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1.
Three different low-temperature plasma-based methods were used to improve the surface hydrophilicity of polyethy- lene (PE) films, and all the modification processes were carried out by employing an atmospheric pressure plasma jet (APPJ) system. (a) PE films were directly modified by APPJ using a gas mixture of He and 02. (b) Acrylic acid (AA) was introduced into the system and a polymer acrylic acid (PAA) coating was deposited onto the PE films. (c) AA was grafted onto the PE surface activated by plasma pre-treatment. It was found that the hydrophilicity of the PE films was significantly improved for all the three methods. However, the samples modified by Process (a) showed hydrophobicity recovery after a storage time of 20 days while no significant change was found in samples modified by Process (b) and Process (c). The Fourier transform infrared spectroscopy (FTIR) results indicated that the most intensive C=O peak was detected on the PE surface modified by Process (c). According to the X-ray photoelectron spectroscopy (XPS) analysis, the ratios of oxygen-containing polar groups for samples modified by Process (b) and Process (c) were higher than that modified by Process (a).  相似文献   

2.
The gas heating mechanism in the pulse-modulated radio-frequency(rf) discharge at atmospheric pressure was investigated with a one-dimensional two-temperature fluid model. Firstly, the spatiotemporal profiles of the gas temperature(T_g)in both consistent rf discharge and pulse-modulated rf discharge were compared. The results indicated that T_gdecreases considerably with the pulse-modulated power, and the elastic collision mechanism plays a more important role in the gas heating change. Secondly, the influences of the duty cycle on the discharge parameters, especially on the T_g, were studied.It was found that T_gdecreases almost linearly with the reduction of the duty cycle, and there exists one ideal value of the duty cycle, by which both the T_gcan be adjusted and the glow mode can be sustained. Thirdly, the discharge mode changing from α to γ mode in the pulse-modulated rf discharge was investigated, the spatial distributions of T_gin the two modes show different features and the ion Joule heating is more important during the mode transition.  相似文献   

3.
胡文娟  谢芬艳  陈强  翁静 《中国物理 B》2009,18(3):1276-1282
With monomer allylamine,amine-containing functional films were prepared in alternative current pulsed dielectric barrier discharge(DBD) at a high pressure.This paper analyses in detail the film properties and structures,such as hydrophilicity,compounds and microstructures as well as amine density by the water contact angle,Fourier transform infrared spectroscopy,atomic force microscopy,and ultraviolet-visible measurement.The influence of discharge param-eters,in particular applied power,on amine density was investigated.As an application the cell adsorption behaviours on plasma polymerization films was performed in-vitro.The results show that at a high pressure pulsed DBD plasma can polymerize films with sufficient amine group on surface,through which the very efficient cell adsorption behaviours was demonstrated,and the high rate of cell proliferation was visualized.  相似文献   

4.
葛道晗  胡州  张立强  祝世宁 《中国物理 B》2022,31(1):10701-010701
A new design of staggered array semi-packed micro gas chromatographic column was presented based on the micro electromechanical system(MEMS)technology.It was a sensor for gas sample analysis.The internal velocity fields of ten types of semi-packed micro gas chromatographic column were studied.The effects of array spacing and dislocation spacing on the flow field distribution were investigated.The results show that on the basis of ensuring the formation of virtual wall,with the increase of array spacing,the maximum velocity difference between the flow channels in the vertical direction decreases gradually,but the velocity difference in the flow channels a and b increases.When the inlet velocity was set to be 0.18 m/s,the maximum velocity difference in the channel of the staggered semi-packed micro gas chromatography column 3(CSAC3)was 0.05610 m/s.The maximum velocity difference in the channel a was 0.09160 m/s.The maximum velocity difference in the channel b was 0.02401 m/s.CSAC3 had a more uniform velocity field distribution,which can effectively suppress the laminar flow effect during chromatographic separation,and had a smaller pressure distribution,which puts forward lower requirements for carrier gas system.The staggered array semi-packed micro gas chromatography column proposed in this paper can effectively improve the velocity field distribution and pressure distribution in the channel,and provide a theoretical basis for the design of the new micro gas chromatography column structure.  相似文献   

5.
The present study experimentally investigated the near-field flow mixing characteristics of two turbulent jets issuing from equilateral triangular and circular orifice plates into effectively unbounded surroundings,respectively.Planar particle image velocimetry(PIV) was applied to measure the velocity field at the same Reynolds number of Re=50,000,where Re = UeDe /with Ue being the exit bulk velocity and the kinematic viscosity of fluid,D e the equivalent diameters.The instantaneous velocity,mean velocity,Reynolds stresses were obtained.From the mean velocity field,the centreline velocity decay rate and half-velocity width were derived.Comparing the mixing characteristics of the two jets,it is found that the triangular jet has a faster mixing rate than the circular counterpart.The triangular jet entrainments with the ambient fluid at a higher rate in the near field.This is evidenced by a shorter unmixed core,faster Reynolds stress and centreline turbulence intensity growth.The primary coherent structures in the near field are found to break down more rapidly in the triangular jet as compared to the circular jet.Over the entire measurement region,the triangular jet maintained a higher rate of decay and spread.Moreover,all components of Reynolds stress of the triangular jet appear to reach their peaks earlier,and then decay more rapidly than those of the circular jet.In addition,the axis-switching phenomenon is observed in the triangular jet.  相似文献   

6.
A plasma jet has been developed which operates using radio frequency (rf) power and produces a stable homogeneous discharge at atmospheric pressure. Its discharge characteristics, especially the dependence of stable discharge operating range on the feed gas, were studied, and the electric parameters such as RMS current, RMS voltage and reflected power were obtained with different gas flows. These studies indicate that there is an optimum range of operation of the plasma jet for a filling with a gas mixture of He and O_2. Two "failure" modes of the discharge are identified. One is a filamentary arc when the input power is raised above a critical level, another is that the discharge disappears gradually as the addition of O_2 approaches 3.2%. Possible explanations for the two failure modes have been given. The current and voltage waveform measurements show that there is a clear phase shift between normal and failure modes. In addition, I-V curves as a function of pure helium and for 1% addition of oxygen have been studied.  相似文献   

7.
The dynamic behavior of a microhollow cathode sustained discharge with split third electrodes is experimentally investigated. The sustained discharge swells isotropically in the presence of a small amount of argon gas flow that is not clearly detectable with a conventional single third electrode. At high flow rates, the sustained discharge transitions to a fast-moving constricted discharge with an are shape. The modified discharge structure causes a shift in current distribution over the third electrodes, and the current peak location varies linearly with the flow rate over a certain flow range. Such linear behavior may be applied to in situ flow velocity measurement.  相似文献   

8.
陈颖超  谢凯  盘毅  郑春满  王华林 《中国物理 B》2011,20(2):28201-028201
Nano-LiMn 2 O 4 cathode materials with nano-sized particles are synthesized via a citric acid assisted sol-gel route.The structure,the morphology and the electrochemical properties of the nano-LiMn 2 O 4 are investigated.Compared with the micro-sized LiMn 2 O 4,the nano-LiMn 2 O 4 possesses a high initial capacity (120 mAh/g) at a discharge rate of 0.2 C (29.6 mA/g).The nano-LiMn 2 O 4 also has a good high-rate discharge capability,retaining 91% of its capacity at a discharge rate of 10 C and 73% at a discharge rate of 40 C.In particular,the nano-LiMn 2 O 4 shows an excellent high-rate pulse discharge capability.The cut-off voltage at the end of 50-ms pulse discharge with a discharge rate of 80 C is above 3.40 V,and the voltage returns to over 4.10 V after the pulse discharge.These results show that the prepared nano-LiMn 2 O 4 could be a potential cathode material for the power sources with the capability to deliver very high-rate pulse currents.  相似文献   

9.
We investigate the effect of chemicals on chemical mechanical polishing (CMP) of glass substrates. Ceria slurry in an ultra-low concentration of 0.25 wt. % is used and characterized by scanning electron microscopy. Three typical molecules, i.e. acetic acid, citric acid and sodium acrylic polymer, are adopted to investigate the effect on CMP performance in terms of material removal rate (MRR) and surface quality. The addition of sodium acrylic polymer shows the highest MRR as well as the best surface by atomic force microscopy after CMP, while the addition of citric acid shows the worst performance. These results reveal a mechanism that a long-chain molecule without any branches rather than small molecules and common molecules with ramose abundant-electron groups is better for the dispersion of the slurry and thus better for the CMP process.  相似文献   

10.
The electric field in a surface discharge type ac-PDP cell with He or He/Xe(0.1%) mixture has been measured over a wide range of pressure (5-50 kPa) using laser induced fluorescence detection. The wall voltage was estimated from the measured electric field. The Stark manifolds of triplet atomic helium Rydberg state (2s^3S) with principal quantum numbers (n=8 and 9) have been used to measure the electric field, as the lifetime of 2s^3S is longer than the single atomic helium Rydberg state (2s^1S) in high pressure discharge. Comparison of the Stark manifolds between the n=9 and n=8 shows that the measurement accuracy of electric field can be increased by 10%. The maximum electric field strength during discharge and the wall voltage at the end of pulse decreases with the increase of pressure. The comparison of He and He/Xe(0.1%) discharge at 13 kPa showed that He/Xe gas mixture discharge can accumulate more wall charge on MgO surface and the electric field was somewhat higher than those of pure helium discharge during pulse off period under the same discharge conditions.  相似文献   

11.
《Composite Interfaces》2013,20(3):271-276
HEC-g-AA/SiO2 hybrid materials are prepared through a graft copolymerization reaction between acrylic acid (AA) monomer and hydroxyethyl cellulose (HEC), in the presence of a silica sol. The microstructure and properties of the hybrid materials are characterized by Fourier transform infrared spectra (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The results show that a rigid inorganic phase SiO2 is dispersed in flexible organic continuous phase uniformly. HEC-g-AA/SiO2 hybrid material has no obvious phase separation in the presence of the crosslinking agent. The thermal performances of HEC-g-AA/SiO2 are excellent, and the glass transition temperature (T g) increases with the increased amount of the crosslinking agent.  相似文献   

12.
An amorphous acrylic acid (AA) polymer coating was generated on TiO2 nanoparticles through pulse radio frequency (RF) plasma polymerization. The AA plasma synthesis mechanism was studied by its optical emission spectrum. The chemical structures of AA–plasma‐polymer were carefully investigated by Fourier transform infrared spectroscopy (FTIR). The dispersion behaviors of AA‐coated and uncoated TiO2 nanoparticles in glycol solution were characterized by ultraviolet absorbency and particle size distribution measurements. The results showed that the aggregation of TiO2 nanoparticles in glycol solution was effectively lowered and the dispersion was improved a lot after AA–plasma‐polymer coating. The pulse plasma coating parameters played an important role in the dispersion enhancement of TiO2 nanoparticles. By properly regulating the pulse discharge parameters, the system could gain the highest radical–monomer reactions rate, the most compatible functional groups on the nanoparticles, and the best dispersion in the background media.  相似文献   

13.
Carboxylic acids based on exo‐substituted tria‐, penta‐, heptafulvenes and ethylene (acrylic acids) were examined in order to determine if they are more sensitive to the substituent effect than benzoic acid – the system originally employed by Hammett. In order to accomplish this task, all possible structural isomers of benzoic acid, tria‐, penta‐ and heptafulvene‐based carboxylic acids, acrylic and methacrylic acids substituted by 13 substiuents (BH2, CHO, CN, COCN, NO2, CF3, Me, Cl, F, OH, OMe, NH2 and NMe2) were optimized at the B3LYP/6‐311++G(d,p) level of theory, and Gibbs free energies of carboxylic group dissociation (ΔGdis) were calculated. These energies were subsequently intercorrelated, and from the slopes of linear regressions, it was estimated which system is associated with greatest changes of ΔGdis due to substitution and thus is most sensitive to the substituent effect. It was found that all fulvene‐based carboxylic acids have greater range of ΔGdis change than benzoic acid, but the largest range of change was observed in the case of acrylic and methacrylic acids. The acrylic acid as the most sensitive system to substitution could replace benzoic acid for an improved version of substituent constant used to measure pi‐electron substituent effect. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

14.
《Composite Interfaces》2013,20(2-3):127-136
Polyurethane (PU) and polystyrene (PS) films were functionalized by ultraviolet (UV) or selective synchrotron radiations (SR) in the presence of reactive gases. The UV-PU results were compared with lowpressure plasma treatments of the same films. Oxygen or acrylic acid vapours (AA) were used as reactive gases. X-ray photoelectron spectroscopy measurements of UV modified films in the presence of oxygen or AA matched the RF-plasma treatments results. It is shown that COO and C=O functional groups were incorporated at the polymer surface efficiently with both methodologies. In addition, near-edge X-ray absorption fine structure showed that a thin film of poly(acrylic acid) is formed over the PU and PS films during the UV irradiation in the presence of AA vapours. These results resemble previous AA low-power plasma treatments. PU and PS films were also selectively functionalized by SR using oxygen as reactive gas. Surface concentrations of COO and C=O functional groups were enhanced by C1s σ* C–C excitation after irradiation and oxygen introduction. This efficient surface functionalization was clearly observed in PS films which do not have CO and COO groups in their molecular structure. Excitations involving transitions to π* orbital (π*C=C, π*C=O) led to much lower functionalization efficiency. The SR results can be explained by taking into account previous photon stimulated ion desorption studies of polymers. SR results may open new ways to functionalize polymer surfaces selectively and efficiently.  相似文献   

15.
The grafting of acrylic acid (AA) monomer (CH2CHCOOH) on polyamide 6.6 monofilaments (PA 6.6) using benzoyl peroxide (BPO) as initiator was carried out in order to enhance the hydrophilic nature of fibers. The grafting rate depends on the AA concentration, the BPO concentration, the time and the temperature of reaction.The best conditions for optimum rate of grafting were obtained with a AA concentration of 0.5 M, a BPO concentration of 0.03 M, a reaction temperature of T = 85 °C and a reaction time of 120 mn.The fiber surface has been investigated by many experimental techniques of characterization such as Fourier transform infrared spectroscopy (FTIR), calorimetric analysis (DSC), scanning electron microscopy (SEM), and contact angle measurements.The effect of grafting of acrylic acid onto PA 6.6 fibers on their moisture and mechanical resistances was analyzed from water sorption and elongation at break measurements.The analysis of the experimental data shows clearly the efficiency of the grafting reaction used, leading to a significant increase of the hydrophilic character of the PA 6.6 surface.  相似文献   

16.
In order to increase the added value of lotus root starch, a new-style hydrogel was prepared by grafting copolymerization by acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), K2S2O8, and N,N′- methylene-bis-acrylamide (MBA) in presence of lotus root starch. The molecular structure was characterized by Fourier transform infrared spectroscopy (FTIR). The different conditions that had an influence on the water absorbency are discussed, such as the ratio of initiator to monomers, the ratio of cross-linker to monomers, the mass ratio of AA and AMPS, the lotus root starch's mass, and the reaction temperature. For the product having the optimal water absorbency of 476 g/g, its water absorption kinetics diffusion model and equation were also researched. The material is friendly to the environment and is suggested to have significant potential to be used in various fields.  相似文献   

17.
Graft polymerization of acrylic acid (AA) onto porous polyethersulfone (PES) membrane surfaces was developed using corona discharge in atmospheric ambience as an activation process followed by polymerization of AA in aqueous solution. The effects of the corona parameters and graft polymerization conditions on grafting yield (GY) of AA were investigated. The grafting of AA on the PES membranes was confirmed by ATR-FTIR and X-ray photoelectron spectroscopy (XPS) analysis. Porosimetry measurements indicate the average pore diameters and porosities of the modified membranes decrease with the increase of the GY. The hydrophilicity and surface wetting properties of the original and modified membranes were evaluated by observing the dynamic changes of water contact angles. It is found that the grafting of AA occurs not only on the membrane surfaces, but also on the pore walls of the cells inside the membrane. The permeability experiments of protein solution reveal that the grafting of PAA endows the modified membranes with enhanced fluxes and anti-fouling properties. The optimized GY of AA is in the range of 150-200 μg/cm2. In addition, the tensile experiments show the corona discharge treatment with the power lower than 150 W yields little damage to the mechanical strength of the membranes.  相似文献   

18.
Plasma surface modification can be used to improve the surface properties of commercial pure Ti by creating functional groups to produce bioactive materials with different surface topography. In this study, a titanium surface was modified with acrylic acid (AA) using a plasma treatment and immobilized with bioactive arginine-glycine-aspartic acid (RGD) peptide, which may accelerate the tissue integration of bone implants. Both terminals containing the -NH2 of RGD peptide sequence and -COOH of poly(acrylic acid) (PAA) thin film were combined with a covalent bond in the presence of 1-ethyl-3-3-dimethylaminopropyl carbodiimide (EDC). The chemical structure and morphology of AA film and RGD immobilized surface were investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). All chemical analysis showed full coverage of the Ti substrate with the PAA thin film containing COOH groups and the RGD peptide. The MC3T3-E1 cells were cultured on each specimen, and the cell alkaline phosphatase (ALP) activity were examined. The surface-immobilized RGD peptide has a significantly increased the ALP activity of MC3T3-E1 cells. These results suggest that the RGD peptide immobilization on the titanium surface has an effect on osteoblastic differentiation of MC3T3-E1 cells and potential use in osteo-conductive bone implants.  相似文献   

19.
The use of a block copolymer, poly (styrene)-b-poly (acrylic acid) (PS-b-PAA) to prepare a magnetic nanocomposite was investigated. Poly (styrene)-poly (t-butyl acrylate) block copolymer, being synthesized by atom transfer radical polymerization, was hydrolyzed with hydrochloric acid for obtaining PS-b-PAA. The obtained PS-b-PAA was then compounded with the modified γ-Fe2O3, and subsequently the magnetic nanocomposite was achieved. The products were characterized by 1H NMR, FTIR, gel permeation chromatography, thermogravimetric analysis, transmission electron microscopy and vibrating sample magnetometer. The results showed that the nanocomposites exhibited soft magnetism, with the mean diameter of 100 nm approximately.  相似文献   

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