Volatile organic compounds (VOCs), especially toluene as the typical indoor air pollutants, are toxic and environmentally persistent whose removal is undoubtedly becoming increasingly urgent matter over these years. Titania is one of the most promising photocatalysts for the degradation of organic compounds, whereas the large band gap of titania and massive recombination of photogenerated charge carriers limit its overall photocatalytic effciency. These defects can be tackled by modifying the electronic band structure of titania including various strategies like metal deposition, non-metal atoms substitution, transition metal ions doping, and coupling with a narrow band gap semiconductor, etc. This review encompasses several advancements made in these aspects, and also the influence factors such as physical morphologies changing, humidity, as well as the presence of O2 etc, are involved. To be practically considering, TiO2 photocatalysts require being fixed on the bulky supports like silica, alumina, clays and activated carbons. Moreover, photocatalytic coatings deposited on external building materials, like roofing tiles and corrugated sheets, is becoming the attractive application potentials to remove toluene from air.
According to the conceptual model of high-level radioactive waste (HLW) geological disposal, first, HLW is carried out solidification treatment. Radioactive nuclide was simulated by Cerium (Ce), and Ce was solidified in the zirconite ceramic, solidified bodies of zircon ceramic with Ce were prepared by sol-gel method. In this paper, the basic principle and technological process of ceramic solidification is introduced. The samples were characterized and analyzed by XRD, SEM and EPMA, etc.. The results show that, the surface properties of ceramic tablet is better, and with high shrinkage after sintering, the lower compression force, the higher shrinkage of the ceramic tablet. Most of the diameter of Ceramic grains are in the range of 0.5-5 μm, existing some amorphous phase among the grains. Washing by ammonia, crystallization degree of sample is higher than without treatment, and can form crystals of (Zr,Ce) O2and (Zr, Ce) SiO4.
Yttrium Aluminium Garnet (YAG) has a extensive applications in many fields because of its excellent properties. In this study the products synthesized by co-precipitation method is regular, and the reaction is complete, the YAG ceramic obtained is white, its density is 2.42g/cm3 and shrinkage is 7.78%. The YAG ceramic tablets were investigated by Field emission scanning electron microscopy (FE-SEM), Electron probe microanalysis (EPMA) and X-ray diffractometer (XRD). The results show that the structure of YAG ceramic is loose with spherical grain size of 0.2-0.3μm. The main mineral phase of YAG ceramic is composed of polycrystalline Al5Y3O12 with good crystallinity, and containing very small amount of unreacted alumina and other impurities.
Bentonite has been regarded as buffer material for high-level radioactive waste (HLW) disposal all over the world, plenty of decay heat released from HLW is conducted through butter material, therefore, thermal conduction of compacted bentonite is very important. This study presents compacted GMZ Na-bentonite(with 8.9% water content, 1.8 g/cm3 compacting density) temperature and relative humidity change pattern with time and position variation taking intermittent warming method and using thermal conduction equipment, it is designed according to the conceptual model of HLW geological disposal repository. The results show that the temperature achieve a balance quickly, the temperature of compacted bentonite block which the distance is 2 cm to heat source reaches the first about 55°C balance stage after about 40 hours, radial temperature gradient (GT) increases with the temperature rising, average of GT during the first stage is 0.85°C/cm, average of GT during the second balance stage about 82°C is 1.57°C/cm; Affected by temperature, relative humidity increase rapidly at the beginning with the temperature rising, when the temperature reaches equilibrium, the relative humidity decreases slowly, the higher temperature of the compacted bentonite block is, the lower relative humidity is, the radial gradient of relative humidity (GHR) increase with heating time, average of GHR during the first stage about 55 °C is 1.32%/cm, average of GHR during the second stage about 82°C is 1.89 %/cm.
Fe-Al-WC composite materials were synthesized via Spark Plasma Sintering process. These obtained Fe-Al-WC composite materials have a nearly full density and uniform hardness distribution. SPS parameters namely relative atomic ratio of WC, sintering temperature and axial pressure were optimized through gray relational analysis with the considerations of multiple performance characteristics including average and mean square deviation of the micro hardness of every sample and their volume density. The result indicated that this SPS process could be improved effectively through this approach, which was useful in the optimization of SPS parameters for synthesizing Fe-Al-WC composite materials.
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