Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework n...Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.展开更多
Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,a...Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins,with a focus on the Chang 7_(3) sub-member of Triassic Yanchang Formation.The research integrates a variety of exploration data,including field outcrops,drilling,logging,core samples,geochemical analyses,and flume simulation.The study indicates that:(1)The paleoenvironment of the Chang 7_(3) deposition is characterized by a warm and humid climate,frequent monsoon events,and a large water depth of freshwater lacustrine basin.The paleogeomorphology exhibits an asymmetrical pattern,with steep slopes in the southwest and gentle slopes in the northeast,which can be subdivided into microgeomorphological units,including depressions and ridges in lakebed,as well as ancient channels.(2)The Chang 7_(3) sub-member is characterized by a diverse array of fine-grained sediments,including very fine sandstone,siltstone,mudstone and tuff.These sediments are primarily distributed in thin interbedded and laminated arrangements vertically.The overall grain size of the sandstone predominantly falls below 62.5μm,with individual layer thicknesses of 0.05–0.64 m.The deposits contain intact plant fragments and display various sedimentary structure,such as wavy bedding,inverse-to-normal grading sequence,and climbing ripple bedding,which indicating a depositional origin associated with density flows.(3)Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows.The initial phase is characterized by a density-velocity differential,resulting in a thicker,coarser sediment layer at the flow front,while the upper layers are thinner and finer in grain size.During the mid-phase,sliding water effects cause the fluid front to rise and facilitate rapid forward transport.This process generates multiple“new fronts”,enabling the long-distance transport of fine-grained sandstones,such as siltstone and argillaceous siltstone,into the center of the lake basin.(4)A sedimentary model primarily controlled by hyperpynal flows was established for the southwestern part of the basin,highlighting that the frequent occurrence of flood events and the steep slope topography in this area are primary controlling factors for the development of hyperpynal flows.(5)Sandstone and mudstone in the Chang 7_(3) sub-member exhibit micro-and nano-scale pore-throat systems,shale oil is present in various lithologies,while the content of movable oil varies considerably,with sandstone exhibiting the highest content of movable oil.(6)The fine-grained sediment complexes formed by multiple episodes of sandstones and mudstones associated with density flow in the Chang 7_(3) formation exhibit characteristics of“overall oil-bearing with differential storage capacity”.The combination of mudstone with low total organic carbon content(TOC)and siltstone is identified as the most favorable exploration target at present.展开更多
Calcium-barium sulfo-ferritealuminate(C_3BA_(3-y)F_(y)$)was synthesized by doping Ba-bearing calcium sulphoaluminate(C_3BA_3$)with Fe^(3+).The effects of calcination temperature,holding time and Fe-doping concentratio...Calcium-barium sulfo-ferritealuminate(C_3BA_(3-y)F_(y)$)was synthesized by doping Ba-bearing calcium sulphoaluminate(C_3BA_3$)with Fe^(3+).The effects of calcination temperature,holding time and Fe-doping concentration on the solid-state reaction process of the C_(3)BA_(3-y)F_(y)$(y=0,0.2,0.25,0.4,and 0.6)were investigated by the Rietveld/XRD quantitative phase analysis.The experimental results show that Fe-doping not only significantly improvs the synthesis of C_(3)BA_(3-y)F_(y)$,but also reduces the solid-state reaction potential energy barrier and then promots mineral formation.Nevertheless,the mineral begins to decompose when the Fe/Al ratio exceeds 2/13 and the calcination temperature exceeds 1300℃.The Ginstling equation is found to be the most appropriate kinetic model for the statistical fitting of C_(3)BA_(3-y)F_(y)$formation process,based on the mathematical model.It is observed that the apparent activation energy of C_(3)BA_(3-y)F_(y)$decreases and then increases with increasing Fe-doping concentration.展开更多
To clarify the mechanism of differential enrichment of intrasource shale oil,taking the third of seventh member of the Triassic Yanchang Formation(Chang 7_(3)submember for short)in the Ordos Basin,NW China as an examp...To clarify the mechanism of differential enrichment of intrasource shale oil,taking the third of seventh member of the Triassic Yanchang Formation(Chang 7_(3)submember for short)in the Ordos Basin,NW China as an example,we integrated high-resolution scanning electron microscopy(SEM),optical microscopy,laser Raman spectroscopy,rock pyrolysis,and organic solvent extraction experiments to identify solid bitumen of varying origins,obtain direct evidence of intrasource micro-migration of shale oil,and establish the coupling between the shale nano/micro-fabric and the oil generation,migration and accumulation.The Chang 7_(3)shale with rich alginite in laminae has the highest hydrocarbon generation potential but a low thermal transformation ratio.Frequent alternations of micron-scale argillaceous-felsic laminae enhance the hydrocarbon expulsion efficiency,yielding consistent aromaticity between in-situ and migrated solid bitumen.Mudstone laminae rich in terrestrial organic matter(OM)and clay minerals exhibit lower hydrocarbon generation threshold but stronger hydrocarbon retention capacity,with a certain amount of light oil/bitumen preserved to differentiate the chemical structure of in-situ versus migrated bitumen.Tuffaceous and sandy laminae contain abundant felsic minerals and migrated bitumen.Tuffaceous laminae develop high-angle microfractures under shale overpressure,facilitating oil charging into rigid mineral intergranular pores of sandy laminae.Fractionation during micro-migration progressively decreases the aromatization of solid bitumen from shale,through tuffaceous and mudstone,to sandy laminae,while increasing light hydrocarbon components and enhancing OM-hosted pore development.The intrasource micro-migration and enrichment of the Chang 7_(3)shale oil result from synergistic organic-inorganic diagenesis,with crude oil component fractionation being a key mechanism for forming sweet spots in laminated shale oil reservoirs.展开更多
WUSCHEL （WUS） plays an essential role for the maintenance of meristem activity in dicots, but its function is still elusive in monocots. We isolated a new monoculm mutant, monoculm 3 （moc3）, in which a point mutat...WUSCHEL （WUS） plays an essential role for the maintenance of meristem activity in dicots, but its function is still elusive in monocots. We isolated a new monoculm mutant, monoculm 3 （moc3）, in which a point mutation causes the premature termination of rice O. sativa WUS （OsWUS）. Morphological observation revealed that the formation of tiller buds was disrupted in moc3. MOC3 was localized in the nuclear and could interact with TOPLESS-RELATED PROTEINS （TPRs）. The expression of MOC3 was induced by cytokinins and defection of MOC3 affected the expression of several two-component cytokinin response regulators, OsRRs and ORRs. Our results suggest that MOC3 is required for the formation of axillary buds and has a complex relationship with cytokinins.展开更多
YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some interm...YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.展开更多
The formation mechanism for the equilateral triangle structure of the He-3(+) cluster is proposed. The curve of the total energy versus the internuclear distance R for this structure has been calculated by the method ...The formation mechanism for the equilateral triangle structure of the He-3(+) cluster is proposed. The curve of the total energy versus the internuclear distance R for this structure has been calculated by the method of a modified arrangement channel quantum mechanics. The result shows that the curve has a minimal -7.81373 a. u at R = 1.55 a(0). The binding energy of He-3(+) with respect to He+He++He was calculated to be 0.1064 a.u. (about 2.89 eV). This means that the He-3(+) cluster may be formed in the equilateral triangle structure stably by the interaction of He+ with two helium atoms.展开更多
As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislo...As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.展开更多
Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al inte...Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al interface;most of TiAl_(3) grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl_(3) grain size increased with increasing annealing time and/or temperature,but the effect of annealing temperature on the TiAl_(3) grain size was far greater than that of annealing time.The growth of the TiAl_(3) phase consisted of two stages.The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol,and the reaction rate constant of the TiAl_(3) phase was larger as the Ti/Al interface was bonded with fresh surfaces.At the second stage,the growth was governed by diffusion,the diffusion activation energy was 33.69 kJ/mol,and the diffusion growth rate constant of the TiAl_(3) phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl_(3) grain size.展开更多
The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularl...The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularly, the trilobite biozones of the formation have been well defined. On the other hand, little has hitherto been studied on conodont microfossils for the formation. This paper reports a diverse and well-preserved protoconodonts and paraconodonts of Series 3 from the formation in the Eodungol Section, exposed along a southern mountain trail of Mt. Sambangsan, Yeongwol, Korea. Five of the 13 samples collected for conodont contain a rich protoconodont and paraconodont assemblage and numerous shelly fossils including trilobites, brachiopods, sponge spicules, hyolithids, and incertae sedis. Sample Eo 5 is extremely fossiliferous （465 elements, 96.5% of total collection）, and the most abundant species was Phakelodus elongatus （236 elements, 62% of the Eo 5 collection）. The preservation is relatively good, but some specimens are corroded and fragmentary. Some of the protoconodonts are exfoliated. Relatively larger ones were commonly preserved as phosphatized internal molds, particularly in specimens of Furnishina bigeminata, Furnishina leei n. sp., Muellerodus pomeranensis, Nogamiconus sinensis, and westergaardodids. Phakelodids were commonly preserved as clusters. Among 20 species referable to nine genera, Furnishina bigeminata, Furnishina leei n. sp., Nogamiconus sinensis, Huayuanodontus tricornis, Proscandodus obliquus, and Westergaardodina grandidens were previously undescribed species in Korea. This assemblage is named herein as the Westergaardodina matsushitai Zone, which is a new biozonal name replacing the old one, i.e., Gapparodus bisulcatus-Westergaardodina matsushitai-Westergaardodina moessebergensis Assemblage. The W. matsushitai Zone corresponds to the Lejopyge armata trilobite Zone and is well correlated with the upper Series 3 conodont biozones of the Westergaardodina matsushitai-Westergaardodina grandidens Zone of South China and the Westergaardodina matsushitai Zone of North China, respectively. The present data allow a useful correlation to China and Baltica in relation to new subdivision of the Cambrian. Furnishina leei n. sp. is newly described.展开更多
Vibrational IR spectra and light‐off investigations show that NH3forms via the“hydrogen down”reaction of adsorbed CO and NO with hydroxyl groups on a CeO2support during the catalytic reduction of NO by CO.The prese...Vibrational IR spectra and light‐off investigations show that NH3forms via the“hydrogen down”reaction of adsorbed CO and NO with hydroxyl groups on a CeO2support during the catalytic reduction of NO by CO.The presence of water in the reaction stream results in a significant increase in NH3selectivity.This result is due to water‐induced hydroxylation promoting NH3formation and the competitive adsorption of H2O and NO at the same sites,which inhibits the reactivity of NO reduction by NH3.展开更多
Effect of TiO2 content on the burnability of clinker with high C3S were investigated by determination of free lime in final product, and the clinker phase formation, microstructural features of C3S and the solubility ...Effect of TiO2 content on the burnability of clinker with high C3S were investigated by determination of free lime in final product, and the clinker phase formation, microstructural features of C3S and the solubility of TiO2 in C3S were further studied by XRD, SEM/EDS analysis. TiO2 accelerates the combination of free lime in the samples, free lime content decreases obviously with TiO2 increasing up to 2% and almost remains above 2%. A new phase CaO·TiO2 was found when TiO2 was up to 3%, and samples with TiO2 displayed well-formed uniform size hexagonal C3S crystal. The limit of solubility of TiO2 in C3S at 1400 ℃ is about 1.7%.展开更多
Bone formation and deposition are initiated by sensory nerve infiltration in adaptive bone remodeling. Here, we focused on the role of Semaphorin 3A(Sema3A), expressed by sensory nerves, in mechanical loads-induced bo...Bone formation and deposition are initiated by sensory nerve infiltration in adaptive bone remodeling. Here, we focused on the role of Semaphorin 3A(Sema3A), expressed by sensory nerves, in mechanical loads-induced bone formation and nerve withdrawal using orthodontic tooth movement(OTM) model. Firstly, bone formation was activated after the 3rd day of OTM,coinciding with a decrease in sensory nerves and an increase in pain threshold. Sema3A, rather than nerve growth factor(NGF),highly expressed in both trigeminal ganglion and the axons of periodontal ligament following the 3rd day of OTM. Moreover, in vitro mechanical loads upregulated Sema3A in neurons instead of in human periodontal ligament cells(hPDLCs) within 24 hours.Furthermore, exogenous Sema3A restored the suppressed alveolar bone formation and the osteogenic differentiation of hPDLCs induced by mechanical overload. Mechanistically, Sema3A prevented overstretching of F-actin induced by mechanical overload through ROCK2 pathway, maintaining mitochondrial dynamics as mitochondrial fusion. Therefore, Sema3A exhibits dual therapeutic effects in mechanical loads-induced bone formation, both as a pain-sensitive analgesic and a positive regulator for bone formation.展开更多
The formation mechanism of stoichiometry Ti_5Si_3 by mechanical alloying (MA)from elemental powders has been investigated. The results of XRD and SEM analyses of the powdershow that Ti_5Si_3 can be synthesized by MA i...The formation mechanism of stoichiometry Ti_5Si_3 by mechanical alloying (MA)from elemental powders has been investigated. The results of XRD and SEM analyses of the powdershow that Ti_5Si_3 can be synthesized by MA in a planetary mill with two different formationmechanisms. Ti_5Si_3 was formed gradually with the mechanical collusion reaction (MCR) mechanismunder a lower impact energy, and the Ti_5Si_3 was formed abruptly with the self-propagatinghigh-temperature synthesis (SHS) formation mechanism under a higher impact energy.展开更多
The simulation of blast furnace slag was prepared by pure chemical reagents.Test methods like DSC,XRD and SEM were used to study the effect of Al2O3 and MgO content on crystallization of blast furnace slag during fibe...The simulation of blast furnace slag was prepared by pure chemical reagents.Test methods like DSC,XRD and SEM were used to study the effect of Al2O3 and MgO content on crystallization of blast furnace slag during fiber formation.The results show that as Al2O3 and MgO contents in the sample changed,blast furnace slag was crystallized at the average temperature below 1232 K.When the ratio of Mg/Al in the samples is 0.6 calculated by Kissinger equation,crystallization activation energy is at the maximum value and the system is in the most stable condition.The sample crystallization phases are mainly calcium akermanite(2CaO?MgO?2SiO2)and gehlenite(2CaO?Al2O3?SiO2).Secondary crystallization phases are anorthite(CaAl2Si2O8),wollastonite minerals(WOLLA)and pyroxene minerals(cPyrA).Meanwhile,the principal crystallization phases of the samples are different types and have different contents,and the microstructures of the sample sections are different due to the difference between MgO/Al2O3 ratio.展开更多
Through microscopic analyses(e.g.,organic macerals,thin section observation,scanning electron microscope(SEM)imaging of fresh bedding planes via argon ion milling,and energy spectrum tests)combined with Rock-Eval anal...Through microscopic analyses(e.g.,organic macerals,thin section observation,scanning electron microscope(SEM)imaging of fresh bedding planes via argon ion milling,and energy spectrum tests)combined with Rock-Eval analyses,this study systematically investigated the organic matter and pyrites in the continental shales in the 3^(rd)submember of the Chang 7 Member(Chang 7^(3)submember)in the Yanchang Formation,Ordos Basin and determined their types and the formation and evolutionary characteristics.The results are as follows.The organic matter of the continental shales in the Chang 7^(3)submember is dominated by amorphous bituminites and migrabitumens,which have come into being since the early diagenetic stage and middle diagenetic stage A,respectively.The formation and transformation of organic matter is a prerequisite for the formation of pyrites.The Ordos Basin was a continental freshwater lacustrine basin and lacked sulphates in waters during the deposition of the Chang 7 Member.Therefore,the syndiagenetic stage did not witness the formation of large quantities of pyrites.Since the basin entered early diagenetic stage A,large quantities of sulfur ions were released as the primary organic matter got converted into bituminites and,accordingly,pyrites started to form.However,this stage featured poorer fluid and spatial conditions compared with the syndepositional stage due to withdraw of water,the partial formation of bituminites,and a certain degree of compaction.As a result,large quantities of pyrrhotite failed to transition into typical spherical framboidal pyrites but grew into euhedral monocrystal aggregates.In addition,pyrites are still visible in the migrabitumens in both microfractures and inorganic pores of mudstones and shales,indicating that the pyrite formation period can extend until the middle diagenetic stage A.展开更多
β-β″-Al2O3precursor powder was successfully prepared by a solid-phase sintering method with Li2CO3, Na2CO3 （as the sources of Li20 and Na20, respectively） and β″-Al2O3 powder as the raw materials. The precursor...β-β″-Al2O3precursor powder was successfully prepared by a solid-phase sintering method with Li2CO3, Na2CO3 （as the sources of Li20 and Na20, respectively） and β″-Al2O3 powder as the raw materials. The precursor was characterized by X-ray diffraction （XRD） and scan- ning electron microscope （SEM）. The results indicate that the amount of Na20 in the raw materials has a great effect on the formation of β″-Al2O3 in the β-β″-Al2O3 precursor. When Na20 content is 10 wt%, the content of β″-Al2O3 phase reaches the maximum value of 86.24 wt% in the precursor. The β-β″-Al2O3 ceramic was prepared from β-β″-Al2O3 precursor powder by isostatic pressing and burying sintering process. The conductive property of the β-β″-Al2O3 ceramic was examined by electrochemical impedance spectroscopy （EIS） method, and the density was measured by the Archimedes method. The results reveal that when 10 wt% Na20 was added, the sample exhibits the best performance with the lowest resistivity of 4.51.cm and the highest density of 3.25 g.cm 3. A solid electrolyte battery of PtlSnQ, Na2SnO3113 β-β″-Al2O3 Na CrO2, Cr2lO3 Pt was assembled by the β-β″-Al2O3 electrolyte tube to measure the open potential of the resulting battery, and the formation free energy of sodium stannate was calculated In the temperature range of 1273-773 K, the relationship between formation free energy of sodiumstannate and temperature was generated as follows：△GNa2SnO3 0=-1040.83＋0.2221T±7.54.展开更多
8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-deso...8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-desorption, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible diffuse reflectance spectroscopy （DRS） and scanning transmission electron microscopy-high-angle annular dark field （STEM HAADF）. The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure： The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster.展开更多
A β”/β-Al_2O_3 solid electrolyte was prepared and used in a Na conentration galvanic cell: (-)O_2(in Ar),SnO_2,Na_2SnO_3|β"/β-Al_2O_3]NaCrO_2,Cr_2O_3,O_2(in Ar)(+).The emf measurements were carried out in te...A β”/β-Al_2O_3 solid electrolyte was prepared and used in a Na conentration galvanic cell: (-)O_2(in Ar),SnO_2,Na_2SnO_3|β"/β-Al_2O_3]NaCrO_2,Cr_2O_3,O_2(in Ar)(+).The emf measurements were carried out in temperature range of 912—1223 K:E=652.1— 0.2092 T+2.3(mV).Using this equation and cited free energies of formation of NaCrO_2, Cr_2O_3 and SnO_2,the molar free energy of formation of Na_2 SnO_3 may be calculated by ΔG°=-1050+0.2544 T±5.4(kJ mol^(-1)).展开更多
At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) ...At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) Sn phase in a cylindrical CuSn/Nb diffusion couple is still controversial.The purpose of this work is to investigate the growth exponent of Nb_(3) Sn phase at the initial stage of annealing by use of scanning electron microscopy(SEM)through which the thickness of Nb_(3) Sn layer can be obtained.In this study,bronze-processed Nb_(3) Sn multifilamentary wires with different annealing time were investigated.The Nb_(3) Sn phase was formed during isothermal annealing at 670 ℃ by solid-state diffusion,which was accomplished by the movement of Sn atoms from the CuSn/Nb_(3) Sn interface to Nb_(3) Sn/Nb interface.However,the formation mechanism of Nb_(3) Sn phase at the initial stage of annealing is still not well understood.Microstructural evolution of Nb_(3) Sn phase during isothermal annealing was studied by SEM.The mean thickness of the Nb_(3) Sn layer(Δ(xNn3 Sn)) is expressed as a power function of the annealing time(t) by the equation A_(x^(2)Nb_(3) Sn)=k(t/t0)^(n),where t0 is the unit time,k is the reaction rate constant and n is the growth exponent.The growth exponent has the average value of 0.82,which means that the formation of the Nb_(3) Sn phase is both governed by the interface reaction and the grain boundary diffusion.展开更多
基金supported in part by the National Natural Science Foundations of China(Nos.61175084,61673042 and 62203046)the China Postdoctoral Science Foundation(No.2022M713006).
文摘Aiming to address the Unmanned Aerial Vehicle(UAV) formation collision avoidance problem in Three-Dimensional(3-D) low-altitude environments where dense various obstacles exist, a fluid-based path planning framework named the Formation Interfered Fluid Dynamical System(FIFDS) with Moderate Evasive Maneuver Strategy(MEMS) is proposed in this study.First, the UAV formation collision avoidance problem including quantifiable performance indexes is formulated. Second, inspired by the phenomenon of fluids continuously flowing while bypassing objects, the FIFDS for multiple UAVs is presented, which contains a Parallel Streamline Tracking(PST) method for formation keeping and the traditional IFDS for collision avoidance. Third, to rationally balance flight safety and collision avoidance cost, MEMS is proposed to generate moderate evasive maneuvers that match up with collision risks. Comprehensively containing the time and distance safety information, the 3-D dynamic collision regions are modeled for collision prediction. Then, the moderate evasive maneuver principle is refined, which provides criterions of the maneuver amplitude and direction. On this basis, an analytical parameter mapping mechanism is designed to online optimize IFDS parameters. Finally, the performance of the proposed method is validated by comparative simulation results and real flight experiments using fixed-wing UAVs.
基金Supported by the CNPC Major Science and Technology Project(2021DJ1806).
文摘Based on recent advancements in shale oil exploration within the Ordos Basin,this study presents a comprehensive investigation of the paleoenvironment,lithofacies assemblages and distribution,depositional mechanisms,and reservoir characteristics of shale oil of fine-grained sediment deposition in continental freshwater lacustrine basins,with a focus on the Chang 7_(3) sub-member of Triassic Yanchang Formation.The research integrates a variety of exploration data,including field outcrops,drilling,logging,core samples,geochemical analyses,and flume simulation.The study indicates that:(1)The paleoenvironment of the Chang 7_(3) deposition is characterized by a warm and humid climate,frequent monsoon events,and a large water depth of freshwater lacustrine basin.The paleogeomorphology exhibits an asymmetrical pattern,with steep slopes in the southwest and gentle slopes in the northeast,which can be subdivided into microgeomorphological units,including depressions and ridges in lakebed,as well as ancient channels.(2)The Chang 7_(3) sub-member is characterized by a diverse array of fine-grained sediments,including very fine sandstone,siltstone,mudstone and tuff.These sediments are primarily distributed in thin interbedded and laminated arrangements vertically.The overall grain size of the sandstone predominantly falls below 62.5μm,with individual layer thicknesses of 0.05–0.64 m.The deposits contain intact plant fragments and display various sedimentary structure,such as wavy bedding,inverse-to-normal grading sequence,and climbing ripple bedding,which indicating a depositional origin associated with density flows.(3)Flume simulation experiments have successfully replicated the transport processes and sedimentary characteristics associated with density flows.The initial phase is characterized by a density-velocity differential,resulting in a thicker,coarser sediment layer at the flow front,while the upper layers are thinner and finer in grain size.During the mid-phase,sliding water effects cause the fluid front to rise and facilitate rapid forward transport.This process generates multiple“new fronts”,enabling the long-distance transport of fine-grained sandstones,such as siltstone and argillaceous siltstone,into the center of the lake basin.(4)A sedimentary model primarily controlled by hyperpynal flows was established for the southwestern part of the basin,highlighting that the frequent occurrence of flood events and the steep slope topography in this area are primary controlling factors for the development of hyperpynal flows.(5)Sandstone and mudstone in the Chang 7_(3) sub-member exhibit micro-and nano-scale pore-throat systems,shale oil is present in various lithologies,while the content of movable oil varies considerably,with sandstone exhibiting the highest content of movable oil.(6)The fine-grained sediment complexes formed by multiple episodes of sandstones and mudstones associated with density flow in the Chang 7_(3) formation exhibit characteristics of“overall oil-bearing with differential storage capacity”.The combination of mudstone with low total organic carbon content(TOC)and siltstone is identified as the most favorable exploration target at present.
基金Funded by the National Key Research and Development Program of China(2021YFB3802002)the National Natural Science Foundation of China(Nos.52172021 and U22A20126)+4 种基金the Science Foundation for Excellent Young Scholars of Shandong Province(No.ZR2023YQ041)the Natural Science Foundation of Shandong Province(ZR2021ME123)the Taishan Scholars Program(No.tsqn202306224)the Science and Technology Innovation Support Plan for Young Researchers in Institutes of Higher Education in Shandong(No.2019KJA017)the'111 Center'。
文摘Calcium-barium sulfo-ferritealuminate(C_3BA_(3-y)F_(y)$)was synthesized by doping Ba-bearing calcium sulphoaluminate(C_3BA_3$)with Fe^(3+).The effects of calcination temperature,holding time and Fe-doping concentration on the solid-state reaction process of the C_(3)BA_(3-y)F_(y)$(y=0,0.2,0.25,0.4,and 0.6)were investigated by the Rietveld/XRD quantitative phase analysis.The experimental results show that Fe-doping not only significantly improvs the synthesis of C_(3)BA_(3-y)F_(y)$,but also reduces the solid-state reaction potential energy barrier and then promots mineral formation.Nevertheless,the mineral begins to decompose when the Fe/Al ratio exceeds 2/13 and the calcination temperature exceeds 1300℃.The Ginstling equation is found to be the most appropriate kinetic model for the statistical fitting of C_(3)BA_(3-y)F_(y)$formation process,based on the mathematical model.It is observed that the apparent activation energy of C_(3)BA_(3-y)F_(y)$decreases and then increases with increasing Fe-doping concentration.
基金Supported by the National Science and Technology Major Project(2024ZD1404901,2017ZX05035)Strategic Priority Research Program(Category B)of the Chinese Academy of Sciences(XDB10050100).
文摘To clarify the mechanism of differential enrichment of intrasource shale oil,taking the third of seventh member of the Triassic Yanchang Formation(Chang 7_(3)submember for short)in the Ordos Basin,NW China as an example,we integrated high-resolution scanning electron microscopy(SEM),optical microscopy,laser Raman spectroscopy,rock pyrolysis,and organic solvent extraction experiments to identify solid bitumen of varying origins,obtain direct evidence of intrasource micro-migration of shale oil,and establish the coupling between the shale nano/micro-fabric and the oil generation,migration and accumulation.The Chang 7_(3)shale with rich alginite in laminae has the highest hydrocarbon generation potential but a low thermal transformation ratio.Frequent alternations of micron-scale argillaceous-felsic laminae enhance the hydrocarbon expulsion efficiency,yielding consistent aromaticity between in-situ and migrated solid bitumen.Mudstone laminae rich in terrestrial organic matter(OM)and clay minerals exhibit lower hydrocarbon generation threshold but stronger hydrocarbon retention capacity,with a certain amount of light oil/bitumen preserved to differentiate the chemical structure of in-situ versus migrated bitumen.Tuffaceous and sandy laminae contain abundant felsic minerals and migrated bitumen.Tuffaceous laminae develop high-angle microfractures under shale overpressure,facilitating oil charging into rigid mineral intergranular pores of sandy laminae.Fractionation during micro-migration progressively decreases the aromatization of solid bitumen from shale,through tuffaceous and mudstone,to sandy laminae,while increasing light hydrocarbon components and enhancing OM-hosted pore development.The intrasource micro-migration and enrichment of the Chang 7_(3)shale oil result from synergistic organic-inorganic diagenesis,with crude oil component fractionation being a key mechanism for forming sweet spots in laminated shale oil reservoirs.
基金supported by grants from the National Natural Science Foundation of China (No.91335204)the Ministry of Science and Technology (No.2013CBA01401)
文摘WUSCHEL （WUS） plays an essential role for the maintenance of meristem activity in dicots, but its function is still elusive in monocots. We isolated a new monoculm mutant, monoculm 3 （moc3）, in which a point mutation causes the premature termination of rice O. sativa WUS （OsWUS）. Morphological observation revealed that the formation of tiller buds was disrupted in moc3. MOC3 was localized in the nuclear and could interact with TOPLESS-RELATED PROTEINS （TPRs）. The expression of MOC3 was induced by cytokinins and defection of MOC3 affected the expression of several two-component cytokinin response regulators, OsRRs and ORRs. Our results suggest that MOC3 is required for the formation of axillary buds and has a complex relationship with cytokinins.
文摘YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.
文摘The formation mechanism for the equilateral triangle structure of the He-3(+) cluster is proposed. The curve of the total energy versus the internuclear distance R for this structure has been calculated by the method of a modified arrangement channel quantum mechanics. The result shows that the curve has a minimal -7.81373 a. u at R = 1.55 a(0). The binding energy of He-3(+) with respect to He+He++He was calculated to be 0.1064 a.u. (about 2.89 eV). This means that the He-3(+) cluster may be formed in the equilateral triangle structure stably by the interaction of He+ with two helium atoms.
基金the Financial support from the National key Research and Development Program of China(Nso.2018YFB0406502,2016YFB1102201)the National Natural Science Foundation of China(Grant No.51321091)+2 种基金the key Research and Development Program of Shandong Province(No.2018CXGC0410)the Young Scholars Program of Shandong University(No.2015WLJH36)the 111 Project 2.0(No.BP2018013)
文摘As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.
基金the financial supports from the S&T Program of Hebei Province,China(No.20373901D)the National Natural Science Foundation of China(Nos.51807047,51804095)+2 种基金the National Science Foundation of Hebei Province,China(No.E2019402433)the Youth Top Talents Science and Technology Research Project of Hebei Province University,China(No.BJ2019003)the Research and Development Project of Science and Technology of Handan City,China(No.19422111008-19).
文摘Cold-rolled Ti/Al laminated composites were annealed at 525−625℃for 0−128 h,and the interfacial microstructure evolution was investigated.The results indicate that only the TiAl_(3) phase was formed at the Ti/Al interface;most of TiAl_(3) grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl_(3) grain size increased with increasing annealing time and/or temperature,but the effect of annealing temperature on the TiAl_(3) grain size was far greater than that of annealing time.The growth of the TiAl_(3) phase consisted of two stages.The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol,and the reaction rate constant of the TiAl_(3) phase was larger as the Ti/Al interface was bonded with fresh surfaces.At the second stage,the growth was governed by diffusion,the diffusion activation energy was 33.69 kJ/mol,and the diffusion growth rate constant of the TiAl_(3) phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl_(3) grain size.
基金supported by the National Research Foundation(NRF) of Korea (No. 110439)
文摘The Machari Formation ranges from the ＂upper Series 3＂ （Middle Cambrian） to Furongian （Upper Cambrian） in the Yeongwol area, Korea. It has been known to yield relatively diverse invertebrate fossils. Particularly, the trilobite biozones of the formation have been well defined. On the other hand, little has hitherto been studied on conodont microfossils for the formation. This paper reports a diverse and well-preserved protoconodonts and paraconodonts of Series 3 from the formation in the Eodungol Section, exposed along a southern mountain trail of Mt. Sambangsan, Yeongwol, Korea. Five of the 13 samples collected for conodont contain a rich protoconodont and paraconodont assemblage and numerous shelly fossils including trilobites, brachiopods, sponge spicules, hyolithids, and incertae sedis. Sample Eo 5 is extremely fossiliferous （465 elements, 96.5% of total collection）, and the most abundant species was Phakelodus elongatus （236 elements, 62% of the Eo 5 collection）. The preservation is relatively good, but some specimens are corroded and fragmentary. Some of the protoconodonts are exfoliated. Relatively larger ones were commonly preserved as phosphatized internal molds, particularly in specimens of Furnishina bigeminata, Furnishina leei n. sp., Muellerodus pomeranensis, Nogamiconus sinensis, and westergaardodids. Phakelodids were commonly preserved as clusters. Among 20 species referable to nine genera, Furnishina bigeminata, Furnishina leei n. sp., Nogamiconus sinensis, Huayuanodontus tricornis, Proscandodus obliquus, and Westergaardodina grandidens were previously undescribed species in Korea. This assemblage is named herein as the Westergaardodina matsushitai Zone, which is a new biozonal name replacing the old one, i.e., Gapparodus bisulcatus-Westergaardodina matsushitai-Westergaardodina moessebergensis Assemblage. The W. matsushitai Zone corresponds to the Lejopyge armata trilobite Zone and is well correlated with the upper Series 3 conodont biozones of the Westergaardodina matsushitai-Westergaardodina grandidens Zone of South China and the Westergaardodina matsushitai Zone of North China, respectively. The present data allow a useful correlation to China and Baltica in relation to new subdivision of the Cambrian. Furnishina leei n. sp. is newly described.
基金supported by the National Natural Science Foundation of China (21463015)the Provincial Applied Fundamental Research Program of Yunnan (2014FA045)the National High Technology Research and Development Program of China (863 Program,2015AA034603)~~
文摘Vibrational IR spectra and light‐off investigations show that NH3forms via the“hydrogen down”reaction of adsorbed CO and NO with hydroxyl groups on a CeO2support during the catalytic reduction of NO by CO.The presence of water in the reaction stream results in a significant increase in NH3selectivity.This result is due to water‐induced hydroxylation promoting NH3formation and the competitive adsorption of H2O and NO at the same sites,which inhibits the reactivity of NO reduction by NH3.
基金Funded by China 973 Program of Fundamental Research of High Performance Cement's Preparation and Application (No.2009CB623102 and 2009CB623104)
文摘Effect of TiO2 content on the burnability of clinker with high C3S were investigated by determination of free lime in final product, and the clinker phase formation, microstructural features of C3S and the solubility of TiO2 in C3S were further studied by XRD, SEM/EDS analysis. TiO2 accelerates the combination of free lime in the samples, free lime content decreases obviously with TiO2 increasing up to 2% and almost remains above 2%. A new phase CaO·TiO2 was found when TiO2 was up to 3%, and samples with TiO2 displayed well-formed uniform size hexagonal C3S crystal. The limit of solubility of TiO2 in C3S at 1400 ℃ is about 1.7%.
基金supported in part by National Natural Science Foundation of China(32271364 & 31971240)Interdisciplinary innovation project from West China Hospital of Stomatology, Sichuan University(RD-03-202305)。
文摘Bone formation and deposition are initiated by sensory nerve infiltration in adaptive bone remodeling. Here, we focused on the role of Semaphorin 3A(Sema3A), expressed by sensory nerves, in mechanical loads-induced bone formation and nerve withdrawal using orthodontic tooth movement(OTM) model. Firstly, bone formation was activated after the 3rd day of OTM,coinciding with a decrease in sensory nerves and an increase in pain threshold. Sema3A, rather than nerve growth factor(NGF),highly expressed in both trigeminal ganglion and the axons of periodontal ligament following the 3rd day of OTM. Moreover, in vitro mechanical loads upregulated Sema3A in neurons instead of in human periodontal ligament cells(hPDLCs) within 24 hours.Furthermore, exogenous Sema3A restored the suppressed alveolar bone formation and the osteogenic differentiation of hPDLCs induced by mechanical overload. Mechanistically, Sema3A prevented overstretching of F-actin induced by mechanical overload through ROCK2 pathway, maintaining mitochondrial dynamics as mitochondrial fusion. Therefore, Sema3A exhibits dual therapeutic effects in mechanical loads-induced bone formation, both as a pain-sensitive analgesic and a positive regulator for bone formation.
文摘The formation mechanism of stoichiometry Ti_5Si_3 by mechanical alloying (MA)from elemental powders has been investigated. The results of XRD and SEM analyses of the powdershow that Ti_5Si_3 can be synthesized by MA in a planetary mill with two different formationmechanisms. Ti_5Si_3 was formed gradually with the mechanical collusion reaction (MCR) mechanismunder a lower impact energy, and the Ti_5Si_3 was formed abruptly with the self-propagatinghigh-temperature synthesis (SHS) formation mechanism under a higher impact energy.
基金Project(51474090)supported by the National Natural Science Foundation of China
文摘The simulation of blast furnace slag was prepared by pure chemical reagents.Test methods like DSC,XRD and SEM were used to study the effect of Al2O3 and MgO content on crystallization of blast furnace slag during fiber formation.The results show that as Al2O3 and MgO contents in the sample changed,blast furnace slag was crystallized at the average temperature below 1232 K.When the ratio of Mg/Al in the samples is 0.6 calculated by Kissinger equation,crystallization activation energy is at the maximum value and the system is in the most stable condition.The sample crystallization phases are mainly calcium akermanite(2CaO?MgO?2SiO2)and gehlenite(2CaO?Al2O3?SiO2).Secondary crystallization phases are anorthite(CaAl2Si2O8),wollastonite minerals(WOLLA)and pyroxene minerals(cPyrA).Meanwhile,the principal crystallization phases of the samples are different types and have different contents,and the microstructures of the sample sections are different due to the difference between MgO/Al2O3 ratio.
基金funded by the subproject of the National Science and Technology Major Project(No.2017ZX05036004).
文摘Through microscopic analyses(e.g.,organic macerals,thin section observation,scanning electron microscope(SEM)imaging of fresh bedding planes via argon ion milling,and energy spectrum tests)combined with Rock-Eval analyses,this study systematically investigated the organic matter and pyrites in the continental shales in the 3^(rd)submember of the Chang 7 Member(Chang 7^(3)submember)in the Yanchang Formation,Ordos Basin and determined their types and the formation and evolutionary characteristics.The results are as follows.The organic matter of the continental shales in the Chang 7^(3)submember is dominated by amorphous bituminites and migrabitumens,which have come into being since the early diagenetic stage and middle diagenetic stage A,respectively.The formation and transformation of organic matter is a prerequisite for the formation of pyrites.The Ordos Basin was a continental freshwater lacustrine basin and lacked sulphates in waters during the deposition of the Chang 7 Member.Therefore,the syndiagenetic stage did not witness the formation of large quantities of pyrites.Since the basin entered early diagenetic stage A,large quantities of sulfur ions were released as the primary organic matter got converted into bituminites and,accordingly,pyrites started to form.However,this stage featured poorer fluid and spatial conditions compared with the syndepositional stage due to withdraw of water,the partial formation of bituminites,and a certain degree of compaction.As a result,large quantities of pyrrhotite failed to transition into typical spherical framboidal pyrites but grew into euhedral monocrystal aggregates.In addition,pyrites are still visible in the migrabitumens in both microfractures and inorganic pores of mudstones and shales,indicating that the pyrite formation period can extend until the middle diagenetic stage A.
基金financially supported by the National Natural Science Foundation of China (No.51234009)
文摘β-β″-Al2O3precursor powder was successfully prepared by a solid-phase sintering method with Li2CO3, Na2CO3 （as the sources of Li20 and Na20, respectively） and β″-Al2O3 powder as the raw materials. The precursor was characterized by X-ray diffraction （XRD） and scan- ning electron microscope （SEM）. The results indicate that the amount of Na20 in the raw materials has a great effect on the formation of β″-Al2O3 in the β-β″-Al2O3 precursor. When Na20 content is 10 wt%, the content of β″-Al2O3 phase reaches the maximum value of 86.24 wt% in the precursor. The β-β″-Al2O3 ceramic was prepared from β-β″-Al2O3 precursor powder by isostatic pressing and burying sintering process. The conductive property of the β-β″-Al2O3 ceramic was examined by electrochemical impedance spectroscopy （EIS） method, and the density was measured by the Archimedes method. The results reveal that when 10 wt% Na20 was added, the sample exhibits the best performance with the lowest resistivity of 4.51.cm and the highest density of 3.25 g.cm 3. A solid electrolyte battery of PtlSnQ, Na2SnO3113 β-β″-Al2O3 Na CrO2, Cr2lO3 Pt was assembled by the β-β″-Al2O3 electrolyte tube to measure the open potential of the resulting battery, and the formation free energy of sodium stannate was calculated In the temperature range of 1273-773 K, the relationship between formation free energy of sodiumstannate and temperature was generated as follows：△GNa2SnO3 0=-1040.83＋0.2221T±7.54.
文摘8wt%WO3/SiO2 metathesis （disproportionation） catalysts with different pore structures were prepared by the incipient-wetness-impregnation method. The as-synthesized catalysts were characterized by N2 adsorpfion-desorption, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, UV-visible diffuse reflectance spectroscopy （DRS） and scanning transmission electron microscopy-high-angle annular dark field （STEM HAADF）. The results of STEM HAADF showed that WO3 species were not uniformly distributed on the SiO2 support. The experimental results of 8wt%WO3/SiO2 performance in ethene/decene metathesis revealed that the catalytic effect of 8wt%WO3/SiO2 catalyst and coke formation over it were closely related to the support pore structure： The 8wt%WO3/SiO2 catalyst with a more complicated pore structure showed better catalytic performance but the coke deposition rate was also faster.
文摘A β”/β-Al_2O_3 solid electrolyte was prepared and used in a Na conentration galvanic cell: (-)O_2(in Ar),SnO_2,Na_2SnO_3|β"/β-Al_2O_3]NaCrO_2,Cr_2O_3,O_2(in Ar)(+).The emf measurements were carried out in temperature range of 912—1223 K:E=652.1— 0.2092 T+2.3(mV).Using this equation and cited free energies of formation of NaCrO_2, Cr_2O_3 and SnO_2,the molar free energy of formation of Na_2 SnO_3 may be calculated by ΔG°=-1050+0.2544 T±5.4(kJ mol^(-1)).
基金financially supported by the Nuclear Material Technology Innovation Center for National Defense Technology and Industry(No.ICNM-2019-YZ-03)。
文摘At present,Nb_(3) Sn superconductors are becoming more popular in high magnetic fields.The growth law of Nb_(3) Sn phase in a planar CuSn/Nb diffusion couple has been studied,whereas the formation mechanism of Nb_(3) Sn phase in a cylindrical CuSn/Nb diffusion couple is still controversial.The purpose of this work is to investigate the growth exponent of Nb_(3) Sn phase at the initial stage of annealing by use of scanning electron microscopy(SEM)through which the thickness of Nb_(3) Sn layer can be obtained.In this study,bronze-processed Nb_(3) Sn multifilamentary wires with different annealing time were investigated.The Nb_(3) Sn phase was formed during isothermal annealing at 670 ℃ by solid-state diffusion,which was accomplished by the movement of Sn atoms from the CuSn/Nb_(3) Sn interface to Nb_(3) Sn/Nb interface.However,the formation mechanism of Nb_(3) Sn phase at the initial stage of annealing is still not well understood.Microstructural evolution of Nb_(3) Sn phase during isothermal annealing was studied by SEM.The mean thickness of the Nb_(3) Sn layer(Δ(xNn3 Sn)) is expressed as a power function of the annealing time(t) by the equation A_(x^(2)Nb_(3) Sn)=k(t/t0)^(n),where t0 is the unit time,k is the reaction rate constant and n is the growth exponent.The growth exponent has the average value of 0.82,which means that the formation of the Nb_(3) Sn phase is both governed by the interface reaction and the grain boundary diffusion.
