Materials Literature
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Stoichiometric and near‐stoichiometric silicon carbide fibers, derived from the polymer polycarbosilane, have been characterized by scanning Auger and transmission electron microscope techniques. Excess carbon usually appeared in the fibers, but it could be eliminated by controlling processing conditions. The fibers c…
Positive and negative ion FAB-MS (fast atom bombardment mass spectrometry) has been used to help characterize large polyoxoanions with molecular weights of up to 6300 mass units, specifically [BU4N]9P2W15Nb3O62 and the important polyoxoanion-supported iridium organometallic complex [Bu(4)N]Na-5(3)[(1,5-COD)Ir.P2W15Nb3…
Abstract The viscosity of thermoplastics above T g was found to greatly affect the room temperature electrical properties of conducting thermoplastic composites made by compression molding of a powder mixture, while the mechanical properties are essentially not affected. The electrical resistivity decreased and the el…
Monolayers of 2-pentadecylaniline were polymerized at the air/aqueous acid interface using ammonium persulfate as the oxidizing agent. Isotherms of 2-pentadecylaniline were measured on a 0.1 M sulfuric acid subphase at different temperatures. The mean molecular area at the surface pressure onset was found to increase…
SUMMARY Pedogenetic processes following a permafrost stage of development in four argillic brown earths with fragipans (Glossic and Ochreptic Fragiudalfs) are investigated by soil microscopy, including SEM observations of unimpregnated soil material, and by determination of clay mineralogy. Micromorphology of the appa…
Abstract Regression analysis of high-precision structural and chemical data on trioctahedral and dioctahedral micas yielded interrelationships between unit-cell parameters, chemical composition and structural details. Regression equations relating b and c sin β parameters of micas to composition were used for estimati…
Ultrasonic attenuation and phase velocity in a solid insulating material are determined in a broad frequency band by studying the propagation of a pressure pulse in a sample of this material submitted to an electric field of known value. During the propagation of the pulse in the sample, which is placed between short-…
The thermal transformation of pyrophyllite was analyzed using 27‐Al and 29‐Si MAS‐NMR spectroscopies, thermal analysis (DTA‐TG), dilatometry, and X‐ray diffraction techniques. Above 800°C, dehydroxylation of pyrophyllite is the origin of a broad component in the 27‐Al NMR spectra which is associated with a distorted p…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdsorption and reactions of tetraethoxysilane (TEOS) on clean and water-dosed titanium dioxide (110)L. Gamble, M. B. Hugenschmidt, C. T. Campbell, Teresa A. Jurgens, and J. W. Rogers Jr.Cite this: J. Am. Chem. Soc. 1993, 115, 25, 12096–12105Publication Date (Print):December…
An electrochemical method has been employed to obtain the population distribution of minimum grain boundary Cr concentrations for sensitized AISI 304 stainless steel (S30400). The detailed information about the extent of Cr depletion provided by the distribution is compared to the average degree of sensitization (DOS)…
The structure of the incommensurate composite crystal of the trigonal sulfide Sr 1.145 TiS 3 , M r =244.42, has been analyzed on the basis of the four-dimensional superspace group P R3m 1s using powder X-ray diffraction data and the Rietveld analysis process. The unit cell and other crystal data are a 1 =a 2 =11.5108…
BaTiO 3 thin films possessing ferroelectric characteristics have been successfully synthesized using the laser ablation technique. The films are polycrystalline when deposited with substrate temperature higher than 550°C at 1 mbar oxygen pressure. All of the films are highly textured and dominated by (111) grains. The…
Abstract A study was made of the ceric ammonium nitrate (CAN) initiated graft copolymerization of methyl acrylate (MA) onto potato starch. The variables affecting the graft were investigated. The optimums have been obtained; they are the concentrations of MA, CAN, and nitric acid (HNO 3 ) (1.08, 5.0 × 10 −3 , and 0.08…
Oxovanadium clusters are intersting both as moels of bulk magnets and in their own right. Results are presented suggesting that in Na 6 [H 6 V 12 O 30 F 2 ]·22H 2 O (see Figure) it is meaningful to decide which particular vanadium centers should be considered at 5⊕ and which as 4⊕. It is shown that in principle ist is…
The activation energy for dc electrical conduction due to alkali ions of binary alkali silicate glasses and due to protons of binary alkaline-earth phosphate glasses decreases linearly with the logarithm of their concentrations (in mol/l). The activation energy is discussed in relation to the ionic radius and concentr…
Abstract Hydrotalcite-like compounds (HT) with 24%–48% Al 3+ -substitution have been synthesized in the Mg 2+ -Al 3+ -Fe(CN) 6 4- system. Conditioning of the synthesized and air-dried compound with K 4 Fe(CN) 6 4- solution at 80°C was essential to obtain the 80%–90% pure ionic Fe(CN) 6 4- form on an equivalent basis.…
Uniform layers of porous Si have been produced that show fine structure in their photoluminescence (PL) spectra characteristic of longitudinal optical cavity modes. This mode spacing can be modified in a predictable way by immersing the porous Si layer in heptane, which changes the average refractive index of the poro…
Abstract Maleation of a thermoplastic elastomer, styrene‐[ethylene‐butylene]‐styrene (SEBS) triblock copolymer, was carried out by a solution grafting reaction with maleic anhydride initiated by dicumyl peroxide. The reaction products from the graft reaction in xylene, commonly chosen as the solvent for maleation graf…
Abstract Natural Kaolinitic clays containing transition metals Fe and Ti in their lattice have been examined for their acidic properties and catalytic activity for the alkylation of benzene with benzyl chloride. Calcination of the clays at 550 °C and subsequent acid-activation using 2 M HCl (1 M = 1 mol dm−3) rendered…
Abstract Finite element simulations on permeability variations of an aligned fiber assembly have been conducted. Two dimensional viscous flow in longitudinal and transverse directions has been studied respectively, using the steady state Navier‐Stokes equation but with small Reynolds numbers. Two groups of packing str…