Crystal structure, microstructure, and mechanical properties of heat-treated oyster shells.

We investigated the crystal structure and mechanical properties of oyster shells subjected to heat treatment under increasing temperature conditions. The shell contained folia and chalky layers. The folia layer comprised two CaCO3 phases: 72.3% calcite and 27.7% aragonite. The lattice parameters of the calcite and aragonite present in the folia layer did not correspond to those of the synthesized sample. The anisotropic lattice expansion was observed in calcite and aragonite in the folia layer during heat-treatment. The chalky layer has also the anisotropic lattice expansion, but the expansion was disappeared at 573 K. The microhardness (HV value) of the folia layer decreased rapidly from 122 to 11 HV at temperatures 573-673 K owing to the phase transformation from aragonite to calcite in this temperature range. The microhardness of the chalky layer at RT was 125 HV, which decreased to 15 HV at 373 K. Crack propagation with increasing temperature was investigated using a micro-Vickers apparatus. In the folia layer, cracks were produced inside the prism, and they propagated along the lamellar structure. The cracks initiated and propagated along the organic biopolymer interlayers in a zigzag manner. No cracks were observed in the chalky layers of the heat-treated samples. The toughness of the chalky layer was superior to that of the folia layer. From our results, we can conclude that oyster shells comprise two types of materials with different mechanical properties.

Crystal Structure of Pr3MgNi14Dx Studied by in Situ Neutron Diffraction.

The crystal structure of Pr3MgNi14D18 was determined by neutron diffraction. The determined structure of Pr3MgNi14D18 consisted of 89.0% Gd2Co7-type structure and 11.0% PuNi3-type structure. The lattice parameters of a and c of Gd2Co7-type structure were refined at 0.52903(7) nm and 3.90179(1) nm. The deuterium atoms were distributed among nine deuterium sites in both the CaCu5-type and MgZn2-type cells. The D2 occupancy in the Pr2Ni4 octahedral sites of the CaCu5-type cell was the largest (0.75) when compared with the other deuterium sites (<0.49). The deuterium content of the CaCu5-type cell showed 0.75 D/M, but the D/M value of the MgZn2-type cell was 1.53. The volume expansions during deuteration of the CaCu5-type and MgZn2-type cells were nearly equal. The cyclic hydrogenation property of Pr3MgNi14 is comparable to that of LaNi5. It is inferred that the similar expansion behavior of the CaCu5-type and MgZn2-type cells during deuteration is the origin of this cyclic stability.

Experimental Realization of a Quantum Pentagonal Lattice.

Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal α-2,6-Cl2-V [=α-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL.

Crystal Structure Analysis of La2Ni6CoD(x) During Deuterium Absorption Process.

The crystal structures of La2Ni6CoD(x) (x = 5.2 and 9.6) were determined by in situ neutron diffraction along the P-C isotherm. La2Ni6CoD(5.2) (phase I) was found to be orthorhombic with lattice parameters a = 0.500670(2) nm, b = 0.867211(4) nm, and c = 2.99569(7) nm. The 10 deuterium sites were located in the MgZn2-type and CaCu5-type cells, with deuterium contents of 0.95 D/M and 0.39 D/M, respectively. The full deuteride La2Ni6CoD(9.6) (phase II) was monoclinic with lattice parameters a = 0.516407(3) nm, b = 0.894496(6) nm, c = 3.11206(1) nm, and ß = 90.15(1)°. The phase II had 11 sites for deuterium occupation. The deuterium contents of the MgZn2-type and the CaCu5-type cell were 1.63 D/M and 0.78 D/M, respectively. The sequence of phase transformation of La2Ni6Co was hexagonal, followed by orthorhombic (phase I), and then monoclinic (phase II), for the first absorption process. The phase transformation resulted in lowered symmetry and the variation of deuterium atom occupation.

Crystal structure and cyclic hydrogenation property of Pr4MgNi19.

The hydrogen absorption-desorption property and the crystal structure of Pr4MgNi19 was investigated by pressure-composition isotherm measurement and X-ray diffraction (XRD). Pr4MgNi19 consisted of two phases: 52.9% Ce5Co19-type structure (3R) and 47.0% Gd2Co7-type structure (3R). Sm5Co19-type structure (2H) and Ce2Ni7-type structure (2H) were not observed in the XRD profile. The Mg atoms substituted at the Pr sites in a MgZn2-type cell. The maximum hydrogen capacity reached 1.14 H/M (1.6 mass%) at 2 MPa. The hysteresis factor, Hf = ln(Pabs/Pdes), was 1.50. The cyclic hydrogenation property of Pr4MgNi19 was investigated up to 1000 absorption-desorption cycles. After 250, 500, 750, and 1000 cycles, the retention rates of hydrogen were reduced to 94%, 92%, 91%, and 90%, respectively. These properties were superior to those of Pr2MgNi9 and Pr3MgNi14.

In situ XRD study of La2Ni7H(x) during hydrogen absorption-desorption.

Structural changes of La2Ni7H(x) during the first and second absorption-desorption processes along the P-C isotherm were investigated by in situ X-ray diffraction (XRD). Orthorhombic (Pbcn) and monoclinic (C2/c) hydrides coexisted in the first absorption plateau, but only a monoclinic (C2/c) hydride was observed in the first desorption plateau. Phase transformation of La2Ni7H(x) was irreversible between the first as well as the second absorption-desorption process. The lattice parameters and expansion of the La2Ni4 and LaNi5 cells during the absorption-desorption process were refined using the Rietveld method. The lattice parameters a and b of the orthorhombic hydride (Pbcn) decreased, while the lattice parameter c increased with increasing hydrogen content in the first absorption. During the first absorption, the volume of the orthorhombic La2Ni4 cell expanded by more than 50%, while the expansion of the LaNi5 cell was below 10%. The monoclinic La2Ni4 cell expanded to approximately four times the size of the LaNi5 cell in the first absorption. The lattice parameters a, b, and c of the monoclinic hydride (C2/c) decreased with decreasing hydrogen content in the first desorption. These La2Ni4 and LaNi5 cells contracted isotropically in the first desorption.

Structural parameters of Pr3MgNi14 during hydrogen absorption-desorption process.

Structural parameters of Pr(3)MgNi(14) after a cyclic hydrogen absorption-desorption process were investigated by X-ray diffraction. Pr(3)MgNi(14) consisted of two phases: 80% Gd(2)Co(7)-type structure and 20% PuNi(3)-type structure. The pressure-composition (P-C) isotherm of Pr(3)MgNi(14) indicates a maximum hydrogen capacity of 1.12 H/M (1.61 mass %) at 298 K. The cyclic property of Pr(3)MgNi(14) up to 1000 cycles was measured at 313 K. The retention rate of the sample was 87.5% at 1000 cycles, which compares favorably with that of LaNi(5). After 1000 cycles, the expansions of lattice parameters a and c and the lengths along the c-axes of the PrNi(5) and PrMgNi(4) cells of the Gd(2)Co(7)-type structures were 0.20%, 1.26%, 0.47%, and 3.68%, respectively. The metal sublattice expanded anisotropically after the cyclic test. The isotropic and anisotropic lattice strains can be refined by Rietveld analysis. The anisotropic and isotropic lattice strains were almost saturated at the first activation process and reached values of 0.2% and 0.1%, respectively, after 1000 cycles. These values are smaller by 1 order of magnitude than those of LaNi(5).

Synthesis of new compound Gd5Ni19 with a superlattice structure and hydrogen absorption properties.

We successfully synthesized the new intermetallic compound Gd(5)Ni(19) and determined its crystal structure by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The structure is a Sm(5)Co(19)-type superlattice structure (2H, space group P6(3)/mmc), and the lattice parameters were determined as a = 0.4950(1) nm and c = 3.2161(5) nm by X-ray Rietveld refinement. The XRD results agreed with the STEM analysis results. The P-C isotherm of Gd(5)Ni(19) was measured at 233 K. In the first absorption cycle, the maximum hydrogen capacity reached 1.07 H/M at 2.0 MPa. The sloping plateau was observed in the first absorption-desorption cycle. The maximum hydrogen capacity decreased by 0.87 H/M in the second absorption cycle, implying that hydrogen in the amount of H/M = 0.20 remained in the alloy before the second absorption-desorption cycle.

Synthesis and crystal structure of a Pr5Ni19 superlattice alloy and its hydrogen absorption-desorption property.

The intermetallic compound Pr(5)Ni(19), which is not shown in the Pr-Ni binary phase diagram, was synthesized, and the crystal structure was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Two superlattice reflections with the Sm(5)Co(19)-type structure (002 and 004) and the Pr(5)Co(19)-type structure (003 and 006) were observed in the 2θ region between 2° and 15° in the XRD pattern using Cu Kα radiation. Rietveld refinement provided the goodness-of-fit parameter S = 6.7 for the Pr(5)Co(19)-type (3R) structure model and S = 1.7 for the Sm(5)Co(19)-type (2H) structure model, indicating that the synthesized compound has a Sm(5)Co(19) structure. The refined lattice parameters were a = 0.50010(9) nm and c = 3.2420(4) nm. The high-resolution TEM image also clearly revealed that the crystal structure of Pr(5)Ni(19) is of the Sm(5)Co(19) type, which agrees with the results from Rietveld refinement of the XRD data. The P-C isotherm of Pr(5)Ni(19) in the first absorption was clearly different from that in the first desorption. A single plateau in absorption and three plateaus in desorption were observed. The maximum hydrogen storage capacity of the first cycle reached 1.1 H/M, and that of the second cycle was 0.8 H/M. The 0.3 H/M of hydrogen remained in the metal lattice after the first desorption process.

Phase transformation and crystal structure of La(2)Ni(7)H(x) studied by in situ X-ray diffraction.

The phase transformation of La(2)Ni(7) during hydrogenation was investigated by in situ X-ray diffraction. We found two hydride phases, La(2)Ni(7)H(7.1) (phase I) and La(2)Ni(7)H(10.8) (phase II), during the first absorption cycle. The metal sublattice of phase I was orthorhombic (space group Pbcn) with lattice parameters a = 0.50128(6) nm, b = 0.8702(1) nm, and c = 3.0377(1) nm. The sublattice for phase II was monoclinic (space group C2/c) with lattice parameters a = 0.51641(9) nm, b = 0.8960(1) nm, c = 3.1289(1) nm, and ß = 90.17(1)°. The lattice parameter c increased with the hydrogen content, while a and b decreased in the formation of phase I from the alloy. Phase transformation from phase I to phase II was accompanied by isotropic expansion. The La(2)Ni(4) and LaNi(5) subunit expanded by 48.9% and 6.0% in volume, respectively, during hydrogenation to phase I. They expanded an additional 14% and 5.8%, respectively, in the formation of phase II. The obtained volume expansion suggested different hydrogen distribution in the La(2)Ni(4) and LaNi(5) subunit during hydrogenation.

Application of gel permeation HPLC for lipoprotein profiling in dogs.

A high performance liquid chromatography system with a gel permeation column (GP-HPLC) and an on-line dual enzymatic system was applied to lipoprotein analysis in dogs. A high density lipoprotein (HDL) fraction obtained by conventional ultracentrifugation gave a single peak at around 28-29 min. Similarly, a low density lipoprotein (LDL) fraction gave single peak at around 24-25 min. The lipoprotein profiles of healthy dogs were contained large HDL peaks and small LDL peaks, and VLDL and CM were only marginally detected. In diabetic dogs, concentrations of VLDL-triglyceride and VLDL-total-cholesterol were elevated significantly. The lipoprotein profile analysis by GP-HPLC method would be useful in explication of abnormality of lipid metabolism in dogs.

Tristimulus colorimetry using a digital still camera and its application to determination of iron and residual chlorine in water samples.

Tristimulus colorimetry using a digital still camera (DSC) as a colorimeter has been developed. A photograph of a sample and standard solutions was taken simultaneously with the DSC, and it was transferred to a PC. On the PC, the colors of the sample and of the standard solutions were analyzed and L* (brightness), a* (red-green component), and b* (yellow-blue component) values were determined with laboratory-made software. A dedicated light-box containing white-color LEDs as light source was made of white acrylic to make constant exposure at each photograph. Various settings of the DSC, such as exposure mode, white balance, and so on, that affect analytical figures, were studied with determination of iron with 1,10-phenanthroline. This method was successfully applied to the determinations of iron in a river water sample and of residual chlorine in tap water samples with N,N-diethylphenylenediamine (DPD).