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Carbon aerogels (CAs) combine unique properties including ultra-high surface area, high electrical conductivity, corrosion resistance, and robust mechanical properties making them ideal materials for electrochemical applications. Traditional CA synthesis results in isotropic, random nanoporous networks that work well for applications relying on diffusional mass transport. However, many applications would benefit from integration of engineered macroporous network structures that enable directed pressure-gradient-driven mass transport. Here, we report on using 3D-printed sacrificial polymeric templates to generate templated CAs (t-CAs) with integrated engineered nonrandom macroporous network structures. Specifically, we used projection micro-stereo-lithography (PμSL) and two-photon polymerization direct laser writing (2PP-DLW) to fabricate millimeter-to-centimeter-sized 3D sacrificial polymeric templates with features ranging from tens of microns (PμSL) to 100s of nanometers (2PP-DLW). T-CAs were fabricated by infiltrating the templates with resorcinol-formaldehyde (RF) precursor solution, followed by carbonization at 1050 °C to simultaneously convert the RF gel to a CA and decompose the 3D-printed template, leaving an embedded templated macroporous network structure behind. X-ray computer tomography confirms integration of the macroporous architecture defined by the template. The templated macroporous architecture improves mass transport in t-CAs compared to traditional bulk CA as demonstrated by more uniform activation and their response in electrochemical cyclic voltammetry and galvanostatic charge-discharge tests.

Nanofabrication techniques that can generate large and complex 3D structures with nanoscale features are becoming increasingly important in the fields of biomedicine, micro-optics, and microfluidics. Direct laser writing via two-photon polymerization (DLW-TPP) is one such technique that relies on nonlinear absorption of light to form nanoscale 3D features. Although DLW-TPP provides the required nanoscale resolution, its built height is often limited to less than a millimetre. This height limitation is driven by the need to tightly focus the laser beam at arbitrary depths within the photopolymer. This requirement necessitates matching the photopolymer's refractive index to specific values but the required techniques have not been disseminated widely in the open scientific literature. To address this knowledge gap, we test two universal, different approaches to generate refractive index-matched polymeric and preceramic resins and demonstrate their performance by printing of fine submicron features in 3D structures as tall as 2.5 mm. Specifically, we achieve index-matching by mixing commercially-available resins or covalent modification of functional monomers. This work investigates the relationship of voxel shape to RI mismatch, and presents tuning of RI through mixing and covalent modification to a nonconventional material system of preceramic resin which has never been demonstrated before. We demonstrate the material flexibility by generating 3D silicon oxycarbide structures from preceramic resists while simultaneously eliminating the part-height limitation of conventional DLW-TPP.

High-precision Hugoniot measurements of heterogeneous materials are a key tool in creating accurate equations of state, but such measurements are prone to larger uncertainties than their homogeneous counterparts. To efficiently reduce these uncertainties one must estimate the relative contributions of different error sources. Sample cracking is one likely source. Here we estimate its contribution through modeling, using computed tomography scans of powdered single crystal quartz samples to estimate typical packing variation within and between samples. Samples were prepared using the same materials and methods. Cracks were prominent in the samples. We describe a simple model to estimate shock transit time variation for a single shot due to cracking, and estimate that up to 3% variation can be attributed to these structures. This suggests that decreasing variation requires addressing such packing heterogeneities during target fabrication rather than experimental diagnostics.

As-processed metals and alloys by selective laser melting (SLM), or laser powder bed fusion (L-PBF), are often full of defects and flaws such as dislocations, twins, elemental segregations, impurities and porosities, which can positively or negatively impact mechanical properties. Here, we systematically characterize the tensile behavior of L-PBF Ti-6Al-4V at quasi-static strain rate and room temperature, including state-of-the-art in situ synchrotron X-ray diffraction (SXRD) and computed tomography (SXCT). These studies reveal that the tensile yield strength and uniform elongation are mainly dictated by the as-built microstructure, while the strain-to-failure is sensitive to the porosity, even in very high-density samples (>99.5%). in situ SXRD reveals that the micro-plasticity in as-built Ti64 initiates at a stress level well below its macroscopic yield strength, signified by the early lattice strain deviation behavior of {0002} and {112¯0} reflections. SXCT reveals pore growth mechanisms when the tensile axis is perpendicular to the build direction, whereas no such behavior is observed as the tensile axis is along the build direction. These anisotropic pore growth mechanisms result in vast differences in the strain-to-failure of L-PBF materials. Our melt-pool dynamics modeling with similar laser conditions to the experiments identifies a previously unknown pore source; i.e., edge-of-track pores. We present a normalized energy diagram to identify the optimized processing window for high quality samples. Keywords: Selective laser melting, Ti-6Al-4V, Synchrotron X-ray diffraction, X-ray computed tomography, Pores, Plasticity