Volume 5, Issue 5, May 2014


Editorial

International Conference On Smart Materials And Surfaces (SMS), Bangkok

Ashutosh Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 234-235
DOI: 10.5185/amlett.2014.5001

We are pleased to announce International Conference on Smart Materials and Surfaces (SMS). It will be organised jointly by SETCOR, IAAM and VBRI Press during 26-28 August 2014 at Sheraton Grande Sukhumvit Hotel, Bangkok, Thailand. Smart Materials and Surfaces (SMS), Bangkok is a three-day event targeting researchers interested in the design, modification, characterisation and applications of Novel Smart & Active Surfaces and Materials. The goal of conference 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 Intelligent Materials science and engineering. The conference will provide opportunities for the delegates to exchange face-to-face their novel ideas and experiences with the international experts during plenary & invited talks, oral presentations and poster sessions. We will set up sessions with keynote forum, panel discussion, project negotiation along with welcome cocktail and gala dinner.

Functional Nanomaterials For Energy And Sustainability

Antonios Kelarakis

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 236-241
DOI: 10.5185/amlett.2014.amwc1026

In view of the continuous decline in fossil fuel reserves, at a time when energy demands are steadily increasing, a diverse range of emerging nanotechnologies promise to secure modern solutions to the prehistoric energy problem. Each one of those distinct approaches capitalizes on different principles, concepts and methodologies to address different application requirements, but their common objective is to open a window to a sustainable energy future. Consequently, they all deserve substantial (though not necessarily equal) consideration from the scientific and engineering community. In this review we present bottom-up strategies that show great promise for the development of a new generation of advanced materials for energy applications without compromising the public safety or the environment.

Oxides For Spintronics: A Review Of Engineered Materials For Spin Injection

M. C. Prestgard; G. P. Siegel; A. Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 242-247
DOI: 10.5185/amlett.2014.amwc1032

In this article we have reviewed the role of oxides in spintronics research, and specifically how these materials stand to further improve the efficiencies and capabilities of spin injection for active spintronic device development. The use of oxides in spintronics is advantageous in that they are stable in air, can be easily modified, and can possess a wide variety of properties which are beneficial to spintronics applications. This paper delineates the progression of spintronics and shows how applying oxide systems, in the form of half-metallic LaSrMnO3, the diluted magnetic semiconductor ZnO:Co, and diluted magnetic dielectrics CeO2:Co and Sm2O3:Co, has influenced and improved spintronics capabilities. An outline of the future potential for oxides in the realm of organic spintronic devices is also given

Mechanical Properties and Deformation Of Ceramic Coated Steels Heat-treated By Scanning Laser

Hirotaka Tanabe; Keiji Ogawa; Yui Izumi; Motoyuki Nishizawa; Tohru Takamatsu; Heisaburo Nakagawa

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 248-254
DOI: 10.5185/amlett.2014.amwc1012

A new surface modification method “laser quenching after coating” using a high power diode laser equipped with a 2-dimensional galvano-scanner unit was developed to process a larger area of ceramic coated steel uniformly and efficiently. The laser irradiation tests for 3 kinds of ceramic-coated steels: CrAlN, TiAlN and CrN, were carried out with the scanning laser, and the appropriate irradiation conditions to achieve the uniformly quenched substrate without any surface damage were clarified for these ceramic-coated steels. The area of the substrate surface wider than the laser spot size could be easily quenched by the scanning laser. The adhesive strength, the film hardness of the laser-irradiated regions and the deformation caused by laser irradiation were evaluated. Laser quenching with the scanning laser can effectively improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of the ceramic-coated specimens. In the deformation of the laser-irradiated specimens, two features were recognized; one is the bending, and the other is the expansion of laser-irradiated part. It was found that the deformation of ceramic-coated steel by laser irradiation under the same heat input condition does not depend on the kind of ceramic thin film but on the steel type of the substrate. It was concluded that “laser quenching after coating” with scanning laser could easily improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of large surface areas in the tested all types of ceramic-coated specimens.

 Study Of Ca Doping On A- Site On The Structural And Physical Properties Of BLTMNZ Ceramics

P. Kumari; R. Rai; A. L. Kholkin; A. Tiwari

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 255-259
DOI: 10.5185/amlett.2013.10547

The ferroelectric Ca doped (Ba0.9575La0.04X0.0025) (Ti0.815Mn0.0025Nb0.0025Zr0.18)0.99O3 was prepared by a high-temperature solid state reaction technique. For the understanding of the electrical and dielectric property, the relation between the crystal structures, electrical transition and ferroelectric transitions with increasing temperature ( –160 to 35°C) have been analyzed. X- ray diffraction analysis of the powders suggests the formation of a single-phase material with monoclinic structure. Capacitance and tanδ of the specimens were measured in the temperature range from -160 to 35°Cat frequencies 1 kHz – 1 MHz. Detailed studies of dielectric and electrical properties indicate that the Curie temperature shifted to higher temperature with the increase in frequency. Moreover, the dielectric maxima dropped down rapidly initially and the dielectric peaks became extremely broad. The AC conductivity increases with increase in frequency. The low value of activation energy obtained for the ceramic samples could be attributed to the influence of electronic contribution to the conductivity.

Crystallization And Grain Growth Behavior Of La2O3-doped Yttria-stabilized Zirconia

Bulent Aktas; Suleyman Tekeli; Serdar Salman

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 260-264
DOI: 10.5185/amlett.2014.amwc1011

The effect of La2O3 addition on the microstructure and grain growth behavior of yttria-stabilized zirconia (8YSZ) was investigated. To this end, 8YSZ was doped with 1–15 wt% La2O3 by means of colloidal processing, and then sintered at 1550 °C for 1 h. XRD results identified a dissolution limit of 5 wt% La2O3 in 8YSZ, the insoluble La2O3 at higher concentrations reacting with ZrO2 during sintering to form a secondary La2Zr2O7 phase. Both undoped and La2O3-doped 8YSZ specimens were annealed at 1400, 1500, and 1600 °C for 10, 50, and 100 h to induce grain growth. Grain growth measurement results showed that an increase in annealing temperature and holding time caused to grain growth in all specimens. Excessive grain growth was observed in the case of the undoped, and 1-5 wt% La2O3-doped 8YSZ specimens; however, the grain growth in 10 and 15 wt% La2O3-doped 8YSZ was inhibited by the formation of a pyrochloric La2Zr2O7 secondary phase around the grains and grain boundaries of 8YSZ. Grain growth exponent (n) and activation energy (Q) values for grain growth of undoped 8YSZ were obtained as 3, and 358 kJ/mol, respectively, while 15 wt% La2O3 containing specimens had a grain growth exponent of 3, and activation energy of 413 kJ/mol. These results indicate that grain growth rate can be controlled by the addition of 10 or 15 wt% La2O3.

Improving The Mechanical And Thermal Properties Of Semi-coke Based Carbon/copper Composites Reinforced Using Carbon Nanotubes

S. Kumari; A. Kumar; P. R. Sengupta; P. K. Dutta; R. B. Mathur

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 265-271
DOI: 10.5185/amlett.2013.10546

Multiwalled carbon nanotubes (MWCNT)- reinforced carbon/copper (C/Cu) composites were developed by powder metallurgy technique and mixed powders of C and Cu were consolidated into plates without using any extra binder followed by sintering at 1000 o C in inert atmosphere. Samples were characterized for structural, mechanical, electrical and thermal properties w.r.t. different mass fraction of MWCNT in C-Cu matrix. In comparison to C/Cu composite, addition of minute amount (0.25 wt%) of CNT in C-Cu substantially improved the mechanical, electrical and thermal properties of composites. These composites were mechanically stable and strong and exhibited high bending strength of 162 MPa, indicating a homogeneous dispersion of MWCNTs in the C-Cu matrix. Maximum thermal conductivity of 37.60 W/mK perpendicular to the pressing direction was obtained for 0.50 wt% CNT reinforced C-Cu composite exhibiting an improvement of 45% over pure C-Cu composite processed under identical conditions. High thermal conducting and mechanically strong composites can be used as heat sink for long time.

Effect Of UV Rays On Degradation And Stability Of High Performance Polymer Membranes

Omkar S. Kushwaha; C. V. Avadhani; R. P. Singh

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 272-279
DOI: 10.5185/amlett.2014.10533

Acid doped polybenzimidazole membranes have emerged as an efficient electrolyte for high temperature polymer electrolyte membrane fuel cells (HTPEMFCs). The long term stability of polybenzimidazole membranes has been recognized as an important issue for commercial applications. Here, we report the oxidative degradation of polybenzimidazole membranes. The photoirradiation of poly(2,2'-ethylene-5,5'-bibenzimidazole) (PBIE) under accelerated photodegradation conditions was carried out by ultraviolet (UV) rays (λ > 300 nm) and characterized by Fourier transform infra red (FT-IR) spectroscopy, scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and contact angle measurements (CAM).  The thermal properties of PBIE membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) which revealed a lowering in thermal stability after photodegradation. FT-IR spectra revealed high absorbance in the carbonyl region in photoirradiated membranes whereas SEM showed nano structures / defects on the polymer film surface. CAM results showed enhancement in hydrophilic behavior and WAXD revealed increase in amorphous nature upon irradiation.

Correlation Between The PH Value And Properties Of Magnetite Nanoparticles

Geeta Rana; Umesh C. Johri

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 280-286
DOI: 10.5185/amlett.2014.10563

Magnetite nanoparticles with particle size ~ 10 and 16 nm are synthesized by varying pH of the initial solution during chemical co-precipitation method. The X-ray diffraction patterns confirm the formation of spinel phase; however, the Raman spectra show an impure phase of antiferromagnetic Fe2O3 in the sample of smaller nanoparticles (10 nm). The cation distribution of these nanoparticles is estimated using the lattice parameter. Lower saturation magnetization of these samples, as compared to bulk, has been attributed to larger surface area of these samples. Same aspect has also been investigated from the optical band gap variation of these nanoparticles. Almost one third value of magnetization of smaller nanoparticles compared to larger one is due to the presence of Fe2O3 phase. The motive of the present study is to correlate the properties of magnetite nanoparticles with the synthesis parameters like pH and hence to tune them according to particular applications.

Stoichiometric LiNb3O8 Thin Films From Microwave Annealing

Anil Tumuluri; K. C. James Raju

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 287-291
DOI: 10.5185/amlett.2013.fdm.11

Mono phase LiNb3O8 (LN), a compound that comes during the processing of LiNbO3 is synthesized as thin films using sol gel process followed by microwave annealing. Initial studies like phase determination, structure and microstructure of this particular compound are done. XRD pattern confirmed LN as monoclinic with no preferred orientation. From Raman spectroscopy, we found that crystallization is not uniform and new peaks are appearing. Untraceable phases have been identified from Raman imaging. The broadening of peak width is increasing with increase in temperature. Low frequency modes are due to the Li deficiency sites occupied by Nb ions and higher frequency peaks are due to oxygen displacement. Non stoichiometric phases can be identified from color contrast in Raman imaging. Microwave annealing is a successful method to obtain LiNb3O8 thin films.

Variation In Mechanical Properties With Substrate Temperature Of SbTi Thin Film Deposited By RF Sputtering Technique

A. Rambabu; Anil Tumuluri; K.C. James Raju

Advanced Materials Letters, 2014, Volume 5, Issue 5, Pages 292-296
DOI: 10.5185/amlett.2013.fdm.12

Nanoindentation technique has been used to determine the mechanical properties of bismuth layered structure ferroelectric thin films, which have been shown to be promising for MEMS based devices used in sensing, actuation and energy harvesting, especially at elevated temperatures. SBTi (SrBi4Ti4O15) is a promising layered ferroelectric material and thin films of this composition are deposited on amorphous fused silica substrates by rf sputtering technique varying the substrate temperature from 600–725 o C. The crystal structure and surface morphology of SBTi thin films are characterized by X-ray diffraction and atomic force microscopy. Depth- sensing nanoindentation system is used to measure the mechanical characteristics of SBTi thin films. Nanoindentation measurements reveal that the Young’s modulus and hardness of SBTi thin films are related with grain size and crystal orientation which in turn depend on substrate temperature. The increase in mechanical properties with grain size is observed, indicating the reverse Hall-Petch effect. Furthermore, hardness and Young’s modulus of the (119) oriented films were higher than those of (0010) oriented films. The tribological properties of these films are confirmed by performing the scratch tests on the same films.