Structure–property interface correlation of fly ash–<Emphasis Type="Italic">isotactic</Emphasis> polypropylene composites

Composites of isotactic semicrystalline polypropylene (PP) reinforced with fly ash (FA) particles (particle size 5–60 μm) were prepared by injection moulding at 210 °C incorporating 20, 45 and 60% by weight of fly ash. Tensile tests were carried out at 25, 50 and 70 °C. WAXRD, DSC and SEM studies were also undertaken. Modulus of elasticity of all composites at all temperatures was higher than that of the corresponding PP samples—the gain ranged between 10 and 60%. The strength of the composites had a mixed trend. At 25 °C, the composites suffered significant loss in strength, as much as 47%, whereas, at 50 and 70 °C, there was up to 15% gain in strength. Strain to failure of the composite samples ranged from as low as 6% at 25 °C to over 50% at 70 °C, coinciding with increase of Pukanszky parameter from 1.5 to 4.1. WAXRD and DSC tests confirm that FA is nucleator of β-crystalline phase the amount of which increases to a maximum of 11% with increasing FA. SEM studies indicated that the polymer had a distinctly high lamellar ductility and showed interfacial interaction with FA in 20% FA composites at 50 and 70 °C. The –OH group on the surface of FA appears responsible for the formation of interfacial interaction with PP chain. Notched Charpy tests showed a maximum gain of 58% impact energy for the composite with 45% FA, tested at 70 °C over that of pure PP at 25 °C.     

Quasi-photon Phase States

Abstract

We introduce quasi-photon phase states of radiation in the single mode, and study the fluctuations in the measured phase operators. We also show that these states exhibit bunching, unlike coherent states which show no bunching.     

Tuning the luminescence color and enhancement of afterglow properties of Sr(4−x−y)CaxBayAl14O25:Eu,Dy phosphor by adjusting the composition

Color point tuning is an important challenge for improving the practical applications of various displays, especially there are very limited white color single hosts that emits in the white spectrum. In this paper, the possibility of color tuning by substituting part of host lattice cation (Sr²⁺ ions) by Ca²⁺ or Ba²⁺ ions in an efficient strontium aluminate phosphor, Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, is reported and found to be very promising for displays. A detail study by replacing part of Sr²⁺ with Ca²⁺ or Ba²⁺ has been investigated. X-ray diffraction study showed that crystal structure of Sr₄Al₁₄O₂₅ is preserved up to 20 mol of Ca²⁺ ion exchange while it is limited to 10 mol of Ba²⁺ ions exchange. Substantial shift in the emission band and color were observed by substitution of Sr²⁺ by Ca²⁺ or Ba²⁺ ions. A bluish-white emission and afterglow was observed at higher Ca²⁺ ions substitution. Further, partial Ca²⁺ substitutions (up to 0.8 mol) resulted in enhanced afterglow of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor. However, Ba²⁺ substitution decreased the fluorescence as well afterglow of the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor significantly. The enhanced phosphorescence by partial Ca²⁺ substitution is explained on the basis of increased density of shallow traps associated with higher solubility of Dy³⁺ ions in to the host lattice due to equivalent size of Ca²⁺ and Dy³⁺ ions. Thus, Ca²⁺ substitution in the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor is a promising method for tuning the emission color and improving the afterglow intensity of the phosphor.     

Chemically modified fly ash for fabricating super-strong biodegradable poly(vinyl alcohol) composite films

Composite films of poly(vinyl alcohol) (PVA) and chemically modified fly ash (MFA) by sodium hydroxide were prepared by aqueous cast method with 5, 10, 15, 20 and 25 wt% MFA treated with 1 wt% cross-linking agent (glutaraldehyde, GLA). The tensile strengths of the composite films were found to increase proportionally with MFA and the maximum strength attained was 414% higher in the case of 20 wt% MFA than that in neat PVA film. The percentage of strain at break exponentially decreased with addition of MFA. The modulus of the composites was determined to increase proportionally up to a maximum 685% at 20 wt% MFA compared to that of neat PVA film. Interfacial networking between the MFA and PVA was evident from scanning electron microscopy (SEM) images of tensile-fractured surfaces, which was not observed for the unmodified fly ash (FA) system. Atomic force microscopy (AFM) analysis showed that the mean square surface roughness of the composite films of PVA–MFA was 53% smoother than the films with FA.     

Effect of Plant Extracts on Quality of Khasi Mandarin (Citrus reticulata Blanco) Fruits During Ambient Storage

Khasi mandarin (Citrus reticulata Blanco) fruits were treated with Azadirachta indica, Ocimum sanctum, Aloe barbedensis, carbendazim, A. barbedensis + A. indica, A. barbedensis + O. sanctum, A. barbedensis + carbendazim and control (water). Treated fruits were packed in corrugated fibre boxes and kept for a total period of 28 days at ambient storage (20?±?2 °C and 65?±?5% RH). Prominent pathogen associated with fruit rot was identified as Penicillium brevicompactum. The fruit quality during storage was evaluated in terms of disease severity (per cent disease index), inhibition of spore germination (%) of P. brevicompactum, decay loss (%), juice content retention (%), total soluble solids (%), acidity (%), ascorbic acid content (mg/100 g) and sensory scores. O. sanctum-treated fruits exhibited minimum decay loss (3.33%) up to a total period of 28 days which was even less than carbendazim (10%). O. sanctum was also highly effective in inhibiting spore germination of P. brevicompactum (96.5%). Overall acceptability score (7.33) was also high in O. sanctum-treated fruits as compared with other treatments at the end of the storage period.     

Transient rotating flow over a moving surface with a magnetic field

The transient flow and heat transfer on a moving surface in a rotating fluid in the presence of a magnetic field have been investigated. The unsteadiness in the flow field has been introduced by the sudden change in the surface velocity or the fluid angular velocity. The parabolic partial differential equations governing the unsteady flow and heat transfer have been solved by using an implicit finite-difference scheme in combination with the quasilinearization technique. The computations have been carried out from the initial steady state to the final steady state. The effects of the sudden change in the surface velocity on the flow and heat transfer are found to be more significant than those of the impulsive change in the angular velocity of the fluid. When the surface velocity is suddenly reduced, the surface shear stress is found to vanish in a small time interval after the start of the impulsive motion, but it does not imply flow separation. The surface shear stress for the primary flow increases with the magnetic field and the fluid angular velocity, but the surface heat transfer decreases. The surface shear stress for the secondary flow increases with the angular velocity of the fluid, but decreases with increasing magnetic field.