BN/SiC Coating on SiC Tows Prepared by Chemical Vapor Infiltration. (November 2019)

• Record Type: Journal Article
• Authors: Qi, Zhe; Lv, Xiaoxu; Zhao, Wenqing; Zhu, Shizhen; Jiao, Jian
• Is Part Of: IOP conference series. Volume 678(2019)
• Publication Date: 2019-11
• Subjects: Materials science -- Periodicals; 620.1105
• DOI: 10.1088/1757-899X/678/1/012062
• Languages: English
• ISSNs: 1757-8981

Abstract

Abstract: Boron nitride (BN) and silicon carbide (SiC) coatings were prepared in sequence on desized SiC tows by chemical vapor infiltration (CVI) at the temperature of 950°C. BN was synthesized by the reaction between boron trichloride (BCl3 ) and ammonia (NH3 ) while SiC was from the thermal decomposition of methyl trichlorosilane (MTS). The thickness of the coatings was uniform on a certain cross section of a monofilament, and the thickest/thinnest ratio is less than ∼2 across the whole SiC tows for both SiC and BN coatings, as observed by scanning electron microscopy (SEM). Distinct β -SiC powder X-ray diffraction (XRD) pattern was obtained for as-prepared CVI SiC while as-prepared BN coating only showed a bump and a tiny peak corresponding to hexagonal BN ( h -BN). This result was verified by transmission electron microscopy (TEM) images, in which CVI BN only had curved diffraction fringes within small pockets, known as turbostractic structures( t -BN). However, t -BN possesses similar short-range structure to h -BN as demonstrated by 11 B solid-state NMR spectrum. SiCf /SiC minicomposites using the interphase coating mentioned above is currently under investigation.