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Aluminas

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The most common material used for structural ceramic parts is alumina. The versatility of alumina stems from its broadly impressive material properties, ease of manufacture, wide availability, and budget-friendly cost. STC’s fully dense, 74% alumina to 99.96% alumina bodies are work-horse materials for applications that require electrical isolation, wear resistance, high temperature resistance, and good mechanical strength. The grade of alumina is selected to best fit the application.

It is used in applications from aerospace to medical, from bearings to analytical instrumentation. In addition, these materials lend themselves well to be hermetically sealed to metals through metallizing and brazing methods.

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Property Charts & Safety Data Sheets
Property ChartsAluminas Comparison Chart
Master Ceramics Property ChartFull Color
Printer Friendly - Color
Printer Friendly - B&W
Safety Data SheetsAlumina AL-33R
Bisque Alumina Ceramic
Dense Alumina Ceramic
Spray Dried Alumina Powder (RTP)
Unfired Alumina Powder
Prime Features
Good Mechanical StrengthHigh Temperature Resistance
High Wear ResistanceGood Chemical Resistance
Good Dielectric StrengthSuitable for Ceramic-to-Metal Assemblies
High Hardness 
Typical Applications
IgnitersSpray Nozzles
Structural Ceramics PartsCeramic Bearings
Wear GuidesElectrical Insulators
BushingsFeed Thru Insulators
Pump Components 

 

Materials Property Chart
 Alumina (Standard)Alumina (High Purity)
 PropertyASTM MethodUnitsAL74 74%AL95 95%AL96 96%AL98 98%AL995 99.5%AL9980 99.8%AL9996 99.96%
GeneralCrystal Size (Average)Thin SectionMicrons131187662
Color----WhiteIvoryWhite Or PurpleWhiteIvory - WhiteIvoryOff White/Blush
Gas Permeability--atms-cc/secgas tight <10-10gas tight <10-10gas tight <10-10gas tight <10-10gas tight <10-10gas tight <10-10gas tight <10-10
Water AbsorptionC 20-97%0000000
Mechanical
DensityC 20-97g/cc3.033.653.713.783.883.913.93
HardnessVickers 500gmGPa (kg/mm2)10.5 (1075)11.5 (1175)12.7 (1300)12.7 (1300)14.3 (1459)15 (1530)19.6 (2000)
Hardness--R45N78798181828690
Fracture ToughnessNotched BeamMPam1/22 - 53 - 44 - 54 - 54 - 53 - 45 - 6
Flexural Strength (MOR)
(3 point) @ RT		F417-87MPa (psi x 103241 (35)310 (45)358 (52)393 (57)338 (49)379 (55)455 (66)
Tensile Strength @ RT--MPa (psi x 103)117 (17)151 (22)200 (29)221 (32)172 (25)200 (29)275 (40)
Compressive Strength @ RT--MPa (psi x 103)1378 (200)1827 (265)2068 (300)2241 (325)2137 (310)2240 (325)2413 (350)
Elastic ModulusC848GPa (psi x 106)172 (25)303 (44)310 (45)345 (50)379 (55)379 (55)393 (57)
Poisson's RatioC848--0.220.220.220.230.230.230.23
ThermalC.T.E. 25 - 100° CC 372-96x 10-6/C5.56.16.06.26.36.56.5
C.T.E. 25 - 300° CC 372-96x 10-6/C5.87.06.86.86.97.97.9
C.T.E. 25 - 600° CC 372-96x 10-6/C6.37.77.57.67.68.18.2
Thermal Conductivity @ RTC 408W/m K4192329303035
Max Use Temp--Fahrenheit (°F)2800300031003100304730473100
--Celsius (°C)1540165017001700167516751700
ElectricalDielectric Strength (.125" Thick)D 149-97AV/mil225250250260270290422
Dielectric Constant @ 1 MHzD 150-98--7.09.09.19.59.89.89.9
Dielectric ConstantD 2520-95----9.29.19.49.710--
@ GigahertzD 2520-95----11.010.99.89.89.6--
Dielectric Loss @ 1 MHzD 150-98--0.00120.00060.00040.00060.0002< .0001< .0001
Dielectric LossD 2520-95----0.00090.00070.0005< .0001< .0001--
@ GigahertzD 2520-95----12.510.99.89.89.6--
Volume Resistivity, 25°CD 257ohms-cm< 1 x 1013> 1 x 1014> 1 x 1014> 1 x 1014> 1 x 1014> 1 x 1014> 1 x 1014
Volume Resistivity, 300°CD 1829ohms-cm4 x 10105 x 10123 x 10128 x 10111 x 10123 x 10121 x 1013
Volume Resistivity, 500°CD 1829ohms-cm3 x 1073 x 1097 x 1092 x 1095 x 10106 x 10105 x 1012
Volume Resistivity, 700°CD 1829ohms-cm2 x 1063 x 1084 x 1082 x 1082 x 1096 x 1091 x 1012
Note: The information in this data sheet is for design guidance only. STC does not warrant this data as absolute values. Forming methods and specific geometry could affect properties. Slight adjustments can be made to some of the properties to accommodate specific customer requirements. Most of the dense materials in the table are resistant to mechanical erosion and chemical attack. STC has performed ASTM testing qualification for certain compositions, in accordance with ASTM D2442. Please consult our technical staff for appropriate material and specific test results.