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The effect of Nb content on the corrosion behavior of in-situ (Ti0.45Zr0.31Be0.17Cu0.07)100−xNbx (x = 4, 6, 8, 10, and 12) was evaluated in 0.5 mol/L H2SO4, 0.6 mol/L NaCl, and 1 mol/L NaOH solutions. A dual-phase microstructure which composed of an amorphous matrix and dendrites was observed. Electrochemical measurements in each corrosion medium showed the same trend. The corrosion resistance first increased and then decreased with the addition of Nb content from 4 to 12 at.%. The results show the best corrosion resistance in terms of × = 8 for the alloys. Notably, Nb addition improved the pitting-corrosion resistance of samples in a chloride-containing solution, whereas spontaneous passivation occurred in chloride-free solutions. A preferential solution was observed in the amorphous matrix region in NaCl solution, but a part of dark spots and dents appeared on the surface after the polarization in chloride-free solutions. X-ray photoelectron spectroscopic measurements showed that Nb addition promoted the formation of metal oxide on the surface film, thus inducing a superior corrosion resistance for the bulk metallic glass matrix composites.

Both the mass density (1.37 kgm/m 3) and sp3/sp2+sp3 bonding fraction (0.15) were determined for an unusual nanoporous amorphous carbon consisting of curved single graphitic sheets. A combination of High-Resolution Transmission Electron Microscopy (HRTEM) and Parallel Electron Energy Loss Spectroscopy (PEELS) was used. The values of these two parameters provide important constraints for the determination of the structure of this relatively low density variety of nanoporous carbon. The results are relevant also in the search for negatively-curved Schwarzite-related carbon structures. New data are also presented for Highly-Oriented Pyrollytic Graphite (HOPG), Chemically Vapour Deposited (CVD) diamond, C60, Glassy Carbon (GC) and Evaporated Amorphous Carbon (EAC); these are compared with the results for NAC. Kramers-Kronig Analysis (KKA) of the low-loss PEELS data shows that the band gaps of both NAC and EAC are collapsed relative to that of CVD diamond.

High-resolution (0.2 nm) images are used to locate chemical domains occurring with length scales of 1–5 nm in the dielectric relaxor lead magnesium niobate (PMN). The experimental HRTEM images are analysed using computer simulations and image matching in order to clarify and characterize the nature of the chemical ordering. Madelung electrostatic energy calculations are used to rank a set of structural models for possible ordered and disordered distributions of Nb and Mg over the B sites of perovskite ABO3. Next, the chemical domain textures are modelled using next-nearest-neighbour Ising (NNNI) models and Monte Carlo methods. These simulations allow us to understand and quantify the local structures of clusters of Nb and Mg atoms and how these interact to form chemical domain walls and other configurations including charged chemical defects. This results in a preferred model for the B-site distribution (the extended NNNI model), which is used for image simulations. Both HRTEM many-beam bright- and dark-field and single-beam dark-field TEM images are obtained and compared with the experimental images. The final result is a realistic atomic model for the Nb, Mg distribution of PMN.