pp 183-188 April 2013
In this paper, we present inorganic–organic hybrid coatings with polymer matrix (water soluble) that contain silver nanoparticles (AgNPs). The structure and morphology of coating materials were determined by infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Therefore, the antimicrobial activities and mechanisms of coatings for several pathogenic bacteria (Bacilius cereus and Staphylococcus aureus) were investigated. It was demonstrated that the obtained material with silver nanoparticles keep their antimicrobial effect even if they are subjected to several cycles of washing with water and detergent.
pp 189-191 April 2013
The effects of chirality and the intercalation of transitional metal atoms inside single walled BN nanotubes on structural, energetic and electronic properties have been considered in this paper. The thermodynamic stability of BN nanotubes can be improved by the intercalation of cobalt or nickel. BN nanotubes can behave like an ideal non-interacting hosts for these one-dimensional chains of metal atoms. Their electronic properties are insignificantly modified.
pp 193-202 April 2013
Diamond-like nanocomposite (DLN) coatings have been deposited over different substrates used for biomedical applications by plasma-enhanced chemical vapour deposition (PECVD). DLN has an interconnecting network of amorphous hydrogenated carbon and quartz-like oxygenated silicon. Raman spectroscopy, Fourier transform–infra red (FT–IR) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) have been used for structural characterization. Typical DLN growth rate is about 1 𝜇m/h, measured by stylus profilometer. Due to the presence of quartz-like Si:O in the structure, it is found to have very good adhesive property with all the substrates. The adhesion strength found to be as high as 0.6 N on SS 316 L steel substrates by scratch testing method. The Young’s modulus and hardness have found to be 132 GPa and 14.4 GPa, respectively. DLN coatings have wear factor in the order of 1 × 10-7 mm3/N-m. This coating has found to be compatible with all important biomedical substrate materials and has successfully been deposited over Co–Cr alloy based knee implant of complex shape.
pp 203-212 April 2013
Deliberately inorganic nanoparticles (NP)s in polymer matrices significantly affect their characteristics and therefore their applications, but key factor to achieve the expected efficiency is well dispersion of the NPs in polymer matrix. The work presented here deals with the polymerization of amino acid-based monomer to synthesize optically active poly(ester-imide) (PEI) with hydroxyl terminated groups, using tosyl chloride/pyridine/𝑁,𝑁-dimethylformamide system as a condensing agent. The synthesized polymer was used for the preparation of bionanocomposite (BNC) containing modified titanium dioxide (TiO2) NPs using ultrasonic irradiation. With the aim of 𝛾-amidopropyl-triethoxylsilicane as a coupling agent, the surface of nanoscale TiO2 was modified to decrease aggregation of the NPs in polymer matrix. The obtained PEI/TiO2 BNCs were characterized with fourier transfer infrared (FT–IR), thermogravimetric analysis, field emission scanning electron microscopy (FE–SEM), X-ray diffraction and transmission electron microscopy (TEM) techniques. Morphology study of resulting PEI/TiO2 BNCs by FE–SEM and TEM analyses demonstrated that the hydroxyl-terminated polymer chains reduced aggregation of the NPs and thus lead to better dispersion of the NPs in the polymer matrix.
pp 213-216 April 2013
A mass of hollow carbon nanospheres (HCNSs) was fabricated by chemical vapour deposition of methane over Ni/Al2O3 catalyst at 600 °C. The products were characterized with high-resolution transmission electron microscope images, and the results showed that the external diameter of the HCNSs was 5–90nm and the thickness of wall was about 10 nm. Microwave absorption of HCNSs/paraffin composites was mainly attributed to dielectric loss. The microwave-absorbing peaks of composites containing HCNSs shifts to low frequencies, and the bandwidth below −10 dB and minimum RL decrease with increasing thickness of HCNSs/paraffin composites.
pp 217-221 April 2013
A modified new method of CVD for formation of pure layers of tin oxide films was developed. This method is very simple and inexpensive and produces films with good electrical properties. The effect of substrate temperature on the sheet resistance, resistivity, mobility, carrier concentration and transparency of the films has been studied. The best sheet resistance obtained at substrate temperature of 500 ◦C was about 27 𝛺/cm2. X-ray diffraction showed that the structure of deposited films was polycrystalline with a grain size between 150–300 Å. The preferred orientation was (211) for films deposited at substrate temperature of about 500 °C. FESEM micrographs revealed that substrate temperature is an important factor for increasing grain size and modifies electrical parameters. UV-visible measurement showed reduction of transparency and bandgap of the layers with increasing substrate temperature.
pp 223-229 April 2013
In this study, pure and manganese-doped zinc oxide (Mn:ZnO) thin films were deposited on quartz substrate following successive ion layer adsorption and reaction (SILAR) technique. The film growth rate was found to increase linearly with number of dipping cycle. Characterization techniques of XRD, SEM with EDX and UV–visible spectra measurement were done to investigate the effect of Mn doping on the structural and optical properties of Mn:ZnO thin films. Structural characterization by X-ray diffraction reveals that polycrystalline nature of the films increases with increasing manganese incorporation. Particle size evaluated using X-ray line broadening analysis shows decreasing trend with increasing manganese impurification. The average particle size for pure ZnO is 29.71nm and it reduces to 23.76nm for 5%Mn-doped ZnO. The strong preferred c-axis orientation is lost due to manganese (Mn) doping. The degree of polycrystallinity increases and the average microstrain in the films decreases with increasing Mn incorporation. Incorporation of Mn was confirmed from elemental analysis using EDX. As the Mn doping concentration increases the optical bandgap of the films decreases for the range of Mn doping reported here. The value of fundamental absorption edge is 3.22 eV for pure ZnO and it decreases to 3.06 eV for 5%Mn:ZnO.
pp 231-237 April 2013
Thin metallic films of Zn and In/Zn were deposited onto glass substrates by thermal evaporation under vacuum. The metallic films were submitted to a thermal oxidation in air, at 623 K, for different oxidation times (30–90 min), in order to be oxidized. Structural andmorphological analyses (X-ray diffraction, transmission electron microscopy and scanning electron microscopy) revealed that the obtained undoped and In-doped ZnO thin films possess a polycrystalline structure. Transmission spectra were recorded in spectral domain from 280 to 1400 nm. The influence of In doping and oxidation parameters as well, on the optical parameters (transmittance, optical bandgap, Urbach energy) were analysed. It was clearly evidenced that by In doping, the optical properties of ZnO films were improved. The temperature dependence of electrical conductivity was studied using surface-type cells with Ag electrodes. The obtained results indicate that In-doped ZnO films exhibit an enhancement of electrical conductivity with few orders of magnitude when compared with non-doped ones.
pp 239-244 April 2013
Porous 𝛼-Co(OH)2 nanoflake array film is prepared by a facile hydrothermal synthesis method. The 𝛼-Co(OH)2 nanoflake array film exhibits a highly porous net-like structure composed of interconnected nanoflakes with a thickness of 15 nm. The pseudo-capacitive behaviour of the Co(OH)2 nanoflake array film is investigated by cyclic voltammograms (CV) and galvanostatic charge–discharge tests in 2MKOH. The 𝛼-Co(OH)2 nanoflake array film exhibits high capacitances of 1017 F g-1 at 2Ag-1 and 890 F g-1 at 40Ag-1 as well as rather good cycling stability for supercapacitor application. The porous architecture is responsible for the enhancement of the electrochemical properties because it provides fast ion and electron transfer, large reaction surface area and good strain accommodation.
pp 245-249 April 2013
The aim of this paper is to study the influence of curing time on the microstructure and mechanical strength development of alkali activated binders based on vitreous calcium aluminosilicate (VCAS). Mechanical strength of alkali activated mortars cured at 65 °C was assessed for different curing times (4–168 h) using 10 molal NaOH solution as alkaline activator. Compressive strength values around 77MPa after three days of curing at 65 °C were obtained. 1.68MPa/h compressive strength gain rate was observed in the first 12 h, decreasing to 0.95MPa/h for the period of 12–72 h. The progress of geopolymeric reaction was monitored by means of TGA and, electrical conductivity and pH measurements in an aqueous suspension. Significant decrease in pH and electrical conductivity were observed in the 4–72 h period, demonstrating the geopolymerization process. Furthermore, SEM images showed an important amount of (N, C)ASH gel and low porosity of the developed matrix.
pp 251-258 April 2013
In this work, we present a new approach to derive the capacitance–voltage characteristic for an abrupt homojunction with uniform doping (𝑁A in 𝑝-region and 𝑁D in 𝑛-region) under forward and reverse polarization. Under thermal equilibrium conditions, we show that it is possible to obtain analytically the exact capacitance–voltage characteristic without any simulation for the symmetric case (𝑁A = 𝑁D). We also propose a model of the total capacitance under forward and reverse polarization for the asymmetric case (𝑁A ≠ 𝑁D).
pp 259-263 April 2013
In this work, cerium oxide thin films were prepared using cerium chloride heptahydrate, ethanol and citric acid as an additive by sol–gel spin-coating technique and further characterized to study the various properties. Chemical composition of deposited films has been analysed by FTIR which shows existence of CeO2. The samples have been optically characterized using ellipsometry to find refractive index of 2.18 and physical thickness which is measured to be 5.56 nm. MOS capacitors were fabricated by depositing aluminum (Al) metal using the thermal evaporation technique on the top of CeO2 thin films. Capacitance–voltage measurement was carried out to calculate the dielectric constant, flat-band voltage shift of 18.92, 0.3–0.5V, respectively and conductance–voltage study was carried out to determine the Dit of 1.40 × 1013 eV-1 cm-2 at 1MHz.
pp 265-270 April 2013
To improve the piezoelectric properties of Bi0.5Na0.5TiO3-based ceramics, a new perovskite-type leadfree piezoelectric (1 – 𝑥 – 𝑦)Bi0.5Na0.5TiO3−𝑥Bi0.5K0.5TiO3−𝑦BiMnO3 system has been fabricated by a conventional solid–state reaction method and their microstructure, dielectric and piezoelectric properties have been investigated. The results of X-ray diffraction (XRD) analysis reveal that the addition of small amounts of BiMnO3 did not cause a remarkable change in crystal structure, but resulted in an evident evolution inmicrostructure. An obvious secondary phase was observed in samples with high Bi0.5K0.5TiO3 content. It is found from dielectric constant curves that low-temperature hump disappeared with increasing y and it appeared again with increasing x. The piezoelectric properties significantly increase with increasing Bi0.5K0.5TiO3 and BiMnO3 content. The piezoelectric constant and electromechanical coupling factor attain maximum values of 𝑑33 = 182 pC/N at 𝑥 = 0.21(𝑦 = 0.01) and 𝑘p = 0.333 at 𝑥 = 0.18 (𝑦 = 0.01), respectively.
pp 271-276 April 2013
𝑝-Carboxyphenoxymethyl polysulfone (CPMPSF) was synthesized in two steps:
chloromethylation of polysulfone (PSF) by in situ generated chloromethyl radical in presence of stannic chloride in tetrachloroethane and
reaction of chloromethylated PSF with 𝑝-hydroxybenzoic acid in presence of potassium carbonate in dimethylformamide.
The structures of the modified PSFs were confirmed by elemental analysis, IR, 1H–NMR and 13C–NMR techniques. The PSF and CPMPSF based ultrafiltration membranes were prepared according to phase–inversion process using water as nonsolvent at 4° and 15 °C, employing casting dope having different amounts of polymer (PSF or CPMPSF), polyvinylpyrrolidone (PVP) and solvent, dimethylformamide (DMF). The membranes were characterized for their pore size, pure water flux and flux and rejection for the permeation of different molecular weight poly(ethylene glycol) (PEG) solutions and sodium chloride (NaCl) solution. The pore radius of the CPMPSF membrane which was prepared without PVP in the casting dope was about 222 Å, whereas, that of the membrane prepared in the presence of PVP (6wt%) in the casting dope was about 124 Å. For the PSF membranes, pore radii were 80 Å (without PVP) and 176 Å (with PVP 6 wt%). The CPMPSF-based membranes exhibited higher flux and rejections for PEG and NaCl solutions, as compared to the PSF membranes, due to the presence of hydrophilic carboxylic acid group. The CPMPSF membrane exhibited about 48% rejection of NaCl when tested for 5000 ppm feed solution at 400 psi.
pp 277-286 April 2013
Saturated polyester resin, derived from the glycolysis of polyethyleneterephthalate (PET) was examined as an effective way for PET recycling. The glycolyzed PET (GPET) was reacted with the mixture of phthalic anhydride and ethylene glycol (EG) with varied compositions and their reaction kinetic were studied. During polyesterification of GPET, acid and EG, the parameters like degree of polymerization (DP𝑛), extent of reaction (𝑝) acid value and hydroxyl values were measured. The thermomechanical properties and the morphologies of the saturated polyester nanocomposites were examined by using a differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle X-ray diffraction (WAXRD) and transmission electron spectroscopy (TEM). There were significant differences observed in 𝑇g, 𝑇m and 𝑇c before and after addition of GPET and clay content. Nanocomposites with lower content of organoclay showed intercalated morphology while by increasing the amount of organoclay, the exfoliated morphology was more prevalent. Water vapour transmission (WVT) was determined for saturated polyester nanocomposite sheets according to ASTM E96-80.
pp 287-291 April 2013
Experiments involving single step hydrothermal reactions of the divalent metal (Zn2+, Cd2+, Pb2+, Cu2+, Ni2+ and Mn2+) salts with ilmenite NaSbO3 yielded pure divalent antimonates in the case of CdSb2O6 crystallizing in the PbSb2O6 type structure and ZnSb2O6 crystallizing in the trirutile structure type. In the case of Pb2+, Cu2+, Ni2+ and Mn2+ divalent cations, phase pure product could not be obtained. The obtained powders were characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and UVvisible diffuse reflectance spectroscopy. The oxide powders obtained possessed lower crystallite size as compared to their solid-state synthesized counterparts. This was evident from the broadening of the powder X-ray diffraction peaks. The antimonates were photocatalytically active for the decomposition of methylene blue (MB) dye under UV light irradiation.
pp 293-299 April 2013
Using multi-walled carbon nanotube (CNT) as an one-dimensional support, we have succeeded in uniformly anchoring of TiO2 and Fe nanoparticles at its surface. The as-prepared Fe–CNT/TiO2 composite photocatalysts have been investigated by degrading methylene blue (MB) under UV and differently intensified visible light irradiation. The ability of CNT to store and shuttle electrons, and Fe nanoparticles demonstrate its capability to serve as a yield and transfer electrons on demand to separate h+/e- pairs. Moreover, the MB photodegradation increase with an increase of visible light intensity can be ascribed to the enhancement MB cationic radical. In addition, chemical oxygen demand (COD) of piggery waste and reduction efficiency of Cr (IV) was done at regular intervals, which gave a good idea about mineralization of wastewater.
pp 301-309 April 2013
DTA and TGA curves of titanium hydride powder were determined in air at different heating rates. Also the thermal decomposition behaviour of the aforementioned powder at high heating rates was taken into consideration. A great breakthrough of the practical interest in the research was the depiction of the 𝑃H2-time curves of TiH2 powder at various temperatures in air. In accordance with the results, an increase in heating rate to higher degrees does not change the process of releasing hydrogen from titanium hydride powder, while switching it from internal diffusion to chemical reaction. At temperatures lower than 600 °C, following the diffusion of hydrogen and oxygen atoms in titanium lattice, thin layers TiH𝑥 phase and oxides form on the powder surface, controlling the process. On the contrary, from 700 °C later on, the process is controlled by oxidation of titanium hydride powder. In fact, the powder oxidation starts around 650 °C and may escalate following an increase in the heating rate too.
pp 311-317 April 2013
Asphaltenes separated from two different crude oils from upper Assam, India, having different geological origins, viz. DK(eocene) and JN (oligocene–miocene) were pyrolysed at 600 °C and the products were analysed by gas chromatography–mass spectrometry (GC/MS) especially for the generated alkylnaphthalenes and alkylphenanthrenes. Both the asphaltenes produce aliphatic as well as aromatic compound classes. Alkylnaphthalenes and alkylphenanthrenes were identified by using reference chromatograms and literature data and the distributions used to assess thermalmaturity of the asphaltenes. The ratios of 𝛽-substituted to 𝛼-substituted isomers of both alkylnaphthalenes and alkylphenanthrenes revealed higher maturity of the JN asphaltenes than the DK asphaltenes. For both the asphaltenes, the abundance of 1-methylphenanthrene dominates over that of 9-methylphenanthrene showing the terrestrial nature of the organic matter.
pp 319-328 April 2013
The compressive behaviour of a new class of sandwich composite made up of jute fiber reinforced epoxy skins and piece-wise linear fly ash reinforced functionally graded (FG) rubber core is investigated in flat-wise mode. FG samples are prepared using conventional casting technique. Presence of gradation is quantified physically by weight method. This paper addresses the effect of weight fraction of fly ash, core to thickness ratio (C/H) and orientation of jute on specific compressive modulus and strength. In each trial five replicates are tested with lower amount of fly ash below the upper skin of sandwich (rubber-up). Results of experimentation are subjected to statistical analysis of variance (ANOVA) to find the influential factor governing the compressive behaviour. Furthermore piece-wise linear gradation is modeled in finite element and strength values are compared with experimental results. Sandwich sample with fly ash content of 40%, C/H of 0.4 and orientations of 30°/60° registered better performance. Specific strength is observed to increase upto 30% filler content followed by stabilization. Finite element results for strength match very well with experimental ones.
pp 329-332 April 2013
The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ∼8 𝜇g mg-1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups.
pp 333-339 April 2013
Lithium ion conducting polymer blend electrolyte films based on poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) with different Mwt% of lithium nitrate (LiNO3) salt, using a solution cast technique, have been prepared. The polymer blend electrolyte has been characterized by XRD, FTIR, DSC and impedance analyses. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR study confirms the complex formation between the polymer and salt. The shifts in 𝑇g values of 70 PVA–30 PVP blend and 70 PVA–30 PVP with different Mwt% of LiNO3 electrolytes shown by DSC thermograms indicate an interaction between the polymer and the salt. The dependence of 𝑇g and conductivity upon salt concentration has been discussed. The ion conductivity of the prepared polymer electrolyte has been found by a.c. impedance spectroscopic analysis. The PVA–PVP blend system with a composition of 70 wt% PVA: 30 wt% PVP exhibits the highest conductivity of 1.58 × 10-6 Scm-1 at room temperature. Polymer samples of 70 wt% PVA–30 wt% PVP blend with different molecular weight percentage of lithium nitrate with DMSO as solvent have been prepared and studied. High conductivity of 6.828 × 10-4 Scm-1 has been observed for the composition of 70 PVA:30 PVP:25 Mwt% of LiNO3 with low activation energy 0.2673 eV. The conductivity is found to increase with increase in temperature. The temperature dependent conductivity of the polymer electrolyte follows the Arrhenius relationship which shows hopping of ions in the polymer matrix. The relaxation parameters (𝜔) and (𝜏) of the complexes have been calculated by using loss tangent spectra. The mechanical properties of polymer blend electrolyte such as tensile strength, elongation and degree of swelling have been measured and the results are presented.
pp 341-344 April 2013
Sliding wear performance of 20% mica-filled polyamide 6 (PA6 + 20% mica) and 20% short glass fibrereinforced polysulphone (PSU + 20 GFR) polymer composites used in electrical applications were investigated using a pin-on-disc wear test apparatus. Two different disc materials were used in this study. These are AISI 316 L stainless steel and 30% glass fibre-reinforced polyphenylenesulphide (PPS + 30%GFR) polymer composite. Wear test was carried out at 10, 20 and 30 N applied load values and 0.5 m/s sliding speed and at ambient temperature and humidity. Different combinations of rubbing surfaces were examined and friction coefficient and specific wear rate values were obtained and compared. For two material combinations used in this investigation, the coefficient of friction shows insignificant sensitivity to applied load values and large sensitivity to material combinations. For specific wear rate, PA6 + 20% mica composite has shown insensitivity to change in load, speed and materials combination while PSU + 20% glass fibre composite has shown high sensitivity to the change in load and material combinations. The friction coefficient of PA6 + 20% mica and PSU + 20 glass fibre rubbing against the AISI 4140 steel disc is between 0.35 and 0.40. In rubbing against PPS + 30% glass fibre their values were between 0.25 and 0.30. Specific wear rate for PA6 + 20% mica and PSU + 20% glass fibre composites are in the order of 10-13 to 10-14 m2/N. Finally, the wear mechanisms are a combination of adhesive and abrasive wear processes. In terms of application, especially in electrical systems, a substantial contribution was provided to extend switch life. Thus, besides robustness, this also ensured safety for the system and the users against undesirable situations.
Volume 42 | Issue 5
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