Applied Mechanics and Materials Vol. 607

Abstract: Plasma spray zirconia gradient thermal barrier coating (TBC) and the traditional double-layer structure thermal barrier coating were both studied in this paper. NiCoCrAlY alloy powder was used as bottom bonding materials, 8YSZ (8mol% yttrium stabilized zirconia) was used as top layer materials and the different proportions mixed powder of 8YSZ and NiCoCrAlY was used as gradient layers materials. Bonding strength of thickness gradient coating was measured by tensile experiment. Thermal cycle experiment was carried on to test the thermal shock resistance of TBC. The microstructure after thermal shock experiment was observed to analyze the failure mechanism of TBC. The research result shows that the bonding strength and thermal shock resistance of gradient TBC are much better than the traditional double-layer structure TBC. With the increasing of top layer thickness, thermal shock life of TBC substantially reduces. With the decreasing of ZrO₂ composition proportion in gradient layer, thermal shock life of TBC significantly rises. This result has important significance for the future study of thick TBC.

Abstract: There are few known parameters which govern tungsten trioxide (WO₃) hydrothermal synthesis process which includes material source concentration, synthesis temperature, duration, pH value and additive level. Using design of experiments (DOE) approach, a systematic experimental procedure was conducted to investigate the effect of each parameter to the final morphology of the synthesized nanostructure. Despite the response obtained from this study is in qulitative form, the analysis still can be done to identify the combination of variables that most likely can produce either 1-D, 2-D or 3-D nanostructure. This insight is essential before further optimization of the process can be done in order to predict the behavior of the WO3 hydrothermal synthesis process.

Abstract: Experimental researches are developed on grey cast iron surface to clarify the micro-crack formation mechanism and influence law of graphite phase in bond area. The results show that unreasonable morphology of flake graphite phase in bond area is an important cause of micro-crack initiation and propagation. Their cusps almost cross toward the molten layer and through the bond area. Then the micro-crack grows along the grain boundary. Additionally, under condition of certain specific energy input, an appropriate increase in laser power and scanning speed can enhance molten mass convection. It can be also helpful for the distribution rationalization of graphite phase and reduce crack sources.

Abstract: Core-shell nanoparticle has created great interest among researchers due to their various unique properties. The new properties created are combination of both the core and the shell. In this work, pre-prepared Nickel (Ni) nanoparticles were coated with Gold (Au) to produce core-shell structure. Formation mechanism of the core-shell structure is investigated via UV-Vis spectrum of the as-synthesized particles and its supernatants. Ni nanoparticles were synthesized using polyol method with hydrazine as the reducing agent. Coating of Au was conducted using sodium citrate as the reducing agent and acid citric to control the pH of the mixture. UV-Vis absorption spectra analysis of as-synthesized nanoparticles and the supernatant results revealed that the coating happened via redox-transmetallation process with a very broad peak at about 540 nm and size range of 26 - 40 nm. XPS results suggest that the coating consists of Au compound.

Abstract: By studying the formation of snowflakes, scientists have found that frequency data can be stored in water. Using the homeopathic principles of dilution and succussion, this study explored the relationship between aqueous information transmission and differences in the formation of water crystals. We utilized three different types of experimental solution: bali water, distilled water, and ionized water, and studied the water crystals sprouting from the resulting ice crystals. From the four significant phases of morphological change (mother tincture, 1X, 4c, and 30c), it was determined that at higher dilution ratios, crystals grown in either distilled or ionized water developed from crystallites into a single-body structure, approaching the higher energy form of straight edge hexagonals. This phenomenon demonstrates the features of coherent domains and water clusters, both of which match the homeopathic principles of energy waves and information transmission.

Abstract: This paper presents the development of a new Wood Plastic Composite (WPC) material for Fused Deposition Modeling (FDM) feedstocks. In this study, a biodegradable polymer matrix (POLYACTIDE, PLA) was mixed with natural wood flour (WF) by Brabender mixer, and the samples produced by injection molding machine. The effect of wood was investigated as a filler material in composite FDM feedstock and the detailed formulations of compounding ratio by weight percentage. Based on results obtained, it was found that, compounding ratio of PLA80%:WF20% has a goods result on the tensile strength and PLA60% : WF40% gave a higher value of flexural strength. An increment of 20% to 40% WF filler affected the flexural strength, and hardness results. The highly filled WF content in PLA composites increases the mechanical properties of PMC material through the injection molding process. The potential of development of a sustainable composite material will be explored as the FDM feedstocks in the rapid prototyping process.

Abstract: This paper provides oil properties study of conventional diesel engine oil enriched with hBN/Al₂O₃ nanoparticles. In this study, an optimal composition (0.5 vol.%) of hBN and Al₂O₃ nanoparticles separately dispersed in SAE 15W40 diesel engine oil by sonication technique. The oil properties were studied by measuring the Viscosity Index (VI), Total Acid Number (TAN), Total Base Number (TBN) and flash point temperature. The results reveal that the nano-oil with hBN nanoparticles could improves or at least maintain the key lubrication properties, though the TAN value is slightly increased. The results presented here may facilitate improvements in the conventional diesel engine oil performance.

Abstract: During the process of chemical mechanical planarization (CMP) of copper, benzotriazole (BTA) is the most commonly used inhibitor in the slurry. Though the corrosion inhibition mechanism has been studied widely, the mechanism of BTA layer on copper surface in CMP slurries should be further investigated. In this paper, the adsorption mechanisms of BTA were studied by static corrosion tests. Besides, the surface composition was measured by XPS. Combining with CMP experiments, the material removal mechanism of copper CMP depending on pH values was investigated. It was found that the formation of passive film, consisting of Cu-BTA complex, adsorption of BTA and copper oxides, played a dominant role under acidic conditions. While the surface film composed of adsorption layer of BTA and copper oxides under alkaline conditions. The inhibition mechanism of BTA varied with pH values, resulted in corresponding changes of material removal rate and coefficients of friction.

Abstract: By application of the theory of complex variable functions, dynamic propagation problems concerning symmetrical mode III interface crack of Aluminum alloys were investigated. The problems dealt with can be very facilely translated into Riemann-Hilbert problem by the approaches of self-similar functions, and the universal representations of analytical solutions of the stresses, displacements and dynamic stress intensity factors for the surfaces of symmetrical mode III interface crack subjected to motive increasing loadings Pt⁵/x⁵ and Px⁶/t⁵ were attained, respectively. After those solutions were utilized by superposition principle, the solutions of discretionally complicated problems could be easily acquired.

Abstract: This paper describes the mixing process and homogeneity analysis of a newly developed binder system based on waste polystyrene (PS) and palm kernel oil (PKO) to produce feedstock for metal injection molding (MIM). Since mixing is a critical step in MIM process, hence the mixture of powder and binder should be homogeneous and injectable. In this study, water atomised Stainless Steel powder was mixed with a new binder system consisting of waste polystyrene and palm kernel oil in a Brabender Plastograph EC rotary mixer. Several tests were performed to assess the homogeneity of the feedstock that was produced at 60 vol.% powder loadings. The 60 vol.% was chosen because the Critical Powder Volume Concentration (CPVC) of the SS316L powder was found to be 64.8 vol.%. The tests conducted were density, binder burn-out and SEM morphology observation. It was found that the feedstock shows good homogeneity and suitable for further processing in MIM.