Advanced Materials Research Vols. 79-82

Abstract: 1-12% {atomic ratio of In/(In+Sn)} indium-doped tin oxide (SnO2:In) films were successfully prepared on sapphire substrates by MOCVD method. HRTEM image showed that the obtained films were single crystalline films. The X-ray photoelectron spectroscopy showed the existence of non-stoichiometric oxide on the film surface. The Hall mobility and carrier concentration of the SnO2:In films varied with the In content increasing.

Abstract: 12% Gallium-doped tin oxide (SnO2:Ga) single crystalline films have been prepared on α-Al2O3 (0001) substrates by the metalorganic chemical vapor deposition (MOCVD) method. The grown temperatures were varied from 400 to 600°C. According to XRD patterns, the film deposited at 500°C has the best single crystalline structure. Subsequently, 3 to 15% doped films were fabricated at 500°C using the same method, except that Gallium organometallic (OM) source was injected in pulsed-mode for the 3, 5 and 10% -doped films. Then, structural and optoelectronic properties of the films were investigated in detail. The obtained films all have the rutile structure of pure SnO2. Film with resistivity of 1.09×10−2Ω cm, carrier concentration of 8.86×1019cm−3 and Hall mobility of 6.49cm2 v−1 s−1 was obtained at 5% of Ga concentration. The average transmittance for the SnO2:Ga films in the visible range were over 90%.

Abstract: In this study, TiAlSiN coatings were synthesized by cathodic arc deposition with Ti and Al88Si12 dual cathodes. The as-deposited coatings were following with post-deposition heat treatment in air and nitrogen atmosphere, respectively, at the temperature of 400 oC for 3 hour. The annealing treatment of the TiAlSiN coating has an expected effect on the wear resistance and cutting performance. The TiAlSiN coating subjected to heat treatment in nitrogen atmosphere presented the best oxidation and wear resistance among the tested coatings. The friction coefficient of the TiAlSiN coatings subjected in nitrogen atmosphere at 400oC was decreased due to the effect of the structure modification by increasing hardness. Using thermogravimetric analyzer (TGA), the result turned out the lowest weight change of TiAlSiN coating after annealing treatment in air if compared to that of all the coatings. The reason my be due to the oxide layer formed on the coating surface acted as a protective layer. Cutting test on the hardened steel with mist oil lubricants, the TiAlSiN-coated WC-Co tool with annealing treatment in nitrogen provides the best wear resistance at the cutting edge.

Abstract: 1-10% {atomic ratio of Zn/(Zn+Sn)} zinc-doped tin oxide (SnO2:Zn) films were successfully prepared on sapphire substrates by MOCVD method. The structural, optical and electrical properties of the SnO2:Zn films were investigated. The obtained films were high quality crystalline films with high a-axis orientation. The optical transmittance of the SnO2:Zn films with the thickness 1-1.4μm was about 80% in visible region. The Hall mobility and carrier concentration of the SnO2:Zn films varied with the Zn content increasing.

Abstract: The self-healing ceramic coating against oxidation for carbon/carbon composite was fabricated via preceramic polymer pyrolysis process using polysilazane as preceramic and MoSi2, B4C powders as fillers. By means of SEM and XRD, the phase compose and microstructure of coating were characterized, and preliminarily study on its anti-oxidation ability and thermal shock resistance were conducted. The results showed that, the coating is composed of the resisting oxidation layer and the sealing layer. The thickness of the coating is about 50μm, and the coating is uniform and densified. Good contact at the interfaces is visible on the SEM photograph. At 1300°C temperature, the thermal shock resistance test was conducted 50 times, the weight loss rate was 2.12%. In range of 1200°C~1500°C, the anti oxidation ability of the coating is good.

Abstract: NiCoCrAlY coatings strengthened by different content of nano-Al2O3p, using crosscurrent CO2 laser, were prepared on Ni-based superalloy substrates, and thermal shock behaviors of these coatings were investigated by cycling between 1050°C and room temperature (forced water quenching).The results show that the thermal shock resistances of nano-Al2O3p-added coatings are definitely better than that without adding nano-Al2O3p. Among the nano-Al2O3p-added coatings, the coating added with 0.5wt% nano-Al2O3p performs best. After 10 thermal shock cycles, the spalled and spalling area in the oxide scale of the no-nano-Al2O3p coating reaches up to 27.7%, and the main failure form of the oxide scale is an expanding unit-spalling type in thermal shock cycles. While the area in the oxide scale of nano-Al2O3p-added coatings is only 10%~60% to the no-nano-Al2O3p one, and the failure of these oxide scales is mainly in the form of unit-spalling type. After 100 thermal shock cycles, many cracks turn up in the cross-section of the no-nano-Al2O3p coating, including propagating crack and internal crack. While no internal crack appeared in nano-Al2O3p-added coatings, and the propagating cracks are smaller than no-nano-Al2O3p one.

Abstract: Using gravitational separation Self-propagating High-temperature Synthesis(SHS) process, ceramic composite coating was made in large cross-section rectangular pipes and hemming plate, which can be use directly and also can be cut into the ceramics clad steel plate. The experimental results showed that the surface of ceramics coating, for using section steel as core of large cross-section rectangular pipes or hemming plate combination pipes, is glossy, and its thickness is among 1.5~3.5mm. Metallurgical bonding between steel substrate and ceramics coating can not come into being and the mode of their joint is mainly mechanical bonding. The cooling process of the ceramic-lined square steel tubular was simulated by use of ANSYS. Temperature-time curves of composite rectangular pipes with different thickness and residual stress distribution were calculated, and the reason for creating bonding force. These provided a reference to choose the technologic parameters.

Abstract: Copper-tin-oxide thin films have been prepared on quartz substrates by the magnetron sputtering method. The structural,optical and electrical properties were investigated. The prepared samples were amorphous, CuSnO3 single crystalline grains with perovskite structure were observed after annealing temperature was above 530°C. The optical and electrical properties had great dependence with reactive gas pressure and annealing temperature. Thermal probe reveals p type conductivity of some samples. Keywords: Magnetron sputtering, CuSnO3, Perovskite structure

Abstract: Ceramic ultrafiltration membrane, pore size from 2 to 50nm, is of growing interest in separation and purification processes because of their higher chemical, thermal and mechanical stability compared to organic membranes. TiO2 mesoporous membranes have gained tremendous popularity due to their photocatalytic activity and because they possess high water flux and chemical resistance. In recent years, visible-light-induced nitrogen-doped titanium dioxide (N-TiO2) materials have been attracted extensive attention. We synthesized asymmetric N-TiO2 membrane based on this material via sol-gel method, in which titanium tetrabutoxide was used as Ti-precursor and formamide as nitrogen resource. A -alumina support with macropores was used and its diameter, thickness and pore size were 28.5 mm, 2.2 mm and 0.10μm, respectively. The alumina supports were pretreated using PVA to prevent permeation of sol into the supports. Sol was coated on this treated supports, and then formed gel under 60°C. The resulting membrane posseses a pore size of 4nm and its pure water permeability is 3.3L/(m2•h•bar). The influences of formamide on the microstructrue and the spectral characteristics were also analyzed by means of BET, UV-vis. As indicated by results, when the molar ratios of formamide and titanium terabutoxide were near 4, the materials had excellent visible light absorption, the absorption band was shifted to about 545nm and the band gap was reduced to 2.65eV. The band gap was 0.55eV less than that of pure TiO2. The membrane has potential application in purifing of micro-polluted surface water under visible-light environment.

Abstract: The composite coatings of self-flux alloy matrix reinforced by WC-12%Co were produced on the surface of 45 steel using laser cladding technology. The effects of CeO2 to macro-morphology, microstructure, hardness, wear resistance and corrosion resistance of cladding layer were investigated. The results show that rare earths oxide (CeO2) added laser cladding coating has distribution, dimension phases and less deficiency. CeO2 could promote liquating process of WC, increasing the quantity and distribute uniformity of intermetallic compounds in laser cladding layer. Because of dispersion precipitation and fine-crystal strengthen effect, laser cladding layer with CeO2 has higher microhardness, wearing resistance and better corrosion resistance properties.