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1.
As a continuation of our work to develop catalysts with high activity for catalytic air wet oxidation process under mild conditions, degradation of wastewater containing 0.3 g/L Safranin-T (ST) by air oxidation over ZnO/MoO3 nanotube catalyst was studied. It was found the decolorization efficiency and the chemical oxygen demand (COD) removal of ST reached above 98% and 95%, respectively, within 18 min at room temperature and atmospheric pressure. And the organic pollutants were totally mineralized to simple inorganic species such as HCO3−, Cl− and NO3−, while the total organic carbon (TOC) decreased 99.3%. The structure and morphology of the catalyst after ten cycling runs showed that the catalyst was stable under such operating condition and the leaching test showed negligible leaching effect. This ZnO/MoO3 nanotube is proved to be an active and stable heterogeneous catalyst in CWAO of ST under extremely mild conditions. 相似文献
2.
SiO2@Gd2MoO6:Eu3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Gd2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrate that the Gd2MoO6:Eu3+ layers on the SiO2 spheres begin to crystallize after annealing at 600 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 600 nm), are not agglomerated, and have a smooth surface. The thickness of the Gd2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). The Eu3+ shows a strong PL luminescence (dominated by 5D0-7F2 red emission at 613 nm) under the excitation of 307 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles. 相似文献
3.
Novel egg-shell structured monometallic Pd/SiO2 and bimetallic Ca-Pd/SiO2 catalysts were prepared by an impregnation method using porous hollow silica (PHS) as the support and PdCl2 and Ca(NO3)2·4H2O as the precursors. It was found from transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) that Pd was loaded on PHS with a particle size of 5-12 nm in Pd/SiO2 samples and the Pd particle size in Ca-Pd/SiO2 was smaller than that in Pd/SiO2 since Ca could prevent Pd particles from aggregating. X-ray photoelectron spectroscopy (XPS) analyses exhibited that Pd 3d5/2 binding energies of Pd/SiO2 and Ca-Pd/SiO2 were 0.2 and 0.9 eV lower than that of bulk Pd, respectively, as a result of the shift of the electron cloud from Pd to oxygen in Pd/SiO2 and to both oxygen and Ca in Ca-Pd/SiO2. The activity of Ca-Pd/SiO2 egg-shell catalyst for CO hydrogenation and the selectivity to methanol, with a value of 36.50 mmolCO mol−1Pd s−1 and 100%, respectively, were much higher than those of the catalysts prepared with traditional silica gel as the support, owing to the porous core-shell structure of the PHS support. 相似文献
4.
J.C. Fan 《Applied Surface Science》2008,254(20):6358-6361
p-Type ZnO:As films with a hole concentration of 1016-1017 cm−3 and a mobility of 1.32-6.08 cm2/V s have been deposited on SiO2/Si substrates by magnetron sputtering. XRD, SEM, Hall measurements are used to investigate the structural and electrical properties of the films. A p-n homojunction comprising an undoped ZnO layer and a ZnO:As layer exhibits a typical rectifying behavior. Our study demonstrates a simple method to fabricate reproducible p-type ZnO film on the SiO2/Si substrate for the development of ZnO-based optoelectronic devices on Si-based substrates. 相似文献
5.
The ternary MoO3-La2O3-B2O3 glasses containing a large amount of MoO3 (10-50 mol%) are prepared, and their structure and crystallization behavior are examined from the Raman scattering spectrum measurements and X-ray diffraction analyses. It is found that the glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing MoO3 content. It is suggested that the main coordination state of Mo6+ ions in the glasses is isolated (MoO4)2− tetrahedral units giving strong Raman bands at 830-860 and 930 cm−1. It is found that the crystalline phases in the crystallized glasses are mainly LaMoBO6 and LaB3O6, and the main crystallization mechanism in MoO3-La2O3-B2O3 glasses is surface crystallization. LaMoBO6 crystals are found to give strong Raman bands at 810-830 and ∼910 cm−1. 相似文献
6.
Di Yin Changzhen Li Junfeng Wang Rui Xiong Jing Shi Congzhi Bi XiangGang Qiu 《Journal of Physics and Chemistry of Solids》2009,70(1):249-3786
Polarized infrared reflectivity measurements between 300 and 10 K have been carried out on charge density waves (CDW) conductor blue bronze Tl0.3MoO3. Three important features are observed: (i) A bump at 1155 cm−1 in the reflectivity spectra of Tl0.3MoO3 at 300 K is a precursor of the Peierls gap due to optical excitations across a pseudogap, and this kind of Peierls-like gap opens gradually with decreasing temperature from 180 to 160 K. (ii) The three sharp modes as “triplet” of infrared reflectivity between 800 and 1000 cm−1 of Tl0.3MoO3 along [1 0 2] axis show red shift compared to K0.3MoO3 and Rb0.3MoO3, which is assigned to the increase of the distance of Mo-O bond with the substitution of thallium ions. (iii) Two peaks at about 514 and 644 cm−1 in the far-infrared reflectivity spectra of Tl0.3MoO3 along [1 0 2] direction are suggested to be the electronic transitions from the valence band to the midgap state and from occupied midgap state to the conduction band, respectively. 相似文献
7.
We report the formation of β′-Gd2(MoO4)3 (GMO) crystal on the surface of the 21.25Gd2O3-63.75MoO3-15B2O3 glass, induced by 250 kHz, 800 nm femtosecond laser irradiation. The morphology of the modified region in the glass was clearly examined by scanning electron microscopy (SEM). By micro-Raman spectra, the laser-induced crystals were confirmed to be GMO phases and it is found that these crystals have a strong dependence on the number and power of the femtosecond laser pulses. When the irradiation laser power was 900 mW, not only the Raman peaks of GMO crystals but also some new peaks at 214 cm−1, 240 cm−1, 466 cm−1, 664 cm−1 and 994 cm−1which belong to the MoO3 crystals were observed. The possible mechanisms are proposed to explain these phenomena. 相似文献
8.
Bifunctional magnetic-optical Fe3O4/ZnO nanocomposites with different molar ratio were successfully synthesized by a facile two-step strategy. Compared with the other methods, it was found to be mild, inexpensive, green, convenient and efficient. Fe3O4 nanocrystal was used as seed for the deposit and growth of ZnO nanoparticle. A series of the characterizations manifested that the combination of Fe3O4 with ZnO nanoparticles was successful. Photocatalytic activity studies confirmed that as-prepared nanocomposites had excellent photodegradating behavior to Methyl Orange (MO) compared to the pure ZnO nanoparticles. The results showed that the degradation percentage of MO was about 93.6% for 1 h when the amount of catalyst was 0.51 g L−1 and initial concentration of MO was 6 × 10−5 mol L−1 in the pH 7 solution. Moreover, the kinetics of photocatalytic degradation reaction could be expressed by the first-order reaction kinetic model. Furthermore, the Fe3O4/ZnO nanocomposites could be also served as convenient recyclable photocatalysts because of their magnetic properties. 相似文献
9.
Hong-Wei Li 《Optics Communications》2009,282(8):1579-1093
Erbium-doped MoO3−Bi2O3−TeO2 (MBT) glasses suitable for broadband optical amplifier applications have been fabricated and characterized optically. The maximum phonon band of undoped glasses is at 915 cm−1, and the emission from the Er3+: 4I13/2 → 4I15/2 transition locates around 1.53 μm with a full width at half maximum (FWHM) of ∼80 nm. The lifetime and quantum efficiency of the 4I13/2 level are 2.13 ms and ∼90%, respectively. Under the same measurement condition, the upconversion emission intensities at 550 nm in Er3+-doped MBT glasses is about 30 times weaker than that in Er3+-doped Na2O−ZnO−TeO2 (NZT) glasses. 相似文献
10.
Zeng LuTang Wanjun 《Physica B: Condensed Matter》2011,406(14):2901-2903
A series of NaY1−yEuy(WO4)2−x(MoO4)x (x=0−2 and y=0.06−0.15) phosphors have been prepared by a combustion route. X-ray powder diffraction, photoluminescence excitation and emission spectra were used to characterize the resulting samples. The excitation spectra of these phosphors show the strongest absorption at about 396 nm, which matches well with the commercially available n-UV-emitting GaN-based LED chip. Their emission spectra show an intense red emission at 616 nm due to the 5D0→7F2 electric dipole transition of Eu3+. As the Mo content increases, the intensity of the 5D0→7F2 emission of Eu3+ activated at wavelength of 396 nm increases and reaches a maximum when the relative ratio of Mo/W is 2:3. The intense red-emission of the tungstomolybdate phosphors at near-UV excitation suggests that the material is a potential candidate for white light emitting diode (WLEDs). 相似文献
11.
Sandwich-structure Al2O3/HfO2/Al2O3 gate dielectric films were grown on ultra-thin silicon-on-insulator (SOI) substrates by vacuum electron beam evaporation (EB-PVD) method. AFM and TEM observations showed that the films remained amorphous even after post-annealing treatment at 950 °C with smooth surface and clean silicon interface. EDX- and XPS-analysis results revealed no silicate or silicide at the silicon interface. The equivalent oxide thickness was 3 nm and the dielectric constant was around 7.2, as determined by electrical measurements. A fixed charge density of 3 × 1010 cm−2 and a leakage current of 5 × 10−7A/cm2 at 2 V gate bias were achieved for Au/gate stack /Si/SiO2/Si/Au MIS capacitors. Post-annealing treatment was found to effectively reduce trap density, but increase in annealing temperature did not made any significant difference in the electrical performance. 相似文献
12.
The Ce6−xYxMoO15−δ solid solution with fluorite-related structure have been characterized by differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), IR, Raman, scanning electric microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. The electric conductivity of samples is investigated by Ac impedance spectroscopy. An essentially pure oxide-ion conductivity of the oxygen-deficiency was observed in pure argon, oxygen and air. The highest oxygen-ion conductivity was found in Ce5.5Y0.5MoO15−δ ranging from 5.9×10−5 (S cm−1) at 300 °C to 1.3×10−2 (S cm−1) at 650 °C, respectively. The oxide-ion conductivities remained stable over 80 h-long test at 800 °C. These properties suggested that significant oxide-ionic conductivity exists in these materials at moderately elevated temperatures. 相似文献
13.
The CaCu3Ti4O12/SiO2/CaCu3Ti4O12 (CCTO/SiO2/CCTO) multilayered films were prepared on Pt/Ti/SiO2/Si substrates by pulsed laser deposition method. It has been demonstrated that the dielectric loss and the leakage current density were significantly reduced with the increase of the SiO2 layer thickness, accompanied with a decrease of the dielectric constant. The CCTO film with a 20 nm SiO2 layer showed a dielectric loss of 0.065 at 100 kHz and the leakage current density of 6×10−7 A/cm2 at 100 kV/cm, which were much lower than those of the single layer CCTO films. The improvement of the electric properties is ascribed to two reasons: one is the improved crystallinity; the other is the reduced free carriers in the multilayered films. 相似文献
14.
Lei Zhou 《Applied Surface Science》2008,254(6):1847-1851
Y2−xTbxSiO5 and Y2−xEuxSiO5 nanophosphors with seven different kinds of silicate sources were synthesized by sol-gel method. The structures have been investigated to be composed of nanometer-size grains of 30-60 nm through X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to compare the different morphology of patterns from seven different silicon sources. The photoluminescence of Y2−xTbxSiO5 was investigated as a function of silicate sources and the results revealed that these nanometer materials showed the characteristic emission 5D4 → 7FJ (J = 6, 5, 4, 3) of Tb ions. The characteristic emission 5D0 → 7FJ (J = 1, 2, 4) of Eu ions was also found in the materials of Y2−xEuxSiO5. 相似文献
15.
P.S. Mbule G.H. Mhlongo Shreyas S. Pitale H.C. Swart O.M. Ntwaeaborwa 《Physica B: Condensed Matter》2012,407(10):1607-1610
In this study, red cathodoluminescence (CL) (λemission=614 nm) was observed from Pr3+ ions in a glassy (amorphous) SiO2 host. This emission was enhanced considerably when ZnO quantum dots (QDs) were incorporated in the SiO2:Pr3+ suggesting that the ZnO QDs transferred excitation energy to Pr3+ ions. That is, ZnO QDs acted to sensitize the Pr3+ emission. The sol–gel method was used to prepare ZnO–SiO2:Pr3+ phosphors with different molar ratios of Zn to Si. The effects of the ZnO QDs concentration and the possible mechanisms of energy transfer from ZnO to Pr3+ are discussed. In addition, the electronic states and the chemical composition of the ZnO–SiO2:Pr3+ phosphors were analyzed using X-ray photoelectron spectroscopy (XPS). 相似文献
16.
Saqlain A. Shah M.U. Hashmi A. Shamim 《Journal of magnetism and magnetic materials》2010,322(3):375-5218
Glass ceramics of the composition xZnO·25Fe2O3·(40−x)SiO2·25CaO·7P2O5·3Na2O were prepared by the melt-quench method using oxy-acetylene flame. Glass-powder compacts were sintered at 1100 °C for 3 h and then rapidly cooled at −10 °C. X-ray diffraction (XRD) revealed 3 prominent crystalline phases: ZnFe2O4, CaSiO3 and Ca10(PO4)6(OH)2. Vibrating sample magnetometer (VSM) data at 10 KOe and 500 Oe showed that saturation magnetization, coercivity and hence hysteresis area increased with the increase in ZnO content. Nano-sized ZnFe2O4 crystallites were of pseudo-single domain structure and thus coercivity increased with the increase in crystallite size. ZnFe2O4 exhibited ferrimagnetism due to the random distribution of Zn2+ and Fe3+ cations at tetrahedral A sites and octahedral B sites. This inversion/random distribution of cations was probably due to the surface effects of nano-ZnFe2O4 and rapid cooling of the material from 1100 °C (thus preserving the high temperature state of the random distribution of cations). Calorimetric measurements were carried out using magnetic induction furnace at 500 Oe magnetic field and 400 KHz frequency. The data showed that maximum specific power loss and temperature increase after 2 min were 26 W/g and 37 °C, respectively for the sample containing 10% ZnO. The samples were immersed in simulated body fluid (SBF) for 3 weeks. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDX) and XRD results confirmed the growth of precipitated hydroxyapatite phase after immersion in SBF, suggesting that the ferrimagnetic glass ceramics were bioactive and could bond to the living tissues in physiological environment. 相似文献
17.
Molybdenum oxide (MoO3) films were deposited on glass and (1 1 1) silicon substrates by sputtering of metallic molybdenum target in an oxygen partial pressure of 2 × 10−4 mbar and different substrate temperatures in the range 303-623 K using dc magnetron sputtering technique. X-ray photoelectron spectrum of the films formed at 303 K showed asymmetric Mo 3d5/2 and Mo 3d3/2 peaks due to the presence of mixed oxidation states of Mo5+ and Mo6+ while those deposited at substrate temperatures ≥473 K were in Mo6+ oxidation state of MoO3. The films formed at substrate temperatures ≥473 K were polycrystalline in nature with orthorhombic α-phase MoO3. Fourier transform infrared spectra of the films showed an absorption band at 1000 cm−1 correspond to the stretching vibration of MoO, the characteristic of the α-MoO3 phase. The electrical resistivity increased from 3.3 × 103 to 8.3 × 104 Ω cm with the increase of substrate temperature from 303 to 473 K respectively due to improvement in the crystallinity of the films. Optical band gap of the films increased from 3.03 to 3.22 eV with the increase of substrate temperature from 303 to 523 K. 相似文献
18.
Mn2+-doped Zn2SiO4 phosphors had been prepared by hydrothermal method in stainless-steel autoclaves. Effects of synthesized methods, reaction temperature, ambience of heat treatment on the structure and the luminescence properties of this silicate were studied with X-ray diffraction apparatus (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) and fluorescence spectrum. Results show that Zn2SiO4 nanocrystalline can be obtained by hydrothermal method at relatively low temperatures. The absorption pattern shows an absorption edge at about 380 nm originated from ZnO crystals and two absorption bands at about 215 and 260 nm. Mn2+-doped Zn2SiO4 has a luminescence band with the wavelength at about 522 nm under 255 nm excitation, and the luminescent intensity increases after being heat treated. 相似文献
19.
This report presents the luminescence properties of Ce3+ and Pr3+ activated Sr2Mg(BO3)2 under VUV-UV and X-ray excitation. The five excitation bands of crystal field split 5d states are observed at about 46 729, 44 643, 41 667, 38 314 and 29 762 cm−1 (i.e. 214, 224, 240, 261 and 336 nm) for Ce3+ in the host lattice. The doublet Ce3+ 5d→4f emission bands were found at about 25 840 and 24 096 cm−1 (387 and 415 nm). The influence of doping concentration and temperature on the emission characteristics and the decay time of Ce3+ in Sr2Mg(BO3)2 were investigated. For Pr3+ doped samples, the lowest 5d excitation band was observed at about 42017 cm−1 (238 nm), a dominant band at around 35714 cm−1 (280 nm) and two shoulder bands were seen in the emission spectra. The excitation and emission spectra of Ce3+ and Pr3+ were compared and discussed. The X-ray excited luminescence studies show that the light yields are ∼3200±230 and ∼1400±100 photons/MeV of absorbed X-ray energy for the samples Sr1.86Ce0.07Na0.07Mg(BO3)2 and Sr1.82Pr0.09Na0.09Mg(BO3)2 at RT, respectively. 相似文献
20.
Yue Tian Baojiu Chen Bining Tian Jiashi Sun Xiangping Li Jinsu Zhang Lihong Cheng Haiyang Zhong Hua Zhong Qingyu Meng Ruinian Hua 《Physica B: Condensed Matter》2012,407(13):2556-2559
Micro-sized NaY(MoO4)2:Tb3+ phosphors with dendritic morphology was synthesized by a ionic liquid-assisted hydrothermal process. X-ray diffraction (XRD) indicated that the as-prepared product is pure tetragonal phase of NaY(MoO4)2. Field emission scanning electron microscopy (FE-SEM) images showed that the as-prepared NaY(MoO4)2:Tb3+ phosphors have dendritic morphology. The photoluminescent (PL) spectra displayed that the as-prepared NaY(MoO4)2:Tb3+ phosphors show a stronger green emission with main emission wavelength 545 nm corresponding to the 5D4→7F5 transition of Tb3+ ion, and the optimal Tb3+ doping concentration for obtaining maximum emission intensity was confirmed to be 10 mol%. Based on Van Uitert's and Dexter's models the electric dipole–dipole (D–D) interaction was confirmed to be responsible for the concentration quenching of 5D4 fluorescence of Tb3+ in the NaY(MoO4)2:Tb3+ phosphors. The intrinsic radiative transition lifetime of 5D4 level is found to be 0.703 ms. 相似文献