Microfabricated rankine cycle steam turbine for power generation and methods of making the same

In accordance with the present invention, an integrated micro steam turbine power plant on-a-chip has been provided. The integrated micro steam turbine power plant on-a-chip of the present invention comprises a miniature electric power generation system fabricated using silicon microfabrication technology and lithographic patterning. The present invention converts heat to electricity by implementing a thermodynamic power cycle on a chip. The steam turbine power plant on-a-chip generally comprises a turbine, a pump, an electric generator, an evaporator, and a condenser. The turbine is formed by a rotatable, disk-shaped rotor having a plurality of rotor blades disposed thereon and a plurality of stator blades. The plurality of stator blades are interdigitated with the plurality of rotor blades to form the turbine. The generator is driven by the turbine and converts mechanical energy into electrical energy

IMECE2005-81435 DEMONSTRATION AND CHARACTERIZATION OF A MULTI-STAGE SILICON MICROTURBINE

Abstract -This paper presents the experimental testing and characterization of a microscale radial outflow turbine with four concentric stages. The device is a five layer structure composed of shallow and deep reactive ion etched silicon wafers and an ultrasonically drilled Pyrex glass wafer that are assembled using anodic and fusion bonding techniques. They enclose a 4mm diameter rotor that was spun up to 330,000 rpm and produced roughly 0.1W of mechanical power from each stage totaling 0.38W with 0.75 atm differential pressure across the microturbine. Modeling of the turbine based on a mean line analysis with loss correlations extracted from CFD suggests a turbine isentropic efficiency of 35% and Re=266 at the maximum speed. The pressure distribution across the blades rows was measured and showed close agreement with the calculation results. Using the model, the microturbine is predicted to produce 3.2 watts with an isentropic efficiency of 63% at a rotor speed of 1.1 million rpm

Atomically thin MoS2: A new direct-gap semiconductor

The electronic properties of ultrathin crystals of molybdenum disulfide consisting of N = 1, 2, ... 6 S-Mo-S monolayers have been investigated by optical spectroscopy. Through characterization by absorption, photoluminescence, and photoconductivity spectroscopy, we trace the effect of quantum confinement on the material's electronic structure. With decreasing thickness, the indirect band gap, which lies below the direct gap in the bulk material, shifts upwards in energy by more than 0.6 eV. This leads to a crossover to a direct-gap material in the limit of the single monolayer. Unlike the bulk material, the MoS2 monolayer emits light strongly. The freestanding monolayer exhibits an increase in luminescence quantum efficiency by more than a factor of 1000 compared with the bulk material.Comment: 15 pages, 4 figure

Synthesis of large-area multilayer hexagonal boron nitride for high material performance

Although hexagonal boron nitride (h-BN) is a good candidate for gate-insulating materials by minimizing interaction from substrate, further applications to electronic devices with available two-dimensional semiconductors continue to be limited by flake size. While monolayer h-BN has been synthesized on Pt and Cu foil using chemical vapour deposition (CVD), multilayer h-BN is still absent. Here we use Fe foil and synthesize large-area multilayer h-BN film by CVD with a borazine precursor. These films reveal strong cathodoluminescence and high mechanical strength (Young’s modulus: 1.16±0.1 TPa), reminiscent of formation of high-quality h-BN. The CVD-grown graphene on multilayer h-BN film yields a high carrier mobility of ~24,000 cm[superscript 2] V[superscript −1] s[superscript −1] at room temperature, higher than that (~13,000 [superscript 2] V[superscript −1] s[superscript −1]) with exfoliated h-BN. By placing additional h-BN on a SiO[subscript 2]/Si substrate for a MoS[subscript 2] (WSe[subscript 2]) field-effect transistor, the doping effect from gate oxide is minimized and furthermore the mobility is improved by four (150) times.Korea Institute of Science and Technology. Institutional ProgramNational Science Foundation (U.S.) (STC Center for Integrated Quantum Materials Grant DMR-1231319)Massachusetts Institute of Technology. Institute for Soldier Nanotechnologie

Continuum elastic modeling of graphene resonators

Starting from an atomistic approach we have derived a hierarchy of successively more simplified continuum elasticity descriptions for modeling the mechanical properties of suspended graphene sheets. The descriptions are validated by applying them to square graphene-based resonators with clamped edges and studying numerically their mechanical responses. Both static and dynamic responses are treated. We find that already for deflections of the order of 0.5{\AA} a theory that correctly accounts for nonlinearities is necessary and that for many purposes a set of coupled Duffing-type equations may be used to accurately describe the dynamics of graphene membranes.Comment: 7 pages, 5 figure