The purpose of this study was to develop a model to predict (1) air and product temperatures, (2) product moisture, and (3) air humidity during an aqueous coating process using a Bohle Lab-Coater. Because of the geometrical properties and the airflow, the drum of the Bohle Lab-Coater can in principle be divided into 2 zones of equal size-the drying and the spraying zones. For each zone, 4 balance equations could be set up describing the change of the air humidity, the product moisture, the enthalpy of the air, and the enthalpy of the product in each zone. For this purpose, knowledge regarding heat and mass transfer and also the motion of the tablets in drums was used. Based on the considerations of the heat and mass transfer, a set of first-order coupled ordinary differential equations (ODEs) was developed. This set of ODEs can be solved numerically. In this part, the development of the model is described in detail, whereas the application of the model can be found in part 2.

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For the prediction of the air and product temperatures, the product moisture, and the air humidity during a coating process in a Bohle Lab-Coater, a model was developed. The purpose of this work was to determine the limit moisture, the critical moisture, and the constant for the exchange rate between both zones and to use these values for other sets of experiments to test the model. The adaptation of the 3 parameters (limit moisture, critical moisture, and exchange rate constant) was done by calculation of the product temperature in both zones for several sets of parameters in order to minimize the sum of square deviation between the calculated and the measured product temperatures. This set of parameters was used to test the validity of the model. By applying the model, the product temperature could be predicted based on the product, process, and equipment-related parameters. Hence, the model can be used to theoretically investigate the influence of different process parameters. The mean difference between the predicted and measured product temperatures in the steady state is approximately 2 up to 3 K using the determined parameter set for the limit moisture, the critical moisture, and the exchange rate constant. The model is useful for the prediction of the air and product temperatures, the product moisture, and air humidity during a coating process in the Bohle Lab-Coater using round, biconvex tablets.

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Chromium nitride layers with CrN and Cr2N stoichiometry were deposited onto silicon substrates by means of reactive RF-magnetron sputtering at different substrate temperatures (300-830 K). The layer thicknesses were 100 to 1500 nm. Composition, surface roughness, grain size, microstructure and phase formation were analysed using RBS (Rutherford backscattering spectrometry), RNRA (resonant nuclear reaction analysis), PAC (perturbed angular correlation), STM (scanning tunnelling microscopy) and XRD (x-ray diffraction). RBS and RNRA depth profiling of the samples revealed for both nitrides homogeneous Cr and N concentrations over the whole layer depth. For Cr2N films, indications of a phase transformation due to the increased target temperature from a disordered Cr/N phase to the ordered Cr2N phase were obtained via XRD and PAC. The lateral grain size measured with STM and the vertical grain size measured with XRD are approximately the same for both nitrides at all deposition temperatures.