以玉米淀粉为原料,三聚磷酸钠为酯化剂,通过正交试验,采用半干法制备具有不同取代度的淀粉磷酸酯。考察酯化剂、催化剂用量及反应温度、时间、pH值等因素对产品取代度的影响。结果表明,半干法合成淀粉磷酸酯的最佳工艺条件为:反应温度14...以玉米淀粉为原料,三聚磷酸钠为酯化剂,通过正交试验,采用半干法制备具有不同取代度的淀粉磷酸酯。考察酯化剂、催化剂用量及反应温度、时间、pH值等因素对产品取代度的影响。结果表明,半干法合成淀粉磷酸酯的最佳工艺条件为:反应温度140℃,反应时间90 m in,pH 5.0,磷酸盐用量4%,尿素用量2%。展开更多
CaGdAlO4 ： Eu^3＋ powder phosphors were prepared using citrate sol-gel （CSG）, haft-dry and half-wet （HDW） and solid state （SS） methods, respectively. X-ray diffraction results confirm the formation of CaGdAlO4...CaGdAlO4 ： Eu^3＋ powder phosphors were prepared using citrate sol-gel （CSG）, haft-dry and half-wet （HDW） and solid state （SS） methods, respectively. X-ray diffraction results confirm the formation of CaGdAlO4：Eu^3＋ at 900 % （CSG）, 1200℃ （HDW） and 1400℃ （SS）, respectively. Field emission scan electron microscopy （FE-SEM） images show that the CaGdAlO4：Eu^3＋ powder prepared by the CSG and HDW method has an elliptical shape and that prepared under the SS method has a flaky shape. Upon excitation with 280 nm UV light, all the CaGdAlO4： Eu^3＋ powders show bright red emission on account of the 4f-4f transitions of the Eu^3＋ ions. Moreover, the size of the phosphor particles and the emission intensity increase with the increase of calcined temperature. At the same calcination temperature of 1400 ℃, the ^5D0→^7F2 emission intensity of the sample prepared by HDW method is the highest. Stark components of the ^5D0→^7FJ emission transitions, both at room temperature and at a low temperature, reveal that the Eu^3＋ ions occupy only one site with non-centrosymmetry in the crystals.展开更多
文摘以玉米淀粉为原料,三聚磷酸钠为酯化剂,通过正交试验,采用半干法制备具有不同取代度的淀粉磷酸酯。考察酯化剂、催化剂用量及反应温度、时间、pH值等因素对产品取代度的影响。结果表明,半干法合成淀粉磷酸酯的最佳工艺条件为:反应温度140℃,反应时间90 m in,pH 5.0,磷酸盐用量4%,尿素用量2%。
文摘CaGdAlO4 ： Eu^3＋ powder phosphors were prepared using citrate sol-gel （CSG）, haft-dry and half-wet （HDW） and solid state （SS） methods, respectively. X-ray diffraction results confirm the formation of CaGdAlO4：Eu^3＋ at 900 % （CSG）, 1200℃ （HDW） and 1400℃ （SS）, respectively. Field emission scan electron microscopy （FE-SEM） images show that the CaGdAlO4：Eu^3＋ powder prepared by the CSG and HDW method has an elliptical shape and that prepared under the SS method has a flaky shape. Upon excitation with 280 nm UV light, all the CaGdAlO4： Eu^3＋ powders show bright red emission on account of the 4f-4f transitions of the Eu^3＋ ions. Moreover, the size of the phosphor particles and the emission intensity increase with the increase of calcined temperature. At the same calcination temperature of 1400 ℃, the ^5D0→^7F2 emission intensity of the sample prepared by HDW method is the highest. Stark components of the ^5D0→^7FJ emission transitions, both at room temperature and at a low temperature, reveal that the Eu^3＋ ions occupy only one site with non-centrosymmetry in the crystals.
