La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(...La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(3)catalysts were characterized by XRD and H_(2) temperature-programmed reduction (TPR).The effects of reaction temperature,oxygen concentration,and gas flow rate on the direct decomposition of nitric oxide over the synthesized catalysts were studied under microwave irradiation (2.45 GHz).The XRD results indicated that the La_(0.8)A_(0.2)NiO_(3) catalysts formed an ABO_(3) perovskite structure,and the H_(2)-TPR results revealed that the relative reducibility of the catalysts increased in the order of La_(0.8)K_(0.2)NiO_(3)>La_(0.8)Ba_(0.2)NiO_(3)>La_(0.8)Y_(0.2)Ni O_(3).Under microwave irradiation,the highest NO conversion amounted to 98.9%,which was obtained with the La_(0.8)K_(0.2)NiO_(3) catalyst at 400℃.The oxygen concentration did not inhibit the NO decomposition on the La_(0.8)A_(0.2)NiO_(3) catalysts,thus the N_(2) selectivity exceeded 99.8%under excess oxygen at 550℃.The NOconversion of the La_(0.8)A_(0.2)NiO_(3) catalysts decreased linearly with the increase in the gas flow rate.展开更多
Microwave-absorbing properties of iron fibers can be adjusted by their aspect ratio. This paper presents several modification techniques for grinding long iron fibers to a suitable aspect ratio. The grinding instrumen...Microwave-absorbing properties of iron fibers can be adjusted by their aspect ratio. This paper presents several modification techniques for grinding long iron fibers to a suitable aspect ratio. The grinding instruments include pulsator, jet mill and muller. The aspect ratio distribution, microstructure, electromagnetic parameter and reflectivity of the samples were analyzed and discussed in detail. The results show that the fractions of 5〈aspect ratio〈40 for the three methods are 69.03%, 81.11% and 80.2% , respectively, that is, suitable short iron fibers can be obtained by the jet mill and muller. Furthermore, the short iron fibers milled by jet mill and muller have better absorbing propterties than those obtained by the pulsator under the same condition. Therefore, their microwave absorption properties can be improved by regulating the electromagnetic parameters with grinding.展开更多
文摘La_(0.8)A_(0.2)NiO_(3) (A=K,Ba,Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method.The crystalline phase and the catalytic activity of the La_(0.8)A_(0.2)NiO_(3)catalysts were characterized by XRD and H_(2) temperature-programmed reduction (TPR).The effects of reaction temperature,oxygen concentration,and gas flow rate on the direct decomposition of nitric oxide over the synthesized catalysts were studied under microwave irradiation (2.45 GHz).The XRD results indicated that the La_(0.8)A_(0.2)NiO_(3) catalysts formed an ABO_(3) perovskite structure,and the H_(2)-TPR results revealed that the relative reducibility of the catalysts increased in the order of La_(0.8)K_(0.2)NiO_(3)>La_(0.8)Ba_(0.2)NiO_(3)>La_(0.8)Y_(0.2)Ni O_(3).Under microwave irradiation,the highest NO conversion amounted to 98.9%,which was obtained with the La_(0.8)K_(0.2)NiO_(3) catalyst at 400℃.The oxygen concentration did not inhibit the NO decomposition on the La_(0.8)A_(0.2)NiO_(3) catalysts,thus the N_(2) selectivity exceeded 99.8%under excess oxygen at 550℃.The NOconversion of the La_(0.8)A_(0.2)NiO_(3) catalysts decreased linearly with the increase in the gas flow rate.
文摘Microwave-absorbing properties of iron fibers can be adjusted by their aspect ratio. This paper presents several modification techniques for grinding long iron fibers to a suitable aspect ratio. The grinding instruments include pulsator, jet mill and muller. The aspect ratio distribution, microstructure, electromagnetic parameter and reflectivity of the samples were analyzed and discussed in detail. The results show that the fractions of 5〈aspect ratio〈40 for the three methods are 69.03%, 81.11% and 80.2% , respectively, that is, suitable short iron fibers can be obtained by the jet mill and muller. Furthermore, the short iron fibers milled by jet mill and muller have better absorbing propterties than those obtained by the pulsator under the same condition. Therefore, their microwave absorption properties can be improved by regulating the electromagnetic parameters with grinding.
