Jiecai Han

Harbin Institute of Technology, Charbin, Heilongjiang Sheng, China

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Publications (177)380.63 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To improve the oxidation-resistance of carbon bonded carbon fiber composites (CBCFs), the low density and porous CBCFs modified with ZrB2 and SiC ceramics with density of 0.26, 0.40, 0.61 and 0.77g/cm-3 were prepared by precursor infiltration and pyrolysis method. The pyrolysis behavior of the Zr and B-containing hybrid polymeric precursor was studied. The densification behavior was investigated through the analysis of the microstructures of CBCFs-SiC-ZrB2 (denoted as CSZ) composites with different density. The mechanical properties and thermo-physical properties of CSZ composites were studied. The results show that the incorporation of ZrB2 ceramic coating does not change the anisotropic properties of CBCF composites. The CSZ composite with a density of 0.77 g/cm3 has a continuous ZrB2 ceramic coated layer on the surface of the carbon fibers and exhibits better mechanical properties and antioxidant properties. This investigation reveals that the lightweight ZrB2 and SiC-modified CBCFs possess remarkable thermal properties and can serves as thermal insulation applications at high temperature.
    RSC Advances 09/2014; · 3.71 Impact Factor
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    ABSTRACT: High-quality few-layer-thick graphitic carbon nitride (g-C3N4) nanosheets (NSs) were fabricated by a simple, highly efficient, and rapid method namely, liquid ammonia (LA)-assisted lithiation. Li intercalation occurred in less than half an hour, importantly, the degree of Li intercalation was indicated by the color change of LA solution from deep blue to colorless. The obtained products were carefully investigated by field-emission transmission electron microscopy, field-emission scanning electron microscopy, atomic force microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Raman scattering spectrometry, UV-visible absorption spectrometry, photoluminescence, soft X-ray absorption and nonresonant soft X-ray emission spectroscopy, and X-ray absorption near-edge structure analyses. Because of the lack of high-temperature or high-energy treatment, high-yield few-layer-thick g-C3N4 NSs were produced with trace O2 impurity. Interestingly, while maintaining the similar crystal structure and chemical stoichiometric ratio relative to the parent bulk materials, the surface structure, electronic and optical properties were significantly varied. Moreover, compared to the bulk counterparts, the as-prepared g-C3N4 NSs show clearly enhanced photocatalytic redox activity with respect to both photocatalytic H2 evolution and hydroxyl radical generation. LA-assisted lithiation is a general method and could be easily extended to exfoliate diverse other layered materials such as molybdenum and tungsten sulfides.
    RSC Advances 07/2014; 4(62). · 3.71 Impact Factor
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    ABSTRACT: A novel plasma exposure technique has been introduced into conventional magnetron sputtering process to enhance the crystallization of indium oxide (In2O3) films at room temperature. The effect of plasma exposure technique with different pulsed DC voltages on the electrical and mechanical properties of In2O3 films was investigated. It is observed that film crystallization can be significantly enhanced when the pulsed DC voltage (|V p|) is higher than |−500 V| (|V p| > |−500 V|). By applying the plasma exposure process, In2O3 films prepared at room temperature with thickness of 135 nm shows low resistivity of 4.11 × 10−4 Ω cm, mobility of 42.1 cm2/Vs, and transmittance over 80 % in the visible range. Compared with the In2O3 films without plasma exposure process, the In2O3 films with plasma exposure show better crystallization and remarkably higher nanohardness. The plasma exposure technique is a useful candidate technique for enhancing film crystallization at low temperature.
    Journal of Materials Science 06/2014; · 2.31 Impact Factor
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    ABSTRACT: The dispersion characteristics of Love wave in an isotropic homogeneous half-space covered with a functionally graded layer is investigated. Governing equations for the anti-plane shear wave in the graded layer are derived, and analytical solutions for the displacement and stress field in the layer are given. Moreover, the general dispersion relations of Love wave in both the half-space and the layer are analyzed. For the layer with shear modulus and mass density varying in a parabolic form, the dispersion equations are solved in terms of iteration method. The obtained dispersion curves reveal that there exists a cut-off frequency in the lowest order vibration mode.
    Applied Mathematics and Computation 03/2014; 231:93–99. · 1.60 Impact Factor
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    ABSTRACT: Hypersonic aircrafts subjected to strong aerodynamic forces and serious aerodynamic heating require a very stringent design of their infrared window. The purpose of this paper is to investigate the thermal shock damage of chemical vapor deposition zinc sulfide (CVD ZnS) infrared window material through finite element analysis and oxygen propane flame experiments. In this paper, a finite element model is developed to simulate the thermal shock behavior of CVD ZnS ablated by an oxygen propane flame. In addition, thermal shock experiments are performed to investigate the thermal shock damage behavior under different conditions. The results show that good agreement between the numerical solutions and the experimental results is achieved. When the heat fluxes are 409.8 kW/m2 and 493.3 kW/m2, the materials have good thermal shock resistance; when the heat flux is 575.9 kW/m2, cracks appeared during the thermal shock resulting in thermal shock damage to the material.
    Journal of Alloys and Compounds 03/2014; 589:101–108. · 2.73 Impact Factor
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    ABSTRACT: A method of introducing a single sharp crack with controllable length and position in brittle materials by thermal shock is proposed. This method is simple to conduct and suitable for the precise testing of critical fracture parameters, with accurate values of fracture toughness of brittle ceramics, such as ZrB2–SiC–graphite (ZSG), able to be obtained. Moreover, this provides an experiment foundation for the study of the relationship between mechanical properties and cracks: The effects of crack length and specimen thickness on the residual strength of ZSG were investigated here. Further comparison between the experimental data and the results of the extended finite-element calculation was made. Through proper control over the thermal shock, a desired number of uniformly distributed and roughly parallel cracks can be obtained.
    Journal of the American Ceramic Society 02/2014; · 2.43 Impact Factor
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    RSC Advances 01/2014; 4:6591-6596. · 3.71 Impact Factor
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    ABSTRACT: The oxidation behavior and phase transition of ZrB2–SiCw–ZrO2f ceramic had been investigated by in situ high-temperature XRD, XPS, SEM, EDS and TEM measurements. The initial oxidation temperature of most ZrB2 was 1000 °C and no significant oxidation of SiC was found up to 1200 °C. The oxidation products formed at lower temperatures would penetrate into the pores and flaws on the surface, which was beneficial to crack healing. In order to improve the oxidation resistance of this system, it should be focused on decreasing the oxygen diffusivity and the volume expansion caused by phase transition.
    Corrosion Science 01/2014; 78:13–21. · 3.69 Impact Factor
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    ABSTRACT: Crosslinked carbon network with interconnected pores were obtained from [furfuryl alcohol (FA) + phenol–formaldehyde resin (PF)] – ethylene glycol (EG) mixtures. The effect of FA/PF weight ratio (WF/P) on the pore structure of the porous carbons has been systematically investigated. The results showed that porous carbons with controlled pore size could be obtained by varying WF/P in the polymer system. With WF/P increased, the average pore size and apparent porosity increased from 11.8 to 127.7 nm and from 40.9 to 51.6%, respectively, and the pore size distribution broadened. The property change of the porous carbons was a result of polymerization dynamics change on curing of resin–glycol mixtures induced by varying WF/P in the polymer system. Increasing the initial WF/P led curing reactions to occur at relatively lower temperatures, and the degree of polymerization to increase after heat treatment at 150 °C for 16 h, thus cured bodies with different chemical structures were obtained.
    Materials Chemistry and Physics 01/2014; 143(2):707–712. · 2.13 Impact Factor
  • Journal of Non-Crystalline Solids 01/2014; · 1.72 Impact Factor
  • Materials Science and Engineering A 08/2013; 558:175-180.. · 2.41 Impact Factor
  • Journal of Luminescence 08/2013; · 2.37 Impact Factor
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    ABSTRACT: Carbon-bonded carbon fiber composites were produced by a simple pressure filtration technique. This method consists of dispersing carbon fibers and phenolic resin to make a slurry and then pressing the water out through a filter cloth, and finally carbonizing the composites at 1000 °C in nitrogen. A homogeneous microstructure without agglomeration and layering was achieved. The compressive strength ranged from 0.2 to 1.1 MPa for different densities. The thermal conductivity for the composites of 0.23 g cm−3 was 0.2–0.43 and 0.11–0.35 W m−1 K−1 for the directions perpendicular and parallel to the pressure, respectively, at 25–1300 °C.
    Carbon 08/2013; 59:551–554. · 6.16 Impact Factor
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    ABSTRACT: The band structures and optical properties of monoclinic HfO2 are investigated by the local density approximation (LDA)+U approach. With the on-site Coulomb interaction being introduced to 5d orbitals of Hf atom and 2p orbitals of O atom, the experimental band gap is reproduced. The imaginary part of the complex dielectric function shows a small shoulder at the edge of the band gap, coinciding with the experiments. This intrinsic property of crystallized monoclinic HfO2, which is absent in both the tetragonal phase and cubic phase, can be understood as a consequence of the reconstruction of the electronic states near the band edge following the adjustment of the crystal structure. The existence of a similar shoulder-like-structure in the monoclinic phase of ZrO2 is predicted.
    Applied Physics Letters 06/2013; 103(7). · 3.52 Impact Factor
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    ABSTRACT: High quality 3C-SiC nanowires are synthesized via thermal treatment of Ni/a-C/Si sandwich films. The nanowires obtained at 900 °C, under a low partial pressure of oxygen, consist of 20–50 mm diameter cores coated by an amorphous phase. The formation of 3C-SiC involves solid–liquid–solid mode and vapor–liquid–solid processes. The ability to synthesize SiC nanowires under the fabrication conditions, both relatively low temperature and a small amount of oxygen, represents an important advance towards their eventual integration for various technological applications.
    CrystEngComm 05/2013; 15(23):4655-4659. · 3.86 Impact Factor
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    ABSTRACT: Observations of the microtopography evolution on a crystallisation surface of sapphire crystal grown from Al2O3 melt show the smooth region was formed by thin atomic layers with wave-like edge trace and the rough region was mainly of aligning long bar-like structure formed by many spiral hillocks spreaded along lines corresponding to the direction [8803]. Moreover, decreasing the undercooling would enhance the width of the bars and decrease the width of the grooves adjacent the bars. According to these observations, the growth mechanism of the smooth region is believed to be the 2D nucleation mechanism and that of the rough region is the spiral growth mechanism. Consequently, a conclusion was drew that the controlling growth mechanism of sapphire crystal grown from melt through SAPMAC method is 2D nucleation mechanism.
    International Journal of Surface Science and Engineering 05/2013; 7:1-13. · 0.44 Impact Factor
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    ABSTRACT: Indium doped cadmium oxide (CdO:In) films were prepared on glass and sapphire substrates by pulsed filtered cathodic arc deposition (PFCAD). The effects of substrate temperature, oxygen pressure, and an MgO template layer on film properties were systematically studied. The MgO template layers significantly influence the microstructure and the electrical properties of CdO:In films, but show different effects on glass and sapphire substrates. Under optimized conditions on glass substrates, CdO:In films with thickness of about 125 nm showed low resistivity of 5.9×10-5 Ωcm, mobility of 112 cm2/Vs, and transmittance over 80% (including the glass substrate) from 500-1500 nm. The optical bandgap of the films was found to be in the range of 2.7 to 3.2 eV using both the Tauc relation and the derivative of transmittance. The observed widening of the optical bandgap with increasing carrier concentration can be described well only by considering bandgap renormalization effects along with the Burstein–Moss shift for a nonparabolic conduction band.
    Journal of Materials Science 05/2013; 48(10):3789-3797. · 2.31 Impact Factor
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    ABSTRACT: The effect of carrier concentration on the Fermi level and bandgap renormalization in over 30 indium-doped cadmium oxide (CdO:In) films with carrier concentrations ranging from 1 to 15×1020 cm-3 was studied by using the two band k•p model with electron-electron and electron-ion interactions. It is shown that the Tauc relation, which is based on parabolic valence and conduction bands, overestimates the optical bandgap in CdO films. Theoretical calculations of the optical bandgap give good agreement with experiments by taking into account the Burstein-Moss effect for a nonparabolic conduction band and bandgap renormalization effects. The band filling and bandgap renormalization in these CdO:In films are about 0.5~1.2 eV and 0.1~0.3 eV, respectively.
    Journal of Physics D Applied Physics 04/2013; 46:195102. · 2.52 Impact Factor
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    ABSTRACT: Variation of microstructure and mechanical behavior was investigated with the content increase of carbon particles and carbon fiber in the reaction bonded silicon carbide composites. The composites were prepared by slip casting and liquid silicon infiltration. The bulk density is raised with the increase of carbon black due to the formation of fine β-SiC particles. The flexural strength increases for the reduction of residual Si and the formation of SiC framework; whereas a very high carbon content reduces the flexural strength. The fracture toughness is controlled by the contents of carbon particle and carbon fiber. Thus, fiber debonding, fiber pullout and crack deflection are considered as the main toughening mechanisms. Annealing treatment can effectively improve both the flexural strength and fracture toughness. An increase by 49% of fracture toughness is obtained. A series of structural models are proposed to illustrate the structure changes of carbon fiber.
    Journal of the European Ceramic Society 04/2013; 33(4):887–896. · 2.31 Impact Factor
  • Jiecai Han, Chunzhu Jiang, Jiaqi Zhu
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    ABSTRACT: Amorphous non‐hydrogenated germanium carbide (a‐Ge1−xCx) films have been deposited using magnetron co‐sputtering technique by varying the sputtering power of germanium target (P Ge). The effects of P Ge on composition and structure of the a‐Ge1−xCx films have been analyzed. The FTIR spectrum shows that the C–Ge bonds were formed in the a‐Ge1−xCx films according to the absorption peak at ~610 cm−1. The Raman results indicate that the amorphous films also contain both Ge and C clusters. The XPS results reveal that the carbon concentration decreased as P Ge increased from 40 to 160 W. The fraction of sp 3 C–C bonds remains almost constant when increasing P Ge from 40 to 160 W. The sp 2 C–C content of a‐Ge1−xCx film decreases gradually to 35.9% with P Ge up to 160 W. Nevertheless, sp 3 C–Ge sites rose with increasing P Ge. Furthermore, the hardness and the refractive index gradually increased with increasing P Ge. The excellent optical transmission of annealed a‐Ge1–xCx double‐layer coating at 400 °C suggests that a‐Ge1−xCx films can be used as an effective anti‐reflection coating for the ZnS IR window in the wavelength region of 8–12 µm, and can endure higher temperature than hydrogenated amorphous germanium carbide do. Copyright © 2012 John Wiley & Sons, Ltd.
    Surface and Interface Analysis 03/2013; 45(3). · 1.39 Impact Factor

Publication Stats

985 Citations
380.63 Total Impact Points

Institutions

  • 1995–2014
    • Harbin Institute of Technology
      • • Center for Composite Materials and Structures (CCMS)
      • • School of Materials Science and Engineering
      • • Department of Physics
      • • Department of Applied Chemistry
      Charbin, Heilongjiang Sheng, China
  • 2009
    • Harbin Institute of Technology Shenzhen Graduate School
      Charbin, Heilongjiang Sheng, China
  • 2008
    • University Town of Shenzhen
      Shen-ch’üan-shih, Zhejiang Sheng, China
    • University of Windsor
      • Department of Mechanical, Automotive, and Materials Engineering
      Windsor, Ontario, Canada