The fate and role of in situ formed carbon in polymer-derived ceramics

As a typical lightweight material, carbon materials have great application prospects in fabricating microwave absorbers. In this work, the Fe3C@Fe/C composites with porous microstructure are obtained by a simple and environmentally friendly method with wasted cornstalks as raw materials. The reflection loss of absorbing composites reaches the minimum value which is less than −50 dB when the thickness is 1.13 mm, while widest effective absorbing bandwidth reaches 5.1 GHz when thickness is 1.50 mm. The stalk-made nanocomposites’ excellent absorbing ability is mainly credit to excellent impedance matching and attenuation characteristics of composites, which is further credit to a synergistic influence of the dielectric loss from the multiple interfaces in porous microstructure and magnetic loss from iron nanoparticles. A low-cost method to obtain microwave absorption materials and realize high-value utilization of agricultural waste to reduce pollution caused by burning cornstalks is put forward.

Lightweight Fe3C@Fe/C nanocomposites derived from wasted cornstalks with high-efficiency microwave absorption and ultrathin thickness

Microwave absorbing properties of ferrites and their composites: A review

A revision on ceramic/graphene composites is presented. The more representative results for a wide number of bulk composites are compared, making special emphasis on their mechanical (fracture toughness, strength) and elastic properties, along with wear and friction topics. The electrical functionality boosted by the contacted graphene network is critically assessed for conducting and dielectric ceramic matrices. Regarding thermal transport, the enhancement or depletion of thermal conductivity is reviewed for different materials and specific orientations. Furthermore, new developments on layered materials and coatings, as well as on three-dimensional cellular composites, which certainly widen the scope of applications for this remarkable group of ceramic materials, are looked over.

https://digital.csic.es/bitstream/10261/190697/1/Miranzo_bulk_JECS-S-16-02603.pdf

From bulk to cellular structures: A review on ceramic/graphene filler composites

In-situ pyrolyzed polymethylsilsesquioxane multi-walled carbon nanotubes derived ceramic nanocomposites for electromagnetic wave absorption

The polymer-derived SiCN ceramics were synthesized at different annealing temperature (900 ∼ 1400 °C). The XRD, SEM, FT-IR, Raman and XPS were used to analyze the phase composition and microstructure. The result indicated that the crystallization degree and content of free carbon gradually improved with the increase of annealing temperature. The resistivity, dielectric and microwave absorption properties of the samples were studied at 2 ∼ 18 GHz. The resistivity decreased gradually as the annealing temperature rose. The dielectric constant of sample decreased with the increase of frequency in 1 ∼ 5 MHz. The existence of free carbon could improve the dielectric properties of polymer-derived SiCN ceramics at high frequency. The reflectance of the sample synthesized at 1100 °C was below −10 dB (> 90% absorption) in a wide frequency range of 6 ∼ 16 GHz and the maximum value of dielectric loss angle tangent was about 0.6 at 16 GHz.

Xue Guo

Papers

The dielectric and microwave absorption properties of polymer-derived SiCN ceramics

Effects of graphene on the thermal conductivity of pressureless-sintered SiC ceramics

Microwave absorption performance of PDCs-SiCN(Fe) ceramics with negative imaginary permeability

Effect of BN content on the mechanical and dielectric properties of porous BNp/Si3N4 ceramics

The influence of carbon materials on the absorption performance of polymer-derived SiCN ceramics in X-band