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Protein crystallization could be promoted with a low concentration of impurities and inhibited with a high concentration of impurities, and this inhibition can be weakened by an audible sound.

Polypropylene is considered to be the material of choice for environmentally friendly high voltage direct current cable insulation. The high power transmission of electrical energy exposes insulating materials to high temperatures and electric fields, resulting in the degradation of material properties. This paper reports that organic molecular semiconductors with strong electron affinity can effectively modulate electrical properties of polypropylene. The charge injection and transport process are analyzed by considering a combination of relations describing various conduction models in dielectrics, including the Richardson–Schottky (RS) emission and the hopping conduction. Based on the performed experiments, a modified Wiesmann–Zeller (WZ) model is proposed to simulate the electrical treeing process of polypropylene. The electrical treeing results are well verified with the simulation results, which offer a valuable tool for further analysis of the effect of intrinsic barrier height, hopping distance, and activation energy on the electrical degradation in the material. This work provides an insightful analysis of multiple charge transport mechanisms affecting the electrical degradation of the polymer, which is crucially essential for the rational design of high-performance insulation materials.

Parallel gaps, as a new mode of "channel" type lightning protection, can do it with the sub insulator arc distance to effectively protect the insulator, but the corresponding line tripping rate will be affected because of this; Development method based on the leader in this paper the calculation method of the lightning path, the typical used tower of guangzhou trip rate change after the application of parallel gap situation has carried on the analysis, got a short distance and adopt reasonable reinforced insulation, the trip rates did not rise significantly.

The fault of transmission line is mostly caused by lightning, and a ground lightning stroke process is often accompanied by multiple strokes. The duration of ground lightning stroke are also different. In this paper, a method for evaluating the reclosing time of reclosure based on lightning parameters is proposed. In addition, this paper also gives an expression for the cumulative rate of the duration of ground lightning stroke, and an expression for probability distribution of the amplitude of lightning current in Guangdong area. We also proposed a method for calculating the probability of tripping of reclosure. By this calculating method, the average probability of tripping of reclosure is less than 1/10000 during a ground lightning stroke process, when the reclosing time t0 is greater than 1.012s.

As a new kind of lightning protection, parallel gaps have simple structure, easy installation, good economy, and many other advantages. The traditional parallel gap due to the large short distance, can lead to lightning trip-out rate increases. Based on arc movement characteristics this paper presents a design of new type of parallel gaps and the analysis of the surface field strength, and the verification test, design a new kind of parallel gap are obtained.

The CaCu3Ti4O12 samples with slight amount of doped bismuth were prepared and tested in this research. No second phase with bismuth was found in the doped samples. It was inferred that the bismuth ions has entered the lattice and take the place of the calcium ions. The grain size was diminished with the increase of the bismuth content. The bismuth atoms can inhibit the grains from growing large, and it could be used to modify the microstructure of CaCu3Ti4O12 ceramic. The reduction of the grain size resulted in the decrease of the relative dielectric constant, according to the “internal barrier layer capacitance (IBLC)” theory. The impedance measurements showed that the doped samples have less conductivity and lower potential barrier at the grain boundaries, and the substitution of the bismuth ions on the calcium cites might be the reason for it. As a result of the lowered potential barrier, the non-ohmic I-V property of the CaCu3Ti4O12 ceramic almost disappears in the doped ones.

The additive of Al(NO3)3 was doped into ZnO varistors in order to reduce their residual voltages. Some of doped Al3+ enter the ZnO grains and infill into the vacancies of Zn2+ ions in the crystal lattice. Then, the resistances of ZnO grains decrease, which finally results in lower residual voltages of varistor samples. However, when most of Zn2+ vacancies inside the ZnO crystal lattice are filled with Al3+, redundant Al3+ ions inside ZnO grains will increase the grains’ resistances contrarily. In this paper, ZnO and Al(NO3)3 binary ceramics sintered at 1300 °C for 2, 4 and 8 hours were studied. The J-E curves of the investigated samples exhibit weak non-linear characteristics which may be due to the formation of grain boundary. Moreover, The resistivity dependence of ZnO ceramics on Al addition behaves as a U-type curve and the lowest resistivity of ZnO ceramics is obtained with doping 0.25mol% Al3+.

The cooling rate effect on the grain boundaries of the CaCu3Ti4¬O12 ceramic was investigated in this research. The resistance at the grain boundaries is found to be reduced as the cooling rate rises. The activation energies at the grain boundaries do not change with the cooling rate, suggesting that the conduction mechanism keeps the same in different cooling conditions. There is no significant difference in the permittivity of the samples. The dielectric loss can be lowered by using a smaller cooling rate. These results give clues to comprehend the conductive mechanism of the CCTO ceramic. The variation of the cooling rate may affect the re-oxidation process and cause the changes in electric properties.

ZnO varistors are multicomponent polycrystalline ceramics with highly nonlinear current-voltage characteristics and surge energy absorption capabilities. The voltage gradient of the ZnO varistor is inversely proportional to its average grain size. Recently, the rare-earth oxides have been reported as growth inhibitor of ZnO grains to obtain high voltage gradient. Although the dopant of rare-earth oxides can remarkably enhance the voltage gradients of varistor samples, their leakage currents and nonlinear coefficients deteriorate at the same time. In this paper, the sintering effects on electrical characteristics and admittance spectroscopies of ZnO varistor samples doped with yttrium oxides were investigated. Samples were fabricated under different sintering temperatures, including 1000 °C, 1100 °C, 1200 °C and 1300 °C. Then, the electrical characteristics and admittance spectroscopies of these varistor samples were measured. The measured current-voltage results behave special U-type curves related to sintering temperature. Furthermore, the admittance spectroscopy of these samples revealed the sintering effects on the intrinsic defects of ZnO varistors.

The average intercept length and related corrective method are proposed to calculate the average grain boundary number. The average value of barrier voltage by direct measurement to single grain boundary is 3.3V in literatures, but from our prepared ZnO varistor samples, the value of the average barrier voltage by the average grain size is only 2.3 V. It is in the range from 3.24 to 3.38 V by the proposed method, which is very close to the direct measured value 3.3V of the single grain boundary. The introduced method to calculate average grain size has an obvious effect to correct the calculated barrier voltage to near the actual one by direct measurement to single grain boundary.

The numerical simulation is an effective method for researching the relationship between macroscopic properties of ZnO varistors and their microstructural characteristics. However, the computing efficiency is a big problem for further researches. In this paper, a quick piecewise linear method for solving the complicated nonlinear resistor networks of ZnO varistors is proposed, which can significantly improve the computing efficiency by a hundred times. The simulating models for the microstructural characteristics of ZnO varistors are improved based on actual conduction mechanism of grain boundaries. The simulations of more bulk characteristics of ZnO varistors become possible, such as alternating current (AC) and surge properties.

This paper systematically analyzes the microstructural nonuniformity of ZnO varistors when Al2O3 dopants are added. The introduction of Al2O3 dopants leads to a decrease of ZnO grain growth rate and correspondingly an increase of the microstructural uniformity of ZnO varistors. Both the average value and the standard deviation of ZnO grain sizes decrease with the increase of Al2O3 content, approximately in a log-linear relation. With detailed experimental results, this study provides quantitative references for the practice of adding Al2O3 dopants to give ZnO varistors desired microstructural and electrical characteristics.

ZnO-Pr6O11-Dy2O3-based varistor ceramics doped with 0~1.5 mol% La2O3 were fabricated by a conventional ceramic method. All the samples were sintered at 1350 oCfor 2 h. The phase composition and microstructure of the ceramic samples have been investigated by XRD, SEM and EDS. The results of SEM micrographs indicated that the La2O3 additives can promote ZnO grain’s growth, and the rare earth elements dispersed mainly in the intergranular phase observed by EDS. The electrical properties of the samples determined by the V-I curves revealed that the breakdown voltage of samples decreases from 508 V/mm to about 100 V/mm with the increase of La2O3, and the nonlinear exponent also decreases from 20.2 to 13.2. The typical leakage current is about 10.2 μA for the sample doped with 0.5 mol% La2O3.

The additive of Al(NO3)3 has been doped into ZnO varistors in order to reduce their residual voltages. However, the leakage currents of samples always increase at the same time. Generally, it is recognized that some of doped Al3+ ions enter the ZnO grains and reduce their resistivity, which results in lower residual voltages of varistor samples. On the other hand, the remnant Al3+ ions appear in the grain boundaries and also reduce their resistivity, which results in larger leakage currents. In this paper, the electrical properties of ZnO varistor samples with various amounts of Al(NO3)3 dopant were measured. The experimental data are compared with the numerical simulation results, which reveals that the increased leakage currents of ZnO varistors with Al(NO3)3 dopant are not only due to the decreased resistivity of grain boundaries, but also the increased donor density of ZnO grains.

The presence of twins in ZnO varistors raises interesting questions concerning the potential role of those electrically distinctive twin boundaries in the characteristics of ZnO varistors. The paper uses Voronoi networks to simulate the microstructures of ZnO varistors. The relation between the relative standard deviation of grain size and the ratio of twin number to grain number is obtained. It indicates that the relative standard deviation decreases with the increasing of the twin ratio. On the other hand, ZnO varistor samples with different content of Al2O3 additive were prepared to gain different twin ratios. The simulation has the same conclusion as that obtained from experiments. The probable mechanism of ZnO grain growth inhibition by twins is that the twins increase the mobility viscosity of ZnO grains and grain boundaries, and drag ZnO grains and liquid grain boundaries during the sintering course, then the grain growth is inhibited, and the microstructure becomes more uniform.

ZnO varistors with higher voltage gradients are expected in the power system, and the key to this property is to diminish the grain size. In this paper, nano-sized ZnO particles are used as the raw material in order to obtain small grains. Pellets are fabricated by two sintering methods: the conventional pressureless sintering and the spark plasma sintering (SPS). For the samples fabricated by the conventional sintering, the average grain size varies from 1 μm to more than 10 μm when the sintering temperature changes from 900 oC to 1200 oC. The voltage gradient can reach as high as 2020 V/mm. The grain size of the SPS samples is less than 1 μm, and the voltage gradients can reach 963 V/mm.