Materials Science Forum Vols. 620-622

Abstract: A lignin-quaternary adsorbent was made from lignin after phenolization and then amination. As-prepared adsorbent was characterized by SEM, IR and DMA. Effects of adsorbent dose, initial pH and concentration on 2, 4, 6-Trinitrotoluene (TNT) removals from aqueous solution by adsorption of this adsorbent were comprehensively investigated. IR spectra showed that the product comprises quaternary ammonium groups in the form of ether bond. The mechanical strength of the adsorbent is enhanced by combining of PVA. It was possible to remove 66% of TNT from aqueous solution with 0.1 g of the adsorbent under certain conditions (100 mg/L and 25 °C). The results indicated that the amount of TNT adsorbed onto the adsorbent increased with increasing initial concentration; however, it decreased with an increase in pH. The adsorption process was determined to be consistent with the Langmuir isotherm.

Abstract: The local wastes, which are sources of SiO2, Al2O3 and CaO, are rice husk ash, waste sediment from aluminum anodizing process and dreg from pulp production, respectively. The wastes are mixed in three different compositions in ranges of 20-50 SiO2, 20-35 CaO and 20-45 Al2O3, wet milled, slip casted and then fired at 1,100 °C. Characterization of the fired bodies reveals the formation of calcium-aluminosilicate compounds: gehlenite and anorthite as major phases, in accordance with the SiO2-CaO-Al2O3 ternary diagram. Their bulk densities and % water absorption lies between 0.95-1.42 g/cm3 and 37.40-67.95%, respectively. While flexural strength and coefficient of thermal expansion are between 4.09-9.56 MPa and 6.14 - 10.1 x 10-6 °C-1, respectively. By simple thermal conductivity comparison, the materials themselves have thermal conductivity comparable to alumina ceramics. These wastes, therefore, may be used as precursors for the production of some insulating refractory members, in place of minerals from natural resources.

Abstract: This research was conducted to investigate the application of the novel upflow-type filtration device using hydrophobia media made of expanded polypropylene (EPP) from driveways site. The higher level of motorway-derived heavy metal contamination exists in stormwater runoff from a road section and the heavy metal levels were higher than the regulated Korean environmental guideline in lake and river. For Cd, Cr, Cu, Pb and Zn, the influent event mean concentrations (EMCs) during 8 storm periods were 2.75, 37.3, 90.5, 118.5 and 546.5 µg/L, respectively. The novel upflow-type filtration device with main mechanism of filtration and adsorption showed removal (>91%, >93%, >85%, >91% and >80%) of the studied heavy metals (Cd, Cr, Cu, Pb and Zn) and differences of medians of removal efficiencies among heavy metals were not statistically signficant by Kruskal-Wallis test (p>0.05) during 8 storm events. It is found that EPP media is very effective at the removal of the heavy metals, and the magnitude of heavy metal removal in a decreasing order is Cr, Cd, Pb, Cu and Zn.

Abstract: Eco-debinding process using supercritical extraction of low molecular organic binders in nano-porous ceramic bodies was examined. The debinding properties related to structural changes during supercritical extraction and conventional solvent extraction were also compared. The debinding rate of supercritical extraction was significantly enhanced compared to the debinding rate of solvent extraction because of the high diffusivity of the supercritical carbon dioxide for the low molecular weight wax binder in the molded bodies with nano-sized pore structure, although both debinding rates showed same a square root of time dependence. The extraction rates with morphological changes varied depending on the degree of saturation at the end of debinding stages. Both the debinding methods experienced morphological changes with a debinding front separating the pendular state region from the undebinded region with fluid state in low molecular paraffin wax based powder compacts during extraction. The capillary structural changes in the green bodies caused severe defects during extraction and degraded the physical properties. In spite of the abrupt changes of the capillary structure, the debinding defect was significantly alleviated for the supercritical debinded ceramic bodies, compared to the solvent extracted bodies.

Abstract: A novel thermoplastic konjac glucomannan(TKGM) was synthesized with KGM and methyl acrylate(MA) initiated by ammonium persulfate. The percentage grafting (PG) and the grafting efficiency (GE) was affected by concentration of initiator and monomer, temperature, and time. The results indicated that the percentage grafting (PG) and the grafting efficiency (GE) can attach 70% and 90% at optimal conditions, respectively. The structure and properties of TKGM were characterized by FTIR and DSC. FTIR results demonstrated that graft copolymerization was occurred between MA and KGM. The results of DSC indicated that a new glass transition temperature (Tg) of TKGM at 16.4°C was appeared compared with KGM with no glass transition temperature. It suggested that product of TKGM can be made through thermoplastic process.

Abstract: Wood is one kind of renewable natural eco-material. Glued laminated timber (glulam) is an engineered wood product made from sawn lumber lamina glued together in horizontal layers. The application of glulam in the construction structure not only has great environmental value, but also reduces energy consumption and carbon emission of the construction. In this study, we evaluated the effects of different factors on the structural properties of glulam and designed several enhancement modes to reinforce the glulam with FRP (Fiber Reinforced Plastic). Then, we measured the mechanical properties of the glulam specimens in the different enhancement modes and selected the optimal reinforcement mode. The reinforcement method obviously increased the value of MOE and MOR of poplar glulam by 5%-15% and 5%-12% respectively. FRP length of 600mm was the optimal and most economic reinforcement length, and finger joint position of 300mm is the optimal position.

Abstract: In this paper, the production technology of laminated veneer lumber was optimized by using the uniform design method. The effects of production technology, such as the press duration, the press temperature, the press pressure and the adhesive spread, were found statistically significant on some mechanical properties of LVL. So in this paper, the thickness of LVL board was a fixed value, but the press duration, the press temperature and the adhesive spread were variable. The modulus of elasticity (MOE) and static bending strength (MOR) as predicted by the ANN approach and the regression functions were compared with the experimental values. It was shown that the proposed neural network model was able to predict valuable mechanical properties, such as the modulus of elasticity and static bending strength, that would facilitate the development of optimum design of properties for manufacturing high quality materials.

Abstract: The objective of this study is to develop a novel powder activated carbon (PAC) by surface modification with magnetite nano-particles for enhanced removal of NOM in water. The PAC used for experiment was two types, SAC (wood-based) and MAC (coal-based). First the PAC was treated by heat at 650 or 900 °C for 1hr under N2. And then the PAC surface was synthesized with magnetite nano-particles at the same condition. Adsorption tests of NOM were carried out to identify functional characteristics of the surface modified. Despite reduced surface area, adsorption capacity of the surface modified PAC was comparable to the virgin one. However much increased adsorption capacity was obtained by heat treatment of the PACs. SEC and SUVA254 results showed no specific selectivity in removal of NOM by the modification of PAC surface characteristics. Enhanced oxidation of the NOM was also observed by the magnetite nano-particle synthetic PACs in contact with ozone. Conclusively the surface modification of the PAC has high potential as a novel adsorption material for advanced water treatment.

Abstract: For non-SF6 process and melt cleanliness, CaO added AZ31 Mg alloy has been developed for strip casting. Mg alloys were usually ignited during conventional casting, the continuous casting and strip casting. Protective gases should be used in order to prevent the ignition of Mg alloys during melting and casting processes. However, protective gases have the disadvantages of global warming potential, high production cost and corrosion of steel based equipments. To solve ignition problem and overcome environmental issue, this paper discussed the effects of CaO addition and amount on strip casting process in terms of non-SF6 process and melt cleanliness.

Abstract: In the present work, the effect of Sn addition on the corrosion behavior of Mg–5Al–1Zn alloys was investigated. Microstructure, potentiodynamic polarization and immersion tests were carried out in 3.5% NaCl solution of pH 7.2 to estimate the corrosion behavior of AZ51 alloys with and without Sn addition. Mg17Al12 and Mg2Sn phases were mainly precipitated in inter-dendrite structures. With increasing the Sn content, the volume fraction of the Mg2Sn phase was increased and coarsening tendency was observed. The corrosion resistance was increased by Sn addition. Especially, the AZ51-5wt.%Sn alloy characterized the superior corrosion resistance among the four alloys. The Sn is known for a high hydrogen overvoltage and the secondary phases effectively formed the network structure, resulting in a drastically decreasing corrosion rate of AZ51 alloy.