Issue 6

 Special Issue In Celebration Of Prof. Anthony PF Turner’s 65th Birthday

Ashutosh Tiwari

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 452-452
DOI: 10.5185/amlett.2015.6001

It is our great pleasure to publish the 6th volume, 6th issue, June 2015 of Advanced Materials Letters in celebration of Prof. Anthony P. F. Turner’s 65th Birthday. Professor Turner was born in London in the United Kingdom on June 5, 1950. He graduated in Applied Biology from the University of East London and gained a Masters in Biochemistry from the University of Kent. In 1980, he received his PhD in Microbiology at the University of Portsmouth. He joined Cranfield University in 1981 to help start the UK’s first Biotechnology Centre and founded the Biosensors group there, where he led the group that developed the world’s most successful type of biosensor, i.e., the hand-held mediated amperometric glucose sensor for people with diabetes.

 State-of-the-art Of Lead Free Ferroelectrics: A Critical Review

Poonam Kumari; ;Ashutosh Tiwari; Radheshyam Rai; Seema Sharma; Mamta Shandilya; and Ashutosh Tiwari

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 453-484
DOI: 10.5185/amlett.2015.4086

Lead based piezoelectric perovskite materials are well known for their excellent piezoelectric properties, which are extensively used in industrial applications. Though, considering the toxicity of lead and its compounds, there is a general awareness for the development of environmental friendly lead-free materials as evidenced from the legislation passed by the European Union in this effect. The different class of materials is now being considered as potentially attractive alternatives to lead zirconate titanate (PZT) based perovskites for various applications. In this review, we review the progresses made on lead-free piezoelectric materials emphasizing on their synthesis, structure–property correlation, etc. Advancement of the various piezo systems such as bismuth sodium titanate, alkali niobates etc. and non-perovskites for example bismuth layer-structured ferroelectrics has been deliberated. It is found that some lead-free compositions show stable piezoelectric responses though they are not as high as the PZT system. This subject is of current interest to the ceramic researchers worldwide as evidenced from the large number of research publications and has motivated us to come out with a critical overview of the field. This article would drive to the researchers to advance the piezoelectric properties of the non-lead based perovskite compounds to achieve materials at par with the PZT system.  

 In Situ Formation Of Tantalum Oxide – PMMA Hybrid Dielectric Thin Films For Transparent Electronic Application

Elena Emanuela Valcu (Herbei); Viorica Musat; Susanne Oertel; Michael P.M. Jank; Timothy Leedham

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 485-491
DOI: 10.5185/amlett.2015.5785

 Solution-processed high-k dielectric hybrid thin films prepared at temperatures below 200 o C represent a subject of increasing scientific interest satisfying current requirements for printable thin film transistors used in transparent flexible electronics. In this work, we propose a new approach for the synthesis of new tantalum oxide-PMMA hybrid dielectric thin films at 160 o C by modified sol-gel method, using as precursors tantalum ethoxide cluster (Ta(OC2H5)5) and methyl methacrylate monomer (MMA). So far it has not been reported in situ formation of tantalum oxide nanocrystals in hybrid dielectric materials at this low temperature. Hybrid sols with 1:1 and 4:1 (Ta(OC2H5)5):MMA molar ratios were used for spin-coating of thin films. The thermal behavior of these sols was observed in order to optimize the post-deposition treatment of the films. The hybrid films were investigated by scanning electron microscopy (SEM) for thickness and morphology, by grazing incidence x-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM) for tantalum oxide phase formation. TaO2 single crystals with a diameter of about 2 nm embedded in an amorphous phase were identified. The dielectric properties of the hybrid thin films were derived from the characterization of Metal-Insulator-Metal (MIM) structures by current-voltage and capacitance-voltage measurements. I-V curves show a leakage current between 10 -12 and 10 -7 A and a constant capacitance in bias range ± 50 V.  For films with  1:1 and  4:1 molar ratio, the leakage current density ranges between 10 -9 - 10 -3 A/cm 2 and  10 -9 - 10 -4 A/cm 2 , and the limit of the current density goes to an electric field of ±1.2 MV/cm and ±2.5 MV/cm, respectively. In the case of films with 1:1 molar ratio, the applied voltage was up to 70 V in positive domain and no breakdown was observed for the dielectric layer. These results show higher current density for a larger voltage range, than the characteristics leakage current values reported for PMMA (10 -8 A/cm 2 ) at 0.3 MV/cm. The value of the permittivity ranges between 3.5 and 7.5 at 1 MHz, depending on the tantalum alkoxyde: MMA molar ratio, suggesting very promising future of these hybrid dielectric thin films for the fabrication of transparent TFTs, which can serve for next generation of transparent and flexible electronic devices.

 Dielectric Diffuseness And Conductivity Behavior Of Ba1-xCuxTi1-x(AlK)xO3 Nanoceramics Prepared By Chemical Route

Prasanta Dhak; A. Kundu; K. Pramanik; P. Pramanik; D. Dhak

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 492-500
DOI: 10.5185/amlett.2014.5752

Small amounts of Cu and Al-K substitution on the A and B site of BaTiO3, respectively resulting a solid solution of the type Ba1-xCuxTi1-x(AlK)xO3 (BCTAK) [x = 0.05, 0.10, 0.15, 0.20] have been investigated. The compositions have been prepared in the nanocrystalline range by chemical route. X-ray diffraction revealed the tetragonal (P4/mmm) phase. Average crystallite size and particle size were found to be in the range between 25 nm and 35 nm which were analyzed through X-ray diffraction and transmission electron microscopy respectively. A dielectric study of these compounds as a function of temperature suggested that with increasing substitution concentration the dielectric constant decreased and the Curie temperature shifted towards the lower temperature side. Discontinuous grain growth accompanied with excellent dielectric diffuseness was found with increasing concentration of substitution. The dielectric diffuseness γ was found to be maximum to 1.91 at the substitution of BCTAK x = 0.20. The activation energy, Ea was found to decrease along with an increase in conductivity with increasing substitution concentration in BCTAK.  

 Facile Growth Of Carbon Nanaotube Electrode From Electroplated Ni Catalyst For Supercapacitor

Visittapong Yordsri; Winadda Wongwiriyapan; Chanchana Thanachayanont

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 501-504
DOI: 10.5185/amlett.2015.SMS6

A facile growth of carbon nanotubes (CNTs) was facilitated by the use of direct-current plating technique for catalyst preparation. Ni nanoparticles (NPs) were deposited on Cu foil at different applied voltages of 1.0, 1.5 and 2.0 V. The Ni-deposited foil was subsequently used as catalyst for CNTs synthesis by chemical vapour deposition (CVD) method. CVD was carried out at 800 ºC using ethanol as carbon source. A voltage of 1.5 V was the optimum condition to deposit uniform Ni NPs that had a narrow size distribution of 55±3 nm, which in turn, yielded synthesized CNTs with a uniform diameter of approximately 60±5 nm with graphitic layers parallel to the CNTs axis. On the other hand, electroplated Ni at 1.0 V produced CNTs with graphitic layers at an angle to the CNTs axis, while electroplated Ni at 2.0 V produced curly CNTs with a wide distribution of diameters. These results show that Ni NPs size distribution could be controlled by electroplated voltage. Our observation was that Ni NPs with a narrow distribution of sizes and a uniform diameter is a key to uniform CNT synthesis. Furthermore, the synthesized CNTs electrode shows a faradic pseudo capacitance property, which can be attributed to the existence of oxidized Ni NPs. These results propose that the synthesized CNTs are promising materials for future super capacitor application. The optimization of ratio of Ni NPs and CNTs may improve the supercapacitors performance.  

 pH Responsive Curcumin/ ZnO Nanocomposite For Drug Delivery

Raman Dhivya; Marichamy Rajasekaran;Jamespandi Annaraj; Jothi Ranjani; Jeyaprakash Rajendhran

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 505-512
DOI: 10.5185/amlett.2015.5766

Curcumin is recognized as an important natural biomaterial which has a wide range of biological importance, unfortunately it lacks in bioavailability predominantly due to its poor aqueous solubility. The intention of the present investigation was to develop a novel nanocomposite of curcumin with ZnO nanoparticle in order to improve its aqueous-phase solubility and develop its efficiency on microbes and cancer cells. Therefore, we have constructed an aqueous solvable curcumin/ZnO nanocomposite from the insoluble commercial curcumin and poorly soluble ZnO nanoparticles, consequently enhancing its biological importance. The synthesized ZnO nanoparticles, nanocurcumin, and the nanocomposite were analyzed with transmission electron microscope (TEM), and X-ray diffraction (XRD) along with spectral techniques. The calculated average particle size of ZnO nanoparticle and nanocomposite from XRD was found to be 21.44 nm and 24.66 nm respectively. The TEM image reveals that this new nanocomposite was found to have narrow particle size of 53 nm. The observed results declared that the title nanomaterials showed excellent antibacterial activity against, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa, and Staphylococcus aureus. Their cytotoxicity performance against gastric cancer (AGS) cells was also carried out and observed that they showed concentration dependency. All the observed results declared that it has great potential for antibacterial and anticancer applications. The observed results of this investigation demonstrate that the present nano-conjugate can effectively deliver the antibacterial, anticancer drug curcumin towards the targeted biomolecules and hence appears to be a promising nano-formulation for chemotherapy and other biomedical applications after a series of in-vivo tests on animal models.

 Structural, Optical And Electrical Properties Of Cu(InGa)SeTe Device With The Varying Laser Pulses

Abhay Kumar Singh; R. Ganesan; Jong Tae Park

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 513-517
DOI: 10.5185/amlett.2015.5774

Next-generation high-performance heterojunction photovoltaic (PV) modules can be fabricated with an appropriate active layer material. Therefore, it is worth to examine physical properties of the recent developed Cu25(In16Ga9)Se40Te10 (CIGST) material for the potential photovoltaic application. This, report demonstrates the structural, optical and electrical properties of the 8000 and 16000 pulses deposited CIGST films on top of the ITO coated soda lime substrate (CIGST/ITO/substrate); whereas, the substrate temperature was 550 0 C. The 16000 pulses deposited thin film surface roughness (45 nm) and thickness (~1.4 μm) are obtained lower and higher than the 8000 pulses thin film. The cross sectional EDS elemental mapping also gives the fewer interlayer inclusions for the 8000 pulses deposited thin film. With the increasing thin films thicknesses a distinguishable UV/Visible peak shift toward the high wavelength side and enhance in optical energy band gap (1.13 and 1.2 eV) are noticed. Device fabricated (CIGST/ITO/substrate) with the 16000 pulses have a sharp current growth upto 2.0 × 10 -2 amp with a lower resistance under the applied voltage range 0-20V. The internal (IQE) and external (EQE) quantum efficiencies charge carriers transport for the fabricated devices are also discussed.

 Visible Light Driven Photocatalytic Degradation Of The Reactive Red-198, Methylene Blue And 3-chloro Phenol By Nb2O5@Zno: Synthesis And Characterization

K. Chennakesavulu; G. Ramanjaneya Reddy; S. Sanjeevi Prasath; S. Supriya; S. Sivanesan

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 518-526
DOI: 10.5185/amlett.2015.5776

In-situ synthesis of ZnO and Nb2O5 composites was carried out in alkaline medium. The obtained composites were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, diffuse reflectance UV-Vis spectrophotometer (DRS), Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area method, N2-sorption isotherms, Thermo gravimetric analysis (TGA), Particle size  and Field emission scanning electron microscopy (FESEM/EDX). The synthesized composite was used as photocatalyst in the degradation of reactive red-198 (RR), methylene blue (MB) and 3-chloro phenol (3CP) under visible light irradiation. The catalytic activity and removal percentage of dye was determined by the spectrophotometric method, it indicates high percentage of degradation for the ZnO:Nb2O5  composite. The kinetic parameters were found to obey pseudo-first order oxidation reaction, which may be due to the fixed amount of the catalyst and concentration of the dye solution. The recycled and purified composites of  ZnO:Nb2O5 was tested the catalytic activity and  was compared with that of the fresh catalyst.

 A Computational Investigation Of Oxygen Reduction Reaction Mechanisms On Si- And Al-doped Graphene: A Comparative Study

Mehdi D. Esrafili; Parisa Nematollahi

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 527-530
DOI: 10.5185/amlett.2015.5751

In this letter, the mechanisms of the oxygen reduction reaction (ORR) on Si- and Al-doped graphene have been investigated to understand the effect of doped graphene on the ORR and predict details of ORR pathways. Density functional theory (DFT) calculations were used to achieve the true mechanism pathways of ORR on the surfaces. Also, free energy diagrams for the ORR were constructed to provide the stability of possible intermediates in the electrochemical reaction pathways. At first stage, the adsorption of O2 molecule on both surfaces was studied with two possible configurations: atop (most stable) and bridge with the Eads of -60.6 and -72.4 kcal/mol, while for bridge site they were about -48.9 and -60.4 kcal/mol, respectively. Then, the most stable configuration (atop) was selected and the pathways formed after the adsorption of four atomic hydrogen to O2 molecule for both surfaces. These mechanisms were similar in both Si- and Al- doped graphene but there was a little difference in the obtained intermediates formed in each surface. In each pathway, the O2 dissociation reaction was neglected because it was unlikely to occur due to the high activation energy (> 45 kcal/mol). The results of this study show an easy and economic way to obtain Si- and Al-doped graphene as a non-metal catalyst for ORR at the cathode electrode in fuel cells.  

 Influence Of Laser Irradiation On The Optical Properties Of As40Se45Sb15 Thin Films By Thermal Evaporation Technique

Ramakanta Naik

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 531-537
DOI: 10.5185/amlett.2015.5753

 The present paper highlights the optical properties change in thermally evaporated As40Sb15Se45 amorphous film of 800 nm thickness with laser irradiation. The as-prepared and illuminated films were studied by X-ray diffraction, Energy dispersive X-ray analysis. The optical properties were calculated from the transmission spectra obtained from Fourier Transform Infrared Spectroscopy. The band gap is decreased by 0.22 eV due to photo induced effects causing photo darkening. The refractive index is found to be increased due to increase in structural disordering. These optical properties changes are due to the change of homopolar bond densities which can be seen from the core level peak shifting in XPS spectra. The optical constants such as refractive index, band gap of the material plays a major role in the preparation of the device for a particular wavelength. Selecting suitable pairs of chalcogenide glasses with different optical gaps, one can modify the parameters of the light sensitive layers and use them for optical recording.  

 Perspective Microscale Piezoelectric Harvester For Converting Flow Energy In Water Way

Krit Koyvanich; Pruittikorn Smithmaitrie; Nantankan Muensit

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 538-543
DOI: 10.5185/amlett.2015.SMS4

This work proposes an energy harvester that captures the mechanical energy caused by water flow and converts into an electrical energy through the piezoelectric effect. A flexible piezo-film has been used as a transducer in the energy harvesting system and the kinetic energy of the water flow is produced by using the vortex induced vibration technique. When placing in water way the transducer is fluctuating in the vortex of the fluid flow, producing the kinetic energy of 44 mW at a low fluid velocity of 6.8 m/s and low frequency of 0.4 Hz. This configuration generates a corresponding open-circuit voltage of 6.6 mV at a matching load of 1 MW, leading to the maximum output power of 0.18 mW. An efficiency power conversion of the harvesting system was evaluated to be about 4.4 %.  It is possible to use the proposed unit under gravitational force where there is a difference in the levels of the fluid no matter in water way or transporting parts such as petroleum pipes. However, rectifying the output voltage generated by the present micro generator is compulsory in order to feed small scale electronics and communication, for instance, wireless sensor networks. Furthermore, multiple arrays of the piezoelectric unit are also promising for delivering higher output power.  

 Mangnetoresistance Of Heavy Fermion-like Compound Ce(Ni1-xCux)2Al3

S. Yadam; Durgesh Singh; D. Venkateshwarlu; M. Gangrade; S. S. Samatham; V. Ganesan

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 544-547
DOI: 10.5185/amlett.2015.5768

CeNi2Al3 system is a potential candidate for low temperature thermoelectrics. Substitution studies, especially at the Ni site are considered to be of importance due to the drastic tuning of its physical properties. Resistivity in magnetic fields and thermoelectric power measurements of Cu doped CeNi2Al3 (x=0.0 to 0.4) system is reported in this investigation. This dense Kondo lattice system is investigated with an aim of understanding its basic transport mechanism. Negative magnetoresistance is seen for x=0.3 and 0.4 in the  magnetic field up to 14 T. Deviation from the Kondo behavior occurs at temperatures close to 2 K with a down turn in  resistivity. The nature of resistivity at low temperatures is investigated in view of the possible evidence for Fermi liquid behavior and also the formation of heavy Fermion in corroboration with specific heat studies. Doping dependence of linear diffusion coefficient and Sommerfeld coefficient of specific heat are analyzed and discussed in connection with the heavy Fermion formation. The results obtained show a promising trend in tuning these materials by way of Kondo route as well as by the substitution especially at the Ni site in the present system.  

 Energy Absorption Capacity Of Empty And Foam Filled Mild Steel Tube Under Low Strain Rate At Room temperature

Dipen Kumar Rajak; L. A. Kumaraswamidhas; S. Das

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 548-553
DOI: 10.5185/amlett.2015.5784

Aluminium foam is an isotropic porous metal of cellular structure in the order of 75-80 vol. % of the pores. In turn the novel mechanical, physical and chemical composition, properties depends on the density of foam, i.e. lies in between 0.4-2.4 g/cm 3 . Aluminium foam filled structures are used in collide, energy absorption, sound absorbing and vibration damping applications. In this article the compressive deformation behaviour of rectangular, square and round aluminium foam (LM 25 + 10wt% SiCp) filled and empty mild steel samples respectively are analyzed to identify the more energy absorption rate per unit volume in diverse strain rate by means of the compressive testing at room temperature. The experiments were performed on a universal testing machine the results showed that the round cross-section had more energy absorption than the rectangular and square cross section respectively. Also the amount of energy absorption will be greater with low foam density for round section tubes. We have seen that an increasing interest in using aluminium foams as inside the thin-wall mild steel tubes for maximum specific energy absorption rate. This work shows the admirable capability of aluminium alloy foam in applications in which it is essential to absorb compression energy.   

 Silicon Nitride Thin Films Deposited By Reactive Gas-timing Magnetron Sputtering For Protective Coating Applications

N. Khemasiri; N. Paleeya; D. Sae-tang Phromyothin; M. Horprathum; A. Sungthong; J. Nukeaw; S. Pratontep

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 554-559
DOI: 10.5185/amlett.2015.SMS5

Silicon nitride is a promising alternative to carbon based materials for protective coatings, owing to its compatibility with existing silicon-based microfabrication. The complexity of the fabrication processes and contaminations hamper fine-tuning to obtain desirable coating properties. We have explored the reactive gas-timing rf plasma sputtering technique for silicon nitride thin film deposition as an alternative method to fine-tune the film properties. The gas-timing technique controls the on-off sequence of the sputtering gas (Ar) and the reactive gas (N2) during deposition. We focus this investigation to the effect of the Ar:N2  gas timing ratio (10:0,  10:1,  10:3,  10:5,  10:7 and 10:10) on the composition, the morphology, the corrosion resistance, and the hardness properties of the films, in comparison to the films deposited by conventional reactive sputtering with Ar-N2 gas mixture. These deposited silicon nitride films were characterized by Auger electron spectroscopy, Raman spectroscopy, and atomic force microscopy. The chemical resistance was measured by the electrochemical corrosion test in sulfuric acid, while the hardness properties were obtained by nanoindentation. The results reveal that although the nitrogen content in the films increases only slightly when the N2 timing is prolonged, the corrosive current of the films decreases abruptly. A thin passivating oxidized layer is found to play a major role in the corrosion resistance. In contrast, the hardness properties exhibit a uniform variation with the N2 timing. The gas-timing sequence may induce morphological changes the underlying silicon nitride films. The highest hardness obtained by the gas-timing technique almost doubles that produced by the conventional mixed gas sputtering. Thus the reactive gas-timing technique suggests a new route to selectively control the properties of silicon nitride films with minor modification to existing microfabrication processes.

 Effect Of Electron Beam On Thermal, Morphological And Antioxidant Properties Of Kraft Lignin

N. Rajeswara Rao; T. Venkatappa Rao; S.V.S. Ramana Reddy; B. Sanjeeva Rao

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 560-565
DOI: 10.5185/amlett.2015.SMS2

Thermal, morphological and antioxidant properties of lignin irradiated with electron beam (EB) of doses 30, 60 and 90 kGy have been investigated by Electron spin resonance (ESR), Fourier transform infrared spectroscopy, Differential scanning calorimetry, Scanning electron microscope and Spectrophotometer techniques. ESR studies confirm the presence of poly-conjugated radicals in unirradiated lignin; whereas irradiated lignin posses both poly-conjugated and peroxy radicals. The peroxy radicals decay near the glass transition point on thermal heating while poly-conjugated radicals are stable even up to a temperature of 450K.  Presence of conjugated structures is confirmed by the presence of 1604 cm -1 absorption band whose concentration increases following radiation dose. Up to a radiation dose of 60 kGy the fall in glass transition temperature (Tg) is very slow, while at 90 kGy Tg decreased abruptly. The decrease in Tg is assigned to be due to intermolecular chain interactions or plasticization effect. Granular structure of lignin is found to be effected by EB irradiation. Cracks were generated on lignin granules on EB irradiation. Due to increase in poly-conjugation, amorphous nature and granular cracks the antioxidant property is observed to increase. The current research trends in lignin materials include modification of lignin, fabrication of biodegradable thermoset/thermoplastic and use of lignin as stabilizers and dispersants.