超声红外热像技术及其在无损评价中的应用

本介绍在光热红外检测的基础上发展的超声红外热像技术。该技术利用超声脉冲作为激发源，当超声脉冲在试样上传播的过程中遇到裂纹等缺陷时，缺陷引起超声附加衰减而局部升温。利用红外照相机获取试样表面的温度分布，可显示裂纹等缺陷。超声红外热像技术发挥了超声和红外技术的优点，可实时地检测裂纹等缺陷，在无损评价和检测中有广泛应用。  

稀土配合物掺杂凝胶的原位光声光谱研究及其共发光效应

采用溶胶-凝胶方法,制备了Ln(Sal)3·H2O(Ln3 :La3 ,Nd3 ,Tb3 ;Sal:水杨酸)稀土配合物掺杂的二氧化硅凝胶样品.首次采用光声光谱对稀土配合物在凝胶中的形成进行研究.结果表明,经110℃热处理后,Tb3 ,La3 和Nd3 配合物掺杂的凝胶样品在配体吸收处的光声强度依次明显增强;而对仅在室温陈化、干燥的湿凝胶样品,其配体吸收处的光声强度几乎完全相同.研究发现,未经适当的热处理过程凝胶样品中稀土配合物尚不能形成.结合荧光光谱,分析了凝胶中稀土离子配位环境的变化和稀土配合物的形成.首次发现了稀土芳香羧酸配合物掺杂凝胶的共发光效应,考察Tb0.8Gd0.2(Sal)3·H2O和Tb0.8Nd0.2(sal)2·H2PO配合物掺杂的凝胶样品,发现Gd3 离子的引入了增强了凝胶样品中Tb3 的发光效率,而Nd3 离子的引入明显减弱了凝胶中Tb3 的发光,并对共发光效应可能的机理进行了讨论.  

纳米SrTiO3的光声光谱研究

利用光声光谱技术对不同退火温度的纳米SrTiO₃粉末进行了研究．结果表明，纳米SrTiO₃粉末随退火温度升高，吸收边红移，说明能隙变窄，这与颗粒长大、晶格参数减小有关．在700nm附近出现的宽吸收带是由氧缺位俘获的电子在缺陷附加能级上的跃迁所产生的，其变化趋势强烈地依赖于颗粒尺寸  

a-Si:H和a-SiNx:H薄膜中的缺陷以及载流子的非辐射复合

应用红外光谱仪、分光光度计、光声谱仪和正电子湮没寿命谱仪,从不同的角度,研究a-Si:H和a-SiN_x:H薄膜中的成分、缺陷以及光生载流子的非辐射复合。  

扫描光声显微镜

本文简单叙述了扫描光声显微镜的原理、应用、发展以及我们现阶段的研制成果,光声信号可以用振幅或相位接收的方式成象,分辨率达到4.5μm,从已获得叉指换能器,集成电路以及材料亚表面结构等样品的光声象可以说明这种显微镜技术在固体物理、材料科学,甚至医学上均具有重要的应用前景。  

光衍射法观测叉指换能器在石英晶体中激发的各种声波

利用声光相互作用所引起的光衍射现象,观测了叉指换能器在石英晶体上激发的各种声波及其倒速度图。着重研究了z-切割石英晶体表面、沿y方向激发表面声波的叉指换能器在这个样品上激发的各种表面声波和体声波。对观察到的不同于瑞利波形式的表面声波进行了探讨,并说明这类波的特性值得进一步研究。  

Calculation of electromechanical coupling coefficient of Lamb waves in multilayered plates

Two methods have been always used to calculate the electromechanical coupling coefficient of a Lamb wave in a multilayered plate: one is an approximate method using the acoustic velocity difference under different electric boundary conditions and the other is the Green's function method. The Green's function method is more accurate but more complicated, because an 8N-order matrix is used for calculating the electromechanical coupling coefficient of the Lamb wave in an N-layered plate, which induces great computation loads and some calculation deviations. In this paper, a transfer matrix method is used for calculating the electromechanical coupling coefficient of Lamb waves in a multilayered plate, in which only an 8-order matrix is needed regardless of the number of layers of the plate. The results show that the transfer matrix method can obtain the same accuracy as those by the Green's function method, but the computation load and deviation are greatly decreased by avoiding the use of a high order matrix used in the Green's function method.  

A dynamical model of subharmonic generation in ultrasonic infrared thermography

Subharmonics are often observed in ultrasonic infrared thermography (UIR) system as samples are excited by ultrasonic transducers, and it is testified that, as the subharmonics appear, the detectability of cracks or defects in the sample is greatly enhanced in the UIR system. A dynamical model to explore the generation mechanism of the subharmonics and simulate the sample motion excited by an ultrasonic transducer in the UIR system is presented in this paper. In the model, the sample is continuously impacted by the transducer as the transducer is pushed to the sample by a constant force, in which the sample is simplified as a damped oscillator and the transducer is simplified as an active oscillator with constant frequency and amplitude. The impact process is also taken into account, in which the acting force is assumed to vary linearly during the impact process. A stable waveform of subharmonics in the sample can be obtained in appropriate conditions.  

Enthalpy and conformational volume changes of mammalian oxy-hemoglobins investigated by pulsed photoacoustic calorimetry

Enthalpy and conformational volume changes induced by laser photo-dissociation reactions of mammalian oxy-hemoglobin, such as human, bovine, pig, horse and rabbit oxy-hemoglobins, are investigated by pulsed photoacoustic calorimetry. Generally, the response time of the photoacoustic calorimetry is restricted by the width of the laser pulse and the bandwidth of the acoustic detector. Considering the time window of the experimental system, the enthalpy and conformational volume changes detected should be caused by the tertiary relaxation of the heme proteins. In order to calculate the enthalpy and conformational volume changes, the quantum yields of the photo-dissociation products of oxy-hemoglobins must be measured and taken into account. Finally, the enthalpy and conformational volume changes of the oxy-hemoglobins connected with the tertiary relaxation are obtained, which show that for all measured mammalian oxy-hemoglobins the values of enthalpy changes are in the range of 30.0-46.8 kcal/mol and volume changes are of 2.3-7.8 ml/mol although the quantum yields for the different species may have much bigger differences. A possible explanation of the results is presented.  

Performance optimization of plate-mode sensors with bi-layered structure

The acoustic characteristics of plate-mode sensors with bi-layered structures composed of a piezoelectric film and a non-piezoelectric substrate are studied by numerical calculations using the transfer matrix method. Performances of the sensors can be evaluated based on the theoretical calculations of the dispersion curves, electromechanical coupling coefficients and sensitivities of the plate-mode sensors with a bi-layered structure. In order to obtain the optimized operating conditions of the sensors, the operating mode, frequency and the ratios of thickness of piezoelectric film to that of the substrate are evaluated when the sensors are applied in gas and/or liquid conditions.