High wave transmittance and low thermal conductivity Y– α-SiAlON porous ceramics for high-temperature radome applications

Abstract

With the development of hypersonic vehicles technology, ceramic based radome materials are highly demanded due to their high operating temperatures, good dielectric properties, and high mechanical properties. Although α-SiAlON is an ideal material for radome application, its intrinsic low transmittance and high thermal conductivity limit its application. Herein, we prepared Y-α-SiAlON porous ceramics through tert-butanol gel-casting using self-synthesised α-SiAlON powder. Y-α-SiAlON porous ceramics exhibited a uniform micron-level connected pore structure with a porosity of 44.2%-58.6%. The real part of permittivity was 3.13-4.18 (8.2-12.4 GHz), which decreased significantly with increasing porosity. The wave transmittance of the sample with a porosity of 58.6% could exceed 80% in the thickness range of 6-10 mm. The thermal conductivity maintained at a low level of 1.38-2.25 W•m -1 •K -1 owing to the introduction of the pore structure. The flexural strength was 44.75-88.33 MPa, which may be increased by rod-like α-SiAlON grains. The results indicate that the prepared Y-α-SiAlON porous ceramics meet the requirements of high-temperature wave-transmitting materials for radome application.

Facile Synthesis and Properties of Highly Porous Quartz Fiber-Reinforced Phenolic Resin Composites with High Strength

“…The content of the curing agent affects the behavior of phenolic resin in the composite. When the resin was mainly attached to the surface of the fiber, thus forming a continuous fiber coating (as shown in Figure 4 e,h), the bearing capacity of the resin phase diminished, and the deformability of the fibers was reduced, so the mechanical properties of the composite were relatively poor [ 42 ].…”

“…The content of the curing agent affects the behavior of phenolic resin in the compo site. When the resin was mainly a ached to the surface of the fiber, thus forming a contin uous fiber coating (as shown in Figure 4e,h), the bearing capacity of the resin phase di minished, and the deformability of the fibers was reduced, so the mechanical properties of the composite were relatively poor [42]. Table 1 compares the comprehensive properties of the quar /porous PR composite in this study with various fire-proof insulation materials based on phenolic resin, includ ing phenolic foams, inorganic modified and fiber-reinforced phenolic aerogels, and vari ous forms of fiber-reinforced phenolic resin composites.…”

Hierarchical porous (Ta 0.2Nb 0.2Ti 0.2Zr 0.2Hf 0.2)C high-entropy ceramics prepared by a self-foaming method for thermal insulation

“…Recently, silicon-based porous ceramics were fabricated using this method, including SiOC foams [21,22], porous Si3N4 ceramics [23], and SiCN ceramic aerogels [24,25]. Compared to conventional sintering methods, fabrication porous ceramics through self-foaming using polymeric precursors requires lower temperatures and can be shaped via diversified plastic-forming techniques such as injection molding [26], gel-casting [27], melt spinning [28], blowing [29], and 3-D printing [30,31].…”