Properties Of Shell Research Articles

Influence of Shell Thickness on the Photophysical Properties of Core—Shell Perovskite Nanocrystals

AbstractCore–shell perovskite nanocrystals (NCs) have emerged as a promising class of materials for optoelectronic applications due to their unique properties and stability. Although much research has been conducted on the shell growth mechanism and properties of the core–shell NCs, little is known about the role of shell thickness in determining their optical properties. Herein, a heteroepitaxial method is employed to prepare a series of core–shell FAPbBr3/CsPbBr3 NCs with different shell thicknesses. Through temperature‐dependent photoluminescence measurement, it is found that the electronic structure of core–shell FAPbBr3/CsPbBr3 NCs evolves from quasi‐type‐II to type‐I with the increase in shell thickness. This abnormal transition can be attributed to the thickened gradient alloy layer FA1‐xCsxPbBr3, which effectively relieves the lattice mismatch and releases strain in the NCs, resulting in variations in the bandgap between the core and the shell. Furthermore, the biexciton Auger lifetimes in these samples exhibit a non‐monotonic dependence on shell thickness, indicating the electronic structure transition. These results provide valuable insights into the relationship between shell thickness, electronic structure, and optical properties in core–shell perovskite NCs, which may offer guidance for the design of high‐performance optoelectronic devices.

Experimental Investigations on Cylindrical GFRP Composite Pipes under Compression Loading

In a wide variety of aerospace applications have the mechanical properties of a thin cylindrical shell are important. Thin cylindrical shell structures are used to store a small and large quantity of fluids and solids. Glass Fabric reinforced epoxy composite is used to prepare the thin cylindrical pipes with different diameters and varying thickness of the composite pipes. The additives as glass flakes are added with 5%, 10% and 15% of the resin content in the matrix. The rolled composites specimens are prepared with the stainless steel (SS) mould. Experiments are test on Universal Testing Machine under lateral compression test to study the breaking load and compressive strength of the specimens. The failure modes are also observed.

Thermoelastic free vibration analysis of functionally graded conical shell based on trigonometric higher-order shear deformation theory

The fundamental frequency of a rotating cantilevered porous functionally graded (FG) twisted conical shell with varying thickness along the longitudinal direction is calculated using a trigonometric higher-order shear deformation theory under thermal loading. Finite element method is employed for this purpose. The shell is discretized using eight-noded isoparametric shell elements with seven degrees of freedom per node. Using a simple power law across the transverse direction, the temperature-dependent material properties of the FG shell are determined. The nonlinear temperature distribution across the thickness direction is calculated using the one-dimensional Fourier heat conduction equation. The dynamic equation of motion is derived using Lagrange's equation. Finally, a parametric investigation of the effects of taper ratio, porosity, pretwist angle, temperature, and rotational speed on the fundamental frequency of the porous FG rotating conical shell is performed. It is also discussed how such characteristics affect mode shapes.

Monatomic ions influence substrate permeation across bacterial microcompartment shells

Bacterial microcompartments (BMCs) are protein organelles consisting of an inner enzymatic core encased within a selectively permeable shell. BMC shells are modular, tractable architectures that can be repurposed with new interior enzymes for biomanufacturing purposes. The permeability of BMC shells is function-specific and regulated by biophysical properties of the shell subunits, especially its pores. We hypothesized that ions may interact with pore residues in a manner that influences the substrate permeation process. In vitro activity comparisons between native and broken BMCs demonstrated that increasing NaCl negatively affects permeation rates. Molecular dynamics simulations of the dominant shell protein (BMC-H) revealed that chloride ions preferentially occupy the positive pore, hindering substrate permeation, while sodium cations remain excluded. Overall, these results demonstrate that shell properties influence ion permeability and leverages the integration of experimental and computational techniques to improve our understanding of BMC shells towards their repurposing for biotechnological applications.

Magnetite core and ZnO shell – What is in between and how does it affect on nanoparticles properties?

Fe3O4 superparamagnetic nanoparticles are one of the most promising material for MRI T2 contrast agent production. Today a problem still exist with magnetite nanoparticles stabilization and protection against the loss of magnetic properties due to the oxidation process. Present work is devoted to the study of the Fe3O4 nanoparticles with ZnO protective shell focusing on the impact of shell properties and the impact of shell synthesis conditions on magnetic properties of the obtained core–shell nanoparticles, including the formation and transformation of transition layer between magnetite and shell.Magnetic core–shell nanoparticles Fe3O4@ZnO were obtained by two different synthesis procedures at three different temperatures to impact shell formation process. All samples were thoroughly characterized with complex of physical and chemical methods, including XRD, FTIR, HR-TEM, BET, DLS, VSM and TGA-DSC measurement. Computer simulations and Mössbauer spectroscopy were engaged to understand the processes occurring between the core and the shell during the shell formation.ZnO shell was successfully synthesized over the magnetite NPs surface, the shell is thick enough to protect magnetite surface from the environment. Presence of an transition layer, which composition depends on the synthesis procedure, was revealed. Correlations between magnetic and thermal characteristics and transition layer composition were found. MRI in vitro experiments have shown that T2 relaxation times decrease with increase of shell density.

Crystal structure, microstructure, and mechanical properties of heat-treated oyster shells

We investigated the crystal structure and mechanical properties of oyster shells subjected to heat treatment under increasing temperature conditions. The shell contained folia and chalky layers. The folia layer comprised two CaCO3 phases: 72.3% calcite and 27.7% aragonite. The lattice parameters of the calcite and aragonite present in the folia layer did not correspond to those of the synthesized sample. The anisotropic lattice expansion was observed in calcite and aragonite in the folia layer during heat-treatment. The chalky layer has also the anisotropic lattice expansion, but the expansion was disappeared at 573 K. The microhardness (HV value) of the folia layer decreased rapidly from 122 to 11 HV at temperatures 573–673 K owing to the phase transformation from aragonite to calcite in this temperature range. The microhardness of the chalky layer at RT was 125 HV, which decreased to 15 HV at 373 K. Crack propagation with increasing temperature was investigated using a micro-Vickers apparatus. In the folia layer, cracks were produced inside the prism, and they propagated along the lamellar structure. The cracks initiated and propagated along the organic biopolymer interlayers in a zigzag manner. No cracks were observed in the chalky layers of the heat-treated samples. The toughness of the chalky layer was superior to that of the folia layer. From our results, we can conclude that oyster shells comprise two types of materials with different mechanical properties.

Use of different food wastes as green biosorbent: isotherm, kinetic, and thermodynamic studies of Pb2.

Lead (Pb2+) can contaminate waters from many sources, especially industrial activities. This heavy metal is an amphoteric, toxic, endocrine-disrupting, bioaccumulative, and carcinogenic pollutant. One of the effective and economical processes used to remove lead from water is adsorption. The fact that the adsorbents used in this method are easily available and will contribute to waste minimization is the primary reason for preference. In this study, the adsorption abilities and surface properties of tea waste (TW), banana peels (BP), almond shells (AS), and eggshells (ES) which are easily available do not need modification and have very high (> 90%) removal efficiencies presented with isotherm, kinetic, and thermodynamic perspectives as detail. The surface structures and elemental distribution of raw adsorbents were revealed with SEM/EDX. Using FTIR analysis, carboxylic (-COOH) and hydroxyl groups (-OH) in the structure of TW, AS, BP, and ES were determined. It was determined that the Pb2+ adsorption kinetics conformed to the pseudo-quadratic model and its isotherm conformed to the Langmuir. The optimum adsorption of Pb2+ was ranked as BP > ES > AS > TW with 100, 68.6, 51.7, and 47.8mg/g qm, respectively. The fact that the process has negative ΔG° and positive ΔH° values from a thermodynamic point of view indicates that it occurs spontaneously and endothermically. According to the experimental data, the possible adsorption mechanism for Pb2+ has occurred in the form of physisorption (van der Waals, electrostatic attraction) and cooperative adsorption including chemisorption (complexation, ion exchange) processes.

Salt Distribution from Freezing Intrusions in Ice Shells on Ocean Worlds: Application to Europa

Several icy moons and dwarf planets appear to have hosted subsurface liquid water. Liquid water intruding upwards into the icy outer shells of these worlds freezes, forming ice and (from ocean solutes) non-ice solids. Here, we model concentrated aqueous solutions below 273 K to simulate the compositional evolution of freezing spherical intrusions. Starting solutions are based on five previously reported compositional end members for Europa’s ocean. For moderate-pH end members dominated by chloride, sulfate, and/or carbonate, the solids formed include Ca-, Mg-, and Na-sulfates and -carbonates, as well as Na- and K-chlorides. For silica-rich, high-pH end members, abundant amorphous silica forms with, potentially, similarly abundant NaOH and KOH. We further develop a new numerical model to compute the spatial distribution of the formed solids and residual brine as freezing progresses. If non-ice solids settle to the bottom, their deposits tend to have stacked hourglass shapes, widening each time the crystallization temperature of a new solid is reached. We discuss the applicability of this model to vertical fractures and global freezing of a subsurface ocean. These results inform (i) how compositional heterogeneities may affect the thermophysical properties of ice shells, which in turn influence convective and cryovolcanic transport, (ii) the compatibility of brine pockets with physicochemical conditions suitable for microbial life, and (iii) possible measurements of compositional heterogeneities within ice shells by spacecraft such as NASA’s Europa Clipper and ESA’s JUICE missions. The methodology developed here is applicable to other ice-covered ocean worlds.

To Determine the Performance Level of GLASS Fibre and Coconut Shell in Concrete

Abstract: Concrete is the most widely used construction material in civil engineering because of its high structural strength and stability. Concrete is the premier construction material around the world and is most widely used in all types of construction works, including infrastructure, low and high-rise buildings, and domestic developments. It is a man-made product, essentially consisting of a mixture of cement, aggregates, water and admixture(s). Inert granular materials such as sand, crushed stone or gravel form the major part of the aggregates. Traditionally aggregates have been readily available at economic prices and of qualities to suit all purposes. But, the continued extensive extraction use of aggregates from natural resources has been questioned because of the depletion of quality primary aggregates and greater awareness of environmental protection. To find a suitable and effective material from the waste product that would considerably minimize the use of material and ultimately reduce the construction cost. In this project GLASS fibre and Coconut shell were used as replacement of cement and coarse aggregate respectively. First physical properties of materials were found out and then the properties of GLASS fibre and coconut shells were also found out. In this project, experimental investigations were carried to find out the workability and strength, Durability characteristics of M20 Grade concrete with different replacement level of cement as (i.e.,5%,10%,15%,20 % ) by coconut shell, 0.5% by fibre and 2% alcofin. The tests will be conducted to determine the performance level of GLASS fibre and coconut shell in concrete. The specimen will be subjected to determine compressive strength, split tensile strength at 7, 14, 28 days and flexural strength at 7, 28 days of curing period. Workability of concrete should increase by combination of GLASS fibre and coconut shell. In this project GLASS fibre will be used to increase the strength of the coconut shell concrete. GLASS fibre along with cement.

R.C.C Shell Structure Design of Selected Head Cap Shape

Abstract: A shell structure is a thin structure composed of curved sheets of material, so that Shell structures are inspired from natural element named “SHELL”. A thin curved member or slab usually of reinforced concrete that function as tension member and shell. The waviness plays an important role in the structural behavior realizing a spatial form. Some of natural elements like eggshell, seashell, fruit shells (walnut) etc are showing shell structure properties. The present reinforced concrete shells as a very efficient structure, spanning wide, architectonically beautiful, relevant and valuable structural solution. Shell structures are very attractive lightweight structures, which are especially suited to Architectural building, industrial application, commercial projects etc.. The actual design of shells, involves theories of shells and the use of appropriate codes of practice. Types of curved shell like Parabolic, Hyperbolic or Cylindrical members are often said to act as tension rigidity hence called tensile members. For achieving the optimized load capability and flexural strength of such an element in form of shell covering structure is checked in for M30 grade concrete. Tensile shell members are structural edifice that caries only tension and without buckling or bending. Tensile structures are the most common type of thin-shell structures used worldwide from past decades. The profile and aspect of structure used are unlike for loading conditions, geographical locations and Architecture design differs as such as horizontal, sloping or curved member (dome and shell member). In this research work the tensile shell (plate) structure is designed in the form of beam and as grid shell slab element (plate). After then load has been applied for analysis via software tool i.e. STAAD Pro. The types of load assigned dead and live loads. The Design code specifications for curved shell member in IS: 2210–1994, IS 2204-1962 “Code of practice for construction of reinforced concrete shell roof” [CED 13: Building Construction Practices including Painting, Varnishing and Allied Finishing] and the load case criteria is to be as per IS: 875(2)–2000. RCC design specifications as per IS: 456–2000

Effect of Al2O3 fibers mixing methods and in-situ formed SiC nanowires on the properties of silica-sol ceramic shells for investment casting

In this study, a silicone resin solution was used as a supplementary binding agent, and two different techniques were employed to add varying amounts and layers of Al2O3 fibers within the shell to improve the performance of investment casting shells. The Al2O3 fiber-toughened shells were characterized using a combination of three-point bending and high-temperature self-loading deformation experiments. Additionally, the fracture morphology of samples and the fiber failure mode were demonstrated through SEM (Scanning Electron Microscope). Results showed that the added Al2O3 fibers greatly improved the bending strength and the high-temperature self-loading deformation of the ceramic shells. After spraying the silicone resin solution, the green and sintered strengths of the shells reached 8.02 MPa and 9.60 MPa, respectively, when Al2O3 fibers were added to the 3–6 layers of the shell. The high-temperature self-loading deformation reached a minimum of 0.44% when Al2O3 fibers were added at 0.4 wt%. SEM analysis indicated that the incorporation of Al2O3 fibers in the backing sand resulted in a disordered and non-directional distribution pattern, which could lead to the splitting of the ceramic matrix. In contrast, Al2O3 fibers within each shell layer could uniformly disperse the external load and increase the fracture resistance of the substrate. Furthermore, the pyrolysis of the silicone resin led to the deposition of free carbon in the matrix pores, resulting in the spontaneous formation of SiC nanowires. These nanowires were observed to attach to the Al2O3 fibers, which ultimately impeded the propagation of matrix cracks.

Bending and eigenfrequency analysis of glass fiber reinforced honeycomb sandwich shell panels containing graphene-decorated with graphene quantum dots

The present study employs a finite element (FE) formulation to examine the free vibration and bending analyses of sandwich shells made of a glass fiber reinforced polymer (GFRP) composite honeycomb core and graphene decorated with graphene quantum dots (GDGQD) reinforced by GFRP composite face layers. The mechanical characteristics of the GFRP composites with GDGQD reinforcement were evaluated using experimental tests. The FE formulation was developed to compute the vibration and bending responses of the sandwich shells via MATLAB software. The Lagrange method is used for dynamic analysis, whereas the principle of potential energy is used for static analysis. The FE model's validity is compared to numerical data reported in the literature in terms of frequencies and deflection, and the results demonstrate excellent agreement. The impacts of the end conditions, core-to-facesheet thickness ratio, curvature ratios, and weight percent of GDGQD are studied further in relation to the bending and dynamic properties of GFRP sandwich shells.

Free Vibration Analysis of Isotropic and Orthotropic Cylindrical Shells using Finite Element Method

The understanding of fundamental natural frequencies and mode shapes is crucial for assessing the resonant behavior of structures. Numerous scholars have investigated the free vibration properties of circular cylindrical shells. These cylindrical shell configurations find applications in diverse engineering fields such as aviation, rocketry, missiles, electric motors, and locomotive engines. Within this paper, an analytical solution is derived using the "first order shear deformation theory" to determine the frequency characteristics of free vibrations in symmetric laminated circular cylindrical composite shells. The outcomes are juxtaposed against classical and higher order theories. The central aim of this research is to scrutinize the influence of various parameters on the frequency traits of laminated composite shells. Furthermore, the analysis extends to laminated composite shells employing diverse stiffening methods, with their free vibration behavior explored through the utilization of FEA software ANSYS. Keywords: Cylindrical shell, free vibration, frequencies, mode shapes, laminated composites.

Alkaline-thermal and mild ultrasonic pretreatments for improving biomethane yields: Impact on structural properties of chestnut shells

The high fiber content of chestnut shells (CS) makes biomethane production inefficient when using the anaerobic digestion (AD) method. Therefore, this study has evaluated for the first time the combined effect of alkaline-thermal (AT) and mild ultrasonic (US) pretreatments prior to the AD of CS. The cumulative biomethane yields (CMY) of untreated and pretreated (4% NaOH + 100 °C thermal + US) CS were 79.10 ± 7.9 and 266.9 ± 9.3 mL CH4/g VS, respectively. The effects of the pretreatment of lignocellulosic biomass at different intensities were interpreted according to amounts of lignocellulosic solubilization, soluble chemical oxygen demand/total chemical oxygen demand, and scanning electron microscope images. Solubilization of the lignin from CS with pretreatments varied between 44.5 and 65.6% w/w. The use of AT pretreatments, together with US pretreatments, successfully increased the solubility of lignocellulosic compounds compared to the first case, whilst CMYs showed a positive correlation with lignocellulosic solubilization amounts. After pretreatments, total volatile fatty acid (VFA) concentrations were measured in the anaerobic process, from which the highest VFA was measured to be 1555 ± 108 mg HAc L-1, well below the appropriate value for AD (≤8000 mg HAc L-1). After pretreatments, the CMYs were successfully simulated by the modified Gompertz and Logistic model (R2 = 0.942–0.984). This study presents a promising strategy in the sense that the biomethane yield of CS containing large amounts of fiber can be significantly increased by combined AT and mild US pretreatment methods.

On the exact equilibrium conditions of irregular shells reinforced by beams along the junctions

The exact, resultant equilibrium conditions for irregular shells reinforced by beams along the junctions are formulated. The equilibrium conditions are derived by performing direct integration of the global equilibrium conditions of continuum mechanics. New, exact resultant static continuity conditions along the singular curve modelling reinforced junction are presented. The results do not depend on shell thickness, internal through-the-thickness shell structure, or material properties of shell and beam elements. In this theoretical approach, the beam’s kinematics is represented by the elastic Cosserat curve. Kinematically, the six-parameter model of shell structures coincides with the Cosserat curve model of the beam. The presented method can be easily applied to cases of connection of three or four shell elements with the reinforcement along the junction.

Stability Analysis of Shear Deformable Inhomogeneous Nanocomposite Cylindrical Shells under Hydrostatic Pressure in Thermal Environment

In this study, the stability of inhomogeneous nanocomposite cylindrical shells (INCCSs) under hydrostatic pressure in a thermal environment is presented. The effective material properties of the inhomogeneous nanocomposite cylindrical shell are modeled on the basis of the extended mixture rule. Based on the effective material properties, the fundamental relations and stability equations are derived for thermal environments. In this process, the first-order shear deformation theory (FSDT) for the homogeneous orthotropic shell is generalized to the inhomogeneous shell theory. This is accomplished using the modified Donnell-type shell theory. The analytical expressions are obtained for hydrostatic buckling pressure of INCCSs in the framework of FSDT and classical shell theory (CST) by obtaining a solution based on Galerkin’s procedure. The numerical examples presented include both comparisons and original results. The last section shows the influences of carbon nanotube (CNT) models, volume fraction, and shell characteristics on the hydrostatic buckling pressure in the thermal environment.

A STUDY OF COCOON FILAMENT OBTAINED IN RE-FEEDING

This article provides information about cocoon automatic- and mechanical cocoon-reeling machines in silk manufacturing enterprises of our republic, as well as the state of cocoon cultivation. The technological properties of the cocoon shells grown repeatedly in local conditions of the hybrids of Chinese silkworms and the compliance of the raw silk produced from them with the requirements of the international standard have been studied. The compensation period in raw silk production is analyzed from a theoretical point of view. The factors influencing the linear density of raw silk during reeling, the methods of controlling the linear density of raw silk produced in mechanical and automatic machines are solved theoretically and according to the results of practice, including the time spent to fill the broken cocoon threads and the amount of defective length determined in 100 grams of cocoon thread. The quality of raw silk that can be obtained from cocoons grown in different seasons was analyzed based on experimental results. It has been proven from a practical point of view that the probability of producing high-quality raw silk from the cocoons of the III-IV seasons is low.

Effect of Microstructure and Macro Size of Walnut Shell Chars on Their Electromagnetic Induction Heating Behavior

With increasing global demand for renewable energy, biomass and renewable electricity will be more and more widely applied in chemical processes. A promising direction is heating biochar directly by electromagnetic induction to support their high-temperature reactions, such as calcium carbide synthesis. To clearly understand the fundamental principles in biochar’s induction heating, this study investigates the relations between the physicochemical properties of walnut shell chars prepared at pyrolysis temperatures of 600–1400 °C and their induction heating behavior. The properties of chars include their electrical conductivity and structure parameters characterized by X-ray diffraction (XRD), Raman spectroscopy, electron spin resonance (ESR), ultimate analysis, as well as chars’ geometrical sizes. It is found that the chars prepared at pyrolysis temperatures equal to and higher than 800 °C are semiconductors with electric conductivities of 44–510 S/m. The threshold parameters for XRD, Raman, ESR, and ultimate analysis as well as geometrical size for induction heating are determined.

Sodium alginate/carboxymethyl starch/κ-carrageenan enteric soft capsule: Processing, characterization, and rupture time evaluation

Although gelatin has good characteristics in preparing soft capsules, its noticeable shortcomings force researchers to further develop substitutes for gelatin soft capsules. In this paper, sodium alginate (SA), carboxymethyl starch (CMS) and κ-carrageenan (κ-C) were used as matrix materials, and the formula of the co-blended solutions was screened through rheological method. In addition, films of the different blends were characterized by thermogravimetry analysis, SEM, FTIR, X-ray, water contact angle and mechanical properties. The results showed that κ-C had strong interaction with CMS and SA, and the mechanical properties of capsule shell were greatly improved by the addition of κ-C. When the ratio of CMS/SA/κ-C was 2:0.5:1.5, the microstructure of the films was more dense and uniform. In addition, this formula had the best mechanical properties and adhesion properties, and was more suitable for the production of soft capsules. Finally, a novel plant soft capsule was successfully prepared by dropping method, and its appearance and rupture properties met the requirements of enteric soft capsules. In simulated intestinal fluid, the soft capsules were almost completely degraded within 15 min, and they were superior to the gelatin soft capsules. Therefore, this study provides an alternative formula for preparing enteric soft capsules.

Negative phototaxis of jumping cocooned parasitoid wasp larvae against short wavelengths and physicochemical properties of the cocoon shell

The parasitoid wasp Bathyplectes anurus (Hymenoptera: Ichneumonidae: Campopleginae) is a successful biocontrol agent against the alfalfa weevil, Hypera postica. This weevil is a serious pest of beneficial fabaceous plants such as alfalfa and Chinese milk vetch. One of the possible reasons for the success of this wasp in hot climates may be the ability of its cocooned larvae to repeatedly jump and roll until they relocate themselves away from detrimental sunlight and heat. It is not yet known which wavelengths of light trigger this avoidance behavior or the microstructure of the cocoon shell that might allow light transmission. Here, the response of the cocooned larvae to different wavelengths, and the microstructure, hardness, and elemental components of the cocoon shell were studied. A population of cocooned larvae were introduced on the boundary line between illuminated and shaded areas with blue, green, red, or near-infrared light-emitting diodes. The cocoons moved away from the blue and green light. The distance from the boundary to the cocoons in the shaded area was longer under these long wavelengths, followed by the red light and shortest under the near-infrared light and nil under darkness. No difference was found in mortality between different wavelengths after three days of illumination. Scanning electron microscope observations of the surface of the cocoon shell revealed that the belt-like central ridge was porous, which likely allows ventilation and light transmission. The surface of the cocoon shell showed a uniform distribution of sulfur, potentially aiding in the capture of green wavelengths. The ridge had twice the thickness of the main body and was 1.9 times harder than the main body. These results may be applied to better understand the individual responses of this biological control agent to modifications to their environment, including light pollution.