氮掺杂酸角衍生多孔碳的制备及电容性能研究

随着化石燃料的加速消耗和能源危机的日益加剧,作为新型储能元件的超级电容器引起了研究人员极大的关注.本文通过水热法制备了生物质衍生多孔碳,并对该材料的微观结构和元素组成进行分析,研究了其作为超级电容器电极材料的电化学性能.结果表明,经过掺氮处理的酸角衍生多孔碳材料其比电容从166 F·g-1提高到了232 F·g-1,说明掺杂能有效提高生物质衍生多孔碳材料的电容性能.     

反应烧结碳材料表面异质外延生长SiO2晶体的研究

利用高温反应烧结在不同结构碳材料表面热蒸发进行二氧化硅(SiO2)晶体的外延生长.采用X-射线衍射仪(XRD)、扫描电镜(SEM)和电子能谱仪(EDS)分析和研究了碳材料表面生成物的物相组成与显微形貌,探讨了SiO2晶体的外延生长机理.研究结果表明,不同结构碳材料表面能外延生长SiO2晶体,但形态不同.在碳纤维表面形成颗粒和短晶须状SiO2晶体,在石墨片上形成凸起团聚状SiO2晶体,而在金刚石表面首先形成了Si-O涂层,然后在Si-O涂层上生长棒状SiO2体.碳材料外延生长SiO2晶体是首先通过热蒸发法使Si沉积到碳材料表面,然后Si与体系中的O反应形成SiO2晶核,在不同结构碳材料表面生长SiO2晶体.     

磁控溅射工艺参数对碳膜表面形貌及浸润性的影响

为了分析磁控溅射工艺对碳膜表面形貌及浸润性的影响,在室温下采用磁控溅射技术在硅片表面沉积碳膜,并利用原子力显微镜(AFM)、扫描电镜(SEM)、静态接触角测量仪对所得碳膜进行表征.结果表明:随着溅射功率的提高,碳膜表面粗糙度先减小后增大,致密性逐渐改善,静态接触角先增大后减小;随着溅射时间的延长,碳膜的表面粗糙度逐渐增加,均匀性在一定的溅射时间内逐渐改善,静态接触角呈现先减小后增大再减小的趋势;随着溅射压强的增加,碳膜表面粗糙度先增大后减小,致密性在过高的溅射压强下会变差,静态接触角先减小后增大.     

用于CdZnTe晶体生长的石英坩埚真空镀碳工艺研究

采用原子力显微镜(AFM)、椭圆偏振光谱仪、Dage-Pc2400推理分析等测试方法研究了石英坩埚真空镀膜工艺获得的碳膜的表面状态、粗糙度,碳膜和石英坩埚的结合力,确定了用于CdZnTe晶体生长的石英坩埚真空镀碳的最优工艺参数.研究表明,以乙醇为碳源,坩埚真空退火9 h后,碳源通入量为1.5 mL时,获得了厚度为0.7163 μm,表面粗糙度为4.7 nm,结合力达8.11 kg的碳膜.采用此工艺镀膜的石英坩埚生长CdZnTe晶体后,碳膜附着完好,晶体表面平整光洁,位错密度降低.     

钴掺杂碳活化过硫酸氢钾降解四环素

本文以无水葡萄糖和六水合硝酸钴为原料，采用水热法与原位负载相结合制备了一种掺钴的碳基化合物，并将其作为过硫酸氢钾活化剂用于催化降解水体中的四环素。对制备的掺钴碳基化合物进行了XRD、SEM、TEM、XPS等表征，从晶形结构、显微形貌、表面化学元素等方面分析了该催化剂降解四环素效果明显高于单一水热碳的原因。此外，考察了催化剂投加量、过硫酸氢钾投加量、溶液pH等因素对四环素催化降解效果的影响。实验结果表明：掺钴碳基化合物在最佳反应条件下催化降解60 min,四环素的降解率达到了95.84%(k=0.051 36 min^-1)。同时还对降解机理进行了探究，分析结果表明掺钴碳基材料中的Co⁰和Co²⁺参与了激活过硫酸氢钾产生·O^-₂、SO₄^·-、¹O₂、·OH的过程，该材料具有高效的催化降解四环素的能力，在处理抗生素废水方面具有良好的前景。     

碳基材料表面TaC涂层的研究进展

碳材料在高温有氧环境中的易氧化性极大地制约了其在航天航空领域中的应用,而TaC涂层能够有效改善碳材料的烧蚀氧化性能.本文综述了TaC陶瓷涂层改性抗烧蚀氧化C/C复合材料的研究进展,包括单相TaC涂层、复合涂层体系、梯度涂层体系、固溶强化涂层体系和微纳结构增韧涂层体系以及TaC涂层的高温(>2000 ℃)氧化机理.并就目前碳基材料表面TaC涂层研究存在的问题,提出了今后研究的方向.     

晶体生长用石英玻璃管镀膜工艺的正交实验研究

运用正交设计,对CdZnTe晶体生长用高纯石英坩埚内壁镀膜过程中的镀膜温度、镀膜时间、气体流量、冷却时间四个因素进行了研究和优化.用金相显微镜,扫描电镜观察分析了不同镀膜工艺条件下得到的碳膜表面形貌,用WS-2005自动划痕仪对碳膜与石英管壁之间的结合力进行了测试.实验结果表明,镀膜温度对碳膜质量影响最为显著,其次是镀膜时间,再次为冷却时间,而气体流量对碳膜质量的影响甚小.镀膜工艺的优化参数:镀膜温度为1010 ℃,气体流量为6 L/h,镀膜时间为4 h,冷却时间为18 h.该工艺参数得到的碳膜较为均匀,且与石英管壁结合强度高.     

AgGaS2单晶生长石英安瓿镀碳工艺研究

研究了镀碳工艺参数对碳膜的表面形貌、厚度、碳膜与石英管内壁结合力的影响,发现在气体流量为30～40ml/min, 镀碳温度为1040～1060℃,镀碳时间为30～40min,冷却时间为10～12h的条件下,可获得均匀、致密且结合牢固的碳膜层.用此工艺镀碳的石英安瓿生长出的AgGaS2晶体表面光洁,完整性好,缺陷较少.     

硫/碳复合材料在锂硫电池正极中的应用

锂硫电池由于具有1675 mAh·g-1的高理论比容量和2600 Wh·kg-1的高理论能量密度,被看做是下一代最有前景的二次电池能源储存系统之一.但是,多硫化物的穿梭效应、活性物质导电性差以及充放电过程中的体积膨胀效应等问题阻碍了其进一步商业化.为了解决这些问题,不同的材料被引入和硫进行复合.在所有材料的选择中,碳材料由于具有高的表面积、优异的导电性、化学稳定性和低成本等优势在锂硫电池正极中得到了广泛应用.本文总结了几种不同的碳材料在硫/碳复合正极中的发展历程,讨论了碳材料的结构、孔径大小以及表面功能化对锂硫电池电化学性能的影响,并对其前景以及发展趋势作了预测.     

直流电弧等离子体喷射法制备氮化碳薄膜研究

以H2、N2和CF4气体为前驱体,用直流电弧等离子体喷射设备在不同基底温度条件下于钼/金刚石过渡层基底上制备了氮化碳薄膜.利用扫描电子显微镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)对表面形貌和组织成分进行了表征.结果表明,当基底温度为900℃时,所沉积材料已初具晶型;所沉积材料含有α-C3N4和β-C3N4相成分.同时,提出在金刚石表面制备氮化碳时金刚石相刻蚀和氮化碳相生长同时进行的模型,较好地解释了不同基底温度条件下的膜材料沉积现象.     

Two-dimensional crystallization of proteins on lipid monolayers at the air–water interface and transfer to an electron microscopy grid

The two-dimensional (2-D) crystallization of proteins on lipid monolayers at the air–water interface is a well established method for crystallizing soluble proteins. The transfer of 2-D crystals from the air–water interface to an electron microscopy (EM) grid constitutes a critical and ill-controlled step in the whole procedure, which is likely to be responsible for the high variability of results obtained with this method. In this paper, we address the following questions: (1) does the material observed on EM grids constitute a true representation of the material present at the air–water interface? (2) is there an optimal method of transfer to obtain well-ordered protein 2-D crystals? To answer these questions, we combine data obtained on three different protein systems, annexin V, streptavidin and cholera toxin, using two types of EM grids, coated with either holey carbon films or continuous carbon films. These combined observations help us draw a coherent picture of the state of the interfacial films at the air–water surface and provide new insight into the perturbing influence of the transfer step. The main conclusions are: (1) both annexin V and streptavidin form crystalline monolayers at the air–water interface, which are well preserved when transfer is performed by means of holey carbon films; (2) a major reorganization of the material present at the water surface accompanies transfer with continuous carbon films; the basal monolayer is extensively damaged, transforming into domains and vesicular structures, which do not pre-exist at the water surface; with the three protein systems studied here, these domains are often crystalline; (3) the most striking structural reorganization induced by transfer with continuous carbon films is observed with annexin V, for which the native p6 crystalline assembly is transformed into another crystal form more ordered, with p3 symmetry. It is most probable that these conclusions also apply to other protein 2-D crystals formed by the lipid monolayer method. The recent in situ observation of 2-D crystals of annexin V formed on solid-supported bilayers, by atomic force microscopy, supports our interpretation that monolayers transferred with holey carbon films represent the genuine material pre-exisiting at the air–water interface.     

Cu@PtCu催化薄膜的构筑及氧还原催化性能研究

采用喷涂或转印方法制备的质子交换膜燃料电池催化层存在活性不均匀或活性位点易失效的问题。本研究用静电纺丝法制备高导电性的柔性碳纳米纤维薄膜，然后将析氢电位较高的Cu以脉冲电沉积的方式均匀沉积到纤维膜上，制备出Cu纳米晶/碳纳米纤维膜，最后通过原位置换还原，合成Cu@PtCu/碳纳米纤维(Cu@PtCu/CNF)催化薄膜。Cu@PtCu/CNF催化薄膜解决了催化层活性不均的问题，且可以直接作为催化层使用。采用SEM、XRD、XPS等对其形貌、结构进行了表征。电化学测试结果表明，在pH=4、氯铂酸浓度为0.25 mg·mL^-1时获得的Cu@PtCu/CNF催化薄膜，其面积比活性为49 m²·g^-1。在5 000个循环的稳定性测试后，电化学活性比表面积保持74%,半波电位下降了9 mV,均优于商业Pt/C催化剂。     

离子轰击对准直碳纳米管生长的影响

利用负偏压增强热丝化学气相沉积系统,在辉光放电的情况下制备出准直碳纳米管,并用扫描电子显微镜研究了不同负偏压对准直碳纳米管生长的影响.结果表明随着负偏压的增大,准直碳纳米管的平均直径减小,平均长度增大.由于辉光放电的产生,在衬底表面附近形成阴极鞘层,以及在阴极鞘层内形成大量的离子和在衬底表面附近形成很强的电场导致了离子对衬底表面的强烈轰击.最后,分析和讨论了离子的轰击对准直碳纳米管生长的影响.     

碳纳米管场发射性能的研究进展

碳纳米管是一种性能优良的场发射冷阴极材料,具有低的阈值电场和高的发射电流密度,在平板显示领域具有广阔的应用前景。本文从Fow ler-Nordhe im s场发射理论出发,阐述了CNT的场发射机制,详细论述了包括CNT的结构、方向性、阵列密度、吸附气体、工作环境等诸多因素对其场发射特性的影响。研究表明,垂直取向,长径比高,密度适中,表面洁净的CNT场增强因子较大,场发射性能较好。     

Transition from amorphous semiconductor to amorphous insulator in hydrogenated carbon–germanium films investigated by IR spectroscopy

Thin a-Ge_XC_1?X:H plasma polymerized films, depending on deposition conditions, can be produced in two very different structures, namely amorphous semiconductor and amorphous insulator. The transition from amorphous insulator to amorphous semiconductor is related to the formation of germanium nanoclusters due to ions bombarding the surface of the growing material. This paper concentrates on investigations of the transition by means of IR spectroscopy. To this end a quantitative analysis of IR spectra obtained for thin films deposited on silicon substrate has been described and used for estimation of hydrogen atom concentration and bonding in the investigated material. It was found that the probability that a given H atom is bonded to a germanium or to a carbon atom is almost the same. This conclusion is true both for a-S and a-I films. The average concentration of hydrogen in the investigated material was found to be about 2.4–3.4 × 10²² cm^?2 which means that there are two times more atoms of the carbon family than hydrogen atoms in the film structure.     

Transport Properties of Epoxy-Binary Filler Composites

This paper presents the results of changes in electrical resistivity and thermal conductivity of polymer composites (CMs) with two-component filler. It is shown that thermal conductivity of epoxy CMs strongly depends on structural and morphological characteristics of carbon fillers. The synergistic effect in electrical and thermal conductivities of the studied CMs is observed upon addition of boron nitride BN. The presence of a sufficiently large number of BN particles in CMs promotes a more efficient formation of chains of carbon filler and reduces thermal (electrical) contact resistance between the filler particles by decreasing the distance between particles of the filler.     

Structure and electrochemical properties of carbon aerogels synthesized at ambient temperatures as supercapacitors

In this paper, the carbon aerogels derived from organic sol-gel process were prepared by means of ambient drying technique. Morphology and physical properties of the carbon aerogels were characterized by scanning electron microscopy (SEM) and N₂ sorption isotherm. It was found that the carbon aerogels were porous materials with pearly network structure, the particle size of carbon aerogels increased with the increase of R/C ratio (molar ratio of resorcinol to catalyst). The BET surface areas of obtained carbon aerogels were in the range 600-1000 m²/g. Electrochemical performances of the carbon aerogels electrodes were studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance measurement. The results indicated that carbon aerogels electrodes had good electrochemical performance, high reversibility and high specific capacitance. Moreover, the utilization efficiency of carbon aerogels was promoted due to excellent electronic conductivity and extensive mesoporous network of carbon aerogels. The specific capacitance of the electrode is 183.6 F/g with R/C ratio 1500. In addition, the carbon aerogel electrode for the application of supercapacitor had low resistance, small leakage current and good electrical conductivity.     

单壁碳纳米管储氢行为的模拟计算研究

利用碳纳米管储氢已经成为了纳米科技领域中的一项研究热点.为了认识碳纳米管的动态储氢过程,本文借助于分子动力学方法,对单壁碳纳米管的储氢行为进行了模拟计算,其结果生动逼真,并得出了储氢的如下结论:被吸附的氢分子主要出现在管内和管外的边缘附近;管内氢分子的分布出现分层现象,且管径越小,则靠近管壁的氢分子分层现象越明显;在管内外靠近管壁处的氢分子与管壁有一定的空隙.这为进一步研究碳纳米管的储氢机理和储氢容量等问题提供了必要的依据.     

Épitaxie en phase liquide des composés III–V sur substrat InP

The surface preparation and characterization of InP substrates have been studied. It is shown that a 1–3% bromine-methanol etching solution gives a smooth surface if 10 μm or more has been removed. Auger spectrometry detected some contamination of carbon and oxygen by the atmosphere during substrate preparation. The concentration of carbon impurities is less than in the case of GaAs. Liquid phase epitaxy of InP and Ga_xIn_1?xAs_1?yP_y was achieved by a slider technique. Equilibrium cooling, supercooling and step-cooling processes have been tried. It is demonstrated that misorientation from a (111) plane gives a “scale” structure, the orientation of which is exactly (111). Smooth LPE surfaces have been obtained with the supercooling and the step-cooling processes.     

超高压下熔媒法人造金刚石合成机制研究的重要进展

本文对熔媒法人造金刚石的实验、观察和分析,包括熔媒金属(FC或m)、石墨(g)和金刚石(D)存在状态、结晶状况、微观结构和结构特征及其各自结果的分析讨论等研究作了报导.在此基础上对人造金刚石的合成机制作出有机统一整体的讨论如下:(1)形成D结晶基元相变必要条件的特征,可以认为在m熔化过程中发生的助熔激发效应.由于m的d带空穴同g的π-电子相互作用产生各种集团和原子,特别是具有近程有序与密排面结构的原子集团,从而形成一种具有适当尺寸和可变组元的类填隙式固溶体-复合原子集团;(2)形成D结晶基元相变充分条件的特征,可以认为在前述的复合原子集团中的密排面间隙部位发生m的催化激发效应.由于m的价电子处于激发态统计权重增高达到d3s或类sp3状态,诱发处于复合原子集团中类g原子集团实现sp2转移sp3状态.形成一种具有可变组分、不稳定的或部分稳定的类间隙相.这种间隙相式复合原子集团是相变的产物,也是在非平衡态下具有扩散性的主要结晶基底和结晶基元;(3)人造金刚石体系中m/g相互作用的必要和充分条件的特征可用它们的界面结合特征方程作判据来描述.这种判据取决于反映在它们表面和界面上几何结构、电子结构和尺寸等效应(与原子-分子层次结构及相互作用状态有关)的表面能、界面能和有效尺寸.所推导的方程对人造金刚石体系中相互作用,即熔媒激发复合效应的最适合状态提供重要的科学依据和有效技术途径.