Jiecai Han

Harbin Institute of Technology, Charbin, Heilongjiang Sheng, China

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Publications (189)427.18 Total impact

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    ABSTRACT: Materials for infrared domes are required to maintain good properties in harsh environments including mechanical strength, optical transmittance over a wide range of wavelengths and low emissivity. The purpose of this work is to sputter Y2O3 film onto a sapphire substrate by a radio frequency magnetron sputtering method and investigate the structural and thermal radiation properties of the films. In addition, the apparent emissivity of the coated sapphire is simulated for different film thicknesses at different temperatures. The experimental results show that the surface of the Y2O3 film is homogeneous, has a dense morphology and is totally polycrystalline. After being coated with the Y2O3 film, the transmission of the sapphire substrate is improved and the emissivity is decreased with increasing film thickness, especially at high temperatures. Simulation results show that apparent emissivity of a sapphire substrate at high temperatures can be reduced effectively by the Y2O3 film when the ratio of the thickness of Y2O3 film and sapphire substrate is larger than 0.01.
    Journal of Alloys and Compounds 04/2015; 627:438-445. DOI:10.1016/j.jallcom.2014.11.233 · 2.73 Impact Factor
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    ABSTRACT: Small but strong carbon nanotubes (CNTs) are fillers of choice for composite reinforcement owing to their extraordinary modulus and strength. However, the mechanical properties of the nanocomposites are still much below those for mechanical parameters of individual nanotubes. The gap between the expectation and experimental results not only arises from imperfect dispersion and poor load transfer but also from the unavailability of strong polymers that can be effectively utilized within the composites of nanotubes. Aramid nanofibers (ANFs) with analogous morphological features to nanotubes represent a potential choice to complement nanotubes given their intrinsic high mechanical performance and the dispersible nature which enables solvent-based processing methods. In this work, we showed that composite films made from ANFs and multi-walled CNTs (MWCNTs) by vacuum-assisted flocculation (VAF) and vacuum-assisted layer-by-layer (LBL) assembly exhibited high ultimate strength of up to 383 MPa and Young's modulus (stiffness) of up to 35 GPa, which represent the highest values among all the reported random CNT nanocomposites. Detailed studies using different imaging and spectroscopic characterizations suggested that the multiple interfacial interactions between nanotubes and ANFs including hydrogen bonding and pi-pi stacking are likely the key parameters responsible for the observed mechanical improvement. Importantly, our studies further revealed the attractive thermo-mechanical characteristics of these nanocomposites with high thermal stability (up to 520 oC) and ultralow coefficients of thermal expansion (2-6 ppm•K-1). Our results indicated that ANFs are promising nanoscale building blocks for functional ultra-strong and stiff materials potentially extendable to nanocomposites based on other nanoscale fillers.
    ACS Nano 02/2015; DOI:10.1021/nn504927e · 12.03 Impact Factor
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    ABSTRACT: Nanoscale materials having the size- and shape- dependent interactions with light provide flexible opportunities for harvesting solar energy. Photocatalysts based on semiconductor nanoparticles (NPs) have been the most effective materials for the conversion of light into chemical energy, the efficiency of which can be further enhanced by the incorporation of metallic NPs forming hybrid nanostructures. The structural parameters of not only constituent components but also the resultant hybrid nanostructures are critical for the optimization of photocatalytic performance of composite catalysts. Here we demonstrated the successful size control over ZnO hexagonal pyramids (HPs) for the first time. The smallest HPs showing the best photocatalytic properties were used for further Au attachment. Interestingly, we found that most of the Au NPs preferred to grow on the apexes of the basal plane. Very occasionally, Au NPs at the tip of ZnO HPs can be observed. The role of light in promoting the reduction of gold salt by sodium citrate was also revealed. Quantum mechanical calculations were used to explain the site-specific growth of Au on the surface of ZnO HPs. Enhanced degradation rate over organic dyes were found for Au/ZnO hybrids under both UV and visible light irradiation.
    The Journal of Physical Chemistry C 02/2015; DOI:10.1021/jp512570b · 4.84 Impact Factor
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    ABSTRACT: Transparency in infrared (IR) light region and high conductivity for electromagnetic (EM) shielding performance are contradictory for conventional window materials. It is challenging to explore new class of materials with both IR transmittance and high electrical conductivity. Herein, middle-IR transmittance and EM shielding performance are realized by graphene network fabrics (GNFs). GNFs are fabricated by chemical vapor deposition (CVD) using copper mesh with different geometric construction as sacrificial substrate. The structure of GNFs endows the as-fabricated material high IR transmittance, good electrical conductivity, and EM shielding efficiency. The grid parameter τ with regard to square aperture and wire width is of paramount importance to affect EM shielding performance. The highest EM shielding efficiency is 12.86 dB at 10 GHz with transmittance of 70.85% at 4500 nm. Meanwhile, the highest IR light transmittance is 87.85% with EM shielding efficiency of 4 dB. Based on the experimental and theoretical analysis, the EM shielding efficiency is prominently dependent on microwave absorption.
    Carbon 02/2015; 87. DOI:10.1016/j.carbon.2015.01.057 · 6.16 Impact Factor
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    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; 4(87). DOI:10.1039/C4RA04089A · 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). DOI:10.1039/C4RA06036A · 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; 49(17). DOI:10.1007/s10853-014-8314-0 · 2.31 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. DOI:10.1016/j.jallcom.2013.11.126 · 2.73 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. DOI:10.1016/j.amc.2013.12.167 · 1.60 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; 97(3). DOI:10.1111/jace.12845 · 2.43 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. DOI:10.1016/j.matchemphys.2013.10.001 · 2.13 Impact Factor
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    ABSTRACT: Carbon-bonded carbon fiber composites (CBCFs) containing SiC particles with uniform microstructure were produced using an innovative dispersion and flocculent approach. The mixed phenolic (P-f), SiC particles and chopped carbon fibers (C-f) were blended uniformly using polyethyleneimine (PEI) as a dispersant and polyacrylamide (PAM) as a flocculating agent. A homogeneous distribution of SiC particles coated CBCFs was obtained with the addition of 0.6 wt% PEI and 0.8 wt% PAM. The effect of PEI and PAM content on the microstructure, slurry dispersibility and stability of SiC-modified CBCFs was investigated. The compressive strength and compression modulus of the SiC-modified CBCFs were improved compared with unmodified CBCFs. This simple and versatile approach can be used to prepare large-scale and modified CBCFs.
    RSC Advances 01/2014; 4(13):6591-6596. DOI:10.1039/c3ra44913k · 3.71 Impact Factor
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    ABSTRACT: Non-hydrogenated germanium carbide (Ge1 - xCx ) films were prepared by magnetron co-sputtering method in a discharge of Ar. The surface topography, chemical bonding configurations and hardness were characterized by means of atomic force microscopy, X-ray photoelectron spectroscopy (XPS) and nanoindentation technique. The substrate temperature (T-s) exhibited important influence on the film surface topography. With the increase of T-s, the films became smoother owing to stronger diffusion. The film mass density varied between 4.40 g/cm(3) and 4.47 g/cm(3) depending on T-s. A progressive densification of the film microstructure occurred with T-s increasing. The XPS results showed that both the content of the Ge Ge bond and the content of the C-Ge bond in the films increased as Ts increased. The relationship between the chemical bonding and the mechanical properties of the Ge1 - xCx films was also explored. It showed that the hardness of the films increases from 7.47 GPa to 11.48 GPa as T-s increases from 200 degrees C to 700 degrees C. Therefore, increasing the substrate temperature led to a more dense and hard Ge1 - xCx .
    Journal of Non-Crystalline Solids 01/2014; DOI:10.1016/j.jnoncrysol.2013.04.011 · 1.72 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. DOI:10.1016/j.corsci.2013.08.002 · 3.69 Impact Factor
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    ABSTRACT: Porous ZrB2-SiC (ZS) ceramics with different microstructures were fabricated by partial hot-pressing or pressureless-sintering, in order to obtain high thermal shock damage resistance. Their thermal shock behavior was investigated by water-quenching. The influences of various microstructural characteristics: porosity, pore size and sintering degree, on mechanical properties were investigated in detail, and their effects on critical crack size, critical thermal shock temperature (Delta T-c) and residual strength retention rate after thermal shock were also discussed. The pressureless-sintered ZS with 11% porosity had an optimum configuration of porosity and pore size, and exhibited the best combination of mechanical properties and thermal shock damage resistance. No cracks were visible under the scanning electron microscope on the surfaces of this specimen after thermal shock, showing its excellent structural stability.
    Materials Science and Engineering A 08/2013; 558:175-180.. DOI:10.1016/j.msea.2013.09.046 · 2.41 Impact Factor
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    ABSTRACT: Nd3+-doped Y(3)A(15)O(12) single crystal was successfully grown by horizontal directional solidification (HDS) method; in addition optical absorption and fluorescence spectra were measured at room temperature. Base on the Judd-Ofelt theory, the intensity parameters of Nd3+ in YAG crystal grown by HDS were determined, and then three spectroscopic parameter Omega(t) (t=2,4,6), radiative transition probabilities, radiative lifetime and branching ratios were obtained according to the absorption spectra and fluorescence spectra, and the results were discussed as well. Furthermore, the stimulated emission cross-section of F-4(3./2)-I-4(11/2) transition of Nd3+ in YAG crystal grown by the HDS technique was calculated as 17.86 x 10(-2)0 cm(2). In comparison with Nd:YAG crystal grown by the Czochraiski technique, those results indicated that lowly Nd3+-doped YAG crystal grown by HDS method had highly efficient stimulated emission for laser materials.
    Journal of Luminescence 08/2013; 140:135-137. DOI:10.1016/j.jlumin.2013.03.002 · 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. DOI:10.1016/j.carbon.2013.03.049 · 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). DOI:10.1063/1.4818765 · 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. DOI:10.1039/C3CE40372F · 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

Publication Stats

1k Citations
427.18 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
      • • Academy of Fundamental and Interdisciplinary Science
      • • Department of Applied Chemistry
      Charbin, Heilongjiang Sheng, China
  • 2009
    • Harbin Institute of Technology Shenzhen Graduate School
      Charbin, Heilongjiang Sheng, China
    • Heilongjiang Institute of Science and Technology
      Charbin, Heilongjiang Sheng, China
  • 2008
    • University Town of Shenzhen
      Shen-ch’üan-shih, Zhejiang Sheng, China
  • 2007–2008
    • University of Windsor
      • Department of Mechanical, Automotive, and Materials Engineering
      Windsor, Ontario, Canada