Boron carbide, one of the boron icosahedra cluster compounds, exhibits attractive thermoelectric properties.

However, boron carbide is hard to sinter because of the strong covalent bonding of boron.

We focused on the Reaction Boronizing Sintering (RBS) method to sintering of boron carbide materials. In RBS, the eutectic liquid phase between metal and boron promotes the densification of the borides. In this study, the effects of metal addition on the thermoelectric properties were investigated. Boron carbide base materials were synthesized by powder metallurgy method using SPS from B, C, and metal powders, Mn and Ni.

According to XRD measurement of SPSed materials, boron carbide and metal boride, MB or MB₂, were appeared. Microstructural observation by SEM results showed that phase formations of metal boride depend on additive metal species. Higher thermoelectric performance can be expected by further optimizing of the SPS condition and grain size and introducing of a mechanical milling process.

In this study, the microstructural and thermoelectric transport properties of Al₂O₃ nanofibers (6 wt. %) doped heat-treated p-type BiSbTe (BST)/Al₂O₃(F) composites were studied. The findings were compared with those of BST/Al₂O₃(S) composites containing spherical Al₂O₃ particles. Initially, BiSbTe powder was manufactured using a water-atomization technique, and BST/Al₂O₃ composite powders were prepared through mechanical alloying, followed by spark plasma sintering to achieve a bulk compact specimen. Further, the bulk composites were heat treated at 743 K to evaluate the thermoelectric properties of the Al₂O₃ doped BiSbTe alloy. The powder morphology of BST/Al₂O₃ milled powder is irregular and in the range of tens of micrometers. The bulk composites' fracture surface showed the lamellar microstructure with random orientations. The temperature-dependent electrical conductivity (σ) trend indicates the highly degenerate semiconducting behavior with marginal variations for both the composites and the +Ve sign of the Seebeck coefficient (S) with its maximum of 206 μV/K at 425K for the BST/Al₂O₃(S) composite. Finally, the maximum power factor (S²σ) of 2.0 mW/m. K² at 325K was observed for BST/Al₂O₃(S).

In this study, the SUS316L gas filter having double layered pore structures was fabricated and pore characteristics were analyzed after coating spherical powder and flake-shaped powder on a tube-shaped pre-sintered SUS316L support using a wet powder spraying (WPS) process. In the WPS process, slurry composed of metal powder, solvent, and binder is sprayed onto the surface of a support tube with a single coarse pore structure. The powder used in the fine pore structure layer was mixed with flake-shaped and sphere-shaped powder in ratios of 3:1, 1:1, and 1:3, respectively. In order to increase the uniformity of the filter surface structure, the surface of the filter was rolled after sintering and the resulting microstructure was analyzed. The thickness of the manufactured gas filter having double pore structure was checked through OM and porosity was measured using the Image analysis program. In addition, air permeability was measured using gas permeameter.

The accurate detection and clear identification of ethylene has been a major challenge, owing to its low chemical reactivity and severe interference with other gases, including water vapor. In this study, we devised a novel sensor capable of detecting ethylene using ZnO nanoflowers embedded with exsolved Ni nanocatalysts. It exhibited remarkable gas selectivity and is expected to possess excellent thermal stability in terms of robust metal-support interactions in the nanocatalysts.

A compressive strength limit is one of critical parameters for thermoelectric materials. In this study, we synthesized a single crystal of Yb-filled Co–Sb based skutterudite. We assessed the compressive pressure dependence of internal strain using high-resolution synchrotron radiation X-rays at SPring-8. The prepared single crystal was identified as Yb_0.148Co₄Sb_12.54, with a lattice parameter of 9.0504 Å. Compressive testing was performed until the sample fractured, revealing a compressive strength limit of 591.3 MPa. The stress–strain curve exhibited a nearly constant slope for strains exceeding 0.07%, leading to an estimated Young’s modulus of 154.6 GPa.

Yb_0.3Co₄Sb₁₂ skutterudite, which is known for its ability to directly convert heat into electricity as a thermoelectric material, is typically manufactured in bulk via pressure sintering. In order to improve productivity, enhancing sinterability to reduce the applied pressure is crucial. Therefore, one approach for improving sinterability involves testing the application of a sintering aid. In pressureless sintering experiments performed under vacuum, Yb_0.3Co₄Sb₁₂ skutterudite showed minimal sintering progress, even at temperatures approaching its decomposition point. Introducing of Mn fine powder as a sintering aid alongside Yb_0.3Co₄Sb₁₂ under no pressure resulted in the formation of a neck structure, with the surrounding area showing evidence of an Mn–Sb phase solid solution near the mixed Mn powder. A liquid phase forms near the eutectic point owing to eutectic reactions between Mn and Sb, facilitating element diffusion and sintering. Therefore, Mn_1.1Sb, a compound near the eutectic point, was chosen as a sintering aid. In hot-pressing experiments at various pressures, the density of the Yb_0.3Co₄Sb₁₂ sintered bodies decreased at pressures of 35 MPa or less when Mn_1.1Sb was not mixed in. However, the sintered bodies containing Mn_1.1Sb maintained a high density even at low pressure (10 MPa). Comparing the sintered bodies hot pressed at 15 MPa, the sample without Mn_1.1Sb exhibited increased electrical resistivity and decreased thermal conductivity, whereas the sample mixed with Mn_1.1Sb showed electrical resistivity and thermal conductivity equivalent to those of the sintered body at 68 MPa. The dimensionless figure of merit ZT, representing thermoelectric performance, was also high at ZT = 1.23 at 500°C.

Metal binder jetting promises cost-effective end-use parts, but quality hinges on green part density. Traditional density measurement methods (e.g., Archimedes, geometric) require extra effort and equipment. This paper presents an in-situ density prediction tool using process images to reduce cost and time. The powder bed is photographed layer by layer with an integrated camera system. Process images are then analyzed using semantic pixel coloring in Python. Subsequently, the layer contours are approximated by unit cells, which are assigned a relative density by counting colored pixels indicating binder infiltration. Although predicted and actual green part densities have a weak linear correlation (R² < 30%), a significant linear relationship (R² > 96%) was found between predicted density and the drift from the geometric density, allowing a reliable forecast of the green part density with an average accuracy of 98.28%.

Aluminum (Al) is one of the most important metals from an industrial viewpoint because of its superior electrical and thermal conductivity, light weight, low cost etc. However, it is well known as one of metals with low sinterability due to the thin but stable oxide layer on the particle surface. This study demonstrates the possibility of Al powder in a powder metallurgy field, especially additive manufacturing techniques, by using lanthanoid metal compounds as sintering aids. Newly developed Al gas-atomized powder recorded sintered density over 97% of that of bulk Al without any pressure, while commercially available Al gas-atomized powder became lower than 83% under the same condition. This sinterability enhancement is attributed to a novel chemical reaction route between Al particle surface and lanthanoid metal cation during the sintering event.

Binder jetting (BJT) metal additive manufacturing uses binder to bind metal powders and build metal parts. Binder jetting has low equipment costs and is highly scalable. However, parts printed by BJT process are difficult to be high density. Conventional densification methods require high temperatures and long sintering hours, but this method results in larger grains and lower strength. Therefore, both densification and fine grains are necessary. This study discusses how pre-sintered body at low temperatures was manufactured, and hot isostatic pressing (HIP) them. However, a pre-sintered body at low temperatures has interconnected open pores. If there were interconnected open pores, HIP can't ensure density. To solve this problem, this study attempted to eliminate the interconnected open pores by coating them with slurry using fine powder. The fine powder on the surface was densified and eliminated interconnected open pores. As a result, a high-density and fine-grained specimen was obtained.

Ceramics materials are widely used in various fields due to their exceptional properties, such as heat resistance, chemical stability, and good mechanical properties. For the development of advanced ceramics, the demand for sophisticated ceramics structures with desired properties has been increasing. Additive manufacturing is deemed as a rapid moldless, prototyping manufacturing method that enables the fabrication of complicated ceramic components. However, after the shapeforming process, subsequent sintering process is important to obtain a rather dense sintered structure exhibiting desired properties, and preferably at a lower sintering temperature to reduce the load on the environment. In this study, the electrostatic assembly method was used to achieve a controlled formation of alumina-alumina ceramic composite particles, exhibiting a homogeneous distribution of additive particles on core particles. This enabled an improved sintering process leading to the formation of void-free and denser microstructure using the electrostatically assembled composite particles that exhibited better packing density compared to those of mechanically mixed powder. Enhancing the green body sintering using ceramic composite particles could be beneficial in ceramic materials development.

The specimen was prepared using the material extrusion additive manufacturing (MEX/M) process. Shot peening was performed using 304 stainless steel media with two different shot sizes (60 μm and 200 μm) at the pressures of 2, 4 and 6 bar. Surface quality was assessed through surface roughness measurements. The results indicated improved surface quality under all processing conditions, with larger media being more effective. Furthermore, shot peening effectively eliminated the Al₂O₃ particles on the surface. Phase analysis was conducted using X-ray diffraction, while microstructural analysis was performed using optical microscopy and scanning electron microscopy. The results showed that martensite formation was observed near the surface and surface microcracks under all peening conditions after shot peening. Mechanical properties, specifically microhardness at a depth of 10 μm, revealed that the larger media and higher peening pressure significantly enhanced surface hardness.

Metal Material Extrusion Additive Manufacturing (M-MEAM) is a building process by extruding filaments composed of metal powders and polymer binder layer-by-layer. M-MEAM has been getting spotlighted because of its superior economic feasibility and accessibility than other metal AMs. In this study, 17-4PH steels were manufactured by M-MEAM with post sintering process. Heat treatments (HT) were also applied to MEAM 17-4PH sintered parts and the microstructures, mechanical properties, and corrosion properties were investigated according to HT conditions. Microstructure observation demonstrated that the size and distributions of precipitates, such as nano-size NbC and Cu-rich precipitates, were altered by HT conditions. The HT improved tensile properties (tensile strength: 1.35 GPa, yield strength: 1.11 GPa, elongation: 7.8%) which were comparable to ASTM standard and the corrosion properties were also improved. The fracture and corrosion mechanisms of 17-4PH alloy manufactured by M-MEAM was also discussed in relation with the microstructures.

Fused Filament Fabrication (FFF) can produce highly loaded filled metal powders by extruding polymeric filaments to create green parts, and then debinding and sintering to produce metal parts. The filaments employed in this paper were prepared from M2 high-speed steel (M2 HSS) powders and polyformaldehyde -based binder, which have been less discussed in previous researches of M2 HSS in FFF printing. As prepared by FFF, the green part was first catalytic debinding under oxalic acid atmosphere, followed by thermal debinding and sintering from a protective atmosphere of N₂ gas. The hardness of the specimens reached a maximum of 60.40 HRC and the average coefficient of friction (COF) was 0.481 under the condition of sintering at 1270 ℃ for 1 h, which was analyzed by microstructure. The research shows that FFF is a potential additive manufacturing technique which could fabricate M2 HSS with excellent mechanical properties.

Metal Binder Jetting (MBJ) is an indirect, non-melting additive manufacturing (AM) technique. It involves selectively spraying a polymer binder onto a powder bed, layer by layer. A green part is obtained after curing and depowdering. A debinding stage removes polymer residues before final sintering to perfect mechanical properties. Poorly controlled debinding leads to carbon contamination, causing carbide precipitation during sintering and impacting the microstructure. Thermogravimetric experiments combined with SEM observations allowed to better understand the thermal and thermochemical degradation of the polymer to achieve optimal sintering. A new debinding cycle has been developed to completely remove the polymer while limiting oxidation of the surface of the powder particles.

Sintering is one of the most crucial steps in the BJT process as it determines the final dimensions and material properties of the metal components. The layer-wise printing process induces non-uniform powder packing in green parts causing anisotropic densification during sintering. This anisotropy in shrinkage needs to be well controlled to reach specified tolerances. While the impact of sintering temperature on densification was extensively researched, the role of the debinding and sintering atmospheres is often overlooked. Therefore, this study investigated the impact of atmospheres on the sintering anisotropy of 17-4 PH stainless steel. Hydrogen and argon atmospheres were the focus of the debinding and sintering trials. The resulting shrinkage curves were connected to the obtained porosities providing insights into the effect of different atmospheres on sintering anisotropy.

Metal binder jet additive manufacturing has attracted industrial attention due to its low production costs. However, the green part strength is low and easily damaged by handling and depowdering. In addition, there are many issues in terms of the binder, such as the residual carbon from the binder in the debinder process, which inhibits powder sintering and has adverse effects on the properties of dissolved carbon in the sintering part. In this study, we investigated the binder that is cured by a thermal polymerization reaction using a thermosetting low molecular weight prepolymer. It can increase the amount of bonding components in the binder, and the green part strength is improved by thermal polymerization of the prepolymer to be high molecular weight. In addition, we designed the binder with less carbon residue by controlling the thermal curing and depolymerization temperature.

The ARBURG freeformer has been enabled to use metal feedstocks known from the metal injection molding (MIM) sector to additively manufacture green parts. By debinding and sintering these green parts, it is possible to economically produce metal components. In this paper, existing guidelines of sintering and additive manufacturing (AM) processes are compared to derive optimized part design and process parameters for the sinter-based process chain. Water-soluble support structures to maximize the freedom of design for metal parts are introduced. A variety of printing strategies for wall thickness, infill structures, and densities are evaluated according to their performance in debinding and sintering, as well as compressive strength, shrinkage behavior, and dimensional tolerance of the sintered part. A reduction in layer height from 0.2 to 0.125 mm has been achieved with a 0.2 mm nozzle to optimize the surface quality of the printed parts.

Al powders with low laser absorptivity are essentially incompatible with laser powder bed fusion, as the retention of a large number of unmelted particles leads to inferior mechanical properties in Al builds. In this study, the influences of different additives on laser-based additive manufacturing of pure Al were studied. Nano-CuO or GO sheets were coated onto the pure Al powders without apparent agglomeration via electrostatic attraction during the hetero-agglomeration process. Apart from retaining a similar shape and particle size to the initial pure Al powders, the decorated powders exhibited improved laser absorptivity and flowability, contributing to satisfactory fusion under laser irradiation. Moreover, the mechanical performance of the Al build was enhanced by the addition of these additives, which is mainly caused by the lower porosity, solid-solution strengthening introduced by Cu, O, or C atoms, and the precipitation-dispersion strengthening. This study will benefit the effective selection of reinforcing materials for Al alloy L-PBF builds.

Al-8Fe-4Ce is an aluminium alloy developed in the 80’s as potential replacement for titanium in structural applications at medium service temperatures (up to 350 °C). This alloy was specifically tailored for powder metallurgy process since both the Fe and the Ce contents are far beyond the equilibrium solid solubility. Indeed, these elements are fundamental for the mechanical properties at high temperature. Nowadays, the study of Al alloys that can withstand service temperatures higher than 200 °C has regained momentum due to the emergence of additive manufacturing (AM) as reliable manufacturing processes. Among them, laser powder bed fusion for metals (PBF-LB/M) guarantees similar cooling rates of traditional rapid solidification techniques but with the ability to produce components with a high degree of complexity. In this study, Al-8Fe-4Ce was processed by press and sinter (P/S) and by PBF-LB/M and then the obtained samples were compared in terms of microstructure and mechanical properties.

The resurgence of interest in tantalum (Ta) within the medical industry is fueled by its refractory nature and exceptional X-ray reflection properties. Despite its commendable malleability, the machining challenges of Ta necessitate the development of powder metallurgy production techniques. While Ta powder metallurgy has found application in condenser production, the deliberate retention of an oxide layer is mandated. In contrast to condenser applications, medical applications demand superior mechanical properties and the impact of oxygen, hydrogen, and nitrogen contamination on Ta is crucial. This research focused on understanding the relationship between the thermal process and mechanical properties, utilising specimens produced through metal injection moulding and lithography-based additive metal manufacturing. The investigation included traditional solvent or thermal debinding, along with an exploration of superheated steam debinding. The findings contribute valuable insights into optimising the thermal processes for Ta in medical applications.

To date, researchers have not succeeded in producing defect-free tungsten parts using laser powder bed fusion (LPBF), hindering the commercial realization of LPBF W-parts or reducing it to a few non-load-bearing products. Therefore, research on the LPBF production of components free of defects such as cracks and pores is of great interest to the refractory metals scientific community. The occurrence of such defects can be minimized by the selection of optimized LPBF parameters and by reaction-controlled response to process instabilities. This study presents the use of dimensionless numbers to predict the effect of a particular set of LPBF parameters. In addition, this study demonstrates the effectiveness of in-situ pyrometric signals in predicting the LPBF process and lays the foundation for in-situ parameter modification using pyrometric data. Although this approach is only demonstrated on tungsten, it is reasonable to assume that these principles can be applied to other materials.

In this research, the microstructure and tensile properties of Cu–2–7 mass% Al alloys in the α single-phase region on the phase diagram fabricated by laser powder bed fusion (PBF-LB) process and casting were systematically examined, and their microstructure formation mechanism and strengthening mechanism were investigated. As a result, the micro-fine cellular structures formed by segregation of Al due to the constitutional supercooling by rapid solidification phenomenon in PBF-LB process leaded to high tensile strength and 0.2% proof stress, which were much higher than those of the castings. It was revealed that the high performance of the Cu–Al alloys in α single-phase region is attributed to heterogeneous microstructure of the alloys formed by rapid solidification phenomenon in PBF-LB process.

Production of magnets by electrically heated powder rolling can potentially solve problems such as the difficulty of mass production by conventional sintering using a die upset. The purpose of this study is to investigate whether plate-shaped Nd-Fe-B magnets can be produced by electrically heated powder rolling, which is a method that has not been applied to magnets. The possibility of producing plate-type magnets through electrically heated powder rolling was determined by evaluating whether densification can be achieved, considering the rolling parameters such as the rolling load, current, and number of rolling passes. The magnet was densified in the case of the lower load and the higher current. Although density was higher with 5 passes than 1 pass, the density change was less dramatic than in the other two parameters. As a result, it was proven that the electrically heated powder rolling method has the potential to produce plate-shaped magnets.

The potential of Field Assisted Sintering Technology (FAST) as a high value manufacturing process for metals is now being realised, with the focus shifting towards the production of larger samples. The challenges presented by thermal gradients leading to grain size and mechanical property heterogeneity within larger parts is well documented. Several methods to reduce such thermal gradients have been developed but often require more complex and costly tooling design. However, the influence of initial grain size heterogeneity on the final part properties after secondary thermomechanical processing is currently unknown. Here, we apply hot rolling to a FAST-produced Ti-5Al-5V-5Mo-3Cr billet (83 mm diameter, 90 mm height) processed with a non-optimised tooling setup and processing parameters. Analysis of grain size, microstructure and hardness was performed at multiple locations in the as-FAST and FAST-rolled conditions. These results provide an indication of the importance of the initial grain size in titanium alloy FAST/SPS parts prior to secondary thermomechanical processing operations.

Ti₃SiC₂ with a nacre-like microstructure was fabricated by slip casting in a strong magnetic field followed by spark plasma sintering (SPS). To determine the effect of the grain size and texture on the mechanical properties, two textured and non-textured Ti₃SiC₂ ceramics with different grain sizes were prepared with the different initial particle size and SPS sintering temperature. A powder with relatively large plate-like Ti₃SiC₂ particles was fabricated by the templated-grain growth method. Increasing the grain size increased the fracture toughness of the textured Ti₃SiC₂ ceramics but decreased the three-point bending strength. The three-point bending strength and fracture toughness of the textured Ti₃SiC₂ with the large grain size were 812 MPa and 7.3 MPa・m^1/2, and those with the small grain size were 1045 MPa and 5.6 MPa・m^1/2, respectively. Furthermore, catastrophic failure of the textured Ti₃SiC₂ ceramics after the fracture toughness test was prevented, similarly to in fiber-reinforced ceramics.

A field assisted sintering technology (FAST) process at a range of temperatures under 20 MPa were interrupted at 0 s of dwell time to study early densification of Ti-6Al-4V samples. Powder compaction simulations were used for comparison to the early densification and quantitatively similar constructions observed to within 1.2% porosity variation. It was inferred from this validation, as well as XCT data that the increased necking in the axial direction was a feature of early densification due to the pulsed electric current percolation through the powder and resulting localised heating at particle-particle boundaries. Columnar features created by this are observed, and some qualitative visual analysis performed to quantify this necking angular development. Additionally, for these 0 dwell time samples, a process lag time was proposed, also seen in FEM simulations from previous work due to heat conduction time from the displacement of the optical pyrometer.

Spark Plasma Sintering (SPS) technology is well-known for allowing enhanced and high-performance materials to be elaborated by fine microstructure control. Nevertheless, process control (repeatability) and change in scale remain technological challenges and a check for the industrialisation of these materials at large-sized dimensions.In this study, we present the case of metal alloy sintering (TA6V, Inconel 718) combined with in-situ reinforcement (TiC) to achieve densification of Metal Matrix Composites (MMC). First, we evaluate the impact of post-treatment (mill), next, the influence of reinforcement material addition and finally the adjustment of process control (external heating, cooling rate, …).The innovative aspect of this article lies in the validation of the material on a small scale and its scale-up to the final product size and the results confirm the relevance of controlling these parameters for sintering dense, homogenous and large-sized composites as a flow production.

Effect of the electric current on the densification behavior of yttria (Y₂O₃) and zirconia (3YSZ) powders during the spark-plasma-sintering (SPS) process has been examined. The powders were densified by the SPS device under two types of die set-up; one is a conductive normal set-up, in which the powders loaded into a graphite die were sandwiched by carbon papers, another is an insulation set-up, in which the powders were sandwiched by BN powder in the die. For the 3YSZ powder, the shrinkage is independent of the die set-ups. Whereas for the Y₂O₃ powder, on the other hand, it was apparently accelerated during the initial and intermediate sintering stages and completed at more than 100 oC lower temperature in the normal die set-up than in the insulation set-up. It is expected that the DC pulsed current applied during the SPS processing enhanced the sintering of the Y₂O₃ powder. This suggests that during the SPS processing, applied pulsed electric field/current is likely to contribute to the sintering of Y₂O₃ ceramics.

We have developed Fe-Si-Al powder with Al₂O₃ insulating film and a new powder magnetic core made by compression molding and annealing this powder for reactors used in electric vehicles. This magnetic core achieves the targeted linear magnetization curve by utilizing the Al₂O₃ insulation film on the surface of the powder particles, which performs the function of magnetic resistance previously provided by gap spacers in the conventional reactor. As a result, we have achieved a 30% reduction in size for miniaturization compared to conventional reactors, a 25% reduction in core loss for lower power loss compared to the conventional model, and a reduction in the number of components. The raw material Fe-Si-Al powder was manufactured adopting gas atomization technology to achieve spheroidization and component control. The Al₂O₃ insulating film was uniformly deposited with a consistent thickness using a novel method based on a metal vapor phase reaction process. Furthermore, the strength of the core was significantly improved, which was achieved by mixing a small amount of glass powder and compression molding the core, then melting and hardening the glass during annealing. This product has been adopted in vehicles released on the market in 2022.

Energy-efficient electric motors are crucial for the progress of electromobility. Soft magnetic materials with a high silicon content, such as Fe6.5Si, offer the possibility of high electrical resistance, relatively high saturation magnetization and comparatively low power losses. However, due to the brittleness of Fe6.5Si, this material is difficult to process by using conventional manufacturing methods (such as stamping). The 3-D screen printing process enables the production of thin Fe6.5Si electrical sheets in end geometry. However, conventional methods for stacking carry the risk, that those thin brittle sheets crack during their processing. For the first time, we are demonstrating the production of monolithic electrical steel stacks by alternately printing soft magnetic and ceramic layers on top of each other. These stacks are then densified in a joint heat treatment process (co-sintering). The material and magnetic properties of the stacks will be discussed in dependence on the sintering parameters and the powder properties.

All-solid-state batteries (ASSBs) have garnered significant attention for their potential use in high-performance Li-ion batteries for next-generation electric vehicles. Warm isostatic pressing (WIP) is a promising technique for the densification of ASSB electrodes. In this study, composite cathodes consisting of a mixture of Li(Ni_1/3Mn_1/3Co1/3)O₂ and Li₆PS₅Cl were processed using WIP and assembled into test cells to investigate the correlation between the structure of the electrodes and their electrochemical performance. The structures of the electrodes were analyzed using X-ray computed tomography (CT) with synchrotron radiation at SPring-8. Electrochemical performance was evaluated through electrochemical impedance spectroscopy and charge-discharge measurements. The voids in the electrodes decreased as the WIP temperature increased, resulting in improved charge-discharge properties, which suggests a reduction in charge transfer resistance. Thus, WIP was found to be effective in the production of ASSBs.

In this study, titanium-nickel (Ti-Ni) alloy pellets with varying compositions (Ti-10Ni, Ti-25Ni, and Ti-50Ni) were fabricated using powder metallurgy. Titanium powders were mixed with different Ni contents, ball-milled, compacted, and sintered to form dense pellets with Ti₂Ni and TiNi phases in Ti-25Ni and Ti-50Ni, and approximately 50% α-Ti and 50% Ti₂Ni in Ti-10Ni. Following polishing, the pellets were anodized at 60 V in fluoride electrolyte to form anodic films preferable with nanotubular structure. The anodic oxide on Ti-10Ni exhibited a nanotubular structure, with nanotube diameters ranging from 80-100 nm, similar to those observed on pure Ti pellets. X-ray diffraction indicated that the nanotubes on Ti-10Ni were predominantly anatase TiO₂ with nickel dopants. Anodized Ti and Ti-10Ni pellets were then tested for their photocatalytic properties in reducing Cr(VI) under UV and sunlight illumination. Ti-10Ni demonstrated complete Cr(VI) reduction to Cr(III) and achieved faster photoreduction compared to anodized pure Ti. This technique offers a straightforward method for Cr(VI) removal from contaminated wastewater, highlighting its potential for industrial applications in water treatment to eliminate heavy metal ions effectively.

In recent years, Zn-based biodegradable metals were considered as one of the most promising candidates for medical implantable metals. Developing biodegradable Zn matrix composites not only could resolve the problem of insufficient mechanical properties of pure Zn, but also could give materials better biocompatibility. However, the easily agglomerative reinforcement and the poor interfacial bonding between matrix and reinforcement would greatly affect the performance of composites. Therefore, based on the above issues, we designed an innovative in situ wetting strategy to strengthen interfacial bonding and improve biocompatibility by using Ag and Fe₂O₃ modified graphene oxide (Ag+Fe₂O₃@GO) as the reinforcement of Zn-based composites. During the subsequent spark plasma sintering (SPS), Fe₂O₃ induced an in-situ redox reaction with Zn matrix, simultaneously resulting in an in-situ generated ZnO interlayer and the elemental Fe. Then, due to the elevated temperature and stress of the SPS process, elemental Fe and Ag could further alloy with Zn matrix contributing to the precipitation of secondary phase and solid solution in the Zn matrix, thereby garnering ZnO@GO/Zn-Ag-Fe biocomposites through only one-step sintering process. Refined microstructure, unique interfacial structure, enhanced mechanical properties were confirmed in the Ag+Fe₂O₃@GO/Zn biocomposites. This work could provide an inspiring and creative approach for the interfacial design and biofunctionalization of advanced Zn matrix biocomposites.

PM technology is considered as a sustainable way of manufacturing high performance parts. Recently, the electrification trend in global industry requires rather higher performance and tighter tolerance of PM parts than ever. Therefore, a suitable manufacturing process needs to be selected based on the stringent component requirement, reaching near full density in the surface working area. This work presents an investigation on manufacturing, mechanical properties including durability bench test and NVH test of surface rolling densified gears aiming at high performance PM parts. The fatigue strength of standard PM FZG gear made by surface rolling densification exhibits comparable results to common steels. The bench test of surface rolling densified PM intermediate gear in reduction gearbox unit of BEV looks quite promising. Besides, PM gear could also have similar NVH performance and static load capacity like wrought steel gear.

An efficient gear design requires minimal safety margins in order to realize a full material utilization in terms of load capacity. This leads to a necessity of increasingly accurate calculation methods for the load capacity of gears. In this paper, a method for the calculation of the stressability of surface densified powder metal gears considering local material properties is presented. The approach to consider local porosity characteristics for the calculation of the gear load capacity is implemented by an image-processing tool that analyses metallographic micrographs. The stressability is calculated based on the local porosity characteristics, regarding porosity distribution and local pore morphology. Based on this, the local load capacity can be calculated by comparing the local stress profile resulting from the tooth mesh and the local stressability profile.

Parking support parts are used for the parking lock system, which keeps a vehicle when it is parked. These parts have a wide variety of shapes depending on the layout of the transmission unit. In applying the PM technology to parking support parts, we advanced techniques such as powder removal compacting, undercut compacting, and irregular-shaped two-piece compacting by proposing product shapes suitable for net shape manufacturing. Furthermore, partial laser hardening was applied where wear resistance is required, ensuring accuracy. This method contributed to a 94.5 % reduction in CO₂ emissions compared with conventional carburizing and quenching and enabled the development of environmentally friendly parking support parts.

ISO Standard 23519:2010 defines the surface roughness of sintered metal parts: Rk and Rpk, and it intends to provide relevant surface roughness data regardless of porosity,- however the data reliability tends to be insufficient in practice. The following parameters might influence the surface roughness data in accordance with the standard such as; measuring probe, instruments, filters, and others. The effect of such parameters was investigated and compared with an optical method using white light interferometry. 3 different measuring instruments were used. The measured surfaces of specimens having density of 6.4, 6.8 and 7.2 are punch facing side. In this study, details of the results are presented.

The optimization of tribological systems is crucial for increasing the efficiency of mechanical systems. The use of advanced materials, specifically self-lubricating composites, is an alternative to reduce mechanical losses and increase the durability of components. In this study, a connecting rod with self-lubricating material was developed, with a Fe0.5Si4Ni matrix and 6.5 vol% graphite and 1 vol% hBN as solid lubricants, using existing industrial infrastructure in the laboratory. Given the novelty of the material, we not only controlled microstructure and properties but also evaluated dimensions to ensure optimal bearing performance. Using statistical process control tools, along with microstructural and tribological analyses, we identified processing parameters to minimize dimensional variability and replicate composite properties. The results showed the technical potential of producing an industrial-level component with the self-lubricating composite, achieving a Cp close to 3.3 and a friction coefficient of 0.14.

One of the strategies to improve mechanical performance in metallic materials is the design of microstructures. For instance, bimodal microstructures can yield a good balance between strength and ductility. However, microstructure engineering cannot be easily performed by conventional processing techniques such as casting. With this aim, powder metallurgy offers high versatility, allowing the modification of the powder prior to sintering, as well as different consolidation techniques that highly influence the resulting microstructure.This work investigates the combination of surface deformation of small sized powder particles by mechanical milling with rapid sintering by Spark Plasma Sintering to manufacture CoCrMo parts with advanced properties. The results show increased hardness through grain size refinement, promising for biomedical applications.

Lithography-Based Metal Manufacturing (LMM) emerges as an advanced additive manufacturing (AM) technology dedicated to crafting functional metal components with superior surface aesthetics and heightened feature resolutions compared to alternative AM methodologies. LMM employs the concept of photopolymerization in metal manufacturing, where metal powder is intricately dispersed within a light-sensitive resin, forming a three-dimensional structure through layered exposure to light.The printed components undergo a subsequent debinding and sintering process, akin to other sinter-based metal manufacturing technologies. Following these steps, mechanical properties comparable to those achieved through Metal Injection Molding (MIM) can be realized. Additionally, the as-sintered parts exhibit Ra surface roughness values below 2 μm.In this work, we explore recent advances in the biomedical field, showcasing application examples in dentistry and surgical tools. Alloys of steels and titanium find utility in these applications, exemplifying the versatility of LMM in contributing to advancements within the healthcare sector.

Metal additive manufacturing (AM) enables the design of complex fuel injectors for gas turbine applications. Despite its advantages, AM injectors display rougher surfaces than conventional counterparts, adversely affecting spray performance through increased droplet size and the promotion of non-circumferential sprays. Design enhancements are believed to mitigate the surface roughness limitations, thereby improving the overall performance of the injector. However, surface roughness is dependent on the AM method chosen to produce the injectors. This study provides a baseline for the correlation between surface roughness and spray performance for plain orifice fuel injectors manufactured in 316L stainless steel by Metal Binder Jetting (MBJ) and Powder Bed Fusion – Laser Beam (PBF–LB). Surface roughness and manufacturing challenges, like shrinkage, significantly impact spray characteristics in smaller channel PBF-LB and MBJ injectors, compromising their spray quality and necessitating additional post-processing steps. Larger channel injectors perform better in maintaining circumferential spray uniformity and directional stability.

PBF-LB/M offers efficient production of complex and functional metal components. Research shows that the mechanical performance of components can be enhanced by incorporating biomimetic shapes, such as banana pseudo stem-inspired biomimetic beams. This work addresses three mechanical topology optimization problems, using AlSi10Mg. Leveraging these models, novel component designs featuring biomimetic beams and novel node designs were developed based on the input topology optimization. The new biomimetic component designs were compared to their topology optimization counterparts that were used as references. Numerical analyses of mass and structural integrity were performed to evaluate improvements. Lightweight biomimetic component designs for additively manufactured components were developed using the developed methods. Weight savings of 12.5-30.3 % were achieved compared to the input topology optimization results. However, further research on the design methodologies is needed to ensure that the mechanical stress criterion is also met within the nodes of the generated biomimetic designs.

Ni-base superalloys are commonly used in aircraft engines due to their exceptional combination of high temperature strength, toughness, great corrosion and oxidation resistance. Superalloys with high γ´ volume fraction, such as Astroloy, are desirable for high temperature applications, in combustors and turbines. However, these alloys are difficult to process by conventional cast and wrought, thus Near Net Shape Hot Isostatic Pressing (NNS-HIP) is the preferred manufacturing option. To increase the as-HIP properties, tedious post-heat treatments are currently applied. This work analysed the microstructural evolution after several heat treatment and relates it with the mechanical properties. Heat-treatments were designed to simplify post-processing with no significant impact in mechanical properties. The microstructural analyses were performed by FEG-SEM and ImageJ to quantify the microstructural features (specifically, γ´). Tertiary γ´ have been proved to be the main strengthening face, and its size and volume fraction are directly related with material’s properties.

This study focuses on the development of a precise defect detection system for powder metallurgy small gears using convolutional neural network (CNN) technology. Through extensive data collection and analysis of images, the CNN model was trained and optimized to accurately identify common defects such as porous characteristics, cracks, and surface irregularities. The executed results validated the system's accuracy and sensitivity in analyzing the porous nature of powder metallurgy sintered parts. This work successfully addresses challenges in gear inspection and establishes a foundation for an automated quality inspection system. These achievements aim to elevate production efficiency and quality standards in the powder metallurgy industry while providing valuable insights for future advancements in inspection technologies.

In this study, Li_1+xNb_xFe_1–2xO₂ (x = 0.05~0.25) with the disordered rocksalt structure were synthesized and the electrode properties and atomic arrangement were investigated. The local structures were examined by X-ray total scattering measurements and reverse Monte Carlo modeling using the data. It is found that the lattice parameter increases with increasing the Li (Nb) content, but the M−O distance in the first coordination shell decreases due to the contribution of the Nb−O correlation. This structural change could increase the space for lithium-ion diffusion. On the other hand, Nb with high valence tends to be localized around Li, suggesting that Nb inhibits ion diffusion during charge and discharge processes. Based on these results, it is necessary to consider not only the size of the constituent cations but also their valence to design new materials.

12CaO･7Al₂O₃ mayenite has positively charged cage which can encapsulate anions inside it. We have successfully synthesized mayenite from hydrogarnet precursor prepared by liquid phase method. In this study, mayenite particles have been fabricated with doped metals such as Sr and Si for ion storage application. Mayenite was obtained by heat treatment of hydrogarnet prepared with Sr or Si source in liquid phase method. C_12-xSr_xA₇ and Ca₂₄Al_14-xSixO₃₃ can be obtained using hydrogarnet precursor. The maximum amount of doped Sr was about 50 mol%, whereas that of doped Si was about 20 mol%. The SEM-EDX analysis indicated that Sr and Si were highly distributed in C12A7 particles.

Mg₂Si is a promising n-type thermoelectric material for thermoelectric power generation in the middle range of temperature and is lightweight. Both Mg and Si, the raw materials of Mg₂Si, are abundant in the Earth’s crust. However, it is hard to make Π-type modules since p-type Mg₂Si materials have not been developed enough, and Mg₂Si has low fracture toughness. The transverse thermoelectric effect occurs by tilting the multilayer composite of thermoelectric and metallic materials. The effect makes it possible to fabricate modules using only one type of thermoelectric material and to enhance mechanical strength by sandwiching the fragile Mg₂Si between metals. In this research, the molds with polylactic acid resin (PLA) were fabricated using a 3D printer. Mg₂Si and Ni powders were packed in the PLA mold, creating the tilted multilayer composite modules by spark plasma sintering (SPS). The power generation performance of the modules was then evaluated.

Metal-bonded diamond grinding wheels for machining cemented carbides are characterized by high hardness and thermal conductivity but also by low porosity and limited dressability. The addition of graphite to these bonds deliberately weakens the bond, improving dressing behaviour while simultaneously reducing bond friction. The influence of sintering parameters and the addition of graphite flakes with varying particle sizes on the grinding layer properties is investigated. Furthermore, the addition of chromium is examined and leads to an additional increase in the critical bond strength of the grinding layer. Subsequent examination of the performance of the manufactured grinding layers with chromium and graphite additions demonstrates improved grinding force ratios. Graphite’s lubricating properties and enhanced coolant delivery contribute to improved grinding force ratios, especially in wheels with higher graphite content. Grinding wheels without graphite exhibit the lowest initial grinding force ratios and lack a self-sharpening mechanism. These findings highlight the complex interplay between graphite content, chromium addition, and particle size in optimizing grinding wheel performance.

This study focuses on developing a new processing route for ferrous matrix composites reinforced with niobium carbide by producing the reinforcement particles in situ using powder metallurgy. The aim is to improve the interfacial adhesion between matrix and reinforcement compared to traditional ex situ methods. Computational thermodynamics and kinetic analysis were used to optimize the raw materials and processing parameters. The raw materials are mixed, uniaxially pressed, and sintered in a tubular furnace. The study finds that liquid phase sintering improves densification but also leads to clustering, niobium-free regions, and abnormal grain growth. The optimal combination of porosity and microhardness is 16.5 ± 0.7% and 952 ± 82 HV0.05, respectively. Although there is room for further adjustments in processing, this study lays the groundwork for creating valuable materials using Brazilian strategic raw materials and technology.

Transition metal carbides and nitrides demonstrate very interesting electrocatalytic properties, close to those of noble metals. Indeed,platinum being a scarce and expensive element, carbides and nitrides could be an interesting alternative to make this technology economically viable. Recently, different authors reported promising (electro)catalytic properties of molybdenum carbides and nitrides. Herein we report the synthesis of Mo nitrides and carbides from original routes using transition metal cluster-based precursors or laser pyrolysis. The resulting nitrides and carbides were characterized by several complementary techniques (XRD, BET, SEM, etc.). These innovative modes of synthesis afford nanostructured compounds and the evaluation of Mo5N6 for the WGS reaction is reported.