Design of high-temperature superconductors at moderate pressures by alloying AlH3 or GaH3

Since the discovery of hydride superconductors,a significant challenge has been to reduce the pressure required for their stabilization.In this context,we propose that alloying could be an effective strategy to achieve this.We focus on a series of alloyed hydrides with the AMH_(6)composition,which can be made via alloying A15 AH_(3)(A=Al or Ga)with M(M=a group IIIB or IVB metal),and study their behavior under pressure.Seven of them are predicted to maintain the A15-type structure,similar to AH_(3)under pressure,providing a platform for studying the effects of alloying on the stability and superconductivity of AH_(3).Among these,the A15-type phases of AlZrH_(6)and AlHfH_(6)are found to be thermodynamically stable in the pressure ranges of 40–150 and 30–181 GPa,respectively.Furthermore,they remain dynamically stable at even lower pressures,as low as 13 GPa for AlZrH_(6)and 6 GPa for AlHfH_(6).These pressures are significantly lower than that required for stabilizing A15 AlH3.Additionally,the introduction of Zr or Hf increases the electronic density of states at the Fermi level compared with AlH3.This enhancement leads to higher critical temperatures(Tc)of 75 and 76 K for AlZrH_(6)and AlHfH_(6)at 20 and 10 GPa,respectively.In the case of GaMH_(6)alloys,where M represents Sc,Ti,Zr,or Hf,these metals reinforce the stability of the A15-type structure and reduce the lowest thermodynamically stable pressure for GaH_(3) from 160 GPa to 116,95,80,and 85 GPa,respectively.Particularly noteworthy are the A15-type GaMH_(6)alloys,which remain dynamically stable at low pressures of 97,28,5,and 6 GPa,simultaneously exhibiting high Tc of 88,39,70,and 49 K at 100,35,10,and 10 GPa,respectively.Overall,these findings enrich the family of A15-type superconductors and provide insights for the future exploration of high-temperature hydride superconductors that can be stabilized at lower pressures.

Water temperature induced interannual variation in spawning of Japanese Spanish mackerel Scomberomorus niphonius in the northern Yellow Sea

Japanese Spanish mackerel Scomberomorus niphonius is a pelagic,neritic species that occurs in the Yellow Sea in high commercial value.The spawning period of this fast-growing species is controlled by water temperature.Based on microstructural analysis of otoliths from 145 young-of-the-year(YoY)S.niphonius collected by trawl in 2017,2018,and 2020,and the temporal variation in the spawning period in the northern Yellow Sea,and its relationship to water temperature were examined.We found that the spawning lasted from late April to late June but differed in year:in 2017 it occurred from April 23 to June 1 and peaked in early May,in 2018 it extended later from May 7 to June 29,and in 2020 from May 6 to June 22 and peaked later from late May to mid-June.The highest temperature in 2017 corresponds with the earliest end of the spawning period and a lower growing degree-day(GDD,℃·day)of 383℃·day.In 2018,slower warming corresponds with a longer spawning period,and a GDD spawning period of 506℃·day.Rapid warming in late 2020 corresponds with a spawning peak,and a GDD spawning temperature of 448℃·day.Despite differences in spawning period,the water temperature when spawning commenced was 10-12℃.Therefore,water temperature is the major determinant of the spawning period,affecting both the starting and the ending of spawning.This study improved our understanding of the spawning dynamics and environmental adaptation of S.niphonius,and how these might change in environments subject to increased warming.

Early life history traits of chub mackerel Scomber japonicus in the Oyashio water revealed by otolith microstructure

Information on survival and growth during the early life stage is essential to understand the mechanism of interannual variations in fish recruitment.Chub mackerel Scomber japonicus is a commercially important pelagic fish widely distributed in the northwestern Pacific.Its catch showed large fluctuations with changes in distribution and migration under climate change and strong fishing.We determined the hatch dates and growth rates of young-of-the-year of chub mackerel through otolith microstructure using samples collected in the Oyashio water in autumn 2018.Results show that the ages of young chub mackerel ranged between 120 and 180 d,and the estimated hatch date lasted from midJanuary to late May with a peak from mid-March to mid-April.Average otolith daily increment width during the early life stages(from hatching to 25 d)showed an increasing trend.Chub mackerel grows slowly in the first 10 d,and then grows faster during the 10thto 25thd.Three groups with dissimilar growth histories and migration routes were identified using unsupervised random forest clustering analysis,but all eventually converge on the same nursery ground.The faster growth of young-of-the-year chub mackerel leads to better recruitment due to the hypothesis of growth-dependent mortality.Most chub mackerels hatched in March and April,the spawning period is longer and earlier,which could lead to strong year classes.These findings on population composition and life history traits of young-of-the-year of chub mackerel provide valuable information on its recruitment processes during the period of stock recovery.

Combining otolith elemental signatures with multivariate analytical models to verify the migratory pattern of Japanese Spanish mackerel(Scomberomorus niphonius) in the southern Yellow Sea

Japanese Spanish mackerel,Scomberomorus niphonius,is a commercially important,highly migratory species that is widely distributed throughout the northwestern Pacific region.However,its life history and migratory patterns are only partially understood.This study used otolith chemistry to investigate the migratory pattern of S.niphonius in the southern Yellow Sea,an important fishing ground.Transverse sections of otoliths from 15 age-1 spawning or spent individuals,comprising up to one complete migration cycle,were analyzed from the core to the margin by using laser ablation inductively coupled plasma mass spectrometry.The ratios of the element to Ca were integrated with microstructural analysis to produce age-related elemental profiles.Combining multielemental analysis of otolith composition with multivariate analytical models,we quantified structural changes in otolith chemistry profiles.Results revealed there were diverse changing patterns of otolith chemistry profiles for detected elements and the elements of Na,Mg,Sr and Ba were important for the chronological signal.Five clusters were identified through chronological clustering,representing the five life stages from the early stage to the spawning stage.Variation of Ba:Ca ratio was most informative,showing a step-decreasing pattern in the first four stages and a rebound in the spawning stage.These results support the hypothesized migratory pattern of S.niphonius:hatching and spending their early life in the coastal sandy ridges system of the southern Yellow Sea,migrating northeastward and offshore for feeding during juvenile stage,aggregating in early October and migrating outward to the Jeju Island for wintering,and returning to the coastal waters for spawning.This study demonstrated the value of life-history related otolith chemistry profiles combined with multivariate analytical models was a means to verify the migration patterns of S.niphonius at regional scales with potential application in fisheries assessment and management.

Experimental Observation of Cubic C_3N_4 Compound in Carbon Nitride Thin Films

Cubic C3N4 compound in the C-N thin films on Si and NaCl substrates was prepared by ion beam sputtering of a pure graphite target with discharge gas of pure N2. X-ray photoelectron spectroscopy indicated that nitrogen atoms combined with sp2- and sp3- coordinated C atoms in the film, respectively. X-ray diffraction, selected area electron diffraction and high-resolution electron microscopy were used to identify the cubic C3N4 phase. The results reconfirm the ab initio calculations on metastable structure in C-N

Diamond gets harder,tougher,and more deformable

Diamonds may not be forever,but research interest in diamond has never ebbed.Owing to its highly symmetric crystal structure and strong covalentC–Cbonds,diamond possesses an exceptional combination of physical properties.Its hardness and thermal conductivity are the highest among covalent materials.It also has a large bandgap and electric breakdown field,as well as optical transparency over a wide range of wavelengths.All of these are essential for a wide range of applications in both industrial and scientific areas.Despite these outstanding advantages,however,diamond is extremely brittle,with inferior toughness and poor deformability.These shortcomings have caused undesired tool breakage and have imposed severe constraints on technological innovations.To surmount these intrinsic deficiencies,tremendous research effort has been dedicated to developing advanced diamond products,with great progress being achieved in the past few years.

Discovery of superhard materials via CALYPSO methodology

The study of superhard materials plays a critical role in modern industrial applications due to their widespread applications as cutting tools, abrasives, exploitation drills, and coatings. The search for new superhard materials with superior performance remains a hot topic and is mainly considered as two classes of materials:(i) the light-element compounds in the B-C-N-O(-Si) system with strong and short covalent bonds, and(ii) the transition-element light-element compounds with strong covalent bonds frameworks and high valence electron density. In this paper, we review the recent achievements in the prediction of superhard materials mostly using the advanced CALYPSO methodology. A number of novel, superhard crystals of light-element compounds and transition-metal borides, carbides, and nitrides have been theoretically identified and some of them account well for the experimentally mysterious phases. To design superhard materials via CALYPSO methodology is independent of any known structural and experimental data, resulting in many remarkable structures accelerating the development of new superhard materials.

Spatio-temporal distribution of Konosirus punctatus spawning and nursing ground in the South Yellow Sea

In recent years,Konosirus punctatus has accounted for a large portion in catch composition and become important economic species in the South Yellow Sea.However,the distribution of K.punctatus early life stages is still poorly understood.In this study,generalized additive models with Tweedie distribution were used to analyze the relationships between K.punctatus ichthyoplankton and environmental factors(longitude and latitude,sea surface temperature(SST),sea surface salinity(SSS)and depth),and predict distribution K.punctatus spawning ground and nursing ground,based on samplings collected in 6 months during 2014–2017.The results showed that K.punctatus’spawning ground were mainly distributed in central and north study area(from 33.0°N to 37.0°N).By comparison,the nursing ground shifted southward,which were approximately located along central and south coast of study area(from 31.7°N to 35.5°N).The optimal models identified that suitable SST,SSS and depth for eggs were 19–26℃,25–30 and 9–23 m,respectively.The suitable SSS for larvae were 29–31.The K.punctatus spawning habit might have changed in the past decades,which was a response to increasing SST and fishing pressure.That needs to be proved in further study.The study provides references of conservation and exploitation for K.punctatus.

Age,growth,and mortality rate of the yellow goosefish Lophius litulon(Jordan,1902)in the Yellow Sea

With the decline in the most fisheries resources in the Yellow Sea,the yellow goosefish Lophius litulon has increased in commercial and ecological importance in recent years.We studied the length distribution,length-weight relationship,age composition,growth pattern,mortality,and exploitation rates of the yellow goosefish in the Yellow Sea.Total length(TL)of females and males ranged from 173 to 582 mm and 178 to 500 mm,respectively.The length-weight relationships were also estimated for females and males.Age classes from 2 to 4 years predominated in the samples.The von Bertalanffy growth function(VBGF),estimated based on non-linear least-squares methodology,showed significant differences between sexes.Females attained a greater estimated asymptotic total length(765 mm TL)compared to males(579 mm TL).The VBGF did not differ significantly between stocks of the northern Yellow Sea and the southern Yellow Sea.Estimated natural instantaneous mortality rate(M)ranged from 0.25/a to 0.33/a based on four age-and length-based methods.Total instantaneous mortality rate(Z)of total samples calculated by the age-based catch curve method was 0.591/a and the average fishing mortality(F)was 0.30/a.Estimated exploitation rate(E)was approximately 0.5,indicating that the population of L.litulon in the Yellow Sea may be sustainable.These results provide a reference for the present status of L.litulon and information for the management.

Using statolith shape analysis to identify fi ve commercial Loliginidae squid species in Chinese waters

Identification of squids in the family Loliginidae is a time-consuming exercise because of the highly overlapping distributions of species and their overall similarity(fin shape and size,sucker ring dentition,and color).Identifying squid based on statolith morphology is considered more accurate than identifying species based on beaks or gladius morphology.We report and compare the statolith shape offive commercially Loliginidae squid(Uroteuthis(Photololigo)duvaucelii,U.edulis,U.chinensis,Loliolus beka,L.japonica)to determine how well these structures discriminate species.Based on statolith morphology,variation in the lateral and dorsal domes enables an 84.8%success rate at classifying species.Environmental factors correlate with statolith shape,and for vertically migrating squid,statolith relative size decreases with increased depth of habitation.Statolith morphology can be used to effectively and accurately identify species of Loliginidae squid occurring in Chinese waters,and may prove valuable for identifying and managing squid resources.

Incorporating mesopelagic fish into the evaluation of conservation areas for marine living resources under climate change scenarios

Mesopelagic fish(meso-fish)are central species within the Southern Ocean(SO).However,their ecosystem role and adaptive capacity to climate change are rarely integrated into protected areas assessments.This is a pity given their importance as crucial prey and predators in food webs,coupled with the impacts of climate change.Here,we estimate the habitat distribution of nine meso-fish using an ensemble model approach(MAXENT,random forest,and boosted regression tree).Four climate model simulations were used to project their distribution under two representative concentration pathways(RCP4.5 and RCP8.5)for short-term(2006–2055)and long-term(2050–2099)periods.In addition,we assess the ecological representativeness of protected areas under climate change scenarios using meso-fish as indicator species.Our models show that all species shift poleward in the future.Lanternfishes(family Myctophidae)are predicted to migrate poleward more than other families(Paralepididae,Nototheniidae,Bathylagidae,and Gonostomatidae).In comparison,lanternfishes were projected to increase habitat area in the eastern SO but lose area in the western SO;the opposite was projected for species in other families.Important areas(IAs)of meso-fish are mainly distributed near the Antarctic Peninsula and East Antarctica.Negotiated protected area cover 23% of IAs at present and 38%of IAs in the future(RCP8.5,long-term future).Many IAs of meso-fish still need to be included in protected areas,such as the Prydz Bay and the seas around the Antarctic Peninsula.Our results provide a framework for evaluating protected areas incorporating climate change adaptation strategies for protected areas management.

Experimental evidence of surface copper boride

To validate the crystal structure and elucidate the formation mechanism of the unexpected surface copper boride,a systematic scanning tunneling microscope,X-ray photoelectron spectroscopy,angle-resolved photoemission spectroscopy,and aberrationcorrected scanning transmission electron microscopy investigations were conducted to confirm the structure of copper-rich boride Cu_(8)B_(14)after depositing boron on single-crystal Cu(111)surface under ultrahigh vacuum.First-principles calculations with defective surface models further indicate that boron atoms tend to react with Cu atoms near terrace edges or defects,which in turn shapes the intermediate structures of copper boride and leads to the formation of stable Cu-B monolayer via large-scale surface reconstruction eventually.

Early life history affects fish size mainly by indirectly regulating the growth during each stage:a case study in a demersal fish

The complex life histories of demersal fishes are artificially separated into multiple stages along with changes in morphology and habitat.It is worth exploring whether the phenotypes expressed earlier and later during the life cycle are related or decoupled.The life stages of first year Pacific cod(Gadus macrocephalus)were tracked over different hatch years and regions to test whether the early life history had a long-lasting effect on subsequent growth.We further explored the contribution of growth in the early and subsequent life history stages to body size at the end of each stage.In addition to the accessory growth centre and the first annual ring,the other two checks on the otolith possibly related to settlement and entering deeper waters were identified in 75 Pacific cod individuals.The direct and indirect relationships among the life history stages was interpreted based on path analysis.The results showed that growth prior to the formation of the accessory growth centre had a significant effect on the absolute growth of the fish before and after settlement and migration to deep water.However,there was no or moderate evidence that early growth affected the body size at each stage,which was mainly regulated by growth during the stage.This study supports the lasting effect of early growth and clarifies that it affects size mainly by indirectly regulating staged growth.Quantifying the phenotype relationships and identifying the internal mechanisms form the basis for assessing population dynamics and understanding the processes behind the changes.

Broadband photodetector of high quality SbS nanowire grown by chemical vapor deposition

Low dimensional semiconductors can be used for various electronic and optoelectronic devices because of their unique structure and property.In this work,one-dimensional Sb2 S3 nanowires(NWs)with high crystallinity were grown via chemical vapor deposition(CVD)technique on SiO2/Si substrates.The Sb2 S3 NWs exhibited needle-like structures with inclined cross-sections.The lengths of Sb2S3 nanowires changed from 7 to 13μm.The photodetection properties of Sb2 S3 nanowires were comprehensively and systematically characterized.The Sb2S3 photodetectors show a broadband photoresponse ranging from ultraviolet(360 nm)to near-infrared(785 nm).An excellent specific detectivity of 2.1×10^(14)Jones,high external quantum efficiency of 1.5×10^(4)%,sensitivity of 2.2×10^(4)cm^(2)W^(-1)and short response time of less than 100 ms was achieved for the Sb2 S3 NW photodetectors.Moreover,the Sb2S3 NWs showed outstanding switch cycling stability that was beneficial to the practical applications.The high-quality Sb2S3 nanowires fabricated by CVD have great application potential in semiconductor and optoelectronic fields.

Extraordinary high-temperature mechanical properties in binder-free nanopolycrystalline WC ceramic

From the perspective of high-temperature applications,materials with excellent high-temperature mechanical properties are always desirable.The present work demonstrates that the binder-free nanopolycrystalline WC ceramic with an average grain size of 103 nm obtained by high-pressure and hightemperature sintering exhibits excellent mechanical properties at both room temperature and high temperature up to 1000℃.Specifically,the binder-free nanopolycrystalline WC ceramic still maintains a considerably high Vicker hardness H_(V)of 23.4 GPa at 1000℃,which is only 22%lower than the room temperature H_(V).This outstanding thermo-mechanical stability is superior to that of typical technical ceramics,e.g.SiC,Si_(3)N_(4),Al_(2)O_(3),etc.Nanocrystalline grains with many dislocations,numerous low-energy,highly stableΣ2 grain boundaries,and a relatively low thermal expansion coefficient,are responsible for the observed outstanding high-temperature mechanical properties.

洋葱式氮化硼粒径对纳米孪晶立方氮化硼组织结构和性能的影响（英文）

拥有极高硬度、韧性和稳定性的纳米孪晶立方氮化硼(ntcBN)在材料领域备受关注.前期研究表明,在高温高压条件下以洋葱式氮化硼(oBN)为前驱物是合成nt-cBN的关键.本文研究发现,前驱物oBN的粒径变化会显著影响最终产物的组织结构和机械性能.随着前驱物oBN的粒径从~320 nm减小到~90 nm,合成的纳米结构块材的硬度从61 GPa逐渐提高到108 GPa.表明大粒径的oBN拥有和普通六方氮化硼类似的平整、有序的外层结构,这与小粒径的oBN纳米粒子中存在大量弯曲、褶皱的氮化硼原子层及高密度层错的结构特点形成鲜明对比;大粒径oBN前驱物中的这些有序结构显著减少了最终产物中超细孪晶亚结构的含量,从而导致相应产物硬度的下降.本研究表明,只有粒径足够小的oBN前驱物才能合成出拥有高密度超细纳米孪晶结构且性能优异的nt-cBN.为进一步提高此类纳米孪晶材料的性能提供了一种切实可行的方案.

Tunable electrical properties of C_(60)·m-xylene and the formation of semiconducting ordered amorphous carbon clusters under pressure

Ordered amorphous carbon clusters(OACC)transformed from m-xylene solvated C_(60)(C_(60)·m-xylene)are known as the first crystalline material constructed from amorphous building blocks and have attracted a lot of attention.The formation mechanism and physical properties of this material are of great importance for the design of more materials with such structural characteristics.In this article,the transport and structural properties of C_(60)·m-xylene are systematically investigated under pressure using impedance spectroscopy,four-probe resistance measurements,and Raman spectroscopy.It is found that C_(60)·mxylene is an insulator at ambient pressure.The resistance decreases sharply starting at the pressure around 8 GPa due to the pressure-induced dimerization of C_(60)verified by the Raman study.The presence of solvent hinders further polymerization of C_(60)under higher pressures.The temperature-dependence of resistance exhibits a semiconducting characteristic at>8-26.9 GPa,and is well described by Mott's three-dimensional variable-range hopping model(3D-VRH),indicating an insulating-tosemiconducting transition accompanied with pressure-induced dimerization.The resistance and hopping energy are both found to decrease monotonically with pressure and reach the minimum near 24 GPa.Above the pressure,resistance and hopping energy values start to rise,suggesting a transition to another semiconducting state,which is attributed to the pressure-induced formation of OACC.The conductivity shows a large hysteresis during decompression from higher than 24 GPa,confirming a different transport behavior of the sample with retained fullerenes versus OACC.The findings of our study suggest that the transport property of fullerene is tunable by introducing solvates and further enhance our understanding of the OACC.

Heat-treated glassy carbon under pressure exhibiting superior hardness,strength and elasticity

Glassy carbon(GC)is a type of non-graphitizing disordered carbon material at ambient pressure and high temperatures,which has been widely used due to its excellent mechanical properties.Here we report the changes in the microstructure and mechanical properties of GC treated at high pressures(up to 5 GPa)and high temperatures.The formation of intermediate sp2-sp3 phases is identified at moderate treatment temperatures before the complete graphitization of GC,by analyzing synchrotron X-ray diffraction,Raman spectra,and transmission electron microscopy images.The intermediate metastable carbon materials exhibit superior mechanical properties with hardness reaching up to 10 GPa and compressive strength reaching as high as 2.5 GPa,nearly doubling those of raw GC,and improving elasticity and thermal stability.The synthesis pressure used in this study can be achieved in the industry on a commercial scale,enabling the scalable synthesis of this type of strong,hard,and elastic carbon materials.

Intersectional nanotwinned diamond-the hardest polycrystalline diamond by design

The hardness of nanotwinned diamond(nt-diamond)is reported to be more than twice that of the natural diamond,thanks to the fine spaces between twin boundaries(TBs),which block dislocation propagation during deformation.In this work,we explore the effects of additional TBs in nt-diamond using molecular dynamics(MD)calculations and introduce a novel intersectional nanotwinned diamond(int-diamond)template for future laboratory synthesis.The hardness of this int-diamond is predicted by first analyzing individual dislocation slip modes in twinned grains and then calculating the bulk properties based on the Sachs model.Here we show that the hardness of the int-diamond is much higher than that of nt-diamond.The hardening mechanism of intdiamond is attributed to the increased critical resolved shear stress due to the presence of intersectional TBs in nt-diamond;this result is further verified by MD simulations.This work provides a new strategy for designing new super-hard materials in experiments.

Rise of correlated dislocations in nanotwinned metals against fatigue

When a metal is subject to cyclic loading with cyclic stress values much lower than its tensile strength,fatigue occurs due to accumulative and irreversible damages developed in the microstructure,causing service failure of the metal workpiece or even fatal disaster in the worst cases.To develop materials with higher fatigue limit and longer fatigue life relies on reducing or suppressing