Papers by Keyword: Voltage Gradient

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Authors: Chang Qi Xia, Qi Bin Liu, Mo He
Abstract: To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, the effect of different sintering temperature (1135~1155 °C) on electrical properties of ZnO varistors were investigated. The experimental results show that with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. When the sintering temperature is at 1135 °C, the voltage gradient of varistor is up to 329V/mm, the leakage current is 8μA and the density is 96.4%. When the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%. Compared the results at 1135 °C with 1140 °C , it is found that the comprehensive electrical properties of ZnO varistors reach maximum at 1140 °C.
31
Authors: Madhuri Karnik, Amitabha Ghosh, Rajiv Shekhar
Abstract: The present study attempts to investigate the polarity dependence of ECD by studying stagnant electrolyte cell (SEC) and the cell used for fused deposition through electrochemical discharge (FDED). Both the cells had identical electrodes and composition of electrolyte. It was judged on the basis of colour of the discharge, voltage gradient developed near the electrode at which discharge takes place (active electrode). It was revealed that the discharge at anode was an arduous phenomenon in both the cells. ECD occurred when the voltage gradient of 106 V/m was developed near the active cathode in the SEC as well as the one in FDED cell. But it took voltage gradient of 107V/m for the discharge to take place at active anode in the SEC. ECD never took place at the anode tip in the FDED cell as the voltage gradient never reached 107 V/m even at the applied voltage of 300 V. The bluish green coloured discharge took place at the cathode in both the cells whereas bright yellow coloured discharge took place at the anode in the SEC.
131
Authors: Chang Qi Xia, Qi Bin Liu, Mo He
Abstract: To obtain ZnO varistors with high voltage gradient, ZnO varistors were fabricated by traditional ceramic sintering technique, which were sintered from 1135 to 1155 °C, the microstructure and properties of varistors were characterized by SEM, X-rays diffraction and DC parameter instrument for varistors. The experimental results show that the spinel phase Zn7Sb2O12 generated during sintering process, very thin amorphous Bi rich films are formed between the ZnO/ZnO grain boundaries, with increasement of sintering temperature, the grain size of ZnO varistor ceramic becomes bigger, the voltage gradient of varistor decreases and the density is improved. The optimized parameters are that when the sintering temperature is at 1140 °C, the voltage gradient of varistor is 301V/mm, the leakage current is 4μA and the density is 96.6%, the comprehensive electrical properties of ZnO varistors reach maximum.
2008
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