Powder Loading Research Articles

Effects of jet milling on W–10 wt.%Cu composite powder for injection molding

Ultrafine W–10wt.%Cu powders synthesized by thermo-chemical method have a good sinterability compared with the mechanically mixed powers, which are suitable for powder injection molding (PIM). The deagglomeration, however, is necessary to improve the flowability of the ultrafine powder to obtain a PIM feedstock with high powder loading. Jet milling (JM) was employed in this study to reduce the strong agglomerations among the particles, which were subsequently used for PIM. Results showed that JM was a proper process to modify the ultrafine powders for mass production with negligible contamination. JM modified the powder characteristics, including agglomeration, size distribution, surface morphology, and tap density, which considerably improved the rheological properties of feedstock. With the increasing of powder fraction in the feedstock from 46vol.% to 52vol.%, the shrinkage of the parts during sintering reduced accordingly, which is favorable for dimensional stability. The resulted W–10wt.%Cu sintered composite has excellent physical properties, such as high thermal and electric conductivity, as well as low coefficient of thermal expansion, which can be attributed to its near full density and homogeneous microstructure.

Synthesis and characterization of bismuth oxide ternary compounds for photocatalytic decolorization of BR 18

In this study, (Er2O3)/(Yb2O3)/(Bi2O3) ternary compounds were synthesized and their photocatalytic activity were investigated for oxidation of an azo dye Basic Red 18 (BR18) in aqueous solutions. The influence of stoichiometric ratios of Er3+ and Yb3+ doping on Bi3+ (2Er5Yb, 4Er10Yb, 8Er15Yb), powder loading (2, 4, 6 g/L), and dye concentration (5, 10, 25 mg/L) were systematically investigated. A complete BR18 decolorization (5 mg/L initial dye concentration) was achieved by 8Er15YbSB at 4 g/L powder loading for 180 min. Synthesized ternary compounds were also characterized.

Moldability of Nano Size Zirconia for Powder Injection Molding Process by Using PEG and PMMA Binders

Powder injection molding (PIM) is a well-known manufacturing technique for the production of metal and ceramic near net shapes. Now-a-days, this technology is largely used in electronics, biomedical, aerospace, automotive, defence and telecommunication industries. In this paper, green parts of ZrO<sub>2</sub> with polyethylene glycol (PEG), polymethyl methacrylate (PMMA) and stearic acid (SA) binders were prepared by PIM process. The average particle size of ZrO<sub>2</sub> powder was 50 nm with pycnometer density of 6.054 g/cm<sup>3</sup>. The ZrO<sub>2</sub> powder was mixed with binder content of 73 wt.% PEG, 25 wt.% PMMA and 2 wt.% SA. The rheological results showed pseudoplastic properties of the feedstock at 140 °C and 160 °C, which was suitable for PIM process. The suitable injection molding parameters for feedstock at 51 vol.% powder loading such as mold temperature, injection temperature, injection pressure and holding time were 60 °C, 160 °C, 10 bar and 8 s, respectively. At the same powder loading, the green part density of 3.60 g/cm<sup>3</sup> was measured, whereas for the three-point flexural, the measured strength was in the range of 13-15 MPa. For structural analysis, the morphological properties of the powder as well as the surface and the cross-section of the green part was examined.

Bi-Material Micro-Part of Stainless Steel and Zirconia by Two-Component Micro-Powder Injection Molding: Rheological Properties and Solvent Debinding Behavior

From the micro-powder injection molding (μPIM) process, a two-component micro-powder injection molding (2C-μPIM) process has evolved due to the growing demand for multi-functional micro-components in avant-garde applications. 2C-μPIM technology provides the opportunity to conjugate distinct materials within one part. Stainless steel (SS 17-4PH) and 3 mol.% yttria-stabilized zirconia (3YSZ) are characteristically recognized for their corrosion resistance and high hardness. In this work, the obtained critical powder volume concentration (CPVC) of SS 17-4PH and 3YSZ powders were 71.7 and 47.1 vol.%, respectively. Solid loadings of 2 and 3 vol.% less than the CPVC were considered as the optimal content for both powders. Feedstocks were obtained by mixing SS 17-4PH and 3YSZ powders with a binder system comprised of palm stearin (PS) and low-density polyethylene (LDPE). The rheological behaviors of the prepared feedstocks were assessed to figure out the feedstocks having the best rheological properties. The feedstocks of SS 17-4PH and 3YSZ with powder loadings of 69 and 44 vol.% were eventually injected to produce bi-material micro-parts. The optimal solvent debinding temperature of the green bi-material micro-part was then investigated, and it was found that 73.3% soluble binder was removed when bi-material was immersed in acetone at 70 °C for 40 min.

Role of elongational viscosity of feedstock in extrusion-based additive manufacturing of powder-binder mixtures

The 3D printing of metals and ceramics by the extrusion of a powder/thermoplastic binder feedstock is an extrusion-based additive manufacturing (EAM) technique and has received significant interest. EAM feedstocks are generally characterized by their shear viscosity. A quantitative comparison with the shear flow data, through an estimation of the Trouton ratio, indicates that the extensional viscosities are three orders of magnitude greater than their shear flow viscosity at a comparable shear rate obtained in three different high loaded polymers retained for this study. This experimental study addresses the unsolved issue of the role of elongational viscosity in the modelling of EAM of highly viscous melts. The study was conducted using three feedstocks with a water-soluble binder and high powder loading. The different powder materials used for this study are stainless steel, alumina and zirconia. Initially, the rheological properties of the feedstocks were assessed using capillary rheometers. A pressure drop model based on the shear and elongational components of the viscosity was proposed to predict the extrusion pressure during capillary tests. The model was adapted to develop a specific EAM machine, namely, an EFeSTO, equipped with a pellet extrusion unit. Experimental EAM tests were conducted, and the pressure drops were analytically predicted and experimentally measured. A total of 31 different combinations of extrusion velocities, nozzle diameters, 3D printed shapes and materials were tested through a total 184 experimental runs. The model predicts well the experimental pressures for the steel feedstock, whereas it underestimates the pressure for the two ceramic feedstocks owing to their different thermal properties. The results of this study clearly demonstrate that the pressure, and therefore the material flow during the EAM processes of viscous materials, cannot be modelled well without considering the elongational viscosity.

Investigation and analysis of corn cob, coir pith with wood plastic composites

The optimization of the resources is a must to overcome the everyday needs of the people. Hence the present research deals with developing environmental and eco-friendly Wood Plastic Composites (WPC) using the corn cob powder and coir pith powder. The composite is made with wood powder, corn cob powder and coir pith which is the most waste produced. The present research work makes use of agriculture residue. Here the hybridized wood powder, hybridized coir pith and corn cob powder are taken as the reinforcement material for the composite. PVC resin and PPA Hardener binds these powder materials to a single structure. This composite with the PVC matrix is obtained by the compression molding method as it undergoes curing for a minimum of 8 h. They are mixed with different proportions and their properties vary with their powder proportions. The percentage of powder loading in this research is maintained at 20%. From the resultant mechanical tests, it is inferred that the tensile and flexural strength rises with the incorporation of corn cob in the proportion of equal ratio to which wood powder is added in the composition. Further, fabricated wood composite shows higher impact strength as compared to other specimens taken for analysis due to the content of both the corn cob and coir pith powder.

Experimental study on the effect of metal protrusions inside silos on electrostatic discharges

This paper experimentally introduces the electrostatic discharges generated from metal protrusions inside a silo during the loading of powders. An industrial-scale pneumatic powder transport facility including a silo and approximately 400 kg of polypropylene powder (PP, 2–3 mm in size) were used for this test. The PP powder loading speed was approximately 0.38 kg/s. Six different diameters (D: 1 cm to 6.3 cm) of metal protrusions were used. The metal protrusions were attached to the silo wall using a 30 cm support rod that was electrically grounded. The height from the accumulated PP powder to the protrusion in the silo varied from 10 cm to 50 cm. An image-intensifier unit was used in order to observe the electrostatic discharges generated from the metal protrusions and a current probe attached to an oscilloscope was used in order to measure the current of the discharges. As for the results, electrostatic discharges (such as brush discharges) from protrusions during the loading of PP powders were clearly observed. Specifically, the electrostatic discharge was the strongest in this paper when the diameter of the protrusion was 4 cm and the height from the accumulated powder was 30 cm. As an important finding, the value of the discharge amount was affected to a greater extent by the maximum discharge current. The maximum charge amount of electrostatic discharges generating from the metal protrusions in all of the test conditions was −122 nC, which is twice as high as the threshold for electrostatic risk assessment in the liquid painting process. These results suggest that, in the chemical process, sensitive powders with MIEs of less than 4 mJ, powders wetted with solvents, and the solvents themselves must be carefully handled, as these kinds of powders may be ignited by brush discharges. In order to prevent and reduce electrostatic accidents, it is important to make sure that no external material enters the silo.

Influence of powder loading on rheology and injection molding of Fe-50Ni feedstocks

ABSTRACTThe feedstock viscosity is a crucial rheological parameter that governs the failure or success of injection molding, whereas viscosity depends upon powder morphology and process parameters. Thus, rheological investigation of the feedstock is essential to find out the optimum loading and suitable processing parameters to produce high-quality defect-free green parts by injection molding. The critical powder volume percentage (CPVP) was determined for both Fe and Ni powders produced by carbonyl and atomization routes. The CPVP value for carbonyl powders was 56.47 vol% while for atomized powders was 60.49 vol%. The higher value for atomized powder was due to regular morphology as compare to spiky irregular shape carbonyl Ni particles. Three feedstocks of carbonyl powders from 52 to 56 vol% loading and three of atomized with loading from 56 to 60 vol% were prepared. The optimum loading was established in terms of activation energy, viscosity, and flow behavior index at three temperatures. The formulations of 54 vol% loading and 58 vol% loading for carbonyl and atomized powders, respectively, were found appropriate for injection molding.

Mechanical performance, corrosion and tribological evaluation of a Co–Cr–Mo alloy processed by MIM for biomedical applications

In this study, the processing parameters mechanical performance, corrosion and tribological evaluation of a low carbon content Co–Cr–Mo alloy are discussed. The production of parts using the Metal Injection Moulding (MIM) process is optimized, specifically concerning the rheological analysis of the prepared feedstocks, the optimum choice of the powder loading and the design of the debinding and sintering cycles. The mechanical properties as regards hardness, tensile strength and bending strength, as well as fatigue tests and wear characterization, are discussed for the full densified specimens obtained. Additionally, corrosion behaviour with the different methods and electrolytic solutions that simulate the biological environment has also been investigated. This approach allows us to confirm that the low-carbon cobalt alloy processed by MIM exhibits an adequate equilibrium between its mechanical and corrosion behaviour, with a notable performance during fatigue and wear tests. In the light of these findings, the use of this material for biomedical applications is discussed.

Modeling and numerical simulation of a 5 kg LaNi5-based hydrogen storage reactor with internal conical fins

Hydrogen absorption by ~5 kg LaNi5 in a metal hydride reactor is simulated. A cylindrical reactor (OD 88.9 mm, Sch- 40s, SS 316) with internal conical copper fins and cooling tubes (1/4”, SS 316) carrying water at 1 m s−1 and 293 K (inlet) is considered. Designs with 10, 13 and 19 equi-spaced fins and 2, 4 and 6 cooling tubes are explored. Hydrogen (15 atm) is supplied through a coaxial metal filter (OD 12 mm, SS 316). Conical fins offer enhanced heat transfer through higher surface area and funnelling effect for efficient loading of metal hydride powder. 19 fins + 6 tubes design requires 290 and 375 s for 80% and 90% hydrogen saturation level, respectively. The fins near the water inlet regions are more effective as the water temperature is lower in these regions. Trade-off exists between times taken for saturation and the mass of metal hydride.

Fabrication and characterization of superhydrophobic PDMS composite membranes for efficient ethanol recovery via pervaporation

Bio-ethanol, clean and renewable, has proved to be a promising alternative energy resource to replace conventional fossil fuels. In its continuous production via the fermentation–pervaporation process, hydrophobic polymer membranes such as polydimethylsiloxane (PDMS) have been developed to enrich ethanol from dilute fermentation broth. However, the efficiency of current ethanol recovery via pervaporation is not high enough for large-scale bioethanol production. To address this issue, we separately fabricated two types of lotus-inspired PDMS composite membranes to combine the beneficial properties (low surface energy and super-hydrophobicity) of superhydrophobic lotus leaves with the pervaporation process and optimized the separation performance. First, we prepared lotus leaf powder/PDMS mixed matrix membranes (MMMs) to exploit the intrinsic properties of lotus leaf’s material. In addition, polydivinylbenzene (PDVB)-coated PDMS composite membranes were fabricated to mimic and make use of the properties coming from the lotus leaf’s hierarchical structure. The morphology, surface chemistry, and pervaporation performance were systematically investigated for all the membranes. And results showed that MMMs at 1.5 wt% lotus powder loading displayed the ideal dispersion condition and increased the total flux of pervaporation process by 22% (750 g∙m−2∙h−1, 6 wt%, 37 °C). For the PDVB-coated PDMS membrane, the hierarchical roughness was successfully established on the PDMS surface, which resulted in a super-hydrophobic surface with water contact angle higher than 150°. As PDVB also has preferential adsorption for ethanol, the PDVB-coated PDMS membrane showed a higher ethanol recovery performance with the separation factor and total flux increased by 13% and 30%, respectively. Therefore, it was demonstrated that PDVB coating is an effective method to fabricate superhydrophobic membranes and both the two lotus-inspired strategies are feasible in optimizing pervaporation performance for ethanol recovery.

Fused Filament Fabrication of Biodegradable PLA/316L Composite Scaffolds: Effects of Metal Particle Content

Polylactic acid (PLA) is a biodegradable polymer suitable for fabricating porous scaffolds in bone tissue engineering. Fillers are often added into PLA matrix to fabricate composite scaffolds in order to improve the performance of pure PLA. In the present study, we fabricated PLA/316L composite scaffolds with stainless steel particle contents from 5 vol% to 15 vol% using fused filament fabrication (FFF) process. The effects on dimensions of pore and strut, surface roughness, as well as thermal, mechanical, and in-vitro degradation properties of the scaffolds were studied. The results showed that the dimensional accuracy was improved, and the surface roughness was tailored by the addition of steel powders that were dispersedly distributed on the strut surface. In addition, PLA/316L composite scaffolds exhibited a lower coefficient of thermal expansion than pure PLA, while glass transition temperature and crystalline phase transition temperature were not significantly affected by steel powder. Moreover, compressive strength and elastic modulus were enhanced when powder loading was set at 10 vol% or 15 vol%. In-vitro degradation tests showed no significant differences on degradation rates between PLA and PLA/316L composite scaffolds.

Effect of powder loading and testing condition on the different properties of metal injection molding parts

In the present fast-growing manufacturing sector, rapid prototyping has been gaining much attention for its low design to the manufacturing time interval. However, most of the recent development in rapid prototyping is concentrated either on metals or polymer. Iron-based metal powder and high-density polyethylene (HDPE) are some of the most commonly used feed materials for rapid prototyping due to their favorable properties. In the present study, an alternative composite material has been suggested that can provide the easy manufacturability of polymer with better mechanical and electrical properties of iron powder. The characterization of composite material properties has been done by analyzing the flow properties, electrical conductivity, and mechanical structural properties of the material. It has been observed that at a higher strain rate, the tensile load carrying capacity of the material increases. The electrical properties study shows that the material follows Ohm’s law. The melt flow properties reveal that formed composite can attain high flowability at elevated temperatures. The surface morphology of the fracture surface shows a subtle mixing of composite material. The morphology study also shows that the pull out mechanism leads to crack propagation and failure of the part.

Rheological Investigation of Prealloyed NiTi Shape Memory Alloy Powders

Usage areas of Nickel-Titanium shape memory alloys (SMA) have become widespread gradually and new production techniques on these alloys have been improved nowadays. Especially its unique shape memory effect (SME) and employability in many areas have a crucial role in making it widespread. In experimental works, rheological studies have been done for powder injection molding by using prealloyed NiTi powders which are 10 µm, 14 µm and 30 µm sizes. In this study, SEM, EDS, TG, DTA and DSC analyses have been used to determine rheological properties, transformation temperatures and appropriate binder system. Polypropylene, polyethylene glycol 8000 and stearic acid have been used for appropriate prescription system in the work. To determine the optimum production conditions with obtained prescription, different powder-binder rates (60-70 wt% powder) between 160˚-200˚ temperature ranges have been tried. Since PEG series binder has been used in production of parts, two stage debiding process has been carried out. The best molding quantifications have been determined with powders which are 10 µm and 14 µm sizes and 62-64% powder loading rates.

The Influence of Different Compounding Sequence and Peanut Shell Powder Loading on Properties of Polylactic Acid/Thermoplastic Corn Starch Biocomposites

Three different blending sequences were used to prepare the peanut shell powder (PSP)‐filled polylactic acid (PLA)/thermoplastic corn starch (TPCS) biocomposites. The blending sequences can be summarized as (1) S1: PLA was added, followed by TPCS and PSP, (2) S2: PLA was added, followed by PSP and TPCS, and (3) S3: TPCS was added, followed by PLA and PSP. Various loadings of PSP filler were used from 0 to 40 wt%. The correlation between different blending sequences and PSP filler loading of PLA/TPCS biocomposites were discussed in terms of processing torque, tensile properties, surface morphology, and thermal degradation. Results showed that S1 system is the best blending sequence to prepare PLA/TPCS biocomposites compared to S2 and S3 systems. S1 system had established the low stabilization torque, better tensile strength, elongation at break, and thermal stability. Scanning electron microscopy (SEM) analysis of S1 system revealed better adhesion between filler and the matrix. Incorporation of PSP had influenced the properties of PLA/TPCS biocomposites. Increment of PSP loading increased stabilization torque and tensile modulus while decreasing tensile strength, elongation at break, and thermal stability of PLA/TPCS biocomposites. SEM analysis also managed to detect holes and cavities as the filler pulled out on the tensile fractured surface due to poor adhesion between filler and matrix.

Effect of slurry composition on the microstructure and mechanical properties of SS316L open-cell foam

This experimental study systematically examines the effect of slurry composition on the microstructure and mechanical properties of open-cell foams, by altering the binder concentration and powder loading of SS316L slurries used in the template replication foam fabrication. The slurry and foam morphologies were observed by Scanning Electron Microscopy (SEM), whereas the rheological properties of the slurry were obtained using a rotational viscometer and parallel plate rheometer. Foam strut densities were measured by a gas pycnometer, which subsequently allowed for the calculation of foam porosity. The mechanical behaviours of the foams were attained through compression test. Results show that increasing both binder and powder contents lead to an increase in slurry viscosity, foam bulk density, green strut density and mechanical strength. A process window for foam fabrication was also proposed based on macroscopic foam morphology, rheological and mechanical properties, and corrosion behaviour of the resulting SS316L foams. Based on the proposed process window, the binder concentration is suggested to be within 10 vol% and 14 vol% and powder loading within Φ = 0.75 and 0.80. This study demonstrates that the microstructure of foam produced by the template replication method can be well-controlled by optimising the composition of the slurry, which is able to attain a higher compression strength than that in the conventional range of Gibson and Ashby scaling law.

Sound absorption performance of sustainable foam materials: Application of analytical and numerical tools for the optimization of forecasting models

Traditional models used to predict acoustic properties of poroelastic materials are usually applied to fibrous layers or polyurethane foams. However, for new materials like complex cellular foams these procedures may not be applied due to the different cell microstructure. To this aim, the sound absorbing properties of novel sustainable foam materials are investigated as a function of the nature and loading of waste powders and their effects on the microstructure and the acoustic properties. The foams are prepared from naturally occurring alginates that are in situ polymerized. The morphology and the acoustic properties of the foam-cells appear linked to the particle size distribution of the starting powder. Determination of the parameters of Johnson–Champoux–Allard acoustic model (tortuosity, viscous characteristic length, thermal characteristic length, porosity and flow resistivity) was performed using five different forecasting methods, including traditional analytical model for fibrous materials as well as inverse procedure. A new procedure for tortuosity computation of foam is proposed and validated. Transfer Matrix Method calculation of the absorption coefficient was performed and compared with the experimental data, in order to assess the validity of the model. Indirect method technique is demonstrated to be dependent on experimental measurement of thermal characteristic length.

Flexural and Izod Impact Properties of Sugarcane Powder Reinforced Epoxy Composite

Currently, the studies of the mechanical behaviour of natural fibre composites have become influential among researchers due to its environmentally friendly, useful by-product and cheap. Due to this it becomes a potential material to be included in the composite materials as a reinforcement. The aim of this study is to investigate the mechanical properties of sugarcane powder reinforced epoxy composites under flexural and Izod impact tests. The sugarcane powder was processed using the crushing machine and planetary mono mill machine and it was added into the epoxy matrix with four different compositions (5 vol%, 10 vol%, 15 vol%, and 20 vol%). The morphological surfaces of the composite after the mechanical tests were observed using a Scanning Electron Microscope (SEM). It was found that the impact strength of the composites decreased with the increase of powder compositions with a range of between 5.7 kJ/m2 to 2.7 kJ/m2. The flexure modulus, on the contrary, showed an increment trend with the increase in powder loading with a modulus ranged in between 757 MPa to 1208 MPa. The potential of this natural fiber have significant contribution on the properties of natural fibres polymer composites. Natural waste consumption of sugarcane fiber could decrease the usage of synthetic polymers and provide the environmental friendly material for further application.

Silicone-based alumina composites synthesized through in situ polymerization for high thermal conductivity and thermal stability

Silicone-based alumina composites for high thermal conductivity and thermal stability were fabricated through in situ polymerization, in which silanol groups were formed by a hydrolysis reaction with methyltriethoxysilane (MTES), dimethyldiethoxysilane (DMDES) and phenyltrimethoxysilane (PhTMS). Then, the silanol groups were polymerized in situ on the surface of alumina powders, which greatly improved the wettability and dispersity of the hybrid alumina powders in the matrix. When the hybrid alumina powder loading was 80 vol%, the silicone-based alumina composites presented a thermal conductivity of 2.92 W m−1 K−1, which was 15.3 times higher than that of the pure silicone resin. Furthermore, the silicone-based alumina composites showed a high thermal stability with a weight loss of less than 2.2% at 400 °C.

Investigation on Green Properties of Magnesium Alloy AZ31 Feedstocks Molded via Metal Injection Molding Process

Powder loading is an important parameter because of its role in part shrinkage, dimensional stability, and final density. Thus, this research investigated the properties of the molded magnesium feedstocks in determining the best powder loading for producing magnesium part through metal injection molding process. In this research, the feedstocks with three magnesium alloy AZ31 powder loading of (63, 65, 67) vol%, was prepared comprising the binder component of paraffin wax, high density polyethylene, waste plastic, and stearic acid (PW/HDPE/WP/SA) with weight fraction 55/21/14/10, respectively. After injection molding, the density, diamensional accuracy, and strength of the green part was investigated. The findings reveal that 65 vol% of powder loading resulting to the best green properties.