Ceramic phase diagrams:
Phase diagrams for ceramic materials obey the same rules as for metal systems. An important difference is that the terminal end phases are usually themselves binary compounds, rather than pure elements. Anumber of binary systems contain oxygen as a common element. We will now look at a few of the more important pseudo-binary systems as examples:
Cr2O3 - Al2O3
SiO2 - Al2O3
MgO - Al2O3
CaZrO3 - ZrO2
1-Cr2O3 - Al2O3:
One of the simplest pseudo- binary phase diagrams. Complete solubility: Al, Cr atoms possess similar size and chemical valence Both oxides have the same crystal structure Al+3 substitutes for the Cr+3 ion in Cr2O3 (and vice versa).
2-SiO2 - Al2O3:
Most commercial refractories are based on the silica-alumina system fireclay refractories contain 25-45 wt. % Al2O3 typically used in furnace construction (insulation) silica refractories (< 7 wt. % Al2O3) are used as load-bearing supports for large industrial furnaces note the absence of solubility on either endpoint one intermediate compound exists: mullite (3Al2O3 - 2SiO2).
Imperfections in Ceramics:
1- Include point defects and impurities.
2- Charge neutral defects include the Frenkel defects(a vacancy- interstitial pair of cations) and Schottky defects (a pair of nearby cation and anion vacancies).
3- Defects will appear if the charge of the impurities is not balanced.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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