Key Engineering Materials Vols. 645-646

Abstract: The influence of polyhedral oligomeric silsesquioxane on heat resistance and curing kinetics of potting materials were studied. The results showed that POSS can promote the cure, but did not change the potting materials curing mechanism. The research results have important significance for improving the performance of potting materials in electronic products.

Abstract: Recently, due to the prediction of the forming phase only focuses on the case which a simple metal ion implants into a single metal matrix, we will study that a simple metal ion is implanted into alloy matrix in this paper. The forming phases in Ni⁺ implantation into Ti6Al4V at elevated temperature will be predicted by the effective heat of formation (EHF) model. The results show that the prediction is consistent with the experimental findings, the first-phase is TiNi with the most negative EHF, the second-phase is Ti₂Ni which component concentrations of Ni limited element is lower and locates on the left in the Ti-Ni binary alloy phase diagram, and the TiNi₃ phase is not found in the experiment. Simultaneously, we explain correctly why the Ni-Al or Ni-V phases don’t generate in Ni⁺ implantation into Ti6Al4V at elevated temperature.

Abstract: A new technology of preparing submicron medium-carbon steel quickly using martensitic steel by equal-channel angular pressing is developed. The technology combines martensite phase transformation with severe plastic deformation. In this research, martensitic steel is heated to 923K quickly and held for appropriate time, then equal-channel angular pressing is implemented. Supersaturated ferrites of average grain size within 0.5μm are obtained by the interaction of dislocation intersection, dynamic recrystallization and strain-induced phase transformation. At the same time, strain-induced phase transformation leads to dispersive precipitation of supersaturated carbon particles in the form of carbide inside grains or in grain boundaries. The optimal size of ferrite grains and the optimal distribution of carbides are acquired by controlling tempering temperature and time. The results show that ultra-fine grained materials prepared by this technology possess superior thermal stability.

Abstract: In this research, the friction and wear characteristics of nanofluids were studied through experimental investigation by dispersing ZnO nanoparticles into 60SN base oil. Oleic acid was used as a surfactant for the improved dispersibility and stability of nanofluids. Nanoparticles were dispersed using a magnetic stirring apparatus and ultrasonic bath. The micro/nano mechanics comprehensive test system UNMT- 1 wear testing machine was used to evaluate the friction properties. The wear track was measured by a Zeiss laser confocal microscope and scanning electron microscope (SEM). The effect of ZnO nanoparticles on the friction and wear performance of the nanofluids was investigated, and the optimal ratio between the surfactant and particle concentration was studied. The results showed that oil-based nanofluids with ZnO nanoparticles could reduce friction and wear under certain conditions. The optimally stable concentration of the fluids was that the oleic acid adding quantity was 5wt%～10wt% and ZnO nano-particles was 0.2wt%～0.7wt%. And when the oleic acid adding quantity was 10wt% and ZnO nanoparticles was 0.2 wt%, the nanofluids had best friction-reducing and anti-wear properties.

Abstract: This study focused on the evaluation of TiO₂ nanofluid coolant for automobile engine cooling applications. It was observed that, about 3% of thermal conductivity enhancement and above 10% convective heat transfer enhancement could be achieved with the usage of 1.0 wt.% TiO₂ nanofluid coolant compared to base coolant without nanoparticles. More importantly, corrosion-inhibiting properties of TiO₂ nanofluid coolant were investigated, which indicated that the nanofluid coolant possess the characteristics of a qualified engine coolant should have. The evaluation results showed that the nanofluid coolant could be a promising engine coolant for automobiles.

Abstract: This paper models the hydrodynamic focusing performance of a micro-fluidic chip with rectangular cross-sections, and the relationships between the aspect ratio, flow rate ratio of sheath flows to the sample flow, and dimensions and position of the focused sample flow are obtained. The simulation results are consistent with theoretical outcomes. And preliminary experiments were carried out to prove the simulation results.

Abstract: The micro-fluidic inertial switch with liquid metal droplet moving under the action of acceleration has overcome the disadvantages of contact bounce, arcing and welding, as are found in the traditional inertial switch. Micro-fluidic inertial switches have no moving parts, a small contact resistance, a long service life and a large current capability. In this paper, we present a micro-fluidic inertial switch that is composed of two-stage micro-valves. This design facilitates tuning of the threshold by adjusting the mercury volume, and so provides better switching performance. Numerical simulation of an orthogonal experiment is used to identify the semi-analytical model of the switch threshold. Results show that the identified model is in accordance with simulation results. Switch prototypes are fabricated by micro-machining techniques including ICP dry etching, sputtering technology and anodic bonding. Centripetal test results show that the switch threshold can be tuned by the careful adjustment of mercury volume.

Abstract: According to the Bernoulli equation and Darcy formula, the flow model of slurry in micro-channels was established, it indicated that slurry viscosity is the main factor affecting the slurry mean velocity. According to the characteristics that liquid viscosity is mainly determined by the liquid temperature and the property that mechanical friction can improve the liquid temperature, the effects of slurry temperature, working pressure and polishing speed on the heterogeneity of polishing rate were investigated. The results showed that the effect of removal rate of each parameter on the central part of the copper film can be described as: slurry temperature > working pressure > polishing speed. In order to obtain the best planarization process, through the central composite experimental method, the technological parameters were optimized regarding the heterogeneity of polishing rate as response value. It was finally concluded that: when the slurry temperature was 21.60°C, the working pressure was 8.83kpa, the system speed was 43.92rpm, the predicted minimum value of the heterogeneity of polishing rate (HOPR) was 0.0574.

Abstract: Illegal cooked oil is a serious food safety issue in China, while an effective authentication method is still lacking. In this paper, a microfluidic device was applied for the discrimination of low-grade oil from edible oil, by creating water droplets of different sizes in different oils.

Abstract: This paper develops an analytical model to investigate the effect of elliptical dimples on hydrodynamic lubrication of surface contact. The hydrodynamic pressure generated by elliptical dimples is solved by the multi-grid method. The evaluation criterion of hydrodynamic effect of dimensionless average pressure is calculated and presented with the variation of elliptical dimple depth, area density, slender ratio and inclination angle. The results indicate that geometrical parameters of elliptical dimples have an obvious influence on the hydrodynamic pressure. The hydrodynamic lubrication performance can be ameliorated by optimizing the geometrical parameters of elliptical dimples according to the operating parameters of the mechanical components.