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[en] In this contribution, we present an alternative detector technology for use in direct absorption spectroscopy setups. Instead of a semiconductor based detector, we use the photoacoustic effect to gauge the light intensity. To this end, the target gas species is hermetically sealed under excess pressure inside a miniature cell along with a MEMS microphone. Optical access to the cell is provided by a quartz window. The approach is particularly suitable for tunable diode laser spectroscopy in the mid-infrared range, where numerous molecules exhibit large absorption cross sections. Moreover, a frequency standard is integrated into the method since the number density and pressure inside the cell are constant. We demonstrate that the information extracted by our method is at least equivalent to that achieved using a semiconductor-based photon detector. As exemplary and highly relevant target gas, we have performed direct spectroscopy of methane at the R3-line of the 2v_3 band at 6046.95 cm"−"1 using both detector technologies in parallel. The results may be transferred to other infrared-active transitions without loss of generality.
[en] Pressure agglomeration of powders is widely applied in various industries and an increasing interest lies in the identification and description of contact mechanisms between particles, which are responsible for the compaction product properties. In this paper, the design and development of a novel micromanipulation particle tester (MPT) is presented. This device makes it possible to measure the deformation kinetics and resulting adhesion of two individual particles in contact under load, which are strongly influenced by the applied process conditions. The MPT set-up is, therefore, designed to offer a unique control over the process conditions most relevant to the compaction of powders: external stress, dwell or holding time at constant deformation, compression velocity as well as relative humidity and temperature determining the physical state and mechanical characteristics of hygrosensitive amorphous particles. The latter are often part of powder formulations, e.g. in the food industry, and have been used for force and contact-zone development studies with the MPT. The experimental results on the microscale level will deliver valuable quantitative information for an improved tailoring of pressure agglomeration process conditions of bulk solids. (paper)