Study On The Carbon Nanotubes Reinforced Alumina Ceramic Composite Material

The agglomerated state of carbon nanotubes seriously damaged to its applications, whichhad excellent mechanical properties with unique advantages in toughened ceramic matrixcomposites. It was a key issue that how to dispersing carbon nanotubes uniformly in thefield of carbon nanotubes composites. In this thesis, with the aim of reinforced ceramic, thestudy of carbon nanotubes reinforced alumina composite was raised, which had greatresearch significance and application value. Dispersing carbon nanotubes uniformly intoalumina powder was studied. Carbon nanotubes reinforced alumina composites werefabricated by hydrogen atmosphere normal pressure sintering, hot pressing sintering andspark plasma sintering.Carbon nanotubes was dispersed into alumina matrix, and alumina composite powderof carbon nanotubes was prepared by shear extrusion method.8times shearing was betterin the results of viscosity, fracture defect rate and SEM. To dispersing carbon nanotubesuniformly, three processes were essential, including breaking agglomeration of carbonnanotubes up, breaking long carbon nanotubes off and dispersing short carbon nanotubes.The model of dispersing carbon nanotubes by shear extrusion method was build. Drivingforces included laminar shear stress of melt flow of organic binder and relativedisplacement of rigid ceramic particles. Steric effect of organic binder kept dispersion stateof carbon nanotubes. Thermodynamic characteristics, kinetic equation and boundaryconditions were shown.Carbon nanotubes reinforced alumina composites were fabricated by hydrogenatmosphere normal pressure sintering, hot pressing sintering and spark plasma sintering. Byhydrogen atmosphere normal pressure sintering, fracture toughness of composite up to6.11MPaï¹'m^1/2with1wt%carbon nanotubes contents, relatively increased93.2%. By hotpressing sintering, fracture toughness of composite up to6.32MPaï¹'m^1/2with2wt%carbon nanotubes contents, relatively increased99.2%. By spark plasma sintering, fracture toughness of composite up to6.55MPaï¹'m^1/2with2wt%carbon nanotubes contents,relatively increased105%.Carbon nanotubes had a better value with1wt%of normal pressure sintering and2wt%of pressing sintering. Increasing contents of carbon nanotubes to continue, fracturetoughness of composites were damaged. In normal pressure sintering, the reason wasreduced density with increased carbon nanotubes contents. In pressing sintering, the reasonwas increased rate of attachment and bonding of carbon nanotubes with increased carbonnanotubes contents.results of XRD of carbon nanotubes reinforced alumina composites prepared bydifferent sintering processes show that alumina matrix peaks of carbon nanotubesreinforced alumina composites drift, compared with alumina material, which may be causedby residual stress. In normal pressure sintering, the peaks drift to low angle by residualtensile stress. In pressing sintering, the peaks drift to high angle by residual compressivestress.Results of SEM show that carbon nanotubes bonded alumina matrix as a dispersedpart. The main toughness mechanisms of carbon nanotubes were broken drawingtoughening and pulling out toughening.