Other

Massachusetts Institute of Technology

Alvin Gabriel Stern

Robert K Reich

Bernard B Kosicki

David C Shaver

Brian F Aull

Andrew H Loomis

Bradley J Felton

Douglas J Young

A hydrogen fuel, sustainable, closed clean energy cycle based on green chemistry is presented for large scale implementation using a cost effective electrolytic cell. A chemical reaction between salinated (sea) or desalinated (fresh) water (HO) and sodium (Na) metal produces hydrogen (H) fuel and sodium hydroxide (NaOH) byproduct. The NaOH is reprocessed in a solar powered electrolytic Na metal production plant that can result in excess chlorine (Cl) from sodium chloride (NaCl) in sea salt mixed with NaOH, used to effect freezing point lowering of seawater reactant for hydrogen generation at reduced temperatures. The method and molten salt electrolytic cell enable natural separation of NaCl from NaOH, thereby limiting excess Clproduction. The recovered NaCl is used to produce concentrated brine solution from seawater for hydrogen generation in cold climates, or becomes converted to sodium carbonate (NaCO) via the Solvay process for electrolytic production of Na metal without Clgeneration.

Method and molten salt electrolytic cell for implementing a hydrogen fuel, sustainable, closed clean energy cycle on a large scale

A compact, chemical-mechanical apparatus, having no electrical components, for storing and generating hydrogen safely, on-demand, at the time and point of use in small or large quantities using the environmentally clean chemical reaction between sodium metal and water to generate hydrogen (H) gas and sodium hydroxide (NaOH) byproduct is presented, for powering electricity generating fuel cells for large scale commercial and private electric motor vehicle transport. The apparatus of the present invention supports hydrogen gas generation by the controlled addition of liquid water to solid sodium metal to produce hydrogen gas and sodium hydroxide using only mechanical components without electrical components that require external power and can generate sparks or short circuits, producing catastrophic failure in hydrogen systems. The sodium hydroxide can be reclaimed and recycled by electrolysis using hydroelectric power to recover the sodium metal for reuse in generating hydrogen, thereby forming a complete clean energy hydrogen power cycle.

Compact, safe and portable hydrogen generation apparatus for hydrogen on-demand applications

A high purity, non-toxic, environmentally friendly method for anisotropically etching single crystal silicon and etching polysilicon, suitable for microelectronics, optoelectronics and microelectromechanical (MEMS) device fabrication, using high purity aqueous ammonium hydroxide (NHOH) solution generated at the point of use, is presented. The apparatus of the present invention supports generation of high purity aqueous NHOH solution from ammonia NHgas dissolved into distilled/deionized water and maintained in equilibrium with an overpressure of NH, within a hermetically enclosed chamber at the optimal temperature between 70-90&#xb0; C., preventing evaporation of NHgas from aqueous NHOH solution for achieving a high anisotropic etching rate. Other liquid anisotropic etching methods for silicon may use tetramethylammonium hydroxide (TMAH). In contrast to carbon containing TMAH, the NHgas and HO precursors of NHOH etchant eliminate risk for solid residues to be deposited on silicon due to being composed entirely of elements having a gaseous form at room temperature.

High purity, environmentally clean method and apparatus, for high rate, liquid anisotropic etching of single crystal silicon or etching of polycrystalline silicon, using an overpressure of ammonia gas above aqueous ammonium hydroxide

A linear, automated apparatus and method for clean, cost-effective, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials is presented, constructed principally from corrosion resistant stainless steel or nickel, enabling utilization of high purity water based abrasive slurry. The circular stainless steel or nickel lapping plate of the apparatus supports a synthetic nylon or rayon pad, whereby material is abraded from the workpiece primarily through the reciprocal, back and forth, linear movement of the workpiece holder, diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction. Intermittent rotation of the circular lapping plate for the sole purpose of ensuring uniform wear on the circular nylon or rayon pad and lapping plate, eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.

Linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials

A very high transmittance, back-illuminated, silicon-on-thin sapphire-on-fused silica wafer substrate design is presented for enabling high quantum efficiency and high resolution, silicon or silicon-germanium avalanche photodiode detector arrays with improved indirect optical crosstalk suppression. The wafer substrate incorporates a stacked antireflective bilayer between the sapphire and silicon, comprised of single crystal aluminum nitride (AlN) and non-stoichiometric, silicon rich, amorphous silicon nitride (a-SiN), as well as a one quarter wavelength, magnesium fluoride (&#x3bb;/4-MgF) back-side antireflective layer which is bonded to a fused silica wafer. The fused silica provides mechanical support, allowing the sapphire to be thinned to optimal thickness below 50 &#x3bc;m, for improved optical transmittance and in conjunction with monolithic sapphire microlenses, suppression of indirect optical crosstalk from multiple reflections of APD emitted light. After solid-state device fabrication, the silicon can be coated with photoresist and the fused silica dissolved in buffered hydrogen fluoride (HF) to recover the thin Si&#x2014;(AlN/a-SiN)-sapphire-(MgF).

Thin, very high transmittance, back-illuminated, silicon-on-saphire semiconductor substrates bonded to fused silica

An advanced, very high transmittance, back-illuminated, silicon-on-sapphire wafer substrate design is presented for enabling high quantum efficiency and high resolution, silicon or silicon-germanium avalanche photodiode detector arrays. The wafer substrate incorporates a stacked antireflective bilayer between the sapphire and silicon layers, comprised of single crystal aluminum nitride (AlN) and non-stoichiometric, silicon rich, amorphous silicon nitride (a-SiN), that provides optimal refractive index matching between sapphire and silicon. A one quarter wavelength, magnesium fluoride (&#x3bb;/4-MgF) antireflective layer deposited on the back surface of the thinned sapphire provides refractive index matching at the air-sapphire interface. Selecting a composition of x=0.62 for a-SiN, tunes an optimal refractive index for the layer. Selecting design thicknesses of 52 nm for single crystal AlN, 30 nm for a-SiN, and 120 nm for &#x3bb;/4-MgFyields a back-illuminated optical transmittance T&#x3e;50% for 250-300 nm, T&#x3e;70% for 300-400 nm and T&#x3e;90% for 400-1100 nm.

Very high transmittance, back-illuminated, silicon-on-sapphire semiconductor wafer substrate for high quantum efficiency and high resolution, solid-state, imaging focal plane arrays

An advanced, back-illuminated, silicon avalanche photodiode (APD) design is presented using silicon-on-sapphire with a novel crystalline aluminum nitride (AlN) antireflective layer between the silicon and R-plane sapphire. The substrate supports optical and electrical integration of a high quantum efficiency silicon APD with a gallium nitride (GaN)-VCSEL diode in each pixel to form a novel, compact, emitter-detector pixel for passive and active 2-D and 3-D high resolution, imaging focal plane arrays. Silicon mesa pixels are anisotropically etched with a central inverted mesa frustum cavity. The APD detector is fabricated in the silicon mesa and the GaN-VCSEL diode is grown epitaxially in the center of the mesa. A sapphire microlens below each pixel collimates the VCSEL beam and focuses optical returns into the APD detector. APDs share a common front-side anode, and VCSELs share a common cathode. The APD cathode is electrically connected to the VCSEL diode anode in each emitter-detector pixel.

Compact, all solid-state, avalanche photodiode emitter-detector pixel with electronically selectable, passive or active detection mode, for large-scale, high resolution, imaging focal plane arrays

A photon-counting Geiger-mode avalanche photodiode intensity imaging array includes an array of pixels, each having an avalanche photodiode. A pixel senses an avalanche event and stores, in response to the sensed avalanche event, a single bit digital value therein. An array of accumulators are provided such that each accumulator is associated with a pixel. A row decoder circuit addresses a pixel row within the array of pixels. A bit sensing circuit converts a precharged capacitance into a digital value during read operations.

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Newton, MA, United States of America

Alvin Gabriel Stern