The A1-Sic reaction in aluminium-matrix Sic composites made by liquid metal infiltration resulted in the formation of silicon, the amount of which increased with increasing Sic volume fraction, but the fraction of Sic consumed by the reaction increased with decreasing Sic volume fraction. For Sic whisker composites made at an infiltration temperature of 800 "C, the fraction of Sic consumed was 18,26 and 55% at Sic volume fractions of 0.31,0.23 and 0.10, respectively. The fraction of Sic whiskers consumed was inversely proportional to the volume fraction of Sic whiskers in the composite. The product of these two fractions provides a scale (called the reactivity index) that describes the Al-Sic reactivity. The index decreased with decreasing infiltration temperature and was higher for Sic whiskers than Sic particles. Even at an infiltration temperature of 670 "C, the fraction of Sic whiskers consumed was 26% at an Sic volume fraction of 0.10. In contrast, the fraction of Sic consumed was only 8.4% for a 55 vol.% Sic particle composite made at an infiltration temperature of 800 "C. The fractional consumption values were obtained by determining the silicon concentration in the aluminium matrix uia calorimetric measurement of the liquidus-eutectic temperature difference.
Carbon nanotube (CNT) is an excellent field while for microwave devices a much larger current density emitter due to its small diameter (1-40 nm), high aspect ratio (> lA/cm2) is preferred.(>103), and high theoretical current limit (-1jA / SWNT).
Methods for assembling and integrating SWNTs orThe applications like CNT-FED or 11PM require uniform MWNTs onto a device surface to form a cathode include distribution of field emission current, low turn-on field, and high current density. However, macroscopic cathodes made plasma enhanced chemical vapor deposition (PECVD) [4], from CNTs for CNT-FED and microwave devices have been p shown to exhibit low emission site density (103-104 sites/cm2) water assisted CVD [5], electrophoresis deposition [6], compared to CNT density (109-101o /cm2 ), non-uniformity in spray coating of CNT mixture [7], and screen printing from emission sites distribution, and lower current density a paste mixture of CNTs [8]. Thermal CVD or PECVD achievable than dispenser cathode. The non-uniformity of can grow CNTs directly inside a 30 ,um hole, but the emission sites distribution is closely related to field screening length and uniformity across a panel size area is difficult to effect at individual sites. Only the CNTs with the highest achieve. Screen printing is a cost effective method, but the local electric field can emit current. The effect of field resolution of an ordinary screen is usually larger than 200,um enhancement factor, which is a strong function of local microstructure and a result of manufacture method, is found and
We have successfully fabricated 4.75‐inch CNT‐FED with sturdy metal plates as spacer. The metal plates were etched numerous holes and coated oxide to supply high efficient passage for electrons. We observed that several metal plates not only helped cathode to shield high electric field from anode but also supplied sturdy spacer between cathode and anode. In this work, a uniformity lighting image is obtained and capable of being applied to large‐area CNT‐FEDs.
Aluminum-matrix composites containing AIN or SiC particles were fabricated by vacuum infiltration of liquid aluminum into a porous particulate preform under an argon pressure of up to 41 MPa. Al/AIN was superior to Al/SiC in thermal conductivity. At 59 vol.% AIN, Al/AlN had a thermal conductivity of 157 W/m. °C and a thermal expansion coefficient of 9.8 × 10−-6°C−1 (35–100 °C). Al/AlN had similar tensile strength and higher ductility compared to Al/SiC of a similar reinforcement volume fraction at room temperature, but exhibited higher tensile strength and higher ductility at 300–400°C. The ductility of Al/AlN increased with increasing temperature from 22 to 400°C, while that of Al/SiC did not change with temperature. The superior high temperature resistance of Al/AlN is attributed to the lack of a reaction between Al and AIN, in contrast to the reaction between Al and SiC in AI/SiC.
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