bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption of Ammonia from Aqueous Solution Using Zeolite-Attapulgite Nano-Pore Structure Ceramisite
Authors: Wang Zheng , Zhang Lin Sheng , Jing Zhao Qian
Published: April 2010

Zeolite-attapulgite nano-pore structure ceramisite was prepared using natural zeolite and attapulgite through compounding, granulation and calcination.After elementary characterization of this ceramisite by mercury porosimeter, batch tests were carried out to examine its removal mechanism of ammonia. The influences of pH, contact time, initial ammonia concentration and temperature on the ammonia removal were investigated. The optimum pH for adsorption of ammonia was found to be less than 7. The adsorption process followed pseudo-second order rate model. Adsorption isotherm studies showed that Freundlich model fitted the experimental data. The sorption of ammonia increased with the rise of temperature because adsorption process was endothermic. The zeolite-attapulgite composite nano- pore structure ceramisite shows very good promise for practical applicability of ammonia removal from aqueous solution.
Electrodeposition of Porous ZnO Electrodes in the Presence of Cetyltrimethylammonium Bromide
Authors: Yang Li Rong , Zhang Wen Li , Duan Man Zhen , Jin Zheng Guo
Published: April 2010

A new strategy involving the introduction of the common cationic surfactant cetyltrimethyl ammonium bromide (CTAB) for the cathodic electrodeposition of ZnO electrodes from Zn(NO3) solutions by cyclic voltammetry has been developed. Frizzily lamellar and porous ZnO films were obtained. The deposited films were characterized by X-ray diffraction (XRD) in the range of low-angle and wide-angle, X-ray photoelectron Spectroscopy (XPS), scanning electron microscopy (SEM), and UV-Vis transmittance spectroscopy. The role of the CTAB was also discussed. Under the optimal contents of CTAB, the XRD pattern shows that the as-synthesized ZnO is lamellar nanostructure and SEM image demonstrates that porous and frizzyly lamellar ZnO crystals are formed; XPS spectra of as-deposited film shows that the electrodeposition mainly consists of Zn and O and the Optical transmittance spectra of ZnO film indicates that optical transmittance is low and gradually decreases with the wavelength lessening in the visible light region. Mechanisms are proposed for the electrochemical deposition and the beneficial role of CTAB.
Preparation of Ni/YSZ Anode Material Using Gel-Tape Casting and Performance Analysis
Authors: Yi Zhong Zhou , Zhai Feng Rui , Li Ying , Liu Wei , Xie Zhi Peng
Published: April 2010

Ni/YSZ cermet is the most widely used anode material for solid oxide fuel cell. In this paper, the NiO/YSZ green body was prepared by gel-tape casting, using 15%wt. starch as pore-forming agent, in the mixed polyvinyl alcohol and acrylamide systems. Ni/YSZ anode material was obtained after sintered at 1450°C for 2h and reduced at 800°C in H2 atmosphere for 4h. The anode porosity, XRD, TGA and microstructures were measured. YSZ formed a continuous network structure and Ni particles were dispersed homogeneously in the YSZ network. It is suitable to fabrication of anode material for solid oxide fuel cell.
Effects of Sol Viscosity on Properties of BST Thin Films Prepared by Sol-Gel Method
Authors: Zhou Zong Hui , Liu Jing
Published: April 2010

A series of BST(Ba0.65Sr0.35TiO3) sol with different viscosity were prepared by using Ba(CH3COOH)2, Sr(CH3COOH)2 and Ti(OC4H9)4 as raw materials. The BST thin films were fabricated by sol-gel method and spin-coating process on Si(100) substrates. The effect of sol viscosity on crystallization, microstructure and dielectric properties of BST thin films were analyzed by using X-ray diffractometry, scanning electron microscopy and impedance phase analyzer. The results show that the BST films coated by sol with viscosity of 3.0cp and annealed at 750°C for 1h are basically non-crystalline. The crystallization degree increases with the increase of sol viscosity at the same annealing temperature. The ABO3 perovskite structure is formed when the sol viscosity increases to 3.5cp. With further increasing sol viscosity to 6.0cp, the crystal grains of the film grow well and range very compact, the surface become smooth, and the films have optimal dielectric properties.
Fracture Dynamics of a Mode III Moving Crack Impacted by Elastic Wave in Functionally Graded Materials
Authors: Li Xin Gang , Wang Zhen Qing , Lü Nian Chun
Published: April 2010

The dynamic stress field under the SH-waves at the moving crack tip of functionally graded materials is analyzed, and the influences of parameters such as graded parameter, crack velocity, the angle of the incidence and the number of the waves on dynamic stress intensity factor are also studied. Due to the same time factor of scattering wave and incident wave, the scattering model of the crack tip can be constructed by making use of the displacement function of harmonic load in the infinite plane. The dual integral equation of moving crack problem subjected to SH-waves is obtained through Fourier transform with the help of the exponent model of the shear modulus and density, then have some process on the even and odd term of the integral kernel. The displacement is expanded into series form using Jacobi Polynomial, and then the semi-analytic and numerical solutions of dynamic stress intensity factor are derived with Schmidt method.
Low Temperature Solid Oxide Fuel Cells with SDC-Carbonate Electrolytes
Authors: Di Jing , Chen Ming Ming , Wang Cheng Yang , Zheng Jia Ming , Zhu Bin
Published: April 2010

Composites consisting of Ce0.8Sm0.2O1.9 (SDC)-carbonate were developed as electrolytes for low temperature solid oxide fuel cells (LTSOFC). The SDC power was prepared by sol-gel method. The carbonates were binary eutectics of (Li/Na)2CO3, (Li/K)2CO3 and (K/Na)2CO3. Conductivity measurements showed that the conductivities were depended on the type of carbonates. Discontinuities were found in the Arrhenius plots for both SDC-(Li/Na)2CO3 and SDC-(Li/K)2CO3. For SDC-(Na/K)2CO3 composite electrolyte, the conductivity increased as temperature rose following one slope. Single cells based on various composites were fabricated by a uniaxial die-press method and tested at 450-600 oC. The results showed all cells exhibited improved performances upon that of pure SDC-based cell. The best power density of 532 mW cm-2 at 600 oC was achieved for LTSOFC using composite of SDC and (Li/Na)2CO3. Conductivity mechanism was also discussed.
An Improved Two-Phase Flow and Transport Model for the PEM Fuel Cell
Authors: Chen Shi Zhong , Wu Yu Hou , Sun Hong , Liu Hong Tan
Published: April 2010

A two-phase flow, multi-component model has been optimized for a PEM (Proton Exchange Membrane) Fuel Cell. The modeling domain consists of the membrane, two catalyst layers, two diffusion layers, and two channels. Both liquid and gas phases are considered in the entire cathode and anode, including the channel, the diffusion layer and the catalyst layer. The Gravity effect on liquid water was considered in channels. Typical two-phase flow distributions in the cathode gas channel, gas diffuser and catalyst layer are presented. Source term and porosity term were optimized. Based on the simulation results, it is found that two-phase flow characteristics in the cathode depend on the current density, operating temperature, and cathode and anode humidification temperatures. Water mass fraction for the fuel cell with anode upward is higher than that the case with cathode-upward. Liquid water with the case of cathode-upward blocks pores in the gas diffuser layer leading to increasing the concentration polarization. Gravity of liquid water exerts the effect on the water mass fraction in the cathode.
Oxygen Reduction Reaction of PEMFC Cathode by Molecular Simulations
Authors: Liu Chuang , Wu Yu Hou , Sun Hong , Tang Yu Lan
Published: April 2010

Cathode catalyst layer plays an important role in PEMFC. Electrochemical reaction in cathode catalyst layer is a control process for the performance in PEMFC. In this paper, oxygen reduction reaction (ORR) is studied by molecular simulations based on a series pathway which consist of four steps. We calculated the free energy of four steps respectively by molecular simulations. Comparing free energy of our steps, we found that the fourth step can release more energy than the other steps. At the same time, we found that the energy released in ORR is decreased with the increase of temperature. The process of the first step in the series pathway release less energy than that of other steps. The results are very helpful for optimization of construction in the cathode and improving performance of PEM fuel cell.
Conversion of Natural Gas to Hydrogen under Super Adiabatic Rich Combustion
Authors: Ma P.Y. , Tang Zhi Guo , Li Y.L. , Nie C.H. , He X.Z. , Lin Q.Z.
Published: April 2010

Interest in fuel cells in recent years has promoted the development of hydrogen sources. Methane (the main composition of natural gas) is an optimal fuel for hydrogen production due to its rich resource and its high ratio of hydrogen to carbon. In this work, several hydrogen processes, such as steam reforming of methane, partial oxidation, and auto thermal reforming, were reviewed. Different processes exhibit different importance for hydrogen production due to their diversity on usages. In this paper the special method of natural hydrogen production from natural gas with super adiabatic rich combustion is depicted in details. Some problems of this method were analyzed and discussed. In view of the existing problems, a new method was developed to be used for conversion of natural gas to hydrogen. The method can solve the problems of flame drift, heat preservation, product cooling, and low transform efficiency. Due to its simple and compact structure, it is attractive for distributing hydrogen production system and solving the transportation and storage problems of hydrogen.
Structure, Magnetic Properties and Defects Distribution of Mn0.5Zn0.5LaxFe2-xO4 Nanocrystals
Authors: Wang Li Qun
Published: April 2010

La-substitution Mn-Zn ferrite nanocrystals, Mn0.5Zn0.5LaxFe2-xO4 (x=0.00, 0.05, 0.10, 0.15, 0.20) were prepared by sol-gel process. X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and positron annihilation lifetime spectroscopy (PALS) studies were carried out. The result of XRD suggests that the mean grain size decreases from 63.8 nm to 44.6 nm with the increment of La-substitution concentration from x=0.00 to 0.20. The VSM measurement shows that the saturation magnetization (MS) increases in the range of x<0.10, then it drastically decreases in the range of 0.10<x<0.20. At last, defects property is discussed using PALS.
Optimal Selection of Several Substrates in Fermentative Biohydrogen Production Technology
Authors: Chen Ming Qi , Ma Tao , Ren Nan Qi
Published: April 2010

Substrates have critical effect on efficiency and cost of hydrogen production technology. Tradition evaluation index system which based on hydrogen production rate and conversion rate has limitation in comparing the economic value of different substrates utilized in hydrogen production system. This paper studies emergy of a fermentative biohydrogen production technology, comparing different biomass: wastewater and sewage sludge, the municipal solid waste and lignocellulosic biomass when they are used as substrates. Net emergy yield ratio, environmental loading ration and emergy-based sustainability index are measured. According to these indices, it shows an important role in reducing hydrogen production cost by developing cheap substrates. The results shows, the values of three indices were best when municipal wastewater was used as a substrate, it can reduce hydrogen production cost dramatically, obtain hydrogen and purify water simultaneously, benefit the environment protection.
Changes of Two Phase Composition in Phase Separation Process of Na2O-CaO-Al2O3-B2O3-SiO2-TiO2 System
Authors: Zhang Wen Li , Gao Shui Jing , Wang Jing Fu , Jin Jian Guo
Published: April 2010

The titaniferous blast furnace slag was selected as a kind of main raw material in the glass preparation. The glass system was separated phase into boron-rich phase and silicon-rich phase in Na2O-CaO-Al2O3-B2O3-SiO2-TiO2 system, and the changes of the two-phase composition after heat treated at different temperatures were studied. Results indicated that the network adjustment oxide existing in boron-rich phase was only CaO when phase separation temperature was below 750°C, and Na2O concentrated in silicon-rich phase. With the phase separation temperature rising, the distribution of Al2O3 and CaO was almost unchanged, whereas Na2O transferred from the silicon-rich phase to boron-rich phase gradually. In the phase separation process, TiO2 concentrated and crystallized on the phase separation interface.
Dynamic Mechanical Properties of CNTs/MoSi2 Composite Material
Authors: Zou Guang Ping , Chang Zhong Liang , Qiao Ying Jie
Published: April 2010

Carbon nanotubes (CNTs) are good reinforcement of composite materials, through add appropriate amount of carbon nanotubes to MoSi2 can be improve the strength and toughness of MoSi2. In this paper, the material of CNTs/MoSi2 was made through vacuum hot pressing technology. And the split hopkison press bar (SHPB) technology was used for testing the dynamic mechanical properties of CNTs/MoSi2 composite material which has different proportion of CNTs. In the SHPB experiment, in order to get better waveforms, the waveform shaping technology was used for improving the waveform quality, and also the strain gauge technology was used for testing the real strain of the specimen in the dynamic loading process. Through calculating, the dynamic stress-strain curves which under different high strain rate are given. At the same time, the strength, deformation and other test results are analyzed, and also compared them with the static compression experiment results of the CNTs/MoSi2 specimen which is tested by the electronic universal testing machine, and then obtained the dynamic performance of CNTs/MoSi2 composite material.
Crystallization Kinetics of Li+-Doped TiO2 Films Prepared by Sol-Gel Dip Coating
Authors: Zhou Feng , Fu Ying Qing , Liang Kai Ming
Published: April 2010

The crystallization behavior and microstructure of Li+-doped TiO2 thin films prepared by sol-gel dip coating were investigated by means of differential themal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization apparent activation energy (E) both in the absence and in the presence of Li+ ion was also measured with Kissinger method. As a result the E values of Li+-doped TiO2 thin film were decreased, thus the crystallization of non-crystalline to anatase and antase to rutile was promoted.
Experimental Study on Stainless Steel Slag Used in Ceramic Making
Authors: Zong Yan Bing , Li Yu , Cang Da Qiang
Published: April 2010

Composition of stainless steel slag was compared with that of ceramic paste first. DTA curves of ceramic samples were obtained to determine the firing temperature schedule. It is concluded that the stainless steel slag mixed with certain chemically pure materials can serve as raw material for the production of high added value ceramics. Pilot plant scale tests show that the principal crystal phase is diopside, contributing to the making of high strength and high density ceramics. Heating rate, cooling rate and holding time should be controlled appropriately during sintering process for the sake of forming and growth of crystals. The total performance detection of ceramic samples accords with national standards in China when stainless steel slag is used to sinter calcium-magnesium-silicon type ceramic in roller kiln. The proportion of stainless steel slag is 45% during pilot tracey. Dissolution rate of chromium during stainless steel slag used as mainly diopside type of building ceramic is only 25.17 mg/kg ceramic, which resolves the harmless of chromium. This work provides a feasible and effective way for resource of stainless steel slag.
Effect of Carbon as Foaming Agent on Pore Structure of Foam Glass
Authors: Lv Dong Sheng , Li Xiu Hua , Wang Lei , Du Juan Juan , Zhang Jie
Published: April 2010

Insulation effect and mechanical performance of foam glass depend, to a large extent, on foam structure. Hence understanding foam formation is not only a problem of significant fundamental interest but also of tremendous practical impact. In this paper, foam growth was modeled comparing to grain growth theory in sintering. TG-DTG analysis of carbon black indicated that pre-oxidation took place prior to foaming temperature. Furthermore effects of heating rate and particle size of carbon black on foam structure have been taken into account. Several borosilicate foam glasses were fabricated by powder sintering process at different heating rates using carbon black of different particle sizes as foaming agent, respectively. It was found that increasing the heating rate tended to decrease the pre-oxidation of carbon black resulting in inhomogeneous foam distribution. Foam structure of sample heated at a rate of 8°C/min using carbon black with particle size of 0.15mm was optimal.
Synthesis of Aluminum Oxynitride Powder by Carbothermal Reduction Method
Authors: Tian Ting Yan , Du Hong Bing , Sun Feng , Jiang Hua Wei
Published: April 2010

γ-aluminum oxynitride (γ-ALON) powder was prepared by carbothermal reduction method using γ-Al2O3 and activated carbon as raw materials. Effects of activated carbon content, synthesizing temperature, holding time and carbon impurity on ALON powder were studied. It was found a ‘two-step’ procedure, first sintering at about 1550°C-1650°C then at about 1750°C-1850°C, was effective to prepare high-purity ALON powder. The removal of carbon impurity was crucial for the preparation of ALON powder, which effectively improved the purity of ALON powder. The prepared powder was characterized by XRD and SEM, which indicated that pure ALON powder prepared by a ‘two-step’ procedure had well-developed crystalline and homogenous granularity. Transparent ALON ceramics were prepared by hot-press sintering at 1850~1900°C for up to 2~4h using ALON powder and some sintering additive, the transmission of sample with thickness of 1mm was 81% at infrared wave.
Preparation of the Barium Strontium Titanate/Magnesium Oxide Plates by Non-Aqueous Gel-Casting
Authors: Jiao Chun Rong , Chen Da Ming , Tong Jian Feng
Published: April 2010

Barium strontium titanate/magnesium oxide composite ceramic plates were prepared by non-aqueous gel-casting using barium strontium titanate and MgO as the raw materials. The rheological properties of the non-aqueous slurries, the dosages of the catalyst and initiator, micro structures and phase structures of the sintering ceramic plates were investigated and analyzed. The results showed that the slurry with solid content of 50wt% in non-aqueous gel-casting had excellent rheological properties and operating characteristics. Ba0.6Sr0.4TiO3/MgO plates with a smooth surface and dense structure were fabricated through desiccation and sintering at 1300°C, and the relative density is up to 4.14g/cm3. The polished surface of the ceramic substrate was composed of 35% MgO and 65% Ba0.6Sr0.4TiO3, and the content of Ba0.6Sr0.4TiO3 was obviously higher compared to the content in the raw materials which was explained by the phenomena of surface phase enrichment.
Using Monte Carlo Simulation to Improve Ceramic R&D Investment Decisions
Authors: He Bao Cheng , Jiang Hong Tao , Yao Shu Zhi , He Bao Yuan
Published: April 2010

The success of ceramic companies is highly dependent on research and development (R&D). Thus, a pivotal aim of management is to allocate resources to the best scientific and financial R&D projects. But the valuation of ceramic R&D is a difficult task for managers. The conventional discounted cash flow (DCF) methods fail to consider the value of managerial flexibility provided by R&D projects. Real options Analysis (ROA) offers a superior way of capturing the value of flexibility. It enables decision-maker to value projects more accurately by incorporating managerial flexibilities into the valuation model. However, ROA can’t effectively deal with the volatility of parameters in itself under high uncertain circumstance. In view of the limitation of ROA, this paper uses Monte Carlo simulation to solve the parameters volatility problems. In the end, the case study proves that Monte Carlo simulation can improve R&D investment decisions, especially for highly unpredictable ceramic R&D projects.
Synthesis of Cordierite with Low Thermal Expansion Coefficient
Authors: Zhu Kai , Yang Dao Yuan , Wu Juan , Zhang Rui
Published: April 2010

Cordierite is an excellent material with good thermal shock resistance and used at high temperature for its low thermal expansion coefficient. Cordierite ceramics were prepared by using talc, alumina and kaolin clay as starting materials. The thermal expansion coefficient, phase composition and microstructure were studied and the results showed that: in order to get samples with low thermal expansion coefficient, the optimum chemical composition was a little rich in Al2O3 compared with the theoretical composition, the optimum sintering temperature was 1350°C, and adding 10% starch as pore-forming agent could effectively decreased the thermal expansion coefficient of the samples even to 0.8×10-6/°C. The samples contained majority of cordierite phase, with trace mullite and glass, the acicular cordierite crystals in samples developed very well and there were 10% starch powder used as pore-forming agent in formula. All these were the reasons to decrease the thermal expansion coefficient of cordierite material.
Preparation of Bulk Ti2AlC Using Ti3AlC2 Powders as a Starting Material
Authors: Chen Xin Hua , Zhai Hong Xiang , Li Shi Bo , Zhou Yang , Huang Zhen Ying
Published: April 2010

Highly pure and dense bulk Ti2AlC was prepared by hot-pressing a mixture of the “312” phase Ti3AlC2 powders, and the element Ti and Al powders. Different ratios of the starting materials and different sintering temperature were attempted in order to obtain a highly pure and dense bulk Ti2AlC sample. Phase analysis and microstructures observing were performed by using by XRD, SEM as well as an X-ray fluorescence spectrometer. The results show that a nearly full dense bulk Ti2AlC sample can be prepared at 1300°C and 30MPa for 30 minutes in argon atmosphere. A dominant mechanism to form the “211” phase Ti2AlC can be attributed to the directly connecting between Al and Ti6C octahedron, which is as an intermediate phase in the Al-rich liquid mediator during the hot pressing.
Phase Analysis of Forsterite in Carbothermal Reduction Processing
Authors: Xin Ou Yang , Huang Sai Fang , Fang Ming Hao , Huang Zhao Hui , Liu Yan Gai
Published: April 2010

In this paper, phase transition of forsterite in carbothermal reduction processing was studied. Phase composition and microstructure of the products were characterized by XRD, SEM and XRF. The influences of calcination temperature (1400, 1500, and 1600 °C), carbon content (lacking 50% and 10%, theoretical content, exceeding 10%, 50% and 100%) and holding time (1 h, 2 h and 4 h) on phase composition of carbothermal reduction products were discussed. The results showed that forsterite can be reduced to β-SiC, Fe and MgAl2O4 when it was reacted with carbon exceeded 50wt% of theoretical content at 1600°C for 4 h, while it was stable when treated below 1500°C.
Mechanical Properties of Aerogel-Ceramic Fiber Composites
Authors: Gao Qing Fu , Feng Jian , Zhang Chang Rui , Feng Jun Zong , Wu Wei , Jiang Yong Gang
Published: April 2010

Aerogel composites were prepared by immersing ceramic fiber into silica aerogel precursor via supercritical fluid drying. The mechanical behavior of silica aerogel composites was investigated with shrinkage, tension, bending and compression. The influences of fiber volume fraction, aerogel density and heat treatment were examined. After reinforced by ceramic fiber, the shrinkage of aerogel and aerogel-fiber composites was retarded obviously. The mechanical property of aerogel-fiber composites increased first and then decreased with increasing fiber volume fraction from 5.8% to 11.5%. For a given fiber volume fraction, the mechanical strength enhanced with increasing aerogel density. In addition, the mechanical property of aerogel composites did not decrease but increased after heat treatment at 600°C.
Treatment of Urban Waste Water Sludges by Means of his Appraisement for Incorporation in Ceramic Matrix
Authors: Martínez-García Carmen , Palomino Cotes Teresa , Corpas-Iglesias Francisco  A. , García Gázquez Fco. , Navarro Navarro José Luís
Published: April 2010

Industrial residues generated by the modern society constitute an environmental problem and are harmful both to the health and to the environment (greenhouse effect). In addition, they can give place to leaching pollutants [1,2] more concretely in the European area; it tends to the politics of them 3R, recovery, recycling and reutilization. It is, in this frame, where the present work is included. On the other hand, like result of environmental regulations, bricks of clay are going to be demanded by an increase in the insulating capacity. A way of increasing the insulating capacity of the bricks is to generate porosity in the counterfoil of clay.
Low Environmental Impact Machining Processes of Composite Materials Applied to the Aerospace Sector
Authors: Álvarez Miguel , Batista Moisés , Salguero Jorge , Sánchez-Carrilero Manuel , Marcos Bárcena Mariano
Published: April 2010

In the last decades, technologically innovative processes performed in advanced materials such as Carbon Fibre (CF) and Metal Matrix Composites (MMC) have continuously increased because of these materials find increasingly applications in the most of the industrial sectors, particularly in aeronautical industry. This is caused by their excellent relationship weight/mechanical properties.
Although there is a high trend to apply and develop non-conventional technologies and methods for machining CF and MMC, other common machining processes are commonly applied for working these materials. Thus, in aeronautical industry, mechanical drilling processes are usually applied for preparing the manufactured elements to be assembled. However, drilling of CF based materials can carry on troubles related to a loss of surface finishing quality and/or quick and high tool wear.
This work reports on the results about an evaluation process of the surface quality of drilled CF samples as a function of the cutting conditions and the tool materials.
Environmental Remediation and the Legacy of Uranium Mining Waste in Portugal and Europe. Lessons to Retain
Authors: Carvalho Fernando P.
Published: April 2010

Radioactive ore mining for the production of radium and uranium in Portugal did span over most of the 20th century and ceased in 2001. It was performed mostly before the development of environmental legislation and radiation protection standards. Environmental remediation of the mining and milling sites is currently underway. Rehabilitated and non-rehabilitated sites require also radioactivity monitoring whose costs are covered by the State. The likely re start of uranium mining, in Portugal as well as elsewhere in Europe, reminds that uranium mining shall be managed under the mine “life cycle approach” in order to include decommissioning and environmental rehabilitation costs in the ore pricing.
Sand Mining Pool Eutrophication (Vale do Paraíba, São Paulo, Brazil): Preliminary Assessment
Authors: de Aquino-Silva Maria Regina , Leone P.R.C. , de Brito Bastos Eduardo Jorge
Published: April 2010

The sand exploration results in ponds, which are formed by groundwater. The supply of nutrients (especially nitrogen and phosphorus) in these environments leads to greater growth of aquatic plants – eutrophication, which can cause interference to the different uses of these ponds. This study aimed to identify the main causes of eutrophication of these environments and propose a management plan to ensure its future use and maintenance of water quality. The experiment was carried out between the cities of São José dos Campos and Jacarei (SP-Brazil) (S 23° 12" 54' e W 45° 57" 47'). The topographic map indicates the flow of water during the rainy season and the places with the greatest possibility of drag of nutrients through laminar erosion. The analysis of water showed the variation in levels of nitrogen (increase) and phosphorus (decrease). This variation occurred in the area of higher elevation to lower elevation. The climatological water balance indicated overland flow and water holding in the soil concentrated in the months of January, February, March and April. The results indicate that the water stored in soil, and environment's topography may influence on the process of eutrophication of the sand mining pool
Free Cooling with Phase Change Materials (PCM)
Authors: Domínguez M* , García C. , Arias J.M.
Published: April 2010

Phase change materials (PCM) are described along with some of their advantages in air conditioning installations, particularly with regard to taking advantage of the free cooling that can be obtained from the ambient air, by using either sensible heat or evaporation. Certain installations are described and the paper concludes by stating that PCMs in microcapsules will facilitate the use of free cooling.
Composites in the Design Optimization of Biconvex Refractive Solar Concentrators. Study and Calculation of Prototypes
Authors: Pérez Calero José Ignacio , Pérez Rendón Cristina Alba
Published: April 2010

The present work tries to study the important role which they carry out the Composites, in the complex process of the design of solar refractive concentrators, that would be unthinkable and unrealizable without their employment, when having necessary the technical characteristics that they make them viable. It contributes, also, the methodologies followed for the accomplishment of optimal prototypes, by means of Numeric Methods of simulation (Finite Elements), experimental on models and of characterization of composite laminates.
SOM-SEM-EDS Identification of Tool Wear Mechanisms in the Dry-Machining of Aerospace Titanium Alloys
Authors: Álvarez Miguel , Gómez Alvaro , Salguero J. , Batista Moisés , Huerta Milagros M. , Marcos Bárcena Mariano
Published: April 2010

Titanium based alloys, mainly UNS R56400 (Ti6Al4V), are increasingly being applied in the airship building industry due to its excellent physicochemical properties. Machining operations are usually required in the manufacturing processes of Ti based aerospace structural elements. However, high reactivity of Ti provokes a quick tool wear. So, in order to reach an economically acceptable production level, it is necessary to minimize the costs associated to tool wear. In this work, Scanning Electron Microscopy (SEM), Stereoscopic Optical Microscopy (SOM) and Energy Dispersive Spectroscopy (EDS) have been used for both analysing and identifying secondary adhesion mechanisms that are taking place when an aeronautical titanium alloy is machined. Special severe cutting conditions have been applied. Thus, titanium alloy have been dry machined with TiN coated WC-Co tools. Results obtained have shown that tool wear is controlled by a secondary adhesion mechanism, which presents two stages. A first stage is constituted by a TiOx multi-film formed onto the tool surfaces. A second step involves the mechanical adhesion of the alloy material to those surfaces. When this material is removed, tool particles are dragged off causing tool wear.
Leds, toward the Best Energy Efficiency in Lighting
Authors: Portela José M. , Pastor Andrés , Huerta Milagros M. , Otero Manuel , González Rafael E.
Published: April 2010

Climate change and increasing energy prices threaten the planet and the economy. The European Union has promised to take the lead, through a reduction in greenhouse gases by 20 to 30% and a 20% energy savings by 2020. In this context, the EU is about to ban some of the most inefficient lightbulbs for everyday. Lighting would set the limit at the level of CFLs/LEDs (most energy efficient existing lamps). The energy savings would be maximized, the target is 86 TWh of electricity saved per year in the EU by 2020. To discover how to use different materials in this technology is a high-priority as it shows the advance; maybe this is the future of lighting.
Structural Modifications of Multiwalled Carbon Nanotubes by Swift Heavy Ions Irradiation
Authors: Dharamvir Keya , Jeet Kiran , Du Chun Sheng , Pan Ning , Jindal V.K.
Published: April 2010

Thin film samples of multi-walled carbon nanotubes (MWCNTs) were irradiated with 120 MeV gold ions. Transmission electron microscopy (TEM) images of the pristine and irradiated samples were obtained. TEM pictures show that in the irradiated sample, the CNTs are in general shorter and some have their inner cores filled, unlike in the pristine sample. We also find from these images that average inner and outer tube diameters change as a result of ion irradiation. The films were also characterized using Raman spectrometry. Modifications of the disorder mode (D mode) and the tangential mode (G mode) under different irradiation fluences were studied in detail. As fluence increases, the MWCNTs first show damage, then healing under somewhat higher fluences and again amorphization under still higher fluence of ion irradiation.
Nano Grained Structure in KOBO Extruded Bulk Products
Authors: Bochniak Włodzimierz , Błaż Ludwik , Korbel Andrzej
Published: April 2010

There are several known severe plastic deformation (SPD) methods, which allow receiving nano-grained structure of materials. One of the methods is called the KOBO method (the name is composed of the first two letters of the surnames of the inventors: KOrbel and BOchniak). The method was used for extrusion of copper alloys at room temperature to manufacture thin-wall tubes. During the KOBO extrusion, reversible cyclic torsion of the material results in multiple changing the deformation path. Hence, a heavy localized plastic flow leads to shear bands development that reduces the total strain hardening effect and results in effective structure refinement. In particular, thin-wall tubes produced from single-phase copper alloys, intensively cooled close to the die outlet, had homogeneous structure consisting of fine grains/subgrains of a few hundreds nanometers in size. The final structure of the material is practically independent on the initial structure of processed billets. If the accelerated cooling of extruded material was omitted, grain coarsening to the size of dozens of micrometers was observed. In multi-phase copper alloys, the grain refinement was limited to about 1 μm, both for intensively cooled and air-cooled products.
Preliminary Study of DLC Coatings Aiming to the Corrosion Protection of Ferrous Materials
Authors: Vourlias G. , Pistofidis N. , Chaliampalias D. , Patsalas Panos , Polychroniadis Efstathios K.
Published: April 2010

Zinc hot-dip galvanizing is one of the most effective methods for the corrosion protection of ferrous substrates. However, the failure of zinc coatings is possible when exposed to harsh environments for rather long periods. The application of a thin diamond like carbon (DLC) film on the top of the zinc coating might be a promising method for promoting their corrosion resistance. In the present work, a DLC thin film was deposited on zinc galvanized coatings by Plasma Enhanced Chemical Vapor Deposition. The as-formed film was composed of nanostructured and amorphous areas. The electron diffraction patterns acquired from the nanograins correspond to carbon phases with d-spacing ranging from diamond to graphite. Additionally, after 18 days of exposure in a simulated marine atmosphere, the DLC coated samples were proven to be more resistant than the naked galvanized coatings indicating its potential to improve the corrosion resistance of galvanized ferrous materials.
Microwave Absorption and Magnetic Studies of Strontium Hexaferrites Nanoparticles Synthesized by Modified Flux Method
Authors: Tyagi Sachin , Agarwala Ramesh Chandra , Agarwala Vijaya
Published: April 2010

M-type strontium hexaferrite nanocrystals of radar absorbing material (NRAM) i.e. SrFe12O19 were synthesized by modified flux method that combine the controlled chemical co-precipitation process for nucleation and complete uniform growth during annealing with NaCl flux. Uniform structural morphological transformation of nanocrystals from needle to hexagonal prism faces were noticed after annealing with increasing of heat treatment (HT) temperature from 800 to 1200°C for 4h. X-ray diffraction (XRD) results show the formation of various phases with increase in annealing temperature. The crystallinity and crystallite size are found to increase with increase in heat treatment temperature (15-40nm). The superparamagnetic behavior of strontium hexaferrite is confirmed by vibrating sample magnetometer (VSM) wherein it was noticed that magnetic field (10000 gauss max) did not have any effect on these materials. The transformation of magnetic properties i.e. from superparamagnetic to ferromagnetic behaviour after heating at various HT temperatures have been revealed by hysteresis loops under VSM study. The increase in saturation magnetization from 2.44 to 75.03 emu/gm is observed. Formation of ultrafine particles has been confirmed through field emission scanning electron microscope (FESEM). About 5 to10% of the needle like crystals in the ‘as synthesized’ condition were transformed to hexagonal pyramidal structure and most of the crystals are found to have plate like hexagonal structures with increase in heat treatment temperatures. The effect of such systematic morphological transformation of nanocrystals was observed in reflection loss properties in X band (8-12 GHz). The maximum reflection loss of -20.05, -24.31, -24.16, -25.22, -25.12, -24.01 dB at 8.1, 8.6, 9.2, 9.6, 10.7, and 12 GHz respectively are observed for the material heat treated at 1200°C. A significant increment from - 6.5 to -25.22 dB at 9.6 GHz in reflection loss (RL) is noticed due to symmetric morphological growth of RAM nanocrystal during annealing.
Structural, Magnetic and Dynamic Mechanical Analysis of Magnetic Nanocomposite Foils by Polymer Ultrasonic Welding
Authors: Christophidou Anna , Viskadourakis Zacharias , Doumanidis Charalabos
Published: April 2010

The main goal of the work presented in this paper is to develop and characterize a manufacturing process that introduces a novel technology for manufacturing magnetic polyvinylchloride (PVC) nanocomposites, from stacked PVC foils, with intermediate sandwiched layers of uniformly dispersed ferro magnetic nanoparticles, by means of solid-state surface ultrasonic welding. Laboratory analysis of nanocomposite samples to investigate their behavior, is performed by microscopic, magnetic, and mechanical testing. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are employed for measuring nanoparticle dispersions and their distribution in the polymer matrix. The magnetic properties of the composites are measured by a physical property measurement system (PPMS), while mechanical behavior is studied by dynamic mechanical analyzer (DMA) and a universal mechanical testing system. The resulting materials are nanocomposite foils with very high ferromagnetic behavior.
Heavy Ion Irradiation Effects on Cadmium Oxide (CdO) Quantum Dots Prepared by Quenching Method
Authors: Virk Hardev Singh , Sharma Poonam
Published: April 2010

Cadmium oxide (CdO) quantum dots were synthesized in the laboratory by quenching method using CdO powder sintered at 9000C and ethyl alcohol kept at ice cold temperature. X-ray diffraction investigations reveal the NaCl cubic structure of CdO quantum dots. Addition of ethylenediamine to a portion of reaction mixture containing quantum dots results in the conversion of nanoparticles to nanorods. Heavy ion irradiation using 90 MeV Carbon (C+6) ion beam accelerated at 15 UD Pelletron, with fluence varying from 1011 to 1013 ions/cm2 , produced enlargement in the size of quantum dots revealed by TEM investigations. Heavy ion irradiation effects need to be investigated further, in view of industrial applications of quantum dots.
Critical Size for Edge Dislocation Free Free-Standing Nanocrystals by Finite Element Method
Authors: Khanikar Prasenjit , Subramaniam Anandh
Published: April 2010

As the size of a free-standing crystal approaches a few tens of nanometers, the image force experienced by a dislocation can exceed the Peierls force. This will lead to dislocations leaving the nanocrystal without the application of an external stress and thus making it dislocation free. In this investigation a finite element methodology is developed for the calculation of the critical size at which a free-standing crystal becomes edge dislocation free. A simple edge dislocation is simulated using Finite Element Method (FEM) by feeding-in the appropriate stress-free strain in an idealized domains corresponding to the introduction of an extra half-plane of atoms. The image force experienced by the edge dislocation is calculated as the gradient of the plot of the energy of the system as a function of the position of the simulated dislocation. In nanocrystals, due to the proximity of multiple surfaces, the net image force due to multiple images has to be calculated. Additionally, surface or/and domain deformations have to be taken into account in nanocrystals; which can drastically alter the image force. For the crystal to become dislocation free, the minimum image force experienced by the dislocation, has to exceed the Peierls force. Minimum image force values calculated from the FEM models are compared with the Peierls stress values obtained from literature to determine the critical domain size at which crystal becomes edge dislocation free.
Malaria: Knowledge and prevention practices among school adolescents in a coastal community in Calabar, Nigeria
Authors: Udonwa Ndifreke E. , Gyuse Abraham N. , Etokidem Aniekan J.
Published: April 2010

Background: Malaria prevention and treatment constitute an unbearable economic burden to most African countries, especially south of the Sahara, where about 500 million cases occur annually. The problem of malaria among adolescents has largely been overshadowed by the huge burden of the disease among young children. Attention to malaria among adolescents has also been diverted by the huge burden of HIV/AIDS among adolescents. Some surveys reveal a lack of knowledge and many misconceptions about the transmission and treatment of malaria, which could adversely affect malaria control measures and antimalarial therapy. Such a knowledge gap could have an adverse effect on school children, who could be used as change agents and as role models for their siblings and peers in the malaria control strategy.Objectives: To determine the malaria prevention practices of school adolescents in the coastal community of Calabar, Nigeria.Method: This was a cross-sectional survey involving secondary schools in southern Calabar. Four hundred adolescents were randomly selected from the 4565 learners in 5 out of 17 secondary schools in southern Calabar, Cross River State, Nigeria. A self-administered, semi-structured questionnaire was administered to the respondents.Results: Most respondents (77.5%) were aware that the vector transmits the malaria parasite through biting. Fewer respondents would prevent malaria attacks by clearing the vegetation in the peri-domestic environment (13.5%), filling up potholes (16.9%), opening up drainage (11%), using insecticide-treated nets (25.7%) or using antimalarial drugs (11.2%). Less than one-tenth (8%) would use various other methods such as not accepting unscreened blood, while only 11% obtained the information from their teachers.Conclusion: The study identified knowledge gaps among school children. There is a need to empower teachers with information about the cause of malaria and prevention strategies.
Net in situ growth rates of phytoplankton in an oligotrophic, tropical shelf ecosystem
Authors: Furnas Miles J.
Published: April 2010

In situ growth rates of phytoplankton in tropical shelf waters of the Great Barrier Reef were measured with diffusion chambers. A broad disparity was observed between the growth responses of diatom species or assemblages (µmax = 2–5 doublings d−1) and assemblages of microflagellates, nonmotile ultraplankton, or phototrophic picoplankton (µmax < 2 doublings d−1). Several diatom species or groups consistently grew faster than the community Chl doubling rate (µmax = 1.6 doublings d−1). Most dominant species and groups, regardless of taxonomic affiliation, exhibited the potential for high relative growth rates (µ/µmax > 0.5) at ambient concentrations of dissolved inorganic N <0.2 µmol liter−1 and the time‐averaged diurnal irradiances in situ >50 µEinst m−2 s−1. If relative constancy in phytoplankton standing crop and composition is to be maintained, grazing rates must vary widely at the species level, but be broadly similar to growth rates over time scales of days. Although the full 40–80‐m water column in the central Great Barrier Reef lies the euphotic zone, phytoplankton growth rates near the bottom seem to be light limited.
Pigment‐specific rates of phytoplankton growth and microzooplankton grazing in the open subarctic Pacific Ocean
Authors: Strom Suzanne L. , Welschmeyer Nicholas A.
Published: April 2010

A long‐standing hypothesis states that low year‐round phytoplankton biomass in the open subarctic Pacific Ocean is maintained by herbivorous grazing. To evaluate the balance between phytoplankton growth and microzooplankton grazing, we carried out seawater dilution experiments at two subarctic Pacific locations in June and September 1987. Pigment‐specific phytoplankton growth and grazing rates were obtained from dilution experiments by HPLC separation of phytoplankton pigments. This approach allowed us to look at the relationship between growth and grazing rates for different phytoplankton taxa. A wide range of rates was observed during any given experiment. Pigment‐specific growth rates ranged from 0.0 to 0.8 d−1; pigment‐specific microzooplankton grazing rates ranged from 0.0 to 0.6 d−1. The highest growth rates appeared attributable to large diatoms, as indicated by both pigment and cell‐count data. Grazing rates were most closely matched with growth rates for small (<10 µm) phytoplankton species; large diatom species seemed to be unaffected by microzooplankton grazing. Higher grazing rates were measured on pigments with the lowest standing stocks.
Diel periodicity in growth and sinking rates of the centric diatom Coscinodiscus concinnus
Authors: Granata Timothy C.
Published: April 2010

Growth and sinking rates varied over a 61.4‐h period for semicontinuous cultures of the marine diatom Coscinodiscus concinnus grown at light intensities of 48 and 9 µEinst m−2 s−1 on a 12L : 12D cycle. The time‐course of sinking rates showed cyclic fluctuations, with sinking rates generally decreasing during the dark part of the light: dark cycle and increasing in the light period. For most of the experiment, sinking rates varied in phase with growth rates. Changes in cell size during growth did not account for the variation in the observed sinking rates. The periodicity in sinking rate was probably the result of internal density changes in the cells rather than of changes in cell volume or area.