Near-infrared to visible up-conversion emissions of Er^3＋ doped Al2O3 powders derived from the sol-gel method

The Er3 doped Al2O3 powders were prepared by the sol-gel method using the aluminium isopropoxide [Al(OC3H7)3]-derived Al2O3 sols with addition of the erbium nitrate [Er(NO3)3.5H2O]. The different phase structure, including three crystalline types of (Al,Er)2O3 phases, γ, θ, α, and two Er-Al-O phases, ErAlO3 and Al10Er6O24, was obtained with the 1 mol% Er3 doped Al2O3 powders at the different sintering temperatures of 600―1200℃. The green and red up-conversion emissions centered at about 523, 545 and 660 nm, corresponding respectively to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3 , were detected by a 978 nm semiconductor laser diodes excitation. The phase structure and OH content had evident influence on the up-conversion emissions intensity. The maximum intensities of both the green and red emissions were obtained respectively for the Er3 doped Al2O3 powders sintered at 1200 ℃, which was composed mainly of α-(Al,Er)2O3, less of ErAlO3 and Al10Er6O24 phases, and with the least OH content. The two-photon absorption up-conversion process was involved in the green and red up-conversion emissions of the Er3 doped Al2O3 powders.     

Effects of Yb～(3 ) codoping on visible and near infrared emissions of Er～(3 )-Yb～(3 ) codoped Al_2O_3 powders by the sol-gel method

The 0.1 mol% Er3 and 0―2 mol% Yb3 codoped Al2O3 powders were prepared by the sol-gel method,and the phase structure,including only two crystalline types of doped Al2O3 phase,γ-(Al,Er,Yb)2O3 and θ-(Al,Er,Yb)2O3,was detected at the sintering temperature of 1000℃. The visible and near infrared emissions properties depended strongly on the Yb3 codoping,and the corresponding maximal peak intensities centered at about 523,545,660 and 1533 nm were obtained respectively for the 0.1 mol% Er3 and 0.5 mol% Yb3 codoped Al2O3 powders,which were composed of θ-(Al,Er,Yb)2O3 and a small amount of γ-(Al,Er,Yb)2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions,and the one-photon absorption process was involved in the near infrared emissions of the Er3 -Yb3 codoped Al2O3 powders.     

直流电弧放电法制备Er^3＋-Yb^3＋：Al2O3纳米粒子的上转换发光特性研究

采用直流电弧放电法成功制备了粒度约60nm的Er^3＋-Yb^3＋共掺杂Al2O3纳米粒子.通过978nm激光二极管（LD）激发,获得位于526,547nm的绿色和677nm的红色上转换发光,分别对应于Er3＋的2H11/2→^4 I15/2,^4 S3/2→^4 I15/2和^4 F9/2→^4 I15/2跃迁.退火对于样品的上转换发光具有较大影响：退火前,红色发光明显,退火后则以绿色发光为主.（ErYb）3Al5O12和α-（Al,Er,Yb）2O3混合相中增强的激发态吸收^4I11/2＋光子→^4F7/2和能量传递^2F5/2（Yb^3＋）＋^4I11/2（Er^3＋）→^2F7/2（Yb^3＋）＋^4F7/2（Er^3＋）过程导致绿色上转换发光显著增加.绿色和红色上转换发光过程均为双光子上转换吸收.结果表明直流电弧放电法是一种极具发展潜力的光学材料制备方法.     

花状Sr3Al2O6：Eu^2＋晶体的干燥方式与发光性能

为研究稀土发光纳米晶的微观结构和形貌对发光性能的影响,用凝胶-微波干燥法和凝胶-烘箱干燥法制备了花状形貌的Sr3Al2O6晶体．研究了微波干燥和烘箱干燥两种不同的干燥方式对溶胶-凝胶法制备的Sr3Al2O6：Eu^2＋发光粉体粒径、形貌、团聚程度、干燥时间及发光性能等的影响,结果表明采用微波干燥不仅可以大大缩短干燥所需时间,而且有利于减弱Sr3Al2O6：Eu^2＋发光粉料的团聚和团聚程度,制得了颗粒分散均匀、团聚程度低、发光强度高的Sr3Al2O6：Eu^2＋花状形貌粉体．研究了Sr3Al2O6：Eu^2＋发光粉体的新型形貌对发光性能的影响,微波干燥法制备的均匀分散的花状形貌发光粉体发光强度高,余辉时间长达20min．     

Al2O3-Cr2O3固溶体烧结动力学研究

以纳米η-Al2O3与工业铬绿为原料,采用固相烧结的方法制备Al2O3-Cr2O3固溶体.以聚乙烯醇为结合剂,经过冷等静压成型后,分别以埋碳和空气两种气氛在1400～1600℃常压烧结.研究不同气氛、不同温度下试样的性能、显微结构和烧结动力学.在烧结过程中,随温度升高,两种不同气氛的Al2O3-Cr2O3固溶体晶粒生长指数减小,晶粒生长活化能下降.埋碳气氛下Al2O3-Cr2O3固溶体平均晶粒生长指数为1.763,晶粒生长主要受晶界的曲率和一小部分体积扩散控制;空气气氛下Al2O3-Cr2O3固溶体平均晶粒生长指数为3.454,晶粒生长主要受离子随机越过晶界和体积扩散控制.对比晶粒生长活化能发现,空气气氛更有利于Al2O3-Cr2O3固溶体晶粒的生长发育,但当温度过高时应考虑CrO3的挥发对晶粒生长的影响.     

Effect of CuO addition on the sintering temperature and microwave dielectric properties of CaSiO3– Al2O3 ceramics

CuO-doped CaSiO3–1 wt% Al2O3 ceramics were synthesized via a traditional solid-state reaction method, and their sintering behavior,microstructure and microwave dielectric properties were investigated. The results showed that appropriate CuO addition could accelerate the sintering process and assist the densification of CaSiO3–1 wt% Al2O3 ceramics, which could effectively lower the densification temperature from1250 1C to 1050 1C. However, the addition of CuO undermined the microwave dielectric properties. The optimal amount of CuO addition was found to be 0.8 wt%, and the derived CaSiO3–Al2O3ceramic sintered at 1100 1C presented good microwave dielectric properties of εr?7.27,Q f?16,850 GHz and τf? 39.53 ppm/1C, which is much better than those of pure CaSiO3 ceramic sintered at 1340oC(Q f?13,109 GHz).The chemical compatibility of the above ceramic with 30 Pd/70 Ag during the cofiring process has also been investigated, and the result showed that there was no chemical reaction between palladium–silver alloys and ceramics.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

高Al2O3炉渣脱硫能力的研究

针对目前高炉的冶炼条件,分析高炉炉渣中Al2O3的来源以及对炉渣脱硫的危害。从热力学和动力学角度分析了Al2O3对炉渣脱硫能力的影响。通过实验研究了Al2O3含量以及MgO／Al2O3对炉渣脱硫能力的影响。实验结果表明Al2O3含量过高不利于高炉渣的脱硫。Mg0／Al2O3适当提高可以增强Al2O3含量较高时炉渣的脱硫能力。     

溶胶-凝胶法制备Al2O3超细粉体

以硝酸铝为原料,柠檬酸为络合剂,采用溶胶-凝胶法制备Al2O3超细粉体,用X射线衍射仪、透射电子显微镜对粉体的晶体结构、粒径及形貌进行表征.考察了柠檬酸用量以及焙烧温度对A12O3粉体的物相、形貌特征的影响.结果表明:硝酸铝与柠檬酸的摩尔比为1:3,pH值为l时,可制备稳定的溶胶,溶胶经过120℃恒温干燥12 h后得到...     

Al2O3晶体中Cu3+离子自旋哈密顿参量及其局域结构研究

利用自旋哈密顿理论,在建立Al2O3Cu3+晶体结构和自旋哈密顿参量之间的定量关系的基础上,采用掺杂离子位移模型,统一计算了Al2O3Cu3+晶体的自旋哈密顿参量,解决了前人工作中可调参量过多的问题.理论结果与实验数据符合很好,说明采用的模型是合理的.结果表明,Cu3+离子掺入Al2O3基质晶体后,并没有准确占据Al3+格位,而是沿C3轴移动了0.0179nm.     

Al2O3无机膜的制备和微观结构表征

以异丙醇铝为主要原料,用溶胶-凝胶法制备Al2O3膜,考察胶溶剂的种类和用量、水解温度、回流时间等制备条件对Al2O3膜微观结构的影响.研究结果表明,选择用HNO3作为胶溶剂,HNO3用量在0.25～0.30(摩尔分数)、加水量为100(摩尔分数)、水解温度为80℃左右、回流时间为10h左右,可以制得微观结构性能比较好的Al2O3膜.     

Up-conversion luminescence of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4

The synthesis and up-conversion luminescent properties of YTaO4：Er^3＋ and YTaO4：Er^3＋/Yb^3＋ are reported for the first time. According to the measurement results of up-conversion spectra, Yb^3＋ co-doping can remarkably enhance the green （^2H11/2/^4S3/2→^4I15/2） and red （^4F9/2→^4I15/2） emissions, but depress the infrared emission （^4I9/2→^4I15/2）. With the increase of the Yb^3＋ concentration, the intensity of green emission increases, after that, when the Yb^3＋ concentration increases continuously, the intensity of green emission decreases, while those of the red and infrared emissions increase and decrease alternately. In addition, the up-conversion mechanisms of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4 are also discussed. It is found that the transform of up-conversion mechanism from two-step energy transfer to cooperating sensitization takes place when Yb^3＋ concentration is increased up to 12 mol%. With the further increase of Yb^3＋ concentration, the energy-back-transfer gradually becomes the dominant up-conversion mechanism, which results in the quenching of the green emission and slight increasing of the red and infrared emissions.     

Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

Synthesis and modification of well-ordered layered cathode oxide LiNi<Subscript>2/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript>

Oxalic-acid-based co-precipitation method was employed to prepare LiNi_2/3Mn_1/3O₂ sample with a high-ordered structure. Li⁺, Ni²⁺ and Mn²⁺ acetates were used as starting materials. The influence of the amount of lithium source in the starting materials on Li⁺ content, disorder of Li⁺-Ni²⁺ ions, and electrochemical performance has been investigated. Rietveld refinement shows that the sample prepared with 20% excess Li-source in the starting materials exhibits a perfect ordered structure. A specific discharge capacity is as high as 172 mAh/g at C/20 in the voltage range of 4.35–2.7 V. However, the cyclability is not satisfactory: about 25.3% fade in capacity was observed over 50 cycles. Chemically stable SiO2 was coated on the surface of LiNi_2/3Mn_1/3O₂ particles. A significant improvement in cyclability was attained with 3 wt% SiO2 coating, which is ascribable to the protection of LiNi_2/3Mn_1/3O₂ particles from being dissolved into the electrolyte.     

Preparation and luminescence properties of YeO3：Er^3＋/TiO2 with high specific surface area

The three composites Y2O3 :Er3+ , Y2O3 :Er3+ /Yb 3+ andY2O3 :Er3+ /TiO2 were prepared using coprecipitation and sol-gel techniques. Their morphology, specific surface area, porosity, UV-vis. absorption spectra and fluorescence spectra were measured using SEM, TEM, surface analysis, UV-vis. absorption and photoluminescence spectrophotometry. SEM and TEM showed that samples prepared using coprecipitation were dispersed, while Y2O3 :Er3+ /TiO2 particles possessed a mesoporous surface and average diameter of ab...     

Resistless photochemical etching of a silicon wafer by UV laser with an H<Superscript>2</Superscript>O<Superscript>2</Superscript> and HF aqueous solution

A new resistless etching method has been developed for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H₂O₂) and hydrogen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd: YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H₂O₂÷HF ratio, where an etch depth of 210 nm was achieved with a fluence of 29 mJ/cm² and shot number of 10000. At the same conditions, the etch depth with H₂O₂ and HF solution was three times of that by using H₂O and HF mixture. In the case of the 266 nm Nd: YAG laser, the optimal etching appeared at twice ratio of H₂O₂/HF, where the etch depth of 420 nm was achieved with a fluence of 12 mJ/cm² and shot number of 30000. Results showed that the etch effect of the 266 nm Nd: YAG laser was more desirable than that of the 193 nm ArF excimer laser.     

Nitric oxide suppresses stomatal opening by inhibiting inward-rectifying K<Stack><Subscript>in</Subscript><Superscript>+</Superscript></Stack> channels in <Emphasis Type="Italic">Arabidopsis</Emphasis> guard cells

We explore nitric oxide （NO） effect on K^＋in, channels in Arabidopsis guard cells. We observed NO inhibited K^＋in, currents when Ca^2＋ chelator EGTA （Ethylene glycol-bis（2-aminoethylether）-N,N,N′,N;tetraacetic acid） was not added in the pipette solution; K^＋in currents were not sensitive to NO when cytosolic Ca^2＋ was chelated by EGTA. NO inhibited the Arabidopsis stomatal opening, but when EGTA was added in the bath solution, inhibition effect of NO on stomatal opening vanished. Thus, it implies that NO elevates cytosolic Ca^2＋ by activating plasma membrane Ca^2＋ channels firstly, then inactivates K^＋in, chartnels, resulting in stomatal opening suppressed subsequently.     

CO<Subscript>2</Subscript> gas emplacement age in the Songliao Basin: Insight from volcanic quartz <Superscript>40</Superscript>Ar-<Superscript>39</Superscript>Ar stepwise crushing

Due to a lack of suitable minerals, the gas/oil emplacement ages have never been accurately obtained before. CH₄-CO₂-saline- bearing secondary inclusions are found in quartz from the volcanic rocks of the Yingcheng Formation, the container rocks of the deep CO₂ gas reservoir in the Songliao Basin. The inclusion fluid was trapped into microcracks in quartz during the gas emplacement and accumulation, providing an optimal target for the ⁴⁰Ar-³⁹Ar stepwise crushing technique to determine the CO₂ gas emplacement age. ⁴⁰Ar-³⁹Ar dating results of a quartz sample by stepwise crushing yield a highly linear-regression isochron with an age of 78.4±1.3 Ma, indicating that the accumulation of the deep CO₂ gas reservoir in the Songliao Basin occurred in the late Cretaceous. This is the first time to report an exact isotopic age for a CO₂ gas reservoir, which indicates that the ⁴⁰Ar-³⁹Ar dating can serve as a new technique to date the oil/gas emplacement ages.     

Chemical quenching and inhibition of positronium in Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The pore structure of Cr2O3/Al2O3 catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimes τ4 and τ3 are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3 content, both τ4 and its intensity I4 show sharp decrease, while τ3 and its intensity I3 keep nearly unchanged. The Doppler broadening S parameters also show sharp decrease with increasing Cr2O3 content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3 content. This indicates that the change of o-Ps lifetime τ4 is due to the chemical quenching by Cr2O3 but not spin-conversion of positronium. The decrease of o-Ps intensity I4 indicates that Cr2O3 also inhibits positronium formation.     

Bi~(3+)/Yb~(3+)共掺GdVO_4近红外发光性能研究

使用高温固相法制备了一种新的Bi3+,Yb3+共掺杂GdVO4量子裁剪近红外发光材料,该材料在波长为250~400nm的紫外光激发下发射出很强的近红外光(900~1100nm).由于体系中Bi3+离子的引入,相对于Gd0.9Yb0.1VO4,Gd0.87Yb0.1Bi0.03VO4在989nm处的近红外发光强度提高近120%,且其激发峰也从323nm红移至341nm,整个激发谱带更宽,更有利于实际应用.由于Yb3+离子既可以利用基质中的VO3-4电荷迁移态跃迁的能量,也可以同时利用Bi3+的1S0-3P1能级跃迁传递能量,相对于目前报道的理论量子裁剪效率最高的YVO4:Bi3+,Yb3+,GdVO4:Bi3+,Yb3+无论其近红外发光强度还是可见光发光强度强度皆有提升,是一种很有希望的紫外宽带激发近红外发光材料.