Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or cove...Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or covering of reinforcement with a plastic bag, a polymer resin is either injected or infused under vacuum through the fiber bed. The engineering fabrics commonly used in LCM possess generally dual scale architecture in terms of porosity: microscopic pores exist between the filaments in the fiber tows, while macroscopic pores appear between the tows as a result of the stitching/weaving fabrication process. On a microscopic scale, capillary flows in fiber tows play a major role on the quality of composites made by resin injection through fibrous reinforcements. In order to better understand the mechanisms that govern the impregnation of fibrous reinforcements in LCM, a study of wicking behavior is carried out in fiber tows. The experimental approach is based on capillary rise experiments, which are less expensive and time-consuming than other more standard characterization techniques often used in porous media. In addition, it allows gathering representative data on the wicking properties of fiber tows as a function of their morphological characteristics such as micro-porosity, total cross-section area, specific surface area, filament diameter and packing configuration. The morphological properties of the fiber tows will also be characterized by other standard experimental methods in order to compare with the results obtained by capillary rise experiments. These standard methods include gravimetry for the micro-porosity and fiber mass density, microscopic analysis to measure the filament diameter, cross-section area and packing configuration of the filaments and capillary flow porometry to evaluate the equivalent pore diameter. The capillary rise method has already been used not only in Soil Mechanics, but also to characterize engineering textiles used in high performance composites. Such experiments are not easy to perform, because of technical difficulties such as textile geometrical alteration during testing, changes in fluid properties due to solvent evaporation and inaccurate observation of the progression of the capillary front (fading). To circumvent these problems, a monitoring technique based on fluorescent dye penetration inspection (DPI) and CCD image acquisition is proposed in this investigation. Visual monitoring of the capillary front is coupled with real-time fluid mass acquisition using a high resolution balance. Experimental observations on the height of the capillary front and the fluid mass absorbed by the fiber tows can be analyzed by four imbibition models. These models consider the evolution of the capillary height with (model I) or without gravity (model II) and of the fluid mass absorbed by capillary effect with (model III) or without gravity (model IV). The models without gravity will be used on short imbibition distances to derive the microscopic properties of fiber tows from the experimentally observed evolutions of the capillary height and the fluid mass absorbed by capillarity. After describing the new capillary rise setup devised for the fiber tow experiments, a set of experiments is carried out to characterize the properties of the fiber tows and investigate the wicking phenomena along the warp and weft directions. The consistency of this approach is compared with more standard methods. At the same time, the impact of fiber sizing on the tow wicking behavior is investigated. Note that experimental evaluations of tow permeability can also be derived from this approach. The results compare well with permeability predictions based on Blake-Kozeny-Carman models. In the future, it will be possible to apply the same experimental approach to engineering fabrics. Indeed, a comprehensive wicking characterization of fibrous reinforcements is expected to provide useful information in order to evaluate the optimal processing conditions of high performance composites fabricated by Liquid Composite Molding.展开更多
Between all precursors of copper complex, bis-(acetylacetonato)-copper (II) and bis-oxalate copper (II) with very close structures are two of the best representatives for copper nanoparticles synthesis. In this resear...Between all precursors of copper complex, bis-(acetylacetonato)-copper (II) and bis-oxalate copper (II) with very close structures are two of the best representatives for copper nanoparticles synthesis. In this research, only bis-(acetylacetonato)-copper (II) in presence of some effective non-ionic surfactants such as Triton X-100, Dodecylamine, Tween 80 and also triphenylphosphine as a reducing agent via thermal decomposition process was used for copper nanopaticles synthesis. Two shif-base E19 and E22 complexes were also used for the investigation of these kinds of shif-base complexes capabilities by this method as precursors and all results were compared with each other. Between all surfactants, Triton X-100 gave the best yield with the largest grains. The techniques used for characterization of copper nanoparticles were TEM, EDX, FT-IR and XRD. TG-DTA and CV were used for characterization of bis-(acetylacetonato)-copper (II) complex.展开更多
The acidity and stability constants of M(Gly)1, M(Ttr)1, and M(Trp)1 M: Cu2+, Cu(Bpy2)2+, and Cu(Phen3)2+ complexes, were determined by potentiometric pH titration. It is shown that the stability of the binary Cu(L), ...The acidity and stability constants of M(Gly)1, M(Ttr)1, and M(Trp)1 M: Cu2+, Cu(Bpy2)2+, and Cu(Phen3)2+ complexes, were determined by potentiometric pH titration. It is shown that the stability of the binary Cu(L), (L: Gly, Ttr, and Trp) complex is determined by the basicity of the carboxylate group on one side and amino group on the other side. It is demonstrated that the equilibrium, Cu(Ha4)2+ + Cu(L) Cu(Har)(L) + Cu2+, is displacement due to the well known experience that mixed ligand complexes formed by a divalent 3d ion, a heteroaromatic N base and an O donor ligand possess increased stability. The stability constants of the 1:1 complexes formed between Cu2+, Cu(Bpy)2+ or Cu(Phen)2+ and L2-, were determined by potentiometric pH titration in aqueous solution (I = 0.1 M, NaNO3, 25?C). The order of the stability constants was reported. A comparative investigation between ternary complexes of Trp, Ttr, and Gly is made. The comparison of stability constants of these ternary complexes show that Cu(Har)(Trp) is found near 100% in closed form but Cu(Har)(Gly) exists in open form. The differences between the above mentioned stability constants are based on stacked form of Cu(Har)(Trp). The last provides increased stability.展开更多
Ab initio calculations of the band structure, total and partial densities of states and the spatial distribution of the electron charge density of crystalline Na2GeS3 are performed in the framework of density function...Ab initio calculations of the band structure, total and partial densities of states and the spatial distribution of the electron charge density of crystalline Na2GeS3 are performed in the framework of density functional theory in the local density approximation for an exchange-correlation potential. According to the calculation results, sodium thiogermanate is a direct-gap crystal with the top of the valence band and the bottom of the conduction band at the point of the Brillouin zone. The calculated band gap is Eg= 2.51 eV. The nature of the components of the electronic states in different subbands of the valence band is determined. The calculated total density of states in the valence band of the crystal is compared with the known experimental X-ray photoelectron spectrum of Na2GeS3 glass. Based on the maps of the electron density distribution, the nature of the chemical bonds and high mobility of Na+ ions in Na2GeS3 crystal is analyzed.展开更多
The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementiti...The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.展开更多
MAGNETO-OPTICAL current transformers (MOCT) based on the Faraday Effect provide numerous advantages over the conventional transformers. However the commonly used materials in MOCT are crystals that are very expensive ...MAGNETO-OPTICAL current transformers (MOCT) based on the Faraday Effect provide numerous advantages over the conventional transformers. However the commonly used materials in MOCT are crystals that are very expensive and temperature dependence thus will cause many problems for the output signal. Cost efficient diamagnetic PbO-Bi2O3-B2O3 (PBB) glass system is fabricated in this study, for the aim of obtaining a good candidate glass with high verdet constant and good temperature resistance to replace crystals. A home-made optical bench was setup, calibrated and used for measuring the verdet constant of the fabricated glasses. Glass with composition of 50%PbO-40%Bi2O3-10%B2O3 in mol showed high Verdet constant (0.1533 min/Gauss.cm) and good value of the figure of merit (0.02635 min/Gauss), which can be considered as the ideal candidate for MOCT applications.展开更多
Several mixed ligand Cu(II), Zn(II) complexes using (benzylidenethiourea) (obtained by the condensation of benzaldehyde and thiourea) as the primary ligand and (acetamide or thioacetamide) as an additional ligand were...Several mixed ligand Cu(II), Zn(II) complexes using (benzylidenethiourea) (obtained by the condensation of benzaldehyde and thiourea) as the primary ligand and (acetamide or thioacetamide) as an additional ligand were synthesized and characterized analytically and spectroscopically, magnetic susceptibility and molar conductance measurements ,as well as by UV-Vis. and IR spectroscopy. The interaction of the complexes with calf thymus (CT)DNA was studied using absorption spectra, while the concentration of DNA in gel electrophoresis remained constant at 10 μl. They exhibit absorption hypochromicity increased during the binding of the complexes to calf thymus DNA. The complexes show enhanced antimicrobial activities complexes with the free ligand. A theoretical treatment of the formation of complexes in the gas phase was studied, this was done using the HYPERCHEM-6 program for the Molecular mechanics and Semi-empirical calculations.展开更多
Photovoltaic tracking sensor monitoring the position of the sun in the sky was developed on the basis of GeS:Sb layered crystals. The operating principle of this sensor is based on the phenomenon of photovoltaic effec...Photovoltaic tracking sensor monitoring the position of the sun in the sky was developed on the basis of GeS:Sb layered crystals. The operating principle of this sensor is based on the phenomenon of photovoltaic effect in GeS:Sb crystals;the magnitude and sign of generated photo-emf depend on the position of the light probe relative to the ohmic contacts, deposited on (001) surface of the crystal.展开更多
The removal of aniline blue dye from aqueous solutions using the A-site doped perovskite Ce1-xBixCrO3 (x = 0, 0.5, 1) was investigated. The perovskite oxides were synthesised using Sol-Gel method and characterised by ...The removal of aniline blue dye from aqueous solutions using the A-site doped perovskite Ce1-xBixCrO3 (x = 0, 0.5, 1) was investigated. The perovskite oxides were synthesised using Sol-Gel method and characterised by conventional powder X-ray diffraction technique. The X-ray diffraction measurements suggested that doping with Bismuth Ion influences both the crystal structure and the particle size of the oxides, and consequently affects the adsorption properties. It was found that both CeCrO3 and Ce0.5Bi0.5CrO3 compounds are orthorhombic and have approximate particle size of 87 and 36 nm respectively, whereas BiCrO3 oxide has rhombohedral space group symmetry and the particle sizes are less than 49 nm. The batch mode study demonstrated that the removal capacities of Aniline Blue at 150 min and pH = 4.3 for Ce0.5Bi0.5CrO3, CeCrO3 and BiCrO3 are 779.67, 705.45 and 440.18 mg/g respectively. The results reflect the influence of the A site doping on the adsorption properties of the oxides. The removal of Aniline Blue was found to be negatively correlated with temperature and pH.展开更多
This paper has presented results of calculations of optical functions for e||c and e^c polarizations in 0 - 12 eV energy interval, band structure and effective masses of electrons and holes of ternary compound InGaTe2...This paper has presented results of calculations of optical functions for e||c and e^c polarizations in 0 - 12 eV energy interval, band structure and effective masses of electrons and holes of ternary compound InGaTe2. Genesis of valence band was investigated by using group-theoretical analyses. The main features of spectra of optical functions, the parameters of transition and their theoretical nature were found out. Identified interband transitions are responsible for the main peaks in the optical functions. Calculated results are in good agreement with the known experimental data.展开更多
A series of glasses were prepared by rapid melt quench method in the glass system (65-x)[(Ba0.6Sr0.4)TiO3]-30[2SiO2-B2O3]-5[K2O]-x[La2O3] (x = 0, 1, 2, 5 and 10). X-ray diffraction of glass samples were carried to che...A series of glasses were prepared by rapid melt quench method in the glass system (65-x)[(Ba0.6Sr0.4)TiO3]-30[2SiO2-B2O3]-5[K2O]-x[La2O3] (x = 0, 1, 2, 5 and 10). X-ray diffraction of glass samples were carried to check its amorphousity. Density of glass samples were measured using Archimedes principle. The refractive index of these glass samples lies between 2.39 to 2.80. Optical properties of these glass samples were studied using Infrared (IR) and Raman spectroscopic techniques. IR measurements were done over a continous spectral range 450 - 4000 cm-1 to study their stucture networking systematically while Raman spectra were recorded over a continous spectral range 200 - 2000 cm-1.IR spectra of all glass samples showed number of absorption peaks. These absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B-O of trigonal BO3. The Raman spectra of all glass samples exhibited different spectral bands and intensity of these bands changes drastically. The network structure of these glass samples is mainly based on BO3 and BO4 units placed in different structural groups.展开更多
Mineral trioxide aggregate (MTA) cement is an attractive material in endodontic dentistry. The purpose of this study was to produce calcium silicate, which is a major component of MTA, from waste materials. A dental a...Mineral trioxide aggregate (MTA) cement is an attractive material in endodontic dentistry. The purpose of this study was to produce calcium silicate, which is a major component of MTA, from waste materials. A dental alginate impression gel and used chalks were selected and mixed in a suitable ratio (Code: EXP). As a control, CaCO3 and a commercial diatomite were used (Code: CON). Each powder was heated to 850。C and 1000。C, and then kneaded with water. TG-DTA, compressive tests, SEM observations, elemental mapping analyses, and XRD analyses were performed. TG-DTA indicated that weight reduction of CaCO3 started at 600。C, and it completely decomposed on heating at 850。C. The strength was affected by the temperature. After heating, CaCO3 was transformed into CaO and/or Ca2SiO4, and Ca(OH)2 was formed by mixing with water. There were no differences between EXP and CON. These data suggested that recycled wastes might be promising MTA sources.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 1,4-naphthoquinone deriv...<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 1,4-naphthoquinone derivatives ligands and their metal—Co(II), Ni(II) and Cu(II) chelates. Continuing our work with another derivatives of 1,4-naphthoquinone ligands, this work had been constructed for synthesis of new ligands derived from 1,4-naphthoquinone such as 3-thioacetyl-2-amino-1,4-naphthoquinone and 2-benzoyl-3-amino-1,4-naphthoquinone (L<span style="white-space:nowrap;"><sup>1</sup></span>-L<span style="white-space:nowrap;"><sup>2</sup></span>) which characterized on the basis of elemental analysis, electronic, IR, mass, <span style="white-space:nowrap;"><sup>1</sup></span>H-NMR spectral data. The synthesized ligands have been carried out to achieve the coordination behavior towards bi-valent metal ions like cobalt, nickel and copper. The solid chelates of the different ligands were prepared and subjected to analytical techniques such as elemental analyses, spectroscopic techniques including mass, <span style="white-space:nowrap;"><sup>1</sup></span>H-NMR, and IR spectroscopy, and thermal analyses techniques. The chelates were found to have octahedral geometry. The biological activity of the prepared ligands and their binary metals complexes were also screened against different antifungal and antibacterial organisms.</span> </div>展开更多
The aim of this work was to investigate by X-ray photoelectron spectroscopy the effect of high pressure on the chemical environments of Si 2p, O 1s and Li 1s in lithium disilicate glass ceramic with stoichiometric com...The aim of this work was to investigate by X-ray photoelectron spectroscopy the effect of high pressure on the chemical environments of Si 2p, O 1s and Li 1s in lithium disilicate glass ceramic with stoichiometric composition Li2O·2SiO2 (LS2). A group of samples was processed at 2.5 GPa, 4 GPa and 7.7 GPa at room temperature and a second group was crystallized under high pressure and high temperature. Large shifts of the binding energy toward higher energies were observed in the X-ray photoelectron spectroscopy spectra for samples of the first group after densification at 2.5 and 4 GPa. For samples processed at 7.7 Gpa, the major component of the binding energy for the Si 2p environment remained practically unchanged compared to the pristine sample but new components, with smaller intensities, appeared in the spectra, indicating the existence of distinct Q-species induced by high pressure. This behavior may be related to changes in the number of bridged and non-bridged oxygen atoms in the glass structure. The results for the second group of samples, crystallized under high pressure, showed evidences of three binding energies for the O atoms, one of them related to non-bridged and two of them to bridged O atoms.展开更多
<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 2-acetyl and 2-formyl-3-...<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 2-acetyl and 2-formyl-3-amino-1,4-naphthoquinone (L<span style="white-space:nowrap;"><sup>1</sup></span> - L<span style="white-space:nowrap;"><sup>2</sup></span>) and their metal-Co(II), Ni(II) and Cu(II) chelates. The newly chelates were characterized by elemental analysis, IR, mass and <span style="white-space:nowrap;"><sup>1</sup></span>HNMR spectra, thermogravimetric analysis (TGA) and biological activity. The antibacterial and antifungal activities of the ligands and its metal complexes were screened against bacterial species (<span style="white-space:nowrap;"><i>Staphylococcus aureus, Bacillus subtilis and Escherichia coli</i></span>) and fungi (<span style="white-space:nowrap;"><i>Candida albicans</i></span>). Ampicillin and amphotericin were used as references for antibacterial and antifungal studies. The activity data show that the metal complexes have a promising biological activity comparable with parent free ligand against bacterial and fungal species.</span> </div>展开更多
The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements ...The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements are carried out with an alternating current at a frequency of 1 kHz using the measuring bridge E-20. Measurements are carried out at temperature range 300 - 450 K, irradiated at doses of 50, 100 and 150 kGy. It is revealed that in all irradiated samples with increasing volumetric filler content increase the dielectric characteristics of composites PE + x vol%. TlGaSe2. Temperature variation of the dielectric parameters, after gamma irradiation are the result of occurring in the electron-ion and polarization at the interface of the matrix polymer with filler of TlGaSe2.展开更多
We report the growth of silver nanowires with varying diameters in porous anodic aluminum-oxide (AAO) membranes by using the electroless deposition approach. This objective is carried out in 2 phases. In Phase 1, AAO ...We report the growth of silver nanowires with varying diameters in porous anodic aluminum-oxide (AAO) membranes by using the electroless deposition approach. This objective is carried out in 2 phases. In Phase 1, AAO membranes on high purity aluminum foils are electrochemically grown by a double anodization procedure. Three different electrolytes, sulphuric acid (H2SO4), oxalic acid (H2C2O4) and phosphoric acid (H3PO4), are employed to produce membranes with varying pore diameters. Other parameters such as interpore distance, barrier layer thickness and membrane thickness are also explored. In addition, characterization to modify the pore diameter and open the barrier layer of free standing AAO templates has been carried out. In Phase 2, metallic silver nanowires are grown by electroless deposition inside pores with varying diameters in AAO membranes. AAO membranes immersed in aqueous silver nitrate solutions are thermally reduced, and the resulting silver nanowires are characterized by using a scanning electron microscope (SEM).展开更多
The nano-infiltration and transient eutectic-phase (NITE) method is one of the most attractive methods for fabrication of SiC and SiC/SiC composites. In the NITE method, preform densification is essential option for d...The nano-infiltration and transient eutectic-phase (NITE) method is one of the most attractive methods for fabrication of SiC and SiC/SiC composites. In the NITE method, preform densification is essential option for damage less near-net shaping technique. However, optimization of preform densification is insufficient yet. The objective of this study is to evaluate the effects of pressure during preform densification on SiC/SiC composites. The preform before preform densification has many pores in the inter-prepreg sheets. These pores were disappeared by preform densification. As the effects of pressure on preform, densification in the intra-fiber-bundle was improved due to increasing pressure. Flexural strength of the preforms with 1 MPa and 17 MPa indicated almost same value. The result suggested that increasing of pressure did not cause any change in fiber properties. In the effects of pressure on the composites, the composites with 17 MPa was exhibited improvement in bulk density and mechanical property, compared with that with 1 MPa.展开更多
The rod-shaped form of crystalline β-FeOOH (akaganeite) was prepared by the template-free hydrothermal method with urea as the homogeneous precipitant. X-ray diffraction, field-emission scanning electron microscope a...The rod-shaped form of crystalline β-FeOOH (akaganeite) was prepared by the template-free hydrothermal method with urea as the homogeneous precipitant. X-ray diffraction, field-emission scanning electron microscope and Fourier transform infrared spectrum were used to characterize the resulting products. The degradation of methyl orange (MO) was studied using the prepared nanostructure materials in a photo-Fenton-like process. MO degradation was effectively achieved by hydroxyl radicals that were generated in the heterogeneous catalysis process. Specific surface area of the prepared β-FeOOH was an important factor affecting the efficiency of MO degradation, which depended on the synthesis conditions such as the reaction temperature, the initial concentration of urea and FeCl3.6H2O as well as the n(urea)/n(Fe3+) ratio. The photodegradation efficiencies slightly decreased with the increase of initial pH in the range of 4.5 - 9.5, which indicated the prepared β-FeOOH catalyst can well overcome the drawback of a narrow pH range of homogeneous Fenton reaction. β-FeOOH catalysts loading and H2O2 concentration also play important effect on the degradation efficiency of MO. The prepared β-FeOOH showed good ability of reuse for multiple trials.展开更多
This paper presents the results of studying the frequency dependence of permittivity and dielectric loss of fishbone (Fb) Kutum and polyethylene composites filled with nanoparticles fishbone Kutum and the influence of...This paper presents the results of studying the frequency dependence of permittivity and dielectric loss of fishbone (Fb) Kutum and polyethylene composites filled with nanoparticles fishbone Kutum and the influence of aluminum(Al) nanoparticles with dimensions 80-nm on the dielectric properties of polymer composites. Studies were carried out at the frequency range of 0 - 1 MHz. It was found that the variation of the volume of filler content of fishbone and aluminum nanoparticles might be prepared composite materials with the required dielectric parameters.展开更多
基金the National Science and Engineering Research Council of Canada(NSERC)the Canada Research Chair(CRC)for their financial support.
文摘Liquid Composite Molding (LCM) is an increasingly used class of processes to manufacture high performance composites. In LCM, the fibrous reinforcement is first laid in a mold cavity. After closure of the mold or covering of reinforcement with a plastic bag, a polymer resin is either injected or infused under vacuum through the fiber bed. The engineering fabrics commonly used in LCM possess generally dual scale architecture in terms of porosity: microscopic pores exist between the filaments in the fiber tows, while macroscopic pores appear between the tows as a result of the stitching/weaving fabrication process. On a microscopic scale, capillary flows in fiber tows play a major role on the quality of composites made by resin injection through fibrous reinforcements. In order to better understand the mechanisms that govern the impregnation of fibrous reinforcements in LCM, a study of wicking behavior is carried out in fiber tows. The experimental approach is based on capillary rise experiments, which are less expensive and time-consuming than other more standard characterization techniques often used in porous media. In addition, it allows gathering representative data on the wicking properties of fiber tows as a function of their morphological characteristics such as micro-porosity, total cross-section area, specific surface area, filament diameter and packing configuration. The morphological properties of the fiber tows will also be characterized by other standard experimental methods in order to compare with the results obtained by capillary rise experiments. These standard methods include gravimetry for the micro-porosity and fiber mass density, microscopic analysis to measure the filament diameter, cross-section area and packing configuration of the filaments and capillary flow porometry to evaluate the equivalent pore diameter. The capillary rise method has already been used not only in Soil Mechanics, but also to characterize engineering textiles used in high performance composites. Such experiments are not easy to perform, because of technical difficulties such as textile geometrical alteration during testing, changes in fluid properties due to solvent evaporation and inaccurate observation of the progression of the capillary front (fading). To circumvent these problems, a monitoring technique based on fluorescent dye penetration inspection (DPI) and CCD image acquisition is proposed in this investigation. Visual monitoring of the capillary front is coupled with real-time fluid mass acquisition using a high resolution balance. Experimental observations on the height of the capillary front and the fluid mass absorbed by the fiber tows can be analyzed by four imbibition models. These models consider the evolution of the capillary height with (model I) or without gravity (model II) and of the fluid mass absorbed by capillary effect with (model III) or without gravity (model IV). The models without gravity will be used on short imbibition distances to derive the microscopic properties of fiber tows from the experimentally observed evolutions of the capillary height and the fluid mass absorbed by capillarity. After describing the new capillary rise setup devised for the fiber tow experiments, a set of experiments is carried out to characterize the properties of the fiber tows and investigate the wicking phenomena along the warp and weft directions. The consistency of this approach is compared with more standard methods. At the same time, the impact of fiber sizing on the tow wicking behavior is investigated. Note that experimental evaluations of tow permeability can also be derived from this approach. The results compare well with permeability predictions based on Blake-Kozeny-Carman models. In the future, it will be possible to apply the same experimental approach to engineering fabrics. Indeed, a comprehensive wicking characterization of fibrous reinforcements is expected to provide useful information in order to evaluate the optimal processing conditions of high performance composites fabricated by Liquid Composite Molding.
文摘Between all precursors of copper complex, bis-(acetylacetonato)-copper (II) and bis-oxalate copper (II) with very close structures are two of the best representatives for copper nanoparticles synthesis. In this research, only bis-(acetylacetonato)-copper (II) in presence of some effective non-ionic surfactants such as Triton X-100, Dodecylamine, Tween 80 and also triphenylphosphine as a reducing agent via thermal decomposition process was used for copper nanopaticles synthesis. Two shif-base E19 and E22 complexes were also used for the investigation of these kinds of shif-base complexes capabilities by this method as precursors and all results were compared with each other. Between all surfactants, Triton X-100 gave the best yield with the largest grains. The techniques used for characterization of copper nanoparticles were TEM, EDX, FT-IR and XRD. TG-DTA and CV were used for characterization of bis-(acetylacetonato)-copper (II) complex.
文摘The acidity and stability constants of M(Gly)1, M(Ttr)1, and M(Trp)1 M: Cu2+, Cu(Bpy2)2+, and Cu(Phen3)2+ complexes, were determined by potentiometric pH titration. It is shown that the stability of the binary Cu(L), (L: Gly, Ttr, and Trp) complex is determined by the basicity of the carboxylate group on one side and amino group on the other side. It is demonstrated that the equilibrium, Cu(Ha4)2+ + Cu(L) Cu(Har)(L) + Cu2+, is displacement due to the well known experience that mixed ligand complexes formed by a divalent 3d ion, a heteroaromatic N base and an O donor ligand possess increased stability. The stability constants of the 1:1 complexes formed between Cu2+, Cu(Bpy)2+ or Cu(Phen)2+ and L2-, were determined by potentiometric pH titration in aqueous solution (I = 0.1 M, NaNO3, 25?C). The order of the stability constants was reported. A comparative investigation between ternary complexes of Trp, Ttr, and Gly is made. The comparison of stability constants of these ternary complexes show that Cu(Har)(Trp) is found near 100% in closed form but Cu(Har)(Gly) exists in open form. The differences between the above mentioned stability constants are based on stacked form of Cu(Har)(Trp). The last provides increased stability.
文摘Ab initio calculations of the band structure, total and partial densities of states and the spatial distribution of the electron charge density of crystalline Na2GeS3 are performed in the framework of density functional theory in the local density approximation for an exchange-correlation potential. According to the calculation results, sodium thiogermanate is a direct-gap crystal with the top of the valence band and the bottom of the conduction band at the point of the Brillouin zone. The calculated band gap is Eg= 2.51 eV. The nature of the components of the electronic states in different subbands of the valence band is determined. The calculated total density of states in the valence band of the crystal is compared with the known experimental X-ray photoelectron spectrum of Na2GeS3 glass. Based on the maps of the electron density distribution, the nature of the chemical bonds and high mobility of Na+ ions in Na2GeS3 crystal is analyzed.
文摘The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.
文摘MAGNETO-OPTICAL current transformers (MOCT) based on the Faraday Effect provide numerous advantages over the conventional transformers. However the commonly used materials in MOCT are crystals that are very expensive and temperature dependence thus will cause many problems for the output signal. Cost efficient diamagnetic PbO-Bi2O3-B2O3 (PBB) glass system is fabricated in this study, for the aim of obtaining a good candidate glass with high verdet constant and good temperature resistance to replace crystals. A home-made optical bench was setup, calibrated and used for measuring the verdet constant of the fabricated glasses. Glass with composition of 50%PbO-40%Bi2O3-10%B2O3 in mol showed high Verdet constant (0.1533 min/Gauss.cm) and good value of the figure of merit (0.02635 min/Gauss), which can be considered as the ideal candidate for MOCT applications.
文摘Several mixed ligand Cu(II), Zn(II) complexes using (benzylidenethiourea) (obtained by the condensation of benzaldehyde and thiourea) as the primary ligand and (acetamide or thioacetamide) as an additional ligand were synthesized and characterized analytically and spectroscopically, magnetic susceptibility and molar conductance measurements ,as well as by UV-Vis. and IR spectroscopy. The interaction of the complexes with calf thymus (CT)DNA was studied using absorption spectra, while the concentration of DNA in gel electrophoresis remained constant at 10 μl. They exhibit absorption hypochromicity increased during the binding of the complexes to calf thymus DNA. The complexes show enhanced antimicrobial activities complexes with the free ligand. A theoretical treatment of the formation of complexes in the gas phase was studied, this was done using the HYPERCHEM-6 program for the Molecular mechanics and Semi-empirical calculations.
文摘Photovoltaic tracking sensor monitoring the position of the sun in the sky was developed on the basis of GeS:Sb layered crystals. The operating principle of this sensor is based on the phenomenon of photovoltaic effect in GeS:Sb crystals;the magnitude and sign of generated photo-emf depend on the position of the light probe relative to the ohmic contacts, deposited on (001) surface of the crystal.
文摘The removal of aniline blue dye from aqueous solutions using the A-site doped perovskite Ce1-xBixCrO3 (x = 0, 0.5, 1) was investigated. The perovskite oxides were synthesised using Sol-Gel method and characterised by conventional powder X-ray diffraction technique. The X-ray diffraction measurements suggested that doping with Bismuth Ion influences both the crystal structure and the particle size of the oxides, and consequently affects the adsorption properties. It was found that both CeCrO3 and Ce0.5Bi0.5CrO3 compounds are orthorhombic and have approximate particle size of 87 and 36 nm respectively, whereas BiCrO3 oxide has rhombohedral space group symmetry and the particle sizes are less than 49 nm. The batch mode study demonstrated that the removal capacities of Aniline Blue at 150 min and pH = 4.3 for Ce0.5Bi0.5CrO3, CeCrO3 and BiCrO3 are 779.67, 705.45 and 440.18 mg/g respectively. The results reflect the influence of the A site doping on the adsorption properties of the oxides. The removal of Aniline Blue was found to be negatively correlated with temperature and pH.
文摘This paper has presented results of calculations of optical functions for e||c and e^c polarizations in 0 - 12 eV energy interval, band structure and effective masses of electrons and holes of ternary compound InGaTe2. Genesis of valence band was investigated by using group-theoretical analyses. The main features of spectra of optical functions, the parameters of transition and their theoretical nature were found out. Identified interband transitions are responsible for the main peaks in the optical functions. Calculated results are in good agreement with the known experimental data.
文摘A series of glasses were prepared by rapid melt quench method in the glass system (65-x)[(Ba0.6Sr0.4)TiO3]-30[2SiO2-B2O3]-5[K2O]-x[La2O3] (x = 0, 1, 2, 5 and 10). X-ray diffraction of glass samples were carried to check its amorphousity. Density of glass samples were measured using Archimedes principle. The refractive index of these glass samples lies between 2.39 to 2.80. Optical properties of these glass samples were studied using Infrared (IR) and Raman spectroscopic techniques. IR measurements were done over a continous spectral range 450 - 4000 cm-1 to study their stucture networking systematically while Raman spectra were recorded over a continous spectral range 200 - 2000 cm-1.IR spectra of all glass samples showed number of absorption peaks. These absorption peaks occurs due to asymetric vibrational streching of borate by relaxation of the bond B-O of trigonal BO3. The Raman spectra of all glass samples exhibited different spectral bands and intensity of these bands changes drastically. The network structure of these glass samples is mainly based on BO3 and BO4 units placed in different structural groups.
文摘Mineral trioxide aggregate (MTA) cement is an attractive material in endodontic dentistry. The purpose of this study was to produce calcium silicate, which is a major component of MTA, from waste materials. A dental alginate impression gel and used chalks were selected and mixed in a suitable ratio (Code: EXP). As a control, CaCO3 and a commercial diatomite were used (Code: CON). Each powder was heated to 850。C and 1000。C, and then kneaded with water. TG-DTA, compressive tests, SEM observations, elemental mapping analyses, and XRD analyses were performed. TG-DTA indicated that weight reduction of CaCO3 started at 600。C, and it completely decomposed on heating at 850。C. The strength was affected by the temperature. After heating, CaCO3 was transformed into CaO and/or Ca2SiO4, and Ca(OH)2 was formed by mixing with water. There were no differences between EXP and CON. These data suggested that recycled wastes might be promising MTA sources.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 1,4-naphthoquinone derivatives ligands and their metal—Co(II), Ni(II) and Cu(II) chelates. Continuing our work with another derivatives of 1,4-naphthoquinone ligands, this work had been constructed for synthesis of new ligands derived from 1,4-naphthoquinone such as 3-thioacetyl-2-amino-1,4-naphthoquinone and 2-benzoyl-3-amino-1,4-naphthoquinone (L<span style="white-space:nowrap;"><sup>1</sup></span>-L<span style="white-space:nowrap;"><sup>2</sup></span>) which characterized on the basis of elemental analysis, electronic, IR, mass, <span style="white-space:nowrap;"><sup>1</sup></span>H-NMR spectral data. The synthesized ligands have been carried out to achieve the coordination behavior towards bi-valent metal ions like cobalt, nickel and copper. The solid chelates of the different ligands were prepared and subjected to analytical techniques such as elemental analyses, spectroscopic techniques including mass, <span style="white-space:nowrap;"><sup>1</sup></span>H-NMR, and IR spectroscopy, and thermal analyses techniques. The chelates were found to have octahedral geometry. The biological activity of the prepared ligands and their binary metals complexes were also screened against different antifungal and antibacterial organisms.</span> </div>
文摘The aim of this work was to investigate by X-ray photoelectron spectroscopy the effect of high pressure on the chemical environments of Si 2p, O 1s and Li 1s in lithium disilicate glass ceramic with stoichiometric composition Li2O·2SiO2 (LS2). A group of samples was processed at 2.5 GPa, 4 GPa and 7.7 GPa at room temperature and a second group was crystallized under high pressure and high temperature. Large shifts of the binding energy toward higher energies were observed in the X-ray photoelectron spectroscopy spectra for samples of the first group after densification at 2.5 and 4 GPa. For samples processed at 7.7 Gpa, the major component of the binding energy for the Si 2p environment remained practically unchanged compared to the pristine sample but new components, with smaller intensities, appeared in the spectra, indicating the existence of distinct Q-species induced by high pressure. This behavior may be related to changes in the number of bridged and non-bridged oxygen atoms in the glass structure. The results for the second group of samples, crystallized under high pressure, showed evidences of three binding energies for the O atoms, one of them related to non-bridged and two of them to bridged O atoms.
文摘<div style="text-align:justify;"> <span style="font-family:Verdana;">The aim of this work is to synthesize, characterize and evaluate the biological activity of 2-acetyl and 2-formyl-3-amino-1,4-naphthoquinone (L<span style="white-space:nowrap;"><sup>1</sup></span> - L<span style="white-space:nowrap;"><sup>2</sup></span>) and their metal-Co(II), Ni(II) and Cu(II) chelates. The newly chelates were characterized by elemental analysis, IR, mass and <span style="white-space:nowrap;"><sup>1</sup></span>HNMR spectra, thermogravimetric analysis (TGA) and biological activity. The antibacterial and antifungal activities of the ligands and its metal complexes were screened against bacterial species (<span style="white-space:nowrap;"><i>Staphylococcus aureus, Bacillus subtilis and Escherichia coli</i></span>) and fungi (<span style="white-space:nowrap;"><i>Candida albicans</i></span>). Ampicillin and amphotericin were used as references for antibacterial and antifungal studies. The activity data show that the metal complexes have a promising biological activity comparable with parent free ligand against bacterial and fungal species.</span> </div>
文摘The purpose of the paper is to study the effect of gamma irradiation on the temperature dependence of the dielectric constant and dielectric loss (tanδ) of composite materials PE + x vol% (0≤ x ≤ 10). Measurements are carried out with an alternating current at a frequency of 1 kHz using the measuring bridge E-20. Measurements are carried out at temperature range 300 - 450 K, irradiated at doses of 50, 100 and 150 kGy. It is revealed that in all irradiated samples with increasing volumetric filler content increase the dielectric characteristics of composites PE + x vol%. TlGaSe2. Temperature variation of the dielectric parameters, after gamma irradiation are the result of occurring in the electron-ion and polarization at the interface of the matrix polymer with filler of TlGaSe2.
文摘We report the growth of silver nanowires with varying diameters in porous anodic aluminum-oxide (AAO) membranes by using the electroless deposition approach. This objective is carried out in 2 phases. In Phase 1, AAO membranes on high purity aluminum foils are electrochemically grown by a double anodization procedure. Three different electrolytes, sulphuric acid (H2SO4), oxalic acid (H2C2O4) and phosphoric acid (H3PO4), are employed to produce membranes with varying pore diameters. Other parameters such as interpore distance, barrier layer thickness and membrane thickness are also explored. In addition, characterization to modify the pore diameter and open the barrier layer of free standing AAO templates has been carried out. In Phase 2, metallic silver nanowires are grown by electroless deposition inside pores with varying diameters in AAO membranes. AAO membranes immersed in aqueous silver nitrate solutions are thermally reduced, and the resulting silver nanowires are characterized by using a scanning electron microscope (SEM).
文摘The nano-infiltration and transient eutectic-phase (NITE) method is one of the most attractive methods for fabrication of SiC and SiC/SiC composites. In the NITE method, preform densification is essential option for damage less near-net shaping technique. However, optimization of preform densification is insufficient yet. The objective of this study is to evaluate the effects of pressure during preform densification on SiC/SiC composites. The preform before preform densification has many pores in the inter-prepreg sheets. These pores were disappeared by preform densification. As the effects of pressure on preform, densification in the intra-fiber-bundle was improved due to increasing pressure. Flexural strength of the preforms with 1 MPa and 17 MPa indicated almost same value. The result suggested that increasing of pressure did not cause any change in fiber properties. In the effects of pressure on the composites, the composites with 17 MPa was exhibited improvement in bulk density and mechanical property, compared with that with 1 MPa.
文摘The rod-shaped form of crystalline β-FeOOH (akaganeite) was prepared by the template-free hydrothermal method with urea as the homogeneous precipitant. X-ray diffraction, field-emission scanning electron microscope and Fourier transform infrared spectrum were used to characterize the resulting products. The degradation of methyl orange (MO) was studied using the prepared nanostructure materials in a photo-Fenton-like process. MO degradation was effectively achieved by hydroxyl radicals that were generated in the heterogeneous catalysis process. Specific surface area of the prepared β-FeOOH was an important factor affecting the efficiency of MO degradation, which depended on the synthesis conditions such as the reaction temperature, the initial concentration of urea and FeCl3.6H2O as well as the n(urea)/n(Fe3+) ratio. The photodegradation efficiencies slightly decreased with the increase of initial pH in the range of 4.5 - 9.5, which indicated the prepared β-FeOOH catalyst can well overcome the drawback of a narrow pH range of homogeneous Fenton reaction. β-FeOOH catalysts loading and H2O2 concentration also play important effect on the degradation efficiency of MO. The prepared β-FeOOH showed good ability of reuse for multiple trials.
文摘This paper presents the results of studying the frequency dependence of permittivity and dielectric loss of fishbone (Fb) Kutum and polyethylene composites filled with nanoparticles fishbone Kutum and the influence of aluminum(Al) nanoparticles with dimensions 80-nm on the dielectric properties of polymer composites. Studies were carried out at the frequency range of 0 - 1 MHz. It was found that the variation of the volume of filler content of fishbone and aluminum nanoparticles might be prepared composite materials with the required dielectric parameters.
