Particle Packing Density Research Articles

Sustainable Heat Generation in Flow from a Molecular Solar Thermal Energy Storage System

As the global deployment of renewable technologies accelerate, finding efficient ways to store energy will aid in responding to shifting energy demands. A prospective option not only in harvesting solar energy but also in emission‐free heating is MOlecular Solar Thermal (MOST) energy storage. A central part of MOST applications is to develop methods to release the stored energy. Herein, the Quadricyclane (QC)‐to‐Norbornadiene catalyzed back reaction is explored in a specially designed packed‐bed reactor. Four distinctly sized and purposely synthesized platinum on activated carbon catalysts are studied to trigger the heat release from the energy‐dense QC isomer. The catalysts are fully characterized using a variety of structural, surface, and spectroscopic techniques. Parameters to optimize catalytic conversion and heat release in flow conditions are explored including particle size and packing behavior, flow rates, and molecular residence times. Moreover, using CO pulse chemisorption technique, site time yield values and a turnover number are reported. Complementary to the flow reactions, computational fluid dynamic simulations applying lattice Boltzmann methods to two catalytic packed beds of different size ranges are done to evaluate fluid‐dynamic behavior within the reactor bed to ascertain the ideal particle size and packing density for catalysis in MOST applications.

Spheroid models to elaborate the broken symmetry and equivalent volume of molecules in crystalline phase.

Dense packing of particles has provided powerful models to elaborate the important structural features of matter in various systems such as liquid, glassy, and crystalline phases. The simplest sphere packing models can represent and capture salient properties of the building blocks for covalent, metallic, and ionic crystals; it, however, becomes insufficient to reflect the broken symmetry of the commonly anisotropic molecules in molecular crystals. Here, we develop spheroid models with a minimal degree of anisotropy, which serve as a simple geometrical representation for a rich spectrum of molecules-including both isotropic and anisotropic, convex and concave ones-in crystalline phases. Our models are determined via an inverse packing approach: Given a molecular crystal, an optimal spheroid model is constructed using a contact diagram, which depicts the packing relationship between neighboring molecules within the crystal. The spheroid models are capable of accurately capturing the broken symmetry and characterizing the equivalent volume of molecules in the crystalline phases. Moreover, our model retrieves such molecular information from low-quality x-ray diffraction data with poorly resolved structures, and by using soft spheroids, it can also describe the packing behavior in cocrystals.

Evaluating 3-parameter packing model with discrete element modeling

Accurate prediction of particle packing density remains challenging. Herein, the particle packing is simulated by discrete element modeling and the packing density results are used to evaluate the 3-parameter particle packing model. When the 3-parameter model is applied to binary and ternary blended mixes, the mean absolute errors in packing density prediction are 0.96% and 1.37%, respectively. Overall, the accuracy of the 3-parameter model is very good when applied to binary blends but not as good when applied to ternary blends, especially when the intermediate size particles are dominant. The discrete element modeling reveals that even when the intermediate size particles are dominant, there are significant particle interactions between the smaller size and larger size particles, which have not been properly accounted for in the existing packing models. Hence, there is still room for improving the existing packing models, requiring further discrete element modeling to study particle interactions.

Optimal analysis of the proportion between modified lime mud and active mineral additive in mortar: Insights from particle size distribution and packing density modeling

The use of lime mud in building materials is becoming more popular. However, its application has been limited by optimizing the proportion of lime mud and other active admixtures. In this study, the lime mud was firstly modified by a mechanochemical method to refine the grain size. Secondly, various particle size distribution functions were used to described the particle size distribution of cementitious materials. Further, based on the modifier Anderson and Andreasen (MAA) function, the optimal mixing proportion of cementitious materials was designed, and its feasibility was confirmed by the orthogonal test and range analysis. According to the hydration analysis through X-Ray Diffraction analysis (XRD), Thermogravimetry-Derivative Thermogravimetry (TG-DTG), Scanning Electron Microscope (SEM), and Mercury Intrusion Porosimetry (MIP), a significant increase in the harmless pore content was observed in the mortar with the optimal blend of MLM, MK, and SF.

Measuring and Simulating the Transient Packing Density During Ultrasound Directed Self‐Assembly and Vat Polymerization Manufacturing of Engineered Materials

AbstractUltrasound‐directed self‐assembly (DSA) uses ultrasound waves to organize and orient particles dispersed in a fluid medium into specific patterns. Combining ultrasound DSA with vat photopolymerization (VP) enables manufacturing materials layer‐by‐layer, wherein each layer the organization and orientation of particles in the photopolymer is controlled, which enables tailoring the properties of the resulting composite materials. However, the particle packing density changes with time and location as particles organize into specific patterns. Hence, relating the ultrasound DSA process parameters to the transient local particle packing density is important to tailor the properties of the composite material, and to determine the maximum speed of the layer‐by‐layer VP process. This paper theoretically derives and experimentally validates a 3D ultrasound DSA model and evaluates the local particle packing density at locations where particles assemble as a function of time and ultrasound DSA process parameters. The particle packing density increases with increasing particle volume fraction, decreasing particle size, and decreasing fluid medium viscosity is determined. Increasing the particle size and decreasing the fluid medium viscosity decreases the time to reach steady‐state. This work contributes to using ultrasound DSA and VP as a materials manufacturing process.

Structural aspects of concrete incorporating recycled coarse aggregates from construction and demolished waste

The study explores the potential of recycling construction and demolition waste into recycled coarse aggregates (RCA) to decrease waste generation and carbon footprint, using a standard compacting effort to calculate compressive strength and particle packing density in a specific cylindrical volume. This study investigates the impact of RCA on concrete’s workability, compressive strength, flexural, split tensile, drying shrinkage, electrical resistivity, rapid chloride penetration, and microstructural characteristics using XRD, SEM, and EDAX. Test findings showed that increasing the replacement percentage beyond the optimum value (RCA 25) had detrimental effects on the strength and microstructure of the concrete. RCA 25 has a higher compressive, flexural, and split tensile strength in the order of 11.56%, 3.06%, and 5.17% respectively compared to reference concrete, as well as 5.23% increase in drying shrinkage, 8.79% higher electrical resistivity, and 4.68% higher resistance to chloride penetration than reference concrete.

Numerical investigation on the densification of granulated porous indium tin oxide powders before compaction

Dense and uniform initial packing structures of powders are of key significance in powder metallurgy process, which can provide the precondition for the fabrication of high-performance components with low cost and high efficiency. In this paper, the packing densification of indium tin oxide (ITO) granulated micro powders with continuous size distributions and internal porosity under three-dimensional vibrations was numerically investigated by discrete element method (DEM). Firstly, the DEM model was validated by physical experiments, and the contact parameters between particles and the porosity therein were determined. Then the effects of operating parameters on the macro/micro properties (e.g., packing density, coordination number (CN), pores, and forces) of the packing structures were analyzed. Results show that the mean CN cannot intuitively reflect the packing structure due to the complex and varied inter-particle contacts caused by the inhomogeneity of the particle size in a multi-sized granular system. Additionally, the excellent packing structure of porous ITO particles is always obtained from low amplitude when the vibration intensity is the same. Corresponding mechanism analyses reveal that higher amplitude normally causes strong convective diffusion, leading to more pores in the packing. This increases the probability of wedging effect occurring during settling, thereby reducing the packing density. However, optimal packing quality with low amplitude can only be achieved when coupled with high frequency. Therefore, applying vibration is an effective way to achieve dense packing of porous spherical particles, especially at low amplitude and high-frequency operating conditions.

Effect of cylinder wall parameters on the final packing density of mono-disperse spheres subject to three-dimensional vibrations

Achieving densely packed particles is desirable within the industries of ceramics, pharmaceuticals, defence and additive manufacturing. In this work, we use the discrete element method (DEM) to determine the effect of wall parameters on the final packing density of mono-disperse spheres subject to 4 varying three-dimensional vibration and fill conditions. We focus specifically on the impact of the container wall parameters on the particles' final packing density. Following on from the validation of the DEM simulation the particle-wall coefficient of restitution, the particle-wall coefficient of rolling friction and the particle-wall coefficient of sliding friction were varied individually and the effect on the final packing density analysed. For relatively low particle-particle friction glass beads, the effect of these wall properties had no discernible effect on the final packing density achieved. Following on from these findings the particle-wall properties were varied at the extreme values of particle-particle coefficient of rolling friction and particle-particle coefficient of sliding friction. For a particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of restitution resulted in a minor increase in the final packing density of particles though this was not statistically significant. For a particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of rolling friction resulted in a minor decrease in the final packing density of the particles though again not to a degree where the trend can, with complete certainty, be distinguished from the random error across the repeats. Finally, when the particle-particle coefficient of sliding friction = 1, increases in particle-wall coefficient of sliding friction resulted in a significant decrease in the final packing density of particles. This decrease was attributed to the propagation of force chains throughout the packing. The significant decrease in final packing density with particle-wall coefficient of sliding friction highlights the need to choose appropriate vessel materials to optimise packing of particles with a high particle-particle coefficient sliding friction. Conversely, for particles with minimal particle-particle friction, the particle-wall friction coefficient has no effect on the final packing density of particles - a potentially valuable finding for certain industrial applications. All simulations were run using the open-source DEM package LIGGGHTS on the University of Birmingham's high-performance computer: BlueBEAR. All the code files used within this paper can be found on Github: https://github.com/Jack-Grogan/DEM-Vibropacking-Wall-Effects.

Rheology of Highly Filled Polymer Compositions-Limits of Filling, Structure, and Transport Phenomena.

The current state of the rheology of various polymeric and other materials containing a high concentration of spherical solid filler is considered. The physics of the critical points on the concentration scale are discussed in detail. These points determine the features of the rheological behavior of the highly filled materials corresponding to transitions from a liquid to a yielding medium, elastic-plastic state, and finally to an elastic solid-like state of suspensions. Theoretical and experimental data are summarized, showing the limits of the most dense packing of solid particles, which is of key importance for applications and obtaining high-quality products. The results of model and fine structural studies of physical phenomena that occur when approaching the point of filling the volume, including the occurrence of instabilities, are considered. The occurrence of heterogeneity in the form of individual clusters is also described. These heterogeneous objects begin to move as a whole that leads to the appearance of discontinuities in the suspension volume or wall slip. Understanding these phenomena is a key for particle technology and multiphase processing.

Novel Ultra-High-Performance Concrete (UHPC) Enhanced by Superhydrophobic and Self-Luminescent Features

This study explores the potential of using basalt reinforced UHPC by incorporating simultaneously self-cleaning and self-luminescent features, paving the way for sustainable advancements in civil engineering. New green formulations of UHPC were developed by integrating supplementary cementitious materials and optimizing water to the binder ratio, followed by using basalt fibers to enhance strength and ductility. The fabricated samples with high particle-packing density exhibit sufficient workability and compressive strength up to 136 MPa, and, when incorporating basalt fibers, a notable reduction in brittleness. The inner microstructure of basalt fibers was observed to be smooth, homogeneously distributed, and well adhered to the UHPC matrix. To ensure the desired long-lasting visual appearance of decorative UHPC and reduce future maintenance costs, a time-effective strategy for creating a light-emitting biomimetic surface design was introduced. The samples exhibit high surface roughness, characterized by micro to nano-scale voids, displaying superhydrophobicity with contact angles reaching up to 155.45°. This is accompanied by roll-off angles decreasing to 7.1°, highlighting their self-cleaning features. The self-luminescence feature showcased intense initial light emission, offering a potential energy-efficient nighttime lighting solution.

Sustainable Concrete: Exploring Fresh, Mechanical, Durability, and Microstructural Properties with Recycled Fine Aggregates

The growing construction industry and global population have led to increased demand for concrete, resulting in increased waste production. Recycling construction and demolition (C&D) waste as recycled fine aggregates (RFA) in concrete could help reduce waste and conserve natural resources. This research delves into the meticulous examination of particle packing density within specific cylindrical volumes under standard compacting efforts, elucidating an order of compressive strength. The study comprehensively explores various concrete properties, including workability, compressive strength, flexural strength, split tensile strength, drying shrinkage, electrical resistivity, rapid chloride penetration, and microstructural characteristics (analyzed through XRD, SEM, and EDAX). RFA particles, ranging from 0.15 to 4.75 mm, were employed as partial replacements for fine aggregates, with replacement percentages varying from 0% to 100% in increments of 25%. The empirical findings underscore that the incorporation of RFA significantly enhances concrete properties. However, it was observed that surpassing the optimum replacement percentage of 25% (RFA 25) adversely impacts the concrete’s strength and microstructure. Specifically, RFA 25 exhibited remarkable improvements, with a 14.75% increase in compressive strength, a 6.61% boost in flexural strength, and a 13.14% enhancement in split tensile strength compared to conventional concrete (RC). Furthermore, RFA 25 demonstrated a 4.16% increment in drying shrinkage, 17.65% higher electrical resistivity, and an 18.83% superior resistance to chloride penetration compared to RC. The analysis of XRD, SEM, and EDAX results elucidated that at lower replacement percentages, the pozzolanic reaction enhances strength by forming additional hydration products. Conversely, at higher replacement levels, strength diminishes.

A continuum model for magnetic particle flows in microfluidics applicable from dilute to packed suspensions.

The manipulation of magnetic microparticles has always been pivotal in the development of microfluidic devices, as it encompasses a broad range of applications, such as drug delivery, bioanalysis, on-chip diagnostics, and more recently organ-on-chip development. However, predicting the behavior and trajectory of these particles remains a recurring and partly unresolved question. Magnetic particle-laden flows can display intricate collective behaviors, such as packed plugs, column-shaped aggregates, or fluidization, which are difficult to predict. In this study, we introduce a finite-element model to simulate highly dense flows of magnetic microparticles. Our method relies on an interpenetrating continuum approach, where both the liquid and particle phases are described by the Navier-Stokes equations, in which the magnetic force, interphase friction, and interparticle forces were included. We demonstrate its applicability across the entire range of particle packing densities and compare the results with experimental data from real microfluidic application cases. The model successfully replicates complex behaviors, such as particle aggregation, plug formation and fluidization. This approach has potential to accelerate microfluidic device development by reducing the need for costly and time-consuming experimental optimization.

Relating early-age hydration and flow loss of mortar prepared with manufactured sand

Cement-based materials prepared with manufactured sand can exhibit quick loss of fluidity. However, the estimation of the flow loss remains difficult given the variable contents and physiochemical properties of the microfines in various sands. This paper studies the fluidity loss of mortar mixtures made with different manufactured sands varying in mineral composition and content of microfines. The effect of microfines on accelerating the early-age hydration of cement before the deceleration period was evaluated by quantifying the generation of early hydration products. Test results show that the growth of yield stress corresponding to the loss of mini-slump flow of mortar mixtures were mainly determined by the formation of early hydration products, in addition to the volume fraction and packing density of aggregate grains and powder particles. An approach was then proposed that can assess the loss of mini-slump flow of mortar mixtures prepared with manufactured sand, regardless of the type and content of the microfine materials in the sand.

The effect of concentrated buttermilk on cheese milk rennet-induced coagulation and rheological properties at various buttermilk to skim milk ratios

Buttermilk (BM) is still undervalued since its incorporation in dairy products negatively impairs physicochemical properties. Concentrating BM could mitigate these adverse outcomes. This study aimed to characterize the impact of 2-fold BM concentration by reverse osmosis (RO) and ultrafiltration (UF) on the rennet-induced gelling characteristics of milk containing varying BM to skim milk (SM) ratios. Oscillatory rheology was used to determine the gel coagulation properties (rennet coagulation time [RCT], storage modulus [G’] at 2 × RCT, maximal firming rate [MFR]), and the gelation regime by determining the fractal dimension (df). Increasing BM protein concentration enhanced rennet gel G′ and MFR. Increasing the ratio of BM to SM significantly decreased the G′ and MFR values. The df values increased from 2.69 for non-concentrated BM, to 2.76 for RO, and to 2.88 for UF, indicating that the gel density increased, whereas the casein (CN) aggregates decreased in size. CLSM and SEM observations also showed a higher CN particle's packing density in UF gels compared to non-concentrated and RO gels. Application of the gel regime model revealed that all gels were in the transition regime. This result contrasted with the microscopy and df values. We conclude that while the df values are a good representation of the gel structure, the gel regime characterization is not, and the model cannot be applied to complex milk rennet gels. This study provides a new rheological characterization of BM rennet gels. UF of BM enhanced rennet gel formation and might facilitate the use of BM in cheese making.

Study on the optimisation of cement and binder content to develop a sustainable high-performance concrete

According to ACI concrete terminology, “High Performance concrete (HPC) is defined as a concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices”. It is a new generation of concrete that has been evolved recently and are well received for its exceptional performance of strength and durability. Due to these characteristics, HPC are utilized in the construction of bridges, hydropower structures, pavements, mass concrete projects etc. HPC is a cementitious composite material composed of an optimized gradation of granular constituents, a water-to-binder ratio of less than 0.3, a high percentage of discontinuous internal fiber reinforcement and HPC can hold compressive strength of more than 60 MPa. HPC considered in this study is made with high-strength steel fibers, fine sand, cement, mineral and chemical admixtures and water. The conventional mix design used for normal concrete cannot be adopted for HPC because of the high compressive strength to be achieved. The main objective is to develop a sustainable HPC mix with optimum particle packing density to achieve the desired strength with the lowest cement and binder content. As part of the investigation, the impact of different constituents of HPC such as cement content and binder content on the compressive strength were examined. Also, the optimum particle packing density of mixes with different amount of cement and binder content were studied using EMMA software. From the results it is observed that the increase in cement or binder content beyond a particular level will have minimal impact on the compressive strength.

A multi-perspective study on the influence of physical and chemical properties of 5 types of fly ash on the performance of high-volume blended fly ash cementitious slurry

The study has investigated the influence of the physical and chemical properties of five types of fly ash on the performance of high volume blended fly ash cementitious (HFC) materials. The study found that the vitreous element composition of fly ash exhibits a superior correlation with compressive strength as compared to the overall element composition. Moreover, the cumulative heat displays a stronger correlation with compressive strength than the heat flow. Besides, the packing density has a significant effect on the compressive strength of HFC materials. Whereas, the slurry flowability largely depends on the water film thickness. In practical engineering, the slurry compressive strength can be predicted by testing the fly ash vitreous content, cumulative heat data and the packing density of mixed particles in concert. The findings are significant as in practical projects, the performance of cementitious materials is often unstable due to different sources and batches of fly ash. The study provides insights into the factors affecting the rheological properties of the slurry and the hydration behaviour of different fly ash blended slurries.

Modified particle packing approach for optimizing waste marble powder as a cement substitute in high-performance concrete

This study explores the potential of utilizing waste marble powder (WMP) instead of cement to develop environmentally friendly high-performance concrete (Eco-HPC). It assesses Eco-HPC's particle packing density, workability, mechanical characteristics, and durability at various stages. High-performance concrete (HPC) mixtures were optimized using a Modified Andreasen and Andersen (MAA) particle packing model to minimize cement content from 550 to 385 kg/m3. The MAA particle packing model demonstrated its ability to enhance and refine mixture microstructures. Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) were employed to optimize and predict the mechanical properties and water absorption of modified Eco-HPC blends at 7, 28, and 56 days. As the coefficient of determination indicates, ANN outperformed RSM in predicting Eco-HPC properties across various ages. Substituting cement with WMP, Silica Fume (SF), and Fly Ash (FA) results in a dense microstructure. The mortar containing 20 % WMP and 10 % SF achieves the highest wet packing density at 0.9749 and the lowest void ratio at 0.025, respectively. The formation of CSH in the 70C/20 M−10SF mixture led to a substantial reduction in calcium hydroxide content, indicating enhanced mechanical properties. SEM analysis at 56 days demonstrated significant pozzolanic reactions in the 70C/20 M−10SF mixture, resulting in substantial CSH formation. Furthermore, the embodied CO2 index for 70C/20 M−10SF was reduced to 5.07 kg/MPa/m3, compared to the 100C/0M with value of 8.17 kg/MPa/m3. Economic and environmental assessments reveal enhanced mechanical properties and microstructure when using WMP. This evaluation confirms the effectiveness of 70C/20 M−10SF utilization, paving the way for further advancements in Eco-HPC development.

Extractable latex yield from Taraxacum kok-saghyz roots is enhanced by increasing rubber particle buoyancy

Taraxacum kok-saghyz (TK) is a leading alternative rubber-producing plant that produces natural rubber (NR) latex in laticifers within its roots. Unlike the tropical rubber tree, Hevea brasiliensis, TK can be grown in temperate regions, such as the northern United States, as the basis of a domestic rubber production industry. To support such an industry, efficient, scalable rubber extraction techniques are needed. In this study, aqueous extraction was used to recover TK natural rubber latex (TNRL) from four harvests of greenhouse-produced TK roots with a new technique that improves rubber particle buoyancy in root homogenate by chelation. The new method includes harvest, cleaning, and homogenization of freshly harvested roots, followed by centrifugation, vacuum collection of latex, and purification. Treatment of homogenate with ethylenediaminetetraacetic acid (EDTA), a divalent cation chelator, allowed more than twice as much latex to be extracted from fresh homogenate. EDTA-treated rubber particles contained lower concentrations of divalent cations than untreated ones in fresh homogenate and homogenate stored for two weeks. Long term (three months) storage of root homogenate similarly yielded more latex than fresh homogenate and had low divalent cation rubber particle concentrations, indicating that heavy cations had slowly leached from the particles into the aqueous medium during storage. Rubber particle size was larger in this treatment suggestive of rubber particle agglomeration but this was prevented and reversed by EDTA. Removal of divalent cations via chelation increased particle packing density of particles in concentrated latex and appeared to increase the gel content of dried latex samples. Molecular characterization of dried samples of purified TNRL established that the rubber was of the high molecular weight needed for product manufacturing.

Influence of PPD and Mass Scaling Parameter on the Goodness of Fit of Dry Ice Compaction Curve Obtained in Numerical Simulations Utilizing Smoothed Particle Method (SPH) for Improving the Energy Efficiency of Dry Ice Compaction Process

The urgent need to reduce industrial electricity consumption due to diminishing fossil fuels and environmental concerns drives the pursuit of energy-efficient production processes. This study addresses this challenge by investigating the Smoothed Particle Method (SPH) for simulating dry ice compaction, an intricate process poorly addressed by conventional methods. The Finite Element Method (FEM) and SPH have been dealt with by researchers, yet a gap persists regarding SPH mesh parameters’ influence on the empirical curve fit. This research systematically explores Particle Packing Density (PPD) and Mass Scaling (MS) effects on the agreement between simulation and experimental outputs. The Sum of Squared Errors (SSE) method was used for this assessment. By comparing the obtained FEM and SPH results under diverse PPD and MS settings, this study sheds light on the SPH method’s potential in optimizing the dry ice compaction process’s efficiency. The SSE based analyses showed that the goodness of fit did not vary considerably for PDD values of 4 and up. In the case of MS, a better fit was obtained for its lower values. In turn, for the ultimate compression force FC, an empirical curve fit was obtained for PDD values of 4 and up. That said, the value of MS had no significant bearing on the ultimate compression force FC. The insights gleaned from this research can largely improve the existing sustainability practices and process design in various energy-conscious industries.

Effect of recycled powder on the yield stress of cement paste with varied superplasticizers

The influence of superplasticizer on the yield stress of cement pastes with recycled powder (RP) was examined in the study. Four superplasticizers were used to obtain the similar fluidity by adjusting the dosage. The results show that the 10% RP decreases the yield stress of paste compared to the reference paste at the same fluidity, but 20% and 30% RP increases the yield stress, ranging from 11 to 599%. The superplasticizer with adsorptive group of phosphate-type minimizes the yield stress of paste than that of polycarboxylate -type, but it made a significant increment in yield stress as the incorporating of RP increased. Besides, the polycarboxylate superplasticizer with the higher molecular weight of side chain and charge density led to lower yield stress. Based on the Yodel model, the yield stress of paste with RP was analyzed by the polymer adsorption and particle packing density of particles to reveal the influence of RP with different superplasticizers on the colloidal interaction and contact network among the particles. The packing density of particles with recycled powder was a little higher than the reference paste, but the higher fraction of fine particles made a stronger PSD effect, which improved the particle contact interaction. On the other hand, due to the higher polymer adsorption of recycled powder than cement, especially for superplasticizer with phosphate group, the average surface coverage was increased, which extended the separation distance, so that colloidal interaction among particles was weaken.