Dependence of Electrical Conductivity of ZnO on Degree of Sintering

The electrical resistivity of ZnO doped with Al₂O₃ was measured in air and under reduced pressure (∼0.5 mm Hg) in the range from 30° to 680°C as a function of the degree of sintering. The data obtained were explained in terms of the effects of the microstructure of the sintered body and the chemisorbed oxygen. There are two mechanisms of electrical conduction involved, only one of which is affected by the microstructure.     

Particle Size Dependence of the Electrical Conductivity of NaCl

The ac and dc conductivities of single-crystal and polycrystalline NaCl were measured as a function of both temperature and particle size. The ac conductivity results for single-crystal NaCl agreed well with the literature: intrinsic activation energy = 1.86 ev; extrinsic, impurity-controlled range = 0.74 ev; extrinsic, association range = 1.16 ev; and the intrinsic-extrinsic knee in the curve was at 10³/ T ∼ 1.4°K⁻¹ and σ₀∼ 6 × 10⁻⁸ ohm⁻¹ cm⁻¹. In the intrinsic range, however, the total conductivity (σ₀) was the sum of two ionic contributions: a steady state, nonblocked contribution (σ_θ and a blocked contribution (σ₀—σ_θ). The activation energy for the dc steady state conductivity was 1.6 ev. When the extrinsic, impurity-controlled contribution to the total conductivity was made insignificant by anion doping, the same 1.6 ev was the activation energy for the intrinsic ac conductivity at low temperatures. The data for the polycrystalline samples showed that ac conductivity increased inversely with particle size and dc steady state conductivity increased only slightly, if any, with decreasing particle size. It is postulated that the steady state conductivity is the result of the nonblocked ionic transport of sodium ions and that the ac portion of the total conductivity is due to the movement of chlorine ions which are blocked, giving rise to the polarization phenomenon. The increase in the ac conductivity with decreasing particle size is correlated with the enhanced movement of Cl⁻ in the subgrain boundary region, as has been previously shown by diffusion measurements.     

Temperature Dependence of the Conductivity in Ceramic Materials Containing Nickel Nanoparticles

We have measured and analyzed the temperature dependence of the conductivity of composites in which nickel nanoparticles are embedded in an insulating matrix. Observing a transition from a variable-range hopping to a near-neighbor hopping, with increasing temperature, is suggested to correspond to the microscopically observed transition from a homogeneous-like to a percolation-like electrical network.     

煤基聚苯胺复合材料的导电性能研究

以煤为基体，不外加质子酸掺杂，制备了煤基聚苯胺复合导电材料，研究了其在不同条件下的导电性能。并对煤基聚苯胺合成反应后的废液进行了回收测试与循环利用研究。结果表明，在压力0．2～1．0MPa时，煤基聚苯胺的电导率随着压力的增大而增大；在30～120℃时，煤基聚苯胺的电导率随着温度的升高而减小；随着在环境中放置时间不同，煤基聚苯胺的电导率会有不同程度的变化；煤基聚苯胺聚合反应后的废液可以进行回收利用。     

Electrical Conductivity of SiOCN Ceramics by the Powder‐Solution‐Composite Technique

SiOCN ceramics have been prepared by the polymer pyrolysis method. The preceramic polymers were synthesized from a polysiloxane cross‐linked with two different N‐containing compounds: a silazane or a ternary amine. The corresponding SiOCN ceramics were obtained by pyrolysis in nitrogen atmosphere at five different temperatures from 1000°C to 1400°C. The electrical conductivity of the powdered SiOCN ceramic samples was determined by the powder‐solution‐composite technique. The results show an increase in room temperature AC conductivity of three orders of magnitude, from ≈10^?5 (S/cm) to ≈10^?2 (S/cm), with increasing pyrolysis temperature from 1000°C to 1400°C. Furthermore, the electrical conductivity of the amine‐derived SiOCN is three to five times higher than that of the silazane‐derived ceramic at each pyrolysis temperature. The combined structural study by Raman spectroscopy and chemical analysis suggests that the increase of electrical conductivity with the pyrolysis temperature is due to the sp³‐to‐sp² transition of the amorphous carbon phase. The higher conductivity of the amine‐derived SiOCN is also discussed considering features like the volume% of the free‐carbon phase and its possible N‐doping.     

反应热压法制备BN—A1N—TiB_2导电复相陶瓷(BAT瓷)

本文探讨了采用反应热压法制造BAT瓷的配方设计、工艺问题及显微结构形成过程,指出在BAT瓷相组成中,BN的作用是提供材料足够的可帆械加工性和抗热震性,但其耐熔铝腐蚀性较差,所以含量要尽量低;AIN的作用是提高材料的耐熔铝腐蚀性,其含量提高是有益的;TiB_2的作用是保证材料具有合适的电阻率。还指出要获得具有优良耐熔铝腐蚀性的BAT瓷,各相的晶粒结晶完整、均匀、粒径较粗以及低的气孔率是有益的。     

Piezoelectric Multilayer Ceramic/Polymer Composite Transducer with 2–2 Connectivity

A multilayer piezoelectric ceramic/polymer composite with 2–2 connectivity was fabricated by thermoplastic green machining after co-extrusion. The multilayer ceramic body was composed of piezoelectrically active lead zirconate titanate (PZN)–lead zinc niobate (PZN)-lead zirconate titanate (PZT) layers and electrically conducting PZN–PZT/Ag layers. After co-extruding the thermoplastic body, which consisted of five piezoelectric layers interspersed with four conducting layers, it was computer numeric-controlled machined to create periodic channels within it. Following binder burnout and sintering, an 18 vol% array of 190 μm thin PZT slabs with a channel size of 880 μm was fabricated. The channels were filled with epoxy in order to fabricate a PZN–PZT/epoxy composite with 2–2 connectivity. The piezoelectric coefficient (effective d ₃₃) and hydrostatic figure of merit ( d _h× g _h) of the PZN–PZT/epoxy composite were 1200 pC/N and 20 130 × 10⁻¹⁵ m²/N, respectively. These excellent piezoelectric characteristics as well as the relatively simple fabrication procedure will contribute in widening the application range of the piezoelectric transducers.     

CuO/ZnO叠层复合薄膜的制备及其光催化活性

分别通过光还原和电还原在以氧化铟锡玻璃为基体的ZnO上沉积Cu和Cu2O,后经400℃空气中热处理,制备了两种CuO/ZnO叠层复合薄膜。用X射线衍射、扫描电子显微镜和X射线能量散射谱分别对复合薄膜的晶相、形貌和化学组成进行表征。以橙黄II在模拟自然光照射下的光催化降解作为探针反应评价其光催化活性。结果表明：由Cu/ZnO经400℃下焙烧1h转化的CuO/ZnO叠层复合薄膜具有更高的光催化活性,反应1h后,橙黄II的降解率比由Cu2O/ZnO经400℃下焙烧1h转化的CuO/ZnO提高了14%。对CuO/ZnO叠层复合薄膜光催化活性提高的原因也进行了讨论。     

高聚物/炭黑复合材料导电性能的研究

本文介绍了炭黑（ＣＢ）对低密度聚乙烯（ＬＤＰＥ）、高密度聚乙烯（ＨＤＰＥ）、聚苯乙烯（ＰＳ）等高分子材料导电性能的影响,研究了其导电性能和导电机理,分析了不同导电体系中基体对炭黑临界值的影响。     

PS／炭黑复合材料导电性能的研究

本文通过炭黑（简称ＣＢ）用量、加工工艺、温度对ＰＳ／ＣＢ复合材料导电性能影响的探讨、复合导电材料亚微观结构的观察，研究了ＰＳ／ＣＢ复合材料的导电性能。结果表明，随着ＣＢ含量的增加，材料的电阻率呈非线性下降，当ＣＢ的质量分数在１０％～４０％的范围内时，电阻率下降明显，在此含量范围以后，体积电阻率变化不大；材料的导电性能与加工工艺有关，溶剂法的导电性能比混炼法好；电阻率随温度的升高均有上升的趋势。由复合材料的亚微观结构表明，随着ＣＢ含量的增加，ＣＢ由分散的单个颗粒逐渐连结在一起，最后与ＰＳ形成了一种相互交错式的结构     

多层石墨烯/钢纤维复合砂浆导电性能研究

制备了多层石墨烯(MG)/钢纤维(SF)复合砂浆.利用四电极法测试复合砂浆的电阻率,研究了测试时间、MG和SF掺量、养护龄期和含水量对砂浆电阻率的影响,并通过扫描电镜观察多层石墨烯在砂浆中的微观形貌.结果表明:砂浆外通电流后,内部产生的极化效应导致测试电阻率随导电时间增长而增大,导电填料抗氧化性越强,极化效应越小;砂浆的电阻率随MG和SF掺量的变化出现了渗流现象,运用GEM理论拟合了单掺MG和SF砂浆的电导率与其掺量的关系;MG和SF的协同作用可以增加导电链条、提高导电能力,其中复掺SM比单掺MG电阻率降低21.7％～41.8％;养护龄期越长,砂浆导电能力越差;砂浆干燥状态下的电阻率比湿润状态增加了29％～199％,复掺不同导电填料或增加导电填料含量,都能降低含水量对电阻率的影响.     

VGCF填充PVDF/PMMA复合材料导电性能的研究

以气相生长碳纤维（VGCF）为导电填料,聚偏氟乙烯（PVDF）、聚甲基丙烯酸甲酯（PMMA）为基体制备复合型导电高分子材料。考察了填料用量、基体种类、配比以及PVDF结晶行为对复合材料导电性能的影响。结果表明,VGCF填充PMMA、PVDF、PVDF／PMMA（50／50）体系的渗滤阔值分别为5、4、3phr的填料用量。VGCF的加入会导致PVDF／PMMA体系发生微观相分离,而且VGCF会选择性富集在PVDF的非晶相中,所以PVDF／PMMA／VGCF体系的导电性呈现双重渗滤现象,该体系的体积电阻率不仅取决于富集相中VGCF的含量,而且还与PVDF相的连续性及其结晶行为密切相关。     

Effect of ZnO and CuO on the Sintering Temperature and Piezoelectric Properties of a Hard Piezoelectric Ceramic

Hard piezoelectrics with high dielectric and piezoelectric constants are used for high-power applications. However, the sintering temperature of these ceramics is high, around 1200°C, restricting the usage of cheap base metal electrodes in fabrication of multi-layer components. This study investigates the effect of CuO and ZnO on the sintering temperature of a hard piezoelectric, APC 841, which is a MnO₂- and Nb₂O₅-modified PZT. The addition of CuO decreased the sintering temperature through the formation of a liquid phase. However, the piezoelectric properties of the CuO-added ceramics sintered at ≤950°C were lower than the desired values. The addition of ZnO resulted in a significant improvement in the piezoelectric properties. This enhancement was attributed to the formation of a homogeneous microstructure with large grains. The APC 841+0.2 wt% CuO+1.1 wt% ZnO ceramics sintered at 950°C showed excellent piezoelectric and dielectric properties with values of k _p=0.532, Q _m=750, d ₃₃=351 pC/N, ɛ₃₃/ɛ_o=1337, and T _c=280°C.     

Electrical and light-emitting properties of (001)-oriented homoepitaxial diamond p–i–n junction

We have realized high-efficiency excitonic emission with deep-UV light at room temperature for a (001)-oriented diamond p–i–n junction diode consisting of the boron-doped p-type, non-doped intrinsic, and phosphorus-doped n-type layers. High-performance p–i–n junction characteristics were confirmed from current–voltage and capacitance–voltage properties. A strong UV light emission at around 240 nm due to free exciton recombination was observed at a forward current, while the broad visible light emission from deep levels was significantly suppressed compared to that of reported electroluminescence in diamond p–n junctions.     

微粒的导电性对复合镀层结构与性能的影响

在复合电沉积过程中辅助施加超声波搅拌,制备出Ni-Al和Ni-Al2O3两种复合镀层。借助扫描电镜、X射线衍射仪、显微硬度计和摩擦磨损试验机研究了微粒的导电性对复合镀层形貌、相结构及性能的影响。结果表明:微粒的导电性对复合镀层的形貌、相结构和显微硬度均有一定影响,但对耐磨性的影响不明显;添加惰性微粒有利于获得形貌良好、结构致密、显微硬度较高的复合镀层。     

石墨/聚丙烯复合板的导电与阻气性能

为寻找具有高导电与气密性能且成本低廉的聚合物膜燃料电池双极板新材料和加工方法，利用热压法制备了石墨与聚丙烯(PP)的复合板，考察了PP质量分数、粒径、混合均匀程度、熔体质量流动速率对复合板导电性能以及阻气性能的影响，并与纯柔性石墨板的导电与阻气性进行了比较。实验表明，PP质量分数及其与石墨颗粒混合的均匀性是对复合板的导电和阻气性产生影响的重要因素；PP与石墨颗粒混合的均匀性对复合板的导电性影响较大，混合均匀则导电率高；PP粒径、MFR等亦可对复合板的导电和阻气性能产生影响，但程度较小。     

Electrical and light-emitting properties from (111)-oriented homoepitaxial diamond p–i–n junctions

We have succeeded in fabricating a (111)-oriented diamond p–i–n junction with high crystalline quality intrinsic layer and with low series resistance. The series resistance of this diamond p–i–n junction was improved by decreasing the resistivity and specific contact resistance of n-type layer, which is allowed to inject higher current while maintaining lower junction temperature. Current density–voltage characteristics showed a rectification ratio of 10⁶ at ± 15 V at room temperature. A clear ultraviolet emission at around 235 nm due to free exciton recombination was observed at a forward current, while the broad visible light emission from deep levels was significantly suppressed. Moreover, stronger excitonic emission by two orders of magnitude than that of (001)-oriented diamond p–i–n junctions with high series resistance was realized.     

改性炭黑填充聚丙烯复合材料导电性能研究

将改性炭黑/聚丙烯熔融共混,制得复合导电材料,研究了填充不同种类的改性炭黑及其质量分数对复合材料导电性产生的影响。结果显示,复合材料呈现显著的渗滤效应,渗滤阈值约为10%;复合材料中填充改性炭黑后,其渗滤阈值下降至约8%。填充的炭黑种类不同,得到的复合材料的渗滤阈值存在较大的差异。复合材料的导电性能与炭黑比表面积也相关,炭黑比表面积越大,粒径越小,导电效果越好。     

CuO/ZnO复合纳米材料的合成及其催化烯烃环氧化性能研究

以醋酸锌和硝酸铜为原料通过离子共沉淀法一步合成了(CuxZn1-x)(OH)m(CO3)n固溶体,并选择在500℃条件下煅烧得到Cu O/Zn O复合纳米晶体。采用扫描电镜和EDS-Mapping等进行表征,分析材料的形貌和组成,证明晶体为疏松结构的小球,且铜元素和锌元素均匀地分散其中。另外,把得到的样品应用于环辛烯氧化中,发现当Cu2+∶Zn2+=3时的催化活性最高。