Preparation and properties of lightweight, conformal, and load-bearing TiC/Si3N4 absorbing composites by gel casting
In view of the lack of conformal, load-bearing, light-weight, and high temperature-resistant integrated wave-absorbing composites suitable for extremely complex conditions, the gel-casting process was successfully applied to porous Si 3 N 4 wave-absorbing composites in this work. A universal low-slurry for gel casting was prepared by using two dispersants acting together (tetramethylammonium hydroxide solution and sodium lauryl sulfate), which ensured the smooth completion of the gel casting process. Combining the thermogravimetric and differential thermal gravity curves of the composite green body, reasonable parameters of the rubber discharge process are given to avoid the problem of the green body swelling and cracking. The porous TiC/Si 3 N 4 composites were successfully prepared by holding them at 1650°C for 3 h. The bending strength, density, minimum reflection loss, absorption bandwidth, and matched thickness in the P-band of the composites with 30 wt.% TiC addition were 54.08 ± 3.02 MPa, 1.906 g/cm 3 , -37.75 dB, 1.9 GHz, and 4.1 mm, respectively. The electromagnetic wave loss mechanisms of the composites are a combination of conductivity loss, multiple reflections and scattering, interfacial polarization, and defect polarization.
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