Glassy Polymeric Carbon Research Articles

Structural and mechanical characterization of ion-irradiated glassy polymeric carbon for TRISO fuel nuclear application

Tristructural isotropic (TRISO) fuel is considered as the fuel design of choice for the next generation of nuclear reactors (Generation IV). Its design consists of a fuel kernel of UO x coated with several layers having different functions. One of these functions is a containment shell/diffusion barrier for the fission fragments. Normally, the material of choice for this shell is pyrolytic carbon (PyC). The material does not offer a perfect barrier, due to its inherent crystalline structure, which is planar (like graphite) and therefore impossible to mold in one continuous sheet around the spherical fuel bead. Plane boundaries allow fragment diffusion at a much higher rate than through the plane. In this study, we investigate the possibility of replacing PyC with a different form of carbon, glassy polymeric carbon (GPC). We prepared samples of GPC and studied the evolution of their physical properties and structure as a function of the radiation environment that they were exposed to. The temperature at which the samples were held during irradiation was very similar to the Generation IV nuclear reactor (∼1000°C). During the fission of U235, the fission fragment mass distribution has two maxima around 98 and 137 amu, which would best correspond to elements Rb and Cs, respectively. However, both ions are hard to produce from our SNICS ion source at the Center for Irradiation of Materials; therefore, we used 107Ag and 197Au as best replacements. The irradiation sessions consisted in various fluences of 5 MeV Ag, and 5 MeV Au. For elemental sample analysis, we used transmission electron microscopy. For mechanical analysis, we used nano-indentation. It is of prime importance to measure the penetration of the implanted 107Ag.and 197Au and the evolution of mechanical properties of GPC irradiated with these ions. A procedure for manufacturing GPC with analysis is presented. This will show how the GPC structure differs as the temperature that it is prepared at increases and how GPC hardness and Young's modulus increased after irradiation.

P.6.d.007 Measuring control beliefs in drug addiction

Glassy Polymeric Carbon (GPC), a biocompatible material, has been proposed for drug encapsulation and delivery. We have shown that a wide range of available porosity in the bulk material can be obtained by careful attention to the method of production and heat treatment of GPC. In addition, ion bombardment is shown to modify the available surface porosity and permeability. These surface characteristics are determined by choice of specie, fluence and energy of the bombarding ions. Together with appropriate drug concentration gradients within the capsule, the capsule can be made to deliver an initial dose rate either higher or lower than the steady state value. The effective surface area, as well as the availability of the pores, can be modified by oxygen or gold ion bombardment either to increase or decrease.

Development of an Alternative Route for Production of Glassy Polymeric Carbon Electrodes in Laboratorial Scale

AbstractA complete alternative and cheaper route for production of glassy polymeric carbon electrodes in laboratorial scale is described. Two kinds of polyphenolic resins were synthesized by mixing the precursors phenol and formaldehyde with 1) ammonium or 2) sodium hydroxide as catalyst. A shorter treatment time of 3.5 days (from 25 to 1000 °C) was employed for preparation of the electrodic material compared with the 5–7 day period proposed in the literature. The obtained materials were inserted into conventional hollow plastic bodies and electrically contacted with copper wire. After proper polishing, the electrodic materials were tested as working electrodes by cyclic voltammetry technique. The data demonstrated that the use of sodium hydroxide causes peculiar problems such as alkaline residues in the electrodic materials and subsequent fading of final product. On the other hand, the materials obtained by the ammonium hydroxide route presented good results in terms of mechanical resistance, glassy appearance, conductivity and voltammetric response, allowing for application of such materials in electrochemistry.

Synthesis, Characterization, and Application of Glassy Polymeric Carbon as Caffeic Acid Sensor

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Investigation of cell growth on ion beam patterns on GPC surface

We have used implanted silver ions near the surface of Glassy Polymeric Carbon (GPC) to completely inhibit cell attachment and adhesion to GPC. The effect improves the safety and function of the GPC heart valve exposed to the blood stream. The strength, durability and low density make GPC a favored material for in vivo medical applications, including transcutaneous electrodes and replacement heart valves. However, the possible release of endothelial tissue that forms on the smooth surfaces of the GPC heart valve has the potential of creating an embolism. We have shown that L929 endothelial cells avoid silver implanted areas of GPC but attach and strongly adhere to areas close to silver implanted surfaces. Patterned ion implantation permits precise control of tissue growth on GPC and other biocompatible substrates. Cell growth inhibited by silver ion implanted patterns on an otherwise biocompatible substrate may be useful for in vitro studies of the way that cells sense and move away from inhospitable environments.

Characterization of Changes in Properties and Microstructure of Glassy Polymeric Carbon Following Au Ion Irradiation

AbstractThe TRISO fuel has been used in some of the Generation IV nuclear reactor designs [1,2]. It consists of a fuel kernel of UOx coated with several layers of materials with different functions. Pyrolytic carbon (PyC) is one of the materials in the layers. In this study we investigate the possibility of using Glassy Polymeric Carbon (GPC) as an alternative to PyC. In this work, we are comparing the changes in physical and microstructure properties of GPC after exposure to irradiation fluence of 5 MeV Au equivalent to a 1 displacement per atom (dpa) at samples prepared at 1000, 1500 and 2000°C. The GPC material is manufactured and tested at the Center for Irradiation Materials (CIM) at Alabama A&M University. Transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used for the analysis.

Effects of Carbon Ion on Glassy Carbon Electrode as Chemical Sensor

AbstractGlassy polymeric carbon (GPC) is a material commonly used for making electrodes for cyclic voltammetric (CV) and amperometric measurements. Previous work done at Alabama A&M University (AAMU) has shown that high energy ion beams can be used to improve the physical properties of GPC in general. In this work, we fabricated a glassy polymeric carbon electrode and we used carbon ions to activate it. Surface analyses including Raman spectroscopy, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were performed to compare the changes in surface morphology and structure before and after carbon ion bombardment.

Determination of Caffeic Acid in Red Wine by Voltammetric Method

AbstractThe electrochemical oxidation of 3,4‐dihydroxycinnamic acid, caffeic acid, leads to a stable electroactive poly(caffeic acid) thin film containing quinone moiety on a preactivated glassy polymeric carbon electrode. The properties of the deposited films as well as the stability study under different experimental conditions were investigated. Taking advantage of the electrochemical behavior, an analytical method based on differential pulse voltammetry for determination of caffeic acid in red wine was proposed.

Ion implantation inhibits cell attachment to glassy polymeric carbon

Implantation of MeV gold, oxygen, carbon ions into GPC alters the surface topography of GPC and enhances the already strong tendency for cells to attach to GPC. We have shown that implantation of silver ions near the surface strongly inhibits cell growth on GPC. Both enhanced adhesion of and inhibition of cell growth are desirable improvements on cardiac implants that have long been successfully fabricated from biocompatible glassy polymeric carbon (GPC). In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that ion beam assisted deposition (IBAD) of silver, as well as silver ion bombardment, can favorably influence the surface of GPC for biomedical applications.

Proton beam effects on phenolic-based composites reinforced with nanopowders

We have introduced various nanopowders in the precursor of glassy polymeric carbon (GPC) and studied the electrical properties as well as the chemical structure. In general the GPC ware produced at Alabama A&M University (AAMU) is used for making crucibles, heat exchangers and for prosthetic devices because of its biocompatibility and inertness. GPC ware at AAMU is synthesized from a phenolic resin solution from Georgia Pacific in a pyrolyzer system at temperatures between 100°C and 2800°C. The heat treatment includes several stages: gelling, curing, postcuring, precarbonization and carbonization. The fabrication of GPC is complicated because of the high production rate of gaseous products in critical temperature ranges where out-diffusion is relatively slow. Special care should be taken in temperature programming to avoid kilning faults and misshapen or porous GPC end results [H. Maleki, L.R. Holland, G.M. Jenkins, et al., Carbon 35 (1997) 227]. In this work we have introduced 1wt% of SiC, carbon nanotubes (CNT) and Al2O3 to the precursor, pyrolyzed composites to 1000°C and studied the effect of 1MeV and 3MeV proton bombardment on the final products.

Enhanced biocompatibility of GPC by ion implantation and deposition

Biocompatible Glassy Polymeric Carbon (GPC) is used for artificial heart valves and in other biomedical applications. Although it is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve sometimes loses adhesion and creates embolisms downstream. We have previously shown that oxygen ion implantation slightly enhances cell adhesion to GPC. Here we compare silver ion implantation and silver deposition, each of which strongly inhibits cell attachment on GPC. Inhibition of cell adhesion is the more desirable improvement to current GPC cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that traces of silver can favorably influence the surface of GPC for biomedical applications.

Investigations of low-energy ion irradiation influence on glassy polymeric carbon

Glassy polymeric carbon (GPC), which is made from phenolic resins, has a high chemical inertness and is used as high temperature and radiation resistant coatings, as high temperature heat-exchangers, as well as a biomaterial in medicine for the manufacture of heart valves and prosthetic devices [G.M. Jenkins, D. Ila, H. Maleki, Mater. Res. Soc. Symp. Proc. 394 (1995) 181]. GPC is also used for the harsh environment of space, as well as for protective coating against extreme environments such as high temperature, highly ionizing radiation, as well as corrosive environments.In this work, we present the results of our investigation of the influence of the low-energy ion irradiation in glow-discharge plasma on GPC.Chemical changes in GPC prepared at 1000°C were studied using FTIR, micro-Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Porosity changes were monitored through introducing lithium from a molten LiCl salt into GPC and using the (p,α) nuclear reaction analysis (NRA) to measure Li concentration in treated GPC.

Patterned Adhesion of Cells

AbstractIt is well known that silver deposition avoids bacterial growth and inhibits the natural process of attachment of connective tissue to biocompatible materials in vivo. We have completed a five year investigation of the precise spatial control of cell growth on glassy polymeric carbon implanted with silver using ion beam techniques, and the persistence of the inhibitory effect on cell growth. Long term inhibition of cell growth on GPC is a desirable improvement on current cardiac implants and other biocompatible materials placed in the blood stream. We have used implanted silver ions near the surface of GPC to completely inhibit cell attachment and adhesion. Cells attach and strongly adhere to areas close to the silver implanted surfaces. Patterned ion implantation permits precise control of tissue growth on GPC and other biocompatible substrates. Cell growth limited to micrometric patterns on a substrate may be useful for in vitro studies of associated biological processes in an otherwise identical environment. The patterned inhibition of cell attachment persists for periods of time significant relative to typical implant lifetimes.

Glassy Polymeric Carbon Resistivity as a Function of Carbon Nanotubes

AbstractGlassy Polymeric Carbon (GPC) is a material widely used because of its high temperature properties, inertness and biocompatibility [1]. GPC samples were prepared from a phenolic resin, cured in a careful process at 100 ºC and pyrolyzed to 1000 ºC. In this work, we have introduced 3wt%, 10wt%, and 20 wt% of Carbon Nano Tubes (CNT) in the precursor resin to study the evolution of the electrical conductivities of the nanocomposite as a function of the CNT concentration.

Study of the Effects of Various Nanopowders in the Properties of GPC

ABSTRACTWe have introduced various nanopowders in the precursor of glassy polymeric carbon (GPC) and studied its electrical, thermal, and mechanical properties as well as its chemical structure. In general the GPC ware produced at AAMU is used for making crucibles, heat exchangers, and for prosthetic devices because of its biocompatibility. GPC ware at AAMU is synthesized from a phenolic resin solution from Georgia Pacific in a pyrolyser system at temperatures between 100 °C all the way to 2800 °C. The heat treatment includes several stages: gelling, curing, postcuring, precarbonization and carbonization. The fabrication of GPC is complicated because of the high production rate of gaseous products in critical temperature ranges where out-diffusion is relatively slow. Special care should be taken in temperature programming to avoid kilning faults and misshapen or porous GPC end results. In this work we have introduced SiC, CNT or Al2O3 to the precursor and studied the properties of the final product treated at 1000oC pyrolysis temperature.

Patterning of Cell Attachment to Biocompatible Glassy Polymeric Carbon by Silver Ion Implantation

ABSTRACTAlthough Glassy Polymeric Carbon (GPC) is ideally suited for implants in the blood stream, tissue that normally forms around the moving parts of a GPC heart valve. There is concern that the tissue lose adhesion and create the condition for embolisms downstream. We have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on GPC, a desirable improvement of current cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in GPC can completely inhibit cell attachment on implanted areas while leaving adjacent areas unaffected. Patterned ion implantation permits precise control of tissue growth on medical applications of GPC.

Surface Modification of Glassy Polymeric Carbon by Glow Discharge

ABSTRACTWe have studied the effects of low energy ion beam produced by glow discharge on glassy polymeric carbon (GPC) produced at pyrolysis temperature ranging from 200C to 1000C. The pristine and irradiated GPC were studied using FTIR, Raman Spectrometry indicating changes at the surface of the GPC samples.

Persistent Inhibition of Cell Growth on Silver Implanted Glassy Polymeric Carbon

ABSTRACTWe have shown that silver ion implantation or argon ion assisted surface deposition of silver inhibits cell growth on Glassy Polymeric Carbon (GPC), a desirable improvement of current cardiac implants. In vitro biocompatibility tests have been carried out with model cell lines to demonstrate that near surface implantation of silver in GPC can completely inhibit cell attachment on implanted areas while leaving adjacent areas vulnerable to strong cell adhesion. After cleaning and sterilization and more than one year in physiologic solution, the silver implanted GPC persists in inhibiting cell attachment.

Chemical, Mechanical and Electrical Properties of Glassy Polymeric Carbon

ABSTRACTGlassy Polymeric Carbon (GPC) is obtained by a molding technique, in various shapes, from a phenolic resin precursor. The heat treatment of the precursor is achieved in three stages up to 1000 °C. Similar GPC materials produced in our laboratory displayed large strain to failure ratio, small thermal expansion coefficient and low density. Like all carbon forms, is attacked by oxygen, especially atomic oxygen. Nevertheless the kinetics for reaction with atmospheric oxygen is very slow. We investigated the composition and structural changes of the phenolic precursor as a function of temperature and evaluated materials stability when exposed to high temperatures in presence of hydrogen or oxygen.

Properties of zinc oxide thin films bombarded with 5 MeV silicon ions

Zinc oxide films are deposited at 300K, on SiO2 quartz or glass and glassy polymeric carbon (GPC), by RF magnetron sputtering using zinc oxide target. The stoichiometry of the deposited oxide was determined by Rutherford backscattering spectrometry (RBS) and the optical band gap by optical absorption measurements. Ion irradiation with 5MeV Si ions was performed to enhance the nucleation process of ZnO islands on the SiO2 surface. The first results show that the stoichiometry of ZnO layers is 1 to 1 and the band gap is 3.3eV. Ion bombardment led to a needle-like surface of the ZnO layer, quite different from the effect of annealing of similar samples. Optical properties and surface morphology of Si bombarded ZnO films were analyzed and compared with ZnO annealed films.