Mineral scaling in industrial pipes causes flow reduction, equipment strain, and increased costs in water and energy systems. Rice University engineers propose lab-grown diamond coatings as a solution to prevent mineral buildup. The study was published in the journal ACS Nano.
Pulickel Ajayan and Xiang Zhang. Image Credit: Jeff Fitlow/Rice University
Industrial piping systems are frequently compromised by the accumulation of mineral deposits, a pervasive issue comparable to the limescale found in household kettles, albeit on a vastly more extensive and economically impactful scale. This mineral scaling represents a critical challenge within water and energy infrastructure, contributing to diminished flow rates, increased stress on equipment, and a significant escalation in operational expenditures.
This innovative material could effectively address the problem, presenting a superior alternative to current mitigation strategies like chemical additives and mechanical cleaning. Both existing methods offer only temporary respite and are often accompanied by considerable environmental drawbacks or operational complexities.
Because of these limitations, there is growing interest in materials that can naturally resist scale formation without constant intervention.
Xiang Zhang, Assistant Research Professor and Study First and Corresponding Author, Materials Science and Nanoengineering, Rice University
“Our work addresses this urgent need by identifying a coating material that can ‘stay clean’ on its own,” adds Xiang Zhang.
Diamond is renowned for its exceptional hardness, chemical inertness, and remarkable thermal resistance – attributes that already render it invaluable in demanding industrial environments. While previous investigations demonstrated diamond's efficacy in resisting biological fouling and bacterial proliferation, its potential for mitigating mineral scaling had not yet been systematically explored.
The research team fabricated diamond films utilizing microwave plasma chemical vapor deposition (MPCVD), a sophisticated technique that employs gaseous precursors to generate a solid coating. In this process, methane and hydrogen gases were introduced into a chamber, where microwave radiation energized their atoms into a high-temperature plasma state.
This action disassociated the gas molecules, liberating carbon atoms that subsequently settled onto a silicon wafer, forming the tightly packed crystalline structure characteristic of diamond. Through the application of post-growth treatments, the researchers were able to precisely customize the surface chemistry of the developing diamond.
The research aimed to determine whether subtle alterations to surface characteristics would influence the initial formation of mineral scaling. Among the tested versions, the nitrogen-terminated diamond demonstrated superior performance, accumulating more than an order of magnitude less scale compared to diamond surfaces treated with oxygen, hydrogen, or fluorine. Microscopic analysis further revealed that while other surfaces developed dense layers, the nitrogen-terminated variant exhibited only scattered crystal clusters.
Molecular simulations offered crucial insights into the observed behavior. These simulations revealed that nitrogen facilitates the formation of a tightly bound layer of water molecules on the diamond surface. This water layer effectively establishes a barrier, making it considerably more challenging for mineral ions to adhere and initiate the process of scale accumulation.
The researchers subsequently applied the identical chemical principle to boron-doped diamond electrodes, which are commonly utilized in electrochemical systems. These modified electrodes demonstrated a significant reduction in scale, collecting approximately one-seventh the amount of scale while crucially maintaining their original performance capabilities.
The integration of microscopy, chemical analysis, and adhesion measurements allowed for the precise determination of both the quantity of scale formed and its adhesive strength.
Such a comprehensive study was previously limited by the cost and availability of high quality diamond films as well as reliable surface treatment methods, which technology has only recently made possible.
Xiang Zhang, Assistant Research Professor and Study First and Corresponding Author, Materials Science and Nanoengineering, Rice University
“These findings identify vapor-grown, cost-effective, polycrystalline diamond films as a powerful, long-lasting anti-scaling material with broad potential across water desalination, energy systems and other industries where mineral buildup is a problem,” said Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor, Engineering and Materials Science and Nanoengineering, Rice University.
The scalable and versatile deposition process of the coating also makes it very attractive for various industry sectors.
Jun Lou, the Karl F. Hasselmann Professor, Materials Science and Nanoengineering, Rice University
Ajayan, Lou, and Zhang are corresponding authors on the study.
Journal Reference:
Zhang, X., et al. (2025) Nitrogen-Terminated Diamond Films for Antiscaling Coatings. ACS Nano. DOI:10.1021/acsnano.5c13554. https://pubs.acs.org/doi/10.1021/acsnano.5c13554