Approaches to Thermoset Resins for Direct-Ink-Write Additive Manufacturing.
Abstract not provided.
Appelhans, Leah↗
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Results for “ink”
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Multifunctional reactive inks, methods of use and manufacture thereof
In one embodiment, a method includes dispersing a plurality of particles in solution to form a dispersion and adding a stabilizing agent to the dispersion in an amount sufficient to cause the dispersion to exhibit one or more predetermined rheological properties. The particles in the dispersion are configured to complete a self-propagating and/or self-sustaining reaction upon initiation thereof. In another embodiment, a method includes depositing a material on a substrate. The material includes: a plurality of particles configured to complete a self-propagating and/or self-sustaining reaction upon initiation thereof, a solvent system, and one or more stabilizing agents.
Sullivan, Kyle T.↗
High-performance solid-state supercapacitors and microsupercapacitors derived from printable graphene inks
Solid-state supercapacitors and microsupercapacitors comprising printed graphene electrodes and related methods of preparation.
Hersam, Mark C.↗
U.S. Coal to Conductive Inks
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01 COAL, LIGNITE, AND PEAT↗
Using Reduced Order Models to Simulate the Nonlinear Dynamics of Direct Ink Write Structures
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Singh, Aabhas [Sandia National Laboratories (SNL-N↗
Methodology to determine printability criteria of highly concentrated pastes through rheological characterization
Material extrusion is an additive manufacturing technique that enables the creation of reproducible and complex hardware by depositing a viscous, shear-thinning ink onto a substrate in a custom-pattern via extrusion through a syringe. Here, the ability of an ink to be extruded onto a substrate in many layers, and maintain the desired shape is what defines the printability. Printability is often investigated by formulating, printing, and postmortem analysis of final parts in an iterative manner. Investigations of printability through rheological characterization have often been concerned with inks that straddle the line between printable and too thin, leaving out an entire class of inks that are highly-filled pastes, where extrudability is the limiting factor. Highly-filled pastes continue to pose issues for researchers as the effect of filler morphology, size, loading, and packing fraction on the ink rheology and corresponding printability is not understood. While traditional rheological characterizations may be useful for some inks, we show that protocols utilizing steady-shear, or large-amplitude oscillatory shear are difficult and unreliable for highly-filled pastes. Through transient rheology paired with real-time images we show that each traditional protocol produces inhomogeneous deformations that violate the assumptions that underly common rheological definitions. Instead, we demonstrate metrics measured with small-amplitude oscillatory shear that are correlated to the printability of various ink formulations ranging in loading. The rheological measures that accurately predict the printability of the inks are the axial stress measured at small amplitudes, and the critical stress amplitude above which rheological characterizations become impossible. In addition, we estimate the maximum packing fraction for each filler, based on the exponent common to hard sphere models, and show that the printability of each ink can be predicted by the ratio of the packing fraction to the theoretical maximum. We show how small-amplitude oscillatory shear allows users to develop printability criteria for any ink to enhance the workflow in the development of new inks, increase the performance of material extrusion printing, and improve the stability of printed parts, with less wasted time and materials.
36 MATERIALS SCIENCE↗
Slot-die-coating operability windows for polymer electrolyte membrane fuel cell cathode catalyst layers
Roll-to-roll (R2R) slot-die coating of polymer electrolyte membrane fuel cell (PEMFC) catalyst layers represents a scalable deposition method for producing 10–20 m 2 ·min -1 of catalyst-coated gas diffusion layers (GDLs). This high-throughput production technique will help lower the cost of PEMFC catalyst layers. The uniformity of the wet layer applied by slot die deposition is affected by process parameters such as substrate speed, vacuum pressure applied at the upstream meniscus, gap between the slot die lips and substrate, ink rheology, and other ink and substrate properties. The set of conditions for producing a defect-free coating with a dilute ink typically requires little to no upstream vacuum pressure, so suitable operating conditions can be found easily through trial and error and operator intuition. However, the higher viscosity of more concentrated inks dramatically shifts the range of settings that result in a homogeneous coating to higher vacuum levels, which are harder to find through hit or miss. A predictive model showing the range of operable conditions decreases material wastage inherent in experimentally searching for suitable parameters. In this study, the defect-free coating parameter window is explored experimentally and theoretically for two concentrations of PEFC cathode inks. Both a full capillary hydrodynamic model and a computationally cheaper viscocapillary model successfully predict the experimentally determined coating window within the experimental and model uncertainty limits for inks with 5.3 wt% and 12.0 wt% solids ink while maintaining the 0.1 mg Pt ·cm -2 Pt areal loading target. Here, this paper demonstrates a viable pathway for meeting the $30/kW net ultimate cost target of the United States Department of Energy (U.S. DOE) Hydrogen Fuel Cells Technologies Office (HFTO). The concentrated ink lowers the thermal energy and capital expenditure (CapEx) budget of the coating process by decreasing the amount of time, energy, and floorspace required for drying the coating.
25 ENERGY STORAGE↗
IPL-Annealed Mixed-Cation Perovskites with Robust Coating Window toward Scalable Manufacturing of Commercial Perovskite Solar Cells
Perovskite solar cells (PSCs) are a promising alternative solar technology, but the technical challenges of (1) stability/durability, (2) efficiency at scale, and (3) manufacturability must be overcome to achieve widespread PSC commercialization. The challenge of balancing solution ink formulation and scalable manufacturing is often overlooked in the literature, where focus is on adopting inks from processes that will not scale. In this study, we apply a classical roll-to-roll manufacturing perspective, utilizing both compositional engineering and intense pulsed light (IPL) annealing, to develop a mixed-cation perovskite ink with a robust coating window that simultaneously solve issues of stability and manufacturability for PSCs. Our method resulted in blade-coated, flexible, mixed-cation PSCs on ITO-PET substrates with a champion power conversion efficiency (PCE) efficiency of 16.7% using IPL annealing of the absorber layer and, to our knowledge, is one of the fastest processing methods for the perovskite layer. This overall reduction in processing time with a stable ink represents an advance toward the scaled production of perovskite solar cells on flexible substrates.
flexible perovskite solar cells↗
Abstract for CRADA between NETL and the University of Massachusetts Lowell (AGMT-1275)
The demand for printed electronics over conventional electronics is growing each year due to their low costs, low material waste during manufacturing, and compatibility with flexible substrates. The development of inks for printed electronics is a challenge because each printing technology requires different viscosities and curing behaviors to create devices with controlled structures at the micron scale, or smaller. Carbon is a great candidate for fabricating printed electronics devices because it is inexpensive and earth abundant, easily functionalized to impart miscibility with solvent systems, and has electrical properties that can be tuned from insulating to conducting. Despite these advantages, carbons are rarely used for printed electronics because there is a scarcity of inks available for non-contact printing technologies. To address these challenges, the National Energy Technology Laboratory (NETL) will collaborate with the University of Massachusetts Lowell (Participant) through its Printed Electronics Research Collaborative (PERC) to develop engineered carbons and ink formulations optimized specifically for printing radio- and microwave-frequency electronic devices using ink jet, aerosol jet, syringe dispensing, and other additive manufacturing techniques. NETL will process coal, petroleum, and other carbon feedstocks to make engineered carbons with the appropriate composition, microstructure, surface functionalization, and particle morphologies needed to stabilize ink suspensions and impart useful electronic properties to printed devices. The University of Massachusetts Lowell will utilize these engineered carbons to determine which solvent systems and ink additives are needed to achieve the appropriate viscosity, stability, and printability to make useful ink formulations. The University of Massachusetts Lowell will then utilize these inks to manufacture printed resistors and conductors using inkjet, aerosol jet, and syringe dispensing printing methods and will characterize device performance using four-point probe resistivity measurements, contact angle measurements to assess wettability, adhesion evaluation to various substrates, and focused ion beam and scanning electron microscopy for surface and density investigations of printed devices.
36 MATERIALS SCIENCE↗
Roll-to-roll production of catalyst coated membranes for low-temperature electrolyzers
Here we demonstrate a roll-to-roll (R2R) process for direct coating of anode catalyst layers on a polymer electrolyte membrane for low-temperature water electrolysis. To develop this process, we studied catalyst ink formulation, ink-membrane interactions, and coating quality. The catalyst inks were a mixture of iridium oxide (IrO2) and Nafion in a water and alcohol dispersion medium. The type of alcohol (methanol, ethanol, propanols) and water-to-alcohol ratio were varied to determine their influence on membrane swelling, dispersion quality, and coatability. Interactions of the ink dispersion medium with the membrane were characterized using sessile-drop contact-angle measurements. These measurements show that the ratio of water to alcohol has a strong influence on how rapidly the dispersion media is absorbed by the membrane. Rheology of the catalyst inks was measured to understand the microstructure of the catalyst particles in the ink. This analysis found that 1-propanol leads to better dispersion of the IrO2 particles than ethanol. Small-scale coating samples were prepared to understand coating uniformity and formation of irregularities. Subsequently, two water/1-propanol ratios (90:10 and 75:25) were down-selected for large-scale R2R slot die coating. The R2R catalyst-coated membrane (CCM) coating process increased catalyst layer production throughput by over 500x compared to our standard lab-scale spray coating. The CCMs obtained from this process were tested as single-cell membrane electrode assemblies. They exhibited a cell voltage of 1.91 V at a current density of 2 A/cm2, which is comparable to spray-coated CCMs. In conclusion, the work presented here demonstrates a continuous, scalable manufacturing process that eliminates the need for the decal transfer step typically used in CCM production.
42 ENGINEERING↗
Toward Optimizing Electrospun Nanofiber Fuel Cell Catalyst Layers: Polymer–Particle Interactions and Spinnability
We investigate the effect of the poly(acrylic acid) (PAA) carrier polymer concentration on the microstructure and rheological properties of catalyst inks for electrospun polymer–electrolyte membrane fuel-cell catalyst layers. Characterization of an ink microstructure using oscillatory shear rheology showed that the catalyst particles (platinum on carbon) are significantly agglomerated in the absence of PAA or an ionomer. Both the ionomer and PAA promoted the stability of the particles against agglomeration via electrosteric stabilization by adsorbing onto the particle surface. Increasing the PAA concentration increased the stability of the particles (or reduced the agglomerated structure) due to increasing PAA coverage onto the free surface area of the particles. However, beyond a certain increase in concentration, PAA was found to predominantly remain as an excess free polymer in the ink due to an insufficient free/available surface area on the particles for further PAA coverage. Extensional rheology measurements demonstrated that PAA enhances the extensional viscosities of the inks. Consequently, increasing the PAA concentration in the ink promoted the evolution of uniform nanofibers. However, beyond a certain concentration, a significant increase in the shear viscosities of the inks led to defective fiber morphologies because of the onset of flow instabilities. Electrochemical performance comparisons between catalyst layers with different PAA concentrations showed maximum performance at the PAA concentration that led to the least agglomerated structure of the catalyst, most uniform fiber morphologies, and low concentrations of free (non-adsorbing) PAA in the electrode. These results provide a rationale for optimization of electrospun catalyst nanofibers for both spinnability and electrochemical performance.
25 ENERGY STORAGE↗
Direct Optical Patterning of Quantum Dot Light-Emitting Diodes via In Situ Ligand Exchange
Precise patterning of quantum dot (QD) layers is an important prerequisite for fabricating QD light-emitting diode (QLED) displays and other optoelectronic devices. However, conventional patterning methods cannot simultaneously meet the stringent requirements of resolution, throughput, and uniformity of the pattern profile while maintaining a high photoluminescence quantum yield (PLQY) of the patterned QD layers. Here, a specially designed nanocrystal ink is introduced, "photopatternable emissive nanocrystals" (PENs), which satisfies these requirements. Photoacid generators in the PEN inks allow photoresist-free, high-resolution optical patterning of QDs through photochemical reactions and in situ ligand exchange in QD films. Various fluorescence and electroluminescence patterns with a feature size down to approximate to 1.5 mu m are demonstrated using red, green, and blue PEN inks. The patterned QD films maintain approximate to 75% of original PLQY and the electroluminescence characteristics of the patterned QLEDs are comparable to thopse of non-patterned control devices. The patterning mechanism is elucidated by in-depth investigation of the photochemical transformations of the photoacid generators and changes in the optical properties of the QDs at each patterning step. This advanced patterning method provides a new way for additive manufacturing of integrated optoelectronic devices using colloidal QDs.
Cho, Himchan↗
Solvation of NiO x for hole transport layer deposition in perovskite solar cells
In this work, a series of nickel oxide (NiO x ) inks, in the perovskite antisolvent chlorobenzene (CB) containing 15% ethanol, were prepared for the fabrication of p-i-n perovskite solar cells by blade coating. The inks included triethylamine (Et 3 N) and alkyl xanthate salts as ligands to disperse NiO x particle aggregates and stabilize suspension. A total of four inks were evaluated: 0X (Et 3 N with no alkyl xanthate), 4X (Et 3 N + potassium n-butyl xanthate), 12X (Et 3 N + potassium n-dodecyl xanthate), and 18X (Et 3 N + potassium n-octadecyl xanthate). The inks were characterized by UV-visible spectroscopy and FT-IR spectroscopy and the resulting films analyzed by thermogravimetry and scanning electron microscopy. Devices prepared using the 0X ink resulted in a peak power conversion efficiency (PCE) of 14.47% (0.25 cm 2 ) and 9.96 % (1 cm 2 ). The 0X devices showed no significant loss of PCE after 100 days in a nitrogen flow box. Devices prepared with inks containing alkyl xanthate ligand had lower PCE that decreased with decreasing chain length, 18X > 12X > 4X.
14 SOLAR ENERGY↗
Cost-Effective Additive Manufacturing of Ambient Pressure-Dried Silica Aerogel
The conventional manufacturing processes for aerogel insulation materials mostly rely on the supercritical drying, which suffers from issues of massive energy consumption, high-cost equipment, and prolonged processing time. Considering the large market demand for the aerogel insulation material in the next decade, a cost-effective and scalable fabrication technique is highly desired. In this paper, a direct ink writing (DIW) method is used to three-dimensionally fabricate the silica aerogel insulation material, followed by room-temperature and ambient pressure drying. Compared with the supercritical drying and freeze-drying techniques, the reported method significantly reduces the fabrication time and costs. The cost-effective DIW technique offers the capability to print complex hollow internal structures, coupled with the porous aerogel structure, it is found to be beneficial for the thermal insulation property. In this work, the addition of fiber to the ink assures the durability of the fabricated product, without sacrificing the thermal insulation performance. The foam ink preparation methods and the printability are demonstrated in this paper, along with the printing of complex three-dimensional geometries. The thermal insulation performance of the printed objects is characterized, and the mechanical properties were also examined. The proposed approach is found to have a 56% reduction in the processing time. The printed silica aerogels exhibit a low thermal conductivity of 0.053 W m –1 K –1 .
36 MATERIALS SCIENCE↗
Use of Atomic Oxygen for the Determination of Document Alteration
Atomic oxygen, which normally is found only the near Earth space environment, causes oxidation and erosion of polymers on spacecraft. The development of technology to prevent this degradation has required NASA to develop ground laboratory facilities that generate atomic oxygen. Atomic oxygen has also been found to be able to oxidize most types of ink from a variety of types of pens. The use of atomic oxygen to identify alteration of documents has been investigated and is reported. Results of testing indicates that for many types of ink, pen, and paper, identification of document alteration of pen and ink numbers and evidence of alteration can be made visible by exposing the questionable writing to atomic oxygen. Atomic oxygen provides discrimination because different inks may oxidize at different rates, the amount of time between delayed alteration may add to ink thickness at crossings, and the end of pen strokes tend to have much thicker ink deposits than the rest of the character. Examples and techniques of using atomic oxygen to identify document alteration indicate that the technology can, in many but not all cases, provide discrimination between original and altered documents.
Banks, Bruce A.↗
3D Printing of Transparent Silicone Elastomers
Here in this paper, inks for transparent elastomers that are formulated by matching the refractive index of silica and polysiloxanes are described. The transparent inks transmit up to ≈90% of 700 nm light through 1 cm and remain transparent when solidified. The inks and solidified materials exhibit a thermochromic effect. This thermochromic effect can be controlled by the refractive index mismatch. Transparency may increase or decrease as temperature increases, depending on the refractive index mismatch of the base polysiloxane and silica. It is found that the rheological properties of the ink depend on the distribution of silica particles, which is dictated by silica functionality, weight content, and processing. Siloxane precursors that vary in chemical functionality are introduced to tailor the mechanical properties of the printed elastomers, which obtain stretchability >65% along with a tensile modulus of 1.9 MPa. After optimizing siloxane chemistry and ink processing, the authors are able to print transparent elastomers. Potential applications are demonstrated for printed structures by printing encapsulation structures for light-emitting diodes, semitransparent dye-filled structures, a microfluidic mixing device, and a multimaterial structure that exhibits temperature-dependent camouflage.
36 MATERIALS SCIENCE↗
Unlocking Larger Scales and Aspect Ratios in 3D Printed Glass: Coupling Active Mixing and UV Curing for Advanced Printability and Crack Resistance
Recent developments in additive manufacturing (AM) of glass via silica-filled inks have facilitated fabrication of previously unattainable geometries and compositions. However, the maximum processable size of 15 mm limits the use of these prints in applications such as optics. A key limitation lies in the trade-off between material printability and green strength: increasing silica content in the feedstock improves crack resistance and reduces shrinkage but results in dramatic changes in viscoelastic properties that hinder flowability. Here, this paper presents a novel approach that offers expanded versatility in processable size, feedstock formulation, and printing. Described here is a direct ink writing (DIW) system coupled with an active high-shear micromixer and UV light source, capable of simultaneously printing multiple inks with a wide range of rheological properties. Choice of silica sourc, solvent, UV-curable binder, and dispersant is used to tune the ink rheology and improve printability and mechanical properties. Imparting high shear with the micromixer while UV-curing the extrudate allows for increased ink viscosities and reduced nozzle diameters, enabling printing finer feature sizes. With these advances, thin-walled high-aspect ratio structures and a crack-free glass disk measuring 44 mm in diameter are demonstrated, an increase of 3× in the greatest dimension compared to current state-of-the-art.
36 MATERIALS SCIENCE↗
Opening twisted polymer chains for simultaneously high printability and battery fast-charge
Fast-charging is key to the widespread adoption of battery-based electric vehicles. However, improving fast-charging through architecture optimization is expensive. To reduce costs and expand to commercialization, we applied roll-to-roll screen printing technology to create channels and decrease the tortuosity of electrodes. For the first time, this work successfully opened twisted polymer chains within high-solid-content inks to improve their screen printability and battery performance of as-printed electrodes. With LiNi 0.6 Mn 0.2 Co 0.2 O 2 as active materials, the 60% solid content ink presents superior screen printability after opening the twisted binder chains. As-printed electrode exhibits 33% higher charge capacity at 6 C than printed electrode with chains twisted ink at mass loading of 6.5 mg/cm 2 . Furthermore, coarse-grained molecular dynamics simulations are performed to study the underlying mechanism systematically. In conclusion, the new ink preparation procedure provides a scalable, effective strategy for manufacturing screen-printable battery ink and promotes screen-printed electrode technology.
25 ENERGY STORAGE↗