Short range order transformation and magnetostriction of Fes3Ga17 ribbons

The relationship between magnetostriction and structure of melt-spun Fes3Ga17 ribbons are investigated by XRD and M5ssbauer spectrum technique （MS）. As the heat-treatment temperature increases from 650℃ to 800℃, the magnetostriction coefficient of Fes3Ga17 ribbon first increases and then decreases. The largest magnetostriction coeiffcient （-578.4 ppm） is achieved in those specimens quenched at 750oc. According to the XRD and MSssbauer spectrum anal- ysis, a small quantity of DO3 phase is precipitated in Fe83Ga17 ribbons when quenched from 650℃ and the DO3 phase is gradually transformed into B2-1ike phase if quenched at higher temperature. However, both DO3 and B2-1ike phases disappear when the temperature increases up to 800℃. From this point of view, B2-1ike phase might be beneficial to the enhancement of magnetostrictive properties of melt-spun ribbons.     

吸铸对2:17型SmCo永磁合金内秉矫顽力的影响

2:17型Sm(CoFeCuZr):合金由于居里温度高、磁性能优良、温度系数低等优点被认为是最有希望实现高温应用的一类永磁体.为了解决具有低内秉矫顽力温度系数特征的合金内秉矫顽力不高的问题,本文提出了一种在不改变成分的前提下通过改进制备工艺、优化热处理工艺提高合金室温内秉矫顽力的思路.本文在真空非自耗电弧熔炼炉中采用铜模吸铸法制备了不同尺寸的2:17型SmCo合金,确定了优化的热处理工艺,并采用永磁测量仪对其磁性能进行表征.研究发现,在不同尺寸吸铸试样中Φ6试样磁性能比较稳定;热处理后其室温内秉矫顽力达到1300 kA·m-1,比相同成分普通铸锭的880 kA·m-1有显著提高.分析认为,吸铸法制备的合金内秉矫顽力的提高与其晶粒细化、取向度提高以及胞状组织的改善有关.     

Local Structure Mediation and Photoluminescence of Ce~(3+)-and Eu~(3+)-Codoped YAG Nanophosphors

Cerium and europium codoped yttrium aluminum garnet(YAG:Ce,Eu) nanophosphors were prepared by sol-gel method.We systematically explored the structure,composition,morphology and photoluminescence(PL) properties by using X-ray diffraction,scanning electron microscope,high resolution transmission electron microscope,energy dispersive spectrometer,photoluminescence emission and excitation spectra techniques,and focused on clarifying the change of local structure surrounding Ce~(3+) ions by utilizing advanced quantitative ~(27)Al magic angle spinning nuclear magnetic resonance spectroscopy.The results show that the lattice constant slightly increases as the Ce~(3+) and Eu~(3+) ions incorporate,and the geometric distortion of local structure surrounding Ce~(3+) activator introduced by the incorporated Eu~(3+) coactivator causes the variation of crystal field,which results in red shift of Ce~(3+) PL emitting in YAG:Ce,Eu nanophosphor.Furthermore,the YAG:Ce,Eu nanophosphors could exhibit several sharp and narrow ~5D_0 → ~7F_J(J = 1~4) emissions of Eu~(3+) ion besides the classic broad ~5d_1 → ~4f(~2F_(5/2),~2F_(7/2)) emissions of Ce~(3+) ion under near ultraviolet(UV) excitation.     

Short range order transformation and magnetostriction of Fe83Ga17 ribbons

The relationship between magnetostriction and structure of melt-spun Fe 83 Ga 17 ribbons are investigated by XRD and M¨ossbauer spectrum technique(MS).As the heat-treatment temperature increases from 650℃ to 800℃,the magnetostriction coefficient of Fe 83 Ga 17 ribbon first increases and then decreases.The largest magnetostriction coefficient(578.4 ppm) is achieved in those specimens quenched at 750℃.According to the XRD and Mo¨ssbauer spectrum analysis,a small quantity of DO 3 phase is precipitated in Fe 83 Ga 17 ribbons when quenched from 650℃ and the DO 3 phase is gradually transformed into B2-like phase if quenched at higher temperature.However,both DO 3 and B2-like phases disappear when the temperature increases up to 800℃.From this point of view,B2-like phase might be beneficial to the enhancement of magnetostrictive properties of melt-spun ribbons.     

电场辅助溶解法实现玻璃表面金纳米粒子的形貌控制

贵金属纳米粒子由于其非常独特的光学特性和表面活性, 在光子学、 催化和生物标识等方面都有非常重要的应用. 采用离子溅射和后续热处理相结合的方法在玻璃表面形成了尺寸大约为60-80 nm的单分散的球形金纳米粒子. 在适当的温度条件下, 采用步进式增加的强直流电场, 实现了金纳米粒子的电场辅助溶解过程. 在玻璃表面的不同颜色区域, 初始球形的金纳米粒子溶解成月蚀状形貌. 结合不同颜色区域内金纳米粒子的表面等离子体共振吸收性质和扫描电镜照片, 研究了实验条件对金纳米粒子性质的影响. 结合电场辅助溶解实验过程中的电流-电压特性, 分析了金纳米粒子在强直流电场辅助下溶解的物理过程: 金粒子中动出的电子向阳极的隧穿过程作为开始, 随后是金阳离子向玻璃基体中的传输过程和阴极提供的电子与带有正电荷的金粒子相结合的过程. 详细讨论了电场辅助溶解法实现金纳米粒子形貌控制的物理机制.     

超声波的干涉实验

1、目的应用压电陶瓷产生超声波,就其干涉现象进行定性的和定量的研究。同时,熟悉电子仪器的使用方法,并测定超声波的波长和速度。 2、理论 (1)位移和波动如果一波数为k(如用波长λ表示则为(2π)/λ),角频率为ω(如用频率ν表示则为2πν)的平面波,从一振源向x方向传播时,在x处时刻t的位     

超低频、音频两用正弦波振荡器

学习交流电路的位相关系、感抗、容抗等基本概念,首先通过实验观察总结出其中的规律,然后进行理论的探讨,对理解和掌握这些概念是行之有效的方法。用两块演示用大电表观察交变电压和电流间的位相关系时,所用设备简单,现象直观、生动,但需要一个频率为1Hz左右的超低频电源;演示感抗、容抗与频率的关系时,需要频率可变而幅值一定的音频信号源。本文介绍一个利用F007通用型运算放大器配以很少的元件和简单的电源制成的超低频、音频两用正弦波振荡器,供作交流电