氧化镍掺杂酚醛树脂热解炭的结构及抗氧化性

在普通酚醛树脂中直接掺杂氧化镍粉末,研究氧化镍掺量和炭化处理温度对树脂热解炭的结构与氧化过程的影响,用X射线衍射仪、拉曼光谱分析仪、扫描电镜和综合差热分析仪等对掺杂改性树脂热解炭的石墨化度、显微结构及氧化过程分析表征,结果表明,在埋炭条件下掺杂改性树脂在450-750℃的炭化处理中三氧化二镍被逐级还原为一氧化镍和单质镍后,碳原子在镍颗粒上沉积生长,形成晶须、片状或块状结构的热解炭,热解炭石墨化程度取决于炭化温度和氧化镍掺杂量,在高于1050℃炭化处理的热解炭中出现明显的石墨化炭峰,随着掺杂量增加,热解炭石墨化程度大大增加,氧化温度比普通树脂明显提高,且以3~5%的掺杂量为佳。     

硝酸镍复合木质素改性酚醛树脂的热解炭结构演变

以木质素磺酸钙为原料,部分替代苯酚,合成具有良好水溶性的木质素改性酚醛树脂(LPF),并在其合成过程中将催化剂前驱体六水硝酸镍(NNH)加入到LPF体系中制备出硝酸镍复合木质素改性酚醛树脂(NLPF),经200°C×24 h固化后,于还原气氛下经800°C×3 h、1000°C×3 h、1200°C×3 h炭化处理,制得NLPF热解炭。探讨催化剂Ni在NLPF复合体系中的分散性,采用X射线衍射仪、激光拉曼光谱仪、场发射扫描电子显微镜、高分辨透射电子显微镜分析NLPF热解炭的晶体结构及显微结构。结果表明,催化剂Ni均匀分散在NLPF复合体系中;NLPF热解过程中NNH被还原成单质Ni,其催化作用使热解炭中生成了结晶程度高的直线型碳纳米管,且呈网状相互交织,均匀的排布在热解炭气孔中;随着NNH添加量的增加,NLPF热解炭的石墨化程度提高,碳纳米管的生成量和直径增加;升高炭化温度同样可以增加碳纳米管的生成量,并使其长度增长。     

掺Fe酚醛树脂合成及其催化石墨化研究

以二茂铁、苯酚、甲醛和草酸为原料,合成了掺Fe热塑性酚醛树脂;红外光谱(FTIR)结果表明,掺Fe酚醛树脂为线型酚醛树脂.利用X射线衍射( XRD)研究了Fe掺入比、炭化温度对酚醛树脂石墨化度的影响,利用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对酚醛树脂炭微观结构进行了表征.结果表明:当炭化温度为600℃时,酚醛树脂炭有明显的石墨化碳(002)峰,Fe元素的掺人大大降低了酚醛树脂炭石墨化温度;在600～1200℃内,酚醛树脂炭石墨化度随着炭化温度和Fe掺人比的升高而增大;掺Fe酚醛树脂炭基体中有石墨化碳纳米管生成.     

石墨化处理对不同高织构含量C/C复合材料微结构的影响

采用化学气相沉积工艺制备出炭毡增强炭/炭(C/C)复合材料和3K炭布叠层增强C/C复合材料,并对材料进行2500℃高温石墨化处理。利用X射线衍射仪;偏光显微镜及拉曼光谱仪对所制材料进行表征。结果表明,炭毡C/C复合材料基体是单一的高织构(HT)热解炭,3K炭布叠层C/C复合材料的基体是带状组织,从纤维表面向外依次为各向同性热解炭、HT和中织构(MT)热解炭,其中HT含量低于50%;沉积态和热处理后,两种C/C复合材料都具有相似的石墨化度,且热处理后的石墨化度超过80%,但Lc值差异明显,炭纤维、MT和HT热解炭的La值均升高,其中HT热解炭升幅明显大于炭纤维和MT热解炭。HT热解炭的含量是导致这两种C/C复合材料具有相似石墨化度而Lc值却显著差异的原因。     

镍改性酚醛树脂及其热解炭的表征

通过配位反应,将镍离子结合在酚醛树脂结构中,得到镍改性酚醛树脂,实现了催化剂前驱体在树脂中的均匀分散。通过红外光谱仪和紫外分光光度计初步确定了镍离子在树脂中的配位结构。采用激光拉曼光谱仪对高温热解炭晶体结构进行表征。结果表明,镍改性酚醛树脂热解炭中有石墨烯生成,炭的结晶度提高。通过场发射扫描电子显微镜、透射电子显微镜对热解炭的形貌和微观结构进行了表征,进一步表明镍改性酚醛树脂热解炭中有石墨烯生成且为少数层石墨烯。     

酚醛树脂热解炭材料的石墨化程度及其电化学性能

研究酚醛树脂中加入ZnCl2的比例不同对热解材料孔径、孔容、比表面积、层间距等微观结构的影响。通过X射线衍射(XRD)和激光拉曼光谱(Raman)等手段对酚醛树脂热解炭材料的石墨化程度进行表征。探讨热解炭材料的石墨化程度与充放电性能之间的关系。     

不同纤维体积分数CVI 炭/ 炭复合材料的石墨化度

为确定不同纤维体积分数的化学气相浸渗(CVI) C/ C 复合材料的最佳热处理工艺, 以40 %、30 %、25 %三种不同纤维体积分数的针刺整体毡为坯体, 经三次CVI 后制得C/ C 复合材料, 采用X射线衍射和拉曼光谱微区分析测试了三种不同纤维体积分数的CVI C/ C 复合材料试样未经热处理及经2200 ℃、2400 ℃热处理下宏观和微区石墨化度。结果表明: 三次CVI 热解炭均为光滑层结构, 且纤维体积分数越高, C/ C 复合材料的石墨化度也越高;纤维与光滑层热解炭界面及两种不同热解炭界面在高温热处理时会发生应力石墨化, 应力石墨化程度前者大于后者, 这是纤维体积分数高的C/ C 复合材料石墨化度高的原因; 热处理温度越高, 应力石墨化程度越大。      

镍源对催化酚醛树脂原位生成碳纳米管的影响

分别将硝酸镍和乙酸镍两种镍源作为催化剂前驱体加入酚醛树脂中,在N2保护气氛中催化碳纳米管原位生成.采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射仪(XRD)分别研究两种镍源对生成碳纳米管的形貌、结构和热解产物石墨化程度的影响.实验结果表明,含硝酸镍酚醛树脂生成的碳纳米管长径比和热解产物的石墨化程度均高于含乙酸镍酚醛树脂.两种镍源在酚醛树脂中的分散状态是影响碳纳米管生成差异的主要原因.     

含碳耐火材料酚醛树脂结合剂的研究现状与展望

含碳耐火材料不仅热导率较高,具有较好的抗热冲击性能,而且与熔渣不润湿,具有良好的抗侵蚀性能,因此大量生产并在冶金工业中广泛应用。酚醛树脂因具有与石墨润湿、残碳率高、环境友好、结合强度较高的特点而广泛用作含碳耐火材料结合剂。然而,酚醛树脂热解碳为脆性的非晶结构,不仅在应力作用下易脆性断裂,而且在高温下容易氧化。很多研究致力于酚醛树脂的化学改性。为提高酚醛热解碳的抗氧化性能或力学性能,提高酚醛树脂残碳率,通常添加过渡金属化合物、纳米碳、半导体陶瓷作为催化剂以提高热解碳的有序度,或者在其酚醛树脂热解碳基体中生成具有较高石墨化度的碳纳米管、碳纳米纤维以及Si C纳米线。     

碳化硼改性酚醛树脂的高温结构演变特性

以B4C陶瓷为改性粒子对酚醛树脂进行改性,研究其高温结构演变．结果表明,随着热处理温度的提高,B4C改性粒子在树脂基体中的分布趋向于均匀化．在450℃热处理后,B4C粒子开始呈现出氧化迹象;650℃以上高温,B4C则大量地氧化为B2O3．通过B4C的改性反应,可有效地将CO等挥发份转化为炭而保留在树脂中,从而有利于提高酚醛树脂高温热处理后的结构完整性．     

炭黑填充Lyocell纤维的制备及其用于炭纤维原丝的研究初探

为了提高Lyocell基炭纤维的得率及其力学性能，制备了不同含量炭黑填充的Lyocell纤维用做炭纤维原丝。采用X-衍射(WAXD)、热重分析(TGA)、扫描电镜(SEM)、强度仪等分析了试样的结构与性能。WAXD表明炭黑填充的LyoceH纤维仍然具有纤维素Ⅱ晶型的结构，同时还保留了炭黑的特征衍射峰；TGA表明该纤维热稳定性不变，添加质量分数为10％和30％炭黑的LyoceH纤维在1000℃时的碳得率可分别提高4．4％和17．1％：SEM显示该纤维表面光滑且截面为圆形，符合优质炭纤维原丝的要求；炭黑填充的Lyocell基炭纤维的WAXD图谱与一般Lyocell基炭纤维图谱不同。选择质量分数为10％的炭黑添加量制备出的Lyocell基炭纤维其强度和模量分别比未填充炭黑的Lyocell基炭纤维提高22％和42％，大样实验已制备出强度和模量分别为0．8GPa和70GPa的炭纤维。     

Preparation and microstructural evolution of carbon/carbon composites

Carbon/carbon (C/C) composites with characteristic matrix-crack pattern are key intermediate materials for preparation of carbon/silicon carbide (C/C–SiC) composites. The C/C composites were prepared by pyrolyzing carbon fiber/phenolic resin preform. The change of density, open porosity, mass loss and specially the microstructural evolution of the composites during pyrolysis at 200–900 °C was analyzed, which provided important information for preparation of C/SiC composites by infiltration of silicon. An increasing number of regular spacing cracks were formed above 400 °C. After pyrolysis at 900 °C, the pore volume was 0.17 cm³/g, and the pores in the radius range of 2.44–122.19 μm occupied 81% of the pore volume.     

Effect of the nature the carbon precursor on the physico-chemical characteristics of the resulting activated carbon materials

Carbon materials, including amorphous carbon, graphite, carbon nanospheres (CNSs) and different types of carbon nanofibers (CNFs) [platelet, herringbone and ribbon], were chemically activated using KOH. The pore structure of carbon materials was analyzed using N₂/77 K adsorption isotherms. The presence of oxygen groups was analyzed by temperature programmed desorption in He and acid–base titration. The structural order of the materials was studied by X-ray diffraction and temperature programmed oxidation. The morphology and diameter distribution of CNFs and CNSs were characterized by transmission electron microscopy. The materials were also characterized by temperature-desorption programmed of H₂ and elemental composition. The ways in which the different structures were activated are described, showing the type of pores generated. Relationships between carbon yield, removed carbon, activation degree and graphitic character were also examined. The oxygen content in the form of oxygen-containing surface groups increased after the activation giving qualitative information about them. The average diameter of both CNFs and CNSs was decreased after the activation process as consequence of the changes produced on the material surface.     

Studying the growth of carbon nanotubes on carbon fibers surface under different catalysts and electrochemical treatment conditions

A special electrochemical anodic oxidation (EAO) method was applied to modify the surface of carbon fibers (CFs) with fatty alcohol polyoxyethylene ether phosphate (O₃P), triethanolamine (TEA), fatty alcohol polyoxyethylene ether ammonium phosphate (O₃PNH₄), and ammonium bicarbonate (NH₄HCO₃) used as the electrolyte respectively. Then different catalysts, including Ni, Co, and Cu, were used to catalyze the growth of carbon nanotubes (CNTs) on the surface of CFs. The variation regulation of structure and property of CNTs on CFs surface was investigated by different methods. The results showed that the optimal effect of surface modification of CFs was achieved when O₃PNH₄ served as an electrolyte and the optimal electrochemical treatment intensity (ETI) was 100C/g. Also, with temperature variety, there are different microstructure changes for CNTs that adopt different catalysts. Through the experiment, a uniform catalyst coating was obtained on the surface of CFs after reduction process, which laid the foundation for the growth of uniform and regular CNTs.     

Structure of carbon nanorings

A new family of carbon nanorings with circular centerlines is predicted. The ring structure is parametrized by the chirality of the precursor graphene sheet that is rolled to produce a nanotube and then bent to form a nanoring, and by the number of repeated units defining the ring diameter. The individual atomic positions over rings with zig-zag, armchair, and intermediate chiralities are found by minimizing the Tersoff–Brenner potential with respect to the Cartesian coordinates of the carbon atoms. Rings with large diameters have nearly circular cross-sectional shapes, whereas rings with small diameters have elliptical, wedding-band, and dog-bone cross-sectional shapes. The inside surface of a chiral (10, 5) ring develops periodic ripples in a range of intermediate diameters. The flattened shapes uncovered are similar to those of inorganic nanorings recently observed in the laboratory.     

由不同碳源合成及制备纳米碳管的进展

纳米碳管可通过石墨、煤炭及炭黑等高含碳固体物，甲烷、乙烯或苯之类的有机化合物，一氧化碳和碳化硅等含碳无机化合物的转化来制备，甚至还可由低分子芳烃化合物来逐级合成。根据各种不同碳源，按不同转化过程及制备方法进行了总结与归纳，期望能对纳米碳管的合成及制备有一总体理解；通过简要、系统地介绍各种转化过程及制备方法，并对其中一些有发展前途的方法特别是电弧法、激光烧蚀法及化学气相沉积法的最新改进和发展进行了考察，分析了这些方法的优缺点；最后概述了目前纳米碳管规模制备方法的进展情况。     

Grafting the surface of carbon nanotubes and carbon black with the chemical properties of hyperbranched polyamines

Controlling the chemistry on the surface of new carbon materials is a key factor to widen the range of their applicability. In this paper we show a grafting methodology of polyalkylamines to the surface of carbon nanomaterials, in particular, carbon nanotubes and a carbon black. The aim of this work is to reach large degrees of covalent functionalization with hyperbranched polyethyleneimines (HBPEIs) and to efficiently preserve the strong chelating properties of the HBPEIs when they are fixed to the surface of these carbon materials. This functionalization opens new possibilities of using these carbon nanotubes-based hybrids. The results show that the HBPEIs are covalently attached to the carbon materials, forming hybrids. These hybrids emerge from the reaction of amine functions of the HBPEIs with carbonyls and carboxylic anhydrides of the carbon surface which become imine and imide bonds. Thus, due to the nature of these bonds, the pre-oxidized samples with relevant number of C=O groups showed an increase in the degree of functionalization with the HBPEIs. Furthermore, both the acid-base properties and the coordination capacity for metal ions of the hybrids are equivalent to that of the free HBPEIs in solution. This means that the chemical characteristics of the HBPEIs have been efficiently transferred to the hybrids. To reach this conclusion we have developed a novel procedure to assess the acid-base and the coordination properties of the hybrids (solids) by means of potentiometric titration. The good agreement of the values obtained for the hybrids and for the free HBPEIs in aqueous solution supports the reliability of the procedure. Moreover, the high capacity of the hybrids to capture Ni²⁺ by complexation opens new possibilities of using these hybrids to capture high-value metal ions such as Pd²⁺ and Pt²⁺.     

Flexible strain sensors fabricated with carbon nano-tube and carbon nano-fiber composite thin films

This paper presents the fabrication of 3 × 3 flexible strain sensor arrays using conductive polymer solutions with fillers including carbon nano-fibers and multi-walled carbon nano-tubes. The strain sensor arrays were made on polyurethane substrates using patterned surface treatment and the tilted-drop process. Atmospheric plasma was used to enhance or reduce the surface energy in specific areas for patterned surface treatment. The performance of fabricated strain sensors made using conductive polymer solutions with different ingredients was investigated. The measured gauge factors were in the 0.34 to 7.98 range for the strain of 3-7%. Under a bending test exceeding 50 times at a 150° angle, sensor damage was not observed. The demonstrated fabrication method is capable of producing conductive polymer sensors with complex designs, high reliability and is suitable for mass production.     

Kinetics of chemical vapor infiltration of carbon nanofiber-reinforced carbon/carbon composites

Preforms containing 0, 5, 10, 15 and 20 wt.% carbon nanofibers (CNFs) were fabricated by spreading layers of carbon cloth, and infiltrated by using the technique of isothermal chemical vapor infiltration (ICVI) at the temperature of 1100 °C under the total pressure of 1 kPa and with the flow of the mixture of propane/nitrogen in a ratio of 13:1. The infiltration rates increased with the rising of CNF content, and after 580 h of infiltration, the achievable degree of pore filling was the highest when the CNF content was 5 wt.%, but the composite could not be densified efficiently as the CNF content ranged from 10 to 20 wt.%. An analysis of the results, based on the effective diffusion coefficient and on the in-pore deposition rates, shows that the CNFs, due to their higher aspect ratio, accelerate overgrowth at pore entrances and thus lead to incomplete pore filling.     

Tribological behaviour and wear of carbon nanotubes grafted on carbon fibres

Carbon nanotubes (CNTs) grafted on fibres are widely used to reinforce composites in order to improve their mechanical properties. This study concerned the tribological properties of CNTs grafted on carbon fibres by the flame method. The aim of this study was to determine whether CNTs on fibres suffer damage under stress, similar to those applied during composite manufacturing, which can damage composite properties, particularly fibre/matrix adhesion. For this purpose, reciprocating friction tests were performed to examine the resistance of CNTs and highlight a wear mechanism. The results showed that the presence of CNTs increased the coefficient of friction in the first friction cycles and then decreased it to close to the COF of the fibre without CNTs. The wear mechanism showed that after a small number of friction cycles, the CNTs were flattened out and formed a transfer film.