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.     

膨胀石墨制备及微孔结构相关性研究

分别用化学法和电化学法制备膨胀石墨，用压汞法测量膨胀石墨的微孔结构参数，研究制备与微孔结构的相关性。结果表明，插层的充分程度、氧化方式和水洗充分程度均会对膨胀石墨的孔结构产生明显影响。     

几种石墨板孔性能与燃烧性能关系的讨论

对三种石墨板进行了压汞法孔径分布测试,并在同步热分析仪上获得上述三种样品的TG-DSC曲线,结果表明石墨板孔结构与热行为之间存在一定的关系,即平均孔径和中值孔径小的样品对应的燃烧温度高。     

多孔钨孔结构的测试方法

采用3种不同粒度的钨粉经过成型、烧结,制备了不同孔隙率的多孔钨。使用排液法、压汞法、扫描电镜测试了多孔钨的孔结构特征。结果表明:排液法和压汞法结合可获得多孔钨总孔隙率、开孔率、孔径分布、闭孔率等孔结构参数,结合扫描电镜测试可对多孔钨的孔结构进行综合评价。     

漂珠低密度水泥石的孔体积分形维数及其与孔结构和力学性能的关系

运用压汞法测试漂珠低密度水泥石孔结构参数、Menger海绵模型计算其孔体积分形维数,分析评价了漂珠低密度水泥石的孔结构分形特征,探讨了孔体积分形维数与孔隙率、孔比表面积、中值孔径及力学性能的关系。研究表明,低密度水泥石孔结构具有明显的分形特性,孔体积分形维数在3.25~3.69;孔体积分形维数越大,其孔隙度、孔比表面积、中值孔径越大,而抗压强度、抗拉强度越小。孔体积分形维数不仅在描述孔隙空间结构时更加具体,同时在一定程度上反映了材料宏观性能的相对优劣。     

压汞法测定水泥基材料孔结构的研究进展

简要论述了压汞法测定孔结构技术,并给出了水泥基材料压汞法应用的假设和修正,检验了这些假设和修正对于孔隙测定数据的影响。利用给出的孔结构数值关系,预测水泥基材料的强度、抗渗性和耐久性。压汞法应用的假设和修正对于孔数据有明显的影响,从而影响总的孔隙率值、孔径尺寸和孔径的曲线形式。由于假设和修正的不同,导致材料强度、抗渗性和耐久性的不同。因此,研究者在给出的孔隙数据中,应详细论述其假设和修正的内容。     

锂离子电池石墨负极微结构数值重建及特征化分析

实际锂离子电池石墨负极由鳞片状石墨层叠而成, 具有明显的各向异性。本文基于椭球颗粒的模拟退火法对其进行三维微结构数值重建。重建微结构乃三相(孔或电解液、石墨和固体添加物)复合结构, 很好地再现了实际电极各向异性特征。对重构电极进行特征化分析, 得到了电极内固/孔相的连通率、比表面积以及孔径分布等信息; 发现石墨颗粒尺寸对电极特性有重要的影响: 椭球形石墨颗粒尺寸越大, 则重建微结构的平均孔径越大, 比表面积越小; 相对于赤道半径, 椭球颗粒的极半径对重建电极特性的影响更为明显。     

腐蚀添加剂对Cu-Mn合金制备孔径可控纳米多孔铜的影响

以铜锰单相固溶体为前躯体合金,利用去合金化法,在盐酸腐蚀液中添加适量不同的络合剂、金属盐可制备出成分纯净、孔形貌可控的三维连通纳米多孔铜(NPC)。采用X射线衍射仪(XRD)、扫描电镜能谱(SEM-EDS)、图像分析软件(Image-Pro Plus)对样品的物相、组分、微观形貌和平均孔径尺寸进行表征。结果表明：腐蚀添加剂的种类和浓度对孔结构形成过程和孔形貌具有重要影响。与未添加络合剂相比,添加硫脲、柠檬酸等络合剂后,腐蚀后的样品的孔径和韧带尺寸都发生不同程度的细化,络合常数越大,铜原子表面扩散系数越小,细化效果越明显;添加硫脲后能显著细化多孔结构,NPC平均韧带尺寸可在18～90 nm之间调控,且其浓度越高,孔径、韧带尺寸越小;添加适量金属盐Fe₂(SO₄)₃、CuSO₄、ZnSO₄后腐蚀液中出现副反应,反应速率大幅度提高,孔结构发生粗化,出现韧带尺寸分布呈纳米级和微米级共存的多孔结构,当CuSO₄添加浓度超过20 mmol/L时,多孔样品断裂截面失去初...     

膨胀石墨孔结构的影响因素

本文简述了膨胀石墨孔结构的特点，研究了电化学法，化学法制造膨胀石墨时工艺参数对膨胀石墨孔结构的影响规律，并讨论了将膨胀石墨蠕虫粉碎后孔结构的变化情况。     

超临界CO_2发泡法制备聚己内酯组织工程支架

利用超临界二氧化碳(SC-CO_2)辅助的无有机溶剂发泡方法,制备了可用于组织工程的聚己内酯(PCL)多孔支架。研究了PCL分子量、发泡压力、温度以及保压时间等参数对支架性能的影响。结果表明,PCL分子量越大,泡孔孔径越小且孔径分布变窄。高压力下容易形成泡孔密度大的微孔支架;聚合物处于高粘弹性时,随着温度升高泡孔尺寸增大,而进一步升高温度时,泡孔会出现塌缩现象。降低泄压速率,泡孔间出现合并成大孔的现象。SC-CO_2发泡法可以实现132～700μm范围内孔径可控的PCL多孔支架材料的制备。通过力学试验,发现这些支架的弹性模量在10 MPa以上,符合组织工程支架的应用要求。     

对GASARITE脱合金制备微-纳复合多孔金属的研究

Gasar工艺是一种制备规则排列微米多孔金属的定向凝固工艺,脱合金工艺是一种通过选择性溶解固溶体合金而制备无序纳米多孔金属的工艺方法,将Gasar和脱合金工艺相结合可以制备一种有序-无序结合、微米-纳米复合的特殊结构多孔金属.选择Cu-Mn二元合金为研究对象,研究了Gasar工艺参数及合金成分对定向凝固多孔Cu-Mn合金结构的影响.脱合金工艺在Gasar工艺制备的定向凝固多孔Cu-Mn合金基础上进行,分析了腐蚀温度等脱合金工艺参数对纳米多孔结构的影响.在优化的Gasar和脱合金工艺参数下,制备得到了一种特殊结构的微-纳复合多孔金属.     

Effect of polyurethane composition and the fabrication process on scaffold properties

The microdomain structure of polyurethanes (PUR) determines their unique physical properties and makes polyurethanes attractive candidates for various tissue engineering applications. 3D scaffolds based on polyurethanes with different contents of hard segments were fabricated by a salt-leaching/polymer coagulation method. The process parameters were carefully considered, particularly the polymer solution concentration and characteristics of the polyurethane, which are the critical parameters for the control of porosity and pore size distribution. In this study, 3D polyurethane scaffolds were fabricated with interconnected pores and porosity from 64% to 80%. Pore size distribution was evaluated using quantitative image analysis and mercury intrusion porosimetry (MIP). The scaffolds fabricated from polyurethanes with 70 wt.% of hard-domain content were found to have the best compression properties.     

Pore space analysis of cement-based materials by combined Nitrogen sorption – Wood’s metal impregnation and multi-cycle mercury intrusion

The analysis of pore space is crucial for a profound understanding of transport and mechanical properties of porous materials. Cement-based materials have a broad pore size distribution ranging from micro- to macro-pores. The analysis of this kind of pore space therefore becomes difficult. Because the resolution of image based methods is limited, indirect analysis methods like Nitrogen sorption or mercury intrusion porosimetry (MIP) are often applied. The standard MIP results in an underestimation of large pores because of its intrinsic limitation due to ink-bottle type pores (i.e., pores that are connected to the surface by smaller neck entrances only). The adsorption of Nitrogen seems to be less influenced by such connectivity effects, but the analysis of pores larger than about 100 nm is not possible.To overcome these limitations, in this study pores were selectively filled with Wood’s metal. The liquid metal (at elevated temperature) is intruded into the samples by applying different pressure regimes and then re-solidified in place. The partial impregnation with this metal allowed the analysis of non-ink-bottle type pore space in a subsequent Nitrogen sorption experiment and its comparison with an empty pore system. Furthermore, Mercury intrusion experiments with an additional pressurization–depressurization cycles (multi-cycle-MIP) were performed. The pore size distributions and pore volumes as calculated from Nitrogen sorption data are then compared with MIP and multi-cycle MIP data.     

Computer diagnostics of the mesoscopic structure of nanoporous aluminas

A method based on the computer analysis of electron microscopic images of the surface of porous anodic aluminas is described for deriving quantitative information about the mutual arrangement of cells and pores (mesoscopic structure). The developed package of programs is used to calculate dimensional parameters of a cellular-porous structure, the size distribution of the image objects, and the morphological functions of the radial distribution of cells/pores, which are analogs of the function of the radial distribution of atoms characterizing the short- and medium-range orders of atoms in amorphous materials. A quantitative analysis is performed for the first time using the method of pair functions, which was used earlier for identification of the atomic structure in amorphous films. The developed package of Spot Calculator and MFRD programs for processing electron microscopic images of the surface can be used to study the mesoscopic structure of not only porous aluminas but also any materials if characteristic features can be distinguished on their surface.     

Characterizing pore structure of cement blend pastes using water vapor sorption analysis

Pore structure is an essential factor that influences the mechanical behavior and durability of cement-based porous materials with or without added binders. An empirical model for water vapor sorption isotherms was employed to evaluate the pore structure of hardened cement pastes incorporating granulated blast furnace slag and silica fume. The model is an extension of the Brunauer–Emmett–Teller multilayer adsorption theory. Assuming cylindrical-shaped pores and an adsorbed liquid-like layer between the pore surface and gas phase, pore size distributions of the blended cement pastes were estimated. Calculated pore size distribution curves were compared with those measured by mercury intrusion porosimetry. Added granulated blast furnace slag and silica fume had minor effects on the monolayer adsorption capacity, but reduced the energy of the first and subsequent adsorption layers. The adsorbed liquid-like layer generated sharper pore size distribution peaks that were shifted to the mesoporous region. The pore size distributions were comparable with those determined by the mercury extrusion branch, but differed from those obtained by the mercury intrusion branch. Hysteresis of the water vapor adsorption–desorption isotherms and mercury intrusion–extrusion curves was due to the entrapment of a non-wetting phase in the porous system, further promoted by residual mercury in the pores following mercury extrusion.     

Characterizations of the pore-crack network architecture of thermal-sprayed coatings

This study aims at developing three techniques permitting to complementary characterize the architecture of the pore-crack network architecture of thermal-sprayed coatings:

(i) image analysis quantifies the coating porous morphology, that is to say the overall porosity level and the crack network orientation;

(ii) electrochemical analysis qualitatively characterizes the ratio of connected pores;

(iii) Archimedean porosimetry quantifies the non-connected porosity level.

These techniques were applied to characterize the pore structure of yttria-partially stabilized zirconia (Y-PSZ) thermal barrier coatings (TBCs) manufactured implementing air plasma spraying and hybrid plasma spraying, which combines plasma spraying and laser remelting. Thermal and mechanical properties of Y-PSZ TBCs are especially dependant from their pore network architecture.     

DETERMINATION OF THE PORE STRUCTURE OF POROUS MATERIALS USING ELECTRICAL CONDUCTANCE

A new method for determining the pore structure of porous materials has been developed. The methodology combines the plastic ice model for solid-liquid phase transitions of pore water with relationships between conductance and temperature, and conductance and pore structure. With these relationships and measurements of the electrical conductance and the corresponding temperature of a saturated porous material subjected to a cycle of capillary freezing and melting, a pore size distribution is obtainable.

Baaed on this methodology a conductometric phase transition poroai-meter was constructed. The pore size distribution of porous Vycor glass was measured using this porosimeter. The modal neck and body radii measured by thia method are 28 and 55 angstroms respectively. These results are comparable to those obtained using other techniques. The modal neck and body radii measured on the same sample by mercury porosimetry are 30 and 85 angstroms and by phase transition porosimetry, 27 and 49 angstroms, respectively.     

Changes in pore structure and mercury contact angle of hardened cement paste depending on relative humidity

Hardened cement paste (hcp) is a porous heterogeneous material consisting of dispersed particles like Calcium Silicate Hydrates (C-S-H). These are of micron to nanometer size forming pores on a nanometer scale. Thus, hcp can be regarded as a colloidal system. Surface forces play a dominant role. Adsorbed water molecules interact with the surface. Capillary condensation occurs in the pores below bulk conditions acting in form of capillary and disjoning forces. All these forces are able to alter the structure and properties of the hardened cement paste depending on the moisture content. Pore size distributions were measured with mercury intrusion porosimetry on hcp specimens, which had been prestored over the entire range of relative humidity. Swelling and shrinkage of hcp tubes were also determined. The pore size distribution is corrected for each humidity step regarding the particular porosity, contact angle and volume change. The pore size distribution as a function of relative humidity is nonlinear and characterized by an extreme value in the medium range of humidity.     

3D polylactide-based scaffolds for studying human hepatocarcinoma processes in vitro

We evaluated the combination of leaching techniques and melt blending of polymers and particles for the preparation of highly interconnected three-dimensional polymeric porous scaffolds for in vitro studies of human hepatocarcinoma processes. More specifically, sodium chloride and poly(ethylene glycol) (PEG) were used as water-soluble porogens to form porous and solvent-free poly(L,D-lactide) (PLA)-based scaffolds. Several characterization techniques, including porosimetry, image analysis and thermogravimetry, were combined to improve the reliability of measurements and mapping of the size, distribution and microarchitecture of pores. We also investigated the effect of processing, in PLA-based blends, on the simultaneous bulk/surface modifications and pore architectures in the scaffolds, and assessed the effects on human hepatocarcinoma viability and cell adhesion. The influence of PEG molecular weight on the scaffold morphology and cell viability and adhesion were also investigated. Morphological studies indicated that it was possible to obtain scaffolds with well-interconnected pores of assorted sizes. The analysis confirmed that SK-Hep1 cells adhered well to the polymeric support and emitted surface protrusions necessary to grow and differentiate three-dimensional systems. PEGs with higher molecular weight showed the best results in terms of cell adhesion and viability.