Two explosively formed composite plates TA1/X65 and TA1/Cu/X65 were welded with flux cored wire of Cu-Ag-Mo-Nb. Then the effect of the intermediate Cu-layer on the microstructure, element distribution, and mechanical property of the butt welding joints are investigated by means of SEM, EDS and mechanical tester. The results show that the two types plates could be well connected by butt welding, and there exist obvious gray transition zones at the interfaces of titanium, steel and the formed transition layer, but no pores, inclusions, cracks and other defects in the weld joints were observed. According to the analysis of SEM, EDS and XRD, the TiFe-phase in the triangle area of the plate TA1/X65 is inevitable. The Cu-layer within of the plate TA1/Cu/X65 can effectively prevent the mutual diffusion of Ti and Fe, thus the diffusion of Ti and Fe onto the transition zone decreased significantly, as a result, the Fe-content in the weld titanium and the Ti-content in the weld steel has also been significantly reduced. Therefore, the weld composite plate TA1/Cu/X65 exhibits better mechanical properties rather than the plate TA1/X65 without Cu-layer in terms of tensile strength, bending modulus and impact strength.
Firstly, polystyrene (PS) microspheres (ca. 260 nm) were surface-modified with polyvinylpyrrolidone (PVP) via a soap-free emulsion polymerization method. Then core-shell composites of PS/MSiO2 with PS as core and mesoporous silica as shell materials were prepared via a synergistic self-assembly process of PVP surfactants and cetyltrimethylammonium bromide micelles. The results indicated that the silica shells were about 60 nm in thickness with radial meso- channels. The specific surface area of the composites and the average pore size of silica meso-channels were 848 g/m2 and 2.54 nm, respectively. The compressive elastic moduli (E) of the individual composite particle were assessed by analyzing the force-displacement curves, measured by scanning probe microscopy, on the basis of the Hertz contact model. The fitted and calculated E values were 4.47±0.83 (Poisson's ratio=0.33) and 4.89±0.89 GPa (Poisson's ratio=0.2), respectively. These results suggest that the improvement of the elastic response of organic/inorganic composite particles may be ascribed to the presence of mesoporous shells, indicating a potential application in optimizing the structural design of novel non-rigid composite abrasives.
Tailing glass-ceramics of quaternary CaO-Al2O3-MgO-SiO2 (CAMS) are prepared by traditional melting method with solid waste such as Bayan Obo east mine tailing and fly ash as main raw materials. The effect of La2O3 on crystallization characteristics, microstructure, bending strength, Vickers hardness and crack propagation behavior of glass-ceramics are characterized by X-ray diffractometer (XRD), differential thermal analysis (DTA) measurement and Raman spectroscopy, bending tester and Vickers hardness tester. The results show that with the increase amount of La2O3, the crystallization temperature of the as-cast glasses shifts to higher temperature; the crystalline degree is gradually decreased but the main crystalline phase does not change. The addition of La2O3 leads to the aggregation of elements and the microstructure variation of glass-ceramics, which thereby suppress the crack propagation of glass-ceramics. As a result, the Vickers hardness and bending strength of glass-ceramics increased.
The uniaxial tensile property of 316LN austenitic stainless steel (ASS) plate at -40 ℃was examined by strain rates of 5×10-4 s-1 and 1×10-2 s-1 respectively, while the microstructure evolution was characterized by means of OM, TEM, SEM, XRD and 3D profile profiler. The results showed that the deformation induced martensite transformation occurred in 316LN austenitic stainless steel at cryogenic temperature, and the martensite transformation decreased with the increase of strain rate. The yield strength increased with the increase of strain rate, while the tensile strength and elongation decreased with the increase of strain rate. The tensile fractured surface showed typical ductile fracture. The deformed microstructure composed mainly of dislocation tangles and T-M(twin-matrix)lamellar structures. With the increase of strain rate, the dislocation tangles aggravated and the interlamellar spacing of T-M(twin-matrix)lamellar structures reduced.
The effect of Sc addition on the microstructure and mechanical properties of 7055 Al-alloy as-cast, as well as after homogenization-, rolling-, solution- and aging-treatment was investigated. The addition of 0.25%(mass fraction) Sc could lead to the formation of Al3(Sc, Zr) phase, which can promote the heterogeneous nucleation during casting. Therefore, the microstructure of the as cast 7055 Al-alloy was refined. The precipitation of nano-sized Al3(Sc, Zr) phase occurred during the homogenization treatment of the 7055-Sc Al-alloy, and this nano-sized Al3( Sc, Zr) phase could effectively inhibit the coarsening of Al grains during homogenization treatment, and play a role in pinning the grain boundaries, therewith inhibiting the recovery and recrystallization, thus retaining the fiber-like structure during subsequent rolling and solution treatments. Compared to the plain 7055 Al-alloy, the 7055-Sc Al alloy exhibited much higher fine grain strengthening effect due to finer grain size and showed higher tensile strength and hardness as high as 642 MPa and 218 HV, respectively.
Fe3O4 nanoparticles coated hollow microspheres of reduced graphene oxide (Air@rGO€Fe3O4) were synthesized via a simple and efficient two-step method consisting of water-in-oil (W/O) emulsion technique and subsequent annealing process. The Air@rGO€Fe3O4 hollow microspheres showed good electromagnetic properties because of the coexistence of magnetic loss and dielectric loss to microwave. The microwave absorbing bandwidth (reflection loss<-10 dB) for Air@rGO€Fe3O4 of thickness in 2.8 mm (with 33.3 mass% paraffin) locates in the range of 7.5~14.7 GHz, while a minimum reflection loss -52 dB at 10.0 GHz. More interestingly, the microwave absorbing properties of the hollow microspheres can be easily controlled by tuning the ratio of the two components in the composites and the thickness of samples, and as the Fe3O4 content increase, the minimum reflection loss valve of Air@rGO €Fe3O4 microspheres move to higher frequency range. These Air@rGO€Fe3O4 hollow microspheres are great potential candidate as microwave absorbents due to their excellent properties such as wide absorbing frequency, strong absorption, low density and controllable absorbing properties.
Electrospinning is a widely used technique to synthesis nanofiber materials. In order to further study the electrospinning process, software simulation method was introduced in many reports. There are two kinds of software, and each of them has its advantage: Software Matlab is good in mathematical computing, and COMSOL Multiphysics can perfom accurate calculation for complicated electric fields. However, the relevant discription for electric fields in Matlab simulation was inacurate. A new method of joint simulation combining Matlab and COMSOL softwares together was used in this report: In the Matlab simulation process, the electric field equation was replaced by COMSOL calculation results. Compared with the Matlab simulation results, the joint simulation results are much close to actual conditions. This method also overcame the inconvenience (incapability) of electric field description in Matlab simulation and provided a solution to simulate fiber trajectories in complicated electric fields, such as parallel or circular auxiliary electrodes, respectively. The joint simulations were carried out for the electrospinning with one and two nozzles respectively. The electrospinning experiments prove that the joint simulation can predict fairly well the experiment results.
The acrylonitrile-butadiene rubber/ ceric sulfate (NBR/Ce(SO4)2·4H2O) composites materials were toughened with poly(propy1ene carbonate) (PPC). And the structure and properties of NBR/PPC/Ce(SO4)2·4H2O composites materials were investigated by differential scanning calorimetry, thermogravimetric analysis, equilibrium swelling method, scanning electron microscopy, curing performance test and mechanical property. The results show that Ce(SO4)2·4H2O mainly serves as coordination crosslinking agent, compatibilizer and reinforcing filler, while PPC mainly plays the role of toughening agent.
Austenitic stainless steels with different Cr / Ni equivalent ratio for CAP1400 reactor coolant pump casings were designed based on thermodynamics consideration. The effect of Cr/Ni equivalent ratio and solution treatment temperature on the ferrite volume fraction and tensile properties of the steel at 350℃ were investigated by microstructure observation and tensile tests. Results show that with the increase of Cr/Ni equivalent ratio the amount of ferrite-phase in austenitic stainless steel increases and the ferrite-phase is more bulky. The austenitic stainless steel with high Cr/Ni equivalent ratio has a higher tensile strength at 350℃, which can meet the requirements of mechanical properties for CAP1400 pump casing. After solution treatment at different temperatures in the range from 1100~1200℃, the content of ferrite-phase in the studied steel was slightly increased with the raising of solution treatment temperature, but it had little effect on the tensile properties at 350℃.
Metastable γ-Bi2O3 was prepared via a solution precipitation method in ethylene glycol-water solvent system at 80℃ for 40 min by ambient atmospheric pressure with Bi(NO3)35H2O as bismuth source and NaOH as precipitant. The effect of additives (glycerol, TrionX-100, CTAB, SDBS, ethanol, and oleic acid) on the microstructure and optical properties of metastable γ-Bi2O3 were investigated by means of X-ray diffractometer (XRD), scanning electron microscope (SEM), ultraviolet-visible spectrum (UV-VIS) and Fluorescence spectrum (PL). The as-prepared product composed mainly of γ-Bi2O3 and little α-Bi2O3 with dimensions of submicron to micron. Products with diversified morphologies such as cube, tetrahedron, and three-dimensional self-assembled hierarchical flower-like respectively were obtained by adding different additives. UV-visible diffuse reflectance spectrum shows that the product presents photo-absorption property from UV light- to visible light-range, which belongs to the absorption caused by electron transition from valence band to conduction band, that is Bi2O3 direct band gap absorption. The band gaps of Bi2O3 are estimated to be 2.30~2.81 eV for different additives. The fluorescence spectrum of the product shows broad emission (400~600 nm) with 5 emission bands (their center located at 449 nm, 466 nm, 480 nm, 491 nm, and 561 nm). The results also show that the additive not only has an important effect on the purity and microstructure of the product, but also has a significant effect on the crystal structure, which will change the physical and chemical properties (such as light properties) of the materials. By adding additives, the final bandgap width of the products can be adjusted.
Bacterial cellulose nanofibers (BCFs) were synthesized by fermentation process and then with the prepared BCFs as carrier material, composite films of Pd-doped bacterial cellulose nanofibers (Pd/BCF) were prepared by depositing nano-particles of Pd (Pd-NPs) on the carrier via chemical reduction process. The prepared Pd-doped BCFs and composite films Pd/BCF were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), chronoamperometry (CA), and chronopotentiometry (CP). The results show that Pd-NPs were well dispersed on BCFs and especially in the mesoporous of BCFs. The composite films contain c.a. 19% (mass fraction) of Pd-NPs with a mean particle size c.a. 10 nm. The composite of Pd/BCF had better catalytic activity in contrast to the traditional carbon carrier material and Pt-catalyst. Besides, the composite of Pd/BCF exhibited relatively high poison tolerance during the ethanol oxidation process.
