Influence of Silicon Addition on the Microstructure and Mechanical Properties of WE43 Alloy

Silicon - The investigation aims to study the microstructure and mechanical property changes of various silicon added WE43 alloys. With the increase in Si addition, the Mg2Si phase forms randomly...     

Performance investigation of double-stage metal hydride based heat pump

In this paper, the performance investigation of a Double-Stage Double-Effect Metal Hydride Heat Pump (DSDE-MHHP) working with LaNi_4.1Al_0.52Mn_0.38, LmNi_4.91Sn_0.15 and Ti_0.99Zr_0.01V_0.43Fe_0.09Cr_0.05Mn_1.5 hydride alloys is presented. The effects of half cycle time (θ), hydride mass ratio (M_R), sensible heat exchange factor (?) and operating temperatures, viz. heat source (T_D), heat sink (T_M), and refrigeration (T_C) temperatures on the amount of hydrogen transferred between the paired reactors, coefficient of performance (COP) and specific cooling power (SCP) of the DSDE-MHHP system are investigated. For the present analysis the heat rejection temperature (T_H) is maintained constant at 373 K. Numerically predicted hydride bed temperatures are compared with experimental data and a good agreement is observed between them. It is observed from the numerical results that the COP and SCP of the DSDE-MHHP system increase with heat source and refrigeration temperatures, and decrease with heat sink temperature. For operating temperatures of 578, 373, 298 and 283 K (T_D, T_H, T_M and T_C), the average COP and SCP of the system are found to be 0.81 and 48.1 W/kg of total alloy mass, respectively.     

Diffusion and Phase Transformation at the Interface between an Austenitic Substrate and a Thermally Sprayed Coating of Ledeburitic Cold‐Work Tool Steel

An overlay coating against wear or corrosion on components is required for various technical applications. Thermal spraying is a well‐established and near‐net‐shape deposition method. In this work, high‐velocity oxy‐fuel spraying of two different ledeburitic cold‐work tool steels was employed to produce wear‐resistant Fe‐base coatings on a stainless steel substrate. This work focuses on the investigation of diffusion processes across the coating/substrate interface. Specimens were heat‐treated for different dwell times and then analyzed by means of EBSD, XRD, OM, as well as SEM. Results of phase formation and diffusion profiles were compared with equilibrium and diffusion calculations obtained with ThermoCALC® and DICTRA®. The influence of diffusion processes across the coating/substrate interface on the mechanical properties, such as adhesive bond strength and hardness, was investigated by shear tests and microhardness profiles.     

Optimization of mechanical properties of polymer concrete and mix design recommendation based on design of experiments

A series of polymer concretes using furan resin, silica aggregates, and microfiller were prepared for statistically designed combinations. The combinations were designed based on the mixture‐design concept of design of experiments. The fillers chosen for the present investigation were high‐purity naturally occurring silica of different particle sizes, their mix proportion optimized to have minimum void. For each polymer concrete combination, the mechanical properties were studied. Each response (mechanical property) was individually optimized for maximum values and compared with the experimental data. To obtain a single‐input combination, having maximum values in all the responses, a combined optimization was done and a mix design was recommended. The coefficient of correlation between the experimental values and predicted values was found to be high, proving the fitness of the selected model. The effect of individual variables on the response was discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1107–1116, 2004     

Treatment of textile dye wastewater by using an electrochemical bipolar disc stack reactor

Textile dye house wastewater from a reactive dye processing unit was treated by using an electrochemical oxidation technique. The experiments were carried out in an electrochemical bipolar disc reactor using RuO₂ coated on titanium as anode and titanium as cathode. The sodium chloride present in the effluent was used as supporting electrolyte. Operating parameters such as current density, reservoir hold‐up and electrolysis time were studied for maximum Chemical Oxygen Demand (COD) reduction and other relevant parameters such as current efficiency and power consumption per kg of COD removal were calculated. The higher flow rate and lower reservoir hold‐up resulted in improved COD removal. The applied current density was also found to significantly influence the reduction of COD. A suitable mathematical model is also proposed to illustrate the relationship between the basic parameters. Pseudo mass transfer coefficients were also evaluated for different experimental conditions. Copyright © 2004 Society of Chemical Industry     

Critical gas velocity in a three‐phase internal loop airlift reactor with low‐density particles

In the present investigation the effects of the addition of organic additives (propanol, benzoic acid, iso‐amyl alcohol and carboxymethyl cellulose) on the critical gas velocity, (U_sg)_c, in an internal airlift loop reactor with low‐density particles (Nylon‐6 and polystyrene) were reported. Whereas the (U_sg)_c was reduced by adding the above additives, it increased with solids loading and density of the particles. The draft tube‐to‐reactor diameter ratio (D_E/D) in the range of 0.5–0.6 gave minimum (U_sg)_c values. The proposed dimensionless correlation predicted the experimental data well. Copyright © 2004 Society of Chemical Industry     

ZnO nanotips grown on Si substrates by metal-organic chemical-vapor deposition

The ZnO nanotips are grown on silicon and silicon-on-sapphire (SOS) substrates using the metal-organic chemical-vapor deposition (MOCVD) technique. The ZnO nanotips are found to be single crystal and vertically aligned along the c-axis. In-situ Ga doping is carried out during the MOCVD growth. The ZnO nanotips display strong near-band edge photoluminescence (PL) emission with negligible deep-level emission. Free excitonic emission dominates the 77-K PL spectrum of the as-grown, undoped ZnO nanotips, indicating good optical properties and a low defect concentration of the nanotips. The increase of PL intensity from Ga doping is attributed to Ga-related impurity band emission. Photoluminescence quenching is also observed because of heavy Ga doping. ZnO nanotips grown on Si can be patterned through photolithography and etching processes, providing the potential for integrating ZnO nanotip arrays with Si devices.     

Thermal Modeling of Mg2Ni-Based Solid-State Hydrogen Storage Reactor

In this paper, a numerical study of coupled heat and hydrogen transfer characteristics in an annular cylindrical hydrogen storage reactor filled with Mg₂Ni is presented. An unsteady, two-dimensional (2-D) mathematical model of a metal hydride reaction bed of cylindrical configuration is developed for predicting the hydrogen storage capacity. The effect of volumetric radiation is accounted in the thermal model. Effects of hydride bed thickness, initial absorption temperature, hydride bed thermal conductivity, and hydrogen supply pressure on the hydrogen storage capacity are studied. A thinner hydride bed is found to enhance the hydriding rate, accomplishing a rapid reaction. At an operating condition of 20 bar supply pressure and 573 K initial absorption temperature, Mg₂Ni stores about 36.7 g hydrogen per kg alloy. For a given bed thickness and an overall heat transfer coefficient, there exists an optimum value of hydride bed thermal conductivity. The present numerical results are compared with the experimental data reported in the literature, and good agreement was observed.     

Development of sulfated polysaccharide-based film reinforced with seaweed biomass-derived nanofillers

Cling films and single-use plastics are difficult to recycle and cause major environmental pollution, leading to an increase in microplastics in nature. To overcome this issue, biodegradable films are being explored more extensively. Seaweed is gaining prominence in the food packaging sector since it is beneficial in all aspects. Two fractions of Indian brown seaweed Sargassum wightii, biopolymer (sulfated polysaccharide [SP]) as base material and nanofillers (cellulose nanocrystals [CNC]) as reinforced filler are employed to develop a sustainable cling film for food packaging. This cellulose filler can be isolated from solid seaweed biomass after the polysaccharide extraction and converted into nanoform using the response surfaces method (RSM) to maximize the yield of CNC. The objective of this research is to construct seaweed-based biodegradable nanocomposite films and to examine their improved properties. It exhibited a gradual decrease in water absorption and water vapor permeability (WVP), along with better wettability, mechanical, and antioxidant properties, and thermal analysis compared with the control SP film. The degradation rates of the films were analyzed using the soil-burial method. According to the results obtained, it is suggested that CNC can be utilized as a functional filler to improve the qualities of seaweed-based cling films.