【作者】 刘雪燕；

【导师】 王春雷； 王成建；

【作者基本信息】 山东大学 ， 凝聚态物理， 2008， 博士

【摘要】 电触点作为电子器件的核心部件在生产和生活中应用非常广泛,而触点材料是制约触点性能的主要因素,世界工业发达国家都十分重视电接触材料的开发应用。在低压电器领域,研究和使用较多的Ag/CdO材料具有优良灭弧性能,但其致命缺点是产生有毒镉蒸气,欧盟已明确规定禁止有害物质镉在电子信息产品中使用。这就给电接触材料研发提出了新的挑战,发展一种类似或超越Ag/CdO性能的新型无毒触点材料具有重要的科学和工程意义。在取代Ag/CdO的触点材料研究中,Ag/SnO₂因综合性能好得到了大力发展,但Ag/SnO₂材料的极大弱点是:温升现象严重,塑性和延展性差导致加工性能差,国内外虽然对此进行了工艺改进,但都没有得到满意的解决方法。到目前为止,Ag/SnO₂替代Ag/CdO的工作仍未得到有效解决,国内外的研究人员一直在探索研制其它的新型电接触材料。为解决上述电接触材料领域存在的问题,我们课题组开展了新型电接触材料的研究工作,把银与具有类金属导电特性的陶瓷化合物进行复合,获得了新型优质电接触材料。主要发展制成了Ag/La₂NiO₄和Ag/LaFe_1-xNi_xO₃两系列复合导电陶瓷材料,其中陶瓷材料的添加量为8%-12%,这种复合触点材料具有良好加工性、抗烧蚀性以及稳定的化学性质。从根本上解决过去单一或混合氧化物材料与银复合制成的触点材料所不能解决的机械加工性差的问题。以陶瓷化合物为添加剂的方法突破了该领域一直沿用的以单一或混合氧化物为添加剂的瓶颈,为电接触材料研究提供了新的途径,拓宽了电接触材料的研究领域,为得到综合性能更佳的新型电接触材料提供了一种新思路。有关触点材料的性能测量与评估是触点材料研究中的另一个重要且极需解决的问题。在这方面开展研究是本论文的重要内容之一。电弧是有触点开关电器动作过程中必然发生的物理现象,是触点烧蚀、退化的最主要原因。利用这种电弧现象,可以很好地探测电弧燃烧和熄灭过程,从而了解触点的工作状态和工作质量。所以这是触点材料中的重要研究内容之一。本论文对触点电弧的燃烧和维持机制展开了系统的研究,测定和分析了电弧等离子体特性,掌握其运动规律,探讨了复合材料的电弧损耗机制。电弧烧蚀机制非常复杂,涵盖了很多方面的研究内容,综合比较多种等离子体诊断技术,非侵入式的等离子体光谱诊断最为适合。因此作者运用光谱分析方法对电弧等离子体特性进行了诊断,综合考评了我们所研究的两类复合电接触材料。结果表明,把传统的材料测试方法和光谱诊断方法相结合,可以全面正确地表征电触点材料的综合性能,也证明我们采用的这种新方法是先进有效的。本论文对以Ag为基的几种新型导电陶瓷复合触点材料进行了系统的工艺和性能研究。结果表明,我们所研究的Ag/La₂NiO₄和Ag/LaFe_1-xNi_xO₃两系列复合材料属优越的新型导电陶瓷复合触点材料,它们具有优异的化学稳定性和温度稳定性,有优良的可加工性,并获得了优良的抗电弧烧蚀性能。这种性能优越的银基导电陶瓷复合材料完全可能成为Ag/CdO的替代品,同时它优良的机械加工性能对Ag/SnO_h也具有很大的挑战性,与此同时这类材料还具有无毒、符合环保要求和使用寿命长的优点。本论文在如下五个方面取得了创新性的结果。1.新型银基导电陶瓷复合电接触材料开发把Ag与电阻率为maΩ·cm量级的导电陶瓷材料复合,研究了Ag/La₂NiO₄和Ag/LaFe_1-xNi_xO₃两系列新型银基导电陶瓷复合触点材料。这两类复合材料的电阻率均在2.1μΩ·cm附近,其比热容具有优良的温度稳定性,电弧烧蚀实验表明,材料具有良好的化学稳定性。复合触点材料变形量可达22%以上,拉断力超过150N,表现出良好的可加工性能;微观形貌中可看到陶瓷颗粒与银基体结合紧密,且陶瓷具有层状断面,有利于提高复合材料的加工性能。这些性能表明,这两类复合材料完全可能成为Ag/CdO的替代品,同时它优良的机械加工性能对Ag/SnO₂也具有很大的挑战性。Ag/LaFe_0.25Ni_0.75O₃和Ag/La₂NiO₄是银基导电陶瓷复合触点材料中性能较优的两个材料系列。2.时间分辨光电光谱检测触点电弧烧蚀机制为获取触点材料的时间分辨光电光谱,设计了一种光谱测量系统。用该系统可以探讨燃弧银原子和银离子的运动变化,根据不同材料谱强变化,可推测材料烧蚀实际状况。用该系统,测量了Ag/La₂NiO₄和Ag/LaFe_1-xNi_xO₃两系列的时间分辨光电光谱,并与其它常见触点材料测试结果进行比较,结果表明,我们研究的这两类复合材料具有优良的抗电弧烧蚀性能。同时证明,该光谱测量系统是分析触点材料抗电弧烧蚀的可行手段。这对新材料的设计有着积极的指导意义。3.实际工作状态下触点电弧行为的测量研究采用触点寿命机,模拟触点的实际工作状态,研究了所制备的两类复合触点材料的触点电弧行为。结果发现,这两类复合触点的平均燃弧时间在4 ms—4.3ms,燃弧时间比常见的触点材料都短,短的燃弧时间可以改善材料的抗电弧侵蚀性能,减少触点材料的烧蚀量和转移量,从而延长了触点材料的使用寿命。金属氧化物的电弧侵蚀机理主要有两种,一种是氧化物的分解与升华,这个过程要消耗大量的能量,从而降低侵蚀。第二种是增强触点表面熔池的表面张力和粘性。在燃弧过程中,金属氧化物会以微粒形式悬浮在表面,增加了表面张力、提高了金属粘性、增加了银对触头的润湿性,有助于降低基体银的喷溅损耗。所以,触点寿命分析表明,金属氧化物的添加可以明显改善电接触材料的动态电弧特性。4.扫描多波长光谱诊断电弧等离子体设计装配了CCD多通道光谱仪,把等离子体光谱诊断法用到触点材料的性能研究中,为触点材料成分设计和性能比较提供了一种有效的监控检测手段。对不同化学计量配比的Ag/La₂NiO₄和Ag/LaFe_0.25Ni_0.75O₃复合陶瓷材料,用光谱仪对电弧等离子体进行了系统的光谱分析。发现在银基导电陶瓷复合电接触材料中适量增加第三相金属Ni的含量,有利于提高材料抗电弧侵蚀性能;适量提高复合电接触材料中导电陶瓷掺加量,有助于增强材料抗电弧侵蚀能力;同样添加量情况下,掺加La₂NiO₄比掺加LaFe_0.25Ni_0.75O₃所得的陶瓷复合材料性能更优。我们的实验结果表明,光谱仪对于触点材料的研制和使用具有非常大的指导意义。5.谱线的曲线拟合与等离子体参量的测定根据两线法及斜率法分别测定了电弧等离子体的电子温度,并用曲线拟合的方法分析了谱线展宽的变化和产生机制。结果表明:斯塔克展宽是Ag/LaFe_0.25Ni_0.75O₃触点电弧的AgI546.5nm谱线产生加宽的主要原因;用洛伦兹拟合得到了谱线的半高全宽度、积分强度以及中心波长等参量,这些拟合参数可以用来推导等离子体的相关特征参量;谱线展宽随输入能量的增加而近似线性增大,也说明等离子体中的电子密度随着能量的增加而增大。利用两线法和斜率法分别测定了24V30A电路条件下Ag/LaFe_0.25Ni_0.75O₃触点电弧的电子温度,斜率法获得的更为精确的电子温度,数值约为1.1×10⁴K。更多还原

【Abstract】 As the essential components of many electric types of equipment,electric contacts are widely used in industry and daily life.However,the property of the contact material is the dominant factor determining the quality of the devices.Many researchers in the developed countries around the world have devoted to the investigation of contact materials because of their importance.Ag/CdO contact materials were well developed and applied as electrical contacts used in electromechanical devices such as relays and connectors operating in low-power conditions where high reliability and long service life are required.In the past,Ag/CdO has been long recognized as the preferred material in make-and-break switching for its outstanding performance.However, because it generates the poison cadmium gas during the service,which is hazardous to human health,Ag/CdO has been prohibited in many countries.Now Ag/SnO₂ is often used as the materials of the electric contacts for their anti-welding and corrosion resisting properties.As the best replacement of Ag/CdO,Ag/SnO₂ contact material has been greatly developed nowadays,especially in European countries.However its contact resistance and temperature rise was higher.The defect microstructure with coarse grains and oxide clusters degraded the deformation abilities and electrical properties.So it is still on the way to real practical application.According to the present study of contact materials and the existing problems in these fields,a new notion was put forward to work on those materials and turn out a kind of Ag-based conductive ceramic contact materials to meet the application demands in low-voltage transformer industry.In this thesis,different series of metalloid conductive ceramics were prepared through conventional technique of ceramic preparation,and then mixed with silver powders to form electrical composite contact materials.We mainly developed two kinds of contact materials,Ag/La₂NiO₄ materials and Ag/LaFe_1-xNi_xO₃ conductive ceramic contact materials with the weight percent from 8%to 12%.The experiment results prove that the materials have merits of good electrical properties and mechanical properties.In a word,it is very possible for the new conductive ceramic materials to replace of Ag/CdO and also they will become a strong challenger to Ag/SnO₂ in the future.The conductive ceramic has particular network microstructure.The electrical contact materials which were mixed up with this kind of ceramics and silver had fine mechanical characteristic,nice corrosion-resisting performance and obvious chemical stability.All the above-mentioned performances made this kind of contact materials nearly satisfy most kinds of demands in electrical contact fields.One of the important investigation subjects of the thesis is to study and discuss the capabilities of contact materials because of their importance.Electrical contacts are widely used in electromechanieal devices such as air switches,relays and connectors. During their performance,ares come into being between the opening contacts during a "break" operation and during the contact bounce period in the "make" operation, when switching low voltage systems.The arc behavior during the closing and opening of electrical contacts not only influences the surface morphology,but also causes the erosion of contact material.Arcs can result in mass transfer,welding loss of contact and the early end of lifetime.To understand the interaction of arc discharge and erosion of contact materials is of great importance.The interaction of arc and erosion of the contact material is an interesting field that attracts much theoretical and experimental attention.Breaking ares quench and establish for a very short period of time,and besides,temperature of arc plasmas even exceed the value 6000K, so that the arc can boil away everything that contact to it directly.For this reason,an indirect and fast spectroscopic diagnostic of electric arc plasma have gained in importance.But the erosion mechanism is very complex and it covers so many contents that it is impossible to include all the aspects in a dissertation.So here we just focus some interesting subjects to discuss,such as spectroscopy diagnostics of arc plasma.Employing with the plasma spectroscopic diagnostic method,we investigated the properties of the two composite materials.The results showed that conventional testing methods of materials associate with spectroscopy diagnostic system can represent the general characteristics of contact materials.In addition,it offered an effective monitoring means for the design and performance comparisons of the compositions of contact materials.The thesis focused on the study of the systematic techniques and the properties of several new Ag-based conductive ceramics contact materials.The results showed that the two series of Ag/La₂NiO₄ and Ag/LaFe_1-xNi_xO₃ composite materials were new conductive ceramics contact materials,owing to their superior chemical and temperature stabilities,ease for fabrication and excellent anti-arc erosion properties. Both of the composite materials demonstrated their superiority over traditionally used contact materials,accompanied with non-toxicity,environmental friendliness and long service life time.The innovations in the thesis are illustrated in 5 aspects as following:1.Investigations of the new Ag-based conductive ceramic contact materialsTwo series of Ag-based conductive ceramic contact materials Ag/La₂NiO₄ and Ag/LaFe_1-xNi_xO₃,combining Ag with conductive ceramics with electric resistance in mΩ·cm scale,were studied.The electric resistances of both composite materials were about 2.1μΩ·cm,and their heat capacities had excellent temperature and chemical stability.The later was confirmed by arc ablation tests.X ray diffraction patterns showed that,under the influence of arc plasma,the ceramic grains were tightly bound to Ag substrate with layer section,which would ease the materials to be fabricated. These properties demonstrated superiority of both of the composite materials over Ag/CdO and Ag/SnO₂ as new contact materials,2.Studies on erosion mechanism of contact arc with time-resolved spectrumA spectroscopy diagnostic system was designed to obtain the time-resolved photoelectric spectroscopy.The system can monitor the motions of Ag atoms and ions during arc ablation,and predict the real conditions of the material erosions based on intensities variations of the spectral lines of different materials.With this system,the time-resolved photoelectric spectra of Ag/La₂NiO₄ and Ag/LaFe_1-xNi_xO₃ were studied, and the comparisons of experimental results with other contact materials were provided.The results showed that the two composite materials had excellent anti-arc erosion properties.In addition,this spectroscopy diagnostic system was an analytical means for anti-arc erosion of materials,as well as helpful for designs of new material.3.Measurements on contact arc behaviors under the real working conditions Contact point life simulation system was used to simulate the real working conditions of the contact point and study the behavior of contact arc plasma of the two composite materials.The results showed that the average ablation time of the arc plasma was in the range of 4 ms-4.3 ms,shorter than that of normally used contact materials.The shortening of ablation time could improve the resistivity of the materials to arc erosion,decrease the amounts of materials being eroded and translocated,and thus prolong the service time of the contact materials.There are mainly two mechanisms of arc erosion of metal oxides:one is the degradation and sublimation of oxides, which consumes a large amount of energy to diminish the erosion;and the other is to increase the surface tension and viscosity of the contact surface melting cell.During the arc plasma ablation,the metal dioxides would suspend in the surface in the form of micro-particles,with increased surface tension,metal viscosity and wettability of Ag to the contact,thus diminishing the lost of Ag due to its spray.The analysis of contact service life showed that addition of metal oxides could drastically improve arc plasma dynamic properties of the electric materials.4.Diagnostics on contact arc plasma through multi-wavelength spectrumThe design was equipped with a CCD multi-channel spectrometer,employing the plasma spectroscopic diagnostic method to the study of the properties of contact materials,and offered an effective monitoring means for the design and performance comparisons of the compositions of contact materials.Spectroscopic analysis of arc plasma with spectrometer with respect to various stoichiometrically composed Ag/La₂NiO₄ and Ag/LaFe_0.25Ni_0.75O₃ composite ceramic materials were implemented. The results showed that moderate increase of the fraction of Ni of the third metal phase in the Ag-based conductive metal composite materials can facilitate the enhancement of resistivity of the materials to arc erosions;with the same amount of injection,the ceramic materials obtained by adding La₂NiO₄ has better performance than which by adding LaFe_0.25Ni_0.75O₃.Results showed that spectrometer was highly instructive to the fabrication and use of metal materials.5.Curve fitting of spectrum lines and calculation on parameters of plasma We measured the electron temperature of arc plasma by methods of two-lines and slope respectively and analyzed the changes of spectrum lines’ broadening as well as their mechanism.The results indicate Stark Broadening is the main reason for brodening of Ag I 546.5nm spectrum line from Ag/LaFe0.25Ni0.7503 contacting arc. Then we fit the spectrum lines by Lorentzian fitting,which is bettor than Gaussian fitting.As a result,we achieved FWHM,intensity of integral,central wavelength and etc.which can be used to deduce relevant characteristics parameters of plasma,such as electron temperature.Broadenings of spectrum lines approximately linearly increase with the increase of inputting energy.It shows electron density of plasma become larger as the energy enhancing.Using both methods of two-lines and slope, we respectively calculated electron temperature of Ag/LaFe_0.25Ni_0.75O₃ contacting arc in a 24V30A circuit.More exact electron temperature,1.1×10⁴ K,was achieved by the method of slope.更多还原