摘要:
A method of coating a fluidizable material onto a surface of a substrate, wherein the substrate is not wettable by the fluidizable material includes depositing a layer of powder particles on the surface of the substrate, the powder particles being wettable by the fluidizable material; contacting the fluidizable material to the layer of powder particles; and allowing the fluidizable material to wick between the powder particles and to contact the surface of the substrate.The method of the invention provides a method which requires little or no binders or organic solvents, is applicable to many different ceramic-metal formulations, allows easy control of the thickness of the tape, forms fairly dense tapes so that little or no shrinkage occurs upon densification at elevated temperatures, and does not require undesirably high processing temperatures.
摘要:
Subject boron carbide to a passivation treatment at a temperature within a range of 1350.degree. C. to less than 1800.degree. C. prior to infiltration with a molten metal such as aluminum. This method allows control of kinetics of metal infiltration and chemical reactions, size of reaction products and connectivity of B.sub.4 C grains and results in cermets having desired mechanical properties.
摘要:
A dense, self-reinforced silicon nitride ceramic body and a method of making such body. The body has a composition that includes: (a) silicon nitride; (b) a glassy grain boundary phase containing oxygen, nitrogen, magnesium, yttrium, silicon, zirconium, and at least one of titanium and aluminum; and (c) a second crystalline phase containing zirconium oxide; and (d) crystalline phases of metal zirconium silicide and/or metal zirconium silicon nitride. The ceramic exhibits high fracture toughness and high fracture strength and has a density at least 98 percent of theoretical.
摘要:
A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powder mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densificaton aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases. The glassy phase may also include a minor amount, e.g., up to 5.0 weight percent, based upon total weight of the ceramic, of aluminum nitride or boron nitride. The glassy phase optionally includes an amount of a secondary reinforcing material such as silicon carbide whiskers.
摘要:
A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powder mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densification aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases. The glassy phase may also include a minor amount, e.g., up to 5.0 weight percent, based upon total weight of the ceramic, of aluminum nitride or boron nitride.
摘要:
A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powdcer mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densification aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases. The glassy phase may also include a minor amount, e.g., up to 5.0 weight percentg, based upon total weight of the ceramic, of aluminum nitride or boron nitride. The glassy phase optionally includes an amount of a secondary reinforcing material such as silicon carbide whiskers.
摘要:
A biologically-active compound which includes an inorganic mixed metal cationic portion having anion exchange properties and an anionic portion containing a biologically-active anion. The mixed metal cationic portion can be an oxide, hydroxide, or both, and can be fully hydrated, partially hydrated, or not hydrated. The biologically-active anion can be, e.g., an antibiotic, an analgesic, an antimicrobial, a pharmaceutical, an antioxidant, or an agricultural chemical such as a herbicide or a pesticide. These biologically-active compounds can have controlled-release properties and can be produced by relatively simple processes, using for the cationic portion relatively common starting materials. These biologically-active compounds are useful, for example, in compositions to form pharmaceuticals, antioxidants, or herbicides, and can be incorporated into a polymeric material to form a shaped body, such as a plastic film which can be utilized to form bags for food storage or transportation. Also included are processes for making the biologically-active compounds.
摘要:
Unsaturated resin compositions, which are curable at elevated temperatures to temperatures below 0.degree. C and which contain a hydroperoxide as the catalyst and a soluble organic vanadium compound as a cure promoter or accelerator, are retarded against gelation without inhibiting the cure by the addition of a ketone peroxide.
摘要:
A reversible liquid/solid phase change composition comprising hydrated Mg(NO.sub.3).sub.2 /MgCl.sub.2, and one or more of Sr(OH).sub.2, Ca(OH).sub.2, CaO or BaO, added to the composition in an effective amount to suppress supercooling of the Mg(NO.sub.3).sub.2 /MgCl.sub.2 liquid phase.
摘要:
A reversible liquid solid phase change composition comprising hydrated Mg(NO.sub.3).sub.2 and one of the group of Sr(OH).sub.2, SrCO.sub.3, Ba(OH).sub.2, BaO, BaCO.sub.3 and/or NaBO.sub.2 added to the composition in an effective amount to suppress supercooling of the MgNO.sub.3 liquid phase.