Yichun Zhou

Xiangtan University, Siangtan, Hunan, China

Are you Yichun Zhou?

Claim your profile

Publications (90)217.66 Total impact

  • Source
  • Source
    Dataset: JAP
  • Source
    Dataset: PNS
  • Source
    Dataset: JMS
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An extended tetrahedron unifies the length scale, geometry, and density of water ice.•O:H–O bond cooperative relaxation stems anomalies of water and ice.•Water prefers 4-coordinated mono-phase with a supersolid skin unless at nanoscale.•An elastic, hydrophobic and less dense skin slipperizes ice and toughens water skin.•H-bond memory and skin supersolidity resolve Mpemba effect - hot water freezes faster.
    Coordination Chemistry Reviews 10/2014; · 12.10 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Thin films of ferroelectric Pb0.82La0.08Sr0.1Ti0.98O3 (PLST) thin films were fabricated on LaNiO3 buffered Pt/Ti/SiO2/Si substrates via the sol–gel deposition method. The dielectric and tunable properties were investigated as a function of DC bias and frequency to exhibit effect of LNO buffer layer on the tunable dielectric thin film. It shows that PLST thin film deposited on LNO/Pt/Ti/SiO2/Si substrates possesses higher dielectric constant and lower dielectric loss compared with the one directly deposited on Pt/Ti/SiO2/Si substrates. Furthermore, the tunability of the LNO-buffered PLST thin film is 68% at the DC bias of 20 V, which is higher than 60% of the pure PLST thin film. The results suggest the addition of LNO buffer layer could effectively improve the dielectric and tunable properties of PLST thin film and make it suitable for high quality dielectric tunable devices.
    Journal of Crystal Growth 10/2014; 404:136–139. · 1.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We present the effects of an amorphous ZrO2 layer on the TiO2-based bipolar resistive switching memory device where the ZrO2 layer plays an important role as a supplementary reservoir of oxygen vacancies. Compared with Pt/TiO2/Pt monolayer device, a remarkably improved uniformity of switching parameters such as switching voltages and resistances in high/low states is demonstrated in the Pt/ZrO2/TiO2/Pt system. The resistive switching mechanism of memory devices incorporating the ZrO2/TiO2 bilayer structure can be attributed to multiple conducting filaments through the occurrence of redox reactions at the ZrO2/TiO2 surface.
    Journal of Applied Physics 09/2014; 116(12):124514-124514-4. · 2.19 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mpemba paradox, that is, hotter water freezes faster than colder water does, has baffled thinkers like Francis Bacon, René Descartes, and Aristotle since B.C. 350. However, a commonly accepted understanding or theoretical reproduction of this effect remains challenging. Numerical reproduction of observations, shown herewith, confirms that water skin supersolidity [Zhang et al., PCCP, in press] enhances the local thermal diffusivity favoring heat flowing outwardly in the liquid path. Analysis of experimental database reveals that hydrogen bond (O:H-O) possesses memory to emit energy at a rate depending on its initial storage. Unlike other usual materials that lengthen and soften all bonds when they are absorbing thermal energy, water performs abnormally at heating to lengthen the O:H nonbond and shorten the H-O covalent bond through inter-oxygen Coulomb coupling [Sun, et al., J. Phys. Chem. Lett., 2013. 4: 3238]. Cooling does oppositely to release energy, like releasing a coupled pair of bungees, at a rate of history dependence. Being sensitive to the source volume, skin radiation, and the drain temperature, Mpemba effect proceeds only in the strictly non-adiabatic ‘source-path-drain’ cycling system for the heat “emission-conduction-dissipation” dynamics with a relaxation time that drops exponentially with the rise of the initial temperature of the liquid source.
    Physical Chemistry Chemical Physics 09/2014; · 4.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The magneto-mechanical coupling effect of amorphous Co40Fe40B20 (CoFeB) films (10-200 nm) on flexible polyethylene terephthalate substrates were investigated in detail. The normalized remanent magnetization (Mr/Ms) of CoFeB films changes significantly (up to 62%) under small tensile or compressive strain. Moreover, the thickness dependence of the magneto-mechanical coupling effect for the flexible CoFeB films was demonstrated. These results provide important information for the development of CoFeB-based magnetic tunnel junction used in flexible spintronic devices.
    Applied Physics Letters 09/2014; 105(10):103504-103504-5. · 3.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Consistency in experimental observations, numerical calculations, and theoretical predictions revealed that skins of water and ice share the same attribute of supersolidity that is characterized by the identical H-O vibration frequency of 3450 cm-1 in comparison to the values of 3200/3150 cm-1 for bulk water/ice. Molecular undercoordination and inter-electron-pair repulsion relax the hydrogen bond (O:H-O) asymmetrically and cooperatively in length and energy associated with a dual process of nonbonding electron polarization. This relaxation-polarization process enhances the dipole moment, elasticity, viscosity, thermal stability of these skins with 25% density loss, which is responsible for the hydrophobicity and toughness of water skin and for the slippery of ice.
    Physical Chemistry Chemical Physics 08/2014; · 4.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Multilayered thin films consisting of both 0.88BaTiO3–0.12Bi(Mg0.5,Ti0.5)O3 ferroelectric layers and PbZrO3 antiferroelectric layers were prepared by sol–gel method, exhibiting high dielectric permittivity, large polarization, high recoverable energy storage density and high energy storage efficiency. A maximum polarization of 93 μC/cm2, recoverable energy storage density of 24.7 J/cm3 and energy storage efficiency of ~60% have been achieved at an electric field of 1050 kV/cm. Furthermore, the energy storage performance of the multilayered thin films was improved by modified layer-by-layer annealing process, where larger polarization (115 μC/cm2), higher recoverable energy storage density (33 J/cm3) and higher energy storage efficiency (~70%) were obtained.
    Ceramics International 05/2014; 40(4):5327–5332. · 2.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Novel hierarchical Bi4Ti3O12 (BIT) micro-cross spheres were prepared by a solvothermal process with surfactant assistance. Experimental results show that the hierarchical BIT micro-cross spheres exhibit a mono-dispersed morphology with a diameter of about 5 μm. And they consist of nano-sheets which assemble into a cross intercalated structure. Moreover, the morphological evolution process indicates that the type and concentration of surfactant play important roles in the shape controlled synthesis and cetyltrimethylammonium bromide is important in determining the self-assembling process of BIT micro-cross spheres. In addition, UV/vis absorption spectra show that the as-synthesized BIT samples have a slightly red-shift behavior and exhibit different band gaps with different morphologies.
    Materials Letters 04/2014; 121:22–25. · 2.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Iron fluoride cathodes have been attracting considerable interest due to their high electromotive force value of 2.7 V and their high theoretical capacity of 237 mA h g(-1) (1 e(-) transfer). In this study, uniform iron fluoride hollow porous microspheres have been synthesized for the first time by using a facile and scalable solution-phase route. These uniform porous and hollow microspheres show a high specific capacity of 210 mA h g(-1) at 0.1 C, and excellent rate capability (100 mA h g(-1) at 1 C) between 1.7 and 4.5 V versus Li/Li(+) . When in the range of 1.3 to 4.5 V, stable capacity was achieved at 350 mA h g(-1) at a current of 50 mA g(-1) .
    Chemistry - A European Journal 03/2014; · 5.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An in situ carbon-encapsulating solution route for the synthesis of Li4Ti5O12@C composite hollow microspheres has been developed. The finally obtained Li4Ti5O12@C hollow microspheres possess a microsized spherical shape, embedded Li4Ti5O12 nanocrystals, and fully encapsulating conductive carbon shells, which endow this Li4Ti5O12 anode material with high specific capacity, rate capability, and cycle stability. Owing to their unique microstructure characteristics, these hollow Li4Ti5O12@C microsphere composites are promising anode materials for highly efficient Li-ion batteries with an excellent rate capability (discharge capacity of 169, 152, 130, 116, 93, and 76 mA h g–1 at 0.2, 1, 2, 5, 30 and 60C, respectively) and a significantly enhanced cycling performance.
    European Journal of Inorganic Chemistry 03/2014; · 2.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: V-doped SrTiO3 (V:STO) thin films on Si and Pt/Ti/SiO2/Si substrates are synthesized by sol–gel method to form metal–insulator–metal (MIM) structures. Bipolar resistive switching (RS) characteristics were investigated in Pt/V:STO/Si and Pt/V:STO/Pt structures respectively. The enhancement of resistive switching behavior in Pt/V:STO/Pt/Ti/SiO2/Si structures were demonstrated in terms of the maximum operation voltage reduced from 20 to 2 V and the improved ROFF/RON ratio increased from 102 to 103. The electrochemical migration of oxygen vacancies resulted from the metal–oxide interfaces was applied to explain the resistive switching behaviors. On the basis of current–voltage characteristics, the switching mechanisms for the low resistance state (LRS) and high resistance state (HRS) currents of V:STO films are considered as Ohmic and trap-controlled space charge-limited current (SCLC) behavior, respectively.
    Japanese Journal of Applied Physics 02/2014; 53(3):035503. · 1.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Multiferroic composite thin films were fabricated based on ferroelectric (FE) Bi3.15Nd0.85Ti3O12 (BNT) and ferromagnetic (FM) La0.7Ca0.3MnO3 (LCMO) parents with different growth sequences of BNT–LCMO/LNO/STO (BL) and LCMO–BNT/LNO/STO (LB). Ferroelectric behaviour along with remnant polarization (2Pr) of 50 μC cm2 and 40 μC cm2 at room temperature, saturated magnetization values around 206 emu cm−3 and 192 emu cm−3 at 100 K were measured for BL and LB composite films, respectively. The temperature dependence of the magnetoelectric (ME) coupling effect was investigated and the ME voltage coefficients of 63 mV cm−1 Oe−1 and 60 mV cm−1 Oe−1 at 100 K were respectively obtained for the BL and LB films. The results show that the composite films exhibit both good ferroelectric and ferromagnetic properties, as well as a substantial ME effect. Moreover, it is demonstrated that the layer sequences and temperature have significant impacts on the magnetoelectric coupling behaviour of these double-layered thin films, which is very likely caused by the magnetic–mechanical–electric interaction, substrate clamping and interface coupling.
    J. Mater. Chem. C. 01/2014; 2(8).
  • [Show abstract] [Hide abstract]
    ABSTRACT: A numerical model is developed to describe the leakage characteristics in ferroelectric thin films under ionizing radiation. The trap-controlled space-charge-limited conduction mechanism is modified by considering radiation-induced charge carriers and changes in the relative dielectric constant. The effect of dose rate is related to the changes in the carrier mobility. Numerical simulation using this model reveals a radiation hardness of 10 Mrad(Si) for barium strontium titanate (BST) thin films at a constant dose rate of 10 Krad(Si)/s. Differences in the leakage behavior under radiation for different conduction regions are also discussed. This model provides a useful tool in predicting the leakage behavior under ionizing radiation and estimating the radiation hardness for ferroelectric materials.
    Radiation Effects and Defects in Solids 01/2014; 169(6). · 0.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spinel cathode materials consisting of LiMn2 O4 @LiNi0.5 Mn1.5 O4 hollow microspheres have been synthesized by a facile solution-phase coating and subsequent solid-phase lithiation route in an atmosphere of air. When used as the cathode of lithium-ion batteries, the double-shell LiMn2 O4 @LiNi0.5 Mn1.5 O4 hollow microspheres thus obtained show a high specific capacity of 120 mA h g(-1) at 1 C rate, and excellent rate capability (90 mAhg(-1) at 10 C) over the range of 3.5-5 V versus Li/Li(+) with a retention of 95 % over 500 cycles.
    Chemistry - A European Journal 12/2013; · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The major limitation of supercapacitors is their low energy densities compared with battery systems. However, there has not been an advanced charge storage mechanism for increasing the electrochemical performance of pseudocapacitors. For the first time, we reported that water-soluble CoCl2 electrodes can show a reversible redox reaction of Co2+ ↔ Co3+ ↔ Co4+ on the electrode and deliver very high specific pseudocapacitance of 1962 F/g. Commercial CoCl2 salt was used directly as pseudocapacitor electrodes in an aqueous electrolyte neglecting the complex synthesis procedures. We further provided electronegativity as a theoretical guideline to identify the promising active metal cations in our pseudocapacitor system. The new charge storage mechanism based on active cations offers critical insights to the rational design of a new generation of energy storage devices.
    ACS Sustainable Chemistry & Engineering. 11/2013; 2(3):440–444.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To optimize the process parameters, it is necessary to exactly predict failure modes during deep drawing of coated metal sheets, where two main failure forms are fracture and wrinkling. In this paper, finite element simulations based on continuous damage mechanics were used to study the failure behavior during a cylindrical deep drawing of metal sheets with nickel coating. It is shown that taking the effect of blank holder force into account, these two failure modes can be predicted. The simulation results are well consistent with that obtained from experiments.
    Journal of Materials Science and Technology -Shenyang- 11/2013; 29(11):1059–1066. · 1.61 Impact Factor