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61.
Kazuhisa Sato Shunya Tashiro Shuhei Matsunaga Yohei Yamaguchi Takanori Kiguchi Toyohiko J. Konno 《哲学杂志》2018,98(21):1945-1960
We have studied three-dimensional (3D) structures and growth processes of 14H-type long-period stacking order (LPSO) formed in Mg97Zn1Gd2 cast alloys by single tilt-axis electron tomography (ET) using high-angle annular dark-field scanning transmission electron microscopy. Evolution of the solute-enriched stacking faults (SFs) and the 14H LPSO by ageing were visualised in 3D with a high spatial resolution in multi-scale fields of views from a few nanometres to ~10 μm. Lateral growth of the solute-enriched SFs and the LPSO in the (0?0?0?1)Mg plane is notable compared to the out-of-plane growth in the [0?0?0?1]Mg direction. The 14H LPSO grows at the cost of decomposition of the (Mg, Zn)3Gd-type precipitates, and accompany a change of in-plane edge angles from 30 to 60°. We have updated the Time–Temperature–Transformation diagram for precipitation in Mg97Zn1Gd2 alloys: starting temperatures of both solute-enriched SFs and LPSO formation shifted to a shorter time side than those in the previous diagram. 相似文献
62.
《化学:亚洲杂志》2018,13(19):2939-2946
The facile preparation of platinum‐based catalysts with designed compositions and structures is of great importance for fuel cells. In this work, a one‐pot method is developed to synthesize monodispersed trimetallic PtPdCo mesoporous nanoparticles (PtPdCo MNs) with uniform morphology and size. The proposed synthetic method does not require any hard template or organic solvent, which greatly simplifies the preparation procedure. PtPdCo MNs, with a highly porous structure, exhibit enhanced electrocatalytic activities and excellent stabilities for both the formic acid oxidation reaction and the oxygen reduction reaction, relative to bimetallic PtPd MNs and commercial Pt/C catalyst. The proposed synthetic method is highly valuable for the design of mesoporous multimetallic catalysts for fuel cells. 相似文献
63.
Microstructural evolution and grain refinement mechanism in AZ31 magnesium alloy subjected to sliding friction treatment were investigated by means of transmission electron microscopy. The process of grain refinement was found to involve the following stages: (I) coarse grains were divided into fine twin plates through mechanical twinning; then the twin plates were transformed to lamellae with the accumulation of residual dislocations at the twin boundaries; (II) the lamellae were separated into subgrains with increasing grain boundary misorientation and evolution of high angle boundaries into random boundaries by continuous dynamic recrystallisation (cDRX); (III) the formation of nanograins. The mechanisms for the final stage, the formation of nanograins, can be classified into three types: (i) cDRX; (ii) discontinuous dynamic recrystallisation (dDRX); (iii) a combined mechanism of prior shear-band and subsequent dDRX. Stored strain energy plays an important role in determining deformation mechanisms during plastic deformation. 相似文献
64.
Ying-Xia Wang Chuan-Fei Liu Man-Li Yang Xi-Hui Zhao Zhi-Xin Xue Yan-Zhi Xia 《中国化学快报》2017,28(1):60-64
Concave nanostructures may be developed to improve the specific mass activity of a catalyst for formic acid and methanol electro-oxidation. In this work, we report the elctrocatalytic oxidation of methanol and formic acid in acid medium over concave Pt-Cu-Fe ternary nanocubes (NCs), obtained by the galvanic exchange of Pt and Fe on Cu NCs. The concave Pt-Cu-Fe NCs exhibited improved electrooxidation performance contrasted to Pt-Cu NCs and purchased commercial Pt/C as demonstrated by their improved durability, lower onset potential, and more preferable anti-poisoning properties. These properties are believed to originate from the tailored concave structure of the catalyst and possible synergetic effects among the components of the Pt-Cu-Fe NCs. 相似文献
65.
The effect of Fe on the phase and magnetocaloric property of LaFe11.6*xSi1.4B0.1 alloys with x = 1.0–1.4 have been studied. The results show that the excess of Fe will make the α-Fe phases increase, but the easy corrosion LaFeSi phase reduces in LaFe11.6*xSi1.4B0.1 alloys. All LaFe11.6*xSi1.4B0.1 alloys keep the first-order magnetic phase transition. The saturation magnetizations of LaFe11.6*xSi1.4B0.1 alloys with x > 1 are much higher than LaFe11.6Si1.4B0.1 alloy under 2T magnetic field. This results in the maximum isothermal magnetic entropy changes, and the relative cooling power of LaFe11.6*xSi1.4B0.1 alloys is bigger than for LaFe11.6Si1.4B0.1 alloys. 相似文献
66.
67.
Surface tensions of some Pb-free solder systems such as Ag–Bi–Sn with cross-sections Ag/Bi = 1/1, Ag/Bi = 1/2, Ag/Bi = 2/1, In–Sn–Zn with cross-sections Sn/In = 1/1, Sn/In = 1/3 and (Ag7Cu3)100?x Snx with cross-section Ag/Cu = 7/3 are calculated from the sub-binary surface tension data using the models, such as the Muggianu, Kohler, Toop models, Butler’s equation and Chou’s General Solution Model (GSM) at 873, 923 and 1073 K, respectively. The surface tension of In–Sn–Zn increases wavily with increasing amount of Zn and it is found that the best models are the GSM for both cross-sections in question while GSM becomes the best model for (Ag7Cu3)100?x Snx alloy in the whole experimental range. Moreover, the surface tension of (Ag7Cu3)100?x Snx decreases slightly with increasing amount of Sn. The Muggianu, Butler and Butler models are determined as the best models for the cross-sections in the order given above for entire measurement range, respectively, and the surface tension of Ag–Bi–Sn decreases slightly with an increasing amount of Bi and Ag but increases with increasing Sn in liquid alloys. 相似文献
68.
Fe-based amorphous ribbons with excellent soft magnetic properties and mechanical properties were prepared in the Fe–Si–P ternary system. Enhanced soft magnetic properties could be achieved through annealing treatment of the ribbons for 1 h at 325 °C, which is far below the glass transition temperatures (462–474 °C). Icosahedral medium-range ordering with a size range of around 2 nm occurred throughout the amorphous matrix during the low-temperature annealing treatment. The annealed ribbons exhibited improved magnetic saturation of over 185 emu/g while maintaining good mechanical flexibility. During icosahedral ordering, the distance between the Fe atoms and the coordination number within the amorphous ribbon can be optimised for achieving high magnetic saturation. However, nanocrystallisation of the SiP and Fe2P transition phases embedded within the amorphous matrix occurred after the annealing treatment for 1 h at 385 °C, which caused deterioration of the soft magnetic properties and mechanical flexibility of the ribbons. Therefore, the combination of high magnetic saturation and mechanical flexibility of the amorphous ribbons could be optimised through low-temperature annealing treatment without any nanocrystallisation. 相似文献
69.
Ngo Ngoc Ha Nguyen Truong Giang Tran Ngoc Khiem Nguyen Duc Dung Tom Gregorkiewicz 《固体物理学:研究快报》2016,10(11):824-827
Photogenerated carriers in Si–Ge alloy nanocrystals (NCs) prepared by co‐sputtering method were investigated by mean of transient induced absorption. The carrier relaxation features multiple components, with three decay life times of τ ≈ 600 fs, 12 ps, and 15 ns, established for Si0.2Ge0.8 alloy NCs of a mean crystal size of 9 nm and standard deviation of 3 nm. Deep carrier traps, identified at the boundary between the NCs and the SiO2 host with the ionization energy of about 1 eV, are characterized by a long‐range Coulombic potential. These are responsible for rapid depletion of free carrier population within a few picoseconds after the excitation, which explains the low emissivity of the investigated materials, and also sheds light on the generally low luminescence of Si/Ge and Ge NCs. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
70.
We have performed first-principles calculations using full-potential augmented-plane-wave method to investigate the fundamental properties of the Cd1–xZnxTe alloys. The composition dependence of the lattice constant and the bulk modulus have been estimated from total energy calculations. By means of the analytical fitting the band structures in the vicinity of the Brillouin center a complete set of effective electron- and hole-masses have also been derived. In order to further understand the effects of the chemical bonding on the above macroscopic properties we then studied the relaxation behaviors and the changes of the electronic states upon alloying for x=0.25 system. The results presented here yield a general understanding of the fundamental properties for the Cd1–xZnxTe crystals studies. 相似文献