The rapid development of new energy vehicles requires permanent magnet materials that can work stably in the temperature range of 120℃~200℃. Sm₂Fe₁₇N₃ with Curie temperature of 476℃ and anisotropic field of 14.7 T has excellent intrinsic magnetic properties, and can be used in this temperature range. In order to improve the magnetic properties of Sm₂Fe₁₇N₃ powder, the particle size of which should be reduced to the critical size close to a single domain, so that to gain high anisotropic field; Meanwhile, surface oxidation caused by particle size reduction should be avoided to ensure high remanence magnetism and maximum magnetic energy product. High performance Sm₂Fe₁₇N₃ can be prepared by powder crushing, mechanical alloying, strip casting, thin strip continuous casting, reduction diffusion and surface plating. At the present, the coercivity and maximum magnetic energy product of Sm₂Fe₁₇N₃ powder prepared in laboratory have reached 28.1 kOe and 43.6 MGOe respectively. In this paper, the research results on the preparation of Sm₂Fe₁₇N₃ powders in recent years are reviewed, including preparation methods and the relevant mechanism, and key problems that remain to be solved, namely the relation of the coercivity and remanence of Sm₂Fe₁₇N₃ powder with the particle size, as well as with the particle magnetic domain structure；the mechanism related with the enhanced effect H₂ within the gas mixture NH₃/H₂ on the nitriding efficiency of the powder still needs to be revealed; further the secondary crushing technique in low oxygen pressures, which can prepare particles with uniform distribution of particle size, while adjust their morphology, remains to be developed; for the present reduction diffusion method, new precursors, and their preparation methods suitable for massive production, and water washing technology for rapid removal of calcium by-products were also needed to develop.

Nanocomposites of reduced graphene oxide coated cobalt or cobalt oxide (rGO@Co/CoO) were synthesized by solvothermal and high-temperature calcination method with solutions of AA grade Co and graphene oxide as raw materials. The prepared products are characterized by means of XRD, Raman spectroscopy, XPS, SEM and TEM. Results show that three type of composites could be fabricated by calcination at 350, 500 and 650°C respectively, namely rGO@CoO of face-centered cubic (fcc) phase, rGO@Co of fcc phase, and rGO@Co of fcc and hcp two-phases. Among others, the fcc rGO@Co (S500) exhibits excellent electromagnetic wave absorption properties (the relevant property was measured on a hollow ring made of the paraffin filled with the composite): The hollow ring with a low mass filling ratio of 10% (mass fraction) fcc rGO@Co (S500) nanocomposite presents the minimum reflection loss (RL_min) and maximum effective absorption bandwidth (EAB), corresponding to the RL_min and EAB are -74.5 dB and 6.1 GHz, respectively for the hollow ring with a wall of 2.5 mm in thickness. We believed that the present approach may be an economic and green route for the controllable synthesis of porous functionalized graphene materials as microwave absorbers.

The phase transition behavior of 0.1%C-3%Mn medium manganese steel was studied via thermal simulation with L78RITA automatic phase transformation instrument, meanwhile the effect of one-step and two-step austenite reverted transformation (ART) treatment on the microstructure and mechanical properties of the steel were also investigated. The results show that the two-step ART treatment produces more residual austenite than the one-step ART treatment, which can significantly improve the forming property of the steel. The hot rolled steel samples were pretreated at 740℃ and then heated to different temperatures for ART treatment, and it was found that 12%~14% of the retained austenite could be produced after treatment in temperature range of 660℃~680℃, which made the total elongation higher than 35% and the uniform elongation higher than 20% of the steel respectively. The steel heat treated in conditions of 740℃×0.5 h+670℃×1.0 h has the best comprehensive properties, namely the yield strength is 470 MPa, the tensile strength is 680 MPa, the total elongation is 40.7%, the uniform elongation is up to 25%, and the impact absorption energy is 163 J.

Alumina-forming austenitic (AFA) stainless steel has good high-temperature-oxidation resistance owing to the addition of Al. However, Al may strongly promote the formation of ferrite, which can seriously decrease the creep resistance of the steel. In order to form single-phase austenite, the amount of austenitic stable elements Ni and Al should be accurately tailored. Therefore, the alumina-forming 190 heat resistant stainless steels were analyzed with the so called cluster-plus-glue-atom model, which was previously developed by our group. In the present case, a 16-atom-cluster formula, including 1 center atom, 12 shell atoms and 3 glue atoms, simplified as [Al₁-Fe₁₂]-Cr₃, is adopted,while the composition proposed by Oak Ridge National Laboratory, and the equivalent complementation of Ni and Cr are taken into consideration. Thereby, two series of AFA stainless steels with a constant carbon content of 0.1% (mass fraction) are designed as: Al _x Si_0.05Nb_0.15-Fe_8.7Ni_3.0Mn_0.3-Cr_3.6-x Mo_0.2 (x=0.8, 1.0 and 1.1) and Al₁Si_0.05Nb_0.15-Fe_11.7-y Ni _y Mn_0.3-Cr_2.6Mo_0.2 (y=3.2, 3.4, 3.7 and 4.0), namely, fixed Ni, but varying Al (instead of Cr) content for the former series, and fixed Al, but varying Ni (instead of Fe) content for the later ones, respectively. The effect of solution treatment (1250℃/1.5 h) plus water quenching and the above treatment plus aging treatment (800℃/24 h) on the two series alloys was carefully characterized by means of X-ray diffractometer, optical microscope, scanning electron microscope and Vickers hardness tester. Results show that for the alloys with fixed Ni content of 3.0 designed according to the 16-atom-cluster formula, the matrix is single-phase austenite when Al is 0.8; while ferrite is formed when Al is 1.0 and 1.1. For the alloys with fixed Al of 1.0, the matrix remains single-phase austenite when Ni ranges from 3.2 to 4.0. However, Ni_3.2 is enough to avoid the formation of ferrite, while also conforming to economic principle. The ideal cluster formula of AFA stainless steels is identified as [(Al,Si,Nb)₁-(Fe,Ni,Mn)₁₂](Cr,Mo,W)₃, which describes the average distribution of atoms in alloys.

The tensile behavior of M2 high speed steel was studied by using an in-situ loading platform in scanning electron microscope (SEM). The results show that during the in-situ tensile process, microcracks mainly initiate and propagate at the interface between large eutectic carbide and the matrix of M2 high speed steel. Compared with the tempered martensite, cracks initiate more easily on the retained austenite. The size, shape and type of carbides also have important effect on the initiation and propagation of microcracks. It follows that reducing the amount and the size of massive residual austenite, primary eutectic carbides, and MC carbides, as well as appropriately adjusting the shape of carbides can slow down the initiation and propagation of microcracks.

The CNTs/metal composite film with excellent electrical conductivity was prepared by magnetron sputtering technique. the electrical conductivity of the CNTs/metal composite film can reach 10 times than that of the as-prepared CNT macrofilm (CMF, 300 S·cm^-1). In addition, a flexible LIBs with this film as the current collector was prepared, which, in comparison with the flexible LIBs with the simple CNTs film, presents higher rate capability. Moreover, its specific capacity can still be maintained at 132.6 mAh·g^-1 at a rate of 5 C, high-rate cycling performance i.e. 74.4% capacity retention rate after 200 cycles at 5 C rate, and larger output current up to 0.4 A.

The existence of defects in oil and gas pipelines will cause rapid changes in local area fluids where the defects located, which during oil and gas transportation may lead to pipeline corrosion failure. For understanding the nature of this phenomenon, the corrosion behavior of defects in CO₂ saturated NACE solution was studied via wire beam electrodes (WBE)- and electrochemical impedance spectroscope (EIS)-techniques, meanwhile, the relevant corrosion mechanism of defects located in different regions in the flow field was analyzed by means of the hydrodynamics modules of the so called "COMSOL Multiphysics". The results show that the variation of flow field on defects in different locations may lead to different appearance of corrosion there. The areas nearby the upper and lower edges of the defect may be subjected to large turbulent kinetic energy and wall shear stress, which may naturally act as anode, hence are suffered from serious corrosion. On the other hand, the bottom area of the defect and the area far away from the defect may act as cathode due to small turbulent kinetic energy and large boundary layer thickness, thus the corrosion progresses slowly there. With the extension of the flow corrosion time, the corrosion of the upper and lower edges of the defect becomes more serious, as a whole, defects have a tendency to expand and deepen vertically.

Titanium oxide nano-tubes (TiO₂ NTs) were firstly prepared by anodic oxidation method, and then Ag and carbonitride g-C₃N₄ were deposited onto TiO₂ NTs under the synergistic action of ultraviolet irradiation and microwave heating to prepare the ternary composite photocatalyst g-C₃N₄/Ag/TiO₂ NTs. Then the prepared composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV Vis diffuse reflectance spectroscopy (UV-Vis) and photoluminescence spectroscopy (PL).The results show that the composite of g-C₃N₄/Ag/TiO₂ NTs presents a higher degradation rate of 51.8% for the carbaryl under the simulated sunlight, in the contrast, that of the simple TiO₂ NTs is 29.1% only. The improvement of photocatalytic activity is related to the combined effect of the surface plasmon resonance effect of Ag, the excellent charge conductivity of Ag and the formation of heterojunction between g-C₃N₄ and TiO₂ NTs.