Search results for: gas barrier properties

Authors: Priyanka Lokhande, Ram P. Sawant, Ganesh Kakad, Avinash Kolhatkar

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In order to evaluate the influence of chemical processing on low-stress mechanical properties and fabric hand of worsted cloth, eight worsted suiting fabric samples of balance plain and twill weave were studied. The Kawabata KES-FB system has been used for the measurement of low-stress mechanical properties of before and after chemically processed worsted suiting fabrics. Primary hand values and Total Hand Values (THV) of before and after chemically processed worsted suiting fabrics were calculated using the KES-FB test data. Upon statistical analysis, it is observed that chemical processing has considerable influence on the low-stress mechanical properties and thereby on handle properties of worsted suiting fabrics. Improvement in the Total Hand Values (THV) after chemical processing is experienced in most of fabric samples.

Keywords: low stress mechanical properties, plain and twill weave, total hand value (THV), worsted suiting fabric

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Authors: Marzena Tokarewicz, Malgorzata Gradzka-Dahlke

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High-entropy alloys (HEAs) have gained significant attention due to their great potential as functional and structural materials. HEAs have very good mechanical properties (in particular, alloys based on CoCrNi). They also show the ability to maintain their strength at high temperatures, which is extremely important in some applications. AlCoCrFeNi alloy is one of the most studied high-entropy alloys. Scientists often study the effect of changing the aluminum content in this alloy because it causes significant changes in phase presence and microstructure and consequently affects its hardness, ductility, and other properties. Research conducted by the authors also investigates the effect of aluminium content in AlₓCoCrFeNi alloy on its microstructure and mechanical properties. AlₓCoCrFeNi alloys were prepared by vacuum induction melting. The obtained samples were examined for chemical composition, microstructure, and microhardness. The three-point bending method was carried out to determine the bending strength, bending modulus, and conventional bending yield strength. The obtained results confirm the influence of aluminum content on the properties of AlₓCoCrFeNi alloy. Most studies on AlₓCoCrFeNi alloy focus on the determination of mechanical properties in compression or tension, much less in bending. The achieved results provide valuable information on the bending properties of AlₓCoCrFeNi alloy and lead to interesting conclusions.

Keywords: bending properties, high-entropy alloys, induction melting, microstructure

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Authors: F. Laatar, S. Ktifa, H. Ezzaouia

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Plasma Enhanced Chemical Vapor Deposition (PECVD) method is used to deposit hydrogenated nanocrystalline silicon films (nc-Si: H) on Porous Anodic Alumina Films (PAF) on glass substrate at different deposition duration. Influence of the deposition time on the physical properties of nc-Si: H grown on PAF was investigated through an extensive correlation between micro-structural and optical properties of these films. In this paper, we present an extensive study of the morphological, structural and optical properties of these films by Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD) techniques and a UV-Vis-NIR spectrometer. It was found that the changes in DT can modify the films thickness, the surface roughness and eventually improve the optical properties of the composite. Optical properties (optical thicknesses, refractive indexes (n), absorption coefficients (α), extinction coefficients (k), and the values of the optical transitions EG) of this kind of samples were obtained using the data of the transmittance T and reflectance R spectra’s recorded by the UV–Vis–NIR spectrometer. We used Cauchy and Wemple–DiDomenico models for the analysis of the dispersion of the refractive index and the determination of the optical properties of these films.

Keywords: hydragenated nanocrystalline silicon, plasma processing chemical vapor deposition, X-ray diffraction, optical properties

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Authors: Abdul Manan

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Dielectric Resonators (DRs) have revolutionized the microwave wireless communication industry globally. There are three directions for research in ceramics for application in telecommunication industry Three key properties of ceramic dielectrics that determine their functionality at microwave and millimetrewave frequencies include relative permittivity (εr), unloaded quality factor Qu- the inverse of the dielectric loss (tanδ) and temperature coefficient of resonant frequency (τf). Each direction requires specific properties. These dielectric properties are affected by a number of factors. These includes tolerance factor, onset of structural phase transitions, dark core formation, processing conditions, raw materials and impurities, order/disorder behavior, compositional ordering, porosity, humidity, grain size, orientation of the crystallites, and grain boundaries. The data related to these factors is scattered. The main purpose of this review is to bring these together and present the effects of these factors on the microwave dielectric properties. Control of these factors is important for improvement in the microwave properties. This review would be very helpful to the novice researchers and technologists in the field.

Keywords: order disorder, sintering, defect, porosity, grain boundaries

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Authors: Amira Abdelrasoul

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This study aimed to ascertain the controlled permeability of biomimetic cellulose triacetate (CTA) membranes by investigating the electrical oscillatory behavior across impregnated membranes (IM). The biomimetic CTA membranes were infused with a fatty acid to induce electrical oscillatory behavior and, hence, to ensure controlled permeability. In situ synchrotron radiation micro-computed tomography (SR-μCT) at the BioMedical Imaging and Therapy (BMIT) Beamline at the Canadian Light Source (CLS) was used to evaluate the main morphology of IMs compared to neat CTA membranes to ensure fatty acid impregnation inside the pores of the membrane matrices. A monochromatic beam at 20 keV was used for the visualization of the morphology of the membrane. The X-ray radiographs were recorded by means of a beam monitor AA-40 (500 μm LuAG scintillator, Hamamatsu, Japan) coupled with a high-resolution camera, providing a pixel size of 5.5 μm and a field of view (FOV) of 4.4 mm × 2.2 mm. Changes were evident in the phase transition temperatures of the impregnated CTA membrane at the melting temperature of the fatty acid. The pulsations of measured voltages were related to changes in the salt concentration of KCl in the vicinity of the electrode. Amplitudes and frequencies of voltage pulsations were dependent on the temperature and concentration of the KCl solution, which controlled the permeability of the biomimetic membranes. The presented smart biomimetic membrane successfully combined porous polymer support and impregnating liquid not only imitate the main barrier properties of the biological membranes but could be easily modified to achieve some new properties, such as facilitated and active transport, regulation by chemical, physical and pharmaceutical factors. These results open new frontiers for the facilitation and regulation of active transport and permeability through biomimetic smart membranes for a variety of biomedical and drug delivery applications.

Keywords: biomimetic, membrane, synchrotron, permeability, morphology

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Authors: Anjana Jain, S. Jayanth Kumar

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Polyvinylidene fluoride (PVDF) is a well-known material for remarkable mechanical properties, resistance to chemicals and superior ferroelectric performances. This endows PVDF the potential for application in supercapacitor devices. The dielectric properties of PVDF, however, are not very high. To improve the dielectric properties of Polyvinylidene fluoride (PVDF), Piezoelectric polymer nanocomposites are prepared without affecting the other useful properties of PVDF. Polyaniline (PANI) was chosen as a filler material to prepare the nanocomposites. PVDF-PANI nanocomposite films were prepared using solvent cast method with different volume fractions of PANI varying from 0.04% to 0.048% of PANI content. The films are characterized for structural, mechanical, and surface morphological properties using X-ray diffraction, differential scanning calorimeter, Raman spectra, Infrared spectra, tensile testing, and scanning electron microscopy. The X-ray diffraction analysis shows that, prepared films were in β-phase. The DSC scans indicated that the degree of crystallinity in PVDF-PANI is improved. Raman and Infrared spectrum further confirm the presence of β-phase of PVDF-PANI film. Tensile properties of PVDF-PANI films were in good agreement with those reported in literature. The surface feature shows that PANI is uniformly distributed in PVDF and also results in disappearance of spherulites. The influence of volume fraction of PANI in PVDF on dielectric properties was analyzed. The results showed that the dielectric permittivity of PVDF-PANI (120) was much higher than that of PVDF (12). The sensitivity of these films was studied on application of a pressure and a constant output voltage was obtained.

Keywords: dielectric Properties, PANI, PVDF, smart materials

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Authors: Shagufta Tabassum, V. P. Pawar, jr., G. N. Shinde

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The study of dielectric relaxation properties of polar liquids in the binary mixture has been carried out at 10, 15, 20 and 25 ºC temperatures for 11 different concentrations using time domain reflectometry technique. The dielectric properties of a solute-solvent mixture of polar liquids in the frequency range of 10 MHz to 30 GHz gives the information regarding formation of monomers and multimers and also an interaction between the molecules of the liquid mixture under study. The dielectric parameters have been obtained by the least squares fit method using the Debye equation characterized by a single relaxation time without relaxation time distribution.

Keywords: excess properties, relaxation time, static dielectric constant, and time domain reflectometry technique

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Authors: Sahari Japar, Rodney Jammy, M. A. Maleque

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The fabrication of melaleuca alternifolia fibre reinforced thermoplastic starch composites was successfully done. This paper aims to show the effect of melaleuca alternifolia fibres on mechanical and physical properties of composites by using starch as a matrix. The fibres were extracted from three different part i.e. tea tree trunk (TTT), tea tree bunch (TTB) and tea tree leaf (TTL) and combined with tapioca starch by casting method. All composites showed superior mechanical properties in comparison to TS. The addition of 5% (v/v) fibres as a filler to TS led to the improvement in young’s modulus by 350% for TTB/TS, 282% for TTT/TS and 220% for TTL/TS. The tensile strength also increased to 34.39% for TTL/TS, 82.80% for TTB/TS and 203.18% for TTT/TS respectively. The trend can be correlated to the amount of cellulose in the fibres. For physical properties, it can be seen that, with the addition of fibres, the water absorption and swelling of composites decreased. The addition of melaleuca alternifolia fibre improved mechanical and physical properties of thermoplastic starch composites.

Keywords: melaleuca alternifolia, fibre, starch, mechanical, physical

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Authors: Rui Wang, Shanfa Tang, Yuanwu Dong, Siyao Wang, Zhaowen Jiang, Di Han

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A sulfonate Gemini surfactant sodium N,N`-bis(tetradecanoyl) propanediamine dipropyl sulfonate (GNS-14) was synthesized from 1,3-propanediamine, tetradecanoyl chloride, and1,3-propanesulfonic lactone. GNS-14 was characterized by FT-IR, 1H NMR. The surface activity, interfacial activity, and emulsification properties of GNS-14 solution were systematically studied. The critical micelle concentration (CCMC) of GNS-14 surfactant was 0.056 mmol/L, and the surface tension (γCMC) was 18.2 mN/m; at 50℃, 0.5% GNS-14 solution can reduce the oil-water interfacial tension to 6.5×10−2 mN/m. GNS-14 has excellent surface activity, interfacial activity, and emulsifying properties.

Keywords: gemini surfactants, surface tension, low interfacial tension, emulsifying properties

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Authors: Štěpán Hýsek, Petra Gajdačová, Milan Podlena

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Annual plants are becoming more and more popular source of lignin and cellulose. In those days a lot of research is carried out in order to evaluate the possibility of utilization of fibres and particles from these plants in composite materials production. These lingo-cellulosic materials seem to be a great alternative to wood, however, due to waxy and silica layers on the surface of these stalks, one additional technological step is needed–erosion of the layers for the purpose of achieving better adhesion between particle and adhesive. In this research, we used several kinds of particle pre-treatment, in order to modify surface properties of these particles. Further, an adhesive was applied to the particles using laboratory blender and board were produced using laboratory press. Both physical and mechanical properties of boards were observed. It was found out that the surface modification of particles had statistically significant effect on properties of produced boards.

Keywords: annual plant, composites, mechanical properties, particleboard

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Authors: Deborah Eric, Abbas Ahmad Khan

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Lead halide perovskites quantum dots have attracted immense scientific and technological interest for successful photovoltaic applications because of their remarkable optoelectronic properties. In this paper, we have simulated CsMAPbI3-xBrx based quantum dots to implement their use in intermediate band solar cells (IBSC). These types of materials exhibit optical and electrical properties distinct from their bulk counterparts due to quantum confinement. The conceptual framework provides a route to analyze the electronic properties of quantum dots. This layer of quantum dots optimizes the position and bandwidth of IB that lies in the forbidden region of the conventional bandgap. A three-dimensional MAPbI3 quantum dot (QD) with geometries including spherical, cubic, and conical has been embedded in the CsPbBr3 matrix. Bound energy wavefunction gives rise to miniband, which results in the formation of IB. If there is more than one miniband, then there is a possibility of having more than one IB. The optimization of QD size results in more IBs in the forbidden region. One band time-independent Schrödinger equation using the effective mass approximation with step potential barrier is solved to compute the electronic states. Envelope function approximation with BenDaniel-Duke boundary condition is used in combination with the Schrödinger equation for the calculation of eigen energies and Eigen energies are solved for the quasi-bound states using an eigenvalue study. The transfer matrix method is used to study the quantum tunneling of MAPbI3 QD through neighbor barriers of CsPbI3. Electronic states are computed using Schrödinger equation with effective mass approximation by considering quantum dot and wetting layer assembly. Results have shown the varying the quantum dot size affects the energy pinning of QD. Changes in the ground, first, second state energies have been observed. The QD is non-zero at the center and decays exponentially to zero at boundaries. Quasi-bound states are characterized by envelope functions. It has been observed that conical quantum dots have maximum ground state energy at a small radius. Increasing the wetting layer thickness exhibits energy signatures similar to bulk material for each QD size.

Keywords: perovskite, intermediate bandgap, quantum dots, miniband formation

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Authors: Ketan Tamirisa, Kathleen P. Tebb

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In the U.S., annually, there are over 1 million pregnancies in teenagers and most (85%) are unintended. The need for proactive prevention measures is imperative to support adolescents with their pregnancy prevention and family planning goals. To date, there is limited research examining the extent to which support from a sexual partner(s) influences contraceptive use. To address this gap, this study assessed the relationship between sexually active adolescents, sex-assigned birth as female, and their perceived support from their sexual partner(s) about their contraceptive use in the last three months. Baseline data from sexually active adolescent females, between 13-19 years who were not currently using a long-acting contraceptive device, were recruited from 32 school-based health centers (SBHCs) in seven states in the U.S. as part of a larger study to evaluate Health-E You/ Salud iTuTM, a web-based contraceptive decision support tool. Fisher’s exact test assessed the cross-sectional association between perceived sexual partner support of contraceptive use in the past three months (felt no support, felt little support, and felt a lot of support), and current use of non-barrier contraception. A total of 91 sexually active adolescent females were eligible and completed the baseline survey. The mean age was 16.7 and nearly half (49.3%) were Hispanic/Latina. Most (85.9%) indicated it was very important to avoid becoming pregnant. A total of 60 participants (65.9%) reported use of non-barrier contraception. Of these, most used birth control pills (n=26), followed by Depo-Provera injection (n=12), patch (n=1), and ring (n=1). Most of the participants (80.2%) indicated that they perceived a lot of support from their partners and 19.8% reported no or little support. Among those reporting a lot of support, 69.9% (51/73) reported current use of non-barrier contraception compared to 50% (9/18) who felt no/little support and reported contraceptive use. This difference approached but did not reach statistical significance (p=0.096). Results from this preliminary data indicate that many adolescents who are coming in for care at SBHCs are at risk of unintended pregnancy. Many participants also reported a lot of support from their sexual partner(s) to use contraception. While the associations only approached significance, this is likely due to the small sample size. This and future research can better understand this association to inform interventions aimed at sexual partners to strengthen education and social support, increase healthcare accessibility, and ultimately reduce rates of unintended pregnancy.

Keywords: adolescents, contraception, pregnancy, SBHCs, sexual partners

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Authors: Ammar Benamrani

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This work investigates the equation of state parameters, elastic constants, and several other physical properties of (B2-type) Yttrium-Copper (YCu) rare earth intermetallic compound using the projected augmented wave (PAW) pseudopotentials method as implemented in the Quantum Espresso code. Using both the local density approximation (LDA) and the generalized gradient approximation (GGA), the finding of this research on the lattice parameter of YCu intermetallic compound agree very well with the experimental ones. The obtained results of the elastic constants and the Debye temperature are also in general in good agreement compared to the theoretical ones reported previously in literature. Furthermore, several thermodynamic properties of YCu intermetallic compound have been studied using quasi-harmonic approximations (QHA). The calculated data on the thermodynamic properties shows that the free energy and both isothermal and adiabatic bulk moduli decrease gradually with increasing of the temperature, while all other thermodynamic quantities increase with the temperature.

Keywords: Yttrium-Copper intermetallic compound, thermo_pw package, elastic constants, thermodynamic properties

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Authors: T. Valdbjørn Rasmussen

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Design criteria for achieving an acceptable indoor radon concentration are presented in this paper. The paper suggests three design criteria. These criteria have to be considered at the early stage of the building design phase to meet the latest recommendations from the World Health Organization in most countries. The three design criteria are; first, establishing a radon barrier facing the ground; second, lowering the air pressure in the lower zone of the slab on ground facing downwards; third, diluting the indoor air with outdoor air. The first two criteria can prevent radon from infiltrating from the ground, and the third criteria can dilute the indoor air. By combining these three criteria, the indoor radon concentration can be lowered achieving an acceptable level. In addition, a cheap and reliable method for measuring the radon concentration in the indoor air is described. The provision on radon in the Danish Building Regulations complies with the latest recommendations from the World Health Organization. Radon can cause lung cancer and it is not known whether there is a lower limit for when it is not harmful to human beings. Therefore, it is important to reduce the radon concentration as much as possible in buildings. Airtightness is an important factor when dealing with buildings. It is important to avoid air leakages in the building envelope both facing the atmosphere, e.g. in compliance with energy requirements, but also facing the ground, to meet the requirements to ensure and control the indoor environment. Infiltration of air from the ground underneath a building is the main providing source of radon to the indoor air.

Keywords: radon, natural radiation, barrier, pressure lowering, ventilation

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Authors: Victoria Yu. Garnova, Vladimir G. Merzlikin, Sergey V. Khudyakov, Valeriy A. Tovstonog, Svyatoslav V. Cheranev

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Long-term scientific forecasts confirm that diesel engines still will be the basis of the transport and stationary power in the near future. This is explained by their high efficiency and profitability compared to other types of heat engines. In the automotive industry carried basic researches are aimed at creating a new generation of diesel engines with reduced exhaust emissions (with stable performance) determining the minimum impact on the environment. The application of thermal barrier coatings (TBCs) and especially their modifications based on semitransparent ceramic materials allows solving this problem. For such researches, the preliminary stage of testing of physical characteristics materials and coatings especially with semitransparent properties the authors proposed experimental operating innovative radiative-and-convective cycling simulator. This setup contains original radiation sources (imitator) with tunable spectrum for modeling integral flux up to several MW/m2.

Keywords: environment saving, radiative and convective cycling simulator, semitransparent ceramic coatings, imitator radiant energy

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Authors: F. A. Hassona, M. M. Abu-Heleika, M. A. Hassan, A. E. Sidhom

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Application of electrical measurements to evaluate engineering properties of soils has gained a wide, promising field of research in recent years. So, understanding of the relation between in-situ electrical resistivity of clay soil, and their mechanical and physical properties consider a promising field of research. This would assist in introducing a new technique for the determination of soil properties based on electrical resistivity. In this work soil physical and mechanical properties of clayey soil have been determined by experimental tests and correlated with the in-situ electrical resistivity. The research program was conducted through measuring fifteen vertical electrical sounding stations along with fifteen selected boreholes. These samples were analyzed and subjected to experimental tests such as physical tests namely bulk density, water content, specific gravity, and grain size distribution, and Attereberg limits tests. Mechanical test was also conducted such as direct shear test. The electrical resistivity data were interpreted and correlated with each one of the measured experimental parameters. Based on this study mathematical relations were extracted and discussed. These results exhibit an excellent match with the results reported in the literature. This study demonstrates the utility of the developed methodology for determining the mechanical properties of soils easily and rapidly depending on their electrical resistivity measurements.

Keywords: electrical resistivity, clayey soil, physical properties, shear properties

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Authors: Nihal Atif Salim

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To improve the quality of life in cities, a variety of interventions are used. Noise is a substantial and important sort of pollution that has a negative impact on the urban environment and human health. According to the complaint survey, it ranks second among environmental contamination complaints (conducted by EEAA in 2019). The most significant source of noise in the city is traffic noise. In order to improve the sound urban environment, many physical techniques are applied. In the local area, noise barriers are considered as one of the most appropriate physical techniques along existing traffic routes. Alexandria is Egypt's second-largest city after Cairo. It is located along the Mediterranean Sea, and El- Gish Road is one of the city's main arteries. It impacts the waterfront promenade that extends along with the city by a high level of traffic noise. The purpose of this paper is to clarify the design considerations for the most appropriate noise barrier type along with the promenade, with the goal of improving the Quality of Life (QOL) and the sonic urban environment specifically. The proposed methodology focuses on how noise affects human perception and the environment. Then it delves into the various physical noise control approaches. After that, the paper discusses sustainable design decisions making. Finally, look into the importance of incorporating sustainability into design decisions making. Three stages will be followed in the case study. The first stage involves doing a site inspection and using specific sound measurement equipment (a noise level meter) to measure the noise level along the promenade at many sites, and the findings will be shown on a noise map. The second step is to inquire about the site's user experience. The third step is to investigate the various types of noise barriers and their effects on QOL along existing routes in order to select the most appropriate type. The goal of this research is to evaluate the suitable design of noise barriers that fulfill environmental and social perceptions while maintaining a balanced approach to the noise issue in order to improve QOL along existing roadways in the local area.

Keywords: noise pollution, sonic urban environment, traffic noise, noise barrier, acoustic sustainability, noise reduction techniques

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Authors: F. Z. Benabid, F. Zouai, N. Kharchi, D. Benachour

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A HDPE/ZnO nano composites have been successfully performed using the co-mixing. The ZnO was first co-mixed with the stearic acid then added to the polymer in the plastograph. The nano composites prepared with the co-mixed ZnO were compared to those prepared with the neat TiO2. The nano composites were characterized by different techniques as the wide-angle X-ray scattering (WAXS). The micro and nano structure/properties relationships were investigated. The present study allowed establishing good correlations between the different measured properties.

Keywords: exfoliation, ZnO, nano composites, HDPE, co-mixing

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Authors: H. Baltache, M. El Amine. Monir, R. Khenata, D. Rached, T. Seddik

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The first principles calculations based on the density functional theory (DFT) by using the full-potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) in order to investigate the structural and electronic properties of Cd1-xVxS alloy at x = 0.25 in zincblende structure. For the structural properties, we have calculated the equilibrium lattice parameters, such as lattice constant, bulk modulus and first pressure derivatives of the bulk modulus. From the electronic structure, we obtain that Cd0.75V0.25S alloy is nearly half-metallic. The analysis of the density of states (DOS) curves allow to evaluate the spin-exchange splitting energies Δx(d) and Δx(pd) that are generated by V-3d states, where the effective potential for spin-down case is attractive than for spin-up case. Calculations of the exchange constants N0α (valence band) and N0β (conduction band) are served to describe the magnetic behavior of the compounds.

Keywords: first-principles calculations, structural properties, electronic properties

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Authors: A. Gulbiniene, V. Jankauskaite

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Textile laminates with breathable membranes are used extensively in protective footwear. Such polymeric membranes act as a barrier to liquid water and soil entry from the environment, but are sufficiently permeable to water vapour to allow significant amounts of sweat to evaporate and affect the comfort of the wearer. In this paper the influence of absorbed humidity amount on the electrical properties of textiles lining laminates with and without polymeric membrane is presented. It was shown that textile laminate structure and its layers have a great influence on the water vapour absorption. Laminates with polyurethane foam layers show lower ability to absorb water vapour. Semi-permeable membrane increases absorbed humidity amount. The increase of water vapour absorption ability decreases textile laminates' electrical resistance. However, the intensity of the decrease in electrical resistance depends on the textile laminate layers' nature. Laminates with polyamide layers show significantly lower electrical resistance values.

Keywords: electrical resistance, humid atmosphere, textiles laminate, water vapour absorption

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Authors: B. Bouadjemi, S. Bentata, T. Lantri, Souidi Amel, W.Bensaali, A. Zitouni, Z. Aziz

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We performed first-principle calculations, the full-potential linearized augmented plane wave (FP-LAPW) method is used to calculate structural, optoelectronic and magnetic properties of cubic halide perovskites CsPbX3 (X= F,I). We employed for this study the GGA approach and for exchange is modeled using the modified Becke-Johnson (mBJ) potential to predicting the accurate band gap of these materials. The optical properties (namely: the real and imaginary parts of dielectric functions, optical conductivities and absorption coefficient absorption make this halide perovskites promising materials for solar cells applications.

Keywords: halide perovskites, mBJ, solar cells, FP-LAPW, optoelectronic properties, absorption coefficient

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Authors: T. Zergoug, S. E. H. Abaidia, A. Nedjar, M. Y. Mokeddem

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Physical properties of uranium di-nitride (UN2) were investigated in detail using first principles calculations based on density functional theory. To treat the strong correlation effects caused by 5f Uranium valence electrons, on-site Coulomb interaction correction via the Hubbard-like term, U (DFT+U) was employed. The UN2 structural, mechanical and thermodynamic properties were calculated within DFT and Various U of DFT+U approach. The Perdew–Burke–Ernzerhof (PBE.5.2) version of the generalized gradient approximation (GGA) is used to describe the exchange-correlation with the projector-augmented wave (PAW) pseudo potentials. A comparative study shows that results are improved by using the Hubbard formalism for a certain U value correction like the structural parameter. For some physical properties the variation versus Hubbard U is strong like Young modulus but for others it is weakly noticeable such as the density of state (DOS) or bulk modulus. We noticed also that up from U=7.5 eV, elastic results become not conform to the cubic cell elastic criteria since the C44 values turn out to be negative.

Keywords: uranium diNitride, UN2, DFT+U, elastic properties

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Authors: Hikmet Cicek

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Metal nitrides show excellence tribological properties and they used for especially on machine parts. In this work, the vacuum gas nitriding proses were applied to the titanium, D2 and 52100 steel substrates at three different proses temperatures (500 °C, 600°C and 700 °C). Structural, mechanical and tribological properties of the samples were characterized. X-Ray diffractometer, scanning electron microscope and energy dispersive spectroscopy analyses were conducted to determine structural properties. Microhardness test and pin-on-disc wear test were made to observe tribological properties. Coefficient of friction, wear rate and wear traces were examined comparatively. According to the test results, the process temperature very effective parameter for the vacuum gas nitriding method.

Keywords: gas nitriding, tribology, wear, coating

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Authors: Ali Ashjaran

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Graphene is undoubtedly emerging as one of the most promising materials because of its unique combination of superb properties, which opens a way for its exploitation in a wide spectrum of applications ranging from electronics to optics, sensors, and biodevices. In addition, Graphene-based nanomaterials have many promising applications in energy-related areas. Graphene a single layer of carbon atoms, combines several exceptional properties, which makes it uniquely suited as a coating material: transparency, excellent mechanical stability, low chemical reactivity, Optical, impermeability to most gases, flexibility, and very high thermal and electrical conductivity. Graphene is a material that can be utilized in numerous disciplines including, but not limited to: bioengineering, composite materials, energy technology and nanotechnology, biological engineering, optical electronics, ultrafiltration, photovoltaic cells. This review aims to provide an overiew of graphene structure, properties and some applications.

Keywords: graphene, carbon, anti corrosion, optical and electrical properties, sensors

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Authors: Bilal Ahmad Ashwar, Asima Shah, S. A. Rather, Asir Gani, S.M. Wani, I.D. Wani, F. A. Masoodi, Adil Gani

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Starches isolated from two newly released rice varieties (K-322 & K-448) were subject to irradiation at 0, 5, 10, and 20 kGy doses. Comparative study between native (not irradiated) and irradiated starch samples was carried out to evaluate the changes in physicochemical, morphological and pasting properties due to gamma irradiation. Significant decrease was found in apparent amylose content, pH, swelling power, syneresis, and pasting properties, whereas carboxyl content, water absorption capacity, transmittance and solubility were found to increase with the increase in irradiation dose. Granule morphology of native and irradiated starches under scanning electron microscope revealed that granules were polygonal or irregular in shape. The starch granules were somewhat deformed by gamma irradiation. X-ray diffraction pattern showed A type of pattern in native as well as irradiated starches.

Keywords: rice starch, gamma irradiation, morphological properties, pasting properties, physicochemical properties.

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Authors: Mustafa Öztas, Metin Bedir, Yahya Özdemir

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Boron doped of In2O3 films were prepared by spray pyrolysis technique at 350 °C substrate temperature, which is a low cost and large area technique to be well-suited for the manufacture of solar cells, using boric acid (H3BO3) as dopant source, and their properties were investigated as a function of doping concentration. X-ray analysis showed that the films were polycrystalline fitting well with a hexagonal structure and have preferred orientation in (220) direction. The changes observed in the energy band gap and structural properties of the films related to the boric acid concentration are discussed in detail.

Keywords: spray pyrolysis, In2O3, boron, optical properties, boric acid

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Authors: Nassima Sotehi

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This article presents experimental and numerical results concerning the thermal properties of the porous materials used as heat insulator in the buildings sector. Initially, the thermal conductivity of three types of studied walls (classic concrete, concrete with cork aggregate and polystyrene concrete) was measured in experiments by the method of the boxes. Then a numerical modeling of the heat and mass transfers which occur within porous materials was applied to these walls. This work shows the influence of the presence of water in building materials on their thermophysical properties, as well as influence of the nature of materials and dosage of fibers introduced within these materials on the thermal and mass transfers.

Keywords: modeling, porous media, thermal materials, thermal properties

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Authors: Moez Selmi, Mariem Kacem, Mehrez Jamei, Philippe Dubujet

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Earth pressure balance (EPB) tunnel boring machines are designed for digging in different types of soil, especially clay soils. This operation requires the treatment of soil by lubricants to facilitate the procedure of excavation. A possible use of this soil is limited by the effect of treatment on the hydro-mechanical properties of the soil. This work aims to study the effect of a foaming agent on the hydro-mechanical properties of clay soil. The injection of the foam agent in the soil leads to create a soil matrix in which they are incorporated gas bubbles. The state of the foam in the soil is scalable thanks to the degradation of the gas bubbles in the soil.

Keywords: EPB, clay soils, foam agent, hydro-mechanical properties, degradation

Procedia PDF Downloads 337

Authors: N. Demirsoy, N. Uçar, A. Önen, N. Kızıldağ, Ö. F. Vurur, O. Eren, İ. Karacan

Abstract:

Polymer composite nano-fibers including (1, 3 wt %) silver nano-particles have been produced by electrospinning method. Polyacrylonitrile/N,N-dimethylformamide (PAN/DMF) solution has been prepared and the amount of silver nitrate has been adjusted to PAN weight. Silver nano-particles were obtained from reduction of silver ions into silver nano-particles by chemical reduction by hydrazine hydroxide (N2H5OH). The different amount of silver salt was loaded into polymer matrix to obtain polyacrylonitrile composite nano-fiber containing silver nano-particles. The effect of the amount of silver nano-particles on the properties of composite nano-fiber web was investigated. Electrical conductivity, mechanical properties, thermal properties were examined by Microtest LCR Meter 6370 (0.01 mΩ-100 MΩ), tensile tester, differential scanning calorimeter DSC (Q10) and SEM, respectively. Also, antimicrobial efficiency test (ASTM E2149-10) was done against Staphylococcus aureus bacteria. It has been seen that breaking strength, conductivity, antimicrobial effect, enthalpy during cyclization increase by use of silver nano-particles while the diameter of nano-fiber decreases.

Keywords: composite polyacrylonitrile nanofiber, electrical conductivity, electrospinning, mechanical properties, thermal properties, silver nanoparticles

Procedia PDF Downloads 379

Authors: M. Al Azri, M. Elzain, K. Bouziane, S. M. Chérif

Abstract:

n-Type 6H-SiC(0001) substrates were implanted with three fluencies of Mn+ 5x1015 Mn/cm2 (Mn content: 0.7%), 1x1016 (~2 %), and 5x1016 cm–2 (7%) with implantation energy of 80 keV and substrate temperature of 365ºC. The samples were characterized using Rutherford Backscattering and Channeling Spectroscopy (RBS/C), High-Resolution X-Ray Diffraction technique (HRXRD), micro-Raman Spectroscopy (μRS), and Superconducting Quantum Interference Device (SQUID) techniques. The aim of our work is to investigate implantation induced defects with dose and to study any correlation between disorder-composition and magnetic properties. In addition, ab-initio calculations were used to investigate the structural and magnetic properties of Mn-doped 6H-SiC. Various configurations of Mn sites and vacancy types were considered. The calculations showed that a substitutional Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. A model is introduced to explain the dependence of the magnetic structure on site occupation. The magnetic properties of ferromagnetically (FM) and antiferromagnetically (AFM) coupled pairs of Mn atoms with and without neighboring vacancies have also been explored.

Keywords: ab-initio calculations, diluted magnetic semiconductors, magnetic properties, silicon carbide

Procedia PDF Downloads 286