pp 291-295 June 2012
Interaction of proline with gold cluster was studied using density functional theory (DFT). Two types of mixed basis sets UB3LYP/6-311++G ∪ LANL2MB and UB3LYP/6-311++G ∪ LANL2DZ were used for optimization of complex structures. Proline interacts with gold cluster either through one anchor bond, N–Au or an anchor bond O–Au associated with a non-conventional O–H…Au hydrogen bond. Among these interactions, higher tendency for interaction is seen with Au cluster through amide terminal. Natural bond orbital analysis (NBO) is used to substantiate the results.
pp 297-303 June 2012
A novel nanocomposite comprising MWNTs and mixed-conducting polymeric components (electronic and ionic) is prepared, characterized and investigated as a support for platinum (Pt). Nanocomposite of MWNTs and poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT–PSS) is prepared by in situ polymerization and characterized using Fourier–Transform infrared spectroscopy (FT–IR), thermogravimetric analysis (TGA) in conjunction with scanning electron microscopy (SEM). Atomic force microscopy (AFM) studies are also carried out to characterize the surface topography of MWNTs/PEDOT–PSS nanocomposite. X-ray diffraction (XRD) studies reveal that MWNTs/PEDOT–PSS nanocomposite provides better backbone for the improved dispersion of Pt as evidenced by the reduced Pt crystallite size over MWNTs/PEDOT–PSS nanocomposite compared to MWNTs. Electrochemical characterization studies performed with Pt/nanocomposite and Pt/MWNTs demonstrate the superior catalytic activity of Pt/nanocomposite under reduced Nafion loadings in relation to Pt/MWNTs. It is observed that mixed conducting nanoporous network ofMWNTs/PEDOT–PSS composite structure promotes the catalytic activity of Pt by enhancing catalyst utilization.
pp 305-311 June 2012
This article reports effects of alignment of embedded carbon nanotubes in a polycarbonate polymer matrix under magnetic, direct and alternating current electric fields on the electrical properties of the resulting nanocomposites. Composites consisting of different quantities of carbon nanotubes in a polycarbonate matrix have been prepared using a solution casting technique. The effects of field strength and nanotube concentration on the resulted network structure and conductivity of the composites were studied by in situ optical microscopy, transmission electron microscopy and four-point probe technique. The results showed that the composites prepared in the presence of field had better conductivity than those of as-prepared composites. It was also concluded that the application of alternating current electric field and magnetic field in this system led to the formation of relatively continuing networks while direct current electric field only prevented agglomeration of the carbon nanotubes in the polycarbonate matrix and created relatively uniform distribution of nanotubes in the matrix.
pp 313-317 June 2012
We studied the self-heating effect during ion bombardment process on polycrystalline Al foils. An anisotropic surface morphology evolution has been observed. The adjacent peaks’ fusion along the direction perpendicular to the ion beam projection smoothen the surface. Fusion along the parallel direction has been suppressed due to Ar+ ion bombardment. It attributes to the result of the competition between the isotropic thermal effect, due to the self-heating effect by energy exchange between incident ions and Al surface, and the suppression by continuous ion bombardment with a certain incident angle. Varying the incident ion beam angle with the angular range 32° < 𝜃 < 82°, the ripple wave vector, 𝜆, is found to be parallel to the ion beam direction, whereas for 𝜃 > 82° , 𝜆 is perpendicular to the beam direction. The critical angle, 𝜃c, is close to 82°, which is different from Bradley and Harper’s prediction and attributes to the self-heating effect.
pp 319-326 June 2012
Clinical administration of paclitaxel is hindered due to its poor solubility, which necessitates the formulation of novel drug delivery systems to deliver such extreme hydrophobic drug. To formulate nanoparticles which makes suitable to deliver hydrophobic drugs effectively (intravenous) with desired pharmacokinetic profile for breast cancer treatment; in this context in vitro cytotoxic activity was evaluated using BT-549 cell line. PLGA nanoparticles were prepared by emulsion solvent evaporation technique and evaluated for physicochemical parameters, in vitro anti-tumor activity and in vivo pharmacokinetic studies in rats. Particle size obtained in optimized formulation was <200 nm. Encapsulation efficiency was higher at polymer-to-drug ratio of 20:1. In vitro drug release exhibited biphasic pattern with initial burst release followed by slow and continuous release (15 days). In vitro anti-tumor activity of optimized formulation inhibited cell growth for a period of 168 h against BT-549 cells. AUC(0−∞) and t1/2 were found to be higher for nanoparticles with low clearance rate.
pp 327-331 June 2012
ZnO nanocrystalline thin films have been prepared on glass substrates by sol–gel dip coating method. ZnO thin films have been coated at room temperature and at four different pH values of 4, 6, 8 and 10. The X-ray diffraction pattern showed that ZnO nanocrystalline thin films are of hexagonal structure and the grain size was found to be in the range of 25–45 nm. Scanning electron microscopic images show that the surface morphology improves with increase of pH values. TEM analysis reveals formation of ZnO nanocrystalline with an average grain size of 44 nm. The compositional analysis results show that Zn and O are present in the sample. Optical band studies show that the films are highly transparent and exhibit a direct bandgap. The bandgap has been found to lie in the range of 3.14–3.32 eV depending on pH suggesting the formation of ZnO nanocrystalline thin films.
pp 333-339 June 2012
A series of novel poly(amide–imide)/ZnO nanocomposites with modified ZnO nanoparticles contents was prepared by ultrasonic irradiation. For this purpose, surface of ZnO nanoparticle was modified with 𝛾-aminopropyltriethoxysilane as a coupling agent. Then the effect of surface modification on dispersion of nanoparticles, thermal stability and UV absorption property of the obtained nanocomposites were investigated. The resulting novel nanocomposites were characterized by several techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses of the nanocomposites were performed in order to study the dispersion of nanofillers in the polymer matrix. According to thermogravimetry analysis results, the addition of ZnO nanoparticles improved thermal stability of the obtained nanocomposites. Since the resulting nanocomposites contain phenylalanine amino acid and ZnO, they are expected to be biocompatible as well as biodegradable.
pp 341-345 June 2012
This paper presents the after shock heated structural and morphological studies of chromium film coated on hypersonic test model as a passive drag reduction element. The structural changes and the composition of phases of chromium due to shock heating (2850 K) are characterized using X-ray diffraction studies. Surface morphology changes of chromium coating have been studied using scanning electron microscopy (SEM) before and after shock heating. Significant amount of chromium ablation and sublimation from the model surface is noticed from SEM micrographs. Traces of randomly oriented chromium oxides formed along the coated surface confirm surface reaction of chromium with oxygen present behind the shock. Large traces of amorphous chromium oxide phases are also observed.
pp 347-352 June 2012
This paper reports morphological and relative humidity sensing behaviour of ZnO–TiO2 nanocomposite powder pellets obtained through solid-state reaction route. Resistance of the pellets is observed to decrease with increase in relative humidity in the 10–90% range. Sensing element with 15 wt%of TiO2 in ZnO shows best results with a sensitivity of 9.08 M𝛺/%RH in 10–90% relative humidity range. This sensing element manifests crystallite size of 71 nm as measured from XRD and average grain size of 207 nm calculated from SEM micrograph. This sensing element manifests low hysteresis, less effect of ageing and good reproducibility. Response and recovery times of this sensing element are measured to be 84 s and 396 s, respectively.
pp 353-356 June 2012
Pb(Zr0.53Ti0.47)O3 (PZT) thin films were prepared on Pt/Ti/SiO2/Si substrate by sol–gel method. The effect of film thickness on microstructure, ferroelectric and dielectric properties was investigated. The single-phase PZT films were obtained with different thicknesses. PZT films with a thickness of 190–440 nm had better dielectric and ferroelectric properties. The epoxy/PZT film/epoxy sandwiched composites were prepared. The thickness of PZT films influenced their damping properties of the composites, and the epoxy-based composites embedded with 310 nm-thick PZT films had the largest damping loss factor of 0.915.
pp 357-364 June 2012
Nanosecond lasers of different intensities were pulsed into sputter-deposited amorphous thin films of near equiatomic Ni/Ti composition to produce partially crystallized highly sensitive 𝑅-phase spots surrounded by amorphous regions. Scanning electron microscopy having secondary and back-scattered electrons, field emission scanning electron microscopy, optical microscopy and X-ray diffraction patterns were used to characterize the laser treated spots. Effect of nanosecond pulse lasering on microstructure, morphology, thermal diffusion and inclusion formation was investigated. Increasing beam intensity and laser pulse-number promoted amorphous to 𝑅-phase transition. Lowering duration of the pulse incidence reduced local film oxidation and film/substrate interference.
pp 365-368 June 2012
Diethyl germanium bis-picolinate, [Et2Ge(O2CC5H4N)2], and trimethyl germanium quinaldate, [Me3Ge(O2CC9H6N)], have been used as precursors for deposition of thin films of germanium by aerosol assisted chemical vapour deposition (AACVD). The thermogravimetric analysis revealed complete volatilization of complexes under nitrogen atmosphere. Germanium thin films were deposited on silicon wafers at 700°C employing AACVD method. These films on oxidation under an oxygen atmosphere at 600°C yield GeO2. Both Ge and GeO2 films were characterized by XRD, SEM and EDS measurements. Their electrical properties were assessed by current–voltage (𝐼–𝑉) characterization.
pp 369-376 June 2012
Vanadium oxides (V3O7.H2O and VO2) with different morphologies have been selectively synthesized by a facile hydrothermal approach using glucose as the reducing and structure-directing reagent. The as-obtained V3O7.H2O nanobelts have a length up to several tens of micrometers, width of about 60–150 nm and thickness of about 5–10 nm, while the as-prepared VO2(B) nanobelts have a length of about 1.0–2.7 𝜇m, width, 80–140 nm and thickness, 2–8 nm. It was found that the quantity of glucose, the reaction temperature and the reaction time had significant influence on the compositions and morphologies of final products. Vanadium oxides with different morphologies were easily synthesized by controlling the concentration of glucose. The formation mechanism was also briefly discussed, indicating that glucose played different roles in synthesizing various vanadium oxides. The phase transition from VO2(B) to VO2(M) were investigated and the phase transition temperature of the VO2(M) appeared at around 68 °C. Furthermore, the electrochemical properties of V3O7.H2O nanobelts, VO2(B) nanobelts and VO2(B) nanosheets were investigated and they exhibited a high initial discharge capacity of 296, 247 and 227 mAh/g, respectively.
pp 377-382 June 2012
Mn-doped ZnO nanoparticles were synthesized by reverse micellar method using Tergitol NP9 as a surfactant for the first time. These nanoparticles were characterized using powder X-ray diffraction, transmission electron microscopy and selected area electron diffraction analysis. Structural analysis and optical studies revealed that manganese is incorporated into the ZnO host lattice forming a solid solution. Transmission electron microscopic studies show that the particle size increases from 20–50 nm on increasing the dopant concentration from 0.05–0.15. The specific surface area of Zn1−𝑥Mn𝑥O (𝑥 = 0.05, 0.10 and 0.15) as calculated using BET method was found to be 202.62, 145.78 and 75.66 m2g-1, respectively which are higher than the reported values so far.
pp 383-386 June 2012
In this article we report the study of mixed mobile ion effect (MMIE) in boroarsenate glasses. DSC and a.c. electrical conductivity studies have been carried out for 𝑥MgO–(25−𝑥)Li2O–50B2O3–25As2O3 glasses. It is observed that strength of MMIE in a.c. conductivity is less pronounced with increase in temperature and frequency. The results were explained on the basis of structural model (SM) proposed by Swenson and his co-workers supporting molecular dynamic results.
pp 387-394 June 2012
Various fluxing materials are added to technical ceramics in an attempt to lower their sintering temperatures and make their processing economical. The effect of 0.3wt%Li2CO3 addition on the phase, microstructure, phase transition temperatures and dielectric properties of BaTiO3 was investigated in the present study. The addition of 0.3wt% Li2CO3 was observed to lower the optimum sintering temperature by ∼200°C with no second phase formation and cause a five-fold reduction in grain size. Rhombohedral-to-orthorhombic and tetragonal-to-cubic phase transitions at the expected temperatures were evident from the Raman spectra, but the orthorhombic-totetragonal phase transition was not clearly discernible. The persistence of various phase(s) at higher temperatures in the flux-added materials indicated that the phase transitions occurred relatively slowly. A decrease in dielectric constant of Li2O-added BaTiO3 in comparison to pure BaTiO3 may be due to the diminished dielectric polarizability of Li+ in comparison to Ba2+.
pp 395-398 June 2012
In this research, an algorithm based on the 𝑄-state Potts model is presented for modeling the austenite to ferrite transformation. In the algorithm, it is possible to exactly track boundary migration of the phase formed during transformation. In the algorithm, effects of changes in chemical free energy, strain free energy and interfacial energies of austenite–austenite, ferrite–ferrite and austenite–ferrite during transformation are considered. From the algorithm, the kinetics of transformation and mean ferrite grain size for different cooling rates are calculated. It is found that there is a good agreement between the calculated and experimental results.
pp 399-404 June 2012
TiC/TiN+TiCN reinforced composite coatings were fabricated on Ti–6Al–4V alloy by laser cladding, which improved surface performance of the substrate. Nano-CeO2 was able to suppress crystallization and growth of the crystals in the laser-cladded coating to a certain extent.With the addition of proper content of nano-CeO2, this coating exhibited fine microstructure. In this study, the Al3Ti+TiC/TiN+nano-CeO2 laser-cladded coatings were studied by means of X-ray diffraction and scanning electron microscope. The X-ray diffraction results indicated that the Al3Ti+TiC/TiN+nano-CeO2 laser-cladded coating consisted of Ti3Al, TiC, TiN, Ti2Al20Ce, TiC0.3N0.7, Ce(CN)3 and CeO2, this phase constituent was beneficial to increase the microhardness and wear resistance of Ti–6Al–6V alloy.
pp 405-414 June 2012
In this article, we report on the results obtained for the efforts we made to bring processability to the conducting polyaniline and substituted polyanilines by designing and synthesizing a new disulphonic acid with a biphenyl moiety as spacer group, viz. 4,4'-biphenyldisulphonic acid (BPSA). When doped, the disulphonic acid acts as a spacer group between the polyaniline chains and facilitates increase in solubility and conductivity. The spacing effect is maximized when BPSA is used as doping agent in in situ polymerization reactions. The conductivity of polyaniline doped by BPSA is 4 S/cm and for the substituted polyanilines it ranged from 2 × 10-5 to 8 × 10-4 S/cm.
pp 415-418 June 2012
Copolymer of starch grafted with lactic acid (LA) could be directly prepared by reaction of cornstarch with lactic acid and with sodium hydroxide (NaOH) as the catalyst. The structure of starch/LA copolymer was characterized by IR, XRD, SEM and 1H-NMR. The effects of NaOH concentration, ratios of starch and LA, reaction temperature and reaction time on the grafting degree were also investigated and the results showed that the highest grafting degree of starch could reach 33.60% when the graft copolymerization was carried out in 0.40 mol l-1 NaOH aqueous solution for 9 h at 90°C with 1: 6 ratio of starch and lactic acid.
pp 419-424 June 2012
Novel solid acid based on carbon/silica composites are synthesized through one-pot hydrothermal carbonization of hydroxyethylsulfonic acid, sucrose and tetraethyl orthosilicate (TEOS). The novel solid acid owned the acidity of 2.0 mmol/g, much higher than that of the traditional solid acids such as Nafion and Amberlyst-15 (0.8 mmol/g). The catalytic activities of the solid acid are investigated through acetalization. The results showed that the novel solid acid was very efficient for the reactions. The high acidity and catalytic activities made the novel carbon/silica composites based solid acid hold great potential for the green chemical processes.
pp 425-431 June 2012
Polycrystalline thermistor ceramics with the stoichiometric formula, Sr𝑥Ba1−𝑥Fe0.6Sn0.4O3−𝜀 (0.2 ≤ 𝑥 ≤ 0.8), had been prepared by a standard solid state reaction route. X-ray diffraction analysis indicates that the ceramic system remains cubic perovskite structure with a very small lattice change. The electrical properties of Sr𝑥Ba1−𝑥Fe0.6Sn0.4O3−𝜀 thermistors were studied using a digital thermometer over a wide range of 298–400 K. The thermistors showed an excellent negative temperature coefficient (NTC) thermistor behaviour. The values of resistivity at 298 K (ρ982), thermistor constant (𝐵298/358) and activation energy (𝐸a) of the Sr𝑥Ba1−𝑥Fe0.6Sn0.4O3−𝜀 thermistors, decreasing with the increase of Sr content, were in the range of 0.37–11.0 k𝛺.cm, 2466–3703 K and 0.212–0.319 eV, respectively. For the thermistors with the compositions 𝑥 = 0.2 and 0.4, the fitting equivalent circuit was composed of three RCPE elements corresponding to grain, grain boundary and ceramic–electrode interface, respectively. From the impedance plots, it was found that the fitting data showed good agreement with the experimental data. The extracted grain boundary resistance exhibited a NTC thermistor behaviour.
pp 433-438 June 2012
The effect of Co+2 doping on Cu+2 and Ti+4 sites in calcium copper titanate, CaCu3Ti4O12, has been examined. The doped compositions, CaCu3−𝑥Co𝑥Ti4O12 and CaCu3Ti4−𝑥Co𝑥O12 (𝑥 = 0.10) ceramics, were prepared by novel semi-wet route. In this method, calcium, copper and cobalt salts were taken in solution form and TiO2 was used in solid form. XRD analysis confirmed the formation of single-phase materials. Structure of CaCu3Ti4O12 does not change on doping with cobalt either on Cu-site or Ti-site and it remains cubic. Scanning electron micrographs (SEM) show average grain size of CaCu2.9Co0.1Ti4O12 to be larger than CaCu3Ti3.9Co0.1O12 ceramic. Energy dispersive X-ray spectroscopy (EDX) studies confined the purity of parent and Co-doped CaCu3Ti4O12 ceramics. Dielectric constant (𝜀r) and dielectric loss (tan 𝛿) of CaCu2.9Co0.1Ti4O12 is comparatively higher than that of CaCu3Ti3.9Co0.1O12 ceramic at all measured frequencies and temperatures.
pp 439-447 June 2012
Mechanical alloying (MA) was used to produce Ti5Si3 intermetallic compound with nanocrystalline structure from elemental powders. The structural changes and characterization of powder particles during milling were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and microhardness measurements. MA resulted in gradual formation of disordered Ti5Si3 intermetallic compound with crystallite size of about 15 nm after 45 h of milling. Also a thermodynamic analysis of the process was carried out using Miedema model. The results showed that in the nominal composition of Ti5Si3 intermetallic phase (𝑋Si = 0.375), formation of an intermetallic compound has the lowest Gibbs free energy rather than solid solution or amorphous phases. So the MA product is the most stable phase in nominal composition of Ti5Si3. This intermetallic compound exhibits high microhardness value of about 1235 HV.
pp 449-451 June 2012
Yttrium barium copper oxide (YBCO) coated conductors are widely used in the conduction-cooled superconducting magnets with rapid development in refrigeration technologies at present. `Quench’ is a state that refers to the irreversible and uncontrolled superconductor to resistive transitions in the superconductor. The propagation of ‘quench’ or `normal zone’ has different characteristics in these high temperature superconductors (HTS) compared to low temperature superconductors. The superconductor to normal index, known as `𝑛’ is much flatter in HTS. The hot spot emerging in local region due to quench and non-uniform critical current may cause permanent damage to whole HTS tape and hence the magnet winding pack. Thus it is necessary to determine the temperature profile along the length of HTS tape under a given energy (joule heating) such that propagation of the hot spot developed locally can be prevented early. In this study, a one dimensional, time dependent heat diffusion equation with appropriate boundary conditions are used to describe the consequences of the normal zone propagation resulting in the temperature diffusion in a HTS tape. The results demonstrate the necessity of adequate cooling of the edges of the flat HTS tapes to prevent irreversible normal zone transitions.
pp 453-457 June 2012
The lyoluminescence (LL) in 𝛾-ray irradiated (KNa)Br : Ce3+ phosphors are reported in this paper. LL of (KNa)Br : Ce3+ have been recorded for different 𝛾-ray doses. The nature of variations of LL peak intensities is found to be linear with 𝛾-ray irradiation dose and LL peak intensity is found to be dependent on concentrations (0.1–10 mol%) of added Ce3+ ions in the (KNa)Br host lattice. Negligible fading in the prepared sample is observed.
pp 459-469 June 2012
The corrosion inhibition effect of two quinoline derivatives, viz. 2-chloro quinoline 3-carbaldehyde (CQC) and (2-chloro-quinoline-3ylmethyl)-𝑝-tolyl-amine (CQA) have been investigated against mild steel (MS) in 1N HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization and electrochemical impedance spectroscopy. The losses in weights of MS samples have proved that both CQC and CQA are efficient inhibitors of corrosion. The mixed mode of inhibition was confirmed by electrochemical polarizations. The results of electrochemical impedance spectroscopy have showed changes in the impedance parameters like charge transfer resistance and double-layer capacitance that confirmed strong adsorption of inhibitors on the MS surface. The inhibition action of these compounds was assumed to occur via adsorption on the steel surface through the active centres contained in the molecules. Furthermore, quantum chemical calculations have been performed at B3LYP/6-31G(𝑑 , 𝑝) level to complement the experimental evidence.
pp 471-480 June 2012
LiNd𝑥Mn2−𝑥O4 samples are synthesized via co-precipitation technique. The activation energies computed from thermogravimetric analyses on the basis of Ozawa method have been observed to linearly increase with increase in dopant concentration. X-ray diffraction analyses indicate the cubic–spinel structure for all the samples. The lattice parameter has been observed to decrease with increasing concentration of Nd3+ doping. The octahedral site preference of neodymium dopant in the LiMn2O4 structure has been elucidated using XRD and FT–IR studies. The porosity and surface roughness obtained from SEM analysis have been observed to decrease with increase in Nd3+ dopant concentration in LiMn2O4 lattice. The electrochemical performances of the electrodes were analysed through cyclic voltammetry, chronopotentiometry and electrochemical impedance techniques. The specific capacity has been observed to decrease initially with increase in Nd3+ dopant concentration, whereas the capacity retention has increased with increase in dopant concentration. The observed percentage capacity retention after 50 cycles of the electrodes LiNd0.05Mn1.95O4, LiNd0.10Mn1.90O4 and LiNd0.15Mn1.85O4 were 88.4%, 97.1% and 96.8%, respectively. The Li ion diffusion coefficient ascertained using electrochemical impedance spectroscopy was found to be higher for LiNd0.10Mn1.90O4 around 3.74 × 10-12 cm2 s-1.
pp 481-487 June 2012
The present work deals with the study of estradiol permeation in chitosan membranes. A fractional factorial design was built for the determination of the main factors affecting estradiol permeation. The independent factors analysed were: concentration of chitosan, concentration of cross-linking agent, cross-linking time and thermal treatment. It was found that concentration of chitosan and cross-linking time significantly affected the response. The effects of thermal treatment and concentration of cross-linking agent were not significant. An optimization process based on response surface methodology was carried out in order to develop a statistical model which describes the relationship between active independent variables and estradiol flux. This model can be used to find out a combination of factor levels during response optimization. Possible options for response optimization are to maximize, minimize or move towards a target value.
Volume 42 | Issue 5
Click here for Editorial Note on CAP Mode