Papers by Author: Judith A. Roether

Abstract: The electrophoretic deposition (EPD) technique was developed for depositing TiO2 films on stainless steel (SS) and titanium substrates. Titania coatings were obtained in conditions of optimal solution stability using acetylacetone suspensions of TiO2 nanoparticles and I2 at pH≈ 5. Deposition tests were carried out at 10V for varying times. The deposit thickness was seen to increase with EPD time, revealing that the deposits grew quickly for times <120 s, reaching a saturation value at longer times. The substrates were treated by physical and chemical methods before EPD in order to improve the adhesion of the films. The EPD coatings were sintered at 700, 800 and 900 °C under controlled argon atmosphere or in vacuum to study the influence of sintering atmosphere on crystalline phase transformation. The TiO2 coatings were characterized by XRD using Rietveld analysis. The results showed that TiO2 films on Ti substrates (chemically leached before deposition) had better adherence, homogeneity and density than those on SS. The coatings sintered al 700°C in vacuum resulted in a major proportion of anatasa phase. The porosity of the titania coatings sintered at 700°C (2 hr) in vacuum was calculated to be 19% .

Abstract: Electrophoretic deposition (EPD) has been demonstrated to be a convenient processing technique to fabricate composite ceramic coatings containing ordered arrays of carbon nanotubes. In this investigation, EPD was used to coat Ti6Al4V medical implants with hydroxyapatite (HA) layers reinforced with surface functionalized multi-walled carbon nanotubes (MWCNTs). The functionalization of MWCNTs by treating them with an acid mixture was successfully achieved in order to create functional groups on the MWCNT surfaces enabling them to be homogeneously dispersed in water. The surface treatment was also used to induce the adsorption of HA nanoparticles on MWCNT surfaces. Some critical issues, such as microcracking and peeling of HA layers after EPD, were effectively solved by the use of MWCNTs.

Abstract: Multi-walled carbon nanotubes (CNTs) were deposited by electrophoretic deposition on stainless steel substrates forming homogeneous porous CNT deposits. These CNT structures were then coated with a thin layer of Ni by electrodeposition. SEM and TEM observations confirmed that the Ni layer covered uniformly the CNT surfaces. This Ni coating treatment could facilitate the dispersion of CNTs in metal matrix composites leading to improved mechanical and thermal properties.

Abstract: Porous bioresorbable and bioactive composite materials designed for applications as scaffolds in tissue engineering are discussed. The systems fabricated by thermally induced phase separation method and based on poly(D,L-lactide) (PDLLA) or poly(lactic acid-co-glycolic acid) (PLGA) with additions of bioactive glass particles (45S5 Bioglass®) are described in detail. The scaffolds exhibit a well-defined, oriented and interconnected porosity. The porosity structure of foams with and without Bioglass® was characterised by scanning electron microscopy. The in vitro bioactivity and degradability of the composite foams were investigated in contact with phosphate buffer saline (PBS) and simulated body fluid (SBF). High chemical reactivity of scaffolds in SBF, which leads to the prompt formation of bonelike hydroxyapatite crystals on the material surfaces, indicates an enhanced bioactive character of the composites and therefore their potential for use as bone tissue engineering scaffolds.