Calcium hexaluminate (CaO·6Al2O3–CA6) is usually associated as the product reaction between alumina and CA2 (CaO·2Al2O3) in cement‐bonded refractory castables. However, some investigations related to the Al2O3–CaO–MgO ternary system have indicated that CA6 could be generated by additional routes, involving two other high‐alumina phases: CaMg2Al16O27 (CM2A8) and Ca2Mg2Al28O46 (C2M2A14). Considering the lack of conclusive studies on this subject in the refractories field, the present study addresses an in‐depth microstructural evolution analysis of high‐alumina castables containing in situ or preformed spinel (MgAl2O4) in order to check the actual CA6 development steps in the presence of an MgO‐containing phase. By scanning electron microscopy (SEM) and thermodynamic calculations, it was observed that CA6 formation took place indeed as a result of the decomposition reaction of CM2A8, which was firstly generated due to the interaction between spinel and Al2O3–CaO–Na2O–SiO2 liquid. Although, the results confirmed this complex CA6 formation route regardless of the spinel incorporation method (pre‐formed grains addition or in situ reaction), the CA6 crystals distribution after the thermal treatment was entirely affected by the previous spinel grains location. Those different microstructural profiles could be the conclusive aspects to explain the poorer slag resistance of preformed spinel‐containing castables when in contact with steel ladle slags.
Although the corrosion performance of spinel‐containing castables has been extensively investigated in recent years, no previous studies accessed the different conditions present in the ladle bottom. In this region, strong variations in the atmospheric environment are often detected, which could drastically change the interactions between refractory and molten slag. In the present work, the main corrosion mechanisms of an alumina–magnesia castable in two environmental conditions (oxidizing – pO2 = 0.21 atm—or reducing – pO2 = 10−15 atm— atmosphere) were evaluated by means of scanning electron microscopy and EDS analyses of the corroded samples and thermodynamic simulations. The attained results showed that the slag penetration was suppressed in the presence of oxygen due to the precipitation of a great amount of calcium monoaluminate (CA) crystals as the refractory interacted with slag. Conversely, the CA phase was not stable under reducing conditions and, therefore, many more refractory components (Al2O3, MgO, and MgAl2O4) had to be dissolved to precipitate calcium dialuminate (CA2) by reacting with infiltrating slag. Thus, besides providing a suitable and more realistic understanding of the castable performance in service conditions, the results also indicated that the prediction of the environmental conditions is of utmost importance for the design of high performance refractories.
Psoriasis patients are at increased risk for cardiovascular disease. Literature on rheumatoid arthritis has shown the association of treatment with tumor necrosis factor (TNF) inhibitors and improvement of cardiovascular disease. Recent literature has also shown similar findings in psoriasis patients. We present a review of the literature on the effect of TNF inhibitors for psoriasis treatment on cardiovascular disease, cardiovascular biomarkers, and insulin resistance. We conclude that TNF inhibitors may be especially beneficial in preventing myocardial infarction, to a degree greater than methotrexate, especially in the Caucasian population. The effects of TNF inhibitors in altering insulin sensitivity or preventing new onset diabetes have been contradictory. Case reports of both hyperglycemia and hypoglycemia developing in patients under TNF inhibitor treatment teach us to warn patients about these side effects. More robust clinical studies are needed to evaluate the true effect of TNF inhibitors in diabetic psoriasis patients. More studies are also needed to assess the effect of TNF inhibitors on hypertension, dyslipidemia, and stroke.
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