13446-18-9Relevant articles and documents
Pb0.5 + xMg xZr2 – x(PO4)3(x = 0, 0.5) Phosphates: Structure and Thermodynamic Properties
Asabina, E. A.,Kovalsky, A. M.,Markin, A. V.,Mayorov, P. A.,Pet’kov, V. I.,Smirnova, N. N.
, p. 711 - 719 (2020)
Abstract—Crystalline Pb0.5 + xMgxZr2 – x(PO4)3 (x = 0, 0.5) phosphates of NaZr2(PO4)3 (NZP) structural type were synthesized. The heat capacity of Pb0.5Zr2(PO4)3 was measured by adiabatic vacuum and differential scanning calorimetry (DSC) within the temperature range 8–660 K. The studied phosphates were found to experience a reversible phase transition in the region 256–426 K. According to the results of Rietveld structural study, this transition occurred due to an increase in disorder of lead cation positions in cavities of the NZP structure. The measurements of PbMg0.5Zr1.5(PO4)3 heat capacity in the temperature range 195–660 K showed that it experienced a similar phase transition at 255–315 K. Based on the measured experimental data, the thermodynamic functions of Pb0.5Zr2(PO4)3, such as Cp 0(T) [H0(T) – H0(0)], S0(T), and [G0(T) – H0(0)] were calculated for the temperature range 0–660 K. The standard formation enthalpy of Pb0.5Zr2(PO4)3 was determined at 298.15 K.
On the photophysics and speciation of actinide ion in MgAl2O4spinel using photoluminescence spectroscopy and first principle calculation: A case study with uranium
Gupta, Santosh K.,Pathak, Nimai,Ghosh,Kadam
, p. 337 - 343 (2017)
Actinide chemistry is very interesting not from scientific perspective but also from technological importance. Elucidating the valence state and coordinating environment of actinide ion like uranium in technologically important magnesium aluminate spinel (MAS) is important to fully understand its hazardous and other harmful effect in human as well as environment. Magnesium aluminate spinel doped with 1.0?mol % of Uranium ion has been synthesized using citric acid assisted gel-combustion route at 800?°C. The as prepared powder is characterised using X-ray diffraction (XRD), time resolved photoluminescence spectroscopy (TRPLS) and density functional theory (DFT) calculations. Uranium is an interesting element because it exhibits multiple oxidation state and each one of them is having characteristics fluorescence behavior. TRPLS is used to investigate the oxidation state and coordination behavior of uranium in MgAl2O4. Indeed in our earlier work on undoped and lanthanide ion doped MAS; it was oberved that in undoped sample itself defect induced emission could be seen in visible region which was probed using DFT. Here on doping uranium in MAS; complete energy of host is transferred to uranium ion which is explained using DFT. From excitation and emission spectroscopy it was observed that uranium stabilizes in?+6 oxidation state in the form of UO22+ ion. Based on luminescence lifetime and its comparison with the emission profile of uranyl fluoride crystal it was inferred that majority of uranium is occupying relatively asymmetric MgO4polyhedra and minority substitutes AlO6. The site stability of the uranyl ion in MAS was also validated using DFT based first principle calculations. Time resolved emission shows the uranyl at Mg2+site differs from the one at Al3+site in terms of peak position and intensity.
Paulik, F.,Paulik, J.,Arnold, M.,Naumann, R.
, p. 627 - 636 (1988)
Synthesis of MgAl2O4 nanopowders
Kuznetsov,Fedorov,Voronov,Osiko
, p. 895 - 898 (2011)
A procedure has been developed for the synthesis of MgAl2O 4 nanopowders with a characteristic particle size of 10-40 nm. Translucent hydrous xerogels have been synthesized as precursors to MgAl 2O4. The synthesized magnesium aluminum spinel nanopowders are promising for the fabrication of optical ceramics.
Preparation of MgO nanoparticles
Fedorov,Tkachenko,Kuznetsov,Voronov,Lavrishchev
, p. 502 - 504 (2007)
MgO nanoparticles have been prepared via hydroxide precipitation from aqueous solutions, followed by the thermal decomposition of the hydroxide. The nanoparticles inherit the platelike shape from the hydroxide and break into isometric particles upon signi
Enhanced photoredox chemistry in surface-modified Mg2TiO4 nano-powders with bidentate benzene derivatives
Medi?, Mina M.,Vasi?, Marija,Zarubica, Aleksandra R.,Trandafilovi?, Lidija V.,Dra?i?, Goran,Drami?anin, Miroslav D.,Nedeljkovi?, Jovan M.
, p. 94780 - 94786 (2016)
Magnesium-orthotitanate (Mg2TiO4) nano-powder was synthesized using a Pechini-type polymerized complex route. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption-desorption isotherms indicated that well-crystallized Mg2TiO4 nanoparticles are small in size (about 10 nm) with large specific surface area (72 m2 g-1). The surface modification of Mg2TiO4 nano-powders with 5-amino salicylic acid and catechol induced a significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of Mg2TiO4 nano-powders have never been reported in the literature. Degradation reactions of an organic dye (crystal violet) were used to test the photocatalytic ability of pristine and surface-modified Mg2TiO4 nano-powders under illumination in different spectral regions. Excitation with UV light indicated, for the first time, photocatalytic ability of Mg2TiO4. Also, improved photocatalytic performance of surface-modified Mg2TiO4 nano-powders was found in comparison to unmodified ones.
Metal-organic phase-change materials for thermal energy storage
McGillicuddy, Ryan D.,Thapa, Surendra,Wenny, Malia B.,Gonzalez, Miguel I.,Mason, Jarad A.
supporting information, p. 19170 - 19180 (2020/12/01)
The development of materials that reversibly store high densities of thermal energy is critical to the more efficient and sustainable utilization of energy. Herein, we investigate metal-organic compounds as a new class of solid-liquid phase-change materials (PCMs) for thermal energy storage. Specifically, we show that isostructural series of divalent metal amide complexes featuring extended hydrogen bond networks can undergo tunable, high-enthalpy melting transitions over a wide temperature range. Moreover, these coordination compounds provide a powerful platform to explore the specific factors that contribute to the energy density and entropy of metal-organic PCMs. Through a systematic analysis of the structural and thermochemical properties of these compounds, we investigated the influence of coordination bonds, hydrogen-bond networks, neutral organic ligands, and outer-sphere anions on their phase-change thermodynamics. In particular, we identify the importance of high densities of coordination bonds and hydrogen bonds to achieving a high PCM energy density, and we show how metal-dependent changes to the local coordination environment during melting impact the entropy and enthalpy of metal-organic PCMs. These results highlight the potential of manipulating order-disorder phase transitions in metal-organic materials for thermal energy storage.
