Carbon
Nanotube
Graphene rolled into a seamless cylinder. One-dimensional quantum wire — electrons travel ballistically for microns without a single collision. A material that simultaneously holds the records for tensile strength, electron mobility, and thermal conductivity along its axis.
INSIDE THE CARBON NANOTUBE
Click each tab to observe a different quantum or mechanical phenomenon — pure CSS animation, zero GPU.
ROLLING VECTOR & CHIRALITY
CNT chirality defined by rolling vector C = na₁ + ma₂. For (8,0) zigzag: n=8, m=0, θ=0°, diameter d = a√(n²+nm+m²)/π = 0.63 nm. Zigzag CNTs (n,0) are semiconductors when n≢0 mod 3, else metallic. Armchair (n,n) always metallic. C-C bond length 1.42 Å is preserved from graphene — the strongest σ-bond in nature.
BALLISTIC 1D ELECTRON TRANSPORT
In a SWCNT, electrons traverse the tube without scattering — ballistic transport. The quantum conductance limit is G = 4e²/h = 155 µS (R = 6.45 kΩ) — two spin-degenerate channels. Mobility exceeds 100,000 cm²/V·s at room temperature, limited only by acoustic phonon scattering. Mean free path λ > 1 µm. Compare copper: ρ = 1.68×10⁻⁸ Ω·m, mean free path 40 nm. CNT carries 10⁹ A/cm² before failure vs copper's 10⁶ A/cm².
TENSILE FRACTURE AT 63 GPa
SWCNT fracture stress σ = 63 GPa, Young's modulus E = 1 TPa, failure strain ~26%. Bond stretching follows Morse potential: V(r) = De[1-e^(-a(r-re))²]. At 1.42 Å (equilibrium) → 1.90 Å (fracture), the sp² C-C bond breaks catastrophically. Compare: Kevlar 3.6 GPa, steel 0.4 GPa. CNT specific strength = 63 GPa / 1600 kg/m³ = 39 MN·m/kg — 62× steel wire.
ELECTRONIC STRUCTURE — CHIRALITY CONTROLS METALLIC NATURE
CNT electronic character determined by zone-folding of graphene band structure. Rule: if (n-m) mod 3 = 0, tube is metallic (Fermi level crosses K-point). Otherwise semiconducting with bandgap Eg ≈ 2γ₀·a/d ≈ 0.9 eV/d(nm). Armchair (n,n) always metallic. One-third of SWCNTs are metallic. Tight-binding overlap integral γ₀ = 2.9 eV governs π-band width.
CHEMICAL VAPOR DEPOSITION — CATALYTIC GROWTH MECHANISM
CVD mechanism: CH₄ decomposes on Fe/Ni/Co nanoparticle surface at 900°C. Carbon atoms dissolve into catalyst, diffuse through bulk, precipitate as CNT at supersaturation. "Tip growth" (catalyst at tube apex) or "base growth" (catalyst on substrate). Growth rate 2–10 µm/s. Catalyst particle diameter sets CNT diameter: d_CNT ≈ d_catalyst. H₂ and CH₄ atmosphere controls chirality distribution — recent advances achieve 90% (6,5) selectivity using CoMoCAT process.
MULTI-WALL CNT — CONCENTRIC QUANTUM CHANNELS
MWCNT consists of 2–50 nested coaxial tubes. Inter-wall spacing 0.34 nm — identical to graphite c-axis spacing, indicating van der Waals coupling. Each shell is independently conducting; outer shells carry current independently. Transport is shell-by-shell: inner shell ballistic, outer shells Ohmic. Total current capacity scales as N_walls. Telescoping motion possible (frictionless at 0.04 nN/µm) — basis for nanoelectromechanical devices. Outer diameter up to 100 nm, length >1 cm in "super-growth" CVD.
SHEAR LAG MODEL — STRESS TRANSFER MECHANISM
Load transfers from polymer matrix to CNT via interfacial shear stress τ_i ≈ 160 MPa. Critical fiber length l_c = σ_f·d/(2τ_i) = 197 nm — fibers longer than l_c achieve full reinforcement. Rule of Mixtures: E_composite = V_f·E_CNT + (1-V_f)·E_matrix. At V_f = 5%, E increases 3× (limited by CNT alignment). Key challenge: CNT-matrix interfacial bonding — functionalization with -COOH groups improves shear strength 3×. Halpin-Tsai model applies for short fiber limit.
PHONON-DOMINATED HEAT TRANSPORT — 3500 W/m·K AXIAL
CNT thermal conductivity κ ≈ 3500 W/m·K at 300K, mediated by acoustic phonons (LA, TA, ZA branches). The ZA (flexural acoustic) branch carries 75% of heat in graphene family materials. Phonon mean free path λ = 775 nm — same scale as electron MFP. Umklapp scattering limits high-T conductivity: κ ∝ T⁻¹ above 300K. Axial thermal conductivity 3500× radial (van der Waals coupling between shells is weak). Foundation for CNT thermal interface materials in microelectronics packaging.
FOWLER-NORDHEIM TUNNELING — CNT AS FIELD EMITTER
CNT sharp tip (radius ~1 nm) produces enormous local field enhancement: E_local = β·E_applied, where β = 1000–10,000 for aspect ratio L/r ≈ 10,000. Work function φ = 5.0 eV for CNT. Turn-on field E_on ≈ 1 V/µm (50× lower than metals). FN equation: J = A(βE)²/φ · exp(-Bφ^1.5/βE). Applications: flat panel displays, X-ray tubes, electron microscopy sources. Current stability 0.5% RMS over 100 hours — critical for practical devices.
SURFACE CHEMISTRY — ENABLING BIOAPPLICATIONS & PROCESSING
Pristine CNTs are insoluble and cytotoxic in bundle form. Covalent functionalization via acid treatment (H₂SO₄/HNO₃, 3:1) introduces –COOH groups at defects and tube ends. Degree of functionalization: 0.1–1 carboxyl per 100 carbons. –COOH → –NH₂ coupling (EDC chemistry) attaches biomolecules, drugs, targeting antibodies. Non-covalent functionalization (pyrene, surfactant) preserves electronic structure — critical for field-effect transistor applications. COOH-CNT solubility: 8 mg/mL in DMF; essential for composite processing.
WHY CARBON NANOTUBES EXIST IN A CLASS ALONE
Electrical
- Mobility: 100,000 cm²/V·s
- Current density: 10⁹ A/cm²
- Quantum resistance: 6.45 kΩ
- Mean free path: >1 µm
Mechanical
- Young's modulus: 1 TPa
- Tensile strength: 63 GPa
- Failure strain: ~26%
- Specific strength: 39 MN·m/kg
Thermal
- Axial κ: 3500 W/m·K
- Phonon MFP: 775 nm
- ZA branch: 75% of heat
- Stable to 2800°C (inert)
READY TO ENGINEER WITH NANOTUBES?
We supply SWCNTs and MWCNTs in gram-to-kilogram quantities. Custom functionalization, dispersion in your solvent system, and integration support.