Microchannel reactors are commonly used in micro-chemical technology. The performance of microreactors is greatly affected by the velocity field in the microchannel. The flow field is disturbed by the cylindrical etch...Microchannel reactors are commonly used in micro-chemical technology. The performance of microreactors is greatly affected by the velocity field in the microchannel. The flow field is disturbed by the cylindrical etch holes caused by air dust on the microchannel surface during its processing procedure. In this approach, a two-dimensional computational fluid dynamics （CFD） model is put forward to study the effect of etch holes on flow field. The influenced area of single or two concave etch holes is studied for the case of laminar flow. The hole diameter, the Reynolds number and the distance between the center of holes are found to have influences on the flow field. Numerical results indicate that the effects of etch hole on the flow field should be evaluated and the way of choosing the economic class of cleanroom for microreactor manufacture is presented.展开更多
Polycrystalline ZnO films are prepared using radio frequency magnetron sputtering on glass substrates which are sputter-etched for different time. Both the size of ZnO grains and the root-mean-square (RMS) roughness d...Polycrystalline ZnO films are prepared using radio frequency magnetron sputtering on glass substrates which are sputter-etched for different time. Both the size of ZnO grains and the root-mean-square (RMS) roughness decrease, as the sputter-etching time of the substrate increases. More Zn atoms are bound to O atoms in the films, and the defect concentration is decreased with increasing sputter-etching time of substrate. Meanwhile, the crystallinity and c-axis orientation are improved at longer sputter-etching time of the substrate. The Raman peaks at 99 cm-1, 438 cm-1 and 589 cm-1 are identified as E2(low), E2(high) and E1(LO) modes, respectively, and the position of E1(LO) peak blue shifts at longer sputter-etching time. The transmittances of the films, which are deposited on the substrate and etched for 10 min and 20 min, are higher in the visible region than that of the films deposited under longer sputter-etching time of 30 min. The bandgap increases from 3.23 eV to 3.27 eV with the increase of the sputter-etching time of substrate.展开更多
基金Supported by the National Natural Science Foundation of China （20676093）.
文摘Microchannel reactors are commonly used in micro-chemical technology. The performance of microreactors is greatly affected by the velocity field in the microchannel. The flow field is disturbed by the cylindrical etch holes caused by air dust on the microchannel surface during its processing procedure. In this approach, a two-dimensional computational fluid dynamics （CFD） model is put forward to study the effect of etch holes on flow field. The influenced area of single or two concave etch holes is studied for the case of laminar flow. The hole diameter, the Reynolds number and the distance between the center of holes are found to have influences on the flow field. Numerical results indicate that the effects of etch hole on the flow field should be evaluated and the way of choosing the economic class of cleanroom for microreactor manufacture is presented.
基金supported by the National Natural Science Foundation of China (No.50972105)the National High Technology Research and Development Program of China (No.2009AA03Z444)the Key Supporting Plan Program of Tianjin (No.10ZCKFGX01200)
文摘Polycrystalline ZnO films are prepared using radio frequency magnetron sputtering on glass substrates which are sputter-etched for different time. Both the size of ZnO grains and the root-mean-square (RMS) roughness decrease, as the sputter-etching time of the substrate increases. More Zn atoms are bound to O atoms in the films, and the defect concentration is decreased with increasing sputter-etching time of substrate. Meanwhile, the crystallinity and c-axis orientation are improved at longer sputter-etching time of the substrate. The Raman peaks at 99 cm-1, 438 cm-1 and 589 cm-1 are identified as E2(low), E2(high) and E1(LO) modes, respectively, and the position of E1(LO) peak blue shifts at longer sputter-etching time. The transmittances of the films, which are deposited on the substrate and etched for 10 min and 20 min, are higher in the visible region than that of the films deposited under longer sputter-etching time of 30 min. The bandgap increases from 3.23 eV to 3.27 eV with the increase of the sputter-etching time of substrate.
