Abstract: Ceramic fibers formed by the pyrolysis of organosilicon preceramic polymers are provided with increased resistivity by treating the fibers in air at temperatures of less than 1,000.degree. C. to oxidize the free carbon content of the fibers.

Abstract: An electrical device is made by partially pyrolyzing polymer material by heating the material to between 500.degree. C. and 800.degree. C. Electrodes are applied to the material at two different locations to define an electrically active element therebetween. The device exhibits negative resistance in a portion of its voltage current domain and function as bi-directional electrical switches.This application is a continuation of application Ser. No. 859,709, filed May 5, 1986, now abandoned, which is a divisional application of application ser. No. 487,401, filed Apr. 21, 1983, now U.S. Pat. No. 4,642,644.

Abstract: Cubelets are made from a piezoelectrically active ceramic material having holes therein which may be cross-cored. The holes are selectively filled with a liquid curable resin, such as an epoxy. The cubelets may also be formed from bonded or sintered "half-shapes" containing half cores, wherein a face bisects one hole or an array of holes or cross-cored holes to form one or an array of semicircular grooves or crossed semicircular grooves. The cubelets, whether filled with resin or having unfilled internal volume, are arranged in a precision array within the snug-fitting cavities of a lattice, whereby the holes are sealed off, to form a cubelet/lattice assembly which is then electroded and poled in an electric field and encapsulated in polymer to form a part of a hydrophone assembly, for example.

Abstract: A method is described for making an electroconductive composite sheet electrode which is conformable and in which a slit-and-expanded or perforated nickel screen is embedded by heat and pressure, so that electrical leads can be easily and strongly attached to the nickel screen before or after integrally bonding a electroconductive sheet electrode to each side of at least one adjacent piezoelectric ceramic/polymer composite sheet electrode which is non-conductive. After poling, the resultant transducer has an increased combined transverse stiffness which increases the hydrostatic voltage coefficient, g.sub.h, as well as the overall hydrophone Figure of Merit.

Abstract: The present invention provides a rechargeable electric storage battery comprising an electrolyte containing charge-transporting positive ions and negative ions capable of intercalating into graphitic carbon, and oppositely charged graphitic carbon electrodes which are simultaneously intercalated by the positive ions and negative ions present in such electrolyte. The graphitic carbon electrodes may be provided in a variety of physical configurations. Such battery is believed to provide reasonably high power density and energy density characteristics, fabrication simplicity, a relatively long lifetime, and potential economic advantages.

Abstract: An electrical device is made by partially pyrolyzing polymer material by heating the material to between 500.degree. C. and 800.degree. C. Electrodes are applied to the material at two different locations to define an electrically active element therebetween. Devices made according to the teachings of the disclosure exhibit negative resistance in a portion of their voltage current domain and function as bi-directional electrical switches.

Abstract: An improved procedure is provided for increasing the electrical conductivity of graphite via intercalation. It has been found that fully halogenated hydrocarbons (as described) have the ability to substantially aid the intercalation of graphite by previously known intercalant mixtures of (a) fluorosulfonic acid, chlorosulfonic acid, or mixtures thereof, and (b) a boron trihalide, a tetrahalide of a Group IV element, a pentahalide of a Group V element, or mixtures thereof. The presence of a fully halogenated hydrocarbon, such as carbon tetrachloride, during the graphite intercalation reaction has been found to expedite the rate at which intercalation takes place and possibly enables the achievement of a greater electrical conductivity than would have otherwise been obtained. In a preferred embodiment the graphite carbon is present within a carbonaceous fibrous material at the time of its intercalation and the resulting product is substantially electrically oriented along the axis of the fiber.

Abstract: An improved procedure is provided for increasing the electrical conductivity of graphite via intercalation. It has been found that sulfur trioxide has the ability to substantially aid the intercalation of graphite by previously known intercalants such as (a) fluorosulfonic acid, chlorosulfonic acid, or mixtures thereof, (b) a boron trihalide, a tetrahalide of a Group IV element, a pentahalide of a Group V element, or mixtures thereof, and (c) mixtures of (a) and (b). Such presence of sulfur trioxide during the graphite intercalation reaction has been found to expedite the rate at which intercalation takes place and possibly enables the achievement of a greater electrical conductivity than would have otherwise been obtained. In a preferred embodiment the graphitic carbon is present within a carbonaceous fibrous material at the time of its intercalation and the resulting product is substantially electrically oriented along the axis of the fiber.

Abstract: Temperature detectors are disclosed which employ, as their active elements, pieces of partially pyrolyzed polymer material which switch to a more highly conductive state under appropriate imposed electrical bias conditions when the ambient temperature increases above the switching temperature of the detector.

Abstract: The formation of improved intercalated graphitic carbon fibers of further diminished electrical resistivity (i.e., increased electrical conductivity) is made possible. Not only is the specific electrical resistivity of the resulting fibers reduced (e.g., to extremely low levels no greater than that of copper in preferred embodiments), but the desirable tensile properties of the fibers are maintained at a satisfactory level even after intercalation. A carbonaceous fibrous material containing the usual turbostratic graphitic carbon which is derived from an acrylonitrile homopolymer or a closely related copolymer (as defined) is selected and is structurally modified in a manner which has been found to render it particularly suited for intercalation as evidenced by a further reduction in the electrical resistivity of the resulting intercalated fibrous material while retaining other desirable properties.

Abstract: An improved process for the relatively rapid thermal stabilization of a multifilamentary acrylic fibrous material in the substantial absence of filament coalescence is provided. The fibrous material is initially contacted with a solution of hydroxylamine (as described), and subsequently with a solution of ammonium permanganate, calcium permanganate, magnesium permanganate, or mixtures thereof (as described). The resulting fibrous material which possesses a chemically altered structure is heated in an oxygen-containing atmosphere until a thermally stabilized acrylic fibrous material is formed which is capable of undergoing carbonization and is non-burning when subjected to an ordinary match flame.

Abstract: Reinforced high temperature molding compositions are provided by a two step precipitation process wherein a polymer matrix comprising either (a) a nitrogenous intractable high temperature resistant polymer such as poly(bisbenzimidazobenzophenanthroline) or (b) an admixture comprising a major amount of the nitrogenous intractable high temperature resistant polymer of (a) and a minor amount of a cross-linkable polymer such as a polybenzimidazole, is affixed to the surface of a partially plasticized organic fiber derived from polymers selected from the group consisting of (1) a nitrogenous intractable high temperature resistant polymer, (2) polybenzimidazoles (3) high temperature resistant aromatic polyamides, and (4) high temperature resistant aromatic polyesters and mixtures thereof.

Abstract: The internal structure of carbon fibers (as defined) is modified to yield a fibrous product having a bound oxygen content of about 3 to 30 percent by weight which exhibits substantially different bulk properties than that of the starting material. The carbon fiber precursor is contacted with a strong acid medium comprising nitric acid and optionally sulfuric acid and water (as defined) under conditions found capable of producing the desired internal chemical modification. In a preferred embodiment of the process the strong acid medium is formed by a combination (as defined) of fuming nitric acid and fuming sulfuric acid. The fibrous product exhibits, inter alia, reduced electrical and thermal conductivities, and particularly is suited for use as an ablative reinforcing medium.

Abstract: An improved process is provided for the formation of carbon fiber reinforced magnesium composite articles wherein substantially pure magnesium or magnesium alloys serve as the continuous matrix phase. A minor quantity of dispersed solid magnesium nitride sufficient to enhance the wettability of the carbon fiber reinforcement is provided in the molten magnesium containing metal when it is contacted with the carbon fiber reinforcement. The usual difficulties encountered when the production of such a composite article is attempted resulting from the inherent poor wettability of the carbon fibers by molten magnesium containing metal effectively are eliminated. The resulting composite article exhibits improved properties resulting from a more complete infiltration of the carbon fibers by the molten magnesium containing metal prior to solidification, and better adhesion between the fiber and metal.

Abstract: Normally intractable high temperature resistant polymers which lack plastic flow characteristics, such as polymers of the BBB type [i.e., poly(bisbenzimidazobenzophenanthroline) and related nitrogenous polymers], are rendered capable of undergoing facile molding to form three-dimensional shaped articles. A minor proportion of a cross-linkable additive polymer exhibiting a recognizable glass transition temperature below its decomposition temperature (e.g., a polybenzimidazole) or precursors capable of forming the same is incorporated in substantially uniform physical admixture with the normally intractable polymer, the admixture shaped to form a three-dimensional article, and the resulting article is heated until the additive polymer is cross-linked and the thermal stability of the article is enhanced.