scholarly journals INFLUENCE OF POWDER CHARACTERISTICS ON THE SPREADABILITY OF PRE-ALLOYED TUNGSTEN- CARBIDE COBALT

2021 ◽  
Vol 32 (3) ◽  
pp. 284-289
Author(s):  
Preyin Govender ◽  
Deborah Clare Blaine ◽  
Natasha Sacks
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Base Plate ◽  
Angle Of Repose ◽  
Critical Parameters ◽  
Powder Bed ◽  
Powder Characteristics ◽  
Particle Size And Shape ◽  
Spray Dried ◽  
Selection Of

With rising interest in additive manufacturing (AM) techniques, there is an increased focus on research that evaluates critical parameters that guide the selection of powders that are suitable for AM. One such parameter is a powder’s spreadability, described by metrics such as powder bed density and percentage coverage. This study focused on three spray-dried WC-Co powders (two 12 wt% and one 17 wt% Co) and evaluated the influence of typical powder characteristics, such as particle size and shape, apparent density, and flow rate, on their spreadability. It was found that particle size distribution influenced the powder spreadability. Larger particles hindered the even spreading of powder over the base plate, resulting in low powder bed density and percentage coverage. This also correlated with the powders’ apparent densities. The flow rate and angle of repose gave an indication of how cohesive the powders are. The more cohesive a powder, the poorer the spreadability, resulting in a lower powder bed density and percentage coverage.

scholarly journals Modelling of Metallic Particle Binders for Increased Part Density in Binder Jet Printed Components

2019 ◽  
Author(s):  
Joseph Roberts ◽  
Peter Green ◽  
Kate Black ◽  
Christopher Sutcliffe
Keyword(s):  
Particle Size ◽  
Critical Radius ◽  
Detailed Knowledge ◽  
Particle Sizes ◽  
Powder Bed ◽  
Beneficial Effects ◽  
Drop Tests ◽  
Maximum Particle ◽  
Packing Efficiency ◽  
Selection Of

Binder jet printed components typically have low overall density in the green state and high shrinkage and deformation after heat treatment. It has previously been demonstrated that, by including nanoparticles of the same material in the binder, these properties can be improved as the nanoparticles can fill the interstices and pore throats between the bed particles. The beneficial effects from using these additive binder particles can be improved by maximising the binder particle size, enabling the space within the powder bed to be filled with a higher packing efficiency. The selection of maximum particle size for a binder requires detailed knowledge of the pores and pore throats between the powder bed particles. In this paper, a raindrop model is developed to determine the critical radius at which binder particles can pass between pores and penetrate the bed. The model is validated against helium pycnometry measurements and binder particle drop tests. It is found that the critical radius can be predicted, with acceptable accuracy, using a linear function of the mean and standard deviation of the particle radii. Percolation theory concepts have been employed in order to generalise the results for powder beds that have different mean particle sizes and size distributions. The results of this work can be employed to inform the selection of particle sizes required for binder formulations, to optimise density and reduce shrinkage in printed binder jet components.

scholarly journals Metallic Powder Flowability: A Comparison Between Testing Methods and The Effect of Particle Size Distribution

2021 ◽  
Author(s):  
Marchetti Lorenzo ◽  
Hulme Christopher
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Testing Equipment ◽  
Angle Of Repose ◽  
Powder Layer ◽  
Testing Methods ◽  
Powder Bed ◽  
Tap Density ◽  
Powder Rheometer

The flowability of a powder is a characteristic dependent on both the particle ensemble's physical properties as well as the testing equipment and conditions. In powder bed additive manufacturing processes (SLM, EBM), flowability can be used to predict the quality of the deposited powder layer. However, how representative flowability is for the powder bed layer quality is not always clear.In this work, we compared several steel powders, as well as different testing methods. Each powder had an individual combination of composition or particle size distribution. Furthermore, the flowability testing equipment and methods were selected according to standards (Tap density, Hall flow) or referring to the published literature (angle of repose, FT4 Powder Rheometer). After measuring the flowability of different samples for each testing method, we created a database to evaluate a first correlation between the different testing methods. Finally, with a Powder Rheometer, we investigated for one sample some flow properties as function of different particle size distributions.

scholarly journals Microflow Nanoprecipitation of Positively Charged Gastroresistant Polymer Nanoparticles of Eudragit® RS100: A Study of Fluid Dynamics and Chemical Parameters

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2925 ◽  
Author(s):  
Cristina Yus ◽  
Manuel Arruebo ◽  
Silvia Irusta ◽  
Victor Sebastián
Keyword(s):  
Fluid Dynamics ◽  
Particle Size ◽  
Flow Rate ◽  
Physicochemical Parameters ◽  
Polymer Concentration ◽  
Critical Parameters ◽  
Synthesis Process ◽  
Size Analysis ◽  
Solvent Ratio ◽  
Microscopy Imaging

The objective of the present work was to produce gastroresistant Eudragit® RS100 nanoparticles by a reproducible synthesis approach that ensured mono-disperse nanoparticles under the size of 100 nm. Batch and micromixing nanoprecipitation approaches were selected to produce the demanded nanoparticles, identifying the critical parameters affecting the synthesis process. To shed some light on the formulation of the targeted nanoparticles, the effects of particle size and homogeneity of fluid dynamics, and physicochemical parameters such as polymer concentration, type of solvent, ratio of solvent to antisolvent, and total flow rate were studied. The physicochemical characteristics of resulting nanoparticles were studied applying dynamic light scattering (DLS) particle size analysis and electron microscopy imaging. Nanoparticles produced using a micromixer demonstrated a narrower and more homogenous distribution than the ones obtained under similar conditions in conventional batch reactors. Besides, fluid dynamics ensured that the best mixing conditions were achieved at the highest flow rate. It was concluded that nucleation and growth events must also be considered to avoid uncontrolled nanoparticle growth and evolution at the collection vial. Further, rifampicin-encapsulated nanoparticles were prepared using both approaches, demonstrating that the micromixing-assisted approach provided an excellent control of the particle size and polydispersity index. Not only the micromixing-assisted nanoprecipitation promoted a remarkable control in the nanoparticle formulation, but also it enhanced drug encapsulation efficiency and loading, as well as productivity. To the best of our knowledge, this was the very first time that drug-loaded Eudragit® RS100 nanoparticles (NPs) were produced in a continuous fashion under 100 nm (16.5 ± 4.3 nm) using microreactor technology. Furthermore, we performed a detailed analysis of the influence of various fluid dynamics and physicochemical parameters on the size and uniformity of the resulting nanoparticles. According to these findings, the proposed methodology can be a useful approach to synthesize a myriad of nanoparticles of alternative polymers.

Effects of the Delivery Tube Diameter on the Qualities of Cu-9.7Sn-0.2P Alloy Powder Produced by Gas Atomization

2018 ◽  
Vol 913 ◽  
pp. 3-10
Author(s):  
Yu Wan Cheng ◽  
Zhi Yu Xiao ◽  
Hai Ping Zou
Keyword(s):  
Particle Size ◽  
Alloy Powder ◽  
Cost Effective ◽  
Tube Diameter ◽  
Gas Atomization ◽  
Delivery Tube ◽  
Powder Characteristics ◽  
Powder Particles ◽  
Particle Size And Shape ◽  
Dendritic Structures

Gas atomization is one of the most cost-effective methods for preparing spherical powders. The Cu-9.7Sn-0.2P alloy powder for 3D printing was prepared by a self-developed double nozzle gas atomization technique with different deliver tube diameters, and the particle size and shape of the powder were characterized. Results show that the powder particles are mostly nearly spherical, mixed with a few irregular powders. The average O. Bluntness of the powders are 60~70%, the average Outgrowths are lower than 18%. The deliver tube diameter affects the powder characteristics directly. The increase of the diameter increases the particle size of the powder and reduces the sphericity. At the same time, the adhesion of the satellite powder decreases, the flowability becomes better and the oxygen content drop. The surface and internal structure of the powder are mainly cellular and dendritic structures.

scholarly journals Effect of Process Conditions on Particle Size and Shape in Continuous Antisolvent Crystallisation of Lovastatin

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 925
Author(s):  
John McGinty ◽  
Magdalene W. S. Chong ◽  
Andrew Manson ◽  
Cameron J. Brown ◽  
Alison Nordon ◽  
...  
Keyword(s):  
Particle Size ◽  
Flow Rate ◽  
Experimental Work ◽  
Downstream Processing ◽  
Process Conditions ◽  
Total Flow ◽  
Total Flow Rate ◽  
Size And Shape ◽  
Acetone Water ◽  
Particle Size And Shape

Lovastatin crystals often exhibit an undesirable needle-like morphology. Several studies have shown how a needle-like morphology can be modified in antisolvent crystallisation with the use of additives, but there is much less experimental work demonstrating crystal shape modification without the use of additives. In this study, a series of unseeded continuous antisolvent crystallisation experiments were conducted with the process conditions of supersaturation, total flow rate, and ultrasound level being varied to determine their effects on crystal size and shape. This experimental work involved identifying acetone/water as the most suitable solvent/antisolvent system, assessing lovastatin nucleation behaviour by means of induction time measurements, and then designing and implementing the continuous antisolvent crystallisation experiments. It was found that in order to produce the smallest and least needle-like particles, the maximum total flow rate and supersaturation had to be combined with the application of ultrasound. These results should aid development of pharmaceutical manufacturing processes where the ability to control particle size and shape would allow for optimisation of crystal isolation and more efficient downstream processing.

scholarly journals Powder Reuse Cycles in Electron Beam Powder Bed Fusion—Variation of Powder Characteristics

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4602
Author(s):  
Gitanjali Shanbhag ◽  
Mihaela Vlasea
Keyword(s):  
Electron Beam ◽  
Nitrogen Content ◽  
Size Distribution ◽  
Angle Of Repose ◽  
Powder Size ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Flow Energy ◽  
Hausner Ratio ◽  
Powder Characteristics

A path to lowering the economic barrier associated with the high cost of metal additively manufactured components is to reduce the waste via powder reuse (powder cycled back into the process) and recycling (powder chemically, physically, or thermally processed to recover the original properties) strategies. In electron beam powder bed fusion, there is a possibility of reusing 95–98% of the powder that is not melted. However, there is a lack of systematic studies focusing on quantifying the variation of powder properties induced by number of reuse cycles. This work compares the influence of multiple reuse cycles, as well as powder blends created from reused powder, on various powder characteristics such as the morphology, size distribution, flow properties, packing properties, and chemical composition (oxygen and nitrogen content). It was found that there is an increase in measured response in powder size distribution, tapped density, Hausner ratio, Carr index, basic flow energy, specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.

Effect of CO2 Flow Rate on the Synthesis Nanosized Precipitated Calcium Carbonate, PCC

2013 ◽  
Vol 481 ◽  
pp. 72-75
Author(s):  
O. Nooririnah ◽  
Azwar Azhari Muhamad ◽  
Y. Yusliza ◽  
Abreeza Manap ◽  
M.J. Md Ashadi
Keyword(s):  
Particle Size ◽  
Wastewater Treatment ◽  
Calcium Carbonate ◽  
Ionic Strength ◽  
Calcium Hydroxide ◽  
Flow Rate ◽  
High Purity ◽  
Precipitated Calcium Carbonate ◽  
Particle Size And Shape ◽  
Spraying Method

The precipitated of calcium carbonate has attractedmuch attention because of its numerous applications in various areas of plastics, textiles, rubbers, adhesives, paints and wastewater treatment. Nanosized of precipitated calcium carbonate,(PCC) will enhance the properties and give better performance. Its high purity and close controlled particle size and shape are making it the white filler of choice. Nanosized precipitated calcium carbonate particles were prepared using spraying method. The particles were prepared using three (3) different concentrations of Calcium Hydroxide,Ca (OH)2, three (3) CO2flow rate and three (3) different calcinations temperature. The three (3) concentration of Calcium Hydroxide that been used are 25g/200ml, 25g/ 400ml and 25g/800ml and each of these initial solution sprayed at three (3) different CO2flow rate, 5l/per-minute, 7l/per-minute and 10l/per-minute. Calcium Carbonate, CaCO3powders were then calcined at three (3) different temperature, 1100°C,1200°C and 1300°C. Images from SEM showed morphology of the particles changed to spindle-like or prismatic when the ionic strength of the Calcium Hydroxide, Ca (OH)2was increased.

Spray Drying of Karkade (Hibiscus sabdariffa L.) Calyces and Evaluation of the Product

2014 ◽  
Vol 10 (1) ◽  
pp. 157-165 ◽  
Author(s):  
Abdel Moneim Sulieman
Keyword(s):  
Particle Size ◽  
Bulk Density ◽  
Spray Drying ◽  
Nutritive Value ◽  
Angle Of Repose ◽  
Chemical Components ◽  
Hibiscus Sabdariffa ◽  
Powder Samples ◽  
Macro And Micronutrients ◽  
Spray Dried

Abstract Karkade calyces’ samples (variety Rahad) collected from different local sites were spray dried, and the powder samples were analyzed physically, chemically and microbiologically. The particle size of the various karkade powder samples ranged from 11.8 to 14.1 μm, while the flowability (angle of repose) ranged from 41° to 43° 20′. The reconstitution properties slightly varied when the various karkade samples were compared. The ranges of wettability, sinkability and dispersibility were 320–370 s, 800–850 s and 0.04–0.05 OD, respectively. The bulk density ranged from 0.57 to 0.65 g/ml, and the yield of karkade powder of the various samples ranged between 31.4 and 34.3%. The spray-dried samples from different sites were comparable in most of the chemical components, and they contained relatively good amount of macro- and micronutrients and high nutritive value. Virtually, all the spray-dried karkade powder samples were devoid of coliform, staphylococci and Salmonella cells.

scholarly journals Compaction behavior of powder bed fusion feedstock for metal and polymer additive manufacturing

2021 ◽  
Vol 27 (11) ◽  
pp. 58-66 ◽  
Author(s):  
Francesco Sillani ◽  
Dominik Wagner ◽  
Marvin Aaron Spurek ◽  
Lukas Haferkamp ◽  
Adriaan Bernardus Spierings ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Flow Behavior ◽  
Powdered Material ◽  
Industrial Applications ◽  
Angle Of Repose ◽  
Content Type ◽  
Powder Bed ◽  
Compaction Behavior ◽  
Tap Density ◽  
Selection Of

Purpose Powder bed-based additive manufacturing (AM) is a promising family of technologies for industrial applications. The purpose of this study is to provide a new metrics based on the analysis of the compaction behavior for the evaluation of flowability of AM powders. Design/methodology/approach In this work, a novel qualification methodology based on a camera mounted onto a commercially available tap density meter allowed to assess the compaction behavior of a selection of AM materials, both polymers and metals. This methodology automatizes the reading of the powder height and obtains more information compared to ASTM B527. A novel property is introduced, the “tapping modulus,” which describes the packing speed of a powdered material and is related to a compression/vibration powder flow. Findings The compaction behavior was successfully correlated with the dynamic angle of repose for polymers, but interestingly not for metals, shedding more light to the different flow behavior of these materials. Research limitations/implications Because of the chosen materials, the results may lack generalizability. For example, the application of this methodology outside of AM would be interesting. Originality/value This paper suggests a new methodology for assessing the flowing behavior of AM materials when subjected to compression. The device is inexpensive and easy to implement in a quality assurance environment, being thus interesting for industrial applications.

Pyrolysis of brown algae (Bifurcaria Bifurcata) in a stainless steel tubular reactor: From a review to a case study

2018 ◽  
Vol 14 (1) ◽  
pp. 31-60 ◽  
Author(s):  
M. Y. Guida ◽  
F. E. Laghchioua ◽  
A. Hannioui
Keyword(s):  
Particle Size ◽  
Stainless Steel ◽  
Flow Rate ◽  
Brown Algae ◽  
Tubular Reactor ◽  
Nitrogen Flow ◽  
Nitrogen Flow Rate ◽  
Bifurcaria Bifurcata ◽  
Bio Oil

This article deals with fast pyrolysis of brown algae, such as Bifurcaria Bifurcata at the range of temperature 300–800 °C in a stainless steel tubular reactor. After a literature review on algae and its importance in renewable sector, a case study was done on pyrolysis of brown algae especially, Bifurcaria Bifurcata. The aim was to experimentally investigate how the temperature, the particle size, the nitrogen flow rate (N2) and the heating rate affect bio-oil, bio-char and gaseous products. These parameters were varied in the ranges of 5–50 °C/min, below 0.2–1 mm and 20–200 mL. min–1, respectively. The maximum bio-oil yield of 41.3wt% was obtained at a pyrolysis temperature of 600 °C, particle size between 0.2–0.5 mm, nitrogen flow rate (N2) of 100 mL. min–1 and heating rate of 5 °C/min. Liquid product obtained under the most suitable and optimal condition was characterized by elemental analysis, 1H-NMR, FT-IR and GC-MS. The analysis of bio-oil showed that bio-oil from Bifurcaria Bifurcata could be a potential source of renewable fuel production and value added chemicals.

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