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The incorporation of spinel particles (MgAl2O4) into MgO improves thermal shock resistance and thereby service life of refractories. In this work, hercynite (FeAl2O4) additions at different ratios has been examined to improve mechanical properties of MgO-spinel composites at different spinel ratios. The relationships between mechanical properties and microstructural variables have been investigated in detail. The important parameters improving the mechanical properties of MgO-Spinel-Hercynite composite refractory materials have been determined as follows: i) as the microcracks formed in the structure come across either with the additives or pores; crack branching and deviation of interlinking microcrack network or crack arresting occur, ii) the trend of fracture type has been converted from transgranular to intergranular fracture with additives, iii) grain size of MgO decreases significantly, as compared to pure MgO material with additives, iv) the density values increase with increasing amount of additives. © Afyon Kocatepe Üniversitesi 1. GirişMgO-krom refrakter malzemelerde, Cr2O3’den üretilen toksin Cr+6 iyonlarının deride alerji, ülser ve kanserojen etkisinden dolayı endişe yaratması, krom içermeyen alternatif MgO-spinel refrakter malzemelerin kullanılması ihtiyacını da gündeme getirmiştir [1]. Çimento fırınında kullanılan magnezya-krom tuğlalardan kaynaklanan çevresel kirliliğin çözümlenmesi için son 20 yıldır krom, MgO’e spinel (MgAl2O4) partikülleri ilavesi, refrakterlerin ısıl şok direncini ve dolayısıyla kullanım ömrünü arttırmaktadır. Bu çalışmada farklı oranlarda spinel içeren MgO-spinel kompozitlerin mekanik özelliklerini iyileştirebilmek için değişik oranlarda hersinit (FeAl2O4) ilave edilmiş, mekanik özellikler ile mikroyapısal değişimler arasındaki ilişkiler detaylı olarak araştırılmıştır. MgO-Spinel-Hersinit kompozit refrakter malzemelerin mekanik özelliklerini arttıran önemli parametreler: i) yapıda oluşan mikroçatlakların katkı tanelerinin üzerine geldiğinde birbirlerine bir ağ şeklinde bağlanarak dallanması, sapması veya gözeneğe ve katkı ilavelerine ulaştığında durması, ii) kırılma tipinin katkı ilaveleriyle taneiçi kırılmadan taneler-arası kırılmaya doğru dönüşme eğilimi göstermesi, iii) kristal tane boyutunun MgO’e göre artan katkı ilaveleriyle önemli ölçüde azalması, iv)yoğunluk değerlerinin katkı miktarıyla yükselmesi olarak belirlenmiştir

14th International Conference on Advances in Materials and Processing Technologies (AMPT) -- JUL 13-16, 2011 -- Istanbul, TURKEY, WOS: 000309565300091, Corrosion resistance of MgO-Spinel (M-S) composite refractories containing various amounts of ZrSiO4-Y2O3 constituents was investigated. Density and open porosity values were measured and evaluated. Corrosion tests of refractories were carried out statically under standard conditions using cylindrical shaped samples in terms of determining the interaction with cement clinker. Corrosion resistance was determined by measuring the values of penetration and depth of the corroded regions of refractories. The influence of corrosion resistance based on the microstructural changes occurred as a result of solubilities of constituents in the interface of clinker-refractory for various regions was examined using SEM and the results were evaluated using EDX analysis. It was observed that there was a significant increase in density values and decrease in porosity data for most of the compositions obtained from the additions of ZrSiO4-Y2O3 to MgO-spinel. As a consequence of microstructural characterisation performed at the interface of clinker-refractory, the observations made were determined as follows: i) the formation of ZrO2 and Mg2SiO4 phases among the MgO grains during sintering, ii) the formation of CaZrO3 phase during penetration, iii) prevention of penetration by new phases formed that make a barrier effect against clinker with the improvement in densification, and iv) the decrease in the amount of CaO based on the EDX analysis made from clinker to refractory in a corroded region. The incorporation of ZrSiO4-Y2O3 into MgO-spinel reduced the values of penetration and depth of the corroded regions of refractories and improved the corrosion resistance. The penetration of clinker to refractory showed a minimum level for the composition of M-20%S-20%(ZrSia(4)d-Y2O3) and an improvement by a factor of 1.42 as compared to M-20%S. This development is also combined with a long service life of M-S-(ZrSiO4+Y2O3) containing composite refractories for industrial uses., Turkish Airlines, TTNET, Gedik Hold, Istanbul Dev Agcy