Pore Size Distribution Of Materials Research Articles

Statistical method of pore size distribution of disordered mesoporous materials based on electron microscope imaging

Mesoporous materials can efficiently treat harmful substances in wastewater by virtue of the pore structure with a high specific surface area. Currently, the characterization of the pore structure of mesoporous materials is generally obtained by physical experiments. However, due to the limitation of experimental conditions, repeated measurement experiments will waste a lot of time and may damage the pore structure. In addition, for disordered mesoporous materials with a large pore size span and irregular pore positions, it is difficult to accurately analyze the pore size distribution law with the human eye observation through electron microscope images. Aiming at this problem, this paper proposes a method to rapidly calculate the pore size distribution of materials based on SEM imaging. Firstly, the image is preprocessed. Secondly, the pore distribution information is obtained by the filling ball method, and finally the probability density curve of the pore size distribution is obtained according to the statistical method. The results show that the pore size probability density curve obtained by this method is very similar to the actual pore size distribution curve and the error is less than 11%. The proposed method provides a new direction for the analysis of disordered mesoporous materials.

Measurement of pore size distribution of building materials by thermal method

The present work focuses on the study of the thermophysical properties of low porous insulation materials. In peculiar, we investigate the pore structure of composite materials and cements by thermal method. This method, adapted for fragile materials, is based on an existing model which allows the determination of pore size distribution. Firstly, the existing analytical model is presented. The thermal conductivity is modeled by assimilating the studied medium to N fluid phases and one solid phase in series / parallel. Secondly, some extensions to this model are proposed. In particular, we show that in the case of a single pore size, it is possible to obtain a finer pore size distribution by means of a normal law. We also show for the first time that the normalization of the thermal conductivity is an interesting way to study the pore size distribution of a material without knowing the overall porosity rate (which strongly depends on the method used). Furthermore, this model and its extensions have been successfully applied to different kinds of materials (plant fiber composites and cements). Fibers reinforced composites have one class of pores around 30 – 60 μm. Chemical treatments do not affect this pore size. Cements show a macroporosity (around 20 μm) which is often underestimated.

"Water-in-salt" electrolyte enhanced high voltage aqueous supercapacitor with carbon electrodes derived from biomass waste-ground grain hulls.

To design high specific surface area and optimize the pore size distribution of materials, we employ a combination of carbonization and KOH activation to prepare activated carbon derived from ground grain hulls. The resulting carbon material at lower temperature (800, BSAC-A-800) exhibits a porous structure with a high specific surface area of 1037.6 m2 g−1 and a pore volume of 0.57 m3 g−1. Due to the synergistic structural characteristics, BSAC-A-800 reveals preferable capacitive performance, showing a specific capacitance as high as 313.3 F g−1 at 0.5 A g−1, good rate performance (above 73%), and particularly stable cycling performance (99.1% capacitance retention after 10 000 cycles at a current density of 10 A g−1). More importantly, the assembled symmetric supercapacitor using a water-in-salt electrolyte (17 m NaClO4) with high discharge specific capacitance (59 F g−1 at 0.5 A g−1), high energy density (47.2 W h kg−1) and high voltage (2.4 V) represents significant progress towards performance comparable to that of commercial salt-in-water electrolyte supercapacitors (with discharge specific capacitance of 50 F g−1, energy densities of ∼28.1 W h kg−1 and voltages of 2.0 V).

Pitch-based porous aerogel composed of carbon onion nanospheres for electric double layer capacitors

The morphology, pore structure and chemical composition of materials are key to supercapacitor performances. To design reasonable morphology and optimize pore size distribution of materials, we employ a combination of sol-gel method and chemical activation with an aid of freeze drying to prepare a three dimensional hierarchical porous pitch-based aerogel (3DHPPA). The aerogel owns hierarchical porous structure ranging from 0 to 100 nm, high specific surface area of 2220 m2 g−1 and is made up of carbon onion-like nanospheres of 20–40 nm with enough electric conductivity (103.2 S m−1). In view of the unique architecture, the supercapacitor assembled from 3DHPPA with the area density of 8.9 mg cm−2 exhibits high specific capacitance of 157 F g−1 at 50 mA g−1, excellent rate performance (95 F g−1 at 10 A g−1), considerable energy density of 24.2 Wh kg−1 at 6.75 kW kg−1 (voltage range of 2.7 V) and outstanding cycling life with 81.5% capacitance retention at 2 A g−1 after 8000 cycles in 1 M TEABF4/PC electrolyte. Furthermore, the formation mechanism of the 3DHPCA is elucidated in this work. The simple, feasible and low-cost strategy makes 3DHPPA applicable in other fields of energy storage, hydrogen storage, capacitive deionization and catalysis.

On the elastic deformation properties of porous ceramic materials obtained by pore-forming agent method

The influence of the pore size distribution on the elastic modulus has been studied using an intermingled fractal model (IFU) capable to reproduce entirely pore size distribution of materials. The results obtained from IFU modelling are in good agreement with experimental ones. The model could be considered as a microstructure simulator to improve mechanical properties of porous ceramic materials.

Numerical Algorithm for Pore Size Distribution Characterization of Materials from 3D Images

This paper presents an image based numerical method proposed to obtain information regarding pore structure and organization of pores within materials based on 3D digital image input. The output of the numerical algorithm is a pore size distribution of materials. The algorithm is based on the combination of the two digital image processing algorithms: 1) a medial axis thinning algorithm to obtain 3D skeleton of the pore structure, and 2) the distance transform of an image. The method is tested on simple 2D and 3D microstructures of packed spheres, demonstrating the performance of the proposed method.

Hybrid Zeolitic Imidazolate Frameworks: Controlling Framework Porosity and Functionality by Mixed-Linker Synthesis

Zeolitic imidazolate frameworks (ZIFs) are a subclass of nanoporous metal–organic frameworks (MOFs) that exhibit zeolite-like structural topologies and have interesting molecular recognition properties, such as molecular sieving and gate-opening effects associated with their pore apertures. The synthesis and characterization of hybrid ZIFs with mixed linkers in the framework are described in this work, producing materials with properties distinctly different from the parent frameworks (ZIF-8, ZIF-90, and ZIF-7). NMR spectroscopy is used to assess the relative amounts of the different linkers included in the frameworks, whereas nitrogen physisorption shows the evolution of the effective pore size distribution in materials resulting from the framework hybridization. X-ray diffraction shows these hybrid materials to be crystalline. In the case of ZIF-8-90 hybrids, the cubic space group of the parent frameworks is continuously maintained, whereas in the case of the ZIF-7-8 hybrids there is a transition from a...

Effect of activated carbon xerogel pore size on the capacitance performance of ionic liquid electrolytes

The use of ionic liquid (IL) electrolytes promises to improve the energy density of electrochemical capacitors (ECs) by allowing for operation at higher voltages. Several studies have also shown that the pore size distribution of materials used to produce electrodes is an important factor in determining EC performance. In this research the capacitative, energy and power performance of ILs 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyT(F5Et)PF3) were studied and compared with the commercially utilised organic electrolyte 1 M tetraethylammonium tetrafluoroborate solution in anhydrous propylene carbonate (Et4NBF4–PC 1 M). To assess the effect of pore size on IL performance, controlled porosity carbons were produced from phenolic resins activated in CO2. The carbon samples were characterised by nitrogen adsorption–desorption at 77 K and the relevant electrochemical behaviour was characterised by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The best capacitance performance was obtained for the activated carbon xerogel with average pore diameter 3.5 nm, whereas the optimum rate performance was obtained for the activated carbon xerogel with average pore diameter 6 nm. When combined in an EC with IL electrolyte EMImBF4 a specific capacitance of 210 F g−1 was obtained for activated carbon sample with average pore diameter 3.5 nm at an operating voltage of 3 V. The activated carbon sample with average pore diameter 6 nm allowed for maximum capacitance retention of approximately 70% at 64 mA cm−2.

A study on compression-induced morphological changes of nonwoven fibrous materials

Pore size is a characteristic parameter that is often defined for fibrous materials used in industrial applications. While there exist many available studies on the pore size distribution of different fibrous materials, the influence of compression load on pore size distribution has not been studied well. Studying the behavior of fibrous materials under compression is important especially because in many applications these materials are subjected to some degree of compression during use. In this work, we present a novel image-based modeling technique to study the changes in the pore size distribution of a fibrous material exposed to compressive load. This was made possible by building a miniature compression cell, and imaging the structure of a hydroentangled fabric under varying levels of compression. The 3D images obtained with Digital Volumetric Imaging were utilized to study the pore size distribution of the material and develop an empirical correlation as a function of compressive stress for these structures. This new correlation indicates that the mean pore diameter of a nonwoven material decreases exponentially with increasing the compressive stress.

NMR cryoporometry with octamethylcyclotetrasiloxane as a probe liquid. Accessing large pores

Octamethylcyclotetrasiloxane is presented and investigated as probe liquid for NMR cryoporometry or DSC-based thermoporometry. This compound which may imbibe into both hydrophilic and hydrophobic pores is shown to exhibit a melting point depression that is larger than that for other cryoporometric probe materials such as cyclohexane. The transverse relaxation time differs by more than three orders of magnitude between the solid and liquid states, separated by a sharp phase transition. Hence, as demonstrated in controlled pore glasses, octamethylcyclotetrasiloxane can provide pore size distributions for materials with pore sizes up to the micrometer range.

Influence of raw materials morphology on properties of magnesia-spinel refractories

The work concerns magnesia-spinel refractories (MSp) used in cement industry. These materials replace magnesia chromite refractories due to environment protection. The paper summarizes results of investigation on influence of raw materials on final properties of magnesia-spinel products. In experiments sintered or fused magnesia, and fused spinel were used. Clinkers differ in chemical composition and morphology. Grain composition of mixtures was calculated on the basis of modified Andreasen curve according to Dinger and Funk's model. Essential influence of clinker morphology on final properties of refractories was established. Porosity and pore size distribution in materials determine their strength and gas permeability. Relations between these parameters allow controlling the final properties of products in a wide range.

Characterization of Worm-Like Micro- and Mesoporous Silicas by Small-Angle Scattering and High-Resolution Adsorption Porosimetry

Mesoporous silica with worm-like pores of 9–10 nm in size were studied by small-angle neutron scattering (SANS) and high-resolution porosimetry, using nitrogen at 77 K and argon at 87 K. The pore sizes determined from SANS are in excellent agreement with those obtained from a recently developed non-local density functional theory (NLDFT) approach. Furthermore, the additional micropores in the mesopore walls could be quantified by SANS and physisorption, and again good agreement between both methods was observed. Our results clearly demonstrate that the NLDFT approach allows an accurate determination of the pore size distribution of materials which contain both narrow micropores and mesopores larger than 10 nm.