다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

A Benchmark Study on the Thermal Conductivity of Nanofluids

Nanofluids—a simple product of the emerging world of nanotechnology—are suspensions of nanoparticles (nominally 1–100 nm in size) in conventional base fluids such as water, oils, or glycols. Nanofluids have seen enormous growth in popularity since they were proposed by Choi in 1995. In the year 2011 alone, there were nearly 700 research articles where the term nanofluid was used in the title, showing rapid growth from 2006 (175) and 2001 (10). The first decade of nanofluid research was primarily focused on measuring and modeling fundamental thermophysical properties of nanofluids (thermal conductivity, density, viscosity, heat transfer coefficient). Recent research, however, explores the performance of nanofluids in a wide variety of other applications. Analyzing the available body of research to date, this article presents recent trends and future possibilities for nanofluids research and suggests which applications will see the most significant improvement from employing nanofluids.

Small particles, big impacts: A review of the diverse applications of nanofluids

Introduction to Nanotechnology

Ultrasonic properties at the nanoscale in some metals

We synthesized gold (Au) nanoparticles via a rapid chemical route by reducing chloroauric acid by trisodium citrate. TEM micrographs revealed that particles were spherical with well-defined lattice structures and most of them were within the size range of 8–12 nm. A single surface plasmon resonance peak observed at 525 nm indicated the uniformness of the spherical morphology of the particles. XRD analysis showed that the particles were well crystalline. An impedance-based humidity sensor device was fabricated for depositing these gold nanoparticles in their non-functionalized state and the sensor revealed fast response time of 54 s, high stability and repeatability, and an impressive average sensitivity of 7.57 MΩ/% RH within the humidity range of 10–95%. SEM micrographs revealed the presence of cracks on the film surface and our analysis of the sensing mechanism correlated the sensitivity and the surface cracks along with smaller particle sizes. Our results show that gold nanoparticles without further functionalization are able to perform as a well-performing humidity sensor.

Non-functionalized Au nanoparticles can act as high-performing humidity sensor

Herein, we report the synthesis of two dimensional, flake-like nanostructures of polyaniline and their nanocomposites in an epoxy matrix with different particle loadings. An anomalous enhancement in the dielectric constant is observed for the synthesized nanocomposites due to the 2D flake-like structure of the polyaniline fillers at room temperature over the wide AC frequency range of 1 Hz to 107 Hz.

High dielectric response of 2D-polyaniline nanoflake based epoxy nanocomposites

Aqueous suspensions of multi-walled carbon nanotubes (MWCNTs + deionised water) have been synthesised. Carbon nanotubes (CNTs) were derived by chemical vapour deposition (CVD). Transmission electron microscopy (TEM) measurements show the formation of MWCNTs. Three samples of CNT-based aqueous nanofluids having MWCNT concentrations of 0.01 vol%, 0.03 vol% and 0.05 vol% were prepared with the help of ultrasonic irradiation. A very small amount of sodium dodecyl sulfate (SDS) was used as a surfactant to minimise the agglomeration of the MWCNTs. An effective enhancement in thermal conductivity was observed at different temperatures. The obtained results are explained with percolation theory.

Raja Ram Yadav

Papers

Ultrasonic properties at the nanoscale in some metals

Non-functionalized Au nanoparticles can act as high-performing humidity sensor

High dielectric response of 2D-polyaniline nanoflake based epoxy nanocomposites

Temperature Dependent Heat Transfer Performance of Multi-walled Carbon Nanotube-based Aqueous Nanofluids at Very Low Particle Loadings

Non-destructive Evaluations of Gallium Nitride Nanowires