Solvent effect on microstructure of yttria-stabilized zirconia (YSZ) particles in solvothermal synthesis

Using methanol or methanol/2-propanol mixtures as reaction media, yttria-stabilized zirconia (YSZ) particles were synthesized with a solvothermal route. The particles were characterized with X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser diffraction technique, and nitrogen adsorption isotherms. Results indicated that cubic/tetragonal YSZ nanocrystals with crystal size lower than 5 nm were obtained and the crystal size depends on solvent composition, reaction temperature and reaction time. For the same reaction temperature and reaction time, the solvent composition also controls YSZ crystal agglomeration behaviour. According to the DLVO theory and analysis of experimental results, the solvent effect on microstructures of YSZ particles in solvothermal synthesis has been discussed. In addition, the mechanism of particle microstructure evolution during solvothermal synthesis has been suggested.     

Study on sulfur diffusion in CuInSe2 thin films using two thermal profiles

An insurmountable disadvantage of CuInSe₂ is the low band gap, which limits the open-circuit voltage to value well below 500 mV in solar cells. The incorporation of sulfur into CuInSe₂ thin film was investigated to establish a scientific basis for the graded band gap CuIn(Se_1 − x,S_x)₂ thin films. CuIn(Se_1 − x,S_x)₂ thin films were obtained by reactive annealing of Cu₁₁In₉ precursors in a mixture of sulfur and selenium atmosphere while post-sulfurization of single phase CuInSe₂ did not result in CuIn(Se_1 − x,S_x)₂ thin films. A band gap of 1.36 eV, was obtained for the prepared CuIn(Se_1 − x,S_x)₂.     

Studies on the Cell Structure and Mechanical Properties of NR/Latex Reclaim/HSR Based Micrqcellular Sheets

In natural rubber/high styrene resin microcellular sheets, part of natural rubber was replaced by latex reclaim prepared from waste latex products. The mechanical properties and cell structure of the products were evaluated. It was found that latex reclaim can replace about 30% of natural rubber without affecting the technical properties of the microcellular sheets.     

Dielectric behavior of natural rubber composites in microwave fields

In this article, we report the preparation of conducting natural rubber (NR) with polyaniline (Pani). NR was made into a conductive material by the compounding of NR with Pani in powder form. NR latex was made into a conductive material by the in situ polymerization of aniline in the presence of NR latex. Different compositions of Pani–NR semi‐interpenetrating networks were prepared, and the dielectric properties of all of the samples were determined in microwave frequencies. The cavity perturbation technique was used for this study. A HP8510 vector network analyzer with a rectangular cavity resonator was used for this study. S bands 2–4 GHz in frequency were used. Thermal studies were also carried out with thermogravimetric analysis and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2682–2686, 2007     

Spectral distribution of photocurrent in poly(6-tert-butyl-3-methyl-3,4-dihydro-2H-1,3-benzoxazine)

The spectral distribution of photoconductivity in poly(6-tert-butyl-3-methyl-3,4-dihydro-2H-1,3-benzoxazine) was studied in the sandwich configuration with indium tin oxide and silver electrodes. The photocurrent was found to originate mainly from the bulk dissociation of excitons with lesser contribution from electrode-mediated exciton dissociation. The molecule was fluorescent, but in the presence of the electron acceptor molecule 2,4,6-trinitrophenol (TNP), the intensity was reduced. The reduction in fluorescence intensity corresponded to an increase in photocurrent. The molecule showed photoconductivity in the visible without any sensitizers, which makes it suitable for stable photorefractive composites.     

Dielectric,Mechanical, and Thermal Properties of Low-Permittivity Polymer–Ceramic Composites for Microelectronic Applications

A new low-permittivity polymer–ceramic composite for packaging applications has been developed. The ceramic-reinforced polyethylene and polystyrene composites were prepared by melt mixing and hot molding techniques. Low-loss, low-permittivity Li₂MgSiO₄ (LMS) ceramics prepared by the solid-state ceramic route were used as the filler to improve the dielectric properties of the composites. The relative permittivity and dielectric loss were increased with the increase in the ceramic loading at radio and microwave frequencies. The mechanical properties and thermal conductivity of the Li₂MgSiO₄-reinforced polymer–ceramic composite were also investigated. The stability of the relative permittivity of polymer–ceramic composites with temperature and frequency was investigated. The experimentally observed relative permittivity, thermal expansion, and thermal conductivity were compared with theoretical models.     

Lattice vibrations of sequentially evaporated CuInSe2 by Raman microspectrometry

Copper Indium Diselenide (CuInSe₂) thin films of different atomic concentrations were prepared using sequential elemental evaporation. Raman analysis has been carried out to determine the structure and the different vibration modes of CuInSe₂ thin film. The analysis reveals that CuInSe₂ films possess chalcopyrite structure with preferential orientation along (112) plane. Vibration modes such as A₁, B₁, B₂ and E were observed in the Raman spectra. It has been observed that the intensity of the A₁ mode is directly proportional to the crystallinity. Also it has been noted that, the intensity of all the vibration modes are varied with respect to the compositions. The Raman spectra of the CuInSe₂ films were interpreted and incorporated with XRD and EDAX.     

Studies on the thermal, optical and dielectric properties of a new nonlinear optical crystal — L-citrulline oxalate grown by slow evaporation technique

In this paper we report the thermal, optical and dielectric properties of L-citrulline oxalate (LCO) monohydrate- a new nonlinear optical (NLO) organic crystal grown from aqueous solution by slow evaporation technique. It has good thermal stability up to 165°C. Optical transmittance of LCO is measured in the range 200–1000 nm and the crystal possesses a wide transparency region from 311nm to the far IR region. It has a band gap of 3.86eV. Hence the material is suitable for application as windows in spectral instruments in this region. The dielectric properties of the crystal have also been investigated. The dielectric constant obtained for LCO is higher at lower frequencies and then it decreases with increasing frequencies and saturates for further increase in the frequency. The second harmonic efficiency is found to be only 0.4 times that of KDP which can be improved by doping with alkali metals like lithium.     

Safety management practices and safety behaviour: Assessing the mediating role of safety knowledge and motivation

Safety management practices not only improve working conditions but also positively influence employees’ attitudes and behaviours with regard to safety, thereby reducing accidents in workplace. This study measured employees’ perceptions on six safety management practices and self-reported safety knowledge, safety motivation, safety compliance and safety participation by conducting a survey using questionnaire among 1566 employees belonging to eight major accident hazard process industrial units in Kerala, a state in southern part of India. The reliability and unidimesionality of all the scales were found acceptable. Path analysis using AMOS-4 software showed that some of the safety management practices have direct and indirect relations with the safety performance components, namely, safety compliance and safety participation. Safety knowledge and safety motivation were found to be the key mediators in explaining these relationships. Safety training was identified as the most important safety management practice that predicts safety knowledge, safety motivation, safety compliance and safety participation. These findings provide valuable guidance for researchers and practitioners for identifying the mechanisms by which they can improve safety of workplace.     

Amidinothiourea as a secondary accelerator in a binary system for the sulphur vulcanization of natural rubber

A study of a binary accelerator system using amidinothiourea as a secondary accelerator with mercaptobenzothiazyl disulfíde (MBTS), in sulphur vulcanization of natural rubber has been undertaken. This system was found to boost MBTS accelerator activity considerably. From the results, a nucleophilic reaction mechanism was established for this system. Different compositions of the amidinothiourea were tried in different mixes using standard recipes, and reference mixes were also vulcanized. Different cure characteristics of the mixes and important physical properties of the vulcanizates were evaluated. Optimum concentrations of amidinothiourea required were derived and the experimental mixes were found to have better cure characteristics, including an advantageous reduction in the optimum cure time. Many of the physical properties of the vulcanizates studied were also found to be better compared to those of the reference mixes. Evaluation of these properties both before and after ageing showed good retention of these properties as well. An attempt was also made to correlate the variation in physical properties to chemical crosslink formation in the various vulcanizates.