氮化矽基陶瓷的破壞韌性雖高於一般結構陶瓷(如氧化鋁)，但仍具改善空間，其破壞的機構一般呈現脆性破壞為主，因此有許多研究透過添加強化相的方式改善氮化矽基陶瓷的機械性質。由於添加於基材中的第二相於混合過程是否均勻，將對複合材料燒結體的性質有重要的影響。因此本研究嘗試利用水解法將前驅物四異丙醇鈦(Ti(OC3H7)4)與Si3N4粉末混合後水解，使TiO2均勻地包覆在Si3N4粉末的表面，再將粉末以氨氣進行氮化處理，製備奈米TiN/ Si3N4複合粉末，探討複合粉末之氮化反應、表面形態；並將氮化後之奈米複合粉末，在10 atm氮氣下進行熱壓燒結，製備TiN/Si3N4複合陶瓷，並探討複合陶瓷的相組成，微結構、機械性質。

實驗結果顯示，經水解法製備所得之TiO2為非晶質結構，並均勻覆著於氮化矽顆粒表面。利用氨氣在900 sccm將TiO2進行氮化處理，TiO2在高於1000℃以上有氮化反應的進行，並在1100℃持溫5小時條件下可將TiO2氮化，形成TiN粒徑約30 nm之奈米TiN/Si3N4複合粉末。

奈米複合粉末經由10 atm氮氣氛下熱壓燒結之燒結體顯示，由水解法製備之奈米TiN有助於Si3N4於燒結過程之相變態，奈米TiN/ Si3N4複合粉末在1750℃可使氮化矽α相完全相變態為β相之Si3N4熱穩定相，燒結體的相組成有TiN、β相Si3N4以及Si2N2O相。燒結體中TiN有明顯的晶粒成長現象，由SEM觀察其晶粒大小約500 nm左右。

比較不同TiN的體積比的機械性質發現，隨著TiN的體積比愈高，其硬度值與抗彎強度會隨著下降，但是韌性值方面，含有10vol% TiN時有最大值韌性值6.56MPa‧m1/2。由電阻率的量測結果可知，隨著TiN的添加量愈多時，電阻率有下降的趨勢，而且在添加30 vol% TiN電阻率有劇烈下降的現象，其電阻率約為70 Ω.cm。

Silicon nitride (Si3N4) has excellent mechanical properties and thermal stability. However, like most ceramics, its brittle nature and difficult to be manufactured into complex shapes has limited its application. When the conductivity of silicon nitride based composite was increased by adding the conductive compound as second phase, these compounds can be easily shaped by electrical discharge machining. Because the homogenous distribution of second phase is important for the properties of composite, the TiN/Si3N4 nanocomposite powders were synthesized by hydrolysis method for homogenous distribution of second phase in this study.

Experimental results indicated that the amorphous TiO2 could cover the surface of the Si3N4 homogenously after the precursor (titanium tetrakisisopropoxide) were hydrolyzed. Using ammonia for nitridation reaction, TiO2 was nitrided completely at 1100℃ for 5 hr and the particles size of TiN were about 30 nm.

The composites were sintered by hot pressing sintering at 1750℃ for 1 hour in 10atm N2. The sintered body consisted of β-Si3N4、Si2N2O、TiN. The grain size of TiN was about 500 nm after sintering, and the larger grain size as increasing as the contents. The addition of 10 vol% TiN has the best toughness 6.56 MPa‧m1/2. The toughening mechanisms of the composites were crack deflection, bridging and branching. The addition 30 vol% TiN has the lowest resistivity 70 Ω.cm.

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