Capillary Flow Porosimetry Research Articles

Lignin Particles for Multifunctional Membranes, Antioxidative Microfiltration, Patterning, and 3D Structuring.

We introduce a new type of particle-based membrane based on the combination of lignin particles (LPs) and cellulose nanofibrils (CNF), the latter of which are introduced in small volume fractions to act as networking and adhesive agents. The synergies that are inherent to lignin and cellulose in plants are re-engineered to render materials with low surface energy (contact angle measurements) and can be rendered water-resistant with the aid of wet-strength agents (WSAs). Importantly, they are most suitable for antioxidative separation (ABTS•+ radical inhibition): membranes with uniform porous structures (air permeability and capillary flow porosimetry) allow effluent oxidation at 95 mL/cm2, demonstrating, for the first time, the use of unmodified lignin particles in flexible membranes for active microfiltration. Moreover, the membranes are found to be nonfouling (protein adhesion and activity rate). The inherent properties of lignin, including UV radiation blocking capacity (UV transmittance analysis) and reduced surface energy, are further exploited in the development of tailorable and self-standing architectures that are almost entirely comprised of nonbonding LP (solids content as high as 92 w/w%). Despite such composition, the materials develop high toughness (oscillatory dynamic mechanical analysis), owing to the addition of minor amounts of CNF. Multifunctional materials based on thin films (casting), 3D structures (molding), and patterned geometries (extrusion deposition) are developed as a demonstration of the potential use of lignin particles as precursors of new material generation. Remarkably, our observations hold for spherical LPs since a much poorer performance was observed after using amorphous powder, indicating the role of size and shape in related applications.

Porous Systems Based on Alkali-Activated Fly Ash

This paper studies possibilities of alkali-activated fly ash (AAFA) for the preparation of systems with preserved certain porosity level. Such systems would be used for example as filtration barriers, which are commonly prepared by both energetically and economically expensive sintering process at high temperatures. Porosity preservation was facilitated by the use of only coarse fraction from fly ash particles together with the use of low water to fly ash ratio and pressure compaction. Two different doses of sodium hydroxide were used to alkali activate fly ash. Prepared specimens were moist cured at 95 °C for 24 hours. Porosity and binder phase among the fly ash grains were investigated using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and capillary flow porosimetry (CFP). The results showed that it is possible to prepare AAFA-based porous systems and modify their properties by changing the activator dose.

A self-setting particle-stabilized porous ceramic panel prepared from commercial cement and loaded with carbon for potential radar-absorbing applications

Porous ceramic materials are in a current research focus because of their outstanding thermal stability, chemical stability and lightweight. Recent research has widened the range of applications to radar absorption to utilize the advantages of porous ceramic materials. There has been long-standing interest in the development of lightweight radar-absorbing materials for military applications such as camouflaging ground-based facilities against airborne radar detection. Therefore, in this study, a novel lightweight radar-absorbing material for X-band frequencies was developed using a self-setting particle-stabilized porous ceramic panel composited with carbon. The panel was prepared using a commercial calcium aluminate cement (as a self-setting matrix), zeolite 13X particles with propyl gallate (as a particle-stabilized pore former) and carbon (as a radar-absorbing material). The panel contained macropores approximately 200 to 400 ?m in size formed by zeolite 13X particles that are irreversibly adsorbed at liquid-gas interfaces. The self-setting particle-stabilized porous ceramic panels were characterized by scanning electron microscopy, mercury porosimetry, physisorption analysis, capillary flow porosimetry and network analysis. When 0.2 wt.% carbon was added to a selfsetting particle-stabilized porous ceramic panel to fabricate a composite 7mm thick, the maximum reflection loss was ?11.16 dB at 12.4GHz. The effects of the amount of added carbon and the thickness variation of a self-setting particle-stabilized porous ceramic panel on the radar-absorbing properties remain important issues for further research.

Optimization for Permeability and Electrical Resistance of Porous Alumina-Based Ceramics

Recently, porous alumina-based ceramics have been extensively applied in the semi-conductor and display industries, because of their high mechanical strength, high chemical resistance, and high thermal resistance. However, the high electrical resistance of alumina-based ceramics has a negative effect in many applications due to the generation of static electricity. The low electrical resistance and high air permeability are key aspects in using porous alumina-based ceramics as vacuum chucks in the semi-conductor industry. In this study, we tailored the pore structure of porous alumina-based ceramics by adjusting the mixing ratio of the starting alumina, which has different particle sizes. And the electrical resistance was controlled by using chemical additives. The characteristics of the specimens were studied using scanning electron microscopy, mercury porosimetry, capillary flow porosimetry, a universal testing machine, X-ray diffraction, and a high-resistance meter.

Porosity features and gas permeability analysis of bi-modal porous alumina and mullite for filtration applications

Bimodal porous structures were prepared by combining conventional sacrificial template and partial sintering methods. These porous structures were analysed by comparing pore characteristics and gas permeation properties of alumina/mullite specimens sintered at different temperatures. The pore characteristics were investigated by SEM, mercury porosimetry, and capillary flow porosimetry. A bimodal pore structure was observed. One type of pore was induced by starch, which acted as a sacrificial template. The other pore type was due to partial sintering. The pores produced by starch were between 2 and 10µm whereas those produced by partial sintering exhibited pore size of 0.1–0.5µm. The effects of sintering temperature on porosity, gas permeability, and mullite phase formation were studied. The formation of the mullite phase was confirmed by XRD. Compressive strengths of 37.9MPa and 12.4MPa with porosities of 65.3% and 70% were achieved in alumina and mullite specimens sintered at 1600°C.

The preparation and characterizations of an alumina support layer as a free-standing membrane for microfiltration

Recently, porous ceramic membranes have become a subject of significant interest because of their outstanding thermal and chemical stability. To reduce the high manufacturing costs and the complex processing steps of porous ceramic membranes that consist of a support layer and a separation layer, recent research has focused on the standalone use of a support layer. Therefore, in this paper, we report the results of our efforts to determine whether we could prepare an alumina support layer as a porous ceramic membrane that could effectively filter particles (an average particle size of approximately 1µm, the ISO 12103-1 A3 test dust) while exhibiting acceptable water permeability. We also discuss the results of an attempt to compare the alumina support layer with the other porous ceramic support layers which have different pore characteristics such as a pyrophyllite–diatomite composite support layer and a silicon carbide support layer. The pore characteristics of the specimens were studied using scanning electron micrography, mercury porosimetry, capillary flow porosimetry, and a dead-end microfiltration system with particle counters.

The effects of diatomite addition on the pore characteristics of a pyrophyllite support layer

Recently, porous ceramic membranes have become a subject of special interest due to their outstanding thermal and chemical stability. To alleviate the manufacturing cost issues of these porous ceramic membranes, recent research has been focused on the utilization of low cost natural materials. Therefore, in this paper, we report the results of our efforts to determine whether we could utilize diatomite as a pore former and whether we could prepare a pyrophyllite–diatomite composite support layer that could effectively control the largest pore size and permeability. The pore characteristics of the specimens were studied by scanning electron micrography, mercury porosimetry, and capillary flow porosimetry.

The effect of an alumina coating on the pore characteristics of a diatomite–kaolin composite support layer

Porous ceramic membranes have recently attracted great interest due to their outstanding thermal and chemical stabilities. In this paper, we report the results of our efforts to determine whether we could prepare an alumina coating to be deposited over a diatomite–kaolin composite support layer that could control the largest pore size and permeability. In addition, we determined under what conditions such an alumina coating over a diatomite–kaolin composite support layer could be prepared with minimum micro-crack generation during heat-treatment. The pore characteristics of an alumina coating on a diatomite–kaolin composite support layer were studied by scanning electron microscopy and capillary flow porosimetry.

The use of a diatomite–kaolin composite coating to design the pore characteristics of a sintered diatomite membrane

Abstract Porous ceramic membranes have lately attracted great interest due to their outstanding thermal and chemical stability. In this paper, we report the results of our efforts to determine whether we could prepare a diatomite–kaolin composite coating to be deposited over a sintered diatomite support layer that could reduce the largest pore size of the sintered diatomite membrane while retaining an acceptable level of permeability. We determined under what conditions such a composite coating over a support layer could be prepared without the generation of micro-cracks during drying and sintering. The pore characteristics of the sintered diatomite membranes were studied by scanning electron microscopy and capillary flow porosimetry.

The effect of kaolin addition on the characteristics of a sintered diatomite composite support layer for potential microfiltration applications

Abstract Porous ceramic membranes have lately become a subject of special interest due to their outstanding thermal and chemical stability. We prepared a sintered diatomite composite support layer with the addition of kaolin, which enhanced the mechanical strength of the diatomite composite matrix while retaining acceptable permeation properties. We also discussed whether the sintered diatomite composite support layer could serve as a separation layer to minimize processing difficulties as well as the feasibility of using a sintered diatomite composite layer without a separation layer as a porous ceramic membrane for microfiltration. The pore characteristics of the sintered diatomite specimens were studied by scanning electron micrography, mercury porosimetry, and capillary flow porosimetry.

The fabrication and characterization of sintered diatomite for potential microfiltration applications

Abstract Porous ceramic membranes have lately become a subject of special interest due to their outstanding thermal and chemical stability. We investigated whether a sintered diatomite support layer could also serve as a separation layer to minimize any processing difficulties, and investigated whether the support layer and the separation layer could be made from the same material to avoid a thermal mismatch during a high-temperature sintering process. We prepared sintered diatomite as a porous ceramic membrane for microfiltration, as diatomite particles are inherently porous and irregular. The pore characteristics of the sintered diatomite specimens were studied by scanning electron micrography, mercury porosimetry, and capillary flow porosimetry.

The effects of pore structures on the air permeation properties of sintered diatomite

In this study, we discussed the pore structure-property relationships by comparing the pore characteristics and air permeation properties of sintered diatomite specimens, with the same densities, prepared by the particle-stabilized direct foaming method and by the sacrificial polymer template method. Although the porous matrix, induced by irregular diatomite particles, of sintered diatomite specimens provided the paths of air permeation, the air permeation properties of the sintered diatomite specimen not only depended on the effective volume for air to pass through, but also on the pore structure. The pore characteristics of the diatomite specimens were investigated by scanning electron micrographs, mercury porosimetry, and capillary flow porosimetry.