Chemical and Microstructural Analysis of a Tin Coin of Sangam Period

An ancient coin from the Tamirabharani river bed was analysed for microstructure and chemical composition with an objective of understanding the nature of manufacture, and for corroborating information on the trade routes between Rome and South India. Advanced synchrotron X-ray and electron microscopy techniques were employed to evaluate the phases and their crystal structures, microstructure and chemistry. The study helped to identify the process route for the manufacture of the coin.     

Failure Analysis of AISI 304 Stainless Steel Sleeve Used in High-Pressure Hose Assembly of Actuation System of a Satellite Launch Vehicle

Hydraulic control actuation systems in launch vehicles use flexible hoses for transmission of forces to actuators at different locations. The hose ends are connected to the interface adapters by AISI 304 stainless steel sleeves. These sleeves are assembled to nipple end fittings of the high-pressure hose by a swaging operation to obtain leak-proof hose assemblies. The swaging operation is carried out at room temperature by a hydraulically operated swaging machine. Performance of the system as a whole requires strict adherence to the quality standards maintaining the critical interface dimensions within specified tolerances and ensuring the compression given to the swaged joint through the sleeve. If the joining forces are less, this can result in loose joints and gross leakage, whereas excessive compression can cause damage to the parts of the system namely the sleeve, stainless steel braid, PTFE or the adapter. The swaged joint is a single-point failure mode, indicating that a failure in the joint can lead to mission failure. It has to withstand harsh environments such as high pressure, low and high temperature extremes, fatigue loading due to pressure cycling as well as vibration. Therefore, as part of design verification, a detailed qualification plan has been prepared and the hoses were tested as per the plan. As per the test plan, these hoses undergo acceptance tests which include pneumatic and hydraulic pressure testing. During acceptance testing of hoses, one of the hose sleeves was found to be cracked. The cracking was observed after carrying out the pneumatic test when the assembly was being prepared for hydraulic pressure set-up. This paper describes the detailed metallurgical investigation carried out to understand the cause of failure and actions taken to avoid similar failures.     

Electrochemical bromination and oxidation of alkyl aromatic compounds by two-phase electrolysis

A simple, regioselective, environmentally clean and economical method for the preparation of side chain/ ring brominated aromatic compounds is reported in 70–98% yield by an electrochemical method using two phase electrolysis technique. Electrochemical reactions were carried out using aqueous 25–50 wt% sodium bromide containing catalytic amount (5 wt%) of hydrobromic acid as an aqueous phase and chloroform containing alkyl aromatic compounds as an organic phase, at a temperature of 0–30 °C in an undivided cell. The same two-phase electrolytic system can be used for the oxidation of benzylic alcohols to the corresponding benzaldehydes in 80–94% yield without over oxidation to carboxylic acids. The advantage of this very mild procedure is a room temperature reaction used with an undivided cell. Excellent conversions are observed. After completion of alcohol oxidation the electrolyte can be reused for a number of times, demonstrating “spent reagent” free electro organic reaction as an attractive one. In the case of side chain/ring bromination of alkyl aromatic compounds, the electrolyte can be reused after making up the concentration of the electrolyte with 47 wt% HBr solution. In some cases homogeneous electrolysis is applied, where the two-phase electrolysis did not work. Styrene epoxidation and α-bromination of ketones underwent homogeneous electrolysis at room temperature without any catalyst. The reaction was performed in CH₃CN-water (3: 2) using equimolar amount of NaBr as an electrolyte to get 68% of styrene epoxide. Use of an ionic liquid 1-butyl 3-methyl imidazolium bromide (Bmim) Br, instead of NaBr improved the yield and current efficiency of styrene epoxide to 86%.     

Prediction of CO2 gas permeability behavior of ionic liquid–polymer membranes (ILPM)

Predicting the gas permeability of ionic liquid‐polymeric membranes (ILPM) is of great importance for the design of efficient gas separation membrane materials. The available models for the prediction of CO₂ gas permeability through ionic liquid‐polymeric membranes were analyzed using the literature data. Maxwell model was selected for modification due to relatively accurate prediction capability. The Maxwell model was modified for ionic liquid‐polymeric membranes by incorporating model parameter k for the effectiveness of volume fraction of dispersed phase. The established methodology was tested for different ionic liquid‐polymeric membrane systems for validation. A satisfactory agreement was observed for predicted and experimental permeability by using the current approach. This method can be used for the prediction of CO₂ gas permeability through ionic liquid‐polymeric membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44761.     

Hybrid-Cells-in-Series Model for Solute Transport in Streams and Relation of Its Parameters with Bulk Flow Characteristics

The conceptualized hybrid-cells-in-series model, consists of a plug flow zone and two thoroughly mixed unequal reservoirs, all connected in series, has three time parameters, namely: (1) residence time of solute in the plug flow zone; and (2) residence times of solute in the two thoroughly mixed reservoirs. The model simulates closely advection-dispersion solute transport in natural streams. The resident time parameters are related to the velocity of flow, width of water surface, and depth of flow in the stream. Through the Péclet number, defined as Pe = (Δxu)/DL (in which Δx=process unit size; u=mean flow velocity; and DL=longitudinal dispersion coefficient), the relations of the model parameters with the longitudinal dispersion coefficient and with the bulk stream flow characteristics have been established. For a given reach of a stream, the parameters are inversely proportional to the flow velocity. By decoupling of pure advection by the plug flow component and dispersion of tracer by the two thoroughly mixed reservoir components, a robust fitting to the observed concentration-time data in natural streams was achieved.     

Polysulfone/poly(ether sulfone) blended membranes for CO2 separation

Polymer blending as a modification technique is a useful approach for augmenting the gas‐separation and permeation properties of polymeric membranes. Polysulfone (PSF)/poly(ether sulfone) (PES) blend membranes with different blend ratios were synthesized by conventional solution casting and solvent evaporation technique. The synthesized membranes were characterized for miscibility, morphology, thermal stability, and spectral properties by differential scanning calorimetry (DSC), field emission scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared (FTIR) spectroscopy, respectively. The permeation of pure CO₂ and CH₄ gases was recorded at a feed pressure of 2–10 bar. The polymer blends were miscible in all of the compositions, as shown by DSC analysis, and molecular interaction between the two polymers was observed by FTIR analysis. The thermal stability of the blend membranes was found to be an additive property and a function of the blend composition. The morphology of the blend membranes was dense and homogeneous with no phase separation. Gas‐permeability studies revealed that the ideal selectivity was improved by 65% with the addition of the PES polymer in the PSF matrix. The synthesized PSF/PES blend membranes provided an optimized performance with a good combination of permeability, selectivity and thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42946.     

Flexible Multifunctionalized Carbon Nanotubes‐Based Hybrid Nanowires

In this work, flexible multifunctionalized carbon nanotube (CNT)‐based hybrid nanowires are synthesized through surface modification processes. The good dispersability of the hybrid nanowire in polar solvents facilitates directly making fine patterns with a minimum width of 40 μm for applications of flexible and stretchable circuits (FSCs). The hybrid nanowire possesses a flexible and highly conductive structure which demonstrates stable electro‐mechanical properties on polydimethylsiloxane (PDMS) substrates under large structural deformation. FSCs fabricated from the hybrid nanowires show a constant resistance of 0.096 Ω □^?1 (equivalent of a resistivity 0.96 Ω μm) under repeated bending cycles. The FSCs also have a low and stable sheet resistance of 0.4 Ω □^?1 for strains up to 30%, which is almost four orders of magnitude lower than that of pure CNT samples (1316 Ω □^?1). Further improved stretchability and electro‐mechanical properties (0.1 Ω □^?1, at the strain of 100%) are achieved with a prestrain PDMS substrate. Repeated deformation tests demonstrate the high reliability of FSCs. The observed stable and reliable electro‐mechanical performance of FSCs suggests the potential use of the material in wearable and portable electronics.     

Performance,emissions and combustion characteristics of CI engine fuel with watermelon (Citrullus vulgaris) methyl esters

In this paper, bio-diesel was prepared from watermelon seed oil by using transesterification processes. The performance, emission and combustion characteristics of the various bio-diesel and diesel blends (B20–B80 and B100) are compared with those of the diesel. The experimental result indicates that owing to a lower heating value of bio-diesel, the brake-specific fuel consumption increased and the brake thermal efficiency decreased. However, bio-diesel and its blends reduced carbon monoxide and hydrocarbon, while the oxides of nitrogen and smoke slightly increased. The combustion analysis proved that increasing bio-diesel blend ratio decreases the cylinder pressure and heat release rate when compared with base diesel.     

Role of ceria in CO2 adsorption on NaZSM-5 synthesized using rice husk ash

Ceria (3, 5, 7, 11, 19 wt%) impregnated NaZSM-5 was synthesized and studied for adsorption of CO₂. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), CO₂-temperature programmed desorption (CO₂-TPD) and Brunauer–Emmett–Teller (BET) techniques. The heat of the reaction (ΔH_r) derived from differential scanning calorimetry (DSC) analysis was 490 Btu/lb. XRD analysis showed a decrease in the intensity of patterns with the increase in the ceria loading but crystallization of ceria to larger size was clearly evident for 11 and 19% loading. The surface area decreased for 3 and 5% loading, but increased for 7, 11 and 19% loading illustrating difference in dispersion. The maximum adsorption capacity of CeO₂(5%)/NaZSM-5 was 130 mg/g of sorbent. Extraction of silica from the agricultural waste, rice husk, and its use in the zeolite synthesis was an advantage in this study. Hence, from the study it was concluded that ceria impregnated NaZSM-5 could be treated as a novel material for CO₂ adsorption, as they were regenerable and recyclable. This study can also be applied to all other zeolites.