28 research outputs found
Direct observation of ion dynamics in supercapacitor electrodes using in situ diffusion NMR spectroscopy
Ionic transport inside porous carbon electrodes underpins the storage of energy in supercapacitors and the rate at which they can charge and discharge, yet few studies have elucidated the materials properties that influence ion dynamics. Here we use in situ pulsed field gradient NMR spectroscopy to measure ionic diffusion in supercapacitors directly. We find that confinement in the nanoporous electrode structures decreases the effective self-diffusion coefficients of ions by over two orders of magnitude compared with neat electrolyte, and in-pore diffusion is modulated by changes in ion populations at the electrode/electrolyte interface during charging. Electrolyte concentration and carbon pore size distributions also affect in-pore diffusion and the movement of ions in and out of the nanopores. In light of our findings we propose that controlling the charging mechanism may allow the tuning of the energy and power performances of supercapacitors for a range of different applications
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Abstract
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
Nanocomposite of Polyaniline Nanorods Grown on Graphene Nanoribbons for Highly Capacitive Pseudocapacitors
A facile
and cost-effective approach to the fabrication of a nanocomposite
material of polyaniline (PANI) and graphene nanoribbons (GNRs) has
been developed. The morphology of the composite was characterized
by scanning electron microscopy, transmission electron microscopy,
X-ray photoelectron microscopy, and X-ray diffraction analysis. The
resulting composite has a high specific capacitance of 340 F/g and
stable cycling performance with 90% capacitance retention over 4200
cycles. The high performance of the composite results from the synergistic
combination of electrically conductive GNRs and highly capacitive
PANI. The method developed here is practical for large-scale development
of pseudocapacitor electrodes for energy storage
Functionalized Graphene Nanoribbon Films as a Radiofrequency and Optically Transparent Material
We
report that conductive films made from hexadecylated graphene nanoribbons
(HD-GNRs) can have high transparency to radiofrequency (RF) waves
even at very high incident power density. Nanoscale-thick HD-GNR films
with an area of several square centimeters were found to transmit
up to 390 W (2 × 10<sup>5</sup> W/m<sup>2</sup>) of RF power
with negligible loss, at an RF transmittance of ∼99%. The HD-GNR
films conformed to electromagnetic skin depth theory, which effectively
accounts for the RF transmission. The HD-GNR films also exhibited
sufficient optical transparency for tinted glass applications, with
efficient voltage-induced deicing of surfaces. The dispersion of the
HD-GNRs afforded by their edge functionalization enables spray-, spin-,
or blade-coating on almost any substrate, thus facilitating flexible,
conformal, and large-scale film production. In addition to use in
antennas and radomes where RF transparency is crucial, these capabilities
bode well for the use of the HD-GNR films in automotive and general
glass applications where both optical and RF transparencies are desired
Composites of Graphene Nanoribbon Stacks and Epoxy for Joule Heating and Deicing of Surfaces
A seemless three-dimensional carbon nanotube graphene hybrid material
Graphene and single-walled carbon nanotubes are carbon materials that exhibit excellent electrical conductivities and large specific surface areas. Theoretical work suggested that a covalently bonded graphene/single-walled carbon nanotube hybrid material would extend those properties to three dimensions, and be useful in energy storage and nanoelectronic technologies. Here we disclose a method to bond graphene and single-walled carbon nanotubes seamlessly during the growth stage. The hybrid material exhibits a surface area 42,000m2 g1 with ohmic contact from the vertically aligned single-walled carbon nanotubes to the graphene. Using aberration-corrected scanning transmission electron microscopy, we observed the covalent transformation of sp2 carbon between the planar graphene and the single-walled carbon nanotubes at the atomic resolution level. These findings provide a new benchmark for understanding the three-dimensional graphene/ single-walled carbon nanotube-conjoined materials
Radio-Frequency-Transparent, Electrically Conductive Graphene Nanoribbon Thin Films as Deicing Heating Layers
Deicing heating layers are frequently
used in covers of large radio-frequency (RF) equipment, such as radar,
to remove ice that could damage the structures or make them unstable.
Typically, the deicers are made using a metal framework and inorganic
insulator; commercial resistive heating materials are often nontransparent
to RF waves. The preparation of a sub-skin-depth thin film, whose
thickness is very small relative to the RF skin (or penetration) depth,
is the key to minimizing the RF absorption. The skin depth of typical
metals is on the order of a micrometer at the gigahertz frequency
range. As a result, it is very difficult for conventional conductive
materials (such as metals) to form large-area sub-skin-depth films.
In this report, we disclose a new deicing heating layer composite
made using graphene nanoribbons (GNRs). We demonstrate that the GNR
film is thin enough to permit RF transmission. This metal-free, ultralight,
robust, and scalable graphene-based RF-transparent conductive coating
could significantly reduce the size and cost of deicing coatings for
RF equipment covers. This is important in many aviation and marine
applications. This is a demonstration of the efficacy and applicability
of GNRs to afford performances unattainable by conventional materials
Radio-Frequency-Transparent, Electrically Conductive Graphene Nanoribbon Thin Films as Deicing Heating Layers
Deicing heating layers are frequently
used in covers of large radio-frequency (RF) equipment, such as radar,
to remove ice that could damage the structures or make them unstable.
Typically, the deicers are made using a metal framework and inorganic
insulator; commercial resistive heating materials are often nontransparent
to RF waves. The preparation of a sub-skin-depth thin film, whose
thickness is very small relative to the RF skin (or penetration) depth,
is the key to minimizing the RF absorption. The skin depth of typical
metals is on the order of a micrometer at the gigahertz frequency
range. As a result, it is very difficult for conventional conductive
materials (such as metals) to form large-area sub-skin-depth films.
In this report, we disclose a new deicing heating layer composite
made using graphene nanoribbons (GNRs). We demonstrate that the GNR
film is thin enough to permit RF transmission. This metal-free, ultralight,
robust, and scalable graphene-based RF-transparent conductive coating
could significantly reduce the size and cost of deicing coatings for
RF equipment covers. This is important in many aviation and marine
applications. This is a demonstration of the efficacy and applicability
of GNRs to afford performances unattainable by conventional materials
Large-Area Bernal-Stacked Bi‑, Tri‑, and Tetralayer Graphene
Few-layer graphene, with Bernal stacking order, is of particular interest to the graphene community because of its unique tunable electronic structure. A synthetic method to produce such large area graphene films with precise thickness from 2 to 4 layers would be ideal for chemists and physicists to explore the promising electronic applications of these materials. Here, large-area uniform Bernal-stacked bi-, tri-, and tetralayer graphene films were successfully synthesized on a Cu surface in selective growth windows, with a finely tuned total pressure and CH<sub>4</sub>/H<sub>2</sub> gas ratio. On the basis of the analyses obtained, the growth mechanism is not an independent homoexpitaxial layer-by-layer growth, but most likely a simultaneous-seeding and self-limiting process