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Catalyst Poisoning During Tar-Sands Bitumen Upgrading
Published in Michael C. Oballa, Stuart S. Shih, Catalytic Hydroprocessing of Petroleum and Distillates, 2020
J. D. Carruthers, J. S. Brinen, D. A. Komar, S. Greenhouse
In the SIMS experiment the surface is irradiated with a beam of ions (or atoms) and material is sputtered off the surface, resulting in the formation of positive ions, negative ions, and neutrals. These ions are detected using a mass spectrometer. SIMS by its nature is a destructive technique, i.e. the surface is continuously being eroded by the ion beam (sort of a chemical sandpaper) and is changing with time. Depending on the ion dose employed in the experiment, SIMS can be divided into two categories, static and dynamic. In static SIMS the ion dose is <3×1012 ions cm-2 (15). It is generally used for the analysis of organics and polymers since the low beam current density causes minimum disruption of chemical bonds thus resulting in the production of molecular species which are observed in the mass spectrum. The experiments described in this study were obtained at higher beam current densities (dynamic SIMS). Under these conditions, sufficient spectral intensity of elemental ions could be generated to allow chemical images and linescans to be obtained.
Characterization of Individual Environmental Particles by Beam Techniques
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2019
C. Xhoffer, L. Wouters, P. Artaxo, A. Van Put, R. Van Grieken
SIMS offers special capabilities for particle analysis. Heterogeneities in the composition in single particles are frequently observed from site to site. The distribution of constituents with depth in a particle is another microstructural feature of interest. SIMS is capable of obtaining signals from a depth of about 1 to 2 nm and this information originates from the surface of the sample. SIMS can also be used as a microanalysis technique with a minimum sampling volume of 0.01 jxm.3 The capabilities of SIMS for detection of all elements, compound detection, isotope ratio measurements, depth profiling, and ion imaging of specific constituents are described25 with special reference to particle studies. Depth profiling can be successfully applied to individual particles; however, irregular topography of particles can degrade the depth resolution. Ion specific images of elemental or molecular constituents can be obtained in the ion microscope or ion microprobe.26 The limiting lateral resolution is about 0.5 μm for the ion microscope and about 1 μm for the scanning ion microprobe.
Established and Emerging Techniques for Characterising the Formation, Structure and Performance of Calcified Structures under Ocean Acidification
Published in S.J. Hawkins, A.L. Allcock, A.E. Bates, L.B. Firth, I.P. Smith, S.E. Swearer, P.A. Todd, Oceanography and Marine Biology, 2019
Susan C. Fitzer, Vera Bin San Chan, Yuan Meng, Kanmani Chandra Rajan, Michio Suzuki, Christelle Not, Takashi Toyofuku, Laura Falkenberg, Maria Byrne, Ben P. Harvey, Pierre de Wit, Maggie Cusack, K. S. Gao, Paul Taylor, Sam Dupont, Jason M. Hall-Spencer, V. Thiyagarajan
Spatial information of elemental distribution in the mineral provides valuable information to predict mechanical properties. Solid-sampling methods have been developed for ICP analysis for this purpose. Electrothermal-vaporisation (ETV) and LA are applied to generate vapour for characterisation. In combination with ICP-OES or ICP-MS, these techniques are suitable for analysis of a solid sample (Limbeck et al. 2017). However, LA-ICP-MS provides resolution of only >5 μm, while secondary ion mass spectrometry (SIMS) distinguishes submicrometre resolution (Becker et al. 2010). Although SIMS has a sensitive detection level of 1 ppm, the technique is not directly quantitative due to its dependence on a solid-state chemical standard, as well as the nonlinear and highly variable nature of the ionisation process of elements in SIMS (Williams 1985). In addition, secondary-ion mass spectrometry (SIMS) can be used to obtain depth profiles of mineral composition of shells (Jeffree et al. 1995). All these methods have an advantage of giving spatial information on the elemental distribution; the differences lie in the resolutions of ICP-MS, ICP-OES and SIMS. ICP-OES is already applied using acid digestion of collected individuals for determination of elemental ratios (Milazzo et al. 2014). The application of SIMS to OA research would enable the analysis of much smaller samples and to examine the response of individual calcifying organisms in terms of growth and survival (Eichner et al. 2017).
Plasma modification of textiles: understanding the mechanisms involved
Published in Textile Progress, 2018
M. R. S. McCoustra, R. R. Mather
SIMS possesses the advantages of extreme sensitivity towards a surface and hence the capability of identifying a wide variety of functional groups. An excellent review has been written by Delcorte et al. [83] of the application of SIMS to the study of plasma treatments of organic surfaces, such as the surfaces of most textile fibres. The surface is bombarded in vacuo by a focused beam of primary ions. This bombardment causes the release not only of atoms and molecular fragments from the surface but also of a small proportion of secondary ions. The mass/charge ratios reveal the nature of the individual chemical constituents at the surface. Analysis of the secondary ions is normally conducted in a time-of-flight (TOF) analyser which separates the ions according to their time of flight from the sample to a detector. SIMS has also recently been applied to depth profiling, in which chemical groups just under the surface up to a depth of 5 nm or more can additionally be identified. Depth profiling on a number of polymers has been reported [83]. However, whilst SIMS is useful for identifying the individual chemical constituents of a surface, it is less reliable for determining their relative proportions, as the fraction of ions released from the surface will vary from one type of ion to another. For this reason, SIMS is often applied in conjunction with XPS (discussed in the next section). To the authors’ knowledge, only a few examples of plasma-treated textiles investigated using SIMS have been published, e.g. by Naebe et al. [85] and Panda et al. [86], a consequence perhaps of the expensive equipment required. Detailed accounts of TOF-SIMS have been compiled in a book edited by Vickerman and Briggs [87].