Increasing Shell Thickness Research Articles

Critical buckling load analysis on spherical shells under various geometric imperfections

The strength of shell structures is mainly determined by their ability to resist buckling. However, the presence of geometric imperfections – a condition which the geometry is no longer the same as the original condition – significantly deteriorates the critical load and often leads to catastrophic failure. Ratio between the actual critical buckling load to the theoretical prediction is called knockdown factor. The study aims to analyse the critical buckling load on spherical dome elastic shells under various geometric imperfections. This study was conducted into several thicknesses (10, 16, 20, 37, 50 mm) and fixed base radius of 4000 mm. Analyses of linear buckling and nonlinear static are performed and aided with finite element program using MIDAS FEA. The result of this study reveals that the critical buckling load decreases sharply in the beginning of imperfection, then reach for quite slow progression until a constant value of Kd = 0.1. In addition, the higher minimum knockdown factor is obtained as the shell thickness increases.

Size effects on the magnetic behavior of γ-Fe2O3 core/SiO2 shell nanoparticle assemblies

Theeffect of core size on the magnetic behavior of nanoparticle assemblies of γ-Fe2O3 core/SiO2 shell morphology is investigated. Long-range magnetostatic interactions are probed in two highly monodispersed experimental test systems of spherical nanoparticles with core diameters of 10 nm and 12.5 nm, and a shell thickness varying from 0 nm (bare particles) to ~50 nm. Zero-Field-Cooled magnetization curves are calculated by employing the Monte Carlo simulation technique in a mesoscopic-scale model for the assembly, assuming spin collinearity and coherent spin-reversal mechanisms. Simulation results reproduce the trend in the behavior of the Zero-Field-Cooled magnetization versus T curves in good qualitative agreement with the experimental findings. They also demonstrate that the increase of the magnetic core size results in a shift of the maximum magnetization peak, Tmax, to higher temperatures due to enhanced dipolar coupling. The results shed light on how interparticle distance and magnetic core size influence the value of Tmax through collective behavior and its transition to a single-particle superparamagnetic blocking temperature, TB, as the assembly becomes magnetically diluted with increasing shell thickness.

Shell-thickness-induced spontaneous inward migration of mercury in porous ZnO@CuS for gaseous mercury immobilization

• Porous structure of ZnO@CuS are beneficial for mercury capture. • The mercury bonding stability depended largely on CuS shell thickness. • ZnO@CuS [4:3] could adapt to a wider temperature window. • Gaseous mercury tended to migrate inward the ZnO@CuS for firmer combination. Inducing gaseous substances to migrate inward into a solid material is one of the effective methods to improve the interfacial adsorption stability. However, the gaseous mercury (Hg 0 ) adsorption on bulk material, especially mineral sulfides, generally occurred on the outer surface owing to their compact structure, resulting in the low bonding stability. This study prepared porous ZnO@CuS with different shell thickness to investigate mercury adsorption performance and bonding stability. The porous shell structure enabled Hg 0 to migrate inward into ZnO@CuS. Such an inducing effect, on one hand, improved the mercury adsorption performance due to the increase of active sites with the thickened shell. On the other hand, the mercury bonding stability was enhanced along with the increase of shell thickness. The initial mercury desorption temperature gradually increased from 50 to higher than 100 °C, and meanwhile, the desorption peak temperature increased from 150 to 275 °C. The improved bonding stability also enlarged its adaption to a wider temperature window (50–150 °C). Moreover, the optimal ZnO@CuS has a saturated adsorption capacity of 60.53 mg/g, and it has high resistance against O 2 , SO 2, and H 2 O. This work thus offers a promising thickness-induced method to enhance the mercury bonding stability on sulfides.

Thicker Shell Eggs with Enriched N-3 Polyunsaturated Fatty Acids and Lower Yolk Cholesterol Contents, as Affected by Dietary Nettle (Urtica cannabina) Supplementation in Laying Hens.

Simple SummaryThe nettle Urtica cannabina (U. cannabina) belongs to the Urticaceae (nettle) family in the major group Angiosperms (flowering plants); it is distributed worldwide in temperate regions. While it was previously considered to be a weed, increasing evidence suggests that it is a valuable nutrient resource and has multiple biological functions when included in both human and animal diets. U. cannabina was given to laying hens in this experiment to study its effect on the hens’ performance, egg quality, yolk fatty acids composition, and serum biochemical parameters. The results revealed that dietary supplementation with U. cannabina has the potential to produce high-quality eggs. The data collected in this experiment can be used to inform further use of this plant to improve the lipid profile and fatty acid composition of eggs produced by hens fed on U. cannabina.The nettle Urtica cannabina (U. cannabina) is not only a functional edible food for humans but also a potential alternative feed resource for poultry, providing protein, fatty acids, vitamins, and minerals. The present study was conducted to evaluate the effects of dietary U. cannabina on the production of high-quality eggs with enriched n-3 polyunsaturated fatty acids (PUFA) and lower cholesterol contents. One hundred and twenty laying hens were assigned to three groups [control, 15% alfalfa meal supplementation (TRTA), and 15% U. cannabina supplementation (TRTU)]. The results showed that the feed intake, yolk color, and shell thickness were increased (p < 0.05) in the U. cannabina group. Moreover, cholesterol contents of the yolk and serum were lower in the U. cannabina group (p < 0.05). The total n-3 PUFA concentration in the yolk was increased while the ratio of n-6/n-3 was reduced in the U. cannabina group (p < 0.01). In conclusion, the dietary inclusion of U. cannabina increased shell thickness, yolk n-3 PUFA levels, and yolk color, and reduced cholesterol contents of the yolk and serum without any negative impacts on health or laying performance.

AlCoCrFeNi high entropy alloy reinforced Cu-based composite with high strength and ductility after hot extrusion

To improve the effectiveness of high entropy alloys (HEAs) as reinforcing agents in metal matrix composites, the 10 vol.% HEA/Cu composite was fabricated by spark plasma sintering, followed by different holding time at 850 °C and hot extrusion. The as-extruded composites were examined by microstructural characterization using scanning electron microscopy, electron probe microanalysis and transmission electron microscopy along with performance tests. The results show that the preheating at 850 °C promotes the diffusion of Al, Co, Cr Fe and Ni from the reinforcement to Cu matrix, along with the diffusion of Cu towards reinforcement, which give rise to the formation of core-shell structure at less than 6 h. However, such core-shell structure is invisible once the preheating time is above 6 h. At less than 6 h, the increased yield strength of the HEA/Cu composite can be ascribed to the solid solution strengthening of Cu matrix stemmed from element diffusion, whereas the improved plasticity is due to the increasing shell thickness in reinforcements with the preheating time. At above 6 h, the strengthening effect of reinforcements decreases significantly, giving rise to the decrease in the yield strength and the improvement in the plasticity.

Suitability of PSMA-PET Biology-Guided Radiotherapy for Low Volume Metastases in Newly Diagnosed Prostate Cancer

Biology-guided radiation therapy (BgRT) guides radiation therapy in real time based on positron emissions detected during treatment delivery. Protein specific membrane antigen (PSMA) is a positron emission tomography (PET) tracer with superior sensitivity and specificity for prostate cancer detection compared with conventional imaging. This study aims to quantify the ratio of standard uptake value (SUV) to background SUV for patients with low volume prostate cancer metastases, in the context of determining suitability of these lesions for BgRT. A single institutional patient subset from the ProPSMA prospective clinical trial underwent Ga-68-PSMA-11 at the time of prostate cancer diagnosis with suspected localized disease. From this cohort of 84 patients, 15 had at least one metastatic site disease diagnosed, 1 to 11 lesions per patient, with a total of 43 metastatic lesions (12 bones/31 viscerals). Metastatic gross tumor volume (GTV) were delineated on PSMA-PET images by using a patient-specific fixed SUV threshold method. In order to determine the suitability of various BgRT tracking zones, 3D shells of thickness 5 mm, 10 mm and 20 mm were constructed around the GTV to represent adjacent non-tumor background. Normalized SUV (nSUV) was calculated as the ratio of SUVmax in the GTV to SUVmean of adjacent shell. Sensitivity of nSUV to shell thickness variation was reported as the difference between nSUV values obtained for each thickness. GTV SUVmax ranged from 2.9 to 48.0 (median, 12.0; IQR, 5.1 to 19.5). nSUV ranged from 2.4 to 42.6 for 5 mm shell, 2.7 to 47.5 for 10 mm shell and 2.6 to 36.4 for 20 mm shell. Bone metastases had increased SUVmax compared with visceral metastases (SUVmax min/median/max 2.9/15.0/48.0 for bone compared with 2.9/11.0/40.0 for visceral). Furthermore, 90% of lesions had nSUV greater than 2.9 for a shell thickness of 5 mm, 3.1 for a shell thickness of 10 mm, and 3.2 for a shell thickness of 20 mm. Moreover, 100%/93%/84% of lesions would be suitable for BgRT by using nSUV cut-off of 2/3/4 and a shell thickness of 10 mm. nSUV decreased with increasing shell thickness for 17 lesions, indicating high signal in adjacent non-tumor tissue due to the proximity of bladder (5), bowel (4), other lesion (4), vessel (3) and liver (1). This study demonstrates that it is feasible to identify metabolically defined radiotherapy targets in the setting of BgRT. High lesion to background signal was observed for metastases visible on Ga-PSMA-EPT-11, however a subset of metastases had adjacent non-tumor uptake which may require exclusion from emission tracking during BgRT. Trial ID ACTRN12617000005358.

Tuning dipolar effects on magnetic hyperthermia of Zn0.3Fe2.7O4/SiO2 nanoparticles by silica shell

Effects of magnetic dipole interactions on specific loss power (SLP) for Zn0.3Fe2.7O4/SiO2 core/shell nanoparticles (NPs) with identical magnetic core size and varying non-magnetic shell thicknesses were systematically investigated. In the case of thin silica shell, NPs form chain-like structures due to strong dipole interactions between NPs. The chain formation induces additional shape anisotropy. With increasing thickness of the silica shell, the dipole interaction and therefore the anisotropy induced by the dipole interactions decrease. Meanwhile, the hydrodynamic size of the NPs shows a counterintuitive reduction with increasing shell thickness, also due to the decrease in interactions. The magnetic anisotropy and hydrodynamic size affect the SLP through changes in the Néel and Brownian relaxation rates, leading to different field-dependent SLP values for NPs with thin and thick shells.

Topological Interlocking and Geometric Stiffening as Complementary Strategies for Strong Plant Shells.

Many organisms encapsulate their embryos in hard, protective shells. While birds and reptiles largely rely on mineralized shells, plants often develop highly robust lignocellulosic shells. Despite the abundance of hard plant shells, particularly nutshells, it remains unclear which fundamental properties drive their mechanical stability. This multiscale analysis of six prominent (nut)shells (pine, pistachio, walnut, pecan, hazelnut, and macadamia) reveals geometric and structural strengthening mechanisms on the cellular and macroscopic length scales. The strongest tissues, found in walnut and pistachio, exploit the topological interlocking of 3D-puzzle cells and thereby outperform the fiber-reinforced structure of macadamia under tensile and compressive loading. On the macroscopic scale, strengthening occurs via an increased shell thickness, spherical shape, small size, and a lack of extended sutures. These functional interrelations suggest that simple geometric modifications are a powerful and resource-efficient strategy for plants to enhance the fracture resistance of entire shells and their tissues. Understanding the interplay between structure, geometry, and mechanics in hard plant shells provides new perspectives on the evolutionary diversification of hard seed coats, as well as insights for nutshell-based material applications.

Convergence, parallelism, and function of extreme parietal callus in diverse groups of Cenozoic Gastropoda

AbstractWe use scanning electron microscopy imaging to examine the shell microstructure of fossil and living species in five families of caenogastropods (Strombidae, Volutidae, Olividae, Pseudolividae, and Ancillariidae) to determine whether parallel or convergent evolution is responsible for the development of a unique caenogastropod trait, the extreme parietal callus (EPC). The EPC is defined as a substantial thickening of both the spire callus and the callus on the ventral shell surface such that it covers 50% or more of the surface. Caenogastropods as a whole construct the EPC convergently, using a variety of low-density, poorly organized microstructures that are otherwise uncommon in caenogastropod non-callus shell construction. Within clades, however, we see evidence for parallelism in decreased regulation in both the shell and callus microstructure. Low-density and poorly ordered microstructure—such as used for the EPC—uses less organic scaffolding and is less energetically expensive than normal shell microstructure. This suggests the EPC functions to rapidly and inexpensively increase shell thickness and overall body size. Tests of functional ecology suggest that the EPC might function both to defend against crushing predation through increased body size and dissipation of forces while aiding in shell orientation of highly mobile gastropods. These interpretations hinge on the current phylogenetic placement of caenogastropod families, emphasizing the essential contribution of phylogeny when interpreting homoplasy.

Selective adsorption behaviours of MOFs@SiO2 with different pore sizes and shell thicknesses

MOF-5@SiO2 and IRMOF-10@SiO2 with different pore sizes and shell thicknesses were synthesized by a layer-by-layer method and used to explore the effects of pore size on dye adsorption behaviour. The characterization results indicated that shell thickness could dramatically influence pore structure. Mesopores and macropores in MOFs@SiO2 existed when the synthetic cycles were less than 10, while micropores could be obtained when MOFs@SiO2 were prepared after 20cycles. The adsorption kinetic and isotherm results showed that adsorption of basic fuchsin onto MOF-5@SiO2 increased but the adsorption capacities decreased with increasing shell thickness. The adsorption rate of basic fuchsin on IRMOF-10@SiO2 was lower and the adsorption capacity was higher than that of MOF-5@SiO2. Meanwhile, the adsorption rates of IRMOF-10@SiO2 decreased, but the capacities increased as the shell thickness increased. Moreover, Fourier transform infrared and X-ray photoelectron spectroscopy were used to investigate possible adsorption mechanisms. The results suggested that basic fuchsin could enter the pores of IRMOF-10@SiO2 but could not enter MOF-5@SiO2 due to the size-exclusion effect.

Opto-electronic characterization of starch capped zinc chalcogenides (core-shell) nanocomposites and their application as Schottky device

Optoelectronic properties of starch capped zinc chalcogenides (ZnO-ZnS and ZnS-ZnO) core-shell nanocomposites are found to be suitable for use in photoconductive devices. An increase in shell thickness can enhance the charge separation that thereby the efficiency. Schottky diodes based on ZnO-ZnS and ZnS-ZnO core–shells nanocomposites exhibit suitable rectifying behaviour in dark. The fundamental device parameters such as barrier height saturation current (Is) and ideality factor (β) are calculated at 300 K (room temperature) from the I–V curve and the effects of the shell thickness on the device performance has thus been investigated. Variation of ideality factor may be attributed to increasing inhomogeneity and interfacial surface defects across the junction. Schottky diodes are also observed as photodetector in response to blue and green LED lights. Responsivity and quantum efficiency of core/shell based Schottky photodiodes are found to be higher than that of core-based Schottky photodiodes.

Tunable optical response of Fe-Ag nanoparticles in core-Shell nanostructures

The core-shell nanoparticles have received much attention due to their potential applications in biomedicine, molecular detection, catalyst, and cancer therapy. In this work, the optical properties of Fe-Ag nanoparticles in core-shell configuration are studied by using the discrete dipole approximation (DDA) method. The Fe-core is coated with varying Ag-shell thicknesses for different shapes and sizes of nanoparticles. The absorption localized surface plasmon resonance (LSPR) peak at the maximum wavelength (λmax.) of Fe@Ag core-shell nanoparticles (NPs) is found in the range of 335–387 nm & 382–749 nm wavelengths for sphere & prolate nanostructures respectively. It is observed that the LSPR peaks are blue-shifted with increasing core-sizes and red-shifted with the increasing shell thickness as well as the aspect ratio. Furthermore, prolate nanostructure shows the shifting of LSPR peaks at λmax towards the longer wavelength regime as compared to spherical shape nanostructures. The 30 nm core-size and aspect ratio of 3 is optimized for high sensitivity and figure of merit (FOM). The calculated results suggest that different Fe-core sizes, Ag-shell thickness, and shapes in core-shell configuration Fe@Ag NPs influence the tunning and enhancement of absorption spectra. These findings can be utilized as basic knowledge for the development of synthesis methods to obtain suitable Fe@Ag core-shell NPs for future applications.

Testing the efficacy of bouncing-bucket nursery systems for enhancing shell strength and thickness in on-bottom cultured Eastern oysters (Crassostrea virginica)

Through physical manipulation, oyster growers can modify the morphological features of young oysters in order to improve their robustness and resiliency to predation. In this study, the efficacy of a novel passive culturing technique using floating buckets that “bounce” oysters prior to the benthic grow-out phase for enhancing shell thickness and strength, while not compromising oyster shape, was investigated. Using a field experiment, we quantified and compared the shell thickness (mm), compressive strength (Newtons), and shape (fan ratios and cup ratios) of juvenile oysters subjected to this bouncing technique with oysters grown in floating bags, the current industry standard. Results indicated that bouncing increased shell thickness and strength for oysters >45 mm shell height compared to control oysters, but also decreased shell thickness and strength for oysters <45 mm shell height compared to control oysters. There was no difference in shell shape between bounced and control oysters, with both groups having similar fan and cup ratios. Ultimately, our results suggest that the size at which bounced oysters are released to the benthos for grow out will dictate the usefulness of bouncing technique for reducing predation-related mortality.

Structural characterization and magnetic properties of core–shell Fe@Fe3O4 nanowires

Core–shell Fe@Fe3O4 nanowires (NWs) were successfully prepared on a homemade anodic aluminum oxide (AAO) template by the anodic oxidation of Fe NWs followed by annealing reduction. A field-emission scanning electron microscope was used to observe the morphology of the AAO template, which shows that the diameter of AAO template was 30 nm. TEM results confirm a thin oxide layer was formed on Fe NWs, confirming the core–shell nature of Fe NWs. The TEM analysis shows that with the increase in anodizing time, the oxide layer thickness was increased from 2.4, 4.6, 5.9 nm, respectively. The elemental composition of core–shell Fe NWs was confirmed by energy-dispersive X-ray spectrometer. The oxide phase of Fe could not be easily distinguished by X-ray analysis, because of the line width broadening of nanocrystals; thus, the valence states of Fe in Fe@Fe2O3 and Fe@Fe3O4 NWs were further analyzed by X-ray photoelectron spectroscopy (XPS). XPS results confirm the oxide nature of Fe2O3 and Fe3O4 in core–shell Fe NWs. The influence of oxide layer thickness on the magnetic properties of core–shell Fe@Fe3O4 NWs was investigated by vibrating sample magnetometry. Magnetic measurement revealed that the coercivity and squareness values of core–shell Fe@Fe3O4 NWs gradually increased with the increase in the Fe3O4 shell thickness. Results clearly showed that the size and magnetism of the core–shell Fe@Fe3O4 NWs can be adjusted to a certain extent by this synthetic method, so as to meet different requirements in desired biomedical applications.

An Insight into the Coating Behavior of Bimetallic Silver and Gold Core-Shell Nanoparticles

Bimetallic Ag(core)/Au(shell) and Au(core)/Ag(shell) core-shell nanoparticles are synthesized in aqueous phase using simple citrate reduction method with variations for both sets in the reaction conditions during the fabrication of shell structure, i.e., change in salt concentration, temperature (from 25 to 100 °C), and pH for salt solutions (from 2 to 12). The surface plasmon resonance effect, size and morphology, elemental composition, crystalline structure, and crystallite size were observed for these bimetallic core-shell nanoparticles using techniques such as UV-Vis spectroscopy, SEM, EDX, and XRD respectively. The size observed for Ag(core)/Au(shell) nanoparticles was 50 ± 6 nm, and Au(core)/Ag(shell) nanoparticles was 64 ± 8 nm. Increasing the concentration of salt for Au or Ag shows better coating and increase in shell thickness as observed by surface plasmon resonance (SPR) peaks. At lower temperatures, generally, agglomeration occurs or in case of Au(core)/Ag(shell) nanoparticles, formation of Ag3O4 occurs; however, at higher temperatures, homogenous small-sized nanoparticles with higher crystallinity are formed. For Ag(core)/Au(shell) nanoparticles, at pH 4, best uniformly distributed nanoparticles are formed with higher crystallinity; however for Au(core)/Ag(shell) nanoparticles, pH 7 is the optimal pH, where uniformly sized nanoparticles with higher crystalline structure are formed.

Controllable synthesis of core-shell Co@C@SiO2 catalysts for enhancing product selectivity in Fischer-Tropsch synthesis by tuning the mass transfer resistance

Fischer-Tropsch synthesis (FTS) is the key step in converting syngas into clean fuels. Traditional supported catalysts for FTS are problematic because the active metal crystalline size is positively related to metal loading. Therefore, increasing active metal loading may reduce the cobalt time yield (CTY) since a high CTY is usually obtained when the Co size is 8 nm. Here, a ZIF-67 (Zeolitic imidazolate framework-67) with a MOF (Metal organic framework) structure is used as a precursor to prepare the [email protected] catalyst with not only high cobalt loading (55.6 wt%) but also with a small cobalt crystal size (as small as 8.6 nm). Core-shell [email protected]@SiO2-X catalysts with different SiO2 shell thicknesses were successfully prepared by coating different amounts of TEOS on the outer surface of [email protected] to modify product selectivity. Compared with 40 wt% Co/SiO2 catalyst, core-shell [email protected]@SiO2-X catalysts exhibited improved FTS performance. Furthermore, different gaseous hourly space velocities (GHSVs) were used to obtain CO conversion at similar levels to compare CTY and the turnover frequency (TOF). Among the catalysts, the [email protected]@SiO2-1 catalyst, with its better mass transfer ability and suitable hydrophilic property, presented the highest TOF (9.75 × 10−3 s−1) and lowest CH4 selectivity (9.75%). In addition, heavy hydrocarbons were effectively suppressed with the increase in shell thickness due to the increased mass transfer resistance.

The morphology regulation and plasmonic spectral properties of Au@AuAg yolk-shell nanorods with controlled interior gap.

Au@AuAg yolk-shell nanorods with tunable and uniform interior gap were synthesized through galvanic replacement reaction, where Au@Ag core-shell nanorods served as sacrificial templates and HAuCl4 solution served as reductant. The effects of HAuCl4, Ag shell thickness and aspect ratio (AR) of Au nanorods on the morphology of Au@AuAg yolk-shell nanorods had been investigated systemically. The results clearly indicated that AuAg alloy shell thickness of Au@AuAg yolk-shell nanorods could be increased from 3.6 to 10.0nm by varying the amount of HAuCl4. Meanwhile, the shape of AuAg alloy shell could be tuned by changing the shape of Ag coating. With the increasing of Ag coating thickness, the interior gap could be finely tuned in the range from 2.6 to 8.1nm. The uniformity of interior gap could be improved by increasing the AR of Au nanorods. All these tunable geometries can further affect the plasmonic spectral properties of Au@AuAg yolk-shell nanorods. Because of the appearance of interior gap, the longitudinal localized surface plasmon resonance (LSPR) peak of Au@AuAg yolk-shell nanorods was located between that of bare Au nanorods and Au@Ag core-shell nanorods without interior gap. The increase of outer AuAg shell thickness can weaken the coupling between the inner and outer surface of the AuAg shell and lead to the decrease of AR, so the transverse and longitudinal LSPR bands gather together. The decrease of Ag coating thickness can enhance the coupling between inner Au nanorod and outer AuAg shell, which results in the red shift of the longitudinal LSPR band. This paper provides a method for studying the plasmonic coupling between two metal surfaces with a metal layer or a dielectric layer, which is also a new approach for regulating the plasmonic spectral properties of bimetallic nanoparticles. The controllability of Au@AuAg yolk-shell nanorods in both the interior gap and outer alloy shells makes them have potential applications in biomedicine, catalysis, nanoreactors, and energy storage.

Promotional effect of palladium in Co-SiO2 core@shell nanocatalysts for selective liquid phase hydrogenation of chloronitroarenes

This study describes the synthesis of palladium-promoted Co@SiO2 catalyst developed by electrostatic immobilization of Pd ionic precursor onto Co3O4 nanoparticles core, coated with a mesoporous SiO2 shell. The oxidized Pd-Co3O4@SiO2 (xPdCo-ox) and partially reduced Pd-Co@SiO2 (xPdCo-red) nanocatalysts were used in the direct synthesis of chloro-arylamines from chloronitroarenes employing heterogeneous hydrogenation process. The effect of palladium content (xPdCo; x = 0.0, 0.5, 1.0 and 3.0 Pd wt%) in the Co3O4 core of the structures on catalytic performance for the hydrogenation of 4-chloronitrobenzene (CNB) to 4-chloroaniline (CAN) was systematically studied. It was found that the incorporation of palladium ionic precursor promotes both Co3O4 core nanoparticles flocculation and an increase in the mesoporous shell thickness in the Pd-promoted catalysts compared to the pristine Co-SiO2 core-shell structure. The TPR, XRD, XPS and magnetic measurements results indicated that the palladium addition promoted the reduction of Co3O4 core during the isothermal H2 treatment at 873 K rendering metallic Pd° and Co° species. The catalytic CNB hydrogenation experiments showed that the 0.5PdCo-red catalyst inhibited both the hydrodechlorination and intermediates accumulation reaching 99% yield in CAN compared to 1.0PdCo-red and 3.0PdCo-red catalysts which provided aniline as undesired product. Additionally, the 0.5PdCo-red catalyst was easily recycled with a moderate catalytic activity after five consecutive reaction cycles. Finally, the catalytic hydrogenation performance of the 0.5PdCo-red catalyst for different pharmaceutical substituted chloro-nitroarenes such as 1-(4-chlorophenoxy)-2-nitrobenzene, 2-chloro-1-((3-fluorobenzyl)oxy)-4-nitrobenzene and 2-chloro-5nitrobenzotrifluoride was also evaluated and revealed high activity (>99% at 3 h of reaction) and selectivity towards the desired chloro-arylmines production, highlighting the potential of this catalyst in these processes.

SiC/SiO2 filler reinforced EP composite with excellent nonlinear conductivity and high breakdown strength

In this paper, silicon carbide/silicon dioxide (SiC/SiO 2 ) filler with core/shell structure, as a filler in epoxy resin (EP), is studied. The effect of the thickness of the SiO 2 shell is studied as it affects the microstructure and electrical properties of the SiC/SiO 2 /EP composites at various temperatures. Compared with SiC/EP composites, the SiC/SiO 2 /EP composites show outstanding electrical properties. The nonlinear coefficient of the 4 nm-SiC/SiO 2 /EP composites increases from 2.88 (5 wt% SiC/EP) to 3.79, and the breakdown field strength increases 1.23 times. With increasing temperature, the electrical conductivity increases and the threshold field strength decreases. Moreover, as the SiO 2 shell thickness increases, the breakdown field strength of the composite increases, and shows a weaker temperature dependence.

Structural and thermal stabilities of Au@Ag core-shell nanoparticles and their arrays: A molecular dynamics simulation**Project supported by the National Key Research & Development Project of China (Grant No. 2016YFA0202300), the National Natural Science Foundation of China (Grant No. 61888102), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000), and the Beijing Nova Program of China (Grant

Thermal stability of core-shell nanoparticles (CSNPs) is crucial to their fabrication processes, chemical and physical properties, and applications. Here we systematically investigate the structural and thermal stabilities of single Au@Ag CSNPs with different sizes and their arrays by means of all-atom molecular dynamics simulations. The formation energies of all Au@Ag CSNPs we reported are all negative, indicating that Au@Ag CSNPs are energetically favorable to be formed. For Au@Ag CSNPs with the same core size, their melting points increase with increasing shell thickness. If we keep the shell thickness unchanged, the melting points increase as the core sizes increase except for the CSNP with the smallest core size and a bilayer Ag shell. The melting points of Au@Ag CSNPs show a feature of non-monotonicity with increasing core size at a fixed NP size. Further simulations on the Au@Ag CSNP arrays with 923 atoms reveal that their melting points decrease dramatically compared with single Au@Ag CSNPs. We find that the premelting processes start from the surface region for both the single NPs and their arrays.