Surfaces, characterization

Laser surface treatment can be used either below or beyond the ablation threshold of the surface. Laser treatment is more often used below the ablation threshold of the material, thus inducing efficient modification of the surface composition [12, 18]. Various laser parameters, such as the wavelength, the fluence (laser intensity), the nature of the environmental gas, or the pulse number, may be changed in order to modify the characteristics of the treated surface as the treatment induces the formation of polar chemical species (hydroxyls, carboxyls, peroxides, etc.). Therefore, the use of laser treatment below the ablation threshold induces adhesion improvement mainly through thermodynamic and chemical parameters. 

Furthermore, the laser treatment may be used beyond the ablation threshold of the polymer matrix. Then it induces partial or complete removal of the polymer, depending on the selected laser parameters. 

using a laser fluence above the ablation threshold of the polymer, but below that of the fiber reinforcement of a composite material, leads to complete removal of the polymeric layer without any fiber degradation [11]. 

As explained above, laser parameters are of primary importance in order to achieve suitable surface characteristics [19]. For example, as can be seen in Fig. 20.4, the increase in laser fluence gradually increases the ablation of the 

based on the parameters available, three different ablation rates were studied corresponding to a weak, a medium, and a full ablation according to laser profilometry (Fig. 20.5). The weakly ablated surface possesses the same surface roughness as an untreated sample (Sa=0.6pm). On the contrary, the medium and the fuUy ablated ones exhibit partial and total removal of the polymer layer at the surface of the composite, respectively. In the case of total ablation, the resulting roughness is directly related to the kind of fiber weaving used for reinforcement. 

TABLE 7.13 Surface Analytical Techniques with Typical Detected 

Analytical technique Typical applications Signal detected 

Auger Smface analysis, high-resolution depth profiling Auger electrons from nearsurface atoms 

AFM/STM Surface imaging with near-atomic resolution Atomic-scale roughness 

There are a variety of different methods available for the inspection of the surface of a material.The techniques available can be divided into groups  

Each of these techniques can provide information on a particular aspect of the surface and add to our understanding of the factors that influence the way molecules are arranged at a surface. 

1 Classical Surface Assessment Methods, Contact Angle Measurements  

The simplest method of assessment of the energy of a surface involves the study of contact angles. The most obvious method is the direct measurement of the tangent between a liquid drop and a solid. A liquid drop in contact with a solid will behave according to eqn (9.4). It is possible to determine the contact angle by measuring the dimensions of a liquid drop. 

For very small drops of the order of 10 ml the distorting effect of gravity is negligible and the drop takes the shape of a spherical segment. In this case, the contact angle 6 can be calculated using 

In this category, we consider those methods of characterization which rely on examination of the surface topology of a natural. 

In both metals and nonmetals, reflection from a polished and etched section is a standard method for delineating grain boundaries. Many methods are available for assessing mean grain size from measurements on such sections. The technique is also of particular value in revealing evidence of second phases which frequently segregate at the grain boundary and are therefore very difficult to detect by X-ray methods. 

Grinding and polishing can also change the surface stress patterns, distortions which could later lead to crack formation and fracture. X-ray diffraction line profile analysis appears to be the best method for determining residual stresses, a method which can be applied to polycrystalline materials as well as single crystals. 

Twin boundaries and low-angle grain boundaries can often be observed directly on intersection with the surface. Frequently, the small tilts associated with internal twinning (as in antiferroelectrics) may be observed by reflection microscopy or multiple-beam interferometry. The etch technique used to identify optical and electrical twins in quartz is of considerable practical importance in fabricating piezoelectric oscillator plates.  

Optical surface studies are useful in judging crystal perfection. Etched surfaces can provide quantitative information on internal surfaces and on line defects. Emerging dislocations show etch pits at the surfaces, and etch pit counting is a standard method for determining dislocation densities in metals. In copper, the method is extremely 

A very important aspect when characterizing polymers especially for potential application in biomedicine or biotechnology is the surface characterization since the surface properties of the materials define largely any biological interactions. Again we will focus on some essential methods with special focus on their importance for polymer film in contact with the biosystems and hydrogels. 

Information that can be gained by the various methods cover  

Laboratory of Membrane Technology and Technical Polymer Chemistry. Department of Chemical Technology, Lappeenranta University of Technology (LUT), Lappeenranta, Finland 

Membranes are utilized widely in very different applications, and the requirements for an optimal membrane might differ strongly. There are several commercial membranes on the market from which to choose a suitable membrane. However, fundamental knowledge of the membrane characteristics affecting its performance in a specific application is needed to ensure a good choice. Yet, the information given in the data sheets of the membrane manufacturers is often insufficient. Thus, different membrane surface characterization methods are needed to obtain enough information on the properties of the membranes. 

Advanced Membrane Technology and Applications. W. S. Winston Ho, and T. Matsuura Copyright 2008 John Wiley Sons, Inc. 

Other methods, for instance, nuclear magnetic resonance (NMR) spectroscopy and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), can also be used in the characterization of the chemical composition. Information on these methods can be found elsewhere (Chan and Chen, 2004). 

Detection limit 1 atom% (ATR) a 0.1 atom% 1 atom% 0.1-1 atom% 0.1 atom% 

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It is now a practice to use a variety of surface characterization techniques in the study of chemisorption and catalysis. The examples given here are illustrative most references in this section as well as throughout the chapter will contain results from several techniques. 

Llorca-lsern N and Espanol M 1997 Advanced microscopic techniques for surface characterization Surf. Modif Technol. XI (Proc. 11th Int. Cent) pp 722-35... 

Keita B, Nad]o L and K]oller K 1991 Surface characterization of a single crystal of sodium decatungstocerate (IV) by the atomic force microscope Surf. Sc/. Lett. 256 L613... 

B1.22 Surface characterization and structural determination optical methods... 

Since its initial development, SERS has been used for the surface characterization of a good iiumber of systems. One important extension to the use of SERS has been in the detemiination of surface geometries. Figure Bl.22.6 shows... 

Although the teclmiques described undoubtedly provide valuable results on various materials, the most useful infonuation almost always comes from a combination of several (chemical and physical) surface characterization techniques. Table B1.25.1 gives a short overview of the techniques described in this chapter. 

Table Bl.25.1 Overview of the surface characterization teclmiques described in this chapter.

The final technique addressed in this chapter is the measurement of the surface work function, the energy required to remove an electron from a solid. This is one of the oldest surface characterization methods, and certainly the oldest carried out in vacuo since it was first measured by Millikan using the photoelectric effect [4]. The observation of this effect led to the proposal of the Einstein equation ... 

Measurement of the work fiinction of a surface is an important part of overall surface characterization. 

Different values of will result if the integral limits (i.e., band width) or modulation transfer function in the integral change. All surface characterization instruments have a band width and modulation transfer function. If rms roughness values for the same surface obtained using different instruments are to be compared, optimally the band widths and modulation transfer functions would be the same they should at least be known. In the case of isotropic surface structure, the spatial frequencies p and q are identical, and a single spatial frequency (/>) or spatial wavelength d= /p) is used to describe the lateral dimension of structure of the sample. 

Smooth Surfaces Characterization of Sampie Bidirectionai Scattering Distribution Function... 

Polovina, M., Babic, B., Kaluderovic, B. and Dekanski, A., Surface characterization of oxidized activated carbon cloth. Carbon, 1997, 35(8), 1047 1052. 

Thermal effects, including the dehydrohalogenation of polymers such as polyvinylchloride (PVC) can also occur. However, these effects are the exception and for the most part, XPS can be considered a non-destructive technique for surface characterization. 

Surface Characterization Methods Principles, Techniques, and Applications, edited by Andrew J. Milling... 

Maxima, minima and saddle points are stationary points on a potential energy surface characterized by a zero gradient. A (first-order) saddle point is a maximum along just one direction and in general this direction is not known in advance. It must therefore be determined during the course of the optimization. Numerous algorithms have been proposed, and I will finish this chapter by describing a few of the more popular ones. 

Being sensitive to the chemical composition of the outermost layers of the surface, contact angle measurement is widely used for characterizing polymer surfaces. Surface characterization for polymers using contact angle measurement and XPS will now be described in detail, as these are the most widely used methods. 

His researches and those of his pupils led to his formulation in the twenties of the concept of active catalytic centers and the heterogeneity of catalytic and adsorptive surfaces. His catalytic studies were supplemented by researches carried out simultaneously on kinetics of homogeneous gas reactions and photochemistry. The thirties saw Hugh Taylor utilizing more and more of the techniques developed by physicists. Thermal conductivity for ortho-para hydrogen analysis resulted in his use of these species for surface characterization. The discovery of deuterium prompted him to set up production of this isotope by electrolysis on a large scale of several cubic centimeters. This gave him and others a supply of this valuable tracer for catalytic studies. For analysis he invoked not only thermal conductivity, but infrared spectroscopy and mass spectrometry. To ex-... 

Surface active material, 79, 81 Surface characterization, 45, 46 Surface coverage, 37 Surface enhanced Raman scattering, 45 Surface tension, 23, 25... 

Due to diffraction effects of micron-sized mirrors in a regular array, commonly used techniques for surface characterization based on interferometry are inefficient. To overcome the diffraction effects we have developed a novel surface characterization method with an incoherent light source, based on the Foucault s knife-edge test (Zamkotsian and Dohlen, 1999). Since Leon Foucault introduced the knife-edge test in the last century (Foucault, 1859), it has been widely used for testing optical surfaces (see Ch. 3). The test offers a simple way of obtaining easily understandable, qualitative information of the surface shape. 

Experimental bench for micro-mirror surface characterization using the knife-edge... 

Cepeda-Jimenez C.M., Pastor-Bias M.M., Ferrandiz-Gomez T.P., and Martm-Martmez J.M., 2000, Surface characterization of vulcanized rubber treated with sulfuric acid and its adhesion to polyurethane adhesive, J. Adhes., 73, 135-160. 

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