SiC－AlN－Y_2O_3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合作在１９２０～２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷．在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ１／２以上运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成．ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石．     

过量PbO和过量MgO对PMN-PT陶瓷相结构及介电性能的影响

采用ＮａＣｌ－ＫＣｌ熔盐法成功地制备了单一钙钛矿相结构的０．８ＰＭＮ－０．２ＰＴ陶瓷,并详细研究了添加过量ＰｂＯ和过量ＭｇＯ对０．８ＰＭＮ－０．２ＰＴ陶瓷样品的相结构和介电性能的影响。结果表明：过量ＰｂＯ和过量ＭｇＯ都能抑制和消除焦绿石相,并提高陶瓷的介电常数,但过量ＭｇＯ的效果更好。     

TiO2对Y掺杂PTCR陶瓷材料性能的影响

本文对ＴｉＯ２原料的晶型、颗粒状况和纯度对Ｙ＾３＋掺杂ＢａＴｉＯ３基ＰＴＣＲ材料的显微结构、电性能的影响作了探讨，结果表明，ＴｉＯ２原料的晶型、颗粒大小和团聚状况都将影响到ＰＴＣＲ陶瓷的显微结构，ＴｉＯ２原料的晶型对ＰＴＣＲ陶瓷半导化过程有影响，原料存在杂质和团聚，将使ＰＴＣＲ陶瓷的电阻－温度特性变差。     

Pb(Ni1/3Nb2/3)O3-PbTiO3系统准同型相界附近的介电异常

用两步合成法制备了（１－ｘ）Ｐｂ（Ｎｉ１／３Ｎｂ２／３）Ｏ３－ｘＰｂＴｉＯ３（ｘ＝０．３０－０．４０）陶瓷,对其相结构和介电性能进行了研究。ＸＲＤ分析表明,准同型相界在ＰＴ含量ｘ＝０．３４－０．３８范围内。介电性能研究结果表明,组成在准同型相界处的试样,其介电常数呈现最大值,同时还发现,准同型相界处的陶瓷出现介电双峰,其中一个为驰豫型铁电相向顺电相转变的相变峰;另一个介电峰处于１３０－１５０℃的高     

SiC—AlN—Y2O3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合体在１９２０￣２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷。在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ＾１／２以上。运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成。ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石。     

以球形α-Ni_(0.8)Co_(0.2)(OH)_2制备锂离子电池正极材料LiNi_(0.8)Co_(0.2)O_2

ＬｉＮｉ０．８Ｃｏ０．２Ｏ２是很有希望取代ＬｉＣｏＯ２的新一代锤离子电池正极材料．采用控制结晶法合成球形 α－Ｎｉ０．８Ｃｏ０．２（ＯＨ）２为前驱体,与 ＬｉＯＨ·Ｈ２Ｏ混合,在７００℃通Ｏ２热处理４ｈ合成锂离子电池正极材料ＬｉＮｉ０．８Ｃｏ０２Ｏ２粉末．Ｘ光衍射分析表明合成的ＬｉＮｉ０．８Ｃｏ０．２Ｏ２粉末结晶良好,具有规整的α－ＮａＦｅＯ２层状结构．扫描电镜分析表明粉末颗粒呈球形,粒径约８μｍ．粉末的流动性好,堆积密度高．充放电测试表明,合成的 ＬｉＮｉ０．８Ｃｏ０．２Ｏ２正极材料具有优良的电化学性能：首次充电比容量为１９７ｍＡｈ·ｇ－１,放电比容量为１７４ｍＡｈ·ｇ－１,１０次充放电循环后保持初始放电比容量的９６．６％．     

炭／炭复合材料在1500℃的抗氧化

本文研究了Ｃ／Ｃ复合材料ＭｏＳｉ２涂层系统的抗氧化性能。结果表明，ＭｏＳｉ＿２涂层系统具有１５００℃长时间抗氧化和优良的抗热震性能，在１５００℃时，２４２ｈ的氧化失重仅为０．７５％；长时间的氧化失重速率稳定在２．４３×１０－５ｇ／ｍ２·ｓ的极低水平。     

PTCR陶瓷材料的超低温烧结

主要研究了ＢＮ对ＰＴＣＲ陶瓷材料低温烧结的作用．对Ｌａ掺杂ＢａＴｉＯ_３ＰＴＣＲ陶瓷,在１１００℃的低温下烧结可以得到室温电阻率为１５０Ω·ｃｍ、升阻比为４．９个数量级的样品．对居里温度为３６０℃的高居里点（Ｂａ_０．４Ｐｂ_０．６）ＴｉＯ_３ ＰＴＣＲ陶瓷材料,选用 Ｎｂ_２Ｏ_５为半导化剂,ＢＮ和ＡＳＴ为助烧剂时,可以在１０００℃左右的超低温下烧成．同时,对ＢＮ助烧剂的液相烧结机制进行了初步的探讨．     

Mn掺杂BaTiO_3基PTCR陶瓷相变的EPR研究

为了探索利用ＥＰＲ谱线对ＰＴＣＲ陶瓷的相变及ＰＴＣ效应的机制研究的可能性,本文对接 Ｍｎ的 ＢａＴｉＯ３基正温度系数热敏电阻（简称ＰＴＣＲ）陶瓷在 １２０～４５０Ｋ温度范围内的电子顺磁共振谱进行了研究．得出了 Ｍｎ２＋离子 ＥＰＲ信号强度、 ｇ因子值和超精细耦合常数｜Ａ｜值的温度分布,发现ＥＰＲ参数与ＰＴＣＲ陶瓷相变有明显的对应关系,并给出微观结构上的初步解释．研究表明ＥＰＲ谱线以及精细结构的分析可以为ＰＴＣＲ陶瓷的相变机制以及ＰＴＣ效应的机制研究提供新的途径．     

SiC－AlN－Y_2O_3复相陶瓷的氧化行为

经研究致密的ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷的氧化行为后发现，陶瓷材料的表面在空气中氧化的反应物随着温度的高低而变化．８００℃、２０ｈ氧化试验后，试样表面无任何变化，１１００℃氧化．２０ｈ，表面形成了极少量的ＳｉＯ２，但两者均无增重．１２５０℃与１３２０℃氧化３０ｈ后，试样的重量和表面发生较明显的变化，形成了ＳｉＯ２与α－Ａｌ２Ｏ３，１３７０℃氧化试验３０ｈ后，陶瓷表面的氧化产物ＳｉＯ２与α－Ａｌ２Ｏ３转化成莫来石（３Ａｌ２Ｏ３·２ＳｉＯ２）结构．试样表面的氧化层均匀而且致密．     

Cyclic crack growth and fracture resistance of Ti-6Al-6V-2Sn as influenced by recrystallization anneal and interstitial oxygen content

This study was undertaken to determine methods for metallurgical improvement of cyclic crack growth and fracture properties in Ti-6A1-6V-2Sn. Two heats of the alloy were studied: an + β processed material containing 0.165% interstitial oxygen and β-processed material containing 0.077% interstitial oxygen. All test specimens were given a mill anneal heat treatment, in addition some specimens from each heat were given a recrystallization anneal treatment Fatigue-crack growth rates were determined using compact tension specimens and fracture toughness was determined using 1 in. dynamic tear specimens for each material/heat treatment combination. The recrystallization anneal treatment resulted in significant improvements in the fracture resistance of both materials, despite metallographic evidence that die recrystallization-annealed β-processed material did not develop a fully recrystallized structure. Improvements in cyclic crack growth resistance resulting from the recrystallization anneal treatment, per se, were modest. However, the combined effects of recrystallizalion anneal plus a reduction B interstitial oxygen content significantly improved the cyclic crack growth properties of Ti-6Al-6V-2Sn.     

New negative temperature coefficient thermistor ceramics in (Y2O3 + CeO2)–LaCr0.5Mn0.5O3 composite system

A new series of composite, negative temperature coefficient (NTC) ceramics based on the (aY₂O₃ + bCeO₂)?0.4LaCr_0.5Mn_0.5O₃ (a + b = 0.6) were carefully prepared and related electrical properties were investigated. All the NTC thermistors showed a linear relationship between the natural logarithm of the resistance and the reciprocal of the absolute temperature, indicative of NTC characteristics. The obtained B _25/85 constants were in range of 2,100–2,700 K. The magnitude order of the resistivity at 25 °C was of 10³–10⁹ Ωcm and activation energies varied from 0.185 to 0.231 eV. The aging coefficient of the NTC thermistors with CeO₂ was less than 2 % for the time period of 900 h, suggesting that NTC thermistors with CeO₂ possessed a better electrical stability in comparison with CeO₂-free thermistors.     

MgxNi1.0Mn2-xO4氧化物热敏纳米粉体的制备及其性能研究

采用溶胶凝胶（Sol-Gel）技术制备MgxNi1.0Mn2-xO（4x=0,0.1,0.2,0.3,0.4）系列氧化物热敏纳米粉体,并经成型、烧结等工艺制得高稳定性的负温度系数热敏电阻,用热分析系统、X射线衍射（XRD）、透射电子显微镜（TEM）和HP34401型数字电压表分析MgxNi1.0Mn2-xO4氧化物热敏纳米粉体的热处理过程、相结构、晶粒形貌以及MgxNi1.0Mn2-xO4氧化物热敏电阻的电学性能,结果表明,经600℃热处理,得到单一尖晶石相结构的MgxNi1.0Mn2-xO4氧化物热敏纳米粉体,纳米粉体粒子的形状为多面体,粒径约为40nm,随着镁离子含量的增加,MgxNi1.0Mn2-xO4氧化物烧结体电阻值和材料常数增大,材料常数B≥3900,老化稳定性有很大提高。     

Formation and performance of ohmic contact electrodes on BaTiO3-based thermistors by localized electroless Cu-plating

Ohmic contact electrodes with high performance were formed on the surface of BaTiO₃-based thermisitors by localized electroless Cu-plating and the physical properties of the coated thermistors were investigated. The adhesive force between the electroless plated layer and the substrate, the voltage-resistance, the resistance, the ageing-resistance properties, and the solderability, all met the industrial production requirements for thermistors. The structure and morphologies of these NiP-Cu composite electrodes as well as the ceramic substrates were characterized by X-ray diffraction and atomic force microscopy, verifying that the film contains a typical Cu crystal structure with preferred orientation of the copper grains.     

A Novel Approach to Modeling and Simulation of NTC Thick-Film Segmented Thermistors for Sensor Applications

This paper describes the design, modeling, simulation, and fabrication of thick-film segmented thermistors. These thermistors were printed on alumina using negative temperature coefficient 3K3 paste, composed of nanometer powder. Their room temperature resistance was measured versus the number of segments and electrode surface value for the fixed layer thickness and electrode spacing. After that, very large thermistors were printed to serve as both the powerful self-heaters and the heat loss sensors in the thermistor volume air flow meter and anemometer. For an application in AC bridges, impedance Z(f) and insertion loss S21 [dB] of the same largest segmented thermistor were measured using network analyzer HP8752A. Impedance modeling was performed using simple equivalent electrical circuit with circuit parameters estimated by fitting procedure (traditional approach), as well as using a commercial electromagnetic simulation program microwave office (MWO, novel approach). This was followed by the modeling of electrical current distribution over a number of segments done within the MWO. The results obtained from simulations and measurements were mutually compared.     

Improvement in oxidation resistance of the intermetallic compound titanium aluminide by heat treatment under a low partial pressure oxygen atmosphere

The improvement in oxidation resistance of an intermetallic compound TiAl was investigated by means of a new type of surface treatment: heat treatment under a low partial pressure oxygen atmosphere. The specimens treated by this method showed superior oxidation resistance compared with a nickel-base superalloy Inconel 713C during cyclic heating to a temperature of 1173 K in static air. The best conditions for the heat treatment under a low partial pressure oxygen atmosphere were found to be: pressure, 6.7 X 10-³ Pa; temperature, 1273 K; time, 7.2 ks (2 h) or more. It was presumed that the excellent oxidation resistance resulting from this method is due to preferential formation of a thin, strong Al₂0₃ surface layer.     

MF5602型低温热敏电阻温度计的特性研究

采用新工艺生产的MF5602型NTC热敏电阻温度计在20-50 K之间进行了电学测量,老化实验后研究了其稳定性和磁场强度对温度计测量结果的影响.结果表明:新工艺生产的MF5602型NTC热敏电阻温度计可在20-50 K之间使用,相对电阻灵敏度、稳定性、磁场诱发的温度测量误差等传感器特性均优于美国Lake Shore公司...     

Methods for decreasing thermoelastic stresses in barium-titanate-based thermistors

We have investigated by numerical methods the temperature stresses in thermistors with a positive temperature coefficient of resistance based on semiconductor barium titanate ceramics under the action of current loads. It has been shown that by changing the form of the ceramic element it is possible to attain an almost 50% decrease in the maximum tensile temperature stresses compared to thermistors of the classical form.     

Effects of Sr-doping on the electrical properties of MnCoNiO4 NTC ceramics

The effects of Sr-doping on Ni–Mn–Co–O spinel-structured NTC ceramics were investigated. And the precursors of Sr-doped NiCoMnO₄ NTC ceramics were attained by solid state reactions at room temperature, with no intermediate compounds. Its formation and the structural evolutions were characterized by thermo-gravimetry-differential scanning calorimetry, X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. Related electrical analyses were also performed. The values of R_298K, B_298/323 constant and the temperature coefficient of resistance α_298K of the thermistors are in the range of 168–1,738 Ω, 3,257–3,359 K and ?3.64 to ?3.78 % K^?1, respectively. Complex impedance analysis shows, for x = 0.2, single semicircular arc whose shape does not have any change with temperature. The grain boundary properties exhibit thermistor parameters with a negative temperature coefficient characteristic. The conduction for the grain boundary could be explained by oxygen vacancies. The results show that the ceramics exhibits a good electrical property because of narrow grain size distribution, controlled morphology, and high purity. This suggests that the electrical properties can be adjusted to desired values by controlling the Sr cation content. This series of materials could be considered as practical materials for NTC thermistor. Most importantly, this new approach greatly simplifies the preparation processes.     

超音速火焰喷涂TiB2-50Co涂层及其性能

在322、402和462 L/min 3种氧气流量条件下采用超音速火焰喷涂技术制备了3种TiB₂-50Co涂层,通过SEM和XRD对涂层的微观组织和物相结构进行分析,测试其硬度,采用水淬法测试涂层的抗热震性能,并研究了涂层的耐熔融铝硅(Al-12.07wt%Si)合金腐蚀和耐磨粒磨损性能.研究结果表明:3种TiB₂-50Co涂层的物相均为TiB₂和Co;3种涂层的组织均致密,其中以氧气流量为322 L/min条件下制备的涂层试样最致密,其孔隙率最低(1.76%),涂层硬度值最高,达到(558±90) HV_0.3;氧气流量为462 L/min条件下制备的涂层抗热震性能最差,涂层截面出现明显裂纹;在熔融Al-12.07wt%Si合金中腐蚀60 h后,3种涂层均具有良好的耐熔融Al-12.07wt%Si腐蚀性能;在载荷为6 N的条件下,3种涂层均具有良好的耐磨损性能,以氧气流量为322 L/min条件下制备的涂层试样最佳.