静电纺丝制备磁性碳纳米复合纤维及其表征

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汤营茂, 缪清清, 肖荔人, 钱庆荣, 陈庆华. 静电纺丝制备磁性碳纳米复合纤维及其表征. 无机材料学报, 2014, 29(8): 827-834
TANG Ying-Mao, MIAO Qing-Qing, XIAO Li-Ren, QIAN Qing-Rong, CHEN Qing-Hua. Preparation and Characterization of Electrospun Magnetic Carbon Composite Nanofibres. 无机材料学报, 2014, 29(8): 827-834 复制到剪切板

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静电纺丝制备磁性碳纳米复合纤维及其表征

汤营茂¹, 缪清清², 肖荔人¹, 钱庆荣², 陈庆华²

福建师范大学 1. 材料科学与工程学院

2. 环境科学与工程学院, 福州350007

通讯作者: 钱庆荣, 研究员. E-mail:qrqian@fjnu.edu.cn

作者简介: 汤营茂(1990-), 男, 硕士研究生. E-mail:ymtang88@163.com

基金:福建省科技厅高校产学研重大项目(2011H6005, 2013H6007); 福建科技厅重点项目(2012H0018, 2013H0017); 福建省自然科学基金(2011J01287);

摘要

以聚丙烯腈(PAN)、乙酰丙酮铁(AAI)、N, N-二甲基甲酰胺(DMF)为原料, 采用静电纺丝-煅烧技术成功制备出磁性碳纳米复合纤维。通过TEM分析发现CF900的直径约为130~210 nm, 磁性纳米颗粒均匀地分散在碳纳米纤维中, 并探讨了碳化温度对碳纳米复合纤维磁性能的影响。结果显示: 饱和磁化强度(M_s)和剩余磁化强度(M_r)均随温度的升高而增大, 样品CF900的饱和磁化强度(M_s)高达27.55 A·m²/kg, 比表面积(S_BET)和总孔容积(V_total)达354.0 m²/g和0.315 mL/g。

关键词: 静电纺丝; 碳纳米复合纤维; 磁性纳米颗粒; 磁性能

中图分类号:TQ174 文献标志码:A 文章编号:1000-324X(2014)08-0827-08

Preparation and Characterization of Electrospun Magnetic Carbon Composite Nanofibres

TANG Ying-Mao¹, MIAO Qing-Qing², XIAO Li-Ren¹, QIAN Qing-Rong², CHEN Qing-Hua²

1. College of Materials Science & Engineering, Fujian Normal University, Fuzhou 350007, China

2 College of Environmental Science & Engineering, Fujian Normal University, Fuzhou 350007, China

Fund:Fujian Key Project of Industry-University-Research Collaboration (2011H6005, 2013H6007); Key Project of Fujian Science and Technology Agency (2012H0018, 2013H0017); Natural Science Foundation of Fujian Province (2011J01287);

Abstract

Magnetic carbon composite nanofibres, using the mixed homogeneous solution consist of polyacrylonitrile (PAN), ferric acetylacetonate (AAI) and dimetbylformamide (DMF) as raw material, were prepared by electrospinning-calcination technology. TEM analysis showed that the carbon nanofibre diameter of sample CF900 was about 130-210 nm, in which magneticnanoparticles were uniformly distributed. The magnetic properties of carbon composite nanofibres under different carbonization temperature was also investigated. Results showed that saturation magnetization (M_s) and remanent magnetization (M_r) increased with the increase of the temperature. When carbonization temperature was 900 ℃, the sample was of good magnetic property with high saturation magnetization (M_s=27.55 A·m²/kg). Moreover, the specific surface area (S_BET) and total pore volume (V_total) were up to 354.0 m²/g and 0.315 mL/g, respectively.

Keyword: electrospinning; carbon composite nanofibres; magnetic nanoparticle; magnetic property

Show Figures

近几十年来, 飞速发展的纳米技术极大地推动了新型多功能纳米材料的研究和发展^{[ 1]}。一维纳米碳材料(如碳纳米纤维、碳纳米管、碳纳米复合材料等) 因具有独特的光学、电学、磁学及化学特性, 引起了广泛关注和研究, 其主要应用于气体传感^{[ 2]}、超级电容器^{[ 3, 4]}、场发射微电子设备^{[ 5]}、催化剂^{[ 6, 7]}和锂离子电池^{[ 8, 9, 10]}等领域。目前静电纺丝被认为是制备一维复合纳米材料有效、简便的方法之一^{[ 11, 12, 13]}, 可制备具有特殊物理、电化学及生物性能的功能纳米材料^{[ 14, 15, 16, 17]}。

在众多功能复合纳米材料当中, 具有电学和磁学性能的材料是当前热点材料之一, 主要应用于制备生物医学领域中的磁转运蛋白、无膜生物燃料电池、微波吸收材料及电池装置等^{[ 18, 19, 20, 21, 22, 23]}。Fe₃O₄纳米颗粒是一种价廉、无毒且室温下具有超顺磁性的材料^{[ 24]}, 通过静电纺丝技术将其引入具有电导性能的碳纳米纤维中, 可制得兼具电性能和磁性能的复合材料, 已有研究者采用聚苯胺(PANI)和聚吡咯(PPy)作为碳纤维前驱体制备磁性碳纳米复合纤维^{[ 25, 26]}, 由于聚丙烯腈(PAN)具有高碳含量、高分子量和分子链高度定向的特点, 是制备碳纳米纤维的优选前驱体。本研究以PAN为前驱体、AAI为模板、DMF为溶剂配制纺丝溶液, 采用静电纺丝技术将其纺成PAN/AAI纳米复合纤维, 使用DSC-TGA分析手段, 探讨适宜的预氧化和碳化工艺条件, 制备出了磁性碳纳米复合纤维, 并借助SEM、TEM、XRD和EDS等分析手段对其进行表征, 同时还探讨了碳化温度对磁性碳纳米复合纤维的磁性能及孔隙结构的影响。

1 实验方法

1.1 药品

聚丙烯腈(PAN, M_w=150, 000), AR, Sigma-Aldrich; 乙酰丙酮铁(AAI, M_w=353.17), AR, 北京益利精细化学品有限公司; N, N-二甲基甲酰胺(DMF, M_w=73.09), AR, 天津市福晨化学试剂厂。

1.2 磁性碳纳米复合纤维的制备

1) 将2.0 g PAN、1.2 g AAI和34 mL DMF溶液加入到50 mL锥形瓶中, 在集热式恒温加热磁力搅拌器中搅拌24 h, 获得均匀的纺丝溶液。

2) 使用10 mL的注射器吸取8 mL的纺丝溶液(金属注射针头的内径为1.07 mm, 针尖与圆形锡箔纸接受板之间的距离为15 cm), 并在注射泵的注射速率为0.4 mL/h, 纺丝电压为13 kV, 纺丝温度为35℃的条件下进行静电纺丝, 圆盘接受板以20 r/min的速度旋转收集纺丝纤维。

3) 先在空气中进行预氧化处理, 以5 ℃/min的升温速率升至260℃, 恒温2 h, 然后再在氮气气氛中进行碳化处理, 升温速率为5 ℃/min, 在相应的碳化温度下恒温2 h, 冷却至室温后得到磁性碳纳米复合纤维。

1.3 表征

采用美国TA仪器公司的SDT Q600热重分析(TGA)-差示扫描量热(DSC)联用仪分析复合纤维的热分解过程; 采用日本电子株式会社的JSM-7500F冷场发射扫描电子显微镜(SEM)和美国FEI公司的NoVaTM Nano SEM 430超高分辨率热场发射扫描电镜(SEM)观察纳米复合纤维的微观形貌; 采用美国FEI公司的Tecnai G20高倍透射电子显微镜(HRTEM)-X射线能谱分析仪(EDS)分析磁性粒子的分散情况和元素组成; 借助日本Rigaku公司的X射线粉末衍射仪(XRD)分析纤维的物相组成(Cu Ka, 扫描速度为5^o/min); 使用英国Renishaw公司的激光显微拉曼光谱仪(inVia-Reflex)对纳米纤维的结构进行分析(激发光波长为633 nm); 采用日本Bel有限公司的多站全自动比表面和孔隙度分析仪(BELSORP- mini II)获取纤维的孔结构信息; 采用美国Quantum Design公司生产的MPMS-XL-7型超导量子干涉磁强计测量样品在室温下的磁性能。

2 结果和分析

2.1 热重-示差分析

图1(a)为PAN/AAI复合纳米纤维在空气中的DSC-TGA图。由TG曲线可知, 在130℃之前, 几乎没有发生失重; 温度在130~230℃之间时, 溶剂DMF开始挥发, 同时PAN发生物理收缩和化学环化收缩, 乙酰丙酮铁也开始熔融。由于Fe-O键的键能较小, 极易发生断裂生成游离的Fe元素, 游离的Fe元素随即被空气中的O₂氧化生成Fe₂O₃, 所以TG曲线上出现了近10%的失重; 当温度升至230~300℃时, 纤维出现10%的失重, 期间复合纤维发生环化、脱氢、氧化反应, H和N元素以气体的形式去除, PAN分子链中形成稳定的梯形结构, 其中Fe元素和Fe₂O₃对环化、脱氢、氧化反应具有催化作用; 温度在300~470℃之间时, C、H、N元素与O₂发生反应生成气体而脱除; 温度高于470℃时, PAN纤维分解完全。一般来说, 预氧化温度定为260℃左右即可, 不宜过高, 否则PAN纤维会被熔融甚至烧蚀^{[ 27]}。图1(b)为预氧化后的纳米复合纤维在氮气氛围中的DSC- TGA图。说明100℃之前发生的失重主要来源于预氧化后纤维中水分的挥发; 在100~330℃之间, 复合纤维几乎没有发生重量的变化, 因为经预氧化反应后, PAN纤维转变为稳定的梯形结构分子, 且Fe₂O₃也没有发生任何化学变化; 在330~580℃范围内, O、H、N元素开始以气体的形式脱除, 纤维发生轻度碳化, 失重率达20%; 温度进一步升高时(580~1000℃), 纤维进一步被碳化为无定形碳, 且Fe₂O₃和C发生还原反应生成Fe₃O₄, 温度过高(900℃和1000℃)还可能产生少量的Fe₃C和α-Fe等磁性粒子^{[ 1, 28, 29, 30]}。1000~1200℃之间, 纳米复合纤维基本无物理和化学变化。

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	图1 PAN/AAI复合纳米纤维(空气氛围)(a)和预氧化后的碳纳米复合纤维(氮气氛围) (b)的DSC-TGA曲线Fig. 1 DSC-TGA results for (a) PAN/AAI composite nanofiber in the air; (b) composite nanofiber after stabilizing treatment under the nitrogen

2.2 微观形貌分析

图2(a)为PAN/AAI复合纳米纤维的扫描电镜照片。由图可知, PAN/AAI复合材料为连续均匀的纳米复合纤维, 其直径范围为160~270 nm, 说明PAN/ AAI/ DMF混合溶液的可纺性较好。如图2(b)经预氧化及碳化后得到的磁性碳纳米复合纤维表面较为粗糙, 纤维出现断裂弯曲收缩现象, 且直径明显变小, 范围为140~220 nm。这主要归因于以下几个方面^{[ 31]}: 1) 高温条件下残留溶剂DMF的挥发; 2) 预氧化过程中氰基的环化加成反应; 3) C、H、O和N元素以气体形式挥发; 4) 乙酰丙酮铁的分解; 5) PAN的高温分解。

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	图2 PAN/AAI复合纳米纤维(a₁, a₂)和磁性碳纳米复合纤维CF900(b₁, b₂)的SEM照片Fig. 2 SEM images of as spun PAN/AAI composite nanofiber (a₁, a₂) and magnetic carbon composite nanofiber of CF900 (b₁, b₂)

为了进一步观察磁性纳米颗粒(Fe₃O₄、α-Fe和Fe₃C)在碳纳米纤维中的分布情况, 本研究借助高倍透射电镜对磁性碳纳米复合纤维进行表征, 测试结果如图3所示。结果表明, 磁性纳米颗粒均匀地分散在碳纤维中, 在磁性纳米颗粒周围具有明显的有序石墨碳层结构, 磁性纳米颗粒的直径约为 5~15 nm (图3 (d))。然而, 高倍透射电镜显示的纤维直径约为130~210 nm, 低于通过冷场扫描电镜测试得到的140~220 nm, 可能是因为SEM测试前需对磁性碳纳米复合纤维进行喷金处理, 而高倍透射电镜测试无需进行喷金前处理。

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	图3 磁性碳纳米复合纤维的高倍透射电镜照片Fig. 3 HRTEM images of magnetic carbon composite nanofiber

2.3 元素定性分析

为验证磁性碳纳米复合纤维中没有其他杂原子,本研究在对磁性碳纳米复合纤维CF900进行高倍透射电镜测试的同时, 也进行了X射线能谱测试, 即采用(HR)TEM和EDS联合测试。图4表明样品只有Fe、C和O元素, 并没有其他杂原子, Cu元素的存在是源于在测试过程的支撑样品的铜网。

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	图4 磁性碳纳米复合纤维的X射线能谱分析图Fig. 4 EDS spectrum of magnetic carbon composite nanofiber

2.4 物相分析

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	图5 各磁性纳米复合材料的XRD图谱Fig. 5 XRD patterns of the samples

图5为碳纳米复合纤维CF500、CF600、CF700、CF800和CF900的X射线粉末衍射图谱。从图5可以看出, 碳纳米复合纤维CF500只有在2 θ=24°和44°晶面, 但没有Fe₃O₄的衍射峰, 说明碳化温度为500℃时, 碳纳米复合纤维中并没有生成Fe₃O₄颗粒^{[ 32]}。当碳化温度升至600℃和700℃时, 碳纳米复合纤维CF600和CF700在30.4°、35.7°、43.5°、56.8°和62.9°显示出微弱的衍射特征峰, 分别对应于Fe₃O₄的(110)、(220)、(311)、(208)、(511)和(440)晶面, 其中2 θ=30.4°、35.7°、56.8°和62.9°同样对应于γ-Fe₂O₃的(220)、(311)、(511)和(440)晶面, 表明纳米纤维CF600和CF700中已经形成少量的Fe₃O₄纳米颗粒和较多的γ-Fe₂O₃纳米颗粒^{[ 33]}。随着碳化温度继续升高至800℃, 在2 θ=18.1°出现对应于Fe₃O₄的(110)晶面的衍射特征峰, 且其他Fe₃O₄的衍射特征峰变得越来越尖锐, 说明γ-Fe₂O₃纳米颗粒被还原为Fe₃O₄纳米颗粒。此外, 还可以观察到2 θ=44.8°处有一个衍射峰, 应为Fe₃C的(1102)特征结晶峰, 而在2 θ=50.8°处出现的是α-Fe晶面的(110)特征峰^{[ 27]}。当碳化温度进一步升高到900℃时, Fe₃C和α-Fe的衍射特征峰变得更加尖锐, 说明γ-Fe₂O₃进一步被C还原为α-Fe和Fe₃C纳米颗粒^{[ 34, 35, 36]}。

2.5 拉曼光谱分析

混层结构特征峰强度( I_G)与石墨层结构特征峰强度( I_D)的比值 R通常被用来表示材料的石墨化程度, R值越大, 材料的石墨化程度越高^{[ 27]}; 石墨晶面间距 L_a可以用方程 L_a≈4.4( I_G/ I_D)计算得到^{[ 37]}。本研究采用拉曼光谱分析仪对碳纳米复合纤维的结构进行分析, 结果如图6所示。结果表明, 所有样品在1350 cm^-1和1600 cm^-1附近均有特征峰存在, 其中1350 cm^-1附近的峰是混层结构特征峰( I_G), 而在1600 cm^-1附近的峰为石墨层结构特征峰( I_D)^{[ 28]}。各样品的 R值和 L_a值如表1所示。当碳化温度从500℃升至800℃时, R值和 L_a值分别从0.84增至1.02和3.70 nm增至4.49 nm, 说明无序碳逐步向高度有序石墨结构转变。这是因为随着碳化温度的逐渐升高, 碳纳米复合材料的石墨化程度不断增大, 且碳化温度的升高会导致Fe₃O₄含量的增加, Fe₃O₄对碳石墨层结构的形成具有催化作用^{[ 38]}。所以在Fe₃O₄的催化和高温双重作用下, 碳纳米复合纤维的石墨化程度越来越高。然而, 当碳化温度进一步升高到900℃时, R值和 L_a值开始变小。这是因为温度过高, C和Fe₃O₄发生还原反应, 损耗了一定的C, 所以碳纳米复合纤维的石墨化程度会有所降低。

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	图6 各磁性碳纳米复合材料的拉曼光谱图Fig. 6 Raman spectra of various samples

表1 各样品的石墨化程度 R值的大小和石墨晶体晶面的 L_a的大小 Table 1 The R values ( R= I_G/ I_D, degree of graphitization) of the carbon fibers and L_a values ( L_a≈4.4× R) of various nanofibers

2.6 氮气吸脱附曲线

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	图7 各磁性碳纳米复合材料的氮气吸脱附曲线(实心符号: 吸附支, 空心符号: 脱附支)Fig. 7 N₂ adsorption-desorption isotherms of (a) CF500; (b) CF600; (c) CF700, CF800; (d) CF900 (Closed symbol: adsorption, open symbol: desorption

图7为碳纳米复合纤维的N₂吸脱附曲线。根据IUPAC的分类^{[ 39]}, 磁性样品CF500的N₂吸脱附曲线为Ⅱ型等温线, 即为非多孔性材料。随着碳化温度的升高(600℃、700、800℃), 低相对压力条件下的N₂吸附量逐渐变大, 且N₂吸脱附等温线出现明显的滞后环, 说明碳纳米复合纤维中的微孔和中孔逐渐增多, 这和表2中依据NLDFT方法计算得到的 V_mic和 V_mes结果一致。可以推测纤维的平均孔径 D_P从12.2 nm减小至大, 主要是因为乙酰丙酮铁和纤维的高温分解及残留溶剂DMF的挥发均能增大纤维的孔隙率。同时C和Fe₂O₃发生了轻度的还原反应, 在一定程度上也促进了纤维孔隙的发展。当碳化温度升高(900℃)时, C和Fe₃O₄发生了进一步的还原反应。导致微孔和中孔转变为中孔和大孔, 因此 S_BET、 V_total、 V_mic和 V_mes均变小, 平均孔径 D_P从3.28 nm增至3.64 nm。

表2 碳纳米复合纤维的表面积和孔容 Table 2 Surface areas and pore volumes of various magnetic carbon nanofibers

2.7 磁性能测试

图8为磁性碳纳米复合纤维在298 K下获得的磁滞回线。从表3中可以看出, 随着碳化温度从 500℃增至700℃, M_s和 M_r分别从1.02 A·m²/kg和0.05A·m²/kg增至16.57 A·m²/kg和3.53 A·m²/kg, H_c也从7.96 kA/m增大为16.00 kA/m。这是因为温度的升高会导致碳的损耗, 且Fe₂O₃与C逐渐发生还原反应生成Fe₃O₄颗粒, Fe₃O₄纳米颗粒不断增多, 在碳纳米复合纤维中所占的比例将大大增加, 从而导致M_s迅速增大^{[ 38]}。当碳温度继续升至800~900℃时, 纤维中将产生M_s更高的α-Fe和Fe₃C, 所以磁性碳纳米复合纤维的M_s分别升高至22.87 A·m²/kg和27.55 A·m²/kg, H_c也相应地升高为19.90 kA/m^{[ 40, 41]}, 但仍远低于纯Fe₃O₄的M_s^{[ 42]}。这是因为碳在Fe₃O₄、α-Fe和Fe₃C纳米颗粒上形成了包覆层, 减弱了磁性纳米颗粒相互间的作用力,导致磁性碳纳米复合纤维的M_s显著降低^{[ 43]}。然而, 磁性碳纳米复合纤维的M_s足以满足废水处理中的固液分离的需要, 且有望于应用微波吸收材料^{[ 44, 45, 46]}、电池^{[ 47]}等领域。

	Figure Option View Download New Window
	图8 CF500、CF600、CF700(a)和CF800、CF900(b)的磁滞回线图Fig. 8 Magnetic hysteresis loops of (a) CF500, CF600, CF700 and (b) CF800, CF900

表3 各磁性碳纳米复合纤维在298 K下的 M_s、 M_r和 H_c值 Table 3 M_s, M_r and H_c of magnetic carbon composite nanofibres at 298 K

3 结论

1) 以PAN为模板, 乙酰丙酮铁为前驱体, DMF为溶剂配制静电纺丝溶液, 借助静电纺丝技术获得PAN/AAI复合纳米纤维, 并采用DAC-TGA分析手段确定预氧化温度和碳化温度, 经过适宜的预氧化和碳化处理后, 成功制备出了磁性碳纳米复合纤维。

2) SEM测试结果显示: 磁性碳纳米复合材料为均匀、连续的纳米纤维; 通过(HR)TEM分析发现试样CF900的直径范围为130~210 nm, 磁性纳米颗粒(Fe₃O₄、α-Fe和Fe₃C)均匀地分散在碳纳米纤维中, 且磁性纳米颗粒周围显现出有序的石墨层结构。

3) 采用振动样品磁强计对磁性纳米复合纤维的磁性能进行研究, 发现 M_s和 M_r均随着碳化温度的升高而增大, 碳化温度为900℃时, 样品CF900的 M_s、 M_r和 H_c分别达到27.55 A·m²/kg、5.10 A·m²/kg和19.90 kA/m, 且 S_BET和 V_total达到354.0 m²/g和0.315 mL/g, 有望应用于废水处理、微波吸收和电池等领域。

参考文献

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2011

0.0

Polymer. 2011, 52(7):1645-1653 DOI:10.1016/j.polymer.2011.01.057

Electromagnetic properties of electrospun Fe₃O₄/carbon composite nanofibers

Abstract In order to develop multifunctional nanofibers, the electrical conductivity and magnetic properties of Fe 3 O 4 /carbon composite nanofibers have been examined. Polyacrylonitrile (PAN) is used as a matrix to produce magnetic composite nanofibers containing different amounts of magnetite (Fe 3 O 4 ) nanoparticles. Electrospun composite nanofibers were thermally treated to produce electrically conductive and magnetically permeable composite carbon nanofibers. The composite nanofibers were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Raman spectroscopy, four-point probe and Superconducting Quantum Interference Device (SQUID). Uniform nanofibers were obtained with successful transferring of magnetic properties of Fe 3 O 4 into the as-spun composite nanofibers. The electromagnetic properties were tuned by adjusting the amount of Fe 3 O 4 in the matrix and carbonization process. The electrical conductivity, magnetic moment and also magnetic hysteresis rise up by adding Fe 3 O 4 and increasing carbonization temperature. The high surface area provided by the ultrafine fibrous structures, the flexibility and tuneable electromagnetic properties are expected to enable the expansion of the design options for a wide rage of electronic devices. Graphical abstract

... 近几十年来, 飞速发展的纳米技术极大地推动了新型多功能纳米材料的研究和发展^[1] ...

... -Fe等磁性粒子^{[1, 28,29,30]} ...

2007

3.535

0.0

Sensors and Actuators B: Chemical. 2007, 122(1):null-null

Carbon nanofiber/polypyrrole nanocable as toxic gas sensor

... 一维纳米碳材料(如碳纳米纤维、碳纳米管、碳纳米复合材料等) 因具有独特的光学、电学、磁学及化学特性, 引起了广泛关注和研究, 其主要应用于气体传感^[2]、超级电容器^[3,4]、场发射微电子设备^[5]、催化剂^[6,7]和锂离子电池^[8,9,10]等领域 ...

2004

2.588

0.0

2006

35.749

0.0

2002

3.794

0.0

1998

3.607

0.0

2001

3.607

0.0

2007

2.163

0.0

J. Mater. Sci.. 2007, 42(1):259-265 DOI:10.1007/s10853-006-1062-z

Carbon-nanofiber composite electrodes for thin and flexible lithium-ion batteries

1.National Kaohsiung University of Applied Sciences Department of Chemical and Material Engineering Kaohsiung 807-78 Taiwan, ROC 2.Industrial Technology Research Institute Materials Research Laboratories Hsinchu 310 Taiwan, ROC

Addition of vapor-grown carbon nanofiber (VGCF) into a LiCoO 2 composite electrode increases electrode’s conductivity and adhesion strength significantly. These increases are attributed to the uniform distribution of network-like VGCF of high conductivity; VGCF not only connects the surface of the active materials, its network penetrates into and connects each active material particle. VGCF composite electrode also improves the electrochemical performance of thin and flexible lithium-ion batteries such as discharge capacity at high current densities, cycle-life stability, and low-temperature (at −20 °C) discharge capacity. These improved electrochemical properties are attributed to the well-distributed network-like carbon nanofibers, VGCF, within the cathode. The addition of VGCF reduces the electron conducting resistance and decreases the diffusion path for lithium ions, hence increases the utilization of active materials during high-current discharge and low-temperature discharge. In addition, network-like VGCF forms a more uniform cathode structure so as to have a lower deterioration rate and correspondingly better life cycle stability.

2004

5.868

0.0

Carbon. 2004, 42(1):21-32 DOI:10.1016/j.carbon.2003.09.021

Novel carbon nanofibers of high graphitization as anodic materials for lithium ion secondary batteries

Abstract Carbon nanofibers (CNFs) of high graphitization degree were prepared by a CVD process at 550–700 °C. They showed different structures according to catalyst and preparation temperatures. The structure of CNF prepared from CO/H 2 over an iron catalyst was controlled from platelet (P) to tubular (T) by raising the decomposition temperature from 550 to 700 °C. The CNFs prepared over a copper–nickel catalyst from C 2 H 4 /H 2 showed the typical herringbone (HB) structure regardless of the reaction temperatures. The CNFs prepared over Fe showed d 002 of 0.3363–0.3381 nm, similar to that of graphite, indicating very high graphitization degree in spite of the low preparation temperature. Such CNFs of high graphitization degree showed high capacity of 297–431 mA h/g, especially in the low potential region. However, low first cycle coulombic efficiency of ≈60% is a problem to be solved. The graphitization of the CNF preserved the platelet texture, however, and formed the loops to connect the edges of the graphene sheets. Higher graphitization temperatures made the loop more definite. The graphitized CNF showed high capacity (367 mA h/g); however, its coulombic efficiency was not so large despite its modified edges by graphitization, indicating that the graphene edges were not so influential for the irreversible reaction of Li ion battery.

2007

9.765

0.0

Advanced Functional Materials. 2007, 17(17):3613-3618

Preparation of Short Carbon Nanotubes and Application as an Electrode Material in Li-Ion Batteries

X. X. Wang 1 ,J. N. Wang 1 ,H. Chang 2 andY. F. Zhang 3

1 School of Materials Science and Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai 200240 (P. R. of China) 2 Samsung Advanced Institute of Technology, P.O. Box 111, Suwon 440-600 (Korea) 3 Institute of Micro/Nano Science and Technology, 800 Dong Chuan Road, Shanghai 200240 (P. R. of China)

> A new approach is developed for cutting conventional micrometer-long entangled carbon nanotubes (CNTs) to short ca. 200 nm long segments with excellent dispersion. CNTs with different lengths are used as anode materials in Li-ion batteries. The reversible capacity of the Li-ion batteries is increased and the irreversible capacity is decreased upon shortening the length of the CNTs. The reason for this is that the insertion/extraction of Li ions is easier into/from short CNTs as compared to long CNTs because of the shortened length and the presence of lateral defects. Moreover, short CNTs have a lower electrical resistance and Warburg prefactor, resulting in better rate performance at high current densities. The present study suggests that short segments of CNTs obtained by cutting long CNTs may possess novel properties that may be useful for a wide variety of applications.

2001

5.868

0.0

Carbon. 2001, 39(4):547-558 DOI:10.1016/S0008-6223(00)00173-1

Synergism of Co and Mo in the catalytic production of single-wall carbon nanotubes by decomposition of CO

Abstract The catalyst composition and operating conditions for the synthesis of single-wall carbon nanotubes (SWNT) from CO decomposition have been systematically varied in order to maximize the selectivity towards SWNT. A simple quantification method based on the standard Temperature Programmed Oxidation (TPO) technique has allowed us to determine the distribution of the different forms of carbonaceous deposits present on the catalysts after the CO decomposition reaction. A synergistic effect between Co and Mo has been observed. When both metals are simultaneously present, particularly when Mo is in excess, the catalyst is very effective. However, when they are separated they are either inactive (Mo alone) or unselective (Co alone). To understand this synergistic effect, X-ray absorption spectroscopy (EXAFS and XANES) has been used to characterize the state of Co and Mo on the catalysts before and after the production of SWNT.

... 目前静电纺丝被认为是制备一维复合纳米材料有效、简便的方法之一^[11,12,13], 可制备具有特殊物理、电化学及生物性能的功能纳米材料^{[14,15,16,17]} ...

2005

2.072

0.0

2003

3.794

0.0

2009

3.379

0.0

Polymer. 2009, 50(17):4189-4198 DOI:10.1016/j.polymer.2009.06.062

Electrospun polyacrylonitrile nanocomposite fibers reinforced with Fe₃O₄ nanoparticles: Fabrication and property analysis

Abstract The manufacturing of pure polyacrylonitrile (PAN) fibers and magnetic PAN/Fe 3 O 4 nanocomposite fibers is explored by an electrospinning process. A uniform, bead-free fiber production process is developed by optimizing electrospinning conditions: polymer concentration, applied electric voltage, feedrate, and distance between needle tip to collector. The experiments demonstrate that slight changes in operating parameters may result in significant variations in the fiber morphology. The fiber formation mechanism for both pure PAN and the Fe 3 O 4 nanoparticles suspended in PAN solutions is explained from the rheologial behavior of the solution. The nanocomposite fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrophotometer, and X-ray diffraction (XRD). FT-IR and XRD results indicate that the introduction of Fe 3 O 4 nanoparticles into the polymer matrix has a significant effect on the crystallinity of PAN and a strong interaction between PAN and Fe 3 O 4 nanoparticles. The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried as-received nanoparticles. Graphical abstract

2005

4.187

0.0

Langmuir. 2005, 21(12):5600–5604-null

Composite Polymer Nanofibers with Carbon Nanotubes and Titanium Dioxide Particles

Shahar Kedem , Judith Schmidt , Yaron Paz , and Yachin Cohen *

Department of Chemical Engineering, Technion Israel Institute of Technology, Haifa 32000, Israel

Composite nanofibers containing nanometric TiO 2 particles and multiwalled carbon nanotubes dispersed in poly(acrylonitrile) (PAN) were prepared by the electrospinning technique. The structure and quality of the precursor dispersions were evaluated by cryo-transmission electron microscopy. The fabricated nanofibers, the diameters of which were in the 20−200 nm range, contained well-oriented nanotubes and spherical TiO 2 nanoparticles in close proximity. Such nanofibers are under investigation as new photocatalytic reactor elements.

2005

3.349

0.0

ChemPhysChem. 2005, 6(8):1461-1465

Biocompatible and Biodegradable Polymer Nanofibers Displaying Superparamagnetic Properties

Song Ting Tan Prof. 1 ,Joachim H. Wendorff Prof. 2 ,Clemens Pietzonka 2 ,Zhi Hong Jia Dr. 2 andGui Qing Wang 1

1 Institute of Polymer Materials, Xiangtan University, Xiangtan 411105, P. R. China, Fax: (+86) 732-82-93-264 2 Department of Chemistry, Center for Materials Science, Philipps-University Marburg, Hans-Meerwein Straße, 35032 Marburg, Germany

> Superparamagnetic polymer nanofibers intended for drug delivery and therapy are considered here. Magnetite (Fe 3 O 4 ) nanoparticles in the diameter range of 5–10 nm were synthesized in aqueous solution. Polymer nanofibers containing magnetite nanoparticles were prepared from commercially available poly(hydroxyethyl methacrylate), PHEMA, and poly- L -lactide (PLLA) by the electrospinning technique. Nanofibers with diameters ranging from 50 to 300 nm were obtained. Nanofibers containing up to 35 wt % magnetite nanoparticles displayed superparamagnetism at room temperature. The blocking temperature was about 50 K for an applied field of 500 Oe, and the saturation magnetization was 3.5 emu g −1 and 1.1 emu g −1 for Fe 3 O 4 /PHEMA and Fe 3 O 4 /PLLA nanofibers, respectively, and depended on the amount of Fe 3 O 4 nanoparticles in the nanocomposites. To test such magnetic nano-objects for applications as drug carriers and drug-release systems we incorporated a fluorescent albumin with dog fluorescein isothiocyanate (ADFI).

2003

14.829

0.0

Advanced Materials. 2003, 15(23):2027-2032

An Electrospun Poly(vinylidene fluoride) Nanofibrous Membrane and Its Battery Applications

S.W. Choi 2 ,S.M. Jo,W.S. Lee 1 andY.-R. Kim 2

1 Polymer Hybrid Research Center, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul, Republic of Korea 2 Department of Chemistry, Yonsei University, 134, Sinchon-dong, Seodaemun-gu, Seoul, Republic of Korea

1999

2.905

0.0

Journal of Electroanalytical Chemistry. 1999, 479(1):null-null

A non-compartmentalized glucose∣O₂ biofuel cell by bioengineered electrode surfaces

... 在众多功能复合纳米材料当中, 具有电学和磁学性能的材料是当前热点材料之一, 主要应用于制备生物医学领域中的磁转运蛋白、无膜生物燃料电池、微波吸收材料及电池装置等^{[18,19,20,21,22,23]} ...

2003

10.677

0.0

J. Am. Chem. Soc.. 2003, 125(3):622–623-null

Acetylcholine Esterase-Labeled CdS Nanoparticles on Electrodes: Photoelectrochemical Sensing of the Enzyme Inhibitors

Vered Pardo-Yissar , Eugenii Katz , Julian Wasserman , and Itamar Willner *

Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel

The photocurrents generated by a monolayer consisting of a CdS nanoparticles/acetylcholine esterase hybrid system associated with an electrode are controlled by the enzyme inhibitors.

2008

3.794

0.0

2004

1.826

0.0

Journal of Magnetism and Magnetic Materials. 2004, 269(1):null-null

Magnetic behaviour of composites containing polyaniline-coated manganese- zinc ferrite

2008

1.635

0.0

Polymers for Advanced Technologies. 2008, 19(3):229-236

Poly (3,4-ethylenedioxythiophene) γ-Fe₂O₃ polymer composite–super paramagnetic behavior and variable range hopping 1D conduction mechanism–synthesis and characterization

Kuldeep Singh,Anil Ohlan,Parveen Saini andS. K. Dhawan *

Polymeric & Soft Materials Section, National Physical Laboratory, New Delhi 110012, India * Polymeric & Soft Materials Section, National Physical Laboratory, New Delhi 110012, India.

> The present paper reports the preparation of poly (3,4-ethylenedioxythiophene) (PEDOT) ferrimagnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix by emulsion polymerization. Synthesis of PEDOT– γ -Fe 2 O 3 composite was carried out by chemical oxidative polymerization of EDOT with ferrite particles in the presence of dodecylbenzenesulfonic acid (DBSA) that works as dopant as well as surfactant in aqueous medium. The resulting conducting composite possesses saturation magnetization (Ms) value of 20.56 emu/g with a conductivity of 0.4 Scm −1 , which was determined by VSM and four probe technique, respectively. B-H curve reveals that ferrimagnetic particles of γ -Fe 2 O 3 show super-paramagnetic behavior at room temperature which was also observed in PEDOT– γ -Fe 2 O 3 composite. The resulting conducting ferrimagnetic composite shows microwave absorption loss of 18.7–22.8 dB in the frequency range of 12.4–18 GHz. Thermogravimetric analysis of the composite revealed that the composite is thermally stable up to 230°C. The characterization of the PEDOT– γ -Fe 2 O 3 composite was carried out using XRD and FTIR spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.

2004

0.71

0.0

2011

1.814

0.0

Curr. Appl. Phys.. 2011, 11(3):462-466 DOI:10.1016/j.cap.2010.08.018

Roles of nanosized Fe₃O₄ on supercapacitive properties of carbon nanotubes

Abstract We synthesized Fe 3 O 4 nanoparticle-dispersed multiwalled carbon nanotubes (MWNTs) to evaluate their potential applicability to supercapacitor electrodes. Nanosized Fe 3 O 4 was deposited by chemical coprecipitation of Fe 2+ and Fe 3+ in the presence of MWNTs in alkaline solutions. Fe 3 O 4 nanoparticles with an average particle size of 14 nm were prepared within several minutes. The structure and morphological characteristics of the Fe 3 O 4 /MWNT composites were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The electrochemical performance of a Fe 3 O 4 /MWNT composite electrode and a pure MWNT electrode was tested by cyclic voltammetry (CV) and galvanostatic charge–discharge in a sulfite electrolyte. The results showed that the Fe 3 O 4 /MWNT electrode had typical pseudo-capacitive behavior in a 1 M Na 2 SO 3 solution and a significantly greater specific capacitance than that of the pure MWNT electrode. It could also retain 85.1% of its initial capacitance over 1000 cycles.

... Fe₃O₄纳米颗粒是一种价廉、无毒且室温下具有超顺磁性的材料^[24], 通过静电纺丝技术将其引入具有电导性能的碳纳米纤维中, 可制得兼具电性能和磁性能的复合材料, 已有研究者采用聚苯胺(PANI)和聚吡咯(PPy)作为碳纤维前驱体制备磁性碳纳米复合纤维^[25,26], 由于聚丙烯腈(PAN)具有高碳含量、高分子量和分子链高度定向的特点, 是制备碳纳米纤维的优选前驱体 ...

2009

3.607

0.0

2008

4.187

0.0

Langmuir. 2008, 24(23):13748–13752-null

Fe₃O₄/Polypyrrole/Au Nanocomposites with Core/Shell/Shell Structure: Synthesis, Characterization, and Their Electrochemical Properties

Hui Zhang , Xue Zhong , Jing-Juan Xu * and Hong-Yuan Chen

Key Laboratory of Analytical Chemistry for Life Science (MOE), Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China * To whom correspondence should be addressed. E-mail: xujj@nju.edu.cn .

Uniform Fe 3 O 4 nanospheres with a diameter of 100 nm were rapidly prepared using a microwave solvothermal method. Then Fe 3 O 4 /polypyrrole (PPy) composite nanospheres with well-defined core/shell structures were obtained through chemical oxidative polymerization of pyrrole in the presence of Fe 3 O 4 ; the average thickness of the coating shell was about 25 nm. Furthermore, by means of electrostatic interactions, plentiful gold nanoparticles with a diameter of 15 nm were assembled on the surface of Fe 3 O 4 /PPy to get Fe 3 O 4 /PPy/Au core/shell/shell structure. The morphology, structure, and composition of the products were characterized by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The resultant nanocomposites not only have the magnetism of Fe 3 O 4 nanoparticles that make the nanocomposites easily controlled by an external magnetic field but also have the good conductivity and excellent electrochemical and catalytic properties of PPy and Au nanoparticles. Furthermore, the nanocomposites showed excellent electrocatalytic activities to biospecies such as ascorbic acid (AA).

2012

3.379

0.0

Polymer. 2012, 53(26):null-null

Influence of iron (III) acetylacetonate on structure and electrical conductivity of Fe₃O₄/carbon composite nanofibers

... 一般来说, 预氧化温度定为260℃左右即可, 不宜过高, 否则PAN纤维会被熔融甚至烧蚀^[27] ...

... -Fe晶面的(110)特征峰^[27] ...

... 5 拉曼光谱分析混层结构特征峰强度(I_G)与石墨层结构特征峰强度(I_D)的比值R通常被用来表示材料的石墨化程度, R值越大, 材料的石墨化程度越高^[27] ...

2008

3.842

0.0

Nanotechnology. 2008, 19(45):455612-null

Synthesis and characterization of magnetically active carbon nanofiber/iron oxide composites with hierarchical pore structures

Jeanne E Panels 1 , Jinwoo Lee 2 , Kang Yeol Park 1 , Seung Yeon Kang 1 , Manuel Marquez 3 , Ulrich Wiesner 4 and Yong Lak Joo 1,5

ylj2@cornell.edu 1 School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY14853,USA 2 Department of Chemical Engineering/School of Environmental Science and Engineering,Pohang University of Science and Technology, Kyungbuk, 790-784,South Korea 3 NIST Center for Theoretical and Computational Nanosciences, Gaithersburg, MD20899,USA 4 Department of Materials Science and Engineering, Cornell University, Ithaca, NY14853,USA 5 Author to whom any correspondence should be addressed

Polyacrylonitrile (PAN) solution containing the iron oxide precursor iron (III) acetylacetonate (AAI) was electrospun and thermally treated to produce electrically conducting, magnetic carbon nanofiber mats with hierarchical pore structures. The morphology and material properties of the resulting multifunctional nanofiber mats including the surface area and the electric and magnetic properties were examined using various characterization techniques. Scanning electron microscopy images show that uniform fibers were produced with a fiber diameter of ~600 nm, and this uniform fiber morphology is maintained after graphitization with a fiber diameter of ~330 nm. X-ray diffraction (XRD) and Raman studies reveal that both graphite and Fe 3 O 4 crystals are formed after thermal treatment, and graphitization can be enhanced by the presence of iron. A combination of XRD and transmission electron microscopy experiments reveals the formation of pores with graphitic nanoparticles in the walls as well as the formation of magnetite nanoparticles distributed throughout the fibers. Physisorption experiments show that the multifunctional fiber mats exhibit a high surface area (200–400 m 2 g −1 ) and their pore size is dependent on the amount of iron added and graphitization conditions. Finally, we have demonstrated that the fibers are electrically conducting as well as magnetically active.

... -Fe等磁性粒子^{[1, 28,29,30]} ...

... 结果表明, 所有样品在1350 cm^-1和1600 cm^-1附近均有特征峰存在, 其中1350 cm^-1附近的峰是混层结构特征峰(I_G), 而在1600 cm^-1附近的峰为石墨层结构特征峰(I_D)^[28] ...

2001

5.868

0.0

Carbon. 2001, 39(11):1627-1634 DOI:10.1016/S0008-6223(00)00281-5

Modification of synthetic mesophase pitch with iron oxide, Fe₂O₃

Abstract Iron oxide (Fe 2 O 3 ) was examined as an additive to improve the yield of the insoluble fraction in the synthetic mesophase pitch and to inhibit the expansion of the pitch during the heat-treatment and the successive carbonization of the insoluble fraction. The pitch was heat-treated at 350°C for 4 h under 500 rev./min stirring by adding 0, 6, 17, and 25 wt.% Fe 2 O 3 . The heat-treated pitch without additive produced swollen semi-coke with the flow domain texture whereas the heat-treated pitch with Fe 2 O 3 produced porous but non-swollen semi-coke with the mosaic texture. Fe 2 O 3 increased the yield of pyridine insoluble (PI) in the heat-treated pitch and inhibited completely swelling of the extracted insoluble fraction at its carbonization. The iron oxide is believed to enhance the oxidative polymerization of the lighter fraction in the pitch and to allow smooth liberation of evolving gases to suppress the expansion of the pitch and its PI during the carbonization. The successive calcination and graphitization gave spherical powders of the graphite. According to X-ray diffraction, Fe 2 O 3 was transformed into Fe 3 O 4 , and then to elemental Fe and Fe 3 C by calcination at 1000°C. At the graphitization stage, elemental Fe was only present in the carbon, catalyzing the graphitization to a limited extent.

... -Fe等磁性粒子^{[1, 28,29,30]} ...

2001

5.868

0.0

Carbon. 2001, 39(4):593-603 DOI:10.1016/S0008-6223(00)00166-4

Growth of iron clusters and change of magnetic property with carbonization of aromatic polyimide film containing iron complex

Abstract Carbonization process of a polyimide film containing iron of 0.6 at% (Fe-PIF) was investigated in detail by the measurements of XRD and mass magnetization. Because of the existence of fine iron particles as a catalyst, the Fe-PIF films heated in a temperature range from 700 to 1200°C showed turbostratic structure having interlayer spacing d 002 of about 0.343–0.344 nm and mean crystallite size L a ranging from 3.6 to 6.0 nm. The formation of α-Fe particles occurred mainly during carbonization process after pyrolysis of Fe-PIF. Mean crystallite size L 110 of the α-Fe particles was evaluated to be 16 nm for the film heated at 800°C and 25 nm at 1200°C. Magnitudes of the magnetization for Fe-PIF and the heat-treated films were independent of magnetic field direction applied, indicating random orientation of the crystallographic directions of iron particles. Films heated at 800°C and below were superparamagnetic (SP), while those at 900°C and above ferromagnetic (FM). However, all the films were found to have both magnetic components, SP and FM ones; 2.55 wt% (0.58 at%) and 0.0007 wt% (0.00016 at%) for Fe-PIF and 6.56 wt% (1.48 at%) and very small, but still present, for the 1200°C treated Fe-PIF, respectively. Irreversible behavior was observed between zero field cooled magnetization and field cooled for the heat-treated films, but not for original Fe-PIF because of fine clusters of iron. The irreversible effect are attributed to freezing of spin directions of iron particles at low temperatures.

... -Fe等磁性粒子^{[1, 28,29,30]} ...

2009

3.379

0.0

Polymer. 2009, 50(13):2999-3006 DOI:10.1016/j.polymer.2009.04.058

Development of carbon nanofibers from aligned electrospun polyacrylonitrile nanofiber bundles and characterization of their microstructural, electrical, and mechanical properties

Abstract Carbon nanofibers with diameters of 200–300 nm were developed through stabilization and carbonization of aligned electrospun polyacrylonitrile (PAN) nanofiber bundles. Prior to the oxidative stabilization in air, the electrospun PAN nanofiber bundle was tightly wrapped onto a glass rod, so that tension existed during the stabilization. We also investigated several carbonization procedures by varying final carbonization temperatures in the range from 1000 to 2200 °C. The study revealed that: (1) with increase of the final carbonization temperature, the carbon nanofibers became more graphitic and structurally ordered; (2) the carbon nanofiber bundles possessed anisotropic electrical conductivities, and the differences between the parallel and perpendicular directions to the bundle axes were over 20 times; and (3) the tensile strengths and Young's moduli of the prepared carbon nanofiber bundles were in the ranges of 300–600 MPa and 40–60 GPa, respectively. Graphical abstract

... 这主要归因于以下几个方面^[31]: 1) 高温条件下残留溶剂DMF的挥发 ...

1996

5.868

0.0

Carbon. 1996, 34(10):null-null

Modeling of disorder and X-ray diffraction in coal-based graphitic carbons

... 晶面, 但没有Fe₃O₄的衍射峰, 说明碳化温度为500℃时, 碳纳米复合纤维中并没有生成Fe₃O₄颗粒^[32] ...

2010

3.328

0.0

Compos. Sci. Technol.. 2010, 70(2):400-409 DOI:10.1016/j.compscitech.2009.11.015

X-band microwave characterization of carbon-based nanocomposite material, absorption capability comparison and RAS design simulation

Abstract This paper presents a microwave characterization of several carbon-based composite materials interesting the future aircraft/aerospace systems. They consist in epoxy resin reinforced with five different carbon species: micro-sized granular graphite, fullerenes, carbon nanofibers, single- and multi-walled carbon nanotubes. Main goal of this work is to show how carbon inclusions size and geometry are able to significantly modify the electromagnetic properties at microwave frequencies. Microwave characterization is performed in terms of microwave permittivity and intrinsic wave impedance evaluation; all the computations are based on microwave scattering parameters measured in the X-band (8.2/12.4 GHz) by waveguide method. A theoretical analysis of the microwave absorbing capability is then performed assuming that a multilayer of nanocomposite material was backed on a conductor plate (such a structure is typically called Radar Absorbing Material). The results obtained for the reflection coefficient indicate that nanoparticles give better absorption properties to the matrix than micro-sized ones: nanocomposite materials could thus be used successfully as microwave absorbers, not only for their absorption performances but also for their light weight.

... -Fe₂O₃纳米颗粒^[33] ...

2010

5.968

0.0

... -Fe和Fe₃C纳米颗粒^[34,35,36] ...

2006

0.214

0.0

... -Fe和Fe₃C纳米颗粒^[34,35,36] ...

2013

1.395

0.0

Journal of Applied Polymer Science. 2013, 127(6):4288-4295

Electrospun magnetic carbon composite fibers: Synthesis and electromagnetic wave absorption characteristics

Ying Yang 1,2,* ,Zhen Guo 3 ,Huan Zhang 1 ,Daqing Huang 3 ,Jialin Gu 3 ,Zhenghong Huang 3 ,Feiyu Kang 3 ,T. Alan Hatton 1 andGregory C. Rutledge 1

1 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 2 Department of Electrical Engineering, Tsinghua University, Beijing 100084, China 3 Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China * Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

> Electrospun polyacrylonitrile (PAN)-based carbon composite fibers embedded with magnetic nanoparticles have been developed as materials for electromagnetic wave absorption. The nanocomposite fibers were prepared by electrospinning from a dispersion of magnetite (Fe 3 O 4 ) nanoparticles stabilized by L -glutamic acid in a solution of PAN and N, N -dimethyl formamide. The Fe 3 O 4 -embedded PAN nanofibers were stabilized at 270°C in air and carbonized at 800°C in nitrogen. The Fe 3 O 4 nanoparticles were crystalline with a particle size of about 7 nm, most of which was reduced to Fe 3 C with agglomerates of up to 50 nm diameter in the carbon fibers. The carbon morphology was mostly disordered, but exhibited a layered graphitic structure in the vicinity of the nanoparticles. The carbon composite fiber exhibited ferromagnetic behavior, and the induced magnetic saturation per unit mass of fibers increased with increasing Fe 3 O 4 content in the precursor. The complex relative dielectric permittivity was tuned by adjusting the amount of Fe 3 O 4 in the carbon fiber precursor. With increasing Fe 3 O 4 content, good electromagnetic wave absorption characteristics were observed below 6 GHz, even for samples with fiber loadings as low as 5 wt %. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

... -Fe和Fe₃C纳米颗粒^[34,35,36] ...

1989

0.691

0.0

... 4(I_G/I_D)计算得到^[37] ...

1998

5.868

0.0

Carbon. 1998, 36(11):null-null

Graphite formation from a mixture of Fe₃O₄ and polyvinylehloride at 1000 ℃

... 这是因为随着碳化温度的逐渐升高, 碳纳米复合材料的石墨化程度不断增大, 且碳化温度的升高会导致Fe₃O₄含量的增加, Fe₃O₄对碳石墨层结构的形成具有催化作用^[38] ...

... 这是因为温度的升高会导致碳的损耗, 且Fe₂O₃与C逐渐发生还原反应生成Fe₃O₄颗粒, Fe₃O₄纳米颗粒不断增多, 在碳纳米复合纤维中所占的比例将大大增加, 从而导致M_s迅速增大^[38] ...

1982

0.0

... 根据IUPAC的分类^[39], 磁性样品CF500的N₂吸脱附曲线为#cod#x02161 ...

2006

3.842

0.0

Nanotechnology. 2006, 17(2):607-null

Novel solid-state synthesis of α-Fe and Fe₃O₄ nanoparticles embedded in a MgO matrix

O Schneeweiss 1,4 , R Zboril 2 , N Pizurova 1 , M Mashlan 2 , E Petrovsky 3 and J Tucek 2

schneew@ipm.cz 1 Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22,616 62 Brno,Czech Republic 2 Departments of Physical Chemistry and Experimental Physics, Palacky University inOlomouc, Svobody 26, 771 46 Olomouc,Czech Republic 3 Geophysical Institute, Academy of Science of Czech Republic, Bocni II/1401, 141 31Prague,Czech Republic 4 Author to whom any correspondence should be addressed

Thermally induced reduction of amorphous Fe 2 O 3 nanopowder (2–3 nm) with nanocrystalline Mg (~20 nm) under a hydrogen atmosphere is presented as a novel route to obtain α-Fe and Fe 3 O 4 magnetic nanoparticles dispersed in a MgO matrix. The phase composition, structural and magnetic properties, size and morphology of the nanoparticles were monitored by x-ray diffraction, 57 Fe Mössbauer spectroscopy at temperatures of 24–300 K, transmission electron microscopy and magnetic measurements. Spherical magnetite nanoparticles prepared at a reaction temperature of 300 °C revealed a well-defined structure, with a ratio of tetrahedral to octahedral Fe sites of 1/2 being common for the bulk material. A narrow particle size distribution (20–30 nm) and high saturation magnetization (95 ± 5 A m 2 kg −1 ) predispose the magnetite nanoparticles to various applications, including magnetic separation processes. The Verwey transition of Fe 3 O 4 nanocrystals was found to be decreased to about 80 K. The deeper reduction of amorphous ferric oxide at 600 °C allows α-Fe (40–50 nm) nanoparticles to be synthesized with a coercive force of about 30 mT. They have a saturation magnetization 2.2 times higher than that of synthesized magnetite nanoparticles, which corresponds well with the ratio usually found for the pure bulk phases. The magnetic properties of α-Fe nanocrystals combined with the high chemical and thermal stability of the MgO matrix makes the prepared nanocomposite useful for various magnetic applications.

... 90 kA/m^[40,41], 但仍远低于纯Fe₃O₄的M_s^[42] ...

2007

1.463

0.0

physica status solidi (a). 2007, 204(12):4013-4016

Shape-controlled synthesis of Fe nanoparticles with high-M_s via modest-temperature reduction method

H. T. Yang 1,* ,T. Ogawa 2 ,D. Hasegawa 2 andM. Takahashi 1

1 New Industry Creation Hatchery Center, Tohoku University, Aoba-yama 10, Sendai 980-8579, Japan 2 Department of Electronic Engineering, Graduate School of Engineering, Tohoku University, Aoba-yama 05, Sendai 980-8579, Japan * Phone: +81 22 795 7134, Fax: +81 22 263 9402

> To minimize the oxidation of Fe nanoparticles, 3 to 12 nm Fe nanoparticles have been synthesized by the modest-temperature reduction of FeCl 2 in a non-polar solvent. Trioctylphosphine oxide and oleylamine were used to avoid additional oxidation introduced by surfactants in comparison with oleic acid. The magnetic properties of Fe nanoparticles with different sizes reveal that the saturation magnetization ( M s ) of larger than 8.0 nm Fe nanoparticles is over 180 emu/g at 300 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

... 90 kA/m^[40,41], 但仍远低于纯Fe₃O₄的M_s^[42] ...

2005

0.0

Journal of Colloid and Interface Science. 2005, 281(2):null-null

Preparation, structure, and magnetic properties of mesoporous magnetite hollow spheres

... 90 kA/m^[40,41], 但仍远低于纯Fe₃O₄的M_s^[42] ...

2004

14.829

0.0

Advanced Materials. 2004, 16(2):137-140

Magnetic-Field-Induced Growth of Single-Crystalline Fe₃O₄ Nanowires

J. Wang,Q. Chen,C. Zeng andB. Hou

Structure Research Laboratory and, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, P.R. China

... -Fe和Fe₃C纳米颗粒上形成了包覆层, 减弱了磁性纳米颗粒相互间的作用力,导致磁性碳纳米复合纤维的M_s显著降低^[43] ...

2008

2.39

0.0

Journal of Alloys and Compounds. 2008, 461(1):null-null

Preparation and study on radar absorbing materials of nickel-coated carbon fiber and flake graphite

... 然而, 磁性碳纳米复合纤维的M_s足以满足废水处理中的固液分离的需要, 且有望于应用微波吸收材料^[44,45,46]、电池^[47]等领域 ...

2006

1.846

0.0

Materials Science and Engineering: B. 2006, 127(2):null-null

Microwave absorbing properties of activated carbon-fiber felt screens (vertical-arranged carbon fibers) /epoxy resin composites

... 然而, 磁性碳纳米复合纤维的M_s足以满足废水处理中的固液分离的需要, 且有望于应用微波吸收材料^[44,45,46]、电池^[47]等领域 ...

2010

1.545

0.0

Appl. Phys. A. 2010, 100(4):1177-1181 DOI:10.1007/s00339-010-5738-5

Electromagnetic and microwave absorption properties of carbonyl iron and carbon fiber filled epoxy/silicone resin coatings

1.State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an Shaanxi, 710072 China

The microwave electromagnetic properties of carbonyl-iron particles as magnetic absorber and carbon fiber as conductive absorber filled insulating epoxy/silicone resin coatings were investigated. The complex permittivity of the coatings increased while the complex permeability remained almost constant in the frequency range of 2–18 GHz, when the carbon fiber content was increased and the carbonyl-iron content kept constant. The minimum reflection loss of the coatings shifted to the lower frequency region by increasing the carbon fiber content or coating thickness. When the content of carbonyl iron was 65 wt% and carbon fiber was 2 wt%, the reflection loss below −10 dB can obtain in the frequency range of 8–18 GHz with coating thickness being 1 mm.

... 然而, 磁性碳纳米复合纤维的M_s足以满足废水处理中的固液分离的需要, 且有望于应用微波吸收材料^[44,45,46]、电池^[47]等领域 ...

2008

4.675

0.0

Journal of Power Sources. 2008, 183(2):null-null

Electrospinning synthesis of C/Fe₃O₄ composite nanofibers and their application for high performance lithium-ion batteries

... 然而, 磁性碳纳米复合纤维的M_s足以满足废水处理中的固液分离的需要, 且有望于应用微波吸收材料^[44,45,46]、电池^[47]等领域 ...