Metallurgy Technology Research Articles

Role of Ti3AlC2 MAX phase in regulating biodegradation and improving electrical properties of calcium silicate ceramic for bone repair applications

Calcium silicate ceramic is a promising bioceramic for various biomedical applications, but its high biodegradation rate and low strength restrict its clinical utility. As a result, the study devised an innovative solution to address these issues by utilizing the titanium aluminum carbide phase, potentially for the first time in biological applications, in conjugation with hydroxyapatite. Then, using powder metallurgy technology, they added these phases to calcium silicate to create nanocomposites. After soaking in simulated body fluid for ten days, the produced nanocomposites were assessed for bioactivity and biodegradability using scanning electron microscopy, inductively coupled plasma-atomic emission spectroscopy, and weight loss assays. Their electrical and dielectric properties were also measured before and after soaking in the simulated body fluid solution. Furthermore, the tribo-mechanical properties of all sintered samples were measured. Interestingly, adding 40% hydroxyapatite nanoparticles to calcium silicate reduced the porosity from 12 to 6%. However, adding five vol% of the titanium aluminum carbide phase to the same sample increased the porosity to 8%. Importantly, these recorded percentages of porosity were comparable to those of compact bone porosity, which range from 5 to 13%. The addition of hydroxyapatite and titanium aluminum carbide phase significantly improved the rapid biodegradation of calcium silicate, albeit with a slight decrease in its bioactive properties, as evidenced by the incomplete surface coverage of the samples with the hydroxyapatite layer in the scanning electron microscopy images. The electrical properties of the nanocomposites were better with the addition of hydroxyapatite and titanium aluminum carbide phase, which helped the bone heal faster. The addition of a titanium aluminum carbide phase significantly improved the mechanical properties of the resulting nanocomposites. For example, the calculated values for compressive strength of all examined samples were 131, 115, 105, 147, and 135 MPa. Based on the results, the prepared samples can be used in orthopaedic and dental applications.

Bubble plume effects on the flotation kinetics of nonmetallic inclusions based on experimental observations

AbstractSteelmaking has shown an increasing concern toward nonmetallic inclusions, leading to new technologies in the secondary metallurgy of steel. Although the typical inclusion removal procedure is by injecting inert gas into the ladle, this vessel does not fulfill all the requirements to accept a porous structure tailored to produce “clean steels.” Consequently, the spotlight has moved to the tundish, the last vessel before solidification, in which gas injection can continuously operate. Therefore, this work focuses on understanding the influence of typical gas flow rates (10–60 NL/min) on the kinetics of inclusion flotation, considering two bubble diameters (0.6 and 1.1 mm). For this purpose, experimental measurements were conducted in a water model, where glass hollow spheres played the role of inclusions, and their concentration was fitted by an exponential decay. In general, injecting bubbles into the system contributed positively to a faster and greater flotation of particles. The smaller bubbles led to a higher maximum efficiency, whereas the larger ones allowed a shorter time scale (i.e., a faster removal), defining a trade‐off to tune the bubble size. Regarding the gas flow rate, the results indicate an optimum range to decrease the time scale, and suggestions for bubble curtains in tundishes are drawn.

Effect of Ti–Mg–Ce Complex Deoxidation on the Inclusions and Mechanical Properties of S355 Steel

Oxide metallurgy technology not only refines the microstructure but also modifies the type, density, and size of inclusions. This study examines the impact of Ti–Mg–Ce composite deoxidation on the inclusions and mechanical properties of S355 steel used for heavy‐duty H‐beams. Compared to base alloy, Ti–Mg–Ce‐added alloy features a higher presence of inclusions such as MgO, TiN (containing Ce), TiOx, and TiS, except for SiO2, Al2O3, MnS, and MnO. Following Ti–Mg–Ce composite deoxidation, the number density of inclusions increases by 16.4%, and the equivalent diameter, length, and width of the inclusions decrease by 41.0%, 41.2%, and 37.9%, respectively. The length of large‐angle grain boundaries in the same area increases by 20%, and the average grain size reduces by 12.5%, resulting in an enhancement of yield strength by 23.6 MPa, tensile strength by 37 MPa, total elongation by 2.1%, and impact energy by 92 J. By employing Ti–Mg–Ce composite deoxidation to optimize inclusions and microstructure, the strength, plasticity, and toughness of the experimental steel are significantly improved.

The corrosion behavior of Al2O3-SiO2 refractory in reducing atmosphere

Hydrogen metallurgy technology is essential for reducing CO2 emissions. Hydrogen (H2) serves as an ideal energy carrier to replace carbon-based fuels, producing only water as a byproduct. Al2O3-SiO2 refractories are commonly used in hydrogen metallurgy technology, including in technologies like HyCROF(Hydrogen-enriched Carbonic oxide Recycling Oxygenate Furnace) and gas heating furnaces. It is important to systematically study their corrosion in high-temperature reducing gas environments. The results indicated that the Al2O3-SiO2 refractory remained stable in pure H2 atmosphere at temperatures below 1200 °C. However, SiO2 and mullite were reduced by H2 when the temperature was increased above 1200 °C. Carbon precipitation was observed in both pure CO atmosphere and H2-CO mixed atmosphere, resulting in an increase weight of the sample. Additionally, the sample developed mullite whiskers after heating treatment at 1200 °C in H2-CO mixed atmosphere. This study aims to clarify the corrosion mechanism of Al2O3-SiO2 refractory in reducing atmosphere and to provide a theoretical basis for the selecting and optimizing refractories for hydrogen metallurgy technology.

When is the right time to invest in hydrogen metallurgy projects for iron and steel enterprises?

Hydrogen metallurgy technology is considered a key technology for the iron and steel industry to achieve carbon neutrality. However, it has been slow to be widely promoted in China due to factors such as stranded costs from carbon metallurgy equipment, hydrogen production costs, consumer preferences, and carbon costs. Based on these comprehensive consideration, this paper establishes a predictive model for investment timing of hydrogen metallurgy projects, takes an example of a Chinese steel enterprise with medium production scale. The research results show that the hydrogen metallurgy project with a hydrogen-rich blast furnace injection technology (hydrogen-rich BF) route is the most economically advantageous after 2026; after 2048, the net income of the hydrogen metallurgy project with a hydrogen-based shaft furnace direct reduction technology (hydrogen-based DRI) route will be greater than the stranded costs of carbon metallurgy projects, making it the most economically advantageous project. However, market dynamics and equipment variations significantly influence project viability.

Preparation and arc erosion mechanism of Ni skeleton reinforced Ag-based contact materials with CuO-coated SnO2

The Ag-SnO2 contact material is widely regarded as the most promising environmental friendly electrical contact material. However, during the make and break operations, SnO2 particles rising to the surface can cause increased contact resistance and temperature rise, which affects the service life of the contact material. In this study, a three-dimensional (3D) Ni skeleton reinforced Ag-based contact material with CuO-coated SnO2 are successfully fabricated via powder metallurgy technology. The basic physical properties of the novel contact material were tested and the microstructures and arc erosion morphologies were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The research demonstrated that the hardness and electrical conductivity of the novel contact material are 128.9 HV and 46 %IACS, respectively. It can be observed that the SnO2-rich phase is uniformly distributed in the Ag matrix without significant upward after arc erosion, which indicates that the SnO2@CuO core-shell structure effectively enhances the wettability between Ag and SnO2. Meanwhile, the study revealed that the Ni phase uniformly distributed at the interface of the Ag phase during the arc erosion process, indicating that the 3D Ni skeleton structure effectively impedes the expansion of the Ag molten pool and improves the anti-arc erosion performance.

Structural, mechanical, and oxidation resistance properties of double glow plasma Ta[sbnd]W alloys

To enhance the performance of surface coatings on weaponry, TaW alloy layers with various W contents (7, 11.5, 13, 14, 14.5 and 16 at. %) were prepared on the surface of a PCrNi3MoVA gun steel substrate using double-glow plasma surface metallurgy technology. Mechanical properties, friction wear, and oxidation resistance were studied using scratch, hardness, and tribometer testers. The mechanical properties, interfacial properties, and effects on the oxidation performance of the gun steel substrate of the TaW alloy layer were calculated using first principles. The results indicated that the surface and cross-sectional microstructures of the TaW alloy layers were dense and free from obvious defects. With increasing W content, the thickness, hardness, and adhesive strength of the TaW alloy layer increased, and the coefficient of friction and wear rate decreased. The results of the calculations indicate that an increase in the W content enhances the elastic modulus of the TaW alloy and improves its brittleness, strength, and hardness. Doping with Ta and W atoms can increase the vacancy formation energy of Fe atoms in the Fe supercell, the adsorption energy of O atoms on the surface of Fe(110), and the diffusion barrier of O atoms in the Fe supercell and on the Fe(110) surface. Interdoping of Ta, W and Fe atoms at the Fe(110)/Ta-W(110) interface improved the bonding strength and stability of the interface, and the FeTa and FeW chemical bonds formed at the Fe(110)/Ta-W(110) interface ensured stable bonding at the interface. The incorporation of W into the TaW alloy layer enhanced both the mechanical and frictional properties of the alloy. It is well established that TaW alloys improve the antioxidant properties of gun steel substrates, thereby enhancing the performance of coatings on weaponry.

Simulation and Algorithmic Optimization of the Cutting Process for the Green Machining of PM Green Compacts.

Powder metallurgy (PM) technology is extensively employed in the manufacturing sector, yet its processing presents numerous challenges. To alleviate these difficulties, green machining of PM green compacts has emerged as an effective approach. The aim of this research is to explore the deformation features of green compacts and assess the impact of various machining parameters on the force of cutting. The cutting variables for compacts of PM green were modeled, and the cutting process was analyzed using Abaqus (2022) software. Subsequently, the orthogonal test ANOVA method was utilized to evaluate the significance of each parameter for the cutting force. Optimization of the machining parameters was then achieved through a genetic algorithm for neural network optimization. The investigation revealed that PM green compacts, which are brittle, undergo a plastic deformation stage during cutting and deviate from the traditional model for brittle materials. The findings indicate that cutting thickness exerts the most substantial influence on the cutting force, whereas the speed of cutting, the tool rake angle, and the radius of the rounded edge exert minimal influence. The optimal parameter combination for the cutting of PM green compacts was determined via a genetic algorithm for neural network optimization, yielding a cutting force of 174.998 N at a cutting thickness of 0.15 mm, a cutting speed of 20 m/min, a tool rake angle of 10°, and a radius of the rounded edge of 25 μm, with a discrepancy of 4.05% from the actual measurement.

Design of a Thermally Stable Heat-Resistant (Al2O3+Al3Ti)/Al Composite with Excellent High-Temperature Mechanical Properties: Multimechanism Synergistic Strengthening Strategy.

The effectiveness of the room-temperature strengthening strategy for aluminum (Al) is compromised at increased temperatures due to grain and precipitate phase coarsening. Overcoming the heightened activity of grain boundaries and dislocations poses a significant challenge in enhancing the high-temperature strength through traditional precipitation strengthening. This study presents novel strengthening strategies that integrate intergranular reinforcements, intragranular reinforcements, refined grain, and stacking faults within an (Al2O3+Al3Ti)/Al composite prepared using sol-gel and powder metallurgy technology. Excellent high-temperature tensile properties are achieved; also, a remarkable fatigue performance at increased temperatures that surpasses those of other existing Al alloys and composites is revealed. These superior characteristics can be attributed to its exceptionally stable microstructure and the synergistic strengthening mechanisms mentioned above. This work offers new insights into designing and fabricating thermally stable Al matrix composites for high-temperature applications.

The application of green hydrogen in iron ore smelting under the target of carbon neutralization

Currently, green development and sustainable development have become a global consensus. In March 2023, the Intergovernmental Panel on Climate Change (IPCC) released the sixth comprehensive assessment report Climate Change 2023, which pointed out that greenhouse gas emissions are currently at the highest level in human history, and the global temperatures has been about 1.1 higher than that before industrialization. In July, 2023, the government of China also emphasized that the construction of ecological civilization in China has entered a critical period with carbon emission reduction as the focus. According to the survey, the steel industry in China has the highest carbon emission in manufacturing industry, and it is also one of the most important areas for China to deal with climate change. Based on the basic principle of blast furnace iron making, this paper first analyzes the causes of high emissions in the steel industry, and draws the conclusion that hydrogen metallurgy technology must be developed to achieve low-carbon development; Then, depending on different energy endowments, the differences in metallurgical technology between China and other countries are analyzed, and brief conclusions and suggestions are given on the basis of analyzing the challenges faced by low-carbon development of Chinas steel industry. This study provides insights into the importance of hydrogen metallurgy technology and enhance our understanding of how to achieve low-carbon development in Chinas iron and steel industry.

Physical, structural and mechanical characterization of Fe-10wt. %Ni-5wt. %Cu alloys manufactured by powder metallurgy (P/M) technology

Abstract Porosity of alloys produced by powder metallurgy remarkably reduces their strength. This study characterizes the effect of addition of 10wt%Ni and 5wt%Cu particles to Fe powder performing an Iron base alloy using P/M technique. The microstructure of the alloy was investigated using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The relative density of the alloy fabricated at different parameters was investigated. Microstructural characterization of the alloy shows a low porosity and existence of spheroid oxide particles. Also EDS elemental analysis reveals a uniform distribution of Ni and Cu within the Fe matrix. In addition, the results reveal that the relative density and hardness increase with increasing the fabrication parameters; pressure and sintering temperature when the time is kept constant and their maximum values were obtained when that alloy fabricated at compaction pressure 700 MPa and sintering temperature 1200°C for 90 min.

Wire-arc directed energy deposition of oxide-modified H13 steel: Microstructural characterization and mechanical properties

The preparation of H13 steel using wire-arc directed energy deposition has broad application prospects; however, the high hardenability of H13 steel makes it prone to forming cold cracks during deposition, thus limiting its further applications. Fortunately, the oxide metallurgy technology holds promise in addressing this issue. Specifically, nano oxides have the capability to refine the grain and facilitate the formation of intracrystalline ferrite, ultimately resulting in an improvement in steel's toughness and subsequently mitigating its propensity towards cold cracking. In this study, H13 steel wires, incorporating Al-Si-Ti composite oxides, were used to deposit part (W-O-H13) with excellent performance and no cold cracks. Owing to the special thermal cycling during wire-arc directed energy deposition, a periodic build unit was formed that could be roughly divided into three zones, namely, fine grain, columnar grain, and heat-affected zones. The microstructure of the parts contained lath martensite, high-alloy martensite, and ferrite. After arc exposure, the oxide formed a complex core-shell structure, with vanadium carbide (VC) encapsulating the amorphous oxide core. Moreover, the oxide particles refine the grain structure and induce the formation of ferrite, thereby enhancing the toughness of the part and further improving its strength and wear resistance. The low mismatch between the VC thin layer wrapping the oxide and ferrite was a crucial factor in the conductive ferrite phase transformation. Additionally, the elemental segregation caused by the rapid cooling rate ultimately led to the formation of high-alloy martensite having a maximum hardness of 5.32 GPa. The results reveal that the average tensile strength of W-O-H13 steel in the X, Y, and Z directions is improved by 21.0 %, 20.3 %, and 14.3 % respectively, compared to the parts fabricated solely from H13 steel wire without the addition of oxide (W-H13). Additionally, the impact toughness of W-O-H13 steel surpasses W-H13 steel in all three directions, achieving an average of 33, 27, and 28 J/cm2 respectively in the X, Y, and Z axes. In comparison to W-H13, the impact toughness of W-O-H13 has witnessed a substantial increase ranging from 10 % to 30 %. Furthermore, the wear resistance of W-O-H13 steel significantly surpasses that of W-H13 steel, particularly under high-temperature wear conditions. Specifically, the average wear volume of W-O-H13 steel at temperatures ranging from 400 to 600 °C is merely 0.163 and 0.224 mm³, representing only 30 % and 40 % of the wear volume exhibited by W-H13 steel under the same wear conditions.

Correlation between the microstructure and deformation behavior of a PM fine-grained duplex steel

A fine-grained duplex steel with a composition of Fe–5Mn–2Al-0.6C (wt.%) was fabricated using a powder metallurgy (PM) technology of thermomechanical consolidation by hot extrusion of powder compact. The microstructure consisted of α′-martensite, residual austenite (RA), and a small amount of Al2O3 particles. Subsequent heat treatment was performed to adjust the microstructure and mechanical properties. This study focuses on the pre-and post-heat treatment microstructure of the material, elucidates the reasons for its formation, and explains how microstructural changes influence tensile deformation behavior. The results show that the heat treatment caused the precipitation of nanoscale carbide within the martensite, which significantly increased the yield strength from 792 MPa to 1078 MPa. While heat treatment altered the size and distribution of RA regions in the microstructure, the amount of RA transformed during deformation remained proportional to the flow stress in both materials, indicating that the flow stress dictates the amount of phase transformation of ultrafine grained RA. Therefore, in the heat-treated material with a higher yield strength, a larger amount of RA transformed during the initial stage of plastic deformation, leaving less RA to sustain a work-hardening rate in subsequent deformation, resulting in a decrease in ductility from 5.5 % to 3.6 % and fracture stress from 1674 to 1453 MPa. In addition, the in-situ formed Al2O3 particles facilitated grain refinement of the extruded rod, but had less effect on the microstructure and properties of the heat-treated sample. This study serves as a valuable reference for comprehending the influence of microstructural changes in PM manganese steel on tensile deformation behavior.

Impact Wear Behavior of the Valve Cone Surface after Plasma Alloying Treatment

Valves are prone to wear under harsh environments, such as high temperatures and reciprocating impacts, which has become one of the most severe factors reducing the service life of engines. As a lightweight ceramic, CrN is considered an excellent protective material with high-temperature strength and resistance to wear. In this study, a CrN coating was applied onto the valve cone surface via double-layer glow plasma surface metallurgy technology. The formation process, microstructure, phase composition, hardness, and adhesion strength were analyzed in detail. Impact wear tests were conducted on the valve using a bench test device. The SEM and EDS results showed that the CrN coating evolved from an island-like form to a dense, cell-shaped surface structure. The thickness of the coating was approximately 46 μm and could be divided into a deposition layer and a diffusion layer, from the outer to the inner sections. The presence of element gradients within the diffusion layer proved that the coating and substrate were metallurgically bonded. The adhesion strength of the CrN coating measured via scratch method was as high as 72 N. The average Vickers hardness of the valve cone surface increased from 377.1 HV0.5 to 903.1 HV0.5 following the plasma alloying treatment. After 2 million impacts at 12,000 N and 650 °C, adhesive wear emerged as the primary wear mode of the CrN coating, with an average wear depth of 42.93 μm and a wear amount of 23.49 mg. Meanwhile, the valve substrate exhibited a mixed wear mode of adhesive wear and abrasive wear, with an average wear depth of 118.23 μm and a wear amount of 92.66 mg, being 63.7% and 74.6% higher than those of the coating. Thus, the CrN coating showed excellent impact wear resistance, which contributed to the enhancement of the service life of the valve in harsh environments.

Preparation method and industrialization of Ta-based ultra high temperature ceramic Tujia jar tea baking jar materials

The production materials of traditional Tujia jar tea often face problems such as poor high-temperature performance and poor durability. To improve the temperature resistance and durability of tea baking utensils, this study proposes a new type of TaC ultra-high temperature ceramic. TaC ceramics with excellent performance were prepared through powder metallurgy technology, including high-energy ball milling to ensure uniform mixing, followed by compression molding and high-temperature sintering. The test results demonstrated excellent mechanical properties, with a maximum depth of 948.67 nm and a contact depth of 954.45 nm, proving outstanding compressive and wear resistance. The hardness reached 21.4±0.5 Gpa, and the elastic modulus was 397.2±8.7 Gpa, both of which indicate its stability under high loads. In addition, the fracture toughness was 2.8±0.2 Mpa*m1/2. At a high temperature environment of 1000 °C, the oxidation rate constant of TaC ceramics was only 0.183 mg2 *cm−4 *h, which demonstrates its excellent high-temperature stability. The development of this TaC ceramic not only strengthened the traditional production process of Tujia teapots and tea roasting teapots, thereby improving the product’s service life, but also holds potential for other industrial applications that demand ultra-high temperature stability. These contributions provide new directions for the high-temperature application of ceramic materials and bring tangible economic and technological value to related industries.

Kesan Tanpa Masa Pegangan Rawatan Haba ke Atas Sifat Mekanikal dan Mikrostruktur Pembuatan Aditif Aloi Titanum (Ti6Al4V) Melalui Proses Peleburan Laser Selektif (SLM)

Additive manufacturing (AM) or better known as 3D printing is a manufacturing method based on powder metallurgy technology that is able to produce a 3D component. Selective laser melting (SLM) is one of the AM methods capable of producing metal 3D components, however, residual stresses are often produced in such component due to repeated melting and solidification of metal during the printing process. The residual stresses can deteriorate the performance of the 3D components’ mechanical properties if not removed or reduced. Heat treatment processes are often used to remove the residual stresses. The basic parameters of heat treatment are heating temperature, heating rate, cooling rate and holding time. Based on the basic parameters, the effect of holding time in heat treatment is still less reported for 3D components printed via SLM. Therefore, in this study, the effect of holding time on the mechanical properties and microstructure of 3D titanium alloy (Ti6Al4V) components was intestigated. A total of 9 sets of cubic samples were printed on different processing parameters such as laser power (225W, 275W, 325W), scanning speed (800mm/s, 1100mm/s, 1400 mm/s), layer height (0.3mm) and hatching distance (0.10mm, 0.12mm, 0.14mm ). It was found that hardness of 383 - 448 HV was obtained where samples P3, P9 and P5 gave the highest, medium and lowest hardness values. Based on the microstructure observation, α + β phase and martensite structures are produced due to the vanadium content of 4% and heat treated at 935°C. A critical review was also studied to compare previous studies that used different holding times on SLM-printed Ti6Al4V 3D components. It was found that different holding times did not have a significant effect on the mechanical properties of Ti6Al4V 3D components where the outcome of previous studies alligns with that of from this study. In addition, past works have also reported that heat treatment is able to lower the residual stresses in SLM-printed Ti6Al4V 3D components. Finally, the effectiveness of heat treatment in reducing the residual stresses in SLM-printed Ti6Al4V 3D components at different printing parameters should also be studied to understand the mechanism of microstructural changes during and after heat treatment.

Direct Regeneration of Spent LiCoO2 Black Mass Based on Fluorenone‐Mediated Lithium Supplementation and Energy‐Saving Structural Restoration

AbstractDegraded LiCoO2 cathode from retired Li‐ion batteries is urgently required to be recycled in a greener way for economic and environmental considerations. The coarse metallurgy technologies for Li/Co extraction with massive CO2 emission and energy consumption cannot satisfy the requirements of carbon neutralization. Herein, it is proposed that direct regeneration of degraded LiCoO2 cathode could be realized via 9‐fluorenone‐mediated Li supplementation and follow‐up structural restoration. The 9‐fluorenone‐lithium reagent is elaborately selected to compensate for the missing Li+ into lattice with targeted stoichiometry owing to its compatible redox potential of 1.95 V versus Li+/Li, which is located just between the reversible intercalation (3.8 V) and irreversible conversion (1.2 V) potentials of LiCoO2 electrode. Then, thermal energy‐driven structure reorganization enables Li/Co atoms to occupy the right sites, accomplishing desirable structure healing within a short annealing time of 4 h. The regenerated LiCoO2 cathode exhibits comparable Li‐storage capability to commercial LiCoO2, benefiting from the non‐destructive direct regeneration technology. In addition, the regeneration route is regarded as environmentally (0.13 kg CO2 kg−1 cell) and economically (10.07 $ kg−1 cell) superior to conventional recycling routes based on life‐cycle analysis. The precise surgery on spent LiCoO2 cathode provides a promising solution for the forthcoming retirement rush of Li‐ion batteries.

Study on Hydrothermal Arsenic Fixation in H3AsO4-FeSO4-Na2SO4-H2O System

In this study, hydrothermal metallurgy technology was used to convert arsenic in the solution into a stable, dense, and granular arsenic-fixing mineral, scorodite (FeAsO4·2H2O), that is conducive to storage. The effect of Na+ on the precipitation rate of arsenic and iron, the phase composition, and the transformation of arsenic residue during the mineralization and arsenic precipitation of hydrothermal scorodite in the H3AsO4-FeSO4-Na2SO4-H2O system were studied. The results show that Fe3+ co-precipitates with As5+ to form scorodite (FeAsO4·2H2O). In the later stage of the reaction, Fe3+ and Na+ combine to precipitate in the form of sodium jarosite [NaFe3(SO4)2(OH)6]. Under the conditions of an initial Na+ concentration of 10 g/L, an arsenic concentration of 10 g/L, a molar ratio of iron to arsenic of 1.5, a pH of 1, a reaction temperature of 160 °C, a stirring speed of 500 r/min, a reaction time of 3 h, and an oxygen partial pressure of 0.6 MPa, the precipitation rates of arsenic and iron were 98.2% and 93.2%, respectively. The phase composition of the arsenic residue is mainly composed of large-grained polyhedral crystal scorodite, and a small amount of irregular, small-grained crystal sodium jarosite is dispersed in it. By controlling the initial molar ratio of iron to arsenic, the concentration of Na+, and prolonging the reaction time, the formation of the sodium jarosite phase can be inhibited, and the transformation of the sodium jarosite phase into the scorodite phase can be promoted, so as to realize the efficient precipitation of arsenic, reduce the amount of arsenic residue, ensure the stability of arsenic residue, and avoid potential environmental pollution risks.

Microstructure and mechanical properties of Ti-Nb alloys: comparing conventional powder metallurgy, mechanical alloying, and high power impulse magnetron sputtering processes for supporting materials screening

At the interface of thin film development and powder metallurgy technologies, this study aims to characterise the mechanical properties, lattice constants and phase formation of Ti-Nb alloys (8–30 at.%) produced by different manufacturing methods, including conventional powder metallurgy (PM), mechanical alloying (MA) and high power impulse magnetron sputtering (HiPIMS). A central aspect of this research was to investigate the different energy states achievable by each synthesis method. The findings revealed that as the Nb content increased, both the hardness and Young’s modulus of the PM samples decreased (from 4 to 1.5 and 125 to 85 GPa, respectively). For the MA alloys, the hardness and Young’s modulus varied between 3.2 and 3.9 and 100 to 116 GPa, respectively, with the lowest values recorded for 20% Nb (3.2 and 96 GPa). The Young’s modulus of the HiPIMS thin film samples did not follow a specific trend and varied between 110 and 138 GPa. However, an increase in hardness (from 3.6 to 4.8 GPa) coincided with an increase in the β2 phase contribution for films with the same chemical composition (23 at.% of Nb). This study highlights the potential of using HiPIMS gradient films for high throughput analysis for PM and MA techniques. This discovery is important as it provides a way to reduce the development time for complex alloy systems in biomaterials as well as other areas of materials engineering.Graphical abstract

Exploring hydrogen metallurgy to CO2 emissions reduction in China’s iron and steel production: An analysis based on the life cycle CO2 emissions – LEAP model

Previous research has primarily assessed the environmental impact of hydrogen metallurgy from technical or project perspectives, lacking a life cycle perspective. The impact of continued cleanliness of the hydrogen production mix and power generation structure on carbon dioxide (CO2) emissions from the hydrogen metallurgy production process has not been investigated on a medium to long-term scale, which does not provide an adequate and comprehensive view of the contribution of hydrogen metallurgy to China’s emissions reduction, resulting in short-sighted technology choices. To address this lack, we construct a bottom-up energy system model that combines life cycle CO2 emissions with long-range energy alternatives planning (LEAP), including iron and steel (IS) production, power generation, and hydrogen production. Setting development paths of two typical hydrogen metallurgy technologies, including business-as-usual (BAU) and hydrogen metallurgy (HM) scenarios, we carefully evaluate the CO2 emissions impact of hydrogen metallurgy from a whole industry perspective and in each IS production stage. The results suggest that the hydrogen metallurgy transition will help the iron and steel industry (ISI) to achieve peak and deep carbon reduction. Under the HM scenario, CO2 emissions from the ISI would decrease to 816.28 million tons (Mt) in 2050, representing an additional 281.13 Mt reduction over the BAU scenario. Hydrogen metallurgy can accelerate CO2 reduction in raw material acquisition and material processing phases but may increase CO2 emissions in manufacturing and recycling phases. In 2050, hydrogen metallurgy will contribute an additional 12.49 Mt and 300.95 Mt of CO2 reduction to the raw material acquisition and material processing phases, respectively. However, CO2 emissions in the manufacturing and recycling phases would be 32.15 Mt and 0.22 Mt more than in the BAU scenario due to the increased electricity consumption and scrap demand of electric arc furnace (EAF) steelmaking, respectively. Over time, the optimization of hydrogen production and power supply mix will gradually reduce CO2 emissions in each IS production process. In 2050, the CO2 intensity of the hydrogen-rich shaft furnace direct reduced iron (H2-DRI)-EAF process will drop to 753.41 kgCO2/t, which is lower than all other processes except the 100 % scrap-based EAF process. Advancing the development of the H2-DRI-EAF process can effectively achieve CO2 emissions reduction while alleviating dependence on scrap resources. The results are expected to inform government policy on the development of hydrogen metallurgy in China and other countries.