Browsing by Author "Palmquist, JP"

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    Comparison of thermal stability in MAX 211 and 312 phases
    (Insitute of Physics, 2010-05-03) Pang, WK; Low, IM; O'Connor, BH; Studer, AJ; Peterson, VK; Sun, ZM; Palmquist, JP
    The susceptibility of four MAX phases (Ti 2 AlC, Cr 2 AlC, Ti 3 AlC 2 , and Ti 3 SiC 2 ) to high-temperature thermal dissociation in vacuum has been investigated using in-situ neutron diffraction. In high vacuum, these phases decomposed above 1400°C through the sublimation of M and A elements, forming a surface coating of MC. The apparent activation energies for the decomposition of sintered Ti 3 SiC 2 , Ti 3 AlC 2 , and Ti 2 AlC were determined to be 179.3, -71.9, and 85.7 kJ mol −1 , respectively. The spontaneous release of Ti 2 AlC and TiC from de-intercalation during decomposition of Ti 3 AlC 2 resulted in a negative activation energy.© 2010, Insitute of Physics
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    Diffraction study on the thermal stability of Ti3SiC2/TiC/TiSi2 composites in vacuum
    (American Institute of Physics, 2009-06-29) Pang, WK; Low, IM; O’Connor, BH; Studer, AJ; Peterson, VK; Palmquist, JP
    Titanium silicon carbide (Ti3SiC2) possesses a unique combination of properties of both metals and ceramics, for it is thermally shock resistant, thermally and electrically conductive, damage tolerant, lightweight, highly oxidation resistant, elastically stiff, and mechanically machinable. In this paper, the effect of high vacuum annealing on the phase stability and phase transitions of Ti3SiC2/TiC/TiSi2 composites at up to 1550° C was studied using in‐situ neutron diffraction. The role of TiC and TiSi2 on the thermal stability of Ti3SiC2 during vacuum annealing is discussed. TiC reacts with TiSi2 between 1400–1450°C to form Ti3SiC2. Above 1400° C, decomposition of Ti3SiC2 into TiC commenced and the rate increased with increased temperature and dwell time. Furthermore, the activation energy for the formation and decomposition of Ti3SiC2 was determined. © 2009 American Institute of Physics
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    Effect of vacuum annealing on the thermal stability of Ti3SiC2/TiC/TiSi2 composites
    (The Australian Ceramic Society, 2009-01-01) Pang, WK; Low, IM; O’Connor, BH; Studer, AJ; Peterson, VK; Palmquist, JP
    Titanium silicon carbide (Ti3SiC2) possesses a unique combination of properties of both metals and ceramics, for it is thermally shock resistant, thermally and electrically conductive, damage tolerant, lightweight, highly oxidation resistant, elastically stiff, and mechanically machinable. In this research, the effect of high vacuum annealing on the phase stability and phase transitions of Ti3SiC2/TiC/TiSi2 composites up to 1550°C was studied using in-situ neutron diffraction. The role of TiC and TiSi2 on the thermal stability of Ti3SiC2 during vacuum annealing is discussed. TiC reacts with TiSi2 between 1400-1450°C to form Ti3SiC2. Above 1400°C, decomposition of Ti3SiC2 into TiC commenced and the rate increased with increased temperature and dwell time. Furthermore, the activation energy for the formatiTitanium silicon carbide (Ti3SiC2) possesses a unique combination of properties of both metals and ceramics, for it is thermally shock resistant, thermally and electrically conductive, damage tolerant, lightweight, highly oxidation resistant, elastically stiff, and mechanically machinable. In this research, the effect of high vacuum annealing on the phase stability and phase transitions of Ti3SiC2/TiC/TiSi2 composites up to 1550°C was studied using in-situ neutron diffraction. The role of TiC and TiSi2 on the thermal stability of Ti3SiC2 during vacuum annealing is discussed. TiC reacts with TiSi2 between 1400-1450°C to form Ti3SiC2. Above 1400°C, decomposition of Ti3SiC2 into TiC commenced and the rate increased with increased temperature and dwell time. Furthermore, the activation energy for the formation and decomposition of Ti3SiC2 was determined. on and decomposition of Ti3SiC2 was determined. © 2009, The Australian Ceramic Society
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    In situ diffraction study of thermal decomposition in Maxthal Ti2AlC
    (Elsevier, 2011-01-05) Pang, WK; Low, IM; O'Connor, BH; Peterson, VK; Studer, AJ; Palmquist, JP
    The thermal stability of Ti2AlC at elevated temperature (1000–1550°C) in vacuum has been investigated using in situ neutron diffraction. At temperatures above 1400°C, Ti2AlC became unstable and began to decompose via sublimation of Al, resulting in a porous surface layer of TiCx being formed. The apparent activation energy for Ti2AlC decomposition was determined to be 85.7 ± 2.6 kJ mol−1. The kinetics of isothermal phase decomposition was modelled using least-squares linear regression fitting and the Avrami equation. The corresponding least-squares regression exponent (R2) and Avrami constants (k and n) for isothermal decomposition were determined to be 0.89, 0.268 min−n and 0.1, respectively. © 2011, Elsevier Ltd.
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    Mapping of composition, phase transitions and properties in oxidized Ti3SiC2
    (Scientific.Net, 2008-02-01) Oo, Z; Low, IM; Palmquist, JP; Avdeev, M
    The oxidation characteristics, composition profile and phase transition of Ti3SiC2 in the temperature range 20-1400°C have been investigated by in-situ neutron diffraction and secondary ion mass spectroscopy (SIMS). Anatase has been observed to form at ~600°C, rutile at ~750°C and cristobalite at ∼1300°C. Depth-profiling results by SIMS and Vickers indentation have revealed a distinct gradient in composition and microhardness within the surface oxide layers. © 2021 by Trans Tech Publications Ltd.