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An accidental explosion occurred in a waste storage tank at an incineration plant in Kawasaki, Japan, on May 11, 1997. The accident was caused primarily by unintended mixing involving reactive chemicals, such as organic peroxides (POs) and acrylonitrile (AN). The PO initiated polymerization of AN and the heat released during the polymerization led to a runaway reaction and explosion. POs are widely used in the chemical industry and can be self-reactive and hazardous when mixed with other chemicals such as acids and alkalis. The goal of this study was to obtain a better understanding of the mixing hazard of chemicals through an evaluation of POs with other chemicals using conventional experimental techniques such as glass test-tube tests, Dewar vessel tests, and differential scanning calorimetry (DSC). Seven types of POs were mixed with AN. Test results were classified into four ranks based on the hazard criteria. In addition, di(2-ethylhexyl)-peroxydicarbonate/AN mixtures were investigated in detail and the influences of the mixing ratio and the stirring rate were examined.

Organic peroxides (POs) have been widely used in chemical industries as initiators of polymerization, hardening or bridge formation agents, and they are known for its self-reactive and also mixing hazard characteristics when mixed with other chemicals such as acids and alkalis. It is the purpose of this investigation to propose a simple but useful evaluation flow of mixing hazards of POs with other chemicals using conventional experimental techniques such as a glass test tube test, Dewar vessel test and DSC is proposed. 7 kinds of POs (DEPD, THP, TBEH, TBTC, MEKPO, DTBP, THHP) were mixed with sulfuric acids with various concentration, sodium hydroxide solutions, α-iron(III) oxide and acrylonitrile (AN). Based on the proposed evaluation flow the testing results were classified into 4 ranks due to the hazard criteria. Futhermore DEPD/acrylonitrile mixtures were investigated in more detail and the influences of the mixing ratio and the stirring speed were discussed.

X-ray absorption (XAS) and emission (XES) spectroscopy near O K edge has been performed on edge-shared CuO chain compounds Ca2+xY2−xCu5O10 ( 0.0 ≤ x ≤ 2.0 ) using poly- and single-crystalline samples. Two large peaks are observed at 528 eV (PH) and 530 eV (PU) in the XAS spectra. The intensity of the PH peak monotonically increases and that of the PU monotonically decreases with hole doping. The two characteristic peaks in the XAS spectra at PH and PU, which are assigned for the polycrystalline samples to the hole and upper Hubbard band (UHB) states, respectively. The theoretical calculations reproduce the experimental XAS results, especially that the PU peak decreases by hole doping. The spectral weight transfer from the PU peak to the PH peak of the edge-shared chain by hole doping is strongly suppressed in comparison with that of the CuO2 plane. From the single crystal measurements of undoped Ca2Y2Cu5O10, the spectra of XAS and XES are interpreted in terms of a square-like CuO4 plaquette for the compound. As for the hole-doped Ca3YCu5O10 sample, the plaquette containing a doped hole is found to be square-like, and the plaquettes with no doped holes are found to be rectangle-like. We concluded that the doped hole is localized associated with the lattice deformation. The electric properties are discussed based on our result.

Properties of oxide layers at the interface between Al metal and YBa 2 Cu 3 O 7− δ ceramics were investigated using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and impedance measurements. There have been found the oriented grains having their c -plane parallel to the surface of YBa 2 Cu 3 O 7− δ . When Al metal was evaporated onto the ceramics sample, the aluminum oxide layer was produced at the interface between Al and YBa 2 Cu 3 O 7− δ because Al metal oxidizes more easily. The oxygen-deficiency was observed at the ceramics side of the interface as examined by X-ray photoelectron spectra. This oxygen-deficiency can be partly replenished by post annealing whereas it can be fully replenished for the sample to which the mechanical polishing is applied beforehand in order to remove the oriented grains. The thickness of aluminum oxide layer was evaluated by means of the impedance measurements using the alternating current three-terminal method.

Resonant photoemission performed at the SRS Daresbury Laboratory is used to investigate the temperature- and doping-dependent spin states in single crystal LaCoO3(111) and La0.9Sr0.1CoO3(111). In an initial study, the surface reactivity of the LaCoO3(111) surface is investigated using H2O as a probe molecule. The results are used to interpret changes which may occur in the spectra as a function of time and temperature in UHV, due to surface reactions. This allows us to distinguish effects on the valence band spectra due to spin changes as a function of temperature. The temperature dependence of low binding energy features primarily associated with Co in the low spin (LS) state in LaCoO3 is investigated in detail. In particular, the intensity and onset energy of the Co 3p→3d resonance associated with these features is measured at small binding energy intervals. Delayed resonance onset associated with the LS state is consistently observed. This is used to locate the separate contributions of the low spin and higher spin states to the low binding energy spectrum. We find the contribution due to the LS state lies around 1 eV to lower binding energy than that due to higher spin states in LaCoO3. In contrast, we find the spectrum of La0.9Sr0.1CoO3(111) to be invariant with temperature, with no delayed resonance effect. The data are discussed in the light of recent models for the spin transitions, including the two stage spin-state model involving an intermediate spin state. Simulation of the temperature variation of the valence band spectra of LaCoO3 using this model provides good agreement with experiment.

Electric field gradients at 117 In(← 117 Cd) nuclei in BaRu 2/3 (M 0.97 116 Cd 0.03 ) 1/3 O 3 (M=Ca, Cd, and Sr) were measured in the temperature range between 4 and 773 K by time-differential perturbed-angular-correlation of the 90-345 keV cascade γ -rays. For each oxide, the quadrupole interaction frequency markedly increases below a specific temperature; the temperatures are between 4 and 77 K for M=Ca, and about 300 and 600 K for M=Cd and Sr, respectively. Combined with the results of the X-ray powder diffraction measurements, it is concluded that a hexagonal-monoclinic structural phase transition, associated with a deformation of MO 6 octahedra, takes place at the temperature.

(Y 1- x Pr x )Ba 2 Cu 4 O 8 compounds with x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7 were synthesized using a high-pressure oxygen technique. The solubility limit x s in this compound system was found to be 0.7. In this composition range, (Y 1- x Pr x )Ba 2 Cu 4 O 8 compounds have the YBa 2 Cu 4 O 8 (124) structure and the lattice parameters a , b and c increase with increasing Pr content x . The superconducting transition temperature T c decreases monotonically with increasing x , and the critical content x c , where superconductivity disappears, has been estimated to be 0.8. There is an obvious effect of Pr substitution on superconductivity, although the effect is smaller in the 124 system than that in the 123 system. X-ray diffraction results suggest that Pr is almost 3+ in this system. A model for the Pr substitution is suggested to make holes immobile to suppress superconductivity as the result of the hybridization of O 2p π with Pr 4f orbitals.

121Sb Mossbauer spectra for ferromagnets, Mn1+x Sb (0.00≤x≤0.22) in e phase were measured at 77 K. The large unique hyperfine magnetic field (H hf=361 kOc) atx=0 tends to decrease and to have a wide distribution with increase ofx. The decreasing ratio of the mean value ofH hf for the nonstoichiometric samples is in accordance with that of their magnetizationM S(x), i.c., the relation\(\overline {H_{hf} } (x)/H_{hf} (0) = M_S (x)/M_S (0)\) holds in this system.

Pr 3d and 4d core levels have been studied for ${\mathrm{Y}}_{0.4}$${\mathrm{Pr}}_{0.6}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{4}$${\mathrm{O}}_{8}$ and ${\mathrm{PrBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ using x-ray-photoelectron spectroscopy to elucidate the valence states. The features of Pr 3d and 4d are close to those for ${\mathrm{Pr}}_{2}$${\mathrm{O}}_{3}$ for both compounds, while they are different from those for ${\mathrm{Pr}}_{6}$${\mathrm{O}}_{11}$. It is concluded that praseodymium is almost trivalent with a 4${\mathit{f}}^{2}$ configuration.

The polarization dependence of x-ray absorption at the oxygen 1 s absorption edge in untwinned LuBa 2 Cu 3 O 7 and PrBa 2 Cu 3 O 7 single crystal specimens was measured. The hole states of oxygen in the CuO 2 plane in PrBa 2 Cu 3 O 7 locate at higher energy position than those of the oxygen in the CuO 2 in superconducting LuBa 2 Cu 3 O 7 , although the hole states of chain sites remain at the same energy position in both Pr123 and Lu123 samples. Although they are mainly of pσ character rather than of pπ and were attributed as an upper Hubbard band, a possibility was pointed out that a trace of pπ character hole states in the CuO 2 plane exists in Pr123. The formation of Zhang-Rice singlet is suppressed by pπ holes in the CuO 2 plane on account of the strong Coulomb interaction on an oxygen site.

The recovery of the electrode conductance for Au metal on YBa2Cu3O7-δ (YBCO) has been investigated. The reduction in the electrode resistance, which is defined as the inverse of the electrode conductance, was measured during heat treatment ranging from 150 to 280° C. The reduction has been characterized by two relaxation processes with activation energies of 0.52±0.04 and 1.40±0.03 eV. The former activation energy corresponds to that of the process in which the oxygen-deficient layer at the YBCO surface is replenished by oxygen diffusion from the bulk, and the latter to that of the process of rearrangement of Au atoms at the YBCO/Au interface which results in improved interconnections between Au metal and YBCO.

Resonant photoemission performed at the SRS Daresbury is used to investigate the temperature- and doping-dependent spin transitions in single crystal samples of the La1-xSrxCoO3 system (x=0, x=0.1). For LaCoO3, the measurements taken over a wide temperature range are interpreted in the light of current models for the spin transitions. The Sr-doped compound is found to be in the same spin state at all temperatures. The temperature dependence of low binding energy features primarily associated with Co in the low spin state is investigated in detail. In particular, the intensity and onset energy of the Co3p→3d resonance associated with these features is measured at small binding energy intervals. This is used to locate the separate contributions of the low spin and higher spin states to these signals. In addition, the surface reactivity of the LaCoO3 (111) surface is investigated using H2O as a probe molecule, and the results are used to interpret changes which may occur in the spectra as a function of time in UHV.