Pure Powder Research Articles

Influence of impurities on the use of Fe-based powder as sustainable fuel.

Sustainable energy production, inherently transient and non-uniformly distributed around the world, requires the rapid development of sustainable energy storage technologies. Recently, pure iron powder was proposed as a high-energy density carrier. While promising, challenges are faced, such as nanoparticle emissions, micro-explosions or cavitation. In this work, a screening of the impact of the most common impurities in iron sources on these mechanisms was conducted through purely thermodynamic simulations. Two idealized models were considered to obtain a range of plausible flame temperatures and emitted gases when considering a purely diffusive regime in standard conditions and stoichiometric air-fuel mixture. The flame temperature and iron evaporation are increasing with the specific energy. A strong evaporation of C, S, Mo, Cu and P is also expected. Most impurities are predicted to decrease cavitation, except for Mn and MnO. The regeneration process by hydrogen-based direct reduction in fluidized bed reactors is also discussed. MgO and CaO are the most promising additions in terms of reducing nanoparticles and porosities, as well as to improve the fluidization and reduction kinetics of the combusted products. The potential of Fe powder as sustainable fuel, already very promising, could be further improved by the addition of selectively chosen impurities.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Area-based composition predictions of materials fabricated using simultaneous wire-powder-directed energy deposition

Functionally graded materials are an emergent method for designing components with programmable site-specific material properties. These materials are typically fabricated using metal additive manufacturing tools by simultaneously feeding multiple wire and/or powder feedstocks at various rates to achieve spatial composition change. The wire-powder-directed energy deposition (WP-DED) technique is of particular interest for many functionally graded material applications by balancing the low raw materials cost of wire with the high resolution of powder. However, feeding wire and powder are inherently different processes since all extruded wire enters the melt pool, while much of the blown powder is scattered, which makes determining the composition of the build challenging. In this study, we devise a simple area-based measurement method for estimating the composition of WP-DED structures. WP-DED single beads are printed using 309L stainless steel wire and commercially pure Fe powder at five wire feed rates (0.5, 0.75, 1.00, 1.25, 1.50 mm/mm) and five powder feed rates (2, 4, 6, 8, 10 rpm). Characteristic defects including interface gaps and macrosegregation (lack of mixing) tendencies are examined. High powder feed rates (8, 10 rpm) result in interface gaps at all wire feed rates, but smooth deposition and complete mixing is achieved at low powder feed rates, particularly with lower wire feed rates as well. The area-based composition measurement method is within ±20% of energy dispersive x-ray spectroscopy measurements for all samples, showing its effectiveness as a rapid composition estimate for WP-DED materials development.

Synthesis of high-entropy Ti-Zr-Nb-Hf-Ta carbides and carbonitrides in high-speed arc discharge plasma jet

The interest in high-entropy materials has increased rapidly in recent decades due to their applications in various fields such as environmental barrier coatings, superhard and wear resistant coatings, nuclear energy, batteries, catalysts, thermoelectrics, supercapacitors, biocompatible structures, and microelectronics. In the present work, comprehensive theoretical and experimental studies are carried out to discover a new way to prepare high-entropy ceramic nanopowders of carbides and carbonitrides of IV-V transition metals. The possibility of (TiZrNbHfTa)CxNy formation is investigated using both ab initio and machine learning approaches. The chosen single-stage plasma dynamic technique allowed us to synthesize high-entropy carbide TiZrNbHfTaC5 and the corresponding carbonitrides (N up to 8 wt%) in the form of single-crystalline nanoparticles. By varying the experimental system conditions, we demonstrate not only the production of pure powders, but also the ability to apply different precursors, including pure metals and their oxides. The presented technique provides a simple and universal way to produce high-entropy nanomaterials and opens the door to the synthesis of many functional ceramic powders composed of other carbonitrides with selective nitrogen content.

Ultrasonic-Assisted Synthesis of Lead Citrate as Precursor for Preparation of Lead Oxide from Lead Sulfate

ABSTRACT In this study, an efficient method of lead recovery from lead sulfate in spent lead-acid batteries assisted by ultrasonic is developed using the citric acid–sodium citrate solution. Ultrasonic-assisted technology is employed to enhance the kinetics of lead sulfate leaching. Initially, the predominance area of the lead citrate complexes was analyzed. The study was conducted to evaluate the effect of ultrasonic-assisted technology on the kinetic behavior of lead sulfate within the citric acid–sodium citrate solution, thereby unveiling the differences between ultrasonic-assisted leaching and the non-ultrasonic-assisted leaching. Kinetic study indicated that the employment of ultrasonic-assisted technology could effectively reduce the apparent activation energy during the desulfurization process, decreasing the energy initially required from 43.27 kJ/mol to 35.15 kJ/mol. Furthermore, the ultrasonic-assisted leaching led to successful preparation of lead citrate precursor, characterized by a smaller particle size and larger specific surface area. Systematic investigations were performed on the thermal decomposition process of these precursors and the effects of calcination temperature and holding time on the properties of calcination products. It was revealed that pure porous lead oxide powder with a purity of 99.9% could be produced successfully under the conditions of calcination temperature at 350°C and holding time of 1 h. The research provides an innovative process for the efficient recovery of lead from spent lead acid batteries.

Spectrophotometric determination of olanzapine, fluoxetine HCL and its impurity using univariate and chemometrics methods reinforced by latin hypercube sampling: Validation and eco-friendliness assessments

Novel univariate and chemometrics-aided UV spectrophotometric methods were tailored to undergo the fundamentals of green and white analytical chemistry for the simultaneous estimation of a ternary mixture of olanzapine (OLA), fluoxetine HCL (FLU), and its toxic impurity 4-(Trifluoromethyl) phenol (FMP) without any prior separation. The dual-wavelength ratio spectrum univariate method was used to determine OLA and FLU in the presence of FMP in the range of (4–20) and (5–50) μg/ml, respectively. In compliance with the International Conference on Harmonization (ICH) standards, the technique was validated and established Remarkable accuracy (98–102%) and precision (< 2%) with limits of quantification (LOQs) of 0.432 and 2.002 μg/ml, respectively. Partial least squares (PLS) and artificial neural networks (ANNs) are chemometric methodologies that have advantages over the univariate method and use significant innovations employing Latin hypercube sampling (LHS), allowing the generation of a reliable validation set to guarantee the effectiveness and sustainability of these models. The concentration ranges used were (2–20), (2–20), and (5–50) μg/ml; for PLS, the LOQs were 0.602, 0.508, and 1.429 μg/ml, and the root mean square errors of prediction (RMSEPs) were 0.087, 0.048, and 0.159 for OLA, FMP, and FLU, respectively; and for ANNs, the LOQs were 0.551, 0.465, and 0.965 μg/ml, with RMSEPs of 0.056, 0.047, and 0.087 for OLA, FMP, and FLU, respectively. The developed methods yield a greener National Environmental Methods Index (NEMI) with an eco-scale assessment (ESA) score of 90 and a complementary Green Analytical Procedure Index (complex GAPI) in quadrants with an analytical greenness metric (AGREE) score of 0.8. The Red‒Green–Blue 12 algorithm (RGB 12) scored 88.9, outperforming on reported methods and demonstrating widespread practical and environmental approval. Statistical analysis revealed no noteworthy differences (P > 0.05) among the proposed and published techniques. Both pure powders and pharmaceutical capsules were analyzed via these methods.

Eco-Friendly Green Synthesis of Chromium Oxide Nanoparticles and Their Characterization and Application

In recent years the nanoparticle design synthesis methods conducted by plants replaced the traditional chemical procedures of nanoparticles preparations. This study demonstrates the environmental kindly preparations of chromium oxide nano particles (Cr2O3-NPs) using leaf extract of Mentha pulegium plant. The obtained Cr2O3-NPs was characterized by Ultra Violet /Visible spectroscopy, Fourier Transform Infra-Red (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectrophotometer (EDX) and X-ray diffraction studying. The presence of the Sharp peak at 462 nm in the Ultraviolet/Visible spectrum and the color changed by surface plasma resonance explains that Cr2O3-NPs is formed. The presence of oxygen and chromium in Cr2O3-nanoparticles is reported by EDX spectrum, which was found to consist of 32.57% Cr and 44.41% O, confirming the high purity of the Cr2O3-NPs powder. Since Scan Electron Microscope studying reported an irregular round morphology shape. In addition, X-ray diffraction studying suggested their crystalline feature by the characteristic peaks at 2θ= 24.3°, 33.5°, 36.2°, 41.5°, 50.3°, 54.8°, 63.4°, and 65.2°, respectively. The average crystallite size for Cr2O3-NPs was found to be 58 nm. The photo catalytic activity of green synthesized chromium oxide-NPs was also analyzed.

Synthesis and Characterization of Ti-13Ta-6Sn Foams Produced Using Mechanical Alloying, the Space Holder Method and Plasma-Assisted Sintering

Highly porous titanium foams are great candidates for replacing bone structures with a low elastic modulus owing to their ability to avoid the stress shielding effect. However, the production of highly porous foams (&gt;70 vol.%) with well-distributed, stable, and predictable porous architectures using powder compaction and space holders is challenging. In this study, pure titanium powder and mechanically alloyed Ti-13Ta-6Sn were mixed with 50, 70, and 80 vol.% KCl powders as a space holder, cold-compacted, and sintered in a plasma-assisted sintering reactor to produce highly porous foams. The space holder was completely removed using heat and plasma species collisions prior to sintering. A Ti-13Ta-6Sn alloy powder with α, β, and metastable FCC-γ phases was synthesized. The characteristics of the alloyed powder, mixing step, and the resulting sintered samples were compared to those of CP-Ti. After sintering, the alloy exhibited α and β phases and a reduced elastic modulus. Foams with an elastic modulus in the range of the cortical and trabecular bones were obtained. The results showed the effects of the space holder volume fractions on the volume fraction, size, distribution, interconnectivity, and shape of the pores. The Ti-13Ta-6Sn foams exhibited a uniform open-celled porous architecture, lower elastic modulus, higher yield strength, and higher passivation resistance than CP-Ti. Ti-13Ta-6Sn exhibited a nontoxic effect for the mouse fibroblast cell line.

Development and characterization of corrosion-resistant plasma-sprayed Ni-Al composite coatings via graphene oxide fillers

In this study, the authors propose a procedure to enhance pure Ni-Al powders through graphene oxide dispersion in water for plasma spraying. The enhanced powders were utilized to coat A36 steel via plasma spraying. Next, the powders and the coatings were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, micro-Raman spectroscopy, and field emission scanning electron microscopy. Given the capability of the generated X-ray to characterize near surfaces to a depth of a few micrometers, the performed X-ray microanalyses convey that the carbon species incorporated within the powders through the graphene oxide dispersion can act as nanofillers reducing the number of holes/pores in the plasma-sprayed coatings. Potentiodynamic polarization testing and electrochemical impedance spectroscopy were used to investigate the corrosion behavior of the samples at two intervals: after 1 h and after 30 days of exposure to a 3.5 % NaCl solution. According to the results of the corrosion testing, the enhanced coatings can display about 2.35 times lower corrosion current density compared to pure Ni-Al coatings, with the corrosion potentials of the enhanced coatings being higher than that of pure Ni-Al coatings (i.e., improved corrosion resistance). This improvement in corrosion resistance is also evident when the enhanced coatings are compared to the A36 substrate after 30 days of exposure to the solution. It appears that the incorporated carbon nanofillers, by reducing deep holes and pores that communicate with the surface of the substrate, ultimately determine the highest corrosion resistance. Thus, the outcome offers enhanced Ni-Al coatings possessing superior anticorrosion properties that typical plasma-sprayed Ni-Al bond coats may not exhibit.

Structural, optical, and dielectric properties of Mn-doped Ce1-xMnxO2 nanocrystals for frequency-dependent device applications

Cerium oxide (CeO2) is a significant oxide semiconductor known for its advantageous electrical, optical, and dielectric properties. This study investigates the effects of manganese (Mn) doping on the structural, optical, and dielectric characteristics of CeO2. Pure and Mn-doped Ce1-xMnxO2 nanocrystalline powders, with Mn concentrations of 0, 1, 3, 5, and 7 %, were synthesized using a co-precipitation method. Structural analysis confirmed the formation of a cubic crystal structure, while surface morphology revealed agglomerated spherical particles. Notably, the band gap of Ce1-xMnxO2 decreased from 2.80 eV to 2.30 eV with increasing Mn content, indicating enhanced electronic properties due to doping. The dielectric properties exhibited a pronounced frequency dependence, with significant variations in dielectric constant and loss, demonstrating the potential of Mn-doped CeO2 as a diluted magnetic semiconductor. These findings underscore the material's applicability in biosensors and optoelectronic devices, paving the way for advancements in frequency-related technologies.

DNA-linked composite probe for the sensitive detection of Salmonella typhimurium in milk

Milk was favored for its nutrient richness which resulted in foodborne bacteria contamination along the production and transportation chain. Hence, there is an urgent necessary to develop high-sensitivity detection assays for early warning of bacteria-contaminated milk. Herein, a fluorescence composite probe that can bind with Salmonella typhimurium (S. typhi) was designed and prepared through a DNA bridge linking several fluorescence single probes. With the assistance of immuno-magnetic beads (IMBs) which can recognize S. typhi, IMBs/S. typhi/composite probe formed and separated from undiluted pure milk with high efficiency. As a result, the S. typhi ranging from 50-1 × 106 CFU/mL can be converted to a detectable fluorescence signal. The detection limit was calculated to be 11 CFU/mL. Meanwhile, the average recovery of S. typhi spiked in pure milk samples and milk powder samples were 95.9 % and 92.9 %, respectively. The strong anti-interference ability also made the assay an effective and promising alternative strategy for rapidly and accurately screening S. typhi in milk and milk powder.

Polymers Enhance Chlortetracycline Hydrochloride Solubility

Chlortetracycline hydrochloride (CTC) is a broad-spectrum tetracycline antibiotic with a wide range of antibacterial activities. Due to low solubility, poor stability, and low bioavailability, clinical preparation development is limited. We sought to improve these solubility and dissolution rates by preparing solid dispersions. A hydrophilic polymer was selected as the carrier, and a solid dispersion was prepared using a medium grinding method, with samples characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), and particle size distribution (PSD). To maximize CTC solubility and stability, different polymer types and optimal drug-to-polymer ratios were screened. The solubility of optimized povidone K30 (PVPK30) (1/0.75, w/w)-, hydroxypropyl-β-cyclodextrin (HP-β-CD) (1/2, w/w)-, and gelatin (1/1, w/w)-based solid dispersions was 6.25-, 7.7-, and 3.75-fold higher than that of pure CTC powder, respectively. Additionally, in vitro dissolution studies showed that the gelatin-based solid dispersion had a higher initial dissolution rate. SEM and PS analyses confirmed that this dispersion had smaller and more uniform particles than PVPK30 and HP-β-CD dispersions. Therefore, successful solid polymer dispersion preparations improved the CTC solubility, dissolution rates, and stability, which may have potential as drug delivery systems.

Структура та властивості багатошарового металу, наплавленого електродними порошковими дротами з осердям із порошків феросплавів та гранульованих твердосплавних матеріалів

Comparative studies of the possibility of using granulated hard alloy powders as a charge of flux-cored wires for electric arc surfacing have been carried out. In the studies, granulated powder of the PG-R6M5 brand with a fraction of 50...300 μm was used. As a standard, a flux-cored wire was used, in the core of which there was a composition of powders of different ferroalloys of the same fraction. The content of the charge components in the core of the standard wire was selected and calculated so as to obtain a similar chemical composition to the wire containing granulated hard alloy powder. The test samples were obtained by layer-by-layer electric arc surfacing under the flux layer with flux-cored wires on low-carbon steel plates. To obtain identical dependences, the flux-cored wires had the same diameter and filling factor and differed only in the content of the core. The test samples were deposited under the same conditions with strict adherence to the deposition regimes, which were monitored using a high-speed analog-to-digital converter. It was determined that the use of granulated hard alloy powder as a charge of flux-cored wire has a positive effect on the melting characteristics of the wire and the stability of the welding process in general in comparison with the standard reference wire, the charge of which contains ferroalloys. This effect can be explained by the greater chemical purity of the granulated powder and the uniformity of the physicochemical properties of its particles in comparison with the powders of various ferroalloys. The determined features of the melting of the wire with a charge with granulated hard alloy powder have a positive effect on the quality of the formation of the multilayer deposited metal and its structure, leading to an increase in its homogeneity, some grinding of the grain and a decrease in the number and size of microdefects, which should positively affect the operational properties of the deposited metal. Keywords: electric arc surfacing, multilayer deposited metal, tool steels, granular hard alloy powder, ferroalloy, metal structure.

Laser energy-dependent processability of non-equiatomic TiNbMoTaW high-entropy alloy through in-situ alloying of elemental feedstock powders by laser powder bed fusion

Pre-alloyed powder, which is primarily used in laser powder bed fusion (LPBF), has the disadvantages of requiring time and high manufacturing costs. To overcome these limitations, in-situ alloying, which mixes pure elemental powders and alloys them in real-time during the LPBF process, has attracted attention. In particular, manufacturing high entropy alloys (HEA) containing high-melting-point refractory elements through in-situ alloying presents considerable challenges. In this study, a non-equiatomic single body-centered cubic (BCC) solid-solution HEA was fabricated via in-situ alloying with Ti, Nb, Mo, Ta, and W powders through the LPBF process. Specifically, by applying a high volumetric energy density (VED), we successfully mitigated the segregation of constituent elements, leading to an enhanced crystallographic texture. Consequently, the reduction in the residual stress and high-angle grain boundary (HAGB) density progressed, contributing to an increased relative density. Thus, this study marks a pioneering endeavor for in-situ alloyed HEA fabrication via LPBF, illustrating the efficacy of in-situ alloying utilizing mixed powders.

Development of Robust Steel Alloys for Laser-Directed Energy Deposition via Analysis of Mechanical Property Sensitivities

To ensure consistent performance of additively manufactured metal parts, it is advantageous to identify alloys that are robust to process variations. This paper investigates the effect of steel alloy composition on mechanical property robustness in laser-directed energy deposition (L-DED). In situ blending of ultra-high-strength low-alloy steel (UHSLA) and pure iron powders produced 10 compositions containing 10–100 wt% UHSLA. Samples were deposited using a novel configuration that enabled rapid collection of hardness data. The Vickers hardness sensitivity of each alloy was evaluated with respect to laser power and interlayer delay time. Yield strength (YS) and ultimate tensile strength (UTS) sensitivities of five select alloys were investigated in a subsequent experiment. Microstructure analysis revealed that cooling rate-driven phase fluctuations between lath martensite and upper bainite were a key factor leading to high hardness sensitivity. By keeping the UHSLA content ≤20% or ≥70%, the microstructure transformed primarily to ferrite or martensite, respectively, which generally corresponded to improved robustness. Above 70% UHSLA, the YS sensitivity remained low while the UTS sensitivity increased. This finding, coupled with the observation of auto-tempered martensite at lower cooling rates, may suggest a strong response of the work hardening capability to auto-tempering at higher alloy contents. This work demonstrates a methodology for incorporating robust design into the development of alloys for additive manufacturing.

Eco-friendly electrochemical assay of oxytetracycline and flunixin in their veterinary injections and spiked milk samples

Two solid-contact electrochemical sensors were developed for detection of each of oxytetracycline HCl (OXY), and the co-formulated non-steroidal anti-inflammatory drug flunixin meglumine (FLU) in veterinary formulations and animal-derived food products. The designed sensors were based on a glassy carbon electrode as the substrate material and high molecular weight polyvinyl chloride (PVC) polymeric ion-sensing membranes doped with multiwalled carbon nanotubes (MWCNTs) to improve the potential stability and minimize signal drift. For determination of OXY, the sensing membrane was modified with potassium tetrakis (4-chlorophenyl) borate (K-TCPB), which was employed as a cation exchanger, and 2-hydroxypropyl-β-cyclodextrin (HP-ßCD), which was used as an ionophore. A linear response within a concentration range of 1 × 10− 6-1 × 10− 2 M with a slope of 59.47 mV/decade over a pH range of 1–5 was recorded. For the first time, two potentiometric electrodes were developed for determination of FLU, where the sensing membrane was modified with tetra dodecyl ammonium chloride (TDDAC) as an anion exchanger. A linear response within a concentration range of 1 × 10− 5-1 × 10− 2 M and a slope of -58.21 mV/decade over a pH range of 6–11 was observed. The suggested sensors were utilized for the selective determination of each drug in pure powder form, in veterinary formulations, and in spiked milk samples, with mean recoveries ranging from 98.50 to 102.10, and without any observed interference. The results acquired by the proposed sensors were statistically analyzed and compared with those acquired by the official methods, and the results showed no significant difference.Graphical

Effect of temperature on the microstructure and mechanical properties of TiC/Fe matrix composites fabricated by spark plasma sintering

The effects of sintering temperatures on the microstructures and mechanical properties of titanium carbide particles reinforced iron matrix composites (TiC/Fe MCs) fabricated by the spark plasma sintering (SPS) process with pure element powders have been systematically investigated. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back scattering diffractometer (EBSD), and energy dispersive spectroscopy (EDS) have been conducted for microstructural analysis. The results show that with increasing sintering temperatures, the porosity of the composites initially decreases and then increases. Simultaneously, the grain size gradually diminishes while element diffusion becomes more uniform. Upon reaching a critical sintering temperature (1120 °C), the original grain size disappears and carbides undergo decomposition and reprecipitation to reach an equilibrium state, with which optimal comprehensive properties can be achieved (porosity decreases to a minimum of 3.85%, grain size of 2.69 μm, Vickers hardness reaches 595 HV0.5, bending strength is at 662 MPa, coefficient of friction is at 0.74, and wear loss to 0.21 mg). These property enhancements have been attributed to reduced porosity in the composites, decreased grain size, and improved anchoring effect of carbides within the matrix. Additionally, the primary fracture mechanisms and wear mechanisms of TiC/Fe MCs with different process parameters have been analyzed. When the temperature is below 1080 °C, intergranular fracture predominates, whereas transgranular and ductile fractures become predominant above this threshold. When the temperature is below 1120 °C, fatigue wear, oxidation wear, and abrasive wear are predominantly observed. Conversely, when the temperature exceeds 1120 °C, oxidation wear and abrasive wear become the primary mechanisms.

Adsorption characteristics and separation behavior of binder and binderless zeolite LiX Pellets: O2, N2, and CO2

In adsorptive gas separation process design, optimal adsorbent selection acts as a critical factor in process efficiency. This study investigated the adsorption equilibria and kinetics of O2, N2, and CO2 (weak, medium and strong affinity, respectively) and the breakthrough performance of four commercial zeolite LiX pellets (one binderless and three binder zeolite LiX pellets) because the performance of pelletized zeolites becomes different by adding binders and pelletizing methods. The adsorption isotherms at 293–323 K and up to 100 kPa were correlated with the dual-site Langmuir and Sips models. For all adsorbents, the order of adsorption amount and isosteric heat of adsorption was CO2 ≫ N2 > O2. However, differences among the four zeolite pellets were also observed, showing the highest values of the binderless zeolite LiX pellet. Furthermore, the adsorption capacity was 20–25 % smaller for CO2 and 40–50 % smaller of N2 and O2 at 100 kPa compared to pure zeolite LiX powder. According to kinetic analysis using a non-isothermal diffusion model, the adsorption rate of N2 was faster than that of CO2 for all adsorbents, showing the order difference in the low-pressure range. The kinetic difference among the zeolite pellets resulted from the effects of heat of adsorption, heat dissipation, and thermal resistance. The breakthrough performance using N2 and O2 was mainly controlled by the adsorption capacity, showing almost constant breakthrough pattern regardless of the samples. This study suggests that detailed evaluation of pelletized adsorbent is essential before designing adsorptive processes because performance of adsorbent powder would lead to under-design of the process. (255 words)

Laser Powder Bed Fusion of Copper-Tungsten Powders Manufactured by Milling or Co-Injection Atomization Process.

The processing of pure copper (Cu) has been a challenge for laser-based additive manufacturing for many years since copper powders have a high reflectivity of up to 83% of electromagnetic radiation at a wavelength of 1070 nm. In this study, Cu particles were coated with sub-micrometer tungsten (W) particles to increase the laser beam absorptivity. The coated powders were processed by powder bed fusion-laser beam for metals (PBF-LB/M) with a conventional laser system of <300 watts laser power and a wavelength of 1070 nm. Two different powder manufacturing routes were developed. The first manufacturing route was gas atomization combined with a milling process by a planetary mill. The second manufacturing method was gas atomization with particle co-injection, where a separate W particle jet was sprayed into the atomized Cu jet. As part of the investigations, an extensive characterization of powder and additively manufactured test specimens was carried out. The specimens of Cu/W powders manufactured by the milling process have shown superior results. The laser absorptivity of the Cu/W powder was increased from 22.5% (pure Cu powder) to up to 71.6% for powders with 3 vol% W. In addition, a relative density of test specimens up to 98.2% (optically) and 95.6% (Archimedes) was reached. Furthermore, thermal conductivity was measured by laser flash analysis (LFA) and thermo-optical measurement (TOM). By using eddy current measurement, the electrical conductivity was analyzed. In comparison to the Cu reference, a thermal conductivity of 88.9% and an electrical conductivity of 85.8% were determined. Moreover, the Vickers hardness was measured. The effect of porosity on conductivity properties and hardness was investigated and showed a linear correlation. Finally, a demonstrator was built in which a wall thickness of down to 200 µm was achieved. This demonstrates that the Cu/W composite can be used for heat exchangers, heat sinks, and coils.

Enhanced soft magnetic properties with high frequency stability of pure iron powder cores via high-pressure compaction – An environment and cost saving solution as a prospective alternative to soft magnetic composites

The paper presents the analysis of the magnetic behaviour of soft magnetic powder compacts vs. the increasing compacting pressure. An unexpectedly positive result was obtained at a pressure of 1500 MPa, as the pure iron compact without coating of powder particles and without subsequent heat treatment showed very good magnetic properties compared to the class of soft magnetic composites (SMCs). In particular, the effective relative permeability of μeff ∼120, stable up to a frequency f ∼200 kHz, the maximum total relative permeability of μtotmax ∼700, and the specific electrical resistivity of ρR ∼10−5 Ω m. This phenomenon was explained on the basis of analyses of the samples microstructure, the magnetic and electrical properties, magnetization processes, inner demagnetizing fields, Barkhausen noise and thermal diffusivity. It was found that the grain size refinement inside iron particles occurs at certain elevated compaction pressure because the deformation bands gradually rise and break up with compaction pressure, leading to a higher resistivity of the compact thus to its SMC-like behaviour, despite the counteracting effect of increasing number of iron-iron bridges among neighbouring particles. The grain size refinement causes also the refinement of magnetic domain structure, which facilitates the magnetization reversal, although, the increased internal stresses and microstructural defects affect domain wall mobility negatively. The most favourable combination of the mentioned factors influences, finally resulting in the soft magnetic properties enhancement, appeared at 1500 MPa. Due to high-pressure compaction, the high density (above ∼95 % of iron density) of a compact was achieved, ensuring sufficient mechanical properties. The presented material can serve as a potential supplanter of SMCs in many applications as it provides evident advantages, such as its easy production with minimum chemical waste (because any additional chemical processes and substances needed for particle coatings in conventional SMCs are completely omitted), as well as easy recycling process, which makes it eco-friendly and cost-effective, nevertheless, maintaining the advantages of SMCs.

Pyrometallurgical processing of manganese ore

Manganese ore contains valuable oxides, such as manganese oxide (MnO2/Mn2O3/Mn3O4), iron oxide (Fe2O3) and silica (SiO2). In the present study, an attempt has been made to separate these oxides through pyrometallurgical processing routes for the extraction of ferromanganese and silicomanganese. Lean manganese ores were subjected to ball milling followed by carbothermic reduction at a temperature of 1200 °C for 2 h. The reduced ores were then subjected to wet magnetic separation to obtain the magnetic constituents in the reduced ores. It was observed that it is not possible to remove the silica content from the ore. It appeared that the reduced sample had oxides of iron, silicon and manganese after its wet magnetic separation. The magnetic constituents were subjected to metallothermic reduction through pure aluminium powders to recover valuable metals/alloys.