Premium
Hafnium Reactivity with Boron and Carbon Sources Under Non‐Self‐Propagating High‐Temperature Synthesis Conditions
Author(s) -
Blum Yigal D.,
Marschall Jochen,
Hui David,
Adair Brian,
Vestel Michael
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02329.x
Subject(s) - boron , materials science , hafnium , melting point , carbon fibers , reactivity (psychology) , particle (ecology) , chemical engineering , microscale chemistry , atmospheric temperature range , metal , homogeneous , chemistry , thermodynamics , zirconium , metallurgy , composite number , composite material , organic chemistry , medicine , alternative medicine , oceanography , mathematics education , mathematics , pathology , physics , engineering , geology
The homogeneous and heterogeneous reactions of hafnium (Hf) with boron (B) or carbon (C) powders were studied under non‐self‐propagating high‐temperature synthesis (SHS) conditions in searching for chemically aided processes of ultra‐high‐temperature ceramics at mild and practical conditions. The threshold interactions of the Hf/B and Hf/C powder mixtures consisting of relatively large Hf particles occur at 700° and 800°C, respectively, with no observation of particle melting as previously postulated for igniting SHS reactions. A microscale melting phenomenon at the Hf surface was observed by scanning electron microscopy analysis in heterogeneous reactions between Hf metal strips and B or C powders at the temperature range of 1100°–1200°C, more than 1000°C below the incipient melting point of the metal. The non‐SHS conditions allow halting the reactions at intermediate stages for analytical purposes. Kinetic studies of the homogeneous and heterogeneous reactions, heat transfer model analyses, and their association with the investigation of microstructural phenomena were used to postulate the mechanism involved in the observed reactions.