Co-reporter:Rongqian Yao, Changping Fu, Yu Mao, Shuaifeng Zhang, Zude Feng, Lifu Chen, Ying Zhang
Synthetic Metals 2015 Volume 207() pp:79-86
Publication Date(Web):September 2015
DOI:10.1016/j.synthmet.2015.06.012
•Aryl groups were introduced into Al-PCS by hydrosilylation polymerization.•Hyperbranched Al-PPCS with extended σ–π conjugation show blue light-emitting property.•Al-PPCS exhibits higher quantum yield, better ultraviolet resistance as compared to Al-PCS.•Excellent PL intensity is attributed to the delocalization of electrons from σ bond to π system.•Al-PPCS may have potential applications including organic electroluminescent (EL) devices.Optical properties of aryl-substituted polyphenylcarbosilane (PPCS) and aluminum-containing polyphenylcarbosilane (Al-PPCS) prepared by hydrosilylation polymerization were studied. Polycarbosilane (PCS), aluminum-containing polycarbosilane (Al-PCS) and styrene were employed as reactants to yield σ–π conjugated PPCS and Al-PPCS using chloroplatinic acid as catalyst, respectively. Phenyl was directly attached to the conjugated main chains with SiC bonds. Effects of divinyl benzene cross-linking, oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were examined. PL spectra show strong blue light emission and the intensity of PCS is enhanced by adding the aryl groups and Al atoms. The excellent luminescent properties are attributed to the delocalization of electrons from the σ bond to π system. The hyperbranched Al-PPCS with extended σ–π conjugation has an obvious red-shifts PL, high quantum yield, excellent oxidation resistance and good UV resistance performance. Thermal analysis reveals that Al-PPCS can keep structure stability below 400 °C under an inert gas atmosphere. The Al-PPCS may have potential applications including organic electroluminescent (EL) devices.The hyperbranched Al-PPCS samples with extended σ–π conjugation, which exhibit strong blue light emission, high quantum yield, good oxidation resistance, excellent thermal stability and UV resistance performance, were synthesized by hydrosilylation polymerization.
Co-reporter:Yu Liu, Chao Xu, ZuDe Feng
Applied Surface Science 2014 Volume 314() pp:392-399
Publication Date(Web):30 September 2014
DOI:10.1016/j.apsusc.2014.07.042
Highlights
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Fe-doped TiO2 films were prepared by liquid phase deposition method.
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Higher photoelectrochemical response was observed for the Fe-doped TiO2 film.
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The sustained anticorrosion behavior for SUS304 stainless steel was observed.
Co-reporter:Cai-Xia Lei, Han Zhou, Chen Wang, Zu-De Feng
Electrochimica Acta 2013 Volume 87() pp:245-249
Publication Date(Web):1 January 2013
DOI:10.1016/j.electacta.2012.09.089
In this paper, the ordered mesoporous TiO2 thin films that served as photoanodes for cathodic protection of SUS304 stainless steel (304SS) were prepared through the sol–gel and evaporation-induced self-assembly method. The as-prepared TiO2 thin films were calcined at 350 °C and 500 °C, and then characterized by scanning electron microscopy (SEM), the small-angle X-ray diffraction (SAXD) as well as the wide-angle X-ray powder diffraction (WAXD). Moreover, the photoelectrochemical properties of the mesoporous TiO2 thin films such as the open circuit potential (OCP), the photocurrent spectra as well as the Tafel polarization curves were also measured. The results showed that the more negative photopotential was observed for the mesoporous TiO2 films compared to the TiO2 films without mesoporous structures. Besides, the mesoporous TiO2 films calcined at 500 °C exhibited the more negative photopotential and larger photocurrent than that calcined at 350 °C. In conclusion, the mesoporous TiO2 films could provide the effective photogenerated cathodic protection for 304SS.Highlights► The ordered mesoporous TiO2 thin films were prepared on FTO substrates. ► The more effective photocathodic protection was observed for mesoporous TiO2 films. ► More negative photopotential was observed for 500 °C-calcined mesoporous TiO2 film. ► The larger photocurrent was observed for mesoporous TiO2 film calcined at 500 °C.
Co-reporter:Caixia Lei, Yu Liu, Han Zhou, Zude Feng, Ronggui Du
Corrosion Science 2013 Volume 68() pp:214-222
Publication Date(Web):March 2013
DOI:10.1016/j.corsci.2012.11.019
Sodium polyacrylate/TiO2 hybrid films that served as photoanodes for cathodic protection application were prepared by liquid phase deposition. Under white-light illumination, the open-circuit potential of the hybrid films coupled with SUS304 stainless steel could shift to a more negative value and offer an effective photogenerated cathodic protection for stainless steel. Moreover, the hybrid films also exhibited stronger photocurrents in both the ultraviolet-light and visible-light regions compared to that of control TiO2 films. In summary, the addition of sodium polyacrylate could greatly improve the photogenerated cathodic protection properties of the liquid-phase-deposited TiO2 films.Highlights► Sodium polyacrylate/TiO2 hybrid films were prepared by liquid-phase deposition. ► Stronger photoelectrochemical response was observed for the hybrid film. ► The photogenerated cathodic protection for SUS304 stainless steel was observed.
Co-reporter:Rongqian Yao, Zude Feng, Lifu Chen, Ying Zhang
Journal of the European Ceramic Society 2013 Volume 33(Issue 10) pp:1675-1683
Publication Date(Web):September 2013
DOI:10.1016/j.jeurceramsoc.2013.01.028
The effects of oxygen pick-up and Al atoms on the formation and microstructure of freestanding SiC(Al) films by melt spinning of polyaluminocarbosilane (PACS) precursor were studied. PACS green films were cross-linked for 1 h, 2 h, 3 h and 4 h, pre-pyrolyzed at 900 °C, respectively. They were continuously pyrolyzed at 1800 °C to convert initial PACS into SiC(Al) ceramic films. Results reveal that the strict control of oxygen content during the oxidation curing is essential to produce near-stoichiometric SiC(Al) films. The microstructure of the dense films is a mixture of β-SiC crystals, α-SiC nano-crystals, C clusters and a small amount of Al4O4C and Al4SiC4. Al atoms which play important roles as both sintering aids and grain growth inhibitor are well distributed in the films due to the presence of stable composition and structure. SiC(Al) films with excellent mechanical properties would be attractive candidate materials for MEMS in harsh environments.
Co-reporter:Rongqian Yao, Haoran Zhao, Zude Feng, Lifu Chen, Ying Zhang
Optical Materials 2013 Volume 35(Issue 12) pp:2638-2642
Publication Date(Web):October 2013
DOI:10.1016/j.optmat.2013.07.033
•Al, Dy, Eu and Er were introduced into PCS by one-pot synthesis.•The PL spectra show a broad blue emission band centered at around 400 nm.•The introduction of metal atoms can improve oxidation and UV radiation resistance.•PACS exhibits a PL red-shift, high emission intensity and excellent oxidation resistance.•PACS with extent σ-conjugation possesses good UV stability due to the AlOx groups.Optical properties of metal atom-doped polycarbosilane (PCS) which originated from σ-conjugation effect were studied. Al, Dy, Er and Eu were introduced into PCS by one-pot method to yield polyaluminocarbosilane (PACS), polydysprosiumcarbosilane (PDCS), polyerbiumcarbosilane (PErCS) and polyeuropiumcarbosilane (PECS), respectively. Effects of oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were investigated. PL spectra show strong blue light-emissions and the intensity of PCS is enhanced by adding metal atoms. PACS with extended σ-conjugation exhibits an obvious PL red-shift, high intensity, high quantum yield and excellent oxidation resistance as compared with those of others. As treated under UV lamp for 3 h in air, PACS retains good UV resistance performance, owing to the AlOx (x = 4, 5, or 6) groups which effectively extend the σ-conjugation. The obtained results are expected to have important applications in active sources for electroluminescence (EL) devices, especially suitable for blue emission.
Co-reporter:C.X. Lei, H. Zhou, Z.D. Feng, Y.F. Zhu, R.G. Du
Journal of Alloys and Compounds 2012 Volume 513() pp:552-558
Publication Date(Web):5 February 2012
DOI:10.1016/j.jallcom.2011.11.005
In this paper, the liquid phase deposition (LPD) technique was developed to prepare TiO2 thin films on ITO conducting glass applied to the photogenerated cathodic protection of SUS304 stainless steel (304SS). The results showed that a dense and crack-free anatase TiO2 film with a thickness of 800 nm was prepared from the LPD process at 80 °C for 3 h. Moreover, the TiO2 films exhibited a decrease in crystal preferential orientation and an increase in optical band gap energy when heat treated at 300 °C and 500 °C. In addition, the results of the photoelectrochemical measurements showed that the photopotential of the as-deposited TiO2 film was stabilized at about −200 mV, whereas those of the films subjected to heat treatment at 300 °C and 500 °C were stabilized at −400 mV and −460 mV, respectively. It was indicated that both the as-deposited and the heat treated LPD-derived TiO2 films exhibited sufficiently negative electrode potential under illumination, which could serve as the photoanodes for effective cathodic protection of 304SS.Highlights► The anatase TiO2 films were obtained on ITO substrate by liquid phase deposition. ► The TiO2 films were dense and crack-free with a thickness of about 800 nm. ► The TiO2 film exhibited an effective photogenerated cathodic protection for 304SS.
Co-reporter:Rongqian Yao, Zude Feng, Lifu Chen, Ying Zhang, Bingjie Zhang
Journal of the European Ceramic Society 2012 Volume 32(Issue 10) pp:2565-2571
Publication Date(Web):August 2012
DOI:10.1016/j.jeurceramsoc.2012.02.004
Freestanding SiC(Ti, B) films with high temperature resistance were fabricated from polymer precursor of polycarbosilane (PCS) blended with 0.26 wt% TiN and 0.74 wt% B powders. Results reveal that SiC(Ti, B) films with good mechanical properties are uniform and dense. After high temperature annealing at 1500 °C in argon, SiC(Ti, B) films exhibit better high temperature resistance as compared to SiC films without additives, which implies their potential applications in ultra-high temperatures (exceeding 1500 °C) microelectromechanical systems (MEMS). Sintering additives are effective in suppressing the growth of SiC crystals and decreasing the content of oxygen and free carbon, which is normally beneficial to enhance high temperature resistance of films.
Co-reporter:Han Zhou, Chen Wang, Zude Feng, Siwei Li, Binbin Xu
Surface and Coatings Technology 2012 207() pp: 34-41
Publication Date(Web):
DOI:10.1016/j.surfcoat.2012.04.067
Co-reporter:Rongquan Xie, Zude Feng, Siwei Li, and Binbin Xu
Crystal Growth & Design 2011 Volume 11(Issue 12) pp:5206-5214
Publication Date(Web):October 18, 2011
DOI:10.1021/cg101708y
Reconstructed layers containing ordered enamel-like structures of fluoride-substituted hydroxyapatite (FHAp) microcrystals were constructed on a human enamel surface using ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA) as the mediating agent under near-physiological conditions (pH 6.00, 37 °C, 1 atm). The effects of initial pH value, fluoride concentration, as well as reaction time on the formation of the FHAp microcrystals, including their microarchitectural structure, crystalline phase, chemical components, and hardness properties, were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Vickers microhardness measurements. The results of these in vitro experiments indicated that EDTA induced the assembly of hexagonal prismlike FHAp microcrystals along their c-axis direction, and the microcrystals further amalgamated with the extended reaction time. In addition, fluoride ions were found to play a critical role in the formation of hexagonal FHAp microcrystals. Interestingly, after reaction for 5 days, the Vickers microhardness of the new layer (347–370 VHN) was harder than that of natural tooth. On the basis of the experimental evidence, a mesoscale self-assembly mechanism was proposed to explain the growth of FHAp microcrystals.
Co-reporter:C.X. Lei, H. Zhou, Z.D. Feng, Y.F. Zhu, R.G. Du
Applied Surface Science 2011 Volume 257(Issue 16) pp:7330-7334
Publication Date(Web):1 June 2011
DOI:10.1016/j.apsusc.2011.03.122
Abstract
The low-temperature synthesis of anatase TiO2 films was an imperative requirement for their application to corrosion prevention of metals. In this paper, a liquid phase deposition (LPD) technique was developed to prepare TiO2 films on SUS304 stainless steel (304SS) at a relatively low temperature (80 °C). The as-prepared films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photon spectroscopy (XPS). It was observed that a dense and crack-free anatase TiO2 film with a thickness about 300 nm was obtained. The film contained some fluorine and nitrogen elements, and the amounts of these impurities were greatly decreased upon calcination. Under the white light illumination, the electrode potential of TiO2 coated 304SS rapidly shifted to a more negative direction. Moreover, the photopotential of TiO2/304SS electrode showed more negative values with increased film thickness. In conclusion, the photogenerated cathodic protection of 304SS was achieved by the low-temperature LPD-derived TiO2 film.
Co-reporter:Rongqian Yao, Zude Feng, Bingjie Zhang, Haoran Zhao, Yuxi Yu, Lifu Chen, Ying Zhang
Optical Materials 2011 Volume 33(Issue 4) pp:635-642
Publication Date(Web):February 2011
DOI:10.1016/j.optmat.2010.11.018
Novel continuous freestanding β-SiC/SiOxCy/Cfree nanocomposite films, namely, β-SiC nano-crystals in amorphous SiOxCy and free C cluster matrix material, were fabricated by melt spinning the polycarbosilane (PCS) precursor. Effects of oxidation curing time and sintering temperatures on the photoluminescence (PL) properties of nanocomposite films were investigated. The PL spectra show two strong blue emissions at 416 nm and 435 nm, which are unchanged neither with oxygen content nor with β-SiC crystallite size. The PL intensity of the films is enhanced by increasing curing time when sintered at 1200 °C. However, a reversed trend is identified after the films were sintered at 1300 °C. Spectroscopy and microscopy studies indicate that the radiative recombination of carriers is ascribed to the oxygen mono- and di-vacancy from SiOxCy at the surfaces of β-SiC nano-crystals, whereas the photogeneration of carriers occurs in the β-SiC nano-crystals cores. The obtained results are expected to have important applications in advanced optoelectronic devices.Research highlights► β-SiC/SiOxCy/Cfree nanocomposite films with different curing time were synthesized. ► The PL spectra show two blue emissions at 416 nm and 435 nm. ► PL intensity of the films sintered at 1200 °C is enhanced by increasing curing time. ► The g-factor value is attributed to unpaired electron trapped on oxygen vacancy site. ► Radiative recombination of carriers is ascribed to the oxygen mono- and di-vacancy.
Co-reporter:Yanjian Feng, Zude Feng, Siwei Li, Weihua Zhang, Xingan Luan, Yongsheng Liu, Laifei Cheng, Litong Zhang
Composites Part A: Applied Science and Manufacturing 2011 Volume 42(Issue 11) pp:1645-1650
Publication Date(Web):November 2011
DOI:10.1016/j.compositesa.2011.07.015
The fabric architecture and porosity of three-dimensional (3D) Cf/SiCm composites are characterized using commercial X-ray microcomputed tomography (microCT). The non-destructive observation exhibits an inhomogeneous structure of the carbon fiber performs with gradiently distributed porosity. The shape of fiber bundles and porosity are investigated with respect to the gas transport during chemical vapor infiltration (CVI). Difference in growth rate of deposition between outer surface and inner porosity are identified through reconstructing the porosity morphology, which coincides well with the “node-bond” theoretical model. Moreover, in the light of the porosity features, gas retention and viscous flow is revealed to play key roles in the formation of the inner structure of Cf/SiCm.
Co-reporter:Siwei Li, Zude Feng, Yongsheng Liu, Wenbin Yang, Weihua Zhang, Laifei Cheng, Litong Zhang
Corrosion Science 2010 Volume 52(Issue 9) pp:2837-2845
Publication Date(Web):September 2010
DOI:10.1016/j.corsci.2010.04.032
Two types of coating-modified 3D C/SiC, coated with CVD SiC/SiC/SiC (type I) and CVD SiC/amorphous-BC/SiC (type II), are subjected to a 14 vol.% H2O/8 vol.% O2/78 vol.% Ar atmosphere at 700, 1000 and 1200 °C up to 100 h. Microstructure and corrosion behaviour are investigated using a variety of characterization techniques. The type II shows a better oxidation resistance than type I during annealing at relatively low temperatures. Nevertheless, residual strength of the type I annealed above 1000 °C is enhanced by healing of many micron-sized defects. Interfacial bond strength of the composites is reasonably improved after annealing.
Co-reporter:R.Q. Yao, Z.D. Feng, B.J. Zhang, Y.X. Yu, L.F. Chen
Thin Solid Films 2010 Volume 518(Issue 24) pp:e165-e168
Publication Date(Web):1 October 2010
DOI:10.1016/j.tsf.2010.03.090
Continuous freestanding SiC(Al) films were fabricated by melt spinning the aluminum-containing polycarbosilane (A-PCS) precursor. The results showed that the films contained β-SiC crystals, α-SiC nano-crystals, C clusters and small amount of Al4O4C and Al4SiC4. The Al atoms in the films played important roles as both sintering aids and grain growth inhibitor. The PL spectrum showed a wide luminescence band from 320 nm to 440 nm, and the origin of PL centered at 385 nm might be related to the α-SiC nano-crystals using quantum size effects. The obtained films are expected to have important applications in MEMS for the environment of high temperature and optoelectronic devices.
Co-reporter:Siwei Li, Bin Zeng, Zude Feng, Yongsheng Liu, Wenbin Yang, laifei Cheng, Litong Zhang
Thin Solid Films 2010 Volume 519(Issue 1) pp:251-258
Publication Date(Web):29 October 2010
DOI:10.1016/j.tsf.2010.08.099
A two-layer boron carbide coating is deposited on a graphite substrate by chemical vapor deposition from a CH4/BCl3/H2 precursor mixture at a low temperature of 950 °C and a reduced pressure of 10 KPa. Coated substrates are annealed at 1600 °C, 1700 °C, 1800 °C, 1900 °C and 2000 °C in high purity argon for 2 h, respectively. Structural evolution of the coatings is explored by electron microscopy and spectroscopy. Results demonstrate that the as-deposited coating is composed of pyrolytic carbon and amorphous boron carbide. A composition gradient of B and C is induced in each deposition. After annealing, B4C crystallites precipitate out of the amorphous boron carbide and grow to several hundreds nanometers by receiving B and C from boron-doped pyrolytic carbon. Energy-dispersive spectroscopy proves that the crystallization is controlled by element diffusion activated by high temperature annealing, after that a larger concentration gradient of B and C is induced in the coating. Quantified Raman spectrum identifies a graphitization enhancement of pyrolytic carbon. Transmission electron microscopy exhibits an epitaxial growth of B4C at layer/layer interface of the annealed coatings. Mechanism concerning the structural evolution on the basis of the experimental results is proposed.
Co-reporter:Bin Zeng, Zude Feng, Siwei Li, Yongsheng Liu, Laifei Cheng, Litong Zhang
Ceramics International 2009 Volume 35(Issue 5) pp:1877-1882
Publication Date(Web):July 2009
DOI:10.1016/j.ceramint.2008.10.020
Abstract
Amorphous boron carbide (α-B4C) coatings were prepared on SiC substrates by chemical vapor deposition (CVD) from CH4/BCl3/H2/Ar mixtures at low temperature (900–1050 °C) and reduced pressure (10 kPa). The deposited coatings were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-Raman spectroscopy, energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results showed that two kinds of α-B4C coatings were deposited with different microstructures and phase compositions, and the effect of deposition temperature was significant. When deposited at 1000 °C and 1050 °C, the coatings exhibited a nodular morphology and had a relatively low content of boron. The free carbon was distributed in them inhomogeneously; in contrast, when deposited at 900 °C and 950 °C, the coatings presented a comparatively flat morphology and had a uniform internal structure and high boron content. They did not contain free carbon. At the last of this paper, the pertinent mechanisms resulting in differences in microstructure and phase composition were discussed.
Co-reporter:Ying-Min Liao, Zu-De Feng, Si-Wei Li
Thin Solid Films 2008 Volume 516(Issue 18) pp:6145-6150
Publication Date(Web):31 July 2008
DOI:10.1016/j.tsf.2007.11.022
Thin hydroxyapatite (HA) coatings, approximately from 1 μm to 10 μm in thickness, had been prepared on human enamel by electrodeposition with the current density of 0.5 mA/cm2 at 55 °C in 1 h. They exhibited an acicular morphology and had a tight contact with the substrate by scanning electron microscope and transmission electron microscope observation. The comparison was made between the enamel specimens with HA coatings in this study and the sound enamel. In this comparison, while the Vickers micro-hardness showed a similar value, the antibacterial activities improved significantly after the formation of HA coatings. In conclusion, electrodeposition was proved to be an effective method for preparing HA coatings on human enamel and could be considered as a promising method to restore the initial enamel lesions in clinic.
Co-reporter:Lizhi He, Zude Feng
Materials Letters 2007 Volume 61(Issue 18) pp:3923-3926
Publication Date(Web):July 2007
DOI:10.1016/j.matlet.2006.12.059
A coating of 60–80 μm in thickness had been prepared on the surface of enamel by rapid growth of highly crystalline dicalcium phosphate dihydrate crystal (DCPD). The DCPD coating was formed by conversion of calcium-deficient hydroxyapatite (CDHA) in strong acidic conditions. The characterization of the coating was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). No obvious gap between the coating and the enamel was detected by SEM observation, which suggested that the coating adhered well to the enamel. Analysis of FT-IR and XRD revealed that the coating was a good match to DCPD. Moreover, the mean Vicker hardness number (VHN) of the coating was approximately 125, as measured by a microhardness tester.
Co-reporter:Ting Wang, Zude Feng
Materials Letters 2005 Volume 59(Issue 18) pp:2277-2280
Publication Date(Web):August 2005
DOI:10.1016/j.matlet.2004.08.048
The purpose of this study was to explore the effect of mineral content on the dynamic mechanical properties and denaturation temperature of cortical bone. Cortical bone specimens from bovine femora were treated with 0.2 mol/l buffered solution of EDTA to reduce bone mineral content (BMC). The viscoelasticity, microstructure and denaturation temperature of bone was characterized by dynamic mechanical thermal analyzer (DMTA), FTIR spectroscopy and differential scanning calorimeter (DSC), respectively. FTIR analysis revealed that EDTA treatment had a negligible effect on the microstructure of the collagen fibers. DMTA analysis indicated that the storage modulus (E′) and loss modulus (E″) of bone specimens decreased upon decreasing BMC, whereas loss factor (tanδ) increased upon decreasing BMC. In addition, tanδ peak broadened and splitted into two peaks upon decreasing BMC. A lessening of transformation temperature with decreasing BMC was observed in DSC testing.
