Novel SnO2–x/g-C3N4 heterojunction nanocomposites composed of reduced SnO2–x nanoparticles and exfoliated g-C3N4 nanosheets were prepared by a convenient one-step pyrolysis method. The structural, morphological, and optical properties of the as-prepared nanocomposites were characterized in detail, indicating that the aggregation of g-C3N4 nanosheets was prevented by small, well-dispersed SnO2–x nanoparticles. The ultraviolet–visible spectroscopy absorption bands of the nanocomposites were shifted to a longer wavelength region than those exhibited by pure SnO2 or g-C3N4. The charge transfer and recombination processes occurring in the nanocomposites were investigated using linear scan voltammetry and electrochemical impedance spectroscopy. Under 30-W visible-light-emitting diode irradiation, the heterojunction containing 27.4 wt.% SnO2–x exhibited the highest photocurrent density of 0.0468 mA·cm–2, which is 33.43 and 5.64 times larger than that of pure SnO2 and g-C3N4, respectively. The photocatalytic activity of the heterojunction material was investigated by degrading rhodamine B under irradiation from the same light source. Kinetic study revealed a promising degradation rate constant of 0.0226 min?1 for the heterojunction containing 27.4 wt.% SnO2–x, which is 32.28 and 5.79 times higher than that of pure SnO2 and g-C3N4, respectively. The enhanced photoelectrochemical and photocatalytic performances of the nanocomposite may be due to its appropriate SnO2–x content and the compact structure of the junction between the SnO2–x nanoparticles and the g-C3N4 nanosheets, which inhibits the recombination of photogenerated electrons and holes.
Cr2O3–CNT/TiO2 composites derived from chromium acetylacetonate, multi-walled carbon nanotubes (MWCNT) and titanium n-butoxide (TNB) were prepared, and the photocatalytic activity of the Cr2O3–CNT and CNT/TiO2 composites was examined. The Cr2O3–CNT/TiO2 composites were characterized by BET surface area measurement, X-ray diffraction, transmission electron microscopy, and energy
dispersive X-ray analysis. The photocatalytic activity was determined from the decomposition of methylene blue (MB) under
visible light irradiation. Methylene blue was photodegraded successfully in the presence of the Cr2O3–CNT/TiO2 composite under visible light irradiation. 相似文献
Ag/α-MoO3 heterojunctions were prepared by a photoreduction process and characterized using XRD, TEM, UV–Vis-DRS, EDS, XPS, PL, EIS and PT. Ag/α-MoO3 heterojunctions exhibited excellent photocatalytic oxidative desulfurization activity for thiophene under visible-light irradiation. The removal efficiency of 5% Ag/α-MoO3 composites could get to 98.3% with 1.5 g L?1 amount of catalyst used under visible-light irradiation for 270 min, which is 2.5 times as high as that of pure α-MoO3 nanobelts. The stability of as-prepared Ag/α-MoO3 heterojunctions were investigated through recycling run experiment, which the desulfurization rate of 5 wt% Ag/α-MoO3 for thiophen still remained 92.8% after five consecutive cycles. Furthermore, the active species trapping experiment confirmed that h+ and ·O2? were the main active in photocatalytic degradation process for thiophene. Additionally, the mechanism of the enhanced photocatalytic activity for Ag/α-MoO3 was proposed. These features demonstrate that the Ag/α-MoO3 heterojunctions have great application potential for refractory pollutants’ removal from fuel oil. 相似文献
The rGO–ZnO–Fe3O4 nanocomposites were synthesized by a simple, economical and environmentally benign solvothermal method. The morphology, structure and photocatalytic activity of rGO–ZnO–Fe3O4 nanocomposites were characterized, and the effects of the preparation conditions were analyzed. The 25 mg of rGO–ZnO–Fe3O4 nanocomposites performed efficient photocatalytic activity for the degradation of 25 mL of 4.79 mg/L Rhodamine B under both ultraviolet and visible light irradiation. The nanocomposites could be easily retrieved from the wastewater by extra magnetic field due to the presence of magnetic Fe3O4 nanoparticles. After the degradation experiment was carried out five times, the degradation ratio is still close to 90% after irradiation after 5 cyclic, indicating that the rGO–ZnO–Fe3O4 nanocomposites have high stability for reuse. Therefore, the prepared rGO–ZnO–Fe3O4 nanocomposites may be a promising potential material for wastewater treatment. 相似文献
In this article, we present a fast and simple method to produce TiO2 nanospheres–graphene nanocomposite with high photocatalytic activity under visible and UV light irradiation. TiO2 nanospheres were adsorbed on graphene in sol–gel process. First, titanium (IV) butoxide underwent hydrolysis in graphene
oxide (GO) ethanol solution resulting in TiO2 nanospheres deposition on GO. Next, the material was calcinated to generate the phase transition of TiO2 into anatase and reduce GO to graphene. The detailed characterization of the material was performed via transmission electron
microscopy, energy dispersive X-rays spectrometer, Fourier-transformed infrared spectroscopy, X-ray diffraction, and Raman
spectroscopy. Interestingly, the band-gap energy of the prepared photocatalyst was drastically decreased in comparison with
the commercial photocatalyst P25 from 3.05 to 2.36 eV. This influenced in the activation of the material under visible light
and resulted in high photocatalytic activity in the process of phenol decomposition in visible and UV irradiation. 相似文献
After being impregnated in the solution containing Mg(NO3)2·6H2O, -Al2O3 was dried and calcined at 500°C which results in the production of a bactericide, highly dispersed MgO loaded on the surface of -Al2O3. The threshold value of the monolayer dispersion of MgO on -Al2O3 is 14.97%, and MgO crystal formed when the load amount beyond this value. The samples with different load amount were characterized by X-ray Diffraction (XRD), Low-temperature N2 adsorption-desorption, Inductively Coupled Plasma (ICP) and High Resolution Scan Electronic Microscope (SEM). The results showed that these MgO microcrystals are highly dispersed and have regular size in the range of 4 to 10.8 nm. The specific surface, pore volume and pore size of the sample decreases with the increase of load amount. It is demonstrated that -Al2O3 with highly dispersed MgO on the surface is efficient bactericide, and the one with 20% load amount of MgO can kill more than 99% bacteria and spore cells. 相似文献
Reactions between thin films of CA2 and (0001)-oriented α-Al2O3 have been studied using a combination of microscopy techniques. Thin films of amorphous CA2 were deposited on sapphire substrates by pulsed-laser deposition at 900 °C in an oxygen ambient atmosphere. After deposition,
the reaction couples were heat treated in air for various times either at 1300 or 1400 °C. Atomic-force microscopy was used
to monitor changes in the microstructure of the films. Interfaces between the different regions were examined by transmission
electron microscopy (TEM) of cross-sectional samples prepared by focused ion-beam milling. The CA2 films had dewetted the substrate surface as a result of the heat treatment. An interfacial reaction layer was observed between
the dewetted CA2 droplets and the substrate. The structure of this reaction layer was found to be consistent with γ-Al2O3 by computer analysis of high-resolution TEM images. There is a perfect epitaxy between the interfacial layer and the substrate.
For the samples heat treated for longer times, hexagonal features were found on the substrate surface. The presence of these
features on (0001)-oriented α-Al2O3 suggests that CA6 platelets form by the transformation of the interfacial reaction layer. The results are discussed in relation to the crystallization
behavior of the various calcium aluminate phases and the equilibrium-phase diagram of the CaO–Al2O3 system. 相似文献
The activities in NO + CO reaction of CuO-loaded TiO2/γ-Al2O3 catalysts prepared by precipitation (P), co-precipitation (C-P), or sol-gel (S-G) were examined using a micro-reactor-gas
chromatography (GC) system. The study showed higher catalytic activity of 12%CuO/15%TiO2/γ-Al2O3 (P) than that of 12%CuO/15%TiO2/γ-Al2O3 (S-G) or 12%CuO/15%TiO2/γ-Al2O3 (C-P) in air condition, compared with higher activity of 12%CuO/15%TiO2/γ-Al2O3 (P) or 12%CuO/15%TiO2/γ-Al2O3 (S-G) than that of 12%CuO/15%TiO2/γ-Al2O3 (C-P) in H2 condition. The specific surface area and crystallite formation had little effect on catalytic activities. H2-temperature programmed reduction (TPR) revealed four reduction peaks of 12%CuO/15%TiO2/γ-Al2O3 (P), three reduction peaks of 12%CuO/15%TiO2/γ-Al2O3 (S-G), but only one reduction peak of 12%CuO/15%TiO2/γ-Al2O3 (C-P). CuO diffraction peaks were detected only in 12%CuO/15%TiO2/γ-Al2O3 (P), indicating that CuO was highly dispersed on the other two TiO2/γ-Al2O3 catalysts. As a result, 12%CuO/15%TiO2/γ-Al2O3 (P) had the highest activity of reducing NO. During NO + CO reaction, the absorption peaks of intermediate product N2O were shown at 150 °C by 12%CuO/15%TiO2/γ-Al2O3 (P), at 200 °C by 12%CuO/15%TiO2/γ-Al2O3 (S-G), and at 100 °C by 12%CuO/15%TiO2/γ-Al2O3 (C-P) after H2 pretreatment at 400 °C for 1 h. 相似文献
BaFe12O19 hexaferrite films have been produced on thermally oxidized single-crystal silicon (SiO2/Si) substrates by sequential ion-beam sputtering of BaFe2O4 and α-Fe2O3 targets in an argon-oxygen atmosphere. Their crystal structure has been studied, and the origin of the impurity phases forming during heat treatment has been identified. The results show that heat treatment may lead to the formation of eutectic melts. As a result, the hexaferrite films may contain spherulites. 相似文献
We present the results of the first domestic experimental investigation of the optically stimulated luminescence (OSL) in
commercial thermoluminescence (TL) detectors based on proton-irradiated anion-defect corundum. It is demonstrated that the
OSL and TL phenomena can, in principle, be jointly used for the dose diagnostics of accelerated particle beams. The observed
phenomena have good prospects for application in radiation physics. 相似文献
Catalytic combustion of methane was investigated on Pt and PdO-supported CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts prepared by a wet impregnation method in the presence of polyvinylpyrrolidone. The catalysts were characterized
by X-ray fluorescence analysis, X-ray powder diffraction, X-ray photoelectron spectra, transmission electron microscopy, and
BET specific surface area measurements. The Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 and PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were selective for the total oxidation of methane into carbon dioxide and steam, and no by-products such as HCHO,
CO, and H2 were obtained. The catalytic activities of the PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalysts were relatively higher than those of the Pt-supported catalysts, due to the facile re-oxidation of metallic Pd
into PdO based on lattice oxygen supplied from the CeO2–ZrO2–Bi2O3 bulk. A decrease in the calcination temperature during the preparation process was found to be effective in enhancing the
specific surface area of the catalysts, whereby particle agglomeration was inhibited. Optimization of the PdO amount and calcination
temperature enabled complete oxidation of methane at temperatures as low as 320 °C on the 11.6 wt% PdO/CeO2–ZrO2–Bi2O3/γ-Al2O3 catalyst prepared at 400 °C. 相似文献
The dc conductivity of the glasses in the Fe2O3-Bi2O3-K2B4O7 system was studied at temperatures between 223 and 393 K. At temperatures from 300 to 223 K, T–1/4 (T is temperature) dependence of the conductivity was found, however, both Mott variable-range hopping and Greaves intermediate range hopping models are found to be applicable. Mott and Greaves parameters analysis gave the density of states at Fermi level N (EF) = 3.13 × 1020–21.01 × 1020 and 1.93 × 1021–16.39 × 1021 cm–3eV–1 at 240 K, respectively. The variable-range hopping conduction occurred in the temperature range T = 300–223 K, since WD was found to be large (WD = 0.08–0.14 eV for these glasses) and dominated the conduction at T < 300 K. 相似文献
The interface between an Mn-doped γ-gallium oxide (Ga2O3) thin film and an MgAl2O4 (001) substrate has been investigated using high-resolution transmission electron microscopy (HRTEM), high-angle annular
dark-field scanning transmission electron microscopy (HAADF-STEM), and first-principles calculations. A high-quality Mn-doped
γ-Ga2O3 film with a defective spinel structure has been epitaxially grown by pulsed laser deposition. The γ-Ga2O3 crystal shows an uniform tetragonal distortion with a tetragonality of 1.05 throughout the film thickness of 75 nm. HRTEM
and HAADF-STEM observations reveal that the γ-Ga2O3 and MgAl2O4 crystals form a coherent interface without any interfacial layers or precipitates. The atomistic structure and energies are
theoretically evaluated for the interfaces with two types of termination plane, i.e., Mg- and Al2O4-termination of MgAl2O4. The cation sublattice is found to be continuous for both interfaces despite the defective spinel structure of Mn-doped γ-Ga2O3 with some vacant cation sites. The Al2O4-termination shows a lower interfacial energy than the Mg-termination under most conditions of the chemical potentials. This
behavior is attributed to the energetic preference of the Mn–Al2O4 local configuration at the interface. 相似文献
Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ≤ x ≤ 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. 相似文献
Novel barium tungstate/nitrogen-doped reduced graphene oxide-graphitic carbon nitride (BaWO4/NRGO-g-C3N4) nanocomposite has been synthesized by a simple one-pot microwave technique. The synthesized nanocomposites are well characterized by diffraction, microscopic and spectroscopic techniques to study its crystal structure, elemental composition, morphological features and optical properties. The material prepared is tested for its performance as an electrocatalyst, photocatalyst and reduction catalyst. The nanocomposite catalyzed the photodegradation of methylene blue (MB) dye in 120 min, reduction of 4-nitro phenol (4-NP) to 4-amino phenol (4-AP) in 60 s, showed an impressive Tafel slope of 62 mV/dec for hydrogen evolution reaction (HER). The observed results suggest that the nanocomposite acts as an efficient multifunctional catalyst. The reported approach provides fundamental insights which can be extended to other metal tungstate-based ternary composites for applications in the field of clean energy and environment in the future. 相似文献
When subjected to electron-beam irradiation in a transmission electron microscope, the grain boundary in an α-Al2O3 bicrystal is observed to migrate even at room temperature. The bicrystal is composed of grains with the same normal direction, and thus the difference in strain energy or surface energy between the two grains cannot explain the observed migration. We attribute this phenomenon to an increase in grain boundary mobility by electron-beam irradiation, especially by radiolysis effects. 相似文献
Gadolinium doped bismuth borate glasses containing up to 30 mol% Y2O3 were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B2O3 · Bi2O3 and B2O3 · Bi2O3 glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic
resonance (EPR) of Gd3+ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the
progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate
that Gd3+ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results. 相似文献
The current study was carried out to investigate the efficiency of using magnetic mesoporous of cetyltrimethylammonium bromide-functionalized silica-coated magnetite for removing amoxicillin (AMX) and tetracycline (TC) from tap water, river water, and medical wastewater as real samples. The properties of the synthesized adsorbent were characterized through transmission electron microscopy (TEM), scanning electron microscopy, X-ray diffraction spectrometry, Fourier transform infrared spectroscopy, vibrating sample magnetometry, pHpzc, and also Brunauer, Emmett, and Teller (BET) methods. The BET surface area and the average diameter of mesoporous Fe3O4/SiO2/CTAB–SiO2 in accordance with TEM were 157.8 m2 g?1 and around 55 nm, respectively. In batch tests, the adsorption parameters, including the initial concentration, contact time, pH of solution, ionic strength, and adsorbent dose, were analysed. The experimental adsorption data were modelled using different classical and recently developed models. According to the results, the maximum adsorption capacities of AMX and TC on mesoporous Fe3O4/SiO2/CTAB–SiO2 were found to be 362.66 and 220.70 mg g?1, respectively. Also, the results indicated that AMX and TC loaded on the adsorbent could be easily desorbed with 0.1 mol L?1 HNO3+ acetonitrile (1:1, v/v) and the adsorbent showed good reusability for the adsorption of the drugs studied. 相似文献
The formation mechanism of spinels on Al2O3 particles in the Al2O3/Al–1.0 mass% Mg2Si alloy composite material has been investigated by transmission electron microscopy (TEM) in order to determine the crystallographic
orientation relationship. A thin sample of the Al2O3/Al–Mg–Si alloy composite material was obtained by the FIB method, and the orientation relationship between Al2O3 and MgAl2O4, which was formed on the surface of Al2O3 particles, was discovered by the TEM technique as follows:
At the interface between the Al2O3 and the matrix the MgAl2O4 (spinel) crystals had facets of {111} planes. Spinels were not grown as thin films, but as particles consisting of {111}
planes. They grow towards both the matrix and the Al2O3 particles. 相似文献