两种沥青炭微观结构和性能的对比研究

将高温煤沥青和浸溃荆沥青在92MPa下炭化，在2500℃下对所得沥青炭进行石墨化处理；测试了所得沥青炭的体积密度、开孔率、比表面积（SBET）；利用扫描电子显微镜（SEM）观察了所得沥青炭的显微结构；利用X射线衍射方法（XRD）检测了所得沥青炭石墨化处理后的石墨化度；测试了所得沥青炭的氧化性能；测试了沥青炭试样的比热容、导热系数、热扩散率和线膨胀系数。结果表明：在92MPa下，两种沥青炭有着相近的密度和开孔率；浸渍剂沥青炭的SBEt高于高温煤沥青炭；浸渍荆沥青炭为流线型结构，高温煤沥青炭为镶嵌型和域型并存的结构；流线型结构沥青炭石墨化度较高；高温煤沥青炭的抗氧化性能要好于浸溃荆沥青炭；随着沥青炭石墨化程度的增大，比热客、导热系数、热扩散率都增大，而线膨胀系数减小。     

沥青炭石墨化度的间接表征方法研究

将高温煤沥青和浸渍剂沥青在不同压力下炭化，在2500℃下对所得沥青炭进行石墨化处理。利用X射线衍射方法（XRD）检测了所得沥青炭试样的石墨化度；对比分析了几种试样的真密度、电阻率和磁阻。结果表明：沥青炭的石墨化度越高，其真密度越大；沥青炭的室温电阻率随石墨化度的增加而下降，随体积密度的增大而下降；在不同磁场强度下，随石墨化度的提高，磁阻增大。     

炭化压力对沥青树脂炭结构影响

为了了解炭化压力对沥青树脂炭结构的影响程度,在不同的炭化压力下对沥青树脂炭进行了炭化处理,并采用XRD、SEM等方法对处理后的沥青树脂炭的结构进行了分析.试验结果显示,随着炭化压力的提高,沥青树脂炭开孔率降低,残炭率提高,微观结构取向性增强,在本次试验中,炭化压力的不同,对沥青树脂炭的石墨化性能影响较小.     

制备工艺对中间相沥青基泡沫炭结构的影响

以煤沥青基中间相沥青为前驱体制备泡沫炭生料,经850℃和2300℃热处理分别得到炭化和石墨化泡沫炭,研究了发泡工艺参数和热处理温度对泡沫炭微观结构的影响。结果表明,较快的升温速率使泡沫炭易形成开孔型结构;随着压力的增大,泡沫炭的孔径减小、密度增大、孔隙率降低;经炭化和石墨化后泡沫炭孔径有所收缩,孔间的连通性增强;泡沫炭石墨化后孔壁及其韧带大部分转化成为高取向度的石墨晶体结构,微晶层间距和石墨化度分别为0.3376nm和0.733。     

炭化压力对编织C/C复合材料致密过程及结构的影响

通过浸渍/高压炭化工艺在不同炭化压力下制备了高温煤沥青炭块及沥青基炭/炭（C/C）复合材料,并研究了不同炭化压力环境下对其密度和孔隙的影响.结果表明,随着炭化压力增大,沥青炭体积密度明显增加,孔隙填充效果明显改善;在编织C/C材料的致密过程中,压力越大其孔隙越小,分布越均匀,故产品致密效果越好.     

发泡条件对中间相沥青基泡沫炭形成的影响

以石油系中间相沥青为原料，在不同发泡时间和压力、温度为440℃时发泡制得生料泡沫炭，经过氧化、炭化等处理得到了具有均一孔结构的泡沫炭。利用SEM观察孔结构并测定体积密度和真密度的方法计算出不同制备条件下所得到的泡沫炭的孔隙率的数据，发现泡沫炭的孔隙率与孔径主要受发泡压力的影响，可利用改变发泡压力的方法控制泡沫炭的孔结构。通过对泡沫炭生料进行氧化、炭化等后处理可有效地提高产物泡沫炭的密度、孔隙率和强度等材料性能。     

溶胶-凝胶法介孔沥青炭微球的制备及电化学性能研究

以水性中间相沥青(AMP)为前驱体,阳离子表面活性剂(CTAB)为结构导向剂,通过控制AMP的凝胶化和自组装过程,采用溶胶-凝胶法来制备介孔沥青炭微球。利用SEM、HRTEM、SAXRD、FT-IR等分析手段,对产物的形貌及结构进行表征,并研究了介孔沥青炭微球的形成机理和电化学性能。结果表明:在制备介孔沥青炭微球的过程中,CTAB与离子化的AMP可通过S+I-静电力作用形成凝胶球,经炭化后得到介孔沥青炭微球。当CTAB/AMP=1.2时(CTAB为2 g),炭化后得到的介孔炭微球之间界面明显,表面光滑,球体粒径为300~500 nm,当增加CTAB胶束在溶液中的浓度时,炭化产物中得到纳米炭棒。所得介孔沥青炭微球C-AMP1.2-800有序度差、石墨化度低,球体为乱层石墨结构,其在50 mV.s-1下的比电容为103.5 F/g。     

石油系中间相沥青基泡沫炭的制备与结构研究

分别以中间相含量为100％和30％的两种石油系中间相沥青为前驱体制备泡沫炭，利用SEM、偏光显微镜观察泡沫炭的孔和孔壁等微观形貌，利用XRD分析石墨化泡沫炭的微晶结构。考察不同中间相含量前驱体的发泡性能，同时探讨了焦化手段对泡沫炭结构和性能的影响。结果表明，两种前驱体均能制备得到孔结构均匀、开孔率高的泡沫炭；100％中间相含量的前驱体相对更适合发泡；通过延长焦化时间可以优化泡沫炭结构、提高石墨化度，进而提高泡沫炭产品性能。     

炭膜的二氧化碳吸附扩散性能的研究

以商业化的Kapton型聚酰亚胺为前驱体制备炭膜,采用容量法研究了不同炭化温度制备的炭膜CO2吸附和扩散行为,并利用Sips模型对实验数据进行拟合,DA方程计算炭膜的孔结构参数,Fick扩散模型求取CO2在炭膜内的扩散系数,采用XRD分析探讨了炭膜的炭结构。结果表明,炭膜孔结构随着热解炭化温度的提高,孔径收缩,且当炭化温度从600℃升高到800℃,炭膜的微孔体积随炭化温度的升高而增大,而800℃以后,微孔体积随炭化温度的升高而下降。CO2在不同炭膜中的扩散系数约为1.04×10-13~8.56×10-12m2·s-1,在实验测定的压力范围内扩散系数随着平衡压力的增大呈现出先增大后减小的规律。     

石墨化无烟煤制备铝用炭阳极研究

采用高温石墨化炉将太西(TX)无烟煤进行热处理，部分替代煅后焦制备铝用炭阳极，先后考察了TX石墨化煤不同添加形式、添加比例对炭阳极质量的影响。结果表明，TX无烟煤在经过超高温处理后真密度、电阻率、石墨化度、固定炭、灰分、微量元素等指标有了很大的改善，但Fe元素的脱除效果不是很明显；相较于颗粒料的添加形式，采用粉料添加形式制备的阳极质量更优；随着粉料添加量的上升，阳极体积密度、真密度、电阻率、空气反应残余率等指标均明显提高，但CO₂反应残余率明显下降。     

针刺成型C／C预制体的研究进展

预制体作为C／C复合材料的增强结构,它的发展必定会推动C／C复合材料应用于更广闾的领域。文章综述了针刺成型C／C预制体技术在国内外研究进展,并概述了影响针刺C／C预制体性能的主要因素,包括炭布、网胎以及针刺工艺参数等,并对我国针刺技术的发展提出了一些建议。     

C/C多孔体的制备及其对C/C-SiC-Si复合材料的影响

C／C—SiC—Si材料是一种新型的复合材料。本文通过反应熔渗法将液态硅渗入C／C多孔体中得到致密的C／C—SiC—Si复合材料。重点研究了制备C／C多孔体的树脂浸渍裂解法，并测定了在不同浸渍次数下得到的不同的C／C多孔体的体积密度和气孔率，用扫描电镜观察了其形貌，讨论了不同的C／C多孔体对C／C—SiC—Si复合材料最终形貌的影响。     

抑制碱-集料反应的工艺措施

碱-集料反应（AAR）在国内外已引起了大量的混凝土建筑物破坏，损失巨大，因此研究抑制AAR的时策非常必要、以冀东水泥厂为例，通过回转窑碱含量平衡计算和快速砂浆棒膨胀试验得出，就水泥而言，降低混凝土AAR的主要工艺措施有二方面：一是选择低碱的原燃材料，以降低水泥中的总碱量；二是改变碱的存在形式，即在总碱量难以控制时设法减少可溶性碱的存在，以有效抑制AAR的危害性．     

High temperature oxidation resistance of Y2O3 modified ZrB2-SiC coating for carbon/carbon composites

To protect carbon/carbon (C/C) composites from oxidation at high temperature, Y₂O₃ modified ZrB₂-SiC coating was fabricated on C/C composites by atmospheric plasma spraying. The microstructure and chemical composition of the coatings were characterized by SEM, EDS, and XRD. Experiment results showed that the coating with 10 wt% Y₂O₃ presented a relatively compact surface without evident holes and cracks. No peeling off occurred on the interface between the coating and substrate. The ZSY10 coating underwent oxidation at 1450 °C for 10 h with a mass loss of 5.77%, while that of ZS coating was as high as 16.79%. The existence of Y₂O₃ played an important role in inhibiting the phase transition of ZrO₂, thus avoiding the cracks caused by the volume expansion of the coating. Meanwhile, Y₂SiO₅ and ZrSiO₄ had a similar coefficient of thermal expansion (CTE), which could relieve the thermal stress inside the coating. The ceramic phases Y₂SiO₅, Y₂Si₂O₇ and ZrSiO₄ with high thermal stability and low oxygen permeability reduced the volatilization of SiO₂.     

La doping effects on intergrowth Bi2WO6–Bi3TiNbO9 ferroelectrics

La doping effects on intergrowth Bi₂WO₆–Bi₃TiNbO₉ ferroelectric ceramics were studied by X-ray diffraction, electron probe microanalysis and dielectric spectroscopy. It was found that the La³⁺ distribution, ferroelectric phase transition and dielectric relaxation behavior are apparently affected by La doping. With increasing La³⁺ content, the site of dopant ion varies, the grain growth of Bi₅TiNbWO₁₅ is restrained, the Curie temperature is reduced and broadened. Furthermore, two dielectric relaxation loss peaks were observed both in temperature and frequency spectra. The calculated relaxation parameters revealed the oxygen vacancy related to the relaxation process.     

Enhanced ferroelectric,magnetic and magnetoelectric properties of multiferroic BiFeO3–BaTiO3–LaFeO3 ceramics

A lead–free multiferroic ceramic 0.7BiFeO₃–0.3BaTiO₃ showed strong ferroelectric and piezoelectric properties, but weak magnetic and magnetoelectric properties. We herein expected that the electrical and magnetic properties of 0.7BiFeO₃–0.3BaTiO₃ ceramics could be enhanced by introducing LaFeO₃. (0.7–x) BiFeO₃–0.3BaTiO₃–xLaFeO₃ (x?=?0–0.2) were synthesized by solid-state reaction. All the ceramics formed a perovskite structure, and a morphotropic phase boundary (MPB) between rhombohedral and orthorhombic phases formed at x?=?0.025. The ceramics with MPB composition had high unipolar strain (S_max = 0.14%), piezoelectricity (d₃₃ = 223 pC/N, d₃₃ * = 350?pm/V), ferroelectricity (P_r = 25.67 mC/cm²) and magnetoelectricity (a_ME = 466.6?mV/cm·Oe), which can be attributed to addition of La ions. The improved phase angle also demonstrated augmentation of ferroelectricity on the microscopic view. The ferromagnetism was evidently improved after LaFeO₃ doping, and the remanent magnetization M_r increased from 0.0207 to 0.0622?emu/g with rising x from 0 to 0.075. In conclusion, with strong magnetoelectric properties, the prepared ceramics may be applicable as promising lead–free multiferroic ceramic materials for novel electronic devices.     

联苯类膦配体在偶联反应中应用的研究进展

联苯类膦配体具有强的供电性和大的空间效应,作为配体在有机合成领域得到越来越多的应用。主要从C—C、C—N、C—O键的合成角度,概括了联苯类膦配体在各种偶联反应中应用的研究进展。     

Investigation of mechanical and thermo-mechanical strength of ceramic foam filters (CFFs)

During aluminium production, the molten metal will always contain varying amounts of impurities, e.g., non-metallic inclusions, and for high-quality products removing such inclusions is essential. This can be achieved by filtration using ceramic foam filters (CFFs). However, these filters are highly brittle materials subjected to strong mechanical and thermo-mechanical stresses during transport and operation, which occasionally leads to failure of the filter material. In the present study, the compression strength of five different Al₂O₃-based CFFs was measured at room temperature and elevated temperature (compressed at 730 °C), as well as while submerged in molten aluminium with varying melt compositions (pure aluminium and an aluminium-magnesium alloy). The compression strengths at room temperature were established to be in the range of 1.19–2.09 MPa depending on the filter type tested. In the case of the CFFs compressed at elevated temperature, a reduction in compression strength in the range of 9.2–58.6% was established to exist depending on filter type and heating duration, except in three of the filter/duration-combinations tested. Compression of CFF samples submerged in molten aluminium led to an even further reduction in compression strength in the range of 42.6–69.4% depending on filter type and duration of exposure. With an exposure time of only 5 min, no difference in compression strength was observed between the two aluminium melts.     

Threshold quantile autoregressive models

This article studies estimation and asymptotic properties of Threshold Quantile Autoregressive processes. In particular, we show the consistency of the threshold and slope parameter estimators for each quantile and regime, and derive the asymptotic normality of the slope parameter estimators. A Monte Carlo experiment shows that the standard ordinary least squares estimation method is not able to detect important nonlinearities produced in the quantile process. The empirical study concentrates on modelling the dynamics of the conditional distribution of unemployment growth after the second world war. The results show evidence of important heterogeneity associated with unemployment and strong asymmetric persistence of unemployment growth in the higher quantiles.