Mechanically activated combustion synthesis of molybdenum silicides and borosilicides for ultrahigh-temperature structural applications

2015 ◽  
Vol 35 (2) ◽  
pp. 2275-2281 ◽  
Author(s):  
Mohammad S. Alam ◽  
Evgeny Shafirovich
Keyword(s):  
Combustion Synthesis ◽  
Molybdenum Silicides ◽  
Structural Applications ◽  
Ultrahigh Temperature

Boron-doped molybdenum silicides for structural applications

1999 ◽  
Vol 261 (1-2) ◽  
pp. 16-23 ◽  
Author(s):  
Mufit Akinc ◽  
Mitchell K. Meyer ◽  
Matthew J. Kramer ◽  
Andrew J. Thom ◽  
Jesse J. Huebsch ◽  
...  
Keyword(s):  
Boron Doped ◽  
Molybdenum Silicides ◽  
Structural Applications

scholarly journals Metallothermic Reduction of MoO3 on Combustion Synthesis of Molybdenum Silicides/MgAl2O4 Composites

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4800
Author(s):  
Chun-Liang Yeh ◽  
Min-Chia Chen
Keyword(s):  
High Temperature ◽  
Combustion Synthesis ◽  
Xrd Analysis ◽  
Metallothermic Reduction ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Molybdenum Silicides ◽  
Front Temperature ◽  
In Situ Production

Combustion synthesis involving metallothermic reduction of MoO3 by dual reductants, Mg and Al, to enhance the reaction exothermicity was applied for the in situ production of Mo3Si–, Mo5Si3− and MoSi2–MgAl2O4 composites with a broad compositional range. Reduction of MoO3 by Mg and Al is highly exothermic and produces MgO and Al2O3 as precursors of MgAl2O4. Molybdenum silicides are synthesized from the reactions of Si with both reduced and elemental Mo. Experimental evidence indicated that the reaction proceeded as self-propagating high-temperature synthesis (SHS) and the increase in silicide content weakened the exothermicity of the overall reaction, and therefore, lowered combustion front temperature and velocity. The XRD analysis indicated that Mo3Si–, Mo5Si3– and MoSi2–MgAl2O4 composites were well produced with only trivial amounts of secondary silicides. Based on SEM and EDS examinations, the morphology of synthesized composites exhibited dense and connecting MgAl2O4 crystals and micro-sized silicide particles, which were distributed over or embedded in the large MgAl2O4 crystals.

Mo-Si-B Alloys for Ultrahigh-Temperature Structural Applications

2012 ◽  
Vol 24 (26) ◽  
pp. 3445-3480 ◽  
Author(s):  
J. A. Lemberg ◽  
R. O. Ritchie
Keyword(s):  
Structural Applications ◽  
Ultrahigh Temperature

Lattice Imaging of Grain Boundaries in Ceramics

1977 ◽  
Vol 35 ◽  
pp. 114-115
Author(s):  
D. R. Clarke ◽  
G. Thomas
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Grain Boundaries ◽  
High Temperature Strength ◽  
Current Interest ◽  
Lattice Imaging ◽  
Special Significance ◽  
Structural Applications ◽  
Refractory Ceramics

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.

Precipitation in Al-Li-Cu Alloys

1981 ◽  
Vol 39 ◽  
pp. 44-45
Author(s):  
J. E. O'Neal ◽  
K. K. Sankaran
Keyword(s):  
Electron Microscopy ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Zone Formation ◽  
Specific Strength ◽  
Hardening Behavior ◽  
Cu Alloys ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

A Tem Study of Slip Systems in MoSi2/WSi2 Alloys

1991 ◽  
Vol 49 ◽  
pp. 942-943
Author(s):  
Stuart A. Maloy
Keyword(s):  
Solid Solution ◽  
Solid Solution Hardening ◽  
Slip Systems ◽  
High Melting ◽  
Group 14 ◽  
Solution Hardening ◽  
Brittle To Ductile Transition ◽  
High Melting Temperature ◽  
Tetragonal Unit Cell ◽  
Structural Applications

MoSi2 has recently been investigated as a potential material for high temperature structural applications. It has excellent oxidation resistance up to 1700°C, a high melting temperature, 2030°C, and a brittle-to-ductile transition temperature at 900-1000°C. WSi2 is isomorphous with MoSi2 and has a body-centered tetragonal unit cell of the space group 14/mmm. The lattice parameters are a=3.20 Å and c=7.84 Å for MoSi2 and a=3.21 Å and c=7.88 Å for WSi2. Therefore, WSi2 was added to MoSi2 to improve its strength via solid solution hardening. The purpose of this study was to investigate the slip systems in polycrystalline MoSi2/WSi2 alloys.

Crystallization sequence of an A1N-Y2O3-SiO2 glass-ceramic

1986 ◽  
Vol 44 ◽  
pp. 446-447
Author(s):  
T.R. Dinger ◽  
G. Thomas
Keyword(s):  
High Temperature ◽  
Glass Ceramic ◽  
Crystallization Behavior ◽  
High Stress ◽  
Crystallization Sequence ◽  
Sio2 Glass ◽  
Structural Applications ◽  
Ceramic Precursors

The use of Si3N4, alloys for high temperature, high stress structural applications has prompted numerous studies of the oxynitride glasses which exist as intergranular phases in their microstructures. Oxynitride glasses have been investigated recently in their bulk form in order to understand their crystallization behavior for subsequent Si3N4 applications and to investigate their worth as glass-ceramic precursors. This research investigates the crystallization sequence of a glass having a normalized composition of Y26Si30Al11 ON11 and lying in the A1N-Y2O3-SiO2 section of the Y-Si-Al-O-N system. Such glasses exist as intergranular phases in the technologically important Y2O3/Al2O3-fluxed Si3N4 alloys.

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