Rice engineers show lab grown diamond films can stop costly mineral buildup in pipes

Pulickel Ajayan and Xiang Zhang
Photo Credit: Jeff Fitlow/Rice University

In industrial pipes, mineral deposits build up the way limescale collects inside a kettle ⎯ only on a far larger and more expensive scale. Mineral scaling is a major issue in water and energy systems, where it slows flow, strains equipment and drives up costs.

A new study by Rice University engineers shows that lab-grown diamond coatings could resolve the issue, providing an alternative to chemical additives and mechanical cleaning, both of which offer only temporary relief and carry environmental or operational downsides.

“Because of these limitations, there is growing interest in materials that can naturally resist scale formation without constant intervention,” said Xiang Zhang, assistant research professor of materials science and nanoengineering and a first author on the study alongside Rice postdoctoral researcher Yifan Zhu. “Our work addresses this urgent need by identifying a coating material that can ‘stay clean’ on its own.”

Xiang Zhang with the microwave plasma chemical vapor deposition setup.
Photo Credit: Jeff Fitlow/Rice University

Diamond is well-known for its hardness, chemical stability and ability to withstand high heat ⎯ qualities that already make it useful in demanding industrial settings. Earlier studies showed that diamond can fend off biological fouling and bacterial growth, but its potential to reduce mineral scaling had not been systematically examined.

The researchers grew diamond films through microwave plasma chemical vapor deposition, or MPCVD, a technique that uses gas to create a solid coating: Methane and hydrogen gases were fed into a chamber where microwave radiation energized the atoms into a hot plasma state. This broke apart the gas molecules, freeing up carbon atoms that settled onto a silicon wafer and linked into the tightly packed structure of diamond. By applying postgrowth treatments, the researchers could tailor the chemistry of the diamond’s surface as it formed.

Their goal was to test whether those subtle surface changes would affect how mineral scaling first takes hold. One version ⎯ the nitrogen-terminated diamond ⎯ stood out in terms of performance: It accumulated more than an order of magnitude less scale than diamond treated with oxygen, hydrogen or fluorine, and microscopy showed only scattered crystal clusters where other surfaces formed dense layers.

Molecular simulations helped explain the behavior. Nitrogen encourages a tightly bound layer of water molecules to form on the diamond, creating a barrier that makes it difficult for mineral ions to attach and begin building scale.

Pulickel Ajayan and Xiang Zhang
Photo Credit: Jeff Fitlow/Rice University

The researchers applied the same chemistry to boron-doped diamond electrodes used in electrochemical systems. Those electrodes collected roughly one-seventh as much scale without losing performance.

Combined microscopy, chemical analysis and adhesion measurements captured not only how much scale formed but also how strongly it stuck. “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,” Zhang said.

“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 of Engineering and professor of materials science and nanoengineering.

Funding: The research was supported by the National Science Foundation (1449500, 1539999), the Welch Foundation (C-2248), the Brazilian agency São Paulo Research Foundation (2023/08122-0), São Paulo State University, National Council for Scientific and Technological Development-Brazil (304957/2023-2) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior-Brasil. 

Disclaimer: The content in this press release is solely the responsibility of the authors and does not necessarily represent the official views of funding organizations and institutions.

Published in journal: ACS Nano

Title: Nitrogen-Terminated Diamond Films for Antiscaling Coatings

Authors: Xiang Zhang, Yifan Zhu, Eliezer F Oliveira, Tymofii S. Pieshkov, Qing Ai, Tianshu Zhai, Michelle T. Chen, Yunrui Yan, Tianyou Xie, Robert Vajtai, Jun Lou, and Pulickel M. Ajayan

Source/Credit: Rice University | Silvia Cernea Clark

Reference Number: ms112125_01

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