Highly-porous hierarchical SiC structures obtained by filament printing and partial sintering

Abstract

Three-dimensional (3D) porous silicon carbide (SiC) structures with total porosity in the range of 64-85% are achieved from nanosized SiC powders by filament printing and partial sintering in a spark plasma sintering (SPS) furnace. The effects of the SPS temperature (1500 and 1700° C) and the addition of oxide sintering aids (7 wt. % Y2O3+Al2O3) on the porosity of the scaffolds are quantitatively compared. More specifically, hierarchical porosity consisting in the presence of meso-pores (< 50 nm) in the struts and macro-pores (in the range of 500-700 µm) defined by the patterned structure is demonstrated for the 1500 °C SPS treatment. The strength of the structures is analyzed as a function of the density as well as the cooling profiles once subjected to rapid heating under a direct flame. By this simple method, an adaptable family of robust light 3D SiC structures with hierarchical porosity is accomplished.

Remarkable Effects of an Electrodeposited Copper Skin on the Strength and the Electrical and Thermal Conductivities of Reduced Graphene Oxide-Printed Scaffolds

“…However, for the 3D Cu/rGO, radiation and convective cooling compete as the two terms show comparable values during the initial part of the cooling, while convection clearly prevails for the remainder of the cooling process. This predominance of radiative cooling is reasonably explained by the higher emissivity of black bodies and the relatively larger specific surface area of the bare rGO structure ( S BET ∼ 65.3 m 2 ·g –1 ) compared to the Cu/rGO structure ( S BET ∼ 4.2 m 2 ·g –1 ), since these two parameters favor radiative heat dissipation …”

“…This predominance of radiative cooling is reasonably explained by the higher emissivity of black bodies and the relatively larger specific surface area of the bare rGO structure (SBET ~65.3 m 2 •g -1 ) compared to the Cu/rGO structure ( SBET ~4.2 m 2 •g -1 ), since these two parameters favor radiative heat dissipation. 62 The cooling profiles of both scaffolds for the minimized convection test (type 2), which would be the conditions that applies for TIM, are compared in Fig. 7b, showing almost linear functions of time, with a comparatively faster cooling rate (0.065 °C•s -1 ) for the Cu/rGO structure than for the rGO one (0.050 ºC•min -1 ).…”

Thermal conduction in three-dimensional printed porous samples by high resolution infrared thermography

“…The specimen section varies between 25 Â 25 and 40 Â 40 mm 2 , thus, similar to those used in TPS. Regarding additively manufactured 3D ceramic structures, to the best of the authors knowledge, there are no experimental works analysing their thermal conductivities, although comparative evaluations of the heat dissipation capability of different printed materials during cooling have recently been addressed [19][20][21][22].…”

“…One of the ceramic samples, labelled as SiC 50 -7, was processed from SiC nanopowders of 50 nm of particle size (Nanostructures & Amorphous Materials Inc., USA, polytype 3C) containing 5 wt.% of Y 2 O 3 and 2 wt.% of Al 2 O 3 , both used as sintering additives. The scaffold was sintered at 1700 C for 5 min in Ar atmosphere (6 Pa of pressure) using the Spark Plasma Sintering (SPS) technique without applying any mechanical pressure [19]. The MAX-phase specimen was printed from 98% pure Cr 2 AlC MAX lab-synthesised powders [25] and densified by pressureless SPS at 1200 C for 10 min in Ar [20].…”

Ultrastrong, elastic, and fatigue‐resistant SiC nanowires network

“…The as-obtained L-SiC NN exhibits a distinct combination of high specific strength and low relative thermal conductivity (Figure 4J). 1,3,[34][35][36][37][38][39][40][41] In comparison with superelastic ceramic aerogels, the L-SiC NN shows a nearly two order magnitude higher strength despite a slightly lower porosity of 90.9% (Figure 4K). The L-SiC NN even exhibits higher strength than conventional porous ceramics with higher porosity.…”