Jiecai Han

Harbin Institute of Technology, Charbin, Heilongjiang Sheng, China

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Publications (213)530.89 Total impact

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    ABSTRACT: Carbon nanosheet–coated micron zirconium diboride particles were achieved by an atmospheric chemical vapor deposition in the presence of methane gas without catalyst. The microstructures and carbon structure for the novel particles were characterized by scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. In addition, the growth process of hybrid particles was analyzed by thermodynamic theory. The results showed that zirconium diboride particles were coated by carbon nanosheets uniformly. The carbon nanosheets/zirconium diboride particles were employed to fabricate ceramic composite using spark plasma sintering process. The fracture toughness of the composite was improved up to 5.9 MPa·m0.5 with only 0.9 wt% of carbon nanosheets, which was 40.9% higher than that of the composite without carbon nanosheets. The toughening mechanisms were mainly known as carbon nanosheets crack bridging and pulling out which lead to the formation of crack deflection in the novel composite.
    No preview · Article · Jan 2016 · Journal of the American Ceramic Society
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    ABSTRACT: The composite film of carbon nanotubes and silicon carbide nanowires was synthesized directly on the silicon substrate by the catalyst-assisted method. The carbon nanotubes crimped together decorated with silicon carbide nanowires covering the whole substrate. The appropriate amount of aluminum powders is a crucial factor to achieve the composite film. The composite film exhibited excellent intrinsic superhydrophobicity without any further functionalization. By using the nano/micropillar composite structure model, the presence of silicon carbide nanowires is found to be the key factor that results in the superhydrophobicity of the films. The feasible synthesis of the superhydrophobic coating could have potential application in water-repelling devices, like biochemical sensors and microfluidic systems.
    Full-text · Article · Dec 2015 · Materials and Design
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    ABSTRACT: The preferentially oriented In2O3 thin films were prepared on glass substrates by conventional magnetron sputtering with Ar+ plasma exposure at room temperature. Based on the x-ray diffraction, x-ray photoelectron spectroscopy, and UV photoelectron spectroscopy results, it was found that the Ar+ plasma exposure not only enhanced the low-temperature crystallization of In2O3 thin films, but also led to a dramatic improvement in the work function. Furthermore, it demonstrated that the shift mechanism of the work function in In2O3 thin films mainly combined with theelimination of oxygen defects and the change of the preferential orientation of In2O3 film surface. [Figure not available: see fulltext.] © 2015, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.
    No preview · Article · Oct 2015 · Electronic Materials Letters
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    ABSTRACT: SiOC and SiZrOC ceramics were obtained starting from the hydrosilane system without and with zirconium n-propoxide (Zr(OnPr)4) by sol–gel route. The precursor architectures indicated that the presence of SiH bonds leads to a different cross-linking mechanism of SiZrOC precursor, where the SiH bonds were involved in the formation of SiOZr bonds. The presence of Zr caused a lower content of sp3 carbon in SiZrOC ceramics. At above 1400 °C, the sp3-C/Si ratio in both ceramics increased due to carbothermal reduction, especially rapidly for SiOC ceramics, suggesting the carbothermal reduction in SiZrOC ceramics has been strongly suppressed with the presence of ZrO2. Raman spectroscopy showed the graphitization degree of free carbon increased with temperature in both ceramics, but was always lower in SiZrOC ceramics. The SiZrOC ceramics has been found to exhibit remarkably high temperature stability with respect to carbothermal decomposition up to 1600 °C in comparison with the SiOC ceramics.
    No preview · Article · Oct 2015 · Journal of the European Ceramic Society
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    ABSTRACT: The coupling effect between nitrogen-vacancies (VN) and aluminum-interstitial sites (Ali) is investigated theoretically and experimentally in AlN helices. First-principles calculations predict a photoluminescence emission peak at approximately 600 nm in AlN doped with complex-defect (VNAli). A typical long afterglow (persistent luminescence) was observed in unintentionally doped AlN helices by introducing the complex-defect of (VNAli). An analysis of the luminescent characteristics indicated that the mechanism behind this afterglow is the complex-defect level and complex-defect density. These findings may further enrich the thoughts of defects in the wide band gap semiconductor of AlN.
    Full-text · Article · Sep 2015 · Nano Letters
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    ABSTRACT: Carbon-based nanomaterials provide an attractive perspective to replace precious Pt-based electrocatalysts for oxygen reduction reaction (ORR) to enhance the practical applications of fuel cells. Herein, we demonstrate a one-pot direct transformation from graphitic-phase C3N4 (g-C3N4) to nitrogen-doped graphene. g-C3N4, containing only C and N elements, acts as a self-sacrificing template to construct the framework of nitrogen-doped graphene. The relative contents of graphitic and pyridinic-N can be well-tuned by the controlled annealing process. The resulting nitrogen-doped graphene materials show excellent electrocatalytic activity toward ORR, and much enhanced durability and tolerance to methanol in contrast to the conventional Pt/C electrocatalyst in alkaline medium. It is determined that a higher content of N does not necessarily lead to enhanced electrocatalytic activity; rather, at a relatively low N content and a high ratio of graphitic-N/pyridinic-N, the nitrogen-doped graphene obtained by annealing at 900 °C (NGA900) provides the most promising activity for ORR. This study may provide further useful insights on the nature of ORR catalysis of carbon-based materials.
    Full-text · Article · Aug 2015 · ACS Applied Materials & Interfaces
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    ABSTRACT: An original catalytic method has been proposed to synthesize carbon nanotubes (CNTs)–ZrB2–ZrO2 heterostructures using ZrB2 polymeric precursor. The pyrolysized gases from the ZrB2 polymeric precursor are identified to be the carbon sources for CNTs growth. A parametric study is conducted to control the CNTs growth by optimizing parameters such as synthesis temperature and catalyst content. Observations show that the in situ grown CNTs are homogeneously dispersed in the powders, and the structure and the amount of CNTs are significantly dependent on the synthesis parameters. There are two kinds of grown CNTs existed in the produced hybrid heterostructures: (i) the kinking structured CNTs that are disordered and incomplete graphitization; (ii) the improved and graphitized CNTs. The ZrB2 polymeric precursor during thermal pyrolysis provides capable of supplying substantial carbon source for CNTs nucleation and growth by homogeneous vapor–liquid–solid reactions.
    No preview · Article · Aug 2015 · Journal of the American Ceramic Society
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    ABSTRACT: SiBOC ceramics with highly graphitized free carbon were prepared from sol-gel derived pre-ceramic gels followed by pyrolysis at 1000-1600°C under nitrogen. The effects of boron incorporation on the precursor architecture, microstructure and crystallization of SiBOC ceramics were discussed. The experimental results showed that the incorporation of boron had little effect on the silicon bonding environment in SiBOC precursor and led to a higher ceramic yield of 89%. The crystallization of both β-SiC and free carbon was enhanced in SiBOC ceramics. Raman spectra showed that the intensity ratio of D to G band was very small for the SiBOC ceramics pyrolyzed at 1600°C, indicating the highly ordering and graphitization of free carbon. The clear presence of D' band at 1610cm-1 in Raman spectra suggested the partial substitution of C with B atoms in graphite layer, which significantly promoted the graphitization of free carbon. The turbostratic graphite with 10-20 layers graphene was observed by TEM.
    No preview · Article · Aug 2015
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    ABSTRACT: This paper investigates the influence of deposition conditions on the properties of yttrium oxide thin films. The paper focuses on the texture, optical and mechanical properties. With this objective, a series of yttrium oxide thin films with different thicknesses were deposited by direct current (DC) unbalanced reactive magnetron sputtering at high and low pumping speed. By changing the oxygen flow, depositions were performed in the three characteristic deposition modes for reactive magnetron sputtering, i.e., metallic, transition and poisoned mode. By using an oxygen flow directed to the substrate, full oxidation of the samples, as shown by X-ray photoelectron spectroscopy (XPS), in the three modes is obtained. Crystallographic characterization by X-ray diffraction (XRD) shows that films crystallize in the cubic phase with a strong (222) out-of-plane orientation at low oxygen flow. As the oxygen flow increases a mixture of cubic and monoclinic phase is obtained. In poisoned mode, the films consist of the cubic phase with preferred (420) orientation. Scanning electron microscopy (SEM) cross sections show, with increasing oxygen flow, a loss of the columnar structure. As the oxygen flow rates increase through the metallic, transition, and the poisoned mode, the grain size becomes gradually smaller. An overview diagram of all experimental results uncovers that the textural changes are closely linked to the oxygen partial pressure rather than the oxygen flow. The optical properties of films were investigated by spectroscopic ellipsometry (SE). The films with a columnar structure demonstrate superior hardness and modulus as well as the high plasticity.
    No preview · Article · Aug 2015 · Surface and Coatings Technology
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    ABSTRACT: A graphene nanosheet reinforced ZrB2-SiC ceramic composite (GNs/ZrB2-SiC) using graphene oxide (GO) was hot pressed at 1950°C and 30 MPa for 1 h. Raman and XPS analysis showed multilayer GNs structures were successfully introduced into the composite by in situ thermal reduction of GO during the hot pressing process. The homogeneous dispersion of GO guaranteed the uniform distribution of GNs structures in the composite. Mechanical properties such as bending strength, fracture toughness and hardness were studied for the ZrB2-SiC composite with different volumes fraction of GO. The addition of approximately 5 vol% graphene nanosheets improved the fracture toughness of ZrB2-SiC up to 7.32 MPa m0.5, and the strength was also raised to 1055 MPa. The toughening mechanisms were graphene crack bridging and pulling out induced crack deflection in the GNs reinforced composite.
    No preview · Article · May 2015 · RSC Advances
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    ABSTRACT: Developing a simple and efficient method to organize nanoscale building blocks into ordered superstructures, understanding the mechanism for self-assembly and revealing the essential collective properties are crucial steps toward the practical use of nanostructures in nanotechnology-based applications. In this study, we showed that the high-yield formation of ZnO nanoparticle chains with micrometer length can be readily achieved by the variation of solvents from methanol to water. Spectroscopic studies confirmed the solvent effect on the surface properties of ZnO nanoparticles, which were found to be critical for the formation of anisotropic assemblies. Quantum mechanical calculations and all atom molecular dynamic simulations indicated the contribution of hydrogen bonding for stabilizing the structure in water. Dissipative particle dynamics further revealed the importance of solvent-nanoparticle interactions for promoting one-dimensional self-assembly. The branching of chains was found upon aging, resulting in the size increase of the ensembles and network formation. Steady-state and time-resolved luminescent spectroscopes, which probed the variation of defect-related emission, revealed stronger Forster resonance energy transfer (FRET) between nanoparticles when the chain networks were formed. The high efficiency of FRET quenching can be ascribed to the presence of multiple energy transfer channels, as well as the short internanoparticle distances and the dipole alignment.
    No preview · Article · May 2015 · ACS Nano
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    ABSTRACT: Interface engineering has emerged as a fertile and efficacious approach to turn functional properties in the field of film systems. In this work, the interfacial properties of sputtered yttrium oxide films on zinc sulfide substrate (Y2O3/ZnS) were analyzed by transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS) depth profile and nano-scratch measurement. An interface layer with the depth of 20 nm between Y2O3 film and ZnS substrate was directly observed by TEM. Under different film growth conditions, although the interfacial features including interfacial width and composition distribution exhibit similar behavior, it is found that higher cohesive strength is obtained under a special substrate bias voltage of -160 V at low substrate temperature. Such an enhanced mechanical property can be understood by the role of physisorbed oxygen in the interfacial region, in which less physisorbed oxygen with van der Waals bonds leads to a strong adhesion. Our results provide a favorable strategy to achieve strong adhesion between oxide and sulfide at low temperature, which are urgent in future micro-electric applications.
    No preview · Article · May 2015 · Applied Surface Science
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    ABSTRACT: Macroporous SiOC ceramics have been prepared by the pyrolysis of the preceramic precursor obtained from methyltrimethoxysilane and dimethyldimethoxysilane. The structural evolution of the sol-gel derived SiOC ceramics at high temperatures was investigated using SEM, TG, FTIR, XRD and Raman spectra. The SiOC xerogel exhibited a porous structure consisting of cross-linked spherical gel particles. The structural rearrangement appeared and the SiOC ceramic particles changed from spherical to irregular shape after thermal pyrolysis. The ceramic yield was found to be approximately 70% until 1400 °C, and decreased to 38% at 1600 °C owing to carbothermal reduction. The SiC nanorods were in situ formed from macroporous SiOC ceramic wall at 1600 °C. The β-SiC nanocrystals precipitated from the SiOC matrix at 1400 °C and grew up to 4.6 nm at 1600 °C. The graphitization degree of free carbon increased with the increase of pyrolysis temperature.
    No preview · Article · May 2015 · Ceramics International
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    ABSTRACT: In order to understand the growth behavior of yttrium oxide films driven by thermodynamics and kinetics, two fundamental growth parameters, substrate heating and biasing, were investigated to control film structure and properties comprehensively. We observed two distinct areas, normal deposition area (area 1) and abnormal deposition area (etching area, area 2) at different substrate bias voltages regardless of the substrate temperature. X-ray diffraction (XRD) results show that heating promotes cubic phase formation, whereas ion bombardment induces monoclinic phase growth. Atomic force microscopy (AFM) measurements exhibit that the ions slightly enlarge the surface islands in area 1, whereas they flatten and smoothen the surface in area 2. X-ray photoelectron spectroscopy (XPS) results demonstrate that high temperature suppresses the physisorbed oxygen, and the ion bombardment favorably selects oxygen etching in area 1, causing excess oxygen vacancies. This selectivity almost disappears in area 2. Furthermore, the refractive index and band gap can be enhanced by both substrate temperature and bias voltage. The surface wettability of films can be modulated by the surface chemical composition.
    No preview · Article · Apr 2015 · Ceramics International
  • Yurong He · Yuanchun Liu · Xing Liu · Jiaqi Zhu · Jiecai Han
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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.
    No preview · Article · Apr 2015 · Journal of Alloys and Compounds
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    ABSTRACT: In order to improve the oxidation-resistance of carbon-bonded carbon fiber composites, a multi-composition coating consisting of multi-layer ZrB2-SiC whiskers(SiCw)-Borosilicate/ZrB2-MoSi2-SiCw-Borosilicate, was prepared on the surface of ZrB2-modified carbon-bonded carbon fiber composites (M-CBCF) by a rapid sintering method in trace amounts of oxygen environment. The inner-layer ZrB2-SiCw -Borosilicate was first prepared by instantaneous vacuum-impregnation to seal the surface pores of M-CBCF, and the outer-layer ZrB2-MoSi2-SiCw -Borosilicate was obtained by slurry spraying. The multi-layer coated composites were embedded in graphite powders and sintered at 1723K for 10 min in atmosphere. The results showed that the prepared ZrB2-SiCw-Borosilicate/ZrB2-MoSi2-SiCw -Borosilicate coating had remarkable oxidation resistance and could protect M-CBCF from high- temperature erosion. The weight loss rate of the double-layer coated composites was only 0.44% after oxidation for 100min at 1773 K, while the weight loss rate of inner-layer coated composites reached 25.35%. The oxidation-resistance of multi-layer coating was mainly attributed to the high viscosity of glass phase, matched thermal expansion coefficient and the toughening effect of SiCw.
    No preview · Article · Mar 2015 · Surface and Coatings Technology
  • Jiaqi Zhu · Wenxin Cao · Mingli Yue · Ying Hou · Jiecai Han · Ming Yang
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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.
    No preview · Article · Feb 2015 · ACS Nano
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    ABSTRACT: The manipulation of the heat flow in a ceramic matrix composite is of great importance in industrial and academic fields. Energy flow, as a typical behavior of heat motion in ceramic surfaces can be confined within specific sites during thermal shock experiments, which weakens the temperature gradient distribution, and hence suppresses the crack propagation. The heat flow can be rationally controlled by the introduction of a nanostructured surface with a diverse forced convection coefficient and heat transfer resistance. Taking inspiration from a nanofin surface, yttria-stabilized zirconia (YSZ) nanostructures were fabricated using the sol-gel method. This bio-inspired coating exhibits a high forced convection coefficient (2.884 times) and high heat transfer resistance (30 times) because of the existence of irregular nanowires arrays and a porous nanostructure. The introduction of the nanostructured coating resulted in the rapid depression of the thermal gradient and stress concentration, and the crack propagation was also effectively suppressed. This sol-gel coating method effectively enhanced the thermal shock resistance of the ceramic materials, and indicates the potential for the application of ceramics in extreme environments.
    Preview · Article · Feb 2015 · Journal of Materials Chemistry A
  • Mingli Yue · Ming Yang · Dan Zhang · Di Xiang · Ying Hou · Jiecai Han
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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.
    No preview · Article · Feb 2015 · The Journal of Physical Chemistry C
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    Jiecai Han · Xiaona Wang · Yunfeng Qiu · Jiaqi Zhu · PingAn Hu
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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.
    Full-text · Article · Feb 2015 · Carbon

Publication Stats

2k Citations
530.89 Total Impact Points

Institutions

  • 1995-2015
    • 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
      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
    • University of Windsor
      • Department of Mechanical, Automotive, and Materials Engineering
      Windsor, Ontario, Canada