Solid State Phenomena Vol. 304

Abstract: Phase formation, impact resistance, and fracture surface were investigated in unreinforced Al6061, Al6061-5wt% fly ash and Al6061 hybrid composites containing 5wt% fly ash and 1,3 wt% CaO. The Al6061 composites were fabricated the stir casting process. The XRD patterns reveal the formation of second phases (MgAl₂O₄, CaAl₄O₇ and MgSiO₃), which were found in the Al6061 hybrid composites. The average grain size of Al6061 hybrid composite are much smaller than that of unreinforced Al6061.The impact resistance was enhanced by approximately 67% in Al6061 hybrid composite as compared to unreinforced Al6061 alloy. Brittle fracture indicting brittle fracture was observed in unreinforced Al6061 alloy while evidence of a mixture of brittle and ductile fracture was found in the Al6061 hybrid composites.

Abstract: A novel nanocomposite fibers were prepared from poly (ethylene terephthalate) (PET) and reduced graphene oxide (rGO) via melt spinning and their thermal and mechanical properties were investigated. Graphite oxide and rGO were characterized by the Fourier transform infrared spectroscopy (FT-IR). FT-IR spectrum of GO and rGO showed the same peak of O-H stretching of the hydroxyl and C=C stretching of aromatic rings as well as C-O stretching. The thermal stability of pristine PET and rGO/PET composite masterbatch was characterized by the thermogravimetric analysis (TGA). The thermal degradation temperature of PET and rGO/PET nanocomposite masterbatch was found at 413.9 °C and 418.1 °C, respectively. The mechanical properties of rGO/PET nanocomposite fibers were investigated and it was found that the mechanical properties were improved in all aspects comparing with neat PET fiber, including tensile strength, young's modulus and elongation at break.

Abstract: Carbon fiber reinforced polymer is mostly used to improve the performance of polymer-based component. Nevertheless, composite material properties depend on many factors such as fiber direction, length of fiber, matrix material and manufacturing process. This work aims to study the effect of fiber length and orientation on material stress-strain relationship. Short carbon fiber length (0.2 and 0.5 mm) reinforced with phenolic resin and long carbon fiber reinforced with commercial matrix material were studied. Long carbon fiber showed higher tensile strength than short carbon fiber with longitudinal direction, whereas slightly difference was observed for transverse direction. The printing path significantly affects failure location as area with lower fiber density exhibit lower local strength. Finite element simulation of the tensile test was carried out with the homogeneous material model which suggested that it could accurately predict the load capacity of printed composite. The bending strength was then computationally predicted. It was found that 0 degree offered higher bending load capacity than 90 degree orientation for all carbon fiber length with smaller difference with shorter fiber. Almost insignificant effect of fiber orientation was observed for 0.2 mm. fiber length.

Abstract: The objective of this work is to study the fiber orientation effect on frictional material properties and tribology performance. Effects of orientation on hardness, maximum load capacity under bending, the friction coefficient and surface wear of the composites were investigated. In this research, 3D printing technique was used to create workpieces in order to control fiber arrangement which is random, 0, 45, and 90 degrees. The results suggested that the fiber direction insignificantly affects material hardness with all specimen showing similar value of average hardness of approx. 90 HRC. However, the fiber orientation had a strong influence on material bending strength. The specimen with forced fiber orientation showed lower bending resistance compared to that with random fiber orientation. This may be caused by the non-uniform distribution of fiber which could promote fracture initiation site in some area with low fiber density. The coefficient of friction of the composite material was found to strongly related to it wear behavior, i.e. higher wear rate results in higher value of friction coefficient. The wear resistance was found to be controlled by both the fiber direction and fiber interface. With fiber oriented at 90 degree to sliding direction, higher coefficient was observed. However, as surface wear took place, the effect of wear debris results in an increase in friction coefficient. For 3D printed specimen, wear was increased with fiber interface density resulting in higher wear rate of specimen with 0-degree fiber orientation compared to those with 45-and 90-degree orientation during. Hence, the specimen with 0 degree fiber direction showed similar value of coefficient of friction to those with random and 90 degree fiber orientation.

Abstract: Octahedral layered birnessite (OL) was synthesized by redox method, and OL supported Ag catalysts (xAg/OL, x = 0.1wt%, 0.2wt%, 0.3wt%, 0.5wt%) were prepared by ion exchange method. Then catalysts were characterized by XRD, SEM, BET, H₂-TPR, TG, O₂-TPD and in-situ DRIFTS, while the catalytic activity of CO was evaluated. Among xAg/OL samples, the 0.3Ag/OL exhibited the best catalytic activity for CO oxidation (T₅₀ = 105 ^oC and T₉₀ = 135 ^oC). The results show that the chemical adsorption of oxygen, the low-temperature reducibility and the strong interaction between the Ag species and OL are related to the excellent catalytic activity of xAg/OL. The reaction mechanism was studied by in-situ DRIFTS. First, O₂ was adsorbed and activated on the oxygen vacancies of xAg/OL, then formed oxygen free radical attacked the adsorbed CO and produced CO₂, subsequently CO₂ desorbed from the catalyst surface. Oxygen vacancies was supplemented by gas O₂, thus circulating.

Abstract: Bioleaching solutions from uranium and arsenic solid waste served as a source of U(VI) and As (V) ions, while plant extract from green tea (Camellia sinensis) – as a reductor for nanoparticle synthesis. Uranium dioxide and As (III) nanoparticles were formed as a product of bioreduction on the hematite and schwertmannite surfaces respectively, which resulted in an increase in the negative zeta potential with an increase in pH. It suggests, that the electrical potential depends on the presence of nanoparticles. The SEM microphotographs revealed the UO₂ nanoparticles on the hematite surface.

Abstract: Physically crosslinked superabsorbent hydrogels based on NaCMC, HPC, and NaAlg were developed to address the effects of water shortage to crop farming and to regulate fertilizer usage. An optimized synthesis was performed using ten different blends. The blend with a NaCMC/HPC/NaAlg ratio of 0.29/0.42/0.29 was found to exhibit the most favorable results, accommodating 1585% moisture and 8.38% fertilizer on a dry basis. Scanning electron microscope images of this blend manifested microporous structures, responsible for its superabsorbent properties. It was found out that applying the hydrogel at 5% loading to silt soil decreases fertilizer runoff by 28% and increases field capacity to 55%. Moreover, phytotoxicity studies showed that the optimum hydrogel blend exhibits no phytotoxic properties to pechay (Brassica rapa subsp. chinensis), lettuce eton (Lactuca sativa), and spinach (Spinacia oleracea), proving its applicability to agriculture.

Abstract: Providing enough water in farming has become a challenge in the Philippines due to insufficient irrigation and escalating drought conditions, thereby decreasing agricultural productivity. The impact of this problem can be lessened through efficient water usage: by reducing water wastage in runoff or evaporation and improving soil water retention. Hydrogels can be used for this purpose due to their water absorption capabilities. In this study, a novel, biodegradable agricultural hydrogel was developed from κ-carrageenan, sodium alginate and carboxymethyl cellulose, crosslinked with Ca²⁺ and K⁺ ions. Scanning electron microscopy analysis confirmed the successful crosslinking while swelling tests revealed them as superabsorbent hydrogels, with maximum absorption reaching 2000%. Soil amended with 2% (w/w) hydrogel showed reduced water-depletion rate and improved field capacity by a maximum of 17.6% and 17.4%, respectively. Fertilizer release test also showed the potential of these hydrogels as fertilizer carriers.

Abstract: This work studied on the development of novel cathodes for proton-conductive solid oxide fuel cells (p-SOFCs) made of powders La₃Ni₂O_7+δ (LNO2) mixed with Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF). The cathodes were constructed by a skeleton of LNO2 whose surface coated by BSCF in the ratio (in wt. %) of LNO2/BSCF varying in 15/85, 30/70, 50/50, 75/25 (denote as LN15, LN30, LN50, and LN75, respectively). The skeleton was responsible for carrier conduction and air transportation; the BSCF coating was responsible for catalytic oxygen reduction reaction (ORR). Nascent powders directly collected from combustion were subject to examination by scanning electron microscope (SEM) and X-ray diffractometer (XRD) and further calcination. Well crystalized with highly pure powders obtained post their calcination at 900 °C. Performing the button cells by means of I-V testing at 600, 700 and 800°C, the data of maximum power density () depicted the order LN75 < BSCF < LN15 < LN30< LN50 regardless of temperatures. Among all the specimens, LN50 could be the best cathode candidate for P-SOFCs.