Effects of silicone acrylate on morphology, kinetics, and surface composition of photopolymerized acrylate mixtures

Films (ca. 150 microm thick) of twelve acrylate mixtures, which contained various proportions of hydrocarbon acrylates [mainly oligo(ethylene glycol) diacrylate, (OEGDA)] and small amounts of a silicone hexaacrylate (in proportion of 5% or less), were cured on a nickel substrate, and X-ray photoelectron spectroscopy analysis of the nickel-side surface compositions showed that for formulations with and without the silicone hexaacrylate, this surface was enriched with OEGDA and saturated (up to 50%) with the silicone hexaacrylate, respectively. The silicone hexaacrylate phase-separated and formed micelles which migrated to the resin-nickel interface. Silicone hexaacrylate, inherently less reactive, also significantly slowed the photopolymerization of the mixtures. The sequential homopolymerization of OEGDA and silicone hexaacrylate in a formulation was elicited using real-time Fourier transform infrared spectroscopy. The design-of-experiment approach was used to quantify the influence of the components on gelation time and the nickel-side surface composition as well as provide the statistical models to predict these two properties for new compositions.     

Asymptotic Behavior of Loss Probability in GI/M/1/K Queue as K Tends to Infinity

We obtain an asymptotic behavior of the loss probability for the GI/M/1/K queue as K for cases of <1, >1 and =1.     

Upgrading of light cycle oil by partial hydrogenation and selective ring opening over an iridium bifunctional catalyst

An iridium catalyst supported on USY zeolite has been evaluated for hydrotreating of light cycle oil (LCO) to reduce its aromaticity and improve its cetane index. The products were analyzed by GC and ¹³C NMR spectrometry to determine quantitatively the aromatic carbon content and the increase in cetane index. Addition of an appropriate amount of potassium was found to be an effective way of optimizing the acid properties of the catalyst; reducing the number of strongly acid sites reduced its cracking activity. The results confirm that 0.9% (w/w) Ir/USY zeolite catalyst doped with 0.75% (w/w) K was highly suitable for partial hydrogenation and ring opening of LCO to improve cetane quality, thus increasing the extent of its blending ratio with the diesel pool.     

Di- and trisubstituted γ-lactams via Rh(II)-carbenoid reaction of N-Cα-branched, N-bis(trimethylsilyl)methyl α-diazoamides. Synthesis of (±)-α-allokainic acid

Acyclic N-C(α)-branched, N-bis(trimethylsilyl)methyl (N-BTMSM) diazoamides undergo regio-, chemo-, and diastereoselective Rh(II)-carbenoid C-H insertion to give 4,5-disubstituted and 3,4,5-trisubstituted γ-lactams. The conformational influence of the N-BTMSM group and the electronic effect of the O-pivaloyl moiety of the C(α)-oxymethylene unit are essential for the observed regioselectivity. The synthesis of α-allokainic acid demonstrates the utility of the method.     

Convenient synthesis of Cu3(BTC)2 encapsulated Keggin heteropolyacid nanomaterial for application in catalysis

Nanomaterial of Cu(3)(BTC)(2) (BTC = benzene tricarboxylic acid) incorporating Keggin heteropolyacid conveniently prepared at room temperature and recovered by freeze drying outperforms ultrastable Y zeolite in acid catalysed esterification reaction.     

Symmetrical transition of an atomic arrangement for 2D Bi films on Rh(111)

The atomic arrangement of submonolayer Bi films on Rh(111) surface was examined using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). With low coverage, the LEED patterns showed incommensurate (IC) spots. The unit cell of IC was close to c(2 × 4) and had twofold symmetry. As the coverage increased, the unit cell shrank continuously along the [$\overline{1}10$] direction, and the commensurate c(2 × 4) was formed at a coverage of 0.5 ML. At the coverage above 0.5 ML, two different structures of c(2 × 4) and (4 × 4) were observed by STM. When the surface is fully saturated by monolayer Bi atoms, Bi atoms formed the uniform (4 × 4) structure with sixfold symmetry. This is due to a strong Bi–Rh attractive interaction resulting in the two-dimensional localization of Bi adsorbates on the surface. As a result, a symmetrical transition of Bi films from twofold to sixfold symmetry occurred on Rh(111).     

Nanosecond laser ablation and deposition of silicon

Nanosecond-pulsed KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) lasers were used to ablate a polycrystalline Si target in a background pressure of <10⁻⁴ Pa. Si films were deposited on Si and GaAs substrates at room temperature. The surface morphology of the films was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Round droplets from 20 nm to 5 μm were detected on the deposited films. Raman Spectroscopy indicated that the micron-sized droplets were crystalline and the films were amorphous. The dependence of the properties of the films on laser wavelengths and fluence is discussed.     

Ferromagnetic resonance study of interface anisotropies in exchange-biased Fe(0 0 1)/KNiF3 bilayers

Magnetic anisotropies at epitaxial Fe/KNiF₃ interfaces were probed by ferromagnetic resonance. Fe(0 0 1) films coupled to single crystal KNiF₃ exhibit four-fold in-plane anisotropy and a unidirectional bias upon field-cooling. In Fe(0 0 1) with polycrystalline KNiF₃, the bias direction deviates from the field-cooling direction. Lattice mismatch strain due to polycrystalline KNiF₃ also induces uniaxial anisotropy in Fe.