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.

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.

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.

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 compounds

Novel Boron Nitride Polymorphs with Graphite-Diamond Hybrid Structure

Both boron nitride(BN)and carbon(C)have sp,sp^(2)and sp^(3)hybridization modes,thus resulting in a variety of BN and C polymorphs with similar structures,such as hexagonal BN(hBN)and graphite,cubic BN(cBN)and diamond.Here,five types of BN polymorph structures are proposed theoretically,inspired by the graphite-diamond hybrid structures discovered in a recent experiment.These BN polymorphs with graphite-diamond hybrid structures possess excellent mechanical properties with combined high hardness and high ductility,and also exhibit various electronic properties such as semi-conductivity,semi-metallicity,and even one-and two-dimensional conductivity,differing from known insulators hBN and cBN.The simulated diffraction patterns of these BN hybrid structures could account for the unsolved diffraction patterns of intermediate products composed of so-called“compressed hBN”and diamond-like BN,caused by phase transitions in previous experiments.Thus,this work provides a theoretical basis for the presence of these types of hybrid materials during phase transitions between graphite-like and diamond-like BN polymorphs.

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.

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.

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.

Design of a Class of New sp^(2)-sp^(3)Carbons Constructed by Graphite and Diamond Building Blocks

The sp^(2)–sp^(3)-hybridized carbon allotropes with the advantage of two hybrid structures possess rich and fascinating electronic and mechanical properties and they have received long-standing attention.We design a class of versatile sp^(2)–sp^(3)carbons composed of graphite and diamond structural units with variable sizes.This class of sp^(2)–sp^(3)carbons is energetically more favorable than graphite under high pressure,and their mechanical and dynamical stabilities are further confirmed at ambient pressure.The calculations of band structure and mechanical properties indicate that this class of sp^(2)–sp^(3)carbons not only exhibits peculiar electronic characteristics adjusted from semiconducting to metallic nature but also presents excellent mechanical characteristics,such as superhigh hardness and high ductility.These sp^(2)–sp^(3)carbons have desirable properties across a broad range of potential applications.

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.

Enhanced thermoelectric performance of Sb-doped Mg_(2)Si_(0.4)Sn_(0.6)via doping,alloying and nanoprecipitation

With the advantages of eco-friendliness,low cost,and low density,Mg_(2)(Si,Sn)solid solutions are promising candidates for thermoelectric applications.In this work,Sb-doped Mg_(2)Si_(0.4)Sn_(0.6)bulks were prepared with a combined method of solid-state reaction and high pressure synthesis,followed by spark plasma sintering.Our investigations show that Sb doping optimizes the carrier concentration,while Si/Sn alloying effectively suppresses the lattice thermal conductivity and induces a convergence of the two lowest-lying conduction bands.Additionally,numerous coherent Sn-rich nanoprecipitates are formed within micron-sized grains.All these factors contribute synergistically to improving the thermoelectric properties of Mg_(2)Si_(0.4)Sn_(0.6).The optimal Mg_(2)(Si_(0.4)Sn_(0.6))_(0.985)Sb_(0.015)exhibits a power factor higher than 4000 mW·m^(-1)·K^(-2)and a lattice thermal conductivity less than 0.8 W·m^(-1)·K^(-1)at temperatures higher than 600 K,leading to the highest ZT of 1.61 at 823 K.Current work demonstrates an effective approach to enhancing the thermoelectric performance of n-type Mg_(2)X solid solutions through doping,alloying,and microstructure modification.

Correction:Incorporating mesopelagic fish into the evaluation of marine protected areas under climate change scenarios

The author wants to highlight the important role of mes-opelagic fish in the conservation of marine living resources.Therefore,in order to further clarify and focus research point on the conservation of marine living resources,the authors replaced the MPA with the protected areas,and slightly modified several other vague places.In these corrections,most of them are the replacement of the terms.

The rise of plastic deformation in boron nitride ceramics

Ceramics are bonded by ionic or covalent bonds,with very limited slip systems for dislocation nucleation and movement[1].The poor deformability and natural brittleness are the major drawbacks of ceramics,especially when compared with metals.Under stress,ceramics tend to fracture before noticeable plastic deformation takes place.Cracks occur and propagate rapidly in ceramics subjected to stress much lower than the theoretical strength[2].As a result,ceramics can only endure very small strains(<1%),absorb limited mechanical energy,and display poor toughness[3].Moreover,microstructure imperfections in ceramics may decrease the toughness even further.Due to the lack of significant plastic deformation capacity for ceramic materials,the catastrophic failures without warning are easy to happen under stress which critically increases the unreliability of ceramics in the applications as structural materials.

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.

Atomic-scale observation of the deformation and failure of diamonds by in-situ double-tilt mechanical testing transmission electron microscope holder

In-situ transmission electron microscopy(TEM)has been demonstrated to be a powerful method in resolving challenging problems such as interactions among various defects.To take advantage of the atomic resolution of advanced TEMs,a compact five-degree-of-freedom nanomanipulator was integrated with an indenter that was made of nanotwinned diamonds,for both the in-situ mechanical testing and double tilting of TEM samples.As a demonstration,in-situ bending tests were performed on the?111?,?110?and?100?single-crystal diamond needles.The tests revealed the{111}cleavage to be the dominant failure mode.The in-situ indentation on a diamond nanoplate led to curved cracks consisting of nanometer-scale steps,which were identified to be atomic flat{111}facets.The atomic-scale observation of the deformation and failure of diamonds demonstrated the stability of the entire system and the durability of the indenter.We expect that more delicate research can be carried out by means of this holder in the near future,including in-situ stimulation,atomic characterization,and tomography.

Small onion-like BN leads to ultrafine-twinned cubic BN

Nanotwinned cubic boron nitride(nt-cBN) with remarkable hardness, toughness, and stability has attracted widespread attention due to its distinct scientific and industrial importance. The key for nt-cBN synthesis is to adopt an onion-like BN(oBN) nano-precursor and induce phase transition under high pressure. Here, we found that the size change of oBN used greatly affected the mechanical performance of products. With the precursor size decreasing from^320 to 90 nm, the Vickers hardness of nanostructured products improved from 61 to 108 GPa, due to the fact that large oBN nanoparticles possessed more flattened, orderly and graphite-like shell layers, in sharp contrast to the highly wrinkled and imperfect layers in small-diameter nanoparticles, thus resulting in the apparent reduction of ultrafinetwin substructure in the synthetic products. This study reveals that only small oBN precursor could produce complete ultrafine nt-cBN with outstanding performance. A practical route was proposed to further improve the performance of this important material.