Search results for "Diffusion"
showing 10 items of 1615 documents
Xenon Recovery by DD3R Zeolite Membranes: Application in Anaesthetics.
2019
Xe is only produced by cryogenic distillation of air, and its availability is limited by the extremely low abundance. Therefore, Xe recovery after usage is the only way to guarantee sufficient supply and broad application. Herein we demonstrate DD3R zeolite as a benchmark membrane material for CO2 /Xe separation. The CO2 permeance after an optimized membrane synthesis is one order magnitude higher than for conventional membranes and is less susceptible to water vapour. The overall membrane performance is dominated by diffusivity selectivity of CO2 over Xe in DD3R zeolite membranes, whereby rigidity of the zeolite structure plays a key role. For relevant anaesthetic composition ( 320 h). Thi…
Ambipolar MoS2 Transistors by Nanoscale Tailoring of Schottky Barrier Using Oxygen Plasma Functionalization
2017
One of the main challenges to exploit molybdenum disulfide (MoS2) potentialities for the next-generation complementary metal oxide semiconductor (CMOS) technology is the realization of p-type or ambipolar field-effect transistors (FETs). Hole transport in MoS2 FETs is typically hampered by the high Schottky barrier height (SBH) for holes at source/drain contacts, due to the Fermi level pinning close to the conduction band. In this work, we show that the SBH of multilayer MoS2 surface can be tailored at nanoscale using soft O-2 plasma treatments. The morphological, chemical, and electrical modifications of MoS2 surface under different plasma conditions were investigated by several microscopi…
Photon assisted-inversion of majority charge carriers in molecular semiconductor-based organic heterojunctions
2021
International audience; Ambipolar molecular materials hold great promises as a building block of next generation highly efficient, less complex and low cost electronics devices. In this endeavor, the present work reports the fabrication of organic heterojunction devices based on halogenated copper Phthalocyanines (CuPc) and lutetium bisphthalocyanine (LuPc2) bilayer, investigates their structural and electrical properties and probes the ambipolar behavior by ammonia sensing. Microstructural analysis of the heterostructure thin films revealed compact and semicrystalline organization, depending on the number of halogen substituents in CuPc. The heterojunction devices reveal a non-linear I(V) …
Homogeneous and inhomogeneous broadening in single perovskite nanocrystals investigated by micro-photoluminescence
2021
Abstract Metal halides with perovskite crystalline structure have given rise to efficient optoelectronic and photonic devices. In the present work, we have studied the light emission properties of single CsPbBr3 and CsPbI3 semiconductor perovskite nanocrystals (PNCs), as the basis for a statistical analysis of micro-photoluminescence (micro-PL) spectra measured on tens of them. At room temperature, the linewidth extracted from PL spectra acquired in dense films of these nanocrystals is not very different from that of micro-PL measured in single nanocrystals. This means that the homogeneous linewidth due to exciton-phonon interaction is comparable or larger than the inhomogeneous effect asso…
Spatially resolved optical studies of F-center diffusion in KBr crystals.
1996
Spatially resolved optical studies of F-center diffusion during and after the photothermal F\ensuremath{\rightarrow}X color center conversion have been performed by optical scanning and holographic methods in electrolytically colored KBr crystals. Average velocities and diffusion coefficients of F centers have been determined for Gaussian and periodical spatial exposing light intensity distributions. A strong influence of the light intensity gradient has been found on F-center diffusion. It manifests itself by a rapid increase of the effective diffusion coefficient when the light intensity gradient is decreased. This behavior allowed us to explain the observed peculiarities of the holograph…
A microscopic model for long-term laser damage in calcium fluoride
2009
Single crystal calcium fluoride (CaF 2 ) is an important lens material in deep-ultraviolet optics, where it is exposed to high radiation densities. The known rapid damage process in CaF 2 upon ArF laser irradiation cannot account for irreversible damage after long irradiation times. We use density functional methods to calculate the properties of laser-induced point defects and to investigate defect stabilization mechanisms on a microscopic level. The mobility of the point defects plays a major role in the defect stabilization mechanisms. Besides stabilization by impurities, we find that the agglomeration of F-centers plays a significant role in long-term laser damage of CaF 2 . We present …
Dynamic light scattering by rodlike particles: [4] examination of the vanadium(V)-oxide system
1999
The dynamics of a suspension of rodlike particles has been investigated using dynamic light scattering. The sols investigated in this contribution are not monodisperse by nature and age with time. An evaluation of the first cumulant of the autocorrelation functions as a function of scattering vector is expected to yield the dimensions of the particles. While the data can be excellently fitted by the theoretical expressions for freshly prepared sols, we found that the theoretically expected interrelation of the (three) diffusion coefficients is not reproduced, which prohibits the unequivocal determination of the particle dimensions. Aged sols, on the other hand, cannot be described at all wi…
Scaling in colloidal crystallization
1994
The process of colloidal crystallization has already been separately investigated by light scattering mearurements of the crystalline order (Bragg peaks) and of long-ranged density fluctuations (small-angle scattering). We present the firstsimultaneous small- and large-angle light scattering experiment. Our measurements have been performed on hard-sphere colloids of different particle densities. We show results for the temporal evolution of crystallization and find two distinct regimes: homogeneous nucleation and diffusion- or reaction-limited growth at early times, followed by ripening of the Lifshitz-Slyozov or Lifshitz-Allen-Cahn type. To our preliminary experience, we can already state …
Development of a Gas Method for Migration Studies in Fractured and Porous Media.
1992
ABSTRACTA gas method for fast measurements of diffusion properties of porous materials has been developed. Diffusion coefficients in the gas phase are typically four orders of magnitude larger than those in the liquid phase. For samples whose structures do not change much upon drying it is possible to estimate the diffpision properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements and therefore they can be used to optimize the liquid-phase measurements which may last months or years. For materials with good correlation between the gas and liquid-phase diffusion, the number of liquid phase measurements can be …
Numerical study of surface waves generated by low frequency EM field for silicon refinement
2018
One of the most perspective methods to produce solar grade silicon is refinement via metallurgical route. The most critical part of this route is refinement from boron and phosphorus due to high segregation coefficients. One possible approach to remove boron is use of reactive gas on surface of silicon melt. An approach of creating surface waves on silicon melt's surface is proposed in order to enlarge its area and accelerate removal of boron via chemical reactions. This paper focuses on numerical analysis of surface wave creation by means of low frequency magnetic field. Frequency of magnetic field and its amplitude significantly change the character of surface waves with most changes occu…