bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Carbon Nanotubes Using Microwave Radiation
Authors: Hong E.H. , Lee K.‐H. , Oh S.H. , Park C.‐G. 
Published: January 2004

AbstractWe report a method for the synthesis of carbon nanotubes (CNTs) by microwave irradiation. CNTs were successfully synthesized by microwave heating of the catalyst loaded on various supports such as carbon black, silica powder, or organic polymer substrates (Teflon and polycarbonate). Microwave (2.45 GHz, 800 W) irradiation used acetylene as a hydrocarbon source, and 3d transition metals and metal sulfides were used as the catalysts. Different carbon yields and morphologies were obtained depending on the reaction conditions. Fibrous nanocarbons—linear or Y‐branched—were observed as well as carbon nanoparticles and amorphous carbon. High‐resolution transmission electron microscopy (HRTEM) revealed that these fibrous nanocarbons are either multiwalled CNTs or graphitic nanofibers (GNFs). This novel method has the potential to grow CNTs virtually on any substrate provided its absorption of microwave energy is small.
Preparation of Hollow Zeolite Spheres and Three‐Dimensionally Ordered Macroporous Zeolite Monoliths with Functionalized Interiors
Authors: Dong A. , Ren N. , Yang W. , Wang Y. , Zhang Y. , Wang D. , Hu J. , Gao Z. , Tang Y. 
Published: January 2004

AbstractA novel and flexible strategy involving hydrothermal transformation of guest‐incorporated zeolite‐seeded mesoporous silica spheres was proposed to prepare guest‐encapsulated hollow zeolite spheres and three‐dimensionally (3D) ordered macroporous zeolite monoliths. The guest species that were pre‐incorporated into the mesopores of silica spheres could be spontaneously encapsulated inside the formed hollow zeolite shells by consuming silica nutrition of the original mesoporous silica cores during the hydrothermal process. A wide range of guest materials with a size ranging from nanometers to micrometers, e.g., Ag and PdO nanoparticles, and mesoporous spheres of carbon and polymer of micrometer size were successfully encapsulated into both discrete hollow zeolite spheres and 3D ordered macroporous zeolite monoliths. Such materials are expected to find a variety of applications such as catalysis, adsorption, and novel microreactors for their special structures with active species inside and zeolitic porous shell outside.
Polyaniline–Silica Composite Conductive Capsules and Hollow Spheres
Authors: Niu Z. , Yang Z. , Hu Z. , Lu Y. , Han C.C. 
Published: January 2004

AbstractIn this paper, we report on the preparation of monodisperse polyaniline (PANi)–silica composite capsules and hollow spheres on monodisperse core–gel‐shell template particles. An extension of the previously reported inward growth method was used. The samples were self‐stabilized without external additives. The core–gel‐shell particles were prepared by the inward sulfonation of monodisperse polystyrene particles. The introduced sulfonic acid and sulfone groups are responsible for the gel properties. The gel‐shell thickness and core size were synchronously controlled over the whole particle radius range. After aniline (ANi) monomer was preferentially absorbed in the sulfonated polystyrene shell, PANi was formed by polymerization. PANi was doped in situ with a sulfonic acid group to give the capsules a high conductivity. PANi hollow spheres were derived after the polystyrene cores were dissolved: their cavity size and shell thickness were synchronously controlled by using different core–gel‐shell particles. The PANi–silica composite capsules and hollow spheres were therefore prepared by a sol–gel process using tetraethylorthosilicate in the conducting shell. The PANi shell became more robust while maintaining the same conductivity level. Morphological results indicate that the PANi and silica formed a bicontinuous network. Fourier‐transform infrared (FTIR) spectra revealed that the hydrogen bonding in the PANi–gel shell was enhanced after the silica phase was incorporated, which could explain the high conductivity level after the silica phase was added. In a converse procedure, silica capsules and hollow spheres were prepared by a sol–gel process that incorporated tetraethylorthosilicate into the core–gel‐shell templates, which was followed by the absorption and polymerization of aniline in the silica shell thus forming PANi–silica composite capsules and hollow spheres. The silica capsules and hollow spheres thereby became conductive.
Copper‐Assisted Weak Polyelectrolyte Multilayer Formation on Microspheres and Subsequent Film Crosslinking
Authors: Schuetz P. , Caruso F. 
Published: January 2004

AbstractThe formation of weak polyelectrolyte films on planar and spherical supports has recently evoked major interest, as such coatings allow novel material properties to be tunable by pH and salt adjustment of the polyelectrolyte deposition conditions. We report on the build up of multilayers of the weak polyelectrolytes poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) on submicrometer‐sized polystyrene (PS) and silica colloid spheres (∼ 500 nm) with the aid of copper ion templating. The copper ions complex to the carboxylate groups of PAA, facilitating the formation of PAA/PAH multilayers on the particles. Regular growth of the layers on the colloid spheres with each polyelectrolyte deposition step was confirmed by microelectrophoresis, single‐particle light scattering (SPLS), and transmission electron microscopy (TEM), with an average bilayer thickness of ∼ 3 nm. The polyelectrolyte multilayer‐coated particles formed stable colloidal dispersions, with ζ‐potentials ranging from 30 mV (PAH outer layer) and –50 mV (PAA outer layer). Complementary quartz‐crystal microbalance and UV‐vis spectrophotometry studies on PAA/PAH multilayers formed on planar supports were performed to examine the film formation and the role of copper ion binding to the layers. PAA/PAH multilayers formed on colloid particles were also chemically crosslinked by using the activator 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC). The degree of film crosslinking could be readily controlled by varying the concentration of EDC employed. Following solvent decomposition of the template particles coated with crosslinked PAA/PAH multilayers, intact hollow polymer capsules were obtained. These capsules were found to be impenetrable to polystyrene.
The Effect of Ultrasound on the Dissolution of Pyrite Ores in Acidic and Fe2(SO4)3 Solutions
Authors: Dogan H.T. , Kurtbas A. , Tekin T. 
Published: January 2004

AbstractThis paper deals with the investigation of the effect of ultrasonic energy on the dissolution of pyrite ores in acidic and Fe2(SO4)3 solution. In the effect of ultrasound on the dissolution at various temperatures was experimentally investigated, while keeping the particle size and the solution concentration constant. The same experimental runs, without using ultrasound, were performed and the results were compared. According to these results, it was observed that ultrasound increased the conversion fraction by approximately 30 % compared with the experimental results without ultrasound.
Cooperation of Ag/Al2O3 and Sn/Al2O3 Catalysts for the Selective Reduction of NO by Propene
Authors: Hao J. , Liu Z. , Fu L. , Zhu T. , Li J. , Cui X. 
Published: January 2004

AbstractCompared to the Ag/Al2O3 catalyst, a two‐stage catalyst composed of an Ag/Al2O3 layer followed by a Sn/Al2O3 layer shows higher low‐temperature activity and a wider temperature window. Its activity below 350 °C is enhanced in the presence of SO2. Even in the presence of H2O and SO2, the performance of the same catalytic system is still satisfactory.
Effective Diffusivities and Convective Coefficients for CaO‐CaSO4 and CaO‐CaCl2 Pellets
Authors: Akosman C. , Zirekgür N. 
Published: January 2004

AbstractDiffusion and convective flow in the pores of pellets formed by compressing mixtures of calcined limestone and CaSO4/CaCl2 powders have been studied experimentally by using the single pellet moment technique. The experiments were conducted in a diffusion cell by flowing nitrogen gas (carrier) through both faces of the pellet. Limestone powder was calcined in an atmosphere of N2 at 800 °C and mixed with CaSO4/CaCl2 for diffusion experiments. Effective diffusivity of helium has been estimated by exposing the upper face of the pellet to a pulse of and matching the response peak on the lower face of the pellet with theoretical expressions. The values of the effective diffusivities increased with temperature, but decreased with increasing CaSO4/CaCl2 content in the pellet. The convective flow contribution to the diffusion flux was found to increase with increasing pressure drop across the pellet.
Utilization of Raw and Activated Date Pits for the Removal of Phenol from Aqueous Solutions
Authors: Banat F. , Al‐Asheh S. , Al‐Makhadmeh L. 
Published: January 2004

AbstractActivated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N2 atmosphere and activation at 900 °C in CO2 atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.
Silo Discharge: Measurement and Simulation of Dynamic Behavior in Bulk Solids
Authors: Böhrnsen J.U. , Antes H. , Ostendorf M. , Schwedes J. 
Published: January 2004

AbstractThis paper deals with the experimental investigation and the numerical simulation of silo discharge processes, including dynamic interactions between the silo filling and the elastic silo walls. The discharge process is described by a system of nonlinear differential equations. Via the Finite Element Method (FEM) based on an EULERian reference frame, the deformation rate, the velocity field, the porosity, and the stress distribution can be calculated without the need of re‐meshing the FE‐grid. To compare simulation results with measured data, the numerical simulation examples are chosen to be similar to an experimental test‐silo of the Institute of Mechanical Process Engineering at the Technical University of Braunschweig. Optical measurement techniques are applied to investigate the flow profile, and load cells on the silo walls register the stress evolution, e.g., a stress peak (switch) moving from the outlet to the transition from hopper to shaft.
Management and Reuse of Mathematical Models in the Industrial Design Process
Authors: Eggersmann M. , von Wedel L. , Marquardt W. 
Published: January 2004

AbstractThe use of model‐based methods to support planning, designing, and operating chemical processes and plants has recently gained an increased importance in the daily work of process engineers. The development of mathematical models through the use of standard flow sheet simulation tools requires the expertise of an experienced designer. Therefore, the value of existing models is not limited to the resources required for their development, but also includes value in the form of knowledge about an enterprise's products and production processes. The reuse of existing models and design experiences in order to lower the costs of model development is therefore economically desirable. This report gives an overview of the systematic long‐term management and use of mathematical models. Some motivating scenarios are used to derive the requirements for a model management system and to evaluate existing methods and tools. The results of these example scenarios are then used to guide the development of a model management system. After presenting a prototypical implementation the article concludes with an outlook on the future importance of model management systems.
Atomic Layer Deposition of Hafnium Dioxide Films Using Hafnium Bis(2‐butanolate)bis(1‐methoxy‐2‐methyl‐2‐propanolate) and Water
Authors: Kukli K. , Ritala M. , Leskelä M. , Sajavaara T. , Keinonen J. , Jones A.C. , Roberts J.L. 
Published: January 2004

AbstractHfO2 films were grown by atomic layer deposition (ALD) from a mononuclear Hf(OtBu)2(OCMe2CH2OMe)2 complex and H2O at temperatures in the range 275–400 °C on borosilicate glass and Si(100) substrates. The growth of the densest films was achieved at temperatures above 300 °C. The growth rate was influenced by the thermal decomposition of the Hf precursor. The as‐deposited films were oxides with an O:Hf ratio of 2.0 ± 0.2, although containing large amounts of impurities. Crystalline monoclinic films were grown at temperatures exceeding 325 °C, whereas at lower temperatures the films mostly remained amorphous. On the whole, the refractive index of the films varied between 1.95 and 2.00. The effective permittivities of the dielectrics in Al/HfO2/p‐Si(100) capacitor structures varied between 12 and 14, slightly increasing with growth temperature.
Growth Per Cycle in Atomic Layer Deposition: Real Application Examplesof a Theoretical Model
Authors: Puurunen R.L. 
Published: January 2004

AbstractIn a previous paper, a theoretical model was derived to describe the growth per cycle in atomic layer deposition (ALD) as a function of the chemistry of the growth when compounds are used as reactants. This paper presents examples of how the model can be applied to investigate the mechanisms of real ALD processes. Three processes that represent different classes of compound reactants were selected for study: the trimethylaluminum/water process to grow aluminum oxide, the yttrium 2,2,6,6‐tetramethyl‐3,5‐heptanedionate (thd)/ozone process to grow yttrium oxide, and the titanium tetrachloride/water process to grow titanium dioxide. The results obtained by applying the model were, in general, consistent with the results obtained through separate investigations of the reaction mechanisms. The model was shown to be a useful tool in investigations of the reaction chemistry of real ALD processes.
Pt Thin Film Collectors Prepared by Liquid‐Delivery Metal–Organic CVD Using Pt(C2H5C5H4)(CH3)3 for LiCoO2 Thin Film Cathodes
Authors: Choi W.‐G. , Choi E.‐S. , Yoon S.‐G. 
Published: January 2004

AbstractPlatinum thin film collectors were deposited onto p‐type Si(100) planar and trench substrates by liquid‐delivery metal–organic (LD‐MO) CVD using Pt(EtCp)Me3, Pt(C2H5C5H4)(CH3)3, for microbatteries. The resistivity and root‐mean‐square (rms) roughness of Pt thin films with (111) preferred orientation increased with the increase of both deposition temperature and system pressure. The deposition of Pt thin films was controlled by a gas‐phase mass‐transfer mechanism and Pt thin films deposited at 350 °C showed the lowest resistivity, rms roughness, and the highest step coverage, 57 %, in trench structure. The LiCoO2 cathode films (step coverage = 51 %) deposited on the trench Pt collector showed an increase in discharge capacity of approximately two and half times that of the planar Pt collector. Platinum thin films deposited by LD‐MOCVD have a possible application as collector materials for LiCoO2 thin film cathodes.
Supplementation of oils with oleanolic acid from the olive leaf (olea europaea)
Authors: Guinda Ángeles , Pérez‐Camino Ma Carmen , Lanzón Augusto 
Published: January 2004

AbstractA method was studied for utilization of olive leaf, which is a byproduct of olive tree pruning and olive oil production. Our strategy involves two stages. The first is a simple procedure for isolating oleanolic acid, a compound with known biological activity. The second stage involves supplementation of different types of oil with this triterpenic acid. Two protocols were used for incorporating this acid into oils, either as a solid or as a solution, at concentrations from 200 to 1000 ppm. Oleanolic acid in the prepared oils was quantified by gas liquid chromatography. At the concentrations analyzed, the oleanolic acid content measured in all oil samples was equal to the amount added (p <0.05). No significant difference was observed (p <0.05) between the two supplementation procedures in any of the oils.
Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils
Authors: Yunus Robiah , Fakhru'l‐Razi Ahmadun , Ooi Tian Lye , Iyuke Sunny E. , Perez Joseph M. 
Published: January 2004

AbstractDue to the global drive towards biodegradable products, trimethylolpropane [2‐ethyl‐2‐(hydroxymethyl)‐1, 3‐propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters were considered: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Lubrication properties such as viscosity, viscosity index (VI) and pour point (PP) were determined according to methods of the American Society for Testing and Materials. Wear and friction properties were evaluated using a four‐ball test machine, while oxidative stability was studied with the Penn State Micro‐oxidation thin‐film test. High VI ranges between 170 to 200 were recorded for these base stocks. PP were relatively high, between 4 to —1 °C, but were improved to at least —33 °C in high oleic palm oil TMP esters. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono‐ and diesters had negative effects at high concentrations. Differences in chemical structures of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids.
One step hydroxybromination of fatty acid derivatives
Authors: Eren Tarık , Küsefoğlu Selim H. 
Published: January 2004

AbstractHydroxybromination of methyl oleate, oleic acid and new sunflower oil (high oleic), in an acetone/water mixture by a one step reaction using N‐bromosuccinimide, was studied. The yield of bromohydrin products from oleic acid, methyl oleate and sunflower oil were 90%, 78% and 40%, respectively. Reaction products were analyzed by 1H and 13C nuclear magnetic resonance spectroscopy, infrared spectroscopy, gas chromatography, and mass spectrometry. The hydrobromide derivative of new sunflower oil was acrylated and polymerized to a new polymer.
γ‐ and δ‐tocopherols are more effective than α‐tocopherol on the autoxidation of a 10% rapeseed oil triacylglycerol‐in‐water emulsion with and without a radical initiator
Authors: Wagner Karl‐Heinz , Isnardy Bettina , Elmadfa Ibrahim 
Published: January 2004

AbstractThe antioxidative effects of γ‐ and mainly δ‐tocopherol in a multiphase system were hardly considered up to now. The aim of this study was i) to assess the effects and ii) to follow the degradation of α‐, γ‐ and δ‐tocopherol in concentrations of 0.01%, 0.05%, 0.1% and 0.25% during the oxidation of a 10% purified rapeseed oil triacylglycerol‐in‐water emulsion at 40 °C in the dark for 15 wk in a system containing a low oxygen concentration. Oxidation experiments were performed weekly by assessing the formation of hydroperoxides and hexanal, and the stability of the tocopherols was determined using high‐performance liquid chromatography. Storage tests were conducted with and without the addition of 0.01% α, α′‐azoisobutyronitrile (AIBN), which is a known radical initiator. α‐Tocopherol increased the formation of hydroperoxides in both tests as well as the generation of hexanal when the radical initiator was added; furthermore it was the least stable. γ‐Tocopherol delayed the formation of hexanal and prolonged the stability of the emulsion in a dose‐dependant manner. δ‐Tocopherol was the most stable and also the most effective in delaying lipid oxidation in the emulsions. Each concentration that was tested reduced the rate of hydroperoxide and especially hexanal formation. Hexanal was only formed to a slight extent after 15 wk of oxidation in the test with AIBN and the lowest dose of 0.01% δ‐tocopherol. For all tocopherols, strong correlations were found between tocopherol stability and the extent of oxidation. Results suggest that i) mainly δ‐tocopherol, but also γ‐tocopherol even less pronounced, are very good antioxidants in order to stabilize and prolong the shelf life of oil‐in‐water emulsions, ii) the antioxidative effects were intensified with increasing amounts.
Oxidative stability of black cumin (Nigella sativa L.), coriander (Coriandrum sativum L.) and niger (Guizotia abyssinica Cass.) crude seed oils upon stripping
Authors: Ramadan Mohamed Fawzy , Mörsel Jörg‐Thomas 
Published: January 2004

AbstractInformation on stability of edible oils is important for predicting the quality deterioration of the oil during storage and marketing. Stripping of crude oils removes most of non‐triacylglycerol components, including polar lipids and phenolics. Oxidative stability of black cumin (Nigella sativa L.), coriander (Coriandrum sativum L.) and niger (Guizotia abyssinica Cass.) crude and stripped seed oils was investigated and compared. The factors influencing the oxidative stability of different seed oils were also discussed. Oil samples were stored under accelerated oxidation conditions for 21 d. The progress of oxidation at 60 °C was followed by recording the ultraviolet absorptivity and measuring the formation of oxidative products (peroxide and p‐anisidine values). Inverse relationships were noted between peroxide values and oxidative stabilities and also between secondary oxidation products, measured by p‐anisidine value and stabilities at termination of the storage. Absorptivity at 232 nm and 270 nm increased gradually with the increase in time, due to the formation of conjugated dienes and polyenes. In general, oxidative stabilities of crude oils were stronger than their stripped counterparts and the order of oxidative stability was as follows: coriander > black cumin > niger seed. Levels of polar lipids in crude oils correlated with oxidative stability. Thus, the major factor that may contribute to the better oxidative stability of crude oils was the carry‐over of their polar lipids.
Synthesis of 2,2′‐Bipyridines: Versatile Building Blocks for Sexy Architectures and Functional Nanomaterials
Authors: Newkome George R. , Patri Anil K. , Holder Elisabeth , Schubert Ulrich S. 
Published: January 2004

AbstractThe latest synthetic strategies to prepare 2,2′‐bipyridine and its mono‐substituted, symmetrical and unsymmetrical 3,3′‐, 4,4′‐, 5,5′‐, and 6,6′‐disubstituted derivatives are critically discussed and evaluated. Different coupling procedures to achieve new symmetrical and unsymmetrical functionalized 2,2′‐bipyridines, such as Stille‐type, Negishi‐type, and Suzuki‐type cross‐coupling reactions are discussed in detail. Moreover, condensation procedures that allow further variations are presented. The application of functional group transformations for access to additional groups is examined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)