Advanced Materials Research Vol. 620

Abstract: Al oxide (Al-O) films used as catalyst-support layer for vertical growth of carbon nanotubes (CNTs) were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission, and scanning electron microscopies (TEM and SEM). EB-deposited Al films (20 nm) were thermally-oxidized at 400 ^o C (10 min, static air) to produce the surface structure of Al-O. The Al-O was found amorphous and after the incorporation with Co catalyst, the grown CNTs were twisted together before vertically grown. The prepared Al-O surface is an electron-acceptor-dominated (oxygen-rich) surface where the formation of active catalyst could be enhanced to promote the vertically aligned CNT growth.

Abstract: The properties of undoped and Mg-doped CaCu₃Ti₄O₁₂ (CCTO) ceramics have been studied. The samples were calcined at 900°C for 12 hours, and sintered at 1030°C for 10 hours. X-ray diffraction analysis on calcined samples shown the formation of CCTO phase with trace of secondary phases meanwhile completed formation of CCTO single phase obtained for sintered pellets. The peak positions of Mg-doped CCTO were slightly left-shifted from the undoped CCTO, attributed to the lattice expansion. Scanning electron microscopy analysis showed that the grains size becomes larger with the increment of dopant amount. Enhanced dielectric constant was observed in the Ca_1-xMg_xCu₃Ti₄O₁₂ ceramics with x = 0.05 for the frequency range from 1 MHz to 1 GHz. The dielectric loss seem to be at lowest value when Ca_1-xMg_xCu₃Ti₄O₁₂ ceramics with x = 0.10 at the same frequency range. The results indicate that Mg ions have effectively changed the properties of CCTO.

Abstract: In the present work, activated carbon was prepared from rubber seed coat by physicochemical activation for the removal of Remazol Brilliant Blue R (RBBR) dye from aqueous solution. The effects of dye initial concentration, contact time, solution temperature and pH on RBBR adsorption onto rubber seed coat based activated carbon (RSCAC) were investigated. The adsorption uptake was found to increase with increase in initial dye concentration and contact time. Change in temperature and pH also played an important role to RBBR adsorption capability. Study showed that rubber seed coat is suitable to be used as activated carbon precursor.

Abstract: CaCu₃Ti₄O₁₂ (CCTO) is a cubical perovskite phase and sintered ceramics exhibit very high dielectric constant at room temperature. The speculated origins of the high dielectric constant are the existence of insulative barrier layer at grain boundaries and domain boundaries which created an internal barrier layer capacitance (IBLC) at the microstructure of CCTO. The relation of grains and domains electrical resistance were studied in this work by using impedance spectroscopy (IS). A series of samples with different heat treatment temperature were tested to investigate their microstructure by using field emission scanning electron microscopy (FESEM). The grains and domains resistance was calculated from a wide frequency range of impedance complex plane measurement (100 Hz to 1 GHz). The FESEM and IS analyses showed the dependency of grains and domains resistance to average grains size of CCTO microstructure.

Abstract: Minerals are always used as filler material in polymer composite application purposely to reduce the price. In order to optimize the use of mineral fillers instead of price reduction, there were several approaches that have been done such as surface treatment, finding suitable coupling agent, and etc. The study on hybridization of minerals with carbon nanotubes (CNT) are rare to be found. CNT has received great attention from researchers due to their superior properties to be used in many applications. Hybridizing CNT with minerals proposes potential fillers for polymer composite. In this study, chemical vapor deposition (CVD) technique was used to synthesize the CNT-minerals hybrid compound. A mixture of CH₄/N₂ was used as the carbon source and nickel as the metal catalyst for the growth of CNT hybrid compound. Three different types of minerals were used namely talc, muscovite and CaCO₃ are used to synthesize the MWCNT-talc, MWCNT-muscovite and MWCNT-CaCO₃ hybrid compound. In short, the process involved precipitation of mineral filler with nickel salt. The process was followed by calcinations and reduction of the catalyst, and methane decomposition. The produced hybrid compounds were then analyzed.

Abstract: Nanocrystalline cadmium oxide (CdO) thin film was successfully synthesized by a vapor transport process (solid-vapor deposition) without catalyst. Cadmium powder was heated to 1235 K in a tube furnace, and the resultant vapor was carried to the silicon substrate zone by a flow argon gas with oxygen. Scanning electron microscopy revealed that the product was of nanocrystalline cadmium oxide. X-ray diffraction and energy dispersive X-ray techniques were used to characterize structural properties. The grown nanocrystalline thin film had a grain size of 35 nm. Photoluminescence spectroscopy was conducted to investigate the optical properties of the CdO. The red-shift direct band gap energy of the nanocrystalline CdO was at 511 nm (2.43 eV), whereas that of CdO bulk was at 491 nm (2.5 eV).

Abstract: Metal oxide surge arrestors (MOSA) are commonly used in the electrical power system to protect the insulation from the damaging effect of lightning. This paper presents the damage characteristics and possible root cause of two exploded ZnO type arrestors. Both failures were not caused by lightning surge. They had degraded due to moisture ingress, leading to contamination and corrosion, accelerating thermal runaway effect in the ZnO elements and eventually caused early voltage breakdown under normal operating voltage. This indicated an inadequacy in the sealing components.

Abstract: The effect of CeO₂ addition in zirconia toughened alumina (ZTA) was examined. The CeO₂ addition in weight percent (wt %) was varied from 0 wt% to 15 wt%. The fabricated samples were sintered at a temperature of 1600°C. The sintered samples were characterized their properties such as fracture toughness and phase determination. X-ray diffraction patterns confirm the constituent phases present in the samples were alumina and zirconia. Fracture toughness for each sample in the range of 5.878.38 MPam^1/2 respectively. It was observed that the addition of ceria increased the fracture toughness of the zirconia toughened alumina ceramic composites.

Abstract: X-ray diffraction (XRD) is a versatile, non-destructive technique that reveals detailed information about the chemical composition and crystallographic structure of materials. In this work Ni-20Cr and Ni-50Cr coatings were deposited on two boiler steels namely T22 and SA 516 steel. The measurement of residual stresses of these cold sprayed coatings was done with the help of X-ray diffraction technique. This paper discussed the XRD study of the as-sprayed coatings. Further the XRD technique was used to study the uncoated and coated steels after cyclic exposure to air, molten salt [Na₂SO₄-60%V₂O₅], and actual boiler environments. The results obtained from the XRD analysis have been shown. The weight change results showed that the coated steels performed better than their uncoated counterparts which might be attributed to the formation of protective phases.

Abstract: Due to environmental concerns, lead-free solders were introduced in replacing the lead-based solders in microelectronics devices technology. Although there are many lead-free solder available, the Sn-Ag-Cu solder was considered the best choice. But the solder has its draw backs in terms of melting temperature and intermetallic formations. In this study, the effect of 0.5wt% Ni addition on the microstructure of the Sn-3.5Ag-1.0Cu solder was investigated. The solder was synthesized via powder metallurgy route which includes blending, compacting and sintering. The solders were characterized for its densities and melting temperatures. SEM was used to observe the microstructure of intermetallic phases. The solders were melted on copper substrate at 250°C for one minute and aged at 150°C from 0 to 400 hours. The phases formed were studied under SEM. The SEM results showed the presence of Cu₆Sn₅, Cu₃Sn, Ag₃Sn and (Cu,Ni)₆Sn₅ intermetallics.