Advanced Materials Research Vols. 26-28

Abstract: Catalytic grown carbon nanofibers have been obtained from decomposition of ethanol over copper plate. Ferric chloride of different concentration was employed as the catalyst precursor. Scanning electron microscopy has shown that different morphologies of carbon nanofibers can be obtained by using different concentration of catalyst precursor solution. The results from the Raman spectroscopic characterization have also demonstrated that the graphitization of carbon nanofibers can be tailored by control of the concentration of catalyst precursor solution. When the information from these characterization are combined with that of the associated morphologies of the carbon nanofibers, it is possible to synthesize perfect carbon nanofibers.

Abstract: The Ti-Hf alloy system forms α-β isomorphous system and does not form any intermetallic compounds, which is also beneficial for good mechanical properties. And in order to avoid the release of materials, surface modifications are generally carried out to form a TiN and ZrN layer on the surface. Electrochemical properties of TiN and ZrN coated Ti-Hf alloy by RFsputtering has been researched using various electrochemical methods. Ti-10wt%, 20wt%, 30wt%, and 40wt% Hf alloys manufactured by non consumable vacuum arc melting furnace. All the specimens were heat treatment at 1000°C for 24hr in Ar atmosphere followed by furnace cooling, respectively. The specimens were coated with TiN and ZrN respectively, by RF-magnetron sputtering method. The microstructures were conducted by using OM, EDX and SEM. The corrosion tests were carried out using potentiodynamic(PARSTAT 2273, EG&G, USA) and potentiostatic test in 0.9% NaCl solution at 36.5 ±1 °C. Microstructure clearly observed that lamellar structure translated to needle-like structure with increased Hf contents. From the analysis of TiN and ZrN coated layer analysis, TiN and ZrN coated surface showed columlar structure with 600nm and 100nm thickness, respectively. The corrosion resistance of TiN and ZrN coated Ti alloys were higher than those of the non-coated Ti-alloy in 0.9%NaCl solution, indicating better protective effect.

Abstract: In this study, AC impedance behaviors of Ti-Zr binary alloys for biomaterials have been investigated using by electrochemical impedance spectroscopy. Ti-10wt%, 20wt%, 30wt%, and 40wt% Zr alloys were prepared by arc melting and homogenized for 24 hr at 1000 °C in argon atmosphere. Phase constitutions and microstructure of the specimens were conducted by using XRD, OM and SEM. The corrosion properties of the specimens were examined through potentiodynamic test (potential range of -1500 ~ 2000 mV), AC impedance spectroscopy(100kHz~10mHz) in artificial saliva solution by potentiostat (EG&G Co, PARSTAT 2273. USA). In as-cast and homogenized Ti-xZr alloys, α-phase was identified by XRD. Microstructures were changed from lamellar structure to needle-like structure as Zr content increased. From the results of polarization behavior in the Ti-xZr alloys, it was found that the corrosion resistance was increased with increasing Zr content. From results of AC impedance spectroscopy, passive film resistance value of homogenized Ti-40Zr specimen(1.60×106 Ωcm2) showed higher than that of as-cast specimen.

Abstract: Effects of TiN, ZrN and tooth-ash coatings on the surface phenomena of Ti-(Nb, Zr, Ta, Hf) dental implant alloys with low elastic modulus has been researched by using electrochemical methods. Ti-(Nb, Ta, Zr, and Hf) alloys were fabricated and surface-coated with TiN, ZrN and tooth-ash (hydroxyapatite) using the RF-sputtering. The electrochemical behaviors of the TiN, ZrN and HA-coated dental implant fixtures were investigated using techniques such as potentiodynamic polarization analysis in 0.9% NaCl solution, as well as examine the detailed structure of these coated alloys using SEM and XRD. From potentiodynamic test of Ti-(Nb, Zr, Ta, Hf) alloy, the corrosion resistance of TiN/ZrN/tooth-ash composite coated Ti-(Nb, Zr, Ta, Hf) alloy were higher than those of the non-coated Ti-(Nb, Zr, Ta, Hf) alloy.

Abstract: The electrode(Ni-MWNTs) containing nickel(Ni) and multi-walled carbon nanotubes (MWNTs) was prepared by composite electrodeposit. Electrochemical hydrogen storage of the electrode was studied. The result showed a high electrochemical discharging capacity of up to 1361.1mA·h·g-1, which corresponds to a hydrogen storage capacity of 4.77Wt%(weight percent). Test of cyclic lifespan showed MWNTs had certain cyclic lifespan. Cyclic voltammetry tests showed that MWNTs can store hydrogen in chemical form.

Abstract: The Sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) / poly(2,6-diphenyl-1,4-phenylene oxide) (S-PPO) was prepared by oxidative coupling polymerization with 2,6-dimethyl phenol, 2,6-diphenyl phenol, CuCl(І) and pyridine, and followed sulfonation with chlorosulfonic acid. Copolymer was consisted of 2,6-diphenyl phenol 30 mol% and 2,6-dimethyl phenol 70 mol%. Organic-inorganic nano composite membranes were prepared with copolymer and a series of SiO2 nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solution. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. S-PPO copolymer and nano composite membranes exhibited proton conductivities from 0.79×10-3 to 0.98×10-3 S/cm, water uptake from 21.70 to 24.77 %, IEC from 0.720 to 0.955 meq/g and methanol diffusion coefficients from 2.97×10-7 to 3.70×10-7 cm2/S.

Abstract: In this paper, R & D on the reinforced and self-humidifying composite membranes for proton exchange membrane fuel cells (PEMFCs) in our group is presented. It is shown that both the reinforced and self-humidifying membrane have attained an enhanced performance.

Abstract: In this paper, novel durable self-humidifying membranes were investigated. It was shown that the cell performance and the durability under dry operation condition have been improved.