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  • How Ultrafast Joule Heating is Advancing Science
    Jun 05, 2023 | ACS MATERIAL LLC

    ACS’s FlashVolt heating system uses ultrafast Joule heating (UJH) to heat materials to extreme temperatures in milliseconds. UJH works by passing a current through a resistive material, which rapidly converts the electricity to heat—thousands of Kelvins in less than a second. This process opens many exciting possibilities, because it can heat to higher temperatures than traditional methods in a fraction of the time.

    Ultrafast Joule heating has found many cutting-edge applications, and new ones are being discovered all the time. Let’s take a closer look at how UJH is advancing the world of materials science.

    Ceramic Applications

    Accelerating Ceramic Development
    In the ceramics field, UJH is being used to accelerate research into new and improved materials.

    Ceramics play a crucial role in many industries, like electronics and energy storage, due to their strength, temperature resistance, and chemical inertness. To achieve these properties, ceramics must be sintered. The sintering process heats and compresses ceramic particles until they coalesce into a single piece of material, which often takes hours.

    This poses a challenge in the development of new ceramic materials. Each iteration must be fully sintered before it can be tested, causing development in this area to progress relatively slowly. As a result, ceramics engineers are constantly looking for faster sintering techniques. Innovative methods like microwave-assisted sintering and spark plasma sintering have been explored, but they only work on certain ceramic materials and geometries, and they are often difficult to scale1.

    A new sintering method uses UJH to sinter ceramics in seconds rather than hours. This involves pressing ceramic powder between Joule-heating carbon strips, which use UJH to heat the ceramic at a rate of 1,000 to 10,000 K/minute. This process can reach temperatures up to 3,200 K, high enough to sinter virtually any ceramic material1.

    This UJH sintering method is also scalable. The short sintering time helps prevent volatile evaporation and undesirable interdiffusion, improving the quality of the finished ceramic part. And it’s fast enough to support the rapid production and qualification of new ceramic materials. UJH has the potential to accelerate scientific development in fields relying on advanced ceramics, like batteries and solid-state electrolytes1.

    Producing High-Entropy Ceramics
    Ultrafast Joule heating is also being used to create advanced materials, like high-entropy ceramics, that are difficult to sinter by traditional means. High-entropy ceramics are a novel class of material incorporating several components, such as oxides, borides, and nitrides. Their high entropy, or disorder, comes from combining these dissimilar materials in a disordered structure.

    High-entropy ceramics are very attractive because the type and amount of each component can be tailored to create a combination of desired properties. This makes them stronger, more durable, and resistant to higher temperatures than traditional ceramics. But they’re also harder to manufacture, requiring higher sintering temperatures and longer sintering times. So far, high-entropy ceramics have seen limited use due to these processing challenges2.

    One potential solution is UJH. A sintering method harnessing UJH has been developed to sinter high-entropy ceramics more efficiently. Carbon-based Joule heaters are used to heat ceramic powder to around 3,000 K for approximately two minutes. This is hotter than what conventional furnaces can achieve, but low enough to avoid melting the material, which would destroy the high-entropy structure2.

    This UJH sintering method has been proven on a high-entropy ceramic made of metal diboride and boron carbide. It successfully sintered the ceramic in a fraction of the time required by traditional methods. It also resulted in high hardness and other desirable properties, showing that the sintering process maintained the material’s high-entropy structure. In theory, this method could be applied to a wide variety of high-entropy ceramics2.

    Nanomaterial Applications

    Creating High-Entropy-Alloy Nanoparticles
    Similar to high-entropy ceramics, high-entropy-alloy (HEA) nanoparticles combine up to eight metallic elements into a single particle. This gives them tailorable properties superior to those of traditional metal alloys.

    But the applications of HEA nanoparticles have been limited by existing manufacturing techniques. Combining elements with vastly different properties is a challenge, especially on the nanoscale. Traditional methods have achieved only a few types of HEA nanoparticles, made with three to five alloying elements3.

    Ultrafast Joule heating has given rise to an exciting new way to synthesize HEA nanoparticles. This method uses UJH to rapidly heat and cool metal compounds at a rate of over 100 K/second. Unlike traditional methods, this can produce HEA nanoparticles with up to eight different elements3.

    By adjusting parameters like substrate, heating and cooling rate, and shock time, the UJH method can be applied to a wide variety of HEA nanoparticles with different elements, structures, and particle sizes. This way, the particles’ properties can be tuned for specific applications like catalysis, energy storage, and bio/plasmonic imaging3.

    Applying Nanoparticles to Textiles
    Another class of nanoparticles, supported metal nanoparticles serve as crucial catalysts in many industries. They’re promising in medical and wearable applications, where they can be dispersed on substrates like textiles and paper to create antibacterial surfaces and detect disease. However, these nanoparticles have conventionally been synthesized using various high-temperature processes—which are incompatible with the low temperature resistance of textile and paper substrates4.

    Ultrafast Joule heating is one way to tackle this challenge. A new method for synthesizing nanoparticles on textile and paper substrates harnesses the rapid heating power of UJH.

    Substrates are loaded with nanoparticle precursors and passed over a carbon nanofiber film, which can be heated up to 3,000 K by UJH. The carbon film heats the nanoparticle precursors by radiative heating, without touching the substrate. Because of the extremely high temperature, the substrate needs to be held over the heat for only one second per half-centimeter before nanoparticles form on the substrate. This short time frame prevents the heat from damaging the substrate4.

    This process can be used for many types of supported metal nanoparticles on various substrates. The temperature can be adjusted by changing the electrical input and the distance from the UJH carbon film. The concentration of precursor elements can be finely tuned to change the size and distribution of the final nanoparticles4.

    Stabilizing Single-Atom Catalysts
    Another class of nanomaterials is single-atom catalysts, which are far more efficient than their traditional counterparts in chemical reactions such as oxidation, hydrogenation, and electrocatalysis. Their increased efficiency has made single-atom catalysts a rising star in the field of sustainable chemical synthesis, but they are challenging to produce.

    Because single atoms are so small, they must be attached to a substrate. Heat can be used to promote bonding between an atom and its substrate, but heat also encourages single atoms to re-agglomerate into their original multi-atom state5.

    High-temperature shockwaves, achieved via UJH, have been shown to effectively synthesize and stabilize single atoms even at temperatures as high as 2,000 K5. Because UJH can reach this temperature so rapidly, the atoms bond to the substrate without having time to re-agglomerate. Single-atom catalysts synthesized this way have superior stability, paving the way for their use in more efficient and “green” chemical reactions5.

    Sustainability Applications

    Regenerating Catalytic Electrodes
    Ultrafast Joule heating has found uses in other eco-friendly applications, such as regenerating catalytic electrodes.

    Catalytic electrodes play an indispensable role in electrochemical devices like batteries and fuel cells, and thus are crucial in meeting the world’s increasing energy demands. But because there is no effective way to recycle these electrodes, they’re also a major contributor to pollution and hazardous waste. Some recycling methods exist, but they can only extract small amounts of certain chemicals, causing the rest of the electrode to be sent to the landfill6.

    UJH could be the key to enabling direct reuse of catalytic electrodes. A new non-destructive recycling method uses UJH to regenerate electrodes, allowing them to be used again up to ten times6.

    During operation, catalytic electrodes accumulate contaminants and byproducts of the chemical reaction, which deactivates them over time. The UJH regeneration method uses carbon Joule heating elements to heat the electrode to 1,700 K in 55 milliseconds. The extreme temperature is sufficient to decompose anything that has accumulated on the electrode’s surface and fully restore the electrode to its original capacity6.

    This UJH regeneration process takes less than a second, but it can extend an electrode’s life by ten-fold. It presents a new and exciting way to recycle catalytic electrodes and make the electrochemical industry far more sustainable6.

    Depolymerizing Plastic
    Plastics are another type of material for which recycling is a major challenge. Plastic pollution has snowballed into a global crisis, threatening both human and ecological health. Developing better plastic recycling methods is a key step in tackling the world’s plastic problem.

    One promising approach is depolymerization, which reduces waste plastic into its constituent monomers, which can then be reused to create new plastic parts. Unfortunately, many commodity plastics can’t be effectively depolymerized using traditional thermochemical methods. This is largely because extended heating of the plastic leads to unwanted side reactions, creating unusable products like gases rather than the desired monomers7.

    A new depolymerization method using UJH has been shown to generate viable monomers from common plastics like polypropylene and PET. This technique uses UJH to pulse an electrical current through waste plastic, generating periodic high temperatures for short times. The temperatures (around 875 K) are sufficient to depolymerize the plastic, but the short duration (on the order of .1 second) suppresses unwanted side reactions. In this way, UJH could present one solution to the multifaceted plastic problem.

    Graphene Applications

    Making Extreme Temperature Sensors
    Ultrafast Joule heating is also used to manufacture an exciting new material called graphene. Although graphene is one of the thinnest, lightest compounds known to science, it’s also stronger than steel, harder than diamond, and an excellent conductor of heat and electricity.

    One form of graphene that holds many promising applications for UJH is reduced graphene oxide, or RGO. RGO is synthesized by making graphene oxide from graphite, then “reducing” it at extreme temperatures via UJH. The reduction process removes the oxygen, purifying the graphene and giving it better properties.

    Though RGO can be reduced at temperatures as low as 1,000 K, a reduction temperature of 3,000 K has been shown to improve its properties—increasing its thermal conductivity three-fold and its electrical conductivity 300-fold. Since these properties are useful in temperature sensing, RGO reduced at 3,000 K by UJH has great potential in the field of extreme temperature sensors8.

    Converting Heat to Electricity
    RGO is also attractive as an ultrahigh-temperature thermoelectric material. Thermoelectric materials convert heat to electricity, which makes them appealing in the constant effort to develop sustainable energy sources.

    These materials could help make the energy industry more efficient by enabling thermoelectric topping of combustion power cycles and extending the range of thermoelectric power generation in solar cells. But thermoelectric applications have historically been limited by traditional thermoelectric materials, which can withstand only 1,500 K9.

    RGO nanosheets, reduced at 3,300 K using UJH, have been shown to perform reliably as thermoelectric materials at temperatures up to 3,000 K. This discovery has the potential to greatly expand the fields of thermoelectricity and sustainable energy9.

    Activating Energetic Materials
    In the electrochemical field, RGO can be used as a substrate for nanoparticle catalysts. One unique application of RGO is as a substrate for aluminum nanoparticles, which are of great interest as a switchable energetic material10.

    Energetic materials are propellants, explosives, and pyrotechnics that rapidly convert stored chemical potential energy to thermal energy. Nanoparticles are particularly exciting for these applications, because they burn faster and have lower ignition temperatures than their larger counterparts. But the same qualities that make nanoparticles so appealing as energetic materials also make them more dangerous, because they are more prone to unplanned ignition10.

    Aluminum nanoparticles could present an ideal solution because they are “switchable,” meaning they have two states. In their activated state, they have all the properties of an energetic material—but in their inactive state, they fail to burn. Activation can be achieved in situ using UJH, essentially functioning as an on-off switch10.

    Aluminum nanoparticles stabilized in RGO can be safely manufactured, transported, and stored in their inactive state. When needed, they can be activated by UJH and effectively switched on. This gives UJH many possible uses in propulsion and military applications10.

    Though ultrafast Joule heating is a relatively new technology, it has already found a variety of applications. From ceramic processing to recycling to nanomaterials, UJH seems poised to play a key role in many scientific developments. If your team could benefit from UJH and you’d like to learn more, contact us about our FlashVolt heating system. The maximum temperature of ACS Material's FlashVolt equipment can reach is up to 3,273.15 K.

    You may also check out our other blogpost here: Ultrafast Joule Heating Technology and 2D Materials 

    Citations 

    1. Wang, Chengwei, et al. “A General Method to Synthesize and Sinter Bulk Ceramics in Seconds.” Science, vol. 368, no. 6490, 2020, pp. 521–526, https://doi.org/10.1126/science.aaz7681.
    2. Xie, Hua, et al. “Rapid Liquid Phase-Assisted Ultrahigh-Temperature Sintering of High-Entropy Ceramic Composites.” Science Advances, vol. 8, no. 27, 2022, https://doi.org/10.1126/sciadv.abn8241.
    3. Yao, Yonggang, Zhennan Huang, Pengfei Xie, Steven D. Lacey, et al. “Carbothermal Shock Synthesis of High-Entropy-Alloy Nanoparticles.” Science, vol. 359, no. 6383, 2018, pp. 1489–1494, https://doi.org/10.1126/science.aan5412.
    4. Jiao, Miaolun, et al. “Fly-through Synthesis of Nanoparticles on Textile and Paper Substrates.” Nanoscale, vol. 11, no. 13, 2019, pp. 6174–6181, https://doi.org/10.1039/c8nr10137j.
    5. Yao, Yonggang, et al. “High Temperature Shockwave Stabilized Single Atoms.” Nature Nanotechnology, vol. 14, no. 9, 2019, pp. 851–857, https://doi.org/10.1038/s41565-019-0518-7.
    6. Dong, Qi, Tangyuan Li, et al. “A General Method for Regenerating Catalytic Electrodes.” Joule, vol. 4, no. 11, 2020, pp. 2374–2386, https://doi.org/10.1016/j.joule.2020.08.008.
    7. Dong, Qi, et al. “Depolymerization of Plastics by Means of Electrified Spatiotemporal Heating.” Nature, vol. 616, no. 7957, 2023, pp. 488–494, https://doi.org/10.1038/s41586-023-05845-8.
    8. Zeng, Yuqiang, et al. “Thermally Conductive Reduced Graphene Oxide Thin Films for Extreme Temperature Sensors.” Advanced Functional Materials, vol. 29, 2019, https://onlinelibrary.wiley.com/doi/10.1002/adfm.201901388.
    9. Li, Tian, et al. “Thermoelectric properties and performance of flexible reduced graphene oxide films up to 3,000 K.” Nature Energy, vol. 3, 148-156, 2018, https://www.nature.com/articles/s41560-018-0086-3.
    10. Chen, Yanan, et al. “Ultra-Fast Self-Assembly and Stabilization of Reactive Nanoparticles in Reduced Graphene Oxide Films.” Nature Communications, vol. 7, no. 1, 2016, https://doi.org/10.1038/ncomms12332.