Catalytic graphitization of Mo-B-doped polyacrylonitrile(PAN)-based carbon fibers

A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.

DSC Study on the Polyacrylonitrile Precursors for Carbon Fibers

Different polyacrylonitrile （PAN） precursor fibers that displayed various thermal properties were studied by using differential scanning calorimetry （DSC）. Results showed that some commercial PAN precursor fibers displayed double separated peaks and these fibers were of high quality because of their process stability during their conversion to carbon fibers of high performance. Some fabrication processes, such as spinning, drawing, could not apparently change the DSC features of a PAN precursor fiber. It was concluded that the thermal properties of a PAN precursor fiber was mainly determined from its comonomer content type and compositions.

Oxadiazole-Functionalized Polyacrylonitrile Fiber as Selective Adsorbent for Mercury Ion

A new oxadiazole-functionalized polyacrylonitrile fiber(PANAOF)was successfully fabricated by immobilizing the organic molecule 2-chloromethyl-5-phenyl-1,3,4-oxadiazole on aminated fiber(PANAF).The fibers were characterized completely by Fourier-transform infrared spectroscopy,elemental analysis,X-ray diffraction,and X-ray photoelectron spectroscopy techniques.Compared with PANAF,PANAOF showed a higher adsorption capability for Hg^2+ions in aqueous solutions.The functionalized fiber PANAOF exhibited a highly selective adsorption for Hg^2+when coexisting with other metal ions viz.Pb^2+,Cd^2+,Cu^2+,Zn^2+,Ni^2+,Co^2+,Cr^3+,Ca^2+,and Mg^2+.The PANAOF presented the best adsorption capacity for Hg^2+at pH 5.Moreover,the adsorption experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm.Notably,the PANAOF almost retained its original adsorption capacity(112 mg/g)after five cycles,indicating its excellent reusability in practical applications.

Polyacrylonitrile/Graphene-Based Coaxial Fiber-Shaped Supercapacitors

Supercapacitors have huge potential applications in the field of wearable electronic devices,such as flexible displays,flexible biosensors and implantable multimedia devices,due to their high-power density,fast charge-discharge rates,long cycling life,and relatively simple configuration.In this paper,we demonstrated hierarchically porous and continuous reduced graphene oxide-polyacrylonitrile@polyacrylonitrile(rGO-PAN@PAN)coaxial fibers with certain strength,excellent electrochemical performance through coaxial wet spinning and thermal reduction.Coaxial fibers are carbonized at high temperature and have a graded porous structure with a conductivity of 1703 S/m.The areal specific capacitance of the supercapacitor assembled by polyvinyl alcohol/sulfuric acid(PVA/H_(2)SO_(4))gel electrolyte is 11.56 mF/cm^(2),and its energy density reaches 0.21 mW·h/cm3,showing good electrochemical performance.Graphene-based coaxial fibers prepared by wet spinning have a great prospect of application in electronic devices due to their excellent properties.

Phase and Structural Transformation of Polyacrylonitrile Fiber during Two-Stage Thermal Stabilization

The influence of two-stage isothermal treatment on the change in the linear dimensions of the fiber, the average sizes of the coherent scattering regions, the texture and phase composition of the polyacrylonitrile fiber in the process of isothermal thermal stabilization is considered by the methods of dilatometry and X-ray diffraction analysis. It is shown that preliminary short-term heat treatment at a lower temperature affects the process of structural transformations of the polyacrylonitrile fiber material and the formation of a new highly dispersed phase of the thermally stabilized fiber.

Structural Evolution of Polyacrylonitrile Fibers in Stabilization and Carbonization

The effect of structural evolution polyacrylonitrile (PAN) on mechanical properties was investigated in stabilization and carbonization. PAN spun fibers were stabilized in a convection oven with a constant tension for various times at 250℃. Fourier Transform Infrared spectroscopy (FTIR) and gel fraction results suggested that intra and intermolecular stabilization reactions occurred simultaneously. X-ray diffractograms revealed a disruption of crystalline structure and an appearance of pre-graphitic structure of PAN fibers due to stabilization. These structural changes by stabilization resulted in the significant decrease of tensile properties of fibers. In Raman spectra with heat treated fibers from 400℃ up to 1200℃, the intensity ratio of the D to G bands (ID/IG) decreased as heat treatment temperature increased, indicating an increase of basal plane of graphitic layer of heat treated fibers. Tensile strength of heat treated fibers at 1200℃ was found to be as high as 2.2 GPa.

Effects of Pre-oxidation Conditions on Adsorption Performance of Activated Carbon Fibers

In order to investigate the effects of pre-oxidation conditions on adsorption performance of activated carbon fibers （ ACFs ）, electrospun polyacrylonitrile （ PAN ） fiber webs were adopted as precursors for preparing ACFs. Firstly, the webs were stabilized under different pre-oxidation conditions; secondly, the pre-oxidative fibers were chemically activated by high temperature treatment in nitrogen. Pre-oxidation temperature, heating rate, and treatment time are the main factors on affecting the adsorption performance of the ACFs. Scanning electron microscope （ SEM）, differential scanning calorimeter （DSC）, and Fourier transform infrared spectroscopy （FTIR） were used to characterize the structure and property of the pre-oxldatlve fibers, and the dynamic benzene adsorption capacity of benzene of ACFs was measured. The results indicate that the moderate pre-oxidation condition is necessary to prepare the ACFs with better adsorption capacity, and the optimal oxidation conditions are to increase from room temperature to 230 ~C with a heating rate of 0.75 ~C ~ min -1 held at the peak temperature for 30min.

A STUDY OF THE IMPOVEMENT OF TENACITY OF POLYACRYLONITRILE PREOXIDED FIBRE BY USING CUPROUS SALT

Polyacrylonitrile preoxided fibre PANOF is an intermediate in carbon fibre preparation. Thequality of PANOF is closely related to the property and structure of carbon fibre. In this paper, thermal mechanical analysis(TMA), thermogravimetric analysis(TGA), swell-ing differential scanning calorimetry(SDSC)and X-ray photoelectron spectroscopy(XPS)wereused to study the increase in tenacity of PANOF from the precursor treated with cuprous salt It has been discovered that the cuprous salt reacts strongly with the uncyclized CN of PANOF,resulting in an increase in the tenacity of PANOF by 30%. The results shwo that the cause of thistenacity improvement is the formation of coordinated complex. Cu^+is the central ion, and PANOFthe ligand. It is due to the coordinate bond that the network structure is formed from uncyclizedCN of PANOF. Therefore the tenacity of PANOF is remarkably increased.

Research on the Dynamic Performance of Polyacrylonitrile Muscles

The dynamic property of polyacrylonitrile (PAN) muscles was tested. The test results can help us to master PAN muscles' mechanical and chemical behaviors, which are indispensable for us to build dynamic model for the artificial muscle. Furthermore, here we provide an important experimental way to study gel muscles.

Review:Processing and Applications of Polyacrylonitrile Derived Carbon Materials

Polyacrylonitrile(PAN) is a well-known polymer with features of great stability, outstanding physical and chemical resistance. Owing to its high carbon yield and stable performance, PAN has been widely used as a carbonizable precursor for preparing carbon materials with inherent N dopant through an oxidative stabilization and a following carbonization process. The structures and compositions of PAN precursors would further influence the formation of the resulting carbon materials. Hence, it is crucial to develop efficient processing methods to prepare PAN-based precursors with suitable morphologies and compositions. The obtained carbon materials with large surface area and good electric conductivity could be employed in a variety of fields such as structural materials, energy storage and conversion as well as adsorption and separation.

KOH Direct Activation for Preparing Activated Carbon Fiber from Polyacrylonitrile-based Pre-oxidized Fiber

The activated carbon fiber（ACF） was prepared from polyacrylonitrile-based pre-oxidized fiber（PANOF） by KOH direct activation. The influence of activation conditions including impregnation ratio（the mass ratio of PANOF to KOH）, activation temperature and activation time on the pore structure and electrochemical properties of ACF was investigated, and the corresponding activation mechanism was proposed. The ACF prepared at an activation temperature of 800℃ and an impregnation ratio（the mass ratio of PANOF to KOH） of 1：2 for an activation time of 1 b in 6 mol/L KOH solution exhibits a specific surface area of 3029 m^2/g, a mesoporosity of 84.2% and a specific capacitance of 288 F/g, and shows a good capacitive performance. The prepared ACF can be used as the electrode material for supercapacitors.

均聚和共聚聚丙烯腈基原丝在预氧化过程中结构变化规律对比研究

采用相同工艺条件对均聚和共聚聚丙烯腈(PAN)基原丝进行梯度预氧化处理,通过有机元素分析、X射线衍射、傅里叶红外光谱、光学显微镜分析两种原丝在预氧化过程中微观结构的变化规律。详细探讨了共聚单体的引入对原丝和预氧丝结构的影响,以期为碳纤维实际生产提供一定的理论基础。研究结果表明,共聚单体的引入影响了PAN分子链的规整度,降低了原丝的结晶度,增大了晶间距和晶粒尺寸,使原丝的晶体结构在预氧化过程中更容易被破坏,可以使原丝的预氧化反应变得缓和,从而使更多的PAN分子链形成稳定的交联结构,同时可以减弱皮芯结构,改善纤维的匀质性。

Robust Composite Separator Randomly Interwoven by PI and Pre-oxidized PAN Nanofibers for High Performance Lithium-ion Batteries

Electrospun nanofibrous separators,despite lacking superior mechanical strength,have gained widespread attention with high porosity and facile processing.Herein,utilizing the fact that thermal imidization temperature of poly(amic acid)(PAA)into polyimide(PI)coincides with the pre-oxidation temperature of polyacrylonitrile(PAN)into carbon fiber,we proposed a new cross-electrospinning strategy to obtain a composite nanofibrous separator(PI/oPAN)randomly interwoven by PI and pre-oxidized PAN(oPAN)nanofibers,via synchronously electrospinning the PAA and PAN onto the same collector and then heat-treating for 2 h at 300℃.The resultant PI/oPAN separator was able to preserve high porosity(71.7%),electrolyte wettability and thermal stability of PI nanofibrous membrane,and surprisingly exhibited high mechanical strength,being 3 times of PI,which mainly because of the numerous adhesion points generated by the melting of PAN in the pre-oxidation process.Meanwhile,the polar groups of oPAN and 3D fibrous network enhanced the PI/oPAN separator's ionic conductivity and Li+transference number,rendering the corresponding cell with more stable cycling performance than cells assembled with pure PI,PAN or commercial PP separator.Therefore,this work might provide a new avenue for the ongoing design and further development of LIB separators capable of high safety and high performance.

接枝法改性聚丙烯腈纤维研究进展

介绍了聚丙烯腈纤维化学接枝改性的主要方法,并对改性后纤维存在的机械性能差、利用率低等问题进行了阐述和分析,指出采用温和的化学改性方法以及扩展规模化改性纤维应用领域是其未来发展的主要方向。

Comparison of Structure and Properties among Various PAN Fibers for Carbon Fibers

To find out the high-quality polyacrylonitrile (PAN) fibers, some differences are sought by comparing domestic PAN fibers with the foreign ones. X-ray diffractometer (XRD), transmission electron microscope (TEM), Fourier transform infrared (FT-IR) spectrometer, elemental analyzer, tensile-testing machine and high-temperature differential scanning calorimeter (DSC) are used to characterize the individual microstructure, chemical structure, elemental content, mechanical properties and thermal properties. It is found that high-quality PAN fibers have high density, lower titre, higher or adequate tensile strength, and they also have better conglomeration structure, smaller crystal dimension with dispersive distribution, less microvoids and flaws.

Surface State of Carbon Fibers Modified by Electrochemical Oxidation

Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5% which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

Comparative Study on Preparing Carbon Fibers Based on PAN Precursors with Different Comonomers

Two different PAN precursors with various comonomers were wet-spun. The properties and structurul changes of PAN precursors and their evolution during preoxidation and carbonization process were characterized by the use of DSC , FTIR and traditional parameters, e g, tensile strength. It is demonstrated that acrylamide（ AAM ） is very effective to make the DSC peak be separated compared to methyl acrylate （ MA ）. As a result, carbon fibers developed from AAM-contained precursors have a better tenacity compared to those developed from MAcontained ones.

DEFORMATION AND FRACTURE OF FIBERS Part 4:Fracture Behaviour of PET and PAN Fibers in Tension

The dynamic observation of the fracture processes of PET(polyethylene terephthalate)andPAN(polyacrylonitrile)fibers in tension was carried out under a scanning electron microscope.Thestepwisc micrographs taken revealed the features of crack initiation and crack growth and of thefailure of the fibers.The fracture behaviour of PET fibers in tension is characterized by theoccurence of shear bands,which initiate a crack whose development leads to the final failure of afiber.For tensile PAN fibers,a high concentration of cracks are initiate in the skin of a fiber,andthen a few or one of them develop themselves by way of pulse and lead to the final failure of the fi-ber.

Sn-Zn合金包覆PAN基碳纤维/聚六氟丙烯有机光纤材料的制备

采用Sn-Zn合金包覆聚丙烯腈(PAN)基碳纤维,以聚六氟丙烯为载体制备塑料光纤(POF)皮层材料,并将POF皮层材料与聚苯乙烯光纤芯材进行匹配,研究了材料在力学性能、传输损耗性、光场强度方面的变化。结果表明:Sn-Zn合金表面包覆PAN基碳纤维与聚六氟丙烯结合紧密,作为POF皮层材料的效果良好,在最常见的650 nm波长、100 m内,传输低于100 Mb/s速率数据信息的能力符合要求,光信号基本环绕着光纤芯材传播,没有过多的光信号因为皮层材质的缘故而散失,表明该皮层材料与聚苯乙烯光纤芯材的匹配性较高。

聚丙烯腈纤维调控水泥基充填材料凝结硬化与力学性能研究

利用聚丙烯腈(PAN)纤维调控水泥基充填材料,对水泥基充填材料的凝结硬化时间、抗压强度、黏结强度、抗弯强度和抗拉强度进行了分析,研究了不同纤维掺量(0.5%、1%、1.5%)和不同长径比(100、200、300)的聚丙烯腈纤维对水泥基充填材料力学性能的影响。结果表明:当PAN纤维掺量为1.5%时,较CM组(不掺PAN纤维)的初凝和终凝时间分别降低了11.1%和5.7%;PAN纤维水泥基充填材料的抗压强度随着PAN纤维含量增加而降低。与CM组相比,当PAN纤维体积含量为0.5%、1.0%和1.5%时,抗压强度分别下降了13.0%、3.7%和7.4%;纤维掺量为1%、长径比为200的水泥基充填材料的抗弯强度较CM组增加了78.6%,增幅最大。水泥基充填材料的黏结强度和抗弯强度先增加,然后随着PAN体积掺量和长径比增加而降低;随着PAN纤维掺入,水泥基充填材料的抗拉强度有所提高,与CM组相比,PAN纤维水泥基充填材料的抗拉强度提高了36.4%~418.2%。