scholarly journals Scale-Up of the Nitridation and Sintering of Silicon Preforms Using Microwave Heating

1996 ◽  
Vol 430 ◽  
Author(s):  
J. O. Kiggans ◽  
T. N. Tiegs ◽  
C. C. Davisson ◽  
M. S. Morrow ◽  
G. J. Garvey
Keyword(s):  
Silicon Nitride ◽  
Microwave Heating ◽  
Diesel Engines ◽  
Scale Up ◽  
Microwave Furnace ◽  
Weight Gains

AbstractScale-up studies were performed in which microwave heating was used to fabricate reactionbonded silicon nitride and sintered reaction-bonded silicon nitride (SRBSN). Tests were performed in both a 2.45 GHz, 500 liter and a 2.45 GHz, 4000 liter multimode cavities. A variety of sizes, shapes, and compositions of silicon preforms were processed in the studies, including bucket tappets and clevis pins for diesel engines. Up to 230 samples were processed in a single microwave furnace run. Data were collected which included weight gains for nitridation experiments, and final densities for nitridation and sintering experiments. For comparison, nitridation and sintering studies were performed using a conventional resistance-heated furnace.

Microwave Processing of Silicon Nitride

1990 ◽  
Vol 189 ◽  
Author(s):  
T. N. Tiegs ◽  
J. O. Kiggans ◽  
H. D. Kimrey
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Microwave Heating ◽  
Grain Growth ◽  
Microwave Power ◽  
Microwave Sintering ◽  
Microwave Processing ◽  
Microwave Furnace

ABSTRACTMicrowave sintering of Si3N4—based materials showed improved densification as compared to samples heated conventionally under similar conditions. Accelerated nitridation of Si in the microwave furnace to produce Si3N4 was also observed. Dense Si3N4, annealed by microwave heating, exhibited enhanced grain growth; however preferential coupling of the microwave power to the grain—boundary phases in the present experiments resulted in their degradation.

scholarly journals Studies on the Scale-Up of the Microwave-Assisted Nitridation and Sintering of Reaction-Bonded Silicon Nitride

1994 ◽  
Vol 347 ◽  
Author(s):  
J. O. Kiggans ◽  
T. N. Tiegs ◽  
H. D. Kimrey ◽  
Jon-Paul Maria
Keyword(s):  
Silicon Nitride ◽  
Boron Nitride ◽  
Microwave Heating ◽  
Scale Up ◽  
Batch Size ◽  
Temperature Uniformity ◽  
Control Groups ◽  
Microwave Assisted ◽  
Nitride Sample ◽  
Powder Compacts

AbstractStudies using laboratory test samples have shown that microwave heating produces sintered reaction-bonded silicon nitride materials with improved properties [1,2]. The final challenge for processing this material by microwave heating is the development of a technology for processing larger batch-size quantities of these materials. Initial microwave scale-up experiments were performed using powder compacts of a bucket tappet geometry. In experiments using microwave-transparent boron nitride sample crucibles, temperature gradients within some crucibles led to larger variations in the sample densities than were obtained with the conventionally processed samples. The use of a microwave-suscepter type crucible made of silicon carbide and boron nitride resulted in an improved temperature uniformity and in density variations comparable to those obtained for the control groups.

Microwave Nitrudation of Silicon Compacts Utilizing a Temperature Gradient

1992 ◽  
Vol 287 ◽  
Author(s):  
Jeffrey J. Thomas ◽  
Hamlin M. Jennings ◽  
D. Lynn Johnson
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Microwave Heating ◽  
Reaction Rate ◽  
Nitrogen Depletion

ABSTRACTSilicon compacts nitrided utilizing the temperature gradient inherent to microwave heating were more fully converted to silicon nitride than was possible with similar compacts nitrided isothermally. Although nitrogen depletion prevented the reaction rate in the center from exceeding that at the surface, the temperature gradient partially counteracted the effect of nitrogen depletion. Thus the microwave-heated specimens could be nitrided fully before the reduction in porosity that accompanies the reaction eliminated the diffusion of nitrogen into the compact.

scholarly journals Numerical modeling of microwave heating

2010 ◽  
Vol 42 (1) ◽  
pp. 99-124 ◽  
Author(s):  
A.K. Shukla ◽  
A. Mondal ◽  
A. Upadhyaya
Keyword(s):  
Thermal Conductivity ◽  
Numerical Modeling ◽  
Temperature Distribution ◽  
Microwave Heating ◽  
Two Dimensional ◽  
Conventional Furnace ◽  
Microwave Furnace ◽  
Simulation Results ◽  
Heating Behavior ◽  
Cylindrical Samples

The present study compares the temperature distribution within cylindrical samples heated in microwave furnace with those achieved in radiatively-heated (conventional) furnace. Using a two-dimensional finite difference approach the thermal profiles were simulated for cylinders of varying radii (0.65, 6.5, and 65 cm) and physical properties. The influence of susceptor-assisted microwave heating was also modeled for the same. The simulation results reveal differences in the heating behavior of samples in microwaves. The efficacy of microwave heating depends on the sample size and its thermal conductivity.

Low-density silicon nitride beads as high-temperature microwave furnace insulation

1997 ◽  
Vol 32 (6) ◽  
pp. 749-754 ◽  
Author(s):  
Ross H. Plovnick ◽  
Zak Fathi ◽  
James O. Kiggans
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Low Density ◽  
Microwave Furnace

Characterization of Sintered Reaction-Bonded Silicon Nitride Processed by Microwave Heating

1992 ◽  
Vol 269 ◽  
Author(s):  
J. O. Kiggans ◽  
T. N. Tiegs
Keyword(s):  
Silicon Nitride ◽  
Microwave Heating ◽  
Microwave Processing ◽  
Conventional Heating ◽  
Processed Material

ABSTRACTSintered reaction-bonded silicon nitride (SRBSN) tiles were fabricated using microwave and conventional heating. Materials from both processes were analyzed at various stages in their fabrication. Microwave processing resulted in a SRBSN material of higher density and strength than the conventionally processed material.

Sinthesys of Mullite Using Microwave Furnace from Kaolin and Alumina Residue

2014 ◽  
Vol 798-799 ◽  
pp. 63-68
Author(s):  
Michelle Félix da Silva ◽  
Valmir José da Silva ◽  
Romualdo Rodrigues Menezes ◽  
Lisiane Navarro de Lima Santana ◽  
Gelmires Araújo Neves ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Microwave Heating ◽  
Conventional Method ◽  
Microwave Power ◽  
Electromagnetic Energy ◽  
The Other ◽  
Heat Flows ◽  
Other Hand ◽  
Microwave Furnace

Heating with microwave power is a process in which the materials take up electromagnetic energy volumetrically and turn it into heat inside a piece. This is the great difference from the conventional method, where the heat flows between objects by means of conduction, radiation and convection, in which the surface of the materials is heated first, and then the heat is transferred to the interior of the piece, thus forming a temperature gradient. On the other hand, microwave heating generates heat first inside the piece, heating the whole volume later. [1]

scholarly journals NT164 Silicon Nitride Gas-Turbine Engine Turbine Blade Manufacturing Development

1995 ◽  
Author(s):  
Eric Bright ◽  
Roger Burleson ◽  
Steve A. Dynan ◽  
William T. Collins
Keyword(s):  
Silicon Nitride ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbine Blades ◽  
Scale Up ◽  
Heat Engine ◽  
Slip Casting ◽  
Development Project ◽  
Turbine Engine ◽  
Sponsored Programs

Norton Advanced Ceramics (NAC) has performed ceramic turbine blade fabrication development as part of several DOD and DOE-sponsored programs including: (1) The Experimental Turbine Engine Concept (ETEC); (2) The Advanced Turbine Technology Applications Project (ATTAP); (3) The Ceramic Turbine Engine Development Project (CTEDP); and (4) The Ceramic Stationary Gas Turbine (CSGT). NAC has developed two HIPed silicon nitide materials for fabricating turbine blades within these programs — One is designated NT154; and the second is designated NT164. Under the ETEC program with AlliedSignal Engines, NT154 blades were fabricated and delivered for proof and engine testing. Blade fabrication development efforts were augmented by NAC’s work under the ATTAP, which was directed at developing manufacturing technologies for rotors, stators, scrolls, vanes, and other components. Under the ATTAP, complex-shape forming was emphasized utilizing pressure slip-casting. NAC has employed pressure slip casting developed under the ATTAP to fabricate ceramic turbine blades and other gas-turbine components for various advanced heat-engine efforts. NT154 nozzles have been delivered to AlliedSignal Engines under internally sponsored and DOD-sponsored programs. NT154 diffusers, nozzles, and monorotors have been delivered to Sundstrand Power Systems. Under the CTEDP and CSGT programs, continued efforts on turbine blade fabrication development are anticipated for 1995 and beyond. Work under the CTEDP program with AlliedSignal Engines is focused on cost reduction through process simplification and scale-up. Under the CSGT program, NAC is participating with Solar Turbines Incorporated to deliver prototype quantities of NT164 silicon nitride blades using a controlled fabrication process. NAC is utilizing its prior experience in fabricating similar blade geometries under the ETEC, ATTAP, and CTEDP programs in the CSGT effort.

Synthesis of Silicon Nitride Whiskers by Microwave Heating

1998 ◽  
Vol 547 ◽  
Author(s):  
S. Gedevanishvili ◽  
K. Cherian ◽  
D. Agrawal ◽  
R. Roy
Keyword(s):  
Silicon Nitride ◽  
Single Crystal ◽  
Microwave Heating ◽  
Polycrystalline Silicon ◽  
Silicon Powder ◽  
Silicon Single Crystal ◽  
Optimum Temperature ◽  
Solid Reaction ◽  
Powder Compacts ◽  
Microstructural Data

AbstractWhiskers of silicon nitride were synthesized by heating silicon powder compacts, silicon single crystal and polycrystalline silicon in microwave in the presence of flowing forming gas or nitrogen. Various gas compositions and form of silicon used resulted in different whisker morphologies. Silicon powder as starting material leads to the formation of needle-like whiskers while silicon single crystal and polycrystalline silicon led to the formation of wool-like and web-like structures respectively. Length of the whiskers apparently depends on the holding time at the optimum temperature ~1350°C; whiskers up to 250 micrometers in length may be grown in 30 minutes. Microstructural data suggest that the silicon nitride whiskers form through gas-solid reaction and vapor-solid mechanism.

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