Advanced Materials Research Vols. 652-654

Abstract: Effects of replacing partial zinc dust with conductive pigments on the anti-corrosion properties of ethyl silicate zinc-rich coatings with low zinc content were investigated. Salt spray test, salt immersion test and open circuit potential(OCP) measurement were utilized to evaluate anti-corrosion properties. Experimental results revealed that the effects of conductive pigments content on anti-corrosion properties are similar for di-iron phosphide powder, graphite powder and aluminum powder employed in this article. For every kind of conductive pigments, protection life in salt spray test, protection life in salt immersion test, galvanic protection life and initial OCP change with conductive pigments content increase in a similar way. They all reach an extreme point, and all the extreme points correspond to a same replacing ratio named best replacing ratio. The best replacing ratio is 20,15 and 15wt% for di-iron phosphide powder, graphite powder and aluminum powder respectively. Comparing with non-replacing coatings, conductive pigments-containing coatings at best replacing ratio possess both lower zinc content and better anti-corrosion properties.

Abstract: In this study, the dense and well-integrated Ir films were electrodeposited on Pt substrate at a constant current process in the NaCl-KCl molten salt system containing IrCl3. The morphology and constitution of the Ir films at different process conditions were examined by scanning electron microscope (SEM), energy dispersive spectroscope (EDS) and X-ray diffraction (XRD) respectively. The results showed that IrCl3 concentration had significantly influenced the surface morphology of the Ir film. The particles of the deposition film surface became lager with increasing the fraction of IrCl3 and gradually decreased with increasing the temperature. However, the film quality decreased due to the formation of some tiny holes when further increasing the temperature. The particle size decreased gradually with the increase of deposition current density. The addition of CsCl could not only reduce the molten salt temperature but also increase the deposition rate of Ir.

Abstract: This paper presents the research on the influence of carburizing and heat treatment on the properties and microstructure of a new medium carbon alloy steel Fe-0.39C-0.99Si -0.37Mn -5.06Cr-1.21Mo-0.75V (wt.%) used for disk cutter ring. The carburized case has secondary cementite besides those appeared in core such as pearlite and some carbides of Cr, Mo and V. Microstructure of the case is coarse and there are more and larger carbide particles than in core. After quenching and tempering, the carburized case and the core transformed into the microstructure comprised mostly of troostite and fully precipitated tiny carbide particles of Cr, Mo and V. The grains in the carburized case are still larger and the quantity of carbide precipitations including cementite is larger compared with that in the core. Finally, the case depth of about 1mm can be obtained; the surface hardness is above 60HRC; the core hardness is above 55HRC; and the impact toughness reaches 16.9 kJ/cm².

Abstract: Based on the experimental optimal designing method, the experimental plan was set up. In order to study anti-fatigue capability of the gear, the laser engraving technology was applied to process the grid type bionic micro-morphology texture on the gear teeth surface. Different anti-fatigue characteristics of the bionic samples were obtained through analyzing the fatigue tests results. The results showed that the pitting ratio of the gear specimens with the grid micro-morphology had been decreased obviously. The grid bionic surface micro-morphology on the gear had improved the anti-fatigue capability of the gear to 139%, and mechanism of anti-fatigue of the bionic gear was ascribed to “Dam Effect”, laser strengthen and changing of lubrication.

Abstract: Hydrothermal synthesized lead titanate (PbTiO3¬) powder was prepared in a Teflon-lined stainless steel bomb at different bath temperatures. X-ray diffraction was performed to examine the phase assignment and crystallographic properties of hydrothermal synthesized lead titanate powder. Silicon dioxide (SiO2) was thermally deposited and adapted as intermediate layer on p-Si (100) substrates for MFIS (Metal/Ferroelectric/ Insulator/Semi-conductor) design. The microstructures of PbTiO3 film for both MFS and MFIS designs were observed by scanning electron microscopy (SEM). Charge conduction mechanism was also interpreted by C-2-V relationship. Polarization and electric field characteristics were measured by Sawyer-Tower circuit and good hysteresis nature was formed for both structures of the films. The loop of MFIS was wider than that of MFS cell. Also, the higher value of polarization (Ps=3.21E-03µC/cm2) for MFIS could be explained on the basis of higher dipole moment in this SiO2 buffer layer.

Abstract: SiO₂ modified fluorosilicone acrylic copolymer hybrids were synthesized via seeding emulsion polymerization in the presence of conventional nonionic and anionic surfactants, in which methyl methacrylate (MMA) and butyl acrylate (BA) were used as main monomers, small amount of methacrylic acid (MAA) and 2-hydroxyethyl methacrylate (HEMA) were used as functional monomers to confer adhesion, hardness and strength upon the latex film, while trifluoroethyl methacrylate (TFMA) and vinyl triethoxy silane (VTES) were used as fluorine- and silicon- containing monomers respectively. Meanwhile, tetraethoxysilane (TEOS) used as the precursor to prepare in-situ SiO₂ nanoparticles, was added during the polymerization process, which resulted in SiO₂ enhanced fluorosilicone acrylic copolymer latexes. SiO₂ nanoparticles were produced in-situ during the polymerization. The nanocomposite latex film revealed better thermal resistance and wear resistance properties as compared with the counterpart free of SiO₂ nanoparticles prepared under similar polymerization conditions.

Abstract: The failure characteristics of silicon nitride thin film deposited on GaAs substrate were investigated by use of nanoscratch. It was found that the film started to failvia delamination or buckling, which should beattributed to interfacial shear stress. The cracks were then formed and propagated around the edge of the delaminated film before it was chipped away by the moving tip. A normal load of 6.5 mN, corresponding to a depth of 150 nm, was found to be the critical threshold for theinterfacial failure. The fracture energy release rateof the film/substrate interface, or the work of adhesion, was calculated as 2.90 J/m2.

Abstract: Ni-P diamond particles (20μm) composite coating on friction shims were prepared by electroless plating. Morphology and phase composition of the composite coating were measured by SEM with EDS and XRD. The friction coefficient of the coating was test with scratch test. The results showed that diamond particles distribution was uniform and not stacked by two steps for 10 min. The diamond particles were half embedded in the Ni-P substrate. The element of the coating was Ni,P,C and the phase composition was Ni and diamond. Adhesion of the composite coating was higher than that of the Ni-P coating. Friction coefficients of the Ni-P coating and Ni-P composite coating were 0.47 and 0.18. Half –naked diamond particles played a pinning role and prevented from wear of the coating to get the big friction coefficient and good wear resistance. This Ni-P composite coating on friction shims would improve friction shims technology and realize the production of localization of friction shims.

Abstract: The Al2O3 gradient ceramics coating was cladded on the high Cr cast steel by 5KW crosscurrent CO2 laser with Ni-based alloy which was used as transition metal in this experiment. The microstructure is analyzed with optics microstructure analyzer and the crystal grain characteristic is studied. The results show that the microstructure of laser cladding layer contains the plane crystal zone which grows along the substrate, the cellular crystal zone, the dendritic crystal zone and the surface equiaxed cryatal zone. The microstructure of the coating compared with the substrate is extremely fine, and the microstructure of multi-layer cladding presents stratification. The phase composition of the cladding layer is composed primarily of NiAl intermetallic compound, also includes γ-FeNi and a little Ni3Al compound. The Al2O3 particles that some present the single crystal form and some accumulate in together, play the dispersion strengthening role in the coating material. The massive twin crystals and the dislocation pile-ups are found to exist in the cladding layer.

Abstract: Because of the problems caused by icing and snow, it is meaningful to develop coatings for anti-icing. In this paper, a superhydrophobic coating was successfully prepared by compounding fluorine-containing acrylate polymer, polysiloxane and nano-SiO₂. Results of Fourier transform infrared spectroscopy (FT-IR) showed that epoxy groups in fluorine-containing acrylate polymer were partially cross-linked with silanol groups in polysiloxane, while self-crosslinking of silanols dominates the curing reaction. It was proven that there was a positive correlation between water contact angle (WCA) and nano-SiO₂ amount, exhibiting a maximum WCA value of 153.6°. Nevertheless, the superhydrophobic coating is subject to collapse and the nano-particles could be scrubbed away during icing. As a result, the superhydrophobicity had trivial contribution to deicing in this experiment.