Martin Fisch

Phase Evolution of Thermally Treated Amorphous Tricalcium Phosphate Nanoparticles

X-ray amorphous tricalcium-phosphate nanoparticles (ATCP) produced by flame spray synthesis were heat-treated at temperatures between 500 and 1000 °C and analyzed in situ by X-ray powder diffraction. The main phase occurring after crystallisation at 525 °C was α-TCP, minor phases were identified as β-TCP and hydroxyapatite. More elevated temperatures induced crystallite growth and the transformation of α-TCP into β-TCP. Above 900 °C no α-TCP was traceable anymore. α’-TCP was not observed in the experiment. This study shows that nanoparticulate α-TCP can be obtained by thermal treatment of an amorphous TCP nanoparticle in a temperature range where sintering effects such as particle growth and densification are moderate or nearly negligible.

Crystal chemical and structural characterization of an Mg-rich osumilite from Vesuvius volcano (Italy)

At Vesuvius, osumilite, (K, Na)(Fe, Mg) 2 (Al, Fe, Mg) 3 (Si, Al) 12 O 30 , has been found for the first time in rare contact-metamorphosed rocks ejected during the 1872 A.D. eruption, one of the most violent eruptions of the 19th century. Chemical analysis shows that osumilite is homogeneous and characterized by high Mg numbers (between 88 and 90). Fe shows an average value of 0.247 apfu and K is always greater than 0.810 apfu, with an average value of 0.872 apfu. Structure refinement is consistent with space group P 6/ mcc .

Dehydration of the natural zeolite goosecreekite CaAl2Si6O16·5H2O upon stepwise heating: A single-crystal and powder X-ray study

Abstract The zeolite mineral goosecreekite CaAl2Si6O16⋅5H2O has been structurally investigated between 25 and 600 °C to monitor structural modifications upon partial dehydration. Temperature-dependent in situ powder and single-crystal X‑ray techniques were combined with TG/DTA experiments. Goosecreekite has a porous framework structure with well-ordered Si,Al distribution. In its natural form extraframework Ca is seven-coordinated. Up to ca. 100 °C, 1 H2O molecule is expelled reducing the Ca coordination from 7 to 6 accompanied by very minor changes of the tetrahedral framework. Depending on humidity and equilibration time a second structural change begins between 150 and 250 °C due to loss of additional 2.8 H2O pfu. The space group P21 is maintained but the c axis doubles and the structure is highly twinned. This new phase may be interpreted with a disordered model having two different framework topologies: one with the original T-O-T linkage and a second one with broken T-O-T links. Starting at ca. 300 °C, another 1.2 H2O are lost and this new orthorhombic, strongly contracted phase of P212121 symmetry has five-coordinated Ca. The X‑ray powder signal of the orthorhombic phase persists up to 600 °C, but the structure becomes increasingly X‑ray amorphous until complete destruction at 675 °C. A single crystal (P21 phase with doubled c axis) partly dehydrated at 200 °C recovers the structure of natural goosecreekite under ambient conditions. Similar rehydration occurs after one month under ambient humidity for a powder sample of the orthorhombic P212121 phase produced by heating of goosecreekite to 325 °C.

Thermal Expansion of Aluminoborates

Borates are known for low thermal expansion due to rigid behavior of BO3 and BO4 groups. Aluminoborates Al5BO9, Al4B2O9, grandidierite (Mg,Fe)Al3BSiO9 and jeremejevite Al6B5O15(F,OH)3 were investigated by temperature dependent X-ray diffraction methods. Thermal expansion of all investigated structures is mainly due to bending and stretching of M-O-M angles and unusual thermal behavior of AlO5 and MgO5 polyhedra. Anisotropic expansion of the studied structures is compared with data of structurally related compounds.

Extraction of heavy metals from MSWI fly ash using hydrochloric acid and sodium chloride solution

Fly ash from municipal solid waste incineration contains a large potential for recyclable metals such as Zn, Pb, Cu and Cd. The Swiss Waste Ordinance prescribes the treatment of fly ash and recovery of metals to be implemented by 2021. More than 60% of the fly ash in Switzerland is acid leached according to the FLUWA process, which provides the basis for metal recovery. The investigation and optimization of the FLUWA process is of increasing interest and an industrial solution for direct metal recovery within Switzerland is in development. With this work, a detailed laboratory study on different filter cakes from fly ash leaching using HCl 5% (represents the FLUWA process) and concentrated sodium chloride solution (300 g/L) is described. This two-step leaching of fly ash is an efficient combination for the mobilization of a high percentage of heavy metals from fly ash (Pb, Cd ≥ 90% and Cu, Zn 70-80%). The depletion of these metals is mainly due to a combination of redox reaction and metal-chloride-complex formation. The results indicate a way forward for an improved metal depletion and recovery from fly ash that has potential for application at industrial scale.

Binding guest molecules to frameworks: pressure-induced chemisorption in breathing MOFs

Arianna Lanza1, Luzia Germann2, Martin Fisch3, Nicola Casati4, Piero Macchi5 1Italian Institute Of Technology, Pisa, Italy, 2Max-Planck Institute for Solid State Research, Stuttgart, Germany, 3University of Bern, Bern, Switzerland, 4Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland, 5Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland E-mail: ari.streghetta@gmail.com