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Characterization Methods
Published in Mark A. Prelas, Galina Popovici, Louis K. Bigelow, Handbook of Industrial Diamonds and Diamond Films, 2018
Karen McNamara Rutledge, Karen K. Gleason
The surfaces of diamond powder exposed to CF4 containing plasmas have been examined using solid-state 19F NMR [Scruggs and Gleason 1993]. Surface coverages between 5% and 50% of the available surface bond density were observed. The 19F MQ NMR experiment shows that this fluorine is not uniformly distributed on these surfaces. High-speed (15 kHz) magic-angle-spinning (MAS) was used to average the effects of 19F chemical shift anisotropy. The isotropic chemical shifts were resolved and assigned relative to CFC13 as follows: CF =148±1 ppm; CF2 = 106±2 and 123 ppm; CF3 = 78±1 ppm. The major species was monofluoride and only 5 to 10% was bonded as CF3. These CFx functionalities were the only fluorine-containing species observed.
Trace Metals in Agricultural Soils
Published in Herbert E. Allen, E. Michael Perdue, David S. Brown, Metals in Groundwater, 2020
Terry J. Logan, Samuel J. Traina
Obviously the application of equilibrium solubility measurements to characterize trace-metal bearing solid phases in soils, without direct observations of the solid-phase, can only lead to questionable conclusions. Fortunately, several emerging technologies have been recently applied to directly study the solid-phase forms of metals in soils and sediments. Using solid state 113Cd NMR, Bank et al. [58] identified four different types of solid-phase Cd: (1) Cd in aCd-Ca-carbonate, (2) an oxo-Cd species present in a “clay-like” matrix, (3) a Cd-hydroxycarbonate, and (4) a Cd-hydroxycarbonate species in a “clay-like” matrix. Hinedi and Chang [59] studied solid phase P-chemistry in two municipal sewage sludges and in sludge-amended soil. Using 31P magic angle spinning nuclear magnetic resonance, the presence of Ca-phosphate, carbonated apatite, pyrophosphate and Al-phosphate solids was established [59]. Equilibrium solubility measurements made on samples of sludge-amended soil, suggested that the solution-phase chemistry was controlled by carbonated-apatite [60]. Essington and Mattigod [61] combined equilibrium solubility measurements with density separation techniques, followed by energy dispersive x-ray analysis (EDAX) analytical electron microscopy to examine the solid-phase forms of La, Ce, and Nd present in municipal sewage sludge and sewage sludge-amended soils. Indirect, solubility measurements indicated that the stable solid phases were cerianite [ CeO2 ,] lanthanite [ La2(CO3)3·8H2O] , Nd-lanthanite Nd2(CO3)3·8H2O] , La-Nd-sulfate [ (La,Nd)2(SO4)3·8H2O ], yet direct EDAX measurements indicated more complex elemental associations. Lanthanum, Ce and Nd were found associated with Th and P, Ce with Si, Ba, and S, and La and Nd with S. Whereas these associations were often suggestive of the presence of standard-state solid phases, many of the EDAX spectra indicated the presence of additional ions suggesting that some mixed solids had formed (Figure 6).
Synthesis and structural characterization of alumina nanoparticles
Published in Phase Transitions, 2020
Puneet Kaur, Atul Khanna, Nirmal Kaur, Priyanka Nayar, Banghao Chen
Nuclear Magnetic Resonance (NMR) employing Magic Angle Spinning (MAS) is a commonly used structural probe to accurately determine the local environments of the atoms. The distribution of aluminum ions at the tetrahedral and octahedral sites can be determined precisely by 27Al MAS-NMR and this technique has provided the knowledge of structural environments of aluminum ions around oxygen lattice [11, 15, 18, 20–23]. In the ideal spinel structure (γ-alumina), octahedrally coordinated cations are twice as many as the tetrahedral ones [18]. Lee et al. found by 27Al MAS-NMR and computational studies that ∼70% of Al ions are octahedrally coordinated in γ-alumina [22]. Ansell et al. studied the changes in Al—O coordination from octahedral to tetrahedral upon melting of Al2O3 [24].
Compressive strength and microstructure evolution of low calcium brown coal fly ash-based geopolymer
Published in Journal of Sustainable Cement-Based Materials, 2020
Muhamed Khodr, David W. Law, Chamila Gunasekara, Sujeeva Setunge, Robert Brkljaca
Solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopic experiments are performed using a 500 MHz console equipped with a triple resonance solid-state MAS probe. 27Al spectra were acquired at 25 °C (77 °F) using the ‘onepul’ pulse sequence with 1024 accumulations. The samples were loaded into 4 mm (0.16 in.) rotors, and rotation frequencies of 10 kHz used. The 27Al MAS-NMR spectra are obtained with a repetition delay time of 2 s and a 40 ms acquisition time for quantitative analysis. Geopolymer mortar samples for Zeta potential, XRD, FT-IR, TGA, and MAS-NMR tests are manually ground and filtered using a 75-µm sieve to achieve the required powder fineness before testing.
Preparation, characterization and application of sorbent envelopes with Carica papaya seeds and Citrus grandis rind for cationic dyes removal
Published in Green Chemistry Letters and Reviews, 2019
Cross Polarisation Magic Angle Spinning Nuclear Magnetic Resonance (13C CP-MAS NMR) measurements of fresh pristine C. grandis rind were made using different spin rates. It was found that 8 kHz spin rate was suitable for obtaining the characteristic NMR trace of the rind sample (see Figures S1 and S2 in Supplementary Information).