The sol-gel preparation of ZnO/silica core-shell composites and hollow silica structure

Three kinds of different ZnO colloid particles (flowerlike particles, nanoribbons and microspheres) and one kind of ZnO film have been coated with silica via a simple sol-gel method in the Stöber system and ZnO/silica core-shell microparticles or films have been obtained. The thickness of silica shell can be controlled by adjusting the concentration of TEOS added into the system. If the ZnO core is etched off by HCl, corresponding, hollow silica particles or film will be generated.     

A novel synthesis of micrometer silica hollow sphere

Silica microcapsules (hollow spheres) were synthesized successfully by a novel CTAB-stabilized water/oil emulsion system mediated hydrothermal method. The addition of urea to a solution of aqueous phase was an essential step of the simple synthetic procedure of silica hollow spheres, which leads to the formation of silica hollow spheres with smooth shell during hydrothermal process. The intact hollow spheres were obtained by washing the as-synthesized solid products with distilled water to remove the organic components. A large amount of silanol groups were retained in the hollow spheres by this facile route without calcination. The morphologies and optical properties of the product were characterized by transmission electron microscopy, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy. Furthermore, on the basis of a series of SEM observations, phenomenological elucidation of a mechanism for the growth of the silica hollow spheres has been presented.     

A novel approach to the synthesis of hollow silica nanoparticles

Hollow silica nanoparticles were synthesized with incorporation of silanol groups (SiOH) onto polymer particles in dispersion polymerization and the polycondensation reaction of tetraethyl orthosilicate (TEOS) exclusively took place at the particles surface in the presence of ammonia following the so-called Stöber process and the silica-coated polymer powers were calcined at 800 °C. The diameters of hollow silica spheres are found to be very close to the original diameter and the average pore diameter is less than 100 nm. Moreover, the hollow silica nanoparticles have uniform aperture, do not agglomerate and collapse.     

The preparation of novel hollow tetragonal starlike polyaniline and its electrochemical performance

Novel hollow tetragonal starlike polyaniline (HTS-PANI) doped with citric acid has been successfully synthesized by hydrothermal method for the first time. Scanning electron microscopy, transmission electron microscopy, UV–visible spectroscopy, Fourier transmission infrared spectroscopy, and X-ray diffraction were employed to analysis the morphology and structure of the obtained PANI. The results show that the HTS-PANI is in semi redox state and highly crystallized, accompanied with good thermal stability. According to the galvanostatic charge–discharge analysis, the specific capacitance of the sample is up to 460 F g^?1 at a current density of 0.2 A g^?1 in 1 M KCl electrolyte, and retains about 58 % after 1,000 charge–discharge processes at a current density of 5 A g^?1.     

Preparation and properties of hollow silica tubes/cyanate ester hybrids for high-frequency copper-clad laminates

A novel kind of hollow silica tube (HST)/cyanate ester (CE) hybrid with high thermal, mechanical, and dielectric properties for high-frequency copper-clad laminates (CCLs) was successfully developed. The curing behavior, the chemical structure of cured networks, and typical performance of HST/CE hybrids were systematically evaluated and compared with that of CE resin. Results disclose that the addition of HST into CE resin can obviously not only catalyze the curing of CE, but also change the chemical structure of resultant networks, and thus result in significantly improved mechanical, thermal, and dielectric properties. The hybrid with 0.7 wt% HST exhibits very good toughness; its impact strength is about 2.2 times of that of CE resin. The outstanding integrated properties show that HST/CE hybrids can be used as high performance structural and functional materials, especially high-frequency CCLs.     

Development of a simple method for the preparation of novel egg-shell type Pt catalysts using hollow silica nanostructures as supporting precursors

A simple method for the preparation of novel egg-shell type platinum catalysts was developed and achieved by utilizing unique hollow silica nanostructures, i.e., hollow silica nanospheres and nanotubes, as supports. The observation by transmission electron microscopy indicated that the well-dispersed hollow silica supported Pt catalysts with a Pt particle diameter of 8-14 nm can be successfully prepared by wet impregnation process and heat treatment. The Pt-loaded hollow silica nanostructures were also characterized by inductively coupled plasma, X-ray diffraction, specific surface area, Fourier transformation infrared spectroscopy, X-ray photoelectron spectroscopy and energy dispersive spectroscopy. It was thus demonstrated that a higher Pt loading amount (0.392%) could be obtained under the same conditions except the addition of ammonia, which was found to be more effective than that (0.061%) with the addition of HCl in the immobilization of Pt. In addition, the effect of soaking time, Pt precursor concentration and calcination temperature on the loading of Pt in hollow silica nanostructures were investigated as well.     

A novel method for preparation of hollow and solid carbon spheres

Hollow and solid carbon spheres were prepared by the reaction of ferrocene and ammonium carbonate in a sealed quartz tube at 500°C. The morphology and microstructure of the product were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The carbon spheres are amorphous and their diameters range from 0·8–2·8 μm. The shell thickness of the hollow carbon spheres is not uniform and ranges from 100–180 nm. It is suggested that ammonium carbonate is crucial for the formation of carbon spheres and its amount also influences the morphology of the product. The method may be suitable for large scale preparation of carbon spheres.     

无机材料纳米空心球的制备方法研究进展

探索新的纳米结构已成为近年来物理、化学、材料等领域的研究热点之一.纳米空心球作为一种新的纳米结构,其特有的核-壳空心结构及纳米厚度的壳层使它具有许多优异的物理化学性能,从而在医学、制药学、材料学、染料工业等领域具有很好的应用前景.本文综述了模板法和由模板法发展而来的L-bL自组装法制备无机材料纳米空心球的一般过程及原理,最后展望了纳米空心球材料的发展前景,并探讨了目前在无机材料纳米空心球研究领域中存在的问题.     

Facile preparation of monodisperse micrometer-sized hollow silica spheres with tunable size and commendable surface topography

The fabrication of hollow silica spheres (HSS) is of great importance due to its plenty of implications. Till now, several methods to prepare HSS have been reported, which existed some drawbacks. Herein, a facile and efficient approach was developed to successfully fabricate micrometer-sized monodisperse HSS based on templating method. The approach was achieved by changing the initial water volume and using ethylene glycol dimethacrylate (EGDMA) as the crosslinking agent. The alteration of water volume was the key factor in controlling the size of HSS, and EGDMA was used to accessorily enlarge the bulk of template spheres. In this way, the uniform HSS were controlled in micrometer scale, which simultaneously possessed the favorable surface topography. This method could achieve high reproducibility and would become a general method to systematically manipulate the size and shape of inorganic spheres as we expected. Most importantly, the formation mechanism for HSS was presented and some key influencing factors were analyzed.     

A sol–gel preparation of silica coated zirconia microspheres as chromatographic support materials

Four silica–zirconia composites were prepared using a sol–gel process and compared with zirconia, which was prepared under the same conditions but without the addition of sodium metasilicate pentahydrate. Spherical particles (1–2 μm) resulted which were free from aggregation and hollow spheres. Raman spectroscopy, differential thermal analysis, thermal gravimetric analysis and electron microscopy were used to evaluate the properties of these composites. Addition of the silica onto the zirconia microspheres prevented the formation of monoclinic zirconia and increased the temperature of crystallization into the tetragonal form. Calcination of the composites at 1300°C produced zircon. This revised version was published online in November 2006 with corrections to the Cover Date.     

Toroidal microporous silica gel

Microporous amorphous silica gel with a characteristic toroidal form of the elementary particles, has been prepared by thermal dissociation of a solution of silicic acid in a spray dryer. The substance obtained was investigated by electron microscopy, infra-red spectroscopy and thermal analysis. The adsorption properties were studied by lowtemperature adsorption of nitrogen.     

新型大直径碳管的制备及应用研究进展

新型大直径碳管不同于普通的圆筒状碳纳米管,其直径大于100 nm,具有新颖的形貌、结构和组成.其具有优异的物理和化学性质,在众多领域里显示出广阔的应用前景,如应用于生物医药、磁性材料和场发射等领域.大直径碳管的常规制备方法包括化学气相沉积法、溶剂热法、爆炸法和电弧放电法等.制备新型大直径碳管及其应用研究已经成为碳材料领域的研究前沿和热点之一.本文综述了新型大直径碳管的制备以及应用的研究进展,探讨了该研究领域亟待解决的问题以及今后可能的发展前景.     

Fabrication of raspberry-like superhydrophobic hollow silica particles

Raspberry-like superhydrophobic hollow silica particles were prepared through a sacrificial polymer template method. The Stöber method was adopted to coat silica onto the surface of cationic polymethylmethacrylate(PMMA) particles by electrostatic interaction. The surface of the PMMA-silica composite particles exhibited raspberry-like morphology with high surface roughness. Hollow silica particles were then obtained by calcination to selectively remove the PMMA core. Subsequent modification with nonafluorohexyltriethoxysilane (NFH-silane) conferred superhydrophobicity on the hollow silica particles. The surface property of this particles were investigated by measuring their water contact angle, and the results showed that such perfluorinated raspberry-like hollow particles had unique superhydrophobic.     

Synthesis and properties of hollow silica nanoparticles

Hollow nanoparticles of silicon dioxide (SiO₂) have been obtained using Cu/SiO₂ core-shell nanoparticles as precursors. An original technique based on heating the precursor nanoparticles to T = 400°C followed by a nanochemical reaction of copper oxide separation from hollow silica particles has been proposed and implemented for the first time. The obtained hollow SiO₂ nanoparticles have been studied by transmission electron microscopy. Mechanisms involved in the formation of hollow silica nanoparticles are discussed.     

Synthesis of cubic type hollow silica particles

Cubic-type hollow silica particles were prepared from Fe₂O₃-SiO₂ core-shell composite particles by selectively leaching the iron oxide core materials using acidic solution. The cubic Fe₂O₃ core particles were obtained by the hydrolysis reaction of iron salts. The Fe₂O₃-SiO₂ core-shell type particles were prepared by the deposition of a SiO₂ layer onto the surface of Fe₂O₃ particles using a two-step coating process. The first step involved primary coating with sodium silicate solution followed by subsequent coating by controlled hydrolysis of tetraethoxysilicate (TEOS). The core Fe₂O₃ was removed by dissolution in an acidic solution which gave rise to the hollow type silica particles. Scanning electron microscopic observation clearly revealed that the morphology is closely related to those of core the Fe₂O₃ particles. The cross sectional view determined by transmission electron microscopy revealed a silica shell with a thickness of about 50 nm. The porous texture of the hollow type silica particles is further characterized by nitrogen adsorption-desorption isotherm measurements.     

Fabrication of hollow silver spheres by MPTMS-functionalized hollow silica spheres as templates

In this study, we provide a strategy to prepare the hollow silver spheres by accumulating the silver nanoparticles on the surface of 3-mercaptopropyltrimethoxysilane (MPTMS)-functionalized silica as templates, which was accomplished by the chemisorption between silver nanoparticles and thiol groups. Then, the resulting hollow silver spheres were obtained through the chemical wet etching process with 10 M HF solution. In conventional method, the fabrication of hollow silver spheres from core-shell spheres was not easy due to the difficulties in retaining the shell structures during core removal. The method in this paper could overcome this limitation. The major focus of study is on understanding the mechanism of formation of the hollow silver spheres through the self-assembly behavior by chemisorption between silver nanoparticles and thiol groups. The silver-coated silica and hollow silver spheres were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and X-ray photoelectron spectroscopy (XPS).