Abstract: By measuring ultralow moisture permeation through a barrier material sample at a temperature substantially above ambient, definitive values are produced on an accelerated basis that can be used to accurately predict long term daily performance of that barrier material. The sample is heated to a desired test temperature where there is controlled access to both its upstream and downstream surfaces, and HTO vapor is then supplied at predetermined relative humidity to the upstream surface by fracturing a glass ampoule containing not more than 10 millicuries of specific radioactivity for each test. Radioactive gas permeating from the downstream surface is collected by circulating a very slow flow of dry carrier gas past the downstream surface, which stream flows to an ionization chamber containing a beta-particle radiation monitor.

Abstract: Method and apparatus for testing ultralow moisture permeation through a sample such as a thin barrier film by exposing one surface of a sample to be tested for moisture permeation to a predetermined humidity of HTO. The HTO permeating therethrough is collected in a stream of dry gas, preferably methane, at a known very slow flow rate, and monitored for its radioactivity content. By very carefully sizing the respective chambers, continuously monitoring using a particularly sensitive device and appropriately converting the signals, accurate assessment of permeation rates even as low as very small fractions of a gram of water per square meter per day can be obtained. Ultralow oxygen permeation is alternatively measured using 14CO. Methods are also shown for measuring permeation that would occur through a perimeter seal and for measuring permeation which would result from gaseous entry into edge surfaces of a composite film.

Abstract: Method and apparatus for testing ultralow moisture permeation through a sample such as a thin barrier film by exposing one surface of a sample to be tested for moisture permeation to a predetermined humidity of HTO. The HTO permeating therethrough is collected in a stream of dry gas, preferably methane, at a known flow rate, and monitored for its radioactivity content. Monitoring over a period of time and appropriate conversion allows accurate assessment of even permeation rates measured as very low fractions of a gram of water per square meter per day.

Abstract: Method and apparatus for testing ultralow moisture permeation through a sample such as a thin barrier film by exposing one surface of a sample to be tested for moisture permeation to a predetermined humidity of HTO. The HTO permeating therethrough is collected in a stream of dry gas, preferably methane, at a known flow rate, and monitored for its radioactivity content. Monitoring over a period of time and appropriate conversion allows accurate assessment of even permeation rates measured as very low fractions of a gram of water per square meter per day.

Abstract: A method for preparing fiber-reinforced refractory composites is provided. A fibrous preform is infiltrated with at least two different refractory material precursors, then heated under conditions suitable to cure and pyrolyze the refractory precursors.