Surface area is important in quantifying mineral-water reaction rates. Specific surface area (SSA) was measured to investigate controls on this parameter for several primary silicate minerals (PSM) used to estimate rates of weathering. The SSA measured by gas adsorption for a given particle size of relatively impurity-free, laboratory-ground samples generally increases in the order: quartz ≈ olivine ≈ albite < oligoclase ≈ bytownite < hornblende ≈ diopside. Reproducibility of BET SSA values range from ±70% (SSA < 1000 cm 2 /g) to ± 5% (SSA > 4000 cm 2 /g) and values measured with N 2 were observed to be up to 50% larger than values measured with Kr. For laboratory-ground Amelia albite and San Carlos olivine, SSA can be calculated using log (SSA, cm 2 /g) = b + m log (d), where d = grain diameter (µm), b = 5.2 ± 0.2 and m = -1.0 ± 0.1. A similar equation was previously published for laboratory-ground quartz. Some other samples showed SSA higher than predicted by these equations. In some cases, high SSA is attributed to significant second phase particulate content, but for other laboratory-ground samples, high SSA increased with observed hysteresis in the adsorption-desorption isotherms. Such hysteresis is consistent with the presence of pores with diameters in the range 2 to 50 nm (mesopores). In particular, porosity that contributes to BET-measured SSA is inferred for examples of laboratory-ground diopside, hornblende, and all compositions of plagioclase except albite, plus naturally weathered quartz, plagioclase, and potassium feldspar. Previous workers documented similar porosity in laboratory-ground potassium feldspar. Surface area measured by gas adsorption may not be appropriate for extrapolation of interfacelimited rates of dissolution of many silicates if internal surface is present and if it does not dissolve equivalently to external surface. In addition, the large errors associated in measuring SSA of coarse and/or impurity-containing silicates suggest that surface area-normalized kinetics in both field and laboratory systems will be difficult to estimate precisely. Quantification of the porosity in laboratory-ground and naturally weathered samples may help to alleviate some of the discrepancy between laboratory-and field-based estimates of weathering rate.*

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Roughness of a surface as characterized by an atomic force microscope (AFM) is typically expressed using conventional statistical measurements including root-mean-square, peak-to-valley ratio, and average roughness. However, in these measurements only the vertical distribution of roughness (z-axis) is considered. Additionally, roughness of a surface as determined by AFM is a function of the scanning scale, sampling interval and/ or scanning methods; therefore, the consideration and quantification of the lateral distribution (x and y) is necessary. Power spectral density (PSD) analysis provides both lateral and vertical signals captured from AFM images. By applying one of the commonly adopted models to the PSD data, the fractal model and k-correlation model, the equivalent root mean squared roughness, correlation length, fractal dimension and Hurst exponent are quantified. These parameters describe the spatial distribution of roughness and spatial length scale of the roughness values. Longer correlation length is preferred for the comprehensive measurement of roughness of surface at a given spatial wavelength. However, a method to enhance correlation length has yet to be discussed. In this paper, we discuss the state-of-the-art issues associated with roughness evaluation from AFM analysis and propose that the spatial correlation length can be enhanced through the combination PSD profiles over a wide range of spatial frequencies.

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Novel Ni-doped titanate derived from protonated layered titanate has been fabricated via a simple ion-exchange process at room temperature. The as-synthesized product was calcined at 400 ºC for 3h to obtain the Ni-TiO 2 (anatase). The crystal structure of Ni-TiO 2 was studied by X-ray diffraction (XRD) and the surface chemistry was studied by X-ray photoelectron spectroscopy (XPS). It was found that doped nickel ions had inhibition effects on the crystallization of TiO 2 during calcination. The electrochemical properties of Ni-TiO 2 and undoped TiO 2 were both tested as anode materials for lithium-ion batteries at room temperature. While the undoped sample exhibited a mediocre performance, having a discharge capacity of 132 mAhg-1 after 50 cycles, the nickel-ion doped sample demonstrated noticeable improvement in both of its discharge capacity and rate capability; with a high capacity value of 226 mAhg-1 after 50 cycles. This improvement of lithium ion storage capability of Ni-TiO 2 can be ascribed to the Ni-doping effect on crystallinity and the modification of electrode/electrolyte interface of the TiO 2 structure.

a b s t r a c tSurface finishing techniques including polishing, etching and heat treatment can modify the topography and the surface chemical composition of glasses. It is widely acknowledged that atomic force microscopy (AFM) can be used to quantify the morphology of surfaces, providing various parameters including average, peak-to-valley, and apparent root-mean-square roughness. Furthermore advanced power spectral density (PSD) analysis of AFM-derived surface profiles offers quantification of the spatial homogeneity of roughness values along different wavelengths, resulting in parameters including equivalent RMS, Hurst exponent, and fractal dimension. Outermost surface (∼8 nm) chemical composition can be quantitatively measured by X-ray photoelectron spectroscopy. In this paper, we first developed a series of surface finishing methods for an aluminoborosilicate glass system by polishing, etching or heat treatment. The chemical composition and environment of prepared glass surfaces were quantified by XPS and topographical analysis was carried out by fractal and k-correlation model fitting of PSD profiles derived via AFM. The chemical environment of elements, as determined via XPS, present on the prepared surfaces are similar to those within the pristine bulk glass. The compositional evolution of polished and melt surfaces are discussed in context of corrosion phenomena associated with the grinding, polishing, and etching of surfaces and the thermal heat treatment utilized for processing, respectively. Good correlation between surface finishing methods, chemical composition and topographical parameters were observed. More importantly, extensive discussions on topographical parameters including equivalent RMS, Hurst exponent, and fractal dimension are presented as a function of processing method.

In this study, methods of surface preparation by polishing, fiber-drawing, melt-casting and chemical etching were evaluated with x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) for a variety of alkali and alkaline earth aluminosilicate glasses. Freshly polished glass surfaces were exposed to a variety of chemical etchants (NaOH, NH 4 OH and HF) and the resulting surface composition and morphology are reported. The polishing and etching parameters were optimized to obtain a smooth surface (root-mean-square (RMS) roughness of ≤3 nm) and a surface composition as close as possible to the bulk composition. In addition, glass melt and fiber surfaces were examined to investigate the effect of thermal processes on surface composition and morphology. It is shown that polishing can alter the surface composition of these multicomponent glasses, and that post-etching of the polished surface to expose the bulk composition is plagued by preferential leaching, contamination and/or roughening. The most significant conclusion is that there is a strong dependence of these surface compositional modifications upon the specific glass; even within specific glass systems, the polish/etch procedure must be modified to yield a surface with the bulk composition. On the other hand, the smoothness of fibers and melt-cast surfaces is ideally suited to AFM and depth profiling; their surface compositions can be close to the bulk values, but careful attention to the annealing conditions is required to achieve this.

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