Intrinsic Lithiophilicity of Li–Garnet Electrolytes Enabling High‐Rate Lithium Cycling

Solid‐state lithium batteries are widely considered as next‐generation lithium‐ion battery technology due to the potential advantages in safety and performance. Among the various solid electrolyte materials, Li–garnet electrolytes are promising due to their high ionic conductivity and good chemical and electrochemical stabilities. However, the high electrode/electrolyte interfacial impedance is one of the major challenges. Moreover, short circuiting caused by lithium dendrite formation is reported when using Li–garnet electrolytes. Here, it is demonstrated that Li–garnet electrolytes wet well with lithium metal by removing the intrinsic impurity layer on the surface of the lithium metal. The Li/garnet interfacial impedance is determined to be 6.95 Ω cm2 at room temperature. Lithium symmetric cells based on the Li–garnet electrolytes are cycled at room temperature for 950 h and current density as high as 13.3 mA cm−2 without showing signs of short circuiting. Experimental and computational results reveal that it is the surface oxide layer on the lithium metal together with the garnet surface that majorly determines the Li/garnet interfacial property. These findings suggest that removing the superficial impurity layer on the lithium metal can enhance the wettability, which may impact the manufacturing process of future high energy density garnet‐based solid‐state lithium batteries.By removing the impurity layer on the surface of the lithium metal, Li–garnet electrolytes are demonstrated to well wet the lithium metal, rendering a Li/garnet interfacial impedance of 6.95 Ω cm2, stable galvanostatic cycling for 950 h, and a current density as high as 13.3 mA cm−2 without showing any sign of short circuiting at room temperature.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154451/1/adfm201906189-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154451/2/adfm201906189.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154451/3/adfm201906189_am.pd

Optimizing Integrated All-Stop, Express, and Short-Turn Services on a Metro Line with Capacity Constraint Considering Passenger Spatio-Temporal Path Choice

Optimization of integrated train service is quite challenging under the situation of express trains overtaking local trains, because passenger path choice becomes more complicated and is largely unknown. To fill this gap, this study proposes a passenger spatio-temporal path choice model to replicate passenger behaviors given the real-time operation information in the metro system. Based on which, a non-linear programming model is developed to optimize integrated train services (i.e., all-stop, express, and short-turn) and the associated train timetables to minimize the total cost for a congested metro line, subject to a set of constraints (i.e., capacity, headway, service pattern, conditions of overtaking, etc.). The genetic algorithm with floating-point number coding is used to perform the optimization. It is applied to a real-world metro line in Chengdu, China, to assess its feasibility and effectiveness. The experimental results indicate that the integrated service is substantially improved in relation to total cost. The sensitivity analysis is conducted to explore the impacts of model parameters on various operation strategies. The proposed modeling approach is beneficial for transit agencies to improve their service planning

Cladding of titanium/hydroxyapatite composites onto Ti6Al4V for load-bearing implant applications

To improve the bioactivity of Ti6Al4V alloy for use as a load-bearing hard tissue replacement, titanium/hydroxyapatite (Ti/HA) composites were bonded to a Ti6Al4V substrate by a novel cladding method. With the aid of a silver foil as the interlayer and an external pressure during sintering, the interfaces between the composites and the substrate were free of defects. The bioactivity of the fabricated materials was evaluated in the simulated body fluid (SBF) and the results demonstrated that the materials could induce nucleation and growth of bone-like apatite in the SBF. Factors that contributed to the bioactivity of the materials were discussed. The release of Ag+ ions from the materials was also detected, which is expected to impart antibacterial effect after implantation, and further enhance the functionalities of the materials.Peer reviewed: YesNRC publication: Ye

Cladding of titanium/fluorapatite composites onto Ti6Al4V substrate and the in vitro behaviour in the simulated body fluid

To improve the bioactivity of Ti6Al4V alloy, an innovative cladding method has been developed to bond a Ti/fluorapatite (FA) composite onto the alloy for load-bearing applications. With the aid of a silver interlayer and external pressure during sintering, a defect-free interface between the composite and the substrate was obtained. The fabricated materials were bioactive and could induce the nucleation and formation of bone-like carbonated apatite after immersed in the simulated body fluid (SBF). Functional ions, such as Ag+ and F 12, were released from the materials during immersion, which could impart favourable activities for the implant. This work demonstrated that a simple and novel method could be applied to enhance functionalities of Ti alloys for load-bearing implant applications.Peer reviewed: YesNRC publication: Ye

Fabrication of metal matrix composites by metal injection molding: A review

Metal injection molding (MIM) is a near net-shape manufacturing technology that is capable of mass production of complex parts cost-effectively. The unique features of the process make it an attractive route for the fabrication of metal matrix composite materials. In this paper, the status of the research and development in fabricating metal matrix composites by MIM is reviewed, with a major focus on material systems, fabrication methods, resulting material properties and microstructures. Also, limitations and needs of the technique in composite fabrication are presented in the literature. The full potential of MIM process for fabricating metal matrix composites is yet to be explored.Peer reviewed: YesNRC publication: Ye

Minimizing Metro Transfer Waiting Time with AFCS Data Using Simulated Annealing with Parallel Computing

Coordinating train arrivals at transfer stations by altering their departure times can reduce transfer waiting time (TWT) and improve level of service. This paper develops a method to optimize train departure times from terminals that minimizes total TWT for an urban rail network with many transfer stations. To maintain service capacity and avoid operational complexity, dispatching headway is fixed. An integrated Simulated Annealing with parallel computing approach is applied to perform the optimization. To demonstrate model applicability and performance, the Shenzhen metro network is applied, where passenger flows (i.e., entry, transfer, and exit) at stations are approximated with the automatic fare collection system (AFCS) data. Results show that the total TWT can be significantly reduced

Characterization of sintered titanium/hydroxyapatite biocomposite using FTIR spectroscopy

Fourier transform infrared (FTIR) spectroscopy was employed to characterize the phase changes of hydroxyapatite (Ca10(PO4)6(OH)2, HA) in a titanium/HA biocomposite during sintering. The effects of sintering temperature and the presence of Ti on the decomposition of HA were examined. It was observed that pure HA was stable in argon atmosphere at temperatures up to 1,200\ub0C, although the dehydroxylation of pure HA was promoted by the increase in sintering temperature. In the Ti/HA system, on the other hand, the presence of Ti accelerated dehydroxylation and the decomposition of HA was detected at a temperature as low as 800\ub0C. Tetracalcium phosphate (Ca4P2O9, TTCP) and calcium oxide (CaO) were the dominant products of the decomposition, but no tricalcium phosphate (Ca3(PO4)2, TCP) was detected due to phosphorus diffusion and possible reactions during the thermal process. The main decomposed constituents of HA in Ti/HA system at high temperatures ( 651,200\ub0C) would be CaO and amorphous phases.Peer reviewed: YesNRC publication: Ye

Sintering behavior of HA/Ti composites

The hydroxyapatite/titanium (HA/Ti) composites are considered promising biomaterials for orthopedic applications due to the excellent biocompatibility of HA and good mechanical properties of titanium. Since the HA/titanium composites are normally fabricated through powder metallurgy routes, a clear understanding of the sintering behavior of the composites are essential for the processing and fabrication of the materials. In this study, the sintering behavior of the HA/Ti composites under various conditions was investigated. The effect of the HA concentration, processing parameters such as sintering temperature and time, on the sintering kinetics, porosity, interface reactions, and microstructures will be discussed.Peer reviewed: NoNRC publication: Ye

Sintering of 17-4 PH feedstock for metal injection molding

NRC publication: Ye

Sintering of 17-4PH injection molding feedstock

The sintering behavior of 17-4 PH steel injection molding feedstock was investigated in the temperature range of 650\ub0-1050\ub0C. Effects of sintering conditions, such as sintering temperature and sintering atmosphere, were examined. Experimental results showed that when sintered in a hydrogen/nitrogen atmosphere, the 17-4 PH feedstock oxidized over the temperature range of the investigation. The degree of oxidization increased with the increase of sintering temperature. The main oxidization product was Cr2O3 as revealed by x-ray diffraction and composition analysis. The oxidation can be avoided by sintering in vacuum or argon atmosphere.Peer reviewed: NoNRC publication: Ye