Alok P. S. Chauhan

Optical absorption and fluorescent behaviour of titanium ions in silicate glasses

Titanium in normal melting conditions in air atmosphere present as Ti4+ ion in basic silicate glasses exhibited an ultra-violet cut-off in silicate glasses, viz. soda-magnesia-silica, soda-magnesia-lime-silica and soda-lime-silica glasses. This indicates that Ti4+ ion can be a good replacement for Ce4+ ion in producing UV-absorbing silicate glasses for commercial applications. The wavelength maxima at which the infinite absorption takes place in glasses was found to be around 310 nm against Ti-free blank glass in UV-region. The mechanism of electronic transition from O2- ligands to Ti4+ ion was suggested as L→ M charge transfer. The low energy tails of the ultra-violet cut-off were found to obey Urbach’s rule in the optical range 360–500 nm. The fluorescence spectra of these glasses were also studied and based on the radiative fluorescent properties it was suggested that the soda-lime-silica glass containing Ti4+ ion with greater emission cross-section would emit a better fluorescence than the corresponding soda-magnesia-lime-silica and sodamagnesia-silica glasses. The shift of emission wavelengths maxima towards longer wavelength in titania introduced silicate glasses was observed on replacement of MgO by CaO which may be attributed due to an increase in basicity of the glass system.

Internal carburization and carbide precipitation in Fe-Ni-Cr alloy tubing retired from ethylene pyrolysis service

The events leading to the failure of an alloy grade HP Nb ethylene pyrolysis heater tubing were examined. X-ray maps indicated that a complex oxide coating, which inhibits carbon (C) diffusion, forms on the process side of the tubing during service. Phase equilibria studies predict that even without process C diffusion, metal carbides will precipitate out of the face centered cubic (FCC_Al) matrix. It was estimated that a 6 mm thick tube operating at 1100 °C would completely carburize in two years if the protective coating is damaged.

Antenatal care among currently married women in Rajasthan, India

Abstract Objective To assess the utilization of antenatal care (ANC) services among currently married women in Rajasthan. Methods The data have been extracted from District Level Household and Facility Survey (DLHS-3) which was conducted during 2007-2008, all over India. A total of 12 458 currently married women in the age group of 15-49 were taken as the sample for the study. Cross tabulation and binary logistic regression method were applied to determine the factors influencing ANC. Results Out of 12 458 respondents, 43.4 percent women not received even a single ANC during their pregnancy period. 45.1 percent of the women not received tetanus toxoid injection and 13.0 percent of the women not received Iron folic acid tablets during their pregnancy period. Only 6.6 percent of women fulfilled the minimum recommendation with regard ANC services. Conclusions The study points to the avenues through which policy makers can formulate and implement policies on a realistic basis by identifying critical variables and target groups for effective utilisation of ANC.

Comparative heat transfer studies of polymer block (PVA) coated with carbon (CB/Graphite) layer using comsol multiphysics ®

The present studies of carbon coating on polymer block shows the effects of using two different forms of carbon layer coating on the thermal behavior of the resultant material. Carbon Black (CB) and Graphite were being considered as conductive layer coating on the polymer block of Poly (vinyl alcohol) (PVA). Heat transfer studies were done by designing a 2D time dependent model using COMSOL Multiphysics® software. It was established that the temperature gradient of Graphite/PVA system was higher as compared to CB/PVA setup for the time period not more than 1 minute.The present studies of carbon coating on polymer block shows the effects of using two different forms of carbon layer coating on the thermal behavior of the resultant material. Carbon Black (CB) and Graphite were being considered as conductive layer coating on the polymer block of Poly (vinyl alcohol) (PVA). Heat transfer studies were done by designing a 2D time dependent model using COMSOL Multiphysics® software. It was established that the temperature gradient of Graphite/PVA system was higher as compared to CB/PVA setup for the time period not more than 1 minute.

Geometrical nonlinearity of 14-node brick finite element

The present work depicts the geometrical nonlinearity analysis for the finite element, PN5X1. Here, the general problem of elasticity is numerically solved using iteration method. The proposed element is passed through different tests in order to prove that it works not only for modeling sheet metal forming process but also for other large deformation problems.

Influence of carbon fillers on the thermal conductivity of Poly (methyl methacrylate)/carbon composites

In the present research on carbon polymer composites, the effects of variation of the concentration of conductive fillers on the thermal conductivity of the resultant composite were studied. Carbon powders in the form of Carbon Fibers (CF) (200µm), Carbon Black (CB) (30-100 nm) and Graphite (75-100µm) were being considered as conductive fillers in the Poly (methyl methacrylate) (PMMA) matrix. Nielsen model was found to be the best proposed model that incorporated geometric configuration comprising of both the orientation and shape of fillers. It was established that the calculated values of thermal conductivity of PMMA composites with single fillers of CF were higher than those of CB followed by Graphite. Furthermore, a visible synergy was observed between the combinations of these fillers such as Graphite and CF, Graphite and CB, CF and CB, as well as CB and CF.

Influence of different grades of furnace carbon blacks on the curing kinetics and reinforcement of natural rubber composites

The effect of different grades (N375, N405, N509) of carbon black (CB) powder on the synthesised carbon black natural rubber (CBNR) composites were investigated to study the curing and reinforcing characteristics of CB structure. The different CB grades depicted; on the one hand, the ascending order of nitrogen surface area (NSA) in conjunction with statistical thickness surface area (STSA) to be N375 < N405 < N509, while on the other hand, relative span factor (RSF) together with pellet hardness were N405 < N509 < N375. The synthesised CBNR composites were analysed for rheological and reinforcement behaviour. It was observed that both, elongation at break and cure rate index (CRI) of the CBNR composites varied with RSF of CB powders. The RSF of CB powders showed association with elongation at break and CRI of the CBNR composites. Moreover, there is a synergy in the hardness, resilience and tensile strength of the CBNR composites.

Scaled Up Pulsed Deposition Technology: Carburization Resistant Ablation Coatings for Ethylene Pyrolysis Coils

Products derived from ethylene have and will continue to replace metallic materials traditionally used for transportation, building materials, and products we use in our everyday lives. As the demand continues to increase, a more suitable material for the outlet coils of ethylene pyrolysis heaters will have to be identified. In this study, we discuss utilization of scaled up pulsed deposition technology to deposit adherent carburization resistant coatings on the inner diameter of ethylene pyrolysis tubing with the intent of extending tube life. Ablation target material selection was based primarily on elevated temperature properties and the ability of the coating to prevent transformation of the inherent protective chromium oxide surface film to metal carbides while in service. The near optimal settings of the processing parameters for pulsed laser deposition of ceramic SiC on heat resistant tubing traditionally used for ethylene service were investigated using a semi quantitative controlled random search methodology. Minimization of the objective function which was based on width, thickness and coverage of the thin film resulted in an optimal deposition time of 4.3 minutes and surface finish of 272 nm.

Limiting Catalytic Coke Formation by the Application of Adherent SiC Coatings via Pulsed Laser Deposition to the Inner Diameter of Tube Material Traditionally Used for Ethylene Pyrolysis Service

Pulsed laser deposited coatings can be used to enhance the corrosion resistant of materials traditionally used for industrial applications. In this paper, we describe our initial results on coating HK40 (a material used for ethylene heater tubing) with silicon carbide (a carburization resistant coating) to increase tube life. A 1 um thick film of silicon carbide was successfully deposited onto a heated HK40 substrate. An array of characterization techniques (scanning electron microscopy, atomic force microscopy, and scratch tests) demonstrated that the processing conditions were suitable for good coverage and promising adhesion behavior.