Nanostructure and mechanical measurement of highly oriented lamellae of melt-drawn HDPE by scanning probe microscopy

Scanning probe microscopy was used to simultaneously determine the molecular chain structure and intrinsic mechanical properties, including anisotropic elastic modulus and friction, for lamellae of highly oriented high-density polyethylene (HDPE) obtained by the melt-drawn method. The molecular-scale image of the highly oriented lamellae by friction force microscopy (FFM) clearly shows that the molecular chains are aligned parallel to the drawing direction, and the periodicities along and perpendicular to the drawing direction are 0.26 and 0.50 nm, respectively. The results indicate that the exposed planes of the lamellae resulting from the melt-drawn method are (200), which is consistent with results of transmission electron microscopy and electron diffraction. Because of the high degree of anisotropy in the sample, coming from alignment of the molecular chains along the drawing direction, the measured friction force, F, determined by FFM is strongly dependent on the angle, theta, between the scanning direction and the chain axis. The force increases as theta is increased from 0 degrees (i.e., parallel to the chain axis) to 90 degrees (i.e., perpendicular to the chain axis). The structural anisotropy was also found to strongly influence the measurements of the transverse chain modulus of the polymer by the nanoindentation technique. The measured value of 13.8 GPa with transverse modulus was larger than the value 4.3 GPa determined by wide-angle X-ray diffraction, which we attributed to anisotropic deformation of the lamellae during nanoindentation measurements that was not accounted for by the elastic treatment we adopted from Oliver and Pharr. The present approach using scanning probe microscopy has the advantage that direct correlations between the nanostructure, nanotribology, and nanomechanical properties of oriented samples can be determined simultaneously and simply.

20世纪稀土科技发展的回顾与前瞻

本文对20世纪各个时期稀土科技的重大发展作了回顾,并对21世纪初期稀土可能取得的重大应用作了展望。

Enhanced crystallization and phase transformation of amorphous silicon nitride under high pressure

The crystallization and phase transformation of amorphous Si3N4 ceramics under high pressure (1.0-5.0 GPa) between 800 and 1700 degreesC were investigated. A greatly enhanced crystallization and alpha-beta transformation of the amorphous Si3N4 ceramics were evident under the high pressure, as characterized by that, at 5.0 GPa, the amorphous Si3N4, began to crystallize at a temperature as low as 1000 degreesC (to transform to alpha modification). The subsequent alpha-beta transformation occurred completed between 1350 and 1420 degreesC after only 20 min of pressing at 5.0 GPa. In contrast, under 0.1 MPa N-2, the identical amorphous materials were stable up to 1400 degreesC without detectable crystallization, and only a small amount of a phase was detected at 1500 degreesC. The crystallization temperature and the alpha-beta transformation temperatures are reduced by 200-350 degreesC compared to that at normal pressure. The enhanced phase transformations of the amorphous Si3N4, were discussed on the basis of thermodynamic and kinetic consideration of the effects of pressure on nucleation and growth.

H_8[P_4W_(14)O_(58)Na_4(H_2O)_(20)]·16H_2O的合成、晶体结构与性质

用水热法合成了 H8[P4 W14 O58Na4 (H2 O) 2 0 ]· 16 H2 O,通过 X射线单晶衍射、元素分析和IR进行了结构表征 ,用 TG- DTA研究了热稳定性 .晶体属三斜晶系 ,P1空间群 ,a=1.1379(2 )nm,b=1.36 32 (3) nm,c=1.6 2 71(3) nm;α=78.2 0 (3)°,β=71.2 0 (3)°,γ=71.6 2 (3)°;V=2 .2 52 5(8) nm3 ,Z=1,Mr=4 374 .38,Dc=3.2 2 5mg/ cm3 ,μ=18.0 0 7mm-1,F(0 0 0 ) =1972 ,R=0 .0 74 2 ,Rw=0 .2 0 0 4 .标题化合物的阴离子是由两个 PW7O2 9Na2 (H2 O) 10 亚单元通过与两个磷原子上键合的氧连接而成 ,分子内形成了一个 0 .6 6 14nm× 0 .3189nm的微孔.

The origin of nonlinearities in K[B5O6(OH)(4)]center dot 2H(2)O crystal

In this paper the origin of nonlinearities of the K[B5O6(OH)(4)].2H(2)O(KB5) crystal has been investigated from a comprehensive view-point by using the bond-valence theory of complex crystals. The results of the calculation (d(31) = -1.18 X 10(-10) esu, d(32) = 0.20 X 10(-10) and d(33) = -1.03 X 10(-9) esu) are in good agreement with experimental data. For the first time we pointed out that its nonlinearities come from the H(2)-O(2) bonds and the [B5O6(OH)(4)](-) group, and estimated its larger nonlinear optical (NLO) coefficient d(33).

活性炭的表面化学性质及对CuO/C催化剂上NO还原性能的影响

活性炭是一种十重要的吸附剂和催化剂载体.它属于微晶结构,主要在低衍射角处产生一个比较大的弥散峰,因而人们尚不能够获得关于活性炭的清晰的空间结构特征.一般认为,活性炭的含氧量是影响其化学性质的一个重要因素.而含氧量和含氧基团分布与活化方式有关.遗憾的是,也还不能通过活化方式控制含氧量和含氧基团分布.目前,关于这些基团的组成和分布在催化剂制备的某些关键步骤中和催化反应中的行为都还知道得很少.本工作选取了4种市售国产活性炭:椰壳炭、山楂核炭、山桃核炭和煤质炭.实验表明,当活性炭本身做催化剂时,含氧基团起到了活性中心作用;在制备负载催化剂的浸渍阶段,含氧基团起着成核中心作用,含氧基团的分布可以影响金属离子的分散度.1 实验部分1.l 反应性能评价以等体积浸渍法制备担载量6.25%质量分数硝酸铜/活性炭催化剂.首先室温下真空干燥24h,然后烘箱中65℃下烘4h,再120℃下烘6℃.性能评价在连续流动微型反应装置上进行.石英反应管内径8mm,催化剂用量500mg(20～35目).反应前催化剂在He气中200℃下处理0.5h,然后350℃下热分解1h.反应气NO浓度1.5%摩尔分数(配在He气中),F/W=50mL/...

5，10，15，20－四（对－山嵛酸乙酯－α－氧代苯基）卟啉LB膜结构研究

５，１０，１５，２０－四（对－山嵛酸乙酯－α－氧代苯基）卟啉ＬＢ膜结构研究王海水，曾广赋，谷淑珍，席时权（中国科学院长春应用化学研究所长春１３００２２）利用ＬＢ膜技术将分子组装成有序的分子单层或多层体系，研究膜内分子间相互作用和分子的结构，对了解结构...

CHOLESTEROL SENSOR-BASED ON ELECTRODEPOSITION OF CATALYTIC PALLADIUM PARTICLES

A layer of palladium particles was electrodeposited on a glassy carbon electrode. The dispersed Pd particles resulted in a large decrease in overvoltage for the electrochemical oxidation of H2O2 down to +0.4 V vs. Ag/AgCl, based on which a new kind of cholesterol sensor was fabricated. Cholesterol oxidase was immobilized on the Pd-dispersed electrode by cross-linking with glutaraldehyde and a layer of poly(o-phenylenediamine) (PPD) film was electropolymerized on the enzyme layer. The sensor shows a linear response in the concentration range 0.05-4.50 mmol l-1 with a rapid response of less than 20 s. The polymer film can prevent interference from uric acid and ascorbic acid and also increases the thermal stability of the sensor. The sensor can be used for 200 assays without an obvious decrease in activity.

STUDIES ON OLEFIN-COORDINATING TRANSITION-METAL CARBENE COMPLEXES .20. SYNTHESIS OF 1,3-CYCLOHEXADIENE(DICARBONYL) [ETHOXY(ARYL)-CARBENE]IRON COMPLEXES AND THEIR PHOSPHINE ADDUCTS - CRYSTAL-STRUCTURE OF C6H8(CO)2FEC(OC2H5)C6H4CH3-O

Reaction of 1,3-cyclohexadiene(tricarbonyl)iron (1) with ortho-substituted aryllithium reagents ArLi (Ar=o-CH3C6H4, o-CH3OC6H4, o-CF3C6H4) in ether at low temperature, and subsequent alkylation of the acylmetalates formed with Et3OBF4 in aqueous solution at 0-degrees-C or in CH2Cl2 at -60-degrees-C gave the 1,3-cyclohexadiene(dicarbonyl)[ethoxy(aryl)carbene]iron complexes (eta4-C6H8)(CO)2FeC(OC2H5)Ar (3, Ar = o-CH3C6H4; 4, Ar = o-CH3OC6H4), and the isomerized product (eta3-C6H8)(CO)2FeC(OC2H5)C6H4CF3-o (5), respectively, among which the structure of 3 has been established by an X-ray diffraction study. Complex 3 is monoclinic, space group P2(1) with a = 8.118(4), b = 7.367(4), c = 14.002(6) angstrom, beta = 104.09(3)-degrees, V = 812.2(6) angstrom3, Z = 2, D(c) = 1.39 g cm-3, R = 0.056, and R(w) = 0.062 for 976 observed reflections. Complexes 3 and 5 were converted into the chelated allyliron phosphine adducts(eta3-C6H8)(CO)2(PR31)FeC(OC2H5)Ar (6, Ar = o-CH3C6H4, R1 = Ph; 7, Ar = o-CH3C6H4, R1 = OPh; 9, Ar = o-CF3C6H4, R1 = Ph), by reaction with phosphines in petroleum ether at low temperatures.

RADIATION-INDUCED CRYSTAL DEFECTS IN PTFE

Changes induced in the crystal structure of PTFE by irradiation at different temperatures have been investigated. In the dose and temperature range examined, the density of PTFE was observed to increase continuously with increasing dose due to the radiation-induced increase in crystallinity, while after post-irradiation annealing at 380-degrees-C, the density was observed to increase for samples irradiated at 20-degrees-C, and to begin to decrease after a certain dose for samples irradiated at 150 and 200-degrees-C. On the basis of the observation of radiation-induced separation of the melting peak of PTFE and its stability relative to the change in the rate of heating, the observed decrease in density was explained as being due to the radiation-induced crosslinking and/or branching inhibiting the process of crystallization and existing in the crystalline region as defects.

5,10,15,20-四(对-乙酯苯基)卟啉LB膜的结构

对卟啉类化合物LB膜的结构、电性质和气敏性的研究已见报道。本文利用膜天平和UV-Vis分光光度计研究了标题化合物在气-液界面上的成膜特性、分子间相互作用和LB膜的结构。5,10,15,20-四(对-乙酯苯基)卟啉(TPEPP)由5,10,15,20-四(对-氰苯基)卟啉和乙醇酯化得到。元素分析测定值与计算值相符。λ(CHCl_3,nm):421,515,550,590,645;ν(KBr压

Enriched accumulation and biotransformation of selenium in the edible seaweed Laminaria japonica

Accumulations of selenium in kelp Laminaria japonica cultured in seawater was achieved by adding selenite (Na2SeO3) with or without N-P (NaNO3 + NaH2PO4) nutrients at different concentrations. Biotransformation of selenium in the kelp was investigated through measuring the selenium of biological samples and different biochemical fractionations. The results showed that the optimal selenite-enrichment concentration is 200 mg L-1, which can allow the kelp to accumulate a total selenium content from 0.51 +/- 0.15 to 26.23 +/- 3.12 mug g(-1) of fresh weight (fw). Selenium composition analysis of kelp (control group) showed that selenium is present as organic selenium, which is up to 86.22% of the total selenium, whereas inorganic selenium is barely 4.85%. When L. japonica was exposed for 56 h in seawater containing 200 mg L-1 Na2SeO3, the organic selenium was 16.70 mug g(-1) of fw (68.23%) and inorganic selenium was 4.71 mug g(-1) of fw (19.26%). The capability of accumulation of selenium was further enhanced by adding N-P nutrients to the selenite-enriched medium. Total selenium is increased to be 33.65 mug g(-1) of fw at optimal concentration of N-P nutrient (150 mg L-1 NaNO3 and 25 mg L-1 NaH2PO4), whereas the inorganic selenium was not increased and remained at 4.597 mug g(-1) of fw (13.36%), and the increased part of selenium was organic selenium. This implied that kelp L. japonica could effectively transform inorganic selenium into organic selenium through metabolism.

Effects of Irradiance and Temperature on the Photosynthesis and Vegetative Propagation of Caulerpa serrulata

The photosynthetic oxygen evolution of Caulerpa serrulata was determined with oxygen electrodes. The effects of light and temperature on the growth and regeneration of fragmented C. serrulata thalli were analyzed. The regenerating rate and establishment of different sizes and portions of C. serrulata were studied. The results showed that the light saturation point of C. serrulata was 200 mu mol photons/m(2) per s and the optimum growth temperature was 25-30 degrees C. Under these conditions, the maximum photosynthetic oxygen evolution rate was 15.1 +/- 0.29 mg O-2/mg Chl a/h, the growth rate and elongation rate reached the highest values, 4.67 +/- 0.09 mg FW/d and 0.78 +/- 0.01 mm/d, respectively. The fragmented C. serrulata thalli was regenerated at 20-35 degrees C and survived at 15 degrees C and 200 mu mol photons/m(2) per s. A different survival rate was detected according to fragment size. All of these results indicated that C. serrulata was a candidate to become an invasive species if introduced into a new place. Therefore, we should pay more attention to C. serrulata for its potential threat to marine ecosystem when it is sold for aquarium use.

The past, present and future of phycology in China

Algae have been part of Chinese life for thousands of years. They are widely used as food and have been cited in Chinese literature as early as 2500 years ago. However, formal taxonomic studies on Chinese algae were initiated by foreign scientists only about 200 years ago, and by Chinese phycologists only about 90 years ago. This paper summarizes the history of modern phycological studies on Chinese algae and provides an overview of the achievements of phycological studies by Chinese scientists, especially on algal taxonomy, morphology, genetics, ecology and environmental research, physiology, biotechnology, algal culture, applied phycology and space phycology, in the last century. Recent development in phycological research focuses on algal floristic and molecular systematics, algal molecular biotechnology, applied phycology including micro and macroalgal cultivation and algal product development, and the roles of algae in environmental pollution control. These areas will also be the main focuses of Chinese phycological research in the foreseeable future.