Transverse Optical Mode Patterns for an RF Excited Ar-He-Xe Laser

Transverse optical modes for an RF excited Ar-He-Xe laser are studied both experimentally and theoretically. A diffraction model for a waveguide with a nonsaturable gain and refractive index gradients placed between two plane mirrors is formulated. The effects of gain and diffraction index gradients and of diffraction in free space are evaluated for typical experimental conditions. A direct comparison between theoretical mode patterns and experimentally measured ones at distances of 17 and 114 cm from the output mirror demonstrated a satisfactory agreement for various laser wavelengths and gas mixture composition

High current diffuse dielectric barrier discharge in atmospheric pressure air for the deposition of thin silica-like films

The diffuse dielectric barrier discharge in atmospheric pressure air was applied for the thin film deposition on polymeric web in industrially relevant roll-to-roll configuration. The silica-like film deposition was performed using the admixture of hexamethyldisiloxane precursor to air flow. Fast discharge imaging at 2 µs exposure time confirms plasma uniformity in a single current pulse time scale. Morphology and composition analyses indicate that the process results in ultrasmooth films (roughness comparable to initial substrate roughness) and shows the possibility to synthesize carbon-free layers. © 2010 American Institute of Physic

Low-Temperature Atmospheric Pressure Plasma Processes for “Green” Third Generation Photovoltaics

Special Issue: Plasma Processing of Materials for Energy Conversion and Storage.International audienceAtmospheric pressure plasmas (APPs) have achieved great scientific and technological advances for a wide range of applications. The synthesis and treatment of materials by APPs have always attracted great attention due to potential economic benefits if compared to low-pressure plasma processes. Nonetheless, APPs present very distinctive features that suggest atmospheric pressure operation could bring other benefits for emerging new technologies. In particular, materials synthesized by APPs which are suitable candidates for third generation photovoltaics are reviewed here

...In die festivitatis: Calendar, liturgy, and ritual structuring of time and space in the Middle Ages.

The dissertation discusses the construction of Europe's new political geography after the Roman empire gave way to kingdoms and principalities of the Middle Ages and shows how the paradigms of imagining time and space constructed in the early medieval period influenced these categories as seen in the High Middle Ages. The rulers who created new political structures in the West successfully addressed a difficult task: by the High Middle Ages they had joined together disparate regional political groups by using ritual associated with the annual calendar of church holidays. The process began when Charlemagne's (742--814) and clerics' interest in calendar at the turn of the ninth century allowed the Frankish ruler to incorporate local elites into the imperial project with its help, expanding the rhythms of church holidays into the cycles of tenurial dependence. In the subsequent period, marred by internal strife between Louis the Pious and his sons, Frankish rulers lost interest in the liturgical calendar, while bishops continuously employed liturgical rituals and calendar to buttress their power in dioceses. Gradual cristallization of new territorial kingdoms in the second half of the ninth century required kings to find the ways of delineating their new possessions; they resorted to the ecclesiastical calendar of remembrance the bishops mastered so well to mark boundaries of their kingdoms with annual celebrations of their birthdays. Carolingian authority fell apart in the late ninth century, but in second quarter of the tenth century bishops resorted to the means Carolingians had used to reestablish their authority: they expanded networks of tenure and structuring its rhythms around the calendar of church holidays. Prelates' vision of dioceses came to be firmly established on representing territory with the help of time (holidays of remembrance and ritual); church holidays began to mark boundaries between ecclesiastical communities. The uses of church calendar and the rituals of remembrance laid the foundations for how space and time come to be imagined in the High Middle Ages: twelfth-century maps, of the world as well of monastic domains, structure spaces with the help of temporal coordinate, represented by holidays as rituals of remembrance.Ph.D.European historyMedieval historySocial SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/123107/2/3059931.pd

Synthesis of metallic nanoparticles by microplasma

The synthesis of metallic nanoparticles has been of long standing interest, primarily induced by their novel and unique properties that differ considerably from bulk materials. Despite various methods have been developed, it is still a challenge to produce high-quality metallic nanoparticles with controllable properties in a simple, cost-effective and environmentally benign manner. However, the development of the microplasma-assisted technology can bring an answer to this formidable challenge. In the present work, four mainmicroplasma configurations used for metallic synthesis of metallic nanoparticles are reviewed. These are hollow-electrode microdischarges, microplasma jets with external electrodes, microplasma jets with consumable electrodes and plasma-liquid systems. The state of the art characterization methodologies and diagnostic techniques for in situ microplasma-assisted precursor dissociation as well as ex situmetallic nanoparticles analysis is also summarized. Further, a broad category of representative examples of microplasma-induced metallic nanoparticle fabrication is presented, together with the discussion of possible synthesis mechanisms. This is followed by a brief introduction to related safety considerations. Finally, the future perspectives, associated challenges and feasible solutions for scale-up of this technique are pointed out

An atmospheric pressure microplasma process for continuous synthesis of titanium nitride nanoparticles

This research studies a continuous process for the direct synthesis of titanium nitride nanoparticles assisted by an atmospheric pressure microplasma. Titanium tetrachloride (TiCl4) is used as precursor and nitrogen is used as reacting gas. Composition and microstructure analysis (SEM, EDX, TEM, HRTEM, XRD and XPS) of the synthesized nanoparticles reveals that nanometer-sized titanium nitride (TiN) with polycrystalline nature can be directly prepared by the studied process, and the admixture of H2 gas in plasma during synthesis process can be an effective way to reduce the oxidation of TiN nanoparticles. The influence of the dissipated power and H2 concentration on the optical emission spectra of the microplasma in the operating reactor is investigated. The characteristics gas temperature of the plasma filament is estimated from the emission averaged spectra. A hypothesized mechanism of TiN synthesis in microplasma is illustrated, and comparisons with preceding researches are carried out. Based on process analysis and experimental results, the feasibility of the upscale towards industrial level production is discussed

Synthesis of iron oxide nanoparticles in microplasma under atmospheric pressure

Microplasma is a novel technology for functional nanomaterial synthesis. In this research, iron oxide nanoparticles are successfully synthesized by a home-built microplasma setup. The setup is specially designed with overall safety considerations and broad operation space, including a smart micro reactor system which allows for flexible process control, easy assembling and direct product collection. The atmospheric pressure gas discharge was sustained in Ar flow with addition of ferrocene vapors as a precursor. The influence of the gas temperature and power dissipated in the discharge on the dissociation process is investigated. Optical emission spectroscopy (OES) is applied to study the impact of discharge parameters on plasma characteristics and possible mechanism of the ferrocene dissociation. The obtained products are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results show that nanometer-sized and well-dispersed iron oxide nanoparticles with polycrystalline nature can be produced by the atmospheric pressure microplasma setup. The increase of temperature and power helps to enhance the precursor dissociation rate. However, it also contributes to the production of larger sized nanoparticles with higher agglomeration degree. Based on experimental data, simplified modeling as well as relevant information from literature, we proposed possible mechanisms for ferrocene decomposition

An atmospheric pressure microplasma process for continuous synthesis of titanium nitride nanoparticles

This research studies a continuous process for the direct synthesis of titanium nitride nanoparticles assisted by an atmospheric pressure microplasma. Titanium tetrachloride (TiCl4) is used as precursor and nitrogen is used as reacting gas. Composition and microstructure analysis (SEM, EDX, TEM, HRTEM, XRD and XPS) of the synthesized nanoparticles reveals that nanometer-sized titanium nitride (TiN) with polycrystalline nature can be directly prepared by the studied process, and the admixture of H2 gas in plasma during synthesis process can be an effective way to reduce the oxidation of TiN nanoparticles. The influence of the dissipated power and H2 concentration on the optical emission spectra of the microplasma in the operating reactor is investigated. The characteristics gas temperature of the plasma filament is estimated from the emission averaged spectra. A hypothesized mechanism of TiN synthesis in microplasma is illustrated, and comparisons with preceding researches are carried out. Based on process analysis and experimental results, the feasibility of the upscale towards industrial level production is discussed

Synthesis of iron oxide nanoparticles in microplasma under atmospheric pressure

Microplasma is a novel technology for functional nanomaterial synthesis. In this research, iron oxide nanoparticles are successfully synthesized by a home-built microplasma setup. The setup is specially designed with overall safety considerations and broad operation space, including a smart micro reactor system which allows for flexible process control, easy assembling and direct product collection. The atmospheric pressure gas discharge was sustained in Ar flow with addition of ferrocene vapors as a precursor. The influence of the gas temperature and power dissipated in the discharge on the dissociation process is investigated. Optical emission spectroscopy (OES) is applied to study the impact of discharge parameters on plasma characteristics and possible mechanism of the ferrocene dissociation. The obtained products are characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Results show that nanometer-sized and well-dispersed iron oxide nanoparticles with polycrystalline nature can be produced by the atmospheric pressure microplasma setup. The increase of temperature and power helps to enhance the precursor dissociation rate. However, it also contributes to the production of larger sized nanoparticles with higher agglomeration degree. Based on experimental data, simplified modeling as well as relevant information from literature, we proposed possible mechanisms for ferrocene decomposition

Method and apparatus for deposition using pulsed atomspheric pressure glow discharge

Method and apparatus for deposition of a chemical compound or element using an atmospheric pressure glow discharge plasma in a treatment space (5) comprising two 5 electrodes (2, 3) connected to a power supply (4) for providing electrical power during an on-time (ton), the treatment space is filled with a gas composition of an active and an inert gas mixture, including a precursor of the chemical compound or element to be deposited.. Dust formation is prevented by using Nitrogen in the gas composition, applying short pulses and using a predetermined residence time of the gas composition 10 in the treatment space. Best results are obtained when using a stabilized plasma