Influence of dispersion state of initial AlN powder on the hydrolysis process in air environment

The research results of the hydrolysis processes of aluminum nitride powders received by the SVS method in dependence on humidity of the storage environment, and grain size distribution are presented in this work. Oxidation kinetics was estimated by means of X- ray Diffraction (XRD) and scanning electron microscopy (SEM). The induction period of the hydrolysis process for various powders, its dependence on powder dispersion and thickness of the oxide layer on surface of particles have been defined

Chemical and physical heterogeneity within native gold: implications for the design of gold particle studies

Studies of populations of gold particles are becoming increasingly common; however, interpretation of compositional data may not be straightforward. Natural gold is rarely homogenous. Alloy heterogeneity is present as microfabrics formed either during primary mineralization or by modification of pre-existing alloys by chemical and physical drivers during subsequent residence in either hypogene or surficial environments. In electron-probe-microanalysis (EPMA)-based studies, the combination of Cu, Hg, and Pd values and mineral inclusion suites may be diagnostic for source style of mineralization, but Ag alone is rarely sufficient. Gold characterization studies by laser-ablation-ICP mass spectrometry linked to both quadrupole and Time-of-Flight (ToF-MS) systems show that only Ag, Cu, and Hg form homogenous alloys with Au sufficiently often to act as generic discriminants. Where present, other elements are commonly distributed highly heterogeneously at the micron or submicron scale, either as mineral inclusions or in highly localized, but low concentrations. Drawing upon our own data derived from individual inspection and analyses of approximately 40,000 gold particles from 526 placer and in situ localities worldwide, we show that adequate characterization of gold from a specific locality normally requires study of a minimum of 150 particles via a two-stage approach comprising spatial characterization of compositional heterogeneity, plus crystallographic orientation mapping, that informs subsequent targeted acquisition of quantitative compositional data by EPMA and/or laser-ablation ICP-MS methods. Such data provide the platform to review current understanding of the genesis of gold particle characteristics, elevating future compositional studies from empirical descriptions to process-focused interpretations

Trace element quantification in gold as a means of distinguishing the genesis of placer gold

Analyses of placer gold has largely been restricted to the major components, Au, Ag, Cu, Hg from electron microprobe analysis (EMPA) due to the relatively high detection limits for other minor elements. LA-ICP-MS has sub-ppm detection limits for most elements in gold, but by comparison with EMPA is both destructive and penetrates the gold to much greater in depth. We have analysed gold grains for a suite of elements to assess which are present in sufficient concentration to form a basis for the discrimination of gold from different localities and different styles of mineralization. High resolution multielement maps of selected grains, analysed by icpTOF-MS, reveal some elements are controlled by crystal structure, grain boundaries or random events

Element Analysis of Small and even Smaller Objects by ICPMS and LA-ICPMS

Inductively coupled plasma mass spectrometry is increasingly used for non-traditional applications such as the analysis of solids at high spatial resolution when combined with laser ablation or the analysis of engineered nanoparticles. This report highlights recent projects and discusses the potentials and limitations these techniques offer. High-resolution laser ablation instrumentation allows element imaging at the ?m-scale and can, therefore, be applied to, e.g., the mapping of metal isotope-labeled antibodies in biological tissues. Despite these advancements, the quantitative analysis of laser-produced aerosols is still a major concern. Here, the accuracy of analysis was found to strongly depend on particle size distribution but also on the morphology and composition of particles. In order to achieve a controlled supply of nanoparticles for analysis by inductively coupled plasma mass spectrometry, a dedicated microdroplet injection system was developed and characterized. This system allows a reproducible injection of single nanoparticles together with internal standards to determine their mass and composition