Induction of chemical and moisture resistance in Saccharum spontaneum L fiber through graft copolymerization with methyl methacrylate and study of morphological changes

In this article, morphological modification of Saccharum spontaneum L, a natural fiber through graft copolymerization with methylmethacrylate using ferrous ammonium sulfate—potassium per sulfate redox initiator has been reported. Different reaction parameters such as reaction temperature, time, initiator molar ratio, monomer concentration, pH and solvent were optimized to get maximum graft yield (144%). The graft copolymers thus formed were characterized by Fourier transform infrared, scanning electron microscopy, X‐ray diffraction and thermogravimetric, differential thermal analysis, and differential thermogravimetric techniques. Graft copolymer has been found to be more moisture resistant and also showed higher chemical and thermal resistance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical properties of teak wood flour‐reinforced HDPE composites

Mechanical properties such as tensile and impact strength behavior of teak wood flour (TWF)‐filled high‐density polyethylene (HDPE) composites were evaluated at 0–0.32 volume fraction (Φ_f) of TWF. Tensile modulus and strength initially increased up to Φ_f = 0.09, whereas a decrease is observed with further increase in the Φ_f. Elongation‐at‐break and Izod impact strength decreased significantly with increase in the Φ_f. The crystallinity of HDPE also decreased with increase in the TWF concentration. The initial increase in the tensile modulus and strength was attributed to the mechanical restraint, whereas decrease in the tensile properties at Φ_f > 0.09 was due to the predominant effect of decrease in the crystallinity of HDPE. The mechanical restraint decreased the elongation and Izod impact strength. In the presence of coupling agent, maleic anhydride‐grafted HDPE (HDPE‐g‐MAH), the tensile modulus and strength enhanced significantly because of enhanced interphase adhesion. However, the elongation and Izod impact strength decreased because of enhanced mechanical restraint on account of increased phase interactions. Scanning electron microscopy showed a degree of better dispersion of TWF particles because of enhanced phase adhesion in the presence of HDPE‐g‐MAH. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Active cellular preform derived from stems of jute and sticks of cane and their suitability for bulk porous Si/SiC ceramics

Stems of Jute (Corchorus capsularis L.) and sticks of Cane (Calamus rotang L.), plants of immense economic importance in the Indian subcontinent, were converted into carbonaceous perform (C-preform) maintaining the circular cylindrical shapes in lengths of 0.02–0.05 m by controlled thermal processing. Plant material precursors were characterized by analysis of elemental (C, H, N) and molecular (cellulose, hemicellulose, lignin) compositions, by determination of Bulk Density (BD) and ash content and by optical microscopy and X-ray diffractometry (XRD). C-preforms were also characterized by measurement of BD and by Scanning Electron Microscopy (SEM) and XRD. The C-preforms were further subjected to infiltration with Si-melt (1823–1923 K) under vacuum. Spontaneous infiltration and reaction yielded composite ceramics preserving the morphology of native Jute Stem (JS) and Cane Stick (CS) precursors on macro and micro scale. The materials were found to be duplex composites with Si and β-SiC as crystalline phases. The end ceramics were characterized by measurement of BD, and also by SEM and by XRD. Measured mean BD of the Si/SiC composites derived from JS and CS were 2190 Kg m⁻³ and 2250 Kg m⁻³. The respective volume fractions of large diameter (>100 μm) bulk pores were 0.134 and 0.204, in the composites derived from JS and CS. Taking into account the measured volume fraction internal pores of 0.11 and 0.149, the volume fractions of SiC were calculated to be 0.136 and 0.307 in the composites derived from JS and CS respectively, closely tallying with those calculated from the C-preform bulk densities. The cellular Si/SiC ceramics derived from JS and CS having special morphologies with long and large porous channels and oriented growth of constituent phases are likely to be suitable for devices such as high temperature insulators, catalyst support structures for gas phase reactions at elevated temperatures, molten metal filters and others.     

Hybrid orientation technology and strain engineering for ultra-high speed MOSFETs

We report here RF MOSFET performance in sub-45-nm hybrid orientation CMOS technology. Based on the combination of hybrid orientation technology (HOT) and process-induced local strain engineering, MOSFET RF performance is investigated using CAD (TCAD) technology. Transistor optimization on (100) substrate via silicon nitride (Si ₃ N ₄ ) cap layer thickness for n-MOSFETs, Ge mole fraction optimization for p-MOSFETs on (110) substrates and channel length scaling have resulted in record RF performance, viz. the cut-off frequency, ${f_{\rm T}}$ .     

On-Demand Local Modification of High-Tc Superconductivity in Few Unit-Cell Thick Bi2Sr2CaCu2O8+δ

High-temperature superconductors (HTSs) are important for potential applications and for understanding the origin of strong correlations. Bi₂Sr₂CaCu₂O_8+δ (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit-cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science. Similarly, modifying superconductivity in HTS locally, on a small length scale, is of immense interest for superconducting electronics. A route to modify superconductivity locally by depositing metal on the surface is reported here by transport studies on few unit-cell thick BSCCO. Deposition of chromium (Cr) on the surface over a selected area of BSCCO results in insulating behavior of the underlying region. Cr locally depletes oxygen in CuO₂ planes and disrupts the superconductivity in the layers below. This technique of modifying superconductivity is suitable for making sub-micrometer superconducting wires and more complex superconducting devices.     

Mechanical behavior of glass polymer multilayer composites

To identify the best reinforcement condition for development of tough glass polymer multi-layer composites (GPMLC) with high failure strain, two such model composite structures were developed. Soda–lime–silica glasses of two different thicknesses viz (A—1.01 mm and B—1.17 mm) were used as the matrix layers. The A-glass and B-glass based GPMLC samples were prepared by a novel, low pressure lamination technique applied to the alternating planar structure of the matrix and reinforcing phases. These GPMLC materials were fabricated with and without a thin sprayed layer of kerosene, between the glass layer and the reinforcing layer in the interface where; the interface was either epoxy (a thermosetting resin) or polyvinyl butyral (PVB, a thermoplastic resin). The GPMLC samples which exhibited stepped load—displacement behaviour in the most pronounced fashion, had the thermoplastic resin at the interface. Most of these GPMLC samples had a thin layer of kerosene intentionally introduced between the glass layer and the reinforcing polymer layer such that a weak interface is obtained. Fractographic evidence suggested that more of controlled delaminaton cracking occurs in such samples. Apart from the chemical nature of the reinforcing polymer phase, the interfacial layer thickness (h _i ) and the interfacial shear stress ( _xy ) were found out to have significant influence on the specific failure load and the failure stress of the current glass polymer multi-layer composites.     

工业控制计算机在轮胎硫化过程控制中的设计应用

立式硫化罐在轮胎生产企业使用比较广泛,手动操作和人为控制很难保证生产工艺和产品质量,保证轮胎质量必须采用比较好的控制系统达到目的,采用工业控制计算机进行轮胎硫化过程控制可以达到硫化三要素的正确控制,从而保证产品质量,降低劳动强度,提高生产效率.     

Synthesis of spherical Al2O3 and AlN powder from C@Al2O3 composite powder

A novel approach has been taken to produce (1) spherical Al₂O₃ particles by decarbonisation and (2) spherical AlN particles by nitridation and subsequent decarbonisation of C@Al₂O₃ composite particles. C@Al₂O₃ composite particles have been prepared by heterogeneous nucleation and crystallisation of Al(NO₃)₃ on surfactant encapsulated carbon nano particles followed by evaporative decomposition of the nitrate. Overpressure (0.4 MPa) of nitrogen and a temperature range (1723–1873 K) have been used for nitridation. Whiskers as well as spherical particles of AlN have been observed in the final product. The final product has been characterised by X-Ray Diffraction, Scanning Electron Microscope and Carbon–Hydrogen–Nitrogen content analysis by Elemental Analyser and the mechanism of the nitridation reaction has been analysed. The average size of the spherical AlN particles consisting of crystallites in nano-dimensions (30–50 nm) could be varied from 100 nm to 8 μm by changing the composition of the sol.     

Prediction of mode I fracture toughness of unidirectional fibre composites with arbitrary crack fibre orientation from its lowest or matrix fracture tougness

Corrigendum

Prediction of mode I fracture toughness of unidirectional fibre composites with arbitrary crack fibre orientation from its lowest or matrix fracture tougnessby P.K. Sarkar and S.K. Maiti