Key Engineering Materials Vols. 512-515

Abstract: The prochlore structure ceramic of Sm₂Zr₂O₇ was synthesized by chermical coprecipitation method. Then the feedstock powder for plasma spraying was prepared by spray drying with proper distribution of particle size about 30–70μm. The thermal barrier coatings with a topcoat of Sm₂Zr₂O₇ and with a two– layer topcoat of Sm₂Zr₂O₇/YSZ were prepared by atmospheric plasma spraying(APS). The cohesive strength of Sm₂Zr₂O₇/YSZ coating presented a value of 15.49 Mpa and 23.37 Mpa, respectively. Microstructure and phase analyses reveal that plasma spraying of complex Sm₂Zr₂O₇ is accompanied with the formation of the transverse crack networks. the TBCs with topcoat of Sm₂Zr₂O₇ and Sm₂Zr₂O₇/YSZ performed a thermal cycles of 35 and 60 separately under the test temperature of 1100°C. The thermally grown oxide at the topcoat–bondcoat interface was also the major factors that lead to the coating failure on thermal cycling at about 1100°C.

Abstract: The high emissivity coating was deposited by Air Plasma Spraying (APS). Ni2O3, Cr2O3 were the main raw materials in this study. The feedstock powder was prepared by spray drying and post-sintering at 1420 °C for 2hours. The microstructure, phase structure, flowability and bulk density of the plasma sprayed powder were characterized. The microstructure, bond strength and infrared emissivity of the high emissivity coating were also analyzed in this paper. The results reveal that the powder before and after sintering presents good flowability and is suitable for plasma spraying process. A dense coating with the bond strength of 28.14MPa was prepared successfully. The normal emissivity of the coating in all waveband is 0.87 at the temperature of 300°C, 600°C, 900°C, 1000°C, 1100°C and 1200°C

Abstract: Compound ceramic coatings with the main crystal phase of Al2TiO5 (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry (XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 had been decomposed in an hour and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al2O3. The content of Al2O3 was decreased from outside to inside layers and Ti2O3 was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air.

Abstract: In order to improve the oxidation resistance of carbon/carbon (C/C) composites, a ZrSiO₄ coating on SiC pre-coated C/C composites was prepared by a hydrothermal electrophoretic deposition process. The phase composition, surface and cross-section microstructure, anti-oxidation property of the as-prepared ZrSiO₄/SiC coating was investigated. Results show that hydrothermal electrophoretic deposition is an effective route to achieve crack-free ZrSiO4 outer coatings. The ZrSiO₄/SiC coating can protect C/C composites from oxidation at 1773 K for 332 h with a weigh loss rate of only 4.83×10^-5g/cm²·h.

Abstract: Hollow glass micro-beads uniformly coated by a shell of titania with thickness of 50 to 300 nm, were fabricated by wet chemical methods. The pigments were dispersed in silica coatings，then the pigmented coatings were deposited on quartz substrates by sol-gel spin-coating method with a thickness of about 80 µm. SEM, TEM and FT-IR techniques were used to characterize the microstructure and properties of the coatings. FT-IR indicated average infrared transmittance of coatings containing the core-shell particles was significantly lower than that of coatings containing no functional particles or containing hollow glass micro-beads, when the volume fraction of core-shell particles was just 5%. In view of its low infrared transmittance, pigmented silica coatings may find applications in high-temperature heat-insulating materials for reducing radiation heat transfer.

Abstract: Abstract. Compound ceramic coatings with the main crystal phase of Al2TiO5 (as-coated samples) were prepared in situ on the surface of Ti-6Al-4V alloy by means of pulsed bi-polar micro-arc oxidation (MAO) in an NaAlO2 solution. The coated samples were calcined in argon and air at 1000 oC, respectively. The phase composition, surface and section morphology, and element contents of the ceramic coatings were investigated by X-ray diffractometry(XRD), Scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). The samples were treated in argon and the as-coated ones were calcined in air at 1000 oC to study the anti-oxidation properties of the samples. The results show that Al2TiO5 had been decomposed in an hour and transformed into α-Al2O3 and rutile TiO2 in air. However, Al2TiO5 had been decomposed in four hours in argon and the final coating surface was completely composed of α-Al2O3. The content of Al2O3 was decreased from outside to inside layers and Ti2O3 was formed in the coating. Furthermore, the morphology of the ceramic coatings after the calcination was different. The coatings calcined in argon were finer; the grains and pores were smaller than those in air. The high oxidation reaction of the TC4 substrate was the fiercest and the weight gains of the coated samples treated in argon was the lowest. The weight gains of the ceramic coatings were nearly changing in the form of parabola law.

Abstract: In this paper, a ceramic coating containing zirconia was produced by micro-arc oxidation (MAO) in a solution of K2ZrF6 and KOH. The composition and structure of the coating were investigated by XRD, EPMA. The results show that the coating consists of t-ZrO2, m-ZrO2, α-Al2O3 and γ-Al2O3. t-ZrO2 and m-ZrO2 distribute in outer layer of the coating, however, α-Al2O3 appears in inner layer of the coating. The coating surface consists of many micro-powders with a size of 1-2μm. It is because K2ZrF6 is unstable in the alkaline solution, and it can form zirconium hydroxide and takes part in the formation of the coating. The result of the hardness shows that the maximum hardness (1900HV) appears at around 30-50μm from the interface of substrate/coating.

Abstract: Cupric hydroxide films with new hierarchical architecture were directly fabricated on copper substrate via a solution-immersion process at a constant temperature of 23°C. Stable superhydrophobic Cu(OH)2 surface was obtained after Cu(OH)2 films were modified with hydrolyzed 1H, 1H, 2H, 2H-Perfluorooctyltrichlorosilane (C8H4Cl3F13Si, FOTMS). In addition, the growth mechanism of the cupric hydroxide films was further discussed.

Abstract: Sulfation performance of a Fe-Ca based sorbent prepared from iron oxide-rich metallurgical dust and lime is investigated using thermogravimetric analysis (TGA) in the temperature range of 300-550°C, and the kinetics of the sulfation reaction is analyzed using the grain model. Comparison between the model simulation results and experimental data demonstrates that the grain model can give a relatively satisfactory description of the experimental results. In detail, the overall rate of the sulfation reaction is mainly controlled by diffusion, despite by chemical kinetics at a very low degree of conversion (lower than 0.056), and that the higher diffusion activation energy (E _D, 25460J/mol) and smaller diffusion frequency factor (D _e0,4.42×10^–2 cm²/min), in relative to those of the sulfation reaction (13008J/mol for E a and 1.65 cm/min for k _s0), may account for the shift in control mechanism, the role of diffusion in the sorbent conversion, and consequently the flat-convex conversion vs. time curves obtained by TGA.

Abstract: The ceramic company financial performance indicator has multilayers, many dimensions and intersect characters, and the comprehensive evaluation on it is a big challenge. Firstly, this paper introduces principal component analysis theory and tool. Secondly, it constructs the four-dimensional evaluating indicator system based on “debt-paying ability, operation capability, profitability, and development capability”. In the end, based on the financial report data, this paper conducts an empirical principal component analysis on 20 typical ceramic enterprises’ financial performance. The conclusion is that the ceramic business finance performance is mainly decided by four greatest factors including “debt-paying ability, profitability, efficiency, development” and the impact of the four greatest factors upon the finance performance degree is different. This research’s innovation lies in using the principal components method to give the weight to the evaluating indicators objectively, providing not only the new tool for the ceramic enterprise financial performance assessment method’s evolution, but also the new mentality for the ceramic enterprise financial performance’s improvement.