Adsorption of carbon dioxide onto BDA-CP-MS41

Carbon dioxide was adsorbed onto mesoporous adsorbent of butylene diamine immobilized CP-MS41 (BDA-CP-MS41), which was synthesized by chloropropyl functionalized MCM-41 (CP-MS41) with butylene diamine in a laboratory-scale packed-bed. The adsorber was operated batchwise with the charge of adsorbent in the range of 1–3 g to obtain the breakthrough curves of CO₂. Experiments were carried out at different adsorption temperatures (20–40 °C) and flow rates of nitrogen (10–20 cm³/min) to investigate the effects of these experimental variables on the breakthrough curves. The deactivation model was tested for these curves by combining the adsorption of CO₂ and the deactivation of adsorbent particles. The observed values of the adsorption rate constant and the deactivation rate constant were evaluated through analysis of the experimental breakthrough data using a nonlinear least squares technique. The experimental breakthrough data fitted very well to the deactivation model than the adsorption isotherm models in the literature.     

Photoreaction of gold ions from potassium gold cyanide wastewater using solution-combusted ZnO nanopowders

Photoreduction of gold ions from potassium gold cyanide wastewater was tried using the ZnO nanopowder which was synthesized by a unique solution combustion method (SCM). The SCM produced instantaneous high pressure and high temperature (1500–1800 °C) conditions which are desirable to obtain high quality ZnO nanopowders, even though it was not intentionally heated at higher than 100 °C during the synthesis reaction. The high crystalline quality of the ZnO nanopowder seemed to result in high efficiency of gold recovery compared to other commercial photocatalysts such as P-25 TiO₂ nanopowder (Degussa). The wastewater contains many kinds of ions such as K, P, Au, Na, Ni, Cu and Zn ions. Only the gold ions were selectively recovered out of these ions. The gold recovery efficiency of the SCM ZnO nanopowder was about 8.6 folds higher than that of the P-25 TiO₂ nanopowder. The very high selectivity of Au³⁺ ions could be explained by the reduction potential which is placed near the edge of valence band.     

Synthesis and characterization of V–C60/TiO2 photocatalysts designed for degradation of methylene blue

C₆₀/TiO₂ and V–C₆₀/TiO₂ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol–gel method. Fullerene had absorptive and semiconducting properties, and vanadium could enhance the photogenerated electron transfer. The V–C₆₀/TiO₂ composite shows a good photo-degradation activity. XRD patterns of the composites showed that the C₆₀/TiO₂ composite contained a mixture of anatase and rutile phase forms while the V–C₆₀/TiO₂ composite contained a typical single and clear anatase phase. The surface properties seen by SEM and FE-SEM present a characterization of the texture on C₆₀/TiO₂ and V–C₆₀/TiO₂ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong V peaks for the V–C₆₀/TiO₂ composite. From the photocatalytic results, the excellent activity of the C₆₀/TiO₂ and V–C₆₀/TiO₂ composites for degradation of methylene blue under UV irradiation could be attributed to both the effects between photocatalysis of the supported TiO₂ and charge transfer of the fullerene, and the introduction of vanadium to enhance the photogenerated electrons transfer.     

Reducing Cr6+ emissions from gas tungsten arc welding using a silica precursor

Hexavalent chromium (Cr⁶⁺) emission from stainless steel welding operations poses a serious threat to worker safety and ambient air quality. In this study, tetraethyloxysilane (TEOS) was used as a silica precursor additive to welding shield gas during gas tungsten arc welding (GTAW) operations to determine the feasibility of using these chemicals for Cr⁶⁺ exposure reduction. Fume aerosol samples were analyzed for Cr⁶⁺ concentration using ion chromatography (IC) and for total Cr by inductively coupled plasma with atomic emission spectroscopy (ICP-AES).At high temperature, silica precursors are pyrolyzed to form amorphous silica (SiO₂) which can condense on the existing metal aerosols. The inert silica layer surrounding the aerosols can prevent further chromium oxidation by insulating chromium aerosols. Experimental results showed approximately 45% Cr⁶⁺ reductions when 3.0% TEOS was added to the shield gas. Nitrate concentration also decreased by 53%, indicating that reactive oxygen species were also reduced. Transmission electron microscopy (TEM) images of collected fume aerosols showed SiO₂ coating on metal particles, verifying the proposed mechanism.     

Kinetics of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics

We did a kinetic analysis of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics using the nonisothermal weight loss technique with heating rates of 10, 20, 30 and 40 °C/min. The weight loss data according to degradation temperature were analyzed by using the integral method based on Arrhenius form to obtain the kinetic parameters. To verify the effectiveness of the proposed kinetic analysis method, the experimental values were compared with those of the numerical integration results using kinetic parameters obtained in this work. It was found that the proposed kinetic analysis method gave reliable kinetic parameters of the thermal degradation of wax materials obtained from pyrolysis of mixed waste plastics.     

High temperature oxidation behavior of Ni-Cr-Al based powder porous metal

This study investigated the high temperature oxidation behavior of newly developed Ni-Cr-Al powder porous metal. High temperature isothermal oxidation tests were conducted at 900, 1000 and 1100 °C temperatures for 24 h under an atmosphere of 79% N₂ + 21% O₂ gas. Oxidation weight gain vs. time curves represented typical oxidation behavior of parabolic shape. Weight gain increased with increasing oxidation temperature. Ni-Cr-Al porous metal mainly created oxides such as α-Al₂0₃, Cr₂O₃, NiCr₂O₄. The α-Al₂0₃ oxide could be still maintained up to 1100 °C oxidation temperature as a thick and stable protective layer. It was noted that Ni-Cr-Al porous metal had better high temperature oxidation resistance than those of other Ni-based and Fe-based porous metals. The catastrophic degradation of oxidation resistance especially at very high temperature was not observed up to 1100 °C in this porous metal. The micro-mechanism of high temperature oxidation of Ni-Cr-Al porous metal was also discussed.     

In-situ deposition of silica layers during the operation of a micro-gas turbine and their effect on the oxidation of superalloy blades

Silica-based oxide layers were deposited in-situ on turbine blades made from Inconel 713 during the operation of a 13 kg_f-class gas turbine, and their effect on the ex-situ oxidation behavior of the blades at 1050 °C was examined. The two turbines were driven by burning liquid petroleum gas (LPG), one turbine at a rotation speed of 35,000 rpm for 4 h (TB04), and the other at 42,000 rpm for 8 h (TB08). For deposition, tetraethylorthosilicate (TEOS) was sprayed into the fuel line immediately ahead of the combustion chamber. The TEOS-to-LPG ratio for TB04 and TB08 was maintained at 5.4 wt. % and 2.3 wt. %, respectively. Directly after operation, the turbine blades were coated with silica layers to a thickness of ∼10 μm, independent of the operating conditions. These oxide layers on the blades provided excellent protection against oxidation during both operation and the ex-situ isothermal oxidation test.     

Structural design of transom pod for outboard motor in polyethylene boat

In a polyethylene boat, a transom pod is subjected to repeated thrust forces generated by an outboard motor. The structural design of the transom pod for the outboard motor must be considered because it is subjected to cyclic bending moments causing thrust forces of the outboard motor. We designed a transom pod reinforced with aluminum alloy plate inside the transom pod in a polyethylene boat and obtained an optimal thickness of the Al alloy plate to ensure the transom pod durability. We then performed a structural analysis for the transom pod reinforced with Al alloy plate and estimated the fatigue life using modified Goodman diagram. The optimal thickness of Al alloy plate was 7 mm.     

Synthesis and characterization of a novel fullerene derivative containing carbazole group for use in organic solar cells

A novel carbazole-group-containing fullerene derivative (CBZ-C₆₀) with good solubility in common organic solvents was synthesized. This derivative was analyzed by using many techniques such as NMR, FAB-MS, FTIR and UV–vis absorption spectroscopy. Further, bulk heterojunction photovoltaic devices were fabricated. Since the LUMO energy level of CBZ-C₆₀ was higher than that of fullerene, the open-circuit voltage (V_oc) of devices based on CBZ-C₆₀ was higher than that of devices based on fullerene. The power-conversion efficiency was highest for devices with composite thin films that have P3HT/CBZ-C₆₀ composition ratios of 1:1 and were annealed at 150 °C for 10 min. The maximum V_oc, short-circuit current density, and PCE of the best device were 0.64 V, 2.32 mA/cm², and 0.48%, respectively.     

Optimum content of Nafion ionomer for the fabrication of MEAs in PEMFCs with spray-coated Pt/CNT electrodes

To enhance the performance of a polymer electrolyte membrane fuel cell (PEMFC), a Pt catalyst was supported on carbon nanotubes (CNTs) and the optimum content of Nafion ionomer in the Pt/CNT electrode was examined by cell performance tests, cyclic voltammetry, and electrochemical impedance spectroscopy. The amount of the Pt catalyst supported on the CNTs was 34 wt.%. The Nafion content significantly changed the protonic and electronic conductivities as well as the mass transfer properties. As such, the performance of the cell was highly dependent on the content of Nafion ionomer. The results of the cell performance tests revealed that the optimum content of Nafion ionomer in the Pt/CNT electrode was about 20 wt.%.