Investigation of the interaction between NS-DBD plasma-induced vortexes and separated flow over a swept wing

The effect of nanosecond pulsed dielectric barrier discharge(NS-DBD) plasma flow separation control is closely related to the actuation frequency,because it involves the interaction between plasma-induced vortexes and separated flow.In order to study the mechanism of NS-DBD plasma flow separation control over a swept wing,especially the influence of the actuation frequency,at first,experimental studies of the actuation frequencies at 100 Hz are conducted to validate the numerical simulation method.Then,numerical studies of different actuation frequencies which are 50 Hz,100 Hz,160 Hz,200 Hz,500 Hz,and 1000 Hz,respectively are conducted.The interaction between the plasma-induced vortexes and the separated flow is analyzed.Results show that there is a range of the actuation frequency which includes the frequency(160 Hz) calculated by the average aerodynamic chord length to make the control effect good,but when the actuation frequencies are too low(50 Hz) or too high(1000 Hz),the control effect will get worse.The former is because plasmainduced vortexes disappear in a period within an actuation cycle;the latter is because plasma-induced vortexes cannot develop completely,resulting in a weak vortex intensity.

SURFACE MODIFICATION OF POLYPROPYLENE MICROFIBRE BY PLASMA-INDUCED VAPOR GRAFTING WITH ACRYLIC ACID

The hydrophilicity, dyeing and antistatic ability of polypropylene microfibre (PPMF) were improved by plasma-induced vapor grafting with acrylic acid. The effects of plasma discharge time, power, liquid phase acrylic acid temperature and environmental temperature on grafting yield were investigated. The existence of grafted polyacrylic acid (PAA) was verified by ESCA and ATR FT-IR. The morphology of grafted PAA was directly observed by SEM. The wicking test shows that the hydrophilicity of modified PPMF is greatly enhanced. The dyeability test of modified PPMF was carried out using Dispersion Yellow. It was found that the dye uptake ratio is linear to the weight percent of grafting. The antistatic ability was indicated by specific resistance. The specific resistance of modified PPMF was reduced to 10(6) similar to 10(7) Ohm . cm, thus the antistatic ability was considerably improved.

Plasma-induced graft polymerization on the surface of aramid fabrics with improved omniphobicity and washing durability

Durable superomniphobic surfaces are desirable for their practical applications,including selfcleaning,non-fouling,protective clothing and the separation of liquids.The plasma-induced polymerization of environmentally friendly C6 from a perfluoralkyl methlacrylate copolymer emulsion,AG-E081,was performed and a durable omniphobic fabric was achieved.C6 is an ecological alternative to C8(eight CF2 groups)fluorinated compounds,and it was thereafter successfully incorporated into aramid fabric to achieve a durable superomniphobic surface.The fabric became water and oil repellent with an extremely high water contact angle of 180°.As tested by the water spray AATCC test and hydrocarbon resistance test,the as-prepared fabric gained 100°(ISO 5)and grade number 4 respectively.Furthermore,the fabrics also showed significantly improved washing durability after ten washing cycles.By scanning electron microscopy(SEM),Fourier-transform infrared spectroscopy(FTIR)and x-ray photoelectron spectroscopy(XPS)tests,it is indicated that the durable superomniphobicity can be attributed to the roughness and activation of the aramid surface by the plasma pre-treatment,which induces more adsorption and chemical graft of the C6 copolymer.

Plasma-induced grafting of acrylic acid on bentonite for the removal of U(VI) from aqueous solution

Fabrication of reusable adsorbents with satisfactory adsorption capacity and using environmentfriendly preparation processes is required for the environment-related applications. In this study,acrylic acid（AA） was grafted onto bentonite（BT） to generate an AA-graft-BT（AA-g-BT）composite using a plasma-induced grafting technique considered to be an environment-friendly method. The as-prepared composite was characterized by scanning electron microscopy, x-ray powder diffraction, thermal gravity analysis, Fourier transform infrared spectroscopy and Barrett–Emmett–Teller analysis, demonstrating the successful grafting of AA onto BT. In addition, the removal of uranium（VI）（U（VI）） from contaminated aqueous solutions was examined using the as-prepared composite. The influencing factors, including contact time,p H value, ionic strength, temperature, and initial concentration, for the removal of U（VI） were investigated by batch experiments. The experimental process fitted best with the pseudo-secondorder kinetic and the Langmuir models. Moreover, thermodynamic investigation revealed a spontaneous and endothermic process. Compared with previous adsorbents, AA-g-BT has potential practical applications in treating U（VI）-contaminated solutions.

THE EFFECTS OF PLASMA-INDUCED GRAFT COPOLYMERIZATION WITH ACRYLIC ACID ON THE STRUCTURE AND DYEING PROPERTIES OF MULBERRY SILK

The effects of plasma-induced graft copolymerization with acrylic acid (AAc) on the structure and dyeing properties of mulberry silk are investigated. Through the transmission infrared spectroscopy(IR) , attenuated total reflection infrared spectroscopy(ATR-IR) and X-ray photoelectron spectroscopy(XPS) studies, changes of the surface structure and composition are observed. The results show that plasma-induced graft copolymerization has a different meehanism from that of chemical graft copolymerization. The plasma graft copolymerization brings AAc branch polymers into the surface of silk through the initiation of some kinds of oxygen and nitrogen groups created by plasma. That is just the reason that the dyeing ability and color fastness of plasma-grafted silk for cationic dyestuff increase and its mechanical properties have not been changed significantly.

Plasma-inducedε-MnO_(2)based aqueous zinc-ion batteries and their dissolution-deposition mechanism

MnO_(2)has attracted great interest in working as the cathode of zinc ion batteries.However,the development of high-capacity,high-energy-density,and durable manganese-based cathodes with an easy synthesis strategy and proper energy storage mechanism remains an ongoing challenge.Herein,a facile plasmainduced strategy was demonstrated to introduce oxygen vacancies into theε-MnO_(2),and the obtained oxygen vacancies-richε-MnO_(2)nanosheets(ε-MnO_(2-x))show satisfactory electrochemical performances.Furthermore,an appropriate energy storage mechanism for dissolution/deposition was proposed.Thanks to a synergistic effect of the oxygen vacancies inε-MnO_(2)nanosheets and the exposed free-standing collector for Mn^(2+) dissolution/deposition,theε-MnO_(2-x) nanosheets electrode delivers a remarkable capacity(337 mAh g^(-1)at 0.1 A g^(-1))and exhibits an ultrahigh energy density of 462 Wh kg^(-1)(based on the weights of the cathode active material).Furthermore,impressive durability with 85.9%capacity retention after 1000 cycles was obtained.The superior electrochemical performance makes the plasma-induced strategy promising for designing advanced metal oxide electrode materials for high-performance aqueous zinc ion batteries.

Vacuum Outgassing Behavior of Carbon Nanotube Cathode with High-Intensity Pulsed Electron Emission

Experimental investigations on the vacuum outgassing of a carbon nanotube （CNT） cathode with high-intensity pulsed electron emission on a 2 MeV linear induction accelerator injector are presented. Under the 1.60 MV diode voltage, the CNT cathode could provide 1.67 kA electron beam with the amount of outgassing of about 0.51 Pa.L. It is found that the amount of outgassing, which determines the cathode emission current, depends on the diode voltage and the vacuum.

INTROMISSION OF WATER-REPELLENT AND HYDROSCOPIC PROPERTIES SIMULTANEOUSLY TO PP BY PLASMA DISCHARGE METHOD

Plasma-induced surface graft copolymerization of acrylic acid on polypropylene non-woven fabric(PP-g-AA)andpolypropylene membrane were reported.The extents of grafting were controlled by the plasma and polymerizationcondition.Hexadecyltrimethyl ammonium bromide was then coupled with the carboxyl group of PP-g-AA to obtain apolyion complex(PIC).At last,CF_4 plasma was used to give PICs hydrophobic property.The moisture regain and water-repellency of the processed PICs was investigated.The surfaces were characterized using ATR FT-IR and XPS.The resultindicates that the products have very high ability to adsorb moisture,even better than cotton fiber.At the same time,theproducts show excellent hydrophobic property,which can't be wetted by those reagents whose surface tensions were higherthan 327 mN/m.

High-sensitive refractive index sensing and excellent slow light based on tunable triple plasmon-induced transparency in monolayer graphene based metamaterial

A patterned monolayer graphene metamaterial structure consisting of six graphene blocks and two graphene strips is proposed to generate triple plasmon-induced transparency(PIT).TriplePIT can be effectively modulated by Fermi levels of graphene.The theoretically calculated results by coupled mode theory show a high matching degree with the numerically simulated results by finite-difference time-domain.Intriguingly,the high-sensitive refractive index sensing and excellent slow-light performance can be realized in the proposed graphene metamaterial structure.The sensitivity(S)and figure of merit can reach up to 5.7115 THz RIU^(-1)and 116.32,respectively.Moreover,the maximum group refractive index is 1036.Hence,these results may provide a new idea for designing graphene-based sensors and slow light devices.

Multi-frequency switch and excellent slow light based on tunable triple plasmon-induced transparency in bilayer graphene metamaterial

We propose a novel bilayer graphene terahertz metamaterial composed of double graphene ribbons and double graphene rings to excite a dynamically adjustable triple plasma-induced transparency(PIT)effect.The coupled mode theory(CMT)is used to explain the PIT phenomenon,and the results of the CMT and the finite-difference time-domain simulation show high matching degree.By adjusting the Fermi levels of graphene,we have realized a pentafrequency asynchronous optical switch.The performance of this switch,which is mainly manifested in the maximum modulation depth(MD=99.97%)and the minimum insertion loss(IL=0.33 dB),is excellent.In addition,we have studied the slow-light effect of this triple-PIT and found that when the Fermi level of graphene reaches 1.2 eV,the time delay can reach 0.848ps.Therefore,this metamaterial provides a foundation for the research of multi-frequency optical switches and excellent slow-light devices in the terahertz band.

Characteristics of Heat-Annealed Silicon Homojunction Infrared Photodetector Fabricated by Plasma-Assisted Technique

In this work, the effect of thermal annealing on the characteristics of silicon homojunction photodetector was studied. This homojunction photodetector was fabricated by means of plasma-induced etching of p-type silicon substrate and plasma sputtering of n-type silicon target in vacuum. The electrical and spectral characteristics of this photodetector were determined and optimized before and after the annealing process. The maximum surface reflectance of 1.89% and 1.81%, the maximum responsivity of 0.495A/W and 0.55A/W, the ideality factor of 1.80 and 1.99, the maximum external quantum efficiency of 76% and 83.5%, and the built-in potential of 0.79V and 0.72 V were obtained before and after annealing, respectively.