Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics with low thermal expansion properties are promising for the rapid preparation of large-scale and complex components by directed energy deposition-laser based(DED-LB)te...Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics with low thermal expansion properties are promising for the rapid preparation of large-scale and complex components by directed energy deposition-laser based(DED-LB)technology.However,the wider application of DED-LB technology is limited due to the inadequate understanding of process conditions.The shaping quality,microstructure,and mechanical properties of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13)(6 mol%TiO_(2))composite ceramics were systematically investigated as a function of energy input in an extensive process window.On this basis,the formation mechanism of solidification defects and the evolution process of microstructure were revealed,and the optimized process parameters were determined.Results show that high energy input improves the fluidity of the molten pool and promotes the uniform distribution and full growth of constituent phases,thus,facilitating the elimination of solidification defects,such as pores and strip gaps.In addition,the microstructure size is strongly dependent on the energy input,increasing when the energy input increases.Moreover,the morphology of theα-Al_(2)O_(3) phase gradually transforms from cellular into cellular dendrite with increasing energy input due to changing solidification conditions.Under the comprehensive influence of solidification defects and microstructure size,the fracture toughness and flexural strength of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics present a parabolic law behavior as the energy input increases.Optimal shaping quality and excellent mechanical properties are achieved at an energy input range of 0.36-0.54 W*min^(2) g^(-1) mm^(-1).Within this process window,the average microhardness,fracture toughness,and flexural strength of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics are up to 1640 Hv,3.87 MPa m^(1/2),and 227 MPa,respectively.This study provides practical guidance for determining the process parameters of DED-LB of melt growth Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics.展开更多
The urgent need for integrated molding and sintering across various industries has inspired the development of additive manu-facturing(AM)ceramics.Among the different AM technologies,direct laser additive manufacturin...The urgent need for integrated molding and sintering across various industries has inspired the development of additive manu-facturing(AM)ceramics.Among the different AM technologies,direct laser additive manufacturing(DLAM)stands out as a group of highly promising technology for flexibly manufacturing ceramics without molds and adhesives in a single step.Over the last decade,sig-nificant and encouraging progress has been accomplished in DLAM of high-performance ceramics,including Al_(2)O_(3),ZrO_(2),Al_(2)O_(3)/ZrO_(2),SiC,and others.However,high-performance ceramics fabricated by DLAM face challenges such as formation of pores and cracks and resultant low mechanical properties,hindering their practical application in high-end equipment.Further improvements are necessary be-fore they can be widely adopted.Methods such as field-assisted techniques and post-processing can be employed to address these chal-lenges,but a more systematic review is needed.This work aims to critically review the advancements in direct selective laser sintering/melting(SLS/SLM)and laser directed energy deposition(LDED)for various ceramic material systems.Additionally,it provides an overview of the current challenges,future research opportunities,and potential applications associated with DLAM of high-perform-ance ceramics.展开更多
Aconitum vilmorinianum,a well-known traditional Chinese herb,is recently being threatened by overexploitation and environment disturbance.This study was conducted to provide propagation methods through in vitro germin...Aconitum vilmorinianum,a well-known traditional Chinese herb,is recently being threatened by overexploitation and environment disturbance.This study was conducted to provide propagation methods through in vitro germination and explant cultivation.Germination was stimulated up to 66.00%on Murashige and Skoog(MS)medium containing 2.0 mg L^(−1)6-benzylaminopurine(BAP),0.1 mg L^(−1)1-napthaleneacetic acid(NAA),and 30 g L^(−1)sucrose.Three bacteria(Pantoea agglomerans,Erwinia persicina,and Pseudomonas tolaasii)would be responsible for consistent contamination during germination.The latter two were effectively eradicated after disinfected.The influence of explant types and hormone combinations on direct and indirect organogenesis was evaluated in the present work.The frequency of shoot induction from axillary bud explants was 100%on the MS fortified with 2.0 mg L^(−1)BAP and 0.3 mg L^(−1)NAA.Shoots multiplication was optimized on MS medium supplemented with 0.1 mg L^(−1)thidiazuron(TDZ)and 0.1 mg L^(−1)NAA.High callus induction percentage(96.67%)was obtained from stem segments on MS medium with 2.0 mg L^(−1)2,4-D,then successfully regenerated into shoots on MS medium in the presence of 0.1 mg L^(−1)TDZ and 0.2 mg L^(−1)NAA.The present work could be useful for the utilization and conservation of this valuable species.展开更多
Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications;however,the rapid preparation of high-performance components remains a challenge.Herein,a novel ...Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications;however,the rapid preparation of high-performance components remains a challenge.Herein,a novel route for 3D printing dense(<99.4%)high-performance melt-grown alumina-mullite/glass composites using directed laser deposition(DLD)is proposed.Key issues on the composites,including phase composition,microstructure formation/evolution,densification,and mechanical properties,are systematically investigated.The toughening and strengthening mechanisms are analyzed using classical fracture mechanics,Griffith strength theory,and solid/glass interface infiltration theory.It is demonstrated that the composites are composed of corundum,mullite,and glass,or corundum and glass.With the increase of alumina content in the initial powder,corundum grains gradually evolve from near-equiaxed dendrite to columnar dendrite and cellular structures due to the weakening of constitutional undercooling and small nucleation undercooling.The microhardness and fracture toughness are the highest at 92.5 mol%alumina,with 18.39±0.38 GPa and 3.07±0.13 MPa-m1/2,respectively.The maximum strength is 310.1±36.5 MPa at 95 mol%alumina.Strength enhancement is attributed to the improved densification due to the trace silica doping and the relief of residual stresses.The method unravels the potential of preparing dense high-performance melt-grown alumina-based composites by the DLD technology.展开更多
Diterpenoid alkaloids(DAs) have been often utilized in clinical practice due to their analgesic and anti-infammatory properties. Natural DAs are prevalent in the family Ranunculaceae, notably in the Aconitum genus. Ne...Diterpenoid alkaloids(DAs) have been often utilized in clinical practice due to their analgesic and anti-infammatory properties. Natural DAs are prevalent in the family Ranunculaceae, notably in the Aconitum genus. Nevertheless, the evolutionary origin of the biosynthesis pathway responsible for DA production remains unknown.In this study, we successfully assembled a highquality, pseudochromosome-level genome of the DA-rich species Aconitum vilmorinianum(A.vilmorinianum)(5.76 Gb). An A. vilmorinianumspecific whole-genome duplication event was discovered using comparative genomic analysis,which may aid in the evolution of the DA biosynthesis pathway. We identified several genes involved in DA biosynthesis via integrated genomic, transcriptomic, and metabolomic analyses. These genes included enzymes encoding target ent-kaurene oxidases and aminotransferases, which facilitated the activation of diterpenes and insertion of nitrogen atoms into diterpene skeletons, thereby mediating the transformation of diterpenes into DAs. The divergence periods of these genes in A. vilmorinianum were further assessed, and it was shown that two major types of genes were involved in the establishment of the DA biosynthesis pathway. Our integrated analysis offers fresh insights into the evolutionary origin of DAs in A.vilmorinianum as well as suggestions for engineering the biosynthetic pathways to obtain desired DAs.展开更多
Two new C ig-diterpenoid alkaloids, 7,8-epoxy-franchetine （1） and N（19）-en-austroconitine A （2）, were isolated from Aconitum iochanicum. Compound 1 was a new C19-diterpenoid alkaloid with a 7,8-epoxy unit. Their...Two new C ig-diterpenoid alkaloids, 7,8-epoxy-franchetine （1） and N（19）-en-austroconitine A （2）, were isolated from Aconitum iochanicum. Compound 1 was a new C19-diterpenoid alkaloid with a 7,8-epoxy unit. Their structures were elucidated by comprehensive spectroscopic analyses including UV, IR, MS, 1D and 2D NMR. Biological ac- tivity tests indicated that two new compounds exhibited inhibitory activity against nitric oxide （NO） production in LPS-activated RAW264.7 macrophages. Compared with positive control, the two new compounds showed weak an- ti-inflammatory effects with the inhibition rate of 27.3% and 29.2%, respectively.展开更多
Paraquat(PQ)has been used as an herbicide worldwide because of its potent activity against weeds.However,it is highly toxic to humans.The very high fatality of PQ poisoning is due to its inherent toxicity and the lack...Paraquat(PQ)has been used as an herbicide worldwide because of its potent activity against weeds.However,it is highly toxic to humans.The very high fatality of PQ poisoning is due to its inherent toxicity and the lack of any effective treatment.Consequently,developing a non-toxic herbicide with comparable efficacy to PQ will contribute to global food security and help prevent PQ-related fatalities.Herein,we report a new herbicide called dienediamine,which was discovered from how to intervene the redox cycle of PQ,an inherent toxicity nature.Dienediamine,the“reduced"form of PQ with no function as an electron transfer agent,was shown to be non-toxic through comprehensive in vivo and in vitro experiments at molar concentrations equivalent to PQ's absolute lethal dose.Remarkably,dienediamine can undergo conversion to PQ under natural sunlight and ambient air conditions,exhibiting herbicidal activities that are comparable to those of PQ.The conversion of dienediamine to PQ,which is toxic to chloroplasts,is the key mechanism underlying its potent herbicidal activity.Our study discovers that dienediamine is a safe and superior alternative to PQ,possessing significant potential for application in sustainable agriculture globally.展开更多
基金funded by the National Natural Science Foundation of China(Nos.51805070,51790172)the Liaoning Province Natural Science Foundation Guidance Program(Nos.2019-ZD-0010,2020-BS-057)the Fundamental Research Funds for the Central Universities(No.DUT19RC(3)060)。
文摘Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics with low thermal expansion properties are promising for the rapid preparation of large-scale and complex components by directed energy deposition-laser based(DED-LB)technology.However,the wider application of DED-LB technology is limited due to the inadequate understanding of process conditions.The shaping quality,microstructure,and mechanical properties of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13)(6 mol%TiO_(2))composite ceramics were systematically investigated as a function of energy input in an extensive process window.On this basis,the formation mechanism of solidification defects and the evolution process of microstructure were revealed,and the optimized process parameters were determined.Results show that high energy input improves the fluidity of the molten pool and promotes the uniform distribution and full growth of constituent phases,thus,facilitating the elimination of solidification defects,such as pores and strip gaps.In addition,the microstructure size is strongly dependent on the energy input,increasing when the energy input increases.Moreover,the morphology of theα-Al_(2)O_(3) phase gradually transforms from cellular into cellular dendrite with increasing energy input due to changing solidification conditions.Under the comprehensive influence of solidification defects and microstructure size,the fracture toughness and flexural strength of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics present a parabolic law behavior as the energy input increases.Optimal shaping quality and excellent mechanical properties are achieved at an energy input range of 0.36-0.54 W*min^(2) g^(-1) mm^(-1).Within this process window,the average microhardness,fracture toughness,and flexural strength of Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics are up to 1640 Hv,3.87 MPa m^(1/2),and 227 MPa,respectively.This study provides practical guidance for determining the process parameters of DED-LB of melt growth Al_(2)O_(3)/Al_(6)Ti_(2)O_(13) composite ceramics.
基金the sponsorship of the following fund projects:the Guangdong Basic and Applied Basic Research Foundation,China(No.2023A1515110578)the Guangzhou Basic and Applied Basic Research Project,China(No.2024A04J00725)the Guangdong Academy of Sciences Project of Science and Technology Development,China(Nos.2022GDASZH-2022010107 and 2022GDASZH-2022010108).Dr.Zhao would particularly like to thank his wife,M.S.Guo,for her help with the language of the manuscript and for the encouragement of their newborn baby.
文摘The urgent need for integrated molding and sintering across various industries has inspired the development of additive manu-facturing(AM)ceramics.Among the different AM technologies,direct laser additive manufacturing(DLAM)stands out as a group of highly promising technology for flexibly manufacturing ceramics without molds and adhesives in a single step.Over the last decade,sig-nificant and encouraging progress has been accomplished in DLAM of high-performance ceramics,including Al_(2)O_(3),ZrO_(2),Al_(2)O_(3)/ZrO_(2),SiC,and others.However,high-performance ceramics fabricated by DLAM face challenges such as formation of pores and cracks and resultant low mechanical properties,hindering their practical application in high-end equipment.Further improvements are necessary be-fore they can be widely adopted.Methods such as field-assisted techniques and post-processing can be employed to address these chal-lenges,but a more systematic review is needed.This work aims to critically review the advancements in direct selective laser sintering/melting(SLS/SLM)and laser directed energy deposition(LDED)for various ceramic material systems.Additionally,it provides an overview of the current challenges,future research opportunities,and potential applications associated with DLAM of high-perform-ance ceramics.
基金Yunnan Fundamental Research Projects(Nos.202101AS070021,202101AT070265)the National Natural Science Foundation of China(Grant Nos.31960082,32160249)the Scientific Research Fund Project of Yunnan Education Department(No.2021J0002).
文摘Aconitum vilmorinianum,a well-known traditional Chinese herb,is recently being threatened by overexploitation and environment disturbance.This study was conducted to provide propagation methods through in vitro germination and explant cultivation.Germination was stimulated up to 66.00%on Murashige and Skoog(MS)medium containing 2.0 mg L^(−1)6-benzylaminopurine(BAP),0.1 mg L^(−1)1-napthaleneacetic acid(NAA),and 30 g L^(−1)sucrose.Three bacteria(Pantoea agglomerans,Erwinia persicina,and Pseudomonas tolaasii)would be responsible for consistent contamination during germination.The latter two were effectively eradicated after disinfected.The influence of explant types and hormone combinations on direct and indirect organogenesis was evaluated in the present work.The frequency of shoot induction from axillary bud explants was 100%on the MS fortified with 2.0 mg L^(−1)BAP and 0.3 mg L^(−1)NAA.Shoots multiplication was optimized on MS medium supplemented with 0.1 mg L^(−1)thidiazuron(TDZ)and 0.1 mg L^(−1)NAA.High callus induction percentage(96.67%)was obtained from stem segments on MS medium with 2.0 mg L^(−1)2,4-D,then successfully regenerated into shoots on MS medium in the presence of 0.1 mg L^(−1)TDZ and 0.2 mg L^(−1)NAA.The present work could be useful for the utilization and conservation of this valuable species.
基金supported by the National Natural Science Foundation of China(51805070 and 51790172)the Natural Science Foundation of Liaoning Province(2019-ZD-0010,2020-BS-057)the Basic Scientific Research Program for the Central Universities(DUT19RC(3)060).
文摘Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications;however,the rapid preparation of high-performance components remains a challenge.Herein,a novel route for 3D printing dense(<99.4%)high-performance melt-grown alumina-mullite/glass composites using directed laser deposition(DLD)is proposed.Key issues on the composites,including phase composition,microstructure formation/evolution,densification,and mechanical properties,are systematically investigated.The toughening and strengthening mechanisms are analyzed using classical fracture mechanics,Griffith strength theory,and solid/glass interface infiltration theory.It is demonstrated that the composites are composed of corundum,mullite,and glass,or corundum and glass.With the increase of alumina content in the initial powder,corundum grains gradually evolve from near-equiaxed dendrite to columnar dendrite and cellular structures due to the weakening of constitutional undercooling and small nucleation undercooling.The microhardness and fracture toughness are the highest at 92.5 mol%alumina,with 18.39±0.38 GPa and 3.07±0.13 MPa-m1/2,respectively.The maximum strength is 310.1±36.5 MPa at 95 mol%alumina.Strength enhancement is attributed to the improved densification due to the trace silica doping and the relief of residual stresses.The method unravels the potential of preparing dense high-performance melt-grown alumina-based composites by the DLD technology.
基金supported by funding from the CAS “Pioneer Hundred Talents” Program and Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31000000) to Y.C.National Natural Science Foundation of China (Nos. 31960082, 32270395, and 31960096)Yunnan Fundamental Research Projects (No. 202101AS070021) to D.Z。
文摘Diterpenoid alkaloids(DAs) have been often utilized in clinical practice due to their analgesic and anti-infammatory properties. Natural DAs are prevalent in the family Ranunculaceae, notably in the Aconitum genus. Nevertheless, the evolutionary origin of the biosynthesis pathway responsible for DA production remains unknown.In this study, we successfully assembled a highquality, pseudochromosome-level genome of the DA-rich species Aconitum vilmorinianum(A.vilmorinianum)(5.76 Gb). An A. vilmorinianumspecific whole-genome duplication event was discovered using comparative genomic analysis,which may aid in the evolution of the DA biosynthesis pathway. We identified several genes involved in DA biosynthesis via integrated genomic, transcriptomic, and metabolomic analyses. These genes included enzymes encoding target ent-kaurene oxidases and aminotransferases, which facilitated the activation of diterpenes and insertion of nitrogen atoms into diterpene skeletons, thereby mediating the transformation of diterpenes into DAs. The divergence periods of these genes in A. vilmorinianum were further assessed, and it was shown that two major types of genes were involved in the establishment of the DA biosynthesis pathway. Our integrated analysis offers fresh insights into the evolutionary origin of DAs in A.vilmorinianum as well as suggestions for engineering the biosynthetic pathways to obtain desired DAs.
文摘Two new C ig-diterpenoid alkaloids, 7,8-epoxy-franchetine （1） and N（19）-en-austroconitine A （2）, were isolated from Aconitum iochanicum. Compound 1 was a new C19-diterpenoid alkaloid with a 7,8-epoxy unit. Their structures were elucidated by comprehensive spectroscopic analyses including UV, IR, MS, 1D and 2D NMR. Biological ac- tivity tests indicated that two new compounds exhibited inhibitory activity against nitric oxide （NO） production in LPS-activated RAW264.7 macrophages. Compared with positive control, the two new compounds showed weak an- ti-inflammatory effects with the inhibition rate of 27.3% and 29.2%, respectively.
基金the National Nature Science Foundation of China(81971822,81270136,82188101,21725205)National Key R&D Program of China(2021YFF0701601,2022YFA1503702).
文摘Paraquat(PQ)has been used as an herbicide worldwide because of its potent activity against weeds.However,it is highly toxic to humans.The very high fatality of PQ poisoning is due to its inherent toxicity and the lack of any effective treatment.Consequently,developing a non-toxic herbicide with comparable efficacy to PQ will contribute to global food security and help prevent PQ-related fatalities.Herein,we report a new herbicide called dienediamine,which was discovered from how to intervene the redox cycle of PQ,an inherent toxicity nature.Dienediamine,the“reduced"form of PQ with no function as an electron transfer agent,was shown to be non-toxic through comprehensive in vivo and in vitro experiments at molar concentrations equivalent to PQ's absolute lethal dose.Remarkably,dienediamine can undergo conversion to PQ under natural sunlight and ambient air conditions,exhibiting herbicidal activities that are comparable to those of PQ.The conversion of dienediamine to PQ,which is toxic to chloroplasts,is the key mechanism underlying its potent herbicidal activity.Our study discovers that dienediamine is a safe and superior alternative to PQ,possessing significant potential for application in sustainable agriculture globally.
