Trivalent dysprosium(Dy) activated nanocrystalline yttrium vanadate(YVO) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrar...Trivalent dysprosium(Dy) activated nanocrystalline yttrium vanadate(YVO) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVOnanocrystals are agglomerated. EDAX confirms the formation of YVO:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm. Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F→~6 Hhyper sensitive transition of Dyions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.展开更多
This work described the preparation of dysprosium oxide, Dy203, nanoparticles using the homogeneous precipitation method. Dy3＋ ions were precipitated using NaOH solution. The obtained product was filtered, dried, and...This work described the preparation of dysprosium oxide, Dy203, nanoparticles using the homogeneous precipitation method. Dy3＋ ions were precipitated using NaOH solution. The obtained product was filtered, dried, and then calcined for 1 h at the temperature range of 300-700 ℃ in static air. The calcination temperature of the Dy-precttrsor was chosen based on its decomposi- tion as indicated by the TGA analysis. The crystalline structure and surface morphology of the calcined solids were studied by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM） and X-ray pho- toelectron spectroscopy （XPS）. The obtained results revealed that Dy203 with crystallites size of 11-21 nm was formed at 500 ℃. Such value increased to 25-37 nm for the sample calcined at 700 ℃.展开更多
A Co32Ni21Cr8Al0.6Y （wt.%） alloy with and without doping 3 wt.% platinum, or co-doping 3 wt.% platinum and 0.1 wt.% dys- prosium was produced by arc melting. The hardness of both base alloy and composition-modified ...A Co32Ni21Cr8Al0.6Y （wt.%） alloy with and without doping 3 wt.% platinum, or co-doping 3 wt.% platinum and 0.1 wt.% dys- prosium was produced by arc melting. The hardness of both base alloy and composition-modified alloy was measured by using a Vickers hardness tester. Isothermal oxidation tests at 1000 ℃ in static air atmosphere were conducted to assess the isothermal oxidation behavior of the alloys. The microstructure and composition of the tested alloys before and after oxidation were investigated by means of X-ray diffraction （XRD）, field emission-scanning electron microscopy （FE-SEM） equipped with energy dispersive spectroscopy （EDS） and back scatter detec- tor. Results showed that platinum had significant influence on microstructure of the tested alloy by the formation of β-（Ni,Pt）AI phase. Addi- tion of 3 wt.% platinum could slightly increase the hardness of the tested alloy. Platinum accelerated phase transformation of alumina from metastable θ-Al2O3 to stable α-Al2O3 and suppressed the consumption of 13-phase. Co-doping both 3 wt.% platinum and 0.1 wt.% dysprosium induced the fastest transformation of θ- to α- alumina and the formation of a fine-grained oxide scales. The most effective reduction of oxida- tion rate was achieved by the Pt-Dy co-doping effects.展开更多
基金the Ministry of Education, Youth and Sport of the Czech Republic for support through project CZ.1.07/2.3.00/30.0005, as well as the Central European Institute of Technology (CEITEC)
文摘多相光催化是一种非常有效的降解各种水污染物的方法.本文以稀土(镝和镨)掺杂的TiO2为光催化剂,考察了制备条件对其物理性质和光催化性能的影响.采用溶胶-凝胶法和不同条件(反应温度450,550,650 oC;反应时间4,8,12 h)的固态反应法制备了TiO2样品.运用X射线衍射分析了该样品的晶相,发现只存在锐钛矿相,并得到Raman光谱的证实.同时采用扫描电镜观察了样品的结构和粒径;以BET法计算了其比表面积;运用紫外-可见光漫反射光谱测得了样品的带隙能量.通过测量紫外光照射下常用除草剂吡唑草胺的降解速率评价了样品的光催化活性,反应过程中吡唑草胺的浓度用高效液相色谱分析.结果表明,稀土掺杂使得TiO2吸收边红移,并提高了其光催化活性;制备时最优的固态反应条件为550 oC反应8 h.
文摘Trivalent dysprosium(Dy) activated nanocrystalline yttrium vanadate(YVO) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVOnanocrystals are agglomerated. EDAX confirms the formation of YVO:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm. Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F→~6 Hhyper sensitive transition of Dyions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.
文摘This work described the preparation of dysprosium oxide, Dy203, nanoparticles using the homogeneous precipitation method. Dy3＋ ions were precipitated using NaOH solution. The obtained product was filtered, dried, and then calcined for 1 h at the temperature range of 300-700 ℃ in static air. The calcination temperature of the Dy-precttrsor was chosen based on its decomposi- tion as indicated by the TGA analysis. The crystalline structure and surface morphology of the calcined solids were studied by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM） and X-ray pho- toelectron spectroscopy （XPS）. The obtained results revealed that Dy203 with crystallites size of 11-21 nm was formed at 500 ℃. Such value increased to 25-37 nm for the sample calcined at 700 ℃.
基金Project supported by National Natural Science Foundation of China (51071089)
文摘A Co32Ni21Cr8Al0.6Y （wt.%） alloy with and without doping 3 wt.% platinum, or co-doping 3 wt.% platinum and 0.1 wt.% dys- prosium was produced by arc melting. The hardness of both base alloy and composition-modified alloy was measured by using a Vickers hardness tester. Isothermal oxidation tests at 1000 ℃ in static air atmosphere were conducted to assess the isothermal oxidation behavior of the alloys. The microstructure and composition of the tested alloys before and after oxidation were investigated by means of X-ray diffraction （XRD）, field emission-scanning electron microscopy （FE-SEM） equipped with energy dispersive spectroscopy （EDS） and back scatter detec- tor. Results showed that platinum had significant influence on microstructure of the tested alloy by the formation of β-（Ni,Pt）AI phase. Addi- tion of 3 wt.% platinum could slightly increase the hardness of the tested alloy. Platinum accelerated phase transformation of alumina from metastable θ-Al2O3 to stable α-Al2O3 and suppressed the consumption of 13-phase. Co-doping both 3 wt.% platinum and 0.1 wt.% dysprosium induced the fastest transformation of θ- to α- alumina and the formation of a fine-grained oxide scales. The most effective reduction of oxida- tion rate was achieved by the Pt-Dy co-doping effects.
