Preparation of Mullite‐ and Zircon‐Based Ceramics Using Kaolinite and Zirconium Oxide: A Sintering Study

Abstract

International audienceThe interactions between zirconia (ZrO2) powder and three Algerian hydrated kaolinitic clays were studied at high temperatures. The analysis by X-ray diffraction of the prepared products allowed to follow the different phase developments during heat treatment and to identify the parameters controlling the zirconia conversion into zircon (ZrSiO4). It was found that ZrSiO4 formation, occurring at temperatures above 1150°C, is enhanced by the presence, in the clays, of fusing impurities such as K, Fe, Ca, and Mn, and by a decrease in zirconia particle size. A reactional mechanism, involving zirconia, a flux, and cristobalite is proposed. Moreover, the effect of zirconia additions on sintering was studied. It was also found that the increase in the porosity ratio of the final products for zirconia levels above 20 wt% was governed by a decrease in the flux amount, due to its lower clay content. Finally, it was shown that ceramics obtained by sintering at 1400°C for 2 h of a mixture of 38 wt% of fine zirconia powder and 62 wt% of the more reactive clay were mainly constituted of zircon and mullite

Mechanical properties of anorthite based ceramics prepared from kaolin DD2 and calcite

“…In this work, the long-term goal is the development of a low cost anorthite from inexpensive raw materials, such as kaolin and calcite (CaCO 3 ) using a modified milling system. Many works have already been published for appreciating these native raw materials including bioceramics [9][10][11][12][13][14][15][16][17], advanced ceramics [18][19][20][21][22][23][24][25][26][27] and ceramic membranes [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Most of these publications are closely related to this work and clearly highlight their possible applications.…”

Development and characterization of tubular composite ceramic membranes using natural alumino-silicates for microfiltration applications

“…The other important advantage is the possibility of reducing the sintering temperature from about 1600 to about 1250°C, when alumina supports are replaced by the raw materials. Other advantages are the relatively lower theoretical density of the prepared supports (2.8 g/cm 3 ) when compared to that of alumina (3.98 g/cm 3 ) and the mechanical strength comparable to that of alumina [14]. Actually, a flexural strength of 87 ± 2 MPa was obtained for 100 wt.% Al 2 O 3 samples sintered at 1620°C for 2 h [28], while nearly the same flexural strength value (87 ± 6 MPa) was also measured for compacts sintered only at 1250°C for 1 h, using the proposed process.…”

“…Algeria is one of the countries in the world that have abundantly available raw materials, such as calcium carbonates (CaCO 3 )(CC), dolomite (CaCO 3 ·MgCO 3 ), bones (natural derived hydroxyapatite (HA): Ca 10 (PO 4 ) 6 (OH) 2 ), kaolin, feldspar and quartz. Many works have already been published for valorizing these native raw materials, for the production of advanced ceramics [1][2][3][4][5][6][7], ceramic membranes [8][9][10][11][12][13][14][15][16][17][18][19] and bioceramics [20][21][22][23][24][25][26][27]. In particular, in the membrane field the possibility of replacing the more expensive starting materials by cheaper raw materials to be used as a support (which constitutes about 99% of the filter mass) is significantly important from economic and energetic points of view.…”

Reaction sintering of kaolin-natural phosphate mixtures

“…The sintering of Algerian kaolin nuances known as (DD1, DD2 and DD3) from Djebel Debbagh has been studied by some researchers [6][7][8]. Natural phosphate is a general term that describes naturally occurring mineral assemblages containing a high concentration of phosphate minerals.…”