Quantitative imaging of freezing at the millimeter scale using neutron radiography

Freezing of fluids in capillary structures affects systems that range from soils to the polymer membranes that are used in fuel cells. Neutron radiography can be used to image phase change within otherwise opaque structures and previous studies have shown the capability of quantitative imaging of freezing at ∼3 mm scale. In this study, a 1.6 mm diameter water column within an aluminum rod was imaged using neutron radiography and fluid density information was extracted. A ray-tracing flux model was developed in order to correct for the effects of beam divergence on the acquired images. The model produced image intensity maps that fit experimental data with R2 values of 0.98. Density measurements for water and ice within the capillary were found to be 1.00±0.03 and 0.93±0.03 g/cm3, respectively, which are within 1% of published density values for both phases.