Xiaonong Cheng

Microstructure and electrical properties of Lu2O3-doped ZnO-Bi2O3-based varistor ceramics

Lu2O3-doped ZnO-Bi2O3-based varistor ceramics samples were prepared by a conventional mixed oxide route and sintered at temperatures in the range of 900-1 000 °C, and the microstructures of the varistor ceramics samples were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM); at the same time, the electrical properties and V-I characteristics of the varistor ceramics samples were investigated by a DC parameter instrument for varistors. The results show that the ZnO-Bi2O3-based varistor ceramics with 0.3% Lu2O3 (molar fraction) sintered at 950 °C exhibit comparatively ideal comprehensive electrical properties. The XRD analysis of the samples shows the presence of ZnO, Bi-rich, spinel Zn7Sb2O12 and Lu2O3-based phases.

Preparation of Negative Thermal Expansion ZrW2O8 Powders and Its Application in Polyimide/ZrW2O8 Composites

Negative thermal expansion (NTE) ZrW 2 O 8 powders were prepared by step-by-step solid-state reaction with ZrO 2 and WO 3 powders. The coefficient of thermal expansion (CTE) of the as-prepared ZrW 2 O 8 was around −5.08×10 −6 K −1 at 20–700°C. Different amounts of ZrW 2 O 8 powders were added in BTDA-ODA polyamic acid to form polyimide/ZrW 2 O 8 composites (PI/ZrW 2 O 8 ). With the increment of ZrW 2 O 8 , experimental results show that ZrW 2 O 8 powders can significantly enhance the thermal stability of the composites, and reduce the thermal expansion. A 50 wt pct ZrW 2 O 8 addition can give rise to a 31% reduction of CTE. It is suggested that the PI/ZrW 2 O 8 composites have potential applications in high performance microelectronic devices.

Effects of high-energy ball milling oxide-doped and varistor ceramic powder on ZnO varistor

ZnO varistor ceramics doped with Bi2O3, Sb2O3, Co2O3, Cr2O3, and MnO2 were prepared separately by two high-energy ball milling processes: oxide-doped and varistor ceramic powder. A comparison in the electrical and microstructural properties of the samples obtained by both methods was made. The best results on these characteristics were achieved through the high-energy ball milling varistor ceramic powder route, obtaining a nonlinear coefficient of 57 and a breakdown field of 617 V/mm at a sintering temperature of 1000 °C for 3 h. The samples synthesized by this technique show not only high density value, 95% of the theoretical density, but also a homogeneous microstructure, which compete with those obtained by the high-energy ball milling oxide-doped powder route. With the advantage that the high-energy ball milling varistor ceramic powder route can refine grain, increase the driving force of sintering, accelerate the sintering process, and reduce the sintering temperature.

Microstructure and electrical properties of sol–gel derived Ni-doped CaCu3Ti4O12 ceramics

Abstract Dielectric properties and varistor performance of sol–gel prepared Ni-doped calcium copper titanate ceramics (CaCu 3 Ni x Ti 4 O 12+ x , x =0, 0.1, 0.2, 0.3) were investigated. SEM and XRD were used in the microstructural studies of the specimens and the electrical properties were investigated for varistors. XRD patterns show that the CCTO ceramics were single phase with no Cu-rich phase. SEM results indicated that the samples had smaller grain sizes than those synthesized by traditional solid-state reaction methods. The experimental results show that the highest dielectric constant and lower dielectric loss occur when x =0.2. When x =0.3, the lowest leakage current is obtained and the maximum value reaches 0.295; meanwhile, the lowest threshold voltage and nonlinear coefficient are found, the minimum values of them are 1326 V/mm and 3.1, respectively.

Microstructure of in situ Al3Ti/6351Al composites fabricated with electromagnetic stirring and fluxes

Abstract The 6351 wrought aluminum alloy and K2TiF6-CaF2-LiCl components were selected as raw materials to fabricate in situ Al3Ti particulate reinforced aluminum alloy at 720 °C via direct melt reaction method with electromagnetic stirring (EMS). CaF2 and LiCl acted as fluxes to lower the reaction temperature of the system. It is shown that the electromagnetic stirring and fluxes accelerate the emulsion process of K2TiF6. Optical microscopy, scanning electron microscopy, transmission electron microscopy and energy dispersive spectrum were utilized to analyze the microstructure and components of composites. Compared to composites fabricated without EMS and fluxes, the sizes of endogenetic Al3Ti are refined from 10–15 μm to 2–4 μm, which are often accompanied with silicon element. The morphology of Al3Ti or Al3TiSi0.22 exhibits triangle, quadrilateral and other clumpy patterns. Because of the Ca elements from CaF2, the sizes of Mg2Si decrease from 8–10 μm to 1–2 μm due to the formation of Ca2Si.

Influence of Yb2O3 doping on microstructural and electrical properties of ZnO-Bi2O3-based varistor ceramics

从 0 ～ 0.4% 在范围与 Yb2O3 做的 ZnO-Bi2O3-based 变阻器陶艺(臼齿的部分) 被一条稳固的反应线路获得。X 光检查 diffractometry (XRD ) 和扫描电子显微镜学(SEM ) 被使用描绘变阻器陶艺，和一台 DC 参数仪器的阶段和微观结构因为变阻器陶艺被使用调查他们的电的性质和 VI 特征。ZnO 阶段， Bi2O3 阶段， Zn7Sb2O12 类型尖晶石阶段和 Zn2Bi3Sb3O14 类型 pyrochlore 是在场的，并且 Yb2O3 分阶段执行， Sb2O4 分阶段执行的样品表演的 XRD 分析与增加 Yb2O3 的数量在变阻器陶艺被发现。ZnO 谷物的平均尺寸第一随 Yb2O3 内容的增加增加然后减少。结果也证明阀值电压在 656 V/mm 和 1 232 V/mm 之间，非线性的系数在 14.122.3 的范围，并且漏电流在 0.60 A 和 19.6 A 之间。在 900 点的 0.20%增加 Yb2O3 的 ZnO-Bi2O3-based 变阻器陶艺 sintered ???  ???????????????????? 瀀? 炸 ? 炸？？

Sol–gel synthesis of Y2O3-doped ZnO thin films varistors and their electrical properties

Abstract Y 2 O 3 -doped ZnO–Bi 2 O 3 thin films were fabricated on silicon substrates by sol–gel process and annealed in air at 750 °C for 1 h. Microstructure and electrical properties of ZnO thin films were investigated. XRD analysis shows that all peaks of ZnO thin films are well matched with hexagonal wurtzite structure of ZnO. SEM results present that the ZnO grain size decreases with the increase of dopant concentration, which means that rare earth doped can refine the grain size. The thickness of each layer is uniform and the value of thickness is about 80 nm. The nonlinear V – I characteristics with the leakage current of 0.46 μA, the threshold field of 110 V/mm and the nonlinear coefficient of 3.1 could be achieved when the films contain 0.2% (mole fraction) yttrium ion.

Influence of Yb 2 O 3 doping on microstructural and electrical properties of ZnO-Bi 2 O 3 -based varistor ceramics

从 0 ～ 0.4% 在范围与 Yb2O3 做的 ZnO-Bi2O3-based 变阻器陶艺(臼齿的部分) 被一条稳固的反应线路获得。X 光检查 diffractometry (XRD ) 和扫描电子显微镜学(SEM ) 被使用描绘变阻器陶艺，和一台 DC 参数仪器的阶段和微观结构因为变阻器陶艺被使用调查他们的电的性质和 VI 特征。ZnO 阶段， Bi2O3 阶段， Zn7Sb2O12 类型尖晶石阶段和 Zn2Bi3Sb3O14 类型 pyrochlore 是在场的，并且 Yb2O3 分阶段执行， Sb2O4 分阶段执行的样品表演的 XRD 分析与增加 Yb2O3 的数量在变阻器陶艺被发现。ZnO 谷物的平均尺寸第一随 Yb2O3 内容的增加增加然后减少。结果也证明阀值电压在 656 V/mm 和 1 232 V/mm 之间，非线性的系数在 14.122.3 的范围，并且漏电流在 0.60 A 和 19.6 A 之间。在 900 点的 0.20%增加 Yb2O3 的 ZnO-Bi2O3-based 变阻器陶艺 sintered ???  ???????????????????? 瀀? 炸 ? 炸？？

The Industry-University-Research Cooperation Innovation of Colleges

It’s a hotspot for current colleges to actively continue and promote coordination innovation with local enterprise. In order to develop the industry-university-institute cooperation in colleges, the experience of innovation cooperation and development was summarized in the paper. Based on presenting the concept of the collaborative innovation, problems existed in the industry-university-research cooperation of colleges were studied, and the methods for resolving these problems were also suggested.