排序方式: 共有12条查询结果,搜索用时 31 毫秒
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M. Mosbacher N. Chaoui J. Siegel V. Dobler J. Solis J. Boneberg C.N. Afonso P. Leiderer 《Applied Physics A: Materials Science & Processing》1999,69(7):S331-S334
We report a quantitative investigation on the efficiency of the steam laser cleaning process using ns and ps pulses. Well-characterized polymer particles with a diameter of 800 nm dispersed on commercial Si wafers were chosen as a modeling contaminant system. As a result of our investigation, we show for the first time the feasibility of performing efficient steam laser cleaning with ps laser pulses and compare the achieved efficiency with the one obtained for ns pulses. For ns pulses, we found a cleaning fluence threshold of 50 mJ/cm2 that is independent of the pulse durations (2.5 ns and 8 ns) and the wavelengths (532 nm and 583 nm) used. The application of ps pulses (FWHM=30 ps, 5=583 nm) lowered this threshold to 20 mJ/cm2. Both cleaning thresholds are far below the melting thresholds for these laser parameters. Cleaning efficiencies >90% were reached for both pulse durations. 相似文献
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Statistical analysis of HDPE fatigue lifetime 总被引:1,自引:0,他引:1
Fatigue lifetime of HDPE structures such as pipes is recognized to show a large scatter. This study aims to compare different
statistical methods and distributions, in order to give convenient modeling of tensile and fatigue test results of commercially
available polyethylene compression molded sheets. The median rank, the maximum likelihood and the Kolmogorov-Smirnov fitting
are compared for the estimation of Weibull parameters. The choice of the best distribution to fit fatigue lifetime is discussed
on the basis of the goodness-of-fit results. It is found that whether the three-parameter distributions of Weibull and lognormal
types are suitable for lifetime prediction, the two-parameter Weibull is more conservative for probabilistic fatigue design. 相似文献
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THF: An Efficient Electron Donor in Continuous Flow Radical Cyclization Photocatalyzed by Graphitic Carbon Nitride
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Dr. Magdalena Woźnica Nicolas Chaoui Soraya Taabache Prof. Dr. Siegfried Blechert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14624-14628
Mesoporous graphitic carbon nitride (mpg‐C3N4) was found to be an efficient heterogeneous photocatalyst for the metal‐free radical cyclization of 2‐bromo‐1,3‐dicarbonyl compounds. Reactions leading to functionalized cyclopentanes proceed under mild conditions and can be conducted in a continuous flow photoreactor. Compared to the batch reaction, the use of a continuous flow reactor resulted in a significant reduction in reaction time (complete conversion of 0.04 mmol of substrate in a batch was achieved after 4 h, whereas in a flow reactor the same amount of substrate was fully converted into a product within 40 min). Mechanistic studies of the reaction showed that THF plays not only the role of solvent, but is also a crucial hydrogen and electron donor. 相似文献
5.
Rui Yan Bikash Mishra Dr. Michael Traxler Dr. Jérôme Roeser Nicolas Chaoui Bidhan Kumbhakar Dr. Johannes Schmidt Prof. Shuang Li Prof. Arne Thomas Dr. Pradip Pachfule 《Angewandte Chemie (International ed. in English)》2023,62(32):e202302276
Lithium-sulphur (Li−S) batteries are a promising alternative power source, as they can provide a higher energy density than current lithium-ion batteries. Porous materials are often used as cathode materials as they can act as a host for sulphur in such batteries. Recently, covalent organic frameworks (COFs) have also been used, however they typically suffer from stability issues, resulting in limited and thus insufficient durability under practical conditions and applications. Herein, we report the synthesis of a crystalline and porous imine-linked triazine-based dimethoxybenzo-dithiophene functionalized COF (TTT-DMTD) incorporating high-density redox sites. The imine linkages were further post-synthetically transformed to yield a robust thiazole-linked COF (THZ-DMTD) by utilizing a sulphur-assisted chemical conversion method, while maintaining the crystallinity. As a synergistic effect of its high crystallinity, porosity and the presence of redox-active moieties, the thiazole-linked THZ-DMTD exhibited a high capacity and long-term stability (642 mAh g−1 at 1.0 C; 78.9 % capacity retention after 200 cycles) when applied as a cathode material in a Li−S battery. 相似文献
6.
The effect of post‐oxidizing treatment on the characteristics of modified surface layers produced by salt bath nitrocarburizing on the industrial American Iron and Steel Institute (AISI) 02 tool steel types is investigated. Nitrocarburizing treatment is performed for 6 h and 8 h at 570 °C and post‐oxidizing treatment for 30, 60 and 90 min at 520 °C, using argon–steam mixture. Formed layers are characterized by their basic properties such as thickness layer, depth, surface hardness and wear resistance. Detailed estimation of the modified metal surface quality, in terms of chemical composition, formed phases, microstructures and diffusion mechanisms are performed by metallographic techniques, EDX, X‐ray diffraction, scanning electron microscopy (SEM) and glow discharge optical electron spectroscopy (GDOES). The corrosion resistance was investigated in 0.4 M H2SO4 solutions, using steady‐state electrochemical polarization methods. The obtained results revealed the existence of a superficial oxide layer which consists of magnetite (Fe3O4) and hematite (Fe2O3) and the presence of an ε‐phase associated with a small amount of γ′‐phase. Important improvements in wear, microhardness and corrosion resistance occur after these treatments and it is specifically concluded that the sole application of a nitrocarburizing treatment does not significantly ameliorate the corrosion resistance of the as‐received steel. In fact, post‐oxidation treatment contributes to increase corrosion resistance by forming a dense magnetite layer and at the same time, it partially covers the compound layer pores. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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This article deals with a fractional diffusion equation of the second-order differential Volterra operator and fractional integral condition. Existence and uniqueness of a weak solution in an appropriate sense as well as some regularity results are obtained by the use of Rothe’s method. Finally, an example is given to demonstrate the effectiveness of the proposed approach. 相似文献
8.
Z. Chaoui 《Applied Surface Science》2006,252(9):3362-3367
Backscattering (Bcs) coefficients for low-energy positrons (∼100 eV) from elemental solids have been simulated using an analytic approach. The model is based on the use of the transport cross-sections (TCSs) and the stopping power calculated from partial wave methods and the best-fit stopping power data of Ashley, respectively. The new result is an extension of recent calculations in the medium energy range. Comparisons, when possible, with experimental and Monte-Carlo (MC) simulation data have been made. 相似文献
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Michaela König Dr. Massimo Rigo Nicolas Chaoui Trung Tran Ngoc Dr. Jan Dirk Epping Dr. Johannes Schmidt Dr. Pradip Pachfule Meng-Yang Ye Dr. Matthias Trunk Prof. Johannes F. Teichert Prof. Matthias Drieß Prof. Arne Thomas 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20002-20006
An iridium dihydride pincer complex [IrH2(POCOP)] is immobilized in a hydroxy-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The introduction of this novel, truly innocent support with remote OH-groups enables the formation of isolated active metal sites embedded in a chemically robust and highly inert environment. The catalyst maintained high porosity and without prior activation exhibited efficacy in the gas phase hydrogenation of ethene and propene at room temperature and low pressure. The catalyst can be recycled for at least four times. 相似文献
10.
A high-sensitivity in situ optical diagnostic technique for laser cleaning of transparent substrates
N. Chaoui J. Solis C.N. Afonso T. Fourrier T. Muehlberger G. Schrems M. Mosbacher D. Bäuerle M. Bertsch P. Leiderer 《Applied Physics A: Materials Science & Processing》2003,76(5):767-771
A differential optical transmission technique has been used to monitor in situ the efficiency of laser cleaning for the removal
of sub-micrometer-sized particles on substrates transparent at the monitoring wavelength. This technique has been applied
to the removal of sub-micrometer polystyrene particles on polyimide substrates using laser pulses of 30 ps duration at 292 nm
while probing the material transmission at 633 nm. The sensitivity achieved -1/104 for the transmission changes induced upon single-pulse laser exposure – allows us to monitor the removal of just a few sub-micron-sized
particles from the probed region inside the irradiated area.
Received: 2 October 2002 / Accepted: 7 October 2002 / Published online: 29 January 2003
RID="*"
ID="*"Corresponding author. Fax: +33-3/87844082, E-mail: nchaoui@iut.univ-metz.fr
RID="**"
ID="**"Present address: Laboratoire de Chimie et Applications, Institut Universitaire de Technologie de Metz, Département
Chimie, Rue Victor Demange, 57500 Saint-Avold, France 相似文献