SynopsisPermeabilities of noble gases, particularly argon, krypton, and xenon, were measured through a number of polymer films and coatings. Extrapolation of the log of the permeation coefficient versus the square of the gas molecular diameter was used to estimate radon permeability. An equation has been developed that can predict permeability to these noble gases as a function of the base polymer structure of the coating.
The focus of this study is to deposit metallic coatings onto ceramic substrates for application in power electronics. One possibility to achieve the required surface activation is to heat the substrate during spraying. An increased substrate temperature significantly influences bond strength and coating properties. This is investigated for cold-gas sprayed copper and aluminum on thermally sprayed Al2O3 layers. The study examines the adhesion of single-impacting Cu particles as well as coating microstructures and mechanical and electrical coating properties. It is found that increasing the substrate temperature as well as increasing the surface roughness enhances the adhesion strength of single particles. Coatings sprayed on heated substrates adhere very well and show low compressive stresses. Their hardness is reduced significantly, while their electrical conductivity is optimized to values of over 90 % IACS (IACS: International annealed Copper standard, 100 % IACS equals 58 MS/m).
Too often the development of laboratory automation systems has proceeded without adequate specifications or design. It is not unusual to find systems which are orders of magnitude too powerful—or, conversely, grossly inadequate—for the automation tasks required. A typical pitfall involves the specification of computer hardware independent of any detailed consideration of the real requirements of the laboratory instrumentation. Presented here will be an outline of a recommended approach to laboratory automation design. This approach recognizes three steps in the development of an automation system: user-level specifications of objectives and constraints; preparation of a hardware-independent functional design; and implementation of the design with specific hardware/software components. Thus, the selection of system components is not made until after the functional characteristics of the system are defined. At this point, hardware/software tradeoffs can take place to achieve an optimum configuration. A specific example will be discussed here to illustrate this approach. The example involves the development of a computer-automated gas chromatograph-mass spectrometer laboratory instrument for nonroutine analytical investigations.
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