Advanced Materials Research Vols. 47-50

Abstract: The Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 powder synthesis through molten salt method was investigated in the temperature range of 650 ~ 700°C for 2 ~ 4h. The XRD results indicated that the optimal synthesizing temperature for molten salt method was 700°C, significantly lower than that for conventional processing route of solid state reaction method, where a calcining temperature of 850°C was needed. The SEM results revealed better crystallization of the powders obtained through molten salt method, compared with those through the conventional processing route of solid state reaction method.

Abstract: Large density of the dispersed phase in magnetorheological (MR) fluids has hindered operating MR test and their industrial application. This present work adopted Fe3O4 nanoparticles to prepare MR fluid because of their moderate density and good magnetic property. Furthermore, in order to resolve aggregation problem of Fe3O4 particles due to their nano-scaled size, conducting polypyrrole (PPY) was synthesized around naono-sized Fe3O4 particles via conventional oxidation polymerization. Weight ratio of PPY to Fe3O4 was adjusted to be 5% to avoid possible deterioration of the magnetic property of Fe3O4 particles. TEM images described the morphology for PPY-Fe3O4, and XRD pattern provided information on structural characterization and particle size. Finally, MR performances of pure Fe3O4 and PPY-Fe3O4 nanocomposites were investigated via rotational and oscillatory tests.

Abstract: The influence of carboxymenthylchitosan(CM-chitosan) on the corrosion of mild steel in different pHs was studied by the quantum chemical calculation and electrochemical measurements. Mulliken atomic charges and LUMO energies calculated by DFT method for CM-chitosan and protonated CM-chitosan show that the protonated CM-chitosan adsorbs easier on the surface of mild steel. The expeimental results of polarization curves and electrochemical impedance spectroscopy (EIS) also indicate that the acid media has the best inhibition efficiency for CM-chitosan. Furthermore, the inhibitive effect of CM-chitosan for mild steel in 1 M HCl solution was studied by weight loss measurements, and the inhibition efficiency increases with the concentration of CM-chitosan to attain 93 % at 200mg/l.

Abstract: We have successfully developed a multifunctional ceramics, europium-doped feldspar MAl2Si2O8:Eu (MASE, M=Ca, Sr, Ba) and demonstrated that MASE was able to emit high mechanoluminescence (ML), strong photoluminescence (PL) and electroluminescence (EL). According to the XRD measurement result, the space group of MASE was identified to P1 .The ML intensity increased proportionally with the increase of the compressive load, which suggests an efficient conversion of mechanical to optical energy. Furthermore, strong PL and EL emission from MASE were confirmed. The PL, ML, and EL spectra were found to be similar in both peak shape and position, which indicates all the emissions result from 5d-4f transition of Eu2+.

Abstract: Calcium sulfate used in this study is newly fabricated to overcome its disadvantages; brittleness, difficult handling properties, rapid resorption and reaction heating. Especially when calcium sulfate is used in the graft procedure, it is difficult to control the setting time, solubility into blood and body fluid. To improve the handling properties, Calcium sulfate is mixed with Carboxylmethylcellulose (CMS). The putty type calcium sulfate used in the present study presented lower values in cementum formation and new bone formation than the control group. This may be due to use of poor osteoinductive calcium sulfate alone in the defect, limiting new bone formation. In addition, complete resorption of calcium sulfate after 8 weeks presents that addition of polymer failed to delay the resorption rate of calcium sulfate. Rather, it seemed to disturb the natural healing of the defect when compared with the findings in the control group. But the favorable result of calcium sulfate is shown when used with alloplast. The material used in the present study was developed for easier formability and manipulation avoiding scattering or dissolving of the material with blood or body fluid. However, the results reveal that further studies on effect of calcium sulfate with various other bone graft materials and ideal ratios in mixing the two should be determined in the future.However, the results reveal that further studies on effect of calcium sulfate with various other bone graft materials and ideal ratios in mixing the two should be determined in the future.

Abstract: Tapping is a technique commonly employed to make internal threads in the fastening industry. However, sudden breakage of tool bits is the most undesirable event often encountered during thread tapping. In particular, this can most readily occur when making internal threads in blind-holes, especially holes smaller than M6. As such, any effort to prolong the life of the tap is both necessary as well as urgent. The present study tried to use the high frequency vibration generated by a piezoelectric actuator to make threads for the titanium alloy. The thread tapping process was analyzed in detail, involving the Taguchi experimentation method, in which an orthogonal array table, L3(34),was employed to design the experimental runs for use in this study. The effects of interacting processing parameters including the frequency of vibration, vibration amplitude, spindle revolution speed and cutting fluid used on the performance of the tapping process were examined. The result was compared with no ultrasonic-assisted tapping.

Abstract: This paper presents a solution of the vibration reduction in driving automotive shafts. Generally, vibration modes in automotive driveshafts are divided into the bending and torsional vibrations. However, the bending vibration is more dominant factor when it excites with the resonance frequencies in automotive driveshafts. In this paper, the vibration damping structure of automotive driveshaft is introduced by incorporating piezofiber composite structure, which is also called as MFC (Macro Fiber Composite). The MFC is an innovative actuator that offers high performance and flexibility than other piezo-materials, so it is the best candidate of actuator to apply to the curved surface of shaft. In order to simulate the bending vibration reduction in the automotive shaft, analytical model based on cylindrical shell theory was developed. Moreover, Finite Element Analysis (FEA) using the piezoelectric-thermal analogy technique was conducted to confirm the analytical results and demonstrate the vibration reduction performance. The effect by the polarity of MFC on the vibration damping is also studied to find the best combination of MFC activation. Thus, the results showcase the optimal vibration damping capabilities using MFC in automotive driveshafts, and provide an outlook for the active damping control using the multi-mode resonance controllers.

Abstract: The graphite nanofiber (GNF) and carbon black filled high-density polyethylene (HDPE) hybrid nanocomposites were prepared by solution mixing and melt blending techniques. The effect of addition of GNF on the positive temperature coefficient (PTC) behavior of the nanocomposites was investigated. The incorporation of small amount of GNF into HDPE/CB composites showed a significant improvement in PTC intensity and repeatability of the hybrid nanocomposites. The maximum PTC intensity was observed for the HDPE/CB/GNF (80/20/0.25) nanocomposite with a relatively low room temperature resistivity.

Abstract: A series of nanocomposite (NC) hydrogels were synthesized by in-situ polymerization of acrylamide (AAm) monomer using laponite XLS clay as a crosslinker. This paper focused on water absorbency of the NC hydrogels with various clay contents, at various pH values and ionic strengths. The influence of pH value on swelling behaviors showed that a maximum swelling ratio was observed at pH 11. The swelling abilities of the NC composites decreased in saline solution strength. Heat treatment of NC hydrogels improved the swelling capacity of the hydrogels.

Abstract: A series of aqueous solutions of blends based on polyethylene oxide (PEO) and hydroxypropyl methyl celloulose (HPMC) were prepared. The solution of the blends thus obtained was analyzed for miscibility. The effects of compositions of blends and temperature (30 and 500C) on miscibility have been reported. The Huggin plots deviate from linearity according to the degree of compatibility of PEO/HPMC blends at entire concentration range. Interaction parameters have been evaluated for all blends to probe the miscibility. The blends were also characterized by sophisticated techniques such as FTIR, DSC, TGA and SEM.