Narrow Results

We successfully obtained Ni–B and Ni–B–Ce coatings with and without sonication on low-carbon steel (Q235) through electroless plating with the deposition time of 60min. The surface morphology and elemental composition of the coatings were evaluated by scanning electron microscopy (SEM) and inductively coupled plasma (ICP). The 11$\mu$m thick sonicated Ni–B–Ce (Son-Ni–B–Ce) coating is uniform with the composition of Ni 87.1%, B 6.2% and Ce 6.6%. X-ray diffraction (XRD) measurements implied a typical broaden peak around 44^∘, considered as amorphous structure which was confirmed by selected area electron diffraction pattern (SAED). Atomic force microscopy (AFM) showed a typical circular pit of Ni–B–Ce coating and Son-Ni–B–Ce coating. X-ray photoelectron spectroscopy (XPS) revealed the chemical status of coating components. The mechanical and corrosion resistance properties were determined by Vickers hardness tester, potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy (EIS) in 3.5wt. % NaCl solution. As a result, the Son-Ni–B–Ce coating revealed the optimum hardness (956HV), minimum roughness $R_a$ (92.38nm) and excellent corrosion resistance (3.65$\mu$Acm${}^{-2})$ among all coatings.

The mixed spin-1/2 and spin-1 Blume–Capel model is studied with randomly alternated coordination numbers (CN) on the Bethe lattice (BL) by utilizing the exact recursion relations. Two different CNs are randomly distributed on the BL by using the standard–random (SR) approach. It is observed that this model presents first-order phase transitions and tricritical points for variations of CNs 3 and 4, even if these behaviors are not displayed for the regular mixed-spin on the BL. The phase diagrams are mapped by obtaining the phase transition temperatures of the first- and second-order on several planes.

We investigated the compressive strength of PAN-based carbon fibers containing both amorphous and crystalline structures using molecular dynamics simulations. In addition, we investigated the buckling behavior of graphene and graphite crystals under compressive loading. The calculated buckling stresses of those crystals with different aspect ratios agree well with the results by the Euler's buckling theory. We finally found that the compressive strength of the PAN-based carbon fiber with a large amount of amorphous structures was 11 GPa. Moreover, a fracture of the PAN-based carbon fiber begins due to the buckling of carbon layers in crystallites, and propagates with the shear slipping in the crystallites. On the other hand, the compressive strength of the carbon fiber with a small amount of amorphous structures was only 2 GPa. Thus, it was found that the amorphous structure significantly affects the compressive strength of PAN-based carbon fibers.

We studied the theoretical Curie temperature of a dual-phase nanomagnetic system by Monte Carlo simulation of a modified Heisenberg model on a 3D complex lattice consisting of single- and cluster-spins. We also systematically investigated the experimental Curie temperature of a dual-phase nanomagnetic alloy and performed a direct comparison between theory and experiment. The exchange coupling between two component magnetic phases substantially affects the Curie temperature of the intergranular amorphous region of a dual-phase nanomagnetic system. The depends upon the nanocrystallite size d, the volume fraction V_c and the interspace among crystallites ξ. Large crystallized volume fraction V_c, small grain size d, and thin interphase thickness ξ lead to an obvious enhancement of Curie temperature (ECT) of intergranular amorphous region, whereas the Curie temperature of nanocrystallites decreases slightly. By simulation, we worked out a relationship between the reduced ECT and ξ, as , and it conforms to the experimental result. In addition, we also simulated the demagnetization of a hard–soft nanocomposite system. The exchange coupling between two component phases affects the cooperativity of two-phase magnetizations, the coherent reversal of magnetizations, and coercivity.

Fe-based amorphous alloys are widely used in the magnetic apparatus and generally produced by the single-roller copper-wheel melt spinning method. Spray forming is one of the rapid solidification techniques as the spinning method is, seldom used to fabricate Fe-based amorphous alloys. However in this paper, a Fe-based alloy with the nominal composition of Fe_73.5Cu₁Nb₃Si_13.5B₉ (at.%) alloy was fabricated by spray forming technique with the aim of investigating the formation of amorphous phases and novel microstructures by the high cooling rate involved in this process. The gas/metal mass flow rate used was 0.15, and nitrogen was used as the atomization gas. The resulting deposit and the overspray powder had a median diameter of about 50 μm with a total weight of about 2.2 kg. The microstructure of the deposit was observed by utilizing the X-Ray Diffraction (XRD) and Optical Microscope (OM), as well as Transmission Electron Microscope (TEM), which revealed a heterogeneous varying with the thickness, presenting at center region 15 mm and at border 8 mm with porosities 4 and 9%, respectively. The thicker region showed a fully crystalline microstructure with grain size of about 250nm, whereas the thinner region had a partially amorphous phase with an average grain size of 40nm. The overspray powder was fully crystallized with the grain size of 80nm which was calculated from XRD spectra using the Scherrer formula. The magnetic properties were measured through VSM, giving a poor magnetic saturation value of about 0.3~0.6T. The coercive force was increased significantly.

Amorphous materials of the Si-(B)-C-N system have recently attracted considerable interest because of its hardness, low density, durability at extremely high temperature and easy to be prepared from precursor compounds by polymer route. The materials show a great potential to be used in the field of the Thermal Protective System (TPS) for the aircrafts, while the microstructure and chemical configuration are still not clearly revealed due to its complicated covalent character for this multi-component amorphous material. This paper focused on the characterization of polymer derived Si-(B)-C-N amorphous ceramic, various method were employed in order to obtain accurate information about the microstructure, chemical composition, bonding mode of components, such as TEM, EPMA, NMR and FT-IR. SiC crystalline was found existing in the amorphous glass, which indicates the preparation process was achieved accompanied by crystallization of SiC from polymer precursor. The microstructure of the researched material was analyzed and relative accurate chemical composition was obtained on the basis of characterization result, furthermore the covalent character of the amorphous material was deduced according to the characterization results obtained.

In this paper, rapid quenching of Ni from crystal to metallic glass (MG) at different external pressures is simulated by molecular dynamics. The pair distribution functions (PDFs), mean-square displacement, glass transition temperature ($T_g$) and elastic property are calculated and compared with each other. The split of the second PDF peak means the liquid’s transition to glass state starts as previously reported for other MGs. And the $R_i/R_1$ ratio rule is found to hold very well in Ni MG and reveals the SPO structural feature in the configurations. Moreover, with high external pressure, $T_g$ values are more approximated by density–temperature and enthalpy–temperature curves. At last, the elastic modulus and mechanics modulus of quenching models produced a monotonous effect with increasing external pressure and temperature.