Effect of the SiC particle size on the dry sliding wear behavior of SiC and SiC–Gr-reinforced Al6061 composites

The effect of size of silicon carbide particles on the dry sliding wear properties of composites with three different sized SiC particles (19, 93, and 146 μm) has been studied. Wear behavior of Al6061/10 vol% SiC and Al6061/10 vol% SiC/5 vol% graphite composites processed by in situ powder metallurgy technique has been investigated using a pin-on-disk wear tester. The debris and wear surfaces of samples were identified using SEM. It was found that the porosity content and hardness of Al/10SiC composites decreased by 5 vol% graphite addition. The increased SiC particle size reduced the porosity, hardness, volume loss, and coefficient of friction of both types of composites. Moreover, the hybrid composites exhibited lower coefficient of friction and wear rates. The wear mechanism changed from mostly adhesive and micro-cutting in the Al/10SiC composite containing fine SiC particles to the prominently abrasive and delamination wear by increasing of SiC particle size. While the main wear mechanism for the unreinforced alloy was adhesive wear, all the hybrid composites were worn mainly by abrasion and delamination mechanisms.     

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     

Effect of storage options on price-based scheduling for a hybrid trigeneration system

Trigeneration is efficient to supply cooling, heat, and power demands. Also, hydro (pumped) storage with zero fuel costs can increase profit when price-based scheduling problem is solved. The goal of this study is to investigate the effects of electric boiler, hydro storage, and heat storage tank on price-based scheduling problem for hybrid trigeneration (trigeneration-conventional-gas boiler) system. A heuristic algorithm is applied to a power system where in validation case, total cost reduction of 0.63% to 0.91% is reached as compared with reported in literature. The results show that the utilization of electric boiler, hydro storage, and heat storage tank leads to profit improvement by 4.58%. Also, a critical sensitivity analysis is conducted and the results show the significant effects of several factors on scheduling results.     

A hybrid data envelopment analysis and multi-attribute decision making approach to sustainability assessment

The concept of sustainability consists of three main dimensions: environmental, techno-economic, and social. Measuring the sustainability status of a system or technology is a significant challenge, especially when it needs to consider a large number of attributes in each dimension of sustainability. In this study, we first propose a hybrid approach, involving data envelopment analysis (DEA) and a multi-attribute decision making (MADM) methodologies, for computing an index for each dimension of sustainability, and then we define the overall sustainability index as the mean of the three measured indexes. Towards this end, we define new concepts of efficiency and cross-efficiency of order (p, q) where p and q are the number of inputs and outputs, respectively. For a given (p, q) , we address the problem of finding efficiency of order (p, q) by developing a novel DEA-based selecting method. Finally, we define the sustainability index as a weighted sum of all possible cross-efficiencies of order (p, q) . Form a computational viewpoint, the proposed selecting model significantly decreases the computational burden in comparison with the successive solving of traditional DEA models. A case study of the electricity-generation technologies in the United Kingdom is taken as a real-world example to illustrate the potential application of our method.     

Analysis and Examination of Aluminum Sheets Suitable for Automotion Body: Ultrasonic Testing,Signal Processing,Simulation

Russian Journal of Nondestructive Testing - There are many changes in the automotive industry, today. All aluminum sheets used in the automotive body must have good weldability. In this article, we...     

Damage evaluation of laminated composite material using a new acoustic emission Lamb-based and finite element techniques

In this paper, a very promising procedure is proposed to evaluate delamination using Acoustic Emission (AE) technique in composite laminates. First, a new procedure was developed to decompose the fundamental Lamb wave modes in small size specimens. The damage mechanisms in End Notched Flexure (ENF) in woven and unidirectional specimens were then discriminated using Fuzzy Clustering Method (FCM). Afterwards, the crack-arrest phenomenon was examined in each specimen. After that, experimental and Cohesive Zone Modeling (CZM) techniques were conducted to characterize the delamination using ENF specimens. The results showed how, it is possible to successfully decrease the effect of propagating media such as attenuation of AE signals using the new proposed methodology. As a final point, the results of this study could lead to efficiently distinguishing different damages in laminated composite using AE Lamb-based technique.     

Sensitivity Investigation of SW-B80N80 Nanotube to Polychlorinated Biphenyl-153 (PCB-153): DFT Methods

Polychlorinated biphenyls (PCBs) is one of the most persistent organic pollutants that exist in the atmosphere and can be concentrated in lithosphere and hydrosphere. Because of low biodegradability and lipophilicity, PCBs accumulate in fatty tissues and through oxidative stress could lead to cancers and central nervous system disorders. Currently, degradation of these synthetic pollutants is one of the environmental issues. The aim of this study is to provide a sensor for detection of PCB-153 (PCB-153). Nano boron nitride compounds (B_nN_m) are magic materials with high stability that can be used as a sensor for detection of chlorinated aromatic compounds. In this study, sensitivity of B₈₀N₈₀ as a form of single-walled boron nitride nanotubes (SW-B₈₀N₈₀ nanotube (8,8)) to PCB-153 has been investigated. The PCB-153 is closed to the SW-B₈₀N₈₀ nanotube and electron exchanges between them have been evaluated using density functional calculations by B3LYP/6–31G^* method. The calculation of the electronic properties has shown that SW-B₈₀N₈₀ nanotube is very sensitive to the presence of PCB-153 molecules. The HOMO/LUMO and gap energy (E_g) changes were considerable. Gap energy decreased from 4.214 eV to 2.022 eV during the formation of complex PCB-153-SW-B₈₀N₈₀ nanotube that leads to conversion of PCB-153 into the other products. According to thermodynamic parameter calculation through the IR-DFT method, it is expected that SW-B₈₀N₈₀ nanotube will be a suitable candidate in the elimination of PCB-153, as well as a gas sensor.