Process Of The Ammonia Nitridation And Its Application In Phosphors And Visible Light Activity

In this paper,a-Si₃N₄ powder?white-emitting phosphors and nitrogen-doped titanium oxides were synthesized by the process of ammonia nitridation.The effects on structures and properties of reaction temperature?the ratio of raw materials?the concentration of additives and activators were studied by means of XRD?UV-vis?SEM?PL,et al.The production technology was simple and the operation was easy,and its cost was low,so it can be considered of good prospect for industrial application.1.?-Si₃N₄ powder was synthesized by the process of ammonia nitridation from crystalline silicon solar cells cutting sludge.The effects of temperature?1000??1200??1450???sintering atmosphere?NH₃?95%N₂+5%H₂?and additives on structural proterties of a-Si₃N₄ were studied in detail.It turned out that 1450? was the better ammonia nitriding temperature;NH₃ was better than 95%N₂+5%H₂;the urea was good to the nitridation of silicon.Nitriding for 4 h under the optimum conditions,the linear ?-Si₃N₄ crystals were obtained.The technology has overcome the limitation of conventional silicon nitride preparation and the production cost is low.2.Eu²⁺-activated white-emitting phosphors were synthesized by the ammonia nitridation at high temperature with the raw material of silicon powder from crystalline slilicon solar cells sludge.The effects of Eu²⁺ doping concentrations on structural and luminescent properties of phosphor were studied in detail.Results indicate that the principal crystalline phase of the sample is the mixture of Ca₂SiO₄.Ca₂Si₅O₈ and CaSiO₃;the optimum doping content of Eu²⁺ is 10.0mol%with the best luminous intensity.There were two luminescence centers in the host locating at 470nm and 570nm which exhibited different emitting intensity and stability,respectively.In terms of white-emitting LED application,Eu²⁺-doping phosphor was efficiently excited by near-ultraviolet light and emitted intense white light with a broad peak from 420nm to 670nm demonstrating CIE chromaticity coordinates of?0.3275,0.3866?and a color temperature of 5705K.The white-emitting phosphor has a promising prospect for its low cost.3.Nitrogen-doped TiO₂ photocatalysts were prepared under the process of ammonia nitridation with P25.The effects of temperature?450??500??550??600??650??and additives?urea?on structural proterties and photocatalytic performance of photocatalysts were studied in detail.The results show that 500? was the better ammonia nitriding temperature;the mole ratio of Ti to N was 1:2.The doping of nitrogen leads to an obvious increase in optical absorption intensity in the visible-light region from 380nm to 500nm.In the experiment of degredation of methyene blue,the degredation rate reaches 88.9%in 240min.