Effect of TiO2 nanoparticle aggregation on marine microalgae Isochrysis galbana

TiO_2 nanoparticles(NPs) could adversely impact aquatic ecosystems. However, the aggregation of these NPs could attenuate this effect. In this work, the biological effects of TiO_2 NPs on a marine microalgae Isochrysis galbana were investigated. The aggregation kinetics of TiO_2 NPs under different conditions was also investigated to determine and understand these effects. Results showed that, though TiO_2 NPs had no obvious impact on the size and reproducibility of algal cells under testing conditions, they caused a negative effect on algal chlorophyll, which led to a reduction in photosynthesis. Furthermore, fast aggregation of TiO_2 NPs occurred under all conditions, especially at the pH close to the p Hzpc. Increasing ionic strength and NP concentration also enhanced the aggregation rate.The aggregation and the following sedimentation of TiO_2 NPs reduced their adverse effects on I. galbana.     

硫酸法钛白生产水洗工序清洁生产技术初探

通过开展水洗工段用水审计并试验了温度、偏钛酸ξ电位和漂白工艺对水洗的影响效果，从实践和理论上探讨了为其提高钛白质量改进水洗工艺的清洁生产方案的可行性和合理性。     

TiO2膜固载型多孔催化剂的光催化分解试验

以多孔基质为载体,用溶胶-凝胶法制备出载ＴｉＯ２薄膜的多孔型光催化剂。用Ｘ射线衍射和扫描电镜对催化剂的物相和形貌进行了表征，此催化剂能在光照下分解水溶液中四环素抗菌素。经１ｈ光照，四环素的分解率可达８５％左右。     

二氧化钛涂覆材料对甲苯的光催化降解作用

在自制的模拟小室中对二氧化钛涂覆材料的光催化性能进行了初步研究，在玻璃、瓷砖和日光灯这3种常见材料表面涂覆了二氧化钛，并以甲苯为模型化合物，测试了3种材料的净化性能。结果表明，3者对甲苯均有一定的降解效果，是有实用前景的光催化净化材料。     

4—氯苯甲酸钠的光催化氧化降解及其影响因素

本试验采用P－25TiO2，光催化剂，对4－氯苯甲酸钠的光催化氧化降解及污染物初始浓度，催化剂投加量和入射光强等因素的影响进行了研究，研究发现污染物初始降解速率与其初始浓度的关系遵循Langmuir-Hinshelwood模式，其中半饱和浓度常数Ks不仅是催化剂和污染物种类的函数，而且也是入射光强的函数，催化剂投加量存在一限值，当低于此限值时，污染物降解速率由于催化剂浓度的不足受到影响而下降，当高于此限值时，污染物降解速率受催化剂投加量的影响变小，在本试验4－CBA－Na浓度为0.15-0.6mmol／L时该催化剂限值浓度大约为0.4g/L，在入射光强为1-7mW/cm^2和催化剂浓度为0.4g／L下，污染物降解速率与光强成0.67次幂关系，经估算其量子效率为6．3％。     

Phenomenological compensation of thermally caused position and orientation errors of rotary axes

Thermal errors of machine tools are one of the major sources of inaccuracy. Therefore, the reduction of temperature induced deviations or the compensation of the resulting tool center point (TCP) errors have been of strong interest to the manufacturing industry for a couple of years. Up to now, the observation of the environment, the main spindle, the linear axes and the machine bed were in the focus of research, but with the rising demand for 5-axis machine tools and the increasing requirements regarding their accuracy, the analysis of the thermal behavior of rotary axes becomes more and more important. This paper gives an overview of corresponding thermal measurements of machine tools. The thermal behavior of rotary and swiveling axes is analyzed in detail. A simulation model and an approach for a phenomenological compensation of the TCP error are introduced and verified by measurements.     

Modulation-assisted high speed machining of compacted graphite iron (CGI)

The application of controlled, low-frequency modulation (～100 Hz) superimposed onto the cutting process in the feed-direction – modulation-assisted machining (MAM) – is shown to be quite effective in reducing the wear of cubic boron nitride (CBN) tools when machining compacted graphite iron (CGI) at high machining speeds (>500 m/min). The tool life is at least 20 times greater than in conventional machining. This significant reduction in wear is a consequence of the multiple effects realized by MAM, including periodic disruption of the tool–workpiece contact, formation of discrete chips, enhanced fluid action and lower cutting temperatures. The propensity for thermochemical wear of CBN, the principal wear mode at high speeds in CGI machining, is thus reduced. The tool wear in MAM is also found to be smaller at the higher cutting speeds (730 m/min) tested. The feed-direction MAM appears feasible for implementation in industrial machining applications involving high speeds.     

3D numerical investigation of thermally assisted high efficiency ductile machining of nanocrystalline hydroxyapatite

This study investigates the effects of four different variables (initial workpiece temperature, side rake angle, edge radius/feed rate, and nose radius/depth of cut) on ductile regime machining of a bioceramic material known as nanohydroxyapatite (nano-HAP) using 3D numerical simulation. AdvantEdge FEM Version 5.9 is used to conduct turning simulations of the nano-HAP workpiece. Tecplot 360 is used to analyze the results of the simulations. Because the workpiece is thin, the entire workpiece is set to a uniform initial temperature to simulate laser preheating of the material. Initial workpiece temperature, rake angle (side rake angle), edge radius, and nose radius are varied, and the effects of these operating conditions on critical feed are investigated. It is found that critical feed increases as initial workpiece temperature increases, and also as negativity of rake angle increases. For the edge radius, it is concluded that an initial increase causes an increase in critical feed – however, at some value of edge radius, critical feed shows no further increase; for the nose radius, critical feed appears to show no significant dependence.     

TiO₂-based nanoparticles released in water from commercialized sunscreens in a life-cycle perspective: structures and quantities

This work investigates the physical-chemical evolution during artificial aging in water of four commercialized sunscreens containing TiO₂-based nanocomposites. Sunscreens were analyzed in terms of mineralogy and TiO₂ concentration. The residues formed after aging were characterized in size, shape, chemistry and surface properties. The results showed that a significant fraction of nano-TiO₂ residues was released from all sunscreens, despite their heterogeneous behaviors. A stable dispersion of submicronic aggregates of nanoparticles was generated, representing up to 38 w/w% of the amount of sunscreen, and containing up to 30% of the total nano-TiO₂ initially present in the creams. The stability of the dispersion was tested as a function of salt concentration, revealing that in seawater conditions, a major part of these nano-TiO₂ residues will aggregate and sediment. These results were put in perspective with consumption and life cycle of sunscreens to estimate the amount of nano-TiO₂ potentially released into AQUATIC environment.     

Photocatalytic degradation of disperse blue 1 using UV/TiO2/H2O2 process

The photocatalytic degradation of a dye derivative, C.I. disperse blue 1 (1), has been investigated under UV light irradiation in the presence of TiO2 and H2O2 under a variety of conditions. The degradation was studied by monitoring the change in substrate concentration employing UV spectroscopic technique as a function of irradiation time. The degradation was studied under different conditions such as different types of TiO2, reaction pH, catalyst and substrate concentration containing hydrogen peroxide (H2O2), besides molecular oxygen in the presence of TiO2. The degradation of dye was also investigated under sunlight and the efficiency of degradation was compared with that of the artificial light source. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 was found to be more efficient for the degradation of the dye.