Silicon nitride fracture strength distribution

Fig. 1 a) Strength data of a silicon nitride ceramic tested in four point bending (4PB) in a Weibull plot and b) the relative frequency distribution of flaw sizes. The data points were determined by fracture experiments. 

TABLE 4. Grain size distributions for the Si3N4-BAS composite from different ratio of starting silicon nitride powders with their indentation fracture toughness and flexural strength... 

Another feature of this material is its narrow distribution of the fracture strength. When the strength distribution was expressed in Weibull statistics, the Weibull modulus was 46 - substantially higher than the value of 26 obtained for a conventional, self-reinforced silicon nitride. Thus, the seeded and tape-cast silicon nitride showed a synergistic improvement in all of the important fracture attributes, such as fracture strength, fracture toughness, and strength stability (Weibull modulus). 

Figure 12.26 The frequency distribution of observed fracture strengths for a silicon nitride material.

Refractory ceramics are widely used in electronic, structural, and machine applications. They are characterized by high strength and fracture toughness, which are achieved in part by reducing the number and size distribution of microcracks in the finished part. Aluminas, silicon carbides and nitrides, sialons, and stabilized zirconias are the most prominent of this category. They are used in applications where heat resistance, hardness, fracture toughness,... 

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