A versatile instrument for the in situ study of catalyst surfaces by surface x-ray diffraction and grazing incidence small angle x-ray scattering in a 13 ml flow reactor combined with reaction product analysis by mass spectrometry has been developed. The instrument bridges the so-called "pressure gap" and "materials gap" at the same time, within one experimental setup. It allows for the preparation and study of catalytically active single crystal surfaces and is also equipped with an evaporator for the deposition of thin, pure metal films, necessary for the formation of small metal particles on oxide supports. Reactions can be studied in flow mode and batch mode in a pressure range of 100-1200 mbar and temperatures up to 950 K. The setup provides a unique combination of sample preparation, characterization, and in situ experiments where the structure and reactivity of both single crystals and supported nanoparticles can be simultaneously determined.
In this article, the construction and initial tests of a frictional force microscope are described. The instrument makes use of a microfabricated cantilever that allows one to independently measure the lateral forces in X and Y directions as well as the normal force. We use four fiber-optic interferometers to detect the motion of the sensor in three dimensions. The properties of our cantilevers allow easy and accurate normal and lateral force calibration, making it possible to measure the lateral force on a fully quantitative basis. First experiments on highly oriented pyrolytic graphite demonstrate that the microscope is capable of measuring lateral forces with a resolution down to 15 pN.
We discuss the design, operation, and performance of a vacuum setup constructed for use in zero (or reduced) gravity conditions to initiate collisions of fragile millimeter-sized particles at low velocity and temperature. Such particles are typically found in many astronomical settings and in regions of planet formation. The instrument has participated in four parabolic flight campaigns to date, operating for a total of 2.4 h in reduced-gravity conditions and successfully recording over 300 separate collisions of loosely packed dust aggregates and ice samples. The imparted particle velocities achieved range from 0.03 to 0.28 m s(-1) and a high-speed, high-resolution camera captures the events at 107 frames/s from two viewing angles separated by either 48.8 degrees or 60.0 degrees. The particles can be stored inside the experiment vacuum chamber at temperatures of 80-300 K for several uninterrupted hours using a built-in thermal accumulation system. The copper structure allows cooling down to cryogenic temperatures before commencement of the experiments. Throughout the parabolic flight campaigns, add-ons and modifications have been made, illustrating the instrument flexibility in the study of small particle collisions.
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