Search

Antiferroelectric materials are proposed as a potential solution to achieve multi-state memories, but the fundamental physical mechanism underlying the memory effect still needs to be clarified. Here, we study the memory effect in a typical antiferroelectric ceramic of Pb0.99Nb0.02[(Zr0.6Sn0.4)0.95Ti0.05]0.98O3 by systematically analyzing various hysteresis loops of polarization intensity and current density vs. electric field, where the kinetic behaviors are concerned about for the first time. The parallel pre-poling electric field reduces the critical electric field of antiferroelectric-ferroelectric phase transition, while the antiparallel field increases it. The memory behavior is significantly enhanced with the increasing of pre-poling time, but exhibits a remarkable weakening with the relaxation time increasing. It is a combined effect of electric-field-induced preferentially oriented antiferroelectric domains and internal bias electric field. This work not only improves comprehending in memory effect in antiferroelectric materials, but also enlightens the deeper understanding of other physical properties related to field-induced phase transitions. more...

The effects of grain boundaries (GBs) on the initiation of hydrogen-induced blisters in pure iron were investigated using synchrotron polychromatic X-ray Laue nano-diffraction. It was found that the random GBs were more susceptible to blistering than the coincidence site lattice grain boundaries. High strain levels and severe plastic deformation were observed around the random GBs after hydrogen charging, but not on the coincidence site lattice grain boundaries. more...

The morphology, surface oxide and strain evolution of nanoporous (np) gold were investigated using atomic force microscopy (AFM). Topographic AFM images show typical np structure with a few nanometers ligament size. Current sensing AFM results revealed semiconductor properties of the surface oxide, which may consist of Ag2O (p-type) and AgO (n-type). The surface oxide can effectively suppress the np structure coarsening. In-situ electrochemical AFM tests exhibit a refined macroscopic dimensional change of 40 nm within 0.35–0.7 V potential range. AFM can be used as an effective method to investigate the morphology and voltage-induced dimension changes in electrolyte. more...

The vacancies and small voids evolution within the ligaments of nanoporous (np) Au(Pt) in dealloying processes were investigated by positron annihilation spectroscopy. The np Au(Pt) samples with 5–8 nm ligaments were prepared by electrochemical dealloying of (Au 0.95 Pt 0.05 ) 25 Ag 75 ingots. The positron lifetime of as-prepared np Au(Pt) consists of the two main components. One is assigned to the positron annihilation at vacancies within the nano-ligaments and the other to the positron annihilation in the enclosed voids in the ligaments. Vacancy concentration increased significantly when silver atoms leached out further from the np structure, which supports the vacancy-mediated lattice diffusion mechanism of porosity evolution. more...

The reduction in ductility and fracture stress of many metals tested in certain liquid metal environments is generally known as liquid metal embrittlement (LME). The evidence for plastic deformation on the fracture surfaces of LME failures has led Lynch to propose that the chemisorption of liquid metal can enhance localized plastic deformation. Up to now, however, direct proof of chemisorption facilitating dislocation emission, multiplication and motion is lacking. The purpose of this paper is to study now chemisorption facilitates dislocation emission, multiplication and motion. An in-situ tensile test in a TEM is the most direct and powerful method for studying the dislocation emission, multiplication and motion. Since there is no way to put the liquid metal into a TEM, a special constant deflection loading device has been designed. Using this device, the effect of chemisorption on dislocation emission and motion can be studied based on the dislocation configuration change ahead of a loaded crack tip after chemisorption of liquid metal atoms but before the propagation of the original crack tip or initiation of a new microcrack. more...