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Grain boundaries typically dominate the electrical properties of polycrystalline ceramics. To understand the effect of grain boundaries on the electrical conductivity of SiC ceramics sintered with 2000 ppm Y 2 O 3 , the electrical resistivity of individual grains and multi-grains across boundaries at the micron scale was measured using a nano-probing system equipped with nano-manipulators. The results revealed that grain resistivity was bimodal because of the existence of a core/rim structure in grains, and the electrical resistivity of multigrain samples slowly increased with an increase in the number of grain boundaries crossed. Specifically, the electrical resistivity of a grain without a core, a grain with a core, a bicrystal with a single boundary, a sample crossing three boundaries, and a bulk polycrystalline sample were 2.36 × 10-1, 5.05 × 10-1, 4.80 × 10-1, 5.04 × 10-1, and 5.84 × 10-1 Ω cm, respectively. The results suggest that the electrical resistivity of polycrystalline SiC ceramics is primarily influenced by the presence of a grain boundary or core and secondarily by the number of boundaries. [ABSTRACT FROM AUTHOR]

This paper presents the design of an XYZ nano-manipulator as well as the model based high precision tracking control of the nano-manipulating system. Aiming at large range and high mechanical bandwidth, the proposed mechanical design employs compound bridge-type amplifiers to increase the workspace without significant drop of stiffness. To further improve the system tracking performance and avoid possible actuator saturations, a robust anti-windup tracking control architecture combining a parallel internal-model based controller and an anti-windup compensator is adopted for the trajectory tracking of the designed nano-manipulating system. As a theoretical extension on a recent result [17] , we further investigate the robust stability condition of the closed-loop system and formulate the optimization design of the anti-windup compensators as a two block H ∞ optimization problem solvable with the Nehari approach. Real time control experiments demonstrate excellent tracking performance and saturation compensation capability with tracking precision error less than 0.28 % , which significantly outperforms relevant algorithms in the literature. [ABSTRACT FROM AUTHOR]