Structural Characterization Of Surfaces Research Articles

Structural characterization and decontamination of dental calculus for ancient starch research

Ancient dental calculus research currently relies on destructive techniques whereby archeological specimens are broken down to determine their contents. Two strategies that could partly remediate a permanent loss of the original sample and enhance future analysis and reproducibility include (1) structural surface characterization through spectroscopy along with crystallographic and spectroscopic analysis of its molecular structure, and (2) surface decontamination protocols in which the efficacy of cleaning dental calculus prior to extraction is demonstrated. Dental calculus provides ancient starch research a niche where granules may be adsorbed to minerals, coated, overgrown, entrapped, and/or protected from chemical degradation. While encapsulation offers protection from degradation, it does not shield the sample’s surface from contamination. The most common approach to retrieving microbotanical particles from archeological calculus has been the direct decalcification of the sample, after a cleaning stage variously consisting of immersion in water, acids, and mechanical dislodgment via gas, sonication, and/or toothbrushes. Little is known about the efficiency of these methods for a complete removal of sediment/soil and unrelated microbotanical matter. In this paper, controlled laboratory experimentation leads to chemical structural characterization and a decontamination protocol to eradicate starch granules. Several concentrations of acids, bases, and enzymes were tested at intervals to understand their potential to gelatinize and fully destroy starch granules; arriving at a procedure that effectively eradicates modern starch prior to dissolution without damaging the matrix or entrapped starch microremains. This is the first attempt at creating synthetic calculus to understand and systematically test effective decontamination protocols for ancient starch research.

Nonlinear anisotropic diffusion filtering for the characterization of stochastic structured surfaces

Structured surfaces enhance the functionality of components. Well known is the influence of the surface structure on friction and wear behavior. Beyond this, structured surfaces are widely used for various purposes such as optical, biological or mechanical applications. Therefore, the characterization of structured surfaces and surface features becomes increasingly important. The functionality of a surface can either be tested directly or indirectly. Due to the correlation of geometric surface features and its functionality, an indirect and self-evident way is by measuring the surface topography. To obtain the geometric essentials of these features, they need to be separated from the raw surface data. The standard procedure of decomposing a surface topography is by the use of a Gaussian filter bank, gaining so called scale-limited surfaces. This procedure shows drawbacks when characterizing structured surfaces by introducing distortions to the feature boundaries. To overcome these limitations, this work proposes the use of an automatic nonlinear anisotropic diffusion filter as an initial step to separate the features from the residual surface topography because of its edge preserving properties. It is shown that the nonlinear anisotropic diffusion serves well the separation of the features and their geometrical characterization.

On the description of the fractal nature of microstructured surfaces of titanium implants

The determination of the fractal dimension is an interesting way for the characterization of rough surfaces. Microstructured titanium surfaces produced by different technologies (polishing, glass and corundum blasting, vacuum plasma spraying) were investigated by a number of physical and electrochemical methods, i.e. surface profiling, scanning electron microscopy, voltammetry and electrochemical impedance spectroscopy. The data sets obtained by these very different methods were used for the estimation of the fractal dimension of all structures. The aim of this work is to examine the suitability of this additional parameter for a better characterization of structured surfaces and to compare the various applied methods regarding their feasibility. Accompanying cell biological examinations were used to verify whether there is a relation between the parameter fractal dimension and cell behaviour.

X-RAY DIFFRACTION FOR SURFACES AND BURIED INTERFACES

The application of X-rays to the structural characterization of surfaces and interfaces, in situ and in UHV, is discussed on selected examples. Grazing incidence X-ray diffraction is not only a very powerful technique for quantitatively investigating the atomic structure of surfaces and interfaces, but is also very useful for providing information on the interfacial registry for coherent interfaces or on the strain deformation, island and grain sizes for incoherent epilayers.

Structural Characterization of Surfaces and Interfaces of Materials by Applying X-ray Total External Reflection Phenomena

An in-house grazing incidence x-ray scattering (GIXS) apparatus has been newly developed for characterizing the surface structure at a microscopic level. Using this apparatus, surface diffraction profiles from the oxidized SUS304 stainless steel were measured in the vicinity of the critical angle with the GIXS geometry. The depth profile was discussed from the integrated intensities of both oxidized phase and stainless steel bulk. An in-house grazing x-ray reflection apparatus (GXR) has also been newly built for studying the liquid surface, and the liquid/solid and liquid/liquid interfaces. This system was tested by measuring x-ray reflectivity profiles from free surface of mercury and the water/mercury interface. In addition, a new method has been proposed for determining the atomic number density of a near-surface element in materials using grazing x-ray reflection and anomalous dispersion effect. The essential equations for analyzing the measured reflection data were given and the capability of this anomalous grazing x-ray reflection (AGXR) method was well-confirmed by obtaining the atomic number densities of near surface elements with some selected examples of ZrO 2 -Y 2 O 3 crystal and the passivated stainless steel.

Structural characterization of surfaces by extended energy-loss fine-structure spectroscopy

We present recent structural investigations by extended energy-loss fine-structure (EELFS) measurements. The EELFS technique relies on the detection of the fine-structure losses above a core edge in the reflection mode. We demonstrate the possibility of extracting the radial distribution F(R) around each investigated atom. This is obtained by applying to the experimental EELFS data the Fourier transformation and the theoretical analysis used for extended x-ray absorption fine structure (EXAFS) spectroscopy. The aim of this paper is to answer the principal questions addressed by the EELFS technique in the last few years (dipole approximation, phase shift, backscattering amplitude transferability, and quantitative structural parameters, etc.). This is obtained by a systematic investigation on different elements around different core levels and by comparing our experimental spectra with EXAFS spectra. Technological application of the surface-EELFS technique for interface formation studies and clusters lattice parameter determination will be presented and discussed.

Application of asymmetric reflections to the X-ray study of structural deformation of surfaces

A discussion is given of the use of X-ray diffraction in the structural characterization of surfaces and thin films with an arbitrary orientation with respect to the diffracted rays. The instrumental effects arising in a general diffraction geometry are considered in detail with reference to a Bragg-Brentano diffractometer. In particular, intensity variations, peak shifts and broadening are analysed as functions of the scattering angle and the surface orientation. These effects generally obscure the intrinsic structural properties so that an appropriate correction is required in an exhaustive X-ray investigation. Applications are discussed and examples are given in the study of the anisotropic structural properties of PbTe thin films prepared by sputtering onto various substrates.