“高性能片式压电陶瓷变压器的研究与开发”课题通过验收

近日，由西安康鸿信息技术股份有限公司和清华大学共同承担的国家863计划特种功能材料主题“高性能片式压电陶瓷变压器的研究与开发”课题在北京通过验收。     

新型陶瓷的开发及其特殊应用

综述了陶瓷的基本性质，新型陶瓷的开发及其特殊应用。     

铁电陶瓷颗粒填充压电复合材料的微结构与性能

采用模塑工艺制备了含铁电陶瓷PZT颗粒填充的PZT／P（VDF－TrFE）压电复合材料,用差热分析研究并确定了复合材料的固化工艺参数,测试并研究了压电复合材料的电性能和显微结构,结果表明,随着PZT质量百分比的增加,电性能参数逐渐增大,当PZT的质量百分比达到85％时,介电常数ε和压电常数d33值最大,铁电陶瓷颗粒分布均匀,当PZT含量较低时,两相材料界面结合良好,而当PZT含量达到90％时,气孔则明显增多,这就是导致复合材料的介电常数和压电常数在PZT高含量区下降的主要原因。     

陶瓷工业热工设备CAD系统开发及应用（Ⅵ）：钢架结构设计计算

本文介绍钢架结构设计计算系统所用主要设计计算公式、数据库结构及数据管理、主要程序结构设计等．     

陶瓷工业热工设备CAD系统开发及应用（VⅡ）———：工程投资与材料概算

本文介绍了工程投资与材料概算子系统具有的功能、主要设计计算公式、数据库结构及数据管理、编程技巧等。     

压电陶瓷/聚氨酯智能阻尼复合材料的制备与表征

以热塑性聚氨酯弹性体为基材,压电陶瓷粉和导电石墨为功能相,制备了压电陶瓷/聚氨酯智能阻尼复合材料,并对其结构性能进行表征分析。结果表明,压电陶瓷粉添加质量份为20和40时,能得到具有较好分散性的压电陶瓷/聚氨酯智能阻尼复合材料;当压电陶瓷粉添加质量份为40时,tgδ峰值达到最大,说明制得的复合材料具有良好的阻尼性能;相对介电常数随着压电陶瓷粉添加量的增加而增加,当压电陶瓷粉质量份为40时,相对介电常数为15.06。热性能测定结果表明,加入压电陶瓷粉后,复合材料的软化点明显提高。     

谈新型驱动装置压电陶瓷电机的应用和发展

压电陶瓷电机是利用压电陶瓷材料激发超声波实现驱动的一种新型电机,具有低速下大力矩输出、无电磁干扰、静音操作、保持力矩大、响应速度快、结构简单等特点。它打破了由电磁效应获得转速和扭矩的传统电机的概念,是当代国内外热门的高新技术之一受到关注。针对压电陶瓷电机的市场潜力巨大,分析了压电陶瓷电机的性能优势,介绍了压电陶瓷电机的结构形式与工作原理,研究了压电陶瓷电机的类型和产品的技术特点。     

压电陶瓷变压器材料PMMN-PZT的研究

研究了一种四元系压电陶瓷变压器材料PMMN -PZT。XRD分析证明 ,采用二步法预合成的PMMN -PZT粉料不如一步法 ;SEM分析进一步证实了一步法预合成的粉料能制成性能更好的陶瓷样品。造粒工艺对陶瓷样品的显微结构和压电性能也有重要的影响。最后制得了性能较好的PMMN -PZT压电陶瓷材料 ,其Kp=0 .5 18,Qm=3887,tanδ =0 .71% ,εT3 3 /ε0 =70 1,d3 3 =2 0 3,基本上能满足压电变压器的要求     

压电陶瓷/NBR复合材料压电与吸声性能研究

以NBR为基体材料,以压电陶瓷为功能相制备压电橡胶复合材料,并对其压电与吸声性能进行研究.结果表明,复合材料的压电常数(d33)随压电陶瓷用量的增大而增大,当压电陶瓷用量为5210份时,d33达到3.1×10-11C·N-1,并随着极化时间的延长而增大,随着极化温度的升高先增大后减小,且最佳极化时间为25min,最佳极化温度为80℃.压电橡胶复合材料的吸声因数在2～3 kHz的频率内随着复合材料压电常数的增大而增大,碳纤维的加入使复合材料内部形成了一定的导电网络,提高了复合材料的吸声因数.     

压电陶瓷在结构振动及声辐射有源控制中的新应用

介绍了压电陶瓷的新应用──作为有源振动、噪声控制中的执行元件和传感器，并讨论了对该材料的性能要求、参数选择以及应用实例。     

Progress in study on new piezoelectric ceramics with high Kt

The first paper¹ which was presented on ISAF'90 reported the high K_t performance of the PZT ceramics with the compositions situated near the ferroelectric(F) and antiferroelectric(AF) phase boundary. In this paper, other two systems PSZT and PLZT ceramics also on F-AF phase boundary were studied and the same character which shows the high K_t for the composition situated near the phase boundary has been examined. The highest K_t is up to 0.56. In case of favorable poling condition and additives, even higher value of K_t can be expected. The possible reasons for this character are discussed.     

新型机械设备在我国陶瓷工业中的应用

陶瓷机械设备在整个陶瓷工业生产中占有非常重要的地位，因此陶瓷设备的研究也越来越受到人们的重视，先进的陶瓷生产设备也层出不穷。目前，一些新型的陶瓷机械设备已经开始在我国的陶瓷工业中得到应用．包括陶瓷工业的原料粉磨机械设备、脱水及干燥设备、成形设备、修坯施釉以及陶瓷精加工机械设备，这些设备大大促进了我国陶瓷工业生产水平的提高。     

Crack deflection in piezoelectric ceramics

Crack deflection can occur in a specimen subject to a stress gradient of high tensile stresses near the surface which decreases with increasing depth. Such a stress gradient can be induced by strain incompatibilities. These can for example arise under electric fields between the electroded and external regions of a piezoelectric material. Such incompatibilities have been realized in thin rectangular model specimens from PZT-piezoelectric ceramics with top and bottom partial electrodes. Under an electric field, controlled crack propagation has been observed in-situ in an optical microscope. The crack paths are reproducible with very high accuracy. Small electrode widths lead to straight cracks with two transitions between stable and unstable crack growth, while large electrode widths result in curved cracks with four transitions. Poling the specimen prior to the experiment alters the crack path and introduces an anisotropy in the R-curve behavior as well as in the achievable strain mismatch. The crack path selection and crack length can be explained by means of a qualitative fracture mechanics analysis.     

A new poling method for piezoelectric ceramics with thick film

The poling process plays an important role in the interaction with the crystal structure in a number of ways to obtain ferroelectricity and piezoelectricity. However, many factors influence the effectiveness of poling process. In the conventional poling process, electric field is applied to the ceramics via the metal electrode. The drawback of conventional poling method is the occasional occurrence of fracture and crack due to subjection to high electric voltage. In this study, a new poling method by using ITO (Indium Tin Oxide) glass for piezoelectric ceramics with thick film is proposed. The constraint of applying high electric field has been overcome and is verified with the use of energy level concept. As compared to conventional method, using ITO for poling will preserve better performance via various experimental testing.     

Stresses developed in reaction-bonded ceramics

A physical model is presented that predicts the stress distribution created in a particle during its reaction with a surrounding reactant to form a uniform layer of reaction product on its surface, when the reaction involves a volume change. The results of the model are applied specifically to the case of silicon reacting with nitrogen to form Si₃N₄. The model predicts the generation of a high, tensile hydrostatic stress in the Si core as well as high tensile radial stress and compressive tangential stress in the nitride layer. Although the model is restricted to elastic deformation only and therefore predicts unrealistically high stresses in some cases, the results are anyway of relevance in the consideration of possible non-elastic processes such as creep and fracture and also in assessing the possible effect of stress on the reaction equilibrium. It is predicted that the nitride reaction layer would fracture during the nitridation process. A second model is also presented predicting the residual stresses arising during cooling of a partially reacted particle as a result of the difference in thermal expansion of the reactant core and the reaction product layer. In the case of the reaction of silicon to silicon nitride these thermal expansion mismatch stresses are significant but small compared to the stresses due to the chemical reaction. ©     

Preparation of tritium breeding Li2TiO3 ceramic pebbles via newly developed piezoelectric micro-droplet jetting

Wet methods as an emerging technique for the preparation of millimeter-sized tritium breeding ceramic pebbles, but the imposed air pressure as the driving forces to extrude slurry droplets are fluctuating during the reciprocating extrusion process, which caused a slight inconsistency in pebble sizes. In this study, a piezoelectric micro-droplet jetting approach was proposed by introducing a piezo-driven valve and modifying the slurry barrel mechanism to realize the air pressure invariable. A self-developed piezoelectric micro-droplet jetting device was successfully utilized to prepare Li₂TiO₃ green pebbles with coefficients of variation being lower than 2.7%. The size of the green pebbles could be precisely controlled in the range of 0.88–1.37 mm by manipulating the nozzle diameter, the air pressure, and the jetting time. The pebbles sintered at 1000°C for 3 h possessed a small grain size of ∼5.9 μm, a satisfied relative density of ∼84.8% T.D., and a high crush load of ∼25.7 N, implying the prepared pebbles could be used as a promising solid tritium breeding material in fusion reactors. These findings are anticipated to provide new opportunities for the highly efficient preparation of size-controllable tritium breeding ceramic pebbles.