Lee M. Smith

Polymer Surface Dynamics

Classical surface chemistry assumes that solid surfaces are rigid, immobile, and at equilibrium. These assumptions allow one to probe adsorption and wetting or contact angle processes purely from the point of view of the liquid phase, because one assumes that the solid phase does not in any way respond, reorient, or otherwise change in the different liquid environments. Although such assumptions may be partially correct for truly rigid solids, they are generally inappropriate for polymers (see also Chapter 7).

The Contact Angle and Interface Energetics

Information on the outermost few angstroms of solid surfaces is very difficult to obtain. One of the most sensitive methods known for obtaining true surface information is solid/liquid/vapor (S/L/V) or solid/liquid/liquid (S/L/L) contact angles. These methods are unique in that the equipment required is relatively simple and inexpensive. Although interpretation of the results obtained is dependent on a number of assumptions, each of which is somewhat controversial, a first-order interpretation is possible and has proven to be very useful in practically all areas of surface science and engineering. Most of the surface science texts briefly referred to in Chapter 1 contain one or more chapters on surface tension, capillarity, or contact angle methods. In addition, a number of the monographs and review serials cited in Chapter 1 also contain chapters on the contact angle technique.

Fiber-coupled high-power external-cavity semiconductor lasers for real-time Raman sensing

High-power, external-cavity semiconductor lasers with narrow bandwidth and fiber-coupled output are designed and constructed. An output power of 540 mW is coupled out of a 100-mum multimode fiber with coupling efficiency of 72% when the laser is operated at 1.1 A. The emission linewidth is as narrow as 22 GHz, and the wavelength is tunable from 779.7 to 793.0 nm. Application of such lasers to remote real-time Raman sensing of materials is also demonstrated.

Raman Scattering Sensor for On-Line Monitoring of Amines and Acid Gases

Sulfur and CO2 removal from hydrocarbon streams and power plant effluents are a major problem. The sulfur is normally in the form of H2S. These two acid gases are scrubbed using aqueous amine solutions that are difficult to control with conventional technology. Process Instruments Inc. developed Raman scattering technology for on-line, real-time monitoring of amine streams to improve their efficiency in scrubbing H2S and CO2 from hydrocarbon streams and power plant effluents. Improved control of amine and acid gas concentrations will allow refineries, natural gas processes and power plants to more efficiently scrub Sulfur and CO2, saving energy, time and financial resources.