Bruno A. Latella

Fabrication and Properties of Recycled Cellulose Fibre-Reinforced Epoxy Composites

Epoxy matrix composites reinforced with recycled cellulose fibre (RCF) were fabricated and characterized with respect to their flexural and impact properties. Reinforcement of the epoxy by RCF resulted in a significant increase in the strain at failure, fracture toughness and impact toughness but only a moderate increase in flexural strength and flexural modulus. The effect of accelerated exposure to seawater on the flexural and impact properties was also investigated. The salient toughening mechanisms and crack-tip failure processes were identified and discussed in light of observed microstructures, in particular the orientation of RCF sheets to the applied load.

Mechanical and Fracture Properties of Bamboo

The microstructure, mechanical, impact and fracture properties of Australian bamboo have been investigated. The graded composition and property has been confirmed by depth-profiles obtained by synchrotron radiation diffraction and Vickers indentation. The mechanical performance of bamboo is stronly dependent on age. Results showed that young bamboo has higher strength, elastic stiffness and fracture toughness than its old counterpart. Both crack-deflection and crackbridging are the major energy dissipative processes for imparting a high toughness in bamboo.

Adhesion of Sol-Gel Derived Zirconia Nano-Coatings on Surface Treated Titanium

The morphology , adhesion and tribological properties of the zirconi a sol-gel coatings on phosphate treated, anodized and un-treated titanium surfaces were investigated. The anodization of titanium involves the formation of a thin, compact, oxide layer, which improves the wettability for further coating. This process involves the conversi on of the rutile structure of the original titanium oxide into a mostly crystalline anatase structure. T he samples were anodized in sulphuric and phosphoric acid at varying concentrations. The samp les were anodized at differing currents and differing time periods ranging from 10 to 30 minute s. Phosphate adsorption treatment involves soaking samples in 10% H 3PO4 solution for 10 minutes. These samples were spin coated with zirconia, yield ing 100 nm thick films. The nanocoatings were prepared by alkoxide sol-gel chemistry, using techni ques and protocols developed in an earlier work and were examined with x-ray diffraction, and scannin g electron microscopy. Interfacial and adhesion properties were measured u sing a micromechanical tensile test. The tribological properties were investigated using an Orthopod machine, with commercial grade ultrahigh molecular weight polyethylene (UHMWPE) pins (3 /8 inch diameter) that can articulate in number of different combinations against opposing c oated and control specimens. The UHMWPE pins were used in a bovine serum environment. The a mount of the wear was measured gravimetrically and wear features were observed using SEM. Introduction Surface coatings offer the possibility of modifying the surface pr operties of an surgical component and thereby achieving improvements in performance, reliability and biocompatibi lity. Zirconia films (both nano and macro) produced by different methods are of great interest for variety of biomedical and engineering applications. As a result, a wide range of different d position techniques for zirconia have been proposed. Many of the common thermal barrier coatings and corrosion resistant coatings use plasma or thermal spraying, while several more rec ent techniques have also been used including physical vapour deposition, sputtering, thermal and electron beam e vaporation, plasma MOCVD, electrochemical vapour deposition, and sol-gel processing [1]. The term sol-gel is currently used to describe any chemical procedure or process capable of producing ceramic oxides, non-oxides and mixed oxides from solutions. In this current work we aimed to modify pure titanium metal surfac es by first anodizing and then phosphotazing with specific phosphate adsorption and photocatalysis treatment s o improve the wettability. The specimens were then coated with a sol-gel der ive alkoxide based zirconia for increased biocompatibility and adhesion. After characterization, in thi s preliminary work, tensile Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 455-458 doi:10.4028/www.scientific.net/KEM.254-256.455

Indentation Creep and Adhesion of Hybrid Sol-Gel Coatings

In this study the creep behaviour and adhesion characteristics of hybrid sol-gel silica-based coatings on copper substrates was examined. Sol-gel technology was used to synthesize the organically modified silanes using mixtures of tetraethoxysilane and glycidoxypropyltrimethoxysilane precursors. The creep properties and adhesion behaviour of the coatings were assessed using nanoindentation and microtensile testing, respectively. The link between film structure and creep behaviour was explored. It is shown that the creep response of the coatings is influenced dramatically by the introduction and quantity of the organic substituent.

Mechanical and Physical Properties of Recycled Cellulose Fibre-Reinforced Epoxy Eco-Composites

Epoxy composites reinforced with recycled cellulose fibre (RCF) have been synthesized and characterized. The reinforcement by RCF has resulted in a significant increase in the strain at break, fracture toughness and impact toughness but moderate increase in flexural strength and flexural modulus. The effect of seawater soaking on the flexural and impact properties has also been investigated. The micromechanisms of toughening and crack-tip failure processes are identified and discussed in the light of observed microstructures from in-situ and ex-situ fracture.

Fracture Toughness of Nanoscale Hydroxyapatite Coatings on Titanium Substrates

In the biomedical field, the surface modification of titanium aims to inhibit wear, reduce corrosion and ion release, and promote biocompatibility. Sol-gel-derived ceramic nanoscale coatings show promise due to their relative ease of production, ability to form a physically and chemically uniform coating over complex geometric shapes, and their potential to deliver exceptional mechanical properties due to their nanocrystalline structure. In this study hydroxyapatite coatings on titanium were investigated for their fracture toughness.

Physical and Mechanical Properties of Mullite-Whisker Reinforced Alumina Composites

Reaction sintering and hot-isostatic-pressing (HIP) have been used for the compaction and densification of mullite-whisker-reinforced alumina composites. The effect of alumina matrix constraints on the in-situ transformation sequence in alumina-halloysite-AlF3 system was studied using differential thermal analysis. The physical and mechanical properties of the HIPed samples have been characterized in terms of bulk density, apparent solid density, porosity, Young’s moduli, flexural strength, hardness and the fracture toughness.