The thermal stability of amorphous borosilicon nitride
(Si3B3N7) and borosilicon carbonitride
(SiBN3C) between 1000°C and 2000oC both in air and
under inert conditions is reported. Both materials are derived from
polymerization and subsequent pyrolysis of a “single source” precursor. On
heating in vacuum or nitrogen SiBN3C remains amorphous up to lCWC
whereas Si3B3N7 crystallizes at about
1800°C under these conditions. At about 2000^ the SiBN(C)-materials
decompose into SiC, BN, B4C and N2.Oxidation studies performed by TEM- and SEM-investigations of oxidized
borosilicon carbonitride grains reveal that an interlayer consisting of B,
N, and only little O is formed between the oxide scale on the surface and
the inner bulk material. The interlayer does not disappear at temperatures
above 1450°C in contrast to the Si2N20-interiayer
observed on oxidized silicon nitride. The oxidation kinetics of the new
ceramics are established in the range from 1000°C to 1600°C indicating a
very high oxidation resistance. Possible applications as matrix materials as
well as materials for fibers and coatings are discussed.
Communication: BC4N, a new carbon material containing boron and nitrogen is formed in high yield by the thermal decomposition of pyridine–borane at 1050°C in argon. X‐ray powder diffraction shows hk0 and 00l reflections indicating a turbostratic structure. X‐ray photoelectron spectroscopy and analytical investigation in the transmission electron microscope reveal the random distribution of BC, BN, and CC bonds present in the carbon residue.
Die thermische Zersetzung von Amin‐Boranen im Temperaturintervall von Raumtemperatur bis 1050°C sowie die Phasenumwandlung des aus BH3 · C5H5N erhaltenen Rückstands bei Temperaturen bis 2200°C wird untersucht. Der Pyrolyseverlauf wird thermogravimetrisch und massenspektroskopisch verfolgt. Nach elementaranalytischen und photoelektronenspektroskopischen (ESCA) Ergebnissen handelt es sich bei den Zersetzungsprodukten um einphasiges Borcarbidnitrid (BxCyNz), einem Bor und Stickstoff enthaltenden pyrolytischen Kohlenstoff. Dies wird auch durch die analytische Elektronenspektroskopie bestätigt. Durch nachfolgende „Auslagerung”︁ des aus Pyridin‐Boran erhaltenen amorphen BxCyNz in einer Heißpresse bei 1800°C und 190 MPa Druck werden whiskerförmige Kristalle, deren d‐Werte auf die Bildung von BN und/oder Graphit hinweisen, erhalten.
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