超声辐照醋酸乙烯酯的乳液聚合

将超声波引入醋酸乙烯酯(VAc)乳液聚合,实现了醋酸乙烯酯的低温快速聚合。考察了超声功率、乳化剂十二烷基硫酸钠(SDS)和引发剂过硫酸钾(KPS)的浓度对聚合反应的影响。实验结果表明,在VAc 7 mL,H2O 63 mL,w(SDS)1%,c(KPS)4 mmol.L-1,900 W的聚合反应条件下,于25℃反应30 min,VAc的转化率高于80%。     

弹性介质形变对超声波传播特性影响的实验研究

弹性介质在受到外力的情况下会发生弹性形变。在弹性介质质量一定的情况下,此弹性形变会使弹性介质的体积和密度伴随着改变。对于超声波而言,在除了弹性介质本身的其他因素不变的情况下,弹性介质体积和密度的改变将会影响到超声波的传播特性。通过理论分析得出超声波幅值和相位随弹性琼脂应力变化的关系。以琼脂作为实验模型,检测琼脂在形变时超声波的信号参数,并且通过实验数据,最终得到二者的曲线和标定公式。此结果有利于今后在介质应力检测及超声波检测技术等方面的深入研究。     

Evaluation of short term–high intensity thermal degradation of graphite fiber reinforced laminates via ultrasonic spectroscopy

In certain fire situations, a structural or load‐bearing polymer matrix composite (PMC) may be exposed to excessive thermal loads that degrade the matrix. In this paper, we report the results of a study to assess the utility of ultrasonic spectroscopy as a means of assessing the residual physical and mechanical characteristics of PMCs exposed to excessive thermal loads. We show that the measured power spectra of ultrasonic energy correlates with performance of graphite fiber epoxy matrix composites exposed to thermal degradation. Unidirectional composites were exposed to short term–high intensity thermal loads at one end of the specimen. Thus, inducing a thermal gradient along the length of the specimen. Simultaneous thermogravimetric analysis–differential scanning calorimetry (TGA/DSC) and Fourier transform infrared spectroscopy (FTIR) analysis of the aged specimens revealed a gradient in thermal degradation. The thermal loads induced substantial degradation of the composite. However, the amplitude of the power spectra is observed to increase gradually then sharply prior to its complete attenuation due to delaminations. Mode I fracture toughness tests correlate with the observed changes in the ultrasonic spectra. FTIR, TGA/DSC, fracture toughness, and ultrasonic spectral analysis all indicate the same critical temperature at which thermally induced damage sharply increased. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2601–2610, 1999     

轴类超声检测的波束扩散成像*

大型轴类工件安装完成后通常只能从其端面进行检测,危害性的裂纹类缺陷不易检出,针对上述问题,本文提出了轴类对象基于波束扩散的端面网格化超声检测层析成像方法,搭建了轴类超声检测试验平台,在端面对其内部的平底孔缺陷进行检测,基于波束扩散设计叠加算法进行数据处理,然后根据结果重构出代表每个深度内部信息的伪彩色横截面图像,以方便快速识别内部缺陷位置和范围。与常规方法对比得出,基于波束扩散的叠加算法处理数据成像质量更佳,提高缺陷检测灵敏度达到12dB以上。     

多层圆柱体锚固结构中超声导波频散特征的研究

超声导波无损检测技术因其高效和快捷的优点成为检测锚杆锚固质量的有效方法。但锚固锚杆结构中超声导波的多模态性、频散性与能量泄露导致完整的锚杆底端反射信号的获得具有不确定性。应用弹性动力学理论并采用全局矩阵法建立超声导波在多层圆柱体锚固结构中的频散方程的通用表达式,然后通过非线性外推法和二分法两步算法求解频散方程的精确解,解决了频散曲线的分类和相交等难题,获得了具有自主知识产权的求解多层圆柱体锚固结构频散曲线的程序。利用该程序计算了不同锚固锚杆结构的频散曲线,并与商用软件Disperse计算的结果吻合较好。同时用本程序计算了实验室有限锚固结构中的频散曲线,验证了低频导波在有限与无限结构中的巨大差异,而这一结构特征的频散特性Disperse并未给出相关算例。     

低温微量超声雾化声学系统

针对低温微量超声雾化声学系统中的关键部件单波长超声雾化喷嘴进行研究。首先基于等效电路原理和传输矩阵法分别建立了带中心孔换能器和带中心孔复合变幅杆的频率方程,并应用数学分析软件获得了准确的数值解,实现了超声雾化喷嘴的全谐振。然后,对其进行有限元动力学分析和振动特性测试,结果表明二者相对于设计频率25 kHz的偏差率在0.6%以内,且空载超声振幅达13.5μm。之后,应用流体仿真分析软件对砂轮-工件磨削区进行流场特性分析,结果表明低温微量超声雾化声学系统可以解决磨削区涡流现象的产生。最后,通过对该系统使用前后两种润滑方式的磨削结果进行测试发现：低温微量超声雾化润滑不仅切削液使用量少,而且可以避免工件表面出现烧伤和硬度降低。     

六面顶压机上常温高压超声测量的样品组装设计

 简要介绍了高压超声测试技术中样品组装的设计原则。设计了一套新的样品组装,并测量了纯Al和纯Cu在常温下的等温状态方程。实验结果表明,新的组装能够实现较理想的准静水压加载,同时也能够测试出良好的超声信号。分析了六面顶压机上常温超声测量的主要误差来源。     

多孔硅光致发光峰半峰全宽的压缩

硅发光对于在单一硅片上实现光电集成是至关重要的.目前已有的使硅产生发光的方法有:掺杂深能级杂质、掺稀土离子、多孔硅、纳米硅以及Si/SiO₂超晶格.声空化所引发的特殊的物理、化学环境为制备光致发光多孔硅薄膜提供了一条重要的途径.实验表明,声化学处理对于改善多孔硅的微结构,提高发光效率和发光稳定性都是一项非常有效的技术.超声波加强阳极电化学腐蚀制备发光多孔硅薄膜,比目前通用的常规方法制备的样品显示出更优良的性质.这种超声波的化学效应源于声空化,即腐蚀液中气泡的形成、生长和急剧崩溃.在多孔硅的腐蚀过程中,由于超声波的作用增加了孔中氢气泡的逸出比率和塌缩,有利于孔沿垂直方向的腐蚀,使多孔硅光致发光峰的半峰全宽压缩到了3.8nm.     

Investigation of Excess Thermo-Acoustic Behavior of Binary Liquid Mixture with Various Temperatures Using Ultrasonic Technique

Ultrasonic methods have been very fruitful in studying the physical properties of binary liquid combinations. In this present study, the thermoacoustic behavior of benzyl propionate with dimethyl sulfoxide (DMSO) is observed using ultrasound, density, and viscosity at different temperatures between 308 and 328 K with a phase of 10 °C. Benzyl propionate is a sweet-smelling liquid that is used in the botanical and fruit fragrance industries, as well as in the flavoring of organic products. DMSO is a dipolar aprotic, naturally soluble compound used for slow drug synthesis, device synthesis, and drug delivery to the body. Estimated values such as adiabatic compressibility, intermolecular free length, internal pressure, and free volume are determined from arbitrary ultrasonic velocity, density, and viscosity data. The same excess parameters of adiabatic compressibility, intermolecular free length, internal pressure, and free volume support finding the nature of the reaction. The sort of interactions has been accounted for utilizing these qualities. In the present work, benzyl propionate with dimethyl sulfoxide has been characterized by using ultrasonic waves and since this wave is a well-known tool for NDT, so the mixture is properly characterized. These thermoacoustic parameters with different concentrations of DMSO at different temperatures have been used to study the complex formation and binding through intermolecular forces.     

活性ZnO的制备及其表征

用传统沉淀法以超声波振荡方式制备出粒径约为32．Onm的六方晶型ZnO超细粉。其结构经IR和X-射线衍射表征,并测定了其粒径、比表面积和电学性质。