Combustion synthesis: Novel routes to novel molecular nanomaterials

Combustion synthesis in a mode of electrothermal explosion was used to synthesize 1D carbon nanostructures by magnesium reduction of various carbonates [Li₂CO₃, Na₂CO₃, CaCO₃, FeCO₃, (NH₄)₂CO₃] either in argon or in air, at an ambient pressure of 0.1 or 1.0 MPa. At the same time, several possible catalysts were tried, such as Fe, Co, Ni, Pd, Nd, Ta, Ti, Nb, W, and NiO powders. The Na₂CO₃ system proved to be the most promising for fabrication of fibrous products. On the other hand, our synthesis of carbon encapsulated metal nanoparticles opens up possibilities for new biomedical applications.     

Methods for modifying proton exchange membranes using the sol-gel process

Over the past 20 years, sol-gel processing has expanded into organic-inorganic hybrid materials. This expansion has benefited from the collaborations between the polymers community and the ceramics community, and the discovery that in many instances sol-gel processing and polymer processing are compatible. An active participant in this field has been Dr James E. Mark [Mark JE. Heterog Chem Rev 1996;3:307-320], and his accomplishments deserve this tribute. One example, which derives from his work in organically-modified silicates (ORMOSILS), is hybrid membranes for fuel cells. We present some recent progress in synthesis of hybrid membranes involving Nafion. These membranes have been prepared by infiltration and recasting, and contain silicates, phosphosilicates, zirconium phosphosilicates and titanosilicates.     

溶胶-凝胶法制备硅酸铝耐火纤维

本文以正硅酸乙酯(TEOS)、异丙醇铝(AIP)、硝酸铝(AN)等为原料，用溶胶-凝胶(so1-ge1)法制备硅酸铝耐火纤维．     

利用模板合成纳米材料研究的新进展

在当今纳米科学技术研究突飞猛进的年代，本文分别介绍了近几年来以无机材料、有机高分子及天然大分子为模板进行的纳米材料合成研究的新进展。     

Kinetic specifics of the synthesis of luminescent materials using the sol-gel method

Based on the sol-gel method for producing luminescent silicate materials, the process kinetics is studied for the initial stages of hydrolysis and polycondensation of tetraethoxysiloxane for different temperatures and component ratios. A model of the process is proposed, and reaction rate constants are determined. A conclusion is made on the limiting effect of the polycondensation stage up to the moment of gel formation. Translated from Steklo i Keramika, No. 3, pp. 8–10, March, 2000.     

Investigation of sol-gel derived nanomaterials with a hierarchical structure

The basic processes of self-assembly in sol-gel technologies during the formation of network nanomaterials with a hierarchical structure have been considered. The gas-sensitive fractal structures have been prepared in systems based on dioxides of tin and silicon. The formation of a structure of nanocomposites has been studied using atomic force microscopy and electron microscopy methods. The gas-sensitive properties of nanomaterials have been investigated. A method for diagnosing objects with a hierarchical structure based on metal oxides has been proposed.     

Solution regeneration in the sol-gel process

Techniques for the recovery of the solvent ethanol from spent solutions are discussed. The recovered ethanol can be recycled to prepare film-forming solutions. The properties of the solutions and of the coatings produced from them are assessed. On this basis, the optimal regeneration procedure is proposed.     

LaMgAl11O19 synthesis using non-hydrolytic sol-gel methods

Polycrystalline LaMgAl₁₁O₁₉ (LMA) was prepared by four different non-hydrolytic sol-gel methods. From stable solutions, four powder precursors containing an amorphous and nanocrystalline phase with specific reactivity were obtained. The particle size, morphology, thermal behaviour, and phase composition of the powder precursors were studied using DLS, TEM, DSC/TG and XRD. Bulk ceramic samples containing LMA were prepared at 1200?°C for 16?h and examined in terms of phase purity and microstructure using XRD, SEM, and TEM. Raman spectroscopy of pure LMA was used to study the structure in detail. A mechanism of LMA formation and a relation between powder precursor properties and final phase composition is proposed. These findings may be useful for designing modern technologies for fabrication of LMA for optical or protective coating applications.     

Evaluation of colloidal and polymeric routes in sol-gel synthesis of a bioactive glass-ceramic derived from 45S5 bioglass

This work studied the influence of two sol-gel synthesis routes in obtaining a bioactive glass-ceramic derived from the 45S5 composition: a polymeric and a colloidal route. The main difference between the routes is in the silica precursor employed. The tetraethyl orthosilicate metal alkoxide (Si(OC₂H₅)₄ - TEOS) is used in polymeric route and the silicic acid (H₄SiO₄) was used in the colloidal route. The synthesized xerogels were calcined at different temperatures to eliminate undesirable compounds and to verify the crystallization behavior. Afterwards, the calcined xerogels were submitted to in vitro bioactivity assay. The samples were also characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and laser diffraction. After calcination, the glass-ceramics obtained by the colloidal route showed greater number of bioactive phases and, consequently, of NBO bonds. The larger amount of NBO bonds resulted in a higher bioactivity of the materials synthesized by the colloidal route. In addition, the long hydrolysis step of the metal alkoxides was eliminated with colloidal synthesis. This allowed a significant reduction in the total synthesis time from 13 days to 24 h. To the best of our knowledge, this seems to be the first time this colloidal route has been employed in the synthesis of bioglass 45S5.     

Size-controlled synthesis of spherical ZrO2 nanoparticles by reverse micelles-mediated sol-gel process

Spherical ZrO₂ nanoparticles have been successfully synthesized by a reverse micelles (RMs)-mediated sol-gel process. Hydrolysis of zirconium n-propanol solution was confined in the microreactors made of water/cetyltrimethyl ammonium bromide (CTAB)/cyclohexane/n-butanol RMs, as well as investigating the template effects of RMs in particle size and shape control. It was found that there was significant particle size and shape replication between RMs and ZrO₂ nanoparticles after polycondensation, indicating that the RMs microreactors stabilized by surfactants could control the nucleation, growth and agglomeration process during the hydrolysis and thus the size and shape of ZrO₂ nanoparticles. Furthermore, spherical ZrO₂ nanoparticles could be customized in the range of 10–30 nm, and their roundness value was greater than 0.90.     

Two alternative synthesis routes for MnZn ferrites using mechanochemical treatments

Two different methodologies to synthesise Mn_xZn_1−xFe₂O₄ (x = 0.5, 0.65 and 0.85) are compared. In the first method, mechanochemically activated mixtures of elemental oxides were thermally treated at 1100 and 1200 °C under N₂ atmosphere. In the second, previously obtained MnFe₂O₄ and ZnFe₂O₄ were well-mixed and treated at 1100 °C under N₂ atmosphere. Both series of materials were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), electron probe microanalysis and density measurements. Through a two-step processing, both methods allowed to obtain MnZn ferrites of several compositions, which exhibited high saturation magnetisations and very low coercivities. In this way, in order to overcome some limitations of the conventional preparation technique, alternative synthesis routes for these ferrites are proposed in this study.     

离子液体在纳米材料合成中的应用

室温离子液体（ionic liquids, ILs）作为一种新型的绿色环保溶剂,由于其特殊的功能化结构及热稳定性好、挥发度低和溶解能力强等特点,目前被广泛应用于纳米材料的制备领域。本文重点介绍了离子液体在纳米材料制备中的应用及相关研究的最新进展,结合一些示例对本领域进行了概述,其中包括离子液体作为溶剂,例如作为反应介质和稳定剂;模板剂,例如利用离子液体的微结构（胶束和囊泡、液晶凝胶、乳液和微乳液）作为纳米材料合成中的模板和软模板;反应物,例如作为反应中的还原剂和反应组分;以及离子液体微乳液在纳米材料制备中的特殊用法进行了总结,并讨论了离子液体在快速发展的纳米材料制备领域中的存在挑战和机遇。     

New routes in the synthesis of quinacridone pigments

The increasing use of complex organic pigments has generally focused interest on more economic pathways for their chemical synthesis. This is particularly true for the red quinacridone pigments, whose large-scale application has so far been hindered by technical difficulties connected with conditioning and the complicated multistage chemical synthesis.

Recently different new synthesis routes have been developed, and that based on the chlorination of diketene has a good chance of supplanting the existing manufacturing process based on diethyl succinate.     

Novel organic-inorganic hybrids prepared from polybenzoxazine and titania using sol-gel process

Novel organic-inorganic hybrids were prepared from polybenzoxazine and titania using sol-gel process by blending titanium isopropoxide as a precursor for titania with a typical benzoxazine monomer, bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)isopropane (Ba). Deep red brown and transparent hybrid materials were obtained after thermal cure at 200 °C. DSC indicated that, in the presence of titania precursor, the onset and maximum temperature of the exothermic peak due to the ring opening polymerization of Ba decreased by ca. 30 and 70 °C, respectively. Viscoelastic analyses revealed that the glass transition temperatures (T_g) of the polybenzoxazine-titania hybrids shifted to higher temperature than the neat polybenzoxazine. The storage moduli below T_g for the hybrids increased with the increase of the titania content, and the storage moduli were maintained constant up to higher temperature than the neat resin. TGA results confirmed that the thermal stability and char yield of polybenzoxazine increased by hybridization with titania.     

纳米四氧化三铁的化学制备方法研究进展

阐述了纳米四氧化三铁在磁性材料、多功能材料、催化材料以及医学领域的应用现状。对纳米四氧化三铁的制备方法如沉淀法、溶胶-凝胶法、微乳液法、水热与溶剂热法、热分解法、静电纺丝法等做了介绍。分析了各种纳米四氧化三铁材料的形态如纳米颗粒、纳米棒、纳米线、纳米膜、杂化、核壳结构纳米晶等的适用领域。总结了各种制备方法的研究进展,分析了其优缺点并结合作者课题组在纳米四氧化三铁制备方面的研究工作,对纳米四氧化三铁的今后的研究方向作了展望：制备特殊形貌的纳米四氧化三铁材料、减少纳米四氧化三铁的团聚和氧化、多种制备方法的结合以及如何实现大规模工业化生产。     

Toward reducing the formation temperature of diopside via wet-chemical synthesis routes using chloride precursors

Reducing the formation temperature of single-phase multioxides is one of the classic challenges in ceramic processing, including wet-chemical synthesis routes. Toward pursuing this aim for diopside (MgCaSi₂O₆), the merit of different sol-gel and coprecipitation processes using the related chloride precursors followed by calcination was compared from the viewpoints of crystallinity and homogeneity. In accordance to the results, the use of the sol-gel techniques, directed with/without an alkaline catalyst, gave rise to the unfavorable creation of multiphase and low-crystallinity structures. Regarding the coprecipitation methods, the one-step addition of a precipitant agent is accompanied by an indirect low-temperature formation of nano-diopside, while a direct crystallization into this phase was explored in the dropwise condition, albeit with a lower crystallinity. Thus, by employing a suitable synthesis processing, it is feasible to take control of a wide range of nanoparticulate diopside-based structures achieved after a low-temperature calcination.     

Structure controlling and process scale-up in the fabrication of nanomaterials

Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.     

Structure controlling and process scale-up in the fabrication of nanomaterials

Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.