Bulk Solid Materials Research Articles

Approach to Validate ISPM-15 Compliance for Commercial Treatment Certification of Dielectric Standard Heating of Bulk Solid Wood Packing Materials using Radio Frequency

Abstract To substantially reduce the risk of alien invasive species moving to new geographic areas, phytosanitary treatment of wood packaging materials (WPM) in compliance with the International Standard of Phytosanitary Measures No. 15 (ISPM-15) is required by trading partners. Approved treatments include conventional heating, methyl bromide and sulfuryl fluoride fumigation, and dielectric heating (DH). The DH standard was officially adopted in 2013 but has not been practiced commercially due primarily to insufficient operational validation at commercial scale. In 2022, we converted our 50-kW radio frequency (RF) unit with a 1,200-board foot capacity from an oscillator electromagnetic field power generator to a solid-state power supply, which allows for selective power input adjustments during treatment; we also switched from a five-plate to a three-plate winged electrode system to improve heating uniformity. Each loading cycle can treat sufficient material to build ∼94 standard Grocery Manufacturers Association pallets. Our research team characterized the dielectric heating pattern and options for monitoring wood temperatures over a wide-ranging test matrix of WPM that varied by wood species, dimension, moisture content, and loading configuration. We found that this upgraded RF system markedly reduced treatment times and improved heating uniformity, allowing us to develop methods that can be used to verify compliance with ISPM-15 for improved technology transfer to industry. We also discuss the operational cost of RF treatment and make general cost comparisons to conventional heat treatment for WPM.

High-Pressure Torsion: A Path to Refractory High-Entropy Alloys from Elemental Powders

For the first time, the refractory high-entropy alloys with equiatomic compositions, HfNbTaTiZr and HfNbTiZr, were synthesized directly from a blend of elemental powders through ten revolutions of high-pressure torsion (HPT) at room temperature. This method has demonstrated its effectiveness and simplicity not only in producing solid bulk materials but also in manufacturing refractory high-entropy alloys (RHEAs). Unlike the melting route, which typically results in predominantly single BCC phase alloys, both systems formed new three-phase alloys. These phases were defined as the Zr-based hcp1 phase, the α-Ti-based hcp2 phase, and the Nb-based bcc phase. The volume fraction of the phases was dependent on the accumulated plastic strain. The thermal stability of the phases was studied by annealing samples at 500 °C for one hour, which resulted in the formation of a mixed structure consisting of the new two hexagonal and cubic phases.

Damage constitutive model of fly ash–cementitious iron tailings powder under small strain

With the vigorous development of industrial economy, the production capacity and level have been significantly improved, but at the same time, a large amount of iron tailings, fly ash and a series of bulk solid waste materials have been accumulated. These industrial wastes have caused serious impact on the ecological environment. How to deal with them effectively is an urgent problem that needs to be solved. The aim of this study was to investigate the effect of cement and fly ash compound admixtures on the mechanical properties of iron tailings powder (ITP). Hence, different mixing ratios of cement and fly ash were used to prepare two kinds of ITP-based materials. A range of uniaxial compressive strength (UCS), resonance column (RC), scanning electron microscopy and X-ray diffraction tests were conducted to investigate the roles of cement, fly ash and curing age in ITP solidification. A random one-dimensional damage model was imported to study the damage evolution of ITP materials using the UCS and RC test results, which showed that cement and fly ash enhanced the unconfined compression strength and small-strain stiffness of ITP. When 5–10% fly ash content was used as a substitute for 10% cement, the unconfined compressive strength and small-strain modulus of cement–fly ash–ITP increased with curing age. The microstructure and mineralogy analysis confirmed that fly ash enhanced the strength of the material. Overall, the damage constitutive model effectively represented the randomness of the compressive strength and stress–strain relationship of ITP materials under unconfined conditions.

Going against the Grain: Atomistic Modeling of Grain Boundaries in Solid Electrolytes for Solid-State Batteries.

Atomistic modeling techniques, including density functional theory and molecular dynamics, play a critical role in the understanding, design, discovery, and optimization of bulk solid electrolyte materials for solid-state batteries. In contrast, despite the fact that the atomistic simulation of microstructural inhomogeneities, such as grain boundaries, can reveal essential information regarding the performance of solid electrolytes, such simulations have so far only been limited to a relatively small selection of materials. In this Perspective, the fundamental properties of grain boundaries in solid electrolytes that can be determined and manipulated through state-of-the-art atomistic modeling are illustrated through recent studies in the literature. The insights and examples presented here will inspire future computational studies of grain boundaries with the aim of overcoming their often detrimental impact on ion transport and dendrite growth inhibition in solid electrolytes.

Numerical study of heat transfer for gravity-driven binary size particle flow around circular tube

As the primary working medium in moving bed heat exchangers, solid bulk materials are composed of multiple size particles. To clarify the effect of particle size distribution (PSD) on heat transfer, the discrete element method (DEM) is used to study the flow and heat transfer of binary size particle flow around a circular tube. The heat transfer model for multiple size particles is developed and coupled with DEM method. The particle flow characteristics with PSD width are analyzed in detail. The results show that particle size segregation, competitive flow and flow instability are the unique characteristics of binary size particle flow around a tube. Wider PSD will enhance these characteristics and have a positive effect on particle renewal in the stagnation zone, which could decrease the local heat resistance. The total heat transfer coefficient between particle flow and tube wall increases at most by 9.73% as PSD is wider. • Binary size particle flow around a circular tube is studied with DEM method. • Binary size particle flow can form local particle size segregation around tube. • Binary size particles can decrease the stagnation zone above the tube. • A wider binary particle size distribution can increase the flow instability. • A wider binary particle size distribution can enhance heat transfer performance.

Photoelectron Spectroscopy and Theoretical Studies of Ge6MnO- Cluster with a MnV≡O Unit Interacting with a Double Aromatic Ge64- Ligand.

The structures and chemical bonding of Ge6MnO- are investigated using anion photoelectron spectroscopy and theoretical calculations. The lowest energy structure of Ge6MnO- is found to have a C5v symmetric structure with an O atom attached to a pentagonal bipyramidal MnGe6. Chemical bonding analyses reveal that Ge6MnO- can be considered as a [MnV≡O]3+[Ge64-] complex with two unpaired 3d electrons on Mn. The Ge64- ligand is highly stable in Ge6MnO- and exhibits double aromaticity with 10 delocalized σ electrons and 6 delocalized π electrons. Our calculations show that the Ge64- ligand could also form [CrIV≡O]2+[Ge64-] in Na2Ge6CrO and [FeIV≡O]2+[Ge64-] in Na2Ge6FeO. The results suggest the possibility of designing and synthesizing a series of stable high-valent metal oxide anionic species with the composition [M≡O]n+[Ge64-] in the gas phase or in the salt-stabilized bulk solid materials.

Amelioration of Energy Dissipation Through Robotic Evacuation Process of Solid Bulk Materials: Effectiveness of Wheel Slip Control System

Amelioration of Energy Dissipation Through Robotic Evacuation Process of Solid Bulk Materials: Effectiveness of Wheel Slip Control System

Carbon Nanomaterial-Based Lubricants: Review of Recent Developments

This review article summarizes the progress of research on carbon nanomaterial-based lubricants witnessed in recent years. Carbon nanomaterials, such as graphene, carbon nanotubes (CNTs), fullerenes and carbon nanostructures, are at the center of current tribological research on attaining superior lubrication performance. The development of nanomaterial-based solid lubricants, lubricant additives and bulk materials and the related issues in their processing, characterization and applications as well as their tribological performance (coefficient of friction and wear rate) are listed in a structured tabulated form. Firstly, regarding nanomaterial-based solid lubricants, this study reveals that carbon nanomaterials such as graphite, graphene, graphene-based coatings and diamond-like carbon (DLC)-based coatings increase different tribological properties of solid lubricants. Secondly, this study summarizes the influence of graphene, carbon nanotubes, fullerene, carbon nanodiamonds, carbon nano-onions, carbon nanohorns and carbon spheres when they are used as an additive in lubricants. Thirdly, a structured tabulated overview is presented for the use of carbon nanomaterial-reinforced bulk material as lubricants, where graphene, carbon nanotubes and carbon nanodiamonds are used as reinforcement. Additionally, the lubricity mechanism and superlubricity of carbon nanomaterial-based lubricants is also discussed. The impact of carbon nanotubes and graphene on superlubricity is reviewed in detail. It is reported in the literature that graphene is the most prominent and widely used carbon nanomaterial in terms of all four regimes (solid lubricants, lubricating additives, bulk material reinforcement and superlubricity) for superior tribological properties. Furthermore, prospective challenges associated with lubricants based on carbon nanomaterials are identified along with future research directions.

Moisture determination. Mass loss on drying – commercial sampling washed away

What is this? Sampling washed away; “samplewashing?” Greenwashing is a known term nowadays, but is there such a thing as “Samplewashing” too? Yes and no: Greenwashing is the process of conveying a false impression or providing misleading information about how a company’s products are more environmentally sound. … Greenwashing is a play on the term “whitewashing”, which means using misleading information to gloss over bad behaviour. And that is what this sampling paper is all about: presenting moisture results on samples of solid bulk materials where the theory of sampling was not applied… and therefore sampling errors are magnified by not only glossing over the representativeness of the process, but at the same time by watering-down the monetary profits of the trade for one whilst condensing them for the other party. It really is “Samplewashing” when it comes to moisture determination!

Analysis of operational window in Freeman Technology uniaxial powder tester

The operational window of the recently developed Freeman Technology Uniaxial Powder Tester (UPT) in terms of specimen aspect ratio (H/D), consolidation stress, and consolidation and failure strain rates is investigated for a range of bulk solid materials. The results show that the measured uniaxial unconfined yield stress (uUYS) decreases as aspect ratio increases but this sensitivity of uUYS to H/D reduces significantly for aspect ratios of greater than 1.5. The sensitivity of uUYS to aspect ratio is attributed to the intersection of slip planes with the top and bottom platens. The critical aspect ratio (defined as a ratio beyond which uUYS becomes independent of aspect ratio) is found to be a material-specific property, but it is increased with increasing consolidation stress. A correlation between the internal angle of friction and the critical aspect ratio is found, but it does not follow previously reported work. This discrepancy could be attributed to the differences in the packing fraction of the samples in uniaxial compression and the shear cell tests which were used to measure the internal angle of friction. uUYS is found to be independent of consolidation strain rate for the range investigated here (0.005 to 0.05 s−1). A very high level of repeatability is observed for the measurement of compressibility response of bulk solids with no sensitivity to consolidation strain rate uniaxial compression; powder flow; flowability; unconfined yield stress; aspect ratio; strain rate; compressibility.

Guest Editorial: Platinum Group Metals: Widespread Use As Functional Material

Platinum group metals (pgms) have widespread applications as functional materials in many different industries. The applications range from catalytic surfaces or particles, sensors, biomedical imaging or drug delivery systems and thermocouples up to jewellery items that we use for special moments of our life. The pgms are used as solid bulk materials, powders, thin films, organic compounds or liquid dispersions of nanoparticles. This astounding variety of applications of pgm materials is reflected in the current issue of Johnson Matthey Technology Review.

Mathematical model and numerical analysis method for dynamic fracture in a residual stress field.

Residual stress field is a self-equilibrium state of stress in the bulk solid material with the inhomogeneous field of the inelastic deformations. The high level of tensile residual stress often leads to dynamic fracture resulting in the instantaneous and catastrophic destruction of the materials because the cracks are fed with the strain energy initially stored in the bulk materials due to the residual stress. The dissipation of the strain energy with crack growth results in the release and the redistribution of the residual stress. In this paper, we propose an effective mathematical model and a numerical analysis method for dynamic fracture in residual stress field. We formulate the dynamic behavior of solid continuum with residual stress field in the context of particle discretization scheme finite element method. This formulation enables the appropriate evaluation of (i) release and redistribution of residual stress due to dynamic propagation of the cracks and (ii) the effect of the elastic wave on crack propagation, which are the most substantial problems on dynamic fracture in residual stress field. We perform the experiments and the simulations of dynamic fracture process in chemically tempered glass sheets with residual stress field to validate the proposed numerical analysis method. The simulation results show remarkable agreement with the experiments of the catastrophic failure of the glass sheets with residual stress field in all aspects of crack behavior. These results indicate that the proposed model and method can rigorously evaluate the release and the autonomous redistribution of the residual stress in the dynamic fracture process.

Analytical Criterion for the Strength of Bonded-Dispersed Gels During Pipeline Transportation

Modern pipeline systems, both main and industrial, allow transporting a wide range of liquid and gaseous substances, including a variety of solid bulk materials, minerals, building materials and mixtures. However, the development of pipeline transport systems today is hindered by the lack of theoretical developments in the implementation of practical engineering projects for the creation of both main and industrial product pipelines for various purposes. Therefore, the further development of the theory of flows of various substances in pipelines and the creation of universal methods for engineering calculations of design parameters of pipeline systems based on this theory are priority tasks for the further development of product pipeline transport. The studies were carried out in accordance with the condition of stochastic transformation of the coagulation-thixotropic structure of the gel flow into sol. Such a stochastic transformation of the coagulation-thixotropic structure can be observed both when reaching the mode that determines the turbulent motion of a viscous colloidal solution, and somewhat earlier – at the stages of the laminar flow regime of the solution. Based on the formal phenomenological analysis, it has been determined that during the transition of the laminar mode of motion of the Newton fluid flow in a cylindrical tube to the turbulent mode, the transported structured gel flow is guaranteed to collapse into a colloidal sol. Based on the example of a typical design calculation of a technological (production) pipeline for the transportation of motor oils of the SAE-10 and SAE-40 grades, the optimal conditional internal diameters of the product pipeline were determined. The compliance of the design structural parameters of the pipelines with the corresponding physical and mechanical properties of the transported liquids was established. The proposed methods of engineering calculations of design parameters for technical objects of pipeline transport should expand and supplement the regulatory documentation for the preparation of projects for the construction of both main product pipelines and technological “interoperable” production pipelines

Solid state processing of titanium chips by an unconventional plastic working

Abstract The aim of this paper is to demonstrate how various titanium chips can be processed into solid bulk materials in the form of rods. In this work, an alternative technology for recycling chips without re-melting is presented. In order to transform chips into a new material, an unconventional plastic working method was applied that involved upsetting, heating and extrusion with a rotating die. Two purities of pure titanium were investigated: Ti Grade4 (the lowest possible purity) and high-purity Ti 99.99 (the highest possible purity). For each of these materials, four geometries of chips were processed, i.e. chips after turning (thin and coarse) and chips after milling (thin and coarse). In this paper, the influence of chip purity and chip geometry on the course and effects of the processing were investigated. In addition, technological aspects such as extrusion force and die wear were analyzed. Independent of the type of chips, the results obtained have proved the efficiency and utility of the applied method. As a result of this processing, solid, bulk products in the form of rods O8 mm in diameter were successfully obtained. The rods were nearly fully consolidated, and their density was practically the same as the density of commercial titanium. The materials obtained exhibited conventional, grained structures. It was also shown that the materials obtained were free from significant structural defects such as porosity and impurities. Additional confirmation of their proper structure and purity was provided by the correct results of hardness (~200 HV10, Ti Gr4, and, ~100 HV10, Ti hp).

Formation of the Submicron Oxidative LIPSS on Thin Titanium Films During Nanosecond Laser Recording.

Laser-induced periodic surface structures (LIPSSs) spontaneously appearing on the laser-treated (melted or evaporated) surfaces of bulk solid materials seem to be a well-studied phenomenon. Peculiarities of oxidative mechanisms of LIPSS formation on thin films though are far less clear. In this work, the appearance of oxidative LIPSSs on thin titanium films was demonstrated under the action of commercially available nanosecond-pulsed Yb-fiber laser. The temperature and energy regimes favoring their formation were revealed, and their geometric characteristics were determined. The period of these LIPSSs was found to be about 0.7 λ, while the modulation depth varied between 70 and 110 nm, with high stability and reproducibility. It was shown that LIPSS orientation is rather easily manageable in the regimes of our interest, which could provide a way of controlling their properties.

Rate of CO2 adsorbent attrition induced by gas jets on perforated plate distributors in bubbling fluidized beds

Particle attrition is a major challenge when handling bulk solid materials with fluidized beds due to its ability to cause particle loss. Herein, the particle attrition induced by the gas jets on a perforated plate distributor in a bubbling fluidized bed was investigated for CO2 adsorbent particles. An attrition tube, which used air as the fluidizing gas, was used as the fluidized bed. At a constant fluidizing velocity, the initial static bed height and orifice gas velocity were considered as variables. It was confirmed that abrasion dominated the particle attrition. The trend indicating the change in the maximum size of the particles (dpm,a) formed by attrition followed that of the attrition rate (i.e., the formation rate of fine particles via attrition). A new stirring factor that combined the model developed by Werther and Xi with the original stirring factor adequately explained the effect of the static bed height on both the attrition rate and dpm,a when the initial static bed height was greater than the length of the orifice gas jet that penetrated the bed. The attrition rate increased linearly with the new stirring factor. However, dpm,a increased exponentially with the new stirring factor. Relationships were successfully proposed to enable the estimation of the attrition rate and dpm,a for the CO2 adsorbent particles. This study provided the evidence indicating the significance of the effect of bed height on particle attrition induced by the gas jet on the distributor. Moreover, proper models for correlating the attrition rate and the maximum size of the fine particles formed by attrition in the bubbling fluidized bed were provided.

Density-Sensitive Implicit Functions Using Sub-Voxel Sampling in Additive Manufacturing

In the context of lattice-based design and manufacturing, the problem of physical realization of density maps into lattices of a particular family is central. Density maps are prescribed by design optimization algorithms, which seek to fulfill structural demands on a workpiece, while saving material. These density maps cannot be directly manufactured since local graded densities cannot be achieved using the bulk solid material. Because of this reason, existing topology optimization approaches bias the local voxel relative density to either 0 (void) or 1 (filled). Additive manufacturing opens possibilities to produce graded density individuals belonging to different lattice families. However, voxel-level sampled boundary representations of the individuals produce rough and possibly disconnected shells. In response to this limitation, this article uses sub-voxel sampling (largely unexploited in the literature) to generate lattices of graded densities. This sub-voxel sampling eliminates the risk of shell disconnections and renders better surface continuity. The manuscript devises a function to produce Schwarz cells that materialize a given relative density. This article illustrates a correlation of continuity against stress concentration by simulating C 0 and C 1 inter-lattice continuity. The implemented algorithm produces implicit functions and thus lattice designs which are suitable for metal additive manufacturing and able to achieve the target material savings. The resulting workpieces, produced by outsource manufacturers, are presented. Additional work is required in the modeling of the mechanical response (stress/strain/deformation) and response of large lattice sets (with arbitrary geometry and topology) under working loads.

The methodology for studying the process of destruction of solid bulk materials from the standpoint of energy efficiency and quality of the final product

The methodology for studying the process of destruction of solid bulk materials from the standpoint of energy efficiency and quality of the final product

Analytical Optimization of the Design of Film-Laminated Thermoelectric Power Generators

Thermoelectric generators directly convert heat into electricity, typically made from bulk solid thermoelectric materials. They are a widely used technology in exhaust gas heat recovery from automotive vehicles or radioisotope power generation in space satellites. We propose a film-laminated device structure for lower cost and higher volume production. The film-laminated thermoelectric generator design includes a wide variety of thin-film materials and insulator polymer films. Despite the simple fabrication process, the challenges in the bypass heat leak across the insulator film would increase in a film-laminated device structure. The insulator films in the device exhibit low thermal conductivities but cannot be neglected compared to the thermoelectric materials. Comprehensive analysis is conducted on laminated film-based thermoelectric power generators. The study includes the impacts of the geometry design and thermal conductivity to the power output. The sensitivity of design parameters and material properties is investigated. Cost of the power ($/W) from the available heat is estimated. Both of the above are influenced by the effective heat transfer coefficient of the external thermal contacts. The normalized power as a function of the thermal conductivity ratio of the laminate to the thermoelectric materials is determined for a given ZT value. This relationship can be utilized to measure the impact of the laminating material for any material combination. The power output monotonical decreases as the thermal conductivity ratio gets closer to unity. It is highly desirable to use a one order of magnitude lower thermal conductivity for the insulator, especially for thin thermoelectric layer design.

Modelling bulk solid flow interactions in transfer chutes: Shearing flow

In the field of handling, storage and transportation, chutes are used to transfer bulk solids between conveyors. In these systems, traditional analysis methods based on the principle of continuum mechanics approximate an accelerated stream that incorporates physical bulk solid properties obtained from standardised tests. Due to difficulties in physically observing the flow within the transfer structure, verification of the method at full scale is scarcely reported. In contrast, Discrete Element Modelling (DEM) allows flow visualization through a transfer chute and enables qualitative and quantitative analysis provided accurate simulation parameters are selected.This paper presents application of the two methods in a real life high throughput installation using a case study comprising of a stacker chute system transferring coal from one incoming conveyor to one outgoing (boom) conveyor. The flow analysed is representative of transfer configurations characterised by a re-directed fast moving, high volume stream in restricted space, where the mode of flow is governed by internal (shear) properties of the bulk solid material. For the study, the velocity of the coal stream on the outgoing conveyor at loading is significantly lower compared to both the incoming and outgoing conveyor belt speeds. In the study presented, application of the traditional and a modified continuum method approach is compared to DEM simulations and site observations. A sensitivity analysis of modelling parameters is also provided.