scholarly journals Optical properties of powder and ceramics of aluminium oxynitride obtained by self-propagating high-temperature synthesis

2021 ◽  
Vol 61 (3) ◽  
Author(s):  
T.G. Akopdzhanyan ◽  
A.A. Kondakov ◽  
S.I. Rupasov ◽  
A.P. Kozlova ◽  
V. Pankratov
Keyword(s):  
High Temperature ◽  
Synthesis Method ◽  
Xrd Analysis ◽  
Band Gap Energy ◽  
Technological Parameters ◽  
Temperature Synthesis ◽  
Starting Mixture ◽  
High Temperature Synthesis ◽  
Aluminium Oxynitride ◽  
Transmission And Reflection

The synthesis method of aluminium oxynitride (AlON) powders by nitriding of Al/Al2O3 mixture under highpressure nitrogen is proposed. The novelty of this method consists in adding KClO4 or Mg(ClO4)2 and extra Al into the starting mixture (Al+Al2O3) to cause the exothermal aluminium oxidation reaction, which therefore initiates the aluminium nitriding reaction. The microstructure and phase composition of the AlON powders obtained by self-propagating high-temperature synthesis are demonstrated by means of SEM and XRD analysis. Diffuse reflection spectra of AlON powders have been measured and the values of band-gap energy have been calculated. Optical transmission and reflection characteristics of the AlON ceramic samples sintered from AlON powders at 1930°C have been studied. The influence of the technological parameters of ceramics production on their transparency is revealed – the most transparent sample is obtained from the powders synthesized with the Mg(ClO4)2 additive and sintered for 6 h.

Self-propagating high-temperature synthesis microalloying of MoSi2 with Nb and V

2003 ◽  
Vol 18 (8) ◽  
pp. 1842-1848 ◽  
Author(s):  
F. Maglia ◽  
C. Milanese ◽  
U. Anselmi-Tamburini ◽  
Z. A. Munir
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Tetragonal Phase ◽  
Synthesis Method ◽  
The Self ◽  
Alloying Elements ◽  
Alloying Element ◽  
Temperature Synthesis ◽  
Starting Mixture ◽  
High Temperature Synthesis

Microalloying of MoSi2 to form Mo(1−x)MexSi2 (Me = Nb or V) was investigated by the self-propagating high-temperature synthesis method. With alloying element contents up to 5 at.%, a homogeneous C11b solid solution was obtained. For higher contents of alloying elements, the product contained both the C11b and the hexagonal C40 phases. The relative amount of the C40 phase increases with an increase in the content of alloying metals in the starting mixture. The alloying element content in the hexagonal C40 Mo(1−x)MexSi2 phase was nearly constant at a level of about 12 at.% for all starting compositions. In contrast, the content of the alloying elements in the tetragonal phase is considerably lower (around 4 at.%) and increases slightly as the Me content in the starting mixture is increased.

Composite materials based on Al2O3‒SiC‒TiB2 obtained by SHS extrusion and their hightemperature annealing

2021 ◽  
pp. 51-55
Author(s):  
A. P. Chizhikov ◽  
A. S. Konstantinov ◽  
M. S. Antipov ◽  
P. M. Bazhin ◽  
A. M. Stolin
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Pressing Pressure ◽  
Technological Parameters ◽  
Temperature Synthesis ◽  
Shs Extrusion ◽  
High Temperature Synthesis ◽  
Before And After

As a result of the combination of the processes of selfpropagating high-temperature synthesis (SHS) and shear high-temperature deformation, realized in the method of SHS-extrusion, ceramic rods based on Al2O3‒SiC‒TiB2 were obtained. The influence of technological parameters of the process (delay time, pressing pressure) on the length of the obtained rods has been studied. The obtained materials were annealed in the range 1000‒1300 °C, and the microstructure and phase composition of the materials were studied before and after heat treatment.

scholarly journals Direct observation of the formation and stabilization of metallic nanoparticles on carbon supports

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhennan Huang ◽  
Yonggang Yao ◽  
Zhenqian Pang ◽  
Yifei Yuan ◽  
Tangyuan Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Metallic Nanoparticles ◽  
Synthesis Method ◽  
Md Simulations ◽  
Graphite Substrate ◽  
Carbon Supports ◽  
Temperature Synthesis ◽  
Excellent Thermal Stability ◽  
High Temperature Synthesis ◽  
Underlying Mechanisms

AbstractDirect formation of ultra-small nanoparticles on carbon supports by rapid high temperature synthesis method offers new opportunities for scalable nanomanufacturing and the synthesis of stable multi-elemental nanoparticles. However, the underlying mechanisms affecting the dispersion and stability of nanoparticles on the supports during high temperature processing remain enigmatic. In this work, we report the observation of metallic nanoparticles formation and stabilization on carbon supports through in situ Joule heating method. We find that the formation of metallic nanoparticles is associated with the simultaneous phase transition of amorphous carbon to a highly defective turbostratic graphite (T-graphite). Molecular dynamic (MD) simulations suggest that the defective T-graphite provide numerous nucleation sites for the nanoparticles to form. Furthermore, the nanoparticles partially intercalate and take root on edge planes, leading to high binding energy on support. This interaction between nanoparticles and T-graphite substrate strengthens the anchoring and provides excellent thermal stability to the nanoparticles. These findings provide mechanistic understanding of rapid high temperature synthesis of metal nanoparticles on carbon supports and the origin of their stability.

A self-propagating high-temperature synthesis method for synthesis of zinc oxide powder

2009 ◽  
Vol 467 (1-2) ◽  
pp. 514-523 ◽  
Author(s):  
Chyi-Ching Hwang ◽  
Cheng-Shiung Lin ◽  
Gaw-Pying Wang ◽  
Cheng-Hsiung Peng ◽  
Shyan-Lung Chung
Keyword(s):  
Zinc Oxide ◽  
High Temperature ◽  
Synthesis Method ◽  
Oxide Powder ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Zinc Oxide Powder

Production of superconducting NbN thin plate and wire by the self-propagating high-temperature synthesis method

1993 ◽  
Vol 12 (7) ◽  
pp. 500-501 ◽  
Author(s):  
M. Ohyanagi ◽  
M. Koizumi ◽  
K. Tanihata ◽  
Y. Miyamoto ◽  
0. Yamada ◽  
...  
Keyword(s):  
High Temperature ◽  
Thin Plate ◽  
Synthesis Method ◽  
The Self ◽  
Temperature Synthesis ◽  
High Temperature Synthesis

Preparation of Submicron Metastable Spherical β-Bi2O3 Particles by Self-Propagating High-Temperature Synthesis Method

2019 ◽  
Vol 19 (11) ◽  
pp. 7436-7441
Author(s):  
Chu Zhang ◽  
Qi-Yu Wang ◽  
Ming-De Li ◽  
Guo-Dong Zhang
Keyword(s):  
High Temperature ◽  
High Efficiency ◽  
Synthesis Method ◽  
Reaction System ◽  
Average Diameter ◽  
Spherical Particles ◽  
Molar Ratio ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
One Step

Sub-micrometer particles of β-Bi2O3 were successfully synthesized via a one-step self-propagating high-temperature synthesis (SHS) method for the first time. The experiments were carried out in the air at room temperature. The products were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). In this study, three experiments were designed to optimize the heat source, Bi source and additive for the reaction system. Results showed that the system composed of Al, Bi2O3 and Al2O3 powders could synthesize monodisperse high-purity β-Bi2O3 spherical particles with the average diameter of 369 nm and the as-prepared products kept stable after being exposed in air for one month. Then, the influences of the ratio of the three components on system were investigated. Interestingly, it was found that a slight adjustment on the ratio of Al:Bi2O3:Al2O3 had significant effects on the reactions happening in a system. Specifically, when the amount of Al2O3 exceeds the molar ratio of 2:1:1 (Al:Bi2O3:Al2O3), it is difficult to ignite the reaction system; when the amount is less than 2:1:0.5, the reaction system becomes too violent to obtain pure products. However, there are no obvious differences on the morphology and structure of final products with the two ratios because of few changes in adiabatic temperature. Preparation of β-Bi2O3 by SHS technique enjoying many advantages, such as high efficiency, inexpensive experimental equipment and simple processes, would has a promising prospect for industrial application.

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