Static secondary ionization mass spectrometry analysis of tributyl phosphate on mineral surfaces: Effect of Fe(II)

The static secondary ionization mass spectrometry (SIMS) spectrum of tri-n-butyl phosphate (TBP) on a variety of basalt and quartz samples is affected by the chemical composition of the mineral surface. When TBP is adsorbed on Fe(II)-bearing surfaces, the compound undergoes concomitant H^? abstraction and reduction, followed by the elimination of two C₄H₈ molecules to form an ion at m/z 137⁺. When TBP is adsorbed to quartz or other nonreducing surfaces, it merely undergoes protonation and elimination of three C₄H₈ molecules to form H₄PO ₄ ⁺ . When TBP is adsorbed to Fe(III)-bearing surfaces, it undergoes H^? abstraction and elimination of two C₄H₈ molecules, to form an ion at m/z 153⁺. These conclusions are supported by model studies that employed FeO, Fe₂0₃, TBP, and tributyl phosphite. The results show that the SIMS spectrum is very sensitive to the mode of TBP adsorption on the mineral surface.     

Interactions of hydrophilic plasticizer molecules with amorphous starch biopolymer—an investigation into the glass transition and the water activity behavior

In this article, we demonstrated that within a hydrophilic biopolymer–plasticizer system, the molecular “activity” of the plasticizer also influenced the extent of these interactions. We demonstrated through an analysis of crystallinity and calorimetry results that the equilibrium moisture content within the starch matrix can preferentially interact with the hydrophilic plasticizers and modify the polymer recrystallization process to an extent that the commonly acknowledged relationship between the crystallinity and the glass transition behavior is disrupted. Two plasticizers, glycerol (three ? OH groups) and xylitol (five ? OH groups), were selected. The water sorption isotherm of polymer samples with 5–20 wt % (dry basis) plasticizers were examined across a water activity range from ～0.11 to ～0.95 and using Guggenheim‐Anderson‐de Boer analysis, we compared the molar sorption enthalpies of various starch–plasticizer mixtures. Finally, the competitive plasticization between water and plasticizer molecules at different water activities was also discussed using known glass transition models. The analyses validated the antiplasticization limit for glycerol to be ～10–15 wt %, but for xylitol, its antiplasticization behavior did not manifest till 20 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

The pyrolytic identification of organic molecules: II. A quantitative evaluation

Results are presented of an investigation made to set up a system for the study of pyrolysis of organic compounds, and to determine some of the important conditions in this system. Acetone, methanol, ethanol, and n-propanol were used as model compounds. Degradation of the compounds was studied quantitatively over a temperature range of 300–1200 °C using flash vaporization into a heated reaction chamber. The volatile products were analyzed by gas chromatographic techniques. A mechanism of the thermal decomposition of acetone by its high-temperature pyrolysis is proposed.     

Initial stage of physical ageing in network glasses

An atomistic view on Johari–Goldstein secondary β-relaxation processes responsible for structural relaxation far below the glass transition temperature (T_g ) in network glasses is developed for the archetypal chalcogenide glass, As₂₀Se₈₀, using positron annihilation lifetime, differential scanning calorimetry, Raman scattering and nuclear magnetic resonance techniques. Increased density fluctuations are shown to be responsible for the initial stage of physical ageing in these materials at the temperatures below T_g . They are correlated with changes in thermodynamic parameters of structural relaxation through the glass-to-supercooled liquid transition interval. General shrinkage, occurred during the next stage of physical ageing, is shown to be determined by the ability of system to release these redundant open volumes from the glass bulk through the densification process of glass network.     

Trinuclear Pd3O2 Intermediate in Aerobic Oxidation Catalysis

The activation of O₂ is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd^II)₃(μ³‐O)₂]²⁺ (L=2,9‐dimethylphenanthroline), was identified during the [LPd(OAc)]₂(OTf)₂‐catalyzed aerobic oxidation of 1,2‐propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd₃O₂ species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.     

Inverse limits on using piecewise linear unimodal bonding maps

In this paper we investigate inverse limits on using a single bonding map chosen from a two-parameter family of piecewise linear unimodal bonding maps. This investigation focuses on the parameter values at the boundary between an hereditarily decomposable inverse limit and an inverse limit containing an indecomposable continuum.

     

Free-surface flows under impacting droplets

A numerical method which fulfils the free-surface boundary conditions and extrapolates the fluid velocity into empty grid cells outside the fluid region on a fixed Cartesian grid system is presented. The complex, three-dimensional, vortex structures formed via surface/vortex interaction and induction between vortices have been computed using the proposed technique implemented within a level-set method for both vertical and oblique droplet impacts in incompressible fluids. The present results have been validated through numerical tests which confirm zero tangential shear at the free-surface and comparisons with experimental observations of cavity and vortex ring formation underneath the impact location. In some cases, transitions from a concentric vortex ring to a fully three-dimensional vortex structure has been confirmed. Whilst the primary vortex ring is initiated at the highly curved contact surface between the droplet and receiving surface, azimuthal instabilities are manifested in the shear layer around the cavity crater developing after the vertical impact, resulting in axial counter-rotating vorticity between the cavity and descending vortex ring. Underlying mechanisms which induce local deformation of the free-surface, creating a so-called scar, due to the sub-surface vortices at the oblique impacts are also discussed.     

Relationship between single and bulk mechanical properties for zeolite ZSM5 spray-dried particles

In this work typical mechanical properties for a catalyst support material, ZSM5 （a spray-dried granular zeolite）, have been measured in order to relate the bulk behaviour of the powder material to the single particle mechanical properties. Particle shape and size distribution of the powders, determined by laser diffraction and scanning electron microscopy （SEM）, confirmed the spherical shape of the spray-dried particles. The excellent flowability of the material was assessed by typical methods such as the Hausner ratio and the Cart index, This was confirmed by bulk measurements of the particle-particle internal friction parameter and flow function using a Schulze shear cell, which also illustrated the low compressibility of the material. Single particle compression was used to characterize single particle mechanical properties such as reduced elastic modulus and strength from Hertz contact mechanics theory. Comparison with surface properties obtained from nanoindentation suggests heterogeneity, the surface being harder than the core. In order to evaluate the relationship between single particle mechanical properties and bulk compression behaviour, uniaxial confined compression was carried out. It was determined that the Adams model was suitable for describing the bulk compression and furthermore that the Adams model parameter, apparent strength of single particles, was in good agreement with the single particle strength determined from single particle compression test.