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.

ZnO@PAN柔性复合纳米纤维膜的制备及压电特性

采用静电纺丝技术,通过两步低温水热法制备了ZnO@聚丙烯腈(PAN)柔性复合纳米纤维膜。研究了静电纺丝电压和滚筒转速对ZnO@PAN柔性复合纳米纤维膜压电和铁电性能的影响。研究结果表明,当静电纺丝电压为20 kV、滚筒速度为1000 r/min时,ZnO@PAN柔性复合纳米纤维膜的输出性能达到最佳,输出开路电压可达到5.5 V,短路电流可达到0.61μA,剩余极化强度可达到0.43μC/cm^(2)。在外部负载电阻为13 MΩ时,柔性复合纳米纤维膜达到最大输出功率0.63μW。经过5000次循环敲击测试,所制备的ZnO@PAN柔性复合纳米纤维膜输出性能保持稳定。通过ZnO@PAN柔性复合纳米纤维膜可实时监测握力器微握、半握、全握三种不同的状态,在自供电柔性压力传感器领域有着广阔的应用前景。

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。

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.

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.

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.

The Coagulation Process of Nascent Fibers in PAN Wet-spinning

The evolvement of microstructure and properties of nascent fibers during coagulation process in the polyacrylonitrile （PAN） wet-spinning and the effect of coagulation bath conditions on the structure and properties of the nascent fibers were investigated by the means of X-ray diffraction （XRD）, scanning electron microscope （SEM）, fiber fineness machine, fiber tensile strength machine, etc. The experimental results indicate that the nascent fibers become denser and have fewer inner defects, the diameter of nascent fibers shrink and the crystallization degree of nascent fibers gradually increases with the increasing of coagulation time. Too large spinning tension leads to grooves occurring on surface of fibers. To obtain circular cross-section of nascent fibers the optimal coagulation conditions are 50 ℃, 65% （concentration） and 0.9 （draw ratio）.

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.

Influence of PAN-Fiber Stretching during Thermal Treatment on the Stabilization Reactions

The stabilization of PAN-fibers without additional co-monomers was investigated with thermo-gravimetry and evolved gas analysis (FTIR-spectroscopy and MS-spectrometry). One fiber type had been drawn after spinning, while the other was used as-spun. During the thermal treatment, fiber shrinkage was either restricted or unrestricted. Investigations of influencing chemical and physical reactions regarding this restriction were conducted. Differences in the mass loss and gas emissions were observed, depending on the strained or unstrained state of the fibers. The change of crystallinity and molecular orientation of the fiber as reason of the measured variations was discussed. The emission of ammonia and other nitrogen containing gases (supposedly nitriles/ isocyanates) could be attributed to different aspects of the stabilization process. The length restriction resulted in a change in ammonia emission, associated with the cyclization reaction of poly acrylonitrile. The onset and amount of side reactions were influenced as well.

Study on the Mechanical Properties of Carbon Nanotube/Polyacrylonitrile Composite Fibers

The method of preparing the multi-walled carbon nanotubes (MWNTs)-polyacrylonitriIe (PAN) composite fibers is described and the effects of draw ratio on the mechanical properties of CNT/PAN fibers have also been discussed. The results show that the degrees of MWNTs dispersion in the polymer matrix have much effect on the mechanical properties.

Effect of UV Irradiation on PAN Precursor Fibers and Stabilization Process

A low-cost rout for modification the polyacrylontrile（PAN） precursor fibers was developed.The approach involved pretreatment PAN precursor fibers with UV irradiation for various periods of time before the fibers were stabilized.The effect of UV irradiation on the chemical structure,orientation factor,density,crystallite size and morphology of the fibers in the process of stabilization was characterized by use of fourier transform infrared spectroscopy（FTIR）,float-sink procedure,X-ray diffraction（XRD）,scanning electron microscope（SEM）,respectively.The results showed that UV irradiation could increase the density of the fibers in stabilization process.FTIR analysis indicated that the cyclization of nitrile groups was initiated at room temperature by UV irradiation.The transformation of C≡N groups to C=N ones was accelerated in the process of stabilization.The orientation factor of irradiated fibers was also increased.The crystallite size was decreased at first and increased later,and the better irradiation time of UV was 3 min according to the XRD test.SEM analysis indicated that irradiation could decrease the internal and surface defects of the stabilized fibers treated at 300 ℃.

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.

基于BTO/PAN复合纳米纤维膜的柔性压电纳米发电机

采用简单的一步水热法合成了钛酸钡纳米颗粒(BTO NP),通过静电纺丝法制备了BTO/聚丙烯腈(PAN)复合纳米纤维膜,并基于该膜制备了柔性复合压电纳米发电机。研究结果表明,随着BTO掺杂质量分数的增加,BTO/PAN柔性复合压电纳米发电机的输出电压先增大后减小。当BTO的质量分数为15%时,BTO/PAN柔性复合压电纳米发电机的输出性能最佳,输出电压可达10.2 V,输出电流可达1.52μA。当负载电阻为12 MΩ时,其最大输出功率约为3.72μW,与纯PAN纳米纤维膜压电纳米发电机相比,输出性能有明显改善。经过5000次循环测试结果表明,BTO/PAN柔性复合压电纳米电机的的输出性能没有明显变化,因此其具有较好的稳定性。同时,该压电纳米发电机能够检测人体的不同状态,为研发高性能和自供电的可穿戴生物电子产品提供了参考。

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.

凝固浴牵伸对微纳层叠带状PAN原丝性能的影响

采用新型微纳层叠挤出技术制备了层叠带状聚丙烯腈(PAN)碳纤维原丝,利用扫描电子显微镜、X射线衍射仪、万能材料试验机和差示扫描量热仪对原丝的性能进行表征,研究了不同凝固浴牵伸倍数对微纳层叠带状PAN原丝截面形态、结晶性能、力学性能以及热行为的影响。研究结果表明,随着凝固浴牵伸倍数的提高,层叠带状PAN原丝的厚度显著减小,线密度显著降低;层叠带状PAN原丝的结晶度和拉伸强度随着牵伸倍数的提高呈现先增加后减小的趋势,凝固浴牵伸倍数为5.5倍时,获得的层叠带状PAN原丝的性能较好。当凝固浴牵伸倍数从5.5倍增加至6.5倍时,原丝的拉伸强度由26.08 MPa降低至23.36 MPa。实验结果表明,凝固浴牵伸倍数为5.5倍下制备的层叠带状PAN原丝具有较好的综合性能,其结晶度为39.1%,拉伸强度和拉伸模量分别为26.08及661 MPa。

湿法纺丝制备PAN/相变微胶囊复合相变纤维及其性能研究

以聚脲包覆正十八烷形成相变微胶囊(MPCM)乳液作为相变改性剂,与聚丙烯腈(PAN)共混制备纺丝原液,通过湿法纺丝制备不同MPCM含量的PAN/MPCM复合相变纤维,分析了MPCM乳液的化学结构、粒径分布、热性能及热稳定性,研究了相变纤维的表面形貌、热性能、结晶性能、力学性能及热循环性能。结果表明:MPCM乳液固体粒子粒径分布均一,平均粒径为634.3 nm,在31.4℃和20.3℃发生相变现象,相变焓值可达166.0 J/g,具有良好的相变性能,且热稳定性较好;相变纤维粗细均匀,直径为175μm左右,随着MPCM含量的增加,纤维表面变得不光滑且有明显凸起的微胶囊小球;随着MPCM含量的增加,相变纤维的热性能明显提高,结晶性能及力学性能也有所提高;当MPCM质量分数为8.7%时,相变纤维的熔化温度为29.3℃,凝固温度为22.1℃,熔化焓为44.1 J/g,凝固焓为44.1 J/g,具有良好的热性能,且经50次热循环后的相变温度及相变焓值与经1次热循环后的基本保持一致,具有良好的热循环稳定性;当MPCM质量分数为8.7%时,相变纤维的断裂强度为0.52 cN/dtex,断裂伸长率为35.01%,模量为1.19 GPa。

仿生矿化改性废弃PAN纤维对SBS沥青低温抗裂性能的影响

为了研究废弃聚丙烯腈纤维(PAN)作为SBS复合改性沥青增强剂的可行性,提高SBS复合改性沥青的低温抗裂性能,促进“双碳”战略的实施和可持续发展,采用仿生矿化方法对废弃聚丙烯腈纤维进行改性处理,并将其与SBS复合于沥青中,制备新型复合改性沥青。扫描电子显微镜和X射线荧光分析仪分析表明,纤维表面成功构建了仿生结构,并确认了仿生矿化改性纤维(HP-PAN)的粗糙表面。纤维表面的仿生矿化结构作为沥青中的缓冲器,增强了纤维和沥青之间的相互作用。动态流变剪切和拉伸试验表明,HP-PAN/SBS改性沥青比PAN/SBS改性沥青表现出更好的黏弹性、抗车辙性和拉伸性能,并且在废弃聚丙烯腈纤维的添加量质量分数为2%时,复合改性沥青的性能最好,其低温抗裂性能相较于普通沥青提高了146.94%。

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.

PAN/rGO纤维膜应变传感器的制备及性能

石墨烯材料被广泛用于应变传感器的制备中,但是如何使其具备更高的灵敏度一直是研究人员的一个困扰。基于石墨烯优异的导电性和拉伸性,结合质量轻且多孔的聚丙烯腈(PAN)纳米纤维膜制备一种高灵敏度柔性应变传感器。通过设置定量的PAN与三个梯度质量的石墨烯形成对照实验,探究石墨烯含量对复合材料的性能影响。结果表明,石墨烯质量分数增加,会促使PAN/rGO复合材料的孔隙结构变大且均匀,石墨烯含量越高,复合材料电阻变化率越大,电导率越大,在吹气实验中,2 s内就可以完成一次气体压力检测,是制备高灵敏度形变传感器的理想材料。