碳源的石墨化度、气孔率与金刚石合成的关系

通过实验研究了碳源的石墨化度和气孔率对金刚石合成的影响 ,分析其影响产生的原因 ,提出了合成金刚石用碳源的技术参数和理论依据。     

炭／炭复合材料可石墨化性能的研究

采用XRD法测量和表征石墨化度，以数种结构组成各异的二维或准二维现役航空刹车用炭／炭复合材料为对象，研究了石墨化度随石墨化处理温度的变化规律，推算出了材料的最终石墨化处理温度，并从材料的结构组成方面对其可石墨化性能特征进行了分析、比较。结果表明：在石墨化度－石墨化处理温度关系曲线上，按温度划分，存在着两个明显不同的区段；近似于直线的快速升高段（AB段）和高温时近似于水平线的缓慢升高段（CD段）。当基体中含有沥青或树脂浸渍炭时，材料的最终石墨化处理温度大多处于AB段，温度为2000－2200℃之间；当基本全部为CVD炭时，材料的最终石墨化处理温度大多处于CD段，温度可能超过2800℃。本所研究的复合材料中的CVD炭的结构皆为RL结构。     

炭材料热物理性能研究

炭材料宏观性能受微观组织多样性的影响表现出极强的多样性。实验制备几种模压炭材料，并对其热物理性能进行表征。结果表明，随着原材料中胶体石墨含量的增加，材料的电阻率下降，热导系数、热扩散率提高；材料的比热容、热导系数、线膨胀系数随温度升高而增大，热扩散率随温度升高而降低。研究结果还表明，用传统的石墨化度G参数表征多相炭材料石墨化度具有一定的局限性，而用G参数与衍射峰高相结合表征更能准确反映多相炭材料的石墨化特性。     

Raman spectroscopy investigation of structural and textural change in C/C composites during braking

The microstructure and texture of C/C composites with a resin-derived carbon, a rough laminar (RL) pyrocarbon and a smooth laminar pyrocarbon, before and after braking tests, were investigated by Raman spectroscopy. The full width at half maximum (FWHM) of the D-band indicates the amount of defects in the in-plane lattice, while the G-to-D band intensity (peak area) ratios (I _G/I _D) is used to evaluate the degree of graphitization. The results show that the FWHM of D-band of sample with RL pyrocarbon changes greatly from 36 cm⁻¹ to 168 cm⁻¹ after braking tests, which indicates that a large number of lattice defects are produced on its wear surface. However, the graphitization degree of resin-derived carbon sample rises significantly, because the I _G/I _D increases from 0.427 to 0.928. Braking tests under normal loading conditions, involving high temperature and high pressure, produce a lot of lattice defects on the wear surface, and induce the graphitization of the surface. Sample with RL pyrocarbon having a low hardness is easy to deform, and has the most lattice defects on the wear surface after braking. While raw materials with resin-derived carbon have the lowest graphitization degree which rises greatly during braking.     

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 °C 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 (d ₀₀₂) of 0.335 8 nm and a crystalline size (L _c) of 28 nm.     

“KDTY—I”孕育剂对可锻铸铁第一阶段石墨化的影响

重点研究了“ＫＤＴＹＩ”孕育剂对可锻铸铁第一阶段石墨化的影响，试验结果表明：“ＫＤＴＹＩ”孕育剂具有较强的白口能力在高温石墨化退火过程中，可以加速共晶渗碳体的分解，从而大大降低第一阶段石墨化的加热温度，缩短退火时间“ＫＤＴＹＩ”孕育剂对共晶渗碳体分解的影响随加热温度的不同差异较大．     

石墨化度及纤维含量对C/C复合材料性能的影响

以短切高模炭纤维为增强体.制备C/C复合材料,并采用XRD、SEM等方法研究了纤维体积含量和石墨化度对复合材料性能的影响.结果表明:当短切高模炭纤维体积含量小于7%时,随着炭纤维体积含量增加,C/C复合材料的力学性能逐渐升高,高于7%时力学性能降低;随着石墨化度提高,C/C复合材料的力学性能显著降低,短切高模炭纤维增强作用下降;C/C复合材料的石墨化度对电阻率影响大,纤维体积含量对电阻率几乎没有影响;C/C复合材料的石墨化度对材料的抗氧化性影响显著.     

Architecting FeNx on High Graphitization Carbon for High-Performance Oxygen Reduction by Regulating d-Band Center

Fe single atoms and N co-doped carbon nanomaterials (Fe-N-C) are the most promising oxygen reduction reaction (ORR) catalysts to replace platinum group metals. However, high-activity Fe single-atom catalysts suffer from poor stability owing to the low graphitization degree. Here, an effective phase-transition strategy is reported to enhance the stability of Fe-N-C catalysts by inducing increased degree of graphitization and incorporation of Fe nanoparticles encapsulated by graphitic carbon layer without sacrificing activity. Remarkably, the resulted Fe@Fe-N-C catalysts achieved excellent ORR activity (E_1/2 = 0.829 V) and stability (19 mV loss after 30K cycles) in acid media. Density functional theory (DFT) calculations agree with experimental phenomena that additional Fe nanoparticles not only favor to the activation of O₂ by tailoring d-band center position but also inhibit the demetallization of Fe active center from FeN₄ sites. This work provides a new insight into the rational design of highly efficient and durable Fe-N-C catalysts for ORR.