scholarly journals Combustion Synthesis of FeAl-based Composites from Thermitic and Intermetallic Reactions

Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 127 ◽  
Author(s):  
Chun-Liang Yeh ◽  
Chih-Yao Ke
Keyword(s):  
Activation Energy ◽  
Combustion Synthesis ◽  
Combustion Wave ◽  
Xrd Analysis ◽  
Synthesis Reaction ◽  
Phase Conversion ◽  
Reaction Series ◽  
Thermally Activated ◽  
Sem Micrograph ◽  
Combustion Wave Velocity

Combustion syntheses involving intermetallic and thermitic reactions were conducted to fabricate FeAl–TiB2–Al2O3 composites. Two combustion systems consisting of Fe, Al, Ti, Fe2O3 and B2O3 were studied for formation of xFeAl–yTiB2–Al2O3 composites with x = 1.5–3.5 and y = 0.5–0.8. In the reaction series, thermitic reduction of Fe2O3 and B2O3 by Al thermally activated the reaction between Fe and Al. As a result, the combustion wave of the synthesis reaction was sufficiently exothermic to propagate in a self-sustaining manner. With an increase in TiB2 and FeAl of the composites, the decrease of reaction exothermicity resulted in a decline of the combustion wave velocity and reaction temperature. The activation energy Ea = 88.92 kJ/mol was deduced for the synergetic combustion reaction. Based on XRD analysis, a thorough phase conversion was achieved and composites composed of FeAl, TiB2, and Al2O3 with different contents were obtained. The SEM micrograph showed the FeAl-based composite with a dense and connecting morphology.

scholarly journals Peculiarities of Self-Propagating High-Temperature Synthesis and Structure Formation of TiB2-Al2O3 and CrB2-Al2O3 Composites

2011 ◽  
Vol 13 (3-4) ◽  
pp. 161
Author(s):  
Z.A. Mansurov ◽  
D.S. Abdulkarimova ◽  
O. Odawara ◽  
A. Gubarevich ◽  
A.S. Rogachev ◽  
...  
Keyword(s):  
High Temperature ◽  
Combustion Wave ◽  
Xrd Analysis ◽  
Product Formation ◽  
Combustion System ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Different Types ◽  
Combustion Wave Velocity ◽  
Quenching Method

Preparation of TiB2-Al2O3 and CrB2-Al2O3 composites with a broad range of phase composition was  conducted by self-propagating high-temperature synthesis (SHS) involving reaction of different types. The formation of fibrous crystals of aluminum oxide with length of about 10-25 microns and with diameter of 200-500 nm at self-propagating high-temperature synthesis in the system 2B2O3-Cr2O3-6A1 was established. Thermite mixtures of Al-TiO2 and Al-TiO2-B2O3 were incorporated with the Ti-B combustion system to produce the composites of TiB2-Al2O3, within which the increase of the thermite mixture for a higher content of Al2O3 decreased the reaction temperature and combustion wave velocity. This implies that the thermite reaction of Al with TiO2 reduces the exothermicity of the overall SHS process. It was found that adoption of B2O3 as one of the thermite reagents improved the product formation effectively. For investigate the combustion wave in 0.75TiO2-0.25Ti-2B-Al system the «quenching» method was used. The XRD analysis shows that the final products containing diborides and aluminium oxide.

scholarly journals Combustion Synthesis of NbB2–Spinel MgAl2O4 Composites from MgO-Added Thermite-Based Reactants with Excess Boron

Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 210 ◽  
Author(s):  
Chun-Liang Yeh ◽  
Yin-Chien Chen
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Combustion Synthesis ◽  
Combustion Wave ◽  
Xrd Analysis ◽  
Activation Energies ◽  
Temperature Synthesis ◽  
Reaction Systems ◽  
High Temperature Synthesis ◽  
Spinel Mgal2o4

The formation of NbB2–MgAl2O4 composites from the MgO-added thermite-based reaction systems was investigated by self-propagating high-temperature synthesis (SHS). Two thermite mixtures, Nb2O5/B2O3/Al and Nb2O5/Al, were, respectively, adopted in Reactions (1) and (2). The XRD analysis confirmed the combination of Al2O3 with MgO to form MgAl2O4 during the SHS process and that excess boron of 30 atom.% was required to yield NbB2–MgAl2O4 composites with negligible NbB and Nb3B4. The microstructure of the composite reveals that rod-shaped MgAl2O4 crystals are closely interlocked and granular NbB2 are embedded in or scattered over MgAl2O4. With the addition of MgAl2O4, the fracture toughness (KIC) of 4.37–4.82 MPa m1/2 was obtained for the composites. The activation energies Ea = 219.5 ± 16 and 167.9 ± 13 kJ/mol for Reactions (1) and (2) were determined from combustion wave kinetics.

Validation of New Mathematical Model of Flank Wear by Different Methods

2012 ◽  
Vol 729 ◽  
pp. 169-174 ◽  
Author(s):  
Zoltán Pálmai ◽  
Márton Takács ◽  
Balázs Zsolt Farkas
Keyword(s):  
Activation Energy ◽  
Mathematical Model ◽  
Flank Wear ◽  
Technological Parameters ◽  
Wear Process ◽  
Oxidation Processes ◽  
Industrial Manufacturing ◽  
Thermally Activated ◽  
Optical Electron ◽  
The Mean

Having reviewed the literature on cutting and based on the optical, electron-optical and morphological examinations of wear processes we have reached the conclusion that it is possible to describe the abrasive, adhesive and thermally activated diffusion, oxidation processes in a single mathematical model. The model is a non-linear autonomous differential equation, which can be solved by simple numerical methods. The complex wear equation was validated by the results of the cutting tests performed with P20 carbide on C45 carbon steel. If we have this data, we can calculate the activation energy of the process determining the nature of the wear process. The apparent activation energy of wear is Q=151,7kJ/mol. The model can even be used with changing technological parameters, and the data necessary for the constants of the wear equation may as well be determined even by measurements performed on the tool during industrial manufacturing. By the mean of this data, we can calculate the activation energy determining the nature of the wear process.

Combustion Synthesis of Si3N4 from Si/NH4Cl at Low Nitrogen Pressure

2008 ◽  
Vol 368-372 ◽  
pp. 1767-1770 ◽  
Author(s):  
Yi Xiang Chen ◽  
Jiang Tao Li ◽  
Zhi Ming Lin ◽  
Guang Hua Liu ◽  
S.L. Yang ◽  
...  
Keyword(s):  
Combustion Synthesis ◽  
Combustion Temperature ◽  
Profile Analysis ◽  
Combustion Velocity ◽  
Nitrogen Pressure ◽  
Analysis Method ◽  
Α Phase ◽  
Steady Combustion ◽  
Combustion Wave Velocity ◽  
Low Nitrogen

Combustion synthesis (CS) of Si3N4 was accomplished by using as-milled Si/NH4Cl as reactants at low nitrogen pressure. The additive of NH4Cl decreased the combustion temperature and promoted the Si nitridation. Full nitridation of Si was achieved by burning Si in pressurized nitrogen with 10 ~ 25 wt. % NH4Cl as additives while no Si3N4 diluent added. The maximum combustion temperature (Tc), the combustion velocity (u) together with the α-Si3N4 content and mean particle size (d50) of the powder products were found to be great dependent on the NH4Cl content added in the reactants. Fine Si3N4 powder products with α-phase content up to 85 wt. % were obtained via steady combustion mode. A mathematical approach named combustion wave velocity methods for the analysis of temperature profiles in CS was proposed and the reaction kinetics was discussed. The apparent activation energy calculated according to the temperature profile analysis method is 29.7 kJ/mol, which agrees well with the corresponding low temperature nitriding combustion of Si.

Flameless Solution Combustion Synthesis of Al3+ Doped LiMn2O4

2011 ◽  
Vol 186 ◽  
pp. 7-10 ◽  
Author(s):  
Gui Yang Liu ◽  
Jun Ming Guo ◽  
Bao Sen Wang ◽  
Ying He
Keyword(s):  
Combustion Synthesis ◽  
Synthesis Method ◽  
Solution Combustion Synthesis ◽  
Xrd Analysis ◽  
Cycling Performance ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
Electrochemical Test ◽  
Micro Morphology ◽  
Better Than

Single phase Al3+ doped LiMn2O4 has been prepared by flameless solution combustion synthesis method at 600oC for 1h. X-ray diffraction (XRD) and scanning electric microscope (SEM) were used to determine the phase composition and micro morphology of the products. XRD analysis indicates that the purities increase and the lattice parameters of the products decrease with increasing Al3+ content. Electrochemical test indicates that the cycling performance of the products with Al3+ doping are better than that of the product without Al3+ doping. The product LiAl0.10Mn1.90O4 gets the best electrochemical performance. At the current density of 30mA/g, the initial discharge capacity of LiAl0.10Mn1.90O4 is 124.8mAh/g, and after 20 cycles, the capacity retention is more than 89%. SEM investigation indicates that the particles of LiAl0.10Mn1.90O4 are sub-micron in size and well dispersed.

scholarly journals Preparation and Characterization of Immobilized Molybdenum Complex on Pillared Montmorillonite K-10

2018 ◽  
Vol 1 (1) ◽  
Author(s):  
Farah Wahida Harun ◽  
Siti Balkis Mahamat Nor ◽  
Siti Salhah Othman
Keyword(s):  
Structural Characteristics ◽  
Xrd Analysis ◽  
Attenuated Total Reflection ◽  
Basal Spacing ◽  
Molybdenum Complex ◽  
X Ray ◽  
Pillared Montmorillonite ◽  
Sem Micrograph ◽  
Pillaring Solution

This study was carried out to immobilize molybdenyl (VI) acetylacetonate (MoO2(acac)2) complex on alumina pillared montmorillonite K-10 (MMT K-10). Pillar MMT K-10 was produced by introducing MMT K-10 with a hydrolysis solution of NaOH with AlCl3. Different concentrations of pillaring solution were prepared in terms of OHto Al3+ ratio (0.5, 1.0, 1.5 and 2.0) to observe the structural characteristics of MMT K-10. The pillared materials were then immobilized with 0.1 M MoO2(acac)2 and were characterized using X-ray diffractometry (XRD), scanning electron microscopy coupled in an energy dispersive X-ray spectrometer (SEM-EDX) and Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) techniques. FTIR bands at ca. 890 – 930 cm-1 indicate that the Mo complex was immobilized on the surface of pillared MMT K-10 not in between the layers. This is supported by the SEM and XRD analysis where the SEM micrograph showed deposition of Mo on the surface of MMT K-10 as well as no modification of basal spacing was observed by XRD. Meanwhile, the d(001) spacing of the alumina pillared MMT K10 samples were seen to increase slightly as the concentration of OH/Al3+ increased.

Static Recovery Activation Energy of Pure Aluminum at Room Temperature

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Yeh An-Chou ◽  
Chuang Ho-Chieh ◽  
Kuo Chen-Ming
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Pure Aluminum ◽  
Pure Copper ◽  
Tensile Tests ◽  
Engineering Strain ◽  
Static Recovery ◽  
Thermally Activated ◽  
Recovered Strain ◽  
Dislocation Annihilation

Thermally activated energy, which varies linearly with static recovered strain, is calculated from static recovery experiments of pure aluminum initially plastically deformed by strain-rate-controlled tensile tests up to 10% engineering strain at room temperature. The activation energy at the initial static recovery is 20 kJ mol−1, which is much less than that of pure copper and attributed to the dislocation annihilation by glide or cross-slip as well as higher stacking fault energy. Once dislocation annihilation processes are exhausted, more energy is required for subgrains to form and then grow. Eventually the recovered strain is slowed down and gradually saturated.

Combustion synthesis of Si3N4 powder

1997 ◽  
Vol 12 (3) ◽  
pp. 805-811 ◽  
Author(s):  
Wei-Chang Lee ◽  
Shyan-Lung Chung
Keyword(s):  
Reaction Mechanism ◽  
Combustion Synthesis ◽  
Combustion Temperature ◽  
Fine Particles ◽  
Minor Amount ◽  
Synthesis Reaction ◽  
Experimental Parameters ◽  
Combustion Synthesis Reaction ◽  
A Minor ◽  
Low Nitrogen

A combustion synthesis (SHS) process has been developed for the synthesis of Si3N4 powder under low nitrogen pressures. Si and NaN3 powders were used as the reactants, and NH4Cl powder was added as a catalytic agent. These powders were mixed and pressed into a cylindrical compact. The compact was wrapped up with an igniting agent (i.e., Ti + C), and the synthesis reaction was triggered by the combustion of the igniting agent. Addition of NH4Cl was found necessary for the combustion synthesis reaction under low nitrogen pressures (< 1.2 MPa). The product as synthesized is mostly in the form of agglomerated fine particles (0.1–1 μm in diameter) and is composed mainly of α-phase and a minor amount of β-phase. Effects of various experimental parameters (N2 pressure, NaN3, NH4Cl, and Si3N4 contents) on the product conversion and the combustion temperature were investigated. A possible reaction mechanism was proposed that explains the effects of the experimental parameters on the synthesis reaction.

The Crystallization of a-ZnTe

1975 ◽  
Vol 53 (22) ◽  
pp. 2481-2484 ◽  
Author(s):  
J. B. Webb ◽  
D. E. Brodie
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Crystallization Process ◽  
Amorphous Material ◽  
Amorphous State ◽  
Zinc Telluride ◽  
Thermally Activated ◽  
Maximum Time

The crystallization of amorphous zinc telluride (a-ZnTe) has been studied as a function of temperature in the range 350 K < T < 390 K. The crystallization process is thermally activated with an activation energy of 1.6 eV. The time for the onset of significant crystallization at room temperature for films of air-annealed a-ZnTe is found to be ~100 years. The study of the crystallization process is essential in order to determine the maximum time allowed for a measurement to be performed at a given temperature on a sample of amorphous material without significantly altering its amorphous state.

Combustion Synthesis of Nanostructured ZrC: Formation Process and Influencing Factors

2021 ◽  
Vol 21 (4) ◽  
pp. 2196-2202
Author(s):  
Xian-Rui Zhao ◽  
Dun-Wen Zuo ◽  
Yong Chen ◽  
Qin-Tao Li ◽  
Gui-Xiang Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Combustion Synthesis ◽  
Influencing Factors ◽  
Combustion Wave ◽  
Formation Process ◽  
Combustion Temperature ◽  
Ceramic Particle ◽  
Displacement Reaction ◽  
Synthesis Mechanism ◽  
By Products

ZrC was produced by the combustion synthesis technology using Cu, Zr, and graphite as the starting element powders. The synthesis mechanism of ZrC was investigated by the combustion wave quenching experiment. Furthermore, the effects of sizes of C and Cu on the combustion synthesis behavior and products were also explored. Results revealed that ZrC was fabricated through the displacement reaction between C and Cu–Zr liquid. The Cu size hardly affected the combustion temperature and resultant products, indicating that the preparation cost of ZrC could be decreased by employing coarse Cu powders. With increasing C size, the burning temperature and ceramic particle size reduced. Graphite with size of 2.6 μm was used as the C source, and only ZrC nanoparticles and Cu were obtained. The products could be employed to prepare nano-sized ZrC/Cu composites without the elimination of by-products.

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