分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Reddy, MP [Reddy, M. Penchal][ 1 ]
Mohamed, AMA [Mohamed, A. M. A.][ 1,2 ]
Zhou, XB [Zhou, X. B.][ 3 ]
Du, S [Du, S.][ 3 ]
Huang, Q [Huang, Q.][ 3 ]
摘要： Mesoporous CoFe2O4 nanospheres with an average size of 180 nm were fabricated via a facile hydro- thermal process using ethylene glycol as solvent and sodium acetate (NaAc) as electrostatic stabilizer. In this method, ethylene glycol plays a vital role in the formation of cobalt nanoospheres as a solvent and reducing agent. The structure and morphology of the prepared materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high- resolution TEM (HRTEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The nanospheres exhibited ferromagnetic properties with high saturation magne- tization value of about 60.19 emu/g at room temperature. The BET surface area of the nanospheres was determined using the nitrogen absorption method. The porous CoFe2O4 nanospheres displayed good magnetic properties, which may provide a very promising candidate for their applications in target drug delivery.
分类： 材料科学 >> 电子、光学、磁材料 提交时间： 2017-03-29
摘要： The phase transformation in two modes, including both displacive and massive growth of τ-phase from ε-MnAl(C), was in situ observed. Temperature dependence of magnetization curves of MnAl(C) under magnetic field were employed for the first time to determine the triggering temperatures of different phase transformation modes. The displacive growth of ε→τ in MnAl(MnAlC) occurs at temperatures below 650 K(766 K), above which both modes coexist. One third or less of the ε-phase can be transformed into τ via displacive mode while the remaining two thirds or more via massive mode. Most large τ-grains formed via massive mode are actually containing a large number of well-distributed τ-nanocrystallline formed via displacive mode. The typical massive growth rate of the τ-phase is 8-60 nm/s, while the displacive growth rate is quite low. The doping of C to MnAl prevents the growth of ε-phase along the basal plane and thus increases the activation temperatures of the phase transformations and the decomposition of τ-phase. Pure τ-phase with highest magnetizations up to 118.3 Am2/kg was obtained. No decomposition was observed in τ-MnAl and τ-MnAl(C) after long-time annealing at selected temperatures, which are crucial in preventing the metastable τ phase from decomposition. These results provide a more complete understanding of the ε→τ phase transformations and thus facilitate the development of high-performance MnAl-based magnets.
分类： 材料科学 >> 材料科学（综合） 提交时间： 2023-12-05
Wang Hongyang
Wu Hao
Wu Zhixing
Geng Zhihui
Zhou Juncheng
Deng Ziqi
Yan Liqin
Qian Peng
Ye Shufeng
Shi Ke
Chen Ning
摘要： This study synthesized copper-substituted lead apatite using the hydrothermal method, starting from hydroxyapatite precursors. For stability, it is recommended to maintain copper substitution below x=2 in the Pb10-xCux(PO4)O apatite. The introduction of copper appropriately reduces the lattice constant, in line with DFT theoretical calculations. Non-equilibrium heat treatment introduces additional charge carriers; oxygen-rich tempering shifts the sample to paramagnetism, while anaerobic tempering leads to complex and unique hysteresis loops. Non-equilibrium annealing can increase carrier concentration, but its efficacy is limited. Although some improvements have been observed, further exploration involving additional element doping or seeking interfaces with suitable conductive phases is needed to achieve superconductivity.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Zhai, WT [Zhai, Wentao][ 1 ]
Chen, YJ [Chen, Yuejuan][ 1 ]
Ling, JQ [Ling, Jianqiang][ 1 ]
Wen, BY [Wen, Bianying][ 2 ]
Kim, YW [Kim, Young-Wook][ 3 ]
摘要： The preparation of lightweight materials with electromagnetic interference-shielding effect- iveness higher than 30dB is critical for most industrial and consumer applications. Compounding polymer resin with conductive filler can generate excellent electromagnetic interference-shielding effectiveness but usually leads to a high-sample density, while the foaming of polymer composite suffers from the significant-reduced electromagnetic inter- ference-shielding effectiveness. In this study, polyetherimide composite foams with loading of 10–80 phr (parts per hundred of resins) nickel particles were fabricated to meet the gap. The polyetherimide/nickel composite foams possessed uniform cell structure and low- sample density such as 0.86 g/cm3 at 70 phr nickel. The coupling effects of gravity settle- ment and cell-structure solidification led to the formation of gradient distribution of nickel particles across the foams. The formed novel structure facilitated the enhancement of multi-reflection and multi-scattering among nickel particles and cells. As a consequence, polyetherimide/nickel foam with 70 phr nickel (PEIN70) possessed a high-electromagnetic interference shielding effectiveness of 86.7–106.5 dB over a frequency range of 50–3000MHz. When the sample density was considered, the specific electromagnetic interference shielding effectiveness of PEIN70 foam was as high as 121.3 dB/(g/cm3) at 1 GHz, which was higher than the reported electromagnetic interference-shielding materials. The excellent electromagnetic interference-shielding properties, lightweight, well-defined resin proper- ties ensure polyetherimide/nickel composite foams useful in many advanced applications.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-05-02
Qin, LF [Qin, Laifen][ 1,2 ]
Xia, YG [Xia, Yonggao][ 1 ]
Cao, HL [Cao, Hailiang][ 1 ]
Luo, LJ [Luo, Linjun][ 1 ]
Zhang, Q [Zhang, Qian][ 1 ]
Chen, LP [Chen, Lipeng][ 1 ]
Liu, ZP [Liu, Zhaoping][ 1 ]
摘要： The preparation of lightweight materials with electromagnetic interference-shielding effect- iveness higher than 30dB is critical for most industrial and consumer applications. Compounding polymer resin with conductive filler can generate excellent electromagnetic interference-shielding effectiveness but usually leads to a high-sample density, while the foaming of polymer composite suffers from the significant-reduced electromagnetic inter- ference-shielding effectiveness. In this study, polyetherimide composite foams with loading of 10–80 phr (parts per hundred of resins) nickel particles were fabricated to meet the gap. The polyetherimide/nickel composite foams possessed uniform cell structure and low- sample density such as 0.86 g/cm3 at 70 phr nickel. The coupling effects of gravity settle- ment and cell-structure solidification led to the formation of gradient distribution of nickel particles across the foams. The formed novel structure facilitated the enhancement of multi-reflection and multi-scattering among nickel particles and cells. As a consequence, polyetherimide/nickel foam with 70 phr nickel (PEIN70) possessed a high-electromagnetic interference shielding effectiveness of 86.7–106.5 dB over a frequency range of 50–3000MHz. When the sample density was considered, the specific electromagnetic interference shielding effectiveness of PEIN70 foam was as high as 121.3 dB/(g/cm3) at 1 GHz, which was higher than the reported electromagnetic interference-shielding materials. The excellent electromagnetic interference-shielding properties, lightweight, well-defined resin proper- ties ensure polyetherimide/nickel composite foams useful in many advanced applications.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要： The structural, electronic, and magnetic properties of ConO (n = 2～10) clusters have been systematically investigated within the framework of the generalized gradient approximation density functional theory. The results indicate that the O atom occupies the surface-capped position on ConO (n = 2～10) clusters. The stabilities of the host clusters are improved by adding one O atom. Maximum peaks of the second-order difference energy of the ground-state ConO clusters are found at n = 3, 6 and 8, indicating higher stability than their neighboring clusters. Compared with corresponding pure Con clusters, the O-doped cobalt clusters have larger gaps between the HOMO and LUMO energy levels, indicating their higher chemical stabilities. In addition, the doping of O atom exhibits different influence on the magnetism of the clusters. This is also further investigated by the local magnetic moment, deformation charge density and partial local density of states analysis.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-04-06
摘要： SnOx films were fabricated by reactive rf magnetron sputtering under various oxygen partial pressures (PO = 1.6%–50%) and then annealed in an air ambient. Four operating window regions of the SnOx films are demonstrated such as metallic Sn dominated films with n-type conduction, polycrystalline SnO dominated films with p-type conduction, SnO-SnO2 composite films with high resistivity, and amorphous SnO2 dominated films with n-type characteristics. TFT devices using the SnO dominated films as channels are investigated. The TFTs with the channels of a hole concentration over 1018 cm−3 show depletion p-type characteristics. The hole concentration can be tunable by changing PO, the channel thickness, and the annealing durations. An ambipolar operating mode is obtained by modulating the hole concentration.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-04-06
摘要： The magnetic circular permeability extracted from impedance measurements of arrays composed of Co- based amorphous wires was studied as a function of the number and distance between the wires. The results showed that a linear array with higher number of wires increased the permeability and thereby magnetoimpedance (MI) response up to 10 MHz. It was also proposed that such variation in circular permeability originated from the magnetostatic interaction among the wires gave rise to a change in the skin depth and finally in impedance. Increasing the distance between the wires had a detrimental effect on permeability and MI ratio due to a weaker mutual interaction. These observations provide support to the complex inductance formalism as an alternative approach to explain MI change in wire arrays.
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