• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.572-577
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• 2010

Reaction-bonded $Si_3N_4$ has cost-reduction merit because inexpensive silicon powder was used as a start material. But its density was not so high enough to be used for structural materials. So the sintered reaction-bonded $Si_3N_4$techniques were developed to solve the low density problem. In this study the sintered reaction-bonded $Si_3N_4$ manufacturing method by using polymer precursor which recently attained significant interest owing to the good shaping and processing ability was proposed. The formations, properties of reaction-bonded $Si_3N_4$ from silicon and polysilazane mixture were investigated. High density reaction-bonded $Si_3N_4$ was manufactured from silicon and silicon-containing preceramic polymers and post-sintering technique. The mixtures of silicon powder and polysilazane were prepared and reaction sintered in $N_2$ atmosphere at $1350^{\circ}C$ and post-sintered at 1600~$1950^{\circ}C$. Density and phase were analyzed and correlated to the resulting material properties.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.67-74
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• 1986

To investigate the effects of unreacted silicon on the $\alpha$/$\beta$transfornation variation of morphology and mechanical strength of Sintered Reaction Bonded Silicon Nitride the mixtures of $\alpha$-$Si_3N_4$ and Si powder and Reaction Bonded Silicon Nitride were heat treated. The heat-treatments were performed in Ar atmosphere in order to inhibit the nitridation of silicon. In the mixtures heat-trated at 1$700^{\circ}C$ the amount of $\beta$-TEX>$Si_3N_4$transformed from $\alpha$-TEX>$Si_3N_4$was sigmoidally increased and the equiaxed $\alpha$-TEX>$Si_3N_4$grains elongated with the amount of silicon and heat treating time. And large $\beta$-TEX>$Si_3N_4$grains grown into silicon were observed. On the other hand there was no change in the heat-treatment of pure $\alpha$-TEX>$Si_3N_4$In case of the heat-treatment of RBSN the same phenomena due to the silicon appearing from the decomposition of $\alpha$-Smatte and needle were observed. From the three point bending test the strength of the sintered specimens with the and without 5wt% silicon addition had 53Kg/$mm^2$ and 73Kg/$mm^2$ respectively.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.622-627
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• 2016

The effects of the debinding atmosphere on the properties of sintered reaction-bonded $Si_3N_4$ (SRBSN) ceramics prepared by tape casting method were investigated. Si green tape was produced from Si slurry of Si powder, using 11.5 wt% polyvinyl butyral as the organic binder and 35 wt% dioctyl phthalate as the plasticizer. The debinding process was conducted in air and $N_2$ atmospheres at $400^{\circ}C$ for 4 h. The nitridation process of the debinded Si specimens was performed at $1450^{\circ}C$, followed by sintering at $1850^{\circ}C$ and 20 MPa. The results revealed that the debinding atmosphere had a significant effect on $Si_3N_4$ densification and thermal conductivity. Owing to the higher sintered density and larger grain size, the thermal conductivity of $Si_3N_4$ specimens debinded in air was higher than that of the samples debinded in $N_2$. Thus, debinding in air could be suitable for the manufacture of high-performance SRBSN substrates by tape casting.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.75-75
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• 1994

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.206.2-206
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• 2000

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.42.1-42.1
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• 2000

• Journal of the Korean Ceramic Society
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• v.20 no.1
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• pp.63-69
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• 1983

It is know that $Si_3-N_4$ bonded SiC has almost all the valuable properties needed for the high temperature material and thus has bery wide range of applicability. Si powder and two different sized SiC powder were used as the raw mateials. Specimens were prepared by heating the green compact mode of the raw materials with polyvinyl alcohol binder in the nitrogen atmosphere. The bond-ing of SiC particles is brought about with the formation of reaction bonded silicon nitride phase between the particles he influences of the variation of the relative amounts of the raw materials and the amount of the organic binder on the density and the bend strength of the specimens were investigated. It was shown that the calculation of the amount of the nitridation of Si is somewhat complicated matter since some portion of the organic binder reacts with the Si during the firing process. Fixing the Si amount to 20w/o the distributions of the size of the SiC particles that gives the maximum density and the maximum strnegth were obtained through experiments. It was observed that the two distributions were not equal to each other. As the amount of Si increased the amount of Si reacted with nitrogen and the strength increased. The fracture mode was intergranular for the most part and the transgranular fracture was scarcely observed.

• Journal of the Korean Ceramic Society
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• v.22 no.1
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• pp.53-59
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• 1985

Experiments related to nitriding silicon with addition of $Si_3N_4$ have provided information on the effects of such inclusion on the phase relationships of Reaction Bonded Silicon Nitride. In the current work specimens containing 0-25wt% Si3N4 which have 55.5wt% $\alpha$ 4.5wt% $eta$, 40wt% amorphous phase were nitrided for 7-20 hours at 1300-135$0^{\circ}C$ The evaluation of nitridation was per-formed by means of $\alpha$-and $\beta$-phase contents determination in nitrided specimens, In order to observe nitrided region between silicon and silicon nitride scanning electron microscopy was used to study reacted region between silicon and silicon nitride particle. For this purpose semiconductor-grade silicon wafer single crystal was used as a silicon source. The incorporation of small amount of $Si_3N_4$ powder is contributed to enhancing the rate of formation of $\alpha$-phase.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.363-368
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• 2012

Nitriding and post-sintering behavior of powder mixture compacts were investigated. As mixture compacts are different from simple Si compacts, the fabrication of a sintered body with a mixture composition has engineering implications. In this research, in specimens without a pore former, the extent of nitridation increased with $Si_3N_4$ content, while the highest extent of nitridation was measured in $Si_3N_4$-free composition when a pore former was added. Large pores made from the thermal decomposition of the pore former collapsed, and they were filled with a reaction product, reaction-bonded silicon nitride (RBSN) in the $Si_3N_4$-free specimen. On the other hand, pores from the decomposed pore former were retained in the $Si_3N_4$-added specimen. Introduction of small $Si_3N_4$ particles ($d_{50}=0.3{\mu}m$) into a powder compact consisting of large silicon particles ($d_{50}=7{\mu}m$) promoted close packing in the green body compact, and resulted in a stable strut structure after decomposition of the pore former. The local packing density of the strut structure depends on silicon to $Si_3N_4$ size ratio and affected both nitriding reaction kinetics and microstructure in the post-sintered body.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.381-387
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• 1993

The silicon oxynitride bonded $Si_3N_4-BN$ composite has been developed based on the selective oxidation behavier of $Si_3N_4$ over BN. The silicon oxynitride phase converted to the reaction between $Si_3N_4$ and $SiO_2$ formed on $Si_3N_4$ powder surface during oxidation treatment at the sintering temperature. The developed composite has excellent high-temperature strength, thermal shock resistance, precision machinability and corrosion resistance to the molten steel. The developed composite may therefore be used as, for example, break ring materials in continuous casting of steel.