Surface Modification of Polyimide Film by Dielectric Barrier Discharge at Atmospheric Pressure

In this paper,polyimide(PI)films are modified using an atmospheric pressure plasma generated by a dielectric barrier discharge(DBD)in argon.Surface performance of PI film and its dependence on exposure time from 0 s to 300 s are investigated by dynamic water contact angle(WCA),field emission scanning electron microscopy(FESEM),and Fourier transform infrared spectroscopy in attenuated total multiple reflection mode(FTIR-ATR).The study demonstrates that dynamic WCA exhibits a minimum with 40 s plasma treatment,and evenly distributed nano-dots and shadow concaves appeared for 40 s and 12 s Ar plasma treatment individually.A short period of plasma modification can contribute to the scission of the imide ring and the introduction of C-O and C=O(-COOH)by detailed analysis of FTIR-ATR.

Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage

Polyimide(PI)film is an important type of insulating material used in inverter-fed motors.Partial discharge(PD)under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors.In order to explore the damage mechanism of PI film caused by discharge,an aging system of surface discharge under bipolar continuous square impulse voltage(BCSIV)is designed based on the ASTM 227501 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage(PDIV).The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy(FTIR)and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50.Finally,the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy(SEM).The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains.The fractures of ether bond(C–O–C)and imide ring(C–N–C)on the backbone of a PI polymer chain leads to the decrease of molecular weight,which results in the degradation of PI polymers and the generation of new chemical groups and materials,like carboxylic acid,ketone,aldehydes,etc.The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field,which would cause the dielectric constantεto increase and dielectric loss tanδto decrease.The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging.The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI polymer bulk.

The Effect of Plasma Surface Treatment on a Porous Green Ceramic Film with Polymeric Binder Materials

To reduce time and energy during thermal binder removal in the ceramic process, plasma surface treatment was applied before the lamination process.The adhesion strength in the lamination films was enhanced by oxidative plasma treatment of the porous green ceramic film with polymeric binding materials.The oxygen plasma characteristics were investigated through experimental parameters and weight loss analysis.The experimental results revealed the need for parameter analysis,including gas material,process time,flow rate,and discharge power,and supported a mechanism consisting of competing ablation and deposition processes.The weight loss analysis was conducted for cyclic plasma treatment rather than continuous plasma treatment for the purpose of improving the film’s permeability by suppressing deposition of the ablated species.The cyclic plasma treatment improved the permeability compared to the continuous plasma treatment.

Comparison of Surface Modification of CR-39 Polymer Film Using RF and DC Glow Discharges Plasma

Surfaces of optical elements are deposited by antireflection coatings (ARCs) to decrease the reflection of light. Surface needs treatment before depositing the ARC one of treatment processes by plasma for adhesion improvement and surface hardening. A comparison of RF and DC glow discharges treated CR-39 polymer films gives insight into the mechanism of these surface processes. The surface properties of the plasma-treated samples are examined by microscopy techniques include contact angle measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), infrared (IR) spectroscopy and refractive index measurements. Results show that the plasma treatment modifies the polymer surface in both composition and morphology. It is found that the surface wettability is enhanced after plasma treatment. It is found that, RF plasma is more effective than DC plasma in CR-39 surface modification, as it implants more oxygen atoms into the surface and makes the contact angle declining to a lower level.

Influence of air addition on surface modification of polyethylene terephthalate treated by an atmospheric pressure argon plasma brush

An atmospheric pressure argon plasma brush with air addition is employed to treat polyethylene terephthalate(PET)surface in order to improve its hydrophilicity.Results indicate that the plasma plume generated by the plasma brush presents periodically pulsed current despite a direct current voltage is applied.Voltage-current curve reveals that there is a transition from a Townsend discharge regime to a glow one during one discharge period.Optical emission spectrum indicates that more oxygen atoms are produced in the plume with increasing air content,which leads to the better hydrophilicity of PET surface after plasma treatment.Besides,an aging behavior is also observed.The hydrophilicity improvement is attributed to the production of oxygen functional groups,which increase in number with increasing air content.Moreover,some grain-like structures are observed on the treated PET surface,and its mean roughness increases with increasing air content.These results are of great importance for the hydrophilicity improvement of PET surface with a large scale.

Peanut Shell Activated Carbon： Characterization, Surface Modification and Adsorption of Pb^2＋ from Aqueous Solution

特别与象铅那样的重金属离子，饮用水和废水的金属离子污染是一个严重、进行中的问题。在这个工作，从花生壳(PAC ) 准备的活性炭从水溶液被用于 Pb^(2+) 的移动。修改酸的碳的 Pb2 吸附能力的影响与 HNO3 氧化了也被调查。PAC 的表面官能团被 Fourier 变换证实红外线(FTTR ) 光谱学， X 射线光电子能谱法(XPS ) ， Boehm 滴定。组织上性质(表面积，全部的毛孔体积)在介绍的试验性的结果显示了的 77 K.The 从氮吸附等温线被评估吸附数据与商业颗粒活性炭(粒状活性炭)与兰米尔吸附 model.A 比较级学习更好适合，这证明 PAC 基于兰米尔是与粒状活性炭相比更有效的 10.3 次最大的吸附能力。由兰米尔方程的进一步的分析结果显示出那 HNO3 [20%( 由质量)] 修改 PAC 从水溶液有 Pb^(2+) 的更大的吸附能力(差不多 35.5 mg · g ^(-1)) 。归功于到毛孔拓宽的吸附能力改进，由氧组的增加的阳离子交换能力，和碳的支持的 hydrophilicity 出现。

Role of Plasma Surface Treatments on Wetting and Adhesion

There are many current and emerging wetting and adhesion issues which require an additional surface processing to enhance interfacial surface properties. Materials which are non-polar, such as polymers, have low surface energy and therefore typically require surface treatment to promote wetting of inks and coating. One way of increasing surface energy and reactivity is to bombard a polymer surface with atmospheric plasma. When the ionized gas is discharged on the polymer, effects of ablation, crosslinking and activation are produced on its surface. In this paper we will analyse the role of plasma and its use in increasing the surface energy to achieve wettability and improve adhesion of polymeric surfaces.

Effect of Surface Modification on Microwave Absorbing Properties of Magnetic Metal Fibers

In order to avoid forming an electrical conductive network due to surface connections,the magnetic metal fibers were coated with SiO 2 for surface modification by the sol-gel process.The microstructure,composition and electromagnetic characteristics of SiO 2 -coated and uncoated metal fibers were studied using SEM,EDAX,and a voter network analyzer.The reflectivity was simulated using the RAMCAD software.The electromagnetic parameters and absorption properties of SiO 2 -coated metal fibers were improved greatly due to optimal impendence matching and the electric conductivity decreased,compared to those of uncoated materials.

Influence of Surface Treatment on the Corrosion Resistance of Stainless Steel in Simulated Human Body Environment

In the present research,the influence of chromium enrichment by surface treatment on corrosion resistance of type 316L stainless steel in body environment was investigated.For this study,weight loss test during 18 months,cyclic and liner polarization tests before and after surface treatment and metallography by electron and light microscopy were used to evaluate the effectiveness of the proposed method.In addition,X-ray photoelectron spectroscopy(XPS)method was used to determine the chromium concentration in the surface layer after surface treatment.Results show that the surface treatment has improved corrosion resistance of the type 316L stainless steel in body environment.

Effect of surface modification on thermal expansion of Zr_(2)WP_(2)O_(12)/aromatic polyimides based composites

Surface modification is a fascinating way to improve the compounding effect between inorganic fillers and polymers.In this study,zirconium tungsten phosphate(ZWP) with negative thermal expansion was surface modified by silane coupling agent 3-(Trimethoxysilyl)propyl methacrylate.The effects of surface modification and the modification mechanism were analyzed in detail by X-ray diffractometer,scanning electron microscopy,Fourier transform infrared spectroscopy and thermal mechanical analysis.The surface modification could effectively reduce the thermal expansion properties of the composite.When the added amount of 3-methacryloxypropyl trimethoxysilaneSilane(trade name:KH570) is 0.50 wt%,the thermal expansion coefficient of ZWP/Aromatic polyimide composite decreased by 9.76%.The surface modification also can effectively improve the dielectric performance of aromatic polyimides.The present work provides one new way to improve the thermal expansion behavior of composites.

Surface-modified Ag@Ru-P25 for photocatalytic CO_(2) conversion with high selectivity over CH_(4) formation at the solid–gas interface

Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert CO_(2) and H_(2)O vapor into highly selective CH4.Ru doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes CO_(2) adsorption.High-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,CO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing CO_(2) reduction activity.The optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent CO_(2) reduction activity into CO,CH4,and C2H6 with a~95%selectivity of CH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases CO_(2) reduction activity.

SURFACE MODIFICATION ON STEEL BY RARE EARTH AND LASER TREATMENT

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Surface modification of polyester film by glow discharge tunnel at atmospheric pressure

A large-area improved dielectric barrier glow discharge tunnel has been developed for modifying the surface of polyester film at atmospheric pressure with argon and oxygen gas mixtures. The electrical properties of the glow discharge tunnel were studied by simultaneous measurement of the voltage and current. In addition, the effect of the glow discharge tunnel treatment on the surface of polyester film were studied. The resultant modifications of the surface properties of the treated samples were investigated through scanning probe microscopy and contact angle measurement.

Surface Modification of Electrospun Poly(L-lactide)/Poly(ε-caprolactone)Fibrous Membranes by Plasma Treatment and Gelatin Immobilization

Biopolymer fibers have great potential for technical applications in biomaterials.The surface properties of fibers are of importance in these applications.In this study,electrospun poly(L-lactide)(PLLA)/poly(ε-caprolactone)(PCL)membranes were modified by cold plasma treatment and coating gelatin to improve the surface hydrophilic properties.The morphologies of the fibers were observed by scanning electron microscopy(SEM).Atomic force microscopy(AFM)was employed to show the surface characteristics of the fibers.The chemical feature of the fibrous membrane surfaces was examined by X-ray photoelectron spectroscopy(XPS).The surface wettability of the fibrous membrane was also characterized by water contact angle measurements.All these results show that plasma treatment can have profound effects on the surface properties of fibrous membranes by changing their surface physical and chemical features.Gelatin-PLLA/PCL membrane has great potential in applications of tissue engineering scaffolds.

Surface Modification of AB_2 and AB_5 Hydrogen Storage Alloy Electrodes by the Hot-Charging Treatment

The effect of the hot-charging treatment on the performance of AB2 and AB5 hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (VPR), the high rate discharge ability (HRDA), the diffusion coefficient of hydrogen DH and the discharge capacity of the AB2 hydrogen storage alloy electrode. The SEM analysis showed that the hot-charging treatment brings about a Ni-rich surface due to the dissolution of Zr oxides. It is also very helpful for the improvement of the kinetic properties of AB2 hydrogen storage alloy electrode because the microcracking of the surface results in fresh surface. This can be the basic modification treatment for NiMH battery used in electric vehicles (EVs) in the future. But for AB5 type alloys, the treatment has the disadvantage of impairing the comprehensive electrochemical properties, because the surface of the alloy may be corroded during the treatment. The mechanism of the surface modification of the electrode is also proposed.

Corrosion protection properties of vanadium films formed on zinc surfaces

Vanadium films were prepared on zinc surfaces by using a solution containing vanadate.Corrosion protection properties of vanadium-treated (V-treated),chromium-treated (Cr-treated),and untreated zinc surfaces in contact with a 3.5 wt.% NaCl solution were studied using potentiodynamic polarization,electrochemical impedance spectroscopy (EIS),and neutral salt spray (NSS) tests.According to these results,the V-treated layer significantly improved the corrosion resistance of zinc surfaces.In comparison with the Cr-treated layer,the V-treated layer exhibited a better corrosion resistance.The composition of the V-treated layer was studied using X-ray photoelectron spectroscopy (XPS).XPS measurements indicated that the vanadium layer formed on zinc surfaces and the vanadium-rich coating was a hydrated oxide with a composition of V2O5,VO2,and its hydrates such as V2O5·nH2O and VO(OH)2.

Influence of Repetitive Impulse Waveforms on Surface Discharge Characteristics and Insulation Life for Polyimide Film

Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics including discharge inception voltage, phase distribution and statistical characteristics on polyimide (PI) surface under different impulse waveforms and the insulation life of PI films are studied in this paper. We carry out experiments based on PD and insulation lifetime test systems, using five different types of repetitive impulses, including three bipolar waves and two unipolar waves. The experimental results show that there is little variation in discharge inception voltage under different waveforms, but great variation in phase distribution and statistical characteristics of PD. In addition, insulation life is approximately the same under different waveforms with the same polarity, and the aging rate under bipolar waveforms is larger than that under unipolar waveforms. We explain the differences between the bipolar and unipolar waveforms on insulation life, which can be concluded that the surface charge under unipolar waveform accumulates more significnatly compared with bipolar waveform and decreases the electric filed strength in discharging the air gap and inhibits surface discharge from occurring.

SURFACE TREATMENT OF POLY (ETHYLENE TEREPHTHALATE) FABRIC WITH POLYETHYLENEIMINE

A branched polyethyleneimine (BPEI) was applied to poly(ethylene terephthalate)(PET) fabric to improve its surface moisture absorption so that the fabric becomes lessliable to retention of electrostatic charg. The durability of this treatment was assessed bywashing and followed by measurement of charge development on the fabric. The treatedsamples showed improved surface wetting compared to the untreated. The results areconsistent with attachment of the BPEI to the PET surface by a cross-linking mechanism.

Surface modification for La_(1-x)Ce_x (NiCoMnAl)_5 hydride electrode by hot charging in potassium borohydride solution

The La 1- x Ce x (NiCoMnAl) 5 alloy electrodes were treated by hot charging in alkaline aqueous solution containing KBH 4. The activation behavior, hydrogen diffusion coefficient and maximum discharging capacity, high rate discharging capability of alloy electrodes were tested. The surface morphology and element content were observed by scanning electron microscope. The results show that the alloy electrode is fully activated after the second charging discharging cycle and has a high rate discharging capability of 85% at 900 mA/g. The surface has a lot of micro cracks and hydrogen diffusion coefficient is about (2～3)×10 -9 cm 2/s . Therefore, this method can markedly improve activation behavior and high rate charging capacity of the alloy electrode. The mechanism of this surface modification of the alloy electrode is also discussed. [