Synthesis and luminescence properties of Pr3+ doped CaxBa1?xTiO3 (0.3?x<1) fine particles

Ca _x Ba_1−x TiO₃ (CBT) fine particles doped with red luminescence center of Pr³⁺ ions (Pr: CBT) were successfully synthesized by salt assisted spray pyrolysis (SASP) process. Scanning electronic microscope (SEM) and laser scattering analysis demonstrate that salt can be removed from the surface of particles by washing with Milli-Q water and the particles can be further separated by ball-milling to get well-dispersed Pr³⁺ ions doped CBT fine particles. The luminescence properties, such as photoluminescence (PL) and mechanoluminescence (ML), of as-synthesized Pr: CBT particles were investigated. For Pr: CBT fine particles with different Ca molar ratios, all the samples show one emission at 612 nm, with increasing Ca molar ratio, PL intensity of Pr: CBT fine particles become stronger and stronger. When pressure was loaded on the Pr: CBT pellet, mechanoluminescence(ML) emission was measured. The results show that the ML intensity is proportional to the applied pressure.     

Study on the thermal stability and electrical properties of the high-k dielectrics (ZrO2)x(SiO2)1?x

(ZrO₂) _x (SiO₂)_1−x (Zr-Si-O) films with different compositions were deposited on p-Si(100) substrates by using pulsed laser deposition technique. X-ray photoelectron spectra (XPS) showed that these films remained amorphous after annealing at 800°C with RTA process in N₂ for 60 s. The XPS spectra indicated that Zr-Si-O films with x=0.5 suffered no obvious phase separation after annealing at 800°C, and no interface layer was formed between Zr-Si-O film and Si substrate. While Zr-Si-O films with x >0.5 suffered phase separation to precipitate ZrO₂ after annealing under the same condition, and SiO₂ was formed at the interface. To get a good interface between Zr-Si-O films and Si substrate, Zr-Si-O films with bi-layer structure (ZrO₂)_0.7(SiO₂)_0.3/(ZrO₂)_0.5(SiO₂)_0.5/Si was deposited. The electrical properties showed that the bi-layer Zr-Si-O film is of the lowest equivalent oxide thickness and good interface with Si substrate. Supported by the National Nature Science Foundation of China (Grant No. 60636010) and the National Basic Research Program of China (“973” Program) (Grant No. 2004CB619004)     

Synthesis and photoluminescence property of red phosphors LiEu1?xYx(WO4)0.5(MoO4)1.5 for white LED

A series of novel red phosphors LiEu_1−x Y _x (WO₄)_0.5(MoO₄)_1.5 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8) were synthesized by conventional solid state reaction method with the starting materials: WO₃, MoO₃, Eu₂O₃, Li₂CO₃ and Y₂O₃. The spectrum and the crystal structure of the phosphors were characterized by F-4500 and XRD respectively. Meanwhile the effects of flux and Y³⁺ concentration on the crystal structure and luminescent properties of the phosphors were investigated. The results showed that the optimal content of flux () was 1 wt% and the optimal doping concentration of Y³⁺ was 0.5 mol. The emission spectrum showed the most intense peak was located at 615 nm, which corresponds to the ⁵ D ₀→⁷ F ₂ transition of Eu³⁺ and that Eu³⁺ occupied the lattice site of noncentrosymmetric environment in the scheelite phases. The excitation spectrum displayed that these phosphors could be effectively excited by ultraviolet (UV) (396 nm) and blue (466 nm) light, nicely in correspondence with the widely applied output wavelengths of ultraviolet or blue LED chips. The influence of flux on the luminescent properties of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 phosphor was analyzed. The XRD spectra indicated that the flux could help to crystallize the phosphor, and no other phases were formed except the tetragonal. When adding flux, the relative intensity of LiEu_0.5Y_0.5(WO₄)_0.5(MoO₄)_1.5 became much stronger and the average particle size of the phosphor decreased. Supported by the Key Programs for Science and Technology Development of Hubei Province (Grant No. 2005AA105A05)     

Thermal expansion properties and hygroscopicity of Y2?xSmxW3O12 (x = 0.0–0.4) compounds

A novel class of solid solutions of Y_2−x Sm _x W₃O₁₂ (x = 0.0−0.4) were synthesized and studied by means of powder X-ray diffraction. All samples crystallize in an orthorhombic space group Pnca. The lattice parameters a, b and c of Y_2−x Sm _x W₃O₁₂ increase with increasing Sm content. Since the compounds of this series hydrate at room temperature, thermogravimetric (TG) analysis was carried out. The result shows that the compound stores less water with increasing Sm content. The thermal expansion properties of Y_2−x Sm _x W₃O₁₂ (x = 0.1, 0.3 and 0.4) were investigated with high temperature X-ray diffraction. Negative thermal expansion coefficient α _I becomes less negative from −6.644×10⁻⁶ to −6.211×10⁻⁶°C⁻¹ when x changes from 0.1 to 0.4.     

Effect of Dy on structure and magnetic properties of DyxFe60.5?xPt39.5 Alloys

Effects of the content of Dy on structure and magnetic properties of Dy _x Fe_60.5−x Pt_39.5 alloys(x=0, 0.5, 1.0, 1.5) were investigated. The results of XRD analysis proved that the phase-transitional temperature of Dy _x Fe_60.5−x Pt_39.5 alloys from disordered face-centered-cubic structure to ordered face-centered-tetragonal cubic structure decreases with the increase of the content of Dy(x). Suitable content of Dy can improve the exchange coupling between soft magnetic phase and hard magnetic phase by refining grain size, while the remanence ratio and coercivity of the Fe_60.5Pt_39.5 alloy can be significantly improved by a small replacement of Fe by Dy, good magnetic properties were obtained in Dy_0.5Fe_60.0Pt_39.5 alloys.     

Microscopic phase-field simulation for coarsening behavior of L12 and DO22 phases of Ni75Cr x Al25? x alloy

Based on the microscopic phase-field dynamic model and the microelasticity theory, the coarsening behavior of L1₂ and DO₂₂ phases in Ni₇₅Cr _x Al_25−x alloy was simulated. The results show that the initial irregular shaped, randomly distributed L1₂ and DO₂₂ phases are gradually transformed into cuboidal shape with round corner, regularly aligned along directions [100] and [001], and highly preferential selected microstructure is formed during the later stage of precipitation. The elastic field produced by the lattice mismatch between the coherent precipitates and the matrix has a strong influence on the coarsening kinetics, and there is no linear relationship between the cube of the average size of precipitates and the aging time, which does not agree with the results predicted by the classical Lifshitz-Slyozov-Wagner. The coarsening processes of L1₂ and DO₂₂ phases are retarded in elastically constrained system. In the concurrent system of L1₂ and DO₂₂ phases, there are two types of coarsening modes: the migration of antiphase domain boundaries and the interphase Ostwald ripening. Foundation item: Project(50671084) supported by the National Natural Science Foundation of China; Project(20070420218) supported by China Postdoctoral Science Foundation     

Ce掺杂0.94MgTiO3-0.06(Ca0.8Sr0.2)TiO3陶瓷的制备及微波介电性能

为了提高MgTiO₃-(Ca_0.8Sr_0.2)TiO₃(MT-CST)微波介质陶瓷的品质因数,通过SEM、XRD、拉曼光谱仪与XPS分析手段,研究了Ce掺杂对MT-CST陶瓷成分晶体结构和微波介电性能的影响.结果表明：高价Ce³⁺取代Mg²⁺可使氧空位缺陷得到有效抑制,从而降低了微波介质损耗,可使品质因数得到较大提升.制备的陶瓷具有优异的微波介电性能：介电常数为20.8,品质因数为61 000 GHz,谐振频率温度系数为-4.99×10^-6/℃.     

Adsorption of NO and NH3 over CuO/γ-Al2O3 catalyst

The selective catalytic reduction reaction belongs to the gas-solid multiphase reaction, and the adsorption of NH₃ and NO on CuO/γ-Al₂O₃ catalysts plays an important role in the reaction. Performance of the CuO/γ-Al₂O₃ catalysts was explored in a fixed bed adsorption system. The catalysts maintain nearly 100% NO conversion efficiency at 350 °C. Comprehensive tests were carried out to study the adsorption behavior of NH₃ and NO over the catalysts. The desorption experiments prove that NH₃ and NO are adsorbed on CuO/γ-Al₂O₃ catalysts. The adsorption behaviors of NH₃ and NO were also studied with the in-situ diffusion reflectance infrared Fourier transform spectroscopy methods. The results show that NH₃ could be strongly adsorbed on the catalysts, resulting in coordinated NH₃ and NH₄⁺ NO adsorption leads to the formation of bridging bidentate nitrate, chelating bidentate nitrate, and chelating nitro. The interaction of NH₃ and NO molecules with the Cu²⁺ present on the CuAl₂O₄ (100) surface was investigated by using a periodic density functional theory. The results show that the adsorption of all the molecules on the Cu²⁺ site is energetically favorable, whereas NO bound is stronger than that of NH₃ with the adsorption site, and key information about the structural and energetic properties was also addressed.     

Synthesis and Dielectric Properties of Ba_3NaBiNb_(10)O_(30) Ceramics

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Fe2(SO4)3对活性污泥微生物活性的影响

为了解Fe₂(SO₄)₃作为絮凝剂对活性污泥中微生物活性的影响,向活性污泥系统中投加质量浓度为20、40、60、80,100 mg·L-1的Fe₂(SO₄)₃,反应4 h后测定活性污泥的脱氢酶活性、比耗氧速率(R_SOU)、胞外聚合物(EPS)及各组分含量,同时测定系统出水的COD等各项指标．结果表明:Fe₂(SO₄)₃质量浓度在20～60 mg·L-1时对活性污泥的脱氢酶活性、R_SOUEPS及各组分含量影响均不大,此时污水中COD、TP、UV₂₅₄等污染物随Fe₂(SO₄)₃质量浓度增加而有较大幅度去除．Fe₂(SO₄)₃质量浓度为80 mg·L-1时,污泥的脱氢酶活性、R_SOU、总EPS含量均明显下降．当Fe₂(SO₄)₃质量浓度增加到100 mg·L-1时,污泥的脱氢酶活性、R_SOU进一步受到抑制,而总EPS含量则大幅度提升．此时污水中COD、TP、UV₂₅₄等污染物去除率增加幅度变缓,SCOD及NH₃-N去除作用有所下降．     

Na3V2(PO4)3/C复合正极材料的合成与表征研究

以Na₃V₂(PO₄)₃(NVP)为基础材料,以海藻酸钠为碳源,采用化学合成方法,对NVP材料进行碳复合、非金属离子掺杂,合成了具有优异电化学性能的NVP/C复合正极材料。探究了材料组成、合成温度、微观结构等对NVP复合材料电化学性能的影响。研究结果表明,海藻酸钠形成的碳骨架结构拥有良好的机械强度,将其在高电流密度下进行充放电时,碳骨架能够保持稳定不坍塌,提高材料的循环性能和倍率性能;当加入50 mL的海藻酸钠水溶液并经800℃烧时,NVP/C复合材料的电化学性能最佳,在0.5 C的低倍率下其首次放电比容量为110.3 mAh·g^-1,当倍率增加到50 C时,其放电比容量为78.1 mAh·g^-1,当循环2 000圈之后其放电比容量保持率高达80.4%,其库伦效率基本保持在100%,远优于已报道的研究结果。     

Composition dependence of phase structure and electrical properties of (1−y)Bi1−xNdxFeO3−yBiScO3 ceramics

In this work, we have studied a new lead-free ceramic of(1-y)Bi_(1-x)Nd_xFeO_(3-y)BiScO_3(0.05≤x≤0.15 and 0.05≤y≤0.15) prepared by a conventional solid-state method, and the influences of Nd and Sc content on their phase structure and electrical properties were investigated in detail. The ceramics with 0.05≤x≤0.10 and 0.05≤y≤0.15 belong to an R3 c phase, and the rhombohedral-like and orthorhombic multiphase coexistence is established in the composition range of 0.125≤x≤0.15 and y=0. The electrical properties of the ceramics can be enhanced by modifying x and y values. The highest piezoelectric coefficient(d33~51 p C/N) is obtained in the ceramics with x=0.075 and y=0.125, which is superior to that of a pure BiFeO_3 ceramic. In addition, a lowest dielectric loss(tan δ~0.095%, f=100 k Hz) is shown in the ceramics with x=0.15 and y=0 due to the involvement of low defect concentrations, and the improved thermal stability of piezoelectricity at 20–600oC is possessed in the ceramics. We believe that the ceramics can play a meaningful role in the high-temperature lead-free piezoelectric applications.     

C-N共掺杂TiO2电极电解水产H2O2的催化机制(英文)

在两电子电解水产H₂O₂过程中,电极表面存在四电子和一电子水氧化等竞争反应,同时在强氧化环境中电催化剂会发生表面重构,这对其活性位点的解析带来了很大困难。本文基于Ti/TiO₂基电极,在空气、氮气或尿素不同环境煅烧后作为H₂O₂电催化剂,通过电化学测试评估其催化的活性与反应选择性;借助扫描电化学显微镜和XPS氩离子束溅射等手段,分析了电极表面形貌和电流变化,以及在深度上化学组分的演变。结果表明,Ti/TiO₂纳米管阵列作为基底,其与尿素共热解得到的羰基和吡咯氮官能团是电解水产H₂O₂的关键活性位点。研究结果为设计高效的H₂O₂电催化剂提供了新的借鉴。     

Dielectric properties of Pb (Zn_(1/3) Nb_(2/3)) O_3-PbZrO_3-PbTiO_3 solid solution near morphotropic phase boundary

The dielectric properties of Pb(Zn1/3Nb2/3)O3-PbZrO3-PbTiO3(PZN-PZ-PT) system near the rhombohedral/tetragonal morphotropic phase boundary (MPB) are carefully studied in this paper. It is found that, for all samples, the curves around the temperatures of dielectric permittivity peak show the characteristics of diffuse phase transition. The change in PbZrO3/PbTiO3 ratio has much influence on the dielectric properties of the samples. The extent of diffuse phase transition increases with the increasing Zr/Ti ratio. The samples in rhombohedral region have typical diffuse phase transition in the temperature range measured. However, for the samples with tetragonal symmetry, a spontaneous normal ferroelectric-relaxor phase transition exists at temperature lower than that of permittivity peak. This normal ferroelectric-relaxor phase transition is confirmed by the experiment of thermally driven current . The analysis of TEM reveals that the samples in tetragonal region show a 90° macrodomain structure , while th     

适用于锂离子电池的新型复合快离子导体Li2.64(Sc0.9Ti0.1)2(PO4)3聚合物PVDF-HFP基凝胶电解质(英文)

随着锂离子电池对能量密度要求的不断提高,更宽的电化学窗口和更高的安全性能将是下一代电解质发展的重要方向。凝胶电解质作为电解质固态化发展研究的过渡阶段,在解决安全性问题、拓宽电化学窗口等方面有着良好的应用前景。然而,较低的离子电导率和较差的力学性能阻碍了凝胶电解质的进一步应用。为此,将一种快离子导体Li_2.64(Sc_0.9Ti_0.1)₂(PO₄)₃(LSTP)添加到聚偏氟乙烯-六氟丙烯基(PVDF-HFP)凝胶电解质中,以提高其力学性能和离子导电性。结果表明,LSTP能够削弱聚合物链间的相互作用力,加强链的热振动,显著提高离子导电性,降低循环过程中的界面电阻。所制备的混合凝胶电解质锂金属电池具有优异的倍率容量(在28°C时1C下为145 mA·h/g,3C下为95 mA·h/g),展现出了可与商品化液体电解质体系相媲美的潜力。     

固态电解质LiZr2(PO4)3的掺杂及其在电极中的应用

NASICON型固态电解质磷酸锆锂(LZP)具有优异的结构稳定性和性能可靠性,但其在室温下的锂离子电导率较低,限制锂离子的传输。针对上述问题,采用溶胶凝胶法对磷酸锆锂电解质材料进行阳离子掺杂,提高材料的电导率,进而提升锂离子在材料中的输运能力。同时,将掺杂的磷酸锆锂电解质对电极进行修饰,提升电极本身的锂离子输运性能。探究了离子掺杂电解质对电极的锂离子扩散动力学性能的影响机理。实验结果表明,LiTi_0.25Zr_1.75(PO₄)₃对电极的锂离子扩散动力学性能提高最为显著,锂离子扩散系数达到3.25×10^-14cm²·S^-1,是未修饰电极的2.95倍,同时在5C倍率下,LiTi_0.25Zr_1.75(PO₄)₃修饰的电极比未修饰电极比容量提高了25.48 mAh·g^-1。     

(K1-xNax)（Ta（1-y）Nby）O3纳米粉体的水热合成研究

采用水热法合成了不同组分的无铅压电(K1-xNax)(Ta1-yNby)O3(KNTN)纳米粉体。研究结果表明,在高介质碱度条件下可以获得K/Na摩尔比为1的KNTN纳米粉体。随着K含量的增加,产物由单斜向四方晶型转变。产物中的Ta/Nb摩尔比与原料中Ta2O5/Nb2O5摩尔比呈线性关系。随着Ta含量的增加,KNTN由正交→四方→立方晶型转变,其微结构则由长方体逐渐转变为立方体结构。     

Preparation and Characterization of Alumina-coated Hollow Quartz Fiber Reinforced Al2O3–SiO2 Aerogel Composite

Al₂O₃-SiO₂ sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane (TEOS) as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnating Al₂O₃-SiO₂ sol into a needle fabric made by coate...