Partial Oxidation of Methane to Synthesis Gas Over Ru-Loaded Y2O3 Catalyst

Ru-loaded Y₂O₃ catalyst was investigated for the partial oxidation of methane to synthesis gas. Ru(0.5 wt%)/Y₂O₃ catalyst afforded a high CH₄ conversion of 27% at a CH₄:O₂ ratio of 5 to give nearly a 1:2 ratio of CO and H₂ with a selectivity of 75% at 873 K. Ru(0.5 wt%)/Y₂O₃ catalyst maintained high catalytic activity over 10 h in the partial oxidation of methane. Carbon deposition of the catalyst surface in the reaction of CH₄ was examined by thermogravimetric analyses, and it was found that no carbon deposition occurred on the Ru(0.5 wt%)/Y₂O₃ catalyst. The synthesis-gas production proceeded basically via a two-step reaction consisting of methane combustion to give H₂O and CO₂, followed by the reforming of methane from CO₂ and steam.     

Effect of a low-fat diet enriched with oleic acid on postprandial lipemia in patients with type 2 diabetes mellitus

The aim of the present study was to compare the effects of a low-fat diet enriched with oleic acid to those of a low-fat diet enriched with linoleic acid on fasting lipids, postprandial lipemia, and oxidative susceptibility of low-density lipoprotein (LDL) in patients with type 2 diabetes mellitus (DM). In a 3-wk randomized crossover study, eight patients with type 2 DM were given an experimental low-fat diet enriched with either oleic acid or linoleic acid. The oleic-acid-enriched diet contained 5, 15, and 5% energy from saturated, monounsaturated, and polyunsaturated fatty acids, and the linoleic-acid-enriched diet contained 5, 5, and 15% energy from saturated, monounsaturated, and polyunsaturated fatty acids, respectively. In addition to evaluating the fasting lipids and oxidative susceptibility of LDL, we evaluated postprandial lipemia using an oral fat load at the end of each 3-wk dietary phase. There were no significant differences in fasting lipid profile or lag time of LDL oxidation between the two experimental dietary phases. The average and maximal increments of remnant-like particle (RLP) cholesterol levels during oral fat load were significantly higher after the oleic-acid-enriched dietary phase than after the linoleic-acid-enriched dietary phase. The area under the curve of RLP cholesterol was also significantly larger after the oleicacid-enriched dietary phase than after the linoleic-acid-enriched dietary phase. These results suggest that the oleic-acidenriched diet was associated with increased formation of postprandial chylomicron remnants compared with the linoleicacid-enriched diet.     

Anomalous oxide scale formation under exposure of sodium containing gases for solid oxide fuel cell alloy interconnects

Reactivity of oxide scale on Fe-Cr alloy with Na-containing gases was examined to estimate the stability against sodium (Na): vapors of NaCl and Na₂SO₄ exposures with air flow at 1073 K. The identified reaction phases were Cr-Mn spinel, Cr₂O₃, and alloy from the X-ray diffraction of surface with no Na-reaction products. However, the protective oxide scales (Mn-Cr spinel and Cr₂O₃ layers) on the Fe-Cr alloy were partially decomposed by reacting with Na to form Na-compounds inside the oxide scale/alloy interfaces. In some parts, anomalous oxide scales were found around the oxide scale/Fe-Cr alloy interfaces, with forming Na-rich compounds: the compounds were distributed inner parts of oxide scales around oxide scale/alloy interfaces. The stability of oxide scales and degradation were discussed based on the observed distribution of elements.     

Liquid-Phase-Assisted Sintering of Calcium-Doped Lanthanum Chromites

Investigations have been made on the low-temperature sinterability of calcium-doped lanthanum chromites which are to be used as interconnectors in solid oxide fuel cells (SOFCs). Nominally chromium deficient lanthanum calcium chromites (La_0.7Ca_0.3Cr₁-_yO₃, y = 0.02) were found to be sinterable to 94% theoretical density at 1573 K in air, whereas no densification was observed for samples with y = 0. The two-step shrinkage process suggests a liquid phase sintering mechanism with calcium oxychromates playing an important role as the liquid phase. After sintering at 1573 K, calcium-rich substances remained at grain boundaries.     

TEM,XPS and SIMS Analyzes on Grain Boundary of Lanthanum Chromites

The morphological characteristics, chromium valence state, and cation transport in the vicinity of grain boundary in La_1-xCa_xCrO₃ were investigated by using TEM/EDS, XPS and SIMS techniques. The width of grain boundary was around 1 nm where anomalous enrichment of calcium was observed. Higher valence state of chromium such as Cr⁶⁺(d⁰) was detected in the grain boundaries whereas Cr³⁺(d³) and Cr⁴⁺(d²) were dominant in the bulk. Very fast interdiffusion of alkaline earths was observed in the Sr²⁺-La_0.75Ca_0.25CrO₃ system. All observed phenomena were correlated by assuming the A-site vacancy which may be induced by the formation of Cr⁶⁺ at grain boundaries.     

Carbonization of adamantane to a graphitizable carbon

Adamantane was carbonized in sealed tubes to 1073 K. Despite the non-planar molecular structure of adamantane, the resulting carbon was graphitizable. Using i.r. and u.v. spectrometry, mass spectrometry and X-ray diffraction, it was found that adamantane begins to decompose at ≈ 823 K to yield such planar molecules as phenanthrene, methyl-phenanthrene and pyrene. These molecules lead to a graphitizing carbon through a carbonization process which is similar to that of a pitch.     

Numerical and Experimental Study on Residual Stress in Gray Cast Iron Stress Lattice Shape Casting

The prediction of residual stress in a stress lattice shape casting (stress lattice) has been conducted and discussed by some researchers via the Finite Element Method (FEM). However, most of the previous studies used the first-order tetrahedral element, which has poor analysis accuracy in problems including bending. The use of the first-order tetrahedral element makes the verification of these studies uncertain because the bending deformation essentially occurs in the stress lattice casting. This study first shows that the thermal stress analysis for the stress lattice should use the element that can represent the bending deformation in principle for bending of the thin parts. Second, the simulated residual stress was compared with the measured value. The thermal stress analysis successfully predicted the residual stress of the stress lattice casting with and 11 pct difference. In addition to the prediction of the residual stress, it is important from the viewpoint of the productivity of castings to reveal the effect of the shake-out temperature on the residual stress. However, in the previous studies, conclusions concerning the effect of the shake-out temperature on the residual stress were not consistent (i.e., the one study said the higher shake-out temperature decreased the residual stress, and another study said a higher shake-out temperature increased the residual stress). Therefore, the current study first discusses the reason for the inconsistent conclusions in the previous studies. Second, stress lattice castings were cast and shaken out at various shake-out temperatures. Then, the current study validated the effect of the shake-out temperature on the residual stress. Consequently, the experimental results supported the conclusion of Kasch and Mikelonis that the shake-out at higher temperature contributed to the increase of the residual stress in the casting.