First principle quantum calculation of the hydroxylation of 2-member ring defect on the amorphous silica surfaces

This study was conducted to find out the initiation mechanism of the hydroxylation of the 2-member ring on the amorphous silica surface. To do this, ab-initio molecular dynamics simulations were performed based on the first principle quantum calculation. The results suggest that the hydroxylation is initiated through the adsorption of water molecule on the surface of acidic silicon atom. The reaction pathway, the transition state and the energy barrier of the ring opening reaction were determined using the nudged elastic band method and dimer method. The present reaction mechanism and energy barrier were quite different from the previous cluster calculations.     

Analysis of onset of buoyancy-driven convection in a fluid layer saturated in anisotropic porous media by the relaxed energy method

A theoretical analysis of buoyancy-driven instability under transient basic fields is conducted in an initially quiescent, fluid-saturated, horizontal porous layer. Darcy’s law is used to explain characteristics of fluid motion, and the anisotropy of permeability is considered. Under the Boussinesq approximation, the energy stability equations are derived following the energy formulation. The stability equations are analyzed numerically under the relaxed energy stability concept. For the various anisotropic ratios, the critical times are predicted as a function of the Darcy-Rayleigh number, and the critical Darcy-Rayleigh number is also obtained. The present predictions are compared with existing theoretical ones.     

Synthesis and decomposition performance of a polymeric foaming agent containing a sulfonyl hydrazide moiety

A new monomer, methacryloyloxybis(benzenesulfonyl hydrazide) (MAOBSH) containing a foamable sulfonyl hydrazide functional group after decomposition by heating, was synthesized from 4,4′‐oxybis(benzenesulfonyl hydrazide) (OBSH) with methacryloyl chloride, and used to obtain poly(MAOBSH) as a polymeric foaming agent (PFA) in dry tetrahydrofuran at 70 °C using azobisisobutyronitrile as an initiator. The structures of the synthesized MAOBSH and poly(MAOBSH) were identified using Fourier transform infrared and ¹ H NMR spectroscopies. The decomposition temperature of poly(MAOBSH) was determined to be 245 °C and this temperature was decreased to around 160 °C by adding an activator such as surface‐treated urea to the polymer. The exothermic temperature and heat determined by the decomposition of the polymer were 256 °C and 287 J g^?1. The amount of gas evolution for poly(MAOBSH) measured at the decomposition temperature was 74 mL g^?1. Furthermore, polymers incorporating the PFA showed better skin and finer cell structure as well as better mechanical properties such as elongation and compression set than polymers with added OBSH due to the better compatibility of the developed PFA with polymers. © 2012 Society of Chemical Industry     

Effects of mechanical force on crystalline structure of electrospun poly(1‐butene) membranes

Fibrous poly(1‐butene) membranes were prepared from solutions using mixed solvents via electrospinning. The electrospun fibrous poly(1‐butene) membranes were stretched at elongations of 8, 16 and 24%, respectively. Scanning electron microscopy and stress–strain analysis showed that the deformation was elastic at an elongation of 8%, while plastic deformation occurred above 16%. The crystalline transformation induced by mechanical stretching was investigated using wide‐angle X‐ray diffraction. The poly(1‐butene) membrane stretched at 24% exhibited decreased diffraction intensity at 2θ = 11.8° and 18.3°, corresponding to the (200) and (213) crystalline reflections, indicating that crystalline transformation from metastable form II to either stable form I or I′ occurred due to mechanical stretching. Copyright © 2011 Society of Chemical Industry