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Stable Microstructures (stable + microstructure)
Selected AbstractsSuperplastic Behavior of Fine-Grained ,-Silicon Nitride Material under CompressionJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2000Guo-Dong Zhan The deformation behavior of a hot-pressed, fine-grained ,-Si3N4 ceramic was investigated in the temperature range 1450°,1650°C, under compression, and the results for strain rate and temperature dependence of the flow stress are presented here. The present results show that the material is capable of high rates of deformation (,10,4,10,3 s,1) within a wide range of deformation temperatures and under a pressure of 5,100 MPa; no strain hardening occurs in the material, even at slow deformation rates, because of its stable microstructure; Newtonian flow occurs, with a stress exponent of approximately unity; and the material has activation energy values for flow in the range 344,410 kJ·mol,1. Grain-boundary sliding and grain rotation, accommodated by viscous flow, might be the mechanisms of superplasticity for the present material. [source] Eutectic Gallium-Indium (EGaIn): A Liquid Metal Alloy for the Formation of Stable Structures in Microchannels at Room Temperature,ADVANCED FUNCTIONAL MATERIALS, Issue 7 2008Michael D. Dickey Abstract This paper describes the rheological behavior of the liquid metal eutectic gallium-indium (EGaIn) as it is injected into microfluidic channels to form stable microstructures of liquid metal. EGaIn is well- ;suited for this application because of its rheological properties at room temperature: it behaves like an elastic material until it experiences a critical surface stress, at which point it yields and flows readily. These properties allow EGaIn to fill microchannels rapidly when sufficient pressure is applied to the inlet of the channels, yet maintain structural stability within the channels once ambient pressure is restored. Experiments conducted in microfluidic channels, and in a parallel-plate rheometer, suggest that EGaIn's behavior is dictated by the properties of its surface (predominantly gallium oxide, as determined by Auger measurement s); these two experiments both yield approximately the same number for the critical surface stress required to induce EGaIn to flow (,0 .5,N/m). This analysis,which shows that the pressure that must be exceeded for EGaIn to flow through a microchannel is inversely proportional to the critical (i.e., smallest) dimension of the channel,is useful to guide future fabrication of microfluidic channels to mold EGaIn into functional microstructures. [source] Synthesis and characterization of photopatternable epoxy hybrid materials for the fabrication of thick and thermally stable microstructures with a high aspect ratioJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Kyung Ho Jung Abstract Photosensitive cycloaliphatic-epoxy oligosiloxane was synthesized using a nonhydrolytic sol,gel reaction for the fabrication of thick and thermally stable microstructures with high aspect ratios. Its formation was confirmed by 29Si and 1H nuclear magnetic resonance spectroscopy, small-angle neutron scattering, and Fourier transform infrared spectroscopy. Photocuring of cycloaliphatic-epoxy oligosiloxane resin resulted in a thermally stable epoxy hybrid material (epoxy hybrimer). Micropatterns with a high aspect ratio (>5), an excellent sidewall shape, and low shrinkage were fabricated directly from these materials using a simple photolithographic process. The fabricated micropattern sustained temperatures of up to 250°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] | ||||||||||