Pyroceram was produced in the 1950s by Corning Glass during their extensive research on photosensitive glass. S. Donald Stookey discovered this material accidentally when an overheated piece of glass turned out to be too tough to break when dropped. This novel material has been classified by NASA as a glass-ceramic and is produced by controlled crystallization. Pyroceram 9606 was certified as a reference standard after being used informally for over 30 years in high temperature applications that demand working at temperatures of about 1000°C (1832°F).
History of Pyroceram
Way back in 1952, Corning Glass chemist Don Stookey was working on his routine experiment, when he placed a photosensitive glass sample in a furnace of 600°C (1112°F). A controller in the furnace malfunctioned and the temperature accidentally soared to 900°C (1652°F). When Stookey opened the furnace door, he was surprised to see that the lithium silicate had been converted into a plate, milky white in color. While trying to remove it, he accidentally dropped the sample only to find that it resisted breakage and bounced instead of shattering like a normal piece of glass.
That marked the invention of the first ever synthetic glass-ceramic, later named by Corning as Pyroceram. This innovative material was not only harder compared to high-carbon steel and lighter than aluminum, but also was much more stronger than ordinary soda-lime glass. Eventually, Pyroceram was used in a wide variety of applications from microwave ovens to chemistry labs and missile nose cones. In the 1959, Corning came up with its now well-known serving dish line called Corningware that used Pyroceram.
Riding on the success of Pyroceram, Corning initiated comprehensive R&D efforts to find more ways of making stronger glass materials. The company’s scientists later discovered another material called Chemcor by dousing glass containing aluminum oxide in a hot potassium salt bath. The addition of aluminum oxide was believed to make the glass extremely durable and at the same time highly flexible. However, due to its high cost, Chemcor could not be successfully marketed.
A Day Made of Glass... Made possible by Corning. (2011)
Material Properties of Pyroceram
Pyroceram is a transparent ceramic glass that is an excellent transmitter of visible light and creates a warm atmosphere with a light amber colored tint. The chemical and physical properties of Pyroceram have been tested in accordance to NF, DIN, EN or ISO specifications.
Pyroceram is made from a magnesium aluminosilicate glass with titania as nucleating agent, and the key crystalline phase has been identified as cordierite (2MgO-2Al2O3-5SiO2). The material is machined and etched to smoothen surfaces.
Pyorceram has under gone extensive testing such as the following:
- Constant stress-rate testing as per ASTM standards
- Tensile testing according to ASTM test methods at three test conditions: room temperature/ distilled water, 93°C (200°F)/distilled water, and 274°C (525°F)/ambient air
- Compression testing at room temperature in distilled water with ‘fortified,’ specimens as per Test Method SACMA SRM-1
- Shear testing at room-temperature in distilled water as per ASTM Test Method D 5379
- Fracture toughness testing using two methods: single edge precracked beam (SEPB) as per ASTM Test Method C 1421 and single edge V-notched beam method.
- Elastic modulus testing using impulse excitation (ASTM C 1259) and strain gauging.
The following table shows the various properties of Pryoceram®lll along with its dimensions.
Thermal Properties
| |
|
| Continuous use |
700°C (1292°F) |
| Limited time, peak use |
800°C (1472°F) |
| Thermal gradient resistance |
ΔT max. = 700K |
| Mean specific heat (20° to 100°C) |
0.8 (J/g. K) |
| Thermal shock resistance |
ΔT max. = 700K |
| Thermal expansion coefficient [20 to 700°C (68 to 1292°F)] |
0± 3.0 x 10-7 K-1 |
Chemical Properties
| Alkali resistance (ISO 695) |
Class 1 |
| Water resistance (ISO 719) |
| Acid resistance (DIN 12 116) |
Optical Properties
| |
|
| Photo elastic coefficient |
3.11 (Brewster) |
| ABBE number |
approx. 55.4 |
| UV transmission at 3mm thickness |
<1% (wavelength < 355 µm) |
| Refractive index |
approx. 1.55 |
Electrical Properties
| Dissipation factor (at 102 Hz) |
40 x 10-3 |
| Dielectric constant (at 102 Hz) |
8.1 |
| Electrical resistivity, where ρ is in Ω.cm |
log10 ρ 6.8 at 250° C (482°F) |
Mechanical Properties
| |
|
| Poisson ratio (µ) |
0.25 |
| Minimal bending strength |
>110 MPa |
| Torsion modulus (G=) |
37.8 GPa |
| Specific mass |
2.55 |
| Knoop hardness (load 1 N) |
705 |
| Young's modulus (E=) |
94.3 GPa |
Dimensions
| Maximum sheet size |
2005x1100mm |
| Glass thickness |
Available in 3, 4, or 5mm |
| Cut sizes |
Customizable |
Applications of Pyroceram
The innovative glass ceramic material, Pyroceram, is used in the following applications:
- Glassware products
- Microwave ovens
- In hot plates and stirrers in chemistry and biology labs
- As nosecones in anti-aircraft missiles
References
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