纳米晶ZrO2∶Dy3+的制备与发光性质研究

利用共沉淀法制备了纳米晶ZrO2∶Dy3+发光粉体,对不同掺杂浓度、不同煅烧温度的系列样品,均观测到Dy3+离子的室温强特征发射.样品的晶相与发射性质的研究表明:所制备的样品经600℃~950 ℃热处理后,晶相经历从四方相到以单斜相为主的变化;由于晶相的变化,发现有两个发光中心,分别位于四方相和单斜相.激发Dy3+的6P7/2能级,当稀土离子处在四方相(格位一)时有利于483 nm和583 nm的发射,当稀土离子处在单斜相(格位二)时有利于490 nm和577 nm的发射.基质ZrO2和Dy3+离子之间有能量传递,950℃时能量传递效果最好.荧光强度与掺Dy3+离子浓度关系表明,Dy3+在纳米晶ZrO2中的最适合掺杂浓度与ZrO2的晶相有关,四方相时,最适合掺杂浓度为0.5%,混合相时为1%.     

Investigation into the photo-induced change in wettability of hydrophobized TiO2 films

The photo-induced change in wettability of hydrophobized TiO₂ films has been investigated for steel coated with acidic TiO₂ nanosols containing varying concentrations of dispersed nanocrystalline titania, such as Degussa P25. The photo-induced change in wettability was evaluated by measuring the time-dependent drop of water contact angle (WCA) after samples had been soaked in either n-octyltriethoxysilane (OTS) or decanoic acid (DA). TiO₂ films treated in this way exhibit superhydrophobic behaviour, with WCA greater than 160°. After radiation with UV (black light), the superhydrophobic properties are transformed into superhydrophilic properties, with WCA of almost 0°. As P25 content and layer thickness increase, high rates of photo-induced change are found, but a moderate calcination regime is required. On the other hand, hardness and E modulus pass through a maximum at 25 wt% P25, so that a P25 content between 25 and 50 wt% is the optimum for practical uses. With such stable coatings, wettability can be controlled over a wide range, and the switch between hydrophobic and hydrophilic states can be carried out repeatedly when DA is used as the hydrophobizing agent. Use of a low calcination temperature (450 °C) for the intermediate annealing of the single layers in multilayer coatings and a short final sintering step at a relatively high temperature (e.g. 630 °C for 10 min) allow the preparation of relatively thin TiO₂ films on steel with a high photoactivity.     

Rare-earth iron-based intermetallic compounds and their carbides: Structure and magnetic behaviors

The structural and magnetic properties of Sm₂Fe_17-xMo_x, its out of equilibrium precursor SmFe_9-yMo_y and their carbides are investigated by means of powder X-ray diffraction, magnetic measurements and high-resolution transmission electron microscopy. The structure of the nanocrystalline Sm_1-s(Fe,Mo)_5+2s alloys are governed by the s Sm vacancy rate and the x amount of Mo. In this work, the Rietveld analysis shows that for s=0.33 the structure is of Th₂Zn₁₇-type and P6/mmm with the stoichiometry 1/9 for s=0.36. Moreover, it points out a lattice expansion along the c-axis after Mo substitution for Fe and reveals a 6c preferential occupation for Mo atoms in structure, and 2e for the out of equilibrium hexagonal precursor. Upon carbon insertion, the lattice expansion favors the Curie temperature increase up to 35% for Sm₂Fe_16.42Mo_0.58C₂ and 49% for the metastable SmFe_8.7Mo_0.3C carbide. The Curie temperature and the coercive field of the 1/9 carbides are higher than those of 2/17 ones. This makes the out of equilibrium hexagonal precursor a competitive candidate for use as permanent magnet.     

Magneto recyclable,green fabricated Fe3O4 nanorods on photo responsive of textile dye degradation and identification products by LC-MS

Prior to being released towards water sources such as rivers, lakes, and groundwater, the efficient technique of removing color out textile effluents seems to have become widely used. Such contaminants are extremely difficult for traditional wastewater treatment methods to completely eliminate. This innovative development of phytonutrients uses Fe₃O₄ nanorods, that have been employed as photocatalytic to change substrate colors in the aqueous layer when exposed to light. Given prominence was adopted to incorporate phytonutrients with Fe3O4 nanorods. The degradation of the methyl violet colour has been acknowledged by the depletion of the UV light (UV) absorption edge that also originated at 581 nm. The significant colour expulsion of the Fe3O4 nanorod was proved to really be 97% after 60 min. The findings demonstrate that ecologically responsible Fe₃O₄ nanorods are immensely beneficial in the photocatalytic reaction of harmful pollutants.