| 261. |
- Jerroudi, M., et al.
(författare)
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Elaboration, Thermal and Structural Approach of Manganese Phosphate Glasses Inside the System of K2O-MnO2-P2O5
- 2020
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Ingår i: International Conference On Advanced Materials, Microscopy And Energy (ICAMME) 2019. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Glasses of the composition (50-x/2) K2O-xMnO(2)-(50-x/2) P2O5 with (0 <= x <= 30%mol), have been prepared by standard melt quenching procedures. The amorphous state of the glasses is evidenced using the X-Ray diffraction. Their physical properties were characterized by thermal analysis and density measurements. The density and the glass transition temperature increase with increasing in MnO2 content. To study the structural role of MnO2 oxide in studied glasses, the FTIR and Raman spectroscopies have been employed. It was highlighted that the presence of MnO2 allows the depolymerisation of the phosphate chains and formation of covalent bonds P-O-Mn, which replace P-O-P and P=O linkages.
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| 262. |
- Jerroudi, M., et al.
(författare)
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Optical and electrical properties of manganese doped-alkali metaphosphate glasses
- 2020
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Ingår i: Materials today. - : Elsevier BV. - 2214-7853. ; , s. 1052-1055
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Konferensbidrag (refereegranskat)abstract
- Phosphate glasses are of large interest for a variety of technological applications due to their several unique properties. In this work we investigate structural, optical and electrical properties of some alkali metaphosphate glasses doped with manganese oxide inside the system (50-x/2) K2O-xMnO(2)-(50-x/2) P2O5 with (0 <= x <= 30%mol). The glassy samples have been prepared using a melt-quench process. The obtained glasses are colored and the valence of manganese is composition dependence. The local structure of Mn2+ in the glasses is evaluated by EPR spectroscopy. The optical absorption spectra have been used to evaluate the values of the optical band gap (E-g) and Urbach energy (Delta E). The variation of these optical parameters as a function of composition is investigated. The presence of Mn3+ in the glasses is established by the optical absorption and this ion is associated with the absorption band at 520-530 nm. dc conductivity of the glasses is studied and it is found that it is thermally activated and followed an Arrhenius behavior.
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| 263. |
- Jerroudi, M., et al.
(författare)
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Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses
- 2021
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Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Nature. - 1388-6150 .- 1588-2926. ; 146, s. 1077-1090
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Tidskriftsartikel (refereegranskat)abstract
- Glasses in the system (1 - x)(0.5NaPO(3)-0.5KPO(3))-xMnO(2), with 0 <= x <= 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn(2+)and Mn(3+)ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (T-g) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (rho) as a structural index is found to increase while the corresponding molar volume decreases with MnO(2)content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn(2+)centers in the glasses. The UV-Visible absorption is utilized to estimate the values of the optical band gap (E-g) and Urbach energy (Delta E). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc's methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (E-c) and the Avrami parameter (n) were determined.
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| 264. |
- Kirkby, Jasper, et al.
(författare)
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Atmospheric new particle formation from the CERN CLOUD experiment
- 2023
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Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 16:11, s. 948-957
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol particles in the atmosphere profoundly influence public health and climate. Ultrafine particles enter the body through the lungs and can translocate to essentially all organs, and they represent a major yet poorly understood health risk. Human activities have considerably increased aerosols and cloudiness since preindustrial times, but they remain persistently uncertain and underrepresented in global climate models. Here we present a synthesis of the current understanding of atmospheric new particle formation derived from laboratory measurements at the CERN CLOUD chamber. Whereas the importance of sulfuric acid has long been recognized, condensable vapours such as highly oxygenated organics and iodine oxoacids also play key roles, together with stabilizers such as ammonia, amines and ions from galactic cosmic rays. We discuss how insights from CLOUD experiments are helping to interpret new particle formation in different atmospheric environments, and to provide a mechanistic foundation for air quality and climate models. The CLOUD experiment provides important insights into new particle formation in different atmospheric environments.
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| 265. |
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| 266. |
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| 267. |
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| 268. |
- Li, S., et al.
(författare)
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Two-dimensional correlation analysis for x-ray photoelectron spectroscopy
- 2021
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Ingår i: Journal of Physics B. - : Institute of Physics Publishing (IOPP). - 0953-4075 .- 1361-6455. ; 54:14
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) measures the binding energy of core-level electrons, which are well-localised to specific atomic sites in a molecular system, providing valuable information on the local chemical environment. The technique relies on measuring the photoelectron spectrum upon x-ray photoionisation, and the resolution is often limited by the bandwidth of the ionising x-ray pulse. This is particularly problematic for time-resolved XPS, where the desired time resolution enforces a fundamental lower limit on the bandwidth of the x-ray source. In this work, we report a novel correlation analysis which exploits the correlation between the x-ray and photoelectron spectra to improve the resolution of XPS measurements. We show that with this correlation-based spectral-domain ghost imaging method we can achieve sub-bandwidth resolution in XPS measurements. This analysis method enables XPS for sources with large bandwidth or spectral jitter, previously considered unfeasible for XPS measurements.
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| 269. |
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| 270. |
- Mishra, Suneeti, et al.
(författare)
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Rapid night-time nanoparticle growth in Delhi driven by biomass-burning emissions
- 2023
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 16:3, s. 224-230
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Tidskriftsartikel (refereegranskat)abstract
- Natural and anthropogenic biomass burning are among the major sources of particulate pollution worldwide that affects air quality, climate and human health. Delhi, one of the world’s most populated cities, experiences severe haze events caused by particulate pollution during winter, but the underlying pathways remain poorly understood. Here we observe intense and frequent nocturnal particle growth events during haze development in Delhi from measurements of aerosols and gases during January–February at the Indian Institute of Technology in Delhi. The particle growth events occur systematically despite the unfavourable condition for new-particle formation, including the lack of photochemical production of low-volatility vapours and considerable loss of vapours under extremely polluted conditions. We estimate that this process is responsible for 70% of the total particle-number concentration during haze. We identify that the condensation of primary organic vapours from biomass burning is the leading cause of the observed growth. The sharp decrease in night-time temperatures and rapid increase in biomass-burning emissions drive these primary organic vapours out of equilibrium, resulting in their condensation and the growth of nanoparticles into sizes relevant for haze formation. This high impact of primary biomass-burning emissions on night-time nanoparticle growth is unique compared with most urban locations globally, where low-volatility vapours formed through oxidation during the day drive particle growth and haze formation. As uncontrolled biomass burning for residential heating and cooking is rife in the Indo–Gangetic plain, we expect this growth mechanism to be a source of ultrafine particles, affecting the health of 5% of the world’s population and impacting the regional climate. Our work implies that regulating uncontrolled biomass-combustion emissions may help inhibit nocturnal haze formation and improve human health in India.
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