scholarly journals Multifrequency EPR study on radiation induced centers in calcium carbonates labeled with 13C

Nukleonika ◽  
2015 ◽  
Vol 60 (3) ◽  
pp. 429-434 ◽  
Author(s):  
Jarosław Sadło ◽  
Anna Bugaj ◽  
Grażyna Strzelczak ◽  
Marcin Sterniczuk ◽  
Zbigniew Jaegermann
Keyword(s):  
Calcium Carbonate ◽  
Epr Spectroscopy ◽  
Orthorhombic Symmetry ◽  
Paramagnetic Centers ◽  
Calcium Carbonates ◽  
Radiation Induced

AbstractIn calcite and aragonite, γ-irradiated at 77 K, several paramagnetic centers were generated and detected by EPR spectroscopy; in calcite, CO3−(orthorhombic symmetry, bulk and bonded to surface), CO33−, NO32−, O3−, and in aragonite CO2−(isotropic and orthorhombic symmetry) depending on the type of calcium carbonate used. For calcium carbonates enriched with13C more detailed information about the formed radicals was possible to be obtained. In both natural (white coral) and synthetic aragonite the same radicals were identified with main differences in the properties of CO2−radicals. An application of Q-band EPR allowed to avoid the signals overlap giving the characteristics of radical anisotropy.

Radiation Defects in Lime Mortars and Plasters Studied by EPR Spectroscopy

Radiocarbon ◽  
2020 ◽  
Vol 62 (3) ◽  
pp. 713-724
Author(s):  
Zuzanna Kabacińska ◽  
Danuta Michalska ◽  
Bernadeta Dobosz
Keyword(s):  
Epr Spectroscopy ◽  
Organic Radical ◽  
Radiation Defects ◽  
Paramagnetic Centers ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Crystalline Materials ◽  
Lime Mortars ◽  
Radiation Induced ◽  
Artificial Uv

ABSTRACTElectron paramagnetic resonance (EPR) spectroscopy is a well-established method of dating based on trapped charges, applied to various crystalline materials, including carbonates, bones, and teeth. It provides a detailed insight into the structure of radiation defects—paramagnetic centers generated by irradiation, without the need of a painstaking sample preparation, often challenging in other methods. Using EPR we studied the effect of γ radiation on lime mortars and plasters from ancient settlement Hippos in Israel, in order to analyze the process of defect generation. Analysis of the complex spectra revealed the presence of radiation-induced species, including CO2–, NO32– and organic radical. Using an artificial UV source, we generated relatively strong signals of paramagnetic centers, analogous to those created by γ irradiation, reaching their maximum intensity after 5–6 hr of UV exposure. Our results confirm the previous reports that radiation defects can also be generated, instead of bleached, in calcite by UV radiation, which is crucial for identifying the issues related to light exposition, affecting the accuracy of age determinations in trapped-charge dating methods.

scholarly journals Characterization of calcium carbonates used in wet flue gas desulphurization processes

2012 ◽  
Vol 10 (5) ◽  
pp. 1556-1564 ◽  
Author(s):  
Simion Dragan ◽  
Alexandru Ozunu
Keyword(s):  
Calcium Carbonate ◽  
Flue Gas ◽  
Absorption Capacity ◽  
Bet Surface Area ◽  
Experimental Characterization ◽  
Calcium Carbonates ◽  
Calcium Carbonate Precipitate ◽  
Influential Parameters ◽  
Flue Gas Desulphurization

AbstractThis paper presents an experimental characterization of two sources of calcium carbonate, limestone and calcium carbonate precipitate (CCP) used in wet flue gas desulphurization processes. Characterization of the two carbonate sources was carried out by chemical analysis, IR spectra, thermal behavior, particle size distribution for CCP, BET surface area and absorption capacity of SO2 in calcium carbonate suspensions. The absorption temperature, suspension concentration and carbonate grain size were found to be the most influential parameters in the absorption capacity measurements.

Radiation-induced paramagnetic centers in Ca3Ga2Ge4O14 crystals

1997 ◽  
Vol 39 (6) ◽  
pp. 938-942 ◽  
Author(s):  
A. E. Nosenko ◽  
R. E. Leshchuk ◽  
B. V. Padlyak ◽  
A. A. Sel’skii
Keyword(s):  
Paramagnetic Centers ◽  
Radiation Induced

The Observations of Paramagnetic Centers in Tellurite Glasses

1994 ◽  
Vol 373 ◽  
Author(s):  
J.D. Prohaska ◽  
J. Li ◽  
S. Kannan ◽  
E. Snitzer ◽  
J.S. Wang ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Room Temperature ◽  
The Other ◽  
Tellurite Glasses ◽  
Hole Center ◽  
Paramagnetic Centers ◽  
First Report ◽  
Esr Spectrum ◽  
Radiation Induced

AbstractThis is the first report of ESR observations of three distinct paramagnetic centers in TeO29 glasses. One center is intrinsic to the glass and the other two are induced by KrFexcimer-laser radiation. The intrinsic center with a broad ESR spectrum is tentatively identified as an oxygen-associated hole center. One radiation-induced center fades slowly at room temperature; its proposed structure is that of an electron trapped in a diffuse orbital associated with a modifier ion. The other radiation-induced center is stable at room temperature and corresponds to the Vo· center observed in crystalline paratellurite.

Effect of Crystal Contolling Agents on Shapes of Nanometer Calcium Carbonate

2010 ◽  
Vol 92 ◽  
pp. 79-85
Author(s):  
Li Mei Bai ◽  
Yue Xin Han ◽  
Li Xia Li ◽  
Ri Xiao ◽  
Shu Juan Dai
Keyword(s):  
Grain Size ◽  
Calcium Carbonate ◽  
Aspect Ratio ◽  
Average Length ◽  
Calcium Carbonates ◽  
Average Grain Size ◽  
Average Size ◽  
The Given ◽  
Grain Diameter

In laboratory, there polymorphs’ nano-calcium carbonates were synthesized through adding on different crystal controlling agents by the bath-type carburizing reagent in the given conditions. When selecting addition J as the crystal controlling agent, lamellar nano-calcium carbonate products with average size about 150×110×15 nm were synthesized. When selecting annexing agent I as the crystal controlling agent, rod nano-calcium carbonates were synthesized, which average grain diameter was 90 nm, average length was 944 nm, and aspect ratio was 10.5. When selecting annexing agent G as the crystal controlling agent, chain nano-calcium carbonate with average grain size 20~30nm, aspect ratio 10~15nm were synthesized.

scholarly journals Evaluation of the Potential of Modified Calcium Carbonate as a Carrier for Unsaturated Fatty Acids in Oxygen Scavenging Applications

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5000
Author(s):  
Bettina Röcker ◽  
Gabriel Mäder ◽  
Fabien Wilhelm Monnard ◽  
Magdalena Jancikova ◽  
Matthias Welker ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Calcium Carbonate ◽  
Surface Area ◽  
Food Packaging ◽  
Unsaturated Fatty Acids ◽  
Oxygen Absorption ◽  
Scavenging Activity ◽  
Oxygen Scavenger ◽  
Calcium Carbonates ◽  
Oxygen Scavenging

Modified calcium carbonates (MCC) are inorganic mineral-based particles with a large surface area, which is enlarged by their porous internal structure consisting of hydroxyapatite and calcium carbonate crystal structures. Such materials have high potential for use as carriers for active substances such as oxygen scavenging agents. Oxygen scavengers are applied to packaging to preserve the quality of oxygen-sensitive products. This study investigated the potential of MCC as a novel carrier system for unsaturated fatty acids (UFAs), with the intention of developing an oxygen scavenger. Linoleic acid (LA) and oleic acid (OA) were loaded on MCC powder, and the loaded MCC particles were characterized and studied for their oxygen scavenging activity. For both LA and OA, amounts of 20 wt% loading on MCC were found to provide optimal surface area/volume ratios. Spreading UFAs over large surface areas of 31.6 and 49 m2 g−1 MCC enabled oxygen exposure and action on a multitude of molecular sites, resulting in oxygen scavenging rates of 12.2 ± 0.6 and 1.7 ± 0.2 mL O2 d−1 g−1, and maximum oxygen absorption capacities of >195.6 ± 13.5 and >165.0 ± 2.0 mL g−1, respectively. Oxygen scavenging activity decreased with increasing humidity (37–100% RH) and increased with rising temperatures (5–30 °C). Overall, highly porous MCC was concluded to be a suitable UFA carrier for oxygen scavenging applications in food packaging.

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