Production of hydrogen and carbon nanofibers through the decomposition of methane over activated carbon supported Ni catalysts

Hydrogen has been produced by decomposing methane thermocatalytically at 1123 K and volume hourly space velocity (VHSV) of 1.62 L/h g in the presence of activated carbon supported Ni catalysts of different compositions (Samples coded as Ni10, Ni20, Ni30 and Ni40 respectively). The studies indicated that the sample coded Ni30 catalyst (with Ni content of 23.33 wt.%) has the highest catalytic activity among all the catalysts tested. The initial methane decomposition rate, accumulated carbon in 4 h and sustainability factor (SF) of Ni30 catalyst are 0.89 mmol/min.g, 7.92 g C/g Ni and 0.7 respectively. SEM image of Ni30 catalyst after methane decomposition reaction showed formation of degenerated carbon fibers. XRD of the above catalyst revealed, moderately crystalline peaks of Ni which may be responsible for the increase in the catalytic life and the formation of carbon fibers.     

The impact resistance of masonry units bound with fibre reinforced mortars

The seismic rehabilitation of stone masonry buildings requires a quantitative understanding of the constituent materials under variable rates of loading. The stress-rate sensitivity of cementitious composites and rock has been intensively investigated. However, the literature on the impact resistance of masonry joints is scarce, particularly with regard to the bond behaviour using fibre reinforced mortars. This paper describes the stress-rate sensitivity of masonry units bound with fibre reinforced Type S mortars. A drop-weight impact machine was used to generate stress rates in the range of 1 kPa/s–10⁸ kPa/s. The dynamic impact factor and stress-rate sensitivity were evaluated for the flexural strength of the mortar and the bond strength and further, the pattern of failure was noted for each mix and loading rate. Polypropylene micro-fibres were incorporated as discrete reinforcement at 0%, 0.25% and 0.5% volume fraction into the mortar. Results show that the impact resistance of the masonry units increased in the presence of fibres. However, the stress-rate sensitivity of the bond strength decreased with an increase in the fibre content. Also, where as the mode of failure in those masonry units bound with plain mortars was through fracture at the mortar-block interface, the addition of fibres transferred the failure plane to within the masonry block.     

Opportunities and Challenges in Biology and Medicine: A Report from the 4th International Congress on Ceramics

This article summarizes the opportunities and challenges for future research in ceramics used in biology and medicine. The summary was prepared from the seven presentations at the 4th International Congress on Ceramics held from July 15 to 19, 2012, in Chicago, USA. The major emerging opportunities identified were as follows: (i) developing fundamental understanding of bioactive ions used in bioceramics, (ii) possibility of using novel manufacturing methods such as 3D printing, (iii) attaching bioceramics to metallic implants, and (iv) enabling collaboration between ceramicist, biologist, industry, and medical professionals.     

Quantitative method for evaluating fingernail induced mar damage of coatings

A traditional method of coating qualification, known as fingernail mar resistance, historically has been practiced in industry where the back of a fingernail is “flicked” across a coating surface. Any resulting permanent mark from this qualitative analysis is deemed a failure. Lack of quantitative analysis and control over experimental parameters in this type of test limits its utility as an analytical test. Fundamental understanding of this specific type of mar damage is hindered, and research efforts to find unique solutions based on changes in polymer structure are frustrated by the binary response of the test. In an attempt to rectify the situation, a high speed mar tester was developed to mimic and quantify the effects of the fingernail flick test. The work described in this report demonstrates the applicability of this tester to produce similar damage to that of the fingernail test. In addition, a quantitative method enabling differentiation of the degree of mar damage of different coatings is described. Finally, the method is demonstrated by differentiating mar resistance of coatings that show similar qualitative results in fingernail flick testing.     

Vaporizing foil actuator: A tool for collision welding

A method for implementing collision welding at moderate to small length scales has been developed. The flyer, instead of being driven by chemical explosives (explosive welding) or magnetic forces (magnetic pulse welding), is launched toward the target by the pressure created from the electrically driven rapid vaporization of a thin metallic conductor. Mechanical impulse is developed from 0.0762 mm thick aluminum foils, which are vaporized using capacitor bank discharge with nominal charging voltage of 5.5 kV and peak current on the order of 100 kA delivered with rise times of about 12 μs. Welding couples of copper–titanium, copper–steel, aluminum–copper, aluminum–magnesium and titanium–steel have been successfully created with the same input parameters such as foil geometry, input energy and standoff distance. Instrumented peel tests, lap shear tests and optical and scanning electron microscopy reveal a wide spectrum of both strengths and interface structures. Copper–titanium and copper–steel welds are strong and have characteristic wavy interfaces with little intermetallics or void formation. The other combinations are seen to have brittle interfaces with intermetallics and defects, with the collision welding parameters used presently. For the titanium–steel system, a thin nickel interlayer is introduced and all the layers are welded in a single experiment. Peel strength of the weld was observed to be quadrupled. Peak velocities of up to 560 m/s were obtained for titanium flyer sheets.     

Superplastic Forming of Multipass Friction Stir Processed Aluminum-Magnesium Alloy

Multipass friction stir processing (FSP) of AA5086 Al-Mg alloy was carried out to obtain bulk fine grain material for superplastic forming. FSP produced inhomogeneous microstructure in the thickness direction. The aim of the present work was to understand superplastic forming behavior of distinct microstructural layers, i.e., nugget layer (NL) containing microstructure from nugget zone, thermo-mechanically affected/heat-affected layer (TL) containing microstructure from thermo-mechanically affected/heat-affected (TMAZ/HAZ) zone, and composite layer (CL) containing microstructure from both the above zones (nugget and TMAZ/HAZ). Superplastic forming of NL, TL, and CL blanks was carried out at constant gas pressure. Three different forming gas pressures of 0.75, 1.15, and 1.5 MPa corresponding to strain rates of 5 × 10^?4 s^?1, 1 × 10^?3 s^?1 , and 5 × 10^?3 s^?1, respectively, were used. Forming characteristics of CL were found to be comparable to that of NL and even better at higher forming pressures. Concomitant microstructural evolution during bulging of CL and NL plays an important role here.     

Simulation of flows in stirred vessels agitated by dual rushton impellers using computational snapshot approach

Flow in baffled stirred vessels involves interactions between flow around rotating impeller blades and stationary baffles. When more than one impeller is used (which is quite common in practice), the flow complexity is greatly increased, especially when there is an interaction between two impellers. The extent of interaction depends on relative distances between the two impellers and clearance from the vessel bottom. In this paper we have simulated flow generated by two Rushton (disc) impellers. A computational snapshot approach was used to simulate single-phase flow experiments carried out by Rutherford et al. (1996). The computational model was mapped on the commercial CFD code FLUENT (Fluent Inc., USA). The simulated results were analyzed in detail to understand flow around impellers and interaction between impellers. The model predictions were verified using the data of Rutherford et al. (1996). The results presented in this paper have significant implications for applications of computational fluid mixing tools for designing multiple impeller stirred reactors.     

New polymer electrolyte for electrochemical application

A solid polymer electrolyte consisting of poly vinylpyrrolidone (PVP) and potassium iodide (KI) were developed, characterized for possible application in dye sensitized solar cell (DSSC) as an electrolyte. Complex impedance spectroscopy revealed the enhancement in electrical conductivity (σ) by salt doping and a conductivity maximum was obtained at 30 wt% KI concentration. Dielectric phenomena also support the σ data. Fourier transform infrared spectroscopy (FTIR) confirmed the composite nature of polymer electrolyte film. Using maximum electrical conductivity film we have fabricated a DSSC which shows 0.14% efficiency at 1 sun condition.     

Ant colony optimization for group technology applications

The problem of grouping of parts into part-families and that of machines into machine-cells has attracted the attention of many researchers particularly for medium variety of parts with medium production volume requirement, which traditionally required their production in batches for achieving economics of production. This kind of grouping, consequently offering benefits of mass production, was aimed to have independent cells processing ideally almost different sets of part-types. For this purpose, a number of approaches are available from various kinds of heuristics to mathematical programming formulations. Evolutionary methods such as neural network, genetic algorithm, and simulated annealing have also been tried and have been found to provide better grouping solutions with much less computational complexity. In the present paper, ant colony optimization approach with number of newer strategies, incorporating more generalised framework of ants’ behaviour, has been applied to the parts and machines grouping problems taken from the literature. The results obtained from their application were found to be encouraging and thus establish the usefulness of the proposed approaches. Average performance of Tabu search with multiple ants was found to be the best and thus the parameter values for this approach were also determined using design of experiments methodology.