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Studying the Effect of Carbon Nanotubes Addition on the Mechanical and Hydration Properties and Microstructure of Magnesia Doloma Refractories

Mohammadi, Hooman | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58019 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali
  7. Abstract:
  8. Magnesia-doloma refractories are alkaline products made by combining sintered or fused dolomite and magnesite. These refractories contain 50-80 wt% magnesium and a higher percentage of magnesium oxide, provides desirable properties such as improved refractoriness and resistance to air moisture absorption. Magnesia-doloma refractories have significant weaknesses, including rapid hydration due to the presence of CaO and MgO phases. These refractories are also primarily used with carbon additives in the industry, where increasing the carbon weight percentage in these refractories weakens their strength and some of mechanical properties. In the present study, the effect of adding carbon nanotubes on the mechanical properties (cold compressive strength, CCS) and hydration resistance was investigated. For this purpose, samples containing 30% calcined magnesite and 70% calcined dolomite with 0.1, 0.3, and 0.5 wt% carbon nanotube additives were prepared and pressed into tablets. The samples were examined using electron microscope images, revealing that the preparation method was suitable due to the good uniformity of the additives and good adhesion to the refractory material surface. The samples were subjected to cold compressive strength analysis, and the results showed that carbon nanotubes could increase the tensile strength from 65 MPa (in the sample without additives) to 77 MPa (in the sample with 0.5 wt% additives). Additionally, samples were prepared for a one-month hydration resistance test and placed in 75% humidity and 50°C temperature. The results showed that with an increase in the percentage of carbon nanotubes, the hydration resistance increased, and in the sample containing 0.5% carbon nanotubes, the hydration resistance increased by 6.5%
  9. Keywords:
  10. Refractory ; Carbon Nanotubes ; Dolomite ; Magnesite ; Magnesia-Doloma Refractories

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