A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorptio...A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorption capacity of the adsorbent was further enhanced by taking advantage of the nitrogenous bases contained in the BA.In the hydrothermal process,the addition of BA significantly increased the content of pyrrole nitrogen in the adsorbent.In the activation process,pyrrole nitrogen gradually changed into pyridine nitrogen and graphite nitrogen.Increased BA addition result in a higher specific surface area and microporosity of the adsorbent.The CO_(2)adsorption performance test proved that the CGFS-50%-CA sample has the strongest CO_(2)adsorption capacity at low temperature,up to 15.59 cm^(3)/g,which is mainly through physical adsorption,and the CGFS-10%-CA sample has the strongest CO_(2)adsorption capacity at high temperature,up to 7.31 cm^(3)/g,which is mainly through chemical adsorption.CO_(2)uptake of the CGFS-10%-CA sample was well maintained after 10 cycles,with regeneration efficiencies above 99%.The results indicate that the novel adsorbents with coexistence of physical and chemical adsorption have great potential for CO_(2)adsorption applications.展开更多
Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ ...Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ measurements performed at a mountain site(1690 m a.s.l.)in southern China,we investigated the formation of NOCs in the cloud droplets and the cloud-free particles,based on their mixing state information of NOCscontaining particles by single particle mass spectrometry.The relative abundance of NOCs in the cloud-free particles was significantly higher than those in cloud residual(cloud RES)particles.NOCs were highly correlated with carbonyl compounds(including glyoxalate and methylglyoxal)in the cloud-free particles,however,limited correlation was observed for cloud RES particles.Analysis of their mixing state and temporal variations highlights that NOCs was mainly formed from the carbonyl compounds and ammonium in the cloud-free particles,rather than in the cloud RES particles.The results support that the formation of NOCs from carbonyl compounds is facilitated in concentrated solutions in wet aerosols,rather than cloud droplets.In addition,we have identified the transport of biomass burning particles that facilitate the formation of NOCs,and that the observed NOCs is most likely contributed to the light absorption.These findings have implications for the evaluation of NOCs formation and their contribution to light absorption.展开更多
Covalent organic frameworks(COFs)are crystalline porous polymeric materials composed of organic monomers connected by strong covalent bonds and offer high stability,good crystallinity,a large specific surface area,and...Covalent organic frameworks(COFs)are crystalline porous polymeric materials composed of organic monomers connected by strong covalent bonds and offer high stability,good crystallinity,a large specific surface area,and controllable structures.COFs are widely used in the fields of adsorption and separation,catalysis,photovoltaics,and drug-delivery.The structural regulation and performance optimization of COFs can be realized through the modification of ligands and the selection of linkage methods.In which,the types of linkage are closely related to the stability and performance of COFs.In this review,nitrogencontaining linkage-bonds(NCLBs)in COFs are divided into N-containing double bonds,N-containing conjugated rings and N-containing unconjugated rings.The association between structure and performance of COFs is elaborated and the synthesis methods of COFs are systematically summarized.Moreover,the structural design,theoretical prediction and machinable application of COFs are prospected.展开更多
The influence of nitrogen-containing polycyclic aromatic hydrocarbons(NC-PAH)on the formation of carbonaceous mesophase remains enigmatic,despite extensive research on the production of carbonaceous materials from aro...The influence of nitrogen-containing polycyclic aromatic hydrocarbons(NC-PAH)on the formation of carbonaceous mesophase remains enigmatic,despite extensive research on the production of carbonaceous materials from aromatic-rich oils.Molecular dynamics simulation was used to investigate the variations in pyrolysis behavior between PAH and NC-PAH based on the composition analysis.Through adjusting the content of NC-PAH,the influence of NC-PAH on the thermal stability of slurry oils(SOs)was evaluated by thermogravimetry,viscosity,coke value,and quinoline insoluble(QI).The morphology and structure of mesocarbon microbeads(MCMBs)prepared with SOs were measured by a polarized-light microscope,SEM,XRD,and Raman.Simulation results indicate that NC-PAH possesses much higher reactivity and tends to produce highly condensed solid and coke products.It corresponds to the QI and high viscosity in thermal stability experiments.Therefore,high concentrations of NC-PAH result in nonuniform morphology and disordered structures.In a system with low viscosity and few QIs,SO,which has a low nitrogen content(475 ppm),reacts gently to produce MCMBs with a uniform particle size(10-40μm)and an excellent spherical shape.As NC-PAH content decreases,the crystalline size of graphitization elevates,as evidenced by parallel layers(10.472-11.764)and stack height(3.269-3.701 nm).The graphitization degree becomes worse and nonuniform with the increase of the content of NC-PAH,and the best is 20.58%evaluated by Raman spectra area ratio(AG/Aall).Overall,this work suggests a nitrogen content reference and a controlling technology of nitrogen for the preparation of superior MCMB.展开更多
Many nitrogen-containing aromatic compounds （NACs）, such as nitrobenzene （NB）, 4-nitrophenol （4-NP）, aniline （AN）, and 2,4-dinitrophenol （2,4-DNP）, are environmentally hazardous, and their removal from conta...Many nitrogen-containing aromatic compounds （NACs）, such as nitrobenzene （NB）, 4-nitrophenol （4-NP）, aniline （AN）, and 2,4-dinitrophenol （2,4-DNP）, are environmentally hazardous, and their removal from contaminated water is one of the main challenges facing wastewater treatment plants. In this study, synthetic wastewater containing NB, 4-NP, 2,4-DNP, and AN at concentrations ranging from 50 to 180 mg/L was fed into a sequencing batch reactor （SBR）. Analyses of the SBR system indicated that it simultaneously removed more than 99% of the NACs at loading rates of 0.36 kg NB/（m^3·d）, 0.3 kg 4-NP/（m^3·d）, 0.25 kg AN/（m^3·d）, and 0.1 kg 2,4-DNP/（m^3·d）. Bacterial groups of Bacteriodetes, Candidate division TM7, α-Proteobacteria, and β-Proteobacteria were dominant in the clone libraries of 16S rRNA genes retrieved from the microbial communities in the SBR system. ＂Cycle tests＂ designed to alter feeding and aeration parameters of the SBR system demonstrated that the resident microbial biome of the SBR system responded rapidly to changing conditions. Consumption of O2 was concomitant with the apparent mineralization of NACs. Aromatic ring-cleaving dioxygenase activities suggested that （1） AN and NB were degraded via catechol 2,3-dioxygenase; （2） 4-NP was degraded via 1,2,4-benzentriol 1,2-dioxygenase; and （3） 2,4-DNP was degraded via an unresolved pathway.展开更多
Soluble portions(SPs) 1-4(SP1-SP4) were afforded from sequentially dissolution and alkanolyses of Baiyinhua lignite(BL) in cyclohexane,CH3OH,CH3CH2OH,and(CH3)2CHOH at 300℃.They were analyzed with a gas chromatograph/...Soluble portions(SPs) 1-4(SP1-SP4) were afforded from sequentially dissolution and alkanolyses of Baiyinhua lignite(BL) in cyclohexane,CH3OH,CH3CH2OH,and(CH3)2CHOH at 300℃.They were analyzed with a gas chromatograph/mass spectrometer and quadrupole exactive orbitrap mass spectrometer(QEOTMS) with an atmosphere pressure chemical ionization source in positive-ion mode,while BL was characterized with an X-ray photoelectron spectrometer(XRPES).The results show that the yields of SP2 and SP3 are much higher than those of SP1 and SP4,and the total SP yield is ca.39.0%.According to the analysis with XRPES,pyrrolic nitrogen atoms are the most abundant nitrogen existing forms in BL.Thousands of nitrogen-containing aromatics(NCAs) were resolved with QEOTMS and their molecular masses are mainly in the range of 200-450 u.The main NCAs are N1O1 and N1O2 class species with double bond equivalent values of 4-18 and carbon numbers of 7-30.The nitrogen atoms appear in pyridine s,quinolines,benzoquinolines or acridine,and dibenzoquinolines or naphthoquinolines,while the oxygen atoms exist in methoxy and furan rings.展开更多
Nitrogen-containing organic pollutants(quinoline,pyridine and indole)are widely distributed in coking wastewater,and bioaugmentation with specific microorganisms may enhance the removal of these recalcitrant pollutant...Nitrogen-containing organic pollutants(quinoline,pyridine and indole)are widely distributed in coking wastewater,and bioaugmentation with specific microorganisms may enhance the removal of these recalcitrant pollutants.The bioaugmented system(group B)was constructed through inoculation of two aromatics-degrading bacteria,Comamonas sp.Z1(quinoline degrader)and Acinetobacter sp.JW(indole degrader),into the activated sludge for treatment of quinoline,indole and pyridine,and the non-bioaugmented activated sludge was used as the control(group C).Both groups maintained high efficiencies(>94%)for removal of nitrogen-containing organic pollutants and chemical oxygen demand(COD)during the long-term operation,and group B was highly effective at the starting period and the operation stage fed with raw wastewater.High-throughput sequencing analysis indicated that nitrogen-containing organic pollutants could shape the microbial community structure,and communities of bioaugmented group B were clearly separated from those of non-bioaugmented group C as observed in non-metric multidimensional scaling(NMDS)plot.Although the inoculants did not remain their dominance in group B,bioaugmentation could induce the formation of effective microbial community,and the indigenous microbes might play the key role in removal of nitrogen-containing organic pollutants,including Dokdonella,Comamonas and Pseudoxanthomonas.Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt)analysis suggested that bioaugmentation could facilitate the enrichment of functional genes related to xenobiotics biodegradation and metabolism,probably leading to the improved performance in group B.This study indicated that bioaugmentation could promote the removal of nitrogen-containing organic pollutants,which should be an effective strategy for wastewater treatment.展开更多
The adsorptive denitrogenation from fuels over three metal-organic frameworks(MIL-96(Al),MIL-53(Al)and MIL-101(Cr))was studied by batch adsorption experiments.Four nitrogen-containing compounds(NCCs)pyridine,pyrrole,q...The adsorptive denitrogenation from fuels over three metal-organic frameworks(MIL-96(Al),MIL-53(Al)and MIL-101(Cr))was studied by batch adsorption experiments.Four nitrogen-containing compounds(NCCs)pyridine,pyrrole,quinoline and indole were used as model NCCs in fuels to study the adsorption mechanism.The physicochemical properties of the adsorbents were characterized by XRD,N2physical adsorption,FT-IR spectrum and Hammett indicator method.The metal-organic frameworks(MOFs),especially the MIL-101(Cr)containing Lewis acid sites as well as high specific surface area,can adsorb large quantities of NCCs from fuels.In addition,the adsorptive capacity over MIL-101(Cr)will be different for NCCs with different basicity.The stronger basicity of the NCC is,the more it can be absorbed over MIL-101(Cr).Furthermore,pore size and shape also affect the adsorption capacity for a given adsorbate,which can be proved by the adsorption over MIL-53(Al)and MIL-96(Al).The pseudo-second-order kinetic model and Langmuir equation can be used to describe kinetics and thermodynamics of the adsorption process,respectively.Finally,the regeneration of the used adsorbent has been conducted successfully by just washing it with ethanol.展开更多
Stress corrosion cracking （SCC） of stainless steels and Ni-based alloys in high temperature water coolant is one of the key problems affecting the safe operation of nuclear power plants （NPPs）. The nitrogen-added ...Stress corrosion cracking （SCC） of stainless steels and Ni-based alloys in high temperature water coolant is one of the key problems affecting the safe operation of nuclear power plants （NPPs）. The nitrogen-added stainless steel is a kind of possible candidate materials for mitigating SCC since reducing the carbon content and adding nitrogen to offset the loss in strength caused by the decrease in carbon content can mitigate the problem of sensitization. However, the reports of SCC of nitrogen-added stainless steels in high temperature water are few available. The effects of applied potential and sensitization treatment on the SCC of a newly developed nitrogen-containing stainless steel （SS） 316LN in high temperature water doped with chloride at 250 ℃ were studied by using slow strain rate tests （SSRTs）. The SSRT results are compared with our data previously published for 316 SS without nitrogen and 304NG SS with nitrogen, and the possible mechanism affecting the SCC behaviors of the studied steels is also discussed based on SSRT and microstucture analysis results. The susceptibility to cracking of 316LN SS normally increases with increasing potential. The susceptibility to SCC of 316LN SS was less than that of 316 SS and 304NG SS. Sensitization treatment at 700℃ for 30 h showed little effect on the S CC of 316LN S S and significant effect on the S CC of 316 S S. The predominant cracking mode for the 316LN S S in both annealed state and the state after the sensitization treatment was transgranular. The presented conditions of mitigating stress corrosion cracking are some useful information for the safe use of 316LN SS in NPPs.展开更多
A new nitrogen-containing epoxy resin (XT resin) was synthesized from chain extension of xylenephenolformaldehyde resin (XPF) and triglycidyl isocyanurate (TGIC) in the presence of base catalyst. FT-IR and H-NMR ana...A new nitrogen-containing epoxy resin (XT resin) was synthesized from chain extension of xylenephenolformaldehyde resin (XPF) and triglycidyl isocyanurate (TGIC) in the presence of base catalyst. FT-IR and H-NMR analysis confirmed the chemical structure of XT resin. It was 1 cured with dicyandiamide (DICY) and diaminodiphenyl sulfone (DDS). Dynamic mechanical analysis (DMA) results showed that the introduction of triazine ring provides epoxy polymer with good thermal stability. Furthermore, high char yields at 800℃ in thermogravimetric (TGA) analysis indicated that XT resin had potential flame retardance.展开更多
The DFT-based （density fimctional theory） ab initio quantum mechanical methods have been applied to study the basicity of the nitrogen-containing compounds in petroleum. The results have indicated that there is a di...The DFT-based （density fimctional theory） ab initio quantum mechanical methods have been applied to study the basicity of the nitrogen-containing compounds in petroleum. The results have indicated that there is a distinct relationship between the protonation energy of nitrogen-containing compounds and their basicity. The more negative the protonation energy, the stronger the basicity is. It has been also found that aliphatic amines are more basic than pyridines or aromatic amines, and all these compounds are more basic than pyrroles. The addition of the aromatic rings can influence the basicity of anilines, while the 5- and 6-membered heterocyclic compounds function differently. The solvent properties may affect the basicity of these nitrogen-containing compounds.展开更多
To elucidate the effects of Fe_(2)O_(3) on nitrogen transformation during sludge pyrolysis,thermogravimetry coupled with mass spectrometry(TG-MS)was used to investigate the influences of Fe_(2)O_(3) on the pyrolysis c...To elucidate the effects of Fe_(2)O_(3) on nitrogen transformation during sludge pyrolysis,thermogravimetry coupled with mass spectrometry(TG-MS)was used to investigate the influences of Fe_(2)O_(3) on the pyrolysis characteristics and the release of important gaseous NO_(x) precursors such as HCN and NH_(3) during pyrolysis of three typical amino acids in urban sludge.The results show that after Fe_(2)O_(3) addition,the total weight loss rate of the three amino acids and the initial decomposition temperature of proline are reduced.The release amounts of NH_(3),HCN,CH_(3)CN,and HNCO from these three representative amino acids—glumatic,arginine,and proline,decrease in the order of arginine,glutamic,proline.The generation of Fe-N complexes,reduces the generation of NH_(3),HCN,CH_(3)CN,and HNCO while the catalysis effects of Fe_(2)O_(3) on the formation of H and H2 play a promoting role in the generation of NH_(3),HCN,CH_(3)CN,and HNCO.The results would provide an experimental and theoretical basis for subsequent research on the NOx precursor formation mechanisms during pyrolysis or combustion of Fe-containing sludge or sludge with additives containing Fe.展开更多
INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This colla...INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This collapse resulted in a pavement failure of approximately 17.9 m in length and covering an area of about 184.3 m^(2)(Chinanews,2024).展开更多
Rockburst precursors are critical for disaster warning,yet the complexity of rockburst has hindered the identification of a unified precursor.Furthermore,the influence of loading rates(LRs)on acoustic emission(AE)prec...Rockburst precursors are critical for disaster warning,yet the complexity of rockburst has hindered the identification of a unified precursor.Furthermore,the influence of loading rates(LRs)on acoustic emission(AE)precursors in different rock types remains poorly understood.This study investigates the AE characteristics and early warning times of rockburst in slate and mica-schist under four LRs(0.05,0.15,0.25,and 0.5 MPa/s)using true triaxial unloading tests.The micro-crack state of the samples was evaluated using entropy,while critical slowing down(CSD)theory was applied to interpret AE precursors.The results reveal that as the LR increases,the rockburst stress of both rocks initially rises and then declines,with mica-schist exhibiting more severe damage and a higher dominance of tensile cracks.Notably,identifying rockburst precursors in mica-schist proved more challenging compared to slate.Among the methods tested,AE amplitude variance outperformed entropy in precursor identification.Additionally,the rockburst early warning time was found to be negatively correlated with the LR,with mica-schist consistently showing shorter warning times than slate.The CSD-derived precursor,due to its enhanced sensitivity,is recommended for early warning systems.These findings provide new insights into the role of LRs in rockburst dynamics and offer practical guidance for improving precursor identification and disaster mitigation strategies.展开更多
Polyacrylonitrile (PAN) precursor is a core precursor for the preparation of high-performance carbon fibers. Its unique chemical structure and physical properties directly contributes to the microstructure and mechani...Polyacrylonitrile (PAN) precursor is a core precursor for the preparation of high-performance carbon fibers. Its unique chemical structure and physical properties directly contributes to the microstructure and mechanical properties of carbon fibers, and therefore affect the overall performance of pultruded composites. This study systematically investigated the influence of PAN precursor properties on the degree of graphitization, surface morphology and mechanical properties of carbon fibers by regulating the molecular weight distribution, stretching ratio and impurity content of PAN precursor, and analyzed the mechanism of action of carbon fiber properties on the interfacial bonding strength and tensile/ bending properties of composites in combination with the pultrusion process. The results showed that when the filament stretchability was increased to 4.5 times, the axial orientation of carbon fibers increased by 18% and the tensile strength reached 520 MPa;Filaments with impurity content below 0.3% increase carbon fiber yield by 5.2% and interlaminar shear strength of composites by 23%. This study provides a theoretical basis for raw material screening and process optimization of high-performance carbon fibers and their composites.展开更多
The increasing sophistication of cyberattacks,coupled with the limitations of rule-based detection systems,underscores the urgent need for proactive and intelligent cybersecurity solutions.Traditional intrusion detect...The increasing sophistication of cyberattacks,coupled with the limitations of rule-based detection systems,underscores the urgent need for proactive and intelligent cybersecurity solutions.Traditional intrusion detection systems often struggle with detecting early-stage threats,particularly in dynamic environments such as IoT,SDNs,and cloud infrastructures.These systems are hindered by high false positive rates,poor adaptability to evolving threats,and reliance on large labeled datasets.To address these challenges,this paper introduces CyberGuard-X,an AI-driven framework designed to identify attack precursors—subtle indicators of malicious intent—before full-scale intrusions occur.CyberGuard-X integrates anomaly detection,time-series analysis,and multi-stage classification within a scalable architecture.The model leverages deep learning techniques such as autoencoders,LSTM networks,and Transformer layers,supported by semi-supervised learning to enhance detection of zero-day and rare threats.Extensive experiments on benchmark datasets(CICIDS2017,CSE-CIC-IDS2018,and UNSW-NB15)demonstrate strong results,including 96.1%accuracy,94.7%precision,and 95.3%recall,while achieving a zero-day detection rate of 84.5%.With an inference time of 12.8 ms and 34.5%latency reduction,the model supports real-time deployment in resource-constrained environments.CyberGuard-X not only surpasses baseline models like LSTM and Random Forest but also enhances proactive threat mitigation across diverse network settings.展开更多
The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields(<40 wt.%)due to the challenges in integrating significant amounts of boron,which ha...The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields(<40 wt.%)due to the challenges in integrating significant amounts of boron,which hampers their conversion into boride-based ultrahigh temperature ceramics.To tackle these challenges,a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors(with different Hf/Si ratios)have been developed.These novel precursors are featured with stable molec-ular structure and high ceramic yield which were successfully created through a novel one-pot polymer-ization process.They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O,Si-O-Hf,Si-O-B,and B-O-Hf which have untapped advantages including uniform component dispersion,and excellent fluidity.The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.%at 1500℃,and their Hf content exceeded 50 wt.%.Of particular interest,the pyrolyzed product HfB_(2)-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2,consist of nanopowders in the 40-60 nm range with a density of 5.23 g cm^(−3).Remarkably,this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environ-ments at 2500℃,showing near-zero ablation with a linear ablation rate of just 2.5×10^(−4) mm s^(−1).Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO_(2) and HfO_(2)-SiO_(2) oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance.The inno-vative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics.This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems,partic-ularly in the construction of hypersonic vehicles,where ultrahigh temperature resilience is crucial.展开更多
This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic ...This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic response mechanism of coal energy evolution is examined, and the energy instability criterion is established. The validity of the instability criterion is explored from the standpoint of damage progression. The results demonstrate that the energy conversion mechanism undergoes a fundamental alternation under impact disturbance. Moreover, the energy release rate as well as the energy dissipation rate undergo comparable changes across distinct levels of impact disturbance. The distinction between the energy release rate and the energy dissipation rate (DRD) increases as coal mass deformation grows. Prior to coal facing instability and failure, the DRD experienced an inflection point followed by a sharp decrease. In conjunction with the discussion on the damage evolution, the physical and mechanical significance of DRD remains clear, which can essentially describe the whole impact loading process. The phenomenon that the inflection point appears and DRD subsequently suddenly decreases can be employed as the energy criterion prior to the failure of instability. Furthermore, this paper provides significant reference for the prediction of dynamic instability of coal under dynamic disturbance.展开更多
Metal composites produced through the liquid metal dealloying(LMD)process feature an advanced matrix-matrix composite structure,where two metallic materials form a continuous,three-dimensional interconnected network.T...Metal composites produced through the liquid metal dealloying(LMD)process feature an advanced matrix-matrix composite structure,where two metallic materials form a continuous,three-dimensional interconnected network.This study investigates the effects of Ti Cu precursor compositions on dealloying behavior and microstructural evolution in liquid Mg,using Ti_(50)Cu_(50)and Ti_(30)Cu_(70)precursors.The initial microstructure of the precursor significantly influences dealloying kinetics and phase transitions.The single-phase Ti_(50)Cu_(50)precursor exhibits a faster initial dealloying rate due to its homogeneous structure,yet complete dealloying requires 90 min.In contrast,the dualphase Ti_(30)Cu_(70)precursor achieves complete dealloying in 30 min,demonstrating the impact of a higher Cu concentration on accelerating the process kinetics.Additionally,the study explores the coarsening behavior and hardness variations during the LMD process,along with the microstructural characteristics of Mg-Ti composites fabricated from these two precursors.The findings highlight the critical role of precursor composition in tailoring the microstructure and properties of Mg-Ti composites produced through the LMD process,demonstrating its potential for advanced composite material manufacturing.展开更多
The growing environmental awareness,the search for alternatives to fossil resources,and the goal of achieving a circular economy have all contributed to the increasing valorization of biowaste to produce bio-based pol...The growing environmental awareness,the search for alternatives to fossil resources,and the goal of achieving a circular economy have all contributed to the increasing valorization of biowaste to produce bio-based polymers and other high-value products.Among the various biowaste materials,lignin has gained significant attention due to its high aromatic carbon content,low cost,and abundance.Lignin is predominantly sourced as a byproduct from the paper industry,available in large quantities from hardwood and softwood,with variations in chemical structure and susceptibility to hydrolysis.This study focuses on softwood lignin obtained through the LignoForce^(TM) technology,comparing the thermal and chemical characteristics,and stability,of a recently produced batch with that of a batch that has been stored for four years.Additionally,the development of lignin-based thermoplastic polymer mixtures using Polyethylene Terephthalate Glycol(PET-G)and a blend of Polycarbonate and Acrylonitrile-Butadiene-Styrene(PC/ABS)with high lignin content(50–60 wt%)is explored,as well as the production of filaments for carbon fiber production.For this purpose,following melt mixing,the lignin-based mixtures were spun into filaments,which were subsequently subjected to thermal stabilization in an oxidative atmosphere.The lignin phase was well distributed in the PET-Gmatrix and the twomaterials presented a good interface,which further improved after thermal treatment under an oxidative atmosphere.After thermal treatment an increase in tensile modulus,tensile strength,and elongation at break of approximately 160%,200%,and 100%,respectively,was observed,confirming the good interface established,and consistent with structural changes such as cross-linking.Conversely,the PC/ABS blend did not form a good interface with the lignin domains after melt mixing.Although the interactions improved after thermal treatment,the tensile strength and elongation at break decreased by approximately 30%,while themodulus increased by approximately 20%.Overall,the good processability of the lignin/polymer mixtures into filaments,and their physical,chemical,and mechanical characterization before and after thermal oxidation are good indicators of the potential as precursors for carbon fiber production.展开更多
基金supported by the National Natural Science Foundation of China(22168032)the National Key Research and Development Program of China(2023YFC3904302,2023YFB4103500)the Key Projects of Ning Dong Energy and Chemical Industry Base(2023NDKJXMLX022).
文摘A new adsorbent was successfully prepared by hydrothermal treatment and chemical activation through coal gasification fine slag(CGFS)and blue algae(BA)as raw materials and used for CO_(2)capture.The CO_(2)chemisorption capacity of the adsorbent was further enhanced by taking advantage of the nitrogenous bases contained in the BA.In the hydrothermal process,the addition of BA significantly increased the content of pyrrole nitrogen in the adsorbent.In the activation process,pyrrole nitrogen gradually changed into pyridine nitrogen and graphite nitrogen.Increased BA addition result in a higher specific surface area and microporosity of the adsorbent.The CO_(2)adsorption performance test proved that the CGFS-50%-CA sample has the strongest CO_(2)adsorption capacity at low temperature,up to 15.59 cm^(3)/g,which is mainly through physical adsorption,and the CGFS-10%-CA sample has the strongest CO_(2)adsorption capacity at high temperature,up to 7.31 cm^(3)/g,which is mainly through chemical adsorption.CO_(2)uptake of the CGFS-10%-CA sample was well maintained after 10 cycles,with regeneration efficiencies above 99%.The results indicate that the novel adsorbents with coexistence of physical and chemical adsorption have great potential for CO_(2)adsorption applications.
基金supported by the National Key Research and Development Program of China(No.2022YFC3701103)the National Natural Science Foundation of China(No.42222705)+1 种基金the Youth Innovation Promotion Association CAS(No.2021354)Guangdong Foundation for Program of Science and Technology Research(No.2023B1212060049).
文摘Nitrogen-containing organic compounds(NOCs)may potentially contribute to aqueous secondary organic aerosols,yet the different formation of NOCs in aerosol particles and cloud droplets remains unclear.With the in-situ measurements performed at a mountain site(1690 m a.s.l.)in southern China,we investigated the formation of NOCs in the cloud droplets and the cloud-free particles,based on their mixing state information of NOCscontaining particles by single particle mass spectrometry.The relative abundance of NOCs in the cloud-free particles was significantly higher than those in cloud residual(cloud RES)particles.NOCs were highly correlated with carbonyl compounds(including glyoxalate and methylglyoxal)in the cloud-free particles,however,limited correlation was observed for cloud RES particles.Analysis of their mixing state and temporal variations highlights that NOCs was mainly formed from the carbonyl compounds and ammonium in the cloud-free particles,rather than in the cloud RES particles.The results support that the formation of NOCs from carbonyl compounds is facilitated in concentrated solutions in wet aerosols,rather than cloud droplets.In addition,we have identified the transport of biomass burning particles that facilitate the formation of NOCs,and that the observed NOCs is most likely contributed to the light absorption.These findings have implications for the evaluation of NOCs formation and their contribution to light absorption.
基金supported by the National Key Research and Development Program of China(Nos.2022YFD1700800 and 2023YFC3905903)the Science and Technology Project of Education Department of Jiangxi Province(No.GJJ2201103)+2 种基金the Fund of Nanchang Hangkong University(Nos.EA202201110 and EA202201065)National Undergraduate Innovation and Entrepreneurship Training Program(No.202310406023)the National Natural Science Foundation of China(No.52470149)。
文摘Covalent organic frameworks(COFs)are crystalline porous polymeric materials composed of organic monomers connected by strong covalent bonds and offer high stability,good crystallinity,a large specific surface area,and controllable structures.COFs are widely used in the fields of adsorption and separation,catalysis,photovoltaics,and drug-delivery.The structural regulation and performance optimization of COFs can be realized through the modification of ligands and the selection of linkage methods.In which,the types of linkage are closely related to the stability and performance of COFs.In this review,nitrogencontaining linkage-bonds(NCLBs)in COFs are divided into N-containing double bonds,N-containing conjugated rings and N-containing unconjugated rings.The association between structure and performance of COFs is elaborated and the synthesis methods of COFs are systematically summarized.Moreover,the structural design,theoretical prediction and machinable application of COFs are prospected.
基金support of National Natural Science Foundation of P.R.China(22308104).
文摘The influence of nitrogen-containing polycyclic aromatic hydrocarbons(NC-PAH)on the formation of carbonaceous mesophase remains enigmatic,despite extensive research on the production of carbonaceous materials from aromatic-rich oils.Molecular dynamics simulation was used to investigate the variations in pyrolysis behavior between PAH and NC-PAH based on the composition analysis.Through adjusting the content of NC-PAH,the influence of NC-PAH on the thermal stability of slurry oils(SOs)was evaluated by thermogravimetry,viscosity,coke value,and quinoline insoluble(QI).The morphology and structure of mesocarbon microbeads(MCMBs)prepared with SOs were measured by a polarized-light microscope,SEM,XRD,and Raman.Simulation results indicate that NC-PAH possesses much higher reactivity and tends to produce highly condensed solid and coke products.It corresponds to the QI and high viscosity in thermal stability experiments.Therefore,high concentrations of NC-PAH result in nonuniform morphology and disordered structures.In a system with low viscosity and few QIs,SO,which has a low nitrogen content(475 ppm),reacts gently to produce MCMBs with a uniform particle size(10-40μm)and an excellent spherical shape.As NC-PAH content decreases,the crystalline size of graphitization elevates,as evidenced by parallel layers(10.472-11.764)and stack height(3.269-3.701 nm).The graphitization degree becomes worse and nonuniform with the increase of the content of NC-PAH,and the best is 20.58%evaluated by Raman spectra area ratio(AG/Aall).Overall,this work suggests a nitrogen content reference and a controlling technology of nitrogen for the preparation of superior MCMB.
基金Project supported by the Pilot Project of Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-G-009)the National Natural Science Foundation of China (No. 20577067, 30230010).
文摘Many nitrogen-containing aromatic compounds （NACs）, such as nitrobenzene （NB）, 4-nitrophenol （4-NP）, aniline （AN）, and 2,4-dinitrophenol （2,4-DNP）, are environmentally hazardous, and their removal from contaminated water is one of the main challenges facing wastewater treatment plants. In this study, synthetic wastewater containing NB, 4-NP, 2,4-DNP, and AN at concentrations ranging from 50 to 180 mg/L was fed into a sequencing batch reactor （SBR）. Analyses of the SBR system indicated that it simultaneously removed more than 99% of the NACs at loading rates of 0.36 kg NB/（m^3·d）, 0.3 kg 4-NP/（m^3·d）, 0.25 kg AN/（m^3·d）, and 0.1 kg 2,4-DNP/（m^3·d）. Bacterial groups of Bacteriodetes, Candidate division TM7, α-Proteobacteria, and β-Proteobacteria were dominant in the clone libraries of 16S rRNA genes retrieved from the microbial communities in the SBR system. ＂Cycle tests＂ designed to alter feeding and aeration parameters of the SBR system demonstrated that the resident microbial biome of the SBR system responded rapidly to changing conditions. Consumption of O2 was concomitant with the apparent mineralization of NACs. Aromatic ring-cleaving dioxygenase activities suggested that （1） AN and NB were degraded via catechol 2,3-dioxygenase; （2） 4-NP was degraded via 1,2,4-benzentriol 1,2-dioxygenase; and （3） 2,4-DNP was degraded via an unresolved pathway.
基金Supported by the Key Project of Joint Fund from National Natural Science Foundation of China and the Government of Xinjiang Uygur Autonomous Region(U1503293)the National Key Research and Development Program of China(2018YFB0604602)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Soluble portions(SPs) 1-4(SP1-SP4) were afforded from sequentially dissolution and alkanolyses of Baiyinhua lignite(BL) in cyclohexane,CH3OH,CH3CH2OH,and(CH3)2CHOH at 300℃.They were analyzed with a gas chromatograph/mass spectrometer and quadrupole exactive orbitrap mass spectrometer(QEOTMS) with an atmosphere pressure chemical ionization source in positive-ion mode,while BL was characterized with an X-ray photoelectron spectrometer(XRPES).The results show that the yields of SP2 and SP3 are much higher than those of SP1 and SP4,and the total SP yield is ca.39.0%.According to the analysis with XRPES,pyrrolic nitrogen atoms are the most abundant nitrogen existing forms in BL.Thousands of nitrogen-containing aromatics(NCAs) were resolved with QEOTMS and their molecular masses are mainly in the range of 200-450 u.The main NCAs are N1O1 and N1O2 class species with double bond equivalent values of 4-18 and carbon numbers of 7-30.The nitrogen atoms appear in pyridine s,quinolines,benzoquinolines or acridine,and dibenzoquinolines or naphthoquinolines,while the oxygen atoms exist in methoxy and furan rings.
基金supported by the National Natural Science Foundation of China(Nos.31970107 and 51508068)the Fundamental Research Funds for the Central Universities(No.DUT19JC17)the Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.QAK201943)。
文摘Nitrogen-containing organic pollutants(quinoline,pyridine and indole)are widely distributed in coking wastewater,and bioaugmentation with specific microorganisms may enhance the removal of these recalcitrant pollutants.The bioaugmented system(group B)was constructed through inoculation of two aromatics-degrading bacteria,Comamonas sp.Z1(quinoline degrader)and Acinetobacter sp.JW(indole degrader),into the activated sludge for treatment of quinoline,indole and pyridine,and the non-bioaugmented activated sludge was used as the control(group C).Both groups maintained high efficiencies(>94%)for removal of nitrogen-containing organic pollutants and chemical oxygen demand(COD)during the long-term operation,and group B was highly effective at the starting period and the operation stage fed with raw wastewater.High-throughput sequencing analysis indicated that nitrogen-containing organic pollutants could shape the microbial community structure,and communities of bioaugmented group B were clearly separated from those of non-bioaugmented group C as observed in non-metric multidimensional scaling(NMDS)plot.Although the inoculants did not remain their dominance in group B,bioaugmentation could induce the formation of effective microbial community,and the indigenous microbes might play the key role in removal of nitrogen-containing organic pollutants,including Dokdonella,Comamonas and Pseudoxanthomonas.Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt)analysis suggested that bioaugmentation could facilitate the enrichment of functional genes related to xenobiotics biodegradation and metabolism,probably leading to the improved performance in group B.This study indicated that bioaugmentation could promote the removal of nitrogen-containing organic pollutants,which should be an effective strategy for wastewater treatment.
基金supported by the Program for New Century Excellent Talents in University (NCET-04-0270)National Basic Research Program of China (2011CB201301)
文摘The adsorptive denitrogenation from fuels over three metal-organic frameworks(MIL-96(Al),MIL-53(Al)and MIL-101(Cr))was studied by batch adsorption experiments.Four nitrogen-containing compounds(NCCs)pyridine,pyrrole,quinoline and indole were used as model NCCs in fuels to study the adsorption mechanism.The physicochemical properties of the adsorbents were characterized by XRD,N2physical adsorption,FT-IR spectrum and Hammett indicator method.The metal-organic frameworks(MOFs),especially the MIL-101(Cr)containing Lewis acid sites as well as high specific surface area,can adsorb large quantities of NCCs from fuels.In addition,the adsorptive capacity over MIL-101(Cr)will be different for NCCs with different basicity.The stronger basicity of the NCC is,the more it can be absorbed over MIL-101(Cr).Furthermore,pore size and shape also affect the adsorption capacity for a given adsorbate,which can be proved by the adsorption over MIL-53(Al)and MIL-96(Al).The pseudo-second-order kinetic model and Langmuir equation can be used to describe kinetics and thermodynamics of the adsorption process,respectively.Finally,the regeneration of the used adsorbent has been conducted successfully by just washing it with ethanol.
基金supported by National Basic Research Program of China (973 Program, Grant No. 2006CB605005)Shanghai Municipal Committee of Science and Technology of china(Grant No. 005207019,Grant No. 08520708000)
文摘Stress corrosion cracking （SCC） of stainless steels and Ni-based alloys in high temperature water coolant is one of the key problems affecting the safe operation of nuclear power plants （NPPs）. The nitrogen-added stainless steel is a kind of possible candidate materials for mitigating SCC since reducing the carbon content and adding nitrogen to offset the loss in strength caused by the decrease in carbon content can mitigate the problem of sensitization. However, the reports of SCC of nitrogen-added stainless steels in high temperature water are few available. The effects of applied potential and sensitization treatment on the SCC of a newly developed nitrogen-containing stainless steel （SS） 316LN in high temperature water doped with chloride at 250 ℃ were studied by using slow strain rate tests （SSRTs）. The SSRT results are compared with our data previously published for 316 SS without nitrogen and 304NG SS with nitrogen, and the possible mechanism affecting the SCC behaviors of the studied steels is also discussed based on SSRT and microstucture analysis results. The susceptibility to cracking of 316LN SS normally increases with increasing potential. The susceptibility to SCC of 316LN SS was less than that of 316 SS and 304NG SS. Sensitization treatment at 700℃ for 30 h showed little effect on the S CC of 316LN S S and significant effect on the S CC of 316 S S. The predominant cracking mode for the 316LN S S in both annealed state and the state after the sensitization treatment was transgranular. The presented conditions of mitigating stress corrosion cracking are some useful information for the safe use of 316LN SS in NPPs.
文摘A new nitrogen-containing epoxy resin (XT resin) was synthesized from chain extension of xylenephenolformaldehyde resin (XPF) and triglycidyl isocyanurate (TGIC) in the presence of base catalyst. FT-IR and H-NMR analysis confirmed the chemical structure of XT resin. It was 1 cured with dicyandiamide (DICY) and diaminodiphenyl sulfone (DDS). Dynamic mechanical analysis (DMA) results showed that the introduction of triazine ring provides epoxy polymer with good thermal stability. Furthermore, high char yields at 800℃ in thermogravimetric (TGA) analysis indicated that XT resin had potential flame retardance.
基金supported by the"973"project envisaged in the State Key Basic R&D Program(2006CB202505).
文摘The DFT-based （density fimctional theory） ab initio quantum mechanical methods have been applied to study the basicity of the nitrogen-containing compounds in petroleum. The results have indicated that there is a distinct relationship between the protonation energy of nitrogen-containing compounds and their basicity. The more negative the protonation energy, the stronger the basicity is. It has been also found that aliphatic amines are more basic than pyridines or aromatic amines, and all these compounds are more basic than pyrroles. The addition of the aromatic rings can influence the basicity of anilines, while the 5- and 6-membered heterocyclic compounds function differently. The solvent properties may affect the basicity of these nitrogen-containing compounds.
文摘To elucidate the effects of Fe_(2)O_(3) on nitrogen transformation during sludge pyrolysis,thermogravimetry coupled with mass spectrometry(TG-MS)was used to investigate the influences of Fe_(2)O_(3) on the pyrolysis characteristics and the release of important gaseous NO_(x) precursors such as HCN and NH_(3) during pyrolysis of three typical amino acids in urban sludge.The results show that after Fe_(2)O_(3) addition,the total weight loss rate of the three amino acids and the initial decomposition temperature of proline are reduced.The release amounts of NH_(3),HCN,CH_(3)CN,and HNCO from these three representative amino acids—glumatic,arginine,and proline,decrease in the order of arginine,glutamic,proline.The generation of Fe-N complexes,reduces the generation of NH_(3),HCN,CH_(3)CN,and HNCO while the catalysis effects of Fe_(2)O_(3) on the formation of H and H2 play a promoting role in the generation of NH_(3),HCN,CH_(3)CN,and HNCO.The results would provide an experimental and theoretical basis for subsequent research on the NOx precursor formation mechanisms during pyrolysis or combustion of Fe-containing sludge or sludge with additives containing Fe.
基金supported by the National Natural Science Foundation of China(Nos.42371094,41907253)partially supported by the Interdisciplinary Cultivation Program of Xidian University(No.21103240005)the Postdoctoral Fellowship Program of CPSF(No.GZB20240589)。
文摘INTRODUCTION.On May 1st,2024,around 2:10 a.m.,a catastrophic collapse occurred along the Meilong Expressway near Meizhou City,Guangdong Province,China,at coordinates 24°29′24″N and 116°40′25″E.This collapse resulted in a pavement failure of approximately 17.9 m in length and covering an area of about 184.3 m^(2)(Chinanews,2024).
基金supported by the National Natural Science Foundation of China(Nos.52374119,42477142 and 42277154)Natural Science Foundation of Jiangsu Province(No.BK20242059)+1 种基金the open fund of State Key Laboratory of Hydraulics and Mountain River Engineering(No.SKHL2306)the High-level Talent Introduction Project of Changzhou University(No.ZMF24020037)。
文摘Rockburst precursors are critical for disaster warning,yet the complexity of rockburst has hindered the identification of a unified precursor.Furthermore,the influence of loading rates(LRs)on acoustic emission(AE)precursors in different rock types remains poorly understood.This study investigates the AE characteristics and early warning times of rockburst in slate and mica-schist under four LRs(0.05,0.15,0.25,and 0.5 MPa/s)using true triaxial unloading tests.The micro-crack state of the samples was evaluated using entropy,while critical slowing down(CSD)theory was applied to interpret AE precursors.The results reveal that as the LR increases,the rockburst stress of both rocks initially rises and then declines,with mica-schist exhibiting more severe damage and a higher dominance of tensile cracks.Notably,identifying rockburst precursors in mica-schist proved more challenging compared to slate.Among the methods tested,AE amplitude variance outperformed entropy in precursor identification.Additionally,the rockburst early warning time was found to be negatively correlated with the LR,with mica-schist consistently showing shorter warning times than slate.The CSD-derived precursor,due to its enhanced sensitivity,is recommended for early warning systems.These findings provide new insights into the role of LRs in rockburst dynamics and offer practical guidance for improving precursor identification and disaster mitigation strategies.
文摘Polyacrylonitrile (PAN) precursor is a core precursor for the preparation of high-performance carbon fibers. Its unique chemical structure and physical properties directly contributes to the microstructure and mechanical properties of carbon fibers, and therefore affect the overall performance of pultruded composites. This study systematically investigated the influence of PAN precursor properties on the degree of graphitization, surface morphology and mechanical properties of carbon fibers by regulating the molecular weight distribution, stretching ratio and impurity content of PAN precursor, and analyzed the mechanism of action of carbon fiber properties on the interfacial bonding strength and tensile/ bending properties of composites in combination with the pultrusion process. The results showed that when the filament stretchability was increased to 4.5 times, the axial orientation of carbon fibers increased by 18% and the tensile strength reached 520 MPa;Filaments with impurity content below 0.3% increase carbon fiber yield by 5.2% and interlaminar shear strength of composites by 23%. This study provides a theoretical basis for raw material screening and process optimization of high-performance carbon fibers and their composites.
文摘The increasing sophistication of cyberattacks,coupled with the limitations of rule-based detection systems,underscores the urgent need for proactive and intelligent cybersecurity solutions.Traditional intrusion detection systems often struggle with detecting early-stage threats,particularly in dynamic environments such as IoT,SDNs,and cloud infrastructures.These systems are hindered by high false positive rates,poor adaptability to evolving threats,and reliance on large labeled datasets.To address these challenges,this paper introduces CyberGuard-X,an AI-driven framework designed to identify attack precursors—subtle indicators of malicious intent—before full-scale intrusions occur.CyberGuard-X integrates anomaly detection,time-series analysis,and multi-stage classification within a scalable architecture.The model leverages deep learning techniques such as autoencoders,LSTM networks,and Transformer layers,supported by semi-supervised learning to enhance detection of zero-day and rare threats.Extensive experiments on benchmark datasets(CICIDS2017,CSE-CIC-IDS2018,and UNSW-NB15)demonstrate strong results,including 96.1%accuracy,94.7%precision,and 95.3%recall,while achieving a zero-day detection rate of 84.5%.With an inference time of 12.8 ms and 34.5%latency reduction,the model supports real-time deployment in resource-constrained environments.CyberGuard-X not only surpasses baseline models like LSTM and Random Forest but also enhances proactive threat mitigation across diverse network settings.
基金supported by the Key Program of the National Natural Science Foundation of China(No.52032003)the Major Program of the National Natural Science Foundation of China(No.52293372)+2 种基金the National Natural Science Foundation of China(No.51972082)the National Natural Science Foundation of China(No.52102093)the National Natural Science Foundation of China(No.52172041)and the science foundation of national key laboratory of science and technology on advanced composites in special environments.
文摘The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields(<40 wt.%)due to the challenges in integrating significant amounts of boron,which hampers their conversion into boride-based ultrahigh temperature ceramics.To tackle these challenges,a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors(with different Hf/Si ratios)have been developed.These novel precursors are featured with stable molec-ular structure and high ceramic yield which were successfully created through a novel one-pot polymer-ization process.They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O,Si-O-Hf,Si-O-B,and B-O-Hf which have untapped advantages including uniform component dispersion,and excellent fluidity.The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.%at 1500℃,and their Hf content exceeded 50 wt.%.Of particular interest,the pyrolyzed product HfB_(2)-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2,consist of nanopowders in the 40-60 nm range with a density of 5.23 g cm^(−3).Remarkably,this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environ-ments at 2500℃,showing near-zero ablation with a linear ablation rate of just 2.5×10^(−4) mm s^(−1).Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO_(2) and HfO_(2)-SiO_(2) oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance.The inno-vative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics.This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems,partic-ularly in the construction of hypersonic vehicles,where ultrahigh temperature resilience is crucial.
基金Projects(51934007,12072363,52004268) supported by the National Natural Science Foundation of ChinaProject(22KJD440002) supported by the Natural Science Fund for Colleges and Universities in Jiangsu Province,China。
文摘This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic response mechanism of coal energy evolution is examined, and the energy instability criterion is established. The validity of the instability criterion is explored from the standpoint of damage progression. The results demonstrate that the energy conversion mechanism undergoes a fundamental alternation under impact disturbance. Moreover, the energy release rate as well as the energy dissipation rate undergo comparable changes across distinct levels of impact disturbance. The distinction between the energy release rate and the energy dissipation rate (DRD) increases as coal mass deformation grows. Prior to coal facing instability and failure, the DRD experienced an inflection point followed by a sharp decrease. In conjunction with the discussion on the damage evolution, the physical and mechanical significance of DRD remains clear, which can essentially describe the whole impact loading process. The phenomenon that the inflection point appears and DRD subsequently suddenly decreases can be employed as the energy criterion prior to the failure of instability. Furthermore, this paper provides significant reference for the prediction of dynamic instability of coal under dynamic disturbance.
基金supported by the National Research Foundation of Korea(NRF)grants funded by the Korea government(MSIT)(Nos.RS-2024–00351052 and RS-2024–00450561)。
文摘Metal composites produced through the liquid metal dealloying(LMD)process feature an advanced matrix-matrix composite structure,where two metallic materials form a continuous,three-dimensional interconnected network.This study investigates the effects of Ti Cu precursor compositions on dealloying behavior and microstructural evolution in liquid Mg,using Ti_(50)Cu_(50)and Ti_(30)Cu_(70)precursors.The initial microstructure of the precursor significantly influences dealloying kinetics and phase transitions.The single-phase Ti_(50)Cu_(50)precursor exhibits a faster initial dealloying rate due to its homogeneous structure,yet complete dealloying requires 90 min.In contrast,the dualphase Ti_(30)Cu_(70)precursor achieves complete dealloying in 30 min,demonstrating the impact of a higher Cu concentration on accelerating the process kinetics.Additionally,the study explores the coarsening behavior and hardness variations during the LMD process,along with the microstructural characteristics of Mg-Ti composites fabricated from these two precursors.The findings highlight the critical role of precursor composition in tailoring the microstructure and properties of Mg-Ti composites produced through the LMD process,demonstrating its potential for advanced composite material manufacturing.
基金funded by Project Better Plastics—Plastics in a Circular Economy—PPS4(Circularity by Alternative Feedstocks)Grant agreement ID:POCI-01-0247-FEDER-046091RR was funded by FCT through the PhD grant with reference UI/BD/154446/2022.
文摘The growing environmental awareness,the search for alternatives to fossil resources,and the goal of achieving a circular economy have all contributed to the increasing valorization of biowaste to produce bio-based polymers and other high-value products.Among the various biowaste materials,lignin has gained significant attention due to its high aromatic carbon content,low cost,and abundance.Lignin is predominantly sourced as a byproduct from the paper industry,available in large quantities from hardwood and softwood,with variations in chemical structure and susceptibility to hydrolysis.This study focuses on softwood lignin obtained through the LignoForce^(TM) technology,comparing the thermal and chemical characteristics,and stability,of a recently produced batch with that of a batch that has been stored for four years.Additionally,the development of lignin-based thermoplastic polymer mixtures using Polyethylene Terephthalate Glycol(PET-G)and a blend of Polycarbonate and Acrylonitrile-Butadiene-Styrene(PC/ABS)with high lignin content(50–60 wt%)is explored,as well as the production of filaments for carbon fiber production.For this purpose,following melt mixing,the lignin-based mixtures were spun into filaments,which were subsequently subjected to thermal stabilization in an oxidative atmosphere.The lignin phase was well distributed in the PET-Gmatrix and the twomaterials presented a good interface,which further improved after thermal treatment under an oxidative atmosphere.After thermal treatment an increase in tensile modulus,tensile strength,and elongation at break of approximately 160%,200%,and 100%,respectively,was observed,confirming the good interface established,and consistent with structural changes such as cross-linking.Conversely,the PC/ABS blend did not form a good interface with the lignin domains after melt mixing.Although the interactions improved after thermal treatment,the tensile strength and elongation at break decreased by approximately 30%,while themodulus increased by approximately 20%.Overall,the good processability of the lignin/polymer mixtures into filaments,and their physical,chemical,and mechanical characterization before and after thermal oxidation are good indicators of the potential as precursors for carbon fiber production.
