OXIDATION OF TiAl,Ni AND Fe IN A DYNAMIC ENVIRONMENTAL SEM

IntroductionInmaterialscience,differentmicrostructuresofthesamematerialsmayinducediversebehaviorsanddifferentcharacteristics.Westwood(1988)showed,asanexample,thatthetreatmentofaluminumsurfacewithcommercialphosphoricacidproducedmechanicallyinterlockedoxide搘hiskers?approximately10nmindiameterand400nminlength,whichmechanicallyinterlocked.Thismicro-structurecankeepsuchaconglomeratebondedoverconsiderablerangesofstressandtemperature.Inahumidatmosphere,especiallythatcontainingchlorine,however,suchox…     

EXTENDING THE KNOWLEDGE BASE OF CHEMICAL ENGINEERING

The obvious current reversion to micro-scale investigations in basic chemical engineering, combined with the need, of a quite different nature, in the rapid growth of high added-value and small-lot functional materials, have been pointing to an area not yet sufficiently covered by the unit operations, transport phenomena and chemical reaction engineering. Although it is difficult to define accurately this area, a cursory scan of the activities already in progress has revealed a few common attributes: multi-phased (structured), multi-scaled, multi-disciplined, nonlinear, needs for resolution to reductionism-solvable subsystems, and pervasive in the process industry. From these activities, the present paper drafts a tentative scheme for studying the related problems: first to dissect a problem into various scales -- spatial, temporal or otherwise as best suits the case in hand -- in order to identify pertinent parameters which are then organized into model formulations. Together with inter-scale model formulations, a zoom-in/zoom-out process is carried out between the scales, by trial-and-error and through reasoning, to arrive at a global formulation of a quantitative solution, in order to derive, eventually, the general from the particular.     

The hierarchical structure of chemical engineering

Around the turn of the present century,scholars began to recognize chemical engineering as a com-plex system,and have been searching for a convenient point of entry for refreshing its knowledge base.From our study of the dynamic structures of dispersed particles in fluidization and the resultingmulti-scale method,we have been attempting to extend our findings to structures prevailing in othermultiphase systems as well as in the burgeoning industries producing functional materials.Chemicalengineering itself is hierarchically structured.Besides structures based on space and time,such hier-archy could be built from ChE history scaled according to science content,or from ChE operation ac-cording to the expenditure of manpower and capital investment.     

Morphological Changes of Oxide Grains During Oxidation of Pure Iron in an Environmental Scanning Electron Microscope

For modeling particles-gas reactions in terms of the morphology of nascent solid reaction products, a technique using the environmental scanning electron microscope (ESEM) was developed to monitor the in situ oxidation of iron. Experimental conditions of the oxidation experiments were selected as the temperature range of 500–750°C and the oxygen partial pressure range 10^–4–45 Pa. The evolution of nucleation and growth of oxide whiskers or grains on the surface of iron specimens under the ESEM was recorded. The characteristics of some specimens were further examined after oxidation by post-analysis. Three sets of experimental results and other relative micrographs are shown. In the light of the surface morphology and textures of the oxide growths in the micrographs, their growth mechanism and reaction kinetics are discussed. Finally, a plausible physical model for oxidation of iron is suggested.     

Message from the Editor in Chief

PARTICUOLOGY is gratified with its accomplishments over the past 6 years. From its modest beginnings, PARTICUOLOGY has developed into an influential journal, publishing best papers in original research, engineering and application in the overall field of particle science and technology.