ASTM C1300 Test for Linear Thermal Expansion of Glaze Frits and Ceramic Whiteware Materials by Interferometric Method

Scope:

ASTM C1300 determines the thermal expansion of glaze frits by the interferometric method. Interferometry is a technique in which waves are superimposed to cause the phenomenon of interference, which is used to extract information. Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature. Thermal expansion leads to crazing (cracking) of the coatings due to mismatching of the thermal expansion between the coating and substrate materials. 

Test Procedure:

In ASTM C1300, three test pieces are assembled between the two interferometer plates in the following manner: 

1. The plate with the frosted side is placed within the refractory specimen crucible. 
2. The three test pieces are placed on this plate in an equilateral triangle. 
3. The clear plate is lowered on the test pieces keeping the mark identifying the “wedge side” in the “up” position. 
4. This assembly is set at a height comparable to that inside the furnace. 

The telescope is rotated and placed over the test specimen assembly. The monochromatic light source is directed down the tube. The setup is correct if four to eight fringes are present. If fewer or more fringes are present, the cone height is adjusted. The height of each cone is measured and recorded. When the proper number of fringes are observed, the refractory ring cover is placed on the crucible, and the fringes are observed again. The crucible is lowered into the furnace, onto the bottom support so that the thermocouple rests at the bottom of the crucible. The top of the furnace is covered with a quartz plate. The telescope is rotated and the fringe pattern is checked. If there is excessive glare or poor contrast, the quartz cover is adjusted, the light source is moved, or the telescope is releveled. The potentiometer is standardized if necessary and set to 38°C (100°F). The furnace is heated slowly to 38°C (100°F). The crosshair of the telescope is centered upon any convenient fringe and the temperature corresponding to each fifth fringe is recorded. The furnace temperature is maintained at 3°C (5.5°F)/ min temperature. Below 100°C a heating rate not exceeding 1.5°C/min is preferred. For frit samples, when the softening temperature has been reached, as shown by the fringes retreating for at least one fringe, the furnace is turned off to avoid reaction with the quartz plates.

Video 01: Michelson interferometer

Specimen size:

The ASTM C1300 test method requires specimens of the following dimensions:

• For frit samples, six fragments are selected with minimum conical dimensions of 3 mm (1⁄8 in.) at the base and 6 mm (1⁄4 in.) high.  

• For fired samples, six samples are selected having minimum conical dimensions of 3 mm (1⁄8 in.) at the base and 6 mm (1⁄4 in.) in height 

• For all samples, the base of the cones should be flat and the flat cone base should be cemented to the flat end of a glass rod with heated sealing wax. 

• The test cone height should be 4.8 mm (3⁄16 in.). These bases must be smooth and flat. 

Data:

In ASTM C1300, the percentage of linear thermal expansion is reported. 

A curve is prepared by plotting each temperature reading, t, on the horizontal axis against the corresponding percentage expansion along the vertical axis. 
The mean coefficient of thermal expansion, E, is calculated for any temperature range, t₂ to t₃°C.

Conclusion:

ASTM C1300 determines the thermal expansion of glaze frits by the interferometric method.