Yuchang Qing
材料科学技术（英）
Microwave absorbing properties of the carbonyl iron particles filled epoxy-silicone resin coatings showed visible degression when the coatings were heat treated at 300°C with different time. The complex permittivity and permeability of the coatings before and after heat treatment were measured. After heat treatment at 300°C, the real part of permittivity of the coatings increased with increasing treatment time and showed frequency dependence dielectric response. The complex permeability showed remarkable variation while the resonance frequency of the coatings heat treated at 300°C shifted from 7 to 12 GHz. The electromagnetic results indicated that microwave absorbing properties of the coatings showed more dependent on the complex permeability. The results showed that the difference of the electromagnetic and microwave absorbing properties before and after heat treatment was mainly attributed to the crystalline state transition of carbonyl iron particles.
关键词:
Microwave absorption
,
Dielectric properties
,
Magnetic properties
,
Heat treatment.
Wei Zhang Hongxia Wang Faling Zhang Zhengnan Qian Wenhui Su
材料科学技术（英）
Two different silica sources have been used for the preparation of Ni0.5Zn0.5Fe2O4 /SiO2 nanocomposites, and their effects on the particle size, crystallinity and the magnetic properties have been investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and physical property measurement system (PPMS). In both cases, Ni0.5Zn0.5Fe2O4 nanoparticles of 11 nm in mean particle size were well dispersed in silica matrix. The coercivity and the blocking temperature of Ni0.5Zn0.5Fe2O4 nanoparticles modified with the silicon coupling agent show little decrease, whereas the saturation magnetization increases obviously with respect to nanoparticles dispersed directly in silica matrix. It is considered that the decrease of the surface anisotropy resulting from the change in the surface coordination is responsible for the observed behavior.
关键词:
Chemical synthesis
,
Silica
,
Magnetic properties
,
Ferrites
王冠伟
,
袁淑娟
,
康保娟
,
鲁波
,
曹世勋
,
张金仓
低温物理学报
通过快速液相烧结法制备了BiFeO3、Bi0.9Gd0.1FeO3和Bi0.9Gd0.1Fe0.95Ti0.05O3 (BGFTO)块材.x射线衍射和拉曼散射光谱表明Gd和Ti共掺杂后的BGFTO样品产生结构相变.共掺杂样品BGFTO室温下的铁磁性得到显著提高,矫顽力达到1.51T,剩余磁矩为0.175 emu/g.磁性得到显著提高的根本原因是共掺杂引起元素替换导致了体系中的螺旋磁结构被抑制.A位和B位共掺杂是引发BiFeO3自发磁化的最有效的方法.
关键词:
BiFeO3
,
共掺杂
,
元素替代
,
磁性质
W.S. Zhang
材料科学技术（英）
The boron-oxide coated iron nanocapsules have been prepared by arc-discharge in a mixture of diborane and nitrogen, and then the boron-nitride coated iron nanocapsules by a subsequent annealing under a nitrogen atmosphere at 1100°C. After the arc-discharge, the boron-oxide coated iron nanocapsules form, which show an amorphous surface layer of B2O3 (and/or B) and a core of γ-Fe, α-Fe, FeB phases. After being annealed, part of the α-Fe phase transforms to the γ-Fe phase, and the FeB phase decomposes while the BN phase forms. The BN shell structure formed in the BN encapsulating iron nanocapsules is incomplete. Magnetic properties of the boron-oxide coated and the boron-nitride coated iron nanocapsules were compared and discussed in terms of the particles sizes, the phase components, and the surface structures.
关键词:
Arc discharge
,
nanocapsules
,
magnetic properties
