BNNT vs carbon nanotubes
Boron nitride nanotubes and carbon nanotubes are structural twins — the same rolled-honeycomb geometry, nearly the same stiffness — yet they behave like different materials. A carbon nanotube conducts, burns, and is black; a boron nitride nanotube insulates, survives to 900 °C, and is transparent. This page compares them property by property, and says when each is the right choice.
At a glance
| Property | Carbon nanotube (CNT) | Boron nitride nanotube (BNNT) |
|---|---|---|
| Lattice | All-carbon honeycomb, non-polar bonds | Alternating B and N, partially ionic bonds |
| Elastic modulus | ~1 TPa | ~1 TPa (comparable) |
| Oxidation in air | Burns at ~400–600 °C | Stable to ~900 °C |
| Electrical | Metallic or semiconducting, set by chirality | Insulator, ~5.5 eV gap, independent of chirality |
| Thermal conductivity | Very high | High — and electrically insulating with it |
| Optical | Black, strongly absorbing | Transparent in the visible; deep-UV active |
| Piezoelectric | No | Yes (intrinsic) |
| Neutron shielding | No | Yes (boron-10 absorbs neutrons) |
| Indicative price | ~$10–20/g research-grade; far less in bulk | ~$150–450/g high-quality |
| Maturity | Mature, mass-produced | Early-stage, pilot-to-kilogram |
Values are representative literature and market ranges for comparison, not single-sample measurements.
Where they are the same
Geometry and stiffness
Both are a single honeycomb sheet rolled into a seamless cylinder, nanometres across and up to microns or millimetres long. Both reach an elastic modulus around one terapascal — among the stiffest materials known — with very high tensile strength and aspect ratios that make them outstanding reinforcing fibres. If your only requirement is "stiff, strong, and light," either will serve; the choice is decided by the other properties below. The first direct modulus measurement on a multi-walled BNNT is the 1998 Chopra & Zettl paper in the library.
Where they diverge
Heat and oxidation — BNNT's signature advantage
This is the difference that matters most in practice. A carbon nanotube oxidises and burns away in air somewhere around 400–600 °C. A well-crystallised boron nitride nanotube resists oxidation in air up to roughly 900 °C. Anywhere hot and oxidising — rocket exhausts, high-temperature composites, thermal-protection systems — carbon simply cannot go, and BNNT can. Both conduct heat well, but BNNT does so while remaining an electrical insulator, which carbon cannot.
Electrical behaviour — geometry vs chemistry
A carbon nanotube's electronic character depends on exactly how the sheet is rolled: about one-third of chiralities are metallic and the rest semiconducting, so using CNTs in electronics usually means sorting or enriching them. A boron nitride nanotube is a wide-gap insulator — a band gap near 5.5 eV — essentially regardless of how it is rolled, a result predicted theoretically in 1994 before any tube had been made. No sorting, no surprises. If you need conductivity, choose carbon. If you need a reliable insulator, only BNNT delivers it.
Optics — black vs transparent
Carbon nanotubes are intensely black and absorb across the spectrum. The wide band gap makes BNNT transparent in the visible range, so it can reinforce a polymer, ceramic, or coating without darkening it, and it is active in the deep ultraviolet. For anything that must stay clear or coloured, this is decisive.
Piezoelectricity — a capability carbon does not have
Because the boron–nitrogen lattice is polar, a boron nitride nanotube is intrinsically piezoelectric: mechanical strain produces an electrical response, and vice versa. Carbon nanotubes, being non-polar, are not. This opens an entire class of nanoscale sensors and energy harvesters to BNNT that is simply closed to carbon.
Neutron shielding — the boron bonus
Boron-10, a natural component of BNNT, is one of the best neutron absorbers known. That makes a BNNT structure double as radiation shielding — valuable where every gram counts, such as spacecraft and space habitats. Carbon offers no equivalent.
Cost and maturity — carbon's advantage
Here carbon wins clearly. Carbon nanotubes are a mature, mass-produced material; research-grade material runs roughly $10–20 per gram and bulk industrial grades far less. High-quality BNNT still sells for about $150–450 per gram, and supply is limited. The gap is not the boron or the energy — it is the difficulty of making tubes selectively at scale, which is exactly the manufacturing problem the BNNT field is built around.
So which should you use?
When you need conductivity or low cost
Electrical conductors, transparent-conductor films, battery and supercapacitor electrodes, EMI shielding, and any bulk composite where cost dominates and the service temperature stays moderate.
When you need insulation, heat, transparency, or shielding
High-temperature and oxidising environments, electrically-insulating thermal management, transparent structural reinforcement, piezoelectric sensing, radiation shielding, and nanofluidic channels — cases where carbon physically cannot do the job.