Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

Sheet-like carbon-nitrogen (CNx)/graphene composites with a high content of nitrogen (x≤0.15) was prepared by the carbonization of polypyrrole (PPy)/reduced-graphene-oxide (rGO) composite at 600-800°C. We used rGO instead of graphene oxide (GO) sheets as a template and a substrate to immobilize PPy since the PPy/GO composite agglomerates easily because of the dehydration of excess oxygen-containing groups on the GO sheets during the drying process. The dried PPy/rGO intermediate and its derived CNx/graphene products retain their high dispersion and loose-powder features. The as-prepared CNx/graphene composites have a total nitrogen content of about 10 at% and their nitrogen state is mainly of pyridinic and graphitic type. CNx/graphene composites exhibit excellent performance for the oxygen reduction reaction (ORR) in terms of electrocatalytic activity, stability and immunity towards methanol crossover and CO poisoning, suggesting their potential as metal-free electrocatalysts for the ORR.     

Carbon-nitrogen/graphene composite as metal-free electrocatalyst for the oxygen reduction reaction

Sheet-like carbon-nitrogen (CNx)/graphene composites with a high content of nitrogen (x≤0.15) was prepared by the carbonization of polypyrrole (PPy)/reduced-graphene-oxide (rGO) composite at 600-800°C. We used rGO instead of graphene oxide (GO) sheets as a template and a substrate to immobilize PPy since the PPy/GO composite agglomerates easily because of the dehydration of excess oxygen-containing groups on the GO sheets during the drying process. The dried PPy/rGO intermediate and its derived CNx/graphene...     

最小二乘曲线拟合在光纤光栅波长解调中的应用研究

本文在分析光谱解调中心波长检测的基础上,从最小二乘法基本原理出发进行曲线拟合,结合实验数据实例,构造一个最佳通用多项式光谱拟合模型,再利用得到的函数关系实现对乙炔吸收光谱中各中心波长的曲线拟合与仿真,降低中心波长飘移,提高检测精度。     

Effects of surface modification on isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings

NiCrAlY coatings were deposited on Ni-based superalloy by high-velocity oxygen-fuel spraying (HVOF). Surface modification by means of grit-blasted, shot-peened and ground methods was used in order to study the effect of surface conditions on the isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings at 1050 ℃. The results showed that surface modification had an obvious effect on the isothermal oxidation behavior of the coatings. There was a large decrease in growth rate compared with the as-sprayed coating. The scale formed on the grit-blasted and shot-peened coatings was a mixture of Al₂O₃ and NiCr₂O₄, while the oxide formed on the ground coating was composed mainly of Al2O3. After surface modification, the content of NiCr₂O₄ spinels decreased compared with the as-sprayed coating.     

安徽省属高校实施《国家学生体质健康标准》的研究——以滁州学院为例

通过对滁州学院实施《国家学生体质健康标准》中的人和物的研究,以学生体质健康标准的实施情况为依据,根据研究目的采用了文献资料、访谈、专家咨询等研究方法,并结合实际对研究进行了相应的分析.研究结果表明：滁州学院在组织实施《国家学生体质健康标准》过程中存在一系列问题：组织管理工作不到位,宣传方式不合理,测试仪器存在质量问题,...     

合肥现代物流业发展状况及对策研究——基于第二次全国经济普查资料的分析研究

现代物流业是国家十大支柱产业之一,已成为国家经济和综合竞争力的新增长点。利用2008年第二次全国经济普查资料,对合肥市现代物流业发展现状进行了分析,并以此提出相应的对策与措施。     

平面上有限级Dirichlet级数和随机Dirichlet级数的增长性

利用型函数及Newton多边形讨论了平面上有限级Dirichlet级数和随机Dirichlet级数的增长性和系数间的关系。通过引理得出:当r=eσ(σ→+∞)时,Dirichlet级数的增长性和系数间的重要关系,以及对于随机变量序列{Xn}满足条件:存在α>0,使得supn 0E(|Xn|α)<∞;存在β>0,使得supn 0E(|Xn|-β)<∞的随机Dirichlet级数f(s,ω)=∞n=0bnXn(ω)eλns和Dirichlet级数f(s)=∞n=0bneλns有几乎相同的关于型函数的增长性。     

基于混合滤波器的大型船舶电力系统谐波抑制分析

设计了一种新的混合型滤波系统,该系统由大容量无源滤波器和较小容量的有源滤波器共同组成.针对船舶的多工况运行方式导致电力系统拓扑结构及参数发生改变这一状况,提出了在电力系统的特定位置安装混合型滤波器,利用较大容量无源滤波器滤除系统特定次谐波,较小容量有源滤波器用于补偿及系统微调的方案.对某大型船舶电力系统的测试结果表明,新型滤波器具有较高的性价比,能适应大型船舶的多工况运行方式.     

规模化养殖场存在的环境问题及防治对策

改革开放以来,随着畜牧业的快速发展,规模化养殖场的环境问题日趋凸显,如何有效防治规模化养殖场污染已成为我国急需解决的环境和社会问题。本文系统阐述了规模化养殖场污染的主要来源及表现,并结合目前研究进展,深入探讨了规模化养殖场污染的综合防治对策。     

Bi/石墨毡电极对铁铬液流电池性能的影响

石墨毡是液流电池的首选电极材料,而Bi增强石墨毡电极材料在铁铬液流电池中的应用参数并不完善.本文将不同浓度的BiCl3加入到电解液中,并将石墨毡电极切割形成交叉型流道,组装铁铬液流电池.通过充放电测试分析BiCl3含量以及流道对铁铬液流电池循环充放电性能的影响,并采用场发射扫描电镜对充放电后的石墨毡进行成分分析,利用循环伏安曲线和交流阻抗谱图分析Bi对正负极反应活性的影响.结果表明,电解液中BiCl3的浓度为5 mmol/L时,铁铬液流电池容量和效率的综合效果最优.