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Dy(OH) 3 : a paramagnetic magnetocaloric material for hydrogen liquefaction
Full text linkDy(OH) 3 has impressive magnetocaloric performance optimised around 20 K making it suitable for hydrogen liquefaction using magnetic cooling.
The magnetic properties of a series of Ln(OH) 3 (where Ln = Gd–Er) coordination polymer materials have been examined to evaluate their potential as magnetocaloric materials. Dy(OH) 3 was found to exhibit an impressive magnetic entropy change of 33.4 J kg −1 K −1 at 12 K for a magnetic field change of 5-0 T, based on magnetisation measurements. Further magnetic heat capacity analysis indicated a maximum adiabatic temperature change of 8.4 K at 22.7 K. The favourable magnetocaloric parameters obtained for Dy(OH) 3 demonstrated its effectiveness to act as a magnetic cooling material for hydrogen liquefaction, since the boiling point of hydrogen aligns well with the temperature for peak magnetocaloric performance of Dy(OH) 3 for high field changes
Dy(OH)3: A Paramagnetic Magnetocaloric for Hydrogen Liquefaction
Full text linkThe magnetic properties of a series of Ln(OH)3 (where Ln = Gd-Er) coordination polymer materials have been examined to evaluate their potential as magnetocaloric materials. Dy(OH)3 was found to exhibit an impressive magnetic entropy change of 33.4 J kg-1 K-1 at 12 K for a magnetic field change of 5-0 T, based on magnetisation measurements. Further magnetic heat capacity analysis indicated a maximum adiabatic temperature change of 8.4 K at 22.7 K. The favourable magnetocaloric parameters obtained for Dy(OH)3 demonstrated its effectiveness to act as magnetic cooling material for hydrogen liquefaction, since the boiling point of hydrogen aligns well with the temperature for peak magnetocaloric performance of Dy(OH)3 for high field changes
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Crystal field and magnetic properties of Dy(OH)/sub 3/, Ho(OH)/sub 3/ and Er(OH)/sub 3/
No full textThe electric quadrupole and magnetic hyperfine interactions measured from the /sup 161/Dy Moessbauer resonance in crystalline Dy(OH)/sub 3/ and from the /sup 166/Er resonance in crystalline Ho(OH)/sub 3/ and Er(OH)/sub 3/ are interpreted using the crystal field and molecular exchange field model. The crystal field parameters established from previous optical spectroscopy results account well for these hyperfine parameters. The crystal-field and magnetic properties of these ferromagnetic insulators are described well within the model
A Simple Method to Synthesize Dy(OH)<sub>3</sub> and Dy<sub>2</sub>O<sub>3</sub> Nanotubes
No full textHere we report the first synthesis of Dy(OH)3 nanotubes by facile hydrothermal treatment of bulky Dy2O3 crystals. Dy(OH)3 nanotubes were calcined to produce Dy2O3 nanotubes. Ho(OH)3 and Ho2O3 nanotubes were also obtained by the same method. The growth of nanotubes occurred through a dissolution−recrystallization process
CRYSTAL FIELD AND MAGNETIC PROPERTIES OF Dy(OH)
No full textThe electric quadrupole and magnetic hyperfine interactions rneasured from the 161Dy Mössbauer
resonance in crystalline Dy(OH)3 and from the 166Er resonance in crystalline Ho(OH)3 and Er(OH)3
are interpreted using the crystal field and molecular exchange field model . The crystal field parameters
established from previous optical spectroscopy results account weIl for these hyperfine parameters.
The crystal-field and magnetic properties of these ferromagnetic insulators are described
weIl within the model
Crystallographic texture and angular dependence of coercivity of ordered CoPt thin film
No full textEffect of crystallographic texture on the angular dependence of coercivity of ordered CoPt thin film was studied by successfully controlling the texture of the ordered CoPt thin film. We have developed, based on the Stoner-Wohlfarth interacting particles model, a micromagnetic simulation technique which can simulate the effect of distribution of magnetocrystalline easy axis on the magnetization behavior of thin film. The good agreement between the experiments and simulation suggested that the magnetization reversal in ordered CoPt thin film occurs not by the domain wall motion but by the Stoner-Wohlfarth interacting particles model. (c) 2005 American Institute of Physics
Structural and phase dependent thermo and photoluminescent properties of Dy(OH)(3) and Dy2O3 nanorods
No full textHexagonal Dy(OH)3 and cubic Dy2O3 nanorods were prepared by hydrothermal method. Dy(OH)3 nanorods was directly obtained at 180 °C for 20 h after hydrothermal treatment whereas subsequently heat treatment at 750 °C for 2 h gives pure cubic Dy2O3. SEM micrographs reveal that needle shaped rods with different sizes were observed in both the phases. TEM results also confirm this. The TL response of hexagonal Dy(OH)3 and cubic Dy2O3 nanorods have been analyzed for γ-irradiation over a wide range of exposures (1–5 kGy). TL glow peak intensity increases with γ dose in both the phases. The activation energy (E), order of kinetics (b), and frequency factor (s) for both the phases have been determined using Chen's peak shape method. The simple glow curve shape, structure and linear response to γ-irradiation over a large span of exposures makes the cubic Dy2O3 as a useful dosimetric material to estimate high exposures of γ-rays
Effect of bias on the as-deposited grain structure of Cr thin film
No full textThe film growth of Cr thin film by DC-magnetron sputter deposition was investigated by experimentally measuring the evolution of grain size distribution and by computing the film growth using Monte Carlo simulation. The as-deposited Cr thin film by sputter deposition typically grows in a columnar grain structure at the substrate temperature 260℃, which is far lower than 0.3 Tm. The stagnation of columnar grain structure does not occur in the case of no-bias condition up to the investigated film thickness of about 800 nm. However, the application of a negative bias of 200 V results in a stagnation of columnar grain structure at film thickness of about 50 nm and at the deposition temperature of 260℃. This is believed to arise from the fact that the mobility of ad-atoms is greatly enhanced and the Ar＋ ions pin the grain boundary as a result of bias application
Rare-Earth Hydroxometalates Ba[RE(OH)<sub>5</sub>] with RE=Tb, Dy, Ho
No full textColorless crystals of the new hydroxometalates Ba[RE(OH)(5)] with the rare-earth elements RE=Tb, Dy, Ho were synthesized under ultra-alkaline conditions in a KOH hydroflux at 200 degrees C. Single-crystal X-ray diffraction revealed that the three compounds crystallize isostructural in the monoclinic space group P2(1)/n (no. 14). In the crystal structure, the rare-earth cations are coordinated by the oxygen atoms of seven hydroxide anions, which define a distorted pentagonal bipyramid. These polyhedra share edges of their basal ring forming infinite chains that run parallel to the [010] direction. Hydrogen bonds connect the chains into layers parallel to the (101) plane. The Ba2+ cations are located between these layers and surrounded by nine oxygen atoms. Ba[Dy(OH)(5)] is paramagnetic and shows no luminescence under UV light. When heated in synthetic air or argon, water is released in well-defined steps. Ba[Dy(OH)(5)] decomposes via DyOOH to Dy2O3, which then reacts with the remaining Ba(OH)(2) to form BaDy2O4. Thus, the hydroxometalates can be used as carbon-free precursors for oxides
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