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.
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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
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TL;DR: A mixture of cubic and hexagonal polytypes of diamond were identified in this paper, and larger particle sizes were observed at lower reactor pressure and higher C to O atomic ratios, while other ratios produced graphite, soot and amorphous carbon phases.
Abstract: Diamond particles 10–500 nm in diameter were produced by microwave‐assisted combustion of acetylene in oxygen. Both premixed and diffusion flame configurations were investigated. A mixture of cubic and hexagonal polytypes of diamond were identified. Larger particle sizes were observed at lower reactor pressure and higher C to O atomic ratios. C to O atomic ratios between 0.83 and 1.0 produced crystalline diamond powder while other ratios produced graphite, soot, and amorphous carbon phases. Diamond formation was not observed when reaction pressures were above 150 Torr.
49 citations
48 citations
TL;DR: In this article, a direct method of producing ultra-fine nitride and carbide powders of 20 to 40 nm by arc plasma in a controlled atmosphere (with ammonia or methane gas) is described.
Abstract: A direct method of producing ultra-fine nitride and carbide powders of 20 to 40 nm by arc plasma in a controlled atmosphere (with ammonia or methane gas) is described. The powders produced were SiC, TiC, WC (+W2C), AIN and Si3N4. Other nitrides and carbides may also be produced using this method. Special attention was paid to the production conditions of silicon nitride.
46 citations
TL;DR: In this article, a simple technique for fabricating Sn nanocrystals in thin SiO2 film using low-energy ion implantation followed by thermal annealing is described.
Abstract: This letter reports on a simple technique for fabricating Sn nanocrystals in thin SiO2 film using low-energy ion implantation followed by thermal annealing. These Sn nanocrystals have excellent size uniformity and position controllability. Their average diameter is 4.8 nm with a standard deviation of 1.0 nm. Most of the Sn nanocrystals reside at the same depth. The lateral edge-to-edge spacing between neighboring Sn nanocrystals is fairly constant: about 3 nm. A narrow as-implanted ion distribution profile and the effect of the SiO2–Si interface are considered to contribute to the size uniformity and position controllability. The features of these nanocrystals will open up new possibilities for novel devices.
45 citations
TL;DR: In this article, a spray-ICP-based ZrO2-SiO2 system was investigated in connection with particle growth and phase change caused by heat treatment, and it was shown that ZRO2 and SiO2 mutually block particle growth.
Abstract: Ultrafine powders of the ZrO2-SiO2 system prepared by spraying aqueous mixed solutions of ZrO(NO3)2·2H2O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO2 (t-ZrO2) and amorphous SiO2 (a-SiO2).a-SiO2 alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO2 converted to monoclinic ZrO2 (m-ZrO2) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO2 anda-SiO2 exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO2 converted tom-ZrO2, and its amount decreased with an increase in SiO2 content. At 1400° C particle growth occurred, and the round particles of ZrO2 were dispersed in ana-SiO2 glass medium. These results indicate that ZrO2 and SiO2 mutually block particle growth, and that SiO2 contributes to the quenching oft-ZrO2 by keeping the particles of ZrO2 within the critical particle size oft-ZrO2.
42 citations