Equation of State Measurements of Materials Using Optical Microscopy and Interferometry*

The high-pressure equation of state (EOS) of mixed-phase, liquid and amorphous materials is difficult to measure using standard x-ray diffraction techniques. An established method for measuring sample volume is presented using optical microscopy and interferometry (OMI) at high pressure in a diamond anvil cell. OMI is an optical method which uses microscopy to measure the area of a sample and white-light interferometry to measure the thickness, allowing for determination of the sample volume. This technique can be used to measure the volume of many different types of samples including amorphous, mixed-phase, and even liquids. The EOS of products of energetic reactions, which tend to be mixed phases ranging from highly graphitic to nano-diamond rich, is important to understanding the chemistry of these reactions. Additionally, the EOS of polymeric binders, which tend to be amorphous or liquid phases, are of high interest to the chemistry of these reactions. We will present high-pressure EOS measurements on mixed phase, amorphous, and liquid materials using OMI techniques.