Identification of functional groups on the surface of modified organic materials using the FT-IR/PAS method

Interactions between NO and the surface of waste plum stones have been studied by FTIR-PAS in order to identify the nitrogen species formed. It is possible that there are some additional active centres generated on their surface. Identification of surface functional groups was needed to characterize their influence on the properties of obtained materials which were used as catalyst support in our further research.     

Thermal diffusion of potassium on the modified iron surface

The diffusion of potassium on the polycrystalline iron surface modified by adsorbed oxygen and nitrogen has been studied by means of AES. The migration of potassium atoms has been observed independently on the constitution of the iron surface in the temperature range between 300 and 450 °C. The final concentration of potassium on the iron surface increases with temperature from 300 to 400 °C, irrespective of what atoms accompany potassium on the surface. At 450 °C, the final level of potassium concentration is decreased. The profiles of the concentration on the surface along the line crossing the source of potassium were also acquired. Applying the diffusion model of finite source, the diffusion coefficient of potassium for oxygen-covered and nitrogen-covered surfaces were evaluated.     

Two component silicone modified epoxy foul release coatings: Effect of modulus, surface energy and surface restructuring on pseudobarnacle and macrofouling behavior

Two component silicone modified epoxy resin based low surface energy and non-toxic foul release coatings were developed. Silicone modified epoxy resin with 15 and 30% silicone content was used as component A and a polyether diamine (Jeffamine-500) was used as the component B. Free standing films were prepared by casting a mixture of components A and B in stoichiometric proportions. The surface composition, surface topography and wetting properties of the coatings were studied by angle resolved X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle goniometry respectively. The mechanical properties of the cured films were evaluated by tensile measurements as well as dynamic mechanical analysis. Pseudobarnacles made of aluminium studs were attached to the coated panels and adhesion tests were carried out by a pseudobarnacle tester. Coated panels were exposed in Mumbai harbor for fouling studies for a period of 90 days. Surface restructuring studies of the coatings upon immersion in seawater were carried out by measuring the changes in advancing and receding contact angles by contact angle goniometry. The effect of surface energy, modulus and surface restructuring of the coatings on the macrofouling and pseudobarnacle adhesion properties has been discussed in detail.     

光辐射吸收材料表面形貌与吸收率关系研究

光辐射吸收材料不同的表面形貌对入射光具有不同的多重反射吸收效果,对光辐射的吸收有较大的影响,合适的表面形貌可以提高光辐射有效吸收率.本文通过光线追迹的方法对V形表面、正弦表面、具有正态倾角(平均倾角)分布的表面以及具有正态高度分布的表面进行模拟, 分析了这四种表面对光辐射吸收率的提升效果及其入射角特性.通过倾角分布分析,得出不同表面形貌提升吸收率共同的必要条件,即倾角中心分布至少大于30°,并指出V形表面在正入射时对吸收率提升的优越性. 关键词： 光吸收材料 表面形貌 吸收率 表面倾角分布     

An effect of particle size on the behavior of ferromagnetic materials

The dependence of magnetic behavior of media upon the particle/grain size is studied here. A model is presented to describe the behavior of nanomagnetic materials as a function of particle size. The model is applied to two types of experiments: (1) the decay rate of the magnetic aftereffect in nanomagnets and (2) the variation of spontaneous magnetization versus temperature. Both of these experiments show a deviation from the behavior of bulk media above a critical temperature.     

理论研究过渡金属原子修饰石墨炔材料的功能性

采用基于密度泛函理论中第一性原理方法分别对石墨炔负载过渡金属原子(M-gra)体系的稳定构型以及对多种气体小分子的灵敏度和选择性进行理论研究.计算结果表明金属原子吸附在孔洞结构的H2位具有高稳定性,不同种类的金属原子能够有效调控石墨炔体系的电子特性和具有不同的磁矩.比较气体分子的吸附能大小,M-gra衬底对O和OH表现出高的灵敏度,单个NO、NO₂和O₂的稳定性高于CO分子.此外,小分子吸附的M-gra体系具有金属、半金属和半导体特性,在电子和气敏器件领域具有潜在应用.     

Spectral analysis on the surface molecular structure of modified polyvinylidene fluoride membrane

Taking advantage of Fourier transform infrared spectrum and X-ray photoelectron spectroscopy, the researcher has conducted a contrastive research on the surface molecular structure of porous PVDF membrane before and after modification. Research results indicate that, though the C-F characteristic peak of the PVDF membrane still exists after modification, the peak is obviously flat, which indicates that the content of F atom decreases evidently; the results also indicate that hydroxyl characteristic peak is sharper, which indicates the content of O atom increases evidently. This proves that chemical binding force has been produced by chemical reactions on the surface of PVDF membrane during the modification. The coexistence of C-F functional group with C-OH one on the surface of PVDF membrane after modification proves that the surface features of the PVDF membrane have been successfully altered. Combination of Fourier transform infrared spectrum with X-ray photoelectron spectroscopy is proved an effective approach for analyzing the surface structure of the membrane.     

On the behavior of suspension of drops on an inclined surface

The flow of drops suspended on an inclined surface, are studied by numerical simulations at finite Reynolds numbers. The flow is driven by the acceleration due to gravity, and there is no pressure gradient in the flow direction. The effect of the Reynolds number, the Capillary number and density ratio on the distribution of drops and the fluctuation energy across the channel are investigated. It is found that drops tend to stay away from the channel floor, which is consistent with the behavior observed in the granular flow regime. Drops that are less deformable will stay further away from the channel floor. Also, drops appear at a larger distance from the floor as the Reynolds number increases. Simulations at large density ratios show that results are more compatible with computer simulations of granular flows. The behavior observed here resembles more the granular flow regime when the restitution coefficient is low.     

水分子在氢化锂表面的吸附行为

运用理论分析方法计算研究了水分子在氢化锂表面的吸附行为,分析了氢化锂表面改性对其疏水性能的影响。结果表明,在LiH-111面和LiH-100面上构建槽结构、柱状结构后,水分子在其上的吸附力比完整表面更强,说明表面微结构的引入的确改变了势能分布。壁相交处存在势能叠加,加强了吸附水分子的能力,但是没有引起表面的亲水性能变化。水分子可以稳定的吸附在完美的LiH（001）表面,其解离能垒仅为0.386 eV,这一解离反应在室温下完全可以进行。水分子极易在具有结构缺陷的LiH表面解离,这是LiH在一定湿度的空气和水环境中极易分解的根本原因。     

The dynamical behavior of periodic surface profiles on metals under the influence of anisotropic surface energy

The kinetics of shaping of periodic surface profiles under the action of surface selfdiffusion were calculated for the special case of anisotropic surface energy. The orientation-dependent surface energy was allowed to contain a local minimum of very high curvature (cusp). The orientation of this cusp was equal to the macroscopic orientation of the crystal surface. The periodic surface profiles exhibited in all cases extended, nearly flat regions centered at the cusp orientation. This type of faceting which causes the profile to be trapezoidal in shape agrees well with experimentally observed profiles on (111) and (100) Ni single crystal surfaces. A procedure is outlined by which the orientation-dependent surface energy along a certain azimuth and the surface self-diffusion coefficient can be extracted from the decay kinetics of faceted periodic surface profiles. This procedure demands the accurate experimental assessment of profile shapes and amplitudes.     

Spectroscopic investigation of thermooxidative destruction of ethers on the surface of modified silica

Thermooxidative processes are investigated by the method of temperature-programmed decomposition with the use of a prism infrared spectrometer. Thermal degradation of —OC₄H₉, —OP(H)(O)OC₄H₉ and —OP(H)(O)OC₂H₅ groups on the surface of modified pyrogenic silicas in air is considered. The resemblance between processes of oxidation of surface PH-groups irrespective of the means of silica modification is shown. Institute of Surface Chemistry, National Academy of Sciences of Ukraine, 31, Nauka Ave., Kiev, 252022, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 326–332, May–June, 1998.     

Effect of plasticizer and surface topography on the cleanability of plasticized PVC materials

A quantitative radiochemical measuring procedure was used to investigate soil adhesion on laboratory-made polyvinyl chloride (PVC) surfaces. The materials contained different plasticizers and microstructures. Both the quality and amount of plasticizers and the microstructure affected the cleanability of the PVC samples. The surface topography and structures were examined with a contact angle meter, atomic force microscopy (AFM) and a contact profilometer.     

基于Jiles-Atherton理论的铁磁材料塑性变形磁化模型修正

Jiles-Atherton(J-A)模型在磁化建模领域应用广泛,但不同文献给出的J-A模型并不一致,致使采用不同表达式建立的塑性变形磁化模型存在多种版本,其正确性难以甄别.通过对无磁滞磁化方程、能量守恒方程和等效磁场强度方程的梳理与比较,发现原有模型中存在将磁化强度和无磁滞磁化强度混用、将不可逆磁化能量等效于全部的磁化能量、等效磁场强度中应力磁化项界定不清等问题.在此基础上,对上述方程进行了修正,推导了基于J-A模型的塑性变形磁化修正模型.将修正模型计算结果与原模型计算结果、相关文献中的试验结果进行对比,结果表明:与原有计算模型相比,修正模型计算结果的饱和磁化强度和剩余磁化强度随塑性变形增加而减小,矫顽力随塑性变形增大而增大,达到饱和磁化强度时的外磁场强度随塑性变形增大而增大的趋势有所减弱,更符合试验结果,可更准确地反映塑性变形对材料磁化的影响.     

亚表面异质缺陷对功能梯度材料表面温度场的影响

基于双曲型热传导方程,采用镜像法和波函数展开法,求解了含亚表面异质圆柱缺陷的半无限功能梯度材料的表面温度场,给出了功能梯度材料中热波散射的一般解.分析了亚表面异质圆柱缺陷的几何参数(如埋藏深度)和热物理参数(如导热系数、热扩散长度、热扩散率及热弛豫时间等)对功能梯度材料表面温度场的影响.温度波由调制的超短脉冲激光在功能梯度材料表面激发,异质圆柱缺陷表面的边界条件为导热边界.研究结果可望为功能梯度材料的红外热波无损检测、导热反问题提供计算方法和参考数据.     

单轴各向异性左手介质表面的Goos-H?nchen位移

分析了单轴各向异性左手介质表面的Goos-H?nchen位移，分别给出了光轴与两种介质的界面垂直和平行情形下的Goos-H?nchen位移解析表达式，并分析了Goos-H?nchen位移产生的条件以及位移的正负情况.还采用菲涅尔近似的方法给出了临界角附近的Goos-H?nchen位移表达式，结果表明临界角附近的Goos-H?nchen位移是入射光的束腰半径和入射角的函数，并且给出了临界角入射时Goos-H?nchen位移的较为简洁的近似表达式，这样就在整个角度的取值范围内都给出了Goos-H?nchen位移的表达式. 关键词： Goos-H?nchen位移 左手介质 单轴各向异性 临界角     

Effect of surface modified hydroxyapatite on the tensile property improvement of HA/PLA composite

In this study, we modified the surface of hydroxyapatite (HA) particle by ring-opening polymerization of lactide (LA). The modified HA particles were characterized by IR and TGA. It was shown that LA could be graft-polymerized onto the surface of HA. A series of composites based on modified HA/PLA were further prepared and characterized. It indicated that the modified HA particles were well dispersed in PLA matrix than unmodified HA particles and the adhesion between HA particle and PLA matrix was improved. The modified HA/PLA composites showed good mechanical properties than that of unmodified HA/PLA.     

纳米Ag颗粒表面等离子激元对上转换材料光致发光性能影响的研究

本文采用共烧结工艺将纳米Ag颗粒引入Yb³⁺, Er³⁺共掺的NaYF₄上转换材料中, 利用X射线衍射及扫描电子显微镜技术对制备的NaYF₄材料进行结构特性和表面形貌的表征, 通过吸收谱及荧光光谱测试技术对NaYF₄材料光吸收及光发射特性进行表征. 通过对纳米Ag颗粒引入量的优化, 获得了Yb³⁺, Er³⁺共掺的NaYF₄上转换材料荧光发射峰的增强, 300—800 nm全光谱范围内增益达28%, 在544 nm处获得最大增益55%, 具有显著的荧光增强效果. 同时分析了不同数量纳米Ag颗粒的引入对NaYF₄材料吸收谱及光致发光特性影响, 指出了表面等离子激元的光猝灭及共振吸收增强作用机理.     

Influence of particle surface properties on the dielectric behavior of silica/epoxy nanocomposites

Silica/epoxy composites have been widely used in functional electric device applications. Silica nanoparticles, both unmodified and modified with the coupling agent KH-550, were used to prepare epoxy composites. Dielectric measurements showed that nanocomposites exhibit a higher dielectric constant than the control sample, and had more obvious dielectric relaxation characteristics. Results showed that particle surface properties have a profound effect on the dielectric behavior of the nanocomposites. These characteristics are attributed to the local ununiformity of the microstructure caused by the large interface area and the interaction between the filler and the matrix. This phenomenon is explained in terms of prolonging chemical chains created during the curing process. The mechanism is discussed with measurements of X-ray diffraction (XRD) and Fourier transform infrared (FTIR).     

Effects of surface and interface energies on the bending behavior of nanoscale multilayered beams

A modified continuum model of the nanoscale multilayered beams is established by incorporating surface and interface energies. Through the principle of minimum potential energy, the governing equations and boundary conditions are obtained. The closed-form solutions are presented and the overall Young's modulus of the beam is studied. The surface and interface energies are found to have a major influence on the bending behavior and the overall Young's modulus of the beam. The effect of surface and interface energies on the overall Young's modulus depends on the boundary condition of the beam, the values of the surface/interface elasticity constants and the initial surface/interface energy of the system. The results can be used to guide the determinations of the surface/interface elasticity properties and the initial surface/interface energies of the nanoscale multilayered materials through nanoscale beam bending experiments.     

Influence of residual surface stress on the fracture of nanoscale piezoelectric materials with conducting cracks

In this paper,we analyze the stress and electric field intensity factors affected by residual surface stress for conducting cracks in piezoelectric nanomaterials.The problem is reduced to a system of non-linear singular integral equations,whose solution is determined by iteration technique.Numerical results indicate that the residual surface stress can significantly alter the crack tip fields at nanometer length scales.Due to the residual surface stress,281he electric field can produce stress around crack tip.This suggests a strong electromechanical coupling crack tip field for nanoscale piezoelectric materials.Such a finding is considerably different from the classical fracture mechanics results.A transit electric field to stress load ratio is identified,for which influences of residual surface stresses vanish.The research is useful for the applications of nanoscale piezoelectric devices.