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A femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated by XRD(two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation.
A set of 59 ancient magical artefacts, mainly made of lead, was selected from the collections of the Staatliche Museen zu Berlin in order to unravel their origins. All the selected artefacts have been studied for their Pb isotope compositions, which covered the whole range of the Mediterranean ore deposits. However, the majority (≈86%) were made of lead matching the small compositional range of the Laurion ore deposits. Only eight out of the 59 artefacts were made of recycled lead or lead from other ore deposits.
Additionally, all but two were approximately dated based on their inscriptions. The lead isotopic composition together with information obtained from the inscriptions, the resulting dating, the context of the find and the known history of each item allowed us to gain more detailed information about the origins of these magical artefacts. The Attic provenance of 36 curse tablets was confirmed, whereas for 11 curse tablets previously classified as non-Attic, the provenance was either confirmed and specified (six artefacts) or changed to Attic (five artefacts). Surprisingly, the majority (six out of eight) of the analysed curse tablets from the Egyptian collection showed a lead isotopic composition closely matching that of Laurion.
A Laurion-like lead isotopic composition was also observed for three of the four analysed oracular tablets from Dodona. Together with the dating information, this points to Laurion as the major and dominant lead source in the Aegean, at least during the fourth–third century B.C. The few curse tablets from earlier than the fourth–third century B.C. point to the use of multiple and thus isotopically more variable lead sources compared with the Roman times.
Morphology and structure of TixOy nanoparticles generated by femtosecond laser ablation in water
(2018)
In this work femto-second pulsed laser ablation in liquid (PLAL) procedure for the generation of titanium oxide nanoparticles (NP) is reported with the purpose of understanding morphology and structure of the newly generated NPs. Ablation duration was varied for optimization of NP generation processes between 10 and 90 min. Surface morphology of NPs as well as their size and shape (distribution) were analysed by various complementary electron microscopy techniques, i.e. SEM, TSEM and TEM. The crystalline structure of titanium oxide particles was investigated byXRD(two instruments operated in different geometries) and HR-TEM. Concentration of generated titanium oxide NPs in liquid was analysed by ICP-MS. A mix of crystalline (mainly anatase), partly crystalline and amorphous spherical titanium oxide NPs can be reported having a mean size between 10 and 20 nm, which is rather independent of the laser ablation (LA) duration. A second component consisting of irregularly shaped, but crystalline titanium oxide nanostructures is co-generated in the LA water, with more pronounced occurrence at longer LA times. The provenance of this component is assigned to those spherical particles generated in suspension and passing through the converging laser beam, being hence subject to secondary irradiation effects, e. g. fragmentation.
This paper reports the first successful synthesis and the structural characterization of nanocrystalline and stacking-disordered β-cristobalite AlPO4 that is chemically stabilized down to room temperature and free of crystalline impurity phases. Several batches of the title compound were synthesized and thoroughly characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy mapping in SEM, solid-state 31P nuclear magnetic resonance (31P-NMR) spectroscopy including the TRAPDOR method, differential thermal analysis (DTA), gas-sorption methods, optical Emission spectroscopy, X-ray fluorescence spectroscopy, and ion chromatography. Parameters that are critical for the synthesis were identified and optimized. The synthesis procedure yields reproducible results and is well documented. A high-quality XRD pattern of the title compound is presented, which was collected with monochromatic copper radiation at room temperature in a wide 2θ range of 5°–100°.
A model system was used to simulate the properties of tribofilms which form during automotive braking. The model system was prepared by ball milling of a blend of 70 vol.% iron oxides, 15 vol.% molybdenum disulfide and 15 vol.% graphite. The resulting mixture was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and various transmission electron microscopic (TEM) methods, including energy dispersive X-ray spectroscopy (EDXS), high resolution investigations (HRTEM) with corresponding simulation of the HRTEM images, diffraction methods such as scanning nano-beam electron diffraction (SNBED) and selected area electron diffraction (SAED). It could be shown that the ball milling caused a reduction of the grain size of the initial components to the nanometer range. Sometimes even amorphization or partial break-down of the crystal structure was observed for MoS2 and graphite. Moreover, chemical reactions lead to a formation of surface coverings of the nanoparticles by amorphous material, molybdenum oxides, and iron sulfates as derived from XPS.
Stocks of high grade phosphate rock are becoming scarce, and there is growing concern about potentially harmful impurities in conventional phosphorus fertilizers. Sewage sludge ash is a promising secondary phosphorus source. However, to remove heavy metals and convert the phosphorus contained in sewage sludge ash into mineral phases available to plants, an after-treatment is required. Laboratory-scale calcination experiments of sewage sludge ash blended with sodium salts using dried sewage sludge as a reducing agent were carried out at 1000 °C. Thus, the Ca3(PO4)2 or whitlockite component of raw sewage sludge ash, which is not readily plant available, was converted to CaNaPO4 (buchwaldite). Consequently, nearly complete phosphorus solubility in ammonium citrate (a well-established indicator for plant availability) was achieved. Moreover, it was shown that Na2CO3 may be replaced by moderately priced Na2SO4. However, molar ratios of Na/P > 2 were required to achieve >80% phosphorus solubility. Such over-stoichiometric Na consumption is largely caused by side reactions with the SiO2 component of the sewage sludge ash – an explanation for which clear evidence is provided for the first time.
For the first time evidence is provided that a nanocrystalline and stacking-disordered, chemically stabilized β-cristobalite form of AlPO4 occurs in a sewage sludge ash (SSA). This proof is based on a combined X-ray powder diffraction and X-ray fluorescence investigation of an SSA produced at a large-scale fluidized bed incineration facility serving a catching area with a population of 2 million. The structural and chemical characterization was carried out on 'as received' SSA samples as well as on solid residues remaining after leaching this SSA in sodium hydroxide solution. Thus, it was ascertained that the observed nanocrystalline and stacking-disordered cristobalite-like component belongs to the aluminum phosphate component of this SSA, rather than to its silicon dioxide component. In addition, a direct proof is presented that the chemically stabilized β-cristobalite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850°C), typical for fluidized bed incinerators.
Evidence is provided that the tridymite component observed in the X-ray diffraction patterns of some sewage sludge ashes (SSAs) should not be interpreted as the tridymite modification of SiO2 but as the tridymite form of AlPO4. This proof is based on a combined X-ray Powder Diffraction (XRD), X-ray fluorescence (XRF) and Mossbauer spectroscopy investigation of two SSAs produced at two fluidized bed incineration facilities, located in different municipalities and operated differently. The structural and chemical characterization was carried out on the 'as received' SSA samples as well as on the residues of these two SSAs pretreated by leaching in citric acid. In addition, direct proof is presented that the tridymite form of AlPO4 does crystallize from X-ray amorphous precursors under conditions that mimic the huge heating rate and short retention time (just seconds at T ≈ 850 °C) typical for fluidized bed incinerators.
The advantages and drawbacks of existing wet chemical phosphorus (P) recovery technologies, their applicability to different types of sewage sludge ash (SSA) and the role of the decay products of detergent zeolites as a source of reactive Al in SSA are analyzed. Since neither a purely acidic nor a purely alkaline treatment are able to provide satisfactory technical solutions a wet chemical phosphorus (P) recovery process for sewage sludge ashes (SSAs) is investigated in detail that is based on a sequential treatment of SSA with an acid and a base. As a result of an acidic pre-treatment, the P fraction of the raw SSA that was bound as – alkaline-insoluble – calcium phosphate (Ca–P) is converted into aluminum phosphate (Al–P). This newly formed Al–P can be easily dissolved via alkaline treatment and then easily separated from the alkaline leachate via precipitation of Ca–P. The Al-component can be reused as precipitant for P-removal in waste water treatment plants (WWTPs). The investigated process requires fewer chemicals than the direct acidic dissolution of all P-compounds contained in the SSA. This is due to the described rearrangement of the P component from Ca–P to Al–P. That such a rearrangement of P occurs indeed was confirmed through a combination of XRD, ICP and XRF analyses together with mass balance calculations. The present investigation proves that the process works for very different types of SSAs: For Al-rich SSAs that come from WWTPs where Al-salt is used for chemical P-removal the described sequential treatment process works best and yields P-recovery rates as high as 70–77%. But even for SSAs from WWTPs where only iron salt is used for chemical P-removal, a considerable amount of the reactive Al necessary for the described P-rearrangement is supplied by decay products of detergent zeolites, a hidden Al-source present in most SSAs produced in Europe.
Sewage sludge and sewage sludge ashes (SSA) are produced in huge amounts at municipal waste water treatment plants (WWTP) all around the world and have become an issue for many urbanized areas. To deal with this unceasing mass flow in an ecologically and economically responsible way a comprehensive chemical and structural characterization of all types of SSA is needed. X-ray powder diffraction (XRD) is one of the most promising analytical methods for this task. Although, there has been ample chemical evidence showing that many SSA contain aluminium phosphate as a major component up to now no aluminium phosphate or aluminium-rich mixed phosphate phase has been reported to be identified by XRD in a SSA produced at a mono-incineration facility. The outcome of the present com-bined XRD and Mossbauer spectroscopy investigation provides comprehensive evidence closing this gap for the first time.