Particle material properties

From the physical picture, it is evident that photophoretic effects in FFF are influenced by a remarkable diversity of particles material properties, including geo-... 

Shock-compression science originated during and after World War II when experimental facilities for creating planar shock waves were developed, along with prompt instrumentation techniques enabling shock velocity and particle velocity measurements to be made. The main thrust of shock-compression science is to understand the physics and to measure the material properties which govern the outcome of shock-compression events. Experiments involving planar shock waves are the most useful in shock-compression science. 

The use of Ni-base superalloys as turbine blades in an actual end-use atmosphere produces deterioration of material properties. This deterioration can result from erosion or corrosion. Erosion results from hard particles impinging on the turbine blade and removing material from the blade surface. The particles may enter through the turbine inlet or can be loosened scale deposits from within the combustor. 

A dependence of both crystal and impeller material properties as well as the probability of crystal-impeller collision on fine particle generation rate has also been demonstrated. Thus the relative effects of impact, drag and shear forces responsible for crystal attrition have been identified. The contribution of shear forces to the turbulent component is predicted to be most significant when the parent particle size is smaller than a 200 pm while drag forces mainly affect larger crystals, the latter being consistent with the observations of Synowiec etal. (1993). 

It is a pleasure for us who are friends, colleagues, and collaborators, to offer this contribution to a volume published in honor of Yngve Ohm s bS " birthday. For most of his career, Yngve has been interested in response properties of various systems to various probes, and we offer this contribution in that spirit. The Generalized Oscillator Strength, the subject of this paper, is the materials property that describes the response of a medium to swift particle, and thus, perhaps, an appropriate subject for this volume. Mostly, we are happy to take this opportunity to thank Yngve for his help, inspiration, and friendship over the years. 

For freely suspended bioparticles the most likely flow stresses are perceived to be either shear or normal (elongation) stresses caused by the local turbulent flow. In each case, there are a number of ways of describing mathematically the interactions between turbulent eddies and the suspended particles. Most methods however predict the same functional relationship between the prevailing turbulent flow stresses, material properties and equipment parameters, the only difference between them being the constant of proportionality in the equations. Typically, in the viscous dissipation subrange, theory suggests the following relationship for the mean stress [85] ... 

The critical moisture content is a complex function of material properties, particle size (the critical moisture content is higher for large granules), and rate of drying during the constant rate period (the lower the rate, the less the critical moisture content). Therefore, the critical moisture content is difficult to predict and should be determined experimentally for the selected drier and conditions of drying. 

The process conditions will influence the particle degradation by generating the stress on the individual particles on the one hand and by affecting the material properties and consequently the particle friability on the other. 

Aburatani, Y., Tsuru, K., Hayakawa, S. and Osaka, A. (2002) Mechanical properties and microstructure of bioactive ORMOSILs containing silica particles. Materials Science and Engineering C, 20, 195-198. 

There is great interest in the electrical and optical properties of materials confined within small particles known as nanoparticles. These are materials made up of clusters (of atoms or molecules) that are small enough to have material properties very different from the bulk. Most of the atoms or molecules are near the surface and have different environments from those in the interior—indeed, the properties vary with the nanoparticle s actual size. These are key players in what is hoped to be the nanoscience revolution. There is still very active work to learn how to make nanoscale particles of defined size and composition, to measure their properties, and to understand how their special properties depend on particle size. One vision of this revolution includes the possibility of making tiny machines that can imitate many of the processes we see in single-cell organisms, that possess much of the information content of biological systems, and that have the ability to form tiny computer components and enable the design of much faster computers. However, like truisms of the past, nanoparticles are such an unknown area of chemical materials that predictions of their possible uses will evolve and expand rapidly in the future. 

---