Porous Alumina Ceramics Obtained by Particles Self-Assembly Combing Freeze Drying Method.

Shujuan Hu,Xiaoxia Tang,Yue Zhang,Bo Feng

doi:10.3390/ma12060897

Shujuan Hu, Xiaoxia Tang + Show 2 more

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https://doi.org/10.3390/ma12060897

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Abstract

An innovative approach for fabricating porous alumina ceramics is demonstrated in this paper. The distinguished feature is that the construction of the porous structure stems from the interaction between ceramic particles, which is a poorly explored area. By tailoring the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy to the second minimum, the dilute ceramic slurry would be gelled by the weakly assembled particle network, and the assembled structure is conserved via a freeze drying strategy. The DLVO theoretical analyses revealed that the second minimum of interaction energy could be obtained when the counter-ion concentration in colloidal suspension is 1.5 × 10−2 mol/L. The properties of the as-assembled samples were compared with one produced by the conventional freeze drying method. Results showed that the self-assembly of alumina particles has a positive influence on micro structures. Unlike the laminar pores generated by the traditional freeze drying procedure, the assembled samples show homogeneously interconnected and hierarchical open pores which were stable even after a 24 h dwell time at 950 °C (open porosity is 79.19% for the slurry of vol 20% solid loading). Particularly, after sintering at 1550 °C for 2 h, open porosity (67.01%) of the assembled samples was significantly greater than that of their un-assembled counterparts (39.97%). Besides, the assembled sample shows a narrower pore size distribution and a relatively higher cumulative pore volume.

Highlights

Porous ceramics have attracted considerable attention for their excellent thermal shock resistance, low density, low thermal conductivity, high refractoriness, high permeability, high specific surface area, constant filter quality and longer lifetime [1,2,3], they are extensively employed in industrial applications including gas filters [4], fluid filtration, sensors, bioreactors, catalytic substrates, bone substitute, insulating lining, random materials, light weight components [5] and so on
Controlled porous structures, narrow pore size distribution plus a relatively high surface area are of vital importance to the development of porous ceramics [6]
Various ways have been employed for preparing porous ceramics, such as the replica technique, free drying, direct foaming, foam gel-casting, reaction bonding, sacrificial template, gel-casting, pore forming agent (PFA), extrusion, sol-gel method and so on, among which freeze drying [7,8,9] and gel casting [10,11] are preferred due to their simplicity and affordability

Summary

Introduction

Porous ceramics have attracted considerable attention for their excellent thermal shock resistance, low density, low thermal conductivity, high refractoriness, high permeability, high specific surface area, constant filter quality and longer lifetime [1,2,3], they are extensively employed in industrial applications including gas filters [4], fluid filtration, sensors, bioreactors, catalytic substrates, bone substitute, insulating lining, random materials, light weight components [5] and so on All those outstanding performances are closely related to the size, distribution and morphology of the pores, as well as their interconnectivity. The green bodies prepared via the gel-casting procedure show a higher porosity, homogeneity and reliability, and further, the polymer-water gel is strong enough for machining into precise parts without any distortion

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Discussion

Conclusion