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Photoinitiated thermoset polymerization through controlled release of metathesis catalysts encapsulated in poly(phthalaldehyde)
Photoinitiated polymerization enables spatiotemporal control of reaction conditions and can thereby generate materials with high complexity while consuming minimal energy. Where ring opening metathesis polymerization (ROMP) is concerned, photo-activated processes are typically enabled by chemical inhibition of ruthenium carbenes via the careful design of complexed ligands such that photoactivation can proceed through an isomerization or ligand dissociation event. In this contribution, we have explored a new approach to photoinitiation of ROMP based on physical inhibition through microencapsulation and controlled release of metathesis catalysts. Micron-sized particles of poly(phthalaldehyde) (PPA), catalyst, and photoacid generator were fabricated by spray drying. The particles were dispersed in dicyclopentadiene monomer, after which polymerization was initiated through temperature or UV exposure, both inducing depolymerization of the PPA particles and in situ catalyst release. The monomer/particle dispersions were found to be stable and reproducibly polymerizable with 3 weeks of storage at room temperature. Furthermore, the dispersions can be used for both photo- and thermal-initiated frontal ROMP, yielding a polymerized thermoset of equivalent properties to conventional bulk- and frontally-polymerized analogues. In conclusion, this work will ultimately enable new manufacturing techniques for ROMP-based materials, due to the modular, easily tunable nature of the underlying initiating system and its unparalleled stability.
Iron Cluster Encapsulated N-Doped Single-Walled Carbon Nanotubes as ORR Electrocatalyst: A First-Principles Study
The ORR electrocatalytic activities of N-doped single-walled nanotubes infused with Fe7 clusters are assessed with DFT calculations. The incorporation of Fe7 leads to enhanced activity and stability via electron donation. The models presented in this work propose a promising strategy for designing non-precious metal ORR catalysts.
A simple and practical wax-encapsulation method for air-sensitive XAS samples
To facilitate X-ray absorption spectroscopy (XAS) measurements of air-sensitive samples, we present a simple method in which materials are encased in common paraffin wax to protect them from air and moisture. We demonstrate the efficacy of this approach using a highly reducing, air- and moisture-sensitive uranium(III) complex, the tris(amide) U[N(SiMe 3 ) 2 ] 3 (1). When finely dispersed in a boron nitride matrix and subsequently encased in inert paraffin wax, samples of 1 remain stable with no visible or spectroscopic degradation after several days under ambient conditions. The viability of this method for XAS measurements was further evaluated across a series of uranium compounds, ranging from uranyl species to highly air- and moisture-sensitive molecular complexes, at the uranium L 3 -edge. Edge energy determinations were highly reproducible (±0.1 eV between replicates) and, where available, showed excellent agreement with literature values. In conclusion, this low-cost, effective, and versatile method offers a viable solution for XAS studies of air-sensitive compounds and materials.
Thermoset Polymerization Through Controlled Release of Metathesis Catalysts Encapsulated in Poly(phthalaldehyde)
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Predicting Molecular Scale Dynamics And Kinetics Occurring During Photovoltaic Encapsulant Degradation
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Understanding Polymer Encapsulant Degradation: A Scale Bridging Computational Framework
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Metal Encapsulation Strategies to Optimize and Minimize PGE Use in Heterogeneous Catalysts
In the three funded years of research (and one additional year of no-cost extension), we focused on several areas of interest towards the goal of reducing the content of PGMs in emission control catalysts.
Oak Ridge National Laboratory Modernizing the Kokkos Build System: Using CMake to Encapsulate the Complexity of Build Instructions for Performance Portable Libraries
Kokkos, a C++ library focused on performance portability, requires a build system that can work with a variety of compilers and hardware. Ideally, users need only select the compiler and architecture and should not have to know or specify how programs using Kokkos are built. CMake can be used to create a flexible, robust build system and automatically configures compilers and settings based on the user’s inputs. Nevertheless, Kokkos’ requirements as a performance portability library for the build system exceed CMake’s current capabilities. This report describes the requirements, solutions, and testing of various implementations to create a CMake-based build system suitable for Kokkos. It compares the strengths and shortcomings of the approaches and evaluates the implementations with respect to the requirements. Because no solution was found to meet all of the requirements, the Kokkos team engaged with the CMake development team to discuss and plan a path toward support for performance-portable build systems in CMake in the future.
Modeling Crystallization and Melting in EVA and Polyolefin Encapsulation to Augment Stress Predictions in Cracked PV Modules Over a 24-hour Period
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MCNP Simulations of an Aluminum Encapsulated Boron Carbide Spheres for Modification of Dosimeter Response
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Encapsulating Grubbs Type Catalysts for Frontal Ring Opening Metathesis
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Exploring encapsulation strategies and compatibility for cell-free protein synthesis
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Thiol-ene dextran-based hydrogels for 3D neuron encapsulation
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Ultra-High-Performance Grout for Encapsulation of Solid Secondary Waste
Ultra-high-performance grout (UHPG); Low H2O/CM; Small aggregate; May include fibers; Admix UHPG has excellent contaminant transport properties: Strong moisture retention; Low porosity; Low permeability; Diffusivity; High resistance to chloride penetration (− < 50 coulombs; ASTM C 1202)
Water reflection analysis of encapsulated photovoltaic modules
A method for moisture testing of a fully assembled photovoltaic (PV) module. An assembled PV module is probed with short wave IR probe energy in the range of 1700-2000 nm. Energy reflected from the assembled PV module is collected and directed to a sensor. Noise is removed from a signal of the sensor with reference to the probe energy. Absorption is of the probe energy is determined. The absorption is correlated to moisture in the PV module. A preferred system that carries out the method provides a signal-to-noise ratio (as defined by standard deviation/mean of measured reflectance) of at least 3800.
Electrochemical Modeling of PID Leakage Current of PV Modules: Steady-State Current, Transient Current, and RC-Equivalent Circuit
Potential-induced degradation (PID) remains a significant reliability concern for photovoltaic (PV) modules, arising when a voltage difference between the module frame and the solar cells drives unintended leakage current through the glass-encapsulant stack. Although PID ultimately manifests as PID-s, PID-p, or PID-c, the underlying behavior of the leakage current-its magnitude and time dependence-requires clearer electrochemical interpretation. Traditional explanations attribute the initial transient current to bulk capacitive elements of the glass, encapsulant, and antireflection coatings, and the steady-state current according to their effective ohmic resistance. More recent studies, however, indicate that electrochemical charge-transfer processes at the encapsulant-metallization interface can play a dominant role in defining the leakage-current path. This paper develops a unified electrochemical framework for modeling PID leakage current. First, an RC-equivalent circuit is formulated by combining conventional RC elements with a Randles-type interface to capture transient leakage current through double-layer capacitance and faradaic processes at ionic-electronic boundaries. Second, the steady-state current-voltage behavior is explained using a linearized Butler-Volmer relationship, showing that the measured ohmic response corresponds to the low-overpotential limit of charge-transfer kinetics. Analytical results demonstrate that, for typical module materials-3.2-mm soda-lime glass and 0.45-mm encapsulant-the dominant modulators to PID leakage current are the glass surface resistance (under dry-surface conditions), the glass bulk capacitance, and the encapsulant resistance (under wet-surface conditions), with soda lime glass surface and EVA/POE encapsulant resistances primarily governing steady-state current. The proposed electrochemical model is validated against measured leakage-current data, showing good agreement in both the magnitude and the time-dependent evolution of PID leakage current.