Abstract: A system and method for detecting gas concentrations in a target environment uses an array of sensors. Each sensor generates a respective voltammogram in response to the environment, and the voltammograms are collectively transformed into bins that each have a distribution and a height. Normalized bins are then matched with a training set to determine whether a selected gas is present. Also, an un-normalized bin is fitted with the training set to ascertain a concentration of the gas. For this operation, the training set includes normalized and un-normalized data references previously derived from empirically defined voltammograms.

Abstract: A portable system and method for producing biofuel from algae are disclosed. In the portable system, a chemostat and a plug flow reactor formed from plastic bladders are interconnected. Further, an algae separator is in fluid communication with the plug flow reactor for removing algae cells. Also, the system includes a device for processing biofuel from the algae cells. Importantly, the system includes a temperature controller to maintain desired temperatures in the chemostat and plug flow reactor for algae growth and intracellular algae production. In order to further support algae cell growth, the system includes a device for capturing carbon dioxide and delivering the carbon dioxide to the chemostat.

Abstract: An electrolyzer for generating hydrogen by the electrolytic dissociation of water employs anode and cathode half-cells, separated by a planar polymer-based solid electrolyte, and includes a water reservoir for independently maintaining a desired level of water in the anode and cathode half-cells. A hydrogen exit chimney extends vertically upward from each cathode half-cell and enters a separation chamber; a gas exit passageway therefrom is closed by a separation membrane that allows the passage of H2 but rejects liquid H2O, while a return water passageway enters near the bottom of the cathode half-cell. The half-cells are preferably formed by molded plastic frames that are arranged as a cell stack containing a plurality of electrolytic cells, with flat metal anodes and cathodes being respectively sandwiched about the solid electrolyte membrane in each cell.

Abstract: An electrolyzer for generating hydrogen by the electrolytic dissociation of water employs anode and cathode half-cells, separated by a planar polymer-based solid electrolyte, and includes a water reservoir for independently maintaining a desired level of water in the anode and cathode half-cells. A hydrogen exit chimney extends vertically upward from each cathode half-cell and enters a separation chamber; a gas exit passageway therefrom is closed by a separation membrane that allows the passage of H2 but rejects liquid H2O, while a return water passageway enters near the bottom of the cathode half-cell. The half-cells are preferably formed by molded plastic frames that are arranged as a cell stack containing a plurality of electrolytic cells, with flat metal anodes and cathodes being respectively sandwiched about the solid electrolyte membrane in each cell.

Abstract: A portable electronic device incorporates PEM fuel cells and is designed to operate by the reaction of hydrogen from a hydride-containing fuel container and oxygen from the air, while efficiently removing the product water by a novel water transportation system. Temperature is effectively controlled by placing a plurality of fuel cell subunits as a generally planar array in the lid of the PC adjacent a heat transfer plate. A particularly efficient resupply system is provided where an electrolyzer that supplies H2 at a pressure sufficient to continue to power the PC and simultaneously recharge an operatively-connected container and a second spare container in the electrolyzer.

Abstract: A multiple cell thermionic converter having a generally tubular member of electrically conductive refractory metal with an internal cavity and a coaxial tubular envelope of electrically conductive refractory metal disposed in surrounding relationship thereto. Bodies of electrically insulating ceramic material disposed on elongated sections of facing surfaces of the tubular member and the envelope support juxtaposed emitters and collectors to provide a series of thermionic cells. Tubular metal connectors having particular aperture patterns respectively join the collector of one cell to the emitter of the next adjacent cell to create a series electrical interconnection. The aperture patterns include sets of slots in a pair of parallel planes that are perpendicular to the axis, providing necessary flexibility to accommodate thermal expansion and contraction while providing low electrical resistance and long fatigue life. Axial keyhole apertures and auxiliary slits located in a central plane may also be included.

Abstract: A method for applying a chromium surface treatment to nickel-based air data sensors to improve the corrosion resistance properties of the components while retaining thermal conductivity in order to efficiently transfer internally generated heat to the exterior of the component during anti-icing or deicing procedures is provided. The method for applying a chromium surface treatment to nickel-based air data sensors includes the steps of: (a) ion plating a nickel-based substrate with chromium atoms using a physical vapor deposition process; (b) interdiffusing the chromium and the nickel atoms at the surface region by means of a first thermal treatment carried out in an inert environment; and (c) oxidizing the chromium atoms at the surface region to create a chromium oxide layer during a second thermal treatment performed in an oxygen-containing environment.

Abstract: An Integrated Solar Upper Stage receiver is shown for efficiently transferring heat from concentrated solar flux to an interior surface of an annular structure having a plurality of parallel passageways through which hydrogen gas flows and is heated to a high temperature to serve as a propellant in order to raise the ISUS from a low earth orbit to a geosynchronous orbit or the like. The receiver comprises a body of refractory material, such as graphite, in which each of the hydrogen flow passageways is lined with a thin tube of wrought rhenium metal. The exterior surfaces of the receiver are similarly clad with wrought rhenium, or coated with CVD rhenium, to prevent evaporation of graphite at high temperatures in outer space. Inlet and outlet manifolds which communicate with the rhenium-lined passageways are also constructed of wrought rhenium metal and serve to totally isolate the hydrogen from the graphite heat sink material so as to avoid chemical reaction therebetween.

Abstract: Methods for making hermetic silicon carbide matrix composite structures by CVI. A fibrous preform is created by winding strands of yarn of refractory fiber material helically about a graphite mandrel. Impregnation of the preform is carried out in a subatmospheric pressure zone at a pressure of about 700 Pa or less by maintaining a relatively slow flow of a mixture of helium and an alkyl chlorosilane through a coating zone heated to a temperature of between about 1100.degree. to 1200.degree. C. at a rate between about 2 and about 10 times the diffusion rate of the gaseous atmosphere in the fibrous preform. Coating is continued until silicon carbide impregnates the interstices of the fibrous preform and preferably deposits an outer layer of dense pore-free silicon carbide thereupon. The resultant structures are hermetic and provide leak-free containment of gases such as helium at temperatures of as high as 1,000.degree. C. and a pressure differential as high as about 20 MPa.

Abstract: An adjustable seal assembly for maintaining a fluid tight seal in a vacuum vessel is provided. The disclosed adjustable seal assembly is particularly suited for sealing a vessel that includes two concentrically disposed sections having a small gap therebetween such that the vessel accommodates relative axial motion between the chamber section and the closure section. The disclosed adjustable seal assembly is comprised of a thin, fiber reinforced polymeric membrane having a first edge attached to a surface of one section of the vessel along the entire perimeter thereof and a second edge attached to a surface of the other section of the vessel thereby sealing the gap between the sections of the vessel. The body of the thin membrane is further disposed such that it generally forms an axially adjustable loop configuration within the small gap allowing the two sections of the vessel to move without breaking the seal.

Abstract: A method for applying a chromium surface treatment to nickel-based air data sensors to improve the corrosion resistance properties of the components while retaining thermal conductivity in order to efficiently transfer internally generated heat to the exterior of the component during anti-icing or deicing procedures is provided. The method for applying a chromium surface treatment to nickel-based air data sensors includes the steps of: (a) ion plating a nickel-based substrate with chromium atoms using a physical vapor deposition process; (b) interdiffusing the chromium and the nickel atoms at the surface region by means of a first thermal treatment carried out in an inert environment; and (c) oxidizing the chromium atoms at the surface region to create a chromium oxide layer during a second thermal treatment performed in an oxygen-containing environment.

Abstract: Dense monolithic SiC or SiC ceramic composites are strongly bonded using brazing compositions which, in their preferred composition, include a braze alloy consisting essentially of less than 50 weight percent silicon and at least two metals from the group of Fe, Cr, Co and V and produce a joint suitable for use in a high neutron flux environment. Brazing is carried out at a temperature of about 1200.degree. to 1500.degree. C. in an inert atmosphere and is complete in about 15 minutes. Broadly, a genus of brazing compounds are disclosed which include between about 10 and about 45 weight percent silicon and at least two elements selected from the following group: Li, Be, B, Na, Mg, P, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, Ga, Ge, As, Rb, Y, Sb, Te, Cs, Pr, Nd, Ta, W and Tl.

Abstract: A method of making a fiber-reinforced ceramic matrix composite of complex shape by first rigidifying a fibrous arrangement made of woven or braided material by impregnating with a preceramic resin, and then curing and pyrolyzing the resin to form a rigid or stiff preform. The rigid preform is then densified by chemical vapor infiltration, e.g., using a forced-flow/thermal-gradient process. Using three-dimensional woven fabrics made of ceramic fibers, such as silicon carbide or silicon nitride, strong high-temperature resistant composites are produced having porosities from about 20 percent to less than about 5 percent.

Abstract: Inexpensive process is provided for the application of substantially uniform metal oxide coatings onto continuous multi-filament refractory fiber tows. The resulting coated refractory fiber tows are useful, for example, for the preparation of refractory fiber composites having excellent physical and mechanical properties. Composites can be prepared employing a ceramic, metal or glass matrix.

Abstract: Refractory filaments in the form of a multifilament tow or fabrics woven therefrom are coated with protective oxide coatings to provide reinforcing materials that are useful in creating refractory composites. The refractory filaments are contacted with a liquid medium which contains a metal oxide or metal oxide precursor so that a substantially continuous coating of metal oxide or metal oxide precursor forms on the surface of each of the filaments. The filaments are then treated to substantially remove residual components of the liquid medium other than the metal oxide or metal oxide precursor. The coated filaments are stabilized, the above steps optionally are repeated to increase the coating thickness, and the coated filaments are heated to convert the metal oxide or metal oxide precursor into substantially continuous, uniform metal oxide coatings on the filaments.

Abstract: A method for preparing fiber-reinforced refractory composites is provided. A fibrous preform is infiltrated with at least two different refractory material precursors, then heated under conditions suitable to cure and pyrolyze the refractory precursors.

Abstract: A method for producing shapes utilizing carbon-based fiber cloth materials embedded in silicon carbide matrices. Boron compound is applied to a preform which may be a plurality of carbon fiber sheets in a stack or which may be a complex three dimensional structure, such as a braided tube or a woven fiber network with filaments running in a plurality of different directions. Alternatively, individual sheets can be treated and then stacked or otherwise formed into a preform. Boron is applied in a form in which it serves as a wetting/bonding agent. The preform or each of the sheets is then impregnated with a polysilane resin. If sheets are used, the sheets are then stacked in mating face-to-face relationships in a desired preform shape.

Abstract: A photoelectrochemical cell (10) is disclosed which has a semiconductor substrate (11) formed of a solid solution of three metal and non-metal elements, with two like elements varying in concentration with depth from an exposed surface (13) of the substrate (11). The band gap energies between the valence and conduction bands varies with the concentration of the two elements from the surface, with the band gap energies being in a proper range to provide emitted light in response to light or electrical stimulation. An electrolyte (14) is maintained in contact with the exposed surface and a counterelectrode (15) is immersed in the electrolyte such that a voltage applied between a counterelectrode (15) and the substrate (11) will vary the color of light emitted from the exposed surface (13) in response to incident light or by stimulation from the electrical current passing through the substrate.