Etching of a low-density polyethylene film by fuming nitric acid

Low-density polyethylene (LDPE) films were treated with fuming nitric acid (FNA). The surface characteristics and also the insertion of polar groups like on the etched LDPE film surface were measured by SEM, IR and XPS analyses, respectively. The mechanical performance of a laminate of the etched film with epoxy resin and also the printability of the etched film surface were tested and compared with the unetched sample. The surface roughening and the presence of polar groups enhance the mechanical strength of the laminate of FNA-treated film due to mechanical interlocking and chemical interaction. The printability of the treated film surface is also superior to that of the untreated LDPE film surface.     

The hydrolysis product of ferric nitrate in sodium hydroxide

The hydrolysis product of ferric nitrate is obtained by adding ferric nitrate solution to a boiling solution of 2.5 N sodium hydroxide. The sample is amorphous to X-rays when heated below 600° C, but it shows X-ray lines of -Fe₂O₃ at 650° C. Thermal analysis of the sample gives an endothermic peak at 80° C and two small exothermic peaks at 280° C and 700° C. Transmission electron microscopy and infrared spectroscopy confirm the primary particles as a defect form of FeOOH · H₂O. The defect FeOOH form of the sample converts to the disordered form of Fe₂O₃ on further heating around 700° C. The drastic fall in the surface area of the sample beyond 600° C suggests sudden growth of particle size, which is confirmed by a small endothermic peak at 700° C.     

Glass formation region and electrical conductivity in the system B2O3-Li2O-Li3PO4

Glass formation region was determined for the B₂O₃-Li₂O-Li₃PO₄ system. Under the present experimental conditions, binary lithium borate glasses could be formed containing a maximum of 27 mol% Li₂O. However, this could be increased to 36 mol% in the ternary system. Electrical conductivity was measured at temperatures ranging from room temperature to 350°C. The temperature dependence of the electrical conductivity of these glasses follows Arrhenius equation. The conductivity increased with increasingly alkali content. Maximum conductivity of the order of 10⁻⁴ ohm⁻¹ cm⁻¹ was obtained with the glass containing about 36 mol% Li₂O at 250°C. Activation energy for conduction also varied with total Li₂O content.     

Comparison of the criteria for mixed mode brittle fracture based on the preinstability stress-strain field

Prediction of the angle of initial crack extension, critical load and unstable crack paths based on the criteria of maximum tangential stress (MTS), maximum tangential principal stress (MTPS), maximum tangential strain (MTSN), and strain energy density (SED) are compared for slit and elliptical cracks under pure shear loading and elliptical cracks under uniaxial compressive loading. Results presented here complement those in Part I of this investigation. Some of the theoretical predictions have been compared with data available in the literature.All the four criteria are found to be more or less equally applicable in the cases studied for the prediction of direction of initial crack extension and critical load. The unstable crack paths based on the four criteria differ, the difference being greatest for the SED criterion. Some difficulties are found on applying this criterion to some situations.

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Résumé On considère des fissures en entaille et elliptiques soumises à des charges de cisaillement pur et des fissures elliptiques soumises à des charges de compression uniaxiale. On établit une comparaison des prédictions de l'angle d'extension initiale de la fissure, de la charge critique et des chemins de fissuration instables, en se basant sur les critères de la tension tangentielle maximale, de la tension principale tangentielle maximale, de la déformation tangentielle maximale et de la densité d'énergie de déformation. Les résultats présentés ici constituent un complément à ceux présentés dans la première partie de cette investigation. Certaines des prédictions théoriques ont été comparées avec des données disponibles dans la littérature.On montre que les quatre critères peuvent être appliqués de manière plus ou moins indifférente dans les cas étudiés pour prédire la direction de l'extension uniaxiale de la fissure ainsi que la charge critique. Néanmoins, les chemins de fissuration instables diffèrent selon les critères utilisés. La différence étant la plus grande dans le cas du critère de densité d'énergie de déformation. On trouve certaines difficultés à appliquer ce critère à certaines situations.

     

Coordinating a three-layer supply chain with uncertain demand and random yield

The paper considers a three-layer supply chain involving one raw-material supplier, one manufacturer and one retailer. The market demand is assumed to be stochastic and productions at the raw-material supplier and manufacturer are subject to random yield. The centralised model is studied as the benchmark case. The decentralised model is solved and Nash equilibrium solutions are obtained. It is shown that buyback contract fails to coordinate such a supply chain. However, a composite contract framed combining buyback, and sales rebate and penalty contracts is shown to coordinate the supply chain. Numerical examples are provided to illustrate the developed models.     

Preparation of graphene–polyaniline composites by simple chemical procedure and its improved field emission properties

Graphene–polyaniline composites have been synthesized using simple chemical procedure in two different ways (i) by mixing of the pre-synthesized graphene and polyaniline nanofibers and (ii) by in situ polymerization in presence of graphite oxide followed by further reduction. Detailed optical spectroscopic studies of the synthesized composites along with the pristine polyaniline nanofibers were performed by Fourier transformed infrared spectroscopy and UV–vis spectroscopy. The structural and morphological characterizations were performed by X-ray diffraction, transmission electron microscope measurements and field emission scanning electron microscope measurements, respectively while the chemical characters were studied by X-ray photoelectron spectroscopic measurement. The graphene–polyaniline composite retained the photoluminescence property of the as synthesized polyaniline nanofibers. The electron field emission property of the composite showed marked improvement compared to pristine polyaniline fibers with a turn-on field as low as 3.91 V/μm at a current density of 1 μA/cm². The field enhancement factor was found to be 7012 which is much higher for the case of a polymer based composite.