Characteristics investigation on heat transfer growth of sonochemically synthesized ZnO-DW based nanofluids inside square heat exchanger

Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...     

The effect of rapid rotation on a vertical bridgman furnace at large Rayleigh number

In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate.     

Rigid-ladder polymers: Polymers containing anthraquinone recurring units

In an attempt to synthesize some processable ladder or partial ladder polymers containing anthraquinone recurring units, leucoquinalizarin was treated with 3,3′-diaminobenzidine. This polymer, which was a black powdery material, was slightly soluble in concentrated sulfuric acid and dimethylsulfoxide. Also, 1,5-diamino-2,6-dimercaptoanthraquinone was condensed with 2,5-dichloro-p-benzoquinone in pyridine to give a black powdery polymer. This was only partially soluble in concentrated sulfuric acid, but could be solubilized in alkali by reduction with sodium dithionite.     

New processable polyaromatic ether-keto-sulfones as colorless,clear film-forming materials

New processable polyaromatic ether-keto-sulfones were prepared from 4,4′-diphenoxydiphenyl sulfone, terephthaloyl chloride, isophthaloyl chloride, and bis-p-carboxyphenylacetylene dichloride (IV) in a Friedel-Crafts-type polymerization. The white polymers obtained form colorless, transparent, strong films and can be cast into a glass-fiber laminate. One polymer was prepared which incorporated biphenylene-2,6-dicarboxylic acid dichloride as crosslinking sites; this heat-cured polymer was completely insoluble in sulfuric acid.     

Aromatic polyether, -ketone, -sulfones as laminating resins. XII. Derivatives of 2,2′-diphenylethynyldiphenyl which cure by an intramolecular cyclization

Polymers made from 2,2′-diiododiphenyl-4,4′-dicarbonyl dichloride, diphenyl ether, and isophthaloyl chloride have been made and converted to the 2,2′-diphenylethynyl derivatives. Introduction of units of isophthaloyl chloride reduced the melting point of these polymers to about 200°C, and they could then be cured by heating. A good glass laminate was prepared and cured from one of the polymers.     

Polymerization using palladium (II) salts II: Polymerization of 2-ethynyl-5-bromothiophene

The title monomer was polymerized using a bis(triphenyl phosphine) palladium (II) chloride, cuprous iodide, triphenyl phosphine catalyst system. The products are low-molecular-weight materials with thermal stabilities somewhat inferior to corresponding phenylacetylene-based polymers.     

Ladder pyrrolone structures with anthraquinone recurring units

1,2,4,5-Tetraaminoanthraquinone and 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride react in dimethylacetamide to give a tetrameric prepolymer with balanced endgroups of anhydride and diamine. When this prepolymer is carefully treated with polyphosphoric acid at elevated temperature it is converted to a soluble polypyrrolone type structure with an inherent viscosity of 2.3–2.7. Polymers of this molecular weight can be wet-spun into pliable fibers from methanesulfonic acid. The TGA curve in air shows little weight loss below 550°C. The polymer can also be solubilized by reduction with sodium dithionite in alkaline aqueous dimethyl sulfoxide.     

Polymers from 4,4′-thiodiphenol

Polyesters were made with aromatic diacid chlorides and 4,4,-thiodiphenol. Isophthaloyl chloride and/or terephthaloyl chloride were used as acid chlorides alone or together with 5-cyanoisophthaloyl chloride or [2.2]p-cyclophane-3,9-dicarboxylic acid chloride. The latter components were incorporated in order to make the polymers useful for crosslinking. A polyether could be obtained by polycondensation of 2,4-dichloro-benzonitrile and 4,4′-thiodiphenol. The polycondensations were run in nitrobenzene as solvent.     

Aromatic polyethers,polysulfones, and polyketones as laminating resins. V. Polymers containing acetylenic side groups

1,3-Bis(p-phenoxybenzenesulfonyl)benzene and 4,4′-diphenoxydiphenyl sulfone were polymerized with isophthaloyl and terephthaloyl chloride in Friedel-Crafts type polymerizations. These polymers had 2,4-diphenoxyacetophenone in the backbone. The acetyl group was then converted into an acetylene group. They were crosslinked effectively by cyclization of the acetylene groups with a catalyst or by cyclo-addition with bisnitrile oxides.     

Polymers from 12-hydroxymethyltetrahydroabietic acid and its vinyl and acrylate esters

12-Hydroxymethyltetrahydroabietic acid has been homopolymerized by melt condensation and homopolyester has been obtained. Vinyl 12-hydroxymethyltetrahydroabietate has been prepared from 12-hydroxymethyltetrahydroabietic acid by vinyl interchange procedure with vinyl acetate, and has been homopolymerized, copolymerized with vinyl chloride, vinyl acetate, and terpolymerized with styrene and acrylonitrile. The acrylate ester of 12-hydroxymethyltetrahydroabietic acid also has been prepared from 12-hydroxymethyltetrahydroabietic acid and acrylyl chloride. The acrylate thus obtained has been homopolymerized and copolymerized with vinyl chloride and vinyl acetate. Polymers thus obtained have been characterized.