Decreasing Pore Diameter Research Articles

The Role of Spacer Length in Macrocyclization Reactions Under Confinement

We studied the influence of the distance of olefin metathesis catalysts from the inner surface of a mesoporous support on macrocyclization and Z‐selectivity under confinement. For these purposes, the cationic molybdenum imido alkylidene N‐heterocyclic carbene (NHC) catalysts [Mo(N‐(2‐tBu‐C6H4)(1‐mesityl‐3‐(3‐trimethoxysilylprop‐1‐yl)‐imidazol‐2‐ylidene)(CHCMe2Ph)(MeCN)Br+ B(ArF)4‐] Mo2, [Mo(N‐(2‐tBu‐C6H4)(1‐mesityl‐3‐(3‐trimethoxysilylprop‐1‐yl)‐imidazol‐2‐ylidene)(CHCMe2Ph)(MeCN)OTf+ B(ArF)4‐] Mo3, [Mo(N‐(2,6‐Me2‐C6H3)(1‐mesityl‐3‐(3‐trimethoxysilylprop‐1‐yl)‐imidazol‐2‐ylidene)(CHCMe2Ph)(MeCN)Br+ B(ArF)4‐] Mo5 and [Mo(N‐(2,6‐iPr2‐C6H3)(1‐mesityl‐3‐(3‐trimethoxysilylprop‐1‐yl)‐imidazol‐2‐ylidene)(CHCMe2Ph)(MeCN)+Br B(ArF)4‐] Mo7 (B(ArF)4 = tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate), all containing a trimethoxysilylpropyl tether, were selectively immobilized inside the mesopores of SBA‐15. Under confinement, both macro(mono)cyclization (MMC) and Z‐selectivity were higher than in solution but lower than with catalysts directly bound to the surface of the mesoporous supports. These findings are in agreement with existing theoretical models on substrate and product distribution in mesopores, which suggest that the highest substrate concentration is found at the pore wall and that it increases with decreasing pore diameter.

Influence of in-situ lunar temperature on the pore structure and solid phases of alkali-activated lunar regolith simulant

The construction of extraterrestrial bases has become an indispensable step in the active exploration of deep space. In this study, alkali-activated lunar regolith simulant (AALRS) activated by sodium hydroxide (SH) and sodium silicate (SS) were prepared and then cured at various lunar temperatures. The compressive strength was tested, and the pore structure characteristics were characterized using mercury intrusion porosimetry (MIP), followed by further in-depth quantitative analysis through fractal theory. The solid phases were characterized using thermogravimetry analysis (TGA) and scanning electron microscopy (SEM). It is found that all the fractal curves are divided into three regions, and the fractal dimensions in all regions are between 2 and 3, suggesting the pores of AALRS paste always have self-similar physical significance. The fractal dimension D1 of the small pore is the largest, followed by fractal dimension D3 of the great pore and fractal dimension D2 of the middle pore. The increase in modulus and temperature leads to an increase in the pore surface area, fractal dimension, amount of N-A-S-H gel and compressive strength and a decrease in total pore volume and characteristic pore diameter, which is mainly attributed to the nucleation effect of soluble Si. The turning pore diameter at the micrometer scale and excessive porosity of AALRS paste, which is distinctly different from that of common cementitious materials, demonstrates looser pore structure of AALRS paste. Based on these results, the influence mechanism of in-situ lunar temperature on the performance of AALRS paste is profoundly discussed and elucidated, which provides a deep understanding of designing and tailoring the various properties of AALRS material.

Synergy of functionalized activated carbon and ZnO nanoparticles for enhancing photocatalytic degradation of methylene blue and carbaryl

This study proposes preparing ZnO and ZnO/activated carbon (AC) for photocatalytic applications. ZnO and AC were synthesized using precipitation and carbonization processes, respectively. Particle sizes of ZnO and ZnO/AC were estimated at 121–135 nm. The crystalline structure analysis confirmed the presence of hexagonal wurtzite structures in ZnO. Microcrystalline graphite and amorphous carbon structures were observed in AC. The combination of these characteristics was observed in ZnO/AC. ZnO/AC exhibited an increase in surface area from 25.36 to 29.86 m2/g and a decrease in pore diameter from 5.66 to 4.31 nm. The chemical states of ZnO and AC remained unchanged. Therefore, the nanocompound structure of ZnO/AC can be inferred. The ZnO/AC nanocompounds were then employed to degrade methylene blue (MB) dye and carbaryl (CBR) insecticide, demonstrating excellent photocatalytic performance compared to pure ZnO. The apparent degradation rate constant reached an average value of 3.49 × 10−3 and 16.25 × 10−3 min−1 for MB and CBR, respectively. AC functions as carrier collectors in the ZnO/AC nanocompound structures due to the suitable energy band level for facilitating electron and hole transfers. This results in recombination suppression and prolonged lifetime, thus enhancing photocatalytic activity. The finding suggests the potential use of ZnO/AC nanocompounds to degrade agricultural chemicals in contaminated natural water under sunlight.

Effects of Micro- and Nanosilica on the Mechanical and Microstructural Characteristics of Some Special Mortars Made with Recycled Concrete Aggregates.

In this paper, we study the influence of densified microsilica and colloidal nanosilica admixtures on the mechanical strength and the microstructural characteristics of special mortars used for immobilizing radioactive concrete waste. The experimental program focused on the replacement of cement with micro- and/or nanosilica, in different proportions, in the basic composition of a mortar made with recycled aggregates. The technical criteria imposed for such cementitious systems, used for the encapsulation of low-level radioactive waste, imply high fluidity, increased mechanical strength and lack of segregation and of bleeding. We aimed to increase the structural compactness of the mortars by adding micro- and nanosilica, all the while maintaining the technical criteria imposed, to obtain a cement matrix with high durability and increased capacity for immobilizing radionuclides. The samples from all the compositions obtained were analyzed from the point of view of mechanical strength. Also, micro- and nanosilica as well as samples of the optimal mortar compositions were analyzed physically and microstructurally. Experimental data showed that the mortar samples present maximum compressive strength for a content between 6 and 7.5% wt. of microsilica, respectively, for a content of 2.25% wt. nanosilica. The obtained results suggest a synergistic effect of micro- and nanosilica when they are used simultaneously in cementitious compositions. Thus, among the analyzed compositional variants, the mortar composition with 3% wt. microsilica and 2.25% wt. nanosilica showed the best performance, with an increase in compressive strength of 23.5% compared to the control sample (without micro- and nanosilica). Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM) images highlighted the decrease in pore diameter and the increase in structural compactness, especially for mortar samples with nanosilica content or a mixture of micro- and nanosilica. This study is useful in the field of recycling radioactive concrete resulting from the decommissioning of nuclear research or nuclear power reactors.

Effects of synthesis conditions on particle size and pore size of spherical mesoporous silica

The particle size and pore size of spherical mesoporous silica materials play significant roles in their application. However, relatively limited systematic research has been conducted on how preparation conditions influence these properties. In particular, the effects of some important factors have not been adequately studied, including reaction time, reaction temperature, and organic solvent type. In this work, octane and water were used as solvents, and tetraethyl orthosilicate was used as the silicon source to systematically study the effects of reaction time, reaction temperature, different organic solvents, octane/water mass ratio, styrene template concentration, and surfactant (cetyltrimethylammonium bromide, CTAB)/H2O mass ratio on the particle morphology, particle size, and pore size of silica. The results suggest that the above-mentioned neglected factors exert a substantial influence on both particle size and pore size. In the experimental temperature range, the pore diameter decreases and the particle size increases with increasing temperature. The maximum particle size and pore size are achieved after a reaction time of 3 h, and a further increase in reaction time leads to a smaller particle size and pore size. As the number of carbon atoms in the organic solvent decreases, the pore size also gradually increases. Styrene and organic solvents that dissolve in CTAB micelles are crucial factors in pore formation, while the aggregation of the swollen CTAB micelles influences the particle size. The changes in the pore structure stability and hydroxyl density of the synthesized samples in water were also studied. After undergoing water treatment at temperatures ranging from 20 to 60 °C for 72 h, both the pore structure and morphology remain relatively unchanged. When the temperature increases, the surface hydroxyl density exhibits a more pronounced increase in the presence of water. After water treatment for 5 h, the surface hydroxyl density reaches saturation.

Experimental study and numerical simulation on porosity dependent direct reducibility of high-grade iron oxide pellets in hydrogen

The transition to more environmentally friendly steel production methods has intensified research into hydrogen-based direct reduction (HyDR) of iron oxide pellets. The aim of this study is to systematically investigate the kinetics of the reduction process, the evolution of porosity and the resulting microstructural changes on the reduction behavior of high-quality pellets during HyDR of iron ore at different temperatures. A modified mathematical model is developed based on the shrinkage kernel model, taking into account both mass and heat transport in a hydrogen atmosphere. The effects of temperature, particle size and time on the reduction behavior of the pellets are investigated. The simulated results are validated and discussed by the results of a batch of iron oxide pellets consisting of ten almost spherical pellets subjected to the direct reduction process with pure hydrogen. The results show that the total energy input to the HyDR process is a complex balance of factors, including chemical reaction rates, diffusion dynamics and entropy generation. The increase in free volume and simultaneous decrease in pore diameter reflect the dynamic nature of the microstructure, which includes additional free volume and defects due to the volume discrepancies and associated stresses between the reactant and product phases. Furthermore, the data show that higher temperatures accelerate the reduction reactions, especially the transformation of wustite into metallic iron. This phase transition is characterized by a significant volume change that cannot be accommodated by elastic deformation alone, leading to the development of lattice defects such as cracks, creep pores and dislocations that serve as stress relief mechanisms. The trends for porosity change at 950 °C and 1000 °C observed in the experimental results are correct and in good agreement with the numerical and simulated results.

Periodical alternation between precipitation and dissolution of camphor solid film on an ethanol solution.

Rhythmic behaviors are generally observed in nonlinear chemical reactions such as the Belousov-Zhabotinsky reaction and enzymatic reactions. Similarly, a simple phase change can also lead to rhythmic behavior. It has been reported previously that camphor solid films alternate between generation and disappearance on ethanol (EtOH) solution, and a phenomenological mechanism has been suggested for this. The evaporation of EtOH decreases the temperature on the surface of the solution via vaporization heat and induces precipitation in the camphor solid film. At this time, the film prevents evaporation, and thus, the surface temperature increases due to thermal diffusion from the atmosphere, resulting in dissolution of the solid film. To verify the previously suggested phenomenological mechanism, we controlled the evaporation rate of EtOH using a porous plastic cover. As a result, the period of oscillation increased with decreasing pore diameter, and finally, the oscillation did not occur without pore in the cover, where the camphor solid film was not observed. Additionally, a new mathematical model was proposed, and the numerical calculations agreed well with experimental observations. Linear stability and bifurcation analyses revealed the detailed mechanism of this phenomenon, which agreed well with the phenomenological explanation mentioned above.

Comparison of the effects of two biodegradable coatings on the characteristics of white-top linerboard used in packaging food materials in cold environments

Effects of two biodegradable coatings were compared relative to the characteristics of white-top linerboard. To coat the surface of the paperboard, nano-polyurethane was sprayed onto the surface using a nozzle. Subsequently, the samples were placed inside a refrigerator and freezer for a period of 2 and 4 months. In the second stage, nano-polyurethane was again sprayed onto the surface, using a nozzle, to improve the performance of the coating material. To further enhance the coating, the surfaces of the coated white-top linerboard were coated with a nanoclay using a laboratory coater. Subsequently, the samples were placed inside a refrigerator and freezer for a period of 2 and 4 months. The properties of the samples were measured thereafter. The results showed a reduction in water absorption of the samples after coating and freezing. This can be attributed to the penetration of the coating solution into the paper pores, resulting in a decrease in pore diameter and, consequently, a decrease in water permeability through the paper pores. In the coated and frozen samples, an increase in thickness and surface smoothness was observed, but most of the mechanical strength properties decreased. These changes were more pronounced in the dual-layer coatings.

Study on sound absorption valley and acoustic absorption performance of small-pore aluminum foam composited with 304 stainless steel fibers

Open-cell aluminum foam exhibits a sound absorption valley (SAV) in the 2500–4000 Hz frequency range, reducing its acoustic absorption in the range of 1000–6300 Hz. A small-pore aluminum foam composited with 304 stainless steel fibers (SP-SS304F aluminum foam) with a porosity of 82 % was fabricated via infiltration casting, and its pore structure, acoustic absorption performance, and mechanism were investigated. The pore structure of SP-SS304F aluminum foam consisted of 223–676 μm main pores, 125–373 μm cell wall pores, and 30–60 μm 304 stainless steel fibers. The fibers existed completely embedded in the cell walls, partially or completely embedded in the cell cavities. As the pore diameter decreases, the SAV value increases and then decreases. With increasing fiber content, the SAV value showed a similar trend. The increased SAV value benefits the enhancement of the average sound absorption coefficient (SAC). The SP-SS304F foam aluminum reaches an optimal SAC value of 0.899. Its static resistivity value is 24,345 Pa.s/m2. Finite element simulations reveal the reasons for the improved acoustic absorption performance of SP-SS304F aluminum foam: First, the small-diameter and pore-embedded fibers improve the acoustic impedance matching, reducing sound reflections at the SAV frequency. Second, the reduced pore diameters and partially or completely pore-embedded fibers increase the pore surface areas, intensifying the acoustic absorption by pore structure.

Assessment of the physicochemical properties of alkali-activated slag blended with belite-rich cement subjected to carbonation attack

The present study investigated the physicochemical transformation of alkali-activated slag (AAS) under CO2 exposure. The belite-rich cement (BRC) used as an additive up to 30 wt% of GGBFS and Ca(OH)2 was used for alkali activation. The threshold ratio of lime/slag and BRC/binder was 4.5% and 20%, respectively, for the improvement in strength and the physicochemical properties. The residual strength after CO2 exposure was higher for an AAS mix prepared with 30% BRC/binder and a 6% lime/slag ratio. Due to the additive (BRC) in AAS, the unreacted β-C2S and portlandite act as a buffer during CO2 exposure. The additional supply of Ca2+ ions provided via Ca(OH)2 contributed to promoting the reactivity of AAS. The decrease in critical pore diameter by 51.6% as the prepared AAS with the higher BRC/binder ratio was exposed to CO2 increased the solid-phase assemblage per unit volume, which also contributed to the physicochemical properties.

Enhancing energy carrier gas storage: Novel MOF-decorated carbons with high affinity toward methane and hydrogen

The low volumetric density of alternative energy sources, like methane and hydrogen, makes their efficient storage challenging. This issue hinders their widespread adoption as clean energy carriers and limits their potential to address the energy crisis and reduce CO2 emissions. To overcome this limitation, a novel hybrid adsorbent was synthesised by incorporating MIL-101(Cr) and pitch-based activated carbon (AC), and its potential for methane and hydrogen adsorption was evaluated through experimental and molecular simulation methods. The adsorption capacity of CH4 and H2 on the MOF-doped ACs was simulated using Grand Canonical Monte Carlo (GCMC). Through the ex-situ method, varying amounts of MIL-101(Cr) were integrated onto the surface of AC, resulting in a nanocomposite with enhanced gas uptake properties. The AC/MIL-101(Cr) nanocomposite with 50 wt% MOF-doping exhibited superior methane loading performance (12.21 mmol.g-1) at room temperature and 35 bar, surpassing MIL-101(Cr) by approximately 20% (10.15 mmol.g-1). In terms of hydrogen adsorption, the AC/MIL-101 composites demonstrated advantageous gas uptake at low pressures (P ≤ 4.5 bar) due to a decrease in pore diameter (2.17 nm to 1.61 nm) and an increase in the number of micropores (60% to 78%). Conversely, at higher pressures, the dominant factor influencing H2 storage was the surface area.

Effect of Anodizing Voltage and Tobacco Extract Addition on the Structure of Porous Anodic Aluminum Oxide (PAAO) Layer

Porous Anodic Aluminum oxide (PAAO) is a porous oxide layer resulting from anodization. The structure of PAAO is influenced by anodization parameters, i.e., voltage and electrolyte composition. Increasing anodization voltage can affect the process of pore formation and oxide growth during anodization. Adding additives such as ethanol, propanol, and polyethylene glycol (PEG) can increase pore regularity and affect the structure of PAAO. In this study, tobacco extract (TE) was added to the oxalic acid-based anodizing solution. TE has many active compounds that may affect pore formation and oxide growth. Morphological analysis shows decreased pore diameter when adding tobacco extracts with concentrations of 0, 0.1, and 0.5 g/L, namely 43.92, 41.42, and 37.8 nm at anodization voltage 40 V. In anodization with a voltage of 60 V, a decrease in pore diameter was obtained with 46.47, 34.24, and 26.8 nm for adding tobacco extract 0, 0.1, and 0.5 g/L. The thickness of PAAO increases from 6.45 µm to 16.87 µm with increasing anodization voltage and tobacco extract concentration. The increase of tobacco extract concentration can lead to the decrease of the XRD peak intensity, where the sequence of the most significant decrease was observed for the peaks of (111), (220), (200), and (311), respectively. A decrease in the intensity ratio of (111) and (220) AAO peaks indicates the influence of tobacco extract on the anodization process. Further thermal analysis by Thermo-gravimetric (TG) shows an increase in mass loss from 1.47 to 5.37% with increasing tobacco extract concentration from 0 g/L to 0.5 g/L. TG results indicate the incorporation of tobacco extract in the inner pore wall.

Confined bicontinuous microemulsions: nanoscale dynamics of the surfactant film.

A confined bicontinuous C10E4-D2O-n-octane microemulsion is studied using neutron spin echo spectroscopy (NSE). Controlled pore glasses serve as confining matrices with pore diameters ranging from 24 to 112 nm. Firstly, the microemulsion in bulk is investigated by NSE and dynamic light scattering, which allows the determination of the unperturbed collective dynamics as well as the observation of the undulation of the surfactant film. In confinement, it is observed that the collective modes are drastically slowed down in all investigated pore sizes. The undulations of the surfactant film in the largest pores are found to be comparable to those of the bulk and decrease with decreasing pore diameter. Fitting procedures of the intermediate scattering function revealed that the long wavelength undulations are cut off from the spectrum of fluctuation modes due to the interactions with the pore walls.

Multi-Stage Transcriptome Analysis Revealed the Growth Mechanism of Feathers and Hair Follicles during Induction Molting by Fasting in the Late Stage of Egg Laying.

Induced molting is a common method to obtain a new life in laying hens, in which periodic changes in feathers are the prominent feature. Nevertheless, its precise molecular mechanism remains unclear. In this study, feather and hair follicle samples were collected during fasting-induced physiological remodeling for hematoxylin-eosin staining, hormone changes and follicle traits, and transcriptome sequencing. Feather shedding was observed in F13 to R25, while newborns were observed in R3 to R32. Triiodothyronine and tetraiodothyronine were significantly elevated during feather shedding. The calcium content was significantly higher, and the ash content was significantly lower after the changeover. The determination of hair follicle traits revealed an increasing trend in pore density and a decrease in pore diameter after the resumption of feeding. According to RNA-seq results, several core genes were identified, including DSP, CDH1, PKP1, and PPCKB, which may have an impact on hair follicle growth. The focus was to discover that starvation may trigger changes in thyroid hormones, which in turn regulate feather molting through thyroid hormone synthesis, calcium signaling, and thyroid hormone signaling pathways. These data provide a valuable resource for the analysis of the molecular mechanisms underlying the cyclical growth of hair follicles in the skin during induced molting.

Mechanical activation of coal gasification fine slag and mechanical and thermal properties of coal gasification fine slag–poly(vinyl chloride) composites

To facilitate the high-value utilization of activate coal gasification fine slag (CGFS), a wet mechanical activation process was used. As a result of this treatment, CGFS samples with different particle size distributions were obtained. The effects of mechanical activation on various physical and chemical properties of CGFS were investigated, including its particle size distribution, mineral composition, specific surface area, pore size, crystallinity, particle morphology, chemical bonding, and binding energy. Poly(vinyl chloride) (PVC)/CGFS composites were prepared via a melt blending process, and their mechanical and thermal properties were evaluated. It was found that with increasing levels of mechanical activation, the CGFS particle size distribution became more concentrated and the particle spacing became more uniform. With the increasing mechanical activation, the crystallinity was found to decrease and the content of amorphous mineral matter (such as SiO2 and Al2O3) increased. The observed increase in specific surface area and decrease in average pore diameter due to the mechanical activation was seen to lead to an increase in the number of active sites. The produced PVC/CGFS composite materials were found to exhibit good mechanical properties and dynamic thermal stability. The thermal stability of the PVC composites was also found to improve relative to the composites produced without the use of mechanical activation.

Real-time pore structure evolution difference between deep and shallow coal during gas adsorption: A study based on synchrotron radiation small-angle X-ray scattering

Coal seam CO2 sequestration is an important option to address global warming. A better knowledge on coal pore structure evolution during gas adsorption can provide guidance for coal seams CO2 sequestration. However, few investigations on the pore structure evolution differences between the deep and shallow coal were conducted during gas adsorption. In this study, based on the real-time synchrotron radiation small-angle X-ray scattering (SAXS) observation, the average pore diameter and pore surface fractal dimension evolution differences between deep and shallow coal were investigated from the aspects of coal compositions and stress history. Two types of coal deformation (inner-swelling and outer-swelling) coexist during gas adsorption. Coal compositions have significant impact on the dominance of deformation type. The dominance of inner-swelling in deep coal is induced by the higher ash contents, and there is the decrease of average pore diameter during gas adsorption. The impact of stress-history (burial depth) on adsorption-induced deformation is more prominent than that of gas adsorption capacity. In deep coal, the surface fractal dimension evolution presents a negative correlation with the evolution of pore diameters. In shallow coal, the surface fractal dimension evolution presents a Langmuir-type correlation with the adsorption time.

Petrography and mineralogy control the nm-μm-scale pore structure of saline lacustrine carbonate-rich shales from the Jianghan Basin, China

Carbonate-rich shale in salt lakes has become a potential target for petroleum exploration. A full understanding of storage space development characteristics is the basis for the efficient development of this kind of shale. In this study, the complex mineral composition and multiple pore structure of a typical carbonate-rich shale from the Paleogene Xin'gouzui Formation in the Jianghan Basin were systematically analyzed. The mixed shale and dolomitic shale were the main lithofacies types in the study area. Both of them were dominated by interparticle (interP) pores. However, their pore sizes are noticeably different. Pores with a size of <100 nm are the main compositions of the mixed shale, with an average volume proportion of 78.24%. Conversely, the dolomitic shale develops mainly micro-sized pores and micro-fractures, with a ratio of 70.46%. The difference in pore structure for different types of shales is closely associated with mineral composition. When particles of different sizes are mixed, most of the interP pores are prone to be filled by fine minerals (e.g., clay), resulting in relatively small pore sizes for the mixed shale. Homogeneous carbonate minerals are favorable for the residual of larger size interP pores. However, recrystallization and secondary enlargement of carbonate minerals can also lead to a significant decrease in pore diameter of interP pores. With these results, a storage space development model for different lithofacies shales was established. This work is crucial to further reveal the reservoir mechanisms and hydrocarbon scales of an argillaceous dolomite reservoir.

Comparative analysis of the properties of biochars produced from different pecan feedstocks and pyrolysis temperatures

Pecan is an important woody oil and nut tree and it generates a large amount of residues during cultivation and management. However, the utilization of pecan residues remains largely unexplored. In this study, three types of pecan feedstocks (branches, leaves and nut shells) were selected as feedstocks to produce biochars at four pyrolysis temperatures (300, 400, 500 and 600 ℃), and their properties were evaluated for agricultural and environmental applications. The biochar yield decreased with increasing temperature, and the highest yield was generally obtained from leaf biochars. As the pyrolysis temperature increased from 400 to 600 ℃, specific surface area and total pore volume increased sharply while with an obvious decrease in the average pore diameter as a whole. The pH of different biochars presented an upward trend with increasing temperature, while the electrical conductivity and cation exchange capacity (CEC) showed a complex trend, among which the CEC of the biochars produced at 500 ℃ was the highest. The application of pecan biochars improved the water holding capacity of saline-alkali soil overall (except for the biochars produced from nut shells at 500 and 600 ℃). The element analysis suggested that the organic carbon contents in the branch and nut shell biochars were significantly higher than those of leaf biochars; the branch and leaf biochars contained significantly higher total phosphate, available phosphate (AP) and zinc contents; the total potassium and available potassium (AK) levels were highest in the branch biochars, and the highest levels of total nitrogen and other metallic elements were obtained in the leaf biochars. Notably, the levels of some elements (AP, AK, calcium, magnesium, iron, manganese and copper) generally increased with increasing temperature. Pearson’s correlation analysis showed the associations among the biochar properties, and principal component analysis demonstrated that the properties of pecan biochars were generally determined by the interactions of feedstock type and pyrolysis temperature. In conclusion, biochar with known properties produced from different feedstocks and pyrolysis temperatures could be chosen as a suitable soil conditioner or adsorbent applied to agricultural and environmental fields.

Characterization of semi-interpenetrating hydrogel based on Artemisia sphaerocephala Krasch Polysaccharide and cellulose nanocrystals crosslinked by ferric ions

Hydrogels are important bionic materials that can be used in a wide variety of biomedical applications. Artemisia sphaerocephala Krasch polysaccharide (ASKP) has been demonstrated to be crosslinked by ferric ions to form three-dimensional network. Here, a semi-interpenetrating network (semi-IPN) hydrogel based on ASKP and cellulose nanocrystals (CNC) crosslinked by ferric ions was fabricated and the effect of specific rod-like CNC was evaluated. It was found that the network of ASKP-Fe3+ hydrogel incorporated by CNC became denser along with the decreased pore diameter and the thickened pore wall. ASKP/CNC-Fe3+ hydrogel displayed an enhanced gel strength and water holding capacity. The dominant interaction of ASKP and CNC was hydrogen bonds proved by FTIR and QCM-D. Additionally, the elasticity of the semi-IPN hydrogel significantly increased along with the decrease of platform height in MSD curves based on particles tracking. These results may be caused by the fact that the rod-shaped CNC can be entangled with ASKP and prone to induce the orderly extension of ASKP chains, resulting in more hydroxyl and carboxyl groups exposed to be crosslinked with ferric ions. What's more, the stiff CNC located on the pore wall of ASKP-Fe3+ hydrogel can also strengthen the rigidity of network. Thus, this study suggests a new strategy to improve the properties of ASKP based hydrogel, and can be developed as a carrier to deliver iron ions.

PRESSURE GRADIENT COMPUTATION FOR FOAMS WITH DIFFERENT GEOMETRIC PROPERTIES: BASED ON ANN AND SVR MACHINE LEARNING MODEL AND TRAINED BY CFD SIMULATIONS

In this research work, a combination of computational fluid dynamics (CFD) simulation and artificial intelligence (AI) methods are conducted to study the effects of geometric properties of aluminum foams on airflow and to compute and predict pressure gradients in foams with such varied geometric parameters as porosity (65-90&amp;#37;) and pore diameter (200-2000 &amp;mu;m). The 3D foam structures are created by the Laguerre-Voronoi tessellations method. Based on the CFD results, pressure gradient for 114 different foams can be calculated in terms of inlet flow velocity (in the range 0.1-8 m/s). Foam pressure gradient is found to increase with increasing inlet flow velocity but with decreasing pore diameter and porosity. Comparisons reveal that the results obtained in the present study for pressure gradient are consistent with the data reported in the literature. It is, therefore, concluded that CFD simulation is a useful tool for pressure gradient estimation in a variety of foam types. Unique simulations are, however, needed each time foam structural properties change, which entails significant increases in the associated computation costs. This drawback may, nonetheless, be at least partially addressed by taking advantage of soft computing methods such as machine learning (ML). Artificial neural network (ANN) and support vector regression (SVR) as subsets of AI are designed (models with input variables inlet velocity and the foam structural parameters: porosity, pore diameter, and strut diameter) and trained using CFD results to predict pressure gradients in a large number of foams. When applied to new foam samples, the ML models exhibit an acceptable performance in predicting pressure gradients. Using such provisions, the method can be effectively used for predicting pressure gradient in various porous media at minimum computation costs.