The practical engineering applications of powder metallurgy (PM) Ti alloys produced through cold compaction and pressure-less sintering are impeded by poor sintering densification, embrittlement caused by excessive O impurities, and severe sintering deformation resulting from the use of heterogeneous powder mixtures. This review presents a summary of our previous work on addressing the above challenges. Initially, we proposed a novel strategy using reaction-induced liquid phases to enhance sintering densification. Near-complete density (relative density exceeding 99%) was achieved by applying the above strategy and newly developed sintering aids. By focusing on the O-induced embrittlement issue, we determined the onset dissolution temperature of oxide films in the Ti matrix. On the basis of this finding, we established a design criterion for effective O scavengers that require reaction with oxide films before their dissolution. Consequently, a ductile PM Ti alloy was successfully obtained by introducing 0.3wt% NdB6 as the O scavenger. Lastly, a powder-coating strategy was adopted to address the sintering deformation issue. The ultrafine size and shell-like distribution characteristics of coating particles ensured rapid dissolution and homogeneity in the Ti matrix, thereby facilitating linear shrinkage during sintering. As a result, geometrically complex Ti alloy parts with high dimensional accuracy were fabricated by using the coated powder. Our fundamental findings and related technical achievements enabled the development of an integrated production technology for the high-performance and accurate shaping of low-cost PM Ti alloys. Additionally, the primary engineering applications and progress in the industrialization practice of our developed technology are introduced in this review.
Solid oxide fuel cells (SOFCs) have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies. However, traditional SOFCs suffer from having a higher volume, current leakage, complex connections, and difficulty in gas sealing. To solve these problems, Rolls-Royce has fabricated a simple design by stacking cells in series on an insulating porous support, resulting in the tubular segmented-in-series solid oxide fuel cells (SIS-SOFCs), which achieved higher output voltage. This work systematically reviews recent advances in the structures, preparation methods, performances, and stability of tubular SIS-SOFCs in experimental and numerical studies. Finally, the challenges and future development of tubular SIS-SOFCs are also discussed. The findings of this work can help guide the direction and inspire innovation of future development in this field.
To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections I and II is less than that of Sections III and IV. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional (3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.
Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem. Recently, new regulators have been proposed for magnesite flotation decalcification, although traditional regulators such as tannin, water glass, sodium carbonate, and sodium hexametaphosphate are more widely used in industry. However, they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests. Inspired by the limonite presedimentation method and the addition of a regulator to magnesite slurry mixing, we used a tannin pretreatment method for separating magnesite and dolomite. Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite. Moreover, the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased, respectively, in the presence of NaOl. Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface. X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.
This paper proposes luteolin (LUT) as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate (NaOL) system. The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing. At pH = 9, with LUT concentration of 50 mg·L−1 and NaOL concentration of 50 mg·L−1, scheelite recovery reaches 80.3%. Calcite, on the other hand, exhibits a recovery rate of 17.6%, indicating a significant difference in floatability between the two minerals. Subsequently, the surface modifications of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing, Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The study investigates the selective depressant mechanism of LUT on calcite. Adsorption capacity testing and Zeta potential analysis demonstrate substantial absorption of LUT on the surface of calcite, impeding the further adsorption of sodium oleate, while its impact on scheelite is minimal. FT-IR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite, forming strong chemisorption bonds between the hydroxyl group and calcium ions present. AFM directly illustrates the distinct adsorption densities of LUT on the two mineral types. Consequently, LUT can effectively serve as a depressant for calcite, enabling the successful separation of scheelite and calcite.
Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize, which makes it difficult to separate the mineral phases through conventional beneficiation. This study proposed a new treatment called flash reduction-melting separation (FRMS) for boron-bearing iron concentrates. In this method, the concentrates were first flash-reduced at the temperature under which the particles melt, and the slag and the reduced iron phases disengaged at the particle scale. Good reduction and melting effects were achieved above 1550°C. The B2O3 content in the separated slag was over 18wt%, and the B content in the iron was less than 0.03wt%. The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and temperature on the reduction and melting steps with and without pre-reducing the raw concentrate. The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.
The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process. In this study, the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments. Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’ diffusion and phase transformation during the roasting process. The results indicated that limestone decomposed into calcium oxide, and magnetite was oxidized to hematite at the early stage of preheating. With the increase in roasting temperature, the diffusion rate of Fe and Ca was obviously accelerated, while the diffusion rate of Si was relatively slow. The order of magnitude of interdiffusion coefficient of Fe2O3–CaO diffusion couple was 10−10 m2·s−1 at a roasting temperature of 1200°C for 9 h. Ca2Fe2O5 was the initial product in the Fe2O3–CaO–SiO2 diffusion interface, and then Ca2Fe2O5 continued to react with Fe2O3 to form CaFe2O4. With the expansion of the diffusion region, the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO2 into CaFe2O4, which can strengthen the consolidation of fluxed pellets. Furthermore, andradite would be formed around a small part of quartz particles, which is also conducive to the consolidation of fluxed pellets. In addition, the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.
High-chromium vanadium–titanium magnetite (HVTM) is a crucial polymetallic-associated resource to be developed. The all-pellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future. By referencing the production data of vanadium-titanium magnetite blast furnaces, this study explored the softening-melting behavior of high-chromium vanadium–titanium magnetite and obtained the optimal integrated burden based on flux pellets. The results show that the burden with a composition of 70wt% flux pellets and 30wt% acid pellets exhibits the best softening-melting properties. In comparison to that of the single burden, the softening-melting characteristic temperature of this burden composition was higher. The melting interval first increased from 307 to 362°C and then decreased to 282°C. The maximum pressure drop (ΔP max) decreased from 26.76 to 19.01 kPa. The permeability index (S) dropped from 4643.5 to 2446.8 kPa·°C. The softening–melting properties of the integrated burden were apparently improved. The acid pellets played a role in withstanding load during the softening process. The flux pellets in the integrated burden exhibited a higher slag melting point, which increased the melting temperature during the melting process. The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden. The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening-melting properties of the integrated burden.
The machine learning models of multiple linear regression (MLR), support vector regression (SVR), and extreme learning machine (ELM) and the proposed ELM models of online sequential ELM (OS-ELM) and OS-ELM with forgetting mechanism (FOS-ELM) are applied in the prediction of the lime utilization ratio of dephosphorization in the basic oxygen furnace steelmaking process. The ELM model exhibites the best performance compared with the models of MLR and SVR. OS-ELM and FOS-ELM are applied for sequential learning and model updating. The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500, with the smallest population mean absolute relative error (MARE) value of 0.058226 for the population. The variable importance analysis reveals lime weight, initial P content, and hot metal weight as the most important variables for the lime utilization ratio. The lime utilization ratio increases with the decrease in lime weight and the increases in the initial P content and hot metal weight. A prediction system based on FOS-ELM is applied in actual industrial production for one month. The hit ratios of the predicted lime utilization ratio in the error ranges of ±1%, ±3%, and ±5% are 61.16%, 90.63%, and 94.11%, respectively. The coefficient of determination, MARE, and root mean square error are 0.8670, 0.06823, and 1.4265, respectively. The system exhibits desirable performance for applications in actual industrial production.
The proper recycling of spent lithium-ion batteries (LIBs) can promote the recovery and utilization of valuable resources, while also negative environmental effects resulting from the presence of toxic and hazardous substances. In this study, a new environmentally friendly hydro-metallurgical process was proposed for leaching lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) from spent LIBs using sulfuric acid with citric acid as a reductant. The effects of the concentration of sulfuric acid, the leaching temperature, the leaching time, the solid–liquid ratio, and the reducing agent dosage on the leaching behavior of the above elements were investigated. Key parameters were optimized using response surface methodology (RSM) to maximize the recovery of metals from spent LIBs. The maximum recovery efficiencies of Li, Ni, Co, and Mn can reach 99.08%, 98.76%, 98.33%, and 97.63%. under the optimized conditions (the sulfuric acid concentration was 1.16 mol/L, the citric acid dosage was 15wt%, the solid–liquid ratio was 40 g/L, and the temperature was 83°C for 120 min), respectively. It was found that in the collaborative leaching process of sulfuric acid and citric acid, the citric acid initially provided strong reducing CO2 ·−, and the transition metal ions in the high state underwent a reduction reaction to produce transition metal ions in the low state. Additionally, citric acid can also act as a proton donor and chelate with lower-priced transition metal ions, thus speeding up the dissolution process.
Iron-rich electrolytic manganese residue (IREMR) is an industrial waste produced during the processing of electrolytic metal manganese, and it contains certain amounts of Fe and Mn resources and other heavy metals. In this study, the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR. The effects of IREMR and H2SO4 mass ratio, current density, reaction temperature, and electrolytic time on the leaching and current efficiencies of Fe were studied. According to the results, high-purity Fe powder can be recovered from the cathode plate, and the slurry electrolyte can be recycled. The leaching efficiency, current efficiency, and purity of Fe reached 92.58%, 80.65%, and 98.72wt%, respectively, at a 1:2.5 mass ratio of H2SO4 and IREMR, reaction temperature of 60°C, electric current density of 30 mA/cm2, and reaction time of 8 h. In addition, vibrating sample magnetometer (VSM) analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m, which reached the advanced magnetic grade of electrical pure-iron powder (DT4A coercivity standard). The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.
The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming (PHF) process directly determines the quality of the formed components. The microstructure stability of the pre-hardened sheets was investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS), while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests. The results indicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging (NA). The deviations of ultimate tensile strength (UTS), yield strength (YS), and sheet formability (Erichsen value) are all less than 2%. Also, after different NA time (from 48 h to 1 month) is applied to alloys before pre-hardening treatment, the pre-hardened alloys possess stable microstructure and mechanical properties as well. Interestingly, with the extension of NA time before pre-hardening treatment from 48 h to 1 month, the contribution of NA to the pre-hardening treatment is limited. Only a yield strength increment of 20 MPa is achieved, with no loss in elongation. The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston (GP) zones at the early stage of pre-hardening treatment, and the formation of θ″ phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.
Al is considered as a promising lithium-ion battery (LIBs) anode materials owing to its high theoretical capacity and appropriate lithation/de-lithation potential. Unfortunately, its inevitable volume expansion causes the electrode structure instability, leading to poor cyclic stability. What’s worse, the natural Al2O3 layer on commercial Al pellets is always existed as a robust insulating barrier for electrons, which brings the voltage dip and results in low reversible capacity. Herein, this work synthesized core–shell Al@C–Sn pellets for LIBs by a plus-minus strategy. In this proposal, the natural Al2O3 passivation layer is eliminated when annealing the pre-introduced SnCl2, meanwhile, polydopamine-derived carbon is introduced as dual functional shell to liberate the fresh Al core from re-oxidization and alleviate the volume swellings. Benefiting from the addition of C–Sn shell and the elimination of the Al2O3 passivation layer, the as-prepared Al@C–Sn pellet electrode exhibits little voltage dip and delivers a reversible capacity of 1018.7 mAh·g−1 at 0.1 A·g−1 and 295.0 mAh·g−1 at 2.0 A·g−1 (after 1000 cycles), respectively. Moreover, its diffusion-controlled capacity is muchly improved compared to those of its counterparts, confirming the well-designed nanostructure contributes to the rapid Li-ion diffusion and further enhances the lithium storage activity.
Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO2-mineralized cementitious materials. In this work, copper-nickel slag-based cementitious material (CNCM) was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO2 mineralization capacity. Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development. Meanwhile, thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO2 adsorption amount and carbonation products of CNCM. Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging (BSE) with energy-dispersive X-ray spectrometry. Results showed that among the studied samples, the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO2 sequestration amount of 8.51wt% at 80°C and 72 h while presenting the compressive strength of 39.07 MPa. This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO2 and exhibit high compressive strength. Although the addition of citric acid did not improve strength development, it was beneficial to increase the CO2 diffusion and adsorption amount under the same carbonation conditions from BSE results. This work provides guidance for synthesizing CO2-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.
The coagulation process is a widely applied technology in water and wastewater treatment. Novel composite polyferric magnesium–silicate–sulfate (PFMS) coagulants were synthesized using Na2SiO3·9H2O, Fe2(SO4)3, and MgSO4 as raw materials in this paper. The effects of aging time, Fe:Si:Mg, and OH:M molar ratios (M represents the metal ions) on the coagulation performance of the as-prepared PFMS were systematically investigated to obtain optimum coagulants. The results showed that PFMS coagulant exhibited good coagulation properties in the treatment of simulated humic acid–kaolin surface water and reactive dye wastewater. When the molar ratio was controlled at Fe:Si:Mg = 2:2:1 and OH:M = 0.32, the obtained PFMS presented excellent stability and a high coagulation efficiency. The removal efficiency of ultraviolet UV254 was 99.81%, and the residual turbidity of the surface water reached 0.56 NTU at a dosage of 30 mg·L−1. After standing the coagulant for 120 d in the laboratory, the removal efficiency of UV254 and residual turbidity of the surface water were 88.12% and 0.68 NTU, respectively, which accord with the surface water treatment requirements. In addition, the coagulation performance in the treatment of reactive dye wastewater was greatly improved by combining the advantages of magnesium and iron salts. Compared with polyferric silicate–sulfate (PFS) and polymagnesium silicate–sulfate (PMS), the PFMS coagulant played a better decolorization role within the pH range of 7–13.
With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(VI) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(VI). The waste amidoxime resin was first modified with H3PO4 and ZnCl2, and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(VI) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(VI) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(VI) to Cr(III) and decrease the toxicity of Cr(VI) during adsorption. PPR-Z exhibited Cr(VI) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(VI) adsorption are the chemical reduction of Cr(VI) into Cr(III) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(VI) pollution and realizes the concept of “treating waste with waste”.
X-ray excited photodynamic therapy (X-PDT) is the bravo answer of photodynamic therapy (PDT) for deep-seated tumors, as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth. However, high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application. To address this issue, this work employed a classical co-precipitation reaction to synthesize NaLuF4:15%Tb3+ (NLF) with an average particle size of (23.48 ± 0.91) nm, which was then coupled with the photosensitizer merocyanine 540 (MC540) to form the X-PDT system NLF–MC540 with high production of singlet oxygen. The system could induce antitumor efficacy to about 24% in relative low dose X-ray irradiation range (0.1–0.3 Gy). In vivo, when NLF–MC540 irradiated by 0.1 Gy X-ray, the tumor inhibition percentage reached 89.5% ± 5.7%. The therapeutic mechanism of low dose X-PDT was found. A significant increase of neutrophils in serum was found on the third day after X-PDT. By immunohistochemical staining of tumor sections, the Ly6G+, CD8+, and CD11c+ cells infiltrated in the tumor microenvironment were studied. Utilizing the bilateral tumor model, the NLF–MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth. Detected by enzyme linked immunosorbent assay (ELISA), two cytokines IFN-γ and TNF-α in serum were upregulated 7 and 6 times than negative control, respectively. Detected by enzyme linked immune spot assay (ELISPOT), the number of immune cells attributable to the IFN-γ and TNF-α levels in the group of low dose X-PDT were 14 and 6 times greater than that in the negative control group, respectively. Thus, it conclude that low dose X-PDT system could successfully upregulate the levels of immune cells, stimulate the secretion of cytokines (especially IFN-γ and TNF-α), activate antitumor immunity, and finally inhibit colon tumor growth.