Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      28 July 2007, Volume 23 Issue 04 Previous Issue    Next Issue
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    Research Articles
    Current Progress of Hf (Zr)-Based High-k Gate Dielectric Thin Films
    Gang HE, Lide ZHANG
    J. Mater. Sci. Technol., 2007, 23 (04): 433-448. 
    Abstract   HTML   PDF (1919KB)
    With the continued downscaling of complementary metal-oxide-semiconductor field effect transistor dimensions, high-dielectric constant (high-k) gate materials, as alternatives to SiO2, have been extensively investigated. Hf (Zr)-based high-k gate dielectric thin films have been regarded as the most promising candidates for high-k gate dielectric according to the International Technology Roadmap for Semiconductor due to their excellent physical properties and performance. This paper reviews the recent progress on Hf (Zr)-based high-k gate dielectrics based on PVD (physical vapor deposition) process. This article begins with a survey of various methods developed for generating Hf (Zr)-based high-k gate dielectrics, and then mainly focuses on microstructure, synthesis, characterization, formation mechanisms of interfacial layer, and optical properties of Hf (Zr)-based high-k gate dielectrics. Finally, this review concludes with personal perspectives towards future research on Hf (Zr)-based high-k gate dielectrics.
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    Overview on the Development of Nanostructured Thermal Barrier Coatings
    Xianliang JIANG, Chunbo LIU, Feng LIN
    J. Mater. Sci. Technol., 2007, 23 (04): 449-456. 
    Abstract   HTML   PDF (850KB)
    Thermal barrier coatings (TBCs) have successfully been used in gas turbine engines for increasing operation temperature and improving engine efficiency. Over the past thirty years, a variety of TBC materials and TBC deposition techniques have been developed. Recently, nanostructured TBCs emerge with the potential of commercial applications in various industries. In this paper, TBC materials and TBC deposition techniques such as air plasma spray (APS), electron beam physical vapor deposition (EB-PVD), laser assisted chemical vapor deposition (LACVD) are briefly reviewed. Nanostructured 7–8 wt pct yttria stabilized zirconia (7-8YSZ) TBC by air plasma spraying of powder and new TBC with novel structure deposited by solution precursor plasma spray (SPPS) are compared. Plasma spray conditions, coating forming mechanisms, microstructures, phase compositions, thermal conductivities, and thermal cycling lives of the APS nanostructured TBC and the SPPS nanostructured TBC are discussed. Research opportunities and challenges of nanostructured TBCs deposited by air plasma spray are prospected.
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    Preparation and Characterization of CeO2/YSZ/CeO2 Buffer Layers for YBCO Coated Conductors
    Jie XIONG, Yin CHEN, Yang QIU, Bowan TAO, Wenfeng QIN, Xumei CUI, Yanrong LI
    J. Mater. Sci. Technol., 2007, 23 (04): 457-460. 
    Abstract   HTML   PDF (1213KB)

    CeO2 seed layer was deposited on rolling-assisted biaxially textured metal substrates by direct-current (DC) magnetron reactive sputtering. The effect of deposition temperature on epitaxial orientation of CeO2 thin films was examined. High quality CeO2 layers were achieved at deposition temperature from 750℃ to 850℃. Subsequently yttria-stabilized zirconia (YSZ) and CeO2 films were deposited to complete the buffer layer structure via the same process. The best samples exhibited a highly biaxial texture, as indicated by FWHM (full width half maximum) values in the range of 4°–5°, and 2°–4° for in-plane and out-of-plane orientations, respectively. Secondary ion mass spectrometer analysis confirmed the effective prevention of buffer layer against Ni and W metal interdiffusion. Atomic force microscope observations revealed a smooth, dense and crack-free surface morphology, which provided themselves as the good buffer structure to the YBa2Cu3O7-δ (YBCO) coated conductors.

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    Influence of Ar/N2 Flow Rate on Structure and Property for TaN/NbN Multilayered Coatings
    Xuehua ZHANG, Yuanbin KANG, Sipeng LIU, Qiang LI, Ying YANG, Xiangyun DENG, Dejun LI
    J. Mater. Sci. Technol., 2007, 23 (04): 461-464. 
    Abstract   HTML   PDF (425KB)
    TaN/NbN multilayered coatings with nanoscale bilayer periods were synthesized at different Ar/N2 flow rate by r.f. magnetron sputtering. XRD and nano indenter were employed to investigate the influence of Ar/N2 flow rate on microstructure and mechanical properties of the coatings. The low-angle XRD pattern indicated a well-defined composition modulation and layer structure of the multilayered coating. All multilayered coatings almost revealed higher hardness than the rule-of-mixtures value of monolithic TaN and NbN coatings. At FAr:FN2 =10, the multilayered coating possessed excellent hardness, elastic modulus, internal stress, and fracture resistance, compared with ones synthesized at other Ar/N2 flow rates. The layered structure with strong mixture of TaN (110), (111), (200) and Nb2N (101) textures should be related to the enhanced mechanical properties.
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    Spatially-Resolved Crystallization of Amorphous Silicon Films on the Glass Substrate by Multi-beam Laser Interference
    Zhongfan LIU, Xuede YUAN, Xue HAO, F.Muecklich
    J. Mater. Sci. Technol., 2007, 23 (04): 465-467. 
    Abstract   HTML   PDF (1036KB)
    Laser interference induced crystallization of amorphous silicon (a-Si) on the glass substrate was performed using a Q-switched Nd:YAG (yttrium aluminum garnet) laser. White light interferometer (WLI) and atomic force microscope (AFM) were used to characterize the morphology of the structured films, while X-ray diffraction (XRD), combined with the AFM, was used to analyse the crystalline structure of the film. The experimental results show that the laser energy density above a certain threshold, in the range of 400–500 mJ/cm2, triggers the patterned crystallizations which take the form similar to the laser intensity distribution. For the patterned crystallization under multipulse exposure, a definite polycrystalline structure with individual phases was observed by XRD. The difference in feature form, e.g., deepened craters or heightened lines, is related to the laser energy density relative to the threshold of evaporation of the material.
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    Reactive DC Magnetron Sputtering Deposition of Copper Nitride Thin Film
    Xing′ao LI, Zuli LIU, Kailun YAO
    J. Mater. Sci. Technol., 2007, 23 (04): 468-472. 
    Abstract   HTML   PDF (1377KB)
    Copper nitride thin film was deposited on glass substrates by reactive DC (direct current) magnetron sputtering at a 0.5 Pa N2 partial pressure and different substrate temperatures. The as-prepared film, characterized with X-Ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy measurements, showed a composed structure of Cu3N crystallites with anti-ReO3 structure and a slight oxidation of the resulted film. The crystal structure and growth rate of Cu3N films were affected strongly by substrate temperature. The preferred crystalline orientation of Cu3N films were (111) and (200) at RT, 100℃. These peaks decayed at 200℃ and 300℃ only Cu (111) peak was noticed. Growth of Cu3N films at 100℃ is the optimum substrate temperature for producing high-quality (111) Cu3N films. The deposition rate of Cu3N films estimated to be in range of 18–30 nm/min increased while the resistivity and the microhardness of Cu3N films decreased when the temperature of glass substrate increased.
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    Structural and Magnetic Studies of CTAC-assisted NiZn Ferrite Films within 0.1–3.5 GHz
    Xiang SHEN, Rongzhou GONG, Zekun FENG, Huahui HE
    J. Mater. Sci. Technol., 2007, 23 (04): 473-476. 
    Abstract   HTML   PDF (580KB)
    Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride (CTAC), adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 2.48×105 A/m and electric resistivity to 5.6×102 mΩ•cm. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ′′ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. The μ′′ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.
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    Controlled Microstructure and Photochromism of Inorganic-organic Thin Films by Ultrasound
    Yanhua PANG, Wei FENG, Jie CHEN, Yan LIU, Weimin CAI
    J. Mater. Sci. Technol., 2007, 23 (04): 477-480. 
    Abstract   HTML   PDF (462KB)
    A series of inorganic-organic thin films based on uniformly dispersed nanoparticles of polyoxometalates (POM) entrapped in polyacrylamide (PAM) matrix were prepared by ultrasonic method with different irradiation time. The microstructure, photochromic behavior and mechanism of the films were studied by transmission electron microscopy (TEM), ultraviolet-visible spectra (UV-VIS) and Fourier transform-infrared spectroscopy (FT-IR). The microstructure and photochromic properties of the hybrid thin films could be controlled by ultrasound. TEM image revealed that the average size of phosphotungstic acid (PWA) nanoparticles decreased from 20 to 10 nm with the ultrasound irradiation time from 30 to 60 min. After irradiated with ultraviolet light, the transparent films changed from colorless to blue and showed reversible photochromism. The hybrid film, with ultrasound irradiation for 60 min had higher photochromic efficiency and faster bleaching reaction than the one with ultrasound irradiation for 30 min. FT-IR spectra showed that the Keggin geometry of heteropolyoxometalate was still preserved inside the composites, and the interactions between polyanions and polymer matrix increased as the ultrasound time prolonged. It is suggested that the mechanism of the different photochromic properties for the inorganic-organic thin films is the variation of the microstructure and interfacial interactions induced by ultrasound.
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    Preparation and Characterization of Boron Thin Film on Iron Substrate
    Ishrat REHANA, D.Muhammad, S.Ahmed, J.I.Akhter
    J. Mater. Sci. Technol., 2007, 23 (04): 481-486. 
    Abstract   HTML   PDF (2411KB)
    The adherent thermal layering was undertaken by chemical vapor deposition (CVD) method using saturated solution of boric acid in ultra pure CH3OH. The influence of temperature was studied by varying temperature from 100 to 600℃ during the process of boron deposition. The most optimum temperature was found to be 200℃. The effect of time span was observed from 6 to 120 h. The generation of micro or nano-scale thickness could be achieved by reducing time span of the experiment. The behavior of CVD was characterized by using scanning electron microscope, absorbance spectrohotometer and atomic emission spectrograph.
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    Interfacial Bonding Strength of TiN Film Coated on Si3N4 Ceramic Substrate
    Dejun KONG, Yongkang ZHANG, Zhigang CHEN, Jinzhong LU
    J. Mater. Sci. Technol., 2007, 23 (04): 487-490. 
    Abstract   HTML   PDF (992KB)
    The fraction of TiN/Si3N4 in the cross section was observed with scanning electric microscope (SEM), and residual stresses of TiN coated on the surface of Si3N4 ceramic were measured with X-ray diffraction (XRD). The hardness of TiN film was measured, and bonding strength of TiN film coated on Si3N4 substrate was measured by scratching method. The formed mechanism of residual stress and the failure mechanism of the bonding interface in the film were analyzed, and the adhesion mechanism of TiN film was investigated preliminarily. The results show that residual stresses of TiN film are all behaved as compressive stress, and TiN film is represented smoothly with brittle fracture, which is closely bonded with Si3N4 substrate. TiN film has high hardness and bonding strength of about 500 MPa, which could satisfy usage requests of the surface of cutting Si3N4 ceramic.
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    Structure and Mechanical Performance of Nitrogen Doped Diamond-like Carbon Films
    Huayu ZHANG, Liangxue LIU, Yulei WANG, Hongtao MA, Fanxin LIU
    J. Mater. Sci. Technol., 2007, 23 (04): 491-494. 
    Abstract   HTML   PDF (838KB)
    Nitrogen doped diamond-like carbon (DLC:N) films were prepared by electron cyclotron resonance chemical vapor deposition (ECR-CVD) on polycrystalline Si chips. Film thickness is about 50 nm. Auger electron spectroscopy (AES) was used to evaluate nitrogen content, and increasing N2 flow improved N content from 0 to 7.6%. Raman and X-ray photoelectron spectroscopy (XPS) analysis results reveal N-sp3C and N-sp2C structure. With increasing the N2 flow, sp3C decreases from 73.74% down to 42.66%, and so does N-sp3C from 68.04% down to 20.23%. The hardness decreases from 29.18 GPa down to 19.74 GPa, and the Young′s modulus from 193.03 GPa down to 144.52 GPa.
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    Diamond Film Synthesis with a DC Plasma Jet: Effect of the Contacting Interface between Substrate and Base on the Substrate Temperature
    Rongfa CHEN, Dunwen ZUO, Feng XU, Duoseng LI, Min WANG
    J. Mater. Sci. Technol., 2007, 23 (04): 495-498. 
    Abstract   HTML   PDF (971KB)
    The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC (direct current) plasma jet. The effects of the solid contacting area, conductive materials and fixing between the substrate and the base were investigated without affecting the other parameters. Experimental results indicated that the preferable solid contacting area was more than 60% of total contacting areal; the particular Sn-Pb alloy was more suitable for conducting heat and the concentric fixing ring was a better setting for controlling the substrate temperature. The result was explained in terms of the variable thermal contact resistance at the interface between substrate and base. The diamond films were analyzed by scanning electron microscopy (SEM) for morphology, X-ray diffraction (XRD) for the intensity of characteristic spectroscopy and Raman spectroscopy for structure.
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    Effect of Reaction Temperature and Time on the Structural Proper-ties of Cu(In,Ga)Se2 Thin Films Deposited by Sequential Elemental Layer Technique
    Saira RIAZ, Shahzad NASEEM
    J. Mater. Sci. Technol., 2007, 23 (04): 499-503. 
    Abstract   HTML   PDF (11917KB)
    Thin films of copper indium gallium selenide Cu(In,Ga)Se2 (CIGS) were prepared by sequential elemental layer deposition in vacuum at room temperature. The as-deposited films were heated in vacuum for compound formation, and were studied at temperature as high as 1250℃ for the first time. These films were concurrently studied for their structural properties by X-ray diffraction (XRD) technique. The XRD analyses include phase transition studies, grain size variation and microstrain measurements with the reaction temperature and time. It has been observed that there are three distinct regions of variation in all these parameters. These regions belong to three temperature regimes: <450℃, 450–950℃, and >950℃. It is also seen that the compound formation starts at 250℃, with ternary phases appearing at 350℃ or above. Whereas, there is another phase shift at 950℃ without any preference to the quaternary compound.
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    Microstructure Control of Nanoporous Silica Thin Film Prepared by Sol-gel Process
    Yiqun XIAO, Jun SHEN, Zhiyong XIE, Bin ZHOU, Guangming WU
    J. Mater. Sci. Technol., 2007, 23 (04): 504-508. 
    Abstract   HTML   PDF (724KB)
    Nanoporous silica films were prepared by sol-gel process with base, acid and base/acid two-step catalysis. Transmission electron microscope (TEM) and particle size analyzer were used to characterize the microstructure and the particle size distribution of the sols. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and spectroscopic ellipsometer were used to characterize the surface microstructure and the optical properties of the silica films. Stability of the sols during long-term storage was investigated. Moreover, the dispersion relation of the optical constants of the silica films, and the control of the microstructure and properties of the films by changing the catalysis conditions during sol-gel process were also discussed.
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    Ar Pressure Dependence of the Properties of Molybdenum-doped ZnO Films Grown by RF Magnetron Sputtering
    Xianwu XIU, Zhiyong PANG, Maoshui LV, Ying DAI, Li′na YE, Shenghao HAN
    J. Mater. Sci. Technol., 2007, 23 (04): 509-512. 
    Abstract   HTML   PDF (1270KB)
    Transparent conducting oxide film of molybdenum-doped zinc oxide (MZO) with high transparency and relatively low resistivity was prepared by RF (radio frequency) magnetron sputtering at room temperature. The structural, electrical, and optical properties of the films deposited under different Ar pressure were investigated. XRD (X-ray diffraction) patterns show that the nature of the films is polycrystalline with a hexagonal structure and a preferred orientation along the c-axis. The resistivity increases as Ar pressure increases. The lowest resistivity achieved is 9.2×10-4 Ω•cm for the samples deposited at Ar pressure of 0.6 Pa with a Hall mobility of 30 cm2•V-1•s-1 and a carrier concentration of 2.3×1020 cm-3. The average transmittance in the visible range exceeds 88% for all the samples. The optical band gap decreases from 3.27 to 3.15 eV with increasing Ar pressure from 0.6 to 3.0 Pa.
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    Synthesis and Characterization of Mesoporous Titania Particles and Thin Films
    Junchao TAO, Yue SHEN, Feng GU, Jinzhuan ZHU, Jiancheng ZHANG
    J. Mater. Sci. Technol., 2007, 23 (04): 513-516. 
    Abstract   HTML   PDF (1008KB)
    Well-organized mesoporous titania particles and thin films were successfully synthesized by using tetrabutyl titanate as the inorganic precursor and triblock copolymer (Pluronic P123) as the template via evaporationinduced self-assembly process. The resulting materials were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM). Macro shape of mesoporous titania would greatly influence the mesostructure of materials, and the probable reasons were also discussed.
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    Microstructural characteristics of epitaxial BaSrNb0.3Ti0.7O3 film
    Li′na CHENG, Xiuliang MA
    J. Mater. Sci. Technol., 2007, 23 (04): 517-520. 
    Abstract   HTML   PDF (715KB)
    Microstructural characteristics in the BaSrNb0:3Ti0:7O3 thin film, grown on SrTiO3 substrate by computercontrolled laser molecular beam epitaxy, were characterized by means of transmission electron microscopy (TEM). It is found that the film is single-crystallized and epitaxially grown on the SrTiO3 substrate forming a flat and distinct interface. Anti-phase domains were identified, and the crystallographic features of mismatch dislocations at the interface between film and substrate were clarified. The high conductivity of the present film was discussed from the viewpoint of Nb dopant and the nitrogen atmosphere.
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    Characterizing the Exchange Interaction of Sm-Co/Co (and Fe65Co35) Magnetic Films
    Caiyin YOU, Zhidong ZHANG, Xiaokai SUN, C.J.Yang, Wei LIU, Xingguo ZHAO
    J. Mater. Sci. Technol., 2007, 23 (04): 521-524. 
    Abstract   HTML   PDF (255KB)
    Exchange interaction plays an important role on magnetic properties of nanocomposite magnets consisting of hard- and soft-magnetic phases. Here the exchange interaction in the Sm-Co/Co (and Fe65Co35) magnetic films was characterized by measuring static (mr(H)) and demagnetized (md(H)) remanence curves. According to conventional method: δm(H)=md(H)- [1- 2mr(H)], the exchange interaction was evaluated. The switching fields Hp′ and Hp, at which static (mr(H)) and demagnetized (md(H)) remanence show the fastest change, were identified. The relative ratio of switching fields H0p and Hp has a linear relationship with the maximum value δmmax of δm(H) curves, proposing an alternative way to characterize the exchange interaction.
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    Influence of Surface Nano-structured Treatment on Pack Boriding of H13 Steel
    Lingyun XU, Xiaochun WU, Hongbin WANG
    J. Mater. Sci. Technol., 2007, 23 (04): 525-528. 
    Abstract   HTML   PDF (778KB)
    In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment (SMAT), which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM (transmission electron microscopy), SEM (scanning electron microscopy), XRD (x-ray diffraction) and microhardness tests, the grain size, thermal stability of the nano-structured (NS) surface and the thickness, appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.
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    Performance of Polyaniline-coated Short Carbon Fibers in Electromagnetic Shielding Coating
    Dongxiu YU, Jiang CHENG, Zhuoru YANG
    J. Mater. Sci. Technol., 2007, 23 (04): 529-534. 
    Abstract   HTML   PDF (1130KB)
    Combined nitric acid oxidation method and polyaniline (PANI)-coated method were applied to modify the surface properties of short carbon fibers (SCF). The electrical and mechanical properties of acrylic coatings with 50 wt pct PANI-coated carbon fiber were investigated by using scanning electron microscope (SEM), UVVis spectrophotometer, four-probe method and the coaxial cable method. The results of the pH measurement and XPS (X-ray photoelectron spectroscopy) patterns showed that the oxygen functional groups, such as -OH and -COOH, were attached on the carbon fiber surfaces after oxidation treatment. The XPS analysis of PANI-coated oxidized SCF (PAOSCF) revealed that PANI may bond on the surface of oxidized SCF with chemical bonds. SEM images and surface roughness analyses showed that PANI-coated layer changed the surface morphology. Compared with SCF/acrylic coating, the surface resistivity of PAOSCF/acrylic coating decreased from17.1 to 5.3 Ω/sq and the shielding efficiency (SE) value increased from 1.54 to 23.3 dB.
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    Kinetic study of SiO2/S coating deposition by APCVD
    Jianxin ZHOU, Hong XU, Li ZHANG, Jinglei LIU, Xuegui QI, Bo PENG
    J. Mater. Sci. Technol., 2007, 23 (04): 535-540. 
    Abstract   HTML   PDF (523KB)
    To alleviate catalytic coking on the inner surface of radiant tube for ethylene production in petrochemical plants, SiO2/S coatings were deposited on HP40 alloy specimens using dimethyldisulfide (DMDS) and tetraethoxysilane (TEOS) by atmospheric pressure chemical vapor deposition (APCVD). A two-dimension mathematical model was made to predict the growth rate of SiO2/S coating and to study the effects of deposition parameters on the deposition rate. The results show that the predicted deposition rate is in good agreement with the experimental one. The deposition rate mainly depends on the concentrations of precursors in the total gas flow, concentrations of intermediates on the deposition surface, total gas flow rate and deposition temperature. The weight of SiO2/S coating linearly increases with the deposition time. When the gas flow rate is below 0.3 m/s, the rate-limiting step of SiO2/S coating deposition is the diffusions of intermediates. However, the surface reactions of intermediates will be the rate-limiting step after the gas flow rate is above 0.3 m/s. When the deposition temperature is below 780℃, the rate-limiting step of SiO2/S coating deposition mainly depends on the surface reactions of intermediates. When the deposition temperature is above 780℃, the rate-limiting step depends on the diffusions of intermediates. The deposition rate increases with increasing the concentrations of the intermediates. However, when the partial pressures of the intermediates reach 8 Pa, the deposition rate keeps constant.
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    The protective properties of high-temperature oxide film in 3.5% NaCl solution
    Huiping BAI, Fuhui WANG
    J. Mater. Sci. Technol., 2007, 23 (04): 541-546. 
    Abstract   HTML   PDF (1119KB)
    The electrochemical behaviors of high temperature oxide film formed on the sputtered microcrystalline coating of M38 alloy (mc-M38) were investigated by potentiodynamic and electrochemical impedance spectroscopy (EIS) techniques in 3.5% NaCl solution. Mott-Schottky analysis was used to study the semi-conductive properties of the surface oxide. The results of the capacitance measurements showed that the oxide films on both the coating and the cast alloy were p-type semiconducting characteristics. Both the carrier density (Na) and the flat band potential (Efb) were obviously frequency-dependent, and the optimal frequency range was from 1000 to 1500 Hz. The oxidized coating exhibited higher protectivity than the oxidized cast alloy due to the lower carrier density compared with that of the oxidized cast alloy. The EIS data of the long-term immersing tests suggested that the oxide film served as an inner-barrier layer against chloride ions. The penetration of the aggressive ions into the surface oxide resulted in the decreased polarization resistance as a function of the immersion time.
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    Influence of nano-TiO2 in thermal behavior of fire-resistant coating
    Zhenyu WANG, Enhou HAN, Fuchun LIU, Wei KE
    J. Mater. Sci. Technol., 2007, 23 (04): 547-550. 
    Abstract   HTML   PDF (391KB)
    The dispersion state of nano-TiO2 particles was studied by using transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FT-IR). Nanoparticles can be fully dispersed by specific hyper-dispersant. The improvement of nano-TiO2 in thermal behavior and flame retardation of acrylic resin and fire-resistant coating was investigated by limiting oxygen index (LOI), thermogravimetry (TG) and fire protection test. Combination of nano-TiO2 and intumescent flame-retardant system (IFR) can greatly improve the thermal stability and flame retardation of acrylic polymer, and nano-TiO2 is helpful for enhancing the anti-oxidation and fire protection properties of fire-resistant coating.
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    Effects of nano pigments on the corrosion resistance of alkyd coating
    Hongwei SHI, Fuchun LIU, Enhou HAN, Yinghua WEI
    J. Mater. Sci. Technol., 2007, 23 (04): 551-558. 
    Abstract   HTML   PDF (1232KB)
    Alkyd coatings embedded with nano-TiO2 and nano-ZnO pigments were prepared. The effects of nano pigments on anticorrosion performance of alkyd coatings were investigated using electrochemical impedance spectrum (EIS). For the sake of comparison, the corrosion protection of alkyd coatings with conventional TiO2 and ZnO was also studied. It was found that nano-TiO2 pigment improved the corrosion resistance as well as the hardness of alkyd coatings. The optimal amount of nano-TiO2 in a colored coating for corrosion resistance was 1%. The viscosities of alkyd coatings with nanometer TiO2 and ZnO and conventional TiO2 and ZnO pigments were measured and the relation between viscosity and anticorrosion performance was discussed.
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    W-Mo-Si/SiC Oxidation Protective Coating for Carbon/Carbon Composites
    Dangshe HOU, Kezhi LI, Hejun LI, Qiangang FU, Jian WEI, Yulei ZHANG
    J. Mater. Sci. Technol., 2007, 23 (04): 559-562. 
    Abstract   HTML   PDF (546KB)
    A W-Mo-Si/SiC double-layer oxidation protective coating for carbon/carbon (C/C) composites was prepared by a two-step pack cementation technique. XRD (X-ray diffraction) and SEM (scanning electron microscopy) results show that the coating obtained by the first step pack cementation was a thin inner buffer layer of SiC with some cracks and pores, and a new phase of (WxMo1-x)Si2 appeared after the second step pack cementation. Oxidation test shows that, after oxidation in air at 1773 K for 175 h and thermal cycling between 1773 K and room temperature for 18 times, the weight loss of the W-Mo-Si/SiC coated C/C composites was only 2.06%. The oxidation protective failure of the W-Mo-Si/SiC coating was attributed to the formation of some penetrable cracks in the coating.
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    Effect of nano Al pigment on the anti corrosive performance of waterborne epoxy coatings
    Lili XUE, Likun XU, Qingfen LI
    J. Mater. Sci. Technol., 2007, 23 (04): 563-567. 
    Abstract   HTML   PDF (793KB)
    This paper presents the results regarding the effect of nano aluminum powder pigment concentration on the protective properties of waterborne epoxy films in 3.5 wt pct NaCl solution. The anticorrosive performance of the coatings with 0.5, 1, and 3 wt pct pigments and none pigment were investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Raman spectroscopy techniques. The results show that adding appropriate amount of nano-aluminium powder pigment can enhance the barrier properties of the epoxy coating, which is attributed to the surface effect of nanoparticles and the compatibility of the pigment with the waterborne epoxy coatings.
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    Role of Y4Al2O9 in High Temperature Oxidation Resistance of NiCoCrAlY-ZrO2•Y2O3 Coatings
    Shuqin YANG, Xiaohua LAN, Ningkang HUANG
    J. Mater. Sci. Technol., 2007, 23 (04): 568-570. 
    Abstract   HTML   PDF (300KB)
    NiCoCrAlY-ZrO2•Y2O3 coatings were deposited on the substrates by using a technology of combining electron, atom and ion beams (three beams). Isothermal oxidation for these samples was performed at 1100℃ for 100–300 h. The results show that a thermally grown oxide (TGO) layer was formed between NiCoCrAlY layer and ZrO2•Y2O3 layers according to the cross-section morphologies of the samples after high temperature isothermal oxidation. The TGO contains α-Al2O3 and Y4Al2O9 etc. oxides. The intensity ratio of α-Al2O3/Y4Al2O9 was monotonously decreased with increasing oxidation time based on XRD (X-ray diffraction) analysis. The Y4Al2O9 phase plays the most important role in high temperature oxidation resistance at 1100℃. The related mechanism was also discussed.
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    Composition and Microstructure of Magnetron Sputtering Deposited Ti-containing Amorphous Carbon Films
    Jun DU, Ping ZHANG
    J. Mater. Sci. Technol., 2007, 23 (04): 571-573. 
    Abstract   HTML   PDF (301KB)
    Ti-containing carbon films were deposited by using magnetron sputtering deposition. The composition and microstructure of the carbon films were characterized in detail by combining the techniques of Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that carbon films contain Ti 18 at pct; after Ti incorporation, the films consist of titanium carbide; C1s peak appears at 283.4 eV and it could be divided into 283.29 and 284.55 eV, representing sp2 and sp3, respectively, and sp2 is superior to sp3. This Ti-containing film with dominating sp2 bonds is nanocomposites with nanocrystalline TiC clusters embedded in an amorphous carbon matrix, which could be proved by XRD and TEM.
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    Preparation of Porous GaN Buffer and Its Influence on the Residual Stress of GaN Epilayers Grown by Hydride Vapor Phase Epitaxy
    Xinhua LI, Kai QIU, Fei ZHONG, Zhijun YIN, Changjian JI, Yuqi WANG
    J. Mater. Sci. Technol., 2007, 23 (04): 574-576. 
    Abstract   HTML   PDF (513KB)
    The preparation of porous structure on the molecular beam epitaxy (MBE)-grown mixed-polarity GaN epilayers was reported by using the wet chemical etching method. The effect of this porous structure on the residual stress of subsequent-growth GaN epilayers was studied by Raman and photoluminescence (PL) spectrum. Substantial decrease in the biaxial stresse can be achieved by employing the porous buffers in the hydride vapour phase epitaxy (HVPE) epilayer growth.
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CN: 21-1315/TG
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