Japan Atomic Energy Research Institute

About: Japan Atomic Energy Research Institute is a based out in . It is known for research contribution in the topics: Neutron & Irradiation. The organization has 7707 authors who have published 14471 publications receiving 207688 citations.

Structural Phase Transitions in CsPbBr 3

Abstract: Structural phase transitions in perovskite-type CsPbBr 3 have been investigated by neutron diffraction method. Phase transitions occur at 88°C and 130°C, which are respectively second and first order. The phase transition at 130°C is caused by condensation of the M 3 mode at the M point of the cubic Brillouin zone, while the one at 88°C results from condensation of the doubly degenerate R 25 -like mode ( Z 9 mode) at the Z point of the tetragonal Brillouin zone. Group theoretical considerations based on these results reveal that the crystal trans-forms from cubic perovskite structure (O h 1 - P m 3 m ) to tetragonal D 4h 5 - P 4/ m b m at 130°C and further to orthorhombic D 2h 16 - P m b n at 88°C. Possible atomic displacements induced at the phase transitions are obtained from the eigenvectors of the condensing modes.

The adsorption mechanism of uranium(VI) from seawater on a macroporous fibrous polymeric adsorbent containing amidoxime chelating functional group

Abstract: To adsorb and recover uranium(VI) from seawater, an improved macroporous fibrous polymeric adsorbent containing amidoxime chelating functional group (FPAO) was synthesized by irradiation-induced graft polymerization utilizing methacrylic acid (MAA) as a hydrophilic monomer. The adsorption mechanism of U(VI) on FPAO adsorbent was investigated in a wide pH range by the method of the thermodynamics. It was found that the pH value at different conditions had significant effect on the adsorption of U(VI) on FPAO adsorbent. The adsorption ability of FPAO for U(VI) increased from pH 2.0 to pH 6.0 and decreased from pH 6.0 to pH 9.0. U(VI) was effectively adsorbed by FPAO adsorbent at around pH 6.0. The predominant composition of resulting the mononuclear complex was determined as UO 2 2R–C(NO)NH 2 by investigating the effect of the concentrations of U(VI), FPAO, H + and Cl − on the adsorption reaction. The adsorption equilibrium equation of U(VI) on FPAO adsorbent was expressed as UO 2 (OH) + (aq) + 2R–C(NOH)NH 2(fp) ↔ UO 2 2R–C(NO)NH 2(fp) + H + (aq) +H 2 O. The overall adsorption equilibrium constant was calculated to be K ad =7.08×10 7 M −1 at ionic strength of 0.1 M at 25 °C. A monolayer molecule adsorption mechanism between U(VI) and FPAO was also determined by examining the relationships between the adsorbed amount of U(VI) and contact time.

Segregation of Solute Atoms to Stacking Faults

Abstract: An experimental evidence was given for the segregation of solute atoms to stacking faults in alpha-brass. The stacking fault energy in an alpha-phase solid solution with face-centered cubic structure usually decreases continuously with the increasing concentration of solute atoms. The solute atoms in that alloy tend to segregate to the stacking faults due to chemical interaction. A simple calculation indicates that the solute atoms segregate to such a high concentration as the stacking fault energy becomes a negative value with considerable magnitude, provided that the concentration of solute atoms is in thermal equilibrium at rather low temperature. The width of an extended dislocation should increase indefinitely if the stacking fault energy becomes lower than a negative value. Alpha-brass with 30% zinc, which was annealed at 120°C and 150°C for a week and two days, respectively, after cold-work reveals extended dislocations with extremely wide stacking faults of the order of several microns. Meanwhile,...

Nonunitary Spin-Triplet Superconductivity in UPt3 : Evidence from 195Pt Knight Shift Study

Abstract: ${}^{195}\mathrm{Pt}$ Knight shift (KS) measurements covering the superconducting multiple phases for major field ( $H$) orientations have been carried out on the high-quality single crystal ${\mathrm{UPt}}_{3}$. For $Hg5$ kOe, the KS does not change below the superconducting transition temperature ${T}_{c}$ down to 28 mK, regardless of major crystal orientations, which provides evidence that the odd-parity superconductivity with the parallel spin pairing is realized. By contrast, the KS decreases below ${T}_{c}$ for ${H}_{b}\ensuremath{\parallel}b$ axis and ${H}_{b}l5$ kOe and for ${H}_{c}\ensuremath{\parallel}c$ axis and ${H}_{c}l2.3$ kOe, whereas the KS for ${H}_{a}\ensuremath{\parallel}a$ axis is $T$ independent across ${T}_{c}$ down to ${H}_{a}\ensuremath{\sim}1.764$ kOe. These novel findings entitle ${\mathrm{UPt}}_{3}$ as the first spin-triplet odd-parity superconductor including a nonunitary pairing characterized by the two-component $\mathbf{d}$ vector like ${\mathbf{d}}_{b}+i{\mathbf{d}}_{c}$ at low $T$ and low $H$.