Uncoated Powders Research Articles

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

The hysteresis effect and eddy currents caused by alternating magnetic fields greatly impede the improvement of the working efficiency and performance stability of soft magnetic powder cores. In this work, modified hydrophobic SiO2 nanoparticles were prepared by tetraethyl orthosilicate (TEOS) and dimethyl-diethoxy-silane (DDS) as co-precursors through sol–gel methods. The effect of different proportions of DDS and TEOS on the amorphous magnetic powder cores performance was studied. It was demonstrated that the insulation layer in DDS and TEOS co-precursors hydrolyzed composite powders exhibited more uniform distribution compared with TEOS hydrolyzed alone counterpart. The introduction of methyl groups reduced the accumulation of hydrolysis intermediates on the surface of FeSiBC powders. Furthermore, the addition of DDS reduced eddy current loss significantly with a low hysteresis loss. The total energy loss of the DDS and TEOS co-hydrolysis powder core were reduced by 16.1 % and 7.7 % at 1 MHz, 0.05 T compared to the uncoated powder core and the TEOS hydrolysis alone counterpart, respectively. The presented results provide insights into improving the application range and energy utilization efficiency for the magnetic powder cores.

Scaling a Gas Phase Residual Lithium Conversion Process on Ni-Rich NMC Cathode Materials in Commercial Fluidized Bed Reactors

‘Residual lithium’, the LiOH and Li2CO3 surface contamination that is ubiquitous to Ni-rich NMC manufacturing, is a significant obstacle in the large-scale production and handling of high-nickel layered oxides. These hydroxide and carbonate surface phases influence reproducibility and shelf stability of the NMC powder and cause gelation and particle aggregation during electrode casting. There is ample evidence in the literature that atomic layer deposition (ALD) possesses a two-fold solution to this problem.1-3 First, reactive organometallic species such as trimethylaluminum (TMA) can convert insulating residual lithium to a Li-rich LixAlyO conducting layer. Customizable ALD layers can then be added to inhibit the re-formation of the carbonate layer and to deter negative side reactions of the CAM surface with the liquid electrolyte. While highly impactful, these studies have mostly been relegated to small, lab-scale demonstrations of <50 g. As such, there remains a need to enable this ALD-assisted-technology for high-throughput commercial applications.In this talk, we will explore the progression of a residual lithium conversion process from lab (10 – 1000 mL) to industrial-scale (10 L – 100 L) fluidized bed equipment and how scale and material-dependent parameters can impact performance. Using a commercial NMC 811 cathode as a case study, we first applied aluminum phosphate ALD coatings on a lab-scale fluidized bed reactor to examine the interfacial and electrochemical changes of the CAM material under various process conditions. ICP-OES measurements confirmed linear and reproducible deposition versus ALD cycle number between 200- 300°C. XPS analysis showed the ALD coated NMC 811 powder had an 80% reduction in Li2CO3 versus the pristine material and that a reduction persisted even after 10 days of storage in atmospheric conditions. At standard (0.5C/1C) cycling to 4.4V, AlPO4 coatings increased cycle life by 44% versus the uncoated powder. Under optimized conditions, the process was scaled first to 1 kg and finally to 10 kg in a pilot-scale reactor. In-situ mass spectrometry indicated that residual lithium conversion byproducts such as CO2 could be used to monitor reaction progress and optimize chemical usage efficiency. Fluidization aids including vibration and mechanical stirring were used to inhibit and break up powder agglomerates. ICP-OES and electrochemical cycling data confirmed reproducible deposition and cycle life benefits versus the small scale runs and pristine materials, demonstrating a pathway for these ALD-enhanced materials to transition from lab-scale demonstration to viable product. We will discuss strategies for continuing the scaling process to 100 kg batches for commercial applications.[1] M. Young et al., The Journal of Physical Chemistry C 2019 123 (39), 23783-23790[2] P. Darapaneni et al., ACS Applied Energy Materials 2022, 5, 8, 9870–9876[3] J. Li et al., Coatings 2022, 12(1), 84

Additive Manufacturing of Cu Using Graphene-Oxide-Treated Powder.

Additive manufacturing of Cu is interesting for many applications where high thermal and electric conductivity are required. A problem with printing of Cu with a laser-based process is the high reflectance of the powder for near-infrared wavelengths making it difficult to print components with a high density. In this study, we have investigated laser bed fusion (L-PBF) of Cu using graphene oxide (GO)-coated powder. The powder particles were coated in a simple wet-chemical process using electrostatic attractions between the GO and the powder surface. The coated powder exhibited a reduced reflectivity, which improved the printability and increased the densities from ~90% for uncoated powder to 99.8% using 0.1 wt% GO and a laser power of 500 W. The coated Cu powders showed a tendency for balling using laser powers below 400 W, and increasing the GO concentration from 0.1 to 0.3 wt.% showed an increase in spattering and reduced density. Graphene-like sheet structures could be observed in the printed parts using scanning electron microscopy (SEM). Carbon-filled inclusions with sizes ranging from 10-200 nm could also be observed in the printed parts using transmission electron microscopy (TEM). The GO treatment yielded parts with higher hardness (75.7 HV) and electrical conductivity (77.8% IACS) compared to the parts printed with reference Cu powder.

2D-axisymmetrical modeling and experimental study of hydrogen absorption in copper coated metal hydride

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi5.

Rotational coating of zinc on Nd-Fe-B powders with improved antioxidation performance

A newly developed rotational coating process has been used to coat Nd-Fe-B flake-shape powders with Zn. A uniform layer of Zn as thin as 1.5 μm can be coated on the Nd-Fe-B powders under a proper rotational coating condition. The coercivity decreases by about 4.23% and magnetization decrease by only 1.64% after Zn coating. The antioxidation, on the other hand, is greatly improved. The large mass increase during oxidation starts at 400 °C for the Zn-coated powders, 150 °C higher than that of the uncoated powders. In addition, during the high-temperature oxidation experiment from 30 °C to 450 °C, the mass of uncoated powders increases by 2.82%, while the mass of Zn-coated powders only increases by 0.40%. These results prove that the rotational coating is a very effective way to enhance the oxidation resistance of Nd-Fe-B powders, owing to the high-quality coating layer and its good isolation ability for the matrix. The process is also low-cost and easy to achieve mass production, making it a promising technique for producing high-performance Nd-Fe-B powders.

Multifunctional Coatings on Sulfide-Based Solid Electrolyte Powders with Enhanced Processability, Stability, and Performance for Solid-State Batteries.

Sulfide-based solid-state electrolytes (SSEs) exhibit many tantalizing properties including high ionic conductivity and favorable mechanical properties for next-generation solid-state batteries. Widespread adoption of these materials is hindered by their intrinsic instability under ambient conditions, which makes them difficult to process at scale, and instability at the Li||SSE and cathode||SSE interfaces, which limits cell performance and lifetime. Atomic layer deposition is leveraged to grow thin Al2 O3 coatings on Li6 PS5 Cl powders to address both issues simultaneously. These coatings can be directly grown onto Li6 PS5 Cl particles with negligible chemical modification of the underlying material and enable exposure of powders to pure and H2 O-saturated oxygen environments for ≥4 h with minimal reactivity, compared with significant degradation of the uncoated powder. Pellets fabricated from coated powders exhibit ionic conductivities up to 2× higher than those made from uncoated material, with a simultaneous decrease in electronic conductivity and significant suppression of chemical reactivity at the Li-SSE interface. These benefits result in significantly improved room temperature cycle life at high capacity and current density. It is hypothesized that this enhanced performance derives from improved intergranular properties and improved Li metal adhesion. This work points to a completely new framework for designing active, stable, and scalable materials for next-generation solid-state batteries.

Tailoring the flow properties of inhaled micronized drug powders by atomic and molecular layer deposition

For dry powder inhaled formulations, good flow behaviour is vital in re-dispersing the powder. However, inhaled drug powders with a particle size below 10 µm are classified as highly cohesive materials with poor flow characteristics. Here we demonstrate how to alter the flow properties of micronized budesonide powders by depositing different materials (organic, inorganic, and hybrid organic–inorganic) in the forms of nanoscale films onto the drug particles using atomic/molecular layer deposition (ALD/MLD) coatings. The angle of repose (static) and pneumatic delivery measurements were performed to access the flow characteristics. The flowability can be effectively improved with the growth of inorganic nanofilm (SiO2, TiO2, or Al2O3) via ALD and hybrid nanofilm (titanicone) via combined ALD-MLD coating. This improvement is reflected by the decrease in the angle of repose and minimum pick-up velocity (Upu), as well as promoting the pneumatic delivery of a much larger amount of drug powders after ALD or hybrid coating. In contrast, the organic PET coated budesonide via MLD exhibits comparable poor flow characteristics as the uncoated budesonide. Rather than being transported in individual particles, the uncoated or PET-coated budesonide powders are pneumatically delivered in form of complex clusters with a size of over 500 μm, whereas the ALD budesonide is dispersed in form of small agglomerates (<100 μm). Despite the difference in agglomerate size, entraining behaviors of all samples agree well with the prediction of Kalman’s pick-up Zone I correlation. The inorganic nanofilm deposited via ALD alters the surface chemistry to reduce the inter-particle forces measured by atomic force microscopy, giving rise to an improved drug delivery performance. Nanoscale surface modification of dry powder particles has good potential for inhaled drug delivery enhancement.

Lithium-compound-coated graphite as an anode material for all-solid-state lithium batteries

We prepared 0.125 and 0.5 mol% LiAlO2-coated graphite powders and 0.125, 0.25, and 0.5 mol% LiGaO2-coated graphite powders by the solvothermal method. The samples had uniformly dispersed fine particles on the graphite surface, except for the 0.5 mol% LiGaO2-coated graphite powder, in which the graphite surface was partially coated with aggregates several micrometers in size. All-solid-state lithium batteries with Li3PS4 glass as a solid electrolyte were assembled to investigate the effect of the coating on the charge-discharge performance. Batteries containing 0.125 mol% LiAlO2 and LiGaO2-coated graphite powder showed a higher initial coulombic efficiency and capacity retention rate than those containing uncoated graphite powder.

Influence of Metal Oxide Nanoparticles as Antimicrobial Additives Embedded in Waterborne Coating Binders Based on Self-Crosslinking Acrylic Latex

This article deals with the simple preparation of environmentally friendly acrylic latex binders, which are functionalized with nanoparticles of metal oxides, namely MgO, ZnO, La2O3 and combinations of MgO and ZnO, serving as functional components to achieve antimicrobial properties, but also to improve physical–mechanical properties and chemical resilience. The incorporation of uncoated powder nanoparticles was performed during the synthesis, using the two-stage semi-continuous emulsion radical polymerization technique, to obtain latexes containing 0.5%–1.3% nanoparticles relative to the polymer content. Changes in latex performance due to nanoparticles were compared from the point of view of the type and concentration of metal oxide nanoparticles in latex. The results of the tests showed that all types of nanoparticles showed very promising properties, while with increasing concentration of nanoparticles there was an improvement in properties. The nanoparticles in latex provided interfacially crosslinked transparent smooth coating films with high gloss and good physical–mechanical properties. Latexes containing the highest concentration of nanoparticles provided coatings with significant antimicrobial activity against all tested bacterial and fungal strains, but also in-can preservative stability of liquid latex. Furthermore, the coatings were resistant to solvents, and in addition, latexes with MgO nanoparticles showed a significant decrease in the minimum film-forming temperature, and latex with a concentration of about 1.3% MgO did not show any flash corrosion under the coating film cast on a steel substrate. The latexes containing MgO and La2O3 nanoparticles provided coatings that were very resistant to water bleaching.

Shelf-Life Prediction of Shallot Powder Using Accelerated Shelf-Life Testing (ASLT) Method by the Arrhenius Equation Approach

The storage process of shallot powder can cause a quality decrease. This study aims to estimate shelf-life of shallot powder at various storage temperatures and determine quality changes during storage. This study used a Completely Randomized Design with two factors to determine quality changes of shallot powder, i.e. the coating and storage temperature. The statistical analysis results showed that the coating, storage temperature, and interaction between the two factors affected Volatile Reducing Substances (VRS) levels. The two factors and their interaction do not influence the water content. Shelf-life estimation was performed using the Arrhenius method. Coated shallot powder has a longer shelf-life than uncoated shallot powder. Shelf-life determination was performed based on water content parameters. The shelf-life of uncoated shallot powder was 337 days at 30 °C, 322 days at 40 °C, and 309 days at 50 °C. The shelf-life of coated shallot powder was 353 days at 30 °C, 340 days at 40 °C, and 328 days at 50 °C. The coating process can extend the shelf-life of shallot powder.

CURCUMIN MICROENCAPSULATION USING CHITOSAN–ETHYL CELLULOSE–GMS MIXTURE FOR PRESERVATION OF MUCOADHESIVE PROPERTIES AND CONTROLLED RELEASE KINETIC

Objective: This research aimed to prepare curcumin microcapsules by the spray drying method and to evaluate their characteristics. Methods: The microcapsules were prepared by the spray drying method. The generated microcapsules were evaluated for organoleptic, morphology, particle size, the percentage of curcumin and water content. Furthermore, the release of curcumin from the microcapsules was tested in vitro and compared to uncoated curcumin powder. In addition, the mucoadhesive properties of uncoated curcumin powder and curcumin microcapsules were also evaluated. Results: The results showed that the microcapsules had spherical shape with particle size in the range of 100–1009 µm and water content of 9.34% (w/w) (FIII) and 8.09% (w/w) (FVI). The release of curcumin from its uncoated powder and the microcapsules FVI within 8 h were 8.87% and 26.32% (w/w), respectively. It was found that the mucoadhesive properties of microcapsules FVI were better than those of FIII and uncoated curcumin powder. Microcapsules FVI rendered the cumulative amount of curcumin remaining on the intestinal mucosa of 55% (w/w) within 3 h. Conclusion: Accordingly, curcumin microcapsules generated by spray drying could be further formulated into various solid dosage forms for a better therapeutic effect.

COATING VITON ON FLAKE ALUMINUM AND ITS EFFECTS ON PERFORMANCE OF THE SOLID ROCKET MOTOR

Aluminum powder is used as an additive in composite propellants to increase the specific impulse. However, the use of aluminum increases the two-phase losses and slag formation in the rocket motor. This study uses Viton as a coating for the aluminum powder for enhancing its reactivity to overcome these drawbacks. Viton-coated aluminum powder exhibited an enhanced reactivity over the uncoated powder. This Viton-coated aluminum demonstrated an increase of around 25% in the burn rates compared to uncoated aluminum when used in the composite solid propellant. The end mix viscosity of the propellant mixture remains constant with the prolonged mixing with the use of Viton compared to an increased viscosity observed with polytetrafluoroethylene as an additive.

Effects of Three Different Types of Aloin on Optical, Mechanical, and Antibacterial Properties of Waterborne Coating on Tilia europaea Surface

The microcapsules were prepared by using melamine-formaldehyde resin as the wall material and aloin as the core material. The aloin was dissolved in ethanol and water to prepare microcapsules. The aloin powder, the aloin microcapsules prepared with ethanol as the solvent, and the aloin microcapsules prepared with water as the solvent were, respectively, added to the waterborne coating with different contents and coated on the surface of Tilia europaea. The effects of different modifiers and contents on the coating’s optical properties, mechanical properties, and antibacterial properties were explored. The results showed that the aloin microcapsules prepared with ethanol as the solvent had good morphology and comprehensive properties. When the content was 7.0%, the color difference of the waterborne coating was small, the adhesion was grade 3, the impact resistance was 12 kg·cm, and the antibacterial rate was 87.8%. In terms of antibacterial properties, the uncoated aloin powder, the coated aloin microcapsules prepared with ethanol as the solvent, and the aloin microcapsules prepared with water all have certain antibacterial properties and the antibacterial rates reached 99.2%, 97.3%, and 67.3%, respectively. This study provides a certain reference for developing antibacterial wood furniture coatings.

Aluminum Powder Preparation for Additive Manufacturing Using Electrostatic Classification

This work aims to study the possibility of using an electrostatic drum-type separator to prepare a powder with a narrow size distribution curve for usage in additive manufacturing. The size distributions of the uncoated commercial aluminum powders ASP-30, ASP-22, and ASP-5 were analyzed. It was shown that the powders ASP-30 and ASP-22 have similar asymmetric distributions with a SPAN of 1.480 and 1.756, respectively. ASP-5 powder, in turn, has a narrow distribution with a SPAN of 0.869. ASP-30 powder was chosen for further experiment because, traditionally, separators are used to classify large-sized materials with particle size more than 100 μm. The optimal mode of electrostatic classification was proposed for the selected powder. Various classification methods, including centrifugal and electrostatic, were compared. The powders before and after classification were studied by XRD, SEM, TEM, and TG–DSC analyses. The obtained results showed that electrostatic classification does not lead to the formation of coatings on the processed powders. Electrostatic separation effectively narrows the particle size distribution, making it a suitable and valuable method to classify initial powders for additive manufacturing.

Development of gastro-resistant coated probiotic granulates and evaluation of viability and release during simulated upper gastrointestinal transit

Probiotics have become one of the most consumed food supplements worldwide. Many probiotic strains are sensitive to low pH and bile concentrations encountered in the gastrointestinal tract upon oral ingestion. This study aimed at developing gastro-resistant probiotic granulates releasing viable cells in the small intestine. Fatty alcohols were investigated as potential coating materials. Cetostearyl alcohol was selected and combined with different plasticizers to further optimize the coating properties. Combining cetostearyl alcohol with olive oil and beeswax in selected concentrations was found promising, and the coatings were applied to L. acidophilus LA3 and B. longum BB536, using hot-melt fluid bed coating. Viability in and release from the coated probiotic granulate was investigated, using a physiological relevant in vitro model simulating conditions in the human stomach, duodenum, jejunum and ileum. L. acidophilus LA3 coated with cetostearyl alcohol and olive oil in the ratio 95:5 (w/w) resulted in significantly higher viability after simulated gastrointestinal transit, compared to the uncoated probiotic powder. Furthermore, the coating showed no release of viable cells after simulated gastric transit. Released viable cells were detected after the remaining steps in the in vitro model, indicating that the coating system provides gastric protection and release during intestinal transit.

Preparation and oxidation of aluminum powders with surface alumina replaced by iron coating

ABSTRACT Aluminum powders are well known for excellent release of energy during oxidation upon heating. However, this release of energy becomes limited due to formation of dense oxide (Al2O3) layer on powder surface. In this study, reactivity of aluminum particles was improved by replacing oxide layer with metallic shell of iron using electroless plating technique. Three different bath compositions were selected for deposition of iron on aluminum particles. The surface morphology of prepared Al/Fe core–shell composite powder was characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Further, iron content in the composite powder was measured quantitatively using helium gas pycnometer while elemental analysis was performed by X-ray diffraction (XRD). Finally, thermo-physical behavior of the composite powder was investigated using simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC). The results showed that the synthesized Al/Fe core–shell composite powder exhibits higher energy release in comparison to the uncoated aluminum powder upon heating in air (up to 1180 °C). The powder with the densest iron coating released the highest energy.

Conformal Coating of Powder by Initiated Chemical Vapor Deposition on Vibrating Substrate.

Encapsulation of pharmaceutical powders within thin functional polymer films is a powerful and versatile method to modify drug release properties. Conformal coating over the complete surface of the particle via chemical vapor deposition techniques is a challenging task due to the compromised gas–solid contact. In this study, an initiated chemical vapor deposition reactor was adapted with speakers and vibration of particles was achieved by playing AC/DC’s song “Thunderstruck” to overcome the above-mentioned problem. To show the possibilities of this method, two types of powder of very different particle sizes were chosen, magnesium citrate (3–10 µm, cohesive powder) and aspirin (100–500 µm, good flowability), and coated with poly-ethylene-glycol-di-methacrylate. The release curve of coated magnesium citrate powder was retarded compared to uncoated powder. However, neither changing the thickness coating nor vibrating the powder during the deposition had influence on the release parameters, indicating, that cohesive powders cannot be coated conformally. The release of coated aspirin was as well retarded as compared to uncoated aspirin, especially in the case of the powder that vibrated during deposition. We attribute the enhancement of the retarded release to the formation of a conformal coating on the aspirin powder.

Atomic layer deposition (ALD) of nanoscale coatings on SrAl2O4‐based phosphor powders to prevent aqueous degradation

AbstractThe aqueous degradation of Eu2+‐activated and Dy3+‐codoped strontium aluminate (SrAl2O4:Eu2+, Dy3+, SA2‐Green) long afterglow phosphors synthesized from solid‐state reaction and coated with nanoscale metal oxide protective layers (≤12 nm) via atomic layer deposition (ALD) is investigated. Uncoated phosphor powders degrade rapidly upon water immersion and lose their green phosphorescence within 48 hours of water exposure. Postmortem investigations reveal hydration and decomposition of the SrAl2O4 phase. ALD of ~10 nm Al2O3 or ~12 nm TiO2 is found to significantly improve the powder's resistance to aqueous degradation. All ALD‐coated powders show minimal structural and chemical degradation and retain phosphoresence after 48 hours of water immersion. This enhanced durability offers a new pathway for applying long afterglow phosphors to outdoor applications like roadway markings or safety signage and for their incorporation into more eco‐friendly waterborne coatings.

Effect of Purity, Surface Modification and Iron Coating on Ignition and Combustion of Boron in Air

ABSTRACT Combustion characteristics of boron powders with varying purity, surface treatment and iron dopant loadings were investigated. Particles were ignited by a CO2 laser and burned in air. Commercial 95% and 99% pure boron powders were used as the starting materials; the former powder was also washed with acetonitrile to reduce the inhibiting oxide layer. All powders were coated with iron by thermal decomposition of iron pentacarbonyl. Optical emission of single burning particles was captured in order to determine combustion temperatures and burn times as a function of particle size. All materials ignited at approximately the same CO2 laser beam energy. For all materials, two-stage combustion patterns were detected for longer emission pulses produced by particles burning in air, which became difficult to resolve for shorter burn times. It was observed that higher purity boron particles burn faster. A reduction in the natural oxide layer thickness achieved by acetonitrile wash did not appreciably change the burn time of boron particles. However, it did lead to a brighter emission during second stage combustion, to oscillatory emission patterns, and to formation of nitride caps on the surface of quenched boron particles. Coating boron with iron was effective for commercial 95% pure boron. It was less effective for washed boron and even less effective for boron of higher purity. Boron coated with iron burned faster than un-coated boron; the effect appeared to scale with the amount of iron present. Additionally, boron coated with iron burned at a higher temperature than the un-coated powders. The increase in the burn rate and temperature caused by the iron coating are consistent with the proposed reaction mechanism, in which iron serves as a shuttle catalyst that is oxidized by external oxygen and then reduced by boron.

Magnetic properties and microstructure of iron-based soft magnetic composites with Al2O3 insulating coating by one-pot synthesis method

In this work, the effects of the Al2O3 insulating coating and surfactant on magnetic properties of the iron powders coated with Al2O3 by one-pot synthesis method were investigated. The morphology, phase composition and magnetoelectric properties of iron powders coated with Al2O3 were tested respectively. Compared with uncoated iron powder, the composite powder of Al2O3 insulating layer not only has better permeability stability in the frequency range of 5–300 kHz, but also has lower core loss, especially eddy current loss in the frequency range of 5–100 kHz. The surface of iron powder modified by surfactant will change crystallization process of aluminum hydroxide. After the addition of dodecyl trimethyl ammonium bromide (DTAB) as the surfactant, the Al2O3 insulating coating becomes denser and smoother, and the core loss of coated powders is further reduced.