N. Stewart McIntyre

The aging of silicate glass surfaces in humid air

Abstract Slicate glass surfaces were observed over several weeks in normally humid laboratory air by atomic force microscopy. Auger spectroscopy and lateral force microscopy measurements were also made. Samples in the study include; vitreous quartz, bulk insulation glass, bulk and fibrous textile e-glass, and bulk container glass. Various features developed on these surfaces are consistent with patterns seen in crystal growth from supersaturated solution. Auger spectroscopy reveals the presence of chemically bound carbon and supports the hypothesis that these crystals are alkali and alkali earth carbonate species. The presence of these crystals is expected to affect the bonding of a coating to silicate surfaces.

Photoelectrochemical properties of indium doped iron oxide

Oxygen photoanodes formed by reactive sputtering of iron oxide onto conducting indium tin oxide (ITO) substrates held at 350 ° C have been investigated by conventional photoelectrochemical, impedance, XPS and auger spectroscopic methods. This fabrication procedure leads to films containing 8 to 20 atomic % indium in the front portion of the film, increasing to much higher values near the ITO interface (back portion of the film). Two interesting effects are observed with the thin-film iron oxide formed in this way. The first is that the as formed films must be vacuum annealed before an appreciable dc photoanodic response is observed. Secondly, films 250 nm thick display the property of giving about double the quantum yield for back face, than for front face, illumination over the spin and parity forbidden transition centered at 535 nm. On correcting for transmission and reflection losses, the resulting true quantum efficiencies satisfy the same inequality, a result that can only be accounted for by a higher ( > 2 × ) primary quantum efficiency for the back, versus the front portion of the film. As these films show substantially higher quantum efficiencies than do indium free films of the same thickness, it is concluded that the indium in the films is responsible for the increase in primary quantum efficiency. This result is discussed in terms of a localized states model for α-Fe2O3.

Imaging of oxidized mineral surfaces

High-resolution SIMS images in conjunction with elastically backscattered electron and energy-dispersive x-ray images have been acquired from a polished slightly oxidized multiphase polycrystalline surface of Ni-Cu sulphide ore. Through correlation of data acquired by the three methods, the extent to which oxidation occurs is shown to be mineral dependent and related to the presence of macroscopic and microscopic surface heterogeneities.

X-Ray fluorescence spectroscopy and mapping using excitation from white and broad bandpass synchrotron radiation

The bend magnet VESPERS beamline on the third generation CLS synchrotron has been equipped with capabilities for X-ray fluorescence (SXRF) excitation with micro-focussed white radiation, as well as with broad and narrow bandpass monochromatised radiation. Using the former two conditions, SXRF studies have been conducted on several reference materials and metals with known elemental concentrations. The resultant spectral line shapes have been analysed using newly developed software that facilitates ready identification of K, L and M lines present as well as their subsequent spatial mapping. Using both white and broad bandpass radiation, K lines for elements from magnesium to indium and L lines from hafnium to uranium were measured and sensitivity values (S) determined. White radiation provided much higher sensitivity for most elements, and a narrower range of S values makes it possible to use a single white radiation experiment to determine a wide range of elements in the periodic table. Additionally, the variances in S values for several low Z matrices were relatively low, thus making it possible to estimate elemental concentration ranges using a reference material.

X-ray Micro Laue Diffraction and Neutron Diffraction Analysis of Residual Elastic Strains in a 1% Uniaxial Tensile Tested Nickel Alloy 600 Sample

The magnitude and distribution of elastic strain for a nickel alloy 600 (A600) sample that had been subjected to uniaxial tensile stress were measured by micro Laue diffraction (MLD) and neutron diffraction techniques. For a sample that had been dimensionally strained by 1%, both MLD and neutron diffraction data indicated that the global residual elastic strain was on the order of 10 −4 , however the micro-diffraction data indicated considerable grain-to-grain variability amongst individual components of the residual strain tensor. A more precise comparison was done by finding those grains in the MLD map that had appropriate oriented in the specific directions matching those used in the neutron measurements and the strains were found to agree within the uncertainty. Large variations in strain values across the grains were noted during the MLD measurements which are reflected in the uncertainties. This is a possible explanation for the large uncertainty in the average strains measured from multiple grains during neutron diffraction.

Imaging fibers by atomic force microscopy

Glass textile fibers have been used to demonstrate an atomic force microscope technique presented in this article. This method can be applied for imaging the surface of any micron or larger sized fibers. The fibers are discovered to have a variable corrugated surface texture, rather than the previously supposed uniformly cylindrical form, with individual ridges about 5–10 nm high. Scanning electron microscopy images of equivalent glass fibers are included for comparison.

The Study of Stress Corrosion Cracking on Alloy 600 C‐Ring Samples by Polychromatic X‐Ray Microdiffraction

Microscopic strains associated with stress corrosion cracks have been investigated in stressed C-rings of Alloy 600 boiler tubing. Polychromatic X-ray Microdiffraction (PXM) was used to measure deviatoric strain tensors and the distribution of dislocations near cracks that had been propagated in electrochemically-accelerated corrosion tests. Stress corrosion cracking (SCC)-generated intergranular cracks were produced in two Alloy 600 specimens after 6h and 18h tests. The diffraction patterns and resultant strain tensors were mapped around the cracked area to a one micron spatial resolution. The strain tensor transverse to the crack growth direction showed tensile strain at the intergranular region just ahead of the crack tip for both specimens. Both cracks were found to follow grain boundary pathways that had the lowest angle of misorientation. Dislocation distributions within each grain were qualitatively obtained from the shapes of the diffraction spots and the effect of “hard” and “soft” grains on the crack pathway was explored for both 6h and 18h specimens.

Ion scattering experiments on some common sulphide minerals using a dynamic SIMS instrument

Abstract Kinetic energy distributions of singly charged, positive 16O+ ions that were sputtered and/or elastically scattered from planar polished surfaces of sphalerite, bornite, chalcopyrite, pentlandite, pyrrhotite, arsenopyrite, pyrite and galena under O2+ bombardment were acquired using a dynamic SIMS instrument. Ion contributions attributed to binary elastic-backscattering (O → element) collisions were identified. Data resolution was such that 32S and 34S contributions were discernable. For higher mass elements, resolution dropped such that isotopic contributions were no longer distinguishable. S peak areas were found not to be related to bulk element concentration, while for Fe a weak relationship between peak area and bulk element concentration was observed.