Mullite matrix composites reinforced with tetragonal zirconia polycrystals stabilized with 3 percent mole of Yttria (3y-tzp)

MENDY, Dominique, Ir. M.Waziz Wildan, M.Sc., Ph.D

2008 | Tesis | S2 Teknik Mesin

Penetilian ini bertujuan untuk mengetahui pengaruh 3Y-TZP (Tetragonal Zirconia Polycrystals Stabilized with 3% mole of Yttria) terhadap sifat fisis dan mekanis komposit dengan matris mullite. Mullite (3Al2O3.2SiO2) telah digunakan secara luas pada industri keramik, termasuk industri bangunan dan bahan optik, serta sistem perlindungan thermal dan liners mesin pesawat. Zirconia (ZrO2) yang dikenal sebagai bahan industri keramik yang sangat baik dan bisa digunakan sebagai media untuk meningkatkan ketangguhan bahan keramik lainnya misalnya yang dikenal dengan ZTC (Zirconia Toughened Ceramics) seperti ZTA (Zirconia Toughened Alumina). Dalam penelitian ini, serbuk kaolin dan 3Y-TZP dicampur dengan memvariasikan fraksi volume 3Y-TZP dari 0, 5, 10, 15, dan 20 % (dalam fraksi volume) terhadap serbuk kaolin. Setiap komposisi ditekan dengan tekanan kompaksi uni-axial 50 MPa untuk membuat green bodies yang berbentuk silindris (dengan diameter 15 mm dan ketebalan 5 mm) dan yang berbentuk balok dengan dimensi (50×7×5) mm3. Spesimen silindris disinter tanpa tekanan pada suhu sinter 1400 dan 1450 ºC selama 1 jam dengan laju pemanasan 5 ºC/min. Spesimen balok juga disinter dengan cara yang sama. Densitas spesimen silindris diukur dengan teori Archimedes. Uji kekerasan dan ketangguhan dilakukan pada spesimen silindris dengan menggunakan masing-masing metode kekerasan Vickers dan metode crack indentation. Uji bending digunakan untuk menguji kekuatan bending pada spesimen balok dengan metode four-point bending. Hasil penelitian ini menunjukkan bahwa densitas relatif meningkat dari 86,08% (monolithic mullite) pada suhu sinter 1400 ºC sampai 92,47% (untuk komposisi zirconia tertinggi) pada suhu sinter 1450 ºC. Kenaikan sebesar 19% juga didapat pada kekerasan Vickers. Ketangguhan naik sampai dua kali lipat lebih dibanding monolithic mullite. Kekuatan bending naik hampir 57%. Efek penguatan diangkat kuat dikarenakan oleh transformasi fase zirconia tetragonal ke monoklinik

The purpose of this research is to investigate the effect of 3Y-TZP (Tetragonal Zirconia Polycrystals Stabilized with 3% mole of Yttria) on the physical and mechanical properties of mullite matrix composites. Mullite (3Al2O3.2SiO2) has been developed for a wide range of applications in modern ceramics, including for building and optical materials, and for thermal-protection systems and in liners for aircraft engines. Zirconia (ZrO2) is known as an excellent advanced ceramic materials and it can be used as a media for fracture toughness enhancement over existing ceramic materials for example ZTC (Zirconia Toughened Ceramics) such as ZTA (Zirconia Toughened Alumina). The kaolin and 3Y-TZP powders were mixed together at various volume fractions of 0, 5, 10, 15, and 20% (all given in vol. %) of 3Y-TZP. Each composition was uniaxially pressed with a pressure of 50 MPa to produce cylindrical (diameter of 15 mm and thickness of 5 mm) and rectangular bar (50×7×5) mm3 shapes of green bodies. The cylindrical green bodies were pressurelessly sintered at various temperatures of 1400 and 1450 ºC for one hour of soaking time with a heating rate of 5 ºC/min. The rectangular bars were also pressurelessly sintered at temperatures of 1400 and 1450 ºC in a similar manner than above. XRD and SEM were used to identify the present phases and microstructures respectively. Density was measured on the cylindrical specimens using Archimedes’ method. Hardness and toughness were conducted on the cylindrical specimens fired at 1400 and 1450 ºC, by using Vickers hardness method and the crack indentation method respectively. Four-point bending test was used to measure the strength on the rectangular bars. The results show that the relative density increased from 86.08 % (monolithic mullite) at sintering temperature of 1400 ºC to 92.47 % (at highest zirconia content) at sintering temperature of 1450 ºC. An increase of 19% is obtained on the Vickers hardness. The fracture toughness increases up to two times higher than that of the monolithic mullite. The bending strength was also increased by 57%. The toughening effect is attributed mainly to the zirconia t-m phase transformation.

Kata Kunci : Mullite,3Y,TZP,Ketangguhan,Transformation toughening,mullite, 3Y-TZP, fracture toughness, transformation toughening