Jun Shen

Technical Institute of Physics and Chemistry, Peping, Beijing, China

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Publications (77)300.79 Total impact

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    ABSTRACT: • Vapor pressures and saturated liquid densities of HFO1234ze(E) were measured.
    No preview · Article · Jan 2016 · International Journal of Refrigeration
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    ABSTRACT: A giant reversible MCE and large RC in EuTiO3 compound were observed. Under the magnetic field changes of 5 T, the maximum value of −ΔSM is evaluated to be 40.4 J/kg K, and the value of RC is 328 J/kg in EuTiO3 compound. Especially, for the magnetic field changes of 1 and 2 T, the large values of −ΔSM are 11 and 22.3 J/Kg K without magnetic and thermal hysteresis are also obtained, respectively. The giant MCE is attributed to field-induced AFM-FM transition and FM-PM transition. Therefore, the giant reversible MCE and large RC make the EuTiO3 compounds could be considered as a good candidate material for low-temperature and low-field magnetic refrigerant.
    No preview · Article · Nov 2015 · Journal of Alloys and Compounds
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    ABSTRACT: Catalyst-free, selective growth of ZnO nanowires directly on the commonly used dielectric SiO2 layer is of great both scientific significance and application importance, yet still a challenge. Here, we report a facile method to large-scale grow single-crystal ZnO nanowires directly on SiO2/Si substrate through vapor-solid mechanism without using any pre-deposited metal catalyst or seed layer. We found that a rough SiO2/Si substrate surface created by the reactive ion etching is critical for ZnO growth without using catalyst. ZnO nanowire array exclusively grows in area etched by the reactive ion etching method. The advantages of this method include facile and safe achieving roughness-assisted, catalyst-free growth of ZnO nanowires on SiO2/Si substrate; and the subsequent transfer-free fabrication of electronic or optoelectronic devices. The ZnO nanowire UV photodetector fabricated by a transfer-free process presented high performance in responsivity, quantum efficiency and response speed, even without any post-treatments. The strategy shown here would greatly reduce the complexity in nanodevice fabrication and give an impetus to the application of ZnO nanowires in nanoelectronics and optoelectronics.
    Full-text · Article · Aug 2015 · ACS Applied Materials & Interfaces
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    ABSTRACT: The magnetic properties and magnetocaloric effect in R2PdSi3 (R = Dy, Dy and Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Néel temperatures. And, it is found that the Dy2PdSi3 and Er2PdSi3 compounds undergo a spin-glass behavior below Néel temperature. Under the magnetic field change of 5 T, the values of reach 11.8 J/kg K for Gd2PdSi3, 16.6 J/kg K for Dy2PdSi3 and 22 J/kg K for Er2PdSi3, respectively. Especially, the values of in the Er2PdSi3 compound are 8 and 14.5 J/kg K for field change of 1 and 2 T, which is attributed to a field-induced metamagnetic transition from AFM to FM states. The large reversible and large RC together with the absence of thermal and field hysteresis indicate that Er2PdSi3 compound could be a promising candidate for magnetic refrigeration at low temperatures.
    No preview · Article · Mar 2015 · Journal of Alloys and Compounds
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    ABSTRACT: A large reversible magnetocaloric effect accompanied by a second order magnetic phase transition from PM to FM is observed in the HoPd compound. Under the magnetic field change of &; and the refrigerant capacity R C for the compound are evaluated to be 20 J/(kg · K) and 342 J/kg, respectively. In particular, large &; (11.3 J/(kg · K)) and R C (142 J/kg) are achieved under a low magnetic field change of 0–2 T with no thermal hysteresis and magnetic hysteresis loss. The large reversible magnetocaloric effect (both the large -ΔS M and the high R C) indicates that HoPd is a promising material for magnetic refrigeration at low temperature.
    No preview · Article · Mar 2015 · Chinese Physics B
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    ABSTRACT: The mechanical properties and magnetocaloric effect (MCE) of bonded La(Fe, Si)13 hydrides have been studied in detail. The mechanical strength increases with increasing the grade of epoxy resin from E-20 to E-51. This occurs because more pores and boundaries are filled with high grade resin since high epoxide content increases the degree of crosslinking and reduces the viscosity and shrinkage of resin. The compressive strength reaches 162 MPa for the bonded LaFe11.7Si1.3C0.2H1.8 with 3 wt. % E-51, which is 35% higher than that of bulk LaFe11.7Si1.3C0.2 compound (120 MPa). The mass ΔSM values remain almost same in bonded hydrides and are in a good agreement with the theoretical value. The maximum volumetric ΔSM values are 61.8, 58.0, and 54.7 mJ/cm3 K for bonded hydrides with epoxy resins E-20, E-44, and E-51, respectively, much higher than those of some magnetocaloric materials in same temperature range. The improved mechanical properties and large MCE indicate that bonded LaFe11.7Si1.3C0.2H1.8 is a promising material for room temperature magnetic refrigeration.
    No preview · Article · Feb 2015 · Journal of Applied Physics
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    ABSTRACT: A large reversible magnetocaloric effect accompanied by a second order magnetic phase transition from paramagnetic (PM) to ferromagnetic (FM) has been observed in TmCoAl intermetallic compound. For the magnetic field change of 5 T, the maximum value of magnetic entropy change (−ΔSMmax) and the value of refrigerant capacity (RC) are evaluated to be 18.2 J/kg K and 211 J/kg, respectively. In particular, a large −ΔSMmax (10.2 J/kg K) is achieved at 7.5 K under a low magnetic field change from 0 to 2 T with no thermal hysteresis and magnetic hysteresis loss. The large reversible magnetocaloric effect (both the large −ΔSM and the high RC) indicates that TmCoAl is one of a promising material for magnetic refrigeration in low temperature.
    No preview · Article · Jan 2015 · Intermetallics
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    ABSTRACT: The magnetic and magnetocaloric properties of TmNi1-xCuxAl (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) compounds have been investigated. With the substitution of Ni by Cu, the Tm-magnetic moment rotates its direction from basal plane to the c-axis and finally becomes canted antiferromagnetism structure with larger projected moments along the c-axis near Tord. Furthermore, large reversible magnetocaloric effects have been observed in TmNi1-xCuxAl compounds around Tord, with no thermal hysteresis and magnetic hysteresis loss. The values of -ΔSMmax and refrigerant capacity are greatly improved when the part of Ni was superseded by Cu. In particular, under the magnetic field change of 2 T, a large -ΔSMmax of TmNi0.7Cu0.3Al (10.7 J/kg K) is almost twice that of TmNiAl (5.5 J/kg K) and 17.2 J/kg K for TmCuAl around 4 K. The present results indicate that TmNi1-xCuxAl (x ≥ 0.3) compounds could be considered as good candidate materials for low-temperature and low-field magnetic refrigerant.
    No preview · Article · Apr 2014 · Journal of Applied Physics
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    ABSTRACT: The magnetic properties and magnetocaloric effect (MCE) in HoNi1−xCuxIn (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi1−xCuxIn compounds around Tord, with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (−ΔSM) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi0.7Cu0.3In. Especially, the value of −ΔSM (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi0.9Cu0.1In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi0.9Cu0.1In and HoNi0.7Cu0.3In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K.
    No preview · Article · Mar 2014 · Journal of Magnetism and Magnetic Materials
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    ABSTRACT: The magnetic properties and magnetocaloric effect (MCE) in RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Neel temperatures. The RCu2Si2 compounds undergo spin-glassy behavior above Neel temperature. Furthermore, a field-induced metamagnetic transition from AFM to ferromagnetic (FM) states is observed in these compounds. The calculated magnetic entropy changes show that all RCu2Si2 and RCu2Ge2 (R = Ho, Er) compounds, especially, ErCu2Si2 exhibits large MCEs with no thermal hysteresis and magnetic hysteresis loss. The value of -ΔSMmax reaches 22.8 J/Kg K for magnetic field changes from 0 to 5 T. In particular, for field changes of 1 and 2 T, the giant reversible magnetic entropy changes -ΔSMmax are 8.3 and 15.8 J/kg K at 2.5 K, which is lower than the boiling point of helium. The low-field giant magnetic entropy change, together with ignorable thermal hysteresis and field hysteresis loss of ErCu2Si2 compound is expected to have effective applications in low temperature magnetic refrigeration.
    No preview · Article · Jan 2014 · Journal of Applied Physics
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    ABSTRACT: A large reversible magnetocaloric effect has been observed in Tm3Co compound. The Tm3Co compound exhibits two successive magnetic transitions with the increasing temperature: antiferromagnetic (AFM) to ferromagnetic (FM) transition at 4.5 K and FM to paramagnetic (PM) transition at 6.5 K. Under a magnetic field change of 5 T, the maximum value of magnetic entropy change −ΔSM is 19.9 J/kg K at 7.5 K and the refrigerant capacity power (RCP) is 300 J/kg with no hysteresis loss. In particular, the large reversible −ΔSM (11.6 J/kg K) is achieved for a low magnetic field change of 2 T. The large reversible magnetocaloric effect (both the large −ΔSM and the high RCP) indicates that Tm3Co could be a promising candidate for magnetic refrigeration.
    No preview · Article · Sep 2013 · Journal of Alloys and Compounds
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    ABSTRACT: The magnetic properties and magnetocaloric effect in TmGa compound are investigated. TmGa exhibits two successive magnetic transitions: ferromagnetic-antiferromagnetic at TFA = 12 K and antiferromagnetic-paramagnetic transition at TN = 15 K. Under field changes of 1 and 2 T, giant reversible values of magnetic entropy change (12.9 and 20.6 J/kg K) and large values of refrigerant capacity (69 and 149 J/kg) are observed, respectively. Additionally, the maximal values of adiabatic temperature change are 3.2 and 5 K for field changes of 1 and 2 T, respectively. The TmGa compound with excellent magnetocaloric effect is expected to have effective applications in low temperature magnetic refrigeration.
    No preview · Article · Jul 2013 · Applied Physics Letters
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    ABSTRACT: A giant low field reversible magnetocaloric effect has been observed in TmCuAl compound around 4 K, which is the boiling point of helium. The maximum value of magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) is 17.2 J/Kg K and 4.6 K without thermal and field hysteresis loss, for field changes of 0–2 T, respectively. Especially, the giant value of −ΔSMmax (12.2 J/Kg K) is obtained for a field change of 0-1 T. The results indicate that the TmCuAl compound could be considered as a good candidate material for low-temperature and low-field magnetic refrigerant.
    No preview · Article · May 2013 · Applied Physics Letters
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    ABSTRACT: A non-monotonic size change of monodisperse Fe(3)O(4) nanoparticles (NPs) with a diameter of 3-20 nm is observed in the scale-up organic-phase synthesis. The crystal structures and the valence state of the Fe ions of the as-prepared NPs were determined by X-ray diffraction (XRD) and Mössbauer spectroscopy, respectively. It is interestingly observed that particle size does not decrease monotonously with either the increase of the molar ratio of oleic acid (OA) to FeO·OH, or the decrease of precursor concentration. Furthermore, the reaction process was investigated via the time-dependent Fourier transform infrared spectra (FTIR) and the transmission electron microscopy (TEM) images, which reveal that the non-monotonic size change results from the different influence of OA on the three reaction stages including monomer formation, nucleation, and growth with increasing precursor amounts.
    No preview · Article · Feb 2013 · Nanoscale
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    ABSTRACT: In this paper, we demonstrate the optical and electrical performance of ZnO nanorod arrays after surface passivation. The material of larger band gaps (HfO2) was chosen for the surface passivation layer through atom layer deposition (ALD), in order to confine the carriers within the core material efficiently. In the case of nanorods with high defects, HfO2 coating treatment not only improved near band edge (NBE) but also greatly enhanced the defect luminescence, while in the case of nanorods with low defects, surface coating suppressed defect luminescence and promoted the NBE emission as well as electrical performance therein. PL investigation at 10 K displayed that after surface coating phonon related emission was confined along c-axis and the exciton emission related to surface states was largely restrained. Therefore, it's suggested that surface passivation of ZnO nanorod arrays decreases the surface defect, enhances the side confinement of nanorod, and thus improves the optical and electrical performance efficiently.
    Full-text · Article · Feb 2013 · Journal of Nanoscience and Nanotechnology
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    ABSTRACT: A series of intermetallic Er3−xGdxCo (x = 0.5–3) compounds were synthesized and their magnetic properties and magnetocaloric effects were investigated. The Neél temperature (TN) could be tuned from 28 to 129 K by partially replacement of Gd with Er. For a field change of 5 T, the Er1.5Gd1.5Co exhibited a minimum −ΔSM of 9.8 J/kg K and maximum refrigerant capacity power (RCP) value of 629 J/kg which originated from an enlarged temperature span of magnetic entropy change in the compound. Results demonstrate that it is a feasible way to search for a large RCP material from the compounds with two magnetic transitions and controlled temperature region.
    No preview · Article · Jan 2013 · Journal of Applied Physics

  • No preview · Conference Paper · Jan 2013
  • Li-Qin Yan · Fangwei Wang · Young Sun · Jun Shen
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    ABSTRACT: A series of Cd1-xCuxCr2S4 (x = 0.01, 0.04, 0.1, and 0.2) ceramics have been prepared by a solid state reaction method. The X-ray diffraction patterns suggest that the samples have a cubic spinel phase with a space group Fd3m and a tiny amount of Cr2O3 impurity phase. X-ray photoemission spectroscopy reveals a bivalence of Cu and trivalence of Cr in Cd0.8Cu0.2Cr2S4. The replacement of Cd by Cu leads to a slight shift of magnetic transition temperature T-C. The saturation magnetic moment per formula unit at 2 K and effective moments in paramagnetic region decrease with Cu content, which is attributed to the coexistence of low spin state Cr3+ with S = 1/2 and high spin state Cr3+ with S = 3/2 as deduced from the M-H and M-T measurements. The transport measurements suggest that the Cu2+ doping enhances the carrier density. In contrast, a significant decrease in magnetoresistance is observed upon Cu doping. The magnetoresistance effect is discussed based on the magnetic polaron theory.
    No preview · Article · Nov 2012 · IEEE Transactions on Magnetics
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    ABSTRACT: The microstructure and magnetic properties for LaFe10.85 Co0.65Si1.5C0.2, LaFe11.5Si1.5C0.2 and LaFe10.85Co0.65Si1.5 compounds were investigated. The ingots were prepared by 5 kilogram Vacuum Induction Melting Furnace. Then LaFe10.85Co0.65Si1.5C0.2 and LaFe11.5Si1.5C0.2 thin strips were prepared by the strip-casting process. The DSC measurement shows that the maximum latent heat of LaFe11.5Si1.5C0.2 thin strips has been obtained after annealing at 1353 K for 12 h, longer time annealing seems to be no good for latent heat. Substitute Co for Fe could cause inhomogeneous distribution of Curie temperature (T-C) in the bulk ingots, but the inhomogeneity can be improved by preparing the strip from the ingot. Under magnetic field changes of 0-1.5 T, the magnetic entropy change near the Curie temperature was about -11.1 J/kg. K and -4.0 J/kg. K for LaFe11.5Si1.5C0.2 and LaFe10.85Co0.65Si1.5C0.2, respectively.
    No preview · Article · Nov 2012 · IEEE Transactions on Magnetics
  • Li-Qin Yan · Fen Wang · Yuelei Zhao · Tao Zou · Jun Shen · Young Sun
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    ABSTRACT: The exchange bias phenomenon has been investigated in multiferroic Eu0.75Y0.25MnO3. The material shows a weak ferromagnetism with cone spin configuration induced by external magnetic field below 30 K. Consequently, the electric polarization coming from the cycloid spin order below 30 K can be suppressed by external magnetic fields. The magnetic hysteresis loops after cooling in a magnetic field exhibit characteristics of exchange bias below the spin glassy freezing temperature (Tg)∼16 K. The exchange bias field, coercivity field, and remanent magnetization increase with increasing cooling magnetic field. The exchange bias effect is ascribed to the frozen uncompensated spins at the antiferromagnetism/weak ferromagnetism interfaces in the spin-glass like phase.
    No preview · Article · Aug 2012 · Journal of Magnetism and Magnetic Materials

Publication Stats

983 Citations
300.79 Total Impact Points

Institutions

  • 2009-2016
    • Technical Institute of Physics and Chemistry
      Peping, Beijing, China
  • 2006-2015
    • Chinese Academy of Sciences
      • • Institute of Physics
      • • State Key Laboratory of Magnetism
      • • Graduate School
      Peping, Beijing, China
  • 2008-2013
    • Peking University
      • • Laboratory for the Physics & Chemistry of Nanodevices
      • • College of Chemistry and Molecular Engineering
      Beijing, Beijing Shi, China
  • 2004-2010
    • Hebei University of Technology
      • School of Materials Science and Engineering
      Ho-pei-ts’un, Beijing, China