Microstructural hot corrosion behaviour of austenitic Fe-29.7Mn-8.7Al-1.04C alloy in fused Na2SO4 and Na2SO4-NaCl mixture

A short-time hot corrosion test was performed on the austenitic Fe-29.7Mn-8.7Al-1.04C alloy in sodium sulphate at 900°C. The corrosion scales formed on the alloy investigated were studied by scanning electron microscopy and X-ray mapping techniques. The hot-corrosion scales morphology of the austenitic Fe-29.7Mn-8.7Al-1.04C alloy were characterized by the formation of Al₂S₃ and α-MnS sulphides at and beneath the internal alumina scale. No fluxing of the scales was observed. The effect of the addition of sodium chloride to the fused sodium sulphate on the hot corrosion scales morphology was also investigated.     

The inhibition of photochemical smog V. Products of the diethylhydroxylamine inhibited reaction

Mixtures of 1.6–26 mTorr C₂H₄ and about half as much NO and either O or $\text{1}\text{4}$ as much diethylhydroxylamine (DEHA) in 10 Torr N₂, ～ 160 Torr O₂ and 0 or 10 Torr H₂O were irradiated to determine the products of reaction. With DEHA present an initial product was HONO. After a short induction period, CH₃CHO, N₂O, and C₂H₅OH were produced. C₂H₅NO₂, NO₂, and some CO₂ were produced after a longer induction period. The CH₃CHO, HONO, N₂O, C₂H₅NO₂, C₂H₅ONO₂, and C₂H₅OH were not produced in the absence of DEHA. The relative maximum concentrations of CH₃CHO, N₂O, C₂H₅NO₂, C₂H₅ONO₂, and C₂H₅OH were 81, 27, 88, 15, and 1.1%, respectively, compared to the initial DEHA concentration.The reaction of NO₂ with DEHA in the absence of O₂ produced CH₃CHO and HONO as major products and C₂H₅OH and C₂H₅ONO₂ as minor products. In the presence of O₂, C₂H₅NO₂ was also produced.A mechanism for the reaction is suggested. Since the presence of DEHA markedly inhibits the reaction (initial rate of C₂H₄ removal reduced by a factor of 5 and initial rate of conversion of NO to NO₂ reduced by a factor of 20), and the only products of reaction not now found in urban atmospheres are the harmless compounds C₂H₅OH and C₂H₅NO₂, it is recommended that DEHA be considered for addition to urban atmospheres to inhibit photochemical smog production.     

Electrochemical comparison of IrO2 prepared by anodic oxidation of pure iridium and IrO2 prepared by thermal decomposition of H2IrCl6 precursor solution

Surface redox activities, oxygen evolution reaction (OER), oxidation of formic acid (FA), and anodic stability were investigated and compared for IrO₂ electrodes prepared by two techniques: the thermal decomposition of H₂IrCl₆ precursor (TDIROF) and the anodic oxidation of metallic iridium (AIROF). Surface redox activities involved on the AIROF were found to be much faster than those involved on the TDIROF. Concerning the oxygen evolution reaction, both films show a similar mechanism and specific electrocatalytic activities. The situation seems to be different for FA oxidation. In fact, on TDIROF, the oxidation of FA and the OER compete involving the same surface redox couple Ir(VI)/Ir(IV) contrary to FA oxidation on AIROF, where the Ir(V)/Ir(IV) surface redox couple is involved. Finally, electrode stability measurements have shown that contrary to TDIROF, which are very stable under anodic polarization, the AIROF are rapidly corroded under anodic treatment. This corrosion is enhanced even further in the presence of formic acid.     

Strength improvement in silty clay by microbial-induced calcite precipitation

Bulletin of Engineering Geology and the Environment - The application of MICP (microbial-induced calcite precipitation) to clays has been restricted due to their low permeability and small pore...     

Synergistic fire-retardancy properties of melamine coated ammonium poly(phosphate) in combination with rod-like mineral filler attapulgite for polymer-modified bitumen roofing membranes

A novel intumescent (carbonization, acid donor and foaming) fire retardant that mimics carbon nanotubes was introduced into bitumen roofing and characterized using cone calorimetry as the main analytical tool. The experimental results indicate that 18% (by mass) attapulgite mineral (ATTP) mixed with base bitumen decreased the peak heat release rate per unit area (pHRRPUA) by 10%. Further, incorporation of melamine coated ammonium polyphosphate (MAPP) decreased the pHRRPUA by 52% and a mixture of these (3:1, ATTP:MAPP) decreased the pHRRPUA by 25% as compared to adding CaCO₃ as a filler. The residual mass loss after the cone test was also improved with up to 3%. The indication of a positive synergistic flame retardant effect of the ATTP-MAPP mixture is supported by thermogravimetric analysis. The addition of this rod-like mineral improved the general fire retardant properties of the base bitumen and increased the viscosity. Therefore, the polymer-modified bitumen with both fire retardant and rheological properties (providing mechanical strength) is a promising novel approach in the design of bitumen roofing membranes.     

Spark Plasma Sintered Hydroxyapatite/Multiwalled Carbon Nanotube Composites With Preferred Crystal Orientation

Hydroxyapatite (HA) and its nanocomposites reinforced with low loading levels of multiwalled carbon nanotubes (MWNTs) are prepared by spark plasma sintering process. The structure, morphology, and hardness of sintered HA and MWNT/HA nanocomposites are characterized by means of X‐ray diffraction (XRD), scanning electron microscopy and nanoindentation techniques. XRD results show that the orientation of crystallographic planes of sintered HA are highly related to the applied pressure direction. The perpendicular section of sintered MWNT/HA nanocomposites shows predominantly oriented HA a‐and b‐planes while the parallel section displays a dominant c‐plane orientation. The hardness of MWNT/HA nanocomposites improves considerably with increasing MWNT content.     

Hydrothermal synthesis and biocompatibility of hydroxyapatite nanorods

A facile micelle precursor having cyclohexane/ethanol/cetyl trimethyl ammonium bromide/aqueous phase was treated hydrothermally to form nanohydroxyapatite. The synthesized products were characterized by means of X-ray diffraction, thermogravimetric analysis, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the synthesized products display the crystalline structure and vibration modes of hydroxyapatite. Transmission electron micrograph revealed that nanohydroxyapatite exhibits elongated rod morphology with large aspect ratios. Nanohydroxyapatite prepared from a surfactant of 1.25 millimole showed good thermal stability at 1000 degrees C on the basis of thermogravimetric analysis. Simulated body fluid immersion test indicated that an apatite layer can be readily deposited on the nanohydroxyapatite surface demonstrating its good bio-resorbability.     

Radiosensitization of Escherichia coli and Salmonella Typhi in ground beef

The radiosensitization of two pathogenic bacteria, Escherichia coli and Salmonella Typhi, was evaluated in the presence of thyme and its principal essential oil constituents (carvacrol and thymol) in ground beef. Ground beef was inoculated with E. coli or Salmonella Typhi (10(5) CFU/g), and each compound was added separately at various concentrations (0 to 3.5%, wt/wt). The antimicrobial potential of carvacrol, thymol, and thyme was evaluated in unirradiated meat by determining the MIC in percentage (wt/wt) after 24 h of storage at 4 +/- 1 degree C. Results showed a MIC of 0.88 +/- 0.12%, 1.14 +/- 0.05%, and 2.33 +/- 0.32% for E. coli in the presence of carvacrol, thymol, and thyme, respectively. MICs of 1.15 +/- 0.02%, 1.60 +/- 0.01%, and 2.75 +/- 0.17% were observed for Salmonella Typhi in the presence of the same compounds, respectively. The best antimicrobial compound (i.e., carvacrol) was selected and added to the sterilized ground beef along with ascorbic acid (0.5%, wt/wt) and tetrasodium pyrophosphate (0.1%, wt/wt). Meat samples (10 g) were packed in air and then irradiated in a 60Co irradiator at doses of 0 to 0.7 kGy for the determination of E. coli radiation D10 and 0 to 2.25 kGy for the determination of Salmonella Typhi radiation D10. Addition of carvacrol increased the relative sensitivity of both bacteria 2.2 times. The radiation D10 was reduced from 0.126 +/- 0.0039 to 0.057 +/- 0.0015 kGy for E. coli and from 0.519 +/- 0.0308 to 0.235 +/- 0.0158 kGy for Salmonella Typhi. The addition of tetrasodium pyrophosphate did not affect significantly (P > 0.05) the radiosensitization of either bacterium. However, the presence of ascorbic acid in the media reduced significantly (P < or = 0.05) the radiosensitivity of both bacteria. An additive effect of carvacrol addition and packaging under modified atmosphere conditions (60% O2-30% CO2-10% N2) was also observed on bacterial radiosensitization at 4 degrees C. Compared with the control packed under air, modified atmosphere packaging conditions in the presence of carvacrol and tetrasodium pyrophosphate improved the relative sensitivity of E. coli by 2.7 times and Salmonella Typhi by 9.9 times.     

The formation of β‐polypropylene crystals in a compatibilized blend of isotactic polypropylene and polyamide‐6

Compatibilized polypropylene (PP)/polyamide (PA6) blends with and without β nucleating agent (β‐NA) are prepared, and are designated as Blend‐0.3 and Blend‐0, respectively. The melting and crystallization characteristic of the blends crystallized under different cooling rates and different crystallization temperatures are studied. It is observed that high β‐PP content can be developed in Blend‐0.3 only at slow cooling rates (<5°C/min), whereas high α‐PP content is formed at fast cooling rates. Isothermal crystallization analysis of Blend‐0 indicates that PA6 is an effective NA for α‐PP in the lower temperature range, whereas the α‐nucleating effect disappears in the higher temperature range. Blend‐0.3 can, therefore, be viewed as a system containing both α‐ and β‐NAs, simultaneously. PA6 is competing with β‐NA in inducing PP crystallization. Under the normal injection of Blend‐0.3, the melt will be cooled through the higher temperature that favors the effectiveness of β‐NA rapidly because of the faster cooling rate. However, the α‐nucleation effect from PA6 predominate at the lower temperature. This explains the difficulty in obtaining high β‐PP content in Blend‐0.3 from injection molding. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Photocatalytic hydrogen production with nickel oxide intercalated K4Nb6O17 under visible light irradiation

Nickel oxide nanoclusters were intercalated to layered niobate, K₄Nb₆O₁₇, to improve the photocatalytic hydrogen production for water splitting under visible light irradiation. A K₄Nb₆O₁₇–SSRx (Ni/Nb ratio range of 0.8–5%) series of nickel oxide intercalated layered niobates was prepared by a two-step solid-state reaction and characterized by Extended X-ray Absorption Fine Structure (EXAFS), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS), X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet–visible spectroscopy (UV–vis). The photocatalytic reaction was carried out in a quartz reactor irradiated under a 500-W halogen lamp. The K₄Nb₆O₁₇–SSR0.2 catalyst exhibited a much higher photocatalytic activity for water splitting than unloaded K₄Nb₆O₁₇ catalyst and NiO_y/K₄Nb₆O₁₇ catalyst prepared by the conventional impregnation method. The high catalytic performance was attributed to the well dispersed nickel oxide nanoclusters intercalated into the bulk structure of K₄Nb₆O₁₇ catalyst and the lack of NiO particles on the external particle surface.