复合氧化物纳米粉体颜料的制备和表征

印染行业重点技术发展的目标之一就是研制开发高效、环保、安全的新型染化料,为了解决纺织印染中的废水污染问题,发展无水印染新技术,是一个引起人们广泛关注的新研究方向。我们受红宝石,蓝宝石结构特征的启发,尝试采用均相沉淀法合成以α-氧化铝为基质,通过少量掺杂呈色离子的复合氧化物颜料。实验中,将结晶氯化铝和一定比例的发色离子氯化物混合,用适量的蒸馏水溶解,再溶入尿素和聚乙烯吡咯烷酮,超声振荡均匀,将上述液体加热回流,煅烧反应后的产物,得到纳米无机颜料。通过XRD测定样品的晶型和纯度,确定新型颜料的主体成分是α-氧化铝,用紫外可见光谱仪测试样品的漫反射光谱,发现掺杂离子周围的配位环境变化导致吸收峰谱带发生变化。在此基础上用分光密度仪表征样品的色度,应用SEM进行微观形貌分析,样品粒径范围在200～300nm。将制成的复合氧化物颜料用饱和盐酸浸泡,对浸出液进行ICP测试,发现掺杂离子溶出量非常少,说明新型颜料具有良好的化学稳定性。上述结果说明,这类新型无机纳米粉体颜料各种耐性良好、无毒害,可以满足熔体纺丝要求,有望在无水印染方面得到应用。     

白光LED蓝光转换材料的发光特性研究

用稀土氧化物作为原料,通过高能球磨与反应烧结的方法,在1 300 ℃合成了高纯度的铈激活和铈、钆共激活的钇铝石榴石蓝光转换材料,采用X射线衍射分析了产物的晶体结构,采用发射光谱和激发光谱研究了基质中Ce3+的发光特性以及Gd3+对它的影响。结果表明,产物为立方晶系的钇铝石榴石晶体,可以被蓝光有效激发,通过调整掺杂离子的摩尔浓度,荧光粉的发射波长可覆盖530～560 nm的黄绿光范围。利用荧光粉转换法制备了白光LED(light emitting diode, 发光二极管),在工作电流为20 mA、工作电压为3.5 V的条件下,所制备的白光LED色坐标x=0.310,y=0.323,光效26.131 m·W-1,显色指数81.8,色温6 605 K。     

黑龙江穆棱地区宝石级石榴石的宝石学及谱学特征

对黑龙江穆棱新生代玄武岩产出的宝石级石榴石进行了宝石学常规测试、电子探针测试、拉曼光谱、红外光谱和紫外-可见光谱测试,以获得该区石榴石的宝石学特征和谱学特征。化学成分分析表明,该区石榴石为镁铝榴石,含有Fe,Ca,Mn,Cr,Ti等杂质元素。其平均晶体结构化学式为 (Mn_0.022Ca_0.455, Fe2+_0.720, Mg_1.793)_∑=2.990(Ti_0.003Cr_0.009Fe3+_0.062Al_1.951)_∑=2.025(SiO₄)₃。拉曼光谱分析表明该区石榴石存在混合相,由石榴石桥氧振动引起的拉曼位移峰反映出该特征。镁铝榴石桥氧弯曲振动拉曼位移峰位于560 cm-1(A₁g模)和641 cm-1(E_g+F₂g模),钙铝榴石和铁铝榴石桥氧弯曲振动E_g+F₂g模形成的拉曼位移峰分别位于507和486 cm-1。官能团区红外光谱显示该区镁铝榴石中不存在分子水,但少数镁铝榴石中存在少量的结构水,它们在3 585,3 566和3 544 cm-1处形成阶梯状的弱小吸收峰。该区镁铝榴石多为褐红色,其颜色由杂质离子Cr3+,Fe3+,Mn2+产生。紫外-可见吸收光谱显示,Fe3+的电子跃迁致570,521和502 nm吸收峰,Mn2+的电子跃迁致460和430 nm吸收峰,Cr3+电子跃迁致690和367 nm吸收峰。     

不同工艺下YAG:Ce3+荧光粉的超声共沉淀合成及表征

用共沉淀正滴及反滴工艺,以普通共沉淀及超声辅助共沉淀的方式制备了不同YAG∶Ce³⁺前驱体,并通过焙烧前驱体粉末合成了YAG∶Ce³⁺荧光粉。利用XRD、SEM、激光粒度分布仪及荧光分光光度计对所制备样品进行了表征。结果表明,所得样品均为纯相钇铝石榴石结构,反滴工艺下制得的YAG∶Ce³⁺荧光粉的发光强度高于正滴工艺下的同类样品。且相对于普通共沉淀来说,无论正滴还是反滴工艺,通过超声共沉淀方式制得的荧光粉样品均具有更均匀的晶粒粒径、更窄的粒径分布及更高的发光强度。     

Er,Yb:YAG微晶玻璃发光特性的研究

高温熔制Er³⁺，Yb³⁺离子掺杂CaO-Y₂O₃-Al₂O₃-SiO₂系统玻璃，并进行微晶化处理，研究了微晶玻璃中Er³⁺离子的发光及上转换发光特性，分析了微晶玻璃上转换发光机理.结果表明：原始玻璃经热处理得到了Er,Yb:YAG微晶玻璃，微晶玻璃中Er³⁺离子在室温下⁴I_13/2→⁴I_15/2跃迁产生横盖1450—1650nm区间的超宽带荧光，荧光半高宽达180nm，这可能由于YAG微晶相中Er³⁺离子与玻璃相中残留Er³⁺离子的共同发光；Er³⁺与Yb³⁺离子局域基质声子能量的降低使微晶玻璃Er³⁺离子上转换发光强度与原始玻璃相比显著提高，绿光、红光上转换荧光强度比玻璃样品分别增强约7和3倍；微晶化后Er³⁺，Yb³⁺离子局域环境发生变化也导致微晶玻璃中Er³⁺离子绿光、红光上转换发光相对强度发生变化. 关键词： 铒 镱:钇铝石榴石 微晶玻璃 荧光光谱     

沉淀过程pH值对铈锆复合氧化物结构与性能的影响

采用加热回流老化技术制备了系列组成为0.6CeO₂-0.4ZrO₂的铈锆复合氧化物,通过N₂物理吸附、Raman光谱、UV-Vis 漫反射光谱等方法对沉淀过程pH值对铈锆复合氧化物结构及储氧性能的影响进行了研究。结果表明,沉淀过程pH值不同,将导致铈锆复合氧化物的组成产生波动,进而影响样品的晶相组成、缺陷性质、结晶程度和孔结构性质。控制沉淀pH值为10.5～11.0,可消除Si的影响,改善铈锆复合氧化物的孔结构,提高相均匀性,提高缺陷浓度,降低结晶度,从而可提高样品的储氧性能。     

YAG及其掺杂纳米粉体的结构与光学特性

由于透明多晶钇铝石榴石(YAG)陶瓷在高功率全固态激光器中巨大的应用价值,所以其研究在近几年引起了广泛的关注。YAG陶瓷与其单晶材料相比,可以实现大尺寸激光晶体,高掺杂浓度,并且制备的成本低。我们报道水热方法制备的纯YAG和硅、铷掺杂YAG陶瓷纳米粉体中掺杂与煅烧温度对陶瓷相组分、晶格参数和晶粒尺寸的影响。通过XRD和透射电子显微镜表征了YAG陶瓷及掺杂粉体的结构及其受到掺杂和烧结的作用,利用光吸收和发射谱研究了共掺杂和煅烧温度对YAG陶瓷粉体光学特性的影响。结果表 Si⁴⁺和Nd³⁺的共掺杂提高了Nd³⁺在YAG纳米体中的可溶度,促进了YAG相的生成,单相纳米Si/Nd:YAG粉体在920℃煅烧温度即可获得。它的光学特性与报道的单晶Nd:YAG一致。     

氚β射线驱动的荧光灯

采用了放射性同位素氚在衰变过程中放射出β粒子激活发光材料发光的原理。因β粒子平均自由程只有4.3 mm,灯型选择直径应在4~8 mm之间。通过实验比对,确定常用的发光材料为:发红光材料硫氧钇 : 铕(Y₂O₂S : Eu);发绿光的发光材料硫化锌 : 铜,铝(ZnS : Cu,Al);发蓝光的发光材料硫化锌 : 银(ZnS : Ag)。经过测试选择发光材料的最佳平均粒度:硫氧钇铕4.6 μm;硫化锌铜铝5.3 μm;硫化锌银5.4 μm。同时探讨了涂屏方法和充氚排气工艺。对制作的氚灯进行了光亮度测试。最后给出了氚灯的使用与保存方法。     

荧光粉Y3Mg2AlSi2O12∶Ce3+的合成及光谱性能研究

采用溶胶-凝胶法合成了Y₃Mg₂AlSi₂O₁₂∶Ce³⁺荧光粉。用X射线粉晶衍射(XRD)仪对其进行了物相分析,用电子扫描电镜(SEM)观察了该荧光粉的形貌,同时测定了激发光谱及发射光谱。结果表明,Y₃Mg₂AlSi₂O₁₂∶Ce³⁺的晶体结构与Y₃Al₅O₁₂(钇铝石榴石)一致,形貌也表现出等轴粒状的特点。发射谱为峰值位于580 nm处的宽带发射,是Ce³⁺的 4f⁶5d¹-4f⁷特征跃迁发射。激发谱表现为340 nm和468 nm的双峰带,可以被蓝光有效的激发。Ce³⁺的浓度对发光强度有明显的影响,当Ce³⁺的摩尔分数为0.06时,发光强度最大。最后考察了成分取代而导致的Y₃Mg₂AlSi₂O₁₂∶Ce³⁺的物相转变和对发光性能的影响。     

高功率二极管泵浦铒激光器

Bradley等人在OPTCON’92 LEOS会议上报告了一种功率高达500mY连续波单片式掺铒激光器。诸如YSGG(钇钪镓石榴石)、GGG(钆镓石榴石)、BYF(氟化钇钡)和YAG(钇铝石榴石)等多数基质晶体掺铒后,连续波激光波长在2.8μm左右。所有晶体部可进行二极管泵浦,这就使固体激光系统能小型化。这种铒激光器能用于激光外科手术和产生可调红外光的泵浦光参量振荡器等方面。     

Synthesis and optical characterization of Gd2O3:Eu nanocrystals: surface states and VUV excitation

This paper reports on the synthesis and characterization of Gd₂O₃:Eu³⁺ nanocrystals of different sizes. The particles have been synthesized by a sol-lyophilization process. This methods allows the synthesis of 7–100 nm diameter cubic-phase particles. The photoluminescence properties have been studied with different excitation from X-ray to VUV and visible wavelengths. Compared to the properties of the bulk materials, some important changes on the luminescence are observed. In particular some bands are strengthened when the size of the particles is diminished. We could therefore ascribe this bands to doping ions on a site close to the surface. Also a very low efficiency of excitation for small particles is observed when exciting with X-ray or high-energy VUV photons (i.e. when exciting the host matrix) compared to the efficiency obtained when exciting in the charge transfer band or in the doping ions related states.     

Fabrication of diarylide yellow pigments/modified SiO2 core-shell hybrid composite particles for electrophoretic displays

Diarylide yellow pigments/modified SiO₂ core-shell hybrid composite particles were fabricated via a newly developed two-step procedure. The surface of diarylide yellow pigments was coated with SiO₂ by the hydrolysis of Na₂SiO₃. The obtained particles were then modified with in situ generated 3-aminopropylsilanetriol or succinic acid to form composite particles containing amino or carboxyl groups. The FT-IR spectra, TGA and TEM showed that the particles had a core-shell structure, the SEM suggested that the surface morphology of the composite particles was smooth, and the XPS and zeta potential measurement indicated that the composite particles had a high charge load. The obtained composite particles have been applied as electrophoretic particles in the electronic paper, which demonstrated that the newly developed procedure is an effective way to produce various organic/inorganic composite particles used for electrophoretic displays.     

聚酰亚胺/钽铌酸钾纳米颗粒复合材料结构与机械性能分子动力学模拟

利用多尺度建模方法构建了聚酰亚胺/钽铌酸钾纳米颗粒复合物模型, 通过分子动力学模拟研究了不同尺寸钽铌酸钾纳米颗粒(5.5, 8.0, 9.4, 10.5, 11.5 Å)对复合材料的结构、弹性模量和相互作用能的影响规律, 并通过计算纳米颗粒表面原子键能和单位表面积原子数目探究了复合物机械性能提高的内部机理. 聚酰亚胺和聚酰亚胺/钽铌酸钾复合材料的杨氏模量分别为2.91和3.17 GPa, 泊松比分别为0.37和0.35, 钽铌酸钾纳米颗粒的引入可以显著改善聚酰亚胺的机械性能. 纳米颗粒表面原子的键能为8.62-54.37 kJ·mol^-1, 表明颗粒与基体主要通过范德华力作用结合且有氢键存在. 计算结果表明, 相同掺杂比例下, 纳米颗粒尺寸越小, 纳米颗粒表面原子数目越大, 颗粒与基体作用更强, 杨氏模量的提高幅度越大, 尺寸效应越显著. 因此, 掺杂小尺寸纳米颗粒是提高聚酰亚胺机械性能的有效途径.     

Preparation of low density TiO2/poly (methyl methacrylate) composite particles by emulsifier-free emulsion polymerization

Based on the 3-(trimethoxysilyl) propylmethacrylate (MPS) modified TiO₂ particles, the TiO₂/poly (methyl methacrylate) (PMMA) composite particles have been prepared successfully via emulsifier-free emulsion polymerization in water. A facile floating-sinking method is proposed to roughly evaluate the composite particles’ density. Chemical component of obtained composite particles was identified by Fourier transform infrared spectra (FTIR). The morphology and grain size of the composite particles were investigated by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Thermal analysis of the composite particles was measured by differential thermal analysis-thermo gravimetric analysis (DTA-TGA). The zeta potential and electrophoretic mobility of composite particles with suitable density in water was measured by dynamic light scattering (DLS).     

Preparation and characterization of nickel nano-Al2O3 composite coatings by sediment co-deposition

Ni-Al₂O₃ composite coatings were prepared by using sediment co-deposition (SCD) technique and conventional electroplating (CEP) technique from Watt's type electrolyte without any additives. The microstructure, hardness, and wear resistance of resulting composites were investigated. The results show that the incorporation of nano-Al₂O₃ particles changes the surface morphology of nickel matrix. The preferential orientation is modified from (2 0 0) plane to (1 1 1) plane. The microhardness of Ni-Al₂O₃ composite coatings in the SCD technique are higher than that of the CEP technique and pure Ni coating and increase with the increasing of the nano-Al₂O₃ particles concentration in plating solution. The wear rate of the Ni-Al₂O₃ composite coating fabricated via SCD technique with 10 g/l nano-Al₂O₃ particles in plating bath is approximately one order of magnitude lower than that of pure Ni coating. Wear resistance for SCD obtained composite coatings is superior to that obtained by the CEP technique. The wear mechanism of pure Ni and nickel nano-Al₂O₃ composite coatings are adhesive wear and abrasive wear, respectively.     

Nanocrystalline oxide (Y2O3, Dy2O3, ZrO2, NiO) coatings on BaTiO3 submicron particles by precipitation

Nanocoatings (5–20 nm) of different compounds on fine BaTiO₃ particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO₃ and Dy(OH)CO₃ were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparticles was produced from zirconyl nitrate solution using ammonia as a precipitating agent after adsorption of a polymeric polyelectrolyte on the BaTiO₃ surface. Composite particles with a peculiar morphology were obtained by inducing heterogeneous nucleation and growth of Ni(OH)₂ lamellae on the BaTiO₃ surface. The different shells can be transformed in a nanocrystalline coating of the corresponding oxide (Y₂O₃, Dy₂O₃, ZrO₂, NiO) by calcination at moderate temperatures (400–700 °C). The overall results indicate that precipitation from solution represents a versatile process to grow a second-phase layer on the surface of BaTiO₃ particles. This approach can be used as an alternative to mechanical wet mixing for controlled doping of ferroelectric materials and for the fabrication of composite materials with specific geometry of the two-phase assembly.     

Nd crystal-field study of weakly doped Nd1−xCaxMnO3

Nd³⁺ crystal-field excitations in Nd_1−xCa_xMnO₃ (x=0.025, 0.05 and 0.1) single crystals are studied via infrared transmission as a function of temperature and external magnetic field. We report excitations associated with Nd³⁺ sites as detected in NdMnO₃ and excitations due to Ca doping. The latter reveal phase separation between the usual A-type antiferromagnetic states and the insulating canted (ferromagnetic) spin states in the vicinity of doped Ca²⁺ ions. Both Nd³⁺ crystal-field levels could be described using calculated parameters for NdMnO₃. Also, while oxygen stoichiometry and coherent Jahn–Teller distortions seem not to be affected by Ca doping, increased absorption bandwidths characterize the doped crystals.     

Preparation and characterization of the electrodeposited Cr-Al2O3/SiC composite coating

To increase the SiC content in Cr-based coatings, Cr-Al₂O₃/SiC composite coatings were plated in Cr(VI) baths which contained Al₂O₃-coated SiC powders. The Al₂O₃-coated SiC composite particles were synthesized by calcining the precursor prepared by heterogeneous deposition method. The transmission electron microscopy analysis of the particles showed that the nano-SiC particle was packaged by alumina. The zeta potential of the particles collected from the bath was up to +23 mV, a favorable condition for the co-deposition of the particles and chromium. Pulse current was used during the electrodeposition. Scanning Electron Microscopy (SEM) indicated that the coating was compact and combined well with the substrate. Energy dispersive X-ray analysis of Cr-Al₂O₃/SiC coatings demonstrated that the concentration of SiC in the coating reached about 2.5 wt.%. The corrosion behavior of the composite coating was studied by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The data obtained suggested that the Al₂O₃/SiC particles significantly enhanced the corrosion resistance of the composite coating in 0.05 M HCl solution.     

Effect of chloride doping concentration on enhancement of protonic conductivity of mesoporous Al2O3

Mesoporous Al₂O₃ was prepared by a sol-gel method with doping different amount of LaCl₃. The proton conductivity of mesoporous Al₂O₃ increased with increasing the doping concentration up to the optimum doping, 0.1 Cl/Al mole ratio. The surface acidities of different samples were investigated by NH₃-TPD method. The change trends of surface acidity are consistent with that of proton conductivity. It indicates that the proton conductivity of mesoporous Al₂O₃ can be increased by enhancing its surface acidity via the chloride doping.     

Improvement in Dielectric Tunability of Ba0.6Sr0.4TiO4-Mg2TiO4 Composite Ceramics via Heterogeneous Nucleation Processing

Dielectric tunable composite ceramics Ba0.6Sr0.4 TiO4-Mg2 TiO4 （BST-MT） are prepared with a heterogeneous nucleation sol-gel approach. The Mg2 TiO4 powders are synthesized by the conventionM solid-state reaction method. The micro-sized MT powders with dispersant Ciba-4010 are introduced into Ba-Sr-Ti sol to obtain uniform and homogeneous mixture compounds with nano-sized BST particles synthesized via heterogeneous nucleation （HN） in the sol-gel process. Thus, the mierostructural and dielectric properties can be tailored. The dielectric constants of BST-MT composite ceramics can be adjusted in a larg＇e range from 294 to 1790, and the dielectric tunability can be adjusted from 29.4% to 37.0% with different MT contents from 60wt% to 20wt%. Compared to the samples prepared by the conventional solid-state （SS） process, the BST-MT composite ceramics by the heterogeneous nucleation sol-gel process exhibit a more uniform microstructure, and improve dielectric properties.