In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles ...In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles on the microstructural evolution of the AZ91 alloy was investigated.The presence of NbB_(2)was shown to have a grain-refining effect on the AZ91 alloy and promoted dynamic recrystallization(DRX)and precipitation of fine Mg_(17)Al_(12)phases via particle-stimulated nucleation(PSN).Tensile testing revealed substantial enhancements in the ultimate tensile strength(UTS),yield strength(YS),and elongation(EL)of the as-rolled AZ91 alloy,with values of 379 MPa,292 MPa,and 14.7%,respectively,owing to the incorporation of NbB_(2)particles.Annealing led to further enhancements in EL with slight reductions in UTS and YS(360 MPa,252 MPa,and 16.8%,respectively).Owing to grain refinement and the PSN effect of the NbB_(2)particles,a significant number of geometrically necessary dislocations(GNDs)were induced in the matrix during the rolling process,which reduces the nucleation barrier and increases the number of nucleation sites for the recrystallized grains and Mg_(17)Al_(12)precipitates.Meanwhile,many residual dislocations and fine Mg_(17)Al_(12)precipitates in the as-rolled alloys were annihilated during annealing,resulting in slight grain growth and coarsening.The strengthening mechanism of the NbB_(2)/AZ91 composite are mainly associated with grain-refinement strengthening,particle-induced dislocation strengthening,strengthening resulting from mismatching coefficients of thermal expansion(CTE),and heterodeformation-induced(HDI)strengthening.Textural weakening,increased activation of non-basal slip systems,more-uniform strain patterns resulting from NbB_(2)particles,and precipitation are mainly responsible for enhancing ductility.展开更多
A simple sol-gel method was employed to prepare gadolinium, nitrogen and sulphur tridoped titania decorated on oxidised multiwalled carbon nanotubes（MWCNT/Gd,N,S-Ti O2）, using titanium（IV） butoxide and thiourea as...A simple sol-gel method was employed to prepare gadolinium, nitrogen and sulphur tridoped titania decorated on oxidised multiwalled carbon nanotubes（MWCNT/Gd,N,S-Ti O2）, using titanium（IV） butoxide and thiourea as titanium and nitrogen and sulphur source, respectively. Samples of varying gadolinium loadings（0.2%, 0.6%, 1.0% and3.0% Gd3＋） relative to titania were prepared to investigate the effect of gadolinium loading and the amounts of carbon nanotubes, nitrogen and sulphur were kept constant for all the samples. Furthermore, the prepared nanocomposites were evaluated for the degradation of naphthol blue black（NBB） in water under simulated solar light irradiation. Higher degradation efficiency（95.7%） was recorded for the MWCNT/Gd,N,S-Ti O2（0.6% Gd）nanocomposites. The higher photocatalytic activity is attributed to the combined effect of improved visible light absorption and charge separation due to the synergistic effect of Gd,MWCNTs, N, S and Ti O2. Total organic carbon（TOC） analysis revealed a higher degree of complete mineralisation of naphthol blue black（78.0% TOC removal） which minimises the possible formation of toxic degradation by-products such as the aromatic amines. The MWCNT/Gd,N,S-Ti O2（0.6% Gd） was fairly stable and could be re-used for five times,reaching a maximum degradation efficiency of 91.8% after the five cycles.展开更多
基金supported by the National Natural Science Foundation of China[52171030]the National Key Research and Development Program of China[2018YFA0702903]。
文摘In this study,a NbB_(2)/AZ91 composite exhibiting desirable mechanical properties was fabricated using a sample casting technique,followed by hard-plate rolling and short-term annealing.The effect of NbB_(2)particles on the microstructural evolution of the AZ91 alloy was investigated.The presence of NbB_(2)was shown to have a grain-refining effect on the AZ91 alloy and promoted dynamic recrystallization(DRX)and precipitation of fine Mg_(17)Al_(12)phases via particle-stimulated nucleation(PSN).Tensile testing revealed substantial enhancements in the ultimate tensile strength(UTS),yield strength(YS),and elongation(EL)of the as-rolled AZ91 alloy,with values of 379 MPa,292 MPa,and 14.7%,respectively,owing to the incorporation of NbB_(2)particles.Annealing led to further enhancements in EL with slight reductions in UTS and YS(360 MPa,252 MPa,and 16.8%,respectively).Owing to grain refinement and the PSN effect of the NbB_(2)particles,a significant number of geometrically necessary dislocations(GNDs)were induced in the matrix during the rolling process,which reduces the nucleation barrier and increases the number of nucleation sites for the recrystallized grains and Mg_(17)Al_(12)precipitates.Meanwhile,many residual dislocations and fine Mg_(17)Al_(12)precipitates in the as-rolled alloys were annihilated during annealing,resulting in slight grain growth and coarsening.The strengthening mechanism of the NbB_(2)/AZ91 composite are mainly associated with grain-refinement strengthening,particle-induced dislocation strengthening,strengthening resulting from mismatching coefficients of thermal expansion(CTE),and heterodeformation-induced(HDI)strengthening.Textural weakening,increased activation of non-basal slip systems,more-uniform strain patterns resulting from NbB_(2)particles,and precipitation are mainly responsible for enhancing ductility.
基金Funding from the University of Johannesburg and DST-NRF Centre of Excellence in Strong Materials is highly appreciated
文摘A simple sol-gel method was employed to prepare gadolinium, nitrogen and sulphur tridoped titania decorated on oxidised multiwalled carbon nanotubes（MWCNT/Gd,N,S-Ti O2）, using titanium（IV） butoxide and thiourea as titanium and nitrogen and sulphur source, respectively. Samples of varying gadolinium loadings（0.2%, 0.6%, 1.0% and3.0% Gd3＋） relative to titania were prepared to investigate the effect of gadolinium loading and the amounts of carbon nanotubes, nitrogen and sulphur were kept constant for all the samples. Furthermore, the prepared nanocomposites were evaluated for the degradation of naphthol blue black（NBB） in water under simulated solar light irradiation. Higher degradation efficiency（95.7%） was recorded for the MWCNT/Gd,N,S-Ti O2（0.6% Gd）nanocomposites. The higher photocatalytic activity is attributed to the combined effect of improved visible light absorption and charge separation due to the synergistic effect of Gd,MWCNTs, N, S and Ti O2. Total organic carbon（TOC） analysis revealed a higher degree of complete mineralisation of naphthol blue black（78.0% TOC removal） which minimises the possible formation of toxic degradation by-products such as the aromatic amines. The MWCNT/Gd,N,S-Ti O2（0.6% Gd） was fairly stable and could be re-used for five times,reaching a maximum degradation efficiency of 91.8% after the five cycles.
