Er~(3+):YAIO_3晶体的吸收光谱及参数计算

测量了Er~(3+):YAlO_3晶体的吸收光谱,并应用Judd-Ofelt理论计算了Er~(3+)离子在YAlO_2晶体中的自发辐射几率、辐射寿命、荧光分支比和积分发射截面,拟合出Er~(3+):YAlO_3晶体的强度參数:Ω_2=0.31×10.10~(-20)cm~2,Ω_4=2.05×10~(-20)cm~2,Ω_6=0.71×10~(-20)cm~2。     

技术答疑(四)

10 用自燃煤矸石作混合材时要注意什么问题? 答:煤矸石是煤矿夹层中的脉石,主要成分为碳质页岩、碳质灰岩、砂质页岩等,其化学成分接近粘土,属硅铝质原料。按其氧化铝含量可分为低铝(Al_2O_315％～25％)、中铝(Al_2O_325％～35％)、高铝(Al_2O_335％～45％)三种。一般说来,煤矸石中二氧     

掺铒铝酸钇(Er~(3+):YAlO_3)单晶生长

开拓新波段的应用是现今固体激光器发展方向之一。掺铒铝酸钇(Er~(3+):YAlO_3)激光晶体是1.66μm及2.7—2.9μm波段固体激光器重要工作物质。本文着重描述Er~(3+)YAlO_3原料硝酸去水、氮气氛加少量氧以及熔体过热等对生长的晶体质量的影响。     

Al_2(WO_4)_3-Na_2O赝二元系相图

用差热分析和X射线衍射方法,研究了Al_2(WO_4)_3-Na_2O赝二元系相平衡关系。体系中生成两个由包晶反应形成的新化合物2Al_2(WO_4)_3·Na_2O和2Al_2(WO_4)_3·3Na_2O,其包晶反应温度分别为800±3℃和682±3℃。化合物2Al_2(WO_4)_3·3Na_2O与Na_2O形成共晶体系,共晶温度592±3℃,共晶点组成为Na_2O73mol％。以Na_2O为助熔剂,长出了Al_2(WO_4)_3:Cr~(3+)的透明单晶体。     

低温煆烧(土凡)土水泥的研究

(土凡)土水泥是法国工程师 Jules Beid 在1908年首先制造的,他把石灰石与铁(土凡)土在水套式的高炉内用熔融法制成。(土凡)土水泥与矽酸盐水泥的主要差别是(土凡)土水泥中以铝酸钙的含量为主,它的化学成分波动范围如下:CaO:28～47%;Al_2O_3:45～70%;SiO_2:0～12%生产(土凡)土水泥的主要原料是(土凡)土和较纯的石灰石,其中最有害的杂质是 SiO_2,因为它与 CaO及 Al_2O_3生成无水硬性的2CaO·Al_2O_3·SiO_2而减少铝酸钙的含量,因此在生产(土凡)土水泥时,要     

Al2（WO4）3相关体系相图及其熔剂挥发动力学

测定了Al_2(WO_4)_3-SrWO_4和Al_2(WO_4)_3-BaWO_4赝二元系相图。Al_2(WO_4)_3与SrWO_4形成共晶体系,共晶温度为103B±3℃,共晶点组成为50％(摩尔含量,以下同)SrWO_4。Al_2(WO_4)_3与BaWO_4也形成了共晶体系,共晶温度为894±3℃,共晶点组成约为42％BaWO_4。用热重法研究了两个体系的熔剂挥发动力学。     

b轴Nd:YAlO_3和Nd Cr:YAlO_3激光晶体的生长

本文介绍Nd(或Nd Cr):YAlO_3单晶的引上法生长。由于该晶体结构上的各向异性(各向异性的热膨胀性能)和高温相的不稳定性,在生长过程中晶体易出现炸裂、孪晶和散射颗粒。作者采用了低气液温差的温场分布,较好地解决了炸裂和孪晶的问题。此外,更加注意了原料纯度、晶体制备中原料的保纯及氮气氛净化去氧。因此,晶体中的铱小片及其它散射颗粒显著地减少。采用上述技术,已生长出一批激光性能良好的晶体。     

壳聚糖碳气凝胶原位负载Fe_(3)O_(4)的制备及其电化学性能EI北大核心CSCD

以壳聚糖(CS)、FeCl_(3)·6H_(2)O为原料,通过原位生长制备了较高比电容的Fe_(3)O_(4)/CS碳气凝胶电极材料,改善了碳基材料比电容低的问题。采用X射线衍射仪、Raman光谱仪分析了样品的晶体结构和结构缺陷,通过X射线光电子能谱仪和扫描电子显微镜对样品的成分和形貌进行了表征,并在三电极体系中测试了其电化学性能。结果表明:Fe_(3)O_(4)成功地负载在CS碳气凝胶上,且两者之间具有良好的结合力。壳聚糖分子上的氨基在碳化过程中实现了N原子自掺杂,复合材料的N含量高达7.21%(摩尔分数)。此外,当在1.0 gCS中引入0.4 gFeCl_(3)·6H_(2)O时,在0.5 A/g的电流密度下复合碳气凝胶表现出315.5 F/g的比容量,与单纯CS碳气凝胶相比,比电容提升了约3倍。     

Nd Ce：YAlO3激光晶体中Ce^3＋→Nd^3＋的能量转移特性

测试并分析了Nd,Ce:YAlO_3晶体的吸收光谱、激发光谱和发光光谱,证实了YAlO_3中存在着Ce~(3+)→Nd~(3+)的能量转移,因此掺入Ce有可能大大提高Nd:YAlO_3的激光效率.     

光折变晶体K(Ta,Nb)O_3的熔盐法生长

本文首次报道在以K_2O-B_2O_3为主要成分的助熔剂体系中,用熔盐法在较低温度(T_(max)<1200℃)下成功地生长出K(Ta,Nb)O_3晶体,初步测量了生成晶体的一些性质。发现含钽量大于一定量后,K(Ta,Nb)O_3晶体在室温下以立方相存在,在生长温度至室温间无相变。本文还讨论了不同体系和添加剂对KTN晶体生长的影响。     

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。     

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%。     

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.     

Ba3Tb(BO3)3:Eu3+的制备与发光性质

采用高温固相法合成了Ba3Tb(BO3)3:Eu3+红色荧光粉,并研究了Ba3Tb(BO3)3:Eu3+的发光特性。Ba3Tb(BO3)3:Eu3+的激发光谱包含250nm～330nm和350nm～400nm的2个宽带,最大峰值位于383nm,可以被紫外-近紫外发光二极管(light-emitting diodes,LED)有效激发。Ba3Tb(BO3)3:Eu3+的发射谱显示出4组发射峰,其主发射峰位于620nm,对应Eu3+的5D0→7F2跃迁;Eu3+掺杂摩尔分数为2%时,Ba3Tb(BO3)3:Eu3+发光亮度最高。经分析发现Ba3Tb(BO3)3:Eu3+存在Tb3+→Eu3+的能量传递。     

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.     

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