China Particuology最新文献

Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced (OR) powders were compared with one from water-atomized (WA) powder. The green specimens were sintered at temperatures from 800 to 1000 °C in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR − 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.

A two-step synthesis was used to control the shape of silver nanoparticles. First, a few spherical silver nanoparticles, ∼10 nm in size, were prepared via reduction of Ag⁺ ions in aqueous Ag(NH₃)₂NO₃ by poly(N-vinyl-2-pyrrolidone) (PVP). Then, in a subsequent hydrothermal treatment, the remaining Ag⁺ ions were reduced by PVP into polyhedral nanoparticles, or larger spherical nanoparticles formed from the small spherical seed silver nanoparticles in the first step. The morphology and size of the resultant particles depend on the hydrothermal temperature, PVP/Ag molar ratio and concentration of Ag⁺ ions. By using UV–visible spectroscopy (UV–vis), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD), the possible growth mechanism of the silver nanoparticles was discussed.

Rutile TiO₂ (0 0 1) quantum dots (or nano-marks) in different shapes were used to imitate uncleaved material surfaces or materials with rough surfaces. By numerical integration of the equation of motion of cantilever for silicon tip scanning along the [1 1 0] direction over the rutile TiO₂ (0 0 1) quantum dots in ultra high vacuum (UHV), scanning routes were explored to achieve atomic resolution from frequency shift image. The tip–surface interaction forces were calculated from Lennard–Jones (12-6) potential by the Hamaker summation method. The calculated results showed that atomic resolution could be achieved by frequency shift image for TiO₂ (0 0 1) surfaces of rhombohedral quantum dot scanning in a vertical route, and spherical cap quantum dot scanning in a superposition route.

This paper presents the energy requirements for mechanical production of fine and ultra-fine particles in comminution. Recent approaches for effective size reduction and energy saving in comminution are described, viz., (a) development and application of new mills/classifiers, (b) adjustment of the bead characterization in stirred bead mills, (c) hybrid comminution systems with roller-press and media mill, (d) assisted methods, and (e) simulation.

An efficient numerical algorithm for computing the light scattering by a coated sphere is proposed. The calculation of relevant functions by different recurrence algorithms is discussed. The new algorithm avoids the numerical difficulties, which give rise to significant errors encountered in practice by prior methods. Exemplifying results such as extinction efficiency, scattering efficiency, light scattering intensity as well as calculation speed are provided. The results show that this algorithm is efficient, fast, numerically stable and accurate.

A nanohybrid sensor of nanosized TiO₂-coated carbon black particles, prepared by sol–gel technology for the detection of NO₂ gas, has been developed. The response of the electric resistance of the hybrid sensor to NO₂ concentration is investigated, showing that the sensitivity of the hybrid sensor is raised as certain ratio of the TiO₂ content in the sensor. Easy and cheap to fabricate, the hybrid TiO₂/carbon black promises to be a practical sensor for detecting NO₂ gas.

Magnetically stabilized beds are packed beds subjected to fluid-driven deformation and controlled by magnetically induced interparticle forces. This paper deals with magnetically stabilized beds as deformable porous media and describes their application in dust filtration. The Richardson–Zaki scaling law, $U/U_{\text{t}}={\epsilon }^n$ describes the field controlled bed expansion via the exponent n, that yields a porosity-dependent flow length scale $d_{\text{c}}=d_{\text{p}}{\epsilon }^n$. The paper addresses two issues: (i) deformation characteristics by assuming homogeneous bed expansion and a definition of bed variable flow length scale; (ii) dust filtration characteristics such as filter coefficient, specific deposit and filtration efficiency expressed in terms of the variable flow length scale and illustrated by experimental data.