A new technology developed by Penn State researchers, called Cold Sintering Process (CSP), has opened a window on the ability to combine incompatible materials, such as ceramics and plastics, into new, useful compound materials, and to lower the energy cost of many types of manufacturing.
Ceramics is the oldest known man-made material, dating back tens of thousands of years. Throughout that time most all ceramics have been made by heating them to high temperatures, either by firing in kilns or sintering ceramic powders in furnaces, both of which require large amounts of energy.
Credit: Jennifer M. McCann/MRI
An artistic interpretation of the cold sintering of ceramic particles (white) and polymer strands (green) using low heat to evaporate added water molecules (blue).
“In this day and age, when we have to be incredibly conscious of the CO2 budget, the energy budget, rethinking many of our manufacturing processes, including ceramics, becomes absolutely vital,” said Clive Randall, professor of materials science and engineering at Penn State who developed the process with his team. “Not only is it a low temperature process (room temperature up to 200 degrees Celsius), but we are also densifying some materials to over 95 percent of their theoretical density in 15 minutes. We can now make a ceramic faster than you can bake a pizza, and at lower temperatures.”
In a recent article in the journal Advanced Functional Materials, Randall and his coauthors describe the co-sintering of ceramic and thermoplastic polymer composites using CSP. Three types of polymer were selected to complement the properties of three types of ceramics, a microwave dielectric, an electrolyte and a semiconductor, in order to highlight the diversity of applicable materials. These composite materials demonstrate new possibilities for dielectric property design, and both ionic and electronic electrical conductivity design. These composites can be sintered to high density at 120 degrees C in a time frame of 15 to 60 minutes.
Just add water
According to the researchers, the process involves wetting ceramic powder with a few drops of water or acid solution. The solid surfaces of the particles decompose and partially dissolve in the water to produce a liquid phase at particle-particle interfaces. Adding temperature and pressure causes the water to flow and the solid particles to rearrange in an initial densification process. Then in a second process, clusters of atoms or ions move away from where the particles are in contact, which aids diffusion, which then minimizes surface free energy, allowing the particles to pack tightly together. The key is knowing the exact combination of moisture, pressure, heat and time required to capture the reaction rates so the material fully crystallizes and gets to very high density.
“I see cold sintering process as a continuum of different challenges,” Randall said. “In some systems, it’s so easy you don’t need pressure. In others you do. In some you need to use nanoparticles. In others, you can get away with a mixture of nanoparticles and larger particles. It really all depends on the systems and chemistries you are talking about.”
The Penn State team has begun building a library of the precise techniques required to use CSP on various materials systems, with 50 processes verified to-date. These include ceramic-ceramic composites, ceramic-nanoparticle composites, ceramic-metals, as well as the ceramic-polymers discussed in this paper.
Other areas that are now open to exploration by CSP include architectural materials, such as ceramic bricks, thermal insulation, biomedical implants and many types of electronic components.
“My hope is that a lot of the manufacturing processes that already exist will be able to use this process, and we can learn from polymer manufacturing practices,” Randall concluded.
Co-authors on “Cold Sintering Process of Composites: Bridging the Processing Temperature Gap of Ceramics and Polymer Materials” were postdoctoral scholars Jing Guo and Hanzheng Guo, Ph.D. candidate Seth Berbano, research and development engineer Amanda Baker, and Michael Lanagan, professor of engineering science and mechanics, all part of Penn State’s Materials Research Institute.
The work was supported by the National Science Foundation as part of the Center for Dielectrics and Piezoelectrics and the NSF-ERC ASSIST program, the 3M Science and Technology Fellowship and the Department of Energy GATE Fellowship.
Prof. Clive Randall at firstname.lastname@example.org
Walter Mills | newswise
Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says
19.07.2018 | Purdue University
Machine-learning predicted a superhard and high-energy-density tungsten nitride
18.07.2018 | Science China Press
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences