Carbon matrix effects on the micro-structure and performance of Pt nanowire cathode prepared by decal transfer method

High performance cathode for polymer electrolyte membrane fuel cell was prepared by depositing Pt nanowires in a carbon matrix coated on a substrate, and using decal transfer method to fabricate the membrane electrode assembly. The effects of carbon and ionomer contents on the electrode micro-structure and fuel cell performance are investigated by physical characterization and single cell testing. The Pt nanowires are gradient distributed across the cathode thickness, and more Pt exists near the membrane. Both the carbon and ionomer contents can affect the Pt nanowires distribution and aggregation. In addition, the carbon loading dominates the transport distance of gas and proton, and the ionomer content affects the triple phase boundaries and porosity in the cathode. The optimal structure of Pt nanowire cathode is obtained at 0.10 mg·cm^-2 carbon loading and 10 wt% ionomer.

“All‐In‐One” integrated ultrathin SnS2@3D multichannel carbon matrix power high‐areal–capacity lithium battery anode

Construction of a thickness‐independent electrode with high active material mass loading is crucial for the development of high energy rechargeable lithium battery.Herein,we fabricate an all‐in‐one integrated SnS2@3D multichannel carbon matrix(SnS2@3DMCM)electrode with in‐situ growth of ultrathin SnS2 nanosheets inside the inner walls of three dimensional(3D)multichannels.The interconnected conductive carbon matrix derived from natural wood acts as an integrated porous current collector to avail the electrons transport and accommodate massive SnS2 nanosheets,while plenty of 3D aligned multichannels facilitate fast ions transport with electrode thickness‐independent even under high mass loading.As expected,the integrated SnS2@3DMCM electrode exhibits remarkable electrochemical lithium storage performance,such as exceptional high‐areal‐capacity of 6.4 mAh cm−2,high rate capability of 3 mAh cm−2 under current of 6.8 mAcm−2(10 C),and stable cycling performance of 6.8 mAcm−2 with a high mass loading of 7mg cm−2.The 3D integrated porous electrode constructing conveniently with the natural source paves new avenues towards future high‐performance lithium batteries.

Aluminum matrix composites reinforced by molybdenum-coated carbon nanotubes

To extend the application of carbon nanotubes （CNTs） and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT （Mo-CNT）/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders.The electrical conductivity of the composites decreases with increasing Mo-CNT content.When the Mo-CNT content is 0.5wt%,the tensile strength and hardness of Mo-CNT/Al reach their maximum values.The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%,while the electrical conductivity only decreases by 7.1%,relative to sintered pure Al.The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.

Synergistic regulation of current-carrying wear performance of resin matrix carbon brush composites with tungsten copper composite powder

Resin matrix carbon brush composites(RMCBCs)are critical materials for high-powered electric tools.However,effectively improving their wear resistance and heat dissipation remains a challenge.RMCBCs prepared with flake graphite powders that were evenly loaded with tungsten copper composite powder(RMCBCs-W@Cu)exhibited a low wear rate of 1.63 mm^(3)/h,exhibiting 48.6%reduction in the wear rate relative to RCMBCs without additives(RMCBCs-0).In addition,RMCBCs-W@Cu achieved a low friction coefficient of 0.243 and low electric spark grade.These findings indicate that tungsten copper composite powders provide particle reinforcement and generate a gradation effect for the epoxy resin(i.e.,connecting phase)in RMCBCs,which weakens the wear of RMCBCs caused by fatigue under a cyclic current-carrying wear.

Carbon matrix/SiNWs heterogeneous block as improved reversible anodes material for lithium ion batteries

A novel carbon matrix/silicon nanowires(SiNWs) heterogeneous block was successfully produced by dispersing SiNWs into templated carbon matrix via a modified evaporation induced self-assembly method. The heterogeneous block was determined by X-ray diffraction, Raman spectra and scanning electron microscopy. As an anode material for lithium batteries, the block was investigated by cyclic voltammograms(CV), charge/discharge tests, galvanostatic cycling performance and A. C. impedance spectroscopy. We show that the SiNWs disperse into the framework, and are nicely wrapped by the carbon matrix. The heterogeneous block exhibits superior electrochemical reversibility with a high specific capacity of 529.3 mAh/g in comparison with bare SiNWs anode with merely about 52.6 mAh/g capacity retention. The block presents excellent cycle stability and capacity retention which can be attributed to the improvement of conductivity by the existence of carbon matrix and the enhancement of ability to relieve the large volume expansion of SiNWs during the lithium insertion/extraction cycle. The results indicate that the as-prepared carbon matrix/SiNWs heterogeneous block can be an attractive and potential anode material for lithium-ion battery applications.

Mechanical, electrical, and thermal expansion properties of carbon nanotube-based silver and silver–palladium alloy composites

The mechanical, electrical, and thermal expansion properties of carbon nanotube（CNT）-based silver and silver–palladium（10：1, w/w） alloy nanocomposites are reported. To tailor the properties of silver, CNTs were incorporated into a silver matrix by a modified molecular level-mixing process. CNTs interact weakly with silver because of their non-reactive nature and lack of mutual solubility. Therefore, palladium was utilized as an alloying element to improve interfacial adhesion. Comparative microstructural characterizations and property evaluations of the nanocomposites were performed. The structural characterizations revealed that decorated type-CNTs were dispersed, embedded, and anchored into the silver matrix. The experimental results indicated that the modification of the silver and silver–palladium nanocomposite with CNT resulted in increases in the hardness and Young＇s modulus along with concomitant decreases in the electrical conductivity and the coefficient of thermal expansion（CTE）. The hardness and Young＇s modulus of the nanocomposites were increased by 30%？40% whereas the CTE was decreased to 50%-60% of the CTE of silver. The significantly improved CTE and the mechanical properties of the CNT-reinforced silver and silver–palladium nanocomposites are correlated with the intriguing properties of CNTs and with good interfacial adhesion between the CNTs and silver as a result of the fabrication process and the contact action of palladium as an alloying element.

Chemical, mechanical, and thermal expansion properties of a carbon nanotube-reinforced aluminum nanocomposite

In the present study,the chemical and mechanical properties and the thermal expansion of a carbon nanotube（CNT）-based crystalline nano-aluminum（nano Al） composite were reported.The properties of nanocomposites were tailored by incorporating CNTs into the nano Al matrix using a physical mixing method.The elastic moduli and the coefficient of thermal expansion（CTE） of the nanocomposites were also estimated to understand the effects of CNT reinforcement in the Al matrix.Microstructural characterization of the nanocomposite reveals that the CNTs are dispersed and embedded in the Al matrix.The experimental results indicate that the incorporation of CNTs into the nano Al matrix results in the increase in hardness and elastic modulus along with a concomitant decrease in the coefficient of thermal expansion The hardness and elastic modulus of the nanocomposite increase by 21%and 20%,respectively,upon CNT addition.The CTE of CNT/A1 nanocomposite decreases to 70%compared with that of nano Al.

Ultrasmall CoS nanoparticles embedded in heteroatom-doped carbon for sodium-ion batteries and mechanism explorations via synchrotron X-ray techniques

Transition metal sulfides have been regarded as promising anode materials for sodium-ion batteries(SIB).However,they face the challenges of poor electronic conductivity and large volume change,which result in capacity fade and low rate capability.In this work,a composite containing ultrasmall CoS(~7 nm)nanoparticles embedded in heteroatom(N,S,and O)-doped carbon was synthesized by an efficient one-step sulfidation process using a Co(Salen)precursor.The ultrasmall CoS nanoparticles are beneficial for mechanical stability and shortening Na-ions diffusion pathways.Furthermore,the N,S,and O-doped defect-rich carbon provides a robust and highly conductive framework enriched with active sites for sodium storage as well as mitigates volume expansion and polysulfide shuttle.As anode for SIB,CoS@HDC exhibits a high initial capacity of 906 mA h g^(-1)at 100 mA g^(-1)and a stable long-term cycling life with over 1000 cycles at 500 mA g^(-1),showing a reversible capacity of 330 mA h g^(-1).Meanwhile,the CoS@HDC anode is proven to maintain its structural integrity and compositional reversibility during cycling.Furthermore,Na-ion full batteries based on the CoS@HDC anode and Na_(3)V_(2)(PO_(4))_(3)cathode demonstrate a stable cycling behavior with a reversible specific capacity of~200 m A h g^(-1)at least for 100 cycles.Moreover,advanced synchrotron operando X-ray diffraction,ex-situ X-ray absorption spectroscopy,and comprehensive electrochemical tests reveal the structural transformation and the Co coordination chemistry evolution of the CoS@HDC during cycling,providing fundamental insights into the sodium storage mechanism.

Unraveling specific role of carbon matrix over Pd/quasi-Ce-MOF facilitating toluene enhanced degradation

Metal organic frameworks(MOFs)derivatives represented by quasi-MOFs have excellent physical and chemical properties and can be applied for the catalytic combustion of volatile organic compounds(VOCs).In this work,Pd/quasi-Ce-BTC synthesized by simple one-step Npyrolysis was applied to the oxidation of toluene,showing excellent toluene catalytic activity(T_(90)=175℃,30000 mL/(g·h)).Microscopic analyses indicate the formation and interaction of a carbon matrix composite quasi-MOF structure interface.The results show that the amorphous carbon matrix formed during the partial pyrolysis of Ce-BTC significantly improves the adsorption and activation capacity of toluene in the reaction,and constructs a reductive system to maintain high concentrations of Ce^(3+)and Pd^(0),which can facilitate the activation and utilization of oxygen in reaction.Quasi in-situ XPS proves that carbon matrix is indirectly involved in the activation and storage of oxygen,and Pd^(0)is the crucial active site for the activation of oxygen.Stability and water resistance tests display good stability of Pd/quasi-Ce-BTC.This work provides a potential method for designing quasi-MOF catalysts towards VOCs effective abatement.

Synthesis of Co3O4 Nanoparticles Wrapped Within Full Carbon Matrix as an Anode Material for Lithium Ion Batteries

A facile polyol-assisted pyro-synthesis method was used to synthesize Co3O4 nanoparticles embedded into carbon matrix without using any conventional carbon source. The surface analysis by scanning electron microscopy showed that the Co3O4 nanoparticles（-20 ± 5 nm） are tightly enwrapped within the carbon matrix. CHN analysis determined the carbon content was only 0.11% in the final annealed sample. The Co3O4@carbon exhibited high capacities and excellent cycling performance as an anode at various current rates（such as 914.4 and 515.5 mAh g^-1 at 0.25 and1.0 C, respectively, after 50 cycles; 318.2 mAh g^-1 at a high current rate of 5.0 C after 25 cycles）. This superior electrochemical performance of the electrode can be attributed to the various aspects, such as,（1） the existence of carbon matrix, which acts as a flexible buffer to accommodate the volume changes during Li^＋ion insertion/deinsertion and facilitates the fast Li^＋and electron transfer and（2） the anchoring of Co3O4 nanoparticles within the carbon matrix prevents particles agglomeration.

Vanadium nitride nanoparticles embedded in carbon matrix with pseudocapacitive behavior for high performance lithium-ion capacitors

Lithium-ion capacitors(LICs)have attracted wide attention due to their potential of achieving merits of high-power output as well as high energy density.How-ever,the key issue of kinetics mismatch between anode and cathode hinders the electrochemical performance of LICs.Therefore,a vanadium nitride composite with nanoparti-cles embedded in carbon matrix(VN-C)was prepared as an efficiently pseudocapacitive anode material with high electronic conductivity and fast Li-ion diffusion rate.The VN-C composites were synthesized through one-step ammonia heating treatment at different temperatures among which the sample annealed at 600℃exhibits high specific capacity(513 mAh·g^(-1)at 0.1 A·g^(-1)),outstanding rate performance(~300 mAh·g^(-1)at 10 A·g^(-1)),and excellent cyclic steadiness(negligible capacity decay over 2000 cycles)in half-cell devices.A high-performance lithium-ion capacitor device was also fabricated by using VN-C-600 as the anode and activated carbon as the cath-ode,delivering a maximum energy density of 112.6 Wh·kg^(-1)and an extreme power density of 10 kW·kg^(-1).

Si_(3)N_(4)nanowires@pyrolytic carbon nanolayers coupled withhydroxyapatite nanosheets as reinforcement for carbon matrixcomposites with boosting mechanical and friction properties

Extensive attention has been drawn to the development of carbon-matrix composites for application in the aerospace and military industry,where a combination of high mechanical strength and excellent frictional properties are required.Herein,carbon-matrix composites reinforced by Si_(3)N_(4)nanowires@pyrolytic carbon nanolayers(Si_(3)N_(4nws)@PyCnls)coupled with hydroxyapatite nanosheets is reported.The Si_(3)N_(4nws)@PyCnls(SP)with coaxial structure could increase the surface roughness of Si_(3)N_(4nws)and promote the stress transfer to the carbon matrix,whereas the porous hydroxyapatite nanosheets favor the infiltration of the carbon matrix and promote the interfacial bonding between the SP and carbon matrix.The carbon matrix composites reinforced by SP coupled with hydroxyapatite nanosheets(Si_(3)N_(4nws)@PyCnls-HA-C)exhibit excellent mechanical strength.Compare with the conventional Si_(3)N_(4nws)reinforced carbon composites,Si_(3)N_(4nws)@PyCnls-HA-C(SPHC)have 162%and 249%improvement in flexural strength and elastic modulus,respectively.Moreover,the friction coefficient and wear rate decreased by 53%and 23%,respectively.This study provides a co-reinforcement strategy generated by SP coupled with hydroxyapatite nanosheets for effective improvement of mechanical and frictional properties of carbon matrix composites that are used for aerospace and military industry applications.

Template-assisted formation of atomically dispersed iron anchoring on nitrogen-doped porous carbon matrix for efficient oxygen reduction

Isolated active metal atoms anchored on nitrogen-doped carbon matrix have been developed as the efficient catalyst for accelerating sluggish reaction kinetics of oxygen reduction reaction(ORR).The facile rational structure engineering with abundant isolated active metal atoms is highly desirable but challenging.Herein,we demonstrate that atomically dispersed Fe sites(Fe-N4 moieties)on the hierarchical porous nitrogen-doped carbon matrix(Fe-SA-PNC)for high ORR activity can be achieved by a dual-template assisted strategy.By thermal decomposition of NH_(4)Cl template,the nitrogen-doped carbon matrix is generated based on the interaction with carbon precursor of citric acid.Meanwhile,the introduction of NaCl template facilitates the formation of hierarchical porous structures,which enable more active sites exposed and improve the mass transfer.Interestingly,the dual-template strategy can inhibit the formation of iron carbide nanoparticles(NPs)by generating porous structures and avoiding of the rapid loss of nitrogen during pyrolysis.The as-made Fe-SA-PNC catalysts with well-defined Fe-N_(4)active sites exhibit highly efficient ORR activity with a half-wave potential of 0.838 V versus the reversible hydrogen electrode,as well as good stability and methanol tolerance,outperforming the commercial Pt/C.The zinc-air battery(ZAB)constructed by Fe-SA-PNC also shows a higher peak power density and specific discharging capacity than that of Pt-based ZAB.The present work provides the facile strategy for tailoring nitrogen doping and porous structures simultaneously to prevent the formation NPs for achieving the well-dispersed and accessible single-atom active sites,paving a new way to design efficient electrocatalysts for ORR in fuel cells.

A Novel Melt Processing for Mg Matrix Composites Reinforced by Multiwalled Carbon Nanotubes

Carbon nanotubes（CNTs） reinforced Mg matrix composites were fabricated by a novel melt processing.The novel processing consisted of two courses：CNTs pre-dispersion and ultrasonic melt processing.Mechanical ball-milling was employed to pre-disperse CNTs on Zinc（Zn） flakes.Serious CNT entanglements were well dispersed to single CNT or tiny clusters on Zn flakes.The ultrasonic melt processing further dispersed CNTs in the Mg melt,especially tiny CNT clusters.Thus,a uniform dispersion of CNTs was achieved in the as-cast composites.Hot extrusion further improved the distribution of CNTs.CNTs increased both the strength and elongation of the matrix alloy.Notably,the elongation of the matrix alloy was enhanced by 40%.Grain refinement and the pulling-out of CNTs resulted in the evident improvement of ductility for the composites.

Oxidation behaviors of carbon fiber reinforced multilayer SiC–Si_(3)N_(4) matrix composites

Oxidation behaviors of carbon fiber reinforced SiC matrix composites(C/SiC)are one of the most noteworthy properties.For C/SiC,the oxidation behavior was controlled by matrix microcracks caused by the mismatch of coefficients of thermal expansion(CTEs)and elastic modulus between carbon fiber and SiC matrix.In order to improve the oxidation resistance,multilayer SiC–Si_(3)N_(4) matrices were fabricated by chemical vapor infiltration(CVI)to alleviate the above two kinds of mismatch and change the local stress distribution.For the oxidation of C/SiC with multilayer matrices,matrix microcracks would be deflected at the transition layer between different layers of multilayer SiC–Si_(3)N_(4) matrix to lengthen the oxygen diffusion channels,thereby improving the oxidation resistance of C/SiC,especially at 800 and 1000℃.The strength retention ratio was increased from 61.9%(C/SiC–SiC/SiC)to 75.7%(C/SiC–Si_(3)N_(4)/SiC/SiC)and 67.8%(C/SiC–SiC/Si_(3)N_(4)/SiC)after oxidation at 800℃for 10 h.

氮碳包封Fe_(3)C纳米颗粒作为高效富氧还原电催化剂

高活性MOF基催化剂的设计和合成为促进动力学不利的氧还原反应(ORR)过程开辟了新的途径.本研究通过在ZIF-8前驱体表面涂覆二茂铁甲酸,然后进行两步炭化工艺,设计和制备了一种具有新型结构的高效电催化剂,以提高ORR性能.两步炭化过程对于将热解Fe_(3)C纳米颗粒封装到碳纳米管(CNTs)中以及将Fe单原子隔离到N掺杂碳(NC)基体上至关重要.此外,Fe元素的相对含量对优化催化剂的ORR性能至关重要.所制得Fe_(3)C@CNTs/NC-M催化剂结构先进,在碱性溶液中表现出良好的长期稳定性和电催化ORR性能,其半波电位和极限电流分别达到0.941 V和6.31 mA cm^(-2).此外,该电催化剂在甲醇溶液中具有较强的耐受性和良好的稳定性.Fe_(3)C@CNTs/NC-M锌空气电池(ZAB)具有1.525 V的开路电位,420 mA cm^(-2)时的峰值功率密度为348 mW cm^(-2),10 mA cm^(-2)时的最大容量为843 mA h g_(Zn)^(-1).因此,这种合成策略为构建具有有效和稳定的ORR性能的MOF基电催化材料提供了一条有效途径.

Recent progress in Li-S and Li-Se batteries

Li–S and Li–Se batteries have attracted tremendous attention during the past several decades, as the energy density of Li–S and Li–Se batteries is high（several times higher than that of traditional Li-ion batteries）.Besides, Li–S and Li–Se batteries are low cost and environmental benign. However, the commercial applications of Li–S and Li–Se batteries are hindered by the dissolution and shuttle phenomena of polysulfide（polyselenium）, the low conductivity of S（Se）, etc. To overcome these drawbacks, scientists have come up with various methods, such as optimizing the electrolyte, synthesizing composite electrode of S/polymer, S/carbon, S/metal organic framework（MOF） and constructing novelty structure of battery.In this review, we present a systematic introduction about the recent progress of Li–S and Li–Se batteries, especially in the area of electrode materials, both of cathode material and anode material for Li–S and Li–Se batteries. In addition, other methods to lead a high-performance Li–S and Li–Se batteries are also briefly summarized, such as constructing novelty battery structure, adopting proper charge–discharge conditions, heteroatom doping into sulfur molecules, using different kinds of electrolytes and binders. In the end of the review, the developed directions of Li–S and Li–Se batteries are also pointed out. We believe that combining proper porous carbon matrix and heteroatom doping may further improve the electrochemical performance of Li–S and Li–Se batteries. We also believe that Li–S and Li–Se batteries will get more exciting results and have promising future by the effort of battery community.

Thermal conductivity and bending strength of SiC composites reinforced by pitch-based carbon fibers

In this work,pitch-based carbon fibers were utilized to reinforce silicon carbide(SiC)composites via reaction melting infiltration(RMI)method by controlling the reaction temperature and resin carbon content.Thermal conductivities and bending strengths of composites obtained under different preparation conditions were characterized by various analytical methods.Results showed the formation of SiC whiskers(SiC_(w))during RMI process according to vapor–solid(VS)mechanism.SiC_(w) played an important role in toughening the C_(pf)/SiC composites due to crack bridging,crack deflection,and SiC_(w) pull-out.Increase in reaction temperature during RMI process led to an initial increase in thermal conductivity along in-plane and thickness directions of composites,followed by a decline.At reaction temperature of 1600℃,thermal conductivities along the in-plane and thickness directions were estimated to be 203.00 and 39.59 W/(m×K),respectively.Under these conditions,bending strength was recorded as 186.15±3.95 MPa.Increase in resin carbon content before RMI process led to the generation of more SiC matrix.Thermal conductivities along in-plane and thickness directions remained stable with desirable values of 175.79 and 38.86 W/(m×K),respectively.By comparison,optimal bending strength improved to 244.62±3.07 MPa.In sum,these findings look promising for future application of pitch-based carbon fibers for reinforcement of SiC ceramic composites.

Chemical composition and source apportionment of PM2.5 and PM2.5-10 in Trombay （Mumbai, India）, a coastal industrial area

PM2.5 and PM2.5 lo concentrations, elemental constituents, and sources in a densely populated coastal industrial area （Trombay, Mumbai） were investigated in 2010 and 2011.The PM2.s and PM2.s lo concentra- tions were 13.50-71.60 and 22.40-127.78 p^g/m3, respectively. The daily PM25 concentrations exceeded the Indian Central Pollution Control Board limit （60 μg/m3） several days in winter. Of the elements analyzed, Si then Al had the highest concentrations in PM2.5- 10, but black carbon then Si had the highest concentrations in PM2.s. The element concentrations varied widely by season. Al, Ca, Fe, Si, and Ti con- centrations were highest in summer, Cl, Mg, and Na concentrations were highest in the monsoon season, and the other trace metal concentrations in both PM2.5 and PM2.5-10 were highest in winter. The PM2.5 and PM2.5-10 sources were apportioned by positive matrix factorization. PM2.5 and PM2.5-10 had six dominant sources, crustal material （8.7% and 25.3%, respectively）, sea salt spray （6.1% and 15.0%, respectively）, coal/biomass combustion （25.5% and 13.8%, respectively）, fuel oil combustion （19.0% and 11.2%, respectively）, road traffic （ 17.7% and 12.6%, respectively）, and the metal industry （ 10.6% and 7.0%, respectively）. Anthropogenic sources clearly contributed most to PM2.5 but natural sources contributed most to PM2.5-10.

S-Doped Carbon-Coated FeS_(2)/C@C Nanorods for Potassium Storage

Potassium-ion batteries(PIBs) are promising scalable energy storage system;however,one of the challenges for its potential application is the huge volume variations during cycling due to the insertion/extraction of large size potassium ions.Here,we fabricated the S-doped carbon-coated rod-like FeS2/C@C,which not only effectively alleviate the volume variations upon cycling but also can improve electrical conductivity and maintain the structural integrity.As an anode material for PIBs,the rod-like FeS2/C@C electrodes delivered excellent rate performance(175 mA h g-1 at 0.5 A g-1) and stable cycle performance(262 mA h g-1 after 100 cycles at 0.1 A g-1).The superior excellent performance is associated with the unique structure of FeS2/C@C.The as-synthesized FeS2/C@C is demonstrated to be a potential anode for PIBs.