4,986 research outputs found
Clues, flow channels, and cognitive states: an exploratory study of customer experiences with e-brokerage services
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A design for Six Sigma case study: creating an IT change management system for a mid-size accounting firm
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Prussian blue-derived Fe2O3/sulfur composite cathode for lithium-sulfur batteries
No full textPorous Fe2O3 was prepared by simple annealing of preformed Prussian blue that was synthesized from a wet chemistry method. The obtained porous Fe2O3 nanoparticles were then mixed with sulfur and used as cathode for lithium-sulfur batteries. The porous Fe2O3 acts as an internal polysulfide reservoir, and thus reduces the shuttle effect. Composite cathode containing 5% porous Fe2O3 shows improved cycling performance as compared to that without porous Fe2O3. A stable reversible discharge capacity of 574.3 mAh/g was obtained after 50 cycles at 0.5 C. (C) 2014 Elsevier B.V. All rights reserved
Introduction to the special section on cocreating the customer service experience with high tech and high touch
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Scalable fabrication of micro-sized bulk porous Si from Fe-Si alloy as a high performance anode for lithium-ion batteries
No full textSilicon has been perceived as one of the most promising anodes in the next generation lithium-ion batteries (LIBs) due to its superior theoretical capacity. However, bulk silicon experiences an enormous volume expansion during the lithiation/delithiation process, resulting in rapid capacity fading. And, its high-cost and low coulombic efficiency also present significant challenges for applications. Here, we presented a facile and large-scale approach for preparing micro-sized porous silicon by acid etching the abundant and inexpensive metallurgical Fe-Si alloy as a high-performance anode in LIBs. Profiting from the unique micro-sized structure, it exhibited a fantastic first-cycle coulombic efficiency of 88.1% and an excellent reversible capacity of 1250 mA h g(-1) at 500 mA g(-1) after 100 cycles. Furthermore, the micro-sized porous silicon without carbon coating could deliver a reversible capacity of 558 mA h g(-1) at a high current density of 5 A g(-1) due to the unique porous structure. This work provides a promising route for a large-scale production of high-performance micro-sized Si as anode materials in LIBs
A lithiation/delithiation mechanism of monodispersed MSn5 (M = Fe, Co and FeCo) nanospheres
No full textA designed Sn based alloy host as a higher capacity and longer cycle life next generation lithium-ion battery, consisting of monodisperse nanospheres of intermetallic MSn5 (M = Fe, Co and FeCo) phases was synthesized by a nanocrystal conversion chemistry method using preformed Sn nanospheres as templates. The same crystal structure, identical particle surface morphology and the similar particle size distribution (30-50 nm) of these intermetallic MSn5 (M = Fe, Co and FeCo) phases are ideal for comparison of the electrochemical performance, reaction mechanism, thermodynamics and kinetics during lithiation/delithiation. Importantly, MSn5 (M = Fe, Co and FeCo) phases with defect structures Fe0.74Sn5, Co0.83Sn5 and Fe0.35Co0.35Sn5, exhibit the highest theoretical capacity of >917 mA h g(-1) among the reported M-Sn (M is electro-chemically inactive) based intermetallic anodes. The ex situ XRD and XAFS illustrate the complete reversibility of MSn5 (M = Fe, Co and FeCo) phases during lithium insertion/extraction for the first cycle. The Fe0.35Co0.35Sn5 anode can take advantage of both high capacity of Fe0.74Sn5 and long cycle life of Co0.83Sn5, providing 736 mA h g(-1) and maintaining 92.7% of initial capacity after 100 cycles with an average capacity loss of only 0.07% per cycle. The excellent electrochemical performance of the Fe0.5Co0.5Sn5 system is attributed to higher reversibility, lower reaction resistance. This work provides a novel insight toward designing and exploring an optimal Sn based alloy anode for next generation Li-ion batteries
Hollow silica-copper-carbon anodes using copper metal-organic frameworks as skeletons
No full textHollow silica-copper-carbon (H-SCC) nanocomposites are first synthesized using copper metal-organic frameworks as skeletons to form Cu-MOF@SiO2 and then subjected to heat treatment. In the composites, the hollow structure and the void space from the collapse of the MOF skeleton can accommodate the huge volume change, buffer the mechanical stress caused by lithium ion insertion/extraction and maintain the structural integrity of the electrode and a long cycling stability. The ultrafine copper with a uniform size of around 5 nm and carbon with homogeneous distribution from the decomposition of the MOF skeleton can not only enhance the electrical conductivity of the composite and preserve the structural and interfacial stabilization, but also suppress the aggregation of silica nanoparticles and cushion the volume change. In consequence, the resulting material as an anode for lithium-ion batteries (LIBs) delivers a reversible capacity of 495 mA h g(-1) after 400 cycles at a current density of 500 mA g(-1). The synthetic method presented in this paper provides a facile and low-cost strategy for the large-scale production of hollow silica/copper/carbon nanocomposites as an anode in LIBs
Understanding Spirituality among Chinese College Students: Xin-Yang (信仰) and its Assessment
No full textIn spite of the effort researchers have made, there still seems to be a lack of cultural appropriateness when it comes to the concept of spirituality. Therefore, the current author considers the cultural appropriateness in the process of developing a scale that measures Chinese college students’ level of spirituality. Three focus groups and face-to-face interviews were conducted to help understand the concept of spirituality among Chinese college students. Xin-Yang 信仰 is the Chinese word the current author decided to use and study among Chinese college students. After the pool of items is developed, a fourth focus group was held among the current researcher and a panel of experts in the field of psychology that enabled the researcher to establish face validity for the current scale. A pilot study was conducted to modify the pool of items. A sample of 2,307 college student participants were recruited online from five different provinces, autonomous regions, and direct-controlled municipality in China. Confirmatory factor analysis, item factor analysis, and structural equation modeling were performed with the data. The final Xin-Yang scale has three factors: characteristics, mental guidance, and relationship to others. Xin-Yang scale is a sound and helpful measurement. Xin-Yang seems to be an important construct to these Chinese college students in relationship to their psychological well-being. Specifically, Xin-Yang is significantly and positively related to hope, self-esteem, and self- efficacy. Xin-Yang is significantly and negatively related to psychological symptoms. In addition, Xin-Yang is significantly and positively related to spirituality. Relationships among these constructs were discussed. Limitations and implications were also discussed
Comment on P. Xin et al./ Advances in Water Resources 91 (2016) 1-10
No full textXin et al. (2016) present an approximate analytical solution to a variable saturated formulation of a drainage problem. They compared their solution to a saturated flow-based model and found a large discrepancy. However, the discrepancy is due to the value of the storage coefficient used and not to the model formulation
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