Preparation of well-aligned carbon nanotubes by pyrolysis of phenolic resin in anodic alumina pores

Well-aligned carbon nanotubes (CNTs) of high quality were synthesized by pyrolysis of phenolic resin at 800 °C in anodic alumina oxide (AAO) pores under argon protection. The innocuous source materials and safe operational conditions permit this method to synthesize well-aligned CNTs in large-scale and low cost. The formation mechanism of the synthesized CNTs is also proposed in this work by a series of visual sketches and is proved with obvious evidence. Firstly, phenolic resin nanotubes form in the template pores through the evaporation of solvent. Heat treatment then transfers these tubes into CNTs.     

The reaction of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones with dinucleophilic reagents: a convenient route to fluoroalkylated nitrogen-containing tricyclic compounds

The reactions of 2-(1-hydropolyfluoro-1-alkenyl)-4H-3,1-benzoxin-4-ones (2) with hydrazine hydrate and phenyl hydrazine were investigated. The reaction of 2 with hydrazine hydrate in ethanol under reflux condition readily gave 2-fluoroalkyl-4H-pyrazolo[5,1-b]quinazolin-9-ones (3) in high yields. The reaction of 2 with phenyl hydrazine, however, resulted in the formation of 2-(2-phenyl-5-fluoroalkyl-2H-pyrazol-3-yl) benzoic acids (7). Further treatment of 7 with PPA gave 1-phenyl-4,9-dihydro-3-fluoroalkyl-1H-pyrozolo[3,4-b]quinolin-4-ones (4) in 65-80% overall yields.     

反胶束模板制备聚甲基丙烯酸甲酯/无机纳米粒子/石墨纳米复合材料及其表征

以甲基丙烯酸甲酯(MMA)和三氯甲烷(CHCl₃)为油相制备反胶束微乳液, 依靠表面活性剂十六烷基三甲基溴化铵(CTAB)自组装形成的“微反应器”作为模板成功地制备了PMMA/Eu(OH)₃/EG和PMMA/Ni(OH)₂/EG纳米复合材料. 并用红外光谱(IR)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和差热-热重(TG-DTA)对该复合材料进行了表征和分析. 研究结果表明, 反胶束法可以有效地应用于有机-无机纳米复合材料的制备.     

固相萃取-离子色谱-积分脉冲安培法测定人血清中游离氨基酸

比较了磺基水杨酸和无水甲醇沉淀人血清中蛋白质的效果,优化了国产732型阳离子交换树脂进行固相萃取净化的条件和Dionex-600离子色谱分析系统的梯度淋洗条件。用该离子色谱仪检测了谷氨酰胺等14种氨基酸,结果表明,峰面积-浓度的校正曲线的相关系数为0.9900~0.9995,检出限为0.02~0.59mg/L;峰面积的相对标准偏差为1.9%~10.4%;回收率为80.6%~114.8%。     

二组元酞菁固相混合法裂解合成直立碳纳米管

通过向两种金属酞菁的混合物添加一定量的硫粉,在800～950 ℃裂解合成了大面积的直立碳纳米管。采用场发射扫描电镜(FE-SEM)、高分辨透射电镜(HRTEM)和拉曼光谱对产物进行了观察和表征,结果显示：所合成的碳纳米管(直径为15～35 nm,长度为200～800 nm)管身平直,具有很好的石墨化程度,且杂质很少。采用两种金属酞菁((M(Ⅱ)Pc, M=Fe, Co))进行混合裂解时,既可以提供碳源,而且可以产生相当均匀的催化剂颗粒,有利直立碳纳米管的沉积。这种将两种酞菁进行固相混合裂解的方法,相当安全高效,有利于大规模生产直立碳纳米管。     

碳纤维增强纸基摩擦材料磨损机理研究

以碳纤维为主要增强纤维,采用湿法工艺制备出1种纸基摩擦材料.研究了不同制动次数条件下样品的摩擦磨损行为,通过分析不同制动次数后样品磨损表面的粗糙度特征、三维轮廓形貌、微观形貌和热失重过程,探讨了碳纤维增强纸基摩擦材料的磨损机理.结果表明：随着制动次数的增加,磨损表面粗糙度大幅度降低,材料磨损过程经历了从＂跑合磨损＂到＂稳定磨损＂的转变;材料在磨损过程中微凸体逐渐被磨平,孔隙逐渐被填充,表现出疲劳磨损的特征;磨损后样品表层的热重曲线在320～450℃之间出现了新的剧烈失重峰,表明产生了热磨损;但是磨粒磨损的特征并不明显.     

碳纳米管含量对炭炭复合材料组织及力学性能的影响

炭纤维上原位合成了均匀生长且具有伸张形貌的碳纳米管,借助化学气相渗透制备了碳纳米管增强的炭炭复合材料,研究了不同含量的碳纳米管对炭炭复合材料组织和力学性能的影响。结果表明：炭纤维上生长碳纳米管改变了热解炭的沉积行为,诱导了各向同性热解炭的生成,且随着碳纳米管含量的增加,各向同性热解炭的厚度增加,但是复合材料的d002值却明显降低。微量的碳纳米管即可显著提高复合材料的力学强度,随着其含量的增加,复合材料的力学强度和模量迅速提高,但材料的断裂行为却急剧恶化,断裂模式由最初的假塑性断裂转变为脆性断裂。     

碳包覆纳米铁镍磁性颗粒的合成

通过在双温控的化学气相沉积炉中热解四吡啶并卟啉铁镍混合物,合成了碳包覆铁镍纳米颗粒。原料中四吡啶并卟啉铁镍的质量比为7∶3;扫描电镜和透射电镜的结果显示碳包覆铁镍纳米颗粒形貌均匀,直径为100~300 nm;能谱结果显示碳包覆铁镍纳米颗粒是由铁、镍和碳组成;拉曼光谱证明产物有大量的缺陷存在,可能是由于球状结构上的碎片引起的;此外,磁性能测试表明室温下,碳包覆铁镍纳米颗粒有很高的饱和磁化强度,为56.3 emu·g^-1;而其产物的矫顽力趋近于零,呈超顺磁性,适合用于催化剂载体。     

Estimates for weighted eigenvalues of a fourth-order elliptic operator with variable coefficients

We investigate the Dirichlet weighted eigenvalue problem for a fourth-order elliptic operator with variable coefficients in a bounded domain in \mathbbRⁿ {\mathbb{R}^n} . We establish a sharp inequality for its eigenvalues. It yields an estimate for the upper bound of the (k + 1)th eigenvalue in terms of the first k eigenvalues. Moreover, we also obtain estimates for some special cases of this problem. In particular, our results generalize the Wang–Xia inequality (J. Funct. Anal., 245, No. 1, 334–352 (2007)) for the clamped-plate problem to a fourth-order elliptic operator with variable coefficients.     

Inequalities for lower-order eigenvalues of a fourth-order elliptic operator

In this paper, we investigate the Dirichlet weighted eigenvalues problem of a fourth-order elliptic operator with variable coefficients on a bounded domain with smooth boundary in ? ⁿ . We establish some inequalities for lower-order eigenvalues of this problem. In particular, our results contain an inequality for eigenvalues of the biharmonic operator derived by Cheng, Huang, and Wei.