Literature

A review on the use of glassy carbon in advanced technological applications

Leonardo de Souza Vieira, 2022

Abstract

Recently, many studies have been conducted on the use of glassy carbon (GC) in advanced technological applications due to its excellent chemical, mechanical, electrical, and thermal properties, making possible fast advances in biomedical, pharmaceutical, electronic, and energy sectors. In this way, this review article reports the latest advances (2017–2021) in the scientific research on the use of GC in diverse technological applications, including scaffolds for tissue engineering, electrochemical sensors for molecular determination, energy storage systems, electrochemical devices for wastewater treatment, tools for precision molding, encapsulation of nuclear waste, and antistatic agent for antistatic packaging. A brief analysis of the number of published articles on the topic is presented, showing how the use of GC has evolved over the years in different technological sectors. The structure, the properties, the production of GC, and the promising areas for further research are also addressed, providing helpful information to foment scientific advances on the use of GC.

A historical review of glassy carbon: Synthesis, structure, properties and applications

Vuk Uskoković, 2021

Abstract

In a letter to her older brother from 1947, soon after she had arrived in Paris, Rosalind E. Franklin said that she was ready to ‘go more primitive’ if this would preserve her freedom. Influential studies on amorphous carbons released prior to her work notwithstanding, fate would have it that by the end of her postdoctoral studies in Paris in 1950, she would provide a seminal insight into the structure of glassy carbon (GC), possibly the most primitive and anarchic of all high-tech materials. Its synthesis, structure, properties and applications are reviewed here from chronological perspectives, focusing on the conceptual milestones in the evolution of the scientific knowledge on it. Fundamentals of the synthesis of GC are elaborated, including the history of its production in the form of particles. Major advances in understanding the complex structure of GC are discussed by focusing on different characterization techniques utilized in the course of these structural elucidations. The most outstanding physical properties of this material, including the anomalous ones, are also summed, along with the complete chronology of reports on its biological properties. In the final section, the numerous applications of GC are being reviewed, including those in electrochemistry, catalysis and self-assembly, as well as in biosensing and biomaterials. Biomedical applications of GC are shown to have been sporadic since its discovery, but a positive trend is traced, showing an increasing interest in this applicative aspect of GC.

Neutron diffraction discriminates between models for the nanoarchitecture of graphene sheets in glassy carbon

Thomas B. Shiell, Dougal G. McCulloch, Jodie E. Bradby, Bianca Haberl, David R. McKenzie, 2021

Abstract

Glassy carbon is a chemically inert, biocompatible, disordered material with the graphene sheet as its basic building block. Structural characterisation techniques have so far been unable to provide definitive distinction between the many proposed models for its structure. Computer based simulation methods have made a step forward by predicting structure from interaction potentials, but the results are sensitive to the choice of the potential. Here we use the white neutron beam of the Spallation Neutron Source at Oak Ridge National Laboratory coupled with the SNAP time-of-flight diffractometer to sample the reciprocal space of glassy carbon and calculate accurate radial distribution functions. From the radial distribution information, we determine graphene sheet dimensions, registration, curvature, and assess defect content to rank the proposed structures in terms of their agreement with experimental data. We find that the recent models derived from empirical potentials give the best agreement.

Graphitization of amorphous carbons: A comparative study of interatomic potentials

Carla de Tomas, Irene Suarez-Martinez, Nigel A. Marks, 2016

Abstract

We perform a comparative study of six common carbon interatomic potentials: Tersoff, REBO-II, ReaxFF, EDIP, LCBOP-I and COMB3. To ensure fair comparison, all the potentials are used as implemented in the molecular dynamics package LAMMPS. Using the liquid quenching method we generate amorphous carbons at different densities, and subsequently anneal at high temperature. The amorphous carbon system provides a critical test of the transferability of the potential, while the annealing simulations illustrate the graphitization process and test bond-making and -breaking. A wide spread of behavior is seen across the six potentials, with quantities such as sp2 fraction, radial distribution function, morphology, ring statistics, and 002 reflection intensity differing considerably. While none of the potentials is perfect, some perform particularly poorly. The lack of transferability can be traced to the details of the functional form, suggesting future directions in the development of carbon potentials.

Modelling of glass-like carbon structure and its experimental verification by neutron and X-ray diffraction

K. Jurkiewicz, S. Duber, H. E. Fischer, A. Burian, 2017

Abstract

Glass-like carbon is a well known carbon form that still poses many challenges for structural characterization owing to a very complex internal atomic organization. Recent research suggests that glassy carbon has a fullerene-related structure that evolves with the synthesis temperature. This article reports on direct evidence of curved planes in glassy carbons using neutron and X-ray diffraction measurements and their analysis in real space using the atomic pair distribution function formalism. Changes in the structure including the degree of curvature of the non-graphitizing glassy carbons as a function of the pyrolysis temperature in the range 800–2500°C (1073–2773 K) are studied using optimized models of the atomic structure. Averaged models of single coherent scattering domains as well as larger structural fragments consisting of thousands of atoms were relaxed using classical molecular dynamics. For such models the diffraction intensities and the pair distribution functions were computed. The compatibility of the computer-generated models was verified by comparison of the simulations with the experimental diffraction data in both reciprocal and real spaces. On the basis of features of the developed structural models for glass-like carbons, the origin of the properties such as high strength and hardness and low gas permeability can be better understood.

Evolution of Glassy Carbon Microstructure: In Situ Transmission Electron Microscopy of the Pyrolysis Process

Swati Sharma, C. N. Shyam Kumar, Jan G. Korvink & Christian Kübel , 2018

Abstract

Glassy carbon is a graphene-rich form of elemental carbon obtained from pyrolysis of polymers, which is composed of three-dimensionally arranged, curved graphene fragments alongside fractions of disordered carbon and voids. Pyrolysis encompasses gradual heating of polymers at ≥ 900 °C under inert atmosphere, followed by cooling to room temperature. Here we report on an experimental method to perform in situ high-resolution transmission electron microscopy (HR-TEM) for the direct visualization of microstructural evolution in a pyrolyzing polymer in the 500–1200 °C temperature range. The results are compared with the existing microstructural models of glassy carbon. Reported experiments are performed at 80 kV acceleration voltage using MEMS-based heating chips as sample substrates to minimize any undesired beam-damage or sample preparation induced transformations. The outcome suggests that the geometry, expansion and atomic arrangement within the resulting graphene fragments constantly change, and that the intermediate structures provide important cues on the evolution of glassy carbon. A complete understanding of the pyrolysis process will allow for a general process tuning specific to the precursor polymer for obtaining glassy carbon with pre-defined properties.

Mechanical Properties for Reliability Analysis of Structures in Glassy Carbon

Cédric Garion, Technology Department, European Organization for Nuclear Research, Geneva, Switzerland., 2014

Abstract

Despite its good physical properties, the glassy carbon material is not widely used, especially for structural applications. Nevertheless, its transparency to particles and temperature resistance are interesting properties for the applications to vacuum chambers and components in high energy physics. For example, it has been proposed for fast shutter valve in particle accelerator. The mechanical properties have to be carefully determined to assess the reliability of structures in such a material. In this paper, mechanical tests have been carried out to determine the elastic parameters, the strength and toughness on commercial grades. A statistical approach, based on the Weibull’s distribution, is used to characterize the material both in tension and compression. The results are compared to the literature and the difference of properties for these two loading cases is shown. Based on a Finite Element analysis, a statistical approach is applied to define the reliability of a structural component in glassy carbon. In this paper, the determination of the mechanical properties of glassy carbon allows the analysis of reliability of structures in glassy carbon.

Approaching theoretical strength in glassy carbon nanolattices

J. Bauer, A. Schroer, R. Schwaiger & O. Kraft, Nature Materials, 2016

The strength of lightweight mechanical metamaterials, which aim to exploit material-strengthening size effects by their microscale lattice structure, has been limited by the resolution of three-dimensional lithography technologies and their restriction to mainly polymer resins. Here, we demonstrate that pyrolysis of polymeric microlattices can overcome these limitations and create ultra-strong glassy carbon nanolattices with single struts shorter than 1 μm and diameters as small as 200 nm. They represent the smallest lattice structures yet produced—achieved by an 80% shrinkage of the polymer during pyrolysis—and exhibit material strengths of up to 3 GPa, corresponding approximately to the theoretical strength of glassy carbon. The strength-to-density ratios of the nanolattices are six times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g cm⁻³ are achieved. Diamond is the only bulk material with a notably higher strength-to-density ratio.

Compressed glassy carbon: An ultrastrong and elastic interpenetrating graphene network

Meng Hu, Julong He, Zhisheng Zhao, Timothy A. Strobel, Wentao Hu, Dongli Yu, Hao Sun, Lingyu Liu,1 Zihe Li, Mengdong Ma, Yoshio Kono, Jinfu Shu, Ho-kwang Mao, Yingwei Fei, Guoyin Shen, Yanbin Wang, Stephen J. Juhl, Jian Yu Huang, Zhongyuan Liu, Bo Xu, and Yongjun Tian, 2017

Abstract

Carbon’s unique ability to have both sp² and sp³ bonding states gives rise to a range of physical attributes, including excellent mechanical and electrical properties. We show that a series of lightweight, ultrastrong, hard, elastic, and conductive carbons are recovered after compressing sp²-hybridized glassy carbon at various temperatures. Compression induces the local buckling of graphene sheets through sp³ nodes to form interpenetrating graphene networks with long-range disorder and short-range order on the nanometer scale. The compressed glassy carbons have extraordinary specific compressive strengths—more than two times that of commonly used ceramics—and simultaneously exhibit robust elastic recovery in response to local deformations. This type of carbon is an optimal ultralight, ultrastrong material for a wide range of multifunctional applications, and the synthesis methodology demonstrates potential to access entirely new metastable materials with exceptional properties.

Glassy carbon electrodes I. Characterization and electrochemical activation

Aleksandar Dekanski, Jasna Stevanović, Rade Stevanović, Branislav Ž Nikolić, Vladislava M Jovanović, 2001

Abstract

Electrochemical properties of glassy carbon electrodes of two types were examined, one thermally treated at 1000°C (sample K) and another thermally treated at 2500° (sample G). Mechanically polished or electrochemically polarized electrodes were characterized in NaOH, HClO₄ and H₂SO₄ solutions by cyclic voltammetry (cv) at different sweep rates in the potential range between the hydrogen and oxygen evolution. The activity of the electrodes depended on the properties of the glassy carbon examined, as determined by both the temperature of thermal treatment and the mechanical or electrochemical pretreatment of the sample. It was noticed that both types of electrodes, when polished exhibited an increase in the double layer charge upon increasing the pH value of the solution. The cv charges, for both types of samples, increase upon anodic polarization. The higher the potential of oxidation, the more pronounced is the increase in charge, particularly in acidic solution. The increase in charge amounts from below 1 mC cm⁻² for polished glassy carbon up to few hundreds of mC cm⁻² for surfaces anodically polarized in acidic solution. Analysis of the dependence of voltammetric charge, as well as morphological changes of the electrode surface, on the time of oxidation suggests the existence of three stages in the electrochemical activation process. The first one occurs only once at the beginning of the activation, while the other two repeat themselves, reflecting a periodical activation and deactivation process. These stages were discussed and ascribed to a surface layer oxidation, graphite oxide layer growth and mechanical destruction of the surface. Independent surface analysis by AES, XPS and STM confirms the results obtained by electrochemical methods.

In Situ Atomic Force Microscopy of Electrochemically Activated Glassy Carbon

D. Alliata, P. Häring, O. Haas, R. Kötz and H. Siegenthaler, 1998

Abstract

Glassy carbon (GC) electrodes were activated by anodic oxidation at a potential of 1.95 V standard calomel electrode in 1 M H2SO4. The activated electrodes were investigated by in situ contact atomic force microscopy. In order to monitor differences between activated and nonactivated areas, part of the electrode surface was covered by a polymeric varnish during electrochemical activation. The edge between activated and nonactivated regions was analyzed after removal of the varnish. The surface of the activated region was significantly higher than that of the nonactivated region, indicating significant swelling of the GC during anodic oxidation. After drying, the activated film collapsed. Swelling of the activated layer was a linear function of activation time and depended on the state of the electrode. In the oxidized state the film thickness was larger than in the reduced state.

Electrochemical corrosion of a glassy carbon electrode

Youngmi Yi, Gisela Weinberg, Marina Prenzel, Mark Greiner, Saskia Heumann, Sylvia Becker, Robert Schlögl, 2017

Abstract

Glassy carbon is widely used in electrochemistry due to its properties of high temperature resistance, hardness, low density and low electrical resistance. The present study focuses on the chemical resistance under electrochemical oxidative conditions, which occur under oxygen-involving reactions like oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The electrochemical performance of glassy carbon investigated in alkaline, neutral and acidic media reveal the same chemical processes during the OER but showing different degradation mechanism.

The electrochemical signature of the corrosion in different media could be directly associated with the formation of oxygen functional groups determined by spectroscopic methods like Raman, infrared (IR) and x-ray photoelectron spectroscopy (XPS). The morphology change of the carbon surface caused by carbon oxidation was investigated by microscopy. A rough surface was obtained in the acidic case, whereas dents were seen in alkaline media.

It is assumed that the glassy carbon electrode in acidic media degrades by forming surface oxides by acid catalyzed process leading to ring opening in the graphitic structure and therefore oxidation in the bulk. In alkaline media OH radicals preferentially react with alkyl site chains, leading to oxidation of the edges of carbon layers until they become hydrophilic and dissolve.

Oxidation Behavior of Glassy Carbon in Acidic Electrolyte

Dr. Sakeb Hasan Choudhury, Dr. Yuxiao Ding, Dr. Youngmi Yi, Dr. Christian Rohner, Wiebke Frandsen, Dr. Thomas Lunkenbein, Dr. Mark Greiner, Prof. Dr. Robert Schlögl and Dr. Saskia Heumann, 2022

Abstract

Glassy carbon is frequently used in electrochemical research due to its presumed robust electrochemical performance. Although it is widely utilized as a rotating disc electrode material, the modification of glassy carbon during electro-catalytic process is rarely emphasized or characterized. In this report, we investigated the structural modification of glassy carbon imparted by electrochemical oxidation in acidic media and compared the behavior with graphite. The functional groups generated from electrochemical oxidation in both electrodes possess similar electrochemical properties. However, above an oxidation potential of 1.8 V (vs. reversibly hydrogen electrode), glassy carbon exhibits a lower electrochemical capacitance compared to graphite. We propose that the existence of electrochemically inactive species, originating from the non-graphitic portion of glassy carbon is attributed to such deterioration. Additionally, high resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM) images corroborate how electrochemical oxidation prevails for glassy carbon electrodes at oxidative potentials. The overall analysis leads us to propose a corrosion mechanism for glassy carbon in acidic solution.

Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

Maria Vomero, Elisa Castagnola, Francesca Ciarpella, Emma Maggiolini, Noah Goshi, Elena Zucchini, Stefano Carli, Luciano Fadiga, Sam Kassegne and Davide Ricci , 2017

Abstract

We report on the superior electrochemical properties, in-vivo performance and long term stability under electrical stimulation of a new electrode material fabricated from lithographically patterned glassy carbon. For a direct comparison with conventional metal electrodes, similar ultra-flexible, micro-electrocorticography (μ-ECoG) arrays with platinum (Pt) or glassy carbon (GC) electrodes were manufactured. The GC microelectrodes have more than 70% wider electrochemical window and 70% higher CTC (charge transfer capacity) than Pt microelectrodes of similar geometry. Moreover, we demonstrate that the GC microelectrodes can withstand at least 5 million pulses at 0.45 mC/cm2 charge density with less than 7.5% impedance change, while the Pt microelectrodes delaminated after 1 million pulses. Additionally, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was selectively electrodeposited on both sets of devices to specifically reduce their impedances for smaller diameters (<60 μm). We observed that PEDOT-PSS adhered significantly better to GC than Pt, and allowed drastic reduction of electrode size while maintaining same amount of delivered current. The electrode arrays biocompatibility was demonstrated through in-vitro cell viability experiments, while acute in vivo characterization was performed in rats and showed that GC microelectrode arrays recorded somatosensory evoked potentials (SEP) with an almost twice SNR (signal-to-noise ratio) when compared to the Pt ones.

Pyrolytic carbon microelectrodes for impedance based cell sensing

Yasmin Mohamed Hassan, Claudia Caviglia, Suhith Hemanth, David M. A. Mackenzie, Dirch H. Petersen1 and Stephan Sylvest Keller, 2016

Abstract

Electrically conductive glass-like carbon structures can be obtained from a polymer template through a pyrolysis process. These structures can be used as electrodes for bio sensing applications such as electrochemical evaluation of cell adhesion and proliferation. This study focuses on the optimization of two dimensional (2D) pyrolytic carbon microelectrodes with the carbon MEMS (C-MEMS) process using the negative epoxy photoresist SU-8. Different electrochemical microchips with carbon working (WE) and counter electrode (CE) were fabricated. More specifically, pyrolysis process was optimized to decrease the resistivity of the resulting carbon material and improve the performance in cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Finally, EIS was used to monitor adhesion and proliferation of HeLa cells.

3D Carbon Scaffolds for Neural Stem Cell Culture and Magnetic Resonance Imaging

Erwin Fuhrer, Anne Bäcker, Stephanie Kraft, Friederike J. Gruhl, Matthias Kirsch, Neil MacKinnon, Jan G. Korvink and Swati Sharma, 2017

Abstract

3D glassy carbon structures with percolated macropores are obtained by pyrolysis of chemically synthesized cryogels featuring tunable porosity. These batch-fabricated structures are used as scaffolds for culturing neural stem cells (NSCs) and are characterized by magnetic resonance imaging (MRI). With the aid of MRI, the successful cultivation of NSCs on a glassy carbon surface and the precise 3D locations of these cell clusters within the opaque scaffold are demonstrated. MRI also yields pore morphology and porosity analyses, pre- and post-pyrolysis. This integrated approach yields a complete 3D dataset of the NSC network, which enables the visual inspection of the morphological details of individual cell clusters without disturbing them or destroying the scaffold. Reported experimental methodology is expected to have an impact on studies designed to understand the mechanism of neurodegenerative disease (ND) development, and can serve as a protocol for the culture of various other types of cells that display compatibility with glassy carbon surfaces.