Design and development of powder processed Fe–P based alloys

The present investigation deals with designing Fe, Fe–P binary and Fe–P–Si ternary alloys produced by an in-house developed powder metallurgical technique based on ‘Hot Powder Preform Forging’. Proper soaking of preforms at high temperature (1050 °C) eliminates iron-phosphide eutectic and brings entire phosphorus into solution in iron. Attempting hot forging thereafter completely eliminates hot as well as cold shortness and thereby helps to form these preforms (alloys) into very thin sheets of 0.5 mm. The use of costly hydrogen atmosphere during sintering has been eliminated by the addition of carbon as a reducing agent to form CO gas within the compact by reacting with oxygen of iron powder particles. The glassy ceramic coating applied over the compact serves as a protective coating to avoid atmospheric oxygen attack over the compact held at high temperature. These alloys so formed were subjected to density examination at various stages. Microstructural study has been carried out to estimate the grain size, volume percentage of porosity in the alloys, and uniform distribution of phosphorus and silicon in an iron matrix. X-ray diffraction studies of these alloys revealed the presence of only ferrite as product phase. Addition of alloying elements such as P and Si has improved the resistivity and magnetic properties of iron. Fe–0.07C–0.2O–0.3P–0.5Si alloy showed a resistivity as high as 31.7 μΩ cm. Coercivity values of the alloys ranged from 0.51 to 1.98 Oe. The total magnetic loss of Fe–0.07C–0.2O–0.3P–0.5Si alloy was the lowest (2.03 W/kg) amongst the alloys developed owing to its high resistivity combined with its low coercivity. These alloys which are drawn to thin sheets could find their possible application in the manufacturing of transformer cores.     

Studies on the Use of N,N,N´,N´-Tetra(2-ethylhexyl) Diglycolamide (TEHDGA) for Actinide Partitioning. I: Investigation on Third-Phase Formation and Extraction Behavior

Abstract

Diglycolamides have emerged as an interesting class of extractants for actinide partitioning from high-level waste (HLW). N,N,N´,N´-tetraoctyl diglycolamide (TODGA) has been extensively studied for lanthanide-actinide co-extraction behavior. The present work deals with a branched isomer of TODGA, that is, N,N,N´,N´-tetra(2-ethylhexyl) diglycolamide (TEHDGA). TEHDGA was studied for the extraction of ²⁴¹Am and third-phase formation. The effect of using different phase modifiers on the prevention of the formation of a third phase during nitric acid extraction by TEHDGA along with the acid uptake behavior by TEHDGA in the presence of the modifiers was studied. The modifiers used for this purpose were di(n-hexyl)octanamide (DHOA), isodecanol, and n-decanol. The effect of the modifiers on the uptake of ²⁴¹Am as a function of acid concentration and as a function of modifier concentration was also examined. DHOA was found to be a suitable modifier, in spite of its high acid uptake. The uptake of lanthanides Ce, La, Eu, Gd, and Nd and elements such as Fe, Ni, Mn, Mo, Ru, Sr, and Cs with DHOA-modified TEHDGA–n-dodecane solvent systems were investigated. The results obtained indicated that, while DHOA-modified TEHDGA/n-dodecane extracted lanthanides and actinides, it did not show any significant uptake of other elements. Thus, the TEHDGA-DHOA/n-dodecane solvent system can be used effectively for the partitioning of lanthanides and actinides from HLW.     

Prediction of water retention capacity of hydrolysed electrospun polyacrylonitrile fibers using statistical model and artificial neural network

Box Behnken design of experiment was used to study the effect of process variables such as alkali concentration, temperature and time on water retention capacity of the alkaline hydrolysed electrospun fibres. The hydrolysis of electrospun polyacrylonitrile fibres was carried out using sodium hydroxide with different processing conditions like concentration of alkali, temperature and time. With the increase in the concentration of alkali, time and temperature, the water retention capacity of membrane was found to increase in the membranes. Water retention capacities of the membranes were modeled and predicted using empirical as well as artificial neural network (ANN model). The fiber diameter and mean flow pore diameter of electrospun polyacrylonitrile fibers and hydrolyzed fibers shown in SEM images were 310 ± 50, 275 ± 75 nm, 0.9258 and 1.12 microns, respectively. The present study indicated that the nanofibrous membranes have potential for the water absorbing applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of high-energy heavy ion irradiation on the crystallization kinetics of Co-based metallic glasses

Differential scanning calorimeter (DSC) is employed to study the crystallization kinetics of irradiated (at three different fluences with high-energy heavy ion; Ni¹¹⁺ of 150 MeV) specimens of two Co-based metallic glasses. It is found that the crystallization process in both the glasses is completed in two phases. The DSC data have been analysed in terms of kinetic parameters viz. activation energy (E _c), Avrami exponent (n), dimensionality of growth (m), bdusing two different theoretical models. The results obtained have been compared with that of virgin samples. The lower activation energy in case of second crystallization occurring at higher temperature indicates the easier nucleation of second phase. The abnormally high value of Avrami exponent in Co-Ni glass indicates very high nucleation rate during first crystallization.     

Synthesis,characterisation and anti‐tumour activity of biopolymer based platinum nanoparticles and 5‐fluorouracil loaded platinum nanoparticles

A facile and green synthesis of platinum nanoparticles [gum kondagogu platinum nanoparticles (GKPtNP)] using biopolymer‐ gum kondagogu was developed. The formation of GKPtNP was confirmed by ultraviolet (UV)–visible spectroscopy, scanning electron microscopy–energy dispersive X‐ray spectroscopy, transmission electron microscopy, X‐ray diffraction, Zeta potential, Fourier transform infrared, inductively coupled plasma mass spectroscopy. The formed GKPtNP are well dispersed, homogeneous with a size of 2–4 ± 0.50 nm, having a negative zeta potential (−46.1 mV) indicating good stability. 5‐Fluorouracil (5FU) was loaded onto the synthesised GKPtNP, which leads to the development of a new combination of nanomedicine (5FU–GKPtNP). The in vitro drug release studies of 5FU–GKPtNP in pH 7.4 showed a sustained release profile over a period of 120 min. Agrobacterium tumefaciens induced in vitro potato tumour bioassay was employed for screening the anti‐tumour potentials of GKPtNP, 5FU, and 5FU–GKPtNP. The experimental results suggested a complete tumour inhibition by 5FU–GKPtNP at a lower concentration than the GKPtNP and 5FU. Furthermore, the mechanism of anti‐tumour activity was assessed by their interactions with DNA using agarose gel electrophoresis and UV‐spectroscopic analysis. The electrophoresis results revealed that the 5FU–GKPtNP totally diminishes DNA and the UV‐spectroscopic analysis showed a hyperchromic effect with red shift indicating intercalation type of binding with DNA. Over all, the present study revealed that the combined exposure of the nanoformulation resulted in the enhanced anti‐tumour effect. Inspec keywords: nanoparticles, transmission electron microscopy, biomedical materials, tumours, ultraviolet spectra, DNA, drugs, electrophoresis, polymers, platinum, pH, drug delivery systems, biochemistry, X‐ray chemical analysis, microorganisms, molecular biophysics, electrokinetic effects, X‐ray diffraction, scanning electron microscopy, cancer, nanofabrication, visible spectra, nanomedicine, Fourier transform infrared spectra, materials preparationOther keywords: 5FU–GKPtNP, 5‐fluorouracil loaded platinum nanoparticles, gum kondagogu platinum nanoparticles, antitumour activity, scanning electron microscopy‐energy dispersive X‐ray spectroscopy, biopolymer‐based platinum nanoparticles, biopolymer‐based platinum nanoparticles, ultraviolet‐visible spectroscopy, UV‐visible spectroscopy, transmission electron microscopy, X‐ray diffraction, zeta potential, Fourier transform infrared spectroscopy, inductively coupled plasma mass spectroscopy, nanomedicine, in vitro drug release studies, sustained release profile, Agrobacterium tumefaciens, in vitro potato tumour bioassay, tumour inhibition, tumour activity, agarose gel electrophoresis, UV‐spectroscopic analysis, DNA, time 120.0 min, Pt     

Optimisation of novel method for the extraction of steviosides from Stevia rebaudiana leaves

Stevioside, a diterpene glycoside, is well known for its intense sweetness and is used as a non-caloric sweetener. Its potential widespread use requires an easy and effective extraction method. Enzymatic extraction of stevioside from Stevia rebaudiana leaves with cellulase, pectinase and hemicellulase, using various parameters, such as concentration of enzyme, incubation time and temperature, was optimised. Hemicellulase was observed to give the highest stevioside yield (369.23 ± 0.11 μg) in 1 h in comparison to cellulase (359 ± 0.30 μg) and pectinases (333 ± 0.55 μg). Extraction from leaves under optimised conditions showed a remarkable increase in the yield (35 times) compared with a control experiment. The extraction conditions were further optimised using response surface methodology (RSM). A central composite design (CCD) was used for experimental design and analysis of the results to obtain optimal extraction conditions. Based on RSM analysis, temperature of 51-54 °C, time of 36-45 min and the cocktail of pectinase, cellulase and hemicellulase, set at 2% each, gave the best results. Under the optimised conditions, the experimental values were in close agreement with the prediction model and resulted in a three times yield enhancement of stevioside. The isolated stevioside was characterised through ¹H-NMR spectroscopy, by comparison with a stevioside standard.     

Poly (N-isopropylacrylamide) microgels for organic dye removal from water

The ability of poly (N-isopropylacrylamide) (pNIPAm), and pNIPAm-co-acrylic acid (pNIPAm-co-AAc) microgels to remove an organic azo dye molecule, 4-(2-Hydroxy-1-naphthylazo) benzenesulfonic acid sodium salt (Orange II) from aqueous solutions at both room and elevated temperature was assessed. At room temperature, we found that the amount of Orange II removed from water (removal efficiency) increased with increasing AAc and microgel concentration. The removal of Orange II from water was also fit by a Langmuir sorption isotherm model. Furthermore, we found the extent of Orange II removal depended on solution temperature; more Orange II was removed from water at elevated temperature and as the microgels were held at that temperature for longer durations of time. Additionally, by increasing the cycles between high and ambient temperature, the removal of Orange II was enhanced, although this was only true for two temperature cycles. We hypothesize that this is a result of the thermoresponsive nature of pNIPAm-based microgels which deswell at elevated temperature expelling their solvating water and when the microgels are cooled back down they reswell with the Orange II containing water. We also hypothesize that the microgels become saturated after the second heating cycle and so the efficiency of removal did not increase further. Finally, we assessed the ability of the microgels to retain the Orange II after it is removed from the aqueous solution. We determined that the microgels "leak" 25.6% of the Orange II that was originally removed from the water.     

Synthesis and characterization of dextrin‐grafted polypropylene

We carried out the graft copolymerization of the water‐soluble natural polymer dextrin onto preirradiated polypropylene (PP) in an aqueous medium using benzoyl peroxide (BPO) as the radical initiator. PP was irradiated by γ rays from a Co⁶⁰ source at a constant dose rate of 3.40 kGy/h to introduce hydroperoxide linkages, which served as the sites for grafting. The graft copolymerization was studied as a function of different reaction parameters, and the maximum percentage grafting (P_g; 55%) of dextrin onto PP was obtained at optimum conditions of [BPO] = 5.165 × 10⁻² mol/L, temperature = 60°C in 120 min with 15 mL of water. Different grafting parameters, such as the percentage apparent grafting, percentage grafting, and percentage true grafting have been evaluated. The graft copolymers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Swelling studies were carried out in pure, binary, ternary, and quaternary solvent systems composed of water, ethanol (EtOH), dimethyl sulfoxide (DMSO), and N,N‐dimethylformamide (DMF) at different ratios. The maximum swelling percentage PP‐g‐dextrin (both composite and true graft) was observed in pure DMSO and DMF followed by EtOH and water. Water‐retention studies of PP and PP‐g‐dextrin (both composite and true graft) were investigated at different time periods, temperatures, and pH values. The maximum percentage water retention of PP‐g‐dextrin (composite, 124%) was observed at 8 h and 50°C in a neutral medium (pH 7). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011