Journal of Rare Earths最新文献

{"title":"Interface structure of α-Mg/14H-LPSO: First-principles prediction and experimental study","authors":"Yuan Shi,&nbsp;Xiaohua Zhang,&nbsp;Hongyan Yue,&nbsp;Chao Li","doi":"10.1016/j.jre.2024.07.009","DOIUrl":"10.1016/j.jre.2024.07.009","url":null,"abstract":"<div><p>The interfacial structure of the <em>α</em><span><span>-Mg/14H-LPSO phase in rare earth-including magnesium alloy<span> was investigated via high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and first-principles calculations of density-functional theory. Eleven possible interfacial models were constructed according to the different terminations of the LPSO phase, and the corresponding </span></span>interfacial energies<span><span> were calculated, from which the four most stable structures (Ter1-MgY-hollow, Ter2-Zn-hollow, Ter3-MgYII-hollow and Ter4-Mg-bridge) were obtained. The interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations, and the most stable interfacial structure was evaluated. Ter1-MgY-hollow and Ter2-Zn-hollow have the lowest </span>interfacial energies in the range of −0.7 eV &lt; Δ</span></span><em>μ</em>_Y<span> &lt; −0.6 eV, where fluctuating change of state is the minimized and the interface is the most stable. The separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the interface. The calculation results show that the maximum interfacial separation work is 1.45 J/m</span>² for the interface model of <em>α</em>-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.</p></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 9","pages":"Pages 1792-1799"},"PeriodicalIF":5.2,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141708176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanism of corrosion behavior induced by precipitates under plastic compressive stress in Mg-Gd-Y alloys","authors":"Lele Liu,&nbsp;Ping Wang,&nbsp;Yimeng Wang,&nbsp;Weiming Li,&nbsp;Min Xu,&nbsp;Haoyan Xue","doi":"10.1016/j.jre.2024.06.041","DOIUrl":"10.1016/j.jre.2024.06.041","url":null,"abstract":"<div><div>Through independently developed stress-loading equipment, stress corrosion tests on Mg-Gd-Y alloy were conducted in a 3.5 wt% NaCl solution. The effects of plastic compressive stress on the corrosion behavior of the alloy were thoroughly investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) among other microscopic analysis techniques. The results indicate that the alloy mainly consists of <em>α</em>-Mg grains, Mg₂₄Y₅ phase, Mg₅Gd phase, and LPSO phase. The corrosion behavior of the Mg-Gd-Y alloy is significantly influenced by the microstructure of the interface between the precipitates and the matrix, the potential difference, and the stress state. In the unstressed state, the Mg₂₄Y₅ phase first induces corrosion at the edges of the <em>α</em>-Mg grain boundaries, which then spreads internally. Upon the application of plastic stress, the corrosion-inducing capability of the LPSO phase on <em>α</em>-Mg grains notably increases. This discovery provides new insights into the mechanisms by which plastic compressive stress affects the corrosion behavior of Mg-Gd-Y alloys and offers an important basis for the theoretical research and anti-corrosion design in the engineering applications of this alloy.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2183-2195"},"PeriodicalIF":5.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141710806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of heat-treatment on microstructure and deformation behavior of Mg-8.5Li-6.6Zn-1.5Y alloy","authors":"Yu Wang ,&nbsp;Penghao Wang ,&nbsp;Jingpeng Xiong ,&nbsp;Jian Wang ,&nbsp;Yong Liu","doi":"10.1016/j.jre.2024.06.039","DOIUrl":"10.1016/j.jre.2024.06.039","url":null,"abstract":"<div><div>The Mg-8.5Li-6.6Zn-1.5Y (wt%) as-cast alloy exhibits a (β+α) duplex phase structure. Interspersed eutectics, primarily reticular I-phase, predominantly form along phase and grain boundaries, enhancing the strength but leading to a reduction in ductility due to the brittle nature of the I-phase. This study focuses on modifying the alloy's microstructure through heat treatment to simultaneously improve both strength and ductility. Heating the alloy at 450 °C/6 h results in the dissolution of continuous reticular I-phase and the massive α-Mg. Subsequent slow cooling facilitates the reintroduction of α-Mg, with the cooling rate directly impacting the mean size of the α-Mg phase. The slower the cooling, the larger the α-Mg phase. The strength and ductility of LZW861 alloy are simultaneously enhanced by heat treatment, particularly in the air-cooled (450 °C/6 h-AC) alloy, while the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) increases from 147 MPa, 189 MPa, and 17.8% to 192 MPa, 242 MPa, and 22.3%, respectively, compared to the as-cast state. This increase in strength can be attributed partly to the precipitation of fine needle-like α-Mg uniformly dispersed in the β-Li matrix. Additionally, the increase in dispersed (Li,Mg)₃Zn nanoparticles contributes to matrix strengthening. The enhancement of ductility after 450 °C/6 h-AC heat treatment is ascribed to the dissolution of reticulated I-phase and the refinement of α-Mg phase, which enhance interphase deformation compatibility and weaken crack initiation at dispersed β/α interface.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2293-2302"},"PeriodicalIF":5.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High strength and high ductility Mg-Gd-Y-Zn-Zr alloys obtained by controlling texture and dynamic precipitation through LPSO phase structure of different initial morphologies","authors":"Yayun He ,&nbsp;Rui Guo ,&nbsp;Xi Zhao ,&nbsp;Zhimin Zhang","doi":"10.1016/j.jre.2024.06.042","DOIUrl":"10.1016/j.jre.2024.06.042","url":null,"abstract":"<div><div>This paper investigated the effects of three different initial phase structures on the microstructure evolution and tensile properties of extruded Mg-Gd-Y-Zn-Zr alloy, using an extrusion ratio of 3.6. These three initial phase structures were obtained by heat treatment, which is narrow spacing long-period stacking ordered phase (LPSO) phase structure alloy (EN alloy), wide spacing LPSO phase structure alloy (EW alloy), and narrow spacing LPSO phase and β phase overlapping phase structure alloy (EO alloy). The dynamic recrystallization (DRX) and dynamic precipitation behavior of extruded alloys with different initial structures, as well as their strengthening and ductility mechanisms were studied in detail. After hot extrusion with a low extrusion ratio, the alloy exhibits a bimodal structure composed of undynamic recrystallization (UN-DRX) grains and dynamic recrystallization (DRX) grains with strong textures. The narrow-spacing LPSO phase structure inhibits DRX and dynamic precipitation, while both the wide-spacing LPSO phase structure and the overlapping phase structure alloys promote DRX and dynamic precipitation. The strength improvement is mainly due to the strong texture and internal dislocation pinning of the undynamic recrystallization zone (UN-DRX) and the high strengthening effect of the narrow spacing LPSO phase. Although the promotion of DRX improves grain boundary strengthening effect, it cannot make up for reducing the UN-DRXed grain strengthening effect. A lower volume fraction of β dynamic precipitation phase is beneficial for improving the ductility of the alloy.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2217-2230"},"PeriodicalIF":5.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanical property and anisotropy of as-extruded Mg–Zn–Y–Mn alloys with different volume fraction of long-period stacking ordered (LPSO) phase","authors":"Dahui Liang ,&nbsp;Mincong Chen ,&nbsp;Chuanqiang Li ,&nbsp;Zhipei Tong ,&nbsp;Yong Dong ,&nbsp;Dong Bian","doi":"10.1016/j.jre.2024.06.034","DOIUrl":"10.1016/j.jre.2024.06.034","url":null,"abstract":"<div><div>Effects of different volume fraction of long-period stacking ordered (LPSO) phase on the microstructure, mechanical property and anisotropy of the as-extruded Mg-<em>x</em>Zn-<em>y</em>Y-0.1Mn (<em>x</em> = 1 wt%, 2 wt%, 4 wt% and <em>y</em> = 2 wt%, 4 wt%, 8 wt%) alloys were studied by an optical microscope, a scanning electron microscope, texture analysis, a transmission electron microscope and tensile testing. The results reveal that the volume fraction of LPSO phase increases from ZW12 to ZW24 to ZW48 alloys with the elevating Zn and Y content but constant Y/Zn value, and the mechanical strength of the LPSO-containing Mg–Zn–Y–Mn system is gradually improved when increasing LPSO phases. With the highest volume fraction of LPSO phase, ZW48 alloy presents the highest ultimate tensile strength (UTS) of 427 MPa along the extrusion direction (ED) when compared with those of ZW12 alloy with the UTS of 307 MPa and ZW24 alloy with the UTS of 347 MPa. Moreover, the elongation ratio of ZW48 alloy is maintained to moderate 9.9%, which is also the highest among three studied alloys. On the other hand, texture analysis demonstrates that the basal texture of the <em>α</em>-Mg phase in the ZW48 alloy is significantly weakened by the generation of more LPSO phases. On the contrary, a high texture intensity of <em>α</em>-Mg phase and obvious mechanical anisotropy can be observed for the ZW12 alloy. However, mechanical anisotropy still exists in the ZW48 alloy containing massive LPSO phases, which is attributed primarily to the zonal distribution of large LPSO along the ED.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2259-2269"},"PeriodicalIF":5.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intergranular deformation mechanism stimulated by {10-12} extension twins in AZ81-La alloy","authors":"Biwu Zhu ,&nbsp;Jing Su ,&nbsp;Xiao Liu ,&nbsp;Changping Tang ,&nbsp;Wenhui Liu ,&nbsp;Luoxing Li ,&nbsp;Congchang Xu ,&nbsp;Pengcheng Guo","doi":"10.1016/j.jre.2024.06.033","DOIUrl":"10.1016/j.jre.2024.06.033","url":null,"abstract":"<div><div>In polycrystalline Mg-RE magnesium alloys, the lattice parameter, dislocation dynamics and critical resolved shear stress (CRSS) for various deformation modes are altered with the addition of RE atom, finally affecting deformation mode and strain accommodation mechanism among neighboring grains. Uniaxial compression tests were performed on as-extruded AZ81-La Mg alloy samples with the <em>c</em>-axis of the majority of crystals vertical to the compression direction. Twin variants and dominant slip systems were examined by electron backscattered diffraction (EBSD) technique. It is found by in-grain misoriention axis (IGMA) analysis that the plastic deformation is mainly accommodated by a combination of the pyramidal &lt;<em>c</em>+<em>a</em>&gt; slip and the basal &lt;<em>a</em>&gt; slip. The dominant twin variant is <span><math><mrow><mrow><mo>{</mo><mn>0</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>12</mn><mo>}</mo></mrow></mrow></math></span> &lt;<span><math><mrow><mn>01</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow></math></span>&gt; and <span><math><mrow><mrow><mo>{</mo><mn>1</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>02</mn><mo>}</mo></mrow></mrow></math></span> &lt;<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>101</mn></mrow></math></span>&gt;. Here, we applied a modified displacement gradient accommodation (m-DGA) method to evaluate the selection mechanism of twin/slip in neighbour grain stimulated by <span><math><mrow><mrow><mo>{</mo><mn>10</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo></mrow></mrow></math></span> extension twin. It is found that the activated slip system and/or twin variant in the neighbouring grain is determined by the accommodation of the major shear strain induced by <span><math><mrow><mrow><mo>{</mo><mn>10</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo></mrow></mrow></math></span> extension twin in such a way that strain concentration along grain boundaries can be relaxed.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2325-2331"},"PeriodicalIF":5.2,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of sodium carboxymethyl cellulose on redispersibility and polishing performance of lanthanum-cerium-based slurry containing sodium hexametaphosphate","authors":"Ning Wang ,&nbsp;Huiqing Han ,&nbsp;Zhenyu Zhang ,&nbsp;Zongyu Feng ,&nbsp;Xianmin Tan ,&nbsp;Yuanyuan Zheng ,&nbsp;Juanyu Yang ,&nbsp;Xiaowei Huang","doi":"10.1016/j.jre.2024.06.021","DOIUrl":"10.1016/j.jre.2024.06.021","url":null,"abstract":"<div><div>The lanthanum-cerium-based slurry (LC-slurry) is extensively utilized in the chemical mechanical polishing (CMP) of TFT-LCD glass substrates, optical lenses, and other glass products. Sodium hexametaphosphate (SHMP), as a dispersant, is commonly employed to enhance the dispersion properties of LC-slurry for improved polishing performance. However, the tendency of sedimentation to form a compacted sediment layer, which is challenging to redisperse, increases storage difficulty and polishing equipment failure risk, thereby limiting its utilization in CMP. In the present study, sodium carboxymethylcellulose (CMC-Na), a long-chain organic polymer, was employed to enhance the redispersibility of LC-slurry containing SHMP. A comprehensive investigation was conducted on the influence of CMC-Na dosage and slurry pH on dispersibility, redispersibility and polishing performance. Additionally, an analysis was carried out to elucidate the underlying mechanism behind the effect of CMC-Na. The study demonstrates that the LC-slurry, containing 250 ppm SHMP and 500 ppm CMC-Na, exhibits excellent dispersibility and redispersibility. Further polishing tests demonstrate that compared to the LC-slurry containing only SHMP, utilizing the slurry containing both SHMP and CMC-Na at various pH for polishing thin film transistor liquid crystal display (TFT-LCD) glass substrates results in a reduction of both material removal rate (MRR) and surface roughness (<em>Sa</em>). Specifically, when adjusting the slurry to a pH range of 5–6, the MRR can reach up to 330 nm/min, which closely approximates the MRR achieved by LC-slurry containing only 250 ppm SHMP at corresponding pH values. Meanwhile, after polishing, the surface roughness of the glass substrate measures approximately 0.47 nm.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"43 4","pages":"Pages 851-858"},"PeriodicalIF":5.2,"publicationDate":"2024-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143679641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recovery of rare earth elements from sedimentary rare earth ore via sulfuric acid roasting and water leaching","authors":"Shanshan Yu,&nbsp;Xianquan Ao,&nbsp;Lijuan Liang,&nbsp;Xingyu Mao,&nbsp;Yu Guo","doi":"10.1016/j.jre.2024.06.006","DOIUrl":"10.1016/j.jre.2024.06.006","url":null,"abstract":"<div><div>Rare earth elements were extracted using a sulfuric acid roasting-water leaching process. The effect of acid roasting on a new type of low-grade sedimentary rare earth ore found in Guizhou Province, China was analyzed using X-ray diffraction and scanning electron microscopy. A systematic study was conducted on process parameters such as amount of acid, roasting temperature, roasting time, water leaching temperature, and leaching time. The results reveal that the total recovery of rare earth elements reaches 81.37%, which is 3.1 times higher than that achieved through direct acid leaching, under the optimal conditions. In addition, the leaching rate of heavy rare earth elements reaches 72.53%. Rare earth elements and some other valuable metals are transformed into soluble sulfate through the local decomposition of clay minerals under the action of the sulfuric acid attack. The dissolution rates of aluminum, iron, and titanium ions are 34.94%, 17.05%, and 62.77%, respectively. The precipitation rate of Ti reaches 99%, and the loss of rare earth ions in the solution is less than 1%. Meanwhile, the results of a leaching kinetics analysis indicate that the leaching process of rare ions is controlled by diffusion. Precious metal ions such as iron and aluminum in the leaching solution can reduce the adsorption of rare earth ions by kaolinite. This study efficiently recovered rare earth ions under conditions of low calcination temperature and direct water leaching, resulting in reduced energy consumption of the extraction process and acidity of the leaching solution. These findings provide a solid foundation for the further separation and extraction of rare earth ions.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"43 4","pages":"Pages 805-814"},"PeriodicalIF":5.2,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141405387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fabrication of Ce-doped macroporous carbon fibers for efficient degradation of tetracycline by activating persulfate","authors":"Chaohai Wang ,&nbsp;Taiyang Cao ,&nbsp;Zheng Lv ,&nbsp;Rongfu Peng ,&nbsp;Yanli Mao ,&nbsp;Jinhui Zhang ,&nbsp;Xinfeng Zhu ,&nbsp;Junning Wang ,&nbsp;Ke Zhao ,&nbsp;Gangfu Song","doi":"10.1016/j.jre.2024.06.018","DOIUrl":"10.1016/j.jre.2024.06.018","url":null,"abstract":"<div><div>Metal–organic frameworks (MOFs) and their derivatives have gained significant attention in recent years for their ability to catalyze the advanced oxidation of persulfates. Cerium-doped MOFs, in particular, have shown promise due to their high catalytic efficiency, practical applicability, and cost-effectiveness. However, their structure, catalytic properties, and mechanisms are not yet fully understood. ZIF-8 was chosen as the raw material to prepare cerium-doped hollow carbon nanofibers (Ce-HCNFs) using the electrostatic spinning-calcination method. The objective is to investigate the structure, catalytic performance, and catalytic mechanism of Ce-HCNFs. The results show that Ce-HCNFs catalyzed the degradation of tetracycline (TC) by persulfate up to 76.9%. Quenching experiments and electron paramagnetic resonance experiments indicate the dominant role of single-linear oxygen. Furthermore, the experiments on the influence factor and cycling demonstrate the exceptional stability and recycling capability of Ce-HCNFs in real-world water environments.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"43 3","pages":"Pages 480-489"},"PeriodicalIF":5.2,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141405632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recovery of rare earth elements from rare earth molten salt electrolytic slag via fluorine fixation by MgCl2 roasting","authors":"","doi":"10.1016/j.jre.2024.06.010","DOIUrl":"10.1016/j.jre.2024.06.010","url":null,"abstract":"<div><div>Rare earth fluoride molten-salt electrolytic slag (REFES) is a precious rare earth element (REE) secondary resource, and considerable amounts of REEs exist in REFES as REF₃; they are difficult to dissolve in acid or water and impede efficient REE extraction. In REFES recovery, the REF₃ species in REFES are usually transformed into acid-soluble rare earth compounds by NaOH roasting or sulfating roasting and then extracted by acid leaching. Moreover, the fluorides in REFES are released as HF gas in the roasting process or enter the liquid phase during the water washing process; both of these processes cause fluorine pollution. Fixing the fluorine into the solid slag provides a way to avoid fluorine pollution. In this study, a novel method was proposed to extract REEs from REFES via MgCl₂ roasting followed by HCl leaching. Thermodynamics calculations and thermogravimetry‒differential thermal analyses (TG-DTA) were conducted to investigate the reactions occurring in the roasting process. First, MgCl₂ reacts with the REF₃ and RE₂O₃ to form RECl₃ and REOCl, respectively. Second, the RECl₃ absorbs water and forms RE(OH)₃. Third, MgCl₂·6H₂O is gradually dehydrated to MgCl₂·2H₂O and reacts with REF₃ and RE(OH)₃, and REOCl, MgF₂ and MgO are formed. Through HCl leaching, the REOCl in the roasting products is leached by HCl acid, while fluoride remains in the solid slag as MgF₂. The optimum experimental conditions are as follows: mass ratio of MgCl₂ to REFES of 30%, roasting temperature of 700 °C, roasting time of 2 h, hydrochloride acid concentration of 4 mol/L, leaching time of 2 h, leaching temperature of 90 °C and leaching L/S ratio of 20:1. The efficiencies for total leaching of the REEs, La, Ce, Pr, and Nd are 99.13%, 99.20%, 98.42%, 99.38%, and 99.08%, respectively. Moreover, the concentration of fluoride in the leaching solution is 2.191 × 10⁻⁶ mol/L. This method has a short process flow with low reagent costs, and the problem of fluoride pollution from REFES recovery is solved; thus, our study has great industrial application potential.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 10","pages":"Pages 1979-1987"},"PeriodicalIF":5.2,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141402494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}