SiO2/M纳米复合材料的结构及催化性能

采用溶胶-凝胶法和超临界干燥法制备了SiO2/M(Cu,Co)纳米复合材料,对其结构、形貌进行了TEM和比表面分析,并研究了SiO2/M纳米复合材料的催化性能.结果表明,制得的SiO2/M纳米复合材料保留了SiO2气凝胶的纳米网络和高比表面积,金属组份Cu与Co均匀地分散在纳米级SiO2气凝胶骨架中,对CO的氧化反应以及CO-NO反应均表现出高的催化活性.     

Highly basic CaO nanoparticles in mesoporous carbon materials and their excellent catalytic activity

Highly basic CaO nanoparticles immobilized mesoporous carbon materials (CaO-CMK-3) with different pore diameters have been successfully prepared by using wet-impregnation method. The prepared materials were subjected to extensive characterization studies using sophisticated techniques such as XRD, nitrogen adsorption, HRSEM-EDX, HRTEM and temperature programmed desorption of CO2 (TPD of CO2). The physico-chemical characterization results revealed that these materials possess highly dispersed CaO nanoparticles, excellent nanopores with well-ordered structure, high specific surface area, large specific pore volume, pore diameter and very high basicity. We have also demonstrated that the basicity of the CaO-CMK-3 samples can be controlled by simply varying the amount of CaO loading and pore diameter of the carbon support. The basic catalytic performance of the samples was investigated in the base-catalyzed transesterification of ethylacetoacetate by aryl, aliphatic and cyclic primary alcohols. CMK-3 catalyst with higher CaO loading and larger pore diameter was found to be highly active with higher conversion within a very short reaction time. The activity of 30% CaO-CMK3-150 catalyst for transesterification of ethylacetoacetate using different alcohols increases in the following order: octanol > butanol > cyclohexanol > benzyl alcohol > furfuryl alcohol.     

Synthesis of mesoporous Co/Ce-SBA-15 materials and their catalytic performance in the catalytic oxidation of benzene

Cerium-containing SBA-15 mesoporous materials, with different Ce/Si molar ratios, were synthesized by a direct hydrothermal synthesis method and further modified by impregnation with 10, 15 and 20 wt.% Co. Characterizations by powder X-ray diffraction (XRD), N₂ sorption, inductively coupled plasma (ICP) and UV-vis spectroscopy were carried out. The small-angle XRD and N₂ sorption characterizations showed that these Co supported materials have less-ordered mesoporous structures with partial blockage of pores, and their specific surface area, pore volume and pore size were relatively lower than those of unsupported cerium-containing SBA-15. Spinel Co₃O₄ constituted the predominant cobalt phase in the prepared catalysts, and CeO₂ was also detected. All the Co supported catalysts exhibited high catalytic activity in the oxidation of benzene.     

Synthesis of Cu3.8Ni/CoO and Cu3.8Ni/MnO nanoparticles for advanced lithium-ion battery anode materials

We synthesized Cu3.8Ni/CoO and Cu3.8Ni/MnO nanoparticles via an easy and scalable solution synthesis.The synthesized Cu3.8Ni/CoO and Cu3.8Ni/MnO nanoparticles were annealed to remove the organic surfactants without phase transitions or side reactions.Electrons can be transferred via metallic Cu3.8Ni,which will not react with lithium ions.The heterogeneous structures of Cu3.8Ni/CoO and Cu3.8Ni/MnO nanopartides could enhance the lithium ion mobility and improve the life cycle,and these materials are therefore promising candidates as highpower-density and high-energy-density anode materials for lithium-ion batteries in diverse applications,such as electrical vehicles.     

纳米Ni和Ni/SiCp纳米复合材料的超塑性

研究了用电沉积方法制备的纳米Ni和Ni/SiCp纳米复合材料的超塑特性,在试验温度410℃和450℃,应变速率为8.3×10-4s-1～5×10-2s-1的条件下,纳米Ni和Ni/SiCp纳米复合材料均表现出超塑性.当温度为450℃、应变速率为1.67×10-2s-1时,在Ni/SiCp中获得最大延伸率为836%;在同样的温度下应变速率为1.67×10-3s-1时纳米Ni获得最大延伸率为550%.对超塑性变形后组织的分析表明,晶界滑移是主要变形机制,晶粒长大至亚微米/微米量级后,变形机制是位错协调晶界滑移和位错滑移塑性.     

介孔Ag/CeO2材料结构及湿式催化氧化性能研究

以硝酸铈、硝酸银为原料,嵌段聚合物F127为模板剂,采用微波辅助软模板法制备了不同Ag负载量的介孔Ag/CeO2复合材料.对材料进行XRD、N2吸附-脱附、XPS、SEM以及EDS表征分析.结果表明,Ag/CeO2复合材料属于介孔结构,具有较大的比表面积,存在Ce3+、Ce4+,Ag离子均匀负载于CeO2表面.考察了影...     

Polymer-matrix nanocomposite gas-sensing materials

A new approach has been proposed for producing nanocomposite gas-sensing materials: in situ preparation of a polymer matrix and metal sulfide or oxide nanoparticles through the frontal polymerization of Co(II), Cd(II), Zn(II) and Pb(II) acrylamide complexes. The composition and structure of the nanocomposites thus obtained have been determined using X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopy. The nanocomposites have been tested as room-temperature liquefied petroleum gas sensors.     

Novel alginate based nanocomposite hydrogels with incorporated silver nanoparticles

Alginate colloid solution containing electrochemically synthesized silver nanoparticles (AgNPs) was investigated regarding the nanoparticle stabilization and possibilities for production of alginate based nanocomposite hydrogels in different forms. AgNPs were shown to continue to grow in alginate solutions for additional 3 days after the synthesis by aggregative mechanism and Ostwald ripening. Thereafter, the colloid solution remains stable for 30 days and could be used alone or in mixtures with aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) while preserving AgNPs as verified by UV–Vis spectroscopy studies. We have optimized techniques for production of Ag/alginate microbeads and Ag/alginate/PVA beads, which were shown to efficiently release AgNPs decreasing the Escherichia coli concentration in suspensions for 99.9% over 24 h. Furthermore, Ag/hydrogel discs based on alginate, PVA and PVP were produced by freezing-thawing technique allowing adjustments of hydrogel composition and mechanical properties as demonstrated in compression studies performed in a biomimetic bioreactor.     

Ni,Co, Cu,Ni-Co,and Ni-Cu nanoparticles in opal matrices and mesoporous silica gels

NiCo solid solutions and Ni-Cu bimetallic particles have been prepared in opal-matrix nanocomposites by reacting Ni, Co, and Cu double salts and oxides with supercritical (SC) isopropanol. According to X-ray diffraction and transmission electron microscopy data, the nanocomposites have an X-ray amorphous opal matrix and contain crystalline nanoparticles of individual metals, solid solutions, or bimetallic materials of various morphologies in the opal pores. Mesoporous silica gel matrix composites remain X-ray amorphous after treatment in SC alcohols because of the small particle size of the metallic phase, or form solid solutions between Ni and Co silicates. The phase composition of the composites can be controlled by varying experimental conditions.     

Enhanced performance of high temperature aluminate cementitious materials incorporated with Cu powders for thermal energy storage

Cementitious materials have been extensively developed in thermal energy storage system of solar thermal power. This paper deals with the volume heat capacity, thermal conductivity, thermal expansion coefficient, and compressive strength of aluminate cementitious thermal energy storage materials with the addition of metal Cu powders. The specimens were subjected to heat-treatment at 105, 350, and 900 °C, respectively. In the heating process, Cu powders gradually oxidized to Cu₂O and CuO, providing a so-called mass compensation mechanism for the composite paste. Meanwhile, it indicates that volume heat capacity and thermal conductivity both increase with increasing Cu powders content and decrease with the rising temperature. The optimum thermal properties were obtained at 15 wt% Cu powders loading. In addition, Calorimetric Test, XRD, TG–DSC, and MIP are performed for characterizing the hydration rates, the phases, the mass/heat evolution, and the pore distribution, respectively.     

Host (nanodimensional pores of mesoporous material)–guest (semiconductor nanoparticles) nanocomposite materials

An aluminosilicate with the MCM-41 structure (AlMCM-41) was used as a host for the synthesis of cobalt sulfide nanoparticles. Cobalt sulfide nanoparticles were introduced in host by ion exchange and hydrothermal methods. Products (CoSAlMCM-41) were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), EDX, IR, BET and UV–vis spectroscopy. The results show that CoS nanoparticles encapsulated into channels of AlMCM-41 material by hydrothermal synthesis and they grow outside the mesopore AlMCM-41 matrix by ion-exchange methods. Absorption peaks at higher energy than the fundamental absorption edge of bulk CoS indicate quantum confinement effect in nanoparticles as a consequence of their small size. The absorption spectra show that the optical band gap for CoS nanoparticles by hydrothermal and ion-exchange methods are 3.73 and 4.89, respectively.     

New families of mesoporous materials

Mesoporous materials have been paid much attention in both scientific researches and practical applications. In this review, we focus on recent developments on preparation and functionalization of new families of mesoporous materials, especially non-siliceous mesoporous materials invented in our research group. Replica synthesis is known as the method to synthesize mesoporous materials composed of various elements using originally prepared mesoporous replica. This strategy has been applied for the syntheses of novel mesoporous materials such as carbon nanocage and mesoporous carbon nitride. Carbon nanocage has a cage-type structure with huge surface area and pore volume, which exhibits superior capabilities for biomolecular adsorption. Mesoporous carbon nitride was synthesized, for first time, by using mixed material source of carbon and nitrogen simultaneously. As a totally new strategy for synthesis of mesoporous materials, the elemental substitution method has been recently proposed by us. Direct substitution of component elements in original mesoporous materials, with maintaining structural regularity, provided novel mesoporous materials. According to this synthetic strategy, mesoporous boron nitride and mesoporous boron carbon nitride have been successfully prepared, for first time. In addition to these material inventions, hybridization of high functional materials, such as biomaterials, to mesoporous structure has been also developed. Especially, immobilization of proteins in mesopores was systematically researched, and preparation of peptide-hybridized mesoporous silica was demonstrated. These new families of mesoporous materials introduced in this review would have high potentials in future practical applications in wide ranges from electronics and photonics to environmental and medical uses.     

Engineering high-temperature stable nanocomposite materials

The low thermal stability of nanoparticles typically restricts their use in catalytic and other applications to low-?to moderate-temperature conditions. We present a novel approach to the stabilization of nanosized noble metal particles by embedding them in a high-temperature stabilized hexa-aluminate matrix. The simple 'one-pot' approach is based on a microemulsion-templated sol-gel synthesis and yields mesoporous nanocomposite materials with pure textural porosity and excellent high-temperature stability up to about 1200?°C. To our knowledge, this is the first time that metal nanoparticles have been stabilized to such high temperatures. We furthermore find that the microemulsion templating allows a tailoring of the ceramic matrix without influencing the size of the embedded Pt particle. This opens up the possibility of a true multiscale engineering of nanocomposite materials. We see these novel materials therefore not only as very promising candidates for a broad range of high-temperature catalytic applications, but generally view this versatile synthesis route as a first step towards expanding the parameter range for nanoparticle applications.     

纳米复合材料的研究进展

研制开发具有特殊性质的新型纳米复合材料具有广阔的发展前景。本文对近几年来纳米复合材料的最新研究进展进行了综合论述。按照复合方式的不同，分别对4种复合体系的纳米复合材料进行了系统介绍，包括材料的结构组成，制备技术，功能特性以及研究进展状况等，并对纳米复合材料的应用与发展前景进行了展望。     

Mg-based hydrogen storage materials: Surface segregation in Mg2Cu and related catalytic effects

Fresh surfaces of Mg₂Cu polycrystals cleaved in UHV have been investigated by AES, XPS and X-ray induced AES at room temperature. They show chemical decomposition of the surface leading to pronounced increase of surface Mg content. In contrast to the Mg the Cu remains essentially metallic, even on air exposed samples. It is suggested that this segregation prevents the formation of a compact oxide or hydroxide layer, thereby enabling dissociation of molecular hydrogen at the metallic Cu precipitations and/or the metallic Mg₂Cu subsurface. The results support comparable conclusions drawn earlier for LaNi₅, FeTi and Mg₂Ni.     

Temperature-sensitivity and cell biocompatibility of freeze-dried nanocomposite hydrogels incorporated with biodegradable PHBV

The structure, morphology, thermal behaviors and cytotoxicity of novel hydrogels, composed of poly(N-isopropylacrylamide)(PNIPAM) and biodegradable polyester poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) under nanoclay hectorite “Laponite XLG” severed as physical cross-linker, were characterized by X-ray diffraction, scanning electron microscopy, gravimetric method, differential scanning calorimetry, and cell culture experiments. It was found that, due to the introduction of hydrophobic PHBV, the homogeneity of interior pore in the pure PNIPAM nanocomposite hydrogel was disrupted, the transparency and swelling degree gradually decreased. Although the weight ratio between PHBV and NIPAM increased from 5 to 40 wt.%, the volume phase transition temperature (VPTTs) of hydrogel were not altered compared with the pure PNIPAM nanocomposite hydrogel. No matter what PHBV content, the PHBV/PNIPAM/Hectorite hydrogels always exhibit good stimuli-responsibility. In addition, human hepatoma cells(HepG2) adhesion and spreading on the surface of PHBV-based hydrogels was greatly improved than that of pure PNIPAM nanocomposite hydrogel at 37 °C due to the introduction of PHBV.     

New families of mesoporous materials

Abstract

Mesoporous materials have been paid much attention in both scientific researches and practical applications. In this review, we focus on recent developments on preparation and functionalization of new families of mesoporous materials, especially non-siliceous mesoporous materials invented in our research group. Replica synthesis is known as the method to synthesize mesoporous materials composed of various elements using originally prepared mesoporous replica. This strategy has been applied for the syntheses of novel mesoporous materials such as carbon nanocage and mesoporous carbon nitride. Carbon nanocage has a cage-type structure with huge surface area and pore volume, which exhibits superior capabilities for biomolecular adsorption. Mesoporous carbon nitride was synthesized, for first time, by using mixed material source of carbon and nitrogen simultaneously. As a totally new strategy for synthesis of mesoporous materials, the elemental substitution method has been recently proposed by us. Direct substitution of component elements in original mesoporous materials, with maintaining structural regularity, provided novel mesoporous materials. According to this synthetic strategy, mesoporous boron nitride and mesoporous boron carbon nitride have been successfully prepared, for first time. In addition to these material inventions, hybridization of high functional materials, such as biomaterials, to mesoporous structure has been also developed. Especially, immobilization of proteins in mesopores was systematically researched, and preparation of peptidehybridized mesoporous silica was demonstrated. These new families of mesoporous materials introduced in this review would have high potentials in future practical applications in wide ranges from electronics and photonics to environmental and medical uses.