多孔高吸水性树脂孔结构的体视学表征

探索了一种对多孔高吸水性树脂的孔结构进行定量表征的研究方法。在用扫描电镜(SEM)对发泡法制备的多孔高吸水性树脂的孔结构进行表征的基础上,将SEM照片转换为灰度图像,利用体视学中的禁线法则和德莱塞定律,通过关联测格覆盖得到了多孔高吸水性树脂的孔面积、孔周长、孔隙率等结构参数。在此基础上,利用分形几何的研究方法,得到了多孔高吸水性树脂的分形维数与形状因子等参数。通过所建立的表征方法,讨论了不同致孔剂加入量对多孔高吸水性树脂结构的影响。     

介孔材料分形表征的研究进展

分形是材料表征中一种新兴的方法。本文介绍了介孔材料的基本特性和表征方法;阐述了分形理论的发展、分形维数的计算测定与分形在介孔材料表征中的应用,分析了介孔材料的分形模型,指出分形在介孔材料表征中的发展前景。     

多孔材料的孔结构表征及其分析

多孔材料的研究已成为当今材料科学研究领域的一大热点,而多孔材料的研究离不开结构表征分析.多孔材料的表征常用X射线小角度衍射法、气体吸附法、电子显微镜观察法等.重点介绍了这些表征方法对多孔材料的孔道有序性、孔形态、比表面积和孔体积及孔径等的表征分析应用,最后简单介绍了孔结构表征的新方法.     

多孔颗粒材料内孔表面分维测算及与保水性能的关系

为考察多孔颗粒材料内孔表面分形特征及与其保水性能的关系,构建了多孔颗粒物内孔表面分维测算数学模型,并基于高精度扫描电子显微镜系统测算了4种多孔颗粒样品的内孔表面分维,测量了材料保水性能。结果表明:多孔颗粒的内孔表面的分维值介于2.088 2~2.193 5之间,且分形拟合曲线相关系数大于0.98,强的相关性说明内孔表面具有显著的分形特征。进一步研究发现,多孔颗粒材料保水性能与其内孔表面分维呈负相关。     

介孔分子筛的孔结构表征及其分析

介孔分子筛的研究已成为当今材料科学研究领域的一大热点，而介孔材料的研究离不开结构表征分析。介孔材料的表征常用X射线小角度衍射法（XRD）、气体吸附法、电子显微镜观察法等。重点介绍了这些表征方法对多孔材料的孔道有序性、孔形态、比表面积和孔体积及孔径等的表征分析应用，最后简单介绍了孔结构表征的新方法。     

NaCl-Na_2CO_3熔盐介质中制备的镁橄榄石多孔材料的气孔分形特征

以NaCl-Na_2CO_3为熔盐介质制备了镁橄榄石多孔材料,采用压汞法研究了材料内部气孔的结构特征,利用SEM表征了材料的显微结构;采用综合热分析仪分析孔的形成机理,并在Menger海绵体构造模型的基础上,用分形理论对材料的孔径参数进行表征;研究了烧成温度与原料中盐配比对气孔分形维数的影响,探讨了气孔的分形维数与孔径分布的关系。结果表明,制备的镁橄榄石多孔材料内部气孔以6.6和66μm为界点,具有三重分形特征,其原因是材料内部气孔的成孔机理不同。原料配比中NaCl和Na_2CO_3的含量都为20%,经1 100℃烧后材料内部气孔的体积分形维数最小,为2.16895;此时材料内部孔径集中分布于6.6~66μm。     

孔径分布对多孔镍孔体积分形维数的影响

用压汞法对用粉末冶金法制备的多孔镍试件进行了测试,得到了多孔镍试件的孔隙率及孔径分布曲线,并以Menger海绵体模型为基础,根据压汞实验数据确定了多孔镍试件的孔体积分形维数,发现多孔镍的孔隙结构具有明显的分形特征,分形维数在2.8～3.0之间.孔径分布范围越宽、平均孔径越大,孔体积分形维数越大.多孔镍的孔体积分形维数在一定程度上反映了多孔镍孔隙结构的均匀性及填充能力.     

纳米羟基磷灰石/聚酰胺多孔支架材料的制备及性能研究

使用多种致孔剂采用粒子沥滤法制备了纳米羟基磷灰石／聚酰胺多孔支架材料，用IR、XRD、SEM等手段对多孔复合材料的组成结构及形貌进行了表征，并检测了其物理性能指标。结果表明，复合材料中两相分散均匀，且发生了界面结合；材料的孔隙率与致孔剂的含量成正比，支架中大孔与微孔并存且相互贯通；以NaCl作致孔剂且孔隙率达到80％左右时的支架材料可以同时满足组织工程对孔隙率和力学强度的双重要求。     

FeAl金属间化合物多孔材料的制备

以Fe、Al粉末为原料,用反应合成工艺制备FeAl金屑间化合物多孔材料,表征了孔结构.结果表明,在FeAl金属间化合物多孔材料的制备过程中烧结坯发生明显的体积膨胀;在1000℃以下,随着烧结温度的升高FeAl烧结坯的孔隙度和最大孔径增大;经1000℃烧结后FeAl多孔材料的孔隙度为35.3%,最大孔径为2.0 μm;造孔机理是Kirkendall效应造孔、反应造孔以及粉末颗粒间隙孔的演变.     

聚甲基硅氧烷纳米多孔薄膜的微孔结构分析

用旋涂工艺和致孔法制备了一组聚甲基硅氧烷纳米多孔薄膜,用红外吸收光谱(FT-IR)、热重分析(TGA)对其进行表征,用同步辐射光源进行小角X射线散射测试,在掠入射模式(GISAXS)下进行微孔结构分析。结果表明,聚甲基硅氧烷前驱体与致孔剂具有良好的相容性;薄膜的小角散射曲线均不遵守Porod定理、形成正偏离;所有纳米多孔薄膜具备孔分形特征;薄膜基体与孔结构之间存在微电子密度起伏,且薄膜孔径小于3 nm。     

等离子涂层孔隙研究进展

总结了等离子涂层孔隙形成原因,孔隙率的测试,孔隙率对涂层弹性模量、热导率、残余应力的影响;介绍了喷涂工艺参数对孔隙率影响及涂层形成过程的数值模拟.目前主要以涂层的孔隙率作为研究重点,但孔隙率仅代表了涂层的密实程度,应进一步研究等离子涂层中孔隙的形状、大小及其对涂层性能的影响以及影响涂层孔隙结构的主要工艺参数.     

分维在超细粉末团聚状态表征中的应用

用激光和Ｘ射线小角散射实验研究超细粉末团聚体的结构，发现分形形态是粉末团聚体的普遍特征。提出了团聚体结构的分维表征，分析了分维与团聚状态及粉末工艺性能间的关系。     

多相材料断裂的分形特征

测量了多相材料复合涂层的断裂挠度和断口表面的分形维数，分析了复合涂层的断裂特征。结果表明：随着硬质相增加，复合涂层的断裂挠度和断口表面的分形维数降低。     

A Fractal Study on Brittle-Ductile Transition forTi-24Al-11Nb Alloy

The mechanical behaviours of Ti-24Al-11Nb alloy in the brittle-ductile transition (BOT) have been investigated by using three-point bending tests. The temperature dependence of the fractal dimensions and fractal characterization of fracture surfaces are presented. The probable mechanism controlling BDT of intermetallic alloys are proposed according to fractal geometry.Additionally. it is found that there is a positive relationship between the fractal dimension and fracture toughness in BDT for Ti-24Al-11Nb alloy     

基于分形的表面形貌特征描述与评定参数的研究

运用Ｗｅｉｅｒｓｔｒａｓ－Ｍａｎｄｅｌｂｒｏｔ函数对表面形貌进行描述，并利用结构函数求出表面形貌的分形维数和形貌系数。研究了分形参数与表面支承长度率曲线的关系。理论分析和实验结果表明：支承长度率曲线主要与分形维数有关，而形貌系数对该曲线的影响较小。用分形理论研究表面形貌时，分形维数是主要的评定参数，它能提供表面接触承载能力的单值定量的评估，从而比支承长度率曲线更简洁而实用。     

Optico-acoustic characterization of the fractal structure of radiation from a laser with unstable resonator

The thermooptical excitation of sound in a liquid by fluctuating laser radiation with sine-modulated intensity is studied theoretically. The intensity is randomly distributed over the beam cross section. It is assumed that the random processes are homogeneous and that the spatial spectrum of intensity fluctuations obeys a power fractal law. Possibilities for the optico-acoustic characterization of the fractal radiation structure of a laser with unstable resonator are discussed.     

A possible method for retrieval of particle size distribution from its phase function in a fractal tissue model

In problems relating to light propagation in soft biomedical tissues, the tissue is generally modeled as a turbid medium. In one of the often used models, the suspended scatterers have been assumed to be of spherical shape following a fractal size distribution law. This paper studies the relationship between scattering phase function features of tissue and the fractal dimension within the framework of a fractal tissue model. It is demonstrated that witin the framework of this model the measurement of scattering phase function at two or three near-forward angles can be employed to infer fractal dimension of the model tissue. This method for tissue characterization therefore could be a potentially useful method for early detection of cancer of soft tissues.     

Statistical Analysis of Reinforcement Characterization in SiC Particle Reinforced Al Matrix Composites

The characterization of reinforcement in 15% SiC particles reinforced Al matrix composites processed by powder metallurgy route was studied by statistical method. During the analysis, a new approach for the estimation of the characterization of reinforcement was presented. The mathematic software MATLAB was used to calculate the area and perimeter of reinforcement, in which the image processing technique was applied. Based on the calculation, the fractal dimension, shape factor, reinforcement size distribut...     

Experimental investigation of the contact mechanics of rough fractal surfaces

The nonstationary character of roughness is a widely recognized property of surface morphology and suggests modeling several solid surfaces by fractal geometry. In the field of contact mechanics, this demands novel investigations attempting to clarify the role of multiscale roughness during physical contact. Here we review the results we recently obtained in the characterization of the contact mechanics of fractal surfaces by depth-sensing indentation. One class of experiments was conducted on organic thin films, load-displacement curves being acquired by atomic force microscopy using custom-designed tips. Another class of experiments focused on well-defined crystalline and mechanically polished ceramic substrates probed by a traditional nanoindenter. We observed the first-loading cycle to be considerably affected by surface roughness. Plastic failure was found to dominate incipient contact while contact stiffness increased on decreasing fractal dimension and roughness. Our findings suggest fractal parameters to drive contact mechanics whenever the penetration depth is kept below the interface width.