Water-based ZnO nanofluids were prepared via the two-step method,and the influences of dispersant type and mass fraction on the stability and particle size distribution of the nanofluids were investigated.The spectral...Water-based ZnO nanofluids were prepared via the two-step method,and the influences of dispersant type and mass fraction on the stability and particle size distribution of the nanofluids were investigated.The spectral transmittances of the nanofluids were obtained by a UV-Vis-NIR spectrophotometer.Thermal conductivities of the nanofluids with various mass fractions were measured at different temperatures and a fitted nonlinear correlated equation was established for low-concentration application and compared with existing models.The photothermal conversion performance of the nanofluids was evaluated by theoretical and experimental methods at three optical depths.The results showed that,CTAB as the dispersant provides better physical stability of water-based ZnO nanofluids than SDBS or GA does.Effect of the temperature on the nanofluid thermal conductivity is remarkable with the increase of nanoparticle mass fraction,especially in the range 55°C to 75°C.The maximum thermal conductivity of the studied nanofluids is 0.9488 W/(m·℃)at 75°C,43.61%higher than that of water.The minimum thermal conductivity of the studied nanofluids is 0.6376 W/(m·℃)at 25°C,5.16%higher than that of water.The photothermal conversion performance of the nanofluids is quite good with a maximum average absorption efficiency of 0.47,135%higher than that of water(η=0.2),and the maximum SAR is 527.5 W/g.展开更多
Fabrication temperature is an important factor affecting the manufacturability of electronic devices,especially for the bottom-up self-assembled nano-device.In this study,we used a lateral-bridged zinc oxide(ZnO)nanow...Fabrication temperature is an important factor affecting the manufacturability of electronic devices,especially for the bottom-up self-assembled nano-device.In this study,we used a lateral-bridged zinc oxide(ZnO)nanowire array UV sensor as a model to investigate the influence of temperature on device performance over the entire manufacturing process,from sensor fabrication to packaging.We found that annealing of the SiO2 substrate would make ZnO seed layer on top of it more compact and uniform,and hence improve the lateral orientation and uniformity of ZnO nanowires grown from the seed layer.With the annealed substrate,the light-to-dark current ratio increased by two orders of magnitude.On the contrary,annealing the ZnO seed layer would deteriorate the light-to-dark current ratio of the sensor,because annealing caused most of the grains in the seed layer to become vertically aligned,which in turn affected the lateral growth of ZnO nanowire arrays.During the packaging process,the surface structure of ZnO nanowires would change if the chip welded at a temperature of 230℃for 2 min,resulting in a decrease of light-to-dark current ratio by three orders of magnitude.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51766012)Natural Science Foundation of Inner Mongolia(NO.2019MS05025)the Inner Mongolia Science and Technology Major Project(NO.2019ZD014).
文摘Water-based ZnO nanofluids were prepared via the two-step method,and the influences of dispersant type and mass fraction on the stability and particle size distribution of the nanofluids were investigated.The spectral transmittances of the nanofluids were obtained by a UV-Vis-NIR spectrophotometer.Thermal conductivities of the nanofluids with various mass fractions were measured at different temperatures and a fitted nonlinear correlated equation was established for low-concentration application and compared with existing models.The photothermal conversion performance of the nanofluids was evaluated by theoretical and experimental methods at three optical depths.The results showed that,CTAB as the dispersant provides better physical stability of water-based ZnO nanofluids than SDBS or GA does.Effect of the temperature on the nanofluid thermal conductivity is remarkable with the increase of nanoparticle mass fraction,especially in the range 55°C to 75°C.The maximum thermal conductivity of the studied nanofluids is 0.9488 W/(m·℃)at 75°C,43.61%higher than that of water.The minimum thermal conductivity of the studied nanofluids is 0.6376 W/(m·℃)at 25°C,5.16%higher than that of water.The photothermal conversion performance of the nanofluids is quite good with a maximum average absorption efficiency of 0.47,135%higher than that of water(η=0.2),and the maximum SAR is 527.5 W/g.
基金supported by the National Natural Science Foundation of China(Grant No.11204009)the Beijing Municipal Natural Science Foundation(Grant Nos.4142005 and 4182014)Beijing Education Commission Science and Technology Program(Grant No.KM201810005025)。
文摘Fabrication temperature is an important factor affecting the manufacturability of electronic devices,especially for the bottom-up self-assembled nano-device.In this study,we used a lateral-bridged zinc oxide(ZnO)nanowire array UV sensor as a model to investigate the influence of temperature on device performance over the entire manufacturing process,from sensor fabrication to packaging.We found that annealing of the SiO2 substrate would make ZnO seed layer on top of it more compact and uniform,and hence improve the lateral orientation and uniformity of ZnO nanowires grown from the seed layer.With the annealed substrate,the light-to-dark current ratio increased by two orders of magnitude.On the contrary,annealing the ZnO seed layer would deteriorate the light-to-dark current ratio of the sensor,because annealing caused most of the grains in the seed layer to become vertically aligned,which in turn affected the lateral growth of ZnO nanowire arrays.During the packaging process,the surface structure of ZnO nanowires would change if the chip welded at a temperature of 230℃for 2 min,resulting in a decrease of light-to-dark current ratio by three orders of magnitude.
