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排序方式: 共有1322条查询结果,搜索用时 8 毫秒
71.
Robert Dittmer Wook Jo Jürgen Rödel Sergei Kalinin Nina Balke 《Advanced functional materials》2012,22(20):4208-4215
Piezoresponse force microscopy (PFM) is used to afford insight into the nanoscale electromechanical behavior of lead‐free piezoceramics. Materials based on Bi1/2Na1/2TiO3 exhibit high strains mediated by a field‐induced phase transition. Using the band excitation technique the initial domain morphology, the poling behavior, the switching behavior, and the time‐dependent phase stability in the pseudo‐ternary system (1–x)(0.94Bi1/2Na1/2TiO3‐0.06BaTiO3)‐xK0.5Na0.5NbO3 (0 <= x <= 18 mol%) are revealed. In the base material (x = 0 mol%), macroscopic domains and ferroelectric switching can be induced from the initial relaxor state with sufficiently high electric field, yielding large macroscopic remanent strain and polarization. The addition of KNN increases the threshold field required to induce long range order and decreases the stability thereof. For x = 3 mol% the field‐induced domains relax completely, which is also reflected in zero macroscopic remanence. Eventually, no long range order can be induced for x >= 3 mol%. This PFM study provides a novel perspective on the interplay between macroscopic and nanoscopic material properties in bulk lead‐free piezoceramics. 相似文献
72.
Pingfan Chen Zhen Huang Changjian Li Bangmin Zhang Nina Bao Ping Yang Xiaojiang Yu Shengwei Zeng Chunhua Tang Xiaohan Wu Jingsheng Chen Jun Ding Stephen John Pennycook A. Ariando Thirumalai Venky Venkatesan Gan Moog Chow 《Advanced functional materials》2018,28(33)
The complex interfacial correlations provide new routes toward tunable functionalities. Here, the wide range of tunabilities for magnetic properties are presented, including Curie temperature (from 245 to 320 K), coercive field (from 2 to 205 Oe), and saturated magnetic moment (from 0.9 to 2.8 µB Mn?1), in a 9‐unit‐cell La2/3Sr1/3MnO3 (LSMO) layer via modifying interfacial boundary conditions. Moreover, the LSMO/PbTiO3‐based multilayers and superlattices that consist of PbTiO3/LSMO/NdGaO3 and PbTiO3/LSMO/PbTiO3 interfaces are characterized by two distinct Curie temperatures and coercive fields. The results reveal the feasibility of the interface‐resolved strategy based on boundary modification in fabricating potential devices with multiple accessible states for information storage. The wide‐range modulations on magnetic properties at LSMO/titanate interfaces are explained in terms of binary controls arising from the oxygen octahedral coupling (OOC) and magnetoelectric coupling (MEC). The results not only shed some light on understanding interfacial correlations in oxide heterostructures, but also pave an alternative path for exploring multiple accessible states in all‐oxide‐based electronic devices. 相似文献
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Dr. Nina Erini Vera Beermann Martin Gocyla Manuel Gliech Dr. Marc Heggen Dr. Rafal E. Dunin-Borkowski Prof. Peter Strasser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6633-6638
Direct ethanol fuel cells are attractive power sources based on a biorenewable, high energy-density fuel. Their efficiency is limited by the lack of active anode materials which catalyze the breaking of the C−C bond coupled to the 12-electron oxidation to CO2. We report shape-controlled PtNiRh octahedral ethanol oxidation electrocatalysts with excellent activity and previously unachieved low onset potentials as low as 0.1 V vs. RHE, while being highly selective to complete oxidation to CO2. Our comprehensive characterization and in situ electrochemical ATR studies suggest that the formation of a ternary surface site ensemble around the octahedral Pt3Ni1Rhx nanoparticles plays a crucial mechanistic role for this behavior. 相似文献
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Bacteriochlorophyll (BChl) derivatives (with central Mg replaced by metal "M") ([M]-BChl with M = 2H, Mg, Zn, Pd, Cu) have been investigated for their photodynamic capacity and stability toward photodegradation in organic solvents and aqueous micellar solution. A protocol has been developed for screening new sensitizers. BChl and [Zn]-BChl are efficient sensitizers, but they are also quickly degraded by the reactive oxygen species (ROS) produced by autosensitization, as well as by hetero-sensitization with 17(4)-methyl-13(2)-demethoxycarbonyl-pheophorbide a (MPP). Photostable [Cu]-BChl is a poor sensitizer, whereas [Pd]-BChl and bacteriopheophytin a are not only very efficient sensitizers but are also very stable toward ROS. beta-Carotene is no efficient physical quencher of ROS in the system; rather, it acts as a photochemical quencher that competes with [M]-BChl and undergoes photooxygenation at high rates. Photolability seems to depend on the pigment oxidation potential and, in parallel, on the presence of central metals preferring coordination numbers higher than 4, whereas photodynamic capacity depends on long excited state life-times of the pigment or efficient intersystem crossing (or both). 相似文献
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Chemical unfolding of bovine testicular hyaluronidase (HAase) has been studied by fluorescence spectroscopy and Fourier transformed
infrared spectroscopy (FTIR). Thermodynamic parameters were determined for unfolding HAase from changes in the intrinsic fluorescence
emission intensity and the formations of several possible unfolding intermediates have been identified. This was further confirmed
by representation of fluorescence data in terms of ‘phase diagram’. The secondary structures of HAase have been assigned and
semiquantitatively estimated from the FTIR. The occurrence of conformational change during chemical unfolding as judged by
fluorescence and FTIR spectroscopy indicated that the unfolding of HAase may not follow the typical two-state model. 相似文献
80.