The sulfur forms in coal have been determined using the variable oxidizing power of HClO{sub 4} which selectively converts the sulfur-containing components to sulfate for nephelometric measurement. Sulfate and pyrite were extracted with HClO{sub 4} boiling at 120{degree}C and 155{degree}C, respectively. Organic sulfur was oxidized with a boiling solution of 9:1 concd. HClO{sub 4} and concd. H{sub 3}Po{sub 4} at 205{degree}C. In all three steps, gaseous sulfur compounds were trapped in 15% H{sub 2}O{sub 2}. Sulfate was then determined in the reaction solution and the trap. For some coals, the total recovered sulfur was 0.1-0.3% (absolute) less than the total sulfur in the coal. One possible explanation was that acidic gases such as H{sub 2}S or SO{sub 2}, might not be trapped by the neutral H{sub 2}O{sub 2}. Therefore, the reaction scheme was performed on a Kentucky No. 9 coal with a 15% H{sub 2}O{sub 2} trap containing NH{sub 4}OH. However, even with the basic H{sub 2}O{sub 2} trap, the recoveries were still slightly low.

Perchloric acid

Oxidizing agent

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Gas-source molecular beam epitaxy of III–V nitrides

Journal of Crystal Growth (1997)

R. F. Davis Michael J. Paisley Zlatko Sitar Daniel J. Kester K. S. Ailey

10.1016/s0022-0248(97)00077-8

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Growth and characterization of cubic boron nitride thin films

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films (1994)

Daniel J. Kester K. S. Ailey Daniel J. Lichtenwalner R. F. Davis

Boron nitride (BN) thin films have been grown on [100] oriented single crystal Si, diamond, Cu and Ni substrates by ion beam assisted deposition using electron beam evaporation of boron together with simultaneous bombardment by nitrogen and argon ions. Characterization by Fourier-transform infrared spectroscopy and high-resolution transmission electron microscopy showed that the films on Si and diamond consisted of initial noncubic (amorphous and hexagonal BN) layers, followed by the growth of cubic BN (c-BN). This growth sequence was attributed primarily to increasing compressive intrinsic stress with increased film thickness. Increasing the substrate temperature above 400 °C led to the onset of c-BN at a greater film thickness while increased ion flux resulted in earlier growth of this phase. These results may be explained by the relaxation of the intrinsic stress in the films at higher temperatures due to increased adatom mobility and to increased intrinsic stress in the films resulting from increased ion bombardment. Lower temperatures led to mixed phase growth. A minimum substrate temperature (200–300 °C) is required for nucleation and growth of single phase c-BN by this technique. It is believed that the interstitial Ar observed in Rutherford backscattering spectrometry studies is primarily responsible for the stress generation in the films. A combination of h-BN and c-BN was deposited on Ni; only h-BN was obtained on Cu substrates.

Rutherford backscattering spectrometry

Ion beam-assisted deposition

10.1116/1.578938

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Citations (142)

Pseudomorphic semiconducting heterostructures from combinations of AlN, GaN, and selected SiC polytypes: Theoretical advancement and its coordination with experimental studies of nucleation, growth, characterization, and device development

R. F. Davis K. S. Ailey R. S. Kern Robert Patterson Satoru Tanaka

Characterization

Wide-bandgap semiconductor

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