HiPCO® – A History
This account of the history of HiPCO® Process was put together from numerous conversations with researchers at Rice University, IISc (Indian Institute of Science), NASA and NoPo Nanotechnologies.
HiPCO® (High-Pressure Carbon Monoxide) is a chemical reaction to produce high purity Single-Walled Carbon Nanotubes. The reaction uses Metal Carbonyls as a catalyst, high temperature (~1000°C) and high pressure (~100 atmospheres) to produce Single-Walled Carbon Nanotubes of small diameter.
Around 1991, at the Indian Institute of Science(Bangalore); researchers in Dr.C.N.R.Rao’s lab were looking for ways to embed metals inside Buckyballs (Fullerenes). Dr.A.Govindaraj was carrying out these experiments using Ferrocene, Iron Carbonyl as catalysts and Carbon gases such as Methane and acetylene. While analyzing products of the reaction under an Electron Microscope he found tubular structures along with the fullerenes. This was unexpected. Govindaraj and colleagues wrote up a paper describing the results but did not publish it immediately as the PI did not permit the same. Finally, the results were published a few months after Ijima’s announcement of the discovery of Carbon Nanotubes.
Similar experiments with Carbonyl were being carried out in Dr Richard Smalley’s laboratory at Rice University. A Quartz tube furnace was fed with Iron Carbonyl and Carbon Monoxide to synthesize Carbon Nanotubes. One of the students in the lab, Dr.Nikolaev Pasha had been running these experiments. He had a strong conviction that a high pressure would lead to the formation of large quantities of Single-Walled Carbon Nanotubes. Quartz tube furnaces are not designed for pressure. It can barely withstand 2-3 atmospheres without blowing up. Carbon Monoxide is inflammable and is used as a fuel (syngas) for this reason. For these reasons, Pasha was denied permission to perform experiments under high pressure.
One fine day when Smalley wasn’t around, Pasha went ahead and increased the pressure with expected consequences. The disaster destroyed the reactor and spewed quartz pieces everywhere. Pasha knew he’d be fired and went about cleaning up the mess. Surprisingly his hypothesis had worked and a large amount of fluffy nanotubes were found. This was the birth of HiPCO®.
Robert Kelley Bradley joined Smalley as a PhD student and proceeded to work on building the first HiPCO® reactor as part of his thesis. These reactors were the first proof of concept to make use of High-pressure Carbon Monoxide and temperature to produce Carbon Nanotubes continuously.
HiPCO® was promising due its ability to one day produce single chiral nanotubes. Smalley’s influence and free samples, helped HiPCO® become one of the best-studied Carbon Nanotubes in history. They were expected to be manufactured in tons with massive factories lining up the Houston area. Unfortunately, this dream could not be realized before Smalley’s death in 2007. It created a vacuum which a few patent trolls tried to fill up. There was minimal real development after this time frame.
These were the times when NoPo was founded in 2011 with the objective of producing high purity Single Walled Carbon Nanotubes at a scale that will enable their properties to trickle down to the real world. NoPo was fixated on a process that was industrially viable from the word go. This necessitated a complete relook at HiPCO®. New reactors were designed and built for the first time in a decade. Components were optimized for efficiency and yield with meticulous work. The core reaction dynamics were altered to improve production.
Since 2018, NoPo Nanotechnologies is the only company in the world with an operational, scaleable HiPCO® technology.