Use of Variable Frequency Microwave Energy as a Flexible Plasma Tool

1994 ◽  
Vol 347 ◽  
Author(s):  
A. C. Johnson ◽  
R. A. Rudder ◽  
W. A. Lewis ◽  
R. C. Hendry
Keyword(s):  
Plasma Etching ◽  
Excitation Frequency ◽  
Chemical Vapor ◽  
Target Surface ◽  
Microwave Energy ◽  
Chemical Vapor Infiltration ◽  
Process Efficiency ◽  
Variable Frequency ◽  
Series Of Experiments ◽  
Multi Mode

ABSTRACTThis paper reports on the use of frequency as a control parameter in the generation of microwave-excited plasmas for applications such as chemical vapor deposition, chemical vapor infiltration, or plasma etching. By changing the excitation frequency of a plasma in a multi-mode chamber, the locations of the maxima and minima of the power density within the chamber are also changed. This allows localization of the plasma discharge in the precise processing area desired in order to increase the process' efficiency. In a similar fashion, sweeping of the processing frequency during the process cycle can theoretically “scan” the plasma across an arbitrarily-shaped target surface. A series of experiments was conducted to evaluate the flexibility of variable frequency microwave energy as a plasma process tool. The results of these tests are presented.

Modeling and Development of a Microwave Heated Pilot Plant for the Production of SiC-Based Ceramic Matrix Composites

2008 ◽  
Vol 6 (1) ◽  
Author(s):  
Beatrice Cioni ◽  
Andrea Lazzeri
Keyword(s):  
Microwave Heating ◽  
Chemical Vapor ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Pilot Scale ◽  
Chemical Vapor Infiltration ◽  
Process Efficiency ◽  
Average Weight ◽  
Matrix Composites ◽  
Pilot Scale Reactor

This paper outlines the development of a microwave heated apparatus for the production of silicon carbide (SiC) based ceramic matrix composites via chemical vapor infiltration. An innovative pilot scale reactor was designed and built. A coupled thermal and electromagnetic model was developed in order to predict the temperature profile inside the reactor. The results obtained from the model demonstrated that the electric field inside the sample was constant. This fact is particularly important in order to prevent the thermal instabilities (run-aways) that are typical in the case of microwave heating. Therefore the heating was uniform with the aid of a mode stirrer that achieved a better distribution of the microwave power and then improved the process efficiency. The infiltration cycles were carried out on SiC fiber preforms and resulted in an excellent average weight increase with respect to the initial sample. By using microwave heating, the treatment times were considerably reduced with respect to the conventional process times reported in the literature. The microstructure of the SiC composites were observed by scanning the electron microscopy in order to evaluate the quality and the degree of densification which was achieved within the fiber tows. The SiC deposition inside of the sample was sufficiently homogeneous and compact, even if a certain degree of inter-tow porosity was still evident.

Characterization of interfaces in CVD-coated nicalon fiber-reinforced SiC

1989 ◽  
Vol 47 ◽  
pp. 556-557
Author(s):  
K.L. More ◽  
R.A. Lowden
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Frictional Stress ◽  
Fiber Reinforced ◽  
Pull Out ◽  
Carbon Coated ◽  
Fiber Matrix

The mechanical properties of fiber-reinforced composites are directly related to the nature of the fiber-matrix bond. Fracture toughness is improved when debonding, crack deflection, and fiber pull-out occur which in turn depend on a weak interfacial bond. The interfacial characteristics of fiber-reinforced ceramics can be altered by applying thin coatings to the fibers prior to composite fabrication. In a previous study, Lowden and co-workers coated Nicalon fibers (Nippon Carbon Company) with silicon and carbon prior to chemical vapor infiltration with SiC and determined the influence of interfacial frictional stress on fracture phenomena. They found that the silicon-coated Nicalon fiber-reinforced SiC had low flexure strengths and brittle fracture whereas the composites containing carbon coated fibers exhibited improved strength and fracture toughness. In this study, coatings of boron or BN were applied to Nicalon fibers via chemical vapor deposition (CVD) and the fibers were subsequently incorporated in a SiC matrix. The fiber-matrix interfaces were characterized using transmission and scanning electron microscopy (TEM and SEM). Mechanical properties were determined and compared to those obtained for uncoated Nicalon fiber-reinforced SiC.

Modeling of Chemical Vapor Infiltration for Pyrocarbon within Capillaries

2016 ◽  
Vol 31 (3) ◽  
pp. 298
Author(s):  
TANG Zhe-Peng ◽  
ZHANG Zhong-Wei ◽  
FANG Jin-Ming ◽  
PENG Yu-Qing ◽  
LI Ai-Jun ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Vapor Infiltration

Microstructures, Strength and Toughness of 2D Cf/(C-SiC) Composites by Chemical Vapor Infiltration

2009 ◽  
Vol 24 (5) ◽  
pp. 939-942 ◽  
Author(s):  
Zhi-Xin MENG ◽  
Lai-Fei CHENG ◽  
Li-Tong ZHANG ◽  
Yong-Dong XU ◽  
Xiu-Feng HAN
Keyword(s):  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Sic Composites ◽  
Strength And Toughness ◽  
Vapor Infiltration

Fracture behavior of 3-d Braided Nicalon/Silicon Carbide Composite

1988 ◽  
Vol 120 ◽  
Author(s):  
J.-M. Yang ◽  
J.-C. Chou ◽  
C. V. Burkland
Keyword(s):  
Fracture Toughness ◽  
Silicon Carbide ◽  
Thermal Shock Resistance ◽  
Fracture Behavior ◽  
Ceramic Composite ◽  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Fiber Architecture ◽  
Structural Ceramic ◽  
Shock Resistance

AbstractThe fracture behavior of a 3-D braided Nicalon fiber-reinforced SiC matrix composite processed by chemical vapor infiltration (CVI) has been investigated. The fracture toughness and thermal shock resistance under various thermomechanical loadings have been characterized. The results obtained indicate that a tough and durable structural ceramic composite can be achieved through the combination of 3-D fiber architecture and the low temperature CVI processing.

scholarly journals Densification of High Thickness C/C Composites by Chemical Vapor Infiltration

2015 ◽  
Vol 109 ◽  
pp. 381-389 ◽  
Author(s):  
M. Albano ◽  
R. Pastore ◽  
A. Delfini ◽  
D. Micheli ◽  
F. Volpini ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Chemical Vapor Infiltration ◽  
Vapor Infiltration
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