Amount Of Micropores Research Articles

Modeling of moisture content during baking with different approaches for effective diffusivity and evaluation of quality variables in baked potato slices.

Baking is a healthier alternative to frying, since texture, color, smell, and flavor are developed, without adding oil. The objective was to estimate the moisture content in potato slices, during baking using Fick's law of diffusion to model internal moisture transport and to assess the impact on quality attributes. Moisture transport kinetics were examined at three baking temperatures of 120, 130, and 140°C. Fick's law was employed to estimate average moisture content using different methods: considering both a constant (method of slopes by subperiods, MSS; and method of successive approximations, MSA) and a variable (represented as a quadratic function of time, QFT) behavior of effective diffusivity (De). Three quality variables were analyzed: water activity (aw, dew point hygrometry), total color difference (∆E, colorimetry), and fracturability (F, universal testing machine). The diffusivity estimated with the time-varying De method provided a more realistic description of moisture migration during baking. The aw, ∆E, and F for baked potato slices ranged from 0.234 to 0.276, 17.9 to 24.6, and 5.20 to 5.49 N, respectively. These attributes imply improved stability and extended shelf life, showing typical colors and texture changes for baked snacks. These changes are linked to variations in diffusivity, influenced by the size and quantity of micropores within the food structure. This study could allow an accurate prediction of mass transfer by considering variable De, facilitating the optimization of baking conditions. PRACTICAL APPLICATION: The analysis of the moisture content using Fick's law, considering a time-varying diffusivity, enables the optimization of the baking process for foods. This helps minimize the occurrence of defective products.

Direct aging treatment of TiN modified Al–Mn–Sc alloy processed by laser powder bed fusion: On the microstructure evolution and mechanical property enhancement

In this study, the TiN nanoparticles modified Al–Mn-Sc composite and Al–Mn-Sc alloy have been fabricated by the laser powder bed fusion (LPBF). The microstructure, mechanical properties and strengthening mechanisms of these materials were discussed in details for both the as-built and artificial aged conditions. The results showed that the aged Al–Mn-Sc/TiN composite exhibits homogeneous nucleation with equiaxed grains ranging from 0.81 μm to 1.30 μm. After direct aging treatment of 300 °C, there are a volume fraction of secondary L12-Al3(Ti, Sc, Zr) nanoparticles precipitated in the composite sample, contributing to an ultra-high fracture strength of 701 ± 16 MPa. The increment in strength brought by TiN mainly comes from fine grains and high volume fraction of L12-Al3(Ti, Sc, Zr) nanoprecipitates. The fracture behaviors suggest that the uniform distribution of reinforced particles and less amount of micro pores can improve the strength and ductility of LPBF particle reinforced aluminum matrix composites.

Production of activated carbons from Quercus cerris acorn shell under various experiment conditions, and their characterizations

Due to the high porosities, large surface areas, insolubilities in solutions, and unique structural and morphological structures, porous materials are utilized in various application areas such as energy conversion and storage, wastewater treatment, adsorption, catalysis and photocatalysis. In this study, activated carbons (QCACs), one type of porous materials, were synthesized from Quercus cerris acorn shells by using ZnCl2 chemical activation under various production conditions. The effects of carbonization temperature, carbonization period, and impregnation ratios on the yields, surface areas, pore developments, and N2 adsorption–desorption isotherms of activated carbons obtained were investigated in detail. The highest surface area (1751.61 m2/g) was reached when utilized at the impregnation ratio of 2.0 at 500 ℃ for 90 min. The total pore volume of QCAC increased with increasing impregnation ratio, however the micropore volume of QCAC reduced. It was found from the pore distribution data that QCACs contained mostly narrow mesopores and a little amount of micropores. Also, N2 adsorption–desorption isotherm data revealed that QCACs produced under different conditions were usually mesopore structures, and the pores were narrow slit-shaped. Moreover, the data provided from SEM, FTIR, Boehm titration, and elemental analysis gave more characterization information about QCACs synthesized.

Facile synthesis of porous TiO2/SnO2 nanocomposite as lithium ion battery anode with enhanced cycling stability via nanoconfinement effect

SnO2 is a potential anode material with high theoretical capacity for lithium-ion batteries (LIBs), however, its applications have been limited by the severe volume expansion during charging-discharging process. In this work, an inverse opal TiO2/SnO2 composite with an interconnect network nanostructure was designed to confine SnO2 nanoparticles in the porous TiO2. Due to this nanoconfinement structure, the volume expansion in the process was effectively alleviated, therefore the safety performance and cycling stability of the battery were effectively improved. At the same time, with a large number of microporous structures in the framework, the appearance of pseudocapacitance improves the rate performance and reversible capacity. In terms of electrochemical kinetics, its framework provides the connected path for charge migration, effectively reducing the charge transfer impedance, meanwhile, quantities of micropores in its skeleton could provide a smoother channel for lithium ions, thus greatly improving the diffusion rate of LIBs. The design of this nanostructure provides a new idea for the research of SnO2-based anode with effectively enhanced electrochemical performance, which is promising anode for practical application.

Local Electrochemical Corrosion of 6061 Aluminum Alloy with Nano-SiO2/MAO Composite Coating.

To improve the corrosion resistance of 6061 Al in electric vehicle battery packs, a composite coating of nano-SiO2/Micro-Arc oxidation (MAO) ceramic structure was prepared on its surface. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves (PDP) were used to evaluate the corrosion resistance of the specimens after 7 days immersion in a 3.5% NaCl solution. The corrosion resistance of the prefabricated coatings was measured via local electrochemical impedance spectroscopy (LEIS). Confocal microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterize the microstructure and phase composition of the specimens. An energy dispersive spectrometer (EDS) was used to detect the elemental composition of the surface of the specimen. The results showed that the specimen with nano-SiO2/MAO composite coating had the least amount of micropores and superior corrosion resistance. The global electrochemical impedance of nano-SiO2/MAO composite coating was 1.1 times higher than that of the MAO coating and 8.4 times higher than that of the 6061 Al. When the coating was defective, the local electrochemical impedance of the nano-SiO2/MAO composite coating was still two times higher than that of the MAO coating. In the presence of scratches, the nano-SiO2/MAO composite coating still showed high corrosion resistance. The collapse corrosion mechanism of the nano-SiO2/MAO composite coating was proposed.

Carbon neutral via catalytic transformation of CO2 into cyclic carbonates by an imidazolium-based ionic zeolitic imidazolate frameworks

On the way toward a carbon–neutral future, anthropogenic chemical recycling of captured carbon dioxide (CO2) into value-added chemicals and reusable materials provides an attractive and promising pathway. A multifunctional zeolitic imidazolate framework (ZIF-9-ImBr) consisting of electrophilic cobalt ions, CO2-philic nitrogen-rich units and nucleophilic imidazolium-based ionic liquids (ILs) was synthesized by simple substitution reaction of amino-functionalized ZIF (ZIF-9-NH2) with 1-(4-bromobutyl)-3-methylimidazolium bromide ([BrBMIM]Br). The obtained ZIF-9-ImBr was employed as heterogeneous catalyst for the solvent-free synthesis of cyclic carbonates from CO2 and epoxides in the absence of any cocatalyst. A certain amount of micropores and abundant nitrogen atoms could facilitate CO2 enrichment and its activation, while the mesopores could enhance the mass transfer of reactant and product molecules. Moreover, the synergistic effect between Lewis-acid cobalt and Lewis-base bromine ions of ZIF-9-ImBr made it promising in the CO2 cycloaddition reaction. As expected, ZIF-9-ImBr displayed good catalytic performance of 93.8 % yield and 98.9 % selectivity of propylene carbonate at 120 °C and 2.0 MPa for 3.5 h. Additionally, the reactions proceeded with a broad substrate scope and high selectivity to give the corresponding cyclic carbonates in good to excellent yields (77.9–95.8 %). Even for the challenging internal epoxide, cyclohexene oxide, a satisfactory 71.4 % yield was obtained by extending the reaction time to 24 h. More importantly, ZIF-9-ImBr can be easily recycled and maintains its reactivity and selectivity after five successive cycles. This work highlights the potential of functional ZIF-based materials for targeting CO2 capture and conversion.

Structure, defect substructure and fracture surface of low-carbon alloy steel welds

By the methods of scanning and transmission electron microscopy a structural phase state, defect substructure and fracture surface of low carbon alloy steel welds produced with use of carbon-containing addition and without it are investigated. The study of etched metallographic section structure of welds revealed a presence of a large amount of second phase particles (carbides, sulfides, oxides, etc.). It is shown that in weld with a carbon-containing addition the particles locate chaotically, and in weld without addition they decorate boundaries of ferrite grains. Dimensions of second phase particles vary in the limits from 0.8 μm to 5 μm and are identical for both types of welds. Analysis of fracture surface structure of welds is carried out. A presence of nonmetallic inclusions is detected. They are typical of mainly weld produced without a carbon-containing addition which may indicate its increased brittleness. Amount of micropores in fracture of weld with carbon-containing addition is many times greater than that in weld without addition, which is indicative of gas removal in use of carbon-containing addition. The quantitative analysis of structure and dislocation substructure parameters of weld metal is carried out, the estimates of contributions of scalar and excess dislocation density to strength of welds are performed. It is shown that higher values of scalar and excess dislocation density in the weld formed without carbon-containing addition in flux may be responsible for material embrittlement. A large quantity of stress concentrators in the weld without carbon-containing addition may result in material embrittlement.

Precisely design PPh3-based polymer by hybrid coupling of monomers for high efficient hydroformylation

A series of hybrid coupling porous organic polymers (HC-3vPPh3-POLs) were designed and synthesized through copolymerizing any two of tris(4-vinphenyl) phosphine (p-3vPPh3), tris(3-vinphenyl) phosphine (m-3vPPh3) and tris(2-vinphenyl) phosphine (o-3vPPh3) in different proportions by solvothermal polymerization. The BET surface area of obtained HC-3vPPh3-POLs is varied from 534 to 1124 m2‧g−1 while the pore volume is changed from 0.43 to 2.25 cm3‧g−1, and the amount of micropores could also be regulated from 43.5 to 66.8%. The afforded Rh/HC-3vPPh3-POLs exhibit different conversions from 91% to 98%, selectivity to aldehyde from 79% to 90%, and the 1/b ratios from 4.0 to 11.1 (the ratio of the linear aldehydes to the branched aldehydes) by adjusting the PPh3 microenvironment and their quantities. The superior recyclability in an autoclave reactor and stability in a fixed-bed reactor of Rh/HC-3vPPh3-POLs demonstrate the excellent potential of this method in preparing functional materials for heterogeneous catalysis. Combined characterization methods were employed and demonstrated that P atoms from different vinyl functional PPh3 were uniformly dispersed and interacted with each other, leading to different structure and PPh3 microenvironment in HC-3vPPh3-POLs.

Biochar Amended Soils and Water Systems: Investigation of Physical and Structural Properties

There are significant regional differences in the perception of the problems posed by global warming, water/food availability and waste treatment recycling procedures. The study illustrates the effect of application of a biochar (BC) from forest biomass waste, at a selected application rate, on water retention, plant available water (PAW), and structural properties of differently standard textured soils, classified as loamy sand, loam and clay. The results showed that soil water retention, PAW, and aggregate stability were significantly improved by BC application in the loamy sand, confirming that application of BC to this soil was certainly beneficial and increased the amount of macropores, storage pores and residual pores. In the loam, BC partially improved water retention, increasing macroporosity, but decreased the amount of micropores and improved aggregate stability and did not significantly increase the amount of PAW. In the clay, the amount of PAW was increased by BC, but water retention and aggregate stability were not improved by BC amendment. Results of the BET analysis indicated that the specific surface area (BET-SSA) increased in the three soils after BC application, showing a tendency of the BET-SSA to increase at increasing PAW. The results obtained indicated that the effects of BC application on the physical and structural properties of the three considered soils were different depending on the different soil textures with a BET-SSA increase of 950%, 489%, 156% for loamy sand, loam and clay soil respectively. The importance of analysing the effects of BC on soil water retention and PAW in terms of volumetric water contents, and not only in terms of gravimetric values, was also evidenced.

Synthesis and formation mechanism analysis of meso‐microporous ZSM‐5 with controllable mesoporous volume

AbstractBACKGROUNDZSM‐5 molecular sieve has an important application value in industrial adsorption. Due to the existence of micropores, it is hard for larger molecules to enter the ZSM‐5 molecular sieve. Meso‐microporous MFI zeolite was prepared by hydrothermal crystallization regarding the organosilane as the structure‐directing agent. Then the samples were characterized by X‐ray diffraction, infrared spectroscopy and so on. The effect of organosilane on mesoporous volume and the mechanism of mesoporous formation were further investigated. Finally the performance of adsorption for volatile organic compounds (VOCs) on meso‐microporous ZSM‐5 were analyzed by static adsorption and dynamic adsorption experiments.RESULTSThe meso‐microporous ZSM‐5, which were prepared with the organosilanes, contained not only large and uniform mesopores but also certain amounts of micropores. The results of N2 physisorption showed that the meso‐microporous ZSM‐5 obtained by propyl trimethoxy silane had the highest specific surface area (438.19 m2 g−1) and mesoporous volume (0.15 cm3 g−1). When the molar ratio of SiO2: octyl trimethoxy silane was 1: 0.1, the specific surface area (508.03 m2 g−1) and mesoporous volume (0.23 cm3 g−1) of the O‐ZSM‐5 were maximum. Compared with traditional ZSM‐5, the toluene adsorption performance of meso‐microporous ZSM‐5 had been effectively improved.CONCLUSIONThis research focused on offering the simple and high efficiency meso‐ microporous ZSM‐5 synthetic routes. The newly intercrystalline mesoporosity in ZSM‐5 zeolite showed a controllable mesoporous channel, which was better than traditional ZSM‐5. The prepared molecular sieve was a promising adsorption material for the volatile organic compounds. © 2021 Society of Chemical Industry (SCI).

The selection of outgas temperature for shale in low-pressure N2 adsorption: An evidence from thermogravimetry

Low-pressure N2 adsorption (LPNA) could provide quantitative data for characterizing the pores in gas shale. However, the inconsistencies of outgas temperature have caused significant deviations in LPNA experiments. To explore the effects of outgas temperature on pore characteristics, two shale samples of Lower Cambrian Niutitang formation from Northern Guizhou, China, were collected for LPNA experiments and thermogravimetry-fourier transform infrared (TG-FTIR) spectroscopy. The samples were outgassed at six temperatures: 80°C, 100°C, 150°C, 200°C, 250°C, 300°C. Larger adsorbed volumes were presented in the isotherms at higher outgas temperatures. Similar regularity is obtained from the relationship between specific surface area, micropore volume and outgas temperature. Comprehensive analysis of TG-FTIR and LPNA at different outgas temperature indicated that at lower outgas temperatures (from 80°C to 100°C), the free water was unlikely to be removed completely, and resulted in large amounts of micropores couldn’t be accessed. An excessive outgas temperature might expulse liquid hydrocarbons or decompose organic matter (from 200°C to 300°C), and could lead to the generation of micropores. When the sample were outgassed at 150°C, TG-FTIR analysis indicated that the sample composition unchanged and a better removal of free water happened. Therefore, 150°C should be a suitable outgas temperature for shale in LPNA experiments. The findings in this research not only provide reliable evidence for the selection of outgas procedure in LPNA for shale, but clarify the important effects of free water and volatile materials on pore accessibility in shale.

Effect of solution treatment on micropore and mechanical properties of DD6 superalloy

Effect of solution treatment on the micropore and mechanical properties is investigated for the DD6 superalloy. The results show that solution treatment has positive and negative effects on the DD6 superalloy, which can weaken the segregation significantly. After solution treatment, the segregation ratio of the major alloying elements tends to 1. However, the amount of micropores increases with increasing solutionising time and can reach 0.46%, which is one order of magnitude higher than that of the as-cast superalloy. The hardness increases slightly, especially for the superalloy solutionised at 1310°C with a 5% increase in hardness compared to the as-cast superalloy. Hardness, tensile and stress rupture properties of the DD6 superalloy can reach the best after solution treatment at 1310°C and 4 h.

Sintering Behavior and Fracture Morphology of NiFe2O4/Nano-TiN Ceramics Synthesized under Argon Atmosphere

NiFe2O4/nano-TiN ceramics were synthesized by a two-step cold-pressing sintering process. Sintering behavior, fracture morphology, mechanical performance and high-temperature conductivity were investigated. The results indicated that besides NiO and NiFe2O4, new Ni3TiO5 and metallic phases (iron and nickel) formed in the sintered samples. TiN accelerated the grain growth along with considerable quantity of micro-pores in the sintered samples. Compared to the un-doped samples, the temperature for the onset of sintering of the NiO-Fe2O3-2.0 wt.% TiN system decreased from 1093 to 985 °C. TiN addition changed the sintering mechanism of the NiO-Fe2O3 from grain boundary diffusion to volume diffusion. TiN additions reduce the apparent sintering activation energy and porosities and improve the density, bending strength, and pyroconductivity. Three-dimensional fracture morphology of the composite ceramics synthesized under argon atmosphere, exhibits self-similarity characteristics and the fractal dimension for NiFe2O4-1.0 wt.% TiN ceramics is 2.0813.

Effects of silica fume on physicochemical properties and piezoresistivity of intelligent carbon black-cementitious composites

Carbon black (CB) filled cementitious composites as cement-based sensors with intrinsic piezoresistivity have the potential applications for structural health monitoring (SHM). Effect of silica fume (SF) replacement ratio on the physicochemical, mechanical and piezoresistive properties, and microstructure of CB-cementitious composite were experimentally investigated in this study. The results show that 5% or 10% replacement ratio of SF can improve the water impermeability, setting time and electrical conductivity, but decrease the fresh flowability. Cementitious composite with 10% SF exhibiteds excellent compressive and flexural strengths. Moreover, cement hydration in the acceleration stage decreased with the increase of SF content in the early stage, but the phase analysis after 28 days curing demonstrates that with the addition of SF, there are more hydrated products and less ettringite. In addition, the microstructures of cementitious composites without SF present more porous structures and CB agglomerations. In contrast, the amount of micropores or voids was significantly reduced by the addition of SF due to the physical filling effect and less CB agglomerations. In terms of piezoresistivity, SF can obviously improve the fractional changes of resistivity (FCR) under cyclic compression. With 10% SF, CB-cementitious composites as cement-based sensors exhibited excellent FCR and electrical stability, which will promote their development and application in the SHM for smart infrastructures.

Microstructure Analysis and Strength Characterization of Recycled Base and Sub-Base Materials Using Scanning Electron Microscope

The reuse of recycled crushed concrete aggregate (RCCA) and reclaimed asphalt pavement (RAP) can provide a sustainable solution for the disposal of C&D waste materials instead of sending them to landfills. More importantly, it will conserve energy and reduce environmental concerns. Several states in the USA have been using RCCA and RAP as base materials for years, focusing on the quality of the recycled materials. The structure of Recycled Aggregate (RA) is more complex than that of Natural Aggregate (NA). RAs have old mortar adhered on them that forms a porous surface at the interfacial transition Zone (ITZ) and prevents new cement mix from bonding strongly with the aggregates. The objective of this study was to correlate microstructural properties such as microporosity, inter and intra aggregate pores with the unconfined compressive strength (UCS) of RAP and RCCA molds, mixed at different proportions. In this paper, the quantity of micropores and their effect on the strength of mixed materials is used as the basis of microstructural analysis of recycled concrete and reclaimed asphalt. Microstructural properties obtained from analyzing scanning electron microscope (SEM) images were correlated with unconfined compressive strength. Intra-aggregate and interaggregate pores were studied for different ratios of cement treated mixture of RAP and RCCA. The results show that addition of RAP considerably increases the number of pores in the mixture, which eventually causes reduction in unconfined compressive strength. In addition, significant morphological and textural changes of recycled aggregates were observed by SEM image analysis.

Improving plasma sprayed Raney-type nickel\u2013molybdenum electrodes towards high-performance hydrogen evolution in alkaline medium

Rationally designed free-standing and binder-free Raney-type nickel–molybdenum (Ni–Mo) electrodes produced via atmospheric plasma spraying (APS) are developed by correlating APS process parameters with the microstructure of electrodes and their electrochemical performance in alkaline media. The results revealed that the electrode morphology and elemental composition are highly affected by the plasma parameters during the electrode fabrication. It is found that increasing plasma gas flow rate and input plasma power resulted in higher in-flight particle velocities and shorter dwell time, which in result delivered electrodes with much finer structure exhibiting homogeneous distribution of phases, larger quantity of micro pores and suitable content of Ni and Mo. Tafel slope of electrodes decreased with increasing the in-flight particles velocities from 71 to 33 mV dec−1 in 30 wt.% KOH. However, beyond a critical threshold in-flight velocity and temperature of particles, electrodes started to exhibit larger globular pores and consequently reduced catalytic performance and higher Tafel slop of 36 mV dec−1 in 30 wt.% KOH. Despite slightly lower electrochemical performance, the electrodes produced with highest plasma gas flow and energy showed most inter-particle bonded structure as well as highest stability with no measurable degradation over 47 days in operation as HER electrode in 30 wt.% KOH. The Raney-type Ni–Mo electrode fabricated at highest plasma gas flow rate and input plasma power has been tested as HER electrode in alkaline water electrolyzer, which delivered high current densities of 0.72 and 2 A cm−2 at 1.8 and 2.2 V, respectively, representing a novel prime example of HER electrode, which can synergistically catalyze the HER in alkaline electrolyzer. This study shows that sluggish alkaline HER can be circumvented by rational electrode composition and interface engineering.

Soil Water Retention Curves for Residual Soils Using Traditional Methods and MIP

This paper presents the pore size distribution and the soil water retention curves (SWRC) for an undisturbed residual soil obtained using traditional methods and using mercury intrusion porosimeter (MIP). The specimens were obtained from two residual soil profiles of the Serra do Mar, SP, Brazil. The results obtained allowed the evaluation of the pore size distribution along the soil profile and its relation to the water retention characteristics of the soil profile. The SWRC obtained using traditional methods, such as suction plate, pressure plate and filter paper method, is compared with the soil water retention curve inferred from the MIP. The results indicated that the amount of meso and macropores tends to increase with depth, while the amount of micropores tends to decrease. The comparison between the SWRC obtained using the MIP technique and the traditional procedures suggested that the former overestimates the water retention capacity for lower suctions.

Evaluation of the Presence of Methane in Z\u0142oczew Lignite: Comparison with Other Lignite Deposits in Poland

Catastrophic cases of methane explosion during exploratory drilling within the Bełchatów ortholignite deposit have led to testing for methane in other Polish ortholignite mining areas, as well as in the Złoczew deposit, where it is planned to begin mining operations. Initial tests have shown Złoczew lignite to have the highest methane content among the Polish deposits so far studied, comparable with lignite from the Bełchatów deposit, with a methane capacity in excess of 2.5 dcm3/kg at a pressure of 10 bar. Based on the computed values of the Langmuir constant, a determination was made of the quantity of methane that can be desorbed from a pressure of 10 bar to 1 bar, as well as the residual methane content. For all of the tested samples, the residual methane content is between 30 and 50% of the sorption capacity at a pressure of 10 bar. The thermal sorption equations were used to compute values of the limiting isosteric heat of adsorption. Higher values of the heat of adsorption at zero surface capacity may indicate the presence of a small quantity of micro-pores. In the case of the samples with the highest sorption capacity, the limiting isosteric heats of adsorption are low, indicating a low proportion of micro-pores in the lignite. This was confirmed by tests of nitrogen adsorption at 77 K. The proportion of micro-pores in the studied lignites is 2–3%, while the dominant pore fraction is the meso-pores, which in lignite from the Złoczew and Bełchatów deposits account for 50–66% of total pores. It is concluded that the significant adsorption of methane in the ortholignite occurs chiefly in meso-pores because of compression of the gas under increased orogenic pressure. A link is made between the higher methane-bearing capacity of the ortholignite deposits and the degree of gelification of the huminite components, based on simple statistical correlations between the methane sorption capacity and the content of humic gelified maceral. The results concerning methane sorption in lignite from the Złoczew deposit have enabled a preliminary classification of the methane-bearing capacity of Polish ortholignite deposits, which may also be of significance for similar deposits in other countries.

Preparation and Catalytic Performance of Microporous Polymer/Au Nanoparticles Composite Microspheres

Polystyrene crosslinked microspheres were prepared by soap-free emulsion polymerization using styrene (St) and divinylbenzene (DVB) as monomers; then, the microporous structure was knitted by the Friedel-Crafts alkylation reaction, and the Au nanoparticles (AuNPs) were loaded into the pores through thermal reduction, to obtain AuNPs/hyper-crosslinked microporous polymer composite microspheres. SEM and particle-size test results show that the microspheres show good monodispersity. The micropore analysis indicates that the specific surface area and the pore volume of the microporous polymer microspheres decrease with increasing DVB content, and when the DVB content is 0.1%, the specific surface area reaches a maximum of 1 174.6 m2/g. After loading AuNPs, the specific surface area and the amount of micropores of the composite microspheres decrease obviously. The results of XRD and XPS analyses suggest that HAuCl4 is reduced to AuNPs. The composite microspheres show a good catalytic performance for the reduction catalyst of 4-nitrophenol.

Experimental investigation into non-collapsible loess-like soil's engineering geological properties under the influence of freeze–thaw cycles

Recurrent freeze–thaw cycling is a powerful weathering process that subjects soil to frost heave and thaw settlement. The cycling significantly changes the soil structure and leads to particle recombination, ultimately causing deterioration of the soil's properties. Herein, we investigated the effect of freeze–thaw cycles on loess-like soil in seasonally frozen regions; specifically with respect to the engineering geological properties, such as changes in grain-size distribution, liquid–plastic limit and collapse behaviour. The results indicate that over the course of 20 freeze–thaw cycles, the soil samples’ dry density decreased, the particle diameter of each soil fraction changed in a bi-directional manner (large particles were broken into finer sizes and fine particles agglomerated into larger particles), and the liquid limit and plasticity index first increased and then decreased. An increase in the initial water content resulted in more significant changes. In contrast to the undisturbed soil samples, the freeze–thaw cycles caused non-collapsible remoulded loess-like soil to collapse. Furthermore, microscopic evaluation allowed us to determine the collapse mechanism. Essentially, after the freeze–thaw cycles, the quantity of micropores in the soil decreased, whereas that of medium pores and macropores significantly increased. In addition, a trellis structure, similar to the typical loess structure, was generated.