Particle Porosity Research Articles

ELECTRICAL CONDUCTIVITY OF RUBBER COMPOUNDS: REVISITING THE INFLUENCE OF FUNDAMENTAL CARBON BLACK PROPERTIES

ABSTRACT Carbon blacks are electrically conductive; however, when carbon black is used as particulate reinforcement in a rubber compound, the compound electrical conductivity can vary from insulative to fully conductive depending on the loading level and properties of the carbon black. An investigation of the influence of three fundamental properties of carbon black—particle size, structure, and porosity—on rubber compound electrical conductivity was conducted. The deconvolution of these three parameters within the study allows for conclusive results to be drawn on what drives compound electrical conductivity and the underlying principles. The work is split into two parts: (1) a determination of the influence of particle size and structure and (2) the influence of porosity. Particle size traces its influence back to numerous particles are in a given volume of rubber compound. Structure’s influence on electrical conductivity varies with the particle size of the carbon black and is for the first time traced back to the aspect ratio of the aggregates. Porosity is separated as a variable in this work by introducing discrete levels of porosity to nascent carbon blacks via gasification. The results show that the impact of carbon black porosity on electrical conductivity in rubber compounds arises from a change in its envelope density and is not due to any change in the inherent aggregate conductivity.

Optimising the feeding system for improving pellet distribution levels in gas-based shaft furnace based on the improved analytic hierarchy process

To improve the gas flow distribution inside the gas-based shaft furnace and ensure the chemical reaction, the discrete element method was used to calculate the effects of revolving chute inclination, particle size mass distribution, particle size distribution width, and hopper angle on the pellet distribution indicators (particle segregation, porosity, gas permeability and feeding time). An improved analytic hierarchy process was presented to fully analyse the nine schemes set up as part of the research. The findings demonstrated that the positive segregation of small particles at the furnace's centre and wall occurred with several feeding systems. The largest influences on porosity were differences in particle size mass distribution and particle size distribution width, and an increase in the proportion of small particles resulted in a significant decrease in porosity. The increase of the mass ratio of large particles made the highest permeability, but also caused uneven distribution of the furnace charge along the radial direction. The simulation results and the ranking of benefits and drawbacks produced by the improved analytic hierarchy process approach agree, demonstrating the applicability of the method to optimise the feeding system as well as its value in identifying the major influences on the feeding system.

Unraveling the contribution of nucleation to the intercalation energy barrier for phase-transforming Li-ion battery materials

Phase-transforming intercalation compounds, such as LiFePO4 (LFP) and Li4Ti5O12 (LTO), are widely utilized in Li-ion batteries, particularly for applications requiring high power and operation at low temperatures. However, the impact of phase transformation kinetics on energy density losses under extreme conditions has been largely unexplored. Specifically, the role of nucleation, the initial stage of phase transformation, in contributing to battery performance losses has not been previously investigated. In this study, we not only quantified the significance of material-level factors, such as interfacial charge transfer, in the low-temperature and high-rate performance of LFP and LTO materials, but also provided the first estimates of the apparent activation energies of nucleation. Our findings revealed that nucleation, particularly in the case of LFP, contributes significantly to overpotential, highlighting its pivotal role among material-level factors. Furthermore, our analysis allowed us to differentiate between material-level and particle-level limitations for the LTO/LFP cell, emphasizing the paramount importance of controlling the porosity of secondary particles to ensure high tolerance towards high-rate/low-temperature discharge.

Tracked evolution of single biochar particle’s morphology during pyrolysis in operando x-ray micro-computed tomography

The engineering of biochars with desired morphologies and pore structures is a far-reaching objective towards sustainable pore-dependent environmental technologies, such as water and soil remediation or catalysis. We hereby report a series of experiments that allow the direct following of the shape and porosity of single biochar particles during pyrolysis. Particles ~ 1–2 mm in diameter of unwashed and water-washed raw walnut shells were continuously 3D imaged during pyrolysis to 575 ℃ at a 10 K min−1 in Ar to obtain time- and temperature-resolved x-ray micro computed tomographies to a 0.82 μm resolution. Results showed visual evidence of a 30% and 70% v/v particle shrinkage for unwashed and washed samples, respectively. Particle swelling between 200 and 300 ℃ in the unwashed sample provided evidence of the softening of native biopolymers associated with lignin in untreated biomass. A purpose-defined parameter Λ shows the temperature-dependence of pore re-distribution towards the center of the particle to be linear for both samples. Λ was found to be 3.2×10-4K-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$3.2\ imes {10}^{-4}{K}^{-1}$$\\end{document} in the washed sample, approximately 3.5 times faster than in the unwashed one. Such linear dependence is significantly slower than an exponential Arrhenius-like trend thereby providing a qualitative measure of the heat and mass transport phenomena limiting the chemical reactions in the porous medium. This evidence is key to resolving the pathways to the thermochemical decomposition of biomass leading to preparation of precision-engineered biochars.Graphical

Pore Network Modeling of Intraparticle Transport Phenomena Accompanied by Chemical Reactions.

In this work, a 3D pore network model (PNM) is introduced for modeling reaction-diffusion phenomena, with and without coupled heat transfer, in a spherical porous catalyst particle. The particle geometry is generated by packing thousands of microspheres inside a large sphere to represent the 3D geometry, porosity, and tortuosity of a spherical catalyst particle. A pore-network representation is extracted from this geometry, and a PNM for diffusion-reaction and heat conduction is constructed. This newly proposed particle-scale PNM allows for the application of realistic 3D nonuniform boundary conditions on the particle's surface, which is commonly encountered in slender packed-bed reactors. Concentration profiles inside the particle, and effectiveness of the reactions, is analyzed.

Investigation on the influence of particle size and porosity on solid phase fluidization and heat transfer in carbon fibre porous media

AbstractIn this paper, the 3D pore structure was reconstructed and solid phase fluidization in porous media was investigated. Based on the two fluid model, a computational fluid dynamics (CFD) model of gas–solid fluidization was established and the influence of particle size and porosity were investigated. When porosity was constant, during the fluidization process, the particle velocity and solid concentration standard deviation gradually decreased, and the bed height increased. At the same time, the smaller the particle size was, the smaller the solid concentration standard deviation was, the faster the bed height increased, and the more the particle temperature decreased. Based on the fixed value of particle size, when studying the effect of porosity on fluidization, it was found that with the enhancement of solid‐phase fluidization, particle velocity, solid concentration standard deviation, and particle temperature decreased, and bed height increased. Moreover, when porosity was large, particle velocity decreased rapidly, and solid concentration standard deviation reached a smaller minimum value, which took a longer time. Within the same time, the particle temperature also decreased less.

Population Balance Modeling of Particle Size and Porosity in Fluidized Bed Spray Agglomeration

Population Balance Modeling of Particle Size and Porosity in Fluidized Bed Spray Agglomeration

Hydrogen-based mineral phase transformation of bastnaesite: Detailed assessment of physicochemical properties and flotation behavior

Iron-bearing rare earth ores are valuable mineral resources, and the hydrogen-based mineral phase transformation (HMPT) process has significant development potential. In this study, the changes in physicochemical properties and flotation behavior of bastnaesites subjected to HMPT were investigated. The results show that bastnaesite decomposed slowly below 600 °C, but increased roasting temperature and time enhanced the decomposition, resulting in a roasted product with over 85 % rare earth oxide (REO) grade. HMPT also increased the initial pH of the flotation pulp from about 7.5 to 11.0 and increased La and Ce ion concentrations. By increasing the dosage of SHA, flotation recoveries comparable to the raw ore can be achieved. The HMPT process converted bastnaesite to REOF, which formed complex phases such as Ce7O12 and REF3 when exposed to air. This process resulted in significant damage to the particle structure, increased porosity, reduced geometric particle size, and improved wettability. After HMPT, Ce on the particle surface existed predominantly as Ce4+, which formed Ce(OH)4 precipitation during flotation, inhibiting SHA adsorption. The increased particle porosity facilitated deeper SHA penetration and greater adsorption, resulting in higher SHA dosage compared to the raw ore.

Multifunctional and Hierarchical Porous ZIF-8: Amine and Thiol Tagged via Mixed Multivariate Ligand Strategies for Enhanced CO2 and Iodine Adsorption.

This study demonstrated a simple and innovative way of using the direct de novo synthesis to fabricate the mesoporous structure and diverse functionality of ZIF-8 for environmental cleanup and gas storage applications. By introducing different ligands, we have developed a version of ZIF-8 that could better capture carbon dioxide (CO2) and iodine. The ZIF-8 was successfully designed to have the hierarchical and mesoporous structure with the functional groups of amine and thiol groups by adjusting the pKa values (from 8 to 12) of ligand instead of original ligand, 2-methyl imidazole (Hmim, pKa~14.2). The modulation of ZIF-8 particle size, porosity, and functional characteristics was achieved through varied ligands and their concentrations, streamlined into a single and room-temperature synthesis condition. The resulting ZIF-8 materials exhibit intricate hierarchical architectures and a high density of functional groups, significantly enhancing molecular diffusion and accessibility. Among the developed materials, ZIF-8-AS, featuring both amine and thiol groups, demonstrates the fastest adsorption kinetics and a twofold increase in iodine adsorption capacity (qm = 1101.5 mg·g-1) compared to ZIF-8 (qm = 514.3 mg·g-1). Furthermore, the hierarchical mesoporosity of ZIF-8-A-10.1 improves CO2 adsorption to 1.0 mmol·g-1 at 298 K, which is 1.3 times higher than that of the microporous ZIF-8.

Autoencoder-based inverse design and surrogate-based optimization of an integrated wet granulation manufacturing process

In pharmaceutical manufacturing, integrating model-based design and optimization can be beneficial for accelerating process development. This study explores the utilization of Machine Learning (ML) techniques as a surrogate model for the optimization of a three-unit wet-granulation based flowsheet model for solid dosage form manufacturing. First, a reduced representation of a wet granulation flowsheet model is developed, incorporating a granulation and milling process, along with a novel dissolution model that accounts for the effect of particle size, porosity, and microstructure on dissolution rate. Two optimization approaches are compared, including an autoencoder-based inverse design and a surrogate-based forward optimization. Both methods address the bi-objective problem of maximizing dissolution time and product yield by identifying the optimal granulation and mill process parameters. For this case study, both approaches were effective and incurred a similar computational cost, averaging under 4 s. However, the autoencoder approach offers an advantage through dimensionality reduction, a feature not available in surrogate-based optimization. Dimensional reduction is particularly beneficial for complex process designs with numerous inputs and outputs. The lower dimensional representation helps improve process understanding through enhanced visualization of the process design space and facilitates feasibility studies involving multiple constraints. The autoencoder-based inverse design introduced in this work showcases an implementation of AI and ML in pharmaceutical process development, demonstrating the potential to enhance process efficiency and product quality in complex manufacturing scenarios.

Energy-Efficient Geopolymer Composites Containing Phase-Change Materials-Comparison of Different Contents and Types.

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H2O2 was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures.

Understanding the role of porous particle characteristics and water state distribution at multi-scale variation on cellulase hydrolysis of lignocellulosic biomass

Porous particle characteristics of lignocellulosic biomass and the water state distribution surrounding particles determine enzyme/solute transfer, while inherently affecting the liquefaction and hydrolysis reactions. For submillimeter biomass particles (<500 μm), deep eutectic solvent pretreatment tended to create additional macropores (∼4%, pore volume of 4.3 mL/g) and micropores (∼3%, pore area of 2.26 m2/g) at the extragranular and cell wall scales, simultaneously with reducing particle size by 15%. The pretreated biomass exhibited preferential rapid liquefaction over sugar production, leading to a ∼70% reduction in particle size only after 3 h hydrolysis. This further increased particle porosity (∼85% after 12 h hydrolysis) with the transition from large surface-pores to interior micropores. The increases in the tissue/cell-scale pore size and intraparticle area had greater significance for improving hydrolysis performance than particle size reduction. Additionally, particle liquefaction released constrained water in capillary pores and enhanced slurry fluidity; capillary water and free water became main transfer carriers during the hydrolysis. Free water activity was positively related to sugar production (r = 0.80–0.85), and integrating it with particle component and porosity allowed for accurate prediction of hydrolysis yields (R2 = 0.98–0.99). Inspired by particle liquefaction, a short-time feeding strategy was proposed to reconstruct high-solid hydrolysis.

Assessment of Physico-Chemical Behavior and Sorptivity-Diatomaceous Earth as Support for Paraffinic Phase-Change Materials.

Diatomite's most common application is its use as a sorbent for petroleum substances. Since paraffin is a petroleum derivative, this paper investigates the sorption capacity of diatomite to absorb it. In this paper, the physical and chemical properties were studied for 4 different fractions of diatomite (0-0.063 mm; 0-2 mm; 0.5-3 mm; and 2-5 mm) in the crude and calcined states, and the sorption capacity of diatomite earth for absorbing paraffinic phase-change substances was determined. The physical and chemical studies of the material included conducting an oxide chemical composition analysis using XRF, examining the composition of the mineral phases using X-ray diffraction, and determining the particle size, porosity, and thermal conductivity of the diatomite. Morphology images were also taken for all 8 diatomite variants using scanning electron microscopy. Each fraction was subjected to static calcination at 850 °C for 24 h. The results showed that the calcination of the diatomite increased the porosity of the material and reduced the thermal conductivity coefficient, and most importantly, the sorption capacity to absorb paraffins. The highest sorption capacity was characterized by calcined diatomite powder, that is, diatomite with the smallest particle size. Absorption of paraffinic substances by diatomite exceeding 200 wt.% is possible. Thus, diatomite is one of the feasible candidates for an economical and lightweight building material for making PCM composites for thermal energy storage in buildings.

Rational Function-Based Approach for Integrating Tableting Reduced-Order Models with Upstream Unit Operations: Dry Granulation Case Study.

We present a systematic and automatic approach for integrating tableting reduced-order models with upstream unit operations. The approach not only identifies the upstream critical material attributes and process parameters that describe the coupling to the first order and, possibly, the second order, but it also selects the mathematical form of such coupling and estimates its parameters. Specifically, we propose that the coupling can be generally described by normalized bivariate rational functions. We demonstrate this approach for dry granulation, a unit operation commonly used to enhance the flowability of pharmaceutical powders by increasing granule size distribution, which, inevitably, negatively impacts tabletability by reducing the particle porosity and imparting plastic work. Granules of different densities and size distributions are made with a 10% w/w acetaminophen and 90% w/w microcrystalline cellulose formulation, and tablets with a wide range of relative densities are fabricated. This approach is based on product and process understanding, and, in turn, it is not only essential to enabling the end-to-end integration, control, and optimization of dry granulation and tableting processes, but it also offers insight into the granule properties that have a dominant effect on each of the four stages of powder compaction, namely die filling, compaction, unloading, and ejection.

Artificial sandstone preparation method

This paper addresses the challenges faced in the CO2 sequestration research project in Kazakhstan due to the limited availability and substandard quality of core samples. It underscores the necessity for using sandstone analogs to ensure reliable and consistent test outcomes, especially in measuring the rock's deformation and failure strength. The paper details the efforts made to create synthetic sandstone samples that closely resemble the original reservoir sandstones in particle size, cement content, mineral composition, and porosity. The study found that metakaolin forms a weak cement bond and that kaolin fully converts to metakaolin at 500°C, but not at 200°C. Additionally, the shear strength of sandstone samples depends on the particle size, mineralogy, and clay content. Furthermore, it explores the triaxial test responses of both the reservoir sand and the synthetic sandstone samples.

Influence of mineral filler characteristics on the filler–asphalt interfacial behavior

The knowledge of mineral filler characteristics and their impacts on filler–asphalt interfacial behavior is not systematic and completed yet. In this paper, eight mineral fillers prepared using the same milling procedure were investigated. The filler–asphalt interfacial behavior was analyzed by differential scanning calorimetric and dynamic shear rheometer tests. Results reveal that in contrast to form factor and specific surface area, particle porosity, particle density, aspect ratio, angularity index, fractal dimension and feature roughness decrease with decreasing particle size. Limestone filler exhibits more regular shape, less significant angularity and richer surface texture than basalt filler. Of all particle characteristics studied, form factor and specific surface area are suggested to be the determining factors affecting filler–asphalt interfacial behavior. Moreover, microscopic morphology analysis provides an insight to interpret the differences explored in mastic interfacial property. The results help employ applicable particle characteristics that fabricate mastic with a stable interface system.

Comparison of non-reactive solute transport models for the evaluation of fluid flow in packed beds with implications for heap leaching practice

This study investigated the effects of mean particle size fraction, bottom particle size, particle porosity and wettability on solution scale preferential flow behaviour via step input tracer tests in drip irrigated, narrowly and mixed-sized beds under steady state fluid flux. Nine solute transport models were used to quantify this behaviour reflected in the residence time distribution (RTD) profiles. Four were empirical models: three compartmental model configurations (CM-1, CM-2, CM-3) and tanks-in-series (TIS) model. The remainder five models were semi-empirical: advection dispersion (AD), piston exchange (PE), piston exchange - diffusion variant (PE-D), piston dispersion and exchange (PDE) and piston dispersion and exchange - diffusion variant (PDED). The model fit results showed that the mono-porosity TIS, AD and CM-2 models were the worst performers, while the dual porosity PDE and novel PDE-D models achieved the lowest average error values across the various systems. Higher levels of particle wettability coupled with capillary effects produced peculiar RTD curves that were relatively more difficult for the mono-porosity models to simulate. The model parameters investigated included the longitudinal dispersion coefficient (Dds), dead to total volume fraction (VD/VT), dynamic to total saturation fraction (βd/βT), overall mass transfer coefficient (Kma) and maximum diffusional pore length (X). The results showed that an increase in the average particle size within the beds led to higher VD/VT, Dds and X values, but lower βd/βT and Kma values. These indicate an overall increase in solution scale preferential flow behaviour. Decreased capillary suction and connectivity between particle pores and inter-particle voids were deemed responsible for the results. Higher levels of particle porosity acted as a buffer against these effects. Overall, the results highlight the benefit of the addition of fines (0.1–1 mm particles) during the agglomeration process in heaps to help reduce solution scale preferential flow behaviour and increase liquid hold-up. This is more necessary when the ore has low to moderate levels of porosity (surface area: <2 m2/g) and will also increase the modelling options available as most models performed better fitting data from such beds.

Utilizing acid-etched Fe-waste for sustainable synthesis of conductive perovskite-type materials from automotive industrial residue

A common method for reducing waste and environmental problems brought on by landfills is to reuse waste, especially heavy metals such as iron. Automotive industrial waste containing Fe-rich metal is successfully transformed into a highly pure structure of Fe2O3 using an etching method with HNO3 acid. This resulting structure serves as a precursor for synthesizing LaNi1-xFexO3±δ perovskite conducting materials. The desired perovskite conductive phase can be produced by substituting Fe2O3-treated waste at the B-site (Ni position) before calcination at 1200 °C. However, LaNiO3±δ and LaNi0.6Fe0.4O3±δ could not be synthesized under ideal conditions, as indicated by XRD analysis using TOPAS software, which revealed the presence of undesirable phases. Both compounds, LaNiO3±δ and LaNi0.6Fe0.4O3±δ demonstrated electrical conductivity with values of 362 S/cm and 42 S/cm at 550 °C, respectively. Nonetheless, electrical conductivity of both compounds decreased due to unintended phase contamination during the synthesis process. The Fe2O3-substituted compounds at the Ni position, in an exact amount of 1 mol, exhibited minimal electrical conductivity. Although the synthesis conditions to produce a single phase of LaFeO3±δ were identified, LaFeO3±δ, despite its low electrical conductivity, is frequently used in electrical devices as a gas detection sensor. The thermal expansion coefficient of all synthesized waste samples is represented in the range of 12–13 × 10−6 °C−1, which is comparable to IT-SOFC electrolyte materials. Furthermore, microstructural investigation revealed that the introduction of Fe into LaNiO3±δ reduced particle size and porosity, ultimately resulting in higher densities. These findings were confirmed through synchrotron radiation x-ray tomographic microscopy (SR-XTM) analysis. The research suggests that converting Fe-waste into a pure phase of Fe2O3 using a strong acid etching technique can serve as a viable precursor for synthesizing conductive materials. This approach enhances the value of industrial waste while also reducing its volume.

Aggregate Cloud Particle Effects in Exoplanet Atmospheres

Aerosol opacity has emerged as a critical factor controlling transmission and emission spectra. We provide a simple guideline for the effects of aerosol morphology on opacity and residence time in the atmosphere, as it pertains to transit observations, particularly those with flat spectra due to high altitude aerosols. This framework can be used for understanding complex cloud and haze particle properties before getting into detailed microphysical modeling. We consider high altitude aerosols to be composed of large fluffy particles that can have large residence times in the atmosphere and influence the deposition of stellar flux and/or the emergence of thermal emission in a different way than compact droplet particles, as generally modeled to date for extrasolar planetary atmospheres. We demonstrate the important influence of aggregate particle porosity and composition on the extent of the wavelength independent regime. We also consider how such fluffy particles reach such high altitudes and conclude that the most likely scenario is their local production at high altitudes via UV bombardment and subsequent blanketing of the atmosphere, rather than some mechanism of lofting or transport from the lower atmosphere.

Synthesis and Characterization of Red Pigment from Acid Regeneration Plant (ARP) By-product Via Rod Milling Process

Iron o xide waste from acid regeneration plants (ARP) is often discarded due to its non-profitability. This research aims to introduce a value-added process to convert iron oxide waste into red pigment via rod milling process. The iron oxide waste collected from ARP was grinded with a rod milling machine at 30 rpm for 24 hours. The ground product was then mixed with industrial-grade red pigment in various ratios. The mixed samples were then rod-milled again into ultra-fine particles. A total of seven samples were prepared, applied onto a canvas and analysed by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) methods. From the analyses, the existence, composition, and orientation of iron oxide were established. The waste-derived red pigments were subsequently subjected to particle size analysis on a scanning electron microscopy (SEM) platform, with results showcasing the efficiency of the rod milling process. Colour-related properties of the samples before and after canvas application were investigated using the L*a*b* system with a chromameter. Empirical outcomes indicated that the a* value plays an important role in determining the redness of the sample. Overall, the a* values obtained were above 15 and gradually increased in accordance to the amount of industrial-grade red pigment added. The oil absorptivity of red pigments was also tested via an oil absorptivity test. Notably, the assay signified that particle size and porosity affect the amount of oil that can be absorbed by the pigment.