Plasma Technology Is Opening New Possibilities in Process Engineering
Non-thermal plasma (NTP) technology enables precise control of chemical reactions and surface processes without significantly heating the material being treated. OuNon-thermal plasma (NTP, also known as cold plasma or low-temperature plasma) technology enables precise control of chemical reactions and surface processes without significantly heating the material being treated. Our expanding portfolio includes atmospheric and low-pressure plasma systems for ozone generation from ambient air, greenhouse gas conversion, medical sterilization, plasma-activated water, PECVD coatings, and powder surface engineering. By combining plasma physics with precise thermal control, each system can be tailored to the chemistry, temperature, and processing requirements of the applicationr expanding portfolio includes atmospheric and low-pressure plasma systems for ozone generation from ambient air, greenhouse gas conversion, medical sterilization, plasma-activated water, PECVD coatings, and powder surface engineering. By combining plasma physics with precise thermal control, each system can be tailored to the chemistry, temperature, and processing requirements of the application.
KEY TAKEAWAYS
- Non-thermal plasma enables targeted chemistry without excessive heating, supporting applications from ozone generation and sterilization to greenhouse gas conversion and advanced surface processing.
- ACT’s patent-pending Packed Electrode Volumetric dielectric barrier discharge (PEVDBD) reactor creates a uniform, arc-free plasma discharge, treating approximately 60–80% of the target gas volume compared with 5–15% in conventional systems.
- Ozone can be generated directly from ambient air at approximately 450 g/kWh with only about a 2°C gas temperature rise, eliminating the need for an external oxygen plant.
- Atmospheric plasma has applications beyond ozone generation, including catalyst-free CO2 and CH4 reforming, in-lumen medical sterilization, and plasma-activated water.
- Low-pressure PECVD expands plasma technology into surface engineering, enabling conductive corrosion barriers, metal bilayers for neutron optics, and de-oxidation and passivation of boron, aluminum, copper, steel, and nickel-alloy powders.
- Precise thermal management is critical to plasma performance. ACT integrates heating and cooling directly into its reactor and electrode designs to create complete process systems.
Plasma is usually associated with extreme temperatures and fusion research. Some of its most useful industrial applications, however, run under closely controlled conditions and, in several cases, close to room temperature.
Non-thermal plasma makes it possible to manipulate chemical reactions without heating an entire gas stream or material to extreme temperatures. By controlling how electrical energy is delivered into a gas, engineers can generate highly reactive species that enable processes ranging from ozone production and sterilization to greenhouse gas conversion and surface modification.
The challenge is controlling that plasma.
Traditional plasma systems can suffer from localized electrical discharges, inefficient treatment of the process gas, unwanted heating, and other effects that limit their performance. New reactor architectures are giving engineers much greater control over where and how the plasma forms and are expanding the range of processes where plasma technology can be applied.
The Challenge with Atmospheric Plasma
One common approach to generating atmospheric non-thermal plasma is the dielectric barrier discharge (DBD). In a conventional DBD reactor, the electrical discharge can often collapse into concentrated filaments rather than remaining evenly distributed throughout the gas.
Those localized electrical filaments create hot regions that can consume energy and even destroy some of the chemical products the plasma is intended to generate. As a result, much of the gas passing through a conventional reactor may never receive effective plasma treatment.
ACT has been developing a different approach through a patent-pending PEVDBD reactor architecture designed to maintain a uniform, arc-free glow discharge.
The reactor packs many quartz-sheathed electrodes into a periodic array, creating millimeter and sub-millimeter triangular voids through which the gas passes. The microscopic dimensions of those passages prevent filamentary breakdown and allow a diffuse plasma discharge to be maintained throughout the treatment region while reducing the pressure drop across the reactor. At that length scale, an electron avalanche never has room to build into a streamer: the Townsend avalanche parameter sits roughly thirtyfold below the threshold for filamentary breakdown. The diffuse glow is therefore held by the geometry itself rather than by a control loop.
The difference is significant. Conventional systems may treat only approximately 5% to 15% of the target gas volume, while the PEVDBD architecture can treat approximately 60% to 80%.
That improvement in plasma uniformity opens the door to several applications.
Generating Ozone Directly from Ambient Air
Ozone is a powerful oxidizing agent used for applications such as sterilization and decontamination. Producing it efficiently, however, can require carefully controlled operating conditions.
The PEVDBD reactor has demonstrated an ozone energy yield of approximately 450 g/kWh while operating entirely on ambient air, with a gas temperature rise of only about 2°C.
This is particularly noteworthy because most other reactor approaches rely on an oxygen feed. In the benchmark below, the air-fed PEVDBD reaches 450.4 g/kWh against 327 g/kWh for the next-highest reactor reported, which runs on oxygen.
Measured ozone energy yield of the PEVDBD on ambient air, benchmarked against reported catalyst-free DBD ozone generators.
By reducing thermal losses and exposing a much larger percentage of the gas to the discharge, diffuse atmospheric plasma can simplify ozone generation for duct, chamber, and other decontamination applications.
Using Plasma to Convert Greenhouse Gases
The same basic atmospheric plasma architecture can be applied to an entirely different chemical challenge: converting greenhouse gases into useful products.
Plasma can provide the energy needed to drive reactions involving carbon dioxide (CO2) and methane (CH4). ACT’s PEVDBD system uses electrical discharge energy to support catalyst-free dry methane reforming, converting these gases into syngas at a hydrogen-to-carbon-monoxide ratio near unity in a single pass, without a fired heater.
This illustrates one of the broader advantages of plasma processing. Instead of heating an entire process stream to drive a reaction, electrical energy can be delivered directly into the discharge, creating reactive chemistry within the gas itself.
Bringing Plasma Inside Medical Devices
Sterilization presents another challenge, particularly when the surfaces that need to be treated are buried deep inside narrow passages.
Medical endoscopes, for example, can contain long, extremely small internal channels that are difficult for traditional sterilization methods to treat effectively.
With support from FDA funding, ACT has developed a plasma-in-lumen approach that generates the discharge directly inside these instrument cavities.
Rather than trying to transport a sterilizing agent through difficult geometry, the approach effectively creates the active sterilization environment within the geometry itself.
Plasma-Activated Water: Transferring Reactive Chemistry to a Liquid
The reactive species created by plasma can also be transferred into water. Plasma-activated water incorporates plasma-generated reactive oxygen and nitrogen species into a liquid, creating another pathway for purification and sterilization. Potential applications described in ACT’s work include water purification and produce sterilization.
This expands plasma processing beyond direct gas or surface treatment: the plasma creates reactive chemistry, while the water becomes the medium that carries it to the application.
Moving from Atmospheric to Low Pressure Plasma for Surface Engineering
Changing the operating pressure changes what plasma technology can accomplish.
At pressures below 1 Torr, the focus shifts from processing the gas itself to engineering the surface of a material. ACT operates showerhead and tubular plasma-enhanced chemical vapor deposition (PECVD) reactors driven either by 13.56 MHz radio frequency or by nanosecond high-voltage pulses. Substrate stages run at 300 to 400 °C for coating work, while powders are treated near room temperature so that they neither sinter nor aggregate.
Both configurations are shown below: a tubular low-pressure reactor treating powder within the plasma glow, and a showerhead PECVD discharge operating over a heated substrate.
Two applications demonstrate the potential of this approach.
Conductive Corrosion Barriers
A hydrogen-plasma-assisted process converts titanium isopropoxide, a safe alternative to titanium tetrachloride, into a Ti/TiCx/amorphous-carbon multilayer on a 304 stainless steel substrate with no detectable titanium dioxide. Carbon deposits at 200 to 237 nm/min, can comply with U.S. Department of Energy contact-resistance targets, and the films survive thermal cycling in pH 3 sulfuric acid. The same reactor also deposits other metal and ceramic layers optical, corrosion, and erosion applications.
For applications requiring both electrical conductivity and corrosion protection, controlling the chemistry and structure of these thin surface layers can be particularly valuable.
Powder De-Oxidation and Passivation
Powders present a different surface-engineering problem.
Materials such as boron, aluminum, copper, steel, nickel, and refractory-alloy powders naturally develop oxide layers that can affect their downstream performance. Plasma processing reduces and removes that native oxide and immediately protects the newly activated surface with an ultra-thin plasma-polymer nanofilm, before the powder ever sees air.
ACT’s low-pressure plasma technology integrates in-situ de-oxidation and conformal passivation for metal micro/nano particles. Depositing protective hydrocarbon or fluorocarbon coatings directly after oxide reduction enhances energetic output while extending material shelf life to years. Through this method, ACT demonstrated up to a 40% gain in energetic performance, validated by successful long-term accelerated aging tests. ACT’s de-oxidation process can also reduce the oxide buildup on expensive additive manufacturing powders thereby extending their usable lifetime for reduced costs and a more resilient domestic supply chain.
Why Thermal Control Matters in Plasma Processing
Although these applications appear very different, they share an important engineering requirement: temperature control.
Ozone generation requires precision cooling. Dry reforming requires active heating. Vacuum PECVD requires maintaining precise substrate temperatures under significant process loads.
That creates an important relationship between plasma physics and thermal engineering.
Rather than treating thermal management as a separate subsystem, ACT integrates temperature control directly into the reactor and electrode architecture. The objective is to maintain the thermal conditions necessary for the desired plasma chemistry while creating a complete process system around the reactor.
Plasma as an Engineering Tool
At atmospheric pressure, plasma can enable efficient ozone generation, greenhouse gas conversion, sterilization, plasma-activated water, and more. Under vacuum, the same underlying physics becomes a multi-purpose tool for many applications including (but not limited to) depositing coatings, modifying surfaces, and processing advanced powders.
For engineers evaluating new manufacturing, sterilization, chemical conversion, or surface-treatment processes, plasma is better viewed as a platform than as a single product: a way to create chemical and surface conditions that are difficult, or inefficient, to reach by conventional means.
