MnCO3添加剂对MgTiO3-CaTiO3系瓷改性的研究

用单因素法分析了MnCO3添加量对MgTiO3-CaTiO3系瓷的结构、吸水率、介电常数、介电损耗和温度系统的影响 ,用XRD确定了其物相组成。结果表明 ,在 10GHz时介电常数为 2 1、频率温度系数为 - 6.3× 10 - 6 ℃、Q(10GHz)≥ 42 0 0的高致密度介电陶瓷 ,具有良好微波特性     

Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3压电陶瓷的电学性能研究

采用固相烧结法制备了0.40Pb(Mg1/3Nb2/3)O3-(0.6-x)PbZrO3-xPbTiO3压电陶瓷,系统研究了其组分变化对晶体结构、介电和压电性能的影响。研究结果表明,所有样品均属于钙钛矿结构,无第二相产生。随着组分的变化,存在三方相向四方相的转变,并且在x = 0.38附近获得准同型相界组分,呈现出最优的电学性能,最高的压电系数d33 = 520 pC/N,居里温度TC = 238 °C,平面机电耦合系数kp = 0.60,厚度机电耦合系数kt = 0.52,纵向机电耦合系数k33 = 0.73。     

3，3，3-三氟丙烯-氟硅材料的桥梁

介绍了3，3，3-三氟丙烯的物理化学性质、制备方法和在氟硅橡胶、氟硅油合成中的应用。     

3，3，3-三甲氧基丙腈的合成与表征

以丙二腈为起始原料通过两步反应合成了3,3,3-三甲氧基丙腈,气相色谱分析产物纯度达到98．08％。采用气质联用、红外光谱、核磁共振氢谱对产物进行了表征。确定了第一步合成甲基氰基乙酰亚氨基盐酸盐的最佳反应条件为：溶剂含水量〈100×10-6^、通气时间3h、72g丙二腈、45mL甲醇、1440mL乙醚、常温搅拌时间7h;第二步合成3,3,3-三甲氧基丙腈的最佳反应条件为：甲基氰基乙酰亚氨基盐酸盐与甲醇的物料比为1g：7．35mL、搅拌时间24h、在反应i0h后移出副产物氯化铵、无水硫酸钠作为干燥剂。     

电荷补偿对KSr4(BO3)3:Dy3+,Tm3+发光性能的影响

通过高温固相法制备出单基质KSr4(BO3)3:n%Dy~(3+),0.5%Tm~(3+)(n=0.5,1.0,1.5)白光荧光粉,对356 nm激发的发射光谱进行了测试,发射光谱包含有Dy~(3+)的特征发射峰(491,574 nm),也包含有Tm~(3+)的特征发射峰(454nm)。随着Dy~(3+)掺杂浓度的增加,Tm~(3+)的发光强度逐渐减弱,而Dy~(3+)的发光强度逐渐增强。计算得到KSr_4(BO_3)_3:n%Dy~(3+),0.5%Tm~(3+)(n=0.5%,1%,1.5%)的色温依次为:12 797,7 180,5 734 K。将掺杂浓度为1.5%的补偿电荷Li~+、Na~+和K~+掺入了KSr4(BO3)3:1.0%Dy~(3+),0.5%Tm~(3+)中,发光强度都有明显的增强,补偿电荷为Na~+时KSr_4(BO_3)_3:1.0%Dy~(3+),0.5%Tm~(3+)在574nm处的发光强度最高。通过XRD表征发现掺入Na~+、K~+后基质结构没有明显的改变,Li~+的掺入导致了一个小杂峰的出现。     

3，3，3-三氟丙烯生产技术研究进展

3，3，3-三氟丙烯（CF3-CH=CH2，简称TFP）是合成氟硅橡胶（γ-三氟丙基甲基聚硅氧烷）、氟硅油、氟硅涂料等高性能高分子材料的基本原料，其中氟硅橡胶堪称当今世界综合性能最好的合成橡胶之一，现已广泛应用于宇航、飞机、汽车、人工器官等现代工业及国防、交通运输、医学等领域。综述了3，3，3-三氟丙烯（简称TFP）的基本特性、主要用途和分别以三氯丙烯、四氯丙烷、五氟丙烷及四氯化碳等为原料的工艺合成方法，并简要说明了各方法的优缺点。     

钙钛矿型LaFeO3和SrFeO3的光催化性能

采用柠檬酸法合成钙钛矿型复合氧化物LaFeO3和SrFeO3,并以其为光催化剂对不同水溶性染料进行光催化降解实验.结果表明:SrFeO3的光催化活性明显高于LaFeO3,这与A位离子(La3+,Sr2+)的电子构型的不同有关.     

MoO_3含量对MoO_3-ZrO_2-Al_2O_3结构及HDS性能的影响

共沉淀法制备了不同MoO_3质量分数的MoO_3-ZrO_2-Al_2O_3三元复合氧化物,利用X射线衍射、N2吸附-脱附分析不同MoO_3质量分数的MoO_3-ZrO_2-Al_2O_3晶相结构和形貌。以FCC柴油馏分为原料,在固定床反应器上进行MoO_3-ZrO_2-Al_2O_3的HDS活性评价。结果表明:适量MoO_3的添加未形成新的物种,但使MoO_3-ZrO_2-Al_2O_3的比表面积增大,催化剂活性中心数目增多。当MoO_3含量达30%(wt)时,MoO_3在复合氧化物表面高度分散,其FCC柴油馏分的脱硫率达83.7%。     

CH_3CF_3的蒸汽压与临界参数实验研究

测量了CH_3CF_3 230K以上的蒸汽压与临界参数.蒸汽压测量精度为|△T|≤28mk和|△р|≤1.4Pa,结果对文献蒸汽压方程呈明显偏差.基于汽液界面消失位置和临界乳光现象,测定了临界密度ρ_c=442±4kg/m~3、临界温度T_c=346.16±0.05K,由本文蒸汽压方程算出临界压力ρ_c=3.781±0.006MPa.文中还给出了一个新的正常沸点推算值T_b=225.69K.     

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