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.

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.

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.

scholarly journals Preparation and application of carbon and hollow TiO2 microspheres by microwave heating at a low temperature

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 200-209
Author(s):  
Caiyun Zhang ◽  
Chunhong Li ◽  
Bolin Ji ◽  
Zhaohui Jiang
Keyword(s):  
Low Temperature ◽  
Microwave Heating ◽  
Raw Material ◽  
Carbon Microspheres ◽  
Microwave Assisted ◽  
The Core ◽  
Good Crystallinity ◽  
Carbon Core ◽  
Microwave Assisted Method ◽  
Uniform Particle Size

Abstract A fast, simple, and energy-saving microwave-assisted approach was successfully developed to prepare carbon microspheres. The carbon microspheres with a uniform particle size and good dispersity were prepared using glucose as the raw material and HCl as the dehydrating agent at low temperature (90°C) in an open system with the assistance of microwave heating. The carbon microspheres were characterized by elemental analysis, XRD, SEM, FTIR, TG, and Raman. The results showed that the carbon microspheres prepared under the condition of 18.5% (v/v) HCl and heating for 30 min by microwave had a narrow size distribution. The core–shell structure of the carbon core and TiO2 shell was prepared with (NH4)2TiF6, H3BO3 using the microwave-assisted method. The hollow TiO2 microspheres with good crystallinity and high photocatalytic properties were successfully prepared by sacrificing the carbon microspheres.

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 Temperature distribution of SiC bed surface in a large-scale microwave-assisted pyrolysis reactor

2021 ◽  
Author(s):  
Ying Duan ◽  
Xiaogen Yi ◽  
Qinglong Xie ◽  
Zhengai Weng ◽  
Peng Yuan ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Low Power ◽  
Large Scale ◽  
Scale Up ◽  
Microwave Pyrolysis ◽  
Microwave Assisted ◽  
Stable Temperature ◽  
Microwave Reactors ◽  
Pyrolysis Reactor ◽  
Scale Reactor

Microwave reactors equipped with microwave absorbent as high-temperature bed are effective for the pyrolysis reactions. The uniformity and stability of temperature distribution on the microwave absorbent bed surface is important to the microwave pyrolysis reactor especially in the large-scale reactor. Herein, the temperature distribution on the SiC microwave absorbent bed in a large-scale microwave pyrolysis reactor without feeding was examined by both infrared thermography and simulation. Considering the economics of using multiple low-power magnetrons in large-scale reactor, the effect of the working magnetrons location on the heating rate of bed surface and the COV of temperature distribution was investigated. The results showed that more uniform and stable temperature distribution of bed surface in the large-scale reactor was obtained when the magnetrons located at the bottom of the reactor were in use. This study provides guidance for the scale-up of microwave-assisted pyrolysis reactor with multiple low-power magnetrons.

Fabrication and mechanical properties of boron nitride nanotube reinforced silicon nitride ceramics

2018 ◽  
Vol 44 (6) ◽  
pp. 6456-6460 ◽  
Author(s):  
Tianfeng Li ◽  
Yongjun Chen ◽  
Wei Li ◽  
Jianbao Li ◽  
Lijie Luo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Boron Nitride ◽  
Boron Nitride Nanotube ◽  
Nitride Ceramics
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