Shell Porosity Research Articles

Insights Into the one‐Step Dimethyl Ether Carbonylation to Ethanol Over Cu/ZnO@Cu‐MOR Core‐Shell Catalysts with Porogen Engagement

AbstractThis study investigates the one‐step ethanol synthesis from dimethyl ether and syngas using the catalysts combining Cu/ZnO oxides and modified Cu‐MOR zeolite. In addition to physically mixed two‐component catalysts, multifunctional catalysts featuring a Cu/ZnO core and modified zeolite (Cu‐MOR and HMOR) shell are also presented. Further, the porogenic agent of dihexadecyldimethylammonium bromide (DHAB) was involved in the synthesis process of the MOR zeolite components of Cu/ZnO@Cu‐MOR and Cu/ZnO/Cu‐MOR catalysts, but not in that of Cu/ZnO@Cu‐MOR° catalyst. A series of characterization measures including XRD, TGA, BET, SEM, TEM and EDS have been systematically studied on the prepared catalysts. Characterizations of the catalyst surface structure and texturing parameters revealed a disturbance in crystallinity upon Cu insertion, facilitating syngas separation and promoting DME carbonylation while preventing undesired CO hydrogenation. The addition of DHAB as a porogen in the synthesis of zeolite shell improved specific surface area and porosity of zeolite shell, and reduced coke deposition, without leaching active metal components, resulting in enhanced reaction properties. Cu/ZnO@Cu‐MOR core‐shell catalyst showed good performance with 28.9 % DME conversion and 43.8 % selectivity for ethanol. The optimized pore structure and enhanced catalytic performance of the modification process validate the effectiveness and efficiency of this strategy.

Integrated System of Semi-submersible Offshore Wind Turbine Foundation and Porous Shells

A novel semi-submersible platform is proposed for 5 MW wind turbines. This concept focuses on an integrated system formed by combining porous shells with a semi-submersible platform. A coupled aerodynamic–hydrodynamic–mooring analysis of the new system is performed. The motion responses of the novel platform system and the traditional platform are compared. The differences in hydrodynamic performance between the two platforms are also evaluated. The influence of the geometric parameters (porosity, diameter, and wall thickness) of porous shells on the motion response behavior of the new system is studied. Overall, the new semi-submersible platform exhibits superior stability in terms of pitch and heave degrees of freedom, demonstrating minimal effects on the motion response in the surge degree of freedom.

Investigation of adsorptive removal of heavy metals onto magnetic core–double shell nanoparticles: kinetic, isotherm, and thermodynamic study

The most perilous environmental hazards arise from the contamination of water by heavy metal ions, owing to the non-biodegradability of these metals, as well as their rapid dissemination throughout components of the environment via the food chain. Nano-based adsorbents have been used for the adsorption removal of many heavy metal cations, but separating and recycling them represent significant difficulties in processing. Magnetic core–double shell nanoparticles provide an attractive solution for processing issues, since they are stable and can be easily separated and recycled. Moreover, the shell thickness, composition, and porosity can be easily tuned. In this work, two samples consisting of magnetic core@TiO2@mesoSiO2 nanoparticles with two shell thicknesses (Mag-T-S-0.2 and Mag-T-S-0.4), along with a magnetic core@SiO2@TiO2 nanoparticle sample (Mag-S-T), were synthesized and characterized by TEM, XRD, magnetic strength measurement and zeta potential. TEM images show the developed core–double shell structure with double shell ranging from 60 to 73 nm. The XRD results indicate the impact of the outer shell on the diffraction pattern. The zeta potential shows that all samples had a negative charge at pH over 4. The magnetic character was suppressed after the formation of the double-shell coating; however, the magnetic core–double shell nanoparticles still had magnetization and could be separated when an external magnetic field was applied. The heavy metal adsorptive ability of Mag-T-S-0.2, Mag-T-S-0.4, and Mag-S-T samples was explored to investigate the effects of shell type and thickness along with kinetic, isotherm, and thermodynamic study. The investigated heavy metals included Cd(II), Ni(II), Mn(II), Pb(II), and Cu(II). The results indicate that, for Mag-T-S-0.2, the equilibrium state occurred after 15 min contact time, with adsorption capacity of 238, 230, 210.6, 181.8, and 245.8 mg/g for Cd(II), Ni(II), Mn(II), Pb(II), and Cu(II), respectively. For Mag-T-S-0.4, the equilibrium state occurred after 15 min contact time, with adsorption capacity of 241, 237.6, 173.8, 189.6, and 257.2 mg g−1, respectively. For Mag-S-T, the equilibrium state occurred after 25 min contact time, with adsorption capacity of 137.8, 131.4, 221, 189.6, and 149.4 mg g−1, respectively. When pseudo-first-order and pseudo-second-order kinetic models were applied to investigate the time interval adsorption data for Mag-T-S-0.2, Mag-T-S-0.4, and Mag-S-T samples, the second-order kinetic model was found to be more suitable for describing the process, indicating a fast adsorption mechanism. The adsorption data did not fit well with the Langmuir model, while they did fit well with the Freundlich model, suggesting heterogeneous material surfaces and multi-layer adsorption. Thermodynamic investigations confirmed the spontaneous nature of adsorptive removal, which helps to promote magnetic core@TiO2@mesoSiO2 and magnetic core@SiO2@TiO2 nanoparticles as effective adsorbents for wastewater treatment.

Using Museum collections to assess the impact of industrialization on mussel (Mytilus edulis) calcification.

Mytilus edulis is a commercially and ecologically important species found along the east coast of the United States. Ecologically, M. edulis improves water quality through filtration feeding and provides habitat formation and coastal protection through reef formation. Like many marine calcifiers, ocean warming, and acidification are a growing threat to these organisms-impacting their morphology and function. Museum collections are useful in assessing long-term environmental impacts on organisms in a natural multi-stressor environment, where acclimation and adaptation can be considered. Using the American Museum of Natural History collections ranging from the early 1900s until now, we show that shell porosity changes through time. Shells collected today are significantly more porous than shells collected in the 1960s and, at some sites, than shells collected from the early 1900s. The disparity between porosity changes matches well with the warming that occurred over the last 130 years in the north Atlantic suggesting that warming is causing porosity changes. However, more work is required to discern local environmental impacts and to fully identify porosity drivers. Since, porosity is known to affect structural integrity, porosity increasing through time could have negative consequences for mussel reef structural integrity and hence habitat formation and storm defenses.

Effect of Feeding Selected Strains of Conserved Breed Hens with Diets Containing Legumes on Egg Quality and Content and Activity of Lysozyme

Abstract The aim of the study was to evaluate the effect of replacing soybean meals with legume grains in diets on laying performance of hens and egg quality, with particular emphasis on egg lysozyme content. The study included 4 breeds/strains of laying hens included in the conservation programme in Poland, i.e.: Green-legged Partridge (Z-11), Yellow-legged Partridge (Ż-33), Rhode Island Red (R-11), and Leghorn (H-22). At 41–56 weeks of age, the hens of each strain were divided into two groups: I (control) − fed ad libitum with a standard diet based soybean meal, and II (experimental) − fed ad libitum with a diet that contained beans, peas and lupins instead of soybean meal. At 56 weeks of age, 32 eggs were taken at random from each group of hens and each strain, which were subjected to quality assessment. The results of the study confirm the possibility of feeding the above-mentioned hens with diets in which soybeans were replaced with 28% of faba bean, pea, and yellow lupin grains without a significant effect on laying performance, but with a change in some egg quality characteristics. In groups of hens fed a diet without soybean, a decrease in egg and albumen weight, albumen and yolk pH values, and an increase in yolk yellowness were recorded, as well as an increase in Haugh units and air cell height and shell porosity. There was a significant effect of genotype and diet and simultaneously of both factors on the content and activity of lysozyme in the thin and thick albumen. In the experimental groups, the average content and activity of lysozyme in the thin albumen decreased and in the thick albumen increased. Regardless of diet, statistically significant variation in egg internal quality and egg shell quality between hen strains was shown, as well as a correlation between the content and activity of lysozyme in eggs and shell colour.

Particle circulation and coating in a Wurster fluidized bed under different geometries

The performance of particle coating is essentially determined by the morphology and uniformity of coating shells, which significantly depend on particle circulation. In this study, the geometry of a Wurster fluidized bed is changed by regulating particle circulation port size and nozzle position, and their effects on particle circulation and coating properties are investigated by combining coating experiments and CFD – Discrete Element Model (DEM). By increasing the circulation port size, the particle circulation rate first increases then decreases slightly, accordingly, the uniformity of particle circulation increases then decreases, while the shell porosity decreases. By increasing the nozzle height, the particle circulation rate decreases slightly, accordingly, the uniformity of particle circulation increases then decreases, while the shell porosity decreases. At extremes with a too small circulation port size or too high nozzle position, particle residence and cycle time distribution are broader, and an obvious nonuniformity of particle growth is observed.

Origin and Formation Mechanism of Carbon Shell-Encapsulated Metal Nanoparticles for Powerful Fuel Cell Durability

Proton exchange membrane fuel cells (PEMFCs) face technical issues of performance degradation due to catalyst dissolution and agglomeration in real-world operations. To address these challenges, intensive research has been recently conducted to introduce additional structural units on the catalyst surface. Among various concepts for surface modification, carbon shell encapsulation is known to be a promising strategy since the carbon shell can act as a protective layer for metal nanoparticles. As an interesting approach to form carbon shells on catalyst surfaces, the precursor ligand-induced formation is preferred due to its facile synthesis and tunable control over the carbon shell porosity. However, the origin of the carbon source and the carbon shell formation mechanism have not been studied in depth yet. Herein, this study aims to investigate carbon sources through the use of different precursors and the introduction of new methodologies related to the ligand exchange phenomenon. Subsequently, we provide new insights into the carbon shell formation mechanism using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Finally, the thermal stability and electrochemical durability of carbon shells are thoroughly investigated through in situ transmission electron microscopy (in situ TEM) and accelerated durability tests.

Pore size-tunable core-shell structured Ni-Ru Nanoparticles catalyst for the reductive amination of isosorbide diketone

Isosorbide has been produced on a large scale and is expected to become the most important raw material for producing diaminoisomannide (DAIS) as a monomer for synthesis of polyamides. However, the direct catalytic amination of isosorbide to DAIS is impossible over heterogeneous catalysts, therefore, a two-step process, consisting of oxidation of isosorbide to isosorbide-diketone (ISDK) and reductive amination of ISDK to DAIS, has been proposed. The second step is key to realize this process. Therefore, a series of core-shell structured Ni-Ru nanoparticles bimetallic catalysts (Ni-Ru@SiO2 and meso-Ni-Ru@SiO2) for the reductive amination of ISDK to DAIS have been developed by doping ruthenium to Ni@SiO2. Among the catalysts, the meso-Ni-Ru@SiO2 catalyst (Ni: Ru = 76, Si: Ni = 0.625, C18TMS: Si = 0.2) demonstrated the highest catalytic activity in the catalytic amination of ISDK to DAIS, and the yield of DAIS reached up to 99 % with a turnover frequency (TOF) of 26.90 s−1. The catalyst also showed excellent performance in the catalytic amination of various aldehydes and ketones including (hetro)aromatic aldehydes and ketones as well as aliphatic aldehydes and ketones. The characterization results revealed that the Ni-Ru nanoparticles in the catalyst are uniformly dispersed and encapsulated within the SiO2 shell, and the doped Ru can adjust the electronic state of Ni. The porosity and pore size of the SiO2 shell can be tuned by adjusting the amount of C18TMS during the formation of the SiO2 shell, which facilitate the performance of the catalyst. Density functional theory (DFT) calculation in combination with experimental validation have shown that the porosity and pore size of the SiO2 shell affect the diffusion efficiency of reactants and products.

Versatile polydopamine-mediated growth of N and C co-doped hollow porous TiO2 spheres with oxygen vacancies for visible-light-driven oxidation of acetaldehyde

Developing visible-light-responsive TiO2-based photocatalysts provides a promising avenue for addressing VOCs pollution. Herein, polydopamine (PDA) template pyrolysis waste was in-situ up-cycled for simultaneous growth of N and C co-doped hollow porous TiO2 microreactors (H-NT-0.2) in air. The resulting H-NT-0.2 with a highly intact hollow structure, thin spherical shell (∼ 13 nm) and high porosity possesses the highest N and C co-doping ratio and largest oxygen vacancies (OVs) amount, leading to the highest concentration of reactive oxygen species (ROS) among all H-NT-x. A crucial role of OVs in enhancing H2O adsorption for the generation of hydroxyl radicals (⋅OH) has been revealed by DFT calculations. As a result, H-NT-0.2 shows the highest photocatalytic oxidation (PCO) efficiency of flowing acetaldehyde gas (90%) under visible light irradiation, which exceeds 3.5 times of commercial TiO2 (P25)), and outperforms most of the reported photocatalysts. The growth mechanism, as well as the photocatalytic reaction pathways, were analyzed based on TG-MS and in-situ DRIFTS results, respectively. This work provides an economical, green and feasible strategy to develop advanced visible-light-responsive photocatalysts for aldehydes VOCs abatement in practical applications.

Effect of pearl guinea fowl eggshell ultrastructure and microstructure on keets hatchability

Variability in shell structure is an evolutionary mechanism in birds that enables them to adapt to specific environmental conditions. This variability may also occur within the same species under the influence of individual indicators, such as the age or health status of females. While interspecies variation is quite obvious and easy to interpret, the reasons for intraspecies variation remain unclear. In this study, we examined the ultra- and microstructure of guinea fowl eggshells to identify the association between variations in shell structure and hatchability outcomes. We analyzed the visual differences between shells with low (L), intermediate (I), and high (H) external porosity using scale invariant feature transform analysis with NaturePatternMatch software. We found that the external pore image was closely related to the overall porosity of the shell before incubation. The total pore area, total porosity, and diffusion index (GH2O) were highest in group H shells (P < 0.001). Posthatching shells were characterized by an increased diameter and total surface area, decreased pore number (P < 0.001), as well as shortened mammillary layer (P < 0.001) and decreased total consumption of mammillary knobs (P < 0.001). The porosity indices of posthatching H shells had intermediate values between L and I. Although the effect of shell structure parameters on hatching was not confirmed, we assumed that all categories (L, I, and H) of shells were ideal for incubation. This suggests that the shell structure adapts to the metabolic rate of developing embryos; however, differences in shell structure affect the duration of incubation and synchronization of hatching. Both L and H shells showed delayed and prolonged hatching. Therefore, we recommended that guinea fowl eggs with different external porosity parameters should be incubated separately for better hatching synchronization. Differences in GH2O between L, I, and H eggs suggest that the shell porosity characteristics of guinea fowl eggs may be a key determinant of the rate of water loss during storage before incubation.

Promoting Electron Transfer Kinetics and Adsorption Capacity for the Detection of Furazolidone in Real Food Samples by Using Ag-core@Fe3O4-Shell-Based Electrochemical Sensing Platform

In this study, the preparation of core/shell Ag@Fe3O4 nanoparticles (NPs) and its potential application toward highly sensitive electrochemical detection of furazolidone (FZD) have been reported. UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, and Zeta sizer are systematically carried out to confirm the formation, size distribution, and composition of Ag@Fe3O4 NPs. By computing the electrochemical characteristic parameters such as electrochemically active surface area (ECSA), electron-transfer resistance (Rct), standard heterogeneous rate constant (k0), adsorption capacity (Γ), and electron transfer rate constant (ks), the Ag@Fe3O4-modified electrode possessed remarkably enhanced electrochemical sensing performance for FZD determination compared to the unmodified screen-printed electrode (SPE). This enhancement of electrochemical activity can be attributed to the fast electron transfer kinetics and great adsorption capacity that arise from the synergistic coupling between the good electrical conductivity of the core AgNPs and the porosity of the protective Fe3O4 shell. Under optimum conditions, the Ag@Fe3O4-based electrochemical nanosensor exhibited not only high sensitivity toward FZD detection of 1.36 μA μM−1 cm−2 in the linear ranges from 0.5–15 μM and 15–100 μM, and low detection limit of 0.24 μM but also long-term stability, repeatability, and anti-interference ability. The applicability of the proposed sensing platform in honey and milk samples was also investigated.

Study on Curing Deformation of Composite Thin Shells Prepared by M-CRTM with Adjustable Injection Gap.

A composite thin shell with a high fiber volume fraction prepared by resin transfer molding (RTM) may have void defects, which create deformations in the final curing and lead to the final product being unable to meet the actual assembly requirements. Taking a helmet shell as an example, a multi-directional compression RTM (M-CRTM) method with an adjustable injection gap is proposed according to the shape of the thin shell. This method can increase the injection gap to reduce the fiber volume fraction during the injection process, making it easier for the resin to penetrate the reinforcement and for air bubbles to exit the mold. X-ray CT detection shows that the porosity of the helmet shell prepared by the newly developed technology is 36.6% lower than that of the RTM-molded sample. The void's distribution is more uniform, and its size is decreased, as is the number of voids, especially large voids. The results show that the maximum curing deformation of the M-CRTM-molded helmet shell is reduced by 13.7% compared to the RTM molded sample. This paper then further studies the deformation types of the shell and analyzes the causes of such results, which plays an important role in promoting the application of composite thin shells.

Porosity vs carbon shell number: Key factor actually affecting the performance of multi-shelled hollow carbon nanospheres in Li-S batteries

• The pores in the carbon shells of HCNs play a key role in the Li + diffusion and Li 2 S x confinement. • Simply increasing the shell number in HCNs can not effectively confine the leakage of Li 2 S x from the S cathode. • Porous 1S-HCNs endow the S cathode with better cycling stability and rate capability than the oligoporous 2S-HCNs and 3S-HCNs do. • After 700 cycles, a capacity of 759 mAh g -1 with 63% retention is achieved for the S@1S-HCNs cathode at 0.2 C. As a type of sulfur host for lithium-sulfur batteries (LSBs), hollow carbon nanospheres (HCNs) are of particular interest due to their high electrical conductivity, available cavities, and unique morphology. However, there is a lack of in-depth study about the pivotal factors affecting their performance in LSBs. Herein, a series of multi-shelled HCNs have been prepared by a template-free method and the corresponding sulfur cathodes have been systematically investigated. A positive dependence of electrochemical properties on the specific surface area and pore volume of HCNs is confirmed. In case of low porosity of carbon shell, increasing the shell numbers in HCNs could not accelerate the Li + diffusion and restrict the dissolution of lithium polysulfide in the S@HCNs cathode. As a result, the highly porous 1S-HCNs endow the sulfur cathode with better cycling stability and rate performance than the oligoporous 2S-HCNs and 3S-HCNs do. This work may not only provide a useful reference in the design of novel sulfur hosts but also shed a light on the understanding of the complicated mechanism behind the sulfur redox reactions.

Tunable SERS activity of Ag@Fe3O4 core-shell nanoparticles: Effect of shell thickness on the sensing performance

Surface enhanced Raman spectroscopy (SERS) with enormous advantages has emerged as a powerful tool for both highly sensitive structural detection of analytes and imaging applications. Among various multifunctional nanomaterials for SERS substrate, nanocomposites of magnetic and plasmonic materials deliver both SERS effect and magnetic manipulation capacity, and thereby, have practical advantages for trace analysis in a broad range of fields. Herein, we investigate the SERS performance of different-sized Ag@Fe3O4 core-shell nanoparticles (NPs) obtained by controlling the Fe precursor concentration in a facile one-pot solvothermal synthesis method. The surface morphology, composition, structure, optical and magnetic properties are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis spectroscopy, and electrochemical techniques. The small shell thickness and high shell porosity of the smallest NPs significantly improve the mass diffusion and therefore SERS performance, making it an ideal substrate for highly sensitive detection of methylene blue (MB) and crystal violet (CV) organic pollutants. Quantitative SERS measurements using the Ag@Fe3O4 NPs are successfully demonstrated with MB as probe analytes. Due to the presence of a porous Fe3O4 shell, the Ag@Fe3O4 NPs showed outstanding SERS sensing performance with a linear concentration range from 10−7 to 10−10 M and the limit of detection (LOD) of 3 × 10−10 M. Moreover, the Ag@Fe3O4 core-shell nanocomposite exhibits high reproducibility and reliability and can be a promising candidate for SERS sensing systems.

Characterization of coating shells in a Wurster fluidized bed under different drying conditions and solution viscosities

Particle coating in fluidized beds is a widely used technique, while the particle growth mechanisms are complex. In this study, porous Al2O3 particles are coated with a sodium benzoate solution in a Wurster fluidized bed with different spray rates, fluidizing gas temperatures, and solution viscosities. The shell porosity, particle size, particle surface, and internal morphology of coated particles are characterized. The growth mechanisms of the coating shell including the effects of drying conditions and solution viscosities are summarized. The growth of the coating shell is distinguished into three modes: layer growth, island growth, and irregular growth. At a slow drying condition, the solute precipitates in the form of crystallization, resulting in the island growth. At a fast drying condition, many fine powders and vapor disturbance exist, leading to the irregular growth. Droplets with smaller viscosity are easier to spread and fill the existing pores, which promotes the layer growth.

Thermo-mechanical response of liquid-core beads as affected by alginate molecular structure

Core-shell hydrogel beads have recently drawn considerable attention to meet ever-changing consumer demand for exciting texture combined with functional properties. Still, the thermal processing of these types of beads remains insurmountable. In this paper, spherical liquid core gel beads were prepared from alginate with distinguishable Mw and M/G ratios and treated at temperatures varying from 60 to 121 °C. The core and the shell both had a precise response and influence towards heat. Improved mechanical properties were observed from beads up to 100 °C, figuring on hydrogels' network structure. High G-content and high molecular weight (Mw) contributed broadly up to a 50% increase in bursting force at high temperatures. Above the boiling point, beads started losing their original geometry since core materials diffused at an accelerated rate with a vapor pressure buildup. An irregular pattern of reduction in shell thickness, depending on crosslinking nature, was observed among alginate beads during heat treatment. A maximum 63.4% thickness reduction was recorded from low Mw alginate. Poorly constructed gel networks produced thermally vulnerable structures, predominantly by shorter chain length or higher M residue. Higher calcium concentration (up to a saturated crosslinking point) enhanced stability within the same alginate group. Heat treatment resulted in a compact shell microstructure with reduced pore size and a smoother surface. The water state and crosslinking of the chains were the decisive factors for the beads' thermo-mechanical response. Thus, a relationship was established between liquid-core beads' structural integrity, stability, and alginate's molecular composition concerning thermal treatment. • A relationship of thermo-mechanical response with alginate gel-structure established. • Beads' mechanical properties were enhanced by heating up to an optimum temperature. • The spherical geometry of liquid core alginate beads (LCB) persist up to 100 °C. • Alginate with High G content was more suitable for heat treatment for LCB. • High temperature reduces roughness and porosity of beads' shell.

Frequency-controlled electrophoretic mobility of a particle within a porous, hollow shell

The unique properties of yolk-shell or rattle-type particles make them promising candidates for applications ranging from switchable photonic crystals, to catalysts, to sensors. To realize many of these applications it is important to gain control over the dynamics of the core particle independently of the shell. HypothesisThe core particle may be manipulated by an AC electric field with rich frequency-dependent behavior. ExperimentsHere, we explore the frequency-dependent dynamic electrophoretic mobility of a charged core particle within a charged, porous shell in AC electric fields both experimentally using liquid-phase electron microscopy and numerically via the finite-element method. These calculations solve the Poisson-Nernst-Planck-Stokes equations, where the core particle moves according to the hydrodynamic and electric forces acting on it. FindingsIn experiments the core exhibited three frequency-dependent regimes of field-driven motion: (i) parallel to the field, (ii) diffusive in a plane orthogonal to the field, and (iii) unbiased random motion. The transitions between the three observed regimes can be explained by the level of matching between the time required to establish ionic gradients in the shell and the period of the AC field. We further investigated the effect of shell porosity, ionic strength, and inner-shell radius. The former strongly impacted the core’s behavior by attenuating the field inside the shell. Our results provide physical understanding on how the behavior of yolk-shell particles may be tuned, thereby enhancing their potential for use as building blocks for switchable photonic crystals.

Experimental and numerical study on the kinetics of CO2–N2 clathrate hydrates formation in silica gel column with dodecyltrimethylammonium chloride for effective carbon capture

The kinetics of carbon dioxide (CO2) and nitrogen (N2) gas mixtures hydrates formation in silica gel (SG) columns of varied pore sizes are studied both experimentally and numerically. Dodecyltrimethylammonium chloride (DTAC) solution with concentrations of 0–0.6 wt% was used to speed up the hydrate formation and improve the CO2 separation performance. A comprehensive shrinking-core model was established to reveal the roles of CO2 and N2 molecules diffusion and reaction in hydrate formation, and to investigate the effects of DTAC on kinetics. The experimental results show that the induction time is much shorter in larger pores of SGs, and is reduced remarkably with the addition of DTAC. The CO2 gas uptakes increase remarkably in the initial 200–270 min but change little later. The final CO2 concentration in gas phase decreased from 70 mol% to 32.6 mol% in the presence of DTAC, showing the CO2 separation factor raised by 36.6%–77.5%. However, N2 is also involved in the hydrate phase. The simulation results show that the combined reaction rate constants of both CO2 and N2 increase with the addition of DTAC. The lower combined rate constant in smaller pores indicates that the diffusion rate constant changes with pore size more strongly than the “reaction” rate constant. The dramatic decreasing trend of the effective diffusion coefficient reflects the higher porosity of the hydrate shell with more DTAC added.

Synthesis of highly monodisperse superparamagnetic iron oxide core@mesoporous silica shell particles with independently tunable size, and porosity

Superparamagnetic iron oxide nanoparticles, SPIONs, especially in the form of nanoscopic aggregates thereof, find broad applications as magnetic resonance imaging contrast agents, as biological tools for straightforward separation of biomolecules and cells, as magnetically tunable colorimetric sensors exhibiting structural colors, etc. Furthermore, if the SPIONs are covered with another oxide, typically silica, the size and refractive index of the particles can be modified. In addition, if the silica layer is mesoporous additional functionalities can be introduced. Such particles could serve as, for example, theranostic nanoparticles capable of serving both as drug carriers and contrast agents, as easily separable high-capacity adsorbers, and if the particles are monodisperse, colorimetric sensors. Many reports cover the synthesis of such SPION core-silica shell particles, but to date the structural tunability and reproducibility aspect has not received deserved attention. Here we report highly reproducible syntheses leading to SPION cores carrying silica shells with independently tunable shell thicknesses and porosities. The products are highly monodisperse in all cases, as evidenced by the fact that pellets of the particles show structural colors. The shell formation process is followed in detail, and is related to the applied synthesis parameters, which allows for rational further fine-tuning of the structural characteristics of the core-shell particles for a given application. • We report results related to the synthesis of highly monodisperse, superparamgnetic aggregates of iron oxide nanoparticles of various sizes with different silica shells of various thicknesses, and porosities. • The silica shell porosity can be adjusted independently of the total particle size and the silica shell thickness. • The possibility for independent tuning of total particle size, shell thickness, and shell porosity makes it possible to rationally optimize these core-shell particles for a given application.

Investigative Study of Effects of Gallus domesticus guano, Cucumeropsis mannii shell and Elaeis guineensis shell Additives on the Refractory Properties of Isiagu Clay

This research investigated the effects of chicken dropping, melon shell and palm kernel additives on the refractory properties of Isiagu Clay. The raw materials were collected locally, processed and analysed using Scanning Electron Microscope/Energy Dispersive X-ray (SEM/EDX). The additives were added to the raw clay in the ratio of 2.5,5.0,7.5 and 10 wt% and fired at 900oC and 1100oC, respectively. The refractory properties measured were; linear shrinkage, apparent porosity and bulk density. The result of the SEM/EDX analyses showed that the clay is a fireclay since it contains 61.68% Al2O3 and 34.97% SiO2 while chicken dropping, melon shell, and palm kernel shell contained 37.41% SiO2, 84.62% P2O5, and 48.31% Nb2O5, respectively. Chicken dropping was responsible for strength, melon for toughness and palm kernel shell for conductivity. SEM/EDX morphological results showed that the clay sample contains tiny to coarse particles. The bulk density measurement confirmed the strength and toughness of melon shell, the only additive which met the international standard for refractory application. XRD analysis results showed the presence of two crystalline phases at 21.4o and 22.4o namely, quartz and calcite in the additives used which are both responsible for strength in the refractory brick. Sudden variation in properties was observed for chicken droppings due to the presence of a reasonable amount of P2O5. From the study, melon shell and palm kernel shell are suitable for refractory brick production and further studies are recommended for chicken dropping. ANOVA results confirmed that for melon shell and apparent porosity only temperature was significant.