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Journal ArticleDOI

Electrical Properties of Nanocomposites

TL;DR: In this article, the state-of-the-art for synthesizing composites of nanometer-sized phases (metal, semiconductor or ceramic) dispersed in a matrix has been reviewed.
Abstract: The present state-of-the-art for synthesizing composites of nanometer-sized phases (metal, semiconductor or ceramic) dispersed in a matrix has been reviewed. Both dc and ac electrical properties of different nanocomposites synthesized have been described. The theoretical models used to explain the experimental results are discussed. It appears that there is a need to have newer theoretical models developed to understand the ac electrical properties of metal-ceramic nanocomposites.
Citations
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Journal Article
TL;DR: In this paper, the self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superiattices (colloidal crystals) is demonstrated.
Abstract: The self-organization of CdSe nanocrystallites into three-dimensional semiconductor quantum dot superiattices (colloidal crystals) is demonstrated. The size and spacing of the dots within the superlattice are controlled with near atomic precision. This control is a result of synthetic advances that provide CdSe nanocrystallites that are monodisperse within the limit of atomic roughness. The methodology is not limited to semiconductor quantum dots but provides general procedures for the preparation and characterization of ordered structures of nanocrystallites from a variety of materials.

36 citations

Journal ArticleDOI
TL;DR: This paper reviews and enhances numerical models for determining thermal, elastic and electrical properties of carbon nanotube-reinforced polymer composites and validated by comparison with various experimental datasets reported in the recent literature.
Abstract: This paper reviews and enhances numerical models for determining thermal, elastic and electrical properties of carbon nanotube-reinforced polymer composites. For the determination of the effective ...

26 citations

Journal ArticleDOI
TL;DR: In this paper, the presence of nickel particles of size ∼20nm in the nano-pores of an alumina-silica nanocomposite has been detected using X-ray diffraction and transmission electron micrograph.

14 citations

Journal ArticleDOI
TL;DR: In this paper, the average particle size of molybdenum carbide is in the range of 5-15 nm and the detailed XRD analyses coupled with thermodynamic arguments show that reduction of ammonium moly bdate is predominantly by in situ generated hydrogen.
Abstract: Molybdenum carbide has been formed in the silica gel matrix by the in situ reduction of ammonium molybdate. The average particle size of molybdenum carbide is in the range of 5-15 nm. The detailed XRD analyses coupled with thermodynamic arguments show that reduction of ammonium molybdate is predominantly by in situ generated hydrogen.

2 citations

Journal ArticleDOI
TL;DR: The low frequency (20 Hz to 1 MHz) ac conductivity and magnetoconductivity behavior of ceramic nanocomposite (Ni-SiO2) at low temperature down to 77 K are reported in this article.
Abstract: The low frequency (20 Hz to 1 MHz) ac conductivity and magnetoconductivity behaviour of ceramic nanocomposite (Ni-SiO2) at low temperature down to 77 K are reported. The frequency dependent conductivity followed the power law, σ(ω) ∝ ω s . The fractional exponent s is a function of temperature and was found to increase with increasing temperature. This type of variation may be attributed to small polaron hopping. A peak present in the loss tangent indicates the presence of a Debye relaxation process. The magnetoconductivity of the samples is positive, which strongly depends on frequency. A firm theoretical explanation of frequency dependent magnetoconductivity is still lacking.

1 citations

References
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Journal ArticleDOI
TL;DR: In this article, a glass-metal nanocomposites involving copper and nickel, respectively, have been synthesized in bulk form by hot pressing sol-gel derived silica-metal nanoparticle composite powders.
Abstract: Glass-metal nanocomposites involving copper and nickel, respectively, have been synthesized in bulk form by hot pressing sol-gel derived silica-metal nanoparticle composite powders. The particle diameters range from 9 to 17.5 nm. The specimens exhibit the characteristic behavior of the metallic species in their nanocrystalline forms.

33 citations

Journal ArticleDOI
TL;DR: In this paper, the absorption spectra of PbI2 clusters incorporated into zeolite cages are reported, and the absorption bands whose energies depend on the size of the cage.

33 citations

Journal ArticleDOI
TL;DR: In this paper, a spin-dependent tunneling was investigated for nanostructured ferromagnetic tunnel junctions, in which an insulating SiO2 matrix is sandwiched between two soft ferramagnetic electrodes, an Fe/Co80Pt20 as a bottom electrode and a Co9Fe as a top electrode.
Abstract: Spin-dependent tunneling has been investigated for nanostructured ferromagnetic tunnel junctions, in which an insulating nanostructured film made of layered hard ferromagnetic Co80Pt20 nanoparticles dispersed in an insulating SiO2 matrix is sandwiched between two soft ferromagnetic electrodes, an Fe/Co80Pt20 as a bottom electrode and a Co9Fe as a top electrode. The junctions investigated have three tunnel barriers and exhibited tunnel magnetoresistance of 9% at room temperature with a small resistance at a low field. The charging energy of the particles with an average diameter of 7 nm was estimated to be 45 meV from the temperature dependence of the resistance. Coulomb blockade was not observed for the junctions because of the low junction resistance.

32 citations

Journal ArticleDOI
TL;DR: In this paper, the dc electrical resistance of films of Ag and Al soot which consists of fine particles has been measured between 1.5 and 300 K. The resistance is constant in the low temperature region, while it increases with temperature above a certain point.
Abstract: The dc electrical resistance of films of Ag and Al soot which consists of fine particles has been measured between 1.5 and 300 K. The specimens are prepared by the gas evaporation method. The resistance is constant in the low temperature region, while it increases with temperature above a certain point. By analyzing the temperature dependence of the resistance, the Debye temperature for fine particles \(\varTheta_{P}\) was estimated. It was about 1/2∼2/3 of that of bulk metal for Al of the particles of size 150∼200A and 3/4∼5/6 for Ag of 100∼300A.

32 citations

Journal ArticleDOI
TL;DR: In this paper, the molar ratio of sodium to titanium was 400 at 750 degrees C for 2 h with diameters of 10-50 nm and lengths of several micrometers.
Abstract: Rutile TiO2, nanowhiskers have been synthesized by annealing a precursor powder in which NaCl and Ti(OH), particles were homogeneously mixed. The precursor powder was prepared by mixing three kinds of inverse microemulsions (mu E) containing TiCl4, aqueous solution, ammonia, and NaCl aqueous solution, respectively, followed by washing with acetone. Annealing temperature and packing density of Ti(OH), in the precursor powder influenced the formation of rutile nanowhiskers. The optimum temperature was 750 degrees C. TiO2, nanowhiskers obtained by annealing a precursor powder in which the molar ratio of sodium to titanium was 400 at 750 degrees C for 2 h had diameters of 10-50 nm and lengths of several micrometers. They were straight rods with square cross sections, and the side surfaces were composed of four equivalent (110) planes.

32 citations