Richard Wuhrer

On the interface development and fracture behaviour of roll bonded copper/aluminium metal laminates

Copper/aluminium laminates were prepared by roll bonding at 430°C with a 60% rolling reduction in a single pass. Sintering treatments at temperatures between 300 and 500°C were applied to the as-rolled laminates. The interface development and fracture behaviour of the sintered materials were studied. It was found that two major diffusion controlled interface reactions, namely interfacial phase transformations and Kirkendall void formation, occurred in the sintering process. Four different types of phase development were detected in the interface region. As the sintering time and/or temperature increased, the Cu9Al4 phase became dominant. Microhardness measurements confirmed that copper-rich phases possessed higher hardness than the aluminium-rich phases, contributing a higher bond strength. On the other hand, as the sintering time and/or temperature increased, Kirkendall void formation was found to became significant with agglomeration of voids, leading to the formation of a weak layer in the interface region. It was found that the resulting bond strengths of the metal laminates generally increased to maximum values under optimum sintering conditions and then decrease substantially after sintering at high temperatures for prolonged periods.

Study on d.c. magnetron sputter deposition of titanium aluminium nitride thin films: effect of aluminium content on coating

Abstract Titanium aluminium nitride thin films have been deposited on glass slides using a dual unbalanced d.c. magnetron sputter arrangement with separate titanium and aluminium targets. A range of Ti/Al/N compositions were produced by varying the aluminium target magnetron current. The thin films were then examined using an atomic force microscope (AFM) and a field emission scanning electron microscope. Aluminium, titanium and nitrogen compositions (wt.%) were determined by using energy dispersive X-ray spectroscopy. It was found that as the aluminium magnetron current increased from 0.1 to 0.4 A, the titanium decreased from 77 wt.% to 53 wt.%, the aluminium increased from 6 wt.% to 25 wt.% and the colour changed from gold to a blue-grey. An increase in the aluminium content had a significant effect on the grain size of the film. Surface measurement analysis using the AFM results revealed that as the aluminium content increased both the rms roughness (6.5 nm → 3.2 nm) and grain size (120 nm → 90 nm) decreased. It is believed that the above effects could result from the increase in aluminium atom bombardment rate with the higher aluminium magnetron current.

A Sinusoidally Architected Helicoidal Biocomposite.

A fibrous herringbone-modified helicoidal architecture is identified within the exocuticle of an impact-resistant crustacean appendage. This previously unreported composite microstructure, which features highly textured apatite mineral templated by an alpha-chitin matrix, provides enhanced stress redistribution and energy absorption over the traditional helicoidal design under compressive loading. Nanoscale toughening mechanisms are also identified using high-load nanoindentation and in situ transmission electron microscopy picoindentation.

Rolling strain effects on the interlaminar properties of roll bonded copper/aluminium metal laminates

Metal laminates of copper/aluminium were prepared by roll bonding at 430°C with various rolling strains. The effect of the rolling strain on the interface development and bond strength of the laminates was examined. It was found that as the rolling strain increased the bond strength of the laminates was generally enhanced in both as-rolled and sintered conditions. Critical post-rolling sintering conditions were found to exist for achieving optimum bond strengths of the laminates. It is evident that the development of optimum strength for the laminates is related to the formation of various intermetallic phases at the interface which is in turn determined by the diffusion activity of the metallic elements in the area. The greatest strength enhancement was generally observed to develop in the 60% rolled samples, suggesting that rolling strain of the roll bonding process may impose great influence on diffusion of the metallic elements. A higher copper content, without significant Kirkendall void formation, was found to build up in the interface area of the material, leading to development of strong interfacial phases. It is believed that a higher rolling strain of the roll bonding process has provided a greater area of physical contact between the bonded metals and imposed diffusion enhancement of the metallic elements across the interface.

A study on the microstructure and property development of d.c. magnetron cosputtered ternary titanium aluminium nitride coatings. Part III. Effect of substrate bias voltage and temperature

Advanced ternary (Ti,Al)N coatings were produced by reactive magnetron co-sputtering technique with separate titanium and aluminium targets at a 30° magnetron configuration under various substrate bias voltages and temperatures. The effect of substrate bias and temperature on the microstructure and property development of the coatings was investigated. It was found that an increase in substrate bias and/or substrate temperature imposed no major effect on the composition and phase formation of the (Ti,Al)N coatings, but had significant influence on the development of their microstructure and surface morphology. As the substrate bias and/or temperature increased, the coating structure was densified with development of fine grain size and reduced surface roughness, resulting in a substantial increase of the coating hardness. However as the substrate bias increased over 200 volts, excessive residual stress was built up, causing a fracture of the coatings. It is believed that the microstructure and property enhancement is attributed to an increased translational kinetic energy of the depositing atoms and a greater thermal energy provided to the substrate and the coating material with increasing substrate bias and/or temperature. The adatom mobility and the surface diffusion of atoms are enhanced to reduce the detrimental effects induced by the statistical roughening and self-shadowing of asputter deposition process. A densified zone T structure with low porosity and improved properties is produced.

Tissue repair strength using chitosan adhesives with different physical-chemical characteristics

A range of chitosan-based biomaterials have recently been used to perform sutureless, laser-activated tissue repair. Laser-activation has the advantage of bonding to tissue through a non-contact, aseptic mechanism. Chitosan adhesive films have also been shown to adhere to sheep intestine strongly without any chemical modification to chitosan. In this study, we continue to investigate chitosan adhesive films and explore the impact on the tissue repair strength and tensile strength characteristics of four types of adhesive film based on chitosan with different molecular weight and degree of deacetylation. Results showed that adhesives based on chitosan with medium molecular weight achieved the highest bonding strength, tensile strength and E-modulus when compared to the other adhesives.

Corundum (sapphire) and zircon relationships, Lava Plains gem fields, NE Australia: integrated mineralogy, geochemistry, age determination, genesis and geographical typing

Abstract Gem minerals at Lava Plains, northeast Queensland, offer further insights into mantle-crustal gemformation under young basalt fields. Combined mineralogy, U-Pb age determination, oxygen isotope and petrological data on megacrysts and meta-aluminosilicate xenoliths establish a geochemical evolution in sapphire, zircon formation between 5 to 2 Ma. Sapphire megacrysts with magmatic signatures (Fe/Mg ~100-1000, Ga/Mg 3-18) grew with ~3 Ma micro-zircons of both mantle (δ18O 4.5-5.6%) and crustal (δ18O 9.5-10.1%) affinities. Zircon megacrysts (3±1 Ma) show mantle and crustal characteristics, but most grew at crustal temperatures (600-800°C). Xenolith studies suggest hydrous silicate melts and fluids initiated from amphibolized mantle infiltrated into kyanite+sapphire granulitic crust (800°C, 0.7 GPa). This metasomatized the sapphire (Fe/Mg ~50-120, Ga/Mg ~3-11), left relict metastable sillimanite-corundum-quartz and produced minerals enriched in high field strength, large ion lithophile and rare earth elements. The gem suite suggests a syenitic parentage before its basaltic transport. Geographical trace-element typing of the sapphire megacrysts against other eastern Australian sapphires suggests a phonolitic involvement.

A study on the microstructure and property development of d.c. magnetron co-sputtered ternary titanium aluminium nitride coatings Part II Effect of magnetron discharge power

Advanced ternary (Ti,Al)N coatings were produced by reactive magnetron co-sputtering technique with separate titanium and aluminium targets at a 30° magnetron configuration. The aluminium magnetron discharge power was adjusted from 0 to 6.0 W/cm2 to investigate the effect of magnetron discharge power on the microstructure and property development of the coatings. It was found that increasing the aluminium magnetron discharge power caused the deposition rate and the aluminium content to increase, and the grain size and surface roughness of the coatings to decrease substantially. Tighter packing of the grain columns occurred and the microstructure changed from a porous zone 1 to a densified zone T structure, resulting in a continuous increase of the coating hardness. The major texture component of the coatings changed from the (111) to (200) orientations. The (101) orientations of the AlN structure also developed. It was found that the microstructure and hardness enhancement of the coatings was associated with an increased formation of the TiAlN and AlN phases and a densified, fine grain structure at higher magnetron discharge powers.

LIFTING THE LIDS OFF RIPOLIN: A COLLECTION OF PAINT FROM SIDNEY NOLAN'S STUDIO

Abstract A collection of 30 cans of Ripolin paint in 19 different tints from the studio of Australian artist Sidney Nolan provides a unique reference set for the study of this brand of paint. The cans date broadly to the period 1935–1953. All the Ripolin paints in cans from this study were manufactured at the companys English factory in Southall, London, which commenced manufacture in 1932. The paint is of two types, flat and gloss, in a range of colors. Observations made during opening, painting out, and drying the paint have provided information on its working properties. The flat paints with a large proportion of volatile solvents were quick to become touch-dry, whereas the thicker oily liquids present in the gloss paints took up to several weeks to lose tackiness. This observation is supported by Nolans own frustrations regarding the slow drying of Ripolin. Instrumental analysis has identified the pigments present in each color tint. By using Meth-Prep GC-MS on 10 samples, the presence of heat-bodied drying oils and a fatty acid marker for castor oil in one color were detected. Copal and colophony resins were also identified in a number of colors. The highly oxidized state of the resins suggested significant heat treatment during processing.

Low voltage imaging and X-ray microanalysis in the SEM: challenges and opportunities

Low voltage imaging, X-ray microanalysis and X-ray mapping has become very important for the investigation of nanomaterials and their surfaces. This is especially true for low voltage imaging of non-conductive samples and beam sensitive samples. Operating the SEM at lower accelerating voltage allows for greater surface sensitivity, the ability to minimize charging effects, nanometre scale lateral X-ray spatial resolution and nanoscale X-ray depth sensitivity. Determining the correct accelerating voltage for imaging in a SEM is dependent on the instruments operating performance at low voltage, the material being viewed, and other factors that limit effectiveness of low voltage microanalysis, which will be discussed in this paper.