Search

The effects of CeO2 addition on the macro-morphology, surface cracks, microstructure, precipitated phases and wear property of laser cladding Ni-based coatings on 35CrMoV steel were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM), x-ray photoelectron spectroscopy (XPS) and friction and wear tester, respectively. The results indicated that the microstructure could be remarkably refined with the addition of CeO2. The width of eutectic structure is reduced from 1.74 μm to 237.5 nm with the amount of CeO2 increases from 0 to 4.0 wt.%. Meanwhile, CeO2 significantly decreases the number of the oxides and it can be obtained the minimal number of cracks when the CeO2 addition reaches 4.0 wt.%. The main phase composition of Ni60 cladding layer is Ni3Fe, Ni3V, Cr23C6 and Fe5C2. The distortional zone was observed around the eutectic of the coating. The average friction coefficient (0.438) and the wear resistance are the best when the addition of CeO2 is 4.0 wt.%. [ABSTRACT FROM AUTHOR]

Porous nanoflower-like, micropancake-like and microflower-like Co 3 O 4 micro/nanostructures were synthesized by a template-free aqueous solution route combined with subsequent thermal treatment. Techniques of X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermal analysis, and transmission electron microscopy were used to characterize the structure and morphology of the products. The experimental results show that three kinds of morphologies of cobalt precursors can be achieved by addition of ammonia at different temperatures. The corresponding Co 3 O 4 hierarchical micro/nanostructures were obtained after 500 °C calcinations. In addition, the obtained porous Co 3 O 4 hierarchical micro/nanostructures were used as catalyst to photodegrade Rhodamine B, methylene blue, p-nitrophenol, eosin B, and methyl orange. Compared with porous Co 3 O 4 micropancakes, the as-prepared porous Co 3 O 4 nanoflowers and microflowers exhibit higher catalytic activities due to their large surface areas and porous hierarchical structures. The photocatalytic reaction rate constant of the porous Co 3 O 4 nanoflowers in photocatalytic decomposition of Rhodamine B under UV light is calculated as 0.0828 min −1 . [ABSTRACT FROM AUTHOR]

TiC-14 wt%TiC 0.4 and TiC-7.63 wt%Ti ceramics were fabricated by spark plasma sintering (SPS) at a sintering temperature of 1600 °C and an applied pressure of 40 MPa. The impact of ex-situ addition and in-situ formation of vacancies on the microstructures and mechanical properties of TiC composites were investigated. The microstructures were analysed by XRD, SEM, EDS and TEM. The results reveal that TiC 1-x phases with different Ti/C ratios exist in the TiC-14 wt%TiC 0.4 ceramics, which have the same crystal structure and similar lattice parameters. In contrast, only a single phase of TiC 1-y exists in the TiC-7.63 wt%Ti ceramics. The introduced carbon vacancies not only lowered the sintering temperature, but also had a toughening effect on the material. At a sintering temperature of 1600 °C, the TiC-14 wt%TiC 0.4 and TiC-7.63 wt%Ti materials had densities of 98.5% and 99.2%, both materials exhibited excellent mechanical properties Vickers hardness and fracture toughness of 22.5 GPa, 5.2 MPa m1/2 and 23.5 GPa, 4.9 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

Spark plasma sintering (SPS) technology has obvious advantages in the preparation of high entropy alloys (HEAs) with high mechanical properties, but the mechanism of their magnetic enhancement is not clear. In this work, HEAs with high saturation magnetization (Ms) and excellent mechanical properties were designed and prepared. The properties of Fe 9.4 Co 6.7 Ni 6.6 Mn 0.9 V 0.9 HEA were optimized by adding Cu element, and the main phase of the HEAs was (face-centered cubic) FCC phase. The addition of Cu element mitigates the distortion of the FCC phase, resulting in an increase in the intensity of Ms value for the alloy from 118 emu/g to 143.7 emu/g. However, this also leads to a slight reduction in yield strength while still maintaining a high level at 1132 MPa. Theoretical calculations based on first principles indicate that the magnetic enhancement of these alloys is facilitated by an increase in the atomic magnetic moments of their ferromagnetic constituents. [ABSTRACT FROM AUTHOR]

The high melting point and the covalent bond between Ti and N made the titanium nitride matrix composites difficult to sinter using conventional sintering methods. TiN 0.3 and onion-like carbon (OLC) were used as starting materials for the preparation of TiN 0.3 /onion-like carbon composites under high pressure and high temperature (HTHP) of 5.0 GPa and 1100–1400 °C for 10 min. The phase formation, microstructure, and mechanical properties of TiN 0.3 composites with different contents of onion-like carbon were systematically investigated by XRD, SEM, and TEM. The experimental results showed that TiC 0.3 N 0.7 was formed by diffusion of TiN 0.3 with onion-like carbon due to the dual effect of high concentration of N vacancies and high pressure, and the onion-like carbon was gradually graphitized with increasing temperature. The composites of TiN 0.3 /5 vol% onion-like carbon sintered at 1200 °C possessed the optimum properties, with hardness of 15.2 GPa and fracture toughness of 3.9 MPa·m1/2. Compared with TiN composites prepared by conventional methods, the non-stoichiometric compound reduced the sintering temperature of the TiN composites. [Display omitted] • The OLC was used as a binding agent component. • The Vickers hardness of the sintered body was enhanced by the diamond. • A new method of forming TiC 0.3 N 0.7 by N vacancies in TiN 0.3 with OLC defects [ABSTRACT FROM AUTHOR]