scholarly journals High-Resolution Ion-Flux Imaging of Proton Transport Through Graphene|Nafion Membranes

2021 ◽  
Author(s):  
Cameron Bentley ◽  
Minkyung Kang ◽  
Saheed Bukola ◽  
Stephen Creager ◽  
Patrick Unwin
Keyword(s):  
Proton Transport ◽  
Hexagonal Boron Nitride ◽  
Equivalent Circuit Model ◽  
Ion Flux ◽  
Monolayer Graphene ◽  
Structure Property ◽  
Ambient Conditions ◽  
Typical Experiment ◽  
Nafion Membranes ◽  
Ion Proton

In 2014, it was reported that protons can traverse between aqueous phases separated by nominally pristine monolayer graphene and hexagonal boron nitride (h-BN) films (membranes) under ambient conditions. This “intrinsic proton conductivity” of the one-atom-thick crystals, with proposed through-plane conduction, challenged the notion that graphene is impermeable to atoms, ions and molecules. More recent evidence points to a defect-facilitated transport mechanism, analogous to transport through conventional ion-selective membranes based on graphene and h-BN. To clarify the nature of proton transmission through graphene, local ion-flux imaging is performed herein on graphene|Nafion membranes using an “electrochemical ion (proton) pump cell” mode of scanning electrochemical cell microscopy (SECCM). Targeting regions that are free from visible macroscopic defects (e.g., cracks, holes etc.), and assessing hundreds to thousands of different sites across the graphene surfaces in a typical experiment, most of the graphene|Nafion membrane is impermeable to proton transport, with transmission typically occurring at only ≈20 – 60 localized sites across a ≈0.003 mm2 area of membrane (>5000 measurements, total). When localized proton transport occurs, it can be a highly dynamic process, with new transmission sites “opening” and a small number of sites “closing” under an applied electric field, on the seconds timescale. Applying a simple equivalent circuit model of ion-transport through a cylindrical nanopore, the local transmission sites are estimated to possess dimensions (radii) on the (sub)nanometer-scale, implying that rare atomic defects are responsible for proton conductance through monolayer graphene. Overall, this work reinforces SECCM as a premier tool for the structure−property mapping of microscopically complex (electro)materials, with the local ion-flux mapping configuration introduced herein being widely applicable for functional membrane characterization and beyond, e.g., for diagnosing failure mechanisms in protective surface coatings.

High-Resolution Ion-Flux Imaging of Proton Transport Through Graphene|Nafion Membranes

2021 ◽  
Author(s):  
Cameron Bentley ◽  
Minkyung Kang ◽  
Saheed Bukola ◽  
Stephen Creager ◽  
Patrick Unwin
Keyword(s):  
High Resolution ◽  
Proton Transport ◽  
Ion Flux ◽  
Nafion Membranes

Synthesis and structure-property relationships of novel poly(p-xylylene)s with aromatic substituents

e-Polymers ◽  
2001 ◽  
Vol 1 (1) ◽  
Author(s):  
Michael Ishaque ◽  
Ralf Wombacher ◽  
Joachim H. Wendorff ◽  
Andreas Greiner
Keyword(s):  
Chemical Vapor ◽  
Coupling Reaction ◽  
Structure Property ◽  
Ambient Conditions ◽  
Structure Property Relationships ◽  
Aryl Bromides ◽  
Phenyl Rings ◽  
Type Coupling ◽  
Derivatives Of ◽  
Conversion Of Alcohols

AbstractTwo step synthesis of educts for the synthesis of poly(p-xylylene)s was accomplished by Grignard-type coupling reaction of 4-bromotoluene and different aldehydes or p-tolylaldehyde and different aryl bromides followed by conversion of alcohols into corresponding chlorides. Derivatives of poly(p-xylylene) (PPX) were obtained by vapor phase pyrolysis/chemical vapor deposition (CVD) or Gilch-type polymerization of these chlorides. Functional groups along the PPX main chain were introduced by substituted phenyl rings in a-position. The resulting PPXs are soluble under ambient conditions and are amorphous in the solid state. The glass transition temperatures varied only slightly with substituents on the phenyl ring in a-position. Significant enhancement by substituents was found for the thermal stability under nitrogen and a considerable decrease of the surface energies by fluorinated substituents.

Exploring the Photovoltaic Properties of Metal Bipyridine Complexes (Metal = Fe, Zn, Cr, and Ru) by Density Functional Theory

2018 ◽  
Vol 73 (4) ◽  
pp. 337-344 ◽  
Author(s):  
Ahmad Irfan ◽  
Ghulam Abbas
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Photovoltaic Performance ◽  
Open Circuit ◽  
Band Alignment ◽  
Structure Property ◽  
Ambient Conditions ◽  
Photovoltaic Properties ◽  
Functional Theory ◽  
Solar Cell Performance

AbstractThe synthesis and characterisation of mononuclear Fe complexes were carried out by using bipyridine (Compound 1) at ambient conditions. Additionally, three more derivatives were designed by substituting the central Fe metal with Zn, Cr, and Ru (Compound 2, Compound 3, and Compound 4), respectively. The ground state geometry calculations were carried out by using density functional theory (DFT) at B3LYP/6-31G** (LANL2DZ) level of theory. We shed light on the frontier molecular orbitals, electronic properties, photovoltaic parameters, and structure–property relationship. The open-circuit voltage is a promising parameter that considerably affects the photovoltaic performance; thus, we have estimated its value by considering the complexes as donors whereas TiO2 and/or Si were used as acceptors. The solar cell performance behaviour was also studied by shedding light on the band alignment and energy level offset.

Screening effect of monolayer van der Waals crystals on surface deicing: a molecular simulation study

2020 ◽  
Vol 22 (47) ◽  
pp. 27873-27881
Author(s):  
Yue Wang ◽  
Yufeng Guo ◽  
Wanlin Guo
Keyword(s):  
Boron Nitride ◽  
Molecular Simulation ◽  
Simulation Study ◽  
Hexagonal Boron Nitride ◽  
Van Der Waals ◽  
Monolayer Graphene ◽  
Screening Effect ◽  
Nitride Coatings

Significant screening effect of monolayer graphene and hexagonal boron nitride coatings on surface deicing of superhydrophilic and superhydrophobic crystals.

scholarly journals Study on the Compressive Behaviour of Sustainable Cement-Based Composites under One-Hour of Direct Flame Exposure

2020 ◽  
Vol 12 (24) ◽  
pp. 10548
Author(s):  
Ajitanshu Vedrtnam ◽  
Chiara Bedon ◽  
Gonzalo Barluenga
Keyword(s):  
Compressive Strength ◽  
Human Life ◽  
Thermal Exposure ◽  
Fe Model ◽  
Structure Property ◽  
Ambient Conditions ◽  
Residual Compressive Strength ◽  
Fire Scenarios ◽  
Compressive Performance ◽  
By Products

Fire is a significant threat to human life and civil infrastructures. Builders and architects are hankering for safer and sustainable alternatives of concrete that do not compromise with their design intent or fire safety requirements. The aim of the present work is to improve the residual compressive performance of concrete in post-fire exposure by incorporating by-products from urban residues. Based on sustainability and circular economy motivations, the attention is focused on rubber tire fly ash, aged brick powder, and plastic (PET) bottle residuals used as partial sand replacement. The selected by-products from urban residues are used for the preparation of Cement-Based Composites (CBCs) in two different proportions (10% and 15%). Thermal CBC behaviour is thus investigated under realistic fire scenarios (i.e., Direct Flame (DF) for 1 h), by following the International Organization for Standardization (ISO) 834 standard provisions, but necessarily resulting in nonuniform thermal exposure for the cubic specimens. The actual thermal exposure is further explored with a Finite Element (FE) model, giving evidence of thermal boundaries effects. The post-fire residual compressive strength of heated concrete and CBC samples is hence experimentally derived, and compared to unheated specimens in ambient conditions. From the experimental study, the enhanced post-fire performance of CBCs with PET bottle residual is generally found superior to other CBCs or concrete. The structure–property relation is also established, with the support of Scanning Electron Microscopy (SEM) micrographs. Based on existing empirical models of literature for the prediction of the compressive or residual compressive strength of standard concrete, newly developed empirical relations for both concrete and CBCs are assessed.

Phenomena Rlated to Concurrent Multiple Complex Plane Representations of the Immittance Data

1995 ◽  
Vol 411 ◽  
Author(s):  
Mohammad A. Alim
Keyword(s):  
Equivalent Circuit ◽  
Complex Plane ◽  
Selection Criteria ◽  
Heterogeneous System ◽  
Equivalent Circuit Model ◽  
Circuit Model ◽  
The Other ◽  
Structure Property ◽  
Processing Variables ◽  
Complex Planes

ABSTRACTThe concurrent multiple complex plane representation of the single/multiple semicircular relaxation(s) for the same immittance data provides a choice of selecting simultaneously operative phenomena within a heterogeneous system. The origin of this representation and the selection criteria of the phenomena are highlighted via structure-property-processing relationships. These include the development of a single equivalent circuit model by acquiring knowledge on the type of aterials, history, chemistry, composition, processing variables, microstructures, etc. The correspondence within the complex planes is attributed to the relative magnitudes of the contributing elements in the equivalent circuit model and dominance of the operative phenomena. The limitations concerning the transformation of the data from one complex plane to the other are reviewed, considering Debye/non-Debye conduction processes within the series-parallel microstructural network of electrical paths.

scholarly journals Direct evidence for 2-fold to 3-fold change of interpenetration in a MOF

2014 ◽  
Vol 70 (a1) ◽  
pp. C636-C636
Author(s):  
Himanshu Aggarwal ◽  
Prashant Bhatt ◽  
Charl Benzuidenhout ◽  
Leonard Barbour
Keyword(s):  
Single Crystal ◽  
Crystal Engineering ◽  
Molecular Level ◽  
Metal Organic Framework ◽  
Structural Rearrangement ◽  
Structure Property ◽  
Ambient Conditions ◽  
Physical Conditions ◽  
Structure Property Relationships ◽  
Metal Organic

Single-crystal to single-crystal transformations has recently received much attention in the field of crystal engineering. Such transformations not only provide insight into the changes taking place within the crystal at the molecular level, but they also aid our understanding of the structure-property relationships. Discrete crystals have been shown to tolerate considerable dynamic behavior at the molecular level while maintaining their single-crystal character. Examples that are common in the literature include bond formation/cleavage,[1] guest uptake,[2] release or exchange as well as polymorphic phase transformations. However, there are rare examples of the structural transformations on the host framework initiated by removal of guest or change in physical conditions such as temperature or pressure. We have investigated a known doubly-interpenetrated metal organic framework with the formula [Zn2(ndc)2(bpy)] which possesses minimal porosity when activated. We have shown not only that the material converts to its triply-interpenetrated analogue upon desolvation, but that the transformation occurs in a single-crystal to single-crystal manner under ambient conditions.[3] This contribution probes the limits to which a single-crystal material can undergo structural rearrangement while still maintaining the macroscopic integrity of the crystal as a discrete entity.

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