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Progress of Novel TiO2 Photocatalytic Separation Membrane
XIAO Yu-Tang,XU Shuang-Shuang,DU Yong-Chao,Fu Q. Shiang
2011 Vol. 26 (4): 337346
Abstract(
4017 )
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TiO2 photocatalytic separation membrane is a kind of novel multifunctional composite membrane integrating photocatalysis and separation technologies for water treatment. TiO2 photocatalyst is loaded on the membrane surface or entrapped in the membrane to obtain the composite membrane that makes the TiO2 recovery problem solved. More significantly, the membrane is efficient to maintain high flux of membranes as the presence of TiO2 photocatalyst can reduce the membrane fouling problem which is a hindrance in the development of membrane process. Moreover, some synergistic effects can also be produced, and thus the efficiency of water treatment is enhanced greatly. A comprehensive review of TiO2 photocatalytic separation membrane is conducted with an insight into its types, preparation methods, properties, and its application. In view of the existing problems, the prospects for future development of TiO2 photocatalytic separation membrane are also proposed.
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Main-group Metal Ions doped Materials—A New Developing Direction of Laser Materials
XU Jun,SU Liang-Bi
2011 Vol. 26 (4): 347353
Abstract(
2956 )
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2131
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Main-group metal ions will be the third class of active ions, subquent to transition-metal and rare-earth ions. Main-group metal ions doped material is proved to be a new developing direction in the field of laser materials. The developments of main-group metal ions doped materials are summarized on the following topics: (1) the characteristics of the near-infrared ultrabroadband luminescence obtained in Bi-doped glasses, glass-fibers and single crystals, (2) the nature of the luminescence; and (3) laser performances of bismuth-doped fiber in various operation modes. The future research directions and applications of main-group metal ions doped laser materials are outlooked. The laser outputs in single crystal will be of milestone significance in its practical application.
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Effect of Cr3+ Dopant on Growth Habit and Optical Properties of Rapid Grown KDP Crystal
Ding Jian-Xu,LIU Bing,Wang Sheng-Lai,Mu Xiao-Ming,GU Qing-Tian,XU Xin-Guang,SUN Xun,SUN Yun,LIU Wen-Jie,LIU Guang-Xia,ZHU Sheng-Jun
2011 Vol. 26 (4): 354358
Abstract(
2805 )
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1602
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KDP crystals were grown by rapid growth method in the presence of different concentrations of Cr3+. Both the growth rate and dead zone influenced by Cr3+ was measured, and the Cr3+ element distribution, UV-Vis transmission spectra, distribution of scatter particles and laser induced damage threshold were characterized as well. The results reveal that Cr3+ is prone to be absorbed onto (100) face, which decreases the growth rate and extends the growth dead zone. Additionally, Cr3+ can induce growth macroscopic growth boundaries between prismatic and pyramidal growth sectors. The element analyses of Cr3+ suggest that Cr3+ is inclined to enter into prismatic sector, which leads to a decrease of transmittance in visible light and ultraviolet band, and brings three strong absorption peaks at 220 nm , 450 nm and 650 nm. The entrance of Cr3+ into crystal lattice can increase the number of scatter particles and decrease laser induced damage threshold. The laser damage threshold at fundamental frequency and the third harmonic generation decrease with the increase of Cr3+ concentration. The damage threshold of KDP prismatic sector is lower than that of pyramidal sector.
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Correlation between Te-rich Particles in CdZnTe Crystals and Corresponding PL Spectra
XU Ya-Dong,JIE Wan-Qi,WANG Tao,YU Peng-Fei,DU Yuan-Yuan,HE Yi-Hui
2011 Vol. 26 (4): 359363
Abstract(
3120 )
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Micron-scale Te-rich particles presented in CdZnTe crystals were directly observed using infrared transmission microscopy (IRTM). The generation of various Te-rich particles was discussed in conjunction with the growth conditions. In order to evaluate the impurities and defects behaviors , and to examine the crystalline quality, photoluminescence (PL) spectra were obtained at 10 K. The corresponding resistivity was evaluated simultaneously. The correlation between different shaped Te-rich particles in CdZnTe crystals and the corresponding PL spectra at 10 K was concluded compared with the characterized photo-peak in PL spectra. Well-defined sphere, hexagonal and triangular shaped incoherent Te-rich particles were generally presented in CdZnTe crystals grown from the charge with excess Te, which the ( D0, X) peak usually dominated in the PL spectra. Cross-shaped Te-rich particles were found in CdZnTe crystals grown under stoichiometric condition where the DAP peak dominated in the PL spectra. Star-shaped Te-rich particles were normally obtained in CdZnTe crystals under Cd-rich conditions where the FWHM of ( D0, X) peak was wide .
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Preparation and Growth Mechanism of Magnesium Borate Whiskers with High Aspect Ratio
DUAN Yu,LU Gui-Min,SONG Xing-Fu,SUN Shu-Ying,YU Jian-Guo
2011 Vol. 26 (4): 364368
Abstract(
2867 )
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1780
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Magnesium borate whiskers were prepared by molten salt method using MgCl2 · 6H2O and Na2B4O7 · 10H2O as raw materials, KCl and NaCl as fluxes. The lengths of the above whiskers varied from 200μm to 800 μm, and the maximum aspect ratio reached 250. The produced samples were characterized by X-ray diffraction (XRD), microscope and scanning electron microscope (SEM). The effects of n(Mg)/n(B), reaction temperature and reaction time on the whisker growth process and product quality were explored. It was found that the best operating parameters of n(Mg)/n(B), reaction temperature and reaction time were 3.0, 900 ℃ and 6h, respectively. According to the XRD analysis, Mg3B7O13Cl is the intermediate product, and the growth of Mg2B2O5 whiskers needs a boron- enriched environment. The whisker growth process agrees to the liquid-solid (L-S) mechanism.
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Electronic Structures and Photocatalysis Properties under Visible Irradiation and of F-doped TiO2 nanotube Nanotube arrays Arrays
CHEN Xiu-Qin,ZHANG Xing-Wang,LEI Le-Cheng
2011 Vol. 26 (4): 369374
Abstract(
2959 )
PDF(718KB)(
1774
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Nanosized TiO2 has excellent photocatalytic activity to degrade most of pollutants.The most important focus has been on the improvement of photocatalytic activity and the efficiency of utilizing solar energy. The researches has proved that nonmetal-doping can activate its visible-light activity.Self-organized F-doped TiO2 nanotube arrays were fabricated by a one-step electrochemical anodization process on a Ti sheet. The prepared samples were annealed in air and detected by SEM, XRD and XPS. SEM images The results show that the well ordered TiO2 nanotube arrays with the average tube diameter of 40 nm and the average tube length of 700 nm are successfully fabricated. The substitutional F atoms that occupied oxygen sites in the TiO 2 crystal lattice cause the appearance of active spices Ti3+ , as evidenced by from XPS. The sample annealed at 673 K exhibits the highest photocurrent intensities under visible light irradiation, w hich may be attributed to the Ti3+ .The removal efficiency reaches 37.2% of AO7 at 180 min and the photoelectrocatalytic synergetic factor is 1.33. DFT study calculations suggests s that the valence and conduction band of F-TiO2 consist of the electrons of O2 p and Ti 3 d, while the small amount of electrons of F 2 p do not change the band gap of TiO2.
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Synthesis and Characterization of Self-cleaning and Anti-reflective SiO2-TiO2 Nanometric Films
JIANG Bo,DUAN Xue-Chen,ZHOU Zhi-Chao,CHENG Ya-Juan,LIU Guo-Cong,LIU Yang-Lin
2011 Vol. 26 (4): 375380
Abstract(
3095 )
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1859
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A series of bi-layer TiO2/SiO2 (ST) and SiO2/TiO2 (TS) films were fabricated respectively by changing the coating sequences and rates, via a Sol-Gel dip-coating method. The morphology, light transmittance, photocatalytic activitiy and hydrophilicity of t he obtained products were characterized by FESEM, spectrophotometer, photo-degradation of methyl orange (MO), etc. The experimental results show that SiO2 layer can enhance the light transmittances of ST and TS films due to its lower refractive index. As to the self-cleaning function, the photocatalytic activity and hydrophilicity of TS bi-layer film are both weakened while increasing the dip-coating speed of the overlayer SiO2 film, owing to that more TiO2 is covered by SiO2. However, it is the opposite for ST bi-layer film. When the dip-coating speed of the overlayer TiO2 film reaches 6mm/min, the obtained film exhibits the best photocatalytic activity and hydrophilicity even without UV illumination, which favors greatly the self-cleaning function of the films.
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Preparation of Composite Oxide SiO2-TiO2-ZrO2 and A pplication in H ydrodesulfurization
DING Bao- H ong.,WANG Hai- Y an,ZHU Xue-Mei,JI Xiao-Fei, ZANG Shu- L iang.
2011 Vol. 26 (4): 381386
Abstract(
3052 )
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1805
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The SiO2-TiO2-ZrO2 composite oxide was prepared by Sol-Gel method. The effects ofn(Si)/n(Ti)/n(Zr)on the specific surface area , pore structure, acidity and crystal structure of the composite oxide were examined, and the thermal stability of samples was also characterized .The samples were tested by XRD, nitrogen absorption and infrared spectroscopy of absorbed pyridine. The feasibility of the composite oxide as the support of hydrofining catalyst was investigated by using dibenzothiophene as a model compound through hydrodesulfurization (HDS) reactions. The results indicated that mesoporous particles of the composite oxide were obtained .Compared with single and binary composite oxide, the specific surface area, the thermal stability and crystal stability ofSiO2-TiO2-ZrO2 composite oxide were obviously improved. When n(Si)/n(Ti)/n(Zr) is equal to 0.163/0.809/0.028 , the specific surface is 315.32 m2/g, pore volume is 0.33 cm3/g and the aperture is 12.0 nm. The dibenzothiophene sulfur removal rate for MoP/SiO2-TiO2-ZrO2 is 99.6% and desulfurization of diesel samples is above 96% . And desulfurization activity of catalyst is stability after 1200 h running.
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Electrical Properties of CuO-doped SrFe0.9Sn0.1O3- δ Thick Film NTC Thermistors
YUAN Chang-Lai,WU Xiu-Fang,LIU Xin-Yu,HUANG Jing-Yue,LI Bo,LIANG Mei-Fang,MO Chong-Gui
2011 Vol. 26 (4): 387392
Abstract(
2875 )
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1424
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CuO-doped SrFe0.9Sn0.1O3- δ (CSFS) thick-film negative temperature coefficient (NTC) thermistors ( 20mol%, 30mol%, 40mol%, 50mol% ) were prepared by the screen printing method. The microstructures and electrical prop erties of CSFS thick films were determined. With the increase of CuO content, the surface morphology of thick films becomes denser. The room-temperature resistance values gradually decreases to about 0.46 M Ω and the thermistor- constant values are basically constant at around 3300 K. After the addition of CuO, SrFe0.9Sn0.1O3- δ is decomposed into various SrFe1- xSn xO3- δ ( 0.1< x<1 ) phases. By two- RQ series equivalent circuit model, impedance characteristics of the thick film containing 40mol% CuO content are investigated over the measured temperature range of 25–250 ℃ . It is found that the total thick-film resistance is mainly attributed to the contribution of grain and grain boundary resistances, both of which show the typical NTC thermistor characteristics. Furthermore, the complete match of peak frequencies between the imaginary parts of impedance and electric modulus suggests that delocalized conduction is the main conduction mechanism in the thick-film NTC thermistors.
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Effect of Residual Stresses on Elastoplastic Properties of SOFC by Nanoindentation Approach
ZHAO Xiang,WANG Feng-Hui,WANG Xia,LIU Zhi-Qiang
2011 Vol. 26 (4): 393397
Abstract(
3354 )
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1582
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Due to the differences of Young’s modulus and the mismatch of thermal expansion coefficients in the half-cell structure (NiO-YSZ/YSZ), the residual stress, which has effects on the fuel cell’s performance, is aroused during sintering . Taking the residual stress into consideration, a modified reverse analysis model was proposed to calculate the mechanical property of electrolyte thin film in SOFC. Nanoindentation tests were carried out at the points with difference distances from the interface of bilayer, the load-displacement curve was presented. The results of material’s mechanical property from experimental showed that the farther the indentation points was from the interface, the greater was the hardness of film. When the temperature related residual stress field was taken as the initial stress field to simulate the load-displacement curve under nanoindentation, it was found that the load-displacement curve was in agreement with the experiment curve if the residual stress was considered, and also the indentation morphology was much deeper and bigger under the residual stress condition.
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Pyrolysis Preparation of Nickel Oxide and Its Electrochemical Capacitance
ZHANG Luo-Jiang,GAO Bo,ZHANG Xiao-Gang
2011 Vol. 26 (4): 398402
Abstract(
3045 )
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1504
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NiO was successfully synthesized by complexing of iminodiacetic acid (IDA) and Ni2+, and then calcined in air at 300℃. XRD, FT-IR, SEM and TG tests were applied to investigate the structure, morphology and the formation mechanism of the as-synthesized NiO. The results showed that the obtained complex firstly turned into elementary substance under pyrolysis and then changed to oxide consisting of nanoparticles and nano-flakes with increase of calcination temperature. Electrochemical properties of the NiO were elucidated by cyclic voltammograms, galvanostatic charge-discharge in 6 mol/L KOH electrolyte. Electrochemical data analysis demonstrated that the as-prepared NiO electrode had a good capacitive behavior and cyclability due to its unique structure and possessed a specific capacitance of 355.8 F/g at a current density of 1 A/g.
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Preparation and Characterization of Co-Se Thin Films by Electrodeposition
WANG Bo,LIU Fang-Yang,LI Ji e,LAI Yan-Qing,ZHANG Zhi-An,LIU Ye-Xiang
2011 Vol. 26 (4): 403410
Abstract(
3354 )
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2853
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Cobalt selenide thin films were prepared onto tin oxide-coated glass substrates by electrodeposition method. The electrochemical mechanisms for this thin film formation were investigated by cyclic voltammetry (CV), and the results show that cobalt selenide compound phases are formed via either surface induced reduction by predeposited selenium or directly reaction with H2Se from six electron reduction of H2SeO3. It is also found that films’ stoichiometry and morphology are significantly influenced by deposition potential, deposition temperature and pH value. Se-rich CoSe thin films with hexagonal crystal structure and compact morphology can be obtained at deposition potential of - 0.5V ( vs SCE), deposition temperature of 50 ℃ and pH value of 2.0. The electrodeposited CoSe film shows an optical absorption coefficient of higher than 1 × 105 cm - 1 , and an optical band gap of (1.53±0.01) eV which is close to the theoretical optimization value of the light absorption layer materials in single-junction solar cell.
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Influence of the Substitution of Cr for Mn on Magnetic Properties of La0.4Ca0.6MnO3
WANG Gui-Ying,,YANG Gang,,GUO Huan-Yin,,MAO Qiang,,YE Wu-Mei,,PENG Zhen-Sheng,
2011 Vol. 26 (4): 411416
Abstract(
2644 )
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1597
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Polycrystalline samples of La0.4Cao.6Mn1 - x Cr xO3 ( x =0.00,0.02,0.04,0.06,0.08,0.10,0.15 ) were prepared by t he solid state reaction method. The influence of Cr3+ substitution for Mn3+ on the magnetic property and charge ordering phase of La0.4Ca0.6MnO3 was studied through the measurements of X-ray diffraction (XRD), magnetization- temperature ( M-T) curves and electron spin resonance (ESR) spectra. The experimental results indicate that the sample of La0.4Ca0.6MnO3 has very complicated magnetic structure. The charge ordering phase of the sample exhibits at 258K, and strong correlated CO-AFM phase shows from 175K to 50K. The spin glass state of the sample appears when the temperature decreases to about 41K. When the Cr substitution amount x is more than 0.06, the charge ordering phase of the sample is destroyed. When x is larger than 0.10, spin-glass state is melt. In addition, experimental resu lts are explained preliminarily as follows: because Cr3+ and Mn4+ have the same electronic structure, Cr3+ substitution for Mn3+ destroys the spin order of CE-type antiferromagnetism, and thus leads to the destruction of charge ordering. It is verified experimentally that the strong coupling between charge ordering and spin ordering exists in the charge order system of CE-type anti-ferromagnetism, and Cr3+ substitution for Mn3+ destroys formation conditions of spin-glass state that small ferromagnetic component exists at the background of antiferromagnetism.
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Preparation and Reaction Mechanism of LaB6 Powder by Solid-state Reaction at Atmospheric Pressure
XU Xiu-Hua,XIAO Han-Ning,GUO Wen-Ming,GAO Peng-Zhao,PENG Su-Hua
2011 Vol. 26 (4): 417421
Abstract(
2748 )
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1552
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The lanthanum hexaboride (LaB6) powders were synthesized under atmospheric pressure using B4C and La2O3 powder as the precursors. The thermodynamic conditions for preparing LaB6 at atmospheric pressure were calculated. The effects of temperature and holding time on the phase composition, morphology, particle size and distribution of LaB6 powders were characterized by X-ray diffraction (XRD), scanning electron microscope(SEM) and laser particle size anslyzer. The reaction mechanism was investigated. The results show that LaB6 powders obtained under atmospheric pressure at 1650 ℃ for 2h have cube structure with 99.22% purity after washed by hydrochloric acid. When the particle size of La2O3 powder is much smaller than that of B4C particle, the synthesis of LaB6 starts on the surface of B4C particle, then the residual La2O3 and LaBO3 will diffuse through LaB6 shell onto B4C core until the reaction is completely with the temperature rising and holding time prolonged. The initial shape and particle size of LaB6 powders are depending on that of B4C particles.
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High Flexural Strength Porous Silicon Nitride Prepared via Nitridation of Silicon Powder
YAO Dong-Xu,ZENG Yu-Ping
2011 Vol. 26 (4): 422426
Abstract(
3514 )
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High flexural strength porous silicon nitride ceramics were prepared via nitridation of silicon powder, using silicon powder and Y2O3 as start powder with different forming pressures. The effects of Y2O3 contents and heating programs on nitridation rate were studied. The high nitridation rate was obtained when 9% Y2O3 was added, which was contributed to Y2O3 reacted with SiO2 at low temperature (1200 ℃ ) to transform to Y5Si3O12N and the elimination of SiO2 on Si surface. Under different sintering conditions, the porous Si3N4 ceramics with porosity of 30% - 50% and the flexural strength of 160 - 50MPa were obtained, respectively. After post-sintering at 175 0 ℃ in 0.5MPa N2 atmosphere, α-Si3N4 was fully transformed into β-Si3N4 by the solution-precipitation process, the rod-like β-Si3N4 promoted the flexural strength of the porous Si3N4 ceramics, and the porous Si3N4 ceramics with a porosity of 46% and a flexural strength of 140MPa was obtained .
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Thermochemical Erosion of Hafnium Carbide Modified Carbon/Carbon Composite Throat in a Small Solid Rocket Motor
SHEN Xue-Tao,LI Ke-Zhi,LI He-Jun,FENG Tao,ZHANG Lei-Lei,WANG Bin
2011 Vol. 26 (4): 427432
Abstract(
3227 )
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1519
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Thermochemical erosion of hafnium carbide (HfC) modified carbon/carbon (C/C) composite throat was investigated using a hot-fire testing system in a small solid rocket motor. Chemical composition of the equilibrium combustion products was calculated by NASA-CEA program based on the principle of free energy minimum. The reaction products between the oxidizing species and HfC in the C/C composites were also calculated by FactSage. The results show that H2O, CO2, and OH are the main oxidizing species to consume carbon and HfC and generate thermochemical erosion to the throat materials. The interface of the fibers and matrix is preferentially ablated, and then erosion extends to the fibers and matrix. The formation of cone-shaped fibers and shell-shaped matrix is attributed to the thermochemical erosion of the flame.
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Formation Mechanism of Zircon Phase in ZrB2-SiC Ceramic Composites during Oxidation
GAO Dong,ZHANG Yue,XU Chun-Lai,SONG Yang,SHI Xiao-Bin
2011 Vol. 26 (4): 433437
Abstract(
3106 )
PDF(879KB)(
1995
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Oxidation of ZrB2-20vol% ceramic composites in air was investigated, and the effects of oxygen partial pressure, oxidation temperature and holding time on the formation of zircon phase ZrSiO4 were analyzed. The formation mechanism of zircon during oxidation in air of zirconium diboride-silicon carbide ceramic composites is proposed. Active oxidation of SiC is the major reason to explain the appearance of zircon according to thermal dynamic calculation results. The experimental results indicate that the formation of zircon can be divided into two steps: (I) Nucleation, which is related to the active oxidation of SiC; (II) Crystal growth, which is fulfilled by the reactions between silicate glass and zirconia crystalline at the interface of the zircon nuclei / melt. Zircon particles with mean size of 100 μm can be observed after oxidation in air for 90 min.
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Synthesis of Nano-sized Tabular Lindgrenite (Cu3(MoO4)2(OH)2) by Aqueous Precipitation
JIANG Wen-Jun,FANG Jin,FAN Zhong-Yong,YANG Xu-Jie,LU Qi-Ting,HOU Yi-Bin
2011 Vol. 26 (4): 438442
Abstract(
3379 )
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Lindgrenite (Cu3(MoO4)2(OH)2) nanocrystals were synthesized by simple aqueous precipitation at 60 ℃ , using Cu(NO3)2·6H2O, Na2MoO4·2H2O and NaOH as the starting materials. X-ray Diffraction ( XRD) patterns confirm the formation of pure Cu3(MoO4)2(OH)2 nano crystals, which belongs to the monoclin ic phase with calculated crystal parameters a = 0.53863 nm, b = 1.40006 nm, c = 0.56003 nm, β = 98.47°, α = γ = 90° . The e nergy d ispersive X-ray spectrum (ED X ) analysis gives an approximate atomic ratio of 3 : 2 : 10 for Cu : Mo: O. The scanning electron microscope(SEM) and transmission electron microscop e (TEM) studies show that the as-prepared nanoparticles are well crystallized with tabular structure and t he interplanar distances of d 021 and dī 2 1 measured are 0. 435 nm and 0.358 nm , coinciding with the theoretical value. It can also be seen that the Cu3(MoO4)2(OH)2 has a good thermal stability and starts decomposing at 320 ℃ through thermogravimetric- differential thermal analysis (TG-DTA) . Moreover, the strong fluorescent property of the Cu3(MoO4)2(OH)2 is measured, with green emission peak at ca. 530 nm upon excitation at ca. 369 nm. Finally, a possible m e ch a nism for the formation of Cu3(MoO4)2(OH)2 nanocrysta ls is proposed.
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Preparation and Effects of Mo-doping on the Electrochemical Properties of Spinel Li4Ti5O12 as Anode Material for Lithium Ion Battery
ZHANG Xin- Long,HU Guo- Rong,PENG Zhong- Dong
2011 Vol. 26 (4): 443448
Abstract(
3652 )
PDF(516KB)(
2126
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Mo -doped Li4Ti5O 12 in the form of Li4Ti4.95Mo0.05O12 was synthesized via solid state reaction. X-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to characterize the structure and morphology of Li4Ti4.95Mo0.05O12. Mo-doping does not change the phase composition and particle morphology, while improves remarkably its cycling stability at high charge/discharge rate. Li4Ti4.95Mo0.05O12 exhibits an excellent rate capability with a reversible capacity of 117.03 mAh/g at 10 C and even 94.24 mAh/g at 30 C . The substitution of Mo for Ti site can enhance the electronic conductivity of Li4Ti5O12 via the generation of mixing Ti4+/Ti3+, which indicates that Li4Ti4.95Mo0.05O12 is a promising as a high rate anode for the lithium-ion batteries .
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