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Abstract

Nanoenergetic materials (nEMs) have improved performances compared to their bulk counterpart or microcounterpart. The authors propose an approach to synthesize an Al/CuO based nEM that has several advantages over previous investigations such as enhanced contact, reduced impurities and Al oxidation, tailored dimensions, and easier integration into microsystem. CuO nanowires are synthesized by thermally annealing Cu film deposited onto silicon. Nano-Al is integrated with the nanowires to realize an Al/CuO based nEM. The synthesized nEM is characterized by scanning electron microscopy, high resolution transmission electron microscopy, x-ray diffraction, differential thermal analysis, and differential scanning calorimetry.

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Abstract

A new planar structure of solid propellant micro-rocket for micro-spacecraft and micro-air-vehicle applications is reported in this paper. We have successfully fabricated an array of micro-rockets using MEMS technology. For a low-power consumption, the micro-igniter used here is a resistor deposited on a low tensile stress thin membrane to ensure a good heat transfer to the propellant. Experimental tests of ignition and microcombustion employing double-base (DB) solid propellant mixed with black-powder (BP) are reported and discussed. Tests have showed successful and continuum combustion of about 1.3 mm diameter during few 100 ms from BP ratio in the mixture (x) of 10%. Thrust force delivered by considered structure dimensions, is ranging from 0.1 to 1 mN for x = 10%, 20% and 30%. We expect that this planar structure will deliver a suitable thrust force of few 10 mN when reducing micro-nozzle throat dimensions.

Abstract

Nano energetic materials (nEMs) offer the promise of much higher energy densities, faster rate of energy release, greater stability and more security and could therefore give response to micro energetics challenges. In that context, nano thermite composites, also termed as Metastable Intermolecular Composites (MIC), have become one intensive research focus. In MIC, oxidizer and fuel are mixed at nano scale, thus leading to the improved performance in terms of energy release, sensitivity, stability, and mechanical properties compared to their bulk or micro counterparts. In the literature, there are different approaches to realize MIC such as physical mixing of nano powders of fuel and oxidizer, employment of sol-gel chemistry, deposition of multi-layer nanofoils of oxidizer and fuel, and embedding an array of Fe2O3 nanowires inside a thin Al film. In this study, we propose a novel approach of synthesis of Al/CuO MIC that is completely compatible with MEMS. We successfully develop large-area, uniform, and vertically aligned pure CuO nanowires (<50nm in diameter) by thermal annealing copper thin film deposited onto silicon substrate. Then nano Al is integrated within the CuO nanowires networks to realize a fascinating Al/CuO based MIC. The experimental processes will be first presented. Then different parameters 277 that affect the growth of CuO nanowires are studied in detail. The realized nanowires are then characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). Our approach has several advantages compared to previous investigations. First, Al/CuO MIC is realized by integrating nano Al with CuO nanowires grown from copper thin film, thus enhancing the interfacial contact area, atomic mixing and reactivity compared to powders. Second, the presence of impurities and Al oxidation are much smaller than that in sol-gel or powder mixing processes because the MIC is fabricated under vacuum. Third, since the dimensions of CuO nanowires can be tailored by adjusting the annealing conditions (temperature, duration, gas flow, etc.), the oxidizer/fuel dimensions can be controlled at nanoscale. Fourth, the homogeneity of the final MIC material is improved because only CuO (not Cu2O). Fifth, basically, the fabrication process is simple and can be integrated into a MEMS process. This will result in potential nano based functional structures, for example, nano energetic material based high performance igniter.

Abstract

Large-area and aligned copper oxide nanowires have been synthesized by thermal annealing of copper thin films deposited onto silicon substrate. The effects of the film deposition method, annealing temperature, film thickness, annealing gas, and patterning by photolithography are systematically investigated. Long and aligned nanowires can only be formed within a narrow temperature range from 400 to 500 °C. Electroplated copper film is favourable for the nanowire growth, compared to that deposited by thermal evaporation. Annealing copper thin film in static air produces large-area, uniform, but not well vertically aligned nanowires along the thin film surface. Annealing copper thin film under a N2/O2 gas flow generates vertically aligned, but not very uniform nanowires on large areas. Patterning copper thin film by photolithography helps to synthesize large-area, uniform, and vertically aligned nanowires along the film surface. The copper thin film is converted into bicrystal CuO nanowires, Cu2O film, and also perhaps some CuO film after the thermal treatment in static air. Only CuO in the form of bicrystal nanowires and thin film is observed after the copper thin film is annealed under a N2/O2 gas flow.

Abstract

A new type of one-shot MEMS based thermal micro switch is described and its performance results are presented. The device consists in mechanically breaking a metallic line or locally soldering two metallic lines. The switching between the two stable states (on or off) is accomplished by a current pulse through an integrated heater underneath the electrical lines needed to be interrupted or connected. Some key features are summarized as follows: switches are bistable, integratable and IC compatible. They are compatible with low voltage operation (5V), no contact resistance (0 © for the on-off and ~0.008© for the off-on); they are low energy consumption during switching (3.5mJ for on-off and 130mJ for off-on); switching current is between 10 and 20mA for on-off and between 50-70mA for off-on concept. The minimum switching pulse width is 7ms and 300ms for the on-off and off-on concept respectively; operation may be possible in ambient environment; lifetime expected is very long and both switches can therefore address long life system. Batch fabrication using planar processing methods are used.

Abstract

We present the conception of a micro pressure source for microfluidics applications

Abstract

Mass transfer, diffusion, adsorption and photochemistry are figured out to be the controlling mechanisms for photocatalytic degradation of volatile organic compounds (VOCs) using nano-TiO2 catalyst. A mathematical model for the non-steady photocatalytic degradation process is developed by incorporating these mechanisms in a plane plate air purification physical model. The governing equation and boundary conditions are solved using finite difference method. The computation results are validated using the data obtained from the experiments. And then the model is employed to study the effects of some key factors on the degradation rate of formaldehyde. These factors include UV light intensity, UV light attenuation coefficient, adsorption, catalyst thickness, diffusion, and flow rate. The model can be employed to assist the design of VOCs photocatalytic degradation system using nano-TiO2 catalyst.

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