Particle Chemical Composition Research Articles

Road performance evaluation of prestressed high-strength concrete pile waste powder as alternative filler in asphalt concrete

As a kind of solid waste, using Prestressed High-Strength Concrete Pile Waste Concrete (PPWC) as the replacement for limestone filler in asphalt concrete can not only reduce the accumulation of PPWC and increase its utilization but also avoid the increased road construction costs and environmental degradation associated with limestone mining. This study aims to investigate the effect of using PPWC filler to replace limestone filler on the road performance of asphalt concrete. Firstly, PPWC was ground into filler particles with a diameter less than 0.075 mm. The particle characteristics such as surface morphology, particle size distribution and chemical composition of PPWC filler and limestone filler were compared. Then, PPWC filler was used to replace limestone filler with different volume fractions to prepare asphalt concrete, and the water damage resistance, high-temperature rutting resistance, low-temperature crack resistance, fatigue resistance and adhesion performance of asphalt concrete were tested. The results showed that PPWC filler has a smaller particle size and rougher surface than limestone filler, and it contains Ca(OH)2 produced by hydration. The addition of PPWC filler can effectively improve the mechanical properties of asphalt concrete without reducing its water damage resistance. PPWC filler can improve the high-temperature rutting resistance and low-temperature crack resistance of asphalt concrete, but reduce its low-temperature fatigue resistance. The low content of PPWC filler will enhance the adhesion between asphalt mortar and aggregate. However, when the content of PPWC filler exceeds 50%, Ca (OH)2 in PPWC will reduce the adhesion between acid asphalt mortar and alkaline basalt aggregate. Therefore, the use of PPWC as filler in asphalt mixtures provides a reliable solution for the sustainable development of road materials.

Synergy of inert granite powder and active mineral admixture in manufactured sand mortar: The effect on mechanical properties, chloride permeability and water absorption properties

Granite powder (GP) and active mineral admixture including ground granulated blast furnace slag (GGBFS), metakaolin (MK) and fly ash (FA) were used to partially replace granite manufactured sand (GMS) and cement to prepare manufactured sand mortar (MSM). Synergistic effect of four mineral admixtures in MSM on mechanical properties, water absorption properties and chloride permeability was studied. Combined with the analysis of cementitious materials hydration and pore characteristics, the synergistic mechanism of four mineral admixtures was comprehensively expounded. The results show that although the synergy of GP can improve the performance of MSM, the replacement of cement by GGBFS and FA leads to the increase of water absorption and chloride diffusion coefficient and the decrease of mechanical properties. Synergistic effect of GP, GGBFS, FA and MK is greater than that of the three of them due to the complementarity of particle size and chemical composition of the four materials, which ends the situation of MSM performance reduction.

Porosity Reduction in 15CDV6 Steel Manufactured by L-DED

The Laser Directed Energy Deposition (L-DED) is an Additive Manufacturing process based on the direct injection of the filler material into the desired areas of a substrate. Damaged components can be repaired or coated in order to enhance their properties and increase their lifespan. However, this process is highly material dependent and to assure the quality of the deposited material, the process parameters need to be optimised. In the present work, a novel material for the L-DED is developed, the 15CDV6 aeronautical steel. The material was atomized ad hoc and the obtained powder was characterized (particle shape, size distribution, and chemical composition) in order to ensure its quality. Once the powder was analysed, the suitability of the 15CDV6 steel for the L-DED process was studied through a methodology consisting of three sequential steps: single clad tests, layer deposition and wall construction. The main process parameters (laser power, feed rate and powder feed rate) were controlled during these tests. Nevertheless, the initial tests showed high levels of porosity, which required considering additional process parameters to reduce them, such as the carrier and shielding gas flows, preheating, or the laser beam diameter. Consequently, the porosity formation mechanisms were identified and the most relevant process parameters established, which for the 15CDV6 steel were the gas flows. The effect of the shielding gas flow in the powder distribution below the nozzle was studied experimentally by digital image analysis to better interpret the obtained results and determine the optimum process parameters for achieving defect free parts. The quality of the deposited material was studied through metallographic analysis and an Acicular Ferrite structure was observed, ensuring good mechanical properties. To summarise, this research work proves the viability of employing 15CDV6 steel in the L-DED process and has determined the main process parameters to obtain porosity-free parts.

Characterisation and standardisation of different-origin end-of-life building materials for assessment of circularity

Construction and demolition waste (CDW) management and recycling practices are crucial for transitioning to a circular economy. The focus of this study was on the detailed characterisation of different CDWs (hollow brick (HB), red clay brick (RCB), roof tile (RT), concrete and glass) collected from seven different demolition sites in Turkey. The CDWs were characterised based on particle size distribution, chemical composition and crystalline nature. Pozzolanic activity was evaluated through compressive strength measurements of cement mortars made with 20% cement replacement by CDWs at 7, 28 and 90 days. The results showed that the clayey CDWs exhibited similar physical/chemical properties and crystalline structures. The compositions of the waste concretes varied significantly based on their original materials. All the CDWs satisfied the minimum strength activity index (SAI) for supplementary cementitious materials, with pozzolanic activity influenced by the fineness and silica + alumina contents. The average SAIs for the HB, RCB, RT, concrete and glass were, respectively, 84.5%, 86.3%, 83.4%, 80.7% and 75.8%. Clayey CDWs contributed to mechanical strength development, while the contribution of concretes was related to the hydration of unreacted cementitious particles. Glass exhibited the weakest pozzolanic activity due to its coarser particle size. Overall, the CDWs demonstrated suitable properties for use as supplementary cementitious materials in Portland cement based systems.

Enhancing lithium-air battery performance through CoPc@CNT composites: Electrochemical analysis and insights

Cobalt-phthalocyanine (CoPc) catalysts have shown great promise for enhancing the performance of lithium‑oxygen (Li-O2) batteries, offering benefits such as efficient lithium storage, high reversible capacity, improved cycle performance, and enhanced charge and discharge capacity. In this study, we focused on the synthesis of CoPc‑carbon nanotube (CNT) composites with porous structure. The composites were prepared by synthesizing CoPc compounds and interacting them with CNTs using a 3D ball mill shaker. Comprehensive spectroscopic techniques including NMR, FTIR, and UV were employed to characterize the newly synthesized phthalonitrile and phthalocyanine compounds. The surface morphologies of the composite materials were investigated using SEM, EDX, mapping and TEM analysis, enabling the determination of particle sizes and chemical compositions. XRD and XPS analyses confirmed that the composite structures were consistent with the existing literature. BET analysis revealed multilayer isotherm for the composites, indicating their favorable properties. The composite catalysts were incorporated into batteries and their performance was evaluated through various electrochemical tests. Notably, the CoPc1-CNT composite exhibited a remarkable discharge capacity of 3400 mAh g−1catalyst in the prepared battery.

Influence of a powder-forming additive on the physical-mechanical properties and structure of a ceramic material

The purpose of the study was to explore the effect of various pore-forming additives on the porosity and permeability of alumina ceramic material. Analysis of mineralogical, particle size distribution and chemical composition of raw materials and ceramics samples was performed using standard research methods, JCM-6000 (JEOL) and field emission scanning electron microscopy (FESEM) microscopes, LW600LT, x-ray diffractometer Rigaku D/max-RA, Hitachi SU-70 and Pore Master. The microstructure of the composite ceramic material in all experiments demonstrated the presence of numerous cross-sectionally elongated pores, which proves the dependence of the pore-forming structure on the shape of the pore-forming agent. The high permeability of samples with lignin is due to the improved plastic properties of the clays. By increasing the clay content from 5 to 10 wt.% it was possible to increase the sintering density of the samples and reduce their overall porosity. The permeability porosity increases with the introduction of more urea, and the strength of the samples is then at its maximum. Samples with the addition of lignin demonstrated resistance to mechanical stress and high permeability. The study identifies the prospects of using crystallised urea and lignin from manufacturing waste as a pore former, which will allow the establishment of environmentally friendly ceramic materials with high permeability and durability and solve the problem of atmospheric pollution.

Monitoring the Particle Size Distribution, Phase Quantification and Chemical Composition of Acid-Leached PtCo Electrocatalyst Under Start-up/Shut-Down Conditions Probed By in-Situ SAXS and WAXS Techniques

Large progress has been made towards commercialization of polymer electrolyte membrane fuel cells (PEMFCs) through the development of highly active and robust Pt-Co alloy catalysts for oxygen reduction reaction (ORR).[1,2] However, most ORR catalyst materials suffer from the extremely corrosive conditions occurring during start-up/shut-down (SUSD).[3] Consequently, understanding the degradation mechanisms during SUSD is highly crucial for designing new catalyst materials with enhanced ORR activity and long-term durability.In this work, we show a comprehensive and complementary combination of different advanced techniques such as in-situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) as well as ex-situ scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) to provide deeper insights into the degradation processes of acid-leached Pt-Co catalyst under SUSD conditions.Firstly, Pt-Co nanoparticles supported on high surface area carbon (HSAC) were synthesized using wet impregnation – freeze-drying – thermal annealing method.[4] Compared to our previous works [4-6], an acid-leaching (1 M H2SO4, 15 °C, 2 h) was applied to dissolve the less noble metal from the surface of alloy nanoparticles forming a Pt-enriched skin. STEM-EELS data has also confirmed the formation of the Pt-enriched skin. In addition, ex-situ WAXS data signifies that the acid-leached PtCo catalyst consists of two face-centered cubic (fcc) disordered crystal phases: Pt90Co10 phase with a crystallite size of 3.6 ± 0.4 nm and Pt70Co30 phase with 4.2 ± 0.4 nm size.In terms of ORR performance, the acid-leached PtCo catalyst exhibits a 2.5- & 2-times higher mass activity (0.61 ± 0.12 A mgPt -1) and a 3.5- and 1.3-times higher specific activity (665 ± 84 µA cmPt -2) at 0.9 VRHE compared to commercial ~2 nm Pt/C (0.24 ± 0.05 A mgPt -1, 187 ± 29 µA cmPt -2) and heat-treated 4-5 nm Pt/HSAC (0.30 ± 0.04 A mgPt -1, 297 ± 42 µA cmPt -2), respectively. After SUSD experiments (800 cycles, 0.5 - 1.5 VRHE, 50 mV s-1, 0.1 M HClO4), the mass activity decreases to 0.21 ± 0.06 A mgPt -1 (-65 %) and 0.15 ± 0.03 A mgPt -1 (-38 %) for the acid-leached PtCo catalyst and commercial Pt/C, respectively.To monitor the potential-dependent changes in particle/crystallite size, phase quantification and chemical composition of the acid-leached PtCo catalyst under the SUSD conditions, in-situ SAXS and WAXS experiments were simultaneously performed at the beamline ID31 at European Synchrotron Radiation Facility (ESRF).In-situ WAXS analysis reveals that the lattice parameter of both Pt90Co10 and Pt70Co30 phases increases as a function of the SUSD cycle number, signifying the successive depletion of cobalt mainly from the Pt70Co30 phase. More precisely, the lattice parameter changed from 3.819 ± 0.004 Å (Pt70Co30) to 3.829 ± 0.004 Å (Pt76Co24) during the first 150 SUSD cycles. Only a slight change in lattice parameter for Pt90Co10 phase is observed during the SUSD protocol. Based on the Rietveld quantification, the amount of the Pt70Co30 phase decreases from 61 ± 2 wt.% to 47 ± 2 wt.% during the first 150 SUSD cycles. Afterwards, the Co depletion from this phase is less pronounced with additional cycle number. Furthermore, STEM-EELS investigations on acid-leached PtCo catalyst after first 150 SUSD cycles has confirmed the drastic Co depletion within the nanoparticles. After the SUSD protocol, the chemical composition of the acid-leached PtCo catalyst alters from Pt67±3Co33±3 to Pt81±3Co19±3 (-42 at.%) obtained from the bulk techniques like EDX and µ-XRF.In addition, the Rietveld refinement reveals an increase in crystallite sizes for both Pt-Co crystal phases over the course of the SUSD protocol which is in excellent agreement to the in-situ SAXS and ex-situ TEM results (from 4.1 ± 1.0 nm to 5.2 ± 0.8 nm, +27 %). In detail, the initial larger Pt70Co30 phase shows only a small increase in crystallite size (from 4.3 ± 0.4 nm to 4.8 ± 0.4 nm, +12 %), whereas for the initial smaller Pt90Co10 phase a gradual increase from 3.2 ± 0.3 nm to 4.5 ± 0.4 nm (+41 %) is observed during the SUSD experiment.Based on the in-situ SAXS/WAXS and the ex-situ STEM-EELS data, the Co depletion is the dominant degradation mechanism for the disordered fcc Pt70Co30 phase during the first 150 SUSD cycles. With increasing SUSD cycle number, the particle growth via Ostwald ripening and particle coalescence predominates. Our degradation model can be used to further improve the ORR performance and durability of acid-leached Pt-Co catalysts under the SUSD conditions.Literature:[1] L.R.Borup et al.,Curr.Opin.Electrochem.,2020,21,192-200.[2] C.Wang et al.,Energies,2016,9,603-642.[3] Y.Yu, et al.,J.Power Sources,2012,205,10-23.[4] M.Oezaslan et al.,J.Electrochem.Soc.,2012,159,B394-B405.[5] D.J.Weber et al.,J.Mater.Chem.A,2021,9,15415-15431.[6] P.Weber et al.,ACS Catal.,2022,12,6394-6408.

Synthesis of plant-based biogenic jarosite nanoparticles using Azadirachta indica and Eucalyptus gunni leaf extracts and its application in Fenton degradation of dicamba

Bio-jarosite, an iron mineral synthesized biologically using bacteria, is a substitute for iron catalysts in the Fenton oxidation of organic pollutants. Iron nanocatalysts have been widely used as Fenton catalysts because they have a larger surface area than ordinary catalysts, are highly recyclable, and can be treated efficiently. This study aimed to explore the catalytic properties of bio-jarosite iron nanoparticles synthesized with green methods using two distinct plant species: Azadirachta indica and Eucalyptus gunni. The focus was on the degradation of dicamba via Fenton oxidation. The synthesized nanoparticles exhibited different particle size, shape, surface area, and chemical composition characteristics. Both particles were effective in removing dicamba, with removal efficiencies of 96.8% for A. indica bio-jarosite iron nanoparticles (ABFeNPs) and 93.0% for E. gunni bio-jarosite iron nanoparticles (EBFeNPs) within 120 min of treatment. Increasing the catalyst dosage by 0.1 g/L resulted in 7.6% and 43.0% increases in the dicamba removal efficiency for EBFeNPs and ABFeNPs with rate constants of 0.025 min−1 and 0.023 min−1, respectively, confirming their catalytic roles. Additionally, the high efficiency of both catalysts was demonstrated through five consecutive cycles of linear pseudo-first-order Fenton oxidation reactions.

Taguchi optimization of tribological properties and corrosion behavior of self-lubricating Al–Mg–Si/MoS2 composite processed by powder metallurgy

Self-lubricating aluminum matrix composites (AMCs) can be used to reduce the wear and coefficient of friction (COF) in automotive engine components in which the use of liquid lubricants is not desirable. High temperatures accelerate the oxidation and thermal degradation of a liquid lubricant. In this study, we used powder metallurgy (PM) technique to prepare self-lubricant (MoS2)-based Al–Mg–Si AMCs, designated as Al–Mg–Si–xMoS2 (x in wt.%; x = 1.5, 2.0, 30, 3.5, and 4.0). The dry sliding wear properties were assessed using a pin-on-disk tribometer at various applied loads (20–50 N) and sliding distances (1000–3000 m), based on the Taguchi model (L9). Furthermore, electrochemical corrosion tests such as open circuit potential (OCP) and potentiodynamic polarization (PDP) were performed in a 3.5 wt% NaCl medium. The morphology of the Al–Mg–Si–xMoS2 composites was observed through scanning electron microscopy and energy dispersive spectroscopy to clarify the particle distribution and chemical composition. The results indicated that the addition of MoS2 to Al–Mg–Si decreased the wear and COF and increased the corrosion resistance, compared with those of the pristine Al–Mg–Si matrix alloy under same operating conditions. As the sliding distance increased to 250 m, the COF fluctuated, but it stabilized as the distance approached 3000 m. The effects of the load and reinforcement concentration were more significant than those of the sliding distance and track diameter, as predicted by the Taguchi model and analysis of variance methods.

Significant changes in size distribution of aerosols in Beijing after clean air actions

Over the past few years, the physicochemical characteristics and sources of aerosols have changed following the implementation of strict clean air policies in Beijing. In this study, size-segregated particulate matters (PM) were collected using a micro-orifice uniform deposit impactor (MOUDI) in Beijing from July 2021 to June 2022 to understand the responses of particle size distribution and chemical composition to the implemented emission reduction measures. The results showed that although particulate pollution greatly improved, it is still severe in Beijing, especially in autumn and winter, with the annual average PM1.8 (aerosol particle with aerodynamic diameter less than 1.8 μm) concentration reaching 46.7 ± 37.4 μg/m3. NO3− was the most abundant ion in the particles throughout all seasons, and its proportion to water-soluble inorganic ions increased significantly with the aggravation of pollution. This highlights the importance and urgency of controlling mobile sources in future control measures. The highest concentration of SO42− occurring during summer demonstrates the effectiveness of fossil fuel combustion control in winter. The measured size distributions of PM and secondary inorganic ions were trimodal, which significantly differed from the observations conducted in Beijing using MOUDI before 2017, in which the measured size distributions of PM and secondary inorganic ions were bimodal. The enhancement of atmospheric oxidation and reduction of gaseous precursors can affect the formation path of aerosols, and thus, their particle size distribution. Aerosol aqueous-phase reactions play a vital role in pollution development, with the droplet mode further growing hygroscopically into a coarse mode during pollution maintenance.

Formation mechanism of Fe-based amorphous powders produced by spark erosion

Spark erosion is a convenient, flexible, and low-cost method to quickly produce fine powders of metals, alloys, and semiconductors in size ranging from nearly a hundred micrometers to submicrometer by repetitive spark discharges. Due to the complexity of the powder-forming journey, normally accompanied by high temperature, high pressure, decomposition, diffusion and rapid quenching caused by discharge plasma, the mechanisms of powder formation and possible contaminant infiltration are still controversial, posing a significant challenge to control particle size and chemical composition of the powder produced by this method. In this study, Fe-based amorphous powders in different particle-size distributions with high sphericity were fabricated by spark erosion under different discharge-energy conditions. The maximum particle size of the resultant powders can be correlated with discharge parameters, crater depth, and crater radius, respectively. A multi-ring-breakup model is proposed to reveal the particle-size distribution of the powder formed from the electrode melt under a single-pulse discharge. Furthermore, a dielectric-element infiltration model is provided to quantitatively evaluate the infiltration mass ratio of the contaminant elements, stemming from the decomposed products of dielectric liquid, in the resultant powder with different particle sizes. The models verified through the experimental data are significant for the development of high-performance fine Fe-based amorphous powder with controlled particle size and chemical composition.

Nano eggshell based slurry as a direct pulp capping material: In vitro characterization and histopathological assessment in an experimental animal model.

Pulp vitality is essential for tooth integrity. Following pulp exposure, choosing a suitable pulp capping material is crucial to maintain pulp vitality. However, the reparative dentine bridge created by calcium hydroxide is generally porous and incomplete. To assess the in vitro and in vivo bioactivity of nano eggshell-based slurry (NES), using NES as direct pulp capping material, compared with calcium hydroxide (Ca(OH)2 ) in rabbit animal model. Nano eggshell powder (NE) was characterized for particle morphology, chemical composition, and ion release. In vitro bioactivity was tested by immersion in simulated body fluid (SBF) for 7 days. For histopathological evaluation, 36 adult New Zealand rabbits (72 pulp exposures) were divided into nine groups (n=8) according to the pulp capping material (NES, Ca(OH)2 and no capping as negative control group) and the animals were sacrificed after 7, 14 or 28 days. The pulps of the two lower central incisors were exposed then directly capped by Ca(OH)2 or NES, or left untreated. The cavities were then sealed with a glass ionomer cement. Teeth were collected for histopathological evaluation using optical microscope. Pulp haemorrhage, inflammation, fibrosis and calcific bridge formation were assessed. Results were statistically analyzed using ANOVA and Tukey's test. NE particles were spherical with 20 nm diameter and were composed mainly of calcite. Statistical analysis showed that there was significant increase in the release of all investigated ions between day 1 and 28, except for copper. NES group showed significantly higher release of all elements as compared to Ca(OH)2 . ESEM micrographs of NES incubated for 7 days in SBF showed the formation of HAp with Ca/P ratio (1.686). For histopathological evaluation, the difference between groups was statistically significant. At day 28, 75% of the pulps of Ca(OH)2 group showed mild calcific bridge in comparison with 100% moderate calcific bridge in NES group. The NES group showed significantly less inflammation at days 7 and 28, and higher fibrosis at day7 as compared with Ca(OH)2 . NES represents a promising novel direct pulp capping material with favourable pulp tissue response.

New data on the transformation of water and sediment runoff into the Lena river delta based on the results of expedition measurements in August 2022

Field hydrological measurements were performed in the Lena River delta from the 10th to the 16th of August 2022. 25 values of water discharge and 58 suspended sediment concentrations (SSC) were measured, multiple chemical composition water samples were taken, along with samples of bottom and bank river sediments, and thermal abrasion coasts were highlighted. Particle size and chemical composition analyses of the sediment samples were carried out. The aim of the study was to estimate the water flow distribution in the delta and to determine the directional SSC, sediment particle size and chemical composition changes along the delta and inside the depth of the river flow, and define the roles of the local hydrological and morphological factors of river flow transformation. Moreover, field measurements are crucial for SSC estimation and monitoring based on satellite image data. The laboratory analyses included particle size definition in suspended and bottom sediment samples, organic matter and SSC definition. The August 2022 expedition results were compared to the previous surveys. It was established that the flow distribution around the Stolb island corresponds with that of 2016: the Bykovsky, Trophimovsky, Tumatsky and Oleneksky branches receive 24.9–25.5, 58–59.2, 6 and 6.6 % of the water discharge from the Kusur gauging station on the Lena River, respectively. However, the role of the Main channel was slightly overestimated. The new data includes water discharges in the branches around the Samoilovsky island and in the channel systems of the Oleneksky and Tumatsky branches. SSC was relatively low and amounted to around 12–24 mg/l, rising from the water surface to the bottom 1.2–2 times. SSC decreased along the course of the Oleneksky and Tumatsky branches (1.5 and 1.1 times, respectively) due to the ratio between SSC and the potential stream transport capacity. SSC rose along the course of the Bykovsky branch, even though it wasn’t shown by the Landsat-8 satellite image (16th of August 2022). A significant sediment source in the delta are eroded and thermo eroded shores of the edoma island systems. The average sediment size proved to be from 0.011 to 0.019 mm. SSC does not vary much around the main channel and the nearest branches. Important relations between SSC, optical turbidity and ADCP backscatter intensity were estimated. The coarse diameter of 30 bottom sediment samples was 0.46 mm. The largest sediments were discovered in the Bykovsky branch, while the smallest sediments were found in the smaller transverse branches. Along the Tumatsky and Oleneksky branches the bottom sediments alternate from fine to medium sands.

Development of a composite product from fibre yielding crop residues

Particleboard is one of the wood-based composite products, developed from wood and wood industry waste in admixture with an adhesive by thermos-compression. Wood is gradually becoming scarce due to deforestation and it leads to search for an alternative raw material. Jute, flax, and hemp plants are important fibre yielding industrial crops since their respective farming provides economic support to the developing nations from the rural areas. After the extraction of fibres from them, a lot of biomasses in terms of shives and sticks are generated as agricultural waste, and recently, these lignocellulosic biomasses have attained a special attention for the development of medium density particleboard. In this present work, an attempt has made to study the effect of flax shive and jute stick particle blends in admixture with phenol formaldehyde resin on the performance of the particleboard in terms of density, modulus of rupture and water swelling. The particle size distribution, bulk density, chemical composition, thermal properties, and surface chemistry of jute stick and flax shive have studied to assess their compatibility. Results inferred that a 50% jute stick: 50% flax shive combination based particleboard met the desirable properties of a medium density particleboard and showed higher performance than other combinations. It could be concluding that the combined use of biomass residuals for the development of a potential industrial product like packaging box, furniture, false ceilings etc, and it could open a new avenue to their farmers for the creation of wealth from the waste.

Mechanical milling/alloying, characterization and phase formation prediction of Al0.1–0.5(Mn)CoCrCuFeNi-HEA powder feedstocks for cold spray deposition processing

In the present work the synthesis of multicomponent nanocrystalline Al0.1- 0.5(Mn)CoCrFeNi HEA powder feedstocks by mechanical alloying (MA) through high energy ball milling to produce HEA coatings with cold spraying were studied. Pure (>99.5) elemental powders of Al (Mn), Co, Cr, Cu, Fe & Ni were mixed in predetermined ratios and mechanically alloyed under Ar gas in a Planetary Ball Mill. MA HEA powder feedstocks were characterized by optical microscopy, SEM+EDAX, XRD & XPS to determine powder particle size, shape & distribution, particle surface condition, chemical composition, crystal & phase structures & microstructures. MA-processed Al-HEA powder feedstocks exhibited tri-modal particle size distribution (PSD) while Mn-HEA had four distinct PSD modes. Fine size fraction of the MA- HEA powders contained A2/B2 (BCC) harder phases with lattice parameters of 2.8831 and .2.8690 Å, respectively and coarse size fraction contained (ductile) softer A1 phase/Cu-rich regions combined (FCC) having a lattice parameter of 3.6181 Å. The ratio of the phases varied depending on the Al and Mn contents in the powder. For higher aluminium contents, there was more disordered A2/B2 phases and less disordered A1 phase in Al0.1–0.5 HEA powder feedstocks. A1 phase contained Fe, Cr, Co and Ni; A2 phase contained Fe, Cr; and B2 phase contained Al, Ni elements in Al0.1–0.5 HEA powder feedstocks. There were passive surface oxide films on the rough surfaces of MA HEA powder feedstocks consisting of a main mixture of surface oxides such as Al2O3, MnO, Cr2O3, Mn2O3, and minor oxides such as CuO, Fe2O3, NiO, Fe3O4, and a few CoCr2O4 spinel oxide. Dual FCC-dual BCC phase prediction of thermodynamic stable phase formation criteria reported in the literature on MA-HEA powder feedstocks were consistent with the experimental results of the present study.

Analysis of Dispersivity in Marine Clays of Cartagena de Indias, Colombia

This study assessed the dispersivity of soils extracted from the northern region of Cartagena de Indias (Colombia) using the pinhole test, crumb test, and chemical–microstructural analyses. Dispersive soils are susceptible to erosive phenomena upon contact with water, yet they have not been adequately characterized in the city. To evaluate the dispersivity degree of different deformed and undisturbed soil samples, soil characterization tests included particle size analysis, chemical composition, Atterberg limits, specific gravity, and compaction. The results showed that the soils are highly plastic clays (i.e., CH) with a slight to moderate dispersivity level (i.e., ND3) according to the pinhole test and a moderate degree of dispersivity confirmed by the crumb test. The extracted soil sample sodium levels ranged from 0.72% to 1.94%, and the soil had an optimal moisture content of 26% and a maximum apparent dry unit weight of 13.87 kN/m3. According to standards and results, Cartagena de Indias’s studied marine clays are unsuitable for civil construction due to the degree of uncertainty in their behavior.

107 Assessment of in Vitro Toxicity of Inhalable Incidental Nanoparticles Originating in the Ceramic Industry

Abstract Assessing exposure to nanomaterials in industrial workplaces is a widespread challenge. Nanoparticle release was evaluated, under real-world operating conditions, in one thermal spraying and one tile firing facility. Nanoparticles were characterised in terms of mass and number concentrations (µg/m3; /cm3), particle size distribution, chemical composition and morphology, and in vitro toxicity. The present work targets especially the toxicological characterisation of the aerosols sampled. Particles <2 microns in size were sampled in cell-culture medium using an SKC Biosampler connected to a pump operating at 12 lpm. Samples were conserved frozen at -20ºC until analysis. Submerged-cell cultures using the commercially-available A549 cell line were used for the in-vitro assays, where cell viability and generation of reactive-oxygen species (ROS) were assessed. Preliminary results evidenced a relatively large variability across samples in terms of cell viability, with reductions ranging between <5% and up to 60% after 2-hour exposures. Results suggested that the initial INP concentration in the samples may play a relevant role in the results, as in highly concentrated samples nanoparticles may interfere with the cellular uptake of the Alamar Blue dye used and, subsequently, on fluorescence results. ROS generation was detected increasingly over time during the test period (1-4 hours). Readings obtained after 3-4 hour became mostly stable. Finally, these results provide the baseline for the subsequent assessment of the expected reduction in INP concentrations and toxicity resulting from the implementation of risk mitigation measures, which will focus on a custom-designed air filtration system developed in the framework of this project.

Zwitterionic Polymer Brushes and Core‐Shell Particles Based thereon for Control of Biofouling

AbstractBiofilm formation on material surfaces – biofouling – has a significant economic impact on a wide range of applications and industries. There is a huge need for the prevention of undesired interactions of coatings with proteins, cells, and bacteria in biomaterials, biosensors, and other applications. In this work, the preparation and characterization as well as the comparison of bio‐fouling properties of surfaces based on planar zwitterionic polymer brushes made of poly(sulfobetaine methacrylate) P(SBMA‐3), poly(carboxybetaine methacrylate) P(CBMA‐2), or poly(2‐methacryloyloxyethyl phosphorylcholine) P(MPC‐2) are reported. Since polymer brushes on planar surfaces have disadvantages with regard to layer stability, industrial scaling, and the coating of complex geometries, nano‐ and microstructured coatings based on polymer‐functionalized core‐shell particles are subsequently produced. It is found that coatings based on poly(phosphorylcholine) P(MPC‐2) modified particles with a diameter of 100 nm have the lowest bioadhesion compared to other particle sizes and chemical compositions. The particle‐based coatings developed can pave the way for developing scalable anti‐fouling coatings in the future.

Assessing the Cleanliness of Dental Implants Using Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy Analysis-A SEM and EDS In Vitro Study.

A wide variety of titanium (Ti) alloy dental implant systems are available and as a result, choosing the correct system has become a challenge. Cleanliness of the dental implant surface affects osseointegration but surface cleanliness may be jeopardized during manufacturing. The purpose of this study was to assess the cleanliness of three implant systems. Fifteen implants per system were examined with scanning electron microscopy to identify and count foreign particles. Particle chemical composition analysis was performed with energy-dispersive X-ray spectroscopy. Particles were categorized according to size and location. Particles on the outer and inner threads were quantitatively compared. A second scan was performed after exposing the implants to room air for 10 min. Carbon, among other elements, was found on the surface of all implant groups. Zimmer Biomet dental implants had higher particle numbers than other brands. Cortex and Keystone dental implants showed similar distribution patterns. The outer surface had higher particle numbers. Cortex dental implants were the cleanest. The change in particle numbers after exposure was not significant (p > 0.05). Conclusion: Most of the implants studied were contaminated. Particle distribution patterns vary with the manufacturer. The wider and outer areas of the implant have a higher probability of contamination.

Advances in the modelling of concentration-dependent relative viscosity data for nanofluids by introducing the Dispersion Factor

The viscosity ratio (relative viscosity) of a nanofluid to its base liquid is related to the nanoparticle volume fraction by various developed theoretical and empirical equations. However, the theoretical framework used up to now is often inadequate for modelling experimental data. Now, a new parameter denoted as the Dispersion Factor (DF) is proposed to advance the accurate modelling of relative viscosities of nanofluids dependent on nanoparticle volume fraction. Literature data of TiO2, γ-Al2O3and SiO2nanofluids have been selected and subjected to our new theoretical treatment using the Chen equation adapted with the Dispersion Factor to model the relative viscosity in relation to the nanoparticle volume fractions.A much better agreement with the experimental data has been obtained. The value of DF that is identified by the mathematical modelling of relative viscosity data reflects the comprehensive effect of particle size, shape and chemical composition on the interactions between the nanoparticle and the base liquid on the one hand, and solvated nanoparticle and nanoparticle interactions on the other hand. The DF parameter may present a possible tool that can be used to tailor and tune the nanofluid design to meet specific application requirements.