Synthesis of offretite: Part 1. Using various organic compounds as templates

During its preparation offretite usually co-crystallizes with erionite. The addition of a suitable template to the reaction mixture reduces the amount of erionite and, therefore, leads to the formation of purer offretite. A number of templates were tested, a few of which gave positive results. It was shown that TMA and choline were located in the gmelinite cages and increased the crystallinity. However, to reduce the erionite content the template has to be located in the linear channels; this situation was found with TMA, monoethanolamine and diaminoethane.     

Modification of offretite and omega zeolites: Part I. Structural characterization

Offretites and omegas were dealuminated by steaming and acid-leaching treatments. XRD, ²⁹Si MAS n.m.r. and i.r. spectroscopy were used in order to follow the structural evolution of these solids. The presence of extraframework AI species causes a random distribution of the structural data (u.c. parameters, structural band position) as a function of the mole AI fraction determined by chemical analysis (m_total). However, totally linear plots are hardly ever obtained, even if we plot the structural data against the skeletal AI fraction (m_IV). This nonlinearity is supposedly due to the existence of two non-equivalent crystallographic sites and to a preferential dealumination of AI atoms located in these two tetrahedral sites. As a consequence, the u.c. contraction appears to be anisotropic. Acid leaching has been shown to give rise to very contrasted structural modifications according to the nature of the zeolite and the dealuminaton degree. Some dilation of the u.c. during acid-leaching treatments seems to demonstrate that an AI reinsertion into the lattice takes place in acidic media. Extraframework residues are believed to have a very minor influence on structural data, if any.     

Dealumination of zeolites: Part V. Influence of the hydrothermal treatment of offretite on its pore structure and acid properties

The pore distribution of a series of offretite samples dealuminated through self-steaming at various temperatures was characterized by adsorption of nitrogen, n-hexane, and 3-methylpentane, and their acidity, by ammonia adsorption followed by calorimetry and by ammonia thermodesorption. From the analysis of the nitrogen adsorption by the α_s-method, it was concluded that during dealumination at least a fraction of the microporous system, characteristic of offretite network, is converted into supermicropores (0.7−2 nm). The aluminum extraframework species resulting from the framework dealumination have practically no effect on the adsorption of nitrogen, but limit that of the n-hexane and, above all, that of 3-methylpentane. The dealuminated samples are much less acidic than is the starting offretite and the number of acid sites shown by ammonia thermodesorption is much smaller than the number of acid sites estimated from the unit cell formula. This can be related to the partial destruction of the zeolite framework owing to the formation of supermicropores, to the dehydroxylation, and maybe to the neutralization of the acid sites by cationic aluminum extraframework species created during dealumination process.     

Synthesis of a thermoresponsive platinum nanocomposite using a three-layer onion-like polymer as template

Using a well-designed three-layer onion-like polymer as template, a one-pot procedure that led to stable, narrow-sized and thermoresponsive Pt nanocomposites is described. The polymer consists of an outer shell of thermoresponsive poly(N-isopropylacrylamide), an inner shell of crosslinked poly(N,N-dimethylaminoethyl acrylate) and a hyperbranched polyglycerol core. The core is physically trapped by the shell, with a few thiol groups located on the interface between the core and the shell. The polymer is used as a template for the synthesis of platinum nanoparticles, ¹H NMR and TEM analyses suggest that the in-situ produced, narrow-sized Pt nanoparticle is loaded in the core part of the polymer so that the nanocomposite retains thermoresponsive activity.     

水凝胶模板制备纳米TiO2及微流控合成TiO2微球

以聚丙烯酰胺丙烯酸和聚乙二醇/聚丙烯酸两种水凝胶作为模板, 丙烯酸做抑制剂合成纳米颗粒。水凝胶的缓慢吸水和网络结构, 减缓了钛酸四丁酯的水解速率, 并抑制TiO₂的颗粒长大, 制备出的TiO₂纳米粉粒径分布窄, 且为锐钛矿相结构。对比研究发现, 聚乙二醇/聚丙烯酸水凝胶的吸水膨胀率更小, 前驱体溶液的稳定性更高。选用聚乙二醇/聚丙烯酸前驱体溶液, 采用微流控技术制备TiO₂微球, 制备出的微球具有球形度好、单分散的优点, 焙烧后TiO₂的晶体结构为锐钛矿。     

聚酰胺-胺型模板法介孔氧化铝制备及性能研究

采用异丙醇铝为铝源,3.5代PAMAM为模板剂,通过油滴球过程合成了介孔γ-Al2O3微球.研究发现在所合成的氧化铝中,介孔相呈海绵状或蠕虫状随机分布的三维网络结构;其孔径主要分布在2～6nm之间,且合成的介孔氧化铝的比表面积可达340m2/g以上.     

Synthesis of vanadium oxide nanofibers and tubes using polylactide fibers as template

A new method to produce vanadium oxide nanofibers with dimensions <140 nm and tubes is reported. Vanadium oxide was coated on polylactide fibers by a sol-gel method using a reaction mix of ammonium vanadate and acetic acid as starting materials and water as solvent. Vanadium oxide tubes, of about 1 μm in diameter, were formed when this coated fiber was heated in nitrogen and oxygen at 300 and 250 °C for 1 h. Hydrothermal treatment of the polylactide fibers with the reaction mix at 160 °C for 12 h followed by heating in oxygen at 300 °C for 1 h formed vanadium oxide nanofibers, 60-140 nm in width and several microns in length. Electrochemical studies reveal that these vanadium oxide nanofibers are redox active and readily undergo reversible reactions with lithium in non-aqueous cells.     

双子表面活性剂为模板纳米二氧化钛的制备及光催化活性

以脱氢松香为原料,通过化学合成的方法制备出一种新颖的双子表面活性剂,采用FT-IR及1 HNMR对其结构进行确证;以酞酸四正丁酯（TNB）为起始原料,通过加入自制的双子表面活性剂,采用水热合成法制备了平均粒径为8.81nm的锐钛矿型纳米二氧化钛颗粒;利用FT-IR、TEM、XRD对纳米二氧化钛进行表征;以紫外光为光源,罗丹明B（RhB）为模型污染物考察了纳米二氧化钛的光催化活性,结果表明其催化活性优于未加表面活性剂制备的纳米二氧化钛,且在紫外光下反应3h,RhB的降解率为99.7%,基本完全降解。     

Synthesis of mesoporous Al2O3 macrospheres using the biopolymer chitosan as a template: A novel active catalyst system for CO2 reforming of methane

A new and simple method to prepare alumina containing mainly mesopores is described. This alumina has a high surface area (464 m²/g) and a large pore volume ranging from about 0.35 to 0.65 cm³/g. The present method was developed using a biopolymer (chitosan) and Al solution. The Al–chitosan solution was added to NH₄OH solution in the form of drops. A hybrid macrosphere compound of aluminum hydroxide and organic polymer is formed. Through polymer elimination by thermal treatment, porous Al₂O₃ spheres with a high specific surface area are obtained. The Ni-impregnated Al₂O₃ spheres showed a high catalytic activity and stability for dry reforming of methane at 650 °C and a CH₄ / CO₂ = 1 molar ratio.     

Force and Stiffness of Passive Magnetic Bearings Using Permanent Magnets. Part 2: Radial Magnetization

This paper deals with the calculation of the force and the stiffness between two ring permanent magnets whose polarization is radial. Such a configuration corresponds to a passive magnetic bearing. The magnetic force exerted between ring permanent magnets is determined by using the Coulombian model. The expressions obtained are semianalytical and we show that it is not possible to find an exact analytical expression of the force between two ring permanent magnets. Then, thanks to these semianalytical calculations, the ring dimensions are optimized in order to have a great force or a great stiffness. Moreover, we show that the relative position of the rings for which the force is the strongest depends on the air gap dimension. This result is new because the curvature effect is taken into account in this paper. We can say that such semianalytical expressions are more precise than the numerical evaluation of the magnetic forces obtained with the finite-element method. Moreover, semianalytical expressions have a low computational cost whereas the finite-element method has a high one. Thereby, as shown in this paper, such calculations allow an easy optimization of quadripolar lenses or devices using permanent magnets.      

Synthesis of WO(3) nanoparticles using a biopolymer as a template for electrocatalytic hydrogen evolution

Tungsten trioxide nanoparticles were prepared by a simple approach using chitosan biopolymer as a template. These nanoparticles were characterized using x-ray diffraction, Raman spectroscopy, transmission electron microscopy and high resolution transmission electron microscopy. The average size of the WO(3) nanoparticles is 42?nm, and they intercalate a larger amount of hydrogen than tungsten trioxide, which is prepared without chitosan. The materials are tested for their electrocatalytic hydrogen evolution in a sulfuric acid medium, where WO(3) nanoparticles show a fourfold higher activity than bulk tungsten trioxide.     

Synthesis of MnO2 nanorods from a ZnO template and their capacitive performances

The synthesis of initial ZnO nanorods as template and subsequent formation of α-MnO₂ nanorods are presented in this paper for the first time. A possible formation mechanism of the nanorods is also proposed. The diameters of the as-synthesized α-MnO₂ nanorods are less than 20 nm and the average lengths are about 100 nm. When investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatical charge-discharge (CD) tests, the resulting α-MnO₂ nanorods exhibit good electrochemical performances in terms of its maximum specific capacitance of 167 F g^− 1 at 0.4 A g⁻¹ and good cycling stabilities during the 1000 cycles, suggesting that it is a promising candidate as supercapacitor materials.     

Synthesis of carbon nanotubes using SBA-15 as a template by the reaction of methane and carbon dioxide

Multiwalled carbon nanotubes (CNTs) were synthesized using Ni loaded mesoporous SBA-15 as a template by reaction of methane and carbon dioxide. The influences of nickel content on the selectivity and crystallinity of CNTs were investigated. It can be seen that the crooked CNTs with a diameter varied from 9.9, 12.5 to 36.5 nm with creasing content of Ni from 5, 15, and 30 wt%/SBA-15. A uniform diameter and good quality CNTs were obtained in our system.     

Synthesis of macro/mesoporous silica and carbon monoliths by using a commercial polyurethane foam as sacrificial template

A commercial macrocellular polyurethane foam was used as template to fabricate macro/mesoporous silica and carbon monoliths. These materials have a cellular structure which is a faithful replica of that of the polymeric foam. In addition, they have a high surface area and a large porosity made up of accessible mesopores. The synthesis of silica monoliths was carried out by impregnating the polymeric foam with a mixture of a silica precursor and a surfactant. The carbon monoliths were prepared by using the silica monoliths as sacrificial templates. They retain the foamy vesicular structure and exhibit a high surface area of 1800 m² g^− 1 and a large porosity made up of framework-confined mesopores of around 3.4 nm.     

Cover cracking as a function of rebar corrosion: Part 2—Numerical model

A numerical model based on standard finite-element techniques is proposed for the simulation of cracking in concrete specimens when subjected to corrosion of their reinforcement. A smeared-crack approach is used to model the behaviour of the concrete finite elements, while the corrosion, which is understood as the applied load on the structure, is modelled by a combination of initial strains and change of elastic properties, which are respectively equivalent to the expansion and softening of the steel elements at the rebar surface when they rust. The model is applied to four examples, which were simultaneously tested experimentally and reported in Part 1 of this paper, and the influence of the main parameters of the model in the response is studied separately. In particular, the effect on the crack-width rate of the specific volume of the rust being formed is quantitatively assessed.     

Synthesis of Eu2O3 hollow submicrometer spheres through a sol–gel template approach

Submicrometer-sized hollow Eu₂O₃ spheres with a shell thickness of about 75 nm and inner diameter about 690 nm have been synthesized through a sol–gel method using PS/PE microspheres as templates. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FESEM), and photoluminescence (PL) spectroscopy have been used for the characterization of the obtained hollow Eu₂O₃ spheres. The PL peak is obviously broadened compared with that of bulk Eu₂O₃. The mechanism of the formation of the hollow Eu₂O₃ spheres was discussed.     

Synthesis and characterization of HAp nanorods from a cationic surfactant template method

Hydroxyapatite (HAp) [Ca₁₀(PO₄)₆(OH)₂] nanorods were synthesized using a surfactant templating method, with cetyltrimethylammonium bromide (CTAB) micelles acting as template for HAp growth. The effects of the sintering temperature on the morphological and crystallographic characteristics and on chemical composition of the “as-prepared” structures are discussed. The experimental results show that low heat-treatment temperatures are preferred in order to obtain high quality nanorods, with diameters ranging between 20 and 50 nm. High heat-treatment temperatures enhance the thermal decomposition of HAp into other calcium phosphate compounds, and the sintering of particles into micrometer ball-like structures. The stability of aqueous suspensions of HAp nanorods is also discussed.     

Designing a laser scanning picoprojector. Part 2: laser-safety-related issues

Laser scanning picoprojectors present a new challenge in the field of laser safety with methods of calculating accessible emission limits still in their infancy. We present a laser safety analysis and a calculation of an example picoprojector. We show that, due to its scanning operation, a picoprojector should be considered an extended laser source, and we also show that a picoprojector with two separate one-axis microelectromechanical systems mirrors offers a higher safe power limit than a projector with a single scanning mirror. Finally, a safety analysis is done under conditions of mirror failure. We show that, if the projector fails to scan in just one of the axes, the ocular hazard rises sharply, highlighting the need for a fail-safe system to be built into laser scanning picoprojectors.     

Synthesis and characterization of silica microcapsules using a sustainable solvent system template

We report direct encapsulation of a sustainable solvent system in silica microcapsules via a sol-gel reaction of silica precursor for potential application of thermoplastic self healing polymeric system. The silica microcapsules were realized by hydrolysis and condensation of tetraethyl orthosilicate (TEOS) using aqueous glycerol microemulsion as template. The pre-hydrolysis of TEOS was found to be useful to obtain isolated free flowing silica microcapsules. Furthermore, the effects of different parameters viz. temperature, rotor speed, the solvent/TEOS ratio on the synthesis of silica microcapsules are studied. A novel micro compression technique to study mechanical properties of the silica microcapsules is reported. The silica microcapsules reported were found to have better mechanical properties compared to incumbent Urea-Formaldehyde (UF) based organic microcapsules.