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Moslemi-firoozabadi Hamidreza,Manafi Sahebali,Ghahremani Davoud 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.6
This study focused on the production of mullite ceramic and composites containing HfN reinforcements through spark plasma sintering. Accordingly, 5, 10 and 15wt% HfN powders with calcined Aluminum nitrate nonahydrate (ANN) and colloidal silica mixture were blended through a high-energy mixer mill in ethanol media. Spark plasma sintering of mullite ceramic and composite was performed under almost the same condition consisting of the initial and fi nal applied pressure of 10 and 50 MPa, respectively, vacuum of 15–25 Pa, and the maximum sintering temperature of 1350 °C. The measured relative den- sities showed the nearly full densifi cation of all prepared samples. The XRD patterns also depicted perfect mullitization for the mullite sample, while in the sintered composites, mullite, HfN and HfO 2 peaks were obtained as the crystalline phases. The uniform distribution of HfN and HfO 2 as the reaction products of ANN water desorption was recognized in the micro- structure of mullite composites with 5 and 10 wt% HfN samples. Meanwhile, the mullite-15wt% HfN composite displayed some agglomerates and porosities. The attained mechanical properties also showed that Vickers hardness was increased by raising HfN contents. However, the maximum bending strength of 424 ± 25 and fracture toughness of 3.74 ± 0.22 MPa m 1/2 were achieved for the composite containing 10 wt% HfN.