Irregular Powder Research Articles

A Preliminary Study of Spherical Surface-Modified Carbon Materials for Potential Application in La3+ (Ac3+) and Bi3+ Separation.

Separation of high-activity 213Bi from 225Ac for targeted alpha therapy is challenging due to the instability of existing sorbents. Surface-modified carbon materials have shown promise for use in inverse 225Ac/213Bi generators. However, previously reported materials with irregular shapes may limit their applications in column separations. In contrast, spherical particles are expected to be more suitable for column chromatography compared to irregular powders as they can ensure uniform flow patterns, lower pressure drop, and effective packing. To address this limitation, a method was developed for the synthesis of spherical carbon beads via the carbonization of cellulose beads. Subsequently, surface modification on the spherical carbon beads was performed via sulfonation or oxidation of the carbon beads. Batch sorption experiments were conducted to assess their selective sorption toward Bi3+ over La3+ (as a surrogate of Ac3+) by varying the concentrations of HNO3 and NaNO3. It was found that the selective sorption of Bi3+ onto spherical surface-modified carbon beads could be achieved by adjusting the concentrations of HNO3 and NaNO3. Furthermore, the sorption capacity of Bi3+ decreased as the concentration of HCl increased due to the formation of bichloride complexes and the H+ competition. This implies that Bi3+ can be effectively eluted from the spherical surface-modified carbon beads when using HCl as the eluate. Consequently, spherical surface-modified carbon beads show potential as alternative adsorbents for inverse 225Ac/213Bi generators.

Theoretical Analysis of Self-Shrinkage Spheroidization of Irregular Degradable Polymer Powder under Thermodynamic Nonequilibrium State

Theoretical Analysis of Self-Shrinkage Spheroidization of Irregular Degradable Polymer Powder under Thermodynamic Nonequilibrium State

Spherical nanocrystalline ScYSZ thermal barrier material by a novel supersonic plasma spheroidization method: Simple synthesis and excellent performance

Spherical nanocrystalline ScYSZ thermal barrier material by a novel supersonic plasma spheroidization method: Simple synthesis and excellent performance

Ceramic fused filament fabrication (CF3) of alumina: Influence of powder particle morphology on processing and microstructure

Ceramic fused filament fabrication (CF3) of alumina: Influence of powder particle morphology on processing and microstructure

A novel powder sheet laser additive manufacturing method using irregular morphology feedstock

A novel powder sheet laser additive manufacturing method using irregular morphology feedstock

Extracting powder bed features via electron optical images during electron beam powder bed fusion

Extracting powder bed features via electron optical images during electron beam powder bed fusion

Preparation of Cold Sprayed Titanium TA2 Coating by Irregular Powder and Evaluation of Its Corrosion Resistance

Titanium coating on a steel substrate by surface technology can improve the corrosion resistance of steel. In this paper, the titanium TA2 coating was deposited on X80 steel by cold spraying equipment with a low-cost irregular powder. The effects of the carrier gas temperature on the microstructure, microhardness, wear resistance, adhesion and corrosion resistance of titanium coatings, especially in a deep sea environment, were studied by methods of porosity analysis, thermal field emission scanning analysis, energy spectrum analysis, Vickers hardness tests, bonding strength tests, friction and wear tests and electrochemical tests. The results showed that as the carrier gas temperature increased from 300 °C to 900 °C, the porosity of the coating decreased to 0.93%, and the hardness and bonding strength of the coating increased to 247 HV0.5 and 46.7 MPa, respectively. With the increase in hydrostatic pressure from 0.1 MPa to 40 MPa, the dimensional blunt current density of the titanium coating with 0.93% porosity was still in the order of 10−7 A·cm−2 with the cast titanium TA2.

Synchrotron X-ray computed tomography analysis of the morphological characterization of aluminum alloy powders produced by gas atomization

Synchrotron X-ray computed tomography analysis of the morphological characterization of aluminum alloy powders produced by gas atomization

Boosted sustained-release with iron-based MOF-derived mesoporous-carbon-spheres as a nitroimidazole drugs carrier

Boosted sustained-release with iron-based MOF-derived mesoporous-carbon-spheres as a nitroimidazole drugs carrier

Recoater crashes during powder bed fusion of metal with laser beam: simulative prediction of interference and experimental evaluation of resulting part quality

In powder bed fusion of metal with laser beam (PBF-LB/M), repetitive melting and solidification of newly added layers lead to thermal stresses and distortions during part build-up. Particularly at critical component features such as unsupported overhangs, super-elevated edges pose a risk in terms of crashes with the recoating system during powder spreading. Damaged recoater lips lead to irregularities in the form of stripes in the powder bed. These local inhomogeneities cause lack-of-fusion porosity and geometric defects on the part surface. However, quantitative information on important quality aspects, such as tensile properties, dimensional accuracy, roughness, and hardness of parts printed under irregular powder bed conditions is scarce. Here, we show that samples from build jobs with recoater crashes maintain their elastic tensile properties and hardness, but lose elongation at break. Finite-element simulations of in-process distortions are used to design an artifact that intentionally damages the silicone rubber lip of the recoater but does not cause machine breakdown. The lowest mean yield strength of the damage-affected samples is 243 MPa, which is still within the material data sheet limits for AlSi10Mg. Therefore, recoater crashes do not necessarily result in rejects, but users must consider the likely presence of porosity.

Effect of tungsten powder particle shape on the emission properties of the barium tungsten cathode

In this research, porous W matrixes for dispenser Ba-W cathodes were prepared by metal injection molding (MIM) using W powders with different particle shapes as raw materials. Other than investigating the effect of the powder particle shape on the pore characteristics of the porous W matrix, the influence of the powder particle shape on the emission properties of the Ba-W cathode was also investigated. Irregular W powder particles had higher surface roughness and specific surface area than the spherical W particles, resulting in sinuous pore channels and higher pore-specific surface area in the prepared W matrix. The emission current density of the cathode processed from the irregular powder was thus improved as the level of Ba–O dipoles, covered on the emission surface, was increased. This is due to the high pore-specific surface area offering a high contact area between W and impregants in the cathode.

Influence of powder size on the moldability and sintered properties of irregular iron-based feedstock used in low-pressure powder injection molding

Initially used for shaping irregular ceramic powders, manufacturing metallic parts via low-pressure powder injection molding (LPIM) from irregular powders has received very little attention. This study investigates the processability of irregular powders for fabricating high-density and low-cost metallic parts using the LPIM process. Three irregular iron-based powder lots were mixed with a low-viscosity binder, injected, debound, and sintered to evaluate their molding and sintering performances via viscosity measurements, real-scale injections, metallographic analysis, and tensile tests. The results revealed that feedstocks formulated from fine and coarse powders exhibit good moldability, predicted by their moldability indexes and validated by spiral flow distances. Furthermore, the feedstock formulated with the finer powder (i.e., 1250 mesh providing a powder particle size <10 μm) produced a homogeneous microstructure along with a low content of oxygen impurities, leading to the highest sintered relative density of ∼90%, an ultimate tensile strength of ∼225 MPa, and an elongation at break of ∼24%. These results confirm that the cost-effective irregular iron powders present a promising alternative to fabricating metallic parts via low-pressure powder injection molding compared to their relatively high-cost spherical powder counterparts (i.e., carbonyl iron powder).

High-Performance Ti-6554 Alloy Manufactured Using Irregular Powder via Vacuum Pressureless Sintering Followed by Forging

High-Performance Ti-6554 Alloy Manufactured Using Irregular Powder via Vacuum Pressureless Sintering Followed by Forging

Research on Spheroidization of Tungsten Powder from Three Different Raw Materials

In this work, three kinds of tungsten powders with different particle sizes were spheroidized by radio-frequency (RF) inductively coupled plasma spheroidization. The spheroidization behavior of these tungsten powders was investigated and compared. The spheroidization effects of irregular tungsten powder improves with the decrease in degree of agglomeration and increases with primary particle size. Spherical tungsten powder from irregular powder with a primary particle size of 19.9 μm and an agglomeration coefficient of 1.59 had the best spheroidization effect; its apparent density, hall flow time, and spheroidization ratio are 9.36 g/cm3, 6.28 s/50 g, and 98%, respectively. The results show that irregular feedstock tungsten powder with a smaller primary particle size and higher agglomeration degree has a poor spheroidization effect because it is easily affected by the gas flow and deviates from the high temperature zone. On the contrary, irregular feedstock tungsten powder with larger primary particle sizes and lower agglomeration degrees has better spheroidization effects.

Synthesis of WTaMoNbZr refractory high-entropy alloy powder by plasma spheroidization process for additive manufacturing

A novel refractory high-entropy alloy (RHEA) spherical powder WTaMoNbZr was synthesized successfully through four-steps: melting, hydrogenation, crushing and spheroidization. The alloy ingot with ~110 mm in diameter and ~120 mm in height was prepared by vacuum electron beam melting. The ingot formed a single body-centered cubic (BCC) solid solution phase, with lattice parameters of 3.244 Å, thereby possessing a good combination of compressive stress (1973 MPa) and strain (17.63%). And this increased the difficulty to pulverize it into fine powder. It was found that hydrogenated treatment can embrittle the ingot, and irregular powders with the particle size ranging from 1.56 µm to 59.5 µm were then easily obtained by using a disk crusher. Finally, highly spheroidized RHEA powders with spheroidization ratio of 95.3% were fabricated by plasma spheroidization. After the plasma treatment, the powders possessed an average particle size of 37.5 µm and a single BCC phase structure was also obtained. The flow property and apparent density were 15.09 s•(50 g)−1 and 7.42 g•cm−3 respectively, indicating a better spheroidization effect. The nano-microhardness of the RHEA powder was 7.99 GPa, which was about 1.68 GPa higher than that of the bulky RHEA with the same composition. These excellent properties endow RHEA powder with broader potential applications, such as protective coatings, additive manufacturing. More importantly, this study provides a new approach to prepare spherical RHEA powder, which is of great significance for the further development.

Effect of reactive B–Ti powder morphology on its removal from a surface and ignition by electro-static discharge

Blast-powder interaction forms an aerosol, which could ignite, affecting production and distribution of fallout products. Full-scale experiments are challenging. Electrostatic discharges (ESD) above powders placed in a cavity serve to generate lab-scale shocks and plasma. Spherical and irregular particles of Ti–B nanocomposites were lifted by ESD. More particles are lifted and ignited by ESD with a higher voltage and when electrodes were located closer to the cavity. Spherical powders were lifted more efficiently than irregular powders. Ignited spherical particles were brighter than irregular powders. Particles lifted nearly instantly traveled at ∼100 m/s. Particles lifted later moved at lower velocities.

Sacrificial template synthesis of (V0.8Ti0.1Cr0.1)2AlC and carbon fiber@(V0.8Ti0.1Cr0.1)2AlC microrods for efficient microwave absorption

The morphology of MAX phase powders significantly influences their microwave absorption properties. However, the traditional synthesis via solid-state reactions produces irregular powders, and the preparation of MAX phase powders with specific morphology remains a challenge. Herein, (V0.8Ti0.1Cr0.1)2AlC MAX phase microrods were fabricated for the first time in NaCl/KCl molten salts using vanadium, titanium, chromium, aluminum, and short carbon fibers as precursors. It was found that despite acting as a carbon source, carbon fibers also acted as sacrificial templates. By adjusting the molar ratio of metal powders and short carbon fibers, a series of carbon [email protected](V0.8Ti0.1Cr0.1)2AlC microrods with core-sheath structure were also obtained. Carbon [email protected](V0.8Ti0.1Cr0.1)2AlC microrods with a molar ratio of 8:2 showed the optimum microwave absorption performance. The reflection loss (RL) value reached up to –63.26 dB at 2.40 mm, and the effective absorption bandwidth (EAB) was about 5.28 GHz with a thickness of 2.02 mm. Based on the electromagnetic parameter analysis and theoretical simulation, the enhanced microwave absorption performance was attributed to the synergistic effect of different factors like dielectric loss, magnetic loss, multiple reflection, and scattering. This work offers a facile route to modulate the morphology of MAX phase powders and may accelerate its application as microwave absorbers.

In situ X-ray imaging of directed energy deposition of metals: The comparisons of delivery performance between spherical and irregular powders

Laser-based powder-blown directed energy deposition (DED) is receiving more and more attention in both academia and industry because it is a competitive method for repairing and remanufacturing. State-of-art DED additive manufacturing processes use both spherical and irregular powders both of which have distinct advantages (e.g. the quality of final built components and fabrication cost respectively). Nowadays, most investigations focus on the comparisons of these two types of powders through the analysis of mechanical and microstructural properties. However, the fundamental differences that cause this variance in properties are still unknown. In situ synchrotron X-ray imaging has proven to be a technique capable of revealing the fundamental physics of phenomena in both DED and laser powder bed fusion processes. Therefore, this study will use this technique to provide a fundamental understanding of how different powders behave in DED AM. Delivery performance comparisons between spherical and irregular powders are conducted in this investigation, including the powder delivery velocity and the interaction between delivered particles and the melt pool.

Preparation of CNTs/PP@Gr composites with a segregated structure and enhanced electrical and thermal conductive properties by the Pickering emulsion method

Conductive and thermal conductive polymer composites have significant advantages in corrosion resistance and mechanical and processing properties. To improve the integrity of the network structure of the conductive filler in a polypropylene (PP) matrix, [email protected] (Gr) with segregated single-network structure, [email protected](carbon nanotubes (CNTs)/Gr) with segregated double-network structure, and (x wt%-CNTs/PP)@Gr with segregated hybrid double-network structure were prepared by the Pickering emulsion method. The original irregular powder was converted into spherical shape by the Pickering emulsion method. Among these composites, the (2 wt%-CNTs/PP)@Gr composite had the highest conductivity and thermal conductivity. The electrical and thermal conductivity of the (2 wt%-CNTs/PP)@Gr composite reached 1.45 S/m and 0.82 W/m·K, respectively, at a Gr loading of 13.01 wt%, and the electrical conductivity was 3 and 0.5 times higher than that of [email protected] and [email protected](CNTs/Gr) composites, respectively. The CNTs acted as "bridges" to form a denser conductive network, and significantly improved the conductivity. The interfacial thermal resistance of the (2 wt%-CNTs/PP)@Gr composite was between 1.5×10-7 and 1×10-6 m2K/W according to the effective medium theory (EMT) fitting results. Additionally, the crystalline peaks of the [email protected] and [email protected](CNTs/Gr) composites showed a significant left shift, while the (2%-CNT/PP)@Gr composite showed a significant right shift, which indicated that the hybridization of CNTs with Gr caused a "bridge effect" and increased the thermal conductivity. This method provides a convenient and time-saving new approach for the study of segregated structural thermally conductive composites by encapsulating the filler on the matrix through a one-step process while meeting the requirements of green environment.

Electron Beam Powder Bed Fusion of Water Atomized Iron and Powder Blends.

In the present state of the art, highly spherical alloy powders are employed as feedstock in powder bed fusion processes. These powders are characterized by high flowability and apparent density. Their elaborate fabrication process is reflected in high powder price, adding a significant fraction to the cost of additively manufactured parts. Thus, the use of non-spherical powders, such as water atomized material, can lower costs significantly. Here, the electron beam powder bed fusion (PBF-EB) of standard water atomized iron powder used for press-and-sinter is studied. Despite raking problems, using the coating mechanism in standard configuration samples with densities exceeding 99% were fabricated. In a further step, the addition of alloying elements by powder blending is explored. Important powder properties of feedstock blended from irregular and spherical powders are characterized. The PBF-EB processing of two alloys is presented. The first represents a low carbon steel. Samples were characterized by metallographic cross-section, energy dispersive X-ray (EDX) mapping, and mechanical testing. The second alloy system is a FeCrAl. After PBF-EB processing of the powder mixture, chemical homogeneity was achieved. Besides the low cost, this approach of using water atomized powder mixed with master alloy offers the advantage of high flexibility for potential application.