functions of flow conditions and geometry parameters. Then, with boundary conditions calculated by the DSD correlation, a droplet dynamics simulation in a reaction tank was performed by computational fluid dynamics coupled with population balance model to obtain the two-phase interfacial area. Finally, the acquired reactor model was substituted into an overall kinetic model, to simulate the epoxidation reaction in HCMR. Model predictions were verified by experimental results measured on an industrial scale HCMR. 相似文献
107.
David Castells-Quintana Vicente Royuela Paolo Veneri 《Papers in Regional Science》2020,99(4):1045-1064
As cities grow, both the productivity of their inhabitants and the income distribution among them is expected to change. While the empirical literature has widely shown how productivity (and income) changes with city size, the empirical evidence on the effects on income inequality remains very limited. The few papers that study the relationship between city size and city-level inequality focus on a single country and do not provide international comparative evidence. In this paper, we study the relationship between city size and income inequality at city level for a sample of 153 functional urban areas (FUAs) across 11 OECD countries. 相似文献
108.
以钢渣颗粒为骨料,分别包裹无机胶凝剂、有机胶凝剂和无机-有机复合胶凝剂制备人造彩砂,研究了胶凝剂掺量对彩砂耐磨性的影响,并利用XRD、SEM及TG等方法测试彩砂的结构组成特性。结果表明,随胶凝剂掺量的增加,彩砂磨损率先快速降低后趋于平缓;单独用无机胶凝剂和有机胶凝剂所得彩砂的磨损率均较高,分别为2.39%~0.58%和1.70%~0.80%;采用在无机胶凝剂中掺加小于10%有机胶凝剂配制的复合胶凝剂,彩砂的磨损率显著降低,最低可降至0.05%。复合胶凝剂中无机组分与有机组分发生协同反应是彩砂磨损率显著降低的原因。 相似文献
109.
110.
通过球磨工艺和添加分散剂相结合的方法对陶瓷结合剂团聚体进行解团聚,研究球磨参数和分散剂添加量对解团聚效果及结合剂机械性能的影响,并用激光粒度分析仪、SEM、万能材料试验机测试结合剂粉体解团聚前后的粒度、显微形貌、抗折强度。结果表明:采用小粒径(5 mm)的磨球,添加质量分数为2.5%的分散剂球磨2 h后,结合剂粉体分散性良好,基本没有团聚现象,其D50可降至0.186 μm,且球磨后的粉体在700 ℃烧结后,其抗折强度达到26.2 MPa,比原始团聚体烧结后样品的强度提升了近45%。 相似文献