Spherical Materials Research Articles

Preliminary Investigation on the Application of a Semi-Lightweight Mullite Spherical Solid Waste Material in Ladle Permanent Layer

The heat dissipation of high alumina castables for ladle permanent layer is a topic worthy of attention and solution. It is proposed to use spherical porous mullite (a solid waste) instead of irregular M70 mullite aggregate in castable to reduce the thermal conductivity and realize a high-strength and lightweight design. The effect of spherical porous mullite content in castables on thermal conductivity, service strength and thermal shock resistance were discussed. The results demonstrated that the substitution amount of spherical porous mullite increased, the bulk densities of the castables dropped from 2.68 to 2.38 g.cm−3, the apparent porosity rose from 15.5 to 25.0%. The thermal conductivities reduced from 1.174 to 0.585 W.m−1.K−1 (1000°C), which can be ascribed to the increased porosity extending the heat transfer path. Furthermore, owing to the high strength of spherical mullite and its excellent bonding with matrix, the mechanical strength of castable was at a high strength level, with modulus of rupture of 18 M Pa and cold crushing strength of 76 MPa at the spherical porous mullite completely substituting M 70 mullite. The semi-lightweight and low thermal conductivity castable containing spherical porous mullite show great application potential in the ladle permanent layer.

Separation of Spherical Nanosilica from Agricultural Wastes in Vietnam via Ultrasonic-Assisted Precipitation and Application for Effective Removal of Methylene Blue from Aqueous Solution

Agricultural wastes including bagasse and rice husk ashes are employed for synthesizing spherical nanosilica materials via the ultrasonic-assisted precipitation process in the present study. The comparison between them and nanosilica prepared from pure sodium silicate is also carried out. The role of the NH4OH : ethanol volume ratio is demonstrated. The obtained nanosilica is characterized by modern methods including X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), infrared spectroscopy (IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms (BET). The nanosilica material is employed as an effective adsorbent for the removal of methylene blue (MB) from an aqueous solution. The suitable pH and adsorbent dosage are determined at 8 and 0.375 g·L−1. The adsorption isotherm study is surveyed based on Langmuir and Freundlich isotherm models. Pseudo-second-order kinetic model and Weber–Morris intraparticle diffusion model well describe the chemical nature of the adsorption. The thermodynamic parameters of the reaction are determined based on the Van’t Hoff equation.

A comparative study on the malachite green dye adsorption of chemically synthesized and green MgFe2O4 nanoparticles using gerbera floral waste extract.

The situation of discharging a large amount of dyes from the textile industries has caused many adverse effects on human health and the ecosystems. Emerging bio-nanomaterials represent a new trend in efficient dye removal in aqueous media. Herein, we mention that MgFe2O4 bioprepared using gerbera extract has been successfully used to adsorb malachite green (MG) in water. A comparison was made to determine the dye removal efficiency between biogenic MgFe2O4 (MFOB) and chemical MgFe2O4 (MFOC). The spherical MFOB material exhibited a large surface area of 85.0 m2 g-1 and high crystallinity. The obtained outcomes showed that the highest adsorption capacity of MG dye was 584.49 mg g-1 at a MFOB dose of 0.05 g L-1 and MG concentration of 10 mg L-1. Higher correlation coefficients in the Langmuir isotherm suggested monolayer adsorption of MG. The Box-Behnken design and response surface method were established to optimize MG removal percentage under the conditions, i.e., initial MG concentration (10-30 mg L-1), adsorbent dose (0.02-0.08 g L-1), and pH of dye solution (6-8). MFOB had good reusability with high removal efficiencies after three continuous cycles. Post reuse, this adsorbent still showed excellent stability through the verification of their structural properties in comparison with fresh MFOB, showing potential for practical applications.

Nitrogen-modified spherical porous carbon derived from aluminum-based metal-organic frameworks as activation-free materials for supercapacitors

Carbon materials derived from metal-organic frameworks (MOFs) retain the precursor's regular unique morphology and net-like voids, which offers them the advantages of large specific surface area (SSA) and high capacitance for energy storage. In this paper, spherical amorphous porous carbon materials with hierarchical pores (DHTAC-2) were prepared using one-step carbonization of Al-MOF. The carbon has a large SSA (2666 m2 g−1) and a large pore volume (2.35 cm3 g−1). The obtained carbon (DHTAC-2) demonstrates an excellent specific capacitance (298.8 F g−1) at 1 A g−1 and capacitance retentions of 97.3 % and 98.0 % after 120,000 cycles at 50 A g−1 and 100 A g−1, respectively. In addition, Nitrogen-doped carbon (N-DHTAC) has increased pyridine-N, pyrrole-N and graphite-N content. The three types of N significantly improved its wettability, reversible pseudocapacitance and conductivity, respectively, resulting in a superior capacitance (355.0 F g−1@1 A g−1) and enhanced energy density (17.7 Wh kg−1@350 W kg−1) of the assembled electric double layer capacitor (EDLC) device. The device exhibits an extremely low decline rate of 10.12 % over 10,000 cycles at 10 A g−1, verifying N-DHTAC material is a promising active material for supercapacitors.

A solution for the neutron diffusion equation in the spherical and hemispherical reactors using the residual power series

A novel analytical solution to the neutron diffusion equation is proposed in this study using the residual power series approach for both spherical and hemispherical fissile material reactors. Various boundary conditions are investigated, including zero flux on the boundary, zero flux on the extrapolated boundary distance, and the radiation boundary condition (RBC). The study also shows how two hemispheres with opposing flat faces interact. We give numerical results for the same energy neutrons diffused in pure P239u. By qualitative comparison with the homotopy perturbation method and Bessel function-based solutions, the residual power series method (RPSM) presents accurate series solutions that converge to the exact solutions, as shown in this study. Moreover, numerical results were shown to be improved by the computer implementation of the analytic solutions.

Latent Thermal Energy Storage for Solar Industrial Drying Applications

Solar heat is an attractive alternative in industrial processes. However, the intermittent and stochastic nature of solar energy necessitates the use of heat storage systems to bridge the gap between heat production and demand. This study introduces a validated numerical analysis approach to investigate the performance of latent storage tanks filled with spherical phase-change materials. A 1D thermal model is developed to describe the charging processes of adipic acid as PCM. The study examines the performance characteristics of latent heat storage in terms of stored energy and duration through parametric investigations. For mass flow rates ranging from 600 to 1000 kg/h, storage durations were found to vary from 440 to 582 min. The storage duration decreased significantly from approximately 1150 min at a charging temperature of 160 °C to 470 min at a charging temperature of 240 °C. The bed porosity affected the storage process, with a porosity of 0.5 achieving a thermal energy storage of around 344 MJ but requiring a longer charging time of about 610 min. Higher heating rates allowed for lower storage durations, with storage durations of approximately 460 min for a heating rate of 3 °C/min, compared to 660 min, for a heating rate of 0.5 °C/min.

Design and Preliminary Results of Debris Flow Analog Model in Laboratory Scale, Case Study of Bentarsari Sub-watershed

Bentarsari sub-watershed is located at Brebes Regency administrative area, Central Java. This sub-watershed is surrounded by hills composed by volcanic breccia of Kumbang Formation (Tpk) and consists of sedimentary rocks at the lower part of the watershed. Volcanic breccia is the oldest rock in the watershed and appears to have a more intensive weathering process, making it more susceptible to landslides which are mostly followed by debris flow. Accordingly, the aim of this research is to conduct a laboratory scale analog modeling of debris flow event in this sub-watershed. The main materials used for modeling are moderate to completely weathered volcanic breccias to residual soils. The rainfall scenario is 50 mm/day as lower bound of heavy rain, 100 mm/day as lower bound of very heavy rain and 150 mm/day as lower bound of extreme rain. As a first step, the computer simulation is used for analyzing material movement of the model, using spherical materials with a density of 1.84 g/cm3 taken from average value of laboratory test results. The simplification process is carried out on spherical material with 4 cm and 2 cm diameter to depict moving material. The solid material volume used in the simulation is 0.07 m3 while the liquid is 0.03 m3. Then, a laboratory scale analog model has been made with a tub having dimensions of 0.5 m high, 2 m long and 1 m wide. When this analog model is tilted 50 degrees, the resulting slip plane then extends to the backward of the slope and the flowing materials move downward colliding with the previously deposited material, forming a flow which bends slightly to the left at the foot slope. The results of this research are expected to lead to a new method for modelling debris flows using analog models at laboratory scale.

Numerical investigation of the melting characteristics of spherical-encapsulated phase change materials with composite metal fins

A spherical phase change material (PCM) capsule with embedded composite fins for latent thermal energy storage is proposed and studied in this paper. A three-dimensional numerical model is established and validated by comparing with experimental data in the literature. The influences of the embedded fins with different structures, capsule size, and heating temperature on the melting performance are analyzed. Results show that the insertion of composite metal fins promotes the melting process owing to the extension of thermal surface. The fin with perforations exhibits higher energy storage performance as compared to the non-perforated one, which can be attributed to the reduction of the blockage effect as well as the increment in the filling volume of PCM. The punched fin with three perforations in each sheet is preferable to adopting in spherical PCM capsule in view of the less time required for completely melting and the higher energy storage capacity. However, as the size of capsule increases, the heat transfer enhancement contributed by the inclusion of the embedded fins reduces. In addition, the melting process can be accelerated significantly by raising the temperature of external shell surface from 340 to 360 K, while such improvement tends to be less pronounced for the further increase in heating temperature. This study can provide useful guidance for the optimal design of thermal energy storage system with spherical PCM capsules.

Numerical study of the melting process of spherical phase change material with variable thermal conductivity

Numerical study of the melting process of spherical phase change material with variable thermal conductivity

Zinc hydroxystannate anchored PAP-activated carbon spheres for enhancing flame protection of aqueous epoxy coatings

Here, carbon spheres (CS), a carbonaceous spherical material with a wide source and easy preparation, were used as enhanced nano-fillers to reinforce the flame retardancy of aqueous epoxy intumescent coatings. To overcome the defects of CS themselves during combustion, polydopamine (PDA) was co-deposited with adenosine triphosphate (ATP) on its surface to obtain activated carbon spheres with C-N-P structure (CS/PAP), which can contribute to the formation of intumescent char layer. Meanwhile, zinc hydroxystannate (ZHS), as a non-halogen, environmentally friendly, and efficient flame retardant, was introduced to the surface of carbon phosphide spheres to obtain a composite functional hybrid reinforcement (CS/PAP@ZHS). Adiabatic performance tests indicated that the backside temperature of the CS/PAP@ZHS filler-reinforced EP expansion specimen was maintained at the minimum fig. (168.8 °C), confirming its highest resistance to heat penetration. Compared to the CS-based EP, the CS/PAP-loaded EP showed reduced smoke emission, indicating the effectiveness of the PAP intumescent phosphate modification for smoke suppression. By comparison, the CS/PAP@ZHS-based EP showed the largest char residue (29.1 % in N2, 12 % in air), expansion height (23.1 mm), and minimal smoke density grade (40.7 %). Additionally, compared with pure EP, the peak heat release rate (PHRR), total heat release rate (THR), peak smoke production rate (PSPR), and total smoke production (TSP) of CS/PAP@ZHS/EP are reduced by 33.3 %, 28.2 %, 37.4 %, and 23.6 % respectively, demonstrating its best fire and smoke suppression properties.

Influence of tank-to-particle diameter ratio on thermal storage performance of random packed-bed with spherical macro-encapsulated phase change materials

Thermal energy storage material is always filled in the packed bed system in a random accumulation manner, and there is an interrelationship between the tank-to-particle diameter ratio (TPDR) and the porosity. Therefore, in this paper, the packed bed latent heat storage system is constructed based on spherical macro-encapsulated phase change materials (PCM). To study the influence of TPDR on the thermal performance of a randomly packed bed, a transient two-dimensional axisymmetric symmetry continuous solid phase model is developed. The experimental and numerical results are compared to verify the accuracy of the model. The heat transfer and pressure drop characteristics between air and PCM capsules are analyzed in detail. The results indicate that the average porosity reaches the maximum at around TPDR≈1.7 position, which is about 0.7. In the same packed bed, when the TPDR is larger, the pressure drop is more affected. The diameter of the heat storage ball changes from 25 mm to 75 mm, the TPDR is reduced by 66.7%, the heat storage of the PCM is almost unchanged, and the heat storage capacity of the stainless-steel spherical shell is reduced by 72%, and the heat storage capacity of the entire heat storage ball is reduced by 12%.

Engineering Strategy for Enhancing the Co Loading of Co-N4-C Single-Atomic Catalysts Based on the ZIF-67@Yeast Construction.

The Co-N4-C single-atom catalysts (SACs) have attracted great research interest in the energy storage and conversion fields owing to 100% atom utilization. However, enhancing the Co loading for higher electrocatalytic performance is still challenging. In this context, we propose an engineering strategy to fabricate the high Co atomic loading Co-N4-C SACs based on the zeolitic imidazolate framework-67 (ZIF-67)@yeast construction. The rich amino groups provide the possibility for Co2+ ion anchorage and ZIF-67@yeast construction via the biomineralization of yeast cells. The functional design induces the formation of Co-N4-C sites and regulates the porosity for exposure of such Co-N4-C sites. As a result, the Co-N4-C sites were anchored on spherical micrometer flower carbonaceous materials through our novel strategy. The as-obtained optimal sample exhibited a Co atomic loading of 12.18 wt % and a specific surface area of 403.26 m2 g-1. High Co atomic loading and large specific surface area delivered excellent electrocatalytic kinetics as well as a high discharge voltage of 1.08 V at 10 mA cm-2 for more than 100 h in Zn-air batteries. This work represents a promising strategy for fabricating high-loading SACs with high activity and good durability.

Malignant mesothelioma cells with characteristic intracytoplasmic vacuolization and lipids.

In this brief report, we described some uncommon cytomorphological features of malignant mesothelioma (MM) cells in pleural effusions. The tumor cells exhibited abundant cytoplasmic vacuolization, with presence of single or multiple eccentric nuclei in several cells. In the Giemsa-stained smear, we observed a glossy spherical material in some cells, which tested positive in Sudan III stain. In immunocytochemical analysis, tumor cells were positive for calretinin, podoplanin, epithelial membrane antigen, and methylthioadenosine phosphorylase; tumor cells were negative for BRCA1-associated protein 1, CD68, and desmin. The intracytoplasmic vacuoles were positive for adipophilin expression.

Coupled electrochemical–mechanical model for fracture analysis in active materials of lithium ion batteries

Mechanical degradation is a significant cause of battery aging: the stress arising in the electrode microstructure during operation causes fractures, leading to capacity and power fade. This work aims to quantify the fracture behavior of LCO-graphite battery by computing the stress intensity factor. At first, the full electrochemistry of the cell is modeled to obtain realistic boundary conditions for the fracture model linked to user-defined battery usage. The fracture model of a spherical active material particle is implemented in Ansys to compute stress intensity factor with modified J-integral for mechanical-diffusive phenomena. Three aspects are deepened: (a) The effects of the mechanical-diffusive coupling at the crack tip, and its influence on the stress intensity factor; (b) Assessing fracture propagation due to static loading and its stability; (c) Creating a fracture diagram which quantifies the level of fracture due to the combination of different operating conditions and geometry of the electrode microstructure. Results show that crack propagation in a single cycle is limited to high current, but it is likely to be unstable. Furthermore, it is quantified how greater current and particle radius increase the stress intensity factor, aiming to provide electrode design advice in the perspective of increasing battery life.

Morphology-Dependent Interaction of Silica Nanoparticles with Intestinal Cells: Connecting Shape to Barrier Function.

The intestinal compartment ensures nutrient absorption and barrier function against pathogens. Despite decades of research on the complexity of the gut, the adaptive potential to physical cues, such as those derived from interaction with particles of different shapes, remains less understood. Taking advantage of the technological versatility of silica nanoparticles, spherical, rod-shaped, and virus-like materials were synthesized. Morphology-dependent interactions were studied on differentiated Caco-2/HT29-MTX-E12 cells. Contributions of shape, aspect ratio, surface roughness, and size were evaluated considering the influence of the mucus layer and intracellular uptake pathways. Small particle size and surface roughness favored the highest penetration through the mucus but limited interaction with the cell monolayer and efficient internalization. Particles of a larger aspect ratio (rod-shaped) seemed to privilege paracellular permeation and increased cell-cell distances, albeit without hampering barrier integrity. Inhibition of clathrin-mediated endocytosis and chemical modulation of cell junctions effectively tuned these responses, confirming morphology-specific interactions elicited by bioinspired silica nanomaterials.

Preparation and characterization of TATB-based energetic composite microspheres by continuous pipe-stream self-assembly technology

Recently, the continuously preparation of molding powder with good flowability has attracted much attention in energetic materials field (EMs), however, the traditional preparation process is inadequate. In this paper, a device that can continuously prepare large-scale energetic composite microspheres was designed and built, and the preparation of TATB-based energetic particles was realized, which has greatly improved the impact sensitivity and mechanical property (Impact energy are 58 ∼ 65 J, increased by 16%∼30%; Compression stress and strain of the PBX increased by 52.04% and 60.81%). SEM reveals that as the composition of the binder’s changes, the particle morphology exhibits several intriguing patterns. Meanwhile, TATB's crystal structure and excellent thermal stability have been preserved through pipe-stream self-assembly technique. This preparation procedure, which has a broad range of potential applications, can also be used to generate energetic particles of different Explosive @ Binder systems and even functional spherical materials in other domains.

High value-added regeneration of anode materials from retired lithium-ion batteries: Structural design and synthesis process

Recovery of anode materials from retired lithium-ion batteries attracted widespread attention because of the environmental and resource factors. Silicon carbon composites are expected to replace graphite due to the high specific capacity, stable voltage platform and abundant reserves of silicon. Herein, we have successfully synthesized spherical silicon/recovered-graphite composite (SSRC) with different silicon content (5%∼20%) via a spray pyrolysis technology. For comparison, we fabricated 10% Si flaky silicon/recovered-graphite composite. The morphological and compositional analysis show Si nanoparticles can be uniformly distributed on the framework, thus the volumetric expansion of Si can be effectively relieved. The electrochemical properties indicate spherical material with 10% Si exhibits an outstanding cycling performance of 91.6% at 1.0C over 200 cycles, surpassing that of flaky material (88.7%). Additionally, NMP and ethanol can be collected separately for recycling. Overall, this work proposed an efficient and environmentally friendly approach for recovering anode materials and enabling their value-added utilization.

Методика расчета тепловлагопереноса в специальной защитной обуви пожарного-спасателя

Разработана методика расчета тепловлагопереноса в специальной защитной обуви пожарного-спасателя, которая позволяет учесть терморегуляционные механизмы в стопе для оценки комфортности обуви, изготовленной из определенных пакетов материалов и эксплуатируемой в широком диапазоне внешних воздействий, как по тепловым и влажностным факторам, так и в зависимости от уровня активности (тяжести выполняемой работы) пожарного-спасателя. Для определения безопасной работы в специальной защитной обуви необходима оценка степени деструкции кожи (степень ожога). The article describes the solution of the problem of non-stationary heat transfer in the «foot – footwear – environment» system for multilayer flat, cylindrical or spherical materials and non-stationary heat transfer from the outer surface of the special protective footwear to firefighter's foot. The well-known biothermal equation and the generalized heat transfer equation are used as the basis for the model of heat and moisture transfer in boot materials, taking into account sweating on the human skin surface. It is possible to get data on the thermal state of the foot under various conditions by solving these equations with appropriate coefficients and boundary conditions: zero heat flow in the center of the foot and convective environmental conditions on the surface of the last layer of porous shoe material. Modeling for three cases of human activity: resting state, walking with a speed of 4.8 km/h, light work (in the office room) under the same environmental conditions was carried out. The obtained results showed that the model of heat and moisture transfer in protective boots, taking into account thermoregulatory processes in the foot, can be used to predict the functionality of the materials for the bottom and top of the boots in terms of the skin burns likelihood. The method for calculating heat and moisture transfer in special protective boots for a firefighter-rescuer has been developed, based on the simulation, which includes: - construction of a geometric image of a model of protective boots; - determination of the firefighter-rescuer operating mode; - selection of material packages for the details of the boot top and bottom. An indication of the thermophysical, structural, geometric characteristics of the materials allows, using the selected climatic conditions and the firefighter-rescuer operating mode, to establish the initial and boundary conditions for solving the basic system of heat and moisture transfer equations. The solution of the system of equations with the boundary and initial conditions makes it possible to assess the comfort of boots, as well as the rate of destruction of the skin under intense thermal effects (the probability of burns of varying degrees). Based on this analysis, further optimization of the boots design can be carried out by choosing different material packages or evaluating the thermal effect under various external influences.

Activated biocarbons derived from molasses as new tailored CO2 adsorbents.

An innovative and cost-effective method for enhancing CO2 capture by modifying the textural properties of derived activated biocarbons was explored. A molasses solution was prepared with a sucrose concentration of 1mol/dm3. A two-step synthesis process was involved, which includes the hydrothermal synthesis of spherical carbonaceous materials from molasses followed by chemical activation. The carbonaceous material to activation agent ratio was studied from 1 to 4. The CO2 adsorption of all activated biocarbons was tested at 0, 10, and 20°C and a pressure of up to 1bar. The results showed a significant correlation between CO2 adsorption and the textural properties of the activated biocarbons. The activated biocarbon with the highest CO2 adsorption of 7.1mmol/g at 1bar and 0°C was successfully produced by modifying with KOH. The selectivity of CO2 over N2 calculated on the basis of the Ideal Adsorbed Solution Theory was excellent (16.5). The Sips model was found to be the most suitable, and the isosteric heats of adsorption were also specified.

Controllable preparation and thermal properties of SiC spherical high temperature shape-stable composite phase change materials based on gel-casting

The development of high-temperature composite phase change materials (CPCMs) suitable for mass-production and high-performance is still a very urgent problem in the efficient utilization of renewable energy. In this study, a SiC spherical high-temperature CPCMs based on aqueous gel-casting suitable for batch molding using commercially available silicone molds is proposed. The porosity of the porous SiC framework can be adjusted by changing the content of starch granules in the slurry. The sample containing 20 wt% starch has relatively high open porosity and thermal conductivity, which is considered to be close to the optimal formulation of CPCMs. This formula possesses a high thermal conductivity of 10.2 W·m−1·k−1 benefiting from the continuous thermal transport channels consisting of the uniformly distributed large spherical pores and interconnected small pores. Meanwhile, the thermal storage density of the CPCMs reaches 395.21 J·g−1 in the temperature range of 550 ℃ and 750 ℃ since up to 89.06% of the pores are filled with molten salts. At the same time, the CPCMs exhibit excellent cycle stability in 100 thermal cycles. In particular, these CPCMs can be easily integrated into thermal energy storage (TES) system. Based on the rapid heat storage simulation of the C-D model, the packed-bed latent thermal energy storage system containing spherical CPCMs will have a more uniform temperature distribution and a 26.7% reduction in charging time compared with the traditional packed-bed system. This work provides a new reference for the design of spherical CPCMs in TES systems.