DATA ADJUSTMENT FOR NON-REACTIVE BATCH OR STEADY-STATE PROCESSES

An analytical method was developed to adjust inconsistent process data by a least-sum-of-squares technique to “best” meet all material balance constraints. One complete data set composed of “M” stream flow rates with “N” components in each stream was used from either batch or steady-state non-reactive processes to define an unconstrained sum-of-squares adjustment function

Derivatives of the unconstrained sum-of-squares adjustment function with respect to each variable were set to zero yielding a set of non-linear algebraic equations. The entire non-linear set was solved by converging on only M— 2 search variables as compared to conventional methods requiring N(M — 1) — 1 search variables.     

In-Plane Cracking Behavior and Ultimate Strength for 2D Woven and Braided Melt-Infiltrated SiC/SiC Composites Tensile Loaded in Off-Axis Fiber Directions

The tensile mechanical properties of ceramic matrix composites (CMC) in directions off the primary axes of the reinforcing fibers are important for the architectural design of CMC components that are subjected to multiaxial stress states. In this study, two-dimensional (2D)-woven melt-infiltrated (MI) SiC/SiC composite panels with balanced fiber content in the 0° and 90° directions were tensile loaded in-plane in the 0° direction and at 45° to this direction. In addition, a 2D triaxially braided MI SiC/SiC composite panel with a higher fiber content in the ±67° bias directions compared with the axial direction was tensile loaded perpendicular to the axial direction tows (i.e., 23° from the bias fibers). Stress–strain behavior, acoustic emission, and optical microscopy were used to quantify stress-dependent matrix cracking and ultimate strength in the panels. It was observed that both off-axis-loaded panels displayed higher composite onset stresses for through-thickness matrix cracking than the 2D-woven 0/90 panels loaded in the primary 0° direction. These improvements for off-axis cracking strength can in part be attributed to higher effective fiber fractions in the loading direction, which in turn reduces internal stresses on weak regions in the architecture, e.g., minicomposite tows oriented normal to the loading direction and/or critical flaws in the matrix for a given composite stress. Both off-axis-oriented panels also showed relatively good ultimate tensile strength when compared with other off-axis-oriented composites in the literature, both on an absolute strength basis as well as when normalized by the average fiber strength within the composites. Initial implications are discussed for constituent and architecture design to improve the directional cracking of SiC/SiC CMC components with MI matrices.     

High resolution XPS characterization of chemical functionalised MWCNTs and SWCNTs

High resolution XPS analysis of chemical functionalised multi-wall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNT) was done with ESCA300 (overall instrument resolution of 0.35 eV). Information to the degree of functionalisation was ascertained by argon ion bombardment of the samples followed by XPS analysis to detect the functional groups, the percentage atomic concentration of various elements present and whether or not the detected functional groups imposed a chemical shift on the CNT atoms. The results show that true chemical functionalisation was achieved and by argon ion bombardment these functional groups can be altered relative to the C 1s carbon atoms of the CNT. The choice of chemicals used for functionalisation, the techniques employed and the types of nanotubes treated are important factors in chemical characterisation. The carbon atom on the nanotube ring to which the functional group (atom) is bonded, the chirality of the CNT, the electronegativity of the functional group, the bond type and whether the CNT is single-wall or multi-wall, or cut (short) could play a role in determining the chemical shift on the CNTs atoms. These investigations are relevant to chemical functionalisation of carbon nanotubes for various applications for example DNA sensors and other biomedical sensors.     

Molecular motion of small molecules in cellulose gels studied by NMR

Measurements of relaxation times, T₁ and T₂, and self-diffusion coefficients, D, for small molecules, viz., H₂O, dioxane and t-butanol, in the gel system cellulose/H₂O are reported and compared with those for H₂O in a polyacrylamide gel of the same polymer content. The temperature dependence of T₁ and D can for all the penetrants be represented by Arrhenius type relations which merely are parallel shifts by the same amount, towards smaller values, of those obtained without polymer. The T₂ values for H₂O in both gels pass through a shallow minimum over the considered temperature interval (14°?44°C). Furthermore, relaxation times T₁ of D₂O in the gel system cellulose/D₂O are reported; in a plot of ln T₁ vs. 1/T, a plateau region is observed at higher temperatures.     

Diffusion in polyacrylamide gels

Using a novel sorption technique, the diffusion of some series of solutes in polyacrylamide gels has been investigated with regard to: (a) molecular size of solute; (b) concentration of solute and gel polymer; and (c) temperature. The approach used also yields the partition coefficient pertaining to sorption equilibrium. The ratio, $\text{D}\text{D}{}_{\mathrm{o}}$, where D_o refers to diffusion in the pure solvent, is found to reflect in part the characteristic interactions between solute and gel polymer. The temperature results indicate that the apparent activation energy for solute diffusion is approximately independent of the polymeric component for dilute gels.     

Chemistry of organosulphur compound types occurring in heavy oil sands: 3. Reaction of thiophene and tetrahydrothiophene with vanadyl and nickel salts

As part of a study of the chemistry of the steam-stimulated recovery of heavy oils, the hydrolysis and subsequent desulphurization of tetrahydrothiophene and thiophene by aqueous solutions of vanadyl and nickel salts was investigated. Vanadyl sulphate and vanadyl chloride were shown to behave very differently, emphasizing that these salts have different molecular species in aqueous solutions.     

Polyether-metal salt complexes: 1. The elevation of the glass transition temperature of polyethers by metal salts

Various metal halides have been dispersed in high and low molecular weight, amorphous poly(propylene oxide), by solution blending techniques, to give single phase polymeric complexes which remained thermoplastic even at very high salt loadings. These complexes were amorphous and showed a single well-defined glass transition temperature (T_g) by differential thermal analysis with the T_g of the complex up to 140°C greater than the T_g of the parent polymer. The T_g elevation depended upon both the amount and the type of salt added and for a given salt the elevation followed a sigmoidal curve which levelled out at high salt concentrations. The T_g data have been interpreted in terms of a chelate ring model involving the co-ordination of two adjacent ether oxygen atoms in the polymer backbone to the salt. Using this model it was possible to consider the complex as a random copolymer consisting of complexed and uncomplexed monomer units. The contribution of crosslinking by metal salts to the elevation of T_g was assessed by studying poly(tetramethylene glycol)-zinc chloride complexes in which chelate formation is entropically unfavourable. Mechanical data are reported for ZnCl₂ complexes with high molecular weight poly(propylene oxide). The results indicate that ZnCl₂ increased the rubbery modulus and this has been interpreted in terms of ZnCl₂ forming a few, weak intermolecular crosslinks.     

Hydrolysis of fish oils containing polymers of triacylglycerols by pancreatic lipasein vitro

Fish oils containing different levels of polymers of triacylglycerols formed during autoxidation were incubated with pancreatic lipase to establish whether these polymers are substrates for lipase hydrolysis. With oils containing low amounts (less than 4%) of triacylglycerol polymers as substrates, both triacylglycerols and polymers of triacylglycerols were almost completely hydrolyzed, and fatty acid monomers and monoacylglycerols were the major lipid products. Under the same incubation conditions, some triacylglycerols remained intact when highly oxidized oils containing 20 or 30% triacylglycerol polymers were the substrate. The fatty acid composition of these residual triacylglycerols was almost identical to that of triacylglycerols present at the start of the assay. When fish oil containing 30% triacylglycerol polymers was incubated with the lipase, the component triacylglycerols and polymers of triacylglycerols were hydrolyzed at similar rates, and fatty acid dimers were detected as a product. It is concluded that the high molecular weight polymers of triacylglycerols present in oxidized fish oils can be hydrolyzed by pancreatic lipasein vitro.     

Studies of space-averaged mass transport in the FM01-LC laboratory electrolyser

Measurements of the mass transport limited current for the reduction of ferricyanide in 1M m potassium hydroxide and of copper(II) in 1.5 m sulphuric acid as a function of electrolyte flow rate are used to characterize the space-averaged mass transport properties of the FM01 laboratory electrolyser, with and without six types of polymer mesh turbulence promoters. In the absence of a promoter, the results followed the equation For the cell with the preferred turbulence promoter, the corresponding equation is Pressure drop data are also reported and it is confirmed that the presence of a turbulence promoter need not lead to a significant increase in the pressure drop over the reactor.