Pip Processing, Microstructure and Properties of Si34N Fiber and Al2O3 Fiber Reinforced Silicon Nitride

1994 ◽  
Vol 365 ◽  
Author(s):  
Stuart T. Schwab ◽  
Richard A. Page ◽  
David L. Davidson ◽  
Renee C. Graef
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
Carbon Composite ◽  
Organic Polymer ◽  
High Temperature Strength ◽  
Fiber Reinforced ◽  
Southwest Research Institute ◽  
Structural Applications ◽  
Al2o3 Fiber ◽  
Manufacturing Techniques

ABSTRACTPolymer infiltration/pyrolysis (PIP) processing has the potential to become an affordable means of manufacturing continuous fiber-reinforced ceramic-matrix components. The PIP method is very similar to the well-known polymer-matrix and carbon-carbon composite manufacturing techniques, the major difference being the use of a preceramic polymer in place of the organic polymer or carbon precursor. To date, the majority of research in the field of preceramic polymers has centered on precursors to silicon carbide (SiC). The Southwest Research Institute (SwRI) has focused on the development of polymeric precursors to silicon nitride (Si3N4) because its high-temperature strength, resistance to oxidation, and other properties make it an attractive candidate for many advanced high-temperature structural applications. PIP Si3N4 composites with NICALON SiC fiber reinforcement have exhibited good fracture toughness (KIC ∼ 16MPa·m1/ 2). We report here processing, microstructure and preliminary mechanical properties of two new PIP Si3N4 composites. One is reinforced with Tonen Si3N4 fiber (plain weave) while the other is reinforced with ALMAX Al2O3 fiber (8 Harness satin weave).

Infiltration/Pyrolysis Processing of Fiber-Reinforced Silicon Nitride

1992 ◽  
Vol 287 ◽  
Author(s):  
Stuart T. Schwab ◽  
Renee C. Graef ◽  
Cheryl R. Blanchard ◽  
Yi-Ming Pan ◽  
David L. Davidson
Keyword(s):  
Silicon Nitride ◽  
Brittle Failure ◽  
High Temperature Strength ◽  
Fiber Reinforced ◽  
Southwest Research Institute ◽  
Resistance To Oxidation ◽  
Structural Applications ◽  
Complex Shapes ◽  
Near Net Shape ◽  
Manufacturing Techniques

ABSTRACTWhile its high-temperature strength, resistance to oxidation, and other properties make silicon nitride an attractive candidate for many advanced structural applications, its propensity for brittle failure has hindered its widespread adoption. One approach to avoiding brittle failure is through incorporation of continuous fiber-reinforcement; however, conventional (powderbased) methods of silicon nitride fabrication can degrade fibers and are not amenable to the production of complex shapes. The Southwest Research Institute has developed a number of polymeric precursors to silicon nitride which are available as thermosetting liquids, and we have shown that these materials can be used in combination with near net-shape manufacturing techniques to produce fiber-reinforced silicon nitride composites. Mechanical property tests conducted at room temperature suggest that these polymer-derived composites exhibit fracture behavior comparable to those produced through conventional techniques; micromechanical investigations conducted at 800°C indicate that non-brittle failure is maintained at elevated 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.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

Microstructural Instability in Mosi2/Sic Nanolayers

1997 ◽  
Vol 3 (S2) ◽  
pp. 399-400
Author(s):  
Y.C. Lu ◽  
H. Kung ◽  
J-P Hirvonen ◽  
T.R. Jervis ◽  
M. Nastasi ◽  
...  
Keyword(s):  
High Temperature ◽  
Ion Irradiation ◽  
High Temperature Strength ◽  
Second Phase ◽  
Microstructural Stability ◽  
Factors Affecting ◽  
Structural Applications ◽  
Thermal Compatibility ◽  
Two Phases ◽  
The Stability

Thin film multilayers have been the focus of extensive studies recently due to the interesting properties they exhibit. Since the improvement in properties can be attributed directly to the unique nanoscale microstructures, it is essential to understand the factors affecting the microstructural stability in these nanolayer structures. The intermetallic compound, MoSi2, despite its superior oxidation resistance and high melting point, suffers from inadequate high temperature strength and low temperature ductility, properties which hinder its high temperature structural applications [1]. SiC is a potential second phase reinforcement due to its high temperature strength and thermal compatibility with MoSi2. The addition of SiC in a nanolayered configuration has been shown to exhibit significant increase in hardness after annealing [2]. It has also been shown that when annealed above 900°C, the layers break down and grain growth sets in, with a significant decrease in hardness and. Due to the lack of a thermochemical driving force, the two phases remain separate at all temperatures investigated. In this study, the stability of the MoSi2/SiC nanolayers structure under ion irradiation has been investigated.

High temperature strength and fractography of sintered silicon nitride

1991 ◽  
Vol 17 (6) ◽  
pp. 335-341 ◽  
Author(s):  
A.K. Mukhopadhyay ◽  
S.K. Datta ◽  
D. Chakraborty
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
High Temperature Strength ◽  
Sintered Silicon

scholarly journals Crack Healing Behaviour and High Temperature Strength of Silicon Nitride Ceramics.

1999 ◽  
Vol 65 (633) ◽  
pp. 1132-1139 ◽  
Author(s):  
Kotoji ANDO ◽  
MinCheol CHU ◽  
Yasuyoshi KOBAYASHI ◽  
Feiyuan YAO ◽  
Shigemi SATO
Keyword(s):  
High Temperature ◽  
Silicon Nitride ◽  
High Temperature Strength ◽  
Crack Healing ◽  
Nitride Ceramics
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