We propose a dual-polarized lens antenna system based on isotropic metasurfaces for 12 GHz applications. The metasurface lens is composed of subwavelength unit cells（0.24λ0） with metallic strips etched on the top a...We propose a dual-polarized lens antenna system based on isotropic metasurfaces for 12 GHz applications. The metasurface lens is composed of subwavelength unit cells（0.24λ0） with metallic strips etched on the top and bottom sides of the unit cell, and a cross-slots metallic layer in the middle that serves as the ground. The multimode resonance in the unit cell can realize a large phase shift（covering 0？–360？）, and the total transmission efficiency of the lens is above 80%.The feed antenna at the focal point of the lens is a broadband dual-polarized microstrip antenna. Both the simulated and the measured results demonstrate that the dual-polarized lens antenna system can realize a gain of more than 16.1 dB, and an input port isolation of more than 25.0 dB.展开更多
The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface anal...The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface analyses,aiming at clarifying the mitigation effects of nitrogen purging on SRB-involved under-deposit corrosion.The electrochemical results show that the variation trend of polarization resistance with immersion time is unchanged,but the corrosion current density is the lowest in the presence of SRB and deposits under nitrogen purging conditions,as compared to that without purging nitrogen,which are confirmed by the cross-sectional corrosion morphology observation after removing the sand deposits.Moreover,it is found that there are no positive synergistic effects between SRB and deposits on corrosion under nitrogen purging conditions,corresponding to the corrosion mitigation.Such mitigation on corrosion can be attributed to the less amount of SRB-produced H2S exhausted by purging nitrogen,which is supported by X-ray photoelectron spectrometry analyses.Therefore,purging nitrogen to the solution could be a practically effective way to mitigate the corrosion of deposit-covered carbon steels in SRB-containing solutions.展开更多
The NiTi cladding with/without Ni interlayer was prepared on stainless steel(SS) by tungsten inert gas(TIG) surfacing process,aiming at achieving good cavitation erosion resistance.The ranking according to the cavitat...The NiTi cladding with/without Ni interlayer was prepared on stainless steel(SS) by tungsten inert gas(TIG) surfacing process,aiming at achieving good cavitation erosion resistance.The ranking according to the cavitation erosion resistance is NiTi plate> NiTi-Ni-TIG cladding> NiTi-TIG cladding> SS.The better cavitation erosion resistance of NiTi-TIG and NiTi-Ni-TIG claddings than SS substrate is due to their higher micro-hardness and superelasticity.Furthermore,the existence of Ni interlayer can decrease the amount of brittle intermetallic compounds,such as Fe2 Ti,and inhibit the crack generation,which results in the higher cavitation erosion resistance of NiTi-Ni-TIG compared with NiTi-TIG cladding.Thus,the cavitation erosion resistance of NiTi cladding prepared by TIG surfacing process can be improved by employing Ni interlayer.展开更多
The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the ...The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the SC exceeds 50 ppm,the hydrogen evolution reaction dominates the cathodic process,and a limiting current region appears in the anodic branch of the polarisation curve due to the formation of a copper sulphide film,which is a diffusion-controlled process.After longterm immersion,the increased mass loss rate of NAB with the sulphide additions of 20 and 50 ppm is attributed to the less protective films,which contains a mixture of copper oxides and sulphides.Moreover,NAB undergoes severe localised corrosion(selective phase corrosion,SPC)at the β’phases and eutectoid microstructureα+κⅢ.By comparison,NAB undergoes general corrosion and a copper sulphide film is formed in 100 and 200 ppm sulphide solutions.Cavitation erosion greatly increases the corrosion rate of NAB in all solutions and causes a negative potential shift in 3.5%NaCl solution due to the film destruction.However,a positive potential shift occurs in the solutions with SC higher than 50 ppm due to the accelerated mass transfer of the cathodic process.The cavitation erosion mass loss rate of NAB increases with the increase of SC.The occurrence of severe SPC decreases the phase boundary cohesion and causes brittle fracture under the cavitation impact.The corrosion-enhanced erosion is the most predominant factor for the cavitation erosion damage when the SC exceeds 50 ppm.展开更多
This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisati...This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.展开更多
基金Project supported by the Open Research Program of the State Key Laboratory of Millimeter Waves,China(Grant No.K201926)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,Chinathe Nanjing University of Posts and Telecommunications Scientific Foundation,China(Grant No.NY215137)
文摘We propose a dual-polarized lens antenna system based on isotropic metasurfaces for 12 GHz applications. The metasurface lens is composed of subwavelength unit cells（0.24λ0） with metallic strips etched on the top and bottom sides of the unit cell, and a cross-slots metallic layer in the middle that serves as the ground. The multimode resonance in the unit cell can realize a large phase shift（covering 0？–360？）, and the total transmission efficiency of the lens is above 80%.The feed antenna at the focal point of the lens is a broadband dual-polarized microstrip antenna. Both the simulated and the measured results demonstrate that the dual-polarized lens antenna system can realize a gain of more than 16.1 dB, and an input port isolation of more than 25.0 dB.
基金This work is financially supported by the Research on CCUS Integrated Collaborative Technology(kt2022-27-6).
文摘The corrosion behavior of a carbon steel covered by sand deposits in the solution containing sulfate-reducing bacteria(SRB)under nitrogen purging conditions was studied by electrochemical measurements and surface analyses,aiming at clarifying the mitigation effects of nitrogen purging on SRB-involved under-deposit corrosion.The electrochemical results show that the variation trend of polarization resistance with immersion time is unchanged,but the corrosion current density is the lowest in the presence of SRB and deposits under nitrogen purging conditions,as compared to that without purging nitrogen,which are confirmed by the cross-sectional corrosion morphology observation after removing the sand deposits.Moreover,it is found that there are no positive synergistic effects between SRB and deposits on corrosion under nitrogen purging conditions,corresponding to the corrosion mitigation.Such mitigation on corrosion can be attributed to the less amount of SRB-produced H2S exhausted by purging nitrogen,which is supported by X-ray photoelectron spectrometry analyses.Therefore,purging nitrogen to the solution could be a practically effective way to mitigate the corrosion of deposit-covered carbon steels in SRB-containing solutions.
基金supported by the Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province (No.2017CL18)The Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Number XDA13040500).
文摘The NiTi cladding with/without Ni interlayer was prepared on stainless steel(SS) by tungsten inert gas(TIG) surfacing process,aiming at achieving good cavitation erosion resistance.The ranking according to the cavitation erosion resistance is NiTi plate> NiTi-Ni-TIG cladding> NiTi-TIG cladding> SS.The better cavitation erosion resistance of NiTi-TIG and NiTi-Ni-TIG claddings than SS substrate is due to their higher micro-hardness and superelasticity.Furthermore,the existence of Ni interlayer can decrease the amount of brittle intermetallic compounds,such as Fe2 Ti,and inhibit the crack generation,which results in the higher cavitation erosion resistance of NiTi-Ni-TIG compared with NiTi-TIG cladding.Thus,the cavitation erosion resistance of NiTi cladding prepared by TIG surfacing process can be improved by employing Ni interlayer.
基金financially supported by the National Natural Science Foundation of China (Nos.51601058 and 51879089)the Fundamental Research Funds for the Central Universities of P.R.China (No.2018B59614)+1 种基金the Natural Science Foundation of Jiangsu Province (BK20191161),the Changzhou Sci & Tech Program (Grant No.CJ20180045)the first group of 2011 plan of China’s Jiangsu province (Grant No.[2013] 56) (Cooperative Innovational Center for Coastal Development & Protection)
文摘The effect of sulphide(Na2S)concentration(SC)on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze(NAB)in 3.5% NaCl solution is investigated in this study.The results show that when the SC exceeds 50 ppm,the hydrogen evolution reaction dominates the cathodic process,and a limiting current region appears in the anodic branch of the polarisation curve due to the formation of a copper sulphide film,which is a diffusion-controlled process.After longterm immersion,the increased mass loss rate of NAB with the sulphide additions of 20 and 50 ppm is attributed to the less protective films,which contains a mixture of copper oxides and sulphides.Moreover,NAB undergoes severe localised corrosion(selective phase corrosion,SPC)at the β’phases and eutectoid microstructureα+κⅢ.By comparison,NAB undergoes general corrosion and a copper sulphide film is formed in 100 and 200 ppm sulphide solutions.Cavitation erosion greatly increases the corrosion rate of NAB in all solutions and causes a negative potential shift in 3.5%NaCl solution due to the film destruction.However,a positive potential shift occurs in the solutions with SC higher than 50 ppm due to the accelerated mass transfer of the cathodic process.The cavitation erosion mass loss rate of NAB increases with the increase of SC.The occurrence of severe SPC decreases the phase boundary cohesion and causes brittle fracture under the cavitation impact.The corrosion-enhanced erosion is the most predominant factor for the cavitation erosion damage when the SC exceeds 50 ppm.
基金the National Science and Technology Major Project of China(No.2016ZX05016-004)the National Natural Science Foundation of China(Nos.51801218 and 51571200)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA13040500)。
文摘This paper clarifies two issues related to the prior cathodic polarisation treatment(PCPT) for the potentiodynamic polarisation test: whether PCPT can(1) remove the air-formed surface film and(2) affect the polarisation test results. X-ray photoelectron spectroscopy analyses of fluoride ion-labelled samples show that PCPT cannot remove the surface film completely due to the low reaction rate. Potentiodynamic polarisation tests demonstrate that PCPT with proper operating parameters,-1.0 V SCE for 5 min with subsequent open circuit potential(OCP) stabilisation in this study, is necessary because it can improve the test reproducibility without affecting the corrosion parameters by unifying the initial surface state. However, PCPT with lower potentials, longer time or no OCP stabilisation has significant effects on the electrochemical corrosion parameters due to the hydrogen absorption under the conditions of this study.
