Magnesium Aluminate
(MgAl2O4) Spinel
Characteristics
As a refractory material, MgAl2O4 spinel has some unique applications in the form of sintered ceramics or
coatings. It is considerably more resistant to slags and fluxes, especially alkalis, than alumina. This spinel,
including various chemical variations, can be used to coat crucibles and tundish nozzles for improved
resistance to molten metals and slag. It is usable as an impact resistant optical window and as an infrared
radiation lens. As this oxide is practically inert to cold concentrated mineral acids and even boiling acids
of moderate concentration, it would be serviceable as a dense coating for chemical reactors. Some
variants of this oxide include MgAl2O4 /Al2O3 and MgAl2O4 /MgO composites and MgAl2O4 /MgCr2O4 solid
solutions. Such chemical alterations permit modification of properties such as thermal expansion and
corrosion resistance.
Depending on the reactivity of the powder required, Trans-Tech prepares pure (min. 99.0%) spinel
and its variants by a variety of techniques including direct reaction of ingredient oxides or salts and
homogeneous precipitation of precursor salts (carbonate, hydroxide, and oxalate). These techniques
provide a variety of powdered products with varying crystallite/particle size and surface area.
These materials can be thermal sprayed using flowable, fully reacted powders to give thick dense
coatings having properties near that of bulk ceramics.
Representative Properties of Spinel (S-71)*
(Non-Conductive)
Melting Point
Density (Theoretical)
Density (Bulk)
Thermal Expansion
(25–1500 °C)
Thermal Conductivity
(100–1200 °C, zero porosity)
Specific Heat
Mechanical (25 °C, 3.51 g/cc)
Tensile
Compressive
Young’s Modulus
Electrical
Optical Transmission
(Visible and IR)
Refractive Index
2135 °C
3.578 g/cc
3.510 g/cc
9.17 x 10-6/ °C
0.147–0.054 W/cm °C
0.29
19.2 x 103 psi
270 x 103 psi
34.5 x 106 psi
See Trans-Tech Bulletin No. 91-76
0.2-8 ,µm
1.72
*Properties for other chemical compositions within this series are available upon request.
Available Materials
Sinterable Powders
Average Particle Size
Surface Area
Firing Temperature
Fired Density
Flowable Powders (Thermal Sprayable)
Morphology
Particle Density
Particle Size Range
—-1 µm
25–50 m2/g
1500–1600 °C
> 98% of theoretical
Spherical
50–95% of theoretical (as required)
10–100 µm
1mm to > 10 mm pellets also available upon request.
Skyworks Solutions, Inc.
5520 Adamstown Road, Adamstown, MD 21710
Phone: (301) 874-6464 • Fax: (301) 695-7065
Email: [email protected] • www.trans-techinc.com