PNC—3型偏铌酸铅压电陶瓷高温性能的研究

(一) 偏铌酸铅压电陶瓷有着一些突出的特点,如低的Qm值(Qm<10)、单一的振动模式(Kt>>Kr)和较高的居里温度(Tc=570 C),在工业检测、医疗诊断与高温传感器方面有着十分广阔的应用前景。但是纯的偏铌酸铅,因高温铁电相在常温下是很不稳定的,因而要制备出具有压电性良好的偏铌酸铅压电陶瓷是比较困难的。为了制得可应用的偏铌酸铅压电陶瓷,大多采用Ba置换与添杂的方法来现实。Ba的置换能大大地提高材料的压电性能,但压电性能的稳定性随着Ba置换量的增加而急剧变坏。虽然以往曾有过一些改性偏铌酸铅陶瓷料材在使用,但工艺性差,不能制作稍大一…     

PMNT陶瓷材料的压电介电性能研究

本文研究了准同型相界处铌镁酸铅－钛酸铅陶瓷材料的介电压电性能,合适的组份和烧结,可使ＰＭＮＴ陶瓷材料具有较好的压电性能,ｄ３３达５４０ｐＣ／ＮＭ,ｋｔ达０．５０以上,观察了不同烧结工艺下陶瓷材料的微观结构,烧结时间过长不仅使晶粒尺寸变大,亦可造成晶粒快速生长,对化学组成和微观结构与压电性能的关系进行了讨论。     

高d_(31)、高 E_c 值压电陶瓷材料的研究

本工作研究了锆—钛—铌锌酸铅和锆—钛—铌锌—铌镍酸铅系压电陶瓷,同时研究了钡、锶和铋等元素置换铅以及工艺条件对压电性能的影响,获得了|d_(31)×E_c|值高达3.56×10~(-4)的压电陶瓷新材料.     

PLN—3型压电陶瓷材料组成对压电参数温度稳定性的影响

在适当的工艺条件下，改变铌锂锆钛酸铅（PLN）三元系压电陶瓷材料组成中的锆钛比，加取代改性物及外加改性添加物，获得了高温稳定的PLN－3型压电陶瓷材料。该材料常温性能优良，高温稳定性好，200℃时相对25℃时的性能参数变化较小，介电常数变化小于45％，谐振频率变化小于2．5％，机电耦合系数变化小于－3％。本文在大量实验的基础上叙述了PLN材料组成与材料压电参数温度稳定性的关系，并对其改性作用机理进行了探讨。     

改性偏铌酸铜压电陶瓷高温特性及应用

文章分析了ＰＮＣ－３型改性偏铌酸铅压电陶瓷的高温特性，并就其可能的应用进行了试验。ＰＮＣ－３型陶瓷具有高居里温度和低Ｑｍ特性，有强耦合系数和大的Ｋｔ／Ｋｐ比值，已成功地制成耐高温抗辐射的ＡＥ传感器和宽频带换能器等器件，并将其高温性能与美国Ｄ９２１５型高温ＡＥ传感器进行了比较。     

改性偏铌酸铅压电陶瓷高温特性及应用

文章分析了ＰＮＣ—３型改性偏铌酸铅压电陶瓷的高温特性，并就其可能的应用进行了试验．ＰＮＣ－３型陶瓷具有高居里温度（５６２℃）和低Ｑｍ特性，有强耦合系数和大的Ｋｔ／Ｋｐ比值．已成功地制成耐高温抗辐射的ＡＥ传感器和宽频带换能器等器件，并将其高温性能与美国Ｄ９２１５型高温ＡＥ传感器进行了比较．     

铌酸钾钠压电陶瓷制备工艺研究进展

压电陶瓷是一种具有力电转换效应的功能陶瓷，已被广泛应用于医疗、传感器、超声马达等领域。由于无铅压电陶瓷在制备过程中避免了铅挥发，属于环境友好型材料，成为目前国内外研究的重点。铌酸钾钠陶瓷是无铅压电陶瓷中电学性能较好的陶瓷之一，其电学性能在很大程度上受制备技术及其工艺的影响。固相烧结技术是目前铌酸钾钠陶瓷制备最成熟的技术。铌酸钾钠陶瓷制备过程主要包括粉体合成、压制成型和烧结成瓷三步。通过粉体合成工艺可制备出高织构化铌酸钾钠陶瓷的粉体模板，但存在不同程度的软团聚和硬团聚现象；压制成型可以制备出简单的陶瓷坯件，但受模具和辅助工具影响较大，精度低、结构简单、需二次加工、不适合批量生产。针对烧结过程中由高温导致的元素挥发不能被很好地抑制的问题，深入研究低温烧结、抑制钠钾元素挥发对铌酸钾钠陶瓷的优异制备有着深远意义。本文综述了近年来铌酸钾钠陶瓷固相烧结制备工艺的研究进展，对粉体合成、压制成型、烧结成瓷三步进行了系统的论述。通过分析粉体合成、压制成型和烧结制备工艺的优点与不足，重点讨论其对铌酸钾钠陶瓷微观组织和电学性能的影响机制，以期为制备高电学性能铌酸钾钠陶瓷提供参考，并为其在医学与工业领域的应用...     

PMN—PT透明光电陶瓷材料的特性及制备技术

以传统的光电材料铌酸锂晶体和透明光电陶瓷材料PLZT（镧改性的锆钛酸铅固熔体）作为比较，介绍了铌镁酸铅（PMN）-钛酸铅（PT）（简称PMN-PT）光电透明陶瓷的结构和性能优势，主要介绍了PMN-PT各种粉末的制备方法、烧结工艺方法及其各自的特点，同时对影响陶瓷透明的因素和基于该材料的器件和应用进行了简要介绍。     

一种新型的压电材料参数的精确表征方法

针对压电材料精确表征问题,本文提出了一种包含材料损耗特性,基于模拟退火(Simulated Annealing,SA)优化算法的压电材料新型表征方法.并采用提出的新型表征方法对厚度振动模式下的高损耗偏铌酸铅压电陶瓷和l-3型压电复合材料样品的材料特性进行了研究,样品电子阻抗共振特性的理论优化结果与实际测量值准确拟合,表明该方法能够精确表征具有损耗特性压电材料参数.     

PZN-PZT压电陶瓷高温石墨还原行为研究

为研制具有超大位移量的 Ｒ Ａ Ｉ Ｎ Ｂ Ｏ Ｗ 新型压电微位移驱动器， 对制备该器件所用铌锌酸铅锆钛酸铅（ Ｐ Ｚ Ｎ Ｐ Ｚ Ｔ） 压电陶瓷材料的还原行为进行了初步研究， 观察到还原样品断口上呈现出清晰的多层层次结构采用 Ｓ Ｅ Ｍ、 Ｘ Ｒ Ｄ 和电导率测量等研究方法， 研究了还原样品各层次的断口形貌、物相组成和导电类型， 对 Ｐ Ｚ Ｎ Ｐ Ｚ Ｔ 压电陶瓷材料在高温下被石墨还原的过程和机理作了初步解释研究表明还原反应是按照先晶界后晶粒的顺序进行， 各层的导电类型随还原程度由浅到深呈现出绝缘体型半导体型金属型的变化规律， 对于轻度还原层， 仍保持着初始的固溶体晶相结构， 相应地对深度还原层， 初始晶相结构已被破坏， 由分解的复相所构成     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.