How to tailor the porous structure of alumina and aluminosilicate gels and glasses

1996 ◽  
Vol 11 (2) ◽  
pp. 518-528 ◽  
Author(s):  
V. Vendange ◽  
Ph. Colomban
Keyword(s):  
Porous Structure ◽  
Pore Structure ◽  
Pore Size ◽  
Boron Oxide ◽  
Pore Diameter ◽  
Average Pore Diameter ◽  
Mesoporous Aluminosilicates ◽  
Average Pore ◽  
Impregnation Process ◽  
Size And Structure

Optically clear monolithic (OCM) gels of mesoporous aluminosilicates (average pore diameter 3.6 nm) and alumina (6 nm) have been prepared by slow hydrolysis-polycondensation of alkoxides and converted into OCM mesoporous glasses by heating. In order to change the properties, different ways of modifying the pore size and structure are proposed. We show that addition of boron oxide reduces the average pore diameter. A higher effect can be obtained by addition of a surfactant. In this case the mesoporous matrix becomes microporous (d < 2 nm). Another way of modifying the pore structure consists of introducing nanoprecipitates inside the porosity by an impregnation process. Modifications of the porous structure are different in alumina and aluminosilicates.

scholarly journals Relationship between the Shear Strength and Microscopic Pore Parameters of Saline Soil with Different Freeze-Thaw Cycles and Salinities

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1709
Author(s):  
Jiaqi Wang ◽  
Qing Wang ◽  
Sen Lin ◽  
Yan Han ◽  
Shukai Cheng ◽  
...  
Keyword(s):  
Shear Strength ◽  
Pore Structure ◽  
Pore Diameter ◽  
Saline Soil ◽  
Soil Samples ◽  
Average Pore Diameter ◽  
Failure Strength ◽  
Average Pore ◽  
Freeze Thaw ◽  
The Relationship

Saline soil is a widely distributed special soil with poor engineering properties. In seasonally frozen regions, the poor properties of saline soil will cause many types of engineering damage such as road boiling, melt sinking, and subgrade instability. These engineering failures are closely related to the shear strength of saline soil. However, there are relatively few studies on saline soil in cold regions. The strength of the soil is always determined by its microstructure; therefore, the study aims to investigate the relationship between the shear strength and microscopic pore structure of saline soil with different freeze–thaw cycles and salinities. The shear strength characteristics of saline soil with different salinities subjected to different freeze–thaw cycles were obtained by triaxial tests. In addition, the microstructure of the soil samples was investigated by scanning electron microscopy (SEM) tests, and the microscopic pore parameters of the soil samples, including porosity (N), average pore diameter (D¯), average shape coefficient (K), surface fluctuation fractal dimension (F), and orienting probability entropy (Hm), were obtained by image processing software quantitatively. Based on the experimental results, the influence of freeze–thaw cycles and salinity on the shear strength characteristics and microstructure of the soil samples were analyzed. Besides that, in order to effectively eliminate the collinearity between independent variables and obtain a stable and reasonable regression model, principal component regression (PCR) analysis was adopted to establish the relationship between the microscopic pore parameters and the failure strength of the soil samples. The fitting results demonstrated that the failure strength of saline soil is mainly related to the size and direction of the pores in the soil, and it has little correlation with pore shape. The failure strength of the soil was negatively correlated with the average pore diameter (D¯) and porosity (N), and it was positively correlated with the orienting probability entropy of the pores (Hm). This study may provide a quantitative basis for explaining the variation mechanism of the mechanical properties of saline soil from a microscopic perspective and provide references for the symmetry between the changes of the macroscopic properties and microscopic pore structure of the saline soil in cold regions.

Research on the Relationship between Permeability and Pore Size Characteristics of Microporous Nonwoven Geotextile

2013 ◽  
Vol 753-755 ◽  
pp. 792-797 ◽  
Author(s):  
Bing Xuan Ni ◽  
Peng Zhang
Keyword(s):  
Pore Size ◽  
Pore Diameter ◽  
Average Pore Diameter ◽  
Flow Index ◽  
Hydraulic Permeability ◽  
Measuring Instrument ◽  
Average Pore ◽  
Vertical Permeability ◽  
Nonwoven Geotextile ◽  
The Relationship

The hydraulic permeability performance of geosynthetics is an important functional technical index in the field of engineering application. In this paper, the pore size characteristics of a series different specifications of spunbond and needlepunched nonwoven geotextile has tested through capillary flow aperture measuring instrument, including average pore diameter, maximum pore size and pore size distribution. The permeability characteristics of nonwoven geotextile has measured by vertical permeability measuring instrument, including flow index and vertical permeability coefficient. We study on the compressive properties of nonwoven geotextile under the different pressure, through the relationship between the average pore diameter and flow index to fit curve, and built the regression equation, so we can calculate and predict the water permeability performance through pore size Characteristics.

Effect of Low Content of Metakaolin Addition on the Properties and Pore Structure of Concrete

2016 ◽  
Vol 680 ◽  
pp. 411-419
Author(s):  
Hai Ning Geng ◽  
Qiu Li ◽  
Zhi Guang Shi ◽  
Zhong He Shui
Keyword(s):  
Compressive Strength ◽  
Pore Structure ◽  
Pore Diameter ◽  
Analytical Techniques ◽  
Average Pore Diameter ◽  
Average Pore

The properties and microstructure of concrete containing 0-6wt% metakaolin (MK) were studied by analytical techniques. The compressive strength increased with the content of MK and reached the maximum by 5wt% MK addition, where the compressive strength increased by 33% at 28 days comparing to the control. The pore structure was refined in the concrete containing MK due to the increase of amount of pores smaller than 10 nm. There is a relationship between average pore diameter and compressive strength.

scholarly journals Структура и механические свойства пористой диатомитовой керамики после деформации сжатием

2021 ◽  
Vol 47 (4) ◽  
pp. 11
Author(s):  
А.А. Скворцов ◽  
М.Н. Лукьянов ◽  
И.Е. Чебенева ◽  
А.А. Скворцова
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Porous Structure ◽  
Dynamic Modulus ◽  
Morphological Analysis ◽  
Pore Diameter ◽  
Porous Ceramics ◽  
Average Pore Diameter ◽  
Dynamic Elastic Modulus ◽  
Average Pore

This work is devoted to the study of the mechanical properties of porous ceramics based on diatomite. Based on the morphological analysis of the studied samples, the porous structure of ceramics (morphology and average pore diameter) was analyzed and the numerical value of the porosity of the samples (35...50%) was determined. The values of the static (70...115 GPa) and dynamic elastic modulus of the samples (37...50 GPa) were measured experimentally. The dependence of the dynamic modulus of porous diatomite ceramics on porosity is studied: the elastic modulus decreases with increasing porosity of the material. A decrease in the porosity of the material after deformation was also found. The formation of diatomite filaments after deformation of samples by compression at a rate of no more than 8 * 10-4 s-1 was detected.

scholarly journals Fractal Dimension of Basalt Fiber Reinforced Concrete (BFRC) and Its Correlations to Pore Structure, Strength and Shrinkage

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3238
Author(s):  
Yue Li ◽  
Aiqin Shen ◽  
Hua Wu
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Pore Size ◽  
Pore Diameter ◽  
Size Range ◽  
Basalt Fiber ◽  
Shrinkage Strain ◽  
Fiber Reinforced Concrete ◽  
Average Pore ◽  
Fractal Characteristics

In this study, we focused on exploring the correlations between the pore surface fractal dimensions and the pore structure parameters, strength and shrinkage properties of basalt fiber-reinforced concrete (BFRC). The pore structure of BFRCs with various fiber contents and fiber lengths was investigated using mercury intrusion porosimetry (MIP) measurements. Through Zhang’s model, the fractal characteristics of BFRCs in the whole pore size range and in different pore size ranges were calculated from the MIP test data. The results showed that the addition of BF increased the total porosity, total pore volume and pore area but decreased the average pore diameter, indicating that BFs refined the pore structure of the concrete. BFRC presented obvious fractal characteristics in the entire pore-size range and individual pore-size ranges; generally, the fractal dimension increased with increasing fiber content. Moreover, correlation analysis suggested that the fractal dimension of BFRC in the whole pore-size range (FD) was closely related to the fractal dimension in the macropore region (Dm) and average pore diameter (APD). The influence of pore structure factors on mechanical strength and shrinkage was studied by grey correlation theory, and the results showed that Dm showed positive correlations with strength and fracture energy, with increasing Dm tending to strengthen and toughen the concrete. An increase in fiber content and length was detrimental to reducing the drying shrinkage strain. In the transition pore region, the fractal dimension (Dt) at diameters ranging from 20 to 50 nm and shrinkage strain exhibited a highly linear relation. These results merit careful consideration in macro-property evaluation by using the pore surface fractal dimension in a specific region instead of the whole region. Finally, grey target theory was applied to evaluate the rank of the mechanical strength and shrinkage of concrete, and the results showed that the overall properties of concrete with a BF length of 18 mm and a BF content of 0.06% ranked the best.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

Pore Structure and Mechanical Properties of ZrC/SiC Multi-Components Modified C/C Composites

2013 ◽  
Vol 833 ◽  
pp. 159-164 ◽  
Author(s):  
Xiu Qian Li ◽  
Hai Peng Qiu ◽  
Jian Jiao
Keyword(s):  
Mechanical Properties ◽  
Pore Diameter ◽  
Testing Machine ◽  
Average Pore Diameter ◽  
Flexural Properties ◽  
Matrix Interface ◽  
Polymeric Precursor ◽  
Average Pore ◽  
Fiber Matrix Interface ◽  
Injection Apparatus

The ZrC/SiC multi-components modified C/C composites were prepared by using a hybrid precursor containning polycarbosilane and organic zirconium-contained polymeric precursor as impregnant and C/C composites of low density as preform. The porosity, microstructure and mechanical properties of samples were characterized with mercury injection apparatus, scanning electron microscopy and universal electron testing machine respectively. The results show that the porosity and average pore diameter decrease firstly and increase subsequently with the increase of organic zirconium content of the precursor. When the content of organic zirconium is 50%, the porosity and average pore diameter reach minimum which were7.27% and 0.0795um respectively. The most probabilistic pore diameter shifted from 10-100um to 1-10um at the same time; Meanwhile, the flexural properties also increases and drops immediately as the content of organic zirconium in the precursor adds. When the content of organic zirconium is 25%, the flexural strength reaches maximum of 245.20MPa.The improved flexural properties is attributed to the proper bonding of fiber-matrix interface and the low porosity of samples.

Investigate on Pore Structure Characteristics of Reactive Powder Concrete after High Temperatures

2012 ◽  
Vol 174-177 ◽  
pp. 1010-1014 ◽  
Author(s):  
Hong Bin Liu ◽  
Yang Ju ◽  
Kai Pei Tian ◽  
Jin Hui Liu ◽  
Li Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Pore Size ◽  
Pore Volume ◽  
Average Pore Size ◽  
Reactive Powder Concrete ◽  
Characteristic Parameters ◽  
Average Pore ◽  
Structure Characteristics ◽  
Temperature Levels ◽  
Reactive Powder

The pore structure characteristics of reactive powder concrete (RPC) were investigated by means of the mercury injection method at seven temperature levels, namely, 20°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, respectively. The characteristic parameters such as porosity, pore volume, average pore size and threshold aperture varied with temperatures were analyzed. The results indicate that the porosity, pore volume, threshold aperture and other characteristic parameters of RPC increased with the temperature increasing.

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