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Published in Orloff Jon, Handbook of Charged Particle Optics, 2017
András E. Vladár, Michael T. Postek
In the past the predominant electron sources in use were the thermionic emission type cathodes, especially tungsten and lanthanum hexaboride (LaB6).2 Lanthanum hexaboride cathodes became more prevalent for low accelerating voltage applications because of their higher brightness and smaller source diameter in comparison to tungsten filaments (Table 9.2). Cerium hexaboride (CeB6) cathode is similar in operation and performance to the lanthanum hexaboride cathode.3 Point cathode electron sources or field emission instrumentation have been available for some time, and today a wide variety of both laboratory type and process type instruments are commonly used with field emission technology (see Chapter 1). For many industrial applications such as those found on the semiconductor processing lines, only the field emission instruments provide the high resolution necessary for this type of work (Table 9.2). This is especially true at the low accelerating voltages needed for nondestructive inspections.4 In the near future, nanometer-sized field emission tips with literally atomic proportions with one or only a few atoms at the very tip may also become available as practical electron and ion sources.5,6
A comparative study of persulfate activation by iron-modified diatomite and traditional processes for the treatment of 17α-ethinylestradiol in water
Published in Environmental Technology, 2021
Celyna K. O. Silva-Rackov, Silvia S. O. Silva, Alessandra R. Souza, Leandro G. Aguiar, Dannielle J. Silva, Marilda M. G. R. Vianna, Claudio A. O. Nascimento, Osvaldo Chiavone-Filho
Raw diatomite (RD), CAT-1 (referred to hereafter as modified diatomite, MD), and recovered modified diatomite (RMD) were characterised using standard methods. RMD was recovered by filtering, washing, and drying MD at room temperature after use. Iron content was determined by X-ray fluorescence (XRF) spectrometry using a Philips PW 2400 XRF spectrometer with Rh-anode. RD and MD were examined by scanning electron microscopy (SEM). Samples were coated with a thin layer of gold and analysed with a JEOL 440I scanning electron microscope. The specific surface area was determined by the Brunauer–Emmett–Teller (BET) method using a Micromeritics ASAP 2020 analyzer. Samples (0.5 g) were placed in a quartz tube under nitrogen atmosphere, heated from room temperature to 110°C at 10°C min−1, and kept at 110°C for 4 h. Electron probe microanalysis (EPMA) was performed using a Shimadzu 1720 electron probe microanalyzer, a scanning electron microscope, and four wavelength-dispersive X-ray spectroscopy (WDS) instruments. The EPMA system was also used for energy-dispersive X-ray spectroscopy (EDS) analyses [31]. Samples were coated with carbon using graphite under vacuum. Beam voltage was set at 15 kV, and a cerium hexaboride (CeB6) filament was used.