Fine Powder Research Articles

THE EROSIVE WEAR OF GRAPHENE OXIDE REINFORCEDEPOXY POWDER COATINGS

Powder coatings are organic coatings that protect the metal substrate against corrosion and wear, and playa decorative role. The doping of paints with nanoparticles is intended to create a barrier to corrosive andchemical agents and to increase abrasion resistance. This work tested the erosion resistance of epoxy powdercoating with graphene oxide flakes and polyethylene wax covered with a layer of micro diamonds. Twomethods of testing resistance to abrasive wear were used, in which the conditions are similar to operatingconditions: solid particle impingement (sandblasting) and barrel finisher with ceramic shapes. Mass loss dueto erosion in a sandblaster using glass beads with a diameter of 200 μm for the paint with graphene was muchlower than for the reference sample. The mass loss of the samples was tested after 15, 30, and 60 seconds ofabrasive jet operation. The surface texture was analyzed during the process and after the test. The test in thebarrel finisher was carried out twice for different times: for the first series weight loss was measured after 30,90, and 210 minutes, for the second Vickers hardness at 40 g load after 90 and 210 minutes. The tests showedthat the epoxy coating with the addition of graphene oxide has a much higher resistance to erosion under theinfluence of an abrasive stream than the reference paint, and a similar resistance to erosion in a containersmoother. It was found that the paints showed a higher Vickers hardness after the wear test.

Dry-Water-System Confined Fabrication of Nanocuring Catalysts for Superior Low-Cure Powder Coating

Dry-Water-System Confined Fabrication of Nanocuring Catalysts for Superior Low-Cure Powder Coating

Size Classification and Material Sorting of Fine Powders with a Deflector Wheel Air Classifier and an Electrostatic Separator

In this study, a two-dimensional separation of microparticles based on their settling velocity and triboelectric charge ability is achieved using an air classifier for size fractionation and simultaneous charging, followed by an electrostatic separator. In the first part, considerations for enhancing particle classification with high sharpness and low-pressure drops are discussed through improvements in blade design investigated with CFD simulations and validated experimentally. Blades with extended lengths towards the center of the classifier prevent the formation of high-velocity vortices, thereby minimizing the back-mixing of particles and enhancing separation sharpness. This approach also reduces pressure drops associated with these flow vortices. In the second part of the study, the modified blades within the classifier are utilized for two-dimensional separation. Powders from two different materials are fed into the classification system, where particles become triboelectrically charged, mainly through collisions with the walls of the classification system components. Coarse particles are rejected at the wheel and exit the classifier, while differently charged fine particles of the two materials are directed into an electrostatic separator for material sorting. An enrichment of approximately 25–35% for both materials has been achieved on the electrodes of the separator.

The mechanics of extruded polylactic acid: an investigation into the effects of its multiple recycling and the inclusion of fly ash

Abstract This study examines variations in the material properties of the 3D printed polylactic acid (PLA) components after they have been recycled multiple times. Additionally, virgin polylactic acid was supplemented with fly ash from the thermal power plant, and the material’s behavior was examined after it was recycled on multiple times. By means of different tests, the impacts of filler addition on the mechanical behavior of the recycled materials are investigated. Using various forms including broken pieces, flakes, and fine powders, the filament extrusion was performed using used polylactic acid material during recycling. Under multiple recycling conditions, the mechanical characteristics of the polylactic acid and fly ash added polylactic (PLA-FA) were investigated. This work also investigates the impact of the polymer’s particulate size during the filament extrusion process. After recycling, it was found that the fine powder additions during the extrusion process provided high tensile strength of 32.61 MPa and flexural strength of 47.32 MPa for the PLA specimens. After recycling processes, the maximum tensile strength of 25.64 MPa and flexural strength of 50.22 MPa were found in fly ash enriched PLA. In contrast, the hardness of both PLA and fly ash-included PLA increased following each recycling procedure. Multiple recycling of PLA material turned the ductile material into brittle material by means of amorphous phase emergence. When compared to other particle sizes which were bigger in size, the specimens developed with filaments extruded with fine powder showed maximum results in all the tests. The tensile strength of PLA material decreased by 17.25%, while the tensile strength of PLA-FA material decreased by 21.35% after recycling. In PLA, the flexural strength drop following three recycling was 17.56% while in PLA-FA material it was 9.01%. After three times of material recycling, the hardness increased by 3.52% in PLA and by 2.48% in PLA-FA.

Evaluation of Pore-Former Size and Volume Fraction on Tape Cast Porous 430 Stainless Steel Substrates for Plasma Spraying

Porous 430L stainless steel disks made by tape casting with various pore-former sizes and volume fractions were evaluated as substrates for solid oxide cell (SOC) fabrication by plasma spraying. This work reports the substrate properties relevant to the SOC operation of disks made by using extra fine metal powder with dense sintering to minimize the fine porosity between particles. In contrast, the coarse porosity is introduced by the pore former. We found that the 60 μm pore former at a 45 vol% fraction has the best application fit; it gives an adequate gas permeability of 3.11 × 10−13 m2 and an average open pore size of 45.90 μm. Compared to a commercial substrate with a similar porosity perimeter/steel area ratio, the porosity and gas permeability are 1.6 and 3 times higher, respectively. The detected maximum surface pore is 49 μm, allowing gas-tight electrolytes fabricated by plasma spray deposition.

Cave morphology and moonmilk deposits of Ryongmun Cavern, Democratic People’s Republic of Korea: A Study for the Conservation of Natural Heritage

The Ryongmun Cavern, registered on the World Heritage Tentative List, is the largest and most beautiful karst cave on the Korean peninsula. The characteristics of the cave morphology and moonmilk deposits in the Ryongmun Cavern were studied. A cross section of the main direction of the cave shows that the Ryongmun Cavern is made up mainly of four strata and this caused 4 stages of decline in underground waterline in the course of cave formation. The cave is mainly characterized by NW–SE-trending, NWW–SEE-trending and NNE– SSW-trending passages. The horizontal passages usually have large and wide spaces, whereas the inclined ones are relatively small and narrow. The cave minerals in the Ryongmun Cavern are mainly calcite and aragonite. In the cave, stalactites, stalagmites, limestone columns, cave pearls, etc. Are calcite; and, anthodites are aragonite. In the cave, speleothems display a wonderful underground landscape in harmony with the cave bedrock and groundwater (streams, waterfalls and ponds). The main scenes of the underground karst landscape in the cave are stalactites, stalagmites, limestone columns, stone waterfalls anthodites, underground waterfalls, and underground ponds.The deposits that have been formed recently on the surface of speleothems and walls in the cave are mainly moonmilk composed of hydromagnesite (Mg5(CO3)4(OH)2•4H2O) with an average particle size of 0.55 μm and chemical composition of MgO–29.43% and CaO–6.28%. The moonmilk is present in a white, fine powder form, a hand-rubbed smooth, and a moisture content of 42.0%. Also, the pH is 10.09, which is alkaline. In the Ryongmun Cavern, moonmilk was formed at sites with very low supply of karst water and relatively high wind speeds. The unique underground karst features provide sufficient evidence for geoheritage value of the cave and the characteristics of moonmilk provide a significant implication for management and preservation of the cave environment.

Thermochemical heat storage and material behavior of calcium hydroxide fine powder in a fluidized bed reactor

The Ca(OH)2/CaO reaction has attracted much attention in thermochemical heat storage. However, commercial Ca(OH)2 is usually offered as a fine powder that tends to agglomerate in the fluidized bed and affects heat storage performance. The experimental study on these issues is incomplete. In this paper, a fluidized bed thermochemical heat storage test system is built to study the heat storage and release process of Ca(OH)2 fine powder. The experimental results indicate that the water vapor is the primary factor in agglomeration. The increase in heat storage temperature, fluidization velocity, and inlet water flow rate can all reduce reaction time. However, the effect of heat storage temperature on agglomeration is negligible. While a high fluidization velocity can alleviate the agglomeration, a high inlet water flow rate intensifies the agglomeration. The heat storage density decreases by about 12 % after 5 cycles owing to the material loss, while the agglomeration is trending upward. The specific surface area and specific pore volume decrease by 46.59 %, and 13.89 % respectively, which slows down the heat storage process. This work can serve as a reference for alleviating the agglomeration, as well as the operation and adjustment of the fluidized bed.

Advancing laser powder bed fusion with non-spherical powder: Powder-process-structure-property relationships through experimental and analytical studies of fatigue performance

This study investigates the multifaceted interdependencies among powder characteristics (i.e., non-spherical morphology and particle size ranging 50-120 or 75-175µm), laser powder bed fusion (L-PBF) process condition (i.e., contouring), post-process treatments (i.e., hot isostatic pressing (HIP) and mechanical grinding) on the pore, microstructure, surface finish, and fatigue behavior of additively manufactured Ti-6Al-4V samples. Microstructure analysis shows a phase transformation α′ → α+β microstructure after HIP treatment (at 899±14 °C for 2h under the applied pressure of 1034±34bar) of the as-built Ti-6Al-4V parts. The findings from pore analysis using micro-computed tomography (μ-CT) show an increase in sub-surface pores when relatively smaller powders are L-PBF processed including contouring. Surface optical profilometry reveals a decrease in surface roughness when fine powder is L-PBF including contouring. Pore analysis conducted through μ-CT reveals that the presence of lack-of-fusion pores within the L-PBF processed coarse powder is more pronounced when compared to the fine powder. Furthermore, HIP treatment does not eliminate these pores. The fracture failure in as-printed parts occurs at the surface, while the combination of HIP and mechanical grinding alters crack initiation to subsurface pore defects. Fractography reveals that HIP and as-built samples followed the facet formation and pseudo-brittle fracture mechanisms, respectively. Fatigue life assessments, supported by statistical analysis, indicate that mechanical grinding and HIP significantly enhanced fatigue resistance, approaching the benchmarks set by wrought Ti-6Al-4V alloy. A fatigue prediction model which considers the surface roughness as a micro-notch has been used.

Effect of powder properties, process parameters, and recoating speed on powder layer properties measured by in-situ laser profilometry and part properties in laser powder bed fusion

In laser-based powder bed fusion of metals (PBF-LB/M), the powder layer is the link between the powder properties and the resulting part quality. Powder layer quality is a key metric related to powder spreadability and ultimately part quality, yet it is still unclear how it can be quantified. This is due to the difficulty of studying powder layer properties during the process. This study investigates the influence of powder properties, process parameters, and recoating speed on the surface roughness of the powder layer and the part, as well as on the effective thickness of the powder layer and solidified layer, and the resulting relative part density. Utilizing in-situ laser profilometry, high-resolution topographical data of the powder layer and the part surface were acquired, with minimal interference to the PBF-LB/M process. Six AlSi10Mg powders with varying particle size distribution, morphology, and flowability were processed using a wide range of recoating speeds and scan speeds to create powder layers with a wide range of properties. The results reveal a strong correlation between energy input and the effective powder layer thickness where lower scan speed results in an increased effective powder layer thickness due to material losses. Additionally, faster recoating decreases the powder layer density, which is moderated by the median particle size where the effect is strongest for fine powders. The surface roughness of the powder layer and top part surface are influenced by the recoating speed, energy input, and particle size, and they are strongly linked to each other. This highlights the importance of considering realistic substrate surface roughnesses in both powder spreading experiments and simulations. Finally, layer properties affect the process stability, resulting in small differences in relative part density.

Spray drying of polymer dispersions for redispersible powder coatings: Effects of stabilization mechanisms and process conditions

Spray drying of polymer dispersions for redispersible powder coatings: Effects of stabilization mechanisms and process conditions

Sustainable lignin-based powder coatings doped with ZnO displayed excellent UV resistance properties

Sustainable lignin-based powder coatings doped with ZnO displayed excellent UV resistance properties

AkzoNobel developed a particle technology for metallic effect powder coatings

AkzoNobel developed a particle technology for metallic effect powder coatings

Powder Coatings Market to Surpass USD 26.3 Billion by 2032

Powder Coatings Market to Surpass USD 26.3 Billion by 2032

Extrusion and Co-extrusion: A Technology in Probiotic Encapsulation with Alternative Materials.

Encapsulation, in particular extrusion and co-extrusion, is a common practice to protect probiotics from the harsh conditions of the digestive tract as well as processing. Hydrocolloids, including proteins and carbohydrates, natural or modified, are a group of ingredients used as the wall material in extrusion. Hydrocolloids, due to their specific properties, can significantly improve the probiotic survivability of the final powder during the microencapsulation process and storage. The present article will discuss the different kinds of hydrocolloids used for microencapsulation of probiotics by extrusion and co-extrusion, along with new sources of novel gums and their potential as wall material.

Synthesis and Characterization of ZnO/Cu<sub>2</sub>O and Co co-doped Ag-ZnO/Cu<sub>2</sub>O Nanoparticles with Possible Photovoltaic Applications

The Photovoltaics phenomenon is one of the major turning points in the battle against the depletion of fossil fuels. Sunlight is the main resource in photovoltaics, but there remains a quest to harvest it efficiently to generate electricity. This study is focused on designing basic, cost-effective prototype solar cells using ZnO/Cu2O nanoparticles (NPs) and Co(cobalt) co-doped Ag-ZnO/Cu2O NPs under normal university laboratory conditions. ITO-coated glass was used as the substrate of the solar cell and a modified low-temperature chemical bath deposition method was used for fabrication. Both ZnO and Cu2O NPs were synthesized by aqueous precipitation methods and the fabrication was performed successfully using ZnO and Cu2O NPs. However, the fabrication with Co co-doped Ag-ZnO and Cu2O NPs requires more research since the Co co-doped Ag-ZnO NPs were synthesized by solvothermal method, and it appeared as a fine powder which was not thick enough to hold onto the Cu2O layer. The UV-spectroscopic analysis confirmed the characteristic band of ZnO NPs at 367.5 nm, Cu2O NPs at 360 nm, and Co co-doped Ag-ZnO NPs at 378 nm. The FTIR spectrum showed sharp peaks at 460 cm-1 and 606 cm-1 for the corresponding Zn-O bond and Cu-O bond, respectively with a broad peak at 1329 cm-1 for Cu2O FTIR, due to the chemisorbed and/or physiosorbed H2O and CO2 molecules on the surface of the nanostructure. The EDX analysis showed the presence of slight carbon impurity in ZnO NPs which resulted in a deviated XRD pattern while Cu2O NPs showed the characteristic XRD pattern. The solar cell illuminated under three different lux conditions, had the characteristic J-V plot when measured through Gamry Potentiostat.

Evaluation of the antibacterial potential of mango (Mangifera indica) seed kernels in Bangladesh

Antimicrobial resistance is a global threat. On the other hand, Bangladesh produces high-quality mangoes, yet the mango coat and seed kernel, which contain medicinal components, remain unused. Therefore, this study investigated the antibacterial potential and toxicity of ethanol extracts from mango (Mangifera indica) seed kernels, which specifically target the bacterial strains Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Klebsiella sp. Amrapali variant mango seeds were collected, dried, ground into a fine powder, and extracted with ethanol at various ratios. The efficacy of the crude extract was tested via the disc diffusion method. The results demonstrated significant antibacterial activity against gram-positive bacteria (S. aureus and B. cereus), with clear zones of inhibition observed, especially in a dose-dependent manner. The pure crude extract inhibited the growth of S. aureus with a zone of 23 mm, identical to that produced by doxycycline. However, the extract exhibited limited activity against gram-negative bacteria (E. coli and Klebsiella sp.). Additionally, the extract was effective against multidrug-resistant S. aureus. The pure crude extract produced a 22.5 mm zone of inhibition against multidrug-resistant S. aureus, which was slightly smaller than that of gentamicin (23 mm) but larger than those of chloramphenicol (21 mm), vancomycin (20 mm), and tetracycline (16 mm). In vivo toxicity was assessed in mice, revealing no significant adverse effects on the hepatic structure or renal cortex at lower doses (100 μl of pure crude extract). However, higher doses caused mild histopathological changes in the liver and kidneys. These findings suggest that mango seed kernel extract holds promise as an alternative antibacterial agent, particularly against gram-positive and antibiotic-resistant bacteria, while being relatively safe at lower doses. Further research is needed to elucidate the active compounds, mechanisms of action, and broader applications of this extract in combating antibiotic-resistant bacterial infections.

Cold Consolidation of Pharmaceutical Waste Glass Powders Through Alkali Activation and Binder Jet 3D Printing.

The recent COVID-19 emergency has led to an impressive increase in the production of pharmaceutical vials. This has led to a parallel increase in the amounts of waste glass; manufacturers typically recover material from faulty containers by crushing, giving origin to an unrecyclable fraction. Coarse fragments are effectively reused as feedstock for glass melting; on the contrary, fine powders (<100 microns), contaminated by metal and ceramic particles due to the same crushing operations, are landfilled. Landfilling is also suggested for pharmaceutical containers after medical use. This study aims at proposing new opportunities for the recycling of fine glass particles, according to recent findings concerning alkali activation of pharmaceutical glass, combined with novel processing, i.e., binder jetting printing. It has already been shown that pharmaceutical glass, immersed in low-molarity alkaline solution (not exceeding 2.5 M NaOH), undergoes surface dissolution and hydration; cold consolidation is later achieved, upon drying at 40-60 °C, by a condensation reaction occurring at hydrated layers of adjacent particles. Binder jetting printing does not realize a full liquid immersion of the glass powders, as the attacking solution is selectively sprayed on a powder bed. Here, we discuss the tuning of key parameters, such as the molarity of the attacking solution (from 2.5 to 10 M) and the granulometry of the waste glass, to obtain stable printed blocks. In particular, the stability depends on the formation of bridges between adjacent particles consisting of strong T-O bonds (Si-O-Si, Al-O-Si, B-O-Si), while degradation products (concentrating Na ions) remain as a secondary phase, solubilized by immersion in boiling water. Such stability is achieved by operating at 5 M NaOH.

Use of metakaolins from Eseka and Dibamba‐Cameroon as an optimization additive of CEM I Portland cement mortar

AbstractThe present study deals with two kaolins from Eseka and Dibamba‐Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low‐carbon cement. X‐ray diffractometry was used to establish the mineralogical composition of two kaolins. X‐ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO2/Al2O3 is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.

A Carbon Capture and Utilization Process for the Production of Solid Carbon Materials from Atmospheric CO2 - Part 1: Process Performance.

The successful operation of a process that converts atmospheric CO2 into solid carbon products is presented as an alternative to fossil based solid carbon production. In a first step, CO2 is removed from the atmosphere by a direct air capture (DAC) unit. The gas is then mixed with hydrogen and enters a methanation unit. Depending on the operation conditions, gas mixtures consisting of mainly methane with either H2 or CO2 as side-component are obtained. After precipitating the water formed during the methanation step, the remaining gas mixture is fed into a bubble column reactor filled with liquid tin. During the rise of the gas bubbles, methane is thermally split up into hydrogen and solid carbon. The latter is continuously removed from the liquid metal surface as a fine powder by pneumatic conveying. This article is the first of two articles, focusing on the performance of the methanation and methane pyrolysis steps. The experimental results are complemented by thermodynamic analyses and reaction modelling. A detailed analysis of the solid carbon product of the process is presented in the second part.

Synthesis of Mo-Cu nanocomposite powder by hydrogen reduction of copper nitrate coated MoO3 powder mixture

The fabrication of Mo-based nanocomposite powder with homogeneous dispersion of Cu was investigated. The fine MoO3 powders were prepared by high energy ball milling, and Cu particles on the ball-milled powder surfaces were formed by calcination of a precursor solution copper nitrate. In the powder mixture calcined at 300 °C, MoO3 and CuO appeared in the form of aggregates with fine particles. Microstructural analysis showed that the oxide powders were changed to Mo-Cu nanocomposite powders with an average particle size of about 150 nm and had microstructural homogeneity by hydrogen reduction at 800 °C for 1 h. These results are help to optimize the synthesis process of homogeneous Mo-Co nanocomposite powders.