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稀土荧光特性与温度关系 总被引:1,自引:0,他引:1
为研究稀土荧光特性与温度关系,从典型稀土材料的能级结构出发,根据激发态多能级间的玻尔兹曼热平衡分布理论,对激发态能级的粒子数分布情况与温度关系进行研究.发现随着温度的上升稀土发光荧光寿命变短,激发态高能级辐射荧光比例增大;而荧光强度由于受到非辐射跃迁系数和能量传递效率的双重影响将会呈现先上升后下降的变化.以钒磷酸钇铕Y(P,V)O4∶Eu3+荧光粉材料为例进行实验研究,测量了95K到510K温度范围内Y(P,V)O4∶Eu3+荧光材料在395nm紫外光激励下所发荧光的荧光寿命、荧光强度和荧光分支比随温度的变化规律,实验结果与理论相符合. 相似文献
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发展了一种非接触式稀土荧光自参比温度传感器,即将有机稀土配合物K[Yb(Az)4]包埋在苯乙烯-甲基丙烯酸甲酯共聚物中,并附着在洁净的石英片上制备得到了温度传感薄膜Yb@PSMM。通过研究不同温度下Yb3+的荧光发射光谱,利用其在近红外波段荧光性质随温度变化的规律,开发了一种比率型稀土荧光温度传感方法,其原理是通过不同温度下Yb3+的荧光发射光谱的形状随温度的变化,结合在不同温度下Yb3+的核外电子在外层Stark劈裂亚能级上的分布符合Boltzmann分布律的特点,利用其近红外荧光发射光谱中900 nm~990 nm波长范围内与990~1 150 nm波长范围内的积分峰面积比的自然对数与温度的倒数呈现的线性关系作为温度测量的标准曲线,实现了-195~105 ℃范围内的温度精确测量。经考察,该发光温度传感器在0 ℃附近的温度测量分辨率达到了0.1 ℃。与已报道的发光温度传感器相比,提出的新型温度传感器具有如下几个优势:其一,所选用的发光材料的Stokes位移大于500 nm,有效地避免了环境背景干扰;其二,由于采用荧光积分峰面积而非荧光强度作为考察对象,大大减小了测量中由于仪器或测量次数较少引入的随机误差;其三,采用同一发光材料的荧光发射光谱中两个荧光峰面积的比值,相当于在体系中引入了自参比,有效避免了由于荧光材料的浓度、几何构型以及光源强度等外界因素变化对测量结果产生的影响;其四,利用稀土发光材料作为温度传感材料,可以利用其荧光寿命长、单色性好、强度高的特点;其五,温度传感膜本身不溶于水,也不在水中扩散,便于直接测量原位温度变化;其六,Yb3+的发光位于900~1 150 nm的近红外波长范围,而这个波段的荧光具有较好的穿透性使得该温度传感器有望在复杂体系的温度传感、成像等领域发挥重要作用。在实际测量的装置中,通过调整光路使得辐照在样品上的入射光斑大小仅约为1 mm2,并将Yb@PSMM固体膜样品的放置方向与入射激发光的夹角设置为225°,从而规避了入射光源的反射光对检测器的影响,而具有较好穿透能力的近红外荧光几乎不受影响,从而进一步确保了该温度传感器的测量结果。 相似文献
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HE Peng WU Xiao-chuan AN Kang DENG Gang WANG Xing ZHOU Zhong-xing WEI Biao FENG Peng 《光谱学与光谱分析》2018,38(12):3929-3933
X射线光子计数探测器是多能谱CT成像技术的核心,其通过能量阈值可以选择记录不同能量的X射线光子,有助于分析不同材质的物理特性。利用搭建的基于光子计数探测器的多能谱CT系统,开展高纯度金属材料K-edge特性识别实验研究。通过设置探测器的不同能量阈值,在不同能量范围获取金属材料投影图像,利用投影图像灰度信息分析不同能量X射线的衰减特性,以识别金属材料K-edge特性。最终实验结果表明,基于光子计数探测器的X射线能谱CT系统,能够识别金属材料与特定能量X射线光子发生相互作用所表现出的K-edge特性。通过计算K-edge特征峰能量阈值与材料K-edge理论能量值之间的线性对应关系,对光子计数探测器的能量阈值进行了标定。 相似文献
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针对传统的X射线CT系统因采用积分探测器难于鉴别材质的关键技术问题,基于MARS系统的X射线能谱CT,开展了X射线能谱K-edge特性的CT成像技术研究。通过对单一材质和混(复)合材质组成的物理模型的多个X射线能量段进行CT断层扫描,获得了材质的K-edge特性曲线,以此重建出了材质的CT图像。借助材质K-edge特性的CT断层图像,可以进行材质的鉴别分析或进行更多的材质认知信息的分析研究。与传统的X射线CT技术相比较,它可以提供更为丰富的X射线衰减信息。 相似文献
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建立了全息光栅光谱烧孔技术中,系统的存储密度,读出信噪比和材料特性,读写条件关系的数理模型,计算机模拟定量分析得到了最佳材料特参量空间。研究表明,全息光栅光谱烧孔技术可放宽系统对材料特性的要求,将为烧孔材料研究提供新的理论依据。 相似文献
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Lijun Li Yingzhou Wang Ke Gong 《International Journal of Infrared and Millimeter Waves》1998,19(9):1293-1298
Millimeter waves is expected to be used for indoor broadband wireless access for its rich frequency spectrum resources. To implement the indoor MMW wireless system, it is important to know its propagation characteristics in building, which are governed by the transmission properties of construction materials. This paper focuses on the measurements of reflection characteristics and refractive indices of some interior construction materials (such as glass, brick, plasterboard, silencing board, etc.) at Ka–band. The free–space reflection method was used to measure the reflection and transmission coefficients. Then the complex refractive indices of various materials could be calculated by using the Fresnel's formula. 相似文献
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Magnetorheological (MR) materials show variations in their rheological properties when subjected to varying magnetic fields. They have quick time response, in the order of milliseconds, and thus are potentially applicable to structures and devices when a tunable system response is required. When incorporated into an adaptive structural system, they can yield higher variations in the dynamic response of the structure. This study presents a detailed analysis of dynamic characteristics of adaptive beam based on MR materials. The relationship between the magnetic field and the complex shear modulus of MR materials in the pre-yield regime is researched using oscillatory rheometry techniques. A structural dynamic modelling approach is discussed and vibration characteristics of MR adaptive structures are predicted for different magnetic field levels. In addition to the model predictions, actual MR adaptive beam is fabricated and tested. Both studies illustrate the vibration minimization capabilities of the MR adaptive beam at different magnetic field levels. 相似文献
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阐述教材是提高教学质量重要且必备的条件之一,回顾我国分析化学工作者编写教材的实践历程,提出编写教材应体现"注重学科基础、关注学科前沿、适当拓展学科交叉,体现知识体系与认知规律相结合"的特点。 相似文献
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纳米银掺杂的高效率全息聚合物分散液晶光栅制备 总被引:3,自引:0,他引:3
报道了一种基于掺杂纳米银聚合物分散液晶(PDLC)材料的高衍射率全息电控光栅的制备及特性。通过在原有聚合物分散液晶材料体系中添加适量的纳米银颗粒以制备体全息光栅,实验研究了掺杂不同质量比的纳米银颗粒对全息聚合物分散液晶(H-PDLC)体光栅的衍射效率、驱动阈值电压、响应时间的影响。实验结果表明,通过掺杂纳米银材料,能够优化聚合物和液晶两相分离结构,使聚合物与液晶分离更加彻底,显著提高H-PDLC体光栅的一级衍射效率,同时能改善体光栅的电光特性,缩短响应时间。初步分析表明,由于纳米银颗粒的表面等离子体效应和体系折射率匹配的优化改善了H-PDLC光栅的特性。 相似文献
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《Ultrasonics》1987,25(4):195-203
This Paper considers quantitative acoustic emission (AE) techniques with real and simulated sources as powerful tools for investigating failure processes in composite materials. Using a simulated source acting as a point source and one or more point receivers whose characteristics are known, one has the necessary components of a materials and structure testing system. Examples are shown in which a composite material's attenuation and wavespeeds can be determined as a function of frequency and propagation direction. It is demonstrated that this testing procedure permits the ultrasonic characterization of ultra-attenuative and irregular shaped, high performance composite materials. The principles of quantitative AE source characterization procedures are also reviewed and applications are demonstrated in which the time characteristics of several simple sources are recovered. 相似文献
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O. V. Malyshkina M. Yu. Gavalyan G. S. Shishkov I. A. Kaplunov A. I. Kolesnikov N. V. Aidinyan 《Physics of the Solid State》2016,58(11):2367-2372
The study of the thermal characteristics of bulk nonferroelectric materials with low heat conductivity coefficient by the pyroelectrical rectangular thermal wave is shown to need the solution of the problem of the thermal conductivity for a three-layer system. The thermal characteristics of a paratellurite crystal with various crystallographic directions were studied. The heat conductivity coefficient is found to depend on the crystallographic direction. 相似文献