Role Of Micropores Research Articles

The Roles of Micro Pores and Minerals in Shale during Hydraulic Fracturing

The Roles of Micro Pores and Minerals in Shale during Hydraulic Fracturing

Slag Corrosion Behavior of Novel Lightweight Magnesia Castable in a High-Basicity Slag: Role of Micropores and Nanosized Zirconia

Slag Corrosion Behavior of Novel Lightweight Magnesia Castable in a High-Basicity Slag: Role of Micropores and Nanosized Zirconia

Spatial Confinement Effect of Mof Derived Carbon Nanoreactor: The Crucial Role of Micropores in Selective Capture of Peroxymonosulfate in Aops-Based Process

Spatial Confinement Effect of Mof Derived Carbon Nanoreactor: The Crucial Role of Micropores in Selective Capture of Peroxymonosulfate in Aops-Based Process

Acetic acid-mediated cellulose-based carbons: Influence of activation conditions on textural features and carbon dioxide uptakes

In this work, we developed a simple methodology for producing highly porous carbons. Herein, we combined the hydrothermal method with chemical activation to fabricate cellulose-based, melamine modified porous carbons, using acetic acid as an additive. The preparation conditions including activation temperature, activation time, and melamine ratio were varied to obtain an optimized adsorbent exhibiting efficient textural features and maximized carbon dioxide (CO2) adsorption uptake. By varying the preparation conditions, high specific surface area (SSA) (1260–3019 m2 g−1), microporosity in the range of 0.21–1.13 cm3 g−1, and a well-developed porous structure was obtained. The optimized adsorbent exhibits an excellent CO2 adsorption uptake of 297.05 mg g−1 (6.75 mmol g−1) and 174.4 mg g−1 (3.96 mmol g−1) at 273 K and 298 K at 1 bar, respectively, due to the existence of ultra-micropores (<0.68 nm, < 0.81 nm), high SSA (3019 m2 g−1), and high nitrogen content (8%). Furthermore, the role of micropores in the CO2 adsorption process suggests that micropores between 0.68 nm and 1 nm exhibit high CO2 adsorption potential. Additionally, all synthesized carbons exhibited a high isosteric heat of adsorption (45 kJ mol−1) and a greater affinity for adsorbed CO2 species than nitrogen (N2) molecules. Thus, as-fabricated porous carbon adsorbents are an effective competitor for CO2 uptake applications to mitigate global warming.

Mechanically robust microporous anion exchange membranes with efficient anion conduction for fuel cells

• Brittleness in polymer of intrinsic microporosity (PIM) membranes is alleviated by high molecular weight. • Role of micropores in developing water/ion conduction channels is investigated. • Microporous anion exchange membrane (AEM) has superior ion conduction efficiency. • H 2 crossover through microporous AEM is minimal in the hydrated state. • Feasibility of microporous AEMs for H 2 /O 2 fuel cell is evaluated. Polymers of intrinsic microporosity (PIMs) present an attractive opportunity for developing new types of anion exchange membranes (AEMs) for fuel cell featuring charged subnanometer-sized micropores. But challenges exist to make mechanically robust PIM AEMs due to their high chain rigidity. Imparting more flexibility improves mechanical properties but sacrifices microporosity. Here, a mechanically robust and highly anion conductive PIM AEM (QPIM-1) fabricated by facile animation and quaternization of PIM-1 membrane is reported, and its structure–property relationships are investigated, especially focusing on the microporous structure. High molecular weight alleviates brittleness, as QPIM-1 AEM shows comparable mechanical properties to conventional AEMs, quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO), at a membrane thickness down to ~35 μm and a high ion exchange capacity (IEC) up to ~2.1 mmol g −1 . The micropores situated among the rigid and contorted polymer chains evolve into water/ion conduction channels when the membrane is hydrated. This results in improved morphology over dense polymeric AEMs by less hindered ion pathways. QPIM-1 AEMs exhibit superior ion conduction efficiency, which is 2.6–5.3 times that of dense QPPO AEM at similar ion exchange capacities (IECs). A high hydroxide ion conductivity of 57 mS cm −1 at 20 °C is obtained, which is among the highest reported anion conductive PIM-based AEMs. Even though the AEMs are microporous, only slight H 2 permeation is observed when hydrated and at high open circuit voltage (OCV) of a single fuel cell.

Role of micropores, mass transfer, and reaction rate in the hydrothermal alteration process of plagioclase in a granitic pluton

Role of micropores, mass transfer, and reaction rate in the hydrothermal alteration process of plagioclase in a granitic pluton

Micropore-induced capillarity enhances bone distribution in vivo in biphasic calcium phosphate scaffolds.

The increasing demand for bone repair solutions calls for the development of efficacious bone scaffolds. Biphasic calcium phosphate (BCP) scaffolds with both macropores and micropores (MP) have improved healing compared to those with macropores and no micropores (NMP), but the role of micropores is unclear. Here, we evaluate capillarity induced by micropores as a mechanism that can affect bone growth in vivo. Three groups of cylindrical scaffolds were implanted in pig mandibles for three weeks: MP were implanted either dry (MP-Dry), or after submersion in phosphate buffered saline, which fills pores with fluid and therefore suppresses micropore-induced capillarity (MP-Wet); NMP were implanted dry. The amount and distribution of bone in the scaffolds were quantified using micro-computed tomography. MP-Dry had a more homogeneous bone distribution than MP-Wet, although the average bone volume fraction, BVF‾, was not significantly different for these two groups (0.45±0.03 and 0.37±0.03, respectively). There was no significant difference in the radial bone distribution of NMP and MP-Wet, but the BVF‾, of NMP was significantly lower among the three groups (0.25±0.02). These results suggest that micropore-induced capillarity enhances bone regeneration by improving the homogeneity of bone distribution in BCP scaffolds. The explicit design and use of capillarity in bone scaffolds may lead to more effective treatments of large and complex bone defects. The increasing demand for bone repair calls for more efficacious bone scaffolds and calcium phosphate-based materials are considered suitable for this application. Macropores (>100μm) are necessary for bone ingrowth and vascularization. However, studies have shown that microporosity (<20μm) also enhances growth, but there is no consensus on the controlling mechanisms. In previous in vitro work, we suggested that micropore-induced capillarity had the potential to enhance bone growth in vivo. This work illustrates the positive effects of capillarity on bone regeneration in vivo; it demonstrates that micropore-induced capillarity significantly enhances the bone distribution in the scaffold. The results will impact the design of scaffolds to better exploit capillarity and improve treatments for large and load-bearing bone defects.

Preparation of hierarchical porous carbon from waste printed circuit boards for high performance electric double-layer capacitors

Renewable clean energy and resources recycling have become inevitable choices to solve worldwide energy shortages and environmental pollution problems. It is a great challenge to recycle tons of waste printed circuit boards (PCB) produced every year for clean environment while creating values. In this work, low cost, high quality activated carbons (ACs) were synthesized from non-metallic fractions (NMF) of waste PCB to offer a great potential for applications of electrochemical double-layer capacitors (EDLCs). After recovering metal from waste PCB, hierarchical porous carbons were produced from NMF by carbonization and activation processes. The experimental results exhibit that some pores were formed after carbonization due to the escape of impurity atoms introduced by additives in NMF. Then the pore structure was further tailored by adjusting the activation parameters. Roles of micropores and non-micropores in charge storage were investigated when the hierarchical porous carbons were applied as electrode of EDLCs. The highest specific capacitance of 210 F g−1 (at 50 mA g−1) and excellent rate capability were achieved when the ACs possessing a proper micropores/non-micropores ratio. This work not only provides a promising method to recycle PCB, but also investigates the structure tailoring arts for a rational hierarchical porous structure in energy storage/conversion.

Role of micropores and nitrogen-containing groups in CO2 adsorption on indole-3-butyric acid potassium derived carbons

Nitrogen-rich carbons for CO2 capture have received much attention in recent years, but the role of N-containing groups in CO2 adsorption has not been clearly elucidated. In this study, indole-3-butyric acid potassium (IBAP) as a new precursor was used to prepare the nitrogen-rich carbons via one-step carbonization. The IBAP-derived carbon prepared at 700°C exhibited high CO2 adsorption of 1.48mmol/g at 0.15bar and 4.53mmol/g at 1bar and 25°C, among the highly efficient activated carbons for CO2 adsorption. The high CO2 adsorption was attributed to not only the high volume of effective micropores, but also the effective N-containing groups on the IBAP-derived carbons. When carbonization temperatures increased from 500°C to 900°C, the nitrogen contents in the IBAP-derived carbons decreased from 6.35% to 0.70%. X-ray photoelectron spectroscopy (XPS) analysis confirmed that the pyrrolic-N in IBAP was converted into pyridinic-N, quaternary nitrogen and pyridinic-N-oxide in the carbonization process, and their contents first increased and then decreased with increasing carbonization temperatures. Only the pyrrolic-N was proved to be effective for CO2 adsorption on the IBAP-derived carbons, and its contribution to CO2 adsorption was pronounced for the carbons prepared at low temperatures. For the well-developed porous carbons, the effective micropores were mainly responsible for CO2 adsorption via micropore filling.

Micromechanical modeling of thermal spallation in granitic rock

While the underlying mechanisms governing thermal spallation in rock have been known since the 1930s, our ability to model this behavior remains largely empirical. Leading models of thermal spallation either rely on experimentally derived relationships linking applied thermal stresses to spall production, or employ idealized representations that ignore the effects of rock microstructure. Although such models are useful for describing systems within a given context, they are less suited to extrapolate outside the range to which they are fitted or to derive new insight into how mechanisms at smaller-scales influence spall production.This paper describes a numerical modeling tool designed to conduct explicit simulations of thermal spallation at the grain-scale. The model uses an Eulerian–Godunov scheme to simulate solid and fluid mechanical behavior, permitting both inter- and intra-granular fracture. Simulations conducted with the model illustrate how differences in rock properties, microstructural geometry and mineral volume fractions, combined with variations in thermal and mechanical loading conditions, influence spallation at the grain scale. We discuss the implications of these results on the processes controlling thermal spallation of rock, in particular, the role of micropores in the onset and extent of spallation.

Adsorption, diffusion, dewetting, and entrapment of acetone on Ni(111), surface-modified silicon, and amorphous solid water studied by time-of-flight secondary ion mass spectrometry and temperature programmed desorption

Interactions of acetone with the silicon surfaces terminated with hydrogen, hydroxyl, and perfluorocarbon are investigated; results are compared to those on amorphous solid water (ASW) to gain insights into the roles of hydrogen bonds in surface diffusion and hydration of acetone adspecies. The surface mobility of acetone occurs at ∼60 K irrespective of the surface functional groups. Cooperative diffusion of adspecies results in a 2D liquid phase on the H- and perfluorocarbon-terminated surfaces, whereas cooperativity tends to be quenched via hydrogen bonding on the OH-terminated surface, thereby forming residues that diffuse slowly on the surface after evaporation of the physisorbed species (i.e., 2D liquid). The interaction of acetone adspecies on the non-porous ASW surface resembles that on the OH-terminated Si surface, but the acetone molecules tend to be hydrated on the porous ASW film, as evidenced by their desorption during the glass-liquid transition and crystallization of water. The roles of micropores in hydration of acetone molecules are discussed from comparison with the results using mesoporous Si substrates.

PEMFC Catalyst Layers: The Role of Micropores and Mesopores on Water Sorption and Fuel Cell Activity

The effects of carbon microstructure and ionomer loading on water vapor sorption and retention in catalyst layers (CLs) of PEM fuel cells are investigated using dynamic vapor sorption. Catalyst layers based on Ketjen Black and Vulcan XC-72 carbon blacks, which possess distinctly different surface areas, pore volumes, and microporosities, are studied. It is found that pores <20 nm diameter facilitate water uptake by capillary condensation in the intermediate range of relative humidities. A broad pore size distribution (PSD) is found to enhance water retention in Ketjen Black-based CLs whereas the narrower mesoporous PSD of Vulcan CLs is shown to have an enhanced water repelling action. Water vapor sorption and retention properties of CLs are correlated to electrochemical properties and fuel cell performance. Water sorption enhances electrochemical properties such as the electrochemically active surface area (ESA), double layer capacitance and proton conductivity, particularly when the ionomer content is very low. The hydrophilic properties of a CL on the anode and the cathode are adjusted by choosing the PSD of carbon and the ionomer content. It is shown that a reduction of ionomer content on either cathode or anode of an MEA does not necessarily have a significant detrimental effect on the MEA performance compared to the standard 30 wt % ionomer MEA. Under operation in air and high relative humidity, a cathode with a narrow pore size distribution and low ionomer content is shown to be beneficial due to its low water retention properties. In dry operating conditions, adequate ionomer content on the cathode is crucial, whereas it can be reduced on the anode without a significant impact on fuel cell performance.

Strain of plates of aluminum, glass, and silicon at sorption of water vapor

It has been suggested and realized a kinetic approach to the investigation of sorbostriction isotherms on plates of aluminum, glass, and monocrystalline silicon at the sorption of water from its vapor. It is established increasing the plate area and decreasing the plate thickness with passing the contraction through a minimum in the process of sorption. The strain observed is explained by the interference of two effects: the influence of variation of the surface tension of the outer surface of samples and the role of micropores (with possible chemisorption in them).