Mehmet Akif HAFIZOĞLU, Ahmet AKKUŞ, Tahsin BOYRAZ

Mullit Takviyeli CaO Katkılı ZrO2 Seramiklerinin İmalatı ve Karakterizasyonu

Bu çalışmada, mullit (3Al2O3.2SiO2) ve %11 mol kalsiyum oksit katkılı zirkonya (%11 mol CaO - %89 mol ZrO2) seramik tozları geleneksel seramik üretim yöntemi ile sentezlenmiştir. Karışımlar, zirkonya bilyalı değirmende aseton ortamında mekanik alaşımlama yöntemiyle hazırlanmıştır. Tozlar karıştırılmadan önce 110 ºC'de 24 saat etüvde kurutulmuştur. Al2O3, SiO2, CaO ve ZrO2 tozlarının stokiyometrik oranlarından oluşan tozların aseton ortamında bilyeli değirmende homojenize edildikten sonra geleneksel sinterleme yöntemiyle Mullit (3Al2O3.2SiO2) ve %11 mol kalsiyum oksit katkılı zirkonya (CaO-ZrO2) seramik tozları sentezlenmiştir. Mullit ve %11 mol kalsiyum oksit katkılı zirkonya seramik tozları sırasıyla 1600 oC'de 3 saat ve 1300 oC'de 2 saat sentezlenmiştir. Daha sonra oluşan seramik fazlar kırma, öğütme ve eleme işlemleri ile seramik - seramik kompozitleri oluşturmaya hazır hale getirilmiştir. Daha sonra ağırlıkça %0 ve %10 mullit (M) takviyeli kalsiyum oksit katkılı zirkonya (CaZ) karışımları toz metalurjisi yöntemiyle hazırlanmıştır. Hazırlanan karışımlar zirkonya bilyalı değirmende 24 saat yaş öğütülmüş ve elenmiştir. Kurutulduktan sonra, tozlar 200 MPa'da tek eksenli presleme ile 56x12x10 mm'lik preformlara sıkıştırılmıştır. Devamında, yüksek sıcaklıklı bir fırında 5 oC/dak ısıtma hızı kullanılarak hava koşullarında 1500-1600 oC'de 1-5 saat sinterlenmiştir. Daha sonra mullit takviyeli kalsiyum oksit katkılı zirkonya seramik kompozitler üzerinde mikroyapı (SEM), faz analizi (XRD), mekanik (sertlik, 3 nokta eğme ve aşınma) ve fiziksel özellikler (% küçülme, su emme, gözeneklilik ve yoğunluk) testleri yapılmıştır. Bu çalışmada, yüksek sinterleme sıcaklıklarında ZrO2 - CaO karışımında faz değişimi olup olmadığı ve mullit katkı maddesinin bu karışımın özelliklerine etkisi araştırılmıştır. Elde edilen veriler grafik ve tablolar halinde sunulmuş ve yorumları yapılmıştır.

Anahtar Kelimeler:

Zirkonya, Mullit, Kalsiyum oksit, Karakterizasyon, Aşınma

Fabrication and Characterization of Mullite Reinforced CaO Added ZrO2 Ceramics

In this study, mullite (3Al2O3.2SiO2) and 11 mol % calcia added zirconia (11 mol % CaO - 89 mol % ZrO2) ceramic powders were synthesized by conventional ceramic production processing route. The mixtures were prepared by mechanical alloying method in acetone environment with zirconia ball mill. The powders were dried in oven at 110 ºC for 24 hours before mixing. Mullite (3Al2O3.2SiO2) and 11 mol% calcia added zirconia (CaO-ZrO2) ceramic powders were synthesized by reaction sintering from the powders made up of stoichiometric proportions of Al2O3, SiO2, CaO and ZrO2 powders after being homogenized in acetone environment in ball mills. Mullite (3Al2O3.2SiO2) and 11 mol% calcia added zirconia (CaO-ZrO2) ceramic powders were synthesized in air at 1600 oC for 3 h and 1300 oC for 2 h, respectively. Then, the ceramic phases formed were made ready to form ceramic - ceramic composites by crushing, grinding and sieving processes. Then 0 and 10% by weight mullite (M) added calcia doped zirconia (CaZ) mixtures were prepared by powder metallurgy method. The prepared mixtures were wet milled with zirconia ball mill for 24 h and sieved. After drying, the powders were compacted to preforms of 56x12x10 mm by uniaxial pressing at 200 MPa. The green compacts were sintered at 1500-1600 oC for 1-5 h in air conditions using a heating rate of 5 oC min-1 in a high temperature furnace. Then, microstructure (SEM), phase analysis (XRD), mechanical (hardness, 3-point bending and wear) and physical properties (% shrinkage, water absorption, porosity and density) tests were performed on the mullite added calcia doped zirconia ceramic composites. In this study, whether there is a phase change in the ZrO2 - CaO mixture at high sintering temperatures and the effect of mullite additive on the properties of this mixture was investigated. The data obtained were presented in graphs and tables and their comments were made.

Keywords:

Zirconia, Mullite, Calcia, Characterization, Wear,

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