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Three-dimensional (3D) hierarchical nanoporous Cu (3DHNP-Cu) is synthesized using a combination of direct ink writing (DIW) based 3D printing, thermal sintering, and chemical dealloying of Mn–Cu alloys. Through tuning processing conditions such as ink composition and cooling rate (after sintering), with consideration of Mn loss during sintering, 3DHNP-Cu with fully bicontinuous nanostructures and negligible residual Mn can be produced after dealloying. The 3DHNP-Cu is comprised of structural features that span seven orders of magnitude, where DIW digitally controls macroscale porous features, thermal sintering and degradation of the binding polymer determines microscale porous features, and dealloying gives rise to nanoscale pores.

Inks compounded of short carbon fibers suspended in polymer resin can be extruded to produce composite materials during additive manufacturing or 3D printing processes. The flow process induces anisotropic orientation of the fibers which is set into the matrix and significantly affects the mechanical and physical properties of the final product. Therefore, the flow of fiber suspensions needs to be understood in order to predict the orientation distribution of the fibers during such manufacturing processes. There is still a lack of knowledge for extrusion of the complex mixture of a non-Newtonian polymer containing a high-volume fraction of fibers with high fiber aspect ratio, where both inter-particle, fluid-particle and fiber-wall interactions are computationally evaluated. This paper presents predictive numerical simulations and experimental results of such confined flow in a concentrated regime. The code is based on Lagrange multiplier technique and resolves each particle and interaction between the fibers and surrounding fluid and nozzle walls. We investigate numerically how the fiber length impacts the fiber alignment during extrusion. We found that a fiber length above 67% of the nozzle's diameter induces dramatic change in the fiber flow, causing fibers to concentrate at the nozzle boundaries with very low concentration of fibers in the center of the nozzle. It was found that the best fiber alignment is reached for fiber lengths equal to 40–50% of the nozzle diameters. Numerical findings are supported by experimental results. This work improves understanding of fiber orientation during 3D printing and is an important milestone for the prediction of the complex mechanical properties of additively manufactured fiber composites.

Summary Retaining sound electrochemical performance of electrodes at high mass loading holds significant importance to energy storage. Pseudocapacitive materials such as manganese oxide (MnO2) deposited on current collectors have achieved outstanding gravimetric capacitances, sometimes even close to their theoretical values. Yet, this is only achievable with very small mass loading of active material typically less than 1 mg cm−2. Increasing mass loading often leads to drastic decay of capacitive performance due to sluggish ion diffusion in bulk material. Here, we demonstrate a 3D printed graphene aerogel electrode with MnO2 loading of 182.2 mg cm−2, which achieves a record-high areal capacitance of 44.13 F cm−2. Most importantly, this 3D printed graphene aerogel/MnO2 electrode can simultaneously achieve excellent capacitance normalized to area, gravimetry, and volume, which is the trade-off for most electrodes. This work successfully validates the feasibility of printing practical pseudocapacitive electrodes, which might revolutionize pseudocapacitor fabrication.

Solid-state laser gain media based on the garnet structure with two spatially distinct but optically contiguous regions have been fabricated. Transparent gain media comprised of a central core of Y2.97Nd0.03Al5.00O12.00 (Nd:YAG) and an undoped cladding region of Y3Al5O12 (YAG) were fabricated by direct ink write and transparent ceramic processing. Direct ink write (DIW) was employed to form the green body, offering a general route to preparing functionally structured solid-state laser gain media. Fully-dense transparent optical ceramics in a “top hat” geometry with YAG/Nd:YAG have been fabricated by DIW methods with optical scatter at 1064 nm of

Electrochemical energy storage (EES) devices, such as lithium-ion batteries and supercapacitors, are emerging as primary power sources for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These EES devices, while renowned for their high energy or power densities, portability, and long cycle life, are still facing significant performance hindrance due to manufacturing limitations. One major obstacle is the ability to engineer macroscopic components with designed and highly resolved nanostructures with optimal performance, via controllable and scalable manufacturing techniques. 3D printing covers several additive manufacturing methods that enable well-controlled creation of functional nanomaterials with three-dimensional architectures, representing a promising approach for fabrication of next-generation EES devices with high performance. In this review, we summarize recent progress in fabricating 3D functional electrodes utilizing 3D printing-based methodologies for EES devices. Specifically, laser-, lithography-, electrodeposition-, and extrusion-based 3D printing techniques are described and exemplified with examples from the literatures. Current challenges and future opportunities for functional materials fabrication via 3D printing techniques are also discussed.

Garnet-type solid electrolytes, such as Li6.4La3Zr1.4Ta0.6O12 (LLZTO), are promising materials for solid-state batteries, but processing remains a challenge, in part due to the high sintering temperature required for densification. This temperature can be lowered by decreasing the initial particle size via solvent-assisted ball milling, but the relationship between solvent choice, particle properties, sintering behavior, and ionic conductivity is not well understood. In this work, we systematically explore these parameters, showing that milling in commonly used protic solvents, such as alcohols, effectively decreases the particle size but results in lithium loss (through Li+/H+ exchange) that leads to poor sintering. By contrast, milling in aprotic solvents with surfactant reduces the particle size to ~220 nm without lithium loss, enabling the fabrication of dense samples (5.1 g/cm3) with good ionic conductivity (0.43 mS/cm at 25 °C) at a lower sintering temperature (1000 °C). We compare ionic conductivities and activation energies for samples prepared with different particle sizes and sintering temperatures and use multiphase-field simulations to identify the mass transport and microstructural mechanisms responsible for the observed sintering dependence on particle size. These results further clarify the relationship between processing parameters and performance and represent important progress toward overcoming fabrication challenges for these materials.

Projection micro stereolithography (PµSL) is an additive manufacturing tool that offers multiple advantages, including unparalleled resolution and throughput, but the ability to print high viscosity resin for large-scale parts is limited. One of the key challenges in PµSL is to separate a newly polymerized layer from the vat floor without damaging the part. Since the separation force scales with the printing area, the risk of damaging the part increases significantly with larger-scale systems and must be addressed. In this paper, a novel roll-to-roll, variable tensioning system is proposed to reduce the separation force during printing. A mathematical model is proposed to predict the separation force for different 2D geometries, and a set of experiments is conducted on an experimental prototype to validate the model. The effects of different separation parameters including peel rate and peel angle are discussed in detail. The results show that the proposed tensioning system reduces the separation force significantly.

Oxide-derived copper (Cu) catalysts often show significantly improved performance for carbon dioxide (CO2) reduction reactions compared with metallic Cu. In this article, we summarize the recently reported methods for preparing oxide-derived Cu catalysts and discuss the current understanding of the reaction mechanisms, including the role of mixed oxidation states of copper, subsurface oxygen, local pH, and electrolyte. Finally, we share our thoughts about the current challenges for oxide-derived Cu catalysts and the potential solutions.

Many attractive options for carbon capture solvents suffer from high viscosity, making it difficult to generate large surface areas for fast absorption, and amine-based aqueous liquids suffer from potential environmental impacts from solvent release. As part of a US-DOE ARPA-E program, a team from the University of Illinois Urbana-Champaign, Babcock and Wilcox, and Lawrence Livermore National Laboratory have created a new encapsulated form of carbon capture solvents in which the operating fluid, amines or carbonates in our tests to date, is enclosed in a thin polymer shell forming 200-400 μm beads. While mass transport across the polymer shell is reduced compared to the neat liquid, the large surface area of the beads lessens this disadvantage. The liquid, as well as any degradation products or precipitates, remains encapsulated within the beads, which can be thermally regenerated repeatedly. Encapsulated solvents have the capacity of liquids and the physical behavior of solid sorbents. We imagine them to be useful in fairly conventional-style capture applications, as well as exotic new approaches facilitated by their high surface area. The beads appear to be both chemically and mechanically stable under typical industrial conditions. Examples of the engineering constraints that the beads must satisfy for several application strategies, including their use in fluidized beds, will be presented. To date we have encapsulated MEA, piperazine, and a variety of carbonate solutions, which appear to be optimal for this application. We have demonstrated rapid CO2 uptake and desorption using colorimetric methods, which permit rapid spectroscopic determination of the extent of CO2 uptake and release (shown to the left, loaded form is yellow). Carbonate capsules are created using a silicone polymer shell which is both rugged and permeable to CO2. Results of mechanical/thermal cycling tests demonstrate long-term stability of silicone- encapsulated carbonate.