Papers by Keyword: Morphology

Abstract: In this research, the effect of ethylene-methyl acrylate copolymer (EMAC or EMAC30) and clay surface modified with aminopropyltriethoxysilane 0.5-5 wt% and octadecylamine 15-35 wt% (Clay-ASO) on the morphological, mechanical, and thermal properties of high density polyethylene (HDPE) were investigated. The polymer blends and composites were prepared by an internal mixer and then samples were molded by compression molding. The morphology analysis showed that the presence of fibrous surface at the specimen fracture surface of HDPE/EMAC30 blends. The phase morphology of HDPE blends with Clay-ASO 3, 5 and 7 phr was observed the phase separation of EMAC30 and aggregate of Clay-ASO at high EMAC30 content. Young’s modulus of HDPE/Clay-ASO composites increased with increasing Clay-ASO composites. The presence of Clay-ASO did not improve Young’s modulus and tensile strength of HDPE/EMAC30/Clay-ASO composites. The strain at break of HDPE/EMAC30 blends increased with increasing EMAC30 content. The incorporation of EMAC30 and Clay-ASO had no effect on the melting temperature of HDPE blends and composites, respectively. The percent crystallinity of HDPE/EMAC30 and HDPE/EMAC30/Clay-ASO was lower than that of pure HDPE. The addition of EMAC30 and Clay-ASO decreased the degradation temperatures of HDPE/EMAC30 blends and composites.

Abstract: 4H-SiC/Si_(liq)/4H-SiC stacks were treated at 1550-1600°C under H₂ in a RF-heated cold-wall reactor in order to generate macrosteps-structuring of the 4°off SiC(0001) wafers. Using 400 μm thick liquid Si, the observed important matter transport from the edges to the center of the same wafer was attributed to RF-induced convection rolls inside the thick liquid Si. When the liquid thickness was reduced down to 30 μm, the matter transport followed this time the vertical thermal gradient like in the case of liquid phase epitaxy. The dissolution rate of the bottom (hotter) wafer was found to increase from 1.7 μm/h at 1550°C to 3.3 μm/h at 1600°C. The use of H₂ gas was found essential to the system since it does not generate gas trapping (unlike Ar) and it participates to the creation of the vertical thermal gradient.

Abstract: This work studied the morphological, mechanical, and thermal properties of poly(lactic acid) (PLA)/polybutylene succinate (PBS)/ethylene-co-methyl acrylate-co-glycidyl methacrylate (EMA-GMA) ternary blends. The polymer blends were prepared in an internal mixer and then molded into films by compression molding. The results showed that the PLA/PBS blends had immiscible morphology in which the PBS phase was dispersed in PLA matrix as spherical shape. The PBS droplet size increased with increasing PBS content. The fractured surface of PLA/PBS/EMA-GMA blends displayed more small crack of plastic deformations than that of PLA/PBS blends and the fracture behavior of PLA/PBA blends was changed to more ductile fracture when added with EMA-GMA. The addition of EMA-GMA in polymer blends improved the compatibility of two phases. The results of the mechanical properties showed that PBS and EMA-GMA addition improved the strain at break of PLA/PBS and PLA/PBS/EMA-GMA blends, respectively. The incorporation of EMA-GMA had no effect on the melting temperature and degradation temperature of PLA blends. The PLA/PBS/EMA-GMA blends had lower percent crystallinity than that of PLA/PBS blends and most of percent crystallinity decreased with increasing EMA-GMA loading due to its more amorphous structure than PLA and PBS.

Abstract: Cerium oxide, also known as CeO₂, can be synthesized by the hydrothermal process with cerium nitrate precursor solution. After drying and sintering at 800,900, and 1100 C, different-sized cerium oxide nanoparticles were produced from the solution. Using x-ray diffractometers, the researchers were able to determine that all of the cerium oxide nanoparticles have a unique structure called fluorite crystalline structures. The structural, morphological and optical properties of films were investigated by a set of characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The estimation of crystallite size is (22.12,27.34 and 42.02 nm), which is confirmed by Scherrer formulae from XRD pattern. The dielectric constant increased with the increase of crystallite size due to the size effect. The crystal size increased with increased sintering temperature. Keywords: Cerium oxide (CeO₂), structural, crystal size, , morphology,Dielectric constant.

Abstract: ZnO nanoparticles were successfully produced via a simple low cost hydrothermal method using different metal precursors. Zn (CH₃COO)₂), (Zn (NO₃)₂) and (ZnCl₂) were the source materials. The obtained nanoparticles were investigated by means XRD, SEM and DRS. The XRD exhibited the high crystallinity of the pure ZnO phase with hexagonal wurtzite crystalline structure for all simples excepted for ZnO synthetized from ZnCl₂ precursor. The crystallite sizes was estimated in the range of 20-37 nm. The precursor type do not affect the E_g of the nanoparticles. The bandgaps energies were between 3.21-3.22 eV. The type of precursor affect the particles morphology. SEM images revealed different morphologies. The photocatalytic activity of the synthetized ZnO NPs in comparison with that of commercial powder for the methylene blue (MB) degradation under UV irradiation, showed the appropriate activity of nanostructures obtained by Zn (NO₃)₂ and Zn (CH₃COO)₂ precursors. The first-order kinetic constant over ZnO from Zn (NO₃)₂ was 1.9, 3.7 and 1.5 times of ZnO commercial powder, ZnO from ZnCl₂ and Zn (CH₃COO)₂, respectively. The ZnO NPs from Zn (NO₃)₂ and Zn (CH₃COO)₂ precursors have the best photocatalytic degradation performance with a degradation rate of 99.3% and 96.4%, respectively. The higher photocatalytic performance was probably due to the larger crystallinity, purity phase and specific morphologies than smaller particle size effect. Thus, the synthetized ZnO nanoparticles by the soft hydrothermal process are a promising candidate for the photocatalytic purposes of dyes from waters.

Abstract: Electrochemical discharge machining (ECDM) is a hybrid method used to generate micro-features in hard and brittle materials (glass, ceramics, and composites) in aerospace, microelectromechanical systems (MEMS), and microfluidic applications. A significant improvement was observed in ECDM process but the effect of the process on the health of working operator are rarely investigated. Sustainability in manufacturing is a major concern for a better environment and safety of human operators. In this paper, analysis of fumes mass concentration (FMC), size and morphology of fume particles, and composition of fume particles along with their biological effects are studied during ECDM of CFRP composites. FMC was calculated by varying the concentration of electrolyte from 20 to 50% and duty cycle from 60 to 90% for a fixed sampling duration of 30 minutes. SEM images indicated the presence of spherical, irregular, and loosely packed fumes particles in the fumes generated during machining. EDS was also performed to study the chemical composition of fumes particles.

Abstract: Magnesium phosphate cements (MPCs) find application as alternative inorganic binders in construction, for crack repair and recycling of hazardous wastes. For the most common formulation, setting occurs through the reaction in water between magnesium oxide and potassium dihydrogen phosphate. The products include MgKPO₄·6H₂O (MKP) and an amorphous phase. Their use is somehow limited by the short working time and excessive release of heat. In this work, glucose has been introduced in the formulation of MPC to extend the setting time and modulate the rate of heat evolution. This can be considered an inexpensive and sustainable solution. The mechanism of action of the additive has been studied by investigating the reaction with isothermal conduction calorimetry, whereas the microstructure and phase composition of the obtained cements have been studied with scanning electron microscopy and X-ray powder diffraction, respectively. Results indicated that the additive influenced the reaction path thanks to the interaction at the molecular level with the dissolution process of magnesium oxide, as well as with the nucleation and growth of MKP. This has been confirmed by the changes induced in the size and shape of MKP crystals observed after the experiments conducted on diluted systems.

Abstract: It was defined that structural elements of a building made from electrically conductive concrete may reduce their performance characteristics due to the corrosion environment. The main reasons for that process are supplement corrosion factors such as a wide range of temperature, humidity as well as chemical agents in the environment. In this article results of different properties (mechanical, electrical) of electrically conductive concrete are discussed including their alterations due to sulphate attack. Also, microstructure as well as physical and chemical properties of modified concrete have been considered after being exposed to sulphate attack (Na₂SO₄) for 112 days. That component has been used for modeling the sulphate attack environment. Compressive strength, rate of the corrosion process, the volume of absorbed SO₄^2– ions from a water-based solution of Na₂SO₄ was defined in order to analyze the effect of sulphate attack. Scanning electron microscopic investigation, energy dispersive spectroscopy, differential thermal analyses were applied for observing morphology and properties changes of modified samples. To assess the influence of sulphate attack on mineral composite materials the approach was suggested and this method might be useful to foresee the durability of concrete while exposing it to the high corrosion environment. In addition to that, a possible method of protection for electrically conductive concrete from sulphate attack was also considered in the article.

Abstract: Transparent conducting oxides (TCO) are semiconducting materials that are electrically conductive as well as optically transparent thus making them suitable for application in photovoltaics, transparent heat transfer windows, electrochromic windows, flexible display, and transparent electronics. One of the methods to enhance the conductivity of metal oxides is doping, however, it can adversely affect the optical transparency of metal oxide. Aluminum (Al) doped zinc (Zn) oxide (AZO) is an important TCO material whose optoelectronic properties heavily rely on the Al doping level. There are various methods to develop AZO thin films. However, since Al and Zn are high vapor pressure materials, and their precise content control isn’t that easy, that’s why we dedicated this study to devise a facile method of Al doping into the ZnO structure. We report a twostep synthesis route to develop AZO thin films over glass substrates. Sub stoichiometric zinc oxide (ZnOx) thin films were sputter deposited over glass employing RF magnetron sputtering at 70W and 9 x 10-3 Torr Ar pressure. To mitigate Zn losses during annealing at 450 °C, the films were first oxidized up to 200 °C in air so as to convert ZnOx into stoichiometric ZnO. To incorporate Al into the ZnO structure, Al was spin coated on top of ZnO from its stabilized sol of 0.07 molar aluminum nitrate nonahydrate in ethanol. The samples were subsequently annealed at 450 °C for 2h in air with a controlled heating ramp of 3 °C/min. The film morphology, microstructure, electronic, and optical characteristics were explored employing scanning electron microscopy, energy dispersive x-ray spectroscopy, Hall effect measurements, and UV-Vis-NIR spectrophotometry, respectively. We found that both the Al and oxygen (O) content affect the optoelectronic behavior of AZO. Even without Al doping, O deficient samples were found to be sufficiently conductive, however, the ZnOx is less transparent relative to O rich stoichiometric ZnO. Furthermore, if ZnOx is annealed at higher temperatures, it causes Zn losses, since Zn is a relatively high vapor pressure material. It degrades the film morphology as well. Once we have ZnO we can confidently treat it at 450 °C to allow Al diffusion into the interiors of the ZnO film. We found that AZO produced via this method is sufficiently conductive as well as transparent.

Abstract: Polymers that are low-cost, lightweight, durable, and eco-friendly can be considered as one of the aims of recent research studies to solve environmental problems, especially those caused by the abundance of plastic wastes. The notable mechanical properties of such polymers could be achieved with reinforcements such as using natural fibers like hemp, sisal, wood-fiber, jute, and the focus of the study, rice husk. Using high-density polyethylene (HDPE) as the matrix, the addition of rice husk fillers was able to improve the mechanical properties of the polymer composites. However, the microstructure of the composite seems to be uneven, and voids could be observed. This must be due to disturbances or inhomogeneity in the interfacial dispersion of the filler (rice husk) and the matrix (polyethylene). This paper aims to introduce a poly (ethylene glycol) methacrylate (PEGMA) compatibilizer that can help provide stronger interfacial dispersion between the filler and matrix to improve the mechanical properties and morphology of the composite. It also offers a broader perspective regarding the possible component combinations and ratios in fabricating polyethylene which may, later on, lead to the manufacture of more efficient polyethylene-based products.