Morphology Of Powders Research Articles

Characterization of CrMnNi Steel Powders Obtained via Gas Atomization

To obtain a successful product during additive manufacturing, the powder as a raw material must have the high quality. The purpose of this work is to investigate CrMnNi steel powders obtained by inert gas atomization with nickel content: 3, 6, and 9 wt% and to identify dependencies between the powder size and morphology, solidification structure, and change in chemical composition and thermophysical properties. Particle size distribution is measured by a laser scattering analyzer: d50 value are 82.02, 69.32, and 75.54 μm for powders with 3, 6, and 9 wt%, respectively. Surface tension (ST) measurements are made by maximum bubble pressure method: for steels with 3, 6, and 9 wt% at temperature 1500 °C, ST is 1.01, 1.07, and 1.15 mN m−1, respectively. It is found that the change in particle size affects the chemical composition, the content of the ferromagnetic phase and secondary dendritic arm‐spacing. Changes in the content of elements such as S, O, N, and Mn are determined, depending on the diameter of the particles. The influence of changes in content of S, O, and N on the thermophysical properties such as ST is investigated.

Bioavailability of Liposomal Vitamin C in Powder Form: A Randomized, Double-Blind, Cross-Over Trial

The purpose of this study was to evaluate the properties and pharmacokinetics of liposomal vitamin C in powder form obtained by a method devoid of organic solvents. The powder and liposome morphology were analyzed using scanning electron microscopy (SEM) and cryogenic transmission electron microscopy (cryo-TEM), respectively. Additionally, the carrier particle size, size distribution (STEP-Technology®; L.U.M. GmbH, Berlin, Germany), and zeta potential value were determined. The pharmacokinetic parameters of liposomal and non-liposomal vitamin C (AUC, Cmax, C10h, and C24h) were compared in a randomized, single-dose, double-blind, cross-over trial (ClinicalTrials.gov ID: NCT05843617) involving healthy adult volunteers (n = 10, 1000 mg dose). The process of spray drying used to transform liquid suspensions of the liposomes into powder form did not adversely affect the quality of the carrier particles obtained. Compared to non-encapsulated vitamin C, oral administration of the liposomal formulation resulted in significantly better absorption of ascorbic acid into the bloodstream, which equated to a higher bioavailability of the liposomal product (30% increase in AUC, p < 0.05). The duration of elevated vitamin C blood levels was also longer (C24h increase of 30%, p < 0.05). Although the results obtained are promising and suggest higher bioavailability for the liposomal form of vitamin C, the limited sample size necessitates further research with a larger cohort to confirm these findings.

The influence of heat treatment on AlSi-polymer abradable coating

Abstract Abradable coatings, as one of the most important technologies for aero and industry gas turbine engines, have an extremely significant influence on engine performance. The macro-hardness of AlSi-Polyester for low-pressure compressor and as-sprayed coating degradation mechanism has been investigated by heat treatment process in imitation service condition. SEM (Scanning Electron Microscope) and OM (Optical Microscope) were used to observe the morphology of powder and coating microstructure in cross-section, respectively. Rockwell hardness tester was used to measure the macrohardness of coatings before and after heat treatment. It shows that AlSi-Polyester powder has an approximately spherical shape and uniform microstructure with alloy phase and polyester phase distribution in the coating prepared by air plasma spraying. Oxidation of the alloy phase and reduced polyester, as well as macrohardness in the as-sprayed coating, occur after the heat treatment process.

Microstructure and tensile properties of transient liquid phase (TLP) sintering repaired Ti–6Al–4V alloys with large area hole defect

Repairing defects in titanium alloy components is economically justified due to their high cost. In this work, Ti–6Al–4V samples with large area hole defects are repaired by transient liquid-phase sintering. The microstructure and tensile properties after repair have been investigated. The factors of different base powder morphology and the ratio of braze metal are also studied. The results show that by using spherical Ti64 alloy powder with 40 wt% TiZrCuNi braze alloy powder, an overall repair effect with high-density repair zone and good interface combination can be obtained at 960 °C for 3 h. The tensile strength of the as-repaired exceeds that of the matrix, but the elongation is lower than that of the matrix. Finally, the repair experiment conducted at various angles demonstrates this technique's strong practical feasibility.

Comparison of quality characteristics of reconstituted glutinous rice flour and sweet dumplings with various beans.

This study blended five types of beans-florid kidney bean, red adzuki bean, chickpea, black bean, and white kidney bean-with glutinous rice flour (GRF) to create a synergistic heat-moisture treatment (HMT). We investigated the effects of this combination on the digestibility of the glutinous rice mixture and the quality of sweet dumplings. The inclusion of beans, along with HMT, altered the granular morphology, adhesive qualities, thermal characteristics, crystallinity, and protein secondary structure of the blended powders compared to GRF. Notably, the starch granules in the glutinous rice flour with red adzuki bean (R-GRF) were more complete in morphology, compact in structure, and exhibited higher heat stabilization and crystallinity, with significant changes in protein secondary structure. These modifications resulted in a low expected glycemic index (eGI) value of 52.01. Additionally, the quality assessment of the fast-frozen sweet dumplings showed that those made with red adzuki bean mixed with glutinous rice flour (R-SD) had superior texture, reduced cracking, and less water loss compared to those made with GRF (G-SD), while maintaining similar color and odor to G-SD. The eGI value of 52.21 for R-SD also fell within the low eGI range, indicating its potential for developing low-eGI foods for patients with T2DM and other special populations.

Evaluating the sintering behaviors of ceramic oxide powders processed via binder jet additive manufacturing

AbstractBinder jet additive manufacturing is well suited for fabricating large (order of cm) and geometrically complex ceramic preforms. However, the main challenge in producing ceramic oxide parts via binder jetting is the high‐temperature postprocess tasked with eliminating internal porosity to achieve full densities. In this work, we demonstrate the ability to produce oxide ceramic parts with desirable densities by sintering binder jetted preforms. We investigate the sintering behavior of binder jetted preforms composed of three oxide powders with distinct morphologies: ball‐milled alumina, gas‐atomized silica, and sintered‐agglomerated zirconia. We fabricate the preform samples using a commercial binder jetting system and a conventional die‐pressing technique to understand the effect of starting densities. Furthermore, we parametrize the heating profiles to understand the effect of sintering temperature, sintering duration, and heating rate on each powder's densification behavior, microstructure, and phase composition. Results show the relatively low starting densities within the binder jetted preforms caused the onset sintering temperature to be higher than what is documented in conventional sintering studies. As expected, we observed sintered densities increase with respect to sintering temperature and duration. These findings were utilized to downselect sintering parameters capable of achieving high densities (>96%). Herein, this study validates the sintering of binder jetted preforms as a suitable way to manufacture ceramic parts, regardless of powder morphologies, thereby increasing the robustness of the supply chain involved in additive manufacturing of ceramic oxides.

Effect of the SiC powder microscopic morphology on properties of Si/SiC ceramics prepared by spark plasma sintering

AbstractTo solve the problem that Si was volatile and dense Si/SiC ceramics were difficult to achieve by spark plasma sintering (SPS) under a low sintering temperature and pressure, three kinds of SiC powders were used for particle grading and then ball‐milled with different time to further change and regulate their particle size and morphology, and finally nearly dense Si/SiC ceramics were prepared by SPS. The effect of milling time on particle size, morphology, tap density, phase, and microstructure of the SiC powders, as well as on bulk density, microhardness, thermal conductivity, phase, and microstructure of the Si/SiC ceramic, was researched. When the mixed SiC powders were ball‐milled for 12 min, the bulk density, microhardness, and thermal conductivity of Si/SiC ceramic were 2.96 g/cm3, 22.95 GPa, and 152.84 W/(m K), respectively. Ball milling changed the particle gradation and micro‐powder morphology and then affected the powder particle stacking state. Forming continuous pore channels was conducive for the volatile liquid Si to flowing and filling pores in a short time, resulting in denser Si/SiC ceramics at a lower sintering temperature and pressure. This study was useful for the preparation of ceramics containing volatile liquid phase by SPS.

Si1-XGex Alloys As Negative Electrodes for Li-Ion Batteries: Impact of Morphology in the Li+ Diffusion, Performance and Mechanism

Si1-xGex alloys present interesting cycling performance as Li-ion anodes, owing to the synergetic effect from silicon’s high capacity and germanium’s electrical conductivity and Li+ diffusion. Various morphologies of Si1-xGex powders were obtained, micron-sized by ball-Milling (BM) and nano-sized by laser pyrolysis (LP) to study the effect of the morphology and composition on the electrochemical behavior. The electrical conductivity was measured and shows an increase with the Ge content, from 4.58E-03 for Si to 0.11 S m-1 for Si0.5Ge0.5. Half-cells were cycled at C/5, LP samples showed a better capacity retention than their BM counterparts (88% vs 72% at the 35th cycle for Si0.5Ge0.5). To rationalize these trends, Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were used to determine the apparent Li+ Diffusion in the Si1-xGex series. It was shown that the apparent Li+ Diffusion is dependent to the state of charge. Moreover, it gave insight about phase transformations during cycling. During lithiation, similar values (10-11 cm2 s-1 ) were obtained for BM and LP Si0.5Ge0.5. However, a big variation (10-13 – 10-10 cm2 s-1) was found for the BM sample delithiation, which is attributed to the conversion of c-Li15(Si0.5Ge0.5)4 phase into amorphous Lix(Si0.5Ge0.5) (x<3.75). Asymmetric C-rate tests evidenced lithiation as the limiting mechanism for the Si1-xGex negative electrodes. Figure 1

Flow-induced defects during metal injection molding: Role of powder morphology

Flow-induced defects during metal injection molding: Role of powder morphology

Comparison of cell morphology and mechanical properties of wheat straw powder/HDPE parts molded by supercritical fluid foamed injection with and without gas counter pressure technology

AbstractComposites were fabricated using maleic anhydride‐grafted high‐density polyethylene as the matrix material and wheat straw as the filler. Differential scanning calorimetry and rheological properties of these composites were investigated to determine the processing parameters for supercritical fluid (SCF) microcellular injection with and without gas counter pressure (GCP) technology. The impacts of different proportions and dimensions of wheat straw, along with process parameters related to GCP, were determined on both the cellular structure and mechanical characteristics of foamed injection molded components. Experimental results revealed that an increase in the ratio of wheat straw and a reduction in its size led to enhancements in both storage modulus and complex viscosity of the composites, while also improving their cell structure when foamed with SCF. By adjusting GCP process parameters, it was possible to regulate both cell morphology and mechanical properties of foamed injection molded parts. Higher GCP or longer GCP holding time resulted in increased skin thickness and tensile strength but decreased notched Izod impact strength.Highlights Built relations between GCP technology parameters and cell morphologies. Compared the influence of wheat straw powder and GCP parameters quantitatively. Explored the correlation between cellular morphology and mechanical properties. The regulatory mechanism of cell morphology, size ratio, and distribution. GCP effectively modulates cell morphologies and mechanical properties.

Impact of Powder Morphology and Coating Microstructure on Mechanical Properties of Plasma-Sprayed Magnesia (24%)-Stabilized Zirconia on Stainless Steels

Impact of Powder Morphology and Coating Microstructure on Mechanical Properties of Plasma-Sprayed Magnesia (24%)-Stabilized Zirconia on Stainless Steels

Influence of Polyethylene Glycol and Methanol Additions on the Mechanical Alloying Behavior of Cu-4B4C Composite Powder

This study investigated the effect of different process control agent (PCA) usage on mechanical alloying behavior of boron carbide (B4C) reinforced copper (Cu) based composite powder. For this purpose, elemental Cu and B4C powders were weighed and powder specimens were prepared with respect to appropriate mass ratios (96% Cu and 4% B4C). Two different PCA additives, namely polyethylene glycol (PEG) and methanol, were also used to prepare powder samples. The amount of PCA was kept constant at 5wt.% for both specimen. These prepared powder samples were then milled using a planetary type ball-mill. After specified milling periods, milling runs were interrupted and powder samples were extracted from the milling vials for further powder characterization including powder morphology using scanning electron microscopy (SEM) and average particle size (APS) via laser diffraction analysis (Mastersizer). Accordingly, after the completion of milling runs, namely 15 hours of ball-milling, methanol addition was found much more effective at reducing particle sizes than PEG. Final APS values for powder specimens having PEG and methanol as PCAs were determined to be 8.237 and 4.101 microns, respectively.

Silica-Reinforced AMP-Calcium Alginate Beads for Efficient and Selective Removal of Cesium from a Strong Acidic Medium.

Due to the significant selectivity for Cs+, ammonium molybdophosphate (AMP) possesses potential to uptake radiocesium from high-level liquid waste (HLLW), whereas its micro-crystalline structure and fine powder morphology limit its industrial application. Although the granulation method with alginate is prospective for the preparation of an AMP exchanger, the mechanical strength of obtained beads may be insufficient for application. In this context, we prepared silica-reinforced AMP-calcium alginate (ACS) beads and evaluated their performance for Cs+ removal from strong acidic solutions. It was found that the addition of silica in the fabrication significantly improved the mechanical strength of the beads in comparison to those without silica. Notably, the beads with an AMP/silica mass ratio of 1.0 exhibited an exceptional mechanical strength, surpassing that of ACS beads composed of other components. The batch experiment results indicated that the Cs+ adsorption follows a non-linear pseudo-second-order rate equation. The distribution coefficient of Cs+ was high even in extreme acidic conditions (∼1.6 × 102 mL/g in 8.0 mol/L HNO3 solution). The Cs+ adsorption can be well fitted with the Langmuir model, and the estimated maximum exchange capacity in 3.0 mol/L HNO3 could reach 23.9 mg/g. More importantly, ACS beads showed excellent selectivity toward Cs+ uptake over eight co-existing metal ions in simulated HLLW, with separation factor values all above 145. The column experiment exhibited that the beads can serve as the stationary phase in columns to effectively remove Cs+. The findings of this study are significant as they provide insights into the development of efficient materials for radiocesium removal from high-level liquid waste. The results demonstrate the potential of silica-reinforced ACS beads for Cs+ adsorption, with promising applications in industrial settings.

The impact of coaxial gas technology on the morphology of powder by gas atomisation and the additive manufactured mechanical performance

ABSTRACT Metal powders are essential for additive manufacturing (AM), with their morphology significantly impacting the performance of AM components. Gas atomisation (GA) is a common method for producing metal powders due to its efficiency and cost-effectiveness. However, GAed powders often exhibit defects such as alien powders, satellite powders, and hollow powders, which can adversely affect the AM process. To address these challenges, coaxial gas technology has been introduced and analysed through numerical simulation. Our study involved comparing GA processes with and without coaxial gas technology to generate two types of powders. These powders were assessed using Synchrotron X-ray computed tomography (SXCT) and classification algorithms. The pores in AM components manufactured from these powders were examined using SXCT, and their mechanical properties were evaluated through tensile tests. The findings of our research validate the effectiveness of coaxial gas technology in reducing powder defects and enhancing the performance of AM components.

Sol-Gel Synthesis of TiO2 with Pectin and Their Efficiency in Solar Cells Sensitized by Quantum Dots.

In this study, titanium oxide TiO2 nanoparticles were produced using the sol-gel approach of green synthesis with pectin as the reducing agent. The synthetized TiO2 nanoparticles with pectin were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), visible light absorption (UV-Vis) and the BET method. The structure and morphology of the TiO2 powder were described with SEM, revealing uniform monodisperse grains with a distribution of 80% regarding sizes < 250 nm; the resulting crystal phase of synthetized TiO2 was identified as an anatase and rutile phase with a crystallinity size estimated between 27 and 40 nm. Also, the surface area was determined by nitrogen adsorption-desorption using the Brown-Emmet-Teller method, with a surface area calculated as 19.56 m2/g, typical of an IV type isotherm, indicating mesoporous NPs. UV-Vis spectra showed that sol-gel synthesis reduced the band gap from the 3.2 eV common value to 2.22 eV after estimating the optical band gap energy using the adsorption coefficient; this translates to a possible extended photo response to the visible region, improving photoactivity. In addition, the power conversion of the photoelectrode was compared based on similar assembly techniques of TiO2 electrode deposition. Quantum dot crystals were deposited ionically on the electrode surface, as two different paste formulations based on a pectin emulsifier were studied for layer deposition. The results confirm that the TiO2 paste with TiO2-synthesized powder maintained good connections between the nanocrystalline mesoporous grains and the deposited layers, with an efficiency of 1.23% with the transparent paste and 2.27% with the opaque paste. These results suggest that pectin could be used as a low-cost, functional sol-gel catalysis agent for the synthesis of controlled NPs of metal oxide. It demonstrates interesting optical properties, such as an increase in photo response, suggesting further applications to photocatalysts and biomedical features.

Minimizing Porosity in 17-4 PH Stainless Steel Compacts in a Modified Powder Metallurgical Process

Nowadays, powder-based manufacturing processes are recognized as cost-efficient methods frequently employed for producing parts with intricate shapes and tight tolerances in large quantities. However, like any manufacturing method, powder-based technologies also have several disadvantages. One of the most significant issues lies in the degree of porosity. By modifying the morphology of the gas-atomized spherical 17-4PH stainless steel powder via prior ball milling and then raising both the pressure of cold compaction (1.6 GPa) and sintering temperature (1275 °C), the porosity could be reduced considerably. In our novel powder metallurgical (PM) experimental process, an exceptionally high green density of 92% could be reached by employing die wall lubrication instead of internal lubrication and utilizing induction heating for rapid sintering. After sintering (at temperatures of 1200, 1250, and 1275 °C), the samples aged in the H900 condition were then mechanically tested (Charpy impact, HV hardness, and tensile tests) as a function of porosity. Sintering at 1275 °C for one hour enabled porosity reduction to below 4%, resulting in 1200 MPa yield strength and 1350 MPa ultimate tensile strength with significant (16%) fracture strain. These values are comparable to those of the same alloy products fabricated via ingot metallurgy (IM) or additive manufacturing (AM).

Different or the same? exploring the physicochemical properties and molecular mobility of celecoxib amorphous forms

The influence of different preparation methods on the physicochemical properties of amorphous solid forms have gained considerable attention, especially with recent publications on pharmaceutical polyamorphism. In the present study, we have investigated the possible occurrence of polyamorphism in the drug celecoxib (CEL) by investigating the thermal behavior, morphology, structure, molecular mobility and physical stability of amorphous CEL obtained by quench-cooling (QC), ball milling (BM) and spray drying (SD). Similar glass transition temperatures but different recrystallization behaviors were observed for CEL-QC, CEL-BM and CEL-SD using modulated differential scanning calorimetry analysis. A correlation between the different recrystallization behaviors of the three CEL amorphous forms and the respective distinct powder morphologies, was also found. Molecular dynamics simulations however, reveal that CEL presents similar molecular conformational distributions when subjected to QC and SD. Moreover, the obtained molecular conformational distributions of CEL are different from the ones found in its crystal structure and also from the ones found in the lowest-energy structure obtained by quantum mechanical calculations. The type and strength of CEL hydrogen bond interactions found in CEL-QC and CEL-SD systems are almost identical, though different from the ones presented in the crystal structure. Pair distribution function analyses and isothermal microcalorimetry show similar local structures and structural relaxation times, respectively, for CEL-QC, CEL-BM and CEL-SD. The present work shows that not only similar physicochemical properties (glass transition temperature, and structural relaxation time), but also similar molecular conformational distributions were observed for all prepared CEL amorphous systems. Hence, despite their different recrystallization behaviors, the three amorphous forms of CEL did not show any signs of polyamorphism.

Mechanically Alloyed FeNi and Fe Powders Crystalline Size, Phase Formation, and Morphology: Investigation on Milling Time Impact

Mechanically Alloyed FeNi and Fe Powders Crystalline Size, Phase Formation, and Morphology: Investigation on Milling Time Impact

Influence of initial powders morphology on structural-dimensional characteristics of porous ceramic materials based on SiC/MgO–SiO2

Synthesis of porous ceramic materials based on fine SiC with sintering silicon oxide and magnesia binders at T = 800–1300 °C is considered. Special attention is paid to the influence of the shape and morphology of the initial powder particles on structural parameters and characteristics of porous ceramic materials. The SiC membranes sintered at 1000–1300 °C had average pore sizes of 0.5–1 μm, open porosity - up to 50 %, bending strength - up to 48.5 MPa and high water permeance - up to 7890 l⋅m−2⋅h−1⋅bar−1. The established filtration efficiency was ∼99 % in the case of screening out model particles of D50 = 0.5 μm in size with maintaining stable permeance and physico-mechanical characteristics after multiple filtration-regeneration cycles.Comprehension of the initial powders morphology impact on the synthesized porous ceramics parameters makes it possible to forecast and ensure the preset structural, dimensional and physico-mechanical parameters of the materials under study properly. This work can be used for practical low-cost production of highly efficient SiC membranes for micro- and ultrafiltration processes, as well as base for catalysts.

Adsorption of Pb2+ ions of natural red lava rock powder in aqueous media

Red lava rock is available in nature and is formed from volcanic eruptions. Volcanic rocks are composed of oxides of diverse metals and have considerable porosity. In this study, lava rock powder was ground to a specific size and dried to test its ability to adsorb heavy metals in water. The morphology of the stone powder was observed to show crystals of 100–300 nm in size clumping into particles of a few μm. The phase structure is mainly in the form of Ca(Mg,Al)(Si,Al)2O6; in addition, the phases CaAl2Si4O12.2H2O, Ca2MgSi2O7, and Ca3MgSi2O8 also exist. The material's maximum Pb2+ ion adsorption capacity reaches 32.05 mg/g at endogenous pH. The isotherm of Pb2+ adsorption on the material follows the Langmuir model, and the adsorption kinetics are pseudo-first-order kinetics.