Nucleation and growth of copper on glassy carbon and steel

The nucleation and growth of copper from sulphate solution have been studied on two substrates, glassy carbon and stainless steel. Investigations were performed by linear sweep voltammetry, potential and current step methods. The results suggest that a copper coating is formed on glassy carbon by three-dimensional nucleation and growth of the crystallites up to coalescence. On steel, after the formation of crystallites by the same mechanism as above, a second step was observed. The oxide layer, which was on the parts of the substrate not covered by the first crystallites, was reduced, allowing copper to deposit on the renewed surface by a non-nucleated process. This may explain the rapid covering of steel, as compared with the slow covering of glassy carbon, and the different morphology of the deposits obtained on the two substrates.     

Adsorption and anodic oxidation of methanol on iridium and rhodium electrodes

Adsorption and electro-oxidation of methanol on smooth iridium and rhodium electrodes have been studied. The regularities obtained were compared with the results of previous measurements on smooth platinum. The adsorption of methanol on iridium has been established as characterized by regularities peculiar to a surface with an exponentially distributed inhomogenity of adsorption sites (Freundlich isotherm, linear change of the activation energy of adsorption with logarithm of surface coverage). The adsorption regularities for rhodium are more complex. The character of the isotherms on iridium and rhodium, as well as on platinum, does not depend on the nature of adsorbed neutral particles (methanol, hydrogen etc) and is apparently determined by the electrode surface properties. As follows from kinetic regularities (influence of potential, concentration and pH of solution, surface coverage) the rate-determining step of steady-state methanol electro-oxidation on iridium and rhodium is the oxidation of carbonaceous chemisorbed particles by adsorbed OH radicals.     

Effect of thermal pretreatment and reduction on acidity and metal state in doped NiH and CuH mordenites

Thermal pretreatment such as calcination and steaming as well as the reduction of cations by hydrogen, affect the zeolitic acidity and activity of nickel- and copper-doped mordenites in heterogeneously catalyzed reactions such as the conversion of n-hexane. Data on acidity changes were obtained by IR spectroscopy, and information on ionic and metallic states by temperature-programmed reduction, CO chemisorption and transmission electron microscopy (TEM). The findings were compared with reaction results from conversion of n-hexane. Trimethylamine (TMA) was selected as a standardization molecule for semi-quantitative determination of acidity. Correlation of relative acidity values with experimental results was possible only to a very limited extent. Results of CO chemisorption, TPR and TEM allow conclusions to be drawn on metallic crystallites, Ni⁺ and Cu⁺ ions and clusters, which appear to exert a stabilizing influence on zeolitic activity. Nickel crystallites with d > 2 nm catalyze both hydrogenation and dehydrogenation of paraffins on the metal in bifunctional catalysis, as was also observed on platinum-doped zeolites.     

精喹禾灵及其S-对映体的手性分离与紫外光谱研究

采用高效液相色谱法完成了精喹禾灵及其S-对映体在NucleosilChiral-2上的手性分离,以正己烷作流动相,选择添加适量异丙醇和微量三氟醋酸作为改性剂,达到了满意的手性分离效果。通过一阶导数光谱和二阶导数光谱,进行R-对映体和S-对映体紫外光谱的比较研究,验证了两个光学异构体在设定试验条件下具有完全一致的紫外光谱特征。     

混联式冷凝器的可视化及传热实验分析

在分析混联式冷凝器中强化凝结传热机理的基础上,选用相同尺寸的平行流冷凝器为基准对比样件,通过高速摄影可视化实验及冷凝器性能测试方法, 对分流孔径为2.5、4.5 mm的两种混联式冷凝器进行可视化分析表明,类似于蒸气喷射流的过热蒸气与气液两相流在集流管中强烈扰动混合,改善了进入下一冷却流道的两相流质量分布的均匀性,扩展了两相流传热区域在混联式冷凝器中的相对占有面积,这使其传热性能比平行流冷凝器可提高9.6%; 同时,制冷系统中的制冷剂质量流量则提高13.43%,为设计更紧凑的空调冷凝器提供了一种新的途径。     

Direct Radiation Effects on the Structure and Stability of Collagen and Other Proteins

In this review, recent progress in understanding the direct effects of radiation on the structure and stability of collagen, the most abundant protein in the human body, and other proteins is surveyed. Special emphasis is placed on the triple-helical structure of collagen, as studied by means of collagen mimetic peptides. The emerging patterns are the dose dependence of radiation processes and their abundance, the crucial role of radicals in covalent-bond formation (crosslinking) or cleavage, and the influence of the radiation energy and nature. Future research should allow fundamental questions, such as charge transfer and fragmentation dynamics triggered by ionization, to be answered, as well as developing applications such as protein-based biomaterials, notably with properties controlled by irradiation.     

Preparation and characterization of carbon foams derived from aluminosilicate and phenolic resin

Aluminosilicate-reinforced carbon foams have been prepared by chemical foaming with phenolic resin as matrix precursor and aluminosilicate as the additive. The effects of the amount of aluminosilicate used on the microstructure, mechanical properties and oxidation resistance of the carbon foams have been investigated by scanning electronic microscopy, mechanical testing, and oxidation weight loss, respectively. The results show that the amount of aluminosilicate added has a significant influence on the surface roughness and the structure uniformity of carbon foams. The compressive strengths are usually higher than that of the pure carbon foam sample by as much as 60%. The percentage of weight loss of the carbon foams drops with increasing aluminosilicate content up to 11 wt%, but then increases.     

螺旋纳米碳纤维及聚乙烯醇复合材料的制备与性能表征

以镍为催化剂,采用化学气相沉积法制备螺旋纳米碳纤维,并通过浓硝酸氧化法对螺旋纳米碳纤维进行处理,在加热条件下,制备了螺旋纳米碳纤维/聚乙烯醇复合材料. 实验考察了螺旋纳米碳纤维含量对复合材料力学性能的影响,当螺旋纳米碳纤维添加量为0.4%(w)时,复合材料的拉伸性能提高32%. 通过扫描电镜对复合材料的拉伸断口进行分析,螺旋纳米碳纤维均匀地分散在基体中,有效增强了复合材料的抗拉性能.     

木糖醇类成核剂的合成与性能研究

以木糖醇和3,4-二甲基苯甲醛为原料,在酸催化下进行醇醛缩合反应,合成了1,3-2,4-二(3,4-二甲基)苄叉木糖醇(DMDBX)。考察了促进剂用量,3,4-二甲基苯甲醛与木糖醇物质的量比和催化剂用量对产品收率的影响。采用DMDBX作为成核剂对聚丙烯进行了透明改性研究,结果表明：DMDBX对聚丙烯的增透能力与Mil- lad3988相当,同时对聚丙烯的其他物理性能也有一定改善效果。     

溶剂型氟硅树脂的制备及应用

以全氟辛基丙烯酸乙酯为主要单体,制备了溶剂型氟硅树脂聚合物,采用红外光谱和激光粒度对聚合物进行了表征,研究了聚合单体、聚合工艺对氟硅树脂的影响,并将该氟硅树脂应用于石材表面处理,通过SEM对石材表面进行了分析。结果表明经过处理后的石材具有良好的拒水、拒油性、抗沾污性。     

Characterization and modification of fillers for paints and coatings

This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO₃, talc, SiO₂,) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported.     

明胶及其酰化产物的沉降性能

本文研究了明胶和酰化明胶溶液的沉降性能,考察了试剂用量及pH值对沉降性能的影响,找出了一些基本的规律,发现了氯化钠盐析与乙醇、丙酮溶剂沉降时,明胶和酰化明胶沉降效率的不同,并从理论上进行了初步的探讨。     

尼龙1010三元纳米复合材料的结构与性能研究进展

论述了尼龙1010(PA1010)三元纳米复合材料的结构与性能的研究进展,对由两种填料共混改性r的PA1010复合材料的结构与性能,以及无机填料、弹性体等几类填充增韧增强体系及分散相形貌的研究进展进行了详细介绍。并指出PA1010复合材料的发展趋势是以三元共混为基础,获得高强度、高韧性的纳米填充材料分散性良好的PA1010复合材料。     

UHPC浆体的工作性和流变性与颗粒膜层厚度的关系

建立超高性能混凝土(UHPC)浆体的工作性和流变性之间的关系可从理论上研究其工作性变化规律。本文以颗粒膜层厚度为UHPC浆体的工作性的综合衡量指标,设计了正交试验,研究水胶比、超细粉煤灰替代率和硅灰掺量对UHPC浆体的工作性与流变性的影响。根据流动度和流变性测试结果,分析了水胶比和超细粉煤灰替代率的共同作用对UHPC浆体的工作性与流变性的影响,探究了UHPC的净浆与砂浆的工作性关系,基于浆膜层厚度给出了UHPC砂浆的工作性与流变性的关系式。研究结果表明:水胶比是UHPC浆体的工作性与流变性的最主要影响因素,水胶比、超细粉煤灰替代率和硅灰掺量提高均造成UHPC浆体的颗粒表面膜层厚度增大;水胶比和超细粉煤灰替代率的共同作用下,UHPC浆体的流动度和黏度系数具有相关性。     

Formulation and processing of virgin and recycled polyolefin/oil blends for the development of lubricating greases

This work has been focused on the development of polyolefins/oil blends potentially suitable as lubricating greases by studying the effect that some thermo-mechanical processing variables exert on their rheological properties and microstructure. Polyolefin/oil blends have been prepared by dispersing recycled and virgin polyolefins such as high-density polyethylenes (HDPEs) and polypropylenes (PPs) in mineral lubricating oil. Linear viscoelasticity functions have been significantly influenced by processing conditions. The nature of polymers used, specially the content of HDPE, has been found to modify the microstructure of blends yielding lower mechanical stability but, on the other hand, higher values of linear viscoelastic functions.     

Effects of NH3 and urea on K distribution in root and rhizosphere of maize

The effects of NH₃ formed by urea hydrolysis on K distribution in maize roots and the rhizosphere were examined by electron probe x-ray microanalysis. Fresh weight of seedlings growing on calcareous soils was decreased by applying 200 ppm N as urea attributable to the inhibition of the development of root hairs and lateral roots. In the U-200 treatment, little K accumulated in the roots but K concentration in the rhizosphere soil increased. Such a pattern does not appear in roots receiving 200 ppm as ammonium sulfate or on calcareous soils with 100 ppm N as urea or with 200 ppm as urea in an acidic clay loam. The results indicate that K efflux is responsible for the growth depression and that K efflux from the high concentration of NH₃ formed when urea is hydrolysed rather than from the NH ₄ ⁺ ion. Applying K fertilizer with urea should alleviate the adverse effects of urea on plant growth on calcareous soils by improving K status of the plant and by the decrease in rhizosphere soil pH which considerably reduces NH₃ concentration. Management designed to limit pH increase during urea hydrolysis should both prevent NH₃ injury and reduced N losses.     

Morphology and rheology of composites based on anisotropic polymer matrix and different clays

Structure and rheological properties of hybrids with polymer matrix and layered silicates as filler were studied. Solution containing 60% wt of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycol (PEG) was used as a matrix. The peculiarity of this study is that the matrix depending on temperature can form different phase states including liquid‐crystalline (LC). So, a possibility of coexistence and superposition of different ordered structures can be realized at different temperatures. Three different fillers were used: natural Na‐montmorillonite (MMT) and organoclays obtained by treating MMT with surfactants varying in polarity of their molecules. Depending on the type of clay, materials with different morphology can be obtained. X‐ray data showed that PEG intercalates all types of clay used whereas penetration of HPC macromolecules into clay galleries during mixing does not occur. Clay modified with more polar surfactant should be treated as the most convenient material to be intercalated by PEG. Rheological studies (included steady‐state and dynamic shear properties in a wide temperature range) demonstrate that composites are viscoplastic materials and the yield stress is observed already at 5% fillers loading. The level of the yield stress depends on the phase state of the matrix being induced by the superposition of structures formed by clay particles as well as by the LC phase (if it exists). The same conclusion can be made on the base of linear oscillatory measurements because the existence of the LC phase and/or the presence of filler lead to a pseudo solid‐like behavior of a system as whole. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

氧化淀粉的制备及其阻垢性能研究

以马铃薯淀粉为原料,稳定二氧化氯为氧化剂,制备氧化淀粉,并对产品结构进行了红外光谱分析。通过静态阻垢试验测定了所制备产品的阻垢效果。试验结果表明产品阻垢效果良好,同时对影响阻垢性能的pH、温度等因素也进行了研究。     

Influence of copolymer's end groups and molecular weights on the rheological and thermomechanical properties of blends of novel thermoplastic copolymers and epoxy resins

In this paper, we present a study on the properties of epoxy resins blended with copolyethersulfones. Several copolyethersulphones were synthesized by varying the molecular weights and the end groups. The obtained thermoplastics were then mixed with diglycidyl ether of biphenol A (DGBEA) (15% wt ratio), cured with methylene bis(2,6‐diethylanine) (MDEA), and the resulting blends characterized by the use of dynamic thermal mechanical analysis (DMTA), rheometry, and fracture mechanics tests. The morphology of the blends was studied by the use of scanning electron microscopy (SEM). The different molecular weights of the copolymers had a significant effect on the rheological and thermomechanical properties of the resins, as well as the different end groups on the reaction rate and on the thermomechanical properties of the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 250–257, 2006     

Pore structure and strength development of cement composites

Two stages are to be distinguished in the development of cement composite pore structure. The first stage is determined by the composition of the mixture as well as by its mixing efficiency and compaction degree. During this stage the initial pore structure, characterized by the initial porosity - P, is being formed. The second stage of the pore structure deveopment is a consequence of the hydration products creation in hardening cement composite. In dependence on the volume as well as on the kind, morphology and other properties of the created hydration products the total porosity diminishes, the hydration micropores arise and the final pore structure -with a characteristic pore size distribution and micropores shape- is formed.

A close relationship between the pore structure and strength of cement based composites follows from the fact that both these properties depend decisively on the volume, kind and other parameters of hydration products created.