Journal of Materials
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Open Access journal
ISSN (Print) 2314-4866 - ISSN (Online) 2314-4874
Published by Hindawi [333 journals]
- Utilizing Fullerenols as Surfactant for Carbon Nanotubes Dispersions
Abstract: Dispersions of individual carbon nanotubes (CNTs) are crucial for nanodevices and polymer/CNTs nanocomposites. In this paper, stable and homogenous dispersions of individual multiwalled carbon nanotubes (MWCNTs) have been synthesized. The factors influencing the dispersibility mechanism, including the surfactant concentration and the pH value, have been investigated. SEM images display the impurities sticking on MWCNTs which have been removed. The oxygen-containing groups on the surface of MWCNTs sample have been detected through FT-IR and Raman spectra. All experimental results illustrate that using fullerenols as surfactant can greatly improve the dispersibility of MWCNTs. Moreover, the prepared dispersions exhibit good stability that the sediment percentage of fullerenols-MWCNTs is only 5.2% after 5 days.
PubDate: Thu, 23 Feb 2017 00:00:00 +000
- Preparation, Characterization, and Cationic Functionalization of
Cellulose-Based Aerogels for Wastewater Clarification
Abstract: Aerogels are a series of materials with porous structure and light weight which can be applied to many industrial divisions as insulators, sensors, absorbents, and cushions. In this study, cellulose-based aerogels (aerocelluloses) were prepared from cellulosic material (microcrystalline cellulose) in sodium hydroxide/water solvent system followed by supercritical drying operation. The average specific surface area of aerocelluloses was 124 m2/g. The nitrogen gas (N2) adsorption/desorption isotherms revealed type H1 hysteresis loops for aerocelluloses, suggesting that aerocelluloses may possess a porous structure with cylindrically shaped pores open on both ends. FTIR and XRD analyses showed that the crystallinity of aerocelluloses was significantly decreased as compared to microcrystalline cellulose and that aerocelluloses exhibited a crystalline structure of cellulose II as compared to microcrystalline cellulose (cellulose I). To perform cationic functionalization, a cationic agent, (3-chloro-2-hydroxypropyl) trimethylammonium chloride, was used to introduce positively charged sites on aerocelluloses. The cationized aerocelluloses exhibited a strong ability to remove anionic dyes from wastewater. Highly porous and low cost aerocelluloses prepared in this study would be also promising as a fast absorbent for environmental pollutants.
PubDate: Tue, 20 Dec 2016 08:15:47 +000
- Superplastic Grade Titanium Alloy: Comparative Evaluation of Mechanical
Properties, Microstructure, and Fracture Behavior
Abstract: In this investigation, static fracture, microstructure, and the mechanical behavior of SP-700 alloy (a superplastic grade) were evaluated and compared with two other titanium alloys. The comparisons were made in terms of suitably designed heat treatment cycles. The heat treatment cycles included annealing and a combination of solutionizing and aging treatments for all three alloys. Tensile properties were determined using MTS Landmark Servohydraulic Test System. Tensile tested samples’ fracture surfaces were investigated with LEO-VP SEM instrument. Ti-15-3-3-3 alloy exhibited relatively a higher combination of strength and ductility in comparison to the other two alloys. All three types of titanium alloys demonstrated a very good level of tensile strength and ductility suitable for applications in military and biomedical fields.
PubDate: Mon, 05 Dec 2016 08:02:45 +000
- Synthesis and Characteristics of Valeric Acid-Zinc Layered Hydroxide
Intercalation Material for Insect Pheromone Controlled Release Formulation
Abstract: A new intercalation compound of insect pheromone, valeric acid (VA), based on zinc layered hydroxide (ZLH) as host release material, was successfully prepared through coprecipitation method. The as-produced organic-inorganic nanolayered material, valerate nanohybrid, VAN, shows the formation of a new peak at lower 2θ angle with basal spacing of 19.8 Å with no ZnO reflections, which indicate that the intercalation of anion between the inorganic ZLH interlamellae was accomplished. The elemental, FTIR, and ATR analyses of the nanohybrid supported the fact that the intercalation with the percentage anion loading was calculated to be 23.0% (w/w). The thermal stability property of the resulting nanohybrid was enhanced compared to the unbound anion. Field emission scanning electron micrograph of the ZnO has a nonuniform granular structure but transforms into flake-like structure with various sizes after the intercalation process. Release kinetics of anion from the interlayer of intercalated compound exhibited a slow release behavior governed by the pseudo-second-order kinetic model at different pHs of aqueous media. The valerate anion was released from VAN with the highest release rate at pH 4. These findings provide the basis to further development of controlled release formulation for insect pheromone based on ZLH intercalation.
PubDate: Tue, 25 Oct 2016 05:58:31 +000
- A Novel Hysteresis Model of Magnetic Field Strength Determined by Magnetic
Induction Intensity for Fe- Si Electrical Steel Applied in Cigarette
Abstract: Hysteresis characteristics of grain-oriented electrical steel were studied through the hysteresis loop. Existing hysteresis fitting simulation methods were summarized, and new Fe-3% Si grain-oriented electrical steel hysteresis loop model was proposed. Undetermined coefficients of the magnetic field intensity and magnetic flux density were determined by both the fixed angle method and the least squares method, and the hysteresis loop model was validated with high fitting degree by experimental data.
PubDate: Tue, 18 Oct 2016 08:10:50 +000
- Fabrication and Microhardness Analysis of MWCNT/MnO2 Nanocomposite
Abstract: Recent research has shown that carbon nanotube (CNT) acts as a model reinforcement material for fabricating nanocomposites. The addition of CNT as a reinforcing material into the matrix improves the mechanical, thermal, tribological, and electrical properties. In this research paper multiwalled carbon nanotube (MWCNT), with different weight percentage (5%, 10%, and 15%), was reinforced into manganese dioxide (MnO2) matrix using solution method. The different weight % of MWCNT/MnO2 nanocomposite powders was compacted and then sintered. The phase analysis, morphology, and chemical composition of the nanocomposites were examined by X-ray diffractometer, Field Emission Scanning Electron Microscope (FESEM), and Energy Dispersive X-Ray (EDX), respectively. The XRD analysis indicates the formation of MWCNT/MnO2 nanocomposites. The FESEM surface morphology analysis shows that MnO2 nanotube is densely grown on the surface of MWCNT. Further, microhardness of MWCNT/MnO2 nanocomposite was measured and it was found that 10 wt% has higher microhardness in comparison to 5 and 15 wt%. The microhardness of the composites is influenced by mass density, nanotube weight fraction, arrangement of tubes, and dispersion of MWCNT in H2SO4(aq) solution.
PubDate: Mon, 10 Oct 2016 10:07:20 +000
- Analysis of Depth of Shade on Mercerized and Unmercerized Fabric among
Different Woven Fabric Structures
Abstract: The main objective of this paper is to analyze and compare the color strengths of mercerized and unmercerized fabric among different fabric structures. In this research work Remazol reactive dye and three types of woven fabrics were used such as sheeting, sheeting, and herringbone. Spectrophotometer was used to find out the amount of dye which is fixed in the fabrics after soap wash. Three different woven fabrics were dyed with reactive dye (Remazol Red, Remazol Yellow, and Remazol Blue) using pad dyeing method. It was found that mercerized fabric had higher depth of shade under the same dye concentration. In case of shade A (0.5%) sheeting showed better color strength compared to other two structures but for shade B (1.5%) and shade C (4%) herringbone fabric showed better dye absorptive capacity than sheeting.
PubDate: Mon, 10 Oct 2016 09:36:10 +000
- Fabrication and Antibacterial Effects of Polycarbonate/Leaf Extract Based
Abstract: We have reported the preparation and antibacterial activities of leaf extract incorporated polycarbonate thin films to improve the antibacterial characteristics of host polycarbonates (PCs). Crude extracts of Azadirachta indica, Psidium guajava, Acalypha indica, Andrographis paniculata, and Ocimum sanctum were prepared by maceration using Dimethylformamide as solvent. The leaf extracts (LE) were incorporated into the PC matrix by solution blending method, and the thin films were fabricated by Thermally Induced Phase Separation (TIPS) technique. The antibacterial activities of the as-prepared films were evaluated against E. coli and S. aureus by disk diffusion method. The inhibitory effects of the PC/LE films are higher for S. aureus than the E. coli, but pristine PC film did not exhibit any remarkable antibacterial characteristics. Further, the model fruit (Prunus) studies revealed that the PC/LE films retained the freshness of the fruits for more than 11 days. This study demonstrates that the PC/LE films have excellent antibacterial activities; thus, the films could be promising candidate for active antibacterial packaging applications.
PubDate: Sun, 09 Oct 2016 09:00:31 +000
- Efficiency Investigations of Organic/Inorganic Hybrid ZnO Nanoparticles
Based Dye-Sensitized Solar Cells
Abstract: The present research study focuses upon the synthesis, characterization, and performances of optoelectronic properties of organic-inorganic (hybrid) ZnO based dye sensitized solar cells. Initially, polymer dye A was synthesized using condensation reaction between 2-thiophenecarboxaldehyde and polyethylenimine and was capped to ZnO nanoparticles. Size and morphology of polymer dye A capped ZnO nanoparticles were analyzed using DLS, SEM, and XRD analysis. Further, the polymer dye was added to ruthenium metal complex (RuCl3) to form polymer-ruthenium composite dye B. Absorption and emission profiles of polymer dye A and polymer-ruthenium composite dye B capped ZnO nanoparticles were monitored using UV-Vis and fluorescence spectroscopy. Polymer dye A and polymer-ruthenium composite dye B capped ZnO nanoparticles were further processed to solar cells using wet precipitation method under room temperature. The results of investigations revealed that, after addition of ruthenium chloride (RuCl3) metal complex dye, the light harvesting capacity of ZnO solar cell was enhanced compared to polymer dye A capped ZnO based solar cell. The polymer-ruthenium composite dye B capped ZnO solar cell exhibited good photovoltaic performance with excellent cell parameters, that is, exciting open circuit voltage () of 0.70 V, a short circuit current density () of 11.6 mA/cm2, and a fill factor (FF) of 0.65. A maximum photovoltaic cell efficiency of 5.28% had been recorded under standard air mass (AM 1.5) simulated solar illuminations for polymer-ruthenium composite dye B based hybrid ZnO solar cell. The power conversion efficiency of hybrid ZnO based dye sensitized solar cell was enhanced by 1.78% and 3.88% compared to polymer dye A (concentrated) and polymer dye A (diluted) capped ZnO based dye sensitized solar cells, respectively. The hybrid organic/inorganic ZnO nanostructures can be implemented in a variety of optoelectronic applications in the future of clean and green technology.
PubDate: Thu, 29 Sep 2016 09:26:28 +000
- Low Energy Gamma Radiation Induced Effects on Ultrasonic Velocity and
Acoustic Parameters in Polyvinylidene Fluoride Solution
Abstract: The modification of polyvinylidene fluoride (PVDF) polymer properties with irradiation is of interest as it possesses unique piezo-, pyro-, and ferroelectric properties. In this paper, we report the results of acoustic parameters of irradiated PVDF mixed with dimethylacetamide (DMAC) solution with low energy -source (Cs-137). The polymer solution covered with mica film assures only -ray passage and the duration was increased from 18 to 50 hours to achieve the higher dose rate. The dose rate was estimated using the strength of the radioactive source and the duration of the exposure. The ultrasonic velocity (), density (), and viscosity () of 0.2 wt% and 0.5 wt% PVDF dissolved in pure DMAC solution, irradiated with different dose rate were measured using ultrasonic interferometer (Mittal make), Pyknometer, and Oswald’s viscometer, respectively. It is observed that the values of , , and change with dose rate. The acoustic parameters such as adiabatic compressibility (), intermolecular free path length (), acoustic impedance (), relative association (RA), ultrasonic attenuation (), and relaxation time () are calculated using the experimental data. These results are interpreted in terms of the solute-solvent interaction in a polymer solution and scissoring chain damage.
PubDate: Thu, 29 Sep 2016 07:59:28 +000
- Optimization for Tribological Properties of Glass Fiber-Reinforced PTFE
Composites with Grey Relational Analysis
Abstract: Most recent history shows that polytetrafluoroethylene (PTFE) is widely used as antifrictional materials in industry for wide speed range. A high antifriction property of PTFE makes it suitable for dry friction bearing. Main disadvantage of using PTFE is its high wear rate, so extensive research had been carried out to improve the wear resistance with addition of filler material. This study focuses on four input parameters load, sliding speed, sliding distance, and percentage of glass fiber as a filler material. Taguchi method was used for experimentation; each parameter is having 3 levels with L27 orthogonal array. Grey relational analysis is used to convert multiple response parameters, namely, wear and coefficient of friction, into single grey relation grade. The optimal input parameters were selected based on the ratio. It was observed that load 3 kg, sliding speed 5.1836 m/s (900 rpm), sliding distance 2 km, and 15% of glass fiber are optimal input parameters for PTFE without significantly affecting the wear rate and coefficient of friction.
PubDate: Wed, 28 Sep 2016 10:13:32 +000
- State-of-the-Art Report on Alkali Silica Reactivity Mitigation
Effectiveness Using Different Types of Fly Ashes
Abstract: Use of fly ash by percent replacement of cement is considered as one of the most economical and effective methods for mitigating alkali-silica reaction (ASR) related distress in the concrete. However, fly ash has been proven to be somewhat variable in its effectiveness in inhibiting alkali-silica reactivity, principally because its composition depends on the coal properties from which it is derived. Typically class C fly ashes are not as efficient as class F ashes due to their higher calcium oxide content. Nevertheless, it is important to find out whether the lime content in the fly ash has linear effect on ASR distress mitigation and if the dosage of fly ash is more influential than type of fly ash. This research conducted extensive testing with nine different types of fly ashes with three in each category of fly ashes, class C, class F, and intermediate class. The results indicated that the effect of increased dosage of fly ash on ASR mitigation is linear for both low-lime and high-lime fly ashes and the dosage effect is more significant with rapid effect with high-lime fly ashes compared to low-lime fly ashes.
PubDate: Tue, 27 Sep 2016 10:01:17 +000
- Investigating Phase Transform Behavior in Indium Selenide Based RAM and
Its Validation as a Memory Element
Abstract: Phase transform properties of Indium Selenide (In2Se3) based Random Access Memory (RAM) have been explored in this paper. Phase change random access memory (PCRAM) is an attractive solid-state nonvolatile memory that possesses potential to meet various current technology demands of memory design. Already reported PCRAM models are mainly based upon Germanium-Antimony-Tellurium (Ge2Sb2Te5 or GST) materials as their prime constituents. However, PCRAM using GST material lacks some important memory attributes required for memory elements such as larger resistance margin between the highly resistive amorphous and highly conductive crystalline states in phase change materials. This paper investigates various electrical and compositional properties of the Indium Selenide (In2Se3) material and also draws comparison with its counterpart mainly focusing on phase transform properties. To achieve this goal, a SPICE model of In2Se3 based PCRAM model has been reported in this work. The reported model has been also validated to act as a memory cell by associating it with a read/write circuit proposed in this work. Simulation results demonstrate impressive retentivity and low power consumption by requiring a set pulse of 208 μA for a duration of 100 μs to set the PCRAM in crystalline state. Similarly, a reset pulse of 11.7 μA for a duration of 20 ns can set the PCRAM in amorphous state. Modeling of In2Se3 based PCRAM has been done in Verilog-A and simulation results have been extensively verified using SPICE simulator.
PubDate: Thu, 22 Sep 2016 16:14:58 +000
- Composites: Preparation and Magnetodielectric Properties
Abstract: Cobalt ferrite (CoFe2O4) and silica (SiO2) nanopowders have been prepared by the microwave hydrothermal (M-H) method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The () (CoFe2O4) + SiO2 (where = 0%, 10%, 20%, and 30%) composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD), Fourier transformation infrared (FTIR) spectra, and scanning electron microscopy (SEM), respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.
PubDate: Wed, 21 Sep 2016 14:30:19 +000
- Synthesis and Study of CdS Thin Films Prepared with Different KMnO4
Abstract: The growth and properties of cadmium sulfide (CdS) thin films were prepared in a controlled manner using chemical bath deposition (CBD) method for different KMnO4 activation time such as 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min on glass substrates. CdS thin films are deposited on KMnO4 activated glass substrates at 85°C with pH value of 10 for 30 min deposition time. In the chemical bath deposition (CBD) technique, KMnO4 activation time plays an important role in the growth of the CdS film. The structure of the CdS film changes with respect to the rate of deposition. The size of the particles is affected by the nucleation rate if the solution does not contain the constant number of Cd2+ and S2− ions throughout the deposition process. This change in structure of CdS is confirmed by the XRD, SEM, and AFM analysis, and the ion-by-ion nucleation growth is also examined. The optical property of the prepared CdS thin film is scrutinized using UV-Vis-NIR absorption analysis.
PubDate: Tue, 30 Aug 2016 14:08:03 +000
- Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthene Derivatives Using H-Zeolite
A as an Efficient and Reusable Catalyst under Solvent-Free Condition
Abstract: H-Zeolite A is an efficient, excellent, and reusable catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives by one-pot synthesis of β-naphthol with various aromatic aldehyde derivatives under solvent-free condition. The synthesized zeolite H-Zeolite A was characterized by XRD, SEM, and FT-IR. The synthesized products were characterized by FT-IR and 1H-NMR spectra. Simple workup procedure, short reaction time, high yield, and reusability of the catalyst are the characteristic features of these reactions.
PubDate: Mon, 29 Aug 2016 11:15:09 +000
- Analyses of Short Channel Effects of Single-Gate and Double-Gate Graphene
Nanoribbon Field Effect Transistors
Abstract: Short channel effects of single-gate and double-gate graphene nanoribbon field effect transistors (GNRFETs) are studied based on the atomistic orbital model for the Hamiltonian of graphene nanoribbon using the nonequilibrium Green’s function formalism. A tight-binding Hamiltonian with an atomistic orbital basis set is used to describe the atomistic details in the channel of the GNRFETs. We have investigated the vital short channel effect parameters such as and , the threshold voltage, the subthreshold swing, and the drain induced barrier lowering versus the channel length and oxide thickness of the GNRFETs in detail. The gate capacitance and the transconductance of both devices are also computed in order to calculate the intrinsic cut-off frequency and switching delay of GNRFETs. Furthermore, the effects of doping of the channel on the threshold voltage and the frequency response of the double-gate GNRFET are discussed. We have shown that the single-gate GNRFET suffers more from short channel effects if compared with those of the double-gate structure; however, both devices have nearly the same cut-off frequency in the range of terahertz. This work provides a collection of data comparing different features of short channel effects of the single gate with those of the double gate GNRFETs. The results give a very good insight into the devices and are very useful for their digital applications.
PubDate: Thu, 25 Aug 2016 07:00:22 +000
- Thermal and Dielectric Behavior Studies of Poly(Arylene Ether Sulfone)s
with Sulfonated and Phosphonated Pendants
Abstract: The present paper discusses the aspects of the synthesizing valeric acid based poly(ether sulfone)s with active carboxylic acid pendants (VALPSU) from solution polymerization technique via nucleophilic displacement polycondensation reaction among 4,4′-dichlorodiphenyl sulfone (DCDPS) and 4,4′-bis(4-hydroxyphenyl) valeric acid (BHPA). The conditions necessary to synthesize and purify the polymer were investigated in some detail. The synthesized poly(ether sulfone)s comprise sulfone and ether linkages in addition to reactive carboxylic acid functionality; these active carboxylic acid functional groups were exploited to hold the phenyl sulphonic acid and phenyl phosphonic acid pendants. The phenyl sulphonic acid pendants in VALPSU were easily constructed by altering active carboxylic acid moieties by sulfanilic acid using N,N′-dicyclohexylcarbodiimide (DCC) mediated mild synthetic route, whereas the latter one was built in two steps. Initially, polyphosphoric acid condensation with VALPSU by 4-bromoaniline and next straightforward palladium catalyzed synthetic route, in both of which acidic pendants are clenched by polymer backbone via amide linkage. Without impairing the primary polymeric backbone modified polymers were prepared by varying the stoichiometric ratios of respective combinations. All the polymers were physicochemically characterized and pressed into tablets; electrical contacts were established to study the dielectric properties. Finally, the influence of the acidic pendants on the dielectric properties was examined.
PubDate: Wed, 24 Aug 2016 11:58:32 +000
- CNT Reinforced Silver Nanocomposites: Mechanical and Electrical Studies
Abstract: Nanoindentation hardness and elastic modulus of the silver/MWCNT (multiwalled carbon nanotubes) composites, fabricated by modified wet mixing technique, are studied in the present work. CNT reinforced silver nanocomposites, fabricated by introducing 4.5 volume percentages of CNT in the silver matrix, have increased elastic modulus and approximately 50% higher hardness than pure nanosilver. It is also observed from the results that the electrical conductivity of the fabricated materials was decreased by increasing the CNTs volume %.
PubDate: Wed, 17 Aug 2016 13:02:10 +000
- The Energy Loss of α-Particles in Ferromagnetic Nickel at Phase
Abstract: The energy loss (EL) of 5.486 MeV α-particles in ferromagnetic nickel foils was measured at different temperatures of the foils. The temperature of the foils was controlled and recorded using a PC-based temperature controller with an accuracy of ±0.01°C. It is observed that the energy loss in ferromagnetic nickel increases by 2–5% as the material goes from ferromagnetic to paramagnetic state. Thus our results show that the phase transition in ferromagnetic materials affects energy loss.
PubDate: Wed, 17 Aug 2016 09:47:00 +000
- Enhancement of Light Localization in Hybrid Thue-Morse/Periodic Photonic
Abstract: The electric field intensity in one-dimensional (1D) quasiperiodic and hybrid photonics band-gap structures is studied in the present paper. The photonic structures are ordered according to Fibonacci, Thue-Morse, Cantor, Rudin-Shapiro, Period-Doubling, Paper-Folding, and Baum-Sweet sequences. The study shows that the electric field intensity is higher for the Thue-Morse multilayer systems. After that the Thue-Morse structure will be combined with a periodic structure to form a hybrid photonic structure. It is shown that this hybrid system is the best for a strong localization of light. The proposed structures have been modeled using the Transfer Matrix Method.
PubDate: Sun, 14 Aug 2016 11:31:06 +000
- Optimization of Cutting Parameters during Dry Turning of Austenitic
Stainless Steel Using nc-AlTiN/Si3N4, TiAlN, and TiN Coated Inserts
Abstract: The nc-AlTiN/Si3N4, TiAlN, and TiN coating were deposited using lateral rotating cathodes (LARC) technology on TNMG 160404 cemented carbide turning inserts. Ultrafine grain treated cemented carbide substrates were used in case of TiAlN and TiN inserts. The coated inserts were tested for their hardness and compositions were determined by X-ray diffraction studies. The grain structures of coatings were observed using scanning electron microscopy. Dry cutting tests were performed on AISI 304 stainless steel to compare the performances of these coatings in terms of wear and surface finish imparted to workpiece. 3D confocal laser microscope was used to determine the flank wear. Grey relation analysis was carried out to optimize the machining parameters. Studies reveal that nc-AlTiN/Si3N4 coating showed the highest hardness of 28 GPa. The coating also shows a dense grain structure. Furthermore, in cutting tests even under severe dry cutting conditions, the wear observed was less than the other two coatings and surface finish imparted to work parts was less than 2 μm by this coating.
PubDate: Thu, 28 Jul 2016 09:19:39 +000
- Cement Pastes and Mortars Containing Nitrogen-Doped and
Oxygen-Functionalized Multiwalled Carbon Nanotubes
Abstract: Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx) or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox) are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD) at an early age (first hours of hydration). The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.
PubDate: Sun, 28 Feb 2016 08:45:22 +000
- Influence of Grain Boundary Character and Annealing Time on Segregation in
Commercially Pure Nickel
Abstract: Commercially pure nickel (Ni) was thermomechanically processed to promote an increase in Σ3 special grain boundaries. Engineering the character and chemistry of Σ3 grain boundaries in polycrystalline materials can help in improving physical, chemical, and mechanical properties leading to improved performance. Type-specific grain boundaries (special and random) were characterized using electron backscatter diffraction and the segregation behavior of elements such as Si, Al, C, O, P, Cr, Mg, Mn, B, and Fe, at the atomic level, was studied as a function of grain boundary character using atom probe tomography. These results showed that the random grain boundaries were enriched with impurities to include metal oxides, while Σ3 special grain boundaries showed little to no impurities at the grain boundaries. In addition, the influence of annealing time on the concentration of segregants on random grain boundaries was analyzed and showed clear evidence of increased concentration of segregants as annealing time was increased.
PubDate: Tue, 16 Feb 2016 08:55:29 +000
- Behavioural Change according to the Si/Al Ratio of Successive
Na-Mordenites Observed through Their Dielectric Relaxation during Water
Vapour Adsorption Process
Abstract: The experimental study of water vapour adsorption phenomenon on a zeolite, by dielectric relaxation measurement, makes it possible to determine the variations in the exchangeable cation hopping activation energy, on the surface of the solid, in relation to the number of adsorbed molecules. The present work shows that it is possible to explain the change observed in the energy, by means of simple assumptions based, on the one hand, on the models used in order to simulate the adsorption process and, on the other hand, on the distribution of the molecules adsorbed near the exchangeable cations. Thus, the phenomenological interpretation suggested here, about the change in the exchangeable cation hopping energy, obtained by dielectric relaxation measurement, makes us with a mind to conceive a simple method for explaining the results leading to new information on the organization of the first adsorbed molecules on the surface of the studied zeolite. Then, it can be verified that these conclusions confirm the assumptions already developed for interpreting the inferences from previous experiments carried out by means of other techniques.
PubDate: Wed, 03 Feb 2016 13:03:23 +000
- Investigation of the Physical and Molecular Properties of Asphalt Binders
Processed with Used Motor Oils
Abstract: In this work we investigated the performance aspects of addition of used motor oils (UMO) to neat and crumb rubber modified asphalts (CRMA) and related that to the change of molecular size distribution of modified asphalt’s fractions; asphaltenes, saturates, naphthene aromatics, and polar aromatics. Based on the results of temperature sweep viscoelastic tests, addition of crumb rubber modifier (CRM) alone or with UMO results in the formation of internal network within the modified asphalt. Based on the results of short and long term aged asphalts, the utilization of combination of UMO and CRM enhanced the aging behavior of asphalt. Bending beam rheometer was utilized to investigate the low temperature behavior of UMO modified asphalts. Based on those tests, the utilization of the UMO and CRM enhanced the low temperature properties of asphalts. Based on the results of the asphalt separation tests and the Gel Permeation Chromatography (GPC) analysis, it was found that saturates and naphthene aromatics are the two asphalt fractions that have similar molecular size fractions as those of UMO. However, UMO only shifts the molecular sizes of saturates after interaction with asphalt. Results also show that polar aromatics pose higher molecular size structures than UMO.
PubDate: Mon, 21 Dec 2015 06:27:40 +000
- Structural and Thermophysical Studies of Composite Na-Cobaltite
Abstract: Polymeric nanofibers have been produced in the last few years by electrospinning of polymer solutions. Polyvinyl alcohol (PVA) was the selected polymer for the preparation of nanofibers. Processing parameters like flow rate, needle gauge, needle to collector distance, and molarity of the solution have been optimized during electrospinning process. Sol-gel method has been used for the preparation of thermoelectric cobaltite nanoparticles having composition NaCoO2. Sol-gel combined electrospinning technique was used to prepare the composites of the NaCoO2 with PVA nanofibers. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used for the structural analysis of the prepared samples. Scanning electron microscopy (SEM) was used to observe the morphology of the prepared fibers. SEM micrographs showed that, by increasing the flow rate, diameter of the fibers increased from 185 nm to 200 nm. Two-probe method and Advantageous Transient Plane Source (ATPS) were used to study the electrical and thermal transport properties, respectively. Thermal conductivity and electrical conductivity showed a direct dependence on temperature. It was observed that particles, sample has lower thermal conductivity (0.610 W/m-K) as compared to that of composite nanofibers (1.129 W/m-K). The measurements reported are novel and are useful for energy applications.
PubDate: Sun, 15 Nov 2015 08:11:31 +000
- Structural Characteristics and Magnetic Properties of Al2O3 Matrix-Based
Co-Cermet Nanogranular Films
Abstract: Magnetic micro- and nanogranular materials prepared by different methods have been used widely in studies of magnetooptical response. However, among them there seems to be nothing about magnetic nanogranular thin films prepared by a cosputtering technique for both metals and insulators till now. This paper presented and discussed preparation, structural characteristics, and magnetic properties of alumina () matrix-based granular Co-cermet thin films deposited by means of the cosputtering technique for both Co and . By varying the ferromagnetic (Co) atomic fraction, , from 0.04 to 0.63, several dominant features of deposition for these thin films were shown. Structural characteristics by X-ray diffraction confirmed a cermet-type structure for these films. Furthermore, magnetic behaviours presented a transition from paramagnetic- to superparamagnetic- and then to ferromagnetic-like properties, indicating agglomeration and growth following Co components of Co clusters or nanoparticles. These results show a typical granular Co-cermet feature for the Co- thin films prepared, in which Co magnetic nanogranules are dispersed in a ceramic matrix. Such nanomaterials can be applied suitably for our investigations in future on the magnetooptical responses of spinplasmonics.
PubDate: Wed, 11 Nov 2015 09:29:33 +000
- Early-Age Strength Measurement of Shotcrete
Abstract: Shotcrete or sprayed concrete is a special concrete designed for spraying onto a surface, as a construction material. With shotcrete application as a ground support system ever-present in both mining and tunnelling sectors, a major requirement of drive progression is to determine when it is safe to reenter beneath freshly sprayed concrete. Accurately determining this time is of paramount importance. Generally, this reentry time is based on measuring the developing strength of shotcrete until an adequate strength value is reached. The issue with current practice is that there is no widely accepted or generally preferred method that accurately assesses the shotcrete lining’s true early-age strength. However, there are a number of strength tests that are commercially available and used in the industry; these include the soil penetrometer, needle penetrometer, bolt screws, beam end testers, and drilled core samples. This paper researches into these testing methods and their characteristics in order to determine their accuracy, testing ranges, and suitability for in situ use in the tunnelling and mining industry. The investigation ultimately reveals that current methods all have substantial shortcomings. Based on these findings, recommendations are proposed for the applicable use of the current testing methods and recommendations for future improvements.
PubDate: Tue, 10 Nov 2015 09:16:44 +000
- Diclofenac Potassium Transdermal Patches Using Natural Rubber Latex
Biomembranes as Carrier
Abstract: The aim of this study was to design a compound transdermal patch containing diclofenac potassium (Dic-K) using natural rubber latex (NRL) biomembrane. The NRL from Hevea brasiliensis is easily manipulated and low cost and presents high mechanical resistance. It is a biocompatible material which can stimulate natural angiogenesis and is capable of adhering cells on its surface. Recent researches have used the NRL for Transdermal Drug Delivery Systems (TDDSs). Dic-K is used for the treatment of rheumatoid arthritis and osteoarthritis and pain relief for postoperative and posttraumatic cases, as well as inflammation and edema. Results showed that the biomembrane can release Dic-K for up to 216 hours. The kinetics of the Dic-K release could be fitted with double exponential function. X-ray diffraction and Fourier Transform Infrared (FTIR) spectroscopy show some interaction by hydrogen bound. The results indicated the potential of the compound patch.
PubDate: Sun, 08 Nov 2015 15:49:46 +000