Z.M.Sun
,
H.Hashimoto
,
S.Sumi
,
Y.H.Park and T.Abe (Materials Engineering Division
,
Tohoku National Industrial Research Institute 4-2-1 Nigatake
,
Miyagino-ku
,
Sendai 983-8551
,
Japan) Z.H. Shan (Research Fellow of Science and Technology Agency of Japan STA)
金属学报(英文版)
Two intermetallic compounds of Ti-50at.% Al and Ti-48at.% Al-2at.% Cr were prepared with a mechanical alloying and pulse discharge sintering process. The as-sintered material showed a microstructure of equiaxed gamma grain with sub-micron size. Heat treatments in vacuum at different temperatures up to 1573K were conducted on the sintered materials. The microstructure of the material coarsened considerably after heat treatment at temperatures higher than 1523K. The mechanical properties of the as-sintered and the heat treated materials were measured at temperatures of up to 973K, with four-point bending tests. Experimental results indicated that the addition of Cr increased the fracture strength of the intermetallic compound at room temperature and at elevated temperatures as well. The bending fracture strength increased with increasing testing temperature up to about 873K and a decreasing followed up. Both fracture strength and fracture strain of the material were found to be improved by heat treatment.
关键词:
titanium aluminide
,
null
,
null
,
null
,
null
汪径尘
,
陈毅东
,
郭旭波
,
张晓平
,
魏斌
,
曹必松
低温物理学报
本文采用插指电容新结构设计了一个Ku波段低温低噪声放大器（LNA）,并通过优化的封装工艺制备了放大器样品,分析了隔离器对LNA性能的影响.在77K温度下测试结果表明,放大器增益约10dB,噪声系数小于2.0dB,反射系数小于-17dB.
关键词:
低温低噪声放大器(LNA)
,
Ku波段
,
隔离器
,
噪声系数
Carbon
The natural resonance appears at 16 GHz for (Fe, Ni)/C nanocapsules with (Fe, Ni) alloys as cores and graphite as shells. Reflection loss (RL) exceeding -10 dB was obtained in the whole Ku-band (12.4-18 GHz) for an absorber thickness of 2.0 mm, while it exceeds -20 dB over the 13.6-16.6 GHz range. In addition, the bandwidth does not change dramatically for the thicknesses of 1.87-2.1 mm for the RL values exceeding -10 dB. The (Fe, Ni)/C nanocapsules with wide bandwidth absorption can be used as excellent electromagnetic-wave-absorption materials in the whole Ku-band. (C) 2008 Elsevier Ltd. All rights reserved.
关键词:
microwave-absorption properties;carbon-coated iron;complex;permittivity;nanocomposites;permeability;composites
Journal of Materials Research
The complex relative permittivity epsilon(gamma) and permeability mu(gamma) of microcoiled carbon fibers (MCCFs) imbedded in paraffin wax were measured at Ku band frequencies (12.4-18 GHz). Both the real and imaginary parts of the complex relative permittivity of the MCCFs/paraffin wax composite decreased with increase of the frequency. The real part of the complex relative permeability of the composite increases with increase of the frequency, and the imaginary part is nonzero and nearly constant over the measured frequency range. The dielectric loss tangent (tan delta(m)), the magnetic loss tangent (tan delta(m)), and amplitude attenuation factor W were determined as well. On the basis of the experimental results, the MCCFs/paraffin wax composite is mainly a kind of dielectric lossy material with small magnetic loss and diamagnetism in the Ku band.
关键词:
chemical-vapor-deposition;growth-mechanism;fibers;pyrolysis;acetylene;coils;temperature
刘海文
,
孙晓玮
,
盛怀茂
,
钱蓉
,
周旻
,
李征帆
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2003.01.013
利用微波晶体管的负阻特性,基于 Agilent(R) ADS软件,设计出一种 Ku波段微带结构、变容 管调谐的 MESFET压控振荡器(简称 VCO).对 VCO进行实测, 结果表明, VCO的中心频率为 14.14GHz,调频带宽大于 100MHz,带内输出功率大于 2mW,满足实际应用.
关键词:
负阻特性
,
微带结构
,
S参数法
,
VCO
,
变容管调谐
Journal of Alloys and Compounds
New type of Fe(Mn)/Mn(7)C(3)/graphite nanocapsules was prepared by a modified arc discharge technique in ethanol vapor, with Fe(Mn) solid solution nanoparticles as the core, Mn(7)C(3) as the inner shell, and graphite as the outer shell. The Cole-Cole semicircle approach was adopted to explain the ternary dielectric resonance, due to a cooperative consequence of the core/shell/shell interfaces and the dielectric Mn(7)C(3) and C shells. A remarkable increase in the anisotropy energy led to a shift in the natural resonance frequency to 6.6 GHz. Dielectric losses come from the ternary dielectric resonance while magnetic losses were from the magnetic natural resonance. An optimal reflection loss (RL) of -142.1 dB was observed at 12 GHz for 5.0 mm thickness layer. RL exceeding -10 dB was obtained at 6.6-18 GHz for 1.4 mm thickness, covering the whole X band (8-12 GHz), Ku band (12-18 GHz), and some of C band (6.6-8.0 GHz). RL exceeding -20 dB was found at 6-10.6 GHz for 2.2 mm thickness. (C) 2011 Elsevier B. V. All rights reserved.
关键词:
Carbon;Complex permeability;Complex permittivity;Electromagnetic wave;absorption;Nanocapsules;Reflection loss;nanocomposites;nanoparticles;composites;iron;nanotubes;nanorods
李启荣
,
魏斌
,
张晓平
,
郭旭波
,
应志军
,
冯骋
,
曹必松
低温物理学报
高温超导滤波器已在移动通信、射电天文、雷达探测等多个领域获得了重要应用．当前高温超导滤波器的研究和应用主要集中于10GHz以下的频段，针对超高频段（〉10GHz）高温超导滤波器的研究很少．本文设计优化了具有无载Q值高、耦合强、尺寸短等特点的H型阶跃阻抗谐振器，并讨论了超高频段滤波器端口激发源的电容效应对滤波器响应的影响，最后采用优化的H型谐振器，应用去嵌入（De-Embed）设计方法消除端口效应，设计了中心频率为16GHz，相对带宽12．5％的6节高温超导滤波器．研制的超导滤波器在未经调谐的情况下，测试结果与仿真结果符合得很好，插入损耗小于0．3dB，反射损耗优于-14dB，带外抑制达到了-70dB．
关键词:
高温超导滤波器
,
Ku波段
,
H型谐振器
黄致新
,
章平
,
张玉龙
,
王辉
,
吴斌
,
张锋
,
李佐宜
稀有金属材料与工程
采用射频磁控溅射法制备了TbCo非晶垂直磁化膜,并就制备工艺及参数对其磁各向异性能的影响进行了研究.结果表明:磁性层组分、溅射气压、基片偏压以及后退火温度对TbCo非晶垂直磁化膜的磁各向异性能都有不同程度的影响.当Tb含量为30%左右,或溅射气压为0.53 Pa时,TbCo薄膜的磁各向异性能Ku会呈现极大值.基片偏压超过-60V以后,TbCo薄膜Ku值开始显著上升,但超过-120 V以后,Ku值开始趋向饱和.200 ℃以上真空退火会使TbCo薄膜磁各向异性能Ku值明显下降.产生这些现象的原因与薄膜微观结构的改变有关.
关键词:
TbCo薄膜
,
磁各向异性
,
磁控溅射
,
工艺参数
杨艳玲
,
鲁燕萍
,
杜斌
,
杨华猛
,
杨振涛
,
刘征
硅酸盐通报
分别采用SPS和无压烧结工艺制备了AlN-SiC微波衰减材料.采用网络分析仪及扫描电镜检测仪,研究了衰减材料在X波段和Ku波段的介电性能及微观结构.研究结果表明:SPS制备的样品相对密度达到98％,介电性能在X波段ε'为14.01 ～13.98,tgδ为0.158 ～0.163,在Ku波段ε'为11.48 ～10.96,tgδ为0.18 ～0.17;采用无压烧结制备的样品密度仅为理论密度的95％,在X波段的ε'为26.97 ～24.26,tgδ为0.326 ～0.327.探讨了两种烧结方式制备样品的损耗机理.
关键词:
AlN-SiC微波衰减材料
,
损耗机理
,
SPS烧结
