凝胶-燃烧法制备掺钕四硼酸铝钇纳米粉体

以硝酸盐为原料、柠檬酸为络合剂,采用凝胶-燃烧法成功制备出了掺钕的四硼酸铝钇[Nd3 :YAl3(BO3)4,Nd:YAB]纳米粉体.分别采用热重-差热分析、X射线衍射、Fourier变换红外光谱和扫描电子显微镜表征了不同温度下焙烧所得粉体的物相、形貌以及前驱体热分解特性.结果表明:Nd:YAB的最低合成温度为1000 ℃,与固相合成方法的最低合成温度相比降低了200 ℃.在反应过程中,首先形成中间相Al4B2O9,YBO3和Y3Al5O12,而最终形成单相的Nd:YAB.在1000 ℃合成Nd:YAB粉体的晶粒尺寸比较均匀,平均粒径为89.3nm.     

Synthesis and Luminescence Properties of Y3Al5O（12）：Eu^（3＋） Phosphors under Vacuum Ultraviolet Excitation

采用凝胶–燃烧法合成了掺Eu3＋的Y3Al5O12（YAG：Eu3＋）荧光粉。分别采用X射线衍射（XRD）、扫描电子显微镜（SEM）、发光光谱等测试手段分析了不同温度下煅烧所得粉体的物相、形貌与发光性质。XRD和SEM结果表明：YAG：Eu3＋的最低合成温度为900℃,并且在该反应过程中没有中间相YAP（YAlO3）和YAM（YAl）的产生。1 100℃合成的晶粒尺寸比较均匀,平均粒径在90 nm左右。发光光谱的测试表明：在592 nm监控下的真空紫外激发光谱由峰值位于147、156、169nm和214nm的系列激发带组成,其分别归属于铝酸根的基质吸收以及Y3＋和Eu3＋的电荷迁移带吸收。在147nm激发下YAG：Eu3＋荧光粉最强发射峰位于592nm处,属于Eu3＋的5D0→7F1跃迁。Eu3＋在基质中的最佳掺杂摩尔分数为4%。     

Gd_3Al_5O_(12)∶Eu~(3 )柠檬酸盐硝酸盐燃烧法合成及其发光性能研究

采用柠檬酸盐硝酸盐燃烧法,在较低的温度(900℃)下成功地合成单一晶相Gd3Al5O12∶Eu3 发光粉体,紫外激发荧光光谱分析表明,粉体615 nm和593 nm荧光发射源于Eu3 的5D0-7F2和5D0-7F1跃迁.该方法中各工艺条件(如pH值、柠檬酸/金属离子比、煅烧温度)对Gd3Al5O12∶Eu3 发光性能均有影响,通过试验得出了获得最佳发光性能荧光粉体的工艺参数.     

正交法优化纳米SrAl2O4:Eu2+,Dy3+制备工艺

采用溶胶-凝胶法合成了SrAl2O4:Eu2+,Dy3+纳米长余辉发光材料,利用正交设计法优化了制备工艺.在传统溶胶-凝胶法基础上,添加了硼酸,在950℃生成单一晶相,该法能使SrAl2O4生成温度降低150℃,生成的磷光体发光强度高、余辉时间长,平均晶粒尺寸为25～90nm.     

Y_2O_3:Eu~(3+)红色荧光粉的水热合成及性能研究

利用水热法合成了Y2O3:Eu3+荧光粉,并对所制得的样品进行了XRD、SEM以及荧光光谱等表征。荧光测试结果表明,Eu3+掺杂浓度为5%时制备的Y2O3:Eu3+荧光粉荧光强度最好。其最大发射峰位于612 nm,对应于Eu3+的5D0→7F2电偶极跃迁,最大激发波长为240 nm对应于从O2-的2p轨道到Eu3+的4f轨道的电荷转移跃迁。通过对比,发现采用水热法制备的荧光粉要比固相法发光性能更强。     

Gd2O3:Eu荧光粉体的制备及其发光特性

分别采用溶胶-凝胶/燃烧合成结合法和共沉淀法合成了Gd2O3:Eu粉体,借助X射线衍射、扫描电镜、透射电镜、分光光度计等分析手段,对比研究了两种工艺制备Gd2O3:Eu荧光粉体的物相组成、形貌及荧光特性.结果表明:共沉淀法合成的Gd2O3:Eu为立方相;溶胶-凝胶/燃烧合成法制备的Gd2O3:Eu为单斜相.溶胶-凝胶/燃烧合成法制备的Gd2O2:Eu粉体蓬松、多孔,但存在一定程度的团聚.共沉淀法制备的立方相Gd2O3:Eu粉体在610 nm处呈现Eu2 的特征荧光;溶胶-凝胶/燃烧合成法制备的单斜相Gd2O3:Eu的发射波长产生红移,其中最强的2个发射峰起源于Eu3 的5D0→7F2跃迁,分别位于612 nm和621 nm.两种工艺制备Gd2O3:Eu粉体荧光特性的差异是由Eu3 在这两种粉体中所处晶格结构的对称性差异引起的.     

溶胶-凝胶法制备SrAl_2O_4∶Eu~(2+),Dy~(3+)纳米发光材料

采用溶胶 -凝胶法在低温、还原气氛下制备了SrAl2 O4∶Eu2 ,Dy3 纳米长余辉光致发光材料。XRD分析表明 ,当焙烧温度为 80 0～130 0℃时 ,所合成的样品为SrAl2 O4单斜晶系晶体结构 ,晶格常数为 :a =0 .8442 4nm ,b=0 .882 2nm ,c =0 .5 160 7nm。 110 0℃以上观察到样品长余辉发光。激发光谱与发射光谱分析表明 :发射光谱是峰值位于 5 2 3nm的宽带谱 ,激发光谱是峰值在 2 40 ,330 ,378,42 5nm的连续宽带谱。样品在自然光照射后持续发出明亮的绿光。样品的合成温度从 110 0℃增加到 130 0℃ ,样品的颗粒尺寸不断增大。TEM和电子衍射分析表明 ,110 0℃烧结 4h的SrAl2 O4∶Eu2 ,Dy3 纳米粉末为结晶相 ,粒径为 30～ 40nm。     

固相反应法制备硼酸铝钇微粉

以氧化铝(Al2O3)、氧化钇(Y2O3)和氧化硼(B2O3)为原料,用固相反应合成法制备硼酸铝钇[YAl3(BO3)4,YAB]粉体.用X射线衍射分析、热重-差热分析和扫描电镜等手段分析YAB的组成和结构.对YAB前驱体在不同温度下进行灼烧,确定了在1200℃保温3h的最佳合成条件.结果表明:固相反应过程中,首先形成中间相硼酸钇(YBO3)和硼酸铝(Al18B4O33),最终形成单相的三方晶体YAB.晶粒尺寸比较均匀,平均粒径为O.5～1μm.     

BaMoO_4:Eu~(3+)红色荧光粉的制备及发光性质

采用柠檬酸溶胶-凝胶法制备了BaMoO4:Eu3+红色荧光粉,差热(DSC) 和X射线衍射(XRD)研究结果表明,经过700 ℃高温烧结后可得到BaMoO4纯物相.粒度分析结果表明,经700 ℃烧结后样品的粒径约为 200 nm,随着烧结温度的升高,产物的粒径明显增大,当烧结温度为800 ℃时,样品的粒径约为 500 nm.分别以392 nm 的近紫外光和 462 nm 的可见光激发样品,BaMoO4:Eu3+荧光粉发红光,对应于Eu3+的4f-4f跃迁,其中以615 nm附近的5D0→7F2电偶极跃迁发光最强,当Eu3+的掺杂浓度约为25 mol %时,在616 nm处的发光强度最大.荧光粉在392 nm和462 nm的吸收分别与紫外光和蓝光LED芯片相匹配.因此,BaMoO4:Eu3+荧光粉是一种可能应用在白光LED上的红色荧光材料.     

Li_2ZnSiO_4∶Eu~(3+)红色荧光粉的制备及其发光性能

采用溶胶-凝胶法合成了适合于近紫外激发的Li2ZnSiO4∶Eu3+红色荧光粉,用X射线衍射、红外光谱和荧光光谱对样品进行了结构及发光性能表征。结果表明:合成样品为四方晶相Li2ZnSiO4晶体。样品的激发光谱由O2--→Eu3+电荷迁移带和Eu3+的离子特征激发峰组成。在波长为395nm的紫外激发下样品发射红光,发射主峰位于613nm,对应于Eu3+离子的5 D0→7 F2跃迁。随着Eu3+掺杂量的增加,其发光强度先增加后减小,Eu3+的最佳摩尔掺量为3.5%。     

Ferroelectric Ceramics in the PbMg1/3Nb2/3O3-PbCd1/3Nb2/3O3 System

Solid solutions (1-x)PbMg_1/3Nb_2/3O₃ + xPbCd_1/3Nb_2/3O₃ with x = 0-0.30 are investigated with purpose to work out a capacitor ceramics with good dielectric properties and low sintering temperature. It is found that the perovskite phase forms at sintering near to 980°C and begins to decompose at higher temperatures. When x grows from 0 to 0.30, the Curie temperature linearly grows from -10°C to +25°C, the dielectric permittivity ε_m in the Curie point T_C decreases from 18000 to 6800 and the phase transition becomes more diffused. The dielectric permittivity at room temperature is rather high and the temperature stability is improved. The system is of interest, because it can serve as a base for working out some ceramic materials for capacitors with low sintering temperature, which needs of no special atmosphere at burning.     

3-溴甲基-3-甲基氧杂环丁烷的合成

以2,2-二溴甲基丙醇（BBMP）为初始原料,通过与碱发生关环反应生成3-溴甲基-3-甲基氧杂环丁烷（BrMMO）。讨论了碱的种类和用量对BBMP关环产率的影响以及反应体系中碱的浓度、反应温度和反应时间对合成BrMMO产率的影响。通过实验确定的最佳工艺条件为：BBMP与NaOH摩尔比为1.0∶1.1,NaOH醇溶液的质量分数为12%,反应温度为78℃,反应时间为4h时,BrMMO产率为65%。最终产品经元素分析、IR和1HNMR检测确定为BrMMO。该试验工艺简单,原料易得,且溶剂便于回收、污染小。     

3-叠氮甲基-3-甲基氧丁环的合成

以三羟甲基乙烷与碳酸二乙酯为原料,经环化反应合成了3-羟甲基-3-甲基氧丁环(HMM O)。在低温下,HMM O与对甲苯磺酰氯反应生成3-磺酸酯甲基-3-甲基氧丁环(M TM O)。M TM O和叠氮化钠发生叠氮化反应形成叠氮单体3-叠氮甲基-3-甲基氧丁环(AMM O)。三步反应收率分别为76%,96%,85%。用核磁、红外、元素分析和DSC表征了化合物的结构与性能。结构鉴定表明为目标化合物AMM O。     

3-溴甲基-3-甲基氧杂环丁烷的合成

以2,2-二溴甲基丙醇(BBMP)为初始原料,通过与碱发生关环反应生成3-溴甲基-3-甲基氧杂环丁烷(BrMMO).讨论了碱的种类和用量对BBMP关环产率的影响以及反应体系中碱的浓度、反应温度和反应时间对合成BrMMO产率的影响.通过实验确定的最佳工艺条件为:BBMP与NaOH摩尔比为1.0∶1.1,NaOH醇溶液的质量分数为12%,反应温度为78℃,反应时间为4 h时,BrMMO产率为65%.最终产品经元素分析、IR和1HNMR检测确定为BrMMO.该试验工艺简单,原料易得,且溶剂便于回收、污染小.     

The Preparation and Crystal Structure of TlMnCl3, TlFeCl3, TlCoCl3 and TlNiCl3

The compounds TlMnCl₃, TlFeCl₃, TlCoCl₃ and TlNiCl₃ were prepared by heating T1C1 with the corresponding transition metal dichloride in an evacuated ampoule. Atomic positions were determined from powder photographs. All four compounds were found to be related to the perovskite type structure. TlMnCl₃ has a cubic structure, space group Pm3m, with a_o = 5.025 Å. The other three compounds are hexagonal, probable space group P6₃mc, with cell dimensions (in Å) a₀ = 6.976 and c₀ = 6.008 for the Fe compound, a₀ = 6.907 and c₀ = 5.981 for the Co compound and a₀ = 6.863 and c₀ = 5.881 for the Ni compound. The three hexagonal compounds are isomorphous. A measureable concentration of basal plane stacking faults was found to occur in TlFeCl₃ and also, to a lesser degree, in TlCoCl_3.     

Tunable color emission in LaScO3:Bi3+,Tb3+,Eu3+ phosphor

LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ (x = 0 − 0.04, y = 0 − 0.05, z = 0 − 0.05) phosphors were prepared via high-temperature solid-state reaction. Phase identification and crystal structures of the LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ phosphors were investigated by X-ray diffraction (XRD). Crystal structure of phosphors was analyzed by Rietveld refinement and transmission electron microscopy (TEM). The luminescent performance of these trichromatic phosphors is investigated by diffuse reflection spectra and photoluminescence. The phenomenon of energy transfer from Bi³⁺ and Tb³⁺ to Eu³⁺ in LaScO₃:xBi³⁺,yTb³⁺,zEu³⁺ phosphors was investigated. By changing the ratio of x, y, and z, trichromatic can be obtained in the LaScO₃ host, including red, green, and blue emission with peak centered at 613, 544, and 428 nm, respectively. Therefore, two kinds of white light-emitting phosphors were obtained, LaScO₃:0.02Bi³⁺,0.05Tb³⁺,zEu³⁺ and LaScO₃:0.02Bi³⁺,0.03Eu³⁺,yTb³⁺. The energy transfer was characterized by decay times of the LaScO₃:xBi³⁺, yTb³⁺, zEu³⁺ phosphors. Moreover absolute internal QY and CIE chromatic coordinates are shown. The potential optical thermometry application of LaScO₃:Bi³⁺,Eu³⁺ was based on the temperature sensitivity of the fluorescence intensity ratio (FIR). The maximum S_a and S_r are 0.118 K⁻¹ (at 473.15 K) and 0.795% K⁻¹ (at 448.15 K), respectively. Hence, the LaScO₃:Bi³⁺,Eu³⁺ phosphor is a good material for optical temperature sensing.     

2,2,3-三氯-3-苯基-3-(3-甲基苯甲酰基)丙腈的合成研究

以苯甲酰氯、四氯化碳、间甲基苯甲酰氰为原料,合成了标题化合物。重点考察了氰化过程中不同原料配比、反应温度、时间、溶剂和催化剂用量对收率的影响。实验结果表明,其最佳反应条件为:n(1,1,2-三氯-2-苯基乙烯)∶n(3-甲基苯甲酰氰)=1∶1.2,二氯甲烷为反应溶剂,3 mmol催化剂三乙胺,室温反应5 h,总收率达80.6%。     

Thermal analyses of poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

Thermal analyses of poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB–HV)], and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by T_o = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight-loss rate was at a maximum was T_p = 0.91B + 320, and the temperature at which degradation was completed was T_f = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), T_o = 0.96B + 308, T_p = 0.99B + 320, and T_f = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), T_o = 1.11B + 305, T_p = 1.10B + 319, and T_f = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight-loss step change. The incorporation of 30 mol % 3-hydroxyvalerate (HV) and 15 mol % 3-hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures T_o, T_p, and T_f relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001