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排序方式: 共有71条查询结果,搜索用时 15 毫秒
1.
Makikazu Takehana Tomomichi Nishino Katsuyasu Sugawara Takuo Sugawara 《Korean Journal of Chemical Engineering》1996,13(5):538-543
Cobalt-, praseodymium-added zinc oxide varistor was prepared through a wet chemical method followed by sintering with or without
calcination. Changes in grain size, compact density, additives distribution, and voltagecurrent/ capacitance-voltage relations
were investigated for the characterization of the samples sintered at temperatures from 1473 to 1573 K without calcination
or with calcination at 773 K for 2 h. The electrical properties were compared with nhose of samples prepared by two types
of ball mill methods. The wet chemical method provided almost the same additives-distribution profile and less impurities
in comparison with the ball grinding method carried out for 10–100 h. The donor concentration and the potential-barrier height
for the samples were evaluated by Double Schottky Barrier Model. Addition of small amount of both cobalt and praseodymium
in preparation by the wet chemical method was effective for a better nonlinearity relation between voltage and current, which
has potential for a smaller sized varistor. 相似文献
2.
Nb2O5掺杂对ZnO压敏电阻器电性能的影响 总被引:5,自引:1,他引:4
本文研究了Nb_2O_5掺杂以及Nb_2O_5与ZnO煅烧对ZnO压敏电阻器电性能的影响。实验表明,Nb_2O_5的掺入使压敏电场减少,当Nb_2O_5含量为0.1%mol时,其压敏电场最小.非线性系数最大。煅烧温度越高,压敏电场越高,非线性系数越大。 相似文献
3.
提出了一种通过晶闸管开关装置直接调节电容器两端电压以调节电容无功功率的方法和相应的原理及接线。同时提出了换级控制方法,分析了故障时产生的断态过电压,采用氧化锌压敏电阻过压保护后,重新对断态过电压进行了仿真。结果表明:补偿装置能多级、大范围调节容性无功,较之于其它快速补偿装置综合工程造价低,有望用于高压电网;装置故障时,会出现严重过电压,若过压保护动作后可使断态电压降低到允许范围内。 相似文献
4.
《Journal of the European Ceramic Society》2020,40(11):3766-3770
Ceramic varistors are electronic components which have a sharp change (over several orders of magnitude) of their electrical resistance at a well-defined voltage (switching voltage). Starting at low voltages, the resistance is large. But by exceeding the switching voltage the resistance drops dramatically and the component acts as a good conductor. Mounted parallel to a consumer, they are used as protection devices against over voltage loading. In the technical routine yearly billions of varistors are used to protect power lines, transformation stations, electronic devices, microelectronic systems or even LEDs.In service large temperature differences may come into existence, which cause severe mechanical stresses that even may destroy the components. The basic principles of the varistor behaviour are explained and examples of mechanical failure are discussed. 相似文献
5.
《Ceramics International》2017,43(4):3465-3474
This study investigated the effect of elemental crystal Ge or/and GeO2 doping on the microstructure and varistor properties of TiO2–Ta2O5–CaCO3 varistor ceramics, which were prepared via the traditional ball milling–molding–sintering process. X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy demonstrated that co-doping with Ge and GeO2 changed the microstructure of TiO2–Ta2O5–CaCO3 ceramics, thereby increasing the nonlinear coefficient and decreasing the breakdown voltage. The optimum doping concentrations of Ta2O5, CaCO3, Ge, and GeO2 exhibited the highest nonlinear coefficient (α=14.6), a lower breakdown voltage (EB=18.7 V mm−1), the least leakage current (JL=10.5 μA cm−2), and the highest grain boundary barrier (ΦB=1.05 eV). In addition, Ge and GeO2 function as sintering aids, which reduce the sintering temperature because of their low melting points. 相似文献
6.
In the present study, the effect of Bi2O3 and Bi2O3+Sb2O3 additions on the size distribution of ZnO grains is investigated. Without the usage of a powder bed, the addition of Bi2O3 provides a transient liquid phase that enhances the densification. The residual Bi segregates alters the surface/grain boundary
energy ratio, which encourages the ZnO grains to grow. The size variation is also increased. The addition of both Bi2O3 and Sb2O3 induces the formation of pyrochlore, spinel and inversion boundary. Their presence reduces not only the average grain size,
but also the size variation. 相似文献
7.
Michael Hofstätter Andreas Nevosad Christian Teichert Peter Supancic Robert Danzer 《Journal of the European Ceramic Society》2013,33(15-16):3473-3476
Due to the scatter of properties of individual grain boundaries, a scatter of the behavior of low-voltage varistor components and asymmetric current–voltage characteristics with respect to the electrical field direction is observed. Using complementary methods (thermography, scanning surface probe microscopy, electron back-scattered diffraction), we investigated the grain boundary behavior of Praseodymium type varistors. Measurements on the relevant grain boundaries revealed a newly observed effect: dependent on the field direction, the main current flows via different spatial paths. 相似文献
8.
Bi-Shiou Chiou Tzuu-Chian Chen Jeng-Jen Li Jenq-Gong Duh 《Journal of Electronic Materials》1990,19(12):1339-1344
Glasses in the PbO-B2O3-Al2O3-BaO-CaO-SiO2 system were employed as the dopant to ZnO varistors. The thermal stability of the varistor is enhanced with glass additives.
The temperature coefficient of threshold field for the sample doped with 1 w/o glass (65 w/o PbO - 23 w/o B2O3 - 12 w/o SiO2) is 1 × 10-4/K as compared to 3.3 × 10-3/K for that of the undoped sample. The change in the temperature dependence of the field-current density characteristics is
more related to the barrier height change than the refractory behavior of the glass employed. Heat treatment is very effective
in recovering the degraded samples by providing the activation energy for the diffusion of Zn interstitials. The experimental
results can be explained with a Schottky barrier model. 相似文献
9.
在砂浆中混掺钢屑和铁砂两种工业废弃料,制备得到环保低成本的水泥基复合材料,在测定其抗压强度的基础上采用交流两电极法研究其导电性能和压敏性能,并分析研究了混掺掺量、弹塑性荷载、不同加载速率以及冲击荷载等对其压敏性的影响。试验结果表明,随着导电材料掺量增加,试件压敏性更加明显。加载速率越大,试件电阻率变化越大;冲击荷载数值对瞬间电阻率与卸载后电阻率均有较大影响。 相似文献
10.
The microstructure, electrical properties, dielectric characteristics, and DC accelerated aging behavior of the ZVM-based varistors were investigated for different sintering temperatures of 800–950 °C. The microstructure of the ZVM-based ceramics consisted of mainly ZnO grain and secondary phase Zn3(VO4)2, which acts as liquid-phase sintering aid. The Zn3(VO4)2 has a significant effect on the sintered density, in the light of an experimental fact, which the decreases of the Zn3(VO4)2 distribution with increasing sintering temperature resulted in the low sintered density. The breakdown field exhibited the highest value (17,640 V/cm) at 800 °C in the sintering temperature and the lowest value (992 V/cm) at 900 °C in the sintering temperature. The nonlinear coefficient exhibited the highest value, reaching 38 at 800 °C and the lowest value, reaching 17 at 850 °C. The varistor sintered at 900 °C exhibited not only high nonlinearity with 27.2 in nonlinear coefficient, but also the highest stability, in which %ΔE1 mA = −0.6%, %Δα = −26.1%, and %Δ tan δ = +21.8% for DC accelerated aging stress of 0.85 E1 mA/85 °C/24 h. 相似文献