Porosity effect on microstructure, mechanical, and fluid dynamic properties of Ti₂AlC by direct foaming and gel‐casting

Abstract

In this study, Ti2AlC foams were fabricated by direct foaming and gel‐casting using agarose as gelling agent. Slurry viscosity, determined by the agarose content (at a fixed solids loading), as well as surfactant concentration and foaming time were the key parameters employed for controlling the foaming yield, and hence the foam porosity after sintering process. Fabricated foams having total porosity in the 62.5‐84.4 vol% range were systematically characterized to determine their pore size and morphology. The effect of the foam porosity on the room‐temperature compression strength and elastic modulus was also determined. Depending on the amount of porosity, the compression strength and Young's modulus were found to be in the range of 9‐91 MPa and 7‐52 GPa, respectively. Permeability to air flow at temperatures up to 700°C was investigated. Darcian (k1) and non‐Darcian (k2) permeability coefficients displayed values in the range 0.30‐93.44 × 10−11 m2 and 0.39‐345.54 × 10−7 m, respectively. The amount of porosity is therefore a very useful microstructural parameter for tuning the mechanical and fluid dynamic properties of Ti2AlC foams.

Hot Air Permeable Preceramic Polymer Derived Reticulated Ceramic Foams

“…Besides, foams O1 and O2 presented slight increases of k 1 and decreases of k 2 with the rise of temperature to 700 °C. Similar trends were observed for freeze cast foams, 55 for gelcasting foams, 56 for porous lanthanum carbide discs, 58 and for SiC granular filters. 38,57 Despite this, no conclusive explanation for this behavior has been proposed so far.…”

Three-Dimensional Digital Reconstruction of Ti2AlC Ceramic Foams Produced by the Gelcast Method

“…Figure 11 shows the interdependence of the pressure drop per unit length with the superficial velocity for all three foam samples examined here. A comparison of simulated results with experimental data is made in the figure that reveals a very satisfactory agreement [8,9]. To be more specific, the quality of the fit of the simulated to the experimental data was measured in terms of a normalized root mean square deviation (NRME) and revealed that the NRME value is 0.028 for the Gelcast93 sample, 0.026 for the Gelcast87 and 0.017 for the Gelcast84.…”

“…This was accomplished by setting the mean Figure 11. Pressure drop as expressed in References [8,9] vs. superficial velocity for the (a) Gelcast84 foam, (b) Gelcast87, (c) Gelcast93 foams. Comparison of simulation results with experimental data.…”

“…Lately, there has been an increased interest in generating porous Ti 2 AlC foams aiming to produce eventually porous materials with the desired mechanical and transport resistance. The research on porous Ti 2 AlC is considered limited; however, extended studies on those foams may reveal ways to improve their functional properties [8]. Moreover, the permeability of porous Ti 2 AlC at room or higher temperature is a critical feature in various applications, such as catalyst devices and filters [9].…”

“…The mass fraction of the suspension components, as well as the time of the suspension and homogenization process, are suitably selected in order to provide a global time frame that is sufficient to allow suspension to cast into the mold before the gelation process takes place and, at the same time, ensuring that the gelation process does not occur too late [13]. As a last step, the foam samples are placed in an alumina boat on a bed of Al-containing powder [8,14].…”