Study of the electroluminescent properties of crystalline silicon wafers in devices based on junctions of indium-doped zinc oxide and porous silicon

In this study we obtained electroluminescent devices (ELD) based on junctions of indium doped zinc oxide (ZnO:In) and porous silicon layers (PSL). The PSL were obtained by electrochemical etching with different types and resistivities of silicon wafers. In the visible part of the electromagnetic spectrum, the porous silicon (PS) exhibits photoluminescence (PL) that is centered around 680 nm. Once the devices were obtained, they were optically and electrically characterized. The PSL were coated with ZnO:In film, which was gotten by the ultrasonic spray pyrolysis technique (USP). When the devices were electrically polarized they showed optical response in the regions corresponding to the visible and infrared band of the electromagnetic spectrum. The observed electroluminescence (EL) in the visible region goes from 400 to 750 nm and the corresponding emission of the infrared part is around 750–1150 nm. The devices presented luminescent spots on the surface which were visible to the naked eye. The analysis of the results shows that the emission source in the visible part is attributed to the filaments present in the PS, and also to the ZnO:In films and the emission in the infrared part is associated to the silicon substrate. The electrical characterization was carried out by current–voltage curves (I–V) that show in the devices a rectifying behavior.     

Investigation of the protonic conduction in Sm doped BaCeO3

In the present work the structural and electrical properties of samarium-doped barium cerate perovskites of BaCe_1−xSm_xO_3−δ formula (with x = 0–0.2), prepared by following the solid state reaction method, are investigated. The crystal structure and microstructure of the samples is determined by employing the techniques of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). According to the XRD analysis at 0 ≤ x ≤ 0.2 the formed continuous series of BaCe_1−xSm_xO_3−δ solid solutions have the structure of cubic perovskite with orthorhombic distortions. It was found that the relative density of the samples is ∼87% for 0.02 < x < 0.05 and ∼94% for 0.05 < x < 0.25. It was also found that the highest conductivity is observed for x = 0.15. Finally, the thermal expansion of BaCe_1−xSm_xO_3−δ (x = 0–0.2) is studied and the thermal expansion coefficients for the high temperature region are calculated.     

Failure analysis of a boiler tube in USC coal power plant

This paper presents failure analysis of final superheater tube in ultra-supercritical (USC) coal power plant. Visual inspection was performed to find out the characteristics of fracture of the as-received material. And the micro-structural changes such as grain growth and carbide coarsening was examined by scanning electron microscope. Detailed microscopic studies were made to find out the behavior of the scale exfoliation on the waterside of tubes. From those investigations, the creep rupture may be caused by the softened structure induced by carbide coarsening and accelerated by the metal temperature increase by the impediment of heat transfer due to voids.     

Passivation techniques to prevent corrosion of iron sulphides in roofing slates

The aim of the present study was to evaluate the efficacy of different methods of sulphide microencapsulation in terms of inhibiting sulphide oxidation in roofing slate. For this, a preliminary test was carried out with ground pyrite and the methods that provided the best results were applied to samples of roofing slate. Protection against oxidation was measured by the amount of iron released after enforced oxidation with H₂O₂ in the tests with pyrite, and by thermal cycle alteration, SO₂ and saline spray tests (EN 12326-2:2000 and EN 14147:2004) in the tests with the slate samples. The results indicate that treatments with potassium phosphate and potassium silicate, proposed for controlling acid mine drainage, were the most effective at protecting pyrite against oxidation, and that these methods are also effective when applied to slate.     

Effect of oxide film on oxygen reduction current for the platinum-cobalt alloy electrodes in PEFC

Effect of surface oxide on Pt-Co alloy electrodes on the oxygen reduction reaction (ORR) was investigated in 0.5 M sulfuric acid solution by electrochemistry, ellipsometry, laser Raman scattering spectroscopy, and XPS. The oxide as thick as 1-2 nm increases the overpotential of ORR and falls down efficiency of PEFC. The thickness of the oxide films is precisely determined by ellipsometry. The oxide film 1.9 nm thick was formed on Pt-50 mol% Co electrode by constant potential oxidation at 1.20 V and the film 1.5 nm thick remains on the electrode at 0.6 V at which ORR already starts. The remaining oxide decreases the current density of ORR and increases the overpotential. On pure Pt electrode, the similar influence of the oxide film was observed.     

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.     

乙二醇后部再沸器封头开裂原因和处理办法

对环氧乙烷乙二醇装置后部再沸器封头应力腐蚀开裂的原因进行了分析,提出了处理办法。     

Distribution of oxide inclusions in H13 castings under super-gravity field with multi-stage rotation speeds

The 42 kg industrial H13 castings were prepared by different super-gravity fields with multi-rotation speeds,and the distribution of oxide inclusions in the castings was studied.In addition,the inward movement Reynolds number and inward movement time of oxide inclusions as well as the solidification time of molten steel at different positions in the castings were calculated to clarify the removal mechanism of oxide inclusions in super-gravity field.The results show that the large size(i.e.,greater than 10 μm)oxide inclusions are mainly concentrated in the inner and outer parts of the super-gravity castings with constant rotation speed(500 r min-1)and five-stage rotation speeds(500,600,750,850,and 950 r min-1),respectively,while there are no large oxide inclusions in the super-gravity castings with three-stage rotation speeds(500,600,and 750 r min-1).Although an increase in the particle size of inclusion and the rotation speed in super-gravity field is conducive to the increase in the inward movement Reynolds number of oxide inclusions and reduction in the inward movement time of oxide inclusions,it will reduce the local solidification time of molten steel.In the range of the rotation speed studied,the super-gravity field with three-stage rotation speeds has the best effect on the removal of inclusions in H13 molten steel.