Preparation of (Mo,Nb)Si2 Ternary Alloys by Self−Propagating High−Temperature Synthesis

2011 ◽  
Vol 266 ◽  
pp. 219-222
Author(s):  
Pei Zhong Feng ◽  
Shuai Zhang ◽  
Xiao Hong Wang ◽  
Wei Sheng Liu ◽  
Jie Wu
Keyword(s):  
High Temperature ◽  
Flame Front ◽  
Propagation Velocity ◽  
Combustion Temperature ◽  
Front Propagation ◽  
Ternary Alloys ◽  
Combustion Mode ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Front Propagation Velocity

An experimental study on the preparation of (Mo,Nb)Si2 ternary alloys was conducted by self-propagating high-temperature synthesis method from elemental powder compacts of different stoichiometries. And the combustion mode, combustion temperature, flame-front propagation velocity and product structure were discussed. The results show that (Mo,Nb)Si2 ternary alloys are characterized by an unsteady state combustion mode with a spiral−trajectory reaction front from top to bottom. The combustion temperature and flame−front propagation velocity decrease with the addition of coarse niobium powder. The combustion temperature and flame-front propagation velocity of MoSi2 are 1629K and 3.13mm/s respectively. However, those of (Mo0.8Nb0.2)Si2 alloy are 1460K and 1.97mm/s. The solid solubility of niobium in MoSi2 is less than 2.5at.%, and the combustion synthesis produce still remains Cllb single-phase structure in (Mo1-x,Nbx)Si2(x<0.075) sample. The C40-type structure appears in (Mo0.925,Nb0.075)Si2 compact and the intensity of diffraction peaks of C40-type phase gradually reinforces with the increase of niobium content. Combustion synthesis is an effective technology for producing (Mo,Nb)Si2 ternary alloys.

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.

Superfast Sintering of Nanocrystalline Y2O3 Ceramics

2009 ◽  
Vol 66 ◽  
pp. 100-103 ◽  
Author(s):  
Xia Zheng ◽  
Zheng Yi Fu ◽  
Jin Yong Zhang ◽  
Wei Min Wang ◽  
Hao Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Heating Rate ◽  
Grain Growth ◽  
Combustion Temperature ◽  
Applied Pressure ◽  
The Self ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Chemical Furnace ◽  
Maximum Combustion Temperature

Dense nanocrystalline Y2O3 ceramics without grain growth have been successfully obtained by a new method, which is based on the self-propagating high temperature synthesis and quick pressing. A suitable self-propagating system with a maximum combustion temperature of 1350 °C and a heating rate of 1300 °C/min was chosen as a chemical furnace to supply the heat to densify nanocrystalline Y2O3. Dense samples without grain growth were obtained when the applied pressure was 120 MPa.

EFFECT OF Al CONTENT ON THE COMBUSTION SYNTHESIS OF (TiB2-Al2O3)/Al PRODUCTS FROM AN Al-TiO2-B2O3 SYSTEM

2010 ◽  
Vol 24 (15n16) ◽  
pp. 3203-3208
Author(s):  
LEI ZHAN ◽  
PING SHEN ◽  
QICHUAN JIANG
Keyword(s):  
High Temperature ◽  
Delay Time ◽  
Combustion Temperature ◽  
Ignition Delay Time ◽  
The Self ◽  
Temperature Synthesis ◽  
Al Content ◽  
High Temperature Synthesis ◽  
Maximum Combustion Temperature ◽  
Opposite Tendency

The effect of Al content on the self-propagating high-temperature synthesis (SHS) reaction among Al , TiO 2 and B 2 O 3 was experimentally investigated. The Al content plays an important role in controlling the reaction behaviors. With the increase in reactant Al , the maximum combustion temperature decreases, the propagating wave velocity first increases and then decreases, while the ignition delay time shows an opposite tendency. More importantly, the increase of the Al content in the reactants has an insignificant effect on the phase constitutions of the synthesized products but reduces the size of the synthesized TiB 2 particles.

Synthesis of Nanostructure MoSi2 Powder by Mechanically Assisted Self-Propagating High-Temperature Synthesis

2010 ◽  
Author(s):  
R. Meshkizadeh ◽  
H. Abdollahpour ◽  
A. Honarbakhsh-Raouf
Keyword(s):  
High Temperature ◽  
Ball Milling ◽  
Powder Mixture ◽  
Combustion Temperature ◽  
Combustion Method ◽  
Temperature Synthesis ◽  
Mixed Powder ◽  
Powder Mixtures ◽  
High Temperature Synthesis

Nanostructured MoSi2 powder has been successfully synthesized by Ball milling of Mo and Si powder mixtures and subsequent self-propagating high-temperature synthesis (SHS) process. It was observed that in comparison with the normally mixed powder, it could be easily ignited and higher combustion temperature was achieved. Based on XRD and SEM, it was confirmed that nanostructure MoSi2 powder could be prepared through self propagating combustion method from the mechanical activated powder mixture.

Self-Propagating High-Temperature Synthesis: Non-Equilibrium Processes and Equilibrium Products

2006 ◽  
Vol 45 ◽  
pp. 36-44 ◽  
Author(s):  
A.G. Merzhanov
Keyword(s):  
Wave Propagation ◽  
High Temperature ◽  
Structure Formation ◽  
Front Propagation ◽  
Combustion Time ◽  
Temperature Synthesis ◽  
Equilibrium Processes ◽  
High Temperature Synthesis ◽  
Non Equilibrium

The nature of SHS process was studied, and conditions under which equilibrium and non-equilibrium regimes take place for wave propagation and structure formation of SHS products are under consideration. The important role of cooling down time is shown. Depending on its magnitude, either autoannealing or autoquenching processes can take place in the products after combustion front propagation. The correlation between transition from non-equilibrium to equilibrium state of the product with prolongation of cooling time was examined as well as character of products and processes was indicated in dependence on relationship between the characteristic times of combustion, time of cooling down, and structure formation in SHS product.

Determination of Non-Stoichiometry of Tubular Titanium Carbide Formed by Self-Propagating High Temperature Synthesis

2007 ◽  
Vol 534-536 ◽  
pp. 1301-1304
Author(s):  
Y. Choi ◽  
Nam Ihn Cho
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Temperature ◽  
Titanium Carbide ◽  
Combustion Temperature ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Scanning Electron ◽  
Shs Method

Titinium carbide (TiCx) was produced by self-propagating high temperature synthesis (SHS) method. The morphology and non-stoichiometric number of the SHS product were observed by scanning electron microscopy and neutron diffractometry, respectively. Tubular titanium carbide with hole inside was formed with different non-stoichiometric number (x), which value increased with combustion temperature.

Phase Formation and Thermodynamic Analysis of Self-propagating High-temperature Synthesis Al–Zr–N System Composites

1998 ◽  
Vol 13 (9) ◽  
pp. 2610-2613 ◽  
Author(s):  
Kexin Chen ◽  
Changchun Ge ◽  
Jiangtao Li
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Phase Formation ◽  
Combustion Temperature ◽  
Xrd Analysis ◽  
The Self ◽  
Composite Ceramics ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
The Relationship

The self-propagating high temperature synthesis (SHS) of Al–Zr–N system composite ceramics was investigated in this paper. The melting point of Al was low (Tm = 660 °C), while that of Zr was high (Tm =1855 °C). Therefore, Al will melt and coalesce during reaction, which inhibit diffusion of nitrogen from outside the metal compact to interior due to collapse of the pore openings, while Zr will not melt under the combustion temperature which is lower than its melting point. It will not affect the permeation of nitrogen under the conditions. Accordingly, the ratio of Al and Zr in the initial mixed powders will affect the permeation of nitrogen from outside the sample to the interior, which results in different phase formation of the products. In this study, the relationship between the combustion parameters and the phase formation of the products will be experimentally determined through XRD analysis, and then thermodynamically analyzed.

Modeling of wave configuration during electrically ignited combustion synthesis

2001 ◽  
Vol 16 (1) ◽  
pp. 93-100 ◽  
Author(s):  
O. A. Graeve ◽  
E. M. Carrillo-Heian ◽  
A. Feng ◽  
Z. A. Munir
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
High Temperature ◽  
Combustion Synthesis ◽  
Small Samples ◽  
Combustion Mode ◽  
Temperature Synthesis ◽  
Ignition Point ◽  
High Temperature Synthesis ◽  
Material Systems

A model was developed to study the process of current-ignited combustion synthesis. In this process, Joule heating raises the temperature to the ignition point, at which the sample reacts to form a product. Two material systems were modeled: the synthesis of SiC and MoSi2. It was found that the mode of combustion is a function of the size (radius) of the sample. The anticipated volume combustion mode was only evident in small samples. At higher values of the radius, the mode becomes wavelike (selfpropagating high-temperature synthesis) in nature. The transition from volume to wave combustion mode also depended on the properties of the material. The results are interpreted in terms of thermal conductivity and heat-transfer conditions.

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