Vitreous carbon — A new form of carbon

Cowlard, F. C.; Lewis, John Courtenay

doi:10.1007/bf00752216

Cited by 250 publications

(121 citation statements)

References 2 publications

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“…Of these forms those most often encountered are diamond and graphite; these two are the allotropes that can be completely characterised. Another form is non-graphitizing vitreous carbon derived from pitches and polymeric precursors or produced by various modern thin film deposition and growth techniques [1]. There are several interpretations of the detailed atomic structure of this class of material, but as shown by Harris [2] the final arrangement is conditional upon the fabrication route adopted.…”

Section: Introductionmentioning

confidence: 99%

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Liu

Flewitt

2017

Carbon

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing AbstractThe local mechanical properties of vitreous carbon and another three porous graphite materials have been investigated using a novel in situ micro-cantilever bending approach.Vitreous carbon is used for validation of the micro-mechanical measurements. Filter graphite is a single phase material with ~52 vol.% porosity. Gilsocarbon graphite is a nuclear-grade graphite that is currently used in the advanced gas-cooled reactors in the UK with ~20 vol.% porosity in the filler particles and matrix; Pile Grade-A graphite (PGA) was extracted from a fuel brick within a Magnox reactor core with 15% weight loss due to neutron irradiation and CO 2 radiolytic oxidation. The 'true' material properties obtained at micro-scale are found to be of much higher value than those measured at the macro-scale due to different failure controlling mechanisms. In particular for the PGA graphite, the micro-mechanical tests allowed the mechanical properties of the filler particles and matrix to be measured separately.The filler particles showed a higher stiffness and flexural strength compared with the matrix indicating the different influence of neutron irradiation on these two constituents. It is demonstrated here that the local mechanical properties of carbonaceous materials with various complex microstructures and even following neutron irradiation can be successfully evaluated.

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Section: Introductionmentioning

confidence: 99%

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Liu

Flewitt

2017

Carbon

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“…18 However, GC is considered to be a nonporous, impermeable and somewhat hydrophobic material, which has subsequently made metals like gold hard to deposit on it. [19][20][21] Given all that, GC oxidation treatment has shown potential of increasing adhesion of metals to GC surfaces. Thermochemical oxidation and electrochemical oxidation pre-treatment of the GC are the two methods that have been reported to address the GC drawbacks as substrate.…”

Section: Npg Based Catalyst On Glassy Carbon (Gc)mentioning

confidence: 99%

Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Xia

Rooney

Ambrozik

et al. 2015

J. Electrochem. Soc.

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Electrochemical (EO) and Thermochemical (TO) oxidation have been considered as means for improved adhesion of metals to glassy carbon (GC) substrates. This paper is aimed at studying the effect of EO on the all-electrochemical processing of nanoporous gold (NPG) catalysts with emphasis on their adhesion to a GC substrate. It has been shown by two independent assessment approaches that EO improves twice the amount of retained NPG on GC helping to keep about 90% originally existing material after a two-hour rotation disk electrode test at 1600 rpm. This work also demonstrates that EO modifies the GC in a way making it more passive in the alloy deposition and subsequent dealloying processes. This effect results in a progressive nucleation density decrease with the depth of oxidation which in turn leads to a lack of continuity of the NPG layer. This trend is also accompanied by a decrease in deposition efficiency as a substantial part of the cathodic current is spent on the reduction of the pre-oxidized GC surface. Our study identifies the best outcome of the trade-off scenario between nucleation density, deposition efficiency and adhesion strength to be associated with depth of oxidation in the range 0.10 to 0.25 μm. NPG based catalyst on glassy carbon (GC).-Nanoporous Au (NPG) is a nano-material with three dimensional (3D) continuous structure featuring Au with interconnected nano-sized pores and ligaments.1 NPG and other nanoporous metals have been intensively investigated in recent years. This conductive material has an open, 3D porous framework with surface areas that even in an ultrathin NPG layer configuration could be an order of magnitude larger than the area of planar Au. Besides its continuous crystal lattice throughout the porous network, it has a pore size that is adjustable via simple thermal post-processing, which makes it potentially applicable in various fields such as electro-and gas-phase catalysis, optics, sensors and actuators. [2][3][4][5] It is known that nanoparticulate gold possesses remarkable catalytic activity toward oxidation reactions, should the particles be well supported and smaller than 5 nmin size. 6 Recently, ultrathin films of NPG have been shown to serve as catalysts for fuel cell applications as an alternative to their nanoparticle (NP) counterparts.7-9 These films are generated electrochemically under precise potential/current control, which minimizes material loss and surface contamination over the multi-step NP synthetic routines. 7,10 Compared to nanoparticle synthesis which often lacks control due to the large number of the processing steps, ultra thin films of NPG are cost effective, simple to fabricate, and show better reproducibility in terms of quality and reactivity. Another advantage of NPG films is that the edge effect that lowers the catalytic activity characteristic for NP based catalysts does not exist in NPG films due to its continuous nature. 11In our previous work, we established an all-electrochemical synthetic method for a NPG-based catalyst that maximized t...

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“…In its unaltered state, GC is considered to be a nonporous, impermeable material [22,23]. At the same time, pores located within the material are closed and can therefore be considered as voids within the impermeable structure.…”

Section: Thermochemical Oxidation For Improved Adhesionmentioning

confidence: 99%

Enhanced Adhesion of Continuous Nanoporous Au Layers by Thermochemical Oxidation of Glassy Carbon

et al. 2014

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Abstract:The fabrication of a nanoporous gold (NPG)-based catalyst on a glassy carbon (GC) support results normally in large isolated and poorly adhering clusters that suffer considerable material loss upon durability testing. This work exploits thermochemical oxidation of GC, which, coupled with the utilization of some recent progress in fabricating continuous NPG layers using a Pd seed layer, aims to enhance the adhesion to the GC surface. Thermochemical oxidation causes interconnected pores within the GC structure to open and substantially improves the wettability of the GC surface, which are both beneficial toward the improvement of the overall quality of the NPG deposit. It is demonstrated that thermochemical oxidation neither affects the efficiency of the Au 0.3 Ag 0.7 alloy (NPG precursor) deposition nor hinders the achievement of continuity in the course of the NPG fabrication process. Furthermore, adhesion tests performed by a rotating disk electrode setup on deposits supported on thermochemically-oxidized and untreated GCs ascertain the enhanced adhesion on the thermochemically-oxidized samples. The best adhesion results are obtained on a continuous NPG layer fabricated on thermochemically-oxidized GC electrodes seeded with a dense network of Pd clusters.

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Vitreous carbon — A new form of carbon

Cited by 250 publications

References 2 publications

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Enhanced Adhesion of Ultrathin Nanoporous Au Deposits by Electrochemical Oxidation of Glassy Carbon

Enhanced Adhesion of Continuous Nanoporous Au Layers by Thermochemical Oxidation of Glassy Carbon

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