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Polyphenylene sulfide (PPS)/multiwalled carbon nanotube (MWCNT) composites were prepared by melt blending and injection molding. The nonisothermal crystallization behavior, morphology, and mechanical properties of the nanocomposites were systematically investigated as a function of MWCNT content. For nonisothermal process, the presence of MWCNTs possesses both acceleration and retardation effect on the crystallization of PPS without affecting the ultimate degree of crystallinity. Due to the interfacial interaction between MWCNTs and PPS, the MWCNTs can be uniformly dispersed in PPS. The interfacial crystallization of PPS on the surface of nanotubes was observed by scanning electron microscopy and transmission electron microscopy. A reinforcing effect of MWCNTs on the mechanical properties of PPS is found, which is considered to be relevant with the uniformly dispersed MWCNTs and the interfacial crystallization.

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Effect of Laves phase formation on mechanical properties in a pressurized T-junction of P91 steel pipe at 849 K for 58,000 h with 25.65 MPa vapor pressure was studied. Thermodynamic calculations had been performed by using the software Thermo-Calc to study the phase at equilibrium state. Counter plot of von Mises stress in the pipe during service life was calculated by finite element analysis to study the effect of the operated stress distribution on the evolution of Laves phase. The change in the microstructure and mechanical properties in the sites with different stress was also studied. The results indicated that the formation of Laves phase in P91 steel was a thermodynamically possible process due to enrichment of Mo and depletion of C adjacent to M 23 C 6 particles or along martensite lath and packet boundaries. The formation of Laves phase had a detrimental influence on the mechanical properties in P91 steel. The mean size of Laves phase would be significantly increased with increasing operated stress, leading to a reduction in tensile properties and impact energy. In particular, crack initiation energy and crack growth energy during impact test rapidly decreased with increasing the mean size and volume fraction of Laves phase.