Vacancy defect MoSeTe embedded in N and F co-doped carbon skeleton for high performance sodium ion batteries and hybrid capacitors

Sodium-ion batteries(SIBs) and hybrid capacitors(SIHCs) have garnered significant attention in energy storage due to their inherent advantages,including high energy density,cost-effectiveness,and enhanced safety.However,developing high-performance anode materials to improve sodium storage performa nce still remains a major challenge.Here,a facile one-pot method has been developed to fabricate a hybrid of MoSeTe nanosheets implanted within the N,F co-doped honeycomb carbon skeleton(MoSeTe/N,F@C).Experimental results demonstrate that the incorporation of large-sized Te atoms into MoSeTe nanosheets enlarges the layer spacing and creates abundant anion vacancies,which effectively facilitate the insertion/extraction of Na^(+) and provide numerous ion adsorption sites for rapid surface capacitive behavior.Additionally,the heteroatoms N,F co-doped honeycomb carbon skeleton with a highly conductive network can restrain the volume expansion and boost reaction kinetics within the electrode.As anticipated,the MoSeTe/N,F@C anode exhibits high reversible capacities along with exceptional cycle stability.When coupled with Na_(3)V_(2)(PO_(4))_(3)@C(NVPF@C) to form SIB full cells,the anode delivers a reversible specific capacity of 126 mA h g^(-1) after 100 cycles at 0.1 A g^(-1).Furthermore,when combined with AC to form SIHC full cells,the anode demonstrates excellent cycling stability with a reversible specific capacity of50 mA h g^(-1) keeping over 3700 cycles at 1.0 A g^(-1).In situ XRD,ex situ TEM characterization,and theoretical calculations(DFT) further confirm the reversibility of sodium storage in MoSeTe/N,F@C anode materials during electrochemical reactions,highlighting their potential for widespread practical application.This work provides new insights into the promising utilization of advanced transition metal dichalcogenides as anode materials for Na^(+)-based energy storage devices.

Ultralong nitrogen/sulfur Co-doped carbon nano-hollowsphere chains with encapsulated cobalt nanoparticles for highly efficient oxygen electrocatalysis

The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is currently an urgent issue.Herein,an efficient bifunctional electrocatalyst featured by ultralong N,S-doped carbon nano-hollow-sphere chains about 1300 nm with encapsulated Co nanoparticles(Co-CNHSCs)is developed.The multifunctional catalytic properties of Co together with the heteroatom-induced charge redistribution(i.e.,modulating the electronic structure of the active site)result in superior catalytic activities toward OER and ORR in alkaline media.The optimized catalyst Co-CNHSC-3 displays an outstanding electrocatalytic ability for ORR and OER,a high specific capacity of 1023.6 mAh gZn^(-1),and excellent reversibility after 80 h at 10mA cm^(-2)in a Zn-air battery system.This work presents a new strategy for the design and synthesis of efficient multifunctional carbon-based catalysts for energy storage and conversion devices.

Rationally designed hollow carbon nanospheres decorated with S,P co-doped NiSe_(2) nanoparticles for high-performance potassium-ion and lithium-ion batteries

Hollow nanostructures with external shells and inner voids have been proved to greatly shorten the transport distance of ions/electrons and buffer volume change,especially for the large-sized potassium-ions in secondary batteries.In this work,hollow carbon(HC) nanospheres embedded with S,P co-doped NiSe_(2)nanoparticles are fabricated by "drop and dry" and "dissolving and precipitation" processes to form Ni(OH)2nanocrystals followed by annealing with S and P dopants to form nanoparticles.The resultant S,P-NiSe_(2)/HC composite exhibits excellent cyclic performance with 131.6 mA h g^(-1)at1000 mA g^(-1)after 3000 cycles for K^(+)storage and a capacity of 417.1 mA h g^(-1)at 1000 mA g^(-1)after1000 cycles for Li^(+)storage.K-ion full cells are assembled and deliver superior cycling stability with a ca pacity of 72.5 mA h g^(-1)at 200 mA g^(-1)after 500 cycles.The hollow carbon shell with excellent electrical conductivity effectively promotes the transporta tion and tolerates large volume variation for both K^(+)and Li^(+).Density functional theory calculations confirm that the S and P co-doping NiSe_(2) enables stronger adsorption of K^(+)ions and higher electrical conductivity that contributes to the improved electrochemical performance.

Direct observation of the distribution of impurity in phosphorous/boron co-doped Si nanocrystals

Doping in Si nanocrystals is an interesting topic and directly studying the distribution of dopants in phosphorous/boron co-doping is an important issue facing the scientific community.In this study,atom probe tomography is performed to study the structures and distribution of impurity in phosphorous/boron co-doped Si nanocrystals/SiO_(2) multilayers.Compared with phosphorous singly doped Si nanocrystals,it is interesting to find that the concentration of phosphorous in co-doped samples can be significantly improved.Theoretical simulation suggests that phosphorous-boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy,which also reduces the formation energy of phosphorous in Si nanocrystals.The results indicate that co-doping can promote the entry of phosphorous impurities into the near-surface and inner sites of Si nanocrystals,which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals such as the observed enhancement of conductivity and sub-band light emission.

Improving the electrocatalytic activity of Fe,N co-doped biochar for polysulfide by regulation of N-C and Fe-N-C electronic configurations

The conversion of agricultural residual biomass into biochar as a sulfur host material for Li-S batteries is a promising approach to alleviate the greenhouse effect and realize waste resource reutilization.However,the large-scale application of pristine biochar is hindered by its low electrical conductivity and limited electrocatalytic sites.This paper addressed these challenges via the construction of Fe-N co-doped biochar(Fe-NOPC)through the copyrolysis of sesame seeds shell and ferric sodium ethylenediaminetetraacetic acid(NaFeEDTA).During the synthesis process,NaFeEDTA was used as an extra carbon resource to regulate the chemical environment of N doping,which resulted in the production of high contents of graphitic,pyridinic,and pyrrolic N and Fe-Nx bonds.When the resulting Fe-NOPC was used as a sulfur host,the pyridinic and pyrrolic N would adjust the surface electron structure of biochar to accelerate the electron/ion transport,and the electropositive graphitic N could be combined with sulfur-related species via electrostatic attraction.Fe-Nx could also promote the redox reaction of lithium polysulfides due to the strong Li-N and S-Fe bonds.Benefiting from these advantages,the resultant Fe-NOPC/S cathode with a sulfur loading of 3.8 mg·cm^(-2)delivered an areal capacity of 4.45 mAh·cm^(-2)at 0.1C and retained a capacity of 3.45 mAh·cm^(-2)at 1C.Thus,this cathode material holds enormous potential for achieving energy-dense Li-S batteries.

Microbial synthesis of N, P co-doped carbon supported PtCu catalysts for oxygen reduction reaction

Developing highly efficient and stable platinum-based electrocatalyst for oxygen reduction reaction(ORR) is critical to expediting commercialization of fuel cells.Herein,several PtCu alloy nanocatalysts supported on N,P co-doped carbon(PtCu/NPC) were prepared by microbial-sorption and carbonization-reduction.Among them,PtCu/NPC-700 ℃ exhibits excellent catalytic performance for ORR with a mass activity of 0.895 A mg_(pt)^(-1)(@0.9 V) which is 8.29 folds of commercial Pt/C.Additionally,the ECSA and MA of PtCu/NPC-700℃ only decrease by 14.2% and 18.7% respectively,while Pt/C decreases by 35.2% and 52.8% after 10,000 cycles of ADT test.Moreover,the PtCu/NPC-700℃ catalyst emanates a maximum power density of 715 mW cm^(-2) and only 11.1% loss of maximum power density after 10,000 ADTs in single-cell test,indicating PtCu/NPC-700℃ also manifests higher activity and durability in actual single-cell operation than Pt/C.This research provides an easy and novel strategy for developing highly active and durable Pt-based alloy catalyst.

Construction of N,O co-doped carbon anchored with Co nanoparticles as efficient catalyst for furfural hydrodeoxygenation in ethanol

Hydrodeoxygenation of furfural(FF)into 2-methylfuran(MF)is a significant biomass utilization route.However,designing efficient and stable non-noble metal catalyst is still a huge challenge.Herein,we reported the N,O co-doped carbon anchored with Co nanoparticles(Co-SFB)synthesized by employing the organic ligands with the target heteroatoms.Raman,electron paramagnetic resonance(EPR),electrochemical impedance spectroscopy(EIS),and X-ray photoelectron spectroscopy(XPS)characterizations showed that the co-doping of N and O heteroatoms in the carbon support endows Co-SFB with enriched lone pair electrons,fast electron transfer ability,and strong metal-support interaction.These electronic properties resulted in strong FF adsorption as well as lower apparent reaction activation energy.At last,the obtained N,O co-doped Co/C catalyst showed excellent catalytic activity(nearly 100 mol%FF conversion and 94.6 mol%MF yield)and stability for in-situ dehydrogenation of FF into MF.This N,O co-doping strategy for the synthesis of highly efficient catalytic materials with controllable electronic state will provide an excellent opportunity to better understand the structure-function relationship.

One-pot solvothermal synthesis of hierarchical Co-doped NiO microspheres with enhanced hydrogen sulfide sensing performances

In this study we report,for the first time,the synthesis of Co-doped NiO microspheres assembled by two-dimension nanosheets using a facile solvothermal method.The H 2 S gas-sensing performance of the as-prepared samples was systematically investigated.The result demonstrates that the Co–NiO sensor with Co/Ni molar ratio of 1%(1%Co–NiO)exhibits high response(12.9)and rapid response speed(110 s)to 20×10^(−6) H_(2)S at 200℃ in comparison with the pure NiO sensor.Moreover,excellent selectivity,repeatability,and stability were achieved.The sensing mechanism illustrates that the superior gas-sensing properties can be attributed to two factors.(1)The hierarchical microspherical construction with an ultrahigh specific surface area of 163.1 m^(2)g^(−1) provides adequate active sites for H_(2)S gas adsorption,porous structures,and an interlayer gap that accelerates the diffusion of H_(2)S gas,resulting in improved sensitivity and response speed of the sensor.(2)Co-doping results in a decrease in the particle sizes(ca.4 nm)and increase in the number of adsorbed ionized oxygen species,which improves sensitivity and selectivity.Therefore,this study provides a facile approach for the synthesis of hierarchical Co–NiO microspheres with enhanced H_(2)S gas-sensing performance.

Improved Corrosion Behavior of Biodegradable Mg-4Zn-1Mn Alloy Modified by Sr/F co-doped CaP Micro-arc Oxidation Coatings

The Sr/F co-doped CaP(Sr/F-CaP)coatings were prepared by micro-arc oxidation(MAO)under different voltages to modify the microstructure and corrosion behavior of Mg-4Zn-1Mn alloy.The surface and interface characteristics investigated using scanning electron microscopy(SEM)and energy dispersive X-ray spectrometer(EDS)showed that the MAO coatings displayed uneven crater-like holes and tiny cracks under lower voltage,while they exhibited relatively homogeneous crater-like holes without cracks under higher voltage.The thickness of MAO coatings increased with increasing voltage.The corrosion behavior of Mg-4Zn-1Mn alloy was improved by the MAO coatings.The MAO coatings prepared under 450 V and 500 V voltages possessed the best corrosion resistance with regard to the electrochemical corrosion tests and immersion corrosion tests,respectively.The MAO coatings fabricated under 450-500 V could provide a better corrosion protection effect for the substrate.

超声振动辅助切削SiCp/Al复合材料的加工机理及试验

切削加工过程中材料损伤形式对加工表面质量会产生较大影响,现有仿真分析难以模拟真实颗粒失效行为,通过建立二维微观多相有限元模型能够深入了解材料损伤与表面质量的关系。基于常规切削(Conventional cutting,CC)与超声振动辅助切削(Ultrasonic vibration-assisted cutting,UVAC)两种加工方式,通过有限元仿真软件Abaqus对20%SiCp/Al复合材料的切削过程进行仿真模拟,阐释加工过程中刀具与工件的相互作用机理,并在同一参数下验证有限元仿真的准确性。通过设计单因素试验,对比两种加工方式及不同加工参数对切削力和表面粗糙度的影响规律,得出最佳加工参数组合,并对最佳加工参数下表面形貌进行分析。模拟和试验结果表明,SiC颗粒断裂、颗粒耕犁、颗粒拔出以及Al基体撕裂是影响SiCp/Al复合材料加工质量的主要原因,刀具与颗粒不同的相对作用位置会产生不同的损伤形式。与常规切削相比,施加超声振动后可以有效抑制颗粒失效和基体损伤,使加工中的平均切削力(主切削力)降低33%,工件已加工表面粗糙度值最大减小量为531 nm,显著提高了表面质量。所建立的二维微观多相有限元模型,能够有效模拟铝基复合材料的加工缺陷和裂纹损伤问题,对提高难加工材料的高质量表面制备有重要借鉴意义。

超声振动辅助车削SiCp/Al切屑形成机理及表面粗糙度研究

目的研究切屑形成机理对加工过程的影响。方法超声振动辅助车削技术通过刀具振动的拟间歇切削特征控制切屑尺寸和切屑形态,从而提高了加工表面质量。针对SiCp/Al复合材料的切屑形成机理,探究常规车削和超声振动辅助车削的切屑形成过程。研究了颗粒分布对第一变形区变形阶段的影响,以及不同加工方式下切削参数对切屑形态的影响。最后,描述了切屑自由表面和刀-屑接触界面的颗粒损伤形式,以直观地描述常规车削与超声振动辅助车削SiCp/Al复合材料加工中切屑的形成过程。结果通过测试加工后工件表面形貌发现超声振动辅助车削的切屑更加连续、切屑尺寸较小的加工表面粗糙度更小,常规车削的表面粗糙度为0.805μm,超声振动辅助车削的表面粗糙度为0.404μm,超声振动辅助车削比常规车削的表面粗糙度降低了49.8%。结论与常规车削相比,超声振动辅助车削有利于减小切屑厚度。超声振动辅助车削得到的切屑更加连续,避免了切屑碎裂,促进了切屑的顺利排出。通过对切屑形态进行研究,选择最优切削参数可以有效提高工件表面质量。

镀铝对CoCrNiAlY-YSZ-LaMgAl_(11)O_(19)双陶瓷热障涂层高温抗氧化行为的影响

采用电弧离子镀(AIP)技术在CoCrNiAlY-YSZ-LaMA双陶瓷涂层表面沉积一层Al镀层,利用XRD、SEM和EDS等微尺度分析表征方法,全面解析涂层在大气暴露过程中的高温氧化行为。研究结果表明,未镀铝LaMA层在氧化过程中发生严重体积收缩,导致纵向微裂纹萌生和扩展。这些微裂纹成为氧气向内部扩散的通道,导致涂层呈现持续氧化增重趋势、TGO快速生长和严重的元素扩散,并最终加剧涂层断裂失效。但镀铝涂层样品表现出更好的高温抗氧化性能与结构稳定性,高温氧化过程中,表面Al镀层与氧气发生原位反应生成致密Al2O3屏障层,有效阻止或延迟氧气内部渗透,使TGO缓慢生长,其氧化增重从20h时的8.59mg/cm^(2)略微上升到80h时的9.46mg/cm^(2)。本研究结果为双陶瓷热障涂层的延寿设计与界面热生长应力调控开辟出全新技术途径和理论视野。

不锈钢表面Al/Cu涂层制备与第一性原理计算

为了研究Al/Cu涂层中金属间化合物的生成顺序和形成机理,在304不锈钢基体表面制备了Al/Cu涂层。对试样进行热处理使得Al/Cu涂层原位反应生成金属间化合物,随后测试了涂层的高温抗氧化性能。采用第一性原理计算Al-Cu金属间化合物的焓、熵、吉布斯自由能和热容等数据。将热力学和扩散动力学相结合,提出有效生成自由能模型来预测化合物在Al/Cu界面的生成顺序。结果表明:Al/Cu涂层中首先形成Al_(2)Cu相,在Al/Cu界面处出现了AlCu相,加热时间增加至20 h后出现了富Cu的Al_(4)Cu_(9)相。由第一性原理计算得出,Al-Cu金属间化合物的形成顺序为Al_(2)Cu→AlCu→Al_(4)Cu_(9),与实验结果一致。此外,氧化实验结果表明,涂层具有良好高温抗氧化性能。

Al/Fe_(2)O_(3)铝热剂粉尘着火敏感性

为明确铝热剂反应的着火特性,利用最低着火温度(minimum ignition temperature,MIT)和最小点火能(minimum ignition energy,MIE)测试装置,结合TG-DSC方法对4种Al粉与Fe_(2)O_(3)质量比为1∶4,1∶3,1∶2,1∶1的层状和云状Al/Fe_(2)O_(3)铝热剂进行了着火敏感性研究.结果表明,4种配比试样的粉尘层、粉尘云MIT均超出相关标准常规测试范围,在空气中质量比为1∶3铝热剂的反应触发温度为888℃,活化能为248.49 kJ/mol,说明铝热反应不容易触发;相同质量比的Al/Fe_(2)O_(3)粉尘云的MIE远高于粉尘层,层状MIE最低值为0.7 J,着火敏感性较强,这是因为Fe_(2)O_(3)在粉尘云状态的反应中充当惰化剂,而在粉尘层状态反应中为反应提供了活性氧自由基.

Al-Mg系合金中合金化元素作用及其对力学性能的影响

铝镁合金是轻量化材料应用领域中一种重要的金属材料,属于中高强度铝合金,具有较高的塑性、良好的耐蚀性以及优良的焊接性等优势,目前在航空航天、交通运输和军工制造等领域具有广阔的应用前景。笔者综述了铝镁合金力学性能特点以及用途,介绍了Al-Mg系合金中的强化机制,重点阐述了Al-Mg系合金中主合金化元素Mg及其含量对合金微观组织和力学性能的影响规律及机理,详细论述了Mn、Zr、Ti、Sc、Er、Y等微合金化元素的作用以及对Al-Mg系合金微观组织和力学性能的影响规律。最后,结合Al-Mg系合金当前研究现状,提出了今后值得研究的方向。

不同形貌Al-Fe金属的块体压制成形模拟研究

文章以含40%Al的Al-Fe复合金属为研究对象,对颗粒状和屑状40Al-Fe复合金属分别进行压制预变形,并对屑状40Al-Fe复合金属预制坯进行了二次热压缩变形,重点研究压制预变形及二次热压缩对Al-Fe复合金属成形性和界面影响。结果表明:压力为16 MPa时,颗粒状40Al-Fe复合金属预制坯(密度为4.54 g/cm^(3))成形性良好且形成致密界面;压力为16 MPa时,屑状40Al-Fe复合金属预制坯(密度为3.50 g/cm3)可以成形但界面存在孔洞,Al屑主要为“片层状”“狗牙状”“圆圈状”“波浪状”,其经二次热压缩变形,“圆圈状”Al屑连成一个整体,“狗牙状”与“波浪状”Al屑均演变为“片层状”,而Fe屑仍为“片层状”“块状”,未发生明显变形。变形温度300℃、变形速率0.5 s^(-1)、变形程度0.1是目前生产工艺最佳参数,此时屑状40Al-Fe复合金属成形性最佳且界面结合良好(密度为4.66 g/cm^(3))。

碳纳米管增韧Al-Mg合金复合材料的制备与性能研究

选择碳纳米管为增强相,通过搅拌铸造法制备了碳纳米管增韧Al-Mg合金复合材料,研究了碳纳米管的添加量对复合材料力学性能、微观组织以及韧性的影响,并探究了碳纳米管对Al-Mg合金的增韧机理。结果表明,掺入适量的碳纳米管后细化了Al-Mg合金复合材料的晶粒,晶粒尺寸约为80μm,当碳纳米管的添加量为0.8%(质量分数)时,复合材料的断口形貌最均匀。随着碳纳米管添加量的增大,复合材料的抗拉强度、断裂伸长率、硬度均表现出先增大后降低的趋势,当碳纳米管的添加量为0.8%(质量分数)时,抗拉强度、断裂伸长率和硬度均达到了最大值,分别为208.6 MPa、15.8%和53.1 HB。适量碳纳米管的添加显著改善了Al-Mg合金的韧性,使断裂延伸率逐渐增大,屈服阶段延长,韧性得到提高,这是因为适量的碳纳米管添加后能够与合金发生较好的结合,并贯穿于合金的裂纹中,发挥出了桥联作用,阻碍了裂纹的萌生和扩展,从而改善了Al-Mg合金复合材料的韧性,延缓了合金的失效过程,延长了合金的屈服阶段。综上分析可知,碳纳米管的最佳添加量为0.8%(质量分数)。

电弧喷涂Zn-Al伪合金涂层耐腐蚀性能研究进展

通过在钢基体表面制备涂层可以很好地延长钢铁材料的服役时间,减少因腐蚀造成的重大事故和人员伤亡。相较于传统的纯Zn涂层、纯Al涂层以及Zn-Al合金涂层,Zn-Al伪合金涂层能够为基体材料提供长久有效的腐蚀防护,在钢铁材料的腐蚀防护中具有巨大的应用潜力。简述了Zn-Al伪合金涂层电弧喷涂制备工艺的特点;介绍了Zn、Al、Zn-Al合金及Zn-Al伪合金涂层在模拟海洋环境下的腐蚀防护原理;在此基础上从组分、喷涂工艺参数(喷涂距离、喷涂电流和喷涂电压)、元素掺杂(Mg、Si及Re)及后处理工艺(封孔、激光重熔)等角度,论述了其对Zn-Al伪合金涂层耐蚀性的影响;讨论了Zn-Al伪合金涂层防腐体系在桥梁、海洋钢结构件、地下运输管道中的应用现状;最后总结了目前研究工作中存在的挑战,提出了电弧喷涂Zn-Al伪合金涂层尚需深入研究的重点问题,为提高钢铁材料使用寿命提供了参考。

Y/Al-5Ti-1B复合变质对Al-7Si合金微观组织和力学性能的影响

在传统铸造Al-Si合金中存在的粗大树枝晶α-Al相以及针状共晶Si严重割裂基体,显著降低合金的力学性能。为细化Al-Si合金的组织,提升其力学性能,本文使用扫描电镜(SEM)、电子探针(EPMA)、X射线衍射仪(XRD)以及万能材料试验机,研究了不同添加量Y/Al-5Ti-1B变质剂(Al-5Ti-1B均为2%,稀土Y分别为0.05%、0.1%、0.2%、0.3%、0.4%、0.5%,质量分数)对Al-7Si合金微观组织和力学性能的影响,并探究了其对Al-7Si合金的变质机理。实验结果表明,当Al-5Ti-1B含量为2%、稀土Y含量为0.4%时,变质效果最佳,共晶Si由粗大针状变为细小颗粒状,长和宽分别减小至2.7和0.8μm,相较于未经变质处理的Al-7Si合金,减小了90.6%和4.7%。合金抗拉强度由原来的168.1 MPa提升至209.1 MPa,增加了24.4%。同时伸长率从6.23%提升至9.62%,增长了54.4%。此外,合金的断裂方式也从脆性断裂转变为韧-脆混合断裂。

Sc和Si相互作用对铸造Al-Si-Sc合金组织和性能的影响

通常在铸造Al-Si合金加入Sc来改善合金的性能,但是Si和Sc的相互作用对合金组织和性能影响仍需要进一步深入研究。本文研究了不同含量的Si和Sc对合金组织和性能的影响,结果表明,Sc通过原位形成初生Al_(3)Sc作为α-Al异质形核质点从而细化α-Al晶粒;在凝固过程中,共晶反应生成了网格状AlSi_(2)Sc_(2)相,包晶反应形成了块状AlSi_(2)Sc_(2)相;两种AlSi_(2)Sc_(2)相都会消耗合金中Sc原子,从而降低了Al_(3)Sc的细化效果;Sc还变质共晶Si为更有序的纤维/片状结构,适当的Si与Sc的比可以避免AlSi_(2)Sc_(2)的形成;Al-6Si中Sc含量从0.3%增加至1%时,抗拉强度和屈服强度均上升,但由于AlSi_(2)Sc_(2)相的存在,其伸长率下降;当Sc含量为1%、Si含量从6%降至3%时,抗拉强度、屈服强度和伸长率分别上升2%、12%和21%,主要是凝固过程中析出了Al_(3)Sc而非AlSi_(2)Sc_(2)相。最后,还讨论了Si-Sc交互作用对组织演变的机制。