ALUMINIUM OXIDE (Al2O3)

Aluminium oxide is a ceramic with properties suitable for a coating material and electrical insulator. Its general properties are as follows :

GENERAL PROPERTIES - ALUMINIUM OXIDE [1]

Physical properties

Melting Point : 2000 +/- 30 C
Density at RT : 3.9 g/cm3
Apparent Porosity : 0 %
Water Absorption-Saturation : 0 %

Electrical properties

Dielectric Constant : 9.0 - 10.1
Dielectric Strength : 10 - 35 kV/mm
Volume Resistivity @ 20 C : > 1014 [[Omega]] cm

Thermal properties

Thermal Conductivity @ 20 C : 28 - 35 W/m-K
Thermal Expansivity, 20 - 1000 C : 8.0 x10-6m/m-K
Upper Continuous Use Temperature : 1800 C

Mechanical properties

Compressive Strength : 2200 - 2600 MPa
Shear Strength : 330 MPa
Hardness-Vickers : 1500 - 1650 kgf/mm2
Tensile Modulus : 330 - 400 GPa

DATA AND CORRELATIONS

It should be noted that the chemical resistance of Al2O3 to concentrated and/or dilute acids, alkalis, halogens and metals is quite good. The thermal and structural properties as a function of temperature are presented in Table 1, refs [2, 3]. Property values in ref [4] are also similar to the values appearing in Table 1.

Figures 1-2 show the variation of properties with temperature and Fig 3 shows the effect of porosity on the thermal conductivity. Polynomial correlations of the thermal and structural properties as functions of temperature in degrees K, using the data of Table 1, are as follows:

(1)

(2)

(3)

(4)

Equations (1) and (4) are valid between 298-2000 K, Eq (2) between 298-1600 K and Eq (3) between 373-2000 K.

          TABLE 1 Thermal and structural properties of aluminium oxide                                  
   T K     [[rho]]    E GPa      [[nu]]     k W/m-K    C J/kg-K   [[sigma]]  [[alpha]]  
           kg/m3                                                  y MPa      (10-6)     
                                                                             m/m-K      
   298     3900       385.169    0.254      37.1754    782.218                          
   300                385.078               36.9601    785.025                          
   373                379.674               30.2503    901.3683              0.0388     
   400                377.696               27.2090    942.030               0.060      
   473                372.348               22.5099    1016.802              0.114      
   500                370.397               20.9300    1046.700              0.134      
   600                363.044               16.3045    1109.502              0.200      
   673                357.696               13.1378    1148.873              0.267      
   700                355.715               12.5580    1151.370              0.288      
   800                348.392               10.4650    1203.705              0.380      
   873                343.044               9.1211     1214.92               0.424      
   900                341.034               8.9999     1224.639              0.446      
  1000                333.740               7.9534     1235.106              0.520      
  1073                328.392               7.1965     1249.819              0.587      
  1100                326.352               7.1792     1256.040              0.609      
  1200                319.0116              6.8023     1272.787              0.700      
  1273                313.740               6.1505     1284.489              0.753      
  1300                311.671               6.2467     1285.348              0.776      
  1400                304.330               5.9651     1297.500              0.860      
  1473                299.088               5.7992     1308.00               0.925      
  1500                296.989               5.8604     1308.375              0.948      
  1573                291.762               5.8604     1308.375              1.012      
  1600                289.649               5.8604     1308.375              1.040      
  1673                284.436                                                1.101      
  1773                277.110                                                1.190      
  1800                274.967                                                1.200      
  1873                269.051                                                12881      
  2000                260.286                                                1.400      


k (W/m-K)                                                       c (J/kg-K)

Temperature (K)

Figure 1: Thermal conductivity and specific heat of aluminium oxide.






E (GPa)                                [[alpha]] (10-6 m/m-K)

Temperature (K)

Figure 2: Elastic modulus and thermal expansion coefficient as a function of temperature for aluminium oxide






k (W/m-K)


Temperature (K)

Figure 3: The effect of porosity on the thermal conductivity of aluminum oxide as a function of temperature.






References

  1. Goodfellow Cambridge Ltd., "Metals, Alloys, Compounds, Ceramics, Polymers, Composites", Catalogue 1993/94.

  2. "Thermophysical Properties of High Temperature Solid Materials", Vol 4., Pt 1, Sect 1, pp. 8 - 47.

  3. Modelling, Analysis and Experiments for Fusion Nuclear Technology, FNT Progress Report : Modelling and Technology.

  4. Frank P. Incropera, David P. Dewitt. Fundamentals of Heat and Mass Transfer. Second Edition, pg759.