尿素作为添加剂低温制备高活性的TiO2光催化剂

以钛酸丁酯为原料,尿素作为添加剂,在酸性水溶液中室温制备了稳定透明的TiO2水溶胶。经过300℃低温焙烧2 h,得到了由锐钛矿和金红石组成的TiO2混晶。用XRD、FT-IR对催化剂进行了表征。以甲基橙为降解对象研究了TiO2的光催化活性,实验结果显示所制备的TiO2具有比Degussa P25更高的催化活性,15m in后的降解率达到了78%(P25,58%)。考察了尿素添加量以及焙烧温度对TiO2催化性能的影响,当尿素与钛酸丁酯物质的量之比为3∶1,300℃下焙烧2 h为较适宜的催化剂制备条件。初步探讨了尿素作为添加剂在低温制备高活性TiO2过程中的作用。     

Alkaline Stable Anion Exchange Membranes Based on Cross-Linked Poly(arylene ether sulfone) Bearing Dual Quaternary Piperidines for Enhanced Anion Conductivity at Low Water Uptake

Alkaline stable anion exchange membranes based on the cross-linked poly(arylene ether sulfone) grafted with dual quaternary piperidine (XPAES-DP) units were synthesized. The chemical structure of the synthesized PAES-DP was validated using ¹H-NMR and FT-IR spectroscopy. The physicochemical, thermal, and mechanical properties of XPAES-DP membranes were compared with those of two linear PAES based membranes grafted with single piperidine (PAES-P) unit and conventional trimethyl amine (PAES-TM). XPAES-DP membrane showed the ionic conductivity of 0.021 S cm⁻¹ at 40 °C which was much higher than that of PAES-P and PAES-TM because of the possession of more quaternary ammonium groups in the cross-linked structure. This cross-linked structure of the XPAES-DP membrane resulted in a higher tensile strength of 18.11 MPa than that of PAES-P, 17.09 MPa. In addition, as the XPAES-DP membrane shows consistency in the ionic conductivity even after 96 h in 3 M KOH solution with a minor change, its chemical stability was assured for the application of anion exchange membrane fuel cell. The single-cell assembled with XPAES-DP membrane displayed a power density of 109 mWcm⁻² at 80 °C under 100% relative humidity.     

Effect of curing accelerators on thermal imidization of polyamic acids at low temperature

The effect of new additives on the thermal conversion of a range of polyamic acids to polyimides at temperatures lower than 100°C was investigated using infrared spectroscopy. Additives such as m-hydroxybenzoic acid, p-hydroxyphenylacetic acid, and p-hydroxybenzenesulfonic acid were found to be highly effective as curing catalysts or accelerators. The degree of imidization of polyamic acids in the presence of additives increased with an increase in the reaction temperature, and complete imidization was achieved at 140–200°C. The reaction was characterized by a rapid rate that slowed with time. © 1996 John Wiley & Sons, Inc.     

新型对开门高低温动态试验箱研制

介绍了新型对开门高低温动态试验箱的研制过程,包括系统热负荷计算、复叠制冷循环系统的热力计算等。并根据系统的热力计算,进行了冷凝器和蒸发器的结构设计以及主要部件压缩机和通风机的设计选型。     

多层绝热材料规模化干燥处理时温度场的测试与分析

对大批量处理多层绝热材料的大型专用干燥箱满负荷运行时工作区域的温度场进行测试,通过温度分布和温度场均匀性的分析,得出了最高温度发生点的位置与成因以及影响温度场均匀性的主要因素,并对温度的控制方法、多层材料的布置方案和干燥设备的改进提出了建议。     

构造低次有理插值函数的一种方法

关于有理插值的算法已有很多[1,4,5],受二元多项式插值迭加算法[6]的启发,我们给出一种简便的求低次有理插值函数的方法,同时给出有理插值函数存在的充分条件,便于检验.所给方法具有可操作性和实际应用价值,且具有较好的灵活性.     

田字形地震超材料甚低频宽带隙机理

在地球中传播的地震波主要有体波和表面波,而表面波中Rayleigh波对建筑物造成的破坏最为强烈。针对Rayleigh波的振动控制,提出一种田字形超材料结构。相比于传统的地震超材料,这种超材料屏障是由外部口字形框体内部嵌套十字形柱体组成,形成4个可填充区域,其外部框体采用部分埋入的方式,具有高强度、强稳定性、填充方式灵活的特点。应用有限元法计算了田字形超材料的能带结构和传输特性,并通过分析带隙边界处模态振型可知,带隙的打开是由于柱体的局域共振。结合带隙机理可知,柱体结构中土壤填充量不同可改变柱体的质量,形成不同的谐振频率,产生甚低频带隙。为进一步拓宽带隙,设计研究了正、负梯度的质量填充方式,均可得到3.3~13.1 Hz甚低频宽带隙,在谐振频率范围内两者的隔震方式分别为Rayleigh波彩虹捕获和Rayleigh波到体波的转化。最后,采用EI-Centro地震波对填充屏障进行了时程验证,加速度最大幅值衰减超过80%,为地震超材料在减震隔震方面应用提供了新的设计思路和方法。     

多振子声子晶体的低频特性研究

本文设计了一种由硅橡胶包覆层包裹4个钨振子的新型声子晶体结构,通过有限元法计算该结构的色散曲线、振动模态和传输损失谱。结果表明,该结构的带隙范围为18.85~225.28 Hz,与传输损失谱频率衰减范围相吻合,能够有效抑制20~200 Hz的弹性波在声子晶体中传播。通过分析色散曲线上点的振动模态,说明带隙产生的原因。本文讨论了声子晶体板的缺口角度和振子之间的纵向和横向间距对带隙的影响,结果表明:当缺口角度减小时,带隙下边界几乎保持不变,带隙上边界升高从而增加了带隙的宽度;振子之间横向或纵向间距增大时,带隙下边界和上边界均上升,带隙变宽,进而优化了声子晶体模型的带隙。同时声子晶体板的缺口设计能够节省材料,从而减轻结构的质量。     

聚氯乙烯／线性低密度聚乙烯共混体系的相容性

用动态力学分析（ＤＭＡ）和傅利叶变换红外光谱（ＦＴＩＲ）研究了氢化聚丁二烯－ｂ－聚甲基丙烯酸甲酯（ＨＰＢＤ－ｂ－ＰＭＭＡ）共聚物增容剂对聚氯乙烯（ＰＶＣ）与线性低密度聚乙烯（ＬＬＤＰＥ）共混体系的增容作用．增容剂使共混物中两相的玻璃化温度发生变化，说明其相容性增加．ＦＴＩＲ的结果表明，增容剂中羰基与ＰＶＣ的α氢形成氢键，使ＣＯ，Ｈ─Ｃ及Ｃ─Ｃｌ的振动频率变化，峰形加宽．