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Biomedical subjects

R Gronsky

Publications and source records attributed to R Gronsky.

11 recordsLinked to original sources
PubMed1998

The influence of sterilization technique and ageing on the structure and morphology of medical-grade ultrahigh molecular weight polyethylene.

The effects of four sterilization treatments (gamma radiation in nitrogen, electron-beam radiation, ethylene oxide gas, and no sterilization) on the structure and morphology of ultrahigh molecular weight polyethylene (UHMWPE) were monitored as a function of ageing time in air for a period of 1.5 y. Characterization techniques employed include differential scanning calorimetry, density gradient column, transmission electron microscopy, and small-angle X-ray scattering. Ethylene oxide gas does not affect the structure of the polymer. Both forms of radiation lead to measurable alterations of the material's structure, including an increase in crystallinity, an increase in density, and the enhancement of lamellae crystalline stacking. Most changes in structure occur in the first few months with little differences observed upon subsequent ageing in air. The sharpness of the crystalline-amorphous boundaries decreases with time for irradiated UHMWPE and is believed to be linked to the oxidation of the polymer.

Journal Article↗
PubMed1997

Oxidation of ultrahigh molecular weight polyethylene characterized by Fourier Transform Infrared Spectrometry.

The effects of processing conditions, sterilization treatment, aging time, and poststerilization aging environment on the oxidation behavior of ultrahigh molecular weight polyethylene (UHMWPE) are examined. Oxidation is monitored by observing changes in the carbonyl peak appearing in Fourier Transform Infrared Spectrometry (FTIR) and is found to be relatively insensitive to processing conditions but strongly influenced by sterilization treatments and aging parameters. Oxygen uptake by UHMWPE increases as a result of gamma or electron beam irradiation and continues to rise during subsequent aging at a rate influenced by the aging environment. A hydrogen peroxide ambient causes more severe oxidation than either air or hyaluronic acid. Control (unsterilized) samples and those sterilized in ethylene oxide are resistant to oxidation under all conditions except hydrogen peroxide aging.

Biocompatible Materials↗
PubMed1995

Preparation of oxide superconductor specimens for TEM examination.

We have investigated a wide variety of oxide superconductors and report here on a number of techniques that can be effectively used to prepare transmission electron microscopy (TEM) specimens from these materials. Crushing, cleaving, ion milling, ultramicrotomy, and jet polishing all were successfully utilized, and details of each technique, as well as equipment used, are described. Selection among these methods depends both on the starting form of the material and the information required. Ion milling and crushing generally give the best results and have the widest applicability in our particular work, while crushing and cleaving involve the least equipment cost. In some cases, particularly with ion milling and jet polishing, small variations in the details of preparation have a dramatic effect on the success rate. We have found it to be a great advantage that the same techniques can be applied in a similar manner to a whole range of oxide materials, even (with some refinements and special precautions) to those that are extremely oxygen or moisture sensitive.

Electric Conductivity↗
PubMed1993

Selected area polishing for precision TEM sample preparation.

A selected area mechanical polishing technique has been developed to improve the precision of cross-sectional TEM sample preparation, based upon the early work of Benedict and colleagues [Benedict et al. (1990) MRS Symp. Proc. Vol. 199, p. 189]. TEM samples were made from a pre-selected section through the middle of a 1 micron wide band of transistors extending laterally for more than 1 mm by precise control over the plane of polish with a corresponding reduction in sample preparation time. To illustrate the application of this technique, a uniformly thin, electron transparent TEM sample of a single, specific, failed transistor is obtained from a 4 mm by 10 mm device array.

Microscopy, Electron↗
PubMed1991

Cross-sectional transmission electron microscopy of X-ray multilayer thin film structures.

A simple method for preparing cross-sectional transmission electron microscopy specimens and discussions of possible artifacts from specimen preparation and observation of x-ray multilayer thin film structures are presented. The specimen preparation method employs mechanical grinding and polishing to approximately 20 microns, followed by ion milling, without dimpling. Artifacts such as preferential ion milling and crystallization under the electron beam, as well as effects of Fresnel fringes at interfaces, are important factors in interpretation of the images. Care in identifying them is required to avoid erroneous results in studies of morphology and microstructures within the layers and at their interfaces. Example high-resolution TEM results of cross-sectional W/C, Ru/C, and Mo/Si multilayers are presented.

Artifacts↗
PubMed1990

Modified embedding procedure for microtomy of large particle zeolites.

A method is described to strengthen the binding of organic resin to inorganic zeolite, allowing large particles to be microtomed. For FeZSM-5 aggregates the particle size limit increased from 3 microns to greater than 20 microns in diameter by application of this method. This technique can be applied to a variety of oxide powder samples, extending the utility of microtomy as a materials science tool.

Aluminum Silicates↗