Chuncheng Yang

Structure and properties of Ni–P–graphite (Cg)–TiO2 composite coating

Abstract Titanium dioxide (TiO2) and graphite (Cg) particles were co-deposited with nickel–phosphorous (Ni–P) coatings through electroless deposition process. Surface morphology of the coatings was analysed by scanning electron microscope (SEM). X-ray diffraction (XRD) was used to detect the structure of the coatings. Microhardness of Ni–P–Cg–TiO2 composite coating showed a moderate hardness between Ni–P–Cg and Ni–P–TiO2 composite coating. DSC thermograms indicated that the thermostability of Ni–P coating could not be affected by TiO2 and/or Cg particles. Moreover, the friction coefficient and corrosion rate of Ni–P–TiO2 composite coating could be decreased by the addition of graphite particles.

Enhancing the efficiency of wastewater treatment by addition of Fe-based amorphous alloy powders with H2O2 in ferrofluid

Using combination of ferrofluid (FF) and Fe-based amorphous alloy in the advanced treatment of high concentration, organic wastewater was investigated. The addition of Fe73.5Nb3Cu1Si13.5B9 amorphous alloy powders into a FF give rise to a dramatic enhancement in decreasing chemical oxygen demand (COD) and decolorization. The removal rate of COD by using FF that combined Fe73.5Nb3Cu1Si13.5B9 metallic glass (MG) particles reached 92% in the presence of H2O2, nearly more than 50% higher than that by using only FF. Furthermore, compared with the FF, the decolorizing effect of the combination was 20% higher. It has been found that MG powders with the amorphous structures have high efficiency of waste water treatment and lead to high catalytic ability.

Metal-based magnetic functional fluids with amorphous particles

Two metal-based magnetic functional fluids, Ga–Sn and Ga–In magnetic liquids, were fabricated by doping with Fe73.5Nb3Cu1Si13.5B9 metallic glass particles and nanoscale Fe3O4 particles, respectively. The saturation magnetization of the metallic glass particles, Fe73.5Nb3Cu1Si13.5B9, is about 125 emu g−1, nearly 50% larger than that of Fe3O4 crystalline particles which are usually used in water-based magnetic fluids. It is discovered that functional fluids, Ga85.8In14.2 and Ga91.6Sn8.4 alloy liquids, with Fe73.5Nb3Cu1Si13.5B9 particles exhibit high saturation magnetization as well as low coercivity and remanence. Furthermore, the magnetic hysteresis curves confirm that the liquid metal-based magnetic functional fluids with Fe73.5Nb3Cu1Si13.5B9 particles have higher magnetization than the metal-based Fe3O4 fluids. Owing to the high alloy boiling point more than 2000 K, the metal-based functional fluids should be useful materials for engineering applications when the surrounding temperature is relatively high. Interestingly, these functional fluids offer the properties of superior thermal or electrical conductivity over conventional water-based fluids.

Application of Fe78Si9B13 amorphous particles in magnetorheological fluids

Fe78Si9B13 amorphous particles are applied in the preparation of silicon oil-based magnetorheological (MR) fluids. The structure and morphology of the Fe78Si9B13 amorphous particles were characterized by X-ray diffraction and scanning electron microscopy, respectively. The magnetic properties of the Fe78Si9B13 amorphous particles and the MR fluids prepared with Fe78Si9B13 amorphous particles were characterized by vibrating sample magnetometry. The MR effect of the MR fluids was investigated with a rotational rheometer. The results of VSM show that the saturation magnetization of Fe78Si9B13 amorphous particles is 169.48 emu g−1, accompanying low remanence and low coercivity. The results of rotational rheometry manifest that the MR fluids with Fe78Si9B13 amorphous particles have an improved magnetorheological response compared with magnetic fluids with Fe3O4 nanoparticles under an applied magnetic field.

Investigation of Fe3O4 Aqueous Ferrofluids Before and After Freezing

The magnetization and magnetoviscous properties of Fe3O4 aqueous ferrofluids before and after zero-field freezing are investigated. The results show that the magnetization of ferrofluids is less than that of Fe3O4 nanoparticles. The saturation magnetization of ferrofluids after freezing is greater than that of ferrofluids before freezing due to the breakage of aggregations in ferrofluids. Our experimental data agree well with the model of gas-like compression. The viscosity-magnetic field hysteretic curves of condensed ferrofluids after freezing are initially studied. The results demonstrate a special curve with increasing and decreasing fields. The viscosity changes under magnetic fields are related to the magnetically induced structures.

Unusual coordination structure in undercooled eutectic Ga-In alloy melt

The local structures in the normal and undercooled liquid eutectic Ga-In alloy are investigated by using X-ray absorption spectroscope (XAS), X-ray diffractometer (XRD) and the ab initio molecular dynamics (AIMD) simulations. The results from these three techniques all indicate that the nearest-neighbor coordination number decreases with decreasing temperature in the liquid eutectic Ga-In alloy. Moreover, the nearest-neighbor interatomic distance increases and the local atomic packing density decreases with decreasing temperature. The X-ray absorption near edge structure (XANES) measurement shows that the atomic rearrangement at the undercooled temperature results in the formation of low-coordinated polyhedron clusters with high symmetries. This finding provides a new perspective for understanding the liquid-solid transition in undercooled conditions.

Ga-based magnetic fluid with Al2O3-coated Ni nanoparticles

Five kinds of metal-based magnetic fluids were prepared by dispersing different kinds of Ni nanoparticles (NPs) into liquid Ga: (a) neat Ni NPs, (b) Al2O3-coated Ni NPs, (c) SiO2-coated Ni NPs, (d) Ni NPs after 573 K heat treatment, (e) Ni NPs after 673 K heat treatment. The stabilities and magnetic properties of the five different magnetic fluids were characterized. The saturation magnetizations of the magnetic fluids with Al2O3-coated and SiO2-coated Ni NPs are 1.56 emu g−1 and 1.36 emu g−1, respectively, higher than 0.81 emu g−1 and 0 emu g−1, which are the saturation magnetizations of magnetic fluids with Ni NPs after 573 K and 673 K heat treatment respectively. Furthermore, the results of magnetic weight experiments show that the magnetic fluid with Al2O3-coated Ni NPs and magnetic fluid with Ni NPs after 573 K heat treatment have less magnetic loss. It can be concluded that Ga-based magnetic fluid with Al2O3-coated Ni NPs has both high magnetic properties and strong stability, which is suitable for practical applications. Compared with the 673 K heat treatment, the 573 K heat treatment of Ni NPs also enhances the stability of the magnetic fluid with relatively less magnetic property loss.

Local atomic structure inheritance in Ag50Sn50 melt

Local structure inheritance signatures were observed during the alloying process of the Ag50Sn50 melt, using high-temperature X-ray diffraction and ab initio molecular dynamics simulations. The coordination number N-m around Ag atom is similar in the alloy and in pure Ag melts (N-m similar to 10), while, during the alloying process, the local structure around Sn atoms rearranges. Sn-Sn covalent bonds were substituted by Ag-Sn chemical bonds, and the total coordination number around Sn increases by about 70% as compared with those in the pure Sn melt. Changes in the electronic structure of the alloy have been studied by Ag and Sn K-edge X-ray absorption spectroscopy, as well as by calculations of the partial density of states. We propose that a leading mechanism for local structure inheritance in Ag50Sn50 is due to s-p dehybridization of Sn and to the interplay between Sn-s and Ag-d electrons