Dispersion Of Powders Research Articles

CFD-DEM investigation of the effects of aperture size for a capsule-based dry powder inhaler

Capsule based dry powder inhalers (DPIs) often require piercing of the capsule before inhalation, and the characteristics of the apertures (punctured holes) affect air flow and the release of powders from the capsule. This work develops a numerical model based on the two-way coupling of computational fluid dynamics and discrete element method (CFD-DEM) to investigate the effect of aperture size on powder dispersion in the Aerolizer® device loaded with only carrier particles (lactose). Powders (carrier particles) in the size range 60–140 μm (d50: 90 μm and span: 0.66) were initialized in a capsule which had a circular aperture at each end. Boundary conditions corresponding to an air flow rate of 45 L/min were specified at each inlet to the mixing chamber (i.e., a total flow rate 90 L/min), and a capsule spin speed of ∼ 4050 rpm. The velocity magnitudes inside the capsule were considerably lower than those in the mixing chamber in the vicinity of the rotating capsule, with the exception of the capsules featuring 2.5 mm and 4 mm apertures. Larger apertures reduced the capsule emptying time and increased the particle evacuation velocity; the fluid drag force on the particles issuing from the capsule peaked for an aperture of 1.3 mm. Inside the capsule, particle–particle (PP) collisions were more frequent than particle–wall (PW) collisions due to high concentration of powder, but PP collisions had smaller (median) impact energy than PW collisions. Larger apertures resulted in fewer collisions in the capsule with higher PW and virtually unchanged PP collision energies. Outside the capsule (i.e., in the inhaler mixing chamber), PW collisions occurred more frequently than PP collisions with median collision energies typically two orders of magnitude higher than inside the capsule. Larger apertures resulted in more collisions with slightly reduced collision energy, but this effect plateaued for aperture sizes larger than 1.3 mm. Powder dispersion, expressed as the fine particle fraction (FPF) of the powder, was predicted using an empirical equation based on carrier PW collisions. Therefore, consistent with the model prediction of the effect of aperture sizes on the chamber collision frequency, FPF increased with aperture size but plateaued beyond 1.3 mm.

Effect of transient inhalation on powder evacuation and dispersion in a typical dual air inlet dry powder inhaler

An optically accessible research dry powder inhaler (DPI) was used to investigate the impact of initial acceleration during inhalation on the powder evacuation and drug dispersion processes. The inhaler featured a swirling chamber connected with two inlets, closely resembling commercial devices such as the Aerolizer® and Osmohaler®. The dimensions of the inhaler were kept similar to the commercial devices, mimicking their flow situations. High-speed microscopic imaging and an in-house developed image processing technique were used to extract relevant statistics. The current literature on DPI flow dynamics provides valuable insights into the correlation between inspiratory flow rate, peak inspiratory pressure, and inhaler performance. However, it lacks data correlating powder evacuation characteristics and deagglomeration mechanisms for transient inhalation conditions inside the DPIs. This paper is an attempt to fill this gap by investigating the evacuation pattern and deagglomeration mechanism for three different initial accelerations qualitatively representing asthma severity and steady-state inhalation conditions representing laminar, transitional, and turbulent channel flow, using both pure drug and carrier particles. The study's key findings revealed that powder evacuation progressed in two stages. The first stage was slow, with a slope ranging from 0.25 to 0.27. Also, the evacuation rate was independent of the initial inhalation acceleration. The second stage was rapid, with a slope ranging from 0.87 to 1.23, which led to faster and complete powder evacuation. The slow stage consumed approximately ∼60 % of the total evacuation time to evacuate only ∼20% of the loaded drug, while the rapid stage evacuated ∼80% of the powder in the remaining time. The data collected from these experiments advances the understanding of the DPI flow dynamics and provides high-quality data for validating computational models used in the analysis of such inhaler systems.

Production of nickel and cobalt metal powders under autoclave conditions

This paper presents the results of studies on the reduction of dispersed cobalt and nickel metal powders from their salts in ammonia-alkaline aqueous solutions under hydrothermal autoclave conditions. A unified and environmentally friendly method for producing these powders has been developed. Hydrazine hydrate, with a 25–50 % excess of the stoichiometric ratio, was used as a reducing agent. This choice allows for obtaining metal phases that are chemically uncontaminated by decomposition products. The experiments determined the conditions for the quantitative reduction of cobalt (II) and nickel (II) ions from ammonia-alkaline aqueous solutions. The synthesis temperature for the dispersed phases ranged from 110 to 155 °C. It has been demonstrated that under the conditions used, the process is completed quantitatively within 60 min. Metal concentrations in the solutions were determined using atomic absorption spectroscopy. The results of the X-ray phase analysis confirm that cobalt forms in the HCP lattice, while nickel forms in the FCC lattice. No other phases, including X-ray amorphous phases, were observed. It was found that with an increase in the hydrothermal synthesis temperature from 110 to 155 °C, the specific surface area of cobalt increased by more than 1.5 times, and that of nickel black powders increased by approximately 2 times. Scanning electron microscopy revealed that cobalt is formed in the shape of lamellar particles with a lateral size of about 500 nm and a thickness of 50 nm, which aggregate into fractal structures. Nickel is represented by spherical particles arranged in chain-like structures. Using X-ray photoelectron spectroscopy, it was determined that the surface of the materials is covered with oxidized forms. The surface atomic concentration of cobalt (0) was approximately 2 %, while that of nickel (0) was about 25 %.

Fe–Pd nanoflakes decorated on leached graphite disks for both methanol and formic acid electrooxidation with excellent electrocatalytic performance

This paper introduces a unique and simple method for fabricating of inexpensive electrocatalysts for use in direct methanol fuel cells. The leached Fe1–Pd1 NFs/graphite (leached Fe1–Pd1/graphite) disk electrode was successfully obtained via uniform dispersion of Zn powder into the matrix of commercial graphite powder (98%), pressing under optimized pressure followed by the treatment in H2SO4 solution containing Fe+2 and Pd+2 cations, leading to the partial leaching out of Zn from graphite matrix, as well as partial electroless substitution of Fe–Pd nanoflakes with Zn metal. Based on the morphology studies, binary Fe–Pd nanoflakes with a large surface area uniformly dispersed on the leached graphite disk. The leached Fe–Pd/G disk showed the exceptional electrocatalytic activity toward methanol and formic acid oxidation without electrocatalyst poisoning being observed, in contrast to the leached Pd/graphite and leached Fe/graphite disks. This is due to the high surface area, and synergistic effect of Pd and Fe. The findings of this work may be used for the mass manufacture of graphite-based disks for commercial fuel cell applications using available graphite powders. The linear range of washed Fe1–Pd1/G electrocatalyst for measuring methanol was about 0.1–1.3 M, and its detection limit was calculated at about 0.03 M. Furthermore, the linear range of the nanocatalyst for measuring formic acid was about 0.02–0.1 M, and its detection limit was calculated at about 0.006 M.

Energy-Intensive Materials with Mechanically Activated Components

The production and study of highly dispersed aluminum-based powders represents one of contemporary science’s priority fields. This is primarily driven by the practical necessity to develop new materials, a feat that, in some cases, can only be achieved through the utilization of powdered components. This article presents the results of the mechanochemical treatment method employed to obtain highly reactive aluminum particles. It also includes a comparative analysis of aluminum particles generated through various methods and their respective properties. Furthermore, the application of these highly reactive aluminum particles in energy-intensive materials is discussed.

Preparation of Bi2O3@PCPA‐KH590/chloroprene composites with good mechanical properties under high‐filling

AbstractAs a “green” radiation protection material with the potential to replace lead oxide, bismuth oxide has more research applications in the field of γ protection. However, due to their different surface properties, there are compatibility and interaction problems between metal oxides and rubber. To enhance the performance of bismuth oxide in neoprene, Bi2O3@PCPA‐KH590 was prepared by coating bismuth oxide with polyphenol/polyamine and grafting KH590 on the surface of bismuth oxide. This allows for creating more active sites with the help of polyphenol/polyamine, enabling KH590 to be grafted onto bismuth oxide particles. The S functional group on the silane coupling agent is then cross‐linked with the rubber substrate, enhancing the dispersibility of the bismuth oxide powder. This improvement not only improves the dispersibility of the bismuth oxide powder but also enhances the mechanical properties of the rubber composite material. Compared with pure CR, the mechanical properties of 60 wt% filler‐modified powder composites can still be maintained at a high level, with the tensile strength reaching 12.83 Mpa. In sum, the proposed method appears feasible for preparing highly filled radiation protection rubber‐based materials.

Dynamic compressive properties of rubberized mortar reinforced with straw-fiber additive

Numerous techniques have been suggested to repurpose and recycle rubber, aiming to mitigate its ecological impact. Among these approaches, incorporating rubber into construction materials stands out as a noteworthy strategy. However, this incorporation of rubber typically leads to a marginal reduction in the mechanical robustness of the mortar. To counterbalance this limitation, innovative substances have been advocated for integration. Notably, straw fiber, renowned for its exceptional fibrous attributes, emerges as a prime candidate. Thus, it is desirable to systematically evaluate its effects on both the mechanical and microstructural attributes and it is the objective of this study to investigate the dynamic compressive properties of straw-fiber reinforced rubberized mortar (SFRM). The investigative methodologies encompass scanning electron microscope (SEM) analysis, X-ray computed tomography (CT) scans, quasi-static and dynamic compression tests employing a split Hopkinson pressure bar. Complementary examinations involving sieving assessments and fractal computations were also conducted. The experimental findings unveil a uniform dispersion of rubber powder and straw fibers within the mortar matrix, although the bonding is relatively weak. The dynamic compressive strength of SFRM exhibits a linear correlation with escalating loading rates, whereas an augmentation in the straw fiber ratio correlates with a reduction in strength. However, the inclusion of fibers significantly improved the capacity for dynamic energy absorption. Furthermore, based on the sieving test and fractal calculation, it was found that the optimal crushing resistance of rubberized mortar is achieved at a fiber ratio of 1.5. This study underscores the augmented capability of SFRM to withstand high-loading-rate compressive forces, thereby fortifying structures against shock and blast loads.

Graphite Separation in Sunflower Oil and a Possible Food Monitoring Sensor via Near-infrared Spectroscopy

Introduction: As a quick and non-destructive testing method, Fourier transform infrared (FTIR) spectroscopy has become more popular for identifying food adulteration, manipulation, and deception. Sunflower oil is a widely used food item that may be contaminated or even adulterated with potentially harmful chemical substances associated with health issues. Methods: In this regard, this study was carried out to examine the applicability of near- and midinfrared spectroscopy to identify modifications in the pure sunflower oil and sunflower oil dispersed with graphite. The dispersion of graphite powder in sunflower oil was achieved using the ultrasonic technique. The samples were analyzed using FTIR spectroscopy and transmission electron microscopy. Results: Changes in the FTIR signal were observed, indicating changes in the hydrogen atoms distribution within the solution. The flattened peak at 3470 cm-1 was associated with the overtone of glyceride ester carbonyl absorption compared to pure SO. Additionally, the stretching vibration of carbonyl groups of triglyceride esters occurred as a significant absorption band at 1754 cm-1, and the FTIR absorption at 1447 cm-1 was absent. Transmission electron microscopy (TEM) analysis showed transparent layers of graphene sandwiched with sunflower oil with a distinct flake-like shape Conclusion: These findings support dispersed graphite in sunflower oil to check the food quality.

Achieving high mechanical and wear properties in the AZ31/(CeO2+ZrO2)p surface composite using friction stir processing: Application of vibration

In this study, the friction stir vibration processing (FSVP) have been devoted to the study the impact of the vibration frequency on the metallurgical and mechanical behavior of the AZ31/CeO2–ZrO2 surface composite. The structure, local shear punching test (SPT), hardness, and wear performance of the produced surface composite were studied. The results showed that with the use of vibration during FSP, the stir zone area broadened and resulted in eradication of the flow voids and enhanced the materials flow and the (ZrO2+CeO2)p powders dispersion in the matrix. It was also found that vibrating motion acted as an auxiliary energy and resulted in the enhancement of the shear punching strength and wear resistance by about 29% and 48% in comparison to that of the FSPed sample. This is attributed to the absence of stress concentration sites and better particle dispersion-strengthening.

Effect of different processing methods on functional and physiochemical properties of turmeric (Curcuma longa Linn.) rhizome Var. Kapurkot Haledo-1

This study was conducted to evaluate the impact of different processing methods on the functional and phytochemical properties of turmeric rhizomes. The experiment consisted of four treatments: Treatment 1 involved oven-drying the turmeric powder, Treatment 2 involved blanching followed by oven-drying, Treatment 3 involved cooking followed by oven-drying, and Treatment 4 involved sun-drying. Each treatment was replicated four times. The major findings of the study revealed that sun-drying (68.50%) and blanching/oven-drying (66.50%) positively influenced the dispersibility of turmeric powder. Blanching/oven-drying (0.32 g/ml) and cooking/oven-drying (0.30 g/ml) significantly improved the bulk density of turmeric powder (p<0.001), with no significant difference observed between these two treatments. The water absorption capacity of the turmeric powders ranged from 3.35 to 5.35 g/ml, with the sun-dried sample displaying the lowest capacity and the cooked/oven-dried sample demonstrating the highest capacity. Similarly, sun-dried powder exhibited the lowest swelling power and solubility, while heat treatment resulted in a substantial increase in both of these parameters. Additionally, the curcumin content was found to be highest in the cooked/oven-dried (3.11%) and sun-dried (2.99%) turmeric powder. In conclusion, this study suggests that blanching and cooking methods have wide applicability in the food industry to enhance the bulkiness of turmeric powder for appropriate packaging and handling. Moreover, these methods contribute to the characteristic flavor and aroma of turmeric. The findings emphasize the importance of considering different processing techniques for optimizing the functional and phytochemical properties of turmeric, thus enabling its effective utilization in various food applications.

Effect of powder dispersity on the optical properties of HIP sintered MgAl2O4 transparent ceramics

Optical scattering centers in transparent magnesium aluminate spinel (MgAl2O4) ceramics substantially limit their applications in infrared domes or transparent windows. In this study, hot isostatic pressing (HIP) sintering was employed to fabricate high-quality transparent MgAl2O4 ceramics without the addition of sintering additive, and revealed that dispersion behavior of starting powders was crucial to the quality of MgAl2O4 ceramics. Microstructural evolution and optical quality of MgAl2O4 ceramics as the function of ball milling speed and pre-sintering temperature were systematically investigated. Despite increasing ball milling speed moderated powder agglomeration, large voids were still observed from the depth direction of the sintered ceramics. These voids could be further eliminated by employing PEI as the dispersant, and the in-line transmittance of the resulting ceramic was 86.5% at 800 nm, which was almost identical to the theoretical limit of MgAl2O4.

Studies of zinc content reduction using flake zinc powder in epoxy zinc-rich coatings

Purpose Epoxy zinc-rich coatings are widely used in harsh environments because of the long-lasting cathodic protection of steel surfaces. The purpose of this paper is to use flake zinc powder instead of the commonly used spherical zinc powder to reduce the zinc powder content. Design/methodology/approach In this paper, the authors have prepared an anticorrosive zinc-rich coating using a flake zinc powder instead of the conventional spherical zinc powder. The optimal dispersion of scaly zinc powder in zinc-rich coatings has been explored by looking at the surface and cross-sectional morphology and studying the cathodic protection time of the coating. Findings The final epoxy zinc-rich coating with 35 Wt.% flake zinc powder content was prepared using sand-milling dispersions. It has a similar cathodic protection time and salt spray resistance as the 60 Wt.% spherical zinc-rich coating, with a higher low-frequency impedance modulus value. Originality/value This study uses flake zinc powder instead of the traditional spherical zinc powder. This reduces the amount of zinc powder in the coating and improves the corrosion resistance of the coating.

Prospects for the use of fine-dispersed recycling products of concrete processing as mineral additives for the manufacture of building mortars

Introduction. One of the most important reserves for saving material and energy resources in the construction industry is the re-involvement of recycling concrete materials (products of disposal of substandard concrete, reinforced concrete structures and products), in particular, highly dispersed powders with the prospect of their use as a mineral additive for the production of mortars for general construction purposes, in the production field. The implementation of this approach will practically ensure the introduction of the most important principle of waste-free technological processes (in the production of prefabricated and monolithic concrete, reinforced concrete structures and products) and create conditions for solving important economic and environmental problems.Aim. The aim of the work were the determining of the main physical and mechanical characteristics, comparative analysis of the mortar on Portland cement, as well as mortars with the replacement of a part of Portland cement (by 10, 15 and 25 %) with a recycling (concrete) fine powder with a specific surface area of 4500 cm2/g.Materials and methods. For the research, the following components were used: recycling (concrete) fine powder with a specific surface area of 4500 cm2/g, construction sand with a size modulus Mk = 2.31 (according to GOST 8736-2014), portland cement with CEMII/V-W 42.5N (according to GOST 31108-2020) slag, chemical additive “CENTRIPOR TFM 411R”.The selection of mortar compositions was carried out according to SP 82-101-98. Tests of mortar mixtures and mortars were carried out according to GOST R 58767-2019. Compliance with the compressive strength of mortars with the grade was determined in accordance with GOST R 58766-2019.Results. As a result of the work carried out, it is shown that fine-dispersed recycling concrete powder with a specific surface area of 4500 cm2/g can be used as a mineral additive (filler) for the production of mortars on a par with additives currently used in the construction industry of the country.Conclusions. The possibility of using fine-dispersed recycling concrete powder with a specific surface area of 4500 cm2/g as a mineral additive (filler) for the roductionof mortars on a par with additives currently used in the construction industry of the country. It has been shown that when 10 % of cement is replaced with recycled (secondary) fine powder with a specific surface area of 4500 cm2/g, the strength of building mortars of the M100–M150 grades increases and its structure improves.

SYNTHESIS OF LEAD TUNGSTATE IN MELTS OF THE SYSTEM (Li<sub>2</sub>WO<sub>4</sub>–Na<sub>2</sub>WO<sub>4</sub>)<sub>evt</sub>–PbSO<sub>4</sub>

The structure of the crystallization surface of the system (Li, Na), Pb // SO4, WO4 has been studied in a wide concentration and temperature range in order to identify compositions with optimal physicochemical parameters that can be used as the basis for the synthesis of highly dispersed lead tungstate with high yield and purity. The system (Li2WO4–Na2WO4)evt–PbSO4, which is a diagonal section of the system (Li, Na), Pb // SO4, WO4, was chosen as a working system for solving the task set in the work. For the first time, the concept of a “complex component” is used in the work, which is a mixture of lithium and sodium tungstates, as well as lithium and sodium sulfates at the vertices of the square of compositions. The complex components are eutectic compositions of the corresponding lithium tungstates, sodium and their sulfates. This approach to the study of the “resulting” triple mutual system (Li, Na), Pb // SO4, WO4 on the vertices of which complex components are located allowed us to take advantage of the noticeable differences between the studied system and the original triple mutual systems Li, Pb // SO4, WO4 and Na, Pb // SO4, WO4. It is shown that the studied system (Li, Na), Pb // SO4, WO4 has a number of advantages both in terms of melting temperatures of the eutectic mixture on the side of Li2,Na2(WO4)2–Li2,Na2(SO4)2, and in terms of the shift of the line of joint crystallization of phases, which leads to a noticeable increase in the crystallization surface lead tungstate. In this regard, before proceeding to the production of lead tungstate, we estimated the thermodynamic probability of the reaction underlying the synthesis of lead tungstate on the basis of the Temkin-Schwarzman method and the Van’t-Hoff isotherm equation of chemical reactions. Calculations have shown that all metabolic processes proceed with high negative Gibbs energies. The obtained samples of lead tungstate were analyzed by the X-ray phase analysis method on the X-ray diffractometer Dron-6, and their dispersion was determined on the Fritsch Analysette 22 Nanotek Plus laser particle analyzer. The presented results of a theoretical analysis of the possibility of implementing a method for synthesizing lead tungstate in melts of the (Li2WO4–Na2WO4)evt–PbSO4 system and experimental material for its implementation can become the basis for the development of technology for obtaining highly dispersed lead tungstate powders.

Effect of preparation conditions on the properties of nano ZnO powders during ultrasonic assisted direct precipitation process.

Transparent conductive thin films (TCO) are widely used for their excellent photoelectric properties. To prepare high-quality ZnO targets, starting with the original ZnO powder is necessary. This paper aims to explore the basic technology and method of ultrasonic-assisted direct precipitation for mass production of ZnO powder and to analyze the effects of factors such as precipitating agent, surfactant, calcination temperature, and solvent on the powder's morphology, particle size, and crystallinity. The study found that the type and amount of precipitants and surfactants affect the powder's morphology and dispersibility, while calcination temperature mainly affects the powder's morphology and crystallinity. The ethanol content in the solvent mainly affects the grain size. After testing different variables, the optimal conditions for preparing spherical ZnO powder were found to be using (NH4)2·CO3 as the precipitant, adding 3% wt of PEG-400 and 3% wt of TEA at a calcination temperature of 320°C and a 60% ethanol solvent. This resulted in a smooth surface, uniform particle size distribution, good dispersibility, high crystallinity, and particle sizes between 26-32nm.

Improvement of Mechanical Strength and Long-Term Durability on Anode Support for Solid Oxide Fuel Cells by Adding Nanomaterials

Ni-8YSZ is widely used as an anode support for Solid Oxide Fuel Cells (SOFC). However, because of its low mechanical strength and high price, it is essential to develop an improved anode support material for commercialization. It has been reported that 3YSZ, which is used for bioceramics (implants) or refractory materials (for metallurgical metals), has more than twice as high mechanical strength as 8YSZ. In addition, since it is about 20 % cheaper than 8YSZ, it is under study as an anode support material. However, it has the disadvantage of significantly degrading the mechanical strength in the high-temperature humidified hydrogen atmosphere, which is the operating condition of the SOFC. In this study, we tried to improve this by adding nano-ZrO2 and nano-WO3. According to the Hall-Petch equation, it has been reported that the addition of nanoparticles has the effect of reducing the grain size and thus improving the mechanical strength. ZrO2 is the same material as the anode support and will not affect the material properties. According to the report, when WO3 is reduced that it will exhibit high mechanical strength in the form of a Ni-W alloy. For uniform dispersion, NiO and 3YSZ powders were ball-milled for 100 hours, and nano-ZrO2 and nano-WO3 were also added, respectively. At that same time, a binder and a pore former were added to secure the same porosity as the SOFC anode support. The mixed slurry was dried for 24 hours in the oven, then sieved, and pelletized. The powders were sintered at 1400 oC for 5 hours. Sintered samples were reduced at 750 oC in a hydrogen atmosphere for 8 hours. The reduced samples were heat treated in a reducing atmosphere (at 900 oC in a humidified hydrogen) for 500 and 1000 hours, respectively, which is an accelerated atmosphere. The three-point bending method was used to evaluate the mechanical strength and SEM microstructure analysis was conducted to analyze the cause of the improvement. As a result, the mechanical strength and long-term durability of the Ni-3YSZ anode support were greatly improved in the case of the sample with nano-ZrO2 added.

Synthesis and Characterization of Silicon–Carbon Powder and Its Resistance to Electron Irradiation

The issue of crystallization of silicon oxide at low temperatures is a topical issue for the electronics of the future. Organosilicon oligomers and polymers are “ideal” sources for obtaining ultrapure silicon ceramics and silicon nanoparticles. This paper presents the results of the synthesis of highly dispersed silicon-carbon powder from an organohydrosiloxane oligomer and the method for increasing its crystallinity at low temperatures. The diffraction pattern of the resulting powder corresponds to the amorphous–crystalline state of the components in this material, as evidenced by two intense and broadened amorphous halos in the region of Bragg angles 2θ = 7–11° and 18–25°. The resulting silicon–carbon powder was subjected to electron irradiation (E = 10 MeV; D = 106–107 Gy). This paper presents the data on the changes in powder properties via IR-Fourier spectroscopy, X-ray phase analysis, and scanning electron microscopy. Irradiation with fast electrons with an absorbed dose of 106 Gy leads to a slight crystallization of the amorphous SiO2 phase. An increase in the absorbed dose of fast electrons from D = 106 to D = 107 Gy leads to the opposite effect. An amorphization of silica is observed. This study showed the possibility of the crystallization of a silicon–carbon powder without a significant increase in temperature, acting only with electron irradiation. It is necessary to continue further research on expanding the boundaries of the optimal doses of absorbed radiation from fast electrons in order to achieve the maximum effect of the crystallization of silicon–carbon powder.

Kinetics and mechanism for efficient Co(II) removal from zinc sulfate solution by ultrasonic-enhanced zinc powder replacement

The purification of zinc sulfate electrolytes in zinc hydrometallurgy has always been a vexing problem. The aggregation of zinc powder and the removal of recalcitrant Co(II) are the most challenging. Here, we propose a new method for removing Co(II) from a zinc sulfate solution using ultrasonic-enhanced zinc powder replacement. The parameters affecting Co(II) removal are investigated to obtain the optimum conditions. The Co(II) removal efficiency increases remarkably by 26.6% and the required amount of zinc powder was correspondingly reduced by 50% after introducing ultrasound and activators. The optimal dosage of activators Sb2O3 and Cu(II) is CCu(II): CSb(III): CCo(II) = 2: 1: 1. Moreover, the addition of Cu(II) does not deteriorate the quality of zinc sulfate solution because of its low residual concentration (0.84 mg/L). The removal kinetics show that the activation energy of Co-precipitation decreases by 32.27 kJ/mol, and the conversion range of the kinetic mechanism is increased to CCo(II),0 = 60–80 mg/L. The particle diameter of the purified slags decreases from 136.22 to 19.81 µm compared with that of conventional experiments. The cobalt removal mechanism mainly involves that ultrasound promotes the dispersion of zinc powder, opens the package and reduces the activation energy; the Co-Sb-Cu alloys reduce the Co-precipitation overpotential and inhibit the redissolution of Co. The proposed method presents a promising solution to the challenging problem of Co(II) removal. This study opens new possibilities for the application of ultrasound in the metallurgical fields for more efficient and energy-saving production.

Dispersion of hydrophobic waste amorphous carbon powder in cementitious environment and its effect on the permeability of cement paste

A Proper dispersion of powder-based hydrophobic admixtures in cementitious composites is challenging due to the presence of water. Studies have shown that amorphous carbon powder (ACP), a hydrophobic by-product of refining waste materials of paraffin production can be used as a hydrophobic agent. However, mixing methods and dispersing agents for modifying cementitious materials with ACP can significantly impact their mechanical properties, workability, water-repellency (hence the durability), and dispersion quality of ACP. Lack of information about the extent of their impact on different aspects mentioned above can hinder the practical use of ACP as a hydrophobic agent. To fill this gap, the objective of this study is to comprehensively investigate factors in the dispersion of ACP in cementitious materials and the tradeoff between mechanical properties and water permeability of ACP-modified cementitious materials when more than one mixing method is adopted. The impacts of different dispersing agents and mixing methods, including ultrasonication, dry mixing, and after mixing, on dispersion quality of ACP in cementitious environment analogous with aqueous solutions and hardened cement paste were assessed. Polycarboxylate ether-based superplasticizer (PCE) proved to be the most effective dispersing agent. Compressive strength of ACP modified cement paste can be increased or decreased with or without the workability reduction effect of ACP along with PCE respectively. Based on volume fraction of ACP clusters in X-ray micro-CT 3D reconstruction of hardened cement paste, ultrasonication was identified as the most effective mixing method and dry mixing was the worst in terms of achieving a uniform distribution of ACP in cement paste. However, all mixing methods presented more than 85% volume fraction of uniformly dispersed ACP areas with no major difference in terms of hydrophobic modification capability. Modifying cement paste with a higher amounts of ACP (5 to 15% by weight of cement) substantially increased water contact angle (up to 171% for w/c ratio of 0.35) and decreased water absorption. The hydrophobic modification capability of ACP increases with a decrease in the quality of cement paste and is diminished by the presence of PCE. Consequently, without PCE, water absorption rate was reduced by up to 92% in similar ACP modified cement paste samples, which also led to a major reduction in compressive strength.

Improved ultraviolet -visible optically transmittance and luminescent properties in Yb, Lu: Sr5(PO4)3F transparent ceramics via Lu3+ co-doping

The asymmetric hexagonal Sr5(PO4)3F (S-FAP) crystal material is considered to be the most suitable solid state laser gain medium for small laser diode pumping in the future due to its large absorption, emission interface, and long fluorescence lifetime. However, the mediocre optical transmittance of S-FAP transparent ceramics and the degradation of luminescence properties due to the doping of Yb activated ions seriously hinder its application prospects. In view of this, a series of 0.02Yb, xLu: S-FAP (x = 0–0.02) transparent ceramics with excellent optical properties were synthesized by hot pressing sintering. The powder SEM results show that Lu doping has no obvious effect on the morphology, grain size, and dispersion of powder. The linear transmissivity curves show that the ultraviolet (200 nm) and visible (500 nm) transmissivity increase by 54 % and 17 %, respectively, with Lu doping compared with the undoped ceramic samples. The surface SEM of ceramics revealed that Lu3+ promoted the increase of ceramic grain size significantly. The emission spectrum and fluorescence decay curves at room temperature also show that the emission intensity and fluorescence lifetime of ceramic samples increase significantly with Lu co-doping.