Structure and properties of some vegetable fibres

The stress-strain curves for pineapple leaf fibre have been analysed. Ultimate tensile strength (UTS), initial modulus (YM), average modulus (AM) and elongation of fibres have been calculated as functions of fibre diameter test length and test speed. UTS, YM, and elongation lie in the range of 362 to 748 MN m^–2, 25 to 36 GN m^–2, and 2.0 to 2.8%, respectively for fibres of diameters ranging from 45 to 205m. UTS Was found to decrease with increasing test lengths in the range 15 to 65 mm. Various mechanical parameters show marginal changes with change in speed of testing in the range of 1 to 50 mm min^–1. The above results are explained on the basis of structural variables of the fibre. Scanning electron microscope studies of the fibres reveal that the failure of the fibres is mainly due to large defect content of the fibre bo1h along the fibre and through the cross-section, The crack is always initiated by the defective cells and further aggravated by the weak bonding material between the cells.     

Glass formation region and lithium ion conduction in the oxyfluorophosphate glasses

Oxyfluorophosphate glasses containing about 80 mol% of [LiF+Li₂O] show unusually high lithium ion conductivity at elevated temperatures. A detailed investigation has been carried out on the glasses prepared by both conventional cooling and a rapid quenching technique. Chemical analysis of the glasses reveals fluorine loss during melting and it becomes difficult to make glasses with exact predetermined compositions. Electrical conductivity of the glasses, determined from complex impedance analysis increases with Li₂O content. A glass with nominal composition 70 LiF15 Li₂O15 Al(PO₃)₃ shows the highest conductivity (~ 1.3×10^–3 ohm^–1 cm^–1 around 200° C) among all the compositions studied. An interesting feature of the impedance plot is the near perfect semicircle for bulk relaxation indicating a narrow distribution of relaxation times. This has been explained on the basis of a relatively small proportion of lithium ions which are mobile. The electrical conductivity of the glasses is found to be essentailly independent of dissolved water content. The infrared spectra of these glasses (2 to 50m region) could not produce much useful structural information.     

Performance Tuning and Reliability Analysis of the Electrostatically Configured Nanotube Tunnel FET with Impact of Interface Trap Charges

Silicon - This paper examines, an electrostatically configured Nano-Tube Tunnel Field-Effect Transistor (ED-NTTFET). During the fabrication process, different charges such as fixed charge, oxide...     

On the issue of urea phase connectivity in formulations based on molded flexible polyurethane foams

Lithium chloride was added to systematically alter the phase separation behavior, and hence, the nature of urea phase connectivity, in a series of plaques based on molded flexible polyurethane foam formulations. The plaques prepared were found to possess varied levels of urea phase connectivity that was examined at different length scales using several characterization techniques. SAXS, TEM, and t‐AFM were used to show that addition of LiCl systematically reduced the formation of the urea aggregate structures typically observed in flexible polyurethane foam formulations and thus led to a loss in urea phase connectivity at the macrolevel. SAXS, DSC, and DMA revealed that formulations with and without LiCl exhibited similar interdomain spacings and soft segment glass transitions, suggesting that incorporation of LiCl did not prevent the plaques from undergoing partial microphase separation. WAXS demonstrated that addition of LiCl led to a loss in the local ordering of the hard segments within the microdomains, i.e., it led to a reduction of microlevel connectivity or the regularity in segmental packing of the urea phase. High‐magnification t‐AFM images showed that increasing the LiCl content dispersed the urea component more homogeneously and in a more uniform manner in the polyol matrix, and thus altered the connectivity of the urea phase at the microdomain level. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2956–2967, 2002     

EXAFS and XPS Investigations of Cu/ZnO Catalysts and Their Interaction with CO and Methanol

Several investigations have been carried out on Cu/ZnO catalysts by employing extended Xray absorption fine structure (EXAFS) and Xray photoelectron spectroscopy (XPS). EXAFS investigations of Cu/ZnO catalysts subjected to hydrogen reduction show the presence of Cu¹⁺ species and Cu microclusters. The proportion of Cu¹⁺ depends on the rate of increase of the reduction temperature and on the amount of alumina added. An XPS study of the interaction of CO with model Cu/ZnO catalysts prepared in situ in the electron spectrometer shows the formation of CO₂ ^-, CO₃ ^2- and C₂O₄ ^2- species, their proportion relative to CO increasing with the Cu¹⁺/Cu⁰ ratio. A study of the interaction of CH₃OH with Cu clusters deposited on ZnO films reveals reversible molecular adsorption and the formation of CH₃O on clean Cu clusters. If the Cu clusters are pretreated with oxygen, however, both CH₃O and HCOO^- species are produced. Model Cu/ZnO catalyst surfaces containing both Cu¹⁺ and Cu⁰ species show interesting oxidation properties. On a Cu⁰-rich catalyst surface, only the CH₃O species is formed on interaction with CH₃OH. On a Cu¹⁺rich surface, the HCOO^- ion is the predominant species.     

EMI shielding of intinsically conductive polymers

Results of this study, in which shielding efficiencies are measured for a number of blends containing various conductive fillers including intrinsically conductive polymers, are reported. It is shown that a very high level of shielding performance can be achieved by use of intrinsically conductive polymers in thermoplastic blends and that the most reliable measure of this performance is obtained from far-field shielding measurements. However, near-field measurements provide a useful method for comparing the relative shielding effectiveness of different samples. A PVC blend containing nearly uniformly dispersed intrinsically conductive polymer proved to be the best performing sample.     

Optimal production of intermediate for zero—first and first—first order reaction sequences in fluidised bed reactors1

An analysis of zero—first and first—first order reaction schemes has been carried out in a fluidised bed with a view to optimising the production of intermediate R for a given bubble diameter. For the zero—first order reaction sequence, the gas residence time at which the maximum concentration of R occurs is shown to be fixed and independent of bubble size in the bed. On the other hand, for a first—first order reaction scheme, an optimum gas residence time exists for the concentration maximum to occur at the bed exit. This interaction between bubble diameter, gas residence time and maximum concentration of intermediate is resolved by recourse to a three dimensional diagram which optimises the production of intermediate for any given value of bubble diameter or gas residence time.     

Simultaneous measurement of flow pattern and mass transfer coefficient in bubble columns

Mass transfer studies were carried out in a bubble column using the chemical method. Catalytic oxidation of sodium sulfite was chosen for the studies and the corresponding specific rates of oxidation were obtained using a stirred cell. Laser Doppler anemometer (LDA) was used to measure the instantaneous velocities in the same stirred cell as well as in bubble columns (100 and i.d.). An efficient algorithm based on the multiresolution analysis of the velocity-time data using wavelets was used for the isolation of data belonging to the gas and liquid phases. Eddy isolation model was used for the characterization of the eddy motion including the estimation of the energy dissipation rate. Using the knowledge of eddy motion, a methodology was developed for the prediction of true mass transfer coefficient (k_L) in a stirred cell as well as in bubble columns. The predicted values of k_L have been compared with the experimental values obtained by the chemical method.     

Synthesis of Biodiesel from Canola Oil Using Heterogeneous Base Catalyst

A series of alkali metal (Li, Na, K) promoted alkali earth oxides (CaO, BaO, MgO), as well as K₂CO₃ supported on alumina (Al₂O₃), were prepared and used as catalysts for transesterification of canola oil with methanol. Four catalysts such as K₂CO₃/Al₂O₃ and alkali metal (Li, Na, K) promoted BaO were effective for transesterification with >85 wt% of methyl esters. ICP-MS analysis revealed that leaching of barium in ester phase was too high (~1,000 ppm) when BaO based catalysts were used. As barium is highly toxic, these catalysts were not used further for transesterification of canola oil. Optimization of reaction conditions such as molar ratio of alcohol to oil (6:1–12:1), reaction temperature (40–60 °C) and catalyst loading (1–3 wt%) was performed for most efficient and environmentally friendly K₂CO₃/Al₂O₃ catalyst to maximize ester yield using response surface methodology (RSM). The RSM suggested that a molar ratio of alcohol to oil 11.48:1, a reaction temperature of 60 °C, and catalyst loading 3.16 wt% were optimum for the production of ester from canola oil. The predicted value of ester yield was 96.3 wt% in 2 h, which was in agreement with the experimental results within 1.28%.     

Polymeric sodium alginate interpenetrating network beads for the controlled release of chlorpyrifos

Novel polymeric sodium alginate (Na‐Alg) interpenetrating network (IPN) beads have been prepared by crosslinking Na‐Alg blend with gelatin (GE) or egg albumin (EA) using glutaraldehyde (GA) as the crosslinking agent. These beads were used for the controlled release of chlorpyrifos. The swelling experiments were performed in water at different temperatures, and these data were used to calculate the molecular mass (M_C) between crosslinks as well as diffusion coefficients. Diffusion coefficients calculated from desorption data were lower by about two orders of magnitude than those calculated from sorption results. Higher values of M_C were obtained for the gelatin‐based IPNs than the neat Na‐Alg and egg albumin‐based matrices. Size of the beads did not vary significantly either by the network or by increasing the exposure time to the crosslinking agent. The scanning electron microscopy (SEM) was used to understand the surface characteristics of the beads. Differential scanning calorimetry (DSC) indicated a molecular level dispersion of chlorpyrifos in the polymer matrix. The percentage entrapment efficiency showed a dependence on the type of network polymer as well as time of exposure to the crosslinking agent. The encapsulation efficiency decreased with an increase in time of exposure to the crosslinking agent. In vitro release experiments have been performed to follow the release kinetics of chlorpyrifos from the matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 911–918, 2002