PALEOMONSOONS OF CHINA OVER THE LAST 130,000 YEARS——PALEOMONSOON RECORDS

The characteristics of the modern monsoon climate o?China may be used as clues for recognizing the records of paleomonsoon climate. The present paper deals primarily with the various paleomonsoon records of the last 130,000 years in the southeast monsoon area. These records mainly come from the following three fields: (i) the historical, (ii) the geological, including loess-paleosol sequence, deserts, lakes, snowlines, timberlines, the phenomena of continental desertization and so on, and (iii) the biological, presented by vegetation and mammals. Among these records, the loess-paleosol sequence in the Loess Plateau reflects a climatic history characterized by alternation of two different climatic periods when the Asian winter monsoon and summer monsoon showed pronounced effects on environment, respectively.     

稀土掺杂聚苯撑ER流体的研究

选用CeCl4和FeCl3等对自制的对苯撑进行掺杂,将制得的高介电聚苯撑粉末加入到硅油中得到电流变体流体,测量了在电场作用下粘度和漏电流密度,以及相关的物理常数。讨论了电场强度、粒子浓度与粘度和漏电流密度的关系,粘度变化的响应速度和恢复时间,并探讨了其相关机制。     

冷速对液态金属Mg凝固过程中微观结构演变的影响

采用分子动力学方法对不同冷速下液态金属镁(Mg)快速凝固过程中的微观结构演变进行了模拟研究.并采用能量-温度(E-T)曲线、双体分布函数、Honeycutt-Andersen键型指数法、原子团簇类型指数法(CTIM-3)以及三维可视化等方法系统地考察了凝固过程中微观结构演变与相转变过程.结果发现:在以冷速为1×10~(11)K/s的凝固过程中,亚稳态bcc相优先形成,随后大量解体,其变化规律符合Ostwald规则,系统最终形成以hcp结构为主体与fcc结构共存,中间还夹杂部分bcc结构的致密晶体结构.在1×10~(12)K/s冷速下,结晶过程呈现迟缓现象,形成bcc结构的初始温度降低,系统形成以hcp居多、与bcc和fcc三相共存的结构,且因相互竞争、相互制约而导致不易形成粗大的晶粒结构.而在1×10~(13)K/s冷速下,系统则形成以1551,1541,1431键型为主的多种非晶态基本原子团组成的非晶态结构.此外,在冷速1×10~(12)与1×10~(13)K/s之间的确存在一个形成非晶态结构的临界冷速.     

Formation of surface adspecies at furan and tetrahydrofuran adsorption on the Pt surface studied by work function changes and Auger electron spectroscopy

The adsorption of tetrahydrofuran (THF) and furan (F) on polycrystalline Pt-foil has been studied by work function change (Δφ) measurements and Auger electron spectroscopy (AES). The results were compared with those obtained earlier for the adsorption of cyclic hydrocarbons. The general character of the adsorption process (i.e. the dependence of ∣Δφ∣ and C/Pt ratio on temperature and exposure, and the ∣Δφ∣ vs. C/Pt correlation) is similar to the one observed during adsorption of cyclic hydrocarbons. THF produces σ-bonded adspecies in a similar manner to cyclopentane. F forms first a π-bonded surface complex, as do benzene and toluene. The π-adsorbed species are then transformed into σ-bonded ones under exposure to excess F. The numeric values characterizing the adsorption of the two heterocycles (mainly the C/Pt values) differ substantially from those measured for the adsorption of cyclic hydrocarbons.     

一种新型的红外成像材料

基于超大磁阻(CMR)材料在绝缘体—金属转变(I—M)点附近的巨大电阻变化，本研究了La位Gd掺杂对La0.7-xGdxSr0.3MnO3(x=0.20、0.30、0.40、0.50)电阻温度系数(TCR)的影响。实验结果表明：Gd掺杂将引起电阻率曲线的急剧变化，导致出现大的TCR；而且随Gd掺杂的增加，TCRR在x＝0．30出现峰值，然后随掺杂量增加逐步降低，大的TCR行为将成为新型的红外成像材料。     

煤及煤焦微观结构特征与气化反应性

研究了不同煤化度煤及煤焦的微观结构及其对气化反应性的影响。结果表明,褐煤焦具有丰富的分支孔系统和较大的比表面积,并含有较多对气化有催化作用的可交换阳离子。无烟煤焦分支孔贫乏,比表面积很小。煤焦的总孔容、比表面积和芳核大小之间有很好的对应关系。不同煤化度煤焦气化反应性差异很大,脱矿物质后煤焦反应性差异显著减小,但是脱矿物质前后煤焦的反应性随煤化程度的变化趋势相似。     

NiO对镁铝尖晶石反应烧结性能的影响

本文以高纯电熔镁砂和煅烧活性氧化铝粉为原料,以氧化亚镍(NiO)为添加剂,通过传统固相烧结法制备镁铝尖晶石材料。将MgO和Al₂O₃粉按理论摩尔比1∶1进行配料,在体系中分别引入质量分数为0%、0.5%、1.0%、1.5%、2.0%的NiO。利用X射线衍射(XRD)仪、扫描电子显微镜(SEM)和能谱仪(EDS)对烧结后试样进行分析,研究了NiO的添加对MgAl₂O₄材料烧结性能、物相组成及显微结构的影响。结果表明:引入适量的NiO可以显著促进MgAl₂O₄相的形成以及晶粒的发育长大;在1 600 ℃时,当NiO含量低于1.5%时,NiO能完全溶入MgAl₂O₄晶格并优先取代Al³⁺,提高了MgAl₂O₄晶体内部的缺陷浓度,活化了晶格,从而促进MgAl₂O₄的烧结。当NiO含量高于1.5%时,其内部开始出现较多第二相NiO,阻碍了物质的迁移和传输,反而不利于MgAl₂O₄烧结性能的提高。     

The Effect of Polymer Microstructure and Thermal Post-Treatment on Latex-Based Pressure Sensitive Adhesive Performance

Summary: Butyl acrylate/acrylic acid/2-hydroxyl methacrylate (BA/AA/HEMA, weight ratio: 96/2/2) latexes were produced via starved seeded semi-batch emulsion polymerization. The microstructure of the latex polymers was controlled by varying the amount of chain transfer agent (1-dodecanethiol). The latexes were characterized for gel content, M_c (molecular weight between two adjacent cross-linking points), M_w (molecular weight of sol polymers) and M_e (molecular weight between entanglements). From these latexes, PSA films were cast, dried, conditioned and then thermally post-treated at 120 °C to react the carboxyl and hydroxyl groups from the AA and HEMA units. Tack, peel strength and shear strength of the PSA films were then measured. The thermal post-treatment was shown to be an effective way to improve latex-based PSA performance. The effectiveness of the post-treatment was observed to depend on the polymer microstructure (M_c relative to M_e relative to M_w) of the untreated latex-based PSAs and on the gel content.     

明胶/Fe2S3纳米生物复合物形成反应的热力学及明胶构象变化

在pH=7.40条件下,采用一锅化学反应法制得水溶性明胶/Fe₂S₃纳米生物复合物,扫描电镜照片显示Fe₂S₃颗粒为棒状.根据吸光度与Fe₂S₃浓度关系,由Benesi-Hildebrand方程计算了不同温度下反应的形成常数K (293 K: 14.47×10² L·mol^-1; 297 K: 9.24×10² L·mol^-1; 309 K: 1.70×10² L·mol^-1)及对应温度下反应的热力学参数(Δ_rG_m = -17.88/-16.68/-13.09 kJ·mol^-1; Δ_rH_m = -105.57 kJ·mol^-1; Δ_rS_m = -299.28 J·K^-1·mol^-1),结果表明明胶/Fe₂S₃纳米生物复合物的形成反应是自发的放热过程,且为焓驱动.傅里叶变换红外光谱表明,Fe₂S₃主要与明胶大分子肽链中的酰胺键结合;对红外光谱进行去卷积拟合,结果表明:明胶蛋白质的 α-螺旋含量减少,β-折叠含量明显增加.结合紫外和红外光谱测试结果对复合物的形成机理作了初步的推测:首先Fe³⁺与明胶大分子中的酰胺键结合形成明胶/Fe³⁺复合物,然后S^2-与明胶/Fe³⁺中的Fe³⁺形成明胶/Fe₂S₃复合物.     

铁素体/珠光体组织对管线钢中氢扩散行为的影响

长距离管道输送是氢气输送的重要发展方向之一。氢在管线钢的扩散和局部聚集导致材料力学性能下降,在外界作用下引发脆性失效。因此,氢在管线钢材中的扩散和富集是评价管线钢相容性与判断管道升级可行性的重要参考依据。以三种不同等级的管线钢（X52,X65,X70）共22种材料为研究对象,结合图像处理技术与基于材料内铁素体/珠光体组织结构的连续介质数值计算,推算长期服役后结构内部氢的扩散和富集。考虑到铁素体和珠光体组织中的氢扩散速率与晶界的扩散阻碍作用,通过对比量化不同铁素体/珠光体的结构分布和组织取向下氢质量浓度和扩散通量的差异,分析铁素体/珠光体组织对管线钢中氢的扩散和富集作用,为长距离输氢管道材料选用提供技术参考。