MATERIALS TECHNOLOGY
·
2020
·
IF 1.738
Huan Yang,Renxin Xu,Yaohui Zhao,Jian Cai
Mg0.2Mn0.8NdxFe2-xO4 (x = 0.000, 0.025, 0.050, 0.075 and 0.010) nano crystalline is synthesized via hydrothermal technique. Single cubic spinel phase is confirmed by XRD and the formation of Mg0.2Mn0.8NdxFe2-xO4 is verified by EDS. The average size of the nanoferrites is examined by TEM image. Nd3+ substituted Mg-Mn nanoferrites exhibit the low saturation magnetization (Ms) and high coercivity (Hc). The ferrite composites present that the resistivity and the magnetic loss are less than 2.8×107 Ω·cm and 0.75 in the range of 2-18 GHz, respectively. The optimized Mg0.2Mn0.8NdxFe2-xO4 (x=0.050) showed the minimum reflection loss of -39.80 dB at 1.4 GHz and effective absorption bandwidth (lower than -10 dB) of 7.58 GHz with a thickness of only 3 mm. The high coercivity, resistivity and excellent wave absorption performance indicate that the addition of Nd3+ contributes to the synthesis of the excellent soft magnetic materials and wave absorbing materials.
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Energy Technology
·
2020
·Vol. 8
·期 5
·2000008
·
IF 3.404
Chengrui Wang,Lei Zhang,Yuhai Dou,Luke Hencz,Lixue Jiang,Mohammad Al-Mamun,Porun Liu,Shanqing Zhang,Dan Wang,Huijun Zhao
Further commercial application of low-cost NiO-based anodes is hindered by their large volume expansion after full lithiation and relatively poor theoretical capacity. To improve these issues, transition metal (Fe, Co, or Mn)-modified triple-shelled NiO microspheres (TS-NiO) are successfully synthesized by using a hard template double-adsorption method. Among them, the Fe-modified TS-NiO (TS-NFO) exhibits an extraordinary lithium storage ability with high reversible capacity and outstanding cycling stability (2061.1 mAh g −1 after 800 cycles at 0.5 A g −1 ), which is the highest performing nickel oxide-based anode reported to date. The outstanding electrochemical performance of TS-NFO can be ascribed to its unique triple-shelled structure. The inner core of TS-NFO is composed of NiO and is encapsulated by two outer shells which are composed of a mixture of α-Fe 2 O 3 and NiFe 2 O 4 , resulting in a unique hollow triple-shelled structure (NiO@α-Fe 2 O 3 /NiFe 2 O 4 ). The void space between the triple shells leaves room for their volume changes during lithiation/delithiation, which improves the cycling stability. In addition, the introduced α-Fe 2 O 3 /NiFe 2 O 4 outer shells increase the energy density and reversible capacity due to a synergistically interactive effect.
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JOURNAL OF THE AMERICAN CERAMIC SOCIETY
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2021
·Vol. 104
·期 11
·5547-5556
·
IF 3.784
Jian Guo,Jianguo Chen,Jinrong Cheng,Qi Tan
Lead-free 0.75BiFeO 3 –0.25BaTiO 3 (0.75BF–0.25BT) ceramics have been extensively studied because of their high Curie temperature. The aging behavior and thermal stability of piezoceramics play decisive roles in their device applications. In this work, effects of Mn doping on the phase structure, aging behavior, and thermal stability of 0.75BF–0.25BT ceramics were characterized and related mechanisms were investigated. With the increase in Mn content, the typical rhombohedral phase of 0.75BF–0.25BT ceramics changed to the coexistence of pseudo-cubic and rhombohedral phases. Mn modification enhanced the aging behavior and thermal stability of ceramics obviously. The aging rates of d 33 and k p for 0.75BF-0.25BT ceramics with 1.0 mol% Mn are 1.3% and 1.1%, respectively, which are only 1/4 those values for the undoped ceramics. The variation of ε r of 0.75BF-0.25BT ceramics with 1.0 mol% Mn is half of undoped ceramics under 500℃. The depoling temperature of 0.75BF-0.25BT ceramics with 1.0 mol% Mn was 450℃, which is about 200℃ higher than that of undoped ceramics. The enhanced aging behavior results from the decreased defect concentrations, and the better thermal stability is owing to the significantly improved poling state due to the enhanced resistivity, large grain size, and decreased crystal distortion by Mn modification. These results reflect that a proper amount of Mn doping is an effective way to enhance the aging behavior and electric thermal stability.
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Journal of Environmental Chemical Engineering
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2021
·
IF 5.909
Xuan Bie,Kai Wu,Kunling Jiao,Kun Zhao,Xiangyang Chen,Suangchen Ma
Generally, using transition metal oxides as catalysts is the typical method for ammonia-selective catalytic reduction (NH 3 -SCR) under the medium temperature zone (150–400 °C). The controllable structure and uniformly distributed active sites of (Fe&Mn)AlOx-based catalysts via a facilely operative and green prepared method were employed for high NO catalyzed efficiency and selectivity . Among them, the Mn 1.2 Al 0.8 O x sample exhibited excellent low-temperature activity, and Fe 1.2 Al 0.8 O x exhibited excellent N 2 selectivity, which could be ascribed to the unique surface feature (more redox sites on Mn 1.2 Al 0.8 O x and more acid sites on Fe 1.2 Al 0.8 O x ). This creative work has directly demonstrated the importance of coordination between the adsorption of species and electron transportation that emerged on active sites. Meanwhile, the reaction process has been clearly presented in in-situ DRIFTS, declaring the synergetic mechanism (Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism) in the systems. The Eley-Rideal mechanism could be the dominant one due to its rapid reaction rate. The predictable insights are beneficial for profoundly understanding the dual-sites synergetic interaction for controllable conversion rate and high selectivity in the medium temperature SCR process.
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SENSORS AND ACTUATORS B-CHEMICAL
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2021
·
IF 7.46
Cong Qin,Bing Wang,Yingde Wang
Improving the gas-sensing performances of p-type oxide semiconductors is an important research issue. Here, we reported the simple fabrication of bare Co 3 O 4 and Mn-doped Co 3 O 4 porous nanosheets by annealing the Co-based metal-organic frameworks (MOFs) nanosheets precursors synthesized from the ion-assisted solvothermal treatment. Different characterization techniques were adopted to verify the physical and chemical morphologies of the as-prepared samples. The results demonstrate that Mn cations have been successfully doped into the lattice of Co 3 O 4 . Besides, these prepared samples were used for detection of carbon monoxide (CO). Results show that 3 mol% Mn-doped Co 3 O 4 nanosheets present enhanced CO-sensing properties [(R g − R a )/R a = 280% to 40 ppm at 125 °C] compared with bare Co 3 O 4 nanosheets. The response reported here for the detection of CO even exceeds those of some n-type oxides under the same conditions. We speculate that the enhanced CO-sensing properties are probably due to the high specific surface area, abundant oxygen vacancies generated by Mn doping, and the relatively high Co 3+ /Co 2+ ratio. The Mn-doped Co 3 O 4 sensor has a huge potential advantage in detecting low concentrations of CO.
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Materials Research Express
·
2019
·Vol. 6
·期 12
·125017
·
IF 1.449
Hanyu Yao,Honglie Shen,Quntao Tang
In this paper, Mn doped NaYF4:Er,Yb phosphors were successfully synthesized by a simple solvothermal method. According to the results of x-ray diffraction, scanning electron microscopy and photoluminescence measurement, Mn doping had a remarkable effect on the crystal phase, size, and especially upconversion (UC) properties of these phosphors. Under 980 nanometer (nm) laser excitation, the UC luminescence intensity could be enhanced by increasing Mn concentration. Temperature-dependence measurement of the samples from 300–30 K showed two green emission bands (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of the Er3+ ion), which meant that the UC phosphors were suitable for temperature sensor by using the fluorescence intensity ratio (FIR) method. The FIR value decreased with temperature, and the experimental data were well fitted with a theoretical function. The higher maximum value of sensitivity (0.0057 K−1) for 20% Mn sample in contrast to that of 0% Mn one (0.0036 K−1) indicated that Mn doped sample had a higher sensitivity for temperature sensing. The results demonstrated that Mn doping would be a good way for optimizing the sensitivity of fluorescence-based temperature sensor.
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Results in Physics
·
2019
·
IF 3.042
Yang Zhou,Xiaoyuan Liu,Ke Wang,Jing Li,Xinglai Zhang,Xin Jin,Xinyue Tang,Xiuhui Zhu,Ruishi Zhang,Xin Jiang,Baodan Liu
Series of “Hopcalite” catalysts for low-temperature CO oxidation are prepared through a facile ultra-sonic spray pyrolysis approach. It has been found that the spray pyrolysis temperature and Cu/Mn atomic ratio in initial precursors show significant impacts on the catalytic activity of Cu-Mn-O catalysts. The catalyst synthesized at 550 °C with Cu/Mn = 1/2 in precursor (Cu1Mn2-550) shows the highest catalytic activity towards CO oxidation (T 100 = 63 °C; E a = 17.04 KJ mol −1 ), owing to the formation of CuMn 2 O 4 phase with poor crystallinity. The synergistic effect of Cu and Mn species in spinel Cu-Mn-O phases attributes to the evaluated catalytic activity compared with those of pure oxides of copper or manganese towards CO oxidation. The results reveal that Cu1Mn2-550 not only provides more defects and vacancies to create more active sites, but also generates more highly active Cu (II) to promote CO oxidation. On the contrary, the decreasing amount of Cu (II) and the higher degree of crystallinity resulting from higher synthesis temperature lead to the deterioration of catalytic activity. Moreover, the phase transformation among the Cu x Mn 3-x O 4 spinels also shows significant effect on CO conversion rate. Finally, the formation mechanism of Cu-Mn-O catalysts and related CO oxidation process are discussed based on series of characterizations.
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NANO
·
2019
·
IF 1.293
Renxin Xu,Huan Yang,Huajun Sun,Jing Zhou,Zhijun Yue,Xinhua Gao
Mg 0 . 2 Mn 0 . 8 Y x Fe 2 − x O 4 ( x = 0 . 0 0 0 , 0.025, 0.050 and 0.075) nanocrystalline is synthesized via hydrothermal technique. Single cubic spinel phase is confirmed by XRD and the formation of Mg 0 . 2 Mn 0 . 8 Y x Fe 2 − x O 4 is verified by EDS. The average size of the nanoferrites is around 80 nm, which is examined by TEM image. Y 3 + substituted Mg-Mn nanoferrites exhibit low saturation magnetization ( M s ) and coercivity ( H c ) . Especially, the nanoferrites with x = 0 . 0 7 5 show the lowest M s and H c of 46.96 emu/g and 12.04 Oe, respectively. The ferrite composites present that the resistivity and the magnetic loss are less than 4 . 5 × 1 0 7 Ω ⋅ cm and 0.7 in the range of 2–18 GHz, respectively. The low coercivity and high resistivity indicate that the addition of Y 3 + contributes to the synthesis of the excellent soft magnetic materials.
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ELECTROCHIMICA ACTA
·
2019
·
IF 5.383
Qiujun Li,Hua Yao,Feng Liu,Zitao Gao,Yangyi Yang
A new Mn-doped coordination supramolecular network (CSN) was synthesized on nickel foam directly by a simple one-step hydrothermal method . Compared with the pure CSN electrode (∼2.46 C cm −2 at 10 mA cm −2 ), this Mn-doped binder-free electrode showed an ultrahigh areal capacity (∼8.12 C cm −2 at 10 mA cm −2 ). In addition, when the current density increased from 10 mA cm −2 to 50 mA cm −2 , it had a good rate capability with 73.33% capacitance retention. For practicality, an asymmetrical supercapacitor (ASC) was assembled by Activated Carbon (AC) electrode and the Mn-doped CSN electrode. The device not only could achieve a maximum energy density of 3.41 mW h cm −3 at the power density of 44.98 mW cm −3 , but also could exhibit excellent stability after 4000 cycles, with the capacitance retention of 90.14%. The above results indicate that the Mn-doped CSNs are promising electrode materials for supercapacitors in energy storage.
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Water
·
2019
·Vol. 11
·期 11
·2302
·
IF 2.524
Dingyun Yan,Zhe Sun,Jiajie Wang,Lili Wang,Ruijun Pan,Qiang Wu,Xiaowei Liu
Mn(III) oxidation technology has attracted increasing interest in recent years because of its fast decontamination kinetics and second-pollution-free characteristic. Whether it can be used as a pre-oxidation step to enhance conventional coagulation process remains to be evaluated. Herein, an Fe-coagulation/sedimentation process combined with Mn(III) pre-oxidation (Mn(III)+C/S), hypochlorite pre-oxidation (Cl2+C/S), and permanganate pre-oxidation (PM+C/S) was applied to treat simulated micro-polluted raw water. The removal performance of routine water quality indices (turbidity, dissolved organic carbon, total nitrogen, nitrate-nitrogen, ammonia-nitrogen, Pb(II), and Cr(VI)) and the emerging pollutants (acesulfame, carbamazepine, bisphenol S, and nano-ZnO) created by these three processes were researched. The mechanism of how Mn(III) pre-oxidation influences C/S was explored by identifying the transformation products of Mn(III), measuring the timely variation of flocs’ zeta potential and size, and scanning flocs’ micromorphology. Compared to Cl2+C/S and PM+C/S, Mn(III)+C/S exhibited its superiority in removing dissolved organic carbon (72.9%), total nitrogen (31.74%), and emerging pollutants (21.78%–93.49%). The enhanced removal of these contaminants by Mn(III)+C/S found its explanation in the strong oxidation power of Mn(III) and the multiple roles of in-situ formed MnO2(e.g., flocculation core, adsorption co-precipitant, and densification agent). The acute toxicity tests confirmed that water treated by Mn(III)+C/S did not show a significant change in the associated toxicity. The findings of the present study indicate that Mn(III) oxidation technology shows great potential as an alternative to pre-oxidation technology of waterworks.Keywords:pre-oxidation;enhanced coagulation;Mn(III);emerging pollutants;micro-polluted raw water
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MATERIALS RESEARCH BULLETIN
·
2019
·
IF 3.355
Lijun Zhu,Hao Cheng,Jianfeng Ma,Yong Kong,Yong Qin,Sridhar Komarneni
Decolorization of methyl orange (MO) by MnO 2 was investigated with and without small molecules of organic acids such as formic acid. It was found that the decolorization could be significantly improved by MnO 2 with the assistance of organic acids. The effect of various conditions was investigated on MO decolorization by using different crystal types of MnO 2 and changing the types of organic acids. One of the optimum treatment conditions was δ-MnO 2 /formic acid system, which led to the removal efficiency of 90.6% at 30 min. The pseudo-second-order kinetic rate constant of δ-MnO 2 /formic acid was 0.1626. A reasonable decolorization mechanism involving Mn(III) species was proposed and the mechanism was validated by simple detection of ionic species such as, Mn(II) and Mn(III) during the reaction. The δ-MnO 2 /formic acid process designed here may lead to a new advanced oxidation technology based on the in-situ generation of active Mn(III) species and their ability for oxidation.
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Materials Research Express
·
2018
·Vol. 5
·期 6
·066106
·
IF 1.151
Renxin Xu,Huan Yang,Huajun Sun,Yueli Liu,Huan Zhou,Jianchun Liu
Mg0.2Mn0.8HoxFe2−xO4 (x = 0.025, 0.050, 0.075 and 0.100) nanocrystalline is synthesized via a hydrothermal technique. Single phase cubic spinel is confirmed by XRD and the formation of Mg0.2Mn0.8HoxFe2−xO4 is verified by EDS. The average size for the nanoferrites is around 80 nm which is examined by TEM with the presence of agglomerated particles. Ho3+ substituted Mg-Mn nanoferrites exhibit the low saturation magnetization (Ms) and coercivity (Hc). Especially, with x = 0.100, the nanoferrites show the lowest Ms and Hc of 46.850 emu g−1 and 46 Oe, respectively. The ferrite composites present the dielectric dissipation less than 0.37 and the magnetic loss less than 0.46 at 2–18 GHz. The low saturation magnetization, low coercivity and low dielectric dissipation indicate that the addition of Ho3+ contributes to synthesize better soft magnetic materials.
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