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680th WEH Seminar “Materials Development for Automotive Propulsion” in Physikzentrum Bad Honnef on Oct. 14th-17th
2018/05/25
Ulrike Kramm, Christina S. Birkel, and Bai-Xiang Xu are organizing the 680th Wilhelm and Else Heraeus Seminar named “Materials Development for Automotive Propulsion” in Physikzentrum Bad Honnef on October 14th-17th.
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On the origins of the inverse electrocaloric effect
2018/05/18
New Publication in “Energy Technology”
We discuss and analyze the occurrence of the inverse (or negative) electrocaloric effect, where the isothermal application of an electric field leads to an increase in entropy and the removal of the field decreases the entropy of the system under consideration. We show that in all these cases the inverse electrocaloric effect is related to the presence of competing phases or states which are close in energy and can easily be transformed with the applied field. …
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Impact of polarization dynamics and charged defects on electrocaloric response of ferroelectric Pb(Zr,Ti)O3 ceramics
2018/05/18
New Publication in “Energy Technology”
the highest electrocaloric effect is observed in poled hard PZT with the field applied along the poling direction, which is related to the reduced hysteresis losses caused by internal electric fields associated with defect complexes. The weak hysteretic dependency of polarization as function of the electric field in hard PZT also allows inducing an inverse electrocaloric effect. …
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Striping Modulations and Strain Gradients within Individual Particles of a Cathode Material upon Lithiation
2018/03/06
New Publication in “Materials Horizons”
The insertion of Li-ions within cathode materials during the discharging of a battery oftentimes brings about one or more structural transformations. Here we demonstrate compositional striping modulations between Li-rich and Li-poor domains along the edges of individual nanowires of Li-ion-intercalated V2O5 based on analysis of hyperspectral X-ray microscopy data. …
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Anisotropic local hardening in hot-deformed Nd-Fe-B permanent magnets
2018/03/06
New Publication in “Acta Materialia”
In this study, we found that for a Nd-Cu diffusion parallel to the texture axis the increase in Hc is higher than for a diffusion perpendicular to it and strongly depends on the diffusion depth whereas remanence develops in an inverse manner. …
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Prof. Xu Gave a Tutorial in APS March Meeting 2018
2018/03/04
Prof. Xu gave a tutorial entitled “Multi-physics Multi-scale Modeling of Li-ion Batteries” in the Energy Research Workshop of APS March Meeting 2018, 4 Match.
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Thermal Properties of SiOC Glasses and Glass Ceramics at Elevated Temperatures
2018/02/10
New Publication in “Materials”
In the present study, the effect of the chemical and phase composition on the thermal properties of silicon oxide carbides (SiOC) has been investigated. Dense monolithic SiOC materials with various carbon contents were prepared and characterized with respect to their thermal expansion, as well as thermal conductivity. …
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Improved vibration-based energy harvesting by annular mass configuration of piezoelectric circular diaphragms
2018/01/29
New Publication in “Smart Materials and Structures”
Vibration-based energy harvesting using piezoelectric circular diaphragms (PCDs) with a structure featuring the central mass (C-mass) configuration has drawn much attention in recent decades. In this work, we propose a new configuration with the annular proof mass (A-mass) where an improved energy harvesting is promised. …
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Session “Mechanics and Electrochemistry of Energy Materials” in SES 2018, Madrid on Oct. 10th-12th
2018/01/19
Matthew T. McDowell, Georgia Tech, and Bai-Xiang Xu are organizing the session 4.1 called “Mechanics and Electrochemistry of Energy Materials” in the 55th Annual Technical Meeting of the Society of Engineering Science 2008 on October 10th-12th in Madrid, Spain.
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Enhanced performance of ferroelectric materials under hydrostatic pressure
2017/12/14
New Publication in “Journal of Applied Physics”
This study investigates the effect of hydrostatic pressure on the ferroelectric behavior of bulk polycrystalline Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3. Polarization versus electric field hysteresis plots were generated as a function of hydrostatic pressure for a range of operating temperatures (298–398 K). …