Powder Extrusion Research Articles

Optimising 3D printed medications for rare diseases: In-line mass uniformity testing in direct powder extrusion 3D printing

Optimising 3D printed medications for rare diseases: In-line mass uniformity testing in direct powder extrusion 3D printing

Microstructure and Properties of Gradient Ti(C,N)-Based Cermets by Powder Extrusion Additive Manufacturing

Ti(C,N)-based cermets are crucial for high-speed cutting tools and other high-temperature applications, yet there remains a considerable gap in their preparation controllability, fracture strength, and toughness compared to cemented carbide. Despite numerous studies having focused on modifying the hardness and toughness of Ti(C,N)-based cermets by varying process parameters and chemical compositions, this research has used gradient Ti(C,N)-based cermets produced by powder extrusion additive manufacturing (PEM) technology, which is rare. This study developed the gradient structure layer by layer using PEM. The microstructure of the printed and sintered parts was studied, and the hardness, fracture toughness, and bending strength of the gradient material were analyzed. The gradient material demonstrates superior mechanical properties compared to traditional Ti(C,N)-based cermets, with a hardness of 1760−23+39 HV20, a fracture toughness of 8.5−0.4+0.3 MPa·m1/2, and a bending strength of 2047−43+22 MPa. The research will assist researchers in assessing the potential application of PEM and broaden the application fields of gradient Ti(C,N)-based cermets.

Controlling η phase distribution and its effects on carburized graded cemented carbides via extrusion additive manufacturing

Functionally Gradient cemented carbides (FGCCs) are promising substrates for polycrystalline diamond composite (PDC). Carburization is the mainstream method for preparing FGCCs, but limited carburizing depth often leads to excessive retention of brittle low-carbon phase (η phase) in the core. This study used Powder Extrusion 3D Printing (PEP) to create dual-layered cemented carbide parts with varying thicknesses of low-carbon outer layers. After pre-sintering and carburization, three new FGCCs were produced. Results showed the η phase was confined to the interface region before carburization. With 3.84 mm carbon-depleted layer, the maximum η phase thickness was 1/10 compared to homogeneous FGCCs, with Co gradient of about 4.5 wt%. The two FGCCs with thinner low-carbon layers had smaller Co gradient with no detected η phase. Additionally, the novel FGCCs displayed enhanced fracture toughness in the core. This study achieved controlled η phase distribution, offering new insights for fabricating high-toughness carburized FGCCs without the η phase.

3D-Printed (CoCrFeMnNi)3O4@C-GR dual core–shell composites: Multilevel control and mechanisms of microwave absorption performance

With the rapid development of modern electronic technology, there is an increasing demand for microwave-absorbing materials in various applications. These include reducing electromagnetic interference, enhancing communication quality, and ensuring stealth capabilities for military equipment. This study has developed a novel microwave-absorbing material, which is a composite system consisting of a high-entropy dual-core–shell (CoCrFeMnNi)3O4@C combined with graphene (GR), and is composed of polylactic acid (PLA) as the matrix. The material is prepared through a process involving high-temperature oxidation, carbonization to form the shell, and Powder extrusion molding techniques. The results demonstrate that when the dual-core–shell (CoCrFeMnNi)3O4@C microspheres are added at a loading of 20 wt%, and GR is added at 7 wt%, with a thickness of 2.22 mm, the composite material achieves a minimum reflection loss (RLmin) value of −51.36 dB and an effective absorption bandwidth (EAB) of 5.20 GHz. This excellent performance is attributed to the lattice distortion, a large number of oxygen vacancies, and abundant heterogeneous interfaces and conductive networks within the composites. These factors work together to stimulate multiple relaxation mechanisms, enhance the magnetic loss effect, and greatly improve the microwave absorption capability. The introduction of high-entropy microspheres effectively modulates the high conductivity of GR, further enhancing the comprehensive absorption performance of the material. This study not only offers a new strategy for designing and preparing high-performance microwave-absorbing materials but also establishes a valuable scientific foundation for materials research and application in related fields.

Optimisation of powder extrusion moulding process for thick ceramic electrodes of LiCoO2 for enhanced energy-density lithium-ion batteries

Lithium-ion batteries are widely used in portable electronic devices because of their high energy and power density. To enhance the energy density of these batteries, one strategy involves increasing the active material loading by increasing the thickness of the electrodes. In previous studies, we demonstrated that powder extrusion moulding (PEM) is a scalable and efficient method for producing additive-free LTO and LFP ceramic electrodes, which exhibit remarkable electrochemical performance with thicknesses up to 500 μm. This study focuses on the preparation and optimisation of the entire manufacturing process for thick ceramic electrodes of LiCoO2 (LCO) with a high mass loading of 180 mg cm−2 using the PEM process. Different powder loadings of mixtures of LCO and a thermoplastic multi-component binder were explored to obtain a formulation suitable for rheology. The optimal formulation comprises 60 vol% of powder. After binder removal via a combination of solvent and thermal treatment, followed by air sintering, parts with varying porosities were obtained. Striking a balance between porosity and thermal degradation is crucial for achieving optimal electrochemical behaviour. Electrochemical evaluations of the electrodes sintered at 900 °C and 1000 °C revealed areal capacity values as high as 17 mAh cm−2 at C/25 and 7 mAh cm−2 at C/6.25, respectively. These values far exceed the 1−2 mAh cm−2 obtained from commercial LCO electrodes. These results indicate a strategy for the production of electrodes to fabricate lithium-ion batteries with a low ratio of inactive materials and, therefore, with higher energy densities.

Production of Permanent Magnets from Recycled NdFeB Powder with Powder Extrusion Moulding

In the last fifteen years, several groups have investigated metal injection moulding (MIM) of NdFeB powder to produce isotropic or anisotropic rare earth magnets of greater geometric complexity than that achieved by the conventional pressing and sintering approach. However, due to the powder’s high affinity for oxygen and carbon uptake, sufficient remanence and coercivity remains difficult. This article presents a novel approach to producing NdFeB magnets from recycled material using Powder Extrusion Moulding (PEM) in a continuous process. The process route uses powder obtained from recycling rare earth magnets through Hydrogen Processing of Magnetic Scrap (HPMS). This article presents the results of tailored powder processing, the production of mouldable feedstock based on a special binder system, and moulding with PEM to produce green and sintered parts. The magnetic properties and microstructures of debinded and sintered samples are presented and discussed, focusing on the influence of filling ratio and challenging processing conditions on interstitial content as well as density and magnetic properties.

3D Printing Direct Powder Extrusion in the Production of Drug Delivery Systems: State of the Art and Future Perspectives.

The production of tailored, on-demand drug delivery systems has gained attention in pharmaceutical development over the last few years, thanks to the application of 3D printing technology in the pharmaceutical field. Recently, direct powder extrusion (DPE) has emerged among the extrusion-based additive manufacturing techniques. It is a one-step procedure that allows the direct processing of powdered formulations. The aim of this systematic literature review is to analyze the production of drug delivery systems using DPE. A total of 27 articles have been identified through scientific databases (Scopus, PubMed, and ScienceDirect). The main characteristics of the three types of 3D printers based on DPE have been discussed. The selection of polymers and auxiliary excipients, as well as the flowability of the powder mixture, the rheological properties of the molten material, and the printing temperatures have been identified as the main critical parameters for successful printing. A wide range of drug delivery systems with varied geometries and different drug release profiles intended for oral, buccal, parenteral, and transdermal routes have been produced. The ability of this technique to manufacture personalized, on-demand drug delivery systems has been proven. For all these reasons, its implementation in hospital settings in the near future seems promising.

The effect of cellulose-derived binder on properties and performance of PM steels

A room-temperature extrusion technique, originally developed for the extrusion of ceramic powders, has been adapted to the extrusion of metal powders. The extrusion technology relies on cellulose-derived binders, which in traditional ceramic practices are burned off during sintering in air. In this work, the influence of hydrogen-debinding on density, carbon and oxygen levels is studied by comparing the effects of hydrogen debinding with the effects of air-debinding in as-debound and as-sintered samples. The study found debinding in hydrogen to result in significant levels of residual carbon, which promote austenite at the sintering temperature, and reduce densification. Debinding in air was effective, resulting in very low carbon concentrations and densification of up to 97 vol.-%, but also a considerable amount of oxides, which were not completely reduced during hydrogen sintering.

Microstructure, Mechanical, and <i>In-Vitro</i> Characterization of a Novel Biodegradable Zinc-Based Composite Fabricated at Room Temperature

A novel Zn biodegradable composite was produced by direct extrusion of Zn powders at room temperature. The powders were efficiently consolidated to a high relative density, and the composite reached a UTS higher than 120 MPa and elongation of almost 70%. Microstructural observations showed ultra-fine Zn grains decorated by well-dispersed ZnO clusters at the grain boundaries. The degradation behavior of the composite and an as-cast Zn reference accessed by immersion tests in HBSS for both materials were similar and gave an equivalent corrosion rate. Additional static immersion tests in DMEM + 5% FSB showed a similar corrosion rate (0.015 mm/y), but SEM analysis of the corroded surface suggested that the degradation process of each as-cast or DE consolidated composite differs. MTT assays with extracts of both as-cast and extruded composites showed similar cytotoxicity, which was dependent on the dilution of the extracts. It was concluded that the proposed methodology brings the potential for an interesting solution to produce a sound Zn-ZnO composite with good biocompatibility, satisfactory corrosion rate, and high yield strength.

Extrusion-based technologies for 3D printing: a comparative study of the processability of thermoplastic polyurethane-based formulations

Thermoplastic polyurethanes (TPU) offer excellent properties for a wide range of dosage forms. These polymers have been successfully utilized in personalized medicine production using fused deposition modeling (FDM) 3D printing (3DP). However, direct powder extrusion (DPE) has been introduced recently as a challenging technique since it eliminates filament production before 3DP, reducing thermal stress, production time, and costs. This study compares DPE and single-screw extrusion for binary (drug-TPU) and ternary (drug-TPU-magnesium stearate [MS]) mixtures containing from 20 to 60% w/w of theophylline. Powder flow, mechanical properties, fractal analysis, and percolation theory were utilized to analyze critical properties of the extrudates. All the mixtures could be processed at a temperature range between 130 and 160 °C. Extrudates containing up to 50% w/w of drug (up to 30% w/w of drug in the case of single-screw extrusion binary filaments) showed toughness values above the critical threshold of 80 kg/mm2. MS improved flow in mixtures where the drug is the only percolating component, reduced until 25 °C the DPE temperature and decreased the extrudate roughness in high drug content systems. The potential of DPE as an efficient one-step additive manufacturing technique in healthcare environments to produce TPU-based tailored on-demand medicines has been demonstrated.

Mechanical properties of a novel tungsten fiber-reinforced tungsten composite prepared through powder extrusion printing and high-pressure high-temperature sintering

Tungsten is one of the most promising candidate materials for plasma-facing materials (PFM) because of its high melting point, superior thermal conductivity, and low sputtering rate. However, its significant brittleness and high ductile-to-brittle transition temperature constrain its broader engineering applications. To address these limitations, we developed a novel tungsten fiber-reinforced tungsten (Wf//W) composite. This composite utilizes commercially available black tungsten wire mesh as the fiber reinforcement phase with a mass ratio of 1 %. The material was synthesized through a combined Powder Extrusion Printing and High-Pressure, High-Temperature sintering process, achieving a relative density exceeding 99 %. Additionally, the composite exhibits a maximum hardness of 589 ± 10 HV, attributable to the presence of high-density dislocations in the matrix. Its compressive strength reaches up to 1530 MPa, and the plastic deformation strain is as high as 15.8 %, both of which are outstanding compared to existing research. These findings offer an alternative route for producing high-density Wf//W materials, in addition to chemical vapor deposition method and powder metallurgy technique.

Achieving high thermal conductivity of Al–50Si alloy through heat treatment and its microstructural evolution

Al–50Si alloys were prepared by powder extrusion and characterized for electronic packaging. The optimization of powder size, extrusion temperature, and heat treatment parameters was performed to enhance the microstructure and thermo-physical properties. The alloy exhibits a high relative density >99 %, a low coefficient of thermal expansion (CTE) < 10 × 10−6/K, and a good thermal conductivity (TC) ∼117 Wm−1K−1 achieved by employing a large size powder and high extrusion temperature during the extrusion process. Subsequent heat treatment of the optimized alloy at 550 °C for various time reveals a fluctuating increasing trend in TC during the heat treatment process. The TC values exhibit periodic fluctuations as they alternate between increments and decrements, primarily resulting from the recrystallization and secondary recrystallization of Al grains during heat treatment process. Notably, the maximum TC value (∼159.1 Wm−1K−1) at room temperature is obtained after heating the alloy to 550 °C for 26 h. Compared to the as-extruded alloy, the TC of heat-treated alloy increases by approximately 36 %, which can be attributed to the elimination of eutectic Si and growth of Si and Al grains within the alloy. The study may shed light on the mechanism underlying the improvement in thermal conductivity of Al–50Si alloy by microstructural evolution.

Control morphology and properties in additive manufacturing of functional gradient cemented carbides for polycrystalline diamond substrates

Cemented carbide substrates contribute mainly to the strength and impact toughness of polycrystalline diamond composites (PDC). By using a PW-MW-HDPE-EVA-SA mixed polymeric binder and combining Powder Extrusion Printing (PEP) with densification sintering processes, the YG10/YG15 functionally gradient cemented carbides (FGCCs) with different powder loadings were prepared. This study focuses on exploring process feasibility and the integrated regulatory mechanisms for FGCCs morphology and performance. The results showed that the configured cemented carbide feedstocks with different powder loadings exhibited uniform composition and good shear-thinning characteristics, making them suitable for extrusion printing. The FGCC green parts formed by PEP have macro-structurally intact, dense surfaces and uniformly stacked extrusion filaments with a roughness of 12.25 μm. After degreasing and sintering, FGCCs with densities exceeding 99.43% were obtained. The shrinkage and Co gradient distribution of the inner and outer layers were regulated by powder loading design, achieving integrated control of FGCCs morphology and properties. With powder loading increase in YG15, the density of FGCCs remained stable between 14.01 and 14.03 g/cm3, the gradient dimensions difference decreased from 14.34% to 7.9%, and the maximum hardness difference increased from 78 to 121 HV1/15.

Development of Subdermal Implants Using Direct Powder Extrusion 3D Printing and Hot-Melt Extrusion Technologies.

Implants are drug delivery platforms that consist of a drug-polymer matrix with the ability of providing a localized and efficient controlled release of the drug with minimal side effects and achievement of the desired therapeutic outcomes with low drug loadings. Direct powder extrusion (DPE) 3D printing technology involves the extrusion of material through a nozzle of the printer in the form of pellets or powder. The present study aimed at investigating the use of the CELLINK BIO X™ bioprinter using DPE 3D printing technique to fabricate and evaluate the impact of different shapes (cuboid, cylinder, and tube) of raloxifene hydrochloride (RFH)-loaded subdermal implants on the release of RFH from the implants. This study further evaluated the impact of different processing techniques, viz., hot-melt extrusion (HME) technology vs. DPE 3D printing technique, on the release of RFH from the implants fabricated by each processing technique. All the fabricated implants were characterized by XRD, DSC, SEM, and FTIR, and evaluated for their water uptake, mass loss, and in vitro RFH release. The current study successfully demonstrated a great opportunity of controlling and/or tuning the release of RFH from the subdermal implants by altering the implant shape, and hence surface area, and could be a great contribution and/or addition to the personalization of medicines and improvement of patient compliance.

Feasibility study of the use of a homemade direct powder extrusion printer to manufacture printed tablets with an immediate release of a BCS II molecule

Among the various 3D printing techniques, FDM is the most studied in pharmaceutical research. However, it requires the fabrication of filaments with suitable mechanical properties using HME, which can be laborious and time-consuming. DPE has emerged as a single-step printing technique that can overcome FDM limits as it enables the direct printing of powder blends without the need of filaments. This study demonstrated the manufacturing of cylindrical-shaped printed tablets containing CBD, a BCS II molecule, with an immediate release. Different blends of PEO/E100 and PEO/SOL, each with 10 % of CBD, were printed and tested according to the Eur. Ph. for uncoated tablets. Each printed cylinder met the Eur. Ph. specifications for friability, mass variation and mass uniformity. However, only the E100-based formulations enabled a CBD immediate release, as formulations containing SOL formed a gel once in contact with the dissolution medium, reducing the drug dissolution rate.

Preparation of core-shell controlled release tablets using direct powder extrusion 3D printing techniques

Preparation of core-shell controlled release tablets using direct powder extrusion 3D printing techniques

A novel approach to prepare high density SiC ceramics by powder extrusion printing (PEP) combined with one-step sintering method

High density (97 %) SiC ceramics containing in-situ synthesized Y4Al2O9 (YAM) have been successfully fabricated by a novel PEP additive manufacturing technology combined with a one-step sintering method without any post-treatments. The process of additively manufacturing SiC green body, debinding and sintering has systematically studied. Meanwhile, the atomic structure of SiC and YAM was characterized, and the mechanical properties of sintered SiC ceramics were measured. The HRTEM results revealed the crystallographic orientation relationships between YAM and SiC as (0 4 0) YAM // (1 0 1- 1) SiC and [1 0 2] YAM // [1 2¯ 1 0] SiC for the first time. The density, Vickers hardness and three-point bending strength of the sintered SiC samples are 3.11 g/cm3, 19.35 ± 0.28 GPa and 225 ± 27 MPa, respectively. Thus, PEP combined with the one-step sintering method provides a new strategy for complex-shaped SiC ceramics with high density and mechanical properties.

Microstructure evolution and mechanical properties of a novel ultrastrong and ductile PM Ti6Al4V composite

Novel in-situ polycarbosilane (PCS)-derived TiC particles reinforced Ti6Al4V composites with ultrahigh strength and good ductility were fabricated by powder extrusion. The grain microstructure, dynamic recrystallization (DRX), texture orientation, mechanical properties and strengthening mechanisms were systematically investigated. The pyrolysis of PCS and in-situ reaction with Ti6Al4V matrix promote the formation of TiC particles and Si atoms solid-solution. TiC particles provide many heterogeneous nucleation sites for DRX and restrict grain growth by pinning effect, forming many fine equiaxed α grains. The average grain size of α-Ti is refined from 50.17 μm in as-sintered Ti6Al4V alloy to 3.17 μm in as-extruded Ti6Al4V-3PCS composite. The basal texture with {0001}<11 2‾ 0> orientation is dominant in the as-extruded microstructures, originating from the deformed α grains during β single-phase extrusion. The incorporation of PCS activates the occurrence of DRX and weakens the {0001}<11 2‾ 0> basal texture. Benefiting from the in situ formed TiC particles, solid solution Si atoms and low interstitial oxygen (O) contamination, the as-extruded Ti6Al4V-3PCS composite achieves the best combination of room-temperature strength and ductility, with 1307 ± 18 MPa in ultimate tensile strength (UTS), 1178 ± 25 MPa in yield strength (YS) and 10.0 ± 0.8% in elongation (EL), much higher than those of wrought Ti6Al4V alloy (ASTM B381). This work offers a feasible route for fabricating novel ultrastrong and ductile Ti6Al4V composites.

A Review of the Mechanical Properties of 17-4PH Stainless Steel Produced by Bound Powder Extrusion

17-4PH Stainless Steel is a mechanically high-performing alloy that is widely used across chemical and mechanical processing industries. The alloy is conventionally fabricated by cast methods, but emerging additive manufacturing techniques are presently offering an economic, efficient, and environmentally friendly alternative. Bound Powder Extrusion (BPE) is a relatively new additive manufacturing technique that is used to fabricate three-dimensional, free-form components. Investigation into the mechanical properties and behavior of 17-4PH stainless steel fabricated by BPE is vital to understanding whether this technique proposes a competitive substitute to the cast alloy within industry. Published literature has investigated the as-fabricated mechanical properties, microstructure, porosity, and post-processing heat treatment of the BPE alloy, with limited comparison evident among the papers. This paper, therefore, aims to review published findings on the mechanical properties of 17-4PH stainless steel produced by additive manufacturing techniques, with a key focus on BPE. It is important to highlight that this review study focuses on the MetalXTM 3D printer, manufactured by Markforged. This printer is among the widely utilized BPE 3D printers available in the market. The key results, together with the impact of post-heat treatments, were discussed and compared to provide a more comprehensive picture of the patterns that this alloy presents in terms of its microstructure and mechanical properties. This enables the manufacture of components relative to desired material performance, improving overall functionality. A comparison of yield strength, ultimate tensile strength (UTS), Young’s modulus, ductility, and hardness was made relative to microstructure, porosity, and density of published literature for the as-fabricated and post-heat-treated states, identifying areas for further research.

Investigation of the performance of recycled copper swarf tool electrode processed through bound powder extrusion for micromachining

This experimental study used recycled copper chips as a base material for electrode manufacturing through the additive manufacturing route utilizing the bound powder extrusion (BPE) process. Initially, the copper chips were collected from a conventional machining centre. Then, the chip size was reduced by the two-step milling process (ball-to-powder ratio, 2:1) to attain the micro-sized fine particles around 44 μm, which is the prerequisite for preparing the base material for the BPE process. Subsequently, the input parameters were optimized to a layer thickness of 0.125 mm, nozzle diameter of 1 mm, and printing speed of 20 mm/s by the Box-Behnken design approach and attained a maximum relative density of 98.57%. Finally, the BPE-recycled copper tool electrode was manufactured in 0° and 90° orientations. Further, the electrical conductivity of the tool, material removal rate, tool wear rate, and surface roughness of the machined surface of manufactured components were evaluated and compared for BPE-90°, BPE-0°, and conventional tools. The result shows that the BPE-90° tool electrode performs better than BPE-0° and conventional tools.