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Topics Covered
IntroductionDescriptionApplications of Fused
MulliteTypical Chemical Analysis of Fused MulliteTypical Physical Properties of Fused MulliteTypical Thermal Properties of Fused MulliteSizes
Available
Introduction
Fused
mullite is produced by the electric furnace fusion of Bayer process
alumina and high purity silica. The result is a needle-like alumina-silica grain
that has low conductivity, excellent thermal shock resistance, and excellent
resistance to deformation under load. Fused mullite
is used in applications such as refractories for glass and steel industries, as
kiln furniture, in investment casting as shell building materials, in spark plug
bodies, and many other applications.
Description
Duramul is a fused, high purity mullite
produced by the electric furnace fusion of Bayer process alumina and high purity
silica. There is an excess of aluminum oxide above the normal mullite ratio
(3 Al2O3 : 2 SiO2) to ensure that all of the
SiO2 is contained within the mullite phase
and is not present in the glass phase. Duramul
receives high intensity magnetic treatment to remove virtually all of the
magnetic iron present. Each lot is sampled and test fired to insure against
contamination.
Applications of Fused Mullite
Duramul is utilized in the manufacture of refractory products where hot
strength, resistance to spalling and low thermal conductivity are important
factors. Such applications include setters and saggers for firing electronic
substrates, spark plug bodies, and laboratory ware.
Typical Chemical Analysis of Fused Mullite
Typical chemical analysis of fused mullite
is described in the table below.
| TYPICAL CHEMICAL ANALYSIS |
| Chemical |
Composition |
| Al2O3 (by difference) |
75.00% |
| SiO2 |
24.70% |
| Na2O |
0.30% |
Typical Physical Properties of Fused Mullite
Typical physical properties of fused
mullite are descibed in the table below.
| TYPICAL PHYSICAL PROPERTIES |
| Physical
Property |
Specification |
| Crystallography |
Fragments of columnar joining crystals in the Orthorhombic system with trace
quantities of hexagonal aluminum oxide crystals. |
| Color |
Brilliant White |
| Specific Gravity |
3.15 |
| Melting Point |
1830º C |
Typical Thermal Properties of Fused Mullite
Typical thermal properties of fused
mullite are descibed in the table below.
| TYPICAL THERMAL PROPERTIES |
| Thermal
Property |
Specification |
| Useful Temperature Ranges |
1800ºC in Air; 1500º - 1700ºC in Vacuum |
Thermal Conductivity
(0% porosity)
(cal / sec · cm · ºC) |
0.0145 at 100ºC ; 0.013 at 200ºC
0.011 at 400ºC ; 0.010 at
600ºC
0.0095 at 800ºC ; 0.009 at 1000ºC
0.008 at 1200ºC ; 0.009 at
1400ºC |
| Coefficient of Linear Expansion |
4.63 x 10-6 per ºC: 25-500ºC
5.13 x 10-6 per ºC:
25-1000ºC
5.62 x 10-6 per ºC: 25-1500ºC |
Sizes Available
Duramul
fused mullite is available in the following sizes:
10/F, 20/F, and 100/F
Other splits are available upon request
Source: Washington Mills
For more information on this source, please visit Washington
Mills.