Preparation and Properties of Mesophase Pitch-Based Carbon Fibers Modified with Isotropic Pitch

制备高性能沥青基碳纤维是国防军工和国民经济的迫切需求，但我国的研究工作还远远落后于国际水平。因此，本文系统研究了各向同性煤沥青(ICP)与中间相萘沥青(AR)在化学组分、物理性质、结构上存在的差异。探索了各向同性煤沥青改性中间相萘沥青的新体系，通过相分离实现了对碳纤维截面结构和力学性能的调控，并系统研究了该体系的氧化性能。 结果表明，ICP含有较多芳香组分，为100%各向同性；AR含有较多脂肪组分，为100%各向异性；由于AR中含有有序堆砌的石墨片层，AR纤维在后续氧化及碳化过程中沿半径方向有序收缩，形成劈裂结构，横截面表现出典型的放射状结构，因此对纤维力学性能有很大损害；而ICP中分子松散...The preparation of mesophase pitch-based carbon fibers with high performance are urgently demanded by the need of national defense and military industry as well as national economy , but our present research work is far behind the international level. Therefore, a systematic study of differentia between isotropic coal tar pitch (ICP) and mesophase pitch (AR resin from Japan's Mitsubishi Gas Chem...学位：理学硕士院系专业：材料学院材料科学与工程系_高分子化学与物理学号：2072007115002

Control of two-phase pitch precursor and microstructure of cross-section of carbon fibers

为给高性能碳纤维的结构设计提供理论参考,利用各向同性煤沥青(IPc)与中间相沥青形成二元不相容共混物的相分离结构,并利用筛网装置改变共混沥青的熔; 体流动状态,研究共混两相沥青的相结构对最终碳纤维结构的影响。结果表明:在共混前驱体中,掺杂的15%; IPc不足以抑制劈裂的形成;而使用15层筛网纺丝装置,促进微畴沿径向折叠排列,抑制了轴向劈裂的出现;进一步提高熔体受剪切程度,各向同性相形成贯穿; 的条带结构,纤维截面重新出现劈裂结构。30%的各向同性相抵抗了碳纤维中的裂纹扩展,碳纤维最终形成介于放射状和无规的截面形貌;使用50层筛网装置,; 纤维截面中出现类似的劈裂结构受到抑制一重新出现劈裂结构的演变过程。结果证实了相分离和筛网装置对中间相微畴在纤维中排布方式的协同影响作用。In order to provide academic reference for structure design of; high-performance carbon fibers (CFs),blends of composed isotropic (IPc); and mesophase pitches in various proportions were used as precursors for; CFs. A filter assembly was further used to disturb the melt flow during; the spinning of precursor fibers. The phase structure of; isotropic/mesophase incompatible blends on the microstructure of the; resultant CFs were studied. Results shows that 15% of IPc in the blended; precursor can not prevent the open crack along the carbon fiber axis,; while the split has been completely depressed in the carbon fibers when; spun with 15 layers of plain-weave, in which the IPc component exhibited; disorder oriented strips form to promote the zigzag connection among the; graphitic microcrystallites along the cross-section of CFs. Shear of the; extrusive pitch melt further increasing, the IPc phase exhibits a; perforative structure and the open crack reappears in the cross-section; of CFs. When the content of IPc is 30%,isotropic phase resists the; evolution of the open crack,and an intermediate morphology between; radial and random type is shown in the CFs. The similar evolution of the; open crack is shown in the cross-section of CFs when the 50 layers of; plain-weave is used. The results confirm the synergy effect of the; incompatible phase-separation of the blends and the filter assembly on; the arrangement of the graphitic microcrystallites along the; cross-section of CFs.中央高校基本科研业务费专项资金项

各向同性沥青改性的中间相沥青纤维预氧化研究

以各向同性沥青改性的中间相沥青为原料,经熔融纺丝、氧化及碳化处理得到沥青基碳纤维,重点研究了原丝的氧化行为.偏光显微镜研究表明,混合沥青为两相不相容共混物,中间相沥青为连续相,各向同性沥青为分散相.氧化过程中,沥青的脂肪氢和芳氢被脱除,主要生成羰基,醚键.随着氧化时间的延长,纤维中含氧量逐渐提高.当氧化时间较短时,纤维氧化不足,碳纤维芯部出现孔洞,微观组织呈现大片层结构.随着氧化程度逐渐提高,截面孔洞逐渐减小并最终消失,同时,碳纤维的强度显著提高;但是当原丝过度氧化时,碳纤维强度反而下降

沥青原料对沥青基碳纤维结构与性能的影响

以中间相萘沥青(AR树脂)和各向同性煤沥青(ICP)为原料,系统研究了沥青原料性质与由其制备的碳纤维结构、性能之间的关系。研究表明,AR树脂中的一维有序中间相结构在纺丝中被拉伸,形成不同中间相间的界面,成为应力集中区,在后续碳化过程因应力释放导致纤维开裂而损害其力学性能;而ICP沥青基本为无定形相结构,在纺丝过程中无明显的择优取向,碳化过程石墨化程度低,故其所成的碳纤维无应力集中和开裂问题,但也正是这无定形结构,使其最终力学性能也较差。以上结果说明,原料的性质可以"遗传"到沥青基碳纤维中。因此,改变沥青原料的性质是改善沥青基碳纤维结构和性能的有效途径之一

同步氢化/热缩聚法制备中间相沥青

通过同步氢化/热缩聚反应,制得中间相沥青(MP);重点研究了四氢萘(THN)用量对MP性质的影响。研究表明THN增加,MP的软化点(SP)随之降低,H/C随之提高,不溶分随之减少;偏振光显微镜研究表明THN用量少于8%时,MP的形貌为分布不均的各向异性与各向同性两种沥青的混合物;而随着THN的增加,各向异性沥青逐渐趋于以中间相小球形态,并且较为均匀地分布到各向同性沥青基质之中。MP经保温处理后,纺丝性能得到改善,最终制得横截面呈无规结构的沥青基碳纤维

沥青原料对沥青基碳纤维结构与性能的影响

以中间相萘沥青(AR树脂)和各向同性煤沥青(ICP)为原料,系统研究了沥青原料性质与由其制备的碳纤维结构、性能之间的关系。研究表明,AR树脂中的一维有序中间相结构在纺丝中被拉伸,形成不同中间相间的界面,成为应力集中区,在后续碳化过程因应力释放导致纤维开裂而损害其力学性能;而ICP沥青基本为无定形相结构,在纺丝过程中无明显的择优取向,碳化过程石墨化程度低,故其所成的碳纤维无应力集中和开裂问题,但也正是这无定形结构,使其最终力学性能也较差。以上结果说明,原料的性质可以"遗传"到沥青基碳纤维中。因此,改变沥青原料的性质是改善沥青基碳纤维结构和性能的有效途径之一

同步氢化/热缩聚法制备中间相沥青的工艺研究

系统地研究了在氢化剂量固定情况下,反应温度与时间对同步氢化/热缩聚法所制得的中间相沥青(MP)性质的影响,并制得了可纺MP。研究表明反应时间同为4h时,MP的软化点和不溶分含量随反应温度的提高而升高;偏光结果显示,低温产物为中间相小球和各向同性基质的混合物,高温产物为连续中间相。反应温度同为410℃时,MP软化点和不溶分含量均随反应时间的延长而显著提高,经历了从中间相小球到小球发生融并,最后形成了马赛克织构的中间相。纺丝性能测试表明,反应温度为410或420℃,反应4h制得的中间相沥青,可以熔融纺丝,经氧化和碳化后制得两组碳纤维

Studies on Tailoring Structures and Properties of Pitch-based Carbon Fibers and In-situ Structural Characterization of Single-walled Carbon Nanotubes

以中间相沥青为先驱体有望获得价格低廉并具有优良传输性质的碳纤维，从液晶态先驱体纺丝制得碳纤维持续吸引着广大的碳工作者。但是中间相沥青纤维的氧化过程往往很耗时，是制备中间相沥青基碳纤维的制约环节，最终碳纤维的制备成本很高。此外中间相沥青基碳纤维的拉伸和压缩强度较低，限制了其应用。本论文的研究目标是对中间相沥青基碳纤维结构与性能进行调控，建立工艺、结构与性能之间的关系。本论文主要研究工作如下： 1.通过各向同性/中间相不相容混合沥青调控碳纤维的结构与性能。本文探索了不相容共混沥青的连续纺丝工作，选取具有相似熔融特性的萘系中间相沥青(AR沥青，Aromaticresin)和煤焦油系各向同性沥青(I...With the mesophase pitch as the precursor, the resultant mesophase pitch-based carbon fibers are anticipated to typically possess high modulus and excellent electrical and thermal properties, as well as low cost. The liquid crystal nature of mesophase pitch imparts the precursor pitch fibers with a high degree of molecular order and orientation structures, therefore has attracted considerable atte...学位：理学博士院系专业：材料学院_高分子化学与物理学号：2072010015347

The influence of oxygen content on the structure and properties of Co-SiC fibers

系统研究了含钴聚碳硅烷交联丝的氧含量对所成含钴碳化硅(CO-SIC)纤维结构与性能的影响。研究结果显示,较之交联丝CO-PCS-AIr,CO-PCS-O2的氧含量较高,陶瓷产率较高,所成纤维的SICXOy相含量较高、β-SIC和COSI晶粒的增长速度较快,晶粒的尺寸较大,达到最大力学性能的烧结温度较低,电阻率也较低。该纤维电阻率在100~103Ω·CM之间可调,且具有一定的磁性,有望用作吸波纤维。In this work,it was systematically studied that how oxygen content of cured cobalt-containing polycarbosilance(PCS) fibers influences the structure and properties of cobalt-containing silicon carbide(Co-Si C) fibers.Compared to cured Co-PCS-air fibers,Co-PCS-O2 fibers have a higher oxygen content and higher ceramic yield.For Co-PCS-O2 fibers derived from cured Co-PCS-O2,lower pyrolysis temperature was required to reach maximum mechanical properties.And higher Si CxOycontent,higher growing speed and final sizes of β-Si C and Co Si grains and lower electrical conductivity were observed.Co-PCS-O2 fibers have a electrical conductivity controllable between 100-103Ω·cm and were magnetic to some degree,enabling this kind of fibers to have the potential to be used as wave-absorbing materials.国家自然科学基金面上资助项目(51002127;51072169

The influence of oxygen content on the structure and properties of silicon oxynitride(Si—O—N)fibers

令不同氧含量的聚碳硅烷氧化交联丝在高纯氨气中氮化热解、脱碳氨化,继而在高纯氮气下高温热引发缩合/转氨基反应,生成硅氧氮烷并最终形成氧含量不同的硅氧氮(SI—O—n)陶瓷纤维。Xrd、EPMA和TEM研究结果显示,所有元素在硅氮氧纤维中均匀分布,随着交联丝O含量增加,SI—O—n陶瓷纤维的O含量随之增加,力学性能下降,而陶瓷产率则先升后降。高氧时纤维陶瓷产率下降是因为在高温热解时发生了相分解。Xrd和TEM结果表明,氧含量不同的陶瓷纤维经1 500℃高温处理后,均仍为无定型。氧可能对氮化硅的结晶有抑制作用。In this work,PCS fibers,cured with different oxygen contents,were conducted by pyrolysis nitridation for carbon removal and amination in the ammonia atmosphere,and then through condensation/nitridation reaction at high temperature in the nitrogen atmosphere to produce silicon oxynitride fibers.Results of XRD, EPMA and TEM showed that,all of the elements in the ceramic fibers dispersed uniformly,and as the oxygen content in the cured fibers increased,it also increased in the ceramic fibers but with a drop in mechanical properties.However,the ceramic yield rose first and then fell because of the phase decomposition at high temperature.Indicated by the results of XRD and TEM,even after heat treatment at 1 500℃,ceramic fibers were still amorphous regardless of how much the oxygen content was.The oxygen maybe play a role like impurity in the fibers,which inhibites the crystallization of silicon nitride.国家自然科学基金面上资助项目(51002127;51072169