Synthesis of mesoporous Co-B alloy in room-temperature ionic liquids and its electrochemical properties

Co-B alloy with mesoporous structure was firstly synthesized using room-temperature ionic liquids as templates and investigated as an anode for secondary alkaline batteries. Investigations indicate that such mesoporous structure facilitated the electrochemical hydrogen storage. It maintained 94% of the initial capacity (336 mA h/g) after 50 cycles. The excellent cycling performance is most likely due to the stable structure during cycling. Meanwhile, it exhibited an excellent rate capability. The results demonstrated that the prepared Co-B-mesoporous is capable of serving as a high power capability anode for the rechargeable alkaline batteries.     

Electroanalytical determination of trace chloride in room-temperature ionic liquids

The electroanalytical quantification of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6] ionic liquids has been explored using linear sweep and square wave voltammetry. Cathodic stripping voltammetry at a silver disk electrode is found to be the most sensitive. The methodology is based on first holding the potential of the electrode at +2.0 V (vs Ag wire), to accumulate silver chloride at the electrode. On applying a cathodic scan, a stripping wave is observed corresponding to the reduction of the silver chloride. This stripping protocol was found to detect ppb levels of chloride in [C4mim][BF4], [C4mim][NTf2], and [C4mim][PF6]. Although other methods for chloride have been reported for [BF4](-)- and [PF6](-)-based ionic liquids, no methods have been reported for [NTf2](-) ionic liquids.     

Polyoxometalate-lyotropic liquid crystal hybrid material formed in room-temperature ionic liquids

Manganese(II)-substituted polyoxometalate, Na6(NH4)4[(Mn(II)(H2O)3)2(WO2)2(BiW9O33)2] x 37H2O (POM-Mn), was assembled within lyotropic hexagonal liquid crystal (LLC) formed in the room-temperature ionic liquids (RT-ILs), ethylammonium nitrate (EAN), fabricating the POM-LLC inorganic-organic hybrid materials. Polarized optical microscope images combined with small-angle X-ray scattering (SAXS) results indicate that the introduction of POM-Mn does not destroy the structure of hexagonal LLCs. The increase of d spacing demonstrates the integration of POM-Mn within the basic unit of the hexagonal LLCs. The FTIR spectra of the POM-LLC hybrid material show the characteristic absorption peaks of W-O bond. The rheological results indicate POM-LLC hybrid materials are highly viscoelastic and that the apparent viscosity is enhanced due to the introduction of the POM-Mn. The tribological properties were explored to greatly extend the applications of POM-LLC composites in RT-ILs as lubricating materials. The research of magnetic properties indicates the POM-LLC composite is ferromagnetic, therefore illuminating the potential application in the fields of magnetic materials.     

Solvent extraction and stripping of silver ions in room-temperature ionic liquids containing calixarenes

We found that a calix[4]arene-bearing pyridine is soluble in a typical room-temperature ionic liquid (RTIL), 1-alkyl-3-methylimidazolium hexafluorophosphate. Pyridinocalix[4]arene showed a high extraction ability and selectivity for silver ions. The extraction performance of the calix[4]arene was greatly enhanced by dissolution in RTILs compared to in chloroform. In a competitive extraction test using five different metal ions (Ag+, Cu2+, Zn2+, Co2+, Ni2+), only silver ions were transferred by the calix[4]arene from the aqueous feed phase into the RTILs, through a cation-exchange mechanism. The pyridinocalix[4]arene was found to form a stable 1:1 complex with silver ions, both by slope analysis and by Job's method. Since it is easy to strip silver ions from RTILs by controlling the aqueous-phase pH, the extraction performance of calix[4]arene in RTILs was maintained after five repeated uses.     

Electrochemical properties of composite materials based on graphite and vanadium disilicide

Electrodes with different composition were prepared by the method of pressing followed by sintering of the graphite and vanadium disilicide powders, and their electrochemical and corrosion properties in water solutions of electrolytes were studied.Translated from Inzhenerno-Fizicheskii Zhuraal, Vol. 52, No. 5, pp. 802–707, May, 1987.     

Determination of binding constants of cyclodextrins in room-temperature ionic liquids by near-infrared spectrometry

Near-infrared spectrometry has been successfully used to determine association binding constants between phenol and alpha-, beta- and gamma-cyclodextrin (CD) in [butylmethylimidazolium][chloride] room-temperature ionic liquid (RTIL). It was found that adding CD into the RTIL solution of phenol resulted in an enhancement in the absorption coefficient of the stretching overtone of the aromatic C-H groups. However, the enhancement induced by CDs in RTIL is much lower (order of magnitude) than those corresponding in D20. The binding constants in RTIL are also much lower than those in D2O ((11 +/- 2), (16 +/- 2), and (40 +/- 6) M(-1) for phenol and alpha-, beta- and gamma-CD, respectively, as compared to 87 and 214 M(-1) for a- and beta-CD in D2O). The results obtained seem to suggest that in ionic liquid, the main interaction between phenol and CDs may not be inclusion complex formation but rather external adsorption. A variety of reasons may be responsible for relatively weaker interactions and lower binding constants in the ionic liquid, including differences in the polarity and viscosity of RTIL and D20. However, the main reason may be due to the possibility that the 1-butyl-3-methylimidazolium cation of the ionic liquid may form inclusion complexes with CDs either through its imidazolium moiety or its butyl group. Such complex formation would prevent phenol from being included in the cavity of the CDs.     

Dielectric properties of composite materials containing aligned carbon nanotubes

This paper presents a study of the electrodynamic properties of polymer-matrix composite materials containing a filler in the form of multiwalled carbon nanotubes. We have examined the effect of filler alignment in the composites on their interaction with electromagnetic radiation. The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction.     

Application of ionic liquids in photopolymerizable holographic materials

The influence of ionic liquids in photopolymerizable holographic materials was investigated extensively. The structures of ionic liquids have important effect on the properties of the materials. Although not all tested ionic liquids can improve the properties of the materials, the ionic liquids based on imidazolium, pyridium, or phosphonium with appropriate counter anions can be used as additives to increase the sensitivity, the diffraction efficiency, and the resolution of the materials in the thin hologram. Polymerizable ionic liquids have also been used as additives. Higher sensitivity, higher diffraction efficiency and higher resolution were obtained as well. These ionic liquids can carry out the photopolymerization during exposure to UV light to recording the hologram. They may assist to form a more stable hologram.     

C/C复合材料飞机刹车盘的结构与性能

采用企业、行业及国家相关标准的试验方法，对超码复合材料公司，英国Dunlop公司，法国CarbonIn-dusty公司，美国B．F．Goodrich、ALS公司等生产的9种C／C复合材料飞机刹车盘的物理、力学、热学、摩擦磨损的性能特征，以及中南大学生产的C／C复合材料刹车盘的有关性能，进行了对比分析。结果表明，选择适宜的炭纤维预制体结构，控制热解炭基体微观结构为光学粗糙层结构，合理的热处理温度是获得高性能炭刹车盘材料的关键。我国拥有自主知识产权研发的大型民机炭刹车盘在高摩擦特性方面获得了重大突破，已用于波音757—200型飞机，实现了国内C／C复合材料具有里程碑意义的第四个重大突破。     

Biological and biochemical properties of the carbon composite and polyethylene implant materials

We studied the biocompatibility of the carbon composites and polyethylene materials with and without collagen or collagen and proteoglycan cover. We used the in vitro technology to study the adhesion of model cells evalution, their metabolic activity and the production of TNF- as a cytokine model. Under in vivo condition, the biocompatibility of tested polymers were studied in the implantation experiment, subcutaneously in the interscapular region in the laboratory rat. We have found in the in vitro assay favorable proliferation and the smallest production of pro-inflammatory TNF- cytokine in cells adherent to the hydrophobic polyethylene material coated with biological macromolecules. Using in vivo tests performed by the implantation of materials to the rat we demonstrated that the materials are not cytotoxic. The tissue capsule surrounding the implants was not significantly influenced by the type of the implant and the pre-treatment by the biological molecules. However, the foreign-body giant multinucleated cells were observed only in the vicinity of the collagen – covered hydrophobic polyethylene implant. Interestingly, while the collagen coating improved the biocompatibility of tested polymers in vitro, the inflammatory reaction against this covered materials was higher under in vivo conditions. The pre-treatment of carbon composites by both types of biological macromolecules reduced the occurrence of carbon debris in the implantation site. The tested carbon composites and polyethylene materials are not toxic. The pre-treatment of the materials by extracelular matrix components increased their biological tolerance in vitro and reduced implant wears in animal experiment, which can be important for the medical application.     

Absorption of water by room-temperature ionic liquids: effect of anions on concentration and state of water

Near-infrared (NIR) spectrometry was successfully used for the non-invasive and in situ determination of concentrations and structure of water absorbed by room-temperature ionic liquids (RTILs). It was found that RTILs based on 1-butyl-3-methylimidazolium, namely, [BuMIm]+ [BF4]-, [BuMIm]+ [bis((trifluoromethyl)sulfonyl)amide, or Tf2N]- and [BuMIm]+ [PF6]-, are hydroscopic and can quickly absorb water when they are exposed to air. Absorbed water interacts with the anions of the RTILs, and these interactions lead to changes in the structure of water. Among the RTILs studied, [BF4]- provides the strongest interactions and [PF6]- the weakest. In 24 hours, [Bu-MIm]+ [BF4]- can absorb up to 0.320 M of water, whereas [Bu-MIm]+ [PF6]- can only absorb 8.3 x 10(-2) M of water. It seems that higher amounts of water can be absorbed when the anion of the RTIL can strongly interact and hence stabilize absorbed water molecules by forming hydrogen bonds with them or inducing hydrogen bonds among water molecules. More importantly, the NIR technique can be sensitively used for the noninvasive, in situ determination of absorbed water in RTILs, without any pretreatment, and at limits of detection as low as 3.20 x 10(-3) M.     

Radiative properties of composite materials based on phenolic carbon and glass reinforced plastics

The article investigates the change of radiative characteristics of composites based on carbon, quartz, and glass fabric and phenol formaldehyde resin in dependence on the wavelength, the temperature, and thermal effects.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 61, No. 4, pp. 663–668, October, 1991.     

木质素基分级多孔碳复合相变材料的制备与性能研究

以木质素为原材料,通过模板法和化学活化法制备出木质素基多孔碳LTC和木质素基分级多孔碳LTCA,以LTCA为载体,采用真空浸渍法负载相变材料聚乙二醇(PEG4000),制备出木质素基分级多孔碳/聚乙二醇(LTCA/PEG)复合相变材料.通过扫描电镜、透射电镜、全自动比表面积及孔隙分析仪、X射线衍射分析、傅里叶变换红外光...     

Dramatic effect of dispersed carbon nanotubes on the mechanical and electroconductive properties of polymers derived from ionic liquids

Free-radical polymerization of an imidazolium ion-based ionic liquid bearing a methacrylate group, gelling with single-walled carbon nanotubes (SWNTs), allows fabrication of a mechanically reinforced, electroconductive soft material (bucky plastic). A film sample of this material displays an excellent conductivity of 1 S cm(-1) and a 120-fold enhancement of the Young's modulus at a 7 wt % content of SWNTs. The conductivity is temperature-dependent in the range 5-300 K, suggesting that the conductive process involves carrier hopping. Scanning electron and atomic force micrographs of a bucky plastic film display the presence of crosslinked networks consisting of finely dispersed SWNTs. Such nanotube networks, developed in the polymer matrix, likely suppress slipping of entrapped polymer molecules via a strong interfacial interaction and also facilitate intertubular carrier transport. Although a bucky plastic derived from a vinylimidazolium ion-based ionic liquid monomer shows a comparable conductivity to that of the methacrylate version, the film is brittle irrespective of the presence or absence of SWNTs.     

室温离子液体在材料合成中的应用

室温离子液体的物理和化学性质相对稳定,具有结构可调的特性.作为一种新功能材料广泛用于材料合成领域.根据离子液体在材料合成中的不同作用,本文从离子液体作为反应溶剂、模板剂、电解液、以及同时作为溶剂和模板剂这4个方面介绍了其在材料合成中的应用研究进展.     

Solvent extraction of sr2+ and cs+ based on room-temperature ionic liquids containing monoaza-substituted crown ethers

A series of N-alkyl aza-18-crown-6 ethers were synthesized and characterized by NMR spectroscopy and mass spectrometry. These monoaza-substituted crown ethers in ionic liquids were investigated as recyclable extractants for separation of Sr(2+) and Cs(+) from aqueous solutions. The pH-sensitive complexation capability of these ligands allows for a facile stripping process to be developed so that both macrocyclic ligands and ionic liquids can be reused. The extraction efficiencies and selectivities of these monoaza-substituted crown ethers for Na(+), K(+), Cs(+), and Sr(2+) were studied in comparison to those of dicyclohexano-18-crown-6 under the same conditions. The extraction selectivity order for dicyclohexano-18-crown-6 in the ionic liquids investigated here was K(+) > Sr(2+) > Cs(+) > Na(+). The extraction selectivity order for N-alkyl aza-18-crown-6, in which the alkyl group is varied systematically from ethyl to n-dodecyl, was Sr(2+) > K(+) > Cs(+) > Na(+) in 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide and K(+) > Sr(2+) > Cs(+) > Na(+) in 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide and 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide. The strong dependence of selectivity on the type of ionic liquid indicates an important role played by solvation in solvent extraction processes based on ionic liquids. The optimization of macrocyclic ligands and ionic liquids led to an extraction system that is highly selective toward Sr(2+).     

Electrochemical properties of V2O5/carbon composite electrodes in aqueous solutions

The reaction mechanism of V₂O₅ xerogel and the electrode properties of V₂O₅/carbon composites in an aqueous electrolyte solution were examined to obtain high-performance electrodes for rechargeable proton batteries. Based on the results of the chemical analysis of the electrode, proton intercalation is suggested to be the dominant reaction mechanism. By using the relationship between the capacity and current density of a thin-film electrode consisting of V₂O₅ xerogel, the diffusion coefficient in the V₂O₅ xerogel was determined to be 8 ± 1 × 10^?11 cm² s^?1. The V₂O₅/carbon composite electrode was prepared by drying a homogeneous dispersion of carbon particles in the V₂O₅ sol. The composite electrodes showed a large capacity of 460 mAh g^?1 at a current density of 1 A g^?1 and maintained a relatively large capacity of 160 mAh g^?1 at 100 A g^?1. These properties were attributed to the homogeneous microstructure of the V₂O₅/carbon composites. The V₂O₅/carbon composite electrodes were thus revealed as high-performance electrodes with large capacities and excellent high-rate capabilities.     

碳包钴纳米颗粒/聚二甲基硅氧烷复合热界面材料的制备和性能

为了制备具有良好的热导率、热稳定性、导电性和柔顺性的纳米颗粒填充硅树脂复合材料,首先以乙基封端聚二甲基硅氧烷(PDMS)为基体材料,以碳包钴纳米颗粒(C@Co)为填料,采用研磨共混法制备了C@Co/PDMS复合热界面材料。然后,运用TEM、XRD、Raman和SEM分别对C@Co的微观结构、物相、石墨化程度和分散性进行了研究。最后,研究了C@Co含量对复合热界面材料的热导率、热稳定性、导电性和柔顺性的影响。结果表明:该复合热界面材料的热导率随着C@Co含量的增加而增大,当C@Co的含量为24wt%时,复合材料的热导率达到最大值1.64 W/(m·K),比纯PDMS的提高了10.7倍;TG分析表明,添加24wt%的C@Co后,复合材料的起始分解温度和最终分解温度比纯PDMS的分别提高了约70℃和80℃,说明C@Co能提高复合材料的热稳定性;随着C@Co含量的增加,复合热界面材料的电导率非线性增大,拟合试差计算的逾渗阀值为10wt%,即C@Co含量小于10wt%时复合材料的绝缘性良好,而填充24wt%的C@Co时复合材料的电导率为9.38×10-3 S·m-1;复合材料的硬度适中,处于17.6~26.8HA范围内,表明该复合材料的柔顺性较好。因此,24wt%C@Co/PDMS复合材料不仅能满足热界面材料电性能的基本要求,且具有良好的热导率、热稳定性和柔顺性。     

Preparation and properties of close-packed composite materials

Monodisperse silica particles of about 0.3m diameter are suspended in methacrylate monomer using a carefully selected dispersant. Many steric dispersants are hydrocarbon chains with a reactive end-group. These are not effective as dispersants for silica in moderately polar solvents, such as esters and the methacrylate monomers. Good dispersion was obtained with a methacrylate polymer terminated by a chlorosilane end group. Settling or centrifugation of these unagglomerated dispersions gives well-packed particle beds. Polymerization of the surrounding monomer produces composite materials with high packing fractions and a high degree of regularity. Moduli and strengths of these composites are reported.