Microwave heated reaction-bonded silicon nitride using an inverse temperature gradient

2003 ◽  
Vol 9 (2) ◽  
pp. 187-191 ◽  
Author(s):  
J. G. Fisher ◽  
K. Bai ◽  
S. K. Woo ◽  
I. S. Han ◽  
K. S. Lee ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Inverse Temperature

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.

Nitridation of Non-Isothermal Silicon Compacts

1992 ◽  
Vol 269 ◽  
Author(s):  
Jeffrey J. Thomas ◽  
Renee R. Jesse ◽  
D. Lynn Johnson ◽  
Hamlin M. Jennings
Keyword(s):  
Silicon Nitride ◽  
Temperature Gradient ◽  
Microwave Heating ◽  
Reaction Rate ◽  
Conventional Heating

ABSTRACTThe use of microwave heating for the processing of reaction-bonded silicon nitride offers at least two advantages over conventional heating methods. First, the reaction can be made to proceed preferentially in the interior of the reacting compact by maximizing the temperature gradient resulting from microwave heating. This helps maintain the flow of nitrogen into the compact during the later stages of the reaction, when the overall porosity is reduced. Second, the reaction rate can be controlled by changing the power, which gives better control over the processing than can be obtained using conventional heating.

scholarly journals Temperature Structure of the Chromosphere-Corona Transition Region

1972 ◽  
Vol 14 ◽  
pp. 670-671
Author(s):  
G. Elwert ◽  
P. K. Raju
Keyword(s):  
Temperature Gradient ◽  
Transition Region ◽  
Temperature Structure ◽  
Spherically Symmetric ◽  
Inverse Temperature ◽  
Line Intensities ◽  
Pressure Parameter ◽  
Best Fit

Starting from the formula for line intensities E for a spherically symmetric atmosphere, considering the pressure parameter P0 = NeTe to be constant the inverse temperature gradient can be determined by taking it out from the integral for E. In this way Dupree and Goldberg (1967) found that the temperature gradient varies considerably whereas the conductive flux factor F=Te5/2(dTe/dh) is nearly constant for Te above 105 K. The best fit was obtained by using photospheric abundances. As the inverse temperature gradient varies considerably in the line forming region, it is, however, not satisfactory to take it out from the integral.

Defects Analysis of Large Size Silicon Nitride Balls Sintered by Gas Pressure Sintering

2010 ◽  
Vol 434-435 ◽  
pp. 61-63
Author(s):  
Feng Sun ◽  
Wei Ru Zhang ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Temperature Gradient ◽  
Raw Materials ◽  
Gas Pressure ◽  
Sintering Process ◽  
The Core ◽  
Large Size ◽  
Defects Analysis ◽  
Gas Pressure Sintering

The sections of Φ55mm silicon nitride balls, sintered by gas pressure sintering were analyzed. The results show that temperature gradient during of the sintering process from the surface to the core of large size silicon nitride balls occurred because of the lower thermal conductivity of Si3N4. With the diameter increasing, the temperature gradient was more visible. The impurity of raw materials, such as free Si, free C and other metal oxides, like the SiO2 could produce gas, such as SiO, CO and so on, during the sintering process through the thermodynamic analysis. The producing gas exhausted more difficultly with the diameter of silicon nitride balls increasing. These factors were the most important to the defects of large size silicon nitride balls during the sintering process and made cracks and crescent on the surface of balls.

scholarly journals Field Measurements of Water Quality in a Partially Overturning Reservoir with Inverse Temperature Gradient in Its Bottom Layer.

1997 ◽  
pp. 33-48 ◽  
Author(s):  
Kohji Michioku ◽  
Tohru Kanda ◽  
Tatsuhei Itoh ◽  
Takaharu Nishikawa ◽  
Katsuhisa Ishikawa ◽  
...  
Keyword(s):  
Water Quality ◽  
Temperature Gradient ◽  
Field Measurements ◽  
Bottom Layer ◽  
Inverse Temperature

Use of the Inverse Temperature Profile in Microwave Processing of Advanced Ceramics

1992 ◽  
Vol 269 ◽  
Author(s):  
J.G.P. Binner ◽  
I.A. Al-Dawery ◽  
C. Aneziris ◽  
T.E. Cross
Keyword(s):  
Silicon Nitride ◽  
Temperature Profile ◽  
Microwave Heating ◽  
Microwave Sintering ◽  
Microwave Processing ◽  
Inverse Temperature ◽  
Advanced Ceramics ◽  
Reaction Bonding ◽  
Microwave Reaction

ABSTRACTAttempts are being made to exploit the inverse temperature profile which can be developed with microwave heating with respect to the processing of certain advanced ceramics. This paper discusses the results obtained to date during the microwave sintering of YBCO high-Tc superconductors and the microwave reaction bonding of silicon nitride.

scholarly journals The Physical Vapor Transport Method for Bulk AlN Crystal Growth

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1562 ◽  
Author(s):  
Wen-Hao Chen ◽  
Zuo-Yan Qin ◽  
Xu-Yong Tian ◽  
Xu-Hui Zhong ◽  
Zhen-Hua Sun ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Temperature Gradient ◽  
Single Crystals ◽  
Low Cost ◽  
Vapor Transport ◽  
Physical Vapor Transport ◽  
Inverse Temperature ◽  
Seeded Growth ◽  
Perforated Sheet

In this report, the development of physical vapor transport (PVT) methods for bulk aluminum nitride (AlN) crystal growth is reviewed. Three modified PVT methods with different features including selected growth at a conical zone, freestanding growth on a perforated sheet, and nucleation control with an inverse temperature gradient are discussed and compared in terms of the size and quality of the bulk AlN crystals they can produce as well as the process complexity. The PVT method with an inverse temperature gradient is able to significantly reduce the nucleation rate and realize the dominant growth of only one bulk AlN single crystal, and thus grow centimeter-sized bulk AlN single crystals. X-ray rocking curve (XRC) and Raman spectroscopy measurements showed a high crystalline quality of the prepared AlN crystals. The inverse temperature gradient provides an efficient and relatively low-cost method for the preparation of large-sized and high-quality AlN seed crystals used for seeded growth, devoted to the diameter enlargement and quality improvement of bulk AlN single crystals.

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