Engineering topics

Chen, Xuefeng

Publications and source records attributed to Chen, Xuefeng.

7 records

DOE OSTI2018

High energy storage properties of (Ni1/3Nb2/3)4+ complex-ion modified (Ba0.85Ca0.15)(Zr0.10Ti0.90)O3 ceramics

Highlights: • BCZT-xNN ceramics showed single phase perovskite structure without an obvious second phase after adding NN, and exhibited both good temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz) stability. • The highest energy storage density can reach 0.66 J/cm{sup 3} and the energy efficiency is 88.1% was achieved in x = 0.3. • The environmental friendly (lead-free) BCZT-xNN ceramics are good candidate for application in energy storage devices. • This paper also developes a new method to obtain high energy storage density and efficiency of ceramic capacitor, which aims to adjust the T{sub c} of ceramics far below room temperature. - Abstract: In this study, paraelectric ceramics, (Ba{sub 0.85}Ca{sub 0.15})(Zr{sub 0.10}Ti{sub 0.90}){sub 1-x}(Ni{sub 1/3}Nb{sub 2/3}){sub x}O{sub 3,} abbreviated as BCZT-xNN (with x = 0.1, 0.2, 0.3, 0.4) were prepared via a solid-state reaction method. By introducing a B-site complex-ion, (Ni{sub 1/3}Nb{sub 2/3}){sup 4+}, the Curie temperature of the ceramic could be reduced to below room temperature. The effects of this B-site (Ni{sub 1/3}Nb{sub 2/3}){sup 4+} complex-ion substitution on the phase structure, surface microstructure as well as the dielectric, ferroelectric, and energy storage properties of the ceramic were systematically investigated. After adding NN, BCZT-xNN shows a single phase perovskite structure without evidence of a second phase . In addition, we observed high stability with respect to both temperature (−55 to 160 °C) and frequency (10{sup 2}–10{sup 7} Hz). Doping with NN produces slim polarization-electric field hysteresis loops and enhanced energy storage properties, while the efficiency decreases. When x = 0.3, the highest energy storage density reached 0.66 J/cm{sup 3} for a high electric field (20 kV/mm), and the respective energy efficiency was 88.1%. These properties indicate that the environmental friendly BCZT-xNN ceramics are promising candidates for commercial energy storage devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2016

High charge-discharge performance of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} antiferroelectric ceramics

The energy storage performance and charge-discharge properties of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} (PLZST) antiferroelectric ceramics were investigated through directly measuring the hysteresis loops and pulse discharge current-time curves. The energy density only varies 0.2% per degree from 25 °C to 85 °C, and the energy efficiency maintains at about 90%. Furthermore, an approximate calculating model of maximum power density p{sub max} was established for the discharge process. Under a relatively high working electric field (8.2 kV/mm), this ceramics possess a greatly enhanced power density of 18 MW/cm{sup 3}. Moreover, the pulse power properties did not show degradation until 1500 times of charge-discharge cycling. The large released energy density, high energy efficiency, good temperature stability, greatly enhanced power density, and excellent fatigue endurance combined together make this PLZST ceramics an ideal candidate for pulse power applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2016

Fully Mechanically Controlled Automated Electron Microscopic Tomography

Knowledge of three-dimensional (3D) structures of each individual particles of asymmetric and flexible proteins is essential in understanding those proteins' functions; but their structures are difficult to determine. Electron tomography (ET) provides a tool for imaging a single and unique biological object from a series of tilted angles, but it is challenging to image a single protein for three-dimensional (3D) reconstruction due to the imperfect mechanical control capability of the specimen goniometer under both a medium to high magnification (approximately 50,000-160,000×) and an optimized beam coherence condition. Here, we report a fully mechanical control method for automating ET data acquisition without using beam tilt/shift processes. This method could reduce the accumulation of beam tilt/shift that used to compensate the error from the mechanical control, but downgraded the beam coherence. Our method was developed by minimizing the error of the target object center during the tilting process through a closed-loop proportional-integral (PI) control algorithm. The validations by both negative staining (NS) and cryo-electron microscopy (cryo-EM) suggest that this method has a comparable capability to other ET methods in tracking target proteins while maintaining optimized beam coherence conditions for imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

A Closed-Loop Proportional-Integral (PI) Control Software for Fully Mechanically Controlled Automated Electron Microscopic Tomography

A closed-loop proportional-integral (PI) control software is provided for fully mechanically controlled automated electron microscopic tomography. The software is developed based on Gatan DigitalMicrograph, and is compatible with Zeiss LIBRA 120 transmission electron microscope. However, it can be expanded to other TEM instrument with modification. The software consists of a graphical user interface, a digital PI controller, an image analyzing unit, and other drive units (i.e.: image acquire unit and goniometer drive unit). During a tomography data collection process, the image analyzing unit analyzes both the accumulated shift and defocus value of the latest acquired image, and provides the results to the digital PI controller. The digital PI control compares the results with the preset values and determines the optimum adjustments of the goniometer. The goniometer drive unit adjusts the spatial position of the specimen according to the instructions given by the digital PI controller for the next tilt angle and image acquisition. The goniometer drive unit achieves high precision positioning by using a backlash elimination method. The major benefits of the software are: 1) the goniometer drive unit keeps pre-aligned/optimized beam conditions unchanged and achieves position tracking solely through mechanical control; 2) the image analyzing unit relies on only historical data and therefore does not require additional images/exposures; 3) the PI controller enables the system to dynamically track the imaging target with extremely low system error.

Ren, Gang↗

DOE OSTI2016

Temperature-dependent dielectric and energy-storage properties of Pb(Zr,Sn,Ti)O{sub 3} antiferroelectric bulk ceramics

The dielectric and energy-storage properties of Pb{sub 0.99}Nb{sub 0.02}[(Zr{sub 0.60}Sn{sub 0.40}){sub 0.95}Ti{sub 0.05}]{sub 0.98}O{sub 3} (PNZST) bulk ceramics near the antiferroelectric (AFE)-ferroelectric (FE) phase boundary are investigated as a function of temperature. Three characteristic temperatures T{sub 0}, T{sub C}, T{sub 2} are obtained from the dielectric temperature spectrum. At different temperature regions (below T{sub 0}, between T{sub 0} and T{sub C}, and above T{sub C}), three types of hysteresis loops are observed as square double loop, slim loop and linear loop, respectively. The switching fields and recoverable energy density all first increase and then decrease with increasing temperature, and reach their peak values at ∼T{sub 0}. These results provide a convenient method to optimize the working temperature of antiferroelectric electronic devices through testing the temperature dependent dielectric properties of antiferroelectric ceramics.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

Temperature-dependent stability of energy storage properties of Pb{sub 0.97}La{sub 0.02}(Zr{sub 0.58}Sn{sub 0.335}Ti{sub 0.085})O{sub 3} antiferroelectric ceramics for pulse power capacitors

The dielectric properties and electrical hysteresis behaviors of Pb{sub 0.97}La{sub 0.02}(Zr{sub 0.58}Sn{sub 0.335}Ti{sub 0.085})O{sub 3} antiferroelectric (AFE) ceramics were investigated in this work with an emphasis on energy storage properties. Three phase transition points can be detected as temperature increases. AFE and paraelectric phases are found to coexist from 100 °C to 170 °C. The room temperature recoverable energy density is 1.37 J/cm{sup 3} at 8.6 kV/mm. With increasing temperature (from 20 °C to 100 °C) and frequency (from 0.01 to 100 Hz) under 8.6 kV/mm, the variation of recoverable energy density was less than 15%, all higher than 1.2 J/cm{sup 3}. All the corresponding energy efficiencies were no less than 75%. The high energy density, high energy efficiency, and their weak dependence on temperature and frequency during a wide scope indicate that these antiferroelectric ceramics are quite promising to be used for pulse power capacitors applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

Editorial: Mathematical Methods and Modeling in Machine Fault Diagnosis

Modern mathematics has commonly been utilized as an effective tool to model mechanical equipment so that their dynamic characteristics can be studied analytically. This will help identify potential failures of mechanical equipment by observing change in the equipment’s dynamic parameters. On the other hand, dynamic signals are also important and provide reliable information about the equipment’s working status. Modern mathematics has also provided us with a systematic way to design and implement various signal processing methods, which are used to analyze these dynamic signals, and to enhance intrinsic signal components that are directly related to machine failures. This special issue is aimed at stimulating not only new insights on mathematical methods for modeling but also recently developed signal processing methods, such as sparse decomposition with potential applications in machine fault diagnosis. Finally, the papers included in this special issue provide a glimpse into some of the research and applications in the field of machine fault diagnosis through applications of the modern mathematical methods.

17 WIND ENERGY↗