纳秒脉冲放电对聚对苯二甲酸乙二酯憎水改性

基于自主研制的ns脉冲电源(上升沿约70ns,脉宽约100ns)激励介质阻挡放电产生大气压低温等离子体,在CF4气氛下对聚对苯二甲酸乙二酯(PET)表面进行了憎水改性处理,测量了改性前后的薄膜表面的水接触角,给出了CF4气流量、放电电压、处理时间和CF4比例等参数对改性效果的影响规律。结果表明,大气压ns脉冲DBD表面处理能够实现PET材料的憎水性,改性后的PET表面水接触角由66°提高到最大100°。     

级联型高压重复频率微秒脉冲源的研制

针对等离子体的应用,基于级联型电压叠加技术研制了一种最高输出电压为20 kV的高压微秒脉冲源,该电源由40个相同的电源模块组成,其单个模块电压等级为500 V,降低了对器件的绝缘耐压要求。电源的输出电压值在0~20 kV之间可调;重复频率在0~10 kHz之间、脉宽在0~30 μs之间可调;该电源的上升沿和下降沿均在1 μs以内。模块化的设计提高了电源的冗余容错能力。将该电源作为产生等离子体的激励源时,其输出的高压脉冲波形稳定,且根据负载对输出高压波形的要求不同,该电源可以方便地进行调节。     

太赫兹器件测试用高重复频率高压脉冲电源

为了开展太赫兹器件试验研究,设计了高重复频率脉冲电源系统。电源输出脉冲电压30 kV,脉冲电流200 mA,最大重复频率3 kHz,脉冲宽度10~100 μs,采用本地PLC加远程计算机控制模式来实现电源的本控及遥控。对系统的核心部件:充电电源和脉冲开关的拓扑结构进行了研究,并开展了仿真和试验。结果表明:采用LC串联谐振恒流充电技术以提高充电电源工作效率以及在负载打火情况下的可靠性;基于MOSFET并进行优化设计的串联脉冲开关可以获得快速的脉冲前后沿。电源系统的输出指标满足负载工作要求,在高重复频率、打火条件下能够稳定工作。     

一种新型等离子体磁控溅射镀膜电源设计

磁控溅射镀膜电源是磁控溅射系统中的关键设备之一。根据铌靶和锡靶溅射处理装置的技术要求,研制了一套输出电压0~800 V可调、脉冲宽度5~200 μs可调、频率0~60 Hz可调、在脉冲电流最大幅值约150 A的磁控溅射镀膜电源,分别给出了该电源在铌靶负载和锡靶负载下的实验结果。设计上采用高压短脉冲预电离一体化高功率双极性脉冲形成电路方法,解决了高功率磁控溅射在重复频率工作下有时不能成功溅射粒子、电离时刻不一致、溅射起弧打火靶面中毒、溅射效率低等问题,降低了磁控溅射装置内气体的工作气压,实现低气压溅射镀膜,提高了靶材的溅射效率,减小薄膜表面粗糙度。通过大量实验论证,该电源达到了理想的溅射效果,满足了指标要求。     

基于半桥结构的双极性脉冲电源的研究

为了满足脉冲电场消融的应用需求,解决单极性脉冲电场分布不均匀的问题,研制了一台基于半桥结构的主电路、具有纳秒级前沿的高重复频率双极性亚微秒高压脉冲电源。该脉冲电源由FPGA提供控制信号,经过驱动芯片放大控制信号后,利用光耦隔离驱动多个SiC MOSFET。驱动电路所需元器件较少,信号控制时序简单,可提供负压偏置,使开关管可靠关断,提高了电路的抗电磁干扰能力,使电源能稳定运行。通过电阻负载实验,对比分析了不同栅极电阻对驱动电压的影响,驱动电压上升沿时间越短对应的双极性高压脉冲前沿越快。实验结果表明：所设计的高频双极性脉冲电源在100Ω纯阻性负载上能够稳定产生重复频率双极性纳秒脉冲,输出电压0～±4 kV可调,脉宽0.2～1.0μs可调,正负脉冲相间延时0～1 ms可调,上升沿和下降沿60～150 ns之间。该双极性脉冲电源电路设计结构紧凑,能满足应用的参数需求。     

μm脉冲电源及其在Z-pinch诊断中的应用

 研制了一种输出连续可调的脉冲恒压电源，该电源电压幅度为0~120V，脉宽为3~14μs，触发延迟时间为0~1μs。将其应用于等离子体辐射的软X射线总能量测量系统中，采用脉冲电源和差值法记录信号，通过分析发，实验中测到的电阻变化与电路中其它电阻无关，是X射线辐射导致镍薄膜电阻的变化引起的。测得的镍薄膜电阻的变化为4.47Ω，以此回推计算得Z-pinch等离子体源辐射的软X射线能量为63.3kJ。     

600 A重复频率脉冲恒流源研制北大核心CSCD

针对国内脉冲恒流源幅值较小、重复频率较低等问题,设计了基于电流闭环反馈控制的恒流电路,建立了相应的数学模型,并采用Pspice仿真验证了电路的功能,最终研制了1台600 A重复频率工作的脉冲恒流电源。电源采取储能放电配合高速开关的工作模式,使用功率场效应三极管作为线性调整开关,可大范围自动恒流,适用于激光二极管负载。输出的脉冲电流幅值最高600 A,上升时间小于40μs,电压幅值最高320 V,脉宽100~600μs可调,工作重复频率最高200 Hz。电源体积较小,结构紧凑,效率可达90%以上。     

双极性脉冲磁控溅射电源设计

双极性脉冲电源是磁控溅射系统中的关键设备之一。根据铌溅射处理装置的技术要求,研制了一套输出电压0~800 V可调、脉冲宽度20~200 μs可调、频率0~60 Hz可调、脉冲电流最大幅值约150 A的双极性脉冲电源,分别给出了该电源在水电阻负载和等离子体负载下的实验结果。设计上采用DSP控制开关电源的方式对储能电容器进行恒流充电;综合应用FPGA,PLC及触摸屏组成人机交互系统,控制输出光脉冲信号,经负压偏置驱动后使桥式结构的脉冲形成网络产生正负交替双极性脉冲。通过大量实验论证,该电源解决了等离子体负载放电打弧等问题,达到了理想的溅射效果,满足了指标要求。     

重复频率纳秒脉冲介质阻挡放电对聚对苯二甲酸乙二酯表面改性

介绍了0.1 MPa下的纳秒脉冲介质阻挡放电(DBD)对聚对苯二甲酸乙二酯(PET)材料表面进行的亲水性改善。分别采用均匀和丝状放电模式对PET表面改性处理,并采用水接触角测量、原子力显微镜观察、X射线光电子能谱分析对改性材料进行表面分析。实验发现介质阻挡放电处理后PET表面水接触角明显减小,接触角从78°下降到25°,但随处理时间的增加有饱和效应;PET表面粗糙程度增加,亲水性含氧基团被引入,从而改善了材料表面亲水性;纳秒脉冲下的均匀DBD比丝状DBD处理效果更为显著。     

磁隔离触发式10 kV级联型脉冲电源研制

采用磁隔离触发式的级联型高压脉冲电源解决了每一级联单元浮动供电的问题,结构紧凑,触发方式简单可靠。利用磁耦合隔离的触发方式,触发信号一致性高,产生的截止偏压信号可以对绝缘栅双极晶体管进行可靠关断。同时,在每一级联单元附加切尾开关支路,降低输出脉冲高压的下降沿,提高级联型脉冲电源的适用性。研制的10 kV级联型脉冲电源,每一个级联单元的额定工作电压为1 kV,总共10组。电压调节范围0~10 kV,工作频率1~10 kHz,脉冲电流0~20 A,脉冲宽度5~50 s。     

高功率紧凑型重频快Marx脉冲驱动源

基于快Marx发生器技术路线,研制了一套具有高功率密度的低阻抗紧凑型重频脉冲驱动源。采用18级Marx发生器电路结构,每级由1只60 nF/100 kV脉冲电容器、1个气体开关及隔离电感构成,每两级构成一个模块,整体采用SF6气体绝缘,储能密度达到25.7 kJ/m3;采取开放式气体开关,其中两级为触发开关,其余为过电压自击穿开关;触发源采用小型化Marx电路及绝缘胶真空灌封设计。实验中脉冲驱动源单次工作时在约18 阻抗负载上输出电压达到765 kV、脉宽约160 ns、前沿约50 ns,功率密度达到157 GW/m3;受充电电源功率限制,重复频率5 Hz充电70 kV,连续5脉冲输出功率约17 GW,脉冲波形重复性较好。     

20 GW紧凑Marx型重复频率脉冲驱动源研制进展

介绍了一种基于电触发技术的重复频率脉冲驱动源,其突破了双电容结构脉冲成形、紧凑型结构高压产生、大电流条件下重复频率稳定运行等关键技术,采用电路结构最简单的Marx电压叠加技术,解决了Marx在重复频率运行中的技术难点。脉冲功率驱动源设计输出功率20 GW、脉冲宽度180 ns、重复频率1~50 Hz,输出功率和重复频率在一定范围内可调。研制的脉冲功率驱动源体积仅2.5 m3,重量低至2.2 t,脉冲形成单元储能密度高达23 kJm-3,驱动源单次工作状态下输出功率约20 GW;在重复频率30 Hz工作状态下,输出功率16 GW、连续运行时间10 s、系统抖动约6 ns,系统运行稳定可靠。     

The effect of nitrogen and oxygen plasma on the wear properties and adhesion strength of the diamond-like carbon film coated on PTFE

Diamond-like carbon (DLC) films were deposited on polytetrafluoroethylene (PTFE) using a radiofrequency plasma chemical vapour deposition method. Prior to DLC coating, the PTFE substrates were modified with O₂ and N₂ plasma to enhance the adhesion strength of the DLC film to the substrate. The effect of the plasma pre-treatment on the chemical composition and the surface energy of the plasma pre-treated PTFE surface was investigated by X-ray photoelectron spectroscopy (XPS) and static water contact angle measurement, respectively. A pull-out test and a ball-on-disc test were carried out to evaluate the adhesion strength and the wear properties of the DLC-coated PTFE.In the N₂ plasma pre-treatment, the XPS result indicated that defluorination and the nitrogen grafting occurred on the plasma pre-treated PTFE surface, and the water contact angle decreased with increasing the plasma pre-treatment time. In the O₂ plasma pre-treatment, no grafting of the oxygen occurred, and the water contact angle slightly increased with the treatment time. In the pull-out test, the adhesion strength of the DLC film to the PTFE substrate was improved with the plasma pre-treatment to the PTFE substrate, and N₂ plasma pre-treatment was more effective than the O₂ plasma pre-treatment. In the ball-on-disc test, the DLC film with the N₂ plasma pre-treatment showed good wear resistance, compared with that with O₂ plasma pre-treatment.     

重复频率低阻抗紧凑Marx脉冲功率源

为了实现重频脉冲功率源小型化,研制了基于快Marx发生器的紧凑型重频低阻抗脉冲功率源。采用大功率重频高压电源对Marx发生器充电,通过对充电电源和脉冲触发源的同步控制,实现对Marx发生器重频充电;Marx发生器中采用薄膜脉冲电容器、小型化气体开关、电感隔离以及SF₆气体绝缘等设计,以8级紧凑Marx发生器进行验证性研究,在16 Ω阻抗负载上实现了重复频率10 Hz、脉宽150 ns、峰值电压大于400 kV连续多脉冲输出;在此基础上,设计了18级紧凑型Marx发生器,在约18 Ω阻抗负载上输出功率达到33 GW,峰值功率密度大于150 GW/m3,实现重复频率5 Hz、脉宽约160 ns、峰值电压大于600 kV的连续多脉冲输出。为了降低Marx发生器的输出阻抗,采用4台电容器并联作为Marx发生器的一级储能模块,研制了同轴紧凑Marx脉冲功率源,有效减小放电回路电感,实现12 Ω低阻抗负载近似匹配输出,前沿减小至50 ns以下,脉宽约130 ns。     

陡化前沿Marx发生器的阻抗特性

 利用50 kV无感电容器与固体电阻制作了10级陡化前沿Marx发生器,实现了电容储能型脉冲功率调制系统的小型化。使用不同阻值的水电阻负载研究了发生器的阻抗特性,并进一步制作了金属膜电阻负载进行实验,测定90 Ω负载可以使发生器处于临界阻尼放电状态,从而确定发生器的内部阻抗约为45 Ω。当充电电压为40 kV时,在金属膜电阻负载上得到了幅值约为210 kV,脉宽约为40 ns,前沿约为5 ns的快前沿高压脉冲。利用此发生器成功地驱动了强流二极管,当二极管阴阳极间距为15 mm时,在30 kV充电情况下,其输出电压约为154 kV,束流约为1 kA。     

Surface modification of diamond-like carbon films with perfluorooctyl functionalities and their surface properties

Photolysis of perfluoroazooctane with diamond-like carbon (DLC) films led to the surface modification to introduce perfluorooctyl functional groups, confirmed by means of FT-IR, XPS, Raman and TOF-SIMS measurements. The DLC films modified with fluorine moieties showed reduction of the surface energy evaluated by contact angle to water, as compared with pristine DLC film. The contact angle of chemically modified DLC film is 105°, comparable to that of polytetrafluoroethylene (PTFE). By monitoring with XPS, we found that the results on the value of fluorine/carbon ratio of fluorinated DLC films depending on irradiation time are consistent with those of contact angle. Chemical modification of DLC films with perfluorooctyl functionalities also led to improvement of their frictional properties. The friction coefficient of the modified film is 0.05 under vacuum condition, whereas that of the pristine film shows very high value (>1).     

Studies on surface graft polymerization of acrylic acid onto PTFE film by remote argon plasma initiation

The graft polymerization of acrylic acid (AAc) was carried out onto poly(tetrafluoroethylene) (PTFE) films that had been pretreated with remote argon plasma and subsequently exposed to oxygen to create peroxides. Peroxides are known to be the species responsible for initiating the graft polymerization when PTFE reacts with AAc. We chose different parameters of remote plasma treatment to get the optimum condition for introducing maximum peroxides (2.87 × 10⁻¹¹ mol/cm²) on the surface. The influence of grafted reaction conditions on the grafting degree was investigated. The maximum grafting degree was 25.2 μg/cm². The surface microstructures and compositions of the AAc grafted PTFE film were characterized with the water contact angle meter, Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Contact angle measurements revealed that the water contact angle decreased from 108° to 41° and the surface free energy increased from 22.1 × 10⁻⁵ to 62.1 × 10⁻⁵ N cm⁻¹ by the grafting of the AAc chains. The hydrophilicity of the PTFE film surface was greatly enhanced. The time-dependent activity of the grafted surface was better than that of the plasma treated film.     

Formation of hydrophobic coating on PMMA surface using unipolar nanosecond-pulse DBD in atmospheric air

Dielectric barrier discharge (DBD) can modify the material surface and result in complicated physical and chemical reactions to improve the surface hydrophilicity, which is proved to be an effective method for surface modification. Compared with the traditional ac-excitation DBD, the DBD using unipolar pulses can avoid local overheat of microdischarges and can improve discharge efficiency under some conditions. In this paper, DBD excited by repetitive unipolar nanosecond generator was used to improve the hydrophobicity of Plexiglass (PMMA) surface by means of the interaction between air plasma and silicone oil. The output voltage had a rise time of 40 ns and a full width at half maximum of about 70 ns. The surface hydrophobicity of the PMMA, before and after the surface modification, was evaluated via the contact angle measurement under different experimental conditions. The values of the contact angle shown in this paper were the average of eight measured values, and the standard deviations were also calculated. The surface energy including polar and dispersion components was calculated using the measured average contact angles of distilled water and polyethyleneglycol. The results showed that, as the increase of the discharge voltage, the contact angle increased but the surface energy decreased. With the increase of treatment time, the water contact angle of the modified surface increased at the beginning, and it would reach to a maximum at 7.5 min treatment, and then decreased. The effect of pulse frequency on the modification results was different at various treatment times. In addition, the possible physical and chemical reaction among the DBD plasma, silicone oil and the PMMA surface was discussed.