Crystal Growth in Glass Formers with Dr. Stephen Hall
Some materials when cooled below their normal freezing point can form a unique state of matter called a glass. It is a state with properties of both liquids and solids. It is hard like a solid, but unlike a solid the molecules are not in an ordered array and in fact are able to flow past each other, albeit very slowly. You might think of it like really, really cold molasses.
Dr. Hall's students can learn about this glass state by studying materials at temperatures above the glass transition where they freeze into normal crystals.
In order to better understand the transition to the glass state, we have been measuring the growth velocity of the crystals as a function of temperature below the normal freezing point.
A very thin layer of material prepared in a liquid state is placed between two microscope slides. The temperature is reduced below the normal freezing point and the crystal growth is video taped. Analysis afterwards can determine the speed of the crystal growth. This is a picture of such a slide with crystals growing from the left.
Experimental Apparatus
The vertical black tube is the CCD camera and lenses. Underneath it is the brass cell that holds the slide containing the OTP material. The temperature of the cell is regulated by pumping temperaure controlled water through the tubes.
The water is maintained at a constant temperature and circulated by the machine in front. The temperature is recorded by a variety of thermometers in the cell and measured by the scanner on the right. The images are displayed on the monitor and recorded by the VCR.