Advanced Materials Research Vols. 557-559

Abstract: Smooth and dense films of CaTiO₃ were prepared on the glass substrate by a sol-gel dip coating method. Characterization of the product was carried out by different techniques such as powder X-ray diffraction (XRD), scanning electron microscope (SEM) and UV–vis optical spectroscopy. The results showed that pH and water contents had a great influence on morphology of CaTiO₃ film. When water content is 0.128 mol at PH=1.56, CaTiO₃ film presents an absorption in the UV region and the band gap is estimated to 3.35 ev. The results show the large potential of this material in electronic structure.

Abstract: In the study we evaluated the effects of the solvents of the coatings and the process temperature on the haze of anti-glare (AG) films. We used the single solvent with different polarity or the mixture of two solvents to prepare the AG coatings on the same composition ratio of polystyrene microbeads to pentaerythritol triacrylate. Experimental results revealed that the haze value increased with the decrease of polarity of solvents, and the haze values of the AG films prepared at elevated temperature led to higher haze values. We speculate the results arose from the affinity of solvents to LSPs.

Abstract: Ni-based TiN-TiC composite coating was fabricated on DZ125 superalloy surface by laser cladding. The phase constitution and microstructures were investigated by means of X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscope (SEM). Microhardness measurements and wear experiments without lubrication were also accomplished. The experimental results showed that a pore- and crack-free coating with metallurgical bonding to the substrate was obtained. Solidification morphologies along the section of the coating varied from directional dendrite in the interface to random dendrite in the surface. The coating was mainly composed of γ-Ni, M23C6, TiN, TiC particles and a small amount of NiTi, respectively. The average microhardness of 705HK for the coating was 2.3 times higher than that of the substrate. Wear tests indicated that wear resistance of the coating was significantly improved compared with that of the substrate. The improvement in hardness and wear resistance was attributed to TiN and TiC phase and chromium carbide uniformly dispersed in the matrix of the Ni-based TiN-TiC composite coating.

Abstract: Microporous polyvinylidene fluoride (PVDF) membranes were prepared by supercritical CO₂-induced phase inversion. The structure and morphology of prepared PVDF membranes were characterized by SEM. The effects of processing parameters such as CO₂ pressure, temperature and PVDF concentration on the membrane morphologies, pore size distribution and especially on the porosity of the membranes were investigated. The results showed that when the PVDF concentration was between 15-35wt.%, the temperature and the pressure were respectively in the range of 35-60°Cand 8-16MPa, the prepared PVDF membrane showed a cellular structure; the porosity changed in the range of 55.2~85.7% and showed a peak valuewith the increase of temperature, CO₂ pressure and PVDF concentration. The effects of process parameters on the membrane porosity were explained based on the properties of supercritical fluids.

Abstract: To repair a directionally solidified aero blade, laser cladding on GH710 substrate using stainless steel powder and Ni-based alloy powder by Nd:YAG laser was carried out. The condition of achieving directional solidification in the open and normal temperature environment was researched. The effect of technical parameter and powder composition on the microstructure of the cladding layer was analysed. The microstructure of the cladding layer was investigated. The results show that the directionally solidified cladding layer was acquired by the appropriate technical parameter. It was difficult for the Ni-based powder cladding layer to get directionally solidified cladding layer in comparison with the stainless steel powder.

Abstract: Laser ceramic modification technology is an effective way to improve the surface performance of titanium alloy, mainly including laser cladding and laser alloying. This paper summarized the dissolution and precipitation behavior of ceramic phases during the laser ceramic process on the surface of titanium alloy.

Abstract: Self-lubricative ceramic coatings were prepared on Q235 carbon steel by plasma electrolytic oxidation (PEO) in aluminate electrolyte containing graphite. The microstructure of the PEO coatings were examined. Influence of graphite in electrolyte on the coating growth properties was analyzed according to the voltage vs. time plots. Effect of graphite concentration on the properties of the coatings such as bonding strength, surface roughness and thickness were studied. The tribological behavior of the coating was primarily evaluated.The results showed that the self-lubricative coatings consisted of FeAl₂O₄, Fe₃O₄ and a certain amount of graphite. With increasing the concentration of graphite in the electrolyte, the coating growth gradually became stable with lower breakdown voltage and end voltage. The bonding strength and the thickness of the coating were not strongly affected by the graphite concentration whose value remained approximately 19Mpa and 110μm, respectively. With increasing the graphite concentration, the surface roughness first decreased and then increased a little. The friction coefficient of the coatings also varied with the concentration of graphite. When the concentration of graphite was 8 g/l, the tribological property of the coatings was the most excellent with the friction coefficient bellow 0.1.

Abstract: Reactive reactive element oxide RexOy (Re=Ce, Y)-modified aluminide coatings were developed by aluminizing the as-codeposited Ni-RexOy composite film using pack cementation method at 1100°C for 4 h. By comparison, aluminizing was also performed with the same condition on an as-deposited Ni film without RexOy particles. SEM/EDAX and TEM results indicated that the co-deposited CeO₂ or Y₂O₃ particls were homogeneously dispersed in the finer-grain nanocrystalline Ni grains. The cyclic oxidation in air at 900°C indicated that the RexOy -modified aluminide coatings were profoundly spallation resistance as compared to the RexOy -free coatings due to the formation of a continuous adherent α-Al₂O₃ scale.

Abstract: The high whiteness tourmaline composite powder was prepared with powder coating method in which TiO₂ as the coating agent and the stearic acid as the coupling agent. The powder coating method system theoretical research was improved to aim at resolving the tourmaline’s limited applications in environmental health field due to the darker color. Theory and test results show that when the tourmaline and the coating agent mass ratio of about 2:1, the best results by scanning electron microscopy indicating that the tourmaline composite powder particle size prepared of this ratio is uniform with the composite powder whiteness of 74.5% which is 23.5% higher than building whiteness of the direct coating agent for mechanical mixing with tourmaline powder. After the composite powder was used to prepare the coating, the results show that the whiteness is 87.1% after formatting coating and negative ions incremental release over the 800 ions/cm3 when the content of tourmaline is 11%.

Abstract: WC-Ni60 composite powders were mixed and deposited on Cr12MoV die steel by vacuum sintering technique. In order to prevent WC powders decomposition at the high temperature, Cr film was coated by D.C. magnetron sputtering and then prepared Cr/WC-Ni60 composite coating. The structure and composition and microhardness were measured by SEM and XRD and hardness tester. Tribological experiments were carried out on an abrasion machine. The results showed that thickness of Cr film is 3~5um. Some WC particles formed hard phases in nickel based solid solution to improve the hardness of the coatings. Due to Cr film preventing WC decomposition, Cr/WC-Ni coating had the higher hardness values compared with WC-Ni60 coating. The coating surface was uniform and compact and had no cracks. During the sliding wear, Cr/WC-Ni coating had a better wear resistance, and mass loss of wear was the least.