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.     

Reduction of nitric oxide with activated PAN fibres

The reductive removal of nitric oxide from flue gases by reaction with polyacrylonitrile-based active carbon fibres (PAN-ACF) activated with sulphuric acid has been studied at 423–632 K, using a circulating flow reactor. Nitric oxide (0.67 mmol) was completely removed via reduction with 1 g activated carbon under optimum conditions in 210 and 60 min at 423 and 623 K, respectively. N₂ was formed as NO was removed. Some oxygen remained on the carbon surface at 423 K, but was desorbed as CO or CO₂ on subsequent heating to 623 K. The bimolecular reaction of NO reduction over PAN-ACF, and the possible active sites of oxygen surface groups are discussed in the light of a kinetic study and a comparison of the fibre activation at different temperatures.     

Characteristics of porous polymer composite columns prepared by radiation cast-polymerization

Porous polymer composite columns having porous structure were prepared by radiation cast-polymerization of hydrophilic monomers at low temperature and their characteristics were studied. The porosity of the polymer increased with decreasing monomer concentration. The elution time of water in the polymer column increased with increasing monomer concentration and with decreasing irradiation temperature. The elution time was dependent on the degree of hydration of the polymer. The polymer with a degree of hydration of 0.2 to 0.4 gave the minimum elution time. The elution time decreased with the addition of porous inorganic substances.     

Interfacial area concentration in bubbly flow

Interfacial area concentration is one of the most important parameters in two-phase flow. It is related to mass, momentum and energy transfer at the interface. In bubbly flow, it has close relation to bubble diameter. Interfacial area concentration was measured with particular attention to bubble diameter at inlet. The relationship between bubble diameter and interfacial area was theoretically considered. The possibilities of measurement methods of interfacial area concentration with multiprobes were discussed and a preliminary experiment for one of these methods was carried out.     

Valence Band Structure of ZnO (1010) Surface by Cluster Calculation

Discrete variational (DV) Xα cluster method has been employed in calculating electronic structures of ZnO. Electronic structures of the bulk and the non-polar surface model clusters are calculated with inclusion of electrostatic potentials in the bulk and near the surface, and the electronic origins of experimental spectra and chemical bonds at the surface are examined in detail. The valence band structure constructed by Zn-3d and O-2p bands is much influenced by electrostatic potentials in ZnO. It is found that the reduction of an electrostatic potential near the surface gives rise to the difference of the valence band structures between in the bulk and at the surface. The calculated density of states at the non-polar surface of ZnO, where the Zn-3d and O-2p bands are more widely separated than in the bulk, is in good agreement with the experimental UPS. In addition, a Zn-O bond at the surface is found to show stronger covalency than that in the bulk, as a result of the change of the valence band structure due to the effect of the electrostatic potential.     

Eleven phthalate esters and di(2-ethylhexyl) adipate in oneweek duplicate diet samples obtained from hospitals and their estimated daily intake

Plasticizers in duplicate diet samples obtained over 1 week were analysed in order to estimate daily intake. The phthalate esters were as follows: diethyl, dipropyl, dibutyl, dipentyl, dihexyl, butylbenzyl, dicyclohexyl, di(2-ethylhexyl), dioctyl, diisooctyl (mixture of isomers) and diisononyl (mixture). Di(2-ethylhexyl) adipate was also determined. Homogenized samples of composite meals were extracted with acetonitrile, lipids were removed by extraction into n-hexane and the acetonitrile layer was cleaned using FlorisilR and R Bondesil PSA dual layer column. Phthalates were determined by GC/MS (SIM). Phthalate recovery from the fortified food mixture by this method was 62.5-140.8%. Quality assurance as assessed by three laboratories indicated coefficient of variance in the levels of detected phthalates in same lot samples as below 10%. Detection limits were 0.1-23ng/g for each phthalate. One-week duplicate diet samples provided by three hospitals in three remote prefectures of Japan were analysed as individual meals. In all 63 samples, DEHP was present at the highest level among all phthalates in the range 10-4400ng/g. The intake of plasticizers estimated from all samples was 519 µ g DEHP/day, 86 µ g DEHA/day, 65 µ g DINP/day, and 4.7 µ g BBP/day. Calculated DEHP in 2-day samples out of 21 days exceeded EU TDI for a person of 50kg body weight (1850 µ g per day). Disposable PVC gloves used during the preparation of meals were suspected as the source of the high DEHP content. One-day intake of the other phthalates and DEHA was below 7% of TDI in all cases. High concentrations of DEHP (5990ng/g) was found in baby food used in quality assurance work. The source of contamination was the PVC-tube used during production and was effectively reduced by replacing the tube by one made of stainless steel.     

Research on corrugated multi‐louvered fins under dehumidification

To enhance automotive evaporator wet‐fin performances, the main task is to promote the draining of condensed water. An accurate and convenient apparatus estimating the fin performances has been developed. Through the measurement of corrugated multi‐louvered fin performances and the visualization of condensed water draining by this apparatus, it was clarified that fin geometries, surface coating, and evaporator installation strongly contributed to the efficiency of draining and fin performances. © 2001 Scripta Technica, Heat Trans Asian Res, 30(5): 383–393, 2001     

Annealing effect on temperature coefficient of resistivity in La1−xSrxMnO3 ceramics

We investigated annealing effects of La_1?xSr_xMnO₃ (x = 0–0.6) on electrical resistivity and the temperature coefficient of resistivity (TCR). The annealed samples’ resistivity was lower than those of non-annealed samples. For example, annealing changed the resistivity of x = 0.3 at 25 °C from 4.50 × 10^?5 to 3.71 × 10^?5 Ω m. Remarkable difference in TCR was observed after annealing, for x = 0.3, 0.45, and 0.5. For x = 0.3, the TCR after annealing was 4000 ppm/°C, which was 1250 ppm/°C greater than that before annealing. We investigated (1) crystal phase, (2) Mn average valence, (3) Mott insulator–metal transition temperature, and (4) microstructure. The microstructure was remarkably varied for annealed x = 0.3 and 0.5. The average grain size of the x = 0.3 increased from 1.60 up to 2.38 μm. Results show that annealing affects resistivity and TCR because of grain growth during annealing.