scholarly journals Effects of long-term flue gas exposure on chemical-structural properties of South African coals: perspective on advanced analytical techniques

2021 ◽  
Author(s):  
Major Mabuza ◽  
Kasturie Premlall ◽  
Michael O. Daramola
Keyword(s):  
South African ◽  
Structural Properties ◽  
Flue Gas ◽  
Analytical Techniques ◽  
Resonance Spectroscopy ◽  
Coal Seams ◽  
Layer Spacing ◽  
X Ray ◽  
Gas Exposure

Abstract The sequestration of carbon dioxide (CO 2 ) in unmineable coal seams is one of the geologic options earmarked to alleviate the emissions of the greenhouse gases to the atmosphere. Direct flue gas injection into unmineable coal seams has been considered to partially offset the cost of the utilizing this technology. This paper presents findings of the evolution of chemical structural properties of two South African coals from Somkhele (Coal SML) and Ermelo (Coal EML) coalfields after long-term (2 232 hours) flue gas exposure by applying advanced analytical techniques. The two coal samples were exposed to a synthetic flue gas simulating coal-fired power plant gas emissions containing 12% CO 2 , 5.5% O 2 , 82% N 2 , 0.38% SO 2 , and 0.12% NO 2 under in-seam temperature and pressure conditions of 60 °C and 9.0 MPa, respectively. The advanced analytical techniques applied included universal attenuated total reflectance-Fourier transform infrared (UATRFTIR), carbon-13 solid state nuclear magnetic resonance spectroscopy ( 13 C ss NMR), and field emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX) wide-angle X-ray diffraction (WAXRD). The UATR-FTIR spectra revealed weakened C─H, aliphatic C─C, C─O, ─OH, and out-of-plane aromatic C─H functional groups. The results from the treated coals of 13 C ss NMR for the structural parameters show notable changes in the oxygen functionalities reporting the aliphatic carbon bonded to oxygen, 𝑓 𝑎𝑙 𝑂 , while the WAXRD data showed some significant changes in the inter-layer spacing and the crystalline diameter as compared to the untreated coals.

scholarly journals The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566

2020 ◽  
Vol 498 (1) ◽  
pp. 718-727
Author(s):  
V L Oknyansky ◽  
H Winkler ◽  
S S Tsygankov ◽  
V M Lipunov ◽  
E S Gorbovskoy ◽  
...  
Keyword(s):  
South African ◽  
Seyfert Galaxy ◽  
Energy Generation ◽  
Astronomical Observatory ◽  
X Ray ◽  
Maximum Period

ABSTRACT We present results of the long-term multiwavelength study of optical, UV, and X-ray variability of the nearby changing-look (CL) Seyfert NGC 1566 observed with the Swift Observatory and the MASTER Global Robotic Network from 2007 to 2019. We started spectral observations with South African Astronomical Observatory 1.9-m telescope soon after the brightening was discovered in July 2018 and present here the data for the interval between 2018 August and 2019 September. This paper concentrates on the remarkable post-maximum behaviour after 2018 July when all bands decreased with some fluctuations. We observed three significant re-brightenings in the post-maximum period during 2018 November 17–2019 January 10, 2019 April 29–2019 June 19, and 2019 July 27–2019 August 6. An X-ray flux minimum occurred in 2019 March. The UV minimum occurred about 3 months later. It was accompanied by a decrease of the LUV/LX-ray ratio. New post-maximum spectra covering (2018 November 31–2019 September 23) show dramatic changes compared to 2018 August 2, with fading of the broad lines and [Fe X] λ6374 until 2019 March. These lines became somewhat brighter in 2019 August–September. Effectively, two CL states were observed for this object: changing to type 1.2 and then returning to the low state as a type 1.8 Sy. We suggest that the changes are due mostly to fluctuations in the energy generation. The estimated Eddington ratios are about 0.055 ${{\ \rm per\ cent}}$ for minimum in 2014 and 2.8 ${{\ \rm per\ cent}}$ for maximum in 2018.

Anthropometric definitions for antiretroviral-associated lipodystrophy derived from a longitudinal South African cohort with serial dual-energy X-ray absorptiometry measurements

2018 ◽  
Vol 29 (12) ◽  
pp. 1194-1203
Author(s):  
Zulfa Abrahams ◽  
Gary Maartens ◽  
Naomi Levitt ◽  
Joel Dave
Keyword(s):  
South African ◽  
Skinfold Thickness ◽  
Dual Energy ◽  
Anthropometric Measures ◽  
X Ray ◽  
Receiver Operating Characteristic Curves ◽  
South Africans ◽  
Arm Circumference ◽  
Patient Reported

The development of lipodystrophy is associated with the long-term use of antiretroviral therapy (ART). We assessed agreement between patient-reported lipodystrophy and body composition measures using dual-energy X-ray absorptiometry (DXA) and developed objective measures to define lipoatrophy and lipohypertrophy in black South Africans. One hundred and eighty-seven ART-naïve HIV-infected adults were enrolled in a 24-month longitudinal study. Self-reported information on regional fat loss and fat gain, anthropometry, and DXA measures were collected at baseline, three, six, 12, 18, and 24 months after starting ART. Receiver operating characteristic curves were used to describe the performance of anthropometric variables using change in limb and trunk fat measured by DXA, as the reference standard. The proportion of men and women who developed lipoatrophy and lipohypertrophy increased over the 24-month period, with lipoatrophy occurring more frequently in men (21% versus 10%). In women, lipoatrophy was best determined by thigh skinfold thickness (80.3% correctly classified) and mid-arm circumference (77.6% correctly classified). None of the anthropometric measures performed well for defining lipoatrophy in men. Anthropometric measures performed well for defining lipoatrophy in women, but not lipohypertrophy.

The Effect of Thermal Treatment on the Structure of Palygorskite Used for Flue Gas SO2 Removal

2011 ◽  
Vol 356-360 ◽  
pp. 698-703 ◽  
Author(s):  
Xian Long Zhang ◽  
Wei Ping Jiang ◽  
Xue Ping Wu ◽  
Bo Wen Shi ◽  
Bao Jun Yang ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Structural Properties ◽  
Flue Gas ◽  
Temperature Programmed Desorption ◽  
Flue Gas Desulfurization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Adsorption Sites ◽  
Transmission Electron ◽  
Temperature Programmed

Palygorskite is widely used as industrial adsorbent and also potential for flue gas desulfurization by adsorption of SO2. The effect of thermal treatment on Palygorskite’s structural properties and its performance in SO2adsorption were investigated. The textural and structural properties of the prepared palygorskite adsorbent were characterized by X-ray diffraction, transmission electron microscopy and temperature programmed desorption. The result showed the channel of Palygorskite is partial collapsed and the structure is not changed ultimately when thermally treated below 300 °C. The structure of Palygorskite is Gradually changed when the treating temperature is higher than 300 °C and is damaged entirety till 800 °C. As a result, the adsorption capacity of SO2on Palygorskite decreased drastically. It is suggested that the presences of surface adorbed water and zeolitic water which occupy a large number of adsorption sites are disadvantage for the adsorption of SO2, and dissimilarly the presence of crystal-bonded water is favorable.

scholarly journals Deciphering composition and connectivity of a natural product with the assistance of MS and 2D NMR

2017 ◽  
Vol 73 (11) ◽  
pp. 994-1002
Author(s):  
Anastasiya I. Vinokur ◽  
Paul B. White ◽  
Maurice Tagatsing Fotsing ◽  
Charmaine Arderne ◽  
Derek Tantoh Ndinteh ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Single Crystal ◽  
Solvent Molecule ◽  
Analytical Techniques ◽  
2D Nmr ◽  
Resonance Spectroscopy ◽  
Aliphatic Chain ◽  
Exact Mass ◽  
X Ray ◽  
Compound Ii

A complementary application of three analytical techniques, viz. multidimensional nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), and single-crystal X-ray diffractometry was required to identify and refine two natural products isolated from Millettia versicolor and solvent of crystallization. The two compounds, namely 3-(2H-1,3-benzodioxol-5-yl)-6-methoxy-8,8-dimethyl-4H,8H-pyrano[2,3-h]chromen-4-one, or durmillone, (I), and (2E)-1-(4-{[(2E)-3,7-dimethylocta-2,6-dien-1-yl]oxy}-2-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one, (II), could not be separated by routine column chromatography and cocrystallized in a 2:1 ratio with 0.13 molecules of ethanol solvent. Compound (II) and ethanol could not be initially identified by single-crystal X-ray analysis due to complex disorder in the aliphatic chain region of (II). Mass spectrometry ensured that (II) represented only one species disordered over several positions in the solid state, rather than several species cohabitating on the same crystallographic site. The atomic identification and connectivity in (II) were established by several 2D (two-dimensional) NMR techniques, which in turn relied on a knowledge of its exact mass. The derived connectivity was then used in the single-crystal analysis to model the disorder of the aliphatic chain in (II) over three positions and allowed identification of a partially occupied ethanol solvent molecule that was disordered over an inversion center. The disordered moieties were refined with restraints and constraints.

Characteristic of Crystallite Sizes and Lattice Deformations Changes in the Oxide Layer Formed on Steel Operated for a Long Time at an Elevated Temperature

2013 ◽  
Vol 203-204 ◽  
pp. 204-207 ◽  
Author(s):  
Monika Gwoździk
Keyword(s):  
Phase Composition ◽  
Elevated Temperature ◽  
Oxide Layer ◽  
Flue Gas ◽  
Phase Identification ◽  
X Ray ◽  
Term Operation ◽  
Long Time ◽  
Crystallite Sizes

The paper presents results of studies on the phase composition, crystallite sizes and lattice deformations of oxide layers formed during a long-term operation on X10CrMoVNb9-1 steel. Test specimens were taken from a live steam pipeline operated at 535°C for 70,000 hours. X-ray studies were carried out on the tube outside surface (on the flue gas side), then the layer’s surface was polished and the diffraction measurements repeated to reveal differences in the originated oxides layer. X-ray phase analysis was performed using a SEIFFERT 3003 T/T X-ray diffractometer, with a cobalt tube of λCo= 0.17902nm wavelength. crystallographic database were used for the phase identification.

scholarly journals Swift J011511.0-725611: discovery of a rare Be star/white dwarf binary system in the SMC

2021 ◽  
Vol 508 (1) ◽  
pp. 781-788
Author(s):  
J A Kennea ◽  
M J Coe ◽  
P A Evans ◽  
L J Townsend ◽  
Z A Campbell ◽  
...  
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
South African ◽  
White Dwarf ◽  
Compact Object ◽  
Type Ii ◽  
Large Telescope ◽  
X Ray ◽  
Be Star

ABSTRACT We report on the discovery of Swift J011511.0-725611, a rare Be X-ray binary system (BeXRB) with a white dwarf (WD) compact object, in the Small Magellanic Cloud (SMC) by S-CUBED, a weekly X-ray/UV survey of the SMC by the Neil Gehrels Swift Observatory. Observations show an approximately 3 month outburst from Swift J011511.0-725611, the first detected by S-CUBED since it began in 2016 June. Swift J011511.0-725611 shows supersoft X-ray emission, indicative of a WD compact object, which is further strengthened by the presence of an 0.871 keV edge, commonly attributed to O viii K-edge in the WD atmosphere. Spectroscopy by South African Large Telescope confirms the Be nature of the companion star, and long term light curve by OGLE finds both the signature of a circumstellar disc in the system at outburst time, and the presence of a 17.4 day periodicity, likely the orbital period of the system. Swift J011511.0-725611 is suggested to be undergoing a Type-II outburst, similar to the previously reported SMC Be white dwarf binary (BeWD), Swift J004427.3-734801. It is likely that the rarity of known BeWD is in part due to the difficulty in detecting such outbursts due to both their rarity, and their relative faintness compared to outbursts in Neutron Star BeXRBs.

scholarly journals Effect of High Temperature Sodium Hydroxide Immersion on Fusion Bond Epoxy Coating

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Amal Al-Borno ◽  
Xianyi Chen ◽  
Shailesh Kewaldas Dhoke
Keyword(s):  
Sodium Hydroxide ◽  
Electrochemical Impedance ◽  
Analytical Techniques ◽  
Attenuated Total Reflection ◽  
Low Molecular Weight ◽  
Scanning Calorimetry ◽  
Premature Failure ◽  
X Ray ◽  
Deposit Layer

Fusion Bond Epoxy (FBE) coating system was exposed to 5% sodium hydroxide at elevated temperature for 30 days. The result of exposure showed formation of adhere deposit layer, a discolored zone underneath and remaining un-affected bulk of the coating. The deterioration of the coating was characterized using analytical techniques like scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX) spectroscopy, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), pull-off adhesion, and electrochemical impedance spectroscopy (EIS). Results obtained indicated chemical deterioration of the coating in the discolored zone and leaching of low molecular weight coating component forming deposit layer. Although the adhesion strength and barrier property were not affected, the polymer matrix in the affected zone undergoes severe changes in its surface microstructure, primary chemical structure, and glass transition temperature. This may inflict serious impairment of the coating functional properties and premature failure of the coating in long term exposure.

Long-term flue gas exposure effects of silica membranes on porous steel substrate

2010 ◽  
Vol 359 (1-2) ◽  
pp. 110-114 ◽  
Author(s):  
Katharina Brands ◽  
David Uhlmann ◽  
Simon Smart ◽  
Martin Bram ◽  
João C. Diniz da Costa
Keyword(s):  
Flue Gas ◽  
Steel Substrate ◽  
Silica Membranes ◽  
Gas Exposure

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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