A process for production of micrometer-sized particles composed of uranium oxide using aerosol spray pyrolysis is characterized with respect to the various production parameters. The aerosol is generated using a vibrating orifice aerosol generator providing monodisperse droplets, which are oxidized in a subsequent heat treatment. The final particles are characterized with microanalytical methods to determine size, shape, internal morphology, and chemical and structural properties in order to assess the suitability of the produced particles as a reference material for microanalytical methods, in particular, for mass spectrometry. It is demonstrated that physicochemical processes during particle formation and the heat treatment to chemically transform particles into an oxide strongly influence the particle shape and the internal morphology. Synchrotron μ-X-ray based techniques combined with μ-Raman spectroscopy have been applied to demonstrate that the obtained microparticles consist of a triuranium octoxide phase. Our studies demonstrate that the process is capable of delivering spherical particles with determined uniform size and elemental as well as chemical composition. The particles therefore represent a suitable base material to fulfill the homogeneity and stability requirements of a reference material for microanalytical methods applied in, for example, international safeguards or nuclear forensics.

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The application of safeguards measures by the International Atomic Energy Agency (IAEA) involves analytical measurements of samples taken during inspections of nuclear facilities. Thus constant development and advancement of analytical techniques is required. For quality control purposes, the IAEA has implemented a dedicated project to enhance its analytical capabilities by producing tailor-made reference materials for the analysis of uranium isotope signatures in (single) particles.To this end, a particle production set-up was developed and implemented at Forschungszentrum Juelich capable to produce uranium oxide microparticles which are intended to be used as (certified) reference materials for particle analysis methods. A step towards the certification process is the evaluation of consistency of the size distribution and homogeneity. A monodisperse particle size distribution as well as the single phase triuranium octoxide structure was confirmed using SEM, µ-XRD and µ-Raman spectroscopy, respectively. Analysis performed on single uranium oxide microparticles confirmed consistency of the uranium isotopic ratios in comparison to the initial precursor solutions. To improve the homogeneity and particle handling, the particles are transferred into suspensions, for which the stability was investigated with respect to dissolution.

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The use of appropriate nebulizers is a major precondition for a successful treatment and prevention of Pneumocystis carinii pneumonia with pentamidine aerosol. The apparatus should supply a sufficient amount of pentamidine with adequate particle size. Using Fisons ultrasonic nebulizer FISO Neb, model FZV 40 BAMKI, De Vilbiss ultrasonic nebulizer, Porta-Sonic, model 8500 GB, and the Marquest Medical Products jet nebulizer Respirgard II, two pentamidine concentrations (300 mg/6 ml and 60 mg/6 ml) were compared by measuring nebulized pentamidine mass distribution and particle size distribution under in vitro conditions by means of a laser light-scattering particle sizer of the type Malvern Master sizer. It was found that there were significant differences among nebulizers. Mass distribution experiments with air flow 6 l/min showed that using FISO Neb the quantity of nebulized pentamidine was 201.4 mg and 36.7 mg, whereas using Porta-Sonic the values found decreased to 85.2 mg and 23.6 mg. Using Respirgard II the values were 80.0 mg and 10.64 mg. The measured total duration times of nebulization were 6 - 8.5 min, 12 min and 25 min for the nebulizers FISO Neb, Porta-Sonic and Respirgard II. A decomposition of pentamidine during nebulization in the case of ultrasonic nebulizers doesn't take place. The measured mass median diameters (MMD) were 5.6 - 6.9 mum, 1.96 - 3.04 mum and 1.9 - 2.5 mum for the nebulizers FISO Neb, Porta-Sonic and Respirgard II. Using 300 mg pentamidine the nebulized amounts of pentamidine containing particles sizes less than or equal to 2 mum predominately available for alveolar deposition were with values of about 43 mg markedly higher for Respirgard II and Porta-Sonic than the measured 10.5 mg for FISO Neb.