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.

scholarly journals SHS robust modes to restore molybdenum by combustion wave in MoO3 – Al system

2020 ◽  
Vol 15 (4) ◽  
pp. 27-32
Author(s):  
Irina V. Milyukova ◽  
Marina P. Boronenko
Keyword(s):  
Spectral Analysis ◽  
High Temperature ◽  
Combustion Wave ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
Preliminary Heating ◽  
X Ray ◽  
Molybdenum Metal ◽  
High Temperature Synthesis ◽  
Oxide Phases

The work is devoted to the technology for the reduction of molybdenum from oxides by the method of self-propagating high-temperature synthesis in the MoO3 AI system with the addition of aluminum. The experiment was carried out in two modes: in a reactor at different pressures without preliminary heating and in a furnace in air until the initiation of the SH-synthesis process. Samples of molybdenum metal were obtained in different synthesis modes. X-ray phase and X-ray spectral analysis showed that molybdenum is the main phase in the synthesized samples. The presence of slag oxide phases Al2O3 and MoO2 was detected.

scholarly journals Observation of Combustion Wave Propagation during Self-Propagation High-Temperature Synthesis of TiC with Gas Formation.

2000 ◽  
Vol 108 (1255) ◽  
pp. 290-297
Author(s):  
Yasuhiro TANABE ◽  
Nobuko OKADA ◽  
Akira MUKOHFUJIWARA ◽  
Takashi AKATSU ◽  
Eiichi YASUDA
Keyword(s):  
Wave Propagation ◽  
High Temperature ◽  
Combustion Wave ◽  
Temperature Synthesis ◽  
Gas Formation ◽  
High Temperature Synthesis ◽  
Combustion Wave Propagation

Effect of Gravity on Titanium Carbide Foams by Self-propagation High-temperature Synthesis

1999 ◽  
Vol 14 (4) ◽  
pp. 1516-1523 ◽  
Author(s):  
Yasuhiro Tanabe ◽  
Takashi Sakamoto ◽  
Nobuko Okada ◽  
Takashi Akatsu ◽  
Eiichi Yasuda ◽  
...  
Keyword(s):  
High Temperature ◽  
Carbon Black ◽  
Titanium Carbide ◽  
Combustion Wave ◽  
Propagation Velocity ◽  
Temperature Synthesis ◽  
Environmental Pressures ◽  
Environmental Pressure ◽  
High Temperature Synthesis ◽  
Microgravity Conditions

Titanium carbide foams are synthesized by a self-propagation high-temperature synthesis technique using carbon black, which generates gases during the synthesis. The synthesis is performed under terrestrial and microgravity conditions. The effects of gravity on the synthesis are evaluated in this study. The foaming is mainly caused by H2O and CO gases from the carbon black. The elongation of the products increases with decreasing environmental pressure and increasing amount of generated gases. Since the gas flows out along the direction of the combustion wave propagation, the products expand only along this direction. The propagation velocity of the combustion wave increases with increasing amount of generated gases and environmental pressure, which is due to the amount of molten Ti transporting into the reaction/preheat zone. Under higher environmental pressures, thermal convection of the environmental gases mainly affects the propagation velocity. However, at lower pressures, the behavior of the molten Ti has a great effect compared with the gases surrounding the specimens.

scholarly journals Mechanism of self-propagating hightemperature synthesis of AlB2‒Al2O3

2019 ◽  
pp. 27-36
Author(s):  
Pan Yang ◽  
Guoqing Xiao ◽  
Donghai Ding ◽  
Yun Ren ◽  
Zhongwei Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
Ignition Temperature ◽  
Combustion Reaction ◽  
Peritectic Temperature ◽  
Composite Powders ◽  
Temperature Synthesis ◽  
Precipitation Mechanism ◽  
High Temperature Synthesis ◽  
Higher Temperature ◽  
Quenching Method

The mechanism of self-propagating high-temperature synthesis (SHS) of AlB2‒Al2O3 composite powders was studied by means of a combustion front quenching method (CFQM). The results showed that combustion reaction started with the melting of B2O3 and Al particles. As the combustion reaction proceeded, the interpenetration of Al and B2O3 in melts happened. The XRD results of the product revealed the reflections of Al2O3, suggesting there had been an exchange of oxygen atoms between Al and B, and evidencing the reaction, B2O3 (l) + 2Al (l) → 2B (s) + Al2O3 (l). Under higher temperature, some of B2O3 volatilized and reacted with B forming gaseous B2O2, which deposited on the surface of Al to precipitate Al2O3 and B. Then B made available dissolved into Al melt, and reacted with the Al in melt to precipitate AlB12 particles. Finally, AlB12 transforms to AlB2 at the peritectic temperature under high cooling rate. Thus, this combustion reaction can be described by the dissolution-precipitation mechanism. In the final products, besides AlB2 and Al2O3 particles, some of Al was also detected. A model corresponding to the dissolutionprecipitation mechanism was proposed, and the ignition temperature of the combustion reaction was determined to be around 800 °C. Ill. 13. Ref. 47.

A time-resolved x-ray diffraction study of Ti5Si3 product formation during combustion synthesis

1997 ◽  
Vol 12 (12) ◽  
pp. 3230-3240 ◽  
Author(s):  
C. R. Kachelmyer ◽  
I. O. Khomenko ◽  
A. S. Rogachev ◽  
A. Varma
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Product Formation ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Time Resolved ◽  
X Ray ◽  
Thermal Expansion Coefficients ◽  
High Temperature Synthesis ◽  
Expansion Coefficients

Time-resolved x-ray diffraction (TRXRD) was performed during Ti5Si3 synthesis by the self-propagating high-temperature synthesis mode for different Ti size fractions. It was determined that the time for product formation (ca. 15 s) was independent of Ti particle size. However, the formation of Ti5Si4 phase occurred when relatively large titanium particles were used. A simultaneous measurement of the temperature and TRXRD allowed us to attribute the shifting of XRD peaks at high temperature to thermal expansion of the Ti5Si3 product. The thermal expansion coefficients differ for different crystal planes, and their numerical values compare well with those reported previously in the literature.

scholarly journals Оценка максимального поперечного размера многослойных биметаллических пленок для протекания в них самораспространяющегося высокотемпературного синтеза на примере структуры Ni/Al

2020 ◽  
Vol 90 (7) ◽  
pp. 1189
Author(s):  
О.Е. Квашенкина ◽  
Е.Д. Эйдельман ◽  
В.С. Осипов ◽  
П.Г. Габдуллин ◽  
Б.Б. Хина
Keyword(s):  
High Temperature ◽  
Combustion Wave ◽  
Solid Phase ◽  
Electronic Components ◽  
Temperature Synthesis ◽  
Phase Diffusion ◽  
Layered Model ◽  
Flame Combustion ◽  
High Temperature Synthesis ◽  
Calculation Results

To simulate self-propagating high-temperature synthesis (solid flame combustion), a layered model is taken as the basis in which the product is formed between the layers of the starting reagents due to solid-phase diffusion in non-isothermal conditions, while the combustion wave propagates along these layers.It turned out that the cords from layers of aluminum and nickel with a thickness of up to 50µmv will completely turn into a high-temperature melt The calculation results will optimize the processes welding-soldering of heat-sensitive materials and parts of electronic components of various devices.

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