Materials
·
2023
·Vol. 16
·期 17
·5984
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IF 3.4
Zhi Li,Chengwei Zhan,Huan Yu,Xitao Wang,Shouqiu Tang,Jixue Zhou,Jianhua Wu
Research on rare-earth fluorides is of urgent and critical importance for the preparation and emerging applications of high-purity alloys. The fluorination of Sc2O3by NH4HF2to fabricate ScF3is investigated. The effects of the fluorination temperature, time and mass ratio of reactant on the fluorination rate and fluoride are discussed in this work. The fluorination reaction was first confirmed using thermodynamic calculation. The thermal and mass stability of the fluorination process were analyzed by thermogravimetric and differential scanning calorimetric (TG-DSC). The as-obtained products at different fluorination temperatures were characterized by Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results indicated that the fluorination began at room temperature (RT) with the formation of (NH4)3ScF6. With the increase of temperature, the reaction proceeded sequentially through the formation of NH4ScF4, (NH4)2Sc3F11, and finally ScF3. The fluorination rate increased with the increase of fluorination temperature and holding time. ScF3with a purity of 99.997 wt.% could be obtained by fluorination at 400 °C for 2 h.Keywords:Sc2O3;(NH4)3ScF6;NH4ScF4;(NH4)2Sc3F11;ScF3
研究领域:
材料科学
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化学工程
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PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2017
·
IF 2.986
Aihu Feng,Yun Yu,Feng Jiang,Yong Wang,Le Mi,Yang Yu,Lixin Song
MXene , a new family of 2D transition metal carbides and carbonitrides , has been proved to possess excellent electrical conductivity and hydrophilicity. In this work, a single-step method to produce the larger interplanar spacing 2D MXene Ti 3 C 2 by etching Ti 3 AlC 2 with NH 4 HF 2 was demonstrated, and the optimal reaction conditions between Ti 3 AlC 2 and NH 4 HF 2 were systematically researched. The morphology and microstructure of samples were characterized by scanning electron smicroscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD). The thermal stability of Ti 3 C 2 was investigated by the thermogravimetry (TG) and differential thermal analyzer (DTA). It was found that the lattice parameter c of obtained Ti 3 C 2 was up to 24.9 Å, and the larger interplanar spacing Ti 3 C 2 was more stable than the sample exfoliated by HF. The transition temperature in air from NH 4 HF 2 -etched Ti 3 C 2 to anatase TiO 2 thoroughly is more than 500 ℃, and the multilayered structure of Ti 3 C 2 could be well retained even afer 900 ℃ heat treatment, while the value of HF-etched Ti 3 C 2 is less than 350 ℃. This work is important for exploring a safe synthesis method and well understanding the thermal stability of 2D MXene materials.
研究领域:
材料科学
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化学工程
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高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2019
·
IF 4.182
Aihu Feng,Yang Yu,Le Mi,Yunzhen Cao,Yun Yu,Lixin Song
In this work, the hierarchical Y zeolites are firstly obtained by etching NaY zeolites with different NH 4 HF 2 solutions. The morphology and microstructure, toluene adsorption property of as-prepared hierarchical Y zeolites are characterized. The results demonstrate that the mesoporous number and size, the n(SiO 2 )/n(Al 2 O 3 ) value of hierarchical Y are increased with NH 4 HF 2 concentration. The 0.3M NH 4 HF 2 -etched NaY exhibits satisfactory crystallinity, suitable mesoporous content and better toluene adsorption performance. The NH 4 HF 2 -etched NaY is an excellent material for pressure swing adsorption. Furthermore, the synthesis mechanism of hierarchical Y has been elaborately demonstrated. The synergistic effect of H + and F − is beneficial to dealumination as well as the introduction of mesoporous. The NH 4 HF 2 ionizes into positive H + and negative F − at a very slow rate, which avoids the concentration of H + and F − going up suddenly. Under the circumstances, the dealumination reaction between NH 4 HF 2 and NaY zeolites is more sustained and mild, and the crystallinity of hierarchical Y zeolites is higher than that of the HCl/NH 4 F-etched or HF/NH 4 F-etched NaY. This work presents an effective method to synthesize the hierarchical Y zeolites.
研究领域:
材料科学
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化学工程
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高影响因子
IONICS
·
2018
·Vol. 25
·期 2
·727-735
·
IF 2.347
Feng Aihu,Yu Yang,Mi Le,Yu Yun,Song Lixin
In this work, the MXene Ti 3 C 2 with excellent electrical conductivity is obtained by etching Ti 3 AlC 2 with NH 4 HF 2 solution. The electrosorption performance, the electrochemical and physicochemical properties of as-prepared Ti 3 C 2 are characterized. The results demonstrate that NH 4 HF 2 -etched Ti 3 C 2 possesses the better intercalation pseudo-capacity and the specific capacitance is up to 78 F∙g −1 , which is an increase of 34% than HF-etched Ti 3 C 2 . In addition, the desalination capacity of NH 4 HF 2 -etched Ti 3 C 2 enhances 35.5% than that of HF-etched Ti 3 C 2 . When the initial conductivity of NaCl is ~ 1000 μS/cm, the desalination capacity of NH 4 HF 2 -etched Ti 2 C 3 electrode is 12.1 mg∙g −1 , and the pseudo-first-order model can well describe the electrosorption kinetics of NH 4 HF 2 -etched Ti 3 C 2 electrode. Furthermore, the regeneration performance of the NH 4 HF 2 -etched Ti 3 C 2 electrode is excellent. This study indicates a new kind of effective electrode material to improve the desalination performance of capacitive deionization (CDI) technology.
研究领域:
材料科学
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环境工程
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高影响因子
CHEMICAL ENGINEERING JOURNAL
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2020
·
IF 10.652
Aihu Feng,Le Mi,Yang Yu,Yunzhen Cao,Yun Yu,Lixin Song
Volatile organic compounds have seriously affected the natural environment and human health, and adsorption is one of the most effective method for controlling VOCs pollution. In this work, the NH 4 HF 2 -etched NaY-s-x zeolites with intracrystalline mesoporosity are obtained via the surfactant-templating process in weak base NH 4 OH solution. The morphology, microstructure, and toluene adsorption property of as-prepared hierarchical Y zeolites are systematically characterized. It is found that the structural and textural properties of NH 4 HF 2 -etched NaY samples are significantly changed by the simple surfactant-templated approach and the large-sized mesopores inside NH 4 HF 2 -etched NaY sample disappear to form the surfactant-templated mesoporosity with a size of ~4 nm. It is demonstrated that the intracrystalline mesoporosity obviously improves the toluene molecular adsorption properties of zeolite samples. Moreover, the mechanism of the surfactant-templating process is elucidated.
研究领域:
材料科学
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环境科学
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DOI
高影响因子
ANALYTICAL CHEMISTRY
·
2019
·
IF 6.35
Tao He,Zhaochu Hu,Wen Zhang,Haihong Chen,Yongsheng Liu,Zaicong Wang,Shenghong Hu
In this study, a simple and effective method for the simultaneous analysis of Cl, Br, and I in geological materials based on NH4HF2 digestion in open vessels (Savillex Teflon vials) is proposed. It is very interesting to note that Cl, Br, and I are not lost during NH4HF2 digestion at temperatures of 200–240 °C for 0.5–12 h in open vessels. This should be related to the alkaline atmosphere environment caused by the NH3 produced during NH4HF2 digestion, which suppresses the volatilization loss of Cl, Br, and I. A 100 mg sample of geological materials can be completely digested by using 400 mg of NH4HF2 at 220 °C for 2 h in Savillex Teflon vials. The use of new Savillex Teflon vials significantly reduced the procedural blanks of halogens compared with the old Savillex Teflon vials. The developed method was successfully applied to the simultaneous determination of Cl, Br, and I in a series of international geological reference materials. Most of the results were found to be in reasonable agreement with values reported in the literature. This simple, rapid, effective, and economical analytical method will significantly promote the development of halogen geochemistry.
研究领域:
地球化学
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分析化学
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DOI
PubMed
高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
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2019
·
IF 4.182
Aihu Feng,Yang Yu,Le Mi,Yunzhen Cao,Yun Yu,Lixin Song
The non-framework aluminum is inevitably formed in the process of preparing the ultra-stable Y zeolite (USY), which severely blocks the mesopores of USY zeolite. It is necessary to treat the USY with the appropriate acid and/or alkali. In this paper, the USY zeolite is firstly dealuminated with NH 4 HF 2 solution and then desiliconized with NaOH or NH 4 OH solution. The effect and mechanism of NH 4 HF 2 and different alkali treatments on the structural and textural property of USY zeolite are elaborately demonstrated. It is found that the non-framework Al remaining in the mesopores of USY is significantly removed by the NH 4 HF 2 solution. The desiliconization reaction is more likely to start near the mesoporous wall because the Al concentration in here is low and the repulsive force against OH − is weak. The OH − ions from NaOH solution not only etch the framework Si near the inner wall of the mesopores, but also remove the Si on the surface of NH 4 HF 2 -etched USY zeolite. However, the concentration of OH − ions is too low when NH 4 OH is used as the desiliconization agent, the OH − ions just react with silicon around the mesopores. Therefore, the NaOH/NH 4 HF 2 -etched USY contains both some micropores and macropores, and the NH 4 OH/NH 4 HF 2 -etched USY only possesses more mesopores with pore sizes of ～10 nm. In addition, NaOH/NH 4 HF 2 -etched USY exhibits excellent toluene adsorption performance at low pressure stage, while NH 4 OH/NH 4 HF 2 -etched USY has the highest adsorption capacity on toluene at high pressure stage.
研究领域:
材料科学
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化学工程
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高影响因子
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
·
2020
·Vol. 217
·期 8
·1900806
·
IF 1.759
Jingbo Li,Yu Liu,Fang Xu,Junping Hu,Nan Chen,Guoping Du,Changshuang Jiang
As a 2D material, Ti 3 C 2 (MXene) has been recently used as electrodes for electrochemical capacitors. Herein, a two-step procedure is used to obtain a highly opened layer structure for Ti 3 C 2 , which differs from the methods used in the literature for synthesizing exfoliated MXene. First, the mild NH 4 HF 2 etching agent is used to prepare the regular Ti 3 C 2 MXene. Second, KOH is added into the obtained solution for K + to intercalate the MXene. The K + intercalation is found to greatly increase the (002) crystal planar spacing of the Ti 3 C 2 from 10.8 to 12.4 Å. More importantly, this K + -intercalated MXene exhibits a highly opened layer structure, whereas the regular MXene only has a partially opened layer structure. Consequently, the former is expected to allow much more active sites exposed to liquid electrolyte, and also facilitates remarkably higher ion and electron transport efficiency. To investigate their electrochemical capacitance properties, the regular and K + -intercalated Ti 3 C 2 MXenes are used to fabricate binder-free electrodes on nickel foams by an electrophoretic deposition method. The K + -intercalated MXene-based electrode is found to have twice higher specific capacitance than the regular MXene. Furthermore, the K + -intercalated Ti 3 C 2 MXene-based electrode exhibits an excellent cyclic stability.
研究领域:
材料科学
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电化学
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DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2026
·
IF 12.5
Xuefeng Sha,Xianyin Song,Qiwei Shangguan,Yawei Lv,Fan Zeng,Xingang Zhang,Xueli Wu,Minghao Yu,Changzhong Jiang
MXene has emerged as a promising alternative to carbon-based capacitor materials since its inception, however, the current practical implementation still faces dual challenges: environmentally hazardous, time-consuming synthesis procedures and intrinsically low-concentration pseudocapacitive active sites. Herein, a short-duration, eco-friendly and high-efficiency double fluoride salt hydrothermal strategy was proposed to fabricate Ti 3 C 2 MXene with unparalleled electrochemical properties. A comprehensive and good balance, including rapid MAX phase etching, just-right titanium terminal water oxidation, and ammonia reduction activation, is achieved via a one-step NH 4 HF 2 hydrothermal reaction at 160 °C for merely 1 h (TOR-MXene). It drastically outperforms conventional HF acid etching at 60 °C for 48 h (P-MXene). Systematic experimental characterizations (HRTEM, SAXS, XPS, EXAFS, EPR and in-situ XRD, in-situ Raman) and DFT calculations consistently reveal that instead of the generally believed pore expansion, the abundant highly-reduced titanium dioxide nanoclusters anchored on the surface of MXene exhibit substantial pseudocapacitive activation, accompanied by the threshold Bader charge of Ti atoms exceeding 10.5 |e|. Consequently, the prepared TOR-MXene delivers a remarkable specific capacitance of 446.1 F g −1 even at the ultrahigh current density of 30 A g −1 , a sixfold improvement over the P-MXene of 74.8 F g −1 . Moreover, the TOR-MXene electrode displays around 91.2% capacitance retention over 50,000 cycles, showing an extremely high cycling stability. This strategy establishes atomic-level design principles for MXene-based energy storage, advancing efficient synthesis and performance optimization.
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高影响因子
GEOSTANDARDS AND GEOANALYTICAL RESEARCH
·
2025
·
IF 3.4
Tao He,Hui Cao,Wang Lang,Zhaochu Hu,Zaicong Wang,Zongqi Zou,Wen Zhang,Haihong Chen,Yongsheng Liu
Silver is a powerful geochemical tracer in various geological processes (e.g., hydrothermal deposit formation and evolution of the terrestrial and Martian mantles). The measurement of the ultra-trace Ag (< 0.1 μg g -1 ) in geological samples by ICP-MS is often hindered due to serious polyatomic interferences arising from Zr, Nb and Y elements presented in samples. In this study, a simple and rapid ammonia coprecipitation method was developed to remove interference elements (Zr, Nb and Y) in NH 4 HF 2 digests for the determination of Ag mass fractions in geological materials by isotope dilution ICP-MS (ID-ICP-MS). The removal of interference elements (Zr, Nb and Y) in digestion solutions of geological materials was achieved using ammonia coprecipitation, effectively eliminating their polyatomic interferences. To compensate for the incomplete recovery of Ag during ammonia coprecipitation, isotope dilution calibration was chosen over internal standard calibration to achieve final accurate results. The limit of quantitation for Ag using the proposed method was 1.83 ng g -1 . The results obtained for Ag mass fractionation in nine international geological reference materials were in good agreement with the published values obtained by ID-ICP-MS and ICP-MS/MS. The proposed simple, rapid and practical analytical method for the determination of Ag mass fractions improves our understanding of the behaviour of silver in cosmochemistry and geochemistry studies.
研究领域:
地球化学
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分析化学
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高影响因子
Solids
·
2025
·Vol. 6
·期 4
·66
·
IF 2.4
Chenxing Liao,Feng Zhou,Wei Xie,Liaolin Zhang
Mn4+-doped fluoride red phosphors are widely used in white LED lighting and display applications due to their excellent luminescent properties. However, their synthesis relies heavily on highly toxic aqueous hydrofluoric acid, which not only causes severe environmental and soil/water pollution but also makes it difficult to control the microstructure of the products due to the rapid reaction rate. In this study, low-melting-point NH4HF2was used as the molten salt, with KMnO4and MnF2as manganese sources, to synthesize the red phosphor K3AlF6: Mn4+via the molten salt method. After the reaction, impurities such as NH4HF2were removed by washing with a dilute H2O2solution. The microstructure, photoluminescence properties, thermal quenching behavior, and application in warm white light-emitting diodes (W-LEDs) of the K3AlF6: Mn4+phosphors were investigated. The results indicate that the phosphors prepared by this method consist of a single pure phase. By adjusting the molten salt content, the morphology of the product can be transformed from nanoparticle-like to nanorod-like structures. All products exhibit the characteristic red emission of Mn4+under blue and violet light excitation, with the optimally doped sample achieving an internal quantum efficiency (IQE) of 69% under blue light excitation. The combination of the obtained K3AlF6: Mn4+with the yellow phosphor YAG enabled the fabrication of W-LEDs. These W-LEDs achieved a color rendering index (Ra) of 86.8, a luminous efficacy (LE) of 77 lm/W, and a correlated color temperature (CCT) of 3690 K, along with excellent color stability under operating conditions.
研究领域:
材料科学
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光电子学
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固态化学
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发光材料
·
LED技术
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DOI
高影响因子
危险品化学品经营许可证（带存储）