Particulate Materials Research Articles

Mixed metal differentiation method using microfluidic oil detection sensors

This paper analyzes the characteristics of iron particles and copper particles in the alternating magnetic field with the change of excitation frequency, and proposes a method of using microfluidic oil detection sensor to achieve the distinction of mixed metals. The magnetic field strength of the coil is changed by changing the excitation frequency, which in turn makes the metal particles of different materials act with different strengths in the magnetic field, and realizes the accurate detection of the particles. In the article, firstly, the magnetization effect of the particles in the alternating magnetic field is simulated by the simulation software, the change of the magnetization effect with frequency is simulated, and the change curve of the inductance signal when the particles pass is obtained. Then the experimental verification is carried out by building a test bench, and the experimental results are consistent with the simulation results, which all confirm the feasibility of realizing the detection of aliased particles by frequency conversion. The method provides a new reference direction for the precise and accurate detection of oil detection technology, and has good research value.

Microstructure and electrochemical properties of Mg/Nb/Zr co-doped LiNi0.94Mn0.04Al0.02O2 cathode materials

The increasing oil scarcity and environmental awareness have accelerated the rise of the new energy vehicle industry, but range and cost issues have hindered the rapid popularization of new energy vehicles. The Co-free Ni-rich layered cathode materials have received a wide attention due to their high energy density, low cost, and stable raw material supply. However, its structure and electrochemical stability still need to be further improved. In this study, the electrochemical properties of LiNi0·94Mn0·04Al0·02O2 (NMA), a Co-free Ni-rich layered cathode material, have been improved by co-doping of Mg, Nb, and Zr. Also, the effects of co-doping on the crystal structure, morphology and electrochemical properties of NMA cathode materials were investigated, too. The results show that the NMA material (NMA-333) with 0.9 mol% doping amount has the best electrochemical performance. The discharge-specific capacity in the first cycle at 1 C was 199.6 mAh g−1, and the capacity retention after 200 cycles reached 73.94 %, which is nearly 24 % higher than that of the original material (NMA-1.03). Meanwhile, the NMA-333 material has a relatively better rate performance, with a discharge-specific capacity of 125.2 mAh g−1 at 10 C. Moreover, the structure and morphology of the modified material were represented by SEM, TEM, XRD, and XPS. And the results showed that the co-doping modification could refine the primary particles of the NMA material, reduce the lithium-nickel mixing, and increase the lattice spacing. The XPS, SEM, and XRD of the post-cycle electrodes further showed that co-doping had stabilized the crystal structure, inhibited the generation and expansion of microcracks, and reduced the occurrence of harmful side reactions, thus improving the cycling performance of the NMA materials at high voltage. The method could be a feasible way to improve the electrochemical performance of layered high-nickel cobalt-free cathode materials.

Sustainable application of waste eggshell as fillers in alkali-activated solid waste-based materials: Varying treated methods and particle sizes

The incorporation of waste eggshells as fillers in construction materials is currently constrained by factors such as shell-membrane separation, particle size, and proportion of incorporation. This study aims to assess the feasibility of utilizing non-calcined eggshell particles (EPs) in alkali-activated solid waste-based materials. Initially, the micro characteristics of water-treated and alkali-treated eggshells were evaluated. Subsequently, nine groups of alkali-activated slag-based paste samples were prepared by using EPs as fillers, and the influence of the particles on the physical and mechanical properties of the materials was assessed based on flowability, density, and compressive strength. Furthermore, the impact of shell-membrane separation and particle size on the microstructure and composition of the alkali-activated materials (AAMs) was characterized by using a combination of SEM-EDS, XRD, FTIR, and TG-DSC techniques. Finally, six groups of alkali-activated slag-red mud-fly ash-based mortar samples were prepared with EPs as fillers, which demonstrates the feasibility of EPs in multi-waste-based materials and expands the application range of non-calcined eggshells. The results show that water treatment and alkali treatment of EPs provide viable methods for shell-membrane separation, albeit with some loss of fine particles. The physical filling of membranes in AAMs does not affect the chemical composition. The EPs (with a particle size less than 0.5 mm) can be used as fillers in AAMs without shell-membrane separation. Moreover, when the EPs content is increased to 33%, the 90-d flexural strength of the AAMs increases by 60% compared to the control group (without EPs), while the compressive strength remains unchanged. Thus, it is feasible to directly crush and sieve non-calcined eggshells for use as fillers in alkali-activated waste-based cementitious materials without the need for shell-membrane separation, and this method does not produce any negative impact. The findings of this research provide an effective technical approach for the application of waste eggshells in eco-friendly construction materials.

DEDALO: Device for Enhanced Dust Analyses with Light Obscuration sensors

Instruments based on light obscuration sensors are widely used for measuring the size distribution of insoluble sub-visible particles in liquid suspensions, being fast and suitable for in situ and real-time measurements. Such instruments are typically calibrated by means of reference polystyrene spherical particles with a specific refractive index, which unavoidably leads to systematic errors when determining the size of particles of different materials. In this paper, we propose a reliable and consistent method to overcome this limitation by setting the refractive index value according to the sample, thus achieving an improved particle size distribution (PSD) measurement. An ad hoc, ready-to-use, open source code with a graphical interface able to drive an in-line instrument and obtain a real-time correction to the PSD has been developed. The method has been extensively validated with several oil emulsions characterized by different refractive index values and the results have been compared with an independent optical method. As an example of application, we have adopted this approach for the analysis of dust suspended in meltwater of an ice core from a glacier in the Aosta Valley (Italy). We believe that our approach will strongly improve the accuracy in characterizing liquid suspensions and reduce discrepancies between data obtained with different methods. The code has been made publicly available at: https://instrumentaloptics.fisica.unimi.it/dedalo/ and on the GitHub page of the corresponding author (https://github.com/LucaTeruzzi/DEDALO).

Dual-modified LiNi0.8Co0.1Mn0.1O2 cathode materials with lithium conducting hybrid oligomer and single-walled carbon nanotube for improving electrochemical performance and thermal stability of lithium-ion batteries: A novel approach for high-power and high-safety applications

In this study, we investigated the synergetic effect of a novel lithium-ion conducting hybrid oligomer [N, N′-bismaleimide-4, 4′-diphenylmethane (BMI), lithiated trithiocyanuric acid (Li-TCA) and Jeffamine®-M1000 (JA®); Li-BTJ] coating layer on a nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode material wrapped with highly electron-conductive single-walled carbon nanotubes (SWCNTs) to enhance electrochemical performance and thermal stability for high-power and high-safety lithium-ion batteries (LIBs). Morphological analyses using scanning electron microscopy/energy dispersive spectroscopy and transmission electron microscopy showed that the NCM811 active material surface was uniformly coated with a hybrid oligomer to form NCM811@Li-BTJ, which was subsequently wrapped with SWCNTs (NCM@Li-BTJ/SWCNT composite cathode). CR2032 coin-type cells with optimized NCM811@1 wt% Li-BTJ/0.2 wt% SWCNT composite electrodes delivered a significantly enhanced capacity retention (CR) of 90.1 % relative to that of bare NCM811 electrodes (CR: 82.1 %) at 1C for 200 cycles from 2.8 to 4.3 V (vs. Li/Li+). Electrochemical impedance spectroscopy and cyclic voltammetry revealed that this superior cycling performance resulted from a lower charge transfer resistance (Rct: 96.2 vs. 324.3 Ω) and a lower polarization voltage (∆V: 0.243 vs. 0.411 V vs. Li/Li+). The in-situ micro-calorimetric results presented the total heat generation (Qt) values of the coin cells with the delithiated NCM811@Li-BTJ and NCM@Li-BTJ/SWCNT electrodes at 5C and 35 °C were substantially lower by ~9.3 % and ~ 14.6 %, respectively, compared to the bare NCM811 counterpart, indicating that the surface modifications on the NCM811 active materials could prevent the LIBs' thermal instability. Furthermore, X-ray photoelectron spectroscopy studies revealed that the Li-BTJ hybrid oligomer coating layer effectively suppressed the formation of residual Li side products such as Li2CO3 evidently on the surface of the NCM811 active material particles, thereby inhibiting undesirable side reactions. Post-mortem analyses of the dual-modified NCM811 electrode after cycling revealed that the microstructure and particle morphology of the NCM composite cathode material were extensively maintained through the synergistic effects of the Li-BTJ ion-conductive and SWCNTs electron-conductive agents.

Biomass Combustion in Boiler: Environmental Monitoring of Sugar Markers and Pollutants

The need to use renewable sources and matrices with energy potential is widely recognized. The development of innovative technologies aimed at the improvement of energy conversion processes and reducing environmental impacts is currently receiving increasing attention from the scientific community and policymakers. The presence of sugars in airborne particle materials is attributed to biomass combustion. For this reason, these compounds are considered markers of biomass burning. The purpose of this work was to evaluate the emissions produced by agroforestry biomass burning (citrus pruning) by simultaneously sampling both stack emissions and atmospheric particulates in the area around a biomass boiler to understand the real contribution of biomass burning to atmospheric pollution. The combustion tests were carried out by comparing the processes with and without particulate abatement system to see how biomass combustion’s contribution to particulate emission can be controlled and reduced. During the tests, the focus was on particulate matter (PM) speciation in terms of sugar marker identification and determination. This study aims to increase knowledge to better understand the contribution of biomass plants to air pollution and differentiate it from the contributions of other sources, such as vehicular traffic or domestic heating.

Mechanism of Silica Nanoparticle-Induced Particulate Fouling in Vacuum Membrane Distillation.

Membrane distillation (MD) is a process driven by the vapor pressure difference dependent on temperature variation, utilizing a hydrophobic porous membrane. MD operates at low pressure and temperature, exhibiting resilience to osmotic pressure. However, a challenge arises as the membrane performance diminishes due to temperature polarization (TP) occurring on the membrane surface. The vacuum MD process leverages the application of a vacuum to generate a higher vapor pressure difference, enhancing the flux and mitigating TP issues. Nevertheless, membrane fouling leads to decreased performance, causing membrane wetting and reducing the ion removal efficiency. This study investigates membrane fouling phenomena induced by various silica nanoparticle sizes (400, 900, and 1300 nm). The patterns of membrane fouling, as indicated by the flux reduction, vary depending on the particle size. Distinct MD performances are observed with changes in the feed water temperature and flow rate. When examining the membrane fouling mechanism for particles with a porosity resembling actual particulate materials, a fouling form similar to the solid type is noted. Therefore, this study elucidates the impact of particulate matter on membrane fouling under diverse conditions.

Comparative electron microscopy particle sizing of TiO2 pigments: sample preparation and measurement.

Titanium dioxide (TiO2) pigment is a non-toxic, particulate material in widespread use and found in everyone's daily life. The particle size of the anatase or rutile crystals are optimised to produce a pigment that provides the best possible whiteness and opacity. The average particle size is intentionally much larger than the 100 nm boundary of the EU nanomaterial definition, but the TiO2 pigment manufacturing processes results in a finite nanoscale content fraction. This optically inefficient nanoscale fraction needs to be quantified in line with EU regulations. In this paper, we describe the measurement procedures used for product quality assurance by three TiO2 manufacturing companies and present number-based primary particle size distributions (PSDs) obtained in a round-robin study performed on five anatase pigments fabricated by means of sulfate processes in different plants and commonly used worldwide in food, feed, pharmaceutical and cosmetic applications. The PSDs measured by the three titanium dioxide manufacturers based on electron micrographs are in excellent agreement with one another but differ significantly from those published elsewhere. Importantly, in some cases, the PSDs result in a different regulatory classification for some of the samples tested. The electron microscopy results published here are supported by results from other complementary methods including surface area measurements. It is the intention of this publication to contribute to an ongoing discussion on size measurements of TiO2 pigments and other particulate materials and advance the development of widely acceptable, precise, and reproducible measurement protocols for measuring the number-based PSDs of particulate products in the size range of TiO2 pigments.

Revisiting the scattering regime map based on transport scattering coefficient for dielectric particulate medium

The independent scattering assumption is frequently employed in radiative transfer, as it is applicable to numerous scientific and practical scenarios involving sparsely distributed scatterers. However, dependent scattering effects must be considered if the particle distribution is not sparse, which requires a relatively more rigorous analysis. A scattering regime map that summarizes the conditions where the independent scattering assumption can be used safely was established in the 1980s. The validity of this regime map and corresponding transition criteria has been questioned due to revealed inaccuracies in certain portions of the map based on the recent experimental studies. This study aims to reevaluate the regime map for dielectric particulate medium through numerical simulations utilizing dense medium radiative transfer theory relying on static structure factor for incorporating the effects of dependent scattering. The transport scattering coefficient, encompassing both the scattering coefficient and the asymmetry parameter, is employed as the metric of evaluation as it accounts for both the quantitative and directional behavior of the scattering. Besides, it also reflects the behavior of reflectance/transmittance closely, which is presented by comparing the regime maps based on transport scattering coefficient and reflectance. While the resulting modified regime map agrees mostly with the established map, it corrects the parts where discrepancies were observed so that the modified map is in agreement with all available data. Moreover, the effects of particle size distribution and material properties are also investigated and it was found that a regime map for lower relative refractive index miss-match between particle and medium produces a demarcation line that is more conservative.

Viscoelastic material properties determine the contact mechanics of hydrogel spheres

Granular materials are ubiquitous in nature and industry; their mechanical behavior has been a subject of academic and engineering interest for centuries. One of the reasons for their rather complex mechanical behavior is that stresses exerted on a granular material propagate only through contacts between the grains. These contacts can change as the packing evolves. This makes any deformation and mechanical response from a granular packing a function of the nature of contacts between the grains and the material response of the material the grains are made of. We present a study in which we isolate the role of the grain material in the contact forces acting between two particles sliding past each other. By using hydrogel particles, we find that a viscoelastic material model, in which the shear modulus decays with time, coupled with a simple Coulomb friction model, captures the experimental results. The results suggest that particle material evolution itself may play a role in the collective behavior of granular materials.

Fabrication Methods of Aluminium Metal Matrix Composite: A State of Review

Aluminium's use in aerospace, marine and automobiles has grown significantly due to its lightweight nature, enhancing fuel efficiency and overall performance. Its corrosion resistance also contributes to longevity, reducing maintenance costs. However, its low hardness, low tensile strength and poor tribological behaviour limit its usage. These demerits can be overcomed by adding specific reinforcement to enrich its properties. As there are two types of fabrication methods for fabrication of MMCs such as Solid state processing and liquid state processing, the above fabrication techniques result in varying mechanical property, tribological property and production cost. So far from the available literature we’ve found that the liquid state processing is more popular than solid-state processing due to the better dispersion of the reinforcement particles in the matrix materials. The Addition of nanoparticles has been found to be essential to provide requisite strength and hardness to these composites. Overall, study concludes that the hybrid aluminium matrix composites will ensure to serve as an alternative for the unreinforced Al-alloys and ceramic reinforced composites in various automotive applications requiring high strength-to-weight ratio, low cost and superior wear resistance.

High-Resolution Printing of Various Electronic Materials by Electrophotography

Electrophotography is a digital, on-demand, dry, and page printing technique that operates based on toner particles of electronic materials using an electrostatic force and generates an electrical circuit via distribution of the toner particles. We developed a 10 μm linewidth resolution with various electronic materials, including conductors, semiconductors, and insulators, without any chemical pretreatments on the substrate films, while a 5 μm resolution was also possible for limited materials. The electrical resistivity of the printed Ag–Ni after an intense pulse light sintering was comparable to that of commercial indium tin oxide transparent films.

Research on seedling sowing method based on high voltage electrostatic characteristics

In response to the difficult problem of high leakage rate and low seed pick-up rate of traditional air-suction seed dischargers. This study proposes a new high-voltage electrostatic vegetable seedling sowing method and system based on phase sucking of opposite charges and repulsive seeding of same charges. This method does away with small orifices and long conductance suction holes. It can solve the technical bottleneck of the traditional air-suction seed rower at the source, which causes a decrease in seed rowing accuracy due to clogging of the suction holes when facing irregular small vegetable seeds that are not pelleted. Combining high voltage electrostatic polarisation for seed vigour with precision seeding technology. Improving seed vigour and crop yield while precision sowing. Modelling the mechanics of adsorption seeding and repulsive seeding systems. Identify the main factors affecting electrostatic adsorption and phase repulsion forces and their interrelationships; Analysis of the decay mechanism of the electrostatic adsorption force upon repeated action. Proposing measures for the rapid restoration of the original equilibrium state of the dielectric insulation by reverse electric field polarization; Analysis of the migration pattern of electric particles during polarisation. Solving the equations for seed dynamics during sowing; At positive input voltages of 16 kV and negative input voltages of 0, 4, 8, 12, 16 and 20 kV. Separate dielectric insulation layer adsorption seeding tests. The test results show that: The reverse electric field polarisation of the dielectric insulating layer is effective in containing the electrostatic adsorption decay. The best containment was achieved at a positive input voltage of 16 kV and a negative input voltage of 16 kV; Seeding performance verification tests at a positive input voltage of 16 kV and a negative input voltage of 16 kV. The test results show that: The sowing conformity index was 90.25 %, the reseeding index 3.40 % and the missed sowing index 6.35 %. In the evaluation of applied research, the multi-objective optimization design with the objective function of maximum seed discharge qualification index, minimum leakage index and replanting index, the optimal parameter combinations of the test factors can be obtained as follows: the size of the type hole is 5.977 mm, and the output voltage of the positive high-voltage electrostatic generator is 16.423 kV, and at this time, the seeding machine's seed discharge qualification index is 90.78 %, the replanting index is 3.05 %, and the leakage index is 6.17 %. To verify the reliability of the optimal design of structural parameters, the seeding performance verification test is carried out, which can be obtained: the qualified index of row seeding is 90.54 %, the index of reseeding is 2.86 %, and the index of leakage is 6.60 %, which meets the technical requirements of precision seeding. The research not only provides a reference for the development of precision sowing machinery and equipment for irregular small-grain vegetable seeds. It also provides an academic reference for the research of quantitative adsorption and rapid separation methods and theories for irregular small particle materials.

Evaluation of particle morphology and size of mineral filler and their effects on mastic rheological and creep behavior: Experimental and numerical characterizations

The primary objective was to evaluate the effects of particle morphology and size of mineral fillers on mastic rheological and creep properties. Experimentally, eight fillers prepared using the same grinding procedure were characterized. Dynamic shear rheometer and bending beam rheometer tests were employed to evaluate mastic rheological and creep behavior, respectively. Numerically, a dynamic viscoelastic model and Burgers creep damage model based on fractional derivatives were established. Results demonstrate that the datasets agree well using fewer model parameters, which can illustrate the availability of the proposed numerical method for the response of all analyzed mastic specimens. As the particle size decreases, material parameter and fractional order are increased by 10.31%, 23.45%, 24.72% and 0.68%, 1.46%, 1.48% for mastics containing limestone filler; and that are increased by 7.07%, 15.38%, 38.06% and 0.76%, 0.85%, 1.18% for mastics with granite filler at 45 °C, respectively. Apart from 150 to 200 mesh size range, the mastic with granite filler is less prone to creep damage accumulation inside the specimen than that containing limestone filler during the loading process. As the particle size increases, relaxation time is rapidly increased by 5.41%, 26.35%, 27.99% and 5.55%, 20.98%, −1.33% for limestone filler-asphalt mastics and granite filler-asphalt mastics, respectively. Moreover, form factor is the determining influential factor for mastic anti-rutting performance, temperature susceptibility and creep damage, while fractal dimension is the most relational factor affecting mastic dissipation capacity, regardless of filler lithology. All the results are conducive to designing mineral filler that fabricates mastic with the desired property.

Adapting the in vitro micronucleus assay (OECD Test Guideline No. 487) for testing of manufactured nanomaterials: recommendations for best practices.

The current Organisation for Economic Co-Operation and Development test guideline number 487 (OECD TG No. 487) provides instruction on how to conduct the in vitro micronucleus assay. This assay is one of the gold standard approaches for measuring the mutagenicity of test items; however, it is directed at testing low molecular weight molecules and may not be appropriate for particulate materials (e.g. engineered nanoparticles [ENPs]). This study aimed to adapt the in vitro micronucleus assay for ENP testing and underpins the development of an OECD guidance document. A harmonized, nano-specific protocol was generated and evaluated by two independent laboratories. Cell lines utilized were human lymphoblastoid (TK6) cells, human liver hepatocytes (HepG2) cells, Chinese hamster lung fibroblast (V79) cells, whole blood, and buffy coat cells from healthy human volunteers. These cells were exposed to reference ENPs from the Joint Research Council (JRC): SiO2 (RLS-0102), Au5nm and Au30nm (RLS-03, RLS-010), CeO2 (NM212), and BaSO4 (NM220). Tungsten carbide-cobalt (WC/Co) was used as a trial particulate positive control. The chemical controls were positive in all cell cultures, but WC/Co was only positive in TK6 and buffy coat cells. In TK6 cells, mutagenicity was observed for SiO2- and both Au types. In HepG2 cells, Au5nm and SiO2 showed sub-two-fold increases in micronuclei. In V79 cells, whole blood, and buffy coat cells, no genotoxicity was detected with the test materials. The data confirmed that ENPs could be tested with the harmonized protocol, additionally, concordant data were observed across the two laboratories with V79 cells. WC/Co may be a suitable particulate positive control in the in vitro micronucleus assay when using TK6 and buffy coat cells. Detailed recommendations are therefore provided to adapt OECD TG No. 487 for testing ENP.

Characterization of road-deposited sediment wash-off and accurate splitting of initial runoff pollution in heterogeneous urban spaces

Particulate materials arising from road-deposited sediments (RDS) are an essential target for the control and management of surface runoff pollution. However, the heterogeneity of urban spaces hinders the identification and quantification of particulate pollution, which is challenging when formulating precise control measures. To elucidate the factors that drive particulate pollution in heterogeneous urban spaces, the accumulation of RDS on dry days and the total suspended solids during six natural rainfall events were investigated across three urban–rural spatial units (central urban, central suburban, and remote suburban). The underlying surface type (asphalt or cement roads) and particle size composition jointly determined the spatial heterogeneity in the static accumulation and dynamic output loads of RDS during rainfall. These two factors explained 59.6% and 18.9% of the spatial heterogeneity, respectively, according to principal component analysis. A novel CPSI exponential wash-off equation that incorporates particle size composition and underlying surface type was applied. It precisely described the spatial heterogeneity of RDS wash-off loads, the estimated values exhibiting event mean concentration errors of 10.8–18.2%. When coupled with the M(V) curve, this CPSI exponential wash-off equation more precisely split the initial volume of runoff: a lower total volume (17.6–38.0%) was shown to carry a higher proportion of the load (70.0–93.7%) compared to the traditional coupled exponential wash-off equation (volume: 31.6–49.0%, load: 37–90%). This study provides a new approach to characterizing RDS wash-off processes and splitting initial runoff in heterogeneous spaces.

Monitoring Aggregation Processes in Multiphase Systems: A Review

Particle aggregation is essential in many industrial processes, spanning the pharmaceutical and food industries, polymer production, and the environment, among others. However, aggregation can also occur, in some processes, as a non-desired side effect. Thus, to be able to monitor aggregation in industrial processes is of high importance to guarantee that the final, required product characteristics are obtained. In this paper, we present an extensive review of the different techniques available for monitoring particle characteristics in industrial processes involving particulate materials, with special emphasis on aggregation processes. These methods include both off-line and on-line techniques, based either on image acquisition techniques or different radiation scattering techniques (light-scattering and ultrasound spectroscopy). The principles behind each technique are addressed, together with their relevant applications, advantages, and disadvantages.

High Performance of Porous, Hierarchically Structured P2‐Na0.6Al0.11 − xNi0.22 − yFex + yMn0.66O2 Cathode Materials

AbstractSodium‐ion‐batteries (SIB) are a low‐cost alternative to currently used lithium‐ion batteries (LIB) but suffer from poor cycling stability. Spray drying provides porous, hierarchically structured particles of cathode active material (CAM) in large amounts, suitable for up‐scaling. Changing the chemical composition of the Na0.6Al0.11 − xNi0.22 − yFex + yMn0.66O2 layered oxides under identical synthesis conditions lead to differences in particle morphology, conductivities, sodium vacancy ordering, and phase transition, therefore influencing the electrochemical performance via several mechanisms. Here, a broad overview on these changes for samples with variable nickel and iron content is presented. With increasing iron content, the particle porosity is reduced and lower initial capacity is received for most cycling windows. Substituting half of the original Ni amount with Fe still leads to high capacities and improved cycling stability. The influence of Al as electrochemically inactive element becomes visible in stabilized cycling stability as well.

Analysis of the Distribution of Relaxation Times (DRT) Responses of Li-Ion Cells as a Function of Their Preparation Conditions

The distribution of relaxation times (DRT) approach was used to analyze the electrochemical impedance spectra obtained for lithium-ion cells as a function of their state of charge as well as the cell preparation conditions. The cells were made using LiFePO4 cathodes with PEDOT:PSS binder and Li anodes. The following parameters were varied: the load of the active mass with LiFePO4, the presence or absence of carbon nanotubes, the presence or absence of the carbon coating of the current collector, die-pressing of the active mass, as well as artificial degradation of the binder using thermal treatment. The results support the view adopted in the literature that the DRT response of Li-ion cells involves 4 main regions attributed to (i) contact resistance between the particles of the active mass or the particles and the current collector; (ii) ionic resistance of the active layer including that of SEI on the surface of the electrodes; (iii) faradaic resistance of the electrochemical charge transfer at the surface of the active material, and (iv) solid-state diffusion/transport of Li+ ions in the particles of active material. Moreover, we identified yet another contribution to the DRT spectra related to the ionic conductivity of the binder and electrolyte in the active mass of the cathode.

Comparative analysis of reinforcement addition techniques on fabricated hybrid surface composite of AA7075-T651/WC/BN through friction stir processing

In the present work, three reinforcement addition techniques such as the slot method (SM), hole method (HM), and zig-zag hole method (ZZHM), are selected to make the hybrid surface composite of AA7075-T651/BN/WC through FSP. The comparative assessment of each method is thoroughly assessed through microstructure, mechanical, and tribological characteristics. Material flow, particle spreading, zone development and phase formation were examined using optical microscopy (OM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Furthermore, the microhardness and wear characteristics were measured and compared. Based on the findings, ZZHM reveals enhanced material flow and more even particle spreading in the nugget zone than SM and HM. The higher grain refinement and excellent interfacial bonding without any reaction between AA7075-T651 and reinforcement particles (BN and WC) are due to higher DRX and severe plastic deformation (SPD) caused by the tool in ZZHM. The composite made with ZZHM had greater hardness and wear resistance due to the reduction in clusters, even the spreading and lubricating effect of particles and a significant reduction in grain size. This study revealed that the ZZHM is superior to the SM and HM for adding reinforcement and fabricating the hybrid surface composite.