Low-Temperature Carbonized Nitrogen-Doped Hard Carbon Nanofiber Toward High-Performance Sodium-Ion Capacitors

Carbon nanofiber(CNF)was widely utilized in the field of electrochemical energy storage due to its superiority of conductivity and mechanics.However,CNF was generally prepared at relatively high temperature.Herein,nitrogen-doped hard carbon nanofibers(NHCNFs)were prepared by a lowtemperature carbonization treatment assisted with electrospinning technology.Density functional theory analysis elucidates the incorporation of nitrogen heteroatoms with various chemical states into carbon matrix would significantly alter the total electronic configurations,leading to the robust adsorption and efficient diffusion of Na atoms on electrode interface.The obtained material carbonized at 600°C(NHCNF-600)presented a reversible specific capacity of 191.0 mAh g^(−1)and no capacity decay after 200 cycles at 1 A g^(−1).It was found that the sodium-intercalated degree had a correlation with the electrochemical impedance.A sodium-intercalated potential of 0.2 V was adopted to lower the electrochemical impedance.The constructed sodium-ion capacitor with activated carbon cathode and presodiated NHCNF-600 anode can present an energy power density of 82.1 Wh kg^(−1)and a power density of 7.0 kW kg^(−1).

Boosting energy-storage capability in carbon-based supercapacitors using low-temperature water-in-salt electrolytes

Supercapacitors(SCs) are high-power energy storage devices with ultra-fast charge/discharge properties.SCs using concentrated aqueous-based electrolytes can work at low temperatures due to their intrinsic properties, such as higher freezing point depression(FPD) and robustness. Besides the traditional organic-and aqueous-based(salt-in-water) electrolytes used in SCs, water-in-salt(WISE) sodium perchlorate electrolytes offer high FPD, non-flammability, and low-toxicity conditions, allowing the fabrication of safer, environmentally friendly, and more robust devices. For the first time, this work reports a comprehensive study regarding WISE system’s charge-storage capabilities and physicochemical properties under low-temperature conditions(T < 0 ℃) using mesoporous carbon-based electrodes. The effect of temperature reduction on the electrolyte viscosity and electrical properties was investigated using different techniques and the in-situ(or operando) Raman spectroscopy under dynamic polarization conditions.The cell voltage, equivalent series resistance, and specific capacitance were investigated as a function of the temperature. The cell voltage(U) increased ~ 50%, while the specific capacitance decreased ~20%when the temperature was reduced from 25 ℃ to -10 ℃. As a result, the maximum specific energy(E = CU^(2)/2) increased ~ 100%. Therefore, low-temperature WISEs are promising candidates to improve the energy-storage characteristics in SCs.

Low-temperature phase transformation from nanotube to sp^3 superhard carbon phase

Numerous new carbon allotropes have been uncovered by compressing carbon nanotubes based on our computational investigation. The volume compression calculations suggest that these new phases have a very high anti-compressibility with a large bulk modulus （B0）. The predicted B0 of new phases is larger than that of c-BN （373 GPa） and smaller than that of diamond （453 GPa）. All of the predicted structures are superhard transparent materials with a larger band gap and possess the covalent characteristics with sp3-hybridized electronic states. The simulated results will help us better understand the structural phase transition of cold-compressed carbon nanotubes.

Study on Low-Temperature Properties of the Asphalt Modified by Carbon Nanotubes(CNTs)and Crumb Rubber(CR)

The effect of adding crumb rubber(CR)and carbon nanotubes(CNTs)on the low-temperature properties of virgin asphalt was studied.Using the force-ductility test and the bending beam rheometer(BBR)test,the deformation resistance and rheological properties of asphalt samples at low temperatures were evaluated,respectively.Based on the result of BBR test,the creep functions of the Burgers model and the Zener model were used to fit the low-temperature creep characteristics of the asphalt samples.Furthermore,the differential scanning calorimetry(DSC)test and the attenuated total reflection-Fourier transform infrared spectroscopy(ATR-FTIR)test were utilized to appraise the low-temperature stability and chemical properties of asphalt samples,respectively.The results showed that CR significantly improved the low-temperature properties of virgin asphalt,while CNTs had little effect.Moreover,during the degradation of CR,aromatic and aliphatic components were released.In particular,the aliphatic components of CR-modified asphalt were much higher than those of virgin asphalt,which had a significant effect on improving the low-temperature properties of the asphalt.The DSC test results showed that CR enhanced the low-temperature stability of the asphalt,while the addition of CNTs presented a slightly negative effect.

Twice-split phosphorus application alleviates low-temperature impacts on wheat by improved spikelet development and setting

Extreme low-temperature incidents have become more frequent and severe as climate change intensifies.In HuangHuai-Hai wheat growing area of China,the late spring coldness occurring at the jointing-booting stage(the anther interval stage)has resulted in significant yield losses of winter wheat.This study attempts to develop an economical,feasible,and efficient cultivation technique for improving the low-temperature(LT)resistance of wheat by exploring the effects of twice-split phosphorus application(TSPA)on wheat antioxidant characteristics and carbon and nitrogen metabolism physiology under LT treatment at the anther interval stage using Yannong 19 as the experimental material.The treatments consisted of traditional phosphorus application and TSPA,followed by a-4℃ LT treatment and natural temperature(NT)control at the anther interval stage.Our analyses showed that,compared with the traditional application,the TSPA increased the net photosynthetic rate(P_(n)),stomatal conductance(Gs),and transpiration rate(T_(r))of leaves and reduced the intercellular carbon dioxide concentration(C_(i)).The activity of carbon and nitrogen metabolism enzymes in the young wheat spikes was also increased by the TSPA,which promoted the accumulation of soluble sugar(SS),sucrose(SUC),soluble protein(SP),and proline(Pro)in young wheat spike and reduced the toxicity of malondialdehyde(MDA).Due to the improved organic nutrition for reproductive development,the young wheat spikes exhibited enhanced LT resistance,which reduced the sterile spikelet number(SSN)per spike by 11.8%and increased the spikelet setting rate(SSR)and final yield by 6.0 and 8.4%,respectively,compared to the traditional application.The positive effects of split phosphorus application became more pronounced when the LT treatment was prolonged.

The Preparation of Mn-Fe/CNTs Catalyst at the Low-Temperature Selective Catalytic Reduction of NO with NH₃

The metal oxide catalyst was prepared by loading MnOx and FeOx on carbon nano-tubes (CNTs) with impregnation method. Then the catalyst was characterized by BET and XPS, and the effect of adding FeOx on MnOx/CNTs catalyst at the low-temperature selective catalytic reduction of NO with NH3 was investigated. The results showed that the active components were loaded suc-cessfully and easily on the carriers by impregnation. The Mn-Fe/CNTs catalyst was chose 10% Fe(NO3)3 solution to impregnate Mn-Fe/CNTs. The species of active components loaded on the catalyst were Fe2O3. The different concentration of impregnant solution played an important role for NO conversion in SCR with NH3. With the increase of the concentration of impregnant solution, the NO conversion of catalysts was increasing initially then decreasing.

Low-temperature Denitration Mechanism of NH_(3)-SCR over Fe/AC Catalyst

To study the modification mechanism of activated carbon(AC)by Fe and the low-temperature NH_(3)-selective catalytic reduction(SCR)denitration mechanism of Fe/AC catalysts,Fe/AC catalysts were prepared using coconut shell AC activated by nitric acid as the support and iron oxide as the active component.The crystal structure,surface morphology,pore structure,functional groups and valence states of the active components of Fe/AC catalysts were characterised by X-ray diffraction,scanning electron microscopy,nitrogen adsorption and desorption,Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy,respectively.The effect of Fe loading and calcination temperature on the low-temperature denitration of NH_(3)-SCR over Fe/AC catalysts was studied using NH_(3)as the reducing gas at low temperature(150℃).The results show that the iron oxide on the Fe/AC catalyst is spherical and uniformly dispersed on the surface of AC,thereby improving the crystallisation performance and increasing the number of active sites and specific surface area on AC in contact with the reaction gas.Hence,a rapid NH_(3)-SCR reaction was realised.When the roasting temperature remains constant,the iron oxide crystals formed by increasing the amount of loading can enter the AC pore structure and accumulate to form more micropores.When the roasting temperature is raised from 400 to 500℃,the iron oxide is mainly transformed fromα-Fe_(2)O_(3)toγ-Fe_(2)O_(3),which improves the iron oxide dispersion and increases its denitration active site,allowing gas adsorption.When the Fe loading amount is 10%,and the roasting temperature is 500℃,the NO removal rate of the Fe/AC catalyst can reach 95%.According to the study,the low-temperature NH_(3)-SCR mechanism of Fe/AC catalyst is proposed,in which the redox reaction between Fe~(2+)and Fe~(3+)will facilitate the formation of reactive oxygen vacancies,which increases the amount of oxygen adsorption on the surface,especially the increase in surface acid sites,and promotes and adsorbs more reaction gases(NH_(3),O_(2),NO).The transformation from the standard SCR reaction to the fast SCR reaction is accelerated.

Hybrid hard carbon framework derived from polystyrene bearing distinct molecular crosslinking for enhanced sodium storage

Exploiting high-performance yet low-cost hard carbon anodes is crucial to advancing the state-of-the-art sodium-ion batteries.However,the achievement of superior initial Coulombic efficiency(ICE)and high Na-storage capacity via low-temperature carbonization remains challenging due to the presence of tremendous defects with few closed pores.Here,a facile hybrid carbon framework design is proposed from the polystyrene precursor bearing distinct molecular bridges at a low pyrolysis temperature of 800℃ via in situ fusion and embedding strategy.This is realized by integrating triazine-and carbonylcrosslinked polystyrene nanospheres during carbonization.The triazine crosslinking allows in situ fusion of spheres into layered carbon with low defects and abundant closed pores,which serves as a matrix for embedding the well-retained carbon spheres with nanopores/defects derived from carbonyl crosslinking.Therefore,the hybrid hard carbon with intimate interface showcases synergistic Na ions storage behavior,showing an ICE of 70.2%,a high capacity of 279.3 mAh g^(-1),and long-term 500 cycles,superior to carbons from the respective precursor and other reported carbons fabricated under the low carbonization temperature.The present protocol opens new avenues toward low-cost hard carbon anode materials for high-performance sodiumion batteries.

Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells

Nitrogen doping of the carbon is an important method to improve the performance and durability of catalysts for proton exchange membrane fuel cells by platinum–nitrogen and carbon–nitrogen bonds. This study shows that p-phenyl groups and graphitic N acting bridges linking platinum and the graphene/carbon black(the ratio graphene/carbon black = 2/3) hybrid support materials achieved the average size of platinum nanoparticles with(4.88 ± 1.79) nm. It improved the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm^(-2) at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping also enhanced the interaction between Pt and the support materials, and the resistance to corrosion, thus improving the durability of the low-temperature hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm^(-2) after 30 k cycles of an in-situ accelerated stress test of catalyst degradation than that of 92 mV in Pt/C, which achieves the target of Department of Energy(<30 mV). Meanwhile,Pt/Nr EGO_(2)-CB_(3) remains 78% of initial power density at 1.5 A cm^(-2) after 5 k cycles of in-situ accelerated stress test of carbon corrosion, which is more stable than the power density of commercial Pt/C, keeping only 54% after accelerated stress test.

Extraordinary Compatibility to Mass Loading and Rate Capability of Hierarchically Porous Carbon Nanorods Electrode Derived from the Waste Tire Pyrolysis Oil

The conversion of waste tire pyrolysis oil(WTPO)into S-doped porous carbon nanorods(labeled as WPCNs)with hierarchical pore structure is realized by a simple template-directed approach.The specific surface area of as-obtained porous carbon nanorods can reach up to 1448 m^(2) g^(−1) without the addition of any activating agent.As the capacitive electrode,WPCNs possess the extraordinary compatibility to capacitance,different electrolyte systems as well as long-term cycle life even at a commercial-level areal mass loading(10 mg cm^(−2)).Besides,only an extremely small capacitance fluctuation is observed under the extreme circumstance(−40 to 80℃),reflecting the excellent high-and low-temperature performance.The relationship between the pore structure and capacitive behavior is analyzed by comparing WPCNs with mesopores-dominated asphalt-derived porous carbon nanorods(APCNs)and micropores-dominated activated carbon.The molecular dynamics simulation further reveals the ion diffusion and transfer ability of the as-prepared carbon materials under different pore size distribution.The total ion flow(NT)of WPCNs calculated by the simulation is obviously larger than APCNs and the N_(T) ratio between them is similar with the experimental average capacitance ratio.Furthermore,this work also provides a valuable strategy to prepare the electrode material with high capacitive energy storage ability through the high value-added utilization of WTPO.

A new family of sp3-hybridized carbon phases

A new family of superhard carbon allotropes C48（2i ＋ 1 ） is constructed by alternating even 4 and 8 membered rings. These new carbon allotropes are of a spatially antisymmetrical structure, compared with the symmetrical structures of bet- C4, Z-carbon, and P-carbon. Our calculations show that bulk moduli of C48（2i ＋ 1 ） are larger than that of c-BN and smaller than that of cubic-diamond. C48（2i ＋ 1 ） are transparent superhard materials possessing large Vicker hardness comparable to diamoud. This work can help us understand the structural phase transformations of cold-compression graphite and carbon nanotubes.

Isotope effects of plasma chemical carbon oxidation in a magnetic field

The influence of different factors on the plasma chemical reactions is widely studied today. However, insufficient consideration is given to the research of paramagnetic phenomena which takes place in plasma systems. The results of modeling the process of redistribution carbon isotopes between different phases while oxidizing it in high-frequency low-temperature plasma in an external magnetic field are shown in the article. The equilibrium concentrations of components involved in the oxidation process in a plasma system are defined. A principle possibility of isotope-selective plasma chemical reactions in a magnetic field was experimentally determined. The increase of concentration of 13C in the gas phase up to 1.3 times relative to natural abundance was obtained. It was found that the content of the carbon heavy isotope in the gas phase depends on the magnetic field action area. The best results were achieved with the combination of magnetic field impact area and the priority area of the appearance of plasma chemical reactions products.

1.1 MW高速内置式永磁同步电机新型转子拓扑设计与强度优化

大功率高速永磁电机中通常采用绑扎碳纤维护套的方式来降低转子应力,然而护套厚度过大会导致等效气隙增加,电机性能随之降低。针对这一问题,设计了一种具有新型转子拓扑结构的1.1 MW、18 000 r/min的内置式高速永磁同步电机。该结构采用永磁体分段设计,并增设加强筋,分担转子隔磁桥处的应力,使护套厚度得到有效降低。同时,将转子外部隔磁桥处替换为非导磁填充块,阻断漏磁路径,提升永磁体利用率。最后,有限元分析结果表明,相较于初始模型,新型结构电机在等效气隙增大1.5 mm的情况下,输出转矩达到600.44 N·m,增加了16.86 N·m,并且新型转子铁心最大应力降低了496.82 MPa,转子结构的机械强度得到显著提高,可为大功率高速永磁电机转子拓扑设计提供参考。

硅钢退火炉炉辊炭套结瘤机理研究及解决对策

冷轧硅钢在连续退火炉中进行脱碳、再结晶退火时,炭套辊表面经常出现结瘤,在高温下极易造成带钢产生凹坑缺陷,影响硅钢片的叠装系数,是硅钢成品的致命缺陷。本文通过对硅钢退火炉炉辊炭套结瘤进行深入机理研究分析,并据此提出控制炭套结瘤的解决对策。

硅钢退火炉高温钢丝炉辊的研究及实践

介绍了一种用于无取向硅钢退火炉的高温钢丝炉辊,新型钢丝炉辊表面无结瘤,无异常磨损,上线使用后能够替代传统炉底碳套辊,减少开炉检修次数,有效提升生产线作业效率。

超深碳酸盐岩裸眼分段完井可溶球研究与应用

针对顺北油田5号条带超深碳酸盐岩储层裸眼分段完井工艺特点,研究设计了一种可控溶解的压裂球,主要用以解决“高耐酸腐蚀性、高速溶解特性、耐高压性能”等3个问题。可溶球采用“基体+涂层”结构,基体材料采用镁铝合金,涂层优选改性聚四氟乙烯+酚醛树脂纳米材料,并使用有机涂层对镁铝合金进行表面处理。对新研制的可溶球分别进行了承压数值仿真分析、耐酸承压测试和高温溶解测试,最后在顺北4-13H井进行了现场应用。研究结果表明:新研制的可溶球能够承受高温160℃、高压70 MPa、耐酸且能高速溶解,平均溶解速率为7.19 g/h,完全溶解只需12 h左右,实现了压裂时承压、生产时快速溶解不堵塞通道的双重要求,能有效提高可溶球在顺北区块裸眼分段完井工艺中的适用性和有效性,满足现场使用需求。研究结果可为油田现场水平井分段完井工艺提供参考。

基于多维可视化的表贴式高速永磁电机转子护套设计

护套厚度和过盈量是影响表贴式高速永磁电机转子强度的主要因素。通过分析永磁转子的受力情况,把三维永磁电机转子的强度模型简化为平面应力问题,在极坐标下推导出考虑护套厚度、过盈量及转速影响的碳纤维护套永磁转子应力解析解。将永磁体和转子铁心接触面间的接触压强及碳纤维护套的最大环向应力作为优化目标,以永磁体和护套的应力极限强度为约束条件,选择碳纤维护套厚度以及永磁体与碳纤维护套之间的静态过盈量作为设计变量,通过多维可视化算法计算求解找到满足条件要求的护套厚度及静态过盈量的优解范围。通过有限元法和解析法的计算结果对比来验证转子的应力分布情况。仿真结果表明,所设计的转子护套能够满足高速下永磁体的强度保护要求,能够实现为高速永磁电机转子表面安装碳纤维护套的优化设计。

Low-temperature synthesis of sp^2 carbon nanomaterials

sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years.As the advanced sp^2 carbon nanomaterials, graphene and carbon nanotubes(CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature,expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp^2 carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.

Low-temperature plasma induced phosphate groups onto coffee residue-derived porous carbon for efficient U(Ⅵ) extraction

For the continuous utilization of nuclear energy and efficient control of radioactive pollution, low-cost materials with high efficient U(VI) removal are of great importance. In this study, low temperature plasma method was applied for the successful modification of Ophosphorylethanolamine(O-PEA) on the porous carbon materials. The produced materials(Cafe/O-PEA) could adsorb U(VI) efficiently with the maximum sorption capacity of 648.54mg/g at 1 hr, T=298 K, and p H=6.0, much higher than those of most carbon-based composites. U(VI) sorption was mainly controlled by strong surface complexation. From FTIR,SEM-EDS and XPS analyses, the sorption of U(VI) was related to the complexation with-NH2, phosphate and-OH groups on Cafe/O-PEA. The low temperature plasma method was an efficient, environmentally friendly and low-cost method for surface modification of materials for the effective enrichment of U(VI) from aqueous solutions.

高速永磁电机转子不同保护措施的强度分析

永磁体在高速旋转时难以承受巨大的拉应力,必须对永磁体采用保护措施,目前最常用的保护措施一种是采用碳纤维绑扎永磁体,另外一种是在永磁体外面加高强度的合金保护套。针对以上两种不同的保护措施,以一台100 kW,60 000 r/min的高速永磁电机为例,分别设计了相应的保护套,并对不同工况下的转子应力分布进行了解析法推导,用3D有限元法对电机冷态和热态运行时的转子强度进行了分析和验证,同时对考虑弯曲应力时的碳纤维保护套进行了设计和计算。总结了两种保护措施的设计规律,为高速永磁电机保护套的设计提供了依据。