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
More filters
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
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
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
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
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
More filters
TL;DR: The surface resistances of the ion-exchanged and reduced glasses range from 0.15ohm/square to 4.1 ohm/square depending on the glass composition as mentioned in this paper.
Abstract: Electrically conducting layers have been induced in some alkali-containing silicate glasses by subjecting them to a Na+⇌Ag+ ion-exchange reaction followed by a reduction treatment in hydrogen. The surface resistances of the ion-exchanged and reduced glasses range from 0.15ohm/square to 4.1 ohm/square depending on the glass composition. Most of the layers give TCR values around 2000 ppm/K. The microstructural studies of the ion-exchanged and reduced layers confirm that such high surface conductances arise due to the formation of continuous chains of metallic silver and bismuth droplets in a glass matrix.
24 citations
TL;DR: In this article, self-assembled monolayers (SAMs) of α,ω-dithiols were prepared on (111)-oriented gold substrates and showed a blocking effect toward electron exchange between the gold substrate and the electroactive species in the solution.
Abstract: Cadmium sulfide (CdS) nanoparticles were prepared using the Aerosol-OT (AOT)/heptane inverse-micelle method. The particle size was controlled by changing the [H 2 O]/[AOT] ratio in the preparation process to be ca. 3 nm, which was estimated from their absorption maximum (ca. 385 nm) and absorption edge (ca. 450 nm) in heptane solutions. Self-assembled monolayers (SAMs) of α,ω-dithiols were prepared on (111)-oriented gold substrates. They were highly stable in aqueous solutions and showed a blocking effect toward electron exchange between the gold substrate and the electroactive species in the solution. Mono- and multi-layers of CdS nanoparticles were prepared by immersing the SAM-covered gold substrates in a heptane solution containing CdS particles. Infrared reflection-absorption spectra revealed that CdS particles on SAMs were surrounded by AOT and that a sequential immersion procedure led to the alternately layered structure of CdS particles and dithiol molecules.
24 citations
TL;DR: In this article, the dielectric properties of cosputtered metal-insulator nanocomposite films with metal volume fraction above the metal-inulator transition were measured in the frequency range between 20 Hz and 30 MHz.
Abstract: Dielectric measurements were done on cosputtered metal-insulator nanocomposite films with metal volume fraction above the metal-insulator transition, in the frequency range between 20 Hz and 30 MHz. At intermediate and high frequency, the dielectric function can be qualitatively described in terms of the percolation theory. In the low-frequency region, we observe a sharp relaxation-type increase of the real part of dielectric constant with decreasing frequency, while the imaginary part is dominated by dc conductivity. We suggest that the low-frequency behavior may be due to a combination of metallic and tunneling conduction in the system.
23 citations
TL;DR: In this paper, a radio-frequency (r.f.) thermal plasma system was developed that overcomes both the low power efficiency and the unstable plasma commonly used, and the main plasma used for preparing ultra fine β-SiC powder was operated stably by the superposition of a small plasma, which worked as the ignitor and stabilizer of a main plasma.
Abstract: A new radio-frequency (r.f.) thermal plasma system has been developed that overcomes both the low power efficiency and the unstable plasma commonly used. The key features of this system are the application of all solid type r.f. power supply units and the superposition of a small r.f. — plasma on a main r.f. — plasma. A high power efficiency of 75% was obtained with the all solid type r.f. power supply units of 30 kW–3 MHz set. The main plasma used for preparing ultra fine β-SiC powder was operated stably by the superposition of a small plasma, which worked as the ignitor and the stabilizer of a main plasma. This new system, that is, the dual r.f. — torch system, has been used to produce ultrafine and ultrapure β-SiC powder. Pure phase of β-SiC powder in the range of 10 to 50 nm was prepared from the stoichiometric reactant composition of CH4 and SiH4. The reaction mechanism was also discussed based on the plasma diagnostics.
23 citations
23 citations