Table of Contents - Volume 11 Number 2

Doping by diffusion is still one of acceptable and important methods that have essential technological applications. A theoretical approach to study diffusion in semi-conductors is introduced. The diffusion equation together with Fick's law and mass balance equation are solved to obtain the concentration function and the mass penetration depth using Fourier Series expansion technique. Doping of indium, phosphorus, gallium and Arsenic in Silicon as illustrative examples are given.

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The tungsten disulfide (WS₂) thin films, considered as inert, non-toxic, non-corrosive lubrication that is resistant to most fuel solvents, is the best solid lubricant for general industry. In this paper, WS₂ thin films were deposited on steel and silicon <110> type substrates by DC sputtering methods with optimized experimental conditions and parameters. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were employed to characterize the surface morphology and determine the geometrical size of WS₂ lamellae or microtubes. The investigation showed that both SEM and AFM analysis revealed oriented WS₂ crystalline lamellae on silicon substrate while they are entangled on the steel substrate. This result leads to say precociously that the WS₂ thin films deposition depend on the substrate type. Moreover, using the AFM results, we could determine the average lamella (or microtube) size which has from 200 nm to 500 nm in width and from 1mm to 1.5mm in length. The EDS tool allows attaining the composition of deposited WS₂ where the tungsten and the disulfide represent about 40 and 55%, respectively.

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Molecular imaging (MI) is an in vivo assessment of characterization and quantitatively measurement of biological processes at the molecular level. Determination of pathologies of malfunctioned tissues without invasive biopsies or surgical procedures, early detection, monitoring of treatment process and visualization of cell trafficking are advantages of this approach. One example of basic requirement of MI is high affinity molecular probe that acts as the source of image contrast. Recent advances in nanotechnology have developed the use of nanoparticles as MI probe. Optical molecular imaging is one of the main categories of molecular imaging with great potentials for in vivo cell trafficking.  Fluorescent nanoparticles are a major group of nanoparticles in optical molecular imaging. Dye-doped, quantum dots and up conversion particles are three classes of fluorescent nanoparticles. This paper reviews the basic principles of molecular imaging based on nanoparticles focusing on the optical molecular imaging. The characteristics of dye-doped nanoparticles, their  as well as of  that are reviewed in this paper.

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Metal matrix composites have superior mechanical properties in comparison to metals over a wide range of operating conditions. This make them an attractive option in replacing metals for various engineering applications. This paper provides a literature review, on machining of Aluminium metal matrix composites (AMMC)especially the particle reinforced Aluminium metal matrix composites. This paper is an attempt to give brief account of recent work to predict cutting parameters &surface generated in AMMC.By suitably selecting the machining parameters, machining of AMMC can be made economical.

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The current –voltage data of the metal –insulator semiconductor Schottky diode are simulated using thermionic emission diffusion equation taking into account the inter facial layer parameters.The computed current – voltage data are fitted into ideal thermionic emission diffusion equation to see the apparent effect of interfacial parameters on current transport.In presence of interfacial layer the Schottky contact behave as an ideal diode of apparently high barrier height. The behavior of apparent height and  ideality factor with the presence of inter facial layer is discussed.

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Though semiconductor technology has advanced significantly in miniaturization and processor speed the “ideal” nonvolatile memory - memory that retains information even when the power goes is still elusive. There is a large demand for non-volatile memories with the popularity of portable electronic devices like cell phones and note books. Semiconductor memories like SRAMs and DRAMs are available but, such memories are volatile. After the advent of ferroelectricity many materials with crystal structures of Perovskite, pyrochlore and tungsten bronze have been derived and studied for the applications in memory devices. Ferroelectric Random Access Memories (FeRAM) are most promising. They are nonvolatile and have the greater radiation hardness and higher speed. These devices use the switchable spontaneous polarization arising suitable positional bi-stability of constituent ions and store the information in the form of charge. This paper is focused on the synthesis and characterizations of BiFeO₃ and xCrFe₂O₄-(1-x) BiFeO₃ nanoceramics which are most promising FeRAM materials. The effect of various-dopant-induced changes in structural, dielectric, ac impedance, ferroelectric hysteresis, mechanism of the dielectric peak broadening and frequency dispersion have been addressed. It also deals with low temperature processing technique of those nanoceramics which has high dielectric and ferroelectric properties. These studies can be further extended to reinforce BiFeO₃ and CrFeO₄ materials with carbon nanotubes to obtain conductive composites using appropriate techniques.

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Films of polyaniline and polyaniline–ZnO composites were synthesized by spin coating. The spin coated films were deposited over glass substrate. In order to confirm the dispersion quality and the size of the dispersed ZnO, Transmission electron microscopy was done. The TEM images show that ZnO nanoparticles were spherical in shape. Dark imaging mode confirmed these particles in solid phase and revealed the uniform distribution of the particles in the PANI matrix. The absorption peaks in FTIR spectra of PANI–ZnO composite film were found to shift to higher wave number when compared with pure PANI. The observed shifts were attributed to the interaction between the ZnO particle and PANI molecular chains. A change in the value of lattice parameter of ZnO as confirmed through the X ray diffraction method in the composite  indicated the presence of interaction between ZnO particles and matrix. The dielectric study of PANI and PANI–ZnO composites demonstrated a significant decrease in the value of dielectric constant after the incorporation of the ZnO nanoparticles in the polymer matrix.

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Microstructural studies on FeCl3 doped Hydroxypropyl methyl cellulose (HPMC)/Poly vinyl pyrrolidone (PVP) blend films were carried out using X-Ray diffraction studies. The XRD data revealed that the crystalline regions of the HPMC/PVP blend film decreases up to a certain percentage of FeCl3 and then increases. Electrical conductivity studies on these doped films suggest complex formation due to doping which affects microstructure and also ac conductivity of polymer films. All these results were analyzed and explained on the basis of micro structural modification of HPMC/PVP blends as function of dopant concentration.

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The urethane polymers of castor oil (COPU) are used in many commercial applications but one of the major limitations of these polymers is their inherent flammability and poor mechanical properties. Polymers containing phosphorous groups belong to the fire retardants, and when blended with castor oil based polyurethane improves the latter’s fire retardant properties. Present work, deals with the synthesis of a monomer bis (m-hydroxy phenyl) phenyl phosphate (BHPPP) and its related polyurethanes. Characterization of the monomer and polyurethanes are discussed. Blending of the polyurethanes with COPU in different proportions improves both the flame retardant and mechanical properties of the COPU.

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In present research work, nanocomposite films of organic polymeric matrix polymethylmethacrylate (PMMA) and its nanocomposites with inorganic nanosized filler, namely titania (TiO₂) nanoparticles, have been prepared and characterized thermally. TiO₂ nanoparticles have been synthesized by chemical route method. Formation of nanoparticles and their average size have been confirmed by Transmission Electron Microscopy (TEM). The average particle size of the nanoparticles has been found to be ~19 nm. PMMA-TiO₂ nanocomposites with different TiO₂ weight percent (e.g. 1%, 2% and 3%) have been prepared by solution casting technique. These prepared samples have been investigated by means of Differential Scanning Calorimetry (DSC) at different heating rates. The effect of heating rate and TiO₂ weight percent on glass transition temperature (T_g) and melting temperature (T_m) have been studied. It has been found that T_g and T_m increases as TiO₂ content increases in PMMA matrix. An effort has also been made to calculate activation energy at glass transition temperature using Kissinger, Moynihan and Lasocka relations.

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