Engi-Mat (United States)

Scandate cathodes have long attracted attention due to their higher emission current density, apparent low work function, and anticipated improved longevity compared to conventional cathodes. However, scandate cathodes have not been applied as extensively as their potential would imply. In this study, the compositional homogeneity of a scandia/tungsten composite powder was investigated by scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. From these techniques, a sample providing the optimal coverage of tungsten by scandia particles was then chosen. A cathode fabricated from this sample displayed a greater than 200°C decrease (improvement) in knee temperature versus the standard M-type cathode.

NanoSpray Combustion™ processing is a versatile and cost-effective manufacturing method for a wide range of materials, including nanopowders and nanostructured thin films. The NanoSpray process is used in combustion chemical vapor condensation (nCCVC) mode for making metal oxide, metal phosphate, and select metal nanopowders while combustion chemical vapor deposition (nCCVD) is used to make thin films. In this chapter, we will use NanoSpray Combustion process as a benchmark and review its capabilities to that of other nanomaterials’ fabrication processes. Examples will mostly be of nanopowders synthesized using nCCVC. Applications of the nanomaterials in the electronic and energy sectors will be discussed.

The solubility of platinum(II) acetylacetonate (Pt(acac)2) in various solvent mixtures of acetone, cyclohexanol, propylene carbonate and 1,2,3,4-tetrahydronaphthalene (THN) have been determined at 25 °C and 1 atm, using thermogravimetric analysis (TGA) and inductively coupled plasma mass spectrometry (ICP-MS). The densities of the saturated solutions were determined by pycnometry. The entropy of fusion and melting point of Pt(acac)2 were determined by differential scanning calorimetry (DSC) to be 41.4 J mol−1 K−1 and 512.5 K, respectively. From this data, the ideal mole fraction at saturation (xideal) of Pt(acac)2 was calculated to be 0.0278, which is more than twice the highest reported solubility of that compound. In this effort, mixtures of acetone, propylene carbonate and THN exhibit cosolvency for Pt(acac)2, with the greatest measured molar solubility of Csat = 0.0675 mol L−1 occurring at the 1 ∶ 1 ∶ 1 v ∶ v ∶ v ratio of these three solvents. A new equation was developed for activity coefficients in solvent mixtures and used to predict ln γ for Pt(acac)2 to within 3.6% of the measured values. The concept of Intercomponent Mixture Parameters (IMPs) is introduced in relation to Scheffe mixture polynomials as applied to the prediction of activity coefficients in solvent mixtures.