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Covalent organic framework (COF) aerogels arehierarchically porous polymeric materials with ultrahigh specific surface area, making them attractive for wide applications such as molecular capture, adsorption, and catalysis. Previous COF aerogel studies have focused on varying their chemical structures and linkage chemistries to fine-tune material properties and functionality, most of which have reported relatively unsatisfying performance (e.g., poor mechanical strength and strain tolerance). This study describes the synthesis and characterization of COF nanocomposite aerogels, whose material properties and functionality are effectively engineered through the incorporation of reinforcing fillers/binders or functional additives. Boron nitride (BN) fillers, cross-linked poly(acrylic acid) (XPAA) binders, and gold nanoparticles (AuNps) are incorporated into 1,3,5-tris(aminophenyl)benzene-terephthaldehyde (TAPB-PDA) COF aerogel matrices to form homogeneous nanocomposite aerogels with enhanced mechanical properties and unique photothermal conversion capabilities. Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy results confirm the successful filler/additive inclusion into the final COF nanocomposite aerogels. Specifically, BN filler loading at ∼17 wt % relative to final COF mass doubles COF aerogel’s Young’s modulus from 11 to 22 kPa according to mechanical compression tests, with only ∼10% reduction in COF’s accessible mesopores’ surface area according to nitrogen porosimeter analyses. Meanwhile, incorporating ∼7 wt % XPAA relative to final COF mass improves the Young’s modulus to 21 kPa, while increasing the aerogel’s yield strain from 10 to 65% strain, although this leads to a ∼35% reduction in COF’s accessible mesopores’ surface area. Furthermore, photothermal AuNps are incorporated to form functional COF nanocomposite aerogels, whose overall temperature increases by 5.5 °C after 1 sun (AM1.5G, 1000 W m−2) irradiation. Overall, this study demonstrates potential routes to fabricate hierarchically porous COF nanocomposite aerogels with high specific surface area, robust mechanical stability, and unique photothermal functionality, which hold promises for applications in adsorption separation, gas storage, and photocatalysis. 

Maraging steels are known for their exceptional strength but suffer from limited work hardening and ductility. Here, we report an intermittent printing approach to tailor the microstructure and mechanical properties of maraging 250 steel via engineering of the thermal history during plasma arc additive manufacturing (PAAM). Through introducing a dwell time between adjacent layers, the maraging 250 steel is cooled below the martensite start temperature, triggering a thermally driven, in-situ martensitic transformation during the printing process. Re-heating or thermal cycling during subsequent layer deposition impedes complete martensitic transformation, enabling coexistence of martensite and retained austenite phases with elemental segregation. The enrichment of Ni in the austenite phase promotes stabilization of the retained austenite upon cooling down to room temperature. The retained austenite is yet metastable during deformation, leading to stress-induced martensitic transformation under loading. Specifically, a 3 min interlayer dwell time produces a maraging 250 steel with approximately 8% retained austenite, resulting in improved work hardening via martensitic transformation induced plasticity (TRIP) during deformation. Meanwhile, the higher cooling rate induced by the dwell time results in substantially refined grain structures with an increased dislocation density, leading to a simultaneously improved yield strength. Notably, the yield strength increases from 836 MPa (0 min dwell) to 990 MPa (3 min dwell), and the uniform elongation increases from 3.2% (0 min dwell) to 6.5% (3 min dwell). This intermittent deposition strategy demonstrates the potential to tune the microstructure and mechanical properties of maraging steels through engineering the thermal history during additive manufacturing. 

Abstract The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early Universe. We present spatially resolved chemical and dynamical properties for a sample of 25 galaxies at 0.5 ≲ z ≲ 1.7 from theMSA-3Dsurvey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST’s diffraction limit and a high spectral resolution ofR ≃ 2700. The metallicity gradients measured in our galaxy sample range from −0.03 to 0.02 dex kpc⁻¹. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient atz ∼ 1 with small intrinsic scatter of 0.02 dex kpc⁻¹. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more “disky.” This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of the JWST NIRSpec microshutter assembly in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution. 

Abstract Polycrystalline yttrium aluminum garnet (YAG) ceramic doped with neodymium (Nd), referred to as Nd:YAG, is widely used in solid‐state lasers. However, conventional powder metallurgy methods suffer from expenses, time consumption, and limitations in customizing structures. This study introduces a novel approach for creating Nd:YAG ceramics with 3D free‐form structures from micron (∼70 µm) to centimeter scales. Firstly, sol‐gel synthesis is employed to form photocurable colloidal solutions. Subsequently, by utilizing a home‐built micro‐continuous liquid interface printing process, precursors are printed into 3D poly(acrylic acid) hydrogels containing yttrium, aluminum, and neodymium hydroxides, with a resolution of 5.8 µmpixel⁻¹at a speed of 10 µm s⁻¹. After the hydrogels undergo thermal dehydration, debinding, and sintering, polycrystalline Nd:YAG ceramics featuring distinguishable grains are successfully produced. By optimizing the concentrations of the sintering aids (tetraethyl orthosilicate) and neodymium trichloride (NdCl₃), the resultant samples exhibit satisfactory photoluminescence, emitting light concentrated at 1064 nm when stimulated by a 532 nm laser. Additionally, Nd:YAG ceramics with various 3D geometries (e.g., cone, spiral, and angled pillar) are printed and characterized, which demonstrates the potential for applications, such as laser and amplifier fibers, couplers, and splitters in optical circuits, as well as gain metamaterials or metasurfaces. 

Abstract High-resolution X-ray observations offer a unique tool for probing the still-elusive connection between galaxy mergers and active galactic nuclei (AGNs). We present an analysis of nuclear X-ray emission in an optically selected sample of 92 close galaxy pairs (with projected separations ≲20 kpc and line-of-sight velocity offsets <500 km s⁻¹) at low redshift ( $\overline{z}\sim 0.07$), based on archival Chandra observations. The parent sample of galaxy pairs is constructed without imposing an optical classification of nuclear activity, thus it is largely free of selection effect for or against the presence of an AGN. Nor is this sample biased for or against gas-rich mergers. An X-ray source is detected in 70 of the 184 nuclei, giving a detection rate of $38{\%}_{-5\%}^{+5\%}$, down to a 0.5–8 keV limiting luminosity of ≲10⁴⁰erg s⁻¹. The detected and undetected nuclei show no systematic difference in their host galaxy properties such as galaxy morphology, stellar mass, and stellar velocity dispersion. When potential contamination from star formation is avoided (i.e.,L_{2−10 keV}> 10⁴¹erg s⁻¹), the detection rate becomes $18{\%}_{-3\%}^{+3\%}$(32/184), which shows no excess compared to the X-ray detection rate of a comparison sample of optically classified single AGNs. The fraction of pairs containing dual AGN is only $2{\%}_{-2\%}^{+2\%}$. Moreover, most nuclei at the smallest projected separations probed by our sample (a few kiloparsecs) have an unexpectedly low apparent X-ray luminosity and Eddington ratio, which cannot be solely explained by circumnuclear obscuration. These findings suggest that close galaxy interaction is not a sufficient condition for triggering a high level of AGN activity. 

Abstract We compare the radial profiles of the specific star formation rate (sSFR) in a sample of 169 star-forming galaxies in close pairs with those of mass-matched control galaxies in the SDSS-IV MaNGA survey. We find that the sSFR is centrally enhanced (within one effective radius) in interacting galaxies by ∼0.3 dex and that there is a weak sSFR suppression in the outskirts of the galaxies of ∼0.1 dex. We stack the difference profiles for galaxies in five stellar-mass bins in the range log( M / M ⊙ ) = 9.0–11.5 and find that the sSFR enhancement has no dependence on the stellar mass. The same result is obtained when comparison galaxies are matched to each paired galaxy in both stellar mass and redshift. In addition, we find that the sSFR enhancement is elevated in pairs with nearly equal masses and closer projected separations, in agreement with previous work based on single-fiber spectroscopy. We also find that the sSFR offsets in the outskirts of the paired galaxies are dependent on whether the galaxy is the more-massive or less-massive companion in the pair. The more-massive companion experiences zero to a positive sSFR enhancement, while the less-massive companion experiences sSFR suppression in their outskirts. Our results illustrate the complex tidal effects on star formation in closely paired galaxies.