Ruiting MA
材料科学技术（英文）
Nanocrystalline nickel zinc ferrite powders (NixZn1-xFe2O4, A for x=0, B for x=0.2, C for x=0.5, D for x=0.8 and E for x= 1) were synthesized by polyacrylamide gel method. X-ray diffraction (XRD), transmission electron microscopy (TEM) and wave-guide were used to characterize the composition. The XRD results show that the dried gel powders are amorphous, and the characteristic peaks of the spinel Ni0.5Zn0.5Fe2O4 appear after the gel is calcined at 400℃ for 1 h. When the calcining temperatures are 600 and 800℃, the average grain sizes are identified by TEM to be 10 and 30 nm, respectively. The NixZn1-xFe2O4 powders have both dielectric loss and magnetic loss in the frequency range of 8.2–11.0GHz. With the increase of Ni2+ ions content, the dielectric parameters (ε′) and permeability (u′) of the NixZn1-xFe2O4 powders decrease while the dielectric loss (ε"), magnetic loss (u") and the reflection loss increase.
关键词:
Nanocrystalline
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ferrite
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electromagnetic
帅永
,
刘林华
,
王雁鸣
,
谈和平
工程热物理学报
本文通过时域有限差分法求解 M-well 方程组,分析微结构表面与入射辐射间的相互作用,结合近场 - 远场辐射转换模型,获得了尺寸、温度和入射波长等参数对表面双向反射分布函数的影响规律,研究结果为热辐射的光谱和方向调控技术提供了数值基础.
关键词:
有限时域差分
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表面辐射特性
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微结构
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热辐射
,
电磁波
S.Y.Huang
金属学报(英文版)
Powder metallurgy is an efficient approach to fabricate varieties of high performance structure materials, function materials and special materials working under limited conditions. Research and development of new efficient technology to form high-density,high-performance and net shape parts is a key to widen application and development of powder materials. Recently, the low-voltage electromagnetic compaction (EMC) has been used by present authors to compacted copper, tin, aluminum powders and the products with 99relative density have been acquired. In this work, the research has been extended to investigation on the density uniformity of pressed parts. The analysis results show that the density of the part compacted by low-voltage EMC decreases gradually in press direction as static compaction. But it is higher and more homogeneous. The densit3"" of the top part increases gradually from the center to the outer, which is just reversal of the bottom part. In some extent, the higher the discharging voltage is, the higher the densiO' is and the more homogeneous the distribution is. In addition, repetitive compaction can improve the density of powder parts and the distribution uniformity.
关键词:
powder
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null
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