Gérard Thomas

TL;DR: In this article, two different methods, nitric acid attack on metallic tin and neutralisation of SnCl4 solution by hydrazine, were used to extract cassiterite-type samples and their evolution as a function of the temperature of calcination in flowing oxygen up to 600°C has been studied.

TL;DR: In this paper, the authors link TPD with Diffuse Reflectance Fourier Transform Spectroscopy (DRIFTS) to identify the nature of the adsorbed species resulting from the interaction of NO and NO2 with the tin oxide surface.

Abstract: In this study the dry coating experiments were performed with two different processes using a high energy impact coater “Hybridizer” (Nara) and a high shear mixer “Cyclomix” (Hosokawa). Silica gel particles (d50 = 55µm) were coated with fine particles of magnesium stearate (d50 = 4.6µm) at two different weight ratio of magnesium stearate, 5% and 15%. Several methods of characterization were used to study the effect of dry coating of the silica gel powder. The uncoated and coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). The images have shown that a more uniform coating was obtained in the case of Hybridizer. The flowability of the different samples obtained with Hybridizer and Cyclomix have been characterized by measurements of the tapped and aerated densities. It has been shown that the flowability of silica gel treated in Hybridizer was not significantly affected whereas the flowability was reduced after treatment in the Cyclomix. The wettability of silica gel was determined by measurements of the contact angle between a water drop and a powder bed prepared for each sample. The results obtained have shown that the coating of silica gel powder by hydrophobic magnesium stearate in the two different devices, Hybridizer and Cyclomix, can improve its hydrophobic properties. The results of the different characterizations have been compared with those concerning the simple mixtures prepared by using a Turbula mixer. To investigate the stability and the ageing of silica gel particles after coating, three samples of silica gel coated with 15% (w/w) of magnesium stearate in the Hybridizer device have been stored under different relative humidities (RH). The temporal evolution of the contact angle and the volume of the drop water on the surface of the bed powder have been determined after 10 days or 36 days storage. The results have shown the influence of the relative humidity on the evolution of the coated silica gel particles. The surface of the host particles recovers its hydrophilic nature after 10 or 36 days storage under different relative humidity. No significant variations of the contact angle and the volume of the drop were recorded for the sample stored under dry atmosphere (RH < 12%). The ESEM observations of the different samples confirmed the results. A mechanism that can explain these ageing effects is proposed.

TL;DR: In this article, dry coating experiments were performed with two different processes using a high energy impact coater "Hybridizer" (Nara) and a high shear mixer "Cyclomix" (Hosokawa).

TL;DR: In this article, the authors used acoustic emission (A.E) measurements to understand and identify many of the phenomena that occur during powder compaction of pharmaceutical products, such as granular rearrangement, fragmentation, visco-plastic deformation of grains or granules.