用于燃料电池质子交换膜的含萘及氮杂环结构的新型磺化聚酰亚胺的合成及性能

将自制的4,4'-二氨基二苯醚-2,2'-二磺酸基(ODADS)、 含氮杂环芳香二胺1,2-二氢-2-(4-氨基苯基)-4-[4-(4-氨基苯氧基)-苯基]-二氮杂萘-1-酮(DHPZ-DA)和1,4,5,8-萘四甲酸二酐(NTDA)进行直接缩合聚合反应, 通过改变磺化二胺单体的含量来改变聚合物的磺化度, 成功地合成了一系列高分子量的不同磺化度的六元环聚酰亚胺(SPIs), 其特性粘度在0.55-1.47 dL/g. 采用FTIR和 1H NMR技术表征了聚合物的结构. 研究了经溶液浇铸成磺化聚合物膜的理化性质. 结果表明, 随着聚合物磺化度的增大, 膜的含水率和离子交换能力增大, 尺寸稳定性、 对水的稳定性以及抗氧化性降低.     

纳米晶型MnCo2O4的微波加热法制备及其电催化性能

以Co和Mn的醋酸盐为原料,采用共沉淀法制得草酸盐前驱物,加入一定量微波吸波剂乙炔黑后,用微波进行热处理制得复合氧化物MnCo2O4.X射线衍射和扫描电镜结果表明,产物为纳米晶型,结晶良好,纯度较高,粒径为10~20nm且分布均匀.在室温下、空气气氛中,以6mol/L的KOH溶液为电解液测试了由MnCo2O4制备的空气扩散电极对氧还原反应的催化效果.极化曲线显示,在-0.2V(vsHg/HgO)电位下,氧还原反应电流密度达96mA/cm2.为显示微波加热法的优越性,用马弗炉煅烧制备了MnCo2O4,并对两种热处理方法所得产物的物化性能进行了比较.     

大尺寸电阻加热式碳化硅晶体生长热场设计与优化

大尺寸低缺陷碳化硅(SiC)单晶体是功率器件和射频(RF)器件的重要基础材料,物理气相传输(physical vapor transport, PVT)法是目前生长大尺寸SiC单晶体的主要方法。获得大尺寸高品质晶体的核心是通过调节组分、温度、压力实现气相组分在晶体生长界面均匀定向结晶,同时尽可能减小晶体的热应力。本文对电阻加热式8英寸(1英寸=2.54 cm)碳化硅大尺寸晶体生长系统展开热场设计研究。首先建立描述碳化硅原料受热分解热质输运及其多孔结构演变、系统热输运的物理和数学模型,进而使用数值模拟方法研究加热器位置、加热器功率和辐射孔径对温度分布的影响及其规律,并优化热场结构。数值模拟结果显示,通过优化散热孔形状、保温棉的结构等设计参数,电阻加热式大尺寸晶体生长系统在晶锭厚度变化、多孔介质原料消耗的情况下均能达到较低的晶体横向温度梯度和较高的纵向温度梯度。     

低压供热涂层材料制备及热性能研究

低压供热技术具有安全系数高和节能降耗等优势,因而成为石化稠油长输管线、风力发电叶片冬季防覆冰和室内供暖等领域的研究热点之一。本文制备了一系列低压供热涂层材料,研究不同碳功能填料对涂层发热速率、发热功率及最高发热温度的影响规律,并揭示石墨烯和碳纤维对提升涂层材料热性能的协同作用。其中石墨烯纳米片的还原程度对材料热性能具有重要影响,降低其表面官能团密度对提升涂层供热特性具有促进作用,但是官能团密度过低会导致石墨烯纳米片的团聚现象,引起涂层发热不均匀。加入适量碳纤维可以提高石墨烯的均匀分散性,提升发热速率。优化石墨烯纳米片和碳纤维的比例后,采用24V电压驱动时,涂层材料的发热速率达到7.1℃·s^-1,功率密度为800W·m^-2,最高发热温度为124℃。     

Kinetic study of the sulfonation of hydrogenated styrene butadiene block copolymer (HSBS): Microstructural and electrical characterizations

In this work homogeneous sulfonation kinetic and both, microstructural and electrical characterizations of hydrogenated styrene butadiene block copolymer (HSBS) were studied. The incorporation of sulfonic groups was checked by infrared spectroscopy (FTIR-ATR) and the sulfonation level was determined by both, elemental analysis (E.A.) and chemical titration. Thermal behavior was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), in order to determine thermal transitions and stability, respectively. Microstructure was studied, by means of dynamic mechanical analysis (DMA). Atomic force microscopy (AFM) was studied for several samples and evidenced a morphology change when the sulfonation level increases. Finally, electrical behavior was recorded by means of electrochemical impedance spectroscopy (EIS) and the four-probe technique (FPT). Results show that sulfonation of the benzene rings, in the styrene units, has effectively occurred and that the sulfonation level increases with reaction time. When incrementing the sulfonation level, a structural change in the copolymer was observed. Interconnected clusters allow proton conduction through the membrane. The ion conductivity obtained was about 10⁻² S/cm.     

非含氟型磺化聚合物质子交换膜材料的研究进展(下)

概述了近十年来非含氟型磺化聚合物质子交换膜材料的研究进展,包括各种材料的制备和性质,详细地讨论了材料的化学结构、形态与其性能(质子导电率、耐水性、尺寸稳定性、吸水率、抗自由基氧化性、甲醇透过率等)之间的关系,其中结合作者在磺化聚酰亚胺方面的研究工作,重点对这类材料进行了系统、深入的介绍和讨论.最后,本文还对今后燃料电池用质子交换膜材料的研究提出了一些设想和展望.本文分为上下两篇,其中下篇主要综述了非含氟型磺化聚合物的性能与结构形态之间的关系.     

Current status of automotive fuel cells for sustainable transport

Automotive proton-exchange membrane fuel cells (PEMFCs) have finally reached a state of technological readiness where several major automotive companies are commercially leasing and selling fuel cell electric vehicles, including Toyota, Honda, and Hyundai. These now claim vehicle speed and acceleration, refueling time, driving range, and durability that rival conventional internal combustion engines and in most cases outperform battery electric vehicles. The residual challenges and areas of improvement which remain for PEMFCs are performance at high current density, durability, and cost. These are expected to be resolved over the coming decade while hydrogen infrastructure needs to become widely available. Here, we briefly discuss the status of automotive PEMFCs, misconceptions about the barriers that platinum usage creates, and the remaining hurdles for the technology to become broadly accepted and implemented.     

侧链结构对磺化聚芳醚性能及微观形貌的影响

比较了3种主链结构相同而侧链结构不同的磺化聚芳醚(SPAE)材料的性能. 分析了侧链结构对聚合物的吸水、 溶胀及质子传导行为的影响. 结果表明, 在相同的离子交换容量(IEC)条件下, 具有柔顺脂肪族侧链的聚芳醚材料具有较高的质子传导率. 其原因是由于柔顺的脂肪族侧链比刚性的芳香族侧链更易运动, 有利于侧链末端磺酸基团的聚集, 进而形成离子簇. 3种聚合物微观形貌的分析结果表明, 含柔顺侧链结构的聚合物薄膜具有更大的质子传输通道, 其结果与聚合物的宏观吸水和传导现象相吻合.     

分级结构氮掺杂碳纳米笼担载的铂基高效甲醇氧化电催化剂

高性能低成本的担载型铂基催化剂是直接甲醇燃料电池(DMFC)实用化过程中的一大挑战.利用高比表面积、高稳定性、容易负载金属的载体实现 Pt颗粒的高度分散,既可提高催化剂的催化性能,又可提高 Pt的利用率以降低成本,是担载型 Pt基催化剂实用化的有效途径.碳材料是一种常用的催化剂载体,近年来我们课题组发展了一种高性能的碳纳米笼材料,并可通过异原子掺杂调变其表面性能,提高其活性和负载能力.我们采用原位氧化镁模板法制备氮掺杂碳纳米笼：以具有多级结构的碱式碳酸镁作为氧化镁模板的前体,吡啶为碳源和氮源,经高温热解沉积,在原位形成的氧化镁模板表面形成氮掺杂的石墨化碳纳米薄层;经稀盐酸浸泡并洗涤,获得高纯度的氮掺杂碳纳米笼.氮掺杂碳纳米笼具有分等级的微纳米结构、高导电性、高比表面积和可调变的孔结构,结合表面氮原子的锚钉作用,氮掺杂碳纳米笼有望成为电化学催化剂 Pt的优良载体.
　　在前期研究基础上,本文探索多级结构氮掺杂碳纳米笼(hNCNC)作为新型载体负载 Pt的能力,并评价所构建的负载型催化剂 Pt/hNCNC的电催化性能.通过简便的微波辅助多元醇还原法,将氯铂酸还原成 Pt纳米粒子负载于 hNCNC的表面.为了揭示氮掺杂的效应,我们对比研究了具有相似分级结构但无掺杂的碳纳米笼(hCNC)以及商业化活性炭(Val-can XC-72)作为载体的情况.经热重(TG)和 X射线光电子能谱(XPS)分析,三种催化剂 Pt/hNCNC、Pt/hCNC和 Pt/XC-72的负载量均接近理论负载量(23.1 wt%),都主要以金属态存在.然而,扫描电子显微镜(SEM)和透射电子显微镜(TEM)结果表明, Pt/hNCNC的 Pt分散状态优于 Pt/hCNC,更远优于 Pt/XC-72. Pt/hNCNC的平均 Pt粒径最小,仅约3.3 nm.这种良好的分散状态主要得益于氮原子掺杂,高负电性的氮原子改变了局域的表面极性,有利于 Pt颗粒的成核,也有利于固定 Pt颗粒.
　　由于 hNCNC对 Pt的优异分散能力, Pt/hNCNC表现出高的电化学活性面积.氢吸附和一氧化碳溶出伏安曲线表明, Pt/hNCNC的电化学活性面积高于 Pt/hCNC和 Pt/XC-72,这与显微观察和 X射线衍射(XRD)结果相吻合. Pt/hNCNC展现出优异的甲醇电催化氧化活性和高稳定性,其催化电流明显高于 Pt/hCNC和 Pt/XC-72,电流衰减亦慢于 Pt/hCNC和 Pt/XC-72. hNCNC的分级微纳米结构有利于孔内传质和电子输运,从而提高反应速度. hNCNC的氮掺杂有利于 Pt在载体表面的分散,增强了载体-金属相互作用,提高了电化学活性面积和催化活性.为了进一步考察 hNCNC对 Pt的负载能力,本文还考察了高负载量 Pt/hNCNC的性能.在负载量高达60 wt%时, Pt/hNCNC中的 Pt颗粒仍无明显聚集,其甲醇氧化电流增加了30%,可以有效提高 DMFC的输出电流密度.
　　综上可见, hNCNC可以有效分散并稳定 Pt颗粒,从而提高电化学活性面积和甲醇电催化氧化活性,优于未掺杂的碳纳米笼和传统碳材料,展示了 hNCNC高分散 Pt颗粒用作 DMFC的高效阳极催化剂的重要前景,也表明 hNCNC有望成为应用广泛的新型载体.     

Analysis of volatile organic compounds in fuel oil by headspace GC-MS

Fuel oils are mostly used in marine applications and in power plants. They are known to contain hazardous volatile organic compounds (VOCs) that are of health and environmental importance. Chlorinated compounds, phenolic compounds, styrenes, indene, dicyclopentadiene, dihydrodicyclopentadiene, cumene, benzene, toluene, ethylbenzene and xylenes are some of the VOCs that have found their way into fuel oil through various streams during bunkering operation. Chromatographic analysis of VOCs in the presence of complex matrices in fuel oil is one of the major challenges encountered when dealing with products of that nature. An analytical procedure using automated static headspace gas chromatography–mass spectrometry was developed for the analysis of these compounds in fuel oil. Styrene D8 and phenol D6 were used as internal standards for quantitation. Phenol D6 was used for the quantitation of phenolic compounds, while styrene D8 was used for the quantitation of other target analytes. The influence of headspace parameters on analyte response such as temperature, incubation time and sample amount were all investigated and optimised. Linear calibration curves were achieved for all components with determination coefficients R² > 0.995. Repeatability, limit of detection, limit of quantitation and recovery were reported. The matrix effect in fuel oil was minimised by 1:1 dilution with mineral oil. This method was successfully applied to the analysis of commercial samples.