Ag改性TiO2／SnO2纳米薄膜及光催化降解甲基橙的性能

以光还原沉积法对TiO2/SnO2薄膜进行Ag改性,制备Ag-TiO2/SnO2纳米薄膜,讨论紫外光照时间、光照强度、AgNjO3浓度等工艺条件埘光催化活性的影响.用XRD和SEM对薄膜的结构、表面形貌和化学组成进行表征,以甲基橙为模拟污染物对光催化性能进行测定.结果表明:在最佳条件下制备的Ag-TiO2/SnO2薄膜,Ag担载量为0.51%(摩尔分数),Ag簇直径在30～90 nm之间:薄膜具有较高的光催化活性,对甲基橙的降解率是修饰前TiO2/SnO2薄膜的2.02倍,是相同质量TiO2/ITO薄膜的3.30倍;催化活性的提高,源于反应机理的改变:薄膜中Ag-TiO2异质结的引入,一方面进一步促使光生电荷的分离,另一方面加速了氧气与激发电子的还原反应.     

High photocatalytic activity of Cu_2O/TiO_2/Pt composite films prepared by magnetron sputtering

Cu_2O/TiO_2/Pt three-layer films were deposited on glass substrates using magnetron sputtering method.The surface morphology and the optical properties of the composite film were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), ultravioletvisible spectroscopy(UV-Vis) and photoluminescence spectroscopy(PL). The photocatalytic activity of the samples was evaluated by the photocatalytic degradation of methyl orange(MO) aqueous solution under visible light irradiation. The results indicate that the Cu_2O/TiO_2/Pt composite films are made up of three layers which are Pt layer,anatase-TiO_2 layer and Cu_2O layer from bottom to top. The surface of the films is even and composed of regular-shaped spherical particles. The photocatalytic activity of the Cu_2O/TiO_2/Pt three-layer film is much higher than that of the Cu_2O/TiO_2 double-layer film. Such enhancement is ascribed to the presence of Pt layer, which further inhibits the photogenerated electron-hole recombination, prolongs the lifetime of the photogenerated carriers, increases the quantum efficiency and hence improves the photocatalytic activity of the film effectively.     

Microstructure characterization and photocatalytic activity of mesoporous TiO2 films with ultrafine anatase nanocrystallites

A series of mesoporous TiO₂ films on borosilicate glass with ultrafine anatase nanocrystallites were successfully synthesized using a non-acidic sol gel preparation route, which involves the use of nonionic surfactant Tween 20 as template through a self assembly pathway. The microstructure of these TiO₂ films was characterized by XRD, SEM, HR-TEM, UV-Vis spectroscopy, and N₂ adsorption-desorption isotherm analysis. Their photocatalytic activities were investigated by using creatinine as a model organic contaminate in water. It was found that all mesoporous TiO₂ films prepared with Tween 20 exhibited a partially ordered mesoporous structure. The photocatalytic activity of the TiO₂ films could be remarkably improved by increasing Tween 20 loading in the sol at the range of 50% (v/v), which yielded large amount of catalyst (anatase) on the glass support and enhanced specific surface area. The optimum Tween 20 loading was 50% (v/v) in the sol, above which good adhesion between TiO₂ films and borosilicate glass could not be maintained. The final TiO₂ film (Tween 20: final sol = 50%,v/v) exhibits high BET surface area (∼ 120 m²/g) and pore volume (0.1554 cm³/g), ultrafine anatase nanocrystallinity (7 nm), uniform and crack free surface morphology, and improved photocatalytic activity.     

二氧化钛负载磷钨钼杂多酸催化合成缩醛(酮)

首次采用回流法制备了二氧化钛负载磷钨钼杂多酸催化剂H3PW6Mo6O40/TiO2,该催化剂的适宜制备条件为原料质量比m(TiO2)∶m(H3PW6Mo6O40)=1∶2.0,水的用量30 mL,回流反应时间2.0 h,活化温度150℃.以H3PW6Mo6O40/TiO2为催化剂,对以环己酮、丁酮、正丁醛、苯甲醛与二元醇(乙二醇、1,2-丙二醇)为原料合成的8种缩醛(酮)反应条件进行对比,较系统研究了醛(酮)与二元醇摩尔比、催化剂用量、反应时间对收率的影响.结果表明,在n(醛(酮∶n(乙二醇(1,2-丙二醇))=1.0∶1.4、催化剂用量占反应物料总质量的0.8%、反应时间1.0 h的条件下,8种缩醛(酮)的收率在53.0%～86.9%之间.     

Ag-decorated 3D flower-like Bi_2MoO_6/rGO with boosted photocatalytic performance for removal of organic pollutants

A series of unique 3 D flower-like Bi_2 MoO_6(BMO)/reduced graphene oxide(rGO) heterostructured composites decorated with varying amounts of Ag nanoparticles(NPs) were fabricated.Their morphological characteristics,structural features,energy band structures and photoelectrochemical properties were systematically studied.All the Ag/BMO/rGO ternary composites(AgBGy;y=1%,2% and 3%) demonstrated greater photocatalytic activity towards efficient removal of our selected organic models [methyl orange(MO),rhodamine B(RhB)and phenol],as compared with the BMO/rGO binary composites(BG-x;x=0.25,2,4 and 5).Particularly,AgBG-2%,which was synthesized with the addition of 2 wt% rGO and 2 wt% Ag in BMO,possessed superior photocatalytic activity.The fitted rate constants(k) for the photocatalytic degradation of RhB,MO and phenol using AgBG-2% were estimated to be 0.0286,0.0301 and 0.0165 min~(-1),respectively,which were over one order of magnitude greater than those obtained using pure BMO.Several factors may contribute to the observed enhancement,including greater specific surface area,enhanced light absorption,promoted spatial separation of electronhole(e~--h~+) pairs and their suppressed recombination,especially benefiting from the synergistic effects among BMO,rGO and Ag NPs.Our work suggests that the rational design of BMO/rGO/Ag ternary composite was an effective strategy to boost the photocatalytic activity of the resulting catalyst towards the highly efficient removal of organic pollutants from water.     

The effects of thermal spray technique and post-deposition treatment on the photocatalytic activity of TiO2 coatings

Titanium dioxide coatings were deposited by two thermal spray methods: high velocity oxygen fuel and atmospheric plasma spray. The coatings were characterized by XRD, SEM, Raman and UV-vis spectroscopy. The photocatalytic activities of the samples towards decomposition of methylene blue were also determined. As-prepared samples showed a very limited photocatalytic activity. In contrast, post-deposition oxidation of the samples in air resulted in significantly improved catalytic performance of the coatings. It appears that the oxidation state of titania played a critical role in photocatalytic activity given that partially reduced coatings resulted a very low activity. This conclusion was consistent with the observation of the Ti₈O₁₅ phase in the as-prepared samples. However, when oxidized, parameters such as the anatase content became a dominant factor in catalytic performance of the samples. The coating sprayed by high velocity oxygen fuel resulted in much higher activity than the atmospheric plasma sprayed coating, which can be attributed to higher anatase content of the former.     

Influence of an O2 Type Oxidizing Environment on SiCf/SiC Composites: Properties/Microstructure Relationship

Ceramic matrix composites have been identified as a potential material of core structure for the fourth generation of fission nuclear reactors. Regarding their excellent mechanical behavior in very harsh conditions (high temperature and high irradiation flux), the CVI–SiC_f/SiC composites with pyrocarbon interlayer are of prime interest for the fuel cladding in the gas-cooled fast reactor. Although the working atmosphere is helium in these advanced reactors, the presence of oxidizing impurities could have a significant role on the mechanical behavior of materials subjected to long-term exposures. Within this framework, this study was intended to investigate the influence of oxidation on the SiC_f/SiC composites mechanical properties. Different pre-damage states were intentionally introduced by mechanical tensile tests on plate specimens before performing an oxidation treatment of 1,000 h at 1,000 °C under helium with 10 ppm of O₂. The degradation of the composite was determined from the mechanical behavior of post-exposure specimens. Results were correlated both with microstructural observations of the damage and with characterizations of the generated oxides at the surface of the composites. The most severe decline of mechanical properties occurs for the higher predamaged loadings. Indeed in this case, the silica formed during the oxidation of SiC is not in sufficient quantities to fill the cracks.     

Carbon quantum dots/Bi4O5Br2 photocatalyst with enhanced photodynamic therapy:killing of lung cancer (A549) cells in vitro

Inorganic photocatalysts have been regarded as a promising candidate in the domain of tumor photodynamic therapy(PDT)due to their inspirational photocatalytic activity.In this study,a Bi₄O₅Br₂photocatalyst was synthesized and it exhibited effective photo-killing activity of A549 cells(a human lung carcinoma epithelial cell line)in vitro.On this basis,we modified Bi₄O₅Br₂with carbon quantum dots(CQDs)via a hydrolysis method at room temperature,which resulted in an improved photo-killing effect of Bi₄O₅Br₂to A549 cells.The samples and the interaction between samples and cells were fully characterized.It has been found that the loading of CQDs on Bi₄O₅Br₂can reduce the hydration ratio,increase the cellular uptake and improve the photogenerated reactive oxygen species(ROS)as compared with pristine Bi₄O₅Br₂.Electron spin resonance(ESR)analysis and radical-trapping experiments manifested that the ROS contributed to PDT may be·O^2-and ·OH.This study may provide a useful strategy to ameliorate the penetrability,cell compatibility and PDT effect upon cancer cells of other inorganic photocatalysts.     

Fabrication of an in-situ nano-Al2O3／Cu composite with high strength and high electric conductivity

A heat-resistant dispersion-strengthening nano-Al2O3/Cu composite with high strength and high electric conductivity was fabricated in a multiplex medium. The internal oxidation product, microstructures and properties of the composite,and the process flow were systematically studied. It is confirmed that this new technique simplifies the process and improves the properties of the composite. X-ray analysis indicates that the alumina particles formed during internal oxidation consist of a large mount of γ-Al2O3 and a certain amount of θ-Al2O3 and α-Al2O3. TEM observation shows that the obtained γ-Al2O3 nano-particles are uniformly distributed in the copper grains; their mean size and space between particles are 7 nm and 30 nm, respectively. The main properties of the composite with 50% cold deformation are as follows: the electric conductivity is 51 MS/m (87%IACS), σo= 628 MPa, and the hardness is HRB86. After annealing at 1273 K, all or most of the above properties remain, and the microstructures are still dependent on elongated fiber-form grains.     

表面TiO2/HA改性Ti-5Zr-6Mo-15Nb的组织相容性及成骨活性

在含有羟基磷灰石的电解液中,通过微弧氧化法在新型近β钛合金Ti-5Zr-6Mo-15Nb (TLE)表面制备一层多孔TiO2/HA(羟基磷灰石)复合涂层,再将试样浸入过硫酸钠和草酸的混合溶液中处理以进行表面活化.借助XRD、SEM和EDS研究了该多孔复合薄膜的组成和表面形貌,并通过动物体内植入实验研究了经上述表面改性处理前后的TLE合金的软组织和硬组织相容性,以及表面改性前后TLE合金的成骨活性.结果表明,经上述处理后的TLE合金表面覆盖一层多孔陶瓷薄膜,该薄膜主要由金红石型TiO2和锐钛矿型TiO2,以及少量HA相组成.改性后的TLE合金具有良好的皮下组织、肌肉组织和骨组织相容性,成骨活性也好于未处理的Ti-5Zr-6Mo-15Nb 合金.     

Influence of addition of Grp/Al2O3p with SiCp on wear properties of aluminum alloy 6061-T6 hybrid composites via friction stir processing

Aluminum alloy base surface hybrid composites were fabricated by incorporating with mixture of (SiC+Gr) and (SiC+Al₂O₃) particles of 20 μm in average size on an aluminum alloy 6061-T6 plate using friction stir processing (FSP). Microstructures of both the surface hybrid composites revealed that SiC, Gr and Al₂O₃are uniformly dispersed in the nugget zone (NZ). It was observed that the addition of Gr particles rather than Al₂O₃ particles with SiC particles, decreases the microhardness but immensely increases the dry sliding wear resistance of aluminum alloy 6061-T6 surface hybrid composite. The observed microhardness and wear properties are correlated with microstructures and worn micrographs.     

The characteristics of the potentiodynamic potential/current profiles obtained with the Ni/0.5N H2SO4 interface. A contribution to the mechanism of the electrode process

Electrochemical data derived from different simple and complex potentiodynamic techniques for the Ni/0.5 N H₂SO₄ interface furnish a new insight about the activation and initial stage passivation of nickel. The anodic dissolution of nickel involves a metal surface which is either partially or completely covered by species such as NiOH, [NiOH.Ni(OH)₂] or [Ni(OH)₂.NiOOH]. The chemical dissolution of the various species in the acid electrolyte occurs at different rates. The relative dissolution rates can be estimated from the data derived from the complex triangular potential perturbations.The change of the E/I profile during cycling is explained through a complex reaction sequence which is in agreement with recently postulated reaction schemes and reported optical data.     

Crystal structure of the (ET)8[Hg4Br12· (PhCl)2] organic metal and the (ET)8[Hg4Br12·(MePbCl)2] organic semiconductor: The products of the same synthesis

X-ray study of the cation-radical salts (ET)₈[Hg₄Br₁₂·(PhCl)₂] (metal up to 90 K) and (ET)₈[Hg₄Br₁₂·(MePhCl)₂] (semiconductor) preparated in the same synthesis has shown considerable differences in the structures of their cationic and anionic layers. It is these differences that account for different electrophysical properties of these compounds.     

The effects of thermal treatment on the physical properties of Sr2FeMo1−xMxO6 perovskite with M = W, Ta and x ≤ 0.3

The Sr₂FeMo_1−xM_xO₆ double perovskites with M = W and Ta and x ≤ 0.3, were obtained by sintering at 1300 °C, during 4 and 8 h, respectively. The perovskites crystallize in a tetragonal structure having I4/mmm space group. The grains are more homogeneous when sintering time is increased. The samples sintered longer time show higher values of saturation magnetizations, resistivities and magnetoresistivities than the samples sintered during 4 h. The intergrain tunnelling magnetoresistance as well as the intragrain contributions, respectively were analysed as function of temperature and external field. The changes in the physical properties, when the sintering time is increased, have been correlated with the number of antisite defects as well as the nature of grain boundaries.     

The in situ synthesis and wear performance of a metal matrix composite coating reinforced with TiC-TiB2 particulates, formed on Ti-6Al-4V alloy by a low oxygen partial pressure fusing technique

A metal matrix composite coating reinforced with TiC-TiB₂ particulates has been successfully fabricated utilizing the in situ reaction of Al, Ti and B₄C by the low oxygen partial pressure fusing technique to improve the wear resistance of Ti-6Al-4V alloy. The results show that increasing the B₄C content is adverse to forming the coating for the formation of interfacial stress; however, the addition of TiC powder as a diluent can favor the formation of this coating and the addition of small amounts of Y₂O₃ can greatly improve the adhesion of the coating. After a pin-on-disc wear test, the wear mass loss of the coating is only about 1/12 that of the Ti-6Al-4V alloy and the wear mechanism of coating is a mixed type of slight peeling-off, adhesion and abrasion.