CNTs

CNT electrical properties

high tunable conductivity (depends on roll vector and doping with B or N); useful in pn junctions; v high e mobility, MWNTs: all conductive, can destroy all metallic CNTs with high current to leave SC

CNT mechanical properties

SWNT: 1TPa youngs modulus, high tensile strenght (10-150GPa); v strong CC bond; 15% tensile strain before fracture, can induce electrical change

CNTs thermal properties

excellent thermal conductivity (>1000W/mK) and heat capacity (700mJ/g/K) but not much better than graphite

CNT chemical properties

very high SA/V ratio good for catalyst, want as loose nontouching CNT arrays for max SA, can attach metal NPs or coatings, potential H2 storage

CNT applications

electronics: diodes, FETs, capacitors; Field emission: displays, electron sources, xray generation, catalysis; Composites: replace glass or fibres; Scanning probe microscopy and nanomechanics: single CNT onto AFM tip, gives better resolution than Si

CNTs in composites

simple cheap and mix easily w polymers with high strength and fracture toughness, alignment not always necessary but can affect properties, better heat resistance; can get pull out due to smoothness, surface roughening can help; also enable conductivity eg for EMI shielding

Problems with CNTs in nonpolymer composites

high sintering T damages them, CNT chemistry incompatible with metallic or ceramic matrix, difficult to disperse in metals or ceramics, can modify ceramic grain size

Field effect transistor

CNT between two metal source/drain contacts on oxidised doped Si, not hugely commercial yet due to difficult manufacturing