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Articles you may be interested inGeneration of frustrated liquid crystal phases by mixing an achiral nematic-smectic-C mesogen with an antiferroelectric chiral smectic liquid crystalThe effects of vacuum-deposited SiO x alignment layers on the thermal generation offocal conic centers in a smectic A liquid crystal were investigated using controlled thermal cycles. Surface defects were found to promote focal conic formation. Focal conic density increases with cooling rate for a given alignment layer, and with the deposition angle of the alignment layer for a fixed cooling rate. An attempt was made to fit these findings to heterogeneous nucleation theory in an effort to better understand the effects of selected thermodynamic properties on the focal conic formation process PACS numbers: 64.70.Ew, 65.90. + i, 82.60.Nh

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This chapter presents adhesion mechanisms in relation to bonding of kenaf fibers. Adhesion mechanisms are dependent on the surface characteristics of various materials. In principle, there are three components for adhesion to occur viz: substrates, adhesive matrices, and interfaces. Being porous, the bond formation in natural fibers generally involves three main adhesion mechanisms: mechanical interlocking, adsorption theory, and chemical bonding. Surface interaction between resin polymer matrices and kenaf fibers is an area that requires more concerted efforts. The bonding characteristics of kenaf were evaluated by determining the wettability through contact angle measurement and the buffering capacity. The characterization of the interface between fiber and matrix provides information on the adhesion strength. The diffusion model explains the concept of adhesion by the compatibility between polymers and the movements that occur in the polymer chains. Chemical bonding is the most widely accepted mechanism for explaining adhesion between two surfaces in close contact.

Proper adhesion of metallization patterns to their substrates is a crucial aspect to overall circuit reliability. The critical role of adhesion is accentuated in situations where the substrate is flexible, soldering or bonding to the metallization is required, or extensive ultrasonic cleaning is necessary. We have developed a non-contact, nondestructive method for detecting local changes in the adhesion of the metal foil to the substrate by monitoring the amplitude of resonant modes of the substrate excited electromagnetically.The advantage of electromagnetic excitation is that the generation is confined to the metallized pattern and this technique probes the impedance match between metal film and substrate. Using design guidelines similar to that used in magnetic recording heads, we have developed EMAT's that incorporate soft magnetic materials t o allow higher spatial resolution and higher flux density than could be obtained without.