Effect Of Powder Characteristics Research Articles

Research Progress on Laser Powder Bed Fusion Additive Manufacturing of Zinc Alloys.

Zinc, along with magnesium and iron, is considered one of the most promising biodegradable metals. Compared with magnesium and iron, pure Zn exhibits poor mechanical properties, despite its mild biological corrosion behavior and beneficial biocompatibility. Laser powder bed fusion (LPBF), unlike traditional manufacturing techniques, has the capability to rapidly manufacture near-net-shape components. At present, although the combination of LPBF and Zn has made great progress, it is still in its infancy. Element loss and porosity are common processing problems for LPBF Zn, mainly due to evaporation during melting under a high-energy beam. The formation quality and properties of the final material are closely related to the alloy composition, design and processing. This work reviews the state of research and future perspective on LPBF zinc from comprehensive assessments such as powder characteristics, alloy composition, processing, formation quality, microstructure, and properties. The effects of powder characteristics, process parameters and evaporation on formation quality are introduced. The mechanical, corrosion, and biocompatibility properties of LPBF Zn and their test methodologies are introduced. The effects of microstructure on mechanical properties and corrosion properties are analyzed in detail. The practical medical application of Zn is introduced. Finally, current research status is summarized together with suggested directions for advancing knowledge about LPBF Zn.

Recent Progress of Iron-Based Magnetic Absorbers and Its Applications in Elastomers: A Review.

As a result of continuing scientific and technological progress, electromagnetic waves have become increasingly pervasive across a variety of domains, particularly within the microwave frequency range. These waves have found extensive applications in wireless communications, high-frequency electronic circuits, and several related fields. As a result, absorptive materials have become indispensable for dual-use applications across both the military and civilian domains because of their exceptional electromagnetic wave absorption properties. This paper, beginning with the operating mechanisms of absorptive materials, aims to provide an overview of the strategies that have been used to enhance the absorption performance of iron-based magnetic absorbers (IBMAs) and discuss the current research status of absorptive material components. The fabrication of a ferromagnetic absorber in terms of morphology, heterointerface coupling, and macrostructural enhancements and the effect of powder characteristics on their electromagnetic properties are discussed. Additionally, the application of IBMAs in elastomers is summarized. Finally, this paper summarizes the limitations of existing ferromagnetic absorber materials and offers a perspective on their potential future developments. The objective of the ongoing research is to fabricate absorptive components that have thin profiles, lightweight construction, wide absorption frequency ranges, and strong absorption capabilities.

Effect of powder characteristics on the microstructure and performance of CuSn10 parts by material extrusion 3D printing

Two water-atomised, one gas-atomised and treated CuSn10 powders were employed as initial materials to prepare bronze products by material extrusion (MEX) printing technology. The results highlight a significant impact of powder morphology and particle size on both the microstructure and mechanical performance of CuSn10 products. Among the single-size powders, the 3D printed parts, utilising −1000 mesh gas-atomised CuSn10 powders as raw materials, achieved a remarkable hardness of 76.5 HB. For dual-granularity CuSn10 powders, the printed parts from 80%/400500 mesh and 20%/−1000 mesh powders have the optimal performance, reaching a relative density of 98.88% and tensile strength of 355.46 MPa. Successful printing and sintering of various gear parts underscore MEX printing as a viable method for producing high-performance bronze components.

Assessing powder processability and melting behavior in powder-bed fusion additive manufacturing

In this study, the effects of powder characteristics on powder bed properties and the subsequent impacts of these properties on melt solidification were investigated. To this end, eight stainless-steel powders with varying characteristics were examined. The process maps generated for these powders were also assessed, focusing on their melt-solidification behavior and their implications for buildability (i.e., product quality). The build density distribution across the process map exhibited substantial variations. This variability was primarily attributed to the distinct melting behaviors associated with the unique characteristics of each powder. Both the real powder layer thickness of the powder bed and the melt-pool depth could be estimated by performing numerical simulations. Powder characteristics, particularly particle size and particle-size distribution, had significant effects on the achieved build density. Considering these findings, we introduced a new parameter zR/D90, which is determined by the powder characteristics and real powder layer thickness. Consequently, zR/D90 emerged as a valuable parameter for predicting the buildability of the powder. Therefore, this parameter can be noted as a reliable predictor of powder buildability, thereby providing guidelines for manufacturing parts with few defects.

Optimization of Segmented Thermal Barrier Coatings (s-TBCs) for High-Temperature Applications

AbstractHot section components of stationary gas turbines, such as turbine blades and vanes, are coated with thermal barrier coatings (TBCs) to increase the component life. TBCs provide thermal insulation to the metallic components from hot gas in the gas turbines. The TBCs represent high-performance ceramics and are mainly composed of yttria-stabilized zirconia (YSZ) to fulfill the thermal insulation function. The microstructure of the TBCs should be porous to decrease heat conduction. Besides the porous TBCs, the subsequently developed vertically segmented thermal barrier coatings (s-TBCs) feature outstanding thermal durability. For the formation of this segmented coating microstructure, the YSZ should be deposited under high thermal tensile stress during the coating process. Therefore, substrates are heated just before the coating by plasma or in an oven in recent research. In this work, the development of process parameters for s-TBCs produced by atmospheric plasma spray (APS) without pre-heating is presented. Within the experiments, the relevant process parameters, such as plasma gases, powder feed rate, surface speed, and pathway strategy, have been optimized to achieve the segmented coating microstructure with high deposition efficiency by a conventional plasma torch. Furthermore, YSZ powders used in this study are characterized, and the effect of powder characteristics on the coating microstructure is investigated. The coating microstructure in this work aims to achieve the formation of a high number of vertical cracks with a combination of low internal residual stress and high adhesive tensile strength for the s-TBCs.

Effects of Powder Characteristics and Chemical Composition on the Properties of 25Cr7Ni Stainless Steel Fabricated by Laser-Powder Bed Fusion and Evaluation of Process Simulation

The 25Cr7Ni stainless steel alloy system is gaining increasing interest in the oil and gas industry because of its combination of high strength and corrosion resistance properties. However, very few studies on the effects of starting powder attributes and chemical composition on the as-printed properties of 25Cr7Ni stainless steel fabricated through laser-powder bed fusion (L-PBF) exist in the literature. This study examined the influence of powder attributes and chemical composition on the samples from gas atomized and water atomized 25Cr7Ni stainless steel powders, fabricated through L-PBF, on their as-printed microstructure and properties. The mechanical properties that were examined included ultimate tensile strength (UTS), elongation (%), and hardness. The corrosion behavior was also studied using linear sweep voltammetry in 3.5 wt.% NaCl solution. The evolved phases were characterized using optical and scanning electron microscopy, as well as through X-ray diffraction. The gas atomized powders, with their spherical and uniform morphology, yielded as-printed parts of higher relative densities when compared to water atomized powders, with irregular morphology due to better powder bed compaction. The higher densification obtained in the L-PBF samples from gas atomized powders translated into the highest UTS, hardness, and yield strength among the L-PBF samples from water atomized powders and wrought–annealed 25Cr7Ni stainless steel. The presence of higher amounts of N and Mn in the chemical composition of the gas atomized powders over water atomized powders promoted the presence of retained austenite in the corresponding L-PBF samples. Higher amounts of Mo, combined with austenite content, yielded a higher corrosion resistance in the L-PBF samples from the gas atomized powder than in the L-PBF samples from the water atomized powders. The latter part of the work is focused on the evaluation of simulation parameters for analyzing the fabrication procedure for the L-PBF process using Simufact software. For a given set of process parameters, Simufact provides the distortion and internal stresses developed in the printed parts as output. The present study sought to evaluate the process simulation by comparing the experimental observations in terms of the part distortion achieved in a stainless steel cube fabricated through L-PBF with Simufact process simulation obtained using the same set of process parameters.

Micro-dosing of powders into capsules using a new automated micro-dosing system: effect of powder characteristics and operating conditions on the filling of 0.5 mg–100 mg weights

Objective To demonstrate the applicability of a novel micro-dosing system for precisely filling low powder doses (down to a few mg) into capsules along with weighing the filled powder mass accurately. Methods Ten commonly used pharmaceutical powders, ranging from cohesive to free-flowing, were selected and filled at three target fill weights (0.5, 1, and 10 mg), to investigate the effect of distinct powder properties on the filling performance. The fill weight and variability, filling speed and yield (% and number of conforming capsules out of all capsules collected), as well as the system’s long-term performance were assessed. Results The filling accuracy was found to be good for all investigated powders. In particular, the results demonstrate that the tested powders, including the challenging cohesive ones, could be dosed at standard deviations within 0.23 mg at a 10 mg target weight, within 0.07 mg at a 1 mg target weight, and within 0.05 mg at a 0.5 mg target weight. In all cases, free-flowing powders showed lower standard deviations. Intermediate and cohesive powders had slightly higher standard deviations but were still within an acceptable range. Conclusion The study shows the suitability of the tested micro-dosing system for filling low powder doses into capsules, which is of particular importance for dosing active pharmaceutical ingredients (APIs) directly in capsules, i.e. an API-in-capsule (AIC) approach for clinical trials (often in conjunction with highly potent APIs), and for low-dose powder filling for inhalation applications.

Influence of the initial powder characteristic on the densified tungsten microstructure by spark plasma sintering and hot isostatic pressing

ABSTRACT The effect of powder characteristics on the sintering behaviour and microstructure of densified W by spark plasma sintering and post-hot isostatic pressing was investigated. W powder was prepared by ultrasonic spray pyrolysis of a W precursor and hydrogen reduction, and a commercially available powder was used for comparison. The synthesised W powders were present in the form of large agglomerates composed of nano-sized particles. The densified specimens prepared by ultrasonic spray pyrolysis showed lower relative density and larger grain size than when commercial powder was sintered under the same conditions. Microstructural observation for the specimen sintered using the powder of ultrasonic spray pyrolysis revealed that the relatively large pores are present along the grain boundaries. The observed microstructural features were discussed by sintering behaviour based on the effect of intra-agglomerate and inter-agglomerate pores in the initial powder on densification and grain growth.

Initial sintering mechanism and additive effect in zirconia ceramics

AbstractY2O3‐stabilized ZrO2 (YSZ) ceramics have been used for various engineering applications because of their excellent mechanical properties or oxide‐ion conductivity applicable to solid‐electrolyte. The performance of YSZ depends on the sintered texture that is directly determined by sinterability of raw powders. A new kinetic analysis method of diffusion mechanism based on an initial sintering theory (grain‐boundary or volume diffusion) is theoretically derived, the initial sintering mechanism of hydrolytic YSZ powder is experimentally determined, and the effects of powder characteristics on sinterability are discussed. Furthermore, the additive‐enhanced sintering is proposed. A small amount of Al2O3 significantly enhances the densification. Using the additive effect, the low‐temperature degradation that is the fault of zirconia ceramics can be improved by decreasing the sintering temperature.

Effect of lanthanum content on physicochemical properties and thermal evolution of spent and beneficiated spent FCC catalysts

Two FCC spent catalysts with different amounts of La2O3 and similar Al2O3/SiO2 ratios and the corresponding residues of an optimized process of La-extraction are studied. The potential of the powders as feedstock for mullite refractories is established. The four powders have been fully characterized – chemical composition, crystalline phases, particle size, specific surface area, porosity, and morphology. Their thermal evolution up to 1500°C has been studied using dynamic techniques – hot stage microscopy, DTA-TG – and isothermal thermal treatments. The effect of powder characteristics on high temperature phase development, in particular, on mullite formation is discussed.Besides La, the La-extraction process also implies partial extraction of the matrix in which zeolites are dispersed, resulting in reduced impurities contents and Al2O3/SiO2 ratios.The powders present differences in the textural properties– porosity and specific surface area – that do not affect the high temperature behavior, which is determined by the impurities and the Al2O3/SiO2 ratio. The four powders can be proposed as precursors for mullite materials. The compositions of the spent catalysts can be envisaged for application up to 1200°C. The compositions of the residues of the La-extraction process can be proposed for higher temperatures once their composition is corrected by adding alumina to avoid extensive cristobalite formation together with mullite.

Effects of powder characteristics and mixing powders on cold sprayability and corrosion properties of tantalum coatings

Tantalum is an expensive ‘exotic’ metal and it is of particular interest in terms of extreme corrosion resistance and bio-compatibility. Previous studies on cold spray of tantalum show that it can be successfully deposited, but limited effort has been performed to investigate and optimize the powder characteristics for improved cold sprayability and corrosion properties. In this study, two spherical (P1: hard, P3: soft) and one angular (P2) tantalum powders were used as the feedstock. Two mixed powders (20 wt% P2 + P1, 20 wt% P3 + P1) were also prepared and were deposited as well as the three single component powders. After cold spray, the coating microstructure (as-polished and etched cross-sections, top surfaces) was characterized via optical and electron microscopy techniques. Several industrial coating metrics, i.e. cold sprayability (porosity, deposition efficiency (DE), cohesion strength) and electrochemical corrosion properties were evaluated. Results show that: i) angular P2 powder, which is preferred for industrial productions due to its lower cost, exhibits the highest DE, corrosion resistance, and high cohesion strength compared to the other two spherical ones (P1, P3); ii) adding either P2 or P3 powders into P1 leads to much improved metrics compared to single component P1.

Effect of Powder Characteristics on Slip Casting Fabrication of Dental Zirconia Implants.

Dense zirconia compacts were fabricated by slip casting and sintering of nanoscale zirconia powders, and the effect of the powder characteristics (crystallite size, specific surface area, yttria content, and agglomeration) on the slurry and sintered properties was investigated. Three types of commercial 3 mol% yttria-stabilized tetragonal zirconia polycrystals powders were used as the starting powders after the powder characteristic analysis. A zirconia slurry for slip casting was prepared by mixing zirconia powder (solid loading of 60, 65, and 70 wt.%), distilled water, and a dispersant of Darvan C. The green compacts obtained from slip casting were cold isostatic pressed to enhance the close packing and densified by sintering at 1450 °C for 2 h. Highly dense zirconia compacts with a relative density of 99.5% and grain size of 350 nm were obtained based on the powder type and solid loading in the slurry. The microstructure and mechanical hardness of the sintered specimen after slip casting were dependent on the yttria content in the 3 mol% yttria-stabilized tetragonal zirconia polycrystal powder and the solid loading within the slurry.

A case study of ceramic processing: Microstructural development and electrical properties of Ce0.8Gd0.2O1.9

The effects of powder characteristics and conformation methods on green microstructure have been investigated, and microstructural evolution was analyzed based on the green density and the different sintering techniques. Colloidal processing of nanopowders with narrow particle size distribution (15 ± 5 nm) can be more problematic than dry processing and can lead to more heterogeneous microstructures. Two-step sintering can be used to obtain dense nanostructured samples with more flexibility than microwave sintering and still at lower temperatures than conventional sintering. The sinterability of Ce0.8Gd0.2O1.9 is significantly improved by Zn addition, which can reduce sintering temperature to values as low as 800, 1150 and 1200 °C for two-step, microwave and conventional sintering, respectively, in order to achieve relative densities above 90%. Microscopic grain boundary conductivity is shown to be improved in nanostructured samples, despite the higher grain boundary density.

The Effect of Powder Characteristics on Build Quality of High-Purity Tungsten Produced via Laser Powder Bed Fusion (LPBF)

Two high-purity tungsten powders, produced via different manufacturing techniques, were characterized to determine size distribution, morphology, thermal properties, and flow characteristics and, thus, the likely suitability for Laser Powder Bed Fusion (LPBF) production. Specimens from duplicate builds were produced with the two powders and characterized for density, defect mechanisms, and thermal penetration into the substrate plate to compare apparent power densities. The first powder was a chemically reduced powder with irregular morphology and the second, a plasma spheroidized powder with highly spherical morphology. The latter was found to have tighter morphological control and size distribution, having a third of particles at the modal particle size in comparison to a fifth of the chemically reduced powder. This led to better flow characteristics, and an increase of 1.5 g cm−3 (1500 kg m−3) in the packing densities seen in the powder bed which corresponds to 57 pct theoretical density vs 50 pct theoretical density in the chemically reduced powder. As a result, the specimens produced from the plasma spheroidized powder had higher densities (97.3 vs 88.5 pct) and the dominant defect mechanism moved from lack of fusion dominated in the chemically reduced powder to cracking dominated in the plasma spheroidized. The plasma spheroidized powder also showed higher apparent power densities (effective absorptivities) as evidenced by an 80 pct deeper penetration of the laser into the substrate plate.

Effect of powder characteristics on production of oxide dispersion strengthened Fe[sbnd]14Cr steel by laser powder bed fusion

In order to assess the potentialities of additive manufacturing in nuclear industry, Oxide Dispersion Strengthened (ODS) Fe14Cr steels are produced by laser powder bed fusion (L-PBF). Such materials are currently manufactured by milling a Fe14Cr atomized powder with Y2O3 and TiH2 powders. The resulting powder has a non-spherical shape being coarser than powders typically used in L-PBF equipment. The influence of powder characteristics on the processability of ODS Fe14Cr by L-PBF are studied in details. Four different powders are used. These powders differ from size, morphology and chemical composition. Finer is the powder; wider is the process range to obtain dense samples. This phenomenon could be mitigated by transferring an amount of energy superior to 110 J.mm−3. The presence of yttrium and titanium gives columnar microstructure for ODS samples, whereas Fe14Cr samples have stirred microstructure. Titanium and yttrium form oxides, which enlarge the melt pool and induce columnar growth.

Effect of ball milling on the powder characteristics and welding mechanism of Mg2B2O5w/6061Al matrix composite

Mg2B2O5w/6061Al matrix composites were fabricated through the powder metallurgy (PM) technique. The morphology of the particles, particle size and the effect of powder characteristics on densification behavior of the compacted samples were investigated. It was found that milling way, milling time, milling speed and whisker content all had different effects on powders characteristics and densification. During the low-energy milling process, the particles morphology changed from spherical to flattened shape and the reinforcement accelerated the process to some extent; during the high-energy milling process, the particles experienced the welding-fracturing process, the Al particles morphology changed from spherical to flattened shape and then back to more equiaxed morphology, the reinforcement whisker apparently accelerated the milling process. During the uniaxial cold pressing process, the particles after high-energy milling achieved better densification, the reverse for the low-energy milled powders because of whiskers clusters. A good linear correlation coefficient was obtained when the experiential data were fitted by the Panelli and Ambrosio Filho equation.

Effect of powder characteristics and oxygen content on modifications to the microstructural topology during hot isostatic pressing of an austenitic steel

The effect of powder size distribution and oxygen content on the extent of multiple twinning and spatial distribution of oxide inclusions in hot isostatic pressed (HIPed) 316L steels was investigated using powders with different characteristics. Modifications to, and differences in their microstructural topology, were tracked quantitatively by evaluating the metrics related to twin related domains (TRDs) on specimens produced by interrupting the HIPing process at various points in time. Results revealed that powder size distribution has a strong effect on the extent of multiple twinning in the fully HIPed microstructure, with specimens produced using narrow distribution showing better statistics (i.e., homogeneously recrystallized) than the ones produced using broad size distribution. The oxide inclusion density in fully HIPed microstructures increased with the amount of oxygen content in the powders while prior particle boundaries (PPBs) were only observed in the specimens that were HIPed using broad powder distribution. More importantly, results clearly revealed that the spatial distribution of the inclusions was strongly affected by the homogeneity of recrystallization. Implications of the results are further discussed in a broader context, emphasizing the importance of utilizing the occurrence of solid state phase transformations during HIPing for controlling the microstructure evolution.

Effect of powder characteristics on the thermal conductivity and mechanical properties of Si3N4 ceramics sintered by Spark plasma sintering

The effect of powder characteristics on the thermal conductivity and mechanical properties of silicon nitride (Si 3 N 4 ) ceramics were investigated systematically by using two α-Si 3 N 4 powders a ...

Studies on the Thoria Fuel Recycling Loop Using Triflic Acid: Effects of Powder Characteristics, Solution Acidity, and Radium Behavior

A convenient recycling loop is one of the key factors that will help to implement the thorium-based nuclear fuel cycle in the future. Herein, a study is presented concerning the recycling loop of thoria production scrap using dissolution with trifluoromethanesulfonic (triflic) acid and recovery by precipitation with oxalic acid. The kinetics of thoria powders and pellet dissolution was assessed and compared with the THOREX process. The effect of the triflic acid concentration on the recovery yield of thorium during oxalate precipitation was examined, as well as the behavior of radium during this reaction. Finally, the effect of the triflic acid concentration on the recovered thoria morphology was investigated. The triflic acid has minimal effect on the recovery yield during oxalate precipitation even in the case of high acid concentrations. In general, the solubility of radium(II) oxalate is higher than for thorium(IV) and has a maximum at a triflic acid solution of 4 M. An interesting observation was that a stable dihydrate of thorium(IV) oxalate is formed in solution of high triflic acid concentration. It might be explained by the hygroscopic medium during precipitation of the oxalate. All above mentioned observations confirm the benefits of usage of the triflic acid-based closed recycling loop for thorium dioxide-based nuclear fuel.

Effect of Powder Characteristics on the Rheological Performance of Resin-based Zirconia Suspension for Stereolithography

Effect of Powder Characteristics on the Rheological Performance of Resin-based Zirconia Suspension for Stereolithography