有机可溶性高折射率聚酰胺酰亚胺的合成与性能

采用含硫二胺1,4-双(4-氨基苯硫基)苯(2SPDA)与偏苯三酸酐反应制备了一种含硫二酸化合物1,4-双(4-三甲酰亚胺基苯硫基)苯(BTPB).以此二酸为原料与两种高硫含量二胺单体,4,4′-双(4-氨基苯硫基)二苯硫醚(3SDA)以及2,7-双(4-氨基苯硫基)噻蒽(APTT)通过高温缩聚法制备了两种聚酰胺酰亚胺(PAI).制备的PAI在室温下可溶解于N-甲基-2-吡咯烷酮(NMP)中.PAI薄膜的起始热分解温度(T5%)超过440℃,玻璃化转变温度(Tg)大于190℃.PAI薄膜在波长大于500nm的可见光区具有良好的透明性.此外,PAI薄膜的折射率大于1.73,双折射小于0.04.     

正丁烷在金属钼酸盐催化剂上的氧化脱氢

 用柠檬酸盐法合成了第一系列过渡金属(Cr,Mn,Fe,Co,Ni,Cu和Zn)及Mg的钼酸盐催化剂,研究 了它们对正丁烷氧化脱氢反应的催化作用. 结果表明,这些钼酸盐催化剂的催化性能受阳离子的影响较大. CoMoO4催化剂具有最高的催化活性和较高的选择性,其催化性能与文献报道的对正丁烷氧化脱氢反应催化性能最好的ZrP2O7和Mg3V2O8催化剂大致相当; MgMoO4催化剂虽然选择性较高,但活性较低; Cr2(MoO4)3上基本没有C4烯烃生成; 其它钼酸盐催化剂对正丁烷氧化脱氢反应的催化活性和对烯烃的选择性都较低. XRD,NH3-TPD和H2-TPR的研究结果表明,催化剂为单一的钼酸盐晶相,催化剂的性能由其氧化还原性决定而与其表面酸量没有直接关系. 通过对产物分布的分析,提出了正丁烷在CoMoO4催化剂上的氧化脱氢反应途径. 在558 ℃,正丁烷发生氧化脱氢生成正丁烯和丁二烯以及氧化燃烧生成CO2三个平行竞争反应的竞争分率分别约为75%,10%和15%. 在正丁烷转化率较高的条件下,产物中的CO2主要来自C4烯烃的再氧化反应,而CO则完全来自C4烯烃的再氧化.     

Studies on crystal transition of polyamide 11 nanocomposites by variable-temperature X-ray diffraction

Polyamide I1 （PAll） and its nanocomposites with different organoclay loadings were prepared by melt-compounding and subsequent pelletizing. The crystal phase transitions of PAl 1 and its clay nanocomposites were investigated by variable-temperature X-ray diffraction. It was found that the Brill transition of the nanocomposite was 20 K higher than that of the neat PAl 1 for both heating and cooling processes. The PAl 1 d-spacings of the nanocomposites were observed to be smaller than those of the neat PAl 1 for melt crystallization. The constraints imposed by the addition of layered clay, restricting the thermal expansion of the polymer chains, are probably responsible for such a reduction of the d-spacing.     

Tm~(3+)掺杂锗碲酸盐玻璃的近2μm光谱性质

用高温熔融法制备了Tm2O3掺杂浓度为0.25,0.5,0.75,1,1.25,1.5 mol%的40 Ge O2-35Te O2-15Pb O-5Al2O3-2.5Ca O-2.5Sr O锗碲酸盐玻璃.热学性质测试表明该玻璃的转变温度为446℃,没有析晶峰.玻璃的最大声子能量约为750 cm-1.利用Judd-Ofelt理论计算了Tm3+的Judd-Ofelt参数Ωt(t=2,4,6)、不同浓度下Tm3+离子各激发态能级的自发辐射概率、荧光分支比以及辐射寿命等参数.采用808 nm波长抽运源测试了Tm3+离子的荧光光谱.发现掺杂浓度为1 mol%时约1.8μm处的荧光强度最强.根据Mc Cumber理论计算了3F4→3H6的发射截面,其峰值发射截面为6.5×10-21cm2.根据速率方程计算了玻璃中OH引起的Tm3+的3F4能级的无辐射弛豫速率,随着Tm3+浓度增加,OH对3F4能级的猝灭速率增加.这种玻璃有望研制成一种新型的约2μm的激光玻璃材料.     

TeO_2-ZnO-ZnF_2三元碲酸盐玻璃的Raman光谱和X射线光电子能谱研究

采用高温熔融法制备了组分为TeO2-ZnO-ZnF2碲酸盐玻璃,利用Raman光谱和X射线光电子能谱研究了TeO2-ZnO-ZnF2三元碲酸盐玻璃的结构.结果表明,体系中存在[TeO4]双三角锥中Te-O-Te键或者O-Te-O键的振动、带有桥氧键的[TeO4]双三角锥振动、[TeO3]三角锥体中Te与非桥氧连接的Te-O键的对称伸缩振动,且随着氧化锌的加入,体系中[TeO4]双三角锥体向[TeO3]三角棱锥转化.     

铋酸盐铒玻璃在1.54 μm处的荧光特性研究

用高温熔融法制备了Er3+单掺和Er3+ /Yb3+共掺铋酸盐玻璃,测量了上述玻璃样品的吸收光谱、荧光光谱、荧光半高宽和荧光寿命.对高浓度掺杂Er3+时的浓度猝灭现象给出了解释.分析了Er3+ /Yb3+双掺样品中Yb3+对Er3+的敏化过程.在对Er3+ /Yb3+共掺时的研究结果发现, Er3+浓度的变化对荧光半高宽和荧光寿命有显著影响,而Yb3+浓度的变化则对吸收光谱和荧光光谱的强度影响显著.实验获得了Er3+ /Yb3+共掺铋酸盐玻璃在1. 54μm处荧光半高宽达76nm,荧光寿命为0. 55ms.     

Origin of the Downturn in Inverse Susceptibility Observed above the Curie Temperature in Perovskite Manganites

The measurement of low-field susceptibility X as a function of temperature T for La2/3Ca1/3MnO3 shows a significant downturn in 1/X(T) above the Curie temperature Tc, a behaviour generally observed in perovskite manganites. Such a downturn is argued to be due to the segregation of ferromagnetic clusters with larger spins in the paramagnetic matrix. Based on this consideration, a phenomenological expression for X(T) is proposed,in which the total susceptibility is assumed to be a sum of two susceptibilities arising from magnetic entities in the PM background and the FM clusters with T-dependent effective spins, respectively. The result is in good agreement with the experimental data obtained in La2/3Ca1/3MnO3.     

Luminescent Properties and Mechanism of Gd1-x-yAlO3Eux,REy

GAP:Eu,Re(Gd1-x-yAlO3Eux,REy?A，RE=Pr or Ce) powders were prepared by a nitrate-citrate process. It is found that luminescent intensity decreases when GAP:Eu is co-doped with Pr or Ce. The phenomena of spectra prove that there is a resonant energy transfer between Eu and Pr, by the absorption and emission of lower-energy phonon, and also Ce sensitizer decreases the activator energy level from host→Eu. The two factors are considered to be the main reasons for decrease of the luminescent intensity for the co-doped GAP:Eu,Re.     

能走路的分子

美国加洲大学Riverside分校的Barrels L博士和他的同事们根据Kansas大学Rahman T教授的理论创造出了一种能走路的单分子；这种分子称为9，10-二硫代氨基甲酸盐（简称为DTA）。它的两条腿作这样的配置，即在同一时刻只有一条腿可以停留在基底上。