钇和铈对AM50镁合金显微组织和力学性能的影响

为了开发低成本、高强度和耐高温的新型镁合金，研究了微量Y，Ce复合对AM50镁合金显微组织和力学性能的影响。结果表明：Y和Ce复合加入AM50镁合金，能明显细化晶粒，由于显微组织的改善，合金的室温和高温力学性能得到明显提高，当稀土加入量为0．6％Ce-0．3％Y（质量分数）时，合金晶粒细化效果较好，其室温和高温（150℃）力学性能比较理想。     

富钇混合稀土对AM60镁合金显微组织与力学性能的影响

在AM60镁合金的基础上添加不同质量分数的富Y混合稀土(分别为0.5%,1.0%,1.5%,2.0%),研究了富钇混合稀土对AM60镁合金显微组织与力学性能的影响。结果表明:富Y稀土的加入使AM60镁合金的显微组织明显细化,并能显著提高合金的抗拉强度、屈服强度及延伸率。加入混合稀土后,合金中形成块状的铝钇化合物Al2Y,Al6Mn6Y,β-Mg17Al12相数量减少。当稀土加入量为1%时,合金的各方面性能达到最好。     

富铈混合稀土对AZ81合金组织与性能的影响

研究了富铈混合稀土对挤压铸造AZ81合金的显微组织和力学性能的影响。结果表明:加入不同含量富铈混合稀土的合金中都出现了一种新相Al11(Ce,La)3相,Al11(Ce,La)3相数量增多而Mg17Al12相则减少,能细化合金的组织晶粒,其细化作用在添加了1.5%富铈混合稀土的镁合金中尤为明显,但是当富铈混合稀土加入量大于2.0%时,合金中Al11(Ce,La)3相开始长大以粗大长杆状存在;在富铈混合稀土含量为1.5%时,AZ81合金的室温和150℃的综合力学性能达到最佳效果,超过2.0%时合金的室温和150℃综合力学性能开始下降;合金试样的拉伸断口带有局部韧窝的解理断裂和韧性断裂的混合特征。     

钕对Mg-5Al-1Si高温蠕变及组织性能的影响

研究了不同Nd含量对Mg-5Al-1Si镁合金的高温蠕变性能影响, 对析出相进行了分析, 研究了微观组织与力学性能的关系. 研究结果表明, 该合金中的主要强化相Mg2Si呈粗大的汉字状, 分布在晶界的周围, 在受到应力时, 这种汉字状相与基体的界面处易产生微裂纹, 降低合金的抗拉强度、塑性等力学性能. 在Mg-5Al-1Si合金中加入微量的Nd以后, 合金的组织得到明显的细化, 并使Mg2Si强化相形貌由粗大的汉字状转变为细小、弥散分布的颗粒状. 由于显微组织的改善, 使得Mg-5Al-1Si镁合金的室温和高温力学性能均有一定的提高, 并明显的改善了Mg-5Al-1Si的抗蠕变性能.     

高性能镁-稀土结构材料的研制、开发与应用

由于镁合金具有低的密度-质轻、高比刚度、卓越的机械性能、高的硬度及良好的铸造性能, 近几十年来镁合金的应用一直是自动化工业的目标之一. 然而, 高温特殊用途, 例如在发动机上的应用, 通常的镁合金就受到了限制, 因为在高温下它们的强度和抗蠕变性能都比较差. 由于镁-稀土合金增加了材料的抗拉强度、延展性及抗蠕变性能, 稀土加入后形成镁-稀土合金就可以满足高温应用的要求. 本文就我国丰富的镁和稀土资源评述了国内外镁-稀土合金的研制、开发与应用状况及发展趋势, 同时结合我国相关单位的研究进展, 对我国镁-稀土合金的发展提出了建议.     

钇对AZ61镁合金组织和性能的影响

在CO2+SF6气体保护条件下感应熔炼制备了不同Y含量的AZ61-x Y(x=0,0.5,1,1.5,2)镁合金,利用光学金相显微镜(OM)、扫描电镜(SEM)、X射线衍射分析(XRD)、能谱分析(EDS)和拉伸及蠕变力学性能测试手段研究了Y添加对AZ61合金显微组织和力学性能的影响。结果表明:合金中添加适量的稀土元素Y后,AZ61合金的显微组织得到明显的细化,合金中除了存在α-Mg和Mg17Al12相,还出现了块状析出相Al2Y。适量的Y显著提高了合金在室温和高温时的强度和塑性,同时合金在150℃/70MPa条件下的抗蠕变性能也有显著的提升。     

钇对Mg-9Al-1Si合金蠕变抗力和微观组织的影响

研究了Mg-9Al-1Si-xY合金的高温蠕变性能及其微观组织与力学性能的关系。该合金中的主要强化相Mg2Si呈粗大的汉字状，分布在晶界的周围，在受到应力时，这种汉字状相与基体的界面处易产生微裂纹，降低合金的抗拉强度、塑性等力学性能。在Mg-9Al-1Si合金中加入微量的Y以后，合金的组织得到明显的细化，Mg2Si强化相形貌由粗大的汉字状转变为细小、弥散分布的颗粒状。显微组织的改善，使得Mg-9Al-1Si合金的室温和高温力学性能均有一定的提高，并明显改善了Mg-9Al-1Si的抗蠕变性能。     

稀土对Al2O3陶瓷烧结温度、显微组织和力学性能的影响

研究了Y2O3, La2O3 等稀土氧化物对Al2O3陶瓷烧结温度、力学性能和显微组织的影响. 结果表明, 添加稀土氧化物可以降低Al2O3陶瓷的烧结温度, 改善显微组织, 提高力学性能. 添加复合稀土氧化物(Y2O3+La2O3)后, Al2O3陶瓷的抗弯强度和断裂韧性分别提高1.8倍和2.08倍. 其性能提高的主要原因是稀土氧化物对细晶强化、净化界面、固溶强化、自增韧补强等作用的贡献.     

热挤压AM50GdX镁合金的腐蚀力学性能研究

通过SEM、光学显微镜、失重测量、拉伸测试等方法研究了热挤压加工对不同Gd含量的AM50GdX镁合金的显微组织及腐蚀力学性能的影响。结果表明:热挤压后,合金内部出现了具有方向性的平行纤维变形组织;随着Gd含量的增加,AM50GdX镁合金组织中β-Mg_(17)A_l(12)相数量减少而Al_2Gd_3相数量和体积增加;1%Gd元素对合金耐蚀性提升作用最大;热挤压处理使合金的晶粒细化,从而使拉伸强度提升了接近50%;由于热挤压处理和1%Gd元素的存在大大改善了AM50镁合金的腐蚀剩余强度性能。     

钇,铈对低铪镍基K444返回合金组织与力学性能的影响

研究了Y,Ce对含铪(Hf)镍基铸造高温合金K444返回料(添加50%返回料)合金的力学性能和组织的影响.研究结果表明:适量Y,Ce(Y<0.03%,Ce<0.015%(质量分数))添加到返回料合金后,一方面,Y,Ce具有去除N,O等有害杂质的作用,使O含量由15×10~(-6)降低到8×10~(-6),N含量由35×10~(-6)降低到18×10~(-6),从而使返回料合金得到净化.另一方面,Y,Ce细化了枝晶组织,减少了共晶和大块状碳化物数量,并且强化了晶界.和未加Y,Ce的返回料合金相比.添加Y,Ce使返回料合金室温拉伸强度提高约100 MPa,塑性提高近一倍;使900℃的高温瞬时拉伸性能波动较为平稳,塑性提高近一倍.添加Y,Ce还可以提高返回合金900℃/274 MPa条件下的持久性能,达到新料水平;可以明显延长K444返回合金900℃/274 MPa条件下的蠕变第二阶段,提高蠕变寿命.     

聚皂的性质和研究进展

较系统地综述了聚皂的性质和研究进展,侧重介绍了近年来利用荧光探针技术研究聚皂在水溶液中的聚集特性,以及利用紫外／可见光探针技术,从动力学催化反应、与甲基橙的相互作用来研究聚皂形成胶束的机理及结构。同时介绍了聚皂在某些些方面的应用。     

Anti-Cancer Properties of Theaflavins

Cancer is a disease characterized by aberrant proliferative and apoptotic signaling pathways, leading to uncontrolled proliferation of cancer cells combined with enhanced survival and evasion of cell death. Current treatment strategies are sometimes ineffective in eradicating more aggressive, metastatic forms of cancer, indicating the need to develop novel therapeutics targeting signaling pathways which are essential for cancer progression. Historically, plant-derived compounds have been utilized in the production of pharmaceuticals and chemotherapeutic compounds for the treatment of cancer, including paclitaxel and docetaxel. Theaflavins, phenolic components present in black tea, have demonstrated anti-cancer potential in cell cultures in vitro and in animal studies in vivo. Theaflavins have been shown to inhibit proliferation, survival, and migration of many cancer cellswhile promoting apoptosis. Treatment with theaflavins has been associated with increased levels of cleaved poly (ADP-ribose) polymerase (PARP) and cleaved caspases-3, -7, -8, and -9, all markers of apoptosis, and increased expression of the proapoptotic marker Bcl-2-associated X protein (Bax) and concomitant reduction in the antiapoptotic marker B-cell lymphoma 2 (Bcl-2). Additionally, theaflavin treatment reduced phosphorylated Akt, phosphorylated mechanistic target of rapamycin (mTOR), phosphatidylinositol 3-kinase (PI3K), and c-Myc levels with increased expression of the tumour suppressor p53. This review summarizes the current in vitro and in vivo evidence available investigating the anti-cancer effects of theaflavins across various cancer cell lines and animal models.     

两性高分子的溶液性质

两性高分子是分子链上同时含有正负电荷基团的一类高聚物、具有独特的溶液性质。本文就两性高分子等电点的构象状态、影响等电点的因素、两性高分子的溶解性以及高分子结构和组成、ｐＨ、溶液离子强度、混合溶剂、温度对流体力学行为的影响进行了综述。     

Properties of CMR composites

Colossal magnetoresistance (CMR) composites form an interesting field of study. The intrinsic CMR, governed by the intragrain transport of the conduction electrons through the double exchange, limits its application owing to the high field requirement and generally low transition temperatures. Extrinsic CMR, a function of the intergrain transport between ferromagnetic (FM) particles, plays a crucial role in enhancing low field magnetoresistance (LFMR) or increasing room temperature magnetoresistance. Since extrinsic CMR is a grain boundary controlled phenomena, magnetically dirty grain boundaries in the virgin state of the sample help in achieving a high LFMR or increase the field sensitivity. In this article, we give the properties of different composites of magnetoresistive LCMO or LSMO where the second component is (a) an insulating phase, (b) a conducting phase, (c) a nonmagnetic phase and (d) a magnetic phase. We present here some of our recent work on CMR composites where the CMR phase is chosen as LCMO and SiO₂, ZnO, ZrO₂ and SiCN have been used as the different second phase of the composites. We summarise some of the salient features of the results. Dedicated to Professor C N R Rao on his 70th birthday     

C60系列螺亚甲基衍生物的电化学性质

考虑到在生物、新型材料等方面的应用，采用循环伏安(CV)的方法，系统研究了11个C60螺亚甲基衍生物的电化学性质. 分析比较了螺碳原子上所连不同基团的性质及链的长度等因素对C60得电子能力的影响.结果发现，引入推电子基团，如烷基，会使C60得电子能力降低，第一个还原电位有较大的负移；引入具有拉电子性质的基团，如羧酸酯基，则会部分抵消由于C60共轭结构被破坏而引起的电位负移，结果使得电位负移值减少.增加引入基团链的长度对C60的得电子的能力影响较小.同时，对于因电化学反应所引起的异构化而使还原峰发生分裂的现象作了解释.     

Properties of Sulfur-Sulfur Bonds

SS bonds are extraordinarily flexible and have properties that are observed only on isolated occasions for other homonuclear bonds: the bond lengths very between 1.8 and 3.0Å, the bond angles between 90 and 180° and the dihedral angles between 0 and 180°; the bond energies amount to up to 430 kJ/mol. The SS stretching frequencies can appear over the range 177–820 cm^?1 and force constants of 1.4 to 6.3 mdyne/Å have been calculated. This variability is illustrated with examples containing isolated and cumulated SS bonds.     

聚苯胺阳极的性能研究

用磺基水杨酸和硫酸为掺杂剂,过硫酸铵为氧化剂,合成了一种高电导率聚苯胺粉末,并压制成聚苯胺阳极。采用FTIR和DSC/TGA对聚苯胺的结构和热稳定性进行分析,同时也采用加速电解寿命测试和电化学阻抗技术,研究了聚苯胺阳极的电化学性能和该电极在硫酸中的使用寿命。结果表明,在电解过程中槽电压从不稳定-稳定-快速增大的变化过程,电化学行为变化也比较明显。把该电极用于处理含酚废水和铅电极进行对比表明,节电率达34%,转化率达96.8%,是一种优良的电化学催化剂。     

Critical Properties of Argon

Abstract

Measurements of P-V-T properties of argon in the critical region are reported. Isothermal compressibilities have been calculated from the data for liquid and vapor along the coexistence curve and for the gas above the critical temperature at the critical density. Densities of the liquid and vapor along the coexistence curve were measured, and the critical temperature, pressure and density of argon were redetermined. These data are compared with those of other workers; in addition critical indices which represent the manner in which these properties vary as one approaches the critical point were determined and compared with the predictions of several theoretical estimates of these quantities.     

Anion-Sensing Properties of Cyclopentaphenylalanine

Cyclic pentaphenylalanine was studied as an efficient anion sensor for halides, thiocyanate and oxoanions in acetonitrile and methanol. Stability constants of the corresponding complexes were determined by means of fluorimetric, spectrophotometric, ¹H NMR, and microcalorimetric titrations. A detailed structural overview of receptor–anion complexes was obtained by classical molecular dynamics (MD) simulations. The results of ¹H NMR and MD studies indicated that the bound anions were coordinated by the amide groups of cyclopeptide, as expected. Circular dichroism (CD) titrations were also carried out in acetonitrile. To the best of our knowledge, this is the first example of the detection of anion binding by cyclopeptide using CD spectroscopy. The CD spectra were calculated from the structures obtained by MD simulations and were qualitatively in agreement with the experimental data. The stoichiometry of almost all complexes was 1:1 (receptor:anion), except for dihydrogen phosphate where the binding of dihydrogen phosphate dimer was observed in acetonitrile. The affinity of the cyclopeptide receptor was correlated with the structure of anion coordination sphere, as well as with the solvation properties of the examined solvents.