Combustion Synthesis of Large Bulk Nanostructured Ni 65

A large bulk nanostructured Ni65Al21Cr14 alloy with dimensions of Φ 100 mm × 6 mm was produced by combustion synthesis technique followed with rapid solidification. The Ni65Al21Cr14 alloy was composed of γ′-Ni3Al/γ-Ni(Al, Cr) eutectic matrix and γ-Ni(Al, Cr) dendrite. The eutectic matrix consisted of 80–150 nm cuboidal γ′-Ni3Al and 2–5 nm γ-Ni(Al, Cr) boundary. The dentrite was comprised of high-density growth twins with about 3–20 nm in width. The nanostructured Ni65Al21Cr14 alloy exhibited simultaneously high fracture strength of 2200 MPa and good ductility of 26% in compression test

Ultrafine Eutectic-Dendrite Composite Bulk Fe-B Alloy with Enhanced Ductility

Bulk Fe 2 B and Fe 3 B alloys have been prepared by a self-propagating high temperature synthesis combining rapid solidification technique. The Fe 2 B and Fe 3 B alloys are composed of t-Fe 2 B dendrite and ultrafine eutectic matrix with t-Fe 2 B and -Fe, and the dendrites are rounded by the matrix. The volume fractions of the dendrite of the Fe 2 B and Fe 3 B alloys are 90% and 20%, respectively. The fracture strength reduces from 3400 MPa to 2660 MPa with the increase of dendrite content, but the strain at fracture rises markedly from 3% to 19%. The result indicates that a small quantity of dendrites embedded in the ultrafine eutectic matrix can reinforce the ductility

Wear Behaviour of Nanocrystalline Fe88Si12 Alloy in Water Environment

Wear behaviour of nanocrystalline Fe88Si12 alloy has been investigated in water environment compared with the coarse grained counterpart. The friction coefficient of the Fe88Si12 alloy changes slightly with the grain size. The wear resistance is enhanced as the grain size decreases first and then reduces when the grain size continues to decrease, although the hardness of the Fe88Si12 alloy decreases monotonically with the grain size. It is contrary to the predications of Archard’s formula. The best wear resistance of Fe88Si12 alloy with grain size of 40 nm in our present work is attributed to the proper grain boundary volume fraction and composite phase structures of disordered B2 and ordered D03

Preparation of Ferrite Magnetic Nano-Catalysts and Their Applications in the Field of Resources and Energy

With the development of exploitation technique, oil resources development and utilization have increased. However, the existing oil resources are complex in composition and high in viscosity. The use of conventional catalysts for upgrading has problems of low utilization efficiency, difficulty in recovery, etc. Biomass has emerged as a potential alternative to the dwindling fossil fuel reserves. Catalytic conversion of biomass has become one of the main routes for the transformation of biomass into a variety of commodity chemicals or liquid fuels. However, the common homogeneous and heterogeneous catalysts used in biomass catalytic conversion also have problems such as difficulty in recycling and big consumption, which limits their applications. Magnetic nano-catalysts, as new catalysts, not only have high catalytic activity, but also can be separated under the external magnetic field, achieving their recovery and reuse, making industry production serialization, reducing the cost of chemical production, and improving the production. Here we review the preparation methods of ferrite magnetic nano-catalysts. We also present their recent advances in the fields of catalytic desulfurization, catalytic conversion of biomass to chemicals, production of biodiesel, coal liquefaction, and analyze the problems to be solved for the specific applications in the field of resources and energy. Finally, the prospects on the application of ferrite magnetic nanoparticles are outlined

Facile synthesis of magnetic recyclable Fe3O4@PDA@MoS2 nanocomposites for effectively hydrocracking of residue

Magnetic nanocomposites provide manifold perspectives for sustainable development. However, the cumbersome operation process and energy consumption after treatment limit its application in the practical industry. Herein, we present a simple and universal strategy to synthesize Fe3O4@PDA@shell nanoparticles via in-situ homogeneous hydrolysis reaction growth different nanomaterials on the PDA modified Fe3O4 nanospheres, which can avoid multistep repetitive washing, redispersing, and drying. As an example, we introduced the synthesis process of Fe3O4@PDA@MoS2 catalyst used for heavy oil hydrocracking in detail. The synthesis processes were significantly simplified and the dispersity and stability of the nanosized MoS2 were improved due to the copious functional groups and strong adhesion properties of polydopamine. The as-prepared Fe3O4@P-DA@MoS2 nanoparticle catalysts showed high activity and excellent stability. The viscosity of residue was decreased by 99.8% and the recovery of the catalyst reached 90% under harsh conditions (405 degrees C at 13 MPa H-2). We also demonstrate the versatility of this strategy for other shell materials, such as WS2, VS2, Pd, and Rh components, which is promising for designing multifunctional core-shell-shell materials for various applications

Novel magnetic carbon supported molybdenum disulfide catalyst and its application in residue upgrading

A novel hybrid material consisted of carbon covered Fe3O4 nanoparticles and MoS2 nanoflower (FCM) was designed and prepared by micelle-assisted hydrothermal methods. Multiple techniques, including X-Ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize it. The results show that FCM has a flower-like morphology with a 330 nm Fe3O4 core as well as 70 nm highly crystalline MoS2 shell. FCM is superparamagnetic with a saturation magnetization of 35 emu g(-1). Then hydrocracking of Canadian bitumen residue (CBR) was applied to estimate its catalytic activity. The results show that FCM exhibits superior catalytic hydrocracking activity compared to bulk MoS2 and commercial oil-dispersed Mo(CO)(6) by the same Mo loading. Further measurement by elemental analysis, XPS and XRD reveals that the MoS2 nanoflower with abundant catalytic active sites and covered carbon layer with anti-coke ability donate to the superior upgrading performance. Besides, the catalysts can be easily recovered by the external magnetic field. This work provides a novel kind magnetic nanocatalyst which is potential for slurry-phase hydrocracking applications. (C) 2020, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communi-cations Co., Ltd

Control of metal-support interaction in magnetic MoS2 catalyst to enhance hydrodesulfurization performance

Studies on the metal-support interaction have been a key step for deeply understanding the catalytic behavior of hydrodesulfurization (HDS) reactions. In particular, modification of the surface hydroxyl groups on alumina can determine its surface metal species and their dispersion degrees and thus influence the reactivity of catalysts. Herein, magnetic MoS2 nanoparticles supported on thiol groups grafted alumina (Fe3O4@Al2O3-SH@MoS2) were synthesized, leading to excellent catalytic hydrodesulfurization performance in a slurry-phase reactor of 40% desulfurization efficiency and high stability of 105 h in the long-term evaluation. Density functional theory calculations and multiple catalyst characterizations demonstrated that the grafting of thiol groups not only significantly weakened the metal-support interaction by bridging the support and active phase but also inhibited the coke formation, improved the cycle performance of the catalyst. This work proves to be an effective method to adjust the metal-support interaction, leading to enhanced catalytic performance. Besides, the magnetic properties of the catalyst enable it to be separated from the reaction media quickly, which is promising to be used in slurry reactors that process heavy crude oil