Materials Literature
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Abstract Two simple related methods for exclusively preparing well‐developed tetragonal bipyramidal crystals of calcium oxalate dihydrate at moderate supersaturations and at ambient temperature are reported. These crystals have an average length of 5.7–7.2 μm and are easy to wash and filter. One of the methods is suit…
Studies are reported on decay and recovery of hydrophobic properties on clean and contaminated surfaces of silicone rubber based RTV coating. Treatment that led to hydrophobicity losses were water immersion and water condensation with and without a presence of dc electric field. Contact angles (receding angles) and su…
Mullite and ZrO 2 ‐toughened mullite (ZTM) were joined with Ag─Cu eutectic braze alloys that contain Ti or Zr as active elements. Although neither the alloy compositions nor the processing conditions were optimized, four‐point bend strengths of joined bars were as high as 108 MPa. Joining reactions were studied by con…
The hexafunctional initiator C6[(CH2)2p-C6H4CH(Cl)Me]6 is synthesized by Fe(η-C5H5)+ induced hexabenzylation of C6Me6 followed by regiospecific acetylation, NaBH4 reduction and chlorination, and allows the living cationic polymerization of styrene which yields hexaarm star-shaped polymers.
A series of nonmesogenic N-acylated derivatives (2) of 1,10-diaza-4,7,13,16-tetrathiacyclooctadecane (1) affords stable cationic complexes upon reaction with [Cu(MeCN)4][PF6]. The products [Cu(2)] [PF6] show thermotropic mesomorphism as a result of copper(I) complexation. Optical microscopy, calorimetry, and low-resol…
Sputtered multilayer films were studied by Fourier‐transform infrared spectroscopy (FTIR) and x‐ray diffraction (XRD), and their bonding structure and crystallization were compared with composite films. The thickness ratio of the multilayer films was fixed at 1:3, and the monolayer thickness was varied from 0.3 to 60…
Three coordinated research programs were undertaken on the fracture toughness of Zr-2.5Nb pressure tubes to determine relationships between irradiated and unirradiated values, the effect of long-term irradiation, and the causes of the variation in toughness. The present paper describes results from these programs and…
The corrosion pattern of dental amalgam in aqueous media was interpreted theoretically by means of log(ai/a(ref))-pe diagrams. The definitions on which the diagrams were based were given, and their features were described. All sparingly soluble compounds which were expected to be formed in reactions with the solvents…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of solvent casting on reduced entanglement density in thin films studied by ellipsometry and neutron reflectionBryan B. Sauer and David J. WalshCite this: Macromolecules 1994, 27, 2, 432–440Publication Date (Print):January 1, 1994Publication History Published online1…
A series of RFe/sub 6/Ge/sub 6/ (B=Y, Gd, Tb, Er) compounds have been prepared by arc-melting. Structural studies using X-ray diffraction (XBD) show that all four as-cast alloys belong to the hexagonal P6/mmm space group with similar lattice parameters (for YFe/sub 6/Ge/sub 6/, a=5.12 /spl Aring/ and c=4.07 /spl Aring…
In an attempt to facilitate crystallization, engineered cysteines were used to promote formation of a 'back-to-back' dimer that occurs in different crystal forms of wild-type and mutant T4 lysozymes. The designed double mutant, N68C/A93C, in which the surface residues Asn68 and Ala93 were replaced by cysteines, formed…
The intrazeolite Aul in NaY zeolite exhibits remarkable catalytic activities in the decomposition of NO to N2(N2O) and O2 at low temperatures; the NO decomposition reaction proceeds through the sequential formation of N2O3 and N2O intermediates on Aul/NaY at 300–673 K.
Nickel–iron hydroxide carbonates with layered reevesite-like structures have been synthesized by coprecipitation and their evolution to high-dispersity oxides has been studied. NiII–FeIII cation substitution in the octahedral positions of the cationic layers for a wide interval of nickel : iron ratios (0.33–3) is dedu…
Abstract Polyacrylonitrile (PAN) films were made by casting a dimethyl sulphoxide (DMSO) solution. After drying, the films were uniaxially drawn by an essentially solid‐state drawing procedure. Using polarised‐infrared (IR) spectroscopy, the dichroism of the nitrile‐stretching vibration was monitored as a function of…
Local atomic arrangements and wide tilings for two types of decagonal quasicrystals, which are formed in alloys with compositions near Al70Ni15Co15, were studied by high-resolution electron microscopy. The decagonal quasicrystals can be interpreted as structures formed with different tilings, so-called rhombic and pen…
Based on literature data and experimental findings at the Jet Propulsion Laboratory (JPL), semiconductors with the skutterudite structure TPn3 (where T is a transition metal element such as Co, Rh, Ir, Ni, and Pd, and Pn is a pnicogen element such as P, As, and Sb) possess attractive characteristics and show a good po…
Two‐dimensional Al 2 O 3 and SiC woven laminate composites, and oxide and nonoxide monolithic ceramics with 5 to 10 wt% of polycarbosilane binder, were consolidated up to 75% of TD (theoretical density) at 1150°C by the multiple impregnations of a polycarbosilane solution. The processing conditions were optimized with…
Webs of Kapton 200-H and Upilex-S polyimide films were treated using oxygen plasma prior to sequential sputter deposition of chromium and copper in a roll metallization system. Two plasma system configurations were employed for treatment. In one configuration, the sample traveled downstream from a microwave plasma; in…
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTElectron paramagnetic resonance studies of metalloporphyrin anion radicals. Effects of solvent, counterion, temperature, and isotopic substitution on the Jahn-Teller active 2Eg ground stateJyoti Seth and David F. BocianCite this: J. Am. Chem. Soc. 1994, 116, 1, 143–153Public…
The molecular first hyperpolarizabilities (β) of a series of asymmetric squaraine dyes have been measured by electric-field-induced second harmonic generation; the dyes have negative β-values whose magnitudes are comparable to 4-N,N-dimethylamino-4′-nitrostilbene (DANS).