Nonequilibrium Dynamics of Chemically Active Particles

Chemically active motion is ubiquitous in many nature and artificial systems where each unit can move directionally by converting chemical energy into kinetic energy.Since the systems are driven by activity far from equilibrium,many dynamical behaviors forbidden in equilibrium systems may be induced.Nonequilibrium dynamics of such systems is then a hot multidisciplinary topic with great challenges.Here,we review our recent theoretical advances in some fundamental problems at the single active particle level,the collective behavior level,as well as in systems where active particles act as baths.

SINO-GERMAN WORKSHOP ON CHEMICAL AND PHYSICAL INTERACTIONS BETWEEN PARTICLES AND FLUIDS

1. Introduction Supported by the Sino-German Center for Research Promotion, and organized jointly by the National Natural Science Foundation of China (NSFC) and the German Research Foundation (DFG), the third Sino-German workshop on particle fluid systems was held on Oct. 24-31, 2004 in Beijing, China, following the two previous successful workshops held on Aug. 30-31,1999 in Hamburg, Germany (Li and Werther, Chem. Eng. Technol., 23(4), 378, 2000) and May 18-19, 2001 in Beijing, China (Li, Ge, Werther and Bruhns, Chem. Eng. Technol., 24(11), 1097, 2001). Thirty-one scientists from China, Germany, Japan and The Netherlands came together for interdisciplinary discussion over the core problem of multi-phase reaction systems in the name of "Chemical and Physical Interactions between Particles and Fluids".

Influence of intrinsic parameters on the particle size of magnetic spinel nanoparticles synthesized by wet chemical methods

The synthesis of magnetic spinel ferrites at the nanoscale is a field of intense study, because the meso- scopic properties enable their novel applications. Spinel nanoparticles have a promising role because of their extraordinary properties compared with those of micro and macro scale particles. Several colloidal chemical synthetic procedures have been developed to produce monodisperse nanoparticles of spinel let- rites and other materials using sol-gel, co-precipitation, hydrothermal, and microemulsion techniques. To improve the synthesis method and conditions, quality and productivity of these nanoparticles, understanding the effect of extrinsic （pH, temperature, and molecular concentration） and intrinsic parameters （site preferences, latent heat, lattice parameters, electronic configuration, and bonding energy） on the particle size during synthesis is crucial. In this review, we discuss the effect of the intrinsic parameters on particle size of spinel ferrites to provide an insight to control their particle size more precisely.

3D CFD modeling of acetone hydrogenation in fixed bed reactor with spherical particles

Acetone hydrogenation in a fixed bed reactor packed with spherical catalyst particles was simulated to study the effects of inlet gas velocity and particle diameter on hydrogenation reaction. Computational results show that the catalyst particles in the reactor are almost isothermal, and the high isopropanol concentration appears at the lee of the particles. With the increase of inlet velocity, the outlet isopropanol mole fraction decreases, and the total pressure drop increases drastically. Small diameter catalyst particles are favorable for acetone hydrogenation, but result in large pressure drop.

A novel coated-particle design and fluidized-bed chemical vapor deposition preparation method for fuel-element identification in a nuclear reactor

Particle coating is an important method that can be used to expand particle-technology applications. Coated-particle design and preparation for nuclear fuel-element trajectory tracing were focused on in this paper. Particles that contain elemental cobalt were selected because of the characteristic gamma ray spectra of 60Co. A novel particle-structure design was proposed by coating particles that contain elemental cobalt with a high-density silicon-carbide （SiC） layer. During the coating process with the high-density SiC layer, cobalt metal was formed and diffused towards the coating, so an inner SiC–CoxSi layer was designed and obtained by fluidized-bed chemical vapor deposition coupled with in-situ chemical reaction. The coating layers were studied by X-ray diffractometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy techniques. The chemical composition was also determined by inductively coupled plasma optical emission spectrometry. The novel particle design can reduce the formation of metallic cobalt and prevent cobalt diffusion in the coating process, which can maintain safety in a nuclear reactor for an extended period. The experimental results also validated that coated particles maintain their structural integrity at extremely high temperatures （～1950 °C）, which meets the requirements of next-generation nuclear reactors.

Growth of SiC as Binder to Adhere Diamond Particle and Tribological Properties of Diamond Particles Coated SiC

The purpose of this work was to grow SiC as binder to adhere diamond particles to graphite substrate by low pressure chemical vapor deposition （LPCVD） at 1100 ℃ and 100 Pa using methyltrichlorosilane （MTS： CH3SiCl3） as precursor. The composite coatings on graphite substrates were analyzed by various techniques. Results show that a dense SiC coating with a cloud-cluster shape was formed both on the diamond particles and the substrate after deposition, The thermal stress （290.6 MPa） strengthened the interfacial bonding between the diamond particle and the SiC coating, which is advantageous for the purpose of adhering diamond particles to graphite substrate. The applied load of sliding wear test was found to affect not only the friction coefficient, but also the wear surface morphology. With increasing loads, the asperity penetration was high and the friction coefficient decreased.

Haze insights and mitigation in China: An overview

The present article provides an overview of the chemical and physical features of haze in China, focusing on the relationship between haze and atmospheric fine particles, and the formation mechanism of haze. It also summarizes several of control technologies and strategies to mitigate the occurrence of haze. The development of instruments and the analysis of measurements of ambient particles and precursor concentrations have provided important information about haze formation. Indeed, the use of new instruments has greatly facilitated current haze research in China. Examples of insightful results include the relationship between fine particles and haze, the chemical compositions and sources of particles, the impacts of the aging process on haze formation, and the application of technologies that control the formation of haze. Based on these results, two relevant issues need to be addressed： understanding the relationship between haze and fine particles and understanding how to control PM2.5.