Structure and Spatial Distribution of Ge Nanocrystals Subjected to Fast Neutron Irradiation

The influence of fast neutron irradiation on the structure and spatial distribution of Ge nanocrystals (NC) embedded in an amorphous SiO2 matrix has been studied. The investigation was conducted by means of laser Raman Scattering (RS), High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The irradiation of GeNC samples by a high dose of fast neutrons lead to a partial destruction of the nanocrystals. Full reconstruction of crystallinity was achieved after annealing the radiation damage at 800 0 C, which resulted in full restoration of the RS spectrum. HR-TEM images show, however, that the spatial distributions of Ge-NC changed as a result of irradiation and annealing. A sharp decrease in NC distribution towards the SiO2 surface has been observed. This was accompanied by XPS detection of Ge oxides and elemental Ge within both the surface and subsurface regio

Unusually high stability of a poly(alkylquaterthiophene-alt-oxadiazole) conjugated copolymer in its n and p-doped states

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Role of Catalyst Oxidation State in the Growth of Vertically Aligned Carbon Nanotubes

The impact of gas-phase pretreatment of supported iron-oxide catalyst utilized in aligned carbon nanotube (CNT) growth is studied to understand the correlation between the catalyst oxidation state and the growth characteristics of the aligned CNT forests. By varying the pretreatment conditions from a reducing to an oxidizing environment, notable changes are observed in both the collective CNT array growth behavior and the individual CNT characteristics. Although the greatest catalytic activity was observed following a full reduction to the zerovalent (metallic) Fe catalyst, growth is also observed from a catalyst composed of both Fe₂O₃ and Fe₃O₄ particles. XPS core-level analysis, following pretreatment of the catalyst, emphasizes the critical nature of the combined catalyst–underlayer interaction to achieve optimal catalyst activity during growth and hence the most efficient catalyst reduction process. Additionally, CNT diameters during growth were strongly affected by the pretreatment process. Overall, this work gives a collective picture of how the catalyst oxidation state affects the CNT growth based on the catalyst pretreatment environment and the nature of the catalyst–underlayer interactions. Such concepts are critical for the rational design of alternative catalyst–underlayer systems for efficient CNT synthetic processes

Advances in Magnesium Electrochemistry — A Challenge for Nanomaterials

875-890In this review, very recent studies related to magnesium electrochemistry (in connection with R&D of Mg batteries) have been reported. These include the study of new electrolyte solutions, based on complexes with the formal stoichiometry, Mg(ALCL4-nRn)2 in ethers, their unique structures and analysis by electrochemical and spectroscopic methods, the study of Mg deposition processes by microelectrodes and microscopy, and the study of Mg insertion into hosts based on the so-called Chevrel phase structure (Mg0-2Mo6X8, X=S, Se). The ionic mobility of Mg2+ ions and their ease of diffusion within these structures are discussed. It is demonstrated that the use of a nanostructured active mass may be highly important for reducing the diffusion length considerably, and hence, for increasing the kinetics of transport of the bivalent cations. We deal herein with some key factors that may affect the possibility of smooth and reversible Mg insertion into inorganic host materials, and the possible advantages in the use of nanoparticles for these systems

Advances in magnesium electrochemistry — A challenge for nanomaterials

875-890In this review, very recent studies related to magnesium electrochemistry (in connection with R&D of Mg batteries) have been reported. These include the study of new electrolyte solutions, based on complexes with the formal stoichiometry, Mg(ALCL4-nRn)2 in ethers, their unique structures and analysis by electrochemical and spectroscopic methods, the study of Mg deposition processes by microelectrodes and microscopy, and the study of Mg insertion into hosts based on the so-called Chevrel phase structure (Mg0-2Mo6X8, X=S, Se). The ionic mobility of Mg2+ ions and their ease of diffusion within these structures are discussed. It is demonstrated that the use of a nanostructured active mass may be highly important for reducing the diffusion length considerably, and hence, for increasing the kinetics of transport of the bivalent cations. We deal herein with some key factors that may affect the possibility of smooth and reversible Mg insertion into inorganic host materials, and the possible advantages in the use of nanoparticles for these systems