The effect of pore nucleation,pore growth and solidification mode of matrix on pore structure and distribution of lotus-type porous Cu were investigated. It is difficult to obtain an ordered pore structure when the matrix is a region of columnar transition. An ordered pore structure could be obtained only when the matrix transforms to columnar grains with increase of pore length and circularity. The pore distribution moved from the grain boundaries to the interior of grain with increasing gas pressure. The average pore diameter decreased and the pore density increased due to decrease of activation energy and increased rate of nucleus formation. Due to slight depressions at grain boundaries regions at the solid/liquid interface, the pore nucleation is favored at grain boundaries and thus the average pore diameter in the grain boundaries is larger than that of in the grains.
The effect of quenching cooling rates on microstructure of a high -strength low-alloy (HSLA) steel plate of 35 mm in thickness was investigated by the finite element software ABAQUS, Formastor thermal dilatometer, metalloscope, TEM and EBSD. The results show that the quenching cooling rate has significant effect on the microstructure and mechanical properties within the near surface band from the surface to the depth 8 mm of the steel plate. With the increase of quenching cooling rate, the amount of lath-like microstructure, the density of dislocation and low misorientation angle boundary have significant increased, and the width of lathes is markedly refined, leading to the obviously increase of the hardness of the band near the surface. With the increase of quenching cooling rate, there were no significant difference on the hardness, the size of lathes, grain boundary characters and MA constituent of the band from the quarter depth to the center of the steel plates. The ABAQUS simulation result is in accordance with the distribution of the hardness and microstructure of steel plates. The distribution of the cooling rate on the cross-section of steel plates determine the microstructure transition types and features.
KH550 silane coupling was used as surfactant to modify the surface of SiC powders. The morphology, surface property and particle size distribution of SiC powders before and after modification were investigated by scanning electron microscope, X-ray diffractometer, laser particle analyzer and infrared spectroscopy. Results show that the surface of SiC powders was coated with a thin layer of KH550 via grafting reaction, which did not change phase constituent and structure of the SiC powders. After modification, the agglomeration of powders alleviated , and thus their average size also decreased. Due to the increase of electrostatic repulsion and steric hindrance among SiC powders, the suspensibility and dispersibility of powders in sol were improved. To simulate the production of vitrified grinding wheel of SiC/ceramic composite, simulate sintered compacts of SiC/ceramic composite were fabricated comparatively with plain- and the modified-SiC by means of a twostep process: forming by in-situ sol-gel method and then sintering at desired temperature. It follows that the produced sintered compact with the modified SiC shows better uniformity in microstructure and higher bending strength as well.
Three kinds of austenitic steels 1Cr18Ni9Ti, 304 and 316L all contain different minor elements. The localized corrosion behavior of them was comparatively investigated, including intergranular corrosion, pitting corrosion and stress corrosion. Results show that the addition of Ti and the low C content are beneficial to the enhancement of intergranular corrosion resistance of the steel. Among others, the solution treated 304 steel has the best pitting corrosion resistance owing to the highest content of Cr and N, while 316L steel has the best stress corrosion resistance in 42% boiling MgCl2 because of its high Ni content.
Superhydrophobic coating of CuO was prepared on X90 pipeline steel substrate by a three step process, i.e. first a Cu protective layer was electrodeposited on the substrate, which then was treated by hydrothermal reaction and finally modified with perfluorooctanoic solution. The phase constitution, microstructure, chemical composition, and wettability of the coating were investigated by X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectrometer, and contact angle tester. Its mechanical stability, anti-adhesion behavior and corrosion resistance were also examined. The results show that the perfluorooctanoic was successfully grafted on the surface of coating consisted of petal-like CuO with micro-nano hybrid structure. The contact angle of water to the coating surface was 161.24°, and the sliding angle was about 3°. Meanwhile, the as-prepared coating surface exhibits excellent mechanical stability, anti-adhesion behavior and corrosion resistance.
Imidazolium-based poly(ionic liquid) (PIL) microspheres, poly(1-dodecyl-3-vinylimidazolium tetrafluoroborate) (P[C12VIm][BF4]), were synthesized through a dispersion polymerization process. The structure and morphology of the PIL microspheres were characterized by means of 1H nuclear magnetic resonance, Fourier infrared spectrometer, X- ray diffractometer and scanning electron microscopy. Their electrorheological and dielectric properties were measured by rotational rheometer and broad-band dielectric spectrometer, respectively. The results show that imidazolium-based PIL material is well-defined microspheres and has excellent thermal stability. In this PIL electrorheological system, a remarkable electrorheological effect was observed, in which shear stress, viscosity and dynamic modulus increase with the increasing electric field strength.
Cementitious materials was prepared with powders of steel slag (SS), blast furnace slag (BFS) and desulfurized gypsum (DG). The influence of SS content on the strength of the concrete composted of all industrial solid wastes was investigated. The hydration mechanism of cementitious materials was characterized by means of XRD, IR, TG-DTA and SEM, while the variation of pH and concentration of the specified ions of cementitious materials were acquired during the hydration process. The results show that when the mass ratio of SS, BFS and DG is m(SS):m(BFS):m(DG)=30:58:12, the concrete possesses a better compressive strength after curing for 3 d, 7 d and 28 d. With the increasing dosage of SS, the pH value and Ca2+ concentration decreased first and then increased. The initial concentration of solutes of silicon (aluminum) was relatively low and then increased later. In the presence of DG, SS and BFS can synergistically promote the hydration and the major hydration products are ettringite (AFt) and calcium silicate hydrate (C-S-H) gels. During the later stage of the hydration process, the quantity of hydration products increased rapidly, forming a composite of C-S-H gel as matrix, within which there existed randomly dispersed needle-like AFt crystallites as strengthening phase, thereby, the hardened cement paste became much dense and hard.
Effect of rhenium (Re) addition on isothermal oxidation behavior of a nickel-base single crystal superalloy was investigated by means of intermittent measurement of weight change as well as scanning electron microscope (SEM) and X-ray diffractometer (XRD). It was shown that, a scale composed of a (Cr, Ti)-enriched outer oxide layer, an inner Al2O3 layer and an inner TiN layer was formed for both the Re-containing and Re-free alloys, however, the Al2O3 layer was much more complete and the amount of TiN was much less on the Re-containing alloy rather than those on the Re-free alloy. Re was found to lower the oxidation rate of the alloy and improve the stability of the entire oxide scale during long-term oxidation by increasing the activity of Cr and thus increasing the content of Cr2O3 in the scale. Enhancement of Cr2O3 formation may then accelerate the selective oxidation of Al and thus promote the formation of a continuous Al2O3 layer beneath the outer oxide scale, as a result, which inhibited the formation of the inner nitride.
The cathode carbon block was regarded as a two-phase composite material composed of aggregates and binder in mesoscopic scale, for description of which, a two-dimensional random aggregate model was established by Monte Carlo method. Then the numerical simulation of sodium expansion induced stress of aggregate model was established by the thermal analysis module of ANSYS finite element software in consideration of different shapes, gradations and contents of the aggregate. The results show that the nonuniformity of the meso-structure in the cathode carbon block causes the nonuniform distribution of the stress induced by the sodium expansion. Particularly, the presence of the tensile stress can lead to the damage of the cathode carbon block. The sodium expansion of the carbon blocks with the carbon aggregate within the gradation of 0.003-0.015 m is the lowest, while those within the gradation of 0.003-0.006 m is the highest. The sodium expansion of the carbon block with 80% carbon aggregate is the lowest, while that with 60% carbon aggregate is the highest. The numerical simulation results are in accordance with the experimental results,which means that this model can reasonably and effectively describe the sodium expansion and stress distribution of the carbon block. Thus it can be used as an effective auxiliary way to study phenomena related with the sodium expansion induced stress.
NiO with maximum specific capacitance of 744 Fg-1 was successfully synthesized by sol-gel method and then simple calcination. The microstructure and aggregation morphology of the as-prepared NiO electrode were characterized by powder X-ray diffract ometer (XRD) and scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET. An asymmetric supercapacitor has been constructed with nickel oxide as the positive electrode and activated carbon as the negative electrode, respectively. The performance of the asymmetric supercapacitor was investigated in 2 mol/L KOH aqueous electrolyte using cyclic voltammetry (CV) and galvanostatic charge/discharge test. The asymmetric supercapacitor exhibited excellent energy density, power density and cycle stability, especially good electrochemical stability, i.e. even after consecutive 1,000 cycles the capacitance of the capacitor still kept at 84.3% of the initial value.
