Ultrastructural mechanical and material characterization of fossilized bone

Bone plays a key role in the paleontological and archeological records and can provide insight into the biology, ecology and the environment of ancient vertebrates. Examination of bone at the tissue level reveals a definitive relationship between nanomechanical properties and the local organic content, mineral content, and microstructural organization. However, it is unclear as to how these properties change following fossilization, or diagenesis, where the organic phase is rapidly removed and the remaining mineral phase is reinforced by the deposition of apatites, calcites, and other minerals. While the process of diagenesis is poorly understood, its outcome clearly results in the potential for dramatic alteration of the mechanical response of biological tissues. In this study, fossilized specimens of mammalian long bones, collected from Colorado and Wyoming, were studied for mechanical variations. Nanoindentation performed in both longitudinal and transverse directions revealed preservation of bone's natural anisotropy as transverse modulus values were consistently smaller than longitudinal values. Additionally, modulus values of fossilized bone from 35.0 to 89.1 GPa increased linearly with logarithm of the sample's age. Future studies will aim to clarify what mechanical and material elements of bone are retained during diagenesis as bone becomes part of the geologic milieu. © 2007 Materials Research Society.

Material parameter extraction in THz-TDS using a converging beam transfer function

We demonstrate a parameter extraction algorithm based on a theoretical transfer function, which takes into account a converging THz beam. Using this, we successfully extract material parameters from data obtained for a quartz sample with a THz time domain spectrometer. © 2010 IEEE.

Material properties and tribological performance of rf-PECVD deposited DLC coatings

Diamond-like carbon (DLC) coatings were deposited on to silicon, glass and metal substrates, using an rf-plasma enhanced chemical vapour deposition (rf-PECVD) process. The resultant film properties were evaluated in respect of material and interfacial property control, based on bias voltage variation and the introduction of inert (He and Ar) and reactive (N2) diluting gases in a CH4 plasma. The analysis techniques used to assess the material properties of the films included AFM, EELS, RBS/ERDA, spectroscopic, electrical, stress, microhardness, and adhesion. These were correlated to the tribological performance of the coatings using wear measurements. The most important observation is that He dilution (>90%) promotes enhanced adhesion with respect to all substrate material studies. Coatings typically exhibit a microhardness of the order of 10-20 GPa in films 0.1material and interfacial property control, based on bias voltage variation and the introduction of inert (He and Ar) and reactive (N2) diluting gases in a CH4 plasma. The analysis techniques used to assess the material properties of the films included AFM, EELS, RBS/ERDA, spectroscopic, electrical, stress, microhardness, and adhesion. These were correlated to the tribological performance of the coatings using wear measurements. The most important observation is that He dilution (>90%) promotes enhanced adhesion with respect to all substrate materials studied. Coatings typically exhibit a microhardness of the order of 10-20 GPa in films 0.1 < d < 2 μm thick, with associated electrical resistivity in the range 108 < ρ < 1012 Ω·cm, coefficient of friction <0.1 and surface RMS roughness as low as 2 A. The results are discussed with respect to surface pre-treatment, ion surface bombardment, interfacial reactivity and changes in plasma gas breakdown processes.