Amorphous platinum dioxide, a-PtO2, films are formed commonly during reactive sputtering of platinum at relatively high power density levels and high oxygen partial pressures. The structure of a-PtO2 is intermediate between the crystalline alpha and beta phases of this compound and either phase may form upon annealing or by lowering the power density during sputtering. Amorphous platinum dioxide is a semiconductor, and its resistivity depends on deposition parameters. Films of a-PtO2 are dense, chemically resistant, smooth, reflective, and have a hardness similar to titanium nitride. The films may be reduced in hydrogen at room temperature or in carbon monoxide at 200 °C to produce metallic platinum with crystallite sizes in the range of 5–10 nm. Any of these properties may be exploited to produce films that could be used in the development of sensors, optical materials, and in microelectronics.
Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) have been used to study the microporosity and micromineralogy of vitrinite in a high-volatile bituminous coal (Illinois No. 6). Sections were selected from samples that contained representative amounts of vitrinite. Micropores and fine minerals with sizes ranging between l0 and 1000 A were observed. The minerals, primarily silicates, were heterogeneously distributed in layers parallel to the bedding plane of the coal. The radii of gyration, surface area, volume fraction, and size distribution of micropores, mesopores, and fine-size minerals were obtained from an analysis of the SAXS curves. The total volume fraction of these components was determined from the integrated intensity to be 0'09 _+ 0"02 cm 3 cm -3. The size distributions were found to be trimodal with peaks at 30, 100, and 220 A. These peaks are associated with micropores, microminerals, and mesopores respectively. The specific surfaces associated with each peak are 140__. 20, 3 _+ l, and 10_ 3 m 2 g-1, respectively, while the corresponding volume fractions are 0"004 +_ 0"001, 0"026 _+ 0-005, and 0"056 _+ 0"018 cm 3 cm-3 respectively. Comparison of the results from SAXS with those from TEM showed good agreement.
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