Advanced Materials Research Vols. 79-82

Abstract: The Cerium-based conversion coating is formed on the industrial aluminum(1060) by using chemical immersion. The microstructures of the conversion coating have been examined by scanning electron microscopy(SEM). The electrochemical measurement result shows that the corrosion resistance of aluminum is significantly improved after the conversion coating was formed. The result of X-ray photoelectron spectroscopy (XPS) shows that the cerium conversion coating mainly consisted of oxide of aluminum, CeO2 and TiO2. The formation mechanism of the Cerium-based conversion coating is investigated.

Abstract: Titanium dioxide (TiO2) thin films were deposited by rf magnetron sputtering, using a Ti target (purity 99.99%), on poly (ethylene terephthalate) (PET) substrate. Argon and oxygen were used as the working and reacting gas, respectively. The surface morphology was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the film composition and structure by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Uniform and compact TiO2 nanoparticles with diameter about 50 nm were deposited on PET substrates within 2 minutes. Many nano-sized particles aggregated and formed larger clusters after 5 minutes. The size of the clusters increased with increased sputtering time. The particles grew perpendicular to the substrate, and the surfaces of the films were smooth and undulate. The Ti2p peak was resolvable into the three valence species Ti4+, Ti3+ and Ti2+. The O/Ti ratio varied with the Ar: O2, ratio, the optimum value of which was in the range 4-8. The TiO2 films deposited on PET substrate were amorphous.

Abstract: In this study, block copolymers of PS-b-PMSMA with various molecular weight were synthesized by atom transfer radical polymerization (ATRP). GPC analysis showed that the molecular weight distribution of the prepared PS-b-PMSMA could be controlled to be lower than 1.3 for the case of molecular weight less than 30,000. The chemical structures of the amphiphilic block copolymers of PS-b-PMSMA were well identified by FTIR. SEM showed that the spherical micelles and compound micelles were produced in hybrid films. The EDX analysis indicated that the nano-sized CdS particles have been successfully prepared in the PS-b-PMSMA composite films. The diameter of CdS particles calculated from Brus formula was about 4-5 nm. PL analysis revealed that the λmax of emission of the prepared composite materials had a red-shift as the CdS particle size increased.

Abstract: Titanium dioxide (TiO2) has received intense interest because of the numerous technical applications. In this work, the TiO2 thin films were deposited on Si substrates by spin coating from a TiO2 solution prepared by a sol-gel method. It was found that the TiO2 film properties strongly depended on the post annealing conditions. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) were used to investigate the compositional and chemical states of the thermal-treated TiO2 samples. For the TiO2 samples annealed in atmosphere, the contents of -C and -OH bonds increased when the process temperature increased. From XPS measurement, the atomic concentrations of carbon and oxygen in the film are determined to be approximately 46% and 37%, respectively. However, for the samples annealed in oxygen, the contents of -C and -OH bonds were found to decrease when the anneal temperature increased. The concentrations of carbon and oxygen in the film were approximately 11% and 59%, respectively. To further investigate the behavior, the in-depth concentration profile of carbon was measured for the TiO2 samples under different etching time. It was found that the carbon concentration drastically decreased from 11% (surface) to 0.2% (near the interface). The result indicates that the pure TiO2 film could be obtained by sol-gel coating with a suitable annealing process.

Abstract: In this study, hydrous ruthenium oxide was deposited on titanium(Ti) and carbon nanotube(CNT) substrate by cathodic deposition method. Combination of amorphous and nanocrystalline structure of hydrous ruthenium oxide was investigated by high resolution electron microscopy. The measured capacitance was found keeping nearly constant through charge/discharge processes for hydrous ruthenium oxide coating on Ti substrate. On the other hand, thin and uniform layer of hydrous ruthenium oxide coating can be deposited on CNT substrate. The thickness of the coating layer was found less than 10nm. Combination of amorphous and nanocrystalline structure of hydrous ruthenium oxide was also investigated on this specimen. The consumption of coating was found very effective for this specimen after 105 charge/discharge cycles which lead to the tremedenously decreasing in the measured capacitance.

Abstract: The different molar ratios of La/Ti (0.025, 0.050, 0.075 and 0.100) photocatalytic electrodes use in this study were synthesized by sol-gel method and dip-coating method. The XRD pattern of TiO2/ITO presents only anatase phases, [1] but for La-TiO2/ITO presents both anatase and rutile phases. The SEM image of the La-TiO2/ITO showed particles of regular shapes with smaller size (＜10nm) compared to the TiO2/ITO, which presented uniform particles of spherical structure and larger size （20nm）.The La-TiO2/ITO photocatalytic electrode with molar ratio 0.050 shows the best ability both on the absorbtion and photocatalytsis. Applied potential 2.0V would effectively increase the photoelectrocatlaytic activity under visible light irradiation.

Abstract: Calcium phosphate coatings were deposited on carbon/carbon composites by induction heating method at 353K. The phase, morphology and composition of the calcium phosphate coatings were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM) and the adhesion strength of these coatings and the scratched morphologies were determined by the scratch test and stereomicroscope (STM). The results show that when the solution concentration is less than 0.00125 M and pH value is large than 6, the phase of as-prepared coating is hydroxyapatite with Ca/P molar ratio of 1.67 or OCP with Ca/P molar ratio of 1.33, and when the solution concentration and pH value are in the range of 0.05-0.0125M and 5-6, the as-obtained coating are blends of brushite, monetite or OCP. These coatings have a porous morphology and are very easy to be scratched off. When the solution concentration is large than 0.05 M and pH value is less than 5, the as-prepared coatings are monetite with Ca/P molar ratio of 1. Among these monetite coatings, the coating on C/C prepared in 0.2M solution have highest bonding strength with a critical load of on average 13 N.

Abstract: Mild steels were coated by hot-dipping in molten aluminum and aluminum-silicon baths at 700 °C for 180 seconds. Phase identification of the Fe-Al or Fe-Al-Si intermetallic compounds in the hot-dipped aluminide steel was carried out by using a combination of scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The results showed that the aluminide layer of the hot-dipped aluminum steel possessed a thicker intermetallic layer than that of the hot-dipped aluminum-silicon steel which was composed of minor monoclinic FeAl3 and major orthorhombic Fe2Al5. The intermetallic layer of the hot-dipped aluminum-silicon steel was composed of not only the same FeAl3 and Fe2Al5 phases in the hot-dipped aluminum steel but also Fe-Al-Si intermetallic compounds of hexagonal Al7Fe2Si and tetragonal (Al,Si)5Fe3.

Abstract: Single-layered FePt films of 30 nm thick were annealed at temperature between 300 and 800 °C for 1–180 sec by a rapid thermal annealing (RTA) with a high heating rate of 100 °C/sec. It is found that both the grain size and magnetic domain size of the FePt film increase with increasing annealing temperature and annealing time. The FePt films exhibited soft magnetic properties and without domain images were observed by magnetic force microscope (MFM) when the films were post-annealed at below 500 °C for 180 sec. The in-plane coercivity (Hc//) and perpendicular coercivity (Hc⊥) of FePt film increases significantly to 7.5 and 6.5 kOe respectively as annealing temperature increases to 600 °C. When the annealing temperature is increased to 700 °C, they are increased to 11.1 and 9.5 kOe, respectively, and the domain structure inclines to isolated domain. However, further increasing the annealing temperature to 800 °C, the Hc// and Hc⊥ values decrease to 9.8 and 8.9 kOe respectively due to largely increase the grain size of FePt and change the domain structure from isolation to continuity. On the other hand, in order to transform the FePt film from disordered γ phase to the ordered L10 phase, the annealing time of over 3 seconds is necessary when the film was post-annealed at 700 °C with a high heating rate of 100 °C/sec by RTA technique.

Abstract: Lanthanum hexaboride (LaB6) films were deposited on SiO2 substrates in a vacuum chamber by d.c. magnetron sputtering from Lanthanum hexaboride pellet target. The fabricate temperature was adjusted from per 50°C. The influence of fabricate temperature on the characteristics of the films was studied. The surface morphology was studied by atom force microscope (AFM). The results of the AFM proved that the films were compact and even. Maximum roughness of the films is no more than 15.1 nm, and the average roughness is less than 3.1nm. The results of XRD showed that the structure of the films is crystal, except the film that fabricated at the temperature of 500°C. It is noticeable that the (100) crystal face is dominated in the film, and that is different from the bulk LaB6. The crystallization of the films changed obviously. Films that fabricated at 400°C crystallized better than others. The film thickness was measure using a Stylus Profiler. The results of the Stylus Profiler proved that the temperature showed little effect on the thickness of the films.