Surfaces of wool scales are imaged using a scanning force microscope (SFM) and a field emission scanning electron microscope (FESEM). Atomic force microscope (AFM) images of wool fiber surfaces can be correlated with FESEM micrographs to provide complementary views of surface features. The AFM images are analyzed for scale height; on average there is a 21% increase when changing from air to water. The variability of scale height changes is large, and a model involving both swelling and scale movement has been proposed. Lateral force microscope (LFM) images show complementary information to topographic AFM images and reveal the effects of surface treatment not available with other imaging techniques. Such images of treated wool surfaces reveal major inhomogeneities in friction, which are interpreted as differences in chemical composition.Images of the fine details on the surfaces of wool fibers have traditionally been obtained using the scanning electron microscope (SEM) [ 24,25 ] . Due to their insulating nature, a conductive metal coating (typically 10 nm of gold) must be applied to fibers before they are inserted into the microscope vacuum. The image resolution detail is thus limited to 10 nm at best, and the fibers cannot be chemically treated for further studies after SEM imaging.Two recent developments have offered major improvements for imaging the surfaces of wool fibers. The field-emission SEM (FESEM) provides a sufficiently bright, focused electron beam to achieve satisfactory image quality at about 1 kilovolt beam energy, at which net charging of the wool surface does not occur. With fine metal coatings, detail down to the level of a few nanometers can be resolved on suitable samples. In contrast, the scanning force microscope (SFM), comprising an atomic force microscope (AFM) and a lateral force microscope (LFM), scans a fine mechanical probe across the sample surface, &dquo;feeling&dquo; the topography and the frictional forces [ 18 ] . Resolution is limited by the surface roughness of the sample being imaged and by the effective diameter of the tip (typically 100 nm). Thus, while atomic resolution can be achieved through the interaction of atomic sized protrusions on the tip with very smooth, flat surfaces ( e.g., on mica), the resolution on a rough surface will be determined by the typical feature heights and their spacing relative to the scanning tip dimensions.The SFM is very useful for imaging biological samples because it is nondestructive to the sample and can operate in both air and liquid. For wool, which is frequently exposed to both air and aqueous environments during processing, this is particularly important because of the well known sensitivity of many of its properties to moisture [ 1 ]]. In particular, felting of wool is worse in water, and there is a common belief that the scales are more prominent when wet [ I 4 ] . The advent of the environmental SEM has produced results indicating that the scales probably are more pronounced when wet, but not under saturated water vapor conditio...

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Heat transfer and fluid flow in a novel class of silicon carbide water-cooled milli-channel heat sinks were investigated. The heat sinks were manufactured using an extrusion freeform fabrication (EFF) rapid prototyping technology and a water-soluble polymer material. Rectangular heat exchangers with 3.2 cm×2.2 cm planform area and varying thickness, porosity, number of channels, and channel diameter were fabricated and tested. The perchannel Reynolds number places the friction coefficients in the developing to developed hydrodynamic regime, and showed excellent agreement with laminar theory. The overall heat transfer coefficients compared favorably with the theory for a single channel row but not for multiple rows.

Heat transfer and fluid flow in a novel class of water-cooled milli-channel heat sinks are investigated. The heat sinks are manufactured using an extrusion freeform fabrication (EFF) rapid prototyping technology and a water-soluble polymer material. EFF permits the fabrication of geometrically complex, three-dimensional structures in non-traditional materials. Silicon carbide, SiC, is TEC-matched to silicon and is an ideal material for heat exchangers that will be mounted directly to heat dissipating electronic packages. This paper presents experimental results on the heat transfer and flow in small SiC heat exchangers with multiple rows of parallel channels oriented in the flow direction. Rectangular heat exchangers with 3.2 cm × 2.2 cm planform area and varying thickness, porosity, number of channels, and channel diameter were fabricated and tested. Overall heat transfer and pressure drop coefficients in single-phase flow regimes are presented and analyzed. The per channel Reynolds number places the friction coefficients in the developing to developed hydrodynamic regime, and showed excellent agreement with laminar theory. The overall heat transfer coefficients for a single row SiC heat exchanger compared favorably with a validation heat exchanger fabricated from copper, however the heat transfer coefficient in multiple row heat sinks did not agree well with the laminar theory.

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