Carbon Composite Layers Research Articles

Flexible in-plane Micro-Supercapacitor Prepared by Laser Annealing and Ablation of a Graphene/Polyamide Acid Composite

An in-plane micro-supercapacitor (MSC) which has a unique interdigitated electrode structure with through-holes was developed by laser annealing and ablation of a carbon/polyamide acid composite coating on a polyimide film. The laser annealing of a composite film consisting of multi-layer graphene or activated carbon remarkably lowered the resistivity by laser carbonization of polyamide acid. The laser ablation was conducted to make an interdigitated electrode with a through-hole structure. The through-holes were effective to improve the capacitance of an in-plane MSC by enhancing the ion diffusion in carbon layer because the surface area of carbon layer can be increased using front and back sides of a polyimide film. An in-plane MSC consisting of an asymmetric interdigitated electrode which had an activated carbon composite layer on the front side and a multi-layer graphene composite on back side of a polyimide film showed the improvement of capacitance.

Unveiling Hidden Chemistry between an Aluminum ALD Precursor and Li Metal Anodes

Trimethylaluminum (TMA) is a widely utilized aluminum precursor for atomic layer deposition (ALD) in various aluminum-based coatings. For example, TMA produces Al2O3 with H2O,[1] AlF3 with HF-pyridine,[2] and Al2S3 with H2S [3] with well-defined ALD mechanisms. These ALD processes have been widely applied into various materials to introduce ultra-thin Al-based coating layers, including energy storage materials such as battery cathodes, anodes, and solid electrolytes. Our group demonstrated that the Al2O3 ALD process using TMA can be used for Li-metal anode coating to improve electrochemical stability and reduce Li-dendrite formation during battery cycling.[4]Although many studies about ALD on Li metal anodes have been reported using TMA, most of them focus on Li-metal battery performance, instead of ALD chemistry. During deep investigation on ALD chemistry of TMA, we recently discovered an interesting chemistry between TMA and reactive metal substrate (i.e. Li metal). Based on our observation, TMA reacts with Li-metal during ALD cycles then producing a carbon composite layer on the top of Li metal, not following conventional ALD mechanisms. It may come from highly reactive nature both of TMA and Li metal. Despite of wide use of TMA, this phenomenon has not been reported to date because Li metal is passivated by several layers such as Li2CO3, LiOH and Li2O even stored in glovebox environment. In this presentation, we will discuss the chemistry between TMA and Li metal found by in-situ QCM, high-resolution XPS, SEM, and Raman studies. Then we will also demonstrate how this unexpected ‘side reaction’ can be utilized in Li-metal battery applications using liquid and solid electrolytes.[1] 1. A. C. Kozen et al., ACS Nano, 9, 5884–5892 (2015).[2] Y. Lee, H. Sun, M. J. Young, and S. M. George, Chemistry of Materials, 28, 2022–2032 (2016).[3] X. Meng, Y. Cao, J. A. Libera, and J. W. Elam, Chemistry of Materials, 29, 9043–9052 (2017).[4] L. Chen et al., Journal of Materials Chemistry A, 5, 12297–12309 (2017). Figure 1

Bi2S3 spheres coated with MOF-derived Co9S8 and N-doped carbon composite layer for half/full sodium-ion batteries with superior performance

Bismuth sulfide (Bi2S3) has attracted particular interest as a potential anode material for sodium-ion batteries (SIBs). However, the low electrical conductivity and dramatic volumetric change greatly restrict its practical applications. In view of the apparent structural and compositional advantages of metal-organic frameworks (MOFs) derived carbon-based composite, herein, as a proof of concept, Bi2S3 spheres coated with the MOF-derived Co9S8 and N-doped carbon composite layer (Bi2S3@Co9S8/NC composite spheres) have been rational designed and synthesized. As expected, the core-shell Bi2S3@Co9S8/NC composite spheres exhibit remarkable electrochemical performance in terms of high reversible capacity (597 mAh g−1 after 100 cycles at 0.1 A g−1), good rate capability (341 mAh g−1 at 8 A g−1) and long-term cycling stability (458 mAh g−1 after 1000 cycles at 1 A g−1) when investigated as anode materials for SIBs. Electrochemical analyses further reveal the favorable reaction kinetics in the Bi2S3@Co9S8/NC composite spheres. In addition, the possible sodium storage mechanism has been studied by ex-situ X-ray diffraction technique. More importantly, a sodium-ion full cell based on Na3V2(PO4)3/rGO as cathode and Bi2S3@Co9S8/NC as anode is also fabricated, suggesting their potential for practical applications. It is anticipated that the present work could be extended to construct other advanced electrode materials using MOFs-derived carbon-based composites as surface coating materials for various energy storage-related applications.

Effective Carbon Composite Electrode for Low‐Cost Perovskite Solar Cell with Inorganic CuIn0.75Ga0.25S2 Hole Transport Material

Perovskite solar cells are well known for being low cost, solution‐based, and efficient solar cells; however, the high price of the conventional hole‐collector electrode (Spiro‐OMeTAD/Gold) and the high price and complexity of depositing gold on large scales are major barriers against commercializing them. Herein, an effective carbon composite electrode is introduced for a low‐cost perovskite solar cell with CuIn0.75Ga0.25S2 hole transport material to solve this problem. The carbon electrode is deposited by the doctor blade method using a paste composed of flakes of graphite, carbon black, and a kind of hydrophobic polymer (polystyrene or poly‐methyl methacrylate). It is investigated how the weight ratio of carbon black to graphite and type of binder affect sheet resistance and resistivity of carbon composite layer. The effects of carbon electrode composition on the charge transport resistance at the CuIn0.75Ga0.25S2/perovskite interface are investigated using impedance spectroscopy in different light intensities of white light and light with different wavelengths of 530, 660, and 740 nm. The best efficiency of 15.9% is obtained for the champion cell (fabricated outside the glovebox), which is close to the best efficiency of the reference cell with conventional Spiro‐OMeTAD/Gold hole‐collector that is 16.3%.

Influence of Carbon Nanotubes on the Interlaminar Properties of Carbon Fiber Aluminum Metal Laminates

The present research work describes the fabrication and interlaminar properties testing of carbon fiber aluminum metal laminates (CARALL). CARALL was fabricated through hand layup process followed by compression molding technique and interlaminar properties were assessed through double cantilever beam (DCB) test short beam and flexural test. Different treatments were performed on the surface of aluminum alloy and parameters were optimized to ensure good adhesion between metal sheet and carbon composite layer. Pull-off adhesion test was performed to gauge the adhesion strength of epoxy resin on aluminum alloy sheet. Effect of Multi-wall carbon nanotubes (MWCNTs) was also investigated on the interlaminar properties of CARALL. Treated surface of aluminum alloy sheet was examined under Optical and Field Emission Scanning Electron Microscopy (FE-SEM). Porous surface was evident on aluminum sample due to surface treatment which contributes towards better adhesion between epoxy resin and metal surface through mechanical interlocking and diffusion mechanism. FE-SEM and stereo microscopy was also performed on fractured DCB samples and underlying fracture mechanism was discussed. Test results demonstrated that addition of MWCNTs deteriorated the interlaminar properties of CARALL by weakening the interface between treated aluminum surface and carbon composite.

Monolithic dye sensitized solar cell with metal foil counter electrode

Abstract Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2 (rutile)@SiO2 with average particle size of 300 nm, duo to the high refractive index of rutile TiO2 nanoparticles and good insulating properties of the shells. The best efficiency of 9.5% (8.0% with mask) is achieved with 20 cycles of Pt deposition and spacer layer fabricated by TiO2 (rutile)@SiO2 particles.

Electronic structure and phase composition of dielectric interlayers in multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200

The multilayer amorphous nanostructure [(CoFeB)60C40/SiO2]200 of alternating composite and dielectric layers was obtained by ion-beam sputtering on a rotating pyroceramic substrate of two targets, one of which was a Co40Fe40B20 metal alloy plate with graphite inserts. The dielectric interlayers of SiO2 were sputtered from a quartz plate (second target). The thicknesses of bilayers of the multilayered nanostructure (MNS) (6 nm), consisting of metal–carbon composite layers (CoFeB)60C40 approximately 4 nm in thickness and a silicon oxide dielectric interlayers with a thickness of approximately 2 nm, were determined by small-angle diffraction. The results of experimental layer-by-layer study without destroying the MNS by ultrasoft X-ray spectroscopy (USXES) showed a significant deviation of the stoichiometric composition of the dielectric interlayers from stoichiometry sputtered quartz towards decreasing oxygen concentration with the formation of SiO1.3 suboxide. As a result of simulation of the Si L2,3 spectra of silicon using reference spectra of known phases, the concentration of the silicon suboxide phase in the amorphous dielectric interlayers reaches about half of the interlayer content, the second half of which is accounted for SiO2 dioxide. A “shielding” effect of carbon in the metal layers is manifested in the absence of silicide formation at the interfaces of the multilayer structure under study and should help to increase the anisotropy of their electromagnetic properties.

Electrochemical Dissolution of a Microneedle System for Controlled Drug Release in Smart Devices

The majority of conventional controlled release technologies tend to be based around encapsulant systems in which a polymeric binder or gel typically responds to changes in the local environment in which the delivery device has been placed. The contents are often released when the particle, capsule, film or droplet is exposed to the appropriate physico-chemical trigger (typically a change in pH) with the time-release-dose delivery characteristics controlled through manipulation of the encapsulant formulation. In this communication, the adaptation of this core strategy for use in the next generation of transdermal microdevices or smart patch is explored. The core rationale of this work relates to the development of microneedle patches through which a drug could be transported across the skin barrier upon activation by an appropriate electrochemical trigger. The microneedle in this case serves as the entry point through the strateum corneum whilst acting as a physical barrier to the transport of the drug from a reservoir within the patch. Upon activation, the microneedle dissolves thereby allowing the release of the therapeutic agent as indicated in Figure 1A,B. The methodology proposed herein focuses on the ability to control the dissolution of the conductive composite microneedle through an application of a specified potential trigger. Central to this approach is the design and fabrication of a novel nanostructured conductive film based on a composite of carbon nanoparticles and cellulose acetate phthalate (CAP). This is created through the solvent cast method onto a silicone microneedle template shown in Figure 1C. Under normal conditions, the conductive coating remains intact but, upon imposing a reducing potential on the carbon composite layer, the local pH is increased which results in the solubilisation of the pH sensitive CAP binder components. The latter is the structural glue that holds the microneedle together and thus the subsequent swelling effectively leads to the dissolution of the microneedle architecture and the release of the drug. The presentation covers three aspects: the design and characterisation of the carbon composite microneedles, the ability to electrochemically manipulate the structural integrity of the needles and the ability to effect the controlled release of model drugs such as codeine, methotrexate and fentanyl. Figure 1

High-Resolution, Large-Area Fabrication of Compliant Electrodes via Laser Ablation for Robust, Stretchable Dielectric Elastomer Actuators and Sensors.

A key element in stretchable actuators, sensors, and systems based on elastomer materials are compliant electrodes. While there exist many methodologies for fabricating electrodes on dielectric elastomers, very few succeed in achieving high-resolution patterning over large areas. We present a novel approach for the production of mechanically robust, high-resolution compliant electrodes for stretchable silicone elastomer actuators and sensors. Cast, 2-50 μm thick poly(dimethylsiloxane) (PDMS)-carbon composite layers are patterned by laser ablation and subsequently bonded to a PDMS membrane by oxygen plasma activation. The technique affords great design flexibility and high resolution and readily scales to large-area arrays of devices. We validate our methodology by producing arrays of actuators and sensors on up to A4-size substrates, reporting on microscale dielectric elastomer actuators (DEA) generating area strains of over 25%, and interdigitated capacitive touch sensors with high sensitivity yet insensitivity to substrate stretching. We demonstrate the ability to cofabricate highly integrated multifunctional transducers using the same process flow, showing the methodology's promise in realizing sophisticated and reliable complex stretchable devices with fine features over large areas.

Improvement of structures vibroacoustics by widespread embodiment of viscoelastic materials

Thin walled structures, e.g. aircraft and helicopter fuselages, but also domestic electrical machines, are characterized by poor acoustic behavior. This is mainly due to the very low damping properties of the high efficiency structural elements and materials, prone to transmitting bending vibrations. Such unsatisfactory behavior leads to the need for acoustic treatments, which engender installation costs, troubleshooting problems and weight penalties, especially undesirable in aircraft applications.A possible solution to improve acoustic performance is to dissipate the vibrational energy during its passage through the structure, before coupling with the air of the cabin and becoming noise. The metal–polymer–metal sandwich technique, also adopted with multiple layering, could be exploited to efficiently dissipate bending waves by viscoelastic layers placed through the thickness. Dynamic and acoustic experimental campaigns have been carried out on specimens and panels made of either aluminum alloy or carbon composite layers with viscoelastic inclusions made with styrene–butadiene rubber, testifying the correctness of the idea. The benefits of such approach are tested also in thick cases where multilayered stacking is very efficient. The approach can be exploited irrespectively to the nature of the structural material (composite or metallic) and related technological problems seem to be solved.

Multi-component force measurement using embedded fiber Bragg grating

The development of new fiber Bragg grating (FBG)-based multi-component force sensors is described. A two-component and a three-component force sensor have been fabricated and tested. The two-component force sensor measures the normal and the longitudinal shear component of the force. The three-component force sensor measures the normal, the longitudinal shear and the transverse shear component, and thus provides the magnitude as well as the direction of the force in the three-dimensional space. In the two-component sensor, one FBG is embedded rectilinearly and another non-rectilinearly within carbon composite layer. In the three-component force sensor, one FBG is embedded rectilinearly and two mutually perpendicular FBGs non-rectilinearly within the carbon composite layer. This paper presents the basic sensor structure and the proof-of-concept experimental demonstration of the two sensors. Force measurement within the range 0–15 N has been successfully conducted within 10% deviation.

Mechanical behavior of PACVD TiC–amorphous carbon composite layers

Hard composite layers consisting of TiC and amorphous carbon have been prepared by plasma-assisted chemical vapour deposition. It could be shown by high-resolution transmission electron microscopy (TEM) that nanocrystalline TiC particles are embedded in a matrix of amorphous carbon. Further TEM investigations revealed the occurrence of cracks in regular distances of approximately 400 nm. The stress state of TiC, amorphous carbon (a-C) and TiC/a-C layers was determined by the measurement of the substrate curvature in dependence on the layer thickness. High compressive stress was found for the TiC layers independent of the layer thickness, whereas a-C layers yielded only a low compressive stress. The stress difference of the two components is the reason for crack formation in the composite layers leading to a stress relaxation increasing with the layer thickness. Sliding tests with layers of compositions corresponding to the maximum hardness demonstrated a sliding and abrasive wear behavior comparable to that of PVD metal containing diamond-like carbon.

Mechanical behavior of PACVD TiC–amorphous carbon composite layers

Hard composite layers consisting of TiC and amorphous carbon have been prepared by plasma-assisted chemical vapour deposition. It could be shown by high-resolution transmission electron microscopy (TEM) that nanocrystalline TiC particles are embedded in a matrix of amorphous carbon. Further TEM investigations revealed the occurrence of cracks in regular distances of approximately 400 nm. The stress state of TiC, amorphous carbon (a-C) and TiC/a-C layers was determined by the measurement of the substrate curvature in dependence on the layer thickness. High compressive stress was found for the TiC layers independent of the layer thickness, whereas a-C layers yielded only a low compressive stress. The stress difference of the two components is the reason for crack formation in the composite layers leading to a stress relaxation increasing with the layer thickness. Sliding tests with layers of compositions corresponding to the maximum hardness demonstrated a sliding and abrasive wear behavior comparable to that of PVD metal containing diamond-like carbon.