Fine Particles: Science and Technology

Abstract

Some readers may wonder about the reasons for having two issues focus on fine particles. Hopefully, this introduction and the articles to follow will offer the necessary justification.It is fully expected by everybody, professional or laie, that the properties of matter will change if its chemical composition is altered. It is less frequently recognized that many characteristics of materials can be dramatically affected by varying dimensions, yet countless examples in everyday life clearly demonstrate such phenomena. Consider water in droplet form. Driving in rain creates little problem, providing the car has working windshield wipers. In contrast fog, which consists of droplets of much smaller size, represents one of the major hazards in transportation. Obviously, the optical properties of the same matter have greatly altered with diminution. In another example, it is well known that finely dispersed carbon is an excellent adsorbent, a property used in gas masks and in many industries as a purifying agent. Large-sized lumps of such carbon would be useless in these applications.The effect of particle size on properties of materials can be readily understood from a simple consideration. The total energy of any System, (Etot), consists of two contributions, the internai energy, Ei, and the surface energy, Ei.