Ductile transient liquid phase(TLP)bonding joints reinforced by multiple precipitates were produced using novel pre-sintered coatings and Au-Si fillers;therefore,the highest strength of NiTi/sapphire joints brazed at ...Ductile transient liquid phase(TLP)bonding joints reinforced by multiple precipitates were produced using novel pre-sintered coatings and Au-Si fillers;therefore,the highest strength of NiTi/sapphire joints brazed at 460℃ for 30 min reached 72 MPa.The pre-sintering process improved the surface-active of sapphire by forming metastable Ti_(3)O and non-stoichiometric Al_(2)O_(3).The typical brazing seam consisted of O-rich compounds,TiSi_(2),and Ti-Ni-Si,wherein the O-rich phase featured different crystallinity depending on the oxygen content.The sapphire/seam interface was either a nanoscale diffusion region or a Si-rich amorphous layer.The breakdown of the Stokes-Einstein relation(SER)occurred,and the deviation from SER increased with a higher cooling rate.The influence of coating thickness was reflected in(i)the supercooling related to the viscosity and fractional exponent of liquids and(ii)the microstructural change of the joint related to the driving force for crystal growth.This work presented a new strategy for joining ceramics to metals at lower temperatures but using the joint at higher temperatures;furthermore,gave an insight into the microstructure evolution and kinetics behaviors based on supercooling in a transient liquid phase bonding joint.展开更多
We propose a catalytically activated duplication model to mimic the coagulation and duplication of the DNA polymer system under the catalysis of the primer RNA. In the model, two aggregates of the same species can coa...We propose a catalytically activated duplication model to mimic the coagulation and duplication of the DNA polymer system under the catalysis of the primer RNA. In the model, two aggregates of the same species can coagulate themselves and a DNA aggregate of any size can yield a new monomer or double itself with the help of RNA aggregates. By employing the mean-field rate equation approach we analytically investigate the evolution behaviour of the system. For the system with catalysis-driven monomer duplications, the aggregate size distribution of DNA polymers αk(t) always follows a power law in size in the long-time limit, and it decreases with time or approaches a time-independent steady-state form in the case of the duplication rate independent of the size of the mother aggregates, while it increases with time increasing in the case of the duplication rate proportional to the size of the mother aggregates. For the system with complete catalysis-driven duplications, the aggregate size distribution αk(t) approaches a generalized or modified scaling form.展开更多
We propose a catalysis-select migration driven evolution model of two-species(A-and B-species) aggregates,where one unit of species A migrates to species B under the catalysts of species C,while under the catalysts ...We propose a catalysis-select migration driven evolution model of two-species(A-and B-species) aggregates,where one unit of species A migrates to species B under the catalysts of species C,while under the catalysts of species D the reaction will become one unit of species B migrating to species A.Meanwhile the catalyst aggregates of species C perform self-coagulation,as do the species D aggregates.We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j) = Jkij.The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration,in which the competition is between JD0 and KC0(D0 and C0 are the initial numbers of the monomers of species D and C,respectively).When JD0 KC0 〉 0,the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form.And in the case of JD0 KC0 〈 0,species A and B exchange their aggregate size distributions as in the above JD0 KC0 〉 0 case.展开更多
The coaggregating behavior of the cationic kinetic probe P16;with different types of surfactants are in complete agreement with predictions based on the newly proposed ESAg concept.
Graphite, as a strategic mineral resource, the recycling from spent lithium-ion batteries(LIBs) has attracted considerable attention for meeting considerable economic value. However, closed-circuit recycling still suf...Graphite, as a strategic mineral resource, the recycling from spent lithium-ion batteries(LIBs) has attracted considerable attention for meeting considerable economic value. However, closed-circuit recycling still suffers from the lack of effective repair methods. Considering the existing defects, a series of Cchain length carbons have been successfully introduced to repair spent graphite. Obviously, with the evolution of carbon resources, the thickness and pores of the coating layer were tailored with the functional groups. Benefitting from the increased active sites and created fold structure, their coulombic efficiency is obviously restored from 14% to 86.89%, while the stable capacity is kept at approximately 384.9 mAh gafter 100 cycles. Moreover, their excellent rate properties are kept about approximately 200 mAh gat2 C, meeting the standard of commercial materials. Supported by the detailed kinetic behaviors, the enhanced rate is mainly dominated by pseudocapacitive behaviors, accompanied by deepening redox reactions. Meanwhile, the cost of the proposed approach for recycling spent graphite is 894.87 $ t^(-1),and the recycling profit for regenerating graphite is approximately 7000 $ t^(-1). Given this, this work is anticipated to shed light on the closed-circuit recycling of spent graphite and offer significant strategies to repair graphite.展开更多
Due to the high theoretical capacity and energy density,conversion-type metal fluorides have captured plenty of attentions but still suffer from the inferior kinetic behaviors and serious capacity fading.For addressin...Due to the high theoretical capacity and energy density,conversion-type metal fluorides have captured plenty of attentions but still suffer from the inferior kinetic behaviors and serious capacity fading.For addressing the issues above,the strategies of surface/interface engineering are utilized for the preparation of sphere-like porous FeF3@C materials,where the as-resulted sample displays the uniform particle size(~150 nm in radii)and the ultrathin carbon layers(thickness of~10 nm).Significantly,benefitting from the rich oxygen of precursor,the interfacial chemical bonds Fe-O-C are successfully constructed between carbon matrix and FeF3 materials,accompanying by the enhancements of ions/electrons(e-)conductivity and stability.When used as Li-storage cathodes,the initial lithium-ions storage capacity could reach up to~400mAh·g^(-1) at 0.1 A·g^(-1).Even at 1.0 A·g^(-1),the capacity could be still remained at about 210 mAh·g^(-1),with the retention of 85%after 400 cycles.Assisted by the detailed kinetic behaviors,the considerable electrochemical properties come from the enhanced diffusion-controlled contributions,whilst the segregation of Fe with LiF is effectively alleviated by unique architecture.Moreover,during cycling,solid electrolyte interface film is reversibly formed/decomposed.Thus,this work is expected to offer rational exterior/interfacial designing strategies for metalbased samples.展开更多
The Zr-2.5Nb alloy with a fine microstructure consisting ofαlaths was successfully prepared by electron beam melting(EBM).The thermal oxidation behaviors and kinetics of the as-built,and the EBM-built and hot isostat...The Zr-2.5Nb alloy with a fine microstructure consisting ofαlaths was successfully prepared by electron beam melting(EBM).The thermal oxidation behaviors and kinetics of the as-built,and the EBM-built and hot isostatically pressed(HIPed)Zr-2.5Nb materials in a temperature range of 450-600°C were in-vestigated and compared with those of the alloy prepared by conventional casting and forging.It was found that the oxidation kinetics of the as-built and the forged materials followed the parabolic rate law during isothermal oxidation at 550°C,but the HIPed materials exhibited a parabolic-to-linear kinetic transition,suggesting that the larger grain sizes enhanced the oxidation.The oxide layers of all materials were composed of a large fraction of monoclinic zirconia phase(m-ZrO_(2))and a small fraction of tetrago-nal zirconia phase(t-ZrO_(2)),and transformed from t-ZrO_(2)to m-ZrO_(2)with increasing oxidation time.The surface hardness of the as-built,the forged and the HIPed materials increased from 215,204,and 188 HV before oxidation to 902,1070,and 1137 HV after oxidation,respectively.The cross-sections of the materi-als showed the presence of micropores and microcracks inside the oxide layers with thicknesses ranging from 4 to 8μm.With the oxidation temperature of 600°C and oxidation time duration of 3 h,a dense black m-ZrO_(2)oxide layer with smooth surface and 902 HV hardness was obtained on the EBM as-built Zr-2.5Nb materials.展开更多
Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been ...Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been well documented. However, the gas-involved dissolution and regrowth have seldom been explored and the mechanisms remain elusive. We report herein, an in situ TEM study of the dissolution and regrowth dynamics of MoO2 nanowires under oxygen using environmental transmission electron microscopy (ETEM). For the first time, oscillatory dissolution on the nanowire tip is revealed, and, intriguingly, simultaneous layer-by-layer regrowth on the sidewall facets is observed, leading to a shorter and wider nanowire. Combined with first-principles calculations, we found that electron beam irradiation caused oxygen loss in the tip facets, which resulted in changing the preferential growth facets and drove the morphology reshaping.展开更多
基金supported by the National MCF Energy R&D Program(No.2019YFE03100100)National Natural Science Foundation of China(NSFC,Nos.51975150,51974101,U21A20128,52175302,and 52105332)+2 种基金National Strategic International Science and Technology Innovation Cooperation Key Project(No.2020YFE0205304)Natural Science Foundation of Heilongjiang Province,China(Nos.JQ2020E003 and LH2020E037)Applied Basic Research Key Project of Yunnan(No.202002AB080001-1).
文摘Ductile transient liquid phase(TLP)bonding joints reinforced by multiple precipitates were produced using novel pre-sintered coatings and Au-Si fillers;therefore,the highest strength of NiTi/sapphire joints brazed at 460℃ for 30 min reached 72 MPa.The pre-sintering process improved the surface-active of sapphire by forming metastable Ti_(3)O and non-stoichiometric Al_(2)O_(3).The typical brazing seam consisted of O-rich compounds,TiSi_(2),and Ti-Ni-Si,wherein the O-rich phase featured different crystallinity depending on the oxygen content.The sapphire/seam interface was either a nanoscale diffusion region or a Si-rich amorphous layer.The breakdown of the Stokes-Einstein relation(SER)occurred,and the deviation from SER increased with a higher cooling rate.The influence of coating thickness was reflected in(i)the supercooling related to the viscosity and fractional exponent of liquids and(ii)the microstructural change of the joint related to the driving force for crystal growth.This work presented a new strategy for joining ceramics to metals at lower temperatures but using the joint at higher temperatures;furthermore,gave an insight into the microstructure evolution and kinetics behaviors based on supercooling in a transient liquid phase bonding joint.
基金supported by the National Natural Science Foundation of China (Grant Nos 10275048,10305009 and 10875086)by the Zhejiang Provincial Natural Science Foundation of China (Grant No 102067)
文摘We propose a catalytically activated duplication model to mimic the coagulation and duplication of the DNA polymer system under the catalysis of the primer RNA. In the model, two aggregates of the same species can coagulate themselves and a DNA aggregate of any size can yield a new monomer or double itself with the help of RNA aggregates. By employing the mean-field rate equation approach we analytically investigate the evolution behaviour of the system. For the system with catalysis-driven monomer duplications, the aggregate size distribution of DNA polymers αk(t) always follows a power law in size in the long-time limit, and it decreases with time or approaches a time-independent steady-state form in the case of the duplication rate independent of the size of the mother aggregates, while it increases with time increasing in the case of the duplication rate proportional to the size of the mother aggregates. For the system with complete catalysis-driven duplications, the aggregate size distribution αk(t) approaches a generalized or modified scaling form.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10875086 and 10775104)
文摘We propose a catalysis-select migration driven evolution model of two-species(A-and B-species) aggregates,where one unit of species A migrates to species B under the catalysts of species C,while under the catalysts of species D the reaction will become one unit of species B migrating to species A.Meanwhile the catalyst aggregates of species C perform self-coagulation,as do the species D aggregates.We study this catalysis-select migration driven kinetic aggregation phenomena using the generalized Smoluchowski rate equation approach with C species catalysis-select migration rate kernel K(k;i,j) = Kkij and D species catalysis-select migration rate kernel J(k;i,j) = Jkij.The kinetic evolution behaviour is found to be dominated by the competition between the catalysis-select immigration and emigration,in which the competition is between JD0 and KC0(D0 and C0 are the initial numbers of the monomers of species D and C,respectively).When JD0 KC0 〉 0,the aggregate size distribution of species A satisfies the conventional scaling form and that of species B satisfies a modified scaling form.And in the case of JD0 KC0 〈 0,species A and B exchange their aggregate size distributions as in the above JD0 KC0 〉 0 case.
文摘The coaggregating behavior of the cationic kinetic probe P16;with different types of surfactants are in complete agreement with predictions based on the newly proposed ESAg concept.
基金financially supported by the National Key Research and Development Program(2019YFC1907801,2019YFC1907804)the National Natural Science Foundation of China(51904340)the Natural Science Foundation of Hunan(2020JJ4733,2021JJ20066)。
文摘Graphite, as a strategic mineral resource, the recycling from spent lithium-ion batteries(LIBs) has attracted considerable attention for meeting considerable economic value. However, closed-circuit recycling still suffers from the lack of effective repair methods. Considering the existing defects, a series of Cchain length carbons have been successfully introduced to repair spent graphite. Obviously, with the evolution of carbon resources, the thickness and pores of the coating layer were tailored with the functional groups. Benefitting from the increased active sites and created fold structure, their coulombic efficiency is obviously restored from 14% to 86.89%, while the stable capacity is kept at approximately 384.9 mAh gafter 100 cycles. Moreover, their excellent rate properties are kept about approximately 200 mAh gat2 C, meeting the standard of commercial materials. Supported by the detailed kinetic behaviors, the enhanced rate is mainly dominated by pseudocapacitive behaviors, accompanied by deepening redox reactions. Meanwhile, the cost of the proposed approach for recycling spent graphite is 894.87 $ t^(-1),and the recycling profit for regenerating graphite is approximately 7000 $ t^(-1). Given this, this work is anticipated to shed light on the closed-circuit recycling of spent graphite and offer significant strategies to repair graphite.
基金financially supported by the National Natural Science Foundation of China(Nos.52004334,52003230,91962223 and 21473258)the Science and TechnologyInnovation Program of Hunan Province(No.2021RC2091)+3 种基金the China Postdoctoral Science Foundation(No.2021M692703)Natural Science Foundation of Hunan Province(No.2021JJ20073)National Key Research and Development Program of China(Nos.2018YFC1901601 and 2019YFC1907801)Collaborative Innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources,Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2017-13)。
文摘Due to the high theoretical capacity and energy density,conversion-type metal fluorides have captured plenty of attentions but still suffer from the inferior kinetic behaviors and serious capacity fading.For addressing the issues above,the strategies of surface/interface engineering are utilized for the preparation of sphere-like porous FeF3@C materials,where the as-resulted sample displays the uniform particle size(~150 nm in radii)and the ultrathin carbon layers(thickness of~10 nm).Significantly,benefitting from the rich oxygen of precursor,the interfacial chemical bonds Fe-O-C are successfully constructed between carbon matrix and FeF3 materials,accompanying by the enhancements of ions/electrons(e-)conductivity and stability.When used as Li-storage cathodes,the initial lithium-ions storage capacity could reach up to~400mAh·g^(-1) at 0.1 A·g^(-1).Even at 1.0 A·g^(-1),the capacity could be still remained at about 210 mAh·g^(-1),with the retention of 85%after 400 cycles.Assisted by the detailed kinetic behaviors,the considerable electrochemical properties come from the enhanced diffusion-controlled contributions,whilst the segregation of Fe with LiF is effectively alleviated by unique architecture.Moreover,during cycling,solid electrolyte interface film is reversibly formed/decomposed.Thus,this work is expected to offer rational exterior/interfacial designing strategies for metalbased samples.
基金supported by the National Natural Science Foundation of China (Nos.52071068 and 51871220)the Major Special Projects of the Plan“Science and Technology In-novation 2025”of China (No.2020Z060)+1 种基金the Fundamental Re-search Funds for the Central Universities (No.N2102013)Shenyang Talents program (RC200230),and the“111 Project”,China (No.B16009).
文摘The Zr-2.5Nb alloy with a fine microstructure consisting ofαlaths was successfully prepared by electron beam melting(EBM).The thermal oxidation behaviors and kinetics of the as-built,and the EBM-built and hot isostatically pressed(HIPed)Zr-2.5Nb materials in a temperature range of 450-600°C were in-vestigated and compared with those of the alloy prepared by conventional casting and forging.It was found that the oxidation kinetics of the as-built and the forged materials followed the parabolic rate law during isothermal oxidation at 550°C,but the HIPed materials exhibited a parabolic-to-linear kinetic transition,suggesting that the larger grain sizes enhanced the oxidation.The oxide layers of all materials were composed of a large fraction of monoclinic zirconia phase(m-ZrO_(2))and a small fraction of tetrago-nal zirconia phase(t-ZrO_(2)),and transformed from t-ZrO_(2)to m-ZrO_(2)with increasing oxidation time.The surface hardness of the as-built,the forged and the HIPed materials increased from 215,204,and 188 HV before oxidation to 902,1070,and 1137 HV after oxidation,respectively.The cross-sections of the materi-als showed the presence of micropores and microcracks inside the oxide layers with thicknesses ranging from 4 to 8μm.With the oxidation temperature of 600°C and oxidation time duration of 3 h,a dense black m-ZrO_(2)oxide layer with smooth surface and 902 HV hardness was obtained on the EBM as-built Zr-2.5Nb materials.
文摘Direct observation of the dissolution behavior of nanomaterials could provide fundamental insight to understanding their anisotropic properties and stability. The dissolution mechanism in solution and vacuum has been well documented. However, the gas-involved dissolution and regrowth have seldom been explored and the mechanisms remain elusive. We report herein, an in situ TEM study of the dissolution and regrowth dynamics of MoO2 nanowires under oxygen using environmental transmission electron microscopy (ETEM). For the first time, oscillatory dissolution on the nanowire tip is revealed, and, intriguingly, simultaneous layer-by-layer regrowth on the sidewall facets is observed, leading to a shorter and wider nanowire. Combined with first-principles calculations, we found that electron beam irradiation caused oxygen loss in the tip facets, which resulted in changing the preferential growth facets and drove the morphology reshaping.