Volume 3, Issue 1, January 2012

Intelligent Nanomaterials For Prospective Nanotechnology

Ashutosh Tiwari

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 1-1
DOI: 10.5185/amlett.2012.13001

Nanomaterials play very prominent role in physical, chemical and biomedical engineering applications due their high surface energies. Also the electronic configuration of atoms within the materials is very important since this principally detrmines the type of bonding and thus electrical, optical, luminescent, mechanical and magnetic properties. At nanoscale dimensions, materials exhibit entirely different properties as compared to thieir bulk counterpart. Noble metallic nanoparticles/nanostructures exhibit interesting feature of localised surface plasmon resonant; absorption can be tuned from ultraviolet region to infrared region of electromagnetic spectrum and this field has been developed to deliver potential applications in photonics, optoelectronics, optical-data storage, solar cells, filters, sensors not to mention the considerable scope in medical engineering, such as DNA labeling, tumor and cancer therapy etc.

Facile Fabrication Of Uniform Silica Films With Highly Luminescent Hydrophobic QDs Through Direct Phase Transfer

Zhongsen Yang; Guangjun Zhou

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 2-7
DOI: 10.5185/amlett.2011.6273

Hydrophobic CdSe/ZnS quantum dots (QDs) were embedded in a transparent functional silica film with thickness of 10-15 µm using a sol-gel method. Namely, the QDs were prepared through an organic synthesis using hexadecylamine as a capping agent. When partially hydrolyzed 3-aminopropyltrimethoxysilane (APS) sol was mixed with a toluene solution of the QDs, the ligand exchange occurred. With subsequent addition of pure H2O, the QDs were transferred into APS sol accompanied with a phase separation. The APS sol with the QDs was condensed to adjust its’ viscosity by the evaporation of solvents at room temperature. After that, functional SiO2 films with tunable QD concentrations and high photoluminescence (PL) efficiency were fabricated by a spin-coating strategy using the condensed APS sol with the QDs. The absorbance at first absorption peak of the QDs revealed a liner increase against the QD concentrations in these films. The PL peak wavelength and full width at half maximum of PL spectra of the QDs in these films remained unchange compared with their initial values in toluene. The QDs were mono-dispersed in these films according to transmission electron microscopy observation. Due to unique properties, these films are utilizable for further applications in optical and electronic devices.

Electrical Properties Of Complex Tungsten Bronze Ferroelectrics; Na2Pb2R2W2Ti4V4O30 (R = Gd, Eu)

Piyush R. Das; B. Pati; B.C. Sutar; R.N.P. Choudhury

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 8-14
DOI: 10.5185/amlett.2011.4252

Complex impedance analysis of new tungsten bronze ferroelectric vanadates, Na2Pb2R2W2Ti4V4O30 (R = Gd, Eu), was carried out on samples prepared relatively at low temperature using a mixed-oxide technique. The formation of the materials under the reported conditions has been confirmed by an X-ray diffraction technique. A preliminary structural analysis exhibits orthorhombic crystal structure of the materials at room temperature. The electrical properties of the materials have been studied using ac impedance spectroscopy technique. Detailed studies of impedance and related parameters exhibit that the electrical properties of the materials are strongly dependent on temperature, and bear a good correlation with their microstructures. The temperature dependence of electrical relaxation phenomenon in the materials has been observed. The bulk resistance, evaluated from complex impedance spectra, is found to decrease with rise in temperature, exhibiting a typical negative temperature co-efficient of resistance (NTCR) – type behavior similar to that of semiconductors. A small contribution of grain boundary effect was also observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation. The ac conductivity spectra exhibit a typical signature of an ionic conducting system, and are found to obey Jonscher’s universal power law.

A Quantum Chemical Study On Structural And Electronic Properties Of New Pi-conjugated Polymer Named Poly(4-methylthioazole-2,5-diyl)

M. Amine; M. Hamidi; S.M. Bouzzine; A. Amine; M. Bouachrine

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 15-20
DOI: 10.5185/amlett.2011.6274

Organic conjugated polymers based on heterocylic ring exhibit semiconducting properties associated with the π molecular orbitals delocalized along the polymer chains. These materials have attracted much interest for potential applications in optoelectronic devices due to their unique electronic and photonic properties. Recently, interesting studies have been devoted to the synthesis, characterization, physical and chemical properties and variety of these materials. In this work, a quantum-chemical investigation on the structural and opto-electronic properties of new polymer named poly (4-methylythioazole-2.5- diyl)s is carried out. We present a detailed DFT study of geometrical structures and electronic properties of this organic material. Calculated results are compared with experimental data and based on such comparison we try first, to propose an oligomer model and then, to obtain a qualitative understanding the properties of polymer. We discuss the influence of chain length on structural and optoelectronic properties. The numerical predictions are compared to our experimental results. The ground state optimized structures and energies are obtained using the molecular orbital theory and the DFT (B3LYP/6-31G (d)) calculations.

Structural, Magnetic And Optical Studies Of nickel Ferrite Thin Films

Gagan Dixit; J.P. Singh; R.C. Srivastava; H.M. Agrawal; R.J. Chaudhary

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 21-28
DOI: 10.5185/amlett.2011.6280

In the present work, structural, morphological, magnetic and optical properties of nickel ferrite thin films having different thickness are reported. All the films were deposited on Si (100) substrate by pulsed laser deposition technique. Thicknesses of the films determined by x-ray reflectivity vary from 62 to 176nm as the deposition time varies from 16 min to 40 min. The films were characterised by x-ray diffractogram, Fourier transform infrared (FTIR) and Raman spectroscopy for structural and phase confirmation. FTIR and Raman spectra confirm mixed spinel nature of nickel ferrite. Surface morphology is studied by Atomic force microscopy. All the films have granular nature. Magnetic properties were studied by vibrating sample magnetometer and magnetic hysteresis curves were recorded for all the films at room temperature and at10K. At 10K, saturation magnetisation was found to increase while coercivity deceases with thickness. The results are explained on the basis of anisotropy induced by cation inversion and strain. Optical properties were studied by UV-vis reflectance spectra. The value of optical band gap (5.7eV) was found to be independent of thickness of the film.

Synthesis Of Monodispersed Barium Sulphate Nanoparticles Using Water-benzene Mixed Solvent

V. Ramaswamy; R.M. Vimalathithan; V. Ponnusamy

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 29-33
DOI: 10.5185/amlett.2011.4240

Precipitation is a hopeful process for nanoparticle production due to rapid expedient, highly economic and uncomplicated. Barium sulphate nanoparticles were prepared through precipitation process via barium chloride and sodium sulphate as the reagents in water-benzene reaction medium. Eight different compositions of mixed solvents, including pure water, 20 vol. %, 30 vol. %, 50 vol. %, 70 vol. %, 80 vol. %, 90 vol. % and 95 vol. % of benzene were practiced. The effects of the volume percentage of benzene in the aqueous medium on the resultant barium sulphate nanoparticles were scrutinized. The products were characterized through X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive X-ray Spectrum (EDX) and Fourier Transform Infrared Spectroscopy (FTIR) techniques. The synthesized nanoparticles are well dispersed and they exhibit an orthorhombic structure and spherical in morphology with an average size of 35.9 nm. From this we establish, water-benzene mixed solvent inhibits barium sulphate nucleation growth.

Non-linear Elastic Properties Of Single-walled Carbon Nanotubes

S.K. Verma; Giridhar Mishra; D.K. Pandey; R.R. Yadav

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 34-37
DOI: 10.5185/amlett.2011.4251

In this paper we have calculated the second and third order elastic constants of SWCNTs at room temperature using the interaction potential model. The approach with some modification has been established for the SWNTs nanomaterials. Further the ultrasonic properties have been determined with help of the non-linear elastic constants and other related parameters for characterization. It is observed that tube length dependent thermal conductivity is prominent reason behind the ultrasonic attenuation.

Dry Sliding Wear Behaviour Of Spray Formed ZrSiO4 Reinforced Al-Si-Sn Alloy

Rashmi mittal; Devendra Singh

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 38-43
DOI: 10.5185/amlett.2011.5258

The wear behaviour of Al-12Si alloy and Al-12Si-Sn/ZrSiO4 composite prepared by spray forming technique has been investigated under dry sliding conditions at different loads and temperatures. The wear rate of spray formed composite was significantly lower than that of as cast Al-12Si alloy. Paricle size of ZrSiO4 was varied from 53 to 105 µm and the amount of Sn was taken 5 and 10 %. Smaller particles of ZrSiO4 were able to reduce the wear rate up to more extent as compared to that of bigger particles in the same matrix. On increasing the amount of Sn the wear rate decreases.

Sol-gel Processing and characterization Of nanometersized (Ba, Sr) TiO3 ceramics

Kavita Verma; Seema Sharma; Dhananjay K Sharma; Raju Kumar; Radheshyam Rai

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 44-49
DOI: 10.5185/amlett.2011.5264

 Ba0.5Sr0.3TiO3 (BST 70/30) nanopowders have been prepared by the modified sol-gel method using barium acetate, strontium acetate and titanium isopropoxide as the precursor. The formation mechanism, phase evolution, and particle size have been investigated using TG/DTA, XRD, and SEM. The fine particles of the nano-powders calcined are homogeneous and well-dispersed and their narrow size distribution is about 15–25 nm. The as-formed gel was dried at 2000 C and then calcined in the temperature range 6500 C to 8500 C for crystallization. Phase evolution during calcination was studied using X-ray diffraction (XRD) technique which exhibited cubic crystal structure with perovskite phase. Sintering of the pellet was performed at 9500 C and the study on the dielectric relaxation and the ac electrical conductivity behavior of modified Barium titanate, Ba0.5Sr0.3TiO3 ferroelectric ceramic exhibit that these are thermally activated process.

Synthesis Of Bismuth Telluride Nanostructures By refluxing Method

Srashti Gupta; S. Neeleshwar; Vinod Kumar; Y.Y. Chen

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 50-54
DOI: 10.5185/amlett.2011.7285

Bismuth telluride (Bi2Te3) nano particles were prepared by refluxing method in different conditions such as varying concentration of KOH and reaction timings. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements have been performed for structural and phase formation studies. The nanoparticles are showing the same structure of bulk except broadening of peak confirmed by XRD. The reaction time and KOH concentration are the key parameters to control the morphology and size of the particles. As the concentration of KOH increases, the particle size decreases from 23 to 15 nm and with increasing reaction time, nanorod like structures (~100 nm length and ~ 20 nm diameter) are formed.

Thickness Uniformity And Microstructure Of Disc shape Spray Formed Al-Si-Pb Alloys

Rashmi Mittal; Aruna Tomar; Devendra Singh

Advanced Materials Letters, 2012, Volume 3, Issue 1, Pages 55-63
DOI: 10.5185/amlett.2011.5261

Spray forming technique was employed to produce a near net-shape disc of Al-Si-Pb alloys. Different substrate distances and inclination angles were studied to obtain the disc shape preforms. The substrate was also offset by 40 mm from the atomizer axis in case of 15 and 30 degree inclination angles. Microstructures were investigated in different regions of the preforms. Results exhibited equiaxed grains of primary Al and Si was present within these grains and along the grain boundary. The size of the Al grains was 20-30 µm and size of Si particles was sub-micron to 5 µm. The size of Pb particles varied from sub-micron to 20 µm and it was uniformly dispersed throughout the aluminum phase.