Chinese scientists have engineered a form of diamond that is simultaneously harder and six times tougher than conventional diamond — a material that reportedly cannot be shattered even by a direct hammer blow, according to a paper published on July 9 in the peer-reviewed journal Nature Synthesis. The breakthrough, led by researchers at the Institute of Physics at the Chinese Academy of Sciences and Beihang University, resolves a long-standing trade-off in materials science.

The Diamond's Fatal Flaw — Now Fixed

Diamond is the hardest naturally occurring material on Earth, yet it shares a critical weakness with glass: brittleness. A sharp, concentrated blow can shatter it along crystallographic planes, limiting its use in high-stress industrial environments. For decades, researchers have attempted to boost toughness — a material's resistance to fracture — without degrading hardness, but gains in one property have historically come at the cost of the other.

The new research sidesteps this compromise entirely. According to the paper, the team engineered an internal support architecture within the diamond matrix that multiplies fracture resistance by six times while leaving hardness intact.

The Secret: Carbon Nanotube 'Cords'

The key innovation lies in the integration of multi-walled carbon nanotubes (MWCNTs) — ultra-fine carbon fibre structures approximately one ten-thousandth the width of a human hair, yet dozens of times stronger than steel, the paper noted. These nanotubes act as internal reinforcing cords, absorbing and redistributing energy from impacts that would ordinarily cause fracture.

The resulting composite material is described as tougher than the tungsten alloys used in armour-piercing ammunition — a benchmark that underscores its potential for extreme-environment applications far beyond conventional gemology or industrial cutting tools.

Who Built It and Where

The research team operated out of facilities including the Synergetic Extreme Condition User Facility at Huairou Science City in Beijing, a national laboratory complex designed for high-pressure and extreme-condition materials research. The involvement of Beihang University — one of China's leading aerospace and defence-oriented engineering institutions — adds significance to the potential downstream applications of the material.

Why It Matters for Industry

Diamonds already underpin a vast industrial ecosystem: cutting, grinding, polishing, drilling, and semiconductor substrate manufacturing all rely on diamond's hardness. A version that resists fracture under shock loading could expand viable use cases into aerospace components, hypersonic vehicle surfaces, and advanced armour systems — sectors where both hardness and impact resistance are non-negotiable.

The tungsten alloy comparison is particularly telling. Tungsten-based materials dominate kinetic penetrator and armour applications precisely because of their toughness; a diamond composite that exceeds that benchmark would represent a step-change in structural materials.

What's Next

The research remains at the laboratory stage, and scaling MWCNT-reinforced diamond synthesis to commercial volumes presents significant engineering and cost challenges. Materials scientists will be watching whether the team can demonstrate reproducibility at larger sample sizes and whether the synthesis process — likely requiring extreme pressures and temperatures — can be made economically viable. If it can, the implications for defence, aerospace, and precision manufacturing could be substantial.