Magnesia ceramics

Figsch V., Bunanova E. Synthesis of spinel-magnesia ceramics from finely milled mixtures of magnesite MgCOs and gibbsite Al(OH)j. In Book of Abstract I Int. Conf. INCOME, Kosice, 23-26 March,1993... 

Misawa T, Moriyoshi Y, Yajima Y, Takenouchi S, Ikegami T (1999) Effect of silica and boron oxide on transparency of magnesia ceramics. J Ceram Soc Jpn 107 343-348... 

Suzuki M, Ikegami T, Yokoyama M, Komatsu T, Fukahori A (2005) Effects of chloride ion on densification transparency magnesia ceramics. J Ceram Soc Jpn 113 149-153... 

Hard-burned magnesias may be used in a variety of appHcations such as ceramics (qv), animal feed supplements, acid neutralization, wastewater treatment, leather (qv) tanning, magnesium phosphate cements, magnesium compound manufacturing, fertilizer, or as a raw material for fused magnesia. A patented process has introduced this material as a cation adsorbent for metals removal in wastewater treatment (132). 

Cements and Ceramics. Refractory cements and ceramics (qv) are prepared from slurries of siUca, 2irconia, alumina, or magnesia and a prehydroly2ed siUcate (see Cement). Calcining at 1000°C yields cured refractory shapes (48,49). 

Nickel—beryllium casting alloys are readily air melted, in electric or induction furnaces. Melt surface protection is suppHed by a blanket of argon gas or an alumina-base slag cover. Furnace linings or cmcibles of magnesia are preferred, with zirconium siUcate or mullite also adequate. Sand, investment, ceramic, and permanent mold materials are appropriate for these alloys. Beryllium ia the composition is an effective deoxidizer and scavenger of sulfur and nitrogen. 

Fig. 16.1. Ionic ceramics, (a) The rocksalt, or NoCl, structure, (b) Magnesia, MgO, has the rocksalt structure. It can be thought of as an f.c.c. packing with Mg ions in the octahedral holes. ( ) Cubic zirconia ZrOj an f.c.c. packing of Zr with O in the tetrahedral holes, (d) Alumina, AljOj a c.p.h. packing of oxygen with Al in two-thirds of the octahedral holes.

Magnesia, MgO, is an example (Fig. 16.1b). It is an engineering ceramic, used as a refractory in furnaces, and its structure is exactly the same as that of rocksalt the atoms pack to maximise the density, with the constraint that like ions are not nearest neighbours. 

Abdelrazig, B. E. I., Sharp, J. H., Siddy, P. A. El-Jazairi, B. (1984). Chemical reactions in magnesia-phosphate cements. Proceedings of the British Ceramic Society, 35, 141-54. 

Montross CS, Yokokawa H, Dokiya M, and Bekessy L. Mechanical properties of magnesia-doped lanthanum chromite versus temperature. J. Am. Ceram. Soc. 1995 78 1869-1872. 

Mg-PSZ represents magnesia, MgO, partially stabilized zirconia, Zr02, ceramics. These ceramics are strong and tough structural materials. The main characteristics of Mg-PSZ ceramics are... 

Gavrilov, K.L., Bennison, S.J., Mikeska, K.R., Chabala, J.M. and Levi-Setti, R., Silica and magnesia dopant distributions in alumina by high-resolution scanning secondary ion mass spectrometry ,, /. Am. Ceram. Soc., 1999 82(4) 1001-1008. 

Magnesia-spinel (MgAI204) refractory ceramic composites 361... 

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