Metallic samples, characterization

The predorninant method for the analysis of alurninum-base alloys is spark source emission spectroscopy. SoHd metal samples are sparked direcdy, simultaneously eroding the metal surface, vaporizing the metal, and exciting the atomic vapor to emit light ia proportion to the amount of material present. Standard spark emission analytical techniques are described in ASTM ElOl, E607, E1251 and E716 (36). A wide variety of weU-characterized soHd reference materials are available from major aluminum producers for instmment caUbration. 

Different parameters are nsed to characterize the corrosion rate the loss of mass by the metal sample within a certain length of time (per nnit area), the decrease in sample thickness, the eqnivalent electric cnrrent density, and so on. For most metals nndergoing nniform general corrosion, these parameters in order of magnitude can be interrelated (while allowing for atomic masses and densities) as 1 g/m -yr 10 " mm/yr 10 " A/m. ... 

Besides standard characterization all the samples were further explored by applying FTIR spectroscopy. The scope was to qnantify the acidity of the samples and to discriminate Bronsted from Lewis acid sites. The results of the acidities of the metalated samples are presented in correlation to the corresponding specific snrface areas (Figures 9.1 and 9.2). That is the zeolite snrface area for the Bronsted acid sites and the total surface area for the Lewis acid sites, obviously because the Bronsted acid sites exist only on the zeolitic component of the catalyst, while the Lewis acid sites are present on both matrix and zeolite. 

Actinide metal samples are characterized by chemical and structure analysis. Multielement analysis by spark source mass spectrometry (SSMS) or inductively coupled argon plasma (ICAP) emission spectroscopy have lowered the detection limit for metallic impurities by 10 within the last two decades. The analysis of O, N, H by vacuum fusion requires large sample, but does not distinguish between bulk and surface of the material. Advanced techniques for surface analysis are being adapted for investigation of radioactive samples (Fig. 11) ... 

Characterization of Metal Sites on Supported Metal Catalysts. Characterization of supported metals is usually more difficult. Considerable variation can frequently be found in the state of the reduced metal as a result of apparently minor differences in pretreatment, impurities in the support, or residual water or other contaminants. The problem is most severe with readily oxidizable metals. Ni (10), Mo (11), Re (12) and other metals can all show major variations depending on sample pretreatment and reduction procedures. Even in the case of platinum group metals many complications exist. The frequencies of bands observed when CO is adsorbed in a given manner (e.g. "linear" or "bridged") can shift by up to 100 cm 1 with coverage by CO or between different samples. 

UHV-high-pressure reaction cell are preferable. Such an instrument that has been successfully applied for several years is shown in Fig. 8 (48,84,118). The UHV section (lx 10 mbar) is equipped with tools for sample preparation (Ar ion gun, metal evaporator, quartz crystal microbalance) as well as sample characterization by FEED, AES, and thermal desorption spectroscopy (TDS). After analysis of the model catalysts under UHV, the samples are transferred (still under UHV) to the SFG cell. When the manipulator is lowered to the SFG level, the sample holder is... 

The development of new catalytic materials needs to be complemented with detailed studies of the surface chemistry of catalysis at the molecular level in order to better define the requirements for the catalytic active sites. The wide array of modem spectroscopies available to surface scientists today is ideally suited for this task (see Surfaces). Surface science studies on catalysis typically probe reaction intermediates on model metal samples under well controlled conditions. This kind of study is traditionally carried out in ultrahigh vacuum (UHV) systems such as that shown in Figure 10. Single crystals or other well-defined metal surfaces are cleaned and characterized in situ by physical and chemical means, and then probed using a battery of surface sensitive techniqnes snch as photoelectron (XPS and UPS), electron energy loss (ELS... 

For metal samples flame and furnace AAS are both important methods of analysis. They find use in the characterization of raw materials and for product analysis. In combination with matrix removal in particular, they are further indispensible for the characterization of laboratory standards. These are used to calibrate direct methods such as x-ray spectrometry and spark emission spectrometry for production control. However, it should be mentioned that specific elements of interest such as B, the rare earths, Hf and Zr, can be determined much better by plasma emission spectrometry. 

Not only is there a need for the characterization of raw bulk materials but also the requirement for process controled industrial production introduced new demands. This was particularly the case in the metals industry, where production of steel became dependent on the speed with which the composition of the molten steel during converter processes could be controlled. After World War 11 this task was efficiently dealt with by atomic spectrometry, where the development and knowledge gained about suitable electrical discharges for this task fostered the growth of atomic spectrometry. Indeed, arcs and sparks were soon shown to be of use for analyte ablation and excitation of solid materials. The arc thus became a standard tool for the semi-quantitative analysis of powdered samples whereas spark emission spectrometry became a decisive technique for the direct analysis of metal samples. Other reduced pressure discharges, as known from atomic physics, had been shown to be powerful radiation sources and the same developments could be observed as reliable laser sources become available. Both were found to offer special advantages particularly for materials characterization. 

The principal reason for the increasing importance of metal NMR as a means for sample characterization is simply the more general availability of commercial broad-band NMR spectrometers, with a typical range of RF components from 5 - 500 MHz. The range from low frequency metals, such as rhodium, on up to relatively high frequency nuclei such as phosphorus can typically be spanned using... 

Characterization. Actinide metal samples for the determination of properties related to bonding have to be characterized for chemical purity and phase homogeneity. Purity is checked by chemical or physical analysis, crystal structure is determined by X-ray or neutron diffraction techniques phase heterogeneities can be observed by metallography. 

Fig. 4(a) presents the reflection spectra from the (111) composite surface at normal light incidence. The spectra were measured at two temperature values below the phase transition temperature (the semiconductor phase) and above it (the metallic phase). The observable peaks are due to the Bragg diffraction of electromagnetic waves by the periodic stmeture of the samples, characterizing the stop band in the [111] direction. 

The La2Ni04samples were obtained from P. Odier. Both semiconducting and metallic samples were prepared and fully characterized by techniques previously described in the literature ll. 

Base-Metal Microstructures. The mill-aimealed base-metal sample exhibited a bimodal microstructure, with bands of cc grains and colonies of transformed p. On the other hand, the P-aimealed microstructure was composed of large prior-p grains decorated with grain-boundary a. The grain interiors were characterized by a lamellar structure of cc -i- p colonies. 

In this chapter we first provide an overview of eommonly applied synchrotron radiation-based X-ray techniques for determining metal speciation in powdered samples, including X-ray absorption spectroscopy, micro X-ray fluorescence, and micro X-ray diffraction (XRD). The seeond part of this ehapter will provide an example of the application of these teehniques to an investigation of lead (Pb) speciation in a house dust sample, characterized by elevated total and bioaccessible Pb concentrations. 

As mentioned earlier, specifications for DU whether it is intended for use in munitions, radiation shielding, or aircraft ballast are difficult to find. In any case, the analytical procedures for its characterization, described earlier for other uranium compounds, are valid also for DU. Dissolution of the metal samples in concentrated nitric acid (HF may be added if residues remain) is required for meticulous analysis of impurities by ICP-OES, ICP-MS, or/and other suitable analytical method. Conversion to UjO in a muffle furnace with steam for impurity determination by DC-arc is also an option. Determination of the H, C, N, O, and S content with dedicated instrumentation may also be carried out. On the other hand, the impurity requirements for DU are not as strictly controlled as they are for other nuclear materials. If the depleted uranium is alloyed, as mentioned earlier to improve the mechanical properties, the concentration of the alloying element must be determined according to specifications. 

Figure 3.4 (a) Schematic diagram (not drawn to scale) of a simple three-electrode cell setup used for electrochemical characterization of CMP-specific metals, (h) A three-electrode setup used for electrochemical studies of metal samples under trihological conditions similar to those used in CMP. 

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