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This paper reports an interlaboratory comparison that evaluated a protocol for measuring and analysing the particle size distribution of discrete, metallic, spheroidal nanoparticles using transmission electron microscopy (TEM). The study was focused on automated image capture and automated particle analysis. NIST RM8012 gold nanoparticles (30 nm nominal diameter) were measured for area-equivalent diameter distributions by eight laboratories. Statistical analysis was used to (1) assess the data quality without using size distribution reference models, (2) determine reference model parameters for different size distribution reference models and non-linear regression fitting methods and (3) assess the measurement uncertainty of a size distribution parameter by using its coefficient of variation. The interlaboratory area-equivalent diameter mean, 27.6 nm ± 2.4 nm (computed based on a normal distribution), was quite similar to the area-equivalent diameter, 27.6 nm, assigned to NIST RM8012. The lognormal reference model was the preferred choice for these particle size distributions as, for all laboratories, its parameters had lower relative standard errors (RSEs) than the other size distribution reference models tested (normal, Weibull and Rosin–Rammler–Bennett). The RSEs for the fitted standard deviations were two orders of magnitude higher than those for the fitted means, suggesting that most of the parameter estimate errors were associated with estimating the breadth of the distributions. The coefficients of variation for the interlaboratory statistics also confirmed the lognormal reference model as the preferred choice. From quasi-linear plots, the typical range for good fits between the model and cumulative number-based distributions was 1.9 fitted standard deviations less than the mean to 2.3 fitted standard deviations above the mean. Automated image capture, automated particle analysis and statistical evaluation of the data and fitting coefficients provide a framework for assessing nanoparticle size distributions using TEM for image acquisition.

SUMMARY We show that the number of atoms in a small supported catalyst cluster can be estimated from the strength of electron scattering into a high angle annular detector in the STEM. The technique is related to the Z contrast methods developed by Crewe, Wall, Langmore and Isaacson. It works best for high atomic number catalyst particles when supported on low atomic number supports, such as Pt on γ‐aluminium oxide. The method is particularly useful for detecting and measuring particles in the sub‐nanometre size range where bright field images are unreliable. Unlike the Z contrast methods, a high angle annular detector is used, which avoids intensity modulations arising from Bragg reflections. The signal is mostly high angle diffuse scattering, which is predominantly Rutherford scattering, and is proportional to the number of atoms probed by the beam, weighted by their individual scattering cross‐sections. Scattering strengths of individual clusters are computed from digitized high angle annular detector images. Data for Pt on γ‐aluminium oxide, when plotted as imaged area1/2 against intensity1/3, define a straight line. Such plots provide calibration of the intensity increment per atom without the need of external calibration, although assumptions about particle morphology must be made. Reliable results require high signal‐to‐noise and optimum sampling of the specimen. For an STEM probe size of 0.35 nm, Pt clusters containing as few as three atoms can be detected when supported on typical, 20 nm thick, γ‐aluminium oxide supports.

Abstract--In an attempt to resolve the structure of opal-CT and opal-C more precisely, 24 opal samples from bentonites, Fuller's Earths, zeolite tufts, biogenic silicas and silicified kaolins have been analyzed by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Results of this examination demonstrate that opal-C and opal-CT are part of a continuous series of intergrowths between end-member cristobalite and tridymite stacking sequences.These findings are consistent with Fl6rke's (1955) interpretation of the most intense opal peak at -4 ,~ as a combination of the (101) cristobalite and (404) tridymite peaks. The position and width of this peak are controlled by the relative volume of the two stacking types and the mean crystallite size. Direct evidence obtained by HRTEM provides data showing various stacking sequences in opals. Broadening due to crystallite size alone was determined by directly measuring crystallite size by TEM and comparing the measured size to the apparent size calculated using the Scherrer equation. XRD peak broadening is also described in terms of various contributions from structural disorder. The mean opal crystallite size ranges from 120 to 320 A.. For samples at either end of the size range, the crystallite size plays a larger role, relative to stacking disorder, in controlling peak broadening.

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This paper reviews the microanalytic and histopathologic findings from studies reported previously by our laboratory describing the nature and significance of solid products of corrosion generated at modular junctions of femoral components for hip replacement. A total of twenty-five retrieved, corroded modular junctions with surrounding tissues were examined from a variety of component designs and material combinations, including head/neck couples of CoCr/CoCr, CoCr/Ti6Al4V, and Al2O3/CoCr. The products were examined using electron microprobe with energy dispersive x-ray analysis, x-ray diffraction, and Fourier-transform infrared spectroscopy. The products of corrosion identified at the modular junctions of all of the various prostheses examined were similar regardless of the implant design or materials coupled, even when a ceramic head was employed. The most prevalent corrosion product was characterized as an amorphous chromium orthophosphate hydrate-rich material. Particles of this material were identified throughout the periprosthetic tissues of most of the cases studied and at the polyethylene bearing surface of several cases. The multitude of particles generated by fragmentation of the corrosion products and the finding that they migrate to sites distant from their origin are of concern because of their potential to increase the production of polyethylene wear debris by a three-body wear mechanism and their direct participation in particle-induced, macrophage-mediated osteolysis.

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