PHYSICA B-CONDENSED MATTER
·
2022
·
IF 2.988
Wei Zhang,Zhiwei Gu,Bingbing Zong,Yueju Fu,Kai Zhang,Yubao Li
Defects is of special importance in tuning the structure and physical properties of layered materials. Here the influence of transition metal Co vacancies on the structure and magnetism in collapsed tetragonal CaCo 2- x As 2 (0 ≤ x ≤ 0.3) solid solutions are systematically investigated. The electrical properties show metallicity in all compounds. The crystal structure refinement exhibits that the lattice constant of the c axis and c / a ratio decreases as Co vacancies increase, revealing the formation of a more collapsed tetragonal structure in CaCo 2- x As 2 . Moreover, these introduced Co vacancies suppress the antiferromagnetic Néel temperature from 80 K down to 18 K until it disappears above 10 K in CaCo 1 · 7 As 2 . X-ray photoelectron spectroscopy reveals increased Co 3+ /Co 2+ value in CaCo 2- x As 2 with higher Co vacancies, which may result in the charge balance and the gradually suppressed T N . This study offers insights into tuning and understanding the magneto-structural characteristics in ThCr 2 Si 2 -type layered materials through transition metal vacancies.
研究领域:
凝聚态物理
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材料科学
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固体化学
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磁学
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晶体工程
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缺陷工程
✓ 已验证
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2020
·Vol. 46
·期 10
·16524-16532
·
IF 3.83
Muhammad Yousaf,Asma Noor,Shuai Xu,Majid Niaz Akhtar,Baoyuan Wang
Yttrium iron garnet (YIG) nanoparticles (NPs) doped with rare earth (RE) metal ions (Y 2.5 Sm 0.5 Fe 5 O 12 , Y 2.5 Nd 0.5 Fe 5 O 12 ) were successfully synthesized by sol-gel auto combustion approach. The cubic crystalline structure and morphology of the prepared garnet ferrite NPs were analyzed by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM). The cubic crystalline garnet phase of the synthesized YIG, Sm-YIG and Nd-YIG samples was successfully achieved at 950 °C sintering temperature . The force constant and absorption bands were estimated by using Fourier transform infrared spectroscopy (FTIR). The doping effect of RE metal ions on the chemical states of YIG were examined by x-ray photoelectron microscopy (XPS). The valence band (from 12.63 eV to 13.22 eV), conduction band (from 10.89 eV to 11.34 eV) edges and optical bandgap values of RE doped YIG samples were calculated using UV–Vis spectroscopy and ultraviolet photo electron spectroscopy (UPS). The magnetic analysis of the prepared NPs was studied using vibrating sample magnetometer (VSM). The XPS analysis of RE doped YIG samples exhibit the existence of RE (Sm +3 , Nd +3 ) contents on the surface of YIG ferrite by decreasing the oxygen lattice in garnet structure. The optical bandgap (from 1.74 eV to 1.88 eV) explains the semiconducting nature of the synthesized NPs. The UPS results confirm the valence band position of YIG doped samples. The saturation magnetization and remanence of RE doped garnet ferrite samples increased from 13.45 to 18.83 emu/g and 4.06–6.53 emu/g, respectively.
研究领域:
材料科学
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纳米科技
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固体物理
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无机化学
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功能材料
✓ 已验证
DOI
高影响因子
Journal of Nanomaterials
·
2018
·Vol. 2018
·期 1
·1465760
·
IF 2.207
Jiamao Li,Jingwei Hou,Yu Gong,Chengjian Xiao,Lei Yue,Linjie Zhao,Huan Ma,Heyi Wang,Shuming Peng,Chao Chen,Hongli Chen
A liquid-phase reducing method of synthesizing Pt nanocrystals was demonstrated, and dendrite-, cube-, and cuboctahedron-shaped Pt nanocrystals (NCs) with well-defined monomorphic were successfully synthesized through iodine ions mediated with the CTAB agent. When the KI concentration was increased to thirty times of K 2 PtCl 4 at the nucleation stage, the high-quality Pt nanodendrites could be obtained. However, no matter how many KI were added at the growth age, only cube- and cuboctahedron-shaped Pt nanocrystals formed. The results of high-resolution TEM, EDX, and XRD indicated that the size and shape of Pt NCs could be turned by changing the concentration and time of KI. In the nucleation stage, it might be due to that some iodine ions adsorb on the surfaces of Pt NCs, which probably cause the rapid growth process resulting in the formation of Pt nanodendrites. In the growth stage, although high concentrations of I − ions could contribute to the shape control and generate bigger particles of Pt NCs, small Pt particles do not grow into dendrites. The insight into the role of I − ions in synthesis of Pt NCs reported here provided a viewpoint for clearly understanding the formation mechanism of anisotropic platinum nanostructures.
研究领域:
纳米材料科学
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物理化学
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无机合成
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催化化学
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材料表征技术
✓ 已验证
DOI
高影响因子
Asia-Pacific Journal of Chemical Engineering
·
2022
·Vol. 17
·期 5
·e2790
·
IF 1.777
Bingyi Zhou,Tao Ge,Xiaoman Luo,Zhaohui Wang,Yueyue Qiao,Chuanchuan Cai,Jingyao Xu
Under the two frequency microwave conditions of 915 and 2450 MHz, orthogonal tests were designed to investigate the effects of organic acid reagent, microwave irradiation time, and mixing time of additives and coal samples on the desulfurization effect of coal. Results show that the effect of irradiation time on the experimental desulfurization efficiency under frequency microwave conditions is large and is the main factor. The desulfurization effect under 915 MHz microwave condition is better than 2450 MHz microwave condition. Two sets of experimental optimal coal samples were used for characterization and analysis. Thermogravimetric analysis revealed that the combustion temperature range of the coal samples is shortened and the integrated combustion index is considerably higher after the microwave irradiation experiment. Fourier-transform infrared spectroscopy analysis showed that the overall chemical structure of the coal samples does not change significantly after the experimental treatment. X-ray photoelectron spectroscopy analysis showed that the intensity of organic sulfur in coal samples is weakened after microwave irradiation, the characteristic peaks of thiols and thioethers are reduced to a great extent, and an increase in the intensity of sulfoxide organic sulfur is observed. On the basis of the results of experimental analysis and quantum chemical simulation calculations, the mechanism of organosulfur structure removal under the action of microwave is revealed.
研究领域:
能源化学
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煤化学
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环境工程
·
材料科学
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物理化学
·
分析化学
·
清洁燃料技术
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）