Geometric Effects of La_(1+x)Mg_(2-x)Ni_9 (x=0.0~1.0) Ternary Alloys on Their Hydrogen Storage Capacities

Structural analysis was made using X-ray diffraction (XRD) Rietveld refinement on a series of La1+xMg2-xNi9 (x=0.0-1.0) ternary alloys. Results showed that each of La1+xMg2-xNi9 alloys was a PuNi3-type structure stacked by LaNi5 and (La, Mg) Ni2 blocks. Electrochemical tests revealed that discharge abilities of these La-Mg-Ni ternary alloys mainly depended on their atomic distances between (La, Mg) and Ni, which could be modified by varying the atomic ratios of La/Mg.     

In Situ Scanning-Tunneling-Microscope Observation on Dissolution of a Cu-20Zr Film

A nanocrystalline coating of Cu-20Zr (in wt pct) was obtained on glass by magnetron sputtering. The corrosion behavior of the Cu-20Zr film in 0.001 mol/L HCI solution was investigated using potentiodynamic polarization and in situ electrochemical scanning-tunneling-microscopy (ECSTM). Results demonstrated that the film exhibits active behavior. Microscopic pitting corrosion and tunneling are caused by localized electrodissolution of Zr atoms and the diffusion of Cu atoms at surface defects.     

Research on the Characteristics of Hot Deformation in BT20 Titanium alloy and Its Optimum Spinning Temperature Range

Hot compression tests were conducted on a Gleeble-1500 simulator to investigate the hot deformation behavior of BT20 Ti alloy (Ti-6Al-2Zr-1Mo-1V) in the temperature range from 550 to 1000℃ at constant strain rate in the range of 0.01～1 s-1, and then the optimum spinning temperature range was determined. Moreover, tube spinning experiments were executed to verify the reasonability of the optimum temperature range. The results show that the flow stress declines gradually with increasing deformation temperature and decreasing strain rate. In α β phase region the dynamic recrystallization is the main softening mechanism and in β phase region the hot deformation softening is controlled by dynamic recovery. In α βphase region with reducing strain rate dynamic recrystallization is fully developed. The optimum temperature of hot spinning is 850～900℃ and that of warm spinning is 600～650℃.Meanwhile, at the temperature above 600℃ tubular workpieces of BT20 Ti alloy have been spun without surface cracks and microstructure inhomogeneity, which proves that the optimum spinning temperature range obtained through hot compression experiments is reasonable.     

A modified pulse charging method for lithium-ion batteries by considering stress evolution,charging time and capacity utilization

The stress evolution, total charging time and capacity utilization of pulse charging (PC) method are investigated in this paper. It is found that compared to the conventional constant current (CC) charging method, the PC method can accelerate the charging process but will inevitably cause an increase in stress and a decrease in capacity. The charging speed for PC method can be estimated by the mean current. By introducing stress control, a modified PC method called the PCCC method, which starts with a PC operation followed by a CC operation, is proposed. The PCCC method not only can accelerate charging process but also can avoid the stress raising and capacity loss occurring in the PC method. Furthermore, the optimal pulsed current density and switch time in the PCCC method is also discussed.     

Application of BIB polishing technology in cross-section preparation of porous,layered and powder materials: A review

For the accuracy of experimental results, preparing a high quality polished surface and cross-section of the materials for further analysis using electron backscattered diffraction (EBSD), electron probe microanalysis (EPMA), and scanning probe microscopy (SPM) is extremely important. Broad ion beam (BIB) polishing, a method based on the principle of ion bombardment, has irreplaceable advantages. It makes up for the drawbacks and limitations of traditional polishing methods such as mechanical polishing, electrochemical polishing, and chemical polishing. The ions will not leave the bombardment area during polishing, which makes the BIB method suitable for porous materials. The energy of the ion beam can be adjusted according to the sample to reduce the deformation and strain of the polishing area, especially for fragile, soft, and hard materials. The conditions that need to be controlled during BIB polishing are simple. This paper demonstrated the unique advantages of BIB polishing technology in porous, layered and powder materials characterization through some typical application examples, and guided more researchers to understand and utilize BIB polishing technology in the development of new applications.     

Intelligent construction technology of railway engineering in China

Intelligent construction technology has been widely used in the field of railway engineering. This work first analyzes the connotation, function, and characteristics of intelligent construction of railway engineering (ICRE) and establishes its system structure from three dimensions, namely, life cycle, layers of management, and intelligent function, to deeply understand the development situation of intelligent railway construction in China. Second, seven key technical support systems of ICRE, which include building information modeling (BIM) standard system for China’s railway sector, technology management platform and life cycle management based on BIM+GIS (geography information system), ubiquitous intelligent perception system, intelligent Internet-of-Things (IoT) commu-nication system based on mobile interconnection, construction management platform based on cloud computing and big data, unmanned operation system based on artificial intelligence, intelligent machinery and robot, and intelligent operation and maintenance system based on BIM and PHM (prediction and health management), are established. Third, ICRE is divided into three development stages: primary (perception), intermediate (substitution), and advanced (intelligence). The evaluation index system of each stage is provided from the aspects of technology and function. Finally, this work summarizes and analyzes the application situation of ICRE in the entire railway sector of China, represented by Beijing–Zhangjiakou and Beijing–Xiong’an high-speed railways. Result shows that the technical support systems of the ICRE have emerged in China and are still in the process of deepening basic technology research and preliminary application. In the future, the ICRE of China’s railway sector will develop toward a higher stage.     

Progress in synthesis and application of zwitterionic Gemini surfactants

Zwitterionic Gemini surfactants have the Gemini molecular structure in which there are both multiple lipophilic groups and multiple hydrophilic groups. However, their hydrophilic groups have different charges. Due to the special molecular structure, this kind of surfactants possesses excellent properties, including high surface activities, isoelectric point (IP), low critical micelle concentration (CMC), less toxicity, low irritating, biodegradability, bioactive, interface modification, and so on. In this review, synthetic strategies of three kinds of zwitterionic Gemini surfactants, i.e., anionic– cationic, cationic–nonionic and anionic–nonionic Gemini surfactants, are discussed, and their potential applications in life sciences, chemical industry and enhanced oil recovery (EOR) are illustrated. Their future development is also prospected.     

Investigation on the layout strategy of gg NMOS ESD protection devices for uniform conduction behavior and optimal width scaling

Gate-grounded NMOS(gg NMOS) transistors have widely served as electro-static discharge(ESD)protection devices for integrated circuits. The layout strategy of gg NMOS greatly influences its ESD protection characteristics. Layout strategies forvariation of the number of substrate-pickup stripes are investigated in this paper. Direct current and transmission-line pulsing test results are presented to verify that adjustable holding voltages are accessed by variation of the number of substrate-pickup stripes. The design with two evenly distributed substrate-pickup stripes among different fingers is found to exhibit the highest second break current and optimal width-scaling characteristics.