In‐situ measurements of mass transport rate in vapour growth of hexamethylenetetramine crystal layers

This paper refers to the implementation of a remote optical imaging system suitable for in‐situ mass transport rate measurements in the growth of crystalline layers when grown in closed cylindrical ampoules by a physical vapour transport (PVT) technique. By means of this system, the measurements are carried out by taking photographs, at regular time intervals, of the source material volume as it reduces itself because of mass transfer. After storing the photographs, in real time, in a PC, a suitable software allows to estimate the mass transport rate during the growth process. The authors report here on the detailed setting up of such system when aimed at measuring the growth rate, as it varies with time, of hexamethylenetetramine (HMT, urotropine) crystal layers. A presentation and discussion of the results of these measurements have previously been reported. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)