A turbine disk alloy was prepared by electron beam sheet lamination(EBSL),giving a refined microstruc-ture and high purity,and the microstructure-property relationship of this alloy has been developed.The alloy showed...A turbine disk alloy was prepared by electron beam sheet lamination(EBSL),giving a refined microstruc-ture and high purity,and the microstructure-property relationship of this alloy has been developed.The alloy showed an outstanding creep life of 1266.3 h at 953 K/500 MPa.Compared with the conventional vacuum induction melted and vacuum arc re-melted alloy,a smaller dendrite arm spacing of less than 23μm was obtained through the EBSL method,which restricted the formation of large inter-dendritic carbides.As a result,the typical intergranular failure mode was observed in the EBSL alloy,whereas the transgranular fracture mode was dominant in the conventional alloy.The inter-dendritic MC carbides formed from the reverse diffusion of Nb are believed to either impede grain boundary sliding or initi-ate cracks,depending on their size and morphology.The tiny grain boundary precipitates of theδphase in the EBSL alloy could reduce the critical stress for microvoid nucleation to 161.07 MPa by decoher-ing the particle/matrix interface,or allowing vacancy condensation near theδinterface,resulting in the formation of grain boundary microcracks.In the conventional alloy,however,the larger-sized MC car-bides which were formed during the solidification process(0.36 vol.%)nucleated the microcracks within the particles,leading to the transgranular fracture.Furthermore,the results indicated that the nanoscaleγ′andγ″precipitates contributed primarily to strengthening and coordinating intragranular deforma-tion during creep,in which the Orowan mechanism and shearing of a/6<211>partial dislocations and a/2<110>doublets were active forγ′andγ″precipitates,respectively.展开更多
Carbon-coated SiC@C nanocapsules （NCs） with a hexagonal platelet-like morphology were fabricated by a simple direct current （DC） arc-discharge plasma method. The SiC@C NCs were monocrystalline, 120-150 nm in size,...Carbon-coated SiC@C nanocapsules （NCs） with a hexagonal platelet-like morphology were fabricated by a simple direct current （DC） arc-discharge plasma method. The SiC@C NCs were monocrystalline, 120-150 nm in size, and approximately 50 nm thick. The formation of the as-prepared SiC@C NCs included nucleation of truncated octahedral SiC seeds and subsequent anisotropic growth of the seeds into hexagonal nanoplatelets in a carbon-rich atmosphere. The disordered carbon layers on the SiC@C NCs were converted into SiO2 shells of SiC@SiO2 NCs by heat treatment at 650 ℃ in air, during which the shape and inherent characteristics of the crystalline SiC core were obtained. The interface evolution from carbon to SiO2 shells endowed the SiC@SiO2 NCs with enhanced photocatalytic activity due to the hydrophilic and transparent nature of the SiO2 shell, as well as to the photosensitive SiC nanocrystals. The band gap of the nanostructured SiC core was determined to be 2.70 eV. The SiC@SiO2 NCs degraded approximately 95% of methylene blue in 160 min under visible light irradiation.展开更多
Mg alloy AZ31 with ~79% （volume fraction of scattering less than 30°） basal-fiber texture through hot extrusion exhibits strong grain-size dependent yield strength, Samples with grain sizes varying from 4,5 to ...Mg alloy AZ31 with ~79% （volume fraction of scattering less than 30°） basal-fiber texture through hot extrusion exhibits strong grain-size dependent yield strength, Samples with grain sizes varying from 4,5 to 22,3 μm were obtained by altering annealing time durations, The Hall-Petch relations of tension and compression are σ.2 = 86＋200d^-1/2 and σ0.2 = 17 ＋ 327d^-1/2, respectively, Considering the correlation between grain orientation and deformation modes, a novel weighted average method of calculating friction stress Cro was proposed, and results of calculation agreed with the experimental ones, which can reasonably understand the yielding behavior in tension and compression,展开更多
Benefitting from higher specific capacities,acceptable cost,nontoxicity and unique crystal structures,the molybdenum oxides have been studied as the anode materials for lithium ion batteries(LIBs).Herein,a direct curr...Benefitting from higher specific capacities,acceptable cost,nontoxicity and unique crystal structures,the molybdenum oxides have been studied as the anode materials for lithium ion batteries(LIBs).Herein,a direct current(DC)arc-discharge plasma technique has been developed to in-situ synthesize carboncoated monocrystal molybdenum oxides((MoO3NRs/MoO2NPs)@C)nanocomposites,using coarse MoO_(3) bulk as the raw material and methane(CH4)gas as the carbon source.It is indicated that crystallographic traits of MoO_(3) and MoO2 nuclei give rise to an anisotropic growth of monocrystal MoO3 nanorods(NRs)along<100>direction and an isotropic growth of monocrystal MoO_(2) nanoparticles(NPs).The carbon shells on MoO3/MoO2 nanostructures are generated from the absorption of carbon atoms in surrounding atmosphere or the release of supersaturated carbon atoms in MoeOeC solid solution.Unique constitution and pseudo-capacitive behavior of(MoO3NRs/MoO2NPs)@C bring merits to excellent cycling performance and rate capability,i.e.a remarkable specific capacity of 840 mAh·g^(-1) after 100 cycles at a current density of 0.1 Ag^(-1) and a retained capacity of 210 mAh·g^(-1) at 6.4 A g^(-1).This work has offered a simple and efficient approach to fabricate the carbon-coated molybdenum oxides nanostructures for promising anode materials of LIBs。展开更多
A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synt...A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.展开更多
This study aims to evaluate the therapeutic effects of laser acupuncture(LA)on articular cartilage degradation at the early stage of postmenopausal osteoarthritis(PMOA)by an ultrasound biomicroscopic technology.Twenty...This study aims to evaluate the therapeutic effects of laser acupuncture(LA)on articular cartilage degradation at the early stage of postmenopausal osteoarthritis(PMOA)by an ultrasound biomicroscopic technology.Twentyone healthy female Sprague-Dawley rats were randomly and evenly divided into three groups-sham,ovariectomized(OVX)and OVXþLA groups.Only the peri-ovarian fatty tissue of the sham rats was exteriorized.The animals in the OVX and OVXþLA groups underwent bilateral ovariectomy to create a menopause model.On day 8 after the ovariectomy,the 2-week LA therapy at acupoints Guanyuan(CV-4),Sanyinjiao(SP-6),and Zusanli(ST36)was performed in the OVXþLA group,while the sham and OVX groups had a sham treatment.All the animals were sacrificed on day 22.The cartilage tissues in the left knee joint were examined by ultrasound and histology.Compared with the sham group,the significantly degenerate alterations(p<0.01)in ultrasound roughness index(URI),reflection coefficient(RC1)and cartilage thickness were found in the OVX group,while the values of these parameters were significantly recovered(p<0.01)in the OVXþLA group.The LA treatment enhanced proteoglycans(PGs)content with a significant reduce of the modified Mankin score(p<0.01).The acoustic assessment strongly correlated with the histologic evaluation.The results showed that LA treatment could alleviate the postmenopause-induced cartilage degradation and promote tissue repair.LA has potential to be a simple and safe non-pharmacological countermeasure against PMOA for geriatric patient population.The ultrasound biomicroscopic technology could be a quantitative evaluation tool of the structural and morphological responses of articular cartilage to LA intervention.展开更多
基金financially supported by the National Key R&D Program of China (No.2019YFA0705300)the National Natural Science Foundation of China (No.52004051)+1 种基金the Doctoral Start-up Foundation of Liaoning Province (No.2021-BS-069)Support Plan for Innovation Teams in Key Areas of Dalian (No.2019RT13).
文摘A turbine disk alloy was prepared by electron beam sheet lamination(EBSL),giving a refined microstruc-ture and high purity,and the microstructure-property relationship of this alloy has been developed.The alloy showed an outstanding creep life of 1266.3 h at 953 K/500 MPa.Compared with the conventional vacuum induction melted and vacuum arc re-melted alloy,a smaller dendrite arm spacing of less than 23μm was obtained through the EBSL method,which restricted the formation of large inter-dendritic carbides.As a result,the typical intergranular failure mode was observed in the EBSL alloy,whereas the transgranular fracture mode was dominant in the conventional alloy.The inter-dendritic MC carbides formed from the reverse diffusion of Nb are believed to either impede grain boundary sliding or initi-ate cracks,depending on their size and morphology.The tiny grain boundary precipitates of theδphase in the EBSL alloy could reduce the critical stress for microvoid nucleation to 161.07 MPa by decoher-ing the particle/matrix interface,or allowing vacancy condensation near theδinterface,resulting in the formation of grain boundary microcracks.In the conventional alloy,however,the larger-sized MC car-bides which were formed during the solidification process(0.36 vol.%)nucleated the microcracks within the particles,leading to the transgranular fracture.Furthermore,the results indicated that the nanoscaleγ′andγ″precipitates contributed primarily to strengthening and coordinating intragranular deforma-tion during creep,in which the Orowan mechanism and shearing of a/6<211>partial dislocations and a/2<110>doublets were active forγ′andγ″precipitates,respectively.
基金This work was financially supported from National Natural Science Foundations of China （Nos. 51331006 and 51271044）.
文摘Carbon-coated SiC@C nanocapsules （NCs） with a hexagonal platelet-like morphology were fabricated by a simple direct current （DC） arc-discharge plasma method. The SiC@C NCs were monocrystalline, 120-150 nm in size, and approximately 50 nm thick. The formation of the as-prepared SiC@C NCs included nucleation of truncated octahedral SiC seeds and subsequent anisotropic growth of the seeds into hexagonal nanoplatelets in a carbon-rich atmosphere. The disordered carbon layers on the SiC@C NCs were converted into SiO2 shells of SiC@SiO2 NCs by heat treatment at 650 ℃ in air, during which the shape and inherent characteristics of the crystalline SiC core were obtained. The interface evolution from carbon to SiO2 shells endowed the SiC@SiO2 NCs with enhanced photocatalytic activity due to the hydrophilic and transparent nature of the SiO2 shell, as well as to the photosensitive SiC nanocrystals. The band gap of the nanostructured SiC core was determined to be 2.70 eV. The SiC@SiO2 NCs degraded approximately 95% of methylene blue in 160 min under visible light irradiation.
基金the support of the National Natural Science Foundation of China(51271046 and 51471041)
文摘Mg alloy AZ31 with ~79% （volume fraction of scattering less than 30°） basal-fiber texture through hot extrusion exhibits strong grain-size dependent yield strength, Samples with grain sizes varying from 4,5 to 22,3 μm were obtained by altering annealing time durations, The Hall-Petch relations of tension and compression are σ.2 = 86＋200d^-1/2 and σ0.2 = 17 ＋ 327d^-1/2, respectively, Considering the correlation between grain orientation and deformation modes, a novel weighted average method of calculating friction stress Cro was proposed, and results of calculation agreed with the experimental ones, which can reasonably understand the yielding behavior in tension and compression,
基金supported by the National Natural Science Foundation of China(No.U1908220)the Research Project of Shanxi Datong University,China.
文摘Benefitting from higher specific capacities,acceptable cost,nontoxicity and unique crystal structures,the molybdenum oxides have been studied as the anode materials for lithium ion batteries(LIBs).Herein,a direct current(DC)arc-discharge plasma technique has been developed to in-situ synthesize carboncoated monocrystal molybdenum oxides((MoO3NRs/MoO2NPs)@C)nanocomposites,using coarse MoO_(3) bulk as the raw material and methane(CH4)gas as the carbon source.It is indicated that crystallographic traits of MoO_(3) and MoO2 nuclei give rise to an anisotropic growth of monocrystal MoO3 nanorods(NRs)along<100>direction and an isotropic growth of monocrystal MoO_(2) nanoparticles(NPs).The carbon shells on MoO3/MoO2 nanostructures are generated from the absorption of carbon atoms in surrounding atmosphere or the release of supersaturated carbon atoms in MoeOeC solid solution.Unique constitution and pseudo-capacitive behavior of(MoO3NRs/MoO2NPs)@C bring merits to excellent cycling performance and rate capability,i.e.a remarkable specific capacity of 840 mAh·g^(-1) after 100 cycles at a current density of 0.1 Ag^(-1) and a retained capacity of 210 mAh·g^(-1) at 6.4 A g^(-1).This work has offered a simple and efficient approach to fabricate the carbon-coated molybdenum oxides nanostructures for promising anode materials of LIBs。
基金Financial support from the National Natural Science Foundation of China(nos.22071205,21772164,and 21572187)NFFTBS(no.J1310024),and PCSIRT is acknowledged.
文摘A unified protecting group-free approach to two stemarene and two betaerene diterpenoids through a bioinspired two-phase strategy has been developed,and three of them were obtained for the first time via chemical synthesis.Starting from a common intermediate,two distinct tetracyclic frameworks containing diastereoisomeric bridged bicycles were constructed by a divergent ring reorganization strategy.Late-stage C–H functionalization through a xanthylation-oxygenation protocol furnished the corresponding oxygenated stereocenters or oxo functionality in high regio-and diastereoselective fashion within a complex hydrocarbon system.The stereochemical puzzles in(–)-2-acetoxybetaer13(17)-ene and(+)-7-acetoxybetaer-13(17)-ene were first predicted by the comparison of density functional theory(DFT)-nuclear magnetic resonance(NMR)data with the reported data and then unambiguously addressed through the total syntheses of natural products and three diastereomers.
基金the Special Funds of Guang Dong Universities for Talents(2050205)the Guangdong Science and Technology Program(grant no.2016A020216017)。
文摘This study aims to evaluate the therapeutic effects of laser acupuncture(LA)on articular cartilage degradation at the early stage of postmenopausal osteoarthritis(PMOA)by an ultrasound biomicroscopic technology.Twentyone healthy female Sprague-Dawley rats were randomly and evenly divided into three groups-sham,ovariectomized(OVX)and OVXþLA groups.Only the peri-ovarian fatty tissue of the sham rats was exteriorized.The animals in the OVX and OVXþLA groups underwent bilateral ovariectomy to create a menopause model.On day 8 after the ovariectomy,the 2-week LA therapy at acupoints Guanyuan(CV-4),Sanyinjiao(SP-6),and Zusanli(ST36)was performed in the OVXþLA group,while the sham and OVX groups had a sham treatment.All the animals were sacrificed on day 22.The cartilage tissues in the left knee joint were examined by ultrasound and histology.Compared with the sham group,the significantly degenerate alterations(p<0.01)in ultrasound roughness index(URI),reflection coefficient(RC1)and cartilage thickness were found in the OVX group,while the values of these parameters were significantly recovered(p<0.01)in the OVXþLA group.The LA treatment enhanced proteoglycans(PGs)content with a significant reduce of the modified Mankin score(p<0.01).The acoustic assessment strongly correlated with the histologic evaluation.The results showed that LA treatment could alleviate the postmenopause-induced cartilage degradation and promote tissue repair.LA has potential to be a simple and safe non-pharmacological countermeasure against PMOA for geriatric patient population.The ultrasound biomicroscopic technology could be a quantitative evaluation tool of the structural and morphological responses of articular cartilage to LA intervention.
