FOAM-GELCASTING PREPARATION OF Zr Si O₄ MODIFIED POROUS MULLITE CERAMICS

Abstract

ZrSiO4 modified mullite-based porous ceramics were fabricated at 1400 o C by using a foam-gelcasting method from industrial grade powder materials. Except for mullite and ZrSiO4 no other phases were identified in the fired samples added with ZrSiO4, implying that at the firing temperature, ZrSiO4 neither decomposed, nor reacted with mullite. In the microstructures of these samples, mullite/ZrSiO4 grains were evenly distributed, and the overall pore sizes were reduced. The addition of ZrSiO4 showed little effect on porosity and bulk density of fired samples, which were respectively around 77% and 0.7g•cm-3. However, it led to the enhanced mechanical strength, and more importantly, the reduced thermal conductivity, especially at high temperatures. When 8 wt% ZrSiO4 was added, flexural and compressive strengths increased respectively to 3.63 and 7.35 MPa, whereas thermal conductivity at 200 and 1000 o C was reduced to 0.160 and 0.277 W•m-1 •K-1 , respectively, which was mainly attributed to the shading effect, decreased size of "large" spherical pores, and more centralized and homogenized pore size distribution.

Open-cell mullite ceramic foams derived from porous geopolymer precursors with tailored porosity

“…℃ The porosity and mechanical characteristics of the mullite prepared using various pore-forming methods and sintered at about 1400 are compared in ℃ Table 3. We can observe that within the sintering temperature range of 1350-1450 , the compressive strength for ℃ the mullite ceramics (S4) obtained in this work was similar or even higher than those of other mullite foams at similar porosity levels [111][112][113][114][115][116][117][118][119], although higher strength than the one for the sample S4, even associated with higher porosity, can be also achieved [104,[120][121][122][123][124]. However, we can state that these mullite foams obtained from the porous geopolymers possessing high mechanical strength, high open porosity, and homogeneous microstructures are competitive at similar porosity levels and sintering temperatures because of using lower-cost raw materials [112,121], being manufactured using easier foaming steps [104,111,121] and not requiring additional sintering aids (SiC and B 4 C) [111,115,121] nor various types of mullite seeds (fiber [111,112,115,121], whisker [104], and powders [114,117,118,120,122,124]).…”

The Renewable of Low Toxicity Gelcasting Porous Ceramic as Fe2O3 Catalyst Support on Phenol Photodegradation

“…This approach has some drawbacks, including being difficult to make, needing high pressure, and necessitating the use of a porous template [23]. The gelcasting method is a well-known and straightforward method than the others and involves in situ polymerization in the slurry [23][24][25]. Also, the distributed polymer serves as a binder and pore template when released during the sintering process, and polyacrylamide is the commonly used polymer [20][21][22].…”