By a polarized light optical microscopy with a hot stage, liquid phase nuclear magnetic resonance 13 C NMR and 1 H NMR, X ray diffractometry and scanning electron microscopy (SEM), the factors that affect the formatio...By a polarized light optical microscopy with a hot stage, liquid phase nuclear magnetic resonance 13 C NMR and 1 H NMR, X ray diffractometry and scanning electron microscopy (SEM), the factors that affect the formation of mesophase in C/C composites, such as pressure, quinoline insolubles (QI) and heterocylic compounds, were analyzed. Further, the graphitizability of the resultant carbon was discussed. The results indicate that to some degree, QI contents accelerate the formation of mesophase at atmospheric pressure; while at high pressure, the coalescence and growth of mesophase spherules are impeded and the resultant coke produced from higher QI content pitch is harder to be graphitized. This is in agreement with the transfer of microstructure from domain anisotropy to fine grained mosaics.展开更多
Ethylene tar is a prospective precursor for preparing carbonaceous materials,which is regarded as a representative soft carbon material after carbonization.However,the introduction of oxygen can influence the morpholo...Ethylene tar is a prospective precursor for preparing carbonaceous materials,which is regarded as a representative soft carbon material after carbonization.However,the introduction of oxygen can influence the morphology of the final carbonaceous materials.For the introduction of oxygen,dealkylation and dehydrogenation will be promoted and the molecules can be linked more effectively.For the subsequent carbonization,the biphenyl structures caused by the deoxygenation via the elimination of CO_(2),as well as the reserved aromatic ether bonds,can facilitate the strong cross-linking,which will restrain the movement of the carbon layers and the formation of the graphitic structures.After the graphitization treatment at 2800℃,the oxidized pitch can lead to short-range ordered and long-range unordered structures,while the sample without oxidation can result in long-range ordered graphitic structures.It can be proved that a simple oxidation-carbonization treatment can transform ethylene tar into hard carbon structures.展开更多
In the present work, three medium softening point coal tar pitches were used for comparative thermal stability and under-storage stability investigation. Powders of the pitches were found to be different under storage...In the present work, three medium softening point coal tar pitches were used for comparative thermal stability and under-storage stability investigation. Powders of the pitches were found to be different under storage： one of the pitches was caked and slumped after 7-day or longer storage. For thermal stability investigation the soft temperature treatment （265℃） of coal tar pitches was used. Detailed study of initial and treated pitches was carried out. Experimental results demonstrated that LMW-HC （high low-molecular-weight hydrocarbons） and oxygen content influence pitch quality characteristics in a negative way under long-term storage and lead to highest properties change after thermal stability treatment.展开更多
The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies ...The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies of MnO_(2)@C materials can be controlled by controlling the dosages of WS-CTPs and KMnO4.Meanwhile,it is aware that MnO_(2)exists in the MnO_(2)@C materials in an amorphous state.Compared with MnO_(2),MnO_(2)@C materials output a remarkable improvement in electrochemical performance.For instance,MnO_(2)@C-0.3 shows the storage capacity at 965.7 mA h g^(−1)after 300 cycles at a current density of 0.1 A g^(−1).In addition,after 600 cycles at a current density of 1.0 A g^(−1),the storage capacity of MnO_(2)@C-0.3 still keeps 450.3 mA h g^(−1),indicating that MnO_(2)@C-0.3 owns tremendous cycle stability at a high current density.In view of the fact that the coal tar pitches possess great cost advantages,the strategy of using WS-CTPs as a carbon source to cover the metal oxides is a competitive way to expand the application of metal oxides in the fabrication of electrodes of LIBs.展开更多
The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D i...The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.展开更多
Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000-60000 tons of low temperature coal output in...Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000-60000 tons of low temperature coal output in inner Mongolia region, China, which has high toxicity and high polluting. To make the low temperature coal be applicable for road constructions, the formaldehyde is used as cross linking agent, the concentrated sulfuric acid is used as catalyst, and the chemical modification of low temperature coal tar pitch in Inner Mongolia region is investigated. The road performance （softening point, penetration and ductility） of modified low temperature coal are tested. Results shown that the road performance of modified low temperature coal is increased significantly. Modification mechanism of low temperature coal is studied by Scanning Electron Microscopy and other analytical tools. Results show that, in the modified low temperature coal, resin content increases and the resin fiber diameter becomes larger with the increasing of formaldehyde content.展开更多
Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation ac...Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation activity were studied.Several different carbon materi-als were produced from them by oxida-tion in air(350℃,300 mL/min)fol-lowed by carbonization(1000℃ in Ar),and the effect of the cross-linked structure on their structure and sodium storage properties was investigated.The results showed that the two pitch fractions were obviously different after the air oxidation.The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization.As a result,a disordered hard carbon with more defects was formed,which improved the electrochemical performance.Therefore,the carbon materials derived from TS(O-TS-1000)had an obvious disordered structure and a larger layer spacing,giving them better sodium storage perform-ance than those derived from the TI-PS fraction(O-TI-PS-1000).The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g,which was 1.67 times higher than that of O-TI-PS-1000(150 mAh/g).展开更多
Reducing the amount of aluminum chloride needed for the catalytic preparation of high quality mesophase and carbon materials is important and we have found that using terephthalic acid(PTA)as a co-catalyst serves this...Reducing the amount of aluminum chloride needed for the catalytic preparation of high quality mesophase and carbon materials is important and we have found that using terephthalic acid(PTA)as a co-catalyst serves this purpose.By adding 3%(mass fraction)AlCl_(3)and 0.9%(mass fraction)PTA to the coal tar pitch,approximately 90%mesophase was synthesized.The product(M-3-0.9)had a high stacking order(L_(c)=3.1 nm,n=10.14)and aromaticity(0.942).By adding PTA,a larger anisotropy content was produced using a smaller amount of AlCl_(3).The PTA participated in the polycondensation reaction through its own benzene ring structure to increase the catalytic activity.However,when its content was higher than 1.5%,the number of oxygen-containing groups in the product increased which was unfavorable for the aromatic lamellar stacking and gave rise to more isotropic structures.The work opens up a new way to prepare mesophase by a catalytic method.展开更多
Mesophase pitch carbon fibers have an ultra-high modulus and thermal conductivity that are unmatched by other carbon fibers,making it irreplaceable in many fields.However,due to the high temperature dependence of the ...Mesophase pitch carbon fibers have an ultra-high modulus and thermal conductivity that are unmatched by other carbon fibers,making it irreplaceable in many fields.However,due to the high temperature dependence of the viscosity of the melted pitch and the poor mechanical properties of pitch fibers,it is difficult to reduce the fiber diameter when using continuous spinning.We used the Mathworks Matlab software to optimize the mesophase pitch melt spinning model and to simulate the effects of spinning temperature,mass flow rate,winder speed,and quenching air temperature near the spinneret on the maximum shear rate during drawing.Simulation results demonstrate that applying gradient cooling to the melt upon exiting the spinneret significantly reduces the maximum shear rate and extends the drawing zone,thereby promoting the spinning stability and helping reduce the fiber diameter.In the experiment,instead of quenching in air,we applied gradient cooling to the melt,whose temperature decreased according to the equation Ta=298+278exp(−11.4z),where Ta is the final air temperature in Kelvin,and z is the distance from the spinneret in meters.It was found the gradient cooling greatly improved the draw-down ratio,reducing the average diameter of the pitch fibers from 20.8 to 13.1μm,along with improved process stability.The experimental results are in excellent agreement with the predictions.At the same time,the tensile strength of the 1150°C carbonized fibers increased from 0.6 to 1.1 GPa.Although the degree of orientation of the fibers decreased slightly,the tight bonding between microcrystals,the suppression of splitting,and the smaller diameter improved the mechanical properties of carbon fibers.This study provides an effective method for reducing the fiber diameter while improving continuity.展开更多
Pitch is a complex mixture of polycyclic aromatic hydrocarbons and their non-metal derivatives that has a high carbon content.Using pitch as a precursor for carbon materials in alkali metal ion(Li^(+)/Na^(+)/K^(+))bat...Pitch is a complex mixture of polycyclic aromatic hydrocarbons and their non-metal derivatives that has a high carbon content.Using pitch as a precursor for carbon materials in alkali metal ion(Li^(+)/Na^(+)/K^(+))batteries has become of great interest.However,its direct pyrolysis often leads to microstructures with a high orientation and small interlayer spacing due to uncontrolled liquid-phase carbonization,resulting in subpar electrochemical performance.It is therefore important to control the microstructures of pitch-derived carbon materials in order to improve their electrochemical properties.We evaluate the latest progress in the development of these materials using various microstructural engineering approaches,highlighting their use in metal-ion batteries and supercapacitors.The advantages and limitations of pitch molecules and their carbon derivatives are outlined,together with strategies for their modification in order to improve their properties for specific applications.Future research possibilities for structure optimization,scalable production,and waste pitch recycling are also considered.展开更多
Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects ...Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects on its surface cause irreversible electrolyte consump-tion and an uneven solid electrolyte interphase film.An advanced molecular engineering strategy to coat hard carbon with polycyclic aromatic mo-lecules is reported.Specifically,polystyrene-based carbon microspheres(CSs)were first synthesized and then coated with polycyclic aromatic mo-lecules derived from coal tar pitch by spray-drying and followed by oxidation.Compared to the traditional CVD coating meth-od,this molecular framework strategy has been shown to reduce the number of defects on the surface of CSs without sacrifi-cing internal storage sites and suppressing transport kinetics in hosting the sodium ions.Besides the lower surface defect con-centration,the synthesized hybrid carbon microspheres(HCSs)have a larger grain size and more abundant closed pores,and have a higher reversible sodium storage capacity.A HCS-P-60%electrode has a capacity of 332.3 mAh g^(-1)with an initial Cou-lombic efficiency of 88.5%.It also has a superior rate performance of 246.6 mAh g^(-1)at 2 C and a 95.2%capacity retention after 100 cycles at 0.2 C.This work offers new insights into designing high-performance hard carbon microsphere anodes,advan-cing the commercialization of sodium-ion batteries.展开更多
To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave att...To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave attenuation in random waves.First,the flow velocity distribution characteristic of the pitching flap at typical times was summarized.Then,the effects of random wave and flap parameters on the flap’s significant pitching angle amplitude θ_(s) and hydrodynamic coefficients were investigated.The results reveal that θ_(s) and wave reflection coefficient K_(r) values increase with increasing significant wave height Hs,random wave steepnessλs,and flap relative height.As Hs andλs increase,the wave transmission coefficient K_(t) increases while the wave dissipation coefficient K_(d) decreases.Additionally,K_(t) decreases with increasing flap relative height.With increasing equivalent damping coefficient ratio,θ_(s) and K_(t) decrease,while K_(r) and K_(d) increase.The relationships betweenλs and flap relative height on the one hand andθ_(s),K_(r),K_(t),and K_(d) in random waves on the other hand are compared to those in regular waves.Based on the equal incident wave energy and the equal incident wave energy flux,the pitching flap performs better in the wave attenuation capability under random waves than in regular waves.Finally,the dimensionless parameters with respect to random wave and flap were used to derive the K_(r) and K_(t) for-mulae,which were validated with the related data.展开更多
The determination of musical pitch has been a major concern of music theory,East and West,in all climes and cultures,throughout the ages.This paper discusses the intricacies of pitch determination from historic,geogra...The determination of musical pitch has been a major concern of music theory,East and West,in all climes and cultures,throughout the ages.This paper discusses the intricacies of pitch determination from historic,geographic,and scientific perspectives.Its standardization nowadays has permitted the manufacture and tuning of musical instruments on a universal scale.展开更多
This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerge...This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerged cylindrical buoy.The system is modeled as a two-layer fluid with infinite horizontal extent and finite depth.The radiation problem is analyzed in the context of linear water waves.The fluid domain is divided into outer and inner zones,and mathematical solutions for the pitch radiating potential are derived for the corresponding boundary valve problem in these zones using the separation of variables approach.Using the matching eigenfunction expansion method,the unknown coefficients in the analytical expression of the radiation potentials are evaluated.The resulting radiation potential is then used to compute the added mass and damping coefficients.Several numerical results for the added mass and damping coefficients are investigated for numerous parameters,particularly the effects of the cylinder radius,the draft of the submerged cylinder,and the density proportion between the two fluid layers across different frequency ranges.The major findings are presented and discussed.展开更多
Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecul...Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecular M/P-helical nanoribbons(HNs) assembled from the chiral L/D-glutamate-based amphiphiles(L/D-Glu C16) and Cu(Ⅱ) ions, with their helical screw pitches adjusted from 217 nm to 104 nm through the facile regulation of their water/organic solvent assembly environment. They were then used as ideal models to reveal the chiral morphology-enantioselectivity relationship by catalyzing the asymmetric Diels-Alder reaction. Better enantioselectivity was achieved with more twist morphology. Experimental evidences of stronger chiral transfer effect from the supramolecular HNs with more twist to the aza-chalcone as reactant were obtained to understand such dependence. Our study demonstrates a new perspective for designing supramolecular catalysts with higher enantioselectivity.展开更多
The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-do...The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-domain impulse theory for subcavitating flow(σ=8.0)and cavitating flow(σ=3.0),and to quantify the distinct impact of individual vortex structures on the transient lift to appreciate the interplay among cavitation,flow structures,and vortex dynamics.The motion of the hydrofoil is set to pitch up clockwise with an almost constant rate from 0°to 15°and then back to 0°,for the Reynolds number,7.5×105,and the frequency,0.2 Hz,respectively.The results reveal that the presence of cavities delays the migration of the laminar separation bubble(LSB)from the trailing edge(TE)to the leading edge(LE),consequently postponing the hysteresis in the inflection of lift coefficients.The eventual stall under the sub-cavitation regime is the result of LSB bursting.While the instabilities within the leading-edge LSB induce the convection of cavitation-dominated vortices under the cavitation regime instead.Having validated the lift coefficients on the hydrofoil through the finite-domain impulse theory using the standard force expression,the Lamb vector integral emerges as the main contribution to the generation of unsteady lift.Moreover,the typical vortices’contributions to the transient lift during dynamic stall are accurately quantified.The analysis indicates that the clockwise leading-edge vortex(−LEV)contributes positively,while the counterclockwise trailing-edge vortex(+TEV)contributes negatively.The negative influence becomes particularly pronounced after reaching the peak of total lift,as the shedding of the concentrated wake vortex precipitates a sharp decline due to a predominant negative lift contribution from the TEV region.Generally,the vortices’contribution is relatively modest in sub-cavitating flow,but it is notably more significant in the context of incipient cavitating flow.展开更多
The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of th...The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of the pitch bearing itself compared with ordinary small bearings and the harsh working environment,the pitch bearing is prone to faults such as cracking and deformation.In severe cases,it will lead to overall damage to the pitch bearing,causing the blade to fall from a high altitude and even injuring personnel.Therefore,this paper conducts a patent analysis and technical decomposition of the deformation monitoring device for pitch bearings,analyzes and summarizes the development process of existing deformation monitoring devices for pitch bearings.Combined with the TRIZ evolution theory and based on the S-curve,it is concluded that the current deformation monitoring device for pitch bearings is in the transitional stage between the infant period and the growth period,and discusses the possible subsequent evolution directions.Through reviewing relevant literature,it is found that inner ring cracks first appear near the upper and lower surfaces of the bolt holes in the inner ring of the pitch bearing.To this end,a new type of deformation monitoring device for pitch bearings is designed.The fiber optic displacement sensor is used for qualitative monitoring of initial cracks near the surface of the bolt holes in the inner ring of the pitch bearing.After cracks are detected,the eddy current sensor is used for quantitative monitoring of whether there are extended cracks between the cracked bolt holes and adjacent bolt holes.Finally,the work done in this paper is summarized and prospected.展开更多
High-salinity wastewater treatment has always been a challenging issue.In this study,coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets(CPN-9)us...High-salinity wastewater treatment has always been a challenging issue.In this study,coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets(CPN-9)using a salt-template method.The desalination performance of CPN-9 was evaluated using flow-electrode capacitive deionization technology.The results showed that CPN-9 has a high specific surface area(466.34 m^(2)/g),a rich pore structure(micro-/meso-pore volume was 0.28),excellent rheological properties,and hydrophilicity(contact angle of 20.44°),thereby accelerating ion transport.Electrochemical results indicated that CPN-9 exhibits a significant double-layer ion storage mechanism,with a specific capacitance of 176.66 F/g at a current density of 0.5 A/g.CPN-9 has a very low charge transfer resistance.The synergistic effect of aromatic carbon and nitrogen doping(the content of pyrrole and pyridine nitrogen was 36.40%and 35.83%,respectively)in coal tar pitch accelerates electron transfer in CPN-9.The good ion diffusion performance and low impedance of CPN-9 accelerate the ion exchange rate,resulting in outstanding desalination performance.At 1.2 V and 3%mass loading,with a CPN-9 to conductive carbon black ratio of 4:1,the average desalination rate,charge efficiency,and energy consumption reached 0.039 mg/(cm^(2)·min),48.47%,and 0.012 kWh/mol,respectively.In summary,this study optimized the structure of CPN-9 from the perspective of electronic and ionic transport,enhancing its desalination performance and providing theoretical support for the deionization of high-salinity wastewater.展开更多
The controversies about the mechanism of sodium storage in hard carbon(HC)hinder its rational structural design.A series of porous HC materials using coal tar pitch show a reversible capacity of 377 mAh g^(−1) and an ...The controversies about the mechanism of sodium storage in hard carbon(HC)hinder its rational structural design.A series of porous HC materials using coal tar pitch show a reversible capacity of 377 mAh g^(−1) and an initial Coulombic efficiency(ICE)of 87%as well as excellent cycling performance.More attention is paid to exploration of the relationships between the sodium status on various storage sites at different sodiation states and the ICE by solidstate^(23)Na nuclear magnetic resonance spectroscopy.The adsorbed Na ions contribute the most to the irreversible capacity.The de-solvated Na ions entering the closed pores are reduced to Na atoms and aggregated to Na clusters.Also,this process contributes the most to the reversible capacity and is characteristic of a long plateau in the voltage profile.Intercalation is partially reversible;it is the main source of capacity for slope-type HCs but plays a minor role in the reversible capacity of plateau-type HCs.Therefore,increasing the content of the closed pores can improve the reversible plateau capacity and reducing the open mesopores of HC increases the ICE.These findings provide insights into the structural design and cost-efficient preparation of high-performance HC anode materials for advanced sodium-ion batteries.展开更多
文摘By a polarized light optical microscopy with a hot stage, liquid phase nuclear magnetic resonance 13 C NMR and 1 H NMR, X ray diffractometry and scanning electron microscopy (SEM), the factors that affect the formation of mesophase in C/C composites, such as pressure, quinoline insolubles (QI) and heterocylic compounds, were analyzed. Further, the graphitizability of the resultant carbon was discussed. The results indicate that to some degree, QI contents accelerate the formation of mesophase at atmospheric pressure; while at high pressure, the coalescence and growth of mesophase spherules are impeded and the resultant coke produced from higher QI content pitch is harder to be graphitized. This is in agreement with the transfer of microstructure from domain anisotropy to fine grained mosaics.
基金financially supported by the National Natural Science Foundation of China(22075081,52372045 and U1710252)the Fundamental Research Funds for the Central Universities(JKD01231701)+1 种基金China Postdoctoral Science Foundation(2023M731084)Shanghai Sailing Program of China(23YF1408900).
文摘Ethylene tar is a prospective precursor for preparing carbonaceous materials,which is regarded as a representative soft carbon material after carbonization.However,the introduction of oxygen can influence the morphology of the final carbonaceous materials.For the introduction of oxygen,dealkylation and dehydrogenation will be promoted and the molecules can be linked more effectively.For the subsequent carbonization,the biphenyl structures caused by the deoxygenation via the elimination of CO_(2),as well as the reserved aromatic ether bonds,can facilitate the strong cross-linking,which will restrain the movement of the carbon layers and the formation of the graphitic structures.After the graphitization treatment at 2800℃,the oxidized pitch can lead to short-range ordered and long-range unordered structures,while the sample without oxidation can result in long-range ordered graphitic structures.It can be proved that a simple oxidation-carbonization treatment can transform ethylene tar into hard carbon structures.
文摘In the present work, three medium softening point coal tar pitches were used for comparative thermal stability and under-storage stability investigation. Powders of the pitches were found to be different under storage： one of the pitches was caked and slumped after 7-day or longer storage. For thermal stability investigation the soft temperature treatment （265℃） of coal tar pitches was used. Detailed study of initial and treated pitches was carried out. Experimental results demonstrated that LMW-HC （high low-molecular-weight hydrocarbons） and oxygen content influence pitch quality characteristics in a negative way under long-term storage and lead to highest properties change after thermal stability treatment.
基金This work was supported by the University of Science and Technology Liaoning(Grant Nos.601009816-39 and 2017RC03)the Liaoning Province Education Department of China(Grant Nos.601009887-16 and LJKQZ2021126)+1 种基金the National Natural Science Foundation of China(Grant Nos.51672117 and 51672118)the Postdoctoral Foundation Project of Shenzhen Polytechnic(Grant No.6020330007K).
文摘The water soluble coal tar pitches(WS-CTPs)were successfully prepared and used to construct the MnO_(2)@C composite materials by a hydrothermal method.It is interestingly observed that the structures and morphologies of MnO_(2)@C materials can be controlled by controlling the dosages of WS-CTPs and KMnO4.Meanwhile,it is aware that MnO_(2)exists in the MnO_(2)@C materials in an amorphous state.Compared with MnO_(2),MnO_(2)@C materials output a remarkable improvement in electrochemical performance.For instance,MnO_(2)@C-0.3 shows the storage capacity at 965.7 mA h g^(−1)after 300 cycles at a current density of 0.1 A g^(−1).In addition,after 600 cycles at a current density of 1.0 A g^(−1),the storage capacity of MnO_(2)@C-0.3 still keeps 450.3 mA h g^(−1),indicating that MnO_(2)@C-0.3 owns tremendous cycle stability at a high current density.In view of the fact that the coal tar pitches possess great cost advantages,the strategy of using WS-CTPs as a carbon source to cover the metal oxides is a competitive way to expand the application of metal oxides in the fabrication of electrodes of LIBs.
基金Supported by the National Natural Science Foundation of China(22378181).
文摘The development of materials with excellent microwave absorption(MWA)and electromagnetic interference(EMI)shielding performances has currently received attention.Herein,mesophase pitch-based carbon foam(MPCF)with 3D interconnected pore structure was prepared through the high pressure pyrolysis of mesophase coal tar pitch.It is found that the 3D interconnected cellular pores of MPCF facilitate multiple reflections of electromagnetic waves,which results in the minimum reflection loss(RLmin)value of MPCF reaches-37.84 dB with the effective absorption bandwidth(EAB)of 5.44 GHz at a thickness of 2.70 mm,and the total average electromagnetic shielding effectiveness(SE_(T))under 3.00 mm thickness achieves 26.52 dB in X-band.Subsequently,MPCF is activated by KOH to obtain activated carbon foam(A-MPCF).The average SE_(T)of A-MPCF achieves 103.00 dB for abundant nanopores on the pore cell walls,which leads to a transition from the multiple reflections of electromagnetic waves on the walls to diffuse reflection.Unfortunately,the reflection coefficient(R)of A-MPCF increases from 0.78 to 0.90.To reduce the R value,Fe_(3)O_(4)/A-MPCF was fabricated via the in situ growth of nano Fe_(3)O_(4)on A-MPCF.Consequently,the R value of Fe_(3)O_(4)/A-MPCF was reduced from 0.90 to 0.74,whereas the MWA performance was only slightly decreased.This work proposes a simple strategy for simultaneously adjusting MWA and EMI shielding performances of materials.
基金Acknowledgements The research performed in this paper is supported by the National Natural Science Foundation of China （No.41372320）, National Science Foundation of Shandong Province （ZR2015EQ009）, and the Fundamental Research Funds for the Central Universities （06500036）.
文摘Rising oil price has brought huge cost pressure for low grade highway construction, and it is urgent to find alternative resources. At the same time, there are nearly 50000-60000 tons of low temperature coal output in inner Mongolia region, China, which has high toxicity and high polluting. To make the low temperature coal be applicable for road constructions, the formaldehyde is used as cross linking agent, the concentrated sulfuric acid is used as catalyst, and the chemical modification of low temperature coal tar pitch in Inner Mongolia region is investigated. The road performance （softening point, penetration and ductility） of modified low temperature coal are tested. Results shown that the road performance of modified low temperature coal is increased significantly. Modification mechanism of low temperature coal is studied by Scanning Electron Microscopy and other analytical tools. Results show that, in the modified low temperature coal, resin content increases and the resin fiber diameter becomes larger with the increasing of formaldehyde content.
文摘Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation activity were studied.Several different carbon materi-als were produced from them by oxida-tion in air(350℃,300 mL/min)fol-lowed by carbonization(1000℃ in Ar),and the effect of the cross-linked structure on their structure and sodium storage properties was investigated.The results showed that the two pitch fractions were obviously different after the air oxidation.The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization.As a result,a disordered hard carbon with more defects was formed,which improved the electrochemical performance.Therefore,the carbon materials derived from TS(O-TS-1000)had an obvious disordered structure and a larger layer spacing,giving them better sodium storage perform-ance than those derived from the TI-PS fraction(O-TI-PS-1000).The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g,which was 1.67 times higher than that of O-TI-PS-1000(150 mAh/g).
文摘Reducing the amount of aluminum chloride needed for the catalytic preparation of high quality mesophase and carbon materials is important and we have found that using terephthalic acid(PTA)as a co-catalyst serves this purpose.By adding 3%(mass fraction)AlCl_(3)and 0.9%(mass fraction)PTA to the coal tar pitch,approximately 90%mesophase was synthesized.The product(M-3-0.9)had a high stacking order(L_(c)=3.1 nm,n=10.14)and aromaticity(0.942).By adding PTA,a larger anisotropy content was produced using a smaller amount of AlCl_(3).The PTA participated in the polycondensation reaction through its own benzene ring structure to increase the catalytic activity.However,when its content was higher than 1.5%,the number of oxygen-containing groups in the product increased which was unfavorable for the aromatic lamellar stacking and gave rise to more isotropic structures.The work opens up a new way to prepare mesophase by a catalytic method.
文摘Mesophase pitch carbon fibers have an ultra-high modulus and thermal conductivity that are unmatched by other carbon fibers,making it irreplaceable in many fields.However,due to the high temperature dependence of the viscosity of the melted pitch and the poor mechanical properties of pitch fibers,it is difficult to reduce the fiber diameter when using continuous spinning.We used the Mathworks Matlab software to optimize the mesophase pitch melt spinning model and to simulate the effects of spinning temperature,mass flow rate,winder speed,and quenching air temperature near the spinneret on the maximum shear rate during drawing.Simulation results demonstrate that applying gradient cooling to the melt upon exiting the spinneret significantly reduces the maximum shear rate and extends the drawing zone,thereby promoting the spinning stability and helping reduce the fiber diameter.In the experiment,instead of quenching in air,we applied gradient cooling to the melt,whose temperature decreased according to the equation Ta=298+278exp(−11.4z),where Ta is the final air temperature in Kelvin,and z is the distance from the spinneret in meters.It was found the gradient cooling greatly improved the draw-down ratio,reducing the average diameter of the pitch fibers from 20.8 to 13.1μm,along with improved process stability.The experimental results are in excellent agreement with the predictions.At the same time,the tensile strength of the 1150°C carbonized fibers increased from 0.6 to 1.1 GPa.Although the degree of orientation of the fibers decreased slightly,the tight bonding between microcrystals,the suppression of splitting,and the smaller diameter improved the mechanical properties of carbon fibers.This study provides an effective method for reducing the fiber diameter while improving continuity.
文摘Pitch is a complex mixture of polycyclic aromatic hydrocarbons and their non-metal derivatives that has a high carbon content.Using pitch as a precursor for carbon materials in alkali metal ion(Li^(+)/Na^(+)/K^(+))batteries has become of great interest.However,its direct pyrolysis often leads to microstructures with a high orientation and small interlayer spacing due to uncontrolled liquid-phase carbonization,resulting in subpar electrochemical performance.It is therefore important to control the microstructures of pitch-derived carbon materials in order to improve their electrochemical properties.We evaluate the latest progress in the development of these materials using various microstructural engineering approaches,highlighting their use in metal-ion batteries and supercapacitors.The advantages and limitations of pitch molecules and their carbon derivatives are outlined,together with strategies for their modification in order to improve their properties for specific applications.Future research possibilities for structure optimization,scalable production,and waste pitch recycling are also considered.
文摘Sodium-ion batteries(SIBs)have emerged as a promising contender for next-gener-ation energy storage systems.Hard carbon is re-garded as the most promising anode for commer-cial SIB,however,the large number of defects on its surface cause irreversible electrolyte consump-tion and an uneven solid electrolyte interphase film.An advanced molecular engineering strategy to coat hard carbon with polycyclic aromatic mo-lecules is reported.Specifically,polystyrene-based carbon microspheres(CSs)were first synthesized and then coated with polycyclic aromatic mo-lecules derived from coal tar pitch by spray-drying and followed by oxidation.Compared to the traditional CVD coating meth-od,this molecular framework strategy has been shown to reduce the number of defects on the surface of CSs without sacrifi-cing internal storage sites and suppressing transport kinetics in hosting the sodium ions.Besides the lower surface defect con-centration,the synthesized hybrid carbon microspheres(HCSs)have a larger grain size and more abundant closed pores,and have a higher reversible sodium storage capacity.A HCS-P-60%electrode has a capacity of 332.3 mAh g^(-1)with an initial Cou-lombic efficiency of 88.5%.It also has a superior rate performance of 246.6 mAh g^(-1)at 2 C and a 95.2%capacity retention after 100 cycles at 0.2 C.This work offers new insights into designing high-performance hard carbon microsphere anodes,advan-cing the commercialization of sodium-ion batteries.
基金supported by the National Natural Science Foundation of China(Nos.52271295,52088102).
文摘To propel the application of a bottom-hinged flap breakwater in real sea conditions,a two-dimensional computational fluid dynamics numerical model was conducted to investigate the pitching motion response and wave attenuation in random waves.First,the flow velocity distribution characteristic of the pitching flap at typical times was summarized.Then,the effects of random wave and flap parameters on the flap’s significant pitching angle amplitude θ_(s) and hydrodynamic coefficients were investigated.The results reveal that θ_(s) and wave reflection coefficient K_(r) values increase with increasing significant wave height Hs,random wave steepnessλs,and flap relative height.As Hs andλs increase,the wave transmission coefficient K_(t) increases while the wave dissipation coefficient K_(d) decreases.Additionally,K_(t) decreases with increasing flap relative height.With increasing equivalent damping coefficient ratio,θ_(s) and K_(t) decrease,while K_(r) and K_(d) increase.The relationships betweenλs and flap relative height on the one hand andθ_(s),K_(r),K_(t),and K_(d) in random waves on the other hand are compared to those in regular waves.Based on the equal incident wave energy and the equal incident wave energy flux,the pitching flap performs better in the wave attenuation capability under random waves than in regular waves.Finally,the dimensionless parameters with respect to random wave and flap were used to derive the K_(r) and K_(t) for-mulae,which were validated with the related data.
文摘The determination of musical pitch has been a major concern of music theory,East and West,in all climes and cultures,throughout the ages.This paper discusses the intricacies of pitch determination from historic,geographic,and scientific perspectives.Its standardization nowadays has permitted the manufacture and tuning of musical instruments on a universal scale.
基金supported by MHRD as researcher C.K.Neog received the MHRD Institute GATE scholarship from Govt.of India.
文摘This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerged cylindrical buoy.The system is modeled as a two-layer fluid with infinite horizontal extent and finite depth.The radiation problem is analyzed in the context of linear water waves.The fluid domain is divided into outer and inner zones,and mathematical solutions for the pitch radiating potential are derived for the corresponding boundary valve problem in these zones using the separation of variables approach.Using the matching eigenfunction expansion method,the unknown coefficients in the analytical expression of the radiation potentials are evaluated.The resulting radiation potential is then used to compute the added mass and damping coefficients.Several numerical results for the added mass and damping coefficients are investigated for numerous parameters,particularly the effects of the cylinder radius,the draft of the submerged cylinder,and the density proportion between the two fluid layers across different frequency ranges.The major findings are presented and discussed.
基金support of this research by the National Natural Science Foundation of China(Nos.22202171,21922202,and 22272146)the Natural Science Foundation of Jiangsu Basic Research Program(No.BK20220559)+1 种基金the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(No.22KJD150009)the Jiangsu Specially-Appointed Professor Plan(Z.Xi)from the Jiangsu Education Department。
文摘Rational tuning of chiral nanostructures of supramolecular assemblies as catalysts and investigating their chiral morphology-enantioselectivity dependence is rarely reported. Herein, we report a series of supramolecular M/P-helical nanoribbons(HNs) assembled from the chiral L/D-glutamate-based amphiphiles(L/D-Glu C16) and Cu(Ⅱ) ions, with their helical screw pitches adjusted from 217 nm to 104 nm through the facile regulation of their water/organic solvent assembly environment. They were then used as ideal models to reveal the chiral morphology-enantioselectivity relationship by catalyzing the asymmetric Diels-Alder reaction. Better enantioselectivity was achieved with more twist morphology. Experimental evidences of stronger chiral transfer effect from the supramolecular HNs with more twist to the aza-chalcone as reactant were obtained to understand such dependence. Our study demonstrates a new perspective for designing supramolecular catalysts with higher enantioselectivity.
基金supported by the National Science Foundation of China (Grant Nos.52279081,and 51839001).
文摘The behaviors of unsteady flow structures and corresponding hydrodynamics for a pitching hydrofoil are investigated numerically and theoretically in the present paper.The aims are to derive the total lift by finite-domain impulse theory for subcavitating flow(σ=8.0)and cavitating flow(σ=3.0),and to quantify the distinct impact of individual vortex structures on the transient lift to appreciate the interplay among cavitation,flow structures,and vortex dynamics.The motion of the hydrofoil is set to pitch up clockwise with an almost constant rate from 0°to 15°and then back to 0°,for the Reynolds number,7.5×105,and the frequency,0.2 Hz,respectively.The results reveal that the presence of cavities delays the migration of the laminar separation bubble(LSB)from the trailing edge(TE)to the leading edge(LE),consequently postponing the hysteresis in the inflection of lift coefficients.The eventual stall under the sub-cavitation regime is the result of LSB bursting.While the instabilities within the leading-edge LSB induce the convection of cavitation-dominated vortices under the cavitation regime instead.Having validated the lift coefficients on the hydrofoil through the finite-domain impulse theory using the standard force expression,the Lamb vector integral emerges as the main contribution to the generation of unsteady lift.Moreover,the typical vortices’contributions to the transient lift during dynamic stall are accurately quantified.The analysis indicates that the clockwise leading-edge vortex(−LEV)contributes positively,while the counterclockwise trailing-edge vortex(+TEV)contributes negatively.The negative influence becomes particularly pronounced after reaching the peak of total lift,as the shedding of the concentrated wake vortex precipitates a sharp decline due to a predominant negative lift contribution from the TEV region.Generally,the vortices’contribution is relatively modest in sub-cavitating flow,but it is notably more significant in the context of incipient cavitating flow.
文摘The pitch bearing is a component in wind turbine units used to adjust the angle of the fan blades to adapt to the wind direction,so as to maximize the utilization of wind energy.Due to the different working mode of the pitch bearing itself compared with ordinary small bearings and the harsh working environment,the pitch bearing is prone to faults such as cracking and deformation.In severe cases,it will lead to overall damage to the pitch bearing,causing the blade to fall from a high altitude and even injuring personnel.Therefore,this paper conducts a patent analysis and technical decomposition of the deformation monitoring device for pitch bearings,analyzes and summarizes the development process of existing deformation monitoring devices for pitch bearings.Combined with the TRIZ evolution theory and based on the S-curve,it is concluded that the current deformation monitoring device for pitch bearings is in the transitional stage between the infant period and the growth period,and discusses the possible subsequent evolution directions.Through reviewing relevant literature,it is found that inner ring cracks first appear near the upper and lower surfaces of the bolt holes in the inner ring of the pitch bearing.To this end,a new type of deformation monitoring device for pitch bearings is designed.The fiber optic displacement sensor is used for qualitative monitoring of initial cracks near the surface of the bolt holes in the inner ring of the pitch bearing.After cracks are detected,the eddy current sensor is used for quantitative monitoring of whether there are extended cracks between the cracked bolt holes and adjacent bolt holes.Finally,the work done in this paper is summarized and prospected.
基金financially supported by National Natural Science Foundation of China(Nos.52374286 and 52274279)the National Key Research and Development Program of China(No.2021YFC2902604)。
文摘High-salinity wastewater treatment has always been a challenging issue.In this study,coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets(CPN-9)using a salt-template method.The desalination performance of CPN-9 was evaluated using flow-electrode capacitive deionization technology.The results showed that CPN-9 has a high specific surface area(466.34 m^(2)/g),a rich pore structure(micro-/meso-pore volume was 0.28),excellent rheological properties,and hydrophilicity(contact angle of 20.44°),thereby accelerating ion transport.Electrochemical results indicated that CPN-9 exhibits a significant double-layer ion storage mechanism,with a specific capacitance of 176.66 F/g at a current density of 0.5 A/g.CPN-9 has a very low charge transfer resistance.The synergistic effect of aromatic carbon and nitrogen doping(the content of pyrrole and pyridine nitrogen was 36.40%and 35.83%,respectively)in coal tar pitch accelerates electron transfer in CPN-9.The good ion diffusion performance and low impedance of CPN-9 accelerate the ion exchange rate,resulting in outstanding desalination performance.At 1.2 V and 3%mass loading,with a CPN-9 to conductive carbon black ratio of 4:1,the average desalination rate,charge efficiency,and energy consumption reached 0.039 mg/(cm^(2)·min),48.47%,and 0.012 kWh/mol,respectively.In summary,this study optimized the structure of CPN-9 from the perspective of electronic and ionic transport,enhancing its desalination performance and providing theoretical support for the deionization of high-salinity wastewater.
文摘The controversies about the mechanism of sodium storage in hard carbon(HC)hinder its rational structural design.A series of porous HC materials using coal tar pitch show a reversible capacity of 377 mAh g^(−1) and an initial Coulombic efficiency(ICE)of 87%as well as excellent cycling performance.More attention is paid to exploration of the relationships between the sodium status on various storage sites at different sodiation states and the ICE by solidstate^(23)Na nuclear magnetic resonance spectroscopy.The adsorbed Na ions contribute the most to the irreversible capacity.The de-solvated Na ions entering the closed pores are reduced to Na atoms and aggregated to Na clusters.Also,this process contributes the most to the reversible capacity and is characteristic of a long plateau in the voltage profile.Intercalation is partially reversible;it is the main source of capacity for slope-type HCs but plays a minor role in the reversible capacity of plateau-type HCs.Therefore,increasing the content of the closed pores can improve the reversible plateau capacity and reducing the open mesopores of HC increases the ICE.These findings provide insights into the structural design and cost-efficient preparation of high-performance HC anode materials for advanced sodium-ion batteries.
