This paper describes the application of calorimetry to the measurement of the excess molar enthalpies for binary mixtures of nonelectrolytes. Batch, displacement, and flow calorimeters are described, using as examples the batch calorimeter of McGlashan;, the displacement calorimeters of Van Ness and of Marsh and Stokes, and the flow calorimeters of Christensen, Wormald, and Picker. Applications are described using calorimeters to measure for {(nonpolar + nonpolar), (polar + nonpolar), and (polar + polar)} mixtures. Excess enthalpies for liquid mixtures containing charge-transfer complexes and hydrogen bonds are used to help in understanding the nature of the molecular interactions in these systems. Applications involving measurements on liquid, gas, and supercritical fluid mixtures, including measurements in the near-critical region, are also described. The use of calorimetric measurements to determine {(liquid + liquid) and (vapor + liquid)} phase equilibria is discussed. Finally, equations used to represent (x) measurements are summarized.

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We have investigated the evolution of structural and optical properties of GaAsN nanostructures synthesized by N ion implantation into epitaxial GaAs, followed by rapid thermal annealing. Transmission electron microscopy and x-ray diffraction indicate the formation of nanometer-sized crystallites with lattice parameters close to those of pure zincblende GaN. The average crystallite size increases with annealing temperature while the size distribution is self-similar and the volume fraction remains constant, suggesting a coarsening process governed by Ostwald ripening. These GaAsN nanostructures exhibit significant photoluminescence in the near infrared range. The apparent lowering of the fundamental band gap is likely due to the incorporation of a small amount of As in GaN.