富钇混合稀土和热处理对Mg—Zn—Zr系镁合金的组织及相结构的影响

富钇混合稀土对Mg-Zn-Zr系镁合金的铸造组织及组成相无显著影响。MB25合金(含高纯金属钇)和MB26合金(含富钇混合稀土)的铸造组织都是在α-Mg晶界上分布着大量的Z+β网状共晶化合物相(以Z相为主),其区别在于铸态MB26合金的晶界共晶相中溶有少量的镧、铈、错、钕、钆和镝等多种稀土元素。均匀化处理和挤压热加工都能使铸态MB26合金发生不同程度的相变,并在不同程度上改变铸态合金的组织和相结构。随着从挤压到均匀化处理温度的提高,其相变过程是从Z相中锌的扩散相变开始到β、W共晶相各自完成共析转变结束。     

富镧稀土对消失模铸造B319合金组织的影响

利用等离子发射光谱仪，差分扫描量热仪（DSC），电镜及金相分析等手段，研究了RE对消失模铸造B319铝合金组织的影响。结果表明，在消失模铸造条件下，0．15％RE可使B319铝合金的硅相得到较好的变质效果。但当RE＞0．2％时，会出现富稀土的粗大块状金属间化合物La3Al2Si2，而对机械性能产生不利影响。当Fe/Mn=1.2时，消失模铸造组织中存在中国文字状的α－Fe和针状β-Fe铁相以及Al2Cu相。AlCu相可以离异共晶的形式析出，β-Fe及Si相均可以作为Al2Cu相的形核基底。而在金属型铸造组织中，铁相则完全以铁状的β-Fe形式存在。研究还表明，0．02％Sr变质使B319合金共晶转变温度下降了7℃。而RE的加入会使合金的共晶温度升高，采用0．2％RE对B319合金进行变质处理，其共晶温度从570．0℃升高到了572．0℃。     

聚甲基丙烯酸甲酯的分子构型对淬火过程中聚偏氟乙烯(PVF_2)β相生成的影响

<正> 聚偏氟乙烯(PVF_2)是一种半结晶聚合物,它至少存在α、β、γ和δ四种晶相结构。其中β相由于其与PVF_2的压电性和热电性直接相关而引起人们的广泛关注。在以前的工作中,我们研究了超速淬火对PVP_2晶相结构的影响。本工作用傅里叶变换红外光谱(FTIR)技术研究了聚甲基丙烯酸甲酯(PMMA)分子构型对淬火过程中PVF_2β相生成温度的影响.     

热处理温度对La-Y-Ni合金相结构和电化学性能的影响

采用磁悬浮感应熔炼法制备了组分为LaY_2Ni_(9.7)Mn_(0.5)Al_(0.3)的合金,在不同温度(1 073～1 373 K)下对合金进行热处理,利用X射线衍射法(XRD)、电子探针(EPMA)和电化学性能测试等方法,系统地研究了热处理温度对合金相结构和电化学性能的影响。结果表明,热处理可以显著提高合金的相均匀度,随着热处理温度的升高合金中的主相Ce_2Ni_7相先增加后减少。电化学研究表明,合金电极的最大放电容量、倍率性能和循环稳定性随着热处理温度的升高均呈现先升高后降低的趋势,与Ce_2Ni_7相含量的变化一致。电化学压力-组成-温度(P-C-T)测试表明,合金具有2个放氢平台,且随着热处理温度的升高合金的放氢坪台压增加。当热处理温度为1 273 K时,合金的Ce_2Ni_7相含量最高为86.53%(w/w),电化学性能最佳,最大放电容量为386.80 mAh·g~(-1)(60mA·g~(-1)),在电流密度为900 mA·g~(-1)时的高倍率性能HRD_(900)=89.45%,循环300周后的容量保持率S_(300)=72.18%(300 mA·g~(-1))。     

La-H化合物对LaMg2Ni合金中Mg2Ni相吸氢过程的影响

采用感应熔炼技术在Ar气氛保护下制备得到LaMg2Ni与Mg2Ni合金。X射线衍射(XRD)图表明LaMg2Ni合金在吸氢过程中分解为LaH3相和Mg2NiH4相,放氢过程中LaH3相转化为La3H7相。与Mg2Ni合金相比,LaMg2Ni合金显示出优良的吸氢动力学性能,这是由于镧氢化合物的存在及其在吸氢过程中所发生的相转变所造成的。LaMg2Ni合金280 s内吸氢即可达到最大储氢量的90%以上,而Mg2Ni合金则需要1200 s才能达到,且在相同温度下LaMg2Ni合金的吸氢反应速率常数大于Mg2Ni合金速率常数。镧氢化合物不仅有利于改善动力学性能,而且可以提高热力学性能。LaMg2Ni合金中的Mg2Ni相氢化反应焓与熵分别为-53.02 kJ.mol-1和84.96 J.K-1.mol-1(H2),这一数值小于单相Mg2Ni氢化反应焓与熵(-64.50 kJ.mol-1,-123.10 J.K-1.mol-1(H2))。压力-组成-温度(P-C-T)测试结果表明在603 K至523 K温度范围内,LaMg2Ni合金储氢容量保持稳定为1.95wt%左右,然而Mg2Ni合金的储氢容量则由4.09wt%衰减为3.13wt%,Mg2Ni合金的储氢容量在523K低温下仅为603 K时的76.5%,表明镧氢化合物能够改善Mg2Ni合金低温下的吸放氢性能。     

微量元素La对Al—Si合金凝固过程的影响

本文用差热分析法系统地研究了La掺杂对Al-Si共晶合金、亚共晶、超共晶的动态凝固过程的影响。结果表明,La促使α(Al)成核,使体系中初晶α(Al)的析出温度比AJ-Si二元合金中Al初晶的实际析出温度明显提高;La对初晶Si的成核和长大起抑制作用,使超共晶中初晶Si相析出温度较二元合金中的Si初晶的实际析出温度明显降低。     

定向凝固Al-Ni-Y三元共晶合金的相组成与凝固特征

在5 K.mm-1温度梯度下,选用1,5,10 mm.min-1三种拉速率对成分为96.0%Al,1.0%Ni,3.0%Y的三元共晶合金进行定向凝固实验,研究下拉速率对合金组织演化的影响规律。通过X射线衍射和光学显微镜分析表明合金由α-Al相、Al3Y相、Al23Ni6Y4相三相组成。当下拉速率为1 mm.min-1时,合金组织呈现三相共晶结构,纵截面有定向凝固趋势;下拉速率为5和10 mm.min-1时,合金组织演变成两种二相共晶:一种是Al3Y相与α-Al相形成菊花状的不规则二相共晶组织,另一种是Al23Ni6Y4相与α-Al相形成层片状的规则二相共晶组织,纵截面上均有明显的定向凝固特征。     

镥配合物的绝热量热法测试和热力学函数

本文合成了Lu(NO3)3 (C2H5O2N)4·H2O,用红外和元素分析对其进行了表征.用高精度全自动绝热量热仪,测定了该配合物在80～ 382 K温区的热容,利用实验热容数据,根据热容与焓、熵的热力学关系,求出了配合物在85～ 350 K温区内每隔5K相对于298.15K的标准热力学函数[HT-H29815]和[ST-S29815].在80～350 K温度区间内,配合物的热容随温度升高而增大,没有相转移点和热力学吸收峰的出现,该配合物在此温度区间内是稳定存在的.     

Al-Ni-Y三元共晶合金高压凝固组织

利用光学显微镜,扫描电镜,X射线衍射仪对不同压力(2,4,6 GPa)下凝固的Al-1Ni-3Y(%,原子分数)共晶合金组织形貌和相组成进行研究,并且与常压条件下合金凝固组织进行对比。实验结果表明,与常压凝固相比,在超高压力条件下凝固的合金的显微组织形貌发生了很大的改变,但是合金的相组成没有发生变化。常压凝固的合金具有共晶团组织,而高压下凝固的合金具有枝晶状亚共晶组织。高压凝固合金显微组织中出现了大量的初生α-Al相,这表明高压条件下凝固的合金共晶点发生偏移,使得常压共晶成分的合金在高压下变成亚共晶成分合金。同时,共晶组织的形貌发生了很大变化,常压下凝固的合金的组织为Al3Y相与α-Al相形成的菊花状的二元共晶和Al23Ni6Y4相与α-Al相形成的层片状的二元共晶,而高压下这两种共晶组织逐渐转化为离异共晶组织。随着压力的增大,共晶第二相的体积分数减小,α-Al的晶格常数增加。     

偏氟乙烯-四氟乙烯共聚物高取向薄膜的形态结构研究

聚偏氟乙烯(PVF_2)至少有四种晶相结构,即α、β、γ和δ相,PVF_2的压电性和热电性直接依赖其β相结构。 本工作报导以特殊的熔体拉伸方法制备不同组成偏氯乙烯(VF_2)和四氟乙烯(VF_4)的共聚物高取向薄膜与对其结构的研究结果。     

Isolation and identification of the anti-isohumulones and the anti-acetylhumulinic acids

The anti-isohumulones [5-(3-methylbutanoyl)-2-(3-methylbut-2-enyl)-4-hydroxy-4-(4-methylpent-3-enoyl)-cyclopentane-1,3-diones] and the anti-acetylhumulinic acids [5-(3-methylbutanoyl)-2-(3-methylbut-2-enyl)-4-ethanoyl-4-hydroxy-cyclopentane 1,3-diones] have been isolated from an isomerisation reaction mixture of humulone [2-(3-methylbutanoyl)-4,6-di(3-methylbut-2-enyl)-6-hydroxy-cyclohexane-l,3,5-trione] by counter-current distribution and identified by spectroscopic techniques. The formation mechanism is presented and the stereochemical consequences are discussed. The anti-isohumulones are the most bitter hop compounds presently known.     

On the transport and trajectories of the chernobyl debris across Canada and the arctic

A scenario is presented for the transport of the Chernobyl radioactive debris across Canada and the Arctic. It is based on the analysis of the¹⁰³Ru/¹³⁷Cs ratios in terms of the Chernobyl release pattern. The ratios which ranged from 0.2 to more than 4.0 were associated with four different phases of the Chernobyl emissions which lasted 10 days, from April 26 to May 6, 1986. Debris from the initial phase /ratios of 0.2 to 0.5/ and the last phase /ratios above 2.5/ would have entered Canada on a very broad front extending from northern Quebec to the North West Territories by way of Greenland and the Arctic; debris from the second phase /ratios of 0.5 to 2.0/ and the third phase /ratios of 2.0 to 2.5/ would have entered Canada from the west after travelling by way of northern Siberia and the Bering Sea.Paper presented at the IVth International Symposium of Radioecology of Cadarache, France, March 1988.     

Analysis and assessment of the occurrence, the fate and the behavior of nanomaterials in the environment

Nanomaterials have one dimension <100 nm and possess physico-chemical properties dictated by their unusually small size, large surface area, shape and chemical composition. New properties of nanomaterials have boosted their production and industrial applications in many fields (e.g., microelectronics, catalysis, fuel cells, materials science, textiles, biotechnology and medicine). In biomedical fields, nanomaterials are of the appropriate dimensions to interact with biological matter. However, they may also have negative effects on biological systems. Nanotechnology is a major, innovative, scientific and economic growth area, but the increasing production and use of nanomaterials have led to calls for more information regarding the potential impacts that their release may have on human health and the environment.This review addresses analytical approaches for characterization and quantification of nanomaterials in the environment and recent studies on their occurrence, fate and behavior.     

The energy pump and the origin of the non-equilibrium flux of the dynamical systems and the networks

The global stability of dynamical systems and networks is still challenging to study. We developed a landscape and flux framework to explore the global stability. The potential landscape is directly linked to the steady state probability distribution of the non-equilibrium dynamical systems which can be used to study the global stability. The steady state probability flux together with the landscape gradient determines the dynamics of the system. The non-zero probability flux implies the breaking down of the detailed balance which is a quantitative signature of the systems being in non-equilibrium states. We investigated the dynamics of several systems from monostability to limit cycle and explored the microscopic origin of the probability flux. We discovered that the origin of the probability flux is due to the non-equilibrium conditions on the concentrations resulting energy input acting like non-equilibrium pump or battery to the system. Another interesting behavior we uncovered is that the probabilistic flux is closely related to the steady state deterministic chemical flux. For the monostable model of the kinetic cycle, the analytical expression of the probabilistic flux is directly related to the deterministic flux, and the later is directly generated by the chemical potential difference from the adenosine triphosphate (ATP) hydrolysis. For the limit cycle of the reversible Schnakenberg model, we also show that the probabilistic flux is correlated to the chemical driving force, as well as the deterministic effective flux. Furthermore, we study the phase coherence of the stochastic oscillation against the energy pump, and argue that larger non-equilibrium pump results faster flux and higher coherence. This leads to higher robustness of the biological oscillations. We also uncovered how fluctuations influence the coherence of the oscillations in two steps: (1) The mild fluctuations influence the coherence of the system mainly through the probability flux while maintaining the regular landscape topography. (2) The larger fluctuations lead to flat landscape and the complete loss of the stability of the whole system.     

麻黄-甘草药对配伍前后主要药效成分及抗炎活性的变化

利用高效液相色谱串联质谱联用法(HPLC-MS/MS)和气相色谱质谱联用法(GC-MS)分析了麻黄与甘草药对配伍前后水煎液中主要药效成分的变化,并通过小鼠的耳廓肿胀试验考察了甘草、麻黄单煎液及药对共煎液的抗炎活性变化.分别通过HPLC法和GC-MS法对甘草与麻黄中主要化学成分,甘草酸、甘草苷、麻黄碱和甲基麻黄碱进行了定量分析,通过单煎液和药对共煎液的对比,发现麻黄与甘草配伍共煎液中麻黄碱(含伪麻黄碱)的含量增加了14.52%;甲基麻黄碱(含甲基伪麻黄碱)的含量增加了64.0%;甘草酸含量增加了13.50%;而甘草苷含量降低了19.38%.药效实验证明,甘草与麻黄配伍后抗炎作用较甘草麻黄单煎液明显增强.从而在主要成分的变化程度上揭示了甘草与麻黄配伍过程中的增效机理.     

Decorating step-by-step and independently the surface and the core of dendrons

Dendrons possessing one activated vinyl group at the core and several chlorine atoms at the end of the branches are used as starting materials to study the possibility to react independently the surface functions and the core function. In particular, the most powerful sequence of reactions for decorating them by organometallic complexes as end groups and amine or alcohol at the core has been determined. In the first step, phenol phosphines are grafted as end groups of the dendrons, and they can be used for the complexation of metals. However, these phosphines must be kept free when amines are used to react with the vinyl core in the next step. Depending on the type of phosphine end groups and on the type of function of the core (amine or alcohol), the complexation of ruthenium ([RuCl₂(p-cymene)]₂) and rhodium ([RhCl(COD)]₂) derivatives by the phosphine end groups can occur without side reaction at the core.     

"地小氢"和"月小氢"

Hydrogen is the most abundant chemical element in the Universe and is tightly related to human life. This article personifies hydrogen, bringing a close interaction between the hydrogen on the moon and the hydrogen on the Earth. Through lively and interesting dialogues, the history of hydrogen discovery and the properties are introduced, and the application of hydrogen in different aspects of the future is prospected.     

McBain and the centenary of the micelle

In 1913, J.W. McBain introduced the word “micelle” into surface and colloid chemistry in the context of the association of surfactant molecules in aqueous solution. This article gives a biographic account of McBain, and reviews the early work on micellar aggregation, leading up to the pioneering ideas of G.S. Hartley who introduced the first model of the spherical micelle that we would recognise today.