A relook at the preferred growth direction of the solid–liquid interface during solidification of pure metals

A simple model for the prediction of the principal growth direction of a solid–liquid interface during solidification of pure metals of different crystal structures is developed. The existing interface controlled growth model for the growth of a solid in a liquid is suitably modified with the incorporation of density change during solidification. The idea of conjugate planes is introduced to construct virtually a unit cell of a solid and, finally, the growth of the conjugate planes is presented with respect to the plane normal. A very good match is shown between the calculated directions of highest growth rate and the experimentally found directions of the primary dendrites of a number of crystal structures. It is also shown that the differential growth of a solid in a liquid along different crystallographic directions is inherently associated with the density change and spatial distribution of atoms on the facing liquid and solid planes on solidification.     

Removal of Pb(II) from aqueous solution by adsorption using activated tea waste

A basic investigation on the removal of Pb(II) ions from aqueous solutions by using activated tea waste was conducted in batch conditions. An inexpensive and effective adsorbent was developed from waste tea leaves for the uptake of Pb(II) from aqueous solution. The influence of different experimental parameters—shaking time, particle size, adsorbent dose, initial pH, temperature, etc.—on lead uptake was evaluated. Lead is adsorbed by the developed adsorbent up to maximum of 99.7%. The initial Pb(II) concentrations were 5, 10, 15 and 20 mg/l in the experiment. The adsorption was found to be exothermic in nature. The Langmuir, Freundlich and Tempkin isotherm models were tried to represent the equilibrium data of Pb(II) adsorption. The adsorption data was fitted very well to the Langmuir isotherm model in the studied concentration range of Pb(II) adsorption. Isotherms have been used to determine thermodynamic parameters of the process: free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°). Column experiments were performed to study the practical applicability of the system. The kinetics and the factors controlling the adsorption process were also discussed. Activated tea waste is a better adsorbent compared to other adsorbents available in literature.     

CuO nano-whiskers: Electrodeposition,Raman analysis,photoluminescence study and photocatalytic activity

An electrochemical route to synthesize CuO thin films with nano-whiskers like structure, from a metallic Cu precursor is reported. Structural characterization showed the formation of cubic phase for both the Cu and CuO films, whereas, the grains were found to change their shapes from cubic to nano-whiskers as an effect of annealing (in air at 600 °C for 30 min). X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis, Photoluminescence (PL) and Raman analyses were carried out with the films. The photocatalytic activity of the prepared CuO films was determined by measuring the degradation of Rose Bengal (RB) dye, to find out its potential application in waste water treatment.     

Correlation of microstructure and magnetic properties in Cu–Co–Ni alloys

The present study concerns correlation of microstructure and magnetic properties of nanocrystalline binary 50Cu–50Co and ternary 50Cu–25Co–25Ni (wt%) alloys prepared by ball milling and subsequent isothermal annealing of the ball milled alloys. High resolution transmission electron microscopic (HR-TEM) investigation has shown deformation-induced microstructural features. Field emission scanning electron microscopy (FE-SEM) has revealed a distinct change in morphology of as-milled CuCoNi alloys after annealing. Differential scanning calorimetric (DSC) and X-ray diffraction (XRD) analysis have revealed that annealing of the CuCoNi alloy above 350 °C results into precipitation of nanocrystalline Co (fcc) in the CuNi matrix by spinodal decomposition. It is also demonstrated that isothermal annealing of the ball milled alloys in the temperature range between 350 and 650 °C significantly influence the magnetic properties, e.g. coercivity (H_c), remanence (M_r) and magnetic saturation (M_s) due to annihilation of defects such as stacking and twin fault along with dissolution and/or precipitation of magnetic phases in the Cu-rich matrix.     

Additive free thermoplastic vulcanizates based on natural rubber

Electron induced reactive processing (EIReP) is an eco-friendly and sustainable reactive processing method based on the use of high energy electrons. It was used to cross-link the elastomeric domain phase during melt mixing in order to prepare natural rubber (NR) and polypropylene (PP) based thermoplastic vulcanizates (TPVs). The electron treatment with various values of absorbed dose showed a prominent effect on mechanical, rheological, and morphological characteristics of the PP/NR TPVs. SEM and TEM studies confirmed that these TPVs can exists across the co-continuous or discrete phase morphology. The maximum set of mechanical properties (tensile strength of 15 MPa and elongation at break of more than 500%) were obtained at an absorbed dose of 100 kGy for a 50/50 blend ratio of NR and PP without addition of any compatibilizer or chemicals. At higher values of absorbed dose the degradation of polypropylene showed a negative impact on the properties of the TPVs. Depending on the morphology and the evaluation of mechanical properties a structure–property co-relationship is drawn on the basis of common phenomenological understanding of the TPVs.     

Bioremediation of 2-chlorophenol containing wastewater by aerobic granules-kinetics and toxicity

2-Chlorophenol (2-CP) degrading aerobic granules were cultivated in a sequencing batch reactor (SBR) in presence of glucose. The organic loading rate (OLR) was increased from 6.9 to 9.7 kg COD m(-3)d(-1) (1150-1617 mg L(-1)COD per cycle) during the experiment. The alkalinity (1000 mg L(-1) as CaCO(3)) was maintained throughout the experiment. The specific cell growth rate was found to be 0.013 d(-1). A COD removal efficiency of 94% was achieved after steady state at 8h HRT (hydraulic retention time). FTIR, UV, GC, GC/MS studies confirmed that the biodegradation of 2-CP occurs via chlorocatechol (modified ortho-cleavage) pathway. Biodegradation kinetics followed the Haldane model with kinetic parameters: V(max)=840 mg2-CPgMLVSS(-1)d(-1), K(s)=24.61 mg L(-1), K(i)=315.02 mg L(-1). Abiotic losses of 2-CP due to volatilization and photo degradation by sunlight were less than 3% and the results of genotoxicity showed that the degradation products are eco-friendly.     

Optimization study of adsorption parameters for removal of fluoride using aluminium-impregnated potato plant ash by response surface methodology

High fluoride level is a major threat to drinking water availability in many countries worldwide. Therefore, knowledge of its removal, using the best technique with optimal efficiency, is needed. In the present study, aluminium-impregnated potato plant ash (Al-IPPA) was used for removal of fluoride from synthetic fluoride solution. The Al-IPPA has high specific area and strong affinity towards fluoride. Synthesized Al-IPPA was characterized by point of zero charge, Fourier Transform infrared, scanning electron micrograph and XRD (X-ray diffraction) studies. Adsorption kinetics indicated that the adsorption equilibrium was reached within 30 min and the adsorption process followed the pseudo second-order model better. The equilibrium data were analysed using Langmuir, Freundlich, D–R and Temkin isotherm models. The Langmuir and D–R isotherm models could fit the experimental data well. Thermodynamic parameters such as Gibbs free energy (?G°), enthalpy (?H°) and entropy (?S°) changes of sorption were also evaluated, which indicated that the adsorption process was spontaneous, feasible and endothermic in nature. Furthermore, the coexisting anions had significant effect on fluoride adsorption. Finally, process parameters were optimized using response surface methodology. The desirability study highlighted the optimized process parameters: initial concentration 94.02 mg/l; pH 4.64; adsorbent dose 2.8 g/l; and contact time 57.0 min. On the other hand, perturbation study revealed that the process parameters such as contact time and initial fluoride concentration are the dominating factors. The desorption study with Al-IPPA showed that nearly 99 % of fluoride could be leached out at pH 12. However, up to pH 8.5, there is no leaching of fluoride. The reusable properties of material supported the possibility of its commercial use.     

Techno-economic performance evaluation of a direct biomass-fired combined cycle plant employing air turbine

Techno-economic performance analysis of a biomass-fired combined cycle plant, employing a topping air turbine (AT) cycle and a bottoming steam turbine cycle, is reported in this paper. The net power output is 500 kWe, the AT producing 350 kWe and the ST producing the rest. Biomass (saw dust) is directly fired in a biomass combustor-heat exchanger (BCHX) duplex unit which supplies heat to the topping cycle. Influences of major plant parameters on the thermo-economic performance of the plant are analysed. Overall efficiency is found to maximise at topping cycle pressure ratio of 4. Higher TIT results in better energetic performance, while higher hot end temperature difference of the BCHX unit lowers the plant efficiency. Thermo-economic analysis reveals that the lowest unit cost of electricity (UCOE) of about 0.12 $/kWh could be achieved for the plant, while still giving an overall efficiency of about 48 %. Based on minimum UCOE, the payback period is estimated to be about 6 years with 50 % capital subsidy and about 13 years with no capital subsidy.     

Processing of PMMA nanocomposites containing biocompatible GO and TiO2 nanoparticles

The present study addresses the synthesis and characterization of polymethyl methacrylate (PMMA)/graphene oxide (GO) and PMMA/GO?+?TiO₂ nanocomposites for potential application as dental materials. PMMA/0.0025?wt% GO and PMMA/0.0025 wt%GO?+?1?wt% TiO₂ were processed using twin-screw extrusion including melt compounding. The mechanical, thermal, and microstructural behaviors of nanocomposites were determined and compared with pure PMMA. The results of this work revealed that PMMA nanocomposites are potential candidates as dental materials.     

Design of Dual-Band Bandpass Filters Using Stub-Loaded Open-Loop Resonators

In this paper, open-loop resonators loaded by shunt open stubs are proposed to design compact dual-band bandpass filters with improved out-of-band rejection characteristics. The second passband of the dual-band filter is obtained by tuning higher resonant modes of the open-loop resonator by the stub length and position. A tapped-line input/output feed structure is used for external coupling. Required external coupling is obtained by adjusting the tapping position and dimension of the stub-loaded resonator. A lossless transmission line model is used to determine the resonance properties of the resonator and the external quality factor. Theoretical predictions are verified by the experimental results of three dual-band filters.