Studies on the Aging Characteristics of Base Oil with Amine Based Antioxidant in Steel-on-Steel Lubricated Sliding

An industrial base oil, a blend of different paraffin fractions, is heated to 130 degrees C (1) in the ambient and (2) for use as a lubricant in a steel pin on a steel disk sliding experiment. The base oil was tested with and without test antioxidants: dimethyl disulfide (DMDS) and alkylated diphenylamine (ADPA). Primary and secondary oxidation products were monitored continuously by FTIR over a 100 h period. In addition, friction and wear of the steel pin were monitored over the same period and the chemical transformation of the pin surface was monitored by XPS. The objective of this work is to observe the catalytic action of the steel components on the oil aging process and the efficacy of the antioxidant to reduce oxidation of oil used in tribology as a lubricant. Possible mechanistic explanations of the aging process as well as its impact on friction and wear are discussed.

Precursors for carbon nitride synthesis

Nano structured carbon nitride films were prepared by pyrolysis assisted chemical vapour deposition. Pyrrole (C4H5N), Pyrrolidine (C4H9N), Azabenzimidazole (C6H5N3) and Triazine (C6H15N3) were used as precursors. The vibrational modes observed for C–N and C  =  N from FTIR spectra confirms the bonding of nitrogen with carbon. XPS core level spectra of C 1s and N 1s also show the formation of bonding between carbon and nitrogen atoms. The nitrogen content in the prepared samples was found to be around 25 atomic %.

Surface modification and paclitaxel drug delivery of folic acid modified polyethylene glycol functionalized hydroxyapatite nanoparticles

Nanoparticles are used for a number of biomedical applications. In this work we report the synthesis of folic acid (FA) modified polyethylene glycol (PEG) functionalized hydroxyapatite (HAp) nanoparticles. The anticancer drug, paclitaxel, is attached to the folic acid modified polyethylene glycol functionalized hydroxyapatite nanoparticles and the in vitro drug release is analyzed. The surface modification and functionalization is confirmed by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA) and UV spectroscopy. The importance of the paper is the investigation of the release behavior of paclitaxel conjugated folic acid modified polyethylene glycol functionalized hydroxyapatite nanoparticles. The results show an initial rapid release and then a sustained release. (C) 2012 Elsevier B.V. All rights reserved.

In vitro cytocompatibility assessment of amorphous carbon structures using neuroblastoma and Schwann cells

The development of scaffolds for neural tissue engineering application requires an understanding of cell adhesion, proliferation, and migration of neuronal cells. Considering the potential application of carbon as scaffold materials and the lack of understanding of compatibility of amorphous carbon with neuronal cells, the carbon-based materials in the forms of carbon films and continuous electrospun carbon nanofibers having average diameter of approximate to 200 nm are being investigated with or without ultraviolet (UV) and oxy-plasma (OP) treatments for cytocompatibility property using mouse Neuroblastoma (N2a) and rat Schwann cells (RT4-D6P2T). The use of Raman spectroscopy in combination with Fourier transform infrared (FTIR) and X-ray diffraction establishes the amorphous nature and surface-bonding characteristics of the studied carbon materials. Although both UV and OP treatments make carbon surfaces more hydrophilic, the cell viability of N2a cells is statistically more significant on OP treated fibers/films compared to UV fiber/film substrates after 4 days in culture. The electrospun carbon fibrous substrate provides the physical guidance to the cultured Schwann cells. Overall, the experimental results of this study demonstrate that the electrospun amorphous carbon nanofibrous scaffolds can be used as a suitable biomaterial substrate for supporting cell adhesion and proliferation of neuronal cells in the context of their applications as artificial nerve implants. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

Zn-nicotinate complex - a precursor for ZnO nanoparticles

A zinc-nicotinate complex has been prepared by direct reaction of zinc acetate and nicotinic acid in the presence of template tetramethylethylenediamine and is characterized by elemental analysis, FTIR, and TGA/DTA. The Zn complex was a precursor for the synthesis of ZnO nanoparticles. A correlation of the thermal and spectral properties of the precursor complex with its structure has been discussed. Thermolysis under air was studied by thermogravimetry, and the resulting ZnO product was characterized by XRD and TEM, showing compact particles with a diameter of about 1750nm.

Structural, electrical and dielectric properties of sputtered TiO2 films for Al/TiO2/Si capacitors

Metal-oxide semiconductor capacitors based on titanium dioxide (TiO2) gate dielectrics were prepared by RF magnetron sputtering technique. The deposited films were post-annealed at temperatures in the range 773-1173 K in air for 1 hour. The effect of annealing temperature on the structural properties of TiO2 films was investigated by X-ray diffraction and Raman spectroscopy, the surface morphology was studied by atomic force microscopy (AFM) and the electrical properties of Al/TiO2/p-Si structure were measured recording capacitance-voltage and current-voltage characteristics. The as-deposited films and the films annealed at temperatures lower than 773 K formed in the anatase phase, while those annealed at temperatures higher than 973 K were made of mixtures of the rutile and anatase phases. FTIR analysis revealed that, in the case of films annealed at 1173 K, an interfacial layer had formed, thereby reducing the dielectric constant. The dielectric constant of the as-deposited films was 14 and increased from 25 to 50 with increases in the annealing temperature from 773 to 973 K. The leakage current density of as-deposited films was 1.7 x 10(-5) and decreased from 4.7 X 10(-6) to 3.5 x 10(-9) A/cm(2) with increases in the annealing temperature from 773 to 1173 K. The electrical conduction in the Al/TiO2/p-Si structures was studied on the basis of the plots of Schottky emission, Poole-Frenkel emission and Fowler-Nordheim tunnelling. The effect of structural changes on the current-voltage and capacitance-voltage characteristics of Al/TiO2/p-Si capacitors was also discussed.

Effect of TiO2 on electrical and magnetic properties of Ni0.35Cu0.12Zn0.35Fe2O4 synthesized by the microwave-hydrothermal method

The nanocomposites of xTiO(2)+(1-x)Ni0.53Cu0.12Zn0.35Fe2O4 (where 0 <= x >= 1) were prepared using microwave hydrothermal (M H) method at 165 degrees C/45 min. The as-synthesized powders were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The particle size of the powder varies from 18 to 35 nm. The as prepared powders were densified at 500 degrees C/30 min using microwave sintering method. The sintered composites were characterized by XRD and scanning electron microscopy (SEM). The bulk densities of the present composites were increasing with the addition of TiO2. The grain sizes of all the composite vary between 65 nm and 90 nm. The addition of TiO2 to ferrite increased the dielectric properties (epsilon' and epsilon `') also the resonant frequency of all the composites was found to be greater than 1 GHz. The imaginary part of permeability mu `' was found to increase with an increase of TiO2.

Liquefied Petroleum Gas Sensing of Polyaniline-Titanium Dioxide Nanocomposites

Polyaniline/titaniurn dioxide nanocomposites were prepared using alpha-dextrose as surfactant and ammonium persulphate as an oxidant. The PANI/TiO2 nanocomposite is characterized by FTIR, XRD and TEM. The FTIR spectra revel that the presence of characteristic peaks of benzenoid, qunoide rings and metal-oxygen stretching. The XRD studies show the monoclinic structure of the nanocomposites. The TEM study shows that the size of TiO2 is in the order of 9 nm where as the composite size is of the order of 13 nm and further it was observed that the TiO2 particles are intercalated to form a core shell of PANI. The maximum sensing response for LPG is found to be 90% for 30 wt.% of PANI/TiO2 nanocomposites at 400 ppm whereas for Benzene and Toluene it is negligibly small (<= 20%) and for the cyclohexane sensing response it is around 30% for different wt.%.

Flexible poly(vinyl alcohol-co-ethylene)/modified MMT moisture barrier composite for encapsulating organic devices

Flexible, nano-composite moisture barrier films of poly(vinyl alcohol-co-ethylene) with surface modified montmorillonite fabricated by solution casting were used to encapsulate organic devices. The composite films were characterized by FTIR, UV-visible spectroscopy and SEM imaging. Thermal and mechanical properties of the composite films were studied by DSC and UTM. Calcium degradation test was used to determine the transmission rate of water vapour through the composite films, which showed a gradual reduction from similar to 0.1 g m(-2) day(-1) to 0.0001 g m(-2) day(-1) with increasing modified montmorillonite loading in the neat copolymer. The increase in moisture barrier performance is attributed to the decreased water vapour diffusivity due to matrix-filler interactions in the composite. The accelerated aging test was carried out for non-encapsulated and encapsulated devices to evaluate the efficiency of the encapsulants. The encapsulated devices exhibited longer lifetimes indicating the efficacy of the encapsulant.

Critical investigation on hydrogen bonding by Fourier transform infrared spectroscopy in hydrogenated amorphous silicon thin films

Fourier Transform Infrared (FTIR) spectroscopic analysis has been carried out on the hydrogenated amorphous silicon (a-Si:H) thin films deposited by DC, pulsed DC (PDC) and RF sputtering process to get insight regarding the total hydrogen concentration (C-H) in the films, configuration of hydrogen bonding, density of the films (decided by the vacancy and void incorporation) and the microstructure factor (R*) which varies with the type of sputtering carried out at the same processing conditions. The hydrogen incorporation is found to be more in RF sputter deposited films as compared to PDC and DC sputter deposited films. All the films were broadly divided into two regions namely vacancy dominated and void dominated regions. At low hydrogen dilutions the films are vacancy dominated and at high hydrogen dilutions they are void dominated. This demarcation is at C-H = 23 at.% H for RF, C-H = 18 at.% H for PDC and C-H = 14 at.% H for DC sputter deposited films. The microstructure structure factor R* is found to be as low as 0.029 for DC sputter deposited films at low C-H. For a given C-H, DC sputter deposited films have low R* as compared to PDC and RF sputter deposited films. Signature of dihydride incorporation is found to be more in DC sputter deposited films at low C-H.

Segmental relaxations and crystallization-induced phase separation in PVDF/PMMA blends in the presence of surface-functionalized multiwall carbon nanotubes

Crystallization-induced phase separation and segmental relaxations in poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blends was systematically investigated by melt-rheology and broadband dielectric spectroscopy in the presence of multiwall carbon nanotubes (MWNTs). Different functionalized MWNTs (amine, -NH2; acid, -COOH) were incorporated in the blends by melt-mixing above the melting temperature of PVDF, where the blends are miscible, and the crystallization induced phase separation was probed in situ by shear rheology. Interestingly, only -NH2 functionalized MWNTs (a-MWNTs) aided in the formation of beta-phase (trans-trans) crystals in PVDF, whereas both the neat blends and the blends with -COOH functionalized MWNTs (c-MWNTs) showed only alpha-phase (trans-gauche-trans-gauche') crystals as inferred from wide-angle X-ray diffraction (WXRD) and Fourier transform infrared (FTIR). Furthermore, blends with only a-MWNTs facilitated in heterogeneous nucleation in the blends manifesting in an increase in the calorimetric crystallization temperature and hence, augmented the theologically determined crystallintion induced phase separation temperature. The dielectric relaxations associated with the crystalline phase of PVDF (alpha(c)) was completely absent in the blends with a-MWNTs in contrast to neat blends and the blends with c-MWNTs in the dielectric loss spectra. The relaxations in the blends investigated here appeared to follow Havriliak-Negami (HN) empirical equations, and, more interestingly, the dynamic heterogeneity in the system could be mapped by an extra relaxation at higher frequency at the crystallization-induced phase separation temperature. The mean relaxation time (tau(HN)) was evaluated and observed to be delayed in the presence of MWNTs in the blends, more prominently in the case of blends with a-MWNTs. The latter also showed a significant increase in the dielectric relaxation strength (Delta epsilon). Electron microscopy and selective etching was used to confirm the localization of MWNTs in the amorphous phases of the interspherulitic regions as observed from scanning electron microscopy (SEM). The evolved crystalline morphology, during crystallization-induced phase separation, was observed to have a strong influence on the charge transport processes in the blends. These observations were further supported by the specific interactions (like dipole induced dipole interaction) between a-MWNTs and PVDF, as inferred from FTIR, and the differences in the crystalline morphology as observed from WXRD and polarized optical microscopy (POM).

Induction of Supramolecular Chirality in the Self-Assemblies of Lipophilic Pyrimidine Derivatives by Choice of the Amino Acid-Based Chiral Spacer

A new family of supramolecular organogelators, based on chiral amino acid derivatives of 2,4,6-trichloro-pyrimidine-5-carbaldehyde, has been synthesized. L-alanine was incorporated as a spacer between the pyrimidine core and long hydrocarbon tails to compare the effect of chirality and hydrogen bonding to that of the achiral analogue. The role of aromatic moiety on the chiral spacer was also investigated by introducing L-phenyl alanine moieties. The presence of intermolecular hydrogen-bonding leading to the chiral self-assembly was probed by concentration-dependent FTIR and UV/Vis spectroscopies, in addition to circular dichroism (CD) studies. Temperature and concentration-dependent CD spectroscopy ascribed to the formation of -sheet-type H-bonded networks. The morphology and the arrangements of the molecules in the freeze-dried gels were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) techniques. Calculation of the length of each molecular system by energy minimization in its extended conformation and comparison with the small-angle XRD pattern reveals that this class of gelator molecules adopts a lamellar organization. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) indicate that the solid state phase behavior of these molecules is totally dependent on the choice of their amino acid spacers. Structure-induced aggregation properties based on the H-bonding motifs and the packing of the molecule in three dimensions leading to gelation was elucidated by rheological studies. However, viscoelasticity was shown to depend only marginally on the H-bonding interactions; rather it depends on the packing of the gelators to a greater extent.

Ionothermal synthesis of TiO2 nanoparticles: Photocatalytic hydrogen generation

Rutile phase TiO2 nanoparticles have been successfully prepared at 120 degrees C for one day via the ionothermal method using imidazolium based functionalized ionic liquid. The obtained products have been characterized by various techniques. XRD pattern shows rutile phase with crystallite size similar to 15 nm. FTIR shows a band at similar to 410 cm(-1) assigned to Ti-O-Ti stretching vibrations and few other bands due to the presence of ionic liquid. UV-vis studies show maximum absorbance at similar to 215 nm due to the imidazolium moiety and a band at 316 nm due to TiO2 nanoparticles. TEM images show that the size of particle is similar to 30 nm. TG-DTA shows weight loss corresponding to the formation of stable TiO2 nanoparticles. The rutile TiO2 nanoparticle is a promising material for hydrogen generation through photocatalysis. (C) 2013 Elsevier B.V. All rights reserved.

Steric and Electronic Interactions Controlling the cis/trans Isomer Equilibrium at X-Pro Tertiary Amide Motifs in Solution

A systematic understanding of the noncovalent interactions that influence the structures of the cis conformers and the equilibrium between the cis and the trans conformers, of the X-Pro tertiary amide motifs, is presented based on analyses of H-1-, C-13-NMR and FTIR absorption spectra of two sets of homologous peptides, X-Pro-Aib-OMe and X-Pro-NH-Me (where X is acetyl, propionyl, isobutyryl and pivaloyl), in solvents of varying polarities. First, this work shows that the cis conformers of any X-Pro tertiary amide motif, including Piv-Pro, are accessible in the new motifs X-Pro-Aib-OMe, in solution. These conformers are uniquely observable by FTIR spectroscopy at ambient temperatures and by NMR spectroscopy from temperatures as high as 273 K. This is made possible by the persistent presence of n(i-1i)* interactions at Aib, which also influence the disappearance of steric effects at these cis X-Pro rotamers. Second, contrary to conventional understanding, the energy contribution of steric effects to the cis/trans equilibrium at the X-Pro motifs is found to be nonvariant (0.54 +/- 0.02 kcal/mol) with increase in steric bulk on the X group. Third, the current studies provide direct evidence for the weak intramolecular interactions namely the n(i-1i)*, the N-Pro center dot center dot center dot Hi+1 (C(5)a), and the C-7 hydrogen bond that operate and influence the structures, stabilities, and dynamics between different conformational states of X-Pro tertiary amide motifs. NMR and IR spectral data suggest that the cis conformers of X-Pro motifs are ensembles of short-lived rotamers about the C-X-N-Pro bond. (c) 2013 Wiley Periodicals, Inc. Biopolymers 101: 66-77, 2014.

Synthesis, structural and optical properties of nanocrystalline Ba2NaNb5O15

Fine powders comprising nanocrystallites of barium sodium niobate, Ba2NaNb5O15 (BNN) were obtained via a citrate assisted sol-gel route at a much lower temperature than that of the conventional solid-state reaction route. The phase evolution of BNN as a function of temperature was investigated by thermogravimetric analysis (TGA), differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). DTA data followed by XRD studies confirmed the BNN formation temperature to be around 923 K. The as-synthesized powders heat-treated at 923 K/10 h attained an orthorhombic structure akin to that of the parent BNN phase. Transmission electron microscopy revealed that the nanocrystallites are associated with dislocations. The optical band gap was calculated using the Kubelka-Munk function. These nanocrystallites exhibited strong visible photoluminescence (PL) at room temperature. The PL mechanism was explained by invoking the dielectric confinement effect, defect states and generation of self-trapped excitons.