Surface Characterization Of Materials Research Articles

Wavelength dependence of scattering properties in the VIS–NIR and links with grain-scale physical and compositional properties

Surface scattered sunlight carries important information about the composition and microtexture of surface materials, thus enabling tracing back the geological and climatic processes that occurred on the planetary body. Here we perform laboratory spectro-goniometric measurements of granular samples (45–75μm fraction) with different composition and physical properties over the VIS–NIR spectral range (0.4–2.5μm). To quantify the evolution of the scattering properties over the VIS–NIR, we use an inversion procedure based on a Bayesian approach to estimate photometric parameters from the Hapke radiative transfer model. The granular samples are also carefully characterized by optical and SEM techniques in order to link these scattering variations with the grains’ physical properties. Results show that the scattering properties are wavelength-dependent and can vary significantly over the VIS–NIR spectral range. In particular, the phase function of a granular material is affected by both the absorptivity and the external and internal structure of the grains, from the millimeter scale down to the wavelength scale. Our results also confirm that the macroscopic roughness parameter, as defined by Hapke, is to first order correlated with the absorptivity of the particles, through multiple scattering effects, and thus mostly corresponds to a measurement of the particles shadowing. Photometric datasets, typically obtained at a given wavelength that can vary from one study to another, should therefore be compared and interpreted with caution when extrapolating across wavelengths. Our results also suggest that multi-wavelength photometry could potentially provide a much richer signature than with single-wavelength photometry, opening new perspectives into the characterization of surface materials.

Atomic Force Microscopy for Solar Fuels Research: An Introductory Review

Although research on solar fuel production via water oxidation, hydrogen evolution, and carbon dioxide reduction (i.e., artificial photosynthesis) has grown tremendously in recent years, practical solar fuel devices remain elusive. For these multi-electron transfer processes to take place efficiently, integrated systems constructed from materials with very different chemical, mechanical, and electrical properties are required. This complicated integration presents numerous challenges, including the need for increased characterization of material surfaces and interfaces for both fundamental studies and device optimization. Atomic force microscopy (AFM) is a powerful tool for surface and interface analysis. Although solar fuel research has frequently utilized the basic AFM function of topographic mapping for routine surface analysis, some researchers have avoided more advanced AFM methodologies due to the complexity of these integrated solar fuel generating systems. This article provides researchers in this area with an introduction to various advanced AFM techniques for mechanical, electrical, and chemical analysis on the nanoscale. It also discusses the possibility of in situ study while providing an outline of the working principles of different AFM application modes.

N2/H2 plasma surface modifications of polystyrene inhibit the adhesion of multidrug resistant bacteria

Adhesion is the first step in biofilm formation, a bacterial lifestyle characterized by antimicrobial resistance usually associated with implant infections. In this way, the modification of material surface by plasma processing represents an attractive strategy to understand and control bacterial–material interactions. This work challenged multidrug resistant pathogenic emerging bacteria to adhere on polystyrene submitted to radio frequency discharges. We used N2 and H2 plasma to treat polystyrene surface and we evaluated, using crystal violet assay, the ability of bacteria possessing hydrophobic or hydrophilic surfaces to adhere on the polymer, at distinct periods of shelf life. The material surface characterization was conducted using X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA) measurements. It is shown that the two employed treatments, which differ in duration and power applied to the plasma, are able to inhibit up to 83% Klebsiella pneumoniae adhesion in the first 24h, without biocidal effect. Results from XPS and WCA measurements reveal that nitrogen concentration in excess of 8.8% or polar component of the surface energy above 15mJm−2 are sufficient to produce the beneficial effects sought. The correlation with biological findings indicates that the limited adhesion of bacteria possessing hydrophilic surface on plasma-treated surfaces may be explained in terms of electrostatic repulsion. Therefore, this work demonstrates that the potential application of plasma surface modification extends the possibility of controlling the adhesion of different bacterial species and genera.

Application of Biochar for Phosphate Adsorption and Recovery from Wastewater

Biochar is environmental friendly materials that can be used for environmental protection. In the research, the application of biochar for phosphate adsorption and recovery from wastewater was examined. The material surface characterization analysis, include Transmission Electron Microscope with energy dispersive X-ray spectroscopy and Fourier Transform Infrared spectroscopy, was performed to characterize the prepared biochar. The application analysis, include optimal solution pH and interfering ions effect, was performed for phosphate adsorption and recovery from wastewater. The research conclusions were drawn as follow: (1) material surface characterization demonstrated the prepared biochar was coarse, unshaped, irregular, and contained a great deal of carbon; (2) application analysis indicated biochar adsorption amount for phosphate was decrease with an increase in solution pH, and biochar adsorption amount for phosphate was also decrease with an increase in interfering ions concentration.

Landsat-TM-Based Discrimination of Lithological Units Associated with the Purtuniq Ophiolite, Quebec, Canada

In order to better constrain the utility of multispectral datasets in the characterization of surface materials, Landsat Thematic Mapper (TM) data were evaluated in the discrimination of geological classes in the Cape Smith Belt of Quebec, a greenstone belt that hosts Early Proterozoic units including those of the Purtuniq ophiolite. Ground-based measurements collected for the study area highlight the importance of chemical alteration in controlling the reflectance properties of key geological classes. The spatial distribution of exposed lithologies in the study area was determined through (1) image classification using a feedforward backpropagation neural network classifier; and (2) generation of fraction images for spectral end members using a linear unmixing algorithm and ground reflectance data. Despite some shortcomings, the database of surface cover generated by the neural network classifier is a useful representation of the spatial distribution of exposed geological materials in the study area, with an overall agreement with ground truth of 87.7%. In contrast, the fraction images generated through unmixing are poor representations of ground truth for several key lithological classes. These results underscore both the considerable utility and marked limitations of Landsat TM data in the mapping of igneous and metamorphic lithologies.

Adsorption Competition between H+ and Cd2+ Ions Toward Active Sites on Ionic Imprinted Mercapto-Silica Hybrid

Adsorption process on Cd2+ionic imprinted mercapto-silica hybrid material (Cd(II)-IIP HMS) has been carried out with studying an adsorption competition between ion H+ and Cd2+ ion upon active sites of Cd(II)-IIP HMS material. Characterization of surface material was based on specific surface area, total volume, and porous diameter. Cd(II)-IIP HMS material with template ionic concentration of each 0.107; 0.214; 0.429; 0.658 mmol g-1 shows that adsorption model is relatively similar, the higher of H+ ion competed, the lower of adsorption capacity of Cd(II)-IIP HMS material upon Cd2+ ion. Keywords: adsorption, active site, mercapto-silica hybrid, ionic imprinted

Computation of surface effects and its influence to critical magnetic field in materials

This paper presents one kind of numerical method for investigating a problems related to the surface effects and surface characterization of materials. The aim of this paper is to show development of technique, which is sufficiently simple but effective to compute the surface critical effects of materials. We study such problems on the frame work of the Ginzburg–Landau equations. We choose nucleation field ( H c 3) and the formation of a superconducting state in isotropic type II superconductors situated in magnetic fields, whose magnitude between H c 2 and H c 3, as our physical case. Firstly we introduce the detailed variational approach which is close to the problem of finding the highest magnetic field for which the superconducting sheath states nucleates at the surface of the specimen. By considering the surface effect we can linearise the Ginzburg–Landau equation to get such kind of equation which is Schrödinger’s equation like. We then describe a method for choosing a suitable trial function, which represents the behavior of superconducting order parameter. With Raleigh–Ritz principle the Eigen value of ground state which is related with critical magnetic field H c 3 at which nucleation on the surface appears found computationally thus the methods used in this paper is useful in computational materials. The numerical relation of H c 2 is represented by h with ε that we have found, can be used to predict the nucleation field on specimen’s surface. Beside that by considering angular variation of external magnetic field we find the relation of H c 3 with H c 2 fulfill H c 3 = 1.7 H c 2 and we show that our results are in agreement with physical argument.

Electron beam‐melted, free‐form‐fabricated titanium alloy implants: Material surface characterization and early bone response in rabbits

Titanium-6aluminum-4vanadium implants (Ti6Al4V) were prepared by free-form-fabrication (FFF) and were used either as produced or after machining and compared with wrought machined Ti6Al4V. Auger electron spectroscopy (AES), depth profiles, and interferometry were used to analyze the surface properties. The tissue response after 6-weeks in rabbit femur and tibia was evaluated using light microscopy and histomorphometry. The results revealed that the bulk chemical and mechanical properties of the reference material and the electron beam-melted (EBM) material were within the ASTM F136 specifications. The as-produced EBM Ti6Al4V implants had increased surface roughness, thicker surface oxide and, with the exception of a higher content of Fe, a similar surface chemical composition compared with machined EBM Ti6Al4V and machined, wrought Ti6Al4V implants. The two latter implants did not differ with respect to surface properties. The general tissue response was similar for all three implant types. Histomorphometry revealed a high degree of bone-to-implant contact (no statistically significant differences) for all the three implant types. The present results show that the surface properties of EBM Ti6Al4V display biological short-term behavior in bone equal to that of conventional wrought titanium alloy. The opportunity to engineer geometric properties provides new and additional benefits which justify further studies.

Detection of surface layers using 7Li MAS NMR

Magic angle spinning solid state NMR is generally used to characterize bulk materials. We show here that it is also a promising tool to detect and characterize the diamagnetic surface layer on a paramagnetic material, which is a novel development. We apply this technique to the very hot topic of positive electrode/electrolyte characterization in the field of lithium rechargeable batteries. We report a 7Li MAS NMR study of physisorbed surface layers on LiNi1/2Mn1/2O2, a positive electrode material for lithium ion batteries. 7Li MAS NMR signals arising from surface layers formed by mixing the material with lithium carbonate or from contact of the material with ambient atmosphere, as well as with electrolyte are collected and analyzed. The progressive broadening of the line shape of the MAS NMR spectra reflects the increasing intimacy of the surface layer or secondary phase with the bulk material and therefore gives extremely useful complementary structural information on the surface not available using XPS or IR. We show that relaxation time measurements can be used as a probe of surface layers, allowing for discrimination of interphases from different origins. We propose a detailed analysis of the relaxation curves with a stretched exponential model allowing the description of the distribution of environments inside the surface layer. Our work indicates that MAS NMR can provide useful information for fine surface characterization of materials.

Effect of H and O termination on the charge transfer of moderately boron doped diamond electrodes

Most studies on the electrochemistry of boron doped diamond electrodes deal with highly doped materials which generally act as semi-metallic electrodes. This paper is concerned with the study of the electrochemical behavior of moderately boron doped diamond. The behavior of as-deposited, annealed, and oxidized electrodes in a 2 M H 2SO 4 medium containing the Ce 4+/Ce 3+ redox couple as an electrochemical probe is analyzed in the light of the material surface characterization given by XPS analysis. The results of Mott–Schottky plots and cyclic voltammetry are reported and show that the electrochemical response of these moderately doped electrodes is characteristic of semiconductors. The p +-type conductivity of the surface hydrogenated layer present on as-deposited samples and the influence of surface bond termination—either hydrogen or oxygen—on charge transfer are evidenced.

Characterization of silk fibroin/S-carboxymethyl kerateine surfaces: Evaluation of biocompatibility by contact angle measurements

Surface characterization of materials has been considered critical in the development of biomaterials, as many unfavorable responses from the body occur at the interface between a material and the body component. The contact angle measurement is one means to characterize the surface properties and to correlate them to the biocompatibility of materials. In this paper, surface characteristics of silk fibroin/S-carboxymethyl kerateine, representative fibrous proteins, were investigated by contact angle measurements and ESCA. The biocompatibility of the blends was evaluated based on minimal interfacial free energy concept, and compared with other potential biomaterials. It was also hypothesized that the enhanced surface polarity of the blends was generated from the conformational transition of proteins. This approach to evaluate the biocompatibility of materials based on surface characteristics may find wide utility in many biomedical applications.

Vacuum as a Basis of Science and Technology. Electronic Characterization of Material Surfaces in Vacuum.

Vacuum as a Basis of Science and Technology. Electronic Characterization of Material Surfaces in Vacuum.

超音波顕微鏡を用いた材料表面評価 ( 可視化技術 : 音を見る・音で見る)

超音波顕微鏡を用いた材料表面評価 ( 可視化技術 : 音を見る・音で見る)

Nanometer-scale characterization of surface materials by STM light emission spectroscopy

Three typical applications of the STM light emission spectroscopy in nanometer-scale characterization of surface materials are reviewed. When electrons (holes) are injected from the tip of a STM to a sample surface, visible light is emitted. Since the beam diameter of electrons from the STM tip is narrower than ∼ 1 nm and moreover the beam energy is very low, one can obtain the light emission spectra of individual nanometer-scale structures without modifying them. By correlating the spectra with the size and shape of the structure, materials information about nanometer-scale individual structures can be obtained.

Overview of applications of micromagnetic Barkhausen emissions as noninvasive material characterization technique

In this concise overview, the physical principles of magnetic Barkhausen effect will be briefly discussed and its recent applications in material characterization will be considered. There are new trends in micromagnetic Barkhausen effect emissions and its applications in the material characterization area. These emissions take place in magnetic materials subjected to changing applied magnetic field, and can be used, for instance, to study noninvasively surface characterization of materials. Since these emissions are quite sensitive to changes in the microstructure and subsurface stress states in magnetic materials, various applications of these of micromagnetic emissions have been found in areas such as nuclear, aerospace, and automotive technologies which use magnetic materials.

Surface Characterization of Materials at Ambient Conditions by Scanning Tunneling Microscopy (STM) and Atomic Force Microscopy (AFM)

Abstract The creation of a new family of scanning probe techniques is one of the most exciting events in surface analysis in the last decade. The unique results have been achieved with the main representatives of these techniques—scanning tunneling microscopy (STM) and atomic force microscopy (AFM)-in the visualization of topographic and electronic features in the atomic scale. These new methods attracted many research teams. In a relatively short time, surfaces of different materials (metals, semiconductors, inorganic layered compounds, organic layers, single crystals, polymers, and biological objects) were examined by these techniques. This review is based on ambient conditions STM and AFM experiments conducted at the Materials Research Center of Freiburg University. Two main aspects of the results of imaging transition metal chalcogenides and halides, conductive organic salts, and polymers are emphasized. One is related to interpretation of the images, with the separation of the contributions of the electronic and topographic surface features being the main goal. The realization of this aim, which demands the development of theoretical approaches and comparative analysis with the participation of other surface techniques, will contribute strongly to our understanding of the surface properties of materials. The other aspect concerns the accumulation of knowledge about new methods because many important questions of STM and AFM are still open. The backgrounds of STM and AFM are discussed before the experimental results are presented.

Imaging of cracks in semiconductors using scanning tunneling microscopy

Scanning tunneling microscopy (STM) has developed into a useful tool for atomic-scale characterization of material surfaces. It has a great advantage over other high-resolution techniques in that no extensive sample modification, such as thinning or polishing, is required to obtain atomic resolution images. This is especially useful in the field of fracture, as the vast majority of high-resolution images of fracture processes are made in the transmission electron microscope, where thin-film effects may greatly modify crack tip stresses and dislocation structures. This investigation involved imaging of cracks introduced in single crystals of galena (PbS) by rapid indentation at 77 K. Images were obtained both at the arrested crack tip and along the flanks of the crack in the dynamic growth region. Measurements were made of both crack-tip morphology and upsets observed along the flanks of the crack. The latter is discussed in terms of plasticity upsets associated with dislocation emission from rapidly growing cracks. Effects of STM tip geometry and scan conditions on the resulting image of the cleavage crack, as well as work in progress on other material systems, is discussed.

Imaging of Cracks in Semiconductor Surfaces Using Scanning Tunneling Microscopy

ABSTRACTScanning Tunneling Microscopy (STM) has developed into a useful tool for atomic-scale characterization of material surfaces. It is proving especially useful in the field of fracture, as the vast majority of high-resolution images of fracture processes are made in the transmission electron microscope, where thin film effects and sample preparation may greatly modify crack tip stresses and dislocation structures. This investigation involved imaging of cracks introduced in Si at room temperature and single crystals of galena (PbS) by rapid indentation at 77K. Images were obtained at the arrested cracktip, around the indentation, and along the flanks of the crack in the dynamic growth region. Measurements were made of both crack-tip morphology and upsets observed along the flanks of the cracks in PbS. Interesting results concerning crack tip geometry in Si, the effect of STM tip geometry and scan conditions on the resulting image of the cleavage crack, as well as work in progress on other material systems, will be discussed.

材料表面のミクロな測定と評価

材料表面のミクロな測定と評価

On Surface Characterization of Materials Targeted for Food Contact

ABSTRACTA measurable parameter related to solid surface energy has recently been suggested to provide an index of contact material interactability with components of fluid food. Employing contact angle methods, two series of aqueous solutions were used to evaluate this parameter for a variety of food contact surfaces. Results were independent of which series of diagnostic liquid was used. This supports the identity of the parameter as a true surface property, unique for a given material, and related to the polar character of its surface. Direction is provided toward a means for contact surface characterization which may aid the development and use of models describing food particle behavior at interfaces.