Engineering topics

Yu, Xinxin

Publications and source records attributed to Yu, Xinxin.

5 records

DOE OSTI2018

RGO/BaFe12O19/Fe3O4 nanocomposite as microwave absorbent with lamellar structures and improved polarization interfaces

Highlights: • RGO/BaFe{sub 12}O{sub 19}/Fe{sub 3}O{sub 4} nanocomposite are prepared via a two-step solvothermal method. • The maximum reflection loss can reach −46.04 dB, and the effective absorption bandwidth under −10 dB is 5.68 GHz. • Interfacial polarization as one of the mechanism for the enhanced absorption properties was detailedly analyzed. - Abstract: In this paper, we designed and prepared a composite of BaFe{sub 12}O{sub 19} (BFO) flakes, two-dimensional graphene and Fe{sub 3}O{sub 4} nanoparticles using a two-step solvothermal method. The combination of BFO flakes and two-dimensional graphene could effectively enhance the heterointerface and is believed to be favorable to enhance the interface polarization. The introduction of inverse spinel Fe{sub 3}O{sub 4} as the third phase could increase the saturated magnetization. The phase structure, morphology, magnetic properties and electromagnetic wave absorption performance of the as-prepared samples were characterized. Due to the enhanced interfacial polarization between the BaFe{sub 12}O{sub 19} flakes and graphene, the composite of RGO/BaFe{sub 12}O{sub 19}/Fe{sub 3}O{sub 4} exhibits excellent microwave absorption properties. The maximum reflection loss can reach -46.04 dB at 15.6 GHz with a thickness of 1.8 mm, and the effective absorption bandwidth reaches 5.68 GHz (from 11.60 GHz to 17.28 GHz). It is believed that the RGO/BaFe{sub 12}O{sub 19}/Fe{sub 3}O{sub 4} composites can find potential application in the field of microwave absorption due to their excellent absorption properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Silver-loaded ZnO/ZnFe2O4 mesoporous hollow spheres with enhanced photocatalytic activity for 2,4-dichlorophenol degradation under visible light irradiation

Highlights: • Visible-light-driven ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres were successfully synthesized. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres have unique mesoporous hollow structures. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres exhibit excellent photodegradation of 2,4-dichlorophenol. • ZnO/ZnFe{sub 2}O{sub 4}/Ag spheres are reusable with the aid of a magnet. - Abstract: Silver-loaded ZnO/ZnFe{sub 2}O{sub 4} (ZnO/ZnFe{sub 2}O{sub 4}/Ag) mesoporous hollow spheres were synthesized via a layer-by-layer technique followed chemical reduction method. The structures and morphologies of the as-prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N{sub 2} adsorption/desorption porosimetry. The photodegradation activities of ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres toward 2,4-dichlorophenol were investigated under UV and visible light irradiation. The experimental results indicated that our mesoporous hollow spheres exhibited much higher photodegradation activities than P25 for the loading of silver particles, the bands matching and the unique structures. There exists an optimal loading dosage of silver particles. Too high or too low loading will reduce the photodegradation activities of ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres. The possible mechanism behind was proposed. Noteworthily, the ZnO/ZnFe{sub 2}O{sub 4}/Ag mesoporous hollow spheres are reusable with the aid of a magnet, which is cost effective.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Highly efficient and controllable method to fabricate ultrafine metallic nanostructures

We report a highly efficient, controllable and scalable method to fabricate various ultrafine metallic nanostructures in this paper. The method starts with the negative poly-methyl-methacrylate (PMMA) resist pattern with line-width superior to 20 nm, which is obtained from overexposing of the conventionally positive PMMA under a low energy electron beam. The pattern is further shrunk to sub-10 nm line-width through reactive ion etching. Using the patter as a mask, we can fabricate various ultrafine metallic nanostructures with the line-width even less than 10 nm. This ion tailored mask lithography (ITML) method enriches the top-down fabrication strategy and provides potential opportunity for studying quantum effects in a variety of materials.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres: The study of photoluminescence and adsorption properties

Graphical abstract: Mesoporous hollow structure of Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphors. - Highlights: • Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres are prepared via the layer-by-layer technique. • The Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibit better adsorption capabilities of Pb{sup 2+}, Fe{sup 3+} than Cd{sup 2+}. • The Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibit strong green emission around 524 nm. • With the increase of doped Mn{sup 2+} concentration, the emission peak shows a red-shift. - Abstract: Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres were prepared via the layer-by-layer technique using CTAB as surfactant. The structures/microstructures and morphologies of the as-synthesized phosphors were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N{sub 2} adsorption–desorption porosimetry. The adsorption capacity to remove toxic metal ions in water was tested and the results showed that the Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibited better adsorption capabilities of Pb{sup 2+}, Fe{sup 3+} than Cd{sup 2+}. Moreover, the as-obtained hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphors exhibited strong green emission around 524 nm at room temperature. When the atomic ratio of Zn to Mn was 97:3, the emission intensity of Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphor was about 1.2 times that of commercial phosphors. Furthermore, with the increase of doped Mn{sup 2+} concentration, the emission peak showed a red-shift.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Quantum Capacitance in Topological Insulators

Topological insulators show unique properties resulting from massless, Dirac-like surface states that are protected by time-reversal symmetry. Theory predicts that the surface states exhibit a quantum spin Hall effect with counter-propagating electrons carrying opposite spins in the absence of an external magnetic field. However, to date, the revelation of these states through conventional transport measurements remains a significant challenge owing to the predominance of bulk carriers. Here, we report on an experimental observation of Shubnikov-de Haas oscillations in quantum capacitance measurements, which originate from topological helical states. Unlike the traditional transport approach, the quantum capacitance measurements are remarkably alleviated from bulk interference at high excitation frequencies, thus enabling a distinction between the surface and bulk. We also demonstrate easy access to the surface states at relatively high temperatures up to 60 K. Our approach may eventually facilitate an exciting exploration of exotic topological properties at room temperature.

36 MATERIALS SCIENCE↗