I am currently doing a literature research on borosilicate glass. The objective of the research is to discover the measurement methods used to measure the thermal expansion composition of borosilicate glass. In my paper, I need to mention the possible causes of inappropriate thermal expansion coefficient of borosilicate glass. Does the chemical composition affect its thermal expansion coefficient? If not, are there any factors that may result in inappropriate thermal expansion coefficient (i.e. a thermal expansion coefficient that is out of the accepted range)? I am a first-year Mechanical Engineering student.
Let me answer this in two parts. First of all you can use a Dilatometer to measure the coefficient of Thermal Expansion. Just be careful when you get to higher temperatures. Above certain temperatures (550 C or so), the glass tends to soften and the PLC (percent linear change) versus Temperature curves loose fidelity.
Any element the changes the glass transition temperature and/or softening temperature will affect thermal expansion (examples are Na and B). In addition, micro-cracking in the glass can also affect the Coefficient of Thermal Expansion.
We worked with glass-foam ceramic, and we needed to form a matrix vitrea-porous (In temperatures up to 800°C), so the presence of SiO2 and Al2O3 are necessary to form a vitrea phase and the presence of Na2O, CaO and MgO are required to form a vitrea phase with too viscosity, and this help in the formation of porous in the material.
I hope helped you. Regards.
Dear Wai Hao Koh,
If you ask, how do the amounts of single oxides (SiO2, B2O3, Al2O3 and Na2O) influence the thermal expansion coefficient of the borosilicate glass, then it looks like this:
1. the more SiO2, the lower the thermal expansion coefficient ( moderate influence with small deviations from target composition)
2. the more Na2O, the higher the thermal expansion coefficient (very big influence with small deviations from target composition )
3,4. Small deviations of Al2O3 and B2O3 contents have practically no influence on the thermal expansion coefficient of the glass.
In summary, it can be said that with small deviations of the composition, only the sodium oxide content can have an influence on the thermal expansion coefficient of the glass.
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