Ammonium dichromate and chromium chloride were examined via thermogravimetric and differential thermal analyses and used to grow α-Cr2O3 via mist chemical vapor deposition. Only the former resulted in noticeable film formation. Using ammonium dichromate, α-Cr2O3 single crystals were grown in a wide growth-temperature range of 300–440 °C. The dependences of the lattice constants a and c on the growth temperature and precursor concentration were explained by combination of (i) lattice reconstruction and (ii) unit-cell volume variation. A maximum growth rate of 10 nm/min; a low (0006) rocking-curve full width at half maximum of 150 arcsec; and low a and c lattice mismatches (with α-Ga2O3) of 0.7 and 1.4%, respectively, were achieved.
Yttrium iron garnet (YIG) thin films were deposited on c-plane sapphire substrates under atmospheric pressure by a mist CVD technique, and their chemical composition and optical properties were examined. The thin films deposited at 450 °C showed an [Y]/[Fe] ratio of 0.57, indicating the deposition of yttrium iron oxide, while the molar ratio of [Y]/[Fe] in the precursor solution was set at 1.5. A thermodynamic model was developed to explain the reaction paths of the YIG thin film fabrication process using thermogravimetric differential thermal analysis (TG-DTA) results. The model indicates that the decomposition rate of yttrium acetylacetonate [Y(acac)3 ∙ nH2O] was much lower than that of iron acetylacetonate [Fe(acac)3], providing a plausible explanation for the large difference between the composition ratio of the thin films and that of the precursor solutions.
The coronavirus disease 2019 symptoms in children are relatively mild and often do not require treatment. Nonetheless, complications caused by the immune response to COVID-19 in children are possible and diverse. We present the case of a 7-year-old girl with persistent fever and lymphadenopathy arising from SARS-CoV-2 infection, diagnosed with Kikuchi-Fujimoto Disease (KFD) on lymph node biopsy. KFD is a rare benign disease, clinically characterized by fever and tender cervical lymphadenopathy affecting posterior cervical lymph nodes. We also reviewed six previously reported cases of COVID-19-associated KFD that occurred in school-aged children and compared them with the present case. The clinical course of COVID-19-associated KFD was similar to that of previous reports of KFD with a favorable prognosis. This is the first report of a school-aged child developing KFD following SARS-CoV-2 infection. KFD should be considered when approaching patients with hyperinflammatory states who present with prolonged fever and cervical lymphadenopathy after COVID-19.
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