介孔碳材料对蛋白质的吸附行为

用紫外分光光度法,找出介孔碳材料对蛋白质的最佳吸附条件,并测定出该介孔碳材料对溶菌酶的最大吸附量。主要从3方面研究介孔碳材料对蛋白质吸附行为的影响。分别是介孔碳材料对蛋白质吸附行为随接触时间的变化产生的影响,pH值的改变对介孔碳材料吸附蛋白质行为的影响,以及介孔碳材料的量的改变对蛋白质吸附行为随接触时间的变化产生的影响。结果表明,当溶菌酶溶液的初始浓度为210μm ol/L,pH值为11.0,接触时间为96h时介孔碳材料对蛋白质即可达到吸附饱和。该介孔碳材料在最佳条件下对溶菌酶的最大吸附量为27.32μm ol/g,表现出优越的溶菌酶吸附性能。     

典型炭材料微观结构及SO2吸附机理研究

采用SEM和低温氮吸附方法研究了碳纳米管和活性炭的表面微观形貌及孔隙结构,通过固定床研究了炭材料SO₂吸附机理。研究结果表明:活性炭大孔直接暴露于表面,中孔和微孔分布于大孔内部,"聚合"是碳纳米管的重要特征;椰壳活性炭是微孔型吸附剂,煤基活性炭孔隙主要由微孔和大孔组成,碳纳米管氮吸附有明显的毛细凝聚现象,中孔和大孔是其孔隙主要组成;活性炭SO₂吸附过程受物理吸附控制,碳纳米管SO₂吸附不同于活性炭,同时受到物理吸附和化学吸附控制;孔径小于0.7 mm的微孔是炭材料SO₂吸附的主要场所。     

Y掺杂空位石墨烯对NO及CO气体表面吸附的第一性原理研究

摘　要：基于第一性原理的计算方法，建立了本征石墨烯、空位石墨烯及钇( Y)掺杂空位石墨烯模型，并计算了CO、NO在三类石墨烯表面的吸附过程. 从表面能、吸附结构、吸附能和态密度四个方面进行分析讨论，研究掺杂Y对CO、NO气体吸附性能的影响. 结果表明：CO、NO与本征石墨烯之间的吸附为弱的物理吸附，掺杂Y后增强了材料表面对CO、NO的吸附效果，最大吸附能分别为7.414eV、6.702eV，属于化学吸附；掺杂Y使空位石墨烯费米能级附近有了更多的活跃电子，其吸附NO后体系由半金属转变为金属特性，该特性能为开发更加优良的石墨烯气敏材料提供理论支持.     

甲烷在多孔硅表面物理吸附特征研究(英文)

在密度泛函理论耦合超软贋势第一性原理的平台上,研究了甲烷在Si(111)表面的物理吸附特性.通过建立硅晶胞的不同吸附位置(top、bridge、fcc)模型,对比分析了甲烷在相应位置吸附界面变化的键结构、吸附能和态密度,获得了相应吸附点的吸附特征.对比分析的结果表明,甲烷只有在fcc位置物理吸附状态较为理想.分析态密度、键长及键角等数据揭示fcc位甲烷吸附对体系硅晶胞有很大的影响,其体系的键能最低,即此时体系结构最稳定.本文所得研究成果可用于Si表面对甲烷气体的敏感性分析及气体传感器领域.     

氢气分子在沸石中的吸附模拟研究

采用巨正则蒙特卡罗方法模拟了氢气在沸石中的吸附行为,并采用Dubinin-Astakhov微孔分析方法,分析了沸石结构对储氢量大小的影响,总结了影响储氢量大小的物理因素,该工作有利于指导合理的设计与合成储存材料,为改善材料储氢能力提供了有力的理论支撑. 关键词： 储氢 吸附等温线 巨正则蒙特卡罗     

单个钛原子储氢能力和储氢机制的第一性原理研究

采用基于密度泛函理论的第一性原理方法研究了单个过渡金属钛原子吸附氢分子的物理机制. 研究表明,单个钛原子最多能吸附8对氢分子,吸附结构为对称的两个类金字塔型结构, 其平均吸附能为- 0.28 eV.通过计算轨道能级和差分电荷密度分布,分析决定吸附结构、 吸附能大小以及吸附氢分子数目的内在物理机制.研究表明,钛原子的4s电子转移到3d轨道上, 从而产生较强的极化电场,导致氢分子极化,钛原子通过静电极化作用吸附氢分子. 本文的研究将对设计高密度储氢材料有一定的指导作用.     

Ni_2P/介孔分子筛催化剂的原位漫反射红外光谱研究

以介孔分子筛MCM-41,MCM-48,SBA-15,SBA-16为载体,硝酸镍为镍源,磷酸氢二铵为磷源,通过浸渍法制备了含有磷化镍前体的介孔分子筛样品,然后在氢气气氛中进行程序升温还原,得到了磷化镍/介孔分子筛催化剂.采用原位漫反射红外光谱法,用CO作为探针分子,对样品的吸附特征进行了研究.结果表明,在介孔分子筛表面CO存在着较弱的物理吸附.在Ni2P/MCM-41催化剂样品表面有四种CO的吸附态:(1)在2055cm-1处形成的Ni(CO)4物种的吸附,(2)在2 091cm-1处的配位不饱和Niδ(0<δ<1)物种上的吸附,(3)在2 127 cm-1处的Ni+物种上的吸附,(4)在2 198～2 202 cm-1范围内的P物种上的吸附.在Ni2P/MCM-48,Ni2P/SBA-15,Ni2P/SBAZ-16催化剂样品表面有二种CO的吸附态:在2 051～2 055cm-1处的Ni(CO)4吸附和在2 093～2 096 cm-1处的配位不饱和Niδ+(0<δ<1)物种上的吸附.     

MCM-41水分吸附特性的调控研究

本文以介孔分子筛MCM-41为研究对象,通过合成与后改性法,调控其孔径、表面性质以及平衡阳离子种类。通过X射线衍射、液氮吸附对介孔材料结构进行结构分析,采用动态水分吸附仪研究其水分吸附特性,并结合吸附等温线热力学模型进行分析。研究结果表明:铝嫁接有效提高MCM-41在低湿度下吸附量,并且随着嫁接浓度的增大而增加;通过阳离子置换强化了低湿度环境下MCM-41的吸附量,不同阳离子置换后的强化效果:Mg~(2+)+Li~+Na~+。热力学模型分析表明阳离子置换后的吸附剂表面均一,且具有较好的亲水性。     

介孔二氧化硅双重孔隙的导热特性研究

介孔二氧化硅颗粒的双重孔隙分布特征对材料的导热性能具有显著影响。本文通过微观形态表征分析了介孔二氧化硅的复合孔道，并基于受限空间内的气体分子动力学理论，构建了双重孔隙结构的热导率关联模型。为了验证理论模型的合理性与准确性，采用瞬态热带法测量了介孔二氧化硅材料(MCM-41和SBA-15)在0～30 MPa和20～550℃的环境压力及温度变化下的有效热导率。实验测量结果表明，本文理论模型可以有效预测介孔二氧化硅颗粒热导率的变化规律。进一步根据模型分析可知，材料热导率随着环境温度及压力的升高而增长，表现出明显的正相关性，同时其微观结构的差异也是热导率变化的决定性因素。     

低密度开孔Kelvin泡沫大变形数值模拟

正十四面体单元胞结构含有8个正六边形和6个正四边形面，由36根等长度支柱构成。十四面体单元胞结构按体心立方堆积，即构成Kelvin模型，这是一种接近于泡沫真实结构的周期性结构模型。分别基于胞壁材料的线弹性和超弹性材料本构，采用ABAQUS有限元软件模拟了低密度开孔Kelvin泡沫的大变形行为，用以考察单轴拉压载荷作用下泡沫材料的变形机理以及基体材料力学特性对泡沫宏观力学行为的影响。数值计算采用二阶空间Timoshenko梁单元模拟开孔泡沫支柱，建立了满足周期性边界条件的有限元模型。     

Pore Structure Analysis of Porous Particles by Modelless and Micropore Method

The modelless (ML) and micropore (MP) methods for the pore structure analysis of porous particles have been studied. Concerning the ML method, it has been shown that the Kiselev equation can only be used to describe condensation and evaporation in capillaries, but cannot be used to describe the increase and decrease of the thickness of the adsorption layer. Strictly speaking, therefore, the ML method is not modelless even for the pore core size distribution. A comparison between the ML method and methods using an equivalent pore model is given. The results of using the ML method in conjunction with a certain pore model are little less accurate than those obtained by adopting the equivalent pore model straightaway. The parameters required for the calculation of both the pore core size and the pore size distribution as well as the conversion between these two calculations are given. Concerning the MP method, it has been shown that the three types of v-t curves, the theoretical foundation of the MP method, are not in one to one correspondance to the three kinds of adsorption mechanism. From the viewpoint of accuracy, the MP method has no advantage over the methods which are based on the condensation mechanism, both have their own merits.     

Pore size distribution calculation from H NMR signal and N2 adsorption–desorption techniques

The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N₂ adsorption–desorption and ¹H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121–134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs–Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.     

气孔分布特性对含水多孔介质气体扩散的影响

本文基于多孔介质的气孔分布特性,计算了多孔介质在含水状态下的扩散性能,并且比较了采用两种方式计算相对渗透率时的相对扩散性能。其结果表明,基于气孔分布的计算结果低于与气孔分布无关的计算结果。另外,疏水性含水多孔介质的扩散性能低于亲水性含水多孔介质的扩散性能,基于气孔分布计算含水多孔介质的气体扩散性能时,Wyllie公式并不适用。     

中国数字人体男性数学模型建立及外辐射模拟

基于中国数字人男一号高分辨人体结构数据集，通过最小包围盒方法获取中国数字人体男性体素模型各器官空间位置和尺寸信息，建立了中国数字人体男性数学模型，并通过变形实现了不同身高模型的构建。采用蒙特卡罗方法进行了不同能量下光子中子的外部辐射模拟。通过结果对比发现，数学模型与体素模型模拟结果趋势一致，但器官位置和质量对剂量影响较大，低能级下尤为明显。对于不同身高模型，小型个体剂量大于大型个体，深层器官剂量较浅层器官对器官尺寸更为敏感。数学模型定义简单，存储空间小，有利于人体辐射剂量的快速计算。     

Effect of drying technique on the physicochemical properties of sodium silicate-based mesoporous precipitated silica

The conventional drying (oven drying) method used for the preparation of precipitated mesoporous silica with low surface area (>300 m²/g) and small pore volume is often associated with a high production cost and a time consuming process. Therefore, the main goal of this study was to develop a cost-effective and fast drying process for the production of precipitated mesoporous silica using inexpensive industrial grade sodium silicate and spray drying of the precipitated wet-gel silica slurry. The precipitated wet-gel silica slurry was prepared from an aqueous sodium silicate solution through the drop-wise addition of sulfuric acid. Mesoporous precipitated silica powder was prepared by drying the wet-gel slurry with different drying techniques. The effects of the oven drying (OD), microwave drying (MD), and spray drying (SD) techniques on the physical (oil, water absorption, and tapping density), and textural properties (specific BET surface area, pore volume, pore size, and % porosity) of the precipitated mesoporous silica powder were studied. The dried precipitated mesoporous silica powders were characterized with field-emission scanning electron microscopy; Brunauer, Emmett and Teller and BJH nitrogen gas adsorption/desorption methods; Fourier-transform infrared spectroscopy; thermogravimetric and differential analysis; N₂ physisorption isotherm; pore size distribution and particle size analysis. There was a significant effect of drying technique on the textural properties, such as specific surface area, pore size distribution and cumulative pore volume of the mesoporous silica powder. Additionally, the effect of the microwave-drying period on the physicochemical properties of the precipitated mesoporous silica powder was investigated and discussed.     

Optimization of STEM-HAADF Electron Tomography Reconstructions by Parameter Selection in Compressed Sensing Total Variation Minimization-Based Algorithms

A novel procedure to optimize the 3D morphological characterization of nanomaterials by means of high angle annular dark field scanning-transmission electron tomography is reported and is successfully applied to the analysis of a metal- and halogen-free ordered mesoporous carbon material. The new method is based on a selection of the two parameters (μ and β) which are key in the reconstruction of tomographic series by means of total variation minimization (TVM). The parameter-selected TVM reconstructions obtained using this approach clearly reveal the porous structure of the carbon-based material as consisting of a network of parallel, straight channels of ≈6 nm diameter ordered in a honeycomb-type arrangement. Such an unusual structure cannot be retrieved from a TVM 3D reconstruction using default reconstruction values. Moreover, segmentation and further quantification of the optimized 3D tomographic reconstruction provide values for different textural parameters, such as pore size distribution and specific pore volume that match very closely with those determined by macroscopic physisorption techniques. The approach developed can be extended to other reconstruction models in which the final result is influenced by parameter choice.     

气体吸附法测定二氧化硅干凝胶的分形维数

提出了一种方便、科学有效的利用气体吸附法测定二氧化硅干凝胶等多孔材料分形维数（表面分形维数和孔分布分形维数）的方法，不需要进行一系列的吸附/脱附实验，只需要利用单一气体的一次吸附/脱附实验得出的样品孔分布、比表面数据，与不同的标尺进行关联，即可同时获得表面分形维数和孔分布分形维数.通过误差分析和校正，保证了结果的可靠性.用上述方法测定了二氧化硅干凝胶的分形维数，以FHH法和SAXS法对所得结果进行了比较和验证，并对吸附/脱附过程所得结果的差异进行了初步分析. 关键词： 分形维数 气体吸附 二氧化硅 干凝胶     

基于ADI-FDTD模拟的岩石核磁共振横向弛豫特征分析

将复杂的骨架-孔隙系统抽象成等效双孔介质,根据Bloch方程构建数学模型,用交替隐式时域有限差分(ADI-FDTD)和联合反演迭代法(SIRT)进行横向宏观磁化矢量的数值模拟与核磁共振T₂谱的反演,定量研究扩散系数、弛豫速率、孔隙组分比和孔隙宽度对核磁响应的影响.结果表明:横向宏观磁化矢量衰减速率与扩散系数和微孔隙分量成正比,与孔隙宽度成反比,与表面弛豫速率基本无关.当扩散系数较大、孔隙宽度较小时,核磁共振T₂谱难以直观反映孔隙组分及孔隙结构.应用核磁共振评价孔隙结构时需特别注意扩散系数和孔隙尺寸的影响.     

Behavior models of gas-filled pores in amorphous and crystalline bodies

A mathematical model of the behavior of an isolated gas-filled pore in amorphous and crystalline bodies is presented. The balance of surface tension forces, the external pressure, and gas pressure in the pore, which affect the pore, is laid at the basis of the variation in the pore size and gas pressure in it. A qualitative analysis of distinctions in the behavior of the pore in amorphous and crystalline bodies is performed, and a set of differential equations that describe the pore behavior in both cases is analyzed. The proposed model of behavior of the gas-filled pore in an infinite space can serve as the basis for the analysis of more complex cases.