Papers by Keyword: Hybrid

Abstract: Carbon nanotubes (CNTs) have a great potential to be used as filler to enhance the mechanical properties of polymer composites due to excellent properties. However, CNTs have limitation of difficult to disperse in polymer matrix. The hybridization of CNTs and inorganic fillers can improve the dispersion and combine their properties in polymer composites. In the present work, the properties of the epoxy composites filled with carbon nanotube-calcium carbonate (CNTs-CaCO₃) hybrid, at various filler loading (i.e., 1-5 wt.%) were studied. The CNTs-CaCO₃ hybrid fillers were prepared by physically mixing (PHY) method and chemical vapor deposition (CVD) method. The tensile properties and hardness of both composites were investigated at different weight percentages of filler loading. The CNTs-CaCO₃ CVD hybrid composites showed higher tensile strength and hardness than the CNTs-CaCO₃ PHY hybrid composites. This increase was associated with the homogenous dispersion of CNT–CaCO₃ particle filler. The morphological studies of fracture surfaces after tensile test by means of SEM showed homogenous dispersion of CNTs-calcium carbonate CVD hybrid in epoxy matrix. The result shows that the CNTs-calcium carbonate CVD hybrid composites are capable in increasing tensile strength by up to 116.4%, giving a tensile modulus of 40.3%, and hardness value of 39.2% as compared to a pure epoxy.

Abstract: Carbon capture and storage (CCS) is one of the method in reducing carbon dioxide (CO₂) emissions into the atmosphere. CO₂ capturing using calcium oxide (CaO) solid sorbents has been considered as an advanced concept for CO₂ capture and recovery. However, the adsorption capacity of CaO decreases during repeated adsorption/desorption cycles. The stability of Ca-based sorbents during cyclic runs can be achieved via the incorporation of inert support materials. Among the available inert materials, MgO is most promising for CO₂ due to high stability and a high Tammann temperature. Most of Ca- based MgO hybrid adsorbent synthesis methods sorbent come with its own limitations which are longer synthesis duration and complex or multistep methods. In this research, Ca-based MgO hybrid adsorbent was prepared via two-step method. Calcium acetate and magnesium nitrate as precursor had dissolved in water, follow by addition of ethanol. The mixture then became gelated and proceeded for calcination at 550°C and 650°C. The prepared sorbent was characterized by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and fourier transfer infrared spectroscopy (FTIR). The XRD analysis of the Ca-based MgO hybrid adsorbent showed the existence of MgO,CaO and CaCO₃. FTIR analysis showed presence of Ca─O bond and Mg═O bond. The morphology of the hybrid adsorbent was found to be spherical to granular shape and agglomerated. The Ca- based MgO hybrid adsorbent structural and morphological shows great potential for CO₂ capturing capacity over multiple carbonation cycles for CO₂ capturing application.

Abstract: The temperature- and time-dependent penetration of surface structures is examined in thermal joining between polypropylene and aluminum. Experimental and numerical investigations were carried out for spot joints in order to describe the main effects on structure penetration. Further investigations were performed in a half-section setup to gain information directly from the joining zone. The thermal expansion of the thermoplastic material as well as the temperature distribution in the melting layer were identified as key parameters for structure filling on the metal surface.

Abstract: Software developers have shown a lot of interest in using agile approaches and methods to manage projects. The Agile Manifesto in 2001 provided a good basis to use this as it formulated its 4 values and 12 principles. Adaptability was a common feature in the Agile Manifesto to make agility happen and there appears a need to combine dynamism to ensure agility takes a more concrete and effective role. Whilst the term adaptability is discussed more often than dynamism by most researchers, the clarity in its meaning needs improvement as the terms are used interchangeably. This paper proposes a useful clarity on its differences and how it should be used. In addition, this approach would also facilitate the current research interest in mixing and combining software development methodologies to create hybrid versions as pure methods (traditional and agile) have not worked well in most software projects.

Abstract: In this work, hybrid membranes were obtained with the addition of calcium chloride (CaCl₂). Hybrids were obtained by the melt intercalation method. Membranes were prepared by phase inversion technique. Hybrid and hybrid membranes were characterized by differential scanning calorimetry (DSC). The DSC curve of the polymer and polymer membrane was changed by addition of the clay, increasing the degree of crystallinity. For all membranes, it was observed the existence of two endothermic peaks corresponding to the two crystalline phases of the polymer characteristics, in the range of 220 °C related to the alpha phase and, in the range of 210 °C related the gamma phase. In addition, there was the appearance of an endothermic peak at about 70 °C, related to the temperature of the dry polymer glass transition. The addition of CaCl₂ changed the crystalline behavior of hybrids, becoming less evident the nucleating effect of the clay.

Abstract: Sol-gel chemistry was adeptly exploited to fabricate polymer based hybrids for solar disinfection to render clean drinking water. The present research study was carried out by inclusion of different proportions of titania (2.5 and 7.5 wt %) that covalently cross-linked with the polymer matrix. In addition to morphological studies, the optical band gap and wavelength absorbed was investigated through UV-Vis absorption spectra. Moreover, the efficacy of photocatalytic antimicrobial activity of polymer based hybrids was evaluated using source water with controlled amount of total coliform that causes waterborne diseases. This research provided a green synthesis approach for water disinfection along with no disinfection byproduct formation, thus, rendering energy efficient and cost-effective water disinfection.

Abstract: Among various composites available for use, carbon fiber reinforced composite is unique in its Nature. Carbon fiber is an extremely strong thin fiber made by pyrolyzing synthetic fibers, such as rayon, until charred. High Strength Composites are made from this fiber by using appropriate matrix material mostly Epoxy resins are used. High Strength, stiffness, light weight and high thermal conductivity are the main advantages over the other composites. Making products with one single composite sheet is not possible always. Some of the intricate or complex shape making is required for joining of two composite sheet. The composites joining can be done in three ways mainly Adhesive, Riveting and Hybrid. Based on the Review among all these joints adhesive joining gives better economic solution in joining. Experimental results point to significant influence of fibre on mechanical properties of sample. The tensile test of the acoustic signal emission (AE) to identify the current state of material integrity in real time. Acoustic system signal correlated to damage events. The carbon fiber composite characteristic failure mechanisms are initiated on the microscale and result in a spontaneous release of elastic energy in terms of mechanical stress waves, the so-called acoustic emissions.

Abstract: Highly crystalline and dispersible zirconia, synthesized by solvothermal reaction of zirconium (IV) isopropoxide isopropanol complex in benzyl alcohol, were functionalized with silane coupling agent and dispersed with o-phenylphenoxyethyl acrylate (OPPEA). Silane coupling agents such as 3-aminopropyltriethoxysilane (APTES) of amino functional silane, decyltrimethoxysilane (DTMS) of alkyl functional silane and 3-(trimethoxysilyl) propyl methacrylate (MPS) of acrylate functional silane have been used to modify nanoparticle surfaces and obtain dispersion of nanoparticles within OPPEA. The surface modified zirconia was compared according to silane coupling agent, FT-IR and TGA demonstrated that APTES, DMTS and MPS are chemically attached to the surface of the zirconia. The MPS-zirconia is dispersed as about 5 nm sized, whereas the APTES-zirconia, DTMS-zirconia are agglomerated. The MPS-zirconia/tetrahydrofuran (THF) sol at 15wt% loading shows high transmittance of 68 % at 550 cm^-1 and the 50wt% surface modified-zirconia/OPPEA sol show refractive index of 1.657.

Abstract: In this work, polyamide 6 membranes (PA6) and hybrids with 1, 3 and 5% of montmorillonite clay (MMT) were obtained, adding potassium chloride (KCl) and calcium chloride (CaCl₂). These different additives are intended to promote formation and increase of the pores in the microporous membranes. The membranes in the form of thin films were prepared by the phase inversion technique, leading to flat selective barriers. The MMT clay was characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The membranes were characterized by XRD, FTIR, scanning electron microscopy (SEM), contact angle, water vapor permeation, flow measurements and yield. The clay XRD results showed characteristic peaks of bentonite containing accessory materials, as well as a peak at 5.93°, indicating the d₀₀₁ basal interplanar distance of 14.95 Å of MMT. In the spectrum in the infrared region of the clay, it was observed the presence of hydroxyls inherent to the adsorbed water, as well as characteristic bands of Si-O-Si bonds and the octahedral layer of MMT. The viscosities of the solutions of PA6 and their hybrids with CaCl₂ were higher compared to solutions containing KCl due the CaCl₂ possess a bivalent ion with a high degree of hydration and a molecular mass higher than KCl. In addition, these salts promote formation of hydroxides that precipitate the particles of MMT, decreasing the viscosities with the increasing percentage of clay. By means of the X-ray diffraction, it was possible to perceive that the hybrid membranes with the inorganic salts suggest an exfoliated and/or partially exfoliated structure. From the results of the FTIR analysis the bands obtained in the PA6 membranes and its hybrids remained practically unchanged, as there was an increase in the clay content and the introduction of the inorganic salts. From the photomicrographs obtained by SEM, it was observed that the addition of clay in the hybrid membranes provided an increase in the number of pores with the gradual increase of the percentage of clay. While the addition of the inorganic salts (KCl and CaCl₂) provided an increase in the pore size of the top surfaces of all membranes, by means of the contact angle, it was verified that the hybrid membranes presented smaller angles when compared to the PA6, probably, due to the superficial peculiarity of the clay to react with water. PA6 membranes with KCl and CaCl₂ showed lower water vapor permeations as compared to hybrid membranes due to the increase in the size and quantity of pores presented on their top surfaces. The distilled water flow in the membranes initially showed a decrease and after 30 minutes a stability of the permeate flow due to a compression occurred in the membranes. The water-oil separation tests of the membranes with CaCl₂, regardless of the pressure used, indicated a significant reduction of permeate oil with promising yields above 87% , presenting potential for the treatment of wastewater contaminated by oil.

Abstract: Magnetite (Fe₃O₄)-graphene nanohybrids having three different weight ratios of magnetite to graphene were synthesized by a facile in-situ deposition method. The combination of dielectric properties of graphene and magnetic properties of magnetite makes the nanohybrids an ideal choice of material for microwave absorption applications. In regards to that, the electromagnetic properties and microwave absorbing characteristics were investigated in a frequency range of 1-18 GHz. The reflection loss (RL) reaches a minimum of-40.44 dB at 6.84 GHz with a thickness of 7 mm for the sample containing 73 wt·% of Fe₃O₄. The bandwidth corresponding to the RL below-10 dB is 7.05 GHz. The as-prepared Fe₃O₄-graphene nanohybrids showed good microwave absorption ability in the low frequency band (C-band) which can be ascribed to improved impedance matching characteristics, enhanced interfacial polarizations as well as the magnetic loss contributions. Moreover, the frequency related to minimum RL could be tuned by varying the weight ratios of magnetite to graphene.