Surface modification of polypropylene microporous membrane （PPMM） was performed by atmospheric pressure dielectric barrier discharge plasma immobilization of N,Ndimethylamino ethyl methacrylate （DMAEMA）. Structura...Surface modification of polypropylene microporous membrane （PPMM） was performed by atmospheric pressure dielectric barrier discharge plasma immobilization of N,Ndimethylamino ethyl methacrylate （DMAEMA）. Structural and morphological changes on the membrane surface were characterized by attenuated total reflection-Fourier transform infrared spectroscopy （FT-IR/ATR）, X-ray photoelectron spectroscope （XPS） and field emission scanning electron microscopy （FE-SEM）. Water contact angles of the membrane surfaces were also measured by the sessile drop method. Results reveal that both the plasma-treating conditions and the adsorbed DMAEMA amount have remarkable effects on the immobilization degree of DMAEMA. Peroxide determination by 1,1-diphenyl-2-picrvlhydrazyl （DPPH） method verifies the exsistence of radicals induced by plasma, which activize the immobilization reaction. Pure water contact angle on the membrane surface decreased with the increase of DMAEMA immobilization degree, which indicates an enhanced hydrophilicity for the modified membranes. The effects of immobilization degrees on pure water fluxes were also measured. It is shown that pure water fluxes first increased with immobilization degree and then decreased. Finally, permeation of bovine serum albumin （BSA） and lysozyme solution were measured to evaluate the antifouling property of the DMAEMA-modified membranes, from which it is shown that both hydrophilicity and electrostatic repulsion are beneficial for membrane antifouling.展开更多
A two-dimensional coupled model of neutral gas flow and plasma dynamics is employed to investigate the streamer dynamics in a helium plasma needle at atmospheric pressure. A parametric study of the streamer propagatio...A two-dimensional coupled model of neutral gas flow and plasma dynamics is employed to investigate the streamer dynamics in a helium plasma needle at atmospheric pressure. A parametric study of the streamer propagation as a function of needle tip curvature radius and helium gas flow rate is presented. The key chemical reactions at the He/air mixing layer which drive the streamer propagation are the direct ionization via collision with electrons, the Penning effect being not so crucial. With increasing the gas flow rate from 0.2 standard liter per minute（SLM） to 0.8 SLM, however, the emissions resulting from reactive oxygen and nitrogen species change from a solid circle to a hollow profile and the average streamer propagation velocity decreases. Air impurities（backdiffusion from ambient air） in the helium jet result in a significant increase in the streamer propagation velocity. Besides, with decreasing the tip curvature radiusfrom 200 μm to 100 μm,the electron avalanche process around the near-tip region is more pronounced. However, the spatially resolved plasma parameters distributions（electron, helium metastables, ground state atomic oxygen, etc.） remain almost the same, except that around the near-tip region where their peak values are more than doubled.展开更多
The deposition of organosilicone thin films from hexamethyldisiloxane（HMDSO） by using a dual-frequency （50 kHz/33 MHz） atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was ...The deposition of organosilicone thin films from hexamethyldisiloxane（HMDSO） by using a dual-frequency （50 kHz/33 MHz） atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was investigated.The topography was measured by using scanning electron microscopy.The chemical bond and composition of these films were analyzed by Fourier transform infrared spectroscopy （FTIR） and x-ray photoelectron spectroscopy.The results indicated that the as-deposited film was constituted by silicon,carbon,and oxygen elements,and FTIR suggested the films are organosilicon with the organic component （-CHx） and hydroxyl functional group（-OH） connected to the Si-O-Si backbone.Thin-film hardness was recorded by an MH-5-VM Digital Micro-Hardness Tester.Radio frequency power had a strong impact on film hardness and the hardness increased with increasing power.展开更多
文摘Surface modification of polypropylene microporous membrane （PPMM） was performed by atmospheric pressure dielectric barrier discharge plasma immobilization of N,Ndimethylamino ethyl methacrylate （DMAEMA）. Structural and morphological changes on the membrane surface were characterized by attenuated total reflection-Fourier transform infrared spectroscopy （FT-IR/ATR）, X-ray photoelectron spectroscope （XPS） and field emission scanning electron microscopy （FE-SEM）. Water contact angles of the membrane surfaces were also measured by the sessile drop method. Results reveal that both the plasma-treating conditions and the adsorbed DMAEMA amount have remarkable effects on the immobilization degree of DMAEMA. Peroxide determination by 1,1-diphenyl-2-picrvlhydrazyl （DPPH） method verifies the exsistence of radicals induced by plasma, which activize the immobilization reaction. Pure water contact angle on the membrane surface decreased with the increase of DMAEMA immobilization degree, which indicates an enhanced hydrophilicity for the modified membranes. The effects of immobilization degrees on pure water fluxes were also measured. It is shown that pure water fluxes first increased with immobilization degree and then decreased. Finally, permeation of bovine serum albumin （BSA） and lysozyme solution were measured to evaluate the antifouling property of the DMAEMA-modified membranes, from which it is shown that both hydrophilicity and electrostatic repulsion are beneficial for membrane antifouling.
基金Project supported partly by the National Natural Science Foundation of China(Grant No.11465013)the Natural Science Foundation of Jiangxi Province+1 种基金China(Grant No.20151BAB212012)in part by the International Science and Technology Cooperation Program of China(Grant No.2015DFA61800)
文摘A two-dimensional coupled model of neutral gas flow and plasma dynamics is employed to investigate the streamer dynamics in a helium plasma needle at atmospheric pressure. A parametric study of the streamer propagation as a function of needle tip curvature radius and helium gas flow rate is presented. The key chemical reactions at the He/air mixing layer which drive the streamer propagation are the direct ionization via collision with electrons, the Penning effect being not so crucial. With increasing the gas flow rate from 0.2 standard liter per minute（SLM） to 0.8 SLM, however, the emissions resulting from reactive oxygen and nitrogen species change from a solid circle to a hollow profile and the average streamer propagation velocity decreases. Air impurities（backdiffusion from ambient air） in the helium jet result in a significant increase in the streamer propagation velocity. Besides, with decreasing the tip curvature radiusfrom 200 μm to 100 μm,the electron avalanche process around the near-tip region is more pronounced. However, the spatially resolved plasma parameters distributions（electron, helium metastables, ground state atomic oxygen, etc.） remain almost the same, except that around the near-tip region where their peak values are more than doubled.
基金supported by National Natural Science Foundation of China(Grant No.11165012,Grant No. 11665012)the Project of the Natural Science Foundation of GanSu(145RJZA159)
文摘The deposition of organosilicone thin films from hexamethyldisiloxane（HMDSO） by using a dual-frequency （50 kHz/33 MHz） atmospheric-pressure micro-plasma jet with an admixture of a small volume of HMDSO and Ar was investigated.The topography was measured by using scanning electron microscopy.The chemical bond and composition of these films were analyzed by Fourier transform infrared spectroscopy （FTIR） and x-ray photoelectron spectroscopy.The results indicated that the as-deposited film was constituted by silicon,carbon,and oxygen elements,and FTIR suggested the films are organosilicon with the organic component （-CHx） and hydroxyl functional group（-OH） connected to the Si-O-Si backbone.Thin-film hardness was recorded by an MH-5-VM Digital Micro-Hardness Tester.Radio frequency power had a strong impact on film hardness and the hardness increased with increasing power.
