Single crystals of (NH 4 ) 3 VOF 5 and (NH 4 ) 3 VO 2 F 4 were obtained from aqueous fluoride solutions and phase transitions in these compounds were investigated using X-ray diffraction, differential scanning microcalorimetry (DSM) and vibrational spectroscopy. The room-temperature (RT) phases of these compounds belong to orthorhombic symmetry [Immm and I222, Z = 6, for (NH 4 ) 3 VOF 5 and (NH 4 ) 3 VO 2 F 4 , respectively] with similar unit-cell parameters and two independent vanadium atoms. Above RT [at 350 and 440 K for (NH 4 ) 3 VOF 5 and (NH 4 ) 3 VO 2 F 4 , respectively], the compounds undergo reversible phase transitions into high-symmetry dynamically disordered elpasolite-like (Fm " 3 3m, Z = 4) structures with six and 12 spatial orientations of the vanadium octahedron for (NH 4 ) 3 VOF 5 and (NH 4 ) 3 VO 2 F 4 , respectively. The ligand atoms are distributed in a mixed (split) position of 24e + 96j, one of the ammonium groups is disordered on the tetrahedron 32f site, but another one forms eight spatial orientations due to disorder of its hydrogen atoms in the 96j position. DSM and spectroscopic data enable the phase transition from high temperature to room temperature to be connected with the transition from isotropic orientations of the octahedron to its two different dynamic states.
In the fast-developing market of customer products, a development lead time becomes more and more critical. However, these technologies have limits. Also, the application of so-called additive manufacturing technologies, particularly FDM 3D printing, is limited by the materials used and the part’s quality. The significant advantage of additive manufacturing is building components without the use of molds or tools. The paper presents an experience of fast prototyping a centrifugal compressor using 3D printing with polymer plastics. 3D printing of parts has the main goal in this study to develop a structural and functional prototype for variation centrifugal compressors testing. Additive manufacturing technologies can fabricate centrifugal compressors with less labor and any configuration. Attention is paid to the choice of 3D printing technology, materials, and the influence of printing parameters on the product's mechanical properties. In conclusion, experimental results are presented for the prototype together with recommendations for serial manufacturing. Also, a laboratory bench is described where variant tests will be carried out. All this will allow the reader to interpret those solutions more reasonably and take into account the specifics in more detail when developing a technical requirement for centrifugal compressors testing.
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