Preparation and antibacterial activity of Ag/TiO2-functionalized ceramic tiles

An Ag/TiO₂ coating was deposited onto glazed ceramic tiles by a sol-gel and spraying method at high temperatures. The coating was characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The results showed that silver was present in rutile-TiO₂, and the temperature did not change the phase composition of the samples. The Ag/TiO₂ coating had a higher roughness than the TiO₂ coating. The tape test (D 3359–08) showed that the coatings prepared at 950 °C and 1000 °C had good adhesion to the ceramic tile substrate. The antibacterial activity of the coating was tested by photocatalytic sterilization experiments. The results showed that the Ag/TiO₂ coating had a higher antibacterial activity than the TiO₂ coating, and the sterilization efficiency of Escherichia coli, Staphylococcus aureus, Shigella, and Salmonella exceeded 99.655% under 2 h of visible light irradiation. This research provides a method to create Ag/TiO₂ coatings with good thermal resistance, adhesion, and antibacterial activity. This improves the low photocatalytic activity caused by the anatase-to-rutile transformation of TiO₂ at high temperatures and the poor adhesion at low temperatures.     

利用热喷涂技术制备二氧化钛光催化涂层研究现状与展望

纳米二氧化钛(TiO_2)因稳定、廉价、无毒等优势,成为研究与应用最广泛的光催化剂。为了解决颗粒状催化剂难以回收、易于造成二次污染等缺点,制备TiO_2涂层是较为理想的选择。热喷涂技术具有成本低、效率高、容易实现大面积制备等优势,在Ti O2涂层制备研究中得到广泛关注。基于此,本文综述了等离子喷涂、火焰喷涂、超音速火焰喷涂、冷喷涂技术在制备纳米TiO_2涂层方面的研究现状,并分析了影响TiO_2涂层光催化性能的关键制备因素,讨论了多种热喷涂技术在涂层微观结构控制与性能调控方面的研究现状,并对未来发展做了展望。     

Fe3O4@SiO2@TiO2@PDA Nanocomposite for the Degradation of Organic Materials

In order to enhance the effectiveness of pollutant removal by photocatalysis under visible light, a multifunctional photocatalyst was prepared by grafting polydopamine (PDA) with the core-shell nanocomposite Fe₃O₄@SiO₂@TiO₂ (FST). The structural, morphological, and magnetic responses of FST@PDA were characterized by X-ray diffraction pattern, Fourier transform infrared spectroscopy, transmission electron microscopy, etc. FST@PDA showed a high degradation rate of rhodamine B, reaching 98.7 % and 95.7 % after 150 min of ultraviolet and visible light radiation, respectively. In addition, the prepared FST@PDA had good safety and high recyclability due to the strong covalent bonds between FST and PDA.     

Acoustic sources from damage propagation in Ti grade 5

In this paper fatigue test results are presented for titanium grade 5 specimens subjected to uniaxial cyclic loads. The material behavior of titanium was studied by comparing the Acoustic Emission (AE) detection technique with the Infrared Thermography (IT). The AE technique consists on attaching a couple of piezoelectric sensors on the surface of the sample in order to allow real-time recording of acoustic activity occurring in the material during the test and to localize the acoustic source, based on the assumption that part of the acoustic activity depends on the crack propagation process. All typical data of AE were collected during the tests and some of them were properly post-processed by using filters or derivative functions in order to better understand the crack propagation phenomenon. At the same time, thermographic analysis was also carried out during the experiments by continuous monitoring of surface temperature of the sample. Results of the fatigue behavior of the analyzed material beside the acoustic emission track and the thermal images of the sample are analyzed and critically discussed, in order to assess the capability of each technique in predicting the imminent failure of material.     

Influence of nitrogen vacancy defects incorporation on densification behaviour of spark plasma sintered non-stoichiometric TiN1−x

Highly nitrogen deficient non-stoichiometric TiN_1?x powders within nitrogen vacancy defects (0.3<1?x<0.5) were prepared through mechanical alloying and consolidated through spark plasma sintering. Increasing nitrogen vacancy defects promoted densification behaviour of TiN_1?x. Nitrogen vacancies accelerated material transport and diffusion during sintering. The altered strong covalent bonding nature of TiN_1?x was believed to enhance the sinterability. TiN_1?x (1?x?=?0.32) ceramic reached relative density of 98.8%, Vickers hardness of 17.0 GPa and grain size of 200–300 nm after sintering at 1000°C, 40 MPa and 10 min.     

刀具几何参数对金属钛纳米切削影响的分子动力学研究

基于分子动力学的基本原理,构建了钛的纳米切削分子动力学仿真模型。工件原子间采用嵌入原子势EAM（Embedded atom method）,工件原子与刀具原子间采用Morse势函数,研究了在不同刃口半径和刀具前角条件下,钛纳米切削过程中工件形态、系统势能、切削力以及工件温度等的变化规律。结果表明：随着刀具刃口半径增大,加工表面粗糙度增加,切削力和工件温度降低,切屑变薄;当刀具前角由负值增加到正值,钛工件承受的压应力逐渐变为剪应力,正前角刀具更有利于切削,同时在不同的刀具前角下,切向力和法向力的大小也有显著变化。     

Carbon-sensitized and nitrogen-doped TiO2 for photocatalytic degradation of sulfanilamide under visible-light irradiation

A novel carbon-sensitized and nitrogen-doped TiO₂ (C/N-TiO₂) was synthesized by a facile sol-gel method using titanium butoxide as both titanium precursor and carbon source, and nitric acid as nitrogen source. The calcination temperature had a great effect on the crystal phase structure, nitrogen incorporation into the TiO₂ lattice and content of carbonaceous species. The incorporated carbonaceous species could serve as photosensitizer, while the nitrogen doping could lead to the remarkable red shift of absorption edge of C/N-TiO₂. The C/N-TiO₂ calcinated at 300 °C (T300) exhibited the highest photocatalytic activity for sulfanilamide (SNM) degradation under irradiation of visible-light-emitting diode (vis-LED). The SNM photocatalytic degradation and mineralization were more efficient in acidic conditions due to the carbon photosensitizing effect. Insignificant inhibitory effects were observed in the presence of chloride, nitrate and sulfate, while bicarbonate, phosphate and silica could inhibit the SNM mineralization to different degrees. Acetate, ammonium and sulfate were released during SNM mineralization. T300 exhibited good photochemical stability and could be reused for 5 times with less than 10% decrease in the SNM removal efficiency. The acute toxicity of SNM solution could be reduced over prolonged photocatalysis according to the Microtox assay.     

Degradation of paracetamol in aqueous solutions by TiO2 photocatalysis

In this study, photo/photocatalytic oxidation of common analgesic and antipyretic drug, paracetamol (acetaminophen), was investigated to determine the optimal operating conditions for degradation in water. UVA (365 nm) radiation alone degraded negligible amount of paracetamol, whereas paracetamol concentration decreased substantially under an irradiation of UVC (254 nm) with marginal changes in total organic carbon (TOC). In the presence of TiO2, much faster photodegradation of paracetamol and effective mineralization occurred; more than 95% of 2.0mM paracetamol was degraded within 80 min. The degradation rate constant decreased with an increase in the initial concentration of paracetamol, while it increased with light intensity and oxygen concentration. The degradation rate also increased with TiO2 loading until a concentration of 0.8 g L(-1). The degradation rate slowly increased between pH 3.5 and 9.5, but significantly decreased with increasing pH between 9.5 and 11.0. Based on the experimental data, a kinetic equation describing paracetamol photocatalytic degradation with various process parameters is obtained.     

Oxidation of sulfamethoxazole and related antimicrobial agents by TiO2 photocatalysis

The widespread detection of pharmaceutically active compounds, including many synthetic antimicrobial agents, in aquatic environments is raising public health concerns. As a result, there is growing interest in the development of innovative technologies to efficiently transform these compounds to non-toxic and pharmaceutically inactive byproducts. This work examines the photocatalytic degradation of sulfamethoxazole (SMX) and related sulfonamide antimicrobial agents in aqueous suspensions of nanophase titanium dioxide (TiO(2)). Experimental results demonstrate that SMX is mineralized by TiO(2) irradiated with ultraviolet-A light (UVA: 324相似文献   

Mechanism of kaolinite and titanium dioxide flocculation using chitosan--assistance by fulvic acids?

Flocculation of kaolinite using chitosan alone as flocculant has been reported to be difficult. Detailed investigations in our laboratory have shown that kaolinite can be easily removed from aqueous suspensions by flocculation and settling using chitosan, provided the suspension medium contains traces of dissolved humic substances. The flocculation is also extremely sensitive to the pH of the suspension. Removal of suspended titanium dioxide particles in water by flocculation using chitosan in presence of humic acids is also reported for the first time. A plausible mechanism explaining these observations is proposed in this paper.