浅析环境友好型稀土长余辉发光涂料

稀土发光材料具有余辉时间长、发光强度高、化学稳定性好等优点,可配制环境友好型长余辉发光涂料。介绍了该发光材料的制备方法及其发光涂料的发光机理。讨论了影响发光涂料性能的因素及其发展趋势。     

稀土发光聚合物的研究进展

稀土发光聚合物既有稀土金属优异的发光特性,又有聚合物良好的成型加工性能,是一类新型的发光材料.阐述了稀土发光聚合物的发光机理,归纳了稀土发光聚合物的制备方法.     

稀土铕配合物发光材料的制备与应用

稀土铕发光材料因其具有较强的特征荧光,而且具有色纯度高、化学稳定性好、激发寿命较长和理论量子效率高等优点,已成为生物、医学、光、电、磁等领域研究的重要内容。本文主要总结了由稀土铕掺杂配合物制备发光材料的研究进展,从发光性质、稀土发光材料以及稀土铕掺杂配合物等方面展开论述。着重讨论近年来稀土铕掺杂配合物在新型发光材料方面发挥的作用以及相关研究成果,并展望了稀土发光材料的应用前景。     

浅谈发光陶瓷的制备工艺和研究现状

本文总结了发光陶瓷的制备工艺、发光性能研究和工业化应用现状。根据现有研究的成果,本文分析了金属硫化物类发光陶瓷和稀土掺杂类发光陶瓷的不同特点,并展望了未来发光陶瓷的前景。     

PP/稀土铝酸锶发光材料的制备及性能研究

采用熔融共混的方法制备了聚丙烯（PP）/稀土铝酸锶复合材料,研究了稀土铝酸锶用量对PP/稀土铝酸锶复合材料结晶性能、力学性能和光学性能的影响。结果表明,稀土铝酸锶的加入没有改变PP的晶型;稀土铝酸锶起异相成核作用,结晶度随着稀土铝酸锶含量的增加有不同程度的增加,与PP相比,复合材料的球晶尺寸细小而均匀;PP/稀土铝酸锶复合材料的拉伸强度和断裂伸长率均随着稀土铝酸锶含量的增加出现先增大后减小的趋势;随着稀土铝酸锶含量的增加,复合材料的初始光强度逐渐增大,而发光强度衰减曲线均呈指数规律衰减。     

稀土掺杂量子剪裁和上转换发光材料的制备及应用进展

稀土元素特殊的电子构型,使其具有优异的光性能,成为新的发光材料的宝库。在照明显示、分析检测等领域,稀土发光材料近年来已经得到了广泛的应用。而且也有多种不同的稀土发光材料问世,如稀土长余辉发光材料和稀土配合物发光材料等。重点介绍了两种新型的稀土发光材料：拥有高效下转换发光效率的稀土掺杂“量子剪裁”发光材料和在生物医学领域有着巨大潜力的稀土掺杂“上转换”发光纳米晶体。对两种发光材料的发光机理进行了描述,并重点展示了两种材料的制备和应用进展。     

稀土荧光粉的制备技术研究与展望

稀土荧光粉作为荧光粉领域的主要类型之一,其工业制备技术成熟,性能优良,应用广泛。稀土荧光粉主要用于现代照明光源、交通信号灯、汽车状态指示、液晶显示（LCD）的背光源和大屏幕显示等方面。要想获得优异性能的荧光粉,对制备工艺的研究是关键。介绍了目前国内外制备稀土荧光粉的各种方法,主要有高温固相反应法、软化学法、物理微波合成法等。对这些方法的优缺点进行了比较。最后对荧光粉合成方法的发展前景及今后的研究趋势进行了展望。     

PA6/稀土复合材料的结构和性能研究

通过熔融共混法制备了聚酰胺6(PA6)/稀土复合材料,采用红外光谱测试仪、差示扫描量热仪、X射线衍射仪等对其结构和性能进行了研究。结果表明,PA6与稀土没有发生化学相互作用,稀土对PA6起到异相成核作用,促进γ晶型的生成,但阻碍了α晶型的完美排列;复合材料的结晶度和结晶温度均高于纯PA6;随着稀土含量的增加,复合材料的拉伸强度略有降低,而断裂伸长率先增加后降低;稀土含量为6 %（质量分数,下同）时,断裂伸长率达到328.25 %;PA6/稀土复合材料的初始亮度随着稀土含量的增加而逐渐增强,而亮度呈指数规律衰减。     

蓄能型发光涂料的研究

发光涂料由最初的具有放射性的自发光涂料发展到如今无放射性危害、性能优异的稀土激活碱土金属铝酸盐基发光材料,给许多领域的新材料研制带来了新的发展空间。本文着重对稀土激活碱土金属铝酸盐发光涂料的发光机理和制备方法进行了论述,并分析了自发光涂料的发展前景。     

稀土掺杂红色长余辉发光材料的研究进展

介绍了稀土掺杂红色长余辉发光材料的研究进展,总结了硫化物、硫氧化物、钛酸盐等基质体系的红色长余辉发光机制。及传统的高温固相法以及溶胶-凝胶法、燃烧法等稀土红色长余辉材料的制备技术,提出了对红色长余辉材料今后发展的看法。     

Performance of Anaerobic Reactors during Pseudo-Steady-State Operation

Four anaerobic reactors were studied for the purposes of this work: two anaerobic fluidized bed reactors (AFBR) using diatomaceous earth and granular activated carbon as immobilization media (R1 and R2, respectively), a packed-bed reactor (R3), and a suspended growth reactor (R4). A nutrient-supplemented wastestream with glucose as the main carbon source was treated. Successful reactor start-up was achieved for all four anaerobic reactors. These reactors were able to handle organic loading rates of more than 12000, 7500, 6000 and 650 mg dm⁻³ day⁻¹ for R1–R4, respectively. Anaerobic fluidized bed reactors were less affected by interruptions and adverse operating conditions than were packed-bed and suspended growth reactors. Immobilized cell reactors and, specifically, AFBRs were clearly superior to conventional high-rate digesters. This enhanced performance is primarily due to the very high cell retention ability of such reactors. High total organic carbon (TOC) removal efficiencies were achievable under pseudo-steady state operation. Removal efficiencies above 98% were observed for all reactors. Specific biogas production rates of 1·5–1·7, 1·4–1·7, 1·1–1·5 and 0·9–1·3 dm³ of methane per gram of TOC removed for R1–R4, respectively, were attained. A consistent biogas methane content of 52·5–55·9% was observed. Biomass concentrations of 84, 91, 21 and 1·9 g VS dm⁻³ were measured for R1–R4, respectively. Extremely high biomass concentrations in AFBRs were possible due to the high available specific surface area. © 1997 SCI.     

Phase evolution and hydraulic properties of low cement castables matrixes

Abstract

To identify the hydration products of aggregate-free, low cement castables (LCC), cement matrixes were examined. Two series of cementing batches based on 33·3 and 50·0 wt-% high alumina cement (HAC) were processed by adding ultra-fine calcined alumina/fumed silica mixtures (FA/FS) with weight ratios of 1·0, 1·5, 2·3, 4·0, and 9·0 to each series. The hydrated batches were investigated for their hydraulic properties. Batches showing the highest cold crushing strength with minimum water of consistency (WOC) and reasonable setting time (ST) were selected and characterised with respect to phase composition, microstructure, and microchemistry, before and after firing up to 1400°C, by XRD, DTA, and SEM techniques. Cementing batches containing ≈33 wt-% HAC, and ≈67 wt-% FA/FS mixtures with ratios of 4·0–9·0 show optimum particle packing and hydration conditions with the least amount of WOC. This results in increases in cold crushing strength (CCS) of cementing batches up to 58 MPa after hydration for 3 d. The hydrated batches are composed mainly of unreacted α-Al₂O₃ particles bonded by CAH₁₀, AH₃, and C₂ASH₈ phases. On firing up to 1400°C, the hydrated phases are transformed into anhydrous CA₂ and CA₆ patches enclosing limited amounts of CAS₂ and/or C₂AS phases. Such batches are suitable for application as cementing matrixes for high alumina low cement castables. The low HAC content with high FA/FS ratio in the presence of more fine alumina in the matrixes of such castables leads to significant improvement in their hot mechanical properties.     

Conduction of (Na,Ce) doped Bi5Ti3FeO15 ceramics after different annealing processes

Abstract

Abstract

Bi_5?xNa_x/2Ce_x/2Ti₃FeO₁₅ (BNTF-100x, x?=?0, 0·05, 0·10, 0·20, 0·30, 0·40 and 0·60) ceramics were prepared via solid state sintering process. With x increasing, the resistivity increases at first and then decreases. The lower the concentration of oxygen vacancies, caused by more (Na,Ce) dopant adding, the less the deep trap energies in the band gap for the activated electrons to be mobile. For the samples containing high concentration of oxygen vacancies, the conductivities are higher when they are annealed in the air and oxygen than that in the vacuum. On the contrary, for the samples containing low concentration of oxygen vacancies, the conductivities of the samples in different annealing conditions behave quite the same way. Most (Na,Ce) doped Bi₅Ti₃FeO₁₅ ceramics exhibit intrinsic conduction at high temperatures with corresponding activation energies of 1·1–1·6 eV, while the extrinsic conduction has a close relationship with the concentration of oxygen vacancies and the activation ability of electrons.     

The evaporation and condensation coefficient of water,ice and carbon tetrachloride

The evaporation and condensation coefficients of water, ice and carbon tetrachloride were determined in the same experimental apparatus. Both low and high values were obtained for all three materials. An unsteady-state experimental method was used and the high values resulted when the evaporating or condensing times were very short. Surface temperature errors of two different types are shown to be the major factor in contributing to low values. The condensation coefficient of water is at least 0·7 and could easily be 1·0. Condensation coefficients of 0·55 were measured for ice and 0·94 for carbon tetrachloride.     

吖啶橙受溶液pH和浓度变化的光谱研究

利用荧光光谱分析仪研究吖啶橙受溶液pH和浓度变化的吸收光谱和荧光光谱的变化。实验表明,当改变吖啶橙溶液pH和浓度时,它的吸收光谱和荧光光谱发生位移。吖啶橙为1×10-6mol/L时,不同pH的吖啶橙溶液均在(490±3)nm出现一个强吸收峰,pH=6.5,吸收光谱的λm ax=430 nm,发生蓝移;而荧光光谱的λm ax随pH增大发生红移,荧光强度减弱。在浓吖啶橙溶液中,不同pH的吖啶橙溶液的吸收光谱的形状基本相同,出现两个吸收峰,λm ax1分别为(455±3)nm和(430±3)nm,λm ax2分别为(505±4)nm和(510±2)nm,吸收光谱红移;荧光光谱的λm ax均为(535±2)nm,荧光强度荧光很弱。pH相同或相近时,吖啶橙溶液的吸收光谱蓝移和荧光光谱红移,浓度越大,荧光强度越弱。还探讨了吖啶橙在水溶液中的赋存状态,结果表明,在稀溶液中,吖啶橙主要以单体的形式存在;在高浓度吖啶橙溶液中则以吖啶橙单体、二聚体,甚至多聚体形式存在。这说明溶液pH主要影响到吖啶橙分子基态的质子化和氢键的形成能力,使得分子的基态与激发态之间的能量间隔发生了变化,吖啶橙被质子化,则引起发光光谱向短波方向移动,而离解作用,则引起发光光谱向长波方向移动;吖啶橙浓度变化影响吖啶橙在水溶液赋存状态,引起吸收光谱向短波方向移动或向长波方向移动。     

Mixed Matrix Silicone and Fluorosilicone/Zeolite 4A Membranes for Ethanol Dehydration by Pervaporation

The ability of homogeneous and mixed matrix membranes prepared using standard silicone rubber, poly(dimethylsiloxane) (PDMS), and fluorosilicone rubber, poly(trifluoropropylmethylsiloxane) (PTFPMS), to dehydrate ethanol by pervaporation was evaluated. Although PDMS is generally considered to be the benchmark hydrophobic membrane material in pervaporation, water/ethanol molar permselectivity of a pure PDMS membrane was found to be 0.89 for a feed containing 80/20 w/w ethanol/water at 50°C, indicating a slight selectivity for water. Fluorinated groups in PTFPMS improved the water-ethanol permselectivity to 1.85, but decreased the water permeability from 9.7 × 10^?12 kmol · m/m² · s · kPa in PDMS to 5.1 × 10^?12 kmol · m/m² · s · kPa (29,000 and 15,200 Barrer, respectively). These water permeabilities are attractive, particularly since the rubbery materials should not experience the steep declines in water permeability observed with most standard dehydration membranes as water concentration in the feed decreases. However, the water selectivity is lower than desired for most applications. Particles of hydrophilic zeolite 4A were loaded into both PDMS and PTFPMS matrices in an effort to boost water selectivity and further improve water permeability. Water-ethanol permselectivities as high as 11.5 and water permeabilities as high as 23.2 × 10^?12 kmol · m/m² · s · kPa were observed for the PTFPMS/zeolite 4A mixed matrix membranes?6 times higher than for the unfilled PTFPMS membrane.     

紫外分光光度法测定聚丙烯酰胺中丙烯酰胺的残留量

研究了在紫外光下,用分光光度法测定聚丙烯酰胺中丙烯酰胺残留量的新方法,该方法简单,准确度、精密度好,摩尔吸光系数为1．28×104L·mol－1·cm－1,丙烯酰胺含量在0～2400μg·L－1范围内呈良好的线性关系。用于实际样品测定,取得了满意的结果。     

Carbon-coated cation-disordered rocksalt-type transition metal oxide composites for high energy Li-ion batteries

Li-excess cation-disordered rocksalt oxides have attracted extensive attention for their high capacity (>210 mA h g^?1) and energy density. In these oxides, both cationic and anionic redox take responsibility for bringing capacity. However, anionic evolution as well as their intrinsic poor electronic conductivity raises the problem in large polarization and inferior rate performance of these oxides, especially for Ni-based ones. Herein, we report a facile strategy to synthesize a series of Li_1·2Ni_0·3Ti_0·3Nb_0·2O₂ (LNTNO20) @ C using different mass ratios of carbon precursor and calcination temperatures. It is found that carbon-coated materials possess impressive electrochemical properties with both high specific capacity and rate performance. Specifically, Li_1·2Ni_0·3Ti_0·3Nb_0·2O₂@C synthesized with ratio of 6:1 (LNTNO20: sucrose) and calcination temperature of 450 ^○C exhibits an initial specific capacity of 268.2 mA h g^?1 and a high capacity retention of 90.1% after 50 cycles. Based on multi-scale test results, we propose that carbon coating process using moderate mass ratio of carbon precursor and calcination temperature will increase tetrahedron height making Li diffuse easily. Besides, carbon coating layer reduces polarization upon cycling, protects cathode from reacting with electrolyte retarding SEI layer thickening and enhances electronic conductivity. Therefore, carbon coating is a facile and effective strategy to improve properties of Ni-based cation-disordered oxides.     

Ultrafiltration Carbon Membranes from Organic Sol-Gel Process

We present a simple approach for preparing mesoporous carbon membranes on macroporous fly-ash-based ceramic supports via sol-gel polymerization of resorcinol with formaldehyde. The support was dip-coated and dried at 45°C under ambient pressure without a special drying process. The mesoporous carbon membrane was obtained after carbonization under a nitrogen atmosphere. The coating–pyrolysis process only required one cycle. The graphitization degree increased with carbonization temperature, as shown by X-ray diffraction. However, Raman spectroscopy revealed that defects emerged at high carbonization temperature. Scanning electron microscopy clearly showed the mesoporous carbon layer and macroporous support, a uniform carbon layer with thickness less than 1 µm forming on the support. The obtained carbon membrane shows uniform pores and high mesopore volume. The flux of pure water through the mesoporous carbon membrane was as high as 167 L · m^?2 · h^?1 · bar^?1. The molecular weight cutoff of this membrane was found to be about 20,000 Da.     

Nonstoichiometry and relaxation kinetics of nanocrystalline mixed praseodymium–Cerium oxide Pr0·7Ce0·3O2−x

The oxygen deficiency and kinetics of oxygen uptake and release of nanocrystalline mixed praseodymium–cerium oxide with composition Pr_0·7Ce_0·3O_2−x were investigated by combining coulometric titration and potentiometric measurements using stabilised zirconia oxygen concentration cells. The P(O₂) versus composition isotherms indicate a two-phase region at high P(O₂) [P(O₂)>0·1 bar at 560°C] and a single-phase region at lower P(O₂). The oxygen pressure dependence in the homogeneous region can be described by a power law with an exponent (−1/6), in accordance with doubly charged oxygen vacancies as majority defects. The enthalpy of reduction amounts to (2·9±0·3) eV. The chemical diffusion coefficients are of the order of 10⁻⁶ cm² s⁻¹ at 640°C with an activation energy of ≈0·3 eV. The low activation energy for diffusion may be related to the high density of interface sites in the nanocrystalline material.