Papers by Keyword: Glassy Carbon

Abstract: For neural applications, materials able to interface with the brain without harming it while recording high-fidelity signals over long-term implants are still sought after. Glassy Carbon (GC) and Poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT-PSS) have proved to be promising materials for neural interfaces as they show – compared to conventional metal electrodes - higher conductivity, better electrochemical stability, very good mechanical properties and therefore seem to be very promising for in vivo applications. We present here, for the first time, a direct comparison between GC and PEDOT-PSS microelectrodes in terms of biocompatibility, electrical and electrochemical properties as well as in vivo recording capabilities, using electrocorticography microelectrode arrays located on flexible polyimide substrate. The GC microelectrodes were fabricated using a traditional negative lithography processes followed by pyrolysis. PEDOT-PSS was selectively electrodeposited on the desired electrodes. Electrochemical performance of the two materials was evaluated through electrochemical impedance spectroscopy and cyclic voltammetry. Biocompatibility was assessed through in-vitro studies evaluating cultured cells viability. The in vivo performance of the GC and PEDOT-PSS electrodes was directly compared by simultaneously recording neuronal activity during somatosensory stimulation in Long-Evans rats. We found that both GC and PEDOT-PSS electrodes outperform metals in terms of electrochemical performance and allow to obtain excellent recordings of somatosensory evoked potentials from the rat brain surface. Furthermore, we found that both GC and PEDOT-PSS substrates are highly biocompatible, confirming that they are safe for neural interface applications.

Abstract: The effect of the addition of glassy carbon on the structure and properties of ZrO₂-Y₂O₂ coatings deposited at the graphite substrate has been investigated. The coatings were deposited by plasma spraying method in an industrial company Plasma System SA Silesian Siemianowice using MIM40 equipment. The microstructure of coatings was investigated by light microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Abrasion was carried out with the use of tribological tester Ducom by pin-on-disc method. The results of investigations showed that the addition of the glassy carbon into coatings materials has increased microhardness and resistance against the wear.

Abstract: This paper presents the manufacturing process and the results of measurements for aluminum – aluminum oxide materials with addition of glassy carbon particles (GC). The composites were manufactured via high energy milling process with hot pressing subsequently. The influence of mass fraction (5, 10 and 15 wt.%) and a size of GC particles (<40, 40-80, 80-120, 120-160, 160-200µm) on the microstructure and properties were analysed. The complex meaning of GC particles for all, milling process, microstructure and final properties were discovered. After based description of materials, the tribological measurement were performed under two loads – 35 and 50N. It was noted, that mass fraction of GC particles have influence on tribological properties of materials. The composite with 5 wt.% revealed the best friction properties without any significant differences between analysed loads. The influence of particles size proved that the most effective fraction for tribological application is 120 – 160µm.

Abstract: Diamond deposition on carbon substrates is difficult, because atomic hydrogen needed for the diamond growth, attacks the graphitic and amorphous carbon of the substrate. To reduce the etching effect, the duration till diamond layer formation should be short.By controlling the diamond deposition conditions, boron addition and seeding with diamond prior to the deposition, the formation of diamond coatings is possible.Diamond coated carbon substrates are of high interest for electrochemical applications because they show electrical conductivity and are chemically inert in a wide range. Boron doped diamond shows high overvoltage for hydrogen and oxygen and allows electrochemical reactions in water without decomposing it. Diamond was deposited on glassy carbon and electro-graphite.

Abstract: In the presented experiments, the influence of a liquid magnesium alloy with Zr and RE reinforced on glassy carbon particles (GCp) in composites obtained by the mechanical mixing of a suspension, its pressureless solidification and by pressure die casting was examined. The microstructure of the as-received GCp and after their isolation from the composite was characterized by SEM and EDS methods. The presence of a thin oxide type layer with a high RE content was found, independent of the applied composite technology.

Abstract: The magnesium alloy ZRE1 (2.7%Zn, 0.53%Zr, 3,14% rare earth elements) was applied as a matrix of composite reinforced with glassy carbon particles obtained by hot pressing of powder mixture. An influence of matrix chemical composition on interaction processes occurring at the interface was analyzed. The interface microstructure was characterized by scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). It was revealed the continuous bonding between components and a presence of zone enriched with zirconium, rare earth elements and oxygen in comparison to the matrix composition.

Abstract: AMCs due to good thermal and tribological properties, they are applied as the material for: pistons in modern combustion engines, drive shafts, shock absorber cylinders and brake nodes. Heavy-duty operation, especially under tribological conditions, frequently in corrosive environment, requires knowledge on their corrosion resistance. This paper presents the initial results of the research on susceptibility of aluminium alloy matrix composite material reinforced by SiC particles and mixture of SiC+C particles to corrosion. The purpose of the research was to determine the influence of reinforcing phases, their type and shape on corrosion behaviour in a typical corrosion environment, with low NaCl concentration, in relation to the matrix alloy. Determination of corrosion resistance of Al/SiC+C hybrid composite is a new issue and falls within the field of interest of the authors of this article.

Abstract: The paper presents the basics information about manufacturing and selected properties of composite with aluminium alloy matrix containing glassy carbon as a solid lubricant. The so far used method based on mixing the prepared glassy carbon particles with a liquid metal matrix, has been compared with a new method elaborated by the authors of the article. With this novel method carbon is introduced into a composite with the application of liquid carbon precursor and porous ceramic foams. It is then followed by precursor pyrolysis where, as the result, glassy carbon is obtained. Ceramic foams help liquid precursor penetrate the ceramic spheroid pores by forming a thin film of glassy carbon on their walls. The composite produced in such a way features uniform distribution of carbon within its entire volume which significantly improves tribological properties of the composite. Costly mixing procedure is not needed. Sliding friction coefficient of the new composite against cast iron (µ = 0.06-0.28 at wearing in and 0,12 after wearing in) is much lower than in case of composite containing only ceramic foam as a reinforcing phase (μ = 0.25-0.32).

Abstract: Focused-ion-beam (FIB) milling is a modern fabrication technique by using focused energetic ions to ablate material and generate features with nanometer resolution. FIB system with Ga ion source was used in our lab to make moulds for laser-based micro/nano lithography. For FIB milling on glassy carbon, particles in the range of tens of nanometers up to 400 nm can often be found around the area subject to milling, with the composition of carbon and gallium. As the laser-based micro/nano lithography involves thermal process, it is important to identify the dynamic process of those compound nanoparticles during heat treatment. Glassy carbon moulds after FIB milling have been heated in air from room temperature up to 550 oC with temperature ramp rate of 10 oC/min. Scanning Electron Microscope (SEM) was used to record the morphology of the machined surface after heat treatments. Energy dispersive X-ray spectroscopy (EDS) was used for elemental analysis. Particles increase their size before the heating temperature reaches 200 oC. With further temperature increase, new particles nucleate, and grow at the neighbouring of the existing particles via coalescence and Ostwald ripening. When the temperature is over 400 oC, the morphology of nanoparticles changes, due to the evaporation of gallium. When the in air heating reaches 525 oC, cracking starts on the surface of glassy carbon. It is suggested that for in air lithographic application, heating temperature should not exceed 500 oC.

Abstract: The wettability of graphite and glassy carbon surfaces by molten alkali chlorides was measured by the sessile drop method. Pure NaCl, KCl and CsCl, binary NaCl-CsCl and NaCl-KCl and ternary NaCl-KCl-CsCl compositions were measured. CsCl was found to be an interfacially active component (at the solid/liquid interface) in both binary NaCl-CsCl and ternary NaCl-KCl- CsCl systems. From the composition dependence of the interfacial energy in the NaCl-CsCl system the hypothesis is made on the possibility of the existence of 3[ 4 ] Cs NaCl complex.