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.

Crosslinked polyacrylonitrile precursor for S@pPAN composite cathode materials for rechargeable lithium batteries

S@pPAN has become promising cathode materials in rechargeable batteries due to its high compressed density,low E/S ratio,no polysulfide dissolution,no self-discharge,and stable cycling.However,it is a big challenge to enhance its sulfur content which determines its practical specific capacity.Herein,we prepare crosslinked PAN as precursor,leading to effective enhancement of sulfur content up to 55 wt%and a reversible specific capacity of 838 mAh g _(composites)^(-1) at 0.2C.Because of the microporous structure and high specific area,crosslinked PAN provides more space to accommodate sulfur molecule and improve the interfacial reaction of S@pPAN as well.This work provides a promising direction to design S@pPAN for lithium sulfur batteries with high energy density.

Catalytic graphitization of polyacrylonitrile(PAN)-based carbon fibers with Fe-Cr_2O_3 composite coating

The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile （PAN）-based carbon fibers and its catalytic graphitization were studied. Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD, Raman spectroscopy and SEM. The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures. When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300℃ the interlayer spacing （doo2） and ratio of relative peak area （AD/AG） reach 3.364/k and 0.34, respectively. Whereas, the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800℃ and the values of doo2 and AD/AG are 3.414 A and 0.68, respectively. The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating. The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution-precipitation mechanism.

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。

高效低时延分级多PAN太赫兹无线网络MAC层优化协议

针对现有分级多PAN太赫兹无线网络MAC(Medium Access Control)协议中存在的子网形成方案不合理以及私有CTA(Channel Time Allocation)与子网内实际负载不匹配等问题,提出了一种高效低时延的MAC层优化协议.该协议采用基于泛听的按需形成子网机制避免了子网分布不均匀以及因子网形成后没有节点加入而造成的私有CTA资源浪费的问题.在子网形成后,子微微网协调器(Piconet Coordinator,PNC)根据子网内实际负载情况自适应选择私有CTA时隙资源优化机制,让有数据传输需求的节点及时将数据发出.仿真结果表明,所提出的方案能有效地降低数据帧平均接入时延,提高吞吐量以及数据帧的传输成功率.

CBCT与PAN预测下颌近中低位阻生第三磨牙拔除术损伤水平的临床比较

目的:运用锥形束CT(CBCT)及口腔曲面断层片(PAN)引导拔除下颌近中低位第三磨牙,探讨CBCT作为术前预测手段是否存在优越性。方法:选取于2022年1月至2023年8月在石河子大学第一附属医院就诊的213例患者,分为PAN组和CBCT组,对两组患者分别进行拔牙手术,采集患者术前及术后龈沟液并采用酶联免疫吸附实验(ELISA)测定炎症及疼痛因子浓度;运用统计学方法对比两组在各类指标的差异性。结果:CBCT作为术前评估手段相较传统PAN在明确牙根与MC接触关系上具有优越性(P <0.05),且CBCT组手术时间短、手术并发症发生率低(P <0.05);通过ELISA测定结果得出CBCT组患者龈沟液中炎症因子及疼痛因子的术前术后浓度变化值相较PAN组浓度变化值低(P <0.05)。结论:CBCT相比PAN在评估牙根与下颌管(MC)接触关系这类风险因素方面具有优越性,且应用CBCT作为术前评估手段进行拔牙手术其手术时间短,并发症少,术后损伤小。

PAN/MgO/Ag复合纳米纤维过滤膜的制备及性能分析

为提高聚丙烯腈(PAN)纳米纤维膜的性能,在PAN溶液中掺杂了MgO和Ag纳米颗粒(MgONPs和AgNPs),通过静电纺丝方法制备了不同质量分数的PAN/MgO/Ag复合纳米纤维过滤膜,采用扫描电镜、X射线衍射仪、红外光谱仪、紫外线透反射分析仪、过滤性能测试仪测试复合纤维过滤膜的微观形态、结晶结构、透气性、透湿性及过滤性能等。结果表明:纯PAN纳米纤维的直径为222.9 nm,PAN/MgO/Ag复合纳米纤维的直径为151.5 nm~258.6 nm。相对于纯PAN纤维膜,PAN/MgO/Ag复合纤维膜具有优良的过滤性能和紫外线防护性能,其紫外线防护系数为38.73~55.37,过滤效率为95.36%~97.59%,阻力压降为46.06 Pa~58.31 Pa。当MgONPs和AgNPs的质量分数都是0.75%时,PAN/MgO/Ag复合纤维膜的品质因子最高,为0.071 4 Pa^(-1),过滤性能最好,属于高效低阻且具有防紫外线功能的过滤膜材料。

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。

石墨烯-PAN基复合纳米纤维的微观形貌及其抗菌性能

为了优化GO-PAN基复合纳米纤维的制备方法,探究石墨烯的质量分数对复合纳米纤维抗菌性能的影响效果,利用静电纺丝法制备了不同石墨烯质量分数的GO-PAN基复合纳米纤维,使用X射线衍射仪、扫描电子显微镜、傅里叶红外光谱、差示扫描量热仪、力学性能分析等对复合纳米纤维的宏观性能和微观结构进行表征。研究结果表明:石墨烯的添加降低了复合纳米纤维的结晶度,GO-PAN基复合纳米纤维微观上呈三维网状结构,纳米纤维无序交错排列,纤维直径为170~230 nm。随着石墨烯质量分数的增加,复合纳米纤维的拉伸强度先增大后降低,断裂延伸率持续降低,且当石墨烯质量分数增大至0.9%时,复合纤维的拉伸强度达到了最大值20.61 MPa;石墨烯的添加改善了复合纳米纤维热学性能,脱水温度提高。GO-PAN基复合纳米纤维对大肠杆菌和金黄色葡萄球菌的抑菌率均超过了95%,且石墨烯质量分数0.9%的复合纳米纤维膜对2种菌种的抑菌效率均达到最大值,抑菌率分别为97.32%、99.85%,其中复合纳米纤维膜对金黄色葡萄球菌的抑菌效率高于大肠杆菌。

Application of activated carbon-decorated polyacrylonitrile nanofibers as an adsorbent in dispersive solid-phase extraction of fluoroquinolones from wastewater

A cheap and simple sample preparation method, consisting of a dispersive solid-phase method and an adsorbent, activated carbon decorated PAN nanofibers, was employed and used for the extraction of antibiotics(ciprofloxacin, danofloxacin, and enrofloxacin) in wastewater. Electrospun PAN nanofibers that were decorated with activated carbon produced from waste tires were used as the solid phase and the antibiotics analyzed by using high-performance liquid chromatography. Parameters such as pH, mass of adsorbent(MA),extraction volume(EV), and extraction time(ET) were optimized owing to their potential effect on the extraction of antibiotics from water. The recovery of all antibiotics was satisfactory, in the range of 90%–99%.The limits of detection and quantification were 0.05, 0.11, 0.20, and 0.53, 1.21, 2.17 mg/L, respectively. The precision was determined from the repeatability and reproducibility and expressed as the intra-day(n=20)and inter-day(n=5) precision. The intra-day and inter-day precision was reported in terms of the percentage relative standard deviation, which was 3% and 4%, respectively. The adsorption capacity of the activated carbon-decorated PAN nanofibers was satisfactory, and the reusability of the adsorbent was impressive when reused ten times. The accuracy of the dispersive solid phase extraction(DSPE) was validated by spike recovery tests; the results proved the reliability and efficiency of adsorbing antibiotics from wastewater. Finally, the proposed method was applied to wastewater samples collected from a wastewater treatment plant, which included influent, secondary, and effluent wastewater.

Artificial solid electrolyte interphase based on polyacrylonitrile for homogenous and dendrite-free deposition of lithium metal

High chemical reactivity, large volume changes, and uncontrollable lithium dendrite growth have always been the key problems of lithium metal anodes.Coating has been demonstrated as an effective strategy to protect the lithium metal.In this work, the effects of polyacrylonitrile(PAN)-based coatings on electrodeposited lithium have been studied.Our results show that a PAN coating layer provides uniform and dendrite-free lithium deposition as well as better cycling performance with carbonate electrolyte.Notably, heat treatment of the PAN coating layer promotes the formation of larger deposit particle size and higher coulombic efficiency(85%).The compact coating layer of heat-treated PAN with a large Young modulus(82.7 GPa) may provide stable protection for the active lithium.Improved homogeneity of morphology and mechanical properties of heat-treated PAN contribute to the larger deposit particles.This work provides new feasibility to optimize the polymer coating through rational modification of polymers.

Large pore size polyacrylonitrile membrane for ultrafiltration

The effects of the components of solution for membrane casting and preparation conditions on the membrane performances are studied in this paper. Polyacrylonitrile (PAN) was used as polymer and DMAC as solvent. The ultrafiltration (UF) membranes whose cut-off of molecular weight is 150000 and flux of pure water reaches 150-200 ml/(cm2&middoth) were prepared by selecting proper components of solution for membrane casting and membrane preparation conditions.

Enhancement of removal efficiency of heavy metal ions by polyaniline deposition on electrospun polyacrylonitrile membranes

This paper describes the preparation of a membrane of polyacrylonitrile(PAN)and its corresponding membrane coated with polyaniline(PANI)for the adsorption of heavy metal ions.Scanning electron microscopy micrographs revealed that all the membranes exhibited nanofibrous morphology.The prepared membranes were characterized by Fourier transform infrared spectroscopy(FTIR).The prepared membranes were used as an adsorbent for hazardous heavy metal ions Pb^(2+) and Cr_(2)O^(2-)_(7).The adsorption capacity and the removal efficiency of the membranes were examined as function of the initial adsorbate concentration and pH of the medium.Coated membranes with PANI showed better adsorption performance and their direct current(DC)conductivities were correlated to heavy metal ion concentrations.Adsorption isotherms were also performed,and the adsorption process was tested according to the Langmuir and Freundlich models.The regeneration and reuse of the prepared membranes to re-adsorb heavy metal ions were also investigated.The enhancement in adsorption performance and reusability of PANI-coated membranes in comparison with non-coated ones is fully discussed.The results show that the maximum adsorption capacities of lead and chromate ions on the PANI-coated membranes are 290.12 and 1202.53 mg/g,respectively.

Effect of additive on the formation of polyacrylonitrile membrane

The effect of additives CaCl\-2 and CaCl\-2/H\-2O on the properties of polyacrylonitrile(PAN) ultrafiltration(UF) membranes prepared by phase inversion process was studied. The dissolving capacity of the casting solution for CaCl\-2 was enhanced by the addition of H\-2O. The membranes are characterized in terms of the pure water flux and molecular weight cut\|off(MWCO). The addition of CaCl\-2 or CaCl\-2/H\-2O to the casting solution increases the resulting membrane permeability.

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.

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.

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.

Facile synthesis of sulfurized polyacrylonitrile composite as cathode for high-rate lithium-sulfur batteries

Sulfurized polyacrylonitrile(SPAN)as a promising cathode material for lithium sulfur(Li-S)batteries has drawn increasing attention for its improved electrochemical performance in carbonate-based electrolyte.However,the relatively poor electronic and ionic conductivities of SPAN limit its high-rate and lowtemperature performances.In this work,a novel one-dimensional nanofiber SPAN(SFPAN)composite is developed as the cathode material for Li-S batteries.Benefitting from its one-dimensional nanostructure,the SFPAN composite cathode provides fast channels for the migration of ions and electronics,thus effectively improving its electrochemical performance at high rates and low temperature.As a result,the SFPAN maintains a high reversible specific capacity^1200 mAh g−1 after 400 cycles at 0.3 A g−1 and can deliver a high capacity of^850 mAh g−1 even at a high current density of 12.5 A g−1.What is more,the SFPAN can achieve a capacity of^800 mAh g−1 at 0℃and^1550 mAh g−1 at 60℃,thus providing a wider temperature range of applications.This work provides new perspectives on the cathode design for high-rate lithium-sulfur batteries.

Zeolitic imidazolate framework-8 modified poly(vinylidene fluoride-cohexafluoropropylene)/polyacrylonitrile composite separators for Li-ion batteries

As one of the most stable metal-organtic framework(MOF),zeolitic imidazolate framework-8(ZIF-8)has been widely studied for applications in the field of energy storage,catalysis,and environment protection.In this paper,ZIF-8 was employed to enhance the electrochemical properties and thermal stability of the electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/polyacrylonitrile(PVDF-HFP/PAN)composite separator.The results indicate that the test cells assembled with the composite separators show improved rate capability,high discharge capacity,and stable cycling performances.The addition of ZIF-8 can improve the affinity of PVDF-HFP/PAN toward liquid electrolytes,and further enhance the ionic conductivity of the composite separators.In addition,the thermal stability of the PVDF-HFP/PAN separator has been improved by ZIF-8 nanoparticles.This work can provide insight into the application of MOF materials in Li-ion batteries.