氟化硼碳平面的第一性原理研究

基于第一性原理的理论计算,研究了不同氟化程度的BC3,BC5,BC7的稳定结构和电子特征,发现通过B原子替代C原子,F原子与平面结构的结合能力更强了,氟化的硼碳结构比氢化的硼碳结构更加稳定.研究发现:当只有C原子与F原子成键时,体系变成半导体,而当B原子与F原子成键时,即所有原子都与F原子成键,体系变成导体.通过不同程度的氟化,BC3发生半导体-金属的转变,BC5和BC7发生金属-半导体-金属的转变.理论分析表明,B原子的pz轨道对电学性质变化有较大影响.由于其丰富的电学特性,此类氟化硼碳平面在纳米电子器件领域中具有潜在应用,并且该结果对实验合成也有一定的指导意义.     

重掺硼快速退火分子束外廷硅的X射线衍射研究

利用Ｘ射线双晶衍射，测量了经过８００－１１００℃快速退火处理的重掺硼的分子束处延硅中的应用情况，发现应变部分驰豫，并得出延层与衬底硅的晶格失配与替位硼浓度成正比，比例系数β为５．１，在此测量基础上，提出硼团簇的形成与分解是外延层格质量电学性质变化的主要原因。     

高压下B12AS2晶体结构及晶格振动的第一性原理研究

利用基于密度泛函理论的第一性原理计算,本文研究了二十面体硼化砷(B12As2)在外部静水压强0～30 GPa范围内的晶格结构变化.计算结果表明:二中心B-B键在高压下压缩率最大,硼二十面体基团相对比较稳定,外界压力对其影响较小.利用基于密度泛函微扰理论的计算,本文给出了在0～30 GPa范围内B12As2晶体所有12个...     

Eu2+掺杂硼硅酸镁玻璃的发光性能

利用高温固相法合成了Eu2+掺杂的新型蓝色硼硅酸盐发光玻璃,讨论了不同掺杂浓度下硼硅酸镁玻璃体系中Eu-O键共价性的变化以及氧原子周围不同配位环境对MgO-SiO2-B2O3玻璃发光性能的影响.利用X射线衍射仪和荧光光谱仪对该玻璃体系进行了结构表征和性能测试.在紫外-可见光激发下,Eu2+掺杂硼硅酸镁玻璃的荧光发射光谱...     

二维硼结构中条带状空位长程有序分布的理论研究

在二维硼结构中,有序分布的高浓度空位可以增强其结构的稳定性,并对材料性能产生显著影响.根据最近的实验进展,本文重点关注二维硼结构中空位呈条带状分布的体系,提出有效模型系统研究结构稳定性随空位分布的变化.结合第一性原理计算结果,对空位不同近邻作用参数进行拟合,预测了不同空位浓度的稳定结构,发现在该体系中空位不同近邻存在竞争,导致长周期分布的趋势,揭示了不同近邻作用的相互竞争导致长周期结构稳定存在的关键机制.     

钻石中硼受主电荷转移引发磷光的直接证据

受主元素硼与不带电荷的替位硼进行电荷重组会导致钻石发出磷光,但Ⅱb型钻石硼含量较高,难以为电荷重组与磷光的相关性提供直接证据。作者针对一粒在常光环境下近无色的钻石,利用DiamondViewTM的深紫外强光源照射样品,使之产生蓝绿色磷光,结合前人研究,推断该类型磷光与含硼元素有关。采集样品红外光谱,在磷光消退前,谱图呈现2 803 cm-1吸收峰,磷光消失后采集的红外谱图不显示2 803 cm-1峰。这一实验中受主硼在紫外光激发下失去电子,成为不带电荷的替位硼原子(B0),B0浓度升高超过红外光谱检测限,红外光谱识别到B0的存在,即引发2 803 cm-1吸收峰。处于激发态的电子返回基态与亚稳态的B0结合过程释放出光子产生磷光。该实验首次直接证实了硼受主与无电荷替位硼之间的电荷重组转移会引发钻石磷光。     

二甲基硅硼烷,o-(SiMe)_2B_(10)H_(10),振动光谱的理论研究

本文利用高斯 94从头计算程序在 6- 31 G基组下对二甲基硅硼烷 ,o- (Si Me) 2 B1 0 H1 0 ,进行几何优化及振动光谱的理论计算 ,并对主要谱带特性进行指认 ,结果与实验基本符合。振动模式分析表明 450 cm-1 以下的两个强带中 32 6cm-1 (计算值为 369cm-1 )似乎是两个 Si原子相对笼骨架中其余 B原子整体的伸缩振动 ,而 399cm-1 (计算值为 42 1 cm-1 )则为 Si- Si(及其联带的 C原子一起参与的 )对称伸缩振动。优化几何及振动光谱的研究表明重的杂原子硅占据二十面体硼笼骨架位置后使笼结构的刚性弱化     

测量大口径光学元件反射率用精密扫描系统误差分析

为测量高能激光传输系统中大口径高反射率光学元件的反射率,设计了一种大口径光学元件二维扫描的精密测量系统。介绍了该系统的结构及其工作原理,分析了影响系统测量精度的因素,从理论上分析了扫描系统的系统误差对测量精度的影响,结果表明在垂直于光束传播方向上,水平偏差在0.29 mm时,测量误差在10-6量级;腔长的变化量较小时,可通过对衰荡腔腔镜的调节,实现对旋转轴偏差的补偿及对系统的精细调节。通过拟合处理光强与时间的数据得到对应的一次指数函数拟合曲线,并通过计算得到衰荡时间和反射率,经过对比分析可知,该误差分析方法能比较有效地测量腔镜的反射率,并能减小实验数据本身带来的误差。     

掺Er~(3+)硼硅酸盐玻璃的吸收光谱与J-O理论分析

采用高温熔融法制备了不同Er3+掺量的硼硅酸盐玻璃。测量和分析了玻璃样品的光密度和吸收光谱,并用最小二乘法拟合了实验与理论吸收谱线。应用Judd-Ofelt理论计算了光谱参数Ωλ(λ=2,4,6)和Er3+的振子强度,计算了拟合过程中的均方根偏差(δ),并讨论了Er3+浓度对对光密度和Ωλ参数的影响。分析结果表明:当Er2O3含量为21mol%时,玻璃在达到了较高的光密度(D0.53=4.0)的同时,Ω2亦达到最大值。此时玻璃中Er3+所处环境的对称性降低而共价性增强。     

大型先进压水堆堆芯机械补偿控制模式

研究了AP1000堆芯物理计算程序的计算方法,分析了该程序尤其是机械补偿（MSHIM）控制模式计算功能的理论模型、计算方法及应用范围,对比了大型先进压水堆堆芯设计与AP1000的差异,评估了AP1000反应堆MSHIM计算功能在大型先进压水反应堆堆芯MSHIM计算功能的适用性。基于大型先进压水堆堆芯物理建模,针对大型先进压水反应堆首循环及平衡循环的典型燃耗点进行典型的100%-70%-100%和100%-50%-100%负荷跟踪运行模式计算分析,并依据计算结果对大型先进压水堆的MSHIM运行模式进行了分析。针对大型先进压水反应堆首循环及平衡循环,开展机械补偿控制初始启动运行、再启动运行计算分析,研究机械补偿控制模式的堆芯初始启动和再启动运行能力。计算结果表明:采用MSHIM运行模式的大型先进压水堆,不调节硼浓度的情况下,在首循环、平衡循环典型燃耗下具有一定的负荷跟踪能力;启动、再启动运行模式则需要配合调节硼浓度才能完成。     

盐水溶液中单硼酸盐物种(B(OH)3和B(OH)-4)的拉曼光谱定量分析

盐湖是天然存在的水和盐类共存的复杂体系,卤水中硼酸盐的赋存形态及分布规律较一般水溶液更为复杂,通常随盐类的浓缩富集而发生复杂的聚合、缔合等作用,存在严重的过饱和性,不利于盐湖硼及其他盐类的分离提取。因此,开展盐湖卤水体系中硼酸盐物种分布规律及离子间相互作用机制研究具有重要的实际意义。激光拉曼光谱因具有原位、无损、且水峰干扰小等特点,被广泛应用于硼酸盐溶液结构光谱学研究中,并表现出较大的优越性。近年来,以化学计量学为核心的现代拉曼光谱定量分析技术已成为快速准确获取复杂体系目标物量关系的有效手段,对光谱解析中面临的光谱重叠、背景干扰、基线漂移等问题具有强大的优势,在分析领域中得到了广泛而深刻的应用。基于化学计量学算法,采用拉曼光谱技术探究了三种回归模型(内标法、多元线性回归和偏最小二乘法)对盐水溶液中单硼物种B(OH)₃和B(OH)^-₄的定量分析,并通过外标样进行方法评估。研究表明,多元线性回归和偏最小二乘法对外标样的预测结果更为准确,相对误差均在1%以内,但前者对低硼含量的预测效果更佳。进一步地,根据建立的多元线性回归模型...     

Hybrid complex polymers of boron and imidazole hydroxide

The possibility of forming supramolecular structures of a polymer complex consisting of products of polycondensation of boric acid and imidazole from aqueous solutions and melts of the components is shown. Depending on the ratio of the components, the heat resistance of the polymer complex lies within 60 and 480°C. The effect of sharp decrease in the heat resistance of the complex and the degree of polycondensation of boric acid upon a slight increase in the imidazole concentration above the stoichiometric ratio is revealed, which was explained by the “blocking” of hydroxyl groups by imidazole molecules and, correspondingly, by a significant decrease in their chemical activity. The energies of the intermolecular bonds in the complexes are calculated.     

铁矿选矿产品中低微量钍的X射线荧光光谱分析

本文介绍用粉末内标压片Ｘ射线荧光光谱法测定铁矿选矿工艺流程产品中的低微量钍，方法简便、快速、准确、经济，较之化学分析法，有它独到之处，满足了选矿研究对于分析的快速、准确的要求。本法以钼为内标元素，硼酸为低吸收粘结剂，与粉末试样混合均匀后，用１５吨压片机压制成直径２５ｍｍ的圆片状的样品，即可进机测量。     

厌氧产甲烷受抑制过程的三维荧光光谱解析

应用三维荧光光谱表征了厌氧产甲烷反应受抑制前后的出水,采用平行因子分析方法分析,得到各主成分的激发发射光谱图以及相对浓度.分析结果显示,运行正常的产甲烷反应器出水以蛋白质、辅酶NADH和F420为主;产甲烷反应受到抑制后,甲烷生成速率迅速下降,同时辅酶F420荧光消失,反应器出水中以蛋白质和辅酶NADH为主.样品稀释后...     

Magnetic resonance imaging of chemical waves in porous media

Magnetic resonance imaging (MRI) provides a powerful tool for the investigation of chemical structures in optically opaque porous media, in which chemical concentration gradients can be visualized, and diffusion and flow properties are simultaneously determined. In this paper we give an overview of the MRI technique and review theory and experiments on the formation of chemical waves in a tubular packed bed reactor upon the addition of a nonlinear chemical reaction. MR images are presented of reaction-diffusion waves propagating in the three-dimensional (3D) network of channels in the reactor, and the 3D structure of stationary concentration patterns formed via the flow-distributed oscillation mechanism is demonstrated to reflect the local hydrodynamics in the packed bed. Possible future directions regarding the influence of heterogeneities on transport and reaction are discussed.     

Spectral signs of reaction between dihydric phenols and boric acid

We have studied the vibrational spectra and thermal curves (DTA, DTG, and TG) for the products of reaction between total shale phenols and boric acid, and also the polymer matrix of a gas-filled alkyl resorcinol polymer modified by mixtures of boric acid and aluminum oxide. Based on analysis of the IR absorption spectra, we show that the reason for the change in the physicochemical properties of the foam polymer is complex formation between the polymer and the additive. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 260–263, March–April, 2006.     

Reactor scale modeling of multi-walled carbon nanotube growth

As the mechanisms of carbon nanotube (CNT) growth becomes known, it becomes important to understand how to implement this knowledge into reactor scale models to optimize CNT growth. In past work, we have reported fundamental mechanisms and competing deposition regimes that dictate single wall carbon nanotube growth. In this study, we will further explore the growth of carbon nanotubes with multiple walls. A tube flow chemical vapor deposition reactor is simulated using the commercial software package COMSOL, and considered the growth of single- and multi-walled carbon nanotubes. It was found that the limiting reaction processes for multi-walled carbon nanotubes change at different temperatures than the single walled carbon nanotubes and it was shown that the reactions directly governing CNT growth are a limiting process over certain parameters. This work shows that the optimum conditions for CNT growth are dependent on temperature, chemical concentration, and the number of nanotube walls. Optimal reactor conditions have been identified as defined by (1) a critical inlet methane concentration that results in hydrogen abstraction limited versus hydrocarbon adsorption limited reaction kinetic regime, and (2) activation energy of reaction for a given reactor temperature and inlet methane concentration. Successful optimization of a CNT growth processes requires taking all of those variables into account.     

Synthesis and properties of boron doped ZnO nanorods on silicon substrate by low-temperature hydrothermal reaction

Boron doped ZnO nanorods were fabricated by hydrothermal technique on silicon substrate covered with a ZnO seed layer. It is found that the concentration of boric acid in the reaction solution plays a key role in varying the morphology and properties of the products. The growth rate along the [0 0 0 1] orientation (average size in diameter) of the doped ZnO nanorods decreased (increased) with the increase of boric acid concentration. Based on the results of XRD, EDX and XPS, it is demonstrated that the boron dopants tend to occupy the octahedral interstice sites. The photoluminescence of the ZnO nanorods related to boron doping are investigated.     

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit of the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.     

杜仲的核磁共振指纹图谱研究

核磁共振氢谱（Proton Nuclear Magnetic Resonance,¹H NMR）是中药指纹图谱中一种鉴定和控制植物中药质量的新方法．本文采用CPMG（Carr-Purcell-Meiboom-Gill）脉冲序列采集了杜仲提取物的¹H NMR谱,通过完整还原振幅频率表（Complete Reduction to Amplitude-Frequency Table,CRAFT）分析技术对杜仲指纹图谱进行特征指纹分析,将待目标合物的信号从混合物图谱中剥离出来,实现了不分离样品而分析目标化合物信息的目的,从而对杜仲的特征化合物——松脂醇二葡萄糖苷（Pinoresinol Glucoside,PDG）进行了定性和定量分析．结果显示贵阳药用植物园所得杜仲的PDG含量为0.275 6%,相对标准偏差（Relative Standard Deviation,RSD）为1.69%,与高效液相色谱（High Performance Liquid Chromatography,HPLC）定量分析结果（含量为0.269 6%,RSD为0.65%）基本一致．另外,通过NMR检测与多变量数据建模相结合分析了杜仲提取物的全指纹图谱,结果显示同一采收期不同产地的杜仲药材有显著差异,这表明该方法可用于鉴定不同产地的药材,具有一定的实用意义．