Category: Transient Plane Source
Abstract: There are three types of reference materials used to verify numerous standard test methods: certified reference material (CRM), transfer standard (TS), and reference material (RM). A qualified reference material must be isotropic, and have reproducible consistency and stability over a wide range of temperatures. Metals and alloys are commonly used reference materials for solids, but they do not extend to lower temperature ranges unlike Pyroceram 9606, which is a popular alternative. When measuring thermal insulations and low conductivity values around 0.01 W/mK, the guarded hot plate is the method of choice. However, the precision limits at higher temperatures are much lower than at ambient temperature, and thus the development of a suitable reference material for higher temperature ranges is required. For high-density materials with values between 10-1000 W/mK, the flash method is popular, however discrepancies in results tend to occur because of uncertain specific heat values. The heat flow meter method is used to measure the thermal resistance of insulating materials around room temperature, but accurate measurements rely on reference materials of the same order of thermal conductance as the samples, which is difficult when testing at higher temperatures. Absolute contact transient techniques (CTS) are new commercial instrumentation systems that use small samples and short measurement times (ex: transient plane source (hot-disc) methods), however adequate reference materials for the three lower orders of magnitude are currently insufficient. Pyrex 7740, Pyroceram 9606, 304 stainless steel, and Armco iron are some of the most widely used reference materials because of their wide range of geometries and thickness, and are essential when confirming the efficacy of measurement methods, and when developing new approaches to high precision measurements.
Reference: Journal of Thermal Analysis and Calorimetry (2017) 1-11