Hughes Aircraft Company

Hiroshi Kimura

Ricardo C Pastor

Chan S Bak

Kevin W Kirby

M DuChesne Courtney

Tetsuo Hadeishi, Deceased

Harold M Olsen

A ceramic sensor comprising a thin film of Cu.sub.x Mn.sub.3-x O.sub.4 is provided that quantitatively measures the partial pressure of CO and hydrocarbon gases in a flowing system. The sensor is specific to both CO and hydrocarbon gases and is negligibly affected by the presence of the common automobile exhaust vapors NO and H.sub.2 O, within the operational temperature range from about 250.degree. to 450.degree. C. The CO/hydrocarbon sensor of the invention has other applications, such as monitoring CO and hydrocarbon levels in laboratories, mines, and industrial smoke stacks, and may be used in environments up to about 700.degree. C.

Carbon monoxide/hydrocarbon thin film sensor

The preparation of an amorphous gel of a hydrated oxide is coupled with the technique of controlled seeding to obtain monosize crystallized particles. Crystalline oxide particles, such as phosphors, are formed by a method comprising: (a) selecting an oxide system; (b) forming an amorphous phase of the oxide system; (c) controllably forming nuclei in the amorphous phase; and (d) converting the amorphous phase to the crystalline oxide particles by growth of the nuclei. The oxide particles have a substantially single size, with a narrow size distribution.

Flux grown, monosize oxide particles

A process is provided for fabricating coated particles of a substantially uniform particle size. The process comprises coating small particles of well-defined crystalline phases with a polymerized gel. The process results in a ball-type sol-gel coating of the particles to provide particles which have a narrow size distribution. In many instances, crystalline particles of irregular shape have a substantially spherical shape upon coating with the sol-gel. In instances where the core is a high melting point material, such as an oxide, nitride, or carbide, the coat formulation can effect a low sintering temperature, which permits forming films of the particles at a much lower temperature than would otherwise be possible.

Process for forming particles having a uniform size distribution

A spark-excited fluorescence sensor (10) is provided which enables monitoring of various gas species (14), such as H.sub.2, CO.sub.x, NO.sub.x, N2, NH.sub.x and hydrocarbons added to a system as source fuels and/or additive agents, or discharged from a system as exhaust including pollutants, for more efficient use of fuels for optimizing performance of the system, and, also, for reducing pollutants in the atmosphere. The spark-excited fluorescence sensor of the invention comprises a spark plug (12) to excite molecules of the gaseous species, an optical fiber window (18) and an optical fiber bundle (20) to collect and transmit, respectively, the fluorescence, bandpass filters ( 24 ) to select predetermined wavelengths corresponding to the gases to be detected, detectors (26), and signal processor (28 ) . The output from the signal processor is then used to improve overall performance of the system.

Spark-excited fluorescence sensor

A ceramic sensor (12) comprising a thin film (14) of Cu.sub.1=x Mn.sub.2-x O.sub.4-y is provided that quantitatively measures the partial pressure of CO gas in a flowing system (22). The sensor is specific to CO gas and is negligibly affected by the presence of the common automobile exhaust vapors NO, H.sub.2 O, and CH.sub.4, within the operational temperature range from about 250.degree. to 450.degree. C. The CO sensor of the invention has other applications, such as monitoring CO levels in laboratories, mines, and industrial smoke stacks, and may be used in environments up to about 700.degree. C.

Chemical sensor for carbon monoxide detection

A high concentration of diatomic molecules is caged in a host crystal by a crystal growth process, in which all other internal degrees of freedom of the diatomic molecule, except the vibrational, are frozen. Such a system provides an efficient mid-infrared, solid-state laser that can be pumped by a laser diode. Other uses include magnetic (Faraday) rotators, electro-optic switches, and Q-switches. The crystal growth process employs Czochralski-type or Bridgman-type processes under high pressure to introduce the diatomic molecule into the host lattice at a temperature slightly above the melting point of the host crystal, followed by slow cooling.

Gas doping of solids by crystal growth

Post-growth gas-impregnation of an ionic crystal is provided to achieve a high level of caged neutral diatomic species or charged diatomic species, where all other internal degrees of freedom of the species, except the vibrational, are frozen. In the former case, the neutral diatomic species (molecules) enter interstitially, while in the latter case, the charged diatomic species (anions) substitute for anions on the crystal lattice. Such a system provides an efficient mid-infrared, solid-state laser that can be pumped by a laser diode. Other uses include magnetic (Faraday) rotators, electro-optic switches, and Q-switches. The impregnation process introduces the species into the host lattice at a temperature below the melting point of the host crystal, and preferably at a phase transition of the crystal, followed by slow cooling. A pressure greater than atmospheric pressure is used to introduce the tenant molecule interstitially, while a pressure of at least 1 atmosphere is used to introduce the dopant anion substitutionally.

Impregnation of a solid from the gas phase

Large single crystals of Pb.sub.1-x -Sn.sub.x -Te are grown in a near-equilibrium condition by applying a minimal driving force such that a high degree of growth reliability is achieved. The process utilized allows the growth mechanism to take place approximately 50.degree. C. below the melting point of the charge materials. Crystals grown by this process are ultra pure and exhibit substantially improved compositional and crystallographic homogenuity throughout.

Method of growing large Pb.sub.1-x -Sn.sub.x -Te single crystals where

Large bulk single crystals of lead tin telluride are synthesized by first mixing desired amounts of lead, tin and tellurium with, if desired, bismuth and reacting the mixture at 950.degree. C to form a source material. The source material is then converted into a single crystal by recrystallization and digestion in a uniform 850.degree. C to 860.degree. C temperature zone in order to prevent transport of material and, hence, variations in composition. Thereafter, these crystals, which are doped with bismuth, or crystals made by Bridgman or Czochralski growth, are cut into wafers and isothermally annealed at 600.degree. C to 650.degree. C under a metal-rich vapor pressure obtained from metal-rich lead tin telluride powder. Lowering of temperature to about 200.degree. C and further annealing is capable of converting p-type crystals to n-type crystals. The result of annealing, whether p-type, n-type, or intrinsic, is a low carrier concentration, high mobility crystal.

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Northridge, CA, United States of America

Hiroshi Kimura