Modeling porous structure of oil-pressboard interface and its effect on electric field distribution

The oil-pressboard insulation is a typical composite insulation system widely used in the design and manufactory of large power apparatus. The implement of oil-pressboard insulation may lead to surface electrification and discharge at the interface under certain condition. It is of significant importance to take an insight into the phenomenon occurring at the interface. Through experiment, the pressboard is found as a porous material. The interface changes abruptly from bulk pressboard to the bulk oil as a result of the porous structure. A new model is proposed which divides the interface into bulk oil region, transition region, and bulk pressboard region. The width of the transition region is decided according to the microtome figure. The effective permittivity of the transition region is calculated using a new model based on fractal theory. The model is validated and compared with previous calculation model. The effect of the existence of transition region on the electric field distribution is discussed.

通过测量电力输入预测磨料/工件界面的条件变化(英文)

A monitoring system is proposed in order to detect the condition changes at abrasive/workpiece interface in abrasive cutoff operation.The system can detect the condition changes from the electric power change consumed by the driving motor of lapping tool.The electric power is strongly related with the abrasive effectiveness.When the abrasive effectiveness has been kept a normal state,the electric power also has been kept a constant value.The bodily removal of abrasive leads to reduce the electric power monotonously.The piling up of cutting chips leads to a peculiar electric power change;the electric power increased gradually at the beginning and then began to fluctuate periodically.The severe adhesion of cutting chips to the cutting edges leads to the loss of nominal function in the cutting edges and the electric power input was thus descended suddenly at an early stage of lapping.

An effective CdS/Ti-Fe_(2)O_(3)heterojunction photoanode:Analyzing Z-scheme charge-transfer mechanism for enhanced photoelectrochemical water-oxidation activity

Z-scheme photocatalytic system has been regarded as a popular field of research in photoelectrochemical(PEC)water splitting.Among the many obstacles facing a Z-scheme photocatalytic system,the analysis methods of interfacial Z-scheme charge transfer still remain a significant challenge.Hence,in this study,CdS/Ti-Fe_(2)O_(3)heterojunction photoanodes are elaborately designed to explore the charge-transfer behavior in PEC water splitting.In this study,photophysical measurements,including the Kelvin probe measurement,surface photovoltage spectroscopy(SPV),and transient photovoltage spectroscopy(TPV),are used to monitor the migration behavior of photogenerated charges at the interface electric field of CdS/Ti-Fe_(2)O_(3)Z-scheme heterojunction photoanodes.The Kelvin probe and SPV measurements demonstrate that CdS/Ti-Fe_(2)O_(3)interfacial driving force favors the rapid transfer of photoexcited electrons to CdS.The double-beam strategy based on TPV indicates that more electrons of Ti-Fe_(2)O_(3)are combined with the holes of CdS owing to the intensive interface electric field.The results of these measurements successfully prove the Z-scheme migration mechanism of CdS/Ti-Fe_(2)O_(3)photoanodes.Benefiting from the desirable charge transfer at the interface electric field,CdS/Ti-Fe_(2)O_(3)photoanodes exhibit superior photocatalytic oxygen evolution reaction performance compared with that of pure Ti-Fe_(2)O_(3).The photocurrent density of the 25CdS/Ti-Fe_(2)O_(3)photoanode reaches 1.94 mA/cm^(2) at 1.23 V versus reversible hydrogen electrode without excess cocatalyst,and it is two times higher than that of pure Ti-Fe_(2)O_(3)photoanode.Therefore,an outstanding strategy is provided in this study to prove the Z-scheme charge-transfer mechanism of photocatalytic systems in PEC water splitting.

Some Interface Electrochemical Properties of Kaolinite

The interface electrochemical properties of clay were theoretically analyzed to obtain some relationships among point of zero net charge （PZNC）, point of zero net proton charge （PZNPC）, intrinsic surface reaction equilibrium constants （K in 1-pK model, Ka1^int and Ka2^int in 2-pK model, ＊KNa^int and ＊KNO3^int in inert electrolyte chemical binding model） and structural negative charge density （σst） of clay, and some interface electrochemical parameters of kaolinite were measured. The following main conclusions were obtained. For clay possessing structural negative charges, the PZNC independent of electrolyte concentration （c） should exist just as amphoteric solid without structural charges such as oxides or hydroxides. A common intersection point （CIP） should appear among the potentiometric （or acid-base） titration curves at different c and the pH at the CIP should be PHPZNC. A CIP among potentiometric titration curves at different c for kaolinite was observed, and the value of PHPZNC of kaolinite was 2.16. The values of pHPZNPC were decreased with increasing c, which arises from the presence of structural negative charges of kaolinite. In addition, it was observed that a good linear relationship existed between pHPZNPC and 1g c. According to the values of PHPZNC and σst measured, the intrinsic surface reaction equilibrium constants, pK and pKa1^int and pKa2^int of 1-pK and 2-pK models could be directly calculated for clay, and the values of pK, pKa1^int and pKa2^int for kaolinite were 2.93, 1.90 and 3.97, respectively. These experimental values of pKa1^int and pKa2^int for kaolinite are obviously lower than those optimized with fitting programs in literatures, which maybe arises from the introduction of a type of permanent negatively charged sites in the models of literatures. An interesting result obtained in this study is that the inert electrolyte chemical binding does not exist for kaolinite, which also arises from the presence of structural negative charges.

Boosting Photocatalytic Oxygen Evolution:Purposely Constructing Direct Z-Scheme Photoanode by Modulating the Interface Electric Field

Ti-Fe2O3 photoanode has received widespread attention in photoelectrochemical(PEC)water spilling because of its optimized oxidative and reductive capability of composites catalyst.However,its low efficiency could limit its development.Herein,in order to improve the efficiency of PEC water spilling,the all-solid-state direct Z-scheme Ti-ZnFe2O4/Ti-Fe2O3(TZFO/Ti-Fe2O3)nanorod arrays composited with the ideal energy band structure are synthesized by modulating the Fermi level of TZFO for PEC water splitting.The photophysical methods in this work,including the Kelvin probe measurement and transient photovoltage spectroscopy(TPV)measurement,are applied to explore the migration behavior of electric charges at the enhanced interface electric field.Finally,the Z-scheme charge transfer mechanism of TZFO/Ti-Fe2O3 photoanode is proved successfully.Benefiting from the desirable charge transfer at interface electric field,the TZFO/Ti-Fe2O3 exhibits the outstanding photocatalytic oxygen evolution reaction(OER)performance,and the photocurrent of 60TZFO/Ti-Fe2O3 photoanode reaches 2.16 mA/cm^2 at 1.23 V vs.reversible hydrogen electrode(RHE),which is three times higher than that of pure Ti-Fe2O3 photoanode.This work provides a facile approach of modulating interface electric field to optimize the Z-scheme charge-transfer process.