Advanced Materials Research Vols. 123-125

Abstract: In this work, nickel (Ni)-loaded activated carbon nanotubes (ACNTs) were prepared for hydrogen storage applications. The process was conducted by chemical activation method at 900oC with KOH:CNTs ratios (4:1, g/g). And then, Ni-loaded ACNTs were also formulated to investigate the hydrogen storage characteristics as a function of Ni content. The microstructures of the Ni-loaded ACNTs were characterized by XRD and TEM measurements. The textural properties of the samples were analyzed using N2 adsorption isotherms at 77 K. The BET, D-R, and BJH equations were used to observe the specific surface areas, the micropore, and mesopore structures, respectively. The hydrogen storage capacity of the Ni-loaded ACNTs was measured at 298 K at a pressure of 100 bar. It was found that the hydrogen storage capacity of Ni-loaded ACNTs was enhanced in proportion to the Ni content, with Ni-5-ACNTs exhibiting the largest hydrogen storage capacity. Therefore, it could be concluded that the significantly created micropores on CNTs by chemical activation had an effect on hydrogen storage behaviors as well as the Ni particles played an important role in hydrogen storage characteristics due to the hydrogen spillover effect.

Abstract: In this study, single-wall carbon nanotube (SWCNT) mixed with hydrous ruthenium oxide was co-deposited on titanium substrate by cathodic deposition method. Titanium substrate was first cleaned thoroughly by acetone and followed by chemical etching of 5%HF for 5 minutes and 50%HCl for 15 minutes. The purpose of acid etching is to increase the adhesion between the coating layer and the Ti substrate. SWCNT has been dispersed by ultrasonic method to avoid agglomeration during deposition processes. The concentration of SWCNT added in the deposition process was 0.05 wt%. The time of specimens which were immersed into the deposition bath is varied from 5minutes to 60 minutes. The electrical capacity characteristics of specimen were examined by cyclic voltammetry. The microstructure of hydrous ruthenium oxide coating is elucidated by high resolution transmission electron microscopy (HRTEM). Combination of amorphous and nanocrystalline structure of hydrous ruthenium oxide was investigated in this study. Nano-sized particles (about 2-3nm) were found embedded in the amorphous matrix. The capacitance was found increased when the deposition time was increased. The maximum capacitance of hydrous ruthenium oxide coating was measured to be 556.7F/g.

Abstract: KCl is usually used as the supporting electrolyte in electrochemical deposition of Zinc oxide materials. Besides the role of supporting electrolyte, it can also influence the morphology of the fabricated materials. In this work, ZnO and zinc hydroxide chloride hydrate (Zn5(OH)8Cl2•H2O) mixture with platelet-like morphology were electrochemically deposited directly on ITO-coated glass substrates at 65°C. The electrolyte was 0.1M Zn(NO3)2•6H2O with KCl concentration varied from 0 to 3.2M. It was found that only ZnO thin film was obtained when the concentration of KCl was below 0.02M. Plates structure appeared as the concentration of KCl increased to 0.04M. Plentiful plates were obtained when the concentration of KCl was 0.05M-0.2M. From the X-ray diffraction, it was confirmed that the plate films was the mixture of ZnO and Zn5(OH)8Cl2•H2O. The plates showed perfect single crystal structure confirmed by selected area electron diffraction. Zn and Zn5(OH)8Cl2•H2O were obtained when the concentration of KCl was above 0.8M.

Abstract: In this paper, we report the synthesis of Fe-filled carbon nanotube arrays by floating catalyst chemical vapor deposition, which employed ferrocene as both catalyst precursor for carbon nanotube growth and the iron source for iron filling. We obtained Fe-filled carbon nanotube arrays perpendicular to the surface of the quartz substrates by floating catalyst chemical vapor deposition. We also conducted controlled experiments at different temperatures. Our results indicated that a higher synthesis temperature is needed for synthesizing Fe-filled carbon nanotube arrays. Magnetic property measurements revealed that the Fe-filled carbon nanotubes exhibited a high average coercivity of about 589.97G.

Abstract: ZnO micro/nano rods were grown　on fluorine doped tin oxide (FTO) substrates by aqueous chemical growth (ACG) using Zn(NO3)2•6H2O and C6H12N4 at low temperature. For comparison, the yield of nanorods on indium-tin-oxide (ITO) substrates with same parameters was also discussed. SEM, TEM, SAED and XRD were utilized to characterize morphologies and structures of ZnO crystals. It was indicated that the temperature and the concentration of the solution significantly leads to the yields of the ZnO. Single-crystalline ZnO micro/nano rods could be synthesized via an aqueous solution route without adding alkali solution at 70°C in large area.

Abstract: The synthesis of lead hydroxide nanowires by solution-phase chemical reactions of lead nitrate with alkali by adding sodium chloride was reported. The obtained lead hydroxide nanowires have a length of a few micrometers and a diameter of about several tens of nanometers. The selected-area electron diffraction reveals that these lead hydroxide nanowires are single crystalline. Controlled experiments indicate that lead hydroxide nanowires prefer to form at higher concentration of chloride ions in lead nitrate precursor solutions, such as Cl- : Pb2+ = 5:1 and 6:1.

Abstract: Fe100-xPtx single-layered films with Pt contents (x) = 32~69 at.% were deposited on natural-oxidized Si(100) substrate by dc magnetron sputtering. Then the films were post-annealed at 700 °C for 3 min by a rapid thermal annealing (RTA) with a high heating ramp rate of 100 °C/sec. Experimental results show that FePt film presented (111) preferred orientation and tended to in-plane magnetic anisotropy as the content of Pt was 32 at.%. When the Pt content was increased to 55 at.%, (001)-textured FePt film was obtained and presented perpendicular magnetic anisotropy. Its out-of-plane coercivity (Hc⊥), saturation magnetization (Ms) and out-of-plane squareness (S⊥) reached to 12.7 kOe, 375 emu/cm3 and 0.8, respectively. These results reveal its significant potential as perpendicular magnetic recording media for high-density recording. Further increasing the Pt content to 69 at.%, the coercivity of FePt film was decreased drastically to below 1 kOe and tended towards in-plane magnetic anisotropy.

Abstract: Nanoscale particle size of metal oxides and hydroxides showed enhanced various physical properties and performance. We established a simple, cost-effective, room-temperature (RT) precipitation method for the preparation of the magnetic, first-raw transition metal (TM) hydrated oxide and hydroxide nanoparticles. This method is based on the use of the TM nitrate, as the metal source, and cyclohexylamine (CHA), as a precipitating agent, either in the water (H2O) or ethanol (EtOH) medium. We found that the precipitation medium and the identity of precipitated TM strongly affect the morphology, particle size, and magnetism of the product. The morphology varies from spherical, to rectangular, to rod shape; while the size varies in the range of 5-30 nm. All samples showed paramagnetic behavior with Curie temperatures span over a wide range (20-150K). Huge hysteresis looses has been observed for manganese (Mn) sample, prepared in H2O. The coercively (Hc) at 4.2K for this sample is about 1.5T, which is comparable to the strongest permanent magnets (Nd-based magnets) available at room temperature. The energy product (Hc*MR) is about 4.5*105 (emu/g)Oe.

Abstract: The (GeSbSn)100-xFex films (x = 0 ~ 12.9) were deposited on nature oxidized silicon wafer, and glass substrate by dc magnetron sputtering. The ZnS-SiO2 films were used as protective layers. The thickness of the (GeSbSn)100-xFex film is 100 nm. We have studied the effects of Fe addition on the crystallization kinetics, and microstructures of the GeSbSn recording film. The crystallization temperatures of (GeSbSn)100-xFex films with x = 0, 7.1, 9.1, and 12.9 were found to be 225 °C, 198 °C, 167 °C, and 165 °C, respectively. The crystallization activation energies of (GeSbSn)100-xFex films with x = 0, 7.1, 9.1, and 12.9 are about 1.74 eV, 1.15 eV, 0.81 eV, and 0.52 eV, respectively.

Abstract: In this study, inverse-hysteresis model, which can inversely calculate input voltage for desired displacement, is suggested for tracking performance. In this paper, tracking performance and movement precision of piezoelectric actuator as operating parts of ultra-precision cutting unit is improved using feedback control of inverse-hysteresis model to remove hysteresis property. PID feedback control is studied as controller to compensate the error in inverse-hysteresis model. In addition, straightness error of spindle, thermal expansion error of mechanical structure is analyzed to detect movement error property in ultra-precision machining. Via machining performance evaluation using ultra-precision machining experiments, the machining precision of ultra-precision CNC lathe can be improved.