Chinese researchers have developed a diamond composite designed to resist fracture while retaining high hardness, according to a study published July 9 in the peer-reviewed journal Nature Synthesis.

The material incorporates a three-dimensional network of multi-walled carbon nanotubes between diamond grains and recorded an average fracture toughness of 31.9 MPa m¹ᐟ², about five times that of single-crystal diamond.

The researchers, led by scientists affiliated with the Institute of Physics of the Chinese Academy of Sciences and Beihang University, reported a hardness of about 91.6 GPa for the composite. The study describes the result as an approach to improving diamond’s fracture resistance without the conventional trade-off between toughness and hardness.

The finding is significant because diamond is exceptionally hard but can fracture under mechanical stress. Hardness and fracture toughness describe different properties: hardness measures resistance to deformation, while fracture toughness measures a material’s ability to resist crack growth.

The study measured its mechanical properties under controlled laboratory tests rather than demonstrating that it cannot be broken by an impact such as a hammer blow.

Carbon Nanotubes Reinforce Diamond

The researchers introduced highly dispersed multi-walled carbon nanotubes, or MWCNTs, into the spaces between diamond grains. These nanotubes form a continuous three-dimensional network throughout the composite.

According to the study, interfaces between the nanotube network and the diamond matrix contain mixed sp²-sp³ carbon bonding. > These interfaces help dissipate energy and impede the propagation of cracks through the material.

The researchers also built a three-dimensional diamond framework with strong diamond-to-diamond bonding. They reported that this structure helped prevent the nanotube addition from causing a substantial loss of hardness.

The material was prepared under high-pressure, high-temperature conditions. The paper’s experimental figures include a composite prepared at 2,000°C and 15 GPa.

The study reported a maximum fracture-toughness measurement of 36.4 MPa m¹ᐟ², compared with an average of 31.9 MPa m¹ᐟ². The researchers said the average value was approximately five times that of single-crystal diamond and exceeded values reported for some tungsten alloys.

Diamond’s Hardness Comes With Brittleness

Diamond’s extreme hardness makes it valuable for cutting, drilling, polishing and other applications where resistance to wear is important. But hardness alone does not prevent a material from cracking.

The distinction has limited attempts to broaden diamond’s use in applications involving repeated impact or mechanical loading. > Increasing toughness can come at the cost of hardness, while preserving hardness can leave a material susceptible to fracture.

The Chinese team’s approach instead places a reinforcing network inside the diamond structure. The researchers described this as an “extrinsic” toughening strategy, in contrast with approaches that modify diamond’s internal microstructure.

The result could be relevant to advanced cutting tools and other components in which both wear resistance and resistance to cracking are important. However, the study does not establish that the material is ready for commercial production or large-scale industrial deployment.

A Separate Diamond Breakthrough

The July composite study followed another Chinese materials-science result published in Nature in March.

Researchers from Zhengzhou University, Nanjing University and Henan University of Science and Technology reported the synthesis of millimeter-sized, phase-pure hexagonal diamond, also known as lonsdaleite. The study was published March 4 in Nature.

Hexagonal diamond differs structurally from conventional cubic diamond. Its existence as a distinct carbon phase had been debated for decades because naturally occurring samples associated with meteorites were extremely limited and often contained other carbon structures.

The researchers produced hexagonal diamond from highly oriented pyrolytic graphite by compressing it along its crystal axis at elevated temperatures. The paper reports that the material was synthesized under pressures around 20 GPa, with one documented sample recovered after treatment at 20 GPa and 1,300°C.

Advanced structural measurements were used to identify the material as hexagonal diamond. The researchers reported that the bulk material had slightly higher hardness than cubic diamond and high thermal stability.

The study measured a Vickers hardness of about 114 GPa, according to reporting on the research and the team’s published results. The figure is above commonly cited hardness values for natural cubic diamond and should not be interpreted as evidence that hexagonal diamond is dramatically harder than all conventional diamond.

The Key Difference between the Studies

The two Chinese studies are related through the broader search for improved carbon materials, but they should not be treated as a single breakthrough.

The Nature Synthesis study focuses on toughness. Its diamond composite uses carbon nanotubes to make the material more resistant to fracture while maintaining high hardness.

The Nature study focuses on structure and hardness. It provides experimental evidence for millimeter-sized, phase-pure hexagonal diamond and reports hardness slightly above that of conventional cubic diamond.

Lee (@MandyKnowsDC) [https://xcancel.com/MandyKnowsDC/status/2086784627809673397]

I’m late, but I didn’t know China had the diamond game on lock with the lab joints

Does this basically mean mined diamonds will be worthless?

Together, the findings illustrate two different strategies for improving diamond-based materials: reinforcing conventional diamond to resist cracking and creating a different carbon crystal structure with potentially different mechanical and thermal properties.

Potential Industrial Applications

Neither study demonstrates that these materials are ready to replace conventional diamond at industrial scale.

For the nanotube-reinforced composite, further work would be needed to assess manufacturing scale, consistency, long-term durability and performance under real operating conditions. For hexagonal diamond, researchers will need to establish whether the material can be produced reliably in larger quantities and whether its measured properties translate into practical advantages.

The studies nevertheless show that researchers are pursuing different ways to address the limitations of conventional diamond, including the long-standing tension between hardness and resistance to fracture.

Alibaba-backed Chinese artificial intelligence startup Moonshot just unveiled its latest model, Kimi K3, and it’s already sending shockwaves through the industry, with some benchmarks showing the model outperforming Anthropic and OpenAI’s best offerings.

The model packs 2.8 trillion parameters, which Moonshot says would make it the largest open-weight model released to date once its weights become available by July 27.

In a blog post, the company acknowledged that K3’s overall performance still trails Claude Fable 5 and GPT-5.6 Sol. Its internal evaluations nevertheless place it close to both models on several tasks, while independent testing by Artificial Analysis ranks it immediately behind the leading proprietary systems on its Intelligence Index and real-world work evaluations.

On Arena.ai’s front-end development leaderboard, K3 even ranks above the two most powerful models, marking a 17-place jump from the company’s previous model, Kimi K2.6. Arena’s CEO, Anastasios Angelopoulos, said Kimi K3 “may be the single biggest release of the year” and “the moment that OSS Chinese models have surpassed US models,” in a post on X.

Anastasios Nikolas Angelopoulos (@ml_angelopoulos) [https://xcancel.com/ml_angelopoulos/status/2077832882673066109]

This may be the single biggest release of the year, and marks the moment that OSS Chinese modles have surpassed US models.

Code Arena, Kimi K3 has BEATEN FABLE.

This is only 6 weeks after the Fable release.

This makes @Kimi_Moonshot the #1 AI lab in the world on frontend coding capability, and more results are rolling in that are likely to continue to show it is at the top of the pack.

The implications of this, whether on the closed-source AI business models or the larger capital ecosystem in the US, are enormous.

Arena.ai (@arena) [https://xcancel.com/arena/status/2077824029126504525]

Big news: Kimi-K3 by @Kimi_Moonshot is now #1 in the Frontend Code Arena with 1679 pts, surpassing Claude Fable 5.

This is a 17-place jump from Kimi-k2.6 (#18 -> #1).

In Frontend, Kimi-K3 ranked #1 in 6 of 7 domains: Brand & Marketing, Reference-Based Design, Data & Analytics, Consumer Product, Simulations, and Content Creation Tools, landing #2 only in Gaming behind Fable 5.

The full model weights will be released by July 27.

Congrats to the @Kimi_Moonshot team on this major milestone!

It’s a remarkable achievement, especially for an open-source model. The results challenge the assumption that China’s leading AI labs remain several months behind their American competitors. Anthropic just released Fable 5 last month, while OpenAI’s GPT-5.6 (and its three tiers, Sol, Terra, and Luna) just dropped last week.

“Kimi k3 is a big moment with multiple implications for the entire industry,” Trump’s former senior White House policy advisor on AI, Sriram Krishnan, said in a post on X.

The last time something like this happened, aka when a Chinese AI lab released a cheaper model that proved competitive with American alternatives, was when DeepSeek released R1 back in January 2025. Following that release and its reception, the market reaction helped wipe roughly $1 trillion from global technology stocks. Meanwhile, the model’s success raised major national security concerns across Washington D.C., and partially informed the Trump administration’s hard-line stance on advanced tech exports to China.

Moonshot’s release also comes only a few months after Anthropic accused the company, along with other Chinese AI companies DeepSeek and MiniMax, of violating their rules to “illicitly” extract the capabilities of its model Claude and use that to improve their own models. The process is called “distillation,” and it’s fairly common in the industry, but the Trump administration has deemed it “adversarial” and vowed to crack down on it.

K3 arrives amid heightened scrutiny of the U.S.-China AI race and growing national-security concerns around frontier models. Its release is likely to renew debate in Washington over export controls, distillation, and whether restrictions on Chinese labs are slowing their progress at all.

Very curious about this … if you have the opportunity to to press a button, and have all of the USA’s AI developments just vanish from the world completely, and the USA could no longer development AI technology at all? But the rest of the world was untouched , and China then was the only country with leading AI technology. Would you choose that?