Crucible Research Articles

Effect of Sintering Conditions on the Microstructure of an FeCrMnNiCo High-Entropy Alloy

We investigated the microstructure of an FeCrMnNiCo alloy fabricated by spark plasma sintering under different sintering temperatures (1000–1100°C) and times (1–600 s). All sintered alloys consisted of a single face-centered cubic phase. As the sintering time or temperature increased, the grains of the sintered alloys became partially coarse. The formation of Cr7C3 carbide occurred on the surface of the sintered alloys due to carbon diffusion from the graphite crucible. The depth of the layer containing Cr7C3 carbides increased to ~110 μm under severe sintering conditions (1100°C, 60 s). A molten zone was observed on the surface of the alloys sintered at higher temperatures (>1060°C) due to severe carbon diffusion that reduced the melting point of the alloy. The porosity of the sintered alloys decreased with increasing time at 1000°C, but increased at higher temperatures above 1060°C due to melting-induced porosity formation.

The Development of a High-Efficiency Small Induction Furnace for a Glass Souvenir Production Process Using Multiphysics

A small induction furnace (SIF), which has the important components of copper coils, a ceramic jig, and a graphite crucible, employed for a glass souvenir production process, has been developed as a form of clean technology for multiphysics, consisting of electromagnetics analysis (EA) and thermal analysis (TA). First, two experiments were established to measure parameters for multiphysics results validation and boundary condition settings. Then, the parameters were applied to multiphysics, in which the EA revealed magnetic flux density (B) and ohmic losses, and the TA reported a temperature consistent with the experimental results, confirming the multiphysics credibility. Next, a ferrite flux concentrator was added to the SIF during development. Multiphysics revealed that PC40 ferrite, as a flux concentrator with a suitable design, could increase B by about 159% compared to the conventional SIF at the power of 1000 W. As expected, the B increases alongside the increase in power applied to the coils, and is more densely concentrated in the flux concentrator than in other regions, enhancing the production process efficacy. Lastly, the developed SIF was employed in the actual process and received good feedback from users. The novel research findings are the developed SIF and methodology, exclusively designed for this research and practically employed for a glass souvenir production process.

Effect of preparation routes on the performance of a multi-component AB2-type hydrogen storage alloy

This article presents experimental results on the preparation and characterisation of a multi-component AB2–type intermetallic hydrogen storage alloy (A = Ti0.85Zr0.15, B = Mn1.22Ni0.22Cr0.2V0.3Fe0.06). The alloy samples were prepared by induction melting using Y2O3-lined alumo-silica and graphite crucibles. The characterisation results were compared with the ones for the reference sample of the same composition prepared by arc melting. It has been shown that the induction-melted samples exhibit reduced hydrogen sorption capacities and sloping plateaux on the pressure composition isotherms (PCI’s). The origin of the observed effects has been shown to be in the inhomogeneity of the induction-melted alloys and their contamination due to crucible—melt interaction, particularly pronounced for the alloy melted in the alumo-silica crucible; this alloy was additionally characterised by the decrease of Zr/Ti ratio and, in turn, higher plateau pressures of the PCI’s.

Analysis of the melting process of carbon-bearing pellets in iron bath, slag bath and graphite crucible

Background With the increase in the amount of scrap steel in society, the proportion of electric furnace steelmaking is increasing year by year, especially in China. Due to the high Zn content, the electric furnace arc dust (EAFD) needs to be recovered by non-blast furnace process. Due to EAFD containing a large amount of zinc ferrite, it needs to be recovered by fire process. It is a promising process to melt the EAFD pellets to get the discount and zinc-rich secondary ash. Methods To clarify the melting behavior of pellets in the metallurgical process, the slag phase diagram and the effect of temperature and FeO on slag viscosity were calculated using FactSage, and the melting process of electric furnace arc dust (EAFD) pellets in a graphite crucible, iron bath, and slag bath were experimentally investigated. Results The experimental results show that the viscosity of the slag system decreases with increasing temperature and FeO content, and the effect of FeO on viscosity is greater. The viscosity decreased from 0.305 to 0.276 Pa·s when the FeO content in the slag was increased from 0 wt. % to 2 wt.% at 1773 K. The melting process of the EAFD pellets in an iron bath and graphite crucible was consistent, and after the formation of liquid-phase slag in the pellets, the liquid-phase slag was diffused to melt the pellets. Conclusions The iron bath improved the heat transfer conditions of the pellets, reducing the smelting time from 600 to 360 s. The slag bath promoted the slagging reaction of the contact part to change the pellet melting process and increase the pellet melting speed, and the EAFD pellets melted within 240 s in a slag bath.

Coproduction of silicon nitride & oxynitride whiskers and precipitated silica from industrial rice husk ash

Rice industrialization generates large amounts of rice husk, and when this husk is burned, substantial volumes of ash are produced as a result. The lack of a sustainable application for these ashes constitutes a serious environmental liability. Employing rice husk ash as a starting material to manufacture higher-value products fulfills both environmental and economical purposes. Particularly, the presence of silica and carbon in intimate contact makes rice husk ash an attractive precursor for carbothermal reduction and nitridation processes. In the present work, a pre-treatment was applied to a locally sourced industrial rice husk ash, aiming to render not only a more appropriate starting material for carbothermal reduction and nitridation, but also precipitated silica as a by-product. This process involved a simple alkaline digestion step followed by filtering and acid precipitation of the solubilized silica. For carbothermal reduction and nitridation, the treated ash was introduced in graphite crucibles with graphite lids and held at soaking temperatures between 1200 °C and 1400 °C under a nitrogen atmosphere for 3 h. The pretreatment imposed on the ash permitted the adjustment of the carbon-to-silica ratio, producing a substantial improvement in the carbothermal reduction and nitridation results, and enabling the simultaneous obtention of precipitated silica. α- and β- silicon nitride, and silicon oxynitride whiskers were obtained through carbothermal reduction and nitridation of the treated rice husk ash. The whiskers obtained had lengths in the millimeter range with cross-sections ranging from about 100 nm up to 500 nm.

Experiments to Improve the Efficiency of Obtaining Brass Nanoparticles by Evaporation by a Continuous Beam of High-Energy Electrons

Composite, copper and zinc containing nanoparticles and brass nanoparticles have been obtained by a high-performance method of evaporation of substances by a relativistic electron beam. The change in the stoichiometry of nanopowders produced by stepwise irradiation of a brass ingot placed in a single-zone graphite crucible is considered. It was found that the production of such particles depends on the concentration of saturated vapors of zinc and copper. A two-zone configuration of the crucible has been developed, which makes it possible to realize the simultaneous evaporation of the constituent components, thereby providing the conditions for the formation of uniform brass nanoparticles with a uniform distribution of elements and a high yield of nanopowder. X-ray diffraction analysis (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray analysis (EDX) were carried out, and the specific surface of the obtained nanoparticles was determined. The mechanism of formation of composite nanoparticles is discussed.

Theoretical and experimental study of the mechanism for preparation of SiC nanowires by carbothermal reduction

High-quality SiC nanowires (NWs) were prepared at 1550 °C by carbothermal reduction of silica with carbon black under normal atmospheric pressure without a metallic catalyst. Linear and chain-beaded SiC NWs were synthesized in graphite and BN crucibles, respectively. The mass of the SiC NWs obtained from the BN crucible was greater than that obtained from the graphite crucible under the same conditions. Thermodynamic analyses and first-principles molecular dynamics simulations were performed to investigate the formation mechanism of the SiC NWs. Thermodynamic analysis revealed that in the carbothermal reduction reaction zone, SiO2 and C reacted to produce SiC particles, SiO, and CO. Subsequently, SiO reacted with CO during condensation, leading to the growth of SiC NWs. The first-principles molecular dynamics simulations indicate that the BN substrate has a greater affinity for gas-phase molecules than the graphite substrate, thereby creating optimal reaction sites for the reaction of SiO and CO molecules. This study provides a valuable reference for understanding the microscopic formation mechanisms and the large-scale production of SiC NWs.

Determination of major and trace elements in silicate rock fused with lithium metaborate using laser ablation-inductively coupled plasma-mass spectrometry

A novel lithium metaborate fusion technique using a homemade fusion furnace and graphite crucibles was developed for the determination of major and trace elements in silicate rocks using LA-ICP-MS.

Boroksit ve üleksit cevherlerinin ferromangan üretiminde kullanımı

This study investigated the possibilities of using low-grade manganese ores in ferromanganese production by smelting process. Fluorspar, ulexite, and boroxide (as flux) were added to manganese ores. Fluxes consisting of activated carbon, charge basicity, and charging materials were used in the smelting experiments. Reference samples without flux were also used for comparison. Charge materials were placed in capped graphite crucibles and smelted at 1650 °C for 2 hours. The metal/slag phases were separated from each other and their chemical analyses were made. At the end of the experiments, it was determined that boron ores instead of fluorspar reduced the manganese leakage in the slag to 1% and increased the manganese in the metal phase to 99%. As a result, it was determined that the fluidity of slag increased more than fluorspar and the smelting time decreased, and it is possible to use boron ores in ferromanganese production.

Graphite crucible interaction with Fe–Si–B phase change material in pilot-scale experiments

Abstract Fe–26Si–9B alloy is a promising high temperature phase change material (HTPCM), due to its high heat of fusion, small volumetric change, abundance, and low cost. Additionally, graphite has been identified as a promising candidate for use as a container material for this alloy. In this study, the feasibility of using graphite for Fe–26Si–9B HTPCM is investigated in a pilot-scale. Specifically, 4–5 kg Fe–26Si–9B master alloys were melted in graphite crucibles using an induction furnace, which underwent 2–3 thermal cycles in the temperature range of 1,100–1,375°C. The results showed that SiC and B4C precipitates were formed in the alloys. However, these carbides were found to be present only on the surface of the solidified alloys and not in the main body. Still, the chemical composition of the Fe–26Si–9B alloy remained relatively stable during the thermal cycles. It was also seen that the graphite crucible withstood the temperature cycles without cracking. Therefore, the use of graphite as a container for Fe–26Si–9B phase change material is a promising approach.

Estimation of hot metal desulfurization by intermediate and final blast-furnace slag when using pellets of different basicity in blast-furnace charge

n the process of blast-furnace smelting, up to 90% of coke sulfur is captured by the iron ore charge, accumulating in hot metal in the amount that was absorbed from the gas phase. Desulphurization of cast iron occurs when it interacts first with the intermediate, and at the final stage, with the final blast-furnace slag. In this regard, it is of interest to evaluate the desulfurizing properties of the intermediate and final slag, which affect the sulfur content in hot metal. Melting mixtures of pellets of different basicity and sinter in a blast furnace leads to the formation of primary and intermediate slags of different chemical composition. When smelting hot metal in blast furnaces, mainly unfluxed pel-lets and fluxed sinter are used. In the course of the study, mixtures of sinter and pellets of different basicity were pre-pared, which ensured the production of final blast-furnace slag with a basicity of CaO/SiO2 = 1.15 units. The mixtures were reduced and melted in graphite crucibles with the smelting products filtered through a coke nozzle. The coeffi-cients of sulfur distribution between intermediate slag and hot metal obtained from iron ore charge with different basicity of sinter and pellets were determined. The lowest sulfur distribution coefficient between the intermediate slag and hot metal is observed when the basicity of the pellets is in the range of 0.5‒1.2 units. To increase the desulfurization capacity of the intermediate slag, it is advisable to use unfluxed and fluxed pellets with a basicity of 0.25 units in the blast-furnace charge and an sinter with a basicity of 1.78‒1.87 units. Studies of the kinetics of the interaction of hot metal and final blast-furnace slag have shown that the final slag provides a high degree of desulfurization of hot metal during their interaction for 1 hour or more

Investigation on mechanical properties and corrosion resistance of Ti-modified AA5083 aluminum alloy for aerospace and automotive applications

Casting of aluminum with different concentration of alloying elements such as Mg, Mn (similar to that in AA5083) with additional percentages of 0.1, 0.2 and 0.3% Ti, are carried out using graphite crucible. The as-cast microstructure is modified by hot rolling to a thickness of ~ 2 mm. Mechanical and metallurgical and characterization of heat-treated thin sheets are carried out using tensile testing, hardness measurement, metallography, image analysis and optical microscope. By increasing the Ti content, the results show grain refinement and increase in the formation of Al3Ti which reflected positively on the mechanical properties. Specifically, Ultimate tensile strength is increased from 260 MPa (0 wt% Ti) to 345 MPa (0.3 wt% Ti) when using water quenching, 32.6% improvement for air cooling, and 23.3% for furnace cooling. Electrochemical corrosion behavior of heat-treated water quenched, air cooled and furnace cooled samples were tested in 3.5% NaCl solution. The results show that the heat-treated alloys have very good resistance against corrosion, while by increasing the Ti content, the corrosion rate increases due to the grain refinement phenomena.

A Novel Induction Heater for Sintering Metal Compacts with a Hybrid Material Extrusion Device

The traditional sintering of metallic components shaped via Material Extrusion Additive Manufacturing (MEAM) is a time-consuming process that involves sophisticated energy-intensive heating systems. This work describes a novel induction heater capable of efficiently tailoring temperature profiles to densify MEAM powder compacts. In situ sintering within the same device is achieved indirectly by heating a graphite crucible, whereby the heater is based on an inverter with a half-bridge topology using the Zero-Voltage Switching (ZVS) technique. The system comprises a bank of capacitors that, in conjunction with a work coil, form a parallel-topology resonant circuit. This design allows the inverter to be used as a current amplifier, thereby increasing its efficiency to deliver an output power of up to 5 kW. The device operates at a 62.86 kHz resonant frequency, achieving a 2.01 mm penetration depth and a 1365.7 °C crucible temperature with only 1.313 kW of consumption, providing an increase in efficiency compared to other low-cost systems. Equipped with a feedback circuit, it offers five distinct control techniques that enable the self-tuning of the crucible temperature. The results indicate that the Cohen–Coon tuning method is more robust compared to the Ziegler–Nichols, damped, no overshoot, and mixed techniques. Sintering with this novel induction heater provides an alternative method for reducing the processing times for MEAM geometries, paving the way for increased efficiency and reduced energy consumption. Circuit diagrams, simulations, and experimental data on the temperature, time, and output voltage are provided in this article.

XRD analysis determined crystal cage occupying number n of carbon anion substituted mayenite-type cage compound C12A7: nC

Abstract In this study, a series of samples of C12A7 derivative was prepared by high temperature sintering in a sealed graphite crucible. The theoretical model of C12A7 derivatives with different carbon occupation numbers was established. The X-ray diffraction (XRD) theoretical calculation was carried out. The conjecture was verified to a certain extent through the comparison of the theoretical calculation of XRD with the experimental results. According to the calculation results, it was found that the XRD patterns of C12A7 and its derivatives changed regularly with the change in the occupation number in the crystal cage. Under the condition that the types of vacancy atoms remained unchanged, the more vacancy atoms occupied in C12A7 crystal, the higher the peak at 2θ = 33.35° in the diffraction pattern. It was also found that the higher the atomic number of vacancy atoms in C12A7 crystal, the higher the peak at 2θ = 33.35° in the diffraction pattern. The carbon occupation number of samples at different experimental temperatures was deduced. The results showed that the carbon occupancy of the samples prepared at 990, 1,353 and 1,680°C were 11, 4 and 8, respectively.

Application of the Solute-Solvent EMF Cell to Measure Activity of NiF2 in Molten FLiNaK

Electromotive force (emf) measurements made using a combination of solute- and solvent-based electrodes were used to determine the activity of NiF2 in molten FLiNaK eutectic at 823 K across a concentration range of x NiF2 = 5.2 × 10–4–1.0 × 10–2. The solute emf values were measured using electrodes consisting of Ni wires immersed in FLiNaK with dissolved NiF2 contained in graphite crucibles. The measured emf values were then converted to the FLiNaK Eutectic Potassium Electrode (FEKE) potential and used to quantify the activity of dissolved NiF2. This quantification was based upon comparative measurements of a reference solvent electrode consisting of a K-Bi alloy immersed in pure FLiNaK contained in a boron nitride crucible and a solute electrode. Short cell lives were characteristic of the measurements due to the corrosive nature of the fluoride salts. Quantifying the activity of NiF2 will improve the utility of Ni2+/Ni reference electrodes in molten fluoride salts, which are notoriously difficult electrolytes to work with because of their reactivity. This work demonstrates the general nature of the solute-solvent approach as a repeatable, easily employed method for measuring the activity values of electroactive species in a variety of molten salts to improve understanding of the electroactive species behavior in these systems.

Dissolution Behavior of Chromite Ore in CaO‐SiO2 System

Numerous investigations proposed that the dissolution of chromite ore is the rate‐controlling step for the smelting reduction of chromite ore. The mechanism of chromite ore dissolution in the binary CaO‐SiO2 system is presented. The effect of basicity, temperature, and reducing conditions on chromite ore dissolution is elaborated. The solubility of chromite ore increases considerably when the basicity increases from 0.56 to 0.65. However, the solubility of chromite ore decreases when the basicity further increases from 0.65 to 0.74. The positive effect of reducing conditions on the solubility of chromite ore is evident. The maximum dissolved Cr2O3 in slag under reducing conditions by using a graphite crucible reaches 2.6 wt% after 15 min of dissolution. The element diffusion behavior at the chromite/slag interface is elaborated through SEM‐EDS technology. The analysis suggests that the rate‐controlling step in the early stage is the interface dissolution reaction. After a certain time, the rate‐controlling step becomes the mass transfer of Cr2O3 from the chromite ore to the chromite/slag interface. The activation energy of the dissolution reaction is = 285.29 kJ mol−1.

Electrothermal processing of chrysotile-asbestos wastes with production of ferroalloy and extraction of magnesium into the gas phase

The article presents the results of an experimental study on the processing of wastes from chrysotile-asbestos production at Kostanay Minerals JSC. An electrothermal technology for the extraction of magnesium and siliceous ferroalloy from the chrysotile-asbestos wastes is proposed. The influence of the amount of coke and steel shavings on the technological parameters of the obtained alloys is determined. The results of derivatographic and SEM analyses of the chrysotile-asbestos waste samples are presented. The studies included planning experiments using the second-order rotatable designs (Box-Hunter plans), graphical optimization of technological parameters, and electric melting of a charge in a graphite crucible using a single-electrode arc furnace. Adequate regression equations were obtained explaining the effect of the amount of coke and steel shavings added to the chrysotile-asbestos waste on the extraction degree of silicon into the alloy and the silicon concentration in the alloy. By the electric melting of the charge, high-quality FS25 grade ferrosilicon with a silicon content of 24.4-29.2% and FS45 grade ferrosilicon with a silicon content of 41.6-45% were obtained. It was established that FS45 grade ferrosilicon with the extraction degree of silicon into the alloy from 75 to 85.4% is formed in the presence of 33.6-38% of coke and 16-20.8% of steel shavings. FS25 grade ferrosilicon is formed in the presence of 30-38% of coke and 29.4-40% of steel shavings; the extraction degree of silicon is 68.6-73.8%.

A microwave-enhanced method able to substitute traditional pyrometallurgy for the future of metals supply from spent lithium-ion batteries

This work presents a new and promising method to recover Li, Co, Mn, and Ni from spent LIBs, based on a hybrid heating mechanism, obtained by using microwave radiation. Due to the presence of graphite, the heating is induced by the interfacial polarization of carbon atoms. The hybrid heating is based on the synergistic combination of an external susceptor with a graphite crucible. The system allows reaching carbothermic reduction conditions of black mass originating from spent LIBs, with a treatment of only a few minutes considering an electromagnetic radiation power ⋜1000 W, without any other additives. This process reduces the required associated energy by more than 2 orders of magnitude in comparison to conventional thermal treatments.The thermal process is followed by leaching in water and l-malic acid, obtaining a recovery process resulting to be competitive with metals extraction from respective ores.

Nanopowders Created by Irradiating Brass with Relativistic Electrons

The paper deals with changes in the stoichiometry of nanopowders obtained under staged irradiation of a brass ingot placed in a graphite crucible. Composite core-shell CuO/ZnO nanoparticles, copper nanoparticles, and copper and zinc oxides were obtained. The use of a relativistic electron accelerator is necessary to produce nanopowders on an industrial scale. Transmission electron microscopy and energy-dispersive analysis of the obtained nanoparticles were carried out. Thermodynamic calculation of the temperature dependence of the equilibrium content of copper and zinc is presented for the condensed and gas phases. The formation mechanism of CuO/ZnO composite nanoparticles is discussed.

Ultrahigh edge‑nitrogen-doped porous carbon anode materials for high-capacity and fast-charging lithium-ion batteries

Most reported nitrogen-doped carbon anode materials of lithium-ion batteries (LIBs) own finite capacities and inferior initial coulombic efficiency (ICE). One effective method to enhance capacities and capacities of the nitrogen-doped carbon anode materials is edge‑nitrogen doping. It still endures obstacles to realize a high edge‑nitrogen doping level owing to the difficulty to control of the nitrogen doping types. In this work, a series of edge‑nitrogen-doped porous carbon (ENPC) with different edge‑nitrogen doping levels are synthesized by annealing sucrose and g-C3N4 in a sealed graphite crucible. The edge‑nitrogen doping level from 8.88 at.% to 12.93 at.% for the ENPC-T can be regulated by changing the annealing temperature. Serving as LIBs anodes, the ENPC-800 exhibits an excellent capacity (1251.1 mAh g−1 at 0.1 A g−1), high ICE (82.9 %) and remarkable cycle life (650.5 mAh g−1 at 1 A g−1 after 1000 cycles with an exceptional capacity retention of 99.3 %). More significantly, by correlating the capacity and conductivity with the nitrogen doping configuration of the ENPC-T materials, the results highlight the effect of edge‑nitrogen on the capacity and conductivity. Meanwhile, the electrochemical characterizations of CV, GITT and EIS illustrate that a higher edge‑nitrogen doping level improves the capacity, electronic conductivity and fast-charging performance of ENPC-T. This new strategy can pave a new approach for the investigation and application of nitrogen-doped carbon anodes.