ABSTRACT
Several prism-based spectrographs employing a mercury cadmium telluride (MCT) focal plane array detector have been interfaced to an infrared microscope. In the combined system, the area-defining aperture of the microscope also served as the entrance slit to the spectrograph. This investigation considered the fundamental limits of diffraction for both the spectrograph and microscope in order to determine both the spatial and spectral resolution of the system as a whole. Experimental results for spectral resolution, spectral range, and peak-to-peak noise have been presented. Finally, the dynamic capabilities of one spectrograph/microscope combination were investigated.
Subject(s)
Spectrophotometry, Infrared/instrumentation , Spectrophotometry, Infrared/methods , Cadmium Compounds/chemistry , Calcium Fluoride/chemistry , Mercury Compounds/chemistry , Polymers/chemistry , Sodium Chloride/chemistry , Xylenes/chemistryABSTRACT
A comparison of prism-based spectrographs to grating-based spectrographs is made when each of the systems is coupled to a modern-day liquid-nitrogen-cooled photovoltaic array detector. A comparison of the systems is also made using a room-temperature microbolometer array detector. Finally, infrared microspectroscopy of samples whose size is approximately 10 micrometers will be demonstrated using a prism spectrograph outfitted with both types of detectors. The results of the study show that prism-based spectrographs offer an economical alternative to grating-based systems when spectral coverage is more critical than spectral resolution. The results also demonstrate that spectra with good signal-to-noise ratios can be collected on any of the systems with a total integration time of 10 seconds or less.
Subject(s)
Refractometry/instrumentation , Signal Processing, Computer-Assisted/instrumentation , Spectrophotometry, Infrared/instrumentation , Transducers , Equipment Design , Equipment Failure Analysis , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Properties of polymer alloys comprising poly(lactic acid) and Nodax copolymers are investigated. Nodax is a family of bacterially produced polyhydroxyalkanoate (PHA) copolymers comprising 3-hydroxybutyrate (3HB) and other 3-hydroxyalkanoate (3HA) units with side groups greater than or equal to three carbon units. The incorporation of 3HA units with medium-chain-length (mcl) side groups effectively lowers the crystallinity and the melt temperature, Tm, of this class of PHA copolymers, in a manner similar to that of alpha olefins controlling the properties of linear low density polyethylene. The lower Tm makes the material easier to process, as the thermal decomposition temperature of PHAs is then relatively low. The reduced crystallinity provides the ductility and toughness required for many plastics applications. When a small amount of ductile PHA is blended with poly(lactic acid) (PLA), a new type of polymer alloy with much improved properties is created. The toughness of PLA is substantially increased without a reduction in the optical clarity of the blend. The synergy between the two materials, both produced from renewable resources, is attributed to the retardation of crystallization of PHA copolymers finely dispersed in a PLA matrix as discrete domains.
