A new class of materials with ultra small grain size has recently been synthesized by combining the methods of inert gas condensation of metal vapors and in situ powder compaction. These ‘nanocrystalline’ materials, with grain sizes of 5-10 nm, can have over 30% of their atoms lying in the highly disordered interfaces or grain boundaries. Because of their unique atomic structure, nanocrystalline materials often have properties far different from their bulk counterparts. In addition, kinetic processes can be rapidly accelerated due to the short diffusion distances between grains. In this review, we will report on the thermodynamic properties and reaction kinetics of nanocrystalline metals and on such kinetic properties as sintering and grain growth in nanocrystalline ceramics.
Abstract-A four-pole elliptic function compact bandpass filter is designed by using interdigital hairpin resonator and step-impedance hairpin resonator.The miniaturized band-pass filter is also implemented using high permittivity dielectric substrate. The fullwave simulator IE3D is used to design the compact hairpin resonator, and to calculate the coupling coefficient of the basic coupling strictures. The responses of the fabricated filters using Al 2 O 3 (ε r = 9.7, Q × f = 350000 GHz) and 0.6Sm(Co 1/2 Ti 1/2 )O 3 -0.4CaTiO 3 (ε r = 37, Q × f = 43000 GHz) dielectric substrates are designed at a center frequency of 2 GHz. The size of the compact hairpin filter using 0.6Sm(Co 1/2 Ti 1/2 )O 3 -0.4CaTiO 3 ceramic substrate, as compared to that of a compact hairpin filter using Al 2 O 3 ceramic substrate, is reduced in size by 45%. The compact size and good agreement have been obtained between simulations and implementation results.
A four-pole elliptic function bandpass filter is designed using miniaturized microstrip interdigital hairpin resonator and stepimpedance hairpin resonator. Miniaturization hairpin resonators are realized by using interdigital structure and step-impedance structure having parallel coupled lines. The full-wave simulator IE3D is used to design the compact hairpin resonator and to calculate the coupling coefficient of the basic coupling strictures. The response of the fabricated filters using Al 2 O 3 (e r ¼ 9.7, Q Â f ¼ 350000 GHz) and 0.6Sm(Co 1/2 Ti 1/2 )O 3 -0.4CaTiO 3 (e r ¼ 37, Q Â f ¼ 43000 GHz) dielectric substrates are designed at a center frequency of 2 GHz. The compact size and the performance of this class of filter have been demonstrated.
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