Applied Mechanics and Materials Vols. 117-119

Abstract: The effect of Sn addition on corrosion behavior of Mg-6Al-1.2Y-0.9Nd alloy in 3.5wt.% NaCl solution has been researched by static corrosion tests, corrosion morphologies observation, microstructure and corrosion scale analysis. The result shows that, with the content of Sn increasing, the corrosion rate decreases at first and then increases. When the addition of Sn is 1wt.%, the corrosion rate is the lowest and the corrosion resistance is improved obviously.

Abstract: To improve the surface hardness，corrosion resistance and wear resistance of the coating substrate, the ternary Ni-W-P alloy coatings were deposited on H12 aluminium alloy by electroless plating. The microstructure, phase transformation, plating velocity and hardness were investigated with X-ray diffraction technique, scanning electron microscope and differential thermal analysis. The results showed that when the PH value of electroless plating solution was 9.0 and the temperature of solution was 85°C, after 3h electroless plating, the substrate was completely covered by Ni-W-P plating, the surface was composed of uniform crystalline grains, their average diameter was about 7μm and they had no obvious defects, the contents of W reached up to 9.60%, and the hardness attained 610HV. In the temperature range of 75-90 °C, the plating rate has been increasing with temperature, when the temperature reached 90 °C, the plating rate reached as high as 13μm / h. When the temperature of heat treatment reached 336°Cfor 1h, the crystallization of Ni3P on the surface began to come into being. The maximum hardness of Ni-W-P plating was up to 920HV after heat treatment at 380 °Cfor 1h.

Abstract: The reinforcement of PLA matrix with natural fibers aims to generate the sustainable biocomposites. Kenaf fiber (KF) and bacterial cellulose (BC) were employed to reinforce and diminish the usage of PLA matrix. Particularly, BC is nano-cellulose which was anticipated to increased interfacial area and therefore low volume fractions of additives. That was consequently to attain mechanical property improvement. Thus, the incorporation of KF and BC reinforced PLA composites was investigated. The extrusion method was utilized and materials were mixed outside prior to adding. The specimens were examined mechanical testing, Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermo Gravimetric Analysis (TGA) and Scanning Electron Microscopes (SEM). The mechanical study revealed that the increment of elastic modulus increased concomitantly with the augmentation of KF content. Interestingly, PLA/KF/BC sample at ratio of 60/39/1 wt.% was efficiently to maintain tensile and flexural strength comparing to 50% reduction of without BC sample with equal fiber volume. Therefore, it could recognize that mechanical properties was improved by using low amount of nano-cellulose. This would be a high aspect ratio of BC that capable to connect between PLA matrix and KF which enhanced a large contact surface and therefore excellent coherence. The temperature dependence of storage, loss and tan delta was determined by DMA. A decrease of storage modulus was consistent with increasing of temperature, result from softening of the composites. Loss modulus was increased approximately at T_g which related to storage modulus cause. In addition, the tan delta peaks of PLA and composites were around 60°C and it did not significantly shift when emerged of fiber. DSC of both composites indicated an influence of fiber on the crystallization and enthalpy. On the other hand, glass transition and melting temperature did not significantly affect. The composites exhibited a small reduction of thermal stability when examined by TGA analysis. Notwithstanding, BC showed an improvement of thermal stability of PLA/KF/BC sample at 40 wt.% total fiber content. The linkage of BC between PLA matrix and KF was monitored by SEM.

Abstract: The development of new alternative type of fly ash bricks using the locally available local soil from Ratchaburi province were mixed with fly ash from Kanchanaburi province, where both sources in western of Thailand, is the main purpose of this study. These are compared to the ratchaburi local soil cement bricks without the mixing of western fly ash in different proportions. It is concluded that the addition of western fly ash reduces the thermal conductivity. The compressive and flexural strength decrease when the ratio of western fly ash is more than 30 percentages. However, considering the various factors it can be concluded that appropriate ingredient toward producing the good commercial western fly ash bricks is 5 percentages of portland cement and 30 percentages of western fly ash by weight basis of ratchaburi local soil. The compositions of western fly ash at more than 25 percentages by weight basis of ratchaburi local soil and since up to 14 days of curing time are proved to be economical mixtures for load bearing panels or brick type structural elements according to the Thai Industrial Standard for structural clay load-bearing tile.

Abstract: Fair-faced light weight aggregate (FLWA) concrete is of good performance. There is a fluorocarbon coating on its surface. This paper studies on how vibration time influences FLWA performance and how this paint influences FLWA durability.

Abstract: A bifunctional reagent of terephthaloyl chloride was initially adopted as a spacer reagent to prepare the bonded types of chiral stationary phase (CSP) with cellulose derivatives. (3,5-dimethylphenyl)carbamates of cellulose (CDMPC) regioselectively bonded to small pore (3-aminopropyl)silica gel (APS) were prepared with terephthaloyl chloride as a spacer at the 6-position of the primary hydroxyl group on the glucose unit of cellulose. Enantioseparations of five racemic samples are evaluated on the prepared CSP under normal-phase high-performance liquid chromatographic mode with hexane- isopropylalcohol as the mobile phase. The influence of flow rates and mobile phase compositions on the resolution were investigated. The prepared stationary phase was exhibited an effective chiral recognition.

Abstract: Galvanizing method is being widely used to the numerous constructional steels such as a guard rail of high way, various types of structural steel for manufacturing ship and for some other fields etc.. However, galvanized structures inevitably may be corroded rapidly with increasing exposed time because the rate of environmental contamination is accelerating due to the rapid development of industrial society. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment etc.. In this study, three types of the test specimens, that is, pure galvanizing, galvalume and chromate treated steels were immersed at inhibitor solution. And the effect of inhibitor for their corrosion resistance improvement was comparatively investigated with an electrochemical method. Corrosion current density of the original galvanizing and galvalume steel exhibited the highest and lowest value respectively in seawater. However, the corrosion resistance of these samples was considerably improved by dipped to a inhibitor solution(H3PO4+ Zn(NO3)2+Q). In particular, the galvanizing steel which dipped to the inhibitor solution exhibited the lowest corrosion current density due to the best effect of corrosion resistance improvement compared to other test specimens.

Abstract: A complex of Cu(II) with 1-(6-hydroxynaphthalen-2-yl) butane-1,3-dione (HNBD) was synthesized and characterized by elemental analysis, IR, UV and TG-DTA techniques. IR spectra as well as UV-visible absorption measurements indicated that Cu(II) ion was coordinated to the HNBD ligand. The TG-DTA curves showed that the thermal decomposition for Cu(II) complex was a three-steps process. At first, the complex had a mass loss of water molecules at temperature below 134°C, then the thermal decomposition of the anhydrous complex was a two-stage process, which corresponded to the loss of two naphthol molecules and the oxidative decomposition of other organic fragments of ligand. The final decomposition product of the complex was CuO.

Abstract: Konjac glucomannan (KGM) gel was prepared by alkali catalyzed in aqueous solutions. The structure of the KGM gel was characterized by Fourier transform infrared (FTIR) spectroscopy and wide angle X-ray diffraction (WAXRD). The gel point of KGM solutions was determined by steady state fluorescence method and It was observed that the gel point of the KGM solutions depend on the concentration of KGM, pH value and temperature effectively. The results showed that the molecular chain structure of KGM gel is more regular than that of the pure KGM.

Abstract: The influence of oxidation behavior on super-plastic microforming of bulk metallic glass Zr₆₅Cu_17.5Ni₁₀Al_7.5 in the super-cooled liquid region was investigated. Samples were heated in air from room temperature to 395°C, 410°C, and 430°C, respectively, and kept under each temperature for 40 minutes. The increased weight of samples and the thickness of oxide layer were measured. Subsequently, the sample was compressed under 410°C with a micro gear silicon mold. In result, the oxide layer of the gear cracked and could be easily removed; also, the X-ray diffractometer showed that the gear core below the oxide layer remained an amorphous structure. It can be concluded that the oxidation behavior of Zr₆₅Cu_17.5Ni₁₀Al_7.5 does not affect the super-plastic deformation, which indicates the feasibility of super-plastic microforming process in air.