| 1. |
- Chernova, E. A., et al.
(författare)
-
The role of oxidation level in mass-transport properties and dehumidification performance of graphene oxide membranes
- 2021
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 183, s. 404-414
-
Tidskriftsartikel (refereegranskat)abstract
- Here we report on gas and vapor transport properties of ultra-thin graphene oxide (GO) membranes, with various C:O ratios. Graphene oxide nanosheets with an average lateral size of 800 nm and C:O ratio ranging from 2.11 to 1.81 have been obtained using improved Hummers' method by variation of graphite:KMnO4 ratio. Thin-film selective layers based on the obtained graphene oxide have been spin-coated onto porous substrates. To extend the C:O range to 2.60, thermal reduction of GO membranes was applied. A decrease in C:O ratio leads to significant water vapor permeance growth to over 60 m(3)(STP).m(-2).bar(-1).h(-1) while the permeance towards permanent gases reduces slightly. According to the permeation and sorption measurements, a decisive role of H2O diffusivity has been established, while the water sorption capacity of the graphene oxide stays nearly independent of C:O ratio in GO. The result is supported by semi-empirical modeling which reveals diminution of H2O jump activation barriers with both increasing GO interlayer spacing and its oxidation degree. The height of the activation barriers was found to vary up to an order of magnitude within the entire range of relative humidity (0-100% RH), lowering significantly for strongly oxidized GO. Our results evidence the necessity of attaining maximum GO oxidation degree for improving water transport in GO, especially at low partial pressures.
|
|
| 2. |
- Akperov, M. G., et al.
(författare)
-
Wind Energy Potential in the Arctic and Subarctic Regions and Its Projected Change in the 21st Century Based on Regional Climate Model Simulations
- 2022
-
Ingår i: Russian Meteorology and Hydrology. - 1068-3739 .- 1934-8096. ; 47:6, s. 428-436
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative estimates of changes in wind energy resources in the Arctic were obtained using the RCA4 regional climate model under the RCP4.5 and RCP8.5 climate change scenarios for 2006–2099. The wind power density proportional to cubic wind speed was analyzed. The procedure for the model near-surface wind speed bias correction using ERA5 data as a reference with subsequent extrapolation of wind speed to the turbine height was applied to estimate the wind power density (WPD). According to the RCA4 simulations for the 21st century under both anthropogenic forcing scenarios, a noticeable increase in the WPD was noted, in particular, over the Barents, Kara, and Chukchi seas in winter. In summer, a general increase in the WPD is manifested over the Arctic Ocean. The changes are more significant under the RCP8.5 scenario with high anthropogenic forcing for the 21st century. According to model projections, an increase in the interdaily WPD variations does not generally lead to the deviations of wind speed to the values at which the operation of wind generators is unfeasible.
|
|
| 3. |
- Cao, Wei, et al.
(författare)
-
Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets
- 2021
-
Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 13:1, s. 1592-1602
-
Tidskriftsartikel (refereegranskat)abstract
- Spray deposition is a scalable and cost-effective technique for the fabrication of magnetic hybrid films containing diblock copolymers (DBCs) and magnetic nanoparticles. However, it is challenging to obtain spray-deposited anisotropic magnetic hybrid films without using external magnetic fields. In the present work, spray deposition is applied to prepare perpendicular anisotropic magnetic hybrid films by controlling the orientation of strontium hexaferrite nanoplatelets inside ultra-high-molecular-weight DBC polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films. During spray deposition, the evolution of DBC morphology and the orientation of magnetic nanoplatelets are monitored with in situ grazing-incidence small-angle X-ray scattering (GISAXS). For reference, a pure DBC film without nanoplatelets is deposited with the same conditions. Solvent-controlled magnetic properties of the hybrid film are proven with solvent vapor annealing (SVA) applied to the final deposited magnetic films. Obvious changes in the DBC morphology and nanoplatelet localization are observed during SVA. The superconducting quantum interference device data show that ferromagnetic hybrid polymer films with high coercivity can be achieved via spray deposition. The hybrid films show a perpendicular magnetic anisotropy before SVA, which is strongly weakened after SVA. The spray-deposited hybrid films appear highly promising for potential applications in magnetic data storage and sensors.
|
|
| 4. |
- Akperov, Mirseid, et al.
(författare)
-
Future projections of wind energy potentials in the arctic for the 21st century under the RCP8.5 scenario from regional climate models (Arctic-CORDEX)
- 2023
-
Ingår i: Anthropocene. - 2213-3054. ; 44
-
Tidskriftsartikel (refereegranskat)abstract
- The Arctic has warmed more than twice the rate of the entire globe. To quantify possible climate change effects, we calculate wind energy potentials from a multi-model ensemble of Arctic-CORDEX. For this, we analyze future changes of wind power density (WPD) using an eleven-member multi-model ensemble. Impacts are estimated for two periods (2020-2049 and 2070-2099) of the 21st century under a high emission scenario (RCP8.5). The multi-model mean reveals an increase of seasonal WPD over the Arctic in the future decades. WPD variability across a range of temporal scales is projected to increase over the Arctic. The signal amplifies by the end of 21st century. Future changes in the frequency of wind speeds at 100 m not useable for wind energy production (wind speeds below 4 m/s or above 25 m/s) has been analyzed. The RCM ensemble simulates a more frequent occurrence of 100 m non-usable wind speeds for the wind-turbines over Scandinavia and selected land areas in Alaska, northern Russia and Canada. In contrast, non-usable wind speeds decrease over large parts of Eastern Siberia and in northern Alaska. Thus, our results indicate increased potential of the Arctic for the development and production of wind energy. Bias corrected and not corrected near-surface wind speed and WPD changes have been compared with each other. It has been found that both show the same sign of future change, but differ in magnitude of these changes. The role of sea-ice retreat and vegetation expansion in the Arctic in future on near-surface wind speed variability has been also assessed. Surface roughness through sea-ice and vegetation changes may significantly impact on WPD variability in the Arctic.
|
|
