TiO 2

As the debate about TiO2 food additive safety is still open, the present study focuses on the extraction and characterisation of TiO2 (nano)particles added as a whitening agent to confectionary products, that is, chewing gum pellets. The aim was to (1) determine the colloidal properties of suspensions mutually containing TiO2 and all other chewing gum ingredients in biologically relevant media (preingestion conditions); (2) characterise the TiO2 (nano)particles extracted from the chewing gum coating (after ingestion); and (3) verify their potential photocatalysis. The particle size distribution, in agreement with the zeta potential results, indicated that a small but significant portion of the particle population retained mean dimensions close to the nanosize range, even in conditions of moderate stability, and in presence of all other ingredients. The dispersibility was enhanced by proteins (i.e., albumin), which acted as surfactants and reduced particle size. The particle extraction methods involved conventional techniques and no harmful chemicals. The presence of TiO2 particles embedded in the sugar-based coating was confirmed, including 17–30% fraction in the nanorange (<100 nm). The decomposition of organics under UV irradiation proved the photocatalytic activity of the extracted (nano)particles. Surprisingly, photocatalysis occurred even in presence of an amorphous SiO2 layer surrounding the TiO2 particles

In-depth component distribution in electrodeposited alloys and multilayers

It is shown in this overview that modern composition depth profiling methods like secondary neutral mass spectroscopy (SNMS) and glow-discharge – time-of-flight mass spectrometry (GD-ToFMS) can be used to gain highly specific composition depth profile information on electrodeposited alloys. In some cases, cross-sectional transmission electron microscopy was also used for gaining complementary information; nevertheless, the basic component distribution derived with each method exhibited the same basic features. When applying the reverse sputtering direction to SNMS analysis, the near-substrate composition evolution can be revealed with unprecedented precision. Results are presented for several specific cases of electrodeposited alloys and mulitlayers. It is shown that upon d.c. plating from an unstirred solution, the preferentially deposited metal accumulates in the near-substrate zone, and the steady-state alloy composition sets in at about 150-200 nm deposit thickness only. If there is more than one preferentially deposited metal in the alloy, the accumulation zones of these metals occur in the order of the deposition preference. This accumulation zone can be eliminated by well-controlled hydrodynamic conditions (like the application of rotating disc electrodes) or by pulse plating where the systematic decrease in the duty cycle provides a gradual transition from a graded to a uniform composition depth profile. The application of composition depth profile measurements enabled detecting the coincidence in the occurrence of some components in the deposits down to the impurity level. This was exemplified by the GD-ToFMS measurements of Ni-Cu/Cu multilayers where all detected impurities accumulated in the Cu layer. The wealth of information obtained by these methods provides a much more detailed picture than the results normally obtained with bulk analysis through conventional integral depth profiling and help in the elucidation of the side reactions taking place during the plating processes

Structure of the chondrules and the chemical composition of olivine in meteorite Jesenice

This paper presents a mineralogical analysis of various chondrule types and chemical analysis of olivine indifferent parts of meteorite Jesenice. Quantitative energy-dispersive X-ray spectroscopy with a scanning electronmicroscope was used in the analyses. The results showed that the chemical composition of the olivine was homogeneousthroughout the meteorite with an average olivine composition of Fa 26.4 ± 0.6. The results of this study werein agreement with previous study of the meteorite, which showed that the meteorite Jesenice was an equilibratedL chondrite

Meteorite Jesenice: Mineral and chemical composition of the fusion crust of ordinary chondrite

The composition of the well-preserved fusion crust of the meteorite Jesenice was characterised by means ofoptical and scanning electron microscopy (SEM). The SEM investigations revealed three structurally distinct layerswithin the crust. The features of the first layer on the surface are precipitates, enriched in metal elements (iron,nickel), and the partial melting of silicate grains, which continues deeper into the second layer. The second layerbeneath has veins with a heterogeneous composition that indicates a different source of melting minerals. The thirdlayer, which is located deeper within the fusion crust, has not undergone any structural changes and its features aresimilar to the interior of the meteorite. This is additionally confirmed by the presence of cracks, which are a consequenceof shock metamorphism, and irregularly shaped metal and sulphide grains. The structural changes of thethin fusion crust on the surface of this stony meteorite indicate high temperatures (more than 1500 °C) accompaniedby high pressures

Classification of stony meteorites and chondrules – the case of meteorite Jesenice

In the first part of the paper there is a description about genesis of meteorites, in particularly about stony meteorites– chondrites, since meteorite Jesenice is an ordinary L chondrite. Chondrules represent main part of the mass ofchondritic meteorites. For this reason the second part of the paper talks about morphology, texture, mineralogy andchemical properties of chondrules. Main theories about chondrule formation and other distinctive textures found inchondrites are also presented. The paper also presents a review across different meteorite classifications. Meteoriteclassifications differ depending on the geochemical and mineralogical properties of meteorites. In this paper are alsoused some new Slovenian terms correlated with the science of meteorites and mineral materials. Classification ofmeteorite Jesenice is based on its macroscopic and microscopic characteristics. We classified meteorite Jesenice onthe basis of shock metamorphosis, grade of weathering, petrological properties and chemical composition of olivine.We found out that meteorite Jesenice is weakly shocked weakly weathered undifferentiated low total iron ordinarychondrite. Our results are in agreement with findings of Bischoff and his colleagues