Thermal Stability of MAX Phases

2014 ◽  
Vol 617 ◽  
pp. 153-158 ◽  
Author(s):  
It Meng Low ◽  
Wei Kong Pang
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Surface Layer ◽  
Neutron Diffraction ◽  
Thermal Dissociation ◽  
High Vacuum ◽  
Max Phases ◽  
Binary Carbide ◽  
Thermal Stability Of

The susceptibility of MAX phases to thermal dissociation at 1300-1550 °C in high vacuum has been studied using in-situ neutron diffraction. Above 1400 °C, MAX phases decomposed to binary carbide (e.g. TiCx) or binary nitride (e.g. TiNx), primarily through the sublimation of A-elements such as Al or Si, which results in a porous surface layer of MXx being formed. Positive activation energies were determined for decomposed MAX phases with coarse pores but a negative activation energy when the pore size was less than 1.0 μm. The insights for tailor-design of MAX phases with controlled thermal stability and intercalated MXenes for energy storage are addressed.

Decomposition Kinetics of MAX Phases in Extreme Environments

2013 ◽  
pp. 34-48 ◽  
Author(s):  
I.M. Low ◽  
W.K. Pang
Keyword(s):  
Elevated Temperatures ◽  
Thermal Dissociation ◽  
High Vacuum ◽  
Extreme Environments ◽  
Decomposition Kinetics ◽  
Avrami Equation ◽  
Max Phases ◽  
Binary Carbide ◽  
In Situ Neutron Diffraction ◽  
Kinetics Of

MAX phases are remarkable materials but they become unstable at elevated temperatures and decompose into binary carbides or nitrides in inert atmospheres. The susceptibility of MAX phases to thermal dissociation at 1300-1550 °C in high vacuum has been studied using in-situ neutron diffraction. Above 1400 °C, MAX phases decomposed to binary carbide (e.g., TiCx) or binary nitride (e.g., TiNx), primarily through the sublimation of A-elements such as Al or Si, which results in a porous surface layer of MXx being formed Positive activation energies were determined for decomposed MAX phases with coarse pores but a negative activation energy when the pore size was less than 1.0 µm. The kinetics of isothermal phase decomposition at 1550 °C was modelled using a modified Avrami equation. An Avrami exponent (n) of < 1.0 was determined, indicative of the highly restricted diffusion of Al or Si between the channels of M6X octahedra. The role of pore microstructures on the decomposition kinetics is discussed.

scholarly journals An Overview of Parameters Controlling the Decomposition and Degradation of Ti-Based Mn+1AXn Phases

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 473 ◽  
Author(s):  
It-Meng Low
Keyword(s):  
Activation Energy ◽  
Surface Layer ◽  
Chemical Etching ◽  
Vacuum Annealing ◽  
Decomposition Kinetics ◽  
Phase Decomposition ◽  
Max Phases ◽  
Binary Carbide ◽  
Kinetics Of ◽  
Critical Overview

A critical overview of the various parameters, such as annealing atmospheres, pore microstructures, and pore sizes, that are critical in controlling the decomposition kinetics of Ti-based MAX phases is given in this paper. Ti-based MAX phases tend to decompose readily above 1400 °C during vacuum annealing to binary carbide (e.g. TiCx) or binary nitride (e.g. TiNx), primarily through the sublimation of A elements such as Al or Si, forming in a porous MXx surface layer. Arrhenius Avrami equations were used to determine the activation energy of phase decomposition and to model the kinetics of isothermal phase decomposition. Ironically, the understanding of phase decomposition via exfoliating or selective de-intercalation by chemical etching formed the catalyst for the sensational discovery of Mxenes in 2011. Other controlling parameters that also promote decomposition or degradation as reported in the literature are also briefly reviewed and these include effects of pressure and ion irradiations.

scholarly journals Synthesis, electrical properties, and kinetic thermal analysis of polyaniline/ polyvinyl alcohol - magnetite nanocomposites film

2019 ◽  
Vol 26 (1) ◽  
pp. 347-359 ◽  
Author(s):  
Huda AlFannakh ◽  
S. S. Arafat ◽  
S. S. Ibrahim
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Thermal Analysis ◽  
In Situ Polymerization ◽  
Poly Vinyl Alcohol ◽  
Electrical Hysteresis ◽  
Current Voltage ◽  
Three Phase ◽  
Thermal Stability Of

AbstractPolyaniline-poly vinyl alcohol (PANI-PVA) conducting blends containing 15 wt% aniline were synthesized by in situ polymerization of aniline. Three-phase polymer blended nanocomposites with different contents of magnetite (5, 10 and 15 wt.%) were also synthesized. We measured the current-voltage (I-V) curves for the conducting blend and its magnetite nanocomposite. We also measured their thermal stability, and performed kinetic analysis through thermogravimetric analysis. We observed that the three phase nanocomposites showed enhanced electrical conductivity compared with that of the conductive blend, and no electrical hysteresis. The PVA/PANi blend was more stable above 350∘C and the addition of Fe3O4 enhanced the thermal stability of the conductive blend. The apparent activation energy of the three phase nanocomposites was greater than those of both the pure PVA and PVA/PANi samples. These results suggest that such three phase nanocomposites could be used in a range of applications.

Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy

1999 ◽  
Vol 567 ◽  
Author(s):  
Masayuki Suzuki ◽  
Yoji Saito
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Oxide Films ◽  
Silicon Surfaces ◽  
Gaseous Mixtures ◽  
X Ray ◽  
Initial Stage ◽  
Thermal Stability Of

ABSTRACTWe tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.

An in situ TEM observation on the thermal stability of a nanocrystalline FeBSi alloy

1993 ◽  
Vol 16 (5) ◽  
pp. 260-264 ◽  
Author(s):  
H.Y. Tong ◽  
B.Z. Ding ◽  
H.G. Jiang ◽  
Z.Q. Hu ◽  
L. Dong ◽  
...  
Keyword(s):  
Thermal Stability ◽  
In Situ Tem ◽  
Thermal Stability Of

Meyer-Neldel Rule on thermal stability parameters (trap depth and frequency factor) of luminescence signals in quartz

2021 ◽  
Author(s):  
Zuzanna Kabacińska ◽  
Alida Timar-Gabor ◽  
Benny Guralnik
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Hydrogen Diffusion ◽  
Dose Range ◽  
Accurate Determination ◽  
Frequency Factor ◽  
Proton Conduction ◽  
High Dose ◽  
Compensation Law ◽  
Thermal Stability Of

&lt;p&gt;Thermally activated processes can be described mathematically by the Arrhenius equation. The Meyer-Neldel Rule (MNR), or compensation law, linearly relates the pre-exponent term to the logarithm of the excitation enthalpy for processes that are thermally driven in an Arrhenian manner. This empirical rule was observed in many areas of materials science, in physics, chemistry, and biology. In geosciences it was found to uphold in hydrogen diffusion (Jones 2014a) and proton conduction (Jones 2014b) in minerals.&lt;/p&gt;&lt;p&gt;Trapped charge dating methods that use electron spin resonance (ESR) or optically or thermally stimulated luminescence (OSL and TL) are based on the dose-dependent accumulation of defects in minerals such as quartz and feldspar. The thermal stability of these defects in the age range investigated is a major prerequisite for accurate dating, while the accurate determination of the values of the trap depths and frequency factors play a major role in thermochronometry applications.&amp;#160;&lt;/p&gt;&lt;p&gt;The correlation of kinetic parameters for diffusion has been very recently established for irradiated oxides (Kotomin et al. 2018). A correlation between the activation energy and the frequency factor that satisfied the Meyer&amp;#8211;Neldel rule was reported when the thermal stability of [AlO&lt;sub&gt;4&lt;/sub&gt;/h&lt;sup&gt;+&lt;/sup&gt;]&lt;sup&gt;0&lt;/sup&gt; and [TiO&lt;sub&gt;4&lt;/sub&gt;/M&lt;sup&gt;+&lt;/sup&gt;]&lt;sup&gt;0&lt;/sup&gt; ESR signals in quartz was studied as function of dose (Benzid and Timar-Gabor 2020). Here we compiled the optically stimulated luminescence (OSL) data published so far in this regard, and investigated experimentally the thermal stability of OSL signals for doses ranging from 10 to 10000 Gy in sedimentary quartz samples. We report a linear relationship between the natural logarithm of the preexponent term (the frequency factor) and the activation energy E, corresponding to a Meyer-Neldel energy of 45 meV, and a deviation from first order kinetics in the high dose range accompanied by an apparent decrease in thermal stability. The implications of these observations and the atomic and physical mechanisms are currently studied.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Benzid, K., Timar Gabor, A. 2020. The compensation effect (Meyer&amp;#8211;Neldel rule) on [AlO&lt;sub&gt;4&lt;/sub&gt;/h&lt;sup&gt;+&lt;/sup&gt;]&lt;sup&gt;0&lt;/sup&gt; and [TiO&lt;sub&gt;4&lt;/sub&gt;/M&lt;sup&gt;+&lt;/sup&gt;]&lt;sup&gt;0&lt;/sup&gt; paramagnetic centers in irradiated sedimentary quartz. &lt;em&gt;AIP Advance&lt;/em&gt;s 10, 075114.&lt;/p&gt;&lt;p&gt;Kotomin, E., Kuzovkov, V., Popov, A. I., Maier, J., and Vila, R. 2018. Anomalous kinetics of diffusion-controlled defect annealing in irradiated ionic solids. &lt;em&gt;J. Phys. Chem. A&lt;/em&gt; 122(1), 28&amp;#8211;32&lt;/p&gt;&lt;p&gt;Jones, A. G. (2014a), Compensation of the Meyer-Neldel Compensation Law for H diffusion in minerals, &lt;em&gt;Geochem. Geophys. Geosyst.&lt;/em&gt;, 15, 2616&amp;#8211;2631&lt;/p&gt;&lt;p&gt;Jones, A. G. (2014b), Reconciling different equations for proton conduction using the Meyer-Neldel compensation rule, &lt;em&gt;Geochem. Geophys. Geosyst&lt;/em&gt;., 15, 337&amp;#8211;349&lt;/p&gt;

Thermal Stability of 40Cr Steel with Surface Nanocrystallization

2006 ◽  
Vol 510-511 ◽  
pp. 434-437 ◽  
Author(s):  
Yu Liang Liu ◽  
Tian Ying Xiong ◽  
Ke Yang
Keyword(s):  
Thermal Stability ◽  
Surface Layer ◽  
Nanostructured Materials ◽  
High Thermal Stability ◽  
New Method ◽  
Nanostructured Surface ◽  
Surface Nanocrystallization ◽  
Nanostructured Layer ◽  
40Cr Steel ◽  
Thermal Stability Of

Surface Nanocrystallization(SNC) is a new method of fabricating nanostructured materials while thermal stability is an important problem for the application of nanostructured materials. A nanostructured layer was fabricated on the surface of 40Cr steel by Supersonic Particles Bombarding method, and the variation of microstructure and microhardness of nanostructured layer was studied. Nanostructured surface layer showed high thermal stability.

In-Situ Annealing Study on the Thermal Stability of Nickel Germanides

2007 ◽  
Vol 50 (3) ◽  
pp. 677 ◽  
Author(s):  
Jae-Wook Jae-Wook ◽  
Kyung-Hwan Kyung-Hwan ◽  
Hyoungsub Hyoungsub ◽  
Cheol-Woong Cheol-Woong ◽  
Dongwon Dongwon ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Nickel Germanides ◽  
Annealing Study ◽  
Thermal Stability Of
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