Effects of V2O5 addition on the corrosion resistance of andalusite-based low-cement castables with molten Al-alloy

Interfacial reactions between Al-alloy and andalusite low-cement castables (LCC) containing 5 wt% V₂O₅ were analyzed at 850 °C and 1160 °C using the Alcoa cup test. Interfacial reaction products and phases formed during heat treatment of the refractory samples were characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. V₂O₅ addition resulted in the formation of glassy phases, which significantly improved the corrosion resistance. These phases were preferentially corroded by the alloy, due to their glassy nature. However, vanadium formed from reduction, formed intermetallic alloys (V–Al–Si–Mg), which formed an interfacial physical barrier to further alloy penetration.     

Aluminum Pitting Corrosion in Halide Media: A Quantum Model and Empirical Evidence

The phenomenon of localized damage of aluminum oxide surface in the presence of halide anions was scrutinized at an atomistic level, through the cluster approach and density functional theory. The phenomenon was also investigated empirically through Tafel polarization plots and scanning electron microscopy. A distinct behavior witnessed in the fluoride medium was justified through the hard-soft acid-base principle. The atomistic investigations revealed the greatest potency for chloride entrance into the metal oxide lattice and rationalized to the severity of damage. The interaction of halide anions with the oxide surface causing some displacements on the position of Al atoms provides a mechanistic insight of the phenomenon.     

Controlling foam morphology of polystyrene via surface chemistry,size and concentration of nanosilica particles

Controlling cell morphologies of polymeric foams is an important part of controlling foam properties. In this study, the effects of particle size, particle content, and particle surface chemistry on cell nucleation in nanosilica/polystyrene (PS) composites are investigated. A theoretical hypothesis on the effect of nanoparticle size on cell nucleation in PS matrix foam was examined. The surface chemistry of nanosilica particles was studied by modifying them with Vinyltriethoxysilane (VTES) silane coupling agent. The microcellular porous materials of neat and composite PS were prepared by batch foaming technique (pressure quench) using supercritical carbon dioxide (ScCO₂) as a blowing agent. It was found that the size of the pores decreases and the cell density increases with the decrease in nanosilica size and the increase of silica loading. It was also observed that the surface treatment of the nanosilica particles have substantial effect on the decrease of the cell size and the increase of the cell density.     

Using waste plastic bottles as additive for stone mastic asphalt

Currently, polymer modified asphalt mixture is a relatively costly mixture for paving roads. One way to reduce the cost of such constructions and rendering them more convenient is by using inexpensive polymers, i.e. waste polymers. The main purpose of this research is to determine the effect of incorporating waste plastic bottles (Polyethylene Terephthalate (PET)) on the engineering properties of stone mastic asphalt (SMA) mixture. The volumetric and mechanical properties of asphalt mixes that include various percentages of PET (0%, 2%, 4%, 6%, 8% and 10%) were calculated and assessed with laboratory tests. The appropriate amount of PET was found to be 6% by weight of bitumen. The outcomes were statistically analysed and the determination of the significance at certain confidence limits was performed with the two factor variance analysis (ANOVA). Moreover, some studies conducted on polyethylene modified asphalt mixture have also been taken into consideration in this paper. The results show that the addition of PET has a significant positive effect on the properties of SMA and it can promote the re-use of waste material in industry in an environmentally friendly and economical way.     

Mechanical and anisotropic behaviors of 7075 aluminum alloy sheets

Formability of 7075 aluminum alloy sheets was studied after annealing of 71% cold worked (CW) samples at different temperatures (270–450 °C). Uniaxial tensile test, deep drawing and Erichsen test were carried out at room temperature to evaluate formability parameters.     

Application of silica gel as an effective modifier for the voltammetric determination of dopamine in the presence of ascorbic acid and uric acid

Amorphous silica gel modified carbon paste electrode (CPE) offers substantial improvements in voltammetric sensitivity and selectivity towards determination of dopamine (DA). Cyclic voltammetry of Fe(CN)₆^3−/4− as a negatively charged probe revealed that the surface of the silica gel modified carbon paste electrode had a high density of negative charge at pH 8.0. Therefore, the modified electrode adsorbed DA (pK_a = 8.9) and enhanced its voltammetric response while repulsed ascorbic acid (AA) (pK_a = 4.2) and uric acid (UA) (pK_a = 5.4) and inhibited their interfering effects. The influence of various experimental parameters including percent of silica gel in the CPE, pH of solution, and accumulation time and potentials, on the voltammetric response of DA was investigated. At the optimum conditions, the analytical curve was linear for dopamine concentrations from 2.0 × 10⁻⁷ to 1.0 × 10⁻⁶ mol L⁻¹ and 2.0 × 10⁻⁶ to 1.5 × 10⁻⁴ mol L⁻¹ with a detection limit (3σ) of 4.8 × 10⁻⁸ mol L⁻¹. The prepared electrode was used for determination of DA spiked into DA injection and human serum samples, and very good recovery results were obtained over a wide concentration range of DA.     

Diameter of Single-Walled Carbon Nanotubes (SWCNTs) as an Effective Factor in the Detection and Degradation of PCBs

Polychlorinated biphenyls (PCBs) are chlorinated organic compounds and well known carcinogenic and toxic pollutants. Currently, their detection and degradation to products with less risk are among environmental and health priorities. Passing 2,2′,4,4′,5,5′-Hexachlorobiphenyl (PCB-153) through the armchair single-walled carbon nanotubes (SWCNTs) (8, 8) and (10, 10) was investigated by Modified Neglect of Diatomic Overlap in the semi-empirical method. The analysis of results suggests that there are meaningful changes in the middle of the tubes. Based on the obtained evidence, the nanotubes have substantial potential to interact with the PCB-153 molecule effectively. The results show that the increased diameter in the armchair SWCNTs improves the detection and degradation potential of the tube to PCBs. According to the calculated thermodynamic parameters, the diameter of nano-structures is an effective factor in PCBs removal efficiency, as it could be helpful to make a more sensitive PCB nano-sensor.     

Reinforcing effects of aminosilane-functionalized graphene on the tribological and mechanical behaviors of epoxy nanocomposites

In this study, aminopropyl trimethoxysilane as an interfacial modifier was introduced on the surface of graphene (Gr) nanoplatelets. The effects of the silane-modified graphene (SGr) loading (0, 0.05, 0.1, 0.3, and 0.5 wt %) and silane modification on the tensile, compressive, interlaminar shear stress (ILSS), and tribological properties of the epoxy-based nanocomposites were investigated. Out of these specimens, the highest values of ILSS and compressive strength were related to the 0.3 wt % SGr–epoxy nanocomposite. The addition of SGr enhanced the tensile strength and strain to failure only at low contents (i.e., 0.05 wt %). Also, the tensile and compressive moduli were improved, and the highest values were observed at a 0.5 wt % SGr loading. In addition, decreases of approximately 40 and 68% in the coefficient of friction and wear rate, respectively, were observed at a 0.3 wt % SGr loading. Enhanced tensile, compressive, ILSS, and wear properties in the SGr–epoxy specimens were observed compared to those in the Gr–epoxy specimens. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47410.     

Multilayer assembly of ionic starches on old corrugated container recycled cellulosic fibers

In this study, old corrugated container recycled fibers were treated with polyelectrolyte multilayers consisting of biopolymer cationic starch with two degrees of substitution (DS) each in combination with one anionic starch. Pulp zeta potential, paper strength and the thin layer ellipsometry technique were applied to examine the influence of cationic starch DS on the formation of polyelectrolyte multilayers. The results indicated a significant interaction between the DS of cationic starch and the number of ionic starch layers formed. When low‐DS cationic starch was used, the pulp zeta potential and the paper strength increased significantly in assembling the first cationic layer. However, in depositing high‐DS cationic starch a greater zeta potential and a stronger influence on the paper strength were observed with a larger number of starch layers. This was confirmed by thin layer ellipsometry when a greater thickness of multilayers was achieved by employing high‐DS cationic starch to form a higher number of layers. © 2017 Society of Chemical Industry