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It is difficult for controlling the micro/nanostructures of composite unit on the surface of two-dimensional (2D) materials to fabricate the new high-efficiency photocatalysts. The ...mes-Fe3O4/g-C3N4 composite is fabricated by the modification of mesoporous Fe3O4 (mes-Fe3O4) nanospheres on the surface of 2D graphitic carbon nitride (g-C3N4) nanosheets. The mes-Fe3O4 nanospheres as the natural nanoreactors enlarge the specific surface area to increase reaction active sites, as well as provide the confined space to accelerate degradation reaction. Meanwhile, the physical and photoelectrochemical properties of mes-Fe3O4/g-C3N4 composite are distinctly improved owing to the electron collection effect of mes-Fe3O4 nanoreactors. The mes-Fe3O4/g-C3N4 composites exhibit the improved degradation performance for removing tetracycline hydrochloride (TC-HCl) relative to single g-C3N4. Moreover, the possible intermediate product and photocatalytic reaction mechanism are revealed in depth. This work gives a new guidance for the controlled fabrication of mesoporous nanoreactors on the surface of 2D materials.
•A deep literature review on DT applications in manufacturing is performed.•Rarely a DT environment offers a large set of services to the real system.•Almost never a DT share the elaborated analysis ...to the real counterpart.•A DT application is proposed in a Simulink environment to overcome these gaps.•The illustrated DT poses the basis for further improvements.
In the Industry 4.0 era, the Digital Twin (DT), virtual copies of the system that are able to interact with the physical counterparts in a bi-directional way, seem to be promising enablers to replicate production systems in real time and analyse them. A DT should be capable to guarantee well-defined services to support various activities such as monitoring, maintenance, management, optimization and safety. Through an analysis of the current picture of manufacturing and a literature review about the already existing DT environment, this paper identifies what is still missing in the implemented DT to be compliant to their description in literature. Particular focuses of this paper are the degree of integration of the proposed DT with the control of the physical system, in particular with the Manufacturing Execution Systems (MES) when the production system is based on the Automation Pyramid, and the services offered from these environments, comparing them to the reference ones.
This paper proposes also a practical implementation of a DT in a MES equipped assembly laboratory line of the School of Management of the Politecnico di Milano. The application has been created to pose the basis to overcome the missing implementation aspects found in literature. In such a way, the developed DT paves the way for future research to close the loop between the MES and the DT taking into consideration the number of services that a DT could offer in a single environment.
The influence of different iron carbides on the activity and selectivity of iron-based Fischer–Tropsch catalysts has been studied. Different iron carbide phases are obtained by the pretreatment of a ...binary Fe/SiO2 model catalyst (prepared by coprecipitation method) to different gas atmospheres (syngas, CO, or H2). The phase structures, compositions, and particle sizes of the catalysts are characterized systematically by XRD, XAFS, MES, and TEM. It is found that in the syngas-treated catalyst only χ-Fe5C2 carbide is formed. In the CO-treated catalyst, Fe7C3 and χ-Fe5C2 with a bimodal particle size distribution are formed, while the H2-treated catalyst exhibits the bimodal size distributed ε-Fe2C and χ-Fe5C2 after a Fischer–Tropsch synthesis (FTS) reaction. The intrinsic FTS activity is calculated and assigned to each corresponding iron carbide based on the phase composition and the particle size. It is identified that Fe7C3 has the highest intrinsic activity (TOF = 4.59 × 10–2 s–1) among the three candidate carbides (ε-Fe2C, Fe7C3, and χ-Fe5C2) in typical medium-temperature Fischer–Tropsch (MTFT) conditions (260–300 °C, 2–3 MPa, and H2/CO = 2). Moreover, FTS over ε-Fe2C leads to the lowest methane selectivity.
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