Microstructured industrial applications

Classical surface and colloid chemistry generally treats systems experimentally in a statistical fashion, with phenomenological theories that are applicable only to building simplified microstructural models. In recent years scientists have learned not only to observe individual atoms or molecules but also to manipulate them with subangstrom precision. The characterization of surfaces and interfaces on nanoscopic and mesoscopic length scales is important both for a basic understanding of colloidal phenomena and for the creation and mastery of a multitude of industrial applications. 

Improved characterization of the morphological/microstructural properties of porous solids, and the associated transport properties of fluids imbibed into these materials, is crucial to the development of new porous materials, such as ceramics. Of particular interest is the fabrication of so-called functionalized ceramics, which contain a pore structure tailored to a specific biomedical or industrial application (e.g., molecular filters, catalysts, gas storage cells, drug delivery devices, tissue scaffolds) [1-3]. Functionalization of ceramics can involve the use of graded or layered pore microstructure, morphology or chemical composition. 

The issue of fluids with microstructure keeps coming up. We should simply take as a given that that is an essential part of modern chemical engineering. There are at least 12 people in this room whose research is primarily concerned with the mechanics of fluids with microstructure. Clearly we re there, and we re going to be there for quite some time. The industrial applications are obvious. 

K. Schubert, W. Bier, J. Brandner, M. Fichtner, C. Franz, G. Linder, Realization and testing of microstructure reactors, micro heat exchangers and micromixers for industrial application in chemical engineering, in W. Ehrfeld, I.H. Rinard, R.S. Wegeng (Eds.), Proceedings of 2nd International Conference on Microreaction Technology (IMRET 2), AIChE, New Orleans, 1998, p. 88. 

Technological uses of conducting polymers may be classified as follows (1) Use based on bulk conductivity of the pure conducting polymer or a blend of the conducting polymer with a conventional polymer (2) Use based on the electrochemical redox properties of the polymer (3) Use based on the formation of an excited state of the polymer (4) Use based on the morphology/microstructure of the polymer. Each of these categories will be summarized below. This summary is based in part on a ery recent concise evaluation of industrial applications of conducting polymers,. ... 

At an industrial applications, the TBC coverings can be produced by thermal spraying method in the air plasma spray (APS) atmosphere, at lowered pressure low pressure plasma spray (EPPS) from APS or by the electron beam physical vapor deposition method (EB-PVD), these are all dry-route processes. By these processes, coatings have different microstructures lamellar microstructure consisting... 

It is easily anticipated that flow microreactors can enjoy industrial applications by virtue of inherent advantages based on their microstructure and flow nature. Significant progress in flow-microreactor-system-controlled polymerization to obtain structurally well-defined polymers has already been made to meet the demands of the chemical industry. The lack of need for cryogenic conditions for anionic polymerizations may enable commercial production. Some pilot plants have already been built and tested to examine the feasibility and durability of polymerization in flow microreactors. For example, a microchemical pilot plant... 

The dispersions of sohd particles in viscous fluids can be found in a wide range of natural and industrial applications. There are some interactiOTis determining the microstructure of the suspension, such as interactions arising from Brownian, interpaiticle, and flow-induced forces. In the equilibrium state, there is a balance between Brownian and interparticle forces. Under the influence of flow, hydrodynamic interactions become craisiderable, in comparison with thermal and interparticle forces. 

The efforts of industry and academia have led to the successful installation of microreactors in existing production plants. In the following, a few examples of the industrial application of microstructured devices are given. 

In summary, the experiments of Barringer and Bowen demonstrate clearly that substantial benefits can be achieved in sintering and microstructure control when the powder quality is carefully controlled and the powder packing is homogeneous, i.e., when careful attention is paid to the processing steps that precede firing. However, this fabrication route is not currently used in many industrial applications where mass production and low cost are important considerations. 

The colloidal techniques described in Chapter 4 provide considerable benefits for the control of the packing uniformity of the green body. The production of green bodies with uniform microstructure from a fully stabilized colloidal suspension of spherical, fine, monodisperse particles has not been incorporated into industrial applications where mass production is desired and fabrication cost is a serious consideration. Colloidal techniques, however, play an important role in the low-cost forming methods of slip casting and tape casting, as well as in the less commonly used methods of eletrophoretic deposition and gel casting. 

R. Wechsung, in Microstructure Components in Polymers. First industrial application, MST news 14/95, MicroParts... 

---