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1.
The effect of curing at different conditions was investigated for flexible model clear coat films for coil coating applications. Based on a commercial polyester binder two formulations with isocyanate based crosslinking agents (hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI)) were prepared. The clear coats were baked at laboratory (145 °C) and industrial processing (300 °C) conditions. While for high temperature curing the baking time was kept constant at 30 s, the curing time at 145 °C, which is above the deblocking temperature of the crosslinking agents, was varied from 10 to 90 min. The clear coat films were characterized as to their thermomechanical and mechanical properties by dynamic mechanical analysis (DMA) and by tensile testing. Regarding DMA loading in tensile and penetration mode was performed. 相似文献
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In this paper thermomechanical and mechanical properties of various free clear coat films for coil-coated steel sheets were studied by dynamic mechanical analysis and tensile testing. To establish structure–property correlations, polyacrylate and polyester binder resins with varying molar mass and functionality were investigated. The clear coat films based on polyacrylate binders exhibited higher glass transitions values, crosslinking densities, elastic modulus and tensile strength values. For both resin types, a relationship of the properties glass transition temperature, crosslinking density, stiffness and tensile strength and the functionality considering the molar mass and the hydroxyl value of the resins was obtained. The elastic strain energy of the investigated brittle clear coat films depended mainly on the elastic modulus. 相似文献
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《Ceramics International》2017,43(12):8873-8878
Film formed by carbon nanotubes is usually called carbon nanotube film (CNTf). In the present study, CNTf fabricated by floating catalyst method was used to prepare CNTf/SiC ceramic matrix composites by chemical vapor infiltration (CVI). Mechanical and electrical properties of the resulting CNTf/SiC composites with different CVI cycles were investigated and discussed, and the results revealed that the CNTf has a good adaptability to CVI method. Tensile test demonstrated an excellent mechanical performance of the composites with highest tensile strength of 646 MPa after 2 CVI cycles, and the strength has a decline after 3 CVI cycles for an excessively dense matrix. While, the elastic modulus of the composite increased with the CVI cycles and reached 301 GPa after 3 CVI cycles. Tensile fracture morphologies of the composites were analyzed by scanning electron microscope to study the performance change laws with the CVI cycles. With SiC ceramic matrix infiltrated into the CNTf, enhanced electrical conductivity of the CNTf/SiC composite compared to pure CNTf was also obtained, from 368 S/cm to 588 S/cm. Conductivity of the SiC matrix with free carbon forming in the CVI process was considered as the reason. 相似文献
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《Ceramics International》2021,47(18):25634-25644
WC-Co pellets electroplated with different Ni coating thicknesses and B318 steel were resistance welded for carbide-tipped saw blade applications. The effects of the Ni coating thickness on the welding process, interfacial microstructures, and mechanical properties of the joints were investigated. The results showed that the shear force increased before decreasing as the Ni coating thickness increased. When the coating thickness was 40 μm, expulsions began to appear during welding, while a thicker coating resulted in longer expulsion times. Voids and macro cracks were generated at the joints because of the expulsions, which reduced the shear force of the joint. The XRD results of the welding slag and the EDS results of the interface indicate that the microstructures can be divided into five phase categories: light gray (Fe3W3C), gray (Co3W3C), white (WC), fishbone eutectic structure (Fe6W6C), and dark [(γ Fe, Ni) solid solutions]. As a thicker Ni coating hinders reactions between molten Fe and dissolved WC, the joint interface contained more Fe6W6C at 20 μm and 30 μm but had more bulk Fe3W3C at 40 μm and 50 μm. The upper part of the joint showed brittle fractures on the WC-Co side, while most of the lower part fractured at the interface. Only the joints at 20 μm and 30 μm had a small fracture area on the steel side. Moreover, the fracture on the steel side at 30 μm showed elongated shear dimples, which explains the maximum shear force of the joint at 30 μm. 相似文献
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Scanning Kelvin Probe (SKP) and FTIR microscopy were applied to study the atmospheric corrosion of galvanized steel coated by electrophoretic epoxy resin (ED) at a defect. 相似文献
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A flat plate in the deposition stage is designed to be tilted flexibly with an angle such that an inclination angle is formed between the ion beam and the direction normal to a polyethylene terephthalate (PET) substrate. Five kinds of PET/aluminum-doped zinc oxide specimen, with 0°, 15°, 30°, 45°, and 60° inclination angles, respectively, were prepared to examine the effect of inclination angle on the mechanical, electrical, and optical properties and morphology of coating films. Using the peaks of the ZnO (002) and ZnO (103) planes in X-ray diffraction analyses, the relative intensity ratios for these two crystallines are defined and used to evaluate the parameters of composite grain size ((g)Composite) and residual stress ((σ)Composite). The experimental results indicate that (σ)Composite increases but (g)Composite mostly decreases with increasing inclination angle. A nearly linear relationship is found between (g)Composite and the d-spacing parameter ((d)Composite). They both decrease with increasing inclination angle. The intensities of ZnO (002) and ZnO (103) planes significantly influence the mean transmittance, absorption, and reflection in the wavelength range of 801–2500 nm (near-infrared). An increase in the relative peak intensity of ZnO (002) increases the mean transmittance and thus lowers the mean absorption and reflectance. The average transmittance decreases and the average reflection increases in the wavelength range of 300–2500 nm with increasing inclination angle. Increasing the composite grain size decreases the average reflection. The ZnO film thickness is proportional to the mean surface roughness of the film. 相似文献
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Effects of ZnO nanoparticles on the mechanical and antibacterial properties of polyurethane coatings 总被引:2,自引:0,他引:2
Polyurethane-based coatings reinforced by ZnO nanoparticles (about 27 nm) were prepared via solution blending. The ZnO/PU films and coats were fabricated by a simple method of solution casting and evaporation. The mechanical properties of the films were investigated by a universal material test, and the abrasion resistance of the prepared coats was evaluated by a pencil-abrasion-resistance tester. It was found that significant improvement of the PU films in Young’s modulus and tensile strength was achieved by incorporating ZnO nanoparticles up to 2.0 wt%, and that the abrasion resistance of the PU coats was greatly enhanced due to the addition of ZnO nanoparticles. Moreover, the antibacterial property test was carried out via the agar dilution method and the result indicated that PU films doped with ZnO nanoparticles showed excellent antibacterial activity, especially for Escherichia coli. 相似文献
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《Journal of the European Ceramic Society》2019,39(2-3):249-254
The effects of two-step sintering on the microstructure, mechanical and thermal properties of aluminum nitride ceramics with Yb2O3 and YbF3 additives were investigated. AlN samples prepared using different sintering methods achieved almost full density with the addition of Yb2O3–YbF3. Compared with the one-step sintering, the grain sizes of AlN ceramics prepared by the two-step sintering were limited, and the higher flexural strength and the larger thermal conductivity were obtained. Moreover, the electrochemical impedance spectroscopy of AlN ceramic was associated with thermal conductivity by analyzing the defects and impurities in AlN ceramics. The fitting grain resistance and the activation energy for the grain revealed the lower concentrations of aluminum vacancy in the two-step sintered AlN ceramics, which resulted in the higher thermal conductivity. Thus, mechanical and thermal properties for AlN ceramics were improved with Yb2O3 and YbF3 additives sintered using two-step regimes. 相似文献
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Taraneh Hezaveh Mohammad Moazami-Goudarzi Arghavan Kazemi 《Ceramics International》2021,47(13):18020-18029
WC-10Co cemented carbides reinforced with 0, 0.5, 1, and 2 wt% graphene nanoplatelet (GNP) were fabricated by ball milling and spark plasma sintering (SPS). The microstructure, structural and phase analysis, hardness, and fracture toughness of WC-10Co/GNP composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and Vickers indenter. Tribological behaviors of the fabricated composites against an alumina counterface were studied using a pin on disk configuration. It was found that GNP refined the microstructure, increased the fracture toughness, and postponed the stable-to-unstable friction transition. While transgranular fracture and crack deflection were observed in the base composite, crack bridging, micro-crack formation, and crack deflection were the major toughening mechanisms in GNP-reinforced cemented carbides. The addition of 1 wt% GNP resulted in the highest hardness and wear resistance. However, at higher GNP contents, both hardness and wear resistance decreased due to the agglomeration of GNPs. Widespread abrasive grooving and Co binder extrusion were characterized as the main controlling mechanisms of wear in GNP-free cemented carbides. The wear of GNP-reinforced cemented carbides was dominated by the formation of a lubricating surface layer and its cracking or fragmentation. Plastic flow is much less likely to occur in the presence of GNPs. 相似文献
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Rui Guo Guoqiang Huang Wei Zhang Wei Guan 《Journal of Adhesion Science and Technology》2018,32(12):1313-1323
Friction stir welding (FSW) was performed on 304 stainless steel sheets. The welding speed was varied from 30 to 70 mm/min. Because the FSW of thin plates is sensitive to heat input. The surface of the welds is smooth and without any macroscopic cracks and cavities only when the rotation speed is 50 mm/min. The stir zone had equiaxed grains with austentic structure due to dynamic recrystallization. There was not any evidence for the presence of sigma phases being found in this study. Meanwhile, there was a weak region in the advancing side because of the flow of plastic metals. However, compared with the base material, mechanical properties of the joint are maintained in a comparatively high level. 相似文献
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《Ceramics International》2021,47(20):28924-28931
In this study, hydroxyapatite (HAp) scaffolds with the pore size of 400, 500, and 600 μm were prepared by stereolithographic 3D printing (SL-3DP). The effects of pore size on mechanical and biological properties of the HAp scaffolds were investigated. Firstly, the macro- and microstructure of the HAp scaffolds were observed. Then, the compressive strength of the HAp scaffolds were tested. Finally, the biological properties of the HAp scaffolds were further characterized in vitro by the synthetic body fluid (SBF) solution immersion testing, as well as by using the cell proliferation and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. From this study, it was found that the HAp scaffold with a pore size of 600 μm had the most promising application prospect. 相似文献
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研究1200℃时效温度下不同时效时间对Cr35Ni45Nb乙烯裂解炉管材料的微观组织、室温和高温(900℃)力学性能的影响。结果表明:在1200℃下,材料力学性能出现先增后减的趋势。当时效135.2 h后,试样抗拉强度、屈服强度、延伸率和冲击韧性达到最大值。时效时间对合金显微组织具有显著的影响。析出并弥散分布的细小的二次碳化物对Cr35Ni45Nb钢综合性能具有强化作用。析出的针状碳化物、碳化物向晶界聚集并粗化、初始的连续网状碳化物结构转变成不连续的链状均导致Cr35Ni45Nb钢力学性能下降和围观组织劣化。 相似文献
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Poly(methyl methacrylate)/zirconia (PMMA/ZrO2) nanocomposites with ZrO2 content as high as 15 wt% were prepared by modifying non-aqueous synthesized ZrO2 nanoparticles with methacryloxypropyltrimethoxysilane (MPS) in tetrahydrofuran, dispersing MPS-functionalized ZrO2 nanoparticles in MMA and following in situ bulk polymerization with controlled pre-polymerization time. The MPS-functionalized ZrO2 nanoparticles showed an efficient crosslinking role in the polymerization, leading to a complete gel of PMMA at 5 wt% of ZrO2 content. Homogeneous dispersion of the ZrO2 nanoparticles at primary particle size level was observed in all nanocomposites, which results in good clarity of the obtained nanocomposites. Hardness tests (pendulum hardness tests and indentation tests) and anti-scratch tests (abrasion tests and nano scratch tests) were employed to probe the surface mechanical properties of the nanocomposites. The properties of nanocomposites as a function of ZrO2 content, revealing from various characterization techniques, are not consistent and discussed in detail. At low ZrO2 content, the mechanical properties are enhanced by the formed crosslinking structure. However, remarkable improvements of hardness and scratch resistance of PMMA were achieved when 15 wt% of ZrO2 content was embedded. 相似文献
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In this work, 316L stainless steel (SS) powder was used. The composition of the powder is as follows: 0.015% C, 1.75% Mn, 0.45% Si, 17.24% Cr, 2.79% Mo, 14.65% Ni, and balance iron. Mixed powder was compressed cold using single action press under 800 MPa pressure. Compressed samples were sintered at 1200 °C, 1250 °C, and 1300 °C into the nitrogen gas atmosphere. In order to determine the mechanical properties of the produced specimens, the fatigue tests, tensile test, three-point bending test, impact test and hardness tests were applied to the specimens. Determined mechanical properties in the result of this work were compared to the properties as stated in ASTM F138-G2. Besides that to define the microstructures of the produced specimens in detail, metallographic studies were performed. 相似文献
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《Ceramics International》2016,42(13):14469-14474
The effect of conventional sintering from 1300 to 1550 °C on the properties of 1 mol% ceria-doped scandia stabilized zirconia was investigated. In addition, the influence of rapid sintering via microwave technique at low temperature regimes of 1300 °C and 1350 °C for 15 min on the properties of this zirconia was evaluated. It was found that both sintering methods yielded highly dense samples with minimum relative density of 97.5%. Phase analysis by X-ray diffraction revealed the presences of only cubic phase in all sintered samples. All sintered pellets possessed high Vickers hardness (13–14.6 GPa) and fracture toughness (~3 MPam1/2). Microstructural examination by using the scanning electron microscope revealed that the grain size varied from 2.9 to 9.8 µm for the conventional-sintered samples. In comparison, the grain size of the microwave-sintered zirconia was maintained below 2 µm. Electrochemical Impedance Spectroscopy study showed that both the bulk and grain boundary resistivity of the zirconia decreases with increasing test temperature regardless of sintering methods. However, the grain boundary resistivity of the microwave-sintered samples was higher than the conventional-sintered ceramic at 600 °C and reduced significantly at 800 °C thus resulting in the enhancement of electrical conduction. 相似文献
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《Ceramics International》2017,43(2):2012-2021
Laser gas assisted texturing of alumina surface is considered and the effects of graphene film on the properties of the textured surface are examined. Since laser texturing under the high pressure nitrogen gas jet environments results in formation of aluminum nitride compounds, free energy of the textured surface reduces considerably. The mismatch between the surface free energies of the graphene film and the laser textured surface makes it difficult to transfer the graphene film on the textured surface without rippling and edge defects. A graphene oxide film is formed at the textured surface prior to transferring of the graphene film. The characteristics of the laser textured and the graphene transferred surfaces are assessed using the analytical tools including electron and atomic force microscopes, Raman spectroscopy, X-ray diffraction, and UV visible absorbance spectroscopy. Surface hydrophobicity of the graphene transferred and laser textured surfaces is determined incorporating the water droplet contact angle measurement technique. Friction coefficient of the graphene transferred and laser textured surfaces are measured using the scratch tester. It is found that laser texturing results in hydrophobic characteristics because of the micro/nano size pillars formed at the surface and reduced surface energy due to aluminum nitride compounds. Transferring of the graphene film on to the laser textured surface reduces both the water droplet contact angle and the contact angle hysteresis. The presence of the graphene film reduces the friction coefficient and it does not alter notably the absorption characteristics of the laser textured surface. 相似文献
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Currently, galvannealed carbon steel has been submitted to phosphatizing and/or chromatizing as surface pre-treatments; however, for economic and environmental issues, the viability of using silanes as an alternative pre-treatment has been studied. The aim of this work is to study the effect of sonication of the solvent solution (50/50%, m/m water/ethanol) with 50 ppm of Ce (IV) ions on the corrosion behavior of bis-1.2-[triethoxysilylpropyl]tetrasulfide (BTESPT) silane film deposited on galvannealed steel. The sonication influence on reactions has been studied and seems to promote the formation of small molecules starting from large ones, the change of the local pH and temperature, beyond the change of the solution viscosity. The corrosion resistance of the steel coated samples was evaluated by electrochemical impedance spectroscopy (EIS), linear polarization resistance (Rp) and potentiodynamic polarization curves. The molecular vibrational and chemical properties of the films were obtained by infrared (IR) and micro Raman spectroscopies. The physical characterization of sonicated solutions was performed by measuring their kinematic viscosity. The images from scanning electron (SEM) microscope were obtained to characterize the aspect and morphology of the film. The results showed that the sonication led to obtaining more homogeneous, compact and corrosion resistant silane films. 相似文献