RE2O3-Al2O3-SiO2玻璃连接氮化硅合成复相陶瓷的研究

采用Ｙ２Ｏ３－Ａｌ２Ｏ３－ＳｉＯ２－Ｘ稀土玻璃进行氮化硅复相陶瓷的连接。用四点弯曲方法测定不同连接工艺下的连接强度。并对连接界面进行ＳＥＭ、ＥＰＭＡ和ＸＲＤ分析。液相钎料玻璃在界面上与氮化硅反应，形成氮化硅／Ｓｉ２Ｎ２Ｏ／Ｙ（Ｌａ）－Ｓｉａｌｏｎ玻璃／Ｙ（Ｌａ）－Ｓｉａｌｏ玻璃的梯度层界面。接头强度随着保温时间、妆温度的增加，先增后。 在ＹＡＳ钎料中添加氧化镧，可以提高接头的高温强度。ＬａＹＯ３的     

DECAY RATE OF SAINT-VENANT END EFFECTS FOR PLANE DEFORMATIONS OF PIEZOELECTRIC-PIEZOMAGNETIC SANDWICH STRUCTURES

This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the same material properties or reversely. The end of the sandwich structure is subjected to a set of self-equilibrated magneto-electro-elastic loads. The upper and lower surfaces of the sandwich structure axe mechanically free, electrically open or shorted as well as magnetically open or shorted. Firstly the constitutive equations of PE mate- rials and PM materials for plane strain are given and normalized. Secondly, the simplified state space approach is employed to arrange the constitutive equations into differential equations in a matrix form. Finally, by using the transfer matrix method, the characteristic equations for eigen- values or decay rates axe derived. Based on the obtained characteristic equations, the decay rates for the PE-PM-PE and PM-PE-PM sandwich structures are calculated. The influences of the electromagnetic boundary conditions, material properties of PE layers and volume fraction on the decay rates are discussed in detail.     

POLYNOMIAL SOLUTIONS TO PIEZOELECTRIC BEAMS (Ⅰ)——SEVERAL EXACT SOLUTIONS

IntroductionDue to its excellent piezoelectric properties,composites made of piezoelectric materialsare found widespread applications and attracted more attentions[1-10].Because of materialanisotropy and couplingbetween mechanical deformation and electric…     

金属基陶瓷复合材料的激光热冲击破坏效应

 研究了激光热冲击条件下静态受拉Sic颗粒增强6061铝合金材料的热断裂行为。热冲击用的激光束的脉宽分别为1.0ms和250μs, 激光束辐照在缺口的根部附近。对于热冲击下裂纹的产生及扩展进行细致的宏、微观观察,发现裂纹的产生和扩展的机制是不相同的。     

THEORY AND APPLICATIONS OF FREQUENCYMETRIC TITRATION

Theory on frequencymetric titration has been proposed based on equivalent circuit of piezoelectric quartz crystal (PQC) in liquid and oscillation equation of TTL-PQC oscillator, and the theoretical equation derived representing the frequency shift with respect to the solution conductivity. Practical examples of various types of titration are given in this paper.     

Direct Synthesis of Ceramic Membranes by Sol-Gel Process

Ceramic ultrafiltration and nanofiltration membranes (TiO₂) are prepared by sol-gel route using a special arrangement which allows the reaction of the reactants directly in the pores of a tubular Al₂O₃ support or on its surface, respectively. By this direct synthesis the number of technological steps can be reduced which is the main advantage of the method. The produced layers are well joined with the Al₂O₃ support and the reaction can be adjusted by various technological parameters. The dried and sintered coatings are characterized by X-Ray diffraction, FESEM and AFM. In addition, pore size distribution and filtration properties are investigated and discussed.     

利用光折变晶体的电光、压电效应实现2×2光开关的原理

讨论了在光折变LiNbO3晶体中建立电场控制的 2× 2直通交换开关的原理设计方案。通过控制读出光栅时外加电场的大小使读出光满足或偏离布拉格条件 ,从而控制衍射效率为 1或 0 ,实现开关的交换和直通操作。全面考虑了电场作用下晶体的压电和电光效应 ,基于衍射效率公式和光栅的布拉格条件 ,给出了为获得最佳衍射效率比时外加电场及写入光束比与记录角度间的关系曲线     

Vibrations of a piezoceramic cylinder subject to nonstationary electric excitation

The paper proposes a method to solve the problem of vibrations of a radially polarized piezoelectric cylinder subject to nonstationary electric excitation. The dynamic electromechanical state of the cylinder is analyzed. The time-dependences of electric and mechanical characteristics are plotted. The distribution of these characteristics over the cross section of a short cylinder is examined. The region of end disturbances in a long cylinder is identified __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 3, pp. 73–79, March 2007.     

Flexural vibration analyses of piezoelectric ceramic tubes with mass loads in ultrasonic actuators

Based on Timoshenko beam model, a theoretical model of radially polarized piezoelectric ceramic tubes is investigated. In the model, the piezoelectric effects are considered, and the shear correction factor is introduced which reveals effects of the size of the cross-section and Poisson’s ratio. Based on the model, the particular attentions are devoted to effects of the boundary conditions at two ends on flexural resonance frequencies of the piezoelectric ceramic tubes. Changing the sizes of the tubes and the mass loads at both free ends, the variations of the flexural resonance frequencies of free–free piezoelectric ceramic tubes are calculated theoretically. Besides, the flexural resonance frequencies of the piezoelectric ceramic tube cantilevers with mass loads at one free end are also investigated theoretically. To verify accuracy of the theoretical mode, the flexural resonance frequencies for different lengths of the piezoelectric ceramic tubes and different loaded masses are measured experimentally. The theoretical results agree well with the experimental measurement, which demonstrates that the model is accurate for analyzing the flexural resonance frequencies of the piezoelectric ceramic tubes with mass loads.     

Study on the radial composite piezoelectric ceramic transducer in radial vibration

A new type of radial composite piezoelectric transducer in radial vibration is developed and analyzed. The radial composite transducer consists of a piezoelectric ceramic thin ring polarized in the thickness direction and a metal thin circular ring. They are connected together and excited to vibrate in the radial direction. The radial vibrations of a piezoelectric ceramic thin ring and a metal thin circular ring are analyzed, respectively. Their radial electro-mechanical equivalent circuits are obtained. Based on the electro-mechanical equivalent circuits and using the boundary conditions between the piezoelectric ceramic thin ring and the metal thin circular ring in the radial direction, the electro-mechanical equivalent circuit of the radial composite piezoelectric transducer is derived out and the resonance frequency equation is obtained. The relationship between the resonance frequency and the geometrical dimensions of the transducer is analyzed. Some radial composite piezoelectric transducers are designed and manufactured. The resonance frequencies and the anti-resonance frequencies, the electro-mechanical equivalent circuit parameters are measured. The effective electro-mechanical coupling coefficient and the mechanical quality factor are calculated. It is illustrated that the measured radial resonance frequencies are in good agreement with the theoretical results from the resonance frequency equation.