Combined role of SiC whiskers and graphene nano-platelets on the microstructure of spark plasma sintered ZrB2 ceramics

This research explores the sintering behavior and microstructure of ZrB₂-based materials containing graphene nano-platelets (GNPs) and SiC whiskers (SiC_w). Spark plasma sintering (SPS) process at 1900 °C was implemented to sinter the specimen, leading to a composite with 100% relative density. High-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), field emission-electron probe microanalyzer (FE-EPMA), and high-resolution X-ray diffractometry (HRXRD) were employed to study the SPSed sample, along with the thermodynamics predictions. According to the HRXRD result and microstructural observations, the sintering process was non-reactive, which was endorsed with the XPS analysis. Furthermore, graphene presented a beneficial role for eradicating the oxide impurities in the sample during the sintering. Such oxide impurities were reduced to the original phases of SiC and ZrB₂, contributing to porosity removal. Nanostructural investigations revealed the formation of ultrathin amorphous interfaces (~10 nm) between ZrB₂/graphene phases, disordered atomic planes in graphene platelets, and dislocations in ZrB₂ grains. One reason for generating crystalline defects in the microstructure was found out to be the mismatches amongst the elastic properties of the available compounds in the system.     

The use of nanotechnology to increase quality and yield of fruit crops

Nanotechnology is currently being widely employed in agriculture and horticulture. The most widely investigated and developed factor related to fruit trees is nanofertilizers (NFs), which play very important roles in increasing vegetative growth, improving reproductive growth and flowering, thereby increasing productivity, product quality and ultimately increasing shelf-life and decreasing fruit waste. These nanomaterials, which are generally sprayed at low concentrations on trees at different time intervals and in frequent sessions, are also considered as growth stimulants. Macro- and micro-scale NFs such as zinc, boron, chitosan, and fertilizer nanocomposites such as ZnFeMnB (zinc, iron, manganese, boron), NPKMg (nitrogen, phosphorus, potassium, magnesium), and calcite have been shown to significantly improve the vegetative and reproductive traits of fruit trees such as pomegranate, strawberry, mango, date, coffee and grape. Knowledge on the effects of NFs on fruit trees and biological reasons for their effects on different traits is incomplete and there is an urgent need for extensive research on these topics. © 2019 Society of Chemical Industry     

Looseness Detection and Assessment of Flange Type Joints Using Vibroacoustic Modulation Method

Russian Journal of Nondestructive Testing - Flanged joints’ looseness is among the common causes for the failure of industrial structures with flanged joints such as wind turbine or...     

Joint behavior and design procedure of a through plate connection for steel beam to hollow or concrete‐filled tubular columns

The through plate connection has a practical reliable configuration for fully restrained connections for a steel I‐beam to hollow or concrete‐filled tubular columns in seismic areas. Based on experimental programs of authors on interior planar moment connections via through plate technique, this paper presents the outcome of the studies focusing on the joint behavior and the shear transfer in the panel zone of through plate connection. Based on the conducted approved three full‐scale tests, the behavior of connection components and panel zone shear force were investigated accurately in order to provide useful information and key parameters to facilitate design calculations and proportioning the connection. The contribution of each component in the total shear capacity of the panel zone region was determined. Load transfer mechanisms were explained and by quantifying the portion of load transfer paths, the calculation approach was described for design purpose. The proposed design procedure was validated for a wide range of beam to column connections using finite element models. Verified numerical models were used to conduct parametric studies. The numerical results revealed that the proposed analysis method can predict well the induced demand in the connection components and also the design procedure is suitable and secure for all cases.     

A multiobjective optimization framework for sustainable design of municipal solid waste processing pathways to energy and materials

A large quantity of municipal solid waste (MSW) is generated worldwide, and its effective management is a major problem in urban areas or particularly the areas where waste is dumped. Numerous technological alternatives are available for waste treatment, each with different costs and environmental footprints. For sustainable waste management, both economic and environmental aspects should be considered. Therefore, this study addresses the systematic design of processing routes for the sustainable management and utilization of MSW under economic and environmental criteria. To address this, a generic superstructure-based multiobjective optimization framework is developed. MSW superstructure composes of the potential processing routes for the waste management where MSW can be utilized for energy generation and other valuable waste-based products. On the basis of superstructure, we develop a multiobjective mixed-integer nonlinear programming (MINLP) model that simultaneously maximizes the net profit and minimizes the greenhouse gas (GHG) emissions. The developed optimization model is coded and solved in GAMS to determine the optimal most promising routes for the sustainable processing of MSW. A case of the Emirate of Abu Dhabi is employed to test the applicability of the developed framework. The optimization results emphasize that pathway 2 shows a decent trade-off between economic and environmental objectives, whereas the two most environmentally sustainable processing pathways have the potential to reduce GHG emissions by 58% and 80%, compared with business as usual (BAU) scenario, and also possess potential economic benefits. The insights gained from this analysis guide the municipality planners to devise a promising and sustainable waste management strategy.     

CH4-Selective Mixed-Matrix Membranes Containing Functionalized Silica for Natural Gas Purification

Mixed-matrix membranes were prepared by incorporating functionalized silica nanoparticles (SNPs) into the poly(ether-block-amide). The gas permeation properties of membranes were investigated for the separation of N₂ and CO₂ from CH₄. Results revealed that chemical modification of SNPs and incorporation of the carboxylic groups on its surface had a strong interaction with the polymer matrix and improved the distribution of the nanofiller in the membrane matrix. According to the gas permeation experiments at various SNPs loadings and feed pressures, different trends were observed for the permeability and selectivity. Incorporation of the modified-SNPs nanofiller into the membrane enhanced the CH₄ permeability, as well as the CH₄/N₂ and CO₂/N₂ selectivities.     

Silane-functionalized Al2O3-modified polyurethane powder coatings: Nonisothermal degradation kinetics and mechanistic insights

This work reports on nonisothermal degradation kinetics of polyurethane (PU)-based powder coatings containing 1, 3, and 5%wt% vinyltrimethoxysilane functionalized Al₂O₃ (V-Al₂O₃) nanoparticles. Thermogravimetric analysis of PU/V-Al₂O₃ powder coatings with different V-Al₂O₃ contents has been performed at different heating rates. Variation of activation energy (E_a) of PU/V-Al₂O₃ powder coatings was modeled as a function of partial mass loss by using Kissinger–Akahira–Sunose, Ozawa–Wall–Flynn and modified Coats–Redfern isoconversional approaches. The results revealed hindered decomposition process of PU/V-Al₂O₃ nanocomposite powder coatings, featured by an increase in activation energy of degradation from ∼158 for blank PU to 225, 183, and 229 kJ/mol for nanocomposites filled with 1, 3, and 5 wt% of V-Al₂O₃, respectively. Likewise, pre-exponential factor values increased for samples containing V-Al₂O₃ nanoparticles compared to that of blank sample. Sestak–Berggren kinetic model appropriately captured thermal degradation behavior of PU/V-Al₂O₃ nanocomposites than that of nth order decomposition kinetic reaction models.     

Study on the formation and structural evolution of bead‐on‐string in electrospun polysulfone mats

Bead‐on‐string is a desirable morphology for some emerging applications of electrospun mats such as superhydrophobic surfaces. In this study, the bead‐on‐string morphology in electrospun polysulfone (PSU) mats was investigated and correlated with the solution concentration, voltage and feed rate. PSU/dimethylformamide solutions with different concentrations (4, 5.5, 7, 15, 18 and 20 wt% PSU) were electrospun at a constant feed rate (3.5 mL h^–1) and voltage (15 kV). Critical chain overlap and entanglement concentrations were found to be 3.65 and 7.12 wt% PSU, respectively. The bead‐on‐string morphology was detected in the concentration range 7–18 wt% PSU, in close agreement with theoretical estimations. The evolution of the bead‐on‐string morphology in mats prepared from 15 wt% PSU solution and electrospun at three feed rates (i.e. 1.5, 2.5 and 3.5 mL h^–1) and voltages (i.e. 12.5, 15 and 18 kV) were also studied. The results showed that the beads appear less in number as either the feed rate or the voltage increases. In addition, the morphology of the beads revealed a transition from a spherical to a spindle‐like appearance with an increase in voltage. The effect of feed rate on bead geometry, however, was revealed to depend on the applied voltage. © 2020 Society of Chemical Industry