共查询到20条相似文献,搜索用时 15 毫秒
1.
Elie Acayanka Duclair S. kuete Georges Y. Kamgang Serge Nzali Samuel Laminsi Peter T. Ndifon 《Plasma Chemistry and Plasma Processing》2016,36(3):799-811
A plasma-assisted synthesis of TiO2/SnO2 nanocomposite is described. In this approach, a precursor containing a mixture of [TiCl3 and SnCl2] exposed to electric discharge was oxidized by plasma-generated reactive species (HO·/H2O = 2.85 eV/SHE). SnO2 microstructures with a diameter of 10–40 µm were coated by thin layers TiO2 nanorods with mean diameter of 6–8 nm. The obtained TiO2/SnO2 nanocomposite was characterized by transmission and scanning electron microscopy, X-ray diffraction and Fourier transform infrared. TiO2/SnO2 nanocomposite was found to be a promising new material for the photocatalytic discoloration of aqueous Remazol Brilliant Blue-R dye under daylight and UVA light sources, due to the combined effects of large specific surface area and heterojunction which efficiently separates the electron–hole pairs delaying the charge recombination. The leaching test indicated that the nanocomposite is stable easily reusable. 相似文献
2.
Fengxiang Li Junlin Xie De Fang Feng He Kai Qi Pijun Gong 《Research on Chemical Intermediates》2017,43(10):5413-5432
A series of Ce–MnO x /TiO2 catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3 at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO x /TiO2 catalyst showed the highest activity and best resistance to SO2 poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H2-temperature-programmed reduction (TPR), and NH3-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO x /TiO2 catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO2 poisoning resistance of the 0.07Ce–MnO x /TiO2 catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH3 and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism. 相似文献
3.
Na Lu Yan Hui Kefeng Shang Nan Jiang Jie Li Yan Wu 《Plasma Chemistry and Plasma Processing》2018,38(6):1239-1258
Plasma catalysis is gaining increasing interest in environmental and energy applications, such as the destruction of gas pollutants and hydrocarbon conversion. In order to further improve the application of plasma catalysis, it is crucial to understand the fundamental mechanisms, especially the mutual interaction between plasma and catalyst. In this paper, a parallel-plate dielectric barrier discharge (DBD) reactor is developed to investigate the plasma behavior and TiO2 properties in the plasma/catalytic hybrid system. The introduction of TiO2 thin film coated on the dielectric improves the discharge intensity, which significantly contributes to the enhancement of reactive species and charges. The energy efficiency of generating ozone in DBD/TiO2 system has been approximately raised by 38% compared to pure DBD when the applied voltage reaches 13 kV. It is fortunately found that the discharge does not change the crystal structure of the TiO2, but the band gap increases from 3.13 to 3.39 eV, which has been proved to enhance the oxidizability of TiO2 in the degradation of methyl orange experiment under UV light. The FTIR and XPS spectra also demonstrate that N element is doped into the structure of TiO2. These results successfully illustrate the plasma behavior and catalyst properties in plasma/catalysis hybrid system and provide reference for the optimization of the plasma catalysis process. 相似文献
4.
So-Eun Kim Youngjong Kang Shiao-Wei Kuo Changwoon Nah Kwang-Un Jeong 《Journal of Sol-Gel Science and Technology》2011,60(2):206-213
Epitaxially grown titanium dioxide (TiO2) nanofibers embedding single crystalline TiO2 nanowires (NWs) were successfully fabricated by electropinning poly(vinyl pyrrolidone)/ethanol solutions mixed with hydrothermally
synthesized TiO2 NWs and titanium isopropoxide precursors and subsequently calcinating the electrospun nanofibers. Utilizing scanning electron
microscopy (SEM) and transmission electron microscopy (TEM), the morphologies of TiO2 NWs and nanofibers were investigated. High resolution TEM (HR-TEM) and selected area electron diffraction (SAED) allowed
us to indentify the fact that, during the calcination process under the optimized condition, titanium isopropoxide precursors
were epitaxially crystallized on the surface of single crystalline TiO2 NWs. Based on the X-ray diffraction (XRD) experiments, it was also realized that the crystalline structure of hydrothermally
synthesized TiO2 NWs and epitaxially crystallized TiO2 nanofibers is anatase and that TiO2 composite nanofibers embedding TiO2 NWs exhibited a higher crystallinity than the pristine TiO2 nanofibers. Additionally, ultraviolet visible (UV–Vis) spectra of nanofibers indicated that optical properties of TiO2 nanofibers can be tuned by introducing the single crystalline TiO2 NWs. 相似文献
5.
A. Mesquita M. I. B. Bernardi L. J. Q. Maia V. R. Mastelaro 《Journal of Thermal Analysis and Calorimetry》2007,87(3):747-751
Pb1–xLaxTiO3
(PLT) nanocrystalline powders were obtained by polymeric precursor method.
The samples were analyzed by differential scanning calorimetry (DSC) and thermogravimetry
(TG) techniques to characterize properly the distinct thermal events occurring
during synthesis. The X-ray diffraction patterns show a tetragonal structure
for the samples with x=0.10 and 0.15. An
increase of the lanthanum concentration to x=0.20
led to a highly symmetric structure, cubic on average. The powders obtained
at the end of the synthesis had an average particle size of 30 to 70 nm. 相似文献
6.
Hoda Nourmohammadi Miankushki Arman Sedghi Saeid Baghshahi 《Journal of Solid State Electrochemistry》2018,22(11):3317-3329
In this study, to improve the specific capacitance of graphene-based supercapacitor, novel quadri composite of G/PPy/MnOx/Cu(OH)2 was synthesized by using a facile and inexpensive route. First, a two-step method consisting of thermal decomposition and in situ oxidative polymerization was employed to fabricate graphene/polypyrrole/manganese oxide composites. Second, Cu(OH)2 nanowires were deposited on Cu foil. Afterwards, for the electrochemical measurements, composite powders were deposited on Cu(OH)2/Cu foil substrate as working electrodes. The synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. The XRD analysis revealed the formation of PPy/graphene, Mn3O4/graphene, and graphene/polypyrrole/MnOx. In addition, the presence of polypyrrole and manganese oxides was confirmed using FT-IR and Raman spectroscopies. Graphene/polypyrrole/MnOx/Cu(OH)2 electrode showed the best electrochemical performance and exhibited the largest specific capacitance of approximately 370 F/g at the scan rate of 10 mV/s in 6 M KOH electrolyte. In addition, other electrochemical measurements (charge–discharge, EIS and cyclical performance) of the G/Cu(OH)2, G/PPy/Cu(OH)2, G/Mn3O4/Cu(OH)2, and G/PPy/MnOx/Cu(OH)2 electrodes suggested that the G/PPy/MnOx/Cu(OH)2 composite electrode is promising materials for supercapacitor application. 相似文献
7.
Nikolina L. Petrova Dimitar S. Todorovsky Veselinka G. Vasileva 《Central European Journal of Chemistry》2005,3(2):263-278
Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal
sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established
in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic
complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating
of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn3O4 (hausmannite) and LaMnO3 respectively. Parasitic phase(s) are observed in LaxCa1−xMnyO3, produced from LaCaMn-citrate. 相似文献
8.
Uraiwan Sirimahachai Nicholas Ndiege Ramesh Chandrasekharan Sumpun Wongnawa Mark A. Shannon 《Journal of Sol-Gel Science and Technology》2010,56(1):53-60
Nanosized TiO2 and nano-anatase TiO2 decorated on SiO2 spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO2 nano particle and TiO2 grafted on SiO2 sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray
photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy
(TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated
using methylene blue as a model pollutant. The synthesized TiO2/SiO2 particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO2 particles. 相似文献
9.
A. I. Gavrilov A. V. Garshev K. A. Kovnir B. R. Churagulov Yu. V. Kolen’ko Yu. D. Tretyakov 《Russian Chemical Bulletin》2005,54(1):71-74
Nanorods of sodium titanium dioxide bronze NaxTiO2 were synthesized by the hydrothermal treatment of the amorphous TiO2·nH2O gel with 10 M NaOH followed by ultrasonication in 0.1 M HCl and thermal treatment (500°C, 10 h). The thermal treatment of the nanorods does not change the morphology of the particles. According to the electron diffraction data, the NaxTiO2 nanorods grow along the c axis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 71–73, January, 2005. 相似文献
10.
Pierre Alphonse Aneesha Varghese Claire Tendero 《Journal of Sol-Gel Science and Technology》2010,56(3):250-263
The optimum processing parameters required to synthesize, by hydrolysis of titanium isopropoxide (TIP), highly stable hydrosols
composed of nanoparticles of the smallest possible size, are deduced both from data available in literature and from our own
experiments. The colloids prepared in these conditions are composed of aggregates of anatase (~90%) and brookite crystallites
(5–6 nm). They are suitable for coatings and have long-term stability (more than one year) in terms of polymorphic composition,
crystallite and agglomerate size. Stable sols composed solely of anatase crystallites (4 nm) can be prepared by partially
complexing the TIP by acetylacetone before hydrolysis. It is not possible to produce porous films with these colloids because
they are stabilized by electrostatic repulsion which causes the particles to organize themselves, during the drying step,
to form materials with a close packed structure. However, coatings with controlled porosity can be prepared from these stable
sols through the post addition of polymers, like PEG or block copolymers. 相似文献
11.
Li Wang Zebin Yu Zhenbo Peng Ying Chen Guoliang Xiang Qing Liu Yuxin Liu Dongmei Chen 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2016,90(4):777-782
We proposed here a new process coupling dielectric barrier discharge (DBD) plasma with magnetic photocatalytic material nanoparticles for improving yield in DBD degradation of methyl orange (MO). TiO2 doped Fe3O4 (TiO2/Fe3O4) was prepared by the sol-gel method and used as a new type of magnetic photocatalyst in DBD system. It was found that the introduction of TiO2/Fe3O4 in DBD system could effectively make use of the energy generated in DBD process and improve hydroxyl radical contributed by the main surface Fenton reaction, photocatalytic reaction and catalytic decomposition of dissolved ozone. Most part of MO (88%) was degraded during 30 min at peak voltage of 13 kV and TiO2/Fe3O4 load of 100 mg/L, with a rate constant of 0.0731 min?1 and a degradation yield of 7.23 g/(kW h). The coupled system showed higher degradation efficiency for MO removal. 相似文献
12.
Influences of α-MnO2, β-MnO2, and δ-MnO2 on the photocatalytic activity of Degussa P-25 TiO2 have been investigated through the photocatalytic degradation of methyl orange. The TiO2 photocatalyst, before and after being contaminated by MnO2, was characterized by UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), and X-ray photoelectron
spectroscopy (XPS). The results showed that photocatalytic activity of TiO2 could be inhibited significantly or completely deactivated due to the presence of even a small amount of MnO2 particles. It was found that the poisoning effect varied with the crystal phases of MnO2 and the effect was in the order δ-MnO2 >α-MnO2 >β-MnO2. The poisoning effect was attributed to the formation of heterojunctions between MnO2 and TiO2 particles. The heterojunctions changed the chemical state of Ti4+ and O2− sites in the crystalline phase of TiO2. MnO2 in contact with TiO2 particles also broadens the band-gap of TiO2, which decreases UV absorption of TiO2. It can also create some deep impurity energy levels serving as photoelectron-photohole recombination center, which accelerates
the electron-hole recombination.
Supported by the National Natural Science Foundation of China (Grant No. 20477009) and the Natural Science Foundation of Hebei
Province (Grant No. E2005000183) 相似文献
13.
Summary. Photooxidation of ethylbenzene with oxygen to give ethylbenzene hydroperoxide has been achieved in a stirred photochemical reactor that was cooled by a water system by irradiation with a 400W high-pressure mercury lamp and using TiO2 powder and metal coated TiO2. The effects of the amount of copper or silver coated on TiO2 and of the temperature on the rate of oxidation have been investigated. It is suggested that thermal cleavage of the O–O bond and photochemically generated singlet oxygen should be considered as the initiating step in a radical chain mechanism. An optimum loading of 6% Ag or 4–5% Cu was observed for photooxidation of ethylbenzene. 相似文献
14.
15.
Li Chen Haixia Shen Zhen Lu Cang Feng Su Chen Yanru Wang 《Colloid and polymer science》2007,285(13):1515-1520
TiO2–SiO2 composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO2–SiO2 composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO2–SiO2) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO2–SiO2 composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO2–SiO2 composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO2–SiO2 core surface via surface functionalized reaction. The particle size of TiO2–SiO2 composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and
Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid
films. The average particle size of the TiO2–SiO2 composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO2–SiO2 composite nanoparticles are well dispersed in the PU matrix. 相似文献
16.
17.
P. G. Tsyrul’nikov 《Russian Journal of General Chemistry》2007,77(12):2328-2336
The effect of thermal activation, sharp increase in the catalytic activity of the system MnO x -Al2O3 in reactions of deep oxidation of CO and hydrocarbons after calcination of the catalyst at 900–1000°C was discovered and investigated. With the use of X-ray phase analysis, X-ray electron spectroscopy, EXAFS, IR spectroscopy, electronic spectroscopy of diffuse reflections, electron microscopy etc. it was established that the effect of thermal activation is related to reversible phase transitions in the system at heating and cooling. On cooling from 1100°C to 650°C disperse particles of cubic spinel of composition Mn2.1 ? x · Al0.9 + x O4 are conserved on the corundum surface. On further cooling the spinel decomposes and finally the nanocristalline species of β-Mn3O*4 containing up to 15 at% of Al3+ form and govern the activity.The thermal activation effect was implemented in an industrial catalyst IK-12-40. Joint Stocks Co “KATALIZATOR” produced and supplied to customers hundreds of tons of this catalyst. The catalyst was awarded with a silver medal of the International exhibition EUREKA in Brussels (1995). 相似文献
18.
Formation mechanism of the MnO2 phase in the reaction of heterogeneous synthesis between Mn2+ and MnO 4 - ions on a solid aluminosilicate surface in aqueous solutions was studied. It was shown that, for lowsilica forms, the Mn2+ ion is oxidized by the MnO 4 - ion uniformly across the grain depth to give the MnO2 phase and manganese manganites. For high-silica materials, the MnO2 phase is formed on the outer surface of grains, with the decomposition of the MnO 4 - ion and formation of the MnO2 phase and molecular oxygen. It was found that, for the clinoptilolite rock used as a solid support, the yield of the MnO2 phase and its distribution over the particle volume depend on the penetration capacity of the MnO 4 - ion into the porous structure of this rock, determined by its composition. It is shown that the amount of the MnO2 phase grows with increasing concentration of the MnO 4 - ion and treatment duration, with the phase thickness being 15–20 and 350–1050 μm for, respectively, high- and low-silica samples. 相似文献
19.
The synthesis of new compounds based on Bi2O3
is investigated because they can be used as new environmentally friendly inorganic
pigments. Chemical compounds of the (Bi2O3)1–x(Er2O3)x type were synthetized.
The host lattice of these pigments is Bi2O3 that is doped by Er3+
ions. The incorporation of doped ions provides interesting colours and contributes
to an increase in the thermal stability of these compounds. The simultaneous
TG-DTA measurements were used for determination of the temperature region
of the pigment formation and thermal stability of pigments. 相似文献
20.
V. Balek N. Todorova C. Trapalis V. Štengl E. Večerníková J. Šubrt Z. Malek G. Kordas 《Journal of Thermal Analysis and Calorimetry》2005,80(2):503-509
Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe3+ and polyethyleneglycol (PEG600) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe3+ containing titania gels. The microstructure development of the Fe2O3/TiO2 gel samples with and without PEG600 admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120°C and the samples preheated for 1 h to 300 and 500°C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600°C. 相似文献