Microstructural evolution and mechanical properties of Mg composites containing nano-B4C hybridized micro-Ti particulates

In this work, the microstructural evolution and mechanical properties of extruded Mg composites containing micro-Ti particulates hybridized with varying contents of nano-B4C are investigated, and compared with Mg-5.6Ti. Microstructural characterization showed the presence of uniformly distributed micro-Ti particles embedded with nano-B4C particulates that resulted in significant grain refinement. Electron back scattered diffraction (EBSD) analyses of Mg-(5.6Ti + x-B4C)(BM) hybrid composites showed that the addition of hybridized particle resulted in relatively more recrystallized grains, realignment of basal planes and extension of weak basal fibre texture when compared to Mg-5.6Ti. The evaluation of mechanical properties indicated improved strength with ductility retention in Mg-(5.6Ti + x-B4C)(BM) hybrid composites. When compared to Mg-5.6Ti, the superior strength properties of the Mg-(5.6Ti + xB(4)C)(BM) hybrid composites are attributed to the presence of nano-reinforcements, the uniform distribution of the hybridized particles, better interfacial bonding between the matrix and the reinforcement particles and the matrix grain refinement achieved by nano-B4C addition. The ductility enhancement obtained in hybrid composites can be attributed to the fibre texture spread and favourable basal plane orientation achieved due to nano B4C addition. (C) 2013 Elsevier B.V. All rights reserved.

Magnetic field induced tailoring of mechanical behavior of fluid filled micro porous carbon nanotube foam

Compressive loading of the carbon nanotube (CNT) has attracted much attention due to its entangled cellular like structure (CNT foam). This report investigates the mechanical behavior of magnetorheological fluid impregnated micro porous CNT foam that has not been realized before at this scale. Compressive behavior of CNT foam is found to greatly depend on the variation in both fluid viscosity as well as magnetic field intensity. Moreover, maximum achieved stress and energy absorption in CNT foam followed a power law behavior with the magnetic field intensity. Magnetic field induced movement of both CNT and iron oxide particles along the field direction is shown to dominate compressive behavior of CNT foam over highly attractive van der Waals forces between individual CNT. Therefore, this study demonstrates a method for tailoring the mechanical behavior of the fluid impregnated CNT foam. (C) 2014 AIP Publishing LLC.

Voltage programmable dual-band bandpass/bandstop filter response in a single micro-electro-mechanical device

This paper reports on a switchable multi-band filter response achieved within a single micro-electro-mechanical device. A prototype device fabricated in a SOI process demonstrates a voltage programmable and tunable, dual-band, band-pass/band-stop response. Both analytical and finite element models are introduced in this paper to elucidate the operating principle of the filter and to guide filter design. Voltage programmability of the filter characteristic is demonstrated with the ability to independently tune the centre frequency and bandwidth for each band. A representative measurement shows that the minimum 3 dB-bandwidth (BW) is 155 Hz, 140Hz, and 20 dB-BW is 216 Hz, 203Hz for the upper-band and lower-band center frequencies located at 131.5 kHz and 130.7 kHz, respectively. © 2011 IEEE.

Micro-electro-mechanical resonant tilt sensor

This paper reports a micro-electro-mechanical tilt sensor based on resonant sensing principles. The tilt sensor measures orientation by sensing the component of gravitational acceleration along a specified input axis. Design aspects of the tilt sensor are first introduced and a design trade-off between sensitivity, resolution and robustness is addressed. A prototype sensor is microfabricated in a foundry process. The sensor is characterized to validate predictive analytical and FEA models of performance. The prototype is tested over tilt angles ranging over ±90 degrees and the linearity of the sensor is found to be better than 1.4% over the tilt angle range of ±20°. The noise-limited resolution of the sensor is found to be approximately 0.00026 degrees for an integration time of 0.6 seconds. © 2012 IEEE.

Micro-electro-mechanical resonant tilt sensor with 250 nano-radian resolution

This paper reports a high-resolution frequency-output MEMS tilt sensor based on resonant sensing principles. The tilt sensor measures orientation by sensing the component of gravitational acceleration along a specified input axis. A combination of design enhancements enables significantly higher sensitivity for this device as compared to previously reported prototype sensors. The MEMS tilt sensor is calibrated on a manual tilt table over tilt angles ranging over 0-90 degrees with a relatively linear response measured in the range of ±20°(linearity error <2.3%) with a scale factor of approximately 50.06 Hz/degree. The noise-limited resolution of the sensor is found to be approximately 250 nano-radians for an integration time of 0.8 s, which is over an order of magnitude better than previously reported results [1]. © 2013 IEEE.

Thermo-mechanical analysis of the packaging process for micro-electronic displays

Micro-electronic displays are sensitive devices and its performance is easily affected by external environmental factors. To enable the display to perform in extreme conditions, the device must be structurally strengthened, the effects of this packaging process was investigated. A thermo-mechanical finite element analysis was used to discover potential problems in the packaging process and to improve the overall design of the device. The main concern from the analysis predicted that displacement of the borosilicate glass and the Y stress of the adhesive are important. Using this information a design which reduced the variation of displacement and kept the stress to a minimum was suggested

Mechanical properties of micro-porous metals produced by space-holding sintering

Micro-porous nickel foams with an open cell structure were fabricated by the space-holding sintering. The average pore size of the micro-porous nickel specimens ranged from 30 μm to 150 μm, and the porosity ranged from 60 % to 80 %. The porous characteristics of the nickel specimens were observed using scanning electron microscopy (SEM). The mechanical properties were studied using compressive tests. For comparison, macro-porous nickel foams prepared by the chemical vapour deposition method with pore sizes of 800 μm and 1300 μm and porosity of 95 % were also presented. Results indicated that the ratio value of 6 and higher for the specimen length to cell size (L/d) is satisfying for obtaining stable compressive properties. The micro-porous nickel specimens exhibited different deformation behaviour and dramatically increased mechanical properties, compared to those of the macro-porous nickel specimens.