Abstract: The structure, polarizability and magnetic properties of ZnnOn and Cu-doped Znn-1On (n=2-12, 16) clusters are theoretically investigated using density-functional theory (DFT) at B3LYP/LanL2DZ level. For pure ZnnOn clusters, Zn3O3, Zn8O8 and Zn12O12 are relatively more stable unit, and the ZnnOn clusters with bigger HOMO-LUMO gap tends to have larger <α>/2n. For Cu-doped Znn-1On clusters, the substitution of Zn by Cu atom narrows the HOMO-LUMO gaps and enhances polarizability. In single-doped CuZnn-1On clusters, the magnetic moments of O atoms bonded with Cu atoms are ferromagnetically coupled to the moments of the Cu atoms.
Abstract: The first-principle quantum mechanical method was used to investigate the structures and electric properties of N-doped. Doping of N atom to clusters is found to be energetically quite favorable except for n=16. Different from bulk material, the LUMO-HOMO energy gaps of the InnSbn (n=6-12,14,16,24) clusters are enlarged by doping of N. The analysis of the electron density of the HOMO and LUMO states was performed to understand the behavior .
Abstract: Multi-walled carbon nanotube (MWCNT) fiber reinforced cement-based composites (MWFRC) with 0.1 wt.% and 0.5 wt.% weight concentration of MWCNT (wcM)were prepared, associated with the reference. The electrical resistances and compressive strains of these cured nanocomposites under cyclic uploading/unloading were real-time collected, to explore their stress/strain-sensitive properties. Results reveal as follows, there is no self-sensing trait for the reference, but exists good piezoresisitivity and high strain sensitivity (above 110) for MWFRC; the fractional change in resistivity (Δρ) regularly descends or ascends following the compressive stress, or the longitudinal strain of MWFRC; the resistance caused by pore electrolyte polarization has obvious impact on the time-stability of the Δρ trendline of MWFRC with 0.1 wt.% wcM, similar to the reference, but negligible effect on that of MWFRC with 0.5 wt.% wcM.
Abstract: A wet etching method for preparing silicon nanowires on silicon substrates at near room temperature is presented. The effect of experiment parameter on the silver nanoparticle forming including concentration of AgNO3, immersing time and solution temperature, and the effect of etching time on the length of silicon nanowires are investigated. It is concluded that solution temperature has more impact to diameter of silicon nanowires than concentration of AgNO3 and immersing time and longer etching time may result in longer silicon nanowires.
Abstract: Field emission (FE) characteristics of well-aligned multiwall carbon nanotube arrays (CNTAs) grown on originally polished and energetic iron ion bombarded Si substrates were investigated. It was found that the FE characteristics have been improved remarkably by the pretreatment of iron ion bombardment, an evident promotion of the highest emission current density from 4.05 mA/cm2 to 54.45 mA/cm2 was as an expression of this enhancement, this enhancement in characteristics is attributed to the improved adhesion between CNTs and Si substrate for the existence of iron buffer layer. The relationship between adhesive force and emission current density has been introduced, and the calculation reveals that the adhesion has been enhanced by 14.4 times due to the energetic ion pre-bombardment on Si substrate.
Abstract: Copper nano-clusters were electrodeposited onto the platinum microelectrode by cyclic voltammetry method to fabricate an electrochemical sensor for nitrate determination. The material properties and morphologies of freshly deposited copper layer were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Compared with the microelectrode surface modified by fixed potential deposition method, the surface modified by cyclic voltammetry electrodeposition is porous and has a larger effective surface area. The reduction of nitrate under acidic conditions (pH=2) was characterized by linear sweep voltammetry. The preliminary experimental results reveal that the microelectrode modified by cyclic voltammetry electrodeposition had higher sensitivity of 22.56 uA/mmol for nitrate detection within the concentration range from 0.1mmolL−1 to 4mmolL−1.
Abstract: A kind of flat micro heat pipe with glass fiber wick structure is designed and fabricated. The structure of the wick is presented and also the excellence of the structure is described. For the glass fiber wick, the maximum heat transports is calculated by one-dimensional steady governing equations. Experimental testing is performed for the fabricated micro heat pipe in vacuum. The testing results is presented and analyzed.
Abstract: In this paper, a MEMS-based piezoelectric energy harvester is studied and the whole fabrication process is discussed. The generator structure of composite cantilever with nickel metal mass is devised. MEMS related techniques such as UV-LIGA, ion etching, XeF2 dry etching, wet chemical etching are developed to fabricate the device. This key process includes the bonding a bulk PZT to a Si wafer, and thinning the PZT down to about 15µm in thickness after bonding by mechanical lapping and polishing method. Epoxy resin with a thickness of about 4µm is used as the intermediate adhesive layer. The formed generator is measured on vibration testing setup. The energy under the first resonant mode can be harvested, corresponding to the resonant frequency of 810 Hz . The maximum output voltage under the resonant operation is about 1.23Vp-p.
Abstract: This paper presents the design, simulation and fabrication of an mm-scale air-driven microturbomachine. The circumferential-flow turbomachine has a plain-shaped structure with an overall size of 8×8×3mm3. The predicted formulas for driving torque and driving power are deduced by analyzing the working condition of the model. Finite element simulation is carried out to determine the driving torque and driving power. Turbine and stator are fabricated using UV-LIGA technique, while other components using pension micromachining. Test results of assembled prototype show that under the air-flow speed of 80m/s, no-load and load rotation speed are 10kr/min and 9.5kr/min respectively, and the output power is 326.57µW. The results indicate micro turbomachine is potential power source for the micro system.
Abstract: In this paper, a polymer-based micro direct methanol fuel cell (µDMFC) has been designed, fabricated and tested. Bipolar plates were manufactured with polydimethylsiloxane (PDMS) by molding method. Stainless steel plates with the thickness of 200μm were chosen to fabricate the current collectors. The 0.49cm2 5-layered MEA was fabricated by the catalyst coated membrane (CCM) method. Experiments revealed that the μDMFC generated a maximum power density of 8.30mW/cm2, when the μDMFC was supplied with 2M methanol solution at 0.1ml/min flow velocity under room temperature (20°C) and normal atmospheric pressure. And the cell behaved very steady operated in constant current mode for 7200 seconds (2 hours).