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Measurement of Partial Pressure at Vacuum Conditions
Published in Igor Bello, Vacuum and Ultravacuum, 2017
Vacuum environment contains reactive gases whose composition changes with decreasing pressure. Accordingly, precise determination of pressure with gauges that measure pressure indirectly may not provide meaningful information. In high vacuum, the major component of residual gases is water vapor, which is reactive with many materials that are prepared under vacuum conditions. The reactive gases of vacuum background may incorporate into the growing structures in amounts proportional to their partial pressures. Particularly, electronic properties of semiconductors can change dramatically with impurities introduced into their microstructures. Very low densities of dopants or traces of chemical elements can be detected by chemical analyses using mass spectrometers. Mass spectrometers are also used in partial pressure measurement of gases in vacuum. These devices analyzing gases in vacuum are called residual gas analyzers (RGAs). RGAs are simple and portable devices, but indispensable at different material analyses, material syntheses, studying sorption and reaction processes, measurements of different physical properties, and many technological processes. However, mass spectrometers used in general chemical analyses are more robust and operate with higher mass resolution, and they are equipped with additional accessories. In material analyses, we use various techniques that enable us to determine the chemical composition of materials and their chemical states, phase structures, or structures of molecules in arbitrary matter phases. Because of this diversity, many instruments based on different physical principles and sampling residual atmospheres have been developed and used. Both solid and liquid materials are often converted to their gaseous phases and then analyzed to deduce the materials composition by mass spectrometric techniques.
Energy
Published in A.P.H. Peters, Concise Chemical Thermodynamics, 2010
A chemical reaction, defined as a change in the chemical state of the system, is typically accompanied by a release of energy to, or an uptake of energy from, the surroundings. This energy transfer typically involves another form of energy, in patterns shown in Figure 1.5.
Antifouling catalytic mixed-matrix membranes based on polyethersulfone and composition-optimized Zn-Cu-Fe-O CWAO catalyst under dark ambient conditions
Published in Environmental Technology, 2023
Hieu Trung Nguyen, Ha Manh Bui, Ya-Fen Wang, Sheng-Jie You
he chemical state of the optimal catalyst was investigated by the XPS (X-ray photoelectron spectroscopy) technique. The chemical states of O 1s, Zn 2p, Cu 2p, and Fe 2p have been shown in the deconvoluted XPS spectra in Figure 4. For O 1s, the peak shape is asymmetric and has been deconvoluted to three peaks with binding energies of 529.2, 530.8, and 532.7 eV. The peak with low binding energy is from oxygen in the lattice of Zn-O, Cu-O, and Fe-O with the highest intensity. The peak with the middle binding energy is due to the presence of oxygen vacancies in the crystal lattice of the catalyst. Peak with high binding energy is attributed to O2, H2O, and CO2 adsorbed onto the catalyst. Figure 4b shows the core-level spectrum of two peaks with binding energies of 1021.9 and 1045.0 eV for Zn 2p3/2 and Zn 2p1/2 of the tetrahedral Zn2+, respectively. In the Cu 2p spectrum, two highly intense asymmetric peaks are assigned for Cu 2p3/2 and Cu 2p1/2. In which, the deconvoluted XPS spectra of each peak show that there are two component peaks; the peak with lower binding energies belongs to Cu+ (932.9 and 952.8 eV) and the peak with higher binding energies belongs to Cu2+ (934.2 and 953.9 eV). Similarly, Figure 4d shows the appearance of Fe 2p peaks of Fe2+ (711.1 and 724.7 eV) and Fe3+ (713.2 and 726.5 eV).
Formation of pyrite in the process of fine coal desulfurization by microwave enhanced magnetic separation
Published in International Journal of Coal Preparation and Utilization, 2023
Zhenxing Zhang, Xinyu Wei, Guanghui Yan, Junwei Guo, Pengfei Zhao, Fan Yang, Hongyu Zhao, Bo Zhang
The chemical state and surface elemental composition of the pulverized coal were analyzed by X-ray photoelectron spectroscopy (XPS). Because of different chemical environment of the elemental atom, the peaks of the same element in the spectrum may also show chemical shift; the chemical environment of the elemental atom is related to the type and quantity of the element and different valence states of the atom itself. Figures 6 (a-c) show the XPS wide scan results of raw coal, cleaner coal, and tail coal, respectively. The diagram indicates that the C absorption peak of raw coal, cleaner coal, and tail coal is very strong, followed by the O absorption peak, indicating that C and O are the main surface elements of raw coal, cleaner coal, and tail coal. During the microwave strengthening and magnetic separation process, the mineral composition on the surface of pulverized coal did not change significantly.
Enhanced electron transfer for activation of peroxymonosulfate via MoS2 modified iron-based perovskite
Published in Environmental Technology, 2022
Sheng Sheng, Jingjing Fu, Siyuan Song, Yuxuan He, Jin Qian, Ziyang Yi
X-ray diffraction (XRD, Rigaku, SmartLab) was used to obtain the crystalline structure of the samples and to characterise the chemical composition of the samples. Scanning electron microscopy (SEM) and high-resolution transmission electron microscope (HRTEM) were used to obtain the morphology and crystalline shape of the prepared samples. The Brunauer–Emmett–Teller (BET) surface area and the porous nature were determined by N2 absorption-desorption isotherm (Micromeritics ASAP 2460). X-ray photoelectron spectroscopy (XPS) analysis provides information on the elemental composition and chemical state of a sample. The LVO and other antibiotics concentration were measured by visible–ultraviolet spectrophotometer (Nanjing Feile Instrument Co., Ltd., Model). The reactive oxygen species (ROS) generating from the catalyst/PMS system were detected by EPR spectrometer (X-band A300-6/1, Bruker) at 9.84 GHz.