Random Composites of Nickel Networks Supported by Porous Alumina Toward Double Negative Materials

Abstract

Random composites with nickel networks hosted randomly in porous alumina are proposed to realize double negative materials. The random composite for DNMs (RC-DNMs) can be prepared by typical processing of material, which makes it possible to explore new DNMs and potential applications, and to feasibly tune their electromagnetic parameters by controlling their composition and microstructure. Hopefully, various new RC-DNMs with improved performance will be proposed in the future.

Ni/Al2O3/epoxy high-k composites with ultralow nickel content towards high-performance dielectric applications

“…In those porous metal/ceramic composites, metal particles dispersed on the pore walls of porous ceramic, leading to the ultralow percolation threshold, hence the suppressed leakage conductance loss and eddy current loss. 10,11,32 Similarly, Ameli et al 33 prepared a class of porous polymer nanocomposites consisting of multi-walled carbon nanotubes (MWCNT) dispersed on the pore walls of porous polymer. And it is shown that the porous MWCNT/polymer composites exhibit signicantly high permittivity, ultralow percolation threshold and low dielectric loss.…”

“…However, the interfacial polarization will gradually lag behind the external electric eld with increasing frequency, leading to the decrease of 3 0 . However, when the nickel content is near or above the percolation threshold, the composites dielectric spectra will follow the Drude model, 10,11,41,42 leading to the anomalous frequency dispersion of permittivity (Fig. 4a).…”

“…Furthermore, when the nickel content exceeds the percolation threshold, negative permittivity behavior will appear, which is very attractive for double negative metamaterials. 10,11,[37][38][39][40] However, the severe leakage conductance phenomenon and high loss are still challenges for meta-composites with negative permittivity. 8,10 As discussed above, in order to obtain high-k and low loss, the nickel contents should be near but lower than the percolation threshold.…”

“…As an alternative, composite materials may be promising candidates for high-k applications. As we know, the dielectric properties of a composite will undergo signicant changes near its percolation threshold, [8][9][10][11] and numerous researches have conrmed that percolative composites are promising candidates for high-k materials with outstanding dielectric properties, such as tunable high permittivity, high dielectric strength, low loss, etc. Therefore, various strategies have been developed to obtain high-k according to percolation theory in composite materials, such as ferroelectric/polymer composites, [12][13][14] binary or ternary metal (or carbon)/polymer composites, [15][16][17] metal (or carbon)/ ceramic composites, etc.…”

Synthesis of Al4SiC4 powders via carbothermic reduction: Reaction and grain growth mechanisms

“…In recent years, carbothermic reduction has become a promising synthesis route for high temperature ceramics because of its low requirements on starting materials. Both industrial raw materials such as commercial alumina and quartz and natural minerals such as sintered bauxite and kaolin can be adopted as starting materials, leading to great industrialization potential [19,20,[22][23][24][25]. Some attempts have been done to synthesize highly pure Al 4 SiC 4 by carbothermic reduction [17].…”