Effect of Magnet Shapes on Metal Contamination Removal

Foreign metal removal is a key process in the quality control of food and pharmaceutical industries. Previously, foreign metal removal involved the use of metal detectors. However, in recent years, magnet separators have been used to capture small metal particles and to improve the manufacturing yield when installed with previous metal detectors. Currently, most foreign metal material is austenitic stainless steel because product process equipment are manufactured using the same in order to make them corrosion proof. SUS304 and SUS316L are used commonly. Small metal particles adhere to the equipment by sliding and other processes thus contaminating the equipment. Austenitic stainless steels are not magnetized; however, weak magnetization is observed through martensite transformation during sliding and collisions. However, it is not easy to remove small stainless steel particles in production processes that involve powder flow. In this study, we investigated the removal rate of small stainless steel particles by three magnets of different shapes under the same conditions.

Single-atom catalysis: a new field that learns from tradition

Much of industrial chemical processing (in the petrochemicals industry, for example), and a great deal of laboratory chemical synthesis, involves catalysts that both lower the energy barrier to reaction and may help steer a reaction along a particular path. Traditionally, catalysts have come in two classes: heterogeneous, typically meaning that the catalyst is an extended solid; and homogeneous, where the catalyst is a small molecule that shares a solvent with the reactants. In heterogeneous catalysis, the reaction generally takes place on a surface, involving molecules attached there by covalent bonds. Homogeneous catalysts are often organometallic compounds, in which a metal atom or small cluster of atoms supplies the active site for reaction. In recent years, these distinctions have become somewhat blurred thanks to the advent of single-atom catalysis, where the catalytic site consists of a single atom (as in many homogeneous catalysts) attached to or embedded in a surface. The emergence of this field might be regarded as the logical conclusion of the use of ‘supported metal clusters’—small metal particles of nanometer scale and below, containing perhaps hundreds, tens or just a few atoms. It has became clear that such clusters can sometimes provide greater product selectivity and activity than macro-sized particles or powders of the same metal, partly because the active sites might be atoms at particular locations (such as edges and corners) in the nanoscale particles. By reducing their scale down to the level of single atoms, one can optimize these properties. At the same time, the potential uniformity of the atoms’ environments makes such catalysts more amenable to rational design and modeling to understand mechanism. This field represents an appealing blend of fundamental chemistry and physics—from the quantum-mechanical level upwards—and applied research aimed at producing many of the products vital to society, such as fuels and materials. Researchers in China have been strongly active in this field in recent years (see, for example, refs [1–5]). Jean Marie Basset of the King Abdullah University of Science and Technology in Thuwal, Saudi Arabia, is one of the leading practitioners in the area, and National Science Review spoke to him about the development and prospects of the field.

Analysis of Small Metal Particles

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.