Microwave Magnetic Properties and Natural Resonance of e-Co Nanoparticles

Owing to the novel crystal structure, ε-Co nanoparticles with an average diameter of 12 nm are synthesized and the microwave magnetic properties of the epoxy resin composite with 50voi% ε-Co particles are measured in the frequency range 0.1-7 GHz. The experimental resonance frequency （4.7 GHz） matches well with the values obtained by the theoretical calculation with the Kittel equation and fitting the experimental permeability dispersion curve via the Landan-Lifshitz equation. Hence the resonance peak is attributed to natural resonance mode. This work is believed to be beneficial for further understanding microwave applications of the novel ε-Co nanoparticles.     

Calculation of High Frequency Complex Permeability of Carbonyl Iron Flakes in a Nomagnetic Matrix

The carbonyl iron flakes are fabricated by high-energy ball milling. The effective permeability is measured and calculated for the composite consisting of flakes embedded in a nonmagnetic matrix. The magnetic flakes with a shape anisotropy and random spatial distribution of normal direction are considered to calculate the complex permeability of magnetic flake materials. Its analytical model is derived from the Landau-Lifshitz-Gilbert equation and Bruggeman ＇s effective medium theory. The calculated results agree well with the experiment.     

基于光电氧化还原反应的离子源内分析研究

激光解析离子化过程非常复杂,在这一过程中形成了大量活性物质例如电子、质子、自由基、离子,这些活性物相互作用得到了最终结果.研究这些源内活性物质的反应对于了解MALDI机理、拓展其分析应用有着重要的意义.     

Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method

As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results.     

端抽运Yb3+:YVO4激光准三能级理论模型研究

立足于Yb离子能级结构、谐振腔增益损耗和布居数分配情况, 利用爱因斯坦辐射理论和速率方程理论, 建立了适合Yb³⁺离子激光的准三能级理论模型. 该模型引入有效腔长增益贡献因子对腔内光强进行了从头计算, 获得了阈值方程. 利用此模型与Yb激光的实验结果相比较, 发现有效腔长对增益的贡献可以改变腔内损耗和粒子数反转的概率, 也继而影响激光阈值和输出功率效率. 应用于LD端抽运Yb³⁺:YVO₄激光实验中, 在971 nm LD抽运, 有效晶体长度 L=1 mm, 输出镜透过率对激光波长1016 nm为1%条件下, 获得阈值为1.1 W; 有效晶体长度L=2 mm, 输出镜透过率为10%条件下, 阈值获得为3.9 W. 关键词： 3+:YVO₄')" href="#">Yb³⁺:YVO₄ 准三能级模型 有效腔长增益贡献因子     

室温固化聚丙烯酸酯涂料

聚丙烯酸酯类涂料以优良的保光、保色、耐候、耐水等性能而在许多领域得到应用 ,为提高涂膜的机械强度、耐久性、耐热和耐溶剂等性能 ,通常需要在涂膜的同时使大分子链相互交联 ,常用的室温交联固化体系主要有环氧 /胺基 [1] 、羟基 /异氰酸根 [2 ] 等 ,其中环氧固化体系的交联密度大 ,但固化产物脆性大且易于光降解 .而基于异氰酸基的固化体系则由于异氰酸酯的毒性和价格问题而受到限制 ,迫切需要研制出新的交联固化技术 .羟基与酸酐的反应已有深入研究 ,但将该反应用于漆膜的交联固化反应却少有报道 .本文以廉价的马来酸酐为原料 ,合成了…     

基于Matlab的迈克尔逊干涉实验仿真

根据光的干涉理论,应用Matlab软件编程,模拟了迈克尔逊等倾干涉条纹和等厚干涉条纹图样。用直观的可视化图像将抽象的相干性理论形象化,对迈克尔逊干涉仪的实验教学具有一定的指导作用。     

High-frequency magnetic properties and core loss of carbonyl iron composites with easy plane-like structures

To fully release the potential of wide bandgap(WBG)semiconductors and achieve high energy density and efficiency,a carbonyl iron soft magnetic composite(SMC)with an easy plane-like structure is prepared.Due to this structure,the permeability of the composite increases by 3 times(from 7.5 to 21.5)at 100 MHz compared with to the spherical carbonyl iron SMC,and the permeability changes little at frequencies below 100 MHz.In addition,the natural resonance frequency of the composite shifts to higher frequencies at 1.7 GHz.The total core losses of the composites at 10,20,and 30 m T are80.0,355.3,and 810.7 m W/cm³,respectively,at 500 k Hz.Compared with the spherical carbonyl iron SMC,the core loss at500 k Hz is reduced by more than 60%.Therefore,this kind of soft magnetic composite with an easy plane-like structure is a good candidate for unlocking the potential of WBG semiconductors and developing the next-generation power electronics.     

Microwave Magnetic Properties of Nd2Fe17N3-δ with Planar Anisotropy

Microwave magnetic properties are studied for rhombohedral structure Nd2Fe17N3-δ with planar magnetic anisotropy. Its resin composites show the permeability μ＇0 = 4.15 at low frequency, the natural resonance frequency fT = 1.71 GHz and the resonance bandwidth 6.66 GHz. The calculated static permeability of Nd2Fe17N3-δ reaches 133. The microwave magnetic properties are determined by the c-axis anisotropy field, basal plane anisotropy field and high saturation magnetization. Based on microwave measurement and theoretical fitting on complex permeability spectra, Nd2Fe17N3-δ may be a promising microwave absorber with bandwidth wider than traditional hexaferrites materials in GHz ranges.     

取向易面各向异性羰基铁粉体的高频磁性研究

研究了取向度对羰基铁粉体复合材料微波磁性的影响.理论上构造了取向片状磁性颗粒磁矩的高斯分布,并通过Landau-Lifshitz-Gilbert方程得到了有取向度的软磁材料复数磁导率的求解方法,模拟计算了羰基铁样品高频复数磁导率随频率的变化.研究发现:随着样品取向角?θ?的变大,高斯分布标准偏差σ减小,取向度f增大;随着片状样品取向度的提高,材料初始有效磁导率的实部值增大.为了对照,利用穆斯堡尔谱得到磁体的取向度,并通过网络分析仪测量了磁体的高频磁导率,所获得的实验结果与理论预期值相符.