Understanding the relationship between pores and the chemical structures of char can help analyze the interaction between chemical reactions and mass transfer during coal gasification. In this paper, ...chars prepared from Naomaohu coal by a drop tube furnace and a fixed bed reactor at 700 ℃, respectively, were gasified in CO2 by the drop tube furnace at 900 ∼ 1000 ℃ to obtain gasified char samples with different pores and chemical structures. The structure characterization results of this gasified char samples indicate that the mesopore-specific surface area increases exponentially from 146.8 to 409.3 m2/g with the decrease of AG/AOther (the ratio of the peak G area to the sum of other peaks except for peak G and peak D in the Raman spectrum) from 0.68 to 0.45, and thus an exponential correlation was proposed to predict this trend. The specific surface area of the pores 0.44–0.60 nm increases with increasing aliphatic carbon content and the specific surface area is 110.5 and 260.2 m2/g when the aliphatic carbon content is 0.07 and 0.17, respectively, while the specific surface area of the pores of 0.72–0.98 nm increases with increasing substituent content (including aliphatic carbon and carbon bonded with oxygen atoms), and the specific surface area is 28.3 and 51.6 m2/g when the substituent content is 0.17 and 0.43, respectively.
Graphene has obtained a great interest both in research and industries due to its potential and promising physical, electrical and mechanical properties. While it has been widely researched for ...advanced applications, its fundamental properties are still being explored and have to be well understood. The physical properties such as specific surface area (SSA), inter-sheet distance (d-spacing) and Raman spectroscopy data for graphene derivatives are closely related to each other, and this work focused on establishing the correlation between these critical factors with respect to their electrical conductivities. Different graphitic materials f(graphene oxide (GO), reduced graphene oxides (rGO), functionalised graphene oxide (frGO) and graphene nanoplatelets (GNP)) were taken in to account to elaborate the underlying mechanisms between extrinsic SSA and other physical parameters, such as intrinsic electrical conductivity. It has been analytically observed that SSA has a direct relationship with d-spacing and defect density of the graphene materials and thus their electrical conductivity highly depends on how large their SSA is the largest the SSA, the highest the electrical conductivity. Materials that poorly reduced were identified to be having low SSA and a higher level of discrepancies. Among different reducing agents used, hydroiodic reduced graphene oxide found to be having larger SSA as 670.98 m2 g−1 and higher electrical conductivity up to 103.3 S cm−1.
•Synthesis of different graphene derivatives and correlations between their physical structure and intrinsic electrical conductivity.•BET specific surface area vs. corresponding interlayer sheet distance.•Relationship between Raman spectroscopy (defect density and aromaticity) and specific surface area.
In this paper, the pore structure and fractal characteristics of coal under liquid nitrogen cold soaking are tested for different coal qualities of anthracite, bituminous coal and lignite, and the ...variation patterns of BET specific surface area, BJH total hole and adsorption pore specific surface area with liquid nitrogen cold soaking times are studied. Among these coal samples, it is found that the raw bituminous coal has the most internal micropore content and the largest adsorption space for gas, followed by anthracite, and lignite is the last. After one time liquid nitrogen cold soaking, the increase of adsorption and percolation pore contents of each coal sample in the order of: anthracite > lignite > bituminous coal; and with the increase of liquid nitrogen cold soaking times, the internal pore size and number of pores of the three coal samples gradually increases, but the specific surface area of adsorption pores decreases. The reduction amplitude of the specific surface area of coal adsorption pores by one time liquid nitrogen cold soaking gradually increases with the increase of metamorphism. With the increase of liquid nitrogen cold soaking times, the average pore size, total BJH hole and percolation hole of each coal sample increases, while the BET specific surface area and adsorption pore specific surface area decreases gradually. The fractal dimension D1 of each coal sample increases linearly with the increase of liquid nitrogen cold soaking times, and the variation of D2 has an opposite trend. The results of this study can provide theoretical and experimental support for further application of liquid nitrogen to increase the permeability of coal seams.
•Pore structure and fractal characteristics of coal under the liquid nitrogen cold soaking are tested.•Liquid nitrogen cold soaking could improve the coal pore connectivity.•Fractal dimension D1 of coal increases linearly with the liquid nitrogen cold soaking number.
•A series of CoS2@MOF-derived hollow carbon spheres were prepared by solvothermal method.•The overpotential of 232 mV at a current density of 10 mA cm−2 was achieved by CoS2–600.•The synergistic ...effect between CoS2 and hollow carbon spheres was discussed.
Electrocatalytic water splitting is a promising method for producing high-purity hydrogen. Metal-organic frameworks (MOFs) have recently emerged as unique electrocatalysts for overall water splitting. With their large specific surface area, high porosity, adjustable composition, and diversified structure, MOFs are widely used as precursors for preparing non-noble metal-based electrocatalysts. This paper presents the preparation of CoS2 particles loaded on carbon spheres derived from Co-MOF microspheres by calcination and sulfide reaction with sulfur. The optimized CoS2–600 particles demonstrate excellent OER and HER electrocatalytic performance in 1 M KOH solution. The MOF does not act as a catalyst, but rather adjusts the phase of the catalytic active material, changes the intermediate adsorbent, and increases the number of catalytic sites. The morphology and physical phases of the CoS2–600 particles were analyzed after cycling to identify the real active components during hydrogen and oxygen evolution.
•Low cost biomass carbon/rGO/nanocellulose hybrid aerogel was synthesized through a one-step self-assembly approach.•The hybrid aerogel exhibits high specific surface area of 1007.9 m2 g−1 and ...excellent mechanical property.•The self-supporting aerogel electrode shows admirable capacitive performance and high MnO2 loading of 33.9 mg cm−2.•The solid-state ASC device exhibits high areal capacitance.
Reasonable design of hybrid graphene aerogels with low cost, high specific surface area (SSA), and excellent mechanical properties is of great significance for future large-scale energy storage applications. Herein, we report a composite aerogel of biomass carbon/reduced graphene oxide (rGO)/nanocellulose (CNF) by a one-step self-assembly method. In the hybrid aerogel, biomass carbon particles with low cost and high SSA are assembled into the framework of rGO effectively preventing the restacking of rGO nanosheets and resulting in high SSA and high conductivity. Negatively charged nanocellulose fibers act as the binder between biomass carbon particles and rGO sheets, facilitating the formation of a strengthening network. As a result, the hybrid aerogel with a high content of biomass carbon (76% mass ratio) demonstrates excellent mechanical strength (240 kPa), high SSA (1007.9 m2 g−1), and efficient MnO2 deposition capability (33.9 mg cm−2). Employing the composite aerogel as electrodes to fabricate a self-supporting supercapacitor, an admirable capacitive performance (4.8F cm−2) was achieved. This work provides an effective method to fabricate low cost hybrid graphene aerogel materials with excellent performances for wide applications.
In this review, the role of surface modification of nanoparticles to enhance their performance as adsorbents was explored. Performance was assessed by comparisons on adsorption capacities of ...differently modified nanoparticles (silica, iron, and alumina based nanoparticles) on different heavy metal ions (Cu, Cd, Co, Ni, Pb, As, Cr, Zn, Mn, and Hg). A comparison of pure and modified materials revealed that the modified materials gave superior adsorption capacities. A close relationship was observed between the various modification methods and the adsorption capacities of particles synthesized by hydrothermal methods giving the highest adsorption capacities. Surface modification also had a direct effect on the specific surface area which decreased with the degree of functionalization. The adsorption capacity was however generally observed to increase with the degree of functionalization.
•Synthesis methods and adsorption capacity of nano particles are summarized.•Silica based modified nano particles are discussed.•The review also covers a bit on iron based modified materials.•Alumina based modified materials are also looked at.•A comparison of pure and modified nano particles is then carried out.
•Porous starches were made via supercritical CO2 and freeze-drying of gels.•The morphology of freeze-dried gels is mainly the replica of sublimated ice crystals.•The properties of starch aerogels ...depend on starch source and retrogradation time.•Specific surface area of aerogels is 20–30 times higher than that of freeze-dried gels.
Porous starch materials with various morphology and properties were made via starch dissolution, retrogradation and drying either with supercritical CO2 (“aerogels”) or lyophilisation (“cryogels”). Their properties were correlated with the rheological response of retrograded starch gels and crystallinity of aerogels and cryogels. All starch cryogels possess very low density (0.07 – 0.16 g/cm3), very large macropores and low specific surface area (around 3–13 m2/g). Their morphology is mainly the replica of sublimated ice crystals. The properties of starch aerogels strongly depend on starch source: the lowest density (around 0.1 g/cm3) and highest specific surface area (170–250 m2/g) was recorded for pea starch aerogels and the highest density (0.3–0.6 g/cm3) and lowest specific surface area (7–90 m2/g) for waxy maize starch aerogels. The morphology and properties of starch aerogels are interpreted by amylose and amylopectin evolution during retrogradation.
•The pore structure of C10-C150 concrete is analyzed by Mercury intrusion porosimetry (MIP).•All fractal curves of concrete are divided into four segments according multi-fractal characteristic.•The ...scale of each fractal region in C10-C150 concrete is different.•Link of the most probable pore diameter and the pore specific surface area with fractal dimension is discussed.•A mathematical model between compressive strength and pore structure is addressed.•The mathematical model between fractal dimension and compressive strength is validated more accurately than other parameters.
Concrete is a heterogeneous, multiphase, and multilayer composite system with extremely intricate microscopic pore structure. The structural characteristics of microscopic pore of concrete are closely related to its mechanical properties and durability. The pore structure of concrete with various strength grades (C10-C150) was analyzed by Mercury intrusion porosimetry (MIP) from the aspects of pore diameter distribution, pore volume, pore specific surface area and fractal feature. The Menger sponge model was used to calculate the fractal dimension of different pore regions in each test group, and the most suitable pore fractal region was selected to establish the mathematical model between fractal dimension and compressive strength. The results showed that all fractal curves are divided into four segments according multi-fractal characteristic of concrete, namely Region I, Region II, Region III and Region IV. Region I is macropores fractal region (d = 10 μm ∼ 950 μm), representing the packing patterns of hydrated cement grains, while Region II - Region Ⅳ is micropores fractal region (d = 0.0064 μm ∼ 10 μm), reflecting mainly the microstructure of C-S-H hydrates. Region I and Region Ⅳ exhibit obvious fractal features and the fractal dimension D is between 2 and 3. However, the fractal dimension D > 3 in Region II and Region III, which are nonphysical from the point of view of surface geometry. The fractal dimension can clearly describe the internal pore characteristic, and it is a real good correlation with the most probable pore diameter and the pore specific surface area. Moreover, the mathematical model between the fractal dimension and the compressive strength both accords with the positive power exponential function in Region I and Region IV. The fractal dimension can be viewed as a comprehensive parameter of pore shape and spatial distribution of pore structure, which can more accurately represent the relationship between the microscopic pore structure features and compressive strength of concrete. In practical engineering, it serves to realize the damage detection of concrete on site.
Layered boron nitrides (BNs) are usually viewed as excellent protective coatings and reinforcing materials due to their chemical inertness and high mechanical strength. However, the attention paid to ...their potential applications in gas sorption, especially in case of hydrogen, has obviously been insufficient. Herein, a novel BN material (i.e., porous microbelts), with the highest specific surface area ever reported for any BN system, up to 1488 m2 g–1, is obtained through one-step template-free reaction of a boron acid–melamine precursor with ammonia. Comprehensive high-resolution transmission electron microscopy, X-ray diffraction, and Raman characterizations all confirm that the obtained BN phase is partially disordered, shows an enlarged average spacing between adjacent (0002) layers (d 0002 = 0.38 nm, compared to normal 0.33 nm for a bulk layered BN), and belongs to an intermediate state between hexagonal (h-BN) and amorphous (a-BN) phases. By changing the synthesis temperatures, the textures of obtained porous microbelts are adjustable. H2 sorption evaluations demonstrate that the materials exhibit high and reversible H2 uptake from 1.6 to 2.3 wt % at 77 K and at a relatively low pressure of 1 MPa.
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