In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstruc...In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.展开更多
A melissopalynological study carried out on 35 bee pollen samples from Romania （Transylvania） shows predominant species as Taraxacum officinale, Tilia sp., Ferbascum sp., Zea mays L., Onobrychis viciifolia Scop., Ge...A melissopalynological study carried out on 35 bee pollen samples from Romania （Transylvania） shows predominant species as Taraxacum officinale, Tilia sp., Ferbascum sp., Zea mays L., Onobrychis viciifolia Scop., Geranium sanguineum L., Filipendula ulmaria L., Cydonia oblonga L., Calluna vulgaris L. and Brassica sp.. This is the first time for the contribution of total phenolic （TP） and total carotenoid （TC） content to the modified oxygen radical absorbance capacity （ORACFL） values in 29 monofloral samples. Hydrophilic ORACFL （H-ORACFL） values ranged between 7.13-10.12 μmol TE/g and 6.94-22.46 μmol TE/g, whereas lipophilic ORACFL （L-ORACFL）values were between 2.19-7.79 μmol TE/g and 1.65-9.96 μmol TE/g, in multifloral and monofloral samples, respectively. It has proved the complex involvement of botanical origins on the antioxidant features with a specific occurrence. Some monofloral samples presented particular high antioxidant potential, such as Salix sp., Taraxacum officinale, Matricaria chamomilla, Cichorium intybus and the poorly studied Cirsium arvense （L.） Scop. and Scilla bifolia L.. New variables, such as soil characteristics, climates together with botanical origins, were introduced in a multivariate analysis of antioxidant data matrix, given a possible important involvement of all of them in affecting, not only the phytochemical composition, but thereafter the antioxidant capacity. All these data could be crucial to a new way of gathering, by beekeepers, depending on the market demand and the purposes for the product that has a potential for further therapeutic bioactivities investigations, and added value in the enrichment of certain products.展开更多
基金Project(2016YFB0700300)supported by the National Key Research and Development Program of China。
文摘In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.
文摘A melissopalynological study carried out on 35 bee pollen samples from Romania （Transylvania） shows predominant species as Taraxacum officinale, Tilia sp., Ferbascum sp., Zea mays L., Onobrychis viciifolia Scop., Geranium sanguineum L., Filipendula ulmaria L., Cydonia oblonga L., Calluna vulgaris L. and Brassica sp.. This is the first time for the contribution of total phenolic （TP） and total carotenoid （TC） content to the modified oxygen radical absorbance capacity （ORACFL） values in 29 monofloral samples. Hydrophilic ORACFL （H-ORACFL） values ranged between 7.13-10.12 μmol TE/g and 6.94-22.46 μmol TE/g, whereas lipophilic ORACFL （L-ORACFL）values were between 2.19-7.79 μmol TE/g and 1.65-9.96 μmol TE/g, in multifloral and monofloral samples, respectively. It has proved the complex involvement of botanical origins on the antioxidant features with a specific occurrence. Some monofloral samples presented particular high antioxidant potential, such as Salix sp., Taraxacum officinale, Matricaria chamomilla, Cichorium intybus and the poorly studied Cirsium arvense （L.） Scop. and Scilla bifolia L.. New variables, such as soil characteristics, climates together with botanical origins, were introduced in a multivariate analysis of antioxidant data matrix, given a possible important involvement of all of them in affecting, not only the phytochemical composition, but thereafter the antioxidant capacity. All these data could be crucial to a new way of gathering, by beekeepers, depending on the market demand and the purposes for the product that has a potential for further therapeutic bioactivities investigations, and added value in the enrichment of certain products.
