Ari Ide-Ektessabi

Adhesion failure behavior of sputtered calcium phosphate thin film coatings evaluated using microscratch testing

It is generally accepted that calcium phosphate (CaP) is one of the most important biomaterials in implant coating applications mainly because of its excellent bioactivity. However, its relatively poor mechanical properties limits its application. This entails that a better understanding of the mechanical properties of a CaP coating is a must especially its behavior and the mechanisms involved when subjected to stresses which eventually lead to failure. The mechanical properties of the coating may be evaluated in terms of its adhesion strength. In this study, a radio frequency-magnetron (RF-MS) sputtering technique was used to deposit CaP thin films on 316L stainless steel (SS). The coatings were subjected to series of microscratch tests, taking careful note of its behavior as the load is applied. The adhesion behavior of the coatings showed varying responses. It was revealed that several coating process-related factors such as thickness, post-heat treatment and deposition parameters, to name a few, affect its scratching behavior. Scratch testing-related factors (i.e. loading rate, scratch speed, scratch load, etc.) were also shown to influence the mechanisms involved in the coating adhesion failure. Evaluation of the load-displacement graph combined with optical inspection of the scratch confirmed that several modes of failure occurred during the scratching process. These include trackside cracking, tensile cracking, radial cracking, buckling, delamination and combinations of one or more modes.

Distribution and chemical state analysis of iron in the Parkinsonian substantia nigra using synchrotron radiation micro beams

Metallic elements and their organic compounds have dynamic regulatory functions in cells. Iron concentrations have been observed in the neuromelanin granules in the substantia nigra of brain tissues of patients with Parkinsons disease. Iron has been linked to cell death because of its potential to promote free radicals, leading to oxidative stress. In the present study, we have used synchrotron radiation X-ray fluorescence spectroscopy (SXRF) and Fe K-edge X-ray absorption near-edge structure (XANES) spectroscopy, to investigate distributions and chemical states of iron. The samples were brain tissues from monkeys which had been injected with MPTP (1-metyl-4-phenyl-1,2,3,6-tetrahydropyridine). SXRF analyses were performed for elemental mapping, using 7.16 keV energy beam. The chemical state analyses were performed between 7.16 and 7.12 keV energies. The lower limit was chosen to be slightly above the Fe 2þ absorption edge, in order to suppress the excitation of Fe 3þ . FeO (Fe 2þ ) and Fe2O3 (Fe 3þ ) powders were used for XANES analyses as reference samples. The data were measured in fluorescence mode for the biological specimens and in transmission mode for the reference samples. The results for the Fe 2þ /Fe 3þ ratios from the neuromelanin granules showed significant variations, which were correlated with the level of iron concentration. Cells containing high level of iron had high level of Fe 2þ . With Fe 2þ having been suggested to potentially promote more free radicals than Fe 3þ , the high concentrations of iron may be the critical factor leading to cell death due to the presence of more free radicals.

Preparation of hydroxyapatite layer by ion beam assisted simultaneous vapor deposition

Abstract Hydroxyapatite layer was prepared by using ion beam assisted simultaneous vapor deposition. The method comprised of an electron beam heater and a resistance heater vaporizing CaO and P 2 O 5 , respectively, while an argon ion beam was focused onto the substrate to assist the deposition. The effects of ion beam assistance during deposition were investigated. All deposited layers were amorphous, regardless of the current density level of the ion beam. Post-heat treatment was applied to crystallize the deposited coatings. The Ca/P ratio increased with increasing ion beam current density presumably due to the high sputtering rate of P compared to that of Ca from the layer being coated. Annealing the samples increased the ratio even further due to the evaporation of P at high temperature. Significant improvement in the bond strength between the layer and the substrate was observed. The formation of an intermixed layer at the interface due to the effect of ion beam bombardment is believed to have caused such adhesion property.

Investigation of cellular metallic elements in single neurons of human brain tissues

The purpose of this report is to introduce the potential of synchrotron radiation X-ray fluorescence (SRXRF) spectroscopy, by describing the application of this method to mapping and quantification of metallic elements in neurons from brain tissues affected by Alzheimers disease (AD). In this study, clear images of Fe, Zn and Ca within certain single neurons were obtained. There was a high degree of correlation between Zn and Ca in the groups of cells with lower and relatively higher levels of Ca. These results demonstrate that further investigation with larger numbers of neurons using SRXRF spectroscopy may contribute to advancing the knowledge of the mechanisms of metal-induced cell degeneration in human brain tissues, including those affected by AD.

A Contrast Adjustment Thresholding Method for Surface Defect Detection Based on Mesoscopy

Titanium-coated surfaces are prone to tiny defects such as very small cracks, which are not easily observable by the naked eye or optical microscopy. In this study, two new thresholding methods, namely contrast-adjusted Otsus method and contrast-adjusted median-based Otsus method, are proposed for automated defect detection system for titanium-coated aluminum surfaces. The two proposed methods were compared with four existing thresholding techniques in terms of accuracy and speed of defect detections for images of 700, 900, and 1000 dpi obtained using high-resolution scanning. Experimental results have shown that the proposed contrast-adjusting methods have performance similar to minimum error thresholding (MET) and are generally better than Otsus method.

Characteristics of ion beam modified magnesium oxide films

In this investigation, a novel technique was applied to MgO films for the purpose of improving the secondary electron emission coefficient. It is believed that a high secondary electron emission coefficient of an MgO protective layer could lead to a high performance of a plasma display panel. An oxygen ion beam irradiation was employed at varying modification time. Characterization of the modified MgO surface was performed using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The secondary electron emission coefficient of MgO films was measured using a newly developed apparatus. It was observed that the oxygen ion irradiation increased the secondary electron emission coefficient of MgO films. A significant increase was observed for the MgO films with low ion irradiation time. Results obtained from XPS and AFM suggested that the secondary electron emission coefficient of MgO films was considerably dependent on the surface nano-morphology. High secondary electron emission coefficient was observed for MgO films with a smooth surface.

Ion beam processing of MgO thin films

Thin film of MgO is widely used as a protecting layer of plasma display panel (PDP). We prepared the MgO thin films using ion beam-assisted deposition (IBAD) technique with the aim of controlling the crystal orientation, density and composition of the films. Oxygen ion beam was utilized to irradiate the growing films. The ion beam irradiation was performed by electron cyclotron resonance (ECR) type ion source. The flux of evaporated MgO was produced using an electron gun. Energy and current density of the ion beam as well as deposition rate were taken as the parameters to control the deposition. Crystallinity, density and composition of the films were measured using X-ray diffraction (XRD) and Rutherford backscattering spectroscopy (RBS). Experimental results suggest that the ion beam irradiation during film growth strongly influences the crystal properties of the films to have the best orientation for high efficiency secondary electron emission. It is also confirmed that the oxygen ion irradiation makes the MgO films oxygen-rich.

Application of synchrotron radiation microbeams to environmental monitoring

The aim of this study was to develop a method of environmental monitoring applying X-ray fluorescence (XRF) analysis using synchrotron radiation (SR) microbeams. Teeth were used as specimen due to their advantages as indicators of environmental exposure. In this study, trace element distribution in teeth was investigated by XRF analysis using SR microbeams, and advantages of the techniques applied to environmental monitoring are also discussed.

Ion beam-assisted deposition of magnesium oxide thin film for PDP applications

Abstract MgO thin film is widely used in plasma display panel (PDP) technology. In this paper experimental results on the preparation of MgO thin films using ion beam-assisted deposition is presented and the effects of simultaneous irradiation with oxygen ion beams during film deposition are discussed. The films were deposited on Si and glass substrates. The ion-beam current density was 10 μA/cm 2 . Film preparation was carried out taking the ion beam energy and the deposition rate as variables. Stable, transparent and uniform films of MgO were prepared. The properties of MgO thin films were investigated using X-ray diffraction and Rutherford backscattering spectroscopy. Measurement results of film composition, density and crystallinity are presented.

The effect of sample preparation and calcination temperature on the production of hydroxyapatite from bovine bone powders

The production of hydroxyapatite (HA) from bovine bones was studied in this paper. Bovine hydroxyapatite (BHA) was produced from bovine bone powders by calcination without compaction. The powders were calcined at temperatures ranging from 700–1100°C. It was discovered that sample preparation has some influence on the calcination behavior of the bovine bone powders. XRD results confirmed that HA has been successfully produced but traces of α-TCP and β-TCP were also found. The Ca/P ratios of the BHA powders produced from the process have values greater than 2.0.