Synthesis of Al2O3\u2013SiO2\u2013MgO ceramics with hierarchical porous structure

Elena F Krivoshapkina,Aleksey A Vedyagin,Pavel V Krivoshapkin

doi:10.1007/s40145-016-0210-4

Abstract

A series of asymmetric cordierite ceramics with hierarchical porous structure were prepared and characterized. The macroporous support was obtained from natural raw materials (bauxite, silica sand, kaolinite, talc, and alumina) via ceramic technology. The prepared ceramic discs were characterized by a narrow pore size distribution. The average pore size was about 9.5 μm, and the open porosity was estimated to be 30%. Coating the discs with micro/mesoporous cordierite layer was performed using the sol–gel approach. Three-component sols were obtained from organic or inorganic precursors. Corresponding gels were calcined at 1200 °C to form the cordierite structure. The nature of precursor was found to affect the pore volume distribution. Narrow pore volume distribution was observed when organic precursors were used. Another key factor to control the parameters of final material was the drying condition. Supercritical drying of the gels has allowed us to increase the surface area in two orders of magnitude comparing with conventional drying procedure.

Highlights

The characteristics of porosity are the properties determining the suitability of ceramic materials for potential applications [1]
According to the X-ray diffraction (XRD) data (Fig. 2), the main identifiable phases for cordierite ceramics prepared from natural raw materials are Mg2Al4Si5O18 cordierite (JCPDS No 13-294) and spinel MgAl2O4
According to mercury porosimetry (Fig. 4), the ceramic is characterized by a narrow distribution of pore size and the average pore size is equal to 9.5 μm

Summary

Introduction

The characteristics of porosity (total amount of pores, ratio of closed/open porosity, average pore size and distribution, pore shape) are the properties determining the suitability of ceramic materials for potential applications [1]. A component containing hierarchical porosity typically possesses simultaneously a wide range of desirable characteristics, which include high accessibility, rapid transport of fluids and gases, high selectivity, fast uptake and release, the possibility of rapid thermal cycling, chemical and mechanical stability, and efficient use of volume. Such components are of significant technological interest, and are successfully used in several industrial processes and household products. Thereby, the combination of ceramic technology with sol–gel approaches permits obtaining of the materials with interpenetrative architecture of the layers which are similar in phase composition but different in particle size and textural characteristics. Hierarchical porous structure within one material provides the reduction of diffusion barriers as well as optimal distribution and accessibility of active components in catalytic applications [19,20]

Experimental

Results and discussion

Conclusions