Ce3+共掺杂BaZn1.06Al9.94O17: Tb3+荧光粉的发光性质及其能量传递机

采用高温固相法合成了BaZn_1.06Al_9.94O₁₇:Tb³⁺,Ce³⁺荧光粉,并对其发光性能和能量传递机理进行了研究.研究结果表明:由于Tb³⁺离子的4f⁸ → 4f⁷5d¹跃迁,使得BaZn_1.06Al_9.94O₁₇:Tb³⁺的激发带中心位于230 nm处.共掺杂Ce³⁺离子后,BaZn_1.06Al_9.94O₁₇:Tb³⁺的激发光谱出现了明显的红移,在240～320 nm范围内的宽带激发归因于Ce³⁺离子的4f → 5d跃迁.由于Ce³⁺与Tb³⁺离子发生了能量传递,使得BaZn_1.06Al_9.94O₁₇:Tb³⁺,Ce³⁺中Tb³⁺离子的⁵D₄ → ⁷F_J(J=6、5、4和3)发射峰的发光强度比未掺杂Ce³⁺离子时提高了约15倍.因此,制备的BaZn_1.06Al_9.94O₁₇:Tb³⁺,Ce³⁺荧光粉可望在照明、显示器件等应用中具有良好的应用价值.     

Ce3+/Tb3+双掺杂SrAl2Si2O8荧光粉的发光性能及其在测温领域的应用

采用高温固相法在弱还原气氛下制备了系列荧光粉材料Sr_{1-3（x+y）/2}Al₂Si₂O₈:xCe³⁺,yTb³⁺,并通过X射线衍射（XRD）、荧光光谱和荧光强度比（FIR）测温法分析了荧光粉样品的晶体结构、发光性能及其温度传感特性。XRD分析结果表明掺杂离子Ce³⁺和Tb³⁺均占据Sr²⁺格位,并且掺杂少量的稀土离子不会改变基质的晶体结构。荧光光谱分析结果表明在近紫外光激发下,该双掺杂荧光粉的发射光谱显示出Ce³⁺和Tb³⁺离子的特征发射峰,最佳掺杂浓度的荧光粉化学式为Sr_0.865Al₂Si₂O₈:0.05Ce³⁺,0.04Tb³⁺。此外,在不同波长的监测下,测得的激发光谱形状十分相似,表明在该荧光粉中存在着Ce³⁺→Tb³⁺能量传递过程。FIR测温法计算结果表明该荧光粉的相对灵敏度随温度的升高而升高,在520 K时有最大值为0.022 4 K^-1。研究结果表明该荧光粉具备的优异光学性能和温度传感性能使其成为一种具有应用前景的测温材料。     

Solution-combustion Synthesized Nano-pellet α-Al2O3 and Catalytic Oxidation of Cyclohexane by Its Supported Cobalt Acetate

Nano-pellet α-Al₂O₃ was prepared using aluminum nitrate as precursor and urea as fuel by a fast method of solution combustion synthesis.The formation of the nano material was dependent on the molar ratio of fuel/oxidant,calcination temperature,and foreign metallic ions.The prerequisite conditions of the formation were a suitable fuel/oxidant molar ratio larger than two and calcination temperature higher than 673 K.Foreign ions,Ce⁴⁺ or Co²⁺,hindered thi...     

稀土Tb3+为荧光探针定量分析色氨酸

提出Tb³⁺荧光可用于色氨酸检测.利用Tb³⁺和色氨酸之间的能量转移,建立Tb³⁺—色氨酸体系,在547 nm处对该体系进行分析,并将其应用于花生中色氨酸的检测.结果发现：色氨酸在0.1～16 mmol·L^-1浓度范围内与Tb³⁺的荧光强度呈线性关系,回归方程为:I=1.096 C+20.37.因此,稀土Tb³⁺可以对色氨酸进行定量分析.此外,测定了花生中的色氨酸含量,并进行了加标回收实验,回收率为96.90%～103.42%.     

Fabrication of YAG:Ce3+ and YAG:Ce3+,Sc3+ Phosphors by Spark Plasma Sintering Technique

In this study,a single-doped phosphors yttrium aluminum garnet(Y₃Al₅O₁₂,YAG):Ce³⁺,single-doped YAG:Sc³⁺,and double-doped phosphors YAG:Ce³⁺,Sc³⁺ were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by th...     

可调色荧光粉LaSrZnNbO6:Bi3+,Sm3+的发光性质及Bi3+和Sm3+离子间的能量传递机理

采用高温固相法合成了系列LaSrZnNbO₆:Bi³⁺,Sm³⁺荧光粉,并对其发光性质以及Bi³⁺、Sm³⁺离子间的能量传递机理进行了研究.结果显示,当以Bi³⁺的¹S₀→ ³P₁激发位置(338 nm)激发Bi³⁺和Sm³⁺共掺杂LaSrZnNbO₆荧光粉时,在LaSrZnNbO₆荧光粉的发射光谱中同时出现了Bi³⁺和Sm³⁺的发射峰,表明在LaSrZnNbO₆基质中存在Bi³⁺→ Sm³⁺的能量传递.经计算, Bi³⁺离子和Sm³⁺离子间的能量传递效率可达到86.9%.通过改变Bi³⁺离子和Sm³⁺离子的掺杂浓度可以使LaSrZnNbO₆荧光粉的CIE色坐标由蓝光区域移动至粉白光区域,表明通过调节掺杂浓度可制备出颜色可调谐的荧光粉.     

空心和多孔Y2O3:Eu3+微球的超声喷雾热解法可控合成及其光致发光性能

以蔗糖或柠檬酸为辅助剂,通过改变超声喷雾热解期间雾滴中溶剂的蒸发方式和溶质聚集状态,进行空心和多孔Y₂O₃:Eu³⁺微球的可控合成。探究了辅助剂的种类和比例对微球形貌的影响,提出了空心和多孔Y₂O₃:Eu³⁺微球形成机制,并分析了空心和多孔Y₂O₃:Eu³⁺微球的晶体结构及光致发光性能。结果表明：Y₂O₃:Eu³⁺微球组分均匀,仍保留立方Y₂O₃结构;添加蔗糖后可获得中空结构,添加柠檬酸则为多孔结构,这归因于添加的蔗糖在雾滴干燥时络合成膜,水分透过膜蒸发,溶质沉积在膜内壁形成空心球壳,而添加的柠檬酸则与溶质形成均匀的螯合物,在高热解温时产生大量原位介孔;空心和多孔Y₂O₃:Eu³⁺微球均在611 nm处表现出典型的红光...     

Sintering Behavior and Microstructure of diphasic β-Sialon /Al_2O_3 Composites

Six compositions with different ratio of β-Sialon/Al2O3 were synthesized from Al2O3, Si3,N4 and SiO2 by sintering with 3%Y2O3(mass fraction) as addition under the cover with powders of SiC+C and at nitrogen atmosphere. Theeffects of atmosphere, sintering temperature and composition on the sintering behavior were studied. The results showedthat the composites reached the best sintering behavior with the highest density about 92% at 1 650℃ under the weakreduction atmosphere. Finally the relative density of diphasic β-Sialon and p-Sialon/Al2O3 composites were studied andpredicted using ANN (Artificial Neural Networks) method and the results were experimental examined by fore randomsamples.     

红色荧光粉Ca3La3（BO3）5:Eu3+的制备及光学性能

由于红色荧光粉具有提高白光发光二极管（LED）显色指数以及降低色温等优点,因此开发性能优异的白光LED用红色荧光粉一直是白光LED领域研究的重要课题。通过传统的高温固相法制备了系列Ca₃La₃（BO₃）_5:3xEu³⁺红色荧光粉,并通过X射线衍射仪、荧光分光光度计和色坐标分析了荧光粉样品的晶体结构及光学性能。实验结果表明掺杂的Eu³⁺进入了Ca₃La₃（BO₃）₅（CLBO）主晶格,并且掺杂少量的Eu³⁺的CLBO主晶格无杂相生成,得到的Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉的结构与CLBO主晶格一致。该荧光粉被紫外光激发后能发射红光。通过对Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉的光致发光光谱进行计算发现在不同波长光的激发下,色坐标都非常接近美国国家电视系统委员会红光标准。Ca₃La₃（BO₃）_5:3xEu³⁺荧光粉是一种性能优异的白光LED用红色荧光粉。     

双钙钛矿结构Sr2GdSbO6:Eu3+荧光粉的制备与表征

采用高温固相法成功制备了双钙钛矿结构的Sr₂GdSbO₆:Eu³⁺红色荧光粉，并表征了其XRD、光致发光光谱和荧光衰减寿命曲线。Sr₂Gd_0.8SbO₆:0.2Eu³⁺荧光粉的XRD图谱的峰位与标准卡片峰位基本吻合，表明Eu³⁺的掺杂并未改变基质的晶体结构，Rietveld精修后的晶体参数也验证了该结果。样品的激发光谱为紫外光区的一个以340 nm为中心的宽光谱；在340 nm光源的激发下，样品的最强发射是一个中心波长为593 nm的橙红光发射波段。运用Dexter理论分析出样品的浓度淬灭机理为偶极-偶极相互作用。常温下Sr₂Gd_0.8SbO₆:0.2Eu³⁺荧光粉的荧光衰减寿命为4.202 ms，外量子效率为24.8%，升温至150℃时其外量子效率仍保持为常温下外量子效率的68.8%。经计算得到Sr₂G...     

Improving Cyclic Stability and Rate Performance of Lithium Ion Batteries Using La3+ Modified LiNi0.6Co0.2Mn0.2O2 Cathode Materials

La₄NiLiO₈-coated NCM622 samples were prepared through a sol-gel method,and the electrochemical performance as cathode materials was investigated.It is revealed that part of the introduced La³⁺ions produce a coating layer on the surface of NCM622 particles,while the rest occupy the 3b position of the lattice.The optimized sample exhibits a capacity retention of 96.54%after 100 cycles under 1C rate with a discharge specific capacity of 117.54 mAh?g^-1 und...     

基质改变对Eu3+、Bi3+发光性能的影响

采用溶胶—凝胶法制备出了CaSiO₃:Eu³⁺Bi³⁺和Sr₂SiO₄:Eu³⁺Bi³⁺,对比分析了两者的激发光谱与发射光谱,探讨了基质改变对Eu³⁺、Bi³⁺发光性能的影响。结果表明Sr₂SiO₄:Eu³⁺Bi³⁺中Bi³⁺—Eu³⁺之间的能量传递效率明显高于CaSiO₃:Eu³⁺Bi³⁺中的。     

Ca1-3x/2Al2Si2O8:xEu3+荧光粉的发光和光温传感特性

为了探究稀土离子掺杂铝硅酸盐的光温特性,本文采用燃烧合成法制备了系列荧光粉材料Ca_1-3x/2Al₂Si₂O₈:xEu³⁺。X射线衍射结果表明掺杂Eu³⁺离子不会改变基质CaAl₂Si₂O₈的晶体结构。荧光光谱结果表明该荧光粉在近紫外光区域具有较强吸收,当被波长为393 nm的近紫外光激发后,其最大特征发射峰为611 nm,且Eu³⁺离子的最佳掺杂浓度为0.05。利用上升时间测温法研究了CaAl₂Si₂O₈:Eu³⁺荧光粉的光温传感特性,结果表明:随着Eu³⁺掺杂浓度的增加,上升时间单调递减,但当掺杂掺杂超过0.100时就会发生淬灭。Ca_0.985Al₂Si₂O₈:0.01Eu³⁺的相对灵敏度随温度的升高先增大后减小,并在520 K时达到最大值（0.024 K^-1）。上述研究表明该荧光粉具备优异的温度传感性能,在测温领域具有广泛的应用前景。     

Energy Band-gap Calculation of d-Ta2O5 Using sX-LDA and B3LYP Methods

The energy band-gap and related factors of tantalum pentoxide with hexagonal phase were investigated using hybrid functional B3 LYP and s X-LDA methods. The results showed that both s X-LDA and B3 LYP techniques reveal the indirect semiconductor nature of δ-Ta2O5, whereas the obtained value of energy band-gap is much higher than previous theoretical reports but closer to the experimental data. The optical bandgap of δ-Ta2O5 is expected to originate from the O 2p→Ta 5d transition which may benefit from the d-s-p hybridization.     

Structural and Magnetic Studies of Ga-doped Yttrium Iron Garnet

Ga-doped Yttrium Iron Garnet (Y₃Ga_xFe_5-xO₁₂,Ga:YIG) was prepared by solid state reaction method and sintering at 1 300 ℃.Rietveld analysis of X-ray diffraction patterns indicated that all samples crystallized in a single cubic structure (space group Ia-3d) with decreasing lattice constant as Ga concentration increased.SEM surface micrograph images of YIG samples showed highly compacted grains with small reduction in the grain size with increasing Ga concentration.Raman spectroscopy measurements confirmed the replacement of Fe³⁺ ions by Ga³⁺ ions in the garnet structure was revealed by the observed blue shifts in Raman spectra.The saturation magnetization decreased from 28.2 to 4.98 emu g^-1 with increasing x from 0.0 to 1.0 due to the preferential substitution of Ga³⁺ ions for Fe³⁺ ions at tetrahedral sites.Room temperature M?ssbauer spectra for the samples revealed a reduction of the hyperfine field values for octahedral and tetrahedral sites,and the development of additional components with increasing Ga concentration.Analysis of the magnetic data and M?ssbauer spectra confirmed that spin canting in the substituted garnets plays an important role in explaining the observed reduction of the saturation magnetization as x increased.     

NaYF4∶Yb3+,RE3+(Ho3+/Tm3+)/Bi2WO6的制备及其光催化性能

研究采用两步水热法制备以Ho或Tm为激活剂、Bi₂WO₆为基础光催化剂的复合光催化剂(NaYF₄∶Yb³⁺,RE³⁺(Ho³⁺/Tm³⁺)/Bi₂WO₆);通过X射线衍射、扫描电镜和光致发光光谱等测试手段对材料的性能进行表征。结果表明：NaYF₄∶Yb³⁺,RE³⁺(Ho³⁺/Tm³⁺)具有较强的上转换能力,受980 nm光激发后,发射出362 nm、388 nm等可被Bi₂WO₆利用的光;此外,NaYF₄∶Yb³⁺,RE³⁺(Ho³⁺/Tm³⁺)复合Bi₂WO₆后也保留Bi_2<...     

Numerical simulation and optimization of the cylinder head water jacket based on the two-phase flow boiling heat transfer

Boiling heat transfer and the controllability of the thermal load of the cylinder head were studied. The thermodynamic phase change characteristics of the cylinder head coolant were considered and the mass, momentum and energy transfers between two phases were calculated with the interface transfer sub-models by using the computational fluid dynamics software CFX. Results showed that compared with the single-phase flow without considering the boiling heat transfer, the sub-cooled boiling heat transfer of the cylinder head was greatly increased. According to the results of the numerical simulation, an optimized structure of the water jacket was proposed. Finally, temperature and velocity of coolant, diameter of flow passage and mean bubble diameter that influences sub-cooled boiling were studied using the orthogonal experiment method.     

Research of Lead-free Na0.5Bi0.5TiO3-BaTiO3 System Piezoelectric Ceramics

To reduce the coercive field of Na_0.5Bi_0.5Ti O₃,Ba Ti O₃ were added as dopant materials.Then the(1-x)Na_0.5Bi_0.5Ti O₃-x Ba Ti O₃ ceramic samples were produced in solid synthetic way.The optimum preparation condition and piezoelectric properties of the samples were investigated.The XRD results show that the fabric transites from rhombohedral to tetragonal gradually with the substitution of the Ba²⁺.T...     

The Effects of WC on the Microstructures and Wear Resistance of FeCoCrNiB0.2 High Entropy Alloy

To improve the wear resistance of the FeCoCrNiB_0.2 high entropy alloy (HEA),the FeCoCrNiB_0.2 (WC₀) and FeCoCrNiB_0.2+20wt%WC (WC₂₀) HEA coatings were prepared on Q235 steel by laser cladding (LC).The microstructure,hardness,and tribometer of the HEA coatings were investigated using scanning electron microscopy with spectroscopy (SEM/EDS),X-ray diffraction (XRD),vickers microhardness tester,and pin-on-disc tribometer,respectively.The experimen...     

Design and optimization of W/Cu divertor mock-ups

Tungsten is a promising candidate for plasma-facing materials to cover the surface of the divertor plate in the design of an international thermonuclear experimental reactor （ITER）. Copper as a heat sink material serves to transfer heat excellently. Divertor mock-ups with W/Cu graded interlayers were designed to reduce thermal stresses. Thermally induced stresses and temperature in a W/Cu divertor mock-up were analyzed using the finite element method. The graded structures with different exponents p and thick- nesses were designed and discussed. The conclusions drawn from these analyses are that thermal stresses reach the minimum and the temperature is suitable when exponent p is 1.5 and the thickness of five graded interlayers is 5 mm.