Volume 5, Issue 7, July 2014

Advanced Materials World Congress, Sweden

Ashutosh Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 366-366
DOI: 10.5185/amlett.2014.7001

We are pleased to announce next Advanced Materials World Congress (AMWC), 25-28 August, 2015, http://vbripress.com/amwc/. It is a four-day international event organised by International Association of Advanced Materials and VBRI Press, which usually meets every two-year. The upcoming world congress is going to host in the city of Nobel Prize, Stockholm, Sweden. The venue of congress will be on the floor of Baltic Sea from Stockholm-Mariehamn-Stockholm via the Viking Cinderella. The goal of congress is to provide a global platform for researchers and engineers coming from academia and industry to present their research results and activities in the field of fundamental and interdisciplinary research of materials science. The World Congress will provide opportunities for the delegates to exchange their face-to-face novel ideas and experiences with the international experts during the plenary and invited talks, oral presentations and poster sessions. We will also set up sessions with keynote forum, panel discussion and project negotiation.

Formation Of TiO2 Thin Films By A Modified Sol-gel Route And Characterization Of Structural, Optical And Electrochromic Properties

Fatma Pinar Gokdemir; vecihe Ece Yuzbasioglu; Bahadir Keskin; Orhan Ozdemir; Kubilay Kutlu

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 367-371
DOI: 10.5185/amlett.2014.amwc.1007

Through a modified sol gel route with titanium isopropoxide (TIP) and acetic acid, titanium dioxide (TiO2) thin films were deposited by dip coating. Employing acetic acid as modifier and without inclusion of water in hydrolysis leaded to control the degree of condensation-oligorimerization of the precursor and formation of anatase phase only upon annealing. Direct allowed energy band gap 3.87 eV verified the anatase phase of the film. Impact of temperature on structural properties was deduced by FTIR and UV-Visible spectroscopies. Due to the reduction in band gap with increase in annealing temperature, injected Li + charge amount dropped in anatase compared to the amorphous (unannealed) films.

Magnetic, Electronic Structure And Interface Study Of Fe/MgO/Fe Multilayer

Jitendra Pal Singh; Sanjeev Gautam; Braj Bhusan Singh; Sujeet Chaudhary; D. Kabiraj; D. Kanjilal; K. H. Chae; R. Kotnala; Jenn-Min Lee; Jin-Ming Chen; K. Asokan

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 372-377
DOI: 10.5185/amlett.2013.105560

MgO based magnetic tunnel junctions (MTJs) exhibit high tunneling magnetoresistance (TMR) and have potential applications in magnetic random access memories. This study addresses the role of interface in the Fe/MgO/Fe based MTJs. For present investigation, Fe/MgO/Fe multilayer stack on Si substrates is grown by electron beam evaporation method and has been investigated for structural, magnetic and electronic properties. All the layers in the stack were of polycrystalline in nature as evidenced from X-ray diffraction studies, and the magnetic measurements show the attributes perpendicular magnetic anisotropy. Results from near edge X-ray absorption spectra at Fe L-edges measured by total electron yield mode and X-ray reflectometry indicate the formation of FeOx at the Fe/MgO interface. These are associated with hybridization of Fe (3d)-O(2p) levels at Fe/MgO interface in the stack and thickness of layers in the stacks. Absence of magnetic de-coupling between top and bottom ferromagnetic layers has been attributed to interface roughness and oxidation at Fe/MgO interface. This study highlights the role of interface and oxidation that need to be considered for improving the TMR for devices.

Nanostructure Of β-type Titanium Alloys Through Severe Plastic Deformation

Hakan Yilmazer; Mitsuo Niinomi; Ken Cho; Masaaki Nakai; Junko Hieda; Shigeo Sato; Yoshikazu Todaka

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 378-383
DOI: 10.5185/amlett.2014.amwc.1120

A novel β-type titanium alloy Ti–29Nb–13Ta–4.6Zr (TNTZ) has been developed and extensively researched to achieve highly desirable mechanical properties such as a high strength while maintaining a low Young’s modulus that is close to that of bone, as an alternative candidate for conventional titanium metallic biomaterials such as Ti-6Al-4V ELI. Therefore, strengthening by grain refinement and increasing dislocation density is expected to provide TNTZ high mechanical strength while keeping a low Young’s modulus because they keep the original β phase. In this case, severe plastic deformation, such as high-pressure torsion (HPT) processing, is a potential treatment for obtaining these properties. Furthermore, HPT processing is effective for producing ultrafine-grained TNTZ having high dislocation density in single β structure. The obtained promising results, which are a tensile strength of around 1100 MPa and a Young's modulus of around 60 GPa, motivated that the above mentioned mechanical properties can be achieved by microstructural refinement through HPT processing However, the mechanism of microstructural refinement is unclear for TNTZ during HPT processing. Therefore, the aim of this study is to investigate microstructural changes of TNTZ through HPT processing by X-ray diffraction analysis and transmission electron microscopy. The microstructures of TNTZ subjected to cold rolling (TNTZCR) and HPT processing (TNTZHPT) comprised single β grains; however, the intense β {110} peak reveals that the preferred orientation is β <110> for TNTZHPT. While the microstructure of TNTZCR shows a comparatively high dislocation density (2.3 x 1016 m -2 ), HPT processing leads to a drastic accumulation of dislocations (5.3 x 1016 m -2 in dislocation density). Dislocations in the microstructures of TNTZHPT are well arranged for the cell wall and/or subgrain boundaries, with a stronger dipole character than random distribution. The dislocation density, arrangement parameter and crystallite diameter (around 11 nm) of TNTZHPT saturate from the center to the peripheral region of a coin shaped specimen at N = 20. Therefore, such a microstructural saturation in a specific strain inducing, N = 20, suggests a threshold for further investigation of β-type titanium alloys.

Frequency And Temperature Dependent Impedance Study In 50% BaTiO3- 50% La0.7Sr0.3MnO3 Nanocomposite

Momin Hossain Khan;Sudipta Pal

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 384-388
DOI: 10.5185/amlett.2014.05552

We report the impedance spectroscopy (IS) behavior of the ferroelectric- ferromagnetic (50% BaTi O3-50% La0.7Sr0.3MnO3) nano-composite prepared by sol-gel method. Frequency and temperature dependence of the complex impedance and conductivity has been measured over the temperature range 310 K-430 K. A distribution of relaxation times and decentralization of the semicircle has been observed from the Cole–Cole plots of real and imaginary parts of the complex impedance. Non-Debye type relaxation has been observed in the investigated composite system. An equivalent circuit has been constructed to describe the IS. Interestingly, a typical universal dielectric response in the frequency-dependent conductivity at different temperature has been found. The frequency dependent ac conductivity at different temperature indicates that the conduction process is thermally activated. The activation energy has been obtained from the Arrhenius fitting. The obtained dc conductivity showed that the system undergoes a positive temperature coefficient resistance (PTCR) to negative temperature coefficient resistance (NTCR) near 350 K. The results would help to understand deeply the relaxation process in these types of materials.

Chemical Vapour Sensing Properties Of Electrospun Nanofibers Of Polyaniline/ ZnO Nanocomposites

Subhash B. Kondawar; Pallavi T. Patil; Shikha P. Agrawal

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 389-395
DOI: 10.5185/amlett.2014.amwc.1037

Zinc oxide (ZnO) nanoparticles were synthesized by simple route of sol-gel method and nanofibers of polyaniline (PANI) and PANI/ZnO nanocomposites prepared using the electrospinning technique. Electrospun nanofibers of PANI and PANI/ZnO nanocomposites were collected on aluminum substrate for characterization and on Cu-interdigited electrodes to prepare chemiresistor sensor. Electrospun nanofibers of PANI and PANI/ZnO nanocomposites have been characterized by UV-Visible (UV-Vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). UV-Visible spectra of nanofibers of PANI/ZnO nanocomposites show hypsochromic shift as that of PANI and some interaction due to ZnO in PANI matrix. The observed changes in the FTIR spectra of the fibers of PANI/ZnO nanocomposites are assosciated with the formation of H-bonding between ZnO and the N-H group present in the PANI chains. X-ray diffraction patterns exhibits hexagonal wurtzite structure of ZnO and broad amorphous peaks of PANI. Heterogeneous structures with fibrous characteristics of diameter less than 300nm of PANI/ZnO nanocomposites are identified in the SEM images. The electrical properties were characterized by I-V characteristic measurements. The changes in resistance of the chemiresistor sensor were utilized for detection of HCl and NH3 chemical vapour at room temperature. The resistance of the sensors was found to be decreased when they were exposed to HCl vapours whereas the resistance of the sensors was found to be increased when they were exposed to NH3 vapours. It was observed that PANI/ZnO nanocomposite sensor shows a high response and sensitivity with good repeatability as compared to that of pure PANI. Sensitivity result shows that PANI/ZnO nanocomposite is highly sensitive to chemical vapours even at room temperature and at very low concentration.

Thermoluminescence Characterization Of Gama-ray Irradiated Dy3+ Activated SrAl4O7 Nanophosphor

Anil Kumar Choubey; Nameeta Brahme; S.J. Dhoble; D. P. Bisen; K.B. Ghormare

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 396-399
DOI: 10.5185/amlett.2014.amwc.1210

Dy doped strontium aluminate phosphor (SrAl4O7:Dy(15% molar concentration)) was synthesized by combustion method using urea as a reducer at initiating temperature of 600oC. The absorption spectra shows the absorption edges at l = 242 nm, thus the band gap of 5.11 eV. The Thermoluminescence (TL) property of Dy(15%) doped SrAl4O7 nanophosphor has been investigated for l-irradiation. The TL glow curve of SrAl4O7:Dy (15%) phosphor with different ?-ray doses show the dose increases the TL- intensity while the temperature corresponding to maximum intensity remains nearly same. The maximum TL-intensity observes around 172.84 oC for the different doses. It was found that TL intensity strongly depends upon the -dose. It shows linear response upto 2.36 kGy. Hence Dy(15%) doped SrAl4O7 could be used for TL Dosimetry upto 2.36 kGy.

Development Of Nanocomposites Based On Polypyrrole And Carbon Nanotubes For Supercapacitors

Ritu P. Mahore; Devendra K. Burghate; Subhash B. Kondawar

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 400-405
DOI: 10.5185/amlett.2014.amwc.1038

Supercapacitors are recognized as one of the most promising energy storage devices for a wide range of civilian and military applications in electric vehicles, uninterruptible power supplies. Conducting polymer nanocomposites are new functional materials suitable for supercapacitors due to synergistic effect of individual components. In present work, polypyrrole/CNT nanocomposites have been prepared by an in-situ chemical polymerization method and studied for supercapacitor. CNTs were well functionalized using 3:1 ratio of H2SO4 and HNO3 before polymerizing the pyrrole. Analytical techniques such as SEM, UV-VIS and FTIR were used to characterize the synthesized materials. The SEM images reveal that the materials have rough and granular morphology. The composites showed good interaction based on the shift to longer wavelengths in the electronic transition, indicating the interaction between PPy and functionalized CNTs as observed in their UV-VIS and FTIR spectra. The electrochemical performance was evaluated by using cyclic voltammetry (CV) in 1M Na2SO4 electrolyte and specific capacitance was obtained at 0.5 V/s for pure polypyrrole and PPy/CNT nanocomposites. Nanocomposite showed the enhanced electrochemical performance as compared to that of pure polypyrrole. The specific capacitance obtained at the scan rate 0.5V/s was found to be 0.825 F/cm -2 for pure polypyrrole and 1.0619 F/cm -2 for PPy/CNT nanocomposite material respectively, indicates that PPy/CNT nanocomposite is suitable material as electrode for supercapacitor as compoared to pure polypyrrole.

Morphological Properties And Birefringences Of Uniaxial Lyotropic Nematic Mesophases Under Influence Of Various Magnetic Field Values

Aykut Evren Yavuz

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 409-413
DOI: 10.5185/amlett.2014.amwc.1040

One has studied time-dependent changes of morphological properties of uniaxial lyotropic nematic-calamitic NC and nematic- discotic ND mesophases with various external magnetic field values. Also, changes of optical birefringence values of NC and ND lyotropic mesophases under influence of the magnetic fields has been investigated based on time. Differences of morphological properties and changing birefringence values between NC and ND mesophases have been interpreted according to magnetic field values. The values of optical birefringence and morphological properties changing in time between NC and ND mesophases which are opposite signs of diamagnetic anisotropy have been compared with increasing magnetic field values.

Synthesis And Characterization Of Nanofibers Of Conducting Polyaniline And Its Substitute Derivative

Subhash B. Kondawar; Suyog M. Pethe

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 414-420
DOI: 10.5185/amlett.2014.amwc.1039

Intrinsically conducting polymers have been extensively studied due to their fascinating electronic properties and potential applications. One dimensional conducting polymer nanostructures have been the focus of quite extensive studies worldwide due to their high aspect ratio, high porosity apart from high surface area to volume ratio. In this paper, we report the synthesis of nanofibers of polyaniline and its substitute derivates and their comparative study in respect of electrical conductivity. Nanofibers of doped polyaniline (PANI), poly(o-methoxyaniline) (POMXA) and poly(o-methylaniline) (POMLA) were synthesized without need of any templates by interfacial polymerization. SEM, TEM, FTIR, UV-VIS and XRD were used to characterize the synthesized conducting polymeric materials. The average diameters of the synthesized nanofibers of conducting polymeric materials were in the range of 70-120 nm. The electrical conductivity was found to be in the range of 0.3 - 1.0 S/cm following the order as POMXA < POMLA < PANI which was found to be closely related to the size dependent electrical properties of the nanofibers. Optical band gap of these polymers was evaluated from UV–VIS absorption studies. Direct and indirect transition energy band gaps were determined from Tauc’s plots. Interfacial polymerization was shown to be readily scalable to produce bulk quantities of nanofibers of substitute derivative of polyaniline.