The formation of CaCO3 is usually discussed within the classical picture of crystallization, i.e. assuming that the formation of CaCO3 crystals proceeds via nucleation and growth. This may be true for the case of low supersaturation. In this work it is shown that the formation process is far more complex at high supersaturation, i.e. during precipitation. New insight into the mechanisms of precipitation is obtained by analyzing structure formation with a time resolution down to the millisecond range from the initiation of the reaction. The techniques used are scanning electron microscopy, electron diffraction, X-ray microscopy and cryo-transmission electron microscopy combined with a special quenching technique. It is seen that upon mixing CaCl2 and Na2CO3 solutions (0.01 M) first an emulsion-like structure forms. This structure decomposes to CaCO3-nanoparticles. These nanoparticles aggregate to form vaterite spheres of some micrometers in diameter. The spheres transform via dissolution and recrystallization to calcite rhombohedra. Once a suitable amount of additive, in our case polycarboxylic acid, is present during the precipitation the nanoparticles are stabilized against compact aggregation; instead they form flocs. This stabilization is either of a temporary nature if the amount of polymer is insufficient to cover the surface of the nanoparticles formed or more long lived if there is enough polymeric material present. By means of Ca-activity measurements it can be shown that the polymers are partially incorporated into the forming crystals.

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To ensure the product safety of nanomaterials, BASF has initiated an extensive program to study the potential inhalation toxicity of nanosize particles. As preparation work for upcoming inhalation studies, the following manufactured nanomaterials have been evaluated for their behavior in an exposure system designed for inhalation toxicity studies: titanium dioxide, carbon black, Aerosil R104, Aerosil R106, aluminum oxide, copper(II) oxide, amorphous silicon dioxide, zinc oxide, and zirconium(IV) oxide. As the physicochemical properties and the complex nature of ultrafine aerosols may substantially influence the toxic potential, the particle size, specific surface area, zeta potential, and morphology of each of the materials were determined. Aerosols of each material were generated using a dry powder aerosol generator and by nebulization of particle suspensions. The mass concentration of the particles in the inhalation atmosphere was determined gravimetrically and the particle size was determined using a cascade impactor, an optical particle counter, and a scanning mobility particle sizer. The dispersion techniques used generated fine aerosols with particle size distributions in the respiratory range. However, as a result of the significant agglomeration of nanoparticles in the test materials evaluated, no more than a few mass percent of the materials were present as single nanoparticles (i.e., < 100 nm). Considering the number, a greater percentage of nanoparticles was present. Based on the obtained results and experience with the equipment, a technical setup for inhalation studies with nanomaterials is proposed. Furthermore, a stepwise testing approach is recommended that also could reduce the number of animals used in testing.

Modern water‐borne paints are applied in different areas ranging from high‐gloss lacquers to flat, scrub‐resistant interior paints. The pigment volume concentration (PVC) is one key‐parameter adjusting the application properties. In this work formulations differing in the type of binder and dispersing agent were investigated by various techniques concerning the distribution of pigments in the liquid paints and films. The structure of the paints was analyzed by Remission Light Spectroscopy (RLS), Disc Centrifugation, Cryo‐Replica Transmission Electron Microscopy (Cryo‐TEM) and Cryo‐Scanning Electron Microscopy (Cryo‐SEM). The pigment distribution in the films was examined by means of Atomic Force Microscopy (AFM), TEM and RLS. The tendency of the pigments to form aggregates was found to depend on both: the type of binder and the dispersing agent. Only by adjusting the properties of the binder in combination with common dispersants it is possible to get well distributed TiO2 particles within the paint. Correlation of application properties e.g. gloss and blocking to the microscopic structure is presented.

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