Kalte Normaldruck‐Jetplasmen zur lokalen Oberflächenbehandlung

Cold non‐thermal plasma jets for local surface treatment under normal pressure Plasmas at normal pressure are of considerable interest for surface technology because the industrial application requires no vacuum devices. Among other approaches, cold non‐thermal plasma jets represent an emerging technique to generate plasmas at normal pressure with attractive advantages. They allow ambient process temperatures and require only moderate operating voltages (1.5‐2.5 kV). They offer the advantage that the treated surfaces are not placed between the electrodes thus favoring local treatment of non flat, structured 3D surfaces. Moreover, the dimension of the sources is scalable and their integration into automated processes is simple. A capacitively coupled version (27.12 MHz) of a cold plasma jet suitable for surface treatment at atmospheric pressure is presented along with its plasma physical and technical properties and a series of successful applications, including plasma activation of surfaces for increasing printability, adhesion control, surface cleaning, microfluidics, decontamination, its use in plasmamedicine and for deposition of thin SiO₂ films as protective coatings. The device allows the operation with rare gases (e.g. Ar) and reactive gases as N₂, air or admixtures of silicon‐containing compounds.     

凹版印刷工业的绿色节能技术

针对当前凹版印刷设备存在的耗能大、尾气排放污染等问题,通过对凹版印刷机热风干燥系统节能、印刷有机废气(VOCs)综合治理和凹印企业主要热源余热循环利用等主要相关技术的探讨,提出了切实可行的节能减排方案.在此基础上,进一步将热力燃烧式氧化器与热水二段型溴化锂机组相结合,解决了热力燃烧式氧化器运行成本较高的问题.研究结果表明,从热风干燥系统、有机废气综合利用、主要热源余热循环利用3个方面入手实施的节能减排方案,可以降低凹版印刷工业运行能耗的20%~40%.     

Plasmabromierung von graphitischen Materialien

Plasma bromination of graphitic materials The high‐yield and high‐selective plasma chemical bromination of polyolefin surfaces was transferred to graphitic materials. Graphene‐like surfaces of highly‐oriented pyrolytic graphite (HOPG), natural graphite, multi‐walled carbon nanotubes(MWCNT) and carbon fibres were exposed to bromine plasma. This bromination proceeds at polyolefin surfaces as radical substitution by hydrogen abstraction and bromine attachment or as nucleophilic substitution. However, bromination of graphitic structures picks up sp³ carbon atoms occurring as structural defects or more probably proceeds as electrophilic addition onto the substituted aromatic double bonds. In this process the planar sp² carbon‐carbon bonds are transferred to the tetrahedral sp³ C‐C bonds with non‐conducting structure. Using the bromine plasma maximal bromination yields varied, were dependent on the type of carbon material and ranged from 10–50% Br/C. Using bromoform as Br‐precursor and accepting layer deposition about 70% Br/C were found. Subsequently, different amines were grafted wet‐ or gas phase chemically by nucleophilic substitution. The grafting yields amounted 1–10 molecules per 100 carbon atoms, which was lower than for grafting yields on brominated polyolefin surfaces ranging between 1–22 molecules per 100 carbon atoms. After grafting more or less all non‐grafted Br‐atoms were also diminished, that indicated a partial reconstruction of the planar sp² graphitic structure.     

Plasmaprozesse für funktionelle Polymeroberflächen

Plasma Processes for Functional Polymer Surfaces Plasma‐based processes were originally developed for microelectronics, but have exceeded this limits since then. Today the plasma technology is a key technology with numerous applications. A great technological potential can be seen particularly in the field of surface modification because in a plasma any organic bond can be broken and thus reactions can be initiated which cannot be carried out wet‐chemically. Besides, the small depth effect leaves the bulk properties of the material unchanged. This article points out the fundamental characteristics of non‐thermal low pressure plasmas and shows some procedure examples, which were developed at the Fraunhofer‐Institut für Angewandte Polymerforschung (IAP). Finally analysis methods (XPS, labeling techniques) are presented, which are essential for an effective development of plasma processes.     

Überwachung der Plasmahomogenität

Monitoring plasma homogeneity A new imaging system has been built up for the fast qualitative monitoring of plasma processes. It is designed to analyze the spatial distribution of the plasma’s emission intensity at different wavelengths. The system consists of a liquid crystal tunable filter for wavelength selection and a CCD‐camera. Its applicability is presented for non‐polymerizing argon plasmas and polymerizing acetylene plasmas. Our investigations were carried out with focus on the effect of the process pressure on the homogeneity of the plasma emission and the resulting layer deposition. Both the emission’s uniformity as well as the homogeneity of the deposition are affected by the process pressure. Low process pressures are favorable for both of the named parameters.     

Flow Visualization in a Rotating-Arc Plasma Jet

Knowledge of the gas flow pattern in a plasma jet exhaust is important in relation to heat transfer and gas temperature estimation. The extreme conditions within the jet, however, have hitherto encouraged the use of water cooled probes for flow measurements to the exclusion of quicker and more convenient optical methods.

An optical system has been developed to indicate gas velocities throughout the volume of a transparent water jacket enclosing the exhaust gas by means of particle track photography. The difficulties caused by the size of the test space and the high gas luminosity are overcome by using a bi-focal lens system to utilize a photographic flash bulb source efficiently.     

大气污染与环境的治理迫在眉睫

我们赖以生存的条件——空气,正随着人类无节制地向空气中排放废气和固体废弃物而造成了污染,引起了气候的变化。介绍了大气和大气污染的定义,由人为因素所引起污染的来源、种类,大气污染源形成的主要原因;大气环境、温室气体的影响对人体健康所产生的危害。还介绍了我国关于环境污染监测的相关检测方法及标准的制定情况。阐述了大气环境治理的必要性以及计量对环境污染治理所起的作用。     

Untersuchung der Verteilung und Intensität filamentierter Barrierenplasmen für die Behandlung von Oberflächen

The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit.     

Spatial distributions of gas composition in rf glow discharge plasmas measured using a quartz sensor

A quartz sensor can detect changes in gas composition caused by plasma because the quartz sensor output depends on the total pressure, viscosity, and molecular weight of the gas. This simple mode of quartz sensor measurement was used to obtain spatial distributions of the gas composition changes in the plasmas between a chamber inner wall and a plasma electrode. These spatial distributions reflect gas phase reactions in the plasmas. For that reason, they are helpful to elucidate the reaction mechanisms occurring in the plasmas. Applying such quartz sensor measurements for hydrogen and argon-hydrogen plasmas, we found that the spatial distributions of the gas composition change, as measured using a quartz sensor, depend on source gases. The positions at which the quartz sensor output show the maximum gas composition change for hydrogen and argon-hydrogen plasmas were at the chamber inner wall and near the edge of the plasma electrodes that are the closest positions to the plasma glow. These results show that the gas composition change detected using the quartz sensor resulted from degassing from the chamber inner wall and the plasma electrodes.     

电站锅炉烟气余热利用技术方案研究

超临界电站锅炉排烟热损失量很大,对锅炉尾部烟气余热进行回收利用可以有效提高电厂的热经济性,减少煤耗,降低环境污染。目前火电厂最广泛提高烟气余热利用效率的方式是加装低温省煤器装置。对某超临界机组锅炉余热利用技术进行研究,分析不同低温省煤器布置方案,提出采用双级低温省煤器回收电站锅炉余热利用技术方案,即采用低温烟气与低加凝结水换热技术、前置式空气预热器与低温省煤器组合的能源梯级利用方式,实现最优节能及最佳投资收益。     

Großflächige Plasmabeschichtungen: Niederdruck oder Atmosphärendruck?

Large area plasma coatings: low pressure or atmospheric pressure? Research in the field of atmospheric pressure plasma is often motivated by the expectation of cost‐saving compared to low pressure plasma processes. A cost analysis based on plasmachemical processes which can also be performed at atmospheric pressure, however, reveals a different picture: high gas flow rates that are required for atmospheric pressure plasmas were found to cause increased costs for large‐area plasma deposition.     

Diagnostics of reactive RF plasmas

Experimental characterization of the plasma state as well as the neutral gas phase in a low pressure discharge is presented. A radiofrequency supply produces plasma driving an electrical discharge in a gas mixture through a resonant inductive coupling. The plasma state has been characterized by means of electrostatic probes, optical emission spectroscopy. Mass spectroscopy of the neutral and of the charged species has been performed too, sampling the gas phase inside the discharge. Results on Ar/SF₆ plasmas are presented to study the effect of argon doping on the production of reactive atomic fluorine in the discharge. More efficient application of Ar/SF₆ plasmas to surface fluorination of polymers could be expected in view of these results.     

Gas sources in fusion devices

Fusion plasmas are routinely produced from pure gas injected into the vacuum vessel of fusion devices at pressures in the range of millitorr. The large surface to volume ratio, characteristic of these fully instrumented devices, makes plasma density and impurity control a difficult task. The problem is further aggravated due to the large fluxes of energetic species produced by the imperfect confinement of particles and energy into the plasma and, additionally, due to the large efficiency of the plasma in pumping the gas released by the interaction of such particles with the vessel walls. Many of these processes have a direct impact in the control of the tritium inventory, of high relevance in the operation of future fusion reactors, and they are presently the focus of very active research.In the present work, the problems associated to the control of gas sources in fusion devices are addressed. First, the impact of the gas release on the particle and impurity control of the fusion plasmas is discussed. Secondly, the different types of sources that are present either before or during plasma formation are identified and finally, the techniques oriented to control the interchange of particles between the plasma and its surroundings are described.     

Characteristics of microwave plasma induced by lasers and sparks

Characteristics of the plasma light source of microwave (MW) plus laser-induced breakdown spectroscopy (LIBS) or spark-induced breakdown spectroscopy (SIBS) were studied. The plasma was initially generated by laser- or spark-induced breakdown as a plasma seed. A plasma volume was then grown and sustained by MWs in air. This MW plasma had a long lifetime, large volume, strong emission intensity, and high stability with time. These characteristics are suitable for applications in the molecular analysis of gases such as OH or N(2). Because the plasma properties did not depend on laser or spark plasma seeds, the resulting plasma was easily controllable by the input power and duration of the MWs. Therefore, a significant improvement was achieved in the spectral intensity and signal-to-noise ratio. For example, the peak intensity of the Pb spectra of LIBS increased 15 times, and that of SIBS increased 880 times without increases in their background noise. A MW-enhanced plasma light source could be used to make the total system smaller and cheaper than a conventional LIBS system, which would be useful for real-time and in situ analysis of gas molecules in, for example, food processing, medical applications, chemical exposure, and gas turbine or automobile air-to-fuel ratio and exhaust gas measurement.     

Enhanced processing of coatings on glass surfaces

In this contribution, basic technically usable interactions of atmospheric pressure plasmas (APP), laser irradiation and solids as well as a technique which combines such plasmas and laser irradiation are introduced. Two examples for plasma‐enhanced laser processing of coatings on glass surfaces are presented in more detail. First, APP‐assisted annealing of amorphous silicon layers is discussed. It is shown that the crystallised area is notably increased by assisting plasmas where the particular improvement factor depends on the particularly applied type of plasma. Second, the impact of assisting plasmas on laser removal of lacquers and varnishes from glass surfaces is presented. By introducing a plasma jet to the laser removal process, the laser energy required for cleaning or delamination is notably reduced.     

快速热平衡式pVTt法气体流量标准装置的设计与研究

设计了基于单侧溢流式恒温水浴系统的快速热平衡式pVTt气体流量标准装置,对水浴及临界流喷嘴进行了实验研究,采用了五路阀门组合控制技术,实现了预抽气功能,降低了压力波动.装置平衡时间为6 min,与其它pVTt法气体流量标准装置相比,平衡时间至少缩短一倍.     

Oxygen plasma induced hydrophilicity of TiO2 thin films

Anatase nano-TiO₂ thin films were fabricated by reactive magnetron sputtering metal Ti target followed by thermal annealing in air at 450 °C for 2 hrs. The crystalline structure of the sample films were characterized by X-ray diffraction (XRD) and the hydrophilicity was characterized with the diameters of 1 μl water drop. The films were irradiated by oxygen plasmas and the effects of the radio frequency (rf) power, the gas pressure and the irradiation time of the oxygen plasmas on the hydrophilicity of the TiO₂ thin films were investigated. Hydrophilicity can be induced by oxygen plasmas and further more the hydrophilicity shows high stability whenever under the natural light or in dark.     

Structure of a weakly ionized gas-discharge plasma

Analysis of the properties of weakly ionized plasmas suggests that strong collective interactions exist in them in spite of the large distance between particles. Arguments supporting this view are presented. First among these is the existence of “hidden” mass, which is observed in experimental measurements of the aerodynamic drag forces. The hidden mass causes an increase in the amplitude of sound waves in a plasma in comparison with an un-ionized gas at identical values of the gas parameters. Analysis of the experimental results shows that gas-discharge plasmas contain previously unknown structural formations that are specific to a plasma and are of a standard type for each species of gas, independent of the pressure and temperature of the plasma. The concentration of particles making up the structure in the plasma of a gas discharge in air is 0.22×10¹⁷ cm⁻³. Pis’ma Zh. Tekh. Fiz. 24, 80–86 (June 12, 1998)     

Resolving Sub‐Molecular Binding and Electrical Switching Mechanisms of Single Proteins at Electroactive Conducting Polymers

Polymer‐based electrodes for interfacing biological tissues are becoming increasingly sophisticated. Their many functions place them at the cross‐roads of electromaterials, biomaterials, and drug‐delivery systems. For conducting polymers, the mechanism of conductivity requires doping with anionic molecules such as extracellular matrix molecules, a process that distinguishes them as biomaterials and provides a means to control interactions at the cellular–electrode interface. However, due to their complex structure, directly observing the selective binding of target molecules or proteins has so far eluded researchers. This situation is compounded by the polymer's ability to adopt different electronic states that alter the polymer–dopant interactions. Here, the ability to resolve sub‐molecular binding specificity between sulfate and carboxyl groups of dopants and heparin binding domains of human plasma fibronectin is demonstrated. The interaction exploits a form of biological ‘charge complementarity’ to enable specificity. When an electrical signal is applied to the polymer, the specific interaction is switched to a non‐specific, high‐affinity binding state that can be reversibly controlled using electrochemical processes. Both the specific and non‐specific interactions are integral for controlling protein conformation and dynamics. These details, which represent the first direct measurement of biomolecular recognition between a single protein and any type of organic conductor, give new molecular insight into controlling cellular interactions on these polymer surfaces.