As additive manufacturing technologies are increasingly adopted for a range of applications across many industries, much of the focus is directed at 3D printing metal or polymer materials. Ceramic 3D printing, however, is maturing and reaching an inflection point as engineers increasingly turn to the superior performance properties of technical ceramic materials.
Traditional ceramic molding processes require expensive tooling with long lead times. The process is also inefficient as de-molding becomes increasingly more complicated by the complex shapes of modern components. The design freedom of additive manufacturing builds new optimized shapes in these traditionally hard-to-process materials that are optimized for weight or shaped for special performance purposes such as deflecting or absorbing energy.
As 3D printing empowers designers to push complexity in part geometry, new material possibilities are leading to true application breakthroughs.
Used in construction for centuries, ceramics have evolved into cutting-edge manufacturing materials. Silica sand, for example, is a ceramic used in metalcasting. Foundries regularly build tooling from the material and have adopted sand 3D printing in recent decades to mass produce increasingly complex designs with faster turnarounds, all without departing from their casting workflow to produce end-use metal parts.
Today, a range of technical ceramic materials with oxides, carbides, or nitrides bonded to them are used for applications with environmental and performance demands higher than can be met by other materials. Technical ceramics like silicon carbide (SiC), alumina, and zirconia are coveted for use in the most extreme applications and in the harshest environments for properties such as biocompatibility, high hardness, ultra-high-temperature stability, or resistance to chemical reactions.
Binder jetting has inherent advantages in the shaping of these ceramics into complex, high-resolution geometries impossible to build with traditional technologies. The print speed, print size, and material flexibility allows the widest range of materials to be processed at the fastest speeds. It is a highly-researched technology and widely identified as the best process for manufacturing SiC, even among other additive technologies, because the dark powder doesn’t UV cure and the high melting point eliminates laser-based processes. Producing near net shape parts also reduces difficult and expensive machining and polishing post-processing steps. Porous green parts can be sintered, impregnated, or infiltrated to achieve versatile material properties specific to the application.
The new design paradigm of additive manufacturing, paired with the most advanced technical ceramic materials, puts binder jetting on the cutting edge of application development.
Collimators are components used in neutron imaging allowing researchers to map properties of a material by absorbing stray neutrons. They enhance resolution and reduce background signals in experiments to capture data down to an atomic level.
Boron carbide (B4C) is a technical ceramic with strong but lightweight properties, as well as energy-absorbing characteristics that are particularly useful in neutron scattering instruments. Manufacturing limitations of the past yielded collimators from blades coated with highly absorbent material, such as enriched boron carbide (10B4C), in arrangements that inherently collimated in only one dimension. The restricted shapes of these traditional designs limited the type of research that could be done with them.
Researchers at JJ X-Ray, a Danish manufacturer of solutions for x-ray, synchrotron radiation, and neutron scattering experiments, used the design freedom of 3D printing to develop more intricate components for 2D collimation. Desktop Metal X-Series binder jetting systems printed cubes in 3D from 10B4C powder. The 20 mm3 collimator prototypes feature 5×5 mm straight-walled channels that could not be produced with any other technology.
The JJ X-Ray team expects the advanced designs achievable with 3D printed collimators to open new research opportunities as the paradigm of future experiments shifts. The team continues to push the design limitations with curved structures, thin-walled parts, and tapered, narrow channels.
Renewable energy sources such as solar and wind will continue to grow, but conventional wisdom in energy circles identifies nuclear power as one of the most reliable, portable, and green baseload energy sources to support a comprehensive modern energy grid. The negative perception of high-profile accidents such as Three Mile Island and Fukushima highlight outdated nuclear technology when advanced materials and their methods of manufacture weren’t available.
Organizations like Ultra Safe Nuclear Corporation (USNC) use advanced manufacturing to make safe, controlled, and reliable nuclear energy a reality. Binder jet 3D printing plays a fundamental role in USNC’s innovative fuel design. This design allows the company to control nuclear fission and prevent accidents altogether.
USNC combines safe micro modular reactor (MMR) system designs with an advanced fuel system. The key to its approach is Fully Ceramic Micro-encapsulated (FCM) fuel manufactured with Desktop Metal binder jetting technology that can 3D print silicon carbide (SiC.)
SiC is a technical ceramic material with extreme environmental stability. The conditions within a nuclear reactor are some of the harshest in all of industry, yet SiC doesn’t shrink or excessively swell like a traditional graphitic matrix. It is also resistant to oxidation and corrosion, offering stability under the demanding conditions of a nuclear reactor core.
However, SiC is cumbersome to manufacture into complex parts. For decades, despite the industry’s desire to work with the material, there was no viable manufacturing process to transform highly pure, crystalline, nuclear-grade SiC into the shapes needed for nuclear applications. Today, Desktop Metal X-Series machines 3D print SiC powder into unique geometries that can safely surround modern nuclear fuel.
Binder jet technology inkjets a binder into a bed of powder particles such as metal, sand, or ceramic to create a solid part, one thin layer at a time. Importantly for 3D printing SiC, the whole process is carried out at low temperatures.
“There was a whole host of additive manufacturing methods out there, but a large portion of those rely on a high-temperature process during deposition,” said Dr. Kurt A. Terrani, executive vice president of USNC’s Core Division. The internationally recognized technology leader explained, “With metals they’re melting the particles to connect them together, but you can’t do that with the high melting point of silicon carbide. Binder jet technology is unique because it really relies on the physical characteristics of the powder, and it’s essentially agnostic to the chemical and phase structure of the material. So, we can select highly pure, highly crystalline carbide feedstock powder, nuclear grade powder, and then form these really complex geometries, and that just wasn’t previously possible.”
By marrying binder jetting with chemical vapor infiltration to fill the porous SiC structure with more high-purity crystalline silicon carbide, USNC creates complex, near-net shapes without the need to sinter, apply any pressure, or introduce secondary phases. Compared to the traditional way of processing technical ceramics, including mixers to create slurries, injection molders, and furnaces, Terrani said binder jet 3D printing is an elegant solution and a “cost-effective and reliable process.”
The ability to create unique designs en masse with 3D printing also allows USNC to add an additional layer of quality assurance to its mission of safe, responsible nuclear energy. “We print an ID on these parts, so from the moment of birth we track the reactors’ manufacturing DNA throughout production, operational lifetime, and upon their discharge,” Terrani said. “Binder jetting allows us to create a new paradigm of safe, reliable, carbon-free nuclear energy for use by industry and remote communities.”
This approach leveraging advanced manufacturing breakthroughs creates a design for a passively safe reactor that transforms a decades-old technology to deliver safer and more efficient nuclear reactors in the 21st century.
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