Kinetic analysis of thermite reaction in Al–Ti–Fe2O3 system to produce (Fe,Ti)3Al–Al2O3 nanocomposite (original) (raw)
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2019
The effect of ball milling on kinetics of the thermite reaction of 3Fe2O3 + 8Al powder mixture to synthesizeFe3Al-Al2O3 nanocomposite was investigated using differential thermal analysis. A model-free methodwas applied to the non-isothermal differential calorimetry (DSC) data to evaluate the reaction kineticsaccording to the Starink method. The activation energy of the thermite reaction in the Fe2O3-Al systemin ball milled 3Fe2O3 + 8Al powder mixture was determined to be 97 kJ/mole, which is smaller thanthat for non-milled powder mixture indicating the change of reaction mechanisms. The change in thereaction mechanism could be resulted from the formation of short-circuit diffusion paths occurring inthe precursors during milling. The change in the reaction mechanism of such nanostructured 3Fe2O3 +8Al powder mixture could be reason of the formation of desired phases (Fe3Al and Al2O3), which suchstoichiometric phases cannot be achieved by conventional molten state thermite reaction.
Reaction characteristics of Al/Fe2O3 nanocomposites
Journal of Industrial and Engineering Chemistry, 2012
Al/Fe 2 O 3 nonacomposites have explosive and high exothermic properties by thermite reaction. In this study, Al/Fe 2 O 3 xerogel nanocomposites were prepared by sol-gel method and thermite reaction performance was compared with those prepared by physical mixing with sonication. Scanning electron microscopy (SEM) images of Al/Fe 2 O 3 xerogel nanocomposites show that network structure of Fe 2 O 3 gel covers Al nanoparticles efficiently and this indicates that improvement of thermite reaction performance due to close contact between a fuel and an oxidizer. Optimum mole ratio of Al/Fe was determined to be 2 by thermite reaction performance by differential scanning calorimetry (DSC) analysis. At Al/Fe ratio of 2, thermite reaction enthalpy of the Al/Fe 2 O 3 xerogel nancomposite was 991.4 J/g, which was higher by a factor of four than that of the nanocomposite prepared by physical mixing.
Mechanochemical behavior of Fe2O3–Al–Fe powder mixtures to produce Fe3Al–Al2O3 nanocomposite powder
Journal of Materials Science, 2008
Mechanical treatment of Fe 2 O 3 , Al and Fe powder mixtures was carried out in a high energy ball mill to synthesize Fe 3 Al-Al 2 O 3 intermetallic matrix nanocomposite. Different compositions including 3Fe + Al, Fe 2 O 3 + 2Al, 3Fe 2 O 3 + 8Al and Fe 2 O 3 + 3Al+Fe were chosen in this study. Phase development and structural changes occurring during ball milling were investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that during MA, Fe 2 O 3 , Al, and Fe react to give a nanocrystalline Fe 3 Al intermetallic compound matrix. The presence of pure Fe in initial powder mixture changed the modality of mechanochemical process from sudden to gradual reaction. The Fe 3 Al-Al 2 O 3 compound had a finer microstructure and particles size compared to the Fe 3 Al compound.
2020
During the last decade, mechanochemical synthesis, which can provide the nanostructured constituents, has been considered as an alternative technique to the conventional thermite reactions to produce the metallic-ceramic composite. Detection of the reinforcement in such nanocomposite powders has been provided challenges as a result of low volume fraction and high induced lattice strain. In this work, the mechanochemical reaction of a non-stoichiometry Fe2O3-Al system (Fe2O3+Al+Fe powder mixture) was performed to produce the Fe3Al-30 vol.% Al2O3 nanocomposite. The progress of the reaction was followed by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). XRD analysis of mechanochemically synthesized Fe3Al-30 vol.% Al2O3 nanocomposite showed no evidence of the produced Al2O3 phase, whereas TEM analysis revealed the crystalline Al2O3 phase. The X-ray absorption by component higher mass absorption coefficient (Fe3Al matrix) in highly strained nanocomposite leads to a...
Mechanochemical synthesis of (Fe,Ti)3Al–Al2O3 nanocomposite
Journal of Alloys and Compounds, 2009
Formation mechanism of (Fe,Ti) 3 Al-Al 2 O 3 nanocomposite prepared by mechanical alloying of Fe, Al and TiO 2 with molar ratio of 6:7:3 was studied. The structural changes of powder particles during mechanical alloying were investigated by X-ray diffractometery. Morphology and microstructure of powder particles were characterized by scanning electron microscopy. It was found that during mechanical alloying Al first reacts with TiO 2 leading to the gradual formation of crystalline Ti and amorphous Al 2 O 3 phases. In the second stage Ti and remaining Al diffuse into the Fe lattice and as a result a Fe(Al,Ti) solid solution develops. This structure transformed to (Fe,Ti) 3 Al intermetallic compound at longer milling times. Heat treatment of this structure led to the crystallization of Al 2 O 3 and ordering of (Fe,Ti) 3 Al phases.
Thermal and X-ray analyses of aluminum–titanium nanocomposite powder
Journal of Thermal Analysis and Calorimetry, 2017
The present study has investigated the complex mechanisms in the aluminum-titanium system with different percentages of titanium through a combination of thermal and X-ray analyses. Thermogravimetry, derivative thermogravimetric, X-ray diffraction, scanning electron microscope and transition electron microscope were used for characterization of the samples. Initially, different Al-Ti powder mixtures were produced by high-energy ball milling and after 30 h of milling the phases generated at different percentages of Ti were analyzed. The XRD results revealed that the intermetallic Al 3 Ti powder is obtained after a certain duration of milling. In addition, L1 2 to D0 23 phase transformation is possible with increase of the Ti percent. Analyses of the powder annealed at different temperatures yielded interesting results, including the effect of stearic acid as the surface control agent on phase transformations of the aluminum-titanium system and also the formation of unexpected phases such as Al 4 C 3 and TiC. Moreover, ductile to brittle transition during phase transformations of the intermetallic Al 3 Ti powder was quite conspicuous, which could result in more homogeneity of the powders and the occurrence of more reactions in the system. For example, formation of D0 23-Al 3 Ti powder which is more brittle compared to L1 2 resulted in the exit of Al from among its layers, leading to the increase of the chances for Al reaction with the system impurities.
Characterization of Al– AL2O3 Nanocomposite Powders Synthesized by High-Energy Ball Milling
JES. Journal of Engineering Sciences, 2012
Metal matrix composite powders of Al-Al2O3 with weight fraction of 20 % Al2O3 could be synthesized by high-energy milling of the mixed powders. Three different experiments were carried out at the same operating conditions, but with three different rotation speeds; 200, 300, and 400rpm. A homogenous distribution of the Al2O3 reinforcement in the Al matrix was obtained after milling the mixed powders for periods of 60, 45, and 30 h. The homogenous distribution of Al2O3 in the Al matrix was achieved by characterizing these nanocomposite powders by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. X-ray patterns were analyzed by using the Williamson-Hall treatment to determine the crystallite size and the lattice strain.
Metallurgical and Materials Transactions A, 2012
Al-30 vol pct Al 2 O 3 nanocomposite powder was synthesized by mechanochemical reaction of Fe-NiO-Al powder mixtures. Structural evolution during mechanical alloying was studied by employing X-ray diffractometry (XRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM). After 78 minutes of milling, the (Ni, Fe) 3 Al-30 vol pct Al 2 O 3 nanocomposite can be synthesized by reaction 3Fe + 7Al + 6NiO with a combustion mode. DTA results revealed that milling for 60 minutes decreases the temperature of reaction from 1040 K to 898 K (767°C to 625°C). TEM images corroborate a homogenous dispersion of reinforcements in the matrix of the nanocomposite proving that the reduction in the crystallite size of both reinforcements and matrix is within the nanometer range.
Al2O3 nanoparticle reinforced Fe-based alloys synthesized by thermite reaction
Journal of Materials Science, 2012
It is very difficult to manufacture oxide nanoparticle strengthened alloys through the conventional casting in the gravity field or even in the space microgravity environment. A thermite reaction process was used to produce molten metal that was then solidified in a graphite mold in super gravity field caused by centrifugal force; we were able to obtain Al 2 O 3 nanoparticle reinforced Fe-based alloys. The formation of Al 2 O 3 nanoparticles was related to the addition of TiO 2 xerogel to the thermite mixture, and their uniform distribution in the alloy can be explained by their assembly in (Ni, Fe)Al intermetallics during solidification owing to the low interfacial energy between them.