0000000000171069
AUTHOR
Cora Lind
Particle size and morphology control of the negative thermal expansion material cubic zirconium tungstate
Cubic ZrW2O8 is a negative thermal expansion (NTE) material that is of interest as filler in controlled thermal expansion composites. It is easily accessible from a hydrated precursor, ZrW2O7(OH)2·2H2O, which can be obtained by hydrothermal synthesis. Different reaction conditions were investigated to gain control over the morphology, and to minimize the particle size. Optimized procedures resulted in rod-shaped particles with widths of 10–30 nm and lengths of 200–500 nm, which showed little agglomeration. The particle size and morphology of the precursor are preserved during conversion to the NTE phase at 600–650 °C.
ChemInform Abstract: Hydrate Networks under Mechanical Stress - A Case Study for Co3(PO4)2·8H2O.
The mechanochemically (ball milling) induced loss of bound H2O in Co3(PO4)2·8H2O is investigated together with an associated phase transition and its kinetics by powder synchrotron XRD and quantitative IR spectroscopy.
Hydrate Networks under Mechanical Stress – A Case Study for Co 3 (PO 4 ) 2 ·8H 2 O
The nature of the bound water in solids with hydrogen-bonded networks depends not only on temperature and pressure but also on the nature of the constituents. The collapse and reorientation of these network structures determines the stability of hydrated solids and transitions to other crystalline or amorphous phases. Here, we study the mechanochemically induced loss of bound water in Co₃(PO₄)₂·8H₂O and compare this process to the behavior under hydrostatic pressure. The associated phase transition and its kinetics were monitored by X-ray powder diffraction with Synchrotron radiation and quantitative IR spectroscopy. High shearing forces are responsible for the degradation of the hydrogen-b…