Surface Pore Research Articles

Morphology controlled fabrication of porous magnesium oxide nanostructures for the efficient elimination of methyl orange

Abstract Magnesium oxide-based adsorbents (MGO-A) with different morphologies were synthesized via the hexamethylene tetramine-assisted hydrothermal method. The role of four anions in the reaction system, chloride (Cl⁻), nitrate (NO3 ⁻), sulfate (SO4 2⁻), and acetate (C2H3O2 2⁻) was systematically investigated to determine the properties of the MgO. Standard characterization techniques were used, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and surface area and pore size interpretations. The kinetics and adsorption isotherm were studied for removal of the dye methyl orange. The dye’s rapid removal led to equilibrium being reached within 5 min. The correlation coefficient values indicate more applicability of pseudo-second-order kinetics than the pseudo-first-order kinetics. Both physisorption and chemisorption can be a pathway towards successfully removing methyl orange. The adsorption isotherm shows that the maximum capacity of the material is very high, 1,062 mg/g for MGO-A. In light of these results, it appears this material holds promise as a dye removal material.

Enhanced sequestration of ciprofloxacin from aqueous solution using composite montmorillonite-kaolin clay adsorbent

Clay minerals are low-cost and environmentally benign natural adsorbents with huge potential for removing micropollutants from aqueous solutions owing to their intrinsic surface properties. In this study, montmorillonite and kaolin clay minerals were activated using NaNO3 and HNO3 to develop activated montmorillonite- kaolin clay composites (AMKCC) material for the sequestration of ciprofloxacin (CIP) from aqueous solution. The developed AMKCC was characterized using X-ray fluorescence (XRF), Brunauer-emmett-teller (BET), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The BET analysis reveals an improved BET surface area, pore volume and pore diameter of 139.13 m2/g, 0.17 cm3/g and 2.18 nm, respectively. At optimum conditions, pH (3.56), initial concentration (16.74 mg/L), time (77.9 mins) and adsorbent dosage (0.4 g), the percentage of ciprofloxacin removed from aqueous solution was 97 %. The adsorption of ciprofloxacin (CIP) using AMKCC was spontaneous, feasible, endothermic, and followed Freundlich isotherm with pseudo-second-order kinetics. The maximum monolayer adsorption capacity of AMKCC is 344.82 mg/g. The desorption studies revealed HCl as the best eluent for AMKCC regeneration. Therefore, AMKCC has considerable potential for the adsorption of pharmaceuticals from aqueous solution.

A three-dimensional unsteady flow of Casson nanofluid with suspension of microorganisms with variable thermal conductivity: A modified Fourier theory approach

The study of nanofluids is important due to valuable applications in drug delivery systems, thermal processes, solar management systems, microfluidic devices, extrusion phenomenon, chemical processes etc. The objective of current analysis is to investigates the enhanced thermal performances of magnetized Casson nanofluid with suspension of microorganisms. An unsteady periodically oscillating flow due to bidirectional moving porous surface have been considered. The analysis is subject to assumptions of variable thermal conductivity. The modelled problem is based on implementation of modified Fourier theories. The Buongiorno nanofluid model is used to predicts the significance of Brownian motion and thermophoresis effects. Chemical reaction species are also attributed. For solution methodology, homotopy analysis scheme is implemented. The convergence region is specified. The physical impact of problem is visualized. The significant applications of parameters have been focused. The claimed results offer significance in cooling systems, chemical reactions, air conditioning, solar thermal systems, automotive radiators, heat exchangers in power plants etc.

Layer-by-Layer Deposition of Kraft Lignin and PEDOT:PSS.

Kraft lignin (KL) is a sustainable carbon-based substance with a potential use in photovoltaic materials. However, its conductivity is low, but it can be improved via incorporation with a conductive polymer, such as poly(3,4-ethylene dioxythiophene) (PEDOT): poly(styrenesulfonate) (PSS). This study examines the factors affecting the interaction of KL and PEDOT:PSS (PS) in a solution state using a quartz crystal microbalance with dissipation (QCM-D) and a stagnation point refractometer (SPAR). The results confirmed that aqueous environments, e.g., pH and ionic strengths, considerably affected particle size and zeta potential of KL and PS due to protonation, deprotonation, particle aggregation, and charge screening. The polymers exhibited the largest adsorbed mass and thickness at pH 6 and 10 mM NaCl on a solid surface, which was attributed to the relatively linear structure of PEDOT chains, exposing more adsorptive sites for interaction with KL. A 10 mM NaCl concentration facilitated the screening of charges on PS and KL surfaces, diminishing repulsive forces and enabling hydrophobic and cationic-π interaction, which led to increased adsorption. Contact angle and SEM investigations of the adsorbed layer revealed the water contact angle increasing and the morphology changing from a smoother layer to a porous surface, providing further evidence of adsorption. Furthermore, the conductivity was improved by the introduction of a PS adlayer on ITO glass when it was sandwiched between KL adsorbed layers. These findings provide insight into KL and PS interaction and suggest that KL can be used with PS for conductive materials, such as photovoltaics, imparting the waterproofness of the films.

A polyhedron-based metal-organic framework with electronegative donor sites for efficient C2H6/C2H4 separation

Ethylene is an important chemical raw material which is widely used in the production of chemical fibers, plastics, rubber, coatings, as well as medicines, and its separation from the gas mixtures of C2H6/C2H4 is of great importance but a challenging task due to their similar physical properties and molecular dimensions. Herein, we report the C2H6 and C2H4 sorption studies on a robust anionic metal-organic framework (MOF) {(NH2Me2)[Co3(μ3OH)(TPT)(TZB)3](H2O)6(DMA)6}n (Co-MOF) formed by connection of Co3(OH) clusters by two N-rich organic ligands 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) and 4-(1H-Tetrazol-5-yl)benzoic acid (H2TZB). The prepared Co-MOF features a polyhedron stacking network structure composed of trigonal bipyramidal cages and octahedral cage which both contribute to a high C2H6 uptake capacity of 6.48 mmol/g and a decent C2H6/C2H4 selectivity of 1.54 at 298 K and 1 bar. Grand Canonical Monte Carlo (GCMC) simulation results agree well with the experimental tendency, both in the adsorption isotherms and sorption heats, which demonstrated that the suitable pore surfaces with electronegative donor sites generated multiple CH ⋅⋅⋅O/N and CH ⋅⋅⋅π interactions between the framework and C2H6, resulting in a stronger interaction between the MOF skeleton and C2H6 molecule than C2H4 as reflected by the dispersion-corrected density functional theory (DFT) calculation.

Petroleum Pitch-Derived Porous Carbon Materials as Metal-Free Catalyst for Dry Reforming of Methane.

Porous carbon materials have gained increasing attention in catalysis applications due to their tailorable surface properties, large specific surface area, excellent thermal stability, and low cost. Even though porous carbon materials have been employed for thermal-catalytic dry reforming of methane (DRM), the structure-function relationship, especially the critical factor affecting catalytic performance, is still under debate. Herein, various porous carbon-based samples with disparate pore structures and surface properties are prepared by alkali (K2CO3) etching and the following CO2 activation of low-cost petroleum pitch. Detailed characterization clarifies that the quinone/ketone carbonyl functional groups on the carbon surface are the key active sites for DRM. Density functional theory (DFT) calculations also show that the C=O group have the lowest transition state energy barrier for CH4* cleavage to CH3* (2.15 eV). Furthermore, the cooperative interplay between the specific surface area and quinone/ketone carbonyl is essential to boost the cleavage of C-H and C-O bonds, guaranteeing enhanced DRM catalytic performance. The MC-600-800 catalyst exhibited an initial CH4 conversion of 51% and a reaction rate of 12.6 mmolCH4 gcat.-1 h-1 at 800 °C, CH4:CO2:N2= 1:1:8, and GHSV = 6000 mL gcat.-1 h-1. Our work could pave the way for the rational design of metal-free carbon-based DRM catalysts and shed new light on the high value-added utilization of heavy oils.

Sequential release of vancomycin and BMP-2 from chitosan/nano-hydroxyapatite thermosensitive hydrogel for the treatment of chronic osteomyelitis

In this study, we developed scaffolds materials with microspheres to form a double sustained release system.Chitosan/nano-hydroxyapatite (CS-HA) was used as a drug carrier to construct a sustained-release system for Bone morphogenetic protein-2(BMP-2) and Vancomycin (VAN). Furthermore, VAN and BMP-2 loaded microspheres (Ms) were prepared by the emulsion ultrasonic method.The resultant composites were characterized by Scanning electron microscope (SEM), compressive strength, porosity, and biodegradation. The characterization results showed uniform porous and rough surface, enhanced thermal stability, and highest compressive strength ((1.912 ± 0.012) Kpa, the surface of the two microspheres was slightly folded and showed a regular spherical shape.The loading rate of BMP-2 was (59.611 × 10-4 ± 0.023 × 10-4)% and the encapsulation rate was (6.022 ± 0.005)%. The release rate of vancomycin and BMP-2 was 57.194% and 12.968% respectively. Osteogenic differentiation of Bone marrow mesenchymal stem cells (BMSCs) was confirmed by alkaline phosphatase quantification. The deposition of late osteogenic markers (calcium phosphates) detected by Alizarin red, which indicated extracellular matrix mineralization. The results showed that BMP-2/VAN in CS-HA hydrogel successfully achieved the sequential release of the double drugs, which could benefit bone regeneration.

Trace DNA and its persistence on various surfaces: A long term study investigating the influence of surface type and environmental conditions – Part two, non-metals

The work presented herein is the second part of a large-scale persistence project aimed at identifying trends in trace DNA persistence. This study aims to show how different environmental storage conditions and target surface characteristics influence the persistence of cellular and cell free DNA (cfDNA) over time. To eliminate variation within the experiment, we used a proxy DNA deposit consisting of a synthetic fingerprint solution, cellular DNA, and/or cfDNA. Samples were collected and analysed from eight non-metal surfaces over the course of 1 year (27 time points) under three different environmental storage conditions. The results of this experiment show that surface characteristics in conjunction with DNA type greatly influence DNA persistence. Variation in the amount of DNA recovered over time was greatly influenced by surface porosity. CfDNA persisted at significantly higher levels on non-porous surfaces, and cellular DNA persisted at higher levels on porous items. Furthermore, statistically significant differences in DNA persistence were found among the items classified as non-porous surfaces and among the items classified as porous surfaces. Additionally, this study showed that the sample storage environment had a larger impact on DNA persistence than previously observed for metal surfaces [1]. When considering DNA type, cellular DNA was shown to persist for longer than cfDNA and persistence as a whole appears to be better when DNA is deposited alone rather than in mixtures. Unsurprisingly, it was found that the amount of DNA recovered from trace deposits decreased over time. However, DNA decay is highly dependent on the surface type and exhibits higher variability at short time points and on porous surfaces. For each of the surfaces tested, DNA persisted 1 year past deposition (in some combination of DNA type and environmental condition), except for wood, on which DNA did not persist in any capacity past four months. This data is intended to add to our understanding of DNA persistence and the factors which affect it.

Architecturing ultra-stable multi-dimensional MXene/MAX self-supporting electrode anchored with Low-Pt for efficient hydrogen evolution reaction in harsh environments

The design of self-supporting structure is particularly important to improve the stability and electrochemical performance of hydrogen evolution reaction electrode. Here, a facile strategy for building novel ultra-stable 0D-2D-3D integrated self-supporting electrode with high conductivity, sufficient diffusion channels and large reactive surface area was proposed. In the heterostructure, 2D Ti3C2Tx flakes in-situ synthesized on 3D network porous Ti3AlC2 surface which provides the multiple reactive surface areas and aggregation resistance to facilitating 0D ultrafine Pt nanoparticles uniform anchorage. Combined with structural characterization and first-principles calculations revealed that, the highly dispersed ultrafine Pt synergistically coupling strong metal-support interactions creates a unique multifunctional catalytic interface with high stability and atomic utilization efficiency of Pt to promote the HER in acidic and seawater. The resultant self-supporting electrode (support 0.48 wt% Pt) exhibits much superior activity to 10 % commercial Pt/C (loaded on foam nickel) in 0.5 M H2SO4 (55 mV@10 mA cm−2) and simulate seawater (196 mV@10 mA cm−2) while reducing the Pt usage by 15 times. Meanwhile, the electrode also illustrates outstanding stability under high current densities (100 h@100 mA cm−2). This study provides a new design idea for developing integrated self-supporting catalytic electrodes to meet the durability of hydrogen evolution reaction applications in harsh environments.

Flux and fouling behavior during constant pressure sterile filtration of nanoemulsions

Nanoemulsions with droplet diameters from 20 to 200 nm have emerged as attractive adjuvants in the development of novel vaccines and as an advanced method of drug delivery for hydrophobic drugs. However, the large size of the nanoemulsion droplets leads to very low capacities during the final sterile filtration step used to ensure sterility of parenteral drug products. The objective of this study was to examine the sterile filtration of a model nanoemulsion made using squalene as the oil and Tween 20 and Span 85 as stabilizing surfactants. Data were obtained with different commercial sterile filters with different morphology and chemistry during constant pressure filtration. In each case, there was essentially no filtration until the transmembrane pressure exceeded a critical value related to the force required to push the deformable nanoemulsion droplets through the membrane pores. The filter capacity increased with increasing pressure, going from 700 g/m2 at 140 kPa to 1300 g/m2 at 280 kPa for a dual layer polyethersulfone sterile filter, with the flux decline well described by the complete pore blockage model. The dual layer asymmetric membranes showed much higher capacities than corresponding single layer filters due to the effectiveness of the upper layer in removing larger nanoemulsion droplets that would otherwise block the pores of the sterile filter. The capacity of the different sterile filters was also well-correlated with the initial filtrate flux, with both of these parameters governed by the pore size distribution and surface chemistry of the filters. These results provide important insights into factors controlling the sterile filtration of highly concentrated nanoemulsions used in the formulation of vaccines and drug products.

Highly Porous Nitrogen and Phosphorus Dual-Doped Carbon with Increased Phosphorus Content As an Efficient Oxygen Reduction Electrocatalyst

Highly porous nitrogen and phosphorus dual-doped carbon (NPC) was synthesized using acetylene black as a carbon source in two steps: (1) solid–gas mechanochemical treatment to prepare nitrogen-doped carbon (NC), (2) heat treatment to dope the NC with phosphorus. X-ray photoelectron spectroscopy and N2 gas adsorption analysis revealed that the solid–gas mechanochemical treatment using a ball mill incorporated nitrogen atoms into the carbon network and increased the pore volume and surface area. Furthermore, the resulting NC exhibited enhanced reactivity with ammonium dihydrogen phosphate, which was used as a phosphorus source, upon heat treatment. The phosphorus content in NPC synthesized by two-step mechanochemical and heat treatments reached 1.91 at%, a 14-fold increase compared to that of phosphorus-doped carbon synthesized by heat treatment. The NPC exhibited higher electrocatalytic activity for the oxygen reduction reaction than NC, suggesting that the additional phosphorus doping into NC can improve its electrocatalytic performance.

Influence of Supercritical Conditions on Isothermal Adsorption Capacity Calculation of Methane and Model Optimization.

The study of isothermal adsorption models for coal and methane under supercritical conditions helps us to understand the gas content distribution in coal seams and improve gas management in coal mines. Coal samples from the Hebi mine and Longshan coal mine were selected for this research. Using the weight method, isothermal adsorption curves of supercritical methane at temperatures of 308, 313, and 318 K were measured. The adsorption phase density of supercritical methane was obtained by using the intercept method and model fitting, and the absolute adsorption capacity of methane was calculated. Simultaneously, the pore volume and specific surface area of the coal samples were tested, and the isothermal adsorption model for supercritical methane was studied and optimized. The results indicate that using mercury intrusion, low-temperature N2, and low-temperature CO2 adsorption methods for testing coal sample pore structures allows for multiscale characterization of the coal pore structure. Based on the Gibbs excess adsorption theory, the phase density of methane obtained from the intercept method and model fitting effectively represent the isothermal adsorption curve of supercritical methane. By combination of the specific surface area and pore volume distribution of the coal with the absolute adsorption capacity of methane, the number of methane adsorption layers on the coal surface was calculated to be between 1.11 and 1.3 layers. This suggests that the isothermal adsorption model for supercritical methane on coal is not solely micropore filling or single molecular layer adsorption but primarily single molecular layer adsorption with concurrent micropore filling adsorption. Based on this adsorption mechanism, an L-DA isothermal adsorption model for supercritical methane on coal was established. The L-DA isothermal model shows good fitting results and effectively explains the adsorption characteristics of supercritical methane on coal.

Enhancement effect of potassium ferrate on self-activation: Significant improvement in pore structure and adsorption performance of activated carbon

This work developed a method using bamboo shoot shells as raw material to produce Fe-modified ACs combining self-activation and chemical modification. Adding small amounts (0.5–5 %) of K2FeO4 accelerated the pyrolysis process and CO2 release, and reduced the activation energy and temperature of self-activation reaction. This increased the reaction rate and activation efficiency, ultimately significantly improving the pore structure of ACs. The addition of 3 % K2FeO4 resulted in a substantial increase in specific surface area and pore volume of AC, from 1340 m2/g and 0.72 cm3/g to 2184 m2/g and 1.34 cm3/g, respectively. Additionally, the introduction of K2FeO4 also enabled iron doping on the surface of the ACs. The improvement of pore structure and iron doping further enhanced the adsorption performance of ACs. The adsorption capacities of ACs for arsenate, ibuprofen, and tetracycline were up to 1.64, 1.50, and 2.38 times higher, respectively, than those of ACs prepared through conventional self-activation.

Composition and structural properties of coal gasification fine slag and its classified products – a case study

ABSTRACT Coal gasification fine slag (CGFS) is a large solid waste in the field of coal chemical industry, and its land occupation and environmental pollution caused by stockpiling and landfill make its comprehensive utilization imminent. The composition and structure of CGFS is the basis of its resource utilization, particle size classification and density classification is the important means to achieve the separation and enrichment of components in CGFS, while there are significant differences in the properties of CGFS in different particle size and different density fractions. Therefore, a CGFS sample from Shaanxi, China was used as an example in this paper, and X-ray diffraction analyzer (XRD), X-ray fluorescence spectrometry (XRF), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and low-temperature N2 adsorption tester were applied to comprehensively analyze the compositional and structural properties of the raw as well as the graded (both size-graded and density-graded) samples. The results show that the proximate composition, mineral composition, elemental composition, surface functional groups, apparent morphology, and pore structure show a good regularity with the particle size and density of the samples. Meanwhile, these properties and their variations with particle size and density were analyzed for their implication in the separation of components and resource utilizations of CGFS. The findings of this study provide ideas and data support for large-scale dissipation and high value-added disposal of CGFS.

Adsorption desulphurization performance of biochar that derived from eucalyptus waste

In this paper, microporous biochar materials with large specific surface area (2592.2 m2/g) and pore volume (1.15 cm3/g) was prepared by eucalyptus waste, and was successfully used for adsorption desulfurization (ADS) where it showed high dibenzothiophene (DBT) adsorption capacity (172.5 mg/g). The biochar materials were characterized by scanning electron microscopy (SEM), N2 adsorption-desorption isotherms and various spectroscopies (Raman, XRD, FTIR) analyses. The adsorption process was well consistent with the pseudo-second-order kinetic model and Langmuir isothermal model. ADS behavior was explained by the intraparticle diffusion model. The adsorption energies of DBT in carbon nanotubes with different pore sizes were calculated by using the density functional theory. It is finally concluded that ADS mainly attributed to π-π interactions between DBT with biochar materials, also includes hydrogen bonding, acid-base interactions and van der Waals force. The present work provides a new idea of ADS, using waste biomass materials to prepare biochar materials.

Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.

Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.

Swelling-assisted surface grafting strategy for multichannel antifouling membranes: Reconstruction of surface pore structure and applications in microalgae harvesting and blood purification

Membrane fouling remains a major challenge in membrane separation. The modification of hydrophilic membrane surfaces can mitigate irreversible fouling deposition, thereby improving antifouling properties. Effective surface modification strategies are essential techniques for developing highly efficient antifouling membranes. In this work, a swelling-assisted surface grafting strategy was proposed for multichannel antifouling membranes, where various lengths of polyvinylpyrrolidone (PVP) brushes were grafted on the surface of polysulfone membrane using reversible addition-fragmentation chain transfer polymerization. The successful grafting of PVP polymer brushes was confirmed using Fourier transform infrared spectrometer and X-ray Photoelectron Spectroscopy. Changes in membrane morphology and pore structure were observed via scanning electron microscope and atomic force microscope. During the grafting process, the amphiphilic macromolecules formed through grafting were selectively swelled by graft solvent, leading to the formation of mesopores in both the surface layer and sublayer of the membrane, which formed additional water transport channels. The introduction of hydrophilic polymer brushes and the change of pore structure significantly boosted the hydrophilicity and permeability of the membranes. As a result, the water contact angle decreased from 85° to 42°, accompanied by an approximate 3.24-fold increase in pure water flux (PWF). Due to superior hydrophilicity, modified membranes demonstrated exemplary performance in microalgae harvesting, boasting a microalgae retention rate nearing 100 % and low fouling resistance (2.12 × 1012 m−1). In algal filtration experiments, a confocal laser scanning microscope was employed to assess the activity of filtered algae on the membrane surface. The prepared membranes effectively maintained the bioactivity of algae while also achieving a high flux recovery rate (90.7 %) following filtration and cleaning. Furthermore, in blood cell compatibility tests, the modified membranes exhibited resistance to blood cell adhesion and sustained a low hemolysis rate (0.06 %). Overall, this strategy offers unique insights into the fabrication of antifouling surfaces and shows considerable promise for large-scale applications in microalgae harvesting and blood purification.

Fabrication of modified Sb2O3 nanospheres for the removal of hazardous malachite green organic pollutant and selective NO2 gas sensor

Sb2O3 and Ni modified Sb2O3 (Ni–Sb2O3) nanospheres were synthesized using low cost co-precipitation method and characterised using various instrumental methods such as X-ray Powder Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FT-IR) spectroscopy. The XRD pattern reveals cubic crystal lattice. The average size of Sb2O3 and Ni–Sb2O3 nanoparticles was calculated to be around 41 nm and 29 nm, respectively. The HR-TEM investigation of the Sb2O3 nanomaterial reveals homogeneous spherical balls with a fine dispersion. The random-shaped nanoparticles with porous surfaces and voids were revealed by SEM. EDS examination confirms the elemental composition of Sb (41.79 %) and O (58.21 %) in Sb2O3 and Sb (36.80 %), O (58.95 %), and Ni (4.25 %) in Ni–Sb2O3. Sb2O3 and Ni– Sb2O3 exhibit band gaps of 3.67 eV and 3.51 eV, respectively, according to UV–Vis analysis. The IR peaks 445.47, 642.18, and 745.18 in Sb2O3 and 438.72, 645.07, and 756.92 in Ni– Sb2O3 support the Sb–O bonding in the synthesized nanomaterials. The synthesized nanomaterials have been used for photocatalytic degradation of malachite green (MG) dye and sensing NO2, SO2, CO2, petroleum vapour and LPG gases. The MG dye was degraded 97.67 % in 120 min using Ni–Sb2O3 at optimized conditions (catalyst dose: 0.1 g/L to 0.3 g/L, pH: 7 and MG dye: 10 ppm). The gas sensing study showed that Ni–Sb2O3 sensor has greater sensitivity and selectivity for NO2 gas.

Shrinkage reduction mechanism of low Ca/Si ratio C-A-S-H in cement pastes containing fly ash

Understanding the drying shrinkage of low Ca/Si ratio cement pastes is crucial for promoting the use of low-clinker ratio cementitious materials and reducing the environmental impact of cement production. We prepared well-hydrated cement paste samples with various fly ash replacement and water-to-cement ratios. The long-term drying shrinkage was measured by 1 mm-thick samples. Results showed that fly ash containing samples exhibited lower shrinkage and the irreversible part of drying shrinkage was less compared to those without fly ash. Chemical composition analysis of the calcium aluminate-silicates hydrate (C-A-S-H) was conducted using X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). Additionally, water vapor sorption isotherms and proton nuclear magnetic resonance (1H NMR) relaxometry were used to determine specific surface area and pore structure. By analyzing these results in conjunction with the C-A-S-H model, we attributed the reduced and more reversible drying shrinkage in fly ash cement to lower Ca ion amounts in the interlayer space and fewer trapped larger pores.