Heating, cooling, and lighting buildings consume an inordinate amount of energy, contributing greatly to the operating costs and carbon footprint of the built environment. The development of a thermochromic material capable of passively modulating the near-infrared (NIR) transmittance of fenestration elements, and thus the overall solar heat gain, has garnered intense interest owing to its potential to increase the energy efficiency of buildings. VO2 is a promising thermochromic material as a result of its characteristic metal–insulator transition (MIT), which engenders a discontinuous modulation of infrared transparency. Given its high thermodynamic transition, 67 °C, much effort has focused on decreasing the MIT of VO2 to near-ambient temperatures. However, dopant incorporation typically degrades crystallinity, which is reflected in a substantial decrease of NIR modulation. In this work, we demonstrate that the postsynthetic annealing of ultrasmall W x V1–x O2 nanocrystals encapsulated within SiO2 shells enables substantial improvements in crystallinity without sintering of the nanocrystals. The dispersion of SiO2-encapsulated W-alloyed nanocrystals within a methacrylic acid/ethyl acrylate copolymer yields a smooth gradation of refractive indices. The nanocomposite films comprising VO2 nanocrystals alloyed with 2.3 at.% tungsten are cast onto glass and demonstrate a ΔT NIR of 12.8% and a ΔT Sol of 10.6%, while maintaining a high degree of visible-light transmission (ca. 77% at 555 nm) and minimal modulation in the visible region (ΔT Lum) at an operational temperature of 35 °C. The processing workflow from alloying of VO2 nanocrystals to their encapsulation within a SiO2 matrix for protected annealing and dispersion within a polymer further represents an entirely aqueous manufacturing route to thermochromic fenestration elements. More broadly, our results demonstrate the ability to access solid solutions of W x V1–x O2 with ultrasmall nanocrystalline dimensions while selectively tailoring the properties of the material for specific climates to achieve the desired combination of high visible-light transparency and NIR modulation.
As a result of the increasing emphasis on accessing unconventional deposits of heavy oil and bitumen to meet global energy needs, there is an intense focus on addressing the rheological challenges involved in the transportation, handling, and processing of viscous hydrocarbons. While the design of superhydrophobic surfaces has been extensively explored, the fabrication of surfaces nonwetted by low-surface-tension and high-viscosity oils that can be scaled to meet industrial needs remains to be adequately addressed. Here, we demonstrate that colloidally templated architectures of TiO2 particles applicable through a facile spray deposition process can form 3D inverse opal coatings adhered to low-alloy steels. Low-temperature sintering induces necking of particles, giving rise to an interconnected framework of plastrons surrounded by necked TiO2 ligaments. Surface functionalization with 1H,1H,2H,2H-perfluorooctanephosphonic acid yields a helical surface monolayer with pendant trifluoromethyl moieties. The combination of interconnected plastrons, re-entrant curvature, and low surface energy suspends liquid droplets, of both water and heavy oil, in the Cassie–Baxter regime, yielding contact angles of 164° ± 5° and 161° ± 2°, respectively. The interconnected network of plastrons further enables the facile gliding of heavy oil (<100 s) upon immersion within a bath, whereas a comparable untreated surface remains completely fouled. The performance of this coating suggests a promising solution to mitigate the challenges of handling viscous oils in midstream applications and furthermore delineates a route to designing coatings for a broad host of rheologically challenging fluids.
Reactions of the homoleptic and heteroleptic antimony ligands Sb Pr, Sb PrPh, SbMePh, and SbMePh with NiI generate rare Ni stibine complexes in either square planar or trigonal bipyramidal (TBP) geometries, depending on the steric size of the ligands. Tolman electronic parameters were calculated (DFT) for each antimony ligand to provide a tabulated resource for the relative strengths of simple antimony ligands. The electronic absorbance spectra of the square planar complexes exhibit characteristic bands [λ ≈ 560 nm (17 900 cm), ε ≈ 4330 M cm] at lower energies compared to the reported phosphine complexes, indicating the weak donor strength of the stibine ligands and resultant low-energy ligand field d→ d transitions. The square planar complex Ni(I)(Sb Pr) reacts with CO to form the TBP complex Ni(I)(Sb Pr)(CO). Lastly, the complexes were investigated for nickel metal deposition on Si|Cu(100 nm) substrates. The complexes with the strongest donating ligand, Sb Pr, deposited the purest layer of NiCu alloy according to the balanced reaction Ni(I)(SbPr) → Ni + Sb( Pr)I; the iodinated Sb byproduct was unambiguously detected in the supernatant by H NMR and mass spectrometry. Complexes with weaker ligands (poor I acceptors/scavengers) resulted undesired deposition of iodine and CuI on the surface. This work thus serves as a guide for the design and synthesis of 3 d metal complexes with neutral, heavy main-group donors that are useful for metal deposition applications.
For transportation of hydrocarbon liquids via pipelines, reducing the frictional forces between internal walls and viscous oils through modification of the interfacial surface chemistry and topography represents a key imperative, enabling viscous oil flow at lower temperatures while mitigating the need for diluents. Although drag reduction of aqueous flows in lithographically patterned microchannels has been widely explored, herein drag reduction of oil flows within macroscopic tubing spanning several feet in length is demonstrated. Multiscale texturation is derived from the introduction of micron‐sized pits during electroless deposition of nickel and is augmented by nanoscale texturation derived from the incorporation of polytetrafluoroethylene (PTFE) beads within the coating. Further functionalization with a monolayer of 1H,1H,2H,2H‐perfluorooctanephosphonic acid yields a surface that is not wetted by water or viscous oils, yielding 17% drag reduction under laminar flow for castor oil and a slip length that approaches 329 μm. The results demonstrate a promising solution for obtaining robust plastronic architectures embedded within the inner walls of macroscopic tubing. The performance of such coatings is constrained primarily by the robustness of plastrons and molecular properties of the flow liquid with the latter modifying the solid/liquid interface energy as a result of surface adsorption.
Laboratory safety teams (LSTs), led by graduate student and postdoctoral researchers, have been propagating across the U.S. as a bottom-up approach to improving safety culture in academic research laboratories. Prior to the COVID-19 pandemic, LSTs relied heavily on in-person projects and events. Additionally, committed Champions from the ranks of safety professionals and faculty were critical to their operation and continued expansion. As was the case for many existing systems, the COVID-19 global crisis served as an operational stress test for LSTs, pushing them to unexpected new limits. The initial spread of COVID-19 brought with it a shutdown of academic institutions followed by a limited reopening that prohibited in-person gatherings and disrupted standard lines of communication upon which LSTs relied. Safety professionals and faculty members were required to take on new duties that were often undefined and time-consuming, substantially impacting their ability to support LSTs. In this case study, we report the impact of this operational stress test on 12 LSTs, detailing the adaptive means by which they survived and highlighting the key lessons learned by the represented LST leaders. The key takeaways were to spend time nurturing relationships with a diverse array of Champions, securing stable funding from multiple sources, and networking with members of LSTs from different institutions to strengthen moral support and broaden ideation for common challenges.
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