Effect of raster angle on the fracture properties of additively manufactured ABS via essential work of fracture

The increasing application of additive manufacturing (AM) technology across various sectors has sparked significant interest in characterizing 3D-printed components. An essential aspect of achieving fracture-resistant designs is gaining a comprehensive understanding of the fracture behavior exhibited by these components. While most studies have focused on linear-elastic fracture mechanics (LEFM), there is a lack of comprehensive studies on the post-yield fracture behavior (PYFM) of 3D-printed components. As a result, this study aims to fill this gap by investigating the impact of raster angle, a critical parameter influencing fracture properties and often leading to premature failures, on the fracture properties of fused deposition modeling (FDM) 3D printed acrylonitrile butadiene styrene (ABS) using essential work of fracture (EWF). Outcomes showed that by changing lay-ups from [90]₅ to [0]₅, the value of w_e or elastic work increased by nearly 306%. Further, the maximum and minimum values of the plastic work (βw_p) were for [45/−45/45/−45/45] and [90]₅ lay-ups, in order. By changing lay-ups from [90]₅ to [45/−45/45/−45/45], the value of βw_p increased by approximately 216%. In addition, the fractured surfaces of tested samples are also analyzed to provide insights into the dominant failure mechanisms for different raster angles.     

Hydrothermal synthesis of lead dioxide/multiwall carbon nanotube nanocomposite and its application in removal of some organic water pollutants

Lead dioxide/multiwall carbon nanotube (PbO₂/MWCNT) nanocomposite was synthesized by hydrothermal formation of lead dioxide on functionalized MWCNT. PbO₂ nanoparticles were formed from 0.015 M Pb(OH) ₃ ^? (75 ml) solution in the presence of polyvinyl pyrrolidone (0.1 g). The solution was mixed with ammonium persulfate (NH₄)₂S₂O₈ as oxidizing agent and transferred to 100 ml Teflon-lined stainless steel autoclave heating it to 60 °C for 3 h. To prepare nanocomposite, PbO₂ formation was carried out in the presence of ultrasonically dispersed MWCNT. A black-brown product was formed in reaction vessel. The product was collected and then dried in an oven at 70 °C for 24 h. The morphology and composition of precipitate were investigated by X-ray power diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy and transmission electron microscopy (TEM). The results of XRD and TEM show globular α-PbO₂ nanoparticles immobilize on the surface of the MWCNTs. Also, TGA results demonstrated the presence of CNT in nanocomposite. The prepared PbO₂/MWCNT nanocomposite is used to construct the solid-phase cartridge. The performance of solid phase in the removal of pesticides from drinking water is determined by gas chromatography–mass spectroscopy (GC–MS) analysis. The average adsorption depends on concentration of spiked pollutants and their relative standard deviations were between 1.4 and 11 %.     

Reductive dissolution of manganese ore in sulfuric acid in the presence of iron metal

The dissolution of a manganese dioxide ore in dilute sulfuric acid facilitated by Fe metal in the form of powdered sponge iron was investigated. Effects of such parameters as molar ratios of sponge iron and sulfuric acid to manganese dioxide, temperature, particle size of sponge iron as well as ore particle size on the dissolution efficiency were studied. The results showed that manganese could be rapidly leached out to a complete degree even at room temperature. Based on both theoretical and experimental facts, it was concluded that the usage of metallic iron for the reductive leaching of manganese dioxide was superior to that of ferrous ion as far as dissolution rate and efficiency were concerned.     

Titania nanostructured coating for corrosion mitigation of stainless steel

Anatase nanostructured coating has been prepared on 316 L stainless steel by sol-gel dip coating. The topography of the coatings surface has been analyzed using atomic force microscopy. The anticorrosion performance of the coatings has been evaluated using polarization curves. Effects of calcination temperature, withdrawal speed and times of coating on corrosion protection have been studied. The results showed calcination temperature of 400°C and withdrawal speed of 10 cm/min are desirable conditions to achieve high corrosion protection of 316 L stainless steel in chloride containing environments. Coatings with 3 times exhibit better resistance against corrosion in 0.5 molar NaCl solutions. This protection against corrosion arises from photocatalytic properties of anatase nanoparticles.     

Effect of pre-treatment and biofouling of proton exchange membrane on microbial fuel cell performance

Nafion^® 117, as the most popular proton exchange membrane, has been studied with regards to the effect of pre-treatment and biofouling for bioelectricity production and wastewater treatment, in dual chamber microbial fuel cells. The obtained results showed that maximum generated power was obtained using pre-treated Nafion^® 117, at approximately 100 mW/m². However, maximum generated power for untreated Nafion^® 117 and biofouled Nafion^® 117 were 52.8 mW/m² and 20.9 mW/m², respectively. Furthermore, the columbic efficiency of pre-treated Nafion^® 117 was 2.32 and 4.15 times higher than untreated and biofouled Nafion^® 117, respectively. Obtained results demonstrated that the pre-treatment of the proton exchange membrane is necessary to reach higher powers, and biofouling is a major obstacle for proton exchange membranes in dual chamber MFCs.     

A Numerical Study on the Forced Convection of Laminar Nanofluid in a Microchannel with Both Slip and No-Slip Conditions

This article provides numerically study of the thermal performance of a microchannel, cooled with either pure water or a Cu-water nanofluid, while considering the effects of both slip and no-slip boundary conditions on the flow field and heat transfer. The microchannel is partially heated at a constant temperature and cooled by forced convection of a laminar flow at a relatively lower temperature. The effects of pertinent parameters such as Reynolds number, solid volume fraction, and slip velocity coefficient on the thermal performance of the microchannel are studied. The results of the numerical simulation indicate that the heat transfer rate is significantly affected by the solid volume fraction and slip velocity coefficient at high Reynolds numbers.     

Continuous devulcanization of waste tires by using a Co‐rotating twin screw extruder: Effects of screw configuration,temperature profile,and devulcanization agent concentration

Recently, for reasons both economical and environmental, recycling of waste tires based on (styrene butadiene rubber)/(natural rubber) (SBR/NR) has been widely considered. Response surface methodology (RSM) has been used to predict SBR/NR devulcanization behavior in a co‐rotating twin screw extruder. In this study, variable parameters were barrel temperature, screw configuration, and content of devulcanization agent. A Box‐Behnken design for the three variables, at three levels, was chosen. The sol fraction of devulcanized rubber, Δtorque (difference between maximum and minimum curing torque), and mechanical properties of revulcanizate samples were considered as the responses. The results indicated that an increase of devulcanization agent content at a certain temperature caused the sol fraction to increase. Samples including a higher sol fraction showed a lower cross‐link density. Sol fraction for high shear rate screw configuration was lower than that for other screw configurations. Tensile strength of revulcanized rubber showed a decrease with a rise of devulcanization temperature. Moreover, a relationship connecting the residence time in the extruder with stagger angle and length of different kneading blocks were obtained. J. VINYL ADDIT. TECHNOL., 19:65–72, 2013. © 2013 Society of Plastics Engineers     

Experimental Comparison of Nitrogen and Carbon Dioxide Oil Displacement in Carbonate Cores

Abstract

The feasibility of nitrogen and carbon dioxide flooding is being investigated experimentally as possible enhanced oil recovery processes in Iranian carbonate oil fields. Laboratory tests were conducted on a tight permeability sample of an Iranian oil field. Three flooding tests were conducted at back pressures of 1,000, 2,000, and 2,500 psi for both nitrogen and carbon dioxide separately. All tests were conducted at constant temperature of 28°C. Experimental results indicate that immiscible carbon dioxide can mobilize more oil than immiscible nitrogen due to the ability of carbon dioxide to dissolve in oil. The key factor in higher recoveries of carbon dioxide injection compared to nitrogen is the ability of carbon dioxide to extract oil components. Extraction dominates after carbon dioxide breakthrough. Although the only mechanism of oil displacement in nitrogen flooding tests was the displacement energy applied by injection pressure, the oil recoveries in nitrogen flooding are considerable, especially at higher pressures.     

Isothermal and non‐isothermal crystallization behavior of PET nanocomposites

Polyethylene terephthalate (PET)/clay nanocomposites (PCNs) containing 1 wt% Cloisite 30B (C30B) were prepared via melt compounding. Modulated differential scanning calorimetry (MDSC) for isothermally crystallized samples revealed that the third endotherm at the highest temperature may be attributed to the recrystalization and melting of crystals, reorganized during heating. The first and second endotherms may be associated with melting of the secondary and primary crystals, respectively. The overall isothermal crystallization rate in PCNs was faster than in the neat resin. Growth kinetics revealed that the work required for chain folding and the equilibrium melting temperature in PCNs were somewhat higher than for neat PET. During isothermal crystallization, the steric hurdles introduced by clay layers lead to a reduction in the transport of the PET chains into crystallites. The effective non‐isothermal activation energy for the PCNs was higher than for PET, possibly leading to less perfect crystals in the PCNs. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers