The objective of this incubation study was to comprehensively evaluate the effects of organic fertilizer and biochar,both individually and in combination,on soil respiration dynamics,key enzyme activities and the conc...The objective of this incubation study was to comprehensively evaluate the effects of organic fertilizer and biochar,both individually and in combination,on soil respiration dynamics,key enzyme activities and the concentrations of various organic carbon components in degraded mollisol.This study used a completely randomized factorial design with three application rates of organic fertilizer(M0:0,M1:13.64 g·kg^(-1),M2:27.27 g·kg^(-1))and biochar(C0:0,C1:1.36 g·kg^(-1),C2:2.73 g·kg^(-1)),resulting in nine treatments with four replicates each.Soil CO_(2) flux,organic carbon fractions including the total,active and microbial biomass carbon,and enzyme activities(sucrase,catalase and polyphenol oxidase)were measured over 120 days.Results indicated that the factors and their interactions significantly influenced all measured parameters.Soil respiration peaked at day 15,with M1C2 treatment exhibiting a rate of 10.90-fold higher than the control.The concentrations of the total,active and microbial biomass organic carbon reached maximum values on days 60,30 and 80,respectively.Notably,M2C1 treatment yielded the highest total organic carbon(86.35%increase)and microbial biomass carbon(17.84%increase).Enzyme activities were significantly enhanced,with the highest catalase activity observed for M0C2 treatment(10.14%increase).These results demonstrated that the co-application of organic fertilizer and biochar was a effective strategy for improving soil biological health and promoting carbon sequestration in degraded mollisol.The treatment combining a high rate of organic fertilizer with a low rate of biochar(M2C1)was identified as the most promising amendment strategy for fertility restoration.展开更多
Old-growth forests play a key-role in reducing atmospheric carbon dioxide(CO_(2)) concentrations by storing large CO_(2)amounts in biomass and soil over time.This quantifies the carbon pool into different forest compa...Old-growth forests play a key-role in reducing atmospheric carbon dioxide(CO_(2)) concentrations by storing large CO_(2)amounts in biomass and soil over time.This quantifies the carbon pool into different forest compartments in three Mediterranean old-growth forests of Southern Italy populated by Pinus laricio,Fagus sylvatica and Abies alba.Ecosystem carbon pools have been assessed per compartment,i.e.,living trees,dead wood,litterfall(foliar and woody),roots and 0-20 cm topsoil,combining the whole old-growth forest mass,(i.e.,using tree allometric relationships,deadwood factor conversions,root-to-shoot ratios,litterfall and soil samplings) by the respective organic carbon concentrations.The results show the considerable capacity of these forest ecosystems in storing CO_(2)in biomass and soil,with carbon pool values ranging from 532.2to 596.5 Mg C ha-1.Living trees and 0-20 cm topsoil had larger carbon pool,contributing 53.0 and 22.1%,respectively.In most cases,organic carbon concentration was higher(more than 60%) than the average carbon conversion rate of 50%,especially in living trees,deadwood,and woody litterfall.This study contributes further scientific evidence of the capacity of old-growth forests in storing CO_(2)in their different compartments,with special evidence on tree biomass,litterfall and mineral soil,thereby highlighting the key role of old-growth forests within the challenge of climate change mitigation.展开更多
A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot...A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot rolling strip mill. In this model, the parameter k in Avrami equation was developed for carbon steels. The wide range of chemical composition, the primary austenite grain size, and the retained strain were taken into account. It can be used to predict the ferrite volume fraction and the carbon concentration in austenite of hot-rolled steel strip during laminar cooling on run-out table. The coiling temperature controlling model was also presented to calculate the temperature of steel strip. The transformation kinetics of austenite to ferrite and the evolution of carbon concentration in austenite at different temperatures during cooling were investigated in the hot rolled Q235B strip for thickness of 9.35, 6.4, and 3.2mm. The ferrite volume fraction along the length of the strip was also calculated. The calculated ferrite volume fraction was compared with the log data from hot strip mill and the calculated results were in agreement with the experimental ones. The present study is a part of the prediction of the mechanical properties of hot-rolled steel strip, and it has already been used on-line and off-line in the hot strip mill.展开更多
To reveal the intricate mechanisms underlying the melting and dissolution processes of scraps in the iron ladle,the melting characteristics of three carbon steels with different C concentrations at the bath temperatur...To reveal the intricate mechanisms underlying the melting and dissolution processes of scraps in the iron ladle,the melting characteristics of three carbon steels with different C concentrations at the bath temperatures of 1623 and 1723 K were studied.Upon immersing scraps into the molten metal,the liquid metal immediately froze around the submerged parts of scrap cylinders.Whereafter,the solid shell completely melted at both bath temperatures after the immersion time of 5 s.The maximum thickness of solidified steel shells significantly decreased with increasing the bath temperature.The findings also suggested that the melting rate of scrap cylinder exhibited a positive correlation with the C concentration in the scrap and the bath temperature.Quantitatively,the mass transfer coefficients of C for the low carbon(0.18 wt.%),medium carbon(0.32 wt.%),and high carbon(0.61 wt.%)concentrations in the scrap cylinders at 1723 K were determined by a kinetic model,which were 8.78×10^(-5),9.57×10^(-5)and 10.00×10^(-5)m s^(-1),respectively,and those corresponding values decreased to 3.87×10^(-5),4.49×10^(-5)and 3.54×10^(-5)m s^(-1)at 1623 K.However,there was little difference observed among the heat transfer coefficients of hot metal for the three carbon steels,which were estimated to have an average value of 16.36 and 18.82 kW m^(-2)K^(-1)at the experimental temperatures of 1623 and 1723 K,respectively.The results from the experiments and mathematical models showed good consistency at both bath temperatures,providing feasible guidance for efficient melting of steel scraps in the iron ladle.展开更多
Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contrib...Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contribute to the large fraction of tree biomass,the canonical value of 50%or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales.However,C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.Methods We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age,size(diameter at breast height and biomass)and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.Important Findings Tree C concentration varied significantly with organs.Stem C concentration of trees was significantly correlated with that of other tree organs,except for barks and reproductive organs.The stem C concentration increased significantly with tree size and age,which contributed to the increases in C contents of stems and trees.Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks(−8.6%to 25.6%and−2.5%to 5.9%,respectively).Our findings suggest that tree C accumulation in forests is related to the size-and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.展开更多
Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbo...Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbon and initial biomass concentrations to enrich polyhydroxyalkanoate（PHA） accumulating mixed microbial cultures（MMCs） from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism（T-RFLP）. The optimum operating conditions for the enrichment process were： SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures（with the maximum PHA content and PHA storage yield（YPHA/S） of61.26% and 0.68 mg COD/mg COD, respectively） was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.展开更多
Reducing greenhouse gas emissions is one of the major challenges in combating global warming.Carbon,including in the form of carbon dioxide(CO_(2)),is considered an essential greenhouse gas under human control to demo...Reducing greenhouse gas emissions is one of the major challenges in combating global warming.Carbon,including in the form of carbon dioxide(CO_(2)),is considered an essential greenhouse gas under human control to demonstrate success in emission reductions.However,many carbon stock quantifications in forest ecosystems still rely on the estimated 50%carbon content instead of more precise species-,tissue-and site-specific values.Thus,this study aimed to thoroughly measure and analyze the carbon content and variability using the 14 major tree species in Northeast China.Over 600 trees were destructively sampled from three different major mountainous regions(i.e.,the Changbai,Daxing’an,and Xiaoxing’an mountains),and the carbon contents of each species were precisely measured to the sub-tissue level.Carbon contents varied significantly between species,with foliage carbon mostly found to be the highest,while root carbon contents were the lowest.Average carbon contents can be ranked as:Ulmus laciniata(43.4%)<Phellodendron amurense(43.5%)<Acer mono(43.8%)<Tilia amurensis(44.2%)<Populus davidiana(44.5%)<Fraxinus mandshurica(44.7%)<Juglans mandshurica(44.9%)<Quercus mongolica(45.3%)<Betulla davurica(45.8%)<Betulla platyphylla(46.7%)<Picea koreansis(46.9%)<Larix gmelinii(47.4%)<Pinus koreansis(48.3%)<Abies nephrolepis(48.3%).Carbon contents were higher in conifers(47.7%)compared to broadleaf species(44.9%).In addition,both tree tissues and growing sites also had a significant effect on carbon content.At the sub-tissue level,only stem’s sub-tissues(i.e.,bark,heartwood,and sapwood)carbon contents showed significant variations.The results suggest that bark should be separated from other stem sub-tissues and considered separately when determining carbon stocks.This research contributes to improving estimates of terrestrial carbon quantifications,and in particular,the values obtained can be used in China’s National Forest Inventory.展开更多
Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utili...Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elevated CO<sub>2</sub>. Six isolines of Harosoy 63 were grown at ambient (380 μmol?mol<sup>-1</sup>) and elevated (560 μmol?mol<sup>-1</sup>) CO<sub>2</sub> concentrations in the field using free-air CO<sub>2</sub> enrichment systems, in air-conditioned glasshouses with natural summer photoperiods, and in indoor chambers with day lengths of 11, 13, 15, and 17 hours. The effect of CO<sub>2</sub> concentration on flowering time varied with genotype, and there was also an interaction between CO<sub>2</sub> and photoperiod in all genotypes, as indicated by ANOVA. Elevated CO<sub>2</sub> accelerated flowering in some cases, and delayed it in other cases. For all three of the isolines with single dominant genes, elevated CO<sub>2</sub> decreased the days to first open flower at the longest photoperiod. At the shortest photoperiod, elevated CO<sub>2</sub> delayed flowering in all but one isoline. The all-recessive isoline had slower flowering at elevated CO<sub>2</sub> at both the shortest and the longest photoperiods, and also in the field and in the glasshouse. Delayed flowering at elevated CO<sub>2</sub> in the field and glasshouse was associated with an increased final number of main stem nodes. It is concluded that the E1, E3, and E4 genes each influenced how the time to first flowering was affected by CO<sub>2</sub> concentration at long photoperiods.展开更多
Soil microbial communities and grassland ecosystem processes are increasingly confronted with multiple global change factors(GCFs).There is still a lack of research on how these multiple GCFs interact and impact soil ...Soil microbial communities and grassland ecosystem processes are increasingly confronted with multiple global change factors(GCFs).There is still a lack of research on how these multiple GCFs interact and impact soil microbial communities and their functions.To address this gap,we conducted a simulation experiment to examine the individual and interactive effects of the four most critical and prevalent GCFs,elevated carbon dioxide concentration(eCO_(2)),elevated temperature(eT),decreased precipitation(dP),and elevated nitrogen(N)deposition(eN).This study focused on their effects on soil physicochemical properties,bacterial and fungal communities,and extracellular enzyme activities(EEAs)related to carbon(C),N,and phosphorus(P)cycles in a temperate grassland.Results showed that eCO_(2),eN,and dP tended to increase EEAs,while having neutral effects on microbial diversity and community composition.On the other hand,eT resulted in decreases in soil pH,total C,total N,EEAs,and microbial diversity,but increases in plant biomass,total P,microbial richness,and network complexity and stability.This shift in the nutrient limitation from P to N under warming conditions resulted in decoupling of nutrients.Neutral or slightly negative relationships were found between enzyme activities and microbial richness,diversity,and dominant species,and the responses of microbial communities and ecological functions were asynchronous under GCFs.Importantly,our results revealed significant higher-order interactions among GCFs and found that they had notable effects on soil physicochemical properties as well as on microbial communities and ecological functions.These findings provide valuable insights and suggestions for ecological adaptations to future global changes.展开更多
Two series of p-GaN films grown at different temperatures are obtained by metal organic chemical vapor deposition（MOCVD）. And the different variation behaviors of resistivity with growth condition for high- temperat...Two series of p-GaN films grown at different temperatures are obtained by metal organic chemical vapor deposition（MOCVD）. And the different variation behaviors of resistivity with growth condition for high- temperature（HT）-grown and low-temperature（LT）-grown p-GaN films are investigated. It is found that the resistivity of HT-grown p-GaN film is nearly unchanged when the NH_3 flow rate or reactor pressure increases. However, it decreases largely for LT-grown p-GaN film.These different variations may be attributed to the fact that carbon impurities are easy to incorporate into p-GaN film when the growth temperature is low. It results in a relatively high carbon concentration in LT-grown p-GaN film compared with HT-grown one. Therefore, carbon concentration is more sensitive to the growth condition in these samples, ultimately,leading to the different variation behaviors of resistivity for HT- and LT-grown ones.展开更多
In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bai...In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.展开更多
The type of technology used to strengthen the surface structure of machine parts,typically by carbon-permeation,has made a great contribution to the mechanical engineering industry because of its outstanding advantage...The type of technology used to strengthen the surface structure of machine parts,typically by carbon-permeation,has made a great contribution to the mechanical engineering industry because of its outstanding advantages in corrosion resistance and enhanced mechanical and physical properties.Furthermore,carbon permeation is considered as an optimal method of heat treatment through the diffusion of carbon atoms into the surface of alloy steel.This study presented research results on the thermodynamic calculation and simulation of the carbon permeability process.Applying Fick’s law,the paper calculated the distribution of carbon concentration in the alloy steel after it is absorbed from the surface into the internal of the sample.Using the SYSWELD software,an analysis was performed on the carbon permeability process to determine the distribution of carbon concentrations in 20CrMo steel that was then followed by a detailed analysis of the microstructure of the sample post the carburizing process.According to the calculation results,the surface carbon content was 0.9%and steadily decreased into the core.After 3 hours,the depth of the absorbent layer was measured at 0.5 mm for both the cylindrical and cubic samples.By analyzing the phase,the distribution of martensite phases such as ferrite/pearlite and residual austenite was also determined after the carburizing process.展开更多
The potential CO2-induced impacts on the geographical shifts of wheat growth zones in China were studied from seven GCMs outputs. The wheat growth regions may move northward and westward under the condition of a doubl...The potential CO2-induced impacts on the geographical shifts of wheat growth zones in China were studied from seven GCMs outputs. The wheat growth regions may move northward and westward under the condition of a doubling CO2 climate. The wheat cultivation features and variety types may also assume significant changes. Climatic warming would have a positive influence in Northeast China, but high temperature stress may be produced in some regions of central and southern China. Higher mean air temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing and more heat-tolerant cultivars.展开更多
The trends and features of China's climatic change in the past and future are analysed by applying station observations and GCM simulation results. Nationally, the country has warmed by 0.3℃ in annual mean air te...The trends and features of China's climatic change in the past and future are analysed by applying station observations and GCM simulation results. Nationally, the country has warmed by 0.3℃ in annual mean air temperatureand decreased by 5% in annual precipitation over 1951-1990. Regionally, temperature change has varied from acooling of 0.3℃ in Southwest China to a'warming of 1 .0℃ in Northeast China. With the exception of South China,all regions of China have shown a declination in precipitation. Climatic change has the features of increasing remarkably in winter temperature and decreasing obviously in summer precipitation. Under doubled CO2 concentration,climatic change in China will tend to be warmer and moister, with increases of 4.5℃ in annual mean air temperatureand 11% in annual precipitation on the national scale. Future climatic change will reduce the temporal and spatialdifferences of climatic factors.展开更多
Rapid changes on nutrient supply and CO2 concentration that occurred in the northern South China Sea(SCS)during the Early Oligocene,provides an ideal natural laboratory,allowing us to peer into the coccolithophores’p...Rapid changes on nutrient supply and CO2 concentration that occurred in the northern South China Sea(SCS)during the Early Oligocene,provides an ideal natural laboratory,allowing us to peer into the coccolithophores’physiology in the geological records.In this study,we established a new nannofossil assemblage index,termed as E^*ratio,which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa(E^*=e/e+c,where e is eutrophic taxa,and c is meso-oligotrophic taxa)Eutrophic taxa include small Reticulofenestra,Reticulofenestra lockeri group,Reticulofenestra bisecta group and Coccolithus pelagicus group,while meso-oligotrophic taxa include Cyclicargolithus spp.The E^*ratio is well correlated with nutrient proxy during the Early Oligocene,while with different covarying patterns under the higher and lower CO2 condition.By comparing the assemblage changes to the published data,we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO2.Furthermore,this implies a possible initiation of the carbon concentrating mechanism.展开更多
The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Gl...The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Glacier retreat is occurring in this region due to climate change,leading to an increase in meltwater outflow with a high debris content.In August 2017,we collected a sediment Core Z3 from the central fjord near the Yellow River Station.Then,we used the widely used chronology method of 210Pb,^(137)Cs,and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord.The results showed that after the mid-late 1990s,the mass accumulation rate of this core increased from 0.10 g/(cm^(2)·a)to 0.34 g/(cm^(2)·a),while the flux of^(210)Pb_(ex)increased from 125 Bq/(m^(2)·a)to 316 Bq/(m^(2)·a).The higher sedimentary inventory of^(210)Pb_(ex)in Kongsfjord compared to global fallout might have been caused by sediment focusing,boundary scavenging,and riverine input.Similarities between the inventory of^(137)Cs and global fallout indicated that terrestrial particulate matter was the main source of^(137)Cs in fjord sediments.The sedimentation rate increased after 1997,possibly due to the increased influx of glacial meltwater containing debris.In addition,the^(137)Cs activity,percentage of organic carbon(OC),and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997,corresponding to a decrease in the mass balance of glaciers in the region.The results ofδ^(13)C,δ^(15)N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3.The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s.All these data indicate that global climate change has a significant impact on Arctic glaciers.展开更多
Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from Oc...Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan （WLG） site. The overall average WlRC mass concentration was （1183 ± 120）ng/m3 （n = 79）, while seasonal averages were 2081 ± 1707 （spring）, 454±205 （summer）, 650 ±411 （autumn）, and 1019 ± 703 （winter） ng/m3. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ13C PDB value （-25.3 ± 0.8）%0 determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion. No seasonal change in δ13C PDB was evident. The average percent Modern Carbon （pMC） for 14C in WIRC for winter and spring was （67.2 ± 7.7）% （n = 29）. Lower pMC values were associated with air masses trans- ported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.展开更多
Developing facile and economical strategies to fabricate nitrogen-doped porous carbon anode is desirable for dual-carbon potassium ion hybrid capacitors(PIHCs).Here,a high-concentration edge-nitrogen-doped porous carb...Developing facile and economical strategies to fabricate nitrogen-doped porous carbon anode is desirable for dual-carbon potassium ion hybrid capacitors(PIHCs).Here,a high-concentration edge-nitrogen-doped porous carbon(NPC)anode is synthesized by a template-free strategy,in which the total content of pyrrolic nitrogen and pyridinic nitrogen accounts for more than 80%of the nitrogen atoms.As a result,the NPC anode displays a capacity of 315.4 mA h g^(−1)at a current rate of 0.1 A g^(−1)and 189.1 mA h g^(−1)at 5 A g^(−1).Ex situ characterizations and density functional theory calculations demonstrate the high-concentration edge-nitrogen doping enhances K^(+)adsorption and electronic conductivity of carbon materials,resulting in good electrochemical performance.The assembled NPC//CMK-3 PIHC delivers an energy density of 71.1 W h kg^(−1)at a power density of 771.9 W kg^(−1)over 8,000 cycles.展开更多
Development of advanced materials with high CO_(2)capture capacity and,inter alia,superior regenerability with low energy consumption(low-temperature CO_(2)release)remains highly desired yet challenging.Herein,we firs...Development of advanced materials with high CO_(2)capture capacity and,inter alia,superior regenerability with low energy consumption(low-temperature CO_(2)release)remains highly desired yet challenging.Herein,we firstly report the precipitation-involved CO_(2)capture from ultradilute sources(e.g.,exhaled gas and indoor air)and the reversible room-temperature CO_(2)release accelerated by mechanical power using a covalent organic superphane cage.This superphane-based operating system enables CO_(2)in ultradilute gas(<6%)to be concentrated up to 83%.As inferred from the control experiments and theoretical calculations,this proof-of-concept CO_(2)capture and concentration system with mechanical power-triggered CO_(2)release by the discrete organic cage could be rationalized by the formation of a sixmembered ring transition state with relatively low energy barrier during the process of the adsorption and desorption of CO_(2)on the cage surface,along with the precipitation-involved phase change.展开更多
Spontaneous nucleation of SiC particles and giant macroscopic steps result in the surface roughness of the grown crystal for the top-seeded solution growth of SiC crystal.To suppress the surface roughness,the temperat...Spontaneous nucleation of SiC particles and giant macroscopic steps result in the surface roughness of the grown crystal for the top-seeded solution growth of SiC crystal.To suppress the surface roughness,the temperature gradient was carefully adjusted by changing the relative position of the crucible and induction coils.The numerical simulation and experimental results show that the surface morphology of the grown crystal becomes smoother and there are fewer spontaneous nucleation particles attached to the growth surface with the decrease in the relative crucible position,due to the increase of temperature at the entire solution surface and the reducing of temperature gradient near the growth surface.Accordingly,a lower temperature gradient,a larger solution velocity,a higher carbon concentration,and a smaller carbon supersaturation near the growth surface can be obtained when the relative position between the crucible and the induction coil is 70 mm,which is demonstrated to be the most favorable for the elimination of spontaneous nucleation of small SiC particles and suppressing surface roughening with the full width at half maximum(FWHM)of 37.5 arcsec of 4Hsingle bondSiC crystals.展开更多
基金Supported by the Special Fund for Agro-scientific Research in Public Interest in China(201503119-06-01)。
文摘The objective of this incubation study was to comprehensively evaluate the effects of organic fertilizer and biochar,both individually and in combination,on soil respiration dynamics,key enzyme activities and the concentrations of various organic carbon components in degraded mollisol.This study used a completely randomized factorial design with three application rates of organic fertilizer(M0:0,M1:13.64 g·kg^(-1),M2:27.27 g·kg^(-1))and biochar(C0:0,C1:1.36 g·kg^(-1),C2:2.73 g·kg^(-1)),resulting in nine treatments with four replicates each.Soil CO_(2) flux,organic carbon fractions including the total,active and microbial biomass carbon,and enzyme activities(sucrase,catalase and polyphenol oxidase)were measured over 120 days.Results indicated that the factors and their interactions significantly influenced all measured parameters.Soil respiration peaked at day 15,with M1C2 treatment exhibiting a rate of 10.90-fold higher than the control.The concentrations of the total,active and microbial biomass organic carbon reached maximum values on days 60,30 and 80,respectively.Notably,M2C1 treatment yielded the highest total organic carbon(86.35%increase)and microbial biomass carbon(17.84%increase).Enzyme activities were significantly enhanced,with the highest catalase activity observed for M0C2 treatment(10.14%increase).These results demonstrated that the co-application of organic fertilizer and biochar was a effective strategy for improving soil biological health and promoting carbon sequestration in degraded mollisol.The treatment combining a high rate of organic fertilizer with a low rate of biochar(M2C1)was identified as the most promising amendment strategy for fertility restoration.
基金the project"Determination of carbon pools in old-growth forests located within the Sila National Park—CARBOSIL"funded by the Ministry of the Environment,Land and Sea Protection—Department for Nature Protection under the Directive on Biodiversity。
文摘Old-growth forests play a key-role in reducing atmospheric carbon dioxide(CO_(2)) concentrations by storing large CO_(2)amounts in biomass and soil over time.This quantifies the carbon pool into different forest compartments in three Mediterranean old-growth forests of Southern Italy populated by Pinus laricio,Fagus sylvatica and Abies alba.Ecosystem carbon pools have been assessed per compartment,i.e.,living trees,dead wood,litterfall(foliar and woody),roots and 0-20 cm topsoil,combining the whole old-growth forest mass,(i.e.,using tree allometric relationships,deadwood factor conversions,root-to-shoot ratios,litterfall and soil samplings) by the respective organic carbon concentrations.The results show the considerable capacity of these forest ecosystems in storing CO_(2)in biomass and soil,with carbon pool values ranging from 532.2to 596.5 Mg C ha-1.Living trees and 0-20 cm topsoil had larger carbon pool,contributing 53.0 and 22.1%,respectively.In most cases,organic carbon concentration was higher(more than 60%) than the average carbon conversion rate of 50%,especially in living trees,deadwood,and woody litterfall.This study contributes further scientific evidence of the capacity of old-growth forests in storing CO_(2)in their different compartments,with special evidence on tree biomass,litterfall and mineral soil,thereby highlighting the key role of old-growth forests within the challenge of climate change mitigation.
文摘A phase transformation model was presented for predicting the phase fraction transformed and the carbon concentration in austenite for austenite to ferrite transformation during laminar cooling on run-out table in hot rolling strip mill. In this model, the parameter k in Avrami equation was developed for carbon steels. The wide range of chemical composition, the primary austenite grain size, and the retained strain were taken into account. It can be used to predict the ferrite volume fraction and the carbon concentration in austenite of hot-rolled steel strip during laminar cooling on run-out table. The coiling temperature controlling model was also presented to calculate the temperature of steel strip. The transformation kinetics of austenite to ferrite and the evolution of carbon concentration in austenite at different temperatures during cooling were investigated in the hot rolled Q235B strip for thickness of 9.35, 6.4, and 3.2mm. The ferrite volume fraction along the length of the strip was also calculated. The calculated ferrite volume fraction was compared with the log data from hot strip mill and the calculated results were in agreement with the experimental ones. The present study is a part of the prediction of the mechanical properties of hot-rolled steel strip, and it has already been used on-line and off-line in the hot strip mill.
基金The present study was supported by the National Natural Science Foundation of China(Grant Nos.52074198,52374342,U21A20113)supported by the Department of Science and Technology of Hubei Province(Grant Nos.2023AFB603,2023DJC140).
文摘To reveal the intricate mechanisms underlying the melting and dissolution processes of scraps in the iron ladle,the melting characteristics of three carbon steels with different C concentrations at the bath temperatures of 1623 and 1723 K were studied.Upon immersing scraps into the molten metal,the liquid metal immediately froze around the submerged parts of scrap cylinders.Whereafter,the solid shell completely melted at both bath temperatures after the immersion time of 5 s.The maximum thickness of solidified steel shells significantly decreased with increasing the bath temperature.The findings also suggested that the melting rate of scrap cylinder exhibited a positive correlation with the C concentration in the scrap and the bath temperature.Quantitatively,the mass transfer coefficients of C for the low carbon(0.18 wt.%),medium carbon(0.32 wt.%),and high carbon(0.61 wt.%)concentrations in the scrap cylinders at 1723 K were determined by a kinetic model,which were 8.78×10^(-5),9.57×10^(-5)and 10.00×10^(-5)m s^(-1),respectively,and those corresponding values decreased to 3.87×10^(-5),4.49×10^(-5)and 3.54×10^(-5)m s^(-1)at 1623 K.However,there was little difference observed among the heat transfer coefficients of hot metal for the three carbon steels,which were estimated to have an average value of 16.36 and 18.82 kW m^(-2)K^(-1)at the experimental temperatures of 1623 and 1723 K,respectively.The results from the experiments and mathematical models showed good consistency at both bath temperatures,providing feasible guidance for efficient melting of steel scraps in the iron ladle.
基金supported by the National Key Research and Development Program of China(grant no.2017YFC0503903)National Natural Science Foundation of China(grant no.31621091).
文摘Aims Forest biomass carbon(C)stocks are usually estimated by multiplying biomass by a C conversion factor,i.e.C concentration.Thus,tree C concentration is crucial to the assessments of forest C cycles.As stems contribute to the large fraction of tree biomass,the canonical value of 50%or other simplified values of stem C concentration are widely used to represent the values of tree C concentration in the estimations of forest C stocks at different scales.However,C concentration variations between tree organs and within tree size and their impacts on forest C stocks are still unclear.Methods We conducted a global analysis of organ C concentration in age-specific trees based on 576 records of tree age,size(diameter at breast height and biomass)and C concentration data to evaluate the relationships between organ C concentrations and the changes of stem C concentration with tree age and size.Important Findings Tree C concentration varied significantly with organs.Stem C concentration of trees was significantly correlated with that of other tree organs,except for barks and reproductive organs.The stem C concentration increased significantly with tree size and age,which contributed to the increases in C contents of stems and trees.Using the C concentration in stems to represent the C concentrations of other organs and the whole tree could produce considerable errors in the estimations of forest C stocks(−8.6%to 25.6%and−2.5%to 5.9%,respectively).Our findings suggest that tree C accumulation in forests is related to the size-and age-dependent increases in stem C concentration and using specific C concentration values of tree organs can improve the estimations of forest C stocks.
基金supported by the National Natural Science Foundation of China(No.51378142)the Program for New Century Excellent Talents in University(No.NCET-12-0156)+1 种基金the Open Project of the State Key Laboratory of Urban Water ResourceEnvironment(Harbin institute of Technology)(No.2015DX10)
文摘Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbon and initial biomass concentrations to enrich polyhydroxyalkanoate（PHA） accumulating mixed microbial cultures（MMCs） from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism（T-RFLP）. The optimum operating conditions for the enrichment process were： SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures（with the maximum PHA content and PHA storage yield（YPHA/S） of61.26% and 0.68 mg COD/mg COD, respectively） was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.
基金This work was supported fi nancially by the Heilongjiang Province Applied Technology Research and Development Program Key Project(GA19B201),National Natural Science Foundation of China(31971649)Provincial Funding for National Key Research and Development Program of China in Heilongjiang Province(GX18B041)+1 种基金the Fundamental Research Funds for the Central Universities(2572019CP08)the Heilongjiang Touyan Innovation Team Program(Technology Development Team for High-effi cient Silviculture of Forest Resources).
文摘Reducing greenhouse gas emissions is one of the major challenges in combating global warming.Carbon,including in the form of carbon dioxide(CO_(2)),is considered an essential greenhouse gas under human control to demonstrate success in emission reductions.However,many carbon stock quantifications in forest ecosystems still rely on the estimated 50%carbon content instead of more precise species-,tissue-and site-specific values.Thus,this study aimed to thoroughly measure and analyze the carbon content and variability using the 14 major tree species in Northeast China.Over 600 trees were destructively sampled from three different major mountainous regions(i.e.,the Changbai,Daxing’an,and Xiaoxing’an mountains),and the carbon contents of each species were precisely measured to the sub-tissue level.Carbon contents varied significantly between species,with foliage carbon mostly found to be the highest,while root carbon contents were the lowest.Average carbon contents can be ranked as:Ulmus laciniata(43.4%)<Phellodendron amurense(43.5%)<Acer mono(43.8%)<Tilia amurensis(44.2%)<Populus davidiana(44.5%)<Fraxinus mandshurica(44.7%)<Juglans mandshurica(44.9%)<Quercus mongolica(45.3%)<Betulla davurica(45.8%)<Betulla platyphylla(46.7%)<Picea koreansis(46.9%)<Larix gmelinii(47.4%)<Pinus koreansis(48.3%)<Abies nephrolepis(48.3%).Carbon contents were higher in conifers(47.7%)compared to broadleaf species(44.9%).In addition,both tree tissues and growing sites also had a significant effect on carbon content.At the sub-tissue level,only stem’s sub-tissues(i.e.,bark,heartwood,and sapwood)carbon contents showed significant variations.The results suggest that bark should be separated from other stem sub-tissues and considered separately when determining carbon stocks.This research contributes to improving estimates of terrestrial carbon quantifications,and in particular,the values obtained can be used in China’s National Forest Inventory.
文摘Changes in the phenology of flowering in soybeans caused by long-term growth at elevated CO<sub>2</sub> may be important to the responses of seed yield to elevated CO<sub>2</sub>. Here we utilized near-isogenic lines of soybeans differing in three genes influencing photoperiod sensitivity to determine whether these genes affected the response of flowering time to elevated CO<sub>2</sub>. Six isolines of Harosoy 63 were grown at ambient (380 μmol?mol<sup>-1</sup>) and elevated (560 μmol?mol<sup>-1</sup>) CO<sub>2</sub> concentrations in the field using free-air CO<sub>2</sub> enrichment systems, in air-conditioned glasshouses with natural summer photoperiods, and in indoor chambers with day lengths of 11, 13, 15, and 17 hours. The effect of CO<sub>2</sub> concentration on flowering time varied with genotype, and there was also an interaction between CO<sub>2</sub> and photoperiod in all genotypes, as indicated by ANOVA. Elevated CO<sub>2</sub> accelerated flowering in some cases, and delayed it in other cases. For all three of the isolines with single dominant genes, elevated CO<sub>2</sub> decreased the days to first open flower at the longest photoperiod. At the shortest photoperiod, elevated CO<sub>2</sub> delayed flowering in all but one isoline. The all-recessive isoline had slower flowering at elevated CO<sub>2</sub> at both the shortest and the longest photoperiods, and also in the field and in the glasshouse. Delayed flowering at elevated CO<sub>2</sub> in the field and glasshouse was associated with an increased final number of main stem nodes. It is concluded that the E1, E3, and E4 genes each influenced how the time to first flowering was affected by CO<sub>2</sub> concentration at long photoperiods.
基金supported by the National Natural Science Foundation of China(No.52470174)the Joint Research Project on Ecological Protection and High-Quality Development in the Yellow River Basin,China(No.2022-YRUC-01-050209-01).
文摘Soil microbial communities and grassland ecosystem processes are increasingly confronted with multiple global change factors(GCFs).There is still a lack of research on how these multiple GCFs interact and impact soil microbial communities and their functions.To address this gap,we conducted a simulation experiment to examine the individual and interactive effects of the four most critical and prevalent GCFs,elevated carbon dioxide concentration(eCO_(2)),elevated temperature(eT),decreased precipitation(dP),and elevated nitrogen(N)deposition(eN).This study focused on their effects on soil physicochemical properties,bacterial and fungal communities,and extracellular enzyme activities(EEAs)related to carbon(C),N,and phosphorus(P)cycles in a temperate grassland.Results showed that eCO_(2),eN,and dP tended to increase EEAs,while having neutral effects on microbial diversity and community composition.On the other hand,eT resulted in decreases in soil pH,total C,total N,EEAs,and microbial diversity,but increases in plant biomass,total P,microbial richness,and network complexity and stability.This shift in the nutrient limitation from P to N under warming conditions resulted in decoupling of nutrients.Neutral or slightly negative relationships were found between enzyme activities and microbial richness,diversity,and dominant species,and the responses of microbial communities and ecological functions were asynchronous under GCFs.Importantly,our results revealed significant higher-order interactions among GCFs and found that they had notable effects on soil physicochemical properties as well as on microbial communities and ecological functions.These findings provide valuable insights and suggestions for ecological adaptations to future global changes.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61474110,61377020,61376089,61223005,and 61176126)the National Natural Science Fund for Distinguished Young Scholars,China(Grant No.60925017)+1 种基金the One Hundred Person Project of the Chinese Academy of Sciencesthe Basic Research Project of Jiangsu Province,China(Grant No.BK20130362)
文摘Two series of p-GaN films grown at different temperatures are obtained by metal organic chemical vapor deposition（MOCVD）. And the different variation behaviors of resistivity with growth condition for high- temperature（HT）-grown and low-temperature（LT）-grown p-GaN films are investigated. It is found that the resistivity of HT-grown p-GaN film is nearly unchanged when the NH_3 flow rate or reactor pressure increases. However, it decreases largely for LT-grown p-GaN film.These different variations may be attributed to the fact that carbon impurities are easy to incorporate into p-GaN film when the growth temperature is low. It results in a relatively high carbon concentration in LT-grown p-GaN film compared with HT-grown one. Therefore, carbon concentration is more sensitive to the growth condition in these samples, ultimately,leading to the different variation behaviors of resistivity for HT- and LT-grown ones.
基金support from the National Natural Science Foundation of China(Nos.52001105 and 52122410)the Hebei Natural Science Foundation(Nos.E2022402107,E2023203259 and E2020402101)+1 种基金the Science and Technology Project of Hebei Education Department(No.BJ2021012)the Central Guidance for Local Science and Technology Development Funding Project(No.236Z1021G).
文摘In this study, a high-carbon nano-bainitic GCr15Si1Mo bearing steel was investigated. Specifically, the effects of content and size of undissolved carbides on the microstructure and transformation kinetics of nano-bainite were analyzed. The results demonstrated that after prolonged austempering at low temperatures, the mixed microstructure composed of nano-bainite (NB), undissolved carbides (UC), and retained austenite (RA) was obtained in GCr15SiMo steel. When the experimental steel was austenitized at 900 ℃, the undissolved carbides gradually dissolved until reaching a stable state with increasing holding time. Furthermore, at the same austempering temperature, despite different volume fractions of undissolved carbides in the substrate, the volume fractions of nano-bainite in the final microstructures remained essentially the same. Moreover, the higher the content of undissolved carbides in steel, the faster the transformation rate of nano-bainite and the shorter the total transformation time.
基金supported by Industrial University of Ho Chi Minh City(IUH)under grant number 68/H-D--DHCN.
文摘The type of technology used to strengthen the surface structure of machine parts,typically by carbon-permeation,has made a great contribution to the mechanical engineering industry because of its outstanding advantages in corrosion resistance and enhanced mechanical and physical properties.Furthermore,carbon permeation is considered as an optimal method of heat treatment through the diffusion of carbon atoms into the surface of alloy steel.This study presented research results on the thermodynamic calculation and simulation of the carbon permeability process.Applying Fick’s law,the paper calculated the distribution of carbon concentration in the alloy steel after it is absorbed from the surface into the internal of the sample.Using the SYSWELD software,an analysis was performed on the carbon permeability process to determine the distribution of carbon concentrations in 20CrMo steel that was then followed by a detailed analysis of the microstructure of the sample post the carburizing process.According to the calculation results,the surface carbon content was 0.9%and steadily decreased into the core.After 3 hours,the depth of the absorbent layer was measured at 0.5 mm for both the cylindrical and cubic samples.By analyzing the phase,the distribution of martensite phases such as ferrite/pearlite and residual austenite was also determined after the carburizing process.
文摘The potential CO2-induced impacts on the geographical shifts of wheat growth zones in China were studied from seven GCMs outputs. The wheat growth regions may move northward and westward under the condition of a doubling CO2 climate. The wheat cultivation features and variety types may also assume significant changes. Climatic warming would have a positive influence in Northeast China, but high temperature stress may be produced in some regions of central and southern China. Higher mean air temperatures during wheat growth, particularly during the reproductive stages, may increase the need for earlier-maturing and more heat-tolerant cultivars.
文摘The trends and features of China's climatic change in the past and future are analysed by applying station observations and GCM simulation results. Nationally, the country has warmed by 0.3℃ in annual mean air temperatureand decreased by 5% in annual precipitation over 1951-1990. Regionally, temperature change has varied from acooling of 0.3℃ in Southwest China to a'warming of 1 .0℃ in Northeast China. With the exception of South China,all regions of China have shown a declination in precipitation. Climatic change has the features of increasing remarkably in winter temperature and decreasing obviously in summer precipitation. Under doubled CO2 concentration,climatic change in China will tend to be warmer and moister, with increases of 4.5℃ in annual mean air temperatureand 11% in annual precipitation on the national scale. Future climatic change will reduce the temporal and spatialdifferences of climatic factors.
基金Foundation item:The National Science and Technology Major Project of the Ministry of Science and Technology of China under contract No.2016ZX05026007-03the National Natural Science Foundation of China under contract Nos 41876046 and 41930536。
文摘Rapid changes on nutrient supply and CO2 concentration that occurred in the northern South China Sea(SCS)during the Early Oligocene,provides an ideal natural laboratory,allowing us to peer into the coccolithophores’physiology in the geological records.In this study,we established a new nannofossil assemblage index,termed as E^*ratio,which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa(E^*=e/e+c,where e is eutrophic taxa,and c is meso-oligotrophic taxa)Eutrophic taxa include small Reticulofenestra,Reticulofenestra lockeri group,Reticulofenestra bisecta group and Coccolithus pelagicus group,while meso-oligotrophic taxa include Cyclicargolithus spp.The E^*ratio is well correlated with nutrient proxy during the Early Oligocene,while with different covarying patterns under the higher and lower CO2 condition.By comparing the assemblage changes to the published data,we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO2.Furthermore,this implies a possible initiation of the carbon concentrating mechanism.
基金The National Natural Science Foundation of China under contract Nos 42107251 and 41706089the Natural Science Foundation of Fujian Province under contract No.2020J05232.
文摘The sedimentary record of climate change in the Arctic region is useful for understanding global warming.Kongsfjord is located in the subpolar region of the Arctic and is a suitable site for studying climate change.Glacier retreat is occurring in this region due to climate change,leading to an increase in meltwater outflow with a high debris content.In August 2017,we collected a sediment Core Z3 from the central fjord near the Yellow River Station.Then,we used the widely used chronology method of 210Pb,^(137)Cs,and other parameters to reflect the climate change record in the sedimentary environment of Kongsfjord.The results showed that after the mid-late 1990s,the mass accumulation rate of this core increased from 0.10 g/(cm^(2)·a)to 0.34 g/(cm^(2)·a),while the flux of^(210)Pb_(ex)increased from 125 Bq/(m^(2)·a)to 316 Bq/(m^(2)·a).The higher sedimentary inventory of^(210)Pb_(ex)in Kongsfjord compared to global fallout might have been caused by sediment focusing,boundary scavenging,and riverine input.Similarities between the inventory of^(137)Cs and global fallout indicated that terrestrial particulate matter was the main source of^(137)Cs in fjord sediments.The sedimentation rate increased after 1997,possibly due to the increased influx of glacial meltwater containing debris.In addition,the^(137)Cs activity,percentage of organic carbon(OC),and OC/total nitrogen concentration ratio showed increasing trends toward the top of the core since 1997,corresponding to a decrease in the mass balance of glaciers in the region.The results ofδ^(13)C,δ^(15)N and OC/TN concentration ratio showed both terrestrial and marine sources contributed to the organic matter in Core Z3.The relative contribution of terrestrial organic matter which was calculated by a two-endmember model showed an increased trend since mid-1990s.All these data indicate that global climate change has a significant impact on Arctic glaciers.
基金supported by the National Natural Sciences Foundation of China(Grant Nos.411751154083010240575013 and 40175032)
文摘Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon （WIRC） component of total suspended particulates （TSP）, collected weekly during 2003, as well as from October 2005 to May 2006 at the WMO-GAW Mt. Waliguan （WLG） site. The overall average WlRC mass concentration was （1183 ± 120）ng/m3 （n = 79）, while seasonal averages were 2081 ± 1707 （spring）, 454±205 （summer）, 650 ±411 （autumn）, and 1019 ± 703 （winter） ng/m3. Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer, although WIRC concentrations were typically higher, especially in winter and spring. The δ13C PDB value （-25.3 ± 0.8）%0 determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion. No seasonal change in δ13C PDB was evident. The average percent Modern Carbon （pMC） for 14C in WIRC for winter and spring was （67.2 ± 7.7）% （n = 29）. Lower pMC values were associated with air masses trans- ported from the area east of WLG, while higher pMC values were associated with air masses from the Tibetan Plateau, southwest of WLG. Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.
基金funding support from the Fundamental Research Funds for the Central Universities(Grants KY2060000150,GG2060127001,and WK2060000040)support from USTC Center for Micro and Nano-scale Research and Fabrication and NEWARE。
文摘Developing facile and economical strategies to fabricate nitrogen-doped porous carbon anode is desirable for dual-carbon potassium ion hybrid capacitors(PIHCs).Here,a high-concentration edge-nitrogen-doped porous carbon(NPC)anode is synthesized by a template-free strategy,in which the total content of pyrrolic nitrogen and pyridinic nitrogen accounts for more than 80%of the nitrogen atoms.As a result,the NPC anode displays a capacity of 315.4 mA h g^(−1)at a current rate of 0.1 A g^(−1)and 189.1 mA h g^(−1)at 5 A g^(−1).Ex situ characterizations and density functional theory calculations demonstrate the high-concentration edge-nitrogen doping enhances K^(+)adsorption and electronic conductivity of carbon materials,resulting in good electrochemical performance.The assembled NPC//CMK-3 PIHC delivers an energy density of 71.1 W h kg^(−1)at a power density of 771.9 W kg^(−1)over 8,000 cycles.
基金funded by the National Natural Science Foundation of China(grant no.22071050 to Q.H.)Fundamental Research Funds for the Central Universities(Startup Funds to Q.H.).
文摘Development of advanced materials with high CO_(2)capture capacity and,inter alia,superior regenerability with low energy consumption(low-temperature CO_(2)release)remains highly desired yet challenging.Herein,we firstly report the precipitation-involved CO_(2)capture from ultradilute sources(e.g.,exhaled gas and indoor air)and the reversible room-temperature CO_(2)release accelerated by mechanical power using a covalent organic superphane cage.This superphane-based operating system enables CO_(2)in ultradilute gas(<6%)to be concentrated up to 83%.As inferred from the control experiments and theoretical calculations,this proof-of-concept CO_(2)capture and concentration system with mechanical power-triggered CO_(2)release by the discrete organic cage could be rationalized by the formation of a sixmembered ring transition state with relatively low energy barrier during the process of the adsorption and desorption of CO_(2)on the cage surface,along with the precipitation-involved phase change.
基金supported by the National Natural Science Foundation of China(Grant No.52302007,52327801,51906086)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20210762).
文摘Spontaneous nucleation of SiC particles and giant macroscopic steps result in the surface roughness of the grown crystal for the top-seeded solution growth of SiC crystal.To suppress the surface roughness,the temperature gradient was carefully adjusted by changing the relative position of the crucible and induction coils.The numerical simulation and experimental results show that the surface morphology of the grown crystal becomes smoother and there are fewer spontaneous nucleation particles attached to the growth surface with the decrease in the relative crucible position,due to the increase of temperature at the entire solution surface and the reducing of temperature gradient near the growth surface.Accordingly,a lower temperature gradient,a larger solution velocity,a higher carbon concentration,and a smaller carbon supersaturation near the growth surface can be obtained when the relative position between the crucible and the induction coil is 70 mm,which is demonstrated to be the most favorable for the elimination of spontaneous nucleation of small SiC particles and suppressing surface roughening with the full width at half maximum(FWHM)of 37.5 arcsec of 4Hsingle bondSiC crystals.
