Structures of Pt clusters on graphene doped with nitrogen, boron, and silicon: a theoretical study

The structures of Pt clusters on nitrogen-,boron-,silicon-doped graphenes are theoretically studied using densityfunctional theory.These dopants(nitrogen,boron and silicon) each do not induce a local curvature in the graphene and the doped graphenes all retain their planar form.The formation energy of the silicon-graphene system is lower than those of the nitrogen-,boron-doped graphenes,indicating that the silicon atom is easier to incorporate into the graphene.All the substitutional impurities enhance the interaction between the Pt atom and the graphene.The adsorption energy of a Pt adsorbed on the silicon-doped graphene is much higher than those on the nitrogen-and boron-doped graphenes.The doped silicon atom can provide more charges to enhance the Pt-graphene interaction and the formation of Pt clusters each with a large size.The stable structures of Pt clusters on the doped-graphenes are dimeric,triangle and tetrahedron with the increase of the Pt coverage.Of all the studied structures,the tetrahedron is the most stable cluster which has the least influence on the planar surface of doped-graphene.     

氨性介质石墨炉原子吸收法测定化探样品中的银

银在地壳中的丰度值仅为1×10^-7,自然界中的银主要以硫化矿物形式存在。矿产资源调查项目中的化探样品,银是必测元素之一。银在化探样品中的含量一般为10^-8～10^-7,通常微量银的测定方法有原子吸收法、发射光谱法、质谱法等,其中原子吸收法应用最为广泛。     

用热重分析法快速测定煤的工业分析

目前我国采用的煤的工业分析方法(GB217-77),有以下缺点:1.对煤样的重量,加热温度,加热时间和气氛条件必须严格控制,因而不同单位和不同操作者所得结果往往有较大偏差;     

Excel在仪器分析数据处理中的应用

Excel是微软公司的一款优秀的数据处理软件,已经被广大分析工作者广泛的用于分析测试的数据处理工作中.根据实际工作经验,将Excel程序中的图表功能用于仪器分析中最常做的校准曲线绘制、计算回归方程和检测数据的处理工作中,使尚未配备计算机的分析仪器的校准曲线绘制和数据处理工作大大简化.本方法适用于所有尚未配备计算机的分析仪器.     

Quantum anomalous Hall effect in real materials

Under a strong magnetic field,the quantum Hall(QH) effect can be observed in two-dimensional electronic gas systems.If the quantized Hall conductivity is acquired in a system without the need of an external magnetic field,then it will give rise to a new quantum state,the quantum anomalous Hall(QAH) state.The QAH state is a novel quantum state that is insulating in the bulk but exhibits unique conducting edge states topologically protected from backscattering and holds great potential for applications in low-power-consumption electronics.The realization of the QAH effect in real materials is of great significance.In this paper,we systematically review the theoretical proposals that have been brought forward to realize the QAH effect in various real material systems or structures,including magnetically doped topological insulators,graphene-based systems,silicene-based systems,two-dimensional organometallic frameworks,quantum wells,and functionalized Sb(111) monolayers,etc.Our paper can help our readers to quickly grasp the recent developments in this field.     

用热分析技术研究煤的热解特性

利用Dupont1090热分析仪研究煤的热解特性,导出了在500℃以上的温度条件下,褐煤及烟煤在热解过程中,挥发份产率随温度变化的关系式:V_t~f=0.27V~f+0.75V~f[1-((t-1250)/750)~2]~(1/2),V_2~r=3.64+0.98V~r,并根据挥发分的总析出率,计算出了挥发分的发热量。     

极谱法测定化探样品中的钨、钼

化探样品经氢氧化钾熔融,用水提取其中的钨、钼,采用二苯乙醇酸代替苯羟乙酸,在硫酸-二苯乙醇酸-二苯胍-氯酸钾体系中,利用极谱催化波测定钨、钼,方法的灵敏度大大提高,钨、钼的峰电位分别为-0.76、-0.26 V(对饱和甘汞电极),钨、钼含量为1.0～100.0 ng/mL时,极谱峰高与浓度呈线性关系.方法经国家一级标准样品检验,测定结果与推荐值吻合,钨、钼测定结果的RSD分别为3.5%～4.1%、3.4%～3.9%(n=11).     

诊断中的判别分析

本文对疾病诊断问题，提出一种判别分析方法．