CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to invest...CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.展开更多
The titanium-based composites were synthesized by powder metallurgy method. The effects of composition and sintering temperature on the microstructure and properties of the titanium-based composites were investigated ...The titanium-based composites were synthesized by powder metallurgy method. The effects of composition and sintering temperature on the microstructure and properties of the titanium-based composites were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy and mechanical properties tests. The results demonstrate that adding ZrO2 particles can improve the mechanical properties of powder metallurgy （P/M） titanium-based composites. The Ti composite with 4% （mole fraction） ZrO2 sintered at 1100 °C for 4 h shows an appropriate mechanical property with a relative density of 93.9%, a compressive strength of 1380 MPa （570 MPa higher than pure Ti） and good plasticity （an ultimate strain above 24%）.展开更多
Coating titanium alloy with the bioceramic material hydroxyapatite(HAP) has been used to improve the poor osteoinductive properties of pure titanium alloy. But in clinical applications, the mechanical failure of HAP-c...Coating titanium alloy with the bioceramic material hydroxyapatite(HAP) has been used to improve the poor osteoinductive properties of pure titanium alloy. But in clinical applications, the mechanical failure of HAP-coated titanium alloy implant suffered at the interface of the HAP coatings and titanium alloy substrate will be a potential weakness in prosthesis. Yttria-stablized zirconia (YSZ) is expected to enhance the mechanical properties of the HAP coating and reduce the coefficient of thermal expansion difference between the coated layer and the substrate. These may reinforce the bonding strength between the coatings and the substrate. In this paper, HAP/YSZ composite coatings were cladded by laser. The effects of zirconia on the microstructure, mechanical properties and formation of tricalcium phosphate (TCP, Ca 3(PO 4) 2) of the HAP/YSZ composite coatings were evaluated. XRD, SEM and TEM were used to investigate the phase composition, microstructure and morphology of the coatings. The experimental results showed that adding YSZ in coatings was favorable to the composition and stability of HAP, and to the improvement of the adhesion strength, microhardness and microtoughness. A well uniform, crack-free coating of HAP/YSZ composites was formed on Ti-alloy substrate by laser cladding.展开更多
Zirconia-mullite composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk. The effects of TiO2 addition on the fabrication of zirconia-mullite composites were investigated....Zirconia-mullite composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk. The effects of TiO2 addition on the fabrication of zirconia-mullite composites were investigated. The ultra-fine zirconia-mullite composite ceramics were prepared from the amorphous bulk treated at 980 ℃ for nucleation and 1 140℃ for crystallization. The phase transformation of the ceramics was examined using differential scanning calorimetry （DSC） and X-ray diffractometry （XRD）. The microstructural features of the samples were evaluated with scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDX） and transmission electron microscopy （TEM）. The mechanical properties were also determined using Vickers indentation. The results show that the TiO2 additives with mass fraction of 1%-7% reduce the formation temperature of t-ZrO2 and mullite. When the mass fraction of TiO2 additives is less than 5%, the phases do not change, and most of TiO2 dissolves in ZrO2. When the mass fraction of TiO2 additives is over 5%, the excessive TiO2 forms a new phase, ZrTiO4. Meanwhile, the results also show that TiO2 additives have a great impact on the microstructure and mechanical properties of zirconia-mullite composites. As the TiO2 content increases from 1% to 7% （mass fraction）, the grain size and the Vickers hardness of zirconia-mullite composites increase. The composite with 3% （mass fraction） TiO2 additives attains relatively higher fracture toughness.展开更多
The design of hollow mesoporous nanostructures for cascade catalytic reactions can inject new vitality into the development of nanostructures. In this study, we report a versatile cooperative template-directed coating...The design of hollow mesoporous nanostructures for cascade catalytic reactions can inject new vitality into the development of nanostructures. In this study, we report a versatile cooperative template-directed coating method for the synthesis of hollow and yolk-shell mesoporous zirconium titanium oxide nanospheres with varying compositions （ZrO2 content from 0 to 100%）, high surface areas （465 m2·g-1） and uniform mesopores. In particular, the hexadecylamine （HDA） used in the coating procedure serves as a soft template for silica@mesostructured metal oxide core-shell nanosphere formation. By a facile solvothermal treatment route with an ammonia solution and calcination in air, the silica@mesostructured zirconium titanium oxide spheres can be converted into highly uniform hollow zirconium titanium oxide spheres. By simply replacing hard template silica nanospheres with core-shell silica nanocomposites, the synthesis approach can be further used to prepare yolk-shell mesoporous structures through the coating and etching process. The approach is similar to the preparation of mesoporous silica nanocomposites from the self-assembly of the core, the soft template cetyltrimethylammonium bromide （CTAB） and a silica precursor and can be extended as a general method to coat mesoporous zirconium titanium oxide on other commonly used hard templates （e.g., mesoporous silica spheres, mesoporous organosilica ellipsoids, polymer spheres, and carbon nanospheres）. The presence of highly permeable mesoporous channels in the zirconium titanium oxide shells has been demonstrated by the reduction of 4-nitrophenol with yolk-shell Au@mesoporous zirconium titanium oxide as the catalyst. Moreover, a cascade catalytic reaction including an acid catalyzed step and a catalytic hydrogenation to afford benzimidazole derivatives can be carried out very effectively by using the accessible acidity of the yolk-shell structured mesoporous zirconium titanium oxide spheres containing a Pd core as a bifunctional catalyst, which makes the hollow zirconium titanium oxide spheres a practicable candidate for advanced catalytic systems.展开更多
基金supported by the Major Research Program of Sichuan Province Science and Technology Department (2012FZ0008)the National Natural Science Foundation of China (21173153)+1 种基金the National High Technology Research and Development Program of China (863 Program,2013AA065304)the Sichuan University Research Foundation for Young Teachers (2015SCU11056)~~
文摘CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.
文摘The titanium-based composites were synthesized by powder metallurgy method. The effects of composition and sintering temperature on the microstructure and properties of the titanium-based composites were investigated by X-ray diffraction, optical microscopy, scanning electron microscopy and mechanical properties tests. The results demonstrate that adding ZrO2 particles can improve the mechanical properties of powder metallurgy （P/M） titanium-based composites. The Ti composite with 4% （mole fraction） ZrO2 sintered at 1100 °C for 4 h shows an appropriate mechanical property with a relative density of 93.9%, a compressive strength of 1380 MPa （570 MPa higher than pure Ti） and good plasticity （an ultimate strain above 24%）.
文摘Coating titanium alloy with the bioceramic material hydroxyapatite(HAP) has been used to improve the poor osteoinductive properties of pure titanium alloy. But in clinical applications, the mechanical failure of HAP-coated titanium alloy implant suffered at the interface of the HAP coatings and titanium alloy substrate will be a potential weakness in prosthesis. Yttria-stablized zirconia (YSZ) is expected to enhance the mechanical properties of the HAP coating and reduce the coefficient of thermal expansion difference between the coated layer and the substrate. These may reinforce the bonding strength between the coatings and the substrate. In this paper, HAP/YSZ composite coatings were cladded by laser. The effects of zirconia on the microstructure, mechanical properties and formation of tricalcium phosphate (TCP, Ca 3(PO 4) 2) of the HAP/YSZ composite coatings were evaluated. XRD, SEM and TEM were used to investigate the phase composition, microstructure and morphology of the coatings. The experimental results showed that adding YSZ in coatings was favorable to the composition and stability of HAP, and to the improvement of the adhesion strength, microhardness and microtoughness. A well uniform, crack-free coating of HAP/YSZ composites was formed on Ti-alloy substrate by laser cladding.
基金Project(50721003) supported by the National High Technology Research and Development Program of China for Creative Research Group
文摘Zirconia-mullite composite ceramics were fabricated by in-situ controlled crystallization of Si-Al-Zr-O amorphous bulk. The effects of TiO2 addition on the fabrication of zirconia-mullite composites were investigated. The ultra-fine zirconia-mullite composite ceramics were prepared from the amorphous bulk treated at 980 ℃ for nucleation and 1 140℃ for crystallization. The phase transformation of the ceramics was examined using differential scanning calorimetry （DSC） and X-ray diffractometry （XRD）. The microstructural features of the samples were evaluated with scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDX） and transmission electron microscopy （TEM）. The mechanical properties were also determined using Vickers indentation. The results show that the TiO2 additives with mass fraction of 1%-7% reduce the formation temperature of t-ZrO2 and mullite. When the mass fraction of TiO2 additives is less than 5%, the phases do not change, and most of TiO2 dissolves in ZrO2. When the mass fraction of TiO2 additives is over 5%, the excessive TiO2 forms a new phase, ZrTiO4. Meanwhile, the results also show that TiO2 additives have a great impact on the microstructure and mechanical properties of zirconia-mullite composites. As the TiO2 content increases from 1% to 7% （mass fraction）, the grain size and the Vickers hardness of zirconia-mullite composites increase. The composite with 3% （mass fraction） TiO2 additives attains relatively higher fracture toughness.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 21171064 and 21071059）.
文摘The design of hollow mesoporous nanostructures for cascade catalytic reactions can inject new vitality into the development of nanostructures. In this study, we report a versatile cooperative template-directed coating method for the synthesis of hollow and yolk-shell mesoporous zirconium titanium oxide nanospheres with varying compositions （ZrO2 content from 0 to 100%）, high surface areas （465 m2·g-1） and uniform mesopores. In particular, the hexadecylamine （HDA） used in the coating procedure serves as a soft template for silica@mesostructured metal oxide core-shell nanosphere formation. By a facile solvothermal treatment route with an ammonia solution and calcination in air, the silica@mesostructured zirconium titanium oxide spheres can be converted into highly uniform hollow zirconium titanium oxide spheres. By simply replacing hard template silica nanospheres with core-shell silica nanocomposites, the synthesis approach can be further used to prepare yolk-shell mesoporous structures through the coating and etching process. The approach is similar to the preparation of mesoporous silica nanocomposites from the self-assembly of the core, the soft template cetyltrimethylammonium bromide （CTAB） and a silica precursor and can be extended as a general method to coat mesoporous zirconium titanium oxide on other commonly used hard templates （e.g., mesoporous silica spheres, mesoporous organosilica ellipsoids, polymer spheres, and carbon nanospheres）. The presence of highly permeable mesoporous channels in the zirconium titanium oxide shells has been demonstrated by the reduction of 4-nitrophenol with yolk-shell Au@mesoporous zirconium titanium oxide as the catalyst. Moreover, a cascade catalytic reaction including an acid catalyzed step and a catalytic hydrogenation to afford benzimidazole derivatives can be carried out very effectively by using the accessible acidity of the yolk-shell structured mesoporous zirconium titanium oxide spheres containing a Pd core as a bifunctional catalyst, which makes the hollow zirconium titanium oxide spheres a practicable candidate for advanced catalytic systems.
