An investigation on the Microstructure and Properties of Alumina-Carbon Nanotube (CNT) Nanocomposite Produced by Conventional and Microwave Sintering

Ghobadi, Hossein | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43599 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Sadeghian, Zahra; Ebadzadeh, Toraj
  7. Abstract:
  8. Carbon nanotubes were coated with boehmite nanoparticles by sol gel method. According to the TGA analysis, formation of gamma-alumina from boehmite was at 500 . SEM investigation revealed the uniform coverage of gamma-alumina nanoparticles on the surface of CNTs. Composite powders containing 1, 2 and 3vol% of coated CNTs were produced by mixing the coated CNTs with alumina suspension. Phase analysis of composite powder calcined at 500 showed the complete decomposition of boehmite and formation of gamma-alumina. Samples were shaped by cold isostatic pressing at the pressure of 180MPa and sintering was performed using two different methods of conventional and microwave. Existance of the CNTs in the fractured surface of the sintered samples were proved by SEM investigations. Maximum flexure strenght was 380Mpa and achieved in composite samples containing 1vol% of CNTs sintered by conventional system. Maximum relative density and hardness were acquired for monolithic alumina samples and were 96.12% and 19.12Gpa, respectively. Addition of the CNTs enhanced the toughness of composite samples continually and the highest toughness (4.36Mpa.m1/2) was achieved for the samples containing 3vol% of CNTs. Likewise the toughness, specific electrical resistance (ρ) of the composite samples reduced continually with CNT addition and the lowest value of 5GΩ.Cm was for the samples having highest CNT content. According to the SEM analysis, three mechanisms of crack deflection, crack bridging, and CNT pull out were responsible to the toughness enhancement. In contrast to the conventional method, microwave sintering process reduced the temperature and time needed to obtain same properties by 65 and 75 min, respectively. Continually toughness enhancement along with the SEM investigations proved the effectiveness of the coating process
  9. Keywords:
  10. Nanocomposite ; Coating ; Alumina-Carbon Nanotube Nanocomposite ; Convertional Sintering ; Microwave Sintering

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