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Abstract The number of charge-discharge cycles in the lithium- iron- phosphate battery is limited by cathode degradation due to phase separation LiFePO4 → FePO4 + LiFePO4 .Same nature separation occurs spontaneously under ambient conditions in an optically transparent solid solution Na1-xAgxBr through formula Na1-xAgxBr → NaBr + AgBr. The mechanism of phase separation in Na1-xAgxBr can be used as a possible model of degradation of LiFePO4 cathode. In this paper, to study the phase separation in Na1-xAgxBr, a thin films of solid solutions at x = 0, 0.25, 0.50, 0.75, 1.0, were fabricated by rapid vacuum deposition (1-5 nm / s) of powder mixture on a glass or quartz substrates. Were also fabricated sandwiched films of the same thickness (100 nm), NaBr (t1) + AgBr (t2) where the thicknesses of layers t1 (t2) varied as 0 (100); 20 (80); 40 (60); 60 (40); 80 (20); 100 (0) nm. The absorption spectra of the films in a broad optical range of 200-900 nm, including the area of transparency of both layers and the absorption band of edge exciton of AgBr were measured with a daily interval. Morphological changes (granulation) in films were photographed through an optical microscope with 1000-fold magnification. The growth of the granules in a film were accompanied by transparency loss due to light scattering at the grains and widening of edge excitonic absorption band of AgBr. Annealing the films at 2000C before and after granulation slowed a growth of the granules, but did not lead to their disappearing. The work offers possible mechanism of granulation process in these films. Keywords: Thin films of a solid solution of Na1-xAgxBr, growth of granules, light scattering on a granules, excitonic absorption. Литература 1. Н.Тувжаргал, Б. Бат-Отгон, Ж. Даваасамбуу, Г. Еколд “ Изучение магнитных свойств и кинетики фазового разделения в LiхFePo4” Ученые записки Монгольского национального университета, серия “Физика” № 362 (17), стр. 108-110 (2012) 2. De Li, Haoshen Zhau “Two-phase transition of Li-intercalation compounds in Li-ion batteries” Materials Today, Volume 17, Issue 9, pages 451-463, November 2014. 3. This work has been done with financial support of the advanced research project of National University 4. of Mongolia on title: “Study of static displacement and phase transitions in solid solutions” (2016), 5. And the research project: “The investigation of heavy metal contamination of soil on Hanbogd and 6. Tsogttsetsii villages of Umnugobi province, where located OyuTolgoi and TavanTolgoi mines” (2015) 7. supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea. Acknowledgement This work has been done with financial support of the advanced research project of National University of Mongolia on title: “Study of static displacement and phase transitions in solid solutions” (2016), and the research project: “The investigation of heavy metal contamination of soil on Hanbogd and Tsogttsetsii villages of Umnugobi province, where located Oyu Tolgoi and Tavan Tolgoi mines” (2015) supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea.
Abstract The number of charge-discharge cycles in the lithium- iron- phosphate battery is limited by cathode degradation due to phase separation LiFePO4 → FePO4 + LiFePO4 .Same nature separation occurs spontaneously under ambient conditions in an optically transparent solid solution Na1-xAgxBr through formula Na1-xAgxBr → NaBr + AgBr. The mechanism of phase separation in Na1-xAgxBr can be used as a possible model of degradation of LiFePO4 cathode. In this paper, to study the phase separation in Na1-xAgxBr, a thin films of solid solutions at x = 0, 0.25, 0.50, 0.75, 1.0, were fabricated by rapid vacuum deposition (1-5 nm / s) of powder mixture on a glass or quartz substrates. Were also fabricated sandwiched films of the same thickness (100 nm), NaBr (t1) + AgBr (t2) where the thicknesses of layers t1 (t2) varied as 0 (100); 20 (80); 40 (60); 60 (40); 80 (20); 100 (0) nm. The absorption spectra of the films in a broad optical range of 200-900 nm, including the area of transparency of both layers and the absorption band of edge exciton of AgBr were measured with a daily interval. Morphological changes (granulation) in films were photographed through an optical microscope with 1000-fold magnification. The growth of the granules in a film were accompanied by transparency loss due to light scattering at the grains and widening of edge excitonic absorption band of AgBr. Annealing the films at 2000C before and after granulation slowed a growth of the granules, but did not lead to their disappearing. The work offers possible mechanism of granulation process in these films. Keywords: Thin films of a solid solution of Na1-xAgxBr, growth of granules, light scattering on a granules, excitonic absorption. Литература 1. Н.Тувжаргал, Б. Бат-Отгон, Ж. Даваасамбуу, Г. Еколд “ Изучение магнитных свойств и кинетики фазового разделения в LiхFePo4” Ученые записки Монгольского национального университета, серия “Физика” № 362 (17), стр. 108-110 (2012) 2. De Li, Haoshen Zhau “Two-phase transition of Li-intercalation compounds in Li-ion batteries” Materials Today, Volume 17, Issue 9, pages 451-463, November 2014. 3. This work has been done with financial support of the advanced research project of National University 4. of Mongolia on title: “Study of static displacement and phase transitions in solid solutions” (2016), 5. And the research project: “The investigation of heavy metal contamination of soil on Hanbogd and 6. Tsogttsetsii villages of Umnugobi province, where located OyuTolgoi and TavanTolgoi mines” (2015) 7. supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea. Acknowledgement This work has been done with financial support of the advanced research project of National University of Mongolia on title: “Study of static displacement and phase transitions in solid solutions” (2016), and the research project: “The investigation of heavy metal contamination of soil on Hanbogd and Tsogttsetsii villages of Umnugobi province, where located Oyu Tolgoi and Tavan Tolgoi mines” (2015) supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea.
Abstract Average copper recovery at the Erdenet Mining Corporation (EMC) is 86.5% and stable without any significant seasonal changes, while molybdenum recovery is lower (46%) and changes drastically during spring-summer season of each year. This molybdenum recovery volatility is the subject of this study. We suggest the bad and random molybdenum recovery is caused by seasonal changes of composition of dissolved salts, oxygen in circulating water that used for flotation enrichment at the EMC. The Central Research Laboratory (CRL) of the EML measures once at every month content of elements Cu, Fe, Ca, Mg, Mo and salt forming ions SO4 2- , HCO3 1- , CO3 2- and pH, hardness, dry residue in the circulating water. As shows our correlation analyses of CRL monthly data with weather data such as monthly average air temperature and moisture, wind speed, and precipitation during 2008-2011 years, content of dominant ions Ca2+, Mg2+ , SO4 2- , HCO3 1- and other ions in the circulating water changes seasonally: in summer-autumn season (July-to-October) content of dominant ions and dissolved oxygen, carbon dioxide changes rapidly in consistent with rainfall net amount and wind intensity; during winter time (November – to - March), when the artificial lake is mostly covered with ice, content of two dominant ions pair Ca2+ - SO4 2- is high and stable, simultaneously, content of dissolved oxygen falls 3-4 times to 2-3 ppm level. During March-April period, artificial lake ice cover melts and dilutes circulating water, decreasing the dry residue of the circulating water up to 15-20%. The end of May-to- end of June period is very special. During this relatively warm, dry, and windy time, the surface water of the artificial lake intensively evaporates and circulating water becomes thick as during winter peak time. At the same time, because of high intense dry winds, artificial lake enriches with dissolved oxygen and carbon dioxide gases. So the circulating water contains higher amount of dissolved oxygen and SO4 2- ions during the spring-to-summer period. Surface of molybdenite particles in the pulp media can be oxidized in two steps if a presence of dissolved oxygen and SO4 2- ions are simultaneous and sufficient. This two step surface oxidation increases hydrophilic property of the molybdenite particles in the pulp and consequently decreases their floatability and finally causes bad recovery of molybdenum at the EMC during the spring-to-summer period. Acknowledgement: This work has been done with financial support of the advanced research project of National University of Mongolia on title “Study of static displacement and phase transitions in solid solutions” (2016) and the research project: “The investigation of heavy metal contamination of soil on Hanbogd and Tsogttsetsii villages of Umnugobi province, where located Oyu Tolgoi and Tavan Tolgoi mines” (2015) supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea.
Molybdenum recovery efficiency seasonal instability at the Erdenet Mining Corporation Average copper recovery at the Erdenet Mining Corporation (EMC) is 86.5% and stable without any significant seasonal changes, while molybdenum recovery is lower (46%) and changes drastically during spring-summer season of each year. This molybdenum recovery volatility is the subject of this study. We suggest the bad and random molybdenum recovery is caused by seasonal changes of composition of dissolved salts, oxygen in circulating water that used for flotation enrichment at the EMC. The Central Research Laboratory (CRL) of the EML measures once at every month content of elements Cu, Fe, Ca, Mg, Mo and salt forming ions SO4 2-, HCO31-, CO32- and pH, hardness, dry residue in the circulating water. As shows our correlation analyses of CRL monthly data with weather data such as monthly average air temperature and moisture, wind speed, and precipitation during 2008-2011 years, content of dominant ions Ca2+, Mg2+ , SO4 2-, HCO31- and other ions in the circulating water changes seasonally: in summer-autumn season (July-to-October) content of dominant ions and dissolved oxygen, carbon dioxide changes rapidly in consistent with rainfall net amount and wind intensity; during winter time (November – to - March), when the artificial lake is mostly covered with ice, content of two dominant ions pair Ca2+ - SO4 2- is high and stable, simultaneously, content of dissolved oxygen falls 3-4 times to 2-3 ppm level. During March-April period, artificial lake ice cover melts and dilutes circulating water, decreasing the dry residue of the circulating water up to 15-20%. The end of May-to- end of June period is very special. During this relatively warm, dry, and windy time, the surface water of the artificial lake intensively evaporates and circulating water becomes thick as during winter peak time. At the same time, because of high intense dry winds, artificial lake enriches with dissolved oxygen and carbon dioxide gases. So the circulating water contains higher amount of dissolved oxygen and SO4 2- ions during the spring-to-summer period. Surface of molybdenite particles in the pulp media can be oxidized in two steps if a presence of dissolved oxygen and SO4 2- ions are simultaneous and sufficient. This two step surface oxidation increases hydrophilic property of the molybdenite particles in the pulp and consequently decreases their floatability and finally causes bad recovery of molybdenum at the EMC during the spring-to-summer period. Acknowledgement: This work has been done with financial support of the advanced research project of National University of Mongolia on title “Study of static displacement and phase transitions in solid solutions” (2016) and the research project: “The investigation of heavy metal contamination of soil on Hanbogd and Tsogttsetsii villages of Umnugobi province, where located Oyu Tolgoi and Tavan Tolgoi mines” (2015) supported by the Asia Research Center, Mongolia and Korea Foundation for Advanced Studies, Korea.
