The continuous drive towards electrified propulsion systems has been imposing ever more demanding performance and cost targets for the future power electronics, machines and drives (PEMDs). This is ...particularly evident when exploring various technology road mapping documents both for automotive and aerospace industries, e.g. Advanced Propulsion Centre (APC) UK, Aerospace Technology Institute (ATI) UK, National Aeronautics and Space Administration (NASA) USA and others. In that context, a significant improvement of the specific performance and cost measures, e.g. power density increase by a factor of 10 or more and/or cost per power unit reduction by 50% or better, is forecasted for the next 5 to 15 years. However, the existing PEMD solutions are already at their technological limits to some degree. Consequently, meeting the performance and cost step change would require a considerable development effort. This paper is focused on electrical machines and their thermal management, which has been recognised as one of key enabling factors for delivering high specific output solutions. The challenges associated with heat removal in electrical machines are discussed in detail, alongside with new concepts of thermal management systems. Several examples from the available literature are presented. These include manufacturing techniques, new materials and novel integrated designs in application to electrical machines.
•Biomass-derived activated carbons with high CO2 uptake are successfully prepared.•The highest CO2 capture capacity of 6.03mmol/g at 273K and 1bar is achieved.•The highest CO2 capture capacity of ...4.18mmol/g at 298K and 1bar is achieved.•Micropore range for CO2 uptake at various temperatures and pressures are revealed.
This work reports on the preparation and examination of biomass-derived activated carbons featuring high CO2 adsorption capacity. A detailed micropore structure analysis and surface characterization were performed using nitrogen adsorption isotherms at 77K and carbon dioxide isotherms at 273K. At 273K and 1bar only micropores in the range of 0.30–0.86nm were mainly effective for CO2 adsorption. When the temperature increased to 298K, the ranges of effective micropores for CO2 adsorption at 1bar decreased to 0.30–0.33nm. For the typical flue gas conditions (partial pressure of CO2 0.15bar), micropores in the range of 0.30–0.57nm were mainly effective for CO2 adsorption. The precursor had a strong effect on the textural properties of the resulting carbon and CO2 adsorption. Activated carbon prepared from pomegranate peels showed the highest CO2 adsorption and selectivity (CO2/N2). The experimental isotherm data of activated carbon produced from pomegranate peels were analysed using Langmuir, Freundlich, Sips, and Toth isotherm equations. The fitting details showed that the multitemperature Toth equation is a powerful tool to mathematically represent CO2 isotherms on activated carbon produced from pomegranate peels. The isosteric heat of adsorption was calculated by fitting the Toth equation to the adsorption isotherms and applying the Clausius–Clapeyron equation. The value of the heterogeneity coefficient and isosteric heat of adsorption suggested heterogeneous interactions between CO2 and sorbent surface.
The adsorption of CO2 on commercial activated carbon WG12 and WG12 modified by ZnCl2 and KOH was investigated using a high pressure Sievert’s apparatus. The experimental data were analyzed using ...Langmuir, Freundlich, Sips, Toth, Unilan, Ftitz–Schlunder, and Redlich–Peterson equations. An error analysis was performed to examine the effect of using different error criteria for the isotherm parameters determination. Five error analysis methods were used: the sum of the squares of errors, the hybrid fractional error function, the average relative error, the Marquardt’s percent standard deviation, and the sum of the absolute errors. The Sips isotherm provided the best quality of fitting for all the experimental data. Error function analysis found that sum of the squares of the errors and hybrid fractional error function provided the best overall results.
This work describes the effect of nitrogen and oxygen functional groups on the sorption properties of activated carbons produced from furfuryl alcohol. The poly(furfuryl) alcohol underwent ...carbonization in nitrogen, ammonia, and ammonia and air (in a 3:2 proportion) atmospheres at 600 °C for 4 h. The resulting materials were subsequently activated in a carbon dioxide atmosphere for 1 h at temperatures of 700 °C, 800 °C, 900 °C, and 1000 °C. The X-ray photoelectron spectroscopy (XPS) findings suggest that ammoxidation is superior to amination in terms of nitrogen doping. The maximum nitrogen concentration achieved after ammoxidation was 25 at.%, which decreased to 4 at.% after activation. Additionally, it was observed that oxygen functional groups have a greater impact on porous structure development compared to nitrogen functional groups. The materials activated through carbonization under an ammonia/air atmosphere attained the highest oxygen concentration of roughly 19 at.% as confirmed by XPS. The materials were evaluated for their sorption capacities for carbon dioxide and ethylene, which were 2.2 mmol/g and 2.9 mmol/g, respectively, at 30 °C.
Display omitted
•Additive manufacturing is used to physically model Reinforced Concrete at a 1:30 scale.•Submillimeter diameter rebars of suitable mechanical and bond behavior are used.•Tuning of ...printing parameters, bar surface roughness and concrete mix is needed to maintain similitude.•Additional surface ribs should be printed with the bars to simulate prototype bond behavior.•Gypsum-based mixes are more similar to prototype concrete than cement-based mixes.
Small scale (∼1:30–1:40) Reinforced Concrete is useful for centrifuge testing. However, manufacturing the reinforcing cages by hand at this scale is practically difficult. This paper suggests that small scale reinforcement can be manufactured using a metal 3D printer. Mechanical properties of 3D printed submillimeter rebars are discussed and compared to properties of typical prototype rebars. Different model concrete mix designs are tested to identify optimal mixes. Pullout tests of rebars with different surface rib configurations embedded in different concrete mixes are discussed.
Based on the test results, by modulating the printing parameters it seems feasible to obtain 3D printed submillimeter bars that can be used as physical models of prototype rebars. A gypsum-based model concrete was more similar to prototype concrete than cement-based mixes. Most importantly, bond slip behavior that is comparable to full-scale concrete could be achieved, something that is vital and has never been reported before.
The aim of this study was to prepare activated carbon materials with different porous structures. For this purpose, the biomass precursor, beech wood, was carbonized in an inert atmosphere, and the ...obtained charcoal was physically activated using carbon dioxide at 1273 K. Different porous structures were obtained by controlling the time of the activation process. Prepared materials were characterized in terms of textural (N
sorption at 77 K), structural (XRD), and sorption properties (CO
, C
H
, C
H
). The shortest activation time resulted in a mostly microporous structure, which provided a high sorption of CO
. Increasing the activation time led to an increasing of the pores' diameters. Therefore, the highest ethene uptake was obtained for the material with an intermediate activation time, while the highest butane uptake was obtained for the material with the highest activation time.
•The catalysts: Fe3O4 (Fe2+ and Fe3+) on AC were obtained by N2 treatment at 550°C.•Studies on the oxidation of limonene were carried out.•All catalysts were active in the oxidation process.•Perillyl ...alcohol was the main product of the process.•The proposed oxidation method is ecologically friendly and save.
The catalysts in the form of an activated carbon EuroPh supported Fe were prepared and characterized structurally and chemically by XRD, nitrogen sorption, FESEM, EDX, and ICP-AES methods. The active phase was magnetite Fe3O4. The concentration of Fe in the catalysts was equal to 0.68, 1.32, 2.64wt%. The catalytic activity of the obtained catalysts was examined in limonene oxidation with hydrogen peroxide and tert-butyl hydroperoxide as oxidants. The studies were carried out in a batch reactor. The catalytic activity of the recovered catalysts was also tested. The research showed that all from the studied catalysts were active in the limonene oxidation. As a result of limonene oxidation the following products were mainly obtained: 1,2-epoxylimonene diol, carveol, carvone and perillyl alcohol – products with a great importance. The reused catalysts were characterized by considerably lover activity in the limonene oxidation than in the first run, especially when the oxidation was performed with t-butyl hydroperoxide.
The formation of palladium subsurface oxygen, i.e., Pd(111) saturated with oxygen below the surface, has been demonstrated. This compound is much more stable than palladium surface oxide or bulk ...palladium oxide, which easily reacts with CO at elevated temperatures. The catalytic activity of an atomically clean Pd(111) surface and of Pd(111) affected by subsurface oxygen (coverage Θ = 0.00–0.46 ML) was studied during the CO oxidation reaction. The measurements were performed for a temperature range of 353–523 K, partial pressures of reactants in the range of 10–7–10–5 mbar, and different subsurface oxygen content. A distinct, previously not observed feature in the dependency of the reaction rate vs temperature was found. Furthermore, it was found that subsurface oxygen reduces the catalytic activity of the Pd(111) surface significantly, which is attributed to reduction of the sticking coefficient of CO and oxygen. In the temperature range applied for investigation of catalytic CO oxidation, the rate of the formation of subsurface oxygen is negligible. However, the formation of this phase starts to be pronounced above ∼600 K. The presence of subsurface oxygen was confirmed by the KLL Auger transition excited by monochromatic X-ray radiation, not by electron beam. It was observed that the classical Auger measurement with an electron beam destroys the subsurface oxygen compound. The combination of the CO titration with Auger peak intensity measurements allows the quantitative analysis of the subsurface oxygen. The problem of subsurface oxygen detection and its impact on the adsorption of CO and oxygen on Pd(111) are discussed. It was suggested that subsurface oxygen and surface oxide can be manufactured simultaneously. Then the obtained activity in the CO oxidation reaction will be a result of two competitive effects, i.e., promoting from surface oxide and inhibiting from subsurface oxide. This might be a source of the discrepancy in results on the influence of surface oxide on the CO oxidation reaction measured by different researchers.
Cost-effective activated carbons for CO2 adsorption were developed from molasses using H2SO4, H3PO4, HCl, NaOH, and KOH as activating agents. At the temperature of 0 °C and a pressure of 1 bar, CO2 ...adsorption equal to 5.18 mmol/g was achieved over activated carbon obtained by KOH activation. The excellent CO2 adsorption of M-KOH can be attributed to its high microporosity. However, activated carbon prepared using HCl showed quite high CO2 adsorption while having very low microporosity. The absence of acid species on the surface promotes CO2 adsorption over M-HCl. The pore size ranges that are important for CO2 adsorption at different temperatures were estimated. The higher the adsorption temperature, the more crucial smaller pores were. For 1 bar pressure and temperatures of 0, 10, 20, and 30 °C, the most important were pores equal and below: 0.733, 0.733, 0.679, and 0.536 nm, respectively.
Activated carbons were prepared from avocado stone through NaOH activation and subsequent carbonization. The following textural parameters were achieved: specific surface area: 817–1172 m2/g, total ...pore volume: 0.538–0.691 cm3/g, micropore volume 0.259–0.375 cm3/g. The well-developed microporosity resulted in a good CO2 adsorption value of 5.9 mmol/g at a temperature of 0 °C and 1 bar and selectivity over nitrogen for flue gas simulation. The activated carbons were investigated using nitrogen sorption at −196 °C, CO2 sorption, X-ray diffraction, and SEM. It was found that the adsorption data were more in line with the Sips model. The isosteric heat of adsorption for the best sorbent was calculated. It was found that the isosteric heat of adsorption changed in the range of 25 to 40 kJ/mol depending on the surface coverage. The novelty of the work is the production of highly microporous activated carbons from avocado stones with high CO2 adsorption. Before now, the activation of avocado stones using NaOH had never been described.
PDF
